Consultation document: protocols and performance specifications for continuous monitoring of gaseous emissions from thermal power generation and other sources (2022)

Draft updated
Report EPS 1/PG/7 (Revision 3)
March 2022

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Last updated: August 2020

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Section 1.0 Introduction

This document provides specifications for the design, installation, and operation of automated continuous emission monitoring systems (CEMS) used to measure releases of sulphur dioxide (SO2), nitrogen oxides (NOx), carbon monoxide (CO), carbon dioxide (CO2), and other contaminants from thermal power generating facilities and other large stationary combustion sources. The document presents procedures used to determine the various CEMS parameters during initial certification, testing and subsequent long-term operation of the monitoring system.

No specific monitoring system is prescribed in this document. Any system that meets initial certification criteria, specified parameters and quality assurance/quality control (QA/QC) requirements is acceptable. In-situ or extractive CEMS based on dynamic dilution or direct measurement of the target species may be used. Time-shared CEMS using a single set of analyzers to determine the emissions of 2 adjacent sources are acceptable.

Guidance is provided to assist the operator in developing a site-specific QA Plan (QAP), in conjunction with the appropriate regulatory agency. The resulting plan is an integral part of the overall requirements for the operation of each CEMS. Each emission monitoring system must produce technically valid data, which may be used for multiple purposes, including emission budget programs. However, this document does not address issues specific to an emission trading program, such as reporting formats, seasonal averaging, data retention requirements, etc., which should be compatible with the policies of the program and defined by the corresponding regulating authority.

While SO2, NOx, CO and CO2 are the pollutants most often associated with the flue gases released from large combustion sources, some or all the concepts and procedures described herein could also be used, as appropriate, for the measurement of emissions of other contaminants and other point sources. In such cases the appropriate regulatory authority that mandates the monitoring may adjust, expand, or reduce the requirements detailed in this document, to reflect the specific concerns and/or constraints related to the need to monitor the particular species in question.

The personnel performing the initial certification and subsequent audits must be trained and experienced in the execution of the tasks and methods described in this document. The application of this guideline may entail health and safety hazards. Individuals performing the certification and audits are responsible for obtaining the required training to meet the occupational health and safety standards applicable to industrial field activities. 

Section 2.0 Summary of specifications and protocols

This section provides various partial summaries of the specifications and procedures for the installation, certification, and continued operation of a CEMS; that may serve a quick reference to those familiar with the subject. Worth mentioning are:

Section 3 outlines the specifications for the overall CEMS and subsystems, along with associate procedures for measuring these parameters. This section will assist the operator during the initial design and/or purchase stages. Specific requirements are provided for the recommended Data Acquisition and Handling System (DAHS).

Specifications for installing the CEMS are given in section 4. These are used to ensure that a test location meets some minimal requirements with respect to representativeness of the gas flow and equipment maintenance accessibility.

After installation, the CEMS is tested following the protocols provided in section 5. The emission data are compared with those from manual or instrumental reference methods to ensure that the specifications have been met. When an installed CEMS has met or surpassed all these specifications, it is deemed certified and capable of generating quality-assured emission data.

A QA plan (QAP) must be developed for each CEMS by the operator or a contractor. Section 6 provides the basis for the development of this plan. The QAP must encompass a diverse range of topics, including calibration procedures, maintenance, performance evaluations, and corrective actions. Each CEMS will require a QAP; however, if a number of identical CEMS are operated, a single QAP is acceptable if appropriate records are maintained for each CEMS.

Section 3.0 Design specifications and test procedures

Most CEMS consist of the following 3 basic subsystems: a) sample interface/conditioning, b) gas analyzers; and c) data acquisition and handling system (DAHS). Such systems may monitor compliance with a regulatory limit in terms of pollutant exhaust concentration at a given excess combustion air level, such as NOx @ 11% O2 or limits in terms of emission per heat input.

With the addition of an adequate exhaust gas flow monitor or a fluid fuel meter, then the CEMS may measure the mass emission rate of all the monitored gaseous contaminants.

Specifications for these subsystems are given in sections 3.1 to 3.5, while section 3.6 outlines the procedure for verification of some critical specifications. The subsystem specifications are summarized in tables 1 and 2.

This guideline does not exclude any emission monitoring technology. Components that met the criteria specified in sections 3.1 to 3.5 and allow the overall CEMS to achieve the certification specifications in section 5, and the evaluations in section 6, are acceptable.

3.1 Sample interface/conditioning subsystem specifications

This section specifies the location of the system calibration gas injection port, which is the sole criteria for the sample interface and condition subsystem specifications.

3.1.1 Location of the calibration gas injection port

The location of the system calibration gas injection port is the sole criterion for the sample/conditioning subsystem, with the location of this port being specific to the type of CEMS. The location of the ports for the various types of CEMS is given in table 2. CEMS installed after 2023 must be able to conduct the daily calibration drift test and the quarterly linearity test using as reference flowing calibration gases.

3.2 Gas analyzer subsystem specification

This section specifies the criteria for operating range, interference, and temperature-response drifts, which are important for the reliable operation of gas analyzer subsystems. This section also specifies the conversion efficiency test frequency for CEMS fitted with NOx converters and the criteria for adoption of FTIR CEMS.

3.2.1 Operating range

The measurement range (MR) of the analyzers must be adequate to the operating conditions of the emission source where it is installed. MR is the design range, in reference to which the manufacturer guarantees specifications such as linearity, drift, and cross-sensitivity. MR is expected to be constant through the analyzer’s life and slightly higher than the maximum probable concentration level, such as 20.9% for O2 analyzers in atmospheric combustion.

Full scale (FS) is a subset of MR, defined as a range such that most normal operation measurements fall between 20.0% and 80.0% of it. The initial FS selection may be based on expected emission values and serves to define the initial calibration gas levels. The FS value must then be adjusted once a year on the basis of the levels measured in the previous 12 months. If ≥ 50% of the valid hourly measurements falls between 20.0% and 80.0% of the FS value, then the FS value may continue to be used for the following 12 months, otherwise a new FS must be set.

Note that in this document, some performance specifications are defined with reference to the full scale (FS) setting of the CEMS analyzer (see tables 1 and 3 in section 5, and tables 6 and 7 of section 6); therefore they are tailored to the emission source characteristics.

Sources that operate with a wide emission range, for example due to the use fuels of variable sulphur content, may not be able to meet the 20.0% to 80.0% FS rule for the entire range. They must install a dual range analyzer to cover the low and high sulphur periods, within which the 20.0% to 80.0% FS rule must apply. Relative Accuracy Test Audits (RATA) should be performed in the range used at the time of the scheduled test.

3.2.2 Interference

The manufacturer of the analyzer (either dry or wet, for single or multiple contaminants) must certify that the sum of all interferences due to other stack gas components is less than 4% of the expected FS of each contaminant monitored. In the case of combustion sources fitted with NDIR or FTIR analyzers, the certification must include wet basis v/v sample levels of 9% CO2 and 18% H2O. The removal of H2O in the sample conditioning component of the CEMS may be credited to the attenuation of H2O interference.

3.2.3 Temperature-response drifts

Each pollutant or diluent gas analyzer of the CEMS must exhibit a zero drift less than 2.0% of the intended FS setting for any 10°C change over the 5 to 35°C temperature range. Additionally, each analyzer must exhibit a span drift of less than 4.0% of the FS setting for any 10°C change over the 5 to 35°C temperature range. Both the zero and span drift tests are to be carried out within the acceptable temperature range of the analyzer, as specified by the manufacturer. The procedures outlined in section 3.6.2 must be followed to determine the temperature-response drift.

Analyzers installed and operated in a temperature-controlled environment are exempt for this specification.

3.2.4 NOx converters

If the CEMS is fitted with a NOx analyzer that converts NO2 to NO before analysis and it is not demonstrated that the source NO2 levels are less than 5% of the NO ppmv levels, then the conversion efficiency must be tested quarterly, by following US EPA Method 7E section 8.2.4 or the Method 7E alternative section 16.2 test. Acceptable conversion efficiency is 90%.

3.2.5 FTIR extractive CEMS

The features that distinguish Fourier Transform Infrared (FTIR) from other gas analyzers are, a) simultaneous monitoring of multiple infrared (IR) absorbing gases; b) computers are necessary to obtain and analyze data; c) chemical concentrations can be quantified using previously recorded IR spectra; and d) analytical assumptions and results, including possible effects of interfering compounds, can be evaluated after the quantitative analysis.

An extractive FTIR may be used as a CEMS component to monitor NOx, SO2 and CO2 emissions from a combustion source, provided that the FTIR meets the applicable analyzer specifications of this document, including the prescribed daily, quarterly, annual or semi-annual QA/QC tests.

The same FTIR CEMS, may be used to monitor emissions of other hazardous contaminants from the source (for example HCL from cement kilns). For this additional purpose it should follow the specifications developed for this technology, such as EPA PS-15 and EPA PS-18.

Table 1: Design specifications for continuous emission monitoring systems
Subsystem Parameter Specification Text references
specification
Text references
test procedures
Sample interface and conditioning Location of calibration ports See table 2 3.1.1 -
Gas analyzers Operating range Most (> 50.0%) annual hourly concentrations between 20.0% and 80.0% of full scale (FS) 3.2.1 -
Gas analyzers Interference < 4.0% FS for the sum of all interferences 3.2.2 3.6.1
Gas analyzers Temperature-response drifts Zero drift < 2.0% for 10°C change within 5-35°C.
Span drift < 4.0% for 10°C change within 5 - 35°C
3.2.3 3.6.2
Flow monitor Operating range Measurement range approximately 1.2 of maximum potential flow rate 3.3.1 -
Data acquisition Measuring time Minimum every minute or shorter interval 3.3.2 -
Data acquisition Averaging time 1 hour 3.4.1 -
Data acquisition Reporting basis As required by appropriate regulatory authority, e.g. as 720-hrs rolling average of kg/MWh 3.4.2 -
Data acquisition Missing data ≤ 168 hours interval - backfill > 168 hours interval - alternate CEM system 3.4.3 -
Time shared systems System cycle time ≤ 15 minutes for complete cycle (7.5 minutes on each of 2 streams) 3.5.1 3.6.3
Table 2 : Location of system calibration gas injection ports for specific CEMS
System Type Subsystem System calibration gas injection port specification
Extractive Direct measurement of gas concentration Calibration gas must be introduced no further than the sampling probe exit
Extractive Dilution (in-stack and external) Calibration gas must be introduced prior to dilution
In-situ Point Calibration gas must flood the measurement cavity of the analyzer
In-situ Path Calibration gas must provide a check on the internal optics and all electronic circuitry. System may also include an internal calibration device for simulating a zero and an upscale calibration value

3.3 Flow monitor subsystem specifications

The gas flow monitor must have the capability of carrying out daily checks at low and high flow rates as part of the daily system calibration procedures. Electronic simulation of low and high flow rates may be adequate in some systems, providing that daily zero and span drift can be calculated. The sensor must cover the full range of gas velocities anticipated in the flue or duct. Any flows beyond the range of the sensor are deemed to be missing and must be backfilled, as described in section 3.4.3 of this document.

3.3.1 Operating range

The measurement range (MR) of the flow monitor should be approximately 1.2 times the maximum potential flow rate. Note that various performance specifications are defined with reference to the FS setting of the CEMS flow monitor (table 1 in this section, table 3 in section 5, and table 6 and 7 in section 6). The flow monitor of the CEMS may be able to measure levels higher than the defined FS level, however, this high level cannot be applied to demonstrate conformance to specifications tailored to the characteristics of the emission source (such as FS).

If flow varies widely, the use of multirange flow monitors may be advisable for a stack serving several combustion units. The highest range should include the maximum potential flow estimated for the combustion processes. Note that data that fall outside the range(s) of the flow monitor are considered as missing and must be backfilled using the criteria discussed in section 3.4.3.

3.4 Data acquisition and handling system (DAHS) specifications

The CEMS shall include a DAHS to process and record the monitoring data. Basic DAHS functions include a) read and display the levels of stack gas pollutants, diluents, flow, and temperature (if applicable), and b) keep a continuous and permanent record of the data. The system must also record and compute daily zero and span drifts, providing for backfilling and substitution for missing data. Additionally, the DAHS shall record the process intervals during which fuel is burned (for combustion-related processes) and during which contaminants are vented (for no combustion-related sources). The data recording minimum resolution shall be ±0.2% FS of each analyzer or monitor, and the time resolution shall be 1 minute or less.

Data shall be reduced to valid 1 hour averages, computed using at least 1 data point in each 15 minute quadrant of an hour during which the unit combusted fuel or vented contaminants. If data are unavailable as result of QA/QC activities or preventive maintenance, then a valid hour may be computed from at least 2 data points separated by a minimum of 15 minutes in which the combustion source operated. All valid measurements during an hour shall be used to calculate the hourly averages.

The availability of the system and each analyzer shall be calculated monthly, using the following equation 3.1:

Equation 3.1

Equation 3.1 - see description below

Where:

Ta = the total monthly hours the system or the analyzer generated quality assured data during hours in which the source operated.

Tso = the total hours the source operated in the month. That is the hours during which fuel was burned (for combustion related processes) or hours during which contaminant were vented (for no-combustion sources). The operational time of combustion sources also includes any period(s) of “cool down” or “purge”.

Process operation and valid CEMS time should be concurrent. When the monitored process operates less than 60 minutes within an hour and the CEMS produces valid data, then for CEMS availability purposes, it is a full hour. For cumulative parameters (for example kg/day, kg/month) only emissions during the operating period should be integrated.

The data handling capabilities of the DAHS may be used to compile a monthly CEMS reporting in the format required by the applicable regulating authority, and to facilitate the annual CEMS audit required by the QAP (table 5, Quality Control Procedures, page 30. All CEMS data pertinent to regulatory requirements or limits shall be archived in the DAHS, including but not limited to Certification tests, cylinder gas audit (CGA), bias factors and backfilling. The data should be securely stored for a minimum of 3 years.

3.4.1 Averaging time

Data must be reduced to 1-hour averages for the pollutant and diluent gases and other CEMS measured parameters. The 1-hour averages must be used to compute the SO2, NOx (as NO2), CO, CO2, and other monitored emissions, expressed in units of the standard. A variety of methods for calculating emissions is provided in appendix B.

For time-shared systems, data shall be reduced to valid 1 hour averages in a manner similar to that described in section 3.4 for CEMS dedicated to a single source. Every quarter hour the CEMS must alternate the analysis of the running sample from each of the 2 sources, so as to compute for each of them at least 1 data point in each 15-minute quadrant of the hour, while the unit burned fuel or vented contaminants. If data are unavailable as a result of QA/QC activities or preventive maintenance, then a valid hour may be computed from at least 2 data points separated by a minimum of 15 minutes in which the combustion source operated. All valid measurements during an hour shall be used to calculate the hourly averages.

3.4.2 Reporting basis

Data should be summarized on a monthly or quarterly basis and expressed in the units and averaging periods required by the appropriate regulatory authority. The data may be available in both digital and analog form, with the analog form presented as a trend plot in units of the standard versus time over the reporting period.

3.4.3 Backfilling of missing data

Backfilling should be tailored to the monitored process and described in the CEMS QAP manual. The following recommendations for simple backfilling are presented as examples.

Following initial CEMS certification, or later on at approximately 3-year intervals, a database of 720 quality-assured monitor operating hours should be developed for missing data backfilling. This valid hour database should include all the CEMS collected parameters (for example concentrations, stack flow, temperature, and moisture). A 720-hour average of each parameter is calculated. 

Emissions data during source operation that are missing due to a malfunction of any CEMS component (such as gas analyzer, flow monitor) may be substituted for a period of up to 168 hours for any single episode by the corresponding 720 hr average from the backfilling data base. For short intervals (such as 1 to 2 hrs) the missing data may be substituted by the average of adjacent operating hours, providing that that the process operated steadily. The backfilling technique must be fully explained in the QAP developed for each CEMS and accepted by the appropriate regulatory authority. Backfilled data must be flagged and included in the monthly or quarterly emission report. 

When a CEMS malfunction extends beyond 168 hours for a single episode, emission values must be generated by another certified CEMS or valid reference method. Temporary CEMS used for this purpose must meet the design and performance specifications given in this document. When using a temporary CEMS, the stack gas sample may be extracted from the sample port(s) used for the reference method during certification and RATA of the permanent CEMS.

Data that are backfilled using a procedure other than a certified alternate CEMS or reference method, cannot be credited towards meeting the CEMS availability criteria specified in section 6.5.1.

All emission data should be quality audited to identify suspected data using procedures described in the QA/QC plan (section 6.1). The procedure may include automatic flagging of a) out-of-range concentrations and flows, b) abnormal system calibration response time, c) abnormal heat rate levels (for systems fitted with fuel flow monitors), d) abnormal flow-to-input or flow-to-output (for systems fitted with stack gas flow monitors), and e) abnormal concentrations during periods when the combustion unit did not burn fuel.

The QA-flagged data must be investigated and either accepted or backfilled. The QA-flagged data should be identified in the monthly or quarterly report, along with a summary of reasons for acceptance or backfilling.

3.5 Overall system specifications

This section stipulates specifications for time-sharing of a CEMS system between 2 adjacent emission sources.

3.5.1. Time-shared systems

This specification applies to time-shared CEMS measuring emissions from 2 adjacent sources using a single set of pollutants and diluent gas analyzers (and, if required, separate exhaust flow monitors). One complete measurement cycle of both sources must be completed within 15 minutes, thus generating for each source 4 measurements of concentration and emissions for each hour. The DAHS shall keep separate records of the data from each source. RATA should be performed while the CEMS is in time-shared mode and must be done for both monitored sources, not necessarily simultaneously.

There are 2 options available to determine the CEMS average while performing the RATA in time-shared mode:

  1. the runs can be 21 minutes long and the average computed from whatever data is recorded by the DAHS for the emission point tested during the 21 minutes; or
  2. the runs can be extended up to 1 hour to capture 2 CEMS sampling cycles for the emission point being tested. Then, match up the DAHS data with the corresponding set of reference method data

3.6 Test procedures for verification of design specifications

This section describes the test procedures for the verification of design specifications laid down by the manufacturer.

3.6.1 Analyzer interference

The manufacturer of the analyzer (either dry or wet, for single or multiple components) must certify that the sum of all interferences due to other stack gas components is less than 4.0% of the expected FS of each monitored contaminant.  In the case of combustion sources fitted with NDIR or FTIR analyzers, the certification should include sample levels of 9% CO2 and 18% H2O (v/v, wet basis). If the CEMS is equipped with a sample drier, the removal of H2O in the dryer may be credited to the attenuation of H2O interference.

3.6.2 Analyzer temperature-response zero and span drifts

The analyzer must be placed in a climate-controlled chamber in which the temperature can be varied from 5 to 35°C. Sufficient time must be allowed for the analyzer to warm up, and then the analyzer must be calibrated at 25°C using appropriate zero and span gases. The temperature of the chamber must be adjusted to 35, 15 and 5°C. It should be ensured that the analyzer temperature has stabilized. The power to the analyzer must not be turned off over the duration of this test.

When the analyzer has stabilized at each climate chamber temperature, each of the calibration gases must be introduced at the same flow or pressure conditions, and the response of the analyzer must be noted.

The temperature-response zero drift is calculated from the difference between the indicated zero reading and the reading at the next higher or lower temperature. The analyzer is acceptable if the difference between all adjacent (such as 5/15, 15/25, and 25/35°C) zero responses are less than 2.0% of the FS setting. The temperature-response span drift is calculated from the differences between adjacent span responses. The analyzer is acceptable if the difference between all adjacent span responses is less than 4.0% of the FS setting.

3.6.3 System cycle time

The system cycle time is set by the manufacturer during design and must meet the specification given in section 3.5.1.

3.6.4. Manufacturer’s certificate of conformance

It may be considered that the specifications for both interference and temperature-response drifts have been met if the analyzer manufacturer certifies that an identical randomly selected analyzer, manufactured in the same quarter as the delivered unit, was tested according to the procedures given in sections 3.6.1 and section3.6.2 and the parameters were found to meet the specifications.

Section 4.0 Installation specifications

This section contains guidance for selecting a suitable sampling site on the flue or duct and to determine if the location would allow sampling in a manner representative of the exhaust gas flow.

4.1 Location of the sampling site

The probe or in-situ analyzer must be installed in a location that is accessible at all times, so that routine maintenance can be performed on schedule, as outlined in the QAP. Sufficient shelter should be provided on outdoor installations so that maintenance can be safely performed during intemperate weather conditions without detriment to either the CEMS or service personnel. The degree of exposure, seasonal weather conditions, servicing and maintenance, susceptibility and protection from lightning strikes, and vibration of the duct and or platform are some of the considerations when siting a probe or in-situ analyzer.

Before a flow rate sensor is permanently installed, it should be ensured that cyclonic flow is not present at the desired sampling location. The presence of a cyclonic flow pattern would add considerable complexity to both certification and operation of the installed sensor. It is recommended that an alternate location be found if cyclonic flow pattern is verified at a proposed site. The protocols given in this report relate only to sources for which the gas flow pattern has been demonstrated to be non-cyclonic.

4.2 Representativeness

The sampling probe or in-situ analyzer must be installed in a location where the flue gases are well mixed. The degree of turbulence and mixing time are major factors that influence the extent of stratification of the flue gases.

The extent of stratification of the flue gases at any location must be determined using applicable test methods. It is therefore recommended that the procedures outlined in section 4.2.1 be carried out at the analyzer installation site to determine the extent of stratification before installing the CEMS. If significant gas stratification of any of the measured species is present at the proposed location, then serious consideration should be given to selecting another location within the exhaust, where the flow has been determined to be non-stratified.

If stack flow monitoring is a component of the CEMS, then it is recommended that the adequacy of the sampling site be assessed with respect to the selected flow monitoring system as well as to the reference method to be used for the initial certification and the annual or semi-annual RATA.

It is recommended that the flow monitor and the reference method ports be located where the flow is unidirectional and fully developed. The guideline for this condition requires a straight length equivalent to 10 diameters of a cylindrical stack or duct, which may be unavailable or too expensive to build. A Computational Fluid Dynamic (CFD) study for less-than-ideal stack locations may estimate the degree of stratification and vorticity that may be expected, prior to selecting the CEMS location. If possible, before the flow monitor is installed, velocity traverses must be carried out following ECCC 1/RM/8 Methods A and B or an equivalent “S” type Pitot tube. If the flow is multidirectional (for example if the average rotational angle ≥ 15 degrees), the installation of straighteners may be considered, or the use of more complex reference methods such as US EPA 2G (2-dimensional probes), Method 2F (3-dimensional probes) and Method 2H (velocity decay near stack wall). These methods then must be used for certification and subsequent RATAs. The location of the sampling ports must be selected to avoid interference between the flow monitor and the reference method.

If a single-point velocity sensor is selected for installation, the sensing tip must be located at a point yielding representative velocity measurements over the full range of loads. The velocity profile data must be used to select the optimum measurement point.

4.2.1 Stratification test procedure

A minimum of 9 sampling points must be used in the stack or duct, applying the procedures for selecting sampling points found in ECCC Reference Method EPS 1/RM/8. If the stratification test is conducted to evaluate the suitability of a sampling location prior to installing a CEMS, then the test is conducted simultaneously with 2 similar portable monitoring systems, 1 sampling at a stationary point (generally the center point) and the other sampling consecutively at all the traverse points. Note that the stratification test must be carried out for each gaseous specie to be monitored by the proposed CEMS, including the diluent gases.

If the concentration of the gas measured at the fixed location (stability reference measurement) varies by more than 10% for more than 1 minute during the test, then the test must be done when more stable conditions prevail. If an extractive CEMS is already installed and the stratification test is only for confirmation purposes, then the CEMS may be used a reference system. The degree of stratification for each specie is calculated at each traverse point using equation 4.1.

Equation 4.1

Equation 4.1 (see long description below)

Where:

 

STi = stratification (%)

Ci = concentration of the measured species at point i

Cavg = average of all measured concentrations

The stack or duct gases are considered to be stratified if any calculated value using equation 4.1 exceeds 10.0%.

Section 5.0 Certification performance specifications and test procedures

To achieve certification, an installed CEMS must meet all the performance specifications summarized in table 3. The specifications are relevant to each pollutant and diluent gas measured, as well as the stack gas flow measurement (if applicable) and the overall CEMS.

Certification of the different sub-systems of the CEMS (flow, pollutants, diluents, moisture, etc.) may be conducted jointly or separately. For example, if certification was attempted jointly and the appropriate regulatory agency determines that all but 1 of the monitoring sub-systems passed the requirements, then only the failed sub-system test must be repeated.

The specifications are described in section 5.1. The gases used during certification are described in section 5.2, while the applicable test procedures are outlined in section 5.3.

Table 3 : Certification performance specifications summary
Parameter Component Level Specification Specification references Test procedure references
24-hr calibration drift SO2, NOx and CO analyzers Low Level (0 - 20% FS) High Level (80 - 100% FS) ≤ 2.5% Full Scale (FS) or 2.5 ppm absolute difference 5.1.2 5.3.2
24-hr calibration drift O2 and CO2 gas analyzers Low Level (0 - 20% FS) High Level (80 - 100% FS) ≤ 0.5% O2 or CO2 5.1.2 5.3.2
24-hr calibration drift Stack gas flow monitor Low Level (0 - 20% FS) High Level (50 - 70% FS) ≤ 3.0% Full scale (FS) or 0.6 m/s absolute difference 5.1.3 5.1.3
3-run set linearity SO2, NOx, and CO analyzers Low Level (0 - 20% FS) Mid Level (40 - 60% FS) High Level (80 - 100% FS) ≤ 5.0% of Ref. or |R-A|≤ 5 ppm 5.3.3 5.3.3
3-run set linearity O2 and CO2 gas analyzers Low Level (0 - 20% FS) Mid Level (40 - 60% FS) High Level (80 - 100% FS) ≤ 5.0% of Ref. or |R-A|≤ 0.5% O2 or CO2 5.3.3 5.3.3
System Response Dedicated analyzer - ≤ 200 seconds for 90% change 5.1.4 5.3.4
System Response Time-shared system - ≤ 5 minutes for 90% change 5.1.4 5.3.4
Relative Accuracy (RA) SO2, NOx and CO analyzers - ≤ 10.0% RA; or 5 ppm average absolute difference 5.1.5 5.3.5
Relative Accuracy (RA) O2 and CO2 gas analyzers - ≤ 10.0% RA or 1.0% O2 (or CO2) average absolute difference 5.1.5 5.3.5
Relative Accuracy (RA) Stack gas flow monitor - ≤ 10.0% RA or 0.6 m/s average absolute difference 5.1.5 5.3.5
Relative Accuracy (RA) Stack gas moisture monitor - ≤ 10.0% RA or 1.5% H2O average absolute difference 5.1.5 5.3.5
Bias SO2, NOx and CO analyzers - ≤ 4.0% FS or 5 ppm average absolute difference 5.1.6 5.3.5
Bias O2 and CO2 gas analyzers - ≤ 4.0% FS or 0.5% O2 (or CO2) average absolute difference 5.1.6 5.3.5
Bias Stack gas flow monitor - ≤ 4.0% FS or 0.6 m/s average average absolute difference  5.1.6 5.3.5
Bias Stack gas moisture monitor - ≤ 4.0% FS or 1.0% H2O average absolute difference 5.1.6 5.3.5
Orientation sensitivity - - ≤ 4% of value measured at zero orientation 5.1.7 5.3.7.1

5.1 Certification performance specifications

It is recommended, but not mandatory, that after a new CEMS has been installed according to the manufacturer’s written instructions, the entire CEMS should operate for a conditioning period of not less than 168 hours, prior to the operational test period (OTP), during which the emission source should be operating. During the conditioning period, the entire CEMS should operate normally (that is, analyzing the pollutant and diluent gases) with the exception of periods during which calibration procedures are carried out as well as other procedures indicated in the QAP (QAP).

5.1.1 Operational test period (OTP)

The OTP is a 168-hour cumulative time period during which most of the performance specification tests are carried out. The process unit (that is the boiler) must be operating when the measurements are made. However, for the 7-day calibration drift test the CEMS may be tested on seven (7) 24-hour intervals on non-consecutive days. No unscheduled maintenance, repairs, or adjustments to the CEMS are allowed during the OTP. The procedures in the QAP must be followed as if the CEMS was generating emission data.

CEMS systems installed at peaking stations may be exempted from the OTP and calibration drift tests.

5.1.2 Calibration drift

The calibration drift specification is applicable to the 2 concentration ranges indicated in table 3 and is applicable to each pollutant and diluent gas analyzer. Table 3 also includes flow monitoring calibration drift specifications.

At 24-hour intervals over the 168-hour OTP, the CEMS response to the pollutant or diluent calibration gases, as indicated by the DAHS, must not deviate from the certified value of the appropriate gas by an amount exceeding:

Pollutant gas analyzer
Low and high level: 2.5% of the FS setting or 2.5 ppm absolute difference
Diluent gas analyzer
Low and high level: 0.5% O2 (or CO2)
Flow monitor
At 24-hour intervals over the 168-hour OTP, the CEMS response to the reference low- and high- values (such as pressure pulse or electronic signal, section 5.1.3) as indicated by the data acquisition system, must not deviate from the set low- and high- values by an amount exceeding:
Low and high level: 3.0% of the FS setting or 0.6 m/s absolute difference

Flow monitors installed on peaking units are exempted from this 7-day calibration error test requirement.

5.1.3 Stack gas flow calibration

Design and equip each flow monitor to allow a daily calibration test consisting of at least 2 reference values: 0 to 20% of FS or an equivalent reference value (for example pressure pulse or an electronic signal) and 50 to 70% of FS. Flow monitor response, both before and after any adjustment, must be recorded by the DAHS. Design the monitor to allow the calibration of the entire system, from the probe tip (or transducer) to the DAHS.

Introduce the reference signal corresponding to the values specified values to the probe tip (or equivalent), or to the transducer. During the 7-day certification test period, conduct the calibration error test while the unit is operating (as close to 24-hour intervals as practicable). In the event that unit outages occur after the commencement of the test, the 7 consecutive operating days need not be 7 consecutive calendar days. Record the flow monitor responses by means of the DAHS. If the flow monitor operates within the calibration error performance specification, the flow monitor passes the calibration drift test. Do not perform any corrective maintenance, repair, or replacement upon the flow monitor during the 7-day test period, other than that required in the QAP.

5.1.4 System response time

CEMS using dedicated analyzers must be able to achieve 90% response in less than 200 seconds to a step change in concentration of gas at the probe exit. This interval includes the time required to convey the sample trough the sampling line. The specification is applicable to SO2, NOx, O2, CO, and CO2 monitoring. It is acknowledged that the specification may be overly stringent for gases, such as NH3 and HCl, which may be tested for sample integrity by other methods.

For time-shared systems, the system response time is acceptable if the average of 3 increasing and 3 decreasing values is not greater than 5 minutes, for each analyzer on each stream, for a 90% response to a step change in concentration of gas at the probe exit. Note that this includes the lag time.

System response time must be tested according to procedures in section 5.3.4.

5.1.5 Relative accuracy (RA)

The RA for an SO2, NOx or CO analyzer must not exceed 10.0% or 5 ppm average absolute difference.

The RA for an O2 or CO2 gas analyzer must not exceed 10.0% or 1.0% O2 or CO2 average absolute difference.

The RA for a stack gas flow monitor must not exceed 10.0% or 0.6 m/s average absolute difference. On average, the stack gas temperature measurements must be within ±10oC of the RM measurements.

The relative accuracy for a stack moisture monitor must not exceed 10% or 1.5% H2O average absolute difference.

RA must be tested according to procedures in section 5.3.5.

5.1.6 Bias

The bias for an SO2 , NOx or CO gas analyzer must not exceed 4.0% of the FS value or 5 ppm average absolute difference.

The bias for an O2 or CO2 gas analyzer must not exceed 4.0% of the FS value or 0.5% O2 or CO2 average absolute difference.

The bias for a stack gas flow monitor must not exceed 4.0% of the FS value or 0.6 m/s average absolute difference.

The bias for a stack gas moisture monitor must not exceed 4.0% of the FS value or 1.0% H2O average absolute difference.

Bias must be tested according to calculations in section 5.3.6.

Should there be any bias as defined in section 5.3.6, either positive or negative, in any measurements made by the CEMS, the data that is subsequently generated must be corrected for the bias, before any subsequent use.

5.1.7 Orientation sensitivity

Some gas flow monitors may be sensitive to the probe orientation in the gas streams. For these monitors, the indicated gas flow rate of the sensor at orientations other than that at the zero-degree measurement must not differ from the zero orientation by more than 4.0%.

Orientation sensitivity must be tested according to procedures in section 5.3.7.1. This only applies to stack gas velocity monitors such as pitot tubes and other based on Bernoulli principle.

5.2 Calibration gases

The gases used by the reference method during the relative accuracy must be U.S. Environmental Protection Agency (EPA) Protocol grade.

Gases used for daily calibration and response time tests must be certified to an accuracy of 2.0% by the manufacturer, but Protocol gases may be used if desired.

The QAP should specify a method of cross-referencing successive gas cylinders to identify out-of-specification cylinders before the new cylinders are used to calibrate the CEMS.

All the applicable table 3 specifications must be met, otherwise the CEMS is not certified and must be fixed and retested.

5.3 Certification test procedures

This section describes the certification test procedures and protocols.

5.3.1 Operational test period (OTP)

During the OTP the process and the CEMS should ideally operate without interruption and produce a record of the emissions data using the DAHS. This record must be kept for the duration required by the appropriate regulatory authority. Sampling may be interrupted if the process shuts down, or for short intervals during the daily calibrations and specified procedures contained in the QAP. 

During the OTP, no unscheduled maintenance, repairs, or adjustments to the CEMS may be carried out. Otherwise the OTP must be restarted. Calibration adjustments may be performed at 24 ± 2 hours intervals or more frequently if specified by the manufacturer and stated in the QAP. Automatic zero and calibration adjustments made without operator intervention may be carried out at any time, but these adjustments must be documented by the DAHS.

If the test period is fragmented due to process shutdown, the times and dates of this period should be recorded, and the test continued when the sources resumes operation. If the test is interrupted due to CEMS failure, the entire test period must be started after the problem has been rectified.

The performance specification tests, outlined in sections 5.3.2 to 5.3.6. must be carried out during the OTP, with the exception of the Relative Accuracy Test Audit (RATA) (section 5.3.5) which may be conducted during the OTP or during the 168 hours period immediately following the OTP. It is recommended that the calibration drift tests be completed before attempting the relative accuracy tests, to minimize the risk associated with repeating the latter.

5.3.2 Calibration drift test protocols

The calibration drift must be determined for each pollutant and diluent gas analyzer, and stack gas flow monitor at approximately 24 ± 2 hours intervals over the 168-hour test period.

On the first day of the operational test period, the low and high calibration gases are injected 3 times sequentially at the primary CEMS port, until a stable level is reached. The values are recorded by the DAHS. Then the CEMS must continue analyzing the stack gas. 24-hours later, without any adjustment to the analyzers, the sequence is repeated, the values are recorded, and if so desired the drift may be corrected before the start of the next 24-hour calibration drift cycle, and so on for 7 days. Calculate the drift with equation 5.1.

Equation 5.1

Equation 5.1 (see long description below)

Where:

 

Dc = concentration calibration drift (%)

A = average of the CEMS responses to the low- or high-level calibration gas (% or ppm)

R = certified concentration of the low- or high- level test gas

FS = full scale setting of the analyzer (% or ppm)

Perform the 7-day calibration drift of the flow monitor, introducing sequentially the 2 reference levels (in other words pressure pulse or electronic signal, section 5.1.3) at about 24-hour intervals, while the unit is operating. At the end of each 24-hour interval the reference levels are introduced sequentially, and the stable levels are recorded in the DAHS. If process outage occurs after the commencement of the drift test, the 7-day testing may be extended to additional days. Calculate the drift with equation 5.2

Equation 5.2

Equation 5.2 (see long description below)

Where:

Df = flow calibration drift (%)

Af = actual stack gas velocity as measured by the CEMS (m/s)

Rf = reference stack gas velocity corresponding to the pressure pulse or electronic signal level (m/s)

FS = flow analyzer full scale (m/s)

5.3.3 Linearity Check Test Protocol

The CEMS must operate normally during the test with all pressures, temperatures and flows at nominal values. Introduce each test gas at the primary CEMS calibration port and allow the system response to stabilize, then record the measured concentration in the DAHS. Challenge the system 3 times with low-, mid-, and high- level of each monitored gas, alternating the order in which the gas is presented to the analyzer. Low level is 20.0 to 30.0% of FS, mid-level is 50.0 to 60.0% of FS, and high-level is 80.0 to 100.0 % of FS. Determine the linearity, at each level with equation 5.3.

Equation 5.3

Equation 5.3 (see long description below)

Where:

LE = percent linearity error, based upon the reference value

R = reference value of low-, mid- or high- level calibration gas introduced into the monitoring system

A = average of the monitoring system responses

Pollutant concentration monitors (for example SO2, NOx) shall not deviate from the reference value by more than 5.0% (as calculated using Eqn. 5.3). Linearity is also acceptable if |R – A| is ≤ 5 ppm.

Diluent gas monitors (such as CO2, O2) shall not deviate from the reference value by more than 5.0%. Linearity is also acceptable if |R – A| is ≤ 0.5 % CO2 or O2.

5.3.4 CEMS response time test protocol

This test may be performed during OTP concurrently with the linearity check test. The test consists on measuring the time required to achieve a 90% response from a step change in the sample concentration level. Sample flow rate, pressure, and other CEMS parameters must be at nominal values specified in the QAP. Low- and high-level calibration gas must be introduced alternately at the system calibration gas injection port while the DAHS records the analyzer output. When a steady state is reached, the input gas is switched to the second calibration gas until again a steady output is reached. The sequence must be carried out a total of 3 increasing and 4 decreasing concentration changes.

Using the output of the DAHS calculate the average time required for the CEMS to achieve 90% response to the low- and high-level gases for both the increasing and decreasing levels. The lag time of extractive systems (that is the time necessary to convey the gas sample though the sampling line) must be included in the calculation of response time.

5.3.5 Relative accuracy (RA) test protocols

This test is a comparative evaluation of CEMS performance using an independent reference method, which may be either manual or automated procedure, as specified by the appropriate regulatory authority. The test is carried out on each pollutant and diluent gas analyzer as well as on the stack gas flow monitor and pollutant mass emissions.

The emission source must be operating at normal load (see the Glossary, page 47) or at greater than 50% maximum heat input (the latter for sources that did not operate in the previous quarter) while combusting the primary fuel normal for that unit. The CEMS must be operated in a routine manner during this test, and no adjustments, repairs, or modifications to any portion of the system may be carried out other than those actions outlined in the QAP. As the system includes the hardware and software of the DAHS, the parameters in the DAHS may not be modified during the test.

5.3.5.1 Reference Method Sampling Point for Non-stratified Exhaust Gases

Where it has been demonstrated, using the procedures outlined in section 4.2.1 that the flue gases are not stratified, the reference method (RM) testing may be carried out at a single test point in the flue or duct, with the gas extraction point being not closer than 7.5 cm from any wall.

When certifying extractive or in situ point systems, the RM probe tip must be located no closer than 30 cm from the inner 50% of the measurement path. The RM probe must be positioned so that it will not interfere with the operation of the CEMS under test.

5.3.5.2 Reference Method Sampling Point in Presence of Stratified Flow

If the gas flow has been found to be stratified using the procedures outlined in section 4.2.1 or if the stratification test has not been performed, the RM sample must be collected at several points in the gas flow.                  

A “measurement line” that passes through the centroids of the flue or duct must be established. This line should be located within 30 cm of the CEMS sampling cross-section. Three sampling points must be located at 16.7, 50, and 83.3% along the length of the “measurement line”. Other sampling points may be selected if it can be demonstrated that they will provide a representative sample of the exhaust gas flow over the test period.

5.3.5.3 Test Methods

Either the reference methods listed in the Glossary (page 47) or those specified by the appropriate regulatory authority may be used as reference methods. Manual grab sampling reference methods are not acceptable for CEMS certification

5.3.5.4 Sampling Strategy

A minimum of 9 comparisons of the RM and the CEMS results must be conducted to evaluate the performance of the CEMS being tested. Within each run, the reference method sampling rate must be carried out at a fixed sampling rate; that is, the sampling rate must not be adjusted over the duration of the run, except to maintain the flow at the initial rate. Sampling must be carried out for 30 minutes during each test, divided equally over the 3 sampling points for stratified flow testing or at the single point for non-stratified flow.

Preliminary testing may be performed before the date set for Certification or RATA. Their results shall not be considered part of the Certification or RATA sets. Back calculating results based on subsequent results is forbidden.

The operator may choose to carry out more than 9 sets of comparisons. Should this option be exercised, the results of a maximum of 3 tests may be rejected from the test data if an appropriate statistical test applied to the data (that is the Grubbs test) demonstrates that these results are outliers. A minimum of 9 RM tests must be available after statistical rejection of data. All data must be reported, including the outliers, along with all calculations.

All diluent gas, moisture, and stack gas flow measurements (if applicable) must be conducted simultaneously with the RM pollutant concentration measurements.

5.3.5.5 Correlating Reference Method and CEMS Measurements

To correlate the data from the CEMS and RM tests, it is imperative that the beginning and end of each test period be clearly marked on the DAHS and that the time be synchronized with the RM crew test time. After each test is completed, compare the CEMS results with the data derived from the RM results over the exact time period that the test was performed.

The CEMS results and the RM results must be correlated on the same basis. Thus, corrections may need to be applied for moisture, temperature, pressure, etc. The auxiliary RM measurements (such as stack gas moisture or barometric pressure) are used to make any adjustments to the RM results, whereas the auxiliary measurements of the CEMS are used to make any adjustments to the CEMS results.

5.3.5.6 Calculations

The relative accuracy of the CEMS must be calculated for each pollutant and diluent gas measured by the system in concentration units (ppm or percent by volume), as well as stack flow in terms of m/s or Sm³/h. Additionally, the relative accuracy for pollutant emissions may be calculated in units of the applicable standard.

  1. Calculation of relative accuracy (RA)

    The RA is calculated using equation 5.4.

Equation 5.4

Equation 5.4 (see long description below)

Where:

 

RA = percent relative accuracy

d = mean difference between the CEM system and RM results

cc = confidence coefficient

RM = average of the reference method results

  1. Calculation of differences

The absolute value of the difference between the CEM system and RM results is calculated using equation 5.5.

Equation 5.5

Equation 5.5 (see long description below)

Where:

di = difference between an RM value and a corresponding CEM system value
(di = CEMi - RMi) for the ith test run

n = number of data pairs

Note: The numeric signs for each data pair must be retained. The absolute value of the sum of differences is used, not the sum of absolute values of the differences.

  1. Calculation of confidence coefficient and standard deviation

The values of the confidence coefficient and standard deviation are determined from equations 5.6 and equation5.7, respectively.

Equation 5.6

Equation 5.6 (see long description below)

Where:

cc = confidence coefficient

t0,025 = t value from table 4 for a one-tailed t-test corresponding to the probability that a measured value will be biased low at a 95% level of confidence

stdev = sample standard deviation of the differences of the data pairs from the relative accuracy test, calculated using equation 5.7

n = number of data pairs

Equation 5.7

Equation 5.7 (see long description below)

where parameters are as defined above.

Table 4: t values
n-1 5 6 7 8 9 10 11 12 13 14
t0,025 2.571 2.447 2.365 2.306 2.262 2.228 2.201 2.179 2.160 2.145

Note: These are t values for one-tailed t-test at a 95% confidence level.

  1. Calculation of reference flow-to-load ratios

If the CEMS includes a stack gas flow monitor, the flow-to-load (load being either gross power or steam flow) during RATA may be used as reference for future quarterly audits of stack gas flow data, carried out from a set of hours in which the unit operated at loads ±10% of the RATA.

If the combustion unit produces exclusively electric power or steam, the reference flow-to-load ratio can be calculated from RATA data by the equation 5.8.

Equation 5.8

Equation 5.8 (see long description below)

Where:

Rref = reference flow-to-load ratio during RATA, in (WSm³/h)/MW or (WSm³/h)/(tonne of steam/h)

Qref = average stack gas flow measured during the most recent flow RATA, WSm³/h

Lavg = average gross electric output or steam output during the most recent flow RATA runs, in MW or (tonne of steam/h)

To perform the quarterly flow-to-load CEMS flow audit, the DAHS must be able to record the hourly stack gas flow and the outputs of electric power or steam, as explained in section 6.3.2.4.

5.3.6 Bias test calculations

A bias or systematic error is considered to be present if in the measurements of a pollutant gas, diluent gas, or stack gas flow the absolute value of the difference between the CEMS and RM results (Eqn. 5.5) exceeds the absolute value of the confidence coefficient (Eqn. 5.6).

Equation 5.9

| ≥ | cc |

Equation 5.10

The bias is acceptable if ( | d | ≥ | cc | ) 4,0% FS

Only In the above case the subsequent CEMS measurements must be corrected by a bias adjustment factor (BAF) using equations 5.11 and equation5.12.

Equation 5.11

CEMSadjusted = CEMSmonitor × BAF

Where:

CEMadjusted = data adjusted for bias

CEMmonitor = data provided by the monitor

BAF = bias adjustment factor, defined by equation 5.12

Equation 5.12

Equation 5.12 (see long description below)

Where:

BAF = bias adjustment factor

CEMRATAavg = average CEM results during RATA

RM = average of the reference method results

The use of a BAF in any measurement must be stated in the QAP.

The SO2 or NOx bias is also acceptable if |d|≤ 5 ppm SO2 or NOx, whereas that for O2 or CO2 bias is acceptable if |d|≤ 0.5% O2 or CO2. For the stack gas flow monitor bias is acceptable if |d|≤ 0.6 m/s, whereas that for the moisture monitor bias is acceptable if |d| ≤ 1.0% H2O. No BAF should apply to the conditions described in this paragraph.

5.3.7 Orientation sensitivity test protocols

This test is intended as a check for flow monitors that are sensitive to the orientation of the sensor in the gas flow, such as differential pressure flow sensors.

5.3.7.1 Test procedures

During a period of steady normal flow condition, the sensor in the gas flow must be rotated a total of 10 degrees on each side of the zero-degree position (directly into the gas flow with no cyclonic flow patterns) in increments of +5 or -5 degrees, noting the response of the sensor at each angle relative to the zero-degree position.

5.3.7.2. Acceptance condition for certification

The performance specification presented in section 5.1.7 must be met.

5.4 Recertification and diagnostic testing

Permanent replacement, modification, or changes to a CEMS that may affect its ability to accurately measure emissions, require system recertification. Examples of these situations include the permanent replacement of an analyzer or the entire CEMS. Change the location or orientation of a sampling probe.

Temporary (<168 hours) replacement of an analyzer with a similar analyzer, for example, requires less than a full battery of recertification tests. It may be limited to diagnostic tests such as an abbreviated linearity check of the replacement analyzer.

Section 6.0 Quality assurance and quality control

The operator must develop a written Quality Assurance Plan (QAP) for each installed CEMS. A quality assurance plan is a management program to ensure that the necessary day-to day quality control activities are adequately performed. The QAP becomes a reference to ensure that the environmental monitoring and reporting procedures are verified and documented, so that uncertainties in the reported data can be controlled and quantified.

6.1 Quality assurance and quality control manual

The written manual of the QAP Plan must describe the complete program of activities to be implemented to ensure that the data generated by the CEMS will be complete, accurate, and precise. As a minimum, the manual must include the QA/QC procedures specified in this report. The recommended Table of Contents of the QAP manual is shown in table 5.

6.1.1 Quality assurance (QA) activities

This section of the manual should describe how the QA program is managed, provide personnel pertinent qualifications, and describe the QA reporting subsystem. It must describe the CEMS, how it operates, and the procedures for calibration and inspection. It must also include preventative maintenance and performance evaluation procedures.

6.1.2 Quality control (QC) activities

This section should provide detailed descriptions of the step-by-step procedures required to operate and evaluate the CEMS, including details about daily, quarterly, semi-annual, and annual performance evaluations. Procedures for these activities are provided in sections 6.2 to 6.5. A summary of acceptable results is outlined in sections 6.2 and section6.3.

Table 5 : Table of contents of the QAP manual
Subsection Contents
Quality assurance policies and system descriptions
1 Quality assurance goals and objectives Specific system goals relating to precision, accuracy, and completeness. Emission standards and emission reporting requirements.
2 CEM system description and design considerations Detailed system description, including principles of operation, sample location layout, flow and temperature measurement, sample conditioning system, analyzer layout, CEM shelter, and data handling system. Design considerations and engineering evaluation of CEMS options, including sample location, extractive vs. in situ, flow monitoring, and supplier. Includes a detailed list of CEMS component serial and model numbers.
3 Exceptions/Clarifications/Alternative methods Any exceptions/clarifications or alternative methods relating to this document or reference test methods.
4 Organization and responsibilities Description of the organization of personnel involved with the CEMS and its quality system. Defines the roles and responsibilities of the personnel involved as related to CEMS operation and maintenance, control of documents/records, and control of data.
5 Calibration and quality control checks Description of the calibrations and QC checks that are performed on a routine basis, generally daily, to determine whether the system is functioning properly. Includes daily zero and calibration checks and visual checks of system operating indicators, such as vacuum and pressure gauges, rotameters, analyzer displays, LEDs, and so on.
6 Data acquisition and analysis Description of the data acquisition system and analysis program. Includes references to data completeness, validation, reporting, storage, and revision management. Includes roles and responsibilities of the personnel involved in the data handling.
7 Preventative maintenance policy Description of the CEMS preventative maintenance program, including how preventative maintenance scheduling is determined and maintained along with roles and responsibilities of the personnel involved.
8 Corrective action program Description of the policies for correcting any CEMS system non-conformance. Parameters such as CEMS downtime/reliability should be addressed. Roles and responsibilities of the personnel involved in the corrective action program.
9 Performance Evaluations/Audits Description of the policies and specifications for performance evaluations/audits (for example stack quarterly audits and RATAs). Describe the action necessary to ensure that the appropriate evaluations are carried out on the appropriate schedule.
10 Document control system Description of the policies and systems used to control all the documents that form part of the CEM system’s quality system. Lists how and where the related documents are located, how they are reviewed and revised, and how they are approved for use by authorized personnel prior to issue.
11 Reports and records Description of all reports and records collected including method of collection, person responsible, data storage location, data security, data distribution, and length of data storage.
12 Modifications and upgrades Description of the policies regarding modifications and upgrades to the CEMS.
13 Training and qualification policy Training and qualification policy for CEMS maintainers, CEMS coordinators, computer and programming technicians, data validators, quarterly audit, and RATA testers. Includes educational and experience requirements, on-the-job training, job shadowing, and classroom training requirements.
14 References References for QA/QC plan.
Quality control (standard operating) procedures
1 Startup and operation Lists in detail complete, step-by-step procedures for the start-up and operation of the CEMS.
2 Daily CEM system operation and inspection Detailed description of daily routine operation and inspection of the CEMS. Includes descriptions of equipment and data validation procedures and examples of daily equipment checks and/or logbook entries.
3 Daily and manual calibration procedures Lists in detail complete, step-by-step procedures for daily and manual calibrations. References to specific OEM documentation/manuals are acceptable. Includes schedule for manual (mid-point) calibration, if done.
4 Gas bottle check procedures Description of procedure to cross-reference cylinder gases. Gases can be cross-referenced to previous gas bottles and quarterly bottles. Specifications for rejection of gas bottle to be stated.
5 Preventative maintenance procedures Detailed description of the CEMS preventative maintenance procedures along with the preventative maintenance schedule.
6 Spare parts list and inventory procedures Detailed descriptions of the spare parts inventory available for the CEMS, along with a description of the procedures for obtaining spare parts from inventory and ensuring that the spare parts inventory is maintained.
7 Corrective maintenance procedures Detailed descriptions of the non-routine maintenance that is performed when the system or part of the system fails. References to specific OEM documentation/manuals are acceptable.
8 Data backfilling procedures Procedures for data backfilling when a CEMS is not available. Data backfilling algorithms to be based on process variables.
9 Data backup procedures Procedures for regular backup of data in hard or soft copy.
10 Data quality assessment procedures Procedures to identify suspected data. Includes automatic flagging of a) out-of-range concentrations and flows, b) abnormal system calibration response times, c) abnormal flow-to-input or flow-to-output levels, and d) abnormal concentrations during periods when the combustion unit burned no fuel.
11 CEM system security Includes security actions for CEMS equipment software and data.
12 Data approval and reporting procedures Procedure for approval and reporting of CEMS data. Includes any systems for review, modifications, approval, summary, and release of data.
13 Quarterly audit procedures Detailed procedures on conducting quarterly audit procedures. Includes roles and responsibilities, gas bottle requirements, scheduling, and test methods.
14 Semi-annual relative accuracy test audit procedures Detailed pretest sampling plan for executing RATAs. Pretest plan to include organization plan, sampling points, scheduling, test methods, calibration requirements, reporting schedule, reporting format, and site safety plan.
15 Bias procedures Describes process of assessing and correcting for bias. Includes roles and responsibilities for assessing and approving bias factors.
16 Annual system audit procedures Describes procedure for annual system audit. Includes selection of auditor, scheduling, audit plan, and reporting.
17 Managing change Procedure for managing change when upgrades are required due to failure of equipment, changes in regulation, changes in system management. Includes approval process for accepting changes with roles and responsibilities. Addresses replacement of CEMS.
 

6.2 Daily performance evaluations

This section presents the protocols for daily performance evaluations.

6.2.1 Calibration drift

Calibration of the CEMS is one of the most important aspects of the QA/QC program. The following summarizes the requirements for calibration drift checks, all of which must appear in the QAP.

6.2.1.1 Frequency

The drift of each gas analyzer and flow monitor must be determined at least once daily, at intervals. It is a good practice to check the drift of each analyzer even during a few days in which the combustion unit is down, but the operator may skip the daily calibration during extended periods in which the combustion unit does not burn fuel. However, the CEMS should be successfully calibrated immediately prior to process restart, to void using the backfilling option (section 3.4.3).

If an on-line calibration check has been passed, and the source is off-line 24 hours later, then this second calibration check may be passed off-line, not later than 26 hours after the previous on-line calibration. The data bracketed between these 2 successful calibrations shall be considered valid.

6.2.1.2 Test gases

EPA Protocol gases or gases certified to an accuracy of 2.0% may be used for the daily calibration of gas analyzers.

6.2.1.3 Calibration gas injection port

The location of the applicable calibration gas injection port for each type of CEMS can be found in table 2. Care must be taken to ensure that the calibration checks are carried out at the same CEMS operating conditions that are used during monitoring (for example pressure, flow, temperature, etc. For path-type analyzers installed before 2023 that do not have the capability of accepting a flowing reference gas, daily calibration checks may continue to be performed with manufacturer supplied sealed cells containing a known concentration of reference gas.

6.2.1.4 Test procedures

Low and high reference levels must be used. For analyzers: low level is 0 to 20% FS, and high level is 80 to 100% FS. For stack gas monitors: low level is 0 to 20% FS, and high level is 50 to 70% FS. Before any adjustment the low and high levels must be read and recorded by the DAHS. If a dual range instrument is used, then the drift of both ranges must be checked daily.

Enough time must be allowed to ensure that the gas analyzer or flow monitor attains a steady output, as indicated by the DAHS.

6.2.1.5 Adjustment of analyzers/monitors

A gas analyzer, flow monitor, or stack gas moisture monitor should be adjusted whenever the daily low- or high- level calibration drift approach the following specifications:

Pollutant gas analyzer
Low- or high-level: 2.5% of the FS setting
Diluent gas analyzer
Low- or high-level: 0.5% O2 (or CO2)
Flow monitor
Low- or high level: 3.0% of the FS setting or 0.6 m/s

A DAHS shall keep a record of the extent of each low- or high-level adjustment carried out. The data collected in the previous 24 hours is considered valid, unless the drift reached twice the section 6.2.1.5 specifications. 

6.2.1.6 Out-of-control period

An out-of-control period occurs when either the low- or high-level calibration drift of a gas analyzer or flow monitor exceeds twice the section 6.2.1.5 specification. This out-of-control period begins with the minute of the calibration drift check and ends with the minute after corrective action has been taken and the system has demonstrated that is operating satisfactorily. When a gas analyzer or flow monitor is out-of-control the data generated by the specific component are considered missing and do not qualify for meeting the requirement for system availability. Missing data must be backfilled using the criteria provided in section 3.4.3.

6.2.1.7 Tabulation of data

All calibration drift data should be recorded and tabulated by day and month, with the magnitude of the drifts in ppm for pollutant analyzers, percent for diluent gas analyzers and flow-related level for flow monitors. These data should be summarized on a QC chart.

6.2.1.8 Quantification of drifts

If the DAHS or CEMS automatically compensates data for drifts, the system must be able to store unadjusted concentrations of the calibration gases, unadjusted flow levels and the magnitude of all adjustments.

6.3 Quarterly performance evaluations

During each quarter, a cylinder gas audit (CGA) and 1 of the options for a stack gas flow test (if applicable) must be performed. Special provisions apply to path-type analyzers installed before 2023 that do not have the capability of accepting a flowing calibration gas. The following summarizes the requirements for these tests, all of which must appear in the QAP.

6.3.1 Cylinder gas audit (CGA)

This audit investigates the linearity error of the analyzers and ranges used during the previous quarter.

A 3-level cylinder gas test must be performed in each quarter of the calendar year, with tests being no closer than 30 days for 2 adjacent quarters. In peaking units, this test must be performed annually, immediately before the RATA.

6.3.1.1 Test gases

Protocol gases at low (0 to 20% FS), mid (40 to 60% FS), and high (80 to 100% FS) levels for each pollutant and diluent gas analyzer must be used.

6.3.1.2 Calibration gas injection port

The CGA test gases must be introduced at the CEMS system calibration gas port specified in table 2.

6.3.1.3 Test procedures

The CEMS must be fitted with a calibration gas injection port that allows a check of the entire measuring system when calibration gases are introduced. For extractive and dilution type systems, the measurement system includes all monitoring components exposed to the sample gas (for example, sample lines, filters, scrubbers, conditioners, and as much of the probe as practicable).

During the test the CEMS must be operating normally with all pressures, temperatures, and sample flows at nominal values. The calibration gas injection (and temporary exclusion of stack gas sample) may be achieved by a 3-way valve system similar to that of Figure 7E-1 of EPA Reference Method 7E. Each test gas must be introduced sequentially, and the system response allowed to stabilize. Then the concentration of the pollutant or diluent gas is indicated and recorded by the DAHS. The average response of the system to the 3 challenges/runs of each pollutant or diluent gas levels must be calculated.

6.3.1.4 Calculations

The average linearity error for the responses to each of the low-, mid- and high-level test gases should be calculated using equation 6.1.

Equation 6.1

Equation6.1 (see long description below)

Where:

LE = percent linearity error, based upon the reference value

R = reference value of low-, mid- or high- level calibration gas introduced into the monitoring system

A = average of the monitoring system responses for each of the reference gas levels

6.3.1.5 Acceptance criteria

Pollutant concentration monitors (such as SO2, NOx) shall not deviate from the reference value by more than 5.0% (as calculated using equation 6.1). Linearity is also acceptable if |R – A| is ≤ 5 ppm. 

Diluent gas monitors (such as CO2, O2) shall not deviate from the reference value by more than 5.0% (as calculated using equation 6.1). Linearity is also acceptable if |R – A| is ≤ 0.5 % CO2 or O2.

6.3.1.6 Alternate quarterly analyzer audit

Where the type of CEMS does not allow a flowing reference gas (that is certain types of in situ path-type analyzers installed before 2023), an independent check on the CEMS performance must be carried out every quarter, when the combustion source is operational. To that effect, the response for each gas being monitored is compared with the measurements of an extractive portable CEMS that meets the corresponding (for example NOx, and O2) reference method specifications. The portable CEMS should extract a stack gas sample from a point within 0.3 m from the permanent CEMS sensing path and is calibrated with low- and high-level reference gas suited to the full scale of the stationary CEMS. Then the portable CEMS start sampling and after a stabilization period the readings are logged every minute for 10 minutes concurrently with the DAHS readings of the permanent CEMS. Then the portable CEMS is fed low-level calibration gas or filtered ambient air until stable readings are obtained. The low-level drift is recorded, and if necessary adjusted. The stack gas extraction and logging are repeated for the next sampling period of the same duration, and so on for a minimum of 6 test periods of 21 minutes each. Finally, the analyzer is fed high-level calibration gas until stable readings are obtained. The relative accuracy of the concurrent CEMS measurements is calculated using equations 5.4 to 5.7 (section 5.3.5.6)

For this audit the acceptable relative accuracy for SO2 and NOx must not exceed 15.0%. The corresponding RA level for O2 and CO2 must not exceed 15.0% or 1.0% absolute difference.

6.3.1.7 Out-of-control period

An out-of-control period occurs when a cylinder gas audit exceeds the specification as presented in section 6.3.1.5 or the alternate audit of section 6.3.1.6, as applicable. This period begins with the minute after the completion of the test and ends with the minute after correction action has been taken and when the system has demonstrated that it is operating satisfactorily. When an analyzer or system is out of control, the data generated by the specific analyzer or system are considered missing and do not qualify for meeting the system availability requirements. Missing data must be backfilled using the criteria provided in section 3.4.3.

6.3.2 Stack gas flow audit

The operation of the stack gas flow monitor must be audited quarterly, by 1 of the following options:

  1. Evaluation of flow-to-load, using quarterly data
  2. Performance of abbreviated flow-to-output tests
  3. Performance of flow RM tests.

Procedures for options a) to c) are outlined in sections 6.3.2.4 to 6.3.2.6.

6.3.2.1 Frequency

A stack gas flow audit must be performed in each quarter of the calendar year, with audits being not closer than 30 days for 2 adjacent quarters. In peaking units, this audit must be performed annually, immediately before the RATA.

6.3.2.2 Acceptance criteria

Acceptance criteria for options a) to c) are presented in sections 6.3.2.4 and 6.3.2.5.

6.3.2.3 Out-of-control period

An out-of-control period occurs when a stack gas flow monitor exceeds the specifications presented in sections 6.3.2.4 to 6.3.2.6, as applicable. This period begins with the minute after completion of the audit and ends with the minute after corrective action has been taken and when the system has demonstrated that it is operating satisfactorily. When a flow monitor is out-of-control, the data generated by the flow monitor are considered missing and do not qualify for meeting the system availability requirements. Missing data must be backfilled using the criteria described in section 3.4.3, or an equivalent accepted by the appropriate regulatory authority.

6.3.2.4 Analysis of flow-to-load

If the source generates exclusively electric or steam and the quarter includes a minimum of 168 hours of valid CEMS data of load levels within ± 10% of the average load of the last RATA, then the average flow-to-load ratio may be calculated using equation 6.2.

Equation 6.2

Equation 6.2 (see long description below)

Where:

Rh = quarterly average flow-to-load ratio from the hours in which the unit load was within ± 10% of the average load of the last RATA , in (WSm³/h)/MW or (WSm³/h)/(tonne of steam/h)

Qh = average stack gas flow from the quarterly hours in which the unit load was within ± 10% of the average RATA load, WSm³/h

Lh = average unit load from the quarterly hours in which the unit load was within ± 10% of the average RATA load, in MW or (tonne of steam/h)

Periods of diverse fuel blends, output ramping, scrubber bypass, or other non-representative hourly data must be excluded from the calculation of average Rh. In peaking electric generating units (EGU), the potential data base may encompass the preceding 12 months of unit operation.

E Δ , the relative absolute difference between Rh and Rref (the latter based on the last RATA and calculated with equation 5.8), is calculated using equation 6.3

Equation 6.3

Equation 6.3 (see long description below)

Where:

E = relative absolute difference between the average flow-to-load ratio and the reference flow-to-load ratio, %

Rh = average flow-to-load ratio, as calculated by Eqn. 6.2

Rref = flow-to-load reference ratio from last RATA, as calculated by Eqn. 5.8

Acceptable flow-to-output results are as follows:

E MWq ≤ 10% for output levels ≥ 60 MW electric output or 274 (tonne of steam/h)
E MWq ≤ 15%, for output levels < 60 MW electric output or 274 (tonne of steam/h)

6.3.2.5 Performance of abbreviated flow-to-load test

An abbreviated flow-to-load test consists of a period of 6 to12 consecutive hours during which the process conditions reproduce as closely as practicable the conditions of the most recent flow RATA. The electric or steam output must be held constant to within ±10% of the average output during the last flow RATA, and the CO2 or O2 to within 0.5% of the corresponding RATA level.

For this period, Rh is calculated using equation 6.2 and EΔ using equation 6.3. Acceptable EΔ levels are the same as in section 6.3.2.4.

6.3.2.6 Performance of flow reference method measurements

This test must be carried out using Method B from Reference Methods for Source Testing: Measurement of Releases of Particulate from Stationary Sources (Environment Canada, December 1993, as amended). If necessary, wall effects and complex velocity patterns may be determined with U.S. EPA Methods 2F, or 2G, or 2H. The audit comprises 3 concurrent RM and CEMS flow measurements. Ef , the average difference between the RM flow measurements and the corresponding CEMS measurements is calculated using equation 6.6.

Equation 6.6

Equation 6.6 (see long description below)

Where:

Ef = percent CEMS error from the average difference with the 3 RM tests.

di = difference between an RM value and the corresponding CEMS measurement for the ith test run in m/s or m³/s

FS = full scale setting of the flow monitor, in m/s or m³/s

Acceptance criteria are: Ef ≤ 5.0% or 0.6 m/s average absolute difference.

Table 6: Daily and quarterly performance evaluations summary
Parameter Component Level Specification Specification references Test procedure references
Daily Performance Evaluations
24-hr calibration drift SO2, NOx and CO analyzers Low Level (0-20% FS) High Level (80 - 100% FS) ≤ 2.5% Full Scale FS or 2.5 ppm absolute difference 6.2.1 5.3.2
24-hr calibration drift SO2, NOx and CO analyzers Out-of-control condition > two times above both levels 6.2.1 5.3.2
24-hr calibration drift O2 and CO2 analyzers Low Level (0-20% FS) High Level (80 - 100% FS) ≤ 0.5% O2 (or CO2) 6.2.1 5.3.2 
24-hr calibration drift O2 and CO2 analyzers Out-of-control condition > two times the above level 6.2.1 5.3.2
24-hr calibration drift Stack gas flow monitor Low Level (0 - 20% FS) High Level (50 - 70% FS) ≤ 3.0% FS or 0.6 m/s absolute difference 6.2.1 5.3.2
24-hr calibration drift Stack gas flow monitor Out-of-control condition > two times above both levels 6.2.1 5.3.2
Quarterly performance evaluations
Analyzers linearity audits (CGA) SO2, NOx and CO analyzers Low Level (0 - 20% FS) Mid Level (40 - 60% FS High Level (80 - 100% FS) ≤ 5.0% of Ref. or |R-A|≤ 5 ppm 6.3.1 6.3.1.3
Analyzers linearity audits (CGA)   O2 and CO2 analyzers Low Level (0 - 20% FS) Mid Level (40 - 60% FS High Level (80 - 100% FS) ≤ 5.0% of Ref. or |R-A|≤ 0.5% O2 or CO2 6.3.1 6.3.1.3
Analyzers linearity audits (CGA) O2 and CO2 analyzers Out-of-control condition > two times above both levels 6.3.1 6.3.1.3
Alternate "CGA" audit* SO2, NOx and CO analyzers ≥ 6 concurrent RM runs RA ≤ 15% 6.3.1.6 6.3.1.6
Alternate "CGA" audit* O2 and CO2 analyzers ≥ 6 concurrent RM runs RA ≤ 15% or 1.0% average absolute difference  6.3.1.6 6.3.1.6
Alternate "CGA" audit* O2 and CO2 analyzers Out-of-control condition > than both above levels 6.3.1.6 6.3.1.6
Alternatives
Stack gas flow audit Flow-to-load evaluation electric output ≥60 MJ/s or heat output ≥171 MJ/s ≤ 10% relative difference in flow-to-load ratios 6.3.2 6.3.2.4
Stack gas flow audit Flow-to-load evaluation electric output <60 MJ/s or heat output <171 MJ/s ≤ 15% relative difference in flow-to-load ratios 6.3.2 6.3.2.5
Stack gas flow audit Abbreviated flow-to-load test electric output ≥60 MJ/s or heat output ≥171 MJ/s ≤ 10% relative difference in flow-to-load ratios 6.3.2 6.3.2.5
Stack gas flow audit Abbreviated flow-to-load test electric output <60 MJ/s or heat output <171 MJ/s ≤ 15% relative difference in flow-to-load ratios 6.3.2 6.3.2.6
Stack gas flow audit Abbreviated flow-to-load test Out-of-control condition > two times above levels 6.3.2  
Stack gas flow audit Flow RM test 3 flow RM runs avg. diff. ≤ 5% FS., or 0.6 m/s 6.3.2 6.3.2.7
Stack gas flow audit Flow RM test Out-of-control condition > two times above both levels 6.3.2  

* for in-situ analyzers installed before 2023 that cannot be calibrated with flowing reference gas

6.4 Semi-annual performance evaluations

Two test procedures are involved in the semi-annual performance evaluation: a relative accuracy test and a bias test. These are carried out for each pollutant and diluent gas measured, as well as for stack gas flow and stack gas moisture (if applicable).

6.4.1 Relative accuracy and bias tests

This section describes the frequency, timing, gases, procedures, criteria, and out-of-control periods for semi-annual performance evaluations.

6.4.1.1 Frequency and Timing of Evaluations

A performance evaluation should be carried out twice a year, no less than 4 months apart. It is recommended that the relative accuracy (RA) and bias evaluation be carried out on a day closely following the cylinder gas audit (CGA).

6.4.1.2 Test gases

The gases used by the reference method must be U.S. EPA Protocol grade, whereas the gases used by the CEMS may be those regularly used for daily calibration checks.

6.4.1.3 Test procedures

RA and bias must be tested according to procedures and calculations in sections 5.3.5 and 5.3.6. Only 1 capacity level, that the source is running at the time, needs to be tested.

6.4.1.4 Acceptance criteria

The performance specifications of section 5.1.5 and section5.1.6 must be met, providing that the CEMS includes the monitored parameter. The bias test and specifications of section 5.3.6 should be followed.

6.4.1.5 Out-of-control period

An out-of-control period occurs when the relative accuracy or bias tests exceed the specifications cited in section 6.4.1.4. This period begins with the minute after the completion of the test and ends with the minute after corrective action has demonstrated that it is operating satisfactorily. When an analyzer, monitor, or system is out of control, the data generated by the specific analyzer, monitor or system are considered missing and do not qualify for meeting the requirements for system viability. Missing data must be backfilled using the criteria provided in section 3.4.3.

6.4.2 Exemptions from semi-annual evaluations

The semi-annual test may be waived and conducted annually if all the following conditions have been met, provided that the CEMS includes the monitored parameters:

6.5 Annual performance evaluations

This section presents the criteria for independent annual inspections.

6.5.1 Availability

The CEMS availability for each pollutant, diluent gas analyzer, or flow monitor is calculated using equation 3.1 of section 3.4. It must be at least 90% for the first year of operation and 95% annually thereafter. CEMS availability for peaking units is at least 80% annually.

6.5.2 Independent inspection

The CEMS and the QA/QC program must be evaluated by an independent inspector every 12 months. The inspector must review the QAP, the CEMS operation and other associated records to determine if the QAP is being followed. The inspector must note any changes in the system or the procedures since the previous inspection and produce a concise report about the following.

Data summary
Narrative

6.6 Criteria for acceptable quality assurance/quality control procedures

Repeated excessive out-of-control periods during quarterly or semi-annual evaluations indicate that the QA/QC procedures are inadequate or that the CEMS is incapable of generating acceptable data. Repeated out-of-control situations from the same cause must be investigated, and corrective action must be taken. Should the out-of- control periods continue to occur after these actions are completed, it may be necessary to replace the monitoring system.

Table 7: Semi-annual or annual performance evaluations summary
Parameter Component Level Specification Specification references Test procedure references
Relative Accuracy Test Audit (RATA) SO2, NOx and CO analyzers Representative load level ≤ 10.0% RA; or 5 ppm average absolute difference 5.1.5 5.3.5, 6.4.1
Relative Accuracy Test Audit (RATA) SO2, NOx and CO analyzers Out-of-control condition > than both above levels 5.1.5 5.3.5, 6.4.1
Relative Accuracy Test Audit (RATA) O2 and CO2 analyzers Representative load level ≤ 10.0% RA or 1.0% O2 (or CO2) average absolute difference 5.1.5 5.3.5, 6.4.1
Relative Accuracy Test Audit (RATA) O2 and CO2 analyzers Out-of-control condition > than both above levels 5.1.5 5.3.5, 6.4.1
Relative Accuracy Test Audit (RATA) Stack gas flow monitor Representative load level ≤ 10.0% RA or 0.6 m/s average absolute difference 5.1.5 5.3.5, 6.4.1
Relative Accuracy Test Audit (RATA) Stack gas flow monitor Out-of-control condition > than both above levels 5.1.5 5.3.5, 6.4.1
Relative Accuracy Test Audit (RATA) Stack gas moisture monitor Representative load level ≤ 10.0% RA or 1.5% H2O average absolute difference 5.1.5 5.3.5, 6.4.1
Relative Accuracy Test Audit (RATA) Stack gas moisture monitor Out-of-control condition > than both above levels 5.1.5 5.3.5, 6.4.1
Bias SO2, NOx and CO analyzers Representative load level ≤ 4.0% FS or 5 ppm average absolute diference 5.1.6 5.3.5, 5.3.6
Bias SO2, NOx and CO analyzers Out-of-control condition > than both above levels 5.1.7 5.3.5, 5.3.7
Bias O2 and CO2 analyzers Representative load level ≤ 4.0% FS or 0.5% O2 (or CO2) average absolute difference 5.1.8 5.3.5, 5.3.8
Bias O2 and CO2 analyzers Out-of-control condition > than both above levels 5.1.9 5.3.5, 5.3.9
Bias Stack gas flow monitor Representative load level ≤ 4.0% FS or 0.6 m/s average absolute difference 5.1.10 5.3.5, 5.3.10
Bias Stack gas flow monitor Out-of-control condition > than both above levels 5.1.11 5.3.5, 5.3.11
Bias Stack gas moisture monitor Representative load level ≤ 4.0% FS or 1.0% H2O 5.1.12 5.3.5, 5.3.12
Bias Stack gas moisture monitor Out-of-control condition > than both above levels 5.1.13 5.3.5, 5.3.13
CEMS availability Non-peaking units - ≥ 90% annually in first year ≥ 95% annually thereafter 6.5.1 3.4
CEMS availability Peaking units - ≥ 80% annually 6.5.2 4.4
Independent inspection - - Evaluation by an independent inspector 6.5.2 -

Section 7.0 Determination of carbon dioxide emissions

Section 7 is a new addition to the existing guidance document to incorporate provisions for monitoring and quantifying CO2 emissions. 

7.1 Introduction

CEMS is a suitable technique for quantifying CO2 emissions from stationary point sources on facilities designated by the Greenhouse Gas Reporting Program of ECCC. It may be an appealing option for large combustion units already fitted with SO2 or NOx. CEMS and equipped with stack gas volumetric flow rate monitor. For this application, the CO2 CEMS is subject to QA activities similar to those described in sections 5 and section6

Currently CEMS can quantify total CO2 emissions and is unable to differentiate biomass and fossil origin. If the monitored source combusts both fuel types, follow the directions of the most recent version of the ECCC Canada's Greenhouse Gas Quantification Requirements, Version 4.0, December 2020. 

The annual CO2 mass emissions must be calculated from hourly average CEMS mass emission rates using equation 7.1.

Equation 7.1

Equation 7.1  (see long description below)

Where:

Eu = CO2 emissions from the combustion source “u”, during the calendar year, in tonnes

ERh = hourly CO2 mass emission rate from the combustion source, in kg/hr

Th = Combustion source operating time, in hours or fraction of an hour

Hr = number of hourly CO2 emission rates during the calendar year

1000 = kg per tonne

The hourly average CO2 mass emission rates, in kg/hour, must be determined according to the equations 7.2 to 7.6, or by the backfilling of missing data discussed in section 3.4.3.

7.2 Wet carbon dioxide measurement systems

When both the stack gas CO2 concentration and flow rate are measured on wet basis, the hourly average CO2 mass emission rate must be calculated using equation 7.2

Equation 7.2

ERh = 1.789 Qw CO2,w

Where:

ERh = hourly CO2 mass emission rate from the combustion source, in kg/hr

1.789 = CO2 gas density in kg/Sm³

Qw = hourly average stack gas volumetric flow rate in WSm³/h

CO2,w = hourly average CO2 stack gas concentration, in volume percent on a wet basis

7.3 Dry carbon dioxide measurement systems

When the stack gas CO2 concentration is measured on dry basis and the stack gas flow is measured on wet basis, then the hourly average CO2 mass emission rate must be calculated using equation 7.3

Equation 7.3

ERh = 1.789 Qw CO2,d (1 − H2O)

Where:

ERh = hourly CO2 mass emission rate from the combustion source, in kg/hr

1.789 = CO2 gas density in kg/Sm³

Qw = hourly average stack gas volumetric flow rate on wet basis, WSm³/h

CO2,d = hourly average CO2 stack gas concentration, as fraction of dry volume.

H2O = hourly average stack gas moisture content, as volume fraction

7.4 Wet oxygen measurement systems

In the combustion of fuels of known composition (Appendix A, table A-1), without the addition of water, steam, or CO2 from calcination, it is possible to calculate the combustion exhaust gas CO2 and H2O levels by monitoring the exhaust gas O2 level. In this case, the QA provisions of sections 5 and 6 will be performed with respect to O2 reference gases, but all the required RATA should be done on a percent calculated CO2 basis.

When both the stack gas O2 concentration and flow rate are measured on wet basis, the hourly average CO2 concentration wet basis must be calculated using equation 7.4, and then the mass emission rate is calculated using equation 7.2.

Equation 7.4

Equation 7.4 (see long description below)

Where:

CO2w = hourly calculated average CO2 concentration during unit operation, as wet volume fraction

Fc = ratio of the carbon dioxide volume generated by the combustion of a given fuel to the amount of heat produced (Appendix A, Eqn. A-13)

Fd = ratio of the stoichiometric volume of dry gas generated by the atmospheric combustion of a given fuel to the amount of heat produced (Appendix A, Eqn. A-11)

H2O = stack gas moisture content, volumetric fraction

O2w = hourly average O2 concentration during unit operation, volumetric wet fraction

For any hour where equation 7.4 results in a negative average CO2 value, then the average CO2 value for that hour shall be recorded as 0.0% CO2w. The stack gas moisture level may be calculated by appendix B, equation B-5 and table B-1. Other stack gas moisture monitoring systems may be proposed providing that are able to calculate stack gas H2O with an error ≤ 2.0% on annual basis.

7.5 Dry oxygen measurement systems

In the combustion of fuels of known composition (Appendix A, table A-1), without the addition or water or steam or the release of CO2 by calcination or other significant side reactions, it is possible to calculate exhaust gas dry CO2 levels by monitoring the exhaust gas dry O2 level. In this case, the QA provisions of sections 5 and 6 will be performed with respect to O2 reference gases, but all the required RATA should be done on a percent calculated CO2 basis.

When the stack gas O2 concentration is measured on dry basis, the hourly average dry CO2 concentration must be calculated using equation 7.5, and then the mass emission rate is calculated using equation 7.3.

Equation 7.5

Equation 7.5 (see long description below)

Where:

 

CO2d = hourly average CO2 concentration during unit operation, percent by volume, dry basis

Fc = ratio of the CO2 volume generated by the combustion of a given fuel to the amount of heat produced (Appendix A, Eqn. A-13)

Fd = ratio of the stoichiometric volume of dry gas generated by the atmospheric combustion of a given fuel to the amount of heat produced (Appendix A, Eqn. A-11)

O2,d = hourly average O2concentration during unit operation, volumetric percent, dry basis

For any hour where equation 7.5 results in a negative CO2 value, then 0.0% CO2w shall be recorded as the CO2 value for that hour.

Glossary

In this document:

"720-hour rolling average" means, for each pollutant, the average of the preceding 720 hours of emission source operation. Downtime intervals of the monitored process are not to be included in the calculation of rolling averages.

"Accuracy" means the extent to which the results of a calculation or the readings of an instrument approach the true value of the calculated or measured quantities, and free from error

"Analyzer" is the device that measures pollutant or diluent concentration in the exhaust stream of an emission source

"Appropriate regulatory authority" means any federal, provincial, territorial or local government that has or could exercise regulatory or other authority over monitored emissions

"Availability" means the number of valid monitoring hours divided by the hours the combustion units burns fuel

"Backfilling" means the substitution of monitoring data during a monitoring out-of-control period by a technique approved by an appropriate regulatory authority

"Bias" means systematic error resulting in measurements that are consistently low or high relative to the reference value. Bias exists when the difference between continuous emission monitoring system data and the reference method exceeds random error

"Calibration gas" means a known concentration of (1) a gas that is traceable to either a standard reference material or the U.S. National Institute of Standards and Technology, (2) an authorized certified reference gas, or (3) a U.S. Environmental Protection Agency protocol gas 

"Calibration" means the procedure of testing a device to bring it to a desired value (within a specified tolerance)for a particular input value (typically the value of the reference standard)

"Calibration check" means the procedure of testing a device against a known reference standard without adjusting its output

"Calibration drift" means the difference between (1) the response of a gas analyzer to a reference gas and the known value of the reference gas, (2) the response of a flow monitor to a reference signal and the known value of the reference signal

"Conditioning period" is a recommended "break in" period in which a continuous emission monitoring system samples and analyzes the stack gas emissions prior the Certification test series.

"Continuous emission monitoring system" means the complete equipment for sampling exhaust gases, conditioning, calculating emissions, and recording data

"Data point" means the measured signal output received from an analyzer or monitor at a scan rate at least as fast as the analyzer response time

"Drift" means an undesired change in CEMS output over a time period, that is unrelated to input or equipment adjustments

 "Flow monitor" is the continuous emission monitoring system component that monitors the actual velocity and temperature of the gas emission stream,

"Full scale" means, in the context of this document, a subset of the measurement range of an analyzer such that most of the normal operating measurements at the emission source falls within 20% and 80% of it.

"Generating unit" means a fuel-fired combustion device used for electricity generation

"Heat input rate" means the product of the gross calorific value of the fuel and the fuel feed rate into the combustion device and does not include the heat derived from preheated combustion air, recirculated flue gases or exhaust from other sources.

"Interference rejection" means the ability of a continuous emission monitoring system to measure a gaseous specie without responding to other gases or substances, within specified limits

"Load" means production rate or output rate of an industrial process unit (such as electric output from a power unit or mass of steam from a boiler)

"Measurement range" is a design concentration interval for which the manufacturer specifies the linearity, drift, and cross sensitivity of the analyzer

"Net energy output" means gross energy output minus unit service power requirements

"Nitrogen oxides" means nitric oxide (NO) and nitrogen dioxide (NO2), collectively expressed as nitrogen dioxide

“Normal load” means, for RATA purposes, the most frequent of the last quarter 3 load ranges: a) <30%, b) between 30% and 60%, or c) > 60%.

"Operational test period" means a mandatory 168-hour period following the installation of a new continuous emission monitoring system, during which most of the performance specification tests are carried out

"Out-of-control period" means a period when the output of the analyzer, flow monitor, or data acquisition and handling system does not accurately represent the stack emissions

"Peaking unit" is combustion unit that is operated for 1500 hours or less within a calendar year

"Performance specification" means a technical guidance document used for evaluating the acceptability of CEMS at the time of installation and whenever specified in regulations

"Precision" means the measure of the range of values of a set of repeated measurements. Indicates reproducibility of the observations

"Protocol gas" means a calibration gas mixture prepared and analyzed according to the EPA Traceability Protocol for Assay and Certification of Gaseous Calibration Standards, May 2012, EPA-600/R-12/531, as amended from time to time

"Quality system" means a structured system consisting of the policies, objectives, principles, organizational authority, responsibilities, accountability, and implementation plan of an organization for ensuring quality in its work processes, products, services and activities

"Range" means the algebraic difference between the upper and lower limit of the group of values within which a quantity is measured, received, or transmitted

"Raw data" means the original, un-manipulated value obtained from an analyzer or device

"Reference method" means any applicable ECCC method for the measurement of stack gas flow, contaminant, or diluent concentration, such as methods A to F, or those by an appropriate regulatory authority such as U.S. EPA methods 2F, 2G, 2H, 3A, 6C, and 7E.

"Relative accuracy" is the absolute mean difference between a series of concurrent measurements made by a continuous emission monitoring system and an appropriate reference method plus the 2.5% error confidence internal coefficient, divided by the mean of the reference method measurements.

"Representative load" is the typical combustion unit operating level forecasted for the following 6 months

"Standard conditions" means at 101.325 kPa pressure and 25oC temperature

"Units of the standard" means any applicable emission limit set by ECCC, or by an appropriate regulatory authority

"Valid data" means data of known and documented quality that satisfy, at a minimum the requirements set out in this document

"Valid hour" means an hour during which the combustion unit burned fuel and the associated continuous emission monitoring system produced a minimum equivalent to 30 minutes of valid data.

"Zero air material" means high purity air, or inert gas such as nitrogen, with less than 0.1 parts per million v/v level of the gas being analyzed, or less than 0.1 percent of the span value, whichever is greater. It may include a) a gas mixture certified by the supplier, b) ambient are conditioned by a certified zero air generator; or c) conditioned and purified ambient air provided by a conditioning system concurrently supplying dilution air to the CEMS

Units, abbreviations, and acronyms

In this document,

|d|
Absolute difference
avg
Average
BAF
Bias adjustment factor
BTU
British Thermal Unit
CEMS
Continuous Emission Monitoring System
CFR
U.S. Code of Federal Regulations
cm
Centimetre
CO2
Carbon dioxide
DSm³/GJ
Dry standard cubic metre per gigajoule
DSm³/MJ
Dry standard cubic metre per megajoule
ECCC
Environment Canada and Climate Change
EPA
U.S. Environmental Protection Agency
F - factor
Fc , Fd , or Fw combustion factors
Fc
Ratio of the carbon dioxide volume generated by the combustion of a given fuel to the amount of heat produced (Sm³/Mj)
Fd
Ratio of the stoichiometric volume of dry gas generated by the atmospheric combustion of a given fuel to the amount of heat produced (DSm³/Mj)
FS
Full scale
Fw
Ratio of the stoichiometric volume of dry gas generated by the dry air combustion of a given fuel to the amount of heat produced (WSm³/Mj)
g/GJ
Grams per gigajoule
GCV
Gross Calorific Value
GJ/h
Gigajoules per hour
GJ/MWh
Gigajoules per megawatt-hour
H2O%
Moisture content of the stack gas (% v/v)
ISO
International Organization for Standardization
K
Kelvin degrees
kg/GJ
Kilograms per gigajoule
kg/h
Kilograms per hour
kg/MWh
Kilograms per megawatt-hour
kg/Sm³
Kilograms per standard cubic metre
kJ/kg
Kilojoule per kilogram
kPa
Kilopascal
LEDs
Light-emitting diodes
m/s
Metres per second
m³/GJ
Cubic metres per gigajoule
m³/kg-mol
Cubic metres per kilogram-mole
m³/s
Cubic metres per second
MJ/MWh
Megajoules per megawatt-hour
MJ/s
Megajoules per second
MW
Megawatt
MWh
Megawatt-hr
ng/J
Nanograms per joule
NO
Nitric oxide
NO2
Nitric dioxide
NOx
Nitric oxides (NO + NO2)
°C
Degree Celsius
OEM
Original Equipment Manufacturer
OTP
Operational Test Period
ppm
arts per million
Pstd
ECCC standard pressure, 101.325 kPa
QA
Quality Assurance
QC
Quality Control
RA
Relative Accuracy
RATA
Relative Accuracy Test Audit
RM
Reference Method
Sm³/GJ
Standard cubic metres per gigajoule
Sm³/h
Standard cubic metres per hour
Sm³/MJ
Standard cubic metres per megajoule
Sm³/MWh
Standard cubic metres per megawatt-hour
SO2
Sulphur dioxide
v/v
Volume per volume basis
WSm³/GJ
Wet standard cubic metres per gigajoule
WSm³/h
Wet standard cubic metres per hour
>WSm³/MJ
Wet standard cubic metres per megajoule
WSm³/MWh
Wet standard cubic metres per megawatt-hour

Bibliography

Appendix A: Emission calculation by combustion F-factors

A.1 Introduction

Combustion F-Factors are used to calculate pollutant emissions rates expressed in units of mass per energy, such as ng/J. They may also be used to give a true mass emission rate (mass per unit time) if the heat input to the combustion process is accurately known.

The Fc factor is the ratio of the carbon dioxide volume generated by the combustion of a given fuel, to the amount of heat produced. The Fd factor is the ratio of the stoichiometric volume of dry gas generated by the complete atmospheric combustion of a given fuel, to the amount of heat produced. The Fw factor is the ratio of the stochiometric volume of wet gas generated by the complete dry air combustion of the fuel, to the amount of heat produced.

The F-Factor to use in calculating emissions is determined by the diluent gas monitored. CEMS with CO2 analyzers should use Fc  factors, whereas those with O2 analyzers should used Fc factors or Fw factors. CEMS with both O2 and CO2 analyzers should use the F-factor that produces the most accurate exhaust volume estimates, taking in consideration the expected O2 and CO2 levels.

Note that the reference conditions of the ECCC F-factors are 25°C and 101.325 kPa. Factors generated at other reference conditions, must be adjusted to the ECCC reference. F-factors for other fuels may be developed using equations A-11, equationA-12 and equationA-13, but their application will require approval by the appropriate regulatory authority before being applied to CEMS.

Table A-1: F-factors for selected fields
Fuel Type Fd (dSm³/GJ)* Fw (wSm³/GJ)* Fc (Sm³CO2/GJ)*
Solid Anthracite 277 288 54.2
Solid Bituminous Coal 267 286 49.2
Solid Subbituminous coal 263 301 49.2
Solid Lignite 273 310 53.0
Solid Petroleum Coke 268   50.5
Solid Tire Derived Fuel 280   49.1
Solid Wood bark 268   50.2
Solid Wood residue 269   52.1
Solid Municipal solid waste 268   50.5
Oil Crude, residual, or distillate 255 289 39.3
Gas Natural Gas 240 295 28.4
Gas Propane 238 281 32.5
Gas Butane 238 284 34.1

* Reference conditions 101.325 kPa and 25°C

CEMS using F factor formulas can potentially produce erroneous high emission values during process start up or shut down periods, in which a formula denominator becomes zero or near zero value (for example when measured stack gas oxygen is approximately 20.9 percent). This is avoided by setting a minimum stack gas carbon dioxide level and a maximum oxygen level. For boilers, a minimum of 5.0 percent CO2 or a maximum 14.0 percent O2 may be substituted for the measured diluent gas value for any operating period in which the hourly average CO2 concentration is < 5.0 percent CO2 or the hourly average O2 Concentration is > 14.0 percent. For stationary turbines, a minimum concentration of 1.0 percent CO2 or a maximum concentration of 19.0 percent O2 may be substituted for the measured diluent gas concentration for any operating period in which the hourly average CO2 concentrations is <1.0 percent CO2, or the hourly average O2 concentration is >19.0 percent. The cap for extreme dilution levels must be disclosed in the QAP.

A.2 Oxygen-based Fd factor measurement systems

When the CEMS measurements are on dry basis for both oxygen (%O2d) and pollutant (Cd) concentrations, the equation A-1 may be used to calculate the emission rate of the pollutant, in kg/GJ units.

Equation A-1

Equation A-1 (see long description below)

Where:

Ex = emission rate of the pollutant x, (kg/GJ)

Cxd = dry-basis concentration of the pollutant x  in stack gas, (ppm, dry)

Fd = ratio of the stoichiometric volume of dry gas generated by atmospheric combustion of a given fuel, to the amount of heat produced, (DSm³/GJ)

Kx = ppm to kg/Sm³conversion factor for pollutant x , (kg/Sm³/ppm)

20.9 = oxygen volumetric fraction on ambient air

%02,d = percent dry-basis concentration of oxygen in stack gas, (%, v/v)

The  Kx values for SO2, NOx, CO and CO2 are:

SO2
2.618 x 10-6 kg/Sm³/ppm
NOx (as NO2)
1.880 x 10-6 kg/Sm³/ppm
CO
1.145 x 10-6 kg/Sm³/ppm
CO2
1.789 x 10-6 kg/Sm³/ppm

The values of Kx for other gases can be calculated using the following formula:

Equation A-2

Equation A-2 (see long description below)

Where:

MWx = molecular weight of gas x

Tstd = ECCC standard temperature (298.15 K)

22.414 = molar volume at 273.15 K (m3/kg-mol)

A.3 Oxygen-based Fw measurement systems

This factor is used in systems employing wet-basis analyzers. The Fw factors may be used where no water, other than that generated by the combustion process, is introduced into the exhaust gas flow.

The emission rate in kg/GJ may calculated using equation A-3.

Equation A-3

Equation A-3 (see long description below)

Where:

Ex = emission rate of pollutant x , (kg/GJ)

Cxw = wet-basis concentration of pollutant x (ppm)

Kx = ppm to kg/Sm³ conversion factor, (kg/Sm³/ppm)

Fw = ratio of the volume of wet gas generated by the stoichiometric combustion of the fuel with dry air, to the amount of heat produced (WSm³/GJ)

H2Oa = concentration of water vapor in the combustion air (volumetric fraction)

%O2w = wet-basis oxygen level in the combustion exhaust gas (%,v/v)

This equation cannot be used in any process in which water is added or removed from the flue gas stream (in other words it is not applicable to CEMS installed after wet scrubbers).

The highest monthly average of H2Oa at the nearest location listed in table B-1 may be used as an estimate for the entire calendar year.

If the moisture fraction of the stack gas (H2Os) is measured, then the emission rate in kg/GJ may calculated using equation A-4.

Equation A-4

Equation A-4 (see long description below)

Where:

Ex = emission rate of pollutant x , (kg/GJ)

Cxw = wet-basis concentration of pollutant x (ppm)

Kx = ppm to kg/Sm³ conversion factor, (kg/Sm³/ppm)

Fd = ratio of the volume of wet gas generated by the stoichiometric combustion of the fuel with dry air, to  the amount of heat produced (WSm³/GJ)

H2Os = concentration of water vapor in the stack gas (decimal, v/v)

%O2w = wet-basis oxygen level in the stack gas (%,v/v)

A.4 Mixed basis measurement systems

When the pollutant concentration is measured on wet basis (Cw ) and the O2 concentration is measured on dry basis (%O2d) then the equation A-5 may be used:

Equation A-5

Equation A-5 (see long description below)

Where:

Ex = emission rate of pollutant x , (kg/GJ)

Cxw = wet-basis concentration of pollutant x, (ppm)

Kx = ppm to kg/Sm³ conversion factor, (kg/Sm³/ppm)

Fd = ratio of the volume of dry gas generated by the stoichiometric combustion of the fuel with dry air, to the amount of heat produced (WSm³/GJ)

H2Os = concentration of water vapor in the combustion air (decimal, v/v)

%O2s = dry-basis oxygen level in the combustion exhaust gas (%,v/v)

When the pollutant is measured on dry basis (Cxd) and the O2 concentration is measured on wet basis (%O2w) then the equation A-6 may be used:

Equation A-6

Equation A-6 (see long description below)

Where:

Ex = emission rate of pollutant x , (kg/GJ)

Cxd = dry-basis concentration of pollutant x, (ppm)

Kx = ppm to kg/Sm³ conversion factor, (kg/Sm³/ppm)

Fd = ratio of the volume of dry gas generated by the stoichiometric combustion of the fuel with dry air, to  the amount of heat produced (WSm³/GJ)

%O2w = wet-basis oxygen level in the stack gas (%, v/v)

H2Ows = concentration of water vapor in the stack gas (volumetric fraction)

A.5 Carbon dioxide-based Fc factor measurement systems

If carbon dioxide has been selected as the diluent gas, the carbon dioxide-based F-factor (Fc) must be used to determine the pollutant emission rate. The Fc factor may be used on either dry- or wet-basis CEMS, provided that the pollutant and CO2 are measured on the same basis. The wet method is applicable to in-situ, dilution, and extractive direct-reading wet-basis CEMS.

When the pollutant concentration is measured on wet basis (Cw) and the CO2 concentration is measured on dry basis, then the emission rate for dry-basis measurements is calculated using equation A-7.

Equation A-7

Equation A-7 (see long description below)

Where:

Ex = emission rate of pollutant x ,(kg/GJ)

Kx = ppm to kg/Sm³ conversion factor, (kg/Sm³/ppm)

Cxd = dry-based concentration of pollutant x, (ppm, v/v)

Fc = ratio of the carbon dioxide volume to the heat produced, (Sm³/GJ)

%O2d = dry-basis CO2 concentration, (%, v/v)

The emission rate for wet-basis measurements is calculated using equation A-8.

Equation A-8

Equation A-8 (see long description below)

Where:

Ex = emission rate of pollutant x, (kg/GJ)

Cxw = wet-based concentration of pollutant x , (ppm, v/v)

Kx = ppm to kg/Sm³ conversion factor, (kg/Sm³/ppm)

Fc = ratio of the carbon dioxide volume to the heat produced, (Sm³/GJ)

%O2w = wet-basis CO2 concentration, (%, v/v)

When the pollutant concentration is measured on wet basis (Cw) and  carbon dioxide concentration is measured on dry basis (%CO2d), the following equation A-9 may be used.

Equation A-9

Equation A-9 (see long description below)

Where:

Ex = emission rate of pollutant x , (kg/GJ)

Cxd = wet-based concentration of pollutant x , (ppm, v/v)

Kx = ppm to kg/Sm³ conversion factor, (kg/Sm³/ppm)

Fc = ratio of the carbon dioxide volume to the heat produced, (Sm³/GJ)

H2Os = concentration of water vapor in the stack gas (decimal, v/v)

%O2d = dry-basis CO2 concentration, (%,v/v)

When the pollutant concentration is measured on dry basis (Cd) and CO2 concentration is measured on wet basis (%CO2w), the following equation A-10 may be used.

Equation A-10

Equation A-10 (see long description below)

Where:

Ex = emission rate of pollutant x , (kg/GJ)

Cxd = dry-based concentration of pollutant x , (ppm, v/v)

Kx = ppm to kg/Sm³ conversion factor, (kg/Sm³/ppm)

Fc = ratio of the carbon dioxide volume to the heat produced, (Sm³/GJ)

H2Os = concentration of water vapor in the stack gas (decimal, v/v)

%O2w = wet-basis CO2 concentration, (%,v/v)

A.6 Calculation of customized F-Factors

For fuels with compositions differing significantly from typical values or fuels not listed in table A-1, F-factors may be calculated using the as-fired ultimate analysis and gross calorific value (GCV) of the fuel. Equations A-11 to A-13 can be used to calculate the various F-Factors.

Equation A-11

Equation A-11 (see long description below)

Equation A-12

Equation A-12 (see long description below)

Equation A-13

Equation A-13 (see long description below)

Where:

Fs,Fw,Fc = gross calorific value of the as-fired fuel (kJ/kg)

%H, %C, %S,  %N, %O, %H2O = concentration of hydrogen, carbon, sulphur, nitrogen, and water, respectively,  from ultimate fuel analysis (mass percent).

GCVd = gross calorific value of the as-fired fuel (kJ/kg)

104 = conversion factor (kJ/GJ/100)

Khd = 22.95 Sm³/kg, volume of dry exhaust gases resulting from the atmospheric stoichiometric combustion of hydrogen in the fuel

Kc = 9.74 Sm³/kg, volume of dry exhaust gases resulting from the atmospheric stoichiometric combustion of carbon in the fuel

Ks = 3.65 Sm³/kg, volume of dry exhaust gases resulting from the atmospheric stoichiometric combustion of sulphur in the fuel

Kn = 0.87 Sm³/kg, volume of dry exhaust gases resulting from the atmospheric stoichiometric combustion of nitrogen in the fuel

Ko = -2.89 Sm³/kg, volume of dry exhaust gases avoided due to oxygen in the fuel

Khw = 35.08 Sm³kg, volume of wet exhaust gases resulting from the atmospheric stoichiometric combustion of hydrogen in the fuel

Kw = 1.36 Sm³/kg, volume of water vapor resulting from the water contained in the fuel

Kcc = 2.04 Sm³/kg, volume of carbon dioxide produced by the complete combustion of the fuel

Appendix B: Determination of mass emission rates

B.1 Introduction

The emission rate of a pollutant, on a mass-per-unit-time basis, may be determined by 1 of 2 methods described in this appendix:

B.2 Energy input method by the metering of fuel flows

The calculation of the mass emission rate of a compound is shown as an example in equation B-1, which applies to the measurement of the pollutant using an oxygen-based dry system:

Equation B-1

Equation B-1 (see long description below)

Where:

ERx = emission rate of pollutant x (kg/h)

HI = gross heat input (GJ/h)

Cx,d = dry-basis hourly average exhaust gas concentration of the pollutant x (ppm, v/v)

Fd = ratio of the volume of dry gas resulting from stoichiometric atmospheric fuel combustion to the amount of heat produced (DSm3/GJ)

Kx = ppm to kg/Sm³ conversion factor for pollutant x

%O2d = dry-basis hourly average exhaust gas concentration of O2 (%, v/v)

Equation B-1 is similar to equation A-1 in appendix A, except of the additional term HI, which converts the mass-per-energy rate into a mass per time. Thus, an accurate heat input rate is required to calculate the desired mass emission rate.

The energy entering the combustion process can be determined by measuring the mass fuel flow and its gross calorific value (GCV). The DAHS should be able to accept the signal of the fuel flow meter, and to calculate the heat input in the equation B-1 units.

B.2.1 Determination of heat input rate for gaseous fuels

The standard volume of gaseous fuel consumed must be measured and recorded by the DAHS and an hourly average calculated. The fuel flow monitor must meet a 2.0% accuracy, as determined by the manufacturer or the system operator. The fuel flow monitor must be calibrated at the frequency recommended by manufacturer to maintain the accuracy within specifications. The volumetric GCV (BTU/Sft³) of the fuel must be obtained from the fuel supplier on a monthly basis.

The hourly average heat input to the combustion unit is determined by the product of the hourly standard volumetric flow rate by the volumetric GCV provided by the fuel supplier.

The applicable pollutant mass emission rate  is determined by inserting the hourly average heat input to the combustion process into equation B-1. When calculating the mass emission rate for a system using wet-basis analyzers or CO2 as diluent gas, the appropriate equations from appendix A should be used, modified to include the value of the hourly heat input (HI).

B.2.2 Determination of heat input rate for liquid fuels

The flow of oil consumed in the combustion process must be measured and recorded on hourly basis. The fuel flow is measured using an in-line flow meter with the data automatically recorded by the DAHS. Any returning fuel flow must be metered by a similar flow meter and the data recorded by the DAHS, that should be able to calculate the net fuel flow.

Each fuel flow meter must meet a 2.0% accuracy specification, as measured by the manufacturer or CEMS operator. Each flow meter must be recalibrated at least annually, or more frequently if specified by the manufacturer in order to meet the cited accuracy specification.

The as-fired liquid fuel must be sampled and analyzed to determine its gross calorific value (GCV). Flow-proportional sampling or continuous-drip sampling must be carried out when the unit is fuel by oil. The hourly samples must be blended into a composite sample and then analyzed for GCV and specific gravity, if necessary. The protocols for fuel sampling and analysis must be included in the QAP, in consultation with the appropriate regulatory agency.

The applicable pollutant mass emission rate is determined by inserting the hourly heat input to the combustion process into equation B-1. When calculating the mass emission rate for a system using wet-basis analyzers or CO2 as diluent gas, then the appropriate equations from appendix A should be used, modified to include the value of the hourly heat input (HI).

B.3 Determination using real-time stack gas flow monitors

The mass emission rate of the target pollutants can be determined from their concentration and the volumetric flow rate of the flue gas. There are several techniques for measuring the flow rate (such as pitot tubes, ultrasonic meters). Any gas flow rate monitoring system that meets the specifications and passes certification is acceptable and may be used in CEMS.

Equation B-2

The procedures to compute hourly mass emissions are the following. The exhaust flow is primarily measured on wet basis, and then adjusted to standard conditions by temperature and pressure measurements using equation B-2.

Equation B-2 (see long description below)

Where:

Qstp = Flue gas volumetric flow rate at standard temperature and pressure, WSm³/h

Qactual = Flue gas volumetric flow rate at actual temperature and pressure, WAm³/h

Tstp = Standard ECCC temperature, K = 273.15 + 25°C

Tstack = Flue gas temperature at flow monitoring location, K = 273.15 + °C

Pstack = Absolute flue gas pressure (site barometric pressure + flue gas static pressure), kPa

Pstd = Standard ECCC pressure, 101.325 kPa

When the pollutant concentration is measured in wet basis, the hourly emissions during source operation are calculated using equation B-3.

Equation B-3

Equation B-3 (see long description below)

Where:

ERx = emission rate of pollutant x, (kg/h)

Qw = wet stack gas volumetric flow rate (WSm³/h)

Cx,w = wet-basis gas pollutant x concentration (ppm, v/v)

Kx = ppm to kg/Sm³ conversion factor for pollutant x

When the pollutant concentration is measured on dry basis (for example extractive CEMS with sample conditioning by condensation or equivalent), the hourly emissions during source operation are calculated using equation B-4.

Equation B-4

Equation B-4 (see long description below)

Where:

ERx = emission rate of pollutant x, (kg/h)

Qw = wet stack gas volumetric flow rate (WSm³/h)

Cx,w = dry-basis gas pollutant x concentration (ppm, v/v)

Kx = ppm to kg/Sm³ conversion factor for pollutant x

H2Os = concentration of water vapor in the stack gas (decimal, v/v)

The mass emission monitoring by equation B-3 requires the installation, operation, maintenance, and quality assurance of a continuous stack gas moisture monitoring system for measuring and adjusting the measured dry basis pollutant concentration. The following systems are acceptable:

If the CEMS includes a suitably installed wet O2 analyzer and a dry O2 analyzer, then the stack gas moisture can be calculated using equation B-5.

Equation B-5

Equation B-5 (see long description below)

Where:

H2Os = hourly average stack gas moisture content (% H2O)

O2w = wet-basis hourly average O2 concentration (% O2)

O2d = dry-basis hourly average O2 concentration (% O2)

In the combustion of fuels of known composition, without the addition or water or steam, it is possible to estimate stack gas moisture by monitoring the wet O2 level of the stack gas and the combustion air moisture. This is accomplished by applying equation B-6 (for combustion in dry air), and then adding the moisture of the combustion air (similar to EPA Method 4 section 12.2.5).

Equation B-6

Equation B-6 (see long description below)

Where:

%H2Os = stack gas moisture content (%, v/v)

Fw = ratio of the volume of wet gas resulting from stoichiometric atmospheric fuel combustion to the amount of heat produced (DSm³/GJ)

Fd = ratio of the volume of dry gas resulting from stoichiometric atmospheric fuel combustion to the amount of heat produced (DSm³/GJ)

O2w = wet-basis concentration of O2 in stack gas (decimal, v/v)

Figure B-1 resulted from applying the equation B-6 to Fd and Fw of 3 common fuels listed in table A-1.

Figure B-1: H2O in exhaust for dry air combustion

Figure B-1 - Graph
Long description for figure B-1

This graph shows the relationship between O2 and H2O in exhaust for dry air combustion of various fuels (natural gas, oil, and coal).

The moisture estimate by equation B-6 requires a single oxygen analyzer, as opposed to the 2 analyzers of equation B-5, but a change in fuel may necessitate a different calculation equation. If the emission source operates year-round with the same fuel and the same excess combustion air level, then it is acceptable to measure stack gas moisture during RATA and, if successful, apply the same moisture factor until the next RATA. If fuel moisture varies, or excess air changes with load levels (such as in gas turbines), then it is recommended to monitor stack gas moisture levels by equations B-5 or B-6.

Other stack gas moisture monitoring systems may be proposed for use with equation B-4 if it is demonstrated that the system calculates stack gas H2O with an error ≤ 2.0% on annual basis. The specific QA activities related to the moisture monitoring system must then be described in the QAP.

On annual average, the adjustment for ambient air moisture is rather minor (~ 1% v/v H2O), given the low temperatures of Canadian weather. Table B-1 shows the 1981 to 2010 average monthly moisture levels in the provincial and territorial capitals, calculated from the ratio of H2O partial pressure to the atmospheric pressure. The use of the site historical ambient air moisture (monthly or annual average) is adequate to add to the combustion moisture calculated by figure B-1.

Table B-1 : Monthly average air moisture on Canadian provincial capitals
Location Jan Feb Mar Apr May June Jul Aug Sep Oct Nov Dec Avg. RSD
Calgary 0.34% 0.34% 0.45% 0.56% 0.79% 1.12% 1.35% 1.23% 0.90% 0.56% 0.45% 0.34% 0.67% 54.00%
Vancouver 0.69% 0.69% 0.79% 0.89% 1.08% 1.28% 1.47% 1.48% 1.28% 1.08% 0.79% 0.69% 0.98% 31.00%
Winnipeg 0.20% 0.20% 0.40% 0.61% 0.91% 1.42% 1.73% 1.52% 1.12% 0.71% 0.41% 0.20% 0.81% 68.00%
Fredericton 0.30% 0.30% 0.40% 0.59% 0.89% 1.29% 1.68% 1.58% 1.28% 0.79% 0.59% 0.40% 0.79% 63.00%
St. John's 0.40% 0.40% 0.50% 0.60% 0.80% 1.10% 1.40% 1.50% 1.20% 0.90% 0.70% 0.50% 0.80% 48.00%
Yellowknife 0.10% 0.10% 0.10% 0.30% 0.50% 0.81% 1.11% 1.11% 0.81% 0.51% 0.20% 0.10% 0.51% 78.00%
Halifax 0.40% 0.40% 0.50% 0.60% 0.90% 1.31% 1.60% 1.70% 1.40% 1.00% 0.70% 0.50% 0.90% 53.00%
Iqaluit 0.10% 0.10% 0.10% 0.20% 0.40% 0.60% 0.80% 0.80% 0.60% 0.40% 0.20% 0.10% 0.40% 69.00%
Toronto 0.40% 0.40% 0.50% 0.70% 1.01% 1.51% 1.71% 1.71% 1.40% 0.90% 0.70% 0.50% 0.90% 56.00%
Charlottetown 0.30% 0.30% 0.40% 0.60% 0.89% 1.29% 1.69% 1.69% 1.29% 0.89% 0.69% 0.40% 0.89% 57.00%
Quebec City 0.20% 0.30% 0.40% 0.50% 0.90% 1.29% 1.69% 1.59% 1.19% 0.79% 0.50% 0.30% 0.80% 66.00%
Regina 0.21% 0.32% 0.42% 0.53% 0.85% 1.27% 1.48% 1.37% 0.95% 0.63% 0.42% 0.21% 0.74% 62.00%
Whitehorse 0.22% 0.22% 0.32% 0.43% 0.54% 0.86% 1.07% 0.97% 0.75% 0.54% 0.32% 0.22% 0.54% 57.00%

Source: 1984 to 2010 ECCC Climate Normals (H2O vapour pressure/ station pressure)

When a CEMS fitted with stack gas monitor is installed after a pollution control device that reduces the flue gas temperature so that the exit gas is water saturated, then the stack gas moisture must be determined from the stack gas temperature by applying equations B-7 and equationB-8.

Equation B-7

Equation B-7 (see long description below)

Where:

%H2O = hourly average stack gas moisture during the operation of the combustion unit (% v/v)

PH2O = hourly average partial water pressure of the stack gases as calculated with Eqn. B-8 (mmHg)

Pstack = hourly average stack gas absolute pressure (mmHg)

Equation B-8

Equation B-8 (see long description below)

Where:

PH2O = hourly average partial water pressure of the stack gases as calculated with Eqn. B-8 (mmHg)

A = constant = 8,0886767

B = constant = 1739,351

C = constant = 234,1

Tstack = hourly average stack gas temperature (°C)

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