Reference methods: releases of vinyl chloride from plants, chapter 1
Part 1: Sampling
Method S-1: Sampling of process vents and stacks in vinyl chloride and polyvinyl chloride plants
- S-1.1 Scope
- S-1.2 Apparatus
- S-1.3 Procedures
- S-1.4 Sampling Bag Purge and Leak Check
- S-1.5 Sample Storage and Analysis
- S-1.6 Calculations
This method applies to the sampling of process vents and stacks in vinyl chloride (VC) and polyvinyl chloride (PVC) plants which are a source of VCreleases into the atmosphere.
(See Figure S-1-1)
A sampling probe may be made of stainless steel, Pyrex glass, Teflon®, or other inert material which does not absorb or react with VC. A glass wool plug shall be placed at the probe inlet to remove particulate from the sample.
The probe shall be connected to the sampling train using the minimum length of Teflon® tubing. Use a clean piece of Teflon® tubing to sample each vent or stack. The sampling train is to be located as close as is practical to the process vent or stack.
A condenser consisting of two glass midget impingers in an ice bath shall be used if moisture condensation is expected in the sampling train. If there is any uncertainty as to whether moisture condensation is expected in the sampling train, then include the condenser as shown in Figure S-1-1.
A rotameter capable of measuring flows in a range from 0 to 0.5 litres/min is required. The rotameter shall have a measurement accuracy of within ±5% of full scale.
An intrinsically safe sampling pump shall be used to fill the sampling bag. The pump shall have both inlet and exhaust ports and a capacity of at least 200 mL/min.
A needle valve is used to adjust the sampling rate indicated on the rotameter during proportional sampling.
A male and a female stainless steel quick-connect, with ball checks, are required to connect the sampling bag to the sampling train and to the sampling recovery loop for analysis.
The gas sample shall be collected in a Tedlar®, or aluminized Mylar® sampling bag. The capacity of the sampling bag shall be adequate to contain the required total sample volume, based on the following calculation -- sampling rate multiplied by duration -- and shall be at least half full at the completion of sampling.
A calibrated S-type (Stausscheibe) pitot tube with a manometer shall be attached to the probe, so that the sampling rate can be maintained proportional to the effluent- flow velocity. If the air-flow velocity is less than 3.5 m/s, a low-flow measuring device shall be used to measure the velocity.
A barometer capable of measuring the atmospheric pressure to within 2.5 mmHg is required.
This section applies to continuous as well as intermittent sources of releases. Select a sampling site in the process vent or stack at least two diameters downstream and one-half diameter upstream from any flow disturbances such as a bend, expansion, contraction, or visible flame. For a rectangular cross-section determination, an equivalent diameter shall be defined as twice the product of the length multiplied by the width of the cross-section, divided by the sum of the length and the width.
Where plants use incineration to control VC releases, the gas composition (carbon dioxide and oxygen) in the process vent or stack shall also be measured.
Measure the ambient temperature and barometric pressure, and the conditions in the process vent or stack both before sampling, and after the sample has been collected. Record these values, and other required information set out in Form S-1.2.
Assemble the sampling train as in Figure S-1-1, but do not connect the bag. Determine whether moisture condensation in the sample train is to be expected. If there is any uncertainty as to whether moisture condensation is expected in the train, then include the condenser as shown. At the end of the sampling run, discard any water collected in the condenser. Check the bag for leaks and purge the bag according to S-1.4 before use. Inspect all connections and verify they are tight. Place the end of the probe at the sampling site and start the pump with the needle valve adjusted to yield a flow of 200 mL/min. Purge the train as long as is required to allow at least three volume exchanges. Stop the pump and connect the bag.
Continuous releases are defined as releases of process vent gases that occur continuously, whenever the plant is operating. Sampling of sources of continuous releases shall be undertaken during normal operating conditions of the plant.
Before beginning to collect the sample, the velocity profile in the process vent or stack shall be determined. Locate the sampling probe near a cross-sectional point of higher velocities. The absolute location of the probe within the process vent or stack is not important, but the probe shall be located at a sampling point which is within the uppermost quartile of the measured velocities. To determine the mass release rate of VC, measure the gas volumetric flow rate (Qs) of the process vent or stack.
Measure the gas velocity at the sampling point and determine the calculated ratio constant, that is, the ratio of the initial sampling rate to the velocity. Use this calculated ratio constant to determine the proportional sampling rate as the velocity of the gas in the process vent or stack varies. Begin sampling using a sampling rate of 200 mL/min. The sampling rate shall be thereafter adjusted every five minutes to maintain the proportional ratio constant with the process vent or stack gas velocity.
The sampling of a continuous source shall be at least 1 hour in duration and continuous. At the end of the sampling period, shut off the pump and disconnect the bag.
The data required, as set out in Form S-1.2 shall be recorded every five minutes during the sampling period.
To be valid, a sample shall satisfy the following criteria:
- the gas velocity in the process vent or stack shall not at any time have deviated by more than ±75% of the average velocity during the sampling period;
- the sampling rate shall be proportional to the gas velocity within 10%; and
- the composition, temperature and pressure of the gas in the process vent or stack do not change significantly during the sampling period.
An intermittent release is defined as one which only occurs when the operation creating it is required by the process, and thus is a release of gases through a process vent or stack on an intermittent basis. Such releases are part of batch processes that operate in a cyclical manner. Continuous releases in which the flow of gas in the process vent or stack does not meet criterion "a" in S-1.3.2 above over the period of one hour, shall be deemed an intermittent release.
Before beginning the sample collection, the velocity of the gas in the process vent or stack is to be measured for a minimum of two batch cycles. The maximum observed process vent or stack gas velocity during any five-minute period is to be noted. Determine the proportional sampling constant by calculating the ratio of the maximum flow of gas in the process vent or stack with a sampling rate of 200 mL/min.
Once sampling has started, adjust the sampling rate so its ratio remains proportional to the velocity of the gas in the process vent or stack using the proportional sampling constant determined above. No sample is to be drawn if there is no flow in the process vent or stack. The velocity of gas in the process vent or stack is measured every 2 1/2 minutes and the sampling rate adjusted, maintaining constant the above ratio of the sampling rate to the gas velocity in the process vent or stack. Form S-1.2 shows the data to be recorded. You may record the data on that form or in the format of your choice.
Sampling shall continue for at least one hour and until at least six litres of sample are collected as measured by the sampling train rotameter.
Before each use, the following two steps shall be taken to ensure the sampling bag is purged and leak-free:
- To purge, alternately fill and evacuate the bag three times with zero air. Zero air is air certified to contain no detectable concentration of the substance that is the subject of analysis. Furthermore, zero air shall contain no contaminant that causes a detectable response to the analyzer or that suppresses or enhances the analyzer's response.
- To leak-check, connect a manometer and pressurize the bag to 5 to 10 cm of H2O. Allow to stand for 10 minutes. Any displacement in the water manometer indicates a leak.
A leaking sampling bag shall not be used.
Sampling bags shall be stored out of direct sunlight. For sample tracking, assign a unique identifier to each bag sample submitted for analysis. Analysis of a sample shall be done using Method A-1 contained in Part 2 of this Reference Method.
Sample test data may be recorded in the units for which the sampling equipment is designed. However, if those units are different than those set out in this sampling method, they shall be converted to the units used in the equations of this sampling method.
(See S-1.6.2 for nomenclature)
Vinyl Chloride Concentration Corrected for Water Vapour
Concentrations of VCshall be calculated on a dry, undiluted basis. The concentration of VC as measured in a sample and reported in Method A-1 as Cb shall be corrected for water vapour and a final concentration reported as Cf. Cf is to be calculated using equation S-1.1:
Vinyl Chloride Concentration Corrected for Combustion Products
If incineration is used as a measure to control the VC releases, the composition of the gas in the process vent or stack is to be measured. Correct the VCconcentration to 10% oxygen using equation S-1.2:
Mass Release Rate
For the calculation of mass release rates, measure the volumetric flow rate of the gases (Qs) in the process vent or stack. The mass release rate of VC in the vent gases is to be calculated using equation S-1.3:
Mass Releases per Unit of Production
For the purpose of determining mass releases per unit of production, the plant production over the shift during which sampling occurred shall be determined by the tester from plant records. The production will then be pro-rated for the sampling period using equation S-1.4:
- B wo
fraction by volume of water vapour content of the sample gas in the sampling bag as calculated, assuming the gas in the bag is saturated at ambient conditions when sampled. If a condenser was used in the sampling train with ice, then the temperature of the gas in the sampling bag shall be assumed to be 0°C
- C b
VCin the sample,
ppm (v/v) (as determined by equation A-1.3 of A-1.6.3 within Part 2 of this Reference Method)
- C f
VC(dry basis) corrected for water vapour,
- C f'
VC(dry basis) corrected to 10% oxygen,
- ER VC
mass release rate of
- ER VC/PVC
mass release rate of
VC per production of
VC per 100
- P PVC
production rate of
PVC resin, in 100
kg increments of
PVC per day
- % O 2
concentration of oxygen in vent gases (dry basis), % by volume
- Q s
volumetric flow rate of vent gases on a dry basis, referenced to 25°C and 101.3 kPa, m
concentration of oxygen in ambient air, % by volume
percentage of oxygen in ambient air, less the 10% to which the correction is being made, % by volume
- 2.56 × 10 -6
3at 25°C and 101.3 kPa
- 8.64 × 10 4
- conversion factor, m 3/s to m 3/day
Figure S-1-1: Sampling train for vinyl chloride releases
Process Vent or Stack Diameter:
Sample Identifier Number:
Pitot Tube Coefficient:
Sample Taken by:
Proportional Sampling Constant:
* Identifier Number or Physical Location of Process Vent or Stack
|Local Time||Sampling Time (min)||Gas Temperature in Process Vent or Stack
|Gas Velocity in Process Vent or Stack||Sampling Flow Rate (mL/min)||Accumulated Sample Volume (L)|
|Δps(cm H2O)||(Δps)½ (m/s)|
Percentage of Oxygen in Stack during incineration Process:
Plant name and street address of site where sample was collected:
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