Reference method for measuring emissions of vinyl chloride from manufacturing: part I S-1

Part I - Sampling: Method S-1

Sampling of Process Vents and Stacks in Vinyl Chloride and Polyvinyl Chloride Plants

S-1.1 Scope

This method applies to the sampling of process vents and stacks in vinyl chloride and polyvinyl chloride plants which are a source of vinyl chloride emissions into the atmosphere.

S-1.2 Apparatus

S-1.2.1 Sampling Train. (Figure S-1-1).

Figure S-1-1: Sampling Train for Vinyl Chloride Emissions

Sampling Train for Vinyl Chloride Emissions

S-1.2.2 Probe.

A suitable sampling probe may be made of stainless steel, Pyrex glass, Teflon or other inert material which does not absorb vinyl chloride. A glass wool plug shall be placed at the probe inlet to remove particulates from the sample.

S-1.2.3 Sampling Line.

The probe shall be connected to the sampling train using the minimum length of Teflon tubing of suitable size.

S-1.2.4 Condenser.

A condenser consisting of two glass midget impingers in an ice bath shall be used if required.

S-1.2.5 Rotameter.

A rotameter capable of measuring flows to ±25 ml/min in a range from 0 to 0.5 litres/min is required.

S-1.2.6 Pump.

A portable, battery-operated, intrinsically safe sampling pump is used to fill the sampling bag. The pump shall have both inlet and exhaust ports and a capacity of at least 200 ml/min.

S-1.2.7 Needle Valve.

Required to adjust the flow rate.

S-1.2.8 Quick-Connect.

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.

S-1.2.9 Sampling Bag.

The sample shall be collected in a 12-litre minimum capacity Tedlar, or equivalent, sampling bag.

S-1.2.10 Pitot Tube and Manometer.

A type-S pitot tube with manometer shall be attached to the probe so that the sampling flow 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 may be used.

S-1.3 Procedures

S-1.3.1 Sampling Site Selection.

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 bend, expansion, contraction or visible flame. For a rectangular cross-section an equivalent diameter shall be defined as twice the product of the length multiplied by the width, divided by the sum of the length and the width. The sampling point is to be at the centroid of the cross-section or near the point of maximum velocity if the velocity profile is atypical.

S-1.3.2 Sampling Continuous Sources.

Continuous sources are defined as sources which normally emit process vent gases continuously, whenever the plant is operating, and where the flow rate does not vary significantly.

Before beginning to collect the sample, the velocity profile in the stack should be determined. If the determination of the mass emission rate of vinyl chloride is required, then Method B, EPS 1-AP-74-1 is to be used to measure the vent gases' volumetric flow rate, Qs.

When incineration is used to control the vinyl chloride emissions, the stack gas composition must also be measured according to Method C, EPS 1-AP-74-1.

Measure the pertinent stack and ambient conditions as required and enter these on Figure S-1-2 before sampling. Repeat these measurements after the sample has been taken.

Figure S-1-2: Sampling Process Vents

Sampling Process Vents

Assemble the sampling train as in Figure S-1-1 but do not connect the bag. If moisture condensation in the train is expected include the condenser as shown. At the end of the run discard the water collected in the condenser. Ensure that the bag has been leak-checked and purged according to section S-1.5 before use. Ensure that all connections are tight. Place the end of the probe at the sampling point and start the pump with the needle valve adjusted to yield a flow of about 200 ml/min. Purge the train thoroughly, stop the pump and connect the bag. Begin sampling using a sample flow rate of approximately 200 ml/min. The sampling flow rate is thereafter adjusted every 5 minutes, maintaining constant the ratio of the sampling flow rate to the stack gas velocity.

The sampling is to be at least 1 hour in duration and continuous. At the end of the sample period, shut off the pump and disconnect the bag.

The data pertinent to the sample collection are entered on Figure S-1-2 every 5 minutes. The flow rates entered shall be the average flow rates indicated for the half-minute interval preceding the recording period.

A valid sample shall satisfy the following criteria:

  1. the stack gas velocity shall not at any time have deviated by more than ± 75% of the average velocity during the sampling period;
  2. the sampling flow rate shall be proportional to the stack gas velocity within 10%.

It is assumed that the vent gas composition, temperature or pressure do not change significantly during the sampling period.

S-1.3.3 Sampling Intermittent Sources.

An intermittent source is defined as one which normally only operates when required by the process and thus emits vent gases on an intermittent basis. Such sources are normally part of batch processes that operate in a cyclical manner. Continuous sources in which the flow varies widely within 1 hour and thus cannot satisfy the criteria for sample validity outlined in section S-1.3.2 shall be considered to fall within this section.

The sampling train described in section S-1.3.2 is to be used for the collection of samples from process vent gases emitted from intermittent sources.

Before beginning the sample collection, the velocity of the vent gases is to be measured for 2 or 3 cycles. The maximum stack gas velocity during any 5-minute period is to be noted.

Sampling may begin at any time. The sampling flow rate is to be proportional to the stack gas velocity with a sampling flow rate of 200 ml/min corresponding to the measured maximum stack gas velocity. No sample is drawn if there is no flow in the stack. The stack gas velocity is measured every 2 1/2 minutes and the sampling flow rate adjusted, maintaining constant the ratio of the sampling rate to the stack gas velocity. The pertinent data are entered on Figure S-1-2.

Sampling shall continue for at least 1 hour and until at least 6 litres of sample are collected as measured by the sampling train rotameter. If it is impossible to collect 6 litres within 4 hours under the sampling conditions described herein, or if the process vent operates sporadically or for relatively short periods, the appropriate regulatory agency shall be consulted before any modifications may be made to the sampling procedures.

S-1.4 Sample Storage and Analysis

Sample bags must be kept out of direct sunlight. Analysis is to be done within 24 hours of sample collection using Method A-1.

S-1.5 Sampling Bag Purge and Leak Check

Before each use, make sure the sample bag is purged and leak-free. To purge, alternately fill and evacuate the bag three times with zero air. To leak-check, connect a water manometer and pressurize the bag to 5-10 cm H2O. Allow to stand for 10 minutes. Any displacement in the water manometer indicates a leak. The leak check may be done during the third purge cycle.

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