measuring temperature to within 5° F, dry gas meter with 2 percent accuracy, and related equipment, described in APTD-0581, to maintain an isokinetic sampling rate and to determine sample volume.

2.1.7 Filter Holder (optional) -Pyrex glass. A filter may be used in cases where the gas stream to be sampled contains large quantitles of particulate matter. The filter holder must provide a positive seal against leakage from outside or around the filter. A heating system capable of maintaining the filter at a minimum temperature of 250° F. should be used to prevent condensation from occurring.

2.1.8 Barometer. To measure atmospheric pressure to ±0.1 in Hg.

2.2 Measurement of stack conditions (stack pressure, temperature, moisture and velocity)-2.2.1 Pitot tube. Type S, or equivalent, with a coefficient within 5 percent over the working range.

2.2.2 Differential pressure gauge, Inclined manometer, or equivalent, to measure velocity held to within 10 percent of the minimum value. Micromanometers should be used if warranted.

2.2.3 Temperature gauge. Any temperature measuring device to measure stack temperature to within 1° F.

2.2.4 Pressure gauge. Pitot tube and inclined manometer, or equivalent, to measure stack pressure to within 0.1 in Hg.

2.2.5 Moisture determination. Wet and dry bulb thermometers, drying tubes, condensers, or equivalent, to determine stack gas moisture content to within 1 percent.

2.3 Sample recovery-2.3.1 Leakless glass sample bottles. 500 ml and 100 ml with Teflon lined tops.

Analysis-2.4.1

2.3.2 Graduated cylinder. 250 ml. 2.3.3 Plastic jar. Approximately 300 ml. 2.4 Spectrophotometer. To measure absorbance at 253.7 nm. Perkin Elmer Model 303, with a cylindrical gas cell (approximately 1.5 in. O.D. x 7 in.) with quartz glass windows, and hollow cathode source, or equivalent.

2.4.2 Gas sampling bubbler. Tudor Scientific Glass Co., Smog Bubbler, Catalogue No. TP-1150, or equivalent.

2.4.3 Recorder. To match output of spectrophotometer.

3. Reagents-3.1 Stock reagents-3.1.1 Potassium iodide. Reagent grade.

3.1.2 Distilled water-3.1.3 Potassium iodide solution, 25 percent. Dissolve 250 g of potassium iodide (reagent 3.1.1) in distilled water and dilute to 1 to 1.

3.1.4 Hydrochloric acid. Concentrated. 3.1.5. Potassium iodate. Reagent grade. 3.1.6 Iodine monochloride (ICI) 1.0M. To 800 ml. of 25% potassium iodide solution (reagent 3.1.3), add 800 ml. of concentrated hydrochloric acid. Cool to room temperature. With vigorous stirring, slowly add 135 g. of potassium iodate and continue stirring until all free iodine has dissolved to give a clear orange-red solution. Cool to room temperature and dilute to 1800 ml. with distilled water. The solution should be kept in amber bottles to prevent degradation.

3.1.7 Sodium hydroxide pellets. Reagent grade.

3.1.8 Nitric acid. Concentrated. grade.

3.1.9 Hydroxylamine sulfate. Reagent 3.1.10 Sodium chloride. Reagent grade. 3.1.11 Mercuric chloride. Reagent grade. 3.2 Sampling-3.2.1 Absorbing solution, 01M ICI. Dilute 100 ml. of the 1.0M ICI stock solution (reagent 3.1.6) to 1 to 1 with distilled water. The solution should be kept in glass bottles to prevent degradation. This reagent should be stable for at least 2 months; however, periodic checks should be performed to insure quality.

3.2.2

water.

Wash acid. 1:1 V/V nitric acid

3.2.3 Distilled, deionized water. 3.2.4 Silica gel. Indicating type, 6 to 16 mesh dried at 350° F. for 2 hours.

3.2.5 Filter (optional). Glass fiber, Mine Safety Appliances 1106BH, or equivalent. A filter may be necessary in cases where the gas stream to be sampled contains large quantities of particulate matter.

3.3 Analysis-3.3.1 Sodium hydroxide, 10 N. Dissolve 400 g of sodium hydroxide pellets in distilled water and dilute to 1 to 1. 3.3.2 Reducing agent, 12 percent hydrozylamine sulfate, 12 percent sodium chloride. To 60 ml of distilled water, add 12 g

of hydroxylamine sulfate and 12 g of sodium chloride. Dilute to 100 ml. This quantity is sufficient for 20 analyses and must be prepared daily.

3.3.3 Aeration gas.—Zero grade air.

3.3.4 Hydrochloric acid, 0.3N.-Dilute 25.5 ml of concentrated hydrochloric acid to 1 to 1 with distilled water.

3.4 Standard mercury solutions-3.4.1 Stock solution.-Add 0.1354 g of mercuric chloride to 80 ml of 0.3N hydrochloric acid. After the mercuric chloride has dissolved, add 0.3N hydrochloric acid and adjust the volume to 100 ml. One ml of this solution is equivalent to 1 mg of free mercury.

3.4.2 Standard solutions.-Prepare calibration solutions by serially diluting the stock solution (3.4.1) with 0.3N hydrochloric acid. Prepare solutions at concentrations in the linear working range for the instrument to be used. Solutions of 0.2μg/ml, 0.4 μg/ml and 0.6 μg/ml have been found acceptable for most instruments. Store all solutions in glass-stoppered, glass bottles. These solutions should be stable for at least 2 months; however, periodic checks should be performed to insure quality.

4. Procedure.-4.1 Guidelines for sour testing are detailed in the following sections These guidelines are generally applicable; however, most sample sites differ to some degree and temporary alterations such as stack extensions or expansions often are required to ensure the best possible sample site. Further, since mercury is hazardous, care should be taken to minimize exposure. Finally, since the total quantity of mercury to be collected generally is small, the test must be carefully conducted to prevent contamination or loss of sample.

4.2 Selection of a sampling site and minimum number of traverse points:

4.2.1 Select a suitable sampling site that is as close as is practicable to the point of atmospheric emission. If possible, stacks smaller than 1 foot in diameter should not be sampled.

venient sampling location and use figure 101-3 to determine the minimum number of traverse points. However, use figure 101-3 only for stacks 1 foot in diameter or larger. 4.2.5 To use figure 101-3, first measure the distance from the chosen sampling location to the nearest upstream and downstream disturbances. Divide this distance by the diameter or equivalent diameter to determine the distance in terms of pipe diameters. Determine the corresponding number of traverse points for each distance from figure 101-3. Select the higher of the two numbers of traverse points, or a greater value, such that for circular stacks the number is a multiple of four, and for rectangular stacks the number follows the criteria of section 4.3.2.

4.2.6 If a selected sampling point is closer than 1 inch from the stack wall, adjust the location of that point to ensure that the sample is taken at least 1 inch away from the wall.

4.3 Cross sectional layout and location of traverse points:

4.3.1 For circular stacks locate the traverse points on at least two diameters according to figure 101-4 and table 101-1. The traverse axes shall divide the stack cross section into equal parts.

4.3.2 For rectangular stacks divide the cross section into as many equal rectangular

areas as traverse points, such that the ratio of the length to the width of the elemental areas is between one and two. Locate the traverse points at the centroid of each equal area according to figure 101-5.

4.4

Measurement of stack conditions:

4.4.1 Set up the apparatus as shown in figure 101-2. Make sure all connections are tight and leak-free. Measure the velocity head and temperature at the traverse points specified by section 4.2 and 4.3.

4.4.2 Measure the static pressure in the stack.

4.4.3 Determine the stack gas moisture. 4.4.4 Determine the stack gas molecular weight from the measured moisture content and knowledge of the expected gas stream composition. A standard Orsat analyzer has been found valuable at combustion sources. In all cases, sound engineering judgment should be used.

4.5 Preparation of sampling train:

4.5.1 Prior to assembly, clean all glassware (probe, impingers, and connectors) by rinsing with wash acid, tap water, 0.1M ICI, tap water, and finally distilled water. Place 100 ml of 0.1M IC1 in each of the first three impingers, and place approximately 200 g of preweighed silica gel in the fourth impinger. Save 80 ml of the 0.1M IC1 as a blank in the sample analysis. Set up the train and the probe as in figure 101-1.

Traverse point number

on a

diameter

16.5 14.6 13.2 28.3 23.6 20.4 18.0 16.1

94.3 87.5 81.2 75.0 98.2 91.5 85.4 79.6

23.0

39.3 32.3 60.739.8

68.5 60.2 73.9 | 67.7°

95.1 89.1 83.5 78.2 72.8

98.4 92.5 87.1 82.0 77.0

95.6 90.385.4 80.6

98.6 93.3 88.4 83.9 96.1 91.3 86.8

98.7 94.0 89.5

96.592.1

9.9

8.5 7.5 6.7 6.0 5.5 12.5 10.9 16.9 14.6

9.7 8.7 7.9

12.911.6 10.5

98.9 94.5

23

24

4.5.2 If the gas stream to be sampled is excessively dirty or moist, the first impinger may clog or become dilute too rapidly for sufficient testing. A filter can be placed ahead of the impingers to collect the particulates. An initial empty impinger may also be used to remove excess moisture. If a fifth impinger is required, the final impinger may have to be carefully taped to the outside of the sample box.

4.5.3 Leak check the sampling train at the sampling site. The leakage rate should not be in excess of 1 percent of the desired sampling rate. If condensation in the probe or filter is a problem, probe and filter heaters will be required. Adjust the heaters to provide a temperature of at least 250° F. Place crushed ice around the impingers. Add more ice during the test to keep the temperature

96.8 98.9

of the gases leaving the last impinger at 70° F or less.

4.6 Mercury train operation:

4.6.1 For each run, record the data required on the example sheet shown in figure 101-6. Take readings at each sampling point at least every 5 minutes and when significant changes in stack conditions necessitate additional adjustments in flow rate.

4.6.2 Sample at a rate of 0.5 to 1.0 cfm. Samples shall be taken over such a period or periods as are necessary to accurately determine the maximum emissions which would occur in a 24-hour period. In the case of cyclic operations, sufficient tests shall be made so as to allow accurate determination or calculation of the emissions which will occur over the duration of the cycle. A minimum sample time of 2 hours is recommended.

Figure 101-5. Cross section of rectangular stack divided into 12 equal areas, with traverse points at centroid of each area.

In some instances, high mercury concentrations can prevent sampling in one run for the desired minimum time. This is indicated by reddening in the first impinger as free iodine is liberated. In this case, a run may be divided into two or more subruns to ensure that the absorbing solutions are not depleted.

4.6.3 To begin sampling, position the nozzle at the first traverse point with the tip pointing directly into the gas stream. Immediately start the pump and adjust the flow to isokinetic conditions. Sample for at least 5 minutes at each traverse point; sampling time must be the same for each point. Maintain isokinetic sampling throughout the sampling period. Nomographs which aid in the rapid adjustment of the sampling rate without other computations are in APTD0576 and are available from commercial suppliers. Note the standard nomographs are applicable only for type S pitot tubes and air or a stack gas with an equivalent density. Contact EPA or the sampling train supplier for instructions when the standard nomograph is not applicable.

4.6.4 Turn off the pump at the conclusion of each run and record the final readings. Immediately remove the probe and nozzle from the stack and handle in accordance with the sample recovery process described in section 4.7.

500 ml sample bottle. Rinse the probe and all glassware between it and the back half of the third impinger with two 50 ml portions of 0.1M ICl solution. Add these rinses to the first sample bottle. For a blank, place 80 ml of the 0.1M IC1 in a 100 ml sample bottle. If used, place the filter along with 100 ml of 0.1M IC in another 100 ml sample bottle. Retain a filter blank. Place the silica gel in the plastic jar. Seal and secure all containers for shipment. If an additional test is desired, the glassware can be carefully double rinsed with distilled water and reassembled. However, if the glassware is to be out of use more than 2 days, the initial acid wash procedure must be followed.

4.8.1 Apparatus preparation.-Clean all glassware according to the procedure of section 4.5.1. Adjust the instrument settings according to the instrument manual, using an absorption wavelength of 253.7 nm.

4.8.2 Analysis preparation.-Adjust the air delivery pressure and the needle valve to obtain a constant airflow of about 1.3 to/ 1/min. The analysis tube should be bypassed except during aeration. Purge the equipment for 2 minutes. Prepare a sample of mercury standard solution (3.4.2) according to section 4.8.3. Place the analysis tube in the line, and aerate until a maximum peak height is reached on the recorder. Remove the analysis tube, flush the lines, and rinse the analysis tube with distilled water. Repeat with another sample of the same standard solution. This purge and analysis cycle is to be repeated until peak heights are reproducible.

4.8.3 Sample preparation.-Just prior to analysis, transfer a sample aliquot of up to 50 ml to the cleaned 100 ml analysis tube. Adjust the volume to 50 ml with 0.1M 1C1 if required. Add 5 ml of 10 N sodium hydroxide, cap tube with a clean glass stopper and shake vigorously. Prolonged, vigorous shaking at this point is necessary to obtain an accurate analysis. Add 5 ml of the reducing agent (reagent 3.3.2), cap tube with a clean glass stopper and shake vigorously and immediately in sample line.

4.8.4 Mercury determination.-After the system has been stabilized, prepare samples from the sample bottle according to section 4.8.3. Aerate the sample until a maximum peak height is reached on the recorder. The mercury content is determined by comparing the peak heights of the samples to the peak heights of the calibration solutions. If collected samples are out of the linear range, the samples should be diluted. Prepare a blank from the 100 ml bottle according to section 4.8.3 and analyze to determine the reagent blank mercury level.