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2.1.6 Metering system. Vacuum gage, leakless pump, thermometers capable of measuring temperature to within 5oF, 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 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 8, or equivalent, with a coefficient within 5 percent over the working range.

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

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

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

2.2.5 Moisture determination. Drying tubes, condensers, or equivalent, to determine stack gas moisture content in hydrogen to within 1 percent.

2.3 Sample recovery-2.3.1 Leakless glass sample bottles. 500 ml and 200 ml with Teflon-lined tops.

2.3.2 Graduated cylinder. 250 ml. 2.3.3 Plastic jar. Approximately 300 ml. 2.4 Analysis-2.4.1 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, equivalent.

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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 percent 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 lodate and continue stirring until all free iodine has dissolved to give a clear orange-red solution. Cool to room temperature and dilute to 1,800 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. 3.1.9 Hydroxylamine sulfate.

grade.

Reagent

3.1.10 Sodium chloride. Reagent grade. 3.1.11 Mercuric chloride. Reagent grade. 3.2 Sampling. 3.2.1 Absorbing solution, 0.1M ICI. Dilute 100 ml of the 1.0M ICI stock solution (reagent 3.1.6) to 11 with distsilled 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 Wash acid. 1:1 V/V nitric acid-water. 3.2.3 Distilled, deionized water. 3.2.4 Silica gel. Indicating type, 6 to 16 mesh, dried at 350°F for 2 hours.

3.3. Analysis-3.3.1 Sodium hydroxide, 10N. Dissolve 400 g of sodium hydroxide pellets in distilled water and dilute to 1 1. 3.3.2 Reducing agent. 12 percent hydroIylamine 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 11 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 callbration 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 0.2 μg/ml, 0.4 μg/ml and 0.6 g/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 source 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 insure 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.

4.2.2 The sampling site should be at least eight stack or duct diameters downstream and two diameters upstream from any flow disturbance such as a bend, expansion or contraction. For rectangular cross section, determine an equivalent diameter from the following equation:

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4.2.3 When the above sampling site criteria can be met, the minimum number of traverse points is four (4) for stacks 1 foot in diameter or less, eight (8) for stacks larger than 1 foot but 2 feet in diameter or less, and twelve (12) for stacks larger than 2 feet.

4.2.4 Some sampling situations may render the above sampling site criteria impractical. When this is the case, choose a convenient sampling location and use figure 102-3 to determine the minimum number of traverse points. However, use figure 102-3 only for stacks 1 foot in diameter or larger.

4.2.5 To use figure 102-3, 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 trav

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erse points for each distance from figure 102-3. 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 stack wall, adjust the location of that point to insure 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 102-4 and table 102-1. 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 102-5.

4.4 Measurement of stack conditions.

4.4.1 Set up the apparatus as shown in agure 102-2. Make sure all connections are tight and leak free. Measure the velocity head and temperature at the traverse points specided by section 4.2 and 4.3.

4.4.2 Measure the static pressure in the stack.

4.4.8 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. 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 IC1,

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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 102-1.

4.5.2 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. Place crushed ice around the impingers. Add more ice during the run to keep the temperature of the gases leaving the last impinger at 70° F or less.

4.6 Mercury train operation.

4.6.1 Safety procedures. It is imperative that the sampler conduct the source test under conditions of utmost safety, since hydrogen and air mixtures are explosive. The sample train essentially is leakless, so that attention to safe operation can be concentrated at the inlet and outlet. The following specific items are recommended:

4.6.1.1 Operate only the vacuum pump during the test. The other electrical equipment, e.g. heaters, fans and timers, normally are not essential to the success of a hydrogen stream test.

4.6.1.2 Seal the sample port to minimize leakage of hydrogen from the stack.

4.6.1.3 Vent sampled hydrogen at least 10 feet away from the train. This can be accomplished easily by attaching a 2-in i.d. Tygon tube to the exhaust from the orifice meter.

4.6.2 For each run, record the data required on the sample sheet shown in figure 102-6. Take readings at each sampling point at least every 5 minutes and when significant changes in stack conditions necessitate additional adjustments in flow rate.

4.6.3 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. 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 lodine is liberated. In this case, a run may be divided into two or more subruns to insure that the absorbing solutions are not depleted.

4.6.4 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, using the following procedures.

Traverse point number

on a

diameter

Table 102-1. Location of traverse points in circular stacks
(Percent of stack diameter from inside wall to traverse point)

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75.0 29.5 19.4 14.6 11.8 9.9 8.5 7.5 6.7 6.0 5.5
93.3 70.5 32.3 | 22.6 17.7 14.6 12.5 10.9 9.7 8.7 7.9
85.3 67.7 34.2 25.0 20.1
95.6 80.6 65.8 35.5 26.9 22.0 18.8 16.5 14.6 13.2

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4.6.4.1 Nomographs which aid in the rapid adjustment of the sampling rate without other computations are in APTD-0576 and are available from commercial suppliers. The available nomographs, however, are set up for use in air streams, and minor changes are required to provide applicability to hydrogen. 4.6.4.2 Calibrate the meter box orifice. Use the techniques as described in APTD-0576.

4.6.4.3 The correction factor nomograph discussed in APTD-0576 and shown on the reverse side of commercial nomographs will not be used. In its place, the correction factor will be calculated using equation 102-2. (CM.) P. Tm AHO Pm M.

C=0.01

the meter box. Convert the hydrogen AP to an equivalent value for air by multiplying by a ratio of the molecular weight of air to hydrogen at the stack moisture content. Insert this value of AP onto the nomograph and read off AH. Again, convert the AH, which is an air equivalent value, to the AH for hydrogen by dividing by 13. This factor includes the ratio of the dry molecular weights and a correction for the different orince calibration factors for hydrogen and air. This procedure is diagrammed below:

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