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Vsoln Total solution volume of sulfur dioxide, 50 ml.

V1 = Volume of sample aliquot titrated, ml.

Vmstd=Volume of gas sample through the dry gas meter (standard conditions), cu. ft., see Equation 6-1.

7. References. Atmospheric Emissions from Sulfuric Acid Manufacturing Processes, U.S. DHEW, PHS, Division of Air Pollution, Public Health Service Publication No. 999-AP-13, Cincinnati, Ohio, 1965.

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m

°R

std

(P) equation 6-1

in. Hg (mbar)

Vm.td- Volume of gas sample through the dry gas meter (standard conditions), cu. ft.

V

m

=

Volume of gas sample through the dry gas meter (meter conditions), cu. ft.

Tstd Absolute temperature at standard conditions, 530° R.

=

Tm Average dry gas meter temperature, °R.

Fbar

Barometric pressure at the orifice meter, inches Hg.

Pstd - Absolute pressure at standard conditions, 29.92 inches Hg.

6.2

Sulfur dioxide concentration.

soln

(Vt-Vtb) N Vmstd

Va

equation 6-2

METHOD 7-DETERMINATION OF NITROGEN OXIDE EMISSIONS FROM STATIONARY SOURCES

1. Principle and applicability. 1.1

Principle. A grab sample is collected in an evacuated flask containing a dilute sulfuric acid-hydrogen peroxide absorbing solution, and the nitrogen oxides, except nitrous oxide, are measure colorimetrically using acid the phenoldisulfonic (PDS) procedure.

1.2 Applicability. This method is applicable for the measurement of nitrogen oxides from stationary sources only when specified by the test procedures for determining compliance with New Source Performance Standards.

2. Apparatus.

2.1 Sampling. See Figure 7–1. 2.1.1

Probe-Pyrex1 glass, heated, with filter to remove particulate matter. Heating is unnecessary if the probe remains dry during the purging period.

2.1.2 Collection flask-Two-liter, Pyrex,1 round bottom with short neck and 24/40 standard taper opening, protected against 'mplosion or breakage.

2.1.3 Flask valve-T-bore stopcock connected to a 24/40 standard taper joint.

2.1.4 Temperature gauge-Dial-type thermometer, or equivalent, capable of measuring 2° F. intervals from 25° to 125° F.

2.1.5 Vacuum line-Tubing capable of withstanding a vacuum of 3 inches Hg absolute pressure, with "T" connection and T-bore stopcock, or equivalent.

2.1.6 Pressure gauge-U-tube manometer, 36 inches, with 0.1-inch divisions, or equivalent.

1 Trade name.

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2.2.3. Glass wash bottle. 2.3 Analysis.

2.3.1 Steam bath. 2.3.2

Figure 7-1. Sampling train, flask valve, and flask.

Beakers or casseroles-250 ml., one for each sample and standard (blank). 2.3.3 Volumetric pipettes-1, 2, and 10 ml. 2.3.4 Transfer pipette-10 ml. with 0.1 ml. divisions.

2.3.5 Volumetric flask-100 ml., one for each sample, and 1,000 ml. for the standard (blank).

2.3.6 Spectrophotometer-To measure absorbance at 420 nm.

2.3.7 Graduated cylinder-100 ml. with 1.0 ml. divisions.

2.3.8 Analytical balance-To measure to 0.1 mg.

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Water-Deionized, distilled.

3.3.6 Phenoldisulfonic acid solutionDissolve 25 g. of pure white phenol in 150 ml. concentrated sulfuric acid on a steam bath. Cool, add 75 ml. fuming sulfuric acid, and heat at 100° C. for 2 hours. Store in a dark, stoppered bottle.

4. Procedure.

4.1 Sampling.

4.1.1 Pipette 25 ml. of absorbing solution into a sample flask. Insert the flask valve stopper into the flask with the valve in the "purge" position. Assemble the sampling train as shown in Figure 7-1 and place the probe at the sampling point. Turn the flask valve and the pump valve to their "evacuate" positions. Evacuate the flask to at least 3 inches Hg absolute pressure. Turn the pump

valve to its "vent" position and turn off the pump. Check the manometer for any fluctuation in the mercury level. If there is a visible change over the span of one minute, check for leaks. Record the initial volume, temperature, and barometric pressure. Turn the flask valve to its "purge" position, and then do the same with the pump valve. Purge the probe and the vacuum tube using the squeeze bulb. If condensation occurs in the probe and flask valve area, heat the probe and purge until the condensation disappears. Then turn the pump valve to its "vent" position. Turn the flask valve to its "sample" position and allow sample to enter the flask for about 15 seconds. After collecting the sample, turn the flask valve to its "purge" position and disconnect the flask from the sampling train. Shake the flask for 5 minutes.

4.2 Sample recovery.

4.2.1 Let the flask set for a minimum of 16 hours and then shake the contents for 2 minutes. Connect the flask to a mercury filled U-tube manometer, open the valve from the flask to the manometer, and record the flask pressure and temperature along with the barometric pressure. Transfer the flask contents to a container for shipment or to a 250 ml. beaker for analysis. Rinse the flask with two portions of distilled water (approximately 10 ml.) and add rinse water to the sample. For a blank use 25 ml. of absorbing solution and the same volume of distilled water as used in rinsing the flask. Prior to shipping or analysis, add sodium hydroxide (1N) dropwise into both the sample and the blank until alkaline to litmus paper (about 25 to 35 drops in each).

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water. Evaporate the solution to dryness on a steam bath and then cool. Add 2 ml. phenoldisulfonic acid solution to the dried residue and triturate thoroughly with a glass rod. Make sure the solution contacts all the residue. Add 1 ml. distilled water and four drops of concentrated sulfuric acid. Heat the solution on a steam bath for 3 minutes with occasional stirring. Cool, add 20 ml. distilled water, mix well by stirring, and add concentrated ammonium hydroxide dropwise with constant stirring until alkaline to litmus paper. Transfer the solution to a 100 ml. volumetric flask and wash the beaker three times with 4 to 5 ml. portions of distilled water. Dilute to the mark and mix thoroughly. If the sample contains solids, transfer a portion of the solution to a clean, dry centrifuge tube, and centrifuge, or filter a portion of the solution. Measure the absorbance of each sample at 420 nm. using the blank solution as a zero. Dilute the sample and the blank with a suitable amount of distilled water if absorbance falls outside the range of calibration.

5. Calibration.

5.1 Flask volume. Assemble the flask and flask valve and fill with water to the stopcock. Measure the volume of water to +10 ml. Number and record the volume on the flask.

5.2 Spectrophotometer. Add 0.0 to 16.0 ml. of standard solution to a series of beakers. To each beaker add 25 ml. of absorbing solution and add sodium hydroxide (1N) dropwise until alkaline to litmus paper (about 25 to 35 drops). Follow the analysis procedure of section 4.3 to collect enough data to draw a calibration curve of concentration in μg. NOз per sample versus absorbance.

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=(6.2x

ml.

C=Concentration of NO, as NO, (dry

basis), lb./s.c.1.

m=Mass of NO, in gas sample, μg. V.. Sample volume at standard conditions (dry basis), ml.

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6.2X10-lb./s.c.f.) (m.)

ug./ml.

7. References.

(

SC

equation 7-2

Standard Methods of Chemical Analysis. 6th ed. New York, D. Van Nostrand Co., Inc., 1962, vol. 1, p. 329-330.

Standard Method of Test for Oxides of Nitrogen in Gaseous Combustion Products

(Phenoldisulfonic Acid Procedure), In: 1968 Book of ASTM Standards, Part 23, Philadelphia, Pa. 1968, ASTM Designation D-1608-60, p. 725-729.

Jacob, M. B., The Chemical Analysis of Air Pollutants, New York, N.Y., Interscience Publishers, Inc., 1960, vol. 10, p. 351–356.

METHOD 8-DETERMINATION OF SULFURIC ACID MIST AND SULFUR DIOXIDE EMISSIONS FROM STATIONARY SOURCES

1. Principle and applicability.

1.1 Principle. A gas sample is extracted from a sampling point in the stack and the acid mist including sulfur trioxide is separated from sulfur dioxide. Both fractions are measured separately by the barium-thorin titration method.

1.2 Applicability. This method is applicable to determination of sulfuric acid mist (including sulfur trioxide) and sulfur dioxide from stationary sources only when specified by the test procedures for determining compliance with the New Source Performance Standards.

2. Apparatus.

2.1 Sampling. See Figure 8-1. Many of the design specifications of this sampling train are described in APTD-0581.

STACK WALL

2.1.1 Nozzle Stainless steel (316) with sharp, tapered leading edge.

1

2.1.2 Probe-Pyrex 1 glass with a heating system to prevent visible condensation during sampling.

2.1.3 Pitot tube-Type S, or equivalent, attached to probe to monitor stack gas velocity.

2.1.4 Filter holder-Pyrex 1 glass.

2.1.5 Impingers-Four as shown in Figure 8-1. The first and third are of the GreenburgSmith design with standard tip. The second and fourth are of the Greenburg-Smith design, modified by replacing the standard tip with a 2-inch ID glass tube extending to one-half inch from the bottom of the im

pinger flask. Similar collection systems, which have been approved by the Administrator, may be used.

2.1.6 Metering system-Vacuum gauge, leak-free pump, thermometers capable of measuring temperature to within 5° F., dry gas meter with 2% accuracy, and related equipment, or equivalent, as required to maintain an isokinetic sampling rate and to determine sample volume.

2.1.7 Barometer-To measure atmospheric pressure to ±0.1 inch Hg.

1 Trade name.

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VALVE

VACUUM LINE

Figure 8-1. Sulfuric acid mist sampling train.

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3.1.1 Filters Glass fiber, MSA type 1106 BH, or equivalent, of a suitable size to fit in the filter holder.

3.1.2 Silica gel-Indicating type, 6-16 mesh, dried at 175° C. (350° F.) for 2 hours. 3.1.3 Water Deionized, distilled.

3.1.4 Isopropanol, 80%-Mix 800 ml. of isopropanol with 200 ml. of deionized, distilled water.

3.1.5 Hydrogen peroxide, 3%-Dilute 100 ml. of 30% hydrogen peroxide to 1 liter with deionized, distilled water.

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4. Procedure.

4.1 Sampling.

4.1.1 After selecting the sampling site and the minimum number of sampling points, determine the stack pressure, temperature, moisture, and range of velocity head.

4.1.2 Preparation of collection train. Place 100 ml. of 80% isopropanol in the first impinger, 100 ml. of 3% hydrogen peroxide in both the second and third impingers, and about 200 g. of silica gel in the fourth impinger. Retain a portion of the reagents for use as blank solutions. Assemble the train without the probe as shown in Figure 8-1 with the filter between the first and second impingers. Leak check the sampling train at the sampling site by plugging the inlet to the first impinger and pulling a 15-inch Hg vacuum. A leakage rate not in excess of 0.02 c.f.m. at a vacuum of 15 inches Hg is acceptable. Attach the probe and turn on the probe heating system. Adjust the probe heater setting during sampling to prevent any visible condensation. 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.

4.1.3 Train operation. For each run, record the data required on the example sheet shown in Figure 8-2. Take readings at each sampling point at least every 5 minutes and when significant changes in stack conditions necessitate additional adjustments in flow rate. To begin sampling, position the nozzle at the first traverse point with the tip pointing directly into the gas stream. Start the pump and immediately adjust the flow to isokinetic conditions. Maintain isokinetic sampling throughout the sampling period. Nomographs are available which aid in the rapid adjustment of the sampling rate without other computations. APTD-0576 details the procedure for using these nomographs. At the conclusion of each run, turn off the pump and record the final readings. Remove the probe from the stack and disconnect it from the train. Drain the ice bath and purge the remaining part of the train by drawing clean ambient air through the system for 15 minutes.

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