NOTE: This method does not include all of the specifications (e.g., equipment and supplies) and procedures (e.g., sampling and analytical) essential to its performance. Some material is incorporated by reference from other methods in this part. Therefore, to obtain reliable results, persons using this method should have a thorough knowledge of at least the following additional test methods: Method 1, Method 4, and Method 5.Content [ show/hide ].
This method is applicable for the determination of CO emissions at petroleum refineries. This method serves as the reference method in the relative accuracy test for nondispersive infrared (NDIR) CO continuous emission monitoring systems (CEMS) that are required to be installed in petroleum refineries on fluid catalytic cracking unit catalyst regenerators [ 60.105(a)(2) of this part].
Adherence to the requirements of this method will enhance the quality of the data obtained from air pollutant sampling methods.
An integrated gas sample is extracted from the stack, passed through an alkaline permanganate solution to remove sulfur oxides and nitrogen oxides, and collected in a Tedlar Bag. The CO concentration in the sample is measured spectrophotometrically using the reaction of CO with p-sulfaminobenzoic acid.
Sulfur oxides, nitric oxide, and other acid gases interfere with the colorimetric reaction. They are removed by passing the sampled gas through an alkaline potassium permanganate scrubbing solution. Carbon dioxide (CO2) does not interfere, but, because it is removed by the scrubbing solution, its concentration must be measured independently and an appropriate volume correction made to the sampled gas.
This method may involve hazardous materials, operations, and equipment. This test method may not address all of the safety problems associated with its use. It is the responsibility of the user of this test method to establish appropriate safety and health practices and determine the applicability of regulatory limitations prior to performing this test method. The analyzer users manual should be consulted for specific precautions to be taken with regard to the analytical procedure.
The following reagents are hazardous. Personal protective equipment and safe procedures are useful in preventing chemical splashes. If contact occurs, immediately flush with copious amounts of water for at least 15 minutes. Remove clothing under shower and decontaminate. Treat residual chemical burns as thermal burns.
Causes severe damage to eyes and skin. Inhalation causes irritation to nose, throat, and lungs. Reacts exothermically with limited amounts of water.
The sampling train shown in Figure 10A-1 is required for sample collection. Component parts are described below:
Stainless steel, sheathed Pyrex glass, or equivalent, equipped with a glass wool plug to remove particulate matter.
Three Greenburg-Smith impingers connected in series with leak-free connections.
Leak-free pump with stainless steel and Teflon parts to transport sample at a flow rate of 300 ml/min (0.01 ft3/min) to the flexible bag.
Installed between the pump and the rate meter to eliminate the pulsation effect of the pump on the rate meter.
Rotameter, or equivalent, to measure flow rate at 300 ml/min (0.01 ft3/min). Calibrate according to Section 10.2.
tedlar, or equivalent, with a capacity of 10 liters (0.35 ft3) and equipped with a sealing quick-connect plug. The bag must be leak-free according to Section 8.1. For protection, it is recommended that the bag be enclosed within a rigid container.
Stainless-steel needle valve to adjust flow rate, and stainless-steel three-way valve, or equivalent.
Fyrite, or equivalent, to measure CO2 concentration to within O.5 percent.
console meter, capable of measuring the sample volume under calibration conditions of 300 ml/min (0.01 ft3/min) for 10 minutes.
A water filled U-tube manometer, or equivalent, of about 30 cm (12 in.) to leak-check the flexible bag.
Single- or double-beam to measure absorbance at 425 and 600 nm. Slit width should not exceed 20 nm.
U-tube mercury manometer, 1 meter (39 in.), with 1-mm divisions, or other gauge capable of measuring pressure to within 1 mm Hg.
Capable of evacuating the gas reaction bulb to a pressure equal to or less than 40 mm Hg absolute, equipped with coarse and fine flow control valves.
Mercury, aneroid, or other barometer capable of measuring atmospheric pressure to within 1 mm Hg.
Pyrex glass, 100-ml with Teflon stopcock (Figure 10A-2), leak-free at 40 mm Hg, designed so that 10 ml of the colorimetric reagent can be added and removed easily and accurately. Commercially available gas sample bulbs such as Supelco Catalog No. 2-2161 may also be used.
Stainless steel, with connections for three reaction bulbs and the appropriate connections for the manometer and sampling bag as shown in Figure 10A-3.
Class A, 10-ml size.
Reciprocating-stroke type such as Eberbach Corporation, Model 6015. A rocking arm or rotary-motion type shaker may also be used. The shaker must be large enough to accommodate at least six gas sample bulbs simultaneously. It may be necessary to construct a tabletop extension for most commercial shakers to provide sufficient space for the needed bulbs (Figure 10A-4).
Stainless steel shut-off valve.
Capable of weighing to 0.1 mg.
Unless otherwise indicated, all reagents shall conform to the specifications established by the Committee on Analytical Reagents of the American Chemical Society, where such specifications are available; otherwise, the best available grade shall be used.
Deionized distilled, to conform to ASTM D 1193-77 or 91, Type 3 (incorporated by reference--see 60.17). If high concentrations of organic matter are not expected to be present, the potassium permanganate test for oxidizable organic matter may be omitted.
7.1.2 Alkaline Permanganate Solution, 0.25 M KMnO4/1.5 M Sodium Hydroxide (NaOH). Dissolve 40 g KMnO4 and 60 g NaOH in approximately 900 ml water, cool, and dilute to 1 liter.
Same as in Section 7.1.1.
Dissolve 40 g NaOH in approximately 900 ml of water, cool, and dilute to 1 liter.
Dilute 50 ml of the 1 M NaOH solution prepared in Section 7.2.2 to 500 ml.
Dissolve 8.5 g AgNO3 in water, and dilute to 500 ml.
Dissolve 10.0 g p-SABA in 0.1 M NaOH, and dilute to 500 ml with 0.1 M NaOH.
To a flask, add 100 ml of 0.1 M p-SABA solution and 100 ml of 0.1 M AgNO3 solution. Mix, and add 50 ml of 1 M NaOH with shaking. The resultant solution should be clear and colorless. This solution is acceptable for use for a period of 2 days.
Traceable to National Institute of Standards and Technology (NIST) standards and containing between 50 and 1000 ppm CO in nitrogen. At least two concentrations are needed to span each calibration range used (Section 10.3). The calibration gases must be certified by the manufacturer to be within 2 percent of the specified concentrations.
While a bag leak-check is required after bag use, it should also be done before the bag is used for sample collection. The bag should be leak-checked in the inflated and deflated condition according to the following procedure:
8.1.1 Connect the bag to a water manometer, and pressurize the bag to 5 to 10 cm H2O (2 to 4 in H2O). Allow the bag to stand for 60 minutes. Any displacement in the water manometer indicates a leak.
8.1.2 Evacuate the bag with a leakless pump that is connected to the downstream side of a flow indicating device such as a 0- to 100-ml/min rotameter or an impinger containing water. When the bag is completely evacuated, no flow should be evident if the bag is leak-free.
Assemble the apparatus as shown in Figure 10A-1. Loosely pack glass wool in the tip of the Probe. Place 400 ml of alkaline permanganate solution in the first two impingers and 250 ml in the third. Connect the pump to the third impinger, and follow this with the surge tank, rate meter, and 3-way valve. Do not connect the Tedlar Bag to the system at this time.
8.2.2 Leak-check the sampling system by plugging the Probe inlet, opening the 3-way valve, and pulling a vacuum of approximately 250 mm Hg on the system while observing the rate meter for flow. If flow is indicated on the rate meter, do not proceed further until the leak is found and corrected.
8.2.3 Purge the system with sample gas by inserting the Probe into the stack and drawing the sample gas through the system at 300 ml/min ± 10 percent for 5 minutes. Connect the evacuated Tedlar Bag to the system, record the starting time, and sample at a rate of 300 ml/min for 30 minutes, or until the Tedlar Bag is nearly full. Record the sampling time, the barometric pressure, and the ambient temperature. Purge the system as described above immediately before each sample.
8.2.4 The scrubbing solution is adequate for removing sulfur oxides and nitrogen oxides from 50 liters (1.8 ft3) of stack gas when the concentration of each is less than 1,000 ppm and the CO2 concentration is less than 15 percent. Replace the scrubber solution after every fifth sample.
Measure the CO2 content in the stack to the nearest 0.5 percent each time a CO sample is collected. A simultaneous grab sample analyzed by the Fyrite analyzer is acceptable.
Same as Method 5, Section 9.2.
NOTE: Maintain a laboratory log of all calibrations.
Weigh the empty bulb to the nearest 0.1 g. Fill the bulb to the stopcock with water, and again weigh to the nearest 0.1 g. Subtract the tare weight, and calculate the volume in liters to three significant figures using the density of water at the measurement temperature. Record the volume on the bulb. Alternatively, mark an identification number on the bulb, and record the volume in a notebook.
Assemble the system as shown in Figure 10A-1 (the impingers may be removed), and attach a volume meter to the Probe inlet. Set the rotameter at 300 ml/min, record the volume meter reading, start the pump, and pull ambient air through the system for 10 minutes. Record the final volume meter reading. Repeat the procedure and average the results to determine the volume of gas that passed through the system.
Prepare at least two sets of three bulbs as standards to span the 0 to 400 or 400 to 1000 ppm range. If any samples span both concentration ranges, prepare a calibration curve for each range using separate reagent blanks. Prepare a set of three bulbs containing colorimetric reagent but no CO to serve as a reagent blank. Analyze each standard and blank according to the sample analysis procedure of Section 11.0 Reject the standard set where any of the individual bulb absorbances differs from the set mean by more than 10 percent.
10.3.2 Calculate the average absorbance for each set (3 bulbs) of standards using Equation 10A-1 and Table 10A-1. Construct a graph of average absorbance for each standard against its corresponding concentration. Draw a smooth curve through the points. The curve should be linear over the two concentration ranges discussed in Section 13.3.
11.1 Assemble the system shown in Figure 10A-3, and record the information required in Table 10A-1 as it is obtained. Pipet 10.0 ml of the colorimetric reagent into each gas reaction bulb, and attach the bulbs to the system. Open the stopcocks to the reaction bulbs, but leave the valve to the Tedlar Bag closed. Turn on the pump, fully open the coarse-adjust flow valve, and slowly open the fine-adjust valve until the pressure is reduced to at least 40 mm Hg. Now close the coarse adjust valve, and observe the manometer to be certain that the system is leak-free. Wait a minimum of 2 minutes. If the pressure has increased less than 1 mm Hg, proceed as described below. If a leak is present, find and correct it before proceeding further.
11.2 Record the vacuum pressure (Pv) to the nearest 1 mm Hg, and close the reaction bulb stopcocks. Open the Tedlar Bag valve, and allow the system to come to atmospheric pressure. Close the bag valve, open the pump coarse adjust valve, and evacuate the system again. Repeat this fill/evacuation procedure at least twice to flush the manifold completely. Close the pump coarse adjust valve, open the Tedlar Bag valve, and let the system fill to atmospheric pressure. Open the stopcocks to the reaction bulbs, and let the entire system come to atmospheric pressure. Close the bulb stopcocks, remove the bulbs, record the room temperature and barometric pressure (Pbar, to nearest mm Hg), and place the bulbs on the shaker table with their main axis either parallel to or perpendicular to the plane of the table top. Purge the bulb-filling system with ambient air for several minutes between samples. Shake the samples for exactly 2 hours.
11.3 Immediately after shaking, measure the absorbance (A) of each bulb sample at 425 nm if the concentration is less than or equal to 400 ppm CO or at 600 nm if the concentration is above 400 ppm.
NOTE: This may be accomplished with multiple bulb sets by sequentially collecting sets and adding to the shaker at staggered intervals, followed by sequentially removing sets from the shaker for absorbance measurement after the two-hour designated intervals have elapsed.
11.4 Use a small portion of the sample to rinse a spectrophotometer cell several times before taking an aliquot for analysis. If one cell is used to analyze multiple samples, rinse the cell with deionized distilled water several times between samples. Prepare and analyze standards and a reagent blank as described in Section 10.3. Use water as the reference. Reject the analysis if the blank absorbance is greater than 0.1. All conditions should be the same for analysis of samples and standards. Measure the absorbances as soon as possible after shaking is completed.
11.5 Determine the CO concentration of each bag sample using the calibration curve for the appropriate concentration range as discussed in Section 10.3.
Carry out calculations retaining at least one extra decimal figure beyond that of the acquired data. Round off figures after final calculation.
A = Sample absorbance, uncorrected for the reagent blank.
Ar = Absorbance of the reagent blank.
As = Average sample absorbance per liter, units/liter.
Bw = Moisture content in the bag sample.
C = CO concentration in the stack gas, dry basis, ppm.
Cb = CO concentration of the bag sample, dry basis, ppm.
Cg = CO concentration from the calibration curve, ppm.
F = Volume fraction of CO2 in the stack.
n = Number of reaction bulbs used per bag sample.
Pb = Barometric pressure, mm Hg.
Pv = Residual pressure in the sample bulb after evacuation, mm Hg.
Pw = Vapor pressure of H2O in the bag (from Table 10A-2), mm Hg.
Vb = Volume of the sample bulb, liters.
Vr = Volume of reagent added to the sample bulb, 0.0100 liter.
Calculate As for each gas bulb using Equation 10A-1, and record the value in Table 10A-1. Calculate the average As for each bag sample, and compare the three values to the average. If any single value differs by more than 10 percent from the average, reject this value, and calculate a new average using the two remaining values.
NOTE: A and Ar must be at the same wavelength.
Calculate Cb using Equations 10A-2 and 10A-3. If condensate is visible in the Tedlar Bag, calculate Bw using Table 10A-2 and the temperature and barometric pressure in the analysis room. If condensate is not visible, calculate Bw using the temperature and barometric pressure at the sampling site.
The estimated intralaboratory standard deviation of the method is 3 percent of the mean for gas samples analyzed in duplicate in the concentration range of 39 to 412 ppm. The interlaboratory precision has not been established.
The method contains no significant biases when compared to an NDIR analyzer calibrated with NIST standards.
Approximately 3 to 1800 ppm CO. Samples having concentrations below 400 ppm are analyzed at 425 nm, and samples having concentrations above 400 ppm are analyzed at 600 nm.
The detection limit is 3 ppmv based on a change in concentration equal to three times the standard deviation of the reagent blank solution.
The individual components of the colorimetric reagent are stable for at least 1 month. The colorimetric reagent must be used within 2 days after preparation to avoid excessive blank correction. The samples in the Tedlar Bag should be stable for at least 1 week if the bags are leak-free.
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2. Ferguson, B. B., R.E. Lester, and W.J. Mitchell. Field Evaluation of Carbon Monoxide and Hydrogen Sulfide Continuous Emission Monitors at an Oil Refinery. U.S. Environmental Protection Agency, Research Triangle Park, N.C. Publication No. EPA-600/4-82-054. August 1982. 100 pp.
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4. Levaggi, D.A., and M. Feldstein. The Colorimetric Determination of Low Concentrations of Carbon Monoxide. Industrial Hygiene Journal. 25:64-66. January-February 1964.
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