Section 336.2006. Reference test method serving as alternate version of federal reference test method 25 by incorporating Byron analysis.

When using the alternate version of federal reference test method 25 incorporating the Byron analysis, the procedures in   method  25, which are described in R 336.2004, shall be followed, except that all of the following parts in method 25 are amended to read as follows:

1.2 Principle. An emission sample  is  withdrawn  from   a  stack  at  a constant rate through a stainless steel absorber tube packed with porasil; the gaseous portion of the sample is pulled past a battery-operated sampling pump into a tedlar bag. After sampling is complete, the contents of the tedlar bag are analyzed on an automated gas chromatograph (GC), and the sample in the porasil packed tube is heated to remove all components   for analysis on the GC. The  GC  separates   CO,  CO2,   and   CH4   from the nonmethane organics (NMO), then converts the NMOs to methane for analysis.

2.    Apparatus. The sampling system consists of a nonmethane organic (NMO) absorber tube, a sampling pump, and a sample bag (figure 25-1).  The analytical system has 2 parts the oven for removing the sample from the absorber tube and an automated gas chromatograph (GC).

2.1  Sampling. All of the following equipment is required,   as    shown   in figure 25-

1:

2.1.1      Heated  probe.   6.4-millimeter  (mm)      (1/4-inch      (in.))       outside diameter

(o.d.) stainless steel tubing  with   a  heating  system   that  is capable of maintaining a gas temperature at the exit end of not less than 129 degrees Centigrade (265 degrees Fahrenheit). The probe shall be equipped  with a thermocouple at the  exit   end  to monitor the   gas temperature. The nozzle is an elbow fitting that is attached  to  the front end of the probe while the thermocouple is inserted in the side arm of a tee fitting that is attached to the rear of the probe. The probe is wrapped with a suitable length of high-temperature heating tape and then covered with 2 layers of glass cloth insulation and 1  layer   of  aluminum foil.

2.1.2  Heated prefilter-only for stacks with possible particulate matter interference. A stainless steel filter holder with a  47-mm  type   A/E fiberglass filter without organic binder. The entire   prefilter   shall   be maintained at 110 degrees Celsius. Note - if it is not possible to use a heating system for safety reasons, an unheated  system with  an  instack filter is a suitable alternative.

2.1.3    NMO absorber tube. 1/2-inch inside diameter (i.d.) stainless steel tube packed with porasil (thermally stable silica gel).

2.1.4  1/4-inch o.d. teflon line that is 2 to 4 feet long.

2.1.5   Battery-operated diaphragm sampling pump with kurz digital mass flow meter. Total flow is integrated electronically to measure flow with an accuracy of 1% at any flow rate. (Byron instruments model 90).

2.1.6    Sample bag. 0.3-mil tedlar, 1/2-cubic foot capacity. The sample bag undergoes nitrogen purge cycle until analysis exhibits zero  carbon content in the sample bag.

2.2  Analysis. The following equipment is required:

2.2.1  Sample recovery on the adsorber tube is done in a  Byron   model    75 oven in 2 stages, each stage requiring a 0.3-mil tedlar bag  that  has  a 1/2-cubic foot capacity.

2.2.2  Analysis is done on a Byron model 401 gas chromatograph   (GC)  that meets all criteria specified in method 25, section 2.2.2.

2.3       NMO analyzer. The NMO analyzer is a   Byron  model  401  gas chromatograph (GC). (Remainder of 2.3 as stated in method 25)

2.3.5.2 Range. A full scale range of 1 to 10,000 parts per million (ppm) CH4. Signal attenuators shall be available to  produce  a  minimum   signal response of 10% of full scale.

3.1.1 Delete (dry ice is not required).

4.1.1  Model 90 and model 75 flow meter calibration. The model 90 sample pump inlet is attached to the outlet of the model 75 oven. Air is passed through the system at the rate that will be used in sampling and for the total volume anticipated to be sampled. If the  flow   meters  on  the  2 instruments do not agree within 0.01 liters, then adjust the meter on the model 90 until agreement is within  0.01   liters.  After making  any correction, run a full calibration again.

4.1.2   Sample train assembly. Assemble the probe (prefilter if needed), adsorber tube, and teflon line to the inlet of the model 90. Attach  a short (8 to 10 inches) flexible line to the outlet of model 90. Have  a completely clean evacuated tedlar sample bag nearby  for   collection  of sample to be analyzed.

4.1.3  Pretest leak check. Stopper the inlet of the probe  and  place   the flexible tube on the outlet of the model 90 in a small  open container of water. Turn on the sampling pump. For a satisfactory leak  check, bubbling should cease within 1 minute. If the leak check is unsatisfactory, tighten the fittings or change parts until a satisfactory leak check is obtained. 4.1.4 Sampling train operation. Place the probe and the front portion of the adsorption tube in the stack. If the stack has a temperature higher than ambient, allow time for the probe to heat before starting the sample pump. Start the model 90 pump and adjust  to   the  desired   flow,   usually about 90 ml/min. After about 0.1 liter of sampling, or equivalent to the volume of air that is displaced in the sample system before the flowmeter, remove the flexible tube from the outlet of the model 90 and install the evacuated tedlar bag. This assures that gaseous components are undiluted by the air originally in the sampling system. Record requested data on the data form during the sample time. The sampling is usually done for 1 hour with a total of 5 to 6 liters sampled. When sampling   is  complete,   record  the precise volume sampled. The process may require different sample times or sample volumes. (Sampling form is figure 25-8.)

4.1.5 Post test leak check. Remove the tedlar bag and replace it with the flexible tube. Stopper the probe and operate the same as the pretest leak check specified in section 4.1.3. If the leak test is not acceptable, invalidate the sample.

4.2   Sample recovery. The tedlar bag is ready for direct analysis on the GC. The adsorber tube shall undergo the following 2-stage preparation:

4.2.1   Sample purge. The absorber tube is placed in the Byron model  75 oven with a clean tedlar bag attached directly to the tube. A volume  of clean dry air is passed through the adsorber tube while holding the oven temperature at about 130 degrees Celsius. The volume of  air  should  be precisely the same as that sampled. This purge is necessary to remove any CO2 on the sample tube, and the elevated temperature is needed to  assure CO2 removal from any absorbed water. The  tedlar bag is  now   ready  for direct analysis on the GC.

4.2.2   Sample digest. The absorber tube, now free of CO2  and  the  lighter NMOs, is now attached to an oxidation catalyst, and another  tedlar  bag  is attached to the outlet of the oxidation catalyst. A volume of clean dry air equal to that sampled is passed through this system while the temperature on the sample tube is brought up to 600 degrees Celsius. If the sampled volume was less than 3 liters, a larger volume shall be used in the digestion to assure completion. Usually a multiple of precisely 1.5 or 2.0 of the sampled volume is sufficient. This third tedlar bag  is  now ready for direct analysis

on the GC. If anything other than CO2 is found in this bag, the model 75 oxidation catalyst   is  probably  in   need    of replacement. In this case the test would be invalid and would have  to  be redone.

4.3    Analysis. Each of the 3 bags is analyzed on the GC. Each bag should be analyzed as soon as possible after being filled. At  the  completion  of analysis, the bags shall be cleaned by repeated fillings with either clean air or nitrogen. Before being used again, the bags  shall   be  checked   by filling with clean air  and   then  analyzed on the GC to assure zero concentrations of all  analyzed  substances. All pertinent calibration, performance, and operational checks in sections 4.4 and 5 of method 25 apply to the Byron system.

6. Calculations.

6.1 Nomenclature.

C1 = Concentration of sample bag, ppm C, (NMO converted to methane). C2 = Concentration of purge bag, ppm C, (NMO converted to methane). C3 = Concentration of digest bag, ppm C, (CO2 converted to methane).

C = Ppm C (NMO).

6.2-6.4 (Delete).

6.5 C1, C2, C3 calculated directly as: ppm C calibration gas x GC reading unknown

= ppm C   GC reading calibration gas                  unknown 6.6 C = C1 + C2 + C3 Delete figures 25.3, 25.4, 25.9, and 25.10 from method 25. Amend figures 25.1 and 25.8 from method 25 to read as follows:

FIGURE 25.1 SAMPLING TRAIN

FIGURE 25.1

History: 1993 AACS.