1、* Revision submitted by ICAC on August 18, 2004ICAC Proposed Conditional Test Method (CTM-042)*Use of Flame Ionization Detector-Methane Cutter Analysis Systems for VOC Compliance Testing of Bakeries1.0 BackgroundPerformance testing of volatile organic compounds (VOC) destruction devices such as ther
2、mal oxidizers and catalytic oxidizers require simultaneous measurements of non-methane hydrocarbons (NMHC) in the gas streams entering and exiting the destruction device. In the past, continuous total hydrocarbon measurements employing testing protocol in accordance with U.S. EPA Test Method 25A (Ga
3、seous Organic Concentration - Flame Ionization) has been combined with laboratory analysis of grab samples taken hourly. This approach has been demonstrated to be labor intensive, costly and does not provide real-time measurements necessary to evaluate the performance of the thermal or catalytic oxi
4、dizer.2.0 PurposeUse of this method is limited to measuring VOC emissions from bakeries. The purpose of this Conditional Test Method (CTM) is to provide an alternate method for making real-time non-methane hydrocarbon measurements for providing immediate information regarding performance of the VOC
5、destruction device. This method describes the use of a hot flame ionization detector (FID) based instrument equipped with a catalytic methane cutter in conjunction with U.S. EPA Test Method 25A to provide real-time differential measurement of total hydrocarbons, methane and by difference non-methane
6、 hydrocarbons.This CTM is directly applicable to large commercial bakeries. The measurement of VOCs in bakeries is required to verify air pollution control equipment destruction efficiency as required by various state regulations. The large majority of these state regulations are State Implementatio
7、n Plan (SIP) driven. A minority of states have “State Only” legislation requiring oxidizes, and testing of them, on bakeries.Extensive commercial data has been gathered from large commercial bakeries, where exhaust gases from ovens baking bread, crackers and other yeast products are tested. These ex
8、haust streams typically contain ethanol in concentrations of 1,000 to 5,000 ppm, methane in concentrations of 50 to 1000 ppm and moisture at 2 to 15%. A catalytic oxidizer on this application will destroy 95-99% of the non-methane hydrocarbons, reducing the ethanol to concentrations of 10 ppm to 250
9、 ppm in the oxidizer exhaust. The other compounds will virtually maintain their concentrations. Due to the large amounts of moisture and the water solubility of the non-methane hydrocarbon, condensation must be avoided. The relatively large amount of methane to non-methane hydrocarbon, especially in
10、 the oxidizer exhaust, makes it more important to make this measurement by one technique. * Revision submitted by ICAC on August 18, 20043.0 Technical ApproachA heated flame ionization analyzer (HFIA) when equipped with a catalytic methane cutter upstream of the detector accepts a continuous flow of
11、 sample delivered by a heat traced sample line maintained above 375F. A catalytic methane cutter is a catalytic device consisting of catalyst in a reactor designed by type of catalyst and operating temperature to combust all non-methane hydrocarbons and leave only methane. Instrument suppliers provi
12、de different approaches to this technology. There are “single detector/single amplifier” instruments and “dual detector/dual amplifier” instruments. Both types of instruments give measurements of total hydrocarbons and measurements of methane in the stream and by difference they measure non-methane
13、hydrocarbons.With “single detector/single amplifier instruments, the sample stream is alternately either passed through or around a selective catalytic combustion reactor (methane cutter) before entering the detector, which alternately measures either methane or total hydrocarbons. Instrument softwa
14、re controls the switching times (usually 1-minute cycles) and continuously displays the THC, CH4 and non-methane results.With “dual detector/dual amplifier” instruments, the sample stream is continuously split. Part of the sample goes to a direct measuring detector measuring total hydrocarbons. The
15、other part of the sample goes to a selective catalytic combustion reactor (methane cutter) followed by a detector, which continuously measures methane. From either of these instruments, the measurements of total hydrocarbons and measurements of methane are subtracted to give the non-methane hydrocar
16、bon result.FID Theory of OperationThe technique of flame ionization detection (FID) relies on the ionization of molecules during high temperature combustion in the reaction zone of the FID-flame to determine the total hydrocarbon concentration within a gaseous sample. The analyzer has an adjustable
17、heated oven (60 to 200C) which contains a heated sample pump and burner in which a small flame is elevated and sustained by regulated flows of air and 100% hydrogen or a 40/60% mixture of hydrogen and helium. The burner jet is used as an electrode and is connected to the negative side of a precision
18、 power supply. An additional electrode, known as the “collector“, is connected to a high impedance, low noise electronic amplifier. The two electrodes establish an electrostatic field. When a gaseous sample is introduced to the burner, it is ionized in the flame and the electrostatic field causes th
19、e charged particles (ions) to migrate to their respective electrodes. The migration creates a small current flow between the electrodes. This current is measured by the precision electrometer amplifier and is directly proportional to the hydrocarbon concentration of the sample.Methane Cutter Theory
20、of OperationOperation of a methane cutter is based upon different combustion temperatures of methane compared to other non-methane hydrocarbon compounds. The methane cutter uses an oxidizing catalyst that is maintained at a temperature specific for the catalyst used, to selectively combust 95% of th
21、e non-methane hydrocarbons in the sample stream, while not reacting the methane content of the sample. As the sample stream is passed through the cutter, non-methane hydrocarbons oxidize to CO2 and H2O, which are not detected by the FID. The FID only measures the unreacted methane in the sample stre
22、am. By taking the difference between the methane-only measurement and the total hydrocarbon measurement, the non-methane hydrocarbon content is determined. * Revision submitted by ICAC on August 18, 20044.0 Equipment SpecificationsEquipment specifications will vary among manufacturers. The table bel
23、ow lists the minimum specifications required for equipment to apply this procedure for continuously measuring methane, non-methane and total hydrocarbons.Flame Ionization DetectorMethod of Operation: Flame ionizationRanges: Minimum of 2 user selectable ranges between 0-10 and 50,000 ppm full scaleRe
24、peatability: 5.0% F.S.Zero Drift: 3%F.S. per 24 hoursSpan Drift: 3%F.S. per 24 hoursLinearity: 3%F.S.Oven Temperature: Between 165C and 190CResponse Time (T90),measured at sample inlet:10 seconds Sample Flow Rate: 0.5 to 3.0 SLPMFuel: 100% H2 or 40% H2 / 60% He mixtureAmbient Operating Temp.: 0 to 4
25、0 C at 90% R.H.Display: Direct digital LED displayOutput Signal: Current: 4-20 mA linear, isolated resistive load of 750Voltage: 0 to 100 mV; 0 to 5 V DC; 0 to 10 VDCPower Requirements: 120 VAC 10% at 50/60 HzConfiguration: 19-inch rack mountableSelective Catalytic CutterAccuracy: 3.0% Repeatability
26、: 3.0%Oxidizing Efficiency: 95% of Ethanol/Methane in air to be oxidized in the 100ppm rangeSample Flow Rate: 0.50 to 3.0 SLPMCatalyst Temperature: Based on catalytic materialCatalyst Life Cycle: 12 months at concentrations of 500 ppm carbonPower Requirements: 115 VAC at 50/60 HzAmbient Operating Te
27、mp.: 0 to 40 C at 90% R.H.* Revision submitted by ICAC on August 18, 20045.0 Test MethodCalibrate the FID THC analyzer using the manufacturers recommended procedure.1. Zero all three channels, (THC, CH4 and NMHC) of the analyzer using an inert zero calibration gas such as N2 or zero air having a hyd
28、rocarbon concentration 0.10 ppm. 2. Following the manufacturers procedure, calibrate of all three channels, (THC, CH4 and NMHC) of the analyzer with a known methane span gas and a known non-methane (ethanol) span gas.Note1: The methane concentration and non-methane (ethanol) concentration of the spa
29、n gases should approximate 80-90% of the measurement range at which the FID will be used to make measurements. Follow Method 25A for guidance on gas concentrations for calibration.Note2: Calibration gases should comply with US EPA Protocol 1 (1%) or RATA Class gas specifications.3. Verify analyzer c
30、alibration on the methane channel with a known methane in air concentration. The analyzer should give a measurement equal to the certified span gas methane concentration of the cylinder (3%).4. Verify analyzer calibration on the non-methane channel with a known non-methane hydrocarbon (ethanol) in a
31、ir concentration. The analyzer should give a NMHC measurement equal to the certified span gas concentration for the cylinder (3%).5. Following system calibration, calculate the efficiency of the methane cutter. If the efficiency of the methane cutter is 95%, replace and re-calibrate the analyzer pri
32、or to proceeding. The methane cutter efficiency should be periodically tested using a gas mixture of methane and non-methane hydrocarbon (ethanol).6. Initiate sample flow from the VOC destruction device and begin making measurements and recording results.6.0 CalculationsThe methodology, equations an
33、d performance specifications follow Method 25A very closely. Calculate the concentrations of methane, non-methane and total hydrocarbons as follows: Cc = K Cmeas / Where:Cc = NMHC (ethanol) concentrationCmeas = THCmeas - MmeasK = Response Factor for the NMHC (ethanol) = determined efficiency fractio
34、n of the methane cutter. This value is 1.0 if no methane is present, as in a calibrated gas cylinder containing only ethanol in air.Mmeas = methane (CH4) concentration as directly measured on the methane channel.THCmeas= Measurement on the total hydrocarbon channel, calibrated to methane.Methane cut
35、ter efficiency can be determined by testing a certified mixture of methane and the NMHC of interest (ethanol). The equation for the methane cutter efficiency is as follows: K Cmeas NMHC / Ccert NMHCNote: the cutter is cutting NMHC, not methane. Therefore the efficiency is calculated by the non-metha
36、ne components. * Revision submitted by ICAC on August 18, 2004Where: =efficiency of the methane cutterCcert NMHC = certified concentration of NMHC (ethanol) in a mixture of methane and NMHC (ethanol)or certified concentration of NMHC (ethanol) with a balance of nitrogenCmeas NMHC = measured NMHC (et
37、hanol) concentration on the methane channelNote: The presence of CH4 in certified NMHC can lead to errors in determining absolute efficiency measurement.* Revision submitted by ICAC on August 18, 2004Appendices of Supporting DataAppendix A Test Data SourceThe data supporting this submittal is taken
38、from a stack test report on a commercial bakery owned and operated by Stroehmann Bakeries L.C. in West Hazleton, Pennsylvania tested on July 12, 2003. The test was conducted by AirRECON, an independent testing company and report submitted to the state for the purpose of verifying air pollution contr
39、ol compliance of a CSM Worldwide catalytic oxidizer on the bakery. The test utilized a flame ionization detector (FID) with a methane cutter as described in the subject submittal. The full report was filed and accepted by the state after submittal on August 16, 2001. Because of its size, the full re
40、port is not included in this submittal, but can be supplied upon request or directly from the state.Subsequently, several other similar tests were conducted at other commercial bakeries. The results were similar to those reported here.Appendix B Certificates of Analysis for Calibration GasesThe gase
41、s used in this test have the attached certificates of analysis. The standard is NIST traceable. The gases were certified according to the EPA protocol procedures. Calibration and Bias gas samples consisted of methane in air. Ethane in nitrogen was used for determining response factor. Mixtures of et
42、hanol and methane in air wee used for measuring cutter efficiency.Spectra Gases prepared all samples.* Revision submitted by ICAC on August 18, 2004Appendix C Pre-Test Calibration of FID Channels to MethaneThe FID used in this test was a JUM 109A with two channels, one measuring Total Hydrocarbons (
43、THC) and one measuring Methane (M). By difference in measurement signals the Non-Methane Hydrocarbon (NMHC) was calculated. Because there are two FIDs in one instrument, both had to be calibrated. Method 25A was followed regarding protocol for sampling, measurements, and calibration and bias checks
44、on the FID. Table 1 shows a summary of the calibration data taken on the THC and M channels using the calibration gases. The table refers to the raw data in strip charts taken continuously during the calibration period.In reviewing strip chart data please note that the data runs up the page from one
45、 page to the next. The date and time print first and the data follow. Also, the printed dates on the charts are off by one day (i.e. the date printed on the chart of July 13, 2001 is really July 12, 2001).TABLE 1Pre-Test Calibration Of FID Channels to MethaneStrip Chart Time/Date Gas Cylinder MEASUR
46、EMENTS (ppm)Ref. Page # Concentration THC M NMHC149 7:46AM; 7/12/01 260ppm CH4 262.9 255 6.9149 7:44 AM; 7/12/01 552ppm CH4 558.6 548.7 7149 7:39A; 7/12/01 858ppm CH4 859.1 867 -4.6156 9:22AM; 7/12/01 858ppm CH4 859.1 863.5 1.6156 9:26AM; 7/12/01 552ppm CH4 564.7 566.6 -4157 9:29AM; 7/12/01 260ppm C
47、H4 268.1 268 -0.7157 9:31AM; 7/12/01 Zero CH4 1.2 0.9 0.1* Revision submitted by ICAC on August 18, 2004Appendix D Ethanol Response Factor and Ethanol/MethaneCutter EfficiencyThe response factor for the FID was determined using gas samples of ethanol in air. Summary data is shown in Table 2. The res
48、ponse factor is calculated using the formulas in section 6.0 above. Note that since the sample has no methane in it, the efficiency fraction of the methane cutter is 1.00. The table refers to the raw data in the strip chart. TABLE 2Response Factor for EthanolResponseStrip Chart Time/Date Gas Cylinde
49、r MEASUREMENTS (ppm) FactorRef. Page # Concentration THC M NMHC K152 8:10AM; 7/12/01 798ppm Ethanol 935.3 1.7 932.3 0.85153 8:18AM; 7/12/01 81.4ppm Ethanol 94.4 0.4 93.8 0.86Methane cutter efficiency was determined by analysis of gas mixtures of ethanol and methane. The data was taken on July 3, 2001, about 10 days before the bakery performance test in West Hazleton, PA. A summary of data results is provided in Table 3 and the raw strip chart data is presented in table format in Table 4. The raw FID Strip
