of Method 6C. except express all

concentrations as percent. rather than ppm. For O2 analyzers that use a low-level calibration gas in place of a zero gas, calculate the effluent gas concentration using Equation 3A-1. Eq. 3A-1 where: Cₘ=Effluent gas concentration, dry basis. percent. Actual concentration of the upscale calibration gas, percent. Actual concentration of the low-level calibration gas, percent. =Average of initial and final system calibration bias check responses for the upscale calibration gas. percent. Average of initial and final system calibration bias check responses for the low-level gas, percent. C=Average gas concentration indicated by the gas analyzer, dry basis, percent. 10. Bibliography. Same as bibliography of Method 6C. METHOD 4-DETERMINATION OF MOISTURE CONTENT IN STACK GASES 1. Principle and Applicability 1.1 Principle. A gas sample is extracted at a constant rate from the source: moisture is removed from the sample stream and determined either volumetrically or gravimetrically. 1.2 Applicability. This method is applicable for determining the moisture content of stack gas. Two procedures are given. The first is a reference method. for accurate determinations of moisture content (such as are needed to calculate emission data). The second is an approximation method, which provides estimates of percent moisture to aid in setting isokinetic sampling rates prior to a pollutant emission measurement run. The approximation method described herein is only a suggested approach; alternative means for approximating the moisture content. e.g., drying tubes, wet bulb-dry bulb techniques, condensation techniques. stoichiometric calculations, previous experience, etc., are also acceptable. The reference method is often conducted simultaneously with a pollutant emission measurement run; when it is. calculation of percent isokinetic, pollutant emission rate, etc., for the run shall be based upon the results of the reference method or its equivalent; these calculations shall not be based upon the results of the approximation method, unless the approximation method is shown. to the satisfaction of the Administrator, U.S. Environmental Protection Agency, to be capable of yielding results within 1 percent H2O of the reference method. NOTE: The reference method may yield questionable results when applied to saturated gas streams or to streams that contain water droplets. Therefore, when these conditions exist or are suspected, a second de. termination of the moisture content shall be made simultaneously with the reference method, as follows: Assume that the gas stream is saturated. Attach a temperature sensor [capable of measuring to ±1' c (2' F)] to the reference method probe. Measure the stack gas temperature at each traverse point (see Section 2.2.1) during the reference method traverse: calculate the average stack gas temperature. Next, determine the moisture percentage, either by: (1) using a psychrometric chart and making appropriate corrections if stack pressure is different from that of the chart, or (2) using saturation vapor pressure tables. In cases where the pyschrometric chart or the saturation vapor pressure tables are not applicable (based on evaluation of the process). alternate methods. subject to the approval of the Administrator, shall be used. 2. Reference Method The procedure described in Method 5 for determining moisture content is acceptable as a reference method. 2.1 Apparatus. A schematic of the sampling train used in this reference method is shown in Figure 4-1. All components shall be maintained and calibrated according to the procedure outlined in Method 5. STACK FILTER WALL CONDENSER-ICE BATH SYSTEM INCLUDING (EITHER IN STACK SILICA GEL TUBE OR OUT OF STACK) PROBE VACUUM THERMOMETERS GAUGE BY-PASS VALVE ORIFICE MAIN VALVE DRY GAS METER AIR-TIGHT PUMP 1 Figure 4-1. Moisture sampling train-reference method. Environment Reporter [Appendix A, Method 4] - -1- - 3 6 7 8 15 2 3 5 7 25 49 45 3 3 2 7 3 7 9 11 12 22 5 2 31 30 34 73 2 3 5 7 11 2 3 X - 1 X - 2 X - 3 X -4 X - 5 X - 6 X 7 - 8 X - - 9 X - 10 X - 11 ) 179 180 63 64 65 66 193 194 195 196 i 71 72 73 74 75 76 77 78 79 80 81 82 83 64 85 86 181 182 89 91 7 8 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 11 12 33 34 35 36 37 38 53 61 62 3 64 19 20 28 29 30 31 32 107 108