40 CFR § 1065.660 - THC, NMHC, NMNEHC, CH4, and C2H6 determination.
(a) THC determination and initial THC/CH4contamination corrections.
(1) If we require you to determine THC emissions, calculate xTHC[THC-FID]cor using the initial THC contamination concentration xTHC[THC-FID]init from § 1065.520 as follows:
(2) For the NMHC determination described in paragraph (b) of this section, correct xTHC[THC-FID] for initial THC contamination using Eq. 1065.660-1. You may correct xTHC[NMC-FID] for initial contamination of the CH4 sample train using Eq. 1065.660-1, substituting in CH4 concentrations for THC.
(3) For the NMNEHC determination described in paragraph (c) of this section, correct xTHC[THC-FID] for initial THC contamination using Eq. 1065.660-1. You may correct xTHC[NMC-FID] for initial contamination of the CH4 sample train using Eq. 1065.660-1, substituting in CH4 concentrations for THC.
(4) For the CH4 determination described in paragraph (d) of this section, you may correct xTHC[NMC-FID] for initial THC contamination of the CH4 sample train using Eq. 1065.660-1, substituting in CH4 concentrations for THC.
(5) You may calculate THC as the sum of NMHC and CH4 if you determine CH4 with an FTIR as described in paragraph (d)(2) of this section and NMHC with an FTIR using the additive method from paragraph (b)(4) of this section.
(6) You may calculate THC as the sum of NMNEHC, C2H6, and CH4 if you determine CH4 with an FTIR as described in paragraph (d)(2) of this section, C2H6 with an FTIR as described in paragraph (e) of this section, and NMNEHC with an FTIR using the additive method from paragraph (c)(3) of this section.
(b) NMHC determination. Use one of the following to determine NMHC concentration, xNMHC:
(1) If you do not measure CH4, you may omit the calculation of NMHC concentrations and calculate the mass of NMHC as described in § 1065.650(c)(5).
(2) For nonmethane cutters, calculate χNMHC using the nonmethane cutter's methane penetration fraction, PFCH4[NMC-FID], and the ethane response factor penetration fraction, RFPFC2H6[NMC-FID], from § 1065.365, the THC FID's methane response factor, RFCH4[THC-FID], from § 1065.360, the initial THC contamination and dry-to-wet corrected THC concentration, χTHC[THC-FID]cor, as determined in paragraph (a) of this section, and the dry-to-wet corrected methane concentration, χTHC[NMC-FID]cor, optionally corrected for initial THC contamination as determined in paragraph (a) of this section.
(i) Use the following equation for penetration fractions determined using an NMC configuration as outlined in § 1065.365(d):
(ii) Use the following equation for penetration fractions determined using an NMC configuration as outlined in § 1065.365(e):
(iii) Use the following equation for penetration fractions determined using an NMC configuration as outlined in § 1065.365(f) or for penetration fractions determined as a function of molar water concentration using an NMC configuration as outlined in § 1065.365(d):
(3) For a GC-FID or FTIR, calculate χNMHC using the THC analyzer's methane response factor, RFCH4[THC-FID], from § 1065.360, and the initial THC contamination and dry-to-wet corrected THC concentration, χTHC[THC-FID]cor, as determined in paragraph (a) of this section as follows:
(4) For an FTIR, calculate χNMHC by summing the hydrocarbon species listed in § 1065.266(c) as follows:
(c) NMNEHC determination. Use one of the following methods to determine NMNEHC concentration, xNMNEHC:
(1) If the content of your test fuel contains less than 0.010 mol/mol of ethane, you may omit the calculation of NMNEHC concentrations and calculate the mass of NMNEHC as described in § 1065.650(c)(6).
(2) For a GC-FID, NMC FID, or FTIR, calculate χNMNEHC using the THC analyzer's methane response factor, RFCH4[THC-FID], and ethane response factor, RFC2H6[THC-FID], from § 1065.360, the initial contamination and dry-to-wet corrected THC concentration, χTHC[THC-FID]cor, as determined in paragraph (a) of this section, the dry-to-wet corrected methane concentration, χCH4, as determined in paragraph (d) of this section, and the dry-to-wet corrected ethane concentration, χC2H6, as determined in paragraph (e) of this section as follows:
(3) For an FTIR, calculate xNMNEHC by summing the hydrocarbon species listed in § 1065.266(c) as follows:
(d) CH4 determination. Use one of the following methods to determine methane concentration, χCH4:
(1) For nonmethane cutters, calculate χCH4 using the nonmethane cutter's methane penetration fraction, PFCH4[NMC-FID], and the ethane response factor penetration fraction, RFPFC2H6[NMC-FID, from § 1065.365, the THC FID's methane response factor, RFCH4[THC-FID], from § 1065.360, the initial THC contamination and dry-to-wet corrected THC concentration, χTHC[THC-FID]cor, as determined in paragraph (a) of this section, and the dry-to-wet corrected methane concentration, χTHC[NMC-FID]cor, optionally corrected for initial THC contamination as determined in paragraph (a) of this section.
(i) Use the following equation for penetration fractions determined using an NMC configuration as outlined in § 1065.365(d):
(ii) Use the following equation for penetration fractions determined using an NMC configuration as outlined in § 1065.365(e):
(iii) Use the following equation for penetration fractions determined using an NMC configuration as outlined in § 1065.365(f) or for penetration fractions determined as a function of molar water concentration using an NMC configuration as outlined in § 1065.365(d):
(2) For a GC-FID or FTIR, χCH4 is the actual dry-to-wet corrected methane concentration as measured by the analyzer.
(e) C2H6determination. For a GC-FID or FTIR, χC2H6 is the C1-equivalent, dry-to-wet corrected ethane concentration as measured by the analyzer.