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:
Example:
(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 an NMC, calculate xNMHC using the NMC's penetration fractions, response factors, and/or combined penetration fractions and response factors as described in § 1065.365, the THC FID's CH4 response factor, RFCH4[THC-FID], from § 1065.360, the initial THC contamination and dry-to-wet corrected THC concentration, xTHC[THC-FID]cor, as determined in paragraph (a) of this section, and the dry-to-wet corrected CH4 concentration, xTHC[NMC-FID]cor, optionally corrected for initial THC contamination as determined in paragraph (a) of this section.
(i) Use the following equation for an NMC configured as described in § 1065.365(d):
Eq. 1065.660-2
Where:
Example:
(ii) Use the following equation for penetration fractions determined using an NMC configuration as outlined in § 1065.365(e):
Example:
(iii) Use the following equation for an NMC configured as described in § 1065.365(f):
Example:
(3) For a GC-FID or FTIR, calculate xNMHC using the THC analyzer's CH4 response factor, RFCH4[THC-FID], from § 1065.360, and the initial THC contamination and dry-to-wet corrected THC concentration, xTHC[THC-FID]cor, as determined in paragraph (a) of this section as follows:
Example:
xTHC[THC-FID]cor = 145.6 µmol/mol
RFCH4[THC-FID] = 0.970
xCH4 = 18.9 µmol/mol
xNMHC = 145.6—0.970 · 18.9
xNMHC = 127.3 µmol/mol
(4) For an FTIR, calculate xNMHC by summing the hydrocarbon species listed in § 1065.266(c) as follows:
Example:
(c) NMNEHC determination. Use one of the following methods to determine NMNEHC concentration, xNMNEHC:
(1) Calculate xNMNEHC based on the test fuel's ethane content as follows:
(i) If the content of your test fuel contains less than 0.010 mol/mol of ethane, you may omit the calculation of NMNEHC concentration and calculate the mass of NMNEHC as described in § 1065.650(c)(6)(i).
(ii) If the content of your fuel test contains at least 0.010 mol/mol of C2H6, you may omit the calculation of NMNEHC concentration and calculate the mass of NMNEHC as described in § 1065.650(c)(6)(ii).
(2) For a GC-FID, NMC FID, or FTIR, calculate xNMNEHC using the THC analyzer's CH4 response factor, RFCH4[THC-FID], and C2H6 response factor, RFC2H6[THC-FID], from § 1065.360, the initial contamination and dry-to-wet corrected THC concentration, xTHC[THC-FID]cor, as determined in paragraph (a) of this section, the dry-to-wet corrected CH4 concentration, xCH4, as determined in paragraph (d) of this section, and the dry-to-wet corrected C2H6 concentration, xC2H6, as determined in paragraph (e) of this section as follows:
Example:
(3) For an FTIR, calculate xNMNEHC by summing the hydrocarbon species listed in § 1065.266(c) as follows:
Example:
(d) CH4 determination. Use one of the following methods to determine methane (CH4) concentration, xCH4:
(1) For an NMC, calculate xCH4 using the NMC's penetration fractions, response factors, and/or combined penetration fractions and response factors as described in § 1065.365, the THC FID's CH4 response factor, RFCH4[THC-FID], from § 1065.360, the initial THC contamination and dry-to-wet corrected THC concentration, xTHC[THC-FID]cor, as determined in paragraph (a) of this section, and the dry-to-wet corrected CH4 concentration, xTHC[NMC-FID]cor, optionally corrected for initial THC contamination as determined in paragraph (a) of this section.
(i) Use the following equation for an NMC configured as described in § 1065.365(d):
Example:
(ii) Use the following equation for an NMC configured as described in § 1065.365(e):
Example:
(iii) Use the following equation for an NMC configured as described in § 1065.365(f):
Example:
(2) For a GC-FID or FTIR, xCH4 is the actual dry-to-wet corrected CH4 concentration as measured by the analyzer.
(e) C2H6 determination. For a GC-FID or FTIR, xC2H6 is the C1-equivalent, dry-to-wet corrected C2H6 concentration as measured by the analyzer.