40 CFR § 1065.660 - THC, NMHC, NMNEHC, CH4, and C2H6 determination.

Link to an amendment published at 88 FR 4686, Jan. 24, 2023.

(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:

$\begin{array}{c}{x}_{\mathrm{THC}[\mathrm{THC}-\mathrm{FID}]\mathrm{cor}}=x_{\mathrm{THC}[\mathrm{THC}-\mathrm{FID}]\mathrm{uncor}}-x_{\mathrm{THC}[\mathrm{THC}-\mathrm{FID}]\mathrm{init}}\\ \text{Eq. 1065.660-1}\end{array}$

Example:

xTHCuncor = 150.3 µmol/mol

xTHCinit = 1.1 µmol/mol

xTHCcor = 150.3 - 1.1

xTHCcor = 149.2 µmol/mol

(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):

$\begin{array}{c}{x}_{\mathrm{NMHC}}=\frac{x_{\mathrm{THC}\left[\text{THC-FID}\right]\mathrm{cor}}-x_{\mathrm{THC}\left[\text{NMC-FID}\right]\mathrm{cor}}·{\mathrm{RF}}_{\mathrm{CH}\$\left[\text{THC-FID}\right]}}{1-{\mathrm{RFPF}}_{C2H6\left[\text{NMC-FID}\right]}·{\mathrm{RF}}_{\mathrm{CH}4\left[\text{THC-FID}\right]}}\\ \text{Eq. 1065.660-2}\end{array}$

Where:

xNMHC = concentration of NMHC.

xTHC[THC-FID]cor = concentration of THC, initial THC contamination and dry-to-wet corrected, as measured by the THC FID during sampling while bypassing the NMC.

xTHC[NMC-FID]cor = concentration of THC, initial THC contamination (optional) and dry-to-wet corrected, as measured by the NMC FID during sampling through the NMC.

RFCH4[THC-FID] = response factor of THC FID to CH4, according to § 1065.360(d).

RFPFC2H6[NMC-FID] = nonmethane cutter combined ethane response factor and penetration fraction, according to § 1065.365(d).

Example:

xTHC[THC-FID]cor = 150.3 µmol/mol

xTHC[NMC-FID]cor = 20.5 µmol/mol

RFPFC2H6[NMC-FID] = 0.019

RFCH4[THC-FID] = 1.05

$x_{\mathrm{NMHC}}-\frac{150.3-20.5·1.05}{1-0.019·1.05}$

xNMHC = 131.4 µmol/mol

(ii) Use the following equation for penetration fractions determined using an NMC configuration as outlined in § 1065.365(e):

$\begin{array}{c}{x}_{\mathrm{NMHC}}=\frac{x_{\mathrm{THC}\left[\text{THC-FID}\right]\mathrm{cor}}·{\mathrm{PF}}_{\mathrm{CH}4\left[\text{NMC-FID}\right]}-x_{\mathrm{THC}\left[\text{NMC-FID}\right]\mathrm{cor}}}{{\mathrm{PF}}_{\mathrm{CH}4\left[\text{NMC-FID}\right]}-{\mathrm{PF}}_{C2H6\left[\text{NMC-FID}\right]}}\\ \text{Eq. 1065.660-3}\end{array}$

Where:

xNMHC = concentration of NMHC.

xTHC[THC-FID]cor = concentration of THC, initial THC contamination and dry-to-wet corrected, as measured by the THC FID during sampling while bypassing the NMC.

PFCH4[NMC-FID] = nonmethane cutter CH4 penetration fraction, according to § 1065.365(e).

xTHC[NMC-FID]cor = concentration of THC, initial THC contamination (optional) and dry-to-wet corrected, as measured by the THC FID during sampling through the NMC.

PFC2H6[NMC-FID] = nonmethane cutter ethane penetration fraction, according to § 1065.365(e).

Example:

xTHC[THC-FID]cor = 150.3 µmol/mol

PFCH4[NMC-FID] = 0.990

xTHC[NMC-FID]cor = 20.5 µmol/mol

PFC2H6[NMC-FID] = 0.020

$x_{\mathrm{NMHC}}-\frac{150.3-0.990-20.5}{0.990-0.020}$

xNMHC = 132.3 µmol/mol

(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):

$\begin{array}{c}{x}_{\mathrm{NMHC}}=\frac{x_{\mathrm{THC}\left[\text{THC-FID}\right]\mathrm{cor}}·{\mathrm{PF}}_{\mathrm{CH}4\left[\text{NMC-FID}\right]}-x_{\mathrm{THC}\left[\text{NMC-FID}\right]\mathrm{cor}}·{\mathrm{RF}}_{\mathrm{CH}4\left[\text{THC-FID}\right]}}{{\mathrm{PF}}_{\mathrm{CH}4\left[\text{NMC-FID}\right]}-{\mathrm{RFPF}}_{C2H6\left[\text{NMC-FID}\right]}·{\mathrm{RF}}_{\mathrm{CH}4\left[\text{THC-FID}\right]}}\\ \text{Eq. 1065.660-3}\end{array}$

Where:

xNMHC = concentration of NMHC.

xTHC[THC-FID]cor = concentration of THC, initial THC contamination and dry-to-wet corrected, as measured by the THC FID during sampling while bypassing the NMC.

PFCH4[NMC-FID] = nonmethane cutter CH4 penetration fraction, according to § 1065.365(f).

xTHC[NMC-FID]cor = concentration of THC, initial THC contamination (optional) and dry-to-wet corrected, as measured by the THC FID during sampling through the NMC.

RFPFC2H6[NMC-FID] = nonmethane cutter CH4 combined ethane response factor and penetration fraction, according to § 1065.365(f).

RFCH4[THC-FID] = response factor of THC FID to CH4, according to § 1065.360(d).

Example:

xTHC[THC-FID]cor = 150.3 µmol/mol

PFCH4[NMC-FID] = 0.990

xTHC[NMC-FID]cor = 20.5 µmol/mol

RFPFC2H6[NMC-FID] = 0.019

RFCH4[THC-FID] = 0.980

$x_{\mathrm{NMHC}}=\frac{150.3·0.990-20.5·0.980}{0.990-0.019·0.980}$

xNMHC = 132.5 µmol/mol

(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:

$\begin{array}{c}{x}_{\mathrm{NMHC}}=x_{\mathrm{THC}\left[\text{THC-FID}\right]\mathrm{cor}}-{\mathrm{RF}}_{\mathrm{CH}4\left[\text{THC-FID}\right]}·x_{\mathrm{CH}4}\\ \text{Eq. 1065.660-5}\end{array}$

Where:

xNMHC = concentration of NMHC.

xTHC[THC-FID]cor = concentration of THC, initial THC contamination and dry-to-wet corrected, as measured by the THC FID.

RFCH4[THC-FID] = response factor of THC-FID to CH4.

xCH4 = concentration of CH4, dry-to-wet corrected, as measured by the GC-FID or FTIR.

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 χNMHC by summing the hydrocarbon species listed in § 1065.266(c) as follows:

Where:

χNMHC = concentration of NMHC.

χHCi = the C1-equivalent concentration of hydrocarbon species i as measured by the FTIR, not corrected for initial contamination.

χHCi-init = the C1-equivalent concentration of the initial system contamination (optional) of hydrocarbon species i, dry-to-wet corrected, as measured by the FTIR.

Example:

χC2H6 = 4.9 µmol/mol

χC2H4 = 0.9 µmol/mol

χC2H2 = 0.8 µmol/mol

χC3H8 = 0.4 µmol/mol

χC3H6 = 0.5 µmol/mol

χC4H10 = 0.3 µmol/mol

χCH2O = 0.8 µmol/mol

χC2H4O = 0.3 µmol/mol

χCH2O2 = 0.1 µmol/mol

χCH4O = 0.1 µmol/mol

χNMHC = 4.9 + 0.9 + 0.8 + 0.4 + 0.5 + 0.3 + 0.8 + 0.3 + 0.1 + 0.1

χNMHC = 9.1 µmol/mol

(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:

Where:

χNMNEHC = concentration of NMNEHC.

χTHC[THC-FID]cor = concentration of THC, initial THC contamination and dry-to-wet corrected, as measured by the THC FID.

RFCH4[THC-FID] = response factor of THC-FID to CH4.

χCH4 = concentration of CH4, dry-to-wet corrected, as measured by the GC-FID, NMC FID, or FTIR.

RFC2H6[THC-FID] = response factor of THC-FID to C2H6.

χC2H6 = the C1-equivalent concentration of C2H6, dry-to-wet corrected, as measured by the GC-FID or FTIR.

Example:

χTHC[THC-FID]cor = 145.6 µmol/mol

RFCH4[THC-FID] = 0.970

χCH4 = 18.9 µmol/mol

RFC2H6[THC-FID] = 1.02

χC2H6 = 10.6 µmol/mol

χNMNEHC = 145.6−0.970 · 18.9−1.02 · 10.6

χNMNEHC = 116.5 µmol/mol

(3) For an FTIR, calculate xNMNEHC by summing the hydrocarbon species listed in § 1065.266(c) as follows:

$\begin{array}{c}{x}_{\mathrm{NMNEHC}}=\sum _{i=1}^N(x_{\mathrm{HCi}}-x_{\text{HCi−init}})\\ \text{Eq. 1065.660-8}\end{array}$

Where:

xNMNEHC = concentration of NMNEHC.

xHCi = the C1-equivalent concentration of hydrocarbon species i as measured by the FTIR, not corrected for initial contamination.

xHCi-init = the C1-equivalent concentration of the initial system contamination (optional) of hydrocarbon species i, dry-to-wet corrected, as measured by the FTIR.

Example:

xC2H4 = 0.9 µmol/mol

xC2H2 = 0.8 µmol/mol

xC3H8 = 0.4 µmol/mol

xC3H6 = 0.5 µmol/mol

xC4H10 = 0.3 µmol/mol

xCH2O = 0.8 µmol/mol

xC2H4O = 0.3 µmol/mol

xC2H2O2 = 0.1 µmol/mol

xCH4O = 0.1 µmol/mol

xNMNEHC = 0.9 + 0.8 + 0.4 + 0.5 + 0.3 + 0.8 + 0.3 + 0.1 + 0.1

xNMNEHC = 4.2 µmol/mol

(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):

$\begin{array}{c}{x}_{\mathrm{CH}4}=\frac{x_{\mathrm{THC}\text{[NMC-FID]cor}}-x_{\mathrm{THC}\text{[THC-FID]cor}}\times {\mathrm{RFPF}}_{C2H6\text{[NMC-FID]}}}{1-{\mathrm{RFPF}}_{\text{C2H6 [NMC-FID]}}\times {\mathrm{RF}}_{\mathrm{CH}4\text{[THC-FID]}}}\\ \text{Eq. 1065.660-9}\end{array}$

Where:

xCH4 = concentration of CH4.

xTHC[NMC-FID]cor = concentration of THC, initial THC contamination (optional) and dry-to-wet corrected, as measured by the NMC FID during sampling through the NMC.

xTHC[THC-FID]cor = concentration of THC, initial THC contamination and dry-to-wet corrected, as measured by the THC FID during sampling while bypassing the NMC.

RFPFC2H6[NMC-FID] = the combined ethane response factor and penetration fraction of the nonmethane cutter, according to § 1065.365(d).

RFCH4[THC-FID] = response factor of THC FID to CH4, according to § 1065.360(d).

Example:

xTHC[NMC-FID]cor = 10.4 µmol/mol

xTHC[THC-FID]cor = 150.3 µmol/mol

RFPFC2H6[NMC-FID] = 0.019

RFCH4[THC-FID] = 1.05

$x_{\mathrm{CH}4}=\frac{10.4-150.3·0.019}{1-0.019·1.05}$

xCH4 = 7.69 µmol/mol

(ii) Use the following equation for penetration fractions determined using an NMC configuration as outlined in § 1065.365(e):

$\begin{array}{c}{x}_{\mathrm{CH}4}=\frac{x_{\mathrm{THC}\text{[NMC-FID]cor}}-x_{\mathrm{THC}\text{[THC-FID]cor}}·{\mathrm{PF}}_{C2H6\text{[NMC-FID]}}}{{\mathrm{RF}}_{\mathrm{CH}4\text{[THC-FID]}}·\left({\mathrm{PF}}_{\mathrm{CH}4\text{[NMC-FID]}}-{\mathrm{PF}}_{C2H6\text{[NMC-FID]}}\right)}\\ \text{Eq. 1065.660-10}\end{array}$

Where:

xCH4 = concentration of CH4.

xTHC[NMC-FID]cor = concentration of THC, initial THC contamination (optional) and dry-to-wet corrected, as measured by the NMC FID during sampling through the NMC.

xTHC[THC-FID]cor = concentration of THC, initial THC contamination and dry-to-wet corrected, as measured by the THC FID during sampling while bypassing the NMC.

PFC2H6[NMC-FID] = nonmethane cutter ethane penetration fraction, according to § 1065.365(e).

RFCH4[THC-FID] = response factor of THC FID to CH4, according to § 1065.360(d).

PFCH4[NMC-FID] = nonmethane cutter CH4 penetration fraction, according to § 1065.365(e).

Example:

xTHC[NMC-FID]cor = 10.4 µmol/mol

xTHC[THC-FID]cor = 150.3 µmol/mol

PFC2H6[NMC-FID] = 0.020

RFCH4[THC-FID] = 1.05

PFCH4[NMC-FID] = 0.990

$x_{\mathrm{CH}4}=\frac{10.4-150.3·0.020}{1.05·(0.990·0.020)}$

xCH4 = 7.25 µmol/mol

(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):

$\begin{array}{c}{x}_{\mathrm{CH}4}=\frac{x_{\mathrm{THC}\text{[NMC-FID]cor}}-x_{\mathrm{THC}\text{[THC-FID]cor}}·{\mathrm{RFPF}}_{C2H6\text{[NMC-FID]}}}{{\mathrm{PF}}_{\mathrm{CH}4\text{[NMC-FID]}}-{\mathrm{RFPF}}_{C2H6\text{[NMC-FID]}}·{\mathrm{RF}}_{\mathrm{CH}4\text{[THC-FID]}}}\\ \text{Eq. 1065.660-11}\end{array}$

Where:

xCH4 = concentration of CH4.

xTHC[NMC-FID]cor = concentration of THC, initial THC contamination (optional) and dry-to-wet corrected, as measured by the NMC FID during sampling through the NMC.

xTHC[THC-FID]cor = concentration of THC, initial THC contamination and dry-to-wet corrected, as measured by the THC FID during sampling while bypassing the NMC.

RFPFC2H6[NMC-FID] = the combined ethane response factor and penetration fraction of the nonmethane cutter, according to § 1065.365(f).

PFCH4[NMC-FID] = nonmethane cutter CH4 penetration fraction, according to § 1065.365(f).

RFCH4[THC-FID] = response factor of THC FID to CH4, according to § 1065.360(d).

Example:

xTHC[NMC-FID]cor = 10.4 µmol/mol

xTHC[THC-FID]cor = 150.3 µmol/mol

RFPFC2H6[NMC-FID] = 0.019

PFCH4[NMC-FID] = 0.990

RFCH4[THC-FID] = 1.05

$x_{\mathrm{CH}4}=\frac{10.4-150.3·0.019}{0.990-0.019·1.05}$

xCH4 = 7.78 µmol/mol

(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.

[76 FR 57462, Sept. 15, 2011, as amended at 81 FR 74184, Oct. 25, 2016; 86 FR 34566, June 29, 2021]