40 CFR § 60.4374a - How do I demonstrate compliance with my SO2 emissions standard and determine excess emissions using a SO2 CEMS?
(a) If you demonstrate continuous compliance using a CEMS for measuring SO2 emissions, excess emissions are defined as the applicable averaging period, either 4-operating-hour or 30-operating-day, during which the average SO2 emissions from your stationary combustion turbine measured by the CEMS exceeds the applicable SO2 emissions standard specified in § 60.4330a as determined using the procedures specified in this section that apply to your stationary combustion turbine.
(b) You must install, calibrate, maintain, and operate a CEMS for measuring SO2 concentrations and either O2 or CO2 concentrations at the outlet of your stationary combustion turbine, and record the output of the system.
(c) The 1-hour average SO2 emissions rate measured by a CEMS must be expressed in ng/J or lb/MMBtu heat input and must be used to calculate the average emissions rate under § 60.4330a.
(d) You must use the procedures for installation, evaluation, and operation of the CEMS as specified in § 60.13 and paragraphs (d)(1) through (3) of this section.
(1) Each CEMS must be operated according to the applicable procedures under Performance Specifications 1, 2, and 3 in appendix B to this part;
(2) Quarterly accuracy determinations and daily calibration drift tests must be performed according to Procedure 1 in appendix F to this part; and
(3) The span value of the SO2 CEMS at the outlet from the SO2 control device (or outlet of the stationary combustion turbine if no SO2 control device is used) must be 125 percent of either the highest applicable standard or highest potential SO2 emissions rate of the fuel combusted. Alternatively, SO2 span values determined according to section 2.1.1 in appendix A to part 75 of this chapter may be used.
(e) If you have installed and certified a SO2 CEMS that meets the requirements of part 75 of this chapter, the Administrator or delegated authority can approve that only quality assured data from the CEMS must be used to identify excess emissions under this subpart. You must report periods where the missing data substitution procedures in subpart D of part 75 are applied as monitoring system downtime in the excess emissions and monitoring performance report required under § 60.7(c).
(f) All required fuel flow rate, steam flow rate, temperature, pressure, and megawatt data must be reduced to hourly averages.
(g) Calculate the hourly average SO2 emissions rate, in units of the emissions standard under § 60.4330a, using lb/MMBtu for units complying with the input-based standard or using equation 1 to paragraph (g)(1) of this section for units complying with the output-based standard:
(1) For simple cycle operation:
(2) The gross or net energy output is calculated as the sum of the total electrical and mechanical energy generated by the stationary combustion turbine; the additional electrical or mechanical energy (if any) generated by the steam turbine following the heat recovery steam generating unit; the total useful thermal energy output that is not used to generate additional electricity or mechanical output, expressed in equivalent MWh, minus the auxiliary load as calculated using equations 2 and 3 to this paragraph (g)(2); and any auxiliary load.
(3) For mechanical drive applications complying with the output-based standard, use equation 4 to this paragraph (g)(3):
(h) For each stationary combustion turbine demonstrating compliance on a heat input-based emissions standard, excess SO2 emissions are determined on a 4-operating-hour averaging period basis using the SO2 CEMS data and procedures specified in paragraphs (i)(1) and (2) of this section and as applicable to the SO2 emission standard.
(1) For each 4-operating-hour period, compute the 4-operating-hour rolling average SO2 emissions as the heat input weighted average of the hourly average of SO2 emissions for a given operating hour and the 3 operating hours preceding that operating hour using the applicable equation in paragraph (i)(2) of this section. Calculate a 4-operating-hour rolling average SO2 emissions rate for any 4-operating-hour period when you have valid CEMS data for at least 3 of those hours (e.g., a valid 4-operating-hour rolling average SO2 emissions rate cannot be calculated if 1 or more continuous monitors was out-of-control for the entire hour for more than 1 hour during the 4-operating-hour period).
(2) If you elect to comply with the applicable heat input-based emissions rate standard, calculate both the 4-operating-hour rolling average SO2 emissions rate and the applicable 4-operating-hour rolling average SO2 emission standard using equation 5 to this paragraph (h)(2).
(i) For each combustion turbine demonstrating compliance on an output-based standard, you must determine excess emissions on a 30-operating-day rolling average basis. The measured emissions rate is the SO2 emissions measured by the CEMS for a given operating day and the 29 operating days preceding that day. Once each operating day, calculate a new 30-operating-day average measured emissions rate using all hourly average values based on non-out-of-control SO2 emission data for all operating hours during the previous 30-operating-day operating period. Report any 30-operating-day periods for which you have less than 90 percent data availability as monitor downtime. Calculate both the 30-operating-day rolling average SO2 emissions rate and the applicable 30-operating-day rolling average SO2 emissions standard using equation 6 to this paragraph (i).
(j) At a minimum, non-out-of-control CEMS hourly averages shall be obtained for 90 percent of all operating hours on a 30-operating-day rolling average basis.