ARCHIVED REPORTS LEC APPLICATION FOR CERTIFICATION

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5.1C:EVALUATION OF BEST AVAILABLE CONTROL TECHNOLOGY • SCAQMD Rule 1134 (Emissions of Oxides of Nitrogen from Stationary Gas Turbines) is the SCAQMD's only prohibitory rule that specifically addresses gas turbines;however, it does not limit SO2 emissions. The SCAQMD adopted Rule 431.1 (Sulfur Content of Gaseous Fuels) to reduce SOx emissions from the burning of gaseous fuels in stationary equipment. Rule 431.1 specifies a sulfur limit of 16 grains/100 scf(as H2S) in natural gas sold within the SCAQMD. The SCAQMD also adopted Rule 407(Liquid and Gaseous Air Contaminants) to limit SO2 emissions from all sources. Rule 407 specifies an emission limit of 2,000 ppm for sulfur compounds (calculated as SO2). 5.1C.1.5.1.3 Conclusions BACT must be at least as stringent as the most stringent limit achieved in practice,federal NSPS, or district prohibitory rule. Based upon the results of this analysis,the CARB database and BAAQMD and SJVAPCD BACT guidelines reflect the most stringent SOx emission limit. These sources established a requirement for the use of natural gas as the primary fuel to control SOx emissions from combustion gas turbines. Therefore,the use of natural gas as the primary fuel source constitutes BACT for SOx emissions from the gas turbine/HRSG. 5.1 C.2 BACT for the CTG/HRSG: Startup/Shutdown Startup and shutdown periods are a normal part of the operation of combined cycle power plants such as LEC. BACT must also be applied during the startup and shutdown periods of gas turbine/HRSG operation. The BACT limits discussed in the previous section apply to steady-state operation,when the turbine,HRSG, and steam turbine have reached stable operations and the emission control systems are fully operational. During gas turbine startup,there are equipment and process requirements that must be met in sequential order to protect the equipment. Many of these require holding the gas turbine at low loads,where operation is inefficient and emissions are relatively high,to allow the HRSG to warm up and steam turbine seals and condenser vacuum to be established. At low turbine loads,the combustors are not yet operating in lean pre-mix mode so turbine-out NOx emission rates are also high during startup. In addition,incomplete combustion at low loads results in higher CO and VOC emission rates. Further,the post-combustion controls that are used to achieve additional emissions reductions (SCR and oxidation catalyst) require specific exhaust temperature ranges to be fully effective. The use of SCR to control NOx is not technically feasible when the surface of the SCR catalyst is below the manufacturer's recommended operating range.When surface temperatures are low, ammonia will not react completely with the NOx,resulting in excess NOx emissions or excess ammonia slip. The oxidation catalyst is not effective at controlling CO emissions when exhaust temperature is outside the optimal temperature range. Therefore,the BACT determinations for NOx, CO, and VOC during normal, steady-state operation are not applicable during startup and shutdown. However, since SO2 and PM10 emissions result from the characteristics of the fuel burned and do not rely on any emissions control system, the BACT determinations for SO2 and PM10 emissions are applicable during startup and shutdown as well. Because NOx, CO, and VOC emissions during startup and shutdown are not effectively reduced by combustion controls or add-on control devices,the emission rates themselves SAC/371322/082330016(LEC_5.1C_APPENDIX.DOC) 5.1C 14