The Oklahoma Department of Environmental Quality began taking public comment on Nov. 19 on a draft air permit that would allow Public Service Co. of Oklahoma (PSO) to install new air emissions controls on the gas-fired Southwestern power plant.
PSO, which is a unit of American Electric Power (NYSE: AEP), has requested a prevention of significant deterioration (PSD) construction permit, with this permitting also including a previous application to incorporate Best Available Retrofit Technology (BART) State Implementation Plan (SIP) requirements into the facility’s Title V operating permit.
“As a result of the Regional Haze Rule and Best Available Retrofit Technology (BART) rules, PSO is installing Low-NOx burners and overfire air (OFA) systems on their Unit No. 3,” said a DEQ permit document. “Unit 3 is a 3,290 MMBTUH gas-fired boiler installed in 1967. In the OFA system, approximately 80% of the necessary combustion air is supplied to the burners directly, with the remaining 20% supplied just above the combustion zone. This reduces the amount of oxygen in the hottest part of the flame and reduces NOx. However, the changes to combustion result in increases in CO and VOC.”
The existing facility produces power using four Babcock and Wilcox pressure-fired steam generators. The total combined steam output from the steam generators is sufficient to generate 500 MW (gross). The steam is produced by these boilers to drive turbine-generators. Boilers are primarily run on natural gas with No. 2 fuel oil as an alternate fuel, along with small periodic quantities of “on-spec” used oil. Pipeline quality natural gas has been the primary fuel for the boilers since 1995. All four boilers are capable of operating on a continuous basis, but only the #3 boiler is actually operated continuously due to business demand. The other generators – #1N, #1S and #2 – are peaking units that operate only when it is economically feasible, such as during peak demand, DEQ noted.
PSO also constructed last decade, with commercial operation in 2008, two natural gas-fired combustion turbine peaking units at the site. The power block consists of two GE7EA simple cycle combustion turbine generators (CTGs). Each of the turbines has a peak heat input of about 1,078 MMBTUH and an average heat input of around 930 MMBTUH. The combustion turbines fire pipeline-quality natural gas only and are equipped with General Electric’s 9/42 Dry low-NOx (DLN) combustor technology. The newer units have a combined nominal electrical generating capacity of 172 MW, the DEQ said.