The Texas Commission on Environmental Quality (TCEQ) went out for comment on Dec. 11 on draft air quality and PSD permits that would authorize new capacity at the city of Austin’s Sand Hill Energy Center in Travis County.
This application was submitted to the TCEQ in September 2013. The City of Austin (COA), which owns and operates the Sand Hill Energy Center, is proposing to add a power block which will generate electric power for the city and for sale on the wholesale electric market. The new facility will consist of one gas fired combustion turbine (CTG) equipped with a duct burners (DB) and a heat recovery steam generator (HRSG). The CTG and DBs are to be fueled with pipeline quality natural gas. The CTG will operate in combined cycle mode.
The turbine will be a General Electric Model 7FA (GE7FA) rated at a nominal capability of 173.9 MW. The DB equipped HRSG will a have maximum heat input of 681.5 million British thermal units per hour (MMBtu/hr).
The CTG will use an aqueous ammonia-based selective catalytic reduction (SCR) system to control nitrogen oxide (NOx) emissions. The system will be comprised of aqueous ammonia storage and handling equipment, an ammonia vaporizer, an ammonia injection grid, and catalyst bed modules. The ammonia injection grids and the SCR catalyst beds will be installed in the HRSG housing at locations where exhaust temperature will promote the NOx reduction reaction.
The existing condenser/cooling tower arrangement will be utilized to cool steam exhausted from the turbine train.
Austin in September 2014 got from the U.S. Environmental Protection Agency a final greenhouse gas PSD permit for this same new unit. EPA has been doing permitting for greenhouse gas PSD approvals, but recently turned most of those pending applications over to the TCEQ, now that the Texas agency has its own PSD program for greenhouse gases. The Sand Hill draft permit issued Dec. 11 is for non-greenhouse gas emissions.