Tampa Electric won a July 18 tentative approval from the Florida Department of Environmental Protection for an air construction permit that allows it to increase the hours of operation that the Polk Power Station Unit 1 is authorized to fire natural gas only from 876 to 3,000 hours per year.
No physical changes are being proposed to Unit 1 to accommodate the increased use of natural gas. Due to the increased emission rate when firing natural gas over syngas, the project will increase annual nitrogen oxides (NOX) emissions by 266.9 tons per year (TPY). Emissions of NOX will be controlled by the use of the existing steam injection and good combustion practices when firing natural gas only to meet an emission limit of 25 parts per million volume dry at 15 percent oxygen (ppmvd @ 15% O2). The facility will continue to use the existing nitrogen diluent injection system with moisture saturation as well as good combustion practices to meet a NOx emission limit of 15 ppmvd @ 15% oxygen when firing syngas or syngas augmented by natural gas.
Polk Unit 1 is a nominal 260-MW solid fuel-based (coal and petcoke) integrated gasification combined cycle (IGCC) plant including: a nominal 192 MW (gross) syngas and natural gas fired General Electric 7FA combustion turbine-electrical generator (CCCT); a heat recovery steam generator (HRSG); a nominal 133 MW (gross) steam turbine-electrical generator (STEG); a solid fuel handling system; an entrained flow solid fuel gasification system; an oxygen plant; a synthetic gas (syngas) cleanup and sulfur recovery system; and a sulfuric acid plant (SAP).
There is also a 120 million British thermal units per hour (MMBtu/hr) auxiliary boiler. Approximately 65 MW are consumed by the oxygen plant and process auxiliary equipment which is the difference between net and gross power production (260 MW versus 325 MW). The startup fuel for the SAP and solid fuel gasifier is natural gas. Natural gas is used as the augmentation and backup fuel for the CCCT, while it is the only operational fuel used in the auxiliary boiler.
Units 2 and 3 at Polk are 165-MW natural gas/fuel oil-fired GE 7FA simple cycle combustion turbines (SCCT), while Units 4 and 5 are two 165-MW natural gas-fired GE 7FA SCCT. Construction is currently underway to convert these units to combined cycle operation.