In 1995, OMPA constructed a 40-MW combustion turbine, a General Electric LM-6000, and a heat recovery steam generator (HRSG) to repower the number one generator, whose boiler was near the end of its economic life. Currently, all generation assets owned by Ponca City Utility Authority (PCUA) are leased to and operated by the Oklahoma Municipal Power Authority (OMPA).
Construction of the Ponca City Repowering Project was essentially completed in October of 1995. The repowering project increased the capacity and generation efficiency of the existing Ponca City Municipal Steam Plant through the repowering of steam unit number one. This 16,500 kW generator was modified to increase its capacity to 18,750 kW when operated at 3,600 revolutions per minute, the same number of revolutions per minute as unit number two.
The project also involved the installation of a General Electric Company LM6000 aeroderivative combustion turbine and a heat recovery steam generator, as well as the refurbishment of the existing unit number one steam turbine. Waste heat from the exhaust of the combustion turbine is used in the HRSG to produce steam, which is used to power unit number one. Operating in this combined cycle mode improves the efficiency of the thermal cycle and has proven to be very cost effective.
Duct burners were installed in the HRSG so that additional steam can be produced if necessary. This addition allows for the maximum capacity from steam unit number one to be obtained. OMPA uses this additional capacity to satisfy a portion of its reserve requirements. The combined cycle capacity of the project without duct firing is approximately 52 megawatts. With duct firing, the capacity is approximately 60 megawatts.
Finally, a 200,000-gallon cooling tower was constructed with two pumps, providing 16,000 gallons per minute to the main condenser to cool steam. Water treatment for the Steam Generation Plant is necessary to provide purified water used in the boilers, which is recirculated.