AVISTA KETTLE FALLS

摘要

When Avista Corp. (then known as Washington Water Power) brought the Kettle Falls Generating Station in northeastern Washington state into operation 20 years ago to meet rising demand for power, the company was also motivated by the environmentally advantageous prospect of eliminating the widespread use of "wigwam burners" to get rid of wood waste. The 46 MW hog-fuel fired plant provided an opportunity to convert waste wood products into valuable electricity in an environmentally responsible manner. Since then, the plant has been a reliable source of renewable energy in the Northwest, and recently, a unique gas turbine-based feedwater heater repowering project has boosted plant'output and improved efficiency. The subcritical natural circulation grate boiler at Kettle Falls produces 415,000 lb/hr steam at 1500 psi and 950 F at the superheater outlet, feeding a condensing single-flow steam turbine. As originally designed, five feedwater extraction ports off the steam turbine pre-heat the boiler feedwater to increase efficiency. The top feedwater heater had a long history of being out of service, hampering plant output and efficiency. Although Kettle Falls determined that the out-of-service heater did not cause any significant operational problems with the steam turbine, the plant kept looking for an effective way to raise the feedwater heater temperature to the boiler's inlet design conditions.