A Cost-Effective Indirect Coal-Fired Gas Turbine Power and Water-From-Air Cycle

An ideal open gas turbine cycle with multiple-stage intercooled compression and multiple-stage reheat expansion theoretically approaches Carnot thermal efficiency. A proposed practicable process to utilize this cycle with indirect firing of coal as fuel, with an air heater in place of the boiler, a turbine inlet temperature of 1700°F (927°C) and top pressure of 788 psia (53.6 atm) gives promise of lowering power plant station heat rates (HHV) from 8970 Btu/kWh currently realized by the best scrubber-equipped coal fired steam plants to 7460, a reduction of 16.8% in fuel consumption and consequently the cost of flue gas scrubbers. In addition, a 316 MW plant delivers at rated output 130,000 gal per day water stripped from atmospheric air. Primarily because of an expensive air heater and regenerator the gas turbine plant is penalized by an estimated increase in initial cost from $1000/kW for a steam plant to $1433/kW. With coal priced at $3/million Btu, water selling at 2¢/gal, money at 8% interest, inflation at 5%, and an 81% plant capacity factor, the payback period is 17 years.