A Potassium-Steam Binary Vapor Cycle for Better Fuel Economy and Reduced Thermal Pollution

Both fuel supply and thermal pollution considerations that are becoming progressively more important strongly favor the development of a higher temperature, and more efficient, thermodynamic cycle for electric power plants. About 200,000 hr of operation of boiling potassium systems, including over 15,000 hr of potassium vapor turbine operation under the space power program, suggest that a potassium vapor topping cycle with a turbine inlet temperature of ∼1500 deg F merits consideration. A design study has been carried out to indicate the size, cost, and development problems of the new types of equipment required. The results indicate that a potassium vapor cycle superimposed on a conventional 1050 deg F steam cycle would give an overall thermal efficiency of about 54 percent as compared to only 40 percent from a conventional steam cycle. Thus the proposed system would have a fuel consumption only 75 percent and a heat rejection rate only 50 percent that of a conventional plant. Further, it appears possible that the capital charges for the proposed plant might be lower than those for a conventional plant. A high grade fuel oil or gas will be required, but this is likely to be necessary anyway to meet increasingly stringent limitations on SO₂, NO_x, and ash emissions.