The use of high temperature heat exchangers to increase power plant thermal efficiency

The thermal efficiency of conventional fossil fuelled steam power plant can be increased up to 55% by increasing the steam turbine inlet temperature to 1300°C at steam pressures in the range 50 b~200 b, resulting in a large reduction in carbon dioxide emissions per unit power output. A novel superheater shell and tube heat exchanger with ceramic tubes can be used to produce steam at the above temperature and pressure conditions. The feasibility of the heat exchanger depends upon the high temperature properties of suitable ceramic materials. Investigations have revealed that pressureless sintered silicon carbide possesses suitable material properties for this particular application. The design proposed results in a mean temperature within the heat transfer tubes of approximately 1450°C~1550°C. With current steam power plants having total installed power output capacities usually in the range of 50 MW to 1000 MW, a preliminary design of a ceramic heat exchanger was undertaken for a 345 MW superheater thermal capacity. At the desired temperatures and pressures it was concluded that for this situation, ceramic heat exchanger units of 14 MW thermal capacity would be feasible