Design and exergy analysis of 1000-MW double-reheat double-turbine regeneration system

Abstract

The development of ultra-supercritical double-reheat technology is a practical choice to further improve the power generation efficiency, reduce coal consumption, reduce carbon emissions, and save resources. Currently, the outer-steam cooler system in double-reheat units has been typically adopted to solve the problem of prodigious superheat degree of an extraction steam. An increasing number of studies show that the double-turbine regeneration system achieves better economy and practicability in resolving the prodigious superheat degree of an extraction steam for double reheat. Through the thermal equilibrium analysis method and exergy analysis method, the performance of the three units under design conditions and off-design conditions is specifically analyzed, and the exergy loss and exergy efficiency of both the steam turbine and regenerative heater are further analyzed. The results show that the energy-saving performance of the double-turbine regeneration system is better than that of the outer-steam cooler system under the design conditions, and the energy-saving performance of the double-turbine regeneration system gradually decreases as the load decreases. At low loads, the performance of the regenerative turbine is significantly reduced, and the energy-saving effect of the double-turbine regeneration system is not as good as that of an outer-steam cooler system.