Keywords: exergy analysis, coal, steam power plants, combustion air, steam generator, stack gas, energy efficiency, exergy efficiency, coal-fired power plants, irreversibilities
Improving steam power plant efficiency through exergy analysis: effects of altering excess combustion air and stack-gas temperature
Modifications are examined to increase coal-fired steam power plant efficiency by reducing irreversibilities in the steam generator, including decreasing the fraction of excess combustion air, and/or the stack-gas temperature. Overall-plant energy and exergy efficiencies both increase by 1.4% when the fraction of excess combustion air decreases from 0.4 to 0.15, and by 3.5% when the stack-gas temperature decreases from 149?C to 87?C. When both decreases occur, plant energy and exergy efficiencies both increase by 4.1%. If theoretical combustion air is used, the plant energy and exergy efficiencies both increase by 4.7% when the stack-gas temperature is 87?C.