Indian Journal of Science and Technology

Abstract

In this paper, the useful concept of energy and exergy utilization is analyzed, and applied to the boiler system. Energy and exergy flows in a boiler have been shown in this paper. The energy and exergy efficiencies have been determined as well. In a boiler, the energy and exergy efficiencies are found to be 89.21% and 45.48%, respectively. A boiler energy and exergy efficiencies are compared with others work as well. It has been found that the combustion chamber is the major contributor for exergy destruction followed by heat exchanger of a boiler system. Furthermore, Modifications are examined to increase gas-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 0.19%, 0.37% respectively when the fraction of excess combustion air decreases from 0.4 to 0.15, and by 0.84%, 2.3% when the stack-gas temperature decreases from 137°C to 90°C
Keywords. Exergy efficiency, energy efficiency, super critical thermal power plant, excess air, stack gas temperature