System Integration and Flowsheet Optimization of 1000 MW Coal-fired Supercritical Power Generation Units

Abstract

For traditional power generation process, energy losses are often caused by heat-and-mass transfer between the boiler and turbine subsystems, especially the heat transfer process with fairly high temperature difference in boiler. Generally, such energy losses are often unavoidable, if heat-and-mass transfer processes occur only in an independent way within certain subsystem or equipment but not in a cascade-integrated way. In this paper, new integration approach was proposed in order to reasonably utilize the heat at different temperature levels from the overall system perspective. Compared with isolated designs of the boiler and turbine subsystems, this approach comprehensively considers the match of heat transfer processes in air preheater and feedwater regeneration subsystem, and takes the principle of feedwater availability in the feedwater preheating process into account. The heat utilization process is reconstructed among the streams of flue gas, air, steam, feedwater and condensate water in a more coupling way. As a consequence, the thermodynamic irreversibility within air-preheating process and feedwater-regenerating system is sharply reduced. The heat-transfer characteristics and energy-saving effect of the integrated system was quantitatively analyzed. The results show that the power output of the novel integrated system is 21.74 MW higher than that of the conventional system. Moreover, the cost of electricity (COE) and the coal consumption rate can be decreased by 1.2% and 5.09g/kWh, respectively. This paper provides useful information for the energy-saving effects and design optimization of heat transfer process in thermal power generation.