A Synthetical Energy-Economy-Environment Evaluation Of Thermal Power Unit With Boiler Flue Gas Heat Recovery System

Under the background of energy-saving and emission-reduction, it has become an important issue that how to reduce the energy consumption and improve the environmental friendliness of the coal-fired generating unit. Reasonable evaluation method can help to find the key points of energy saving of the system, the internalization of environmental cost is an important way to alleviate environmental problems. Thermoeconomics is an interdiscipline which takes both the Thermodynamics and Economics into consideration, and we can make energy, economy and environment comprehensive evaluation of the energy system by using it.Setting flue gas recovery exchangers to heat the condensate is an effective way for rational utilization of the power plant waste heat. We made thermoecnomic cost analysis and environmental assessment for a 350 MW coal-fired generating unit with boiler flue gas heat recovery system. We took the lower integration level to make detailed division for the system, defined the Fuel-Product for boiler heating surface and boiler flue gas heat recovery system, and calculated the thermoeconomic costs and thermoeconomic performance indexes of each component. On the basis of the thermoeconomic cost model, we introduced the environmental cost model for the system. In the calculation of environmental cost, we considered the pollutant SO2, NOx, CO2, TSP and selected three kinds of measurement principle: environmental damage model, remove model, revenue model.The result showed that each device in the system needs to assume the environmental cost because the device releasing pollutants into the environment located in the production forefront. Thermoeconomic is a powerful method that can internalize the external environmental cost into each flow in the system, and the environmental cost accounts for a significant proportion in the total cost, so the environmental cost internalization is quite meaningful. The device which has great influence on the system performance due to its irreversible loss can be identified by the results such as the exergy cost, thermoeconomic cost, irreversible cost, relative cost difference and so on.