Sensitivity analysis of oxy-fuel power plant system

Abstract

A comprehensive sensitivity analyses has been conducted to assess the performance of a purpose-designed 600MW supercritical steam oxy-fuel bituminous coal-fired power plant system, which includes three modes for the recirculation of flue gas (RFG), i.e. dry, half-dry and wet. The assessment was conducted by considering the changes to eight major operating parameters, the flue gas acid dew point, and the fuel consumption rate. Optimization of the system was also considered to minimize the energy loss of the oxy-fuel process. The results suggest that air leakage exerts the largest impact on the output of the system. The half-dry RFG oxy-fuel system is the most practical due to its high efficiency and easiness in operation, compared with the other two flue gas recirculation modes. The acid dew point of the half-dry RFG system is about 10°C higher than that of the dry RFG system and approximately 5°C lowers than the wet RFG system. For the optimization purpose, the improvement in the turbine system through utilizing the thermal energy of the hot flue gas is of prime importance. By heating the feed water at the outlet of the secondary feed water heater upstream of the deaerator and cooling down the hot flue gas to a temperature which is 10°C above its acid dew point, the net efficiency of an oxy-fuel process can raise by around 1.0%, which narrows the energy penalty to less than 10% compared to the reference air-firing system. This is smaller than an energy penalty of around 12% for the oxy-fuel process without the recovery of heat in the hot flue gas. It is also found that the efficiency elevation through the thermal integration with turbine system is greater for the wet model than the other two models. The oxy-fuel mode has a slightly larger net efficiency gain upon decreasing the fuel consumption rate from 600MW to 300MW.