Design on a novel waste heat recovery system integrated with the bypass flue and outside primary air preheater for bitumite-fired power plants

Abstract

Bitumite is widely used in coal-fired power plants. However, due to its high volatile content, the temperature of primary air to coal mills is limited to a lower value because of its high risk of spontaneous combustion. The method to reduce primary air temperature by mixing with cold air leads to irreversible loss and reduces the power generation efficiency of the power plant. To address the issue, a novel flue gas waste heat recovery system integrated with the bypass flue and outside primary air preheater for bitumite-fired power plants was suggested. The thermo- and techno-economic analysis models of the waste heat recovery system were developed, and the design parameters were optimized to maximize profit. The thermo-economic analysis shows that the exergy efficiency of the waste heat recovery system can reach 49.8 %, and the coal consumption rate can be reduced by 4.75 g (kW h)−1 by integrating the optimal waste heat recovery system. The techno-economic analysis shows that the net present value of the power plant during ten years can reach 10.6 M$, and the discounted payback period is 0.6 years. The novel waste heat recovery system can effectively improve the thermo- and techno-economic performance of bitumite-fired power plants.