System Analysis on Supercritical CO_2 Power Cycle with Circulating Fluidized Bed Oxy-Coal Combustion

作     者：SHI Yan ZHONG Wenqi SHAO Yingjuan XIANG Jun 

作者机构：Key Laboratory of Energy Thermal Conversion and Control of Ministry of Education School of Energy and Environment Southeast University State Key Laboratory of Coal Combustion School of Energy and Power Engineering Huazhong University of Science and Technology 

出 版 物：《Journal of Thermal Science》 (热科学学报（英文版）)

年 卷 期：2019年第28卷第3期

页      面：505-518页

核心收录：

学科分类：07[理学] 0702[理学-物理学] 

基　　金：supported by the National key research and development program of China (project number: 2017YFB0601802) the project of the National Natural Science Foundation of China (project number: 51876037) the Key Research and Development Program of Jiangsu Province, China (No.BE2017159) 

主　　题：S-CO2 oxy-coal combustion CO2 capture CFB boiler process simulation 

摘      要：Supercritical carbon dioxide(S-CO_2) Brayton power cycle is a competitive technology to achieve high efficiency in a variety of applications. However, in coal power applications, the CO_2 generated from coal combustion still discharges into the atmosphere causing a series of environment problems. In this work, an 300 MWe S-CO_2 power cycle with circulating fluidized bed(CFB) oxy-coal combustion was established including air separation unit(ASU), CFB boiler, recuperator system and carbon dioxide compression and purification unit(CPU). Based on the material and energy conservation, the cycle efficiency of S-CO_2(620°C, 25 MPa) Brayton power cycle with CFB oxy-coal combustion is evaluated compared to the oxy-coal combustion steam Rankine cycle and S-CO_2 Brayton power cycle with the 31.65 kg/s coal supply. After that, the influence of several factors, e.g., exhaust flue gas temperature, split ratio in recuperator system and the oxygen supply on the cycle efficiency was investigated and analyzed. The results show that the net efficiency of S-CO_2 power cycle with CFB oxy-coal combustion(32.67%) is much higher than the steam Rankine cycle utilizing CFB with 17.5 Mpa, 540°C steam(27.3%), and 25 Mpa, 620°C steam(30.15%) under the same exhaust flue gas temperature. In addition, lower exhaust flue gas temperature and higher split ratio are preferred to achieve higher cycle efficiency. Lower oxygen supply can reduce the energy consumption of ASU and CPU, further increasing the system net efficiency. However, the energy losses of ASU and CPU are still very large in oxy-coal combustion and need to be improved in further work.