部分冷却二氧化碳循环燃煤发电系统热力学性能分析

Thermodynamic performance analysis for coal-fired power generation system with partial cooling carbon dioxide cycle

再压缩二氧化碳布雷顿循环具有结构简单、循环效率高的优点。然而,再压缩循环应用于燃煤电站时面临锅炉压降大、冷却壁温高和余热利用难的问题。部分冷却二氧化碳循环凭借其本身的循环特点,在与燃煤锅炉集成时可有效缓解以上问题。利用MATLAB软件编写了600 MW部分冷却二氧化碳循环燃煤发电系统的热力计算程序。首先研究了单一参数变化时系统循环效率的变化情况。结果表明:主压缩机入口压力和温度在临界点附近约7.8 MPa/32℃时循环效率达到最大值;预压缩机工作在临界点附近时系统效率突降;分流系数和再热压力分别在0.35和17 MPa时系统效率达到最高。随后,应用粒子群算法对部分冷却循环进行参数优化,结果表明部分冷却循环在合适的设计参数条件下,可以实现接近于再压缩循环的效率。相比于再压缩循环,部分冷却循环的质量流量下降了17.46%,锅炉入口温度从462.45℃降低到429.39℃。

The recompression carbon dioxide Brayton cycle has the advantages of simple structure and high cycle efficiency.However,the recompression cycle faces the problems of large boiler pressure drop,high cooling wall temperature and difficult waste heat utilization when applied to coal-fired power plants.The partial cooling carbon dioxide cycle can effectively alleviate the above problems when integrated with coal-fired boilers by virtue of its own circulation characteristics.A thermal calculation program for a 600 MW coal-fired power generation system with partial cooling carbon dioxide cycle is written using MATLAB.Firstly,the effect of single parameter variation on the thermodynamic performance of the system is investigated.The results show that the system efficiency is highest when the main compressor inlet pressure and temperature are near the critical point;the system efficiency drops suddenly when the pre-compressor works near the critical point;the system efficiency is highest when the split ratio and reheat pressure are 0.35 and 17 MPa,respectively.The particle swarm optimization is applied to the partial cooling cycle,and the results show that the partial cooling cycle can achieve the efficiency close to that of the recompression cycle under the suitable design parameters.Compared with the recompression cycle,the mass flow rate of the partial cooling cycle decreased by 17.46%and the boiler inlet temperature decreased from 462.45℃to 429.39℃.