燃煤超临界CO_(2)发电系统锅炉换热面布置及优化  

Layout and optimization of heat-transfer surfaces in boilers for coalfired supercritical CO_(2) power system

作　　者：刘超[1] 徐进良[1,2] 刘国华[1] LIU Chao;XU JinLiang;LIU GuoHua(Beijing Key Laboratory of Multiphase Flow and Heat Transfer for Low Grade Energy Utilization,North China Electric Power University,Beijing 102206,China;Key Laboratory of Power Station Energy Transfer Conversion and System,Ministry of Education,North China Electric Power University,Beijing 102206,China)

机构地区：[1]华北电力大学低品位能源多相流与传热北京市重点实验室,北京102206 [2]华北电力大学电站能量传递转化与系统教育部重点实验室,北京102206

出　　处：《中国科学：技术科学》2021年第12期1507-1518,共12页Scientia Sinica(Technologica)

基　　金：国家重点研发计划(编号:2017YFB0601801);国家自然科学基金(批准号:51821004)资助项目。

摘　　要：超临界二氧化碳(sCO_(2))循环用于燃煤发电系统时,由于循环流量大,锅炉内将产生超大压降,大幅降低循环效率.本团队前期提出的基于1/8减阻原理的分流流动模式能够解决以上问题,同时使锅炉换热面成为模块化设计.当对锅炉换热面模块进行布置时,存在两个核心难点,一是由于sCO_(2)入炉温度高,换热系数低,炉膛内冷却壁极易超温;二是sCO_(2)循环热效率对压降敏感,需兼顾压降惩罚.基于此,本文以1000 MWe一次再热燃煤sCO_(2)发电系统为研究对象,耦合热力学循环计算及锅炉热力与冷却壁流动传热计算,以降低冷却壁壁温为目标,兼顾循环热效率,对模块化锅炉的换热面进行了布置及优化.本文提出了烟道内对流换热面的"再分流"设计,可大幅降低压降;提出了一种炉膛冷却壁包含四个模块的创新布置方案("4-Part"方案),与冷却壁包含三个模块的布置方案("3-Part"方案)相比,"4-Part"方案使锅炉内主流、再热的低温工质全部进入冷却壁,可显著降低壁温,同时使循环热效率升高;发现随冷却壁再热模块出口温度的改变,"4-Part"方案存在最优设计工况,最优工况下冷却壁危险点壁温比"3-Part"方案降低18.66°C,达到628.64°C,可使现有材料在现有炉型下满足设计要求.本文提出的一次再热燃煤sCO_(2)锅炉换热面布置方案,为后续燃煤锅炉的研究提供了新的思路及参考.When a supercritical carbon dioxide(sCO_(2)) cycle is applied in coal-fired power systems,the thermal efficiency is severely reduced by the ultra-large pressure drop in the boiler due to the large sCO_(2) mass flow rate.This can be solved using the partial flow mode based on the 1/8 principle of reducing pressure drop,which separates the heat-transfer surfaces in the boiler into several modules.To arrange the heat-transfer modules in the boiler,two key points should be noted.First,cooling wall tubes in the furnace can be overheated due to the high temperature of sCO_(2) entering the boiler and the low heat-transfer coefficient.Second,enough attention should be paid to the effect of pressure drop to obtain high thermal efficiency.In this study,we optimized the layout of heat-transfer modules in a boiler to decrease the temperature of the cooling wall,considering the effect of pressure drop.A 1000-MWe coal-fired sCO_(2) power system with a single reheating is analyzed.We developed a numerical model coupling the thermodynamic cycle of the system,heat transfer in the boiler,and thermal-hydraulic characteristics of the cooling wall.We propose a design for the “partial-partial flow mode” for convective heat-transfer modules located in the flue passage.The pressure drops decreased to a large extent.We propose an innovative layout for the heating modules,which we term “4-Part layout” because the cooling wall in the furnace is divided into four parts.Compared with the “3-Part layout” that contains three parts in the furnace,the total flow of sCO_(2) at lower temperatures from the main heater and reheater enters the furnace to cool the cooling wall tubes in “4-Part layout.” The maximum wall temperature is significantly reduced,and the thermal efficiency is increased.With an increase in the outlet temperature of the reheating modules,the maximum wall temperature decreases at first and then increases,indicating an optimal design condition.Under the optimal condition,the maximum wall temperature is 628.64°C,1

关 键 词：sCO_(2)循环 燃煤发电 锅炉 模块化设计 换热面布置 

分 类 号：TM621.2[电气工程—电力系统及自动化]