200MW富氧燃煤锅炉传热特性研究

Study on Heat-transfer Characteristics of a 200 MW Oxy-fuel Coal-fired Boiler

对常规空气燃烧传热计算方法进行了修正,使其适用于富氧燃烧方式,并对灰气体加权模型(WSGG)的参数进行优化和修正,得到了烟气发射率与温度、辐射层有效厚度和分压比的关系;以美国国家标准技术局(NIST)数据库数据为标准,对富氧燃烧方式下烟气各组分的导热系数、运动黏度和普朗特数等物性参数进行拟合,采取先组分后混合的方式对对流传热计算方法进行了改进,并对200MW富氧燃煤锅炉进行传热性能研究.结果表明:富氧燃烧方式下烟气中CO2物性参数的拟合结果与真实值的误差小于0.61%;在富氧燃烧干循环26%O2体积分数、湿循环29%O2体积分数下,各受热面的吸热量和出口烟气温度等主要参数均能与空气燃烧方式下的对应参数较好吻合,基本可以达到同一锅炉系统2种燃烧方式的兼容运行.

Amendments were made to the heat-transfer calculation method for conventional air combustion to make it applicable to oxy-fuel combustion mode.Moreover,parameter optimization and modification were conducted to the weighted sum of gray gases(WSGG)model,so as to obtain the variation law of gas emissivity with the flue gas temperature,effective thickness of radiation layer and with the pressure ratio.Taking the database of American National Institute of Standards and Technology(NIST)as the criteria,physical parameters such as heat conductivity,kinematic viscosity and Prandtl number of gas components under oxy-fuel combustion mode were fitted,and the method for convective heat-transfer calculation was improved by calculation steps of first single components then their mixtures,which subsequently was used to a 200 MW oxy-fuel coal-fired boiler.Results show that the error between fitted physical parameters and actual measurements of CO2 in flue gas is less than 0.61%under oxy-fuel combustion mode;main parameters such as the heat absorption of various heating surfaces and the outlet gas temperatures under oxy-fuelcombustion mode with both 26%oxygen concentration in dry recycle condition and 29%oxygen concentration in wet recycle condition agree well with those under corresponding air combustion mode,indicating that the compatibility can basically be reached between above two combustion modes for the same boiler.