循环流化床内煤矸石一维燃烧模型

为研究煤矸石在循环流化床锅炉内的燃烧性能,建立了预测煤矸石在锅炉内燃烧后的飞灰底渣残炭量的一维燃烧数学模型。建模采用"小室模型"的方法,将炉膛沿高度方向划分为多段小室,分别建立了质量平衡、动量平衡和组分平衡方程,计算得到了煤矸石燃烧特性沿炉膛高度的一维分布结果。与其他煤矸石燃烧模型不同的是,该模型详细考虑了锅炉内部气固流动、多孔介质传质和化学反应过程,并且耦合了颗粒在循环流化床锅炉的一维停留时间分布模型,模拟了颗粒在炉膛内部的流动过程。通过对模型的计算,得到矸石在循环流化床锅炉中的燃烧速率控制因素,以及矸石燃烧后的飞灰底渣残炭量与矸石物性参数和锅炉运行参数的关系。利用该模型计算并分析得到:矸石燃烧速率由灰层传质速率控制;选取灰层孔隙率大的矸石、增大锅炉热负荷、选取7m/s的风速、投入100~1 000μm的颗粒燃烧效率最高,飞灰或底渣残炭量最低。

One-dimensional model of coal gangue combustion in circulating flu-idized bed boiler

In order to study the combustion performance of coal gangue in circulating fluidized bed boiler，a one-dimensional model of coal gangue combustion process was established to predict the residence carbon in fly ash and bottom slag.A set of mass conservation equations，momentum conservation equations and species mass conservation equations are calculated in a cell model along the height dimension of active furnace area and the results of one-dimension distribution of coal gangue combustion parameters along the height are obtained.Unlike other combustion models，this model contains three periods including gas-solid flowing，mass transferring in porous media and chemical reactions.In addition，the model couples the one-dimension model of particle residence time in CFB boiler which simulates the internal circulating behavior.The calculating results include the key controlling factor of coal gangue combustion rate，and the relationship among the residence carbon of fly ash and bottom slag，the physical parameters of coal gangue and the boiler operation parameters.By data processing and analyzing the results，some conclusions are made:the controlling factor of combustion is the grieshoch mass transfer process.The following operating conditions shall improve the combustion efficiency and decrease the residual carbon fraction:putting into larger porosity coal gangue，increasing the boiler maximum continuous rating，keeping the boiler wind speed as 7 m/s，and maintaining the diameters of particle as 100-1 000 μm.