转底炉直接还原工艺综合数学模型

Comprehensive mathematical model of direct reduction for rotary hearth furnaces

为发展和深入认识转底炉直接还原工艺技术，建立了转底炉综合数学模型，该模型由转底炉本体热化学平衡、转底炉区域热平衡计算模型、余热回收模型、生球干燥模型、炉膛温度校核与尾气露点校核模型和转底炉流程模型组成．采用综合模型计算了该工艺流程的基本工艺参数．计算结果表明：煤气热值、废气排放温度和余热回收利用方案对整体能量消耗有不同程度影响，煤气发热值每增加50kJ．m-3，理论燃烧温度提高22-25℃，煤气用量减少41-47m0．t-1；空气预热温度平均每增加100℃，理论燃烧温度提高35-40℃，煤气用量减少90-103m3.t-1．此外，应用此模型还可以计算任何原料和燃料等条件下的直接还原工艺参数，研究不同余热回收方案条件下的各个工艺参数的变化规律．

A comprehensive mathematical model was established to develop and deeper understand direct re- duction technology for rotary hearth furnaces （RHF）. The model consists of the overall thermal and chemical balance model, the calculation model of heat balance at different zones, the waste heat recovery process model, the drying model of green pellets, the checking model of furnace box temperature and waste gas dew point, and the RHF process model. The basic process parameters of RHF were calculated by the model. Calculation results show that the overall energy consumption is effected by gas calorific value, waste gas temperature, and the recycling scheme of waste heat recovery. When the gas calorific value increases by 50 kJ.m-3, the theoretical combustion temperature increases by 22 to 25 ℃, and the gas consumption decreases by 41 to 47 m3.t-1. But when the preheating temperature increases by 100 ℃, the theoretical combustion temperature increases by 35 to 40 ℃, and the gas consumption decreases by 90 to 103 m3.t-1. Furthermore, the model can be applied to calculate technical parameters when the raw materials and fuel conditions are different, and the change laws of these technical parameters under different waste heat recovery processes can also be studied by this model.