菱镁矿输送床轻烧过程模拟与分析

Process Simulation and Analysis of Magnesite Calcination in a Transport Bed

利用Aspen Plus对菱镁矿输送床轻烧过程进行系统模拟.通过外接菱镁矿分解动力学方程Fortran子程序建立第一级旋风预热器内同时进行气固换热(煅烧炉出口的高温烟气与预热菱镁矿原料)与菱镁矿预分解反应模型(简称气固换热预分解模型),并与先进行气固换热、后发生固体绝热预分解反应的模型(简称固体绝热预分解模型)进行对比.结果表明气固换热预分解模型计算得到的预分解率更大、系统的能量效率更高、能耗更低.基于此模型,进一步研究轻烧温度、菱镁矿含水量对轻烧过程的影响,结果表明:随着轻烧温度和菱镁矿含水量的增加,系统能量效率逐渐降低、能耗逐渐增加,特别是菱镁矿含水量对整个轻烧系统的可操作性影响显著.

A transport bed calcination process applied to magnesite was systematically investigated through Aspen Plus process simulator.By connecting the external Fortran subroutine of magnesite decomposition kinetics,a pre-decomposition model of magnesite simultaneously considering gas-solid heat transfer(the fed magnesite preheated by the high-temperature calciner flue gas)and magnesite pre-decomposition reaction in the first-stage cyclone-type preheater was established(i.e.,gas-solid heat transferpre-decomposition model).Compared with the model considering gas-solid heat transfer without magnesite pre-decomposition first and then occurring the adiabatic pre-decomposition of magnesite(i.e.,solid adiabatic pre-decomposition model),the calculated result of pre-decomposition conversion based on the gas-solid heat transfer pre-decomposition model was greater,and the system had higher energy efficiency and lower energy consumption.Based on this model,the influence of calcination temperature and water content of magnesite on the light calcination process was further studied.It could be seen that with the increase of calcination temperature and water content of magnesite,the energy efficiency of the system gradually decreased and energy consumption rise.Especially,the water content of magnesite had a significant impact on the operability of the whole light calcination system.This paper provides guidance and reference for its industrial design as well as operation of light calcination process of magnesite.