竖式石灰窑煅烧过程动态建模及特性分析
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摘要
采用数值仿真的方法对石灰窑煅烧过程进行研究。基于煅烧过程的物理机理建立竖式石灰窑的数学模型,该模型相比于以往模型,将窑内堆积的石灰石视为球形堆积床式非惰性多孔介质,考虑煅烧过程中各参数的时变性,以及气、固移动和反应引起的组分、能量变化;在此基础上,分别进行燃料量变化静态仿真实验和燃料量、进料量、冷却风扰动仿真实验,得到了几个主要位置的特性参数及传递函数。结果表明:以燃料量为控制参数,煅烧带固体温响应的放大系数K为0.75,其他监测位置的放大系数也为最大,表明其调节作用显著;以冷却风量为控制参数,过程响应无纯滞后,且煅烧带固体温度响应的时间常数T为195.25,其他监测位置的时间常数均较小,表明以冷却风为控制变量的调控效果比较灵敏;以进料量为控制参数,控制效果适中,但会引起产量变化。
The dynamic characteristics of calcination process in lime kiln are the important basis of control and operation optimization. Based on the physical mechanism of the calcination process,a predicting model of the vertical lime kiln was established in this paper. Compared with the previous models,the limestone deposited in the kiln was treated as a spherical packed bed reactive porous medium,and the timevarying properties of parameters in the calcination process were considered,as well as the material and energy change caused by flue gas and solid movement and chemical reaction. Both steady state simulations with different fuel quantity and dynamic testing with disturbance in fuel loading and cooling air were carried out. The characteristic parameters and transfer function of main stages were obtained. The results showed that the regulation effect is significant with the fuel quantity as the control parameter,because the amplification coefficient K of the calcined zone is 0. 75,and the amplification coefficient of other monitoring locations reaches the maximum. With the cooling air as the control parameter,the process response has no delay,the time constant T of the calcined band solid temperature response is 195. 25,and the time constant of the other monitoring positions is small,indicating the control effect of the cooling air as the control variable is sensitive. With the inlet quantity as the control parameter,the control effect is moderate with a change in output.
The dynamic characteristics of calcination process in lime kiln are the important basis of control and operation optimization. Based on the physical mechanism of the calcination process,a predicting model of the vertical lime kiln was established in this paper. Compared with the previous models,the limestone deposited in the kiln was treated as a spherical packed bed reactive porous medium,and the timevarying properties of parameters in the calcination process were considered,as well as the material and energy change caused by flue gas and solid movement and chemical reaction. Both steady state simulations with different fuel quantity and dynamic testing with disturbance in fuel loading and cooling air were carried out. The characteristic parameters and transfer function of main stages were obtained. The results showed that the regulation effect is significant with the fuel quantity as the control parameter,because the amplification coefficient K of the calcined zone is 0. 75,and the amplification coefficient of other monitoring locations reaches the maximum. With the cooling air as the control parameter,the process response has no delay,the time constant T of the calcined band solid temperature response is 195. 25,and the time constant of the other monitoring positions is small,indicating the control effect of the cooling air as the control variable is sensitive. With the inlet quantity as the control parameter,the control effect is moderate with a change in output.
引文
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[15]刘伟,范爱武,黄晓明.多孔介质传热传质理论与应用[M].北京:科学出版社,2006.LIUWei,FAN Ai-wu,HUANG Xiao-ming.Theory and application of heat and mass transfer in porous media[M].Beijing:Science Press,2006.
[2]CUI C,CHEN Y,WANG Y.Numerical simulation of temperature field in gas burning shaft lime kiln[J].Journal of University of Science&Technology Liaoning,2014,37(3):247-251.
[3]HE P,GU H,MEI S,et al.Numerical simulation of coal and natural gas co-combustion in a rotary lime kiln[C].International Conference on Computational Intelligence and Software Engineering,2009,1-4.
[4]周乃君,易正明,王强,等.石灰石煅烧分解率在线监测模型[J].化工学报,2001,52(7):612-615.ZHOU Nai-jun,YI Zheng-ming,WANG Qiang,et al.Online monitoring model for the decomposition of baked limestone in lime furnace[J].Journal of Chemical Industry and Engineering,2001,52(7):612-615.
[5]周乃君,易正明,周萍,等.石灰炉炉内过程数值仿真[J].中南大学学报(自然科学版),2000,31(5):422-424.ZHOU Nai-jun,YI Zheng-ming,ZHOU Ping,et al.Numerical simulation of the processes in lime furnace[J].Journal of Central South University of Technology(Natural Science Edition),2000,31(5):422-424.
[6]段润林,石灰石在竖式石灰窑内的煅烧过程分析[J].山西化工,2000(3):39-41.DUAN Run-lin.The process analysis of calcining limestone in the upright lime kiln[J].Shanxi Chemical Industry,2000(3):39-41.
[7]周孑民,易正明,周乃君,等.石灰窑窑内热工分析与操作优化[J].工业加热,2000(4):13—16.ZHOU Jie-min,YI Zheng-ming,ZHOU Nai-jun,et al.Thermal analysis and operating optimization in lime kiln[J].Industrial Heating,2000(4):13-16.
[8]向召洋,段嫦娥,宋杨,等.双膛并流式石灰竖窑燃烧过程数学模型[J].材料与冶金学报,2014,13(1):32-36.XIANG Shao-yang,DUAN Chang-e,SONG Yang,et al.Mathematical model of combustion process for the parallel flow regenerative lime shaft kiln[J].Journal of Materials and Metallurgy,2014,13(1):32-36.
[9]A.C.克兰姆.竖式石灰窑[M].北京:重工业出版社,1956.KLEMM A C.Vertical lime kiln[M].Beijing:Heavy Industry Press,1956.
[10]DELGADO JMPQ,LIMA AGBD,SILVA MVD.Numerical analysis of heat and mass transfer in porous media[M].Berlin Heidelberg:Springer,2012.
[11]陈凯锋,薛正良,李建立.高温煅烧下快速加热石灰石的热分解反应动力学[J].硅酸盐学报,2016,44(5):754-762.CHEN Kai-feng,XUE Zheng-liang,LI Jian-li.Kinetics of thermal decomposition reaction of limestone for flash heating of limestone at high temperature[J].Journal of Silicate,2016,44(5):754-762.
[12]WAKAO N.Particle-to-fluid transfer coefficients and fluid diffusivities at low flow rate in packed beds[J].Chemical Engineering Science,1976,31(12):1115-1122.
[13]高怀斌,屈治国,陶文铨,等.辐射模型和弥散效应对多孔介质内燃烧影响的数值模拟[J].工程热物理学报,2010,31(2):321-323.GAO Huai-bin,QU Zhi-guo,TAO Wen-quan,et al.Numerical study of radiation model and diffusion effects on combustion in porous media[J].Journal of Engineering Thermophysics,2010,31(2):321-323.
[14]史俊瑞,解茂昭,韩春福,等.多孔介质燃烧-换热器的二维数值研究[J].化工学报,2009,60(5):1116-1120.SHI Jun-rui,XIE Mao-zhao,HAN Chun-fu,et al.Two-dimensional numerical study of porous media combustion-heater[J].Journal of Chemical Industry and Engineering,2009,60(5):1116-1120.
[15]刘伟,范爱武,黄晓明.多孔介质传热传质理论与应用[M].北京:科学出版社,2006.LIUWei,FAN Ai-wu,HUANG Xiao-ming.Theory and application of heat and mass transfer in porous media[M].Beijing:Science Press,2006.