隔壁塔分离混合醇的稳态设计和动态控制研究

发布时间：2018-04-09 22:33

本文选题：分隔壁塔　切入点：混合醇　出处：《太原理工大学》2017年硕士论文

【摘要】：低碳醇作为重要的化工产品和潜在的替代燃料具有较大应用潜力。合成气制低碳醇是煤间接液化和清洁利用的重要手段之一,对其产物的分离是该技术实现工业化的重点。本文以课题组前期研究为基础,进料中甲醇265kg/h,乙醇255.8kg/h,正丙醇197.4kg/h,正丁醇110.3kg/h,要求产品纯度均为0.99。采用先脱水后分离得到单醇的策略,利用普通精馏分离甲醇,再利用分隔壁塔分离乙醇-正丙醇-正丁醇的工艺流程。基于模拟软件Aspen Plus和Aspen Dynamics对该过程的稳态设计和动态控制做了全面研究。通过软件自带函数和全年总费用法(TAC)得到了分隔壁塔最优操作参数,并找到了最佳热集成方式和操作压力;在稳态运行的基础上,添加流量变化±5%的恒定扰动,对比考察了4种控制结构的动态响应效果。主要结论如下:(1)通过软件自带函数对隔壁塔分离的稳态过程进行计算和调优,在满足分离要求的情况下对工艺参数进行优化。研究发现4个参数存在最佳范围,其中液相分配比LR最佳范围为0.38-0.42,气相分配比VR最佳范围为0.6-0.63,最佳进料位置与初馏塔塔板数的比约为0.33,最佳出料位置与主塔塔板数的比为0.5;固定上述4个参数后,通过TAC法求出主塔塔板数为54块,初馏塔塔板数为27块,侧线抽出位置为第12块,分隔壁塔回流比为2.17。在此条件下,全年总费用174478美元。(2)以节能为目标,研究了不同的热集成方式,发现两塔最优方式为逆流型,最优压力组合方式为低压(前效压力,0.3atm)-常压(后效压力,1atm)。相对于传统两塔流程,整个过程耗能265.2kW,总节能效率为51.4%。(3)采用塔顶冷凝器负荷QC控制主塔塔顶压力,并且考虑塔板存在滞后效应,得出以下4种控制结构:LQR/DSB、LB/DSQR、DB/LSQR、DQR/LSB,来分析其抗干扰性能。在忽略液相分配量LL控制初馏塔压力的情况下发现纯度控制不理想,原因是初馏塔塔顶压力的不可控。在添加LL控制初馏塔压力后,发现上述4种控制策略中DB/LSQR(塔顶采出量D控制塔顶液位、塔釜采出量B控制塔釜液位、回流量L控制塔顶产品纯度、侧线采出量S控制侧线产品纯度、再沸器负荷QR控制塔釜产品纯度)在面临流量扰动时,控制效果最理想,且通过添加温度-组成串级控制可以进一步缩短调节时间,减小最大偏差。
[Abstract]:Low-carbon alcohols as important chemical products and potential alternative fuels have great application potential.The synthesis of low carbon alcohols from syngas is one of the important methods for indirect liquefaction and clean utilization of coal, and the separation of its products is the focus of industrialization.Based on the previous research of our group, the purity of methanol in feed was 265kg / h, ethanol was 255.8 kg / h, n-propanol 197.4kg / h, n-butanol 110.3kg / h, and the purity of product was 0.99kg / h.The strategy of dehydration and then separation of monool was adopted, methanol was separated by ordinary distillation, and the process of separation of ethanol-n-propanol-n-butanol in the next row column was used.Based on the simulation software Aspen Plus and Aspen Dynamics, the steady state design and dynamic control of the process are studied.The optimal operating parameters of the adjacent tower are obtained by using the software self-contained function and the annual total cost method, and the optimal thermal integration mode and operating pressure are found, and a constant disturbance of 卤5% flow rate is added on the basis of steady-state operation.The dynamic response effects of four control structures are compared and investigated.The main conclusions are as follows: (1) the steady-state process of the separation of the adjacent tower is calculated and optimized by the software self-contained function, and the process parameters are optimized under the condition of satisfying the separation requirements.The study found that there is an optimal range of four parameters.The optimum range of LR is 0.38-0.42, the best range of Vapor partition ratio VR is 0.6-0.63, the ratio of the best feed position to the number of plates in the primary column is about 0.33, the ratio of the optimal discharge position to the number of main tray is 0.5.By TAC method, the main tower plate number is 54, the primary column plate number is 27, the side line extraction position is the 12th block, and the reflux ratio of the next column is 2.17.Under this condition, the total cost of the whole year is $174478. The purpose of energy saving is to study different thermal integration methods. It is found that the optimal mode of two towers is countercurrent and the optimal pressure combination is low pressure (pre-effect pressure 0.3atmg-normal pressure).It is found that the purity control is not ideal because the top pressure of the primary distillation tower is not controllable.After adding LL to control the pressure of the primary distillation tower, it is found that among the four control strategies mentioned above, DB-LSQR (top recovery D) controls the top liquid level of the tower, the tank yield B controls the liquid level of the tower, and the reflux L controls the purity of the top product of the tower.The side line yield S controls the purity of the side line product and the product purity of the reboiler load QR control tower. When the flow is disturbed, the control effect is the most ideal, and the adjustment time can be further shortened by adding temperature and composition cascade control.Reduce the maximum deviation.
【学位授予单位】：太原理工大学
【学位级别】：硕士
【学位授予年份】：2017
【分类号】：TQ223.1;TQ028.31

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