Energy-saving investigation of separation for methanol-water with different feed compositions through double-effect distillation

doi:10.16085/j.issn.1000-6613.2019-0929

Abstract

Abstract: Methanol-water mixtures with different compositions exist in many industrial processes, and the main consideration is energy consumption when separating methanol and water. In view of the separation process of methanol-water with methanol concentration of 10%-90% (mass fraction), different distillation models with light split forward, light split reverse and feed splitting were adopted. Using "Design Spec/Vary" function to find the values of distillate flowrate and reflux ratio that the distillate composition to 99.85% (mass fraction) methanol and the bottoms composition to 10^-5 methanol. The sensitivity analysis method was used to optimize the number of trays and the feed trays to obtain the minimum annual total cost (TAC). Furthermore, the energy loss of each process under the minimum TAC condition is compared and analyzed. When the methanol concentration of the raw methanol-water mixtures is 30% or less, the TAC of the feed splitting is the smallest; when the methanol concentration of the raw methanol-water mixtures is 50% or more, the TAC of light split reverse configuration is the smallest. In the case of minimum TAC for each process, the exergy loss of feed splitting process is the smallest when the methanol concentration of the raw methanol-water mixtures is 10% or less; the exergy loss of light split reverse process is the smallest when the methanol concentration of the raw methanol-water mixtures is 30% or more. The TAC and exergy loss analysis of methanol-water mixtures separation can provide a theoretical reference for the optimal double-effect distillation of methanol-water with different feed compositions in industry.

Key words: methanol-water, double-effect distillation, simulation, optimization, exergy

摘要： 不同浓度的甲醇水溶液存在于诸多工业过程中，精馏分离甲醇和水时最主要考虑能耗问题。本文针对甲醇质量分数为10%~90%甲醇水溶液的分离过程，分别采用双塔顺流串联、双塔逆流串联和双塔并联的不同精馏模型，通过设计规定，以回流比和塔顶采出量为操纵变量，分别控制甲醇产品纯度大于99.85%（质量分数），以及废水甲醇含量小于10^-5；以最小年度总费用（TAC）为优化目标，用灵敏度分析法优化塔板数及进料位置，并对比分析了各流程在最小TAC条件下的（火用）损失。结果表明，当原料甲醇质量分数在30%及以下时，TAC最小的是并联精馏；当原料甲醇浓度在50%及以上时，TAC最小的是逆流串联精馏。在各流程最小TAC情况下，原料甲醇质量分数在10%及以下时，有效能损失最小的是并联精馏；原料甲醇质量分数在30%及以上时，有效能损失最小的是逆流串联精馏。对于甲醇水溶液精馏分离的TAC和（火用）损失分析，可为工业中不同甲醇浓度下，甲醇水溶液的最佳双效精馏方案提供理论参考。

关键词: 甲醇水溶液, 双效精馏, 模拟, 优化, (火用)

CLC Number:

TQ015

ZHANG Ting, WEI Shun'an, SHEN Weifeng. Energy-saving investigation of separation for methanol-water with different feed compositions through double-effect distillation[J]. Chemical Industry and Engineering Progress, 2019, 38(s1): 52-58.

张婷, 魏顺安, 申威峰. 双效精馏分离不同浓度甲醇水溶液的节能分析[J]. 化工进展, 2019, 38(s1): 52-58.

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