Abstract: The traditional method of phosgene recovery for 3-chloro-4-methyl phenyl isocyanate (CMPI) equipments has following disadvantages：The phosgene cannot be recovered completely. Once the phosgene goes to the off-gas，there would be some bad consequence such as：the security of system is decrease；the security of system，the cost of production，the consumption of sodium hydroxide and the discharge of waste water are increase. The research in references which studied the phosgene recovery for producing toluene diisocyanate cannot be used in CMPI system for the difference of reactive conditions. An equipment of 2000 t/a for producing CMPI was taken for example，the phosgene recovery system was simulated and optimally designed：Under the condition of meeting the technological requirements，the number of theoretical plates was identified as 12 and the optimal feeding rate was defined as 780 kg/h. We as compared the phosgene recovery systems of normal pressure reactive system and that of high pressure. The results showed that under normal pressure system，the phosgene recovery system needed more absorbent than that of under high pressure，but no intercooler in the absorber was needed and the theoretical explanation for the phenomenon was provided. Considered the generility for various kinds of isocyanate production processes，the conclusion of this study can be applied in other similar isocyanate equipments.

Key words: isocyanate, phosgene recovery, optimal design, simulation and optimization

摘要： 传统冷凝回收3-氯-4-甲基苯基异氰酸酯（CMPI）生产装置尾气的方法具有以下不足：不能保证光气完全回收，而一旦光气进入尾气破坏系统，不仅会增加产品的成本，而且还会降低系统安全性、增加碱液消耗和废水排放；文献中研究的甲苯二异氰酸酯装置的尾气回收系统，由于反应条件的不同，不能适用于常压CMPI装置。本文以年产2000 t CMPI常压反应装置为例，对其光气回收系统进行了模拟分析和优化设计，确定了满足工艺要求的最佳理论塔板数为12，最佳吸收剂甲苯用量为780 kg/h。对常压装置与高压装置光气回收系统进行了比较，认为常压装置的光气回收系统需要更多的吸收剂用量，但是不需要在塔中增加中间冷却器，并给出了理论上的解释。考虑异氰酸酯生产工艺的共性，本文研究结论可以推广应用于其他类似异氰酸酯装置。

关键词: 异氰酸酯, 光气回收, 优化设计, 模拟优化