环氧丙烷尾气甲醇吸收及纯化工艺

doi:10.11949/0438-1157.20191392

摘要/Abstract

摘要：

针对环氧丙烷生产中环氧丙烷尾气难回收问题，提出了甲醇吸收和环氧丙烷萃取精馏解吸回收的环氧丙烷回收新工艺。该工艺同时考虑无催化环氧丙烷水解和与甲醇反应，并采用共沸精馏分离获得高附加值产品丙二醇单甲醚。选用NRTL热力学方法，对上述流程进行了全流程模拟和优化设计，分析了溶剂比、理论塔板数、吸收剂进料温度等主要工艺参数对分离的影响规律，发现新工艺对环氧丙烷质量回收率达到99.99%。研究结果对环氧丙烷工业装置产能提升、节能降耗和挥发性有机物(VOC_S)治理具有指导作用。

关键词: 双氧水法, 环氧丙烷, 吸收, 萃取精馏, 共沸分离

Abstract:

Aiming at the difficulty of recovering the propylene oxide tail gas in the process of producing propylene oxide by the hydrogen peroxide method, a new propylene oxide recovery process using methanol in the reaction unit as the absorbent and extraction distillation column in the refining unit as the desorption tower was proposed. The reactions of both PO hydrolysis and PO and methanol reaction without catalyst were considered and the high-value product of propylene glycol monomethyl ether was additionally obtained through azeotropic distillation technology. The simulation and design optimization for the full process using Aspen Plus package with NRTL thermodynamic model was carried out, and the influence of the main technological parameters, such as solvent ratio, the number of theoretical plates, and the feed temperature of methanol was discussed. The calculations showed that the mass recovery yield of PO was up to 99.99%. The presented process would play an important role in product capacity improvement, energy saving and volatile organic compounds (VOCs) treatment in HPPO plant.

Key words: hydrogen peroxide process, propylene oxide, absorption, extractive distillation, azeotrope separation

中图分类号:

TQ 028.8

胡松, 李进龙, 杨卫胜. 环氧丙烷尾气甲醇吸收及纯化工艺[J]. 化工学报, 2020, 71(4): 1657-1665.

Song HU, Jinlong LI, Weisheng YANG. Propylene oxide offgas recovery and purification process with methanol solvent[J]. CIESC Journal, 2020, 71(4): 1657-1665.

图/表 16

表1 不同组分间结合能

Table 1 Binding energies of different components/(kJ/mol)

N₂-PO	N₂-CH₃OH	PO-CH₃OH	H₂O-CH₃OH	H₂O-PO	CH₃CHO-CH₃OH	CH₃OOCH-CH₃OH
-1.59	-0.42	-7.89	-15.35	-13.60	-13.47	-3.46

图1 极化的表面链节电荷密度分布

Fig.1 σ profiles for different molecules

图2 水对PO-甲醇相对挥发度的影响

Fig.2 Effect of water on relative volatility of PO to methanol

图3 环氧丙烷尾气回收及循环甲醇纯化工艺流程简图

Fig.3 Flowsheet of propylene oxide (PO) offgas recovery and recycle methanol purification process

图4 体系蒸馏残余曲线

Fig.4 Distillation residue curves of research system

图5 UNIFAC（线）和COSMO-SAC（点）预测的二元汽液平衡

Fig.5 VLE for binary mixtures predicted from UNIFAC(line) and COSMO-SAC(dot) at 101.3 kPa

图6 OAC溶剂比对吸收过程的影响

Fig.6 Effect of mass ratio of absorbent to offgas on absorption process

图7 吸收剂温度对分离过程的影响

Fig.7 Effect of absorbent temperature on absorption process

图8 OAC理论级数对分离过程的影响

Fig.8 Effect of OAC theoretical stages on absorption process

图9 EDC溶剂比对分离过程的影响

Fig.9 Effect of solvent ratio on separation process

图10 EDC理论塔板数对分离过程的影响

Fig.10 Effect of number of theoretical stage on separation process

图11 EDC回流比对产品和再沸器能耗的影响

Fig.11 Effect of reflux ratio on PO product and reboiler heat duty

图12 萃取剂(a)和粗PO(b)进料位置对分离过程的影响

Fig.12 Effect of feed stage of solvent (a) and crude PO (b) on process

表2 流程模拟优化工艺条件

Table 2 Optimization parameters for flowsheet simulation

Unit block	Parameter	Value
absorption column (OAC)	operating pressure	180 kPa
	operating temperature	20.0℃
	theoretical stage	12
	feed stage of PO offgas	12
	temperature of solvent	20.0℃
	solvent ratio	1.0
extractive distillation column (EDC)	operating pressure	50 kPa
	theoretical stage	54
	feed stage of solvent	26
	feed stage of crude PO	44
	solvent ratio(mass)	0.12
	reflux ratio(mass)	2.9
methanol recovery column (MRC)	operating pressure	20 kPa
	theoretical stage	42
	feed stage of feeding	20
	stage of side product	24
	reflux ratio(mass)	2.2
azeotropic distillation column (ADC)	operating pressure	20 kPa
	theoretical stage	11
	stage of feeding	5
	solvent ratio(mass)	6.72

图13 吸收塔(a)、萃取精馏塔(b)、甲醇回收塔(c)和共沸精馏塔(d)温度和关键组分分布

Fig.13 Profiles of temperature and key components in OAC(a), EDC(b), MRC(c) and ADC(d)

图14 全流程物流平衡图

Fig.14 Balance of mass flow for all key components(F—mass flow, kg/h; unit of mass composition,%)

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