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Research and optimization of separation technology of methanol to propylene
Zizong WANG, Hongqian LIU, Jiming WANG
CIESC Journal    2019, 70 (1): 136-145.   DOI: 10.11949/j.issn.0438-1157.20171033
Abstract   (557 HTML20 PDF(pc) (925KB)(198)  

Based on the actual equipment of 1.7 million tons/year methanol to propylene (MTP), this paper studies and optimizes the MTP separation process, draws on the experience of separation of naphtha ethylene unit, and optimizes the formation characteristics of MTP product gas. The process combination, process simulation and optimization of the separation technology are carried out together with de-methanizer tower and its exhaust gas recovery system, highly thermal coupling decarburization system (de-ethanizer and ethylene rectifying column), sorbent selection, and screen out a more suitable separation technology consisting of the following process unit: pre-cutting front-end deethanizer, recovery of de-methanizer tail gas by combination of intercooling oil absorption and throttle expansion, highly thermally coupled deethanizer system, take carbon four mixture as absorbing agent, etc.Assuming that there are no ethylene, carbon four and carbon five cycles back to the MTP reactor, the ethylene loss in the exhaust meets the design requirements, using the optimized separation technique, the dual power of the compressor and propylene compressor is 19.8 MW. The simulation results show that the optimized flow has a good application prospect.


组分 摩尔分数/%
H2 0.2
N2 0
O2 0
CO 0.4
CO2 0.15
H2S 0
oxide 1.7
CH4 3.8
C2H2 0
C2H6 2.2
C2H4 14.3
C3H8 0.7
C3H6 25.2
C3H4 0
C4 20.1
C5 + 31.25
Table 1 Composition of product gas from methanol-to-propylene device[3]
Extracts from the Article
混合烯烃分离流程主要有顺序、前脱丙烷和前脱乙烷三种[9,11,12,13],为便于流程模拟和对比,首先对现有170万吨/年 Lurgi MTP装置进行标定,对现有装置进行模拟,在物料平衡和换热器热负荷距设计值误差5%的前提下,确定了后续流程方案对比的模拟策略和方法。在此基础上,设计如下:(1)假设粗乙烯全部进入脱碳二系统分离得到聚合级乙烯产品,不考虑粗乙烯和混合碳四返回MTP反应器进行歧化反应;(2)分离部分关键塔器如脱甲烷塔、脱乙烷塔、脱丙烷塔、乙烯精馏塔、丙烯精馏塔和凝液汽提塔的分离任务完全按照170万吨MTP装置相关塔器的设计规定,其中乙烯精馏塔产品纯度为聚合级乙烯,丙烯精馏塔产品纯度为聚合级丙烯; (3)装置处理甲醇能力为170万吨/年,产品气压缩机和丙烯压缩机的多变效率取83%,丙烯冷剂温度等级分别为7℃、-27℃和-40℃;(4)产品气采用四段压缩;(5)分别用丙烷C3H8、混合碳四C4S做吸收剂;(6)用中冷油吸收和膨胀节流技术回收脱甲烷塔尾气中的乙烯[14,15];(7)中冷油吸收采用组合吸收塔技术 [14,15,16,17,18,19];(8)暂不考虑甲醇和二甲醚脱除对流程的影响;(9)先假定前脱丙烷和前脱乙烷流程采用清晰切割技术; (10)产品气压缩机一段吸入的物料组成见表1。
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