Research and optimization of separation technology of methanol to propylene

doi:10.11949/j.issn.0438-1157.20171033

Abstract

Abstract:

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.

Key words: methanol to propylene, simulation and optimization, separation technology, absorption, heat integration distillation

摘要：

以170万吨/年甲醇制丙烯（MTP）实际装置为背景，对MTP分离流程进行了研究和优化，借鉴石脑油乙烯装置分离的经验，并针对MTP产品气的组成特点，优化形成了适合MTP产品气分离的顺序、前脱丙烷和前脱乙烷分别组合装置自身物料做吸收剂的中冷油吸收技术的三种分离流程，省去了乙烯制冷系统。通过对全流程模拟计算数据的对比分析，优选出了前脱乙烷组合装置自身物料做吸收剂的中冷油吸收技术分离流程。对优化组合采用脱乙烷预分离技术、脱甲烷塔尾气回收分凝分馏塔技术、吸收剂物流的选择、碳二分离高度热耦合技术进行了研究，并通过对全流程模拟计算数据的比较分析，优选出了最优化的分离流程，即前脱乙烷中冷油吸收流程组合预分离技术、用自身物流混合碳四做吸收剂、分凝分馏塔回收脱甲烷塔尾气技术和高度热耦合的脱碳二分离技术。在没有乙烯、碳四和碳五循环回MTP反应器及尾气中乙烯损失满足设计要求的前提下，采用此优选分离流程，产品气压缩机和丙烯压缩机双机功率为19.8 MW。

关键词: 甲醇制丙烯, 模拟优化, 分离流程, 吸收, 热偶合精馏

CLC Number:

TQ 021.8

Zizong WANG, Hongqian LIU, Jiming WANG. Research and optimization of separation technology of methanol to propylene[J]. CIESC Journal, 2019, 70(1): 136-145.

王子宗, 刘洪谦, 王基铭. 甲醇制丙烯分离流程的研究与优化[J]. 化工学报, 2019, 70(1): 136-145.

Figures/Tables 18

Table 1 Composition of product gas from methanol-to-propylene device[3]

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

Fig.1 Schematic diagram of sequential separation technique (C3H8 as absorbent)

Fig.2 Schematic diagram of front-end depropanization separation technique (C3H8 as absorbent)

Fig.3 Schematic diagram of front-end deethanizer separation technique (C3H8 as absorbent)

Table 2 Utility consume of sequential separation, front-end depropanizer and front-end deethanizer processes (C3H8 as absorbent)

流程	产品气压缩机/MW	丙烯压缩机/MW	冷却水消耗/(kt/h)	低压蒸汽消耗/（t/h）	高压蒸汽消耗/（t/h）
顺序分离	12.80	8.43	43.95	160.5	143.7
前脱丙烷	13.74	10.31	46.266	183	162.8
前脱乙烷	13.3	8.3	51.331	186	149.3

Fig.4 Comparison of standard fuel oil consumption in sequential separation, front-end depropanizer and front-end deethanizer processes (C3H8 as absorbent)

Fig.5 Schematic diagram of sequential separation technique (C4S as absorbent)

Fig.6 Schematic diagram of front-end depropanizer separation technique (C4S as absorbent)

Fig.7 Schematic diagram of front-end deethanizer separation technique (C4S as absorbent)

Table 3 Utility consume of sequential separation, front-end depropanizer and front-end deethanizer processes (C4S as absorbent) （clear cutting rectification）

流程	产品气压缩机/MW	丙烯压缩机/MW	冷却水消耗/(kt/h)	低压蒸汽消耗（t/h）	高压蒸汽消耗/（t/h）
顺序分离	12.80	7.66	39.60	129	139
前脱丙烷	14.00	10.01	37.165	89	162.8
前脱乙烷	13.00	8.26	37.036	90.6	143

Fig.8 Comparison of standard fuel oil consumption in sequential separation, front-end depropanizer and front-end deethanizer processes(C4S as absorbent) (clear cutting rectification)

Fig.9 Standard fuel oil consumption of separation section using C3H8 and C4S as absorbent individually

Fig.10 Schematic diagram of front-end deethanizer separation process (C4S as absorbent, non-clear cutting)

Table 4 Utility consume of front end de-deethanizer (C4S as absorbent)

流程

产品气压缩机/MW

丙烯压缩机/MW

冷却水消耗/

(kt/h)

低压蒸汽消耗/

（t/h）

高压蒸汽消耗/

（t/h）

Fig.11 Comparison of fuel oil consumption of front-deethanizer process (clear cutting and non-clear cutting)

Fig.12 Thermally coupled non-clear cutting process of front-end deethanizer separation technique (C4S as absorbent)

Table 5 Utility consume of thermally coupled front-end deethanizer separation technique (C4S as absorbent)

产品气压缩机/MW	丙烯压缩机/MW	冷却水消耗/(kt/h)	低压蒸汽消耗/（t/h）	高压蒸汽消耗/（t/h）
12.8	7.05	210	77.4	135.2

Fig.13 Comparison of standard fuel oil consumption in conventional and thermally coupled for non-clear cutting front-end deethanizer separation

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