MTO烯烃分离过程的多目标操作优化

doi:10.11949/0438-1157.20200698

Abstract

Abstract:

In modern coal processing industries, methanol-to-olefins (MTO) is an important equipment. Its olefin separation process is facing with problems such as the change of raw materials, the loss of olefin products and the high consumption of utilities. Operation optimization is required to achieve maximum benefits under the circumstance of quality assurance and requirements. This article takes the pre-depropanized olefin separation process of Lummus as the research object. And the optimization objectives are the total yield of ethylene and propylene as well as the total energy consumption. Modeling, simulation and multi-objective optimization of the process are conducted. Non-dominated sorting genetic algorithm (NSGA-II) is used to solve multi-objective optimization problem. The simultaneous optimization of 15 operational variables is achieved. Under the current yield, the optimal operation point is found by reducing the reflux ratio of low pressure depropanizer, deethanizer and 1^# propylene tower and so on. The results show that the optimal operating point can reduce energy consumption by 20 MW compared with the existing operating point. The optimization interval of each operation variable corresponding to different trade-off points is determined by the comprehensive analysis of decision variables. It is also found that distillation equipment can operate in different optimal operation intervals.

Key words: methanol-to-olefins, olefin separation, multi-objective optimization, olefin yield, energy conservation

CLC Number:

TQ 221.2

Lu YANG, Shuoshi LIU, Xiaoyan LUO, Siyu YANG, Yu QIAN. Multi-objective operation optimization of olefin separation process for MTO plant[J].CIESC Journal, 2020, 71(10): 4720-4732.

Figures/Tables 12

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塔名称	压力/MPa(G)	塔顶/塔底温度/℃
DP1	1.85	15.8/80
DP2	0.77	14.4/79.2
DM	2.65	-11.1/13.8
DE	2.40	-20.4/62.7
ET	1.64	-34.3/-11.6
PT2	1.94	51.9/59.1
PT1	1.80	45.8/51.8
DB	0.37	46.8/92.6

Stream	Temperature/ ℃	Pressure/ MPa(G)	Mass flow/ (t/h)	Mole flows/(kmol/h)	Mole fraction/%
Stream	Temperature/ ℃	Pressure/ MPa(G)	Mass flow/ (t/h)	Mole flows/(kmol/h)	H₂,N₂,CO	CH₄	C₂H₆	C₂H₄	C₃H₈	C₃H₆	C₄H₁₀	C₄H₈	C₄H₆	C5	CH₃OCH₃
feed 1^①	12.2	2.139	47.89	1190	0.35	0.41	0.71	33.27	3.02	45.12	0.54	12.57	0.31	3.64	0.05
feed 2^①	11.5	1.87	49.12	1638	5.85	6.26	1.04	60.8	1.47	22.77	0.08	1.55	0.04	0.13	0.02
1	-34.1	1.641	38.52	1373	trace	0.01	0.04	99.95	0	trace	0	0	0	0	0
2	46	1.803	38	903	0	trace	0.02	0	0.35	99.64	0	0	0	0	0
3	40.1	0.369	10.5	188	0	0	0	0	0.1	0.15	4.08	92.85	2.25	0.5	0.07
4	89.2	0.407	3.37	48	0	0	0	0	0	1×10^-12	0.01	0.62	0	99.37	0
1^①	-34.2	1.641	38.52	1373	0	0.01	0.04	99.95	0	0	0	0	0	0	0
2^①	45.8	1.803	38	903	0	0	0.02	0	0.35	99.63	0	0	0	0	0
3^①	39.6	0.369	10.5	188	0	0	0	0	0.1	0.15	4.09	92.87	2.24	0.5	0.07
4^①	92.6	0.407	3.37	48	0	0	0	0	0	0	0.01	0.62	0	99.37	0

符号	变量	下限	上限
x₁	高压脱丙烷塔(DP1)塔顶采出量, kg/h	101000	105000
x₂	高压脱丙烷塔(DP1)回流比	1.18	1.23
x₃	低压脱丙烷塔(DP2)回流比	1.0	1.4
x₄	低压脱丙烷塔(DP2)塔顶采出量, kg/h	7600	8240
x₅	脱丁烷塔(DB)回流比	0.95	1.2
x₆	脱丁烷塔(DB)塔顶采出量, kg/h	10200	10700
x₇	脱甲烷塔(DM)塔顶采出量, kg/h	4150	4350
x₈	脱甲烷塔(DM)丙烷流量, kg/h	16200	17400
x₉	脱乙烷塔(DE)回流比	1.3	1.6
x₁₀	脱乙烷塔(DE)塔顶采出量, kg/h	40000	43000
x₁₁	乙烯塔(ET)塔顶采出量, kg/h	143000	147000
x₁₂	乙烯塔(ET)中间测线采出量, kg/h	37000	40000
x₁₃	2^#丙烯塔(PT2)塔顶采出量, kg/h	524000	536000
x₁₄	1^#丙烯塔(PT1)塔顶采出量, kg/h	37350	39000
x₁₅	1^#丙烯塔(PT1)回流比	14.0	18.0

符号	变量	A (150.49 MW, 33.59%)	B (155.22 MW, 34.44%)	Q_P (153.42 MW, 34.23%)	Q^* (174 MW, 34.15%)	Q_P与Q^* 偏差%
x₁	DP1塔顶采出量, kg/h	101220	101860	101740	104450	-2.6
x₂	DP1回流比	1.219	1.219	1.219	1.219	0
x₃	DP2回流比	1.332	1.000	1.024	1.203	-14.8
x₄	DP2塔顶采出量, kg/h	7680	8160	8070	7960	+1.5
x₅	DB回流比	1.038	0.962	0.954	0.988	-3.3
x₆	DB塔顶采出量, kg/h	10370	10280	10280	10500	-2.1
x₇	DM塔顶采出量, kg/h	4240	4225	4225	4255	-0.7
x₈	DM丙烷流量, kg/h	17000	16360	16330	16940	-3.6
x₉	DE回流比	1.30	1.37	1.41	1.50	-6.7
x₁₀	DE塔顶采出量, kg/h	41800	40890	40790	40580	+0.5
x₁₁	ET塔顶采出量, kg/h	145080	146670	146650	147050	-0.3
x₁₂	ET中间测线采出量, kg/h	39600	40000	40000	40000	0
x₁₃	PT2塔顶采出量, kg/h	528415	524650	524315	531350	-1.3
x₁₄	PT1塔顶采出量, kg/h	37460	39000	38520	38340	+0.5
x₁₅	PT1回流比	15.00	15.20	15.08	18.00	-16.2

位置	项目	主要设备节能占比			主要设备节能相对变化率
位置	项目	再沸器	冷凝器	总和	再沸器	冷凝器	总和
A	DP1	1.33%	2.75%	4.08%	5.03%	-27.31%	11.18%
	DP2	0.42%	-0.13%	0.29%	5.04%	1.75%	1.81%
	DB	-0.75%	-0.89%	-1.64%	-9.58%	10.12%	-9.86%
	DE	0.99%	1.12%	2.11%	3.03%	-5.27%	3.91%
	PT2	5.70%	—	91.06%	3.31%	—	18.38%
	PT1	39.76%	45.60%	91.06%	53.57%	-18.31%	18.38%
	other	—	—	4.10%	—	—	1.88%
B	DP1	1.22%	2.30%	3.52%	3.67%	-18.27%	7.70%
	DP2	1.29%	0.64%	1.93%	12.39%	-6.78%	9.72%
	DB	-0.34%	-0.48%	-0.82%	-3.43%	4.42%	-3.95%
	DE	2.28%	1.93%	4.21%	5.55%	-7.25%	6.22%
	PT2	9.04%	—	86.88%	4.20%	—	14.01%
	PT1	34.34%	43.50%	86.88%	36.96%	-13.95%	14.01%
	other	—	—	4.28%	—	—	1.73%
Q_P	DP1	1.22%	2.37%	3.48%	3.93%	-19.97%	8.35%
	DP2	1.21%	0.60%	1.76%	12.43%	-6.75%	9.72%
	DB	-0.28%	-0.43%	-0.69%	-3.08%	4.14%	-3.64%
	DE	1.96%	1.54%	3.39%	5.07%	-6.15%	5.49%
	PT2	8.04%	—	90.74%	4.09%	—	15.62%
	PT1	37.15%	45.55%	90.74%	42.58%	-15.56%	15.62%
	other	—	—	3.64%	—	—	1.55%

Multi-objective operation optimization of olefin separation process for MTO plant

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