与换热网络热集成的精馏塔压优化

doi:10.11949/0438-1157.20220046

摘要/Abstract

摘要：

调整精馏塔的操作条件是节省塔能耗的有效途径之一，然而在对已有装置进行用能优化时，需同时考虑精馏塔操作条件对塔能耗和换热网络能耗的影响。基于装置所有流股的冷热复合曲线，针对跨夹点的精馏塔，同时考虑了精馏塔的再沸、冷凝以及过程流股，分析了塔压变化对装置公用工程消耗的影响，并对某连续重整装置汽提塔进行了案例分析。结果显示，塔压降低可使冷凝器能耗增加，再沸器能耗减小，而对于塔顶塔底出装置流股，塔压降低可节省冷却公用工程但增加加热公用工程。装置总体的节能效果为塔顶冷凝器、塔底再沸器和塔顶塔底出装置流股节能效果的综合作用。对某连续重整装置汽提塔分析表明，塔压降低200.0 kPa时，其加热公用工程用量将减少577.5 kW。

关键词: 系统工程, 换热网络, 精馏塔, 压力, 集成, 优化, 冷热复合曲线

Abstract:

Adjusting operation conditions of a distillation column is one of the effective ways to save energy consumption of the column. However, operation conditions of a distillation column will affect the energy consumption of both the column and the heat exchanger network. Based on the cold and hot composite curves with all streams including the reboiler, condenser, and process streams, this paper analyzes the influence of the pressure variation of an across pinch distillation column on the utility consumption of the whole process. The stripper column in a continuous reforming process is taken as a case study. The results show that the reduction of the column pressure can increase the heat duty of condenser and decrease the heat duty of reboiler. However, for the streams from the top or bottom of the column, the reduction of the column pressure can save cooling utilities but increase heating utilities. The overall energy saving effect of the unit is the comprehensive effect of the condenser, reboiler and streams from the top or bottom of the column. Analysis of the stripper of a continuous reformer shows that when the tower pressure is reduced by 200.0 kPa, the heating utility usage will be reduced by 577.5 kW.

Key words: systems engineering, heat exchanger network, distillation column, pressure, integration, optimization, cold and hot composite curves

中图分类号:

TQ 021.8

段文婷, 任思月, 冯霄, 王彧斐. 与换热网络热集成的精馏塔压优化[J]. 化工学报, 2022, 73(5): 2052-2059.

Wenting DUAN, Siyue REN, Xiao FENG, Yufei WANG. Distillation column pressure optimization integrated with the heat exchanger network[J]. CIESC Journal, 2022, 73(5): 2052-2059.

图/表 10

图1 T101塔流程及不同塔压下再沸器和冷凝器的负荷

Fig.1 The process of column T101 and the heat load of reboiler and condenser under different pressure of distillation column

图2 连续重整装置部分流程示意图

Fig.2 The related flow diagram of the continuous reforming process

图3 换热网络冷热复合曲线

Fig.3 The cold and hot composite curves of the heat exchanger network

表1 换热网络的物流数据

Table 1 Stream data of the heat exchanger network

物流编号	物流名称	换热器	初始温度/℃	目标温度/℃	热负荷/ kW
H1	R204底	E201	493.4	117.0	58300.0
H2	R204底-2	E202	490.8	190.0	42.4
H3	T101底	E105	208.5	132.3	9914.0
H4	T102底	E102	156.3	102.6	6031.0
H5	蒸汽冷凝水	E100	150.0	70.0	4690.0
H6	A201流股	A201	117.2	42.0	7860.0
H7	T102顶	A103	87.4	30.5	4060.0
H8	T101顶	E104	69.1	59.4	2152.0
H8	T101顶	A102	59.4	38.7	1374.0
C1	F201流股	E201	85.5	453.9	58300.0
C1	F201流股	F201	453.9	525.9	11070.0
C2	T101底-2	F102	208.5	221.1	8538.0
C3	吹扫氢	E202	27.0	180.6	42.4
C4	T101进料	E102	48.7	102.0	6031.0
C4	T101进料	E105	102.0	179.8	9914.0
C5	T102底-2	F103	156.3	164.4	9440.0
C6	预加氢进料	E104	40.0	58.0	2152.0

图4 T101压力降低200.0 kPa前后复合曲线对比

Fig.4 Comparison of the composite curves before and after 200.0 kPa pressure reduction of T101

表2 T101压力降低200.0 kPa前后相关流股数据

Table 2 Stream data before and after 200.0 kPa pressure reduction of T101

物流	改变	入口温度/℃	出口温度/℃	压力/kPa	热负荷/kW	热容流率/(kW/℃)
H3	前	208.5	132.3	1241.0	9914.0	130.1
H3	后	201.9	132.3	1041.0	9007.0	129.4
H8	前	69.1	38.7	1187.0	3526.0	116.0
H8	后	61.8	32.2	987.0	3605.0	121.8
C2	前	208.5	221.1	1241.0	8538.0	677.6
C2	后	201.9	209.8	1041.0	6751.0	854.5
C4	前	48.7	179.8	1241.0	15945.0	121.6
C4	后	48.7	179.8	1041.0	16244.0	123.9

表3 T101操作压力降低200.0 kPa前后换热器热通量

Table 3 Heat flux of the heat exchangers before and after 200.0 kPa pressure reduction of T101

换热器名称	热通量/ (kJ/(℃·h))	降低200.0 kPa后热通量/(kJ/(℃·h))	增加倍数
E102	401263.7	498896.5	1.2
E104	520916.9	1037990.3	2.0
E105	1209558.0	1533242.4	1.3
E1	—	51069.6(26.8 m²)	—

图5 夹点之上源复合曲线变化

Fig.5 Variation of source composite curve above the pinch

图6 夹点之上阱复合曲线变化

Fig.6 Variation of sink composite curve above the pinch

图7 夹点之下复合曲线对比

Fig.7 Comparison of the composite curves below the pinch

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