Process design and energy saving for benzene/cyclohexane/cyclohexene extractive distillation process

doi:10.11949/0438-1157.20241076

Abstract

Abstract:

Cyclohexene is an important chemical raw material, and the partial hydrogenation of benzene is a primary method of production. However, the process generates unconverted benzene and cyclohexane as a by-product. The distillation of cyclohexene consumes a lot of energy. This study explores the potential for energy savings in the distillation processes of benzene, cyclohexane, and cyclohexene. Aspen Plus simulation was employed to optimize and compare the economic viability of a four-column industrial extractive distillation process (FC) and a three-column extractive distillation process (TC), identifying the three-column process as more efficient. Based on the TC process, the heat integrated process (TH), heat pump assisted heat integrated process (THP), dividing wall tower-benzene tower process (EC1), cyclohexane tower-dividing wall tower process (EC2), heat pump assisted dividing wall tower-benzene tower process (EHP1) and heat pump assisted cyclohexane tower-dividing wall tower process (EHP2) were proposed. The results indicate that the heat pump-assisted cyclohexane column-dividing wall column process is the most optimal, achieving reductions in annual total cost, energy consumption, and CO₂ emissions by 21.1%, 32.6%, and 31.7%, respectively, compared to the three-column extractive distillation process.

Key words: distillation, purification, separation, simulation, cyclohexene

摘要：

环己烯是重要的化工原料，苯部分加氢法是生产环己烯的重要途径，其加氢产物中存在未转化的苯和副产物环己烷，精馏分离过程能耗巨大。以苯/环己烷/环己烯精馏过程的节能为研究对象，采用Aspen Plus模拟进行了工业四塔萃取精馏流程（FC）和三塔萃取精馏流程（TC）的优化设计和经济性对比，并确定TC流程为较优流程。在TC流程基础上，提出了热集成流程（TH）、热泵辅助热集成流程（THP）、隔壁塔-苯塔流程（EC1）、环己烷塔-隔壁塔流程（EC2）、热泵辅助隔壁塔-苯塔流程（EHP1）和热泵辅助环己烷塔-隔壁塔流程（EHP2）。结果表明，与三塔萃取精馏流程相比，改进流程相比于TC流程在TAC、能耗和CO₂排放量上均有不同程度的降低，其中EHP2流程的年度总成本、能耗和CO₂排放量分别降低了21.1%、32.6%和31.7%，是最佳的流程。

关键词: 精馏, 纯化, 分离, 模拟, 环己烯

CLC Number:

TQ 028.4

Linrui YANG, Jianyi LIU, Ling LI, Yongchao HE, Kaitian ZHENG, Jianpo REN, Chunjian XU. Process design and energy saving for benzene/cyclohexane/cyclohexene extractive distillation process[J]. CIESC Journal, 2025, 76(2): 731-743.

杨林睿, 刘鉴漪, 李玲, 何永超, 郑凯天, 任建坡, 许春建. 苯/环己烷/环己烯萃取精馏过程的流程设计与节能[J]. 化工学报, 2025, 76(2): 731-743.

Figures/Tables 25

Fig.1 Ternary diagram of benzene/cyclohexane/cyclohexene at 101.325 kPa

Fig.2 The predicted data by NRTL and the experimental data

Table 1 Utility parameters

项目	数值	单位
冷凝水，298~308 K	0.354	USD/GJ
低压蒸气，433.15 K	13.280	USD/GJ
中压蒸气，462.15 K	14.190	USD/GJ
电费	16.800	USD/GJ

Fig.3 Block diagram of the optimization for FC

Fig.4 Optimized design of FC

Fig.5 Block diagram of the optimization for TC

Fig.6 Optimized design of TC

Fig.7 Temperature profile of C1 for TC

Fig.8 Optimized design of TH

Fig.9 Temperature profile of stripping section in C1 column for TH

Fig.10 Optimized design of THP

Fig.11 Temperature profile of stripping section in C1 column for THP

Fig.12 Equivalent flowsheet for simulating the dividing wall column

Fig.13 Block diagram of the optimization for EC1

Fig.14 Optimized design of EC1

Fig.15 Block diagram of the optimization for EC2

Fig.16 Optimized design of EC2

Fig.17 Temperature profile of cyclohexene rectifying section and stripping section in C1 for EC1

Fig.18 Optimized design of EHP1

Fig.19 Temperature profile of stripping section in C1 for EHP1

Fig.20 Optimized design of EHP2

Fig.21 Temperature profile of stripping section in C1 for EHP2

Fig.22 Comparison of TAC for processes

Fig.23 Comparison of energy for processes

Fig.24 Comparison of CO2 emission for processes

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