费托合成水中混合醇初步分离工艺的实验与模拟

Experiment and simulation of preliminary separation process of mixed alcohols in Fischer-Tropsch water

  • 摘要: 针对费托合成水中混合醇的分离问题,提出了利用隔壁塔(DWC)精馏技术初步分离混合醇的工艺。在忽略隔板传热的情况下,利用DWC小试实验装置进行了实验研究,并通过Aspen Plus模拟软件利用四塔模型严格模拟计算用于混合醇初步分离的DWC工艺。根据DWC小试实验参数进行模拟设定,并以产品关键组成和塔内温度分布为依据对比模拟与实验结果,进而验证了模拟过程的准确性。以寻求精馏过程再沸器热负荷最小值为目标,并将产品分离要求作为约束条件,使用序列二次规划(SQP)优化方法结合灵敏度分析工具对常规精馏序列工艺和DWC工艺进行参数优化。通过分析最佳参数条件下常规精馏序列工艺和DWC工艺的温度分布和关键组分浓度分布,对常规精馏序列工艺中间组分的返混现象和DWC工艺模拟过程忽略隔板传热的可行性做出了阐述。基于公平的优化模拟结果,分析对比了常规精馏序列工艺和DWC工艺的经济性和二氧化碳(CO2)排放量。结果表明,DWC工艺相比常规精馏序列工艺可降低47.8%的能源消耗和47.8%的CO2排放量,并且减少24.1%的设备总投资成本(CTI)和475%的年度总运营成本(CTO含量),从而使年度总成本(CTA)降低了43.8%。因此,将DWC技术应用于费托合成水中混合醇的分离具有非常显著的优势。

     

    Abstract: A dividing wall column ( DWC) process was proposed for the preliminary separation of mixed alcohols in Fischer-Tropsch water. In the case of neglecting the heat transfer across the dividing wall,the experimental study was carried out using the DWC laboratory scale device for the separation of mixed alcohols,and the four-column model was used to strictly simulate the DWC process by Aspen Plus software. The simulation was set according to the DWC exper- imental parameters. By comparing the simulated and experimental results based on the key composition of products and the temperature distribution in the column,the accuracy of the simulation was verified. The sequential quadratic pro- gramming (SQP) optimization method combined with sensitivity analysis tool from Aspen Plus was used to optimize the parameters of the conventional distillation sequence ( CDS) process and DWC process. The optimization process aimed to seek the minimum reboiler duty,and took the product separation requirements as a constraint. By analyzing the temperature distribution and key components concentration distribution of CDS and DWC under the optimal param- eters,the back-mixing phenomenon of intermediate components in CDS and the feasibility of ignoring the heat transfer across the dividing wall in the DWC simulation were elaborated. Based on the fair optimization and simulation results, the economics and carbon dioxide (CO2 ) emissions of the CDS process and DWC process were compared. The results show that the DWC process could reduce 47. 8% of energy consumption and 47. 8% of CO2 emissions, and save 24. 1% of total investment cost (CTI ) and 47. 5% of total operating cost (CTO ),thus leading to 43. 8% savings in to- tal annual cost (CTA ) compared with the CDS process. Therefore,the application of DWC technology in the separation of mixed alcohols in Fischer-Tropsch water has very significant advantages.

     

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