Performance Prediction of Structured Packing Column for Cryogenic Air Separation with Hybrid Model

doi:10.1016/j.cjche.2014.06.004

Abstract

Abstract: A detailed investigation of a thermodynamic process in a structured packing distillation column is of great importance in prediction of process efficiency. In order to keep the simplicity of an equilibrium stagemodel and the accuracy of a non-equilibrium stage model, a hybrid model is developed to predict the structured packing column in cryogenic air separation. A general solution process for the equilibrium stage model is developed to solve the set of equations of the hybrid model, in which a separation efficiency function is introduced to obtain the resulting tri-diagonal matrix and its solution by the Thomas algorithm. As an example, the algorithm is applied to analyze an upper column of a cryogenic air separation plant with the capacity of 17000 m³·h^-1. Rigorous simulations are conducted using Aspen RATEFRACmodule to validate the approach. The temperature and composition distributions are in a good agreementwith the two methods. The effects of inlet/outlet position and flowrate on the temperature and composition distributions in the column are analyzed. The results demonstrate that the hybrid model and the solution algorithms are effective in analyzing the distillation process for a cryogenic structured packing column.

Key words: Distillation, Cryogenic air separation, Structured packings, Hybrid model, Aspen

摘要： A detailed investigation of a thermodynamic process in a structured packing distillation column is of great importance in prediction of process efficiency. In order to keep the simplicity of an equilibrium stagemodel and the accuracy of a non-equilibrium stage model, a hybrid model is developed to predict the structured packing column in cryogenic air separation. A general solution process for the equilibrium stage model is developed to solve the set of equations of the hybrid model, in which a separation efficiency function is introduced to obtain the resulting tri-diagonal matrix and its solution by the Thomas algorithm. As an example, the algorithm is applied to analyze an upper column of a cryogenic air separation plant with the capacity of 17000 m³·h^-1. Rigorous simulations are conducted using Aspen RATEFRACmodule to validate the approach. The temperature and composition distributions are in a good agreementwith the two methods. The effects of inlet/outlet position and flowrate on the temperature and composition distributions in the column are analyzed. The results demonstrate that the hybrid model and the solution algorithms are effective in analyzing the distillation process for a cryogenic structured packing column.

关键词: Distillation, Cryogenic air separation, Structured packings, Hybrid model, Aspen

Xiaobin Zhang, Jiakai Zhu, Zhao Wu, Wei Xiong, Xuejun Zhang, Limin Qiu. Performance Prediction of Structured Packing Column for Cryogenic Air Separation with Hybrid Model[J]. Chin.J.Chem.Eng., 2014, 22(8): 930-936.

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