Method for modeling and optimizing separation process of C8-aromatics simulated moving bed

Abstract

The invention relates to a method for modeling and optimizing separation process of a C8-aromatics simulated moving bed. The method comprises the following steps that the constant pressure and temperature of the adsorption and separation process are considered, a liquid phase is assumed to be a dispersion piston flow, a solid phase is assumed to be a piston flow, a linear pushing force model is a mass transfer rate model, the adsorption balance is described by virtue of Langmuir isotherms, a C8-aromatics adsorption and separation process model is built, and multi-target operation problem of two typical simulated moving beds are optimized by a multi-target teaching optimization algorithm based on the model as follows: (a) the PX yield is maximized and the use amount of a desorption reagent is minimized; and (b) the PX yield and purity are maximized at the same time. The built model is capable of obtaining information of components of each bed layer of an adsorption and separation tower, the yield and the purity of main products in extraction and raffinate; with the combination of analysis of operation variables such as the flow of desorption reagent, the extraction liquid flow and the raffinate flow in the model by the optimization algorithm, the operation level of the simulated moving bed can be guided.

Description

technical field [0001] The invention relates to a modeling and optimization method for C8 aromatics simulated moving bed separation process, and the method can be used for simulation and operation optimization of simulated moving bed separation process. Background technique [0002] Paraxylene (PX) is an important organic chemical raw material and a leading product in the polyester product chain. The separation of mixed xylenes is the most difficult link in the PX production process. The main industrial methods for separating mixed xylenes include cryogenic crystallization and adsorption separation, followed by complex extraction, eutectic and sulfonation methods, among which Molecular sieve adsorption separation technology based on continuous countercurrent simulated moving bed is currently the mainstream technology for producing p-xylene. [0003] Simulated moving bed (SMB) separation technology is a continuous countercurrent chromatographic separation technology that eme...

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Problems solved by technology

However, the mechanism of the simulated moving bed adsorption separation process is complicated, and there are many operating variables and strong coupling, so it is difficult to analyze it systematically. Therefore, there has been a lack of effective methods to determine the operating conditions for actual working conditions.

[0006] At present, many scholars have carried out in-depth research on the operation optimization process based on the triangle theory, but the triangle theory ignores the axial diffusion and mass transfer resistance, and only optimizes the model in an ideal state, and the predicted results cannot be well described real separation process

In addition, some scholars use traditional multi-objective optimization algorithms to optimize the operation process of the simulated moving bed, such as the NSGA-II algorithm, etc., but the Pareto solution set obtained by these methods has poor distribution and convergence, which is not conducive to finding the optimal Operating point, which brings great limitations to the operation selection of actual working conditions

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