Process Simulation And Parameter Optimization Of CO₂ Removal By Alkanolamine And Membrane For Biogas Purification

As a Natural Gas surrogate,biomethane can be obtained by biogas purification,and it has the advantages of environmental protection,safety,reliability and renewable.Biogas decarbonization is an indispensable and vital part of its high-value utilization.Low-consumption and high-efficiency decarbonization technology is the key of development.This paper uses process simulation to systematically study the biogas decarbonization process and optimize the parameters to reduce energy consumption.In order to solve the problem of high CO₂ concentration（30～50%）in biogas and very low CO₂ content in product gas（50ppm）,this paper proposes three options:two-stage decarbonization by amine,one-stage decarbonization by amine,decarbonization by coupling of membrane and amine,using Aspen Hysys to simulate the five working conditions of CO₂in the biogas as 30%,35%,40%,45%,and 50%respectively.The decarburization process model was established and compared with the existing amine experimental results and plant operating data,and the relative error of more than 93%data is less than 6%,verifying simplified assumptions,mathematical model and calculation method of the simulation model.Analysis of the CO₂ content in the product gas is less than 50ppm,and all three options are feasible.Based on the simulation of the decarbonization process,the energy consumption calculation model was established,and the variables that had a significant impact on the process energy consumption were determined.With the goal of the lowest unit energy consumption,genetic algorithm and sequential method are selected,combined with Matlab software,to optimize the main parameters of the amine ratio,absorption tower and regeneration tower of the one-stage biogas decarbonization process by amine.The results show that the use of genetic algorithm and sequential method to optimize process parameters can significantly reduce process energy consumption.From the three aspects of equipment investment,operating expenditure,and raw material cost,an economic evaluation model was established,and the unit cost under three scenarios and five working conditions was calculated.The schemes were compared and selected based on the three dimensions of CH₄ recovery rate,product purity and product economy.The recovery rate of CH₄ in the two-stage decarbonization by the amine is the highest but the energy consumption is higher.The CO₂ content in the sweet gas of the one-stage decarbonization by amine is the lowest but the energy consumption is slightly higher.The energy consumption of decarbonization by coupling of membrane and amine is the lowest but the recovery rate of CH₄ is low,the three options have their own advantages and disadvantages.The research methods and results obtained in this paper provide a theoretical reference for the selection and optimization of biogas and other high CO₂ gas decarburization processes,and provide a data reference for the unit energy consumption and economy of the decarburization process.