Simulation Optimization And Control Study On Extractive Distillation And CO₂ Absorption Process With Green Solvents

At present,most of extractants used in industry are traditional organic solvents,which have the disadvantages of being volatile,environment polluted and high energy consumption.Therefore,searching for a new type of“green solvent”to replace the traditional organic solvents has become a hot research.The emergence of ionic liquids?ILs?and low-transition-temperature solvents?LTTMs?as novel solvents open up new avenues for solving the problems of traditional extractants.Based on this,this paper is focused on applying ILs to extractive distillation for separating isopropanol-water,LTTMs to extractive distillation for separating ethanol-water and CO₂ absorption process,which is helpful to provide some guidance for the future industrial design.Firstly the paper studies the separation process of isopropanol-water system using ionic liquids?[emim][N?CN?₂]?as extractant,and multi-objective genetic algorithm optimization of the two separation processes is carried out to achieve economic analysis.The optimization results show that the modified process with two flashes is more economical than the traditional process with one flash,and the TAC is reduced by 4.26%;Then LTTMs?ChCl/urea 1:2?is applied to extractive distillation for the separation of ethanol-water.The optimization results show that the energy consumption of this process is reduced by 37.22%,26.42%and 12.56%respectively when compared with ethylene glycol,[EMIM][BF4]and GC?3:1?as solvents respectively,which achieves remarkable energy saving.Finally LTTMs?TBA/LA 1:2?is applied to the CO₂ absorption process.The optimization results show that the absorption effect of the LTTMs is approximately equal to the traditional chemical absorbent,but it avoids the problems of solvent loss and chemical corrosion.The absorption effect of the LTTMs is weaker than ILs([C₁₀mim][TfO])reported in literature,but it overcomes the disadvantages of high price and toxicity of ILs.So this LTTMs is still applicable.Dynamics control is studied for every process in this paper.The proposed control structures can well resist the disturbance of feed flow and feed composition and achieve good control effect,which provides a strong theoretical basis for the industrial application.