Study On The Solid-liquid Equilibrium Of Two Organic Acids And Simulation And Optimization Of Solvent Recovery Process

Crystallization technology has the advantages of green and high efficiency,and it is more and more widely used in chemical production.The study of solid-liquid phase equilibrium is one of the important theoretical supports for the feasibility of crystallization technology.In this paper,the solubility data of two organic carboxylic acids with benzene ring,3-methylsalicylic acid and phenoxyacetic acid,are determined experimentally.Among them,the solvents used for 3-methylsalicylic acid are:alcohols and esters.Benzene pure solvent and methanol-n-butanol mixed solvent.The selected solvents for phenoxyacetic acid are:alcohols,esters,pure water and acetone solvents,and water-ethanol mixed solvents.Experiments show that the increase in temperature is beneficial to both The dissolution of the solute.The solubility curve of the solute is drawn and its dissolution law and co-dissolution phenomenon are analyzed.This paper studies the thermodynamic behavior of the solute dissolution process,and calculates the partial thermodynamic state of the dissolution process.From the results,it appears that the solute dissolution process is an endothermic,entropy-increasing and non-spontaneous process.This article uses Apelblat,Van't Hoff,?h,NRTL,Wilson mathematical models commonly used in solid-liquid equilibrium studies to correlate with experimental data,calculate the model parameters of the model,and calculate the relative deviation of each model and the average relative Bias,calculations show that the average relative deviation is less than 3.5%,except for the average relative deviation associated with the Wilson model and the 3-methylsalicylic acid mixed solvent data.This may be because the solubility of 3-methylsalicylic acid in water is very small.Reasons for inaccuracies.This paper uses simulation software to design the separation of the raw materials in the PVA separation section for the relevant solvents involved in the experiment.The main separation is 99.5%methanol and methyl acetate that meets the production requirements.This process is a four-column rectification,which is optimized separately.The theoretical plate number N of the optimization results T1,T2,T3,and T4 are 29 trays,16 trays,26 trays,and 20 trays,respectively.The feed position NF is 8,7,19,12,the reflux ratio R is 1.90,0.25,2.15,0.69,and the operating pressure is 1.01 atm,1.01 atm,2.60atm,1.01 atm.On the basis of this process,the double-effect rectification scheme was used to design and optimize a new energy-saving scheme to realize the three towers sharing one heat source.The energy consumption before and after the use of energy-saving was compared and found that after using the new energy-saving scheme,the reboiler energy consumption was reduced by 21.13%,the energy consumption of the condenser is saved by 29.02%,and the energy saving effect is very significant.