Simulation And Design Of Purification Process Of Byproduct N-Butanol In 1,4-Butanediol Production

1,4-butyl glycol (1,4-butanediol, BDO) is an important chemical raw material, In our country, annual production capacity of 1,4-butanedio has reached 2 million tons. N-butanol is the main by-product of BDO production, and can be separated and used as organic solvent, raw materials of plasticizer dibutyl phthalate and surface active agent. which can not only improve the utilization of raw materials, but also obtain better economic benefits from the byproduct solution in BDO production.In this paper, the NRTL equation was first applied to predict the gas-liquid equilibrium and liquid-liquid equilibrium in modeling simulation of the preliminary separation system in the BDO production using software Aspen Plus, and good agreement between the calculated results and practical data displays that the NRTL equation can be used to calculate the phase equilibrium data of the system andthe simulation results are reasonable and reliable. The different separation and purification processes were proposed for purifying n-butanol from the by-product solutions in BDO production based on the physical properties of by-products to be separated and the integration of distillation and liquid-liquid laminator, and then the simulation models were developed the purification processes using Aspen Plus. The simulation of a two-column purification process was carried out. The effect of operating parameters of the methanol tower, the butanol tower and the cooler was observed at product n-butanol concentration of 99.8% by comparing the n-butanol output and heat duty. The simulation results indicated that the recovery rate of n-butanol was 90.59%.Lower n-butanol recovery rate can be due to n-butanol lost in the aqueous phase as emission waste water. A modified two-column purification process was is proposed bycirculating the aqueous phase containing n-butanol back to the methanol tower. Simulation results show that the n-butanol recovery rate of 99.66% could be obtained and that the concentration of organic copounds in emission waste wateris less than 0.2%. However, the theoretical plate number of methanol tower increased obviously, resulting higher investment cost. A three-column purification process was proposed, the n-butanol recovery rate of 99.81% was achieved. Economic analysis results show that the construction cost decreases due to the reduction of total theoretical plate number of three columns. Finally, both the two-column process and the three-column process were combined with preliminary purification of the n-butanol, and the simulation was carried out.The cost estimation results show that the n-butanol separation and purification processes proposed in this paper not only has a higher recovery rate but also get better economic benefits.