Study On The Operation Policy Of Hybrid Batch Distillation-adsorption Process

A new hybrid batch distillation-adsorption process was studied consisting ofbatch distillation column and fixed bed adsorption. Batch distillation alone has highoperating cost and low recovery for separating close-boiling mixtures, whileadsorption alone has low capacity. By combining these two, leveraging the merits ofadsorption separation mechanism, which is based on inter-molecular forces instead ofrelative volatility, the recovery of batch distillation in separating close-boiling mixturewas increased by combining adsorption in the hybrid configuration. At the same time,the effect on separation process variables, operation time and rate were also studied.The mathematic models of the proposed hybrid process were established and usedto simulate the hybrid separation process. For the illustrative mixture Methanol and1,2-Dimethoxyethane (DME), the adsorption parameters were measured throughisotherm and kinetics studies of methanol on5A molecular sieves at differenttemperatures, with the data well fitted with Langmuir and Quadratic LumpedResistance (QLR) models. Results showed the adsorption equilibrium and rate werelittle temperature sensitive, with maximum methanol adsorption always above0.15g/g adsorbent. Study of the fixed bed adsorption showed the capability of models indescribing the adsorption column.With fitted adsorption parameters from experimental data, the separation ofmethanol and DME mixture was simulated with the proposed models, the profile ofdistillate and bottom streams were studied, and the product recovery and operationtime. The experimental data verified that the calculation models could describe thebottom and product streams’ profile. Both the calculation and experimental resultsindicated18%~27%improvement of DME recovery compared with batch distillation.More amount to be adsorbed, higher recovery, longer operation time, larger amount ofadsorbent used, and less number of distillation column plates required.