| About 5 million kilograms of benzoic acid residue is produced by benzoic acidunit each year in Shijiazhuang Chemical Fiber Co. Ltd.,which produces benzoic acidby oxidating toluene. The content of benzoic acid as much as 21% in theresidue.Besides benzoic acid,theresidue contains several highvalue compounds suchas benzyl benzoate, fluorenone and so on. How to deal with this kind of residue is adifficult problem which has not been settled worldwide. They have been burned asfuel in this company. This method leads to a huge waste of resources. The suitblemethodistoseparatetheresidueintopurecomponents,butitisdifficulttoseparateasits complicated composing. In this article, an effective way is provided which is thecoupling of flash-vacuum distillation method. The influence of operating parameters,such as top pressure, reflux ratio, top and bottom temperature were researched, andthe best operating conditions were found, meanwhile, products with high purity wereobtained.The process was simulated with commercial software ProII. Distillationcolumns were designed based on the simulation results. Some parameters, such ascolumn diameter, the type and the height of packings are given. Fluid dynamicperformance such as pressure drop, liquid holdup, flood point gas velocity, arecalculated. The type of major auxiliary equipments and inner parts of packed columnhave been specified: Channel liquid distributor is selected as liquid distributor andre-distributor.Gridplateisselectedasbedlocator.Beamsupportingisusedtosupportthe packings. Cover-plate liquid collector is selected as liquid collector. Inner refluxcondenser is selected as the condenser, it can reduce the pipeline and the pressuredrop.Complete process package for benzoic acid residue separation unit could beobtainedfromthisstudy.
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