Research On New Mode Of Operation For Slop Cut In Cyclic Total Reflux Batch Distillation

Cyclic total reflux operation is one of the new operating modes of batchdistillation. This operation is one of the most promising modes of batch distillation forits unique advantages over conventional partial reflux mode in highest enrichingefficiency under total reflux and fastest product collection under total withdrawal,together with high efficiency, energy saving and convenient controlling. Fewresearches are focused on the development and optimization of the control method forthis new operation mode which needs more precise and optimized control in order togive full play to its potential.Operation strategy of cycle total reflux batch distillation with middle reflux drumwas studied in this paper. Operation steady flat was put forward and tri-componentmethanol-ethanol-propanol was adopted as the experimental mixture to validate theseparation process. According to this new operation strategy, tri-temperature controlstrategy was referred with multi-temperature sensors. Combined with systemidentification and predictive control theory, an on-line control platform wasconstructed and experiment as well as simulation was executed in order to getfeasibility verifying.Contrast simulation and experiment of constant reflux ratio withmulti-temperature control strategies were carried out. Seven temperature sensors,equally distribute along the column, were used to control the alternation of the statesof total reflux and total withdrawal of the column and in result to keep the column runwith the highest enrichment efficiency,。The results indicated that with this newoperation and control strategy, the productivity increased 26.2%, the amount ofcollecting slop cut decreased 39.3%.The product yield increases and the amount ofslop cut decreases significantly with the same product specification. Therefore,multi-temperature control strategy holds obvious advantage over the other strategy.