Study On Semi-continuous Constant Total Reflux Distillation And Liquid Series Operation

Existing batch distillation had many problems, including low separation efficiency, large energy consumption, taking a lot of time, and the operation could get either light or heavy constituent as product with high purity. On the basic of conventional batch distillation, the article put forward a new operation – Semi-continuous constant total reflux distillation. In this new operation, two accumulation tanks were set at the top and bottom of the column, and the tank volume was changed depending on the feed mode. The entire distillation was performed in the condition of total reflux operation. Through the feeding and accumulation of the liquid phase inside the tanks, the semi-continuous process was carried out, and both light and heavy constituent with high purity were obtained as product.With liquid series operation, the other two operations were presented, semi-continuous liquid exchange distillation and semi-continuous liquid consecutive distillation. In the separation process, the twin columns were operated respectively with non-interference, and be connected through the exchange of the liquid phase inside the tanks. These two methods reduced the disturbance caused by concentration change of liquid phases effectively. On equal feed concentration, the semi-continuous liquid exchange operation was better. On low or high feed concentration, the semi-continuous liquid consecutive operation had a good performance.The method was improved and simplified in subsequent research and the operation – Semi-continuous liquid series distillation was presented. The operation included three stages: driving, extraction-exchange-feed process of light or heavy component in the top or bottom. The driving was mainly used for establishing the concentration gradient, which could be carried out by top-bottom liquid exchange, loop interchange, and the operation of feed programme.In this paper, the feasibility of the operations mentioned above was verified through laboratory distillation. The total reflux numerical model was used to simulate the process under different parameters, such as feed concentration, input quantity and tank volume. Comparing the data, the advantages or disadvantages were summarized to optimize the operating conditions. As the result showed, the advantages of the new operations presented in the paper were concluded as below: both light and heavy constituent with high purity could be obtained during the process, the new operations were flexible, they could be applied to various separation tasks with different feed concentration, had huge edge in separation efficiency, operation time, and energy consumption. Above all, the paper offered some new tools to solve different problems, and meet the needs of various separation tasks.