Abstract
A short-cut method for batch distillation columns working at constant reflux was applied to solve a problem of four components that needed to be separated and purified to a mole fraction of 0.97 or better. Distillation columns with 10, 20, 30, 40, and 50 theoretical stages were used; reflux ratio was varied between 2 and 20. Three quality indexes were used and compared: Luyben’s capacity factor, total annual cost, and annual profit. The best combinations of theoretical stages and reflux ratio were obtained for each method. It was found that the best combinations always required reflux ratios close to the minimum. Overall, annual profit was the best quality index, while the best combination was a distillation column with 30 stages, and reflux ratio’s of 2.0 for separation of benzene (i), 5.0 for the separation of toluene (ii), and 20 for the separation of ethylbenzene (iii) and purification of o-xylene (iv).
Highlights
Distillation is the most commonly used separation process in the chemistry and petrochemical industry, mostly employed in continuous processes and used in discontinuous processes
The best combinations of theoretical stages and reflux ratio were obtained for each method
One advantage of batch distillation is the possibility to separate a mixture of several components with only one column and, a batch distillation column uses more energy than a continuous column, many times it is convenient to operate in batch mode
Summary
Distillation is the most commonly used separation process in the chemistry and petrochemical industry, mostly employed in continuous processes and used in discontinuous processes. Batch distillation is widely used for the separation of specialty and fine chemicals and for the recovery of small quantities of solvent during the production of high purity and added value products. Batch processing is the main feature of the pharmaceutical, biochemical, and specialty chemical industries. One advantage of batch distillation is the possibility to separate a mixture of several components with only one column and, a batch distillation column uses more energy than a continuous column, many times it is convenient to operate in batch mode. For these reasons the design, analysis, and optimization of batch distillation columns have obtained attention by several researchers.
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