Direct Computations To Describe Batch Distillation With Rectification

Abstract

An analog of the Rayleigh Equation has been applied for many years to describe batch distillation with rectification for binary mixtures. A solution is obtained by iterative graphical computations followed by numerical integration. When the batch distillation algorithm is stated in terms of distillate composition a computational non-iterative soluton may be obtained. For a binary separation this expression may be solved on a programmable calculator and the integral may be obtained in segments to describe the progress of the operation expressed in terms of the quantity remaining in the still-pot. This variable is not a linear function of time since even at constant reboiler duty the boil-up rate varies as the still-pot composition changes. If the time rate of the operation is to be determined, this effect must be considered. Procedures have been developed to describe the time-responses of the plate compositions and temperatures, the boil-up rate as well as the conventional variable, the volume remaining in the still-pot. Application of this procedure is illuatrated by evaluating operating strategies for batch distillation. A capacity factor is based on the time required to make a complete separation so that both the distillate product and the heel meet specific composition and disposition of a slop cut (if any) is accounted for. The reboiler is specified to operate at capacity but it is recognized that the boil-up rate will then drop off as the still-pot material becomes heavier and warmer. The distillate composition profiles and the boil up profiles are used to designate changes in objectives during the over-all runs. Batch processing. The chemical processing industry has been using batch operations increasingly during recent years and these procedures have been drawing increasing attention in chemical engineering publications. Batch distillation is often selected as a significant purification in these processes and has likewise enjoyed a resurgence in investigations and reported advances and results. Major companies have reported a broad use of batch processing. Chowdhury (1988) has reported that DuPont and Rohm and Haas operate numerous processing lines for hundreds of product variations. Professor G.V. Reklaitis of Purdue has developed a simulation program for designing, scheme selection, and scheduling batch processes and has founded a company, Batch Processing Technologies, Inc. to distribute results from his program. Batch processing units are most often used in one of two ways. A sequence of equipment may be required to manufacture several different products. This method is often encountered when the products are based on various formulations and rely primarily on mixing and purification to meet customer requirements. Batch processing may also be specified when a particular product is produced from different raw materials and through various processing routes. In either case the same equipment is used repeatedly to perform similar but different operations and is scheduled to operate almost continuously by rapid turnarounds between functions to minimize downtime. © 1990, Taylor & Francis Group, LLC. All rights reserved.

Department(s)

Chemical and Biochemical Engineering

Keywords and Phrases

Batch distillation; Complete specifications; Time response

International Standard Serial Number (ISSN)

1563-5201; 0098-6445

Document Type

Article - Journal

Document Version

Citation

File Type

text

Language(s)

English

Rights

© 2023 Taylor and Francis Group; Taylor and Francis, All rights reserved.

Publication Date

01 Jan 1990

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