DISTILLATION COLUMN

Introduction:

       The separation of liquid mixtures into their various components is one of the major operations in the process industries, and distillation, the most widely used method of achieving this end, is the key operations in any oil refinery. In processing the demand for purer products, coupled with the need for greater efficiency, has promoted continues research into techniques of distillation. This process of getting pure products is accomplished by partial vaporization and subsequent condensation.

Distillation:

           “Process in which a liquid or vapor mixture of two or more substances is separated into its component fractions of desired purity, by the application and removal of heat”

TYPES OF DISTILLATION COLUMNS;

                  There are basically two types of distillation columns used in industries.

·        Batch columns

·        Continuous columns

There selection criteria depends upon total number of stages and reflux ratio. As it is shown that when a large number of plates are used, then continuous distillation has the lowest reflux requirements and hence operating costs. If a smaller number of plates are used and high purity product is not required, then batch distillation is probably more attractive.

Batch Columns:

                           In batch distillation the more volatile component is evaporated from the still which therefore becomes progressively richer in the less volatile constituent. Distillation is continued, either until the residue of the still contains a material with an acceptably low content of the volatile material, or until the distillate is no longer sufficiently pure in respect of volatile content. In batch operation, the feed to the column is introduced batch-wise. That is, the column is charged with a 'batch' and then the distillation process is carried out. When the desired task is achieved, a next batch of feed is introduced. Most distillation processes operate in a continuous fashion, but there is a growing interest in batch distillation, particularly in the food, pharmaceutical, and biotechnology industries. The advantage of this separation process is that the distillation unit can be used repeatedly, after cleaning, to separate a variety of products. The unit generally is quite simple, but because concentration are continuously changing, the process becomes more difficult to control. 

Continuous Distillation:

                                        In contrast to batch columns, a continuous feed is given to the column. No interruptions occur unless there is a problem with the column or surrounding process units. They are capable of handling high throughputs and are the more common used. I will put light only on this type of distillation column.