PRESENTED BY: ANAS SALEEM

Distillation

Distillation is a method of separating mixtures based on differences in their boiling points.

Distillation is a unit operation, or a physical separation process, and not a chemical reaction.

History:

Distillation has been around for a long time. Earliest references are to Maria the Jewess who invented many types of stills and reflux condensers. Common Middle Ages and Renaissance uses of distillation included the manufacture of brandy and other spirits from wine. Another early use was the manufacture of perfumes and essences. Other early users of distillation include the Alchemists. Of course, the history of distillation does not end there. Today we use it for more than just spirits.

Principle of Distillation:

Its operation is based on differences in boiling points between the components being separated. The lighter components move up the column and the heavier components fall down. When the relative volatility between the components being separated is high, distillation tends to be cheaper than other separation methods.

Description:

 Distillation is a widely used method for separating mixtures based on differences in the conditions required to change the phase of components of the mixture. To separate a mixture of liquids, the liquid can be heated to force components, which have different boiling points, into the gas phase. The gas is then condensed back into liquid form and collected.

Cont…..Distillation is based on the fact that the vapor of a boiling mixture will be richer in the components that have lower boiling points.Therefore, when this vapor is cooled and condensed, the condensate will contain more volatile components. At the same time, the original mixture will contain more of the less volatile material

Application of Distillation It has a number of applications. It is used to separate crude oil into more fractions for specific uses such as 

transport, power generation and heating. Water is distilled to remove impurities, such as salt from seawater. Air is distilled to separate its components notably oxygen, nitrogen, and argon for

industrial use. Distillation of fermented solutions has been used since ancient times to produce 

distilled beverages with higher alcohol content. The premises where distillation is carried out, especially distillation of alcohol are known as a distillery.’’

Many industries use distillation for critical separations in making useful products. These industries include petroleum refining, beverages, chemical processing, petrochemicals, and natural gas processing.

Distillation is used for many commercial processes, such as production of gasoline, distilled water, xylene, alcohol, paraffin, kerosene, and many other liquids

TYPES OF DISTILLATION

There are many types of distillation c, each designed to perform specific types of separations, and each design differs in terms of complexity.

Batch distillationContinuous distillation

CONT…..Batch : 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.

Continuous : In contrast, continuous columns process a continuous

feed stream. 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 of the two types.

BATCH DISTILLATIONBatch distillation: Batch distillation refers to the use of distillation in batches, meaning that a mixture is distilled to separate it into its component fractions before the distillation still is again charged with more mixture and the process is repeated. 

Main components of Batch distillationDistillation columns are made up of several

components, each of which is used either to transfer heat energy or enhance material transfer. A typical distillation contains several major components:

a vertical shell where the separation of liquid components is carried out

column internals such as trays/plates and/or packings which are used to enhance component separations

a reboiler to provide the necessary vaporization for the distillation process

CONT……a condenser to cool and condense the vapor

leaving the top of the columna reflux drum to hold the condensed vapor from

the top of the column so that liquid (reflux) can be recycled back to the column…….

Cont….The vertical shell

houses the column internals and together with the condenser and reboiler, constitute a distillation column. A schematic of a typical distillation unit with a single feed and two product streams is shown

Basic Operation and Terminology

The liquid mixture that is to be processed is known as the feed and this is introduced usually somewhere near the middle of the column to a tray known as the feed tray. The feed tray divides the column into a top (enriching or rectification) section and a bottom (stripping) section. The feed flows down the column where it is collected at the bottom in the reboiler.

cont….Heat is supplied to the reboiler to generate vapour.

The source of heat input can be any suitable fluid, although in most chemical plants this is normally steam. In refineries, the heating source may be the output streams of other columns.  The vapour raised in the reboiler is re-introduced into the unit at the bottom of the column. The liquid removed from the reboiler is known as the bottoms product or simply, bottoms.

The vapor moves up the column, and as it exits the top of the unit, it is cooled by a condenser. The condensed liquid is stored in a holding vessel known as there flux drum. Some of this liquid is recycled back to the top of the column and this is called the reflux. The condensed liquid that is removed from the system is known as the distillate or top product.

Cont….

Thus, there are internal flows of vapor and liquid within the column as well as external flows of feeds and product streams, into and out of the column.’

Factors

 The performance of a distillation column is determined by many factors, for example:

feed conditions:state of feedcomposition of feedtrace elements that can severely affect the VLE of

liquid mixturesInternal liquid and fluid flow conditions:State of trays weather conditions

Why to Use Batch Distillation: There may be several reasons for running a batch process such as this: Small capacity doesn’t warrant continuous operation. Separation is to be done only occasionally. Separation is preparative to produce a new product. Upstream operations are batch wise or feedstock’s vary with time or from batch

to batch. Feed materials are not appropriate for a continuous flow system.

Batch processes are economical for small volumes. Batch processes are flexible in accommodating changes in product formulation. Batch processes are flexible in changing production rate allow the use of

standardized multi-purpose equipment for the production of a variety of products from the same plant are best if equipment needs regular cleaning because of fouling or needs regular sterilization.

Batch process allow better product integrity: each batch of product can be clearly identified in terms of the feeds involved and conditions of processing. This is particularly important in industries such as pharmaceuticals and foodstuffs.

Advantages of Batch Distillation:

Batch distillation is often preferable to continuous distillation where relatively small quantities of material are to be handled at regularly scheduled periods. It is often more economical for small volumes productions.

Probably the most outstanding attribute if batch distillation is its flexibility. Little change is required when switching from one mixture to another. It is flexible in accommodating changes in product formulation, changes in production rate, changes in feed composition, etc. Batch distillation allows the use of standardized multi-purpose equipment for the production of a variety of products from the same plant. They are preferred when the equipment needs regular cleaning because of fouling or regular sterilization.

Batch distillation may be preferable for processing temperature-sensitive materials, because distillation pressure can be lowered as the MVC are removed, thus maintaining lower still pot temperature within the constraint of the condenser temperature. The minimum pressure in continuous distillation is constrained by the temperature required to condense the lowest-boiling component, resulting in higher operating temperature.

Another important factor favoring the use of batch distillation is that it permits better product integrity to be achieved: each batch of product can be clearly identified in terms of the feeds involved and conditions of processing. This is particularly important in industries such as pharmaceuticals and foodstuffs.

Disadvantages of batch distillation:A disadvantage of batch distillation is the

long time the mixture is exposed to high temperatures. This increases the risk of thermal degradation or decomposition of the substances. Furthermore, energy requirement is generally higher in batch distillation than in continuous distillation.

Applications:

Batch distillation has always been an important part of the production of seasonal, or low capacity and high-purity chemicals.

It is a very frequent separation process in the pharmaceutical industry and in wastewater treatment units.

In batch distillation, the composition of the source material, the vapors of the distilling compounds and the distillate change during the distillation.

In batch distillation, a still is charged (supplied) with a batch of feed mixture, which is then separated into its component fractions which are collected sequentially from most volatile to less volatile, with removed at the end. The still can then be recharged and the process repeated.