Etiket Arşivleri: Distillation

Distillation Principles

Definition of distillation, Types of columns, Simple Distillation methods (Flash, batch, Steam), Basic distillation Equipment and operation, Column internal, Reboilers, Distillation principles, Vapor `liquid equilibria, Distillation column design, Effect of the number of trays or stages, Factors affecting distillation column operation, Introduction to multi-component Distillation

Definition of Distillation

A process in which a liquid or vapour mixture of two or more substances is separated into its component fractions of desired purity, by the application and removal of heat.

• Distillation is based on the fact that the vapour of a boiling mixture will be richer in the components that have lower boiling points.

• Therefore, when this vapour 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.

•Distillation columns are designed to achieve this
separation efficiently.

Although many people have a fair idea what “distillation” means, the important aspects that seem to be missed from the manufacturing point of view are that:

◘ distillation is the most common separation technique

◘ it consumes enormous amounts of energy, both in terms of cooling and heating requirements

◘ it can contribute to more than 50% of plant operating costs

The best way to reduce operating costs of existing units, is to improve their efficiency and operation via process optimization and control. To achieve this improvement, a thorough understanding of distillation principles and how distillation systems are designed is essential.

The purpose of this introduction is to expose you to the terminology used in distillation practice and to give a very basic introduction to:

Types of columns
Simple distillation methods (Flash, batch and Steam distillation)
Basic distillation equipment and operation
Column internals
Reboilers
Distillation principles
Vapor liquid equilibria
Distillation column design
Effect of the number of trays or stages
Factors affecting distillation column operation
Introduction to multi-component distillation

TYPES OF DISTILLATION COLUMNS

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

Batch and Continuous Columns

One way of classifying distillation column type is to look at how they are operated. Thus we have: batch and continuous columns.

Batch Columns

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 Columns

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 most common of the two types. We shall concentrate only on this class of columns.

Types of Continuous Columns
Continuous columns can be further classified according to:

◘ The nature of the feed that they are processing,
binary column – feed contains only two components
multi-component column – feed contains more than two components

◘ The number of product streams they have
multi-product column – column has more than two product streams

extractive distillation – where the extra feed appears in the bottom product stream

◘ Where the extra feed exits when it is used to help with the separation,

 azeotropic distillation – where the extra feed appears at the top product stream

◘The type of column internals

tray column – where trays of various designs are used to hold up the liquid to provide better contact between vapor and liquid, hence better separation

packed column – where instead of trays, ‘packings’ are used to enhance contact between vapor and liquid

Separation Methods

Separation Methods

Ways to separate mixtures – Chapter 3: Matter & Its Properties

How do we separate …?

Separating Mixtures

Substances in a mixture are physically combined, so processes bases on differences in physical properties are used to separate component

Numerous techniques have been developed to separate mixtures to study components

Filtration

Used to separate heterogeneous mixtures composed of solids and liquids

Uses a porous barrier to separate the solid from the liquid

Liquid passes through leaving the solid in the filter paper

Distillation

Used to separate homogeneous mixtures

Based on differences in boiling points of substances involved

Crystallization

Separation technique that results in the formation of pure solid particles from a solution containing the dissolved substance

As one substance evaporates, the dissolved substance comes out of solution and collects as crystals

Produces highly pure solids

Rocky candy is an example of this

Centrifuging

A magnet

Can be used to separate a magnetic substance from a non-magnetic substance

Chromatography

Separates components of a mixture based on ability of each component to be drawn across the surface of another material

Mixture is usually liquid and is usually drawn across chromatography paper

Separation occurs because various components travel at different rates

Components with strongest attraction for paper travel the slowest

Decantation

Decanting is done to separate particulates from a liquid by allowing the solids to settle to the bottom of the mixture and pouring off the particle-free part of the liquid. Another method is to allow two immiscible liquids to separate and the lighter liquid is poured off.

Sieving

a porous material is used to separate particles of different sizes.

method is most commonly used to effect gross separations, as of liquids from suspended crystals or other solids.

to accelerate filtration, pressure usually is applied.

a series of sieves is stacked, with the screen of largest hole size at the top

Distillation

Distillation is the process of heating a liquid solution, or a liquid-vapour mixture, to derive off a vapour and then collecting and condensing this vapour. The products of a distillation process are most often limited to an overhead distillate and a bottoms, whose compositions differ from that of the feed.

Distillation 1 ( Dr. Ali Coşkun DALGIÇ )

Distillation with Reflux and McCabe-Thiele Method

Definition

Distillation is the process of heating a liquid solution, or a liquid-vapour mixture, to derive off a vapour and then collecting and condensing this vapour. The products of a distillation process are most often limited to an overhead distillate and a bottoms, whose compositions differ from that of the feed.

Distillation 2 ( Dr. Ali Coşkun DALGIÇ )

FE 301 Mass Transfer

Distillation with Reflux and McCabe-Thiele Method

Part 2

Dr. Ali Coşkun DALGIÇ

Today we will discuss:

1) McCabe-Thiele graphical construction

2) Determination of N and XB

3) Minimum number of stages N

4) Minimum reflux

5) Example

6) Subcooled Reflux

7) Multiple Feeds

8) Side stream products

9) Open steam

10) Non-ideal distillation: Murphree efficiency