BASIC PRINCIPLES OF DISTILLATION AND ‘DWC’

Ali Shoeb Moon

30/10/2010

OUTLINE: DISTILLATION: > Definition and Applications. > Brief History. > Basic Types of Distillation. > Significance of Distillation (Why ‘DWC’??) DWC: > Definition and Basics. > Commercial Background. > Principle Behind. > Appropriate Applications.

DISTILLATION:

Definition:- A physical unit operation used to separate the components of a boiling liquid mixture, based on the differences in their volatilities.

Applications:- Some important commercial ones include Crude oil fractionation, Removal of impurities from water, Separation of Air into it’s components, distilled beverages with higher Alcohol content.

BRIEF HISTORY:

Archaeological excavations in northwest Pakistan show that the distillation of Alcohol was known in the Indian subcontinent since 500 B.C.

The evidence comes from Greek alchemists

working in Alexandria as early as 1 A.D.

Distilled water has been known since 200 A.D.

Fraction Distillation was developed by ‘Tadeo Alderotti’ in the 13th Century.

TYPES OF DISTILLATION Simple Distillation:- It is practiced for a mixture

in which the boiling point of the components differ by atleast 70 degree celcius.

Steam Distillation:- Used for the mixture which has temperature or heat sensitive components.Steam is introduced by heating water, which allows the compounds to boil at lower temperature. Thus the temp. sensitive compounds are separated before decomposition. Used in large scale separation of Essential oils and Perfumes.

Vaccum Distillation:- Separation at a pressure lower than standard atmospheric pressure.Best suited for compounds with higher boiling points(˃200˚C), which tend to decompose at their B. Pt. ‘Most important example is petroleum Refining’.

Short Path Distillation :- This also used for thermal sensitive compounds. Separated compounds condensed immediately. Product loss is minimized . Condenser is configured in a vertical manner b/w heating and collecting flask. Used for High Mol. Wt. Organic compounds (Pharma Industries)

Fractional Distillation:- Used in case of mixtures in which the volatility of the components is nearly similar.A series of compounds is separated simultaneously one after the other. With the least B.Pt component at the top and the highest B pt. component at the bottom.Generally used for Alcohol purification and in Petroleum refining industries.

SIGNIFICANCE OF DISTILLATION:( WHY ‘DWC’ ????):

Studies indicate that separations consume 50%-70% of capital and energy of a chemical process.

Distillation makes 95% of all current separation processes.

So, Seeking improvements in this area are on the top of the list.

A DWC can cut capital and energy costs by approximately 30% compared to a traditional two column system and that too with reduced Carbon Emissions.

DWC BASICS:

A distillation column with a vertical partition wall in the central section.

The feed side acts as the Pre-fractionator and the product side as the main column.

It can be used to produce three products from a single column(in case of sharp split).

It can bring value to ‘non-sharp’ applications i.e. those with intermediate component between A-B or B-C.

The column may contain either trays or packing.

DWC:COMMERCIAL BACKGROUND

The original patent of the concept was granted to ‘Wright’ of Standard Oil in 1949.

For the first time, a DWC was built and taken into operation by BASF in Ludwigshafen, Germany, in 1985.

Presently, there are around 70 packed DWCs’ in operation worldwide built by BASF in cooperation with Montz.

>Conventional column scheme. >Loss in the middle component

dueto remixing.

For a three component mixture.

PRINCIPLE BEHIND ‘DWC’

>Entire A and some fraction of B from top. >The remaining fraction of B and entire C from

bottom.

ALTERNATE ARRANGEMENT

>Thermal integration of the two towers by using a

single re-boiler and condenser.

THERMALLY COUPLED COLUMN

>Pre-fractionator moved inside the second tower.

THERMAL COUPLING APPROACH IN SINGLE SHELL RESULTS INTO A ‘DWC’.

HOW DOES IT LOOK??

APPROPRIATE APPLICATIONS(GENERAL HEURISTICS):

DWC should be considered when the middle component (‘B’) is atleast 20% of the total stream flow.

It should not be used if the pressure difference between the conventional sequence is high.

-Because a DWC operates as a single tower, so it runs at a single pressure.

Level of energy being used should be carefully evaluated.

ANY QUESTIONS???

THANK YOU!!!!