what is distillation column, Types of distillation column, advantage and disadvantage of distillation,how to distillation column works.

hello guys, today we are going to

discuss about distillation column let's

quickly see what we are going to discuss

1:-Distilation principal

2:- mode of operations which includes batch           and continues distillation

3:- three column

internals which includes trays and

packings 3.1 trays covers sieve bubble

cap and valve trays 3.2 packings

packings covers random packings and

structure packings 

4:- how to select column internals

5:- tray hydraulic

6 tray technology

7 general design

8 steps for designing

distillation column 9 some rules for

designing distillation column 10 types

of distillation x'

so what is distillation tower

distillation definition 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 what are the

uses of distillation so distillation is

used for many commercial processes such

as the production of gasoline distilled

water

xylene alcohol paraffin kerosene and

many other liquids gas may be liquefied

and separate for example nitrogen oxygen

and argon are distilled from air

distillation is by far the most

important separation process in the

petroleum and chemical industries it is

the separation of key components in a

mixture by the difference in their

relative volatility or boiling points

it is also known as fractional

distillation or fractionation in most

cases distillation is the most

economical separating method for liquid

mixtures however it can be energy

intensive distillation can consume more

than 50% of a plants operating energy

cost there are alternatives to

distillation process such as solvent

extraction membranes separation or a

desorption process on the other hand

these processes often have higher

investment costs therefore distillation

remains the main choice in the industry

especially in large scale applications

now let's talk about mode of operation

distillation towers can be classified

into two main categories based on their

mode of operation the two classes are

batch distillation and continuous

distillation in batch distillation the

feed to the column is introduced batch

wise the column is first charged with a

batch and then the distillation. process

is carried out when the desired task is

achieved the next batch of feed is

introduced batch distillation is usually

preferred in the pharmaceutical

industries and for the production of

seasonal products on the other hand

continuous distillation handles a

continuous feed stream no interruption

occurs during the operation of a

continuous distillation column unless

there is a problem with the column or

surrounding unit operations continuous

columns are capable of handling high

throughput

besides additional variations can be

utilized in a continuous distillation

column such as multiple feed points and

multiple product drawing points

therefore continuous columns are the

more common of the two modes especially

in the petroleum and chemical industries

next important part is column internals

column internals are installed in

distillation columns to provide better

mass and heat transfers between the

liquid and vapor phases in the column

these include trays packings

distributors and Redistributor x'

baffles and etc they promote an intimate

contact between both phases the type of

internals selected would determine the

height and diameter of a column for a

specified Duty because different designs

have various capacities and efficiencies

the two main types of column internals

discussed in this guideline arteries and

packing there are many types of trays or

plates such as sieve bubble cap and

Valdres packing on the other hand can be

categorized into random and structured

packing in random packing rings and

saddles are dumped into the column

randomly while tructured packing is

stacked in a regular pattern in the

column if we talk about sieve trays then

sieve deck trays perforated plate with

holes punched into the plate usually has

holes 3/16 inches to 1 inches diameterf

vapor comes out from the holes to give

multi orifice effect the vapor velocity

keeps the liquid from flowing down

through the holes weeping the number and

hole size are based on vapor flow up the

tower the liquid flow is transported

down the tower by downcomers

a dam and overflow device on the side on

the plate sieve deck tray has a minimum

capacity approximately 70 percent

👉advantages:-

simple construction low entrainment low

cost low maintenance cost low fouling

tendency disadvantages less flexible to

varying loads than other two types next

is bubble cap tray a bubble cap trays

perforated flat which has a riser

chimney for each hole cover with a cap

mounted usually equipped with slots to

allow the passage of vapor then the

vapor will contact with liquid forming

bubble on the next tray it is able to

operate at low vapor and liquid rates

less than two GPM per foot of average of

flow width advantages moderate capacity

most flexible high and low vApp and

liquid rates can provide excellent

turndown disadvantages high entrainment

high fouling tendency high cost

pressure drop valve tray valve trays

using valve witches Rises vapor rate

increase and then reduces vapor rate

fails this stop the liquid from weeping

valve can be round or rectangular with

or without caging structured valve disk

Rises vapor rate increase valve tray has

minimum capacity approximately 60%

advantages excellent liquid / vapor

contacting higher capacity

flexibility than sift raise can handle

higher loadings low pressure drop and

bubble cap disadvantages high

installation cost packing random

packings structure packings

the selection of column internals the

selection of column internals has a big

impact on the column performance and the

maintenance cost of a distillation tower

there are several choices of column

internals and the two major categories

are trays and packing the choice of

which to utilize depends on their 1

pressure to fouling potential 3 liquid

to vapor density ratio for liquid

loading and 5 most importantly the

lifecycle cost figure shows a schematic

diagram of an example distillation

column or fractionator the feed enters

the column as liquid vapor or a mixture

of vapor liquid the vapor phase that

travels up the column is in contact with

the liquid phase that travels down

column distillation is divided to stages

there are rectifying stages and striping

stages a rectifying stages the process

above the feed tray is known as

rectification where the vapor phase is

continually enriched in the light

components which will finally make up

the overhead product a liquid recycle

condenses the less volatile components

from rising vapor to generate the liquid

recycle cooling is applied to condense a

portion of the overhead vapor it's named

reflux be stripping stages the process

below the feed tray is known as

stripping as the heavier components are

being stripped off and concentrated in

the liquid phase to form the bottom

product at the top of the column vapor

enters the condenser where heat is

removed some liquid is returned to the

column as reflux to limit the loss of

heavy components overhead

each separation stage tray or stage in

the packing the vapour enters from the

stage below to higher temperature while

the liquid stream enters from the stage

above at a lower temperature tray

hydraulic tray design is combination

theory and practice trade I mention are

kept within the range of values known to

give satisfactory performance one

provide good vapor liquid contact to

provide sufficient liquid holdup for

good mass transfer high efficiency three

have sufficient area and spacing to keep

the entrainment and pressure drop within

acceptable limits

four have sufficient down comer area for

the liquid to flow freely from greater

tray tray terminologies one tray spacing

tray spacing is the distance between two

trays generally tray spacing ranges from

8 to 36 inches prime factor in setting

tray spacing is the economic trade off

between column height and column

diameter most columns have 600

millimetres tray spacing cryogenic

columns have tray spacing of 200 to 300

millimetres see this table for reference

to outlet Weir's an outlet where

maintains the desired liquid level on

the tray as the liquid leaves the

contacting area of the tray it flows

over the tray we are to enter into the

down comer 3 down come a clearance HCl

this is the vertical distance between

the tray floor and the bottom edge of

the down comer a prong the normal

practice is to use a down comer

clearance of half inch less than the

overflow we hike to provide a static

liquid seal for downcomers passage of

liquid from the top tray to the bottom

of tray occurs via down comers down

comers are conduits having circular

segmental or rectangular cross-sections

that convey liquid from a per tray to a

lower tray in a distillation column five

turn down ratio turn down ratio defines

the range of vapor load between which

the column can operate without

substantially affecting its primary

separation objective that is

fractionation efficiency or over which

acceptable tray performance is achieved

the tray efficiency stays at or above

the design value throughout the turndown

range now most important part is

designing of distillation column so

start with general design consideration

one process design - mechanical design

purpose of the process design is to

calculate the number of required

theoretical stages column diameter and

tower height on the other hand the

mechanical design focuses on the tower

internals and heat exchanger

arrangements many factors have to be

considered in designing a distillation

column such as the safety and

environmental requirements column

performance economics of the design and

other parameters which may constrain the

work the first step in distillation

column design is to determine the

separation sequences which depends on

the relative volatility and

concentration of each component in the

feed King has outlined a few design

rules as follows one direct sequences

that remove the components one by one in

the distillate are generally favored two

sequences that result in a more equal

molar division of the feet between

distillate and bottoms products should

be favored three separations where the

relative volatility of two adjacent

components is close to unity should be

performed in the absence of other

components e-reserve such a separation

until the last column in the sequence

for separations involving high specified

recovery fractions should be reserved

until last in the sequence now the steps

for designing distillation column one

performing a material balance for the

column two determining the tower

operating pressure and/or temperature

three calculating the minimum number of

theoretical stages using the Fenske

equation for calculating the minimum

reflux rate using the underwood

equations five determining the operating

reflux rate and number of theoretical

stages six selection of column internals

tray or packings seven calculating the

tower diameter and height these are the

thumb rules for designing distillation

column so every time before designing we

can use the experience and make the use

of this thumb rules some general design

rules that should be

Dara's follows one distillation is

usually the most economical method of

separating liquids - for ideal mixtures

low pressure medium temperature and

nonpolar relative volatility is the

ratio of vapor pressures that is alpha

equals P 2 / P 1 3 tower operating

pressure is determined most often by the

temperature of the available cooling

medium in the condenser or by the

maximum allowable reboiler temperature

for tower sequencing a easiest

separation first least trees and reflux

B when either relative volatility nor

feed concentrations vary widely remove

components one by one as overhead

products see when the adjacent ordered

components in the feed vary widely in

relative volatility sequence the splits

in order of decreasing volatility D when

the concentration in the feed varies

widely but the relative volatilities do

not remove the components in the order

of decrease in concentration in the feed

5 economically optimum reflux ratio is

about 120 percent to 150 percent of the

minimum reflux ratio 6 the economically

optimum number of stages is about 200

percent of the minimum value 7 a safety

factor of at least 10 percent above the

number of stages by the best method is

advisable 8 a safety factor of at least

25 percent about the reflux should be

utilized for the reflux pumps 9 reflux

drums are almost always horizontally

mounted and designed for a 5 minutes

holdup at half of the drums capacity 10

for towers that are at least three feet

0.9 meters in diameter for feet

1.2 meters should be added to the top

for vapor release and 6 feet 1.8 meters

should be added to the bottom to account

for the liquid level and reboiler return

eleven limit tower heights to 175 feet

53 meters due to wind load and

foundation considerations 12 the length

diameter ratio of a tower should be no

more than 30 and preferably below 2013 a

rough estimate of reboiler duty as a

function of tower diameter is given by Q

equals 0.5 d2 for pressure distillation

Q equals zero point three d2 for

atmospheric distillation Q equals 0.15

d2 for vacuum distillation where Q

energy in million Btu per hour d tower

diameter in feet types of distillation

x'

steam distillation vacuum distillation

isaiah tropic distillation

of distillation

pressure swing distillation reactive

catalytic distillation first is steam

distillation many organic compounds tend

to decompose at high temperatures steam

distillation is a special type of

distillation process for temperature

sensitive materials like natural

aromatic compounds by adding water or

steam and distillation apparatus the

boiling points of the compounds are

depressed allowing them to evaporate at

lower temperatures after distillation

vapors are condensed as usual yielding a

two-phase system of water and the

organic compounds allowing for simple

separation for example the boiling point

of bromobenzene is 156 degrees Celsius

and the boiling point of water is 100

degrees Celsius but a mixture of the two

boils of 95 degrees Celsius the

necessary condition for employing stream

distillation is that product must be

practically immiscible with water

vacuum distillation similar to

conventional distillation except that it

operates at very low near vacuum

pressure allows the mixture to boil at a

lower temperature and thus avoids the

thermal degradation problem mentioned

earlier separation of azeotropic

mixtures liquid mixture that boils at a

constant temperature at a certain

composition such mixture cannot be

separated using conventional

distillation methods separation of

azeotropic mixtures classified into the

following methods by addition of an in

Trainor / solvent

changing system pressure separation by

changing system pressure pressure swing

distillation distillation columns are

operated at different pressures as it

has been known that the azeotropic

concentration can be shifted

substantially by changing system

pressure as shown in the figure the

pressure change as follows one low

pressure rectification a2b2

high pressure rectification C 2 D 3 low

pressure stripping eat a target purity

extractive distillation extractive

distillation is defined as distillation

in the presence of immiscible high

boiling relatively non volatile

component solvent that forms no

azeotrope with the other components in

the mixture the method is used for

mixtures having a low value of relative

volatility nearing unity the solvent

interacts differently with the

components of the mixture thereby

causing their relative volatilities to

change this enables the mixture to be

separated by normal distillation

original component with the greatest

volatility separates out as the top

product the bottom product consists of a

mixture of the solvent and the other

component which can again be separated

easily because the solvent doesn't form

an azeotrope bottom product can be

separated by any of the methods

available boiling point of the solvent

is generally much higher than the

boiling points of the feed mixture so

that formation of new azeotropes is

impossible the high boiling point will

also ensure that the solvent is will not

appreciably vaporize in the distillation

process selection of suitable separation

solvent solvent must alter the relative

volatility quantity cost and

availability of the solvent should be

considered solvent should be easily

separable from