Reactors Can Be Selected Depending Upon Following Factors

8/2/2019 Reactors Can Be Selected Depending Upon Following Factors

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CHEMICAL REACTORS

Basic classification

No. Type of

Reactor

Principle

of Working

Advantage

s

Limitation

s

Area of

Application

1. BatchReactor

Allreactantsare addedat thecommencement andthe productwithdrawnat the

completionof thereaction.They areconductedin tanksattachedwithimpellers,gasbubbles or

pumps.

Suitablefor smallscaleproduction Suitableforprocesseswhere a

range ofdifferentproducts orgrades is tobeproduced inthe sameequipment Suitableforreactions

requiringlongreactiontimes Suitableforreactionswithsuperiorselectivity

Notsuitable forlarge batchsizes It is aclosedsystem inwhich once

thereactantsare addedin thereactor,they willcome outas productsonly afterthecompletion

of thereaction

Batchprocessesare used inchemical(inks, dyes,polymers)and foodindustry


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Continuous Stirred TankReactor (CSTR)

One ormore fluidreagentsareintroduced

into a tankreactorequippedwith animpellerwhile thereactoreffluent isrecovered.A steppedup

concentration gradientexists

Highlyflexibledevice By

productsmay beremoved inbetweenthereaction

It iseconomicallybeneficial

to operateseveralCSTRs inseries or inparallel. Reactioncan becarried outinhorizontalas well as

verticalreactors

Morecomplex

andexpensive

than tubularunits Allcalculationsperformedwith CSTRsassumeperfectmixing At steadystate, the

flow rate inmust equalthe flow rateout,otherwisethe tank willoverflow orgo empty

Chemicalindustryespeciallyinvolvingliquid/gas

reactions

3 Plug FlowReactor(PFR)

One ormore fluidreagentsarepumpedthrough apipe ortube.

These arecharacterized bycontinuousgradientsofconcentration in the

Higherefficiencythan aCSTR ofthe samevolume PFRs

may haveseveralpipes ortubes inparallel Bothhorizontaland vertical

Noteconomicalfor smallbatches

The tubularreactor isspeciallysuited tocasesneedingconsiderable heat

transfer,where highpressuresand veryhigh or verylowtemperatures occur


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direction offlow

operationsarecommon They canbe jacketed

Reagentsmay beintroducedat locationseven otherthen inlet

Reactors can be selected depending upon following factors;

Process-based classification

Phase-based classification

Transfer-based classification

Process-based classification1) Batch process

Batch reactors are used.(i.e Batch processes are suitable for small production

and for processes where a range of different products or grades is to be

produced in the same equipment for example, pigments, dye stuff and polymers)

2) Contiouous processContinuous stirred tank reactors are uesd.(i.e For example, Haber Process for

the manufacture of Ammonia)

3) Semibatch process

Semi-batch reactors are uesd.(i.e chlorination of a liquid.)

4) Catalytic process

Mostly followings are used;

Packed-bed reactors where solid acts as catalyst.

Batch reactors are used where enzymes are involved.

5) Biological processes

Bioreactors are used depending upon mode of operation.

Bioreactor may be classified as

batch,

fed batch

or continuous

moving media, also known as Moving Bed Biofilm Reactor (MBBR)
http://en.wikipedia.org/wiki/Batch_reactorhttp://en.wikipedia.org/wiki/Fed-batchhttp://en.wikipedia.org/wiki/Continuous_reactorhttp://en.wikipedia.org/wiki/Moving_Bed_Biofilm_Reactor_(MBBR)http://en.wikipedia.org/wiki/Moving_Bed_Biofilm_Reactor_(MBBR)http://en.wikipedia.org/wiki/Continuous_reactorhttp://en.wikipedia.org/wiki/Fed-batchhttp://en.wikipedia.org/wiki/Batch_reactor


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packed bed fibrous bed membrane photobioreactor (PBR)

Phase-based classification

1) Homogeneous phase reactions

For gaseous phase

Tubular reactors are used.(i.e. in the thermal cracking of petroleum, crude

oil fractions to ethylene, and the thermal decomposition of dichloroethane

to vinyl chloride.)

For liquid phase

Batch or CSTR are used.

2) Heterogeneous phase reactions

For Solid-liquid Gas phase we can use;1) Trickle bed reactors

2) Flooded reactors

3) Slurry reactors

4) Fluidized bed reactors

For liquid-liquid and Liquid-Gas phase we often use;

CSTR

For Gas and Gas-liquid phase we use;

Packed bed reactors

3) Isolated elementary reaction or multi-step reaction mechanism

Laminar flow reactors(LFR) are often used to study them.

Transfer-based classification

Agitated CSTRs are used for good Mass and Heat transfer based

reactions depending upon the Phase and Process-type match with the

given prerequities of CSTR.

Fluidized bed reactors are used for excellent Mass and Heat transfer

purposes if reaction conditions fullfill the requirements to go for FBR. Thus

FBRs are well suited to exothermic reactions

Tubular reactors are often used for high Heat transfer rates if thereaction conditions are

Packed bed reactor often with large diameter are used where poor heat

transfer is required.

Laminar flow reactor (LFR) are operated at constant temperature

systems. (i.e LFR is generally a long tube with constant diameter that is
http://en.wikipedia.org/wiki/Moving_Bed_Biofilm_Reactor_(MBBR)http://en.wikipedia.org/wiki/Moving_Bed_Biofilm_Reactor_(MBBR)http://en.wikipedia.org/wiki/Packed_bedhttp://en.wikipedia.org/w/index.php?title=Fibrous_bed&action=edit&redlink=1http://en.wikipedia.org/wiki/Photobioreactorhttp://en.wikipedia.org/wiki/Elementary_reactionhttp://en.wikipedia.org/wiki/Reaction_mechanismhttp://en.wikipedia.org/wiki/Exothermichttp://en.wikipedia.org/wiki/Exothermichttp://en.wikipedia.org/wiki/Reaction_mechanismhttp://en.wikipedia.org/wiki/Elementary_reactionhttp://en.wikipedia.org/wiki/Photobioreactorhttp://en.wikipedia.org/w/index.php?title=Fibrous_bed&action=edit&redlink=1http://en.wikipedia.org/wiki/Packed_bed


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kept at constant temperature. conversion from methane to higher

hydrocarbons have been studied in a laminar flow reactor.)

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Reactors Can Be Selected Depending Upon Following Factors