Batch Reactor 224

8/2/2019 Batch Reactor 224

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WAQAR AHMAD NASEER

2009-CH-224


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Contents

Selection of Batch reactors.

Kinetics of Batch reactors.

Calculations i.e. (different balances, residencetime e.t.c.)

Designing the reactor on the basis of these

calculations.


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Why we need a Batch Reactor?

Commonly said..

Because we need high conversion per unit

volume

Is it the main character while choosing the

B.rs????

But the conversion per unit timedecreases!!!!


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Main reason

1.The reactants feed for B.rs is usually a

catalyst+ reactants

The catalytic reactions are usually of timeconsuming and need high residence time.

So the choice of B.rs for these kind of

reactions is perfect.2. Where small volumes of high-value products

are made.


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Kinetics of B.rs

In a batch reactor the reactants and the catalystare placed in the reactor and the reaction isallowed to proceed for a given time whereupon

the mixture of un reacted material togetherwith the products is withdrawn.

In an ideal batch reactor, the concentrationand temperature are assumed to be uniform. Inpractice, the condition can be approximately

realized by vigorous agitation or stirring.


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Cont.

All the elements of the fluid spend the sameamount of time in the reactor, and hence have

the same residence time.Some of the reactions like enzyme reactions,are exothermic hence the temperaturecontrolling is an important phenomenon.

Due to the presence of catalyst (enzyme e.t.c)the controlling of reaction conditions is muchmore difficult than other reactors.


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Reaction kinetics and calculations:

Considering an enzyme reaction occurring inside the

reactor.

the rate equation given by (Michaels & Menten)

Dr/dt =k3*[A] [ Eo] / [M]+[A]

Rate depends

1.Enzyme

2.Concentration of A if [A]M]


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Designing the batch reactors


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Before designing we must know.

Agitation and cooling media selection

Kinetics of reaction i.e. rate of reaction e.t.c.

Enzyme characteristics i.e. (temperaturepressure controlling)

Reaction feasibilities i.e. (temperature e.t.c

requirements)Phases involving

Residence time


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Mixing and cooling media selection

This depends upon the reaction conditionsand requirements:

Agitation should be proper and at steadystate so not to interrupt the enzymemechanism

Cooling depends upon the heat ofreaction, must be enough to remove theheat fro the vessel but not freezing it.


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Kinetics of reaction

Idea of rate of reaction

Variations on reaction by changingtemperature pressure conditions.

Heat of reaction to be remove from thereactor

Effects of heat changing on reactionefficiency


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Enzyme characteristics &Reaction

feasibilities

The reaction should be controlled in sucha way that enzyme should be free to do

his work.The feasibility of reaction should also beaccounted to increase the efficiency


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Phases involved

They may be liquid, solid or gaseousphases present, some time the gaseousproduct is important and some time the

liquid or solid.

So there should be a proper mechanism toget our product safely and precisely from

the reactor.


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Residence time

Important to find the range of conversionsof reaction.

To find the completion time required tocomplete the reaction


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Calculating the residence of reaction

Considering a general reaction and applying

the mole balance


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Cont.

Conversion X=Na/Nao

dx=dNa/Nao

dx/dt=dNa/dt.Naodx/dt=(dNa/dt.v).v/Nao

dx/dt=-ra.v/Nao

t=integral(0-x) dx.Nao/-ra.V


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Complementary Equipments with

batch reactors

Heat Exchangers

Sepration process

Temprature and pressure control

Pumps e.t.c


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QUESTIONS

Documents

Batch Reactor 224