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the mixture of un reacted material togetherwith the products is withdrawn.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