Know the types of Reactors

Batch reactors

This is a type of reactor, where materials are charged into it, allowed to mix together over a certain period of time. The contents are discharged(products). In an unsteady state condition, the reaction composition changes with time and it is uniform throughout the reaction.

For material balance of the reactor; we consider all content of the reactor since it doesn’t change with time. No input and output during reaction.


Disappearance= -(accumulation)

-RA  =


(Considering a reactant A in a batch reactor)

In an iso-thermal or non isothermal condition, the volume of fluid and rate of reaction changes. Integrating, we have that the total time for conversion of a reactant is given as

T = –


Space Time and Space Velocity

Space time is the time required to process a unit reactor volume of feed at specified condition .i.e. one volume of reactor

τ =1/s

Space velocity is the number of reactor volume of feed that can be processed in a unit time. It means the number of reactors a plant can process in given time under specified conditions.

s= 1/τ  =


steady state mixed reactor

This is a condition of plug flow and batch reactor. The compositions are uniform throughout. There is no accumulation of reactant.

Input=Output + disappearance of reactants

steady plug flow reactor

This is a type of reactor that the materials flow from one point to the other as reaction takes place. There is an orderly flow of materials. No material overtakes each other behind or after. The compositions of the reactor content changes with position. The equation of this kind of reactor is given as

Input=Output + Disappearance


In performance of a plug flow reactor, under constant density, the performance equations are identical. Space time is equivalent to space velocity of a batch flow reactor. Reverse is the case in varying density. The size of a plug flow reactor during reaction is given as

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