Reactor Design: multiple mixed flow reactor System

multiple mixed flow reactor system

Reactor Design:multiple mixed flow reactor system. This has to do with the connection of reactor for operation in a plant. They can be connected in series or parallel.

Considering N number of reactors connected in series; with fractional conversion of Y1-Yn


For total volume of reactors in series is equal to the conversion of a single plug flow reactor of volume(V). When a system is a combination of series and parallel connection it can be treated as a single plug flow. This is done by adding the volume of individual units in each branch; so as to have the same conversion.

Example: The reactor setup below consists of four plug flow reactors in two parallel branches. Branches reactor of volume 30 liters followed by a reactor of volume 20 liters. Branch B has a reactor of volume 40 liters followed by a reactor of volume 60 liters. What fraction of the feed should go to Branch B?

Reactor 1 and 2 are in series and 3 and 4 in branch B are in series while the two branches are in parallel.

VA=30 +20 = 50 liters

VB=40 +60 = 100 liters

FA/FB = 50/100 = 0.5

Therefore half of the feed will be fed into the branch B.


In general, the concentration of reactants in reaction decreases gradually as the reaction proceeds. While the concentration of products increase. In a plug flow, the same attribute applies. But in a mixed flow reactor, the concentration of the reactant decreases immediately to a low value. Reason being that a plug flow reactor is more efficient than mixed flow reactor.

This is for reaction whose rate increase with reactant concentration. (i.e irreversible reactions). Now, when there is a series connection of mixed flow reactors with equal concentration of reactant. As the reactants move from one reactor to another as reaction process; they attain the state or behavior of a plug flow reactor.

For second order reaction: Here, much of the evaluation of the performance equation is done using a chart. But, it should be noted that; there will not be excess reactant in the system.



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