Polymer/Chemical Reactor Design Muhammad Zafar Iqbal
Recycle Reactors and some important considerations
Autocatalytic Reactors and their important considerations
Optimum temperature Progression
Reactor Operating Line
Basics of Non-linear flow: Fundamental Concept
A reactor for which product stream is split and a part of that split stream is sent back to reactor to enhance the reactor performance is called a Recycle Reactor.
Recycle Stream is defined as:
Recycle stream is introduced to enhance the degree of mixing.
Therefore it is conventionally said that for R=0, the behavior is totally plug and for R=very large, the behavior is mixed flow reactor.
Types of recycle reactor
Ref: Chemical Process design and Integration by Smith, Ch-13,14
Performance Equation For this plug flow reactor, the performance equation is given as:
The actual conversion at inlet is given by: The concentration at inlet to the reactor is given by So finally we get the following results: The final equation for any expansion factor value is: Also in terms of concentration,
In general, when conc. Of reactants is high (at start) the rate of reaction is also high. When conc. Is lowered, the reaction proceeds slowly.
In autocatalytic reactions, the rate of reaction at the start is slow but as the product is formed more and more, the speed of reaction increases up to a certain level then drops.
Therefore there is always a need for optimization of reactors for autocatalytic reactions.
A general representation of autocatalytic reaction is given as:
Mixed flow Vs Plug flow Reactor
Temperature and Pressure Effects in Single Reaction based Reactors
There is a great influence of operating conditions on the reactor set up and optimization.
Normally the following three step procedure is adopted:
1- T and P effects on equilibrium composition, rate of reaction and product distribution
2- The Heat effects and their impact on operating Temp.
3- Economic optimization of process
Two factors are considerable:
1- Conversion Level no product distribution
2- Reactor stability
Optimum Temperature Progression
Reactor Operating Line
The size of a reactor for a given duty and for a given temperature progression is found from following procedure:
Draw X A Vs T (Reactor Operating Line)
Find Reaction rates at different X A along this path
Plot 1/-r A Vs X A for this path
Find the area under the curve or area of the rectangle depending upon the type of reactor used.
Ref: Chemical Reaction Engineering by Levenspiel Chapter 9.
Non-Ideal Flow: Fundamental Concepts
Three main factors which can describe the flow are:
State of Aggregation
Earliness and Lateness of Mixing
Residence Time Distribution
States of Aggregation of the flowing stream
Mixing Ref: Chemical Reaction Engineering by Levenspiel Chapter 11.