Reactor Design 9
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Reactor Design 9

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Reactor Design 9 Reactor Design 9 Presentation Transcript

  • Polymer/Chemical Reactor Design Muhammad Zafar Iqbal
  • Today
    • 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
  • Recycle Reactors
    • 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,
  • Graphical representation
  • Autocatalytic Reactors
    • 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
    • Single Reactions:
    • 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.
  • n
  • Non-Ideal Flow: Fundamental Concepts
    • Three main factors which can describe the flow are:
    • RTD
    • 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.