Reactor Design 9


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Reactor Design 9

  1. 1. Polymer/Chemical Reactor Design Muhammad Zafar Iqbal
  2. 2. Today <ul><li>Recycle Reactors and some important considerations </li></ul><ul><li>Autocatalytic Reactors and their important considerations </li></ul><ul><li>Optimum temperature Progression </li></ul><ul><li>Reactor Operating Line </li></ul><ul><li>Basics of Non-linear flow: Fundamental Concept </li></ul>
  3. 3. Recycle Reactors <ul><li>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. </li></ul><ul><li>Recycle Stream is defined as: </li></ul><ul><li>Recycle stream is introduced to enhance the degree of mixing. </li></ul><ul><li>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. </li></ul>
  4. 4. Types of recycle reactor
  5. 6. Ref: Chemical Process design and Integration by Smith, Ch-13,14
  6. 7. Performance Equation For this plug flow reactor, the performance equation is given as:
  7. 8. 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,
  8. 9. Graphical representation
  9. 10. Autocatalytic Reactors <ul><li>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. </li></ul><ul><li>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. </li></ul><ul><li>Therefore there is always a need for optimization of reactors for autocatalytic reactions. </li></ul><ul><li>A general representation of autocatalytic reaction is given as: </li></ul>
  10. 12. Mixed flow Vs Plug flow Reactor
  11. 13. Temperature and Pressure Effects in Single Reaction based Reactors <ul><li>There is a great influence of operating conditions on the reactor set up and optimization. </li></ul><ul><li>Normally the following three step procedure is adopted: </li></ul><ul><li>1- T and P effects on equilibrium composition, rate of reaction and product distribution </li></ul><ul><li>2- The Heat effects and their impact on operating Temp. </li></ul><ul><li>3- Economic optimization of process </li></ul><ul><li>Single Reactions: </li></ul><ul><li>Two factors are considerable: </li></ul><ul><li>1- Conversion Level no product distribution </li></ul><ul><li>2- Reactor stability </li></ul>
  12. 14. Optimum Temperature Progression
  13. 15. Reactor Operating Line <ul><li>The size of a reactor for a given duty and for a given temperature progression is found from following procedure: </li></ul><ul><li>Draw X A Vs T (Reactor Operating Line) </li></ul><ul><li>Find Reaction rates at different X A along this path </li></ul><ul><li>Plot 1/-r A Vs X A for this path </li></ul><ul><li>Find the area under the curve or area of the rectangle depending upon the type of reactor used. </li></ul>Ref: Chemical Reaction Engineering by Levenspiel Chapter 9.
  14. 16. n
  15. 17. Non-Ideal Flow: Fundamental Concepts <ul><li>Three main factors which can describe the flow are: </li></ul><ul><li>RTD </li></ul><ul><li>State of Aggregation </li></ul><ul><li>Earliness and Lateness of Mixing </li></ul>
  16. 18. Residence Time Distribution
  17. 19. States of Aggregation of the flowing stream
  18. 20. Mixing Ref: Chemical Reaction Engineering by Levenspiel Chapter 11.