Dv r f f v j j j ideal steady state cstr design

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dV r F F V j j 0 j = + Ideal Steady State CSTR Design Equation V r F F j j 0 j = 0 V r F F j j 0 j = + Rearrange r j is evaluated at the outlet because C j,exit = C j,tank
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Copyright © 2011, Prof. M. L. Kraft. All rights reserved L2-13 Ideal SS CSTR Design Equation j j 0 j r F F V = Reactor volume required to reduce the entering flow rate of species j from F j0 to F j at the outlet (and in the tank) What is the molar flow rate, F j ? ( ) ( ) ν j j C F = = time volume volume moles time j moles j j 0 j r C C V = ν ν C j : concentration of j ν : volumetric flow rate Ideal SS CSTR design equation in terms of concentration:
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Copyright © 2011, Prof. M. L. Kraft. All rights reserved L2-14 Plugged Flow Reactor (PFR) Properties Also called a tubular reactor Cylindrical pipe with openings at both ends Operated at steady state Steady movement of material down length of reactor Reactants are consumed as they flow down the length of the reactor No radial variation in temperature, concentration, or reaction rate All fluid/gas elements have the same residence time
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Copyright © 2011, Prof. M. L. Kraft. All rights reserved L2-15 Industrial PFRs
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Copyright © 2011, Prof. M. L. Kraft. All rights reserved L2-16 V F A0 F A In a plug flow reactor the composition of the fluid varies from point to point along a flow path; consequently, the material balance for a reaction component must be made for a differential element of volume V Mole Balance – PFR j j r dV dF = j V j V V j r V F F = Δ Δ + V j j V V j V j dV dN V r F F Δ Δ + = Δ + V r j Δ F j0 F j dt dN j + - = 0 0 V r F F j V V j V j = Δ + Δ + Divide by Δ V 0 r V F F j V V j V j = + Δ Δ + lim Δ V 0 Ideal SS PFR Design Eq. If we assume the PFR is ideal, its shape is not important to the degree of completion, only its volume
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Copyright © 2011, Prof. M. L. Kraft. All rights reserved L2-17 Packed Bed Reactors (PBR) Cylindrical shell, vertically oriented Often gravity-driven flow Heterogeneous reaction: fixed bed of catalyst inside Reactants enter top and flow through the packed bed of catalyst Concentration gradient of reactant (and product) down the length of the reactor Reaction occurs on the surface of the catalyst pellets Reaction rate is based on the mass of the solid catalyst, W, not reactor volume V
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Copyright © 2011, Prof. M. L. Kraft. All rights reserved L2-18 Mole Balance- Packed Bed Reactor (PBR) j j r dV dF = Similar to PFR, but we want to express this in terms of catalyst weight instead
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  • Spring '10
  • LIU
  • Chemical reaction, Chemical reactor, Prof. M. L. Kraft, M. L. Kraft, Prof. M. L.

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