Using this plot show that the behavior of a recycle reactor approaches that of

Using this plot show that the behavior of a recycle

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Using this plot, show that the behavior of a recycle reactor approaches that of a CSTR at R >> 1 for any type of kinetics. For example, note that XA1approaches XA2, so the conditions within the PFR section are approximately constant.Verify that a recycle reactor will require a larger reactor volume (e.g., volume or weight of catalyst) for a given conversion with a positive-order reaction than required with a straight PFR. Sketch the inverse rate plot for a negative-order reaction and compare the behavior of a recycle reactor to a CSTR.Sketch the inverse rate plot for a reaction that is positive order at low reactant concentration (high conversion) and negative order at high reactant concentration (low conversion). Can you show conditions under which a recycle reactor will let you use a smaller reactor or catalyst volume than either a PFR or CSTR? Membrane reactor This type of reactor has been studied in the laboratory for hydrocarbon dehydrogenation reactions. By selectively removing the hydrogen product through a permeable reactor wall, conversion can exceed equilibrium conversion with no separation. The permeable wall might be a porous ceramic tube coated on one side with a thin palladium coating. The annulus between this tube and an outer tube would contain the flow of hydrogen product. A membrane reactor can be modeled in a way similar to that for a semi-batch reactor with selective product removal. See CRE notes 10. This is a type of hybrid, reactor-separator process unit. Reactive distillation Another type of hybrid, reactor-separator process unit is a distillation column in which reactions occur in addition to separation of components. An example is "catalytic distillation" in which porous solid catalyst pellets are placed on some of the stages. By separating products as they are formed, conversion can exceed equilibrium conversion with no separation. Methanol dehydration to dimethyl ether (DME) and water is an example reaction. DME is potentially useful as a sootless diesel fuel. Packed bed reactors The reactors are usually packed with catalyst pellets. If you are given a rate equation, then you can model the reactor in one of the several ways you know: PFR, CSTRs in series, dispersion model. The catalyst pellets are porous in order to obtain high active area per unit reactor volume. This means that reactants must diffuse and be carried from the bulk fluid flow to the pellet and then diffuse into the pellets. Products must diffuse out. R. K. Herz, [email protected], CRE notes part 15, p. 16 of 18
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