Reactor Design

الجمهور : هو احنا هناخد إيه النهاردة؟ أنا : هناخد Reactor الجمهور : بس؟ أنا : آه بس الجمهور : هو السكشن طويل أنا : آه الجمهور : يعني هناخد السكشن ونص أنا : آه الجمهور : بس احنا تعبانين أنا : وأنا تعبانة أكتر منكم الجمهور : بس احنا صايمين أنا : ربنا يتقبل إن شاء الله الجمهور : طب احنا هناخد إيه في ال Reactor ؟ أنا : Combined Reactors الجمهور : بس احنا ما أخدناهاش في المحاضرة؟ وال gas phase هناخده امتى؟ أنا : ماهي بتاخد في السكشن بس ، بعد العيد إن شاء الله

Exercise

WHAT IS THE BEST ARRANGEMENT FOR REACTORS TO GET THE MAXIMUM CONVERSION?

Order of ReactionReactor Arrangement n = 1Equal size reactor

Order of ReactionReactor Arrangement n > 1Smaller reactor should be put first

Order of ReactionReactor Arrangement n < 1Larger reactor should be put first

SERIES COMBINATION OF CSTR AND PFR

When PFRs and CSTRs are both available and to be used in series, the order of the reactors can affect the total conversion, as the conversion will be dependent on the inlet concentration to each reactor. Therefore, the overall will depend on the order in which the reactors are placed. For first order reactions, the overall conversion will be independent of reactors order.

For n > 1, PFR should be placed before CSTR, Why? High rates (at high concentrations) are required in order to maximize the conversion. As PFR takes the advantage of the high reaction rates, it should be placed before CSTR. The reverse occurs when n <1.

If we have more than one CSTR of different sizes together with the PFR, the smallest one should be placed immediately after the PFR so as to keep higher concentrations and hence higher rates of reaction.

WHAT ABOUT PARALLEL CONFIGURATION FOR CSTR S AND PFR S IN SERIES?

HIPPOPOTAMUS’S DIGESTIVE SYSTEM

The hippopotamus digestive system is modeled as a CSTR and a PFR in a series. For the system above A represents the grass that makes up the bulk of the hippos normal diet. F is the molar flow of A, m is the mass flow and X represents the conversion of A into proteins, vitamins, minerals and everything else that the hippo needs to survive.

Finding correct values of X is of course impossible but fairly good estimates can be done. We further assumed that about 75% of the total conversion occurred in the first part of the digestive system, i.e. the CSTR or the stomach, and 25% in the second part, i.e. the PFR or the intestines. The assumption is based on the volume ratio between the two parts. Studies made of the stomach contents of the hippo are not extensive enough to make any final conclusions but at least the protein contents in different parts of the stomach are in concord with the aforementioned assumption.

SHEET 5

4.The kinetics of the aqueous – phase decomposition of A is investigated in two mixed reactors in series, the second having twice the volume of the first reactor. At steady state with a feed concentration of 1 mole A/lit. and mean residence time of 96 sec in the first reactor, the concentration in the first reactor is 0.5 mole A/lit. and in the second is 0.25 mole A/lit. Find the kinetic equation for the decomposition.