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THE FINAL EXAMINATION of
ChE 345 REACTION ENGINEERING I
15.02.2021 Exam Time: 09:00 - 12: Loading Time: 12:00 - 12:
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Q 1 2 3 4 TOTAL
M 25 25 25 25 100
E
1) The irreversible gas-phase nonelementary reaction A → B+C is to be carried out isothermally in a constant volume batch reactor using pure gas A. The reaction is second order in A. Laboratory data are collected at different runs to calculate specific reaction rate at 100 °C:
RUN 1 RUN 2 RUN 3 RUN 4 Initial pressure of A, PA0, atm 1 2.5 5 7. Half-time, t1/2, min 10 4 2 1.
a) From the given data above, calculate the specific reaction rate at 100 °C.
b) If the reaction is proceeded in Plug Flow Reactor ( PFR) calculate the residence time in PFR to achieve 70% conversion of A at a temperature of 100 °C. The inlet pressure is 1 atm and there is no pressure drop in the PFR. Pure A enters the reactor.
Hint: ∫
(1+εX)^2 (1−X)^2 dX = 2ε(1 + ε)ln(1 − X) + ε
(^2) X + (1+ε)^2 X (1−X)
X 0
2) The following irreversible nonelementary liquid phase reaction in a constant volume batch reactor is realized for the production of reactant C:
A + 2B 3C + D
The reaction rate may be presented by a third order irreversible equation, second order with respect to A and first order with respect to B. The reaction rate constant (k) is 1.5 (dm^3 )^2 /mol^2 ∙hr at 400K. The initial concentrations of A and B are 2.0 mol/L and 4.0 mol/L, respectively.
The reactor will be run isothermally at 400K. The concentration of A in the final product must be 0.50 mol/L, and the molecular weight of C is 100 kg/kmol. An average of 5 hours is required between the batches in order to empty and clean the reactor, and prepare for the next batch. How large must the reactor be in order to produce 200,000 kg of C annually (with 7500 hours per year of operation)?
3) The elementary liquid phase reaction
A + B → C + D
is carried out in a continuous stirred tank reactor (CSTR) at a constant temperature of 100C. The inlet concentrations of A and B in the individual feed streams are 0.4 mol/dm^3 and 1.6 mol/dm^3 , respectively. Reactant A with a 0.1 dm^3 /s volumetric flow rate is fed to the reactor together with an equal volumetric flow rate of reactant B. The specific reaction rate constant is 0. dm^3 /mol.s.
a) If 80% conversion is to be achieved, determine the necessary single CSTR volume (V).
b) If two equal volume (V/2) small CSTRs are arranged in series, what are the conversions in the first and second CSTR? What is the total conversion?
c) Make a final comment in terms of reactor volumes. Which reactor system (two equal volume (V/2) CSTRs connected in series or a single CSTR (V)) would you prefer to use?
