Chemical Engineering - Chemical Reaction Engineering and Applied Chemical Kinetics

Full exam

CRE – 08.09.15 - Exam D 1 096116 Chemical Reaction Engineering 8 September 2015 Family name _________________________________________________ First name _________________________________________________ ID number _________________________________________________ Signature _________________________________________________ Please, consider that the sum of percentages of proposed exercises (4) is equal to 110%. This means that the maximum mark you can reach is 33. Remember to write on the top of each sheet you submit: your name, ID number, and signature. Use of mobile phones and internet connection is not allowed. 1. Packed bed reactor and CSTR in series (40%) The irreversible elementary gas phase reaction: 2������������→������������+������������ is currently carried out in a packed bed reactor containing 50 kg of catalyst. The entering pressure is 20 atm and the exit pressure is 8 atm. Currently, 80% conversion is achieved. It is proposed to add a CSTR with 100 kg of catalyst downstream of the PBR. There is no pressure drop in the CSTR. The flow rate and temperature remain unchanged. a. What would be the overall conversion in such an arrangement (PBR+CSTR)? b. Is there a better way to carry out the reaction, and if so w hat is it? Please explain in max 6 lines. 2. Catalytic reaction (20%) The catalytic reaction ������������→������������ to be carried out in a flow reaction system has the following rate law: ������������=������������ ������������ ������������ ( 1+������������ ������������������������������������)2 ������������� =1 ������������������������������������ −1 ������������������������=1 ������������ ������������ 3 ������������������������������������ The entering mixture is pure A ������������ ������������ ������������������������=2 ������������������������������������/������������������������������������ and the inlet concentration of A is 2 mol/dm3 and the entering flow rate . What type of reactor or combination of reactors (CSTRs and PFRs) would have the smallest volume (please, quantify it) to: a. achieve 50% of conversion? b. achieve 80% of conversion? CRE – 08.09.15 - Exam D 2 3. Analysis of experimental data (25%) In order to study the photochemical decay of aqueous bromine (MW=79.9 g/mol) in bright sunlight, a small quantity of liquid bromine was dissolved in water contained in a glass battery jar and placed in direct sunlight. The following data were obtained: Time (min) 0 10 20 30 40 50 Br (ppm) 2.45 1.74 1.23 0.88 0.62 0.44 a. Determine whether the reaction rate is zero-, first-, or second-order in bromine, and calculate the reaction rate constant in units of your choice. b. Assuming identical exposure conditions, calculate the required daily rate of injection of bromine into a sunlit body of water 25,000 l in volume in order to maintain a sterilizing level of bromine of 1 ppm . 4. Trimerization reaction in a PFR (20%) The trimerization reaction: 3������������( ������������) →������������ 3( ������������, is carried out isothermally and without pressure drop in a PFR at 298 K and 0.8 atm. As the concentration of ������������ 3 increases down the reactor, ������������3 begins to condense. The vapor pressure of ������������3 at 298 K is 0.2 atm. If an equal molar mixture of ������������ and inert, I, is fed to the reactor at what conversion of ������������ will ������������3 begin to condense?