last name first name student # university of toronto

Last Name First Name Student #

University of Toronto Faculty of Applied Science and Engineering

Final Examination, April 24, 2017 CHE333S1 - Chemical Reaction Engineering

Examiner: B.A. Saville

Closed Book Examination-i The Course Textbook or Official Course Notes Package may be used

Calculators without a Graphical Interface may be used

Both sides of the page may be used

Question: Marks Possible Marks Earned

1 30

2 20

3 25

4 25

5 50

Total 150

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1. Please answer each of the following independent questions. (10 marks) Provide two types of reactions/processes for which a PFR with recycle would be a preferred choice of reactor. Explain your reasoning. (10 marks) Which reactor configuration provides the highest fractional conversion: (i) a CSTR, or (ii) a reactor with an RTD equivalent to back-mixed flow, but with complete segregation at the molecular level. Provide two responses, first based on a reaction that is first order, and second, for a reaction that is second order. Explain your reasoning. (10 marks) You need to determine the operating conditions for a BR for the following liquid phase reactions:

A D; (-rA) = 0.45CA2 - A4 U; (-rA) 0.12cA

What process conditions (concentrations, conversion) would maximize the yield of the desired product, D? EXPLAIN AND JUSTIFY YOT JP ANSWER

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2. An endothermic liquid phase reaction A 4 2C is conducted in a 100L batch reactor that operates isothermally at 25°C due to careful control of the temperature of the heat transfer fluid in the reactor jacket. Given the following:

.

(-rA)—kAcA, with kA-1.2xlO10 (-7500/7) e mm-1

CAO 0.25 mol/L cp4.0Jg K 1 p = 0.95 g/L (-AHRA) = 90 kJ per mol of A UAc = 100W/K td = 30 minutes Determine:

The time required for 90% conversion of A The overall production rate of C, in mollmin The initial temperature of the heat transfer fluid

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3. A gas phase reaction A + B - C takes place in a CSTR, operating isothermally and isobarically. The reaction is first order with respect to each reactant. The feed is delivered at a total molar flow rate of 0.60 molls, and contains equal amounts of A, B, and an inert.

Determine the mean residence time in the reactor, and the inlet volumetric flow rate, given that the reaction rate constant is 0.5 L moi' min 1, the feed concentration of A is 0.40 mollL, and the desired fractional conversion of A is 0.75. For the same mean residence time in a PFR, would the fractional conversion be greater, smaller, or the same as that in the CSTR? Explain and justify your answer.

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4. Experiments were performed to evaluate the performance of a first order reaction A -* C with different sizes of catalyst pellets. Pure reactant A at l00kPa and 400°C was fed through the catalyst, and the observed reaction rate was measured for several sizes of the spherical catalyst, ranging from 0.25 to 10 mm in diameter. The following data were obtained:

0.50 5.0 kr

d ,mm ObS, mol L s' 0.020 1 0.0079

Stating ALL assumptions:

Determine the effectiveness factor and Thiele modulus (4') for each particle. Determine the rate constant for the intrinsic reaction and the effective diffusivity

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5. Renewable hydrogen can be produced from biomass via gasification, which produces syngas, a mixture of carbon monoxide and hydrogen. The yield of renewable hydrogen can be increased by way of the shift reaction, in which additional hydrogen is produced from the shift reaction between steam (H20) and carbon monoxide (A). A three-stage fixed bed catalytic reactor was to be designed for this shift reaction, which can be used to produce hydrogen from steam and carbon monoxide. The feed contains steam, carbon monoxide (A), hydrogen (C) and nitrogen (N2, inert, I). The catalyst sinters at 450°C. Assuming that the pseudohomogeneous one-dimensional plug flow model is valid, and that each stage operates isobarically and adiabatically:

What is the final CO:H2 molar ratio at the outlet of the 3rd stage, based upon the specified conditions? Assume that each stage operates adiabatically, the outlet temperature from each stage is (at least) 15°C less than equilibrium temperature, and that interstage heat exchangers reduce the temperature by 50°C between each stage. What mass of catalyst is required for the first stage of this reaction, ASSUMING 30% CONVERSION OF CO, and that the Thiele Modulus (4c) is 0.75. For the integration, use a step size of 0.10 for fco.

Data: FAO = 0.5 mol/s; F 00 = 3 mol/s; F0 = 1.25 mol/s; F1 = 1.0 mol/s. To = 407°C; P0 = 2.0 bar; AHRA = -40 kJ/mol; Cp = 2.1 J g' K 1 ; (-rA) = kA(pApH20 - (pco2pH2)IKP); kA = 800 mol (tonne cat)' s1 bar-2; K = 8.9 x 1 0 e48/T;

Molar masses: H= 1; C= 12;N = 14; 0=16 Graph provided on next page

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Name Student #

Shift Reaction Equiulibrum Curve

1

o0.7 U 0

0.6

05 --4---+---H -----------4-

---

0.1

0

600.0 650.0 700.0 750.0 800.0 850.0 900.0 950.0 1000.0

Temperature, K

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Name Student #

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last name first name student # university of toronto

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