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2. Hydrogen generation reactor Hydrogen is produced by the reversible water-gas shift reaction CO + H2O + CO2 + H2 which is carried out in an isothermal catalytic packed bed. The catalyst pellets are cylindrical and have a diameter and a height of 3.2 mm. The temperature in the reactor is 683 K and the total pressure is 1 atm. The reaction rate (based on catalyst pellet weight) is given by: r'= k'Cco (1 - B) where B = Cco2 CH2/(K Cco Ch2o), K is the equilibrium constant of the reaction, and k'is the first-order rate constant. The reactor inlet contains by volume 7% CO, 3% CO2, 20% H2, 20% N2, 50% H20. a) What is the equilibrium conversion at the reactor conditions? [4] b) Assuming no external mass transfer resistances and pressure drop, calculate the space time required to achieve 80% conversion of CO. [12] c) Plot the partial pressures of all the components as a function of space time [5] d) What is the effect of decreasing particle size on conversion? What would your recommendations be in terms of what pellet size to use? [4] State any assumptions you are making clearly. Additional Information for Question 2. Catalyst bed density: PB = 0.95 g cm3 Catalyst porosity and tortuosity: ε/t=0.25 Density of the catalyst pellet: pp= 1.55 g cm3
= Equilibrium constant of the reaction (where T is in Kelvin): K = e(4577.8/7–4.33) Molecular diffusion coefficient of CO: Dm= 1.27 cm? s-1 Knudsen diffusion coefficient of CO: Dk = 0.104 cm²/s cm2 s-1 Reaction rate constant: k' = 5.81 cm²/g s cm’g?s-1 =