Homework10+rev1 - Chemical Engineering 142 Homework Set #10...

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Chemical Engineering 142 Homework Set #10 100 points total Due Wednesday April 14, 2010 Problem 1 (25 points) Consider the case of oxygen diffusion through a porous matrix to react with a core of carbon (shrinking core with porous matrix problem) that is described in page 794 of Fogler. Instead of complete combustion, the reaction that is now occurring is: C (s) + (1/2)O 2(g) b CO (g) Assume the concentration of O 2 in the gas, C A0, is sufficiently low that dilute mixture approximations can be used to describe the diffusion. a) For an effective diffusivity that is now changing with radial position, we have: D e = (r/R o )D o For this case, find the time necessary for the solid carbon interface to recede inward to a radius R. b) What time is necessary for complete regeneration of the catalyst (all C removed) if R o = 1 cm? c) What initial particle diameter is necessary if we wanted to regenerate the catalyst in 3 s? Additional information: C A0 = 0.0015 mol/cm 3 Volume fraction of C: 0.06 D o = 0.05 cm 2 /s ρ c = 0.2 mol/cm 3 Problem 2 (25 points)
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Homework10+rev1 - Chemical Engineering 142 Homework Set #10...

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