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Unformatted text preview: Chemical Engineering 142 Homework Set #8 300 points total (This set is treated as 3 separate sets) Due Wednesday March 31, 2010 Problem 1 (40 points) Consider the first-order, irreversible exothermic liquid-phase reaction This reaction is carried out in a steady-state jacketed CSTR. An equimolar mixture of species A and an inert I is fed to the reactor; the inlet molar flow rate of A is 80 mol min-1 . (a) What is the reactor temperature (T) for a feed temperature (T ) of 450 K? (b) Plot the reactor temperature as a function of the feed temperature. Hint: There are multiple steady states possible in this system, and you are requested to list them all in your answer (c) To what temperature must the inlet stream be preheated in order for the reactor to operate at a high (>99%) conversion? What are the corresponding temperature and conversion of A in the CSTR at this inlet temperature? (d) What is the maximum inlet temperature at which the conversion stays on the lower branch (i.e. the inlet extinction temperature for this system)? The following data may be useful C p,I = 30 cal mol-1 C-1 H rxn = -7500 cal mol-1 = 100 min C p,A = C p,B = 20 cal mol-1 C-1 UA = 8000 cal min-1 C-1 T a = 300 K E act = 40 kcal mol-1 k = 6.6 x 10-3 min-1 at 350 K Consider all heat capacities to be independent of temperature. Problem 2 (40 points) Consider the following reversible, elementary, gas phase reaction occurring in a packed bed reactor (2.5 kg catalyst) with pressure drop k = 0.004 L 2 gcat-1 mol-1 s-1 at 310 K K c = 1000 at 303 K This exothermic reaction ( = -20 kcal mol-1 ) is contacted with a coolant stream at a constant temperature of 325 K. The feed to the reactor is F A0 =F B0 =F I = 5 mol s-1 at 325 K, where F I is the molar flow rate of an inert gas whose function is to help dissipate the heat generated from the reaction. Treat all gases as ideal. You have also been supplied with the following information: C pA =C pB =C pC = 20 cal mol-1 K-1 C pI = 40 cal mol-1 K-1 P = 1000 kPa E act = 25 kcal mol-1 Ua/ B = 0.5 cal g-1 s-1 K-1 = 2 x 10-4 g-1 Obtain profiles for (i) the conversion of A, (ii) the equilibrium conversion, and (iii) the temperature of the reactor as a function of the catalyst mass....
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