11-Lect-Pressure Drop in Reactors0

Stoichiometry liquid gas liquid gas flow ca fa gas

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Unformatted text preview: 1 2 −rA + = kPA / 3 PB2 / 3 = kRTC1 / 3CB / 3 A 3. Stoichiometry Flow Batch 3. Stoichiometry € € Liquid Gas Liquid Gas Flow CA = FA υ Gas υ = υ 0 (1 + εX ) P0T PT0 4. Combine dV=dV(X) dt=dt(X) (1 − X ) P CA€ CA 0 = (1 + εX ) P0 4. Combine ȹ b ȹ ȹ Θ B − X ȹ ȹ a Ⱥ P €C =C B A0 (1 + εX ) P0 5. Evaluate V=V(X) t=t(X) dW = € dW = FA 0 dX 2/3 Ⱥ ȹ b ȹ Ⱥ 1/ 3 ȹ Θ B − X ȹ Ⱥ Ⱥ Ⱥ − (1€ X ) P Ⱥ ȺC ȹ a Ⱥ P Ⱥ € kRTȺCA 0 Ⱥ (1 + εX ) P0 Ⱥ Ⱥ A 0 (1 + εX ) P0 Ⱥ Ⱥ Ⱥ Ⱥ Ⱥ Ⱥ 5. Evaluate FA 0 dX −r + €A dW = FA 0 dX 2 kRTC1 / 3CB / 3 A How does P vary along the reactor length? Pressure Drop in Reactors Chemical Reaction Engineering - Musgrave Lecture 11 - Page 4 € 2 A mass transport analysis of the pressure drop of a gas through a packed bed of particles results in P(z), for example, the Ergun eqn: Ⱥ dP G ȹ 1 − φ ȹȺ150(1 − φ )µ =− + 1.75GȺ ȹ 3 ȹȺ dz ρgc Dp ȹ φ ȺȺ Dp Ⱥ P = pressure, kPa φ = porosity gc = conversion factor (32.174 lbft/s) € Dp = particle diameter (ft) µ = gas viscosity (lb/ft h) z = length down the reactor ρ  = gas density (lb/ft3) dm 1 G = superficial mass velocity G = ρu = dt Ac € The gas (ideal) density ρ depends on T, P and the FT according to: ρ = ρ 0 PT0 FT 0 P0TFT So: Ⱥ P TF dP G ȹ 1 − φ ȹȺ150(1 − φ )µ =− + 1.75GȺ 0 T ȹ 3 ȹȺ dz ρ 0 gc Dp ȹ φ ȺȺ Dp Ⱥ PT0 FT 0 € € Which in compact form is: dP P TF = −β 0 0 T dz PT0 FT 0 β0 ≡ Ⱥ G ȹ 1 − φ ȹȺ150(1 − φ )µ + 1.75GȺ ȹ ȹȺ ρ 0 gc Dp ȹ φ 3 ȺȺ Dp Ⱥ Lecture 11 - Page 5 Pressure Drop in Reactors Chemical Reaction Engineering - Musgrave € € Our mole balance for a PBR is in terms of the weight of catalyst, not the length down the reactor. To change variables we use: Catalyst weight = catalyst density x volume W = (1 − φ ) Ac zρc So: FA0 FA dW = (1 − φ ) Ac ρ c dz dW = (1 − φ ) Ac ρ c dz So in terms of W we have: € € € dP P TF = −β 0 0 T dz PT0 FT 0 dP β0 P0TFT =− dW (1 − φ ) Ac ρc PT0 FT 0 And...
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This note was uploaded on 04/25/2010 for the course CHEN 4330 taught by Professor Staff during the Spring '08 term at Colorado.

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