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By Final Year Chem. Engg. (Roll no:11-20) U.I.C.T,Mumbai-400019

Packed Column Extractor. By Final Year Chem. Engg. (Roll no:11-20) U.I.C.T,Mumbai-400019. An Overview. Same packing as used in G-L operations Advantage of using Packings Material of Packing to be used. Tower design. The Problem statement : Flow rate of organic stream= 1m 3 /hr

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By Final Year Chem. Engg. (Roll no:11-20) U.I.C.T,Mumbai-400019

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  1. Packed Column Extractor By Final Year Chem. Engg. (Roll no:11-20) U.I.C.T,Mumbai-400019

  2. An Overview • Same packing as used in G-L operations • Advantage of using Packings • Material of Packing to be used

  3. Tower design • The Problem statement: Flow rate of organic stream= 1m3/hr Impurity in inlet organic stream=10000ppm Desired impurity in exit stream=500ppm

  4. Approach • We assume that the dispersed and the continuous phases are in plug flow • We find the minimum value of Ud/Uc • Then we assume different values for Ud/Uc • Calculate hold up at flooding using • εf={[(Ud/Uc)2+8 (Ud/Uc)]0.5-3(Ud/Uc)}/[4*(1- Ud/Uc)] • Assume a certain percentage of flooding hold up as operating hold up and hence calculate ε • We find the terminal velocity of a drop using • eUo=C(a*ρc/(e3*g*Δ ρ)) (-0.5) formula given in the book by Degallson and Laddha where C=0.637 • Then we calculate Ud using the correlation for slip velocity

  5. Find diameter of the column: • D=((Qc/Uc)*(4/3.142))0.5 • Drop diameter is found using • d=1.6(γ/(ρc-ρd)g) 0.5 • Size of Raschig rings were taken as 1”,0.75” and 0.5”. • Overall Height of transfer unit: Koc.a=0.06* φ*(1- φ)/[(a*ρc/(g*e 3 *Δρ))0.5*(γ/(Δρ*g)) 0.5 *{(Sc)c 0.5 +(Sc)d 0.5 /m}] (This corellation is for packing size greater than drop size)

  6. [HTU oc]plug flow = Uc/Koc.a • [NTU oc]plug flow=(Cc1-Cc2)/(ΔC)LM • Height of column: Zt=[HTU oc]plug flow * [NTU oc]plug flow • Distributor design: We take nozzle velocity = 0.5*eUo Nozzle diameter value should be comparable with droplet diameter value. Hence, we take nozzle diameter= 6 mm. No of orifices = Qd/( Area of nozzle*Vn)

  7. Sample Calculations • Overall mass balance • Qo*ρo*(10,000-500)=Qa*ρa*(50,000-0) • 1*900*9500= Qa*1000*50000 • Thus Qa= .9*9500/50000 = 0.171 • Thus, the flow rate ratio (aq:org) or velocity ratio should be > 0.171

  8. Sample calculations- continued • Consider Raschig ring packings of size 1”. • Let the operating holdup=60% of holdup at flooding. • Let Ud/Uc=1.1. • εf = 0.3403 • Operating holdup = 0.2042 • Terminal velocity = 0.03191 m/s • By slip velocity relation, Ud= 0.00385 m/s • Uc= 0.0035 m/s • Column diameter: 0.318m • Drop diameter: 8 mm • Koc.a= 12.407 • HTU=3.327 ft=1.01m • NTU=3.429 • Column height=11.41 ft = 3.477 m • No of orifices for the distributor (orifice diameter=6 mm)= 70(approx)

  9. Observations • With increase in Ud/Uc, height of column decreases, diameter increases. • The diameter of the column increases when packings of smaller nominal diameter are used. • With increase in %flooding the total height of the column decreases.

  10. Thank You

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