Project ForgeMass Transfer
Mass Transfer Operations
GATE 2012
Hard
If the flow rate of B (in the extraction problem above) is 2400 kg/h, then the theoretical number of stages in the column, using Kremser's equation (adjusted to the next integer) is
- A5
- 9
- C11
- D13
Explanation
Extraction (absorption) factor A=B/(m·A_flow)=2400/(2×800)=1.5. Kremser: N=ln{[(Y0−Y*)/(YN−Y*)](1−1/A)+1/A}/ln(A), with Y0=0.25, YN=0.0025, Y*=0. (Y0/YN)=100; (1−1/1.5)=0.3333; 100×0.3333+0.6667=34.0. N=ln(34.0)/ln(1.5)=3.526/0.4055≈8.7, rounded up to 9 stages.
Source: GATE CH 2012 (2012)
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