Question

Problem 3 G1-1.665 kmol/h of a binary gas mixture containing ammonia (vi-35%, molar basis) and air enter an absorption column operating at 1 atm and 20 °C, where a liquid mixture of water and ammonia (x-2.11%, molar basis) is used to remove 90% of the ammonia from the gas stream. Equilibrium data for this system is given in the table below: (kg NH;) / (100 kg Partial pressure of NH H2O) Mole fraction of NHs in Mole fraction of NHs in liquid,x 0.02073 in gas phase, mmHg 12.0 gas, y 0.01578 0.04171 0.05027 31.7 0.09574 0.1371 0.09158 10 69.6 114 0.1500 15 0.2184 0.1748 166 20 0.2096 0.2411 0.2987 0.3921 227 298 25 30 For (Ls/Gc) -2.38, determine graphically the number of equilibrium stages required for this separation. Try to determine N from the Kremser equation (you would need first to fit the equilibrium line to a straight line, y -mx), and compare both results.

Answer 1

0.7 0.65 0.6 0.55 0.5 0.45 0.4 0.35 0.3 0.25 0.2 0.15 0.1 0.05 0.05 0.1 0.15 0.2 0.25 0.3 0

Y-y/(1-y) kgNH3/100kgH20 X-moles NH3/moles H20 y 0.020737327 0.01578 0.016033 0.050279330.04171 0.043525 0.095744681 0.09158 0.100812 10 0.15 0.176471 0.137055838 15 0.174757282 0.2184 0.279427 20 0.209302326 0.2987 0.425923 25 0.2410714290.3921 0.645007 30

Civen 108223)m and o 22 kndd gai phatK 30 1、982.2. O- O211

0.7 0.65 0.6 0.55 y2.0189x 0.5 0.45 0.4 Equilibrium curve 0.35 0.3 Operating line 0.25 Linear (Equilibr ium curve) 0.2 0.15 0.1 0.05 0.05 0.25 0.1 0.15 0.2 0.3

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