Question

A gas absorption process is used to purify sour natural gas before being sold to user. In the current process, sour natural gas stream, G1, containing 15 mole% of carbon diaoxide (CO2) and the remaining methane (CH4) is fed to the bottom of the absorption column and leaves the top column as stream G2. The stream G1 is in contact with fresh amine solvent, stream L1, which is fed from the top of the column. The stream, L2, in which the solvent leaves the bottom of the column contains absorbed CO2. The molar ratio of L1/G1 is equal to 10 and the flow rate of L1 is 1000 kmol/min. The column has an efficiency of 98% with respect to CO2 removal. Assume that the absorption of CH4 to amine solvent is negligible and the evaporation of solvent in the column is also negligible.

a. Draw the flowchart of the process and perform the degree of freedom analysis for the process.

b. Calculate the flow rates of stream G1, G2 and L2.

c. Determine weather the quality of stream G2 meets the customer specification if CO2 in stream G2 is limited to maximum 200 ppm.

Answer 1

b. C a. 0% CH LI 드 1000 ABSDRBER 15% C02. 857. CH4 0% CHa Duee h Freedomn Annlyci () İİ) Component-bal

0 15 015Y 10o) (ax 62 015 X100 CH Content doesnt change. beau re C44, a G2-0.3 2 0.003542 84따 03 b = o-99646 0:3, 0.003542 mol 3542 ppm