31.8. A natural gas stream with a total volumetric flow rate of 880 standard cubic meters (SCM) per hour (std m3 /h), te
Posted: Fri Jul 08, 2022 6:08 am
31.8. A natural gas stream with a total volumetric flow rate of880 standard cubic meters (SCM) per hour (std m3 /h), temperatureof 40 degC and total system pressure of 405 kPa is contaminatedwith 1.0 %mol hydrogen sulfide (H2S). A packed-bed gas absorptiontower of 2.0m diameter is used to lower the H2S concentrations inthe natural gas down to 0.050 %mol so that the H2S will not poisona steam-reforming catalyst used to convert the natural gas tohydrogen gas. Since H2S is not very soluble in water, the agentmonoethanolamine (MEA, molecular weight 61 g/mol) is added to waterto increase the equilibrium solubility of the H2S in aqueoussolvent systems. In the present problem, an aqueous 15.3 wt% MEAsolvent containing no H2S at a total flow rate of 50 kmol/h isadded to the top of the tower to selectively remove the H2S fromthe natural gas stream.
a) From a process material balance, determine mole fractioncomposition of H2S in the liquid scrubbing solvent exiting thetower. xA1 = 0.0074
b) Using the equilibrium distribution data in the table providedbelow, provide a plot of yA vs. xA for the process, showing theequilibrium and operating lines. Equilibrium distribution data at40 degC for 15.3 wt% MEA in water (A = H2S)*:
pA (mmHg): 0.96, 3.0, 9.1, 43.1, 59.7, 106,143
kgH2S/100kg MEA: 0.125, 0.208, 0.306, 0.642, 0.729, 0.814,0.842
a) From a process material balance, determine mole fractioncomposition of H2S in the liquid scrubbing solvent exiting thetower. xA1 = 0.0074
b) Using the equilibrium distribution data in the table providedbelow, provide a plot of yA vs. xA for the process, showing theequilibrium and operating lines. Equilibrium distribution data at40 degC for 15.3 wt% MEA in water (A = H2S)*:
pA (mmHg): 0.96, 3.0, 9.1, 43.1, 59.7, 106,143
kgH2S/100kg MEA: 0.125, 0.208, 0.306, 0.642, 0.729, 0.814,0.842