Chapter 6, Problem 6.79P

A two-unit process is used to separate H₂S from a gas containing 96% H₂ and 4% H₂S by volume. The H₂S is absorbed in a solvent, which is then regenerated by air in a stripping column. The Henry’s law constant for the absorption of H₂S in the solvent at 0°C is 22 atm/mole fraction.

1. Brie?y explain in your own words the functions of the three process units. Include in your explanation the purpose of the air in the stripper and the reason the stripper operates at a higher temperature than the absorber.
2. Calculate the molar ?ow rate of pure solvent and the volumetric ?ow rate of the gas at G₄, neglecting evaporation of solvent in both columns. (See ?owchart.)
Exploratory Exercise—Research and Discover (c) The objective of the process described above is to produce puri?ed hydrogen. However, in doing so the process also generates an effluent stream containing H ₂S. Identify at least three concerns with simply releasing this stream into the air. Suggest an add-on to the process that allays as many of these concerns as possible. Calculate the mass per 100 mol of G ₁ of any reactant required by the add-on. Identify any new concerns created by the add-on.