In a packed absorption column, hydrogen sulphide (H2S) is removed from natural gas by dissolution in an amine solvent. A

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In A Packed Absorption Column Hydrogen Sulphide H2s Is Removed From Natural Gas By Dissolution In An Amine Solvent A 1 (178.01 KiB) Viewed 58 times

In a packed absorption column, hydrogen sulphide (H2S) is removed from natural gas by dissolution in an amine solvent. At a given location in the packed column, the mole fraction of H2S in the bulk of the liquid is 5 x 10-3, the mole fraction of H2S in the bulk of the gas is 3 x 10-2, and the molar flux of H2S across the gas- liquid interface is 2 x 10-5 mol s1 m2. The system can be considered dilute and is well approximated by the equilibrium relationship, YA* = 5xA. a) Find the overall mass-transfer coefficients based on the gas-phase, Kga, and based on the liquid phase, KLA: [4 marks] b) It is also known that the ratio of the film mass-transfer coefficients is KLA = 4. KGA Determine the mole fractions of H2S at the interface, both in the liquid and in the gas. [8 marks] c) In another absorption column with a superior packing material there is a location with the same bulk mole fractions as stated above. The molar flux has a higher value of 3 x 10-5 mol s1 m2. The ratio of film mass-transfer coefficients remains, - = 4. The same equilibrium relationship also applies. Explain how KGA you would expect the overall mass-transfer coefficients and the interfacial mole fractions to compare to those calculated in parts a) and b). [4 marks] d) In the previous parts of this problem you have considered the thin-film model of diffusion across a gas-liquid interface. Explain what you would expect to be the ratio of the widths of the thin-films in the gas and liquid phases for this system if the diffusion coefficient is 105 times higher in the gas than in the liquid, but the overall molar concentration is 103 times higher in the liquid than in the gas.