The Prism gas permeation process developed by the Monsanto Company is highly selective for hydrogen when using hollow-fiber membranes of materials such as silicone-coated polysulphone. In a typical application, a gas at 16.7 WIPa and 40oC, containing the following components in kmol/h: 42.4 H2, 7.0 CH4, and 0.5 N2, is separated into a nonpermeate gas at 16.2MPa and a permeate gas at 4.56MPa.
(a) If the membrane is nonpermeable to nitrogen, the Prism membrane separation index, on a mole basis (SP) for hydrogen relative to methane is 33.13, and the split fraction (SF) for hydrogen to the permeate gas is 0.6038, calculate the kmol/h of each component and the total flow in kmol/h of both the nonpermeate gas and the permeate gas.
(b) Compute the percent purity of the hydrogen in the permeate gas.
(c) Using an average heat capacity ratio, γ, of 1.4. estimate the outlet temperatures of the two exiting gas streams by assuming the ideal gas law and reversible expansions for each gas and no heat transfer between the two exiting gas streams.
(d) Draw a process-flow diagram of the membrane process and indicate on the diagram for each stream the pressure, temperature, and component flow rates.