Purification by Pressure Swing Adsorption

H. A. Stewart and J. L. Heck, Hydrogen Purification By Pressure Swing Adsorption, Union Carbide Corp., Linde Division, New York. 

Description The generic flowsheet consists of feed pre-treatment, prereforming (optional), steam-HC reforming, shift conversion and hydrogen purification by pressure swing adsorption (PSA). However, it is often tailored to satisfy specific requirements. 

Tondeur, D. and P. C. Wankat, Gas Purification by Pressure Swing Adsorption, Separation and Purification Methods, 14,157-212 (1985). 

MenU F, Lucat C, Debich A (1994) The thick-film route to selective gas sensors. Sens Actuators B 25 415- 20 Miller JB (2001) Catalytic sensors for monitoring explosive atmospheres. IEEE Sensors J l(l) 88-93 Park J-H, Yang RT (2005) Simple criterion for adsorbent selection for gas purification by pressure swing adsorption processes. Ind Eng Chem Res 44 1914-1921... 

Carbon Dioxide and Water Removal from Ethylene, 1076 Carbon Dioxide Removal from Cryogenic Plant Feed Gas, 1076 Removal of Sulfur Compounds, 1078 Hydrogen Purification by Pressure Swing Adsorption (PSA), 1081... 

Stewart, H. A., and Heck, J. L., 1967. Hydrogen Purification by Pressure Swing Adsorption. paper presented at the AIChE 64th National Meeting, New Orleans, LA, March 16-20. 

Recovery and Purification of Light Gases by Pressure Swing Adsorption... 

A cell model is presented for the description of the separation of two-component gas mixtures by pressure swing adsorption processes. Local equilibrium is assumed with linear, independent isotherms. The model is used to determine the light gas enrichment and recovery performance of a single-column recovery process and a two-column recovery and purification process. The results are discussed in general terms and with reference to the separation of helium and methane. 

Carbon monoxide is first stripped off particulate matter in a cyclone separator or in a scrubber. Scrubbing also removes tar or heavy hydrocarbon fractions. Acidic gases, if present, are removed by absorption in monoethanol amine or in potassium carbonate. This pretreated gas is sent to the next section for further purification. Commercial processes for final purification are based on the absorption of carbon monoxide by salt solution, low-temperature condensation, or fractionation, or by pressure-swing adsorption using a solid material. 

Malek, A. and Farooq, S. Hydrogen purification from refinery fuel gas by pressure swing adsorption. AIChE Journal, 1998, 44, 1985. 

The remaining gas is then subjected to CO shift conversion using steam to convert the CO to CO2 and hydrogen. Hydrogen purification to >99% can be effected by pressure swing adsorption (PSA) as shown in Figure 98, either with or without prior CO2 removal. An alternative scheme of CO2 removal followed by methanation produces a 98 % pure H2 product with < 10 ppm carbon oxides. 

A 2.0 0.5 27 >21 Drying and purification of air, oxygen production by pressure swing adsorption... 

Figure 4.1. A process for producing hydrogen by steam reforming of hydrocarbons (1) reforming furnace (2,3) purification section, (4) shift converter, (5) pressure swing adsorption.

The equations for a local equilibrium cell model of pressure swing adsorption processes with linear isotherms have been derived. These equations may be used to describe any PSA cycle composed of pressurization and blowdown steps and steps with flow at constant pressure. The use of the equations was illustrated by obtaining solutions for a single-column recovery process and a two-column recovery and purification process. The single-column process was superior in enrichment and recovery of the light component at large product cuts. The two-column process was superior at small cuts ... 

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