Pressure swing adsorption hydrogen purification

Pressure-swing adsorption. Although adsorption is most often used as a purification process to remove small amounts of material, a number of applications involve separations of gas mixtures with moderate to high concentration of adsorbates. These are called bulk separations, and they often use different operating procedures than for gas purification. Pressure-swing adsorption (PSA) is a bulk separation process that is used for small-scale air separation plants and for concentration of hydrogen in process streams. 

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

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.

In most hydrogen plants, a pressure-swing adsorption (PSA) system is used for hydrogen purification. In these plants, a major portion of reformer fuel is PSA offgas with a hydrocarbon stream for makeup fuel. 

Cyclic adsorption processes such as parametric pumping, cycling zone adsorption and heatless adsorption have received much attention both theoretically and experimentally in the past several years (3j. Skarstrom (4J has reviewed applications of heatless adsorption (synonymous with pressure swing adsorption) to air drying, hydrogen purification and air fractionation. 

Pressure swing adsorption (PSA) processes are widely applied industrially for gas separations. Applications are numerous and include hydrogen and helium recovery and purification, air drying, the production of oxygen from air, and the separation of normal paraffins from isoparaffins. 

Pure Hydrogen Generation with Pressure Swing Adsorption (PSA) Purification... 

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. 

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

Table VII presents the estimated investments. The methanol case investment reflects the same gasifier type as used for the IBG and SNG cases. A conceptual Chem Systems methanol synthesis step is used. EPRI is sponsoring the development of the Chem Systems technology (5 ). The ammonia case investment reflects the same wood gasification concepts, employs pressure swing adsorption for hydrogen gas purification (based on information provided by the Linde Division, Union Carbide Corporation), and uses a conventional high-pressure ammonia synthesis loop.

When producing hydrogen as the final product, impurities such as CO, sulfur compounds, and other trace contaminants must be removed, particularly for application in fuel cells. Currently, pressure swing adsorption (PSA) is commonly used for the separation and purification of hydrogen from mixed gas streams. PSA systems are based on selective adsorbent beds. The gas mixture is introduced to the bed at an elevated pressure and the solid adsorbent selectively adsorbs certain components of the gas mixture, allowing the unadsorbed components, in this case hydrogen, to pass through the bed as purified gas. 

The process used for this project will be a SMR with a pressure swing adsorption (PSA) or membrane based purification system. The project does not include the hydrogen compression, storage or distribution system required for the high-pressure filling of FCVs. A process diagram of the system is shown in Figure 1. 

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