Hydrogen recovery by pressure swing adsorption

Pressure swing adsorption (PSA) on zeolite molecular sieves (see Section 4.3.2.6) may be also used for hydrogen recovery from purge gas [761]. The process, originally developed by Union Carbide under the name HYSIV, is now marketed as Polybed PSA by UOP [970], [973], [974], PSA technology is also offered by Linde and other companies. If required, the process also offers the possibility to supply pure hydrogen from 

Hydrogen Recovery with Mixed Metal Hydrides  

A proprietary hydrogen separation process utilizing the reversible and selective adsorption capability of mixed metal hydrides has been proposed. The hydride, forming compounds, such as LaNi5, FeTi, or Mg2Cu, are in the form of ballasted pellets. 

The ballast material serves as a heat sink to store the heat of adsorption. Subsequently, this is used to supply the heat of desorption. The ballast also is the binder for the pellets, preventing attrition. Each type of metal hydride is susceptible to certain contaminants. Therefore, selection of the metal hydride must be based on the analysis of the gas to be treated. No ammonia removal step is required upstream of the unit. 

The system yields 99 mol % hydrogen product at a recovery efficiency of 90-93% 

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Hydrogen recovery by pressure swing adsorption from the synthesis loop of an ammonia synthesis process. (Union Carbide Corp.). US 4077780 (1976). 

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