Pressure Swing Adsorption
Pressure Swing Adsorption (PSA) units are commonly used to separate and purify a wide range of industrial gases. Typically for syngas streams, the PSA unit is used to produce a pure hydrogen stream which can then be used in a variety of downstream processes including hydrotreating and hydrocracking applications. The resulting hydrogen stream can achieve purities of 99.999% hydrogen.
The PSA unit utilizes a timed cycle of steps of adsorption, pressure equalization, depressurization, blowdown, purge, and repressurization across multiple beds loaded with various types of adsorbent (activated alumina, silica gel, activated carbon, mol sieves). When a bed is on-line, the syngas flows upward through the bed where at normal operating pressure components are physically adsorbed while the preferred hydrogen flows through the unit. The bed is taken out of service and goes through a series of depressurizations where the adsorbed components are released. The released components are an offgas that is then typically used as a fuel in SMR units. The bed is then repressurized and returned to service.