Pressure-swing adsorption blowdown

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 ... 

Figure 18-11. Pressure swing adsorption (A) steps for single column in Skarstrom cycle, (B) use of two columns in parallel for continuous feed and product. Period of feed step = period of blowdown +...

Steps. A pressure-swing cycle has at least three steps adsorption, blowdown, and repressurization. Although not always necessary, a purge step is normally used. In finely tuned processes, cocurrent depressurization and pressure-equalization steps are frequendy added. 

Most of the flow directions in a pressure-swing process are fixed relative to one another. The most common configuration is for adsorption to take place upflow, thus the name blowdown for counteicunem depressurization. Therefore, some precautions must be taken to assure that no bed lifting or crashing occurs (see below). Pressure-swing stqis are more diflicuh to assess because many steps such as depressurization, blowdown, pressurization, and equalization b in at a high flow rale and decrease to low or no flow. 

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