Edmonton Refinery - Plant 55   Pressure Swing Adsorption Unit

The function of the pressure swing adsorption unit, PSA is to separate hydrogen from the mixture of hydrogen, nitrogen, methane, carbon dioxide, and carbon monoxide that is produced by reforming and shift reactions in the steam - methane reformer (Plant 53).  The hydrogen produced has a typical purity of 99.9% and the waste product, called tail gas, is used as the main source of fuel in the reforming furnace. The basic principle of operation is that at adorption pressure (approximately 320 psig) only hydrogen is allowed to pass freely through an adorption vessel from bottom to top and all impurities are trapped in the molecular sieve adsorbent.  At desorption pressure (less than 34 psig) the impurities are released and then purged out the bottom of the vessel with hydrogen product; this stream is called tail gas. Since the adsorption and desorption cycle is not steady state, there are ten adsorbers in the pressure swing adsorption unit and their state of pressure is controlled by a programmable logic controller called a Modicon.  When a vessel finished desorption is put online, the Modicon controls the length of time for adorption and switches to a new vessel before the impurities break through the top of the adsorbent.  To conserve hydrogen remaining in a vessel after the switch has occurred, the hydrogen is used to pressure up a vessel that has been cleaned and readied for a new adsorption cycle. General Information: Refinery Area:   Syncrude area, Block K Process Name:   Pressure swing adsorption unit Process Technology:   Union Carbide / UOP       Commissioned Date:   1983 Major Revamps:   PLC / PLCG Revamp (1994)       Nameplate Capacity:   31.4 MMSCFD of product hydrogen Major Feedstock(s):   hydrogen rich gas Major Product(s):   99.9 % pure hydrogen, tail gas Process Flow Diagram (PDF) Plot Plan (PDF) Equipment List [BACK TO OTHER UNITS]