home.gif The PRESSURE RECOVERY is defined as the pressure rise realized by secondary product gas relative to the pressure rise after total repressurization. By assuming adsorber vessels to contain only nonadsorb-
ents (zero capacity), all at the same temperature and only filled by a perfect gas and further neglecting adiabatic thermal effects on pressure changes, different PSA systems may be compared on an equal basis in terms of an APPARENT PRESSURE RECOVERY (APR), without having to resort to lengthy calculations.
      For instance, the APR-value for two adsorber vessels exchanging gas until pressure equilibration under above assumed conditions is 50 %, however if some external slip stream contributes in the pressure rise of the gas receiving adsorber, said equilibrium pressure will be higher, resulting into a lower APR-value, because less (secondary product) gas from the gas releasing adsorber will have contributed in the pressure rise of the gas receiving adsorber.

Below some examples of typical APR-values are given for a number of PSA adsorber configurations.

UNIT SIZE                 TYPE                          OPERATING OPTIONS       % APR-VALUE
4-BED
4-BED
4-BED
6-BED
6-BED
10-BED
10-BED
12-BED
12-BED		 CONVENTIONAL, DIRECT DUMP
CONVENTIONAL, TAILR(¹)
SORPTION MODULATION(¹)
CONVENTIONAL, DIRECT DUMP
SORPTION MODULATION
CONVENTIONAL, DIRECT DUMP
SORPTION MODULATION
CONVENTIONAL, DIRECT DUMP
SORPTION MODULATION 		/DD/NPE1/PAR0(/LO-FIN)(²)
/TAILR/NPE1/PAR0(/LO-FIN)(²)
/NPE1/PAR2/SM/SMEQ/LOFIN
/DD/NPE2/PAR2
/DD/NPE2/PAR2/SM/SMEQ
/DD/NPE3/PAR3
/DD/NPE3/PAR3/SM/SMEQ
/DD/NPE4/PAR4
/DD/NPE4/PAR4/SM/SMEQ		 42.8
48.9
61.5
64.3
72.7
71.4
78.3
77.8
82.1

(¹) Holding drum required for offgas continuity, other types
    require holding drum(s) mainly for offgas quality conditioning.

(²) LO-FIN is optional and has no effect on APR-value.