Gas separation: processes – Solid sorption – Including reduction of pressure
Patent
1998-12-10
2000-05-30
Spitzer, Robert H.
Gas separation: processes
Solid sorption
Including reduction of pressure
95130, 96112, 96130, 96144, B01D 53047
Patent
active
060686790
DESCRIPTION:
BRIEF SUMMARY
TECHNICAL FIELD OF THE INVENTION AND PRIOR ART
The present invention relates to a process of separating a gas, containing at least one component, from a gas mixture. Moreover, the present invention relates to a device for separating a gas, containing at least one component, from a gas mixture.
It is known to produce gases, such as oxygen and nitrogen, by the separation of air. Furthermore, it is known to provide such a separation by means of a so called PSA-process (Pressure Swing Adsorption). A conventional PSA-process uses one or more adsorption beds containing an adsorbent provided in one or more layers. Typically, the adsorbent comprises molecular sieve particles having a size of 1-3 mm. Thus, such a PSA-process may produce oxygen by pressurising air through the adsorbing bed where nitrogen can be selectively adsorbed and being removed from the adsorbing bed by de-pressurization. There are several different processes based on this principle described in patents and literature. All these processes have the common feature that the adsorption part of the process cycle is performed at a higher pressure while the desorption (regeneration) part of the cycle is made at lower pressure.
Ideally, such a process should be run under an isothermal condition. However, in practice the temperature in the adsorption bed is not constant but varies both during the various steps of the cycle and from one point to another within the adsorption bed. Typically, the molecular sieve particles are heated during the adsorption phase, which influences the adsorption efficiency negatively, and cooled down during the desorption (regeneration), which influences the desorption efficiency negatively. Furthermore, it has been demonstrated by practical experiments on conventional processes that the adsorption bed develops a temperature gradient after some hours of operation. The gradient is such that the bed is colder in the feed end and warmer in the product end. Some 50.degree. C. temperature difference across the bed has been observed. The molecular sieve particles used for oxygen production have an optimum temperature where they give the best performance. The temperature gradient may lead to a non optimum performance of the process.
One such known conventional PSA-process for oxygen production features two adsorption vessels (A and B) and a full cycle involving the following steps disclosed in TABLE 1:
TABLE 1 __________________________________________________________________________
Step
Vessel A Vessel B
__________________________________________________________________________
1 Air feed to vessel inlet and oxygen
Regeneration by evacuation of waste
production via vessel outlet to
through the vesset inlet
receiver
2 Air feed to vessel inlet and oxygen
Regeneration by evacuation of waste
production via vessel outlet to
through the vessel inlet and oxygen
receiver and for purge to vessel B
purge via vesset outlet
3 Pressure equalisation. vessel A
Pressure equalisation, vessel B
gives oxygen via vessel outlet to
receives oxygen via vessel outlet from
vessel B vessel A
4 Regeneration by evacuation of
Air feed to vessel inlet and oxygen
waste through the vessel inlet
production via vessel outlet to receiver
5 Regeneration by evacuation of
Air feed to vessel inlet and oxygen
waste through the vessel inlet and
production via vessel outlet to receiver
oxygen purge via vessel outlet
and for purge to vessel A
6 Pressure equalisation. vessel A
Pressure equalisation. vessel B gives
receives oxygen via vessel outlet
oxygen via vessel outlet to vessel A
from vessel B
__________________________________________________________________________
SUMMARY OF THE INVENTION
The object of the present invention is to improve the efficiency of a process and a device for the separation of gases. More particular, the object is to prevent the development of a temperature gradient in the separation bed and thereby enable more appropriate conditions f
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AGA Aktiebolag
Spitzer Robert H.
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