Gas stream purification method utilizing electrically driven oxygen ion transport
a technology of oxygen ion transport and gas stream, which is applied in the direction of liquefaction, separation process, lighting and heating apparatus, etc., and can solve the problems of voltage not being applied optimally, reducing oxygen separation, and increasing voltage without achieving oxygen separation
Inactive Publication Date: 2006-10-26
PRAXAIR TECH INC
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Benefits of technology
The present invention provides a method for purifying gas streams by removing oxygen from the gas stream using electrically driven oxygen separation zones. The method involves applying a voltage to the zones to separate the oxygen from the gas stream and produce a purified gas stream. The oxygen is separated from the gas stream at a successively lower partial pressure as the gas stream moves through the zones. The method optimizes the purification process by applying a voltage to each zone so that the oxygen ion current approaches a limiting oxygen ion current. The purification process can be used in the purification of crude argon and nitrogen streams. The invention also includes a method for vaporizing the crude liquid argon stream and liquefying the product stream using indirect heat exchange. The technical effects of the invention include improved purification efficiency, reduced power consumption, and improved process control.
Problems solved by technology
At the limiting oxygen ion current, a further increase in voltage fails to produce an increase in oxygen separation.
However, as the gas stream traverses the device, it becomes evermore dilute in oxygen.
Thus, a voltage is not optimally being applied because as the gas to be treated passes through the membrane, the partial pressure of the gas decreases and the same voltage is not necessary.
Method used
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[0029] With reference to FIG. 1 an electrically driven oxygen separation device 10 is illustrated that is designed to purify a gas stream 12 to produce a purified gas stream 14 through separation of oxygen from gas stream 12. The oxygen is separated within electrically driven oxygen separation zones 16, 18 and 20 that are defined by three cathode and anode assemblies having cathode and anode electrodes 22, 24; 26, 28 and 30, 32, respectively. Although not illustrated, but as would be known to those skilled in the art, the cathode and anode assemblies would also be provided with conventional current collectors. Said electrodes and current collectors are all porous and sandwich an electrolyte 34, which as will be discussed may have separate sections. The cathode and anode assemblies and electrolyte 34 are housed within a casing 35 to define passageways 36 and 37 on opposite sides of electrolyte 34. It is to be noted as used herein and in the claims, the term “cathode and anode assembl...
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A method of purifying a gas stream by removing oxygen from the gas stream in which the gas stream is introduced into a series of electrically driven oxygen separation zones that separate the oxygen from the gas stream. Each of the electrically driven oxygen separation zones has an electrolyte that conducts oxygen ions upon the application of the voltage to electrodes sandwiching the electrolyte. The voltage applied to each of the electrodes of the separation zones is selected such that an ionic current induced in the electrolyte within a particular zone that is no greater than a limiting current. When voltage is applied in such manner, the electrical power that is consumed is reduced over the power that would otherwise be consumed had a constant voltage been applied to all zones. The gas stream can be a crude argon stream obtained from a crude argon column or a crude nitrogen stream obtained from a pressure swing adsorption unit or a polymeric membrane unit.
Description
FIELD OF THE INVENTION [0001] The present invention relates to a method of purifying a gas stream in which the gas stream is introduced into a series of electrically driven oxygen separation zones having one or more oxygen ion conducting electrolytes to separate oxygen from the gas stream. More particularly, the present invention relates to such a purification method in which voltages are applied to each of the separation zones to induce an oxygen ion current that approaches a limiting value beyond which a further increase in voltage will not produce an increase in oxygen separation. BACKGROUND OF THE INVENTION [0002] Electrically driven oxygen transport membranes are utilized to purify feeds by separating oxygen. Such membranes employ an electrolyte which is normally an ionic conductor such as gadolinium doped ceria or yttrium stabilized zirconia. If the electrolyte is subjected to an elevated temperature and an electric potential is applied to electrodes sandwiching the electrolyt...
Claims
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IPC IPC(8): F25J3/00
CPCB01D53/226B01D53/32B01D2256/10F25J2230/58B01D2257/104F25J3/04733F25J2205/80B01D2256/18F25J3/00
InventorLANE, JONATHAN ANDREWBONAQUIST, DANTE PATRICKSHREIBER, ERICARMAN, BAYRAM
OwnerPRAXAIR TECH INC