Argon recovery from silicon crystal furnace
AssigneeAir Products and Chemicals, Inc.
InventorsThomas Hsiao-Ling Hsiung, Zbigniew Tadeusz Fidkowski, Rakesh Agrawal
Life of this patent
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Abstract
The present invention is directed to two embodiments of a process for recycling an impure argon effluent from a silicon crystal growing furnace using cryogenics. The first embodiment uses cryogenic distillation techniques, and the second embodiment uses cryogenic adsorption, both of which use catalytic treatments and adsorption in conjunction with their cryogenic process steps to provide a pure argon recycle stream for a silicon crystal growth furnace.
Claims15
A process for the recovery and purification of impure argon containing residual dopants from a silicon crystal growth furnace using the steps of:
- (1) contacting the impure argon with a deoxygenation catalyst and hydrogen to remove any contained oxygen;
- (2) contacting the impure argon with a zeolitic adsorbent selective to the adsorption of water and carbon dioxide from the impure argon to remove any water and carbon dioxide from the impure argon;
- (3) further purifying the impure argon in a cryogenic temperature separation to remove remaining impurities from the impure argon and produce an argon product stream having a purity of at least 99.5% by volume;
- the improvement comprising removing dopants from the impure argon prior to step (1) by contact of the impure argon with a liquid absorbent to strip the dopants from the impure argon.
A process for the recovery and purification of impure argon containing residual dopants from a silicon crystal growth furnace using the steps of:
- (1) contacting the impure argon with a deoxygenation catalyst and hydrogen to remove any contained oxygen;
- (2) contacting the impure argon with a zeolitic adsorbent selective to the adsorption of water and carbon dioxide from the impure argon to remove any water and carbon dioxide from the impure argon;
- (3) introducing the impure argon into a cryogenic distillation column to separate nitrogen from the impure argon to produce an argon product stream having a purity of at least 99.5% by volume;
- and
- (4) recycling the argon product stream to the silicon crystal growth furnace;
- the improvement comprising removing the dopants from the impure argon prior to step (1) and performing step (3) in a cryogenic dual column distillation separation with a high pressure distillation column separation of nitrogen, hydrogen and carbon monoxide from the impure argon and a low pressure distillation column separation of hydrocarbons from the impure argon.
A process for the recovery and purification of impure argon containing residual dopants from a silicon crystal growth furnace using the steps of:
- (1) contacting the impure argon with a deoxygenation catalyst and hydrogen to remove any contained oxygen;
- (2) contacting the impure argon with a cupric oxide catalyst to convert carbon monoxide and hydrogen to water and carbon dioxide;
- (3) contacting the impure argon with a zeolitic adsorbent selective to the adsorption of water and carbon dioxide from the impure argon to remove any water and carbon dioxide from the impure argon;
- (4) contacting the impure argon at a cryogenic temperature with calcium X-zeolite adsorbent to remove nitrogen and hydrocarbons from the impure argon and produce an argon product stream having a purity of at least 99.5% by volume;
- and
- (5) recycling the argon product stream to the silicon crystal growth furnace;
- the improvement comprising removing the dopants from the impure argon prior to step (1) by contact of the impure argon with aqueous sodium hydroxide to strip the dopants from the impure argon.
Dependencies are inferred from the claim text.