Cryogenic Distillation Method and System for Air Separation

Abstract

Methods and apparatus for air separation by cryogenic distillation in a double or triple air separation column. The column in the system with the highest operating pressure is said to be operating at medium pressure. All the air to be distilled is pressurized to a high pressure, which is about 5 bar greater than the medium pressure. The air is purified at this high pressure, and a portion of the purified air is cooled in a heat exchange line, while another portion is expanded in a turbine. Part of the cooled air is drawn from the exchange line with a cold booster, which is mechanically coupled to at least one turbine. An energy dissipation device is also provided which is coupled to the turbine not coupled to the cold booster. The energy dissipation device is either another booster, an oil break system, or an electrical generator.

1 . A method which may be used for the separation of air by cryogenic distillation in a system of columns, said method comprising:
 a) providing a system of columns comprising a double column or a triple column, wherein   said column operating at the highest pressure is operating at a pressure called medium pressure;   b) providing an exchange line;   c) taking all the air to be distilled to a high pressure, wherein said high pressure is at least about 5 bar greater than said medium pressure;   d) purifying said air at said high pressure;   e) cooling at least a portion of said purified air in said exchange line, and dividing said purified air into a first and a second fraction;   f) expanding said first and said second fractions in at least one turbine, wherein:   1) said turbine has an intake pressure which is at least 5 bar greater than said medium pressure; and   2) at least one said turbine has a delivery pressure substantially equal to said medium pressure;   g) sending at least a portion of air from said turbine to a medium pressure column in said system of columns;   h) drawing cooled air from said exchange line with a cold booster, wherein said cold booster is mechanically coupled to at least one said turbine;   i) reintroducing compressed air from said cold booster to said exchange line, wherein:
 1) said reintroduced air has temperature greater than an intake temperature of said cold booster; and 
 2) at least a portion of said reintroduced air condenses, or pseudo-condenses, in said exchange line; 
   j) vaporizing, or pseudo-vaporizing, at least one pressurized liquid from said columns, wherein said vaporizing, or pseudo-vaporizing, occurs in said exchange line at a vaporization temperature; and   k) providing an energy dissipation device, wherein:
 1) said energy dissipation device is provided to at least one turbine not coupled to said cold booster; and 
 2) said energy dissipation device comprises at least one member selected from the group consisting of:
 i) a mechanically coupled booster, followed by a cooler, wherein said mechanically coupled booster is not said cold booster; 
 ii) an oil break system; and 
 iii) an electrical generator. 
 
   
   
   
       2 . The method of  claim 1 , wherein said intake temperature of said cold booster is close to said liquid's vaporization, or pseudo-vaporization, temperature. 
   
   
       3 . The method of  claim 1 , wherein said air sent to said turbine is at said high pressure. 
   
   
       4 . The method of  claim 1 , wherein:
 a) said air sent to said at least one turbine has a pressure greater than said high pressure; and   b) said air sent to said at least one turbine is from either said cold booster or said dissipation device.   
   
   
       5 . The method of  claim 4 , wherein:
 a) all said air sent to said at least one turbine comes from said dissipation device; and   b) said air boosted in said cold booster continues to be cooled in said exchange line, and is then expanded, liquefied, and sent to said system of columns.   
   
   
       6 . An apparatus which may be used for air separation by cryogenic distillation, said apparatus comprising:
 a) at least one double or triple air separation column, wherein said column operating at the highest pressure is operating at a pressure called medium pressure;   b) at least one exchange line;   c) at least one pressurizing means which pressurizes all the air to be distilled to a high pressure;   d) at least one purifying means which purifies said air at said high pressure;   e) at least one cooling means which sends a portion of said purified air to said exchange line in order to cool said portion of purified air;   f) at least one dividing means which divides said cooled air into at least two fractions;   g) at least two turbines, wherein each said turbine comprises an inlet means which directs at least one said fraction to each said turbine;   h) at least one medium pressure column inlet means which sends at least one expanded portion of air from said turbine to a medium pressure column of said double or triple column;   i) at least one cold booster, wherein said cold booster is coupled to said turbine, and said cold booster comprises:
 1) a cold booster inlet means which sends air from a first intermediate point on said exchange line to said cold booster; and 
 2) a cold booster outlet means which sends air from said cold booster back to a point upstream of said first intermediate point; 
   j) at least one pressurizing means which pressurizes at least one liquid from said columns;   k) at least one liquid injection means which injects said pressurized liquid into said exchange line;   l) at least one vaporized liquid withdraw means which extracts vaporized liquid from said exchange line; and   m) at least one energy dissipation device, wherein:
 1) said energy dissipation device is coupled to said turbine not coupled to said cold booster; and 
 2) said energy dissipation device comprises at least one member selected from the group consisting of:
 i) a mechanically coupled booster, followed by a cooler, wherein said mechanically coupled booster is not said cold 
 
 booster;
 ii) an oil break system; and 
 iii) an electrical generator. 
 
   
   
   
       7 . The apparatus of  claim 6 , further comprising an energy dissipation device injection means which sends at least one portion of air into said energy dissipation device.