MXPA97003268A - Method and separation apparatus of a - Google Patents

Abstract

The present invention relates to an air separation method comprising: cooling a stream of compressed and purified air at an appropriate temperature for rectification, rectifying the air stream to produce a vapor fraction containing thin oxygen in heavy components; an oxygen-rich stream composed of the vapor fraction containing oxygen in two subsidiary streams, and separately condensing the two subsidiary streams and separating the two subsidiary streams in a separating column of light components from the air stream so as to produce ultrahigh-purity liquid oxygen as oclumna waste within the separation column, one of the two subsidiary streams being condensed through indirect heat exchange with the column residues of the separation column, to thereby produce boiling within the separation column

Description

AIR SEPARATION METHOD AND APPARATUS BACKGROUND OF THE INVENTION The present invention relates to a method and apparatus for separating air in which the air is separated to produce a liquid oxygen product of ultra high purity. More particularly, the present invention relates to said method and apparatus in which the air is separated into a single column nitrogen generator. It will produce a vapor fraction containing thin oxygen in heavy components of the air which, after the liquefaction, is separated from the light components in a scrubbing column. Even more particularly, the present invention relates to said method and apparatus in which the oxygen-containing vapor fraction is divided into two subsidiary streams which are respectively liquefied in a continuous distillation column within the scrubbing column and in a top condenser of the single-row nitrogen generator. . It is well known in the art how to separate air to produce an oxygen rich fraction which is thin in heavy components such as carbon dioxide, water and hydrocarbons then purify a liquid stream, composed of the fraction Ri ca in oxigen, components lightweight such as nitrógneo, argon, neon, crypton and helium. For example, the Patent of E.U.A. No. 5,043,173 discloses a simple column nitrogen generator in which a liquid stream is withdrawn from the nitrogen generator at a location thereof in which the liquid stream is composed of oxygen-rich, thin liquid in the heavy components. The liquid stream is subsequently purified at the end of a scrubbing column by introducing the liquid towards the top of the column to produce a descending liquid phase that becomes increasingly concentrated in liquid oxygen and each more diluted in the liquid components. . The patent of E.U.A. No. 5,043,173 also describes a method for purifying a vapor stream containing oxygen removed from a high pressure column of a double column distillation unit. The vapor stream containing oxygen is subsequently liquefied in a heat transfer equipment of the separation column before being separated. In order to ex bring liquid from the separation column, liquid nitrogen must be added to the separation column. The problem in adding a liquid composed of nitrogen to a vapor stream containing liquefied oxygen 2s that the seperating column must be roughly sized to separate the resulting combined stream having a lower purity than a liquid-liquid stream composed of oxygen-rich liquid. . In addition, nitrogen production will suffer from a direct liquid nitrogen removal. As will be discussed, the present invention will provide a method and apparatus for separating air in which a vapor stream containing thin oxygen in heavy components is liquefied and separates into a separation column without addition of a stream of liquid nitrogen to reflux the separation column.

SUMMARY OF THE INVENTION The present invention provides a method of air separation in which a stream of compressed and purified air is cooled to an appropriate temperature for rectification. The air stream is then rectified to produce a steam fraction. that contains thin oxygen in heavy components An oxygen-containing stream, composed of the fraction of vapor that contains oxigen, is divided into two subsidiary currents that condense separately. The two subsidiary streams after the condensation are then separated in a separation column of light components present within the air stream so that ultra high purity liquid oxygen is produced as the bottom of the column inside the column. separation. One of the subsidiary streams is condensed through indirect heat exchange with the column bottom of the separation column, in this way to produce boiled inside the separation column. In another aspect, the present invention provides an air separation apparatus having an element for cooling a stream of compressed and purified air at an appropriate temperature for recirculation. An even element is provided to rectify the air stream to produce a fraction of va by containing thin oxygenate in heavy components. A separation column is provided with a heat transfer equipment in the lower region thereof to provide clearance within the separation column. The transfer transfer kit is connected to a rectification element so that one of the two subsidiary correctors composed of the vapor fraction containing oxygen condenses within the color transfer equipment. Also one element is connected to the rectification element to condense the other of the two subsidiary currents. The condensing element and the heat transfer equipment are connected to an upper region of the separation column so that the two subsidiary streams are separated within the separating column of light co-ordinates and ultra-pure liquid oxygen. produce as' column residues within the separation d column. As is clear from the foregoing description, the present invention has api icabiity to a single column nitrogen generator which is integrated with a ultra pure purity liquid oxygen column having heat transfer equipment. Since both liquid streams are condensed separately, the separation column needs only to be designed to separate the oxygen-rich fraction and a non-oxygen-rich fraction combined with the nitrogen. Ad plus, in the case of a nitrogen generator, the other subsidiary stream can be condensed within an upper capacitor used in connection therewith. ) This, from a later date, will reduce the production of nitrogen product. However, this digestion will be less than would be the case if the nitrogen had been removed because it is the refrigerant, usually liquid rich in oxygen, which is condensing this subsidiary current instead of the liquid. Therefore, the production of nitrogen does not suffer to the same extent as in the oxygen purification schemes of the prior art where it is desired to remove an oxygen-containing vapor fraction for further purification within a separation column. As used herein and in the claims, high purity nitrogen is nitrogen having an impurity content of less than about 100 parts by volume in oxygen. Liquid oxygen of ultra high purity is oxygen that has an impurity content of less than about 100 parts per billion (of impurities other than oxygen) in volume. Also, the term "fully heated" com is used herein and in the claims means slowed down to a hot end temperature of the main thermal exchange or complete thermal exchange. The term "fully cooled" as used herein means cooled to a cold end temperature of the main or complete thermal intermixing heat exchanger. The terms "partially heated" or "partially cooled" as used herein and in the claims mean heated or cooled to a temperature between the hot and cold ends of the main heat exchanger or complete main heat exchanger. Addition, the term "light components" as used in the patent and in the claims includes, but is not limited to, nitrogen, argon, neon, helium, and hydrogen and the term "heavy components" includes, but it is not limited to carbon dioxide, water, cripton and hydrocarbons.

BRIEF DESCRIPTION OF THE DRAWINGS Even though the specification with claims that distinctly note the subject matter that the Applicant considers to be his invention, it is agreed that the invention will be better understood when taken in connection with the accompanying drawing, in the that the only figure is a schematic view of an apparatus and method in accordance with the present invention.

DETAILED DESCRIPTION With reference to the Figure, there is illustrated an air separation plant 1 which is designed to separate towards a high purity nitrogen fraction and an ultra high purity oxygen liquid fraction. After having been compressed and processed in a manner well known in the art, it is cooled in a complete heat exchanger at an appropriate temperature for its rectification which would normally be or be near the dew point of the air. The air is then rectified within a single-column nitrogen generator 12 to a high-purity nitrogen-rich fraction as the tower's overhead product and a fraction of oxygen-enriched liquid as column waste. A vapor fraction containing oxig is not removed from the single column nitrogen generator 10 at a location thereof where said vapor fraction is thin in heavy components. After condensation, the vapor fractions are separated within a standing column 14 to produce the liquid oxygen product of ultra high purity. One point worth mentioning here is that the present invention is not limited to single column nitrogen generators and in fact, it has wider applicability to multi-column piñatas. Having generally described the operation of the apparatus 1, a more detailed description follows. A stream 16 of compressed and purified air which, as mentioned above, is cooled inside the heat exchanger complex 10, is formed by compressing the air, stirring the heat of compression and then purifying the air of heavier components such as carbon dioxide, moisture and hydrocarbons. It will be noted that even after said purification however, these heavy components will still exist within the stream 15 of compressed and purified air and will concentrate within liquid fractions produced from the rectification thereof. The stream 16 of compressed and purified air is then introduced into the single column nitrogen generator 12. The single column nitrogen generator 12 contains liquid-vapor contact elements such as trays, random or structured packing to rectify the air to richa fractions in high purity nitrogen and liquid enriched with oxygen. A stream 18 of nitrogen product is produced which is composed of the rich fraction of high purity nitrogen. A portion 20 of the nitrogen product stream 18 is condensed into an upper condenser 22 and then returned to the single column nitrogen generator 12 as a flow. In this regard, the upper capacitor 22 is a single-pass unit of plate-fin construction. The other part 24 of the nitrogen product stream 18 is heated completely inside the main heat exchanger complex 10 where it is expelled at ambient temperatures as a nitrogen product (PGN). It is supplied by cooling the upper condenser 22 through the removal of a stream 26 of liquid air and a stream 28 enriched with liquid oxygen. The liquid air stream 26 d and the oxigene enriched stream are expanded by valve within the valves 30 and 32, respectively, and vaporized within the upper condenser 22. The stream 26 of vaporized liquid air is recompressed within a recirculation compressor 34 at the operating pressure of the single column nitrogen generator 12 to produce a recirculation current 36., which after being partially cooled within the heat exchanger complex 10, is introduced into a lower region of the single-column nitrogen generator. In the illustrated embodiment, the recirculation stream 36 is not completely cooled so as to prevent liquefaction. The oxygen-rich liquid stream 28 having been vaporized is introduced into a turbo-expander 3 to produce a stream 40 of cooling. The cooling stream 40 can be combined with other waste streams and then completely heated within the main heat exchanger complex 10 as a waste stream 42. This heating decreases the enthalpy of the entered air in order to compensate for the irreversible changes such as heat leakage to the air separation plant 1. The recirculation coker 34 and the turboexpander 38 can be coupled by an energy release oil brake or a generator or released so that part of the energy of the expansion work can be recovered to activate the recirculation compressor 34. . It should be noted that the embodiments of the present invention are possible using a liquid stream having the same composition as the oxygen-rich liquid stream 28 as the sole refrigerant for the upper condenser 22 and which is then recirculated back to the column . However, the illustrated use of the vapourized liquid air stream 26 is particularly advantageous because it has a higher nitrogen content than the oxygen rich liquid stream 28. As such, it has a higher dew point pressure for the same temperature of the oxygen rich liquid. Therefore, the vaporized air supply pressure 26 of vaporized air to the compressor is higher and, thus, more flow can be compressed for the same amount of work. This increase in flow allows an increase in the heat pump action that accelerates the recovery on that which would have been obtained from having recirculated and returned to the column the liquid stream rich in oxygen. Additionally, the current stream composition 26 of vaporized liquid air is close to the equilibrium vapor composition in the column pump. This allows the bottom of the column to operate more reversibly than in the prior art. The vapro fraction containing thin oxygen in the heavy components is removed from the single-column nitrogen generator 12 as an oxygen-containing vapor stream 46 which is divided into two subsidiary streams 48 and 50. The subsidiary stream 48 is condensed by weighing through a heat transfer equipment 52 into a lower region 54 of the separation column 12. This provides a booster for the separation column 14. The resulting condensate is then reduced in pressure by the pressure reduction valve 56. The other of the two subsidiary streams is condensed within the upper condenser 22 and then reduced in pressure by a pressure reducing valve 58. The two subsidiary currents 48 and 50 are combined and then introduced to the separation column 14 to separate and thereby produce ultra-pure liquid oxygen as a stream of ultra-pure liquid oxygen product. Although the present invention has been described with reference to a preferred embodiment, numerous changes, additions and omissions can already be made to those experiments in the field without abandoning the spirit and scope of the present invention.

Claims (10)

CLAIMS:

1. - An air separation method comprising: cooling a stream of compressed and purified air at an appropriate temperature for rectification; rectifying the air stream to produce a fraction of vapor containing thin oxygen in heavy components; dividing a compound-rich oxygen stream from the fraction of vapor containing oxigene into two subsidiary streams; and separately condensing the two subsidiary streams and separating the two subsidiary streams in a separating column of light components from the air stream so as to produce ultrahigh-purity liquid oxygen as column heads within the separation column; one of the two subsidiary streams being condensed through indirect heat exchange with the waste column d of the separation column, so as to produce boiling within the separation column.

2. The air separation method of claim 1, wherein: the air stream is rectified within a single column nitrogen generator to produce a nitrogen product stream; an upper condenser connected to the single column nitrogen generator condenses part of the nitrogen product stream, in order to thereby produce reflux for the single column nitrogen condenser; a remaining part of the nitrogen product stream is completely heated; and the other of the two subsidiary streams condenses inside the thermal condenser.

3. The air separation method of claim 2, wherein: the refrigerant for the upper condenser is produced by extracting a liquid stream from the single-column nitrogen generator and valve expansion of the liquid stream. vaporizes inside the upper condensate; and the liquid stream after the vaporization is compressed at column pressure of the single column nitrogen generator, cooled to the appropriate temperature for rectification and recirculated to the column nitrogen generator.

4. The air separation method of claim 3, further comprising: supplying additional refrigerant to the upper condenser and removing a liquid stream rich in oxygen from a lower region of the single column nitrogen generator, and valve expander the oxygen rich liquid stream vaporizes the oxygen rich liquid stream within the upper condenser and partially heats the liquid stream rich in vaporized oxygen; turboexpander the oxygen-rich lithium current to produce a stream of refrigerant; and to fully heat the refrigerant stream through thermal exchange within the compressed and purified air stream, to thereby add cooling.

5. The rei indication method 4, where the upper tower part of the separation column is completely heated together with the refrigerant stream and the remaining part of the product nitrogen stream through the inter- Indirect thermal change with the compressed air stream and rif.

6. An air separation apparatus comprising: elements for cooling the stream of compressed and purified air to a temperature suitable for rectification; elements for rectifying the air stream to produce a fraction of vapor containing thin oxygen in heavy impurities; a separation column having heat transfer equipment in a lower region thereof to provide boiling within the separation column; the heat transfer equipment connected to the rectification element so that one of the two subsidiary streams composed of the fraction of vapor containing oxygen is condensed within the heat transfer equipment; elements also connected to the rectification element to condense the other of the two subsidiary streams; the condensing element and the heat transfer equipment connected to an upper region of the separation column so that the two subsidiary streams are released inside the separating column of thin impurities and ultra high purity liquid oxygen is produced from this way as column residues within the separation column.

7. The air separation apparatus of claim 6, wherein: the rectification element comprises a single column nitrogen generator for producing a nitrogen product stream; an upper condenser is connected to the single column generator, to condense part of the nitrogen product stream, in order to produce reflux for the single column nitrogen generator; the upper capacitor is configured to receive to condense the other of the two subsidiary currents and this one to act as the condensing element; the cooling element completely heats a remaining part of the nitrogen product stream.

8. The air-conditioning apparatus of claim 7, wherein: the upper condenser is also connected to the single-column nitrogen generator and is configured to receive a liquid stream thereof as refrigerant for the upper condenser, the liquid stream vaporizing in this way inside the upper condenser; an expansion valve is interposed between the upper condenser and the single column nitrogen generator to expand the liquid stream with valve; and a recirculation compressor is connected to the upper condenser to recompress the liquid stream after the column pressure vaporization of the simple column nitrogen generator; and the cooling element also cools the liquid stream after vaporization and recompression thereof at the appropriate temperature for rectification; and the single column nitrogen generator is connected to the cooling element so that the liquid stream after cooling is recirculated to the single column nitrogen generator.

9. The air separation method of claim 3, which also comrpenses: the upper condenser is also connected to the single column nitrogen generator and is configured to receive a liquid stream rich in oxygen from the generator. of simple column nitrogen as additional refrigerant to thereby vaporize the liquid stream rich in oxygen; another expansion valve is interposed between the upper condenser and the single column nitrogen generator to expand the oxygen-rich liquid stream by valve; the cooling element partially heating the liquid stream rich in vaporized oxygen; a turbo expander connected to the cooling element so that the liquid stream rich in oxygen is turbo-vented to produce a cooling current; and the cooling element by heating the refrigerant stream through indirect heat exchange within the compressed air stream and then adding cooling.

10. The apparatus of claim 9, wherein the cooling element completely kills the upper tower product of the separation column together with the cooling stream and the remaining part of the product nitrogen stream through exchange. indirect thermal with the flow of compressed and purified air.