TW200912229A - Process and apparatus for low-temperature air fractionation - Google Patents

Abstract

The process and the apparatus are used for low-temperature air fractionation. Input air (8) is cooled in a main heat exchanger (9) and introduced into a single column (12) for obtaining nitrogen (11, 43). A nitrogen product stream (15, 16, 17) is removed from the upper region of the single column (12). A first residual fraction (18, 29) is removed from the lower or central region of the single column (12), re-compressed (30) and then fed to the single column (12) again (32). An oxygen-containing stream (36) is removed from the single column (12) at an intermediate point and fed to a pure oxygen column (38) (39). A pure oxygen product stream (41) in the liquid state is removed from the lower region of the pure oxygen column (38). The pure oxygen product stream (41, 56) is evaporated and warmed with respect to input air (8) in the main heat exchanger (9) and finally obtained as a gaseous product (57).

Description

200912229 IX. Description of the invention: [Technical field to which the invention pertains] A method for fractional distillation of low temperature air is disclosed in the first item of the patent application. [Prior Art] This type of method is disclosed in European 807 792 B1, claim 1 1 /676, 77 3, in which, in addition to the material, pure oxygen can also be obtained as a product, and the process of extracting the liquid into a liquid state and removing the economic method from the method Only 1 to 2% of the relatively small amount of product is allowed to be obtained. Nitrogen is often used in the manufacture of conductors of such equipment; wherein the nitrogen removal is above the amount of the foregoing product. SUMMARY OF THE INVENTION Accordingly, the present invention is based on the related apparatus at the outset, which can generate a considerable amount of this purpose by evaporating and warming the pure oxygen product stream, input air, and finally, in principle, this step is It is called a double column. If you want to obtain a gaseous product under pressure, replace it with compression (external compression). However, the object of the present invention is different: it is used to recover the liquid liquefied cooling energy contained in the extracted liquid. This is because 'it has steamed the clause of the narrative character, and the United States and 20.02.2007 applied for a nitrogen product from a single-column procedure in which the oxygen product was produced from pure oxygen. However, this is essentially a very large amount of oxygen, which is about the number of air supplied to the electronics industry for the purpose of the semi-requisite and often required pure oxygen. The pure oxygen product is in it. This is achieved with respect to the gaseous product in the main heat exchanger. The internal compression of the law. Using this procedure as a gaseous product, the product is used herein to evaporate the main form of the pure oxygen product stream to the limit of the amount of oxygen product formed by the refrigeration performance of the equipment to 200912229. In the case of the present invention, the liquefied cooling energy that is withdrawn from the oxygen product in the conventional method is transferred to the input air or to the partial flow of the input air to the main heat exchanger, and thus can be utilized in the method ( Usually exchanging losses). The "main heat exchanger" is preferably formed from a single heat exchange block. In the case of larger equipment, it may be convenient for the process of temperature to be formed by a plurality of parallel connected streams and formed by separate components as the main heat exchanger. In principle, the main heat exchanger or each of these streams may be formed by two or more blocks connected in series. The term "evaporation" as used herein includes pseudo-evaporation at supercritical pressure. Thus, the pressure at which the pure oxygen product stream is introduced into the main heat exchanger can also be above the critical pressure, and the pressure of the heat exchange medium is equally likely to cause (pseudo) condensation of the pure oxygen product stream. If oxygen is required to be at a location under increased pressure, the increased pressure is above the operating pressure of the pure oxygen column, and it is advantageous if the liquid pure oxygen product stream is at an increased pressure. As a result, within the scope of the present invention, the warm oxygen compressor can be eliminated or at least designed to be relatively small. It is also advantageous if the recompression of the first residual fraction is carried out by means of a cold compressor. Here, the cold compressor refers to a compressor operated using an inlet temperature of less than 200 K, preferably less than 150 K, particularly preferably between 90 and 120 K. In a further refinement of the invention, the second residual fraction is removed from the lower region of the single column and depressurized in a pressure reducer to provide work, and the mechanical energy generated during the work of providing the work under reduced pressure is used, at least to some extent. To recompress the first residual fraction. The transfer of mechanical energy to the recompressor is preferably mechanically advanced into the line 200912229, such as via a common shaft of the pressure reducer and the recompressor. In particular, when the recompressor is constructed as a cold compressor, preferably, the mechanical energy generated by the pressure reducer is only partially transferred to the recompressor; the rest is passed to a warm brake device, such as a brake blower, starter or dissipator Brake. In a further refinement of the invention, the single column has a top condenser in which the vapor from the upper region of the single column is at least partially condensed, and before it is recompressed, the first residual fraction is at least partially in the top condenser Evaporation and/or at least partial evaporation in the overhead condenser before the second residual fraction provides a reduced pressure of work. At least some of the condensate obtained in the top condenser is discharged to a single column for reflux. If the two residual fractions have the same composition, they can be collectively directed through the top condenser. Preferably, however, they are introduced into separate channels of the top condenser, especially if they have different compositions. It is also advantageous if the second residual fraction is taken at the bottom of the single column. In principle, the first residual fraction can be introduced from the single column together with the second residual fraction, for example at the bottom (EP 4 1 2793 B2). However, in many cases, this is more convenient if the first residual fraction has a higher nitrogen content than the second residual fraction. Thus, the first residual fraction is withdrawn from the intermediate point of the mono-column, which is disposed at the bottom of the cartridge, particularly at the point where the second residual fraction is removed. The two residual fractions are then separately evaporated in a top condenser and fed separately to a recompressor for decompression to provide work. Further, according to the eighth aspect of the patent application, the present invention relates to a device for fractional distillation of low temperature air. [Embodiment] Further details of the invention and the invention will be explained in more detail below using the exemplary embodiments illustrated in the drawings. The atmospheric air 1 is taken in by the air compressor 3 via the filter 2 and compressed therein to an absolute pressure of 6 to 20 bar, preferably about 9 bar. After the flow, through the subcooler 4 and the water separator 5, the compressed air 6 is purified in a purification unit 7, which has a container filled with one of the adsorbent materials, preferably divided into uterine ridges. The purified air 8 is cooled in the main heat exchanger 9 to a dew point and partially liquefied. The first portion 1 of the cooling air 10 is introduced into the single column 12 via the throttle valve 51. The feed is preferably carried out to a lower number of practical or theoretical plates than at the bottom. The operating pressure (at the top) of the single column 12 is 6 to 20 bar, preferably about 9 bar. The top condenser was cooled using a first residual fraction 18 and a second residual fraction 14. The second residual fraction 14 is withdrawn from the bottom of the mono-column 12 and the first residual fraction 18 is withdrawn from some of the practical or theoretical plates above the intermediate point 'air feed (or at the same height as the latter). The gaseous nitrogen 15 5 is extracted from the top of the single column 1 2 as a main product, and they are warmed to the approximate ambient temperature in the main heat exchanger 9 and finally the gaseous pressurized product (PGAN) is passed through the line 1 7 lead. Portion 53 of condensate 52 from top condenser 13 can be obtained as liquid nitrogen product (PLIN); the remainder 54 is discharged to the top of the single column to reflux. The first residual fraction 18 is vaporized in a top condenser 13 at a pressure of 2 to 9 bar, preferably about 4 bar, and flows in a gaseous form via line 29 to the condenser 30, where it is again Compressed to approximately the operating pressure of a single column. -9- 200912229 The recompressed residual fraction 31 is again cooled in the main heat exchanger 9 to the column temperature and finally supplied via line 3 2 to the bottom of the single column 12. The second residual fraction 14 is vaporized in a top condenser 13 (preferably at about 4 bar) at a pressure of 2 to 9 bar and flows in a gaseous form via line 19 to the cold end of the main heat exchanger 9. From the latter, it is again removed from line 20 at an intermediate temperature and depressurized to about 300 mbar above atmospheric pressure to provide work in a pressure reducer 21, which in this example is formed into a turboexpander. The pressure reducer is mechanically coupled to the cold compressor 30 and the brake device 22, which in the illustrated example r'k is formed by an oil-filled brake. The reduced residual second residue fraction 23 is warmed in the main heat exchanger 9 to about ambient temperature. The warm second residual fraction 24 is blown into the atmosphere (line 25) and/or used as the regeneration gas 26, 27 in the purification unit 7, and if appropriate, then heated in the heating unit 28. The oxygen-containing stream 36 (which is free of low volatility contaminants on its body) is withdrawn from the intermediate point of the single column 12 in a liquid form, and this intermediate point is placed between 5 and 25 theoretical or practical plates above the air feed. If appropriate, the oxygen-containing stream 36 is supercooled in a bottom evaporator 37 of a pure oxygen column {.38 and discharged via line 39 and a throttle valve 40 to the top of the pure oxygen column 38. The operating pressure (at the top) of the pure oxygen column 38 is 1.3 to 4 bar, preferably about 2.5 bar. The bottom evaporator 37 of the pure oxygen column 38 is additionally cooled by the second portion 42 of the cooled input air 1〇. In this case, the input air stream 42 is at least partially condensed (e.g., completely condensed) and flows via line 43 to the single column 1 2 ' where it is introduced into the height of the feed substantially at the other input air 11 . From the bottom of the pure oxygen column 38, the pure oxygen product stream 41 is shifted in a liquid state - 10, 2009, 229. 'By pumping 55 liters to an increased pressure of 2 to 100 bar, preferably about 12 bar, leading to the main via line 56. The cold end of the heat exchanger 9, where it is vaporized under increased pressure and heated to approximately ambient temperature, is finally obtained as a gaseous product (GOX-IC) via line 57. The top gas 58 from the pure oxygen column 38 is mixed with the second residual fraction 23 under reduced pressure. If appropriate, a portion of the input air is directed to the inlet of the condenser 30 via the bypass line 59 in order to prevent the latter from pumping (anti-fluctuation control). If desired, liquid oxygen can be removed from the apparatus upstream and/or downstream of the pump 55 (not illustrated) as a liquid product. Alternatively, an external liquid from the liquid bath, such as liquid argon, liquid nitrogen or liquid oxygen, may be vaporized in the main heat exchanger 9 for indirect heat exchange with the input air (not illustrated in the drawings). BRIEF DESCRIPTION OF THE DRAWINGS Fig. 1 is a diagram showing an embodiment. [Explanation of component symbols] 8,11 Input air 9 Main heat exchanger 12 Single column 15,16 Gaseous nitrogen 18 First residual distillation 30 Cooling compressor 32 Line 36 Oxygen stream 38 Pure oxygen column -11- 200912229

4 1 14 2 1 13 1 2 3 4 5 6 7 8 10 11

40,5 1 PGAN 25,20,19,32,17,29,39,43,56,57 53 52

PLIN 54 3 1 22 23 pure oxygen product stream second residual fraction decompressor top condenser atmospheric air filter air compressor recooler water separator compressed air purification unit purification air cooling air cooling air first part throttle valve Condensate condensate of the gas pressurized product line section Liquid nitrogen product Remaining condensate Recompressed residual fraction Brake device decompressed second residual fraction -12- 200912229 24 26,27 28 37 42 55 58 59 Two residual fraction regeneration gas heating device bottom evaporator inlet air flow pump top gas bypass line

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Claims (1)

200912229 X. Patent application scope: 1. A method for fractional distillation of low temperature air, wherein one of the input air (8) is cooled in a main heat exchanger (9) and introduced into a single column (12) to obtain nitrogen (1,1). 4 3 ), - removing the nitrogen product stream (15, 16, 17) from the upper region of the single column (12), - taking the first residual fraction (18, 29) from the lower or central portion of the single column (12) The zone is removed, recompressed (30) and then fed from (32) to a single column f K ( 12) - an oxygen containing stream (3 6 ) is removed from the intermediate point of the single column (1 2 ) and fed to pure oxygen Column (38), (39) and - a liquid pure oxygen product stream (4 1 ) is removed from the lower region of the pure oxygen column (38) and is characterized by a stream of pure oxygen product (41, 56) In contrast to the main heat father (9), the input air (8) is used for evaporation and warming'. Finally, the gas product is obtained as a gas product (57) ° 2. The method of claim 1 wherein the liquid state is obtained The pure oxygen product stream (41) is subjected to an increased pressure (55). 3. The method of claim 1 or 2 wherein the recompression (30) of the first residual fraction (18, 29) is carried out by means of a condenser. 4. The method of any one of claims 1 to 3, wherein the second residual fraction (14, 19) is removed from the lower region of the single column (12) and is in a pressure reducer (2 1 ) The reduced pressure, providing work, will be used to recompress the first residual fraction, at least to some extent, during the work provided under reduced pressure. 5. The method of any one of claims 1 to 4 wherein the single column (12) has a top condenser (13) in which the vapor from the upper region of the single column is at least partially condensed, in which Before the compression (30), the first residual fraction (18) is at least partially evaporated in the overhead condenser and/or the second residual fraction (1 4) is obtained before the reduced pressure provides work (2 1 ). At least partially evaporated. 6. The method of any one of claims 1 to 5, wherein the second residual fraction (14) is taken at the bottom of the single column (12). 7. The method of any one of claims 1 to 6, wherein the first residual fraction (18) is taken from an intermediate point of the single column (12), the intermediate point being disposed above the bottom , particularly above the point at which the second residual fraction (1 4 ) is removed. 8. A cryogenic air fractionation apparatus having: - a main heat exchanger (9) for cooling input air (8), - equipment (11, 43) for introducing cooled input air into a single column (12) In order to obtain a nitrogen, nitrogen product line (1 5,1 6,1 7 ), which is connected to the upper part of the single column (1 2 ), the first residual fraction line (18, 29, 31, 32) Using the bottom portion of the single column (12), or the central zone, to remove the first residual fraction, which is then reconnected to the single column (12) by a recompressor (30), using equipment from a single column (12) The intermediate point is removed from the oxygen-containing stream (36, 39) -15- 200912229 and used to introduce it into the pure oxygen column (38), and has a pure oxygen product line (4 1 , 5 6 ) from the pure oxygen column ( The lower region of 3 8 ) removes the liquid pure oxygen product stream, characterized by = a pure oxygen product line (4 1,5 6 ) connected to the main heat exchanger (9), and - the device has a gas product line (57) used to remove the gaseous pure oxygen product from the autonomous heat exchanger (9). 9. Apparatus according to claim 8 wherein the means for increasing the pressure in the liquid state (5 5 ) is disposed in the pure oxygen product line (4 1,5 6 ). 10. The apparatus of claim 8 or 9, wherein the recompressor (30) is constructed as a cold compressor. -16-