Method for obtaining one or more air products, and air separation unit

Abstract

A method for obtaining one or more air products by means of an air separation unit comprising a first booster, a second booster, a first decompression machine, and a rectification column system which has a high-pressure column operated at a first pressure level and a low-pressure column operated at a second pressure level below the first pressure level. All of the air supplied to the rectification column system is first compressed to a third pressure level, which lies at least 3 bar above the first pressure level, as a feed air quantity. A first fraction of the feed air quantity is supplied to a first booster at the third pressure level and at a temperature level of 140 to 70 C. and is compressed to a fourth pressure level using the first booster.

Claims

1. A method for obtaining one or more air products in an air separation unit comprising a first booster, a second booster, a first decompression turbine, and a rectification column system which has a high-pressure column-operated at a first pressure level and a low-pressure column operated at a second pressure level below the first pressure level, said method comprising: supplying a feed air quantity to the air separation unit wherein the feed air quantity is at a third pressure level, which is at least 3 bar above the first pressure level, supplying a first fraction of the feed air quantity to the first booster at the third pressure level and at a temperature level of 140 to 70 C. and compressing the first fraction in the first booster to a fourth pressure level, supplying (a) a second fraction of the feed air quantity and/or (b) a first portion of the first fraction which has been compressed in the first booster to the fourth pressure level to the first decompression turbine, which is used to drive the first booster, and is decompressed in the first decompression turbine to the first pressure level, and supplying a further portion of the first fraction which has been compressed to the fourth pressure level in the first booster to the second booster and is compressed in the second booster to a fifth pressure level, and wherein the first fraction of the feed air quantity is at a temperature level of 120 to 60 C. at the outlet of the first booster, and wherein the further portion of the first fraction which is compressed to the fifth pressure level using the second booster is heated to a temperature level of 20 to 40 C. prior to being compressed in the second booster.

2. The method according to claim 1, further comprising supplying air at the third or at the fourth pressure level to a second decompression turbine, which is used to drive the second booster, and the air supplied to the second decompression turbine is decompressed to the second pressure level in the second decompression turbine, wherein the air supplied to the second decompression turbine is a fraction of the air compressed to the fourth pressure level in the first booster, or is a third fraction of the feed air quantity compressed to the third pressure level.

3. The method according to claim 1, wherein the first pressure level is 5 to 7 bar, the second pressure level is 1.2 to 1.9 bar, the third pressure level is 11 to 15 bar, the fourth pressure level is 18 to 25 bar, and the fifth pressure level is 30 to 40 bar absolute pressure.

4. The method according to claim 1, wherein the second fraction of the feed air quantity and/or the first fraction compressed to the fourth pressure level in the first booster is supplied to the first decompression turbine at a temperature level of 160 to 130 C.

5. The method according to claim 2, wherein the air supplied to the second decompression turbine is brought to a temperature level of 90 to 10 C. before being supplied to the second decompression turbine.

6. The method according to claim 1, wherein an additional portion of the first fraction compressed to the fourth pressure level in the first booster is cooled to a temperature level of 177 C. to 160 C. and then is partially or completely fed into the high-pressure column.

7. The method according to claim 1, wherein the second fraction of the feed air quantity which has been decompressed to the first pressure level in the first decompression turbine is partially liquefied by the decompression and, after a phase separation of the decompressed second fraction of the feed air quantity, a non-liquefied fraction of the decompressed second fraction of the feed air quantity is partially or completely fed into the high-pressure column, and a non-liquefied fraction of the decompressed second fraction of the feed air quantity is partially or completely fed into the low-pressure column.

8. The method according to claim 1, wherein the further portion of the first fraction that has been compressed to the fifth pressure level in the second booster is cooled to a temperature level of 177 C. to 160 C. and fed into the high-pressure column.

9. The method according to claim 2, wherein the air which has been decompressed to the second pressure level in the second decompression turbine is fed into the low-pressure column.

10. The method according to claim 2, wherein the air which has been decompressed to the second pressure level in the second decompression turbine is supplied at the second pressure level to a main heat exchanger of the air separation unit and cooled.

11. The method according to claim 1, wherein one or more liquid mass flows are extracted from the rectification column system, pressurized in the liquid state, thereafter evaporated or transformed into supercritical state, and discharged from the air separation unit as compressed products.

12. The method according to claim 1, wherein the first booster is operated at a step pressure ratio of 1.7 to 2.2, and the second booster is operated at a step pressure ratio of 1.4 to 1.8.

13. An air separation unit for obtaining one or more air products, comprising: a first booster, a second booster, a first decompression turbine, and a rectification column system which has a high-pressure column that is configured for operation at a first pressure level and a low-pressure column that is configured for operation at a second pressure level below the first pressure level, wherein the air separation unit is configured a line for supplying a feed air quantity at a third pressure level which is at least 3 bar above the first pressure level to the air separation unit, a line for supplying a first fraction of the feed air quantity at the third pressure level and at a temperature level of 140 to 70 C. to the first booster, wherein said first fraction is compressed to a fourth pressure level in the first booster, a line for supplying a second fraction of the feed air quantity or a line for supplying a first portion of the first fraction of the feed air quantity compressed to the fourth pressure level in the first booster to the first decompression turbine, which is used to drive the first booster, and to decompress said second fraction or first portion of the first fraction to the first pressure level using the first decompression turbine, a line for supplying a further portion of the first fraction of the feed air quantity compressed to the fourth pressure level to a second booster which is used to compress said further portion to a fifth pressure level, and wherein that the air separation plant further comprises a main heat exchanger which is configured to provide the first fraction of the feed air quantity to the first booster at a temperature level of 100 to 60 C., and wherein the main heat exchanger of the air separation unit is further configured to heat the further portion of the first feed air quantity to a temperature level of 20 to 40 C. prior to compression of the further portion in the second booster.

14. A method for obtaining one or more air products using the air separation unit according to claim 13, the method comprising: supplying the feed air quantity compressed to the third pressure level, which is at least 3 bar above the first pressure level, to the air separation unit supplying the first fraction of the feed air quantity to the first booster at the third pressure level and at the temperature level of 140 to 70 C., and compressing the first fraction to the fourth pressure level in the first booster, supplying either (a) the second fraction of the feed air quantity or (b) the first portion of the first fraction of the first feed air quantity compressed to the fourth pressure level in the first booster is supplied to the first decompression turbine, which is used to drive the first booster, and decompressing the second fraction or the first portion of the first fraction of the first feed air quantity to the first pressure level in the first decompression turbine, and supplying the further portion of the first fraction of the first feed air quantity compressed to the fourth pressure level in the first booster to the second booster and compressing the further portion to the fifth pressure level in the second booster, and wherein the first fraction of the feed air quantity is at the temperature level of 100 to 60 C. at the outlet of the first booster, wherein the further portion of the first fraction of the feed air quantity is heated to the temperature level of 20 to 40 C. prior to being compressed in the second booster, and wherein air at the third or at the fourth pressure level is supplied to a second decompression turbine, which is used to drive the second booster, and is decompressed to the second pressure level in the second decompression turbine, wherein the air supplied to the second decompression turbine is formed by an another portion of the first fraction of the feed air quantity compressed to the fourth pressure level in the first booster, or is formed by a third fraction of the feed air quantity at the third pressure level.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

(1) FIG. 1 shows an air separation unit according to an embodiment of the invention in a simplified schematic representation.

(2) FIG. 2 shows an air separation unit according to another embodiment of the invention in a schematic partial representation.

(3) FIG. 3 shows an air separation unit according to another embodiment of the invention in a schematic partial representation.

(4) FIG. 4 shows an air separation unit according to another embodiment of the invention in a schematic partial representation.

(5) FIG. 5 shows an air separation unit according to another embodiment of the invention in a schematic partial representation.

(6) In the figures, elements corresponding to one another are indicated by identical reference signs and are not explained repeatedly for the sake of clarity.

DETAILED DESCRIPTION OF THE DRAWINGS

(7) In FIG. 1, an air separation unit according to an embodiment of the invention is shown in a greatly simplified schematic representation and designated as a whole as 100. For a more detailed explanation of unit parts not shown in FIG. 1, reference is made to the technical literature, such as Hring (see above), for example.

(8) In the air separation unit 100, a compressed, purified, and pre-cooled feed air flow a is provided in what is known as a warm part 20 via devices not individually illustrated here. For example, in the warm part 20 for providing the feed air flow a, atmospheric air may be drawn in across a filter by means of a main air compressor, which in particular may be designed in multiple stages and to which one or more aftercoolers may be connected downstream, and be compressed to a pressure level referred to herein as third pressure level. The air may subsequently be cooled and in particular purified by means of adsorbers.

(9) The air separation method carried out in the air separation unit 100 is a high air pressure method explained above so that the third pressure level is at least 3 bar above a pressure level at which a high-pressure column 11 of a rectification column system 10 is operated and which is referred to herein as first pressure level. The rectification column system 10 furthermore comprises a low-pressure column 12 operated at a pressure level below the first pressure level, referred to herein as second pressure level.

(10) The rectification column system 10 moreover has a crude argon column 13 and a pure argon column 14, which are not explained in greater detail here for reasons of clarity. Reference is again made to the technical literature, in particular FIG. 2.3A in Hring (see above) and there also to pages 26 ff., Rectification in the Low-pressure, Crude and Pure Argon Column, as well as pages 29 ff., Cryogenic Production of Pure Argon.

(11) The total air quantity supplied to the rectification column system 10, which is compressed to the third pressure level, is referred to herein as feed air quantity. In the shown example, this feed air quantity is divided, upstream and inside a main heat exchanger 3 of the air separation unit 100, into a total of four mass flows b, c, d, e, wherein the mass flows b and c are initially supplied here to the main heat exchanger 3 in the form of a common mass flow, and the actual formation of the individual mass flows b and c takes place only via the extraction from the main heat exchanger 3 at different temperature levels.

(12) Here, the mass flows b and c are thus supplied jointly to the main heat exchanger 3 of the air separation unit 100 but are extracted therefrom at preferably different intermediate temperature levels. These temperature levels have already been explained above. The mass flow b is subsequently supplied to a further compression in a cold booster 1 (referred to herein as first booster) which is coupled to a (first) decompression turbine 1a. This further compression takes place at a pressure level that is referred to herein as fourth pressure level. The mass flow c is decompressed in the first decompression turbine 1a, and in fact in particular to the first pressure level of the high-pressure column 11. In the shown example, it is partially liquefied by the decompression in the decompression turbine 1a and is subsequently fed into a separator 4. A remaining gaseous fraction is fed in the form of a mass flow f into the high-pressure column 11. Liquid from the separator 4 is decompressed in the low-pressure column 12 in the form of a mass flow g (see connection point A).

(13) The mass flow b is supplied again to the main heat exchanger 3 at the fourth pressure level and warmed there to form a first fraction, and is subsequently supplied in the form of a mass flow h to a warm (second) booster 2 and further compressed there, and in fact to a pressure level which is also referred to herein as fifth pressure level. By contrast, a further fraction of the mass flow b is cooled in the main heat exchanger 3 and fed into the high-pressure column 11 in the form of a mass flow i which is combined with the mass flows d and h, which are likewise cooled in the main heat exchanger 3. The partial flow h is cooled in an aftercooler 5 before it is cooled in the main heat exchanger 3. The mass flows d, h, and i are respectively conducted through the main heat exchanger 3 to the cold end.

(14) The mass flow e is cooled down to an intermediate temperature level in the main heat exchanger 3 and is subsequently decompressed in a (second) decompression turbine 2a that is coupled to the second booster 2. This decompression takes place to the second pressure level. The mass flow e is fed (see connection point B) into the low-pressure column 12. The second decompression turbine 2a is therefore a typical Lachmann turbine.

(15) The air separation unit 100 is configured for internal compression. In the shown example, for this purpose, nitrogen-rich head gas is extracted from the high-pressure column 11, liquefied in a heat-exchanging manner in a main condenser (not separately designated) which connects the high-pressure column 11 and a low-pressure column 12, and supplied as a liquid in the form of a mass flow k to an internal compression pump 6. After the mass flow k in the internal compression pump 6 has been brought to a higher pressure level, for example to a supercritical pressure level, it is evaporated in the main heat exchanger 3 or transformed from the liquid state into the supercritical state. A corresponding nitrogen-rich air product may be output at the system boundary. A liquid, oxygen-rich air product may be withdrawn from the sump of the low-pressure column 12 in the form of a mass flow I, correspondingly pressurized in an internal compression pump 7, evaporated or transformed into the supercritical state in the main heat exchanger 3, and ultimately be output as an oxygen-rich air product at the system boundary.

(16) The additional mass flows that are shown in FIG. 1 and are in particular conducted through the main heat exchanger 3 may be learned from the cited technical literature. The air separation unit 100 inasmuch works as usual.

(17) Parts of air separation units according to further embodiments of the invention are shown schematically in greatly simplified form in FIGS. 2 to 5. Only the schematically represented warm part 20, the main heat exchanger 3, the first booster 1, the first decompression turbine 1a, the second booster 2, the second decompression turbine 2a, and the aftercooler 5 are respectively illustrated. The separator 4, the high-pressure column 11, and the low-pressure column 12 are indicated merely to illustrate the further treatment of the mass flows designated in FIG. 1.

(18) While the interconnection according to FIG. 2 essentially corresponds to that according to FIG. 1, and only the mass flows b and c are already formed upstream of the main heat exchanger 1, the interconnection according to FIG. 3 differs from those of FIGS. 1 and 2 essentially in that, instead of the mass flow e, a partial flow of the mass flow h is supplied to the second decompression turbine 2a here. This partial flow is designated as e in FIG. 3. The mass flow e is warmed before the decompression in the second decompression turbine 2a, whereas the mass flow e of the previously explained figures is correspondingly cooled.

(19) With respect to the treatment of the mass flow e, the interconnection according to FIG. 4 corresponds again to FIG. 2; however, in this regard, a flow routing according to FIG. 3 may also be provided. The mass flow e that is decompressed in the second decompression turbine 2a is here further cooled in the main heat exchanger 3, within the scope explained above, before it is supplied here to the low-pressure column 12.

(20) With respect to the treatment of the mass flow e, the interconnection according to FIG. 5 corresponds again to FIG. 3; however, in this regard, a flow routing according to FIG. 2 or 4 may also be provided. In a deviation from the previous embodiments, a sub-quantity of the first feed air quantity which has been compressed to the fourth pressure level using the first booster (1) is decompressed here in the first decompression turbine 1a.