METHOD FOR THE CRYOGENIC SEPARATION OF AIR, AND AIR SEPARATION PLANT

Abstract

The invention relates to an air separation plant for cryogenic separation, said plant being designed to carry out a high-air-pressure process, wherein nitrogen is removed from the pressure column, expanded in a turbine that is coupled to a cold booster, and heated. Separately from the nitrogen which is removed from the pressure column, nitrogen is removed from the low-pressure column and heated to the same temperature. Before expansion in the turbine that is coupled to the cold booster, the nitrogen removed from the pressure column is heated to a temperature in a temperature range of 100 to 50 C. During expansion, the nitrogen cools down to a temperature in a temperature range of 150 to 40 C. and is then heated again. The invention also relates to a corresponding air separation plant.

Claims

1. A method for the cryogenic separation of air using an air separation plant comprising a rectification column arrangement with a pressure column and a low-pressure column, wherein the pressure column is operated in a first pressure range and the low-pressure column is operated in a second pressure range, which is below the first pressure range, and at least 90% of a total quantity of air separated in the rectification column arrangement is compressed to a pressure in a third pressure range that is more than 4 bar above the first pressure range, a partial quantity of the total separated air quantity is successively supplied to a first booster driven by a first turbine at a temperature in a first temperature range of 30 to 100 C., compressed using the first booster from the pressure in the third pressure range to a pressure in a fourth pressure range, which is above the third pressure range, cooled to a temperature in a second temperature range of 160 to 60 C., supplied at the temperature in the second temperature range to a second booster driven by a second turbine, compressed using the second booster from the pressure in the fourth pressure range to a pressure in a fifth pressure range, which is above the fourth pressure range, cooled to a temperature in a third temperature range of 200 to 150 C., and fed into the pressure column, gaseous nitrogen is removed from the pressure column at a pressure in the first pressure range and successively heated to a temperature in a fourth temperature range, expanded in the second turbine while cooling to a temperature in a fifth temperature range to a pressure in the second pressure range, and heated to a temperature in a sixth temperature range from 0 to 50 C., and gaseous nitrogen is removed from the low-pressure column and heated to the temperature in the sixth temperature range, wherein the gaseous nitrogen removed from the low-pressure column is heated separately from the gaseous nitrogen removed from the pressure column to the temperature in the sixth temperature range, and the fourth temperature range is from 100 to 50 C. and the fifth temperature range is from 150 to 40 C.

2. The method according to claim 1, with which the first pressure range is 4 to 7 bar, the second pressure range is 1 to 2 bar, the third pressure range is 10 to 18 bar, the fourth pressure range is in a pressure range of 1.2 times to 1.5 times the third pressure range and the fifth pressure range is in a pressure range of 1.6 times to 2.5 times the fourth pressure range.

3. The method according to claim 1, with which a further partial quantity of the total separated air quantity is successively supplied to the first booster at the temperature in the first temperature range, compressed using the first booster from the pressure in the third pressure range to the pressure in the fourth pressure range, cooled to the temperature in the second temperature range or a further temperature range, expanded in the first turbine to a pressure in the first pressure range and fed into the pressure column.

4. The method according to claim 1, with which a further partial quantity of the total separated air quantity at the pressure in the third pressure range is cooled to the temperature in the third temperature range and fed into the pressure column.

5. The method according to claim 1, with which the gaseous nitrogen removed from the low-pressure column and the gaseous nitrogen removed from the pressure column are combined at the temperature in the sixth temperature range after separate heating to the temperature in the sixth temperature range.

6. The method according to claim 1, with which one or more liquids are removed from the rectification column arrangement, subjected to one or each internal compression, and discharged from the air separation plant in the form of one or more gaseous internal compression products.

7. The method according to claim 6, with which the one or more gaseous internal compression products is or comprises a gaseous internal compression product produced using oxygen-rich liquid from the low-pressure column.

8. The method according to claim 6, with which no liquid products are removed from the air separation plant or with which one or more liquid products are removed from the air separation plant in a total amount that does not exceed 10% of a total amount of the one or more gaseous internal compression products.

9. The method according to claim 1, with which an argon-rich liquid is removed from the low-pressure column and supplied to an argon recovery system for the recovery of argon.

10. The method according to claim 1, with which gaseous nitrogen is removed from the pressure column, heated to a temperature in the sixth temperature range and recovered at a pressure in the first pressure range as nitrogen-rich air product.

11. An air separation plant for the cryogenic separation of air, which has a rectification column arrangement with a pressure column and a low-pressure column, wherein the air separation plant is designed to operate the pressure column in a first pressure range and the low-pressure column in a second pressure range that is below the first pressure range, and to compress at least 90% of a total quantity of air separated in the rectification column arrangement to a pressure in a third pressure range, which is more than 5 bar above the first pressure range, to supply a partial quantity of the total quantity of separated air successively at a temperature in a first temperature range of 30 to 100 C. to a first booster driven by a first turbine, using the first booster to compress it from the pressure in the third pressure range to a pressure in a fourth pressure range, which is above the third pressure range, to cool it to a temperature in a second temperature range of 160 to 60 C., to supply it at the temperature in the second temperature range to a second booster driven by a second turbine, using the second booster to compress it from the pressure in the fourth pressure range to a pressure in a fifth pressure range. which is above the fourth pressure range, to cool it to a temperature in a third temperature range of 200 to 150 C., and to feed it into the pressure column, to remove gaseous nitrogen from the pressure column at a pressure in the first pressure range and to heat it successively to a temperature in a fourth temperature range, to expand it in the second turbine while cooling it to a temperature in a fifth temperature range to a pressure in the second pressure range, and to heat it to a temperature in a sixth temperature range of 0 to 50 C., and to remove gaseous nitrogen from the low-pressure column and heat it to the temperature in the sixth temperature range, wherein the air separation plant is designed heating the gaseous nitrogen removed from the low-pressure column separately from the gaseous nitrogen removed from the pressure column to the temperature in the sixth temperature range, wherein the fourth temperature range is from 100 to 50 C. and the fifth temperature range is from 150 to 40 C.

Description

DESCRIPTION OF THE FIGURES

[0060] FIG. 1 illustrates an air separation plant according to an advantageous embodiment of the present invention.

[0061] In the figure, elements that correspond to one another structurally or functionally are denoted by identical reference signs and, for the sake of clarity, are not repeatedly explained. Explanations relating to plants and plant components apply in the same way for corresponding methods and method steps.

[0062] In FIG. 1, an air separation plant according to an embodiment of the present invention is illustrated in the form of a simplified process flow diagram and is designated as a whole by 100.

[0063] In the air separation plant 100, air is drawn in by means of a main air compressor 2 via a filter 1 and compressed to a suitable pressure level. After pre-cooling in a pre-cooling device 3, the compressed air flow A formed in this way is freed of residual water and carbon dioxide in a pre-cleaning unit 4, which can be designed in a manner known per se. For the design of the mentioned components, reference is made to the technical literature cited at the outset.

[0064] In the example illustrated here, the compressed air flow further designated as A is now divided into two partial flows B and C, of which the partial flow B is guided as a Joule-Thomson flow from the hot to the cold end through a main heat exchanger 4 and fed into the pressure column 11 of a rectification column arrangement 10. The partial flow C is first boosted in a hot booster 6 (previously described as the first booster), to which it is supplied at a temperature in a corresponding temperature range (previously the first temperature range), and then cooled in the main heat exchanger 4. In the embodiment shown in FIG. 1, partial flows D and E are formed after removal from the main heat exchanger 4 at a temperature in a corresponding temperature range (previously the second temperature range). However, a removal from the main heat exchanger 4 at different temperatures can also be effected

[0065] The partial flow D is now further increased in pressure in a cold booster (previously the second booster), then cooled in the main heat exchanger 4 to a temperature in a cold-side temperature range (previously the third temperature range) and fed into the pressure column 11 as a high-pressure Joule-Thomson flow. The partial flow E is expanded in the turbine coupled to the first booster 6 (previously the first turbine) and also fed into the pressure column 11. A partial flow F of the partial flow C is also fed into the pressure column 11 (as a further Joule-Thomson flow).

[0066] Nitrogen is withdrawn from the pressure column 11 in the form of a material flow G, heated in the main heat exchanger 4 to a temperature in a suitable or advantageous temperature range (previously the fourth temperature range), expanded in the turbine coupled to the second booster 8 (previously the second turbine) while cooling to a temperature in a corresponding temperature range (previously the fifth temperature range), and then heating it again in the main heat exchanger 4 to a temperature in a temperature range on the hot side of the main heat exchanger 4 (previously the sixth temperature range).

[0067] Gaseous nitrogen in the form of a material flow H is removed from the low-pressure column 12 and heated to the temperature in the sixth temperature range. After heating, it is combined with the material flow H to form a corresponding collective flow I.

[0068] In the rectification column arrangement 10, the pressure column 11 is connected to the low-pressure column 12 via a main condenser 13 for heat exchange. A subcooling counterflow device 14 is assigned to the rectification column system 10. An internal compression pump is designated by 15. The air separation plant 100 can have an argon recovery unit of a known type (not shown here).

[0069] As explained, the pressure column 11 is fed with cooled, pressurized and, if necessary, liquefied air from material flows B, D, E and F. Immediately downstream of the feed-in point of the material flow F, liquid in the form of a material flow K is withdrawn from the pressure column 11, guided through the subcooling counterflow device 14 and fed into the low-pressure column 12. The low-pressure column 12 is also fed with oxygen-enriched liquid in the form of a sump liquid flow L from the pressure column 11, which is likewise previously guided through the subcooling counterflow device 14. Further top gas from the pressure column 11 is guided through the main condenser 13. The main condenser 13 is operated in a known manner, wherein in particular a material flow M is also transferred to the low-pressure column 12. Impure nitrogen can be withdrawn from the low-pressure column 12 in the form of a material flow h, pure low-pressure nitrogen in the form of a material flow g.

[0070] Oxygen-rich sump liquid in the form of a material flow N is withdrawn from the low-pressure column 12 and pressurized in liquid form in the internal compression pump 15. A partial flow O can be provided as a gaseous internal compression product after evaporation in the main heat exchanger. A further partial flow P can be subcooled in the subcooling counterflow device 14 and discharged from the air separation plant 100 in liquid form.

[0071] Liquid can also be collected at the top of the low-pressure column 12 and discharged in the form of a material flow Q as a liquid nitrogen product. An impure nitrogen flow R can be withdrawn from the low-pressure column 12 and used in a known manner.