PROCESS AND PLANT FOR PROVIDING A NITROGEN PRODUCT, AN OXYGEN PRODUCT AND A HYDROGEN PRODUCT

Abstract

A method for providing a nitrogen product, an oxygen product and a hydrogen product, wherein an air separation installation is used which is designed for the low-temperature separation of feed air and which has a rectification column system, the rectification column system comprising an air-fed rectification column and a main heat exchanger. The provision of the nitrogen product comprises, in particular, subjecting feed air to low-temperature rectification using the air-fed rectification column such that a tops gas is obtained, and using part of the tops gas as the nitrogen product. The provision of the oxygen product and the hydrogen product comprises subjecting water to water electrolysis in an electrolyzer, such that a water-containing oxygen stream and a hydrogen stream are obtained, the water-containing oxygen stream or part thereof being subjected, at least in one operating phase, to drying and, in an unmixed state, to liquefaction in the air separation installation.

Claims

1. A method for providing a nitrogen product, an oxygen product and a hydrogen product, wherein an air separation installation is used which is designed for the low-temperature separation of feed air and which has a rectification column system, the rectification column system comprising an air-fed rectification column and a main heat exchanger for cooling the feed air, the provision of the nitrogen product comprising subjecting feed air to low-temperature rectification using the rectification column system and taking the nitrogen product or a precursor thereof from the rectification column system, wherein the provision of the oxygen product and the hydrogen product comprises subjecting water to water electrolysis in an electrolyzer, such that a water-containing oxygen stream and a hydrogen stream are obtained, the water-containing oxygen stream or part thereof being subjected, at least in one operating phase, to drying and optionally to further purification steps such that a liquid oxygen stream is obtained, and the dried oxygen stream thereafter being introduced into the air separation installation without being mixed with a process stream of the air separation installation, and being subjected in an unmixed state to liquefaction in the air separation installation, and the liquid oxygen stream produced in the process or part thereof being used to provide the oxygen product.

2. The method according to claim 1, wherein the liquefaction of the dried oxygen stream is performed in the main heat exchanger, a supercooling counterflow unit of the air separation, in the supercooling part of a combined main heat exchanger-supercooler or in a separate heat exchanger of the air separation installation independent of the main heat exchanger and optionally the supercooling counterflow unit.

3. The method according to claim 1, wherein the feed air is subjected to the low-temperature rectification using the air-fed rectification column such that a tops gas is obtained, part of the tops gas being used as the nitrogen product or a precursor of the nitrogen product, two material streams with different oxygen contents being formed in a condenser evaporator by evaporating liquid from the air-fed rectification column, and a further part of the tops gas being condensed in the condenser evaporator and returned to the air-fed rectification column .

4. The method according to claim 1, wherein the water-containing oxygen stream is provided using electrolysis, in particular high-pressure electrolysis.

5. The method according to claim 1, wherein the water-containing oxygen stream or part thereof is subjected to compression after drying (21) and before liquefaction in the main heat exchanger.

6. The method according to claim 1, wherein the provision of the oxygen product comprises purification, in particular rectification for depletion of argon.

7. The method according to claim 1, wherein the liquid oxygen stream is formed only in a first operating phase, the liquid oxygen stream being temporarily stored in the first operating phase for later provision of the oxygen product, and the oxygen product being obtained in a second operating phase using the temporarily stored liquid oxygen stream or part thereof with heating in the main heat exchanger as a gaseous pressurized oxygen product.

8. The method according to claim 7, wherein, in the second operating phase, a gaseous nitrogen stream is subjected to liquefaction in the main heat exchanger so as to obtain a liquid nitrogen stream, the liquid nitrogen stream or part thereof being used as the or a further nitrogen product or being temporarily stored for later provision of the or a further nitrogen product.

9. The method according to claim 1, wherein the liquefaction is performed using liquid air.

10. The method according to claim 1, wherein the air-fed rectification column is operated using a condenser evaporator, in which a first and a second material stream are formed below an operating pressure level of the air-fed rectification column by evaporating liquid from the air-fed rectification column, further tops gas from the air-fed rectification column being condensed in the condenser evaporator and returned to the air-fed rectification column as a return flow.

11. The method according to claim 10, wherein the first material stream is formed with a first oxygen content and the second material stream is formed with a second oxygen content above the first oxygen content, the first material stream or part thereof being subjected to recompression to the first pressure level and being fed into the air-fed rectification column, and the second material stream or part thereof being subjected to a work-performing expansion and being discharged from the installation.

12. The method according to claim 10, wherein a further rectification column fed from the air-fed rectification column is used, wherein bottoms liquid from the second rectification column is used to provide the oxygen product.

13. The method according to claim 12, wherein the liquid oxygen stream is fed into the further rectification column.

14. An installation for providing a nitrogen product, an oxygen product and a hydrogen product, the installation comprising an air separation installation for low-temperature separation of feed air, which air separation installation in turn has a rectification column system comprising an air-fed rectification column, a main heat exchanger for cooling the feed air, the installation for providing the nitrogen product being designed to subject feed air to low-temperature rectification using the rectification column system and to take the nitrogen product or a precursor thereof from the rectification column system, wherein the installation comprises an electrolyzer designed to subject, for the provision of the oxygen product and the hydrogen product so as to obtain a water-containing oxygen stream and a hydrogen stream, to a water electrolysis, the installation being designed to subject the water-containing oxygen stream or part thereof, at least in an operating phase, to drying (21), so as to obtain a liquid oxygen stream and without mixing with a process stream of the air separation installation, and thereafter, in an unmixed state, to liquefaction in the air separation installation and to use the liquid oxygen stream produced in this process or part thereof to provide the oxygen product.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

[0072] FIG. 1 shows a installation according to an embodiment of the invention.

[0073] FIG. 2 shows a installation according to a further embodiment of the invention.

[0074] FIG. 3 shows a system according to the invention incorporating a main heat exchanger and a supercooling counterflow unit.

[0075] In the figures, elements corresponding functionally or structurally to one another are indicated by identical reference signs and only for the sake of clarity are not repeatedly explained below.

DETAILED DESCRIPTION OF THE DRAWINGS

[0076] FIG. 1 illustrates a installation 100 according to one embodiment of the invention in the form of a schematic installation diagram.

[0077] The installation 100 is designed for the low-temperature separation of air and for this purpose comprises a rectification column system 10 with an air-fed rectification column 11 which is designed for nitrogen recovery and is operated with a condenser evaporator 13. A further rectification column 12 fed from the air-fed rectification column 11 for the recovery of oxygen is not present, but is nevertheless shown (crossed out) to illustrate the modification of a installation according to the prior art carried out within the scope of the invention.

[0078] By means of a main air compressor 1 of the air fractionation installation 100, air is sucked in from the atmosphere via a filter (not separately designated) and compressed. After cooling in an aftercooler (likewise not designated separately) downstream of the main air compressor 1, the feed air stream a formed in this way is further cooled in a direct contact cooler 2 operated with water. The feed air stream a is then subjected to cleaning in an adsorber unit 3. For further explanations in this context, reference is made to the technical literature, for example in connection with FIG. 2.3A in Hring (see above).

[0079] After cooling in the main heat exchanger 4, the feed air stream a is fed into the air-fed rectification column 11, in which the correspondingly fed air is rectified. Tops gas of the air-fed rectification column 11 is partially discharged from the air separation installation 100 in the form of a material stream d as a nitrogen product or sealing gas.

[0080] In the condenser evaporator 13, in the specific embodiment illustrated here, a first material stream g and a second material stream h are subjected to evaporation below an operating pressure level of the air-fed rectification column 11 (for this purpose, in particular, a corresponding expansion takes place in valves not separately designated).

[0081] The first material stream g is formed using liquid taken from the air-fed rectification column 11 with a first oxygen content, and the second material stream h is formed using liquid (in particular bottoms liquid) taken from the air-fed rectification column 11 with a second oxygen content above the first oxygen content.

[0082] Further tops gas of the air-fed rectification column 11 is condensed in the form of a material stream i in the first condenser evaporator 13 and returned to the air-fed rectification column 11 as a return flow. As illustrated here in the form of a material stream k, a part can also be supercooled in a supercooling counterflow unit 5 and provided as liquid nitrogen F. It is also possible to feed in liquid nitrogen. A material stream I heated thereby is treated as explained in more detail below. A further discharge in the form of a purge stream m may also be provided. A possible (further) feeding of liquid nitrogen (LIN injection) is illustrated in the form of a material stream x.

[0083] After its evaporation or partial evaporation in the first condenser evaporator 13, gas of the first material stream g is subjected in a compressor 6 to recompression to the first pressure level and fed into the air-fed rectification column 11. A portion indicated by a dashed line can also be returned to compression in the compressor 6. Part of the material stream g can also be discharged into the atmosphere in the form of a material stream n.

[0084] After being evaporated or partially evaporated in the first condenser evaporator 13 in the example illustrated here, gas of the second material stream h is subjected to expansion in an expansion machine 7 coupled to the compressor 6 and, after heating in the main heat exchanger 4, is used as regeneration gas in the adsorber unit 3 or released into the atmosphere and thus discharged from the air separation installation 100.

[0085] In an electrolyzer 20, a hydrogen stream (not shown) and an oxygen stream o are formed by water electrolysis in a first operating phase. The former is provided as a hydrogen product. The latter is water-containing due to the type of production and is therefore freed of water and other components in a dryer 21. (The dryer consists, for example, of a conventional pair of adsorber containers that are operated alternately, as indicated in FIG. 3.) The dried oxygen stream, further designated as o, is conducted through the main heat exchanger 4, liquefied there, then supercooled in the supercooling counterflow unit 5 and fed into a tank unit 22 in a liquefied, supercooled state. In this way, an oxygen product is thus formed.

[0086] If required, in particular in a second operating phase, the oxygen stored in the tank unit, as further illustrated here with an oxygen flow o, can be pressurized, for example by means of a pressure build-up compression, heated in the main heat exchanger 4 and thereby evaporated and provided as a corresponding (further) oxygen product.

[0087] Alternatively, in FIG. 1, the supercooling counterflow unit 5 could be integrated into the main heat exchanger 4 in a manner known per se.

[0088] FIG. 2 illustrates a installation 200 according to one embodiment of the invention in the form of a schematic installation diagram.

[0089] In this installation, the already mentioned further rectification column 12 for oxygen recovery is present. This further rectification column 12 is fed with a side stream p of the air-fed rectification column 11, which is first conducted through a bottoms evaporator 14 of the further rectification column 12 and liquefied therein and then fed in an upper region to the further rectification column 12.

[0090] A portion of the air stream a, which is illustrated here in the form of a material stream b, is also conducted through the bottoms evaporator 14 and is then fed in a liquefied state into the air-fed rectification column 11.

[0091] Bottoms liquid of the further rectification column 12 is fed into the tank unit 23 in the form of a material stream q and can be used from this, as previously explained for the material stream o, to provide the oxygen product, as illustrated with a material stream q further designated by q. The oxygen stream o previously liquefied in the main heat exchanger 4 and then supercooled in the supercooling counterflow unit 5 is fed into the further rectification column 12 for further purification.

[0092] Alternatively, in FIG. 2, the supercooling counterflow unit 5 could be integrated into the main heat exchanger 4 in a manner known per se.

[0093] FIG. 3 shows an exemplary embodiment of the configuration 3 with cooling and liquefaction of the oxygen stream o in a separate heat exchanger 300. the liquefied oxygen is fed into the tank unit 22 via the outputs 201 and 302. All other features of FIG. 3 correspond to those of FIG. 2.