Method and system for producing hydrogen from ammonia cracking

Abstract

A method and system for producing hydrogen products from ammonia, including: at least one pre-cracking reactor, e.g., an adiabatic pre-cracking reactor, optionally configured to receive an ammonia feed material stream, thereby producing a partially converted ammonia feed material stream containing ammonia, hydrogen, and nitrogen; an ammonia cracking reactor, e.g., an electroheated reactor. The reactor is configured to receive a partially converted ammonia feed material stream or an ammonia feed material stream to produce an effluent gas stream containing hydrogen and nitrogen, and optionally also unconverted ammonia; a hydrogen recovery unit is configured to receive an effluent gas stream to produce hydrogen products, as well as an off-gas stream containing hydrogen, nitrogen, and optionally unconverted ammonia.

Claims

1. A method for producing hydrogen products from ammonia, comprising the following steps: i) Providing an ammonia supply material stream; ii) Passing the ammonia supply material stream through at least one ammonia pre-cracking reactor to produce a partially converted ammonia supply material stream containing ammonia, hydrogen, and nitrogen; iii) Passing the partially converted ammonia supply material stream through an ammonia cracking reactor to produce an effluent gas stream containing hydrogen, nitrogen, and unconverted ammonia; iv) Passing the spilled gas stream through a hydrogen recovery unit to generate the hydrogen product and an off-gas stream containing hydrogen, nitrogen and optionally unconverted ammonia, In a method including, Step iv) includes cooling the outlet gas stream by heat exchange with the ammonia supply material stream before passing the outlet gas stream through the hydrogen recovery unit; Step iv) further includes recovering unconverted ammonia in the effluent gas stream by a flushing step in an ammonia recovery flushing system, such as a flash column, after the cooling of the effluent gas stream by heat exchange with the ammonia supply material stream, after the cooling and before the flushing step, the thus cooled effluent gas stream is supplied to an effluent gas separator, such as an effluent gas scrubbing unit using water as a scrubbing medium, to generate an overhead stream containing nitrogen and hydrogen and a bottom liquid stream containing unconverted ammonia in the effluent gas separator, and the overhead stream is sent to the hydrogen recovery unit. The aforementioned method.

2. The method according to claim 1, wherein the bottom liquid stream containing unconverted ammonia is provided as a feed material to the flushing step, the flushing step provides an overhead stream, and the method further comprises combining the overhead stream with at least a portion of the off-gas from the hydrogen recovery unit, the effluent gas from step iii) or a combination thereof to form a fuel gas, and supplying at least a portion of the fuel gas to the ammonia cracking reactor.

3. The method according to claim 1 or 2, wherein the at least one ammonia pre-cracking reactor and / or the ammonia cracking reactor operates in a temperature range of 300 to 700°C, and further, the at least one ammonia pre-cracking reactor and / or the ammonia cracking reactor operates with an ammonia cracking catalyst, such as an Fe-Co catalyst, comprising a metal or metal alloy selected from Fe, Co, Ru, optionally Ni, or a combination thereof.

4. The at least one ammonia pre-cracking reactor is operated with a catalyst comprising 20-50% by weight of Fe, 20-50% by weight of Co, and 20-50% by weight of alumina, which is optionally promoted by an alkali metal oxide, a lanthanide metal oxide and / or an oxide of Ca, Si, Al or a combination thereof, and the ammonia cracking reactor is operated with a Ni catalyst, which comprises 20-60% by weight of Ni and 40-80% by weight of any oxide of Al, Ca, Mg or a combination thereof, which is optionally promoted by a lanthanide metal oxide, such as La ２ O ３ The method according to claim 1 or 2, as promoted by [the present invention].

5. The method according to any one of claims 2 to 4, wherein the fuel gas is preheated by the outlet gas stream before the cooling of the outlet gas stream by heat exchange with the ammonia supply material stream in step iv).

6. In step iv), the cooling of the outflow gas stream by heat exchange with the ammonia supply material stream before passing the outflow gas stream through the hydrogen recovery unit is as follows: - To pass the exhaust gas stream, after transferring heat to the fuel gas, through an ammonia evaporator, thereby providing a cooled exhaust gas stream; - Diverting at least a portion of the cooled exhaust gas stream as additional fuel gas and supplying it to the ammonia cracker reactor; - Diverting another portion of the cooled outlet gas stream to be supplied to the outlet gas separator, A method according to any one of claims 1 to 5, including the method described in any one of claims 1 to 5.

7. The method according to any one of claims 1 to 6, wherein the ammonia cracking reactor is a combustion heating reactor, a convection heating reactor, an electric heating reactor, an induction heating reactor, or a combination thereof, each including one or more catalyst-filled tubes.

8. The method according to claim 7, wherein the ammonia cracking reactor is either a combustion heating reactor or a convection heating reactor, and the method is as follows: - A portion of the off-gas stream from the hydrogen recovery unit is mixed with an air stream and / or with a separate fuel stream and sent to the combustion heating reactor or convection heating reactor, thereby generating the heat required for the combustion heating reactor or convection heating reactor. The further includes, wherein the separate fuel stream is a) a fuel gas supplied from an external source, such as natural gas, and / or b) a portion of the fuel gas. The aforementioned method.

9. The method according to claim 7, wherein the ammonia cracking reactor is an electric heating reactor or an induction heating reactor, and the method is as follows: - A portion of the off-gas stream, for example another portion, is mixed with an air stream, or optionally with a separate fuel stream, and sent to a combustion heater, thereby preheating the ammonia supply material gas stream. The further includes, wherein the separate fuel stream is c) a fuel gas supplied from an external source, such as natural gas, and / or d) a portion of the fuel gas stream. The aforementioned method.

10. Furthermore, the method according to any one of claims 1 to 9, including the following: Electrically heating either the ammonia supply material gas stream, the fuel gas stream, the combustion air, or a combination thereof.

11. The method according to any one of claims 8 to 10, including the following: - Diverting a portion of the ammonia stream, for example, a portion of the ammonia supply material stream, and supplying it as at least a portion of the separate fuel stream.

12. The method according to any one of claims 1 to 11, wherein the ammonia supply material stream is generated from liquid ammonia, for example, liquid ammonia taken in from a storage unit, and the ammonia supply material stream is subjected to evaporation and preheating before evaporation.

13. The method according to any one of claims 1 to 12, wherein the flushing step provides a bottom ammonia dilute aqueous stream that is led to the outlet gas separator as a wash stream, and optionally the wash stream is further mixed with makeup water and then supplied to the outlet gas separator.

14. The hydrogen recovery unit includes at least one pressure swing adsorption (PSA) unit to generate the hydrogen product and the off-gas stream; Optionally: - The hydrogen recovery unit includes first and second PSA units for generating the hydrogen product, and the method further includes generating the off-gas stream by taking a first off-gas stream from the first PSA unit, compressing it, and passing it through the second PSA unit; or - The hydrogen recovery unit includes a membrane unit and a PSA unit, The method according to any one of claims 1 to 13.

15. The method according to any one of claims 12 to 14, further comprising: supplying a portion of the overhead stream, including nitrogen and hydrogen from the exhaust gas separator, to a turbine for generating electricity, which generates an exhaust gas stream; To provide at least a portion of the exhaust stream as a heat exchange medium for preheating the ammonia supply material stream.

16. The method according to claim 15, wherein the preheating of the ammonia supply material stream includes the following: - Preheating of the ammonia supply material stream from the ammonia evaporator, i.e., preheating of the ammonia supply material stream as it passes through the at least one ammonia precracking reactor; and / or - Preheating of the ammonia supply material stream prior to evaporation, i.e., preheating for liquid ammonia.

17. Furthermore, the method according to any one of claims 1 to 16 includes the following: - To generate a hydrogen-rich gas stream and a nitrogen-rich gas stream, at least a portion of the off-gas stream, which contains hydrogen, nitrogen, and optionally unconverted ammonia, is sent from the hydrogen recovery unit to a nitrogen recovery unit selected from a PSA unit, a cryogenic separation unit, a membrane unit, or a combination thereof; - At least a portion of the hydrogen-rich gas stream is supplied to the ammonia cracking reactor as a separate fuel gas, where preferably the ammonia cracking reactor is a combustion heating reactor.

18. The method according to any one of claims 1 to 17, further comprising step iii): - Generating a high-temperature flue gas stream and recovering its heat by at least one of the following: preheating the ammonia supply material stream before passing it through the at least one adiabatic ammonia pre-cracking reactor; and preheating the partially converted ammonia supply material stream, i.e., the ammonia supply material stream after passing it through the at least one adiabatic ammonia pre-cracking reactor; - Nitrogen oxides (NO ｘ To perform selective non-catalytic removal (SNCR) of ammonia, ammonia is introduced into the high-temperature flue gas stream prior to heat recovery, preferably having a temperature in the range of 800 to 1000°C, for example, 850 to 950°C; - Ammonia is introduced into the high-temperature flue gas after heat recovery, and the high-temperature flue gas is converted to NO ｘ and N ２ The gas is then sent to selective catalytic reduction (SCR) for further removal of oxygen; where preferably the high-temperature flue gas has a temperature in the range of 300 to 500°C, for example, 325 to 475°C.

19. The method according to claim 18, further comprising: - The high-temperature flue gas is routed after the SCR unit, N ２ For further removal of O, N ２ To send to the catalyst unit.

20. - The SCR unit includes a catalyst comprising (a) an iron (Fe)-promoted zeolite, preferably an iron-promoted beta zeolite (Fe-beta zeolite); or (b) a catalyst containing vanadium (V), optionally tungsten (W), on a carrier selected from at least one of titania (TiO ２ ), alumina (Al ２ O ３ ), and silica (SiO ２ ); - The aforementioned N ２ The catalyst unit contains a catalyst containing cobalt (Co), The method according to claim 18 or 19.

21. The ammonia is added to the high-temperature flue gas, and NO is added to the high-temperature flue gas. ｘ Introduced in a molar ratio >1 relative to the content, excess ammonia is released onto a catalyst containing one of the following noble metal catalysts: silver (Ag), platinum (Pt), palladium (Pd), ruthenium (Ru), and rhodium (Rh). ｘ The method according to any one of claims 18 to 20, which is broken down into:

22. Furthermore, the method according to any one of claims 18 to 21, including the following: - Diverting a portion of the ammonia stream, for example, a portion of the ammonia supply material stream, as ammonia to the high-temperature flue gas stream.

23. below: - At least one pre-cracking reactor, e.g., an adiabatic pre-cracking reactor, arranged to receive an ammonia supply material stream, wherein the optional at least one pre-cracking reactor preferably has a catalyst fixed bed located therein and provides a partially converted ammonia supply material stream containing ammonia, hydrogen and nitrogen; - An ammonia cracking reactor arranged to receive the partially converted ammonia supply material stream and provide an outflow gas stream containing hydrogen, nitrogen, and unconverted ammonia; - A hydrogen recovery unit arranged to receive the spilled gas stream and provide hydrogen products and an off-gas stream containing hydrogen, nitrogen, and optionally unconverted ammonia; A system for producing hydrogen products from ammonia, including The hydrogen recovery unit includes at least one heat exchanger located upstream of the hydrogen recovery unit to cool the outflow gas stream by heat exchange with the ammonia supply material stream, Furthermore, see below: - An outlet gas separator arranged to receive the thus cooled outlet gas stream and provide: an overhead stream containing nitrogen and hydrogen, a conduit for sending the overhead stream containing nitrogen and hydrogen to the hydrogen recovery unit, and a bottom liquid stream containing unconverted ammonia; - An ammonia recovery flushing system, such as a flash column, is arranged to receive the bottom liquid stream containing unconverted ammonia and to provide an overhead stream. The system including the above.

24. The system according to claim 23, wherein the ammonia recovery flushing system is further arranged to provide a bottom ammonia dilute aqueous stream, and the system further includes a conduit for leading the bottom ammonia dilute aqueous stream as a wash stream to the outflow gas separator.

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