METHOD AND SYSTEM FOR PRODUCING HYDROGEN

Abstract

The present invention relates to a method of producing hydrogen from ammonia and to a system for producing hydrogen from ammonia.

Claims

1. A method of producing hydrogen from ammonia, the method comprising: (a) providing liquid ammonia; (b) heating the liquid ammonia in an evaporator to provide gaseous ammonia, wherein the evaporator is in thermal contact with an inert gas loop which heats and evaporates at least a portion of the liquid ammonia in the reactor; (c) contacting in a reactor at least a portion of the gaseous ammonia with a metal amide and/or a metal imide to produce hydrogen and nitrogen, wherein the reactor is in thermal contact with the inert gas loop which thereby heats at least a portion of the reactor; (d) cooling at least a portion of the hydrogen and nitrogen produced in the reactor in a first heat exchanger, wherein the first heat exchanger is in thermal contact with the inert gas loop and heat is transferred from at least a portion of the hydrogen and nitrogen produced in the reactor to the inert gas loop; wherein the inert gas loop is a loop containing at least one inert gas being pumped such that the at least one inert gas is brought into thermal contact with the first heat exchanger before being brought into thermal contact with the reactor and subsequently being brought into thermal contact with the evaporator; wherein the at least one inert gas is heated by a heater after being brought into thermal contact with the first heat exchanger and before being brought into thermal contact with the reactor.

2. The method of claim 1, wherein the metal amide and/or a metal imide is lithium amide and/or lithium imide.

3. The method of claim 1, wherein the at least one inert gas is nitrogen.

4. The method of claim 1, wherein the heater heats the at least one inert gas to at least 600° C.

5. The method of claim 1, wherein the method further comprises heating at least a portion of the gaseous ammonia provided in step (b) in a pre-heating zone before passing the gaseous ammonia to the reactor in step (c); wherein the pre-heating zone is in thermal contact with the inert gas loop which heats at least a portion of the gaseous ammonia in the pre-heating zone; wherein the at least one inert gas in the inert gas loop is pumped such that the at least one inert gas is brought into thermal contact with the pre-heating zone after being brought into thermal contact with the reactor and before being brought into thermal contact with the evaporator.

6. The method of claim 1, wherein heat is transferred in a second heat exchanger from the at least one inert gas after it has been brought into thermal contact with the reactor and/or the pre-heating zone but before it has been brought into thermal contact with the evaporator to a further portion of the at least one inert gas after it has been brought into thermal contact with the evaporator but before it has been brought into thermal contact with the first heat exchanger.

7. The method of claim 1, wherein the evaporator, the reactor, the first heat exchanger and optionally the pre-heating zone and optionally the second heat exchanger are contained in a vacuum chamber.

8. The method of claim 1, wherein the heater is an electric heater or a third heat exchanger connected to an ammonia burner.

9. The method of claim 1, wherein the reactor is at least partially surrounded with at least one concentric radiation shield.

10. The method of claim 1, further comprising passing at least a portion of the cooled hydrogen and nitrogen obtained in step (d) to a separator to produce a stream of hydrogen.

11. The method of claim 10, wherein the separator is a palladium membrane separator.

12. A system for producing hydrogen from ammonia, the system comprising: an evaporator for receiving and evaporating liquid ammonia to produce gaseous ammonia, wherein the evaporator is in thermal contact with an inert gas loop for heating and evaporating at least a portion of the liquid ammonia in the evaporator; a reactor for reacting gaseous ammonia to produce hydrogen and nitrogen, the reactor being in fluid communication with the evaporator, wherein the reactor is in thermal contact with the inert gas loop for heating at least a portion of the reactor; a first heat exchanger for cooling at least a portion of the hydrogen and nitrogen produced in the reactor, the first heat exchanger being in fluid communication with the reactor, wherein the first heat exchanger is in thermal contact with the inert gas loop for transferring heat from at least a portion of the hydrogen and nitrogen produced in the reactor to the inert gas loop; wherein the inert gas loop is a loop containing at least one inert gas, a pump and a heater, wherein the loop is configured such that the at least one inert gas can be pumped by the pump to be brought into thermal contact with the first heat exchanger before being brought into thermal contact with the reactor and subsequently being brought into thermal contact with the evaporator; wherein the loop is further configured such that the heater heats the at least one inert gas after being brought into thermal contact with the first heat exchanger and before being brought into thermal contact with the reactor.

13. The system of claim 12, wherein the reactor contains a metal amide and/or a metal imide, preferably wherein the metal and/or imide is lithium amide and/or lithium imide.

14. The system of claim 12, wherein the at least one inert gas is nitrogen.

15. The system of claim 12, wherein the system further comprises a pre-heating zone for heating gaseous ammonia received from the evaporator, the pre-heating zone being in fluid communication with the evaporator and the reactor, wherein the pre-heating zone is in thermal contact with the inert gas loop for heating at least a portion of the gaseous ammonia in the pre-heating zone; wherein the loop is configured such that the at least one inert gas can be pumped by the pump to be brought into thermal contact with the pre-heating zone after being brought into thermal contact with the reactor and before being brought into thermal contact with the evaporator.

16. The system of claim 12, wherein the loop further comprises a second heat exchanger, wherein the second heat exchanger is configured such that heat can be transferred from the at least one inert gas after it has been brought into thermal contact with the reactor and/or the pre-heating zone but before it has been brought into thermal contact with the evaporator to a further portion of the at least one inert gas after it has been brought into thermal contact with the evaporator but before it has been brought into thermal contact with the first heat exchanger.

17. The system of claim 12, wherein the evaporator, the reactor, the first heat exchanger and optionally the pre-heating zone and optionally the second heat exchanger are contained in a vacuum chamber.

18. The system of claim 12, wherein the heater is an electric heater or a third heat exchanger connected to an ammonia burner.

19. The system of claim 12, wherein the reactor is at least partially surrounded with at least one concentric radiation shield.

20. The system of claim 12, further comprising a separator in fluid communication with the first heat exchanger for separating at least a portion of the cooled hydrogen and nitrogen.

21. The system of claim 12, wherein the separator is a palladium membrane separator.

Description

[0079] These and other aspects of the invention will now be described with reference to the accompanying FIGURES, in which:

[0080] FIG. 1: is a diagram showing a preferred system for producing hydrogen according to the method described herein.

[0081] Liquid ammonia is provided by a liquid ammonia source (145) at a pressure of 1 MPa and a temperature of around 20° C. via a valve (150) and enters the evaporator (140) which is in thermal contact with an inert gas loop. The pathway taken by ammonia and products formed therefrom is represented by a bold dashed line in FIG. 1. Heat from the inert gas is transferred to the liquid ammonia which is heated and evaporated. The gaseous ammonia produced is at a temperature of around 48° C. This gaseous ammonia then passes to a pre-heating zone (135) which is in thermal contact with the inert gas loop. Heat from the inert gas is transferred to the gaseous ammonia which is heated to a temperature of around 390° C. This gaseous ammonia is then passed to a reactor (130) containing lithium amide and lithium imide (160), where the ammonia reacts to form hydrogen and nitrogen. The reactor (130) is in thermal contact with the inert gas loop. Heat from the inert gas is transferred to the reactor which is heated to a temperature of around 700° C. The hydrogen and nitrogen gas, as well as any unreacted gaseous ammonia, produced in the reactor (130) is at a temperature of around 592° C. and this is passed to a first heat exchanger (120) where heat is transferred from the hydrogen and nitrogen gas, as well as any unreacted gaseous ammonia, to the inert gas in the inert gas loop, thereby cooling the hydrogen and nitrogen gas, as well as any unreacted gaseous ammonia, that was produced in the reactor, and heating the inert gas. The hydrogen and nitrogen, as well as any unreacted gaseous ammonia, now at a temperature of around 300° C. and at a pressure of around 0.85 MPa, is then passed to a palladium membrane separator (155), which separates the products, resulting in a high purity product hydrogen stream (165) and a waste-gas stream (170) comprising nitrogen, hydrogen and ammonia. Both the high purity product hydrogen stream (165) and the waste-gas stream (170) are passed through respective magnesium chloride ammonia absorbers (175, 180) to remove any residual ammonia.

[0082] An inert gas (a mixture of argon and nitrogen) is provided by an inert gas source (100) to the inert gas loop through a sealable entrance (105), e.g. a valve. The inert gas loop is represented by a solid line in FIG. 1. The inert gas passes through a pump/circulator (110), which pumps the inert gas around the inert gas loop. After leaving the pump (110), the inert gas enters the second heat exchanger (115), where it is heated by heat from the inert gas which has just been brought into thermal contact with the reactor (130) and the pre-heating zone (135) but before it has been brought into thermal contact with the evaporator (140). The heated inert gas exits the second heat exchanger (115) at a temperature of around 247° C. and enters the first heat exchanger (120), where it is heated by heat transferred from the hydrogen and nitrogen gas, as well as any unreacted gaseous ammonia, that was produced in the reactor (130). The heated inert gas is then heated further by a heater (125), e.g. an electric heater. The heated inert gas, now at a temperature of around 770° C. is then brought into thermal contact with the reactor (130), where it heats the reactor (130) to cause the reaction to produce hydrogen and nitrogen from ammonia. The inert gas is at a temperature of around 442° C. after being brought into thermal contact with the reactor (130). The inert gas is then brought into thermal contact with the pre-heating zone (135), where it heats the gaseous ammonia therein. The inert gas is at a temperature of around 360° C. after being brought into thermal contact with the pre-heating zone (135). The inert gas then enters the second heat exchanger (115), where it transfers heat to the inert gas which has just left the pump (110) and before it has entered the first heat exchanger (120). The cooled inert gas exits the second heat exchanger (115) at a temperature of around 247° C. and is then brought into thermal contact with the evaporator (140), transferring heat to evaporate the liquid ammonia therein. After being brought into thermal contact with the evaporator (140), the cooled inert gas is at a temperature of around 130° C. This cooled inert gas is then passes through the pump (110) and is pumped around the inert gas loop once more.

[0083] In this illustrated embodiment, the evaporator (140), the reactor (130), the first heat exchanger (120), the pre-heating zone (135), the second heat exchanger (115) and the heater (125) are contained in a vacuum chamber (185).

[0084] The method and system according to the present invention are suitable for use, for example, in internal combustion engines, stationary gas turbines, jet engines, proton-exchange membrane fuel cells and household heating systems.

[0085] When introducing elements of the present disclosure or the preferred embodiments(s) thereof, the articles “a”, “an”, “the” and “said” are intended to mean that there are one or more of the elements. The terms “comprising”, “including” and “having” are intended to be inclusive and mean that there may be additional elements other than the listed elements.

[0086] The foregoing detailed description has been provided by way of explanation and illustration, and is not intended to limit the scope of the appended claims. Many variations in the presently preferred embodiments illustrated herein will be apparent to one of ordinary skill in the art, and remain within the scope of the appended claims and their equivalents.