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EP-4741335-A1 - PROCESS FOR PRODUCING A HYDROGEN PRODUCT FROM A FEED STREAM

EP4741335A1EP 4741335 A1EP4741335 A1EP 4741335A1EP-4741335-A1

Abstract

The invention relates to a process for producing a hydrogen product (2) from a feed stream (4). Said process comprising the following steps: - providing an ammonia stream (6), in particular a liquid ammonia stream (6); - directing said feed stream (4) derived from the provided ammonia stream (6) to a succession of at least two gas heated reactors (8) arranged in series to perform a succession of ammonia cracking reactions in the gas heated reactors (8), so as to produce at least one intermediate cracked gas (10) passing from a gas heated reactor (8) to the subsequent gas heated reactor (8) and thus producing downstream of the succession of said gas heated reactors (8), a cracked gas (12) from which the hydrogen product (2) is derived.

Inventors

  • SHRIVASTAVA, Swatantra Kumar

Assignees

  • L'AIR LIQUIDE, SOCIETE ANONYME POUR L'ETUDE ET L'EXPLOITATION DES PROCEDES GEORGES CLAUDE

Dates

Publication Date
20260513
Application Date
20241106

Claims (14)

  1. A process for producing a hydrogen product (2) from a feed stream (4), said process comprising the following steps: - providing an ammonia stream (6), in particular a liquid ammonia stream (6); - directing said feed stream (4) derived from the provided ammonia stream (6) to a succession of at least two gas heated reactors (8) arranged in series to perform a succession of ammonia cracking reactions in the gas heated reactors (8), so as to produce at least one intermediate cracked gas (10) passing from a gas heated reactor (8) to the subsequent gas heated reactor (8) and thus producing downstream of the succession of said gas heated reactors (8), a cracked gas (12) from which the hydrogen product (2) is derived.
  2. Process according to claim 1, comprising the step of: - heating at least one of the gas heated reactors (8) with said cracked gas (12) as a heating medium stream.
  3. Process according to claim 2, wherein the at least one gas heated reactor (8) is heated with said cracked gas (12) circulating in said at least one gas heated reactor (8) in a co-current manner with the feed stream (4) or with the intermediate cracked gas (10).
  4. Process according to claim 2 or 3, comprising directing the cracked gas (12) as the heating medium stream successively to said gas heated reactors (8).
  5. Process according to any one of the preceding claims, comprising the steps of: - directing the ammonia stream (6), in particular a vaporized ammonia stream (22), and/or a superheated vaporized ammonia stream (26), to a heating system (9); and - providing heat to the ammonia stream (6), in particular to the vaporized ammonia stream (22), and/or to the superheated vaporized ammonia stream (26), with said heating system (9), thereby obtaining a heated ammonia stream (28).
  6. Process according to claim 5, wherein said feed stream (4) is derived from the vaporized ammonia stream (22), the superheated vaporized ammonia stream (26), or the heated ammonia stream (28).
  7. Process according to any one of the preceding claims, said process comprising: heating the intermediate cracked gas (10) at a predetermined temperature so as to provide a heated intermediate cracked gas (11) to said subsequent gas heated reactor (8), in particular to a last gas heated reactor (8), of the succession of gas heated reactors (8).
  8. The process according to claim 7, said process comprising the following steps of: - directing the cracked gas (12) from the last gas heated reactor (8) to the heating system (9), - heating the cracked gas (12) with said heating system (9), thereby obtaining a heated cracked gas (13), and - directing the heated cracked gas (13) as the heating medium stream to at least one of said at least two gas heated reactors (8) arranged in series.
  9. The process according to claim 8, comprising the following steps of: - directing the cracked gas (12), in particular the heated cracked gas (13) heated with said heating system (9), as the heating medium stream to a heating medium inlet (42) of one of said gas heated reactors (8); and - directing a cooled cracked gas (44) from a heating medium outlet (46) of said gas heated reactor (8) to a heating medium inlet (42) of another of the gas heated reactors (8), for example a heating medium inlet (42) of the last of said gas heated reactors (8).
  10. The process according to claim 9, comprising the step of: - heating again the cooled cracked gas (44) between said gas heated reactors (8).
  11. The process according to claim 9 or 10, comprising a step of recovering heat from the cooled cracked gas (44), thereby obtaining said hydrogen product (2).
  12. The process according to any one of the preceding claims, said process comprising the step of: - directing a liquid ammonia stream (6) to a vaporizer (20) configured to receive said liquid ammonia stream (6) and to vaporize said liquid ammonia stream (6) so as to obtain a vaporized ammonia stream (22).
  13. The process according to claims 11 and 12, wherein the step of recovering heat from the cooled cracked gas (44) comprises: - directing said cooled cracked gas (44) from a heating medium outlet (46) of the last gas heated reactor (8) to said vaporizer (20) configured to receive said cooled cracked gas (44); and - vaporizing the liquid ammonia stream (6) by recovering residual heat from the cooled cracked gas (44).
  14. The process according any one of the preceding claims, said process comprising removing unconverted ammonia from said hydrogen product (2), for example with a wash column (50), so as to obtain an ammonia depleted hydrogen product (52).

Description

The present invention relates to a process for producing a hydrogen product from a feed stream. Hydrogen is renowned for its lightweight nature and optimal combustion properties as a fuel and its environment-friendliness during its combustion or during its electrochemical conversion, for example for a fuel cell. That is, there is no emission of any carbon dioxide (CO2), particulate or sulfur during the use of hydrogen as a fuel. This makes hydrogen a vector for the energy transition. As a matter of fact, a hydrogen product can be produced from a cracking reaction of an ammonia as feedstock, or from an ammonia cracking reaction. In particular, a vaporized ammonia stream can be used in the ammonia cracking reaction to produce the hydrogen. Typically, the ammonia cracking reaction takes place in an ammonia cracking reactor comprising tubes filled with catalysts and extending in a furnace. Heat is supplied to said tubes, via external firing of a fuel in said furnace, for example with a firebox supplied by the fuel. However, the adaptation of the current process at a larger scale is not simple. Indeed, in a conventional ammonia cracking reactor, a significant amount of waste heat is left unused in the flue gas and in the cracked gas. A typical radiant efficiency of such ammonia cracking reactor is comprised between 55 and 60%. That is, about 40% of firing duty ends up as waste heat in the flue gas (the higher the radiant efficiency is, less will be the loss of the firing duty as a waste heat). For the conventional ammonia cracking reactor, increasing the radiant efficiency is done at the expense of increasing the number of catalysts filled tubes, thus the dimension of the ammonia cracking reactor and the firebox. Moreover, in addition to the over-sizing of these, an attempt to increase said radiant efficiency by increasing the temperature at which the reaction takes place, will inevitably lead to the requirement of high-grade temperature resisting materials for said tubes, which are expensive and which increase the overall cost of the installation. As a consequence, there is a need to overcome the aforementioned issues, in particular a need to cope with avoiding the loss of the waste heat during the process for producing a hydrogen product from a feed stream, while reducing the space requirement and the overall cost of said installation. For this purpose, the invention proposes a process for producing a hydrogen product from a feed stream, said process comprising the following steps: providing an ammonia stream, in particular a liquid ammonia stream;directing said feed stream derived from the provided ammonia stream to a succession of at least two gas heated reactors arranged in series to perform a succession of ammonia cracking reactions in the gas heated reactors, so as to produce at least one intermediate cracked gas passing from a gas heated reactor to the subsequent gas heated reactor and thus producing downstream of the succession of said gas heated reactors, a cracked gas from which the hydrogen product is derived. The ammonia conversion rate of the intermediate cracked gas is inferior to the ammonia conversion rate of the cracked gas. Thanks to the invention the number of the gas heated reactors can be adapted for an existing heating system, it is possible to modularize the size and the overall conversion efficiency of the process, without oversizing the heating system while simplifying the design of an installation configured to operate the process. For example, over 80 % of overall ammonia conversion can be achieved with the two gas heated reactors coupled with a heating system. This allows to revamp an existing installation or plant. In one embodiment, the process comprises the step of: - heating at least one of the gas heated reactors with said cracked gas as a heating medium stream. In particular, the at least one gas heated reactor is heated with said cracked gas circulating in said at least one gas heated reactor in a co-current manner with the feed stream or with the intermediate cracked gas. Thus, this allows to reduce the loss of the waste heat, thereby improving the overall conversion efficiency (or the overall thermal efficiency) of the process. The invention enables improving the overall efficiency of the process, while reducing the space requirement and the overall cost of an installation operating said process. In one embodiment, the process comprises directing the cracked gas as the heating medium stream successively to said gas heated reactors. By "directing the cracked gas as the heating medium stream successively to said gas heated reactors", it is referred that the heating medium stream provides heat to the gas heated reactors in series. In one embodiment, the process comprises the step of: - directing a liquid ammonia stream to a vaporizer configured to receive said liquid ammonia stream and to vaporize said liquid ammonia stream for obtaining a vaporized ammonia stream. In one embod