Autothermal steam reforming process

• US 5,011,625 A
• Filed: 12/11/1989
• Issued: 04/30/1991
• Est. Priority Date: 12/11/1989
• Status: Expired due to Term

• Current Assignee: MW Kellogg Limited (KBR Incorporated)
• Original Assignee: MW Kellogg Limited (KBR Incorporated)
• Inventors: Le Blanc, Joseph R.
• Primary Examiner(s): MARS, HOWARD
• Application Number:
  US07/448,422
• Time in Patent Office: 505 Days
• Field of Search: 252/376
• US Class Current: 252/376
• CPC Class Codes: B01J 2219/1946 conical
• CPC Class Codes: B01J 8/025 in a cylindrical shaped bed
• CPC Class Codes: B01J 8/0488 the beds being placed in separate reactors
• CPC Class Codes: B01J 8/06 in tube reactors; the solid particles being arranged in tubes
• CPC Class Codes: C01B 2203/0233 the reforming step being a steam reforming step
• CPC Class Codes: C01B 2203/0244 the reforming step being an autothermal reforming step, e.g. secondary reforming processes
• CPC Class Codes: C01B 2203/068 Ammonia synthesis
• CPC Class Codes: C01B 2203/0844 the non-combustive exothermic reaction being another reforming reaction as defined in groups C01B2203/02 - C01B2203/0294
• CPC Class Codes: C01B 2203/0883 by indirect heat exchange
• CPC Class Codes: C01B 2203/141 At least two reforming, decomposition or partial oxidation steps in parallel
• CPC Class Codes: C01B 2203/142 At least two reforming, decomposition or partial oxidation steps in series
• CPC Class Codes: C01B 2203/82 Several process steps of C01B2203/02 - C01B2203/08 integrated into a single apparatus
• CPC Class Codes: C01B 3/025 Preparation or purification of gas mixtures for ammonia synthesis
• CPC Class Codes: C01B 3/382 Multi-step processes
• CPC Class Codes: C01B 3/386 Catalytic partial combustion
• CPC Class Codes: Y02P 20/129 Energy recovery, e.g. by cogeneration, H2recovery or pressure recovery turbines

Abstract

Ammonia synthesis gas is produced by reaction of steam, an oxidant, and a major portion of fresh hydrocarbon feed in an exothermic catalytic reforming zone to a first reformed gas having very low methane content. The balance of the fresh feed is reacted with steam in an endothermic catalytic reforming zone to a second reformed gas having a low methane content. The first and second reformed gases are combined and passed in indirect heat exchange with reactants in the endothermic reforming zone to provide all of the heat required therein and are then recovered as raw ammonia synthesis gas.

Claims

1. A method for producing a raw ammonia synthesis gas from a fresh hydrocarbon feed which consists of:

(a) forming a first mixed feed comprising steam, a major portion of the fresh hydrocarbon feed, and an oxidant selected from the group consisting of air and oxygen-enriched air, introducing the first mixed feed to an exothermic catalytic steam reforming zone wherein there is produced a first reformed gas containing less than 1.0 volume percent, dry basis, residual hydrocarbon, and withdrawing the first reformed gas therefrom;

(b) forming a second mixed feed comprising steam and a remaining minor portion of the fresh hydrocarbon feed, introducing the second mixed feed to an endothermic catalytic steam reforming zone wherein there is produced a second reformed gas containing less than 4.0 volume percent, dry basis, residual hydrocarbon, and withdrawing the second reformed gas therefrom;

(c) combining the first and second reformed gases and cooling the combined first and second reformed gases by passing the combined gases in indirect heat exchange with the second mixed feed within the endothermic catalytic steam reforming zone whereby all of the heat required for the endothermic catalytic steam reforming of the second mixed feed therein is provided; and

(d) withdrawing and recovering the resulting cooled combined gases as raw ammonia synthesis gas product.

2. The method of claim 1 wherein the major portion of the fresh hydrocarbon feed is between 55 and 85 volume percent of the fresh hydrocarbon feed.

3. The method of claim 2 wherein the fresh hydrocarbon feed is preheated to a temperature between 450°

and 650°

C.

4. The method of claim 3 wherein the fresh hydrocarbon feed is preheated by indirect heat exchange with the raw ammonia synthesis gas.

5. The method of either claim 1 or claim 3 wherein the oxidant is air preheated to a temperature between 480°

and 720°

C. the steam to C₁ ratio of the first mixed feed is between 1.5 and 3.5, and the steam to C₁ ratio of the second mixed feed is between 4.0 and 5.0.

6. The method of either claim 1 or claim 3 wherein the oxidant is oxygen-enriched air preheated to a temperature between 480°

and 720°

, the steam to C₁ ratio of the first mixed feed is between 2.5 and 4.5, and the steam to C₁ ratio of the second mixed feed is between 4.0 and 5.0.