CO-PRODUCTION OF METHANOL AND AMMONIA

• US 20100133472A1
• Filed: 11/25/2009
• Published: 06/03/2010
• Est. Priority Date: 11/28/2008
• Status: Active Grant

• Current Assignee: Topsoe
• Original Assignee: Haldor Topsã¸E A/S (Haldor Topsã¸E Holding A/S)
• Inventors: HAN, PAT A.
• Granted Patent: US 8,303,923 B2
• Time in Patent Office: Days
• US Class Current: 252/372
• CPC Class Codes: C01B 2203/0233 the reforming step being a steam reforming step
• CPC Class Codes: C01B 2203/025 containing a partial oxidation step
• CPC Class Codes: C01B 2203/061 Methanol production
• CPC Class Codes: C01B 2203/068 Ammonia synthesis
• CPC Class Codes: C01B 2203/1241 Natural gas or methane
• CPC Class Codes: C01B 3/382 Multi-step processes
• CPC Class Codes: C01C 1/0405 from N2 and H2 in presence of a catalyst
• CPC Class Codes: C01C 1/0488 Processes integrated with preparations of other compounds, e.g. methanol, urea or with processes for power generation
• CPC Class Codes: C07C 29/1518 one step being the formation of initial mixture of carbon oxides and hydrogen for synthesis
• CPC Class Codes: C07C 31/04 Methanol
• CPC Class Codes: Y02P 20/52 using catalysts, e.g. selective catalysts

Abstract

Process for the co-production of methanol and ammonia from a hydrocarbon feed without venting to the atmosphere carbon dioxide captured from the methanol or ammonia synthesis gas and without using expensive air separation units, water gas shift and carbon dioxide removal steps.

Claims

1. Process for co-producing methanol and ammonia from a hydrocarbon feedstock comprising the sequential steps of:

(a) producing a methanol synthesis gas containing hydrogen, carbon oxides and nitrogen by steam reforming the hydrocarbon feedstock in a primary reforming stage and subsequently in an air-blown secondary reforming stage;

(b) catalytically converting the carbon oxides and hydrogen of the methanol synthesis gas in a once-through methanol synthesis stage and withdrawing an effluent containing methanol and a gas effluent containing nitrogen, hydrogen and unconverted carbon oxides;

(c) producing an ammonia synthesis gas without the use of water gas shift and without the use of carbon dioxide removal by removing the unconverted carbon oxides of the gas effluent of step (b) in a catalytic methanation stage and withdrawing an ammonia synthesis gas having a H₂;

N₂ molar ratio of 3;

1;

(d) catalytically converting the nitrogen and hydrogen of the ammonia synthesis gas in an ammonia synthesis stage and withdrawing an effluent containing ammonia and an off-gas stream containing hydrogen, nitrogen and methane.

2. Process according to claim 1 wherein the hydrocarbon feedstock is natural gas or substitute natural gas (SNG).

3. Process according to claim 1 wherein the methanol synthesis stage in step (b) is conducted by passing the synthesis gas through one boiling water reactor and subsequently through an adiabatic fixed bed reactor, or by passing the synthesis gas through a series of boiling water reactors and subsequently through an adiabatic fixed bed reactor.

4. Process according to claim 3 wherein the boiling water reactor is in the form of a single reactor of the condensing-methanol type which comprises within a common shell a fixed bed of methanol catalyst particles and cooling means adapted to indirectly cooling the methanol synthesis gas with a cooling agent.

5. Process according to claim 3 further comprising cooling the synthesis gas withdrawn from each methanol reactor to condense methanol and passing the gas through a separator, withdrawing a bottom fraction from the separator containing the raw methanol, withdrawing an overhead fraction containing synthesis gas which is passed to the subsequent methanol reactor, and forming a single liquid effluent containing methanol by combining the bottom fractions of the separators of each reactor containing the raw methanol.

6. Process according to claim 1 further comprising withdrawing a hydrogen-rich stream from the ammonia synthesis stage and adding this stream to step (b).

7. Process according to claim 1 in which the off-gas stream containing hydrogen, nitrogen and methane of step (d) is returned to step (a).