Process for the co-production of methanol and ammonia in parallel

Abstract

A process for co-production of methanol and ammonia in parallel based on autothermal reforming with oxygen enriched air from electrolysis of water and separation of air and preparation of ammonia with hydrogen from the electrolysis of water and nitrogen from the separation of air.

Claims

1. Process for the co-production of methanol and ammonia in parallel, comprising the steps of: (a) providing a hydrocarbon feed stock; (b) preparing a separate hydrogen stream and a separate oxygen stream by electrolysis of water; (c) preparing a separate oxygen stream and a separate nitrogen stream by separation of air; (d) introducing at least part of the separate oxygen stream from step (b) and at least part of the separate oxygen from step (c) into an autothermal reformer; (e) in the autothermal reformer, autothermal reforming the hydrocarbon feed stock from step (a) to a methanol synthesis gas comprising hydrogen and carbon oxides; (f) converting the methanol synthesis gas to raw methanol in a methanol synthesis stage; and in parallel (g) introducing the at least part of the separate hydrogen stream from step (b) and the separate nitrogen stream from step (c) into an ammonia synthesis loop, and converting the nitrogen and hydrogen stream to ammonia.

2. Process of claim 1, wherein module (M=(H.sub.2−CO.sub.2)/(CO+CO.sub.2)) of the methanol synthesis gas from step (e) is adjusted to a value of between 1.9 and 2.2 by adding a part of the separate hydrogen stream from step (b) into the methanol synthesis gas from step (e).

3. Process of claim 1, wherein the separate hydrogen stream from step (b) and the separate nitrogen stream from step (c) are introduced into the ammonia synthesis loop in amounts to provide a molar ratio of the hydrogen to the nitrogen of 2.7-3.3.

4. Process of claim 1, wherein the electrolysis of water and/or the separation of air is powered by renewable energy.

Description

(1) The present invention is based on a combination of autothermal steam reforming using oxygen from the electrolysis of water and from an air separation (ASU) in the partial oxidation of hydrocarbon feed stock in the autothermal reforming process. Hydrogen from the electrolysis and nitrogen from the ASU in a parallel process used for the preparation ammonia synthesis gas.

(2) Thus, this invention is a process for the co-production of methanol and ammonia in parallel comprising the steps of

(3) (a) providing a hydrocarbon feed stock;

(4) (b) preparing a separate hydrogen stream and a separate oxygen stream by electrolysis of water;

(5) (c) preparing a separate oxygen stream and a separate nitrogen stream by separation of air;

(6) (d) introducing at least part of the separate oxygen stream from step (b) and at least part of the separate oxygen from step (c) into an autothermal reformer;

(7) (e) in the autothermal reformer autothermal reforming the hydrocarbon feed stock from step (a) to a methanol synthesis gas comprising hydrogen, carbon oxides;

(8) (f) converting the methanol synthesis gas to raw methanol in a methanol synthesis stage; and in parallel

(9) (g) introducing the at least part of the separate hydrogen stream from step (b) and the separate nitrogen stream from step (c) into an ammonia synthesis loop and converting the nitrogen and hydrogen stream to ammonia.

(10) Methanol synthesis gas preferably has a composition corresponding to a so-called module (M=(H2−CO2)/(CO+CO2)) of 1.9-2.2 or more preferably slightly above 2 (eg. 2.0-2.1). Depending on the composition of the hydrocarbon feed stock, the module in the methanol synthesis gas from the autothermal reforming step can be lower than preferred value. In such circumstances a part of the hydrogen from the water electrolysis can be added to the synthesis gas in order to adjust the module to the preferred value.

(11) Thus, in an embodiment of the invention, module (M=(H2−CO2)/(CO+CO2)) of the methanol synthesis gas from step (e) is adjusted to a value of between 1.9 and 2.2 by adding a part of the separate hydrogen stream from step (b) into the methanol synthesis gas from step (e).

(12) In further an embodiment all or a part of the hydrogen from the electrolysis is introduced together with nitrogen from the air separation unit into the suction section of a makeup gas compressor in the ammonia loop amounts to provide a molar ratio of the hydrogen to the nitrogen of 2.7-3.3 in the ammonia synthesis gas as prepared in step (g).

(13) The advantages of the process according to the invention are essentially no or only a minor loss of energy in the water electrolysis and the air separation together with a reduced size of the ASU due to a part of the oxygen used in the autothermal reforming is produced by the water electrolysis.

(14) In a preferred embodiment of the invention, the electrolysis of water and/or the separation of air is powered by renewable energy resulting in a further advantage of reduced CO.sub.2 emission.