A Process for Co-Production of Ammonia and Methanol

Abstract

In a process for co-production of ammonia and methanol, the outlet stream from the reformer is split into two parts, one of which is subjected to shift, carbon dioxide removal, methanation, compression and ammonia synthesis, while the other part is compressed and fed to a once-through methanol synthesis section. Methanol is withdrawn from the methanol synthesis section, and the remaining effluent from said section is divided into two streams comprising hydrogen, of which one is fed to the shift section, while the other is recycled to the desulfurization unit. This way a favourable co-production method is obtained because recycle hydrogen for the desulfurization is provided, and furthermore a compression step is avoided.

Claims

1. A process for co-production of ammonia and methanol comprising desulfurization of a hydrocarbon feed gas in the presence of hydrogen, addition of steam to the desulfurized natural gas followed by reforming, shift, carbon dioxide removal and methanation, wherein the outlet stream from the reformer is split into two parts, one of which is subjected to shift, carbon dioxide removal, methanation, compression and ammonia synthesis, while the other part is compressed and fed to a once-through methanol synthesis section, methanol is withdrawn from the methanol synthesis section, and the remaining effluent from said section is divided into two streams comprising hydrogen, one of the two streams comprising hydrogen is fed to the shift section, and the other stream comprising hydrogen is recycled to the desulfurization unit.

2. The process according to claim 1, wherein the methanol synthesis section comprises one methanol synthesis reactor or two or three such reactors connected in series.

3. The process according to claim 1, wherein the part of the reformer outlet stream, which is compressed and fed to the methanol synthesis section, is compressed to 40-100 bars.

4. The process according to claim 3, wherein the part of the reformer outlet stream, which is compressed and fed to the methanol synthesis section, is compressed to around 80 bars.

5. The process according to claim 1, wherein the stream comprising hydrogen, which is transferred to the shift section, is directed to a point between the high temperature shift and the low temperature shift.

Description

EXAMPLE

[0028] A reformer outlet gas obtained by desulfurization of a hydrocarbon feed gas in the presence of hydrogen has the following composition (dry gas) in percent:

TABLE-US-00001 Ar 0.22 CH.sub.4 0.56 CO 12.76 CO.sub.2 7.81 H.sub.2 59.73 N.sub.2 18.92

[0029] The flow of this dry gas is 22996 Nm.sup.3/h.

[0030] The gas is split into two streams, and one of these (43.5%) is passed through the methanol section, where it is compressed to a pressure above 80 bar and converted to 18950 kg/h methanol and 56763 Nm3/h of a hydrogen-rich gas with the following composition (dry gas) in percent:

TABLE-US-00002 Ar 0.38 CH.sub.3OH 0.05 CH.sub.4 0.97 CO 3.43 CO.sub.2 8.38 H.sub.2 53.58 N.sub.2 33.31

[0031] For the desulfurization of the hydrocarbon feed gas in the presence of hydrogen, 3275 Nm.sup.3/h of the dry hydrogen-rich gas with a pressure above 45 barg has to be recycled to the desulfurization section.

[0032] The ammonia production from the combined reformer and methanol section effluent is 60854 kg/h.