A PROCESS FOR GENERATION OF SNTHESIS GAS BY FLUE GAS RECYCLE

Abstract

A novel process for synthesis gas generation comprises treating a hydrocarbon feed in a primary reformer (PR), compressing at least part of the flue gas from the primary reformer in a compressor (C1), and feeding the compressed flue gas to a secondary reformer (SR) together with the primary reformer effluent. In the process, enriched air (EA) is added either to the primary reformer, to the secondary reformer or both. The process is especially suited for co-production of ammonia and methanol or for production of either ammonia or methanol. The total CO.sub.2 emission is lowered considerably by using the process of the invention.

Claims

1. A process for synthesis gas generation, said process comprising the following steps: treating a hydrocarbon feed in a primary reformer (PR), compressing at least part of the flue gas from the primary reformer in a compressor (C1), and feeding the compressed flue gas to a secondary reformer (SR) together with the primary reformer effluent, wherein enriched air (EA) is added either to the primary reformer or to the secondary reformer or both.

2. The process according to claim 1, further including the following steps: passing the secondary reformer effluent through a shift conversion section, removing CO.sub.2 from the shift conversion effluent, performing a synthesis gas clean-up of the CO.sub.2 removal section effluent, and compressing the resulting stream in a compressor (C3) and transferring it to an ammonium loop (AL) for ammonia synthesis, wherein the amount of CO.sub.2 removed in the CO.sub.2 removal step is sufficient to convert all the ammonia produced in the ammonium synthesis to urea.

3. The process according to claim 1, further including the following steps: optionally passing the secondary reformer effluent or part thereof through a shift conversion section, optionally removing all the CO.sub.2 or part thereof from the shift converter effluent, compressing the CO.sub.2 removal section effluent in a compressor C2 and optionally passing part or all of it through a methanol synthesis section (M), performing a synthesis gas clean-up of the methanol synthesis section effluent, optionally compressing the resulting stream further in the compressor C3, and transferring the resulting stream to an ammonium loop (AL) for ammonia synthesis, wherein the amount of CO.sub.2 removed in the CO.sub.2 removal step is sufficient to convert all the ammonia produced in the ammonium synthesis or part thereof to urea.

4. The process according to claim 1, further including the following steps: feeding the secondary reformer effluent directly to the compressor (C2), and passing the effluent from the compressor C2 through a methanol synthesis section, wherein the module M in the synthesis gas is in the range from 2.0 to 3.0, preferably in the range from 2.0 to 2.5 and most preferably in the range from 2.0 to 2.2.

5. The process according to claim 1, wherein the enriched air is obtained by using an air separation unit (ASU).

6. The process according to claim 5, wherein the ASU is based on membrane separation technology.

7. The process according to claim 1, wherein the hydrocarbon feed is a mixture of steam and optionally pre-reformed hydrocarbons, said hydrocarbons originating from any hydrocarbon source that can be used for reformer feeding, such as natural gas (NG).

Description

EXAMPLE

[0037] The flue gas recycle method according to the invention was compared to two prior art methods without flue gas recycle, one with combined ammonia and methanol co-production and one with production of ammonia only.

[0038] In the following table 1, the process according to the invention is compared to both prior art combined ammonia and methanol production and prior art ammonia production only. In table 2, the process according to the invention is compared to a prior art urea production with a lean gas. In the latter case, the process according to the invention is used for ammonia production only.

TABLE-US-00001 TABLE 1 prior art NH.sub.3 prior art NH.sub.3 and CH.sub.3OH production process of co-production only invention Total HC 81255 76276 72738 (feed + fuel), Nm.sup.3/h Flue gas 0 0 11472 recirc., Nm.sup.3/h EA, 0 0 38995 Nm.sup.3/h NH.sub.3 prod., 1492 2050 1910 MTPD CH.sub.3OH prod., 667 0 301 MTPD Total CO.sub.2 57.4 50.8 22.5 emission, MT/h

TABLE-US-00002 TABLE 2 process of the in- prior art urea vention, NH.sub.3 prod. production only Total HC (feed + 76256 72738 fuel), Nm.sup.3/h Flue gas recirc., 0 11472 Nm.sup.3/h EA, Nm.sup.3/h 0 38995 NH.sub.3 prod., MTPD 2050 1910 NH3 to storage, 99 0 MTPD urea prod., MTPD 3443 3368 Total CO.sub.2 50.8 22.5 emission, MT/h

[0039] The CO.sub.2 emission is from the reformer stack only. Even if it is postulated that part of this can be used for urea production, the CO.sub.2 emission will still be around 45 MT/h for prior art production, i.e. twice as much as for production according to the invention.

[0040] Thus it appears from the comparisons in tables 1 and 2 that the total CO.sub.2 emission is lowered considerably by using the process of the invention.