Low carbon hydrogen fuel

Abstract

A plant and process for producing a hydrogen rich gas are provided, said process comprising the steps of: reforming a hydrocarbon feed in an autothermal reformer thereby obtaining a syngas; shifting said syngas in a shift configuration including a high temperature shift step; removal of CO.sub.2 in a CO.sub.2-removal section by amine wash thereby forming a hydrogen rich stream, a portion of which is used as low carbon hydrogen fuel, as well as a CO.sub.2-rich gas and a high-pressure flash gas stream. The high-pressure flash gas stream is advantageously integrated into the plant and process for further improving carbon capture.

Claims

1. A plant for producing a H.sub.2-rich stream from a hydrocarbon feed (1, 2), said plant comprising: an autothermal reformer, said ATR being arranged to receive a hydrocarbon feed and convert it to a stream of syngas; a shift section, said shift section comprising one or more water gas shift (WGS) units, said one or more WGS units arranged to receive the stream of syngas from the ATR and shift it in one or more WGS steps, thereby providing a shifted syngas stream; a CO.sub.2 removal section, arranged to receive the shifted syngas stream from said shift section and separate a CO.sub.2-rich stream from said shifted syngas stream, thereby providing said H.sub.2-rich stream and also a high-pressure flash gas stream; one or more fired heaters, arranged to pre-heat said hydrocarbon feed (1 prior to it being fed to the ATR; wherein said plant is arranged to feed at least a part of said H.sub.2-rich stream as hydrogen fuel for at least said one or more fired heaters; wherein said plant is absent of a hydrogen purification unit such as a pressure swing adsorption (PSA) unit, a hydrogen membrane or a cryogenic separation unit; and the CO.sub.2-removal section is an amine wash unit which comprises a CO.sub.2-absorber and a CO.sub.2-stripper as well as a high-pressure flash drum and low-pressure flash drum, thereby separating said CO.sub.2-rich stream, said H.sub.2-rich stream and said high pressure flash gas stream; and the plant is arranged to feed at least part of said high-pressure flash gas stream to a unit or a stream of the plant.

2. The plant according to claim 1, wherein p1 a) the plant is arranged to feed at least a part of said high-pressure flash gas stream as fuel for said at least one fired heaters; and/or b) the plant is arranged to recycle at least part of said high-pressure flash gas stream to said CO.sub.2-absorber of the amine wash unit; and/or c) the plant is arranged to mix at least part of said high-pressure flash gas stream with said H.sub.2-rich stream.

3. The plant according to claim 1, wherein the plant is arranged to combine a) and c) by having arranged therein a mixing point for mixing at least part of the H.sub.2-rich stream as hydrogen fuel, with said high-pressure flash gas stream upstream said one or more fired heaters.

4. The plant (100) according to claim 1, wherein: in a) the plant is arranged to recycle the entire high-pressure flash gas stream as fuel for said at least one fire heaters; or in b) the plant is arranged to recycle the entire high-pressure flash gas stream to said CO.sub.2-absorber; or in c) the plant is arranged to mix the entire high-pressure flash gas stream with said H.sub.2-rich stream.

5. The plant according to claim 1, said plant being arranged to provide an inlet temperature of said hydrocarbon feed to the ATR of below 600° C.

6. The plant according to claim 1, wherein said plant is arranged to provide a steam-to-carbon ratio in the ATR of 2.6-0.1, and/or wherein the ATR is arranged to operate at 20-60 barg.

7. The plant according to claim 6, wherein said plant is arranged to provide a steam-to-carbon ratio in the ATR of 0.4 or higher, yet said steam-to-carbon ratio being not greater than 2.0, and/or wherein the ATR is arranged to operate at 20-30 barg.

8. The plant according to claim 1, wherein the at least one or more WGS units comprise: a high temperature shift unit (HTS-unit); and a medium temperature shift (MTS-unit) and/or a low temperature shift unit (LTS-unit).

9. The plant according to claim 8, further comprising a steam superheater which is arranged for being heated by shifted syngas.

10. The plant according to claim 1, further comprising one or more prereformer units arranged upstream the ATR, said one or more prereformer units being arranged to pre-reform said hydrocarbon feed prior to it being fed to the ATR.

11. The plant according to claim 1, wherein said plant is absent of a prereformer unit.

12. The plant according to claim 1, said plant further comprising a hydrogenator unit and a sulfur absorption unit which are arranged upstream said one or more pre-reformer units or upstream said ATR, and said plant being arranged for mixing a portion of the H.sub.2-rich stream with the hydrocarbon feed before being fed to the feed side of the hydrogenator unit.

13. A process for producing a H.sub.2-rich stream from a hydrocarbon feed, said process comprising the steps of: providing a plant according to claim 1; supplying a hydrocarbon feed to the ATR, and converting it to a stream of syngas; withdrawing a stream of syngas from the ATR and supplying it to the shift section, shifting the syngas in a HTS-step and optionally also in a MTS and/or LTS-shift step, thereby providing a shifted syngas stream; supplying the shifted gas stream from the shift section to the CO.sub.2 removal section, said CO.sub.2-removal section being an amine wash unit which comprises a CO.sub.2-absorber and a CO.sub.2-stripper as well as a high-pressure flash drum and low-pressure flash drum, and separating a CO.sub.2-rich stream from said shifted syngas stream, thereby providing a a H.sub.2-rich stream and also a high-pressure flash gas stream; omitting feeding at least a part of said H.sub.2-rich stream to a hydrogen purification unit such as a pressure swing adsorption (PSA) unit, a hydrogen membrane or a cryogenic separation unit; feeding at least a part of said H.sub.2-rich stream as hydrogen fuel to the at least one or more fired heaters; the process further comprising: a) feeding at least a part of said high-pressure flash gas stream as fuel to said one or more fired heaters; and/or b) recycling at least part of said high-pressure flash gas stream to said CO.sub.2-absorber of the amine wash unit; and/or c) mixing at least part of said high-pressure flash gas stream with said H.sub.2 rich stream.

14. The process of claim 13, comprising: mixing said H.sub.2-rich stream, with said high-pressure flash gas stream upstream said one or more fired heaters, suitably by mixing the high-pressure flash gas stream with the H.sub.2-rich stream prior to feeding to the one or more fired heaters.

15. The process of claim 13, comprising: recycling the entire high-pressure flash gas stream as fuel for said at least one fire heaters; or recycling the entire high-pressure flash gas stream to said CO.sub.2-absorber; or mixing the entire high-pressure flash gas stream with said H.sub.2-rich stream.

16. The process of any of claim 13, wherein the steam-to-carbon ratio in the ATR is 2.6-0.1; and/or wherein the pressure in the ATR (110) is 20-60 barg.

17. The process of claim 16, wherein the steam-to-carbon ratio in the ATR is 0.4 or higher, yet said steam-to-carbon ratio being not greater than 2.0; and/or wherein the pressure in the ATR is is 20-30 barg.

Description

BRIEF DESCRIPTION OF THE FIGURES

[0137] FIG. 1 illustrates a layout of an ATR-based hydrogen process and plant.

[0138] FIG. 2 illustrates a layout of the ATR-based hydrogen process and plant of FIG. 1 with integration of high-pressure flash gas stream from CO.sub.2-removal section into the process, in accordance with embodiments of the invention.

DETAILED DESCRIPTION

[0139] With reference to FIG. 1, there is shown a plant/process 100 in which a hydrocarbon feed 1 such as natural gas is passed to a reforming section comprising a pre-reforming unit 140 and ATR 110. The reforming section may also include a hydrogenator and sulfur absorber unit (not shown) upstream the pre-reforming unit 140. Prior to entering the hydrogenator, the hydrocarbon steam 1 is mixed with a hydrogen-recycle stream 8′″diverted from a H.sub.2-rich stream 8 produced in downstream CO.sub.2-removal section 170. Prior to entering the pre-reforming unit 140, the hydrocarbon feed 1 is also mixed with steam 13 and the resulting prereformed hydrocarbon feed 2 is fed to the ATR 110, as so is an oxidant stream formed by mixing oxygen 15 and steam 13. Steam may also be added separately, as also shown in the figure. The oxygen stream 15 is produced by an air separation unit (ASU) 145 to which air 14 is fed. In the ATR 110, the hydrocarbon feed 2 is converted into a stream of syngas 3, which is withdrawn from the ATR 110 and passed to a shift section. The hydrocarbon feed 2 enters the ATR at 650° C. and the temperature of the oxygen is around 253° C. The steam/carbon ratio of the the ATR is preferably 0.4 or higher, such as 0.6 or higher, or such as 0.8 or higher, yet no greater than 2.0. Preferably also, the pressure in the ATR 110 is 24-28 barg. This syngas exits the ATR at about 1050° C. through a refractory lined outlet section and transfer line to waste heat boilers (not shown) in the syngas i.e. process gas cooling section.

[0140] 5 The shift section comprises a high temperature shift (HTS) unit 115 where additional or extra steam 13′ also may be added upstream, thereby a steam-to-carbon ratio in the shift section of preferably about 1.0 or higher is used. Additional shift units, such as a low temperature shift (LTS) unit 150 may also be included in the shift section. Additional or extra steam may also be added downstream the HTS unit 115 yet upstream the LTS unit 150 for increasing the above steam-to-carbon ratio. From the shift section, a shifted gas stream 5 enriched in hydrogen is produced which is then fed to a CO.sub.2-removal section 170. The CO.sub.2-removal section 170 is suitably an amine wash unit which comprises a CO.sub.2-absorber and a CO.sub.2-stripper, which separates a CO.sub.2-rich stream 10 containing more than 99 vol. % CO.sub.2 and a H.sub.2-rich stream 8 containing 98 vol. % hydrogen or higher. The CO.sub.2-removal section 170 also generates a high-pressure flash gas stream 12. The plant 100 is absent of a hydrogen purification unit, such as a PSA.

[0141] The H.sub.2-rich stream 8 is divided into a H.sub.2-product 8′ for supplying to end customers such as refineries, a low carbon hydrogen fuel 8″ which is used in fired heater unit(s) 135, and a hydrogen-recycle 8— for mixing with the hydrocarbon feed 1. The fired heater 135 provides for the indirect heating of hydrocarbon feed 1 and hydrocarbon feed 2.

[0142] Now with reference to FIG. 2, embodiments integrating the use of the high-pressure flash gas stream 12, are shown. The CO.sub.2-removal section 170 comprises a CO.sub.2-stripper 170′, low and high-pressure drums 170″ and CO.sub.2-absorber 170′″. In an embodiment, at least a part of said high-pressure flash gas stream 12 is fed as fuel 12′ to the fired heater 135. In another embodiment, at least part of the high-pressure (HP) flash gas stream 12 is recycled as stream 12″ to the CO.sub.2-absorber 170′″, i.e. as an internal HP recycle stream. While the figures show the shifted gas stream 5 entering the CO.sub.2-removal section 170 at one end thereof away from the CO.sub.2-absorber 170″, it would be understood that the shifted gas stream 5, suitably after removing its water content as a process condensate, enters the CO.sub.2-removal section 170 by being introduced to the CO.sub.2-absorber 170′″. Suitably also, the internal HP recycle stream 12″ is combined with the shifted gas stream 5 prior to being introduced to the CO.sub.2-absorber 170′″. In another embodiment, at least part of said high-pressure flash gas stream 12, as stream 12′″, is mixed with the H.sub.2-rich stream 8, prior to feeding to the fired heater 135.