BLUE HYDROGEN PROCESS AND PLANT

Abstract

A plant and process for producing a hydrogen rich gas are provided, said process comprising the steps of: steam reforming a hydrocarbon feed into a synthesis gas; shifting the synthesis gas and conducting the shifted gas to a hydrogen purification unit, subjecting CO.sub.2-rich off-gas from the hydrogen purification unit to a carbon dioxide removal and recycling CO.sub.2-depleted off-gas rich in hydrogen to the process.

Claims

1. A plant for producing a hydrogen product from a hydrocarbon feed, said plant comprising: a reforming unit, said reforming unit being arranged to receive a hydrocarbon feed and convert it to a stream of syngas; a shift section arranged to receive a stream of syngas from the steam reforming unit and shift it, thereby providing a shifted syngas stream; a hydrogen purification unit, arranged to receive said shifted syngas stream and separate it into a high-purity H.sub.2 stream as said hydrogen product, and CO.sub.2-rich off-gas stream; a CO.sub.2-removal section for removal of CO.sub.2 from the CO.sub.2-rich off-gas stream into a CO.sub.2-product stream and a CO.sub.2-depleted off-gas stream, and wherein said plant is arranged for recycling said CO.sub.2-depleted off-gas stream or a portion thereof, at least to the feed side of the reforming unit; wherein the plant further comprises at least one fired heater arranged to pre-heat said hydrocarbon feed prior to it being fed to the reforming unit, and wherein said plant is arranged to feed at least a part of the CO.sub.2-rich off-gas stream from said hydrogen purification unit, or at least part of said CO.sub.2-depleted off-gas stream as fuel for said fired heater.

2. The plant according to claim 1, wherein: said shift section comprises a high or medium temperature shift unit.

3. The plant according to claim 1, wherein the reforming unit is: an autothermal reformer; a partial oxidation reformer; a convection heated reformer; a steam methane reformer; or combinations thereof.

4. The plant according to claim 1, wherein said plant is arranged to directly provide said shifted syngas stream to said hydrogen purification unit.

5. The plant according to claim 1, wherein the CO.sub.2 removal section is selected from: an amine wash unit, or a CO.sub.2 membrane, CO.sub.2-PSA, or a cryogenic separation unit.

6. The plant according to claim 1, wherein said plant-{100} further comprises one prereformer 140 arranged upstream the reforming, said prereformer unit being arranged to pre-reform said hydrocarbon feed prior to it being fed to the reforming unit and wherein said plant is arranged to feed at least a part of the CO.sub.2-depleted off-gas stream to the feed side of the prereformer unit; and/or said plant is arranged to feed at least a part of the CO.sub.2-depleted off-gas stream to the feed side of the shift section; and/or said plant is arranged to feed at least a part of said CO.sub.2-depleted off-gas stream to the feed side of the hydrogen purification unit.

7. The plant according to claim 1, further comprising: a compressor i.e. CO.sub.2-rich off-gas recycle compressor arranged for compressing said CO.sub.2-rich off-gas stream, said compressor being adapted upstream said CO.sub.2 removal section, and optionally a compressor being adapted downstream said CO.sub.2 removal section, for recycling said CO.sub.2-depleted-gas stream or a portion thereof, to the feed side of the reforming unit, and/or to the feed side of the shift section, and/or to the feed side of the prereformer unit, and/or to the feed side of the hydrogen purification unit.

8. The plant according to any claim 6, wherein the reforming unit is an ATR with said one prereformer unit arranged upstream.

9. The plant according to claim 1, wherein the hydrogen purification unit is selected from a pressure swing adsorption unit, a hydrogen membrane or a cryogenic separation unit.

10. The plant according to claim 1, wherein the plant is arranged to directly recycle said CO.sub.2-depleted off-gas stream or a portion thereof to at least the feed side of the reforming unit.

11. A process for producing a hydrogen product from a hydrocarbon feed, said process comprising the steps of: providing a plant according to any one of the preceding claims; supplying a hydrocarbon feed to the reforming unit and converting it to a stream of syngas; supplying a stream of syngas from the reforming unit to the shift section, and shifting it in a shift step, thereby providing a shifted syngas stream; supplying the shifted gas stream from the shift section to a hydrogen purification unit, and separating it into a high-purity H.sub.2 stream as said hydrogen product and a CO.sub.2-rich off-gas stream; and the process further comprising: optionally providing a step for compressing said CO.sub.2-rich off-gas stream i.e. a CO.sub.2-rich off-gas compression step; and a CO.sub.2-removal step in CO.sub.2-removal section, thereby providing a step for removing CO.sub.2 from the thus optionally compressed CO.sub.2-rich off-gas stream into a CO.sub.2-rich off-gas stream as CO.sub.2-product stream and a CO.sub.2-depleted off-gas stream, said optional step for compressing said CO.sub.2-rich off-gas stream being conducted prior to said CO.sub.2 removal section, and feeding said CO.sub.2-depleted off-gas stream or a portion thereof, optionally via a further compressing step, to the feed side of the reforming unit, and/or feed side of the shift section, and/or feed side of the hydrogen purification unit, and/or the feed side of optional prereformer unit arranged upstream said reforming unit, and/or as fuel for at least one fired heater arranged to pre-heat said hydrocarbon feed prior to it being fed to the reforming unit.

Description

BRIEF DESCRIPTION OF THE FIGURE

[0119] The sole figure (FIG. 1) illustrates a layout of an ATR-based hydrogen process and plant in accordance with an embodiment of the invention.

DETAILED DESCRIPTION

[0120] FIG. 1 shows a plant 100 in which a hydrocarbon feed 1, i.e. main hydrocarbon feed 1, such as natural gas, is passed to a reforming section comprising a pre-reforming unit 140 and a reforming unit here illustrated as an autothermal reformer 110. The reforming section may also include a hydrogenator and sulfur absorber unit (not shown) upstream the pre-reforming unit 140. The hydrocarbon steam 1 is mixed with steam 13. The resulting hydrocarbon feed 2 is fed to ATR 110, as so is oxygen 15 and steam 13. The oxygen stream 15 is produced by means of an air separation unit (ASU) 145, to which air 14 is fed. In the ATR 110, the hydrocarbon feed 2 is converted to a stream of syngas 3, which is then passed to a shift section 115, 150.

[0121] The shift section comprises for instance a high temperature shift (HTS) unit 115 where additional or extra steam 13 also may be added upstream. Additional shift units, such as a low temperature shift (LTS) unit 150 may also be included in the shift section. It would be understood that the shift section may include any of HTS, MTS and LTS, or combinations thereof. Additional or extra steam 13 may also be added downstream the HTS unit 115 but upstream the low temperature shift unit 150. From the shift section, a shifted gas stream 5 is then fed, e.g. directly fed, to a hydrogen purification unit 125, e.g. a PSA-unit, from which a high-purity H.sub.2 stream as hydrogen product 8 is produced, as well as a CO.sub.2-rich off-gas stream 9. This CO.sub.2-rich off-gas recycle stream 9 is conducted via a recycle compressor (not shown), to CO.sub.2-removal section 180, from which CO.sub.2-product stream 11 is generated, as well as a CO.sub.2-depleted off-gas stream 17, 17, 17. The plant 100 is arranged for recycling, e.g. directly recycling, the CO.sub.2-depleted off-gas stream or a portion thereof 17, 17, 17 to the feed side of the prereformer 140, or to the feed side of the reforming unit, here ATR 110, or to the shift section (not shown). The plant 100 further comprises at least one fired heater (not shown) arranged to pre-heat the hydrocarbon feed 1, 2 prior to it being fed to pre-reforming unit 140 or reforming unit 110, and the plant (100) is arranged to feed, e.g. directly feed, at least a part of the CO.sub.2-rich off-gas stream 9 from said hydrogen purification unit 125, or at least part of said CO.sub.2-depleted off-gas stream 17, 17, 17 as fuel for the fired heater.

EXAMPLE

[0122] In a process and plant 100 for removing carbon dioxide from a CO.sub.2 rich syngas 5, CO.sub.2-depleted off-gas 17 is generated after removal of CO.sub.2 as CO.sub.2-product stream 11 in CO.sub.2-removal section 180. The composition of the CO.sub.2-depleted off-gas may be as follows: hydrogen 85 mol %, methane 7 mol %, CO 7 mol %, nitrogen+argon 1 mol %. The CO.sub.2-depleted off-gas 17 is recycled back directly to the reforming unit 110, here specifically an exemplified as an ATR, and further with an upstream prereformer unit 140. This results in more reforming of methane into hydrogen as well as shifting of CO into CO.sub.2 in shifting units 115, 150. The benefits of this include reduction of hydrocarbon feed (e.g. natural gas) consumption for the same required hydrogen production while increasing the CO.sub.2 capture and hence reducing the CO.sub.2 emission. A part of the CO.sub.2-depleted off-gas is also used as fuel to a fired heater. This results in low carbon emission from the flue gas generated in the fired heater.

[0123] 10 Furthermore, the power consumption in a compressor i.e. CO.sub.2-rich off-gas recycle compressor (not shown in the appended figure) arranged for compressing said CO.sub.2-rich off-gas stream 9, is reduced by adding the CO.sub.2-depleted off-gas back to reforming unit 110, here the ATR.