CN116829498A - Syngas production from CO2 and steam for fuel synthesis - Google Patents

Abstract

This article describes a system for providing a hydrocarbon product stream. The electrolysis section provides a synthesis gas stream from a first feed containing _CO2 and a second feed containing _H2O , which is then passed to the F-T section where it is converted into a hydrocarbon product stream and a tail gas stream. The electric steam reformer section receives the off-gas stream and converts it into a second synthesis gas stream, which is then recycled upstream of the FT section. Also provided is a method of converting a first feed comprising CO ₂ and a second feed comprising H ₂ O into a first hydrocarbon product stream in a system according to the invention. The system of the present invention can be combined with the upgrading section in gas-to-liquids (GTL) equipment.

Description

Syngas production from CO2 and steam for fuel synthesis

Technical field

The present invention relates to a system for providing a hydrocarbon product stream. The system includes a Fischer-Tropsch (FT) section, an electrolysis section arranged upstream of the FT section, a first feed containing CO ₂ supplied to the electrolysis section, a second feed containing H ₂ O supplied to the electrolysis section, and The first electric steam reformer section. Also provided is a method of converting a first feed comprising CO ₂ and a second feed comprising H ₂ O into a first hydrocarbon product stream using a system according to the present invention. The system can be combined with the upgrading section in gas-to-liquids (GTL) equipment.

Background technique

Gas-to-liquids (GTL) plants for the production of synthetic hydrocarbons or fuels (e.g. diesel, kerosene, jet fuel, naphtha) from e.g. natural gas usually consist of three main sections:

1) Syngas production

2) Produce crude hydrocarbon products through Fischer-Tropsch synthesis

3) Upgrade crude products into final products

The synthesis gas used to produce hydrocarbons via Fischer-Tropsch synthesis is primarily a mixture of carbon monoxide and hydrogen. Syngas may also include other components such as _CO2 , steam, nitrogen and methane, often in trace amounts. Today, synthesis gas production is typically performed by autothermal reforming (ATR) using natural gas or similar hydrocarbonaceous feedstocks. Oxygen for ATR is typically supplied by an air separation unit (ASU). The process can be carried out with considerable carbon and energy efficiency. However, some of the feed will inevitably be converted into carbon dioxide, with negative consequences for the climate.

Significant progress is being made in developing and optimizing technologies for generating electricity from renewable energy sources (e.g., wind, solar). However, it is expected that heavy-duty transportation and aviation will require hydrocarbon-based fuels for many years to come.

In natural gas-based GTL plants with ATR, part of the FT tail gas can be recirculated to the ATR. This is done both to adjust the desired H ₂ /CO ratio of the syngas and to improve the carbon efficiency of the GTL plant. However, in equipment that takes _CO2 and _H2O as feeds and produces syngas by electrolysis, recycling of the tail gas to the electrolysis unit is not feasible. Adding tail gas to the SOEC unit may cause carbon formation in the SOEC electrolysis unit. The tail gas cannot be converted into syngas in the low-temperature electrolysis unit. Therefore, there is a need to find a way to use exhaust gases to maximize the carbon efficiency (and energy efficiency) of equipment.

One approach is to direct the off-gas to a steam reformer to produce additional syngas. However, steam reforming is an endothermic reaction that requires extensive combustion in a furnace to provide the required energy. This combustion will result in additional CO2 emissions and reduce overall carbon efficiency. In addition, the fuel required for combustion will initially be produced by electrolysis using electricity. This significantly increases the power consumption of the device.

Therefore, it is desirable to develop a technology for the production of synthetic hydrocarbons such as diesel and jet fuel that uses _CO2 as the main carbonaceous feedstock and utilizes renewable energy sources. This could reduce climate impact compared to the technologies used today. Ideally, this technology should convert the highest possible proportion of carbon dioxide in the feed into the desired end products, such as diesel and kerosene.

Related technology is described in the applicant's co-pending application EP20216617.9.

Contents of the invention

It has now surprisingly been found that utilizing an electric steam reformer to convert tail gas from the FT section into syngas reduces the overall electricity demand for syngas production and/or reduces _CO2 emissions in GTL plants. This is surprising because such electric steam reformers inherently utilize electricity.

Accordingly, in a first aspect, the invention relates to a system for providing a first hydrocarbon product stream, said system comprising:

-Fischer-Tropsch (F-T) section,

-The electrolysis section arranged upstream of the F-T section,

- a first feed containing _CO2 to the electrolysis section,

- a second feed containing H ₂ O to the electrolysis section,

-The first electric steam reformer section,

in

- the electrolysis section is arranged to provide a first synthesis gas stream from the first feed and the second feed,

- said F-T section is arranged to receive at least a first portion of said first synthesis gas stream and convert it into a first hydrocarbon product stream and a tail gas stream,

- and wherein optionally said first electric steam reformer section is arranged to receive at least a second portion of said first synthesis gas stream and convert it into a second synthesis gas stream,

- the first electric steam reformer section is arranged to receive at least a first part of the off-gas stream and convert it into a second synthesis gas stream,

And wherein the second synthesis gas flow is arranged to be preferably mixed with the first synthesis gas flow and supplied to the F-T section.

In another aspect, the present invention provides a GTL plant comprising the system described herein, the GTL plant further comprising an upgrading section arranged to receive a first hydrocarbon product stream and to provide a final product stream.

Also provided is a method of converting a first feed comprising CO ₂ and a second feed comprising H ₂ O into a first hydrocarbon product stream in a system according to the present invention.

Additional aspects and details of the invention are provided in the following description and appended claims and drawings.

Brief description of the drawings

Figures 1-2 show schematic layouts of various embodiments of systems according to the invention.

Detailed description of the invention

Unless otherwise stated, any given percentage of gas content is % by volume.

The term "synthesis gas" is used interchangeably with the term "syngas" and refers to gases containing hydrogen, carbon monoxide, carbon dioxide and small amounts of other gases (such as argon, nitrogen, methane, steam, etc.) gas.

Detailed ways

A system for providing a first hydrocarbon product stream is described.

Generally speaking, the system includes:

-Fischer-Tropsch (F-T) section,

-The electrolysis section arranged upstream of the F-T section,

- a first feed containing _CO2 to the electrolysis section,

- a second feed containing H ₂ O to the electrolysis section,

-The first electric steam reformer section.

These components of the system and their relationships are described below.

First feed containing _CO2

A first feed containing carbon dioxide is provided to the electrolysis section. Suitably, the first feed consists essentially of _CO2 . The first feed of _CO2 is suitably " _CO2 -rich", meaning that a major part of the feed is _CO2 ; i.e. more than 75%, such as more than 85%, preferably more than 90%, of the feed, More preferably more than 95%, even more preferably more than 99% is _CO2 . One source of the first feed of carbon dioxide may be one or more off-gas streams from one or more chemical plants. One source of the first feed of carbon dioxide may also be carbon dioxide captured from one or more process streams or the atmosphere. Another source of the first feed may be _CO2 captured or recovered from flue gases, for example from fired heaters, steam reformers and/or power plants. In addition to _CO2 , the first feed may contain, for example, steam, oxygen, nitrogen, oxygenates, amines, ammonia, carbon monoxide and/or hydrocarbons.

In one aspect, the first feed contains trace amounts of hydrocarbons (usually methane), preferably in an amount of less than 10%, such as less than 5%, or most preferably less than 3%, of the volume of said first feed.

Before being provided to the electrolysis section, the first feed containing carbon dioxide can be passed through a CO ₂ cleaning unit to remove impurities such as Cl (eg HCl), sulfur (eg SO ₂ , H ₂ S, COS), Si (eg silica alkane) and/or As. This ensures the protection of downstream units, especially the subsequent electrolysis section.

Second feed containing H ₂ O

A second feed comprising water (for example in the form of steam) is provided to the electrolysis section. Suitably, the second feed consists essentially of _H2O . The second feed of _H2O is suitably " _H2O -rich" meaning that a major part of the feed is _H2O ; i.e. more than 75% of the feed, such as more than 85%, preferably more than 90%, more preferably more than 95%, even more preferably more than 99% is _H2O .

One source of secondary feed of _H2O is process steam, which is typically available in industrial plants. The second feed of _H2O may also be obtained from other units, reactors or sections in the system or plant of the invention. In one embodiment, steam is provided by a waste heat boiler used to cool the effluent stream from the electrical reforming reactor.

In addition to _H2O , the second feed may, for example, contain traces of nitrogen, argon, carbon dioxide, hydrogen and/or hydrocarbons.

Third feed containing _CO2

Optionally, a third feed comprising _CO2 may be provided to the first electric steam reformer section in the system described above. Suitably, the third feed consists essentially of _CO2 . All details related to the first feed containing CO ₂ (described above) apply equally to the third feed containing CO ₂ . In a preferred system, a single feed comprising _CO2 is supplied to the system and arranged to be split into a first feed and a third feed comprising _CO2 . Feeding _CO2 to the electric steam reformer section is advantageous as this allows the high temperatures typical of this section to be exploited to produce CO from _CO2 .

In one embodiment, the third feed is part of the effluent of the electrolysis section and will therefore contain CO and _CO2 . In this configuration, _unconverted CO from the electrolysis section can be converted to CO in the electric steam reformer section at a higher yield. This flow may be provided by, for example, the first electrolysis unit or a single electrolysis unit.

In another embodiment, the third feed may comprise _H2 , and suitably be part of the effluent of the electrolysis section. This flow may be provided by, for example, a second electrolysis unit or a single electrolysis unit. _H2 may be advantageous as a co-feed when used as a reactant in the _CO2 reverse water gas shift reaction according to the reaction scheme. Additionally, _H2 helps reduce the risk of carbon formation typically associated with CO production.

Electrolysis section

The electrolysis section is arranged to provide a first synthesis gas (syngas) stream from the first feed and said second feed.

The electrolysis section may include one or more electrolysis units. A single electrolysis unit may include multiple electrolysis stacks with associated equipment. The electrolysis section may additionally include a compressor unit and/or a mixer unit as needed.

The electrolysis of steam and _CO2 proceeds via reactions (1) and (2):

H ₂ O→H ₂ + ¹ / ₂ O ₂ (1)

CO ₂ →CO+ ¹ / ₂ O ₂ (2)

The electrolytic products of reactions (1) and (2) are _H2 and CO; the main components of syngas.

In some cases it is not possible to convert all _CO2 and/or _H2O in one or more electrolysis units. Separation of the product stream can be performed downstream of the electrolysis unit, with subsequent recycling of part or all of the unconverted _CO2 and/or steam to the inlet of the electrolysis unit.

In some cases (with or without recycle), unconverted _CO2 is included in the first synthesis gas. Most of the unconverted _H2O will usually condense downstream of the electrolysis unit, leaving only a small amount of _H2O (usually less than 5%, preferably less than 2%) in the first synthesis gas.

Both of the above reactions require electricity to take place in the electrolysis unit. The electrolysis section therefore includes an electricity supply, which is preferably at least partly a renewable energy supply, such as wind energy and solar energy.

Reaction (1) can be carried out in a low-temperature electrolysis unit such as alkaline electrolysis (AEL) or polymer electrolyte electrolysis (PEM). Reaction (1) can also occur in high temperature electrolysis units such as solid oxide electrolysis (SOE) units. Reaction (2) can also occur in SOE units.

Reactions (1) and (2) can occur in separate electrolysis units with separate feeds containing steam and _CO2 respectively. In this case, the effluent streams from the steam electrolysis unit and the CO _electrolysis unit are combined to produce a synthesis gas stream. Accordingly, in this aspect, the electrolysis section comprises at least a first electrolysis unit and a second electrolysis unit, wherein the first electrolysis unit is arranged to convert a first feed comprising _CO2 into a first stream comprising CO, and wherein the second electrolysis unit The unit is arranged to convert a second feed comprising H ₂ O into a second stream comprising H ₂ , and wherein the electrolysis section is further arranged to combine the first stream comprising CO with the third stream comprising H ₂ The two streams are combined into the first synthesis gas stream.

Another possibility is that both reactions (1) and (2) occur in the same electrolysis unit with a feed containing both steam and _CO2 . Therefore, in the system according to the invention, the electrolysis section may comprise a single electrolysis unit arranged to convert said first feed and said second feed into a first synthesis gas stream, preferably wherein a first synthesis gas stream One feed and said second feed are arranged to be mixed before being fed to the electrolysis section. In other words, the first and second feeds are converted in the same "single" electrolysis unit. In this case, various other reactions may also occur:

CO+H ₂ O→CO ₂ +H ₂ (3)

3H ₂ +CO→CH ₄ +H ₂ O (4)

Regardless of the type of electrolysis unit used, complete conversion of steam and _CO2 is usually not possible. Specifically, for _CO2 conversion, the risk of carbon formation often sets a finite limit on how high a conversion rate can be achieved, otherwise the Bowden reaction may occur according to:

2CO→C+CO ₂ (5)

In the case where a single electrolysis unit is used for the electrolysis of both _H2O and _CO2 , the CO decomposition reaction also limits the allowable conversion to CO according to the following reaction:

CO+H ₂ →C+H ₂ O (6)

Carbon formation is an undesirable side reaction.

In this case, the methane (and any other hydrocarbons) produced in reaction (4) passes directly through the F-T section, and a portion of the hydrocarbons discharged from the F-T section may be included in the tail gas. The hydrocarbons are then converted in an electric steam reformer section (described in detail below). This arrangement also provides improved flexibility in the systems and methods of the present invention.

One or all electrolysis units in the electrolysis section may include solid oxide electrolysis (SOE) units. The second electrolysis unit (second feed for electrolysis of _H2O ) may be an alkaline/polymer electrolyte membrane electrolysis unit, such as an alkaline/PEM electrolysis unit. When the electrolysis of H ₂ O into H ₂ is based on liquid water, the heat of evaporation of water is saved. SOE and alkaline/PEM electrolysis units are well known in the art, especially alkaline/PEM electrolysis. For example, Applicant's WO 2013/131778 describes SOEC-CO2. One embodiment is a combination of SOEC-CO2 and alkaline/PEM electrolysis.

As stated, the electrolysis section is arranged to provide a first synthesis gas (syngas) stream from the first feed and said second feed. The first synthesis gas stream may have the following composition (by volume):

-40-70% H ₂ (dry)

-10-30% CO (dry)

-2-30% CO ₂ (dry)

-0.5-8% _CH4 , preferably 0-8% _CH4

In one aspect, the electrolysis of _CO2 can occur partially. Therefore, the syngas produced can have a CO/ _CO molar ratio of 0.2 or higher. The electrolysis can be carried out purposefully so that more CO is produced and the resulting molar ratio of CO to CO is higher than 0.2, such as higher than 0.3 or higher than 0.4 or 0.5, such as 0.6 or 0.7, or 0.8 or 0.9 _, thus The relative contents of CO, _CO2 and _H2 in the resulting syngas can be more easily adjusted to the appropriate modulus for subsequent conversion as described below.

In one aspect, a pressure swing adsorption (PSA) unit, a temperature swing adsorption (TSA) unit, and/or a recirculation compressor system may be present to purify the stream from CO _electrolysis . The PSA unit provides a CO-rich stream, typically above 90%, such as above 95% or even above 99% CO, and a _CO2 -rich stream, which is discharged at low pressure so it can be compressed and recycled to _CO electrolysis.

Various operations may be performed on the first synthesis gas stream (and the second synthesis gas stream, or the combined first and second synthesis gas streams) before being supplied to the F-T section.

In most cases, the syngas stream will be cooled below the dew point to condense out some of the water before the syngas stream is delivered to the FT section. Other adjustments to the syngas, such as removal of part or all of the _CO2 or part or all of the _H2O , can also be performed before the syngas is directed to the FT section.

The desired H ₂ /CO molar ratio in the combined first and second synthesis gases is called (H ₂ /CO) _Ref . At the entrance of the FT section, the (H ₂ /CO) _Ref is usually 1.8 to 2.2, such as 1.9 to 2.1 or about 2.

Synthesis gas is transported from the electrolysis section to the F-T section.

Fischer-Tropsch (F-T) section

The F-T section is arranged to receive at least a portion of the first synthesis gas stream (ie the first portion) and convert it into a first (crude) hydrocarbon product stream and a tail gas stream. The hydrocarbon product stream is usually sent to an upgrading section for further refinement. The composition of the crude hydrocarbon product stream from the F-T section depends on the type of catalyst used in the F-T process, reaction temperature, etc.

The F-T section includes one or more F-T reactors. FT technology is well known in the art and reference is made in particular to Steynberg A. and Dry M. "Fischer-Tropsch Technology", Studies in Surface Sciences and Catalysts, Vol. 152.

The tail gas typically includes various components such as H ₂ (5-40%), CO (5-40%), CO ₂ (10-70%), CH ₄ (5-40%), and various other components components, such as C ₂ -C ₆ paraffins and C ₂ -C ₆ olefins, in smaller amounts, usually less than 5% (for each component).

Electric steam reformer section.

The exhaust gas from the Fischer-Tropsch section is directed to the electric steam reformer section. Accordingly, the first electric steam reformer section is arranged to receive at least a first portion of said tail gas stream, and preferably greater than 70%, greater than 80%, greater than 90% or greater than 95%, and convert it into a second synthesis gas stream .

In an optional aspect, the first electric steam reformer section is arranged to receive at least a second portion of the first synthesis gas stream and convert it into a second synthesis gas stream. In other words, the first synthesis gas stream is sent to both the FT section and the first electric steam reformer section. This allows the high temperatures of the electric steam reformer section to be exploited to convert a portion of the unconverted _CO2 in the first syngas stream to CO, as well as steam reforming the latent methane in the first syngas stream, likewise in accordance with a reverse water gas shift unit. This thereby reduces the amount of unreacted gas in the syngas and creates a more efficient Fischer-Tropsch section.

The first electric steam reformer section may include one or more electric steam reformers. Suitable electric steam reformers for use in the electric steam reformer section of the invention are as disclosed in co-pending applications WO2019228797 and WO/2019/228798.

In the electric steam reformer, the following reactions occur:

(7, the reverse reaction of the above reaction 4)

(8, equal to reaction 3 above)

That is, (7) is steam methane reforming, and (8) is water gas shift, and the reverse reaction of (8) is reverse water gas shift.

Higher hydrocarbons (hydrocarbons with 2 or more carbon atoms) may also be present in F-T exhaust gas. If this is the case, these are also transformed according to the following reaction:

C _n H _m +nH ₂ O→nCO+(m/2+n)H ₂ (9)

Reaction (7) is very endothermic and requires significant energy input to achieve the desired conversion. Preferably, the outlet temperature of the electric steam reformer is 850°C or higher, such as 900°C or higher, such as 950°C or even 1000°C or higher.

In some cases, it may be preferable to pretreat the off-gas before directing it to the electrical reformer. The off-gas may contain olefins, in which case some or all of the olefins may be converted to paraffins upstream of the electric steam reformer. This proceeds according to the following hydrogenation reaction:

C _n H _m +H ₂ →C _n H _(m+2) (10)

Therefore, the system according to the invention may further comprise a hydrogenation section arranged in the tail gas flow between the F-T section and the first electric steam reformer section, said hydrogenation section being arranged to hydrogenate the tail gas flow.

Suitably, hydrogenation stages are known to the skilled person. The hydrogenation can be carried out, for example, in an adiabatic reactor before adding steam. Suitable catalysts may include copper. The hydrogenation temperature can be between 100°C and 200°C, but other temperatures can also be used.

Exhaust gas also contains CO. It may be desirable to reform a portion of the CO upstream of the electric steam reformer. This can be carried out, for example, in an adiabatic gas shift reactor according to reaction (8). Therefore, the system according to the invention may further comprise a CO conversion section arranged in the tail gas stream between the F-T section and the first electric steam reformer section, said CO conversion section being arranged to perform a water gas shift reaction on the tail gas stream and /or methanation. Suitable CO conversion sections, in particular suitable adiabatic gas shift or methanation reactors, are known to the skilled person.

If tail gas pretreatment is performed, a preferred embodiment is to perform olefin hydrogenation followed by steam addition and water gas shift reaction. The resulting gas leaving the water gas shift reactor is then directed to an electrical reformer.

Therefore, the system according to the invention may comprise a CO conversion section and a hydrogenation section arranged in the tail gas flow between the F-T section and the first electric steam reformer section, wherein the hydrogenation section is arranged upstream of the CO conversion section.

The treatment of tail gases from F-T reactions is described in particular in EP1860063 and WO2011151012.

The tail gas may also contain higher hydrocarbons (hydrocarbons with 2 or more carbon atoms, such as ethane, propane, etc.). It may be desirable to remove or reduce the content of such higher hydrocarbons upstream of the electrical reformer. This can be achieved, for example, in an adiabatic pre-reformer. In the adiabatic prereformer, higher hydrocarbons are converted according to reaction (9). In an adiabatic pre-reformer, reactions (7) and (8) (including the reverse reactions of these reactions) typically also occur, according to which gases are produced at or near chemical equilibrium. Adiabatic prereforming is usually carried out using granular catalysts with nickel as the active material.

The electric steam reformer section provides a second synthesis gas stream. The composition of this second synthesis gas stream is typically (by volume):

-40-70% H ₂ (dry)

-10-30% CO (dry)

-2-20% CO ₂ (dry)

-0.5-5% CH ₄

The second synthesis gas flow is arranged to be fed to the F-T section, preferably mixed with the first synthesis gas flow.

Gas-to-liquid (GTL) equipment

The present invention also provides a GTL equipment, which includes the system described herein and an upgrading section. The upgrading section is arranged to receive a first hydrocarbon product stream (ie, a "crude product stream") and to provide a final product stream. The final product stream is preferably a diesel stream, a kerosene stream, a liquefied petroleum gas (LPG) stream, a naphtha stream, or two or more thereof, either alone or in combination.

The crude product stream from the F-T section can be upgraded into desired end products such as kerosene, diesel, naphtha and LPG.

In some cases, only diesel, kerosene and naphtha are the desired end products. In this case, LPG can be recycled to the syngas generation unit. However, it is not possible to process recycled LPG in an electrolysis unit without carbon formation. Instead, steam can be added to the LPG and the LPG can be processed into additional synthesis gas according to reaction (9), for example in an electric steam reformer section. Reaction (9) will be accompanied by methanation reaction and water gas shift reaction (8).

Accordingly, in the case where the upgrading section is arranged to provide an LPG stream, the GTL plant may further comprise a second electric steam reformer arranged to receive at least a portion of said LPG stream and convert it into a third synthesis gas stream. Work section. The third synthesis gas stream is arranged to be fed to the F-T section. Any LPG or naphtha formed can be added as tail gas to the same electric steam reformer.

In one embodiment, the first electric steam reformer section (which converts off-gas to a second synthesis gas stream) and the second electric steam reformer section (which converts LPG to a third synthesis gas stream) are the same electric steam reformer section. Whole device. Accordingly, the first and second electric steam reformer sections consist of a combined electric steam reformer section, wherein a combined synthesis gas stream is produced from at least a portion of said LPG stream and said at least a first portion of said tail gas stream, wherein said combined synthesis gas flow is arranged to be fed to the F-T section as said second synthesis gas flow.

In some cases, LPG may contain catalyst poisons such as sulfur. In this case, the sulfur is removed upstream of the associated electric steam reformer. If the LPG contains olefins, these can be converted upstream of the electroreformer according to reaction (10).

It may also be desirable to convert all or part of the higher hydrocarbons in the LPG to reduce the likelihood of carbon formation in the electrical reformer. In one embodiment, this can be achieved through the use of an adiabatic pre-reformer. In the adiabatic pre-reformer, higher hydrocarbons react with steam according to reaction (9). Reactions (7) and (8) will also occur in the adiabatic pre-reformer. Typically, adiabatic pre-reformers operate at temperatures from 350°C to 550°C. The effluent from the adiabatic pre-reformer is directed to the electrical reformer.

In some cases, naphtha may not be the desired end product. In this case, the naphtha can be recycled back to the syngas generation unit for additional syngas production in a manner similar to LPG as described above.

method

The invention also provides a method of converting a first feed comprising CO ₂ and a second feed comprising H ₂ O into a first hydrocarbon product stream in a system described herein. All details of the system described above are relevant mutatis mutandis to the method of the invention.

The method includes the following general steps:

- converting said first feed and said second feed into a first synthesis gas stream in said electrolysis section,

- supplying at least a first portion of said first synthesis gas stream to the F-T section and converting it into a first hydrocarbon product stream and a tail gas stream,

- optionally, feeding at least a second portion of said first synthesis gas stream to a first electric steam reformer section and converting it into a second synthesis gas stream,

- feeding at least a portion of said off-gas stream to said first electric steam reformer section and converting it into a second synthesis gas stream, and

- The second synthesis gas flow is preferably mixed with the first synthesis gas flow and fed to the F-T section.

In the method of the invention, at the entrance of the FT section, the (H ₂ /CO) _Ref is usually 1.8 to 2.2, such as 1.9 to 2.1 or about 2.

To reduce the carbon footprint of the process, the electricity required to drive the electrolysis section and/or the electric steam reformer section can be provided at least in part by renewable sources, such as wind and solar energy.

The invention also describes a method for providing a final product stream (i.e. a purified product stream) such as a diesel stream, a kerosene stream, an LPG stream or a naphtha stream, the method comprising carrying out the above process and subsequently passing it through an upgrading section (in In the upgrading section), the first hydrocarbon product stream is upgraded and a final product stream is provided.

Detailed description of the drawings

Figure 1 shows an illustrative system 100 according to the present invention. A first feed 11 comprising _CO2 (and preferably pure _CO2 ) is fed to the electrolysis section 20. In this embodiment, the electrolysis section 20 includes at least a first electrolysis unit 20b and a second electrolysis unit 20c. The first electrolysis unit 20b receives a first feed 11 and is arranged to convert the first feed 11 into a first stream 24 comprising CO.

Similarly, a second feed 12 comprising H ₂ O is supplied to the electrolysis section 20 , in particular to the second electrolysis unit 20 c therein. The second electrolysis unit 20c receives the second feed 12 and converts it into a second stream 25 containing _H2 .

The first stream 24 containing CO is combined with the second stream 25 containing _H , for example in a compressor unit to provide a first synthesis gas stream 21. In this embodiment, the entire first synthesis gas stream 21 is sent to FT section 30 where it is converted into a first hydrocarbon product stream 31 and a tail gas stream 32.

The first hydrocarbon stream 31 is sent to an upgrading section (not shown in Figure 1) for further processing.

The off-gas stream 32 is partially purged and a portion 32a is fed to the first electric steam reformer section 40. This first portion 32 a of the off-gas stream 32 is converted into a second synthesis gas stream 41 in the first electric steam reformer section 40 . The second synthesis gas stream 41 is arranged to be fed to the F-T section 30 at the inlet of the F-T section 30 , where it can be processed into an additional hydrocarbon product stream 31 and a tail gas stream 32 . As shown in FIG. 1 , the second synthesis gas flow 41 is preferably arranged to be mixed with the first synthesis gas flow 21 and supplied to the F-T section 30 .

Figure 2 shows a system similar to Figure 1. In Figure 2, the electrolysis section 20 comprises a single electrolysis unit 20a arranged to convert the first feed 11 and the second feed 12 into a first synthesis gas stream 21. Preferably, the first feed 11 and the second feed 12 are arranged to be mixed before being fed to the electrolysis section 20, 20a.

In each of the above embodiments, electricity is provided to the electrolysis section 20 and the first electric steam reformer section 40, preferably from a renewable source.

Although the invention has been described with reference to various aspects and embodiments, those skilled in the art may combine elements from the various aspects while remaining within the scope of the invention as defined in the claims.

Claims (19)

1. A system (100) for providing a first hydrocarbon product stream, the system (100) comprising:

a Fischer-Tropsch (F-T) section (30),

an electrolysis section (20) arranged upstream of said F-T section (30),

-CO-containing feed to the electrolysis section (20) ₂ Is fed into the furnace (11),

-H-containing feed to the electrolysis section (20) ₂ A second feed (12) of O,

a first steam reformer section (40),

wherein the method comprises the steps of

-said electrolysis section (20) being arranged to provide a first synthesis gas stream (21) from said first feed (11) and said second feed (12),

said F-T section (30) being arranged to receive at least a first portion of said first synthesis gas stream (21) and convert it into a first hydrocarbon product stream (31) and an off-gas stream (32),

and wherein optionally the first steam reformer stage (40) is arranged to receive at least a second portion of the first synthesis gas stream (21) and convert it into a second synthesis gas stream (41),

said first steam reformer section (40) is arranged to receive at least a first portion (32 a) of said tail gas stream (32) and convert it into a second synthesis gas stream (41),

and wherein the second synthesis gas stream (41) is arranged to be fed to the F-T section (30), preferably mixed with the first synthesis gas stream (21).

2. A system according to claim 1, wherein the electrolysis section (20) comprises a single electrolysis unit (20 a), the single electrolysis unit (20 a) being arranged to convert the first feed (11) and the second feed (12) into a first synthesis gas stream (21), preferably wherein the first feed (11) and the second feed (12) are arranged to be mixed before being fed to the electrolysis section (20).

3. The system according to claim 1, wherein the electrolysis section (20) comprises at least a first electrolysis unit (20 b) and a second electrolysis unit (20 c), wherein the first electrolysis unit (20 b) is arranged to contain CO ₂ Is converted into a first stream (24) comprising CO, and wherein the second electrolysis unit (20 c) is arranged to convert the first feed (11) comprising H ₂ Conversion of the second feed (12) of O to H ₂ And wherein the electrolysis section (20) is further arranged to combine the first stream (24) comprising CO with the second stream (25) comprising H ₂ Is combined into the first synthesis gas stream (21).

4. A system according to any one of the preceding claims, wherein one or all electrolysis units (20 a, 20b, 20 c) in the electrolysis section (20) are Solid Oxide Electrolysis (SOE) units.

5. A system according to any of claims 1 or 3-4, wherein the second electrolysis cell (20 c) is an alkaline/polymer electrolyte membrane electrolysis cell, such as an alkaline/PEM electrolysis cell.

6. The system according to any of the preceding claims, further comprising a hydrogenation section arranged in the off-gas stream (32) between the F-T section (30) and the first steam reformer section (40), the hydrogenation section being arranged to hydrogenate the off-gas stream (32).

7. The system according to any of the preceding claims, further comprising a CO conversion section arranged in the off-gas stream (32) between the F-T section (30) and the first steam reformer section (40), the CO conversion section being arranged to perform a water gas shift reaction and/or methanation of the off-gas stream (32).

8. A system according to any of the preceding claims, comprising a CO conversion section and a hydrogenation section arranged in the off-gas stream (32) between the F-T section (30) and the first steam reformer section (40), wherein the hydrogenation section is arranged upstream of the CO conversion section.

9. The system according to any of the preceding claims, further comprising a waste heat boiler arranged to cool a second synthesis gas stream (41) from the first steam reformer section (40), and wherein steam provided by the waste heat boiler is provided as the second feed (12).

10. A method according to any preceding claimFurther comprising CO-containing feed to the first steam reformer section (40) ₂ Is a third feed of (c).

11. The system of claim 10, wherein the third feed further comprises H ₂ 。

12. GTL plant comprising a system according to any of the preceding claims, further comprising a upgrading section (50), the upgrading section (50) being arranged to receive a first hydrocarbon product stream (31) and to provide a final product stream (51), wherein the final product stream (51) is preferably a diesel stream, a kerosene stream, a Liquefied Petroleum Gas (LPG) stream or a naphtha stream.

13. GTL plant according to claim 12, wherein the upgrading section (50) is arranged to provide an LPG stream (51 a), and wherein the GTL plant further comprises a second steam reformer section (60) arranged to receive at least a portion of the LPG stream (51 a) and convert it into a third synthesis gas stream (61).

14. GTL plant according to claim 13, wherein the first (40) and second (60) steam reformer sections consist of combined steam reformer sections, wherein a combined synthesis gas stream is produced from at least a part of the LPG stream (51 a) and the at least a first part of the off-gas stream (32), wherein the combined synthesis gas stream is arranged to be fed as the second synthesis gas stream (41) to the F-T section.

15. A system (100) according to any of claims 1-11, comprising CO ₂ And comprises H ₂ A process for converting a second feed (12) of O to a first hydrocarbon product stream (31), the process comprising the steps of,

converting said first feed (11) and said second feed (12) into a first synthesis gas stream (21) in said electrolysis section (20),

supplying at least a first portion of said first synthesis gas stream (21) to said F-T section (30) and converting it into a first hydrocarbon product stream (31) and a tail gas stream (32),

optionally, feeding at least a second portion of said first synthesis gas stream (21) to a first steam reformer section (40) and converting it into a second synthesis gas stream (41),

-feeding at least a portion of said tail gas stream (32) to said first steam reformer section (40) and converting it into a second synthesis gas stream (41), and

-feeding said F-T section (30) with a second synthesis gas stream (41), preferably mixed with the first synthesis gas stream (21).

16. The method of claim 15, wherein comprising CO ₂ Preferably the amount of hydrocarbons is less than 10%, such as less than 5%, or most preferably less than 3% of the volume of the first feed (11).

17. A process according to any one of claims 15-16, wherein H in the synthesis gas at the inlet of the F-T section (30) ₂ the/CO ratio is 1.8 to 2.2, for example 1.9 to 2.1, or about 2.0.

18. A method according to any one of claims 15-17, wherein the electrical power required to drive the electrolysis section (20) and/or the steam reformer section (40) is at least partly provided by renewable sources, such as wind and solar energy.

19. A process for providing a final product stream (51), such as a diesel stream, a kerosene stream, an LPG stream or a naphtha stream, the process comprising carrying out the process according to any one of claims 15-18, followed by upgrading the first hydrocarbon product stream (31) by means of an upgrading section (50) and providing the final product stream (51).