Modular unit for the conversion of a co2-rich gas stream to a co-rich gas stream

Abstract

The current invention relates to a modular unit for the conversion of a CO2-rich gas stream to a CO-rich gas stream. The current invention further relates to a Method for the conversion of a CO2-rich gas stream to a CO-rich gas stream, utilizing a plasma reactor. Finally, present application relates to an iron production method comprising the steps of : reducing iron ore using a CO-rich gas stream, thereby producing iron and a CO2-rich gas stream; extracting said CO2-rich gas stream; converting said CO2-rich gas stream to a CO-rich gas stream; and recycling said CO- rich gas stream to said blast furnace.

Description

[0001] MODULAR UNIT FOR THE CONVERSION OF A CO2-RICH GAS STREAM TO A CO-RICH GAS STREAM

[0002] FIELD OF THE INVENTION

[0003] The present invention concerns a method and system for treating carbon dioxide (CO2) exhausted by CO2 producing installations, preferably blast furnaces, thereby recovering carbon monoxide (CO). The present invention is particularly applicable to CO-consuming methods and systems, such as iron extraction methods and systems.

[0004] BACKGROUND

[0005] Blast furnaces are the main tool of metallurgy. They operate on the principle of chemical reduction, where metal ores are reduced to their main metal components by reacting with gases or other solids at high temperature. The most common reduction reaction is the reduction of iron ore, typically in the form of ferric oxide (Fe20s) with CO to iron (Fe) and CO2:

[0006] As can be seen from the reaction, for every ton of iron (Fe), approx. 1.2 tons of CO2 are produced. Indeed, nearly 7% of the global CO2 emissions emerge from steel production. In the light of the efforts for CO2 emissions reduction, the present invention aims to provide a means to reduce, and even eliminate, the CO2 emission footprint of the steel industry.

[0007] In fact, the present invention aims to reduce CO2 emissions of applications which consume CO. Hereto, the present invention particularly aims to provide a method and system for recovering CO from CO2, such as is produced in blast furnaces to produce iron from iron ore.

[0008] SUMMARY OF THE INVENTION

[0009] The present invention and embodiments thereof serve to provide a solution to one or more of above-mentioned disadvantages. To this end, the present invention relates to a modular unit according to claim 1.

[0010] The invention pertains to a modular unit and a method for converting a CO2-rich gas stream to a CO-rich gas stream. The modular unit comprises a plasma reactor vessel with a pre-plasma chamber, a post-plasma chamber containing a carbon bed, multiple parallel electrode pairings, a cooling unit, an inlet for the CO2-rich gas stream, a carbon storage unit, a recycle line, an outlet for the CO-rich gas stream, and a power supply unit. Advantageously, the unit can be used in combination with existing blast furnace equipment. In order to achieve these goals, a robust modular unit which can scale, operate at a variety of conditions and utilize a variety of CO2- rich inlet gasses is desired. Furthermore, energy efficiency is of the utmost importance to be usable at scale.

[0011] The unit is designed to ensure efficient gas management, promote sustainable operations, and offer flexibility in feedstock sourcing.

[0012] The present invention further relates to a method according to claim 10.

[0013] The method includes supplying a CO2-rich gas stream and a carbon donor to the plasma reactor vessel, igniting a plasma, extracting a CO-rich gas stream, and recycling a part of the CO-rich gas stream. The invention provides a significant reduction in greenhouse gas emissions with an improved resource efficiency and energy efficiency.

[0014] The present invention finally relates to a method for the reduction of iron ore according to claim 15. This method significantly reduces carbon emissions related with iron ore production, while allowing continued use of presently existing infrastructure with respect to blast furnaces.

[0015] DETAILED DESCRIPTION OF THE INVENTION

[0016] The present invention concerns a modular unit for the conversion of a CO2-rich gas stream to a CO-rich gas stream. The prevent invention further relates to a method of conversion. Finally, the present invention relates to a method of iron production.

[0017] Unless otherwise defined, all terms used in disclosing the invention, including technical and scientific terms, have the meaning as commonly understood by one of ordinary skill in the art to which this invention belongs. By means of further guidance, term definitions are included to better appreciate the teaching of the present invention.

[0018] As used herein, the following terms have the following meanings: "A", "an", and "the" as used herein refers to both singular and plural referents unless the context clearly dictates otherwise. By way of example, "a compartment" refers to one or more than one compartment.

[0019] "About" as used herein referring to a measurable value such as a parameter, an amount, a temporal duration, and the like, is meant to encompass variations of + / - 20% or less, preferably + / -10% or less, more preferably + / -5% or less, even more preferably + / -1% or less, and still more preferably + / -0.1% or less of and from the specified value, in so far such variations are appropriate to perform in the disclosed invention. However, it is to be understood that the value to which the modifier "about" refers is itself also specifically disclosed.

[0020] "Comprise", "comprising", and "comprises" and "comprised of" as used herein are synonymous with "include", "including", "includes" or "contain", "containing", "contains" and are inclusive or open-ended terms that specifies the presence of what follows e.g. component and do not exclude or preclude the presence of additional, non-recited components, features, element, members, steps, known in the art or disclosed therein.

[0021] Furthermore, the terms first, second, third and the like in the description and in the claims, are used for distinguishing between similar elements and not necessarily for describing a sequential or chronological order, unless specified. It is to be understood that the terms so used are interchangeable under appropriate circumstances and that the embodiments of the invention described herein are capable of operation in other sequences than described or illustrated herein.

[0022] The recitation of numerical ranges by endpoints includes all numbers and fractions subsumed within that range, as well as the recited endpoints.

[0023] The expression "% by weight", "weight percent", "%wt" or "wt%", here and throughout the description unless otherwise defined, refers to the relative weight of the respective component based on the overall weight of the formulation.

[0024] Whereas the terms "one or more" or "at least one", such as one or more or at least one member(s) of a group of members, is clear per se, by means of further exemplification, the term encompasses inter alia a reference to any one of said members, or to any two or more of said members, such as, e.g., any >3, >4, >5, >6 or >7 etc. of said members, and up to all said members.

[0025] Unless otherwise defined, all terms used in disclosing the invention, including technical and scientific terms, have the meaning as commonly understood by one of ordinary skill in the art to which this invention belongs. By means of further guidance, definitions for the terms used in the description are included to better appreciate the teaching of the present invention. The terms or definitions used herein are provided solely to aid in the understanding of the invention.

[0026] Reference throughout this specification to "one embodiment" or "an embodiment" means that a particular feature, structure or characteristic described in connection with the embodiment is included in at least one embodiment of the present invention. Thus, appearances of the phrases "in one embodiment" or "in an embodiment" in various places throughout this specification are not necessarily all referring to the same embodiment, but may. Furthermore, the particular features, structures or characteristics may be combined in any suitable manner, as would be apparent to a person skilled in the art from this disclosure, in one or more embodiments. Furthermore, while some embodiments described herein include some but not other features included in other embodiments, combinations of features of different embodiments are meant to be within the scope of the invention, and form different embodiments, as would be understood by those in the art. For example, in the following claims, any of the claimed embodiments can be used in any combination.

[0027] In a first aspect, the invention relates to a modular unit for the conversion of a CO2- rich gas stream to a CO-rich gas stream, said unit comprising : Modular unit for the conversion of a CO2-rich gas stream to a CO-rich gas stream, said modular unit comprising:

[0028] - a plasma reactor comprising a plasma reactor vessel,

[0029] - an inlet for the CO2-rich gas stream,

[0030] - an outlet for the CO-rich gas stream, and

[0031] - a power supply unit (PSU).

[0032] At its core, the present invention is related to a modular unit allowing the conversion of CO2 to CO in a plasma reactor. Preferably the plasma reactor is a gliding arc plasma reactor, powered by an electric power supply. This allows decarbonization of at least some of the energy demand related to the production of CO suitable for iron ore reduction, as well as the decarbonization of its emissions. Advantageously in comparison to carbon capture and storage, the CO2 emissions are appropriately recycled to high value products rather than long term storage.

[0033] More preferably, said plasma reactor vessel comprises a pre-plasma chamber and a post-plasma chamber. The preferably pre-plasma chamber comprises a feedstock inlet, fluidly connected to said inlet for the CO2-rich gas stream. The post-plasma chamber preferably comprises a post-plasma chamber comprising a product outlet. In a preferred embodiment, the pre-plasma chamber and post-plasma chamber are fluidly connected by multiple electrode pairings. These electrode pairings are electrically connected to the power supply unit and suited to ignite a plasma.

[0034] The pre-plasma and post-plasma chamber can act as pressure chambers suitable for providing multiple electrode pairings in parallel; without needing to determine in advance the amount of electrode pairings that will be operating.

[0035] This modular design allows for easy upscaling and downscaling without the requirement to add additional reactor vessels or modular units. The inventors found that operating several electrode pairings in parallel is required over increasing the throughput of a single electrode pairing in order to achieve greater energy efficiency.

[0036] The inventors found that operating a series of electrode pairings in parallel at these conditions shows significantly better results in terms of conversion, conversion rate and energy efficiency compared to working outside of this range. At lower operating power, the conversion of the CO2 to CO conversion in the plasma declines leading to lower conversion. At higher operating power, the temperature in the plasma afterglow is too high resulting in recombination of the products towards the reactant, also leading to lower conversion and a decrease in energy efficiency.

[0037] In a preferred embodiment, the multiple parallel reactor cathodes consist of at least 2, more preferably at least 3, more preferably at least 4, more preferably at least 5, more preferably at least 7, more preferably at least 10, more preferably at least 12, more preferably at least 15, more preferably at least 20, more preferably at least 25 parallel reactor cathodes. Scaling with a series of modular, parallel reactor cathodes results in higher energy efficiency and conversion rate than a single, larger reactor. It was found that operating, in parallel, several plasma reactor electrode pairings with an optimized power profile allows for much larger throughput without significant decreases in energy efficiency or conversion or the need for complex equipment.

[0038] In a preferred embodiment, said electrode pairings comprise :

[0039] • an anode plate, said anode plate separating the reactor vessel into a preplasma chamber and a post-plasma chamber, and

[0040] • multiple parallel reactor cathodes, wherein said multiple parallel reactor cathodes are mounted on said anode plate, wherein each parallel reactor cathode is electrically insulated from said anode plate, preferably by an insulation ring. The anode plate can serve as separation between pre- and post-plasma chambers and anode simultaneously. More preferably, the anode plate is grounded and each active cathode plug is electrically connected to the power supply unit. By using the anode plate as grounded electrode, safety is significantly enhanced as the anode plate which is connected to the reactor vessel are grounded. Only the cathode plugs, which are locked within the reactor vessel, are connected to the power supply. Furthermore, this setup allows for decoupling cathode plugs as desired.

[0041] More preferably, each parallel reactor cathode comprises a tangential gas inlet for fluid communication with the pre-plasma chamber and an axial plasma outlet for fluid communication with the post-plasma chamber. The reactor cathode is preferably a plug- or cylinder-shaped hollow object, which is in fluid communication with the pre-plasma chamber and the post-plasma chamber. Inside its hollow volume, a plasma is ignited. A tangential inlet from the pre-plasma chamber is preferred as this produces a vortex within the cathode internal volume, allowing efficient mixing and desirable plasma conditions. An axial outlet is preferred to evacuate the very reactive plasma species into the common post-plasma chamber; where downstream reaction conditions to maximize conversion to the desired products are maintained.

[0042] In a further preferred embodiment, the reactor vessel is cooled. In a preferred embodiment, the reactor housing comprises a cooling unit. Preferably said cooling unit is configured to cool the post-plasma chamber. More preferably, the reactor housing comprises a fluid jacket. More preferably, the reactor housing comprises a fluid jacket around the post-plasma chamber. The use of a cooling fluid within the fluid jacket allows cooling of the post-plasma chamber. This allows quenching of the post-plasma chamber. More preferably, the fluid jacket is further connected to a heat exchanger. The heat exchanger is preferably used to preheat the inlet CO2-rich gas stream; to improve energy efficiency of the modular unit. In another embodiment, the modular unit may comprise connections for cooling fluids. This allows the heat captured by the hot working fluid to be utilized to its maximum value on the site.

[0043] In a preferred embodiment, the modular unit further comprises a heat exchanger, wherein said heat exchanger has a cold and a hot circuit, wherein said hot circuit is fluidly connected to said CO2 inlet for the CO2-rich gas stream and wherein said cold circuit is fluidly connected to said fluid jacket, preferably said cold circuit is a closed circuit. This operation significantly improves the energy efficiency of the modular unit, while advantageously being entirely contained within the modular unit.

[0044] In another preferred embodiment, the post-plasma chamber comprises a carbon bed. A carbon bed in the post-plasma chamber allows fixation of oxygen species with carbon, thereby limiting recombination of CO to CO2 and producing higher CO content. In a further preferred embodiment, a cooling unit and a carbon bed can both be utilized.

[0045] By providing the carbon bed in the post-plasma chamber, no solid particles are introduced within the pre-plasma chamber and the electrodes. This significantly reduces the material requirements and wear on these parts, particularly the electrodes in which high temperatures are combined with vortices.

[0046] In a preferred embodiment, the post-plasma chamber comprises a carbon bed. Present reactor setup allows a single carbon bed to be operated in combination with as many parallel electrode pairings as required. This is desired to simultaneously provide the optimal conditions for the electrode pairings, where plasma upscaling remains difficult to achieve, and both the operating conditions and practical limitations of a carbon bed. Preferably, the carbon bed is substantially parallel to said anode plate. In a further preferred embodiment, the carbon bed is connected with a carbon storage unit. The carbon bed is preferably a series of trays or meshes, suitable for holding carbonaceous granular material. More preferably, carbon is carried from said carbon storage unit to said carbon bed by a sufficiently high pressure gas. In a particular preferred embodiment, said high pressure gas is CO2- rich inlet gas. In another preferred embodiment, said high pressure gas is recycled CO-rich outlet gas. In a preferred embodiment, the anode plate is a single solid element, more preferably made of stainless steel, comprising a series of bores through which individual reactor cathodes are mounted. Each of said cathodes is enveloped by an electrical insulator and inserted into a corresponding bore, such that all cathodes are mounted on a common anode plate. Preferably, the anode plate does not comprise any protrusions or surface irregularities on the side of the post-plasma chamber. More preferably, the post-plasma facing side of the anode plate is substantially flat, except for the through-bores accommodating the cathode outlets. This geometry ensures an even heat distribution across the post-plasma chamber, which is particularly advantageous for stabilizing the temperature of the carbon bed, notably during reactor start-up and during or after refilling of the carbon bed. The resulting improved thermal management contributes to a more stable plasma discharge, which is critical for maintaining performance when operating multiple parallel electrode pairings.

[0047] In a further preferred embodiment, the carbon bed is arranged substantially parallel to the common anode plate. Preferably, multiple reactor cathodes are mounted onto said common anode plate. In this configuration, the distance between the anode plate and the closest surface of the carbon bed— measured in the direction of the plasma exhaust, i.e. substantially orthogonal to the anode plate— is preferably between 25 mm and 100 mm, more preferably between 30 mm and 80 mm, more preferably between 40 mm and 70 mm, more preferably between 45 mm and 65 mm, and most preferably between 50 mm and 60 mm. The carbon bed preferably has a thickness, in the same direction, of between 20 mm and 100 mm, more preferably between 25 mm and 80 mm, more preferably between 30 mm and 60 mm, more preferably between 30 mm and 50 mm, and most preferably between 30 mm and 40 mm. The length of the carbon bed is herein defined as the thickness of the packed bed of carbonaceous material during operation, in the flow direction from the anode plate into the post-plasma chamber. It was found that a carbon bed placed too close to the plasma exhaust significantly destabilizes the plasma, whereas an excessively large distance between the plasma exhaust and the carbon bed leads to a reduction in energy efficiency

[0048] In a further preferred embodiment, the total volume of the carbon bed is limited to ensure optimal performance. While larger carbon beds were experimentally tested, these were found to introduce significant disadvantages, including increased pressure drop, prolonged start-up durations, and only marginal or no improvement in CO2 conversion once steady-state conditions were achieved. Preferably, the total volume of the carbon bed is between 100 cm3and 1000 cm3, more preferably between 150 cm3and 800 cm3, more preferably between 180 cm3and 600 cm3, more preferably between 200 cm3and 500 cm3, and most preferably between 200 cm3and 400 cm3. In a further embodiment, the carbon bed volume is defined relative to the number of electrode pairings. Preferably, the carbon bed has a volume between 10 cm3and 100 cm3per electrode pairing, more preferably between 20 cm3and 80 cm3, more preferably between 30 cm3and 60 cm3, more preferably between 35 cm3and 50 cm3, and most preferably between 35 cm3and 45 cm3per electrode pairing. Most preferably, the number of electrode pairings is at least four. It was observed that plasma reactors equipped with only a limited number of electrode pairings exhibit pronounced fluctuations in CO concentration, particularly during start-up and after carbon bed refilling. These fluctuations are primarily attributed to the insufficient thermal mass and suboptimal temperature of the carbon bed during these phases. In contrast, excessively large carbon beds significantly impair flow dynamics and delay thermal stabilization, outweighing any benefits in conversion.

[0049] In a further preferred embodiment, the carbon bed volume is defined relative to the gas flow rate through the plasma reactor, thereby establishing a carbon bed residence time. Said residence time, defined as the quotient of the carbon bed volume (in litres) and the volumetric flow rate of the CO2-rich feed gas (in L / s), is preferably between 1 and 60 seconds, more preferably between 5 and 45 seconds, more preferably between 10 and 30 seconds, more preferably between 12 and 25 seconds, and most preferably between 15 and 20 seconds. In an additional embodiment, the carbon bed volume is also defined relative to the total plasma power of the reactor, expressed as a volume-to-power ratio in L / kW. Preferably, this ratio lies between 0.01 and 0.30 L / kW, more preferably between 0.02 and 0.20 L / kW, more preferably between 0.03 and 0.15 L / kW, more preferably between 0.04 and 0.12 L / kW, and most preferably between 0.04 and 0.10 L / kW. The lower end of this most preferred range is particularly suited for start-up phases and subsequent to large batchwise carbon bed refilling, especially in systems employing dynamic power control. The higher end of the range is more suited for steady-state operation, once the carbon bed has reached a thermally stable condition. Maintaining the carbon bed volume within these preferred ranges ensures consistent and stable reactor performance, effectively minimizing fluctuations in output CO concentration, temperature within the post-plasma chamber, and plasma discharge stability, while simultaneously avoiding excessive pressure drop or diminished CO2 conversion and energy efficiency. These parameters further allow for relatively short start-up times— defined as the period between reactor ignition from cold and the achievement of steady-state operating conditions across all electrode pairings and the carbon bed.

[0050] In a further preferred embodiment, dynamic power control is employed to optimize the operation of the plasma reactor in response to thermal conditions within the post-plasma chamber. More preferably, during start-up or after a carbon bed refill, the plasma reactors are operated at a relatively high total power to expedite heating of the carbon bed and surrounding structures. Once the post-plasma chamber has reached the desired operational temperature, the power input is preferably reduced to sustain steady-state operation under optimal energy efficiency. In embodiments comprising multiple parallel electrode pairings, this overall power reduction is more preferably achieved not by lowering the power per electrode pairing, but rather by selectively deactivating one or more electrode pairings while maintaining full gas flow through the deactivated cathodes. The active electrode pairings remain powered at or near their optimal operating conditions. This approach allows dynamic adjustment of reactor-wide power while preserving individual plasma stability and avoiding sub-optimal discharge conditions across active pairings.

[0051] In a preferred embodiment, the reactor operation comprises at least two distinct power regimes: a heat-up phase and a steady-state phase. The total power supplied by all electrode pairings combined during the heat-up phase is preferably at least 10%, more preferably at least 20%, more preferably at least 25%, and most preferably between 25% and 40% higher than the power supplied during the steadystate phase. Correspondingly, the carbon bed volume-to-power ratio is preferably adapted between these two regimes. During heat-up, said ratio is preferably between 0.01 and 0.08 L / kW, more preferably between 0.02 and 0.07 L / kW, more preferably between 0.025 and 0.06 L / kW, and most preferably between 0.03 and 0.05 L / kW. During steady-state operation, the carbon bed volume-to-power ratio is preferably between 0.05 and 0.20 L / kW, more preferably between 0.06 and 0.18 L / kW, more preferably between 0.07 and 0.16 L / kW, and most preferably between 0.08 and 0.20 L / kW. These dynamic ratios allow responsive adaptation to varying thermal conditions, while ensuring that energy efficiency, conversion rate, plasma stability, and thermal consistency within the post-plasma chamber remain within optimal performance ranges. In a further preferred embodiment, the carbon bed is provided with one or more thermocouples configured to measure the temperature within the bed during operation. More preferably, at least one thermocouple is positioned in proximity to the inlet through which carbonaceous material is introduced into the carbon bed. These temperature sensors provide critical feedback for regulating reactor operation and, more preferably, are operatively connected to a central processing unit or control system capable of dynamically adjusting the power input to the plasma reactors based on the measured carbon bed temperature. Preferably, the dynamic power control described above is regulated by the actual temperature of the carbon bed.

[0052] The optimal operating temperature of the carbon bed is preferably between 400°C and 600°C. At temperatures within this range, efficient fixation of oxygen species and stable downstream reaction kinetics are achieved. Higher temperatures in the carbon bed are not required and may lead to energy consumption. In a preferred embodiment, the reactor control system is configured such that the higher heat-up power regime is activated when the carbon bed temperature falls below 350°C, more preferably below 400°C, more preferably below 450°C, and most preferably below 500°C. This temperature-based switching mechanism allows the modular unit to rapidly reach and maintain thermally stable conditions while avoiding excessive energy use and ensuring consistent conversion performance during transient phases such as start-up or carbon bed refilling.

[0053] The high-pressure CO2-rich gas is most preferred for several reasons. By carrying carbon material utilizing CO2-rich gas stream, several functions are achieved simultaneously. Generally the feedstock gas is provided at a higher pressure than suitable for plasma operation, thus the feedstock gas is provided at a sufficiently high pressure to carry the granules into the reactor. In other words, higher pressure CO2-rich gas stream is available without the need for a compressor and additional energy inputs. Introducing a CO2 gas stream in the post-plasma reactor is additionally advantageous as it can reactive oxygen species in a similar manner to the carbon material. By controlling the temperature, quenching of the post-plasma chamber independently of the plasma conditions upstream also provides additional reactor control.

[0054] In a further preferred embodiment, the reactor vessel comprises a solid waste disposal container. More preferably, spent carbon is carried out of said carbon bed and reactor by a sufficiently high pressure gas. Both provision of new carbon granules and removal of spent carbon granules can be achieved by a flow perpendicular to the direction between the feedstock inlet and the product outlet of the plasma reactor vessel. It is desired to evacuate granular, solid material separately from the product outlet as much as possible. This reduces the wear on downstream operations and reduces the requirements for separation. Advantageously, the presence of sooth and particles downstream can be substantially reduced or avoided entirely.

[0055] In a preferred embodiment, the plasma reactor is powered by a switching-type high voltage power supply. In a preferred embodiment, the gliding arc plasma reactor is powered by a current-regulated power supply. In a preferred embodiment, the gliding arc plasma is powered by a DC power supply. More preferably, the gliding arc plasma reactor is powered by a current regulated, switching type high voltage power supply. Most preferably, the gliding arc plasma reactor is powered by a current regulated, switching type, high voltage DC power supply. As previously described, the power supply is most preferably connected to the active cathodes; which are mounted on but electrically insulated from a common grounded anode.

[0056] In a preferred embodiment, said plasma reactor comprises:

[0057] • a cylindrical reactor vessel, wherein said cylindrical shape is characterized by a cross section in a radial plane and extends in an axial direction perpendicular to said radial plane;

[0058] • an anode plate parallel to the radial plane, said anode plate separating the reactor vessel into a pre-plasma chamber and a post-plasma chamber,

[0059] • a feedstock inlet allowing fluid communication to the pre-plasma chamber,

[0060] • a product outlet allowing fluid communication to the post-plasma chamber,

[0061] • multiple parallel reactor cathodes, wherein said multiple parallel reactor cathodes are mounted on said anode plate, wherein each parallel reactor cathode is electrically insulated from said anode plate by an insulation ring; wherein each parallel reactor cathode comprises a tangential gas inlet for fluid communication with the pre-plasma chamber and an axial plasma outlet for fluid communication with the post-plasma chamber;

[0062] • said post-plasma chamber comprising a carbon bed substantially parallel to the radial plane, said carbon bed comprising an array of trays or meshes suitable for holding carbonaceous material, preferably said carbon bed is fluidly connected with a carbon storage unit on a first radial end; and said carbon bed is fluidly connected to a waste disposal unit on a second radial end opposite to said first radial end; and • a power supply unit connected to said multiple parallel reactor cathodes.

[0063] In a preferred embodiment, the carbonaceous material in the carbon bed are selected from the list of : charcoal, coal, cokes or a combination thereof, most preferably cokes. Preferably these are granular material which is not too fine. This avoids carbonaceous material being introduced into the gas flows in substantial amounts.

[0064] In a preferred embodiment, the carbon bed is filled with carbonaceous particles having a median particle size (dso) between 0.5 mm and 5 mm, more preferably between 0.7 mm and 4.0 mm, more preferably between 0.8 mm and 3.0 mm, more preferably between 0.9 mm and 2.5 mm, and most preferably between 1.0 mm and 2.0 mm. More preferably, the particle size distribution is such that the dio is at least 0.5 mm, more preferably at least 0.6 mm, more preferably at least 0.8 mm, most preferably at least 1.0 mm; and the d9o is at most 5 mm, more preferably at most 4.5 mm, more preferably at most 4.2 mm, and most preferably at most 4.0 mm. As used herein, "dio" refers to the particle diameter below which 10% of the sample volume resides, "dso" is the median particle diameter, and "doo" is the diameter below which 90% of the sample volume resides. This particle size range allows for optimal gas permeability, sufficient reactive surface area, and stable mechanical packing within the carbon bed. Preferably, the carbon particles comprise amorphous carbon, more preferably amorphous carbon with a high surface area. Although amorphous carbon is strongly preferred for its reactivity and thermal behavior, activation of the carbon (e.g. via steam or chemical treatment) is not required. Other allotropes of carbon, in particular crystalline forms such as graphite, are preferably avoided, as they show significantly reduced reactivity in the present application. In a further preferred embodiment, the moisture content of the carbon particles is below 5 wt.%, more preferably below 2 wt.%, more preferably below 1 wt.%, and most preferably below 0.5 wt.%. Elevated moisture levels, particularly above 2 wt.%, have been found to negatively impact reactor performance, especially in systems with larger carbon beds. Water content influences both the reactivity of the carbon and its thermal inertia, leading to slower thermal ramp-up and destabilized plasma discharge if not properly controlled. In a preferred embodiment, the carbonaceous material used to fill the carbon bed comprises solid carbon particles with a high amorphous content or high degree of amorphicity. In a preferred embodiment, the carbonaceous material is selected from the group consisting of pyrolytic carbon, granular petroleum coke, biomass-derived char, and carbon obtained from the pyrolysis of synthetic polymers. These types of carbon have been found to be particularly suitable for use in the post-plasma chamber, offering favourable thermal and reactive properties under the operating conditions of the present invention. More preferably, said carbon is produced by thermal or catalytic decomposition processes, including but not limited to: pyrolytic carbon obtained from methane cracking or other hydrocarbon cracking processes; granular petroleum coke derived from thermal cracking of heavy oil fractions, such as vacuum residuum or tar; charred biomass resulting from slow or fast pyrolysis; and pyrolytic carbon derived from the pyrolysis of synthetic polymer waste. In a particular embodiment, carbon obtained from methane cracking is most preferred due to its high purity, low ash content, and inherently amorphous microstructure. Granular petroleum coke obtained via delayed or fluid coking exhibits high mechanical strength and desirable particle size distributions, while still retaining substantial amorphous character when produced under appropriate conditions. Advantageously, these carbon sources not only yield carbon suitable for efficient post-plasma operation, but are generally produced as a co-product of processes aimed at generating higher-value outputs, such as hydrogen, upgraded hydrocarbons, or the depolymerization of synthetic waste. As such, their use in the present invention supports integration into industrial ecosystems, enhances resource efficiency, and facilitates environmentally and economically favorable reactor operation. Biomass pyrolysis offers a renewable, carbon-neutral feedstock route and enables incorporation of biogenic carbon into the chemical cycle. Likewise, pyrolysis of synthetic polymers enables valorization of plastic waste streams, supporting broader circular economy targets.

[0065] In preferred embodiment, the inlet for a CO2-rich gas stream is fluidly connected to the feedstock inlet of the plasma gas reactor and to the carbon storage unit. More preferably, the fluid connection between said inlet for a CO2-rich gas stream and said feedstock inlet comprises a pressure reduction unit. This is required to reduce the pressure to between 0.90 and 1.5 bar suitable for atmospheric plasma. Preferably, there is a fluid connection between said inlet for a CO2-rich gas stream, through said carbon storage unit, to said carbon bed within said post-plasma chamber preferably perpendicular to the gas flow within said post-plasma chamber. Preferably this fluid connection is controlled by at least one valve. This valve allows for carrying carbonaceous material from the carbon storage unit to the carbon bed on demand. In a further preferred embodiment, a second fluid connection from the carbon bed within the reactor vessel connects to a solid waste disposal unit. This connection preferably connects the carbon bed from the opposite end of the fluid connection with the carbon storage unit. Preferably, this connection is also provided with a valve suitable. By having separate valves to control both inlet and outlet of fresh and spent carbon material from the carbon bed, the rate of each can be controlled separately. Furthermore, the ratio of CO2-rich gas introduced in the postplasma chamber relative to the amount of carbonaceous material can also be varied as sufficiently high flow rates through the carbon bed are required to carry the solid material within the gas stream.

[0066] The product outlet of the plasma is fluidly connected to the outlet for the CO-rich gas stream. In a preferred embodiment, the modular unit further comprises a recycle line. More preferably, the recycle line fluidly connects the product outlet of the plasma reactor to the feedstock inlet. More preferably, said recycle line further comprises a heat exchanger. More preferably, said recycle line further comprises a compressor pump. More preferably, said recycle line further comprises a control valve or "recycle valve". The control valve is suitable to control the recycle ratio, thereby controlling the ratio of recycled product to the ratio of product extracted from the modular unit through the outlet for CO-rich gas. By being able to adjust this ratio, the modular unit is suitable for a wide range of CO2-rich inlet gas conditions; allowing the modular unit to operate in a broader range of conditions. The compressor pump is desirable to bring the pressure of the recycle gas back up to the desired operating conditions of the plasma regardless of the recycle rate and valve closure. Most preferably, said recycle line comprises in the direction of product outlet to feedstock inlet said control valve, followed by a one-way valve, followed by said compressor. This is desirable to avoid the dangers of blowback.

[0067] In a particular preferred embodiment, the modular unit comprises:

[0068] - a plasma reactor vessel, wherein said plasma reactor comprises a pre-plasma chamber comprising a feedstock inlet, a post-plasma chamber comprising a product outlet and multiple parallel electrode pairings, wherein said electrode pairings fluidly connect said pre-plasma chamber to said post-plasma chamber;

[0069] - wherein said post-plasma chamber comprises a carbon bed;

[0070] - wherein said plasma reactor vessel comprises a cooling unit; - an inlet for the CO2-rich gas stream, wherein said inlet for the CO2-rich gas stream is fluidly connected to said feedstock inlet;

[0071] - a carbon storage unit, which is fluidly connected to said carbon bed;

[0072] - a recycle line, which fluidly connects the product outlet to said plasma reactor vessel;

[0073] - an outlet for the CO-rich gas stream, wherein said product outlet is fluidly connected to said outlet for the CO-rich gas stream; and

[0074] - a power supply unit (PSU), said power supply unit being electrically connected to at least one of said electrode pairings.

[0075] In a further preferred embodiment, the modular unit further comprises a measurement unit. Preferably, the modular unit further comprises a central processing unit. Preferably, said central processing unit is connected to the recycle valve. Preferably, said central processing unit is connected to the valves controlling the flow from CO2-rich inlet gas through the carbon storage unit to the carbon bed. Preferably, said central processing unit is connected to the valves controlling the flow from the carbon bed to the carbon disposal unit. Preferably, said central processing unit is connected to the recycle line compressor. Preferably, said central processing unit is connected to the measurement unit. Preferably, said central processing unit is connected to said power supply unit. Preferably, modular unit comprises an information connector, more preferably an ethernet or wireless connector, connected to said central processing unit. This allows remote control of the operating conditions and continuous data to and from said modular unit.

[0076] In a preferred embodiment, the reactor vessel comprises at least three temperature sensors. A first temperature sensor in the pre-plasma chamber; a second temperature sensor in the post-plasma chamber upstream of said carbon bed. A third temperature sensor in the post-plasma chamber downstream of said carbon bed. These temperature sensors are particularly useful to regulate the power supply to the cathodes, the flow rate of CO2-rich inlet to the feedstock inlet as well as the flow rate of CO2-rich gas through the carbon storage unit into the carbon bed. These temperature sensors are preferably thermocouples. These temperature sensors preferably consist of the measurement unit and are coupled with the central processing unit.

[0077] In a preferred embodiment, the flow rate and pressure sensors are included just upstream of the feedstock inlet and just downstream of the product outlet. More preferably, an 02-sensor is included downstream of the product outlet. More preferably, a CO-sensor is included downstream of the product outlet. More preferably, a CO2-sensor is included downstream of the product outlet. Increases in 02 concentration in the output indicate the carbonaceous material in the carbon bed is spent; suggesting spent material should be removed and new carbonaceous material from the carbon storage unit should be provided. This is preferably achieved by opening respective C02-rich gas valves so new carbonaceous material is carried from the carbon storage unit to the carbon bed.

[0078] In a further preferred embodiment, the modular unit further comprises a housing. Said housing is preferably in the format of a standard shipping container in accordance with ISO 668. More preferably, a 20-foot container which is 20 feet long, 8 feet wide and 8.5 feet high. By providing the modular unit in its entirety with dimensions of a standard shipping container, the modular unit can be produced in its entirety, moved and placed in a relatively simple manner. As the modular unit is designed to be suited for decarbonizing existing blast furnace plants, it is highly desirable to be able to efficiently move it to and place it at existing blast furnace sites.

[0079] In a second aspect, present invention relates to a method for the conversion of a C02-rich gas stream to a CO-rich gas stream, utilizing a plasma reactor vessel, wherein said plasma reactor comprises a pre-plasma chamber comprising a feedstock inlet, a post-plasma chamber comprising a product outlet and multiple parallel electrode pairings, wherein said electrode pairings fluidly connect said preplasma chamber to said post-plasma chamber; wherein said post-plasma chamber comprises a carbon bed; the method comprising the steps of: supplying a C02-rich gas stream to said feedstock inlet; supplying a carbon donor to said carbon bed; applying a power supply to said multiple parallel electrode pairings, thereby igniting a plasma in said plasma reactor vessel; extracting a CO-rich gas stream from said product outlet; and recycling at least a part of said part of said CO-rich gas stream to said plasma reactor vessel.

[0080] This method and system have several major advantages:

[0081] The energy requirements are predominantly in the plasma reactor; allowing efficiency gains as well as electrification of the energy demand. In current processes, energy demand is predominantly from oxidating fossil carbon sources; making electrification difficult.

[0082] CO2 emissions are drastically to entirely reduced. CO2 is efficiently recycled and reused.

[0083] Carbon demand is drastically reduced. Most carbon comes from recycled CO2. Regardless of previous point, adding a relatively small amount of carbon in the form of carbon donor particles reduces almost all free oxygen radicals and 02. This further reduces the energy requirements by removing the need for extraction or separation of free oxygen after plasma dissociation of C02. This also simplifies the required separation equipment.

[0084] In a preferred embodiment, said carbon donor is supplied to said carbon bed by a gas stream, preferably said gas stream is said C02-rich gas or said CO-rich gas.

[0085] In a preferred embodiment, said C02-rich gas stream comprises at least 1 vol% of C02, more preferably at least 2 vol% of C02, more preferably at least 3 vol% of C02, more preferably at least 4 vol% of C02, more preferably at least 5 vol% of C02, more preferably at least 8 vol% of C02, more preferably at least 10 vol% of CO2, more preferably at least 12 vol% of CO2, more preferably at least 14 vol% of

[0086] CO2, more preferably at least 15 vol% of CO2, more preferably at least 16 vol% of

[0087] CO2, more preferably at least 20 vol% of CO2, more preferably at least 25 vol% of

[0088] CO2, more preferably at least 30 vol% of CO2, more preferably at least 35 vol% of

[0089] CO2, more preferably at least 40 vol% of CO2, more preferably at least 45 vol% of

[0090] CO2, more preferably at least 50 vol% of CO2, more preferably at least 55 vol% of

[0091] CO2, more preferably at least 60 vol% of CO2, more preferably at least 65 vol% of

[0092] CO2, more preferably at least 70 vol% of CO2, more preferably at least 75 vol% of

[0093] CO2, more preferably at least 80 vol% of CO2, more preferably at least 85 vol% of

[0094] CO2, more preferably at least 90 vol% of CO2, more preferably at least 95 vol% of

[0095] CO2, most preferably at least 98 vol% of CO2. Advantageously, present modular system is suitable to convert CO2 even in relatively low volumes. Commonly, the exhaust of a blast furnace will comprise other gasses, particularly N2 in large amounts due to the use of air intake.

[0096] Advantageously, present modular unit makes iron production without the intake of air more economical. Generally utilizing pure oxygen is more costly for limited benefits in traditional blast furnace operation. However, as the CO2 is recycled to CO; thus the majority of carbon in the system is recycled and fresh carbon is predominantly added in the carbon bed, avoiding the introduction of air into the system becomes significantly more appealing. Avoiding the introduction of air beneficially reduces the amount of nitrogen gas and other dilutants in the gas cycle from blast furnace to modular unit and back.

[0097] In a preferred embodiment, said CO-rich gas stream comprises at least 1 vol% of

[0098] CO, more preferably at least 2 vol% of CO, more preferably at least 3 vol% of CO, more preferably at least 4 vol% of CO, more preferably at least 5 vol% of CO, more preferably at least 8 vol% )f CO, more preferably at least 10 vol% of CO, more preferably at least 12 vol% of CO, more preferably at least 14 vol% of CO, more preferably at least 15 vol% of CO, more preferably at least 16 vol% of CO, more preferably at least 20 vol% of CO, more preferably at least 25 vol% of CO, more preferably at least 30 vol% of CO, more preferably at least 35 vol% of CO, more preferably at least 40 vol% of CO, more preferably at least 45 vol% of CO, more preferably at least 50 vol% of CO, more preferably at least 55 vol% of CO, more preferably at least 60 vol% of CO, more preferably at least 65 vol% of CO, more preferably at least 70 vol% of CO, more preferably at least 75 vol% of CO, more preferably at least 80 vol% of CO, more preferably at least 85 vol% of CO, more preferably at least 90 vol% of CO, more preferably at least 95 vol% of CO, most preferably at least 98 vol% of CO. A higher concentration of CO is desirable, both in particular for the blast furnace operation. However, purification of these gas mixtures is an energy-intensive and thus expensive endeavour. In a preferred embodiment, no separation is required. This is achieved through the combination of a carbon bed to fixate oxygen species and reduce recombination of CO and oxygen species to CO2; the recycling of product to feedstock to increase conversion, optimized plasma conditions by operating each electrode pair at optimal conditions and scaling through addition of electrode pairs rather than increasing throughput and / or plasma power.

[0099] In another embodiment, the product feedstock is separated. In such case, a CO2- rich separator product and a CO-rich separator product are preferably obtained. The CO-rich separator output is then preferably fluidly connected to a blast furnace for iron ore reduction to iron ore. The CO2-rich separator output is preferably recycled to the feedstock inlet of the plasma reactor. The separation preferably comprises, more preferably consists of, a cryogenic flash or cryogenic distillation.

[0100] It was found that operating, in parallel, several plasma electrode pairings with an optimized power profile allows for higher conversion rates and throughput without sacrificing absolute conversion and energy efficiency. The applicants found that the optimal operating condition is defined by the specific energy input (SEI).

[0101] In a particular preferred embodiment, the specific energy input is divided over multiple parallel electrode pairings operating at a limited power. In a preferred embodiment, each electrode pairing of the multiple parallel electrode pairings operating at an operating power between 0.5 and 2.0 kW, more preferably between 0.8 and 1.8 kW, more preferably between 0.9 and 1.5 kW, more preferably between 1.0 and 1.5 kW, preferably between 1.1 and 1.4 kW, more preferably between 1.1 and 1.3 kW, more preferably between 1.15 to 1.30 kW, most preferably around 1.25 kW. In another preferred embodiment, each electrode pairing of the multiple parallel electrode pairings operates at an operating power of at least 1.0 kW, more preferably at least 1.1 kW, more preferably at least 1.2 kW, more preferably at least 1.25 kW.

[0102] The inventors found that operating a series of electrode pairings in parallel at these conditions shows significantly better results in terms of conversion, conversion rate and energy efficiency compared to working outside of this range. At lower operating power, the conversion of the CO2 to CO conversion in the plasma declines leading to lower conversion. At higher operating power, the temperature in the plasma afterglow is too high resulting in recombination of the products towards the reactant, also leading to lower conversion and a decrease in energy efficiency.

[0103] In a preferred embodiment, the operating pressure Pois at least 0.2 atm, more preferably at least 0.5 atm, more preferably at least 0.8 atm, more preferably at least 0.9 atm, more preferably at least 0.95 atm, more preferably at least 0.97 atm, more preferably at least 0.99 atm, more preferably at least 1.00 atm, more preferably at least 1.01 atm, more preferably at least 1.03 atm, more preferably at least 1.05 atm. In another preferred embodiment, the operating pressure is preferably at most 5 atm, more preferably at most 4 atm, more preferably at most 3 atm, more preferably at most 2.5 atm, more preferably at most 1.5 atm. Present method obtains high energy efficiency and high conversion rate at atmospheric pressures. This is desirable as it allows higher throughput, no need for complex vacuum equipment as well as high energy requirements associated with such vacuums.

[0104] In a further preferred embodiment, the specific energy input is at least 4.0 kJ / L CO2, more preferably at least 4.5 kJ / L CO2, more preferably at least 4.8 kJ / L C02, more preferably at least 4.9 kJ I L CO2, more preferably at least 5.0 kJ / L

[0105] CO2, more preferably at least 5.1 kJ I L C02, more preferably at least 5.2 kJ / L

[0106] CO2, more preferably at least 5.3 kJ I L C02, more preferably at least 5.4 kJ / L

[0107] CO2, more preferably at least 5.5 kJ / L C02. In another further preferred embodiment, the specific energy input is at most 8.0 kJ / L CO2, more preferably at most 7.0 kJ / L C02, more preferably at most 6.5 kJ / L C02, more preferably at most 6.0 kJ / L C02, more preferably at most 5.9 kJ / L C02, more preferably at most 5.8 kJ / L C02, more preferably at most 5.7 kJ / L C02, more preferably at most 5.6 kJ / L CO2, more preferably at most 5.5 kJ / L CO2. In another preferred embodiment, the specific energy input is between 4 and 6 kJ / L CO2, more preferably between 4.5 and 6 kJ / L CO2, more preferably between 5.0 and 6.0 kJ I L CO2, more preferably between 5.0 and 5.7 kJ / L CO2, more preferably between 5.0 and 5.5 kJ / L CO2, most preferably about 5.3 kJ / L CO2.

[0108] Lower specific energy input reduces the absolute conversion. In addition, lower specific energy input implies lower reactor throughput. The combined lower conversion and lower reactor throughput lead to a significant reduction in conversion rate or production rate of the product; even if relatively high energy efficiency can be obtained.

[0109] Higher specific energy input also reduces the absolute conversion. Initially, near the upper range of the specific energy input, the conversion rate will drop but the energy efficiency remains relatively high. Without being bound to theory, the initial drop in conversion rate is partially offset by higher reactor throughput resulting in similar energy efficiency and higher conversion rate or production rate of product, despite lower absolute conversion. Further increases in SEI quickly lead to a drastic reduction in conversion due to recombination of products. This drastic reduction cannot be offset by higher throughput. In this regime both energy efficiency and conversion rate drop substantially.

[0110] In a preferred embodiment, CO2 is supplied to the gliding arc plasma reactor at a flow rate of at least 20 L CO2 I min, more preferably at least 40 L CO2 I min, more preferably at least 50 L CO2 I min, more preferably at least 60 L CO2 / min, more preferably at least 70 L CO2 I min, more preferably at least 80 L CO2 I min, more preferably at least 100 L CO2 I min, more preferably at least 120 L CO2 I min, more preferably at least 150 L CO2 I min, more preferably at least 200 L CO2 I min, more preferably at least 300 L CO2 / min, more preferably at least 500 L CO2 / min, more preferably at least 1000 L CO2 I min. Present application allows significant upscaling of the reactor throughput, allowing large amounts of CO2 to be converted without significant decreases to the conversion and energy efficiency. In addition, present method achieves these results with relatively inexpensive equipment.

[0111] In a preferred embodiment, the gliding arc plasma reactor is cooled downstream of the multiple electrode pairings. This is done to prevent recombination of the products CO and oxygen species (O or 02 or oxygen radicals) towards the reactant CO2. In a further preferred embodiment, the heat transfer capacity of the cooling unit is between 5% and 100% of the total operating power of the gliding arc plasma reactor. Preferably, the heat transfer capacity of the cooling unity is at least 5% relative to the total operating power of the gliding arc plasma reactor, more preferably at least 10%, more preferably at least 20%, more preferably at least 30%, more preferably at least 40%, more preferably at least 50%, more preferably at least 60%, more preferably at least 70%, more preferably at least 80%. A plasma reactor operating five electrodes at 1.2 kW per electrode; with a cooling unit subtracting 6 kW of heat from the downstream plasma zone, preferably the post-plasma chamber, this would correspond to a heat transfer capacity of the cooling unit of 100%.

[0112] In a further preferred embodiment, CO and CO2 are separated with a cryogenic flash or cryogenic distillation, more preferably a cryogenic flash. In preferred embodiment, the cryogenic flash or distillation operates at a temperature of at most -100°C, more preferably at most -110°C, more preferably at most -120°C, more preferably at most -130°C, more preferably at most -140°C. In a preferred embodiment, the cryogenic flash operates at a temperature of at least -180°C, more preferably at least -170°C, more preferably at least -160°C, more preferably at least -150°C. In preferred embodiment, the cryogenic flash or distillation operates at a pressure of at least 10 bar, more preferably at least 20 bar, more preferably at least 24 bar, more preferably at least 25 bar, most preferably about 26 bar. In preferred embodiment, the cryogenic flash or distillation operates at a pressure of at most 50 bar, more preferably at most 40 bar, more preferably at most 30 bar. The operating temperature and pressure of a distillation tower is a range; and the entirety of the range preferably falls within these specified ranges. In a preferred embodiment, the cryogenic distillation has at most 80 trays, more preferably at most 60 trays, more preferably at most 50 trays, more preferably at most 40 trays, more preferably at most 30 trays, more preferably at most 20 trays, more preferably at most 15 trays, more preferably at most 10 trays, more preferably at most 9 trays, more preferably at most 8 trays, more preferably at most 7 trays, more preferably at most 6 trays, more preferably at most 5 trays, more preferably at most 4 trays, more preferably at most 3 trays, more preferably at most 2 trays, more preferably at most 1 tray. A cryogenic distillation with only 1 tray is considered a cryogenic flash herein. The applicant surprisingly found that CO2 can be extracted, and assuming no further consistuents, high purity CO can be obtained with a limited number of trays. Limiting the number of trays is then advantageous to reduce both complexity of installation as well as operating energy requirements.

[0113] In a preferred embodiment, the plasma is a warm plasma. A warm plasma is a nonthermal, non-equilibrium plasma. The gas temperature is lower than the electron temperature therein. Preferably the plasma temperature is between 3000 and 5000K. Sufficiently high temperatures are required for plasmolysis of CO2. It is preferred to avoid plasma temperatures above 6000K. This may lead to the formation of carbon particles, requiring heterogeneous separation of particles from the gas stream downstream of the plasma reactor as well as appropriate piping and equipment.

[0114] In a preferred embodiment, the gas temperature downstream of the plasma is at most 800°C, more preferably at most 700°C, more preferably at most 600°C, more preferably at most 500°C, more preferably at most 400°C, more preferably at most 300°C. Preferably, the gas temperature downstream of the plasma reactor is measured within 10 cm of said plasma reactor, more preferably at a distance 5 cm from the electrode pairing. By maintaining lower temperatures downstream of the electrode pairings, recombination of CO to CO2 is limited or avoided.

[0115] Advantageously, the removal of (most) oxygen from the plasma stream by fixation with carbon particles allows the separation of a predominantly binary rather than tertiary system. This allows for far easier and cheaper separation. In a further preferred embodiment, CO and CO2 are separated with cryogenic distillation, cryogenic flash or pressure-swing absorption (PSA). More preferably, CO and CO2 are separated with cryogenic flash. Advantageously, a single stage vapor I liquid separation method is considerably simpler, requires smaller, less technologically advanced equipment as well as lower energy requirements than cryogenic distillation. The inventors surprisingly found cryogenic distillation is sufficient to purify the CO-rich separator outlet to 99 wt.% CO. For purities over 99.99%, cryogenic distillation is likely preferred. For blast furnace applications this additional purity does not weigh up against the additional energy requirements.

[0116] In a third aspect, the present invention relates to a iron production method comprising the steps of: reducing iron ore using a CO-rich gas stream, thereby producing iron and a CO2-rich gas stream; extracting said CO2-rich gas stream; converting said CO2-rich gas stream to a CO-rich gas stream according to any of claims 10-14; optionally purifying said CO-rich gas; and recycling said CO-rich gas stream to said blast furnace.

[0117] As maintained throughout this disclosure, the modular unit described herein is particularly advantageous for use in combination with a blast furnace. Blast furnaces are used all around the world and are a major emitter of CO2. While green alternatives for steel production are being produced, a major issue is these techniques require large changes to the existing blast furnace plants. Carbon capture and storage (CSS) is also considered as an option, but this option is limited to sites from where carbon storage is possible. Furthermore, carbon storage is significantly less desirable than converting CO2 to a high value product as CO. In particular if the blast furnace requires carbon as a feedstock to reduce iron ore.

[0118] The modular unit and method in accordance with the third aspect of present invention can operate exclusively on inputs which exist at every blast furnace plant: CO2 exhaust, carbonaceous material and electricity. Furthermore, it can be produced in a modular fashion, shipped and placed at these locations. It allows operation in an energy-efficient manner for a wide variety of conditions. This is particularly difficult to achieve for plasma processes, where reactors are generally designed for specific inputs and outputs at maximized conditions due to the difficulty of scaling a plasma reactor.

[0119] In a particular preferred embodiment, CO2 is extracted from said CO2-rich flu gas by absorption. In another preferred embodiment, the modular unit according to the first aspect of the invention is fluidly connected with a CO2 absorber. More preferably an amine-based CO2 absorber. Preferably, the regeneration or stripper unit of the CO2-absorber is fluidly connected to inlet for the CO2-rich gas stream of the modular unit according to the first aspect.

[0120] In a further preferred embodiment, the CO2-absorber comprises absorption of CO2 with an amine. More preferably, CO2-rich flu gas from a blast furnace is contacted with a liquid amine solvent in an absorber. Preferably, said liquid amine solvent comprises: monoethanolamine (MEA), diethanolamine (DEA), methyldiethanolamine (MDEA) or mixtures thereof, most preferably, monoethanolamine (MEA).

[0121] The liquid amine solvent absorbs CO2 through reaction of the amine with CO2, resulting in an enriched amine solvent. The enriched amine solvent can then be redirected to a stripper, in which the enriched amine solvent is heated. This reverses the reaction, releasing a CO2-rich gas stream. The modular unit according to present invention can advantageously convert this CO2-rich gas directly. Further purification or removal of impurities is not required, resulting in a reduction of transport and purification needs.

[0122] In a further preferred embodiment, the liquid amine solvent is an aqueous solution comprising MEA in an amount of 15 to 30 wt.% prior to enrichment. Preferably, the absorber operates at a temperature between 40 and 80°C, more preferably between 50 and 75°C, more preferably between 55 and 70°C, most preferably between 55 and 65°C. Preferably, the absorber operates at a pressure between 0.90 and 2.5 atm, more preferably 0.90 and 1.5 atm, more preferably 0.9 and 1.4 atm, more preferably 0.9 and 1.3 atm, more preferably 0.9 and 1.2 atm, more preferably 0.9 and 1.1 atm.

[0123] In a further preferred embodiment, the stripper or regenerator operates at a temperature between 100 and 140°C, more preferably between 120 and 140°C, most preferably between 130 and 140°C.

[0124] Typically absorption and regeneration of CO2 is a highly energy-intensive process. This reduces the CO2-emissions reduction achieved. The majority of the energy requirement is during regenerating, particularly heating the enriched amine liquid. Present modular unit allows for large efficiency gains through immediate further use as well as heat exchange. The warm CO2 gas stream is further heated through plasma, unlike carbon capture and storage. High-temperature fluid streams from the modular unit can be utilized as heat sources for the regeneration unit, as advantageously provided by the modular unit of present application. This results in significant energy-efficiency gains compared to separate production units, let alone carbon capture and storage methods.

[0125] Figures

[0126] Example 1

[0127] Example 1 relates to an embodiment of a plasma reactor comprising a a pre-plasma chamber comprising a feedstock inlet, a post-plasma chamber comprising a product outlet and multiple parallel electrode pairings, wherein said electrode pairings fluidly connect said pre-plasma chamber to said post-plasma chamber; wherein said postplasma chamber comprises a carbon bed.

[0128] To better exemplify reference is made to figure 1, which shows a cross-sectional view of a fixed bed plasma reactor (110) for the conversion of CO? gas. A carbon bed (101) is added to the post-plasma chamber (102) as a fixed bed, which is positioned downstream to multiple reactor modules (103, 109). The multiple reactor modules consist of multiple gliding arc cathodes (103) mounted on a common grounded anode plate (109). Each cathode is connected to an individual power supply (not shown) allowing activation and operation of each cathode independently.

[0129] A CO2 rich feedstock gas (104) is supplied to the feedstock inlet (106) to the plasma jet generators (103) via a pressure chamber (105). Pressure chamber 105 divides the feedstock gas over the available reactor pairings in an even and consistent manner. A plasma is ignited in the CO2 rich feedstock gas (104), by provision of power to the reactor modules, thereby obtaining a plasma jet comprising CO and O species. The afterglow of the plasma jet is introduced in the post-plasma chamber (102) comprising the carbon bed (101). The carbon bed (101) is a fixed bed comprising carbonaceous material and promotes fixation of O species towards CO, preventing recombination of O species with CO towards CO2. The post-plasma chamber is provided with product outlet (108) for the extraction of a CO-rich gas stream.

[0130] Figure 2 displays four embodiments (A, B, C, D) of multiple reactor modules. As can be seen in Figure 12, by 5, 6, 7 or even 20 parallel gliding arc reactor modules can be provided as a series of reactor cathodes mounted on a common anode plate, separated by an insulation ring. Preferably, the power provided to each reactor module can be chosen independently from the other modules. More preferably, each reactor module or group of 1, 2, 3, 4 or 5 reactor modules is connected to their own power supply unit.

[0131] The inventors surprisingly found that operating a limited number of reactor pairings at optimal conditions is desirable over operating all available reactor pairings at reduced flow rates and I or energy inputs. This is surprising when the non-active reactor pairings remain open, and thus allow for throughput of reactant without ignition of plasma therein. It should be noted that present design still allows for reaction of CO2 which passes through an inactive reactor pairing. The plasma tail of the active reactor pairings comes into contact with gas flow from inactive reactor pairings quickly in the post-plasma chamber. This allows for reaction between CO2 from an inactive reactor module and oxygen species from active reactor modules. Furthermore, it reduces the buildup of heat in the post-plasma chamber which is beneficial to the energy efficiency of the reactor.

[0132] Consequently, providing an anode plate with a multitude of reactor pairings, each individually connected to a power supply unit, allows for an easy yet clear reactor design that can be operationally adjusted to the required reactor throughput by increasing and decreasing the amount of operational reactor pairings. This allows operating each reactor pair at near optimal conditions; while the remaining reactor pairings are not powered on but still allow fluid throughput. As a result, a modular design is obtained that can operate at sufficiently high conversion and energy efficiency for a wider range of throughput volumes and conditions. Furthermore, the operational parameters and throughput can be adjusted for without stopping operation.

[0133] Example 1

[0134] A reactor setup was assembled comprising a single reactor vessel divided into a preplasma chamber and a post-plasma chamber by a grounded anode plate. Seven (7) parallel reactor cathodes were mounted on the anode plate, each electrically insulated therefrom by an insulating ring. A carbon bed was positioned within the post-plasma chamber. The distance between the anode plate exhaust and the nearest carbon particles was 5 cm. The carbon bed had a thickness of 3 cm in the direction of gas flow and a diameter of 11 cm. The reactor was operated at a total plasma power of 5 kW, with a combined CO2 feed of 60 L / min distributed across all electrode pairings. The CO2 gas stream was sourced from a carbon capture unit downstream of a steel plant flue gas treatment system. The carbon bed was filled with carbon particles having a diameter distribution between 0.5 mm and 5 mm. Following a warm-up period of approximately 6 minutes, during which the outlet CO concentration gradually increased, steady-state operation was achieved. During steady-state, the concentration of CO in the product gas stream exceeded 80 vol%. The specific energy input under these conditions was determined to be approximately 1.2 kWh per kg of CO produced.

[0135] Examples 2-6

[0136] A simplified reactor setup was constructed, comprising a single plasma reactor electrode pairing mounted on an anode plate separating the reactor into a preplasma and post-plasma chamber. A carbon bed was placed in the post-plasma chamber. The reactor was operated under fixed plasma power and CO2 flow rate conditions, while five different carbon sources were tested for comparative performance. The carbon materials were filled into the carbon bed and weighed before and after a fixed-duration experiment to determine the consumption rate. The resulting CO concentrations in the outlet gas were measured throughout. The results are summarized in Table 1.

[0137] The tested carbon materials included commercially available grades (Jacobi EcoSorb™, Carbuna CPK4, Norit PK 3-5), a sample provided by BASF produced via dry reforming of methane, and a granular pyrolytic carbon sample referred to as "circular carbon." The latter was obtained through pyrolysis of mixed post-consumer plastic waste, yielding a high-amorphous-content carbon fraction.

[0138] Table 1 : Examples 2 to 6

[0139] EXAMPLE CARBON NAME CONSUMPTION RATE CO CONC.

[0140] (G / H) (VOL.%)

[0141] EX. 2 Jacobi EcoSorb™ CS 19.8048 ± 0.0006 48 ± 4

[0142] EX. 3 Carbuna CPK4 53.7793 ± 0.0006 49 ± 3

[0143] EX. 4 Norit PK 3-5 32.6046 ± 0.0006 52 ± 3

[0144] EX. 5 BASF (methane 9.5268 ± 0.0006 24 ± 1 reforming)

[0145] EX. 6 Circular carbon 36.3726 ± 0.0006 54 ± 2

[0146] Importantly, all carbon sources with a high degree of amorphicity demonstrated similarly high CO yields and consistent performance, confirming that a high amorphous content is a key determinant of effective carbon functionality in the postplasma zone. The carbon sample provided by BASF, derived from methane reforming, exhibited noticeably lower performance compared to the other references. This is attributed in part to its lower surface area, but more significantly to its structural characteristics, which suggest a closer resemblance to a crystalline carbon allotrope rather than an amorphous form. While the BASF sample still facilitated CO formation in the range of 24-30 vol.%, its carbon consumption rate was markedly lower than that of the more amorphous samples, indicating reduced reactivity under the tested plasma conditions.

Claims

CLAIMS1. Modular unit for the conversion of a CO2-rich gas stream to a CO-rich gas stream, said modular unit comprising:- plasma reactor comprising a plasma reactor vessel comprising a preplasma chamber comprising a feedstock inlet, a post-plasma chamber comprising a product outlet and multiple parallel electrode pairings, wherein said electrode pairings fluidly connect said pre-plasma chamber to said post-plasma chamber;- wherein said post-plasma chamber comprises a carbon bed;- wherein said plasma reactor vessel comprises a cooling unit;- an inlet for the CO2-rich gas stream, wherein said inlet for the CO2-rich gas stream is fluidly connected to said feedstock inlet;- a carbon storage unit, which is fluidly connected to said carbon bed;- a recycle line, which fluidly connects the product outlet to said feedstock inlet;- an outlet for the CO-rich gas stream, wherein said product outlet is fluidly connected to said outlet for the CO-rich gas stream; and- a power supply unit (PSU), said power supply unit being electrically connected to at least one of said electrode pairings.

2. Modular unit in accordance with claim 1, wherein said carbon storage unit is fluidly connected with said inlet for the CO2-rich gas stream or said recycle line, preferably said inlet for the CO2-rich gas stream.

3. Modular unit in accordance with claims 1-2, wherein said cooling unit comprises a fluid jack surrounding at least part of the post-plasma chamber.

4. Modular unit in accordance with claim 3, wherein the modular unit further comprises a heat exchanger, wherein said heat exchanger has a cold and a hot circuit, wherein said hot circuit is fluidly connected to said CO2 inlet for the CO2-rich gas stream and wherein said cold circuit is fluidly connected to said fluid jacket, preferably said cold circuit is a closed circuit.

5. Modular unit in accordance with any of claims 1-4, wherein said recycle line further comprises a compressor.

6. Modular unit in accordance with any of claims 1-5, wherein said plasma reactor comprises at least 5 electrode pairings.

7. Modular unit in accordance with any of claims 1-6, wherein said reactor vessel comprises an anode plate, wherein said anode plate separates said preplasma chamber from said post-plasma chamber, and wherein said reactor vessel comprises multiple parallel reactor cathodes, wherein said multiple parallel reactor cathodes are mounted on said anode plate, wherein each parallel reactor cathode is electrically insulated from said anode plate.

8. Modular unit in accordance with claim 7, wherein each parallel reactor cathode comprises a tangential gas inlet for fluid communication with the preplasma chamber and an axial plasma outlet for fluid communication with the post-plasma chamber.

9. Modular unit in accordance with claim 8, wherein said anode plate is grounded and wherein each parallel reactor cathode is electrically connected to said power supply unit.

10. Method for the conversion of a CO2-rich gas stream to a CO-rich gas stream, utilizing a plasma reactor, wherein said plasma reactor comprises a plasma reactor vessel comprising a pre-plasma chamber comprising a feedstock inlet, a post-plasma chamber comprising a product outlet and multiple parallel electrode pairings, wherein said electrode pairings fluidly connect said preplasma chamber to said post-plasma chamber; wherein said post-plasma chamber comprises a carbon bed; the method comprising the steps of: supplying a CO2-rich gas stream to said feedstock inlet; supplying a carbon donor to said carbon bed; applying a power supply to said multiple parallel electrode pairings, thereby igniting a plasma in said plasma reactor; extracting a CO-rich gas stream from said product outlet; and recycling at least a part of said part of said CO-rich gas stream to said plasma reactor vessel.

11. Method according to claim 10, wherein said carbon donor is supplied to said carbon bed by a gas stream, preferably said gas stream is said CO2-rich gas or said CO-rich gas.

12. Method according to claim 10 or 11, wherein said CO2-rich gas stream comprises at least 10 vol% of CO2, more preferably at least 20 vol% of CO2.

13. Method according to claim 10 or 11, wherein said CO-rich gas stream comprises at least 10 vol% of CO, more preferably at least 15 vol% of CO.

14. Method according to any of claims 10-13, wherein the carbon donor is selected from the list of : charcoal, coal, cokes or a combination thereof, most preferably cokes.

15. An iron production method comprising the steps of: reducing iron ore using a CO-rich gas stream, thereby producing iron and a CO2-rich gas stream; extracting said CO2-rich gas stream; converting said CO2-rich gas stream to a CO-rich gas stream according to any of claims 10-14; optionally purifying said CO-rich gas; and recycling said CO-rich gas stream to said blast furnace.

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