Method for storing solid carbon and / or carbon dioxide

Abstract

The invention relates to a method for storing solid carbon and / or carbon dioxide.

Description

[0001] Methods for storing solid carbon and / or carbon dioxide

[0002] background

[0003] Since the beginning of the industrial revolution, there has been an extraordinary increase in greenhouse gases in the atmosphere. In particular, the increased emission of carbon dioxide from industrial plants is leading to progressive global warming. Limiting this effect and other associated negative impacts on the environment is one of the greatest and most urgent challenges of our time.

[0004] A key step towards achieving this goal lies in avoiding industrial carbon dioxide emissions. This often requires a fundamental transformation of the relevant processes. In many cases, carbon dioxide emissions can be avoided by replacing fossil fuels with hydrogen as an energy carrier. This important pathway for limiting carbon dioxide emissions is currently still limited by the restricted availability of climate-neutral hydrogen. The latter can be produced on an industrial scale, for example, via electrolysis or steam reforming of methane.

[0005] The electrolysis of hydrogen is technically complex and requires large amounts of energy. To make hydrogen production climate-friendly, this energy must be as green as possible, i.e., generated with no or minimal carbon dioxide emissions. Since the availability of green energy is currently limited in many parts of the world, the technically much simpler and more energy-efficient method of steam reforming of methane is often used for industrial-scale hydrogen production. However, this process releases carbon dioxide. Thus, the green transformation of many industrial processes, e.g., in the steel industry, often results in residual carbon dioxide emissions. Other industrially generated carbon dioxide emissions, such as those from cement production or waste incineration, cannot currently be avoided (economically) through alternative processes.To prevent the carbon dioxide produced during these processes from having a harmful effect on the climate, it can be captured and permanently stored geologically. This method is also known as Carbon Capture & Storage (CCS).

[0006] In currently established CCS processes, the resulting carbon dioxide is stored as a gas, liquid, or supercritical fluid. In the long term, however, it would be desirable to split the carbon dioxide in such a way that the carbon it contains is released as a solid and the oxygen it contains is either released into the atmosphere or can be used in further processes or process steps.

[0007] An energy-efficient alternative process that allows for the industrial-scale production of hydrogen is the pyrolysis of methane. In this process, methane is split to form hydrogen and solid carbon.

[0008] CH4 (g) --> C (s) + 2 H2 (g) .

[0009] The aim of the current invention is to geologically store the solid carbon obtained in this or other ways together with carbon dioxide – i.e., as a mixture of carbon dioxide-containing fluid and solid carbon. The carbon can positively support the storage of the carbon dioxide, e.g., by adsorbing carbon dioxide on the surface of the mixed powder or by stabilizing the geological structures involved. Summary

[0010] The invention is defined by the attached claims.

[0011] In particular, a method for storing solid carbon and / or carbon dioxide is provided, comprising the steps of: a) providing a first composition comprising carbon in solid form and providing a second composition comprising a carbon dioxide-containing fluid; and b) mixing the first and second compositions to form a third composition; c) storing the third composition in an underground storage facility of a storage site.

[0012] Brief character description

[0013] Fig. 1 schematically illustrates the setup of the process.

[0014] Detailed description

[0015] Introduction

[0016] To prevent the release of climate-damaging carbon dioxide generated in industrial processes, or to remove carbon dioxide already present in the atmosphere, carbon dioxide is captured in established processes and subsequently stored as a fluid, particularly as a gas, liquid, and / or supercritical fluid, in underground geological structures. This method is known as Carbon Capture and Storage (CCS), and the corresponding established plants and processes represent the state of the art. Storage, as defined in this disclosure, means that the component is initially contained within the storage site, but it is not entirely impossible that a component may escape from the storage site, at least partially, after this initial containment.

[0017] The idea is to store carbon dioxide not in its pure form, but in combination with solid carbon. Ideally, the mixture is an aerosol or a dispersion. The solid carbon contained in the aerosol or dispersion can act as an adsorbent for the carbon dioxide, thus supporting safe storage. Furthermore, the added solid can enhance the stability of the geological storage structures. At the same time, the positive effects of carbon dioxide avoidance processes would be further increased, making these technologies even more attractive.

[0018] Origin of carbon dioxide and carbon

[0019] The carbon dioxide can originate from industrial processes, such as the production of hydrogen, directly reduced iron, pig iron, steel, glass, or cement, or directly from the atmosphere and be captured through appropriate processes. The solid carbon can originate from a carbon dioxide emission-avoiding process, such as the production of hydrogen via the pyrolysis of a hydrocarbon, particularly natural gas, biogas, methane, or an aliphatic hydrocarbon, or from other processes, such as those that split or further convert (captured) carbon dioxide. The stored carbon dioxide and the stored carbon can originate from the same process or process chain, or from different processes or process chains. This makes it possible, in particular, to reduce the amount of carbon dioxide emitted into the atmosphere during industrial processes.

[0020] In the disclosure presented here, carbon is added to carbon dioxide or a carbon dioxide-containing fluid. The carbon can be in solid form as a fluid-conveyable bulk material, particularly as a powder. Advantageously, the carbon particles have a high specific surface area, resulting in high adsorption of the carbon dioxide-containing fluid.

[0021] A method for storing solid carbon and / or carbon dioxide is therefore disclosed, comprising the steps of: a) providing a first composition comprising carbon in solid form and providing a second composition comprising a carbon dioxide-containing fluid; b) mixing the first and second compositions to form a third composition; and c) storing the third composition in an underground storage facility of a storage site.

[0022] The displacement of the carbon dioxide-containing fluid and the solid carbon can take place at or far from their respective points of origin and / or storage. To achieve a positive effect on carbon dioxide storage, the solid carbon can be introduced into an underground storage facility either simultaneously with the carbon dioxide or independently, either at the same time and / or in the same location.

[0023] Carbon dioxide from the first composition may be partially or completely adsorbed onto the carbon from the second composition.

[0024] Description of Carbon Dioxide-Containing Fluid: The fluid used to mix in the solid carbon can be a gas, a liquid, and / or a supercritical fluid. The mixture of carbon and fluid can therefore be an aerosol or a dispersion.

[0025] The fluid can contain at least 10 vol.% carbon dioxide, 20 vol.% carbon dioxide, 30 vol.% carbon dioxide, 40 vol.% carbon dioxide, 50 vol.% carbon dioxide, 60 vol.% carbon dioxide, 70 vol.% carbon dioxide, 80 vol.% carbon dioxide or 90 vol.% carbon dioxide.

[0026] Description of carbon

[0027] In the powder, the carbon is present as particles. The diameter of the carbon particles can range from 1 nanometer to 1000 micrometers. The specific surface area (calculated using the BET method according to ISO 9277) can be at least 10, 50, 100, 150, 200, 250, 300, 500, 1000, 2000 m² / g, or more.

[0028] Advantageously, the carbon particles have a high specific surface area, resulting in high adsorption of carbon dioxide-containing fluid.

[0029] To achieve an increased specific surface area, the carbon production process, e.g., methane pyrolysis, can be carried out under conditions that increase the specific surface area. Alternatively or additionally, one or more processing steps can be added downstream of the carbon production process to modify the surface area of ​​the carbon towards a higher specific surface area.

[0030] Description of the mixture: The mixture of carbon dioxide-containing fluid and solid carbon can have a pressure in the range of > 1 bar and < 400 bar, > 10 bar and < 400 bar, or > 80 bar and < 400 bar, and / or a temperature in the range of > -56.6 °C and < 250 °C, > -14 °C and < 250 °C, or > 0 °C and < 250 °C. The measuring point for these values ​​can be the inlet of the delivery line for the mixture into the storage tank.

[0031] Optional addition of a liquid

[0032] The process may further include a step of providing the first composition which comprises: providing carbon in solid form, mixing the carbon in solid form with a fluid, in particular water, to form the first composition.

[0033] The transfer of fluid can only take place in or on the way to the storage site itself.

[0034] Therefore, the step of mixing the carbon in solid form with a fluid can take place a) in the storage site, further comprising separately introducing the first composition and the second composition into the underground storage; or b) during transport to the storage site, further comprising introducing the third composition into the underground storage.

[0035] Description of underground storage

[0036] The underground storage facilities used can be natural or artificial, such as porous or cavern reservoirs. Porous reservoirs are typically naturally occurring, porous geological structures. The pore size can be microscopic or macroscopic. Examples of porous reservoirs include depleted oil or gas reservoirs, saline aquifers, coal seams, or basalts.

[0037] Cavern storage facilities are typically large, artificially created cavities ranging in size from several meters to several hundred meters in diameter or height. These can be created, for example, by leaching underground salt domes or through other mining methods.

[0038] Carbon dioxide in these storage facilities is typically present as a gas, a liquid, and / or a supercritical fluid, either pure or, for example, as an aqueous solution. Storage can be purely physical and / or supported by physical and / or chemical binding or mineralization.

[0039] Description of the facility

[0040] Furthermore, a plant for storing solid carbon and / or carbon dioxide is disclosed, comprising the following units: a) a unit for providing a first composition comprising carbon in solid form and a unit for providing a second composition comprising a carbon dioxide-containing fluid; b) a unit for mixing the first and second compositions to form a third composition; and c) a unit for storing the third composition in an underground storage facility of a storage site.

[0041] The plant is specifically designed to carry out the procedure as described above. The plant may also include a plant control system for controlling and / or regulating the plant and its processes according to the procedures described above.

[0042] The system may also include instrumentation for data acquisition of system and process behavior for monitoring, evaluation and / or optimization of system behavior.

[0043] Exemplary carbon source

[0044] In the present disclosure, hydrocarbon-containing gas can be introduced into the molten iron and / or slag in a reactor chamber. Temperatures exceeding 1000°C in the molten iron and / or slag (or even lower temperatures when using catalysts) enable methane pyrolysis and thus the production of free carbon and hydrogen directly in the molten iron and / or slag, without the need to produce the hydrogen in a separate process before introducing it into the molten iron and / or slag. Therefore, it is possible to use the energy required for heating and melting the feedstocks (e.g., iron, iron ore) for the production of free carbon and hydrogen, and thus the reducing agent.

[0045] The carbon and hydrogen obtained can react with the metal oxides of the iron ore to reduce the metal oxide to metal. The main byproducts are carbon dioxide and water. Any gaseous and solid products of the methane pyrolysis that are not consumed during the reduction can be separated from the reactor chamber and thus recovered. The disclosed process can therefore include a process for the production of solid carbon, and optionally also steel, ferroalloys, or pig iron, comprising the steps:

[0046] - Providing a melting furnace system with at least one electrode and / or induction coil for electrical energy input, wherein molten iron and / or slag is present in the reactor space of the melting furnace system, obtained from at least one feedstock;

[0047] - Introducing a hydrocarbon-containing first gas into the molten iron and / or slag via a gas introduction device;

[0048] - At least partial pyrolytic conversion of the gas to solid carbon and at least one second gas, wherein the at least second gas exhibits a reducing effect towards metal oxide; and

[0049] - Obtaining carbon, and optionally steel, ferroalloys or pig iron.

[0050] The at least one solid and / or liquid ingredient can comprise 0-3 wt.%, 0-2 wt.% or 0-1 wt.% carbon.

[0051] The process is also suitable for using feedstocks with a low carbon content, since solid carbon is produced during pyrolysis.

[0052] Advantageously, this process makes it possible to increase the carbon content in feedstocks with only a low carbon content, in order to increase the carbon content to over 3 wt%, as is typical for pig iron.

[0053] The feedstock can include metal ores, metal (e.g., scrap), slag formers, and / or substances containing carbon. The process can also largely or completely eliminate the need for adding carbon from sources other than the hydrocarbon-containing initial gas.

[0054] The carbon introduced into the reactor chamber should consist of 5-100 wt% from the hydrocarbon-containing first gas, based on the total amount of carbon in the entirety of the hydrocarbon-containing first gas and feedstock.

[0055] The feedstock can be an iron carrier with a metallization level of 50%-100% or 60%-95%.

[0056] Therefore, it is advantageously possible to use incompletely reduced material alone or as a subset with this method.

[0057] For example, incompletely reduced material can be Direct Reduced Iron and / or Hot Briquetted Iron.

[0058] The amount of the first gas introduced may be sufficient to adjust the metal melt to a predetermined carbon content, optionally at least 3 wt.%.

[0059] This makes it more advantageous, for example, to obtain pig iron.

[0060] As soon as the quantity and / or composition of the first gas introduced leads to the formation of solid carbon and / or carbon-containing compounds outside the molten metal, these can appear in the slag.

[0061] The carbon-containing compounds can be free carbon or gaseous carbon compounds. This approach is advantageous because solid or gaseous carbon compounds can be obtained through the process.

[0062] Thus, the formation of carbon-containing compounds in the atmosphere and / or of carbon as a solid can occur, and these compounds and the carbon can be removed from the reactor space.

[0063] The energy input can be controlled by the electrode and / or induction coil and / or the quantity introduced and / or the inlet temperature of the first gas.

[0064] Gas can be introduced completely or in portions, either through a hollow electrode or via a separate gas introduction device. If the gas introduction device is a lance, the reaction process can also be controlled by the position of the lance's outlet within the reactor chamber.

[0065] The lance is movable at least vertically, thus allowing control of the vertical position of the lance outlet within the reactor chamber. This, in turn, allows control over the height at which the first gas escapes within the molten rock or slag.

[0066] By simultaneously controlling at least two of the aforementioned or further factors, the methane pyrolysis or metallurgy process can be monitored via suitable sensors and controlled by actuators. Suitable model- or data-driven algorithms (with and without the use of AI) can be employed to optimize process control. The initial gas can have a temperature of 25°C (ambient or room temperature up to 1000°C, preferably 400°C to 800°C) upon introduction at the inlet of the gas introduction device.

[0067] In principle, the initial gas can be introduced at room temperature, and heating it to the desired reaction temperature can take place in the reactor chamber. However, it may also be desirable to heat the initial gas to a temperature above room temperature in order to optimize the methane pyrolysis process.

[0068] The temperature in the molten metal during operation can be 1000°-1700°C.

[0069] The gas supply system is located outside the reactor chamber. This means that the point of entry for the first gas is separated from the reactor chamber.

[0070] The second gas may have a ratio in vol.-% of (H2+ CO) to (H20 + carbon dioxide) greater than 10, 30, 50, 70 or 90 .

[0071] The first gas can be conditioned in composition and / or temperature and / or pressure before being introduced.

[0072] This allows the reaction conditions of methane pyrolysis and metallurgy to be optimized.

[0073] The free carbon can

[0074] - be dissolved exclusively in the molten metal,

[0075] - be dissolved in the molten metal and present in the slag, or - be dissolved in the molten metal, present in the slag and / or present as a separate solid in the reactor space.

[0076] If the free carbon is to be dissolved exclusively in the molten metal, only enough first gas is introduced to bring the molten metal up to the desired carbon content (maximum up to carbon saturation).

[0077] If free carbon is required outside the molten metal, methane pyrolysis is carried out with excess carbon. Excess free carbon can be removed from the reactor in solid form, and / or the CO or carbon dioxide produced can be removed from the reactor chamber. These products can be reused for other purposes.

[0078] Therefore, the procedure can include the following steps:

[0079] - Production of a first product exhibiting free carbon outside the melt, and

[0080] - Removal of the product.

[0081] Furthermore, the procedure may include the following step:

[0082] - Reworking or processing the first product into a second product containing free carbon.

[0083] The product can be, for example, atomic carbon, graphite, or fullerenes. Further processed products can be carbon black, nanotubes, or graphene. This product represents solid carbon as defined in this disclosure. The first product can be used to manufacture any second product that uses free carbon as a starting material.

[0084] The procedure may also include the following steps:

[0085] - at least partial removal of gas from the reactor space;

[0086] - Removal of the non-reducing components from the extracted gas and / or removal of the reducing gas components from the extracted gas, where optionally the reducing gas components are H2, CO, or hydrocarbons; and

[0087] - Use of the reducing gas components in a further process, whereby optionally the reducing gas components are used as reducing agents or energy carriers in the further process.

[0088] The gases extracted from the reactor chamber can include hydrogen, hydrocarbons (e.g., alkanes, alkenes), CO, carbon dioxide, H2O, and / or N2.

[0089] This makes it advantageously possible to use even the gaseous byproducts in further processes.

[0090] For example, one could combine the steam reforming process based on natural gas with the pyrolysis process based on natural gas and mix the carbon dioxide captured during steam reforming with the solid carbon from methane pyrolysis, then store them together in the underground storage facility as described above. Other carbon dioxide sources can also be used.

[0091] Detailed description of the figures: Fig. 1 schematically shows two variants of the disclosed method.

[0092] Carbon (1) and carbon dioxide-containing fluid (2) are provided from one (a) or more separate input processes and / or sources (here b and c). It is also possible that some of the carbon (1) and / or carbon dioxide-containing fluid (2) originates from one process (a) but is supplemented with carbon (1) and / or carbon dioxide-containing fluid (2) from other sources (b and / or c). The composition comprising the carbon and / or the carbon dioxide-containing fluid can be pressurized (e.g., greater than 1 bar) before mixing.

[0093] Carbon (1) and carbon dioxide-containing fluid (2) are introduced into a suitable device 3, thereby producing a dispersion with the desired composition.

[0094] In this dispersion, some of the carbon dioxide-containing fluid can adsorb onto the solid carbon (4) .

[0095] The mixture (4) is then transferred from the device (3) below the earth's surface (5). This can be done under pressure (e.g., greater than 1 bar). There, the mixture (4) is stored in an underground storage tank (6).

[0096] Alternatively, carbon dioxide-containing fluid (2) and carbon can be used.

[0097] (1) can also be introduced separately into the underground storage facility (not illustrated). The composition comprising the carbon and / or the carbon dioxide-containing fluid can be pressurized during introduction (e.g., greater than 1 bar). In the underground storage facility (6), it can lead to the adsorption of the carbon dioxide.

[0098] (2) come into contact with the carbon (1). The carbon (1) can be mixed with a fluid, e.g. water, at the location of the underground storage (6) or during transport to the underground storage (6) (not illustrated).

[0099] Reference symbol list

[0100] 1: C; Carbon

[0101] 2: CO2; Carbon dioxide 3: Mixing

[0102] 4: Adsorption of CO2 onto C

[0103] 5: Earth's surface

[0104] 6: Underground storage

Claims

1. Patent claims 1. A method for storing solid carbon and / or carbon dioxide, comprising the steps of: a) providing a first composition comprising carbon in solid form and providing a second composition comprising a carbon dioxide-containing fluid; b) mixing the first and second compositions to form a third composition; and c) storing the third composition in an underground storage facility of a storage site.

2. Method according to claim 1, wherein the solid carbon acts as an adsorber towards the carbon dioxide directly or after suitable treatment with respect to its surface properties; and / or carbon dioxide from the first composition is adsorbed onto the carbon from the second composition.

3. Method according to one of the preceding claims, wherein the step of providing the first composition comprises: providing carbon in solid form, mixing the carbon in solid form with a fluid, in particular water, to form the first composition.

4. Method according to claim 3, wherein the step of mixing the carbon in solid form with a fluid a) takes place in the storage site, further comprising separately introducing the first composition and the second composition into the underground storage; or b) takes place during transport to the storage site, further comprising introducing the third composition into the underground storage.

5. Method according to any of the preceding claims, wherein the fluid for mixing the solid carbon is a gas, a liquid, in particular water, and / or a supercritical fluid.

6. Method according to any of the preceding claims, wherein the mixture of carbon and fluid is an aerosol and / or a dispersion.

7. A method according to any of the preceding claims, wherein the carbon dioxide is provided from industrial processes, in particular a combustion, cracking, or steam reforming process, or from a process for the production of direct reduced iron (DRI), pig iron, steel, glass, clinker or cement.

8. Method according to one of the preceding claims, wherein the carbon is provided in solid form by pyrolysis of at least one hydrocarbon, in particular in the production of hydrogen from natural gas, biogas, methane or from an aliphatic hydrocarbon.

9. Method according to any of the preceding claims, wherein the artificial and / or natural underground reservoir is a saline aquifer, a porous reservoir or a cavern reservoir.

10. Method according to any of the preceding claims, wherein the underground storage facility for introduction is an original reservoir for the extraction of fossil fuels, in particular oil, coal or natural gas.

11. Method according to any of the preceding claims, wherein the mixture has a pressure in the range of > 1 bar and < 400 bar, > 10 bar and < 400 bar or > 80 bar and < 400 bar and / or a temperature in the range of > -56.6 °C and < 250 °C, > -14 °C and < 250 °C, or > 0 °C and < 250 °C.

12. Method according to one of the preceding claims, wherein the carbon is in solid form as bulk material, in particular as fluid-conveyable bulk material, in particular as powder.

13. Installation for the storage of solid carbon and / or carbon dioxide, comprising: a) a unit for providing a first composition comprising carbon in solid form and a unit for providing a second composition comprising a carbon dioxide-containing fluid; b) a unit for mixing the first and second compositions to form a third composition; and c) a unit for storing the third composition in an underground storage facility of a storage site.

14. The system according to claim 13 is set up to carry out the method according to claims 1-12.

15. Plant according to claim 13 or 14, further comprising a plant control system for controlling and / or regulating the plant and its process control according to the aforementioned claims.

16. Plant according to one of claims 13-15, further comprising plant instrumentation for data acquisition of plant and process behavior for monitoring, evaluation and / or optimization of system behavior.

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