WO2022268789A1

WO2022268789A1 - Carbonation method and carbonation mixture

Info

Publication number: WO2022268789A1
Application number: PCT/EP2022/066844
Authority: WO
Inventors: Hermann Wotruba; Dario KREMER; Christian DERTMANN; Simon ETZOLD; Bernd Friedrich
Original assignee: Rheinisch-Westfälische Technische Hochschule (Rwth) Aachen
Priority date: 2021-06-25
Filing date: 2022-06-21
Publication date: 2022-12-29
Also published as: EP4359113A1; DE102021116491A1

Abstract

The invention relates to a carbonation mixture and to a carbonation process, for example for sequestering carbon dioxide, which enables a particularly high reaction conversion of the carbonation reactant.

Description

RWTH Aachen Templergraben 55 52062 Aachen

Carbonation Process and Carbonation Mixture

The present invention relates to a carbonation process and a carbonation mixture, which can be used, for example, in sequestering carbon dioxide (CO2). The present invention relates in particular to a method and a mixture which make it possible to improve the reaction conversion of the carbonation reaction, for example in the context of carbon dioxide sequestration.

The sequestration of carbon dioxide is a method known per se to remove carbon dioxide from the atmosphere and chemically bind it securely.

In detail, when carbon dioxide is sequestered, ex-situ carbonation takes place, for example, in which a carbonation educt or components thereof are subjected to a chemical reaction with carbon dioxide in an aqueous solution. In particular, this serves the purpose of removing carbon dioxide from the atmosphere and chemically binding it safely and with long-term stability.

It is known that the reaction products are precipitated on the surface of the carbonation educt and form a passivation layer there, which limits the reaction turnover. In this regard, US 2015/0044757 A1 describes methods and systems for capturing and storing carbon dioxide, comprising: mixing materials containing magnesium or calcium with one or more acids and chelating agents to form a magnesium- or calcium-rich solvent; using the organic acids derived from biogenic wastes as acids or chelating agents; generating carbonate ions by reacting a gas containing carbon dioxide with a carbonic anhydrase biocatalyst; reacting the solvent with the carbonate ions to form magnesium or calcium carbonates; recycling a solution containing the biocatalyst after the formation of magnesium or calcium carbonates for reuse in the generating step; Using the magnesium and calcium carbonates as carbon neutral packing materials and using the silica product as green packing materials or low cost absorbents.

WO 2012/068639 A1 describes a method for extracting an alkali metal and/or an alkaline earth metal from a mineral containing an alkali metal and/or an alkaline earth metal, or a rock containing the mineral, the method involving contacting the mineral with an aqueous Composition containing formic acid. For example, such a method can be carried out in the sequestration of carbon dioxide. It is pointed out that a passivation layer can form on the rock.

Michael J. McKelvy et al., in the article "Carbon Sequestration via Aqueous Olivine Mineral Carbonation: Role of Passivating Layer Formation", Environ. Be. Technolo., 40, 4802-4808, the CO 2 sequestration by carbonization of minerals, especially olivine. It is revealed that a passivation layer rich in silicon dioxide forms on the mineral particles. The passivation layer can be mechanically removed locally by using high stirrer speeds. The document US 7,722,842 B2 describes a method for mineral sequestration of noxious gases resulting from the combustion of carbon-based fuels such as carbon and sulfur dioxides, the provision of a particulate magnesium-containing mineral and exposing the magnesium-containing mineral to a weak acid to magnesium from the mineral to dissolve and form a magnesium-containing solution. The surface of the particulate magnesium-bearing mineral is physically activated to expose and dissolve additional magnesium in solution. For this purpose, for example, grinding media can be added.

WO 2011/047070 A1 describes a method for sequestering carbon dioxide minerals using mine waste and recovering valuable metal from the mine waste, comprising: (a) contacting a mine waste stream and water to form a slurry; (b) contacting the slurry and CO2 in a reaction vessel to provide a reacted slurry; (c) separating the reacted slurry into solids, liquid and gas; (d) recovering metals from the reacted slurry; and (e) recycling CO2 from the separated gas.

US 2019/0009211 A1 describes a method for performing mineral carbonation, comprising the following steps: providing a bed of hydroxylated magnesium silicate mineral particles in a heating vessel; agitating the bed of particles under conditions of subatmospheric pressure and at a temperature of at least 600°C to produce particles of dehydroxylated magnesium silicate mineral; and reacting the dehydroxylated magnesium silicate mineral with carbon dioxide, carbonate ion and/or bicarbonate ion to form magnesium carbonate. WO 2011/155 830 A1 describes a process for converting metallic silicate minerals into silicon compounds and metal compounds. Such a method comprises the following steps: providing a dispersion of solid particles of silicate minerals in water; conveying the dispersion provided through a first channel of a reactor in a descending direction such that a descending flow of dispersion is obtained in the first channel; Reacting the solid particles of silicate minerals in the dispersion with one or more reactants by adding the reactants to the downflow of the dispersion and discharging the silicon compounds and metal compounds formed during the conversion reaction through a second channel of the reactor in an upflow.

WO 2008/061305 A1 describes a method for carbonizing minerals, characterized in that the silicate feedstock is thermally activated using heat generated by the combustion of fuel before the activated slurry feedstock is reacted with carbon dioxide. In this case, a slurry of the starting material can be used, which comprises, for example, a bicarbonate solution.

Such solutions known from the prior art can still have potential for improvement, in particular with regard to a reliably high reaction conversion of the carbonation starting material.

It is therefore the object of the present invention to provide a measure by which at least one problem of the prior art is at least partially overcome. It is in particular an object of the present invention to create a measure by means of which a high reaction conversion of the carbonation starting material is made possible. The object is achieved according to the invention by a method having the features of claim 1. The object is also achieved according to the invention by a mixture with the features of claim 8. Preferred configurations of the invention are in the subclaims, in the description, and in the example is disclosed, wherein other features described or shown in the dependent claims or in the description or example, individually or in any combination, may constitute subject matter of the invention, unless the context clearly indicates the contrary.

The present invention relates to carbonation processes, comprising the process steps: a) providing a carbonation educt, wherein the carbonation educt is suitable for reacting with carbon dioxide; and b) carrying out a reaction of the carbonation starting material in a reaction mixture with carbon dioxide with chemical bonding of the carbon dioxide; characterized in that c) at least one nucleating agent is added to the reaction mixture, on which at least one reaction product formed in process step b) is deposited, the nucleating agent comprising at least one material that is a reaction product of the carbonation starting material with carbon dioxide.

With such a method, a high reaction conversion of the carbonation starting material can be made possible in a reliable manner.

The process described here is therefore a carbonation process and can be used in particular in a process for sequestering carbon dioxide. In the context of the present invention, such a method is understood in particular to mean a method in which carbon dioxide reacts with a carbonation starting material or a component thereof and can thus be bound in chemical form. As a result, sequestration serves in particular to remove carbon dioxide from the atmosphere and store it in chemically bound form. The process thus includes a carbonation, such as a mineral ex-situ carbonation, of the carbonation starting material.

For this purpose, the method according to method step a) comprises the provision of a carbonation educt, wherein the carbonation educt is suitable for reacting with carbon dioxide. A reaction of the carbonation starting material with carbon dioxide should be understood in the sense of the present invention that the carbonating starting material as a whole or parts thereof can or can react with carbon dioxide in order to chemically bind carbon dioxide. For example, individual ions contained in the carbonation starting material, in particular cations, can react with carbon dioxide and form the corresponding carbonates, for example.

The carbonation starting material can therefore in principle be freely selected and is not restricted in principle insofar as a reaction with carbon dioxide can be made possible as described above.

Correspondingly, the method comprises the further method step b), namely carrying out a reaction of the carbonation starting material in a reaction mixture with carbon dioxide, with the carbon dioxide being chemically bonded. For example, the carbon dioxide can be added to the reaction mixture in a targeted manner so that it comes into contact with the carbonation starting material or the reactive components thereof. For this purpose, the reaction mixture can be present under an excess pressure of carbon dioxide.

For example, as is known from the prior art, the reaction mixture can be an aqueous solution to which the carbonation educt is added and in which Cations of the carbonation reactant go into solution. In particular, alkali metal cations or alkaline earth metal cations can go into solution from the carbonation reactant in order to be able to react with the carbon dioxide.

This is possible, for example, using an aqueous reaction mixture and adding an acid so that the pH of the aqueous solution is adjusted accordingly. In principle, one or more acids and/or one or more chelating agents can thus be added to the reaction mixture. In addition, other parameters, such as a suitable reaction temperature and/or a suitable partial pressure of the carbon dioxide, can be set so that the carbonation takes place with the formation of corresponding reaction products within an economically reasonable time frame. The setting of such parameters as well as the basic implementation of such a carbonation is basically known to the person skilled in the art.

An exemplary reaction equation of a carbonation reaction that can take place within the meaning of the present invention corresponds to the following equation:

Me _x Si0 ₂ + _x + xC0 ₂ xMeC0 ₃ + Si0 ₂ , where Me is an alkali or alkaline earth metal and where x represents the number of the respective atoms in the chemical compound, so that x is dependent on the person skilled in the understandable way carbonation reactant used.

After formation, the reaction products of the carbonation usually also deposit on the surface of the carbonation educt. This leads to the formation of a passivation layer, which increasingly impedes the reaction of the carbonation reactant with carbon dioxide, for example by making it more difficult or by the Preventing the release of the corresponding cations from the carbonation educt. This limits the reaction conversion of the carbonation educt.

In order to prevent this, the method described here provides that at least one nucleating agent is added to the reaction mixture according to method step c), on which at least one reaction product formed in method step b) is deposited. The nucleating agent is in particular a particulate nucleating agent or the nucleating agent is in particular a solid.

Basically, it should be pointed out that both the carbonation starting material and the nucleating agent can each be a substance or a mixture of substances, so that the respective description applies to one or a plurality of substances. In addition, the other features of the nucleating agent, ie in particular its particle size, type and quantity, relate to the nucleating agent when it is added to the reaction mixture, ie in particular before the reaction product is deposited on it.

In addition, in particular a nucleating agent is added to the substances present or arising in process steps a) and b). The nucleating agent is thus not formed by process step b) but is added in addition to the product formed in the reaction. This is important because in this way passivation of the starting materials can be effectively prevented from the outset and the reaction is particularly effectively and advantageously influenced.

By adding the nucleating agent, i.e. by adding the nucleating agent in addition to the carbonation educt, it is thus achieved that reaction products from the carbonation reaction, such as corresponding carbonates or amorphous silicon dioxide, are predominantly deposited on the surface of the nucleating agent, the particles of the Carbonation reactant, however, remain essentially free of these. The latter can be made possible in particular by the fact that the nucleating agent comprises at least one material which is a reaction product of the carbonation starting material with carbon dioxide. This exploits the fact that primary grain growth requires less energy than nucleation and that this is energetically more favorable on matching crystal planes, i.e. a corresponding nucleating agent, than on the reactive starting material. It can thus be achieved that a precipitation of the reaction products, such as in particular alkaline earth metal or alkali metal carbonates or amorphous silicon dioxide, preferably takes place on the nucleating agents, but the starting material, i.e. the carbonation educt, is free of the precipitated or formed reaction products at least for a longer period of time remain.

It is advantageous here that the nucleating agent is added to the reaction mixture before the start of the carbonization reaction or at the start of the carbonization reaction. In other words, it can be advantageous for method step c) to be carried out at least in part, for example completely, before method step b). As can be seen by a person skilled in the art, corresponding reaction products can also form during the reaction, ie in process step b). However, these should preferably not be nucleating agents according to the present invention, rather the nucleating agent should preferably be added in addition to the carbonation starting material. This can be recognized, for example, by the fact that after process step b) there is stoichiometrically more of the reacted starting material of the carbonation starting material as reaction product than was originally added to the reaction by the carbonating starting material.

For example, in a batch process, a reaction mixture can be initially introduced, which comprises the carbonation educt and the nucleating agent, for example in an aqueous mixture, before the carbon dioxide is fed to the reaction mixture. In a continuous process, for example, nucleating agents can be added to the reaction mixture in addition to the addition of carbonation educt. This can be done continuously, for example, or in batches, ie in batches that can be defined in particular.

The fact that the nucleating agent is added to the reaction mixture, in particular before the start of the carbonation reaction or at the start of the carbonating reaction, can make it possible for the reaction products to be deposited on the nucleating agents particularly effectively and passivation of the carbonating starting material to be at least partially prevented. This is because the formation of a passivation layer can be effectively prevented or at least slowed down right at the beginning of the reaction, which can already provide a high level of activity at the beginning of the reaction.

The method described thus makes it possible to enable a particularly high reaction conversion of the carbonation starting material. In particular, the formation of a passivation layer on the surface of the particles of the carbonation starting material can effectively prevent the reaction thereof from ending without the reaction conversion being very advanced or even complete.

It is thus possible, for example in the context of sequestering carbon dioxide, to enable effective removal of carbon dioxide from the environment with comparatively little material use of the carbonation educt. As a result, the sequestration process can be designed effectively and the use of materials can also be reduced. This saves costs and resources. This is also because the product formed can be used in other processes or batch reactions, which can further save costs and resources. In addition, it is advantageous that a passivation layer that forms is not only destroyed after formation, as is sometimes proposed in the prior art, but that the formation of the passivation layer is already prevented or at least reduced. As a result, even a slight reduction in the activity of the carbonation reactant caused by a passivation layer that forms can be prevented and an effective reaction can be ensured throughout the entire process. This can further increase effectiveness.

Carbon dioxide sequestration as an application of carbonation is desirable because it is an effective method of removing the greenhouse gas carbon dioxide from the atmosphere and chemically sequestering it safely and permanently, with the reaction products not posing a significant environmental threat. The present invention now makes it possible to make the carbonation within the framework of the sequestration of carbon dioxide more economically sensible and thus contribute to the fact that the mineral carbonation can be used industrially in the future, for example within the framework of the sequestration of carbon dioxide. This is because the invention described above makes it possible to significantly increase the chemically bound amount of carbon dioxide per tonne of carbonation reactant.

In addition to relieving the burden on the environment, the process also offers advantages with regard to processes that can be used on an industrial scale and in which carbon dioxide is produced. This is because in the event of potential increases in the costs of CCh production that are to be expected, for example due to rising costs of CCh certificates, the present invention can ensure fundamental or improved feasibility of this technology by improving sequestration.

The present invention thus makes an important contribution to protecting the environment and improving CCh-emitting processes. Preferably, the nucleating agent can be selected from carbonates and amorphous silicon dioxide. It has been shown that such substances in particular are formed as reaction products in conventional carbonation reactions, for example as part of the sequestration of carbon dioxide, and are therefore particularly effective as nucleating agents. In addition, these materials are usually readily available and enable the use of effective carbonation educts together with the nucleating agents to be used.

Examples of carbonates as nucleating agents include magnesite, calcite, aragonite or dolomite. Examples of amorphous silica include, for example, that which can be produced synthetically or can occur naturally in volcanic glasses and tektites. Particularly in combination with these nucleating agents, it is possible to use effective carbonation starting materials that are easy to use, and it has also been found that very effective nucleation activity is possible, which can effectively prevent or at least reduce the formation of a passivation layer.

The nucleating agent can particularly advantageously have a particle size in a range of less than or equal to 100 μm. For example, the particle size mentioned according to this invention can be a particle size D90. The particle size can be determined approximately by laser diffractometry. The nucleating agent can particularly advantageously have particles with a particle size D90 in a range of less than or equal to 50 μm, for example less than or equal to 30 μm, in which case a lower limit of the particle size can in principle be due to technical reasons and/or can be in a range of around 0 1pm or 1pm.

It has been shown that in particular nucleating agents that are in the aforementioned size range are effective as precipitating carriers for the products of the carbonation or the sequestration reaction. This can be due in particular to that due to the small particle size there is a high specific surface, which results in effective nucleation. In addition, such small particles in particular can ensure that the coated nucleating agent is not damaged during stirring, for example, which further simplifies the process control.

It can furthermore be preferred that the carbonation starting material comprises at least one material which is selected from the group consisting of oxides and silicates of the alkali metals and the alkaline earth metals. Carbonation educts of this type in particular are well suited for binding carbon dioxide, since the metal cations are usually easy to dissolve and, moreover, a reaction to form the corresponding carbonates or amorphous silicon dioxide is effectively possible. In addition, these materials are usually readily available, either as minerals or rocks, such as including peridodite, olivine, basalt, materials from the serpentine group, or as secondary raw materials, such as including slag, fly ash, filter dust and mining waste or tailings.

In principle, however, any material known from the prior art for carbonation can be used.

It can further be preferred that the nucleating agent is added to the reaction mixture in an amount which is less than or equal to 65% by weight, based on the amount of the carbonation starting material used in process step b). As already indicated above, the above-described amount can preferably be added at least in part before carrying out process step b). However, it cannot be ruled out that the corresponding amount is also or only added continuously or intermittently while process step b) is being carried out. It has been shown that the nucleating agent in the amount described above is very effective in nucleation and thus passivation of the sequestrant can be effectively prevented and at the same time due to the small amount, the process can be carried out economically within a reasonable time frame.

For example, the nucleating agent can be added to the reaction mixture in an amount ranging from greater than or equal to 2% by weight to less than or equal to 50% by weight, such as from greater than or equal to 5% by weight to less than or equal to 25% by weight, based in each case on the amount of carbonation starting material used in process step b).

For other technical features or advantages of the carbonation process, reference is made to the description of the carbonation mixture and to the example, and vice versa.

A carbonation mixture is also described, the mixture having at least one carbonation starting material which is suitable for reacting with carbon dioxide with chemical bonding of the carbon dioxide, the mixture further comprising at least one nucleating agent for separating at least one reaction product from the reaction of the carbonating starting material with carbon dioxide, wherein the nucleating agent comprises at least one material that is a reaction product of the carbonation educt with carbon dioxide.

As explained in detail above, such a mixture is suitable for increasing the reaction conversion of the carbonation of the carbonation starting material compared to the prior art. The fact that the reaction mixture comprises a nucleating agent for separating at least one reaction product from the reaction of the carbonation reactant with carbon dioxide, the nucleating agent comprising at least one material that is a reaction product of the carbonation reactant with carbon dioxide, can prevent or significantly reduce the risk that reaction products of carbonation on the carbonation educt. Rather, what is achieved is that the reaction products are deposited on the nucleating agent. The formation of a passivation layer, which is usually known from the prior art as an amorphous silicon dioxide layer or, for example, magnesite, can thus be prevented or its occurrence can at least be significantly reduced.

In this case, deposition of the reaction products on the nucleating agent can be reduced in particular by the nucleating agent comprising at least one material that is a reaction product of the carbonation starting material with carbon dioxide. This exploits the fact that primary grain growth requires less energy than nucleation and that this is energetically more favorable on matching crystal planes, i.e. a corresponding nucleating agent, than on the reactive starting material. It can thus be achieved that a precipitation of the reaction products, such as in particular alkaline earth metal or alkali metal carbonates or amorphous silicon dioxide, preferably takes place on the nucleating agents, but the starting material, i.e. the carbonation educt, remains free of the precipitated or formed reaction products at least for a longer period of time .

With regard to the nucleating agents, what was said above essentially applies. Preferably, the nucleating agent can be selected from carbonates and amorphous silicon dioxide. Non-limiting examples of carbonates include, but are not limited to, magnesite, calcite, aragonite, or dolomite. Non-limiting examples of silica include, for example, natural or synthetic amorphous silica.

The nucleating agent can particularly advantageously have a particle size D90 which is in a range of less than or equal to 100 μm. The nucleating agent can particularly advantageously have particles with a particle size D90 in a range of less than or equal to 50 μm, for example less than or equal to 30 μm, with a lower limit of the Particle size D90 may be due to technical reasons and/or may be in a range of 0.1 gm, for example 1 gm.

It can also be preferred that the carbonation starting material comprises at least one material which is selected from a group consisting of oxides and silicates of the alkali metals and the alkaline earth metals. Carbonation educts of this type in particular are well suited for binding carbon dioxide, since the metal cations are usually easy to dissolve and, moreover, a reaction to form the corresponding carbonates or amorphous silicon dioxide is effectively possible. Furthermore, these materials are mostly readily available either as minerals or rocks, such as including peridodites, olivines, basalts, serpentine group materials, or also as secondary raw materials, such as including slags, fly ash, fly ash, fly ash and mining tailings or tailings.

It can further be preferred that the nucleating agent is added to the reaction mixture in an amount which is in a range of less than or equal to 65% by weight, based on the amount of carbonation reactant present. For example, the nucleating agent can be added to the reaction mixture in an amount ranging from greater than or equal to 2% by weight to less than or equal to 50% by weight, such as from greater than or equal to 5% by weight to less than or equal to 25% by weight, based in each case on the amount of the carbonate starting material used.

For other technical features or advantages of the carbonation mixture, reference is made to the description of the carbonation process and to the example, and vice versa. The invention is explained below by way of example with reference to the attached example, with the features presented below being able to represent an aspect of the invention both individually and in combination, and with the invention not being limited to the following exemplary embodiment.

Example:

The carbonation educt, which may be an oxide and/or silicate of an alkali metal and/or alkaline earth metal, e.g. peridodite, and the nucleating agent, such as a carbonate or amorphous silicon dioxide, e.g. magnesite, are combined with water as a solvent and optional additives such as acids and/or chelating agents, filled into a reactor. The nucleating agent was present in an amount of 10% by weight based on the carbonation educt. The agitator of the reactor is set to, for example, 600 revolutions per minute. Then CO2 is added, at about an exemplary partial pressure of 30 bar, and the temperature of the reaction mixture is increased to 175°C, resulting in a pressure increase to about 60 bar. The process remains at this temperature for four hours, during which the pressure of the CO2 understandably decreases as a result of the reaction. Thereafter, it is cooled to room temperature.

It could be shown that the carbonation educt remained essentially free of a passivation layer, so that a very good reaction conversion could be achieved.

The invention on which this patent application is based came about in a project funded by the BMBF under the grant number 033RC014B.

Claims

patent claims

1. Carbonation method, comprising the method steps: a) providing a carbonation educt, wherein the carbonation educt is suitable for reacting with carbon dioxide; and b) carrying out a reaction of the carbonation starting material in a reaction mixture with carbon dioxide with chemical bonding of the carbon dioxide; characterized in that c) at least one nucleating agent is added to the reaction mixture, on which at least one reaction product formed in process step b) is deposited, the nucleating agent comprising at least one material that is a reaction product of the carbonation starting material with carbon dioxide.

2. The method according to claim 1, characterized in that the nucleating agent is selected from carbonates and amorphous silicon dioxide.

3. The method according to claim 2, characterized in that the nucleating agent is a material selected from the group consisting of magnesite, calcite, aragonite, dolomite or amorphous silica.

4. The method according to any one of claims 1 to 3, characterized in that the nucleating agent has a particle size which is in a range of less than or equal to 100 μm.

5. The method according to any one of claims 1 to 4, characterized in that the carbonation educt comprises a material which is selected from the group consisting of oxides and silicates of alkali metals and alkaline earth metals.

6. The method according to any one of claims 1 to 5, characterized in that the nucleating agent is added to the reaction mixture in an amount which is in a range of less than or equal to 65 wt .-%, based on the amount of in process step b) carbonation reactant used.

7. The method according to any one of claims 1 to 6, characterized in that method step c) is carried out at least in part before method step b).

8. carbonation mixture, wherein the mixture has at least one carbonation starting material which is suitable for reacting with carbon dioxide with chemical binding of the carbon dioxide, characterized in that the mixture further comprises at least one nucleating agent for separating at least one reaction product from the reaction of the carbonating starting material with carbon dioxide , wherein the nucleating agent comprises at least one material that is a reaction product of the carbonation educt with carbon dioxide.

9. Mixture according to claim 8, characterized in that the nucleating agent is present in the mixture in an amount which is in a range of less than or equal to

65% by weight, based on the amount of carbonation starting material.

10. Mixture according to one of claims 8 or 9, characterized in that the nucleating agent has a particle size which is in a range of less than or equal to 100 μm.