Method and mixture for recycling concrete

Abstract

The invention relates to a method for recycling concrete (6) or concrete-building material mixtures and to a mixture for coating paper and / or for producing cement and / or toothpaste, and / or formulations, coatings and / or dispersions made of polymers, paints, sealants and / or silicones. The method has the steps of mixing (5) a second fluid (3) with the concrete (6) or the concrete-building material mixture; dissolving Ca out of the concrete (6) or the concrete-building material mixture in the second fluid (3) in order to obtain a Ca-enriched second fluid (3a); isolating (7) the Ca-enriched second fluid (3a); precipitating (8) CaCO3 (9) from the Ca-enriched second fluid (3a) by mixing with a first fluid (2) at a pressure ranging from 1.1 bar to 500 bar; isolating the CaCO3 (9), in particular by means of a solid-liquid separation (10) of the CaCO3 (9) precipitated from the second fluid (3), and drying (11) the isolated CaCO3 (9).

Description

[0001] Process and mixture for the material recycling of concrete

[0002] Description

[0003] The invention relates to a process for the material recycling of concrete or concrete-building material mixtures according to claims 1 and 2 and to a mixture according to claim 10.

[0004] Concrete is a building material that mainly consists of cement, sand and gravel.

[0005] Cement acts as a binding agent in concrete and ensures that the other components and materials hold together. Cement is produced by firing limestone and clay at high temperatures and contains calcium silicates as a key component. When converted into concrete, cement reacts with the addition of water to form calcium silicates and calcium hydroxide, among other substances, which act as the concrete's binding agents. In addition to concrete, concrete building material mixtures also include other building material components, such as metals like steel, steel reinforcement elements, glass, Plexiglas, wood, asphalt, and / or masonry.

[0006] Sand and gravel are added to concrete as aggregates and provide strength and volume. Sand and gravel are used in different grain sizes to achieve the desired mechanical properties of the concrete.

[0007] The material recycling of concrete is important for conserving natural resources and reducing waste. Furthermore, the components of concrete are valuable and can be reused. Currently, there is a particularly high demand for sand, gravel, and cement. Recycling concrete also reduces the amount of landfill space required. Cement production is also very energy-intensive. Recycling concrete typically involves several steps. First, concrete or concrete mixes are collected and, optionally, cleaned of contaminants such as steel, wood, or plastic. The collected concrete is then crushed to increase its surface area and make it easier to transport. The cleaned and sorted material can then be used as aggregate for the production of new concrete.This well-known form of concrete recycling is known as downcycling, in which the concrete is only partially used and as a low-quality filler. To ensure that concrete is not only recycled as a low-quality filler, the CaO contained in the concrete would have to be converted into CaCO3 for subsequent reuse, for example, in cement production. A process for obtaining CaCO3 from CaO is described in EP 0 429 707 A1.

[0008] The disadvantage of the existing system is that the material recycling of concrete does not sufficiently address the aspect of CaCO2 recovery, and the existing processes are energy-intensive and slow. Furthermore, the CO2 footprint of the resulting CaCO2 is very high, at up to 800 kg CO2e / t.

[0009] Based on this, the present invention is based on the object of providing an improved process for the material recycling of concrete.

[0010] In the following, any reference to an object or feature (including the indefinite articles "a" and "an" and the definite articles "the"), two objects or two features, or any other number of objects or features, unless expressly stated otherwise or a logical contradiction arises, is to be understood as meaning that the presence of further such objects and features is not excluded from the invention, but is also encompassed by the invention. The words "comprising", "having" and "with" do not exclude further objects, features, elements or steps. The reference signs in the claims are not to be understood as limiting but serve merely to improve the readability of the claims.

[0011] A first aspect of the invention relates to a process for the material recycling of concrete or concrete building material mixtures comprising the steps:

[0012] - Providing a first fluid, in particular a CC>2-containing gas with a CO2 content of 10 vol.% to 100 vol.% and a second fluid, in particular water and / or recycled water;

[0013] - Mixing the second fluid with the concrete or concrete-building material mixture;

[0014] - dissolving Ca from the concrete or the concrete-building material mixture in the second fluid to obtain a Ca-enriched second fluid;

[0015] - Isolating the Ca-enriched second fluid;

[0016] - precipitation of CaCOs from the Ca-enriched second fluid by mixing with the first fluid at a pressure of 1.1 bar to 500 bar;

[0017] - isolating the CaCO, in particular by a solid-liquid separation of the precipitated CaCO from the second fluid, preferably by filtration;

[0018] - Drying of the isolated CaCO3; the steps are preferably carried out in the order in which they are mentioned.

[0019] A second aspect of the invention relates to a process for the material recycling of concrete or concrete building material mixtures comprising the steps:

[0020] - Providing a CO2-containing first fluid, in particular a CO2-containing gas with a CO2 content of 10 vol.% to 100 vol.% and a second fluid, in particular water and / or recycled water;

[0021] - Enriching the second fluid with CO2 from the first fluid;

[0022] - Mixing the CO2-enriched second fluid with the concrete or the concrete-building material mixture;

[0023] - dissolving Ca from the concrete or the concrete-building material mixture in the second fluid and reacting the dissolved Ca with CO2 from the second fluid to form CaCOs to obtain a CaCOs-enriched second fluid;

[0024] - Isolating the CaCO3-enriched second fluid; - Precipitating CaCCh from the CaCCh-enriched second fluid;

[0025] - isolating the CaCCh, in particular by a solid-liquid separation of the precipitated CaCCh from the second fluid, preferably by filtration;

[0026] - Drying of the isolated CaCO3; the steps are preferably carried out in the order in which they are mentioned.

[0027] A third aspect of the invention relates to a mixture, in particular for coating paper and / or for producing cement and / or toothpaste, and / or formulations, coatings and / or dispersions of polymers, paints, sealants and / or silicones, in particular produced by a process according to one of the preceding claims, comprising from 99.9 wt% to 90.0 wt% CaCCh and from 10.0 wt% to 0.01 wt% MgCCh and wherein the mixture has a whiteness as an L* value greater than 70 and a particle size of less than 100 pm, preferably less than 80 pm, particularly preferably less than 75 pm, most preferably from 0.5 pm to 20 pm and a decomposition temperature of 300°C to 950°C, preferably from 340°C to 900°C, most preferably greater than or equal to 700°C to 900°C.

[0028] A first preferred aspect of the invention relates to a system, preferably for carrying out the method according to the first aspect of the invention, comprising a reactor for mixing a second fluid with concrete or a concrete-building material mixture to obtain a Ca-enriched second fluid; a hydrocyclone and / or a sedimenter and / or a sand filter for isolating the Ca-enriched second fluid and preferably for isolating sand and a fine fraction; a precipitation tank for precipitating CaCOs from the Ca-enriched second fluid by mixing with a first fluid at a pressure of 1.1 bar to 500 bar; a CaCCh filter and / or a Nutsche filter and / or a centrifuge for isolating the precipitated CaCOs; a dryer for drying the isolated CaCOs.

[0029] A second preferred aspect of the invention relates to a system, preferably for carrying out the method according to the second aspect of the invention, comprising a saturator and / or an absorber for mixing a CO2-containing first fluid with a second fluid, such that the second fluid is enriched with CO2 from the first fluid to obtain a CO2-enriched second fluid; a reactor for mixing the CO2-enriched second fluid with concrete or a concrete building material mixture to obtain a CaCCh-enriched second fluid; optionally a hydrocyclone and / or a sedimenter and / or a sand filter for isolating the Ca-enriched second fluid and preferably for isolating sand and a fine fraction; a precipitation tank for precipitating CaCOs from the CaCCh-enriched second fluid; a CaCOs filter and / or a Nutsche filter and / or a centrifuge for isolating the precipitated CaCOs; a dryer for drying the isolated CaCOs.

[0030] It is understood that the subject matter of the independent claims or the following description of preferred embodiments of the invention comprise similar and / or identical developments and embodiments. In particular, the claimed methods comprise similar or identical preferred embodiments. Furthermore, the individual steps and features of the claimed methods and / or of the preferred system can be used in a compatible manner. Advantageous embodiments and developments of the invention are the subject matter of subclaims and the following description. The inventive achievement is based in particular on the concept that materially recyclable components of concrete or concrete-building material mixtures are recycled by reacting with CO2 from exhaust gases or from carbon capture processes.Furthermore, the inventive process is characterized by its extremely low energy requirements, making it particularly resource-efficient and cost-effective. Preferably, the energy required for the process is obtained entirely from renewable sources, particularly photovoltaics. Compared to previously known processes, the inventive process also allows the production of several materially recyclable products. Furthermore, the carbon footprint of the resulting CaCO or mixture is advantageously negative, and at less than -100 g CO2e / t, preferably less than -300 g CO2e / t, it is significantly lower than that of the known processes.

[0031] The products which are preferably obtained by the process according to the invention are:

[0032] CaCOs with a purity of 99.9 wt% to 90.0 wt% CaCOs or the mixture according to the invention; and solids such as, in particular, sand and / or gravel and / or a fine fraction.

[0033] If reference is made to CaCOs in the description or in the claims, this includes, in particular, not only high-purity CaCOs but also the mixture according to the invention, which also contains other components in addition to CaCOs.

[0034] Advantageously, the process according to the invention produces a high-quality, powdered, and pure CaCO3 or the mixture according to the invention, which is characterized by a particularly low carbon footprint and particularly high quality. Furthermore, the process according to the invention preferably does not use any harmful process chemicals, and in particular no phosphorus-containing adsorbents, making the process resource-efficient and also resulting in a higher purity of the CaCO3 or the mixture according to the invention. Advantageously, the process according to the invention extracts and isolates over 90% of the Ca contained in the concrete, and the CaCO3 is obtained with a purity of up to over 99%.

[0035] The “concrete” or the “concrete building material mixture” is preferably crushed and used as a fine fraction in the process, in particular with a particle size of less than or equal to 5 mm, particularly preferably less than or equal to 2 mm.

[0036] The "first fluid" is preferably a CO2-containing exhaust gas or a CO2-containing gas obtained by a CO2 capture process. The CO2-containing exhaust gas originates, for example, from a combustion process of carbon-containing energy sources, such as, in particular, the fossil energy sources coal, crude oil, or natural gas. The CO2-containing exhaust gas can also be obtained from chemical plants and / or from processes involving fermentation, for example, alcoholic fermentation. Preferably, the first fluid comprises a CO2-containing gas released during the precipitation of the CaCO3. Particularly preferably, the CO2-containing gas is mixed with purer CO2 and used as the first fluid. Advantageously, the CO2-containing gas released during the precipitation is thus fully or at least partially recycled as the first fluid.

[0037] The CO2 content can be determined using infrared spectroscopy, in which the absorption of infrared radiation by CO2 molecules is recorded using an infrared spectrometer, and the CO2 content is determined from the resulting absorption pattern of the fluid. Alternatively or additionally, the CO2 content can be determined using gas chromatography, in which a gas mixture is passed through a column containing a stationary phase, and the various gases in the gas mixture separate based on their interactions with the stationary phase. The CO2 content can be determined by detecting the gas after it has been eluted from the column by a detector. Mass spectrometry can be used for this purpose, determining the mass and concentration of molecules.Alternatively, or in addition, the CO2 content can be determined using chemical sensors, which contain, for example, chemical substances that react or interact with CO2 and produce a measurable change in a specific parameter, such as changes in electrical conductivity, pH, or color. These changes can then be used to determine the CO2 content in the fluid.

[0038] The "recycled water" is preferably a component of the second fluid and, in addition to water, also comprises dissolved CaCCh and / or suspended solids, for example, CaCO3 and optionally MgCCh. In contrast to the "water," the recycled water therefore contains, in particular, further components. The Ca content in the recycled water is preferably less than 3%, particularly preferably less than 0.5%. The recycled water is preferably obtained after isolating the CaCCh by solid-liquid separation, optionally diluted with water, and then provided again as the second fluid—in other words, recycled.Preferably, the second fluid is mixed with the recycled water and / or the concrete, wherein the second fluid is enriched with Ca from the recycled water and / or from the concrete, particularly preferably at a pressure of 1 bar to 20 bar, most preferably at ambient pressure and / or a residence time of 0.1 h to 3 h and / or a temperature of 20°C to 100°C, most preferably from 20°C to 50°C, optionally with stirring in the reactor. The recycled water is preferably enriched with CO2, which was released in particular as a CO2-containing gas during the precipitation of the CaCO3.

[0039] The "dissolution of Ca", i.e. the dissolution of calcium from the concrete, occurs in particular when Ca-containing concrete components such as Ca(OH)2 are transferred into the second fluid, whereby the second fluid initially penetrates the porous structure of the concrete, for example due to capillary forces and / or osmotic pressure. The Ca-containing concrete components, in particular calcium compounds, are dissolved in the second fluid and, for example, as calcium ions (Ca 2+ ) hydrolyzed. In addition to Ca, other concrete components such as Mg-containing concrete components, especially as magnesium ions (Mg 2+ ), and / or magnesium hydroxide, Mg(OH)2, are dissolved in the second fluid. When Ca is dissolved from the concrete, the fine fraction is preferably also retained, which can particularly preferably be separated from the second fluid by solid-liquid separation.

[0040] The "fine fraction" preferably comprises solids, in particular solid impurities, with a particle diameter of less than 0.050 mm, in particular less than 0.063 mm. The fine fraction preferably comprises CaO, silicon species, such as silicates, and / or aluminum species, such as aluminum oxides, and / or iron species, such as iron oxides. The fine fraction may also comprise a coagulum.

[0041] The "isolation" preferably takes place as a solid-liquid separation, whereby the CaCCh-enriched second fluid or the Ca-enriched second fluid is separated from solids by filtration, sedimentation, centrifugation, flotation, or any combination of these processes. The isolated solids are preferably used as aggregates for the material recycling of concrete and are thus advantageously recycled.

[0042] The "conversion" of the dissolved Ca with CO2 from the second fluid to form CaCO3 preferably takes place directly after the Ca has been dissolved from the concrete with the CO2 from the second fluid. The amount of the CO2-enriched second fluid is preferably selected such that at least one equivalent of CO2 is stoichiometrically available for each equivalent of Ca. During the conversion of the dissolved Ca with CO2, dissolved Mg can also be converted with the CO2 to form MgCCh. For this purpose, the first fluid is preferably introduced into the second fluid while stirring, preferably for a period of 5 to 30 minutes, and particularly preferably while stirring.

[0043] The "isolation of the CaCO3" preferably takes place as a solid-liquid separation, whereby the precipitated CaCCh is separated from the second fluid as a solid by filtration, sedimentation, centrifugation, flotation, or any combination of these processes. A CaCO3 filter is particularly preferably used. The isolated CaCCh is dried, in particular, in a subsequent step. The CaCO3, preferably isolated as a crystalline solid, particularly preferably has a purity of 99.9 wt% to 90.0 wt% CaCCh.

[0044] The isolated second fluid is preferably recycled as recycled water.

[0045] Drying preferably takes place in a countercurrent or crosscurrent flow. In particular, the isolated CaCO3 is dried using the waste heat from the first fluid. Drying preferably takes place at a temperature of 80°C to 200°C and a pressure of 0.05 bar to 1 bar.

[0046] The "whiteness" specifically indicates how white and / or how bright the mixture is compared to an ideal white. The whiteness is expressed as an L* value. Whiteness is preferably determined according to CIELAB. CIELAB is a color space defined by the International Commission on Illumination, CIE. According to CIELAB, the L* value indicates brightness or luminance, with an L* value equal to 0 corresponding to black, while an L* value equal to 100 corresponds to perfect white. Whiteness can be measured using colorimeters, whereby reflected light from a sample of the mixture is collected and analyzed to calculate the L* value and determine the whiteness.

[0047] The "particle size" refers to the average diameter of the individual particles that make up the mixture. The particles are solid and preferably crystalline. Particle size is determined, for example, by light scattering, where the intensity and scattering angle of the scattered light are measured based on the scattering of light by the particles and compared with theoretical models to calculate the particle size. Particle size can also be determined by dynamic light scattering (DLS), where fluctuations in light scattering caused by the Brownian motion of the particles are measured, and the particle size is determined based on these measured data. Furthermore, particle size can be determined by X-ray diffraction (XRD), where X-rays are shone through a sample containing the particles, and information about the particle size is obtained from analysis of the diffraction patterns.Alternatively, or in addition, particle size can be determined using sedimentation analysis, in which the sedimentation velocity of the particles in a fluid is measured and the particle size is inferred from the measured sedimentation velocity using mathematical models such as Stokes' equation. Alternatively, or in addition, particle size can be directly observed and measured using a microscope, either manually or using image analysis software.

[0048] The "decomposition temperature" is the temperature at which chemical components of the mixture decompose into smaller molecules or even their chemical elements, or transform into other chemical compounds. The decomposition temperature can be determined using thermogravimetric analysis (TGA), in which the mass of a sample of the mixture is continuously measured while it is heated. Decomposition of the sample leads to a loss of mass at the decomposition temperature. Alternatively or additionally, the decomposition temperature can be determined using differential thermal analysis (DTA), in which the temperature difference between a sample of the mixture and a reference material is measured while the sample and reference material are heated together. The decomposition temperature of the sample is determined by a characteristic change in the heat flow curve.Alternatively or additionally, the decomposition temperature can be determined by differential scanning calorimetry, DSC, where, similar to DTA, a heat flow change is determined during heating of a sample of the mixture and a reference material, whereby the decomposition temperature of the sample is determined by peaks or jumps in the heat flow curve, which indicate changes in the energy conversion of the sample.

[0049] Preferably, the method comprises at least one or more of the following steps:

[0050] - Enriching the second fluid with CO2 from the first fluid; and / or - Mixing the CO2-enriched second fluid with the concrete or the concrete-building material mixture; and / or

[0051] - dissolving Ca from the concrete or the concrete-building material mixture in the CO2-enriched second fluid to obtain a Ca-enriched second fluid; and / or

[0052] - Converting the dissolved Ca with CO2 from the second fluid to CaCCh; and / or

[0053] - precipitation of CaCCh from the Ca-enriched second fluid by mixing with the first fluid at a pressure of 1.1 bar to 500 bar; and / or

[0054] - Drying of the isolated CaCCh by waste heat from the first fluid.

[0055] In a first preferred embodiment, the second fluid is enriched with CO2 from the first fluid at a temperature of 5°C to 40°C and / or at a pressure of 1.0 bar to 40.0 bar, preferably 1.1 bar to 21.0 bar. Advantageously, under these conditions, the second fluid is particularly well enriched with CO2. Enrichment under these conditions is particularly efficient and energy-saving.

[0056] In a second preferred embodiment, the method comprises the steps:

[0057] Providing a first container, in particular a saturator and / or an absorber, and a second container, in particular a reactor; wherein the enrichment of the second fluid with CO2 from the first fluid takes place in the first container, and the mixing of the CO2-enriched second fluid with the concrete or the concrete-building material mixture then takes place in the second container, and preferably the CO2-enriched second fluid is isolated after the enrichment in the first container and then transferred to the second container. Preferably, the concrete or the concrete-building material mixture is already mixed with the second fluid in the first container.

[0058] The saturator preferably comprises a first saturator and a second saturator, wherein particularly preferably in the first saturator the first fluid is mixed with the second fluid and / or in the second saturator the second fluid is mixed with the CC>2-containing gas, which is obtained in particular during the precipitation of the CaCO3. The mixing of the first fluid with the second fluid particularly preferably takes place at a temperature of 5°C to 40°C and / or a pressure of 1.0 bar to 40 bar. Advantageously, under these conditions the second fluid is particularly well enriched with CO2 and at the same time the energy consumption is minimized.

[0059] The reactor is preferably segmented and / or comprises a first reactor segment and a second reactor segment, through which the second fluid particularly preferably flows one after the other. The CC>2-containing gas is preferably fed to the reactor.

[0060] In a further preferred embodiment, after mixing the CO2-enriched second fluid with the concrete or the concrete-building material mixture, the CO2-enriched second fluid is kept in contact with the concrete or the concrete-building material mixture for a residence time of 10 minutes to 4 hours at a pressure of 1.0 bar to 40.0 bar and / or at a temperature of 5°C to 60°C and / or a pH value of less than 9, in particular in order to obtain the CaCOs-enriched second fluid, which is then isolated. The pressure is preferably from 1.1 bar to 21.0 bar, particularly preferably from 5 bar to 15 bar and / or the temperature is from 10°C to 50°C, particularly preferably from 20°C to 30°C and / or the pH is particularly preferably less than 7, most preferably less than 6.Preferably, the second fluid is isolated in the second container, with the second fluid particularly preferably being separated from solids by sedimentation. The solids include, in particular, concrete, concrete-building material mix, sand, gravel, fines, undissolved CaCO3, undissolved MgCO3, and / or larger stones.

[0061] Advantageously, under these conditions, a particularly large amount of Ca is dissolved from the concrete and converted to CaCOs, whereby the CaCOs most advantageously remain completely or at least largely dissolved in the second fluid, which enables a simple and inexpensive separation of the CaCOs-containing second fluid.

[0062] In a preferred embodiment, the precipitation of CaCO3 from the CaCCh-enriched second fluid is carried out by a pressure change, preferably a pressure reduction, and / or by a temperature change, preferably a temperature increase. The pressure reduction and the temperature increase preferably occur suddenly and / or simultaneously. The pressure reduction preferably occurs to a pressure of 0.01 bar to 1.2 bar, particularly preferably from 0.5 bar to 1.1 bar. The temperature increase preferably occurs to a temperature of 5°C to 60°C, particularly preferably from 20°C to 60°C, most preferably from 20°C to 40°C. Advantageously, the precipitation of the CaCCh is particularly rapid and efficient under these conditions. Preferably, a CC>2-containing gas is released during the precipitation, in particular from the second fluid, for example due to the pressure reduction.This CO2-containing gas is preferably reintroduced into the saturator or the reactor and is thus advantageously recycled as the first fluid.

[0063] In a preferred embodiment, the Ca-enriched second fluid is isolated by sedimentation and / or filtration, whereby the Ca-enriched second fluid is preferably separated from solids, particularly preferably by a two-stage solid-liquid separation in which sand is first separated by sedimentation, a hydrocyclone, or filtration, and then the fines or other solid contaminants are separated from the second fluid in a filtration. Preferably, the solid-liquid separation takes place before precipitation. Preferably, the separated sand and / or the separated fines are isolated and then, particularly preferably, sieved or used directly for material recycling for the production of concrete.The second fluid is preferably reused as recycled water after separation from the solids and then particularly preferably fed into the first container and re-enriched with CO2 there. In a further preferred embodiment, the CaCCh is kept in solution in the CaCCh-enriched second fluid until precipitation. For this purpose, in particular, the temperature and / or pressure of the second fluid is kept constant until precipitation. This advantageously allows for particularly efficient process control through simple separation of the CaCCh-containing second fluid and, moreover, a particularly high purity of the CaCCh.Particularly advantageously, the CaCCh-containing second fluid can be separated and isolated from sand and / or the fines and other insoluble solids, in particular by the hydrocyclone and / or by sedimentation, for example in the sedimenter, and / or by filtration, in particular through the sand filter or the fines filter. This advantageously allows particularly pure products, in particular a particularly pure CaCCh, to be obtained.

[0064] In a preferred embodiment, the method steps are carried out successively in the order in which they are mentioned in the independent method claim or claims or in the order in which they are mentioned in the dependent claims or in the order in which they are mentioned in the description.

[0065] Preferably, the CaCCh or mixture has a crystal composition of 75% to 100% calcite and 0% to 25% vaterite and 0% to 10% aragonite.

[0066] The CaCCh or the mixture preferably has a biogenic carbon content of more than 30%, more preferably more than 50%, and most preferably more than 90%. The biogenic carbon content can be determined, in particular, by isotope analysis. The biogenic carbon was preferably fixed in the CaCCh after the industrial revolution, particularly preferably after 2000. CaCCh and MgCCh are preferably components of the mixture, and the whiteness, particle size, crystal composition, biogenic carbon content, and decomposition temperature are properties of the mixture.

[0067] Preferably, the mixture comprises from 99.9 wt% to 99.7 wt% CaCCh and from 0.03 wt% to 0.01 wt% MgCCh and has in particular the claimed properties or all of the properties disclosed above.

[0068] Preferably, the mixture consists of 99.9 wt.% to 90.0 wt.% CaCCh and 10.0 wt.% to 0.01 wt.% MgCOa and has the claimed properties. Preferably, the mixture has all of the properties disclosed above.

[0069] Preferably, the mixture consists of all the aforementioned components and has all the aforementioned and / or claimed properties.

[0070] Surprisingly, a cooperative effect of CaCO3 and MgCCh was observed when used as a cement, resulting in a particularly fast-setting and stable cement. Surprisingly, the mixture exhibits a particularly advantageous high surface reactivity and improved pouring properties, possibly due to its crystal composition. The mixture can also be used to produce a concrete that reflects particularly high levels of incident light, thus protecting a building constructed from this concrete from excessive heating due to solar radiation.

[0071] Preference is given to using the mixture or the CaCO for producing coated paper, wherein the mixture is used as a paper coating, in particular to color and substitute the pulp of the paper and to improve the mechanical properties of the paper, in particular the tear resistance;and / or for the production of cement, in particular for the material recycling of concrete and for the production of concrete, wherein the mixture is used as a starting material for recycled cement and / or for the production of toothpaste, wherein the mixture is preferably used as an abrasive material for removing plaque and / or for adjusting the pH value, in particular as a pH buffer, and / or for the production of formulations, coatings and / or dispersions from polymers, paints, sealants and / or silicones, wherein the mixture is used, for example, as a dye and / or filler and / or for improving the flow properties and / or for improving the mechanical properties.;

[0072] The use of CaCO or the mixture and sand from the concrete production process is preferred. The use of all products from the concrete production process is particularly preferred.

[0073] Advantageously, the CaCOs has a product carbon footprint of less than 2000.0 g CC>2e / kg CaCCh, particularly advantageously less than 500.0 g CC>2e / kg CaCCh if the electrical energy required for the process is obtained in accordance with the German Electricity Mix 2021 and less than - 100.0 g CO2e / kg CaCCh, particularly advantageously less than - 300.0 g CO2e / kg CaCCh if the electrical energy required for the process is obtained from photovoltaics.

[0074] The calculation of the Product Carbon Footprint is based on the product life cycle (LCA) of precipitated calcium carbonate, as described in Hottenroth, H. (2014). Carbon Footprints for Products: A Handbook for Small and Medium-Sized Enterprises. Münster: Monsenstein and Vannerdat and / or

[0075] DIN EN ISO 14067:2019-02, Greenhouse gases - Carbon footprint of products, requirements and guidelines for quantification (ISQ_14067:2018); German and English version EN_ISQ_14067:2018. Beuth Verlag GmbH. https: / / doi.org / 10.31030 / 2851769. The data refer to 1 kg of precipitated CaCO3 or the mixture produced and distributed in the immediate vicinity of a European metropolitan area.

[0076] The system preferably comprises a pump for pumping the second fluid into the reactor. The system preferably comprises a compressor for compressing the CO2-containing gas released during precipitation and introducing it into the reactor or the saturator. The system preferably comprises a fines filter for isolating the second fluid, in particular the CaCO3-enriched second fluid and / or the Ca-enriched second fluid, and preferably for isolating the fines. The fines filter preferably has a pore size of 1 μm to 50 μm, particularly preferably 1 μm to 20 μm.

[0077] The sand filter preferably has a pore size of 0.1 mm to 0.5 mm. Alternatively or additionally, the system comprises a hydrocyclone and / or a sedimentation unit, in particular for isolating the Ca-enriched second fluid and preferably for isolating sand.

[0078] The CaCO3 filter preferably has a pore size of 0.1 μm to 20 μm. Alternatively or additionally, the system comprises a Nutsche filter and / or a centrifuge, in particular for isolating the precipitated CaCO3. The Nutsche filter and / or the centrifuge preferably has a filter stage of 0.1 μm to 20 μm. The system preferably comprises a heat exchanger which is arranged in thermally conductive connection with the dryer and the first fluid, or is arranged in the dryer, in order to dry the isolated CaCCh using waste heat from the first fluid. The system preferably comprises a heat pump which is arranged in thermally conductive connection with the dryer and the first fluid, or is arranged in the dryer, in order to dry the isolated CaCCh using waste heat from the first fluid.

[0079] The system preferably comprises an energy recovery device, for example an expansion turbine, which is arranged on a drive shaft of the compressor or the pump. The energy recovery device is preferably designed to use energy from the pressurized second fluid, in particular after the solid-liquid separation, directly to compress the second fluid in the reactor or to convert it into electrical energy. For this purpose, the energy recovery device can be designed as a turbine which uses the pressure difference between the reactor and the precipitation vessel to generate energy, which is released in particular when the second fluid is expanded. Alternatively or additionally, the energy recovery device is designed to convert thermal energy of the first fluid and / or the second fluid into electrical energy.Advantageously, the system comprises a photovoltaic module or other renewable energy generation systems, in particular to cover the electrical energy demand of the process by more than 20%, preferably by more than 30%.

[0080] A preferred embodiment comprises any combination of the dependent claims and / or the features described in the description with an independent claim or all independent claims, provided that the resulting combination of features does not result in a logical contradiction.

[0081] Further features and advantages of the invention will become apparent from the following description based on exemplary embodiments and the drawings. Although the invention is illustrated and disclosed in detail in the figures and the above description, these representations and descriptions are to be considered purely illustrative or exemplary and not restrictive.

[0082] Figure 1 shows schematically the steps of the method in a flow chart;

[0083] Figure 2 shows a system for carrying out the process in which the waste heat of the first fluid is used to dry the precipitated CaCO;

[0084] Figure 3 shows a system for carrying out the process with a compressor in which the recycled water is recycled after solid-liquid separation and a CO2-containing gas is recycled after precipitation;

[0085] Figure 4 shows a system for carrying out the process, with a Ca extractor in which the recycled water after the solid-liquid separation and a CO2-containing gas after the precipitation are recycled;

[0086] Figure 5 shows a system for carrying out the process with a saturator;

[0087] Figure 6 shows a system for carrying out the process with a saturator in which the waste heat of the first fluid is used to dry the precipitated CaCO.

[0088] The same reference symbols used in the figures denote the same or at least similarly functioning elements.

[0089] Figure 1 shows a process for the material recycling of concrete 6 or concrete building material mixtures. In a first step, a first fluid 2 is provided 1, which in the present example is a CO2-containing gas with a CO2 content of 10 vol.% to 100 vol.%, and a second fluid 3 is provided 1, which in the present example is water, which is mixed with recycled water 4. In a second step, the second fluid 3 is mixed 5 with the concrete 6 and then Ca from the concrete 6 is dissolved in the second fluid 3, whereby a Ca-enriched second fluid 3a is obtained. The Ca-enriched second fluid 3a is isolated 7 in a next step. In a further step, precipitation 8 of CaCCh 9 takes place from the Ca-enriched second fluid 3a by mixing with the first fluid 2 at a pressure of 1.1 bar to 500 bar.In a subsequent step, the CaCCh 9 precipitated as a solid is isolated by a solid-liquid separation 10 of the precipitated CaCO 9 from the second fluid 3, preferably by filtration, wherein the second fluid 3 is obtained as recycled water 4 and is made available again 1 in the process, i.e., in other words, is recycled. The isolated CaCO 9 is subjected to drying 11 in a subsequent step. The product of the process is the dried CaCO 9 or the mixture according to the invention, wherein, for reasons of simplicity, CaCCh 9 is also used synonymously with the mixture in the descriptive examples. Optionally, the first fluid 2 can also be used alternatively or additionally directly in the precipitation 8.

[0090] Figure 2 shows a system 12 for carrying out a process in which waste heat from the first fluid 2 is used to dry 11 the precipitated CaCO 9. In the example shown here, the first fluid 2 is a warm gas containing CO2 and the second fluid 3 is water. The warm gas containing CO2 is mixed with CO2 in a saturator 13 to enrich the water and is then removed from the saturator 13 as low-CO2 exhaust gas 2a. The CO2-enriched water is fed from the saturator 13 into a reactor 14 and mixed there with concrete 6. In the process, Ca is dissolved from the concrete 6 and reacted with the CO2 to form CaCO 9. In addition, sand 15 dissolves from the concrete 6, which is removed from the reactor 14 and used separately for the material recycling of concrete. The CaCOs 9 is then precipitated 8, in particular in a precipitation tank and separated from the water by filtration, which is then fed back to the reactor 14.The precipitated and isolated CaCO3 9 is placed in a dryer and dried therein 11 . The necessary heat energy is obtained from waste heat of the warm gas containing CC2 by a heat exchanger 16 or a heat pump. The products of this process are CaCO3 9 or the mixture according to the invention and sand 15. The process is particularly energy-saving and energy-efficient due to the utilization of the waste heat of the first fluid 2.

[0091] Figure 3 shows a system 12 in which a first fluid 2 and water as a second fluid 3 are mixed in a reactor 14 with a concrete 6 fine fraction in order to dissolve Ca from the concrete 6. The first fluid 2 is preferably liquefied CO2 from a carbon capture process at a pressure of 60 bar and a temperature of 20°C, which is fed into the reactor 14 at a mass flow of 586 kg / h. The water is fed into the reactor 14 at a mass flow of 7614 kg / h, which preferably has a volume of 314 m 3 and is operated at a temperature of 20°C, a pressure of 20 bar, and with stirring at a stirring speed of 50 revolutions / min. The concrete 6 is fed in as a fine fraction and has a particle size of <5 mm, approximately 9 wt% Ca, approximately 80 wt% sand, approximately 4 wt% other minerals, and approximately 3 wt% water. The degree of carbonization of the Ca is 10%. The concrete 6 is fed into the reactor 14 at a mass flow rate of 6944.4 kg / h.

[0092] In a subsequent step, a first solid-liquid separation 10a takes place, in which sand 15 is separated as a solid from the second fluid 3, for example by a hydrocyclone or a sedimenter or by filtration with a sand filter having a pore size of 0.1 mm to 0.5 mm. Subsequently, in a second solid-liquid separation 10b, a fine fraction 17 is separated as a solid from the second fluid 3, for example by filtration with a fine fraction filter having a pore size of 1 pm to 50 pm, preferably 3 pm to 20 pm, in order to isolate the CaCCh-enriched second fluid. The sand 15 is preferably obtained at a mass flow rate of 5556 kg / h and the fine fraction at a mass flow rate of 306 kg / h.

[0093] Thereafter, the precipitation 8 of CaCCh 9 from the CaCCh-enriched second fluid 3 takes place by a sudden pressure reduction of the second fluid 3 to 0.1 bar at a temperature of 20°C, whereby the CaCCh 9 precipitates as a solid and a CC>2-containing gas is released from the second fluid 3. The CC>2-containing gas is compressed by a compressor 19 from a pressure of 0.1 bar to a pressure of 20 bar and fed back to the reactor 14 at an inlet temperature of 20°C, preferably at a mass flow of 42552 kg / h.

[0094] The precipitated CaCO3 9 is separated and isolated from the second fluid 3 in a third solid-liquid separation 10c, for example, by a Nutsche filter or a centrifuge or by filtration with a CaCO3 filter having a pore size of 0.3 pm to 20 pm. The second fluid 3 is pumped back into the reactor 14 by a pump 20, in particular as recycled water with a volume flow of 1257 m3 / h. The isolated CaCOs 9 is finally dried 11 , in particular at a temperature of 120°C and a pressure of 50 mbar. The products of this process are CaCOs 9 or the mixture according to the invention, sand 15, and the fine fraction 17, which are recycled.

[0095] Advantageously, the energy requirement of this process is 1096 kWh / t concrete 6. Particularly advantageously, the CaCOs 9 is preferably obtained as a powder with a residual moisture content of <0.1% and a purity >99% in a mass flow of 1544 kg / h, with a product carbon footprint of less than 1200.0 g CO2e / kg CaCOs, preferably of 1606.8 g CO2e / kg CaCOs, if the electrical energy required for the process is obtained according to the German Electricity Mix 2021 and less than - 150 g CO2e / kg CaCOs, particularly advantageously - 196.2 g CO2e / kg CaCOs, if the electrical energy required for the process is obtained from photovoltaics.

[0096] Figure 4 shows a system 12 in which water as the second fluid 3 is mixed in a Ca extractor 18 with a concrete 6 fine fraction, which preferably has a particle size of <1 mm with 38 wt% CaO, 58 wt% sand and 4 wt% other minerals. The concrete 6 fine fraction is preferably fed into the Ca extractor 18 at a mass flow rate of 1000 kg / h. The Ca extractor 18 is a container in which Ca from the concrete 6 is extracted into the second fluid 3, in particular as Ca 2+ , is dissolved. In the example shown here, the second fluid 3 is water, which is preferably added to the Ca extractor 18 at a mass flow of 1000 kg / h. The temperature in the extractor is preferably 20°C and the pressure is 1 bar. Furthermore, the Ca extractor 18 has a volume of 70 m 3 and a stirrer which operates at a stirring speed of 20 revolutions / min.

[0097] The Ca-enriched second fluid 3a is separated from the sand 15 in a first solid-liquid separation 10a and from the fine fraction 17 in a subsequent second solid-liquid separation 10b. The first solid-liquid separation 10a is preferably carried out with a hydrocyclone or with a sedimenter or with a sand filter with a pore size of 0.1 mm to 0.5 mm. The second solid-liquid separation 10b is preferably carried out with a fine fraction filter with a pore size of 1 μm to 50 μm, particularly preferably 3 μm to 20 μm. The sand 15 is obtained with a residual moisture content of 50% at a mass flow rate of 580 kg / h. The fine fraction 17 contains, in particular, unreacted CaO and is discharged at a mass flow rate of 325 kg / h and thus obtained.

[0098] After the second solid-liquid separation 10b, the second fluid 3 is mixed in the reactor 14 with a CO2-containing first fluid 2, wherein the dissolved Ca is reacted with CO2 from the first fluid 2 to form CaCOs to obtain a CaCOs-enriched second fluid 3. The first fluid 2 is preferably liquefied CO2 from a carbon capture process. The first fluid 2 is fed into the reactor 14, in particular at a pressure of 60 bar and a temperature of 20°C, and in particular at a mass flow of 373 kg / h, where it is mixed with the second fluid 3.

[0099] Subsequently, CaCO3 9 is precipitated from the CaCO3-enriched second fluid 3. For this purpose, it is depressurized in a precipitation vessel to a pressure of 1 bar at a temperature of 20°C. The precipitated CaCO3 9 is then isolated by a third solid-liquid separation 10c. A CaCCh filter, a Nutsche filter, or a centrifuge with a filter stage of 0.1 pm to 20 pm is used for the third solid-liquid separation 10c.

[0100] After the third solid-liquid separation 10c, the second fluid 3 is at least partially pumped back into the Ca extractor 18 by a pump 20. Optionally, water can be removed at a mass flow rate of 420 kg / h, which is indicated in Figure 3 by the downward-pointing arrow at 10c. The CaCCh 9 isolated by the third solid-liquid separation 10c is dried 11, in particular at a temperature of 120°C and at a pressure of 50 mbar.

[0101] The products of this process are CaCOs 9, preferably as powder with a residual moisture content of <0.1% and a purity of >99% in a mass flow of in particular 383 kg / h, sand 15 and the fine fraction 17, which are sent for material recycling.

[0102] Advantageously, the energy requirement of this process is 60 kWh / t concrete 6. Particularly advantageously, the CaCOs or the mixture has a product carbon footprint of less than - 283.0 g CO2e / kg CaCCh if the electrical energy required for the process is obtained according to the German Electricity Mix 2021 and less than - 300 g CO2e / kg CaCCh, particularly advantageously - 394.4 g CO2e / kg CaCCh if the electrical energy required for the process is obtained from photovoltaics.

[0103] Figure 5 shows a system 12 for carrying out a process in which the concrete 6 preferably has a particle size of <5 mm with 9 wt% Ca, 80 wt% sand, and 3 wt% other minerals. The degree of carbonization of the Ca is 10%. The first fluid 2 is a CO2-containing gas, in particular an exhaust gas from natural gas combustion with 14.5 wt% CO2, which is supplied at a mass flow of 5290 kg / h. The second fluid 3 is water, which is supplied at a mass flow of 7614 kg / h.

[0104] The CC>2-containing exhaust gas is mixed with CO2 in the saturator 13 at a temperature of 20°C and a pressure of 10 bar to enrich the water and is then removed from the saturator 13 as CO2-poor exhaust gas 2a. The CO2-enriched water is passed from the saturator 13 into a reactor 14, where it is mixed with concrete 6, which is preferably added at a mass flow rate of 6944.4 kg / h, whereby Ca is dissolved from the concrete 6 and reacted with the CO2 to form CaCCh 9 to obtain a CaCCh-enriched second fluid 3. The temperature in the reactor 14 is preferably 20°C and the pressure 10 bar. The reactor also has a stirrer operated at a stirring speed of 50 revolutions / min.

[0105] This is followed by a first solid-liquid separation 10a to separate and isolate sand 15, which has been dissolved out of the concrete 6, from the CaCCh-enriched second fluid 3. Preferably, the mass flow of the sand 15 is 5556 kg / h. A hydrocyclone, a sedimenter, or a sand filter with a pore size of 0.1 mm to 0.5 mm is preferably used for the first solid-liquid separation 10a. The CaCCh-enriched second fluid 3 is then separated from a fine fraction 17 in a second solid-liquid separation 10b, preferably using a fine fraction filter with a pore size of 1 pm to 50 pm, particularly preferably 3 pm to 20 pm.

[0106] In a subsequent step, CaCO2 9 is precipitated 8 from the CaCCh-enriched second fluid 3. Precipitation 8 occurs by a sudden pressure reduction of the second fluid 3 to a pressure of 1 bar at a temperature of 20°C, whereby a CO2-containing gas is released from the second fluid 3. The CO2-containing gas is compressed by a compressor 19 and fed back to the reactor 14 with an inlet temperature of 20°C. The compressor 19 compresses the CO2-containing gas from 0.05 bar to 10 bar.

[0107] The precipitated CaCO3 9 is separated from the water by a subsequent third solid-liquid separation 10c, which is then fed back to the saturator 13 by a pump 20. The third solid-liquid separation 10c takes place through a CaCO3 filter, a Nutsche filter, or a centrifuge with a filter stage of 0.1 pm to 20 pm, which can correspond in particular to the pore size of the CaCO3 filter. The precipitated and isolated CaCCh 9 is placed in a dryer and dried therein at a temperature of 120°C and a pressure of 50 mbar 11 . The products of this process are CaCC>39, in particular as a powder with a residual moisture content of <0.1%, a purity of >99% at an exemplary mass flow of 1544 kg / h, sand 15, and the fine fraction 17, which are then recycled.

[0108] Advantageously, the energy requirement of this process is 420 kWh / t concrete 6. Particularly advantageously, the CaCOs or the mixture has a product carbon footprint of less than 400.0 g CO2e / kg CaCCh, preferably of 373.7 g CO2e / kg CaCCh, if the electrical energy required for the process is obtained in accordance with the German Electricity Mix 2021 and less than - 300 g CO2e / kg CaCCh, particularly advantageously - 325.5 g CO2e / kg CaCCh, if the electrical energy required for the process is obtained from photovoltaics.

[0109] Figure 6 shows a system 12 for carrying out a process in which waste heat from the first fluid 2 is used to dry 11 the precipitated CaCO 9. The first fluid 2 is a warm exhaust gas containing CC>2 from a natural gas combustion with 14.5 wt% CO2 and is fed into a saturator 13, in particular, at a mass flow rate of 5290 kg / h. The second fluid 3 is water, which is fed into the saturator 13 at a mass flow rate of 7614 kg / h.

[0110] The warm exhaust gas containing CO2 is mixed with CO2 in the saturator 13 at a temperature of 20°C and a pressure of 10 bar to enrich the water and is then removed from the saturator 13 as CO2-poor exhaust gas 2a. The CO2-enriched water is passed from the saturator 13 into a reactor 14 and mixed there with concrete 6. A fine fraction with a particle size of <5 mm, 9 wt% Ca, 80 wt% sand, 4 wt% other minerals and 3 wt% water is preferably used as concrete 6. The concrete 6 fine fraction in particular has a degree of carbonization of Ca of 10% and is preferably fed into the reactor 14 at a mass flow of 6944.4 kg / h and mixed there with the CO2-enriched water at a temperature of 20°C, a pressure of 10 bar and a stirring speed of 50 revolutions / min. Preferably, reactor 14 has a volume of 314 m 3 .

[0111] In this process, Ca is dissolved from the concrete 6 and reacted with the CO2 to form CaCCh 9. In addition, sand 15 dissolves from the concrete 6, which is separated and isolated from the CaCCh-enriched second fluid 3 in a subsequent first solid-liquid separation 10a, with a mass flow of the sand 15 preferably being 5556 kg / h. A hydrocyclone, a sedimenter, or a sand filter with a pore size of 0.1 mm to 0.5 mm is preferably used for the first solid-liquid separation 10a.

[0112] The CaCCh-enriched second fluid 3 is then separated and isolated from a fine fraction 17 in a second solid-liquid separation 10b, with a mass flow of the fine fraction 17 preferably being 306 kg / h. For the second solid-liquid separation 10b, a fine fraction filter with a pore size of 1 pm to 50 pm, particularly preferably 3 pm to 20 pm, is preferably used.

[0113] In a subsequent step, CaCOs 9 is precipitated 8 from the CaCCh-enriched second fluid 3, in particular in a precipitation vessel at a pressure of 1 bar and a temperature of 20°C, and separated from the water by a subsequent third solid-liquid separation 10c, in particular by a CaCCh filter or a Nutsche filter or a centrifuge, each with a separation sharpness of 0.3 pm to 20 pm, which is then fed back to the saturator 13 by a pump 20, in particular with a volume flow of 1257 m 3 / h. During precipitation 8, a CCh-containing gas is released from the second fluid 3. The CCh-containing gas is compressed by a compressor 19 from a pressure of 1 bar to a pressure of 10 bar and fed back to the reactor 14 with an inlet temperature of 20°C at a preferred mass flow rate of 19,422 kg / h. The precipitated and isolated CaCO3 9 is fed into a dryer and dried therein at a temperature of 120°C and a pressure of 50 mbar 11 . The thermal energy required for this is obtained by a heat exchanger 16 or a heat pump from waste heat of the warm exhaust gas containing C02.

[0114] The products of this process are CaCOs 9 as a powder with a residual moisture content of <0.1% and a purity of >99% in an exemplary mass flow of 1544 kg / h, sand 15 and the fine fraction 17. The process is particularly energy-saving and energy-efficient due to the use of the waste heat of the first fluid 2. Advantageously, the energy requirement of this process is 311 kWh / t concrete 6. Particularly advantageously, the CaCOs or the mixture has a product carbon footprint of less than 200.0 g CO2e / kg CaCCh, preferably of 174.9 g CO2e / kg CaCCh, if the electrical energy required for the process is purchased according to the German Electricity Mix 2021 and less than - 300 g CO2e / kg CaCCh, particularly advantageously

[0115] - 346.3 g CChe / kg CaCCh if the electrical energy required for the process is obtained from photovoltaics.

[0116] In a slightly different process, precipitation 8 is carried out at a pressure of 0.1 bar and a temperature of 20°C. At this lower pressure, a correspondingly larger amount of CCh-containing gas is released from the second fluid 3. The CCh-containing gas is compressed by the compressor 19 from a pressure of 0.1 bar to a pressure of 20 bar and fed back into the reactor 14 with an inlet temperature of 20°C at a preferred mass flow rate of 42,552 kg / h.

[0117] Advantageously, the energy requirement of this process is 1164 kWh / t concrete 6. Particularly advantageously, the CaCOs or the mixture has a product carbon footprint of less than 1800.0 g CO2e / kg CaCOs, preferably of 1730.8 g CO2e / kg CaCOs, if the electrical energy required for the process is purchased in accordance with the German Electricity Mix 2021 and less than

[0118] - 150 g CO2e / kg CaCOs, particularly advantageously - 183.2 g CO2e / kg CaCCh, if the electrical energy required for the process is obtained from photovoltaics.

[0119] Exemplary experiments are described below. The exemplary experiments, in particular, are carried out in a 500 ml pressure reactor with a stirrer. The lid of the reactor has the following four inlets: a gas inlet, a pressure sensor and gas outlet, a liquid outlet, and a safety valve. The gas inlet has a pressure reducer for control and a safety orifice to limit the flow. The pressure in the reactor is measured and recorded every second via the pressure sensor. At the beginning of the experiment, a specific amount of a concrete sample is weighed into a beaker and placed in the pressure reactor. The beaker is rinsed with demineralized water, and the reactor is filled with a total of 400 ml of demineralized water. The reactor is then closed and the stirrer switched on. The CO2 gas inlet is opened and the appropriate pressure is set.After each experiment, the reactor is preferably rinsed first with a citric acid solution (at least 5 wt%) and then with deionized water.

[0120] Example Experiment 1: Extraction of CaCO2 from recycled standard concrete. A sample of standard concrete with the composition 20% cement CEM 1 42.5R (Probau) and 80% quartz sand (Probau) and a water-cement ratio of 0.5 with a sand particle size of 0.1 mm to 0.4 mm is reacted at 22°C (PT 100) and 20 bar CO2 partial pressure. The concrete to water ratio is 15 g per 400 ml. The stirring speed is 500 rpm. The contact time is 25 minutes. The liquid portion is then fed into a precipitator and filtered twice (20 μm plastic coarse filter and 2 μm metal fine filter). The precipitate is then reduced to 0.05 bar at a temperature of 22°C. From 15 g of recyclate containing 1.94 g of CaO, 0.8 g of CaCO3 is recovered as a solid. 1.28 g of CaCO3 is dissolved in the water phase. The total Ca yield is 62.5%.The precipitated CaCO3 has an average particle size, determined as the particle diameter, of 3.4 pm (Keyence VHX-7100 method with image analysis) and a crystal composition of >95% calcite and the remainder vaterite (SEM method with image analysis). Contamination with foreign particles is <0.5% of the sample surface (Keyence VHX-7100 method with image analysis). The decomposition temperature was determined by mass loss due to the outgassing of CO2 and begins at 740°C and is completed at 810°C (TGA method).

[0121] Example Experiment 2: Extraction of CaCO3 from recycled residual water sludge from fresh concrete production. A 1 g sample with a 38% CaO content and a particle size of <1 mm is mixed with 100 ml of water at 22°C (PT 100) and contacted. 0.095 g of the CaO contained passes into the aqueous phase. The sample is filtered, and the homogeneous liquid filtrate is mixed with CO2 at 1 bar and contacted. This precipitates 0.1695 g of solid CaCO3. 1.4 mg of CaCO3 is dissolved in the aqueous phase.

[0122] Example Experiment 3: Extraction of CaCO3 from recycled concrete, source: MinE-RALIX GmbH Concrete Recycler. A 1 g sample from the particle size fraction less than or equal to 2 mm with a CaO content of 12% is contacted with 100 ml of water at 100°C (PT 100). 0.05 g of the CaO contained passes into the aqueous phase. The sample is filtered, and the homogeneous liquid filtrate is contacted with CO2 at 1 bar. This precipitates 0.088 g of solid CaCO3. 1.4 mg of CaCO3 is dissolved in the aqueous phase.

[0123] The calcium oxide content of concrete samples is preferably determined by acid-base titration. The concrete sample is ground, sieved, and dried. The calcium oxide or calcium hydroxide contained in the concrete in an aqueous solution is decomposed with hydrochloric acid and dissolves as calcium chloride. The subsequent titration can be used to determine the hydrochloric acid consumed in the reaction and thus also the amount of calcium. For this purpose, for example, 1 g of a concrete sample is weighed into a 100 ml Erlenmeyer flask (Sartorius™ analytical balance, accuracy 0.1 mg). 9 ml of hydrochloric acid (2.12 M, 0.0191 mol) is then added using a volumetric pipette. The solution is stirred with a glass rod for 2 minutes and then transferred to a 500 ml volumetric flask half-filled with deionized water. To transfer, the Erlenmeyer flask is tilted and the solution decanted using a volumetric pipette. The Erlenmeyer flask is rinsed with 20 ml of deionized water and transferred using a volumetric pipette.In the next step, the volumetric flask is filled with deionized water to a volume of 500 ml. 50 ml of the diluted acidic sample is transferred into a beaker for titration, along with 5-7 drops of a bromothymol blue indicator solution (0.1% in EtOH). While continuously swirling, the stock solution of sodium hydroxide solution (0.05 M) is slowly added dropwise until the tipping point is reached. The volume of sodium hydroxide solution is recorded, and the titration is repeated two more times. From this triplet of titrations, the corresponding CaO content is calculated, particularly by taking the mean value.

[0124] For example, an acid-base titration is also used to measure the calcium carbonate content of the aqueous solution before and after precipitation. The first 10 ml of the sample is discarded, and a further 35 ml is transferred to a beaker. Using a volumetric pipette, 25 ml of the sample solution is removed from the beaker and heated to dryness in a clean beaker. During transfer, care is taken to ensure that no gas bubbles remain in the pipette. The beaker is allowed to stand at room temperature for 5 minutes to cool. The precipitated calcium carbonate is then dissolved in 5 ml of hydrochloric acid (2.12 M, 0.106 mol) and, after swirling for 2 minutes, diluted to 500 ml with deionized water in a volumetric flask. The beaker is rinsed several times with water. For titration, 50 ml of the diluted acidic solution as well as 5-7 drops of bromothymol blue and sodium hydroxide solution (0.05 M) are used.

[0125] Contamination with foreign particles is determined, for example, using a Keyence VHX-7100™ digital microscope at 100x optical magnification with illumination (full ring 0 / 255, transillumination 255 / 255, preset 1 / 250s, gain ODB) using the autograin function (brightness 0, original image). In addition, the particle size and / or particle size distribution are determined using the Keyence VHX-7100 digital microscope at 100x and 400x optical magnification with illumination (full ring 0 / 255, transillumination 255 / 255, preset 1 / 60s, gain ODB). The crystal structure is determined, for example, using a SEM Zeiss SUPRA™ 60 VP (3 kV and 10 kV, without and with 20 nm Ag coating, 100x to 50,000x magnification) and image analysis.

[0126] Thermal stability and material contamination are determined, for example, using thermogravimetric analysis with a Mettler Toledo™ TGA 2. The sample is heated at 10 °C per minute up to 1000 °C. Mettler STAR SW™ 14.00 software is used for evaluation.

[0127] All temperatures are measured using standard PT 100 resistance thermometers. Pressures are measured both analogously and simultaneously using piezo sensors (0-40 bar, 0-85°C, linearity <1%, hysteresis <0.5%).

[0128] All features of the described and claimed subject matter are usable both in isolation and in combination with one another, are compatible with one another, and are intended and usable for further development of one another, provided no logical contradiction arises, and are hereby disclosed to that effect. The mere fact that certain features are mentioned in different claims does not mean that a combination of these features cannot be advantageous.

[0129] Upon reading the present disclosure, further modifications of the invention will become apparent to those skilled in the art. Such modifications may include other features already known in the art that may be used instead of or in addition to the features already described herein. Modifications of the disclosed invention and its embodiments may be understood and implemented based on the drawings, the disclosure, and the claims. Reference symbols

[0130] Provide

[0131] First fluid a low-CO2 exhaust gas

[0132] Second fluid a Ca enriched second fluid

[0133] Recycled water

[0134] Mix

[0135] concrete

[0136] Isolating the Ca-enriched second fluid

[0137] Precipitation

[0138] CaCO30 Solid-Liquid Separation 1 Drying 2 System 3 Saturator 4 Reactor 5 Sand 6 Heat Exchanger 7 Fines 8 Ca Extractor 9 Compressor 0 Pump

Claims

Claims 1. Process for the material recycling of concrete (6) or concrete building material mixtures comprising the steps: - Providing (1) a first fluid (2), in particular a CC>2-containing gas with a CC>2 content of 10 vol.% to 100 vol.% and a second fluid (3), in particular water and / or recycled water (4); - Mixing (5) the second fluid (3) with the concrete (6) or the concrete-building material mixture; - dissolving Ca from the concrete (6) or the concrete building material mixture in the second fluid (3) to obtain a Ca-enriched second fluid (3a); - isolating (7) the Ca-enriched second fluid (3a); - Precipitation (8) of CaCCh (9) from the Ca-enriched second fluid (3a) by mixing with the first fluid (2) at a pressure of 1.1 bar to 500 bar; - isolating the CaCCh (9), in particular by a solid-liquid separation (10) of the precipitated CaCCh (9) from the second fluid (3), preferably by filtration; - drying (11) of the isolated CaCCh (9); the steps are preferably carried out in the order in which they are mentioned.

2. Process for the material recycling of concrete (6) or concrete building material mixtures comprising the steps: - Providing (1) a CO2-containing first fluid (2), in particular a CC>2-containing gas with a CO2 content of 10 vol.% to 100 vol.% and a second fluid (3), in particular water and / or recycled water (4); - enriching the second fluid (3) with CO2 from the first fluid (2); - Mixing (5) the CO2-enriched second fluid (3) with the concrete (6) or the concrete building material mixture; - Dissolving Ca from the concrete (6) or the concrete-building material mixture in the second fluid (3) and reacting the dissolved Ca with CO2 from the second fluid (3) to CaCC>3 to obtain a CaCCh-enriched second fluid (3); - isolating (7) the CaCCh-enriched second fluid (3); - precipitation (8) of CaCCh (9) from the CaCCh-enriched second fluid (3); - isolating the CaCC>3 (9), in particular by a solid-liquid separation (10) of the precipitated CaCCh (9) from the second fluid (3), preferably by filtration; - drying (11) of the isolated CaCO (9); the steps are preferably carried out in the order in which they are mentioned.

3. The method according to claim 2, wherein the enrichment of the second fluid with CO2 from the first fluid (2) takes place at a temperature of 5°C to 40°C and / or at a pressure of 1.0 bar to 40.0 bar, preferably from 1.1 bar to 21.0 bar.

4. Method according to one of claims 2 or 3, comprising the steps of providing (1) a first container, in particular a saturator (13) and / or an absorber, and a second container, in particular a reactor (14); wherein the enrichment of the second fluid with CO2 from the first fluid (2) takes place in the first container and then the mixing (5) of the CO2-enriched second fluid with the concrete (6) or the concrete-building material mixture takes place in the second container and preferably the CO2-enriched second fluid is isolated after the enrichment in the first container and then transferred to the second container.

5. Method according to one of claims 2 to 4, wherein after mixing (5) the CO2-enriched second fluid with the concrete (6) or the concrete-building material mixture, the CO2-enriched second fluid is used to dissolve Ca from the concrete (6) or the concrete-building material mixture and to react the dissolved Ca with CO2 from the second fluid (3) to CaCCh for a Residence time of 10 min to 4 h with the concrete (6) or the concrete-building material mixture at a pressure of 1.0 bar to 40.0 bar and / or at a temperature of 5°C to 60°C and / or at a pH of less than 9, preferably from 1.1 bar to 21.0 bar and / or from 10°C to 40°C and / or at a pH of less than 7, most preferably less than 6, in order to obtain the CaCCh-enriched second fluid, which is then isolated (7).

6. Method according to one of the preceding claims, in which the precipitation (8) of CaCCh (9) from the CaCCh-enriched second fluid (3a) is carried out by a sudden pressure reduction and / or a temperature increase, wherein the pressure reduction and the temperature increase preferably take place simultaneously and in particular the pressure reduction takes place to a pressure of 0.01 bar to 1.1 bar and / or the temperature increase takes place to a temperature of 5°C to 60°C.

7. Method according to one of the preceding claims, in which the drying (11) of the isolated CaCCh (9) is carried out by waste heat of the first fluid (2).

8. Method according to one of the preceding claims, in which the isolation (7) of the Ca-enriched second fluid (3a) is carried out by sedimentation and / or filtration, whereby the Ca-enriched second fluid (3a) is preferably separated from solids, particularly preferably by a two-stage solid-liquid separation (10), in which sand is first separated by sedimentation or a hydrocyclone or filtration and then a fine fraction or other solid impurities are separated from the second fluid in a filtration.

9. A method according to any one of the preceding claims, wherein the CaCCh is kept in solution in the CaCCh-enriched second fluid until precipitation (8).

10. Mixture particularly for coating paper and / or for producing cement and / or toothpaste, and / or formulations, Coatings and / or dispersions of polymers, paints, sealants and / or silicones, in particular produced by a process according to one of the preceding claims, comprising from 99.9 wt% to 90.0 wt% CaCCh (9) and from 10.0 wt% to 0.01 wt% MgCCh and wherein the mixture has a whiteness as L* value greater than 70 and a particle size of less than 100 pm, preferably less than 80 pm, particularly preferably less than 75 pm, and a decomposition temperature of 300°C to 950°C, preferably from 340°C to 900°C.

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