CO2 sequestration

Abstract

The present invention relates to a CO ferromagnetic material processing method, comprising the steps of: preparing a starting product comprising at least 20% by mass of one or more of ultramafic rock, weathering products of ultramafic rock, olivine and / or industrial waste; homogenizing the starting product; and hydrothermally treating the homogenized starting product in a heat treatment device at a temperature above 100° C. for at least 24 hours. 2 The method further relates to a method for sequestering CO. The converted starting product is then dehydrated of bound water by thermal treatment and / or reactive grinding. 2 In contact with CO 2 and combine.

Description

[Technical Field]

[0001] This invention relates to a method for sequestering CO2. [Background technology]

[0002] Carbon dioxide (CO2) acts as a greenhouse gas in the atmosphere and is considered one of the main causes of anthropogenic global warming. In addition to fundamentally reducing CO2 emissions, efforts are also being made to bind the CO2 already present in the atmosphere. By binding CO2, it is possible to make CO2-neutral manufacturing processes that emit large amounts of CO2, such as cement production.

[0003] CO2 sequestration specifically refers to removing CO2 from the atmosphere, ideally preventing it from being released again by binding with other substances. Various proposals for this are known. One possibility is the use of olivine.

[0004] Olivine is a mineral with a general composition of A2[SiO4], where A can be various divalent ions such as magnesium (forsterite, Mg2SiO4), iron (Fe2SiO4, fayalite), and manganese (Mn2SiO4, tefloite), as well as other ions and various combinations of cations. Olivine is a solid solution series.

[0005] The patent literature on accelerating carbon dioxide sequestering through reactions with olivine is very extensive. Many methods for sequestering carbon dioxide using olivine are based on the following principles, differing mainly in how the reaction is accelerated.

[0006] [ka]

[0007] According to International Publication No. 2007 / 069902, the reaction should be accelerated by grinding and adjustment to a specific pH value, while International Publication Nos. 2008 / 140821 and 2008 / 061305 suggest that the reaction is accelerated by high temperature, high CO2 partial pressure, and high olivine fineness. International Publication No. 2008 / 101293 proposes the addition of ammonium, International Publication No. 2007 / 106883 proposes the addition of a base, and U.S. Patent No. 4944928 proposes the addition of hydrochloric acid.

[0008] In addition to these methods, there are many other ways that can accelerate carbon dioxide sequestration during the reaction with olivine, but all of these processes use complex techniques and expensive starting materials.

[0009] The CO2min project attempted to combine olivine carbonation with cement production. Its objective was to separate CO2 emissions from the cement industry by carbonating olivine. As a result, cement production could continue without alteration while maintaining the existing high-temperature process. The resulting carbon dioxide was combined with olivine in the form of magnesium carbonate and SiO2. This generated material was then added to the cement and disposed of. However, it is clearly impossible to completely convert olivine to magnesium carbonate (see D. Kremer and H. Wotruba, "Separation of products from mineral sequestration of CO2 with primary and secondary materials," Minerals, Vol. 10 (2020), pp. 1098 et seq.). This project utilized very high CO2 partial pressures (17 bar) and high temperatures (175°C). Despite autoclaving, the olivine conversion rate was only 23%, requiring a very large amount of olivine to compensate for the low conversion rate. The selected process technology is also likely unsuitable for carbon dioxide fusion on an industrial scale.

[0010] Another idea developed in the Netherlands involves binding carbon dioxide through a reaction with olivine (see RDSchuiling and P. Krijgsman, "Enhanced Weathering: An effective and cheap tool to sequeter CO2," Climate Change, Vol. 74 (2006), pp. 349–354). This allows olivine to be spread on arable land or coastlines. When olivine dissolves in magnesium ions, rainwater or seawater reacts with HCO3 according to the following equation. - It can simultaneously absorb carbon dioxide in the form of ions.

[0011] [ka]

[0012] However, laboratory experiments at the University of Hamburg have shown that the described reaction does not occur in the described form. Even if olivine were spread across the entire world's arable land, it would only capture a mere 0.2% of global carbon dioxide emissions (see T. Amann et al., "Enhanced weathering and related element fluxes - a cropland mesocosm approach," Biogeosciences, Vol. 17 (2020), pp. 103-109). [Overview of the Initiative] [Problems that the invention aims to solve]

[0013] Therefore, an object of the present invention is to provide an efficient method for sequestering CO2. [Means for solving the problem]

[0014] According to the present invention, this object is achieved by a method having the features of claim 1.

[0015] Further advantageous embodiments are defined in the dependent claims, the further description and the exemplary embodiments.

Brief Description of the Drawings

[0016] [Figure 1] FIG. 1 is a graph showing the hydration process of a product manufactured by the method of the present invention. [Figure 2] FIG. 2 is a graph showing the curve of CO2 concentration during the binding of CO2 by a product manufactured using the method of the present invention.

Embodiments for Carrying Out the Invention

[0017] According to claim 1, first, a starting product is provided that contains one or more of the following components at least 20% by mass, preferably at least 40% by mass, more preferably at least 60% by mass, and even more preferably at least 80% by mass. These components may be ultra-mafic rocks such as dunite, serpentine, weathering products of ultra-mafic rocks such as olivine, or industrial waste. It is essential that all of these raw materials have a MgO concentration or MgO content of at least 10% by mass, preferably 20% by mass, more preferably 30% by mass or more, and ideally 40% by mass or more. This starting product has a fineness corresponding to a BET surface area of 0.1 m 2 / g or more. The BET surface area of the starting product is advantageously 0.5 m 2 / g, and more preferably 1.0 m 2 / g or more.

[0018] The important mineral in hyper-bitter ferruginous rock is olivine. Olivine is a mixed crystal series of fayalite (Fe2SiO4), forsterite (Mg2SiO4), tephroite (Mn2SiO4) and other minerals of the A2[SiO4] type. Natural olivine deposits are recorded, and olivine is often a substance rich in magnesium containing iron. Examples of industrial waste that can be used in the present invention include foundry sand and refractories.

[0019] Once the starting product is provided, if necessary, the starting product is homogenized. The possible components of the starting product described above are often materials from natural rocks or natural deposits. Empirically, these cannot be obtained in pure form and are not homogenized. Homogenization can be carried out, for example, using a mixer or simultaneously with grinding to the desired fineness.

[0020] Following homogenization, the starting product thus prepared is hydrothermally treated. This treatment is carried out in a heat treatment device at a temperature exceeding 100°C for at least 24 hours. The heat treatment device is a heat tunnel, but may be, for example, an autoclave. An autoclave is generally understood to be an airtight and sealable pressure vessel that can be used for heat treatment of substances in the overpressure range. The heat treatment device is preferably understood as a combination of devices such as a container, an oven or a closed type, or a device for confining volume. The treatment is preferably carried out at a temperature of 100°C or higher, particularly 150°C or higher, more preferably 250°C or higher. Also, when the treatment is carried out for 36 hours or more, more preferably 48 hours or more, good conversion can be obtained. However, particularly good results can be obtained by carrying out the treatment for an even longer period, for example, several days, for example, 4 days, more preferably 7 days or more.

[0021] Furthermore, water is added to the homogenized starting product by adding water before, after, and / or simultaneously with homogenization in the previous step and mixing the water with the starting product. Alternatively or additionally, steam can also be introduced into the heat treatment device.

[0022] During the hydrothermal treatment of the homogenized starting product, the presence of H2O at least partially produces magnesium hydroxide (Mg(OH)2) and magnesium silicate hydrate (Mg3Si2O5(OH)4, Mg3Si4O 10 It is converted to (OH)2). The basic reaction here is as follows. Here, it is shown in a simplified form starting with forsterite (Mg2SiO4).

[0023] [ka]

[0024] Here, reaction equation (1) mainly occurs. This is also preferred in the present invention. This is because Mg3Si2O5(OH)4 is Mg3Si4O 10 This is because it is more suitable for bonding CO2 than (OH)2. Furthermore, it should be noted that the amount of each product and their ratios depend, in particular, on the exact composition of the starting products.

[0025] Magnesium hydroxide (Mg(OH)2) can exist as brucite (talc). Magnesium silicate hydrate (Mg3Si2O5(OH)4, Mg3Si4O 10 (OH)2) exists in forms such as lizardite, antigorite, and talc. It is noteworthy that the stoichiometric water content of antigorite can be lower than the 16% to 20% range that can be measured by testing (e.g., 13% by mass). This can be explained by the fact that some materials are so fine that water can adhere to the surface.

[0026] Similarly, such deviations from stoichiometry also apply to the ratio of Mg to Si. Furthermore, heteroions such as Fe may also be incorporated into the reaction products. However, other reaction products such as hydromagnesite, hematite, magnetite, and gibbsite may also be formed. This depends on the exact composition of the starting products in each case. All or part of the reaction products may contain iron, carbonates, alkalis, or other heteroions.

[0027] The converted starting product is at least partially dehydrated of bound water by heat treatment and / or reaction grinding. Bound water is also called crystal water. Bound water should be distinguished from unbound water, which can be considered as free H2O. Complete dehydration can be achieved at considerable expense. According to the present invention, the water content of bound water needs to be reduced by at least 60%, preferably at least 80%, and more preferably at least 90%.

[0028] In heat treatment, the converted starting product can be heated to temperatures between 180°C and 1000°C. Depending on the fineness of the starting product, heating for just a few minutes may be sufficient. Heating is preferably between 300°C and 800°C, and more preferably between 500°C and 700°C. Alternatively or additionally, the converted starting product can also be subjected to reactive grinding to rearrange its crystal structure. In so-called reactive grinding, crystal water can also be removed from the converted starting product by rearranging its crystal structure. For this purpose, auxiliary materials such as quartz can be added to the grinding process.

[0029] In this step, the magnesium hydroxide (Mg(OH)2) present in the converted starting product is converted at least partially to magnesium oxide (MgO), and the present magnesium silicate hydrate (Mg3Si2O5(OH)4, Mg3Si4O 10(OH)2) is converted to at least partially dehydrated magnesium silicate hydrate, which can be abbreviated as xMgO·SiO2·yH2O. Dehydration refers to the reduction of crystal water or water in the crystals within the converted starting product. The underlying chemical process here can be simplified again and expressed as follows:

[0030] [ka]

[0031] Here, reaction equation (4) produces a nearly amorphous reaction product with an Mg-to-Si ratio of 1.5:2 and a bound water content of approximately 3%. The reaction product formed by reaction equation (5) has an even lower Mg-to-Si ratio. Therefore, the variables a, b, c, x, y, and z also change. This depends on the exact composition of the starting products and the processing parameters in each case.

[0032] After dehydration, the water content of bound water in the converted and dehydrated starting product is preferably less than 10% by mass, more preferably less than 5% by mass, even more preferably less than 3.5% by mass, and particularly preferably less than 2.5% by mass.

[0033] Therefore, the converted and dehydrated starting products exist as multiphase products. Other possible secondary phases include hematite, magnetite, enstatite, feldspar, pyroxene, quartz, and amorphous phases.

[0034] Once the converted starting products are dehydrated, they come into contact with CO2. Here, CO2 reacts with present magnesium oxide (MgO), present dehydrated magnesium silicate hydrate (xMgO·SiO2·yH2O), and / or present magnesium hydroxide (Mg(OH)2). CO2 primarily binds to the resulting magnesium carbonate (MgCO3) and / or magnesium carbonate hydrate (MgCO3-mH2O). The underlying chemical processes can be expressed in a simplified and generalized way as follows:

[0035] [ka]

[0036] Here, m, n, p, q, x, and y represent corresponding variables. At least one of these can be 0. Also note that in reaction equation (7), the dehydrated magnesium silicate hydrate is only shown as xMgO·SiO2·yH2O because it is (incompletely) dehydrated. Reaction equation (8) shows forsterite (Mg2SiO4), which may still be present. At this point, forsterite from the starting products may still be present. Also note that xMgO·SiO2·yH2O is very similar to forsterite and can be considered, simply put, amorphous forsterite.

[0037] For example, if a starting product is provided that already contains at least 20% by mass, preferably at least 40% by mass, more preferably at least 60% by mass, and even more preferably at least 80% by mass of magnesium silicate hydrate, as in the case of serpentinite, the steps of adding water and hydrothermal treatment can be omitted. Serpentinite is a metamorphic rock formed by the natural transformation of ultramafic rocks, particularly by weathering.

[0038] According to the present invention, it has been recognized that by combining hydrothermal treatment with the removal of crystalline water from natural materials such as ultramafic rock, an intermediate material suitable for highly binding CO2 can be produced.

[0039] Examples of olivine-rich rocks that can be used in this invention include dunite, walelite, and hapsburgite. These rocks are often of low weathering degree. However, weathered rocks with similar chemical composition and high water content can also be used. Examples of weathered rocks include serpentinite.

[0040] In this way, a large amount of CO2 can be bound with a relatively small energy input. For example, using the method of the present invention, approximately 0.6 tons of CO2 can be bound to about 1 ton of forsterite in a few hours.

[0041] The hydrothermal treatment for converting the homogenized starting material to magnesium hydroxide and / or magnesium silicate hydrate is one of the longest method steps according to the present invention. Therefore, it is desirable to perform one or more treatments during the hydrothermal treatment to accelerate the reaction. For this purpose, various treatment methods are available, which can be performed individually or in combination with each other. These are described in detail below. All, but only partially, of the treatment methods described can be combined with each other.

[0042] One possibility is to continuously or discontinuously grind or decompose the homogenized starting product, especially to a very fine degree, during or between heat treatments within the heat treatment apparatus to facilitate the transformation.

[0043] Continuous or discontinuous grinding can prevent or reduce the aggregation or cohesiveness of materials present during hydrothermal treatment. This ensures a surface area large enough to carry out the above process. Several options are available for precise implementation.

[0044] On the other hand, it is possible to interrupt the hydrothermal treatment, remove the material from the heat treatment apparatus, crush or decompose it, for example, by crushing it, and then return it to the heat treatment apparatus.

[0045] On the other hand, it is also possible to provide a corresponding grinding system within the heat treatment apparatus that performs grinding continuously or discontinuously during hydrothermal treatment.

[0046] Another option is to operate the heat treatment apparatus continuously, discharging a portion of the material from the apparatus during hydrothermal treatment, grinding it, and returning it to the apparatus. This is particularly useful when the starting product is present in a suspension within the heat treatment apparatus, or at least in a form that can be pumped out. In this case, for example, a line can be provided leading from the autoclave to a grinding device such as a mill and back to the autoclave. This is an example of a heat treatment apparatus in the sense of the present invention. In this case, it can be described as an uninterrupted circulating process.

[0047] Another option is to add nucleating agents, pH-raising agents, heteroions, and / or other auxiliary materials to the starting product at the start of homogenization, before homogenization, during homogenization, immediately after homogenization, or in the heat treatment apparatus, in order to accelerate the reaction process.

[0048] For example, brucite, lizardite, antigorite, pre-hydrated olivine-containing rock, or mixtures of these materials can be added as nucleating agents. The amount of nucleating agent added is preferably at least 2% by mass.

[0049] Substances that release NaOH, KOH, NaCl, KCl, Na2SO4, MgSO4, K2SO4, Na2CO3, Ca(OH)2, and / or K2CO3 after addition can be added as pH-raising agents, thereby modifying the solution in which the reaction occurs, raising the pH value of the solution, and allowing the reaction to proceed more rapidly.

[0050] Other additives that can accelerate the reaction include, for example, magnesite, hydromagnesite, neskehonite, dolomite, SiO2, feldspar, pyroxene, and mixtures thereof. Adding these substances may lead to the formation of new reaction products. Examples of heteroionic compounds include aluminum, sulfates, and alkalis. These, too, may lead to the formation of new reaction products.

[0051] To increase the purity of the product obtained as a result of CO2 sequestration, these auxiliary materials can be removed again, at least partially, after the hydrothermal treatment is complete.

[0052] In principle, the reaction process can also be achieved by increasing the temperature. In particular, it can be carried out at a temperature of 150°C or higher, preferably 200°C or higher, and even more preferably 250°C or higher.

[0053] A further method to accelerate the reaction is to have the homogenized starting product present in a suspension for hydrothermal treatment within a heat treatment apparatus, and to continuously or discontinuously stir this suspension during the hydrothermal treatment. For example, a stirrer can be provided to ensure the movement of the suspension.

[0054] In this specification, alternative or additional grinding may be performed as described above. Wet grinding is particularly suitable in this case. This allows a portion of the suspension to be transferred from the heat treatment apparatus, wet-ground, and then returned to the heat treatment apparatus. However, wet grinding can also be performed directly within the heat treatment apparatus.

[0055] Another option is to sonicate the homogenized starting product. Similar to grinding, this separates substances formed on the starting product (such as magnesium hydroxide or magnesium silicate hydrate) from the remaining substances within the starting product, ensuring a sufficiently large surface area again to allow the reaction to proceed rapidly. Sonication can be performed using, for example, an ultrasonic horn.

[0056] Depending on further desired treatment and processing of the homogenized and transformed starting product, it may be useful to remove unbound water by drying before the dehydration step, i.e., separation of bound water. This is particularly useful when the hydrothermal treatment of the starting product is carried out in an aqueous suspension.

[0057] The dried starting product is then fed to a dehydration step. The heat treatment proposed for this purpose is also called annealing or firing. This can be carried out by means of a rotary furnace or a circulating fluidized bed of hot gas. When using a fluidized bed, dehydration takes place within a few seconds. Alternatively, the required energy can also be supplied electrically, for example in a muffler furnace. In this case, a time of about 5 to 10 minutes is required. In principle, an open system using, for example, a flame is preferred because it is easier to remove the generated water vapor and the reaction is accelerated.

[0058] In principle, the converted and dehydrated starting product forms a bond with CO2 simply by coming into contact with the CO2 present in the air. However, if the contact between the converted and dehydrated starting product and the CO2 in the aqueous suspension is carried out, for example, by blowing in a CO2-containing gas such as air, the bonding process can be enhanced and accelerated. It has been demonstrated that this method step enables CO2 to be bonded more rapidly than when treating with only normal ambient air without the presence of water.

[0059] The contact between the converted and dehydrated starting product and the CO2-containing gas can be carried out at a partial pressure of at least 200 ppm, 400 ppm, 1000 ppm, 10,000 ppm, 100,000 ppm, 200,000 ppm, particularly in the range of already indoor pressure (atmospheric pressure) or a maximum of 2 bar (corresponding to 2 million ppm). According to the invention, there is no need to apply high pressure to achieve rapid and sufficient bonding of CO2. However, the bonding of CO2 is further accelerated by a higher partial pressure.

[0060] The fineness of the starting product is 0.1 m in BET surface area 2To achieve a particle size of 1 / g or finer, it is preferable to grind the starting material, particularly through wet grinding. Even if the starting material is already partially very fine due to natural weathering, it is usually not possible to obtain a finer particle size. This fineness can be easily increased by grinding. Furthermore, wet grinding is preferred here because it is often more energy-efficient than dry grinding. Next, since the starting material is subjected to a hot water treatment in contact with water, the advantages of wet grinding can already be taken advantage of at this stage, especially since there is no need to dry the ground material.

[0061] The converted and dehydrated starting products can be used as a binder for concrete production before CO2 is bonded, for example, as a complete or partial substitute for cement. Here, the water / binder ratio is preferably in the range of 1:2 or less. This means a ratio of 1:2.22, preferably 1:2.5, ideally 1:2.86, and even more preferably 1:3.33 or less. It has been found that the higher the ratio, i.e. the higher the water ratio, the longer the hardening and the lower the strength. Concrete produced in this way has already bonded CO2 from the ambient air at room temperature. In principle, the bonding process can be further accelerated by heating or pressurizing treatment.

[0062] In another embodiment, the converted, dehydrated, and CO2-bound starting product can preferably be solidified and supplied as aggregate or filler for the manufacture of concrete and / or mortar. After CO2 binding, it can be dried again. However, this is not absolutely necessary, as a solid has already been formed from the converted and dehydrated starting product, or the strength of the hardened material is continuously increasing during CO2 binding.

[0063] The resulting material is inert and suitable for further processing into concrete with a hydraulic binder such as cement clinker. Further grinding may be necessary for this purpose. In principle, it is advantageous that the starting products of the method of this invention do not contain cement clinker. In particular, this means that the starting products contain little to no alite phase and / or belite phase (less than 0.1% by mass). Empirically, the materials contained in cement clinker are undesirable because they partially slow down the reaction described here. However, a small amount of cement clinker is acceptable.

[0064] If necessary, other substances can be added to improve reactivity or alter the properties of the hardened material. These substances include organic additives, particularly high-performance water-reducing agents, rock powders, especially limestone, dolomite, olivine, truss, glass powder, coal fly ash, and / or pozzolanic additives such as thermoactivated clay.

[0065] The starting products provided by the present invention are usually not pure substances and therefore contain a considerable amount of impurities. However, it is advantageous if the molar ratio of Mg to Ca is at least 10:1 and / or the molar ratio of Si to Al is also at least 10:1. It is known that the presence of calcium and aluminum relative to magnesium and silicon, respectively, slows down the reaction or, in some cases, completely stops it. Therefore, it is not important to significantly shift the corresponding molar ratios toward magnesium or silicon. Preferably, the molar ratio of Mg to Ca is at least 20:1 and / or the molar ratio of Si to Al is at least 20:1. [Examples]

[0066] The present invention will be described in more detail below with reference to the drawings, based on exemplary embodiments. Figure 1 is a graph showing the hydration process of the product produced by the method of the present invention, and Figure 2 is a graph showing the curve of CO2 concentration during CO2 binding in the product produced using the method of the present invention.

[0067] To verify the present invention, the tests described in detail below were carried out, in particular. In these tests, pure forsterite was used in the first test, and natural olivine was used in the second test.

[0068] Pure forsterite In the initial study, pure forsterite (Mg2SiO4) was produced by calcining a mixture of magnesium hydroxide carbonate and amorphous SiO2 in a laboratory furnace. After calcination, the starting product was pulverized using a vibrating disc mill. The specific surface area after BET treatment was 1 m². 2 It was / g.

[0069] Next, a mixture of forsterite and 1 mole of NaOH solution in a 1:2.2 ratio was prepared and treated in an autoclave at a temperature of 200°C. During this time, the reaction was interrupted, and the material was dried and pulverized. After a 4-week treatment period, X-ray phase analysis was used to examine the treated and washed material, and no forsterite was detected. The loss on ignition after autoclaving was 19.3% by mass.

[0070] 3.0 g of the dried and pulverized material was placed in a platinum crucible and calcined in a muffle furnace at temperatures of 450°C, 600°C, and 750°C for 1 hour, respectively. The ignition loss of the samples was 13.5% by mass (450°C), 2.8% by mass (600°C), and 0.52% by mass (750°C), respectively.

[0071] isolation This material was used to sequestrate CO2. For this purpose, 1 g of the sample, calcined at 600°C, was placed in a glass beaker with 50 g of water, and the suspension was continuously stirred. Simultaneously, gaseous CO2 (100% concentration) was introduced into the suspension. After 6 hours, the suspension was filtered and separated, and the solid was subjected to X-ray diffraction after drying.29 Analysis was performed using Si MAS NMR.

[0072] X-ray phase analysis revealed that Neskehonite (MgCO3·3H2O) was the only crystalline reaction product. 29 Si MAS NMR demonstrated that all silicon exists as amorphous SiO2. Therefore, the following reaction is demonstrated. Here, only the initial and final states are shown, and the intermediate steps are omitted.

[0073] [ka]

[0074] Therefore, carbon dioxide can be sequestered by using the method of the present invention.

[0075] Binder (binding agent) The reactivity of the materials before isolation as a binder was investigated by measuring the water binding after 7 days of hydration. For this purpose, materials calcined at different temperatures were ground by hand, mixed with water in a water-to-binder ratio of 0.50 (1:2), and stored in a sealed container at 22°C for 7 days. Subsequently, the hydration of the samples was stopped by drying at 60°C, and the loss on ignition was measured by thermal analysis. As a result, the ignition loss was 20.5% by mass (450°C), 25.3% by mass (600°C), and 7.1% by mass (750°C), respectively. Therefore, hydrated water and bound water are present in all three binders.

[0076] The hydration process of samples calcined at 600°C was analyzed by calorimetry (DCA) at 25°C. This process exhibited a very rapid reaction, with the main hydration stage reaching its peak after approximately 2 hours, and the reaction completing in less than 24 hours. As shown in Figure 1, a total heat of approximately 450 J / g was released.

[0077] As a result, the binder reacts faster than most conventional cements. 29Examination of hydrated and dried samples after DCA analysis using Si MAS NMR spectroscopy showed that all silicon was present as magnesium silicate hydrate.

[0078] Natural olivine In the following study, natural olivine collected from a source in Norway was used. Chemical analysis revealed the following composition of the natural olivine: SiO2 41.9% by mass, MgO 49.9% by mass, Fe2O 36.9% by mass, Al2O 30.6% by mass, CaO 0.1% by mass, and loss on ignition 0.5% by mass.

[0079] The material is 7300cm² in a ball mill. 2 The material was ground to a fineness of 1 / g bran and mixed with 1 molar NaOH solution in a 1:2 ratio. The material was processed in an autoclave at 200°C for 22 days, with one interruption during this time to grind the material further. After autoclaving, the intermediate product was dried, pulverized, and the loss on ignition was analyzed (16.3% by mass).

[0080] isolation Next, the sequestration of carbon dioxide was investigated. For this purpose, 10 g of an intermediate product calcined at 600°C was used. This intermediate product was heat-treated with triethanolamine in a disc vibrating mill at 700 revolutions per minute for 4 minutes, and then pulverized. The olivine pretreated according to the present invention was added to 1 liter of water and continuously stirred. Normal ambient air was blown into this suspension using a simple water tank pump. The CO2 concentration of the ambient air was approximately 400 ppm. In a sealed room, the CO2 concentration is usually somewhat higher, typically 500-600 ppm.

[0081] During the experiment, the CO2 concentration in the air rising from the suspension was measured. The concentration continuously and rapidly decreased throughout the experiment, reaching approximately 200 ppm. Over several days, carbon dioxide was successfully removed from the introduced air. Therefore, this material can react with CO2 in the air and permanently bind it in the form of magnesium carbonate. This result is shown in Figure 2.

[0082] Binder (binding agent) Individual batches of the intermediate product were calcined at different temperatures and hydrated at 22°C for 7 days to investigate water bonding. The ignition loss before hydration (6.8 mass% after 550°C, 3.1 mass% after 600°C, 2.2 mass% after 650°C, and 1.7 mass% after 700°C) was lower than that after reaction with water and drying at 60°C (20.1 mass% after 550°C, 23.7 mass% after 600°C, 24.7 mass% after 650°C, and 22.8 mass% after 700°C).

[0083] As a result, natural materials such as olivine can also be used in the manufacture of binders, and the aforementioned post-pretreatment hydration may be demonstrated.

[0084] Therefore, it has been demonstrated that CO2 can be efficiently bound using the method of the present invention. Furthermore, a binder for concrete production can be produced as a byproduct, which can also be used for CO2 sequestration.

Claims

1. a) A step of preparing a starting product containing at least 20% by mass of one or more of the following components, Ultramafic rocks, - Weathering products of ultramafic rocks, Olivine, Industrial waste, (Each has an MgO concentration of at least 10% by mass, and 0.1 m ２ (Having a fineness equivalent to a BET surface area of ​​1g or more) b) A step of homogenizing the starting product, c) The homogenized starting product is subjected to hydrothermal treatment at a temperature of 100°C or higher for at least 24 hours in a heat treatment apparatus; d) Adding water to the homogenized starting product by adding water immediately before, after, and / or simultaneously with the homogenization in step b), mixing the water with the starting product, and / or introducing steam into the heat treatment apparatus, wherein after step c), the starting product is H ２ At least partially magnesium hydroxide Mg(OH) in the presence of oxygen ２ and / or converted to magnesium silicate hydrate, e) A step of at least partially dehydrating the bound water from the converted starting product by heat treatment and / or reaction grinding, f) The converted and dehydrated starting product is converted to CO ２ A step of bringing into contact with CO ２ A method of isolating, In step e), during the heat treatment, the converted starting product is treated at a temperature of 180°C to 1000°C, and during the reaction grinding, a rearrangement of the crystal structure of the converted starting product occurs. After step e), the magnesium hydroxide present in the converted and dehydrated starting product is at least partially dehydrated to magnesium oxide, and the present magnesium silicate hydrate is at least partially dehydrated to dehydrated magnesium silicate hydrate. In step f), the CO ２ The magnesium oxide reacts with the dehydrated magnesium silicate hydrate and / or magnesium hydroxide, and the CO ２ CO is characterized by binding to the resulting magnesium carbonate and / or magnesium carbonate hydrate. ２ How to isolate it.

2. The method according to claim 1, wherein one or more treatments are performed to promote the reactions occurring during the hydrothermal treatment for at least a partial conversion of the starting product in step c).

3. The method according to claim 1 or 2, wherein the homogenized starting product is continuously or discontinuously pulverized during the hydrothermal treatment in the heat treatment apparatus in step c) to promote the transformation.

4. The method according to any one of claims 1 to 3, wherein a nucleating agent, a pH-raising agent, heteroions and / or auxiliary substances are added to the starting product in step a), b), c) and / or d).

5. The method according to claim 4, wherein after step c), the auxiliary substance is removed again, at least partially.

6. The method according to any one of claims 1 to 5, wherein, in order to hydrotherm the homogenized starting product in the heat treatment apparatus, the homogenized starting product is present in a suspension that is continuously and / or discontinuously stirred during the hydrothermal treatment.

7. The method according to any one of claims 1 to 6, wherein in step c), the homogenized starting product is subjected to ultrasonic treatment.

8. In step f), the contact between the converted and dehydrated starting product and the CO ２ is carried out in an aqueous suspension by blowing in a CO ２ -containing gas, according to the method according to any one of claims 1 to 7.

9. The converted and dehydrated starting product and the CO ２ The method according to any one of claims 1 to 8, wherein contact with a gas containing is performed at a partial pressure of at least 200 ppm.

10. The method according to any one of claims 1 to 9, wherein the converted starting product is dried before step e) to remove unbound water.

11. The aforementioned starting product contains 0.1 m ２ The method according to any one of claims 1 to 10, wherein the starting product is pulverized in order to give it a fineness equivalent to a BET surface area of ​​1 / g or more.

12. After step f), the CO2 is converted, dehydrated, and ２ The method according to any one of claims 1 to 11, wherein the combined starting products are solidified and supplied as aggregate or filler for the manufacture of concrete and / or mortar.

13. The method according to any one of claims 1 to 12, wherein, after step e), the converted and dehydrated starting product is used as a binder for the production of concrete, in which case the water:binder ratio is 1:2 or less.

14. The method according to any one of claims 1 to 13, wherein the starting product has a molar ratio of Mg to Ca of 10:1 or more, and / or a molar ratio of Si to Al of 10:1 or more.

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