A method for enhancing the mineralization of CO2 by forsterite

Abstract

The present invention relates to the fields of carbon sequestration and mineral utilization, and in particular to a method for enhancing the mineralization of CO2 by forsterite, comprising the following steps: pretreating forsterite with a strong acid to obtain pretreated forsterite and a magnesium-containing solution; activating the pretreated forsterite to obtain activated forsterite; heating the activated forsterite with ammonium sulfate to react to obtain magnesium sulfate and ammonia; and mixing the magnesium-containing solution, magnesium sulfate, ammonia, and a CO2-containing gas to obtain magnesium carbonate and ammonium sulfate. The present invention improves the reactivity of forsterite through pretreatment and activation, providing conditions for a high conversion rate in a subsequent solid-solid contact reaction, and solving the problems of high energy consumption and low solid-solid reaction conversion rate in conventional ammonium sulfate thermal decomposition.

Description

Technical Field

[0001] The present invention relates to the fields of carbon fixation and mineral utilization, and in particular to a method for enhancing the mineralization of CO2 by forsterite. Background Art

[0002] Climate change caused by greenhouse gas CO2 emissions is gradually impacting human survival and production. Geological storage of CO2 is considered a key strategy for reducing carbon emissions and advancing technology from demonstration to large-scale industrial scale. However, geological storage is highly location-dependent. Many countries lack suitable geological structures, or the distance from the storage site to the CO2 generation site can be thousands of kilometers, resulting in high pipeline construction costs.

[0003] CO2 mineralization is another potential option for long-term CO2 storage. Mineral carbonation (mineralization) refers to the process in which magnesium-rich minerals, such as olivine (Mg2SiO4), react with carbon dioxide to form stable mineral carbonates. This process simulates naturally occurring rock weathering and can form stable magnesium carbonates. Currently, one type of technology uses CO2-containing gas to directly contact olivine solids for mineralization, but the direct gas-solid reaction process is extremely slow and requires high temperature and high pressure conditions, and the utilization rate of magnesium is usually low. Another type uses an indirect mineralization process, that is, by introducing a strong acid (such as sulfuric acid) to dissolve the magnesium in the olivine (such as magnesium sulfate) into the solution, and then reacting with CO2 under alkaline conditions to form magnesium carbonate. This process enhances the reaction rates of the dissolution and mineralization processes by introducing acid and base, but the process will cause a large amount of acid and base consumption. Even if ammonium salt thermal decomposition is used to obtain acid and base recycling, the thermal decomposition process also consumes a lot of energy, which cannot be achieved for large-scale application and "carbon negativity".

[0004] In view of this, the present invention is proposed. Summary of the Invention

[0005] The purpose of the present invention is to provide a method for enhancing the mineralization of CO2 by forsterite. The present invention improves the reactivity of forsterite through pretreatment and activation, provides conditions for a high conversion rate of the subsequent solid-solid contact reaction, and solves the problems of high energy consumption and low solid-solid reaction conversion rate of traditional ammonium sulfate thermal decomposition.

[0006] The present invention provides a method for enhancing the mineralization of CO2 by forsterite, comprising the following steps:

[0007] S1. Pretreating forsterite with a strong acid to obtain pretreated forsterite and a magnesium-containing solution;

[0008] S2, activating the pretreated forsterite to obtain activated forsterite;

[0009] S3, heating the activated forsterite with ammonium sulfate to react to obtain magnesium sulfate and ammonia;

[0010] S4. Mixing the magnesium-containing solution, magnesium sulfate, ammonia and CO2-containing gas to obtain magnesium carbonate and ammonium sulfate.

[0011] In the method of strengthening forsterite mineralization of CO2 of the present invention, first, a strong acid is added to forsterite for pretreatment. On the one hand, the corrosiveness of the strong acid is used to increase the specific surface area of ​​forsterite, thereby increasing the contact area of ​​the reaction between ammonium sulfate solid and forsterite; on the other hand, forsterite is a discrete silicate, and its SiO4 4- The four sides and the metal ion Mg 2+ connection, during strong acid treatment, the Mg in the crystal structure 2+ Replaced by protons, therefore, strong acids can destroy the lattice of forsterite, thereby reducing its lattice energy and increasing its reactivity.

[0012] Then, the pretreated forsterite is activated to transform the less active serpentine mineral phase (Mg3Si2O5(OH)4) in the forsterite into the relatively more active olivine phase (Mg2SiO4) and clinoenstatite (MgSiO3). The chemical reactions involved are as follows:

[0013] Mg3Si2O5(OH)4→Mg2SiO4+MgSiO3+2H2O

[0014] The present invention further fully mixes the activated forsterite solid with ammonium sulfate solid and heats the mixture to react. The ammonium salt reacts directly with the forsterite solid to complete the extraction of magnesium and the regeneration of alkali in one step, and provides raw materials and an alkaline environment for the subsequent CO2 mineralization process. The reaction equation involved is as follows:

[0015] Mg2SiO4+2(NH4)2SO4→2MgSO4+SiO2+2H2O+4NH3↑

[0016] Finally, the magnesium-containing solution, magnesium sulfate, ammonia and CO2-containing gas are mixed to carry out a CO2 mineralization reaction. The generated ammonium sulfate is crystallized and separated to obtain ammonium sulfate solid, which can be further recycled. The reaction equation involved is as follows:

[0017] MgSO4+H2O+2NH3+CO2→MgCO3↓+(NH4)2SO4

[0018] Therefore, the present invention improves the reactivity of forsterite through pretreatment and activation, provides conditions for a high conversion rate of the subsequent solid-solid contact reaction, improves the extraction rate of magnesium, and the process is simple and easy to operate, solving the problems of high energy consumption and low solid-solid reaction conversion rate of traditional ammonium sulfate thermal decomposition.

[0019] As a preferred embodiment of the present technical solution, in step S1, the strong acid includes but is not limited to any one or more of sulfuric acid, nitric acid and hydrochloric acid. The selection of the strong acid needs to consider not only its ability to increase the specific surface area of ​​forsterite, destroy the crystal lattice of forsterite, and reduce the lattice energy, but also the effect of facilitating the separation of the final product ammonium sulfate from other ammonium salts.

[0020] As a preferred embodiment of the present technical solution, in step S1, the amount of the strong acid used is calculated based on a molar ratio of hydrogen ions in the strong acid to magnesium oxide in forsterite of 1:(25-40), and preferably 1:30.

[0021] The present invention does not impose strict restrictions on the mass fractions of strong acids such as sulfuric acid, hydrochloric acid and nitric acid. For example, the mass fraction of sulfuric acid can be 75-98%, the mass fraction of hydrochloric acid can be 15-35%, and the mass fraction of nitric acid can be 20-45%.

[0022] As a preferred embodiment of this technical solution, the specific surface area of ​​the pretreated forsterite should be no less than 2m 2 / g.

[0023] As a preferred embodiment of the present technical solution, in step S2, the activation specifically refers to heating the pretreated forsterite, and during heating, the pretreated forsterite can be heated to 200-500°C and maintained for 2-6 hours to transform the less active serpentine mineral phase (Mg3Si2O5(OH)4) in the forsterite into the relatively more active olivine phase (Mg2SiO4) and clinoenstatite (MgSiO3) mineral phase.

[0024] As a preferred embodiment of the present technical solution, in step S3, the activated forsterite and ammonium sulfate are fully mixed and then heated to react. During the reaction, water is used to absorb the ammonia generated by the reaction. After the reaction is completed, water is added to the mixed solid obtained by the reaction to dissolve the generated magnesium sulfate, and the mixed solid is washed and filtered to remove the iron and aluminum precipitates therein.

[0025] Since both the activated forsterite and ammonium sulfate are solid, in order to improve the reaction efficiency of the two, the activated forsterite and ammonium sulfate need to be fully mixed by grinding, stirring, screening, etc., but the present invention does not strictly limit the method for fully mixing the two.

[0026] As a preferred embodiment of the present technical solution, in step S3, during the heating reaction, the reaction temperature can be controlled to be 300-450°C, and the reaction time can be 2-6 hours. The present invention does not strictly limit the reaction conditions, so long as the activated forsterite and ammonium sulfate can fully react.

[0027] As a preferred embodiment of the present technical solution, in step S3, the mass ratio of the activated forsterite to ammonium sulfate is preferably 1:(3-6), and the amount of ammonium sulfate is excessive relative to the activated forsterite, thereby improving the extraction rate of magnesium.

[0028] As a preferred embodiment of the present technical solution, in step S4, the magnesium-containing solution, magnesium sulfate solution and ammonia solution are mixed, and the pH value of the mixed solution is controlled to be 8-9. Studies have shown that the mineralization reaction of magnesium sulfate can be promoted under alkaline conditions.

[0029] As a preferred embodiment of the present technical solution, in step S4, the volume fraction of CO2 in the CO2-containing gas is 10-90%. The present invention does not strictly limit it. When used, the gas flow rate can be adjusted according to the volume fraction of CO2 to control the progress of the mineralization reaction.

[0030] As a preferred embodiment of the present technical solution, in step S4, the ammonium sulfate solution obtained by the reaction is crystallized to obtain ammonium sulfate solid, which is reused.

[0031] For example, when the strong acid used is sulfuric acid, the mineralization reaction produces magnesium carbonate precipitate and ammonium sulfate solution. The ammonium sulfate solution is evaporated and crystallized to obtain ammonium sulfate solid, which is repeatedly used for solid-solid reaction with activated forsterite.

[0032] When the strong acid used is hydrochloric acid, the mineralization reaction produces magnesium carbonate precipitate, ammonium sulfate solution and ammonium chloride solution. At this time, the difference in solubility of ammonium sulfate and ammonium chloride can be utilized to separate ammonium sulfate and ammonium chloride through repeated evaporation and dissolution processes. The obtained ammonium sulfate solid can be repeatedly used for solid-solid reaction with activated forsterite.

[0033] When the strong acid used is nitric acid, the mineralization reaction produces magnesium carbonate precipitate, ammonium sulfate solution and ammonium nitrate solution. Similarly, the difference in solubility of ammonium sulfate and ammonium nitrate can be utilized to separate ammonium sulfate from ammonium nitrate, and the obtained ammonium sulfate solid can be reused for the solid-solid reaction with activated forsterite.

[0034] The method of enhancing the CO2 mineralization of forsterite of the present invention has at least the following beneficial effects:

[0035] In the method of the present invention, a crystal-modified and activated forsterite is obtained through strong acid pretreatment and activation. The activated forsterite is then thoroughly mixed and heated with solid ammonium sulfate, completing the extraction of magnesium and the regeneration of the alkali in one step. This not only integrates the exothermic process of magnesium leaching and the endothermic process of ammonium sulfate decomposition, achieving comprehensive energy utilization, but also allows the ammonium sulfate to be regenerated and recycled through the subsequent CO2 mineralization process. Therefore, the present invention improves the reactivity of forsterite through pretreatment and activation, providing conditions for a high conversion rate in the subsequent solid-solid contact reaction, and solving the problems of high energy consumption and low solid-solid reaction conversion rate in traditional ammonium sulfate thermal decomposition. BRIEF DESCRIPTION OF THE DRAWINGS

[0036] In order to more clearly illustrate the specific embodiments of the present invention or the technical solutions in the prior art, the following briefly introduces the drawings required for use in the specific embodiments or the description of the prior art. Obviously, the drawings described below are some embodiments of the present invention. For ordinary technicians in this field, other drawings can be obtained based on these drawings without paying any creative work.

[0037] Figure 1 is the XRD pattern of forsterite of the present invention;

[0038] Figure 2 The forsterite of the present invention is shown in SEM images before and after pretreatment;

[0039] Figure 3 The XRD patterns of forsterite before and after activation of the present invention are shown in FIG.

[0040] Figure 4 It is a comparison diagram before and after the solid-solid reaction of the present invention. DETAILED DESCRIPTION

[0041] It should be noted that the following detailed descriptions are illustrative and intended to provide further explanation of the present application. Unless otherwise specified, all technical and scientific terms used herein have the same meaning as commonly understood by those skilled in the art to which the present application belongs.

[0042] It should be noted that the terms used herein are only for describing specific embodiments and are not intended to limit the exemplary embodiments according to the present application. As used herein, unless the context clearly indicates otherwise, the singular also includes the plural. In addition, it should be understood that when the terms "comprise" and / or "include" are used in this specification, they indicate the presence of features, steps, operations, devices, components and / or combinations thereof.

[0043] The following will clearly and completely describe the technical solutions of the present invention in conjunction with the embodiments. Obviously, the embodiments described are only some embodiments of the present invention, not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without making creative efforts are within the scope of protection of the present invention.

[0044] Example 1

[0045] The main composition of the forsterite selected in this embodiment is as follows: 32.71% magnesium oxide, 51.88% silicon dioxide, 10.62% iron oxide, and 2.67% calcium oxide.

[0046] S1. 100 g of the 200-mesh forsterite was added to 157 ml of a sulfuric acid solution having a mass fraction of 85% (the molar ratio of hydrogen ions in the strong acid to magnesium oxide in the forsterite was 1:30), stirred for 30 minutes, and filtered and dried to obtain 99.4 g of pretreated forsterite;

[0047] S2, heating the pretreated forsterite to 250°C for activation and maintaining the temperature for 2 hours;

[0048] S3, the activated forsterite and 324g ammonium sulfate (the mass ratio of forsterite to ammonium sulfate solid is 1:3.3) are mixed uniformly by grinding, heated to 380 ° C, maintained for 4h, the generated ammonia is absorbed by 1 liter of water, 1 liter of water is added to the mixed solid after the reaction, the generated magnesium sulfate is dissolved into magnesium sulfate solution, the iron and aluminum precipitates in the mixed solution are washed and filtered to remove, and the extraction rate of magnesium in the forsterite is calculated to be 89.2% according to the content of magnesium in the determination solution;

[0049] S4, after mixing the magnesium-containing liquid, magnesium sulfate solution and part of the ammonia solution, controlling the pH of the solution to 8.5, passing CO2 gas containing 20% ​​by volume of CO2 to carry out a mineralization reaction to obtain 61.2g of magnesium carbonate precipitate and ammonium sulfate solution;

[0050] S5. After evaporation and crystallization, the ammonium sulfate solution is reused for mixing with forsterite.

[0051] Figure 1 The XRD pattern of forsterite shows that the main mineral phases of natural forsterite are olivine (Mg2SiO4), serpentine and talc;

[0052] Figure 2 The SEM images before and after strong acid treatment in this example show that after acid treatment, forsterite has a porous structure. The specific surface area of ​​forsterite is 2.64 m 2 / g;

[0053] Figure 3 The XRD diagram of the crystal form change of forsterite before and after activation in this example shows that the serpentine mineral phase in forsterite decreases, while the olivine phase (Mg2SiO4) and clinoenstatite (MgSiO3) mineral phases increase;

[0054] Figure 4 This is a comparison diagram before and after the solid-solid reaction of the present invention. The color of the reactant is significantly different from the color of the product, indicating that forsterite solid and ammonium sulfate solid can directly react to generate magnesium sulfate solid.

[0055] Example 2

[0056] This embodiment uses the forsterite in Example 1 as the raw material, and the operation and process are basically the same as those in Example 1, except that this embodiment uses hydrochloric acid as the strong acid pretreatment agent.

[0057] S1. 100 g of the 200-mesh forsterite was added to 497 ml of a 20% hydrochloric acid solution (the molar ratio of hydrogen ions in the strong acid to magnesium oxide in the forsterite was 1:30), stirred for 30 minutes, filtered and dried to obtain 99.3 g of pretreated forsterite. The specific surface area of ​​the pretreated forsterite was measured to be 2.74 m 2 / g;

[0058] S2, heating the pretreated forsterite to 250° C. for activation and maintaining the temperature for 2 h;

[0059] S3, the activated forsterite and 323g ammonium sulfate (the mass ratio of forsterite to ammonium sulfate solid is 1:3.3) are mixed uniformly by grinding, heated to 380 ° C, maintained for 4h, the generated ammonia is absorbed by 1 liter of water, 1 liter of water is added to the mixed solid after the reaction, the generated magnesium sulfate is dissolved into magnesium sulfate solution, the iron and aluminum precipitates in the mixed solution are washed and filtered to remove, and the extraction rate of magnesium in the forsterite is calculated according to the content of magnesium in the determination solution, and is 90.7%;

[0060] S4, after mixing the magnesium-containing solution, the magnesium sulfate solution and part of the ammonia solution, the pH of the solution was controlled to 8.5, and a CO2 gas containing 30% CO2 by volume was introduced to carry out a mineralization reaction to obtain 62.3g of magnesium carbonate precipitate and ammonium sulfate and ammonium chloride solutions;

[0061] S5. By utilizing the difference in solubility of ammonium sulfate and ammonium chloride, ammonium sulfate and ammonium chloride are separated through repeated evaporation and dissolution processes. The obtained ammonium sulfate can be reused for mixing with forsterite.

[0062] Example 3

[0063] This embodiment uses the forsterite in Example 1 as the raw material, and the operation and process are basically the same as Example 1, except that this embodiment uses nitric acid as the strong acid pretreatment agent.

[0064] S1. 100 g of the 200-mesh forsterite was added to 430 ml of a 30% nitric acid solution (the molar ratio of hydrogen ions in the strong acid to magnesium oxide in the forsterite was 1:40), stirred for 30 minutes, filtered and dried to obtain 99.6 g of pretreated forsterite. The specific surface area of ​​the pretreated forsterite was measured to be 2.53 m 2 / g;

[0065] S2, heating the pretreated forsterite to 500° C. for activation and maintaining the temperature for 2 h;

[0066] S3, the activated forsterite and 295g ammonium sulfate (the mass ratio of forsterite to ammonium sulfate solid is 1:3) are mixed uniformly by grinding, heated to 450 ° C, maintained for 2h, the generated ammonia is absorbed by 1 liter of water, 1 liter of water is added to the mixed solid after the reaction, the generated magnesium sulfate is dissolved into magnesium sulfate solution, the iron and aluminum precipitates in the mixed solution are washed and filtered to remove, and the magnesium extraction rate in the forsterite is calculated according to the content of magnesium in the determination solution, which is 86.3%;

[0067] S4, after mixing the magnesium-containing solution, the magnesium sulfate solution and part of the ammonia solution, the pH of the solution was controlled to 9, and a CO2 gas containing 50% by volume of CO2 was introduced to carry out a mineralization reaction to obtain 59.2g of magnesium carbonate precipitate and ammonium sulfate and ammonium nitrate solutions;

[0068] S5. By utilizing the difference in solubility of ammonium sulfate and ammonium nitrate, ammonium sulfate and ammonium nitrate are separated through repeated evaporation and dissolution processes. The obtained ammonium sulfate can be reused for mixing with forsterite.

[0069] Example 4

[0070] This embodiment uses the forsterite in Example 1 as the raw material, and the operation and process are basically the same as those in Example 1, except that the reaction conditions in each step are different.

[0071] S1. 100 g of the 200-mesh forsterite was added to 398 ml of a 30% hydrochloric acid solution (the molar ratio of hydrogen ions in the strong acid to magnesium oxide in the forsterite was 1:25), stirred for 60 minutes, filtered and dried to obtain 99.3 g of pretreated forsterite. The specific surface area of ​​the pretreated forsterite was measured to be 2.67 m 2 / g;

[0072] S2, heating the pretreated forsterite to 200° C. for activation and maintaining the temperature for 6 hours;

[0073] S3, the activated forsterite and 588g ammonium sulfate (the mass ratio of forsterite to ammonium sulfate solid is 1:6) are uniformly mixed by grinding, heated to 300 ° C, maintained for 6h, the generated ammonia is absorbed by 1 liter of water, 1 liter of water is added to the mixed solid after the reaction, the generated magnesium sulfate is dissolved into magnesium sulfate solution, the iron and aluminum precipitates in the mixed solution are washed and filtered to remove, and the extraction rate of magnesium in the forsterite is calculated according to the content of magnesium in the determination solution, and the magnesium content is 93.8%;

[0074] S4, after mixing the magnesium-containing solution, the magnesium sulfate solution and part of the ammonia solution, the pH of the solution was controlled to 8, and a CO2-containing gas with a CO2 volume fraction of 85% was introduced to carry out a mineralization reaction to obtain 64.4g of magnesium carbonate precipitate and ammonium sulfate and ammonium chloride solutions;

[0075] S5. By utilizing the difference in solubility of ammonium sulfate and ammonium chloride, ammonium sulfate and ammonium chloride are separated through repeated evaporation and dissolution processes. The obtained ammonium sulfate can be reused for mixing with forsterite.

[0076] Comparative Example 1

[0077] This comparative example uses the forsterite in Example 1 as a raw material, and the operation and process are basically the same as those in Example 1, except that this comparative example does not perform strong acid pretreatment.

[0078] S1. The specific surface area of ​​200-mesh forsterite was measured to be 1.62 m 2 / g;

[0079] S2. 100 g of the 200-mesh forsterite was heated to 250° C. for activation and maintained at this temperature for 2 h.

[0080] S3, the activated forsterite and 330g ammonium sulfate (the mass ratio of forsterite to ammonium sulfate solid is 1:3.3) are mixed uniformly by grinding, heated to 380 ° C, maintained for 4h, the generated ammonia is absorbed by 1 liter of water, 1 liter of water is added to the mixed solid after the reaction, the generated magnesium sulfate is dissolved into magnesium sulfate solution, the iron and aluminum precipitates in the mixed solution are washed and filtered to remove, and the extraction rate of magnesium in the forsterite is calculated according to the content of magnesium in the determination solution, which is 57.2%;

[0081] S4, after mixing the magnesium-containing solution, the magnesium sulfate solution and part of the ammonia solution, the pH of the solution was controlled to 8.5, and a CO2 gas containing 20% ​​by volume of CO2 was introduced to carry out a mineralization reaction to obtain 39.3 g of magnesium carbonate precipitate and ammonium sulfate solution;

[0082] S4. The ammonium sulfate solution is evaporated and crystallized and then reused for mixing with forsterite.

[0083] The results show that since the olivine in this comparative example was not surface treated, its specific area was lower than that of the forsterite after surface treatment, and the solid-solid reaction contact area was reduced, resulting in a lower magnesium extraction rate.

[0084] Comparative Example 2

[0085] This comparative example uses the forsterite in Example 1 as a raw material, and the operation and process are basically the same as those in Example 1, except that no activation treatment is performed in this comparative example.

[0086] S1. 100 g of 200-mesh forsterite was added to 157 ml of 85% sulfuric acid solution (the molar ratio of hydrogen ions in the strong acid to magnesium oxide in the forsterite was 1:30), stirred for 30 minutes, filtered and dried, and 99.3 g of surface-treated forsterite was obtained. The specific surface area of ​​the forsterite was measured to be 2.68 m 2 / g;

[0087] S2, the pretreated forsterite and 327.7g ammonium sulfate (the mass ratio of forsterite to ammonium sulfate solid is 1:3.3) are uniformly mixed by grinding, heated to 380 ° C, maintained for 4h, the generated ammonia is absorbed by 1 liter of water, 1 liter of water is added to the mixed solid after the reaction, the generated magnesium sulfate is dissolved into magnesium sulfate solution, washed and filtered to remove the iron and aluminum precipitates in the mixed solution, and the extraction rate of magnesium in the forsterite is calculated according to the content of magnesium in the determination solution, which is 71.6%;

[0088] S3, after mixing the magnesium-containing solution, the magnesium sulfate solution and part of the ammonia solution, the pH of the solution was controlled to 8.5, and a CO2 gas containing 20% ​​by volume of CO2 was introduced to carry out a mineralization reaction to obtain 49.2g of magnesium carbonate precipitate and ammonium sulfate solution;

[0089] S4. After evaporation and crystallization, the ammonium sulfate solution is reused for mixing with forsterite.

[0090] The results showed that since the olivine was not activated in this comparative example, the serpentine phase in the forsterite did not change, and the reaction activity was low, resulting in a reduced magnesium extraction rate.

[0091] Comparative Example 3

[0092] This comparative example uses the forsterite in Example 1 as a raw material, and the operation and process are basically the same as those in Example 1, except that this comparative example does not undergo pretreatment and activation treatment.

[0093] S1. 100 g of 200-mesh forsterite and 330 g of ammonium sulfate (the mass ratio of forsterite to ammonium sulfate solid is 1:3.3) were mixed uniformly by grinding, heated to 380° C., maintained for 4 h, and the generated ammonia was absorbed by 1 liter of water. 1 liter of water was added to the mixed solid after the reaction to dissolve the generated magnesium sulfate into a magnesium sulfate solution, and the iron and aluminum precipitates in the mixed solution were washed and filtered to remove the iron and aluminum precipitates. The magnesium extraction rate in the forsterite was calculated to be 41.8% based on the magnesium content in the determination solution;

[0094] S2, after mixing the magnesium-containing solution, the magnesium sulfate solution and part of the ammonia solution, the pH of the solution was controlled to 8.5, and a CO2 gas containing 20% ​​by volume of CO2 was introduced to carry out a mineralization reaction to obtain 28.7g of magnesium carbonate precipitate and ammonium sulfate solution;

[0095] S3. After evaporation and crystallization, the ammonium sulfate solution is reused for mixing with forsterite.

[0096] The results showed that due to the lack of pretreatment and activation of olivine, the solid-solid contact area was small, the serpentine phase in forsterite did not change, and the reaction activity was low, resulting in a very low magnesium extraction rate.

[0097] Table 1 shows the extraction rates of magnesium from forsterite in Examples 1-3 and Comparative Examples 1-3.

[0098] Table 1

[0099]

[0100]

[0101] In summary, the present invention can obtain forsterite after crystal form change and activation through strong acid pretreatment and activation means, and the activated forsterite is fully mixed and heated with ammonium sulfate solid, and the extraction of magnesium and the regeneration of alkali are completed in one step, which not only integrates the exothermic process of magnesium leaching and the endothermic process of ammonium sulfate decomposition, realizes the comprehensive utilization of energy, but also can regenerate the ammonium sulfate through the subsequent CO2 mineralization process. Therefore, the present invention improves the reactivity of forsterite through pretreatment and activation, provides conditions for the high conversion rate of the subsequent solid-solid contact reaction, improves the extraction rate of magnesium, and the process is simple and easy to operate, solving the problems of high energy consumption and low solid-solid reaction conversion rate of traditional ammonium sulfate thermal decomposition.

[0102] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention, rather than to limit it. Although the present invention has been described in detail with reference to the above embodiments, those skilled in the art should understand that they can still modify the technical solutions described in the above embodiments, or replace some or all of the technical features therein with equivalents. However, these modifications or replacements do not cause the essence of the corresponding technical solutions to deviate from the scope of the technical solutions of the embodiments of the present invention.

Claims

1. A method for enhancing the mineralization of CO2 by forsterite, characterized in that: The following steps are involved: S1. Pretreating forsterite with a strong acid to obtain pretreated forsterite and a magnesium-containing solution; S2, activating the pretreated forsterite to obtain activated forsterite; S3, heating the activated forsterite with ammonium sulfate to react to obtain magnesium sulfate and ammonia; S4, mixing the magnesium-containing solution, the magnesium sulfate solution, and part of the ammonia solution with the CO2-containing gas to obtain magnesium carbonate and ammonium sulfate; In step S2, the pretreated forsterite is activated to transform the less active serpentine mineral phase (Mg3Si2O5(OH)4) in the forsterite into the relatively more active olivine phase (Mg2SiO4) and clinoenstatite (MgSiO3) mineral phase. During the activation, the pretreated forsterite is heated to 200-500°C and maintained for 2-6h; In step S3, the activated forsterite and ammonium sulfate are fully mixed and heated to react. After the reaction is completed, water is added to the mixed solid obtained by the reaction, and the mixture is dissolved, washed and filtered in sequence; In step S3, during the heating reaction, the temperature is controlled to be 300-450° C. and the time is 2-6 hours.

2. The method for enhancing forsterite mineralization of CO2 according to claim 1, characterized in that: In step S1, the strong acid includes any one or more of sulfuric acid, nitric acid and hydrochloric acid.

3. The method for enhancing forsterite mineralization of CO2 according to claim 1, characterized in that: In step S1, the amount of the strong acid used is calculated based on a molar ratio of hydrogen ions in the strong acid to magnesium oxide in forsterite of 1:(25-40).

4. The method for enhancing forsterite mineralization of CO2 according to claim 1, characterized in that: In step S3, the mass ratio of activated forsterite to ammonium sulfate is 1:(3-6).

5. The method for enhancing forsterite mineralization of CO2 according to claim 1, characterized in that: In step S4, the magnesium-containing solution, the magnesium sulfate solution and part of the ammonia solution are mixed, and the pH value of the mixed solution is controlled to be 8-9.

6. The method for enhancing forsterite mineralization of CO2 according to claim 1, characterized in that: In step S4, the volume fraction of CO2 in the CO2-containing gas is 10-90%.

7. The method for enhancing forsterite mineralization of CO2 according to claim 1, characterized in that: In step S4, the ammonium sulfate solution obtained by the reaction is crystallized to obtain ammonium sulfate solid, which is reused.

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