Sand processing method and system for concrete applications

Abstract

The sand aggregate (180) includes a plurality of aggregate grains (182), at least one of which includes desert sand grains (120) that are too small for use in concrete applications, carbonate particles (150) distributed on the outer surfaces (122) of the desert sand grains (120), and a sand-based adhesive (170) that clumps the desert sand grains (120) together. The at least one aggregate grain (182) has a size comparable to that of river sand grains, while the desert sand grains (120) have a smaller size than the river sand grains, making the at least one aggregate grain (182) suitable for concrete applications.

Description

[Technical Field]

[0001] CROSS-REFERENCE TO RELATED APPLICATIONS This application claims priority to U.S. Provisional Patent Application No. 63 / 412,650, filed October 3, 2022, entitled "DESERT SAND TREATMENT FOR ITS UTILIZATION IN CONCRETE MANUFACTURING," the disclosure of which is incorporated herein by reference in its entirety.

[0002] Embodiments of the subject matter disclosed herein generally relate to systems and methods for converting sand that is not suitable for concrete applications (non-compliant sand) into an aggregate (composition) that is suitable for concrete applications, and more particularly, to systems and methods for changing the shape and / or size of the non-compliant sand so that it becomes suitable. [Background technology]

[0003] Concrete is an important building material widely used by modern civilization, but its production requires large amounts of natural resources, particularly sand and cement. Furthermore, the process of producing cement is highly energy-intensive and generates large amounts of carbon dioxide (CO2). In the face of growing concerns about climate change, particularly due to CO2 emissions, carbon dioxide capture and storage (CCS) has emerged as a strategy to curb greenhouse gas emissions and mitigate the adverse effects of global warming. As human activities continue to release excess CO2 into the atmosphere, finding effective and sustainable ways to capture and store this CO2 has become a pressing issue.

[0004] Various research groups have attempted to solve each of these problems individually. For example, with regard to the concrete problem, traditional concrete production relies on riverbed and coastal sand (referred to herein as "river sand"), leading to concerns about environmental degradation and resource depletion. One potential solution lies in transforming desert sand or other fine sands, which are abundant but currently unsuitable for concrete production, into a valuable construction resource. In this regard, desert sand is a largely untapped resource covering vast swathes of the Earth's surface. Unlike the river sand used in traditional concrete production, desert sand is readily available in regions with arid climates. Because traditional sand mining can lead to erosion, habitat destruction, and the destruction of local ecosystems, utilizing desert sand in concrete production can contribute to sustainable resource management. By transitioning to desert sand or other fine sands, these concerns can be alleviated, allowing natural river and coastal environments to recover and thrive. Such a transition would promote responsible land use and contribute to the preservation of valuable ecosystems.

[0005] Researchers and engineers are constantly exploring innovative ways to refine desert sand for concrete production. Advanced processing techniques, such as selective sifting, washing, and classification, can modify the properties of desert sand to meet the requirements of concrete production. These technological advances offer the potential to convert desert sand into a valuable construction resource while maintaining the integrity and durability of concrete structures. However, none of these methods are currently economically and industrially viable for achieving this goal.

[0006] With regard to mitigating climate change, because excess CO2 emissions are a key driver of global warming, leading to rising temperatures, melting ice caps, rising sea levels, and more frequent extreme weather events, capturing and storing CO2 from industrial processes and power generation could prevent a significant portion of these emissions from entering the atmosphere, thereby slowing the pace of climate change. In this regard, various geological formations, such as depleted oil and gas reservoirs and deep saline aquifers, offer potential sites for safe and secure CO2 storage. Ongoing research and innovation, including monitoring and verification techniques to ensure the long-term effectiveness and safety of stored CO2, are driving advances in CCS technology. Summary of the Invention [Problem to be solved by the invention]

[0007] Each of the above—the use of desert and other fine sands for the production of concrete and the storage of CO2 emissions—faces its own challenges. Therefore, to overcome these challenges together, new strategies are needed to address both issues simultaneously in an integrated system that can make concrete components (e.g., sand) more readily available without damaging the environment and simultaneously act as a CO2 storage agent. [Means for solving the problem]

[0008] According to one embodiment, there is a sand aggregate comprising a plurality of aggregate particles, at least one of which comprises a desert sand particle that is too small for use in concrete applications, carbonate particles distributed on an outer surface of the desert sand particle, and a sand-based adhesive that clumps the desert sand particle together, wherein the at least one aggregate particle has a size comparable to that of river sand particles, while the desert sand particle has a size smaller than that of the river sand particle, such that the at least one aggregate particle is suitable for concrete applications.

[0009] According to another embodiment, there is a method of converting desert sand grains into suitable sand for concrete applications, the method including the steps of providing desert sand grains; treating the desert sand grains with a carbon dioxide sequestering agent to produce enhanced sand grains; carbonating the enhanced sand grains to produce carbonate enhanced sand grains while storing carbon dioxide on the exterior surfaces of the carbonate enhanced sand grains; and agglomerating the carbonate enhanced sand grains to form a sand aggregate having a size similar to that of river sand grains, the sand being suitable for concrete applications.

[0010] According to yet another embodiment, there is a plant for converting desert sand grains into suitable sand for concrete applications, the plant including: a first mixer configured to receive and mix the desert sand grains and a CO2 capture agent to form enhanced sand grains; an absorption chamber configured to receive and mix the enhanced sand grains with a CO2 stream and a water stream to form carbonate enhanced sand grains; a second mixer configured to mix the fine desert sand grains with a base stream to form a sand-based adhesive; and a third mixer connected to the absorption chamber and the second mixer, configured to receive the carbonate enhanced sand grains and the sand-based adhesive and mix the carbonate enhanced sand grains with the sand-based adhesive to form sand aggregate. The desert sand grains are incompatible with concrete applications, while the sand aggregate is suitable for concrete applications. [Brief explanation of the drawings]

[0011] For a more complete understanding of the present invention, reference is now made to the following descriptions taken in conjunction with the accompanying drawings, in which: [Figure 1A] FIG. 1 is a schematic diagram of river sand grains with good size and coarseness for concrete applications. [Figure 1B] 1 is a schematic diagram of desert sand grains that are smooth and too small for concrete applications. [Figure 2] FIG. 1 is a diagram showing the length, width, and thickness of a sand grain. [Figure 3A] FIG. 1 illustrates various parameters associated with the shape and size of sand grains. [Figure 3B] FIG. 1 illustrates various parameters associated with the shape and size of sand grains. [Figure 3C] FIG. 1 illustrates various parameters associated with the shape and size of sand grains. [Figure 3D] FIG. 1 illustrates various parameters associated with the shape and size of sand grains. [Figure 4] 1 is a flow chart of a method for converting non-conforming desert sand grains into aggregate suitable for concrete applications. [Figure 5] FIG. 1 shows the conversion of desert sand grains into reinforced sand grains by the addition of a CO2 sequestering agent. [Figure 6] FIG. 1 is a diagram of a plant used to convert non-conforming desert sand grains into aggregate suitable for concrete applications. [Figure 7] FIG. 6 illustrates the conversion of the enhanced sand grains of FIG. 5 to carbonate enhanced sand grains and the conversion of the scavenger to carbonate compounds by the addition of CO2. [Figure 8] FIG. 5 is a diagram schematically illustrating aggregate obtained based on the process shown in FIG. 4. [Figure 9] FIG. 1 illustrates the parameters of various experiments conducted to convert desert sand grains into aggregate suitable for concrete applications. [Figure 10] FIG. 1 shows some measurements of aggregate and raw desert sand grains. [Figure 11] 10A and 10B show other measurements of aggregates formed under different conditions. [Figure 12] FIG. 5 shows the results of thermogravimetric analysis for different desert sand grain samples treated with the method of FIG. 4. DETAILED DESCRIPTION OF THE INVENTION

[0012] The following description of the embodiments refers to the accompanying drawings. The same reference numbers in different drawings identify the same or similar elements. The following detailed description is not intended to limit the invention. Instead, the scope of the invention is defined by the appended claims. For simplicity, the following embodiments are described with reference to desert sand, which is typically unsuitable for concrete applications. However, the embodiments discussed next are not limited to desert sand and may be applied to other types of sand that are unsuitable for concrete applications.

[0013] References throughout this specification to "one embodiment" or "an embodiment" mean that a particular feature, structure, or characteristic described in connection with an embodiment is included in at least one embodiment of the disclosed subject matter. Thus, the appearances of the phrase "in one embodiment" or "in an embodiment" in various places throughout this specification are not necessarily all referring to the same embodiment. Furthermore, particular features, structures, or characteristics may be combined in any suitable manner in one or more embodiments.

[0014] According to one embodiment, a method and system are introduced for storing CO2 on the surface of desert sand to make it suitable for concrete applications. This method can simultaneously store CO2 in the desert sand grains and agglomerate these grains, increasing the size and / or surface roughness of the desert sand to make it suitable for concrete applications. Various materials may be used to treat the sand with the intent of producing aggregates with increased size sufficient to be suitable components of concrete and to interact with ambient or supplied CO2 to store them. In one application, portions of the unsuitable sand are etched to form a sand-based adhesive that is used within the aggregate to "glue" multiple sand grains together. Details of the process and system for producing such suitable sand that stores CO2 will now be described with reference to the figures.

[0015] Fine aggregate (sand), coarse aggregate (gravel), and hydraulic binder (cement) are the primary raw materials used in the production of concrete and mortar, which, when combined with water, produce the highly popular building materials. Of these three raw materials, aggregates (sand and gravel) constitute the largest percentage of primary material inputs and are the most extracted material group worldwide. Sand is not homogeneous and can be classified by shape, with shapes and characteristics ranging from ellipsoidal and angular to nearly spherical and smooth. Medium to coarse sands with rough surfaces and sharp edges, such as riverbank sand or beach sand grains, are preferred for creating concrete. On the other hand, desert sand and other fine sands, classified as nearly ellipsoidal, spherical, and smooth, are considered unsuitable for use in concrete and cement or for filling new land at sea.

[0016] Desert sands such as yellow sand, dune sand, Qatar desert sand, Arabian desert sand, Gobi desert sand, red desert sand, or black desert sand are siliceous in nature but contain other impurities (i.e., iron oxide, iron silicate, mixed silicon-iron oxide, etc.) and may have a coarseness ratio of less than 2.1. The coarseness ratio is calculated based on sieve analysis of the aggregate. In sieve analysis, a series of standard sieves with various mesh sizes are used to separate the aggregate into different size fractions. The retained weight of the material on each sieve is determined, and then the coarseness ratio is calculated using the following formula:

[0017] Fractional fraction of fine particles (FM) = (cumulative % total retained on standard sieves) / 100

[0018] The coarseness index value is a single number that represents the average size of aggregate particles. Higher coarseness index values ​​indicate coarser aggregates, while lower values ​​indicate finer aggregates. Typical ranges of coarseness index values ​​for fine aggregates used in concrete are between 2.2 and 3.2. Engineers and concrete mix designers use coarseness index as a guide to selecting the appropriate combination of aggregates to achieve the desired concrete properties for a particular building application. This helps ensure that the particle size distribution of the fine aggregate is appropriate to produce a properly graded, workable concrete mix.

[0019] The grain size or particle size of the sand is another parameter that is considered when determining the suitability characteristics of the sand. These sizes and their potential uses are as follows:

[0020] Coarse sand has a grain size of about 2.0-4.0 mm and is used as a base material for construction works such as roads and foundations. It is suitable for mixing concrete and mortar.

[0021] Medium sand has a particle size of approximately 0.25-2.0mm and is commonly used in sandboxes and recreational areas, landscaping and surface leveling. This sand can also be used in brick and block laying.

[0022] Fine sand has a particle size of approximately 0.075-0.25 mm and is used in sandblasting to clean and etch surfaces. It is suitable for the production of mortar and stucco, and also for sand filters for water purification. It is not suitable for concrete applications.

[0023] Ultrafine sand has a particle size of approximately 0.05-0.075 mm and is used in the production of glass and ceramics. It is also suitable for polishing wood and metal surfaces.

[0024] Silt has a particle size of about 0.002-0.05 mm and is often considered intermediate between sand and clay. It can be used for soil improvement and composting.

[0025] Clay has a particle size of less than about 0.002 mm and is used in pottery and ceramics due to its plasticity. It is an important component of soils for agriculture.

[0026] Construction sand mixes are various combinations of sand sizes used in construction projects to achieve specific properties in concrete, mortar, and other building materials.

[0027] Beach sand is the natural sand found on beaches, often composed of a mixture of grain sizes. It is used for recreational purposes, sandcastles, and beach volleyball courts.

[0028] River sand (conformable sand) and desert sand (inconformable sand) have different compositions and properties due to their different geological origins and environments. A summary of these compositions is provided below. River sand is typically composed of a mixture of various minerals, rock fragments, and organic matter. Its composition can vary depending on the geological features of the particular river and its surroundings.

[0029] Generally, river sand is composed of silica (SiO2) in the form of quartz. Silica is an important component of most sand types and gives sand its characteristic hardness and weatherability.

[0030] Mineral fragments are found as small pieces of minerals and rocks that have eroded from the surrounding land. These fragments can include feldspar, mica, and other minerals.

[0031] Organic matter may also be present in river sand, such as decomposed plant material and small organisms, especially if it is close to the riverbed.

[0032] Smaller amounts of various other minerals may be present depending on local geological conditions, such as calcite, hematite, and magnetite.

[0033] Unlike river sand, desert sand is often characterized by its finer grain size and unique composition, which is attributed to the specific weathering processes and environment of the desert region.

[0034] Desert sands are composed of feldspar, which may be found in higher proportions compared to river sands. Feldspar is a group of minerals that are abundant in desert environments and contribute to the reddish or orange color of some desert sands.

[0035] Quartz can be found in significant amounts and gives it its overall hardness and texture.

[0036] Lithic fragments are weathered fragments of rocks and minerals, often with rounded edges due to wind erosion.

[0037] Iron oxides can be found in greater amounts, which contributes to their reddish or yellowish coloration. Iron oxides are produced by the weathering and oxidation of iron-containing minerals in desert regions.

[0038] Calcium carbonate can be found in some desert sands due to water evaporation and mineral buildup in dry environments.

[0039] River sand used in concrete is also called "concrete sand" or "sharp sand." This type of sand is specifically selected and graded to meet the requirements of concrete production. It plays an important role in the strength, workability, and durability of the concrete mix. Concrete sand is generally characterized by the following properties:

[0040] Particle size: Concrete sand has a well-sorted particle size distribution, meaning it contains a range of particle sizes from fine to coarse. This distribution helps fill the voids between the larger aggregates, providing a dense mix.

[0041] Shape and texture: Sand particles are typically angular or "sharp" in shape, which improves the mechanical interaction between particles and increases the overall strength of the concrete.

[0042] Cleanliness: Concrete sand is usually free of excess organic matter, clay, silt, and other impurities that may adversely affect the properties of concrete.

[0043] Consistency: Sand should have consistent properties from batch to batch to ensure uniformity of the concrete mix.

[0044] From an industry classification perspective, sand used in concrete is often classified based on its particle size distribution. Common classification systems include the Unified Soil Classification System (USCS) and the AASHTO (American Association of Highway Transportation Officials) classification. These systems classify soils and aggregates based on particle size and other characteristics.

[0045] In the AASHTO classification, concrete sand is typically referred to as "ASTM C33 sand" or simply "Type F sand" and is included in the "fine aggregate" category. Fine aggregates are further divided into three grades: A, B, and C. Type F sand typically falls below the "A" grade, meaning it has a relatively uniform particle size distribution and is suitable for use in concrete.

[0046] Based on these classifications, Figures 1A and 1B show the difference between compatible and incompatible sands, with Figure 1A showing a compatible sand grain 110 and Figure 1B showing an incompatible sand grain 120. The river sand grain 110 is river sand with an average size L greater than 2 mm, even greater than 1 mm, while the desert sand grain 120 is desert sand with an average size L less than 1 mm, even less than 0.8 mm. The coarseness of the river sand grains is greater than that of the desert sand grains. The authors of [1] reported that the average volume and surface area of ​​a river sand grain are 2.17 mm, respectively. 3 and 9.32mm 2 , while the average volume and surface area of ​​a desert sand grain are 929,378.2 μm, respectively. 3 and 49,913.6 μm 2 Therefore, these properties of desert sand grains are much smaller than those of river sand grains.

[0047] In one application, "desert sand" is defined as any sand having (1) an average volume per grain that is less than half the average volume of a grain of river sand, and / or (2) an average surface area per grain that is less than half the average surface area of ​​a grain of river sand. In another application, "desert sand" is defined as any sand having (1) an average volume per grain that is less than half the average volume of a grain of river sand, and / or (2) an average surface area per grain that is less than one-quarter the average surface area of ​​a grain of river sand. In another application, "desert sand" is defined as any sand having (1) an average volume per grain that is less than half the average volume of a grain of river sand, and / or (2) an average surface area per grain that is less than one-tenth the average surface area of ​​a grain of river sand. Those skilled in the art will understand that either of the above definitions of desert sand relative to river sand can be used, as each quantitatively defines a grain of desert sand.

[0048] A further distinction can be made between river and desert sand grains. Figure 2 shows a single desert sand grain 120 oriented along different directions, with its length (L), width (W), and thickness (T) visible. L is greater than or equal to W, and W is greater than or equal to T, with each dimension perpendicular to the other two dimensions. Note that the same grain 102 is also shown in Figure 2. Based on these three sand grain characteristics, an elongation index (EI) and a flatness index (FI) can be defined for each grain. The elongation index (EI) is defined as the ratio of W to L, i.e., W / L, and the flatness index (FI) is defined as the ratio of T to W, i.e., T / W. Sand grains with different elongation and flatness indices are shown in Figures 3A through 3D. Their EI and FI values ​​are also shown. These figures also show the volume-equivalent spherical diameter (VESD), which is the diameter of a perfect sphere with a volume equal to the actual volume of the sand grain. In one application, "desert sand" is defined as any sand whose elongation index and flatness index are, on average, smaller than those of river sand.

[0049] According to one embodiment, because the surface and size (or volume) of desert sand grains are, on average, smaller than the surface and size (or volume) of river sand grains, a novel process and corresponding system are implemented to increase the unconformable desert sand so that it becomes conformable. In one method discussed herein, CO2 is used to partially increase the surface and size of the desert sand grains, in addition to other chemical elements discussed below. The novel process also uses a by-product of the desert sand to cause multiple desert sand grains to clump together. However, in another method, CO2 is not used to conform the desert sand grains.

[0050] More specifically, as shown in FIG. 4, the desert sand grains 120 received in step 400 are treated in step 402 with a selected CO2 capture agent 130 to adhere to the outer surface 122 of the sand grains, as shown generally in FIG. 5. The agent 130, in this embodiment, is selected to be calcium hydroxide, Ca(OH), which is typically obtained from the reaction of calcium oxide (CaO, also known as quicklime) with water. However, the agent 130 may also include other metal hydroxides, i.e., magnesium hydroxide, Mg(OH), where the metal may be any divalent or monovalent metal (e.g., Li, Mg, Ca, Zn, Fe, Ba, Sr, etc.). The agent 130 may also be a metal oxide, e.g., magnesium oxide, MgO, where the metal may be any divalent or monovalent metal, as described above. Therefore, any of LiO, LiOH, MgO, CaO, ZnO, Zn(OH)2, FeO, Fe(OH)2, BaO, Ba(OH)2, SrO, Sr(OH)2, etc., in other words, any basic oxide or hydroxide of a divalent or monovalent metal may be used as agent 130.

[0051] In one application, the agents may be extracted from industrial waste streams from various industrial processes. Such waste streams include, but are not limited to, mining waste, fossil fuel combustion ash (e.g., fly ash), slag (e.g., iron slag, phosphorus slag), cement kiln waste, refinery / petrochemical refinery waste (e.g., oil field and methane seam brines), coal seam waste (e.g., gas production brines and coal seam brines), paper processing waste, water softening waste brine (e.g., ion exchange effluent), silicon processing waste, agricultural waste, metal finishing waste, high pH textile waste, and caustic sludge.

[0052] FIG. 6 schematically illustrates a corresponding plant 600 configured to receive desert sand grains 120 and chemical 130 and mix them in a first mixer device 610. This process can be performed by physical mixing of the sand grains 120 with the Ca(OH)2 chemical 130 or by stirring a suspension of the oxide or hydroxide in a mixture of water, alcohol, or solvent for a time period ranging from 1 to 24 hours. Any common solvent can be used instead of water and / or alcohol. Mixing can occur over a wide range of temperatures (i.e., 20 to 1000°C), with room temperature (25°C) being preferred. If the temperature needs to be higher than room temperature, a heater 612 may be provided adjacent to the first mixer 610 to maintain the desired temperature. A controller 621, e.g., a processor, may be provided to maintain the desired temperature within the first mixer 610. The controller 621 may be connected to the first mixer 610 via wire or wirelessly and may be configured to control the speed of a mixing blade 614, which mixes the sand and chemical. Physical mixing results in a more uniform final mixture and is preferred over the others for use in further steps.

[0053] The islands 132 of agent 130 formed on the outer surface 122 of the desert sand grain 120 impart non-uniformity to the desert grain and alter its original morphology. This increases the dimensions L, W, and T, as well as the roughness of the grain surface. However, these increases are not sufficient to conform the non-conforming desert sand grain 120; i.e., after processing in step 402, the desert sand grain with the islands of agent, referred to herein as "reinforced sand grain" 140, still meets the definition of "desert sand" but possesses properties that do not conform to "river sand."

[0054] Next, in step 404, the enhanced desert sand grains 140 are carbonated. The carbonation step occurs in an adsorption chamber 620 (see FIG. 6 ), where a CO stream 622 and a water stream 624 are simultaneously fed to react with the enhanced desert sand grains 140. Carbon dioxide is obtained from an industrial waste stream in aqueous solution by precipitating one or more carbonate compounds from the aqueous solution, dewatering the precipitate, and in some embodiments, further processing the dewatered precipitate to produce aggregate. The industrial waste stream may be any suitable waste stream described herein. In some embodiments, the industrial waste stream is flue gas from a coal-fired power plant. Contacting the CO with the sand may be carried out by any suitable apparatus and procedure, such as by a flat-jet contactor or by aerosol contactor, as described herein. In some embodiments, the CO in the industrial waste stream is contacted with the aqueous solution using a flat-stream contactor. More specifically, the water stream may be contacted with the CO stream using any convenient protocol. When CO2 is a gas, contemplated contacting protocols include, but are not limited to, direct contacting protocols, e.g., bubbling the gas into a volume of water or brine; cocurrent contacting means, i.e., contact between gas and liquid phases flowing in one direction; countercurrent contacting means, i.e., contact between gas and liquid phases flowing in opposite directions; etc. Thus, contacting may be accomplished as may be convenient by using injectors, bubblers, fluid venturi reactors, spargers, gas filters, sprays, trays, or packed column reactors, etc. In one embodiment, contact between a flat jet liquid sheet and a gas is achieved, with the sheet and gas potentially moving in countercurrent, cocurrent, or crosscurrent directions, or in any other suitable manner.

[0055] The chamber may be equipped with a heater 612 to control the temperature therein via a controller 621. When the agent 130 reacts with the silica and water 624 from the sand grains 120 and CO2 622, the following reaction occurs: Ca(OH)2 → Ca 2+ +2OH - CO2 + H2O → CO2 H2O CO₂·H₂O+2OH - →CO3 2- +2H2O Ca 2+ +CO3 2- →CaCO3 This results in the formation of carbonate particles 150 on the surfaces 122 of the sand grains 120, as shown schematically in FIG. 7. Note that the calcium carbonate particles 150 are the result of the conversion of the agent 130 during the carbonation reaction of step 404. If the agent 130 is not Ca-based, the formed carbonate particles 150 are magnesium carbonate particles or other types of particles (e.g., sodium carbonate, potassium carbonate, ammonium carbonate, barium carbonate, etc.), depending on the type of agent 130. The resulting sand grains are referred to herein as "carbonate-enriched sand grains" 160. The carbonate-enriched sand grains will increase in size as they store CO2 during the process of step 404.

[0056] Step 404 can be performed under either flowing or static conditions; that is, the enhanced sand grains 140 move through the adsorption chamber 620 or are stationary within the chamber during this step. In one application, a conveyor belt (not shown) can be used to transport the enhanced sand grains from the first mixer device 610 to the chamber 620. In one application, the chamber 620 can be a vertical quartz tube with a frit on which the sand rests. The CO2 flow flows from top to bottom through the sand bed. The CO2 flow (diluted with an inert gas, e.g., N2, or not) can pass through a bubbler to carry water to the reactants. Alternatively, the sand can be wetted prior to reaction. Any unreacted CO2 remains at the bottom of the chamber. In one application, the tube can be horizontal (without a frit). In yet another application, the sand can enter the adsorption chamber from top to bottom, bottom to top, side to side, or any combination of these configurations. In this process, the sand comes into contact with the gas that may enter the reactor in any of the configurations described above. If the sand stays on the surface and does not flow during the adsorption process, the sand is placed on top of a porous material (100 nm to 1 cm) to allow the gas to pass through.

[0057] The concentration of the carbon dioxide stream fed into chamber 620 can vary between atmospheric and 100%, and the process can be carried out at atmospheric or other pressures (0.1 to 300 bar) and over a wide range of temperatures (0 to 1000°C). Step 404 may be carried out in the absence of humidity, but the addition of water vapor results in higher carbonization yields (5 to 60%). Higher temperatures also favor faster carbonization yields.

[0058] While this step is described with respect to a CO2 stream, other acid gases, such as SO2, SO3, H2S, P2O3, P2O5, Cl2O, Cl2O3, Cl2O5, Cl2O7, N2O5, N2O3, and N2O, may also be used. The average weight gain of the original desert sand grains 120 in the process of becoming carbonate-enhanced sand grains 160 has been observed to be approximately 1 to 30%, depending on the applied temperature and CO2 concentration in the stream. The carbonate-enhanced sand grains 160 may be further processed to increase their size, making them comparable to river sand grains. However, if the carbonate-enhanced sand grains 160 are used to make concrete at this stage, the compressive strength of such concrete will be approximately 43.8 N / mm after 28 days. 2 For reference, the International Building Code (IBC) (Section 1905.1.1) and the ACI 318 Standard (Section 5.1.1) recommend a minimum stress of 2500 psi (17 MPa or 17 N / mm) for structural concrete. 2 ) indicates the minimum specified compressive strength.

[0059] The method discussed with respect to FIG. 4 may further process the carbonate-enhanced sand grains 160 to further increase their size. Because not all desert sand grains 120 acquire the scavenger 130 and / or carbonate particles 150 during steps 402 and 404, their original small size is barely increased during this stage. These fine desert sand grains 120′, characterized by their very small size, are separated from the carbonate-enhanced sand grains 160 in chamber 620 in step 406, and these grains are introduced into a second mixer device 640. The separation in step 406 can be achieved by sieving. This step can be performed before or after carbonization, with the former being preferred. Generally, the order of steps 404 and 406 can be changed. Since only very small, unprocessed particles are used to prepare the “glue” (or “water glass”), step 406 can be considered the very first step. Therefore, if step 406 is performed first, the sand for the adhesive is not carbonated. In another embodiment, the separation of step 406 may be achieved by using a cyclone.

[0060] Note that the output of step 404 is flue gas 626 emitted from chamber 620. Also note that the fine sand granules 120' removed from chamber 620 and fed to second mixer apparatus 640 may also contain small amounts of reinforced sand granules 150 and / or carbonate reinforced sand granules 160 that have a very small size and are not yet suitable for concrete applications. All of these components of the incompatible sand are referred to herein as fine desert sand granules 120'.

[0061] In the second mixer device 640, the fine desert sand grains 120′ rejected from the chamber 620 can be treated with an aqueous base solution 642 in step 408. The base can be NaOH, KOH, or LiOH at a concentration of 2-8 M at a temperature range of 20-200°C. This step is performed with the purpose of attacking the silica on the surface of the fine desert sand grains 120′ with a strong base and dissolving it by forming a silicate solution in water, i.e., creating an in-situ “glue” (a term used for in-situ water glass, an aqueous solution of silicates) 170. The resulting solution 170 contains the base and dissolved silica in the form of sodium silicate. This material is used further in the procedure, as discussed next. This colloidal solution 170 is called SBG, which stands for sand-based glue. The SBG can be concentrated by partially evaporating the present water (e.g., between 10 and 90%), using, for example, a heater 612.

[0062] The above-described steps 402 to 404 can be replaced by a single step 407 in which carbonate is applied directly to the desert sand grains 120 to obtain direct carbonate-reinforced sand grains 162. This application step consists of combining the carbonate powder with the desert sand grains in a slightly basic environment in a mixing chamber. The slightly basic environment can be achieved by spraying an aqueous solution of a base onto the mixture during mixing. The base can be either an inorganic or organic base, including but not limited to NaOH, KOH, NH4OH, NH3, amines, etc. The inventors have created concrete samples using this type of direct carbonate-reinforced sand grain and have demonstrated a compressive strength of 50.0 N / mm after 28 days. 2 , which was found to be slightly better than carbonate-enhanced sand grain 160. However, CO2 storage is not achieved when this step is used.

[0063] Note that step 407 in FIG. 4 may or may not be followed by step 410. In other words, it is possible to simply stop the method at step 407. The same is true for step 404, as at this point the resulting carbonate-enhanced sand grains are ready to be utilized in construction. Overall, carbonation step 407 or 404 can be considered a terminal step. Step 408, which produces "glass water" and then mixes it with the carbonate-enhanced sand grains in step 410, is an optional method that can be applied to treated or untreated sand to further enhance the compressive strength of the resulting concrete.

[0064] Returning to the process shown in FIGS. 4 and 6 , the carbonate-reinforced sand grains 160 (or direct carbonate-reinforced sand grains 162) are fed into a third mixing device 650 along with a sand-based adhesive 170, where they are mixed together in step 410 for the purpose of agglomerating the multiple grains 160 or 162 together to obtain a sand aggregate 180. In one application, prior to this step, a binder is provided to the carbonate-reinforced sand grains 160. The binder may be added to help hold the powder material together to provide structural stability or to act to hold the powder in place during further processing. Typical binders include, but are not limited to, Portland cement, fly ash, silica, citric acid, xanthan gum, or combinations thereof. Binders include those that become relatively fluid during heating and re-harden upon cooling. In one application, the sand-based adhesive 170 may be replaced with a binder.

[0065] The agglomeration of the carbonate-enhanced sand grains 160 (or 162) is achieved by processing the resulting adhesive 170 in a third mixing device 650 at a given temperature T, either under static conditions, stirring, or shaking. The temperature is achieved using a heater 612 controlled by a controller 621. In one application, the adhesive 170 is pre-concentrated by water evaporation, although this step is optional. The resulting sand aggregate 180, whose grains 182 are shown schematically in FIG. 8, contains multiple carbonate-enhanced sand grains 160 (or 162), which significantly increase the corresponding sizes L', W', and T', transforming the original desert sand grains 120 from non-conforming to conforming, i.e., having these sizes comparable (substantially the same) as river sand grains. FIG. 8 shows that the multiple carbonate-enhanced sand grains 160 (or 162) are fully embedded in the adhesive 170, thus forming concrete aggregate grains 182. Note that grains 160 or 162 may be only partially embedded / covered by adhesive 170. Also, note that sand aggregate 180 includes multiple grains 182, with at least one single grain 182 having the structure shown in FIG. 8. Note that some carbonate-enhanced sand grains 160 (or 162) may be in direct contact with each other, as shown by grain 160-1, while other grains 160-2 may not be in direct contact with the remainder of the grain 160. As shown schematically in FIG. 8, spaces 164 may exist between grains 160. These spaces may be filled with adhesive 170. Hardening of adhesive 170 around grains 160 / 160-1 / 160-2 occurs at temperatures ranging from 20 to 300°C, either under static conditions, stirring, shaking, or by spraying the resulting slurry. Depending on the methodology used, hardening can occur instantly or within a range of 1 to 72 hours. Similar techniques can be used to agglomerate non-carbonated sand particles, but the presence of carbonate greatly accelerates hardening and results in the formation of larger particles that are more suitable for concrete.

[0066] In one application, the newly formed sand aggregate 180 has an average size (e.g., length) ranging from 0.5 to 10 mm. In another application, the average size is greater than 1 mm. In yet another application, the average size is greater than 2 mm. A cross-section of this newly formed sand aggregate shows smaller original sand particles embedded within the hardened adhesive 170. Following the procedure shown in Figure 4, utilizing a 2M solution of calcium hydroxide, sodium hydroxide, and a 4-hour wet CO2 flow treatment, the overall mass gain of the sand aggregate 180 is 7.2%, which is the contribution from the trapped carbon dioxide. To increase the size of the sand grains 120 or 160 and cause them to agglomerate in the millimeter range, other colloidal solutions of silica (i.e., Ludox® colloidal silica) can be used for similar purposes. This technique results in large, compact particles. Other colloidal solutions of silica may also be used with desert sand grains.

[0067] In one application, seawater brine may be used to make the process CO2-negative. In this embodiment, the carbon dioxide capture agent 130 is magnesium oxide. Magnesium oxide is obtained from magnesium hydroxide by a simple dehydration reaction. Magnesium hydroxide is then obtained by reacting magnesium chloride and magnesium sulfate (which may be part of the concentrated brine) with sodium hydroxide. Magnesium chloride and magnesium sulfate are obtained from seawater by common methods, such as seawater evaporation. Magnesium ions, i.e., magnesium salts, are the second most abundant anion in seawater. Sodium hydroxide can also be obtained from seawater by simple electrolysis. Seawater is mostly sodium chloride, with sodium ions being the most abundant ion in seawater. Electrolysis can be performed using renewable energy. Solar panels are one sustainable option here. The chemical reactions involved in this process are as follows: NaCl (水溶液) →NaOH + Cl2 + H2 (driven by electrolysis) MgCl2 + 2NaOH → Mg(OH)2 + 2NaCl MgSO4 + 2NaOH → Mg(OH)2 + Na2SO4

[0068] The inventors have carried out several experiments based on the method shown in Figure 4 and the plant 600 shown in Figure 6. For these experiments, the following types of sand were used: A) South Beach sand (Red Sea coast) B) Relationship between South Beach sand and Ca(OH)23:1 (m:m) C) Relationship between South Beach sand and Ca(OH) 25:1 (m:m) D) Relationship between South Beach sand and Ca(OH)27:1 (m:m)

[0069] A solid mixture was obtained by adding raw sand containing Ca(OH)2 powder.

[0070] The desert sand sample contained: A) Sand collected near Thuwal, Saudi Arabia B) Relationship between sand collected near Toile and Ca(OH)25:1 (m:m)

[0071] Each of these sands was prepared and treated as discussed above with respect to FIG. 4. The conditions and parameters used in these experiments are listed in the table of FIG. 9. Note that when treating the sand grains with a CO flow in step 404, a N flow was also added to the mixture (in chamber 620 in FIG. 6). The weights of the sample sands used in the experiments and the weights of the sample sands after treatment (i.e., the weight of the sand aggregate) are also listed in the table of FIG. 9. The second to last column of this table shows the mass gain of each sample.

[0072] Note that both types of sand exhibit similar weight gain after the experiment, becoming more similar as reaction time increases. Weight gain is similar for the 23-hour experiment, with 9% vs. 8.2% gain using South Beach sand and Toile sand, respectively (Experiments 1 and 3 in the table in Figure 9). For the 4-hour experiment, weight gain is slightly different, with 9% vs. 7.4% gain using South Beach sand and Toile sand, respectively (Experiments 5 and 6 in the table).

[0073] The effect of reaction time was also investigated. The 4 and 23 hour experiments show approximately the same increase in sample weight. The weight gain observed for South Beach sand is approximately 9% for experiments during 4 and 23 hour reaction times, i.e., experiments 1 and 5 in the table. For Toile sand, there is a slight change (weight gain from 8.2% to 7.4%) for experiments 3 and 6 in the table.

[0074] We also studied the effect of the water foaming system 625 (see FIG. 6) used to supply water to the chamber 620. To evaluate this effect, two experiments were performed. Experiment 2 was performed without the foamer and showed no increase in sample weight after the experiment, indicating that CO2 is not adsorbed in the absence of water. Experiment 4 was performed using only N2 flow through the foamer without CO2. The sample showed a 4% weight gain, which can be attributed to the adsorption of water vapor.

[0075] The effect of the sand / Ca(OH)2 (m / m) ratio was also studied. It was observed that as the Ca(OH)2 content in the sand / Ca(OH)2 mix increased, more CO2 was adsorbed. The weight gain ranged from 6.8% when the sand / Ca(OH)2 ratio was 7:1 to 14.6% when the ratio was 3:1 (Runs 5, 7, and 8 in the table in Figure 9).

[0076] We also analyzed the chemical composition of the original desert sand grain 120 (collected in Thuwal, Saudi Arabia) and the carbonate-enhanced sand grain 160, and FIG. 10 shows the corresponding X-ray diffraction curves 1020 and 1060. Note that while the original desert sand grain 120 had small amounts of Ca(OH)2 and CaCO3 present, these amounts are considered insignificant (i.e., less than 1% by mass) when compared to the amounts obtained with the carbonate-enhanced sand grain 160 (1 to 50% by mass of carbonate). In one application, the carbonate-enhanced sand grain contains 8-20% by mass carbonate.

[0077] We also performed the method discussed above with respect to Figure 4 in ambient air, i.e., carbonation step 404 was performed in ambient air, resulting in ambient CO2 and ambient air humidity being used in streams 622 and 624 supplied to chamber 620 in Figure 6. Sand was exposed to ambient conditions for 24 hours at approximately 75% relative humidity within a temperature range of 24-34°C. The results for raw desert sand grains 120 and carbonate-enhanced sand grains 160 exposed to ambient CO2 and HO are shown in the table in Figure 11. Note that sand 120 mixed with agent 130 exhibited a weight gain of approximately 1.5%, while raw sand sample 120 exhibited a negative weight gain, likely due to the evaporation of water present within the sand grains. Compared to the experiments performed in the table in Figure 9 (Experiments 3 and 6), a lower weight gain is observed at ambient conditions. This may be due to the lower amount of CO2 the sample was exposed to in the ambient environment compared to the experimental setup, as well as the lower relative humidity. Thus, although not as efficient as when the carbonation reaction occurs within chamber 620, carbonating sand in an open environment still achieves a small weight gain.

[0078] Another experiment we performed was thermogravimetric analysis (TGA) of the resulting sand to verify the formation of calcium carbonate through carbonation. Figure 12 shows the change in sample weight as the sample temperature increases. According to [2], Ca(OH)2 decomposes to CaO and HO between 400 and 500°C, and CaCO3 decomposes to CaO and CO2 above 600°C. Figure 12 shows that the mass of the sand sample (Run 3 in Figure 9) decreases just above 600°C, indicating the presence of CaCO3, while the mass of the sand sample (Run 2 in Figure 11) first decreases between 400 and 500°C, and then decreases just above 600°C, indicating the presence of both Ca(OH)2 and CaCO3. In other words, the sand sample exposed to ambient conditions (curve 1220 in Figure 12) exhibits a mixture of both Ca(OH)2 and CaCO3 materials. The sand sample from the experiment performed with the experimental setup (curve 1210 in Figure 12, experiment 3 in Figure 9) shows the presence of only CaCO. Both sand samples show a similar weight loss (approximately 15%) in the TGA analysis.

[0079] As discussed above, the resulting sand aggregate 180 behaves like compatible sand and can therefore be used in place of river sand grains in any concrete application. The sand aggregate 180 can, in fact, be used in any application where river sand can be used, not just concrete applications, i.e., as a sublayer in the construction of roads, patios, driveways, sidewalks, railroad tracks, etc. In one embodiment, the sand aggregate 180 is primarily used to store CO2, and the material may then be used to fill caves, abandoned mines, abandoned wells, etc. In yet another embodiment, the sand aggregate may simply be buried underground to store CO2. In yet another application, the sand aggregate 180 may be used in cementless applications, for example, mixed with resin or any known binding element to form bricks, staves, tiles, or other flooring or other common building materials.

[0080] Aggregate 180 may be combined with pure Portland cement or used in place of traditional natural rock aggregates used in conventional concrete to form a Portland cement blend. The term "Portland cement blend" includes hydraulic cement compositions containing a Portland cement component and a significant amount of non-Portland cement components. Because the cement in this embodiment is a Portland cement blend, the cement includes a Portland cement component. The Portland cement component may be any convenient Portland cement. As known in the art, Portland cement is a powder composition produced by grinding Portland cement clinker (greater than 90%) with limited amounts of calcium sulfate to control setting time, and up to 5% of minor components (as allowed by various standards).

[0081] Although the sand aggregate 180 has been described with respect to storing CO, in some embodiments, the aggregate can store (or sequester) one or more components of human-generated waste streams, typically industrial waste streams, including but not limited to gaseous components. Generally, the one or more components sequestered by the aggregate are components whose release into the atmosphere or environment is generally undesirable. For example, in the case of a flue gas waste stream, the undesirable components may include CO, sulfur oxides (SO), sulfur dioxide (SO), and sulfur dioxide (SO), such as SO. x ), nitrogen oxides (NO, NO2, etc. x ), heavy metals such as mercury, cadmium, lead, and / or others known in the art, particulates, radioactive materials, organic compounds, and other undesirable components, such as any components regulated by a government or other regulatory agency. Thus, sand aggregate 180 may be treated to contain / store any of these undesirable materials by modifying stream 622 fed to chamber 620 to include such elements. These elements may be mixed with the CO2 stream.

[0082] The process of FIG. 4 has been discussed in relation to the use of calcium carbonate, CaCO3, because those skilled in the art will understand that many forms of this or similar materials may be used. In this regard, [3] appropriately describes carbonate compounds as including precipitated crystalline and / or amorphous carbonate compounds, or even bicarbonate compounds. Particular carbonate minerals of interest include, but are not limited to, calcium carbonate minerals, magnesium carbonate minerals, and calcium magnesium carbonate minerals. Calcium carbonate minerals of interest include, but are not limited to, calcite (CaCO3), aragonite (CaCO3), vaterite (CaCO3), ikaite (CaCO3), and argonite (CaCO3). 3. 6H2O), and amorphous calcium carbonate (CaCO 3. Magnesium carbonate minerals of interest include, but are not limited to, zipinsite (Mg(COMOH)2.5(HO), the term zipinsite is used herein to include zipinsite minerals of this formula), magnesite (MgCO3), barringtonite (MgCO3. 2H2O), nesquehonite (MgCO 3. 3H2O), Ranfordite (MgCO 3. 5H2O) and amorphous magnesium carbonate (MgCOynH2O). Calcium magnesium carbonate minerals of interest include, but are not limited to, dolomite (CaMgCO3), huntite (CaMg(CO3)4) and surgeite (Ca2Mg 11 (CO3)13H2O). In certain embodiments, non-carbonate compounds such as brucite Mg(OH)2 can also be formed in combination with the above minerals. As noted above, the carbonate compounds can be metastable carbonate compounds (and may include one or more metastable hydroxide compounds) that are more stable in saltwater than in freshwater, such that upon contact with freshwater they dissolve and reprecipitate into other freshwater-stable compounds, e.g., minerals such as low-Mg calcite.

[0083] The term "about" is used in this application to mean a variation of up to 20% of the parameter characterized by this term. Terms such as "first," "second," etc. may be used to describe various elements in this specification, but it is understood that these elements should not be limited by these terms. These terms are used only to distinguish one element from another. For example, a first object or step can be referred to as a second object or step, and similarly, a second object or step can be referred to as a first object or step, without departing from the scope of this disclosure. Although a first object or step and a second object or step are both objects or steps, respectively, they should not be considered the same object or step.

[0084] The terms used in the description herein are for the purpose of describing particular embodiments and are not intended to be limiting. As used in this specification and the appended claims, the singular forms "a," "an," and "the" are intended to include the plural forms unless the context clearly dictates otherwise. The term "and / or," as used herein, will also be understood to refer to and encompass any possible combination of one or more of the associated listed items. It will be further understood that the terms "includes," "including," "comprises," and / or "comprising," as used herein, specify the presence of stated features, integers, steps, operations, elements, and / or components, but do not exclude the presence or addition of one or more other features, integers, steps, operations, elements, components, and / or groups thereof. Furthermore, as used herein, the term "when" can be interpreted to mean "when" or "when," or "in response to determining" or "in response to detecting," depending on the context.

[0085] The disclosed embodiments provide methods and systems for processing desert sand grains to meet concrete aggregate requirements and / or sequestering CO2 in the formed aggregate. It should be understood that this description is not intended to limit the invention. On the contrary, the embodiments are intended to cover alternatives, modifications, and equivalents that are included within the spirit and scope of the invention as defined by the appended claims. Furthermore, in the detailed description of the embodiments, numerous specific details are set forth in order to provide a comprehensive understanding of the claimed invention. However, those skilled in the art will understand that various embodiments may be practiced without such specific details.

[0086] Although the features and elements of the present embodiments are described in the embodiments in particular combinations, each feature or element can be used alone without the other features and elements of the embodiments or in various combinations with or without the other features and elements disclosed herein.

[0087] This specification uses examples of the disclosed subject matter to enable any person skilled in the art to practice it, including making and using any devices or systems, and performing any incorporated methods. The patentable scope of the subject matter is defined by the claims, and may include other examples that occur to those skilled in the art. Such other examples are intended to be within the scope of the claims.

[0088] References The entire contents of all publications cited herein are incorporated by reference into this patent application. [1] Liu, X.;Liu, R.;Lyu, K.;Gu, YAQuantitative Evaluation of Size and Shape Characteristics for Desert Sand Particles.Minerals 2022, 12, 581.doi.org / 10.3390 / min12050581 [2] Hossen, SKB; Gallant, A.; Ashraf, Wa. Elemental Testing of Carbonated Silty Sand Treated with Lime. Geo-Congress 2020: Foundations, Soil Improvement, and Erosion [3] U.S. Patent No. 7,753,618 [Explanation of symbols]

[0089] 102 grains 110 Grains of River Sand 120 desert sand grains, sand samples, 120' Fine desert sand grains 122 External surface, surface 130 Carbon dioxide sequestering agents, drugs, Ca(OH)2 agents 132 islands 140 Enhanced Desert Sand 150 carbonate particles, calcium carbonate particles, reinforced sand particles 160 Reinforced carbonate sand grains, carbonate reinforced sand grains 160-1 grains 160-2 grains 162 Direct carbonate-strengthened sand grains 164 Space 170 Sand-based adhesive, colloidal solution 180 Sand aggregate 182 Concrete aggregate granules 600 plants 610 First mixer device, first mixing device, adsorption chamber 612 Heater 614 Mixed Blade 620 Adsorption Chamber 621 Controller 622 CO2 flow 624 Flowing Water 625 Water Foaming System 626 Flue Gas 640 second mixer device, second mixing device 642 Aqueous solution of base, base flow 650 Third Mixing Device 1020 X-ray diffraction curve 1060 X-ray diffraction curve 1210 curve 1220 curve L length, average size, dimension L' size W width, dimensions W' size T Thickness, temperature, dimensions T' size

Claims

1. A sand aggregate (180), A plurality of aggregate particles (182), At least one aggregate particle (182) among the plurality of aggregate particles (182) Desert sand grains (120) are too small for concrete applications, carbonate particles (150) distributed on the outer surface (122) of the desert sand grains (120); a sand-based adhesive (170) that clumps the desert sand grains (120) together; A plurality of aggregate particles (182) including Equipped with the at least one aggregate particle (182) has a size comparable to that of river sand particles, while the desert sand particles (120) have a size smaller than that of the river sand particles, such that the at least one aggregate particle (182) is suitable for concrete applications; Sand aggregate (180).

2. 10. The aggregate of claim 1, wherein the sand-based adhesive is obtained from additional desert sand grains that have been treated with a base.

3. 3. The aggregate of claim 2, wherein the base is NaOH.

4. 3. The aggregate of claim 2, wherein the desert sand grains and the additional desert sand grains have the same origin.

5. 2. The aggregate of claim 1, wherein the desert sand grains have an average length of less than 1 mm, while the river sand grains have an average length of greater than 1 mm.

6. The average volume and surface area of ​​the river sand grains are approximately 2.17 mm 3 and 9.32 mm 2 , while the average volume and average surface area of ​​the desert sand grains are approximately 929,378.2 μm 3 and 49,913.6 μm 2 The aggregate according to claim 1,

7. 2. The aggregate of claim 1, wherein the average volume of a grain of desert sand is less than half the average volume of a grain of said river sand.

8. 8. The aggregate according to claim 7, wherein the average surface area of ​​each desert sand grain is less than half the average surface area of ​​said river sand grains.

9. 8. The aggregate of claim 7, wherein the average surface area per desert sand grain is less than 1 / 4 of the average surface area of ​​the river sand grain.

10. 8. The aggregate of claim 7, wherein the average surface area per desert sand grain is less than 1 / 10 of the average surface area of ​​the river sand grain.

11. The carbonate particles are CaCO 3 The aggregate of claim 1, comprising:

12. 2. The aggregate of claim 1, wherein the carbonate particles comprise one of Li, Mg, Zn, Fe, Ba, Sr, or Na.

13. 1. A method for converting desert sand grains (120) into suitable sand for concrete applications, the method comprising: providing (400) said desert sand grains (120); treating (402) the desert sand grains (120) with a carbon dioxide sequestering agent (130) to produce enhanced sand grains (140); carbonating (404) the enriched sand grains (140) to form carbonate enriched sand grains (160) while simultaneously storing carbon dioxide on the outer surface of the carbonate enriched sand grains (160); agglomerating the carbonate-enhanced sand grains (160) to form a sand aggregate (180) that is suitable for concrete applications and has a size similar to that of river sand grains; A method comprising:

14. 14. The method of claim 13, wherein the desert sand grains (120) are too small to be used in concrete applications.

15. separating (406) fine desert sand grains from the carbonate-enhanced sand grains (160); treating the separated fine desert sand particles with a base to form a sand-based adhesive; 14. The method of claim 13, further comprising:

16. adding the sand-based adhesive to the agglomerating step to form the sand aggregate.

16. The method of claim 15, further comprising:

17. 16. The method of claim 15, wherein the base is NaOH.

18. 14. The method of claim 13, wherein the desert sand grains have an average length of less than 1 mm, while the river sand grains have an average length of greater than 1 mm.

19. The average volume and surface area of ​​the river sand grains are approximately 2.17 mm 3 and 9.32 mm 2 while the average volume and average surface area of ​​the desert sand grains are approximately 929,378.2 μm 3 and 49,913.6 μm 2 14. The method of claim 13, wherein:

20. 14. The method of claim 13, wherein the average volume of a grain of desert sand is less than half the average volume of a grain of river sand.

21. 21. The method of claim 20, wherein the average surface area per grain of desert sand is less than half the average surface area of ​​said grains of river sand.

22. 21. The method of claim 20, wherein the average surface area per grain of desert sand is less than one-quarter of the average surface area of ​​the grain of river sand.

23. 21. The method of claim 20, wherein the average surface area per grain of desert sand is less than 1 / 10 of the average surface area of ​​the grain of river sand.

24. The carbonate particles are CaCO 3 14. The method of claim 13, comprising:

25. 14. The method of claim 13, wherein the carbonate particles comprise one of Li, Mg, Zn, Fe, Ba, Sr, or Na.

26. 1. A plant (600) for converting desert sand grains (120) into suitable sand for concrete applications, said plant (600) comprising: Desert sand grains (120) and CO 2 a first mixer (610) configured to receive and mix the scavenging agent (130) to form the reinforced sand grains (140); receiving the reinforced sand grains (140), and dissolving the reinforced sand grains (140) in CO 2 an adsorption chamber (620) configured to mix with the stream (622) of carbonate-enhanced sand and the stream (624) of water to form carbonate-enhanced sand grains (160); a second mixing device (640) configured to mix fine desert sand particles (120') with the base stream (642) to form a sand-based adhesive (170); a third mixer (650) connected to the adsorption chamber (620) and the second mixer (640) for receiving the carbonate-enhanced sand granules (160) and the sand-based adhesive (170), and configured to mix the carbonate-enhanced sand granules (160) and the sand-based adhesive (170) to form a sand aggregate (180); Equipped with The desert sand grains (120) are unsuitable for concrete applications, while the sand aggregate (180) is suitable for concrete applications. Plant (600).

27. 27. The plant of claim 26, wherein the fine desert sand grains (120') are separated from the carbonate-enriched sand grains (160) after treatment in the adsorption chamber.

28. 27. The plant of claim 26, wherein the base is NaOH.

29. The CO 2 The scavenger is CaCO 3 27. The plant of claim 26, comprising:

30. The CO 2 27. The plant of claim 26, wherein the scavenger comprises one of Li, Mg, Zn, Fe, Ba, Sr, or Na.

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