A method for thermal activation of coal gangue

Abstract

This invention discloses a method for thermal activation of coal gangue. Using coal gangue and an activating admixture as raw materials, the method involves sequential crushing, mixing and mechanical activation, homogenization, molding, drying, calcination and thermal activation, cooling, and grinding to prepare active powder. This invention uses coal gangue as the main raw material. By adding an activating admixture, the thermal activation temperature of the coal gangue is reduced to below 1000℃, significantly stimulating its activity. Simultaneously, combined with mechanical activation, unsaturated residual bonds are formed in the quartz minerals within the coal gangue, producing active silica, further stimulating the activity of the coal gangue and increasing its activation rate. The prepared active powder exhibits a pozzolanic activity of over 75%, achieving the goal of "waste treatment" and reducing costs. This active powder can be directly added as a mineral admixture during concrete preparation, showing promising application prospects.

Description

Technical Field

[0001] This invention belongs to the field of solid waste comprehensive utilization technology, specifically relating to a method for thermal activation of coal gangue. Background Technology

[0002] Coal gangue is a type of silty, carbonaceous, or sandy shale with low carbon content and an ash content of over 40%, extracted from the top, bottom, or surrounding coal seams during coal mining. It is an industrial waste from coal mines. As of 2020, coal still accounted for 59% of my country's energy structure, and coal gangue emissions accounted for approximately 10% to 25% of coal mining, sometimes reaching as high as 30%, accumulating to a total of 7 billion tons, and increasing at a rate of 800 million tons per year. This not only causes enormous resource waste but also damages the ecological environment surrounding mines. Recycling and reusing this coal gangue can not only turn waste into treasure, improving resource utilization, but also improve the environment, reducing costs, conserving resources, and increasing economic benefits.

[0003] In recent years, coal gangue has been increasingly used in the production of building materials both domestically and internationally. Activating the activity of coal gangue and using it as a cementitious admixture is becoming an effective way to treat this solid waste. However, the stable chemical structure of coal gangue results in low chemical reactivity, which is the main obstacle to its recycling. To promote the resource utilization of coal gangue, scholars at home and abroad have explored activation methods, including mechanical activation, chemical activation, microwave irradiation activation, and thermal activation. However, the recycling of coal gangue is currently constrained by imperfect activation processes and unstable raw material composition. Summary of the Invention

[0004] The technical problem to be solved by this invention is to provide a method for thermal activation of coal gangue, addressing the shortcomings of the prior art. This invention uses coal gangue as the main raw material and, by adding an activating admixture, lowers the thermal activation temperature of the coal gangue to below 1000℃, greatly stimulating its activity. Simultaneously, combined with mechanical activation, it causes the quartz minerals in the coal gangue to form unsaturated residual bonds, producing active silica, further stimulating the activity of the coal gangue and improving its activation rate.

[0005] To solve the above-mentioned technical problems, the technical solution adopted by the present invention is as follows: a method for medium-temperature activation of coal gangue, characterized in that coal gangue and an activating admixture are used as raw materials, and the raw materials are successively crushed, mixed and mechanically activated, homogenized, shaped, dried, calcined and medium-temperature activated, cooled and ground to prepare active powder.

[0006] Coal gangue contains clay minerals. The crystal structure of clay minerals is mainly composed of silicon-oxygen tetrahedra [SiO4]. 4- Composed of (Si2O5) nThe AlO(OH)₂ layer, composed of layers of silicon and aluminum octahedrons connected at their vertices, has a layered structure that largely determines the various properties of clay. Generally speaking, the more internal defects a crystal has, the better its activity; the greater the degree of lattice distortion, the better its activity; the more obvious the amorphous morphology, the better its activity; and breaking the spatial network, i.e., high deagglomeration ability, also results in good activity. Stable lattice atoms and other particles with regular and ordered particle order can be said to have no activity. For clay minerals, the same general law of activation applies: the more stable the degree of crystallization, the worse the activity. The activation of its activity requires the cleavage of silicon-oxygen tetrahedra, especially the destruction of the aluminum-oxygen octahedral framework, to produce a composition and structure similar to volcanic ash, thus exhibiting higher activity. Clay mineral particles undergo intense thermal motion at high temperatures, causing the bound water in the particles to be removed. Furthermore, silicon-oxygen tetrahedra and aluminum-oxygen octahedra cannot aggregate into long chains, thus forming a thermodynamically unstable structure that enhances their activity. Simultaneously, after absorbing heat, the internal molecules of aluminosilicates (Si-O-Si, Si-O-Al) vibrate, breaking the surface network and releasing more disordered and irregular active basic units. Alternatively, they may disintegrate [SiO4] and [AlO4] tetrahedra, further depolymerizing monomers or dimers, and gradually transforming into active ingredients.

[0007] Therefore, existing coal gangue activation processes mainly target the activation of kaolin, a clay mineral in coal gangue. Because kaolin has a relatively pure crystal structure and fewer substitution elements, its activation performance is also excellent. The basic mechanism is that when the calcination temperature of kaolin exceeds 500℃, its dehydroxylation structure is destroyed. While maintaining the layered structure, large dislocations appear, and it eventually transforms from a crystal to an amorphous material. The material in the transition phase is metakaolin, which has strong pozzolanic activity.

[0008] Studies on the activation of non-kaolinite clay materials (taking illite as an example) show that when the temperature exceeds 1100℃, illite undergoes a significant amorphization process, a change characteristic completely similar to that of kaolinite under thermal action. Specifically, the removal of hydroxyl groups disrupts the basic valence balance of the illite crystal structure, weakens the interatomic bonds, and leads to a corresponding adjustment in the original lattice structure. In particular, the coordination mode of Al in the [Al-O(OH)] octahedron inevitably changes due to the removal of hydroxyl groups, causing the octahedral structural units to disappear and transform into new Al-O tetrahedral structural units. However, compared to the activation of kaolinite, the illite activation process has two drawbacks: firstly, high activation energy consumption (activation temperature around 1100℃); and secondly, low activation efficiency, because the activation of illite produces amorphous substances, accompanied by the formation of mullite (which is inactive), with the production temperature ranges of the two substances overlapping.

[0009] This invention uses coal gangue as the main raw material. Targeting coal gangue with clay components including kaolinite, montmorillonite, illite, chlorite, and other minerals, an activating admixture is added to lower the optimal thermal activation temperature of the clay components in the coal gangue to below 1000℃. This causes a change in the crystal structure, generating activity and significantly enhancing the activity of the coal gangue. Simultaneously, mechanical activation causes unsaturated residual bonds to form in the quartz minerals in the coal gangue, producing active silica, further stimulating the activity of the coal gangue. This invention solves the problems of imperfect activation processes and unstable raw material composition in existing technologies, thereby improving the activation rate of coal gangue.

[0010] The above-mentioned method for thermal activation of coal gangue is characterized in that the activated powder possesses pozzolanic activity, exhibits hydraulic properties when used in conjunction with cement, and the method for testing the pozzolanic activity of the activated powder refers to GB / T 12957-2005 "Test Method for Activity of Industrial Waste Residue Used in Cement Admixtures". Depending on the different activating admixtures, the pozzolanic activity, i.e., the activation rate, of the activated powder of this invention varies, but the activation rates measured according to the above standard all exceed 75%.

[0011] The above-mentioned method for thermal activation of coal gangue is characterized in that the dry basis mass content of the coal gangue in the raw material is 85%~90%, the dry basis mass content of the activating admixture is 10%~15%, the mineral composition of the coal gangue includes more than 40% quartz sand and more than 50% clay minerals, and the chemical composition of the coal gangue includes less than 1% SO3, more than 50% SiO2, and more than 10% Al2O3. This invention ensures the successful preparation of active powder from coal gangue by controlling the content of silicon dioxide and aluminum oxide, substances with active potential, in the coal gangue.

[0012] The above-mentioned method for thermal activation of coal gangue is characterized in that the activating admixture is composed of a flux and a solid waste admixture in a mass ratio of 30:70, wherein the flux is composed of potassium feldspar, sodium feldspar, and diopside in a mass ratio of 30:20:50, and the solid waste admixture is domestic sewage sludge, carbide slag, or aluminum ash, wherein the chemical composition of the domestic sewage sludge contains more than 5% Al2O3 and SiO2 by mass, and the SiO2 / Al2O3 ratio is greater than 1.18; the chemical composition of the carbide slag contains more than 40% CaO by mass; the chemical composition of the aluminum ash contains more than 40% Al2O3 by mass, and the mineral composition contains less than 15% AlN by mass; the dry basis mass content of the activating admixture is less than 15%, wherein the dry basis mass content of the domestic sewage sludge is less than 5%, the dry basis mass content of the carbide slag is less than 10%, and the dry basis mass content of the aluminum ash is less than 5%. This invention controls the content of solubilizing alkaline oxides (such as K2O, Na2O, Al2O3, SiO2, and CaO) by controlling the composition of the activating admixture from flux and solid waste admixtures. The flux consists of potassium feldspar (K2O·Al2O3·6SiO2), sodium feldspar (Na2O·Al2O3·6SiO2), and diopside (CaMg(SiO3)). The solid waste admixtures are sewage sludge, carbide slag, or aluminum ash. This effectively controls the content of solubilizing alkaline oxides (such as K2O, Na2O, Al2O3, SiO2, and CaO), lowers the eutectic temperature, and ensures the activity of coal gangue. When activated, coal gangue undergoes a small amount of liquid-phase reaction at a relatively low thermal activation temperature range (usually 600℃~950℃), generating active substances. This avoids the excessive addition of activating admixtures, which can negatively impact the molding effect of the coal gangue. Depending on the type and amount of molten material in the activating admixture, the optimal activation temperature fluctuates within the range of 850℃~950℃. Simultaneously, a small amount of calcium oxide and silicon dioxide melt to form calcium silicate, i.e., cement, which is beneficial for improving the activation performance of the active powder.

[0013] The above-mentioned method for thermal activation of coal gangue is characterized by comprising the following steps:

[0014] Step 1, Crushing: The raw materials are pre-treated and crushed to a particle size of less than 1 mm for coal gangue, and the activating admixture is crushed to a particle size of less than 0.5 mm;

[0015] Step 2, Mixing: Mix the pre-treated and crushed raw materials from Step 1 with the crushed and activated admixture, then stir at low speed for 2-5 minutes, followed by high speed for 2-5 minutes to obtain a homogeneous dry material. Add water to the homogeneous dry material in several batches to obtain a wet material; the total mass of water added is 8%-10% of the mass of the homogeneous dry material.

[0016] Step 3, Homogenization: After sealing the wet material obtained in Step 2, homogenize it at a temperature of 25℃~35℃ for 36h~48h, and shake the sealed bag 10 times every 12h to break up the clumps of wet material.

[0017] Step 4, Molding: The homogenized wet material from Step 3 is subjected to static pressing to obtain a billet;

[0018] Step 5: Drying: Dry the billet obtained in Step 4 until the residual water content is less than 3% by mass;

[0019] Step 6, Firing: The dried billet from Step 5 is kept at a thermal activation temperature of 850℃~950℃ for 6h~8h to obtain a sintered billet;

[0020] Step 7: Cooling: Cool the sintered billet obtained in Step 6 to room temperature at a cooling rate of more than 10℃ / min, and store it in a sealed container;

[0021] Step 8, Grinding: Grind the sintered blank sealed in Step 7 to below 180 mesh using a ball mill, and then seal and store it to obtain active powder; the grinding process is as follows: first grind at a low speed of 400 rpm for 20 min to 30 min, and then grind at a high speed of 650 rpm for 15 min to 20 min.

[0022] This invention first crushes the raw materials and activating admixtures to a certain particle size before mixing them in a specific ratio, which facilitates uniform mixing. The mixture is then thoroughly mixed using both low-speed and high-speed stirring. Water is then added in stages. Since the raw materials and activating admixtures have different sensitivities to water, adding water in stages promotes thorough mixing of each material with water, avoiding agglomeration caused by adding water all at once. Homogenization at room temperature further promotes the mixing of the raw materials and water, which is beneficial for maximizing the plasticity of the raw materials and improving their molding performance. The material is then further processed by static pressing to obtain a blank, which is then dried. Controlling the residual water content prevents excessive residual moisture from causing the blank to crack due to thermal expansion during thermal activation and calcination. Further thermal activation through calcination yields a sintered blank. By controlling the thermal activation temperature and holding time, the crystal structure changes and becomes active, significantly stimulating the activity of the coal gangue and ensuring the production of active powder. Rapid cooling further promotes the disintegration of the crystal structure to enhance the activity of the active powder, while preventing the active powder from losing activity due to moisture absorption. The final product is an active powder.

[0023] The above-mentioned method for thermal activation of coal gangue is characterized in that, when the solid waste admixture in the activation admixture of step one is domestic sewage sludge, the dried billet in step six is ​​heated to a thermal activation temperature of 850℃~900℃ at a heating rate of 5℃ / min and held at that temperature for 6h~8h; when the solid waste admixture in the activation admixture of step one is carbide slag, the dried billet in step six is ​​heated to a thermal activation temperature of 850℃~950℃ at a heating rate of 5℃ / min and held at that temperature for 6h~8h; when the solid waste admixture in the activation admixture of step one is aluminum ash, the dried billet in step six is ​​heated to a thermal activation temperature of 800℃~900℃ at a heating rate of 5℃ / min and held at that temperature for 6h~8h.

[0024] Compared with the prior art, the present invention has the following advantages:

[0025] 1. This invention uses coal gangue as the main raw material. By adding an activating admixture, the thermal activation temperature of coal gangue is reduced to below 1000℃, which greatly stimulates the activity of coal gangue. At the same time, combined with mechanical activation, the quartz minerals in the coal gangue form unsaturated residual bonds, producing active silica, which further stimulates the activity of coal gangue and improves the activation rate of coal gangue.

[0026] 2. The pozzolanic activity of the active powder prepared by adding an activating admixture in combination with thermal activation and mechanical activation reaches more than 75%.

[0027] 3. Compared with other activation methods, the active powder preparation process of the present invention does not involve the addition of special chemical reagents. Both the main material and the activation admixture are solid wastes, thus achieving the goal of "waste treatment" and reducing costs.

[0028] 4. This invention enables large-scale activation of coal gangue without pollution or secondary emissions, truly achieving a zero-pollution, zero-emission approach to coal gangue waste utilization. It is an environmentally friendly new method for coal gangue activation and utilization.

[0029] 5. The active powder prepared by this invention can be directly added as a mineral admixture during the concrete preparation process, and has good application prospects.

[0030] 6. The preparation method of the present invention can activate coal gangue that is not made of kaolinite clay, and the activation temperature is low (650℃~950℃), effectively disposing of sludge, carbide slag and aluminum ash, thus improving resource utilization.

[0031] The technical solution of the present invention will be further described in detail below with reference to the accompanying drawings and embodiments. Attached Figure Description

[0032] Figure 1This is a process flow diagram of the thermal activation of coal gangue in this invention. Detailed Implementation

[0033] The chemical compositions of the coal gangue, sewage sludge, carbide slag and aluminum ash used in Examples 1 to 9 of this invention are shown in Tables 1 to 4 below.

[0034] Table 1 Chemical composition of coal gangue

[0035]

[0036] Table 2 Chemical composition of sewage sludge

[0037]

[0038] Table 3 Chemical composition of carbide slag

[0039]

[0040] Table 4 Chemical composition of aluminum ash

[0041]

[0042] The coal gangue used in Examples 1 to 9 of this invention came from a region in Fujian Province. Testing showed its natural moisture content was 5%, and its mineral composition consisted of quartz sand and clay minerals such as chlorite, illite, and sodium nitrate. The mass content of quartz sand was 53.7%, chlorite 32.3%, illite 12.2%, and sodium nitrate 1.8%. The domestic sewage sludge used contained kaolinite (1.9%), hard chlorite (4.8%), and mica (%). The amount is 4.2%; the mineral composition of the carbide slag used is 54.4% by mass of calcite, 36.2% by mass of dolomite, and 9.4% by mass of mica; the mineral composition of the aluminum ash used is 9.0% by mass of aluminum, 10.1% by mass of alumina, 14.4% by mass of aluminum nitride, 12.5% ​​by mass of spinel, 5.2% by mass of hydrated calcium silicate, 15.4% by mass of hydromanganese, and 33.4% by mass of halite.

[0043] Example 1

[0044] The active powder in this embodiment is prepared by mixing raw materials including coal gangue and an activating admixture, followed by thermal and mechanical activation; the dry basis mass content of the raw materials is 90% for coal gangue and 10% for the activating admixture.

[0045] The activating admixture is composed of flux and solid waste admixture in a mass ratio of 30:70. The flux is composed of potassium feldspar, sodium feldspar, and diopside in a mass ratio of 30:20:50. The solid waste admixture is domestic sewage sludge. The dry basis mass content of domestic sewage sludge in the activating admixture is 2.8%.

[0046] like Figure 1 As shown, the active powder in this embodiment is prepared by a method including the following steps:

[0047] Step 1, Crushing: The raw materials are pre-treated and crushed to a particle size of less than 1 mm for coal gangue, and the activating admixture is crushed to a particle size of less than 0.5 mm;

[0048] Step 2, Mixing: Mix the pre-treated and crushed raw materials from Step 1 with the crushed and activated admixture, then stir at low speed for 2 minutes, followed by high speed for 2 minutes to obtain a homogeneous dry material. Add water to the homogeneous dry material in several batches to obtain a wet material; the total mass of water added is 8% of the mass of the homogeneous dry material.

[0049] Step 3, Homogenization: After sealing the wet material obtained in Step 2, homogenize it at a temperature of 25℃~35℃ for 48 hours, and shake the sealed bag 10 times every 12 hours to break up the clumps of wet material.

[0050] Step 4, Molding: The homogenized wet material from Step 3 is subjected to static pressing to obtain a blank; the static pressing pressure is 25MPa, and the blank size is 50mm in diameter × length × (15~20)mm;

[0051] Step 5: Drying: Dry the billet obtained in Step 4 until the residual water content is 2% by mass;

[0052] Step 6, Firing: The dried billet from Step 5 is heated to the thermal activation temperature of 900℃ at a heating rate of 5℃ / min and held at that temperature for 6 hours to obtain the sintered billet;

[0053] Step 7: Cooling: Cool the sintered blank obtained in Step 6 to room temperature at a cooling rate of 10℃ / min, and store it in a sealed container;

[0054] Step 8, Grinding: Grind the sintered blank sealed in Step 7 to 180 mesh using a ball mill, and then seal and store it to obtain active powder; the grinding process is as follows: first grind at a low speed of 400 rpm for 30 min, and then grind at a high speed of 650 rpm for 15 min.

[0055] The activity index of the active powder prepared in this embodiment was determined at 7 days and 28 days according to GB / T 12957-2005 "Test Method for Activity of Industrial Waste Residue Used in Cement Blends". The strength of the test blocks at 7 days and 28 days was tested according to GB / T 2847-2005 "Pozzolanic Blends Used in Cement". The results showed that the active powder has pozzolanic activity, has hydraulic properties after being used in combination with cement, and the activation rate of the active powder was 75%.

[0056] Example 2

[0057] The active powder in this embodiment is prepared by mixing raw materials including coal gangue and an activating admixture, followed by thermal and mechanical activation; the dry basis mass content of the raw materials is 90% for coal gangue and 10% for the activating admixture.

[0058] The activating admixture is composed of flux and solid waste admixture in a mass ratio of 30:70. The flux is composed of potassium feldspar, sodium feldspar, and diopside in a mass ratio of 30:20:50. The solid waste admixture is municipal sewage sludge. The dry basis mass content of the municipal sewage sludge in the activating admixture is 4%.

[0059] like Figure 1 As shown, the active powder in this embodiment is prepared by a method including the following steps:

[0060] Step 1, Crushing: The raw materials are pre-treated and crushed to a particle size of less than 1 mm for coal gangue, and the activating admixture is crushed to a particle size of less than 0.5 mm;

[0061] Step 2, Mixing: Mix the pre-treated and crushed raw materials from Step 1 with the crushed and activated admixture, then stir at low speed for 2 minutes, followed by high speed for 2 minutes to obtain a homogeneous dry material. Add water to the homogeneous dry material in several batches to obtain a wet material; the total mass of water added is 10% of the mass of the homogeneous dry material.

[0062] Step 3, Homogenization: After sealing the wet material obtained in Step 2, homogenize it at a temperature of 25℃~35℃ for 36 hours, and shake the sealed bag 10 times every 12 hours to break up the clumps of wet material.

[0063] Step 4, Molding: The homogenized wet material from Step 3 is subjected to static pressing to obtain a blank; the static pressing pressure is 25MPa, and the blank size is 50mm in diameter × length × (15~20)mm;

[0064] Step 5: Drying: Dry the billet obtained in Step 4 until the residual water content is 3% by mass;

[0065] Step 6, Firing: The dried billet from Step 5 is heated to a thermal activation temperature of 900℃ at a heating rate of 5℃ / min and held at that temperature for 8 hours to obtain a sintered billet;

[0066] Step 7: Cooling: Cool the sintered blank obtained in Step 6 to room temperature at a cooling rate of 10℃ / min, and store it in a sealed container;

[0067] Step 8, Grinding: Grind the sintered blank sealed and stored in Step 7 to 180 mesh using a ball mill, and then seal and store it to obtain active powder; the grinding process is as follows: first grind at a low speed of 400 rpm for 20 min, and then grind at a high speed of 650 rpm for 20 min.

[0068] The activity index of the active powder prepared in this embodiment was determined at 7 days and 28 days according to GB / T 12957-2005 "Test Method for Activity of Industrial Waste Residue Used in Cement Blends". The strength of the test blocks at 7 days and 28 days was tested according to GB / T 2847-2005 "Pozzolanic Blends Used in Cement". The results showed that the active powder has pozzolanic activity, has hydraulic properties when used in combination with cement, and the activation rate of the active powder was 75.5%.

[0069] Example 3

[0070] The active powder in this embodiment is prepared by mixing raw materials including coal gangue and an activating admixture, followed by thermal and mechanical activation; the dry basis mass content of the raw materials is 90% for coal gangue and 10% for the activating admixture.

[0071] The activating admixture is composed of flux and solid waste admixture in a mass ratio of 30:70. The flux is composed of potassium feldspar, sodium feldspar, and diopside in a mass ratio of 30:20:50. The solid waste admixture is domestic sewage sludge. The dry basis mass content of the domestic sewage sludge in the activating admixture is 5%.

[0072] like Figure 1 As shown, the active powder in this embodiment is prepared by a method including the following steps:

[0073] Step 1, Crushing: The raw materials are pre-treated and crushed to a particle size of less than 1 mm for coal gangue, and the activating admixture is crushed to a particle size of less than 0.5 mm;

[0074] Step 2, Mixing: Mix the pre-treated and crushed raw materials from Step 1 with the crushed and activated admixture, then stir at low speed for 5 minutes, followed by high speed for 5 minutes to obtain a homogeneous dry material. Add water to the homogeneous dry material in several batches to obtain a wet material; the total mass of water added is 10% of the mass of the homogeneous dry material.

[0075] Step 3, Homogenization: After sealing the wet material obtained in Step 2, homogenize it at a temperature of 25℃~35℃ for 48 hours, and shake the sealed bag 10 times every 12 hours to break up the clumps of wet material.

[0076] Step 4, Molding: The homogenized wet material from Step 3 is subjected to static pressing to obtain a blank; the static pressing pressure is 25MPa, and the blank size is 50mm in diameter × length × (15~20)mm;

[0077] Step 5: Drying: Dry the billet obtained in Step 4 until the residual water content is 2% by mass;

[0078] Step 6, Firing: The dried billet from Step 5 is heated to the thermal activation temperature of 850℃ at a heating rate of 5℃ / min and held at that temperature for 8 hours to obtain the sintered billet;

[0079] Step 7: Cooling: Cool the sintered blank obtained in Step 6 to room temperature at a cooling rate of 10℃ / min, and store it in a sealed container;

[0080] Step 8, Grinding: Grind the sintered blank sealed in Step 7 to 180 mesh using a ball mill, and then seal and store it to obtain active powder; the grinding process is as follows: first grind at a low speed of 400 rpm for 30 min, and then grind at a high speed of 650 rpm for 20 min.

[0081] The activity index of the active powder prepared in this embodiment was determined at 7 days and 28 days according to GB / T 12957-2005 "Test Method for Activity of Industrial Waste Residue Used in Cement Blends". The strength of the test blocks at 7 days and 28 days was tested according to GB / T 2847-2005 "Pozzolanic Blends Used in Cement". The results showed that the active powder has pozzolanic activity, has hydraulic properties after being used in combination with cement, and the activation rate of the active powder was 76.2%.

[0082] Example 4

[0083] The active powder in this embodiment is prepared by mixing raw materials including coal gangue and an activating admixture, followed by thermal and mechanical activation; the dry basis mass content of the coal gangue in the raw materials is 85%, and the dry basis mass content of the activating admixture is 15%.

[0084] The activating admixture is composed of flux and solid waste admixture in a mass ratio of 30:70. The flux is composed of potassium feldspar, sodium feldspar, and diopside in a mass ratio of 30:20:50, and the solid waste admixture is calcium carbide slag. The dry basis mass content of the calcium carbide slag in the activating admixture is 10%.

[0085] like Figure 1As shown, the active powder in this embodiment is prepared by a method including the following steps:

[0086] Step 1, Crushing: The raw materials are pre-treated and crushed to a particle size of less than 1 mm for coal gangue, and the activating admixture is crushed to a particle size of less than 0.5 mm;

[0087] Step 2, Mixing: Mix the pre-treated and crushed raw materials from Step 1 with the crushed and activated admixture, then stir at low speed for 5 minutes, followed by high speed for 5 minutes to obtain a homogeneous dry material. Add water to the homogeneous dry material in several batches to obtain a wet material; the total mass of water added is 8% of the mass of the homogeneous dry material.

[0088] Step 3, Homogenization: After sealing the wet material obtained in Step 2, homogenize it at a temperature of 25℃~35℃ for 36 hours, and shake the sealed bag 10 times every 12 hours to break up the clumps of wet material.

[0089] Step 4, Molding: The homogenized wet material from Step 3 is subjected to static pressing to obtain a blank; the static pressing pressure is 25MPa, and the blank size is 50mm in diameter × length × (15~20)mm;

[0090] Step 5: Drying: Dry the billet obtained in Step 4 until the residual water content is 3% by mass;

[0091] Step 6, Firing: The dried billet from Step 5 is heated to the thermal activation temperature of 850℃ at a heating rate of 5℃ / min and held at that temperature for 8 hours to obtain the sintered billet;

[0092] Step 7: Cooling: Cool the sintered blank obtained in Step 6 to room temperature at a cooling rate of 10℃ / min, and store it in a sealed container;

[0093] Step 8, Grinding: Grind the sintered blank sealed in Step 7 to 180 mesh using a ball mill, and then seal and store it to obtain active powder; the grinding process is as follows: first grind at a low speed of 400 rpm for 30 min, and then grind at a high speed of 650 rpm for 15 min.

[0094] The activity index of the active powder prepared in this embodiment was determined at 7 days and 28 days according to GB / T 12957-2005 "Test Method for Activity of Industrial Waste Residue Used in Cement Blends". The strength of the test blocks at 7 days and 28 days was tested according to GB / T 2847-2005 "Pozzolanic Blends Used in Cement". The results showed that the active powder has pozzolanic activity, has hydraulic properties when used in combination with cement, and the activation rate of the active powder was 77.8%.

[0095] Example 5

[0096] The active powder in this embodiment is prepared by mixing raw materials including coal gangue and an activating admixture, followed by thermal and mechanical activation; the dry basis mass content of the raw materials is 90% for coal gangue and 10% for the activating admixture.

[0097] The activating admixture is composed of flux and solid waste admixture in a mass ratio of 30:70. The flux is composed of potassium feldspar, sodium feldspar, and diopside in a mass ratio of 30:20:50, and the solid waste admixture is calcium carbide slag. The dry basis mass content of calcium carbide slag in the activating admixture is 7.5%.

[0098] like Figure 1 As shown, the active powder in this embodiment is prepared by a method including the following steps:

[0099] Step 1, Crushing: The raw materials are pre-treated and crushed to a particle size of less than 1 mm for coal gangue, and the activating admixture is crushed to a particle size of less than 0.5 mm;

[0100] Step 2, Mixing: Mix the pre-treated and crushed raw materials from Step 1 with the crushed and activated admixture, then stir at low speed for 2 minutes, followed by high speed for 2 minutes to obtain a homogeneous dry material. Add water to the homogeneous dry material in several batches to obtain a wet material; the total mass of water added is 10% of the mass of the homogeneous dry material.

[0101] Step 3, Homogenization: After sealing the wet material obtained in Step 2, homogenize it at a temperature of 25℃~35℃ for 48 hours, and shake the sealed bag 10 times every 12 hours to break up the clumps of wet material.

[0102] Step 4, Molding: The homogenized wet material from Step 3 is subjected to static pressing to obtain a blank; the static pressing pressure is 25MPa, and the blank size is 50mm in diameter × length × (15~20)mm;

[0103] Step 5: Drying: Dry the billet obtained in Step 4 until the residual water content is 3% by mass;

[0104] Step 6, Firing: The dried billet from Step 5 is heated to the thermal activation temperature of 950℃ at a heating rate of 5℃ / min and held at that temperature for 6 hours to obtain the sintered billet.

[0105] Step 7: Cooling: Cool the sintered blank obtained in Step 6 to room temperature at a cooling rate of 10℃ / min, and store it in a sealed container;

[0106] Step 8, Grinding: Grind the sintered blank sealed and stored in Step 7 to 180 mesh using a ball mill, and then seal and store it to obtain active powder; the grinding process is as follows: first grind at a low speed of 400 rpm for 20 min, and then grind at a high speed of 650 rpm for 20 min.

[0107] The activity index of the active powder prepared in this embodiment was determined at 7 days and 28 days according to GB / T 12957-2005 "Test Method for Activity of Industrial Waste Residue Used in Cement Admixtures". The strength of the test blocks at 7 days and 28 days was tested according to GB / T 2847-2005 "Pozzolanic Admixtures Used in Cement". The results showed that the active powder has pozzolanic activity, has hydraulic properties after being used in combination with cement, and the activation rate of the active powder was 76%.

[0108] Example 6

[0109] The active powder in this embodiment is prepared by mixing raw materials including coal gangue and an activating admixture, followed by thermal and mechanical activation; the dry basis mass content of the raw materials is 90% for coal gangue and 10% for the activating admixture.

[0110] The activating admixture is composed of flux and solid waste admixture in a mass ratio of 30:70. The flux is composed of potassium feldspar, sodium feldspar, and diopside in a mass ratio of 30:20:50, and the solid waste admixture is calcium carbide slag. The dry basis mass content of calcium carbide slag in the activating admixture is 4.8%.

[0111] like Figure 1 As shown, the active powder in this embodiment is prepared by a method including the following steps:

[0112] Step 1, Crushing: The raw materials are pre-treated and crushed to a particle size of less than 1 mm for coal gangue, and the activating admixture is crushed to a particle size of less than 0.5 mm;

[0113] Step 2, Mixing: Mix the pre-treated and crushed raw materials from Step 1 with the crushed and activated admixture, then stir at low speed for 2 minutes, followed by high speed for 2 minutes to obtain a homogeneous dry material. Add water to the homogeneous dry material in several batches to obtain a wet material; the total mass of water added is 10% of the mass of the homogeneous dry material.

[0114] Step 3, Homogenization: After sealing the wet material obtained in Step 2, homogenize it at a temperature of 25℃~35℃ for 48 hours, and shake the sealed bag 10 times every 12 hours to break up the clumps of wet material.

[0115] Step 4, Molding: The homogenized wet material from Step 3 is subjected to static pressing to obtain a blank; the static pressing pressure is 25MPa, and the blank size is 50mm in diameter × length × (15~20)mm;

[0116] Step 5: Drying: Dry the billet obtained in Step 4 until the residual water content is 3% by mass;

[0117] Step 6, Firing: The dried billet from Step 5 is heated to the thermal activation temperature of 950℃ at a heating rate of 5℃ / min and held at that temperature for 6 hours to obtain the sintered billet.

[0118] Step 7: Cooling: Cool the sintered blank obtained in Step 6 to room temperature at a cooling rate of 10℃ / min, and store it in a sealed container;

[0119] Step 8, Grinding: Grind the sintered blank sealed and stored in Step 7 to 180 mesh using a ball mill, and then seal and store it to obtain active powder; the grinding process is as follows: first grind at a low speed of 400 rpm for 20 min, and then grind at a high speed of 650 rpm for 20 min.

[0120] The activity index of the active powder prepared in this embodiment was determined at 7 days and 28 days according to GB / T 12957-2005 "Test Method for Activity of Industrial Waste Residue Used in Cement Blends". The strength of the test blocks at 7 days and 28 days was tested according to GB / T 2847-2005 "Pozzolanic Blends Used in Cement". The results showed that the active powder has pozzolanic activity, has hydraulic properties after being used in combination with cement, and the activation rate of the active powder was 75.3%.

[0121] Example 7

[0122] The active powder in this embodiment is prepared by mixing raw materials including coal gangue and an activating admixture, followed by thermal and mechanical activation; the dry basis mass content of the raw materials is 90% for coal gangue and 10% for the activating admixture.

[0123] The activating admixture is composed of flux and solid waste admixture in a mass ratio of 30:70. The flux is composed of potassium feldspar, sodium feldspar, and diopside in a mass ratio of 30:20:50, and the solid waste admixture is aluminum ash. The dry basis mass content of aluminum ash in the activating admixture is 4.1%.

[0124] like Figure 1 As shown, the active powder in this embodiment is prepared by a method including the following steps:

[0125] Step 1, Crushing: The raw materials are pre-treated and crushed to a particle size of less than 1 mm for coal gangue, and the activating admixture is crushed to a particle size of less than 0.5 mm;

[0126] Step 2, Mixing: Mix the pre-treated and crushed raw materials from Step 1 with the crushed and activated admixture, then stir at low speed for 2 minutes, followed by high speed for 2 minutes to obtain a homogeneous dry material. Add water to the homogeneous dry material in several batches to obtain a wet material; the total mass of water added is 10% of the mass of the homogeneous dry material.

[0127] Step 3, Homogenization: After sealing the wet material obtained in Step 2, homogenize it at a temperature of 25℃~35℃ for 36 hours, and shake the sealed bag 10 times every 12 hours to break up the clumps of wet material.

[0128] Step 4, Molding: The homogenized wet material from Step 3 is subjected to static pressing to obtain a blank; the static pressing pressure is 25MPa, and the blank size is 50mm in diameter × length × (15~20)mm;

[0129] Step 5: Drying: Dry the billet obtained in Step 4 until the residual water content is 3% by mass;

[0130] Step 6, Firing: The dried billet from Step 5 is heated to the thermal activation temperature of 800℃ at a heating rate of 5℃ / min and held at that temperature for 8 hours to obtain the sintered billet;

[0131] Step 7: Cooling: Cool the sintered blank obtained in Step 6 to room temperature at a cooling rate of 10℃ / min, and store it in a sealed container;

[0132] Step 8, Grinding: Grind the sintered blank sealed and stored in Step 7 to 180 mesh using a ball mill, and then seal and store it to obtain active powder; the grinding process is as follows: first grind at a low speed of 400 rpm for 25 min, and then grind at a high speed of 650 rpm for 20 min.

[0133] The activity index of the active powder prepared in this embodiment was determined at 7 days and 28 days according to GB / T 12957-2005 "Test Method for Activity of Industrial Waste Residue Used in Cement Blends". The strength of the test blocks at 7 days and 28 days was tested according to GB / T 2847-2005 "Pozzolanic Blends Used in Cement". The results showed that the active powder has pozzolanic activity, has hydraulic properties when used in combination with cement, and the activation rate of the active powder was 76.3%.

[0134] Example 8

[0135] The active powder in this embodiment is prepared by mixing raw materials including coal gangue and an activating admixture, followed by thermal and mechanical activation; the dry basis mass content of the raw materials is 90% for coal gangue and 10% for the activating admixture.

[0136] The activating admixture is composed of flux and solid waste admixture in a mass ratio of 30:70. The flux is composed of potassium feldspar, sodium feldspar, and diopside in a mass ratio of 30:20:50, and the solid waste admixture is aluminum ash. The dry basis mass content of the aluminum ash in the activating admixture is 5%.

[0137] like Figure 1 As shown, the active powder in this embodiment is prepared by a method including the following steps:

[0138] Step 1, Crushing: The raw materials are pre-treated and crushed to a particle size of less than 1 mm for coal gangue, and the activated admixture, domestic sewage sludge, is crushed to a particle size of less than 0.5 mm;

[0139] Step 2, Mixing: Mix the pre-treated and crushed raw materials from Step 1 with the crushed and activated admixture, then stir at low speed for 2 minutes, followed by high speed for 2 minutes to obtain a homogeneous dry material. Add water to the homogeneous dry material in several batches to obtain a wet material; the total mass of water added is 10% of the mass of the homogeneous dry material.

[0140] Step 3, Homogenization: After sealing the wet material obtained in Step 2, homogenize it at a temperature of 25℃~35℃ for 36 hours, and shake the sealed bag 10 times every 12 hours to break up the clumps of wet material.

[0141] Step 4, Molding: The homogenized wet material from Step 3 is subjected to static pressing to obtain a blank; the static pressing pressure is 25MPa, and the blank size is 50mm in diameter × length × (15~20)mm;

[0142] Step 5: Drying: Dry the billet obtained in Step 4 until the residual water content is 3% by mass;

[0143] Step 6, Firing: The dried billet from Step 5 is heated to the thermal activation temperature of 800℃ at a heating rate of 5℃ / min and held at that temperature for 8 hours to obtain the sintered billet;

[0144] Step 7: Cooling: Cool the sintered blank obtained in Step 6 to room temperature at a cooling rate of 10℃ / min, and store it in a sealed container;

[0145] Step 8, Grinding: Grind the sintered blank sealed and stored in Step 7 to 180 mesh using a ball mill, and then seal and store it to obtain active powder; the grinding process is as follows: first grind at a low speed of 400 rpm for 25 min, and then grind at a high speed of 650 rpm for 20 min.

[0146] The activity index of the active powder prepared in this embodiment was determined at 7 days and 28 days according to GB / T 12957-2005 "Test Method for Activity of Industrial Waste Residue Used in Cement Admixtures". The strength of the test blocks at 7 days and 28 days was tested according to GB / T 2847-2005 "Pozzolanic Admixtures Used in Cement". The results showed that the active powder has pozzolanic activity, has hydraulic properties after being used in combination with cement, and the activation rate of the active powder was 76.9%.

[0147] Example 9

[0148] The active powder in this embodiment is prepared by mixing raw materials including coal gangue and an activating admixture, followed by thermal and mechanical activation; the dry basis mass content of the raw materials is 90% for coal gangue and 10% for the activating admixture.

[0149] The activating admixture is composed of flux and solid waste admixture in a mass ratio of 30:70. The flux is composed of potassium feldspar, sodium feldspar, and diopside in a mass ratio of 30:20:50, and the solid waste admixture is aluminum ash. The dry basis mass content of the aluminum ash in the activating admixture is 3.6%.

[0150] like Figure 1 As shown, the active powder in this embodiment is prepared by a method including the following steps:

[0151] Step 1, Crushing: The raw materials are pre-treated and crushed to a particle size of less than 1 mm for coal gangue, and the activated admixture, domestic sewage sludge, is crushed to a particle size of less than 0.5 mm;

[0152] Step 2, Mixing: Mix the pre-treated and crushed raw materials from Step 1 with the crushed and activated admixture, then stir at low speed for 2 minutes, followed by high speed for 2 minutes to obtain a homogeneous dry material. Add water to the homogeneous dry material in several batches to obtain a wet material; the total mass of water added is 8% of the mass of the homogeneous dry material.

[0153] Step 3, Homogenization: After sealing the wet material obtained in Step 2, homogenize it at a temperature of 25℃~35℃ for 48 hours, and shake the sealed bag 10 times every 12 hours to break up the clumps of wet material.

[0154] Step 4, Molding: The homogenized wet material from Step 3 is subjected to static pressing to obtain a blank; the static pressing pressure is 25MPa, and the blank size is 50mm in diameter × length × (15~20)mm;

[0155] Step 5: Drying: Dry the billet obtained in Step 4 until the residual water content is 3% by mass;

[0156] Step 6, Firing: The dried billet from Step 5 is heated to the thermal activation temperature of 900℃ at a heating rate of 5℃ / min and held at that temperature for 6 hours to obtain the sintered billet;

[0157] Step 7: Cooling: Cool the sintered blank obtained in Step 6 to room temperature at a cooling rate of 10℃ / min, and store it in a sealed container;

[0158] Step 8, Grinding: Grind the sintered blank sealed in Step 7 to 180 mesh using a ball mill, and then seal and store it to obtain active powder; the grinding process is as follows: first grind at a low speed of 400 rpm for 30 min, and then grind at a high speed of 650 rpm for 20 min.

[0159] The activity index of the active powder prepared in this embodiment was determined at 7 days and 28 days according to GB / T 12957-2005 "Test Method for Activity of Industrial Waste Residue Used in Cement Blends". The strength of the test blocks at 7 days and 28 days was tested according to GB / T 2847-2005 "Pozzolanic Blends Used in Cement". The results showed that the active powder has pozzolanic activity, has hydraulic properties after being used in combination with cement, and the activation rate of the active powder was 75.2%.

[0160] The above description is merely a preferred embodiment of the present invention and is not intended to limit the invention in any way. Any simple modifications, alterations, and equivalent changes made to the above embodiments based on the inventive essence shall still fall within the protection scope of the present invention.

Claims

1. A method for thermal activation of coal gangue, characterized in that, Using coal gangue and an activating admixture as raw materials, the process involves crushing, mixing and mechanical activation, homogenization, molding, drying, calcination with medium-temperature activation, cooling, and grinding to prepare activated powder. The activating admixture is composed of flux and solid waste admixture in a mass ratio of 30:

70. The flux is composed of potassium feldspar, sodium feldspar, and diopside in a mass ratio of 30:20:

50. The solid waste admixture is sewage sludge, carbide slag, or aluminum ash. The sewage sludge contains more than 5% Al2O3 and SiO2 by mass, and the SiO2 / Al2O3 ratio is greater than 1.

18. The carbide slag contains more than 40% CaO by mass, and the aluminum ash contains more than 40% Al2O3 by mass and less than 15% AlN by mass. The method includes the following steps: Step 1, Crushing: The raw materials are pre-treated and crushed to a particle size of less than 1 mm for coal gangue, and the activating admixture is crushed to a particle size of less than 0.5 mm; Step 2, Mixing: Mix the pre-treated and crushed raw materials from Step 1 with the crushed and activated admixture, then stir at low speed for 2-5 minutes, followed by high speed for 2-5 minutes to obtain a homogeneous dry material. Add water to the homogeneous dry material in several batches to obtain a wet material; the total mass of water added is 8%-10% of the mass of the homogeneous dry material. Step 3, Homogenization: After sealing the wet material obtained in Step 2, homogenize it at a temperature of 25℃~35℃ for 36h~48h, and shake the sealed bag 10 times every 12h to break up the clumps of wet material. Step 4, Molding: The homogenized wet material from Step 3 is subjected to static pressing to obtain a billet; Step 5: Drying: Dry the billet obtained in Step 4 until the residual water content is less than 3% by mass; Step 6, Firing: The dried billet from Step 5 is kept at a thermal activation temperature of 850℃~950℃ for 6h~8h to obtain a sintered billet; Step 7: Cooling: Cool the sintered billet obtained in Step 6 to room temperature at a cooling rate of more than 10℃ / min, and store it in a sealed container; Step 8, Grinding: Grind the sintered blank sealed in Step 7 to below 180 mesh using a ball mill, and then seal and store it to obtain active powder; the grinding process is as follows: first grind at a low speed of 400 rpm for 20 min to 30 min, and then grind at a high speed of 650 rpm for 15 min to 20 min.

2. The method for thermal activation of coal gangue according to claim 1, characterized in that, The active powder has pozzolanic activity and exhibits hydraulic properties when used in conjunction with cement. The pozzolanic activity test method for the active powder refers to GB / T 12957-2005 "Test Method for Activity of Industrial Waste Residue Used in Cement Admixtures".

3. The method for thermal activation of coal gangue according to claim 1, characterized in that, The raw material contains 85% to 90% dry basis mass of coal gangue, and the activating admixture contains 10% to 15% dry basis mass of coal gangue. The mineral composition of the coal gangue contains more than 40% quartz sand and more than 50% clay minerals. The chemical composition of the coal gangue contains less than 1% SO3, more than 50% SiO2, and more than 10% Al2O3.

4. The method for thermal activation of coal gangue according to claim 1, characterized in that, The dry basis mass content of the activating admixture is less than 15%, of which the dry basis mass content of domestic sewage sludge is less than 5%, the dry basis mass content of carbide slag is less than 10%, and the dry basis mass content of aluminum ash is less than 5%.

5. The method for thermal activation of coal gangue according to claim 1, characterized in that, When the solid waste admixture in the activating admixture described in step one is domestic sewage sludge, the dried billet in step six is ​​heated to a thermal activation temperature of 850℃~900℃ at a heating rate of 5℃ / min and held at that temperature for 6h~8h; when the solid waste admixture in the activating admixture described in step one is carbide slag, the dried billet in step six is ​​heated to a thermal activation temperature of 850℃~950℃ at a heating rate of 5℃ / min and held at that temperature for 6h~8h; when the solid waste admixture in the activating admixture described in step one is aluminum ash, the dried billet in step six is ​​heated to a thermal activation temperature of 800℃~900℃ at a heating rate of 5℃ / min and held at that temperature for 6h~8h.

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