Coal-based solid waste mineralization material reinforced by multi-walled carbon nanotubes and preparation method of coal-based solid waste mineralization material

Abstract

The invention discloses a coal-based solid waste mineralization material reinforced by multi-walled carbon nanotubes and a preparation method thereof, and the coal-based solid waste mineralization material comprises the following components in parts by weight: 5-30 parts of an alkaline excitation solution, 0.01-5 parts of a multi-walled carbon nanotube suspension, 10-140 parts of fly ash and 10-50 parts of slag. According to the method, the multi-walled carbon nanotubes are doped into the coal-based solid waste mineralization material, the multi-walled carbon nanotubes are used as effective nucleation sites in the hydration process of the coal-based solid waste material, deposition and growth of hydration products at micro-pores and micro-cracks are promoted, defect filling is achieved, and the bridging effect is achieved; the multiwalled carbon nanotubes can better adsorb CO2, and the adsorbed CO2 and active ions such as calcium oxide and magnesium oxide in the solid waste are mineralized to form a compact filling body, so that the strength of the coal-based solid waste mineralizing material is further improved; and the coal-based solid waste mineralization material also has high heat-conducting property by utilizing the high heat-conducting property of the multi-walled carbon nanotubes.

Description

Technical Field

[0001] This invention belongs to the field of coal-based solid waste resource utilization technology, specifically relating to a coal-based solid waste mineralization material reinforced with multi-walled carbon nanotubes and its preparation method. Background Technology

[0002] Coal, as a crucial basic energy source, generates massive amounts of coal-based solid waste through its large-scale mining and utilization. This waste (such as slag and fly ash) contains many harmful substances, and improper disposal can lead to ecological and environmental risks. Simultaneously, coal utilization is a major source of carbon dioxide emissions, and reducing carbon emissions urgently requires energy structure adjustments and an increase in the proportion of low-carbon energy. Therefore, expanding efficient and synergistic utilization pathways for coal-based solid waste and carbon dioxide is vital for mitigating their negative environmental impacts.

[0003] Geothermal energy, as a competitive low-carbon energy source, is receiving increasing attention for its development in mining. To achieve effective development and utilization of geothermal energy throughout the entire lifecycle of a mine, a strategy combining backfill mining with geothermal energy extraction has been proposed. However, current research in this field primarily focuses on optimizing the heat transfer performance of heat exchange pipes within the backfill material, while key thermal properties such as high heat storage capacity and high thermal conductivity of the backfill material itself have not received sufficient attention. Therefore, there is an urgent need to develop a mineralized solidified coal-based solid waste backfill material with high heat absorption performance to promote the synergistic development of mining geothermal energy, solid waste resource utilization, and carbon dioxide emission reduction. Summary of the Invention

[0004] The purpose of this invention is to provide a coal-based solid waste mineralization material reinforced with multi-walled carbon nanotubes and its preparation method. By adding multi-walled carbon nanotube suspension to the coal-based solid waste mineralization material, the heat absorption and mechanical properties of the material can be improved, thereby achieving the purpose of developing and utilizing geothermal energy and filling goaf areas.

[0005] To achieve the above objectives, the present invention provides a coal-based solid waste mineralization material reinforced with multi-walled carbon nanotubes. By weight, the coal-based solid waste mineralization material comprises: 5-30 parts of alkaline activation solution, 0.01-5 parts of multi-walled carbon nanotube suspension, 10-140 parts of fly ash, and 10-50 parts of slag.

[0006] This invention provides a method for preparing coal-based solid waste mineralization materials reinforced with multi-walled carbon nanotubes, the specific steps of which are as follows:

[0007] Step 1: Mix sodium hydroxide granules and water at a mass ratio of (1-20):100 to obtain a sodium hydroxide solution. After the sodium hydroxide solution cools to room temperature, add sodium silicate to the sodium hydroxide solution at a mass ratio of (1-15):100. Stir well to obtain an alkaline activation solution.

[0008] Step 2: Mix multi-walled carbon nanotubes, surfactants and water at a mass ratio of (0.01-5):(0.1-20):100, stir the mixture at 200 r / min for 1 min-10 min, and then sonicate for 10 min-60 min to obtain a multi-walled carbon nanotube suspension.

[0009] Step 3: Grind the fly ash to a particle size of 0.1μm to 250 μm and the slag to a particle size of 0.1μm to 250 μm. Then, mix them evenly according to the mass ratio of fly ash to slag (1 to 14): (1 to 5) to obtain a solid material.

[0010] Step 4: Add the alkaline activation solution and multi-walled carbon nanotube suspension prepared in Step 1 and Step 2 to the solid material in Step 3 and stir to obtain coal-based solid waste slurry. The mass ratio of alkaline activation solution, multi-walled carbon nanotube suspension and solid material is (5~30):(0.01~5):(20~190).

[0011] Step 5: Under normal temperature and pressure conditions, carbon dioxide gas is injected into the coal-based solid waste slurry from Step 4, and a mineralization reaction is carried out under stirring to prepare a coal-based solid waste mineralization slurry. During this process, the flow rate of injected carbon dioxide and the flow rate of outflowing carbon dioxide are recorded.

[0012] Step 6: Pour the coal-based solid waste mineralization slurry after the mineralization reaction in Step 5 into a mold, and after curing and solidification, obtain the coal-based solid waste mineralization material.

[0013] Preferably, in step 1, the sodium silicate is Na2O·nSiO2, wherein the Na2O content is 10% to 19.8% and the SiO2 content is 20% to 35.6%.

[0014] Preferably, in step 2, the multi-walled carbon nanotubes have a length of 1 μm to 50 μm, an outer diameter of 1 nm to 15 nm, an inner diameter of 0.5 nm to 5 nm, and a specific surface area of ​​50 m². 2 / g~2500 m 2 / g, density is 0.01 g / cm³ 3 ~15 g / cm 3 .

[0015] Preferably, in step 2, the surfactant is a water-soluble polymeric surfactant or an ionic surfactant, wherein the surfactant is selected from at least one of polyvinyl alcohol, polyvinylpyrrolidone, sodium dodecyl sulfate, and polycarboxylate.

[0016] Preferably, in step 2, the ultrasonic disperser is used to ultrasonically treat the obtained mixed solution in a pulse mode of 3 seconds on and 3 seconds off. The frequency of ultrasonic treatment is 20 kHz to 40 kHz, and the cumulative ultrasonic time is 10 min to 60 min. During this period, the water in the ultrasonic disperser is replaced every 2 min to 5 min to control the water temperature during ultrasonic treatment to be below 45 ℃.

[0017] Preferably, in step 4, the stirring rate is 120 r / min to 1000 r / min, the stirring time is 2 min to 10 min, and the yield stress of the prepared coal-based solid waste slurry is 4.5 Pa to 80 Pa, and the spread is 195 mm to 350 mm.

[0018] Preferably, in step 5, when the coal-based solid waste slurry is 100g to 3500g, the injected carbon dioxide flow rate is 0.1 L / min to 10 L / min, the stirring rate is 100 r / min to 850 r / min, the reaction time is 5 min to 60 min, and the carbon dioxide mineralization rate is 2 mgCO2 / g to 40 mgCO2 / g.

[0019] Preferably, in step 6, the curing temperature is 20°C to 25°C, the curing humidity is 90% to 95%, and the curing time is 3 to 28 days.

[0020] Preferably, the compressive strength of the coal-based solid waste mineralization material is 1.85 MPa to 13.76 MPa, the thermal conductivity is 0.24 W / (m·K) to 0.75 W / (m·K), the specific heat capacity is 0.57 KJ / (kg·K) to 1.89 KJ / (kg·K), and the heat storage coefficient is 4.28 W / (m·K). 2 ·K)~12.46 W / (m 2 ·K).

[0021] Compared with the prior art, the beneficial effects of the present invention are as follows:

[0022] This invention significantly improves the performance of coal-based solid waste mineralization materials by appropriately incorporating multi-walled carbon nanotubes (MWCNTs). The main advantages are: MWCNTs act as effective nucleation sites during hydration, promoting the deposition and growth of hydration products in micropores and microcracks, thus filling defects and providing a bridging effect; the hydration products tightly encapsulate the MWCNTs to form a high-strength matrix, and the uniformly dispersed MWCNTs interconnect within the matrix to construct a three-dimensional network structure, whose high thermal conductivity forms a "thermal pathway network"; furthermore, the high specific surface area of ​​the MWCNTs serves as CO2 adsorption sites, where the adsorbed CO2 mineralizes with active ions such as calcium oxide and magnesium oxide in the solid waste to form a dense filling body, further enhancing the strength of the coal-based solid waste mineralization material; this structure effectively transfers loads, strengthens the connection between different matrix regions, and ultimately forms a reinforced framework with higher structural integrity, improving the mechanical properties and microstructure of the coal-based solid waste mineralization material.

[0023] The coal-based solid waste mineralization material prepared by this invention can also have high thermal conductivity due to the high thermal conductivity of the multi-walled carbon nanotubes. After the coal-based solid waste mineralization material fills the goaf, it can absorb more geothermal energy from the surrounding rocks. Moreover, the thermal conductivity of geothermal energy in the coal-based solid waste mineralization material is relatively high, which improves the overall thermal diffusivity after the coal-based solid waste mineralization material is filled. In addition, it can also improve the heat exchange rate of the heat exchange medium in the pre-buried heat exchange pipe, thereby improving the utilization rate of geothermal energy. Detailed Implementation

[0024] The present invention discloses a coal-based solid waste mineralization material reinforced by multi-walled carbon nanotubes, comprising, by weight: 5-30 parts of alkaline activation solution, 0.01-5 parts of multi-walled carbon nanotube suspension, 10-140 parts of fly ash, and 10-50 parts of slag.

[0025] As a specific implementation, the alkaline activation solution is a solution prepared by mixing sodium silicate, sodium hydroxide and water in a mass ratio of (1-15):(1-20):100.

[0026] As a specific embodiment, the multi-walled carbon nanotube suspension is a suspension prepared by multi-walled carbon nanotubes, surfactants and water in a mass ratio of (0.01-5):(0.1-20):100.

[0027] The specific steps for preparing the above-mentioned coal-based solid waste mineralization materials are as follows:

[0028] Step 1: Add sodium hydroxide granules to water at a mass ratio of (1-20):100. Mix and stir until the sodium hydroxide granules are completely dissolved in the water to obtain a sodium hydroxide solution. After the sodium hydroxide solution cools to room temperature, add sodium silicate to the sodium hydroxide solution at a mass ratio of (1-15):100. Mix and stir until a basic activation solution is obtained.

[0029] Step 2: Mix multi-walled carbon nanotubes, surfactants and water at a mass ratio of (0.01-5):(0.1-20):100. Stir the mixture with a magnetic stirrer at a speed of 200 r / min for 1 min-10 min. Then, use an ultrasonic disperser to treat the resulting mixture with ultrasound for 10 min-60 min to obtain a multi-walled carbon nanotube suspension.

[0030] Step 3: Grind the fly ash to a particle size of 0.1 μm to 250 μm and the slag to a particle size of 0.1 μm to 250 μm. Then, mix them evenly according to the mass ratio of fly ash to slag (1 to 14): (1 to 5) to obtain a solid material.

[0031] Step 4: Add the alkaline activation solution and multi-walled carbon nanotube suspension prepared in Step 1 and Step 2 to the solid material in Step 3 and mix them to obtain coal-based solid waste slurry. The mass ratio of alkaline activation solution, multi-walled carbon nanotube suspension and solid material is (5~30):(0.01~5):(20~190).

[0032] Step 5: Inject carbon dioxide gas into the coal-based solid waste slurry from Step 4 under normal temperature and pressure conditions, and carry out a mineralization reaction while stirring to prepare a coal-based solid waste mineralization slurry; during this process, record the flow rate of injected carbon dioxide and the flow rate of outflowing carbon dioxide.

[0033] Step 6: Pour the solid waste material slurry from the mineralization reaction in Step 5 into a mold, and then cure and solidify it to obtain coal-based solid waste mineralized material. After that, compressive strength test and microstructure analysis are performed.

[0034] In a specific embodiment, in step 1, the sodium silicate is Na2O·nSiO2, wherein the Na2O content is 10% to 19.8% and the SiO2 content is 20% to 35.6%.

[0035] In a specific embodiment, in step 2, the length of the multi-walled carbon nanotubes is 1 μm to 50 μm, the outer diameter is 1 nm to 15 nm, the inner diameter is 0.5 nm to 5 nm, and the specific surface area is 50 m². 2 / g~2500 m 2 / g, density is 0.01 g / cm³3 ~15g / cm 3 The surfactant is a water-soluble polymeric surfactant or an ionic surfactant; wherein the surfactant may be selected from at least one of polyvinyl alcohol, polyvinylpyrrolidone, sodium dodecyl sulfate, and polycarboxylate.

[0036] In a specific implementation, the ultrasonic disperser was used to ultrasonically treat the resulting mixed solution in a pulse mode of 3 seconds on and 3 seconds off. The frequency of the ultrasonic treatment was 20 kHz to 40 kHz, and the cumulative ultrasonic time was 10 min to 60 min (per 250 mL of mixed volume). During this period, the water in the ultrasonic disperser was replaced every 2 min to 5 min to control the water temperature during the ultrasonic treatment process to be below 45 ℃, ensuring that the multi-walled carbon nanotubes were fully dispersed and avoiding the influence of excessively high temperature on the properties of the multi-walled carbon nanotubes and surfactants.

[0037] As a specific implementation method, the proportions of each component in the fly ash used in step 3 by mass ratio are: CaO:SiO2:Al2O3:Others = (1.5~8.5):(30~55):(18.6~51.2):(3.2~9.8); the proportions of each component in the slag used are: CaO:SiO2:Al2O3:Others = (25.5~45.0):(15.5~34.7):(8.6~23.2):(19.3~32.2).

[0038] In a specific implementation, the stirring rate in step 4 is 120 r / min to 1000 r / min, the stirring time is 2 min to 10 min, and the yield stress of the prepared coal-based solid waste slurry is 4.5 Pa to 80 Pa, and the spread is 195 mm to 350 mm, ensuring that the solid waste slurry has sufficient fluidity.

[0039] As a specific implementation method, the carbon dioxide injection flow rate in step 5 meets the following conditions: when the coal-based solid waste slurry is 100g to 3500g, the carbon dioxide injection rate is 0.1 L / min to 10 L / min, the stirring rate is 100 r / min to 850 r / min, the reaction time is 5 min to 60 min, and the carbon dioxide mineralization rate is 2 mgCO2 / g to 40 mgCO2 / g.

[0040] In a specific implementation, in step 6, the curing temperature is 20°C to 25°C, the curing humidity is 90% to 95%, the curing time is 3 days to 28 days, and the compressive strength of the coal-based solid waste mineralization material is 1.85 MPa to 13.76 MPa.

[0041] As a specific implementation method, the thermal conductivity of the coal-based solid waste mineralization material is 0.24 W / (m·K)~0.75 W / (m·K), the specific heat capacity is 0.57 KJ / (kg·K)~1.89 KJ / (kg·K), and the heat storage coefficient is 4.28 W / (m·K). 2 ·K) ~12.46 W / (m 2 ·K), performance is obtained through the following standardized tests:

[0042] Method 1:

[0043] Step 1: Shape the coal-based solid waste mineralization material into a cylinder with a diameter of 50±0.5 mm and a height of 100±0.5 mm. The parallelism of the two end faces should be ≤0.05 mm, and the surface roughness R should be... a ≤1.6 μm;

[0044] Step 2: Measure the thermal conductivity λ using the heat shield method under axial heat flow: heat shield temperature T h =100±5 °C, cold plate temperature T c =50±5 °C, contact pressure 0.1 MPa~0.3 MPa;

[0045] Step 3: Drill a subsample (mass 10±2 mg) from the non-test area of ​​the cylinder and measure the specific heat capacity C by differential scanning calorimetry (DSC) at 10 K / min under nitrogen atmosphere;

[0046] Step 4: Calculate the density ρ using the geometric volume method, and calculate the heat storage coefficient using λ and C. In the formula, λ is the thermal conductivity (W / (m·K)) and ρ is the density (kg / m³). 3 C is the specific heat capacity (kJ / (kg·K)), and t is the temperature change period (s), which is generally taken as 8640 s.

[0047] Method 2:

[0048] Step 1: Shape the coal-based solid waste mineralization material into a cylinder with a diameter of 50 ± 0.5 mm and a height of 100 ± 0.5 mm. Cut the cylinder into two circular pieces of equal thickness (≥15 mm), with the parallelism of the two end faces ≤0.05 mm and the surface roughness R. a ≤1.6 μm;

[0049] Step 2: Using the transient planar source method, a Hot Disk probe is clamped in the coal-based solid waste mineralization material, and the thermal conductivity λ and thermal diffusivity α are simultaneously fitted by transient heating and temperature response curves.

[0050] Step 3: Calculate the thermal storage coefficient using λ and α. In the formula, λ is the thermal conductivity (W / (m⋅K)) and α is the thermal diffusivity (m 2 / s), where t is the temperature change period (s), typically taken as 8640 s.

[0051] Method 3:

[0052] Step 1: Shape the coal-based solid waste mineralization material into a cylinder with a diameter of 50 ± 0.5 mm and a height of 25 ± 0.5 mm. The parallelism of the two end faces should be ≤0.05 mm, and the surface roughness R should be... a ≤1.6 μm;

[0053] Step 2: Clamp the coal-based solid waste mineralization material between the heating unit and the cooling unit of the thermal conductivity meter;

[0054] Step 3: Use a VarioCAM HD 880 uncooled infrared thermal imager to face the sample surface, set the sampling frequency to ≥10 Hz, and the temperature sensitivity to ≤0.02℃;

[0055] Step 4: Activate the thermal conductivity meter to apply a transient thermal pulse with a pulse width of 0.1 s to 0.5 s and an energy density of 50 W / m³. 2 ~200 W / m 2 The thermal conductivity λ of the sample is measured, and the time series matrix T(x, y, t) of the temperature field on the sample surface is acquired simultaneously using an infrared thermal imager.

[0056] Step 5: Based on the one-dimensional heat conduction model, extract the temperature rise curve ΔT(t) of the characteristic region (excluding the edge effect region that is less than 10% of the side length of the sample edge) from the temperature field matrix.

[0057] Step 6: Fitting the equation The thermal diffusivity α is retrieved, where Q is the heat of the thermal pulse and d is the depth of the characteristic region. During the retrieval process, for... and Perform linear fitting, and calculate the slope k. .

[0058] Step 7: Calculate the thermal storage coefficient using λ and α. In the formula, λ is the thermal conductivity (W / (m·K)) and α is the thermal diffusivity (m² / kJ). 2 / s), where t is the temperature change period (s), typically taken as 8640 s.

[0059] Example 1

[0060] To further understand the preparation method of coal-based solid waste mineralization material reinforced with multi-walled carbon nanotubes provided by the present invention, the following detailed description is provided in conjunction with embodiments, and the specific steps are as follows:

[0061] Step 1: Add sodium hydroxide granules to water at a mass ratio of 15:100 and stir until the sodium hydroxide is completely dissolved in the water to obtain a sodium hydroxide solution. After the sodium hydroxide solution cools to room temperature, add sodium silicate to the sodium hydroxide solution at a mass ratio of 10:100 and stir until well mixed to obtain an alkaline activation solution.

[0062] Step 2: Mix multi-walled carbon nanotubes, surfactant, and water at a mass ratio of 0.04:4:100. Stir the mixture with a magnetic stirrer at 200 r / min for 1 min to 10 min. Then, use an ultrasonic disperser with a pulse mode of 3 s on and 3 s off to sonicate the resulting mixture for a cumulative sonication time of 20 min (per 250 mL of mixed solution volume). During this process, replace the water every 3 min to keep the water temperature below 45 ℃, ensuring thorough dispersion of the multi-walled carbon nanotubes and avoiding the negative effects of excessively high temperatures on the properties of both the multi-walled carbon nanotubes and the surfactant. The resulting ultrasonically treated mixture yields a multi-walled carbon nanotube suspension.

[0063] Step 3: Grind the fly ash to a particle size of 100 μm and the slag to a particle size of 100 μm. Then, mix them evenly at a mass ratio of 4:1 (fly ash to slag) to obtain a solid material.

[0064] Step 4: Add the alkaline activation solution and multi-walled carbon nanotube suspension prepared in Step 1 and Step 2 to the solid material in Step 3 and mix them to obtain coal-based solid waste slurry. The mass ratio of alkaline activation solution, multi-walled carbon nanotube suspension and solid material is 9:3:30.

[0065] Step 5: Inject carbon dioxide gas into the coal-based solid waste slurry from Step 5 under normal temperature and pressure conditions, and carry out a mineralization reaction while stirring. The injected carbon dioxide flow rate is 5 L / min, the stirring rate is 600 r / min, and the reaction time is 30 min to prepare the coal-based solid waste mineralization slurry. During this process, the injected carbon dioxide flow rate and the outflow carbon dioxide flow rate are recorded.

[0066] Step 6: Pour the coal-based solid waste mineralization slurry after the mineralization reaction in Step 5 into a mold. After curing and solidification, the coal-based solid waste mineralization material is obtained. The curing temperature is 25°C, the curing humidity is 90%, and the curing time is 28 days. After that, the compressive strength test and microstructure analysis are carried out.

[0067] Example 2

[0068] The difference from Example 1 is that the mass ratio of multi-walled carbon nanotubes, surfactant and water in step 2 is adjusted to 0.08:4:100, while the rest of the preparation steps are the same.

[0069] Example 3

[0070] The difference from Example 1 is that the mass ratio of multi-walled carbon nanotubes, surfactant and water in step 2 is adjusted to 0.12:4:100, while the rest of the preparation steps are the same.

[0071] Example 4

[0072] The difference from Example 1 is that the mass ratio of multi-walled carbon nanotubes, surfactant and water in step 2 is adjusted to 0.12:8:100, while the rest of the preparation steps are the same.

[0073] Example 5

[0074] The difference from Example 1 is that the mass ratio of multi-walled carbon nanotubes, surfactant and water in step 2 is adjusted to 0.12:12:100, while the rest of the preparation steps are the same.

[0075] This invention mainly studies the effects of the amount of multi-walled carbon nanotubes and surfactants added on the performance of coal-based solid waste mineralization materials. Therefore, in Examples 1-5, only the amount of multi-walled carbon nanotubes and surfactants added is set as a variable.

[0076] Comparative Example

[0077] The difference from Example 1 is that multi-walled carbon nanotubes are not added, but the rest of the preparation steps are the same.

[0078] The performance of the coal-based solid waste mineralization materials prepared in Examples 1-5 and the comparative examples was compared, as shown in Tables 1 and 2.

[0079] Table 1. Numerical values ​​of yield stress, expansion, CO2 uptake rate, and 28-day compressive strength of the coal-based solid waste mineralized materials prepared in Examples 1-5 and the comparative examples.

[0080]

[0081] As shown in Table 1, the CO2 absorption rate of the coal-based solid waste mineralization materials prepared in Examples 1-5 is higher than that of the comparative example, proving that the coal-based solid waste mineralization materials prepared in Examples 1-5 can absorb more CO2. With more CO2, they can mineralize with more active ions such as calcium oxide and magnesium oxide in solid waste, resulting in a dense structure of the coal-based solid waste mineralization materials and further improving their strength.

[0082] The difference between Examples 1-5 and the comparative examples is that multi-walled carbon nanotubes were added in Examples 1-5. The yield stress and 28-day compressive strength of the coal-based solid waste mineralization materials prepared in Examples 1-5 were higher than those in the comparative examples. The performance of the coal-based solid waste mineralization materials with multi-walled carbon nanotubes added to the surface was better than that of the coal-based solid waste mineralization materials without multi-walled carbon nanotubes added.

[0083] Table 2. Values ​​of thermal conductivity, specific heat capacity, and heat storage coefficient of the coal-based solid waste mineralization materials prepared in Examples 1-5 and the comparative examples.

[0084]

[0085] As shown in Table 2, the thermal conductivity, specific heat capacity, and heat storage coefficient of the coal-based solid waste mineralization materials prepared in Examples 1-4 are all higher than those of the comparative examples. Since the temperature of the circumferential rocks in the goaf is generally high, after the coal-based solid waste mineralization materials are filled into the goaf, the coal-based solid waste mineralization materials can quickly absorb the heat of the circumferential rocks, improve the overall thermal diffusivity of the coal-based solid waste mineralization materials, and conduct the heat of the circumferential rocks to the ventilation roadway or cooling system, thereby improving the working environment and reducing cooling energy consumption.

[0086] Geothermal energy can also be utilized by pre-burying heat exchange pipes within coal-based solid waste mineralization materials. Due to the high thermal conductivity and heat storage properties of coal-based solid waste mineralization materials, after filling the goaf, these materials can absorb and store more geothermal energy. The heat exchange medium within the heat exchange pipes can also absorb more geothermal energy from the coal-based solid waste mineralization materials. The geothermal energy absorbed by the heat exchange medium can be used for power generation or heating. Afterward, the cooled heat exchange medium is reinjected into the heat exchange pipes of the coal-based solid waste mineralization materials, forming a closed loop, thereby improving the utilization rate of geothermal energy.

[0087] The above are merely preferred embodiments of the present invention and do not constitute any limitation on the present invention. Any equivalent substitutions or modifications made by those skilled in the art to the technical solutions and content disclosed in the present invention without departing from the scope of the present invention shall be deemed to have remained within the protection scope of the present invention.

Claims

1. A coal-based solid waste mineralization material reinforced with multi-walled carbon nanotubes, characterized in that, By weight, the coal-based solid waste mineralization material includes: 5-30 parts alkaline activation solution, 0.01-5 parts multi-walled carbon nanotube suspension, 10-140 parts fly ash, and 10-50 parts slag.

2. A method for preparing coal-based solid waste mineralization materials reinforced with multi-walled carbon nanotubes as described in claim 1, characterized in that, The specific steps are as follows: Step 1: Mix sodium hydroxide granules and water at a mass ratio of (1-20):100 to obtain a sodium hydroxide solution. After the sodium hydroxide solution cools to room temperature, add sodium silicate to the sodium hydroxide solution at a mass ratio of (1-15):

100. Stir well to obtain an alkaline activation solution. Step 2: Mix multi-walled carbon nanotubes, surfactants and water at a mass ratio of (0.01-5):(0.1-20):100, stir the mixture at 200 r / min for 1 min-10 min, and then sonicate for 10 min-60 min to obtain a multi-walled carbon nanotube suspension. Step 3: Grind the fly ash to a particle size of 0.1μm to 250 μm and the slag to a particle size of 0.1μm to 250 μm. Then, mix them evenly according to the mass ratio of fly ash to slag (1 to 14): (1 to 5) to obtain a solid material. Step 4: Add the alkaline activation solution and multi-walled carbon nanotube suspension prepared in Step 1 and Step 2 to the solid material in Step 3 and stir to obtain coal-based solid waste slurry. The mass ratio of alkaline activation solution, multi-walled carbon nanotube suspension and solid material is (5~30):(0.01~5):(20~190). Step 5: Under normal temperature and pressure conditions, carbon dioxide gas is injected into the coal-based solid waste slurry from Step 4, and a mineralization reaction is carried out under stirring to prepare a coal-based solid waste mineralization slurry. During this process, the flow rate of injected carbon dioxide and the flow rate of outflowing carbon dioxide are recorded. Step 6: Pour the coal-based solid waste mineralization slurry after the mineralization reaction in Step 5 into a mold, and after curing and solidification, obtain the coal-based solid waste mineralization material.

3. The method for preparing coal-based solid waste mineralization materials reinforced with multi-walled carbon nanotubes according to claim 2, characterized in that, In step 1, the sodium silicate is Na2O·nSiO2, wherein the Na2O content is 10% to 19.8% and the SiO2 content is 20% to 35.6%.

4. The method for preparing coal-based solid waste mineralization materials reinforced with multi-walled carbon nanotubes according to claim 2, characterized in that, In step 2, the multi-walled carbon nanotubes have a length of 1 μm to 50 μm, an outer diameter of 1 nm to 15 nm, an inner diameter of 0.5 nm to 5 nm, and a specific surface area of ​​50 m². 2 / g~2500 m 2 / g, density is 0.01 g / cm³ 3 ~15 g / cm 3 .

5. The method for preparing coal-based solid waste mineralization materials reinforced with multi-walled carbon nanotubes according to claim 2, characterized in that, In step 2, the surfactant is a water-soluble polymeric surfactant or an ionic surfactant, wherein the surfactant is selected from at least one of polyvinyl alcohol, polyvinylpyrrolidone, sodium dodecyl sulfate, and polycarboxylate.

6. The method for preparing coal-based solid waste mineralization materials reinforced with multi-walled carbon nanotubes according to claim 2 or 5, characterized in that, In step 2, the ultrasonic disperser is used to ultrasonically treat the resulting mixed solution in a pulse mode of 3 seconds on and 3 seconds off. The frequency of ultrasonic treatment is 20 kHz to 40 kHz, and the cumulative ultrasonic time is 10 min to 60 min. During this period, the water in the ultrasonic disperser is replaced every 2 min to 5 min to control the water temperature during ultrasonic treatment to be below 45 ℃.

7. The method for preparing coal-based solid waste mineralization materials reinforced with multi-walled carbon nanotubes according to claim 2, characterized in that, In step 4, the stirring rate is 120 r / min to 1000 r / min, the stirring time is 2 min to 10 min, and the yield stress of the prepared coal-based solid waste slurry is 4.5 Pa to 80 Pa, and the spread is 195 mm to 350 mm.

8. The method for preparing coal-based solid waste mineralization materials reinforced with multi-walled carbon nanotubes according to claim 2, characterized in that, In step 5, when the coal-based solid waste slurry is 100g to 3500g, the injected carbon dioxide flow rate is 0.1 L / min to 10 L / min, the stirring rate is 100 r / min to 850 r / min, the reaction time is 5 min to 60 min, and the carbon dioxide mineralization rate is 2 mgCO2 / g to 40 mgCO2 / g.

9. The method for preparing coal-based solid waste mineralization materials reinforced with multi-walled carbon nanotubes according to claim 2, characterized in that, In step 6, the curing temperature is 20°C to 25°C, the curing humidity is 90% to 95%, and the curing time is 3 to 28 days.

10. The method for preparing coal-based solid waste mineralization materials reinforced with multi-walled carbon nanotubes according to claim 9, characterized in that, The coal-based solid waste mineralization material has a compressive strength of 1.85 MPa to 13.76 MPa, a thermal conductivity of 0.24 W / (m·K) to 0.75 W / (m·K), a specific heat capacity of 0.57 KJ / (kg·K) to 1.89 KJ / (kg·K), and a heat storage coefficient of 4.28 W / (m·K). 2 ·K)~12.46 W / (m 2 ·K).

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