A low-carbon preparation method of a coal mine underground filling material

Abstract

The application discloses a kind of low-carbon preparation methods of coal mine underground filling material, steps are as follows: first, prepare carbon sequestration precursor mineralization water, and after premixing with cement, fly ash, composite coal gangue aggregate;Utilize CO2 and calcium-magnesium active component to generate calcium carbonate, form dense mineralization coating on the surface of particle, improve structural compactness;Based on strength increment dynamic adjustment cement content, realize low-carbon substitution.The application can still guarantee that the uniaxial compressive strength of filling body reaches 3.10MPa (exceeds 55% of underground safety standard) under the condition that cement consumption is reduced by 70% by the structural reinforcement of calcium carbonate coating and dynamic cement adjustment, while realizing that CO2 50-100kg is fixed per cubic meter of material, and coal-based solid waste content is increased to 95.38%.The low-carbon preparation process of the application provides an integrated innovation scheme of "negative carbon-low cost-high solid waste utilization" for mine filling field.

Description

TECHNICAL FIELD

[0001] The application belongs to the technical field of underground mine filling, and particularly relates to a low-carbon preparation method of underground filling material in a coal mine. BACKGROUND

[0002] In the field of mine exploitation, underground filling technology is the core means to ensure mining safety and control surface subsidence. However, the traditional filling material system has long relied on cement-based cementitious materials, resulting in high filling costs and serious environmental burden. According to statistics, the average price of ordinary Portland cement in a certain mining area in 2024 reached 500 yuan / ton, and the cement consumption in a single filling operation can reach a scale of thousands of tons, with the cost of cementitious materials alone exceeding 500,000 yuan. More seriously, cement production is a key field of global carbon emissions, with the decomposition of raw material carbonate and fuel combustion contributing 0.44 tons of CO2 / ton of CaCO3 decomposition and 2.66-2.72 tons of CO2 / ton of standard coal emission intensity, respectively. In 2023, global cement-related CO2 emissions accounted for 8% of total human activity emissions, and it is estimated that by 2030, when cement production increases to 5 billion tons, annual emissions will exceed 3.8 billion tons.

[0003] On the other hand, there is a significant imbalance in the field of industrial solid waste resource utilization. Taking fly ash as an example, China's production in 2023 reached 899 million tons, accounting for more than 55% of the world's total, but existing technologies still limit its application to low-value-added scenarios. The upgrading of dust and desulfurization technology in thermal power plants has improved the collection efficiency of fly ash, but has not simultaneously promoted its deep utilization in high-value building materials. At the same time, traditional filling materials generally use a simple compounding system of sand and gravel aggregates and cement, which has slow early strength development (3d compressive strength of only 0.5-1.0 MPa) and 7d strength of less than 2.0 MPa, making it difficult to meet the stringent requirements of deep mining for rapid loading of filling bodies. To make up for the strength defect, the cement content is often forced to be increased in engineering practice, forming a vicious cycle of "high cost-high emission-low performance".

[0004] The existing technology has three structural contradictions: first, the filling material excessively relies on the cementitious system, which not only increases the mining cost (the comprehensive filling cost reaches 300-500 yuan / m 3 ) but also exacerbates the pressure of carbon emission reduction; second, although bulk solid wastes such as fly ash have pozzolanic activity, they are not effectively activated, and there is a key bottleneck in the resource recycling chain; third, the mechanical properties of the material and the construction efficiency are difficult to optimize simultaneously, and the lack of early strength directly threatens mine safety. These problems seriously hinder the progress of green mine construction, and it is urgent to develop a new low-carbon filling material system to achieve a breakthrough balance between cost reduction and environmental friendliness. SUMMARY

[0005] In view of the deficiencies of the prior art, the present application provides a low-carbon preparation method of coal mine underground filling material, aiming to solve the technical problems of high cement proportion, high cost, low strength of underground filling material, and low utilization rate of fly ash in the prior art.

[0006] The present application is realized by the following technical solutions:

[0007] A low-carbon preparation method of coal mine underground filling material, comprising the following steps:

[0008] Step 1) In a sealed, vacuum mineralization test device, water is placed in a mineralization reaction kettle, CO2 is introduced for mineralization stirring, and the rotation speed of the mineralization reaction kettle is set. After stirring, carbon sequestration precursor mineralized water is obtained;

[0009] Step 2) The carbon sequestration precursor mineralized water prepared in step 1) is placed in a stirring reaction kettle with cement and fly ash, and then coal gangue is added for mixing and stirring to obtain a filling material sample;

[0010] Step 3) The filling material without CO2 is used as the original control group, the 7-day uniaxial compressive strength of the filling material sample prepared in step 2) is tested, and the strength is compared with that of the original control group. When the strength of the filling material sample is greater than that of the original control group, the cement content in step 2) is gradually reduced to reduce the strength of the filling material sample. When the strength of the filling material sample is less than that of the original control group, the mineralization parameter CO2 input in step 1) is gradually reduced, the mineralization reaction stirring time in step 1) is gradually reduced, and the stirring time in step 2) is gradually extended to improve the strength of the filling material sample;

[0011] Step 4) When the cement content is gradually reduced to a certain specific proportion, if the strength of the filling material sample is consistent with that of the original control group at this time, the cement content ratio at this time is the low-carbon preparation ratio. Repeat steps 1) and 2) according to this ratio to obtain the coal mine underground filling material.

[0012] Preferably, the amount of CO2 introduced in step 1) is 1-3L, and the stirring time is 1-30min.

[0013] Preferably, the pH value of the carbon sequestration precursor mineralized water in step 1) is 5.0-5.6.

[0014] Preferably, the stirring time in step 2) is adjusted according to the pH value of the carbon sequestration precursor mineralized water. When the pH value of the carbon sequestration precursor mineralized water is greater than or equal to 5.4, the stirring time is 20-30min; when the pH value is less than or equal to 5.2, the stirring time is 10-20min; and when the pH value is between 5.2 and 5.4, the stirring time is 0-10min.

[0015] Preferably, the stirring speed of step 1) and step 2) is 300-500 r / min.

[0016] Preferably, in step 3), the cement content in step 2) is gradually reduced, specifically, the cement content is reduced by 2% each time.

[0017] Preferably, in step 3), the CO2 input amount in step 1) is gradually reduced, specifically, the input amount is reduced by 0.5-1 L each time; the mineralization reaction stirring time in step 1) is gradually reduced, specifically, the stirring time is reduced by 5-10 min each time; the stirring time in step 2) is gradually extended, specifically, the stirring time is extended by 5-10 min each time.

[0018] Preferably, the specific ratio of cement in step 4) is a mass ratio, which is 100 wt%, and the specific ratio is as follows:

[0019] The carbon sequestration precursor mineralization water:cement:fly ash:coal gangue is 19:(4-12.5):(37.5-46):31.

[0020] The beneficial effects of the present application are as follows:

[0021] (1) Compared with traditional filling materials, the present application can make the strength and the control group flat by the structure strengthening of calcium carbonate coating and the dynamic cement parameter adjustment, while reducing the cementitious material, under the premise of meeting the strength demand of underground filling, the cement-based adhesive material is reduced by more than 70% (the mass ratio in cementitious material is 7.5% at least), and fly ash, coal gangue and other coal-based solid waste are introduced as core components (the mass ratio of coal-based solid waste in solid material is 95.38%, and the mass ratio of fly ash in cementitious material is 92.5%), which greatly reduces the cost of cementitious material by more than 50%. Combined with CO2 mineralization sequestration technology, 1 L of CO2 is injected to prepare filling material, which can simultaneously realize carbon emission reduction and cement replacement (cement content is reduced by 14%), and the comprehensive cost of single filling operation is reduced by 30%-40% compared with the traditional scheme, the carbon emission intensity of whole life cycle is reduced by more than 50%, and the material cost and whole life cycle carbon emission are significantly reduced.

[0022] (2) The present application realizes the high-value utilization of coal-based solid waste (fly ash+coal gangue) in filling materials (the content is more than 90%) by activating the pozzolanic activity of fly ash and coupling CO2 synergistic mineralization reaction. Taking a coal mine with an annual output of millions of tons as an example, the present application can annually consume 300,000-500,000 tons of coal-based solid waste, promote the comprehensive utilization rate of solid waste in the mining area to more than 95%, and completely solve the industry pain points of coal-based solid waste storage difficulty and slow consumption, thereby providing a technical closed loop for building a "zero emission" green mine.

[0023] (3)In the preparation process of the filling material, the application permanently stores the industrial captured CO2 in the filling body by the CO2 directional mineralization reaction, forming a "negative carbon" effect. Combined with the indirect emission reduction of 70% cement reduction (0.89-1.22 tons of CO2 emission per ton of cement reduction), the carbon footprint per filling amount under the double path is reduced by 60%-80% compared with the traditional process, providing a quantifiable low-carbon transformation path for the mining industry.

[0024] (4) Compared with the traditional solid filling and paste filling, the application significantly improves the early strength growth rate of the filling body under the premise that the 7-day compressive strength of the filling body is 1.5-2.0 MPa (meeting the underground safety standard), significantly shortens the mining-filling connection period, has the characteristics of high fluidity and short setting time, and can reach the required strength in a very short time, thereby flexibly adapting to various scenes such as overburden isolation grouting, paste filling, etc., breaking through the limitation of poor spatial adaptability of traditional solid filling.

[0025] (5) The application converts coal-based solid waste from low-end landfill resources into high-value filling base materials, drives cross-industry cooperation of thermal power-coal-construction materials, forms an integrated industrial chain of "solid waste recycling-carbon capture and utilization-green mining", creates a new growth point for regional economy, and has significant economic and environmental benefits, which is suitable for popularization and application. BRIEF DESCRIPTION OF DRAWINGS

[0026] Figure 1 A graph of the uniaxial compressive strength results of the filling material sample prepared in Example 2. DETAILED DESCRIPTION

[0027] The application will be further described in detail below in combination with the drawings and specific examples.

[0028] Unless otherwise specified, the technical means used in the following examples are conventional means known to those skilled in the art. The experimental methods not specified are conventional methods in the art.

[0029] The materials, reagents, etc. used in the following examples can be obtained from commercial sources unless otherwise specified.

[0030] A low-carbon preparation method of a coal mine underground filling material, the specific steps are as follows:

[0031] (1) In a sealed, vacuum mineralization test device, take an appropriate amount of water and put it into a mineralization reactor, introduce 1-3 L of CO2 for mineralization and stirring for 1-30 min, set the rotation speed of the mineralization reactor to 300-500 r / min, and after stirring, obtain carbon sequestration precursor mineralization water (pH = 5.0-5.6).

[0032] (2) The carbon sequestration precursor mineralized water prepared above is placed in a reactor with cement and fly ash and stirred. Then coal gangue is added and stirred for 10 to 30 minutes. The stirring speed of the reactor is set to 300 to 500 r / min to obtain a filling material sample.

[0033] The stirring time should be adjusted according to the pH value of the mineralized water of the carbon sequestration precursor. When the pH value of the mineralized water of the carbon sequestration precursor is ≥5.4, the stirring time is 20-30 min; when the pH value is ≤5.2, the stirring time is 10-20 min; and when the pH value is between 5.2 and 5.4, the stirring time is 0-10 min.

[0034] (3) The filling material without CO2 was used as the original control group. The 7-day uniaxial compressive strength of the filling material samples prepared above was tested and compared with the strength of the original control group. The parameters were adjusted in the following ways:

[0035] When the strength of the filling material sample is greater than that of the original control group, the strength of the filling material sample is reduced by gradually reducing the cement content in step (2) (each reduction is 2%).

[0036] When the strength of the filling material sample is less than that of the original control group, the strength of the filling material sample is improved by gradually reducing the CO2 injection rate in step (1) (each reduction is 0.5 to 1 L), gradually reducing the stirring time of the mineralization reaction in step (1) (each reduction is 5 to 10 min), and gradually extending the stirring time in step (2) (each increase is 5 to 10 min).

[0037] (4) When the amount of cement is gradually reduced to a certain proportion, if the strength of the filling material sample is consistent with the strength of the original control group, then the cement content ratio of this specific proportion is the low-carbon preparation ratio. Repeat steps (1) to (2) according to this ratio to obtain the coal mine underground filling material.

[0038] Example 1

[0039] A low-carbon preparation method for underground coal mine backfill material, the specific steps of which are as follows:

[0040] (1) Weigh 19 parts by weight of water and pour them into the reaction vessel. Assemble the mineralization reaction vessel and seal it. Then place the reaction vessel under vacuum and maintain the ambient temperature at 15-25℃. Introduce 1L, 2L and 3L of CO2 respectively, and start stirring at a rate of 500r / min for 10min. Obtain carbon sequestration precursor mineralized water (19 parts each) with pH values ​​of 5.4, 5.1 and 5.0 respectively.

[0041] (2) Weigh 12.5 parts of cement and 37.5 parts of dry fly ash by weight, mix them evenly and put them into a stirred reactor. Then add 19 parts of carbon sequestration precursor mineralized water with pH values ​​of 5.4, 5.1 and 5.0 obtained in step (1) and mix them at a rate of 500 r / min for 10 min. Then weigh 31 parts of coal gangue by weight, mix them evenly with the above slurry and put them into a stirred reactor. Mix them at a rate of 500 r / min for 10 min to obtain the final product.

[0042] Using the filling material prepared by the traditional method (i.e., using water instead of mineralized water for carbon sequestration precursors, while keeping other raw material amounts and preparation parameters unchanged) as the original control group, its 7-day uniaxial compressive strength was only 5.80 MPa. In contrast, the 7-day uniaxial compressive strength of the filling material prepared in this embodiment was 8.21 MPa (pH=5.4), 8.13 MPa (pH=5.1), and 7.82 MPa (pH=5.0), respectively, which is an improvement of 34.8% to 41.6% compared to the original control group.

[0043] Comparative Example 1

[0044] The filling material is prepared using a traditional preparation method, specifically through direct wet mineralization. The specific steps are as follows:

[0045] Weigh out 9.5 parts cement, 28.6 parts fly ash, and 14.3 parts water by weight and pour them into a reaction vessel. Assemble the mineralization reaction vessel and seal it. Then, place the reaction vessel under vacuum and maintain the ambient temperature at 15–25°C. Introduce 1L and 2L CO2 respectively, and start stirring at a rate of 500 r / min for 10 minutes. Next, weigh out 47.6 parts coal gangue by weight, mix it evenly with the above slurry, and put it into the stirred reaction vessel. Mix and stir at a rate of 500 r / min for 10 minutes to obtain the final product.

[0046] Using the backfill material prepared by the traditional non-mineralization method (that is, directly stirring water, cement, fly ash and coal gangue) as the original control group, its 7-day uniaxial compressive strength was 4.75 MPa. The 7-day uniaxial compressive strengths of the backfill material prepared by the above-mentioned direct wet mineralization were 5.45 MPa and 4.27 MPa, respectively. Compared with the original control group, the strength of the backfill material prepared by direct wet mineralization only increased by 14.7% at a CO2 injection volume of 1L, and even decreased by 10.1% at a CO2 injection volume of 2L.

[0047] Comparative Example 2

[0048] The filling material is prepared using a traditional preparation method, specifically through direct wet mineralization. The specific steps are as follows:

[0049] Take 19.2 parts of cement, 57.8 parts of fly ash and 23 parts of water by weight, pour into the reaction kettle. Assemble the mineralization reaction kettle to make it airtight, then put the reaction kettle into a vacuum state, keep the environmental temperature at 15-25℃, respectively inject 1L and 2L CO2, start stirring the mineralization at a rate of 500r / min, the time is 10min, and the mineralization water (19 parts) with pH value of 5.4 is obtained.

[0050] The filling material prepared by using the traditional non-mineralization preparation method (i.e. mixing water, cement and fly ash and then directly stirring) is used as the original control group, and the 7-day uniaxial compressive strength thereof is 8.98MPa. The 7-day uniaxial compressive strength of the filling material prepared by the above direct wet mineralization is 6.86MPa and 6.44MPa respectively. Compared with the original control group, the strength of the filling material prepared by the direct wet mineralization under the condition of 1L CO2 injection decreases by 23.6%, and the strength of the filling material prepared by the direct wet mineralization under the condition of 2L CO2 injection decreases by 28.3%.

[0051] Example 2

[0052] A low-carbon preparation method of a coal mine underground filling material, the specific steps are as follows:

[0053] (1) Take 19 parts of water by weight, pour into the reaction kettle. Assemble the mineralization reaction kettle to make it airtight, then put the reaction kettle into a vacuum state, keep the environmental temperature at 15-25℃, inject 1L CO2, start stirring the mineralization at a rate of 500r / min, the time is 10min. The carbon sequestration precursor mineralization water (19 parts) with pH value of 5.4 is obtained.

[0054] (2) Take 4-12.5 parts of cement and 37.5-46 parts of fly ash by weight respectively, mix the dry materials uniformly and put them into the stirring reaction kettle, then add the carbon sequestration precursor mineralization water (19 parts) with pH value of 5.4 prepared in step (1) and mix and stir at a rate of 500r / min for 10min, then take 31 parts of coal gangue by weight, mix it with the above slurry uniformly and put it into the stirring reaction kettle, mix and stir at a rate of 500r / min for 10min, and the filling material samples S1-S5 are prepared. At the same time, the filling material without CO2 is taken as the original control group, and the specific amount and parameters are shown in Table 1.

[0055] Table 1 Low-carbon preparation experimental parameters

[0056]

[0057]

[0058] The uniaxial compressive strength of the finally prepared filling material samples under the conditions of 3-day and 7-day curing is shown in Table 2. Figure 1

[0059] ​Table 2 Uniaxial compressive strength of 3-day and 7-day curing

[0060]

[0061] By Figure 1 As can be seen from Table 2, the low-carbon preparation process of the present application has a significant advantage compared to the prior art (original control group), and referring to the experimental data of Comparative Examples 1 and 2, the specific analysis is as follows:

[0062] 1. The amount of cement is significantly reduced, and the cost and carbon emissions are reduced simultaneously

[0063] (1) Breakthrough improvement in cement replacement rate

[0064] The prior art (original control group) requires the use of 0.6 kg of cement per unit material (25% of the mass of cementitious materials), while the amount of cement used in the present application is significantly reduced under the premise of ensuring that the 7-day strength meets the standard, for example, the cement usage of the S1 group (0.54 kg of cement) is reduced by 10%, and the 7-day strength is 7.70 MPa, which is 6.9% higher than the original control group; the cement usage of the S4 group (0.3 kg of cement) is reduced by 50%, and the 7-day strength is still 4.10 MPa, which is more than twice the underground safety standard (1.5-2.0 MPa); the cement usage of the S5 group (0.18 kg of cement) is reduced by 70% (only 7.5% of the mass of cementitious materials), and the 7-day strength is 3.10 MPa, which still meets the underground demand.

[0065] (2) CO2 mineralization efficiency and strength are improved simultaneously

[0066] The 7-day strength of the S1 group (1L CO2 injection) is 7.70 MPa, while the comparative example 1 (traditional wet mineralization) is only increased by 14.7%, indicating that the present application optimizes the interfacial reaction of CO2 and fly ash / coal gangue through directional activation (10 min) in the mineralization reactor, avoiding the increase in porosity caused by excessive CO2 in traditional wet mineralization (such as the strength of the comparative example 1 decreases by 10.1% after 2L CO2 injection).

[0067] (3) Comprehensive benefits

[0068] Using the low-carbon preparation process of the present application, the amount of cement can be reduced to as low as 30% of the original level, and the cost of single filling cementitious materials can be reduced by 40%-60%.

[0069] 2. CO2 sequestration and solid waste disposal synergistic effect

[0070] (1) Carbon emission reduction path innovation

[0071] All experimental groups (S1-S5) are injected with 1L CO2, which is permanently sequestered in the filling body through mineralization reaction, forming a "negative carbon" effect. For example, in the S5 group, about 50-100 kg of CO2 is sequestered per cubic meter of material (based on the injected amount), and the indirect emission reduction of 70% cement reduction (0.89-1.22 tons of CO2 emitted per ton of cement production) is added, achieving a reduction of more than 60% in the carbon footprint of the whole life cycle.

[0072] (2) High-content resource utilization of coal-based solid waste (fly ash + coal gangue)

[0073] The coal-based solid waste content of the original control group is 3.3 kg (coal-based solid waste accounts for 84.62% of the mass of solid materials, and fly ash accounts for 75% of the mass of cementitious materials), while the coal-based solid waste content of the S5 group is increased to 3.72 kg (coal-based solid waste accounts for 95.38% of the mass of solid materials, and fly ash accounts for 92.5% of the mass of cementitious materials) through optimized proportioning in the present application, and 8.75% more coal-based solid waste can be consumed in a single filling; based on the production of millions of tons of coal mines per year, the annual consumption of coal-based solid waste can be increased by 100,000 to 150,000 tons, and the comprehensive utilization rate can be increased to more than 95%.

[0074] 3. Strength performance adaptation to underground engineering requirements

[0075] (1) 7-day strength safety redundancy improvement

[0076] The 7-day uniaxial compressive strength of the prior art (original control group) is 7.20 MPa, which is much higher than the requirement of 1.5-2.0 MPa in underground, and there is a problem of "overdesign". The present application realizes the improvement of safety redundancy through precise control, for example, the 7-day uniaxial compressive strength of the S3 group (cement dosage is reduced by 30% compared with the original control group) is 4.65 MPa, which is 2.3 times the underground standard, and has both safety and economy; the 7-day uniaxial compressive strength of the S5 group (cement dosage is reduced by 70% compared with the original control group) is 3.10 MPa, still with 55% safety redundancy.

[0077] (2) Early strength optimization potential

[0078] The 3-day uniaxial compressive strength of the S1 group (cement dosage is reduced by 10% compared with the original control group) is 3.05 MPa, close to that of the original control group (3.60 MPa), which proves that the early strength and cement dosage demand can be balanced through process optimization.

[0079] 4. Enhanced process compatibility and engineering adaptability

[0080] (1) Optimized flowability and pipeline transportation

[0081] All experimental groups (S1-S5) maintain a 20-minute stirring time, but due to the increased mass proportion of coal-based solid waste in the cementitious material (92.5%) and the CO2 micro-pore regulation effect, the filling material flowability is significantly improved, the pipeline wear is reduced, and it is more suitable for long-distance transportation scenarios.

[0082] (2) Multi-scenario flexible adaptation

[0083] The strength gradient of S3-S5 groups (4.65 MPa to 3.10 MPa) covers different burial depths and ground pressure conditions, which can match the requirements of various processes such as overburden isolation grouting and paste filling.

[0084] 5. Technical defects of traditional wet mineralization and principles of the present invention

[0085] In Comparative Example 1, 2L CO2 injection resulted in a 10.1% decrease in strength. Due to the inability of traditional processes to control CO2 diffusion paths, excessive CO2 generates loose carbonate crystals, weakening the cementing structure. In Comparative Example 2, without coal gangue, the CO2 mineralization reaction intensifies the dispersion of fly ash particles, resulting in a decrease in material density (strength decreased by 28.3%). However, the present invention utilizes the reaction between carbon dioxide and calcium-magnesium active components to generate calcium carbonate and form a dense mineralized coating on the particle surface, making up for the strength loss after cement reduction. The mechanism of action is as follows: During the mineralization process, mineral deposition can fill the micro-pores, cracks, or defects in the matrix, making the material structure more dense. Mineralized materials usually form a multi-level structure, such as from nanocrystals to micrometer fibers, and to macroscopic layered structures. Each level of structure contributes to the strength of the material, effectively improving the overall structural density of the material.

[0086] In summary, the application realizes the structural reinforcement of the calcium carbonate coating and dynamic cement parameter adjustment, and guarantees that the uniaxial compressive strength of the filling body reaches 3.10 MPa (55% of the safety standard under the well) under the condition that the cement dosage is reduced by 70%, while realizing that 50-100 kg of CO2 is stored per cubic meter of material, and the mass ratio of coal-based solid waste in solid materials is increased to 95.38%. Compared with the prior art, the core advantages of the application are: (1) Technological breakthrough: the application realizes CO2 directional mineralization + solid waste synergistic activation, and still maintains 3.10 MPa of 7-day strength (55% of the underground standard) under the condition that the cement dosage is reduced by 70%, while the traditional wet mineralization will cause significant strength reduction (the highest reduction is 28.3%) due to the extensive process, CO2 excess or single solid waste. (2) Low-carbon economy: 50-100 kg of CO2 is stored per cubic meter of material, and the cement reduction indirectly reduces emissions, and the whole life cycle carbon footprint is reduced by 60%-80%; the cost of cementitious materials is reduced by 40%-60%, and the comprehensive utilization rate of fly ash / coal gangue is more than 95%. (3) Engineering universality: by adjusting the cement dosage (0.18-0.6 kg) and CO2 mineralization parameters, different geological conditions (strength range 3.10-7.70 MPa) can be adapted, and the fluidity is significantly improved, so that the equipment wear degree is reduced. The low-carbon preparation process of the application provides an integrated solution of "negative carbon - low cost - high solid waste utilization" for the field of mine filling, and can promote the green transformation of the power coal-building material industry chain.

[0087] The above-described embodiments are only some of the embodiments of the application, not all the embodiments. The detailed description of the embodiments of the application is not intended to limit the scope of the claimed application, but only represents selected embodiments of the application. The protection scope of the application is subject to the scope claimed in the claims, and all other embodiments obtained by those of ordinary skill in the art without creative labor based on the embodiments in the application belong to the protection scope of the application.

Claims

1. A low carbon method of preparation of a coal mine underground backfill material characterised in that, The method comprises the following steps: Step 1) placing water into a mineralization reactor in a closed and vacuum mineralization test device, introducing CO2 for mineralization stirring, setting the rotation speed of the mineralization reactor, and obtaining carbon sequestration precursor mineralized water after stirring; Step 2) placing the carbon sequestration precursor mineralized water obtained in step 1), cement and fly ash into a stirring reactor for stirring, and then adding coal gangue for mixing and stirring to obtain a filling material sample; Step 3) taking the filling material without CO2 as an original control group, testing the 7-day uniaxial compressive strength of the filling material sample obtained in step 2) and comparing the strength with that of the original control group; when the strength of the filling material sample is greater than that of the original control group, the strength of the filling material sample is reduced by gradually reducing the cement content in step 2); when the strength of the filling material sample is less than that of the original control group, the strength of the filling material sample is increased by gradually reducing the CO2 introduction amount in step 1), gradually reducing the mineralization reaction stirring time in step 1), and gradually extending the stirring time in step 2); Step 4) when the cement content is gradually reduced to a certain specific proportion, if the strength of the filling material sample is consistent with that of the original control group at this time, the cement content ratio at this time is the low-carbon preparation ratio, and steps 1) and 2) are repeated according to the ratio to obtain the coal mine underground filling material; The specific cement content ratio is a mass ratio, which is 100wt% in total and is as follows: Carbon sequestration precursor mineralized water: cement: fly ash: coal gangue = 19: (4-12.5): (37.5-46):

31.

2. A low carbon method of producing a backfill material for underground coal mines as claimed in claim 1, characterised in that, In step 1), the amount of CO2 introduced is 1-3 L, and the stirring time is 1-30 min.

3. A low carbon method of producing a backfill material for underground coal mines as claimed in claim 1, characterised in that, In step 1), the pH value of the carbon sequestration precursor mineralized water is 5.0-5.

6.

4. A low carbon method of producing a backfill material for underground coal mines according to claim 3, characterised in that, In step 2), the stirring time is adjusted according to the pH value of the carbon sequestration precursor mineralized water; when the pH value of the carbon sequestration precursor mineralized water is greater than or equal to 5.4, the stirring time is 20-30 min; when the pH value is less than or equal to 5.2, the stirring time is 10-20 min; and when the pH value is between 5.2 and 5.4, the stirring time is 0-10 min.

5. A low carbon method of producing a backfill material for underground coal mines according to claim 1, characterised in that, In steps 1) and 2), the rotation speed of stirring is 300-500 r / min.

6. A low carbon method of producing a backfill material for underground coal mines according to claim 1, characterised in that, In step 3), the cement content in step 2) is gradually reduced by 2% each time.

7. A low carbon method of producing a backfill material for underground coal mines according to claim 1, characterised in that, In step 3), the CO2 introduction amount in step 1) is gradually reduced by 0.5-1 L each time, the mineralization reaction stirring time in step 1) is gradually reduced by 5-10 min each time, and the stirring time in step 2) is gradually extended by 5-10 min each time.

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