Solid waste-based underground filling material and preparation method thereof

Abstract

This invention provides a solid waste-based downhole backfill material and its preparation method. The preparation method includes: A) pre-treating CFB fly ash by removing impurities and screening to obtain pre-treated CFB fly ash A; B) activating gasification slag to obtain activated gasification slag; then decarbonizing the activated gasification slag to obtain activated gasification slag powder B; C) mixing the pre-treated CFB fly ash A obtained in step A), the activated gasification slag powder B obtained in step B), a composite activator, a composite water-reducing agent, and a composite thickener to obtain activated cementitious powder C; D) mixing coarse and fine gasification slag to obtain mixed gasification slag aggregate D; E) mixing the activated cementitious powder C, the mixed gasification slag aggregate D, and water to obtain the solid waste-based downhole backfill material; wherein steps A) and B) are not in any particular order, and steps C) and D) are not in any particular order. This invention enables waste utilization and meets the performance requirements of downhole backfill materials.

Description

Technical Field

[0001] This invention relates to the field of solid waste utilization technology, and in particular to a solid waste-based well filling material and its preparation method. Background Technology

[0002] In recent years, with the gradual replacement of traditional thermal power generation by circulating fluidized bed (CFB) boiler combustion technology, the emissions of fly ash (CFB fly ash) produced by CFB boilers are enormous. Due to the significant differences in characteristics between this fly ash and traditional fly ash, its large-scale utilization in building materials is restricted. Furthermore, various other solid wastes exist in industry, most of which are stockpiled or landfilled, polluting the environment and consuming substantial land resources.

[0003] Coal mine goaf filling requires a large amount of filling materials. If solid waste could be used to prepare underground filling materials, it would not only save a significant amount of traditional cementitious materials such as cement and slag, greatly reducing filling costs, but also achieve large-scale disposal of solid waste, saving on treatment costs. However, due to the significant differences in characteristics between solid waste and raw materials, and the fact that most solid waste is discarded due to its poor properties, its practical application is greatly limited, making it very difficult to develop useful materials that meet performance requirements from waste. Summary of the Invention

[0004] In view of this, the present invention provides a solid waste-based downhole filling material and its preparation method. The preparation method provided by the present invention can make large-scale use of solid waste, realizing waste utilization, while meeting the performance requirements of downhole filling materials, thus having significant economic and social benefits.

[0005] This invention provides a method for preparing solid waste-based downhole filling material, comprising the following steps:

[0006] A) CFB fly ash is pretreated by removing impurities and screening to obtain pretreated CFB fly ash A;

[0007] B) The gasification slag is activated to obtain activated gasification slag; then the activated gasification slag is decarbonized to obtain activated gasification slag powder B.

[0008] C) Mix the pretreated CFB fly ash A obtained in step A), the activated gasification slag powder B obtained in step B), the composite activator, the composite water-reducing agent and the composite thickener to obtain activated gelling powder C.

[0009] D) Mix the coarse and fine gasification slag to obtain gasification slag aggregate D;

[0010] E) Mix the active cementitious powder C, the gasification slag mixed aggregate D, and water to obtain solid waste-based downhole filling material;

[0011] in,

[0012] There is no order restriction between steps A) and B), and there is no order restriction between steps C) and D).

[0013] Preferably, in step A), the goal of the pretreatment is to ensure that the proportion of CFB fly ash with a particle size <20 is greater than 90 wt% and the loss on ignition is <1%.

[0014] Preferably, in step B):

[0015] The activation treatment is a ball milling process;

[0016] The degree of ball milling is such that the proportion of particles with a particle size of <45μm is above 90wt%.

[0017] The decarbonization process is combustion decarbonization;

[0018] The combustion decarburization temperature is >500℃, and the time is 1 to 4 hours.

[0019] Preferably, in step C), the composite activator is calcium hydroxide, calcium sulfate, sodium hydroxide, and calcium carbonate;

[0020] The preferred mass ratio of calcium hydroxide, calcium sulfate, sodium hydroxide, and calcium carbonate is 60:30:5:5.

[0021] Preferably, in step C), the composite water-reducing agent is CP1901X water-reducing agent and polycarboxylate early-strength high-performance water-reducing agent ZY-HPWR-A;

[0022] The mass ratio of the CP1901X water-reducing agent to the polycarboxylate early-strength high-performance water-reducing agent ZY-HPWR-A is 3:2.

[0023] Preferably, in step C), the composite thickener is a CMC thickener and an HPMC thickener;

[0024] The mass ratio of the CMC thickener to the HPMC thickener is 1:1.

[0025] Preferably, the amounts of each material used in step C) are as follows, by mass:

[0026]

[0027] Preferably, in step D), the particle size of the gasification slag coarse slag is 0.5-20 mm;

[0028] The particle size of the gasification slag fine residue is ≤0.3mm;

[0029] The dry basis mass ratio of the coarse gasification slag to the fine gasification slag is (1-10):1.

[0030] Preferably, in step E), the mortar ratio of the active gelling powder C to the gasification slag mixed aggregate D is 1:(1-8).

[0031] The amount of water used is such that the mass percentage concentration of the mixed solid waste-based downhole filling material is 40% to 95%.

[0032] The present invention also provides a solid waste-based downhole filling material prepared by the preparation method described in the above technical solution.

[0033] The preparation method provided by this invention involves pre-treating CFB fly ash by removing impurities and screening to obtain pre-treated CFB fly ash A; furthermore, activating gasification slag to obtain activated gasification slag; then decarbonizing the activated gasification slag to obtain activated gasification slag powder B; next, mixing the pre-treated CFB fly ash A, the activated gasification slag powder B, a composite activator, a composite water-reducing agent, and a composite thickener to obtain activated cementitious powder C; further mixing coarse and fine gasification slag to obtain mixed gasification slag aggregate D; finally, mixing the activated cementitious powder C, the mixed gasification slag aggregate D, and water to obtain solid waste-based underground backfill material. The preparation method provided by this invention is simple, requiring no crushing of raw materials, no additional addition of cementitious agents or aggregates, and achieving full activation of the solid waste powder by adding a small amount of additives. After the uniform slurry is transported into the underground goaf, it develops compressive strength after a certain period of curing, providing structural support. This method features abundant raw material sources and low preparation costs, while significantly improving the utilization rate of gasification slag and CFB fly ash, resulting in substantial economic benefits. The application areas of this cementitious material include, but are not limited to, underground coal mine backfilling, and it can also be applied to building materials, road engineering, and thermal insulation materials. Detailed Implementation

[0034] Unless otherwise defined, all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art to which this application belongs. The terminology used herein is for the purpose of describing particular embodiments only and is not intended to be limiting of the application.

[0035] In this article, the technical features described in an open-ended manner include both closed technical solutions composed of the listed features and open technical solutions that include the listed features.

[0036] The term “and / or” as used herein includes any and all combinations of one or more of the related listed items.

[0037] In this document, numerical ranges are referred to as continuous unless otherwise specified, and include the minimum and maximum values ​​of the range, as well as every value between the minimum and maximum values. Furthermore, when a range refers to an integer, it includes every integer between the minimum and maximum values ​​of the range. Additionally, when multiple ranges are provided to describe a feature or characteristic, the ranges may be combined. In other words, unless otherwise specified, all ranges disclosed herein should be understood to include any and all subranges to which they are incorporated.

[0038] In this article, when referring to units for data ranges, if the unit is only followed by the right endpoint, it indicates that the units for the left and right endpoints are the same. For example, 0.3~0.5m / s means that the units for the left endpoint "0.3" and the right endpoint "0.5" are both m / s (meters per second).

[0039] This document only specifically discloses some numerical ranges. However, any lower limit can be combined with any upper limit to form an unspecified range; and any lower limit can be combined with other lower limits to form an unspecified range, just as any upper limit can be combined with any other upper limit to form an unspecified range. Furthermore, each individually disclosed point or single value can itself serve as a lower or upper limit and be combined with any other point or single value or with other lower or upper limits to form an unspecified range.

[0040] This invention provides a method for preparing solid waste-based downhole filling material, comprising the following steps:

[0041] A) CFB fly ash is pretreated by removing impurities and screening to obtain pretreated CFB fly ash A;

[0042] B) The gasification slag is activated to obtain activated gasification slag; then the activated gasification slag is decarbonized to obtain activated gasification slag powder B.

[0043] C) Mix the pretreated CFB fly ash A obtained in step A), the activated gasification slag powder B obtained in step B), the composite activator, the composite water-reducing agent and the composite thickener to obtain activated gelling powder C.

[0044] D) Mix the coarse and fine gasification slag to obtain gasification slag aggregate D;

[0045] E) Mix the active cementitious powder C, the gasification slag mixed aggregate D, and water to obtain solid waste-based downhole filling material;

[0046] in,

[0047] There is no order restriction between steps A) and B), and there is no order restriction between steps C) and D).

[0048] Regarding step A) :

[0049] A) CFB fly ash is pretreated by removing impurities and screening to obtain pretreated CFB fly ash A.

[0050] In this invention, the CFB fly ash is the fly ash conventionally defined in the art, namely, fly ash obtained from combustion in a circulating fluidized bed boiler. Specifically, the pretreatment of CFB fly ash for impurity removal and screening includes using sieving and particle size / density sorting methods to remove impurities from the CFB fly ash, thereby improving its quality and ensuring stable application performance. The goal of this pretreatment is to ensure that the proportion of CFB fly ash with a particle size <20 mm is greater than 90 wt%, and the loss on ignition is <1%. Through the above pretreatment, the quality of CFB fly ash is improved, resulting in high-quality pretreated CFB fly ash A.

[0051] Regarding step B) :

[0052] B) The gasification slag is activated to obtain activated gasification slag; then the activated gasification slag is decarbonized to obtain activated gasification slag powder B.

[0053] Gasification slag is the tailings emitted during the coal gasification process. With the vigorous development of coal gasification technology, the amount of gasification slag emitted in my country is also increasing year by year. Due to the characteristics of high water content, high residual carbon and well-developed pore structure, the resource utilization rate of gasification slag is low. Most of it is stockpiled or landfilled, which pollutes the environment and occupies a large amount of land resources.

[0054] In this invention, the particle size of the gasification slag used for treatment is preferably 0.5–20 mm. The gasification slag is first activated. Preferably, the activation is performed using a mechanical-physical activation method, specifically ball milling. Preferably, the proportion of particles with a particle size <45 μm is above 90 wt% after ball milling, thus obtaining activated gasification slag.

[0055] In this invention, after the above activation treatment, decarbonization is performed. The decarbonization treatment in this invention is physical decarbonization or chemical decarbonization, specifically including one or more of the following methods: cyclone classification-spiral separation gravity separation, TBS separation, classification separation, flotation, oil agglomeration separation, carrier flotation, gravity separation-flotation combined method, and combustion decarbonization; more preferably, combustion decarbonization. In this invention, the combustion decarbonization temperature is preferably >500℃, more preferably 550-600℃, specifically 550℃, 560℃, 570℃, 580℃, 590℃, and 600℃; the roasting time for the carbonization decarbonization is preferably 1-4 hours, specifically 1 hour, 2 hours, 3 hours, and 4 hours. After the above combustion decarbonization, decarbonized gasification slag particles with a carbon content (or loss on ignition) meeting the requirements are obtained, wherein the carbon content is preferably controlled to be <3%. After the above treatment, activated gasification slag micro powder B is obtained.

[0056] Regarding step C) :

[0057] C) Mix the pretreated CFB fly ash A obtained in step A), the activated gasification slag powder B obtained in step B), the composite activator, the composite water-reducing agent, and the composite thickener to obtain activated gelling powder C.

[0058] In this invention, the composite activator is preferably calcium hydroxide, calcium sulfate, sodium hydroxide, and calcium carbonate. The preferred mass ratio of calcium hydroxide, calcium sulfate, sodium hydroxide, and calcium carbonate is 60:30:5:5.

[0059] In this invention, the composite water-reducing agent is preferably a polycarboxylate-based water-reducing agent. Specifically, it is preferably a composite of CP1901X water-reducing agent produced by Nanjing Xinyi Synthetic Technology Co., Ltd. and ZY-HPWR-A, a polycarboxylate early-strength high-performance water-reducing agent produced by Hunan Zhongyan Building Materials Technology Co., Ltd. This invention uses the above-mentioned composite water-reducing agent, which can form a comb-like three-dimensional structure, hindering the approach between particles and effectively achieving a water-reducing effect. In this invention, the preferred mass ratio of CP1901X water-reducing agent produced by Nanjing Xinyi Synthetic Technology Co., Ltd. and ZY-HPWR-A, a polycarboxylate early-strength high-performance water-reducing agent produced by Hunan Zhongyan Building Materials Technology Co., Ltd., is 3:2.

[0060] In this invention, the composite thickener is preferably a combination of CMC and HPMC thickeners. The CMC thickener can be provided by Jinan Zhiheng Zhiyuan Chemical Technology Co., Ltd. The HPMC thickener is preferably HPMC400, which can be provided by Wuhan Runxingyuan Technology Co., Ltd. In this invention, the mass ratio of the CMC thickener to the HPMC thickener is preferably 1:1.

[0061] In this invention, the preferred amounts of each material in step C) are as follows, based on parts by weight:

[0062]

[0063] The specific amounts of the pretreated CFB fly ash A can be 30 parts, 35 parts, 40 parts, 45 parts, 50 parts, 55 parts, or 60 parts. The specific amounts of the activated gasification slag powder B can be 30 parts, 35 parts, 40 parts, 45 parts, 50 parts, 55 parts, or 60 parts. The specific amounts of the composite activator can be 5 parts, 6 parts, 7 parts, 8 parts, 9 parts, 10 parts, 11 parts, 12 parts, 13 parts, 14 parts, 15 parts, 16 parts, 17 parts, 18 parts, 19 parts, or 20 parts. The specific amounts of the composite water-reducing agent can be 0.5 parts, 1.0 parts, 1.5 parts, 2.0 parts, 2.5 parts, or 3.0 parts. The specific amounts of the composite thickener can be 0.5 parts, 1.0 parts, 1.5 parts, 2.0 parts, 2.5 parts, or 3.0 parts.

[0064] In some embodiments of the present invention, the amounts of each material in step C) are: 45 parts of pretreated CFB fly ash A, 40 parts of activated gasification slag powder B, 10 parts of composite activator, 3 parts of composite water-reducing agent, and 2 parts of composite thickener. More specifically, the amounts of each material in step C) are: 45 parts of pretreated CFB fly ash A, 40 parts of activated gasification slag powder B, 10 parts of composite activator, 3 parts of composite water-reducing agent, and 2 parts of composite thickener; wherein, the composite activator is a composite activator with a mass ratio of calcium hydroxide:calcium sulfate:sodium hydroxide:calcium carbonate = 60:30:5:5; the composite water-reducing agent is a composite water-reducing agent with a mass ratio of CP1901X:ZY-HPWR-A = 3:2; and the composite thickener is a composite thickener with a mass ratio of CMC:HPMC400 = 1:1.

[0065] In some other embodiments of the present invention, the amounts of each material in step C) are: 40 parts of pretreated CFB fly ash A, 45 parts of activated gasification slag powder B, 10 parts of composite activator, 3 parts of composite water-reducing agent, and 2 parts of composite thickener. More specifically, the amounts of each material in step C) are: 40 parts of pretreated CFB fly ash A, 45 parts of activated gasification slag powder B, 10 parts of composite activator, 3 parts of composite water-reducing agent, and 2 parts of composite thickener; wherein, the composite activator is a composite activator with a mass ratio of calcium hydroxide:calcium sulfate:sodium hydroxide:calcium carbonate = 60:30:5:5; the composite water-reducing agent is a composite water-reducing agent with a mass ratio of CP1901X:ZY-HPWR-A = 3:2; and the composite thickener is a composite thickener with a mass ratio of CMC:HPMC400 = 1:1.

[0066] In some other embodiments of the present invention, the amounts of each material in step C) are: 30 parts of pretreated CFB fly ash A, 55 parts of activated gasification slag powder B, 10 parts of composite activator, 3 parts of composite water-reducing agent, and 2 parts of composite thickener. More specifically, the amounts of each material in step C) are: 30 parts of pretreated CFB fly ash A, 55 parts of activated gasification slag powder B, 10 parts of composite activator, 3 parts of composite water-reducing agent, and 2 parts of composite thickener; wherein, the composite activator is a composite activator with a mass ratio of calcium hydroxide:calcium sulfate:sodium hydroxide:calcium carbonate = 60:30:5:5; the composite water-reducing agent is a composite water-reducing agent with a mass ratio of CP1901X:ZY-HPWR-A = 3:2; and the composite thickener is a composite thickener with a mass ratio of CMC:HPMC400 = 1:1.

[0067] In this invention, the mixing equipment used to mix the pretreated CFB fly ash A obtained in step A), the activated gasification slag powder B obtained in step B), the composite activator, the composite water-reducing agent, and the composite thickener includes, but is not limited to, a V-type mixer, a double cone mixer, a ribbon mixer, a gravity-free mixer, a twin-shaft stirring mixer, and a planetary ball mill. There are no special restrictions on the mixing conditions; any condition sufficient to ensure uniform mixing of the above materials is acceptable. After the above mixing, activated gelling powder C is obtained.

[0068] Regarding step D) :

[0069] D) Mix the coarse and fine gasification slag to obtain gasification slag aggregate D.

[0070] Gasification slag is the waste residue produced by coal gasification, and it includes coarse slag and fine slag depending on the discharge location. This invention mixes the coarse and fine gasification slag to obtain mixed gasification slag aggregate D. In this invention, the particle size of the coarse gasification slag is 0.5–20 mm; the particle size of the fine gasification slag is ≤0.3 mm. In this invention, the dry basis mass ratio (i.e., the mass ratio under dry, anhydrous conditions) of the coarse and fine gasification slag is preferably (1–10):1, specifically 1:1, 2:1, 3:1, 4:1, 5:1, 6:1, 7:1, 8:1, 9:1, 10:1, and more preferably 2:1 or 4:1.

[0071] This invention does not impose any particular restrictions on the method of mixing the coarse and fine gasification slag, as long as conventional mixing methods in the art can be used to mix the two evenly. After mixing, the gasification slag mixed aggregate D is obtained.

[0072] Regarding step E) :

[0073] E) The active gelling powder C, the gasification slag mixed aggregate D, and water are mixed to obtain solid waste-based downhole filling material.

[0074] In this invention, the mortar ratio (i.e., the mass ratio of the active cementitious powder C to the gasification slag mixed aggregate D) is preferably 1:(1 to 8), specifically 1:1, 1:2, 1:3, 1:4, 1:5, 1:6, 1:7, 1:8, and more preferably 1:4.

[0075] In this invention, the amount of water used is preferably such that the mass percentage concentration of the mixed slurry (i.e., downhole filling material) is 40% to 95%, specifically 40%, 45%, 50%, 55%, 60%, 65%, 70%, 75%, 80%, 85%, 90%, and 95%.

[0076] This invention does not impose any special restrictions on the mixing method; any conventional mixing method in the art that can mix the materials evenly, such as stirring, is acceptable. The agitator used for stirring can be a concrete mixer, such as a free-fall concrete mixer, a forced-action concrete mixer, a stationary concrete mixer, or a mobile concrete mixer, or it can be a twin-cone mixer, a twin-shaft mixer, a single-shaft mixer, or a vertical-shaft planetary mixer, as long as it meets the mixing requirements of the adhesive. After mixing, a slurry is obtained, which is the solid waste-based well filling material.

[0077] The present invention also provides a solid waste-based downhole filling material prepared by the preparation method described in the above technical solution.

[0078] The preparation method provided by this invention involves pre-treating CFB fly ash by removing impurities and screening to obtain pre-treated CFB fly ash A; furthermore, activating gasification slag to obtain activated gasification slag; then decarbonizing the activated gasification slag to obtain activated gasification slag powder B; next, mixing the pre-treated CFB fly ash A, the activated gasification slag powder B, a composite activator, a composite water-reducing agent, and a composite thickener to obtain activated cementitious powder C; further mixing coarse and fine gasification slag to obtain mixed gasification slag aggregate D; finally, mixing the activated cementitious powder C, the mixed gasification slag aggregate D, and water to obtain solid waste-based underground backfill material. The preparation method provided by this invention is simple, requiring no crushing of raw materials, no additional addition of cementitious agents or aggregates, and achieving full activation of the solid waste powder by adding a small amount of additives. After the uniform slurry is transported into the underground goaf, it develops compressive strength after a certain period of curing, providing structural support. This method features abundant raw material sources and low preparation costs, while significantly improving the utilization rate of gasification slag and CFB fly ash, resulting in substantial economic benefits. The application areas of this cementitious material include, but are not limited to, underground coal mine backfilling, and it can also be applied to building materials, road engineering, and thermal insulation materials.

[0079] To further understand the present invention, preferred embodiments of the present invention are described below in conjunction with examples. However, it should be understood that these descriptions are only for further illustrating the features and advantages of the present invention, and not for limiting the scope of the claims of the present invention.

[0080] Example 1

[0081] A) Using sieving and particle size classification / density sorting methods, impurities in CFB fly ash are removed to obtain high-quality pretreated CFB fly ash A with a particle size <20μm and a CFB fly ash content greater than 90wt% and a loss on ignition <1%.

[0082] B) The gasification slag (particle size 0.5-20 mm) is ball-milled and activated until the proportion of particles <45 μm is above 90 wt%, thus obtaining activated gasification slag. Then, the activated gasification slag is placed in an electric furnace at 550℃ and calcined for 3 hours to make the carbon content of the gasification slag <3%, thus obtaining activated gasification slag micro powder B.

[0083] C) Add the pretreated CFB fly ash A obtained in step A), the activated gasification slag powder B obtained in step B), the composite activator, the composite water-reducing agent, and the composite thickener into the mixing device and mix them thoroughly to obtain activated gelling powder C.

[0084] The usage of each material is as follows:

[0085]

[0086] The composite activator is a composite activator with a mass ratio of calcium hydroxide:calcium sulfate:sodium hydroxide:calcium carbonate = 60:30:5:5; the composite water-reducing agent is a composite water-reducing agent with a mass ratio of CP1901X:ZY-HPWR-A = 3:2; and the composite thickener is a composite thickener with a mass ratio of CMC:HPMC400 = 1:1.

[0087] D) Mix coarse gasification slag (particle size 0.5-20 mm) and fine gasification slag (particle size ≤ 0.3 mm) at a dry basis mass ratio of 4:1 to obtain gasification slag mixed aggregate D.

[0088] E) Add the active gelling powder C and the gasification slag mixed aggregate D into the mixer at a mortar-to-gel ratio of 1:4, add a certain amount of tap water, and stir evenly to obtain solid waste-based well filling material (slurry concentration of 70%).

[0089] Example 2

[0090] A) Using sieving and particle size classification / density sorting methods, impurities in CFB fly ash are removed to obtain high-quality pretreated CFB fly ash A with a particle size <20μm and a CFB fly ash content greater than 90wt% and a loss on ignition <1%.

[0091] B) The gasification slag (particle size 0.5-20 mm) is ball-milled and activated until the proportion of particles <45 μm is above 90 wt%, thus obtaining activated gasification slag. Then, the activated gasification slag is placed in an electric furnace at 550℃ and calcined for 3 hours to make the carbon content of the gasification slag <3%, thus obtaining activated gasification slag micro powder B.

[0092] C) Add the pretreated CFB fly ash A obtained in step A), the activated gasification slag powder B obtained in step B), the composite activator, the composite water-reducing agent, and the composite thickener into the mixing device and mix them thoroughly to obtain activated gelling powder C.

[0093] The usage of each material is as follows:

[0094]

[0095] The composite activator is a composite activator with a mass ratio of calcium hydroxide:calcium sulfate:sodium hydroxide:calcium carbonate = 60:30:5:5; the composite water-reducing agent is a composite water-reducing agent with a mass ratio of CP1901X:ZY-HPWR-A = 3:2; and the composite thickener is a composite thickener with a mass ratio of CMC:HPMC400 = 1:1.

[0096] D) Mix coarse gasification slag (particle size 0.5-20 mm) and fine gasification slag (particle size ≤ 0.3 mm) at a dry basis mass ratio of 4:1 to obtain gasification slag mixed aggregate D.

[0097] E) Add the active gelling powder C and the gasification slag mixed aggregate D into the mixer at a mortar-to-gel ratio of 1:4, add a certain amount of tap water, and stir evenly to obtain solid waste-based well filling material (slurry concentration of 70%).

[0098] Example 3

[0099] A) Using sieving and particle size classification / density sorting methods, impurities in CFB fly ash are removed to obtain high-quality pretreated CFB fly ash A with a particle size <20μm and a CFB fly ash content greater than 90wt% and a loss on ignition <1%.

[0100] B) The gasification slag (particle size 0.5-20 mm) is ball-milled and activated until the proportion of particles <45 μm is above 90 wt%, thus obtaining activated gasification slag. Then, the activated gasification slag is placed in an electric furnace at 550℃ and calcined for 3 hours to make the carbon content of the gasification slag <3%, thus obtaining activated gasification slag micro powder B.

[0101] C) Add the pretreated CFB fly ash A obtained in step A), the activated gasification slag powder B obtained in step B), the composite activator, the composite water-reducing agent, and the composite thickener into the mixing device and mix them thoroughly to obtain activated gelling powder C.

[0102] The usage of each material is as follows:

[0103]

[0104] The composite activator is a composite activator with a mass ratio of calcium hydroxide:calcium sulfate:sodium hydroxide:calcium carbonate = 60:30:5:5; the composite water-reducing agent is a composite water-reducing agent with a mass ratio of CP1901X:ZY-HPWR-A = 3:2; and the composite thickener is a composite thickener with a mass ratio of CMC:HPMC400 = 1:1.

[0105] D) Mix coarse gasification slag (particle size 0.5-20 mm) and fine gasification slag (particle size ≤ 0.3 mm) at a dry basis mass ratio of 2:1 to obtain gasification slag mixed aggregate D.

[0106] E) Add the active gelling powder C and the gasification slag mixed aggregate D into the mixer at a mortar-to-gel ratio of 1:4, add a certain amount of tap water, and stir evenly to obtain solid waste-based well filling material (slurry concentration of 70%).

[0107] Product Testing :

[0108] The cementitious slurry was prepared according to GB / T 17671-1999 "Test Method for Strength of Cement Mortar (ISO Method)" as follows: The filling material obtained in the example was immediately mixed using a JJ-5 planetary mortar mixer to obtain a uniform cementitious slurry. The uniformly mixed slurry was immediately poured into a 40×40×40mm steel mold, compacted using a ZT-96 cement mortar vibrating table (120s), and the surface was smoothed before being placed in a YH-40B constant temperature and humidity chamber for standard curing. The curing temperature was set at 20±1℃, and the relative humidity was set at ≥90%. The compressive strength of the cementitious body was tested using a WYA-300 pressure testing machine with a pressure loading rate of 2400±200 N / s. The test ages were 3d, 7d, and 28d. The arithmetic mean of the three measured values ​​was taken as the test result. The test results are shown in Table 1.

[0109] Table 1: Product Test Results

[0110]

[0111] As can be seen from the test results in Table 1, the 28-day strength of the downhole filling material obtained by the present invention can reach more than 4.5 MPa. In particular, the 28-day strength of the downhole filling material obtained in Example 1 is as high as 5.14 MPa, which can fully meet the requirements of downhole filling for the strength of the filling body over age.

[0112] This document uses specific examples to illustrate the principles and implementation methods of the present invention. The descriptions of these embodiments are merely to aid in understanding the method and core ideas of the present invention, including the best mode, and to enable any person skilled in the art to practice the present invention, including manufacturing and using any device or system, and implementing any combined method. It should be noted that those skilled in the art can make various improvements and modifications to the present invention without departing from its principles, and these improvements and modifications also fall within the scope of protection of the claims. The scope of protection of this patent is defined by the claims and may include other embodiments that can be conceived by those skilled in the art. If these other embodiments have structural elements similar to those expressed in the claims, or if they include equivalent structural elements that are not substantially different from those expressed in the claims, then these other embodiments should also be included within the scope of the claims.

Claims

1. A method for preparing a solid waste-based downhole filling material, characterized in that, Includes the following steps: A) Using sieving and particle size classification / density sorting methods, impurities in CFB fly ash are removed to obtain high-quality pretreated CFB fly ash A with a particle size <20μm and a CFB fly ash content greater than 90wt% and a loss on ignition <1%. B) The gasification slag with a particle size of 0.5~20mm is ball-milled and activated until the proportion of particles with a particle size <45μm is more than 90wt%, thus obtaining activated gasification slag; then, the activated gasification slag is placed in an electric furnace at 550℃ and calcined for 3h to make the carbon content of the gasification slag <3%, thus obtaining activated gasification slag micro powder B. C) Add the pretreated CFB fly ash A obtained in step A), the activated gasification slag powder B obtained in step B), the composite activator, the composite water-reducing agent and the composite thickener into the mixing device and mix them thoroughly to obtain the activated gelling powder C. The usage of each material is as follows: Pre-treated CFB fly ash A, 45 parts; 40 parts of activated gasification slag powder B; 10 parts of composite activator; 3 parts of composite water-reducing agent; Two parts of compound thickener; Among them, the composite activator is a composite activator with a mass ratio of calcium hydroxide: calcium sulfate: sodium hydroxide: calcium carbonate = 60:30:5:5; the composite water reducing agent is a composite water reducing agent with a mass ratio of CP1901X:ZY-HPWR-A = 3:2; and the composite thickener is a composite thickener with a mass ratio of CMC:HPMC400 = 1:

1. D) Mix coarse gasification slag with a particle size of 0.5~20mm and fine gasification slag with a particle size of ≤0.3mm at a dry basis mass ratio of 4:1 to obtain gasification slag mixed aggregate D; E) Add the active gelling powder C and the gasification slag mixed aggregate D into the mixer at a mortar-to-gel ratio of 1:4, add a certain amount of tap water, and stir evenly to obtain a solid waste-based well filling material with a slurry concentration of 70%.

2. A solid waste-based well filling material prepared by the method described in claim 1.

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