Special solid waste-based solidifying agent for sludge and preparation method and application thereof

Abstract

The present application relates to solid waste resource utilization and sludge treatment technical field, provide a kind of sludge special solid waste base curing agent and its preparation method and application.The curing agent takes fly ash base calcium-aluminum layered double hydroxide as core, with converter steel slag micro powder, coal gasification slag micro powder as main cementitious material, composite powder of biochar-layered double hydroxide is prepared by loading process, using calcium chloride, sodium sulfate composite excitation system, supplemented by desulfurization gypsum, alkali modified waste glass powder and other components.The present application effectively eliminates the inhibition of organic matter on hydration reaction, solves the problems of poor volume stability and poor heavy metal solidification effect of traditional curing agent, and the curing agent has high sludge strength, good water stability and low heavy metal leaching concentration, and can be widely used in the solidification treatment of various types of water-soft sediment.

Description

Technical Field

[0001] This invention relates to the field of solid waste resource utilization and sludge treatment technology, and more specifically, to a solid waste-based solidifying agent for sludge, its preparation method, and its application. Background Technology

[0002] With the large-scale construction of water conservancy projects, urban water environment management, and port and waterway dredging projects in my country, more than 2 billion tons of various types of water-bearing soft sediments are generated annually. These sediments are generally characterized by high water content, high organic matter content, low strength, high compressibility, and serious heavy metal pollution. If they are directly piled up or landfilled, they will not only occupy a large amount of land resources, but also cause a series of environmental problems such as groundwater pollution, soil degradation, and ecological damage.

[0003] Currently, solidification and stabilization technology is one of the most economical and effective methods for treating aquatic soft sediments, but existing technologies still have many insurmountable drawbacks: 1) Traditional hardeners such as cement and lime are extremely ineffective in treating sludge with high organic matter content. The humic acid, fulvic acid, and other organic matter in the sludge adsorb onto the surface of the cementitious material particles, forming a dense organic film that hinders the hydration reaction, resulting in low early strength and slow strength gain in the solidified body. When the organic matter content in the sludge exceeds 5%, ordinary cement-based hardeners become almost completely ineffective and cannot meet engineering requirements.

[0004] 2) Single sulfate activators can easily lead to the formation of excessive needle-shaped ettringite crystals inside the solidified body, resulting in volume expansion and cracking; industrial solid wastes such as converter steel slag contain a large amount of free calcium oxide and free magnesium oxide, which will slowly hydrate in the later stage to form Ca(OH)2 and Mg(OH)2, which will lead to a large volume expansion, causing cracks, reduced strength, or even destruction of the solidified body.

[0005] 3) Traditional curing agents mainly rely on physical encapsulation to cure heavy metals. Under harsh environments such as acidic conditions, alternating wet and dry conditions, or freeze-thaw cycles, the encapsulation layer is easily damaged, and heavy metals will dissolve out again, posing a serious risk of secondary pollution.

[0006] 4) In the existing technology, when biochar is used as an organic matter adsorbent, ordinary biochar has a limited adsorption capacity and cannot simultaneously achieve efficient solidification of heavy metals; although layered double hydroxides (LDH) have excellent adsorption performance, they are prone to agglomeration when prepared alone, resulting in poor dispersibility and significantly reduced practical application effect; the excitation system is singular and it is difficult to balance the relationship between early strength development and later volume stability.

[0007] Therefore, how to develop a solid waste-based sludge solidifying agent that can effectively eliminate the inhibitory effect of organic matter while achieving high strength, high stability and efficient heavy metal solidification is a technical problem that urgently needs to be solved by those skilled in the art. Summary of the Invention

[0008] In view of this, the present invention proposes a solid waste-based solidifying agent for sludge, its preparation method and application, aiming to eliminate the inhibition of hydration reaction by organic matter and solve the problems of poor volume stability and poor solidification effect of traditional solidifying agents.

[0009] This invention proposes a solid waste-based solidifying agent for sludge, which, by mass, consists of the following components: 100 parts of fly ash-based calcium-aluminum layered double hydroxide, 4-8 parts of calcium chloride, 2-4 parts of sodium sulfate, 20-40 parts of converter steel slag powder, 15-30 parts of coal gasification slag powder, 35-55 parts of alkali-modified biochar, 10-25 parts of desulfurized gypsum, 25-45 parts of alkali-modified waste glass powder, 0.3-1.8 parts of triethanolamine, and 0.8-2.2 parts of polypropylene fiber.

[0010] Preferably, the preparation method of the fly ash-based calcium-aluminum layered double hydroxide is as follows: fly ash is mixed with hydrochloric acid solution and stirred to react, and then filtered to obtain an acid leaching solution; calcium hydroxide is added to the acid leaching solution to adjust the pH, and the stirring reaction is carried out again. After the reaction is completed, the fly ash-based calcium-aluminum layered double hydroxide is obtained by sequentially filtering, washing, drying and grinding.

[0011] Preferably, the hydrochloric acid solution has a mass fraction of 18% to 28%, the solid-liquid ratio of fly ash to hydrochloric acid solution is 1:4 to 1:6, the temperature of the mixing and stirring reaction is 55 to 75°C, the time is 3 to 5 hours, and the stirring rate is 300 to 500 rpm.

[0012] Preferably, the pH is adjusted to 10.5~12.5; the temperature for the second stirring reaction is 55~75℃, the time is 5~7h, and the stirring rate is 400~500rpm; the washing is performed until neutral; the drying temperature is 60~80℃; and the grinding specification is to pass through a 400~800 mesh sieve.

[0013] Preferably, the fly ash further includes a pretreatment step before use: grinding the raw fly ash until it all passes through a 200-mesh sieve, removing magnetic iron impurities by magnetic separation, and then calcining it at 900°C for 1.5 hours and naturally cooling it to room temperature.

[0014] Preferably, the converter slag powder is ground to pass through a 300-600 mesh sieve.

[0015] Preferably, the coal gasification slag powder is ground to pass through a 200-500 mesh sieve.

[0016] Preferably, the pretreatment step before grinding converter steel slag into micro powder includes: crushing the raw converter steel slag to a particle size ≤5mm using a jaw crusher, and then aging it with water for 35 days, during which water is sprayed once every 7 days.

[0017] Preferably, the process before grinding the coal gasification slag into micro powder includes a pretreatment step: mixing the raw coal gasification slag with water at a solid-liquid ratio of 1:2.5, stirring and washing for 2 hours, filtering to remove soluble impurities and residual ammonia, drying at 105°C, and then calcining at 600°C for 1 hour.

[0018] Preferably, the polypropylene fiber has a length of 6-12 mm and a diameter of 10-20 μm.

[0019] Preferably, the method for preparing the alkali-modified biochar is as follows: agricultural straw is crushed and pyrolyzed to obtain biochar; the biochar and sodium hydroxide solution are mixed and stirred to react; and then filtered, washed, dried and ground in sequence to obtain alkali-modified biochar.

[0020] Preferably, the agricultural straw includes wheat straw, corn straw, rice straw, cotton straw, or potato straw; the pyrolysis temperature is 450~650℃, and the time is 3~5h.

[0021] Preferably, the sodium hydroxide solution has a mass fraction of 8% to 15%; the solid-liquid ratio of the biochar and sodium hydroxide solution is 1:6 to 1:9; the stirring reaction temperature is 75 to 95°C, the reaction time is 2.5 to 4 hours, and the stirring rate is 400 to 600 rpm; the washing is performed until neutral; the drying temperature is 80 to 100°C; and the grinding is performed until the material passes through a 200 to 400 mesh sieve.

[0022] Preferably, the method for preparing the alkali-modified waste glass powder is as follows: waste glass is washed, dried, crushed, ground to obtain waste glass powder, mixed with sodium hydroxide solution and stirred to react, and then filtered, washed and dried in sequence to obtain the powder.

[0023] Preferably, the grinding process is completed to pass through a 100-200 mesh sieve; the mass fraction of the sodium hydroxide solution is 8%-15%; the solid-liquid ratio of the waste glass powder to the sodium hydroxide solution is 1:2-1:4; the stirring reaction temperature is 60-80℃, and the time is 1.5-2.5h; the stirring rate is 300-500rpm; and the drying temperature is 100-110℃.

[0024] The present invention also aims to provide a method for preparing the aforementioned sludge-specific solid waste-based solidifying agent, comprising the following steps: S1: Add fly ash-based calcium-aluminum layered double hydroxide and alkali-modified biochar to water, adjust the pH value, and then stir the reaction. After the reaction is completed, filter and wash in sequence to obtain the loaded composite powder. S2: Mix converter steel slag powder, coal gasification slag powder, desulfurization gypsum and alkali-modified waste glass powder to obtain mixed powder; S3: Add calcium chloride, sodium sulfate and triethanolamine to water and stir to obtain a mixed solution; S4: Mix the mixed solution and mixed powder, and stir to obtain a slurry; S5: Add the loaded composite powder and polypropylene fiber obtained in step S1 to the slurry and stir to obtain a solid waste-based solidifying agent for sludge.

[0025] Preferably, in step S1, the solid-liquid ratio of fly ash-based calcium-aluminum layered double hydroxide to alkali-modified biochar and water is 1:3 to 1:5, the pH value is adjusted to a range of 9.5 to 10.5, the stirring reaction temperature is 50 to 70°C, the time is 2 to 4 hours, and the stirring rate is 400 to 600 rpm.

[0026] Preferably, in step S2, the mixing is carried out under stirring conditions, with a stirring rate of 350~550 rpm and a stirring time of 6~12 min.

[0027] Preferably, in step S3, the mass of water is 35% to 55% of the mass of the mixed powder; and the stirring speed is 400 to 600 rpm.

[0028] Preferably, in step S4, the stirring rate is 550~850 rpm and the stirring time is 12~18 min.

[0029] Preferably, in step S5, the stirring rate is 900~1300 rpm and the time is 8~15 min; and nitrogen gas is introduced for protection during the stirring process.

[0030] The present invention also aims to provide an application of the silt-specific solid waste-based solidifying agent in the solidification and stabilization of water-bearing soft sediments, including river dredging silt, lake and reservoir silt, municipal drainage network silt, building foundation pit silt, port and waterway dredging silt, heavy metal contaminated silt, tailings pond tailings, aquaculture pond silt, and bay tidal flat silt; the solidified product is used as roadbed filler, engineering backfill soil, slope protection engineering material, dike reinforcement material, or greening planting soil.

[0031] Compared with the prior art, the beneficial effects of the present invention are as follows: 1) This invention uses industrial solid waste such as fly ash, converter steel slag, coal gasification slag, desulfurization gypsum, and waste glass as the main raw materials. The solid waste utilization rate exceeds 90%, realizing the high-value utilization of industrial solid waste, reducing the production cost of curing agents, reducing carbon emissions caused by cement production, and conforming to the concept of green and low-carbon development.

[0032] 2) This invention employs an on-site loading process to uniformly grow fly ash-based calcium-aluminum layered double hydroxides on the surface of alkali-modified biochar, constructing a "biochar-LDH" core-shell structure. Biochar captures large-molecule organic matter through physical adsorption, while LDH adsorbs small-molecule organic matter through interlayer ion exchange and surface complexation. The two work synergistically to effectively eliminate the interference of organic matter on the hydration reaction, solving the problem of solidification of high-organic-matter sludge.

[0033] 3) This invention employs a calcium chloride-sodium sulfate composite salt activation system. Calcium chloride provides chloride ions that react with tricalcium aluminate to generate Friedel's salt, promoting the formation of early hydration products. Sodium sulfate provides sulfate ions that react with calcium and aluminum ions to generate ettringite, filling the internal pores. The combined use of these two components avoids the expansion and cracking problem caused by excessive ettringite formation due to a single sulfate activator, significantly improving the volume stability and durability of the solidified body.

[0034] 4) This invention immobilizes heavy metal ions through multiple mechanisms, including physical adsorption, chemical complexation, and gel encapsulation. Biochar and LDH lock in heavy metals through physical adsorption and chemical complexation. The interlayer ion exchange of LDH can embed heavy metal ions into the interlayer. The CSH gel generated by hydration further encapsulates the heavy metals, significantly reducing the leaching concentration of heavy metals and preventing secondary pollution.

[0035] 5) This invention incorporates alkali-modified waste glass powder and polypropylene fibers. The active silica provided by the alkali-modified waste glass powder can react with calcium hydroxide to produce more CSH gel, thereby increasing the density and strength of the solidified body. The polypropylene fibers construct a three-dimensional network structure inside the solidified body, enhancing tensile strength and crack resistance. After solidification, the sludge exhibits high unconfined compressive strength, excellent water stability, and superior volume stability, making it widely applicable in various fields such as river dredging, lake management, and municipal engineering. Detailed Implementation

[0036] Various exemplary embodiments of the present invention will now be described in detail. This detailed description should not be considered as a limitation of the present invention, but rather as a more detailed description of certain aspects, features, and embodiments of the present invention. It should be understood that the terminology used in this invention is merely for describing particular embodiments and is not intended to limit the present invention.

[0037] Furthermore, regarding the numerical ranges in this invention, it should be understood that each intermediate value between the upper and lower limits of the range is also specifically disclosed. Every smaller range between any stated value or intermediate value within a stated range, and any other stated value or intermediate value within said range, is also included within this invention. The upper and lower limits of these smaller ranges may be independently included or excluded from the range.

[0038] Unless otherwise stated, all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art. While only preferred methods and materials have been described herein, any methods and materials similar or equivalent to those described herein may be used in the implementation or testing of this invention. All references to this specification are incorporated by way of citation to disclose and describe methods and / or materials associated with those references. In the event of any conflict with any incorporated reference, the content of this specification shall prevail.

[0039] Various modifications and variations can be made to the specific embodiments described in this specification without departing from the scope or spirit of the invention, as will be apparent to those skilled in the art. Other embodiments derived from this specification will also be apparent to those skilled in the art. This specification and embodiments are merely exemplary.

[0040] The terms “include,” “including,” “have,” “contain,” etc., used in this article are all open-ended terms, meaning that they include but are not limited to.

[0041] This invention proposes a solid waste-based solidifying agent for sludge, which, by mass, consists of the following components: 100 parts of fly ash-based calcium-aluminum layered double hydroxide, 4-8 parts of calcium chloride, 2-4 parts of sodium sulfate, 20-40 parts of converter steel slag powder, 15-30 parts of coal gasification slag powder, 35-55 parts of alkali-modified biochar, 10-25 parts of desulfurized gypsum, 25-45 parts of alkali-modified waste glass powder, 0.3-1.8 parts of triethanolamine, and 0.8-2.2 parts of polypropylene fiber.

[0042] In this invention, the preferred method for preparing the fly ash-based calcium-aluminum layered double hydroxide is as follows: fly ash is mixed with hydrochloric acid solution and stirred to react, then filtered to obtain an acid leaching solution; calcium hydroxide is added to the acid leaching solution to adjust the pH, and the mixture is stirred to react again. After the reaction is completed, the mixture is filtered, washed, dried, and ground in sequence to obtain the fly ash-based calcium-aluminum layered double hydroxide.

[0043] In this invention, the mass fraction of the hydrochloric acid solution is preferably 18%~28%, more preferably 20%~25%; the solid-liquid ratio of fly ash and hydrochloric acid solution is preferably 1:4~1:6, more preferably 1:4.5~1:5.5; the temperature of the stirring reaction after mixing is preferably 55~75℃, more preferably 60~70℃; the time is preferably 3~5h, more preferably 3.5~4.5h; and the stirring rate is preferably 300~500rpm, more preferably 350~450rpm.

[0044] In this invention, the pH adjustment is preferably to 10.5-12.5, more preferably 11-12; the temperature for the second stirring reaction is preferably 55-75°C, more preferably 60-70°C; the time is preferably 5-7 hours, more preferably 5.5-6.5 hours; the stirring rate is preferably 400-500 rpm, more preferably 420-480 rpm; the washing is preferably to neutralize; the drying temperature is preferably 60-80°C, more preferably 65-75°C; and the grinding specification is preferably through a 400-800 mesh sieve, more preferably 500-700 mesh.

[0045] In this invention, the fly ash further includes a pretreatment step before use: grinding the raw fly ash until it all passes through a 200-mesh sieve, removing magnetic iron impurities by magnetic separation, and then calcining it at 900°C for 1.5 hours and naturally cooling it to room temperature.

[0046] In this invention, the converter steel slag powder is preferably ground to pass through a 300-600 mesh sieve, more preferably 400-500 mesh.

[0047] In this invention, the coal gasification slag powder is preferably ground to pass through a 200-500 mesh sieve, more preferably 300-400 mesh.

[0048] In this invention, the length of the polypropylene fiber is preferably 6-12 mm, more preferably 8-10 mm; the diameter is preferably 10-20 μm, more preferably 12-16 μm.

[0049] In this invention, the pretreatment step before grinding converter steel slag micro powder is also included: the original converter steel slag is crushed to a particle size ≤5mm by a jaw crusher, and then watered and aged for 35 days, during which water is sprayed once every 7 days.

[0050] In this invention, the pretreatment step before grinding the coal gasification slag into micro powder is also included: mixing the raw coal gasification slag with water at a solid-liquid ratio of 1:2.5, stirring and washing for 2 hours, filtering to remove soluble impurities and residual ammonia, drying at 105°C, and then calcining at 600°C for 1 hour.

[0051] In this invention, the method for preparing the alkali-modified biochar is as follows: agricultural straw is crushed and pyrolyzed to obtain biochar; the biochar and sodium hydroxide solution are mixed and stirred to react; and then filtered, washed, dried and ground in sequence to obtain alkali-modified biochar.

[0052] In this invention, the agricultural straw includes wheat straw, corn straw, rice straw, cotton straw, or potato straw; the pyrolysis temperature is 450~650℃, and the time is 3~5h.

[0053] In this invention, the mass fraction of the sodium hydroxide solution is 8%~15%; the solid-liquid ratio of the biochar and sodium hydroxide solution is 1:6~1:9; the temperature of the stirring reaction is 75~95℃, the reaction time is 2.5~4h, and the stirring rate is 400~600rpm; the washing is performed until neutral; the drying temperature is 80~100℃; and the grinding is performed until the material passes through a 200~400 mesh sieve.

[0054] In this invention, the method for preparing the alkali-modified waste glass powder is as follows: waste glass is washed, dried, crushed, ground to obtain waste glass powder, mixed with sodium hydroxide solution and stirred to react, and then filtered, washed and dried in sequence to obtain the powder.

[0055] In this invention, the grinding process is described as passing through a 100-200 mesh sieve; the mass fraction of the sodium hydroxide solution is 8%-15%; the solid-liquid ratio of the waste glass powder to the sodium hydroxide solution is 1:2-1:4; the stirring reaction temperature is 60-80℃, and the time is 1.5-2.5h; the stirring rate is 300-500rpm; and the drying temperature is 100-110℃.

[0056] The present invention also aims to provide a method for preparing the aforementioned sludge-specific solid waste-based solidifying agent, comprising the following steps: S1: Add fly ash-based calcium-aluminum layered double hydroxide and alkali-modified biochar to water, adjust the pH value, and then stir the reaction. After the reaction is completed, filter and wash in sequence to obtain the loaded composite powder. S2: Mix converter steel slag powder, coal gasification slag powder, desulfurization gypsum and alkali-modified waste glass powder to obtain mixed powder; S3: Add calcium chloride, sodium sulfate and triethanolamine to water and stir to obtain a mixed solution; S4: Mix the mixed solution and mixed powder, and stir to obtain a slurry; S5: Add the loaded composite powder and polypropylene fiber obtained in step S1 to the slurry and stir to obtain a solid waste-based solidifying agent for sludge.

[0057] In this invention, in step S1, the solid-liquid ratio of fly ash-based calcium-aluminum layered double hydroxide to alkali-modified biochar and water is 1:3 to 1:5, the pH value is adjusted to a range of 9.5 to 10.5, the stirring reaction temperature is 50 to 70°C, the time is 2 to 4 hours, and the stirring rate is 400 to 600 rpm.

[0058] In this invention, in step S2, the mixing is carried out under stirring conditions, with a stirring rate of 350~550 rpm and a stirring time of 6~12 min.

[0059] In this invention, in step S3, the mass of water is 35% to 55% of the mass of the mixed powder; the stirring speed is 400 to 600 rpm.

[0060] In this invention, in step S4, the stirring rate is 550~850 rpm and the stirring time is 12~18 min.

[0061] In this invention, in step S5, the stirring rate is 900~1300 rpm and the time is 8~15 min; and nitrogen gas is introduced for protection during the stirring process.

[0062] The present invention also aims to provide an application of the silt-specific solid waste-based solidifying agent in the solidification and stabilization of water-bearing soft sediments, including river dredging silt, lake and reservoir silt, municipal drainage network silt, building foundation pit silt, port and waterway dredging silt, heavy metal contaminated silt, tailings pond tailings, aquaculture pond silt, and bay tidal flat silt; the solidified product is used as roadbed filler, engineering backfill soil, slope protection engineering material, dike reinforcement material, or greening planting soil.

[0063] To better understand the present invention, the following embodiments are provided for further illustration, but the content of the present invention is not limited to the following embodiments.

[0064] Example 1 1. Group composition ratio: 100 parts of fly ash-based calcium-aluminum layered double hydroxide, 4 parts of calcium chloride, 2 parts of sodium sulfate, 20 parts of converter steel slag powder, 15 parts of coal gasification slag powder, 35 parts of alkali-modified biochar, 10 parts of desulfurized gypsum, 25 parts of alkali-modified waste glass powder, 0.3 parts of triethanolamine, and 0.8 parts of polypropylene fiber.

[0065] 2. Component parameters and preparation methods: 1) Preparation of fly ash-based calcium-aluminum layered double hydroxides: Fly ash pretreatment: Grind the raw fly ash until it all passes through a 200-mesh sieve, remove magnetic iron impurities by magnetic separation, and then calcine at 900℃ for 1.5 hours and cool naturally to room temperature; Acid leaching extraction: Activated fly ash and 20% hydrochloric acid solution were mixed at a solid-liquid ratio of 1:4.5 and stirred at 350 rpm for 3.5 h at 60 °C. The mixture was then filtered to obtain an acid leaching solution rich in aluminum ions. Coprecipitation synthesis: Add calcium hydroxide to the acid leaching solution to adjust the pH to 11, stir at 420 rpm for 5.5 h at 60 °C, filter and wash until neutral, dry at 65 °C, and grind until all passes through a 500 mesh sieve.

[0066] 2) Preparation of alkali-modified biochar: Corn stalks were crushed and pyrolyzed at 450℃ for 3 hours to obtain biochar; the biochar was mixed with 8% sodium hydroxide solution at a solid-liquid ratio of 1:6, and stirred at 400 rpm at 75℃ for 2.5 hours. The mixture was filtered, washed until neutral, dried at 80℃, and ground until it passed through a 200-mesh sieve.

[0067] 3) Preparation of converter steel slag powder: The original converter steel slag is crushed to a particle size of ≤5mm by a jaw crusher, watered and aged for 35 days, watered once every 7 days during the period, and then ground until all of it passes through a 400-mesh sieve.

[0068] 4) Preparation of coal gasification slag powder: Mix raw coal gasification slag with water at a solid-liquid ratio of 1:2.5, stir and wash for 2 hours, filter to remove soluble impurities and residual ammonia, dry at 105℃, then calcine at 600℃ for 1 hour to remove unburned carbon, and grind until all of it passes through a 300-mesh sieve.

[0069] 5) Preparation of desulfurized gypsum: Dry the original desulfurized gypsum at 45℃ until the moisture content is ≤1%, and grind it until it all passes through a 100-mesh sieve.

[0070] 6) Preparation of alkali-modified waste glass powder: After cleaning and drying the waste glass, crush it and grind it until it all passes through a 100-mesh sieve. Then mix it with an 8% sodium hydroxide solution at a solid-liquid ratio of 1:2. Stir the mixture at 300 rpm for 1.5 h at 60℃, filter and wash it until neutral, and dry it at 100℃.

[0071] 7) Polypropylene fiber: length 6~12mm, diameter 10~20μm.

[0072] 3. Curing agent preparation method: S1. Fly ash-based calcium-aluminum layered double hydroxide and alkali-modified biochar were added to deionized water in a certain proportion, with a solid-liquid ratio of 1:3. The pH value was adjusted to 9.5, and the mixture was stirred at 400 rpm for 2 hours at 50℃. The mixture was then filtered and washed until neutral to obtain the loaded composite powder. S2. Add converter steel slag powder, coal gasification slag powder, desulfurization gypsum and alkali-modified waste glass powder to a mixer in proportion, and stir at 350 rpm for 6 minutes to obtain mixed powder. S3. Add calcium chloride, sodium sulfate and triethanolamine to water in a certain proportion, with the mass of water being 35% of the mass of the mixed powder. Stir at 400 rpm until completely dissolved to obtain a mixed solution. S4. Add the mixed solution to the mixed powder and stir at 550 rpm for 12 min to obtain a slurry; S5. Add the loaded composite powder and polypropylene fiber to the slurry, stir at 900 rpm for 8 minutes, and purge with nitrogen during the stirring process to obtain the sludge-specific solid waste-based solidifying agent.

[0073] Example 2 1. Group composition ratio: 100 parts of fly ash-based calcium-aluminum layered double hydroxide, 6 parts of calcium chloride, 3 parts of sodium sulfate, 30 parts of converter steel slag powder, 22.5 parts of coal gasification slag powder, 45 parts of alkali-modified biochar, 17.5 parts of desulfurized gypsum, 35 parts of alkali-modified waste glass powder, 1.1 parts of triethanolamine, and 1.5 parts of polypropylene fiber.

[0074] 2. Component parameters and preparation methods: 1) Preparation of fly ash-based calcium-aluminum layered double hydroxides: Fly ash pretreatment: Same as in Example 1; Acid leaching extraction: Activated fly ash and 22.5% hydrochloric acid solution were mixed at a solid-liquid ratio of 1:5, and stirred at 400 rpm for 4 hours at 65°C. The mixture was then filtered to obtain an acid leaching solution rich in aluminum ions. Coprecipitation synthesis: Add calcium hydroxide to the acid leaching solution to adjust the pH to 11.5, stir at 450 rpm for 6 h at 65℃, filter and wash until neutral, dry at 70℃, and grind until all passes through a 600 mesh sieve.

[0075] 2) Preparation of alkali-modified biochar: Wheat straw was crushed and pyrolyzed at 550℃ for 4 hours to obtain biochar; the biochar was mixed with a sodium hydroxide solution with a mass fraction of 11.5% at a solid-liquid ratio of 1:7.5, and stirred at 85℃ at 500 rpm for 3.25 hours. The mixture was filtered, washed until neutral, dried at 90℃, and ground until it passed through a 300-mesh sieve.

[0076] 3) Preparation of converter steel slag powder: The pretreatment is the same as in Example 1, and the powder is ground until it all passes through a 450-mesh sieve.

[0077] 4) Preparation of coal gasification slag powder: The pretreatment is the same as in Example 1, and the powder is ground until it all passes through a 350-mesh sieve.

[0078] 5) Preparation of desulfurized gypsum: The pretreatment is the same as in Example 1, and the gypsum is ground until it all passes through a 150-mesh sieve.

[0079] 6) Preparation of alkali-modified waste glass powder: After cleaning and drying the waste glass, crush it and grind it until it all passes through a 150-mesh sieve. Then mix it with a sodium hydroxide solution with a mass fraction of 11.5% at a solid-liquid ratio of 1:3. Stir the mixture at 70°C and 400 rpm for 2 hours. Filter and wash until neutral, and dry at 105°C.

[0080] 7) Polypropylene fiber: length 6~12mm, diameter 10~20μm.

[0081] 3. Curing agent preparation method: S1. Fly ash-based calcium-aluminum layered double hydroxide and alkali-modified biochar were added to deionized water in a certain proportion with a solid-liquid ratio of 1:4. The pH value was adjusted to 10, and the mixture was stirred at 500 rpm for 3 hours at 60℃. The mixture was then filtered and washed until neutral to obtain the loaded composite powder. S2. Add converter steel slag powder, coal gasification slag powder, desulfurization gypsum and alkali-modified waste glass powder to a mixer in proportion, and stir at 450 rpm for 9 minutes to obtain mixed powder. S3. Add calcium chloride, sodium sulfate and triethanolamine to water in a certain proportion, with the mass of water being 45% of the mass of the mixed powder. Stir at 500 rpm until completely dissolved to obtain a mixed solution. S4. Add the mixed solution to the mixed powder and stir at 700 rpm for 15 minutes to obtain a slurry; S5. Add the loaded composite powder and polypropylene fiber to the slurry, stir at 1100 rpm for 11.5 min, and purge with nitrogen during the stirring process to obtain the sludge-specific solid waste-based solidifying agent.

[0082] Example 3 1. Group composition ratio: 100 parts of fly ash-based calcium-aluminum layered double hydroxide, 8 parts of calcium chloride, 4 parts of sodium sulfate, 40 parts of converter steel slag powder, 30 parts of coal gasification slag powder, 55 parts of alkali-modified biochar, 25 parts of desulfurized gypsum, 45 parts of alkali-modified waste glass powder, 1.8 parts of triethanolamine, and 2.2 parts of polypropylene fiber.

[0083] 2. Component parameters and preparation methods: 1) Preparation of fly ash-based calcium-aluminum layered double hydroxides: Fly ash pretreatment: Same as in Example 1; Acid leaching extraction: Activated fly ash and 25% hydrochloric acid solution were mixed at a solid-liquid ratio of 1:5.5 and stirred at 450 rpm for 4.5 h at 70 °C. The mixture was then filtered to obtain an acid leaching solution rich in aluminum ions. Coprecipitation synthesis: Add calcium hydroxide to the acid leaching solution to adjust the pH to 12, stir at 480 rpm for 6.5 h at 70 °C, filter and wash until neutral, dry at 75 °C, and grind until all passes through a 700 mesh sieve.

[0084] 2) Preparation of alkali-modified biochar: Rice straw was crushed and pyrolyzed at 650℃ for 5h to obtain biochar; the biochar was mixed with a 15% sodium hydroxide solution at a solid-liquid ratio of 1:9, stirred at 95℃ and 600rpm for 4h, filtered and washed until neutral, dried at 100℃, and ground until all of it passed through a 400-mesh sieve.

[0085] 3) Preparation of converter steel slag powder: Same as in Example 1, grind until all of it passes through a 500-mesh sieve.

[0086] 4) Preparation of coal gasification slag powder: Same as in Example 1, grind until all of it passes through a 400-mesh sieve.

[0087] 5) Preparation of desulfurized gypsum: Same as in Example 1, grind until all of it passes through a 200-mesh sieve.

[0088] 6) Preparation of alkali-modified waste glass powder: After cleaning and drying the waste glass, crush it and grind it until it all passes through a 200-mesh sieve. Then mix it with a 15% sodium hydroxide solution at a solid-liquid ratio of 1:4. Stir the mixture at 80°C and 500 rpm for 2.5 hours. Filter and wash until neutral, and dry it at 110°C.

[0089] 7) Polypropylene fiber: length 6~12mm, diameter 10~20μm.

[0090] 3. Curing agent preparation method: S1. Fly ash-based calcium-aluminum layered double hydroxide and alkali-modified biochar were added to deionized water in a certain ratio, with a solid-liquid ratio of 1:5. The pH value was adjusted to 10.5, and the mixture was stirred at 600 rpm at 70℃ for 4 hours. The mixture was then filtered and washed until neutral to obtain the loaded composite powder. S2. Add converter steel slag powder, coal gasification slag powder, desulfurization gypsum and alkali-modified waste glass powder to a mixer in proportion, and stir at 550 rpm for 12 minutes to obtain mixed powder. S3. Add calcium chloride, sodium sulfate and triethanolamine to water in proportion, with the mass of water being 55% of the mass of the mixed powder. Stir at 600 rpm until completely dissolved to obtain a mixed solution. S4. Add the mixed solution to the mixed powder and stir at 850 rpm for 18 min to obtain a slurry; S5. Add the loaded composite powder and polypropylene fiber to the slurry, stir at 1300 rpm for 15 min, and purge with nitrogen during the stirring process to obtain the sludge-specific solid waste-based solidifying agent.

[0091] Example 4 1. Group composition ratio: 100 parts of fly ash-based calcium-aluminum layered double hydroxide, 4.8 parts of calcium chloride, 2.4 parts of sodium sulfate, 24 parts of converter steel slag powder, 18 parts of coal gasification slag powder, 39 parts of alkali-modified biochar, 13 parts of desulfurized gypsum, 29 parts of alkali-modified waste glass powder, 0.6 parts of triethanolamine, and 1.0 part of polypropylene fiber.

[0092] 2. Component parameters and preparation methods: same as in Example 1.

[0093] 3. Preparation method of curing agent: Same as in Example 1.

[0094] Example 5 1. Group composition ratio: 100 parts of fly ash-based calcium-aluminum layered double hydroxide, 7.2 parts of calcium chloride, 3.6 parts of sodium sulfate, 36 parts of converter steel slag powder, 27 parts of coal gasification slag powder, 51 parts of alkali-modified biochar, 22 parts of desulfurized gypsum, 41 parts of alkali-modified waste glass powder, 1.5 parts of triethanolamine, and 2.0 parts of polypropylene fiber.

[0095] 2. Component parameters and preparation methods: same as in Example 2.

[0096] 3. Preparation method of curing agent: Same as in Example 2.

[0097] Comparative Example 1 The only difference from Example 2 is that the fly ash was not subjected to magnetic separation and calcination pretreatment and was directly used to prepare fly ash-based calcium-aluminum layered double hydroxide.

[0098] Comparative Example 2 The only difference from Example 2 is that the converter slag was directly ground after being crushed, without undergoing water spraying and aging treatment.

[0099] Comparative Example 3 The only difference from Example 2 is that the coal gasification slag is directly dried and ground without water washing and calcination.

[0100] Comparative Example 4 The only difference from Example 2 is that the on-site loading process in step S1 is omitted, and fly ash-based calcium-aluminum layered double hydroxide and alkali-modified biochar are directly mixed with other components.

[0101] Comparative Example 5 The only difference from Example 2 is that sodium sulfate is not added, but only 9 parts of calcium chloride are added as an activator.

[0102] Comparative Example 6 The only difference from Example 2 is that calcium chloride is not added, but only 9 parts of sodium sulfate are added as an activator.

[0103] Comparative Example 7 The only difference from Example 2 is that no alkali-modified waste glass powder is added; instead, an equal amount of converter steel slag powder is used.

[0104] Performance testing 1. Testing Method ① Unconfined compressive strength test: River dredging silt was taken, with the following basic properties: water content 72%, organic matter content 9.2%, liquid limit 58%, and plastic limit 26%. The curing agent prepared in each example and comparative example was mixed with the silt at a mass ratio of 1:10 and poured into a cylindrical mold with a diameter of 39.1 mm and a height of 80 mm. The compaction degree was 95%. After demolding, the silt was cured under standard curing conditions (temperature 20±1℃, relative humidity above 95%) for 7 days and 28 days. The unconfined compressive strength was tested according to the "Standard for Geotechnical Testing Methods" (GB / T 50123-2019).

[0105] ② Water stability test: The sample cured for 28 days was immersed in water for 28 days. The unconfined compressive strength after immersion was tested, and the water stability coefficient was calculated (water stability coefficient = unconfined compressive strength after immersion / unconfined compressive strength before immersion).

[0106] ③ Volume stability test: The samples cured for 28 days were cured for another 90 days, and their linear expansion rate was tested to evaluate volume stability.

[0107] Test Results and Analysis 1. The test results of the mechanical properties and volume stability of the solidified sludge are shown in Table 1: Table 1 Mechanical properties and volume stability of solidified sludge Application Example 1 River dredging sludge solidification treatment The river dredging silt had a water content of 75%, an organic matter content of 8.7%, a liquid limit of 56%, and a plastic limit of 24%. The curing agent prepared in Example 2 was mixed evenly with the silt at a mass ratio of 1:11. The mixture was then spread using a paver to a thickness of 30 cm and compacted to 93% using a road roller. Natural curing was carried out for 28 days.

[0108] Performance test results: 7-day unconfined compressive strength is 1.28 MPa, 28-day unconfined compressive strength is 3.95 MPa, and water stability coefficient is 0.91. It meets the requirements for roadbed fill material in the "Code for Construction and Quality Acceptance of Urban Road Engineering" (CJJ 1-2008) and can be directly used for urban roadbed filling.

[0109] Application Example 2 Solidification and stabilization treatment of heavy metal contaminated sludge Heavy metal contaminated sludge from an industrial site was collected. The sludge had a moisture content of 68% and heavy metal content of: Cd 7.5 mg / kg, Pb 182 mg / kg, Cu 269 mg / kg, and Zn 578 mg / kg. The curing agent prepared in Example 2 was mixed with the sludge at a mass ratio of 1:7, compacted to 95%, and cured in a sealed environment for 28 days.

[0110] Performance test results: 28-day unconfined compressive strength is 3.62 MPa, and the heavy metal leaching concentrations are: Cd 0.009 mg / L, Pb 0.035 mg / L, Cu 0.058 mg / L, Zn 0.136 mg / L, which are lower than the limits of the "Identification Standard for Hazardous Waste - Leaching Toxicity Identification" (GB 5085.3-2007), and can be safely landfilled or used as engineering backfill soil.

[0111] Application Example 3 Solidification treatment of silt from building foundation pits Silt from the construction pit was collected, with a water content of 82%, an organic matter content of 10.5%, a liquid limit of 62%, and a plastic limit of 28%. The curing agent prepared in Example 2 was mixed evenly with the silt at a mass ratio of 1:9. The mixture was then used for construction using a mixing pile process, with a pile diameter of 500 mm and a pile length of 12 m, and natural curing for 28 days.

[0112] Performance test results: The 28-day unconfined compressive strength of the pile body is 3.27 MPa, and the characteristic value of the single pile bearing capacity is 180 kN, which meets the requirements of the foundation pit support project and can effectively improve the stability of the foundation pit slope.

[0113] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention and not to limit it. Although the present invention has been described in detail with reference to the above embodiments, those skilled in the art should understand that modifications or equivalent substitutions can still be made to the specific implementation of the present invention. Any modifications or equivalent substitutions that do not depart from the spirit and scope of the present invention should be covered within the protection scope of the claims of the present invention.

Claims

1. A solid waste based solidifier for sludge, characterized by, include: 100 parts of fly ash-based calcium-aluminum layered double hydroxide, 4-8 parts of calcium chloride, 2-4 parts of sodium sulfate, 20-40 parts of converter steel slag powder, 15-30 parts of coal gasification slag powder, 35-55 parts of alkali-modified biochar, 10-25 parts of desulfurized gypsum, 25-45 parts of alkali-modified waste glass powder, 0.3-1.8 parts of triethanolamine, and 0.8-2.2 parts of polypropylene fiber.

2. The sludge-specific solid waste-based solidifying agent according to claim 1, characterized by, The preparation method of the fly ash-based calcium-aluminum layered double hydroxide is as follows: fly ash is mixed with hydrochloric acid solution and stirred to react, and then filtered to obtain an acid leaching solution; calcium hydroxide is added to the acid leaching solution to adjust the pH, and the stirring reaction is carried out again. After the reaction is completed, the fly ash-based calcium-aluminum layered double hydroxide is obtained by filtering, washing, drying and grinding in sequence. The hydrochloric acid solution has a mass fraction of 18% to 28%, the solid-liquid ratio of fly ash to hydrochloric acid solution is 1:4 to 1:6, the temperature of the mixing and stirring reaction is 55 to 75°C, the time is 3 to 5 hours, and the stirring rate is 300 to 500 rpm. The pH is adjusted to 10.5-12.5; the temperature for the second stirring reaction is 55-75℃, the time is 5-7h, and the stirring speed is 400-500rpm; the washing is performed until neutral; the drying temperature is 60-80℃; the grinding specification is to pass through a 400-800 mesh sieve. The fly ash also includes a pretreatment step before use: grinding the raw fly ash until it all passes through a 200-mesh sieve, removing magnetic iron impurities by magnetic separation, and then calcining it at 900℃ for 1.5 hours and naturally cooling it to room temperature.

3. The dewatered sludge specific solid waste based solidifying agent according to claim 1 or 2, characterized by, The converter steel slag powder is ground to pass through a 300-600 mesh sieve; The coal gasification slag powder is ground to pass through a 200-500 mesh sieve; The polypropylene fibers have a length of 6-12 mm and a diameter of 10-20 μm; Before grinding converter steel slag into micro powder, a pretreatment step is also included: the raw converter steel slag is crushed to a particle size of ≤5mm by a jaw crusher, and then watered and aged for 35 days, with water sprayed once every 7 days during the period. Before grinding coal gasification slag into micro powder, a pretreatment step is also included: the raw coal gasification slag is mixed with water at a solid-liquid ratio of 1:2.5, stirred and washed for 2 hours, filtered to remove soluble impurities and residual ammonia, dried at 105℃, and then calcined at 600℃ for 1 hour.

4. The dewatered sludge specific solid waste based solidifying agent according to claim 3, characterized by, The method for preparing the alkali-modified biochar is as follows: agricultural straw is crushed and pyrolyzed to obtain biochar; the biochar and sodium hydroxide solution are mixed and stirred to react; and then filtered, washed, dried and ground in sequence to obtain alkali-modified biochar. The agricultural straw includes wheat straw, corn straw, rice straw, cotton straw, or potato straw; the pyrolysis temperature is 450~650℃, and the time is 3~5h; The sodium hydroxide solution has a mass fraction of 8% to 15%; the solid-liquid ratio of the biochar and sodium hydroxide solution is 1:6 to 1:9; the stirring reaction temperature is 75 to 95°C, the reaction time is 2.5 to 4 hours, and the stirring rate is 400 to 600 rpm; the washing is performed until neutral; the drying temperature is 80 to 100°C; and the grinding is performed until the material passes through a 200 to 400 mesh sieve.

5. The specialized solid waste-based solidifying agent for sludge according to claim 1, 2 or 4, characterized by, The preparation method of the alkali-modified waste glass powder is as follows: waste glass is washed, dried, crushed, ground to obtain waste glass powder, mixed with sodium hydroxide solution and stirred to react, and then filtered, washed and dried in sequence to obtain the powder. The powder is ground to pass through a 100-200 mesh sieve; the mass fraction of the sodium hydroxide solution is 8%-15%; the solid-liquid ratio of the waste glass powder to the sodium hydroxide solution is 1:2-1:4; the temperature of the stirring reaction is 60-80℃, and the time is 1.5-2.5h; the stirring rate is 300-500rpm; and the drying temperature is 100-110℃.

6. A method of producing a solid waste-based solidifying agent for sludge according to any one of claims 1 to 5, characterized by, Includes the following steps: S1: Add fly ash-based calcium-aluminum layered double hydroxide and alkali-modified biochar to water, adjust the pH value, and then stir the reaction. After the reaction is completed, filter and wash in sequence to obtain the loaded composite powder. S2: Mix converter steel slag powder, coal gasification slag powder, desulfurization gypsum and alkali-modified waste glass powder to obtain mixed powder; S3: Add calcium chloride, sodium sulfate and triethanolamine to water and stir to obtain a mixed solution; S4: Mix the mixed solution and mixed powder, and stir to obtain a slurry; S5: Add the loaded composite powder and polypropylene fiber obtained in step S1 to the slurry and stir to obtain a solid waste-based solidifying agent for sludge.

7. The method of claim 6, wherein the solid waste-based solidification agent for sludge is prepared by adding 0.1 to 0.5 parts by weight of the inorganic binder to 100 parts by weight of the solid waste, and then mixing the mixture. In step S1, the solid-liquid ratio of fly ash-based calcium-aluminum layered double hydroxide to alkali-modified biochar and water is 1:3 to 1:5, and the pH value is adjusted to a range of 9.5 to 10.5; the stirring reaction temperature is 50 to 70°C, the time is 2 to 4 hours, and the stirring rate is 400 to 600 rpm.

8. The method of claim 6 or 7, wherein the method is characterized by, In step S2, mixing is carried out under stirring conditions, with a stirring rate of 350~550 rpm and a time of 6~12 min. In step S3, the mass of water is 35% to 55% of the mass of the mixed powder; the stirring speed is 400 to 600 rpm.

9. The method of claim 8, wherein the solid waste-based solidification agent for sludge is prepared by mixing the solid waste-based solidification agent for sludge with water in a ratio of 1:0.5 to 1:

2. In step S4, the stirring speed is 550~850 rpm and the stirring time is 12~18 min; In step S5, the stirring rate is 900~1300 rpm and the time is 8~15 min; and nitrogen gas is introduced for protection during the stirring process.

10. Use of a solid waste-based solidifier specific for sludge according to any one of claims 1 to 5 for the consolidation stabilization of aqueous soft sediments, characterized in that, The water-bearing soft sediments include river dredging silt, lake and reservoir silt, municipal drainage network silt, building foundation pit silt, port and waterway dredging silt, heavy metal polluted silt, tailings pond tailings, aquaculture pond silt, and bay tidal flat silt; the solidified products are used as roadbed fill, engineering backfill soil, slope protection engineering materials, dike reinforcement materials, or greening planting soil.

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