Preparation method of modified circulating fluidized bed combustion ash, in-situ polymerizable sludge curing material and preparation method thereof

Abstract

The invention discloses a preparation method of modified circulating fluidized bed combustion ash, an in-situ polymerizable sludge curing material and a preparation method thereof. The preparation method of the modified circulating fluidized bed combustion ash comprises the following steps: mixing the circulating fluidized bed combustion ash with an acid solution, stirring, drying, performing vacuum suction to remove air, injecting a potassium persulfate solution under a negative pressure condition, drying again to obtain circulating fluidized bed combustion ash particles loaded with potassium persulfate, mixing the circulating fluidized bed combustion ash particles with an acrylic emulsion, and curing and coating to form a film. The curing material is prepared from the following components in parts by mass: 126 to 400 parts of sludge, 56 to 84 parts of silicon-calcium slag, 24 to 36 parts of modified circulating fluidized bed combustion ash, 10 to 20 parts of gypsum, 7 to 24 parts of water glass, 4 to 7 parts of sodium hydroxide, 35 to 44 parts of water, 4 to 8 parts of acrylamide and 0.025 to 0.08 part of N, N '-methylene bisacrylamide. The material toughness can be improved, and the problems that solidified soil is large in brittleness and prone to cracking are solved.

Description

Technical Field

[0001] This invention relates to a method for preparing chemical fuel ash, a solidification material and preparation method, and more particularly to a method for preparing modified circulating fluidized bed fuel ash, an in-situ polymerizable sludge solidification material and preparation method. Background Technology

[0002] Silt typically forms in environments with slow water flow. According to statistics, dredging projects generate up to 160 million cubic meters of silt annually to ensure the normal passage of waterways. The natural water content of silt can be as high as 1.2 to 2 times the liquid limit, and the porosity is greater than 1.5. It has poor mechanical properties, high compressibility, and high organic matter content, making it difficult to use directly.

[0003] Driven by the requirements of green development and the circular economy, sludge solidification is a simple and efficient method. Its advantage lies in overcoming limitations imposed by site constraints and large equipment requirements, enabling in-situ solidification of sludge. Currently, various technologies are used to solidify sludge in engineering practice. However, the high moisture content of sludge leads to a dilution effect on the solidifying agent, significantly reducing solidification efficiency. Therefore, its current application is generally limited to low-strength applications such as roadbed fillers, where strength requirements are typically below 2 MPa. This greatly limits the possibility of solidifying sludge into relatively high-strength products (such as building materials).

[0004] While using alkali-activated materials to solidify sludge can improve the utilization efficiency of industrial waste to some extent, enabling it to participate in hydration reactions and embodying the sustainable development concept of "treating waste with waste," the moisture in the sludge dilutes the alkali activator, reducing hydration efficiency and adversely affecting mechanical properties. Even after the system hardens, a large amount of moisture remains internally. Under the influence of the humidity difference between the inside and outside, the internal moisture evaporates outward, easily leading to significant shrinkage cracking under capillary forces. Furthermore, alkali-activated materials solidify sludge primarily by encapsulating sludge particles with hydration products to form a solidified body. The bond between the matrix and sludge particles contains pores, weak interfacial areas, and microscopic defects, making crack initiation highly likely. In the absence of an effective toughening mechanism, cracks can propagate rapidly and directly under low resistance. Summary of the Invention

[0005] Purpose of the invention: The purpose of this invention is to provide a method for preparing modified circulating fluidized bed ash that can be loaded with potassium persulfate;

[0006] The second objective of this invention is to provide a sludge solidification material that is tough, has high water conversion efficiency, and can be polymerized in situ;

[0007] A third objective of this invention is to provide a method for preparing the above-mentioned in-situ polymerizable sludge solidification material.

[0008] Technical solution: The preparation method of modified circulating fluidized bed ash according to the present invention includes the following steps:

[0009] A1. During the stirring process, the acid solution is dripped into the circulating fluidized bed ash to carry out the acidification reaction. After the reaction is completed, the product is separated and dried to obtain the acidified circulating fluidized bed ash.

[0010] B1. After the acidified circulating fluidized bed ash is evacuated, potassium persulfate solution is injected under negative pressure to force the potassium persulfate solution into the pores of the circulating fluidized bed ash. Then, the circulating fluidized bed ash particles loaded with potassium persulfate are obtained by vacuum drying.

[0011] C1. Circulating fluidized bed ash particles loaded with potassium persulfate are mixed with acrylic emulsion, so that the particle surface is fully coated with emulsion and solidified into a film.

[0012] In step A1, the mass of the acid solution is 4% to 8% of the mass of the circulating fluidized bed ash; the concentration of the acid solution is 80% to 90%; and the type of acid solution is phosphoric acid.

[0013] In step A1, the circulating fluidized bed ash is placed in a three-necked flask and stirred evenly with an electric stirrer. An acid solution is dripped into the three-necked flask using a peristaltic pump. After titration, stirring is continued to ensure complete reaction. After drying, the acidified circulating fluidized bed ash is obtained.

[0014] In step A1, the circulating fluidized bed ash is mixed with the acidic solution and stirred continuously at a speed of 400~500 r / min. The interval between each drop of acid solution titration is 5 s. After titration, stirring is continued for 2~3 h to ensure complete reaction. After the reaction is completed, the mixture is placed in a vacuum drying oven at 100~105 ℃ and dried for 12~24 h.

[0015] In step B1, the mass ratio of the acidified circulating fluidized bed ash to the potassium persulfate solution is 2.5~3:1; the concentration of the potassium persulfate solution is 0.08~0.1 mol / L.

[0016] In step B1, the acidified circulating fluidized bed ash is placed in a vacuum dryer and continuously evacuated for 10-15 minutes. The air inlet valve is slowly opened to allow atmospheric pressure to slowly force the potassium persulfate solution into the pores of the circulating fluidized bed ash. The ash is then soaked at atmospheric pressure for 4-6 hours to ensure full penetration. Subsequently, it is dried in a vacuum drying oven at 100-105 ℃ for 12-24 hours.

[0017] In step C1, the gel content in the acrylic emulsion is 30% to 40%.

[0018] In step C1, the film is cured in an environment of 25~35 ℃.

[0019] The in-situ polymerizable sludge solidification material of the present invention comprises the following components in parts by weight:

[0020] The mixture contains 126-400 parts of sludge, 56-84 parts of calcium silicate slag, 24-36 parts of modified circulating fluidized bed ash obtained by the above method, 10-20 parts of gypsum, 7-24 parts of water glass, 4-7 parts of sodium hydroxide, 35-44 parts of water, 4-8 parts of acrylamide, and 0.025-0.08 parts of N,N'-methylenebisacrylamide.

[0021] The natural water content of the silt ranges from 40% to 80%.

[0022] The particle size of the calcium silicate slag and the circulating fluidized bed ash is less than 75 μm.

[0023] The gypsum is one or a mixture of two or more of the following: natural gypsum, desulfurized gypsum, and phosphogypsum.

[0024] The water glass has a modulus of 2.5 to 3.5 and a water content of 60% to 66%.

[0025] The above-mentioned method for preparing the in-situ polymerizable sludge solidification material includes the following steps:

[0026] A2. Thoroughly mix sodium hydroxide with a portion of water, cool, and pour into water glass to prepare an alkaline activator;

[0027] B2. Mix acrylamide and N,N'-methylenebisacrylamide evenly and dissolve them in the remaining water. Stir thoroughly and then pour the mixture into the alkaline activator to form a mixed solution.

[0028] C2. Mix and stir the calcium silicate slag and modified circulating fluidized bed ash with the mixed solution from step B2 to obtain an alkali-activated gel slurry;

[0029] D2 involves mixing and stirring the alkali-activated gelatinous slurry with silt to obtain a slurry;

[0030] E2. Plaster is slowly added to the slurry and stirred to obtain a sludge solidification material that can be polymerized in situ.

[0031] In step B2, the water used accounts for 70% to 80% of the total water consumption.

[0032] Invention principle:

[0033] (1) The multi-component synergistic protection system ensures continuous hydration throughout the entire life cycle. In the early stage, the calcium silicate slag, rich in CaO and SiO2, can quickly dissolve and efficiently form C-(A)-SH gel under the action of water glass and NaOH. The C-(A)-SH gel forms a network structure while consolidating free water in the sludge, which leads to rapid increase in early strength. Acrylic emulsion modification treatment can form a film on the surface of circulating fluidized bed ash, delaying its hydration reaction time. The film-forming material on the surface can slowly dissolve in an alkaline environment. When it dissolves to a certain age, the circulating fluidized bed ash begins to be exposed to the system and begins to participate in the hydration reaction. The chemical composition of circulating fluidized bed ash is mainly CaO, SiO2, and Al2O3, which can continuously hydrate to form C-(A)-SH gel. This gel, while binding free water, helps improve mid-to-late-stage strength. Furthermore, the presence of CaSO4 in the circulating fluidized bed ash acts as a supplementary activator, stimulating the active SiO2 and Al2O3 within the ash, as well as the unreacted silica-calcium slag from the initial stage, further enhancing the hydration degree of the cementitious material. The mid-to-late-stage hydration of modified circulating fluidized bed ash effectively improves the matrix strength and prevents shrinkage cracking caused by differences in internal and external humidity during curing.

[0034] (2) The alkaline-activated system induces the formation of ettringite, simultaneously achieving efficient water consolidation and effective compensation for shrinkage. The gypsum and circulating fluidized bed ash containing CaSO4 ensure sufficient SO4. 2– The source can promote the formation of a large amount of ettringite. Tettringite (3CaO·Al2O3·3CaSO4·32H2O) has a strong water-binding capacity, which can efficiently convert free water in sludge into chemically bound water, reduce the dilution effect of water on cementitious materials, thereby improving the degree of hydration and mechanical properties; in addition, the micro-expansion characteristics of ettringite can effectively compensate for shrinkage, effectively reduce the potential shrinkage risk caused by water loss in the system, and fundamentally improve the volume stability of the system.

[0035] (3) Acid treatment regulates the pore structure of circulating fluidized bed ash to achieve precise phased pH control. First, acid treatment increases the specific surface area by etching the surface of circulating fluidized bed ash to enhance the activity of the alkali-activated reaction. Vacuum suction can remove gas from the pores to the maximum extent, allowing potassium persulfate to be fully loaded into the pores inside the particles. Second, since the pH range for the stable existence of ettringite is limited to 10.43~12.52, the pH range for the alkali-activated reaction using water glass and NaOH as activators is 13.1~13.7, which is almost contradictory to the formation of ettringite. The modified circulating fluidized bed ash temporarily seals the acid components to ensure the full progress of the early alkali-activated reaction, while the acid components are gradually released in the middle and later stages, actively reducing the pH value of the pore solution to create an environment conducive to the formation of ettringite.

[0036] (4) Polyacrylamide formed by in-situ polymerization has both toughening and internal curing effects. Potassium persulfate is loaded in circulating fluidized bed ash. After the surface film dissolves, it initiates in-situ polymerization of acrylamide monomers in the pores and microcracks of the matrix. The in-situ polymerization time is controlled after the early alkali activation reaction to avoid polyacrylamide hindering the contact between the activator and the cementitious material, thus preventing the alkali activation reaction from being inhibited. By forming a penetrating three-dimensional, flexible polyacrylamide organic network, it is closely interwoven and interpenetrating with the early-formed rigid hydration products at the microscale, thus forming a unique "organic-inorganic dual-network structure", which significantly improves toughness and reduces the risk of cracking. In addition, polyacrylamide has hygroscopic properties. While adsorbing free water in the system, it can also play an internal curing role, preventing the formation rate of ettringite from being too fast and reducing local cracking caused by water loss.

[0037] Beneficial effects: Compared with the prior art, the present invention achieves the following significant effects: (1) Early-stage calcium silicate slag rapidly participates in the alkali-activated reaction to form C-(A)-SH gel, improving early strength. Modified circulating fluidized bed ash continues to hydrate in the middle and late stages, and the CaSO4 contained therein activates the residual components, improving the later-stage strength, thus achieving continuous hydration of the system throughout its entire lifespan. (2) Etnacite can efficiently solidify free water, improving the system's reaction efficiency. Furthermore, its expansion characteristics can effectively compensate for shrinkage, effectively solving the problems of poor mechanical properties and large shrinkage deformation of traditional sludge solidification materials. (3) Acid treatment of circulating fluidized bed ash improves its activity through surface etching, providing loading sites for potassium persulfate. Moreover, the acid component helps to lower the pH value of the system, promoting the formation of ettringite. Acrylic emulsion can regulate the hydration process of circulating fluidized bed ash through coating and film formation, delaying the premature formation of polyacrylamide, thereby weakening its inhibitory effect on the alkali-activated reaction. (4) The polyacrylamide formed by in-situ polymerization not only adsorbs free water to exert an internal curing effect, but also the organic network can be evenly distributed in the system, which solves the problems of poor toughness and poor crack resistance of traditional sludge solidification materials. Detailed Implementation

[0038] The present invention will now be described in further detail.

[0039] Example 1

[0040] A sludge solidification material capable of in-situ polymerization comprises the following components in parts by weight: sludge with a natural moisture content of 40%, comprising 126 parts by weight; calcium silicate slag, comprising 56 parts by weight; modified circulating fluidized bed ash, comprising 24 parts by weight; phosphogypsum, comprising 10 parts by weight; water glass with a modulus of 2.5 and a moisture content of 60%, comprising 7 parts by weight; sodium hydroxide, comprising 4 parts by weight; water, comprising 36 parts by weight; acrylamide, comprising 4 parts by weight; and N,N'-methylenebisacrylamide, comprising 0.025 parts by weight.

[0041] The preparation method of the above-mentioned modified circulating fluidized bed ash includes the following steps:

[0042] (1) Place 60 parts of circulating fluidized bed ash in a three-necked flask and stir evenly with an electric stirrer at a speed of 400 r / min. Use a peristaltic pump to drop in 2.4 parts of 80% phosphoric acid solution at a titration interval of 5 s. After titration, continue stirring for 2 h to ensure complete reaction. After the reaction is complete, place in a vacuum drying oven at 100 ℃ and dry for 12 h.

[0043] (2) The acidified circulating fluidized bed ash was placed in a vacuum dryer and vacuumed for 10 min. The air inlet valve was slowly opened to allow atmospheric pressure to slowly press 20 parts of 0.1 mol / L potassium persulfate solution into the pores of the circulating fluidized bed ash. The ash was soaked at atmospheric pressure for 4 h to ensure full penetration. Then it was placed in a vacuum drying oven at 100 ℃ and dried for 12 h to obtain circulating fluidized bed ash particles loaded with potassium persulfate.

[0044] (3) The obtained circulating fluidized bed ash particles loaded with potassium persulfate were mixed with 200 parts of acrylic emulsion with a gel content of 30% to fully coat the particle surface with the emulsion, and then placed in an environment of 25 °C to solidify into a film.

[0045] The preparation method of the above-mentioned in-situ polymerizable sludge solidification material includes the following steps:

[0046] (1) Mix sodium hydroxide with 26 parts water thoroughly, cool and pour into water glass to make an alkali activator.

[0047] (2) Mix acrylamide, potassium persulfate and N,N'-methylenebisacrylamide evenly and dissolve them in the remaining 10 parts of water. Stir thoroughly and pour into the alkaline activator in step (1) to form a mixed solution.

[0048] (3) Place the calcium silicate slag and modified circulating fluidized bed ash with the mixed solution of step (2) in a mixer and stir at low speed for 3 min to obtain alkali-activated gel slurry;

[0049] (4) Mix the alkali-activated gelatinous slurry from step (3) with the sludge and stir at low speed for 1 min;

[0050] (5) Slowly add the gypsum to the slurry in step (4) and stir at low speed for 3 minutes. After the addition is complete, stir at high speed for 0.5 minutes.

[0051] Example 2

[0052] A sludge solidification material capable of in-situ polymerization comprises the following components in parts by weight: sludge with a natural moisture content of 50%, comprising 220 parts by weight; calcium silicate slag, comprising 62 parts by weight; modified circulating fluidized bed ash, comprising 28 parts by weight; phosphogypsum, comprising 10 parts by weight; natural gypsum, comprising 5 parts by weight; water glass with a modulus of 2.8 and a moisture content of 62%, comprising 10 parts by weight; sodium hydroxide, comprising 5 parts by weight; water, comprising 39 parts by weight; acrylamide, comprising 5 parts by weight; and N,N'-methylenebisacrylamide, comprising 0.043 parts by weight.

[0053] The preparation method of the above-mentioned modified circulating fluidized bed ash includes the following steps:

[0054] (1) Place 60 parts of circulating fluidized bed ash in a three-necked flask and stir evenly with an electric stirrer at a speed of 425 r / min. Use a peristaltic pump to drop in 3.2 parts of 83% phosphoric acid solution at a titration interval of 5 s. After titration, continue stirring for 3 h to ensure complete reaction. After the reaction is completed, place in a vacuum drying oven at 105 ℃ and dry for 16 h.

[0055] (2) The acidified circulating fluidized bed ash was placed in a vacuum dryer and vacuumed for 12 min. The air inlet valve was slowly opened to allow atmospheric pressure to slowly press 20 parts of 0.1 mol / L potassium persulfate solution into the pores of the circulating fluidized bed ash. The ash was soaked for 5 h under normal pressure to ensure full penetration. Then it was placed in a vacuum drying oven at 105 ℃ and dried for 18 h to obtain circulating fluidized bed ash particles loaded with potassium persulfate.

[0056] (3) The obtained circulating fluidized bed ash particles loaded with potassium persulfate were mixed with 200 parts of acrylic emulsion with a gel content of 33% to fully coat the particle surface with the emulsion, and then placed in an environment of 28 °C to solidify into a film.

[0057] The preparation method of the above-mentioned in-situ polymerizable sludge solidification material includes the following steps:

[0058] (1) Mix sodium hydroxide with 29 parts water thoroughly, cool and pour into water glass to make an alkali activator.

[0059] (2) Mix acrylamide, potassium persulfate and N,N'-methylenebisacrylamide evenly and dissolve them in the remaining 10 parts of water. Stir thoroughly and pour into the alkaline activator in step (1) to form a mixed solution.

[0060] (3) Place the calcium silicate slag and modified circulating fluidized bed ash with the mixed solution of step (2) in a mixer and stir at low speed for 4 min to obtain alkali-activated gel slurry;

[0061] (4) Mix the alkali-activated gelatinous slurry from step (3) with the sludge and stir at low speed for 1.5 min;

[0062] (5) Slowly add the gypsum to the slurry in step (4) and stir at low speed for 4 minutes. After the addition is complete, stir at high speed for 0.75 minutes.

[0063] Example 3

[0064] A sludge solidification material capable of in-situ polymerization comprises the following components in parts by weight: sludge with a natural moisture content of 60%, comprising 150 parts by weight; calcium silicate slag, comprising 77 parts by weight; modified circulating fluidized bed ash, comprising 33 parts by weight; desulfurized gypsum, comprising 10 parts by weight; natural gypsum, comprising 5 parts by weight; water glass with a modulus of 3.0 and a moisture content of 66%, comprising 18 parts by weight; sodium hydroxide, comprising 6 parts by weight; water, comprising 42 parts by weight; acrylamide, comprising 6 parts by weight; and N,N'-methylenebisacrylamide, comprising 0.061 parts by weight.

[0065] The preparation method of the above-mentioned modified circulating fluidized bed ash includes the following steps:

[0066] (1) Place 60 parts of circulating fluidized bed ash in a three-necked flask and stir evenly with an electric stirrer at a speed of 450 r / min. Use a peristaltic pump to drop 4.0 parts of 86% phosphoric acid solution, with a titration interval of 5 s. After titration, continue stirring for 2 h to ensure complete reaction. After the reaction is complete, place it in a vacuum drying oven at 100 ℃ and dry for 20 h.

[0067] (2) The acidified circulating fluidized bed ash was placed in a vacuum dryer and vacuumed for 14 min. The air inlet valve was slowly opened to allow atmospheric pressure to slowly press 20 portions of 0.1 mol / L potassium persulfate solution into the pores of the circulating fluidized bed ash. The ash was soaked under normal pressure for 6 h to ensure full penetration. Then it was placed in a vacuum drying oven at 100 ℃ and dried for 20 h to obtain circulating fluidized bed ash particles loaded with potassium persulfate.

[0068] (3) The obtained circulating fluidized bed ash particles loaded with potassium persulfate were mixed with 200 parts of acrylic emulsion with a gel content of 36% to fully coat the particle surface with the emulsion, and then placed in an environment of 30 °C to solidify into a film.

[0069] The preparation method of the above-mentioned in-situ polymerizable sludge solidification material includes the following steps:

[0070] (1) Mix sodium hydroxide with 32 parts water thoroughly, cool and pour into water glass to make an alkali activator.

[0071] (2) Mix acrylamide, potassium persulfate and N,N'-methylenebisacrylamide evenly and dissolve them in the remaining 10 parts of water. Stir thoroughly and pour into the alkaline activator in step (1) to form a mixed solution.

[0072] (3) Place the calcium silicate slag and modified circulating fluidized bed ash with the mixed solution of step (2) in a mixer and stir at low speed for 5 min to obtain alkali-activated gel slurry;

[0073] (4) Mix the alkali-activated gelatinous slurry from step (3) with the sludge and stir at low speed for 2 min;

[0074] (5) Slowly add the gypsum to the slurry from step (4) and stir at low speed for 5 minutes. After the addition is complete, stir at high speed for 1 minute.

[0075] Example 4

[0076] A sludge solidification material capable of in-situ polymerization comprises the following components in parts by weight: sludge with a natural moisture content of 80%, comprising 380 parts by weight; calcium silicate slag, comprising 70 parts by weight; modified circulating fluidized bed ash, comprising 30 parts by weight; phosphogypsum, comprising 10 parts by weight; desulfurized gypsum, comprising 5 parts by weight; water glass with a modulus of 3.5 and a moisture content of 66%, comprising 20 parts by weight; sodium hydroxide, comprising 7 parts by weight; water, comprising 44 parts by weight; acrylamide, comprising 8 parts by weight; and N,N'-methylenebisacrylamide, comprising 0.08 parts by weight.

[0077] The preparation method of the above-mentioned modified circulating fluidized bed ash includes the following steps:

[0078] (1) Place 60 parts of circulating fluidized bed ash in a three-necked flask and stir evenly with an electric stirrer at a speed of 500 r / min. Use a peristaltic pump to drop in 4.8 parts of 90% phosphoric acid solution at a titration interval of 5 s. After titration, continue stirring for 3 h to ensure complete reaction. After the reaction is complete, place in a vacuum drying oven at 105 ℃ and dry for 24 h.

[0079] (2) The acidified circulating fluidized bed ash was placed in a vacuum dryer and vacuumed for 13 min. The air inlet valve was slowly opened to allow atmospheric pressure to slowly press 20 parts of 0.1 mol / L potassium persulfate solution into the pores of the circulating fluidized bed ash. The ash was soaked at atmospheric pressure for 4 h to ensure full penetration. Then it was placed in a vacuum drying oven at 105 ℃ and dried for 24 h to obtain circulating fluidized bed ash particles loaded with potassium persulfate.

[0080] (3) The obtained circulating fluidized bed ash particles loaded with potassium persulfate were mixed with 200 parts of acrylic emulsion with a gel content of 40% to fully coat the particle surface with the emulsion, and then placed in an environment of 32 °C to solidify into a film.

[0081] The preparation method of the above-mentioned in-situ polymerizable sludge solidification material includes the following steps:

[0082] (1) Mix sodium hydroxide with 35 parts water thoroughly, cool and pour into water glass to make an alkali activator.

[0083] (2) Mix acrylamide, potassium persulfate and N,N'-methylenebisacrylamide evenly and dissolve them in the remaining 9 parts of water. After stirring thoroughly, pour the mixture into the alkaline activator in step (1) to form a mixed solution.

[0084] (3) Place the calcium silicate slag and modified circulating fluidized bed ash with the mixed solution of step (2) in a mixer and stir at low speed for 4 min to obtain alkali-activated gel slurry;

[0085] (4) Mix the alkali-activated gelatinous slurry from step (3) with the sludge and stir at low speed for 1.5 min;

[0086] (5) Slowly add the gypsum to the slurry from step (4) and stir at low speed for 4 minutes. After the addition is complete, stir at high speed for 1 minute.

[0087] Comparative Example 1

[0088] Based on Example 3, the difference is that the mass fraction of gypsum in the in-situ polymerizable sludge solidification material is set to 0.

[0089] Comparative Example 2

[0090] Based on Example 3, the difference from Example 3 is that the circulating fluidized bed ash in the in-situ polymerizable sludge solidification material is replaced with unmodified circulating fluidized bed ash.

[0091] Comparative Example 3

[0092] Based on Example 3, the difference is that the mass fraction of acrylamide in the in-situ polymerizable sludge solidification material is set to 0.

[0093] Comparative Example 4

[0094] Based on Example 3, the difference from Example 3 is that the modified circulating fluidized bed ash omits only the first step of the acidification process.

[0095] Comparative Example 5

[0096] Based on Example 3, the difference is that the modified circulating fluidized bed ash is not loaded with potassium persulfate.

[0097] Comparative Example 6

[0098] Based on Example 3, the difference is that the modified circulating fluidized bed ash is not mixed with acrylic emulsion.

[0099] Comparative Example 7

[0100] Based on Example 3, the difference is that in the process of modifying circulating fluidized bed ash, the mass of acid solution used is 2% of the mass of circulating fluidized bed ash.

[0101] Comparative Example 8

[0102] Based on Example 3, the difference is that hydrochloric acid is used in the process of modifying circulating fluidized bed ash.

[0103] Comparative Example 9

[0104] Based on Example 3, the difference is that in the process of modifying circulating fluidized bed ash, the mass ratio of acidified circulating fluidized bed ash to potassium persulfate solution is 5:1.

[0105] Table 1 shows the performance evaluation indicators of this invention. The flexural strength and compressive strength are tested according to GB / T 17671-2021 "Test Method for Strength of Cement Mortar", the drying shrinkage is tested according to JGJ / T70-2009 "Standard Test Method for Basic Performance of Building Mortar", and the autogenous shrinkage is tested according to the American standard ASTM C1698-09 "Standard Test Method for Autogenous Strain of Cement Paste and Mortar". The specific operation method is to inject the freshly mixed mortar into a corrugated pipe (420 ± 5 mm in length and 29 ± 0.5 mm in outer diameter), remove air bubbles, seal both ends, and place it in an environment with a temperature of 20 ± 3 ℃ and a humidity of 55 ± 3%. The longitudinal strain change is automatically recorded using an autogenous shrinkage strain tester.

[0106] Table 1

[0107]

[0108] As can be seen from Table 1, Examples 1-4 demonstrate that the sludge solidification material prepared by the present invention has excellent mechanical properties, low shrinkage deformation, and good appearance quality with no obvious cracks.

[0109] The results of Comparative Example 1 show that if the system lacks the formation of an ettringite phase that combines the functions of consolidating moisture and compensating for shrinkage, the mechanical properties are significantly reduced, shrinkage deformation is obvious, and severe cracking occurs. The results of Comparative Example 2 show that if the circulating fluidized bed ash lacks modification, it participates in the hydration reaction early on. Due to the lack of potassium persulfate, there is a lack of polymerization kinetics between acrylamide monomers, resulting in a low degree of polymerization and significant shrinkage cracking in the system. The results of Comparative Example 3 show that the lack of acrylamide monomers prevents the formation of an organic flexible network, leading to significant shrinkage cracking in the system. The results of Comparative Example 4 show that if the circulating fluidized bed ash lacks acidification treatment, its activity is reduced, the degree of hydration decreases, and the alkaline environment of the system reduces the amount of ettringite formed, increasing shrinkage cracking. The results of Comparative Example 5 show that if the circulating fluidized bed ash lacks potassium persulfate loading, the degree of polymerization of acrylamide monomers is low, and the system exhibits significant shrinkage cracking. The results of Comparative Example 6 show that if the circulating fluidized bed ash lacks acrylic emulsion coating to form a film, potassium persulfate prematurely initiates the polymerization of acrylamide monomers in the early stage of the reaction. The resulting polymer network encapsulates the cementitious material particles, significantly inhibiting the alkali-activated reaction, greatly reducing the hydration degree of the system, and causing severe shrinkage and cracking of the system.

[0110] As can be seen from Table 1, Examples 1-4 demonstrate that the sludge solidification material prepared by the present invention has excellent mechanical properties, low shrinkage deformation, and good appearance quality with no obvious cracks.

[0111] Comparative Example 1 shows that if the system lacks the formation of an ettringite phase that combines the functions of consolidating moisture and compensating for shrinkage, the mechanical properties are significantly reduced, shrinkage deformation is obvious, and severe cracking occurs. Comparative Example 2 shows that if the circulating fluidized bed ash lacks modification, it participates in the hydration reaction early on. Due to the lack of potassium persulfate, there is a lack of polymerization kinetics between acrylamide monomers, resulting in a low degree of polymerization and significant shrinkage cracking. Comparative Example 3 shows that the lack of acrylamide monomers prevents the formation of an organic flexible network, leading to significant shrinkage cracking. Comparative Example 4 shows that if the circulating fluidized bed ash lacks acidification treatment, its activity is reduced, the degree of hydration decreases, and the alkaline environment of the system reduces the amount of ettringite formed, increasing shrinkage deformation. Comparative Example 5 shows that if the circulating fluidized bed ash lacks potassium persulfate loading, the degree of polymerization of acrylamide monomers is low, and the system exhibits significant shrinkage cracking. Comparative Example 6 shows that if the circulating fluidized bed ash lacks acrylic emulsion coating, potassium persulfate prematurely initiates acrylamide monomer polymerization in the early stages of the reaction. The resulting polymer network encapsulates the cementitious particles, significantly inhibiting the alkali-activated reaction, drastically reducing the system's hydration level, and causing severe shrinkage and cracking. Comparative Example 7 shows that if the quality of the acid used for modification in the circulating fluidized bed ash is too low, the ash activity will be low, the potassium persulfate loading will be reduced, the polymerization reaction degree will decrease, strength will decrease, and shrinkage deformation will increase. Comparative Example 8 shows that if a strong acid is used to modify the circulating fluidized bed ash, the modified pore size and number will be larger. While this is beneficial for potassium persulfate loading, it also inhibits the alkali-activated reaction to some extent, leading to a decrease in strength. Comparative Example 9 shows that if too little potassium persulfate is used, the system's polymerization degree will be low, resulting in a decrease in strength and an increase in shrinkage deformation.

Claims

1. A method for preparing modified circulating fluidized bed combustion ash, characterized in that, Includes the following steps: A1. During the stirring process, the acid solution is dripped into the circulating fluidized bed ash to carry out the acidification reaction. After the reaction is completed, the product is separated and dried to obtain the acidified circulating fluidized bed ash. B1. After the acidified circulating fluidized bed ash is evacuated, potassium persulfate solution is injected under negative pressure to force the potassium persulfate solution into the pores of the circulating fluidized bed ash. Then, the circulating fluidized bed ash particles loaded with potassium persulfate are obtained by vacuum drying. C1. Circulating fluidized bed ash particles loaded with potassium persulfate are mixed with acrylic emulsion, so that the particle surface is fully coated with emulsion and solidified into a film.

2. The method for preparing modified circulating fluidized bed ash according to claim 1, characterized in that, In step A1, the mass of the acid solution is 4% to 8% of the mass of the circulating fluidized bed ash; the concentration of the acid solution is 80% to 90%.

3. The method for preparing modified circulating fluidized bed ash according to claim 1, characterized in that, In step B1, the mass ratio of the acidified circulating fluidized bed ash to the potassium persulfate solution is 2.5~3:1; the concentration of the potassium persulfate solution is 0.08~0.1 mol / L.

4. The method for preparing modified circulating fluidized bed ash according to claim 1, characterized in that, In step C1, the gel content in the acrylic emulsion is 30%~40%.

5. A sludge solidification material that can be polymerized in situ, characterized in that, Components comprising the following parts by weight: The mixture contains 126-400 parts of sludge, 56-84 parts of calcium silicate slag, 24-36 parts of modified circulating fluidized bed ash obtained by the method described in claim 1, 10-20 parts of gypsum, 7-24 parts of water glass, 4-7 parts of sodium hydroxide, 35-44 parts of water, 4-8 parts of acrylamide, and 0.025-0.08 parts of N,N'-methylenebisacrylamide.

6. The in-situ polymerizable sludge solidification material according to claim 5, characterized in that, The natural moisture content of the silt ranges from 40% to 80%.

7. The in-situ polymerizable sludge solidification material according to claim 5, characterized in that, The particle size of the silicon-calcium slag and the modified circulating fluidized bed ash is less than 75 μm.

8. The in-situ polymerizable sludge solidification material according to claim 5, characterized in that, The water glass has a modulus of 2.5 to 3.5 and a water content of 60% to 66%.

9. A method for preparing the in-situ polymerizable sludge solidification material according to claim 5, characterized in that, Includes the following steps: A2. Thoroughly mix sodium hydroxide with a portion of water, cool, and pour into water glass to prepare an alkaline activator; B2. Mix acrylamide and N,N'-methylenebisacrylamide evenly and dissolve them in the remaining water. Stir thoroughly and then pour the mixture into the alkaline activator to form a mixed solution. C2. Mix and stir the calcium silicate slag and modified circulating fluidized bed ash with the mixed solution from step B2 to obtain an alkali-activated gel slurry; D2. Mix the alkali-activated gelatinous slurry with the silt and stir to obtain the slurry; E2. Plaster is slowly added to the slurry and stirred to obtain a sludge solidification material that can be polymerized in situ.

10. The method for preparing the in-situ polymerizable sludge solidification material according to claim 9, characterized in that, In step A2, the water used accounts for 70% to 80% of the total water consumption.

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