High-activity papermaking sludge incineration ash as well as preparation method and application thereof

Abstract

The invention relates to the technical field of sludge treatment, in particular to high-activity papermaking sludge incineration ash as well as a preparation method and application thereof. The preparation method of the high-activity paper mill sludge incineration ash comprises the following steps: S1, carrying out sectional type hot air drying on dewatered paper mill sludge, so that the water content of the sludge is reduced to 15-25%; s2, feeding the dried sludge into a circulating fluidized bed incinerator, and pyrolyzing the papermaking sludge at 450-550 DEG C under an anoxic condition; carrying out activated combustion on the pyrolysis product under the conditions of oxygen enrichment and superheated steam injection at the temperature of 650-750 DEG C; then carrying out short-time stabilizing treatment on ash particles generated by activated combustion at 850-950 DEG C, and quenching; and S3, the cooled ash is ground, and the high-activity paper mill sludge incineration ash is obtained. The high-water-absorption material is prepared from the sludge incineration ash, and efficient treatment and resource utilization of dredged soil, river and lake bottom mud and engineering slurry are achieved.

Description

Technical Field

[0001] This invention relates to the field of sludge treatment technology, and in particular to a highly active papermaking sludge incineration ash, its preparation method, and its application. Background Technology

[0002] With the rapid development of the paper industry, a large amount of sludge is inevitably generated during the production process. As an industrial waste, papermaking sludge is mainly composed of cellulose, organic matter, mineral fillers, heavy metal ions, chemical additives, and other substances, and its composition varies depending on different production processes, raw material types, and added chemicals.

[0003] Typically, papermaking sludge is characterized by high moisture content and a loose structure. Undehydrated papermaking sludge is large in volume, heavy in weight, and highly fluid, posing significant challenges to its transportation, storage, and final treatment. During transportation, the excessively high moisture content significantly increases the weight and volume of the sludge, leading to high transportation costs. During storage, its high moisture content and loose structure make it prone to putrefaction in the storage environment, producing foul-smelling gases and further exacerbating the risk of environmental pollution.

[0004] Furthermore, sludge often contains certain amounts of toxic substances, such as heavy metal ions and organic pollutants. If these substances are not effectively treated, they may pose a serious threat to the environment and human health. Therefore, how to effectively dewater, reduce, stabilize, and treat this sludge has become a major challenge for the paper industry.

[0005] Currently, the main methods for treating paper mill sludge include physical, chemical, and biological methods. Physical methods mainly rely on filtration, centrifugation, and evaporation to dewater the sludge. However, the dewatered sludge cakes obtained by these methods still have a high water content and complex composition. Direct landfilling or simple incineration not only consumes land resources but also fails to realize its potential material value. Chemical methods improve the dewatering performance of sludge by adding coagulants or flocculants. However, the use of chemical agents not only increases disposal costs but may also cause secondary pollution. Biological treatment methods usually utilize microorganisms to decompose the organic matter in the sludge. Although this can reduce the organic load of the sludge, the treatment cycle is long and requires certain environmental conditions.

[0006] Furthermore, with the large-scale development of infrastructure projects in my country, a large amount of dredged soil, river and lake sediment, tunnel boring machine excavation soil, and engineering mud urgently need to be treated. These materials typically have high water content, complex composition, and are highly mobile. While existing mechanical dewatering, chemical conditioning, and thermal drying methods have improved treatment efficiency to some extent, they still face problems such as low dewatering efficiency, high treatment costs, and pollutant residues. In addition, with the continuous reduction of available landfill and disposal sites in cities, there is an urgent need to develop efficient resource utilization technologies to solve the disposal problems of these sludge and soil materials.

[0007] The information disclosed in this background section is intended only to enhance the understanding of the overall background of the present invention and should not be construed as an admission or in any way implying that the information constitutes prior art known to those skilled in the art. Summary of the Invention

[0008] The first objective of this invention is to provide a method for preparing highly active papermaking sludge incineration ash, which modifies the chemical and physical structure of the sludge step by step and in a targeted manner by precisely controlling the temperature and atmosphere.

[0009] The above-mentioned technical objective of the present invention is achieved through the following technical solution: A method for preparing highly active papermaking sludge incineration ash includes the following steps: S1 Drying treatment stage: The dewatered papermaking sludge is subjected to segmented hot air drying to reduce the sludge moisture content to 15%~25%; Paper mill sludge mainly comes from the mixture of primary and secondary sludge produced during the paper mill wastewater treatment process. Its composition is complex and specific, primarily including: The organic fiber components that make up the skeleton of sludge specifically include cellulose, hemicellulose, lignin, and microbial flocs composed of a large number of microbial cells and their secreted extracellular polymers (EPS). Among them, microbial flocs have extremely high water content, which is one of the main difficulties in sludge dewatering and drying treatment.

[0010] The inorganic fillers and coating pigments that constitute the ash content of sludge specifically include calcium carbonate, kaolin, talc, titanium dioxide, and other inorganic additives.

[0011] Preferably, the dewatered papermaking sludge referred to in this step is a sludge cake obtained by mechanical dewatering during the papermaking wastewater treatment process, such as plate and frame filter press, belt filter press, or centrifugal dewatering. This invention uses this sludge cake as raw material and performs segmented hot air drying. The initial moisture content of the sludge cake is between 30% and 40%. The segmented hot air drying includes: preheating at 85℃ to 100℃ for 0.5 to 1 hour, followed by high-temperature drying at 120℃ to 150℃ for 1 to 3 hours. After drying, the sludge moisture content is reduced to 15% to 25%. The physical structure of the sludge cake facilitates hot air penetration and moisture migration. The segmented drying first gently breaks down the colloidal structure of the sludge cake at a lower temperature to prevent surface hardening; then, it efficiently removes internal bound water at a higher temperature, ensuring uniform drying and avoiding localized over-drying or coking, thus achieving a stable and controllable decrease in moisture content.

[0012] This invention utilizes multi-stage temperature-controlled hot air drying to avoid damage to organic matter and surface crusting while ensuring the smooth removal of internal moisture. This allows for precise control of the moisture content of the feed material within a low range of 15% to 25%, providing a relatively stable feed material in terms of composition and calorific value for the circulating fluidized bed incinerator. This not only reduces energy consumption and the risk of sludge charring but also ensures stable and efficient combustion in the subsequent circulating fluidized bed.

[0013] Preferably, before step S1, the dewatered papermaking sludge cake can be homogenized, for example by short-term in-silo stirring or aging, to make its composition and moisture content more uniform, thereby ensuring the stability of the subsequent incineration process.

[0014] S2 Incineration Stage: The dried sludge is fed into a circulating fluidized bed incinerator and pyrolyzed at 450-550°C under anaerobic conditions. Then, the pyrolysis products are activated and burned at 650-750°C under oxygen-rich conditions with the injection of superheated steam. After that, the ash particles generated by the activated combustion are briefly stabilized at 850-950°C and then rapidly cooled. The incineration stage combines temperature-controlled sequential incineration with circulating fluidized bed incineration. The dried papermaking sludge undergoes anoxic pyrolysis, oxygen-enriched steam activation, and short-term high-temperature stabilization treatment in sequence. The circulating fluidized bed incineration uses a multi-stage distributed airflow control and enhanced airflow circulation system to ensure more thorough contact between the sludge and the hot airflow, thereby improving incineration efficiency and reducing pollutant emissions. Ultimately, the incinerated sludge is converted into ash. This process, through step-by-step control, aims to systematically solve the problems of low ash activity and poor stability in traditional incineration.

[0015] Preferably, in step S2, the dried sludge can be fed into the lower dense phase zone of a circulating fluidized bed incinerator and subjected to anoxic pyrolysis for 30-90 minutes at 450-550℃ and an excess air coefficient of 0.6-0.8. Traditional incineration aims for complete combustion, resulting in dense, inert ash with a low specific surface area. This step, through precise anoxic control, actively transforms the sludge into a porous precursor rich in a fixed carbon skeleton. Under anoxic conditions, the organic matter (cellulose, lignin, etc.) in the sludge undergoes pyrolysis rather than complete combustion, volatile components escape, and the remaining fixed carbon forms a robust three-dimensional network carbon skeleton. The pre-constructed pore structure in the ash during this process greatly increases the specific surface area and reactive sites. At the same time, bound water and some crystal water are removed at this temperature, while calcium carbonate has not yet decomposed in large quantities, which is beneficial for maintaining structural stability.

[0016] Preferably, in step S2, the pyrolysis products enter the upper dilute phase zone of the furnace with the airflow. Secondary air is added and superheated steam is injected in this zone to achieve an operating temperature of 650~750℃ and an excess air coefficient of 1.2~1.5. Oxygen-enriched steam activation is then performed for 30~60 minutes. The oxygen-enriched environment ensures that the carbon skeleton formed in the first step is burned rapidly and completely, thereby further expanding and connecting the pores. At the same time, the injected superheated steam reacts with the fresh inorganic surfaces newly exposed due to carbon combustion: on the one hand, it reacts with highly reactive f-CaO and promotes its contact with active SiO2 and Al2O3 to generate precursors of active transition phases such as calcium silicate hydrate (CSH) and calcium aluminate hydrate (CAH); on the other hand, the steam produces a hydrothermal etching effect on the aluminosilicate glass, breaking its stable Si-O-Si and Si-O-Al covalent bond networks and generating a large number of amorphous, highly reactive transition phases. This step synergistically achieves physical pore expansion and chemical activation, enabling the ash to achieve pozzolanic reactivity far exceeding that of ordinary incinerator ash.

[0017] Preferably, in step S2, the flue gas and ash particles after activation and combustion enter the high-temperature flue / retention chamber connected to the furnace outlet, where the temperature is maintained at 850~950℃ and held for 5~60s to complete the short-term stabilization treatment of the ash. Subsequently, the high-temperature ash collected by the cyclone separator is rapidly cooled to fix the highly active amorphous phase by quenching.

[0018] This step first ensures the complete decomposition of complex organic pollutants. Secondly, it promotes micro-melting and sintering on the surface of the ash particles, effectively encapsulating the highly active free calcium oxide (f-CaO) inside, significantly reducing its hydration rate, thereby greatly improving the volume stability of the final product. Based on this, it facilitates the formation of alkali metal ions (K... + Na + The reaction with aluminosilicates to form insoluble complex salts provides energy, which is then solidified in the crystal lattice, thus suppressing alkali blooming at its source and reducing the risk of damage to subsequent organic additives (such as PAM).

[0019] Preferably, in step S2, the superheated steam injection temperature is 200~400℃, the injection pressure is 0.5~1.0MPa, and the superheated steam injection point is preferably located in the dilute phase region of the circulating fluidized bed. A surrounding multi-nozzle injection method is used to ensure maximum contact area between the steam and the high-temperature ash, achieving uniform and efficient activation. The 200~400℃ temperature ensures that the steam is injected in a completely gaseous state, and after injection, it forms a drastic but controllable local temperature difference with the furnace, effectively driving strong heat and mass exchange and significantly improving activation efficiency. Simultaneously, due to the inherent large thermal inertia and strong turbulence of the circulating fluidized bed, this local disturbance is rapidly homogenized, thereby ensuring the overall temperature stability of the main reaction zone and preventing any impact on system operation.

[0020] Preferably, in step S2, the feed particle size of the dried sludge is controlled to be ≤50mm. Specifically, a screw feeder or a sealed belt scale is used for feeding to ensure that the material flow rate entering the circulating fluidized bed is stable and controllable, and to avoid bridging or material interruption.

[0021] Preferably, in step S2, the apparent fluidization velocity of the circulating fluidized bed is controlled at 1.5~2.5 m / s. This ensures that the material is in a state of intense turbulent fluidization, achieving efficient heat and mass transfer, while also preventing excessive entrainment of bed material.

[0022] Preferably, in step S2, the high-temperature flue gas and ash from the circulating fluidized bed need to pass through a two-stage cyclone separator. The coarse ash collected by the first-stage separator can be returned to the furnace for further reaction, while the fine ash collected by the second-stage separator is the main component of the highly reactive ash. The high-temperature flue gas from the cyclone separator enters the waste heat boiler for heat recovery, and the generated steam can be used for sludge drying or as a superheated steam source, reducing overall energy consumption.

[0023] S3 Grinding and Screening Stage: The cooled ash is ground to obtain highly active papermaking sludge incineration ash.

[0024] Preferably, in step S3, zirconium oxide or steel grinding media with a diameter of 10-30 mm are used to grind the ash in a ball mill at a speed of 300-500 rpm for 2-4 hours; the average particle size of the ground incinerator ash is 2-5 μm.

[0025] Through this process, the average particle size of sludge ash can be reduced from the initial 100-200 μm to 2-5 μm, with particles smaller than 10 μm accounting for over 90%. Simultaneously, the specific surface area can be increased from the original 20-40 m². 2 / kg increased to 400~800m 2 / kg, where 2μm corresponds to a specific surface area of ​​approximately 750m². 2 / kg, the specific surface area corresponding to 5μm is approximately 450m². 2 / kg, by effectively exposing potential active components, enhances the reaction efficiency and composite effect between them and organic monomers or cementitious materials.

[0026] The second objective of this invention is to provide a highly active papermaking sludge incineration ash, which is obtained by the above preparation method. Its performance indicators far exceed those of conventional incineration ash, and it has the advantages of uniformity, stability, high activity, and high stability.

[0027] The above-mentioned technical objective of the present invention is achieved through the following technical solution: A highly reactive papermaking sludge incineration ash prepared by the above method has a specific surface area of ​​400-800 m². 2 / kg, with a free calcium oxide content not exceeding 5.0%, and a total soluble potassium and sodium ion content not exceeding 2.0%.

[0028] The papermaking sludge incineration ash prepared by this invention is rich in active oxides such as SiO2, Al2O3, and Fe2O3, which can participate in adsorption reactions and gel complexation. It also possesses high specific surface area, porosity, and a certain degree of alkalinity, making it suitable as a water-absorbing matrix for superabsorbent materials, providing support for water absorption. The high specific surface area and abundant amorphous active phase give it excellent pozzolanic activity and physical adsorption capacity. Controlling the free calcium oxide content to no more than 5.0% fundamentally solves the engineering problem of cracking and pulverization of the solidified body caused by the later-stage hydration expansion of f-CaO. Furthermore, the total amount of soluble potassium and sodium ions is ≤2.0%, inhibiting efflorescence from the source and avoiding damage to the engineering appearance and chemical destruction of subsequent organic polymer additives (such as PAM).

[0029] The third objective of this invention is to provide a highly absorbent material prepared from highly active papermaking sludge incineration ash, which solves the technical problems of slow dehydration rate, low early strength of solidified body, poor long-term stability, and high cost and easy secondary pollution caused by the use of pure chemical agents when treating sludge with high water content using traditional methods.

[0030] The above-mentioned technical objective of the present invention is achieved through the following technical solution: A highly absorbent material prepared from the above-mentioned highly active papermaking sludge incineration ash comprises the following components by weight: 30-80 parts of papermaking sludge incineration ash, 10-30 parts of industrial by-product gypsum, 0.1-2 parts of polyacrylamide, 1-2 parts of aluminum sulfate octadecylhydrate, 5-20 parts of mineral powder, 5-15 parts of carbide slag, 0.1-1 parts of lithium carbonate, and 1-5 parts of magnesium oxide.

[0031] In this invention, incineration ash from papermaking sludge provides a solid framework, forming a porous structure. After being uniformly mixed with other components to prepare a superabsorbent material, when the superabsorbent material is mixed with wet sludge, polyacrylamide and aluminum sulfate octahydrate first rapidly flocculate the particles through charge neutralization and adsorption bridging, achieving instantaneous dehydration. Subsequently, the dissolution of carbide slag provides a high concentration of OH-. - Ions and Ca 2+ This creates a strongly alkaline environment, effectively disrupting the silica-alumina glass structure in the incinerator ash and promoting the dissolution of active SiO2 and Al2O3. During this process, trace amounts of lithium carbonate act as a highly efficient catalyst, significantly lowering the reaction energy barrier and driving the rapid formation of a three-dimensional ettringite crystal network from gypsum, aluminum source, and calcium ions. This process involves the binding of a large amount of water of crystallization and generates expansion stress, which together promote dehydration and provide early strength. Simultaneously, Ca... 2+ Al provided by aluminum sulfate octahydrate 3+In a humid environment, the components work synergistically to generate Ca-Al bimetallic hydrated complexes, forming an ionic cross-linking network that provides three-dimensional structural support for water absorption, thereby increasing the material's water absorption capacity. In a continuously alkaline environment, mineral powder and residual incineration ash undergo a pozzolanic reaction, continuously generating CSH gel. Magnesium oxide provides supplementary gelling and micro-expansion through slow hydration, jointly densifying the structure. This invention achieves efficient sequential mechanisms of physical flocculation water absorption, chemical water binding, and gel solidification through multi-component synergy. It can not only quickly remove a large amount of free water but also form a high-strength, stable solidified body. At the same time, it treats waste with waste, possessing outstanding advantages of high efficiency, economy, and environmental protection.

[0032] Preferably, the effective Ca(OH)2 content of the carbide slag is not less than 60%; the industrial by-product gypsum is one or more of desulfurized gypsum, phosphogypsum or titanium gypsum; and the mineral powder is S95 grade or S105 grade slag powder.

[0033] Preferably, the polyacrylamide is anionic with a molecular weight of 8 million to 22 million. The carboxyl and amide groups on the chain segments can form hydrogen bonds or electrostatic bonds with the surface of ash particles, forming a polymer gel system during water absorption, which significantly improves the water retention capacity.

[0034] Preferably, aluminum sulfate octahydrate hydrolyzes in aqueous solution to produce Al 3+ It can neutralize the negative charge on the particle surface, compress the double electric layer, and promote particle aggregation and sedimentation. The solubility of aluminum sulfate octahydrate in water at 25℃ is not less than 80g / 100mL, ensuring that it can dissolve quickly and exert flocculation and chemical cross-linking effects rapidly.

[0035] Preferably, magnesium oxide slowly hydrates in water to form Mg(OH)2, which participates in the secondary cementation process to stabilize the structure and regulates the water absorption rate, which is beneficial for construction. The conversion of MgO to Mg(OH)2 is accompanied by volume expansion. This slow and controllable expansion helps to squeeze the pores of the silt, promoting drainage and compaction.

[0036] Preferably, lithium carbonate provides a small amount of Li. + It can enhance the cation exchange capacity between minerals and promote the activity of active components (such as Si) in ash. 4+ Al 3+The dissolution and migration of lithium carbonate facilitate the formation of subsequent gels, thereby enhancing the density of the network structure. In the high-alumina, high-calcium, and high-alkali system of this invention, which focuses on the formation of ettringite, trace amounts of lithium carbonate can significantly accelerate the nucleation and growth of ettringite, resulting in superior early strength for the entire system. By introducing trace amounts of highly efficient lithium carbonate, this invention overcomes the fatal weakness of slow early strength development in papermaking sludge incineration ash-based materials, successfully reconciling the contradiction between rapid physical dehydration and long-term chemical coagulation, and achieving the technical effect of both rapid dehydration and stable high-strength solidification of high-moisture sludge.

[0037] The fourth objective of this invention is to provide a method for preparing a superabsorbent material that ensures that each component achieves uniform mixing at the molecular level while maintaining its own chemical stability, thereby ensuring that the final product can effectively exert a synergistic effect in actual use.

[0038] The above-mentioned technical objective of the present invention is achieved through the following technical solution: A method for preparing a superabsorbent material includes: A1. Papermaking sludge incineration ash, industrial by-product gypsum, mineral powder, and carbide slag are placed in a high-speed mixer in proportion and mixed evenly at a speed of 300-500 rpm for 3-5 minutes. Then, magnesium oxide and lithium carbonate are added and dry-mixed to obtain a uniform gelling base material. This step achieves micro-region pre-activation of inorganic cementitious components. High-speed mixing ensures full contact between carbide slag and incineration ash. The surface of carbide slag particles adheres to the porous surface of incineration ash, forming an alkaline microenvironment. This initially disrupts the glassy structure of the incineration ash surface, establishing a pre-reaction interface for subsequent hydration. The subsequently added magnesium oxide and lithium carbonate are uniformly embedded in this matrix, forming a stable solid-state reaction precursor.

[0039] A2 Subsequently, the dry powders of polyacrylamide and aluminum sulfate octadecylhydrate were added to the gelling base for a second-stage dry mixing process. The rotation speed was increased to 400-500 rpm, and the mixing time was not less than 10 minutes to ensure that the organic and inorganic components were fully dispersed. This step achieves molecular-level dispersion through mechanochemical action. Under high-speed shearing, polyacrylamide segments interact with the inorganic particle surface by charge, and the aluminum sulfate octahydrate crystals are broken down and embedded into the composite system, forming the prototype of an organic-inorganic hybrid network. During this process, the amide groups of polyacrylamide form hydrogen bonds with the hydroxyl groups on the surface of incineration ash, enabling the material to form a stable gel network immediately upon contact with water.

[0040] A3 uses a high-speed impact pulverizer or turbine pulverizer to further pulverize the uniformly mixed material at a speed of 8000~12000 rpm for 2~4 min. The material is then further sieved through a high-frequency vibrating screen to ensure that D90≤10μm and D50 is between 2~5μm, ultimately obtaining the target highly absorbent material.

[0041] This step generates a mechanical activation effect through high-speed impact crushing, further opening the closed pores of the incinerator ash and exposing new active surfaces; at the same time, it causes lattice defects at the interfaces of each component, significantly increasing the surface energy. Precise particle size control (D90<10μm) ensures the optimal balance between specific surface area and reaction kinetics, giving the material both rapid solubility and long-lasting water retention.

[0042] The fifth objective of this invention is to provide a method for applying highly absorbent materials, which is suitable for the rapid drying and solidification of various high-moisture-content materials such as river silt and engineering mud.

[0043] The above-mentioned technical objective of the present invention is achieved through the following technical solution: Application of a superabsorbent material in the rapid drying or solidification of dredged soil, river and lake sediment, tunnel boring machine excavation soil, and engineering slurry. Specific steps are as follows: B1: Pretreatment and Initial Dispersion The high water content sludge is initially screened to remove large-sized debris. Then, 30% to 50% of the total amount of super absorbent material is evenly distributed on the sludge surface by pneumatic spraying or mechanical spreading. B2: Level 1 low-to-medium speed mixing After the sludge and the initially added powder have been in static contact for 1 to 5 minutes, a mixing device with plow-shaped and spiral stirring arms is used to carry out the first stage of mixing at a speed of 20 to 60 rpm; this achieves the initial wetting and distribution of the powder and sludge, forming a mixture with a roughly uniform appearance. B3: Secondary high-speed shear mixing After completing the first stage of mixing, immediately add the remaining 50% to 70% of the superabsorbent material. Then, switch to or start the high-speed shear mixing device and perform strong shear mixing of the mixture at a speed of 300 to 800 rpm for 2 to 8 minutes; use high mechanical shear force to thoroughly break up powder clumps and sticky lumps in the sludge, and achieve uniform dispersion at the microscale. B4: Static Curing and Subsequent Care After the secondary mixing is completed, let the mixture stand for 10-30 minutes to cure. At this time, the water-absorbing material begins to play its role, and the viscosity of the sludge decreases significantly. If necessary, simple turning and conditioning can be carried out after this stage to obtain a homogeneous mixture for final dehydration and solidification.

[0044] The superabsorbent material produced by this invention, through full utilization of the physical water absorption properties and chemical modification effects of modified papermaking sludge ash, not only significantly improves sludge treatment efficiency but also achieves efficient treatment and resource utilization of dredged soil, river and lake sediment, and engineering mud. This technology provides an innovative solution for sludge reduction, harmlessness, and resource utilization, with good environmental and economic benefits.

[0045] Compared with the prior art, the present invention has the following beneficial effects: This invention employs a sequential incineration process consisting of anaerobic pyrolysis, oxygen-enriched steam injection activation combustion, and short-duration high-temperature stabilization. By transforming organic matter in sludge into a robust, porous, fixed carbon framework under an oxygen-deficient environment, it significantly increases the specific surface area and reactive sites of the material. Subsequently, the oxygen-enriched steam injection activation combustion step, based on the well-developed pores formed in the previous step, achieves efficient and complete combustion of the fixed carbon. The injected superheated steam interacts with the exposed fresh inorganic surface, effectively preventing the sintering of active components and transforming them into a transition phase with high pozzolanic reactivity, thus elevating the traditional incineration process to a material activation process. Finally, the short-duration high-temperature stabilization step utilizes the activated ash, ensuring complete decomposition of pollutants while promoting micro-melting of the particle surface. This effectively encapsulates highly reactive free calcium oxide, significantly improving the volume stability of the final product and solidifying soluble alkali metal ions within the silicate network, fundamentally suppressing the risk of efflorescence.

[0046] This invention achieves the clean and efficient conversion of papermaking sludge resources through full-process thermal control and physical refinement. The resulting sludge ash is characterized by uniform particle size, good activity, and low impurities, making it a high-quality raw material for high-performance absorbent materials. Specifically, the papermaking sludge incineration ash is used as the main raw material, in conjunction with various solid wastes such as industrial by-products gypsum, carbide slag, and mineral powder. Through the synergistic effect of organic and inorganic cementing systems, a dense, porous absorbent network structure is formed, exhibiting high water absorption capacity. It is suitable for the rapid drying and solidification of various high-moisture materials such as river silt and engineering mud. This invention significantly enhances the added value of resource utilization of papermaking sludge incineration by-products, possessing good environmental protection benefits and industrial promotion potential; it also achieves high-proportion, high-value-added utilization of solid waste, reducing costs and demonstrating good environmental and economic benefits. Detailed Implementation

[0047] To further illustrate the technical means and effects adopted by the present invention to achieve its intended purpose, the specific implementation methods, features, and effects of a highly active papermaking sludge incineration ash, its preparation method, and its application, based on the present invention, are described in detail below. It should be understood that the specific embodiments described herein are merely illustrative of the invention and are not intended to limit the invention.

[0048] Example 1: A method for preparing highly active papermaking sludge incineration ash includes the following steps: S1 Drying Treatment Stage: Take 1 ton of papermaking sludge cake with an initial moisture content of 35% after dewatering by plate and frame filter press and send it into a segmented belt dryer. First, preheat and slowly dewater at 90℃ for 30 minutes, and then perform enhanced drying at 135℃ for 2 hours. After drying treatment, the sludge moisture content is reduced to 20%. S2 Incineration Stage: The dried sludge is fed into a circulating fluidized bed incinerator and pyrolyzed for 60 minutes under anoxic conditions of 500°C and an excess air coefficient of 0.7. Then, the pyrolysis products are activated and burned for 40 minutes under oxygen-enriched conditions of 700°C and an excess air coefficient of 1.3, with the injection of superheated steam at 300°C. After that, the ash particles generated by the activated combustion are subjected to short-term stabilization treatment at 900°C for 30 seconds, and then rapidly cooled to 200°C. S3 Grinding and Sieving Stage: Using 20mm diameter zirconia grinding media, the ash was ground in a ball mill at 400 rpm for 3 hours. The average particle size of the ground ash was 2-5μm, yielding highly active papermaking sludge incineration ash. Testing showed that the specific surface area of ​​the highly active papermaking sludge incineration ash was 400-800 m². 2 / kg, with a free calcium oxide content of 3.8% and a total soluble potassium and sodium ion content of 1.5%.

[0049] A highly absorbent material prepared from the above-mentioned highly active papermaking sludge incineration ash comprises the following components by weight: 60 parts of papermaking sludge incineration ash, 20 parts of desulfurized gypsum, 0.5 parts of polyacrylamide, 1.5 parts of aluminum sulfate octadecylhydrate, 15 parts of S95 mineral powder, 5 parts of carbide slag, 0.2 parts of lithium carbonate, and 2 parts of magnesium oxide.

[0050] A method for preparing a superabsorbent material includes: A1. Papermaking sludge incineration ash, industrial by-product gypsum, mineral powder, and carbide slag are placed in a high-speed mixer in proportion and mixed evenly at 400 rpm for 4 minutes. Then, magnesium oxide and lithium carbonate are added and dry-mixed for 2 minutes to obtain a uniform gelling base material. A2 Subsequently, the dry powders of polyacrylamide and aluminum sulfate octadecylhydrate were added to the gelling base material for a second-stage dry mixing process. The speed was increased to 450 rpm and the mixing time was not less than 10 minutes to ensure that the organic and inorganic components were fully dispersed. A3 uses a high-speed impact pulverizer or turbine pulverizer to further pulverize the uniformly mixed material at a speed of 10,000 rpm for 3 minutes. The material is then further sieved through a high-frequency vibrating screen to ensure that D90 < 10 μm and D50 is between 2 and 5 μm, ultimately obtaining the target highly absorbent material.

[0051] Performance testing: The superabsorbent material prepared in Example 1 was mixed with Taihu Lake silt with a water content of 85% at an addition rate of 10%. The mixture was stirred rapidly using a high-speed mixer. After stirring, a portion was molded and placed into a test mold to measure the change in compressive strength at 3d, 7d, and 28d. The other portion was measured to measure the change in water content at 10min, 30min, 60min, 120min, and 180min. The test results are shown in the table below.

[0052] Table 1. Changes in moisture content over time Test results show that this superabsorbent material system can significantly reduce the water content of high water content sludge in a short time, reducing the water content from 85% to 20% within 180 minutes, demonstrating excellent rapid dehydration performance.

[0053] Table 2. Changes in compressive strength with age The results show that the material system has a certain early strength capability in the early stage, is suitable for the rapid drying and solidification of engineering mud with high water content, and can meet the requirements of early load-bearing capacity.

[0054] Example 2: The difference between this embodiment and Embodiment 1 is that: A highly absorbent material prepared from the above-mentioned highly active papermaking sludge incineration ash comprises the following components by weight: 80 parts of papermaking sludge incineration ash, 30 parts of desulfurized gypsum, 0.8 parts of polyacrylamide, 1.7 parts of aluminum sulfate octadecylhydrate, 25 parts of S95 mineral powder, 15 parts of carbide slag, 0.5 parts of lithium carbonate, and 3 parts of magnesium oxide.

[0055] The rest is the same as in Example 1, and will not be repeated here.

[0056] Performance testing: The superabsorbent material prepared in Example 2 was mixed with engineering slurry with a water content of 125% at an addition rate of 10%. The mixture was stirred rapidly using a high-speed mixer. After stirring, a portion was molded and placed into a test mold to measure the change in compressive strength at 3d, 7d, and 28d. The other portion was measured to measure the change in water content at 10min, 30min, 60min, 120min, and 180min. The test results are shown in the table below.

[0057] Table 3. Moisture content changes over time Test results show that this superabsorbent material system can significantly reduce the water content of high water content engineering mud in a short time, reducing the water content from 125% to 33% within 180 minutes, demonstrating excellent rapid dehydration performance.

[0058] Table 4. Changes in compressive strength with age The results show that the material system has a certain early strength capability in the early stage, is suitable for the rapid drying and solidification of engineering mud with high water content, and can meet the requirements of early load-bearing capacity.

[0059] Example 3: A method for preparing highly active papermaking sludge incineration ash includes the following steps: S1 Drying Treatment Stage: Take 1 ton of papermaking sludge cake with an initial moisture content of 35% after dewatering by plate and frame filter press and send it into a segmented belt dryer. First, preheat and slow dewater at 90℃ for 30 minutes, and then perform enhanced drying at 135℃ for 1.5 hours. After drying treatment, the sludge moisture content is reduced to 22%. S2 Incineration Stage: The dried sludge is fed into a circulating fluidized bed incinerator and pyrolyzed for 80 minutes under anoxic conditions of 450°C and an excess air coefficient of 0.6. Subsequently, the pyrolysis products are activated and burned for 30 minutes under oxygen-enriched conditions of 650°C and an excess air coefficient of 1.2, with the injection of 200°C superheated steam. After that, the ash particles generated by the activated combustion are subjected to short-term stabilization treatment at 850°C for 60 seconds, followed by rapid cooling. S3 Grinding and Sieving Stage: Using 20mm diameter zirconia grinding media, the ash was ground in a ball mill at 300 rpm for 4 hours. The average particle size of the ground ash was 2-5μm, yielding highly active papermaking sludge incineration ash. Testing showed that the specific surface area of ​​the highly active papermaking sludge incineration ash was 400-800 m². 2 / kg, with a free calcium oxide content of 2.9% and a total soluble potassium and sodium ion content of 1.2%.

[0060] In this embodiment, the weight proportions of each component of the superabsorbent material prepared from the above-mentioned highly active papermaking sludge incineration ash and the preparation method of the superabsorbent material are the same as in Example 1, and will not be repeated here.

[0061] Performance testing: The superabsorbent material prepared in Example 3 was mixed with shield slurry with a water content of 85% at an addition rate of 10%. The mixture was stirred rapidly using a high-speed mixer. After stirring, a portion was molded and placed into a test mold to measure the change in compressive strength at 3d, 7d, and 28d. The other portion was measured to measure the change in water content at 10min, 30min, 60min, 120min, and 180min. The test results are shown in the table below.

[0062] Table 5. Changes in moisture content over time Test results show that this superabsorbent material system can significantly reduce the water content of high water content shield tunneling mud in a short time, reducing the water content from 85% to 18% within 180 minutes, demonstrating excellent rapid dehydration performance.

[0063] Table 6. Changes in compressive strength with age. The results show that the material system has a certain early strength capability in the early stage, is suitable for the rapid drying and solidification of engineering mud with high water content, and can meet the requirements of early load-bearing capacity.

[0064] Example 4: A method for preparing highly active papermaking sludge incineration ash includes the following steps: S1 Drying Treatment Stage: Take 1 ton of papermaking sludge cake with an initial moisture content of 35% after dewatering by plate and frame filter press and send it into a segmented belt dryer. First, preheat and slowly dewater at 95℃ for 25 minutes, and then perform enhanced drying at 145℃ for 1.5 hours. After drying treatment, the sludge moisture content is reduced to 21%. S2 Incineration Stage: The dried sludge is fed into a circulating fluidized bed incinerator and pyrolyzed for 45 minutes under anoxic conditions of 550°C and an excess air coefficient of 0.8. Subsequently, the pyrolysis products are activated and burned for 60 minutes under oxygen-enriched conditions of 750°C and an excess air coefficient of 1.5, with the injection of superheated steam at 300°C. After that, the ash particles generated by the activated combustion are subjected to a short-term stabilization treatment at 900°C for 10 seconds, followed by rapid cooling. S3 Grinding and Sieving Stage: Using steel grinding media with a diameter of 20mm, the ash was ground in a ball mill at 500 rpm for 2 hours. The average particle size of the ground ash was 2~5μm, yielding highly active papermaking sludge incineration ash. Testing showed that the specific surface area of ​​the highly active papermaking sludge incineration ash was 400~800m². 2 / kg, with a free calcium oxide content of 4.5% and a total soluble potassium and sodium ion content of 1.8%.

[0065] In this embodiment, the weight proportions of each component of the superabsorbent material prepared from the above-mentioned highly active papermaking sludge incineration ash and the preparation method of the superabsorbent material are the same as in Example 1, and will not be repeated here.

[0066] Performance testing: The superabsorbent material prepared in Example 4 was mixed with river silt with a water content of 85% at an addition rate of 10%. The mixture was stirred rapidly using a high-speed mixer. After stirring, a portion was molded and placed into a test mold to measure the change in compressive strength at 3d, 7d, and 28d. The other portion was measured to measure the change in water content at 10min, 30min, 60min, 120min, and 180min. The test results are shown in the table below.

[0067] Table 7. Moisture content changes over time Test results show that this superabsorbent material system can significantly reduce the water content of high water-content sludge in a short time, reducing the water content from 85% to 22% within 180 minutes, demonstrating excellent rapid dehydration performance.

[0068] Table 8. Changes in compressive strength with age The results show that the material system has a certain early strength capability in the early stage, is suitable for the rapid drying and solidification of engineering mud with high water content, and can meet the requirements of early load-bearing capacity.

[0069] Comparative Example 1: The difference between this comparative embodiment and Embodiment 1 is that: In step S2, the dried sludge is directly incinerated at 750°C with an excess air coefficient of 1.0 for 2 hours without undergoing the three-step treatment. Steps S1 (drying) and S3 (grinding) are identical to those in Example 1. The resulting incineration ash has the following properties: specific surface area 200~400 m². 2 / kg, free calcium oxide content 9.2%, total soluble potassium and sodium ions 3.8%.

[0070] This ash was used to prepare a highly absorbent material according to the formulation in Example 1, and the same sludge was treated using the same method.

[0071] Performance testing: The superabsorbent material prepared in Comparative Example 1 was mixed with Taihu Lake silt with a moisture content of 85% at an addition rate of 10%. The mixture was stirred rapidly using a high-speed mixer. After stirring, a portion was molded and placed into a test mold to measure the change in compressive strength at 3d, 7d, and 28d. The other portion was measured to measure the change in moisture content at 10min, 30min, 60min, 120min, and 180min. The test results are shown in the table below.

[0072] Table 9. Moisture content changes over time Table 10. Changes in compressive strength with age The results showed that the absorbent material made from the sludge incineration ash prepared by this method had poor effects on the rapid drying and solidification of sludge.

[0073] Comparative Example 2: The difference between this comparative example and Example 1 is as follows: A highly absorbent material prepared from the above-mentioned highly active papermaking sludge incineration ash comprises the following components by weight: 60 parts of papermaking sludge incineration ash, 20 parts of desulfurized gypsum, 0.5 parts of polyacrylamide, 15 parts of S95 mineral powder, 5 parts of carbide slag, and 2 parts of magnesium oxide.

[0074] The rest is the same as in Example 1, and will not be repeated here.

[0075] Performance testing: The superabsorbent material prepared in Comparative Example 2 was mixed with Taihu Lake silt with a moisture content of 85% at an addition rate of 10%. The mixture was stirred rapidly using a high-speed mixer. After stirring, a portion was molded and placed into a test mold to measure the change in compressive strength at 3d, 7d, and 28d. The other portion was measured to measure the change in moisture content at 10min, 30min, 60min, 120min, and 180min. The test results are shown in the table below.

[0076] Table 11 Changes in moisture content over time Table 12 Changes in compressive strength with age The results showed that the dehydration effect and compressive strength decreased significantly after removing aluminum sulfate octahydrate and lithium carbonate, indicating that the two materials have a synergistic effect on water absorption activation and structural strength formation.

[0077] Comparative Example 3: No super absorbent materials were added; the silt from Taihu Lake with a water content of 85% was simply dehydrated naturally, with all other conditions remaining the same.

[0078] Table 13 Changes in moisture content over time The sample remained in a fluid state and could not be demolded for testing; the compressive strength was 0 MPa.

[0079] Comparative Example 4: Quicklime was used as the treatment material to treat Taihu Lake silt with a moisture content of 85%, and the dosage was the same as in Example 1. The results are shown in the table below.

[0080] Table 14. Moisture content changes over time Table 15. Changes in compressive strength with age The results showed that traditional quicklime had poor effects on the rapid drying and solidification of sludge, resulting in low treatment efficiency and high carbon emissions, which is not conducive to green construction.

[0081] Those skilled in the art should understand that this invention is not limited to the above embodiments. The embodiments and descriptions in the specification are merely illustrative of the principles of the invention. Various changes and modifications can be made to this invention without departing from its spirit and scope, and all such changes and modifications fall within the scope of the invention as claimed. The scope of protection of this invention is defined by the appended claims and their equivalents.

Claims

1. A method for preparing highly active papermaking sludge incineration ash, characterized in that, Includes the following steps: S1 performs segmented hot air drying on the dewatered papermaking sludge, reducing the sludge moisture content to 15%~25%; S2 feeds the dried sludge into a circulating fluidized bed incinerator, where the papermaking sludge is pyrolyzed at 450-550°C under anaerobic conditions. Subsequently, the pyrolysis products are activated and burned at 650-750°C under anaerobic conditions with the injection of superheated steam. The ash particles generated by the activation and combustion are then subjected to short-term stabilization treatment at 850-950°C, followed by rapid cooling. S3 grinds the cooled ash to obtain highly active papermaking sludge incineration ash.

2. The method for preparing highly active papermaking sludge incineration ash according to claim 1, characterized in that, The segmented hot air drying in step S1 includes: preheating at 85℃~100℃ for 0.5~1h, followed by high-temperature drying at 120℃~150℃ for 1~3h.

3. The method for preparing highly active papermaking sludge incineration ash according to claim 1, characterized in that, In step S2, the excess air coefficient is controlled to be 0.6 to 0.8 at 450 to 550°C; the excess air coefficient is controlled to be 1.2 to 1.5 at 650 to 750°C; and the short-term stabilization treatment time is 5 to 60 seconds at 850 to 950°C.

4. The method for preparing highly active papermaking sludge incineration ash according to claim 1, characterized in that, In step S2, the injection temperature of the superheated steam is 200~400℃.

5. The method for preparing highly active papermaking sludge incineration ash according to claim 1, characterized in that, In step S3, grinding media with a diameter of 10~30mm are used in a ball mill at a speed of 300~500rpm for 2~4h; the average particle size of the incinerator ash after grinding is 2~5μm.

6. A highly active papermaking sludge incineration ash prepared by the method according to any one of claims 1 to 5, characterized in that, The specific surface area of ​​highly active papermaking sludge incineration ash is 400~800 m². 2 / kg, with a free calcium oxide content not exceeding 5.0%, and a total soluble potassium and sodium ion content not exceeding 2.0%.

7. A highly absorbent material prepared from the highly active papermaking sludge incineration ash as described in claim 6, characterized in that, The product comprises the following components by weight: 30-80 parts of papermaking sludge incineration ash, 10-30 parts of industrial by-product gypsum, 0.1-2 parts of polyacrylamide, 1-2 parts of aluminum sulfate octadecylhydrate, 5-20 parts of mineral powder, 5-15 parts of carbide slag, 0.1-1 parts of lithium carbonate, and 1-5 parts of magnesium oxide.

8. The superabsorbent material according to claim 7, characterized in that, The industrial by-product gypsum is one or more of desulfurized gypsum, phosphogypsum, or titanium gypsum; the mineral powder is S95 or S105 grade slag powder; and the effective Ca(OH)2 content of the carbide slag is not less than 60%.

9. A method for preparing the superabsorbent material as described in claim 7, characterized in that, include: A1 mixes papermaking sludge incineration ash, industrial by-product gypsum, mineral powder, and carbide slag in a high-speed mixer in proportion, then adds magnesium oxide and lithium carbonate for dry mixing to obtain a uniform gelling base material. A2 Subsequently, dry powders of polyacrylamide and aluminum sulfate octadecylhydrate were added to the gelling base material for a second-stage dry mixing process to ensure full dispersion of organic and inorganic components. A3 further crushes and sieves the uniformly mixed material to make D90≤10μm and D50 between 2~5μm, thus obtaining a highly absorbent material.

10. The application of the superabsorbent material as described in claim 7 in the rapid drying or solidification of dredged soil, river and lake bottom sediment, shield tunneling slag and engineering mud.

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