A waste incineration fly ash stabilizing and forming agent, application thereof and a waste incineration fly ash treatment method

Abstract

This invention belongs to the field of waste incineration fly ash technology, and provides a waste incineration fly ash stabilizing and molding agent, its application, and a method for treating waste incineration fly ash. The agent comprises the following components in parts by weight: 5-8 parts cement, 5-10 parts stabilizing agent, 7-10 parts binder, and 15-18 parts coating agent. The waste incineration fly ash stabilizing and molding agent provided by this invention not only physically adsorbs and chemically binds with washed fly ash, achieving stable bonding without high addition amounts, resulting in molded bodies with excellent cold and hot pressing strength, solving the problems of easy pulverization and dust generation and secondary pollution caused by fly ash during remelting; it also complexes and solidifies with heavy metals in fly ash, achieving heavy metal mineralization; simultaneously, it ensures that the agent can co-combust with fly ash particles, without producing difficult-to-burn residues, avoiding coking and ash accumulation in the furnace, and poses no environmental risk or secondary pollution during use.

Description

Technical Field

[0001] This invention relates to the field of waste incineration fly ash technology, and in particular to a waste incineration fly ash stabilizing and molding agent, its application, and a method for treating waste incineration fly ash. Background Technology

[0002] Municipal solid waste incineration is currently the core means of reducing, recycling, and harmlessly disposing of urban solid waste. However, the fly ash produced by incineration is clearly defined as hazardous waste because it is rich in heavy metals such as chlorides, lead, zinc, and cadmium, as well as persistent organic pollutants such as dioxins. Therefore, the safe, efficient, and harmless disposal of fly ash has become a key bottleneck restricting the green development of the waste incineration industry.

[0003] The harmless disposal of fly ash is a core link in the overall management of waste incineration. Among them, water washing pretreatment has become the mainstream technology for pretreatment of fly ash resource utilization due to its simple process and high dechlorination efficiency. It can effectively remove most of the soluble chloride salts in fly ash, creating conditions for subsequent resource utilization. However, the subsequent disposal of fly ash after water washing is mostly carried out by solidification landfill or separate high-temperature melting, without linkage with the original waste incineration system. This not only wastes the heat energy and equipment resources of the incineration system, but also significantly increases the overall disposal cost of fly ash. On the other hand, direct recycling of water-washed fly ash to the incinerator (hereinafter referred to as recycling) can rely on the high-temperature environment of the original waste incineration system to achieve heavy metal mineralization and dioxin degradation, and does not require additional investment in disposal equipment, making it a disposal direction that combines economy and environmental protection. However, due to the high moisture content, poor powder flowability, and dispersed composition of the washed fly ash, direct recycling can easily lead to problems such as uneven feeding, sudden drop in furnace temperature, and disordered combustion conditions. This not only reduces combustion efficiency but also easily induces secondary dioxin formation. At the same time, the recycling process of powdered fly ash can easily generate dust, which aggravates the corrosion of the furnace body and heating surfaces and shortens the service life of the equipment. Although some technologies have attempted to perform simple drying treatment on the washed fly ash before recycling, they have not solved the problem of powdered fly ash formation and still cannot avoid the above-mentioned process defects, making it difficult to guarantee the stability and safety of fly ash recycling.

[0004] To address the challenges of recycling washed fly ash into powder form, granulation has become a crucial pretreatment step. Granulation can produce uniformly sized, appropriately strong, and controllable-moisture-content shaped particles from the washed fly ash, improving its feeding stability and combustion compatibility. However, simple granulation only addresses the morphology of the washed fly ash. Ensuring proper combustion and contaminant solidification within the furnace remains critical aspects of the granulation process. Summary of the Invention

[0005] The purpose of this invention is to overcome the deficiencies in the prior art and provide a stabilizing agent for waste incineration fly ash, its application, and a method for treating waste incineration fly ash.

[0006] To achieve the above-mentioned objectives, the present invention provides the following technical solution: This invention provides a waste incineration fly ash stabilizing and molding agent, comprising the following components in parts by weight: 5-8 parts cement, 5-10 parts stabilizing agent, 7-10 parts binder, and 15-18 parts coating agent.

[0007] Preferably, the cement is P·II 42.5 nuclear power cement.

[0008] Preferably, the stabilizing agent comprises calcium metaphosphate and hydrazine hydrate; The mass ratio of calcium metaphosphate to hydrazine hydrate is 1~2:1~2.

[0009] Preferably, the adhesive comprises clay, polyvinyl alcohol, and polyacrylamide; The mass ratio of clay, polyvinyl alcohol, and polyacrylamide is 1:2~3:0.5~1.

[0010] Preferably, the coating agent comprises borax and red mud; The mass ratio of borax to red mud is 2~6:1.

[0011] The present invention also provides the application of the aforementioned waste incineration fly ash stabilizing and molding agent in the treatment of waste incineration fly ash.

[0012] The present invention also provides a method for treating fly ash from waste incineration, comprising the following steps: The process involves mixing fly ash from waste incineration with a fly ash stabilizing agent and then curing the mixture to obtain molded products.

[0013] Preferably, the mass ratio of waste incineration fly ash to waste incineration fly ash stabilizing agent is 1:0.2~0.4.

[0014] Preferably, the moisture content of the mixed material is 10-20%.

[0015] Preferably, the curing temperature is 20~30℃, the humidity is ≥95%, and the time is ≤72h.

[0016] This invention provides a stabilizing and molding agent for waste incineration fly ash, comprising the following components in parts by weight: 5-8 parts cement, 5-10 parts stabilizing agent, 7-10 parts binder, and 15-18 parts encapsulating agent. This invention provides a stabilizing and molding agent specifically formulated for waste incineration fly ash, and the functions of each component are as follows: This invention constructs a core stabilization system of "high-strength physical framework and deep chemical stability". P·II 42.5 nuclear power cement, with its excellent characteristics of high purity and low alkali content, generates a high-density CSH gel network structure through hydration reaction. This not only provides solid initial physical strength for the solidified body but also maintains the alkaline environment of the system, avoiding the poor volume stability caused by excessive impurities in ordinary cement. At the chemical stabilization level, calcium metaphosphate, as a long-acting slow-release agent, continuously releases phosphate ions in the alkaline environment. These phosphate ions combine with heavy metal ions such as lead and cadmium to form extremely difficult-to-dissolve phosphate minerals, achieving lattice solidification of heavy metals. Through the reduction effect of hydrazine hydrate, highly toxic and easily migrating hexavalent chromium is reduced to less toxic trivalent chromium and precipitated. The reaction products are nitrogen and water, without introducing additional impurities, perfectly achieving the synergistic treatment of heavy metal detoxification and reduction.

[0017] The binder components significantly improve the mechanical properties and microstructure of the cured body through a "micro-aggregate filling and organic toughening" mechanism. Clay particles act as fine aggregates, filling the voids between fly ash and cement particles, effectively reducing the system's porosity and increasing its density. Polyacrylamide utilizes the "adsorption bridging" effect of its long-chain molecules to flocculate fine fly ash particles into agglomerates, greatly improving the workability and uniformity of the mixture and preventing segregation and delamination during molding. Polyvinyl alcohol plays a crucial flexible bonding role; the hydroxyl groups on its molecular chains can form a strong hydrogen bond network with the particle surface. The continuous flexible film formed after drying connects the various phases, giving the cured body excellent flexural strength and crack resistance, effectively overcoming the cracking problem during the remelting process.

[0018] The design of the encapsulating agent is key to ensuring the durability and leaching resistance of this formulation, forming a dual protection mechanism of "water-resistant cross-linking and a sealing layer." Borax acts as a retarder to regulate cement setting time, preventing "flash setting" caused by high salt content in fly ash. Furthermore, the borate ions it releases can chemically cross-link with PVA, transforming water-soluble linear PVA molecules into a water-insoluble three-dimensional network structure. This fundamentally solves the problem of organic binders dissolving and leaching in water, significantly improving the water resistance of the solidified body. Combined with the high alkalinity activating effect of red mud and the physical filling effect of its fine particles, the capillary channels inside the solidified body are effectively blocked, ultimately constructing a high-quality fly ash molded body with stable internal chemical properties, a dense external structure, and excellent water and leaching resistance.

[0019] The waste incineration fly ash stabilizing and molding agent provided by this invention can not only physically adsorb and chemically bind with the washed fly ash, achieving stable bonding without high addition amounts, thus giving the molded body excellent cold and hot pressing strength, solving the problems of easy pulverization and dust generation and secondary pollution caused by fly ash during the remelting process; it can also undergo complexation and solidification reactions with heavy metals in fly ash, realizing heavy metal mineralization; at the same time, it ensures that the agent can co-burn with fly ash particles, without producing difficult-to-burn residues, avoiding coking and ash accumulation in the furnace, and has no environmental risks or secondary pollution during use. Detailed Implementation

[0020] This invention provides a waste incineration fly ash stabilizing and molding agent, comprising the following components in parts by weight: 5-8 parts cement, 5-10 parts stabilizing agent, 7-10 parts binder, and 15-18 parts coating agent.

[0021] In this invention, the mass fraction of cement is preferably 5.2 to 7.8 parts, more preferably 5.5 to 7.5 parts, and even more preferably 6 to 7 parts.

[0022] In this invention, the mass fraction of the stabilizing agent is preferably 6 to 9 parts, more preferably 7 to 8 parts, and even more preferably 7.4 to 7.6 parts.

[0023] In this invention, the adhesive is preferably 7.5 to 9.5 parts by mass, more preferably 8 to 9 parts, and even more preferably 8.4 to 8.8 parts by mass.

[0024] In this invention, the mass fraction of the wrapping agent is preferably 15.5 to 17.5 parts, more preferably 16 to 17 parts, and even more preferably 16.4 to 16.6 parts.

[0025] In this invention, the cement is P·II 42.5 nuclear power cement.

[0026] In this invention, the stabilizing agent comprises calcium metaphosphate and hydrazine hydrate.

[0027] In this invention, the mass ratio of calcium metaphosphate to hydrazine hydrate is preferably 1~2:1~2, more preferably 1.2~1.8:1.2~1.8, and even more preferably 1.4~1.6:1.4~1.6.

[0028] In this invention, the adhesive comprises clay, polyvinyl alcohol, and polyacrylamide.

[0029] In this invention, the mass ratio of clay, polyvinyl alcohol and polyacrylamide is preferably 1:2~3:0.5~1, more preferably 1:2.2~2.8:0.6~0.9, and even more preferably 1:2.4~2.6:0.7~0.8.

[0030] In this invention, the coating agent comprises borax and red mud.

[0031] In this invention, the mass ratio of borax to red mud is preferably 2~6:1, more preferably 2.5~5.5:1, and even more preferably 3~5:1.

[0032] The present invention also provides the application of the aforementioned waste incineration fly ash stabilizing and molding agent in the treatment of waste incineration fly ash.

[0033] The present invention also provides a method for treating fly ash from waste incineration, comprising the following steps: The process involves mixing fly ash from waste incineration with a fly ash stabilizing agent and then curing the mixture to obtain molded products.

[0034] In this invention, the mass ratio of waste incineration fly ash to waste incineration fly ash stabilizing agent is preferably 1:0.2~0.4, more preferably 1:0.25~0.35, and even more preferably 1:0.28~0.32.

[0035] In this invention, the moisture content of the mixed material is preferably 10-20%, more preferably 12-18%, and even more preferably 14-16%.

[0036] In this invention, the temperature for curing is preferably 20~30℃, more preferably 22~28℃, and even more preferably 24~26℃; the humidity is preferably ≥95%, more preferably ≥96%, and even more preferably ≥98%; and the time is preferably ≤72h, more preferably ≤50h, and even more preferably ≤30h.

[0037] The technical solutions provided by the present invention will be described in detail below with reference to the embodiments, but they should not be construed as limiting the scope of protection of the present invention.

[0038] Example 1

[0039] Prepare the reagents according to the following mass proportions: 8 parts of P·II 42.5 nuclear power cement, 10 parts of stabilizing agent, 8 parts of binder, and 16 parts of encapsulating agent.

[0040] The mass ratio of calcium metaphosphate to hydrazine hydrate in the stabilizing agent is 1:2.

[0041] The mass ratio of clay, polyvinyl alcohol, and polyacrylamide in the adhesive is 1:2.5:0.5.

[0042] The mass ratio of borax to red mud in the coating agent is 4:1.

[0043] The treatment process of waste incineration fly ash is as follows: The collected waste incineration fly ash and waste incineration fly ash stabilizing agent are mixed at a mass ratio of 1:0.3, the moisture content is controlled at 10%, and then cured at 25℃ and 95% humidity for 3 days to obtain the molded product.

[0044] Example 2

[0045] Prepare the reagents according to the following mass proportions: 5 parts of P·II 42.5 nuclear power cement, 7 parts of stabilizing agent, 10 parts of binder, and 16 parts of encapsulating agent.

[0046] The mass ratio of calcium metaphosphate to hydrazine hydrate in the stabilizing agent is 2:1.

[0047] The mass ratio of clay, polyvinyl alcohol, and polyacrylamide in the binder is 1:3:1.

[0048] The mass ratio of borax to red mud in the coating agent is 6:1.

[0049] The treatment process of waste incineration fly ash is as follows: The collected waste incineration fly ash and waste incineration fly ash stabilizing agent are mixed at a mass ratio of 1:0.2, the moisture content is controlled at 15%, and then cured at 25℃ and 95% humidity for 3 days to obtain the molded product.

[0050] Example 3

[0051] Prepare the reagents according to the following mass proportions: 8 parts of P·II 42.5 nuclear power cement, 9 parts of stabilizing agent, 7 parts of binder, and 15 parts of encapsulating agent.

[0052] The mass ratio of calcium metaphosphate to hydrazine hydrate in the stabilizing agent is 1.5:1.

[0053] The mass ratio of clay, polyvinyl alcohol, and polyacrylamide in the binder is 1:2.3:0.8.

[0054] The mass ratio of borax to red mud in the coating agent is 3:1.

[0055] The treatment process of waste incineration fly ash is as follows: The collected waste incineration fly ash and waste incineration fly ash stabilizing agent are mixed at a mass ratio of 1:0.4, the moisture content is controlled at 15%, and then cured at 25℃ and 95% humidity for 3 days to obtain the molded product.

[0056] The molded products obtained in Examples 1-3 were subjected to cold pressing strength tests, and the heavy metals were tested according to the "Identification Standard for Leaching Toxicity of Hazardous Waste" (HJ / T299-2007). After the test, the products were remelted and the hot pressing strength was measured. The results are recorded in Table 1.

[0057] Table 1 Performance Test Results

[0058] As shown in Table 1, the stabilizing agent provided by this invention, after being mixed with fly ash and cured into a mold, can achieve efficient chemical fixation of heavy metal ions, making them undetectable in leaching toxicity tests and effectively eliminating the risk of secondary pollution. Simultaneously, the molded body possesses excellent cold-pressing strength, maintaining its integrity during material transportation and remelting, significantly improving upon the defects of traditional processes where insufficient strength leads to pulverization and breakage. More importantly, after high-temperature remelting, its internal structure undergoes a benign mineral phase transformation, still maintaining excellent hot-pressing strength, ensuring the structural stability and long-term safety of the material in its final application or disposal scenario.

[0059] The above description is only a preferred embodiment of the present invention. It should be noted that those skilled in the art can make several improvements and modifications without departing from the principle of the present invention, and these improvements and modifications should also be considered within the scope of protection of the present invention.

Claims

1. A waste incineration fly ash stabilizing and molding agent, characterized in that, Components comprising the following parts by mass: 5-8 parts cement, 5-10 parts stabilizing agent, 7-10 parts binder, and 15-18 parts coating agent.

2. The waste incineration fly ash stabilizing and molding agent as described in claim 1, characterized in that, The cement is P·II 42.5 nuclear power cement.

3. The waste incineration fly ash stabilizing and molding agent as described in claim 2, characterized in that, The stabilizing agent comprises calcium metaphosphate and hydrazine hydrate; The mass ratio of calcium metaphosphate to hydrazine hydrate is 1~2:1~2.

4. The waste incineration fly ash stabilizing and molding agent as described in claim 3, characterized in that, The adhesive comprises clay, polyvinyl alcohol, and polyacrylamide; The mass ratio of clay, polyvinyl alcohol, and polyacrylamide is 1:2~3:0.5~1.

5. The waste incineration fly ash stabilizing and molding agent as described in claim 4, characterized in that, The coating agent contains borax and red mud; The mass ratio of borax to red mud is 2~6:

1.

6. The application of the waste incineration fly ash stabilizing and molding agent according to any one of claims 1 to 5 in the treatment of waste incineration fly ash.

7. A method for treating fly ash from waste incineration, characterized in that, Includes the following steps: The process involves mixing fly ash from waste incineration with a fly ash stabilizing agent and then curing the mixture to obtain molded products.

8. The method for treating fly ash from waste incineration as described in claim 7, characterized in that, The mass ratio of waste incineration fly ash to waste incineration fly ash stabilizing agent is 1:0.2~0.

4.

9. The method for treating fly ash from waste incineration as described in claim 8, characterized in that, The moisture content of the mixed materials is 10-20%.

10. The method for treating fly ash from waste incineration as described in claim 9, characterized in that, The curing temperature is 20~30℃, the humidity is ≥95%, and the time is ≤72h.

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