Fly ash dioxin separation method, fly ash dioxin separation equipment, fly ash treatment method and fly ash treatment system

Abstract

The invention discloses a fly ash dioxin separation method, fly ash dioxin separation equipment, a fly ash treatment method and a fly ash treatment system, and solves the technical problems of high energy consumption, high cost and lack of efficient and low-energy-consumption dioxin dissociation and enrichment separation means in a fly ash treatment process in the prior art. Comprising the following steps: mixing fly ash with water to prepare fly ash slurry; the method comprises the following steps: adding an oxidizing agent into fly ash slurry to carry out oxidation reaction so as to carry out oxidation treatment on reducing substances on the surface of the fly ash, adding acid into the fly ash slurry subjected to oxidation treatment to carry out modification reaction so as to etch the fly ash by using the acid to dissociate dioxin particles from the surface of the fly ash and show hydrophobicity; or adding acid into the fly ash slurry to carry out modification reaction, and controlling the pH value of the fly ash slurry after the modification reaction to be 6-12.5; bubbles are generated or introduced into the fly ash slurry after the modification reaction, the dioxin particles are captured by the bubbles and float upwards to form scum, so that the scum is separated from mother liquor, and detoxified slurry is obtained.

Description

Technical Field

[0001] This disclosure relates to the field of fly ash treatment technology for solid waste (such as garbage) incineration products, specifically to fly ash dioxin separation methods, equipment, and fly ash treatment methods and systems. Background Technology

[0002] Fly ash refers to the ash collected by flue gas purification systems and settled at the bottom of flues and chimneys during the incineration of municipal solid waste or industrial waste. Fly ash possesses both heavy metal hazard characteristics and persistent organic pollutant (POP) hazard characteristics. Incineration fly ash contains high concentrations of easily leached heavy metals such as Pb, Cd, Cu, Cr, and Zn, as well as highly hazardous dioxins. These pollutants can contaminate water bodies and soil, thereby harming the health of plants, animals, and humans.

[0003] Fly ash resource recovery is a technology that removes pollutants such as heavy metals and dioxins from fly ash and recovers soluble salts, converting fly ash into usable resources. It is primarily applied in building materials production and other fields. Currently, the main methods for fly ash resource recovery include high-temperature melting, cement kiln co-processing, sintering, and low-temperature pyrolysis. These processes utilize high-temperature equipment of varying degrees, feeding all fly ash into the equipment to cause complex chemical reactions between dioxins and heavy metals, thereby achieving detoxification.

[0004] However, these processes generally suffer from high energy consumption and high equipment investment and operating costs. Summary of the Invention

[0005] The purpose of this disclosure is to provide a method, equipment, and system for separating dioxins from fly ash, and to solve the technical problems of high energy consumption, high cost, and lack of efficient and low-energy-consumption dioxin dissociation and enrichment separation methods in the existing fly ash treatment process.

[0006] In a first aspect, a method for separating dioxins from fly ash includes: mixing fly ash with water to prepare a fly ash slurry; adding an oxidant to the fly ash slurry to carry out an oxidation reaction, thereby oxidizing the reducing substances on the fly ash surface; adding an acid to the oxidized fly ash slurry to carry out a modification reaction, thereby using the acid to etch the fly ash, causing dioxin-like particles to dissociate from the fly ash surface and reveal hydrophobicity; generating or introducing bubbles into the modified fly ash slurry, using the bubbles to capture the dioxin-like particles and float them to the surface to form scum, thereby separating the scum from the mother liquor to obtain a detoxified slurry.

[0007] Secondly, a method for separating dioxins from fly ash includes: mixing fly ash with water to prepare a fly ash slurry; adding acid to the fly ash slurry to carry out a modification reaction, thereby using the acid to etch the fly ash, causing dioxin-like particles to dissociate from the fly ash surface and reveal hydrophobicity; generating or introducing bubbles into the modified fly ash slurry, using the bubbles to capture the dioxin-like particles and float them to the surface to form scum, thereby separating the scum from the mother liquor to obtain a detoxified slurry; wherein, by controlling the amount of acid used in the modification reaction, the pH value of the modified fly ash slurry is controlled to be 6-12.5.

[0008] Thirdly, a fly ash dioxin separation device is provided for implementing the fly ash dioxin separation method of the first or second aspect above, comprising: a slurry preparation device for mixing fly ash with water to obtain fly ash slurry; and a slurry pretreatment device for adding an oxidant to the fly ash slurry to carry out an oxidation reaction, thereby oxidizing the reducing substances on the fly ash surface, and then adding an acid to the oxidized fly ash slurry to carry out a modification reaction, thereby using the acid to etch the fly ash, causing dioxin particles to dissociate from the fly ash surface and reveal hydrophobicity; Alternatively, the slurry pretreatment device is used to add acid to the fly ash slurry for a modification reaction, thereby using the acid to etch the fly ash, causing dioxin-like particles to dissociate from the fly ash surface and reveal hydrophobicity. By controlling the amount of acid used in the modification reaction, the pH value of the fly ash slurry after the modification reaction is controlled to be 6-12.5. The gas-liquid-solid three-phase coupling separation device is used to generate or introduce bubbles into the fly ash slurry after the modification reaction, using the bubbles to capture the dioxin-like particles and float them to the surface to form scum, thereby separating the scum from the mother liquor to obtain a detoxified slurry.

[0009] Fourthly, a fly ash treatment method, after obtaining scum and detoxified slurry through the fly ash dioxin separation method of the first or second aspect above, further treatments are performed on the scum and the detoxified slurry respectively; the further treatment of the scum includes pyrolyzing the scum to decompose dioxins; the further treatment of the detoxified slurry includes separating different metal salts from the mother liquor of the detoxified slurry through multi-stage wastewater purification treatment.

[0010] Fifthly, a fly ash treatment system includes: a fly ash dioxin separation device as described in the third aspect above; a pyrolysis device for pyrolyzing the scum discharged from the fly ash dioxin separation device to decompose dioxins; and a multi-stage wastewater purification treatment device for performing multi-stage wastewater purification treatment on the detoxified slurry discharged from the fly ash dioxin separation device to separate different metal salts from the mother liquor of the detoxified slurry.

[0011] The basic technical concept of the aforementioned fly ash dioxin separation method, equipment, and fly ash treatment method and system lies in mixing fly ash with water to prepare a fly ash slurry, and then using an acid modification reaction to etch the fly ash, destroying its surface structure and forcing dioxin-like particles to dissociate from the fly ash surface and reveal hydrophobicity. Subsequently, bubble technology is introduced to capture the dioxin-like particles and float them to the surface to form scum. Finally, the scum is separated from the mother liquor to obtain a detoxified slurry. Through efficient physicochemical separation methods, most of the dioxin-like particles are enriched in a small amount of scum, achieving a significant reduction in pollutant volume. This allows for subsequent high-temperature harmless treatment of only a small amount of scum, while the large amount of detoxified slurry can be directly utilized for resource recovery or simple treatment. This avoids the high energy consumption and high cost associated with high-temperature treatment of the entire fly ash volume, solving the technical problems of high energy consumption, high cost, and lack of efficient and low-energy-consumption dioxin dissociation and enrichment separation methods in existing fly ash treatment processes. Without modification, the carbon particles in fly ash are hydrophobic, so the bubbles actually capture a large number of carbon particles, resulting in a significant increase in the yield of scum and making it impossible to achieve efficient dioxin enrichment. This greatly increases the load and cost of subsequent scum treatment.

[0012] In the first aspect of the fly ash dioxin separation method, adding an oxidant to the fly ash slurry for oxidation is of great significance. Since fly ash contains sulfites originating from the flue gas desulfurization process, if acid is added directly for modification without prior treatment, the sulfites will decompose under acidic conditions, producing sulfur dioxide gas. The generation of sulfur dioxide gas not only causes secondary pollution, endangering the environment and personnel safety, but may also disrupt the fluid state of the fly ash slurry and interfere with the subsequent bubble capture process. Therefore, first oxidizing the reducing substances on the fly ash surface with an oxidant can oxidize the sulfites in the fly ash to sulfates and oxidize at least some low-valence metal ions to high-valence metal ions. This, combined with the subsequent modification reaction, effectively avoids the formation of sulfur dioxide, ensuring the safety and stability of the dioxin-like particle dissociation process from the fly ash surface. Simultaneously, it lays a good material foundation for the subsequent treatment of the detoxified slurry—oxidizing metal ions to high-valence states typically makes them easier to remove through sedimentation or flocculation in subsequent multi-stage wastewater purification treatment.

[0013] In the second aspect of the fly ash dioxin separation method, deep acidification is cleverly avoided through modification reactions. Instead, the pH value of the fly ash slurry is adjusted to 6-12.5 by controlling the amount of acid used. The core of this method lies in "precise etching"—by introducing a limited and controllable amount of hydrogen ions into the fly ash slurry, these hydrogen ions can directionally dissolve the calcium-based (such as calcium oxide and calcium sulfate) hard shell surrounding the dioxins, destroying their physical storage structure. However, this does not cause the complete disintegration of the fly ash skeleton or the dissolution of a large number of heavy metal ions. This strategy achieves efficient removal of dioxin-like particles from fly ash particles while cleverly avoiding the serious corrosion risk to industrial equipment that a strong acid environment may cause, achieving a balance between microscopic interface control and macroscopic engineering safety. The modification reaction is sufficient to destroy the binding force between dioxins and fly ash, causing them to dissociate and reveal hydrophobicity, while avoiding the potential corrosion risk to equipment caused by a strong acid environment. The benefits are obvious: first, it avoids the consumption of large amounts of acid, significantly reducing operating costs; second, it greatly extends the service life of the equipment.

[0014] The present disclosure will now be further described in conjunction with the accompanying drawings and specific embodiments. Additional aspects and advantages provided by the present disclosure will be set forth in part in the description which follows, and in part will be obvious from the description or may be learned by practice. Attached Figure Description

[0015] The accompanying drawings, which form part of this specification, are used to aid in understanding this disclosure. The contents provided in the drawings and their related descriptions in this specification may be used to interpret this disclosure, but do not constitute an undue limitation of this disclosure.

[0016] Figure 1 This is a schematic flowchart illustrating an embodiment of a fly ash treatment method according to the present disclosure.

[0017] Figure 2 This is a schematic diagram of a first preferred embodiment of the gas-liquid-solid three-phase coupling separation device of this disclosure.

[0018] Figure 3 for Figure 2 Sectional view along line AA.

[0019] Figure 4 for Figure 2 View from direction B in the middle.

[0020] Figure 5 This is a schematic diagram of a second preferred embodiment of the gas-liquid-solid three-phase coupling separation device of this disclosure.

[0021] Figure 6 for Figure 5 Sectional view along line AA.

[0022] Figure 7 for Figure 5 Sectional view along the BB direction.

[0023] Figure 8 for Figure 5 A schematic diagram of the structure at point C (the second Venturi tube device).

[0024] Figure 9 This is a schematic diagram of the structure of the fly ash slurry oxidation modification and / or acid washing modification device in this disclosure.

[0025] Figure 10 This is a test report of fly ash (raw ash) before pulping in an experimental example of the fly ash treatment method disclosed herein.

[0026] Figure 11 In an experimental example of the fly ash treatment method disclosed herein, a test report of gypsum was obtained.

[0027] The diagram is labeled as follows: Coarse selection zone 101, Fine selection zone 102, Separation zone 103, Slurry outlet 104, Slurry inlet 105, Perforated plate gas distributor 106, Conical bottom 107, Circulating liquid outlet 108, Filter 109, First Venturi tube device 110, Microwave generator 111, Wash water spray device 112, Low-end opening 113, Purge vent 114, Slurry inlet 201, Slurry outlet 202. Baffle 203, second venturi tube device 204, first chamber 205, second chamber 206, gas inlet 207, separation aid inlet 208, stirring impeller 209, overflow trough 210, scum collection pipe 211, scum 212, transmission device 213, shell 301, stirring assembly 302, fly ash slurry inlet 303, fly ash slurry outlet 304, baffle 305, dosing pipe 306, exhaust port 307. Detailed Implementation

[0028] The present disclosure will now be clearly and completely described in conjunction with the accompanying drawings. Those skilled in the art will be able to implement the present disclosure based on these descriptions. Before describing the present disclosure in conjunction with the accompanying drawings, it should be particularly noted that:

[0029] The technical solutions and features provided in the various sections, including the following description, can be combined with each other without conflict. Furthermore, where possible, these technical solutions, features, and related combinations can be given specific technical subject matter and protected by relevant patents.

[0030] The embodiments described below are generally only some embodiments and not all embodiments. All other embodiments obtained by those skilled in the art based on these embodiments without creative effort should fall within the scope of patent protection.

[0031] The terms "comprising," "including," "having," and any variations thereof in this specification, the corresponding claims, and related sections are intended to cover non-exclusive inclusion. Other related terms and units can be reasonably interpreted based on the relevant content provided in this specification.

[0032] As described in the background section, fly ash refers to the ash collected by flue gas purification systems and settled at the bottom of flues and chimneys during the incineration of municipal solid waste or industrial waste. Fly ash possesses both heavy metal hazard characteristics and persistent organic pollutant (POP) hazard characteristics. Incineration fly ash contains high concentrations of easily leached heavy metals such as Pb, Cd, Cu, Cr, and Zn, as well as highly hazardous dioxins. These pollutants can contaminate water bodies and soil, thereby harming the health of animals, plants, and humans.

[0033] Currently, the main methods for the resource utilization and disposal of fly ash include high-temperature melting treatment, co-processing in cement kilns, sintering, and low-temperature pyrolysis. These processes mainly utilize high-temperature equipment of varying degrees, feeding all fly ash into the high-temperature equipment to cause dioxins and heavy metals to undergo corresponding complex chemical reactions, thereby achieving detoxification. However, these processes generally suffer from high energy consumption and high equipment investment and operating costs.

[0034] The core technical approach of this disclosure lies in avoiding high-temperature treatment of the entire fly ash volume. Instead, it first uses efficient physicochemical separation methods to dissociate and enrich dioxin-like particles from the fly ash mass. Specifically, acid is added to modify and etch the fly ash, disrupting the bond between dioxin-like particles and fly ash particles, causing the particles to dissociate from the fly ash surface and become hydrophobic. Subsequently, bubble capture technology is used to enrich the dissociated dioxin-like particles in a small amount of scum, while a large amount of detoxification slurry is separated. In this way, the vast majority of dioxins are concentrated in the scum, which constitutes a very small proportion of the total fly ash volume. Only this small amount of scum needs to be subjected to subsequent high-temperature pyrolysis treatment to completely decompose the dioxins, while the large amount of detoxification slurry can be utilized for resource recovery or further treatment. This "volume reduction and enrichment + targeted disposal" technical approach fundamentally solves the problems of high energy consumption and high cost in existing fly ash treatment processes.

[0035] However, in realizing the above-mentioned technical approach, several key technical problems have been identified that need to be solved. First, fly ash contains reducing substances such as sulfites originating from the flue gas desulfurization process. During the incineration of municipal solid waste or industrial waste, in the dry or semi-dry desulfurization stage of the flue gas, when sulfur dioxide reacts with alkaline desulfurizing agents such as calcium hydroxide, due to the limited oxygen content in the flue gas, the short reaction time, and the constraints of temperature and humidity, some sulfur dioxide is only partially oxidized to sulfites such as calcium sulfite, rather than being completely oxidized to sulfates. These sulfites, as intermediate or byproducts of the desulfurization reaction, are captured by the dust removal system along with the desulfurization products and ultimately accumulate in the fly ash. Research has found that if acid is directly added to the fly ash slurry for modification, the sulfites will decompose under acidic conditions, producing sulfur dioxide gas that escapes. The generation of sulfur dioxide gas not only causes secondary pollution, endangering the environment and personnel safety, but also disrupts the fluid state of the fly ash slurry, generating a large number of bubbles that interfere with the subsequent bubble capture and separation process, leading to a significant decrease in separation efficiency. Therefore, it is proposed to oxidize the reducing substances on the fly ash surface before adding acid for modification.

[0036] Secondly, during the acid modification reaction, it was discovered that excessive acid usage led to a series of problems. Previously, a full leaching approach was adopted, involving the addition of large amounts of acid to dissolve heavy metals and other components in the fly ash to the greatest extent possible, while simultaneously etching the fly ash thoroughly. However, this method was found to have a dual negative impact: on the one hand, the large consumption of acid resulted in high operating costs; on the other hand, the strong acid environment caused severe corrosion to the equipment materials (containers, pipes, and pumps used in the reaction), significantly shortening equipment lifespan, increasing maintenance costs, and creating safety hazards. In-depth analysis revealed that the complete dissociation of dioxin-like particles does not require the strong acid conditions of heavy metal leaching; excessive acid leaching actually resulted in resource waste and equipment damage. Therefore, by establishing a quantitative relationship between acid dosage and the dissociation effect of dioxin-like particles, the amount of acid added can be precisely limited. Only moderate etching of fly ash is needed to fully dissociate dioxin-like particles and expose their hydrophobicity. At the same time, the pH value of the modified fly ash slurry can be controlled within a reasonable range that meets the process requirements without causing significant corrosion to the equipment. This ensures separation efficiency while reducing operating costs and protecting equipment safety.

[0037] Third, dioxin particles are typically very small in size, while conventional bubbles are relatively large with limited surface area, resulting in a low probability and frequency of contact and collision with dioxin particles, leading to low capture efficiency. Improving the capture efficiency of bubbles for fine dioxin particles and achieving efficient dioxin separation is a crucial issue that needs to be addressed for commercialization.

[0038] Fourth, during the gas-liquid-solid three-phase coupling separation process, it was found that fly ash slurry is more prone to forming a non-uniform flow field distribution compared to ordinary slurry. If the flow path design within the reaction vessel of the gas-liquid-solid three-phase coupling separation device is unreasonable, a "short-circuit" phenomenon can easily occur, meaning that some fly ash slurry is discharged from the slurry outlet without sufficient treatment. This results in the ineffective removal of dioxins adsorbed in this portion of the fly ash slurry, affecting the overall quality of the detoxified slurry. Therefore, it is necessary to optimize the internal structure of the reaction vessel of the gas-liquid-solid three-phase coupling separation device to ensure that the fly ash slurry flows along a predetermined path, allowing all dioxin-like particles to undergo a sufficient bubble capture process as much as possible.

[0039] Fifth, the oxidation reaction and the modification reaction by adding acid must be carried out in a specialized reaction apparatus to ensure thorough mixing and contact between the oxidant, acid, and fly ash slurry, minimizing reaction blind zones and guaranteeing the uniformity and completeness of the reaction. Simultaneously, the design of the reaction apparatus must also consider the heat and gases that may be generated during the reaction process to ensure the safety and controllability of the reaction.

[0040] Sixth, after obtaining scum and detoxified slurry from dioxin separation, both need to be properly treated. For the scum, the enriched dioxins need to be completely decomposed through pyrolysis or other methods to achieve harmless disposal. For the detoxified slurry, although the dioxin content has been significantly reduced, it still contains heavy metal ions, soluble salts, and other substances. Therefore, it needs to undergo multi-stage wastewater purification treatment to separate different metal salts from the mother liquor, achieving resource utilization.

[0041] This disclosure, based on in-depth research and experimentation, proposes a complete method, equipment, and system for the separation of dioxins from fly ash and the treatment of fly ash, addressing the aforementioned technical problems. Through oxidation pretreatment, precise control of acid addition for modification reaction, bubble refinement technology, graded separation structure, dedicated equipment, and systematic post-treatment processes, it achieves efficient separation and harmless disposal of dioxins in fly ash, while significantly reducing energy consumption and operating costs.

[0042] Figure 1 This is a schematic flowchart illustrating an embodiment of a fly ash treatment method according to this disclosure. Figure 1 As shown, the fly ash treatment method in this embodiment includes two main parts: a fly ash dioxin separation stage and a subsequent treatment stage.

[0043] I. Dioxin Separation Stage from Fly Ash

[0044] The core objective of the fly ash dioxin separation stage is to dissociate and enrich dioxin-like particles from the fly ash bulk, obtaining scum rich in dioxin-like particles and detoxified slurry after detoxification treatment. This stage mainly includes the following steps.

[0045] Step S1: Pulping.

[0046] Fly ash is mixed with water to prepare fly ash slurry. This step corresponds to... Figure 1 The "first-order reaction" in the context.

[0047] The purpose of this step is to convert solid fly ash into a liquid slurry, facilitating subsequent chemical reactions and physical separation. When mixing fly ash with water, the amount of water added can be controlled according to actual needs. In one or more specific embodiments, the mass ratio of water to fly ash after mixing is 4-8, preferably 5-7. This solid-liquid ratio ensures good slurry flowability, facilitating transport and reaction, without increasing the burden on subsequent processing due to excessive water.

[0048] The particle size of fly ash also affects the effectiveness of subsequent reactions and separation. In one or more specific embodiments, during the mixing of fly ash and water, the D90 particle size of the fly ash particles is 40-250 micrometers. The D90 particle size refers to the particle size corresponding to a cumulative particle size distribution percentage of 90%. Fly ash particles within this size range have sufficient specific surface area for adequate contact and reaction with oxidants and acids, without causing difficulties in subsequent solid-liquid separation due to excessive particle size. If the particle size of the fly ash raw material does not meet the requirements, it can be crushed (e.g., ball milling, see details) before pulping. Figure 1 Pretreatment methods such as [methods] are used to bring the fly ash particle size to the required range.

[0049] Step S2: Oxidation reaction (optional).

[0050] An oxidant is added to the fly ash slurry to induce an oxidation reaction, thereby oxidizing the reducing substances on the fly ash surface. This step is optional but strongly recommended, especially when the fly ash contains a high amount of reducing substances such as sulfites.

[0051] As mentioned earlier, fly ash contains sulfites originating from the desulfurization process of incineration flue gas. If acid is added directly for modification without prior oxidation treatment, the sulfites will decompose under acidic conditions, producing sulfur dioxide gas, causing secondary pollution and interfering with subsequent separation processes. Through oxidation, the sulfites in fly ash can be oxidized to sulfates, and at least some low-valence metal ions can be oxidized to high-valence metal ions. For example, sulfites (such as calcium sulfite) are oxidized to sulfates (such as calcium sulfate), and ferrous ions are oxidized to ferric ions. In this way, sulfur dioxide gas will not be generated in the subsequent acid modification reaction, ensuring the safety and stability of the process. At the same time, oxidizing metal ions to high-valence states usually makes them easier to remove in subsequent multi-stage wastewater purification treatment through precipitation or flocculation, laying a good material foundation for the subsequent treatment of detoxified slurry.

[0052] A wide range of oxidants can be selected. In one or more specific embodiments, the oxidant is selected from at least one of hydrogen peroxide, ozone, oxygen, sodium hypochlorite, calcium hypochlorite, potassium permanganate, sodium persulfate, ammonium persulfate, and sodium chlorate. These oxidants all have strong oxidizing power and can effectively oxidize reducing substances in fly ash. Among them, hydrogen peroxide is a preferred oxidant due to its strong oxidizing power, the reaction product being water, the absence of secondary pollution, and its relatively low price.

[0053] In one or more specific embodiments, hydrogen peroxide solution is added to the fly ash slurry to carry out an oxidation reaction. Based on a 27.5% by mass hydrogen peroxide solution, the amount of hydrogen peroxide solution added is 1%-5% of the fly ash mass, preferably 2%-4%. For example, if there are 100 kg of fly ash, then 2 kg-4 kg of a 27.5% by mass hydrogen peroxide solution is added. This dosage range ensures that the reducing substances in the fly ash are fully oxidized without increasing costs and subsequent processing burden due to excessive oxidant.

[0054] The oxidation reaction is usually carried out at room temperature and pressure. The reaction time depends on the content of reducing substances in the fly ash and the type and amount of oxidant used, generally ranging from 10 to 60 minutes, preferably from 20 to 40 minutes. During the reaction, stirring can promote full contact between the oxidant and the fly ash slurry, thereby improving the reaction efficiency.

[0055] Step S3: Add acid to carry out the modification reaction.

[0056] An acid is added to the oxidized fly ash slurry (or directly to the pulped fly ash slurry, if step S2 is skipped) to carry out a modification reaction, thereby using the acid to etch the fly ash, causing dioxin-like particles to dissociate from the fly ash surface and reveal hydrophobicity.

[0057] This step is one of the core steps in the entire fly ash dioxin separation method. Dioxin-like particles in fly ash are usually adsorbed or encapsulated within the fly ash particles, tightly bound to the fly ash matrix. By adding acid, the hydrogen ions in the acid can chemically react with calcium-based substances (such as calcium oxide CaO, calcium hydroxide Ca(OH)2, etc.) on the fly ash surface, dissolving or destroying these substances, thereby etching the fly ash surface. This etching effect disrupts the physical containment structure of dioxins and fly ash, causing the originally encapsulated or tightly adsorbed dioxin-like particles to dissociate from the fly ash surface.

[0058] More importantly, the dissociated dioxin-like particles exhibit their inherent hydrophobicity. Dioxin compounds themselves are strongly hydrophobic and lipophilic, and this hydrophobic characteristic is fully manifested when they dissociate from the fly ash surface and are exposed to the slurry. This provides a physicochemical basis for subsequent use of bubbles to capture dioxin-like particles—the hydrophobic dioxin-like particles easily adhere to the bubble surface and float to the surface with the bubbles, forming scum.

[0059] There are several options for the choice of acid. In one or more specific embodiments, the acid is selected from at least one of sulfuric acid, hydrochloric acid, and nitric acid. These inorganic acids all have strong acidity and etching ability. Among them, sulfuric acid is the preferred acid because of its advantages such as strong acidity, low price, and easy availability, and because sulfate ions can combine with calcium ions in fly ash to form calcium sulfate precipitate, which is beneficial for subsequent processing.

[0060] The precise control of acid dosage is a key technical feature of this disclosure. On the one hand, the amount of acid must be sufficient to ensure effective etching of fly ash and full dissociation of dioxin-like particles; on the other hand, the amount of acid must not be excessive to avoid excessively low pH values ​​in the fly ash slurry, which could lead to equipment corrosion and increased operating costs.

[0061] In one or more specific embodiments, concentrated sulfuric acid is added to the oxidized fly ash slurry. The amount of concentrated sulfuric acid added, calculated as 98% by mass, is 20%-35% of the fly ash mass. For example, if there are 100 kg of fly ash, then 20 kg-35 kg of 98% concentrated sulfuric acid is added. This moderate amount of acid effectively etches the fly ash surface, causing dioxin-like particles to dissociate and reveal hydrophobicity, and typically also controls the pH of the slurry within the range of 6-12.5.

[0062] By controlling the amount of acid used in the modification reaction, the pH value of the fly ash slurry after the modification reaction can be controlled to 6-12.5, preferably 8-11, and more preferably 10±0.5. The pH value of 6-12.5 greatly reduces the risk of corrosion to the equipment, extends the service life of the equipment, and reduces maintenance costs.

[0063] This technique of controlling the pH value of the slurry by precisely controlling the amount of acid used embodies an important innovation of this disclosure: a clever balance is achieved between microscopic interface control (dioxin dissociation) and macroscopic engineering safety (equipment corrosion prevention, cost control). By introducing a limited and controllable amount of hydrogen ions into the fly ash slurry, these hydrogen ions directionally dissolve the calcium-based hard shell surrounding the dioxin-like particles, destroying their physical storage structure, but without causing the complete disintegration of the fly ash skeleton or the dissolution of a large number of heavy metal ions.

[0064] The modification reaction is usually carried out at room temperature and pressure. The reaction time depends on the type and amount of acid used and the properties of the fly ash, generally ranging from 10 to 60 minutes, preferably from 20 to 40 minutes. During the reaction, stirring can also promote sufficient contact between the acid and the fly ash slurry, thereby improving the etching effect.

[0065] It should be noted that controlling the pH value of the modified fly ash slurry by controlling the amount of acid used can be achieved in several ways. For example, the initial pH value and alkalinity of the fly ash slurry can be measured before adding acid, and the required amount of acid can be calculated based on the alkaline content of the fly ash; alternatively, the pH value of the slurry can be monitored in real time during the acid addition process, and acid addition can be stopped when the pH value drops to a predetermined value; or, based on empirical data, a standard acid dosage range can be determined for fly ash from specific sources and with specific properties, and acid can be added according to this standard dosage in actual operation. This disclosure does not specify the specific method for controlling the amount of acid used, as long as the goal of controlling the pH value of the modified fly ash slurry to 6-12.5 can be achieved.

[0066] It should be noted that step S2 (which is an optional step) and step S3 above correspond to... Figure 1 The "second-order reaction" step in the process.

[0067] Step S4: Gas-liquid-solid three-phase coupling separation.

[0068] Bubbles are generated or introduced into the modified fly ash slurry. These bubbles capture dioxin-like particles, which float to the surface and form scum. This scum is then separated from the mother liquor to obtain a detoxified slurry. This step corresponds to... Figure 1 "Dioxin separation" in the context of dioxin separation.

[0069] This step is another core step in the fly ash dioxin separation method. After acid modification, the dioxin-like particles have dissociated from the fly ash surface and become hydrophobic. At this point, by introducing air bubbles, the buoyancy of the bubbles and the hydrophobicity of the dioxin-like particles are utilized to achieve an effective combination of the two.

[0070] Specifically, as bubbles move upwards in the slurry, they collide and come into contact with dioxin-like particles in the slurry. Because these particles are hydrophobic, they tend to adhere to the bubble surface (gas-liquid interface) to reduce the system's surface free energy. Once attached, the dioxin-like particles rise with the bubbles. A large number of bubbles carrying dioxin-like particles rise to the surface and aggregate to form a scum layer. The fly ash particles and the bulk slurry that were not captured by the bubbles are discharged from the slurry outlet as detoxified slurry.

[0071] This process utilizes the selective adhesion characteristics of hydrophobic particles and air bubbles to achieve efficient separation of dioxin-like particles from the main fly ash. Through this step, most of the dioxins are enriched in the scum, which accounts for a very small proportion of the total fly ash, while a large amount of fly ash is converted into detoxified slurry, significantly reducing the dioxin content and creating conditions for subsequent resource utilization or compliance with emission standards.

[0072] There are several ways to generate or introduce bubbles. Bubbles can be generated by introducing gas (such as air or nitrogen) into the slurry through a bubble generating mechanism (such as a perforated plate gas distributor or a Venturi tube device); bubbles can also be generated in the slurry through mechanical stirring, jetting, or other methods. The specific method of bubble generation is not limited here.

[0073] In a preferred embodiment, the gas-liquid-solid three-phase coupling separation process is achieved through a specially designed gas-liquid-solid three-phase coupling separation device. This device includes: a reaction vessel having an inner cavity for containing fly ash slurry, and a slurry inlet and outlet communicating with the inner cavity; a bubble generating mechanism located inside the reaction vessel at its lower interior or bottom for generating an upward-moving bubble flow within the reaction vessel; and a slag removal mechanism located at the top of the reaction vessel for removing floating slag.

[0074] The modified fly ash slurry enters the reaction vessel through the slurry inlet, where it comes into contact with an upward-moving stream of air bubbles. As the bubbles rise, they capture dioxin-like particles and carry them to the surface, forming scum. The bulk of the slurry, not captured by the bubbles, is discharged through the slurry outlet, becoming detoxified slurry. The scum is then removed by a slag discharge mechanism and proceeds to subsequent processing stages.

[0075] To further improve the capture efficiency of dioxin-like particles by bubbles, in one or more specific embodiments, during the separation process in the gas-liquid-solid three-phase coupling separation device, a first separation aid and a second separation aid are also added to the fly ash slurry in the reaction vessel.

[0076] The first separation aid is an alcohol compound selected from one or more of methyl isobutyl methanol, fusel oil, pine oil, and long-chain alcohols with 8-14 carbon atoms. The addition amount is 2‰-6‰ of the fly ash mass, preferably 3‰-5‰. The function of the first separation aid is to regulate the stability of bubbles and the surface tension of the slurry, promoting effective contact and adhesion between bubbles and dioxin-like particles.

[0077] The second separation aid is a hydrocarbon oil and / or an organic acid compound, selected from one or more of kerosene, diesel oil, fuel oil, natural gas condensate, oleic acid, oxidized paraffin soap, talc oil, and naphthenic acids. The addition amount is 5‰-10‰ of the fly ash mass, preferably 6‰-8‰. The function of the second separation aid is to enhance the hydrophobicity of dioxin-like particles, making them easier to adhere to the bubble surface.

[0078] By adding a first separation aid and a second separation aid, the recovery rate of dioxin particles can be improved, further ensuring the enrichment of dioxins in the scum, while reducing dioxin residue in the detoxified slurry and improving the overall separation effect.

[0079] At this point, the dioxin separation stage of fly ash is completed, yielding scum rich in dioxin-like particles and detoxified slurry after detoxification treatment.

[0080] II. Follow-up processing stage.

[0081] After separating dioxins from fly ash to obtain scum and detoxified slurry, the scum and detoxified slurry need to be further treated to achieve complete harmlessness of dioxins and resource utilization of fly ash.

[0082] (I) Subsequent treatment of scum

[0083] The scum contains the majority of dioxins. Although its mass accounts for only a small proportion of the original fly ash (usually less than 10%, or even less than 5%), the dioxin concentration is very high and must be thoroughly rendered harmless.

[0084] The subsequent treatment of scum includes pyrolysis to decompose dioxins. Pyrolysis refers to the thermochemical decomposition of organic matter by heating under anaerobic or oxygen-deficient conditions. Dioxin-like compounds decompose under high-temperature conditions, transforming into harmless or less harmful substances.

[0085] In one or more specific embodiments, the temperature for pyrolysis treatment of the scum is 300℃-600℃, preferably 350℃-550℃, and more preferably 400℃-500℃. Within this temperature range, dioxin-like compounds can be effectively decomposed, while avoiding the problems of increased energy consumption and higher equipment requirements caused by excessively high temperatures. The pyrolysis time depends on the properties of the scum and the pyrolysis temperature, generally ranging from 30 minutes to 120 minutes, preferably from 60 minutes to 90 minutes.

[0086] The pyrolysis process can be carried out in specialized pyrolysis equipment, such as rotary kilns, fluidized bed reactors, and pyrolysis furnaces. The gaseous products generated by pyrolysis need to be condensed and purified to remove any potentially harmful substances before being discharged or recycled. The solid products (pyrolysis residues) can be used as building material raw materials or for other resource utilization after passing testing.

[0087] Through pyrolysis, the dioxins in the scum are completely decomposed, achieving harmless disposal. Because the amount of scum is very small, the energy consumption and cost required for pyrolysis are far lower than those for high-temperature treatment of the entire amount of fly ash, which is one of the core advantages of this disclosed technical solution.

[0088] (II) Subsequent treatment of detoxified slurry.

[0089] Although the dioxin content in the detoxified slurry has been significantly reduced, it still contains heavy metal ions, calcium ions, magnesium ions, and soluble salts such as sodium chloride and potassium chloride.

[0090] In order to achieve resource utilization and meet emission standards, multi-stage wastewater purification treatment is required for the detoxified slurry to separate different metal salts from the mother liquor of the detoxified slurry.

[0091] In one or more specific embodiments, the multi-stage wastewater purification treatment includes the following steps in sequence according to the operation order:

[0092] Step P1: First solid-liquid separation process.

[0093] The detoxified slurry undergoes a first solid-liquid separation process to obtain a first solid phase and a first mother liquor. This step corresponds to... Figure 1 The solid-liquid separation step between the "dioxin separation" and the "tertiary reaction" in the process.

[0094] The purpose of this step is to separate the solid particles from the liquid phase in the detoxified slurry. Solid-liquid separation can be achieved using conventional methods such as sedimentation, filtration, and centrifugation. In a preferred embodiment, a filter press is used for solid-liquid separation to obtain a filter cake (first solid phase) with low water content and a filtrate (first mother liquor).

[0095] The main components of the first solid phase depend on the type of acid used in the preceding acid modification reaction. If sulfuric acid is used in the acid modification reaction, the acid reacts with calcium-based substances in the fly ash (such as calcium oxide and calcium hydroxide) to form calcium sulfate. Therefore, the first solid phase mainly consists of gypsum and fly ash residue that has not been dissolved by the acid.

[0096] Step P2: Heavy metal capture and second solid-liquid separation treatment.

[0097] A heavy metal scavenging agent is added to the first mother liquor, causing the heavy metal ions in the first mother liquor to react and form a first type of metal salt precipitate. After a second solid-liquid separation process, a second solid phase mainly containing the first type of metal salt precipitate and a second mother liquor are obtained. This corresponds to... Figure 1 The "third-order reaction" step in the process.

[0098] The first mother liquor contains heavy metal ions dissolved from fly ash, such as lead ions (Pb). 2+ ), cadmium ions (Cd) 2+ ), copper ions (Cu) 2+ ), chromium ions (Cr 3+ / Cr 6+ ), zinc ions (Zn) 2+ These heavy metal ions are toxic and cannot be directly discharged. By adding heavy metal scavenging agents, the heavy metal ions can react chemically with the scavenging agents to form insoluble metal salt precipitates, thereby removing the heavy metals from the liquid phase.

[0099] There are many types of heavy metal scavenging agents, commonly used ones include sodium sulfide, sulfide-based scavengers, and organic chelating agents. In one or more specific embodiments, sodium sulfide is used as the heavy metal scavenging agent, and the dosage is determined based on the concentration of heavy metal ions in the first mother liquor, generally 0.1%-1% of the mass of the first mother liquor. Sodium sulfide reacts with heavy metal ions to form sulfide precipitates, such as lead sulfide (PbS), cadmium sulfide (CdS), and copper sulfide (CuS). These sulfides have extremely low solubility and can effectively remove heavy metals.

[0100] After the reaction is complete, a second solid-liquid separation process is performed to separate the generated first-type metal salt precipitates (mainly heavy metal sulfides) to obtain the second solid phase. This second solid phase is classified as hazardous waste and must be safely disposed of in accordance with relevant regulations or sent to a qualified facility for treatment. The separated liquid phase is the second mother liquor, in which the heavy metal content has been significantly reduced.

[0101] Step P3: Hardening and third solid-liquid separation treatment.

[0102] Add a hardening agent to the second mother liquor and adjust its pH to cause calcium and / or magnesium ions in the second mother liquor to react and form a second type of metal salt precipitate (corresponding to...). Figure 1 The "fourth-order reaction" in the process, after the third solid-liquid separation treatment, yields a third solid phase mainly containing second-type metal salt precipitates and a third mother liquor.

[0103] The second mother liquor still contains a high concentration of calcium ions (Ca). 2+ ) and magnesium ions (Mg 2+ These ions originate from the dissolution of calcium and magnesium-based substances in fly ash during the acid modification reaction. Calcium and magnesium ions increase water hardness, affecting subsequent evaporation and crystallization processes and product quality; therefore, hardness removal treatment is necessary.

[0104] Hardening agents are usually alkaline substances such as sodium carbonate or sodium hydroxide. The hardening agent is added, and the pH of the second mother liquor is adjusted to alkaline (usually pH 9-11) as needed, so that calcium and magnesium ions react with carbonate or hydroxide ions to form second-type metal salt precipitates such as calcium carbonate and magnesium hydroxide.

[0105] After the reaction is complete, a third solid-liquid separation process is performed to precipitate and separate the second type of metal salt, yielding a third solid phase. This third solid phase mainly consists of calcium carbonate and / or magnesium hydroxide, which can be used as building material raw materials or for other resource utilization. The separated liquid phase is the third mother liquor, in which the calcium and magnesium ion content is significantly reduced, and the hardness is noticeably decreased.

[0106] Step P4: Evaporation and crystallization.

[0107] The third mother liquor is subjected to evaporation and crystallization treatment to obtain crystalline salt mainly containing sodium chloride and / or potassium chloride, as well as condensate.

[0108] The main components of the third mother liquor are soluble salts such as sodium chloride (NaCl) and potassium chloride (KCl). These salts originate from the soluble salts originally present in the fly ash, as well as salts generated during acid modification and neutralization reactions. Through evaporation and crystallization, these salts can be recovered in solid form, while simultaneously yielding pure condensate.

[0109] Evaporation crystallization typically employs equipment such as multi-effect evaporators and MVR (mechanical vapor recompression) evaporators. By heating, the water in the third mother liquor evaporates, causing salts to crystallize out due to decreased solubility. The water vapor produced during evaporation is condensed to obtain condensate, which can be reused in processes such as pulping, achieving water resource recycling. The crystallized salts are then separated and dried to obtain crystalline salt products.

[0110] Crystalline salts mainly contain sodium chloride and / or potassium chloride. Depending on their purity and impurity content, they can be sold as industrial salt, de-icing agents, or further purified for other uses, thus realizing the resource utilization of soluble salts in fly ash.

[0111] In some implementations, the difference in solubility between sodium chloride and potassium chloride at different temperatures can be utilized to separate them using stepwise crystallization or cooling crystallization methods. Specifically, during the evaporation process, the temperature is first controlled to allow sodium chloride, with lower solubility, to crystallize preferentially. Solid-liquid separation yields sodium chloride product and a mother liquor rich in potassium chloride. Subsequently, evaporation or cooling of the mother liquor continues to allow potassium chloride to crystallize out, thereby obtaining sodium chloride and potassium chloride products with higher purity, increasing product added value and market competitiveness. This corresponds to... Figure 1 The term "salt separation" in Chinese. Figure 1 The "five-stage reaction" before "salt separation" mainly involves adjusting the pH of the third mother liquor to the optimal range for salt separation, preventing scaling during the evaporation and crystallization process.

[0112] Step P5: Preparation of gypsum products (optional).

[0113] When sulfuric acid is used in the acid modification reaction, the first solid phase mainly consists of gypsum. To improve the purity and quality of the gypsum, the first solid phase can be washed with water.

[0114] In one or more specific embodiments, the first solid phase is washed with condensate from the evaporation and crystallization process to obtain the gypsum product. This utilizes the condensate, reducing the consumption of fresh water, and also removes soluble impurities from the gypsum through washing, improving the purity of the gypsum. The washed gypsum product can be used in the production of building materials (such as gypsum board, gypsum blocks, etc.) or as a cement retarder, thus achieving resource utilization.

[0115] At this point, the subsequent treatment of the detoxified slurry was completed, achieving the removal of heavy metals, reduction of hardness, recovery of soluble salts, and resource utilization of by-products such as gypsum. At the same time, recyclable condensate was obtained. The whole process embodies the principles of "reduction, harmlessness, and resource utilization".

[0116] III. Technical effects of the overall process.

[0117] In summary, the fly ash treatment method disclosed herein achieves the following technical effects through the organic combination of the fly ash dioxin separation stage and the subsequent treatment stage:

[0118] 1) Significantly reduce energy consumption and costs: Through efficient physicochemical separation methods, most of the dioxins are concentrated in the scum, which accounts for a very small proportion of the total fly ash. Only a small amount of scum needs to be pyrolyzed at high temperature, while a large amount of detoxified slurry does not need to be treated at high temperature. This avoids the huge energy consumption and high cost caused by high-temperature treatment of the entire fly ash.

[0119] 2) Achieving efficient separation and harmless treatment of dioxins. Through oxidation pretreatment and acid modification, dioxin-like particles are fully dissociated from the fly ash surface, revealing their hydrophobicity. Then, through gas-liquid-solid three-phase coupling separation, dioxin-like particles are efficiently captured by bubbles, achieving the enrichment and separation of dioxins. After pyrolysis treatment of the scum, the dioxins are completely decomposed, achieving harmless disposal.

[0120] 3) Prevent equipment corrosion and extend service life. By precisely controlling the amount of acid used, the pH value of the modified fly ash slurry is maintained within the range of 6-12.5. This ensures the complete dissociation of dioxins and significantly reduces the risk of equipment corrosion. Compared with a strong acid environment, the corrosion rate of equipment can be reduced by more than an order of magnitude under pH 6-12.5 conditions, extending equipment service life several times and significantly reducing maintenance costs.

[0121] 4) Achieve resource utilization of fly ash. Through multi-stage wastewater purification treatment, heavy metals, calcium and magnesium ions, soluble salts and other substances in the detoxified slurry are recovered or removed respectively, resulting in gypsum products, industrial salt products and recyclable condensate, thus achieving resource utilization of fly ash.

[0122] 5) The process is safe and environmentally friendly. Oxidation pretreatment prevents the decomposition of sulfites under acidic conditions, thus eliminating the risk of secondary pollution. Controlling the pH value also prevents the large-scale generation of sulfur dioxide. The entire process can be carried out at normal temperature and pressure (except for the pyrolysis stage), is simple to operate, and has high safety. Waste gas and wastewater are effectively treated and discharged in compliance with standards, resulting in minimal environmental impact.

[0123] 6) Advanced technology and wide applicability. This method comprehensively utilizes multiple technologies such as oxidation, acid modification, air flotation separation, pyrolysis, and multi-stage wastewater treatment. The process route is scientifically sound and technologically advanced. This method is not only suitable for the treatment of fly ash from municipal solid waste incineration, but can also be extended to the treatment of fly ash from industrial waste incineration and hazardous waste incineration, demonstrating broad applicability.

[0124] To implement the above-mentioned methods for separating dioxins from fly ash and for treating fly ash, this disclosure also provides corresponding equipment and apparatus. These devices and apparatus are specifically designed for the characteristics of the fly ash dioxin separation process, ensuring efficient and stable operation of each process step and guaranteeing separation effectiveness and treatment quality.

[0125] To verify the actual effectiveness of the disclosed technical solution under low acid dosage conditions, experimental examples were conducted. For example... Figure 10 As shown, the fly ash raw material (raw ash) used in the experiment was tested and found to contain 1.5 × 10⁻⁶ dioxins. 2 ng TEQ / kg (i.e., 150 ng TEQ / kg). In the modification reaction stage, concentrated sulfuric acid is added to the fly ash slurry. Using 98% concentrated sulfuric acid as an example, the amount added is 25% of the fly ash mass. After the modification reaction, the pH value of the fly ash slurry is approximately 10. After the complete fly ash treatment process, the first solid phase (gypsum product) obtained from the first solid-liquid separation treatment is tested. For example... Figure 11 As shown, the dioxin content in this gypsum product is only 29 ng TEQ / kg, significantly lower than the 50 ng TEQ / kg limit specified in the "Technical Specification for Pollution Control of Fly Ash from Municipal Solid Waste Incineration HJ1134-2020". This experimental result fully demonstrates that the fly ash treatment method disclosed herein can effectively achieve the separation and enrichment of dioxins under appropriate acid dosage conditions, ensuring that the detoxification products (such as gypsum), which constitute the majority of fly ash mass, meet safe utilization standards. This verifies the superiority and effectiveness of this technical solution in balancing separation effect with equipment corrosion prevention and cost control.

[0126] IV. Overall Composition of Fly Ash Dioxin Separation Equipment

[0127] The fly ash dioxin separation equipment, used to implement the aforementioned fly ash dioxin separation method, includes: a slurry preparation device, a slurry pretreatment device, and a gas-liquid-solid three-phase coupling separation device.

[0128] A pulping unit is used to mix fly ash with water to produce fly ash slurry. A pulping unit typically includes a slurry mixing tank, a mixer, a fly ash inlet, and a water inlet. Fly ash enters the slurry mixing tank through the fly ash inlet, and water enters through the water inlet. Under the action of the mixer, the fly ash and water are thoroughly mixed to form a homogeneous fly ash slurry. The pulping unit can also be equipped with monitoring devices such as flow meters and level gauges to precisely control the fly ash to water ratio, ensuring that the produced fly ash slurry has a suitable solid-liquid ratio.

[0129] The slurry pretreatment unit is used to perform oxidation and / or acid modification reactions on fly ash slurry. Depending on the technical solution adopted, the slurry pretreatment unit can be configured as follows:

[0130] (1) In the first technical solution, the slurry pretreatment device is used to add an oxidant to the fly ash slurry to carry out an oxidation reaction, thereby oxidizing the reducing substances on the fly ash surface. Then, an acid is added to the oxidized fly ash slurry to carry out a modification reaction, thereby using the acid to etch the fly ash, so that dioxin particles are dissociated from the fly ash surface and reveal hydrophobicity.

[0131] (2) In the second technical solution, the slurry pretreatment device is used to add acid to the fly ash slurry for modification reaction, thereby using acid to etch the fly ash, so that dioxin particles are dissociated from the fly ash surface and exposed to hydrophobicity, and by controlling the amount of acid used in the modification reaction, the pH value of the fly ash slurry after the modification reaction is controlled to be 6-12.5.

[0132] In a preferred embodiment, the slurry pretreatment device is configured to control the pH value of the fly ash slurry after the modification reaction to 6-12.5 by controlling the amount of acid used during the modification reaction. This configuration is applicable to both the second and first technical solutions to further optimize the pH value of the slurry and reduce the risk of corrosion to subsequent equipment.

[0133] The gas-liquid-solid three-phase coupling separation device is used to generate or introduce bubbles into the modified fly ash slurry. These bubbles capture dioxin-like particles, which float to the surface and form scum. The scum is then separated from the mother liquor to obtain a detoxified slurry. The gas-liquid-solid three-phase coupling separation device is a key piece of equipment for achieving efficient dioxin separation, and its structural design and performance directly affect the separation effect.

[0134] The following section will detail the specific structure and technical features of the slurry pretreatment device and the gas-liquid-solid three-phase coupling separation device.

[0135] V. Fly ash slurry oxidation modification and / or acid washing modification unit

[0136] like Figure 9As shown, a fly ash slurry oxidation modification and / or acid washing modification device, as a preferred embodiment of the slurry pretreatment device, is specifically designed in terms of structure and function for the oxidation and acid modification reactions of fly ash slurry. It includes a reactor and a feeding device.

[0137] (a) Reactor.

[0138] The reactor is the main part of the fly ash slurry oxidation modification and / or acid washing modification device, providing reaction space for oxidation and / or acid modification reactions. The reactor includes a shell 301, a reaction chamber, a stirring assembly 302, a fly ash slurry inlet 303, and a fly ash slurry outlet 304.

[0139] The shell 301 is typically a cylindrical or rectangular closed container, and the material can be acid and alkali resistant, such as stainless steel, rubber-lined steel, or fiberglass. The dimensions of the shell 301 are determined by the processing capacity; for industrial-scale applications, the reactor volume is typically 1 m³. 3 up to 50m 3 between.

[0140] The reaction chamber is located inside the shell 301 and is used to contain the fly ash slurry and carry out the reaction. The volume of the reaction chamber should be able to accommodate the fly ash slurry for a certain residence time to ensure that the oxidation reaction and / or acid modification reaction are fully carried out. In one or more specific embodiments, the residence time of the fly ash slurry in the reaction chamber is 20 to 60 minutes, preferably 30 to 50 minutes.

[0141] The stirring assembly 302 is disposed within the reaction chamber and is used to stir the fly ash slurry, promoting thorough mixing and contact between the oxidant, acid, and fly ash slurry, ensuring the uniformity and completeness of the reaction. The stirring assembly 302 typically includes a stirrer, a stirring shaft, and a drive unit. The stirrer can be a paddle stirrer, turbine stirrer, frame stirrer, ribbon stirrer, etc., with the appropriate stirrer type selected based on the viscosity and flowability of the slurry. The stirring shaft can be vertically or inclined. The drive unit (such as a motor or reducer) is located at the top or side of the reactor, driving the stirring shaft to rotate, thereby driving the stirrer to agitate the slurry.

[0142] The fly ash slurry inlet 303 is located on the shell 301 and is used to introduce the fly ash slurry prepared by the slurry preparation device into the reaction chamber. The fly ash slurry inlet 303 may be equipped with a feed pipe and valve to control the feed rate of the fly ash slurry.

[0143] The fly ash slurry outlet 304 is located on the shell 301 and is used to discharge the reacted fly ash slurry (i.e., the fly ash slurry after oxidation treatment and / or acid modification treatment) to the gas-liquid-solid three-phase coupling separation device. The fly ash slurry outlet 304 can also be equipped with a discharge pipe and valve to control the discharge rate.

[0144] In a preferred embodiment, a partition 305 is vertically arranged in the reaction cavity, dividing the reaction cavity into a first reaction zone and a second reaction zone that are interconnected. This partitioning design improves the targeting and efficiency of the reaction.

[0145] Specifically, the fly ash slurry inlet 303 is connected to the first reaction zone and is located on the side of the first reaction zone away from the partition 305. After the fly ash slurry enters the first reaction zone through the fly ash slurry inlet 303, it first undergoes an oxidation reaction (if the first technical solution is adopted) or an acid modification reaction (if the second technical solution is adopted) in the first reaction zone.

[0146] The fly ash slurry outlet 304 leads to the second reaction zone and is located on the side of the second reaction zone away from the baffle 305. The slurry treated in the first reaction zone flows into the second reaction zone through the fluid channels around the baffle 305, where it undergoes further reaction (such as acid modification reaction, in the first technical solution), and then is discharged from the fly ash slurry outlet 304.

[0147] The stirring assembly 302 includes a first stirrer and a second stirrer respectively disposed in the first reaction zone and the second reaction zone. The first stirrer and the second stirrer can be driven by their respective independent drive devices, or they can be driven simultaneously by the same drive device through a coupling, gear transmission, or other means. By setting stirrers in the first reaction zone and the second reaction zone respectively, it can be ensured that the slurry in each reaction zone is fully stirred, thereby improving the reaction efficiency.

[0148] In one or more specific embodiments, both the first and second agitators include a vertically arranged main shaft, a drive device located at the top of the reactor for driving the main shaft, and at least two layers of impellers spaced at different heights on the main shaft. By arranging multiple layers of impellers at different heights on the main shaft, the slurry at different heights within the reaction chamber can be stirred, avoiding dead zones and ensuring the uniformity of the slurry. The impellers can be paddle-type, turbine-type, frame-type, etc., and the number of impeller layers is typically 2-5, with the spacing between the impellers determined according to the height of the reaction chamber.

[0149] To facilitate slurry flow and local circulation between the first and second reaction zones, in one or more embodiments, fluid channels are provided between the upper end of the partition 305 and the top of the reaction chamber, and between the lower end of the partition 305 and the bottom of the reaction chamber. These fluid channels allow the slurry to flow between the first and second reaction zones, forming local circulation, which helps to achieve uniform mixing of the slurry and equalization of reactant concentration. The gap height between the upper end of the partition 305 and the top of the chamber is typically 5%-15% of the total height of the reaction chamber, and the gap height between the lower end of the partition 305 and the bottom of the chamber is also 5%-15% of the total height of the reaction chamber.

[0150] (ii) Feeding device.

[0151] A feeding device is disposed on the shell and communicates with the reaction chamber, for adding oxidant and / or acid into the reaction chamber. The feeding device includes a first feeding structure and / or a second feeding structure.

[0152] The first feeding structure is used to add an oxidant to the reaction chamber, which is used to oxidize the reducing substances on the fly ash surface in the fly ash slurry. The first feeding structure is necessary when adopting the first technical solution (i.e., oxidation followed by acid modification); when adopting the second technical solution (i.e., direct acid modification), the first feeding structure can be omitted.

[0153] The second feed structure is used to add acid into the reaction chamber. The acid is used to etch the fly ash in the fly ash slurry, causing dioxin-like particles to dissociate from the fly ash surface and reveal hydrophobicity. The second feed structure is necessary in both technical solutions.

[0154] In one or more specific embodiments, both the first feeding structure and / or the second feeding structure include a metering pump and a dosing pipe. The metering pump is used to precisely control the addition rate of the additive (oxidant or acid). By adjusting the flow rate of the metering pump, the amount of oxidant or acid can be precisely controlled according to the flow rate and properties of the fly ash slurry, ensuring the controllability of the reaction. The dosing pipe is used to introduce the additive into the reaction chamber. One end of the dosing pipe is connected to the outlet of the metering pump, and the other end is inserted into or opens into the reaction chamber.

[0155] The design of the outlet position of the dosing pipe has a significant impact on the reaction effect. In a preferred embodiment, the outlet of the dosing pipe of the first feeding structure is located above the liquid surface of the fly ash slurry or inserted into the upper layer of the fly ash slurry; the outlet of the dosing pipe 306 of the second feeding structure is inserted into the lower layer of the fly ash slurry.

[0156] Setting the dosing pipe outlet of the first feed structure above the liquid surface or in the upper slurry has the following advantages: Oxidizing agents (such as hydrogen peroxide solution) usually have a density close to that of water. After being added from above the liquid surface or in the upper layer, they can gradually diffuse downwards under the action of gravity and stirring, and fully contact and react with the reducing substances in the slurry; at the same time, if the oxidation reaction produces gas (such as oxygen), the gas can easily escape from the liquid surface and will not accumulate in the lower layer of the slurry, affecting the reaction.

[0157] Setting the outlet of the dosing pipe 306 of the second feed structure (acid feed) in the lower slurry layer has the following advantages: the density of acid (such as concentrated sulfuric acid) is usually greater than that of water, and adding it from the lower layer can utilize the density difference to promote the mixing of acid and slurry; at the same time, the reaction between acid and alkaline substances (such as calcium oxide and calcium hydroxide) in fly ash is an exothermic reaction, and adding it from the lower layer can utilize the convection and stirring of the slurry to distribute the reaction heat more evenly and avoid local overheating; in addition, after the acid is added from the lower layer, it diffuses upward, increasing the contact time between acid and fly ash particles and improving the etching effect.

[0158] In an embodiment where the reaction chamber is divided into a first reaction zone and a second reaction zone by a partition, when the feeding device includes both a first feeding structure and a second feeding structure, the first feeding structure adds an oxidant to the first reaction zone, and the second feeding structure adds an acid to the second reaction zone. In this way, the oxidation reaction takes place in the first reaction zone, and the acid modification reaction takes place in the second reaction zone. The two reactions are spatially separated and do not interfere with each other, ensuring the sufficiency of each reaction while avoiding adverse reactions that may be caused by the simultaneous addition of an oxidant and an acid (such as the decomposition of the oxidant in an acidic environment).

[0159] (iii) Other auxiliary components.

[0160] To ensure the safety and environmental friendliness of the reaction process, an exhaust port 307 can be installed on the top of the shell, which is connected to a waste gas collection pipeline. Small amounts of gases (such as oxygen, water vapor, and trace amounts of sulfur dioxide) may be generated during the oxidation and acid modification reactions. Although sulfur dioxide production has been significantly reduced through oxidation pretreatment or pH control, trace amounts may still be produced. These gases are discharged from the reactor through the exhaust port 307 and then sent to a waste gas treatment system for purification before being released, thus avoiding environmental pollution.

[0161] The reactor can also be equipped with monitoring devices such as temperature sensors, pressure sensors, pH sensors, and liquid level sensors to monitor parameters such as temperature, pressure, pH value, and liquid level in the reaction chamber in real time, and feed these parameters back to the control system. Based on the monitoring data, the control system automatically adjusts operating parameters such as the flow rate of the metering pump, the speed of the agitator, and the feed and discharge rates to achieve automated control of the reaction process, ensuring that the reaction proceeds stably, safely, and efficiently.

[0162] The above-mentioned fly ash slurry oxidation modification and / or acid washing modification device can provide a precise and controllable reaction environment for oxidation and / or acid modification reactions, ensuring sufficient mixing and contact between the oxidant and / or acid and the fly ash slurry, minimizing reaction blind zones, and ensuring the full dissociation of dioxin particles from the fly ash surface, thus laying a good foundation for subsequent gas-liquid-solid three-phase coupling separation.

[0163] VI. A gas-liquid-solid three-phase coupling separation device with bubble refinement function.

[0164] like Figures 2-4 As shown, a gas-liquid-solid three-phase coupling separation device with bubble refinement function is presented as a first preferred embodiment of the gas-liquid-solid three-phase coupling separation device. By innovatively introducing a bubble refinement component, external field energy is applied to the bubble flow to promote bubble breakage and refinement, thereby improving the bubble capture efficiency of fine dioxin particles.

[0165] (a) Reaction vessel.

[0166] The reaction vessel is the main body of the gas-liquid-solid three-phase coupling separation device, providing space for the contact between bubbles and slurry, the capture and flotation of dioxin-like particles, and the separation of scum from the mother liquor. The reaction vessel has an inner cavity to contain the slurry being treated, and a slurry inlet and outlet communicating with the inner cavity. In this application, the slurry being treated is the modified fly ash slurry.

[0167] The reaction vessel is typically a vertically positioned cylindrical or rectangular container, and the shell material can be corrosion-resistant materials such as stainless steel, rubber-lined carbon steel, or fiberglass. The ratio of the height to the diameter (or side length) of the reaction vessel (i.e., the height-to-diameter ratio) is usually 2:1 to 5:1, preferably 3:1 to 4:1. This ratio ensures that the bubbles have sufficient rising distance and time to capture dioxin-like particles, while avoiding structural stability problems and increased manufacturing costs caused by excessively tall containers.

[0168] The inner cavity can be divided into different functional areas along the height direction. In a preferred embodiment, the inner cavity is divided into a coarse selection area 101, a fine selection area 102, and a separation area 103 from bottom to top along the height direction.

[0169] The coarse separation zone 101 is located at the bottom of the reaction vessel, accounting for 20%-35% of the total height of the reaction vessel, preferably 25%-30%. A bubble generating mechanism is located in this coarse separation zone to generate an upward-moving bubble flow. The slurry outlet 104 is located at the bottom of this coarse separation zone and is used to discharge the bulk slurry (i.e., the detoxified slurry) that was not captured by the bubbles. In the coarse separation zone 101, bubbles are newly generated, numerous, and relatively large in size, mainly capturing dioxin-like particles with larger particle sizes and stronger hydrophobicity, achieving preliminary coarse separation.

[0170] The selection zone 102 is located in the middle of the reaction vessel, accounting for 40%-60% of the total height of the reaction vessel, preferably 45%-55%. The slurry inlet 105 is located in the lower middle part of this selection zone, through which the modified fly ash slurry enters the reaction vessel. A bubble refining component is located in this selection zone, applying external energy to the bubble flow to promote bubble breakage and refinement. In the selection zone, the refined bubbles have a larger specific surface area, enabling them to more effectively capture small dioxin-like particles, achieving fine separation and improving separation efficiency.

[0171] The separation zone 103 is located at the top of the reaction vessel, accounting for 15%-30% of the total height of the reaction vessel, preferably 20%-25%. The slag discharge mechanism is located in this separation zone. In the separation zone, bubbles carrying dioxin-like particles rise to the liquid surface. After the bubbles burst, the dioxin-like particles aggregate on the liquid surface, forming a stable slag layer. The separation zone provides space for the formation and aggregation of slag, and also acts as a buffer to prevent fluctuations in the slurry from affecting the stability of the slag layer.

[0172] (ii) Bubble generating mechanism.

[0173] The bubble generating mechanism is located inside the lower part or bottom of the reaction vessel to generate an upward-moving bubble flow within the reaction vessel. As the bubble flow rises, it comes into contact with the slurry being treated, which enters from the slurry inlet 105 and flows towards the slurry outlet. The bubble captures the target particles (i.e., dioxin-like particles) in the slurry and carries them to the surface to form scum, while the bulk of the slurry that is not captured by the bubbles is discharged through the slurry outlet 104.

[0174] Bubble generating mechanisms can take various forms, including perforated plate gas distributors, venturi tube devices, microporous aerators, and jet injectors. In one or more specific embodiments, the bubble generating mechanism includes a perforated plate gas distributor 106. The perforated plate gas distributor is a plate with a plurality of evenly distributed small holes, disposed at the bottom of the reaction vessel or below the coarsening zone. Compressed gas enters from the gas inlet at the bottom of the reaction vessel and is ejected upwards through the small holes in the perforated plate, forming a large number of bubbles.

[0175] In an embodiment where a porous plate gas distributor 106 is provided in the coarsening zone 101, the coarsening zone 101 has a downwardly concave conical bottom 107, and a purge air hole 114 is provided on the side wall of the conical bottom 107. The purge air hole 114 is used to inject gas into the conical bottom 107 to prevent mineral sedimentation. A bubble generating mechanism is provided above the conical bottom 107 and includes the porous plate gas distributor 106.

[0176] The conical bottom 107 is designed to guide uncaptured solid particles towards the center, facilitating their discharge from the slurry outlet 104. However, the conical bottom 107 also carries the risk of solid particle settling and accumulation, especially for larger, denser particles. By providing purge vents 114 on the sidewall of the conical bottom 107, gas (such as compressed air) is injected into it. The impact and agitation of the gas prevent solid particle settling and accumulation, maintaining the unobstructed flow of the conical bottom 107 and ensuring smooth slurry discharge from the outlet. The purge vents 114 are typically evenly distributed circumferentially along the sidewall of the conical bottom 107.

[0177] In a more preferred embodiment, the coarse selection zone 101 is further provided with a slurry circulation system, which includes a circulation outlet 108 and a circulation inlet. The circulation outlet 108 is located at the bottom of the coarse selection zone 101 (a filter 109 may be installed at the circulation outlet 108); the circulation inlet is located at the top of the coarse selection zone 101, and the treated slurry drawn out is sent back to the coarse selection zone 101.

[0178] The slurry circulation system enhances the flow and mixing of the slurry in the coarsening zone, improving the contact efficiency between bubbles and the slurry. In one or more specific embodiments, the circulating fluid inlet employs a first Venturi tube device 110. A Venturi tube device is a device that generates negative pressure using changes in fluid velocity. When a high-speed fluid passes through the throat section of the Venturi tube, the pressure decreases, allowing gas or other fluids to be drawn in.

[0179] The first Venturi tube device 110 includes a contraction section, a throat section, and a diffuser section. The contraction section has a central fluid channel and an outer annular fluid channel surrounding the central fluid channel. A mixture of slurry and separation aid drawn from the circulating liquid outlet enters through the central fluid channel. The flow velocity gradually increases in the contraction section, reaching its maximum and decreasing to its minimum when entering the throat section. The outer annular fluid channel serves as a gas inlet; gas is drawn in under the negative pressure at the throat section and mixes with the slurry from the central fluid channel, forming a slurry containing numerous microbubbles. The mixed slurry enters the diffuser section, where the flow velocity gradually decreases and the pressure gradually recovers, before returning to the coarse separation zone 101 from the circulating liquid inlet.

[0180] The slurry circulation system employing the first Venturi tube device 110 not only achieves slurry circulation but also generates additional microbubbles during circulation, further increasing the total number of bubbles and improving the capture opportunity of dioxin-like particles. Simultaneously, the separation aids (first and second separation aids) can be pre-mixed with the circulating slurry and introduced together through the central fluid channel, ensuring uniform dispersion of the separation aids in the slurry.

[0181] (III) Bubble refining components.

[0182] The bubble refinement component is the core innovation of this embodiment. It is set in the bubble flow rising area in the height direction of the reaction vessel and is used to apply external field energy to the bubble flow in the reaction vessel to promote bubble breakage and refinement.

[0183] By introducing a bubble refiner and applying external energy to the bubble flow, larger bubbles can be broken down into smaller ones. The refined bubbles can have diameters of 0.1 mm to 1 mm or even smaller, resulting in a significant increase in specific surface area. This increased specific surface area means a larger contact area between the bubbles and the slurry, increasing the probability and frequency of collisions between the bubbles and dioxin-like particles, thereby improving the bubble's capture efficiency for fine dioxin particles.

[0184] The bubble refining component can take many forms. In one or more specific embodiments, the bubble refining component is one or a combination of microwave generator 111, ultrasonic generator, and mechanical vibration device.

[0185] The microwave generator 111 emits microwaves (typically at a frequency of 2.45 GHz). The microwave energy is absorbed by polar molecules (mainly water molecules) in the slurry, causing high-speed molecular oscillation and frictional heating. The rapidly alternating electromagnetic field of the microwaves also generates intense oscillations and disturbances at the bubble interface, promoting bubble breakage and refinement. In one or more embodiments, the bubble refining component uses a microwave generator 111 with a power of 500W-3000W, preferably 1000W-2000W. The microwave emitting head of the microwave generator 111 is positioned on the sidewall of the refining zone or inserted into the refining zone, applying microwave energy to the bubble flow in the refining zone.

[0186] An ultrasonic generator emits ultrasonic waves (typically 20kHz-100kHz). As the waves propagate through the slurry, they generate high-frequency vibrations and cavitation effects. Cavitation refers to the pressure fluctuations caused by the ultrasonic waves in the liquid, leading to the formation, oscillation, and collapse of tiny bubbles. The collapse of these bubbles generates strong localized shock waves and microjets; these mechanical forces can tear large bubbles into smaller ones. The ultrasonic transducer of the ultrasonic generator is positioned on the sidewall of the refining zone or inserted into the refining zone, applying ultrasonic energy to the bubble flow within the zone.

[0187] Mechanical vibration devices generate vibrations through mechanical vibrators (such as electromagnetic vibrators, eccentric vibrators, etc.). This vibration is transmitted to the shell or internal vibrating plates of the reaction vessel, and then to the slurry and bubble flow. Mechanical vibration can also impact and disturb the bubbles, promoting bubble breakage. The vibration frequency of mechanical vibration devices is typically 10Hz-500Hz, and the amplitude is 0.5mm-10mm.

[0188] In a preferred embodiment, a bubble refining component is disposed on the sidewall of the refining zone 102 for applying external field energy within the refining zone. The bubble refining component is disposed in the refining zone because after bubbles are generated in the coarse selection zone, they travel a certain rising distance before entering the refining zone. At this point, the bubbles have already completed the initial capture of larger particles. Refining the bubbles in the refining zone allows the refined bubbles to better capture fine particles, achieving graded capture and improving overall separation efficiency. If bubble refining were performed in the coarse selection zone, the refined microbubbles would rise slowly and may remain in the coarse selection zone for too long, affecting processing efficiency.

[0189] To adapt to variations in fly ash properties and dioxin content, in one or more specific embodiments, the magnitude of the external field energy applied by the bubble refining component is adjustable. For example, the output power of the microwave generator is adjustable, the frequency and power of the ultrasonic generator are adjustable, and the amplitude and frequency of the mechanical vibration device are adjustable. By adjusting the magnitude of the external field energy, the degree of bubble refining can be controlled, optimizing energy consumption and achieving economical and efficient operation while ensuring separation effectiveness.

[0190] (iv) Slag discharge mechanism.

[0191] The scum removal mechanism is located at the top of the reaction vessel and is used to remove scum. Scum is a concentrated substance formed when bubbles carrying dioxin-like particles rise to the liquid surface, burst, and the particles aggregate, appearing as a foamy or thick floating layer. Timely removal of scum is essential to ensure the continuous and stable operation of the separation process.

[0192] Slag removal mechanisms come in various forms, commonly including slag scrapers, overflow weirs, and vacuum slag suction machines. In one or more specific embodiments, a washing water spray device 112 is provided in the upper part of the separation zone, and a downward-sloping slag discharge chute is provided in the lower part of the separation zone.

[0193] A washing water spray device 112 is installed at the top of the separation zone and is used to spray clean water or recycled water onto the liquid surface. The function of the spray water is to push the scum on the liquid surface towards the scum discharge chute, while simultaneously washing the scum, removing some of the mother liquor entrained in it, and improving the grade of the scum. The flow rate and pressure of the spray water can be adjusted and controlled according to the scum generation rate and thickness.

[0194] The slag discharge chute is angled downwards, with its high-end opening located near the liquid surface within the separation zone, and its low-end opening 113 located outside the reaction vessel, connecting to a slag collection container or conveying pipeline. Under the action of the washing water spray device and the natural flow of the slurry, the slag slides down the slag discharge chute, is discharged from the reaction vessel, and enters subsequent slag treatment stages (such as pyrolysis treatment).

[0195] (V) Overall work process.

[0196] The modified fly ash slurry enters the lower part of the refining zone 102 of the reaction vessel through the slurry inlet 105. At the same time, compressed gas is introduced from the bottom of the reaction vessel and generates a large number of bubbles through the porous plate gas distributor 106 in the coarse selection zone 101. The bubbles move from bottom to top, forming a bubble flow.

[0197] In the coarsening zone 101, the bubble flow comes into countercurrent contact with the downward-flowing slurry. The bubbles capture some of the hydrophobic dioxin-like particles (mainly larger, more hydrophobic particles) and carry them to the surface. The slurry that is not captured by the bubbles continues to flow downward and is discharged from the slurry outlet 104 at the bottom of the coarsening zone 101, becoming the detoxified slurry.

[0198] After the bubble stream enters the refining zone 102, it is subjected to external field energy applied by the bubble refining component (such as the microwave generator 111), causing larger bubbles to break down into microbubbles. The specific surface area of ​​the microbubbles is significantly increased, enabling them to more effectively capture small dioxin-like particles. In the refining zone, the slurry entering from the slurry inlet 105 comes into full contact with the refined bubbles, and the dioxin-like particles in the slurry (including fine particles not captured in the coarse selection zone) are captured by the bubbles.

[0199] If a first separation aid and a second separation aid are added to the slurry, these separation aids will further enhance the hydrophobicity of dioxin-like particles and their ability to capture bubbles, thereby improving separation efficiency.

[0200] The bubbles carrying dioxin-like particles continue to rise and enter separation zone 103. In separation zone 103, the bubbles rise to the liquid surface, and after the bubbles burst, the dioxin-like particles accumulate on the liquid surface to form a scum layer. The washing water spray device 112 sprays water onto the liquid surface, pushing the scum towards the scum discharge chute, and the scum slides down the chute and is discharged from the reaction vessel.

[0201] The gas-liquid-solid three-phase coupling separation device with bubble refinement function described above significantly improves the capture efficiency of bubbles for fine dioxin particles by utilizing bubble refinement technology, thus achieving efficient separation of dioxins.

[0202] VI. A gas-liquid-solid three-phase coupling separator with cascade efficiency enhancement function.

[0203] like Figures 5-8 As shown, a gas-liquid-solid three-phase coupling separator with cascaded efficiency enhancement is presented as a second preferred embodiment of the gas-liquid-solid three-phase coupling separation device. By setting a staged separation structure inside the reaction vessel, the internal space is divided into at least two separation functional zones that are sequentially connected along the slurry flow path. This allows the slurry to undergo at least two stages of separation within the internal cavity, thereby achieving "cascaded efficiency enhancement," effectively preventing slurry "short-circuiting," and ensuring separation performance.

[0204] (I) Reaction vessel and hierarchical separation structure.

[0205] The reaction vessel also has an inner cavity for containing the slurry to be treated, and a slurry inlet 201 and a slurry outlet 202 communicating with the inner cavity. In this application, the slurry to be treated is the modified fly ash slurry.

[0206] The core feature of this embodiment is that the inner cavity is provided with a hierarchical separation structure, which is configured to divide the space of the inner cavity into at least two separation functional areas that are sequentially connected along the flow path of the slurry being treated, so that the slurry being treated undergoes at least two stages of separation process in the inner cavity.

[0207] In a preferred embodiment, the hierarchical separation structure includes a baffle 203 vertically disposed in the inner cavity. The baffle 203 divides the inner cavity horizontally into a first chamber 205 and a second chamber 206 connected by a reserved fluid channel around the baffle. The first chamber 205 constitutes a first-level separation functional area, and the second chamber 206 constitutes a second-level separation functional area.

[0208] The baffle 203 is typically a vertical flat or curved panel, made of corrosion-resistant materials such as stainless steel or rubber lining. The height of the baffle 203 is approximately the same as the height of the inner cavity, but fluid channels are pre-reserved between the upper end of the baffle 203 and the top of the inner cavity, and between the lower end of the baffle 203 and the bottom of the inner cavity. These pre-reserved fluid channels connect the first chamber 205 and the second chamber 206 at the top and bottom, allowing the slurry to flow from the first chamber 205 to the second chamber 206, while also creating localized fluid circulation, which helps to ensure uniform mixing of the slurry and adequate capture of dioxin-like particles.

[0209] The gap height between the upper end of the baffle 203 and the top of the inner cavity is typically 5%-15% of the total height of the inner cavity, preferably 8%-12%; the gap height between the lower end of the baffle 203 and the bottom of the inner cavity is also 5%-15% of the total height of the inner cavity, preferably 8%-12%. Such gaps ensure that the slurry can flow smoothly from the first chamber to the second chamber, while avoiding excessive gaps that would weaken the baffle's separating effect.

[0210] The slurry inlet 201 is located in the first chamber on the side away from the baffle 203, usually in the middle or lower-middle part of the first chamber. The modified fly ash slurry enters the first chamber through the slurry inlet and undergoes the first-stage separation in the first chamber.

[0211] The slurry outlet 202 is located in the second chamber on the side away from the baffle 203, typically at the bottom of the second chamber. The detoxified slurry, after being separated in the first and second chambers, is discharged from the slurry outlet 202.

[0212] (ii) Bubble generating mechanism.

[0213] The bubble generating mechanism includes a first bubble generating unit located below or at the bottom of the first chamber and a second bubble generating unit located below or at the bottom of the second chamber. By setting bubble generating units in the first and second chambers respectively, a sufficient supply of bubbles can be ensured for each separation functional zone, thereby improving the efficiency of each separation stage.

[0214] The first bubble generating unit and the second bubble generating unit may employ the same or different bubble generating methods. In one or more specific embodiments, the first bubble generating unit and / or the second bubble generating unit have a plurality of second venturi tube devices 204 arranged in a planar array inside the lower part or bottom of the reaction vessel.

[0215] The second Venturi tube device, as follows: Figure 8 As shown, it includes a contraction tube section, a throat section, and a diffuser section. Unlike the aforementioned first Venturi tube device 110, the contraction tube section of the second Venturi tube device 204 has a central fluid channel and an outer annular fluid channel surrounding the central fluid channel. The central fluid channel serves as a gas inlet 207, and the outer annular fluid channel serves as a separation aid inlet 208.

[0216] Compressed gas enters through the central fluid channel, where its velocity increases in the contraction section, reaching its maximum and pressure minimum upon entering the throat section. Separation aids (first and / or second separation aids) enter through the outer annular fluid channel and are drawn into the central gas flow under the negative pressure at the throat section, mixing with the gas. The mixed gas-separation aid flow enters the diffuser section, where its velocity decreases, pressure recovers, and numerous tiny bubbles containing the separation aids form at the diffuser section outlet. These bubbles rise, contact the slurry, and capture dioxin-like particles.

[0217] The advantages of using the second Venturi tube device 204 are: on the one hand, the Venturi tube device can generate tiny and uniform bubbles, improving the bubble capture efficiency; on the other hand, the separation aid is introduced at the same time as the bubble is generated, ensuring that the separation aid can be adsorbed on the surface of each bubble, thereby enhancing the affinity of the bubble for dioxin-like particles.

[0218] The second Venturi tube devices in the first and second bubble generating units are arranged in a planar array. For example, multiple second Venturi tube devices 204 are evenly distributed at the bottom of the first and second chambers, respectively. The outlet of the diffuser section of each device faces upward, spraying a stream of bubbles containing the separation aid upward. The array arrangement ensures that the bubbles are evenly distributed across the cross-section of the entire chamber, avoiding the problem of bubbles being concentrated in certain areas while other areas have insufficient bubbles, thus improving bubble utilization and separation effect.

[0219] (III) Stirring system.

[0220] To further enhance the fluidity and mixing effect of the slurry, the reaction vessel is also equipped with a stirring system. The stirring system includes a first stirring mechanism located in the first chamber and a second stirring mechanism located in the second chamber.

[0221] Both the first and second stirring mechanisms include a vertically arranged main shaft, a drive device located at the top of the reaction vessel for driving the main shaft, and at least two layers of stirring impellers 209 spaced apart at different heights of the main shaft.

[0222] The main shaft is vertically positioned at the center of the first and second chambers. The drive unit (such as a motor or reducer) is installed at the top of the reaction vessel and drives the main shaft to rotate via a coupling or drive shaft. The stirring impeller is fixed to the main shaft and rotates with it to stir the slurry.

[0223] The impeller 209 typically has 2 to 4 layers, preferably 3 layers. The spacing between the impellers is determined by the height of the chamber, generally 1 / 4 to 1 / 3 of the chamber height. By setting multiple layers of impellers at different heights, comprehensive stirring of the slurry throughout the chamber can be achieved, promoting the vertical circulation and uniform mixing of the slurry, and avoiding slurry stratification or local concentration differences.

[0224] The type of impeller can be selected based on the properties of the slurry. For fly ash slurry, paddle impellers, turbine impellers, or frame impellers can be used. Paddle impellers have a simple structure and are suitable for low-viscosity slurries; turbine impellers have strong shear force and are suitable for applications requiring enhanced mixing; frame impellers cause gentler disturbance to the slurry and are suitable for applications where bubble breakage needs to be avoided. In this application, since it is necessary to maintain bubble stability (although bubble refinement technology was used in the previous embodiment, in this embodiment, if bubble refinement components are not configured, excessive bubble destruction caused by agitation needs to be avoided), paddle impellers or frame impellers are preferred.

[0225] The first and second stirring mechanisms can be driven by their respective independent drive devices, and their respective speeds can be adjusted independently; or they can be driven simultaneously by the same drive device through gear transmission, belt transmission, or other means, but a suitable transmission ratio needs to be set so that the stirring intensity of the first and second chambers matches their respective separation tasks.

[0226] (iv) Slag discharge mechanism.

[0227] A slag removal mechanism is located at the top of the reaction vessel to remove slag. In this embodiment, the design of the slag removal mechanism is coordinated with the flow direction of the slurry and slag to improve slag removal efficiency.

[0228] If the arrangement direction between the first chamber and the second chamber is horizontal and longitudinal, then an overflow trough 210 is provided on one side of the reaction vessel along the horizontal and transverse direction. The scum removal mechanism removes the scum by discharging it into the overflow trough.

[0229] The overflow tank is an upward-opening tank located on one side of the top of the reaction vessel. When the scum on the liquid surface reaches a certain thickness, or when pushed by the scum discharge mechanism, the scum overflows the liquid surface and flows into the overflow tank. The bottom of the overflow tank is connected to a scum collection pipe 211, through which the scum is discharged from the reaction vessel and enters a scum collection container or subsequent treatment equipment.

[0230] In one or more specific embodiments, the slag discharge mechanism includes a transmission device 213 and a scraper. Driven by the transmission device, the scraper pushes the scum towards the overflow tank. The scraper may be one or more horizontally arranged plates fixed to the transmission device 213 (such as a chain or push rod). The transmission device drives the scraper to perform linear reciprocating motion or rotational motion along the liquid surface. When the scraper passes the liquid surface, it pushes the scum 212 towards the overflow tank 210. After the scum 212 reaches the overflow tank 210, it overflows into the overflow tank 210.

[0231] The speed and frequency of the scraper movement can be adjusted and controlled according to the rate and thickness of scum formation. The scraper is made of stainless steel, rubber, or polyurethane, and must have sufficient strength to move the scum while avoiding excessive disturbance to the liquid surface, which could affect the stability of the scum.

[0232] (V) Overall working process and the principle of cascading efficiency enhancement.

[0233] The modified fly ash slurry enters the first chamber 205 through the slurry inlet. In the first chamber 205, bubbles generated by the first bubble generating unit move upwards, contact the slurry, capture some dioxin-like particles, and carry them to the surface. The stirring action of the first stirring mechanism promotes full contact between the slurry and the bubbles, improving the capture efficiency.

[0234] After initial separation in the first chamber, a portion of the slurry enters the second chamber through pre-reserved fluid channels at the bottom or top of baffle 203. In the second chamber 206, a second bubble generating unit produces new bubbles that come into contact with the slurry entering from the first chamber 205, further capturing dioxin-like particles that failed to be captured in the first chamber. The second stirring mechanism also promotes the contact between the slurry and the bubbles.

[0235] Through two-stage separation in the first and second chambers, the slurry undergoes two bubble capture processes, significantly improving the removal rate of dioxin-like particles. Even if some dioxin-like particles are not captured in the first chamber, they have a high chance of being captured in the second chamber, thus preventing these particles from being discharged with the detoxified slurry.

[0236] Bubbles carrying dioxin-like particles rise to the surface of the liquid in the first and second chambers, respectively, forming scum 212. The scum 212 is pushed towards the overflow tank by the scum discharge mechanism, overflows into the overflow tank, and is then discharged from the reaction vessel.

[0237] After two-stage separation, the detoxified slurry is discharged from the slurry outlet of the second chamber, containing extremely low levels of dioxins, achieving the goal of highly efficient detoxification.

[0238] The principle of cascading efficiency enhancement lies in dividing the inner cavity into multiple series of separation functional zones. The slurry must pass through each functional zone sequentially, undergoing a bubble capture and separation process in each zone. This "multi-line defense" design effectively prevents the "short-circuit" phenomenon of the slurry—that is, some slurry flows directly from the slurry inlet to the slurry outlet without sufficient air flotation.

[0239] The foregoing has described the relevant content of this disclosure. Those skilled in the art will be able to implement this disclosure based on these descriptions. All other embodiments obtained by those skilled in the art based on the foregoing content of this specification without inventive effort should fall within the scope of this disclosure.

Claims

1. A method for separating fly ash dioxins, characterized by: include: Fly ash is mixed with water to prepare fly ash slurry; An oxidant is added to the fly ash slurry to carry out an oxidation reaction, thereby oxidizing the reducing substances on the fly ash surface. An acid is added to the oxidized fly ash slurry to carry out a modification reaction, thereby using the acid to etch the fly ash, causing dioxin-like particles to dissociate from the fly ash surface and reveal hydrophobicity. Bubbles are generated or introduced into the fly ash slurry after the modification reaction. The bubbles are used to capture the dioxin-like particles and float to the surface to form scum, thereby separating the scum from the mother liquor to obtain a detoxified slurry.

2. The fly ash dioxin separation process of claim 1 wherein: The oxidant is selected from at least one of hydrogen peroxide, ozone, oxygen, sodium hypochlorite, calcium hypochlorite, potassium permanganate, sodium persulfate, ammonium persulfate, and sodium chlorate; the acid is selected from at least one of sulfuric acid, hydrochloric acid, and nitric acid.

3. The fly ash dioxin separation process of claim 1 wherein: Before generating or introducing bubbles into the modified fly ash slurry, the pH value of the modified fly ash slurry is controlled to be 6-12.

5.

4. The fly ash dioxin separation process of claim 3 wherein: By controlling the amount of acid used in the modification reaction, the pH value of the fly ash slurry after the modification reaction is controlled to be 6-12.

5.

5. The fly ash dioxin separation process of claim 4 wherein: By controlling the amount of acid used in the modification reaction, the pH value of the fly ash slurry after the modification reaction is controlled to be 8-11.

6. The fly ash dioxin separation process of claim 1 wherein: The oxidation reaction oxidizes sulfites in fly ash to sulfates and at least some low-valence metal ions to high-valence metal ions.

7. The fly ash dioxin separation process of claim 1 wherein: The process of adding an oxidant to the fly ash slurry for oxidation reaction is as follows: add hydrogen peroxide solution to the fly ash slurry, with a mass fraction of 27.5% and the amount of hydrogen peroxide solution added being 1%-5% of the mass of fly ash.

8. The fly ash dioxin separation process of claim 1 wherein: The process of adding acid to the oxidized slurry for modification is as follows: concentrated sulfuric acid is added to the oxidized fly ash slurry. The amount of concentrated sulfuric acid added is 20%-50% of the fly ash mass, calculated as 98% concentrated sulfuric acid.

9. A method for separating fly ash dioxins, characterized by: include: Fly ash is mixed with water to prepare fly ash slurry; Acid is added to fly ash slurry to carry out a modification reaction, thereby using acid to etch fly ash, causing dioxin-like particles to dissociate from the fly ash surface and reveal hydrophobicity; Bubbles are generated or introduced into the fly ash slurry after the modification reaction. The bubbles are used to capture the dioxin particles and float to the surface to form scum, thereby separating the scum from the mother liquor to obtain detoxified slurry. In this process, the pH value of the fly ash slurry after the modification reaction is controlled to be 6-12.5 by controlling the amount of acid used in the modification reaction.

10. The fly ash dioxin separation process of claim 9 wherein: By controlling the amount of acid used in the modification reaction, the pH value of the fly ash slurry after the modification reaction is controlled to be 8-11.

11. The fly ash dioxin separation process of claim 9 wherein: The process of adding acid to fly ash slurry for modification reaction is as follows: concentrated sulfuric acid is added to fly ash slurry. The amount of concentrated sulfuric acid added is 20%-35% of the mass of fly ash, calculated as 98% concentrated sulfuric acid.

12. The fly ash dioxin separation process of any of claims 1-11, wherein: In the step of mixing fly ash with water, the D90 particle size of the fly ash particles is 40 micrometers to 250 micrometers.

13. The fly ash dioxin separation process of any of claims 1-11, wherein: When fly ash is mixed with water, the ratio of the mass of water to the mass of fly ash is 4-8.

14. The fly ash dioxin separation process of any of claims 1-11, wherein: The process of generating or introducing bubbles in the fly ash slurry after the modification reaction, capturing the dioxin particles by the bubbles and floating to form dregs, thereby separating the dregs from the mother liquor and obtaining detoxified slurry, is realized by a gas-liquid-solid three-phase coupling separation device; The gas-liquid-solid three-phase coupling separation device comprises: a reaction container having an inner cavity containing fly ash slurry, and a slurry inlet and a slurry outlet communicating with the inner cavity; a bubble generating mechanism arranged inside or at the bottom of the reaction container for generating a bubble flow moving from bottom to top in the reaction container, which contacts the fly ash slurry entering from the slurry inlet and flowing to the slurry outlet, captures the dioxin particles and carries them to float to the liquid surface to form dregs, while the main body of the slurry not captured by the bubbles is discharged as detoxified slurry through the slurry outlet; a dregs removal mechanism arranged at the top of the reaction container for removing the dregs.

15. The fly ash dioxin separation process of claim 14 wherein: In the separation process in the gas-liquid-solid three-phase coupling separation device, a first separation aid and a second separation aid are also added to the fly ash slurry in the reaction container; The first separation aid is an alcohol compound selected from one or more of methyl isobutyl carbinol, fusel alcohol, pine oil, long-chain alcohol with carbon number of 8-14, and the addition amount is 2‰-6‰ of the mass of fly ash; The second separation aid is a hydrocarbon oil and / or an organic acid compound selected from one or more of kerosene, diesel oil, fuel oil, natural gas condensate oil, oleic acid, oxidized paraffin soap, tar oil, naphthenic acid, and the addition amount is 5‰-10‰ of the mass of fly ash.

16. Fly ash dioxin separation apparatus characterized by: For implementing the fly ash dioxin separation method as claimed in any one of claims 1-15, comprising: a slurry preparation device for mixing fly ash with water to prepare fly ash slurry; a slurry pretreatment device for adding an oxidizing agent to the fly ash slurry for oxidation reaction, thereby oxidizing the reducing substances on the surface of fly ash, and then adding acid to the fly ash slurry after oxidation treatment for modification reaction, thereby etching fly ash with acid to make dioxin particles dissociate from the surface of fly ash and expose hydrophobicity; Alternatively, the slurry pretreatment device is used to add acid to the fly ash slurry for modification reaction, thereby etching fly ash with acid to make dioxin particles dissociate from the surface of fly ash and expose hydrophobicity, and by controlling the amount of acid used in the modification reaction, the pH value of the fly ash slurry after the modification reaction is controlled to be 6-12.5; a gas-liquid-solid three-phase coupling separation device for generating or introducing bubbles in the fly ash slurry after the modification reaction, capturing the dioxin particles by the bubbles and floating to form dregs, thereby separating the dregs from the mother liquor and obtaining detoxified slurry.

17. A method of fly ash treatment characterized by: After obtaining the dregs and detoxified slurry by the fly ash dioxin separation method as claimed in any one of claims 1-15, subsequent treatment is performed on the dregs and the detoxified slurry, respectively; The subsequent treatment of the scum includes pyrolyzing the scum to decompose dioxins; The subsequent treatment of the detoxified slurry includes the operation of separating different metal salts from the mother liquor of the detoxified slurry through multi-stage wastewater purification treatment.

18. The fly ash treatment method of claim 17, wherein: The multi-stage wastewater purification treatment includes the following steps in the order of operation: The detoxified slurry is subjected to a first solid-liquid separation treatment to obtain a first solid phase and a first mother liquor, respectively. A heavy metal scavenging agent is added to the first mother liquor to cause the heavy metal ions in the first mother liquor to react and form a first type of metal salt precipitate. After a second solid-liquid separation process, a second solid phase mainly containing the first type of metal salt precipitate and a second mother liquor are obtained. Add a hardening agent to the second mother liquor and adjust the pH of the second mother liquor to cause the calcium ions and / or magnesium ions in the second mother liquor to react and form a second type of metal salt precipitate. After the third solid-liquid separation treatment, a third solid phase containing mainly the second type of metal salt precipitate and a third mother liquor are obtained. The third mother liquor is subjected to evaporation and crystallization treatment to obtain crystalline salt mainly containing sodium chloride and / or potassium chloride, as well as condensate.

19. The fly ash treatment method of claim 18, wherein: The acid is sulfuric acid, and the first solid phase mainly contains gypsum. The first solid phase is washed with water from the condensate of the evaporation and crystallization process to obtain the gypsum product.

20. A fly ash treatment system characterized by: include: The fly ash dioxin separation device as described in claim 16; A pyrolysis device, wherein the pyrolysis device is used to pyrolyze the scum discharged from the fly ash dioxin separation device to decompose dioxins; as well as A multi-stage wastewater purification treatment device is used to perform multi-stage wastewater purification treatment on the detoxified slurry discharged from the fly ash dioxin separation device, thereby separating different metal salts from the mother liquor of the detoxified slurry.

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