Fly ash washing method and washing tank used by same

Abstract

The invention discloses a fly ash washing method which comprises the following steps: step 1, introducing CO2 gas into a first-stage washing tank, and meanwhile, feeding fly ash slurry into the first-stage washing tank for first-stage washing; 2, the solid obtained after primary water washing is sent into a secondary water washing tank, microbubbles of CO2 and ozone are introduced into the secondary water washing tank, and secondary water washing is carried out; 3, the solid obtained after second-stage washing is sent into a third-stage washing tank for third-stage washing, CO2 and ozone microbubbles are introduced into the third-stage washing tank, and washing liquid obtained after second-stage washing is sent back to the first-stage washing tank; and 4, the solid obtained after third-stage washing enters a follow-up treatment procedure, and washing liquid is sent back to the second-stage washing tank. According to the washing method of the fly ash, microbubbles of CO2 and ozone are introduced into the washing liquid, so that dioxin in the fly ash can be effectively removed.

Description

Technical Field

[0001] The present invention relates to the field of fly ash washing, in particular to a fly ash washing method and a washing tank used therefor. Background Art

[0002] Fly ash, the tiny particles emitted during waste combustion, has a complex composition, containing significant amounts of dioxins, soluble salts, and heavy metals. Dioxins are highly toxic, stable, and difficult-to-degrade organic pollutants that easily accumulate in organisms. They not only severely pollute the environment but also pose significant risks to human health, including causing cancer, impairing the immune system, and affecting reproductive development.

[0003] Currently, fly ash disposal typically requires water washing pretreatment. The primary function of water washing pretreatment is to dissolve soluble salts in the fly ash, thereby reducing the chlorine content in the solids. During the water washing process, soluble chlorine is dissolved. Traditional fly ash water washing pretreatment processes typically utilize three-stage countercurrent water washing, which relies primarily on mechanical agitation. This process is limited to physically dissolving soluble salts in the fly ash solids and is unable to remove dioxins. Summary of the Invention

[0004] The purpose of the present invention is to provide a fly ash washing method and a washing tank used therein, wherein the fly ash washing method can effectively remove dioxins in the fly ash by introducing microbubbles of CO2 and ozone into the washing liquid.

[0005] In order to achieve the above object, the present invention provides a method for washing fly ash, comprising:

[0006] Step 1: Introduce CO2 gas into the primary water washing tank, and at the same time, send the fly ash slurry into the primary water washing tank for primary water washing;

[0007] Step 2: The solid after the primary water washing is sent to a secondary water washing tank, and microbubbles of CO2 and ozone are introduced into the secondary water washing tank for secondary water washing;

[0008] Step 3: The solid after the secondary water washing is sent to the tertiary water washing tank for tertiary water washing, microbubbles of CO2 and ozone are introduced into the tertiary water washing tank, and the washing liquid after the secondary water washing is sent back to the primary water washing tank;

[0009] Step 4: The solids after the tertiary water washing enter the subsequent processing process, and the washing liquid is sent back to the secondary water washing tank.

[0010] Preferably, in step 2 and step 3, CO2 and ozone are connected to the secondary water washing tank and the tertiary water washing tank through a microbubble generator.

[0011] Preferably, CO2 and ozone are introduced into the water washing tank in the form of microbubbles respectively.

[0012] Preferably, the diameter of the microbubbles is set to 1-50 μm.

[0013] Preferably, the ozone concentration in the secondary water washing tank and the tertiary water washing tank is set to 5-15 mg / L.

[0014] Preferably, in step 2, the washing liquid after the primary washing is sent to a water purification unit for decalcification, weight removal and neutralization reaction.

[0015] The present invention also provides a water washing tank used in the fly ash water washing method, comprising a tank body (1) and a microbubble generator connected to the tank body (1), wherein the top of the tank body (1) is provided with a feed port (11) and an exhaust port (12), and the bottom is provided with a discharge port (13), and a tubular distributor (31) is further provided in the tank body (1), and the microbubble generator inputs microbubbles into the tank body (1) through the tubular distributor (31).

[0016] Preferably, a stirrer (15) for stirring the slurry is provided in the tank body (1).

[0017] Preferably, a slurry discharge port (14) is further provided at the lower portion of the tank body (1).

[0018] Preferably, the tubular distributor (31) is located above the slurry discharge port (14).

[0019] According to the above technical solution, the present invention first pumps the fly ash slurry into a primary water washing tank for primary water washing. During the primary water washing process, the washing liquid has a high chloride ion concentration and a high calcium ion concentration. The main functions of this process include: lowering the pH value and dechlorinating the fly ash.

[0020] During the primary water washing stage, the initial pH of the fly ash slurry is typically greater than 12, indicating a strong alkalinity. In this highly alkaline environment, many metal ions readily combine with hydroxide ions to form insoluble hydroxide precipitates. For example, calcium ions combine with hydroxide ions to form calcium hydroxide, a slightly soluble substance that easily precipitates.

[0021] When CO2 gas is introduced into the water wash tank, it dissolves in water to form carbonic acid (H2CO3), a weak acid that lowers the pH of the system. As the pH of the system decreases, the fly ash slurry in the primary water wash tank gradually changes from strongly alkaline to neutral or weakly alkaline.

[0022] Under strong alkaline conditions, calcium ions easily form precipitates, which will encapsulate the soluble chlorine (such as calcium chloride CaCl2) in the fly ash, thereby hindering the further dissolution of the soluble chlorine. By introducing CO2 gas to lower the pH value, as the pH value of the system decreases, under the condition that the pH value is gradually lowered by introducing CO2 gas, these precipitates will gradually dissolve, so that the calcium ions exist mainly in a dissolved state, thereby releasing the soluble chlorine that was originally encapsulated, achieving the effect of promoting the dissolution of soluble chlorine. Therefore, the introduction of CO2 gas suppresses the precipitation reaction of calcium ions and hydroxide ions by lowering the pH value, reducing the generation of precipitates such as Ca(OH)2. This avoids the encapsulation of soluble chlorine by the precipitate, allowing the soluble chlorine to be more fully dissolved in the water wash solution, thereby improving the efficiency of water washing and dechlorination.

[0023] After CO2 is introduced into the primary water wash, CO2 can react with Ca in the liquid phase. 2+ The reaction generates CaCO3 precipitate, which prevents soluble chloride salts such as CaCl2 from re-precipitating due to excessive calcium ion concentration, and achieves the effect of decalcifying the fly ash slurry.

[0024] Introducing CO2 into the primary water wash can also promote the dissolution of insoluble chloride salts, such as CaClOH, Friedel salt, and Ca6(CO3)5(OH)2Cl. CO2 accelerates the decomposition of insoluble chloride salts through acidification reactions. For example, CaClOH is originally insoluble, but under acidic conditions it can be converted into soluble CaCl2 and removed through water washing.

[0025] Therefore, by introducing CO2 gas into the primary water washing tank, the pH value of the system can be lowered, the dissolution efficiency of chlorine can be increased, and thus the effect of water washing and dechlorination can be improved.

[0026] After the primary wash, the fly ash slurry is pumped to a solid-liquid separator for solid-liquid separation. The solids enter the secondary wash tank for secondary washing. The wash liquid then enters the water purification unit for decalcification, weight removal, and neutralization. Decalcification is performed using sodium carbonate precipitation, and neutralization is performed using hydrochloric acid. By introducing CO2 into the primary wash process, sodium carbonate consumption can be reduced by 10% and hydrochloric acid consumption by 90%. Therefore, adding CO2 to the primary wash significantly reduces the treatment costs of the water purification unit.

[0027] During the secondary water wash process, a microbubble generator introduces CO2 and ozone microbubbles into the wash liquid. The high surface area and low buoyancy of the microbubbles significantly improve ozone dissolution efficiency. In the secondary water wash tank, the use of ozone microbubbles can increase the peak liquid-phase ozone concentration to over 1.5 times that of traditional aeration, while also extending the gas-liquid contact time to tens of seconds or even minutes. Increasing the ozone content in the wash tank effectively increases ozone's efficiency in degrading dioxins.

[0028] Ozone microbubbles generate local high temperature and high pressure when they collapse, and through the pyrolysis reaction O3→O2+O( 1 D), triggering a chain reaction: O( 1 D) + H2O → 2·OH. The generated hydroxyl radical (·OH) has an oxidation potential of 2.8V, making it more susceptible to attacking the C-Cl bond (bond energy 339 kJ / mol) and aromatic ring system of dioxins than ozone molecules (2.07V). Therefore, the addition of ozone microbubbles to the secondary water wash can effectively remove dioxins from fly ash slurry.

[0029] Preferably, during the secondary water washing process, microbubbles of a mixed gas of CO2 and ozone are introduced, utilizing the local high temperature and high pressure generated when the CO2 microbubbles collapse to assist in the oxidation and removal of dioxins by ozone. Because the microbubble surface can generate an electric potential difference, which is a key factor affecting the adsorption properties of the bubble surface, the microbubbles introduced with the two mixed gases can utilize the strong electric potential difference generated by the CO2 microbubbles to fully adsorb dioxins. Simultaneously, as the ozone microbubbles shrink, the charge density of the double layer rapidly increases. When the bubbles burst, the dramatic disappearance of the gas-liquid interface releases the energy accumulated by the high concentration of positive and negative ions at the interface, which in turn stimulates the generation of a large number of hydroxyl radicals. Hydroxyl radicals have a strong oxidizing effect and are used to degrade dioxins in the water washing liquid. The adsorption of dioxins by the CO2 microbubbles allows the ozone microbubbles located around the CO2 microbubbles to act more effectively on dioxins, thereby achieving efficient degradation of dioxins in the water washing liquid.

[0030] At the same time, introducing CO2 into the wash water can maintain a low pH value. A low pH environment is conducive to the generation of hydroxyl radicals (·OH). Therefore, by introducing microbubbles of CO2 and ozone into the secondary wash, the generation of hydroxyl radicals (·OH) in the wash tank is increased by 40% to 60% compared to traditional aeration, significantly improving the dechlorination and ring-opening efficiency of dioxins.

[0031] Microbubbles form a gas-liquid-solid three-phase mixed layer in the fly ash-water washing liquid system, and the microjets generated by the bubble collapse promote the stripping and oxidation of dioxins on the surface of fly ash particles. At the same time, in the water washing liquid containing calcium ions, the microbubbles of carbon dioxide and ozone can simultaneously induce Ca 2+ CaCO3 precipitate is generated, thereby achieving synergistic treatment of dioxin degradation and system decalcification in the secondary water washing stage.

[0032] Therefore, introducing CO2 and ozone microbubbles into the secondary water wash can improve the removal efficiency of ozone microbubbles on dioxins, and can also achieve decalcification of the system.

[0033] After the secondary wash, the fly ash slurry is pumped to the solid-liquid separator for solid-liquid separation. The solids enter the tertiary wash tank for tertiary washing, and the wash liquid is returned to the primary wash tank for reuse. The wash liquid obtained from the secondary wash solid-liquid separation is stored in the wash liquid storage tank and can be pumped back into the primary wash tank when needed.

[0034] During the tertiary water washing process, a microbubble generator is used to continue to introduce CO2 and ozone microbubbles into the water washing liquid. With the assistance of CO2, the hydroxyl groups generated when the ozone microbubbles collapse are used to fully degrade the dioxins in the fly ash slurry. After the tertiary water washing, the fly ash slurry is pumped to the solid-liquid separation device for solid-liquid separation. The solid enters the next process, such as drying in the drying device, and the water washing liquid returns to the secondary water washing tank for reuse.

[0035] The fly ash washing method uses CO2 to adjust the pH value of the fly ash slurry in the first-stage washing tank, thereby improving the dechlorination effect of the washing. In the second-stage and third-stage washing, the hydroxyl radicals generated by the collapse of ozone microbubbles are used to remove dioxins in the fly ash slurry. At the same time, the CO2 microbubbles are used to increase the content of hydroxyl radicals in the system, thereby improving the dioxin removal efficiency of the washing process.

[0036] Other features and advantages of the present invention will be described in detail in the following detailed description. BRIEF DESCRIPTION OF THE DRAWINGS

[0037] The accompanying drawings are used to provide a further understanding of the present invention and constitute a part of the specification. Together with the following detailed description, they are used to explain the present invention but do not constitute a limitation of the present invention. In the accompanying drawings:

[0038] Figure 1 is a flow chart of a method for washing fly ash;

[0039] Figure 2 It is a structural diagram of a water washing tank;

[0040] Figure 3 It is a structural diagram of a tubular distributor.

[0041] Description of Reference Numerals

[0042] 1 tank body 31 pipe distributor

[0043] 14 slurry outlet 11 feed port

[0044] 12 Exhaust port 13 Discharge port

[0045] 32 gas interface 15 stirrer DETAILED DESCRIPTION

[0046] The following describes the specific embodiments of the present invention in detail with reference to the accompanying drawings. It should be understood that the specific embodiments described herein are only used to illustrate and explain the present invention and are not intended to limit the present invention.

[0047] In the present invention, unless otherwise specified, directional words such as "top, bottom, lower, above" contained in the terms merely represent the orientation of the terms in normal usage, or are common names understood by those skilled in the art, and should not be regarded as limitations on the terms.

[0048] See also Figure 1 The fly ash washing method comprises:

[0049] Step 1: Introduce CO2 gas into the primary water washing tank, and at the same time, send the fly ash slurry into the primary water washing tank for primary water washing;

[0050] Step 2: The solid after the primary water washing is sent to a secondary water washing tank, and microbubbles of CO2 and ozone are introduced into the secondary water washing tank for secondary water washing;

[0051] Step 3: The solid after the secondary water washing is sent to the tertiary water washing tank for tertiary water washing, microbubbles of CO2 and ozone are introduced into the tertiary water washing tank, and the washing liquid after the secondary water washing is sent back to the primary water washing tank;

[0052] Step 4: The solids after the tertiary water washing enter the drying device for drying, and the washing liquid is sent back to the secondary water washing tank.

[0053] Through the implementation of the above technical solution, the fly ash slurry is first pumped into the primary water washing tank for primary water washing. During the primary water washing process, the washing liquid has a high chloride ion concentration and a high calcium ion concentration. The main functions of this process include: lowering the pH value and dechlorinating the fly ash.

[0054] During the primary water washing stage, the initial pH of the fly ash slurry is typically greater than 12, indicating a strong alkalinity. In this highly alkaline environment, many metal ions readily combine with hydroxide ions to form insoluble hydroxide precipitates. For example, calcium ions combine with hydroxide ions to form calcium hydroxide, a slightly soluble substance that easily precipitates.

[0055] When CO2 gas is introduced into the water wash tank, it dissolves in water to form carbonic acid (H2CO3), a weak acid that lowers the pH of the system. As the pH of the system decreases, the fly ash slurry in the primary water wash tank gradually changes from strongly alkaline to neutral or weakly alkaline.

[0056] Under strong alkaline conditions, calcium ions easily form precipitates, which will encapsulate the soluble chlorine (such as calcium chloride CaCl2) in the fly ash, thereby hindering the further dissolution of the soluble chlorine. By introducing CO2 gas to lower the pH value, as the pH value of the system decreases, under the condition that the pH value is gradually lowered by introducing CO2 gas, these precipitates will gradually dissolve, so that the calcium ions exist mainly in a dissolved state, thereby releasing the soluble chlorine that was originally encapsulated, achieving the effect of promoting the dissolution of soluble chlorine. Therefore, the introduction of CO2 gas suppresses the precipitation reaction of calcium ions and hydroxide ions by lowering the pH value, reducing the generation of precipitates such as Ca(OH)2. This avoids the encapsulation of soluble chlorine by the precipitate, allowing the soluble chlorine to be more fully dissolved in the water wash solution, thereby improving the efficiency of water washing and dechlorination.

[0057] After CO2 is introduced into the primary water wash, CO2 can react with Ca in the liquid phase. 2+ The reaction generates CaCO3 precipitate, which prevents soluble chloride salts such as CaCl2 from re-precipitating due to excessive calcium ion concentration, and achieves the effect of decalcifying the fly ash slurry.

[0058] Introducing CO2 into the primary water wash can also promote the dissolution of insoluble chloride salts, such as CaClOH, Friedel salt, and Ca6(CO3)5(OH)2Cl. CO2 accelerates the decomposition of insoluble chloride salts through acidification reactions. For example, CaClOH is originally insoluble, but under acidic conditions it can be converted into soluble CaCl2 and removed through water washing.

[0059] Therefore, by introducing CO2 gas into the primary water washing tank, the pH value of the system can be lowered, the dissolution efficiency of chlorine can be increased, and thus the effect of water washing and dechlorination can be improved.

[0060] After the primary wash, the fly ash slurry is pumped to a solid-liquid separator for solid-liquid separation. The solids enter the secondary wash tank for secondary washing. The wash liquid then enters the water purification unit for decalcification, weight removal, and neutralization. Decalcification is performed using sodium carbonate precipitation, and neutralization is performed using hydrochloric acid. By introducing CO2 into the primary wash process, sodium carbonate consumption can be reduced by 10% and hydrochloric acid consumption by 90%. Therefore, adding CO2 to the primary wash significantly reduces the treatment costs of the water purification unit.

[0061] During the secondary water wash process, a microbubble generator introduces CO2 and ozone microbubbles into the wash liquid. The high surface area and low buoyancy of the microbubbles significantly improve ozone dissolution efficiency. In the secondary water wash tank, the use of ozone microbubbles can increase the peak liquid-phase ozone concentration to over 1.5 times that of traditional aeration, while also extending the gas-liquid contact time to tens of seconds or even minutes. Increasing the ozone content in the wash tank effectively increases ozone's efficiency in degrading dioxins.

[0062] Ozone microbubbles generate local high temperature and high pressure when they collapse, and through the pyrolysis reaction O3→O2+O( 1 D), triggering a chain reaction: O( 1 D)+H v O → 2·OH. The generated hydroxyl radical (·OH) has an oxidation potential of 2.8V, making it more susceptible to attacking the C-Cl bond (bond energy 339kJ / mol) and aromatic ring system of dioxins than ozone molecules (2.07V). Therefore, the addition of ozone microbubbles to the secondary water wash can effectively remove dioxins from fly ash slurry.

[0063] Preferably, during the secondary water washing process, microbubbles of a mixed gas of CO2 and ozone are introduced, utilizing the local high temperature and high pressure generated when the CO2 microbubbles collapse to assist in the oxidation and removal of dioxins by ozone. Because the microbubble surface can generate an electric potential difference, which is a key factor affecting the adsorption properties of the bubble surface, the microbubbles introduced with the two mixed gases can utilize the strong electric potential difference generated by the CO2 microbubbles to fully adsorb dioxins. Simultaneously, as the ozone microbubbles shrink, the charge density of the double layer rapidly increases. When the bubbles burst, the dramatic disappearance of the gas-liquid interface releases the energy accumulated by the high concentration of positive and negative ions at the interface, which in turn stimulates the generation of a large number of hydroxyl radicals. Hydroxyl radicals have a strong oxidizing effect and are used to degrade dioxins in the water washing liquid. The adsorption of dioxins by the CO2 microbubbles allows the ozone microbubbles located around the CO2 microbubbles to act more effectively on dioxins, thereby achieving efficient degradation of dioxins in the water washing liquid.

[0064] At the same time, introducing CO2 into the wash water can maintain a low pH value. A low pH environment is conducive to the generation of hydroxyl radicals (·OH). Therefore, by introducing microbubbles of CO2 and ozone into the secondary wash, the generation of hydroxyl radicals (·OH) in the wash tank is increased by 40% to 60% compared to traditional aeration, significantly improving the dechlorination and ring-opening efficiency of dioxins.

[0065] Microbubbles form a gas-liquid-solid three-phase mixed layer in the fly ash-water washing liquid system, and the microjets generated by the bubble collapse promote the stripping and oxidation of dioxins on the surface of fly ash particles. At the same time, in the water washing liquid containing calcium ions, the microbubbles of carbon dioxide and ozone can simultaneously induce Ca 2+ CaCO3 precipitate is generated, thereby achieving synergistic treatment of dioxin degradation and system decalcification in the secondary water washing stage.

[0066] Therefore, introducing CO2 and ozone microbubbles into the secondary water wash can improve the removal efficiency of ozone microbubbles on dioxins, and can also achieve decalcification of the system.

[0067] After the secondary wash, the fly ash slurry is pumped to the solid-liquid separator for solid-liquid separation. The solids enter the tertiary wash tank for tertiary washing, and the wash liquid is returned to the primary wash tank for reuse. The wash liquid obtained from the secondary wash solid-liquid separation is stored in the wash liquid storage tank and can be pumped back into the primary wash tank when needed.

[0068] During the tertiary water washing process, a microbubble generator is used to continue to introduce CO2 and ozone microbubbles into the water washing liquid. With the assistance of CO2, the hydroxyl groups generated when the ozone microbubbles collapse are used to fully degrade the dioxins in the fly ash slurry. After the tertiary water washing, the fly ash slurry is pumped to the solid-liquid separation device for solid-liquid separation. The solid enters the next process, such as drying in the drying device, and the water washing liquid returns to the secondary water washing tank for reuse.

[0069] The fly ash washing method uses CO2 to adjust the pH value of the fly ash slurry in the first-stage washing tank, thereby improving the dechlorination effect of the washing. In the second-stage and third-stage washing, the hydroxyl radicals generated by the collapse of ozone microbubbles are used to remove dioxins in the fly ash slurry. At the same time, the CO2 microbubbles are used to increase the content of hydroxyl radicals in the system, thereby improving the dioxin removal efficiency of the washing process.

[0070] Exhaust ports 12 are located above the primary, secondary, and tertiary water wash tanks. These ports collect gases from these tanks and deliver them to the gas purification system. Because fly ash contains organic components, volatile organic compounds (VOCs), such as benzene, toluene, and xylene, may be released during the water washing process. These substances are toxic and can negatively impact air quality and human health, requiring treatment in the gas purification system before discharge.

[0071] Preferably, a rotary microbubble generator is used to introduce CO2 gas into the washing tank, and the diameter of the microbubbles is controlled to be 1-50 μm. At the same time, the input amount of the bubbles is controlled to ensure that the bubble density is ≥10 5 pieces / mL.

[0072] Microbubbles have a small diameter of 1-50 μm, resulting in a much larger specific surface area than conventional bubbles. This increase in specific surface area means a larger contact area between gas and liquid per unit volume, significantly improving gas-liquid mass transfer efficiency. Furthermore, due to the small size of microbubbles, they experience less buoyancy in the liquid, allowing them to remain in the liquid longer and even remain suspended. This significantly improves the dissolution efficiency of CO2 in water, enabling more efficient carbonic acid generation, and thus allowing the introduction of CO2 gas to more effectively adjust pH.

[0073] In this embodiment, preferably, in step 2 and step 3, CO2 and ozone are connected to the secondary water washing tank and the tertiary water washing tank through the microbubble generator.

[0074] During the secondary and tertiary water washing processes, CO2 microbubbles are needed to assist ozone oxidation in removing dioxins. Therefore, CO2 microbubbles and ozone microbubbles need to be introduced into the water washing tanks respectively.

[0075] Since microbubbles generate local high temperature (greater than 2000K) and high pressure (greater than 5MPa) when they collapse, the pyrolysis reaction O3→O2+O( 1 D), triggering a chain reaction: O( 1 The hydroxyl radical (·OH) generated by the reaction D) + H2O → 2·OH has an oxidation potential of 2.8V, making it more susceptible to attacking the C-Cl bond (bond energy 339 kJ / mol) and aromatic ring system of dioxins than ozone molecules (2.07V). Therefore, using ozone microbubbles can reliably degrade dioxins.

[0076] If CO2 microbubbles are introduced into the water washing tank at the same time to maintain the pH of the water washing liquid at a low level, this will be very conducive to the formation of hydroxyl radicals, thereby effectively improving the degradation efficiency of dioxins by ozone microbubbles.

[0077] Ozone microbubbles are introduced into the water washing tank at the same time as CO2 microbubbles. Since the surface of the microbubbles can generate an electric potential difference, and this electric potential will lead to better adsorption performance of the microbubble surface, the strong electric potential difference generated by the CO2 microbubbles can be used to fully adsorb dioxin-like organic matter. At the same time, when the nearby ozone microbubbles collapse, the energy accumulated in the high concentration of positive and negative ions on the gas-liquid interface is released, and at the same time, a large number of hydroxyl free radicals are stimulated to generate, which are used to degrade these adsorbed dioxin-like substances.

[0078] When CO2 and ozone microbubbles burst, they generate microjets and localized high pressure, disrupting the liquid film resistance and accelerating the diffusion of CO2 and ozone within a specific spatial range. Preferably, tubular distributor 31 is positioned below the wash tank, preferably at a location with high fly ash content. This utilizes the microjets generated by the bursting of microbubbles to rapidly diffuse the hydroxyl radicals produced by the ozone microbubbles, allowing them to act on a wider range of dioxins.

[0079] Under the combined action of CO2 microbubbles and ozone microbubbles, the Ca in the washing tank is 2+ CaCO3 precipitation is generated, thereby achieving synergistic treatment of dioxin degradation and system decalcification.

[0080] In one embodiment, CO2 microbubbles and ozone microbubbles are respectively introduced into the tubular distributor 31 in the water washing tank through two interfaces. The CO2 microbubbles and ozone microbubbles are mixed in the tubular distributor 31 and enter the water washing tank through the outlet of the tubular distributor 31. In this way, the CO2 microbubbles and ozone microbubbles can be effectively mixed before entering the water washing tank, which can improve the mixing efficiency of the CO2 microbubbles and ozone microbubbles, so that the CO2 microbubbles and ozone microbubbles entering the water washing tank are close to each other. The CO2 microbubbles can more effectively adsorb dioxin-like substances near the ozone microbubbles, thereby improving the removal efficiency of dioxins in the water washing tank.

[0081] In one embodiment, the CO2 microbubbles and the ozone microbubbles are respectively connected to the same inlet of the tubular distributor 31, which can achieve a better mixing effect of the CO2 microbubbles and the ozone microbubbles.

[0082] In this embodiment, preferably, CO2 and ozone are introduced into the water washing tank in the form of microbubbles respectively.

[0083] Adding CO2 and ozone into the water washing tank in the form of microbubbles can significantly improve their mass transfer efficiency.

[0084] Microbubbles have a high specific surface area. Microbubbles with a diameter of 1-50μm have a specific surface area 3-5 times higher than traditional bubbles with a diameter greater than 1mm, which can accelerate the transfer of ozone from the gas phase to the liquid phase.

[0085] Microbubbles have low buoyancy, so using a microbubble generator to generate gas into microbubbles can extend the time the bubbles remain in the liquid. Microbubbles rise slowly, for example, a 50μm diameter microbubble rises at approximately 0.1mm / s. Therefore, gas entering the water wash tank in the form of microbubbles has a longer dissolution time, thereby improving gas dissolution efficiency.

[0086] At the same time, the cavitation effect of microbubbles can also promote the dissolution of gases. According to Henry's law, the local high pressure generated when microbubbles burst allows the gas to diffuse effectively under high pressure, thus further promoting the dissolution of gases.

[0087] Introducing CO2 and ozone into the wash tank in the form of microbubbles significantly improves their mass transfer efficiency, thereby increasing their concentrations in the wash tank and facilitating the capture of dioxins and calcium ions during the wash process. Preferably, ozone microbubbles are primarily used to remove dioxins. Therefore, in actual production, the amount of ozone introduced can be significantly greater than the amount of CO2 to prevent CO2 from occupying too much space in the wash tank and affecting ozone dissolution.

[0088] In this embodiment, preferably, the diameter of the microbubbles is set to 1 to 50 μm.

[0089] The high specific surface area and low buoyancy of microbubbles can improve the gas dissolution efficiency.

[0090] When the diameter of ozone microbubbles is 1 to 50 μm, the ozone dissolution efficiency can be significantly improved. The mass transfer coefficient at this time can reach 3.6 times that of traditional aeration, which increases the amount of ozone dissolved in the water washing tank by 3.6 times per unit time, thereby effectively improving the degradation rate of dioxins.

[0091] In this embodiment, preferably, the ozone concentration in the secondary water washing tank and the tertiary water washing tank is set to 5-15 mg / L.

[0092] By introducing ozone microbubbles into the water washing tank and controlling the diameter of the ozone microbubbles to 1-50μm, the microbubbles increase the peak liquid phase concentration of ozone to more than 1.5 times that of traditional aeration, and at the same time extend the gas-liquid contact time to tens of seconds or even minutes, so that the ozone concentration in the water washing tank reaches 5-15mg / L.

[0093] In this embodiment, preferably, in step 2, the washing liquid after the primary washing is sent to a water purification unit for decalcification, weight removal and neutralization reaction.

[0094] The fly ash slurry after the first-level water washing is pumped to the solid-liquid separation device for solid-liquid separation, and the solid enters the secondary water washing tank for secondary water washing. The separated washing liquid enters the water purification unit for decalcification, weight removal and neutralization reaction. Sodium carbonate is used for precipitation reaction during decalcification, and hydrochloric acid is used for neutralization reaction.

[0095] Since a large amount of CO2 is introduced during the primary water washing process, the calcium ions in the washing liquid have been initially precipitated. Therefore, the consumption of sodium carbonate Na2C and ozone can be reduced by 10% during the decalcification and weight removal stage; and after the pH value is lowered through the primary water washing, the consumption of hydrochloric acid can be reduced by 90%.

[0096] The present invention also provides a water washing tank used in the fly ash water washing method, comprising a tank body 1 and a microbubble generator connected to the tank body 1. The top of the tank body 1 is provided with a feed port 11 and an exhaust port 12, and the bottom is provided with a discharge port 13. The tank body 1 also includes a tubular distributor 31, and the microbubble generator inputs microbubbles into the tank body 1 through the tubular distributor 31.

[0097] Through the implementation of the above technical solution, a microbubble generator is used to generate microbubbles of a desired diameter, which are then fed into the tubular distributor 31 through the gas interface 32 and discharged into the tank body 1 through the outlet of the tubular distributor 31. These microbubbles that enter the tank body 1 are annihilated and dissolved in the solution in the tank body 1, reacting with the harmful chemicals in the solution to treat the solution.

[0098] When both CO2 and ozone microbubbles need to be introduced into the water wash tank, two microbubble generators are provided to process the CO2 and ozone gases, respectively. Microbubbles of both gases are then added to the water wash tank, and the CO2 microbubbles are used to assist the ozone microbubbles in degrading dioxins. The two microbubble generators can be connected to two gas interfaces 32, allowing the CO2 and ozone microbubbles to enter the water wash tank from both ends of the tubular distributor 31. Alternatively, each microbubble generator can have two outlet pipes, each connected to two gas interfaces 32, to ensure more thorough mixing of the CO2 and ozone microbubbles within the tubular distributor 31.

[0099] A feed port 11 is provided at the top of the tank body 1. Fly ash slurry or solids obtained by solid-liquid separation after water washing can enter the water washing tank through the feed port 11. The undissolved gas in the water washing tank will separate from the solution and enter the upper part of the water washing tank, and finally be discharged from the exhaust port 12.

[0100] A discharge port 13 is provided at the bottom of the water washing tank, and the discharge port 13 is connected to a pump, which pumps the fly ash slurry to a solid-liquid separation device for separation.

[0101] In this embodiment, preferably, an agitator 15 for agitating the slurry is provided in the tank body 1 .

[0102] In order to ensure that the solids entering from the feed port 11 can be evenly distributed in the liquid of the water washing tank, an agitator 15 is also provided in the tank body 1. Under the action of the agitator 15, the fly ash will be mixed with the water washing liquid in the water washing tank and distributed as evenly as possible, which is not only beneficial to the dissolution of soluble substances, but also beneficial to improving the working efficiency of CO2 and ozone microbubbles.

[0103] Preferably, the agitator 15 is configured as a multi-layer agitator 15. Due to the effect of gravity, the fly ash concentration below the water washing tank is higher, and the fly ash concentration above the water washing tank is lower. In addition, the capacity of the water washing tank is larger and the height is usually higher. By configuring such a multi-layer agitator 15, the uniform dispersion of fly ash in the water washing tank can be more effectively promoted.

[0104] In this embodiment, preferably, a slurry discharge port 14 is further provided at the lower portion of the tank body 1 .

[0105] If the discharge port 13 is blocked, the slurry in the washing tank can be discharged through the slurry discharge port 14 , or the blockage of the discharge port 13 can be cleared through the slurry discharge port 14 .

[0106] In this embodiment, preferably, the pipe distributor 31 is located above the slurry discharge port 14 .

[0107] The tubular distributor 31 is positioned above the slurry discharge port 14 to prevent excessive fly ash concentration from clogging the outlet of the tubular distributor 31 .

[0108] The outlets of the tubular distributor 31 are evenly distributed along the circumference of each pipeline of the tubular distributor 31, so that the microbubbles can enter the water washing tank more evenly. These entering microbubbles will stir the liquid in the water washing tank, promote the uniform distribution of fly ash around the tubular distributor 31, and help improve the working efficiency of ozone microbubbles.

[0109] The preferred embodiments of the present invention are described in detail above in conjunction with the accompanying drawings. However, the present invention is not limited to the specific details in the above embodiments. Within the technical concept of the present invention, various simple modifications can be made to the technical solution of the present invention, and these simple modifications all fall within the scope of protection of the present invention.

[0110] It should also be noted that the various specific technical features described in the above specific embodiments can be combined in any appropriate manner without contradiction. In order to avoid unnecessary repetition, the present invention will not further describe various possible combinations.

[0111] In addition, the various embodiments of the present invention may be arbitrarily combined, and as long as they do not violate the concept of the present invention, they should also be regarded as the contents disclosed by the present invention.

Claims

1. A method for washing fly ash, characterized in that: include: Step 1: Introduce CO2 gas into the primary water washing tank, and at the same time, send the fly ash slurry into the primary water washing tank for primary water washing; Step 2: The solid after the primary water washing is sent to a secondary water washing tank, and microbubbles of CO2 and ozone are introduced into the secondary water washing tank for secondary water washing; Step 3: The solid after the secondary water washing is sent to the tertiary water washing tank for tertiary water washing, microbubbles of CO2 and ozone are introduced into the tertiary water washing tank, and the washing liquid after the secondary water washing is sent back to the primary water washing tank; Step 4: The solids after the tertiary water washing enter the subsequent processing process, and the washing liquid is sent back to the secondary water washing tank.

2. The fly ash washing method according to claim 1, characterized in that: In step 2 and step 3, CO2 and ozone are connected to the secondary water washing tank and the tertiary water washing tank through the microbubble generator.

3. The fly ash washing method according to claim 2, characterized in that: CO2 and ozone are introduced into the water washing tank in the form of micro bubbles.

4. The method for washing fly ash according to claim 3, characterized in that: The diameter of the microbubbles is set to 1 to 50 μm.

5. The method for washing fly ash according to claim 4, characterized in that: The ozone concentration in the secondary water washing tank and the tertiary water washing tank is set to 5-15 mg / L.

6. The method for washing fly ash according to claim 1, characterized in that: In step 2, the washing liquid after the primary washing is sent to a water purification unit for decalcification, weight removal and neutralization reaction.

7. A water washing tank used in the fly ash water washing method according to any one of claims 1 to 6, characterized in that: The invention comprises a tank body (1) and a microbubble generator connected to the tank body (1); a feed port (11) and an exhaust port (12) are provided at the top of the tank body (1); a discharge port (13) is provided at the bottom; a tubular distributor (31) is also provided in the tank body (1); and the microbubble generator inputs microbubbles into the tank body (1) through the tubular distributor (31).

8. The water washing tank according to claim 7, characterized in that: A stirrer (15) for stirring the slurry is provided in the tank body (1).

9. The water washing tank according to claim 7, characterized in that: The lower part of the tank body (1) is also provided with a slurry discharge port (14).

10. The water washing tank according to claim 9, characterized in that: The tubular distributor (31) is located above the slurry discharge port (14).

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