A method and system for efficiently detoxifying, improving and reusing waste incineration fly ash

Abstract

The present invention relates to hazardous waste treatment technology, and aims to provide a method and system for efficient detoxification, quality improvement and reuse of fly ash from garbage incineration. The method utilizes a stirred ball mill reactor, a secondary water washing unit, a tertiary water washing unit and a fired-free brick preparation unit arranged in sequence, and couples a wet mechanochemical method with a carbonation, multi-stage water washing and fired-free pressing treatment process to achieve detoxification, quality improvement and reuse of fly ash from garbage incineration; before the flue gas is introduced to start the carbonation reaction, the fly ash is first subjected to a wet mechanical ball milling pretreatment, and a heavy metal composite stabilizer is added according to the characteristics of the reaction system, so that phosphate and tris-mercapto-s-triazine trisodium salt react with heavy metals respectively to stabilize the heavy metals in the solid phase medium. The present invention can improve the ability of fly ash to seal carbon dioxide, and the hardness of the obtained water washing liquid is lower than , and the heavy metal content is extremely low, which reduces the cost of the existing evaporation crystallization process; the risk of heavy metal leaching is low, the fly ash dechlorination efficiency is high, and the mechanical properties of the prepared fired-free bricks are better than those of the prior art.

Description

Technical Field

[0001] The present invention relates to hazardous waste treatment technology, in particular to a method and system for efficient detoxification, quality improvement and reuse of waste incineration fly ash, and involves efficient desalination, heavy metal stabilization and resource utilization of waste incineration fly ash. Background Art

[0002] Municipal solid waste incineration has become the mainstream technology for harmless waste treatment. Incineration not only effectively sterilizes, reduces volume, and reduces waste quantity, but also generates significant amounts of heat and electricity, providing power and heating for urban development and maximizing waste-to-energy utilization. However, fly ash, a byproduct of waste incineration, is rich in toxic and hazardous substances such as chlorides, heavy metals, and dioxins, and is listed on the National List of Hazardous Wastes.

[0003] In addition to being a hazardous waste, fly ash from garbage incineration also has resource properties. Fly ash is rich in chloride salts, potassium salts, calcium oxide, silicon dioxide, aluminum oxide, etc. If it is disposed of by landfill, it will occupy land and waste resource materials in the fly ash. Relevant studies have shown that the fly ash can be washed with water to remove chloride salts, and then sodium chloride and potassium chloride can be evaporated and crystallized and recovered through steam mechanical recompression technology. The washed fly ash can be solidified and stabilized by heavy metals and dioxins can be removed to achieve harmless and resource-based modification of the fly ash. However, the dechlorination effect of fly ash washing is limited. During the washing process, a large amount of calcium dissolves into the washing liquid, which increases the hardness removal (decalcification) cost of the subsequent washing liquid evaporation and crystallization process. In addition, the compatibility and heavy metal stability of the hydration reaction of the washed fly ash are poor. Both the washing liquid and the washed fly ash have heavy metal environmental risks.

[0004] To improve the dechlorination efficiency of fly ash during the water washing process and reduce carbon emissions during fly ash disposal, the Chinese invention patent "A method for simultaneous solidification of carbon dioxide and deep dechlorination of waste incineration fly ash" (CN 114888056 A) introduces a method for improving the three-stage countercurrent water washing process of fly ash. This method introduces flue gas carbon dioxide during the first and second water washing processes of the fly ash, thereby achieving deep dechlorination of the fly ash and carbon dioxide sequestration. However, this technology does not solve the problem of high calcium concentration in the water washing liquid, and other heavy metals other than Pb and Zn (such as Cd, Cu, Cr, Ni) are not efficiently stabilized. In addition, the calcium carbonate precipitate generated during the carbonation process easily wraps around the fly ash particles, thereby hindering the carbon fixation and dechlorination of the fly ash, resulting in relatively limited carbon fixation efficiency and dechlorination effect. This method only considers the dechlorination and carbon fixation of the fly ash, and does not consider the subsequent resource utilization activity of the fly ash. The silicon, calcium, and aluminum components in the fly ash exist in the form of low-activity oxides, and the resource utilization potential is weak.

[0005] In order to further improve the carbon fixation and dechlorination capacity of fly ash, and to activate the silicon and aluminum components in fly ash to improve its resource utilization potential, the Chinese invention patent "A method for efficient solidification and synergistic carbon fixation of heavy metals in waste incineration fly ash" (CN114210716A) introduces a method for dry ball milling pretreatment of fly ash, followed by carbonation treatment. This method reduces the average particle size of fly ash to below 5 microns, greatly increasing the specific surface area and reaction activity of fly ash particles, and can effectively improve the carbon fixation capacity and dechlorination effect of fly ash during the carbonation treatment process. However, this method still cannot avoid the negative impact of the inert layer of calcium carbonate on the carbonation and dechlorination reactions, and also does not solve the problems of high calcium concentration and heavy metal stabilization in the water wash.

[0006] In view of the above technical status, there is an urgent need to propose new technologies for the low-carbon, high-efficiency and low-cost resource utilization of waste incineration fly ash, which can be used to simultaneously achieve efficient carbon fixation and deep dechlorination of fly ash, as well as efficient decalcification of water washing liquid and efficient solidification and stabilization of heavy metals. Summary of the Invention

[0007] The technical problem addressed by this invention is to overcome the shortcomings of existing technologies and provide a system and method for the efficient detoxification, quality improvement, and reuse of waste incineration fly ash. This technology simultaneously achieves efficient carbon fixation and deep dechlorination of fly ash, as well as efficient decalcification and heavy metal solidification and stabilization of the wash solution. This effectively reduces wash solution processing costs and heavy metal environmental risks, while improving the quality and efficiency of fly ash resource utilization.

[0008] To solve the technical problem, the solution of the present invention is:

[0009] A method for efficiently detoxifying, upgrading and reusing waste incineration fly ash is provided. The method utilizes a stirred ball mill reactor, a secondary water washing unit, a tertiary water washing unit and a fired-free brick preparation unit arranged in sequence, and couples a wet mechanochemical method with a carbonation, multi-stage water washing and fired-free pressing treatment process to achieve detoxification, upgrading and reusing waste incineration fly ash. The method specifically comprises the following steps:

[0010] (1) Adding waste incineration fly ash, sodium hydroxide, a heavy metal composite stabilizer, and a secondary water wash solution into a stirred ball mill reactor, first starting stirring to perform wet mechanical ball milling pretreatment; then continuously introducing flue gas into the reactor while maintaining stirring to perform a wet mechanochemical coupled carbonation reaction; after the reaction is terminated, a primary slurry is obtained;

[0011] (2) The first-stage slurry is subjected to a centrifugal solid-liquid separation operation to obtain a first-stage water wash liquid and a first-stage water-washed fly ash. The first-stage water wash liquid is sent out of the system for evaporation and salt extraction, and the second-stage water-washed fly ash is sent to a second-stage water-washing stirring kettle. The third-stage water wash liquid is added to the second-stage water-washing stirring kettle, and stirring is started to perform water washing. After the water washing is completed, the second-stage slurry is obtained.

[0012] (3) performing a centrifugal solid-liquid separation operation on the secondary slurry to obtain a secondary water wash liquid and a secondary water-washed fly ash, the former of which is fed into a stirred ball mill reactor, and the latter is fed into a tertiary water-washing stirred tank; adding clean water into the tertiary water-washing stirred tank, starting stirring and performing water washing, and obtaining a tertiary slurry after the water washing is completed;

[0013] (4) performing a centrifugal solid-liquid separation operation on the tertiary slurry to obtain a tertiary water wash liquid and a tertiary water-washed fly ash. The former is fed into a secondary water-washed stirred tank, and the latter is used to prepare unburned bricks;

[0014] (5) Add the tertiary washed fly ash, waste incineration slag, mining tailings, fly ash, and cement into a mixer, add appropriate amount of water and mix thoroughly to obtain unburned brick slurry;

[0015] (6) Pressing the unburned brick slurry into shape and performing natural curing to finally obtain unburned bricks.

[0016] As a preferred embodiment of the present invention, in step (1), the heavy metal composite stabilizer is a mixture of sodium hydrogen phosphate and tris-mercapto-s-triazine trisodium salt, and the mass ratio of the two components is 5 to 9:1; the mass ratio of waste incineration fly ash, sodium hydroxide, and heavy metal composite stabilizer is 100:5 to 10:2 to 5; and the liquid-to-solid ratio of the reaction materials in the stirred ball mill reactor is 2 to 5:1, unit L / kg.

[0017] As a preferred embodiment of the present invention, in step (1), the time for wet mechanical ball milling pretreatment is 20 to 40 minutes, and the time for wet mechanochemical coupled carbonation reaction is 30 to 60 minutes; the mass ratio of balls to materials in the kettle is 1 to 3:1, calculated as kg-milling balls / kg-dry base material, and the stirring speed during the pretreatment and reaction process is controlled at 500 to 700 rpm.

[0018] As a preferred embodiment of the present invention, in step (1), the flue gas introduced into the kettle is waste incineration flue gas, the volume fraction of carbon dioxide in the flue gas is 10% to 15%, and the flue gas introduction rate is 10 to 50 L / min / kg-fly ash.

[0019] As a preferred embodiment of the present invention, in steps (2) to (4), when performing high-speed centrifugal solid-liquid separation operations on each level of slurry, the centrifuge speed is set to 5000 to 10000 rpm, and the centrifugation time is set to 10 to 20 minutes, which is the time required for centrifugal treatment of all the slurry produced by the ball mill reactor.

[0020] As a preferred embodiment of the present invention, in steps (3) and (4), the liquid-to-solid ratio in the secondary water washing stirring tank and the tertiary water washing stirring tank is 3 to 6:1, unit L / kg; the stirring rate during water washing is 500 to 1000 rpm, and the time is 15 to 30 minutes.

[0021] As a preferred embodiment of the present invention, in step (4), the moisture content of the tertiary washed fly ash is controlled to be 20-40%.

[0022] As a preferred embodiment of the present invention, in step (5), tertiary washed fly ash, waste incineration slag, mining tailings, fly ash, and cement are taken according to a dry basis mass ratio of 20-35:0-20:0-20:15-25:20-40; the amount of water added is controlled so that the water-cement ratio of the material in the mixer is 0.3-0.5, with the unit of kg-water / kg-dry basis ash; the stirring speed is 200-400 rpm, and the stirring time is 10-30 minutes.

[0023] As a preferred embodiment of the present invention, in step (5), during the pressing process, the pressure is set at 20-30 MPa; during the natural curing process, the temperature is maintained at 10-40°C, the humidity is maintained at 90-98%, and the curing time is 15-20 days.

[0024] The present invention also provides a system for realizing the above-mentioned method for efficient detoxification, quality improvement and reuse of waste incineration fly ash, which comprises a wet mechanochemical coupled carbonation treatment unit, a secondary water washing unit, a tertiary water washing unit, and a fired-free brick preparation unit arranged in sequence; wherein:

[0025] The mechanochemical method coupled with carbonation treatment unit includes a stirred ball mill reactor, a first-stage centrifuge, and various material conveying pipelines. The upper part of the stirred ball mill reactor is equipped with a fly ash / additive inlet, a second-stage water wash liquid inlet, and an exhaust gas outlet. The bottom of the reactor is equipped with a flue gas inlet and a first-stage slurry outlet.

[0026] The secondary water washing unit includes a secondary water washing agitator, a secondary centrifuge and various material conveying pipelines; the upper part of the secondary water washing agitator is provided with a primary water washing fly ash inlet and a tertiary water washing liquid inlet, and the bottom of the tank is provided with a secondary slurry outlet;

[0027] The three-stage water washing unit includes a three-stage water washing mixing kettle, a three-stage centrifuge and various material conveying pipelines; a secondary water washing fly ash inlet and a clean water inlet are provided on the upper part of the three-stage water washing mixing kettle, and a three-stage slurry outlet is provided at the bottom of the kettle;

[0028] The unburned brick preparation unit includes a three-stage water-washed fly ash storage bin, a mixer, a pressing machine, and a curing bin arranged in sequence;

[0029] In this system, each level of centrifuge has a slurry inlet, a water-washed fly ash outlet and a water-washing liquid outlet. The slurry inlet is connected to the slurry outlet at the bottom of the kettle in this unit through a pipeline, the water-washed fly ash outlet is connected to the next-level water-washing agitator or fly ash storage bin through a pipeline, and the water-washing liquid outlet is connected to the previous-level water-washing agitator, ball mill reactor or external evaporation and salt extraction equipment through a pipeline; based on this setting, the conveying direction of the water-washing liquid is opposite to the conveying direction of the fly ash; that is, the water-washing liquid of each level is conveyed in the order of the third-level water-washing agitator, the second-level water-washing agitator and the stirred ball mill reactor, and the water-washing fly ash of each level is conveyed in the order of the stirred ball mill reactor, the second-level water-washing agitator and the third-level water-washing agitator.

[0030] Description of the invention principle:

[0031] The system and method for efficiently detoxifying, upgrading, and reusing waste incineration fly ash proposed in this invention not only achieves efficient fly ash detoxification and carbon sequestration, but also significantly increases the potential for building materials from disposed fly ash. The main technical principles of this solution are as follows:

[0032] (1) Deep dechlorination:

[0033] The present invention applies mechanical grinding during the wet carbonation dechlorination process of fly ash. The repeated impact and compression of the mechanical force of the agitated ball mill breaks up the fly ash particles, disrupting the mineral structure that originally encapsulates and adsorbs chloride salts. This allows most of the chloride salts to come into contact with water and, under the action of the strong mechanical force, rapidly dissolve into the water. Insoluble chloride salts (such as Friedel's salt) are also exposed and fully react with CO2 to form soluble chloride salts, which dissolve and are then eluted.

[0034] The calcium carbonate produced during conventional wet carbonation processes tends to coat fly ash particles, inhibiting the removal of chloride salts from them. However, in the present method, the resulting calcium carbonate minerals are subjected to high-intensity mechanical forces, which not only prevent them from coating the fly ash particles but also transform them into micro- and nano-scale calcium carbonate. These three effects fully dissolve the chloride salts in the fly ash.

[0035] In addition, during the subsequent secondary and tertiary washing processes of the fly ash treated by the primary wet mechanochemical method coupled with carbonation, the chloride salts remaining in the solid material are further dissolved and removed. Since the direction of water flow is opposite to the direction of fly ash transportation, clean water is used as the washing liquid during the third stage of washing. In addition, the chloride salt content in the fly ash washed in the secondary stage has dropped to a low level after the first two stages of washing. Therefore, the chlorine content in the tertiary washing liquid is also low, making the chlorine content remaining in the fly ash washed in the tertiary stage less than 0.5%.

[0036] (2) Deep and efficient carbon sequestration:

[0037] Similar to the principle of deep dechlorination mentioned above, under the action of the mechanical force of ball milling, calcium hydroxide and basic calcium chloride are fully exposed to the carbonation reaction system. When flue gas containing high concentration of carbon dioxide is introduced, carbonation reaction occurs. During the generation process, calcium carbonate is squeezed and crushed by mechanical force and converted into micro-nano-scale calcium carbonate particles, avoiding the wrapping effect of calcium carbonate minerals, thereby effectively promoting the diffusion of CO2 and the release of alkaline substances inside the fly ash particles, inducing further occurrence of carbonation reaction.

[0038] In addition, the method of the present invention adds an appropriate amount of sodium hydroxide to the reaction system. The addition of sodium hydroxide can provide hydroxide ions for calcium chloride in the reaction system to react with CO2 for precipitation, which not only improves the carbon fixation efficiency of the reaction system but also greatly reduces the calcium ion concentration in the water washing liquid, significantly reducing the subsequent hardness removal (decalcification) cost required before the water washing liquid is evaporated and crystallized. The amount of sodium hydroxide added in the present invention should be controlled according to the addition ratio of the present invention. Too high or too low is not appropriate. When the amount of sodium hydroxide added is too low, the effective removal of calcium ions in the water washing liquid cannot be achieved; when the amount of sodium hydroxide added is too high, on the one hand, not only the reagent cost is increased but also the desalination pressure is increased. On the other hand, the high alkaline environment provided by sodium hydroxide makes it easier for amphoteric heavy metals to be released, exacerbating the risk of heavy metal pollution.

[0039] In addition, when the flue gas is introduced into the stirred ball mill, not only does a carbonation reaction occur to reduce the CO2 in the flue gas, but the acidic gases in the flue gas (such as sulfur dioxide and hydrogen chloride) are also absorbed by the highly alkaline fly ash, thereby achieving the effect of efficient decarbonization and deacidification of the flue gas.

[0040] (3) Detoxification of dioxins and efficient stabilization of heavy metals:

[0041] During the mechanical ball milling pretreatment and carbonation process, high-energy mechanical forces activate the Fe, Al, Mg, and Si oxides in the fly ash, generating oxygen vacancies that release electrons to attack the C-Cl bonds of the dioxins, leading to dioxin degradation via a dechlorination reaction. During the deep carbonation process, high concentrations of heavy metals such as Zn, Pb, and Ni in the fly ash react with carbon dioxide to form carbonate precipitates with low solubility. The resulting calcium carbonate minerals easily co-precipitate with zinc, lead, and nickel carbonates.

[0042] Furthermore, when the carbonation reaction is complete, the pH of the reaction system is controlled between 7 and 8, which not only ensures complete carbonation of the fly ash but also reduces the solubility of amphoteric heavy metals such as Pb and Zn within this pH range. Through the aforementioned carbonate chemical (co)precipitation and pH control, heavy metals such as Pb and Zn are effectively stabilized.

[0043] However, there are some toxic heavy metals (Cd, Cr, Cu) in the fly ash that are not affected by the stabilization effect of carbonate minerals. Therefore, for the specific reaction system of the present invention, a heavy metal composite stabilizer (mainly a mixture of phosphate and tri-mercapto-s-triazine trisodium salt) is added thereto. Under the action of mechanical force, the toxic heavy metals (Cd, Cr, Cu) on the surface and inside of the fly ash particles can fully react with the heavy metal composite stabilizer. Among them, phosphate forms a stable phosphate mineral with the heavy metal, and tri-mercapto-s-triazine trisodium salt chelates with the heavy metal to stabilize the heavy metal in the solid phase medium. In addition, by appropriately proportioning the two heavy metal stabilizers and setting a suitable addition ratio, the heavy metals are efficiently stabilized without affecting the subsequent evaporation and crystallization of the water washing liquid and the construction material utilization of the treated fly ash.

[0044] (4) Activated fly ash for building materials:

[0045] Before the carbonation reaction begins (i.e., before the flue gas is introduced), the present invention first performs a wet mechanical ball milling pretreatment on the fly ash for a period of time. During the pretreatment process, two principles are mainly involved: on the one hand, since the metallic aluminum in the fly ash easily reacts to produce hydrogen in a strong alkaline environment, which is not conducive to the subsequent use as a building material, the metallic aluminum in the fly ash is allowed to react and consume in advance under alkaline conditions to avoid the pH drop of the reaction system after the carbonation reaction begins, which is not conducive to the consumption of metallic aluminum; on the other hand, SiO2 in the fly ash can be activated and dissolved by alkaline substances such as Ca(OH)2 in the fly ash under the action of water environment and mechanical ball milling to generate calcium silicate minerals, thereby greatly improving the volcanic ash activity of the fly ash.

[0046] In addition, whether in the pretreatment stage or in the flue gas carbonation reaction stage, the fly ash particles in the aqueous phase system enhance the dispersion effect, thereby enhancing the effect of ball milling mechanical force squeezing and crushing the fly ash particles, producing more new surface and crystal defects, significantly reducing the particle size of fly ash particles and increasing the specific surface area and homogeneity of fly ash particles, playing a good role in filling pores in the hydration process of unfired bricks and providing more hydration sites.

[0047] According to the reaction principles described in the above three paragraphs, the calcium carbonate generated by the carbonation reaction of the present invention is micro-nano calcium carbonate. Calcium carbonate provides more nucleation sites during the cement hydration reaction and participates in the reaction in the later stage of the hydration reaction to further enhance the product strength. In addition, the chlorine content in the three-stage washed fly ash obtained by the present invention is lower than 0.5%, which avoids the negative impact of chloride ions on the performance of subsequent unburned brick products. In view of the characteristics of the prepared three-stage washed fly ash, the present invention proposes specific unburned brick material combinations and preparation process conditions. Within the scope specified by the present invention, high-performance unburned bricks can be prepared with a compressive strength greater than 30MPa.

[0048] Compared with the prior art, the present invention has the following beneficial technical effects:

[0049] (1) The present invention greatly improves the ability of fly ash to store carbon dioxide through mechanical force, so that the carbon storage capacity reaches more than 90%;

[0050] (2) The water wash liquid obtained by the treatment of the present invention has a hardness of less than 100 mg / L and an extremely low heavy metal content, and can be directly fed into the evaporation crystallization system, reducing the cost of the existing evaporation crystallization process by more than 20%.

[0051] (3) The stabilization efficiency of most toxic heavy metals in the fly ash obtained by the present invention is higher than 95%, and the risk of heavy metal leaching is significantly reduced, meeting the HJ / T 1134 fly ash recycling standard.

[0052] (4) The fly ash dechlorination efficiency obtained by the present invention is higher than 97%, and the chlorine content is lower than 0.5%, which is better than the 2% of the actual water washing process in existing projects and far lower than the HJ / T 1134 fly ash recycling standard.

[0053] (5) The hydration activity of the fly ash obtained by the present invention is significantly improved, and the mechanical properties of the unburned bricks prepared are better than those of the prior art.

[0054] (6) Compared with the existing fly ash disposal methods in the market, the method of the present invention not only reduces the fly ash treatment cost by more than 40%, but also the unburned brick products can generate considerable economic benefits. BRIEF DESCRIPTION OF THE DRAWINGS

[0055] Figure 1 It is a connection diagram of the device of the present invention;

[0056] Figure 2 It is a process flow chart of the present invention.

[0057] Figure 1 The figures are marked as follows: 1- stirred ball mill reactor, 2- fly ash / additive inlet, 3- tail gas outlet, 4- grinding balls, 5- flue gas pipeline, 6- primary slurry pipeline, 7- primary water washing liquid pipeline, 8- primary centrifuge, 9- primary water-washed fly ash pipeline, 10- secondary water washing liquid pipeline, 11- secondary water-washed stirring kettle, 12- secondary slurry pipeline, 13- secondary centrifuge, 14- secondary water-washed fly ash pipeline, 15- tertiary water washing liquid pipeline, 16- tertiary water-washed stirring kettle, 17- tertiary slurry pipeline, 18- clean water pipeline, 19- tertiary centrifuge, 20- tertiary slurry pipeline, 21- tertiary water-washed fly ash storage bin, 22- mixer, 23- pressing machine, 24- curing bin. DETAILED DESCRIPTION

[0058] The present invention will be further described below with reference to the accompanying drawings and specific embodiments.

[0059] Part I. Description of the System Composition of the Invention

[0060] like Figure 2 As shown, the present invention provides a waste incineration fly ash efficient detoxification and quality improvement reuse system, which comprises a wet mechanochemical coupled carbonation treatment unit, a secondary water washing unit, a tertiary water washing unit, and a fire-free brick preparation unit.

[0061] The wet mechanochemical coupled carbonation treatment unit includes a stirred ball mill reactor, a first-level centrifuge and a variety of material conveying pipelines; a fly ash / additive inlet and a second-level water washing liquid inlet are respectively arranged on the left and right sides of the upper part of the stirred ball mill reactor, and an exhaust gas outlet is also arranged on the upper part of the stirred ball mill reactor, and the second-level water washing liquid inlet is connected to the second-level water washing liquid pipeline; a flue gas inlet and a first-level slurry outlet are arranged at the bottom of the stirred ball mill reactor, the flue gas inlet is connected to the flue gas pipeline, and the first-level slurry outlet is connected to the first-level slurry pipeline; the first-level centrifuge is provided with a first-level slurry inlet, a first-level water-washed fly ash outlet, and a first-level water washing liquid outlet, the first-level slurry inlet is connected to the first-level slurry pipeline, the first-level water-washed fly ash outlet is connected to the first-level water-washed fly ash pipeline, and the first-level water washing liquid outlet is connected to the first-level water washing liquid pipeline; the first-level water washing liquid pipeline is connected to the inlet of the evaporation and salt extraction equipment.

[0062] The secondary water washing unit includes a secondary water washing stirring kettle, a secondary centrifuge and multiple material conveying pipelines; a primary water washing fly ash inlet and a tertiary water washing liquid inlet are respectively provided on the left and right sides of the upper part of the secondary water washing stirring kettle, the primary water washing fly ash inlet is connected to the primary water washing fly ash pipeline, and the tertiary water washing liquid inlet is connected to the tertiary water washing liquid pipeline; a secondary slurry outlet is provided at the bottom of the secondary water washing stirring kettle, and the secondary slurry outlet is connected to the secondary slurry pipeline; the secondary centrifuge is provided with a secondary slurry inlet, a secondary water washing fly ash outlet and a secondary water washing liquid outlet, the secondary slurry inlet is connected to the secondary slurry pipeline, the secondary water washing fly ash outlet is connected to the secondary water washing fly ash pipeline, and the secondary water washing liquid outlet is connected to the secondary water washing liquid pipeline.

[0063] The tertiary water washing unit includes a tertiary water washing stirring kettle, a tertiary centrifuge and a variety of material conveying pipelines; a secondary water washing fly ash inlet and a clean water inlet are respectively provided on the left and right sides of the upper part of the tertiary water washing stirring kettle, the secondary water washing fly ash inlet is connected to the secondary water washing fly ash pipeline, and the clean water inlet is connected to the clean water pipeline; a tertiary slurry outlet is provided at the bottom of the tertiary water washing stirring kettle, and the tertiary slurry outlet is connected to the tertiary slurry pipeline; the tertiary centrifuge is provided with a tertiary slurry inlet, a tertiary water washing fly ash outlet and a tertiary water washing liquid outlet, the tertiary slurry inlet is connected to the tertiary slurry pipeline, the tertiary water washing fly ash outlet is connected to the tertiary water washing fly ash storage bin, and the tertiary water washing liquid outlet is connected to the tertiary water washing liquid pipeline.

[0064] The unburned brick preparation unit comprises a three-stage water-washed fly ash storage bin, a mixer, a pressing machine and a curing bin which are sequentially connected by a conveying pipeline.

[0065] When the wet mechanochemical method is coupled with the carbonation treatment unit, the secondary water washing unit and the tertiary water washing unit, the water washing liquid conveying direction is opposite to the fly ash conveying direction. The water washing liquid is conveyed in sequence through the tertiary water washing stirring kettle, the secondary water washing stirring kettle and the stirring ball mill reactor, and the water-washed fly ash is conveyed in sequence through the stirring ball mill reactor, the secondary water washing stirring kettle and the tertiary water washing stirring kettle.

[0066] Part II Description of the Implementation Method of the Invention

[0067] Based on the above system, the present invention provides a method for efficiently detoxifying, upgrading and reusing waste incineration fly ash, which is a method for detoxifying, upgrading and reusing waste incineration fly ash as well as for making it into building materials, by using the aforementioned efficient detoxification, upgrading and reusing waste incineration fly ash system to achieve deep carbonization and dechlorination, efficient stabilization of heavy metals, and effective improvement of the quality of building materials.

[0068] The method specifically includes:

[0069] (1) The waste incineration fly ash is transported into a stirred ball mill reactor, and sodium hydroxide and a heavy metal composite stabilizer are added to the stirred ball mill reactor in a ratio of 5-10% and 2-5% of the fly ash mass, respectively. The heavy metal composite stabilizer is a mixture of sodium hydrogen phosphate and tris-mercapto-s-triazine trisodium salt, and their mass mixing ratio is set to 5-9:1. The mass ratio of balls to materials in the stirred ball mill is 1-3:1 (kg-grinding balls / kg-dry base material). Subsequently, a secondary water wash liquid is added to the stirred ball mill reactor to make the liquid-solid ratio reach 2-5:1 (L / kg). The stirred ball mill reactor is started to start wet mechanical ball milling pretreatment. The stirring speed of the stirred ball mill reactor is 500-700 rpm, and the pretreatment is carried out for 20-40 minutes. Flue gas is continuously introduced into the stirred ball mill reactor at a flue gas introduction rate of 10-50 L / min / kg-fly ash. The flue gas is waste incineration flue gas with a carbon dioxide content of 10% to 15%. At the same time, the ball mill continuously stirs the material to promote a wet mechanochemical coupled carbonation reaction, with a reaction time of 30 to 60 minutes. After the reaction is terminated, a first-grade slurry is obtained.

[0070] (2) performing a high-speed centrifugal solid-liquid separation operation on the primary slurry, wherein the high-speed centrifugal speed is set to 5000-10000 rpm, and the centrifugal time is set to 10-20 minutes, thereby obtaining a primary water wash liquid and a primary water-washed fly ash. The primary water wash liquid is directly used for evaporation and salt extraction, and the primary water-washed fly ash is transported into a secondary water-washing stirring kettle, and then a tertiary water wash liquid is added to the secondary water-washing stirring kettle so that the liquid-solid ratio reaches 3-6:1 (L / kg). The water washing time is set to 15-30 minutes, and the stirring rate is 500-1000 rpm. After the water washing is completed, a secondary slurry is obtained;

[0071] (3) The secondary slurry is subjected to a high-speed centrifugal solid-liquid separation operation, the high-speed centrifugal speed is set to 5000-10000 rpm, and the centrifugal time is set to 10-20 minutes, thereby obtaining a secondary water wash liquid and a secondary water-washed fly ash, the secondary water wash liquid is transported into the stirred ball mill reactor, the secondary water-washed fly ash is transported into the tertiary water-washing stirring kettle, and clean water is input into the tertiary water-washing stirring kettle, the liquid-solid ratio is set to 3-6:1 (L / kg), the water washing time is set to 15-30 minutes, the stirring rate is 500-1000 rpm, and after the water washing is completed, the tertiary slurry is obtained;

[0072] (4) subjecting the tertiary slurry to a high-speed centrifugal solid-liquid separation operation, with the high-speed centrifugal speed set at 5,000 to 10,000 rpm and the centrifugal time set at 10 to 20 minutes, thereby obtaining a tertiary water wash liquid and a tertiary water-washed fly ash, the tertiary water wash liquid entering the secondary water-washing agitator, and the tertiary water-washed fly ash being used for the subsequent preparation of unburned bricks, wherein the moisture content of the tertiary water-washed fly ash is controlled at 20 to 40%;

[0073] (5) adding the tertiary washed fly ash, waste incineration slag, mining tailings, fly ash, and cement into a mixer in a dry basis mass ratio of 20-35:0-20:0-20:15-25:20-40, adding an appropriate amount of water, controlling the water-cement ratio to 0.3-0.5 (kg-water / kg-dry basis ash), fully stirring, setting the mixer speed to 200-400 rpm, and stirring for 10-30 minutes to obtain a slurry for unburned bricks;

[0074] (6) Pressing the unburned brick slurry into shape, setting the pressing pressure to 20-30 MPa, and then performing natural curing at a curing temperature of 10-40°C, a humidity of 90-98%, and a curing time of 15-20 days, ultimately obtaining unburned bricks with high compressive properties.

[0075] Part III Specific implementation examples

[0076] The following specific examples are used to further illustrate the application of the present invention.

[0077] Example 1

[0078] A method for efficiently detoxifying, improving and reusing waste incineration fly ash comprises the following steps:

[0079] Step 1: Waste incineration fly ash is transferred into a stirred ball mill reactor, and sodium hydroxide and a heavy metal composite stabilizer are added to the stirred ball mill reactor at a ratio of 5% and 2% of the fly ash mass, respectively. The heavy metal composite stabilizer is a mixture of sodium hydrogen phosphate and tris-mercapto-s-triazine trisodium salt, and their mass blending ratio is set to 5:1. The mass ratio of balls to materials in the stirred ball mill is 1:1 (kg-grinding balls / kg-dry base material). Subsequently, a secondary water wash solution is added to the stirred ball mill reactor to achieve a liquid-to-solid ratio of 2:1 (L / kg). The stirred ball mill reactor is started to begin wet mechanical ball milling pretreatment at a stirring speed of 500 rpm. After 40 minutes of pretreatment, flue gas is continuously introduced into the stirred ball mill reactor at a rate of 10 L / min / kg-fly ash. The flue gas is waste incineration flue gas, and the volume fraction of carbon dioxide in the flue gas is 10%. At the same time, the ball mill continuously stirs to promote the wet mechanochemical coupled carbonation reaction of the material, and the reaction time is set to 60 minutes. After the reaction is terminated, a first-level slurry is obtained;

[0080] Step 2: The primary slurry is subjected to a high-speed centrifugal solid-liquid separation operation, with the high-speed centrifugal speed set to 5000 rpm and the centrifugal time set to 20 minutes, thereby obtaining a primary water wash liquid and a primary water-washed fly ash. The primary water wash liquid is directly used for evaporation and salt extraction, and the primary water-washed fly ash is conveyed into a secondary water-washing agitator. Subsequently, a tertiary water wash liquid is added to the secondary water-washing agitator to achieve a liquid-solid ratio of 3:1 (L / kg). The water washing time is set to 30 minutes and the stirring rate is 500 rpm. After the water washing is completed, a secondary slurry is obtained;

[0081] Step 3: The secondary slurry is subjected to a high-speed centrifugal solid-liquid separation operation, the high-speed centrifugal speed is set to 5000 rpm, and the centrifugal time is set to 20 minutes, thereby obtaining a secondary water wash liquid and a secondary water-washed fly ash. The secondary water wash liquid is conveyed into the stirred ball mill reactor, and the secondary water-washed fly ash is conveyed into the tertiary water-washing stirring kettle. Clean water is input into the tertiary water-washing stirring kettle. The clean water can be tap water. The liquid-solid ratio is set to 3:1 (L / kg). The water washing time is set to 30 minutes, and the stirring rate is 500 rpm. After the water washing is completed, the tertiary slurry is obtained;

[0082] Step 4: The tertiary slurry is subjected to a high-speed centrifugal solid-liquid separation operation. The high-speed centrifugal speed is set to 5000 rpm and the centrifugal time is set to 20 minutes, thereby obtaining a tertiary water washing liquid and a tertiary water-washed fly ash. The tertiary water washing liquid enters the secondary water-washing stirring kettle. The tertiary water-washed fly ash is used for the subsequent preparation of unburned bricks. The moisture content of the tertiary water-washed fly ash is controlled at 40%; the chlorine content of the tertiary water-washed fly ash is less than 0.5%, and the heavy metal leaching risk meets the "Technical Specifications for Pollution Control of Fly Ash from Municipal Waste Incineration" (HJ / T 1134-2020).

[0083] Step 5: Add the tertiary washed fly ash, waste incineration slag, mining tailings, fly ash, and cement into a mixer in a dry mass ratio of 30%: 0%: 15%: 15%: 40%, add an appropriate amount of water, control the water-cement ratio to 0.3 (kg-water / kg-dry basis ash), stir thoroughly, set the mixer speed to 200 rpm, and stir for 30 minutes to obtain a fire-free brick slurry;

[0084] Step 6: Press the unfired brick slurry into shape, set the pressing pressure to 20 MPa, and then carry out natural curing at a curing temperature of 10°C, a humidity of 90%, and a curing time of 20 days, ultimately obtaining high-performance unfired bricks with a compressive strength of more than 30 MPa.

[0085] Example 2

[0086] A method for efficiently detoxifying, improving and reusing waste incineration fly ash comprises the following steps:

[0087] Step 1: Waste incineration fly ash is transferred to a stirred ball mill reactor, and sodium hydroxide and a heavy metal composite stabilizer are added to the stirred ball mill reactor in a ratio of 7.5% and 3.5% of the fly ash mass, respectively. The heavy metal composite stabilizer is a mixture of sodium hydrogen phosphate and tris-mercapto-s-triazine trisodium salt, and their mass blending ratio is set to 7:1. The mass ratio of balls to materials in the stirred ball mill is 2:1 (kg-grinding balls / kg-dry base material). Subsequently, a secondary water wash solution is added to the stirred ball mill reactor to achieve a liquid-to-solid ratio of 3.5:1 (L / kg). The stirred ball mill reactor is started to begin wet mechanical ball milling pretreatment at a stirring speed of 600 rpm. After 30 minutes of pretreatment, flue gas is continuously introduced into the stirred ball mill reactor at a rate of 30 L / min / kg-fly ash. The flue gas is waste incineration flue gas, and the volume fraction of carbon dioxide in the flue gas is 12.5%. At the same time, the ball mill continuously stirs to promote the wet mechanochemical coupled carbonation reaction of the material, and the reaction time is set to 40 minutes. After the reaction is terminated, a first-level slurry is obtained;

[0088] Step 2: The primary slurry is subjected to a high-speed centrifugal solid-liquid separation operation, with the high-speed centrifugal speed set to 7500 rpm and the centrifugal time set to 15 minutes, thereby obtaining a primary water wash liquid and a primary water-washed fly ash. The primary water wash liquid is directly used for evaporation and salt extraction, and the primary water-washed fly ash is conveyed into a secondary water-washing agitator. Subsequently, a tertiary water wash liquid is added to the secondary water-washing agitator to achieve a liquid-solid ratio of 4.5:1 (L / kg). The water washing time is set to 20 minutes and the stirring rate is 750 rpm. After the water washing is completed, the secondary slurry is obtained;

[0089] Step 3: The secondary slurry is subjected to a high-speed centrifugal solid-liquid separation operation, the high-speed centrifugal speed is set to 7500 rpm, and the centrifugal time is set to 15 minutes, thereby obtaining a secondary water wash liquid and a secondary water-washed fly ash. The secondary water wash liquid is conveyed into the stirred ball mill reactor, and the secondary water-washed fly ash is conveyed into the tertiary water-washing stirred tank. Clean water is input into the tertiary water-washing stirred tank, and the clean water is selected from river water. The liquid-solid ratio is set to 4.5:1 (L / kg). The washing time is set to 20 minutes, and the stirring rate is 750 rpm. After the washing is completed, the tertiary slurry is obtained;

[0090] Step 4: The tertiary slurry is subjected to a high-speed centrifugal solid-liquid separation operation. The high-speed centrifugal speed is set to 7500 rpm and the centrifugal time is set to 15 minutes, thereby obtaining a tertiary water washing liquid and a tertiary water-washed fly ash. The tertiary water washing liquid enters the secondary water-washing stirring kettle. The tertiary water-washed fly ash is used for the subsequent preparation of unburned bricks. The moisture content of the tertiary water-washed fly ash is controlled at 30%; the chlorine content of the tertiary water-washed fly ash is less than 0.5%, and the heavy metal leaching risk meets the "Technical Specifications for Pollution Control of Fly Ash from Municipal Waste Incineration" (HJ / T 1134-2020).

[0091] Step 5: Add the tertiary washed fly ash, waste incineration slag, mining tailings, fly ash, and cement into a mixer at a dry mass ratio of 35%: 20%: 0%: 20%: 25%, add an appropriate amount of water, control the water-cement ratio to 0.4 (kg-water / kg-dry basis ash), stir thoroughly, set the mixer speed to 300 rpm, and stir for 20 minutes to obtain a slurry for unburned bricks;

[0092] Step 6: Press the unfired brick slurry into shape, set the pressing pressure to 25 MPa, and then carry out natural curing at a curing temperature of 25°C, a humidity of 94%, and a curing time of 18 days, ultimately obtaining high-performance unfired bricks with a compressive strength of more than 30 MPa.

[0093] Example 3

[0094] A method for efficiently detoxifying, improving and reusing waste incineration fly ash comprises the following steps:

[0095] Step 1: Waste incineration fly ash is transferred into a stirred ball mill reactor, and sodium hydroxide and a heavy metal composite stabilizer are added to the stirred ball mill reactor at a ratio of 10% and 5% of the fly ash mass, respectively. The heavy metal composite stabilizer is a mixture of sodium hydrogen phosphate and tris-mercapto-s-triazine trisodium salt, and their mass blending ratio is set to 9:1. The mass ratio of balls to materials in the stirred ball mill is 3:1 (kg-grinding balls / kg-dry base material). Subsequently, a secondary water wash solution is added to the stirred ball mill reactor to achieve a liquid-to-solid ratio of 5:1 (L / kg). The stirred ball mill reactor is started to begin wet mechanical ball milling pretreatment at a stirring speed of 700 rpm. After 20 minutes of pretreatment, flue gas is continuously introduced into the stirred ball mill reactor at a rate of 50 L / min / kg-fly ash. The flue gas is waste incineration flue gas, and the volume fraction of carbon dioxide in the flue gas is 15%. At the same time, the ball mill continuously stirs to promote the wet mechanochemical coupled carbonation reaction of the material, and the reaction time is set to 30 minutes. After the reaction is terminated, a first-level slurry is obtained;

[0096] Step 2: The primary slurry is subjected to a high-speed centrifugal solid-liquid separation operation, with the high-speed centrifugal speed set to 10,000 rpm and the centrifugal time set to 10 minutes, thereby obtaining a primary water wash liquid and a primary water-washed fly ash. The primary water wash liquid is directly used for evaporation and salt extraction, and the primary water-washed fly ash is conveyed into a secondary water-washing agitator. Subsequently, a tertiary water wash liquid is added to the secondary water-washing agitator to achieve a liquid-solid ratio of 6:1 (L / kg). The water washing time is set to 15 minutes and the stirring rate is 1,000 rpm. After the water washing is completed, a secondary slurry is obtained;

[0097] Step 3: The secondary slurry is subjected to a high-speed centrifugal solid-liquid separation operation, the high-speed centrifugal speed is set to 10,000 rpm, and the centrifugal time is set to 10 minutes, thereby obtaining a secondary water wash liquid and a secondary water-washed fly ash. The secondary water wash liquid is conveyed into the stirred ball mill reactor, and the secondary water-washed fly ash is conveyed into the tertiary water-washing stirred tank. Clean water is input into the tertiary water-washing stirred tank, and the clean water is distilled water obtained by evaporation and crystallization. The liquid-solid ratio is set to 6:1 (L / kg), the washing time is set to 15 minutes, and the stirring rate is 1,000 rpm. After the washing is completed, the tertiary slurry is obtained;

[0098] Step 4: The tertiary slurry is subjected to a high-speed centrifugal solid-liquid separation operation. The high-speed centrifugal speed is set to 10,000 rpm and the centrifugal time is set to 10 minutes, thereby obtaining a tertiary water washing liquid and a tertiary water-washed fly ash. The tertiary water washing liquid enters the secondary water-washing stirring kettle, and the tertiary water-washed fly ash is used for the subsequent preparation of unburned bricks. The moisture content of the tertiary water-washed fly ash is controlled at 20%; the chlorine content of the tertiary water-washed fly ash is less than 0.5%, and the heavy metal leaching risk meets the "Technical Specifications for Pollution Control of Fly Ash from Municipal Waste Incineration" (HJ / T 1134-2020).

[0099] Step 5: Add the tertiary washed fly ash, waste incineration slag, mining tailings, fly ash, and cement into a mixer in a dry mass ratio of 20%: 15%: 20%: 25%: 20%, add an appropriate amount of water, control the water-cement ratio to 0.5 (kg-water / kg-dry basis ash), stir thoroughly, set the mixer speed to 400 rpm, and stir for 10 minutes to obtain a slurry for unburned bricks;

[0100] Step 6: Press the unfired brick slurry into shape, set the pressing pressure to 30 MPa, and then carry out natural curing at a curing temperature of 40°C, a humidity of 98%, and a curing time of 15 days, ultimately obtaining high-performance unfired bricks with a compressive strength of more than 30 MPa.

[0101] The efficient detoxification, quality improvement and reuse system and method for waste incineration fly ash provided by the present invention have the advantages of low carbon, water saving and environmental protection. Compared with the traditional fly ash carbonation and water washing technology, the alkaline substances (calcium hydroxide, basic calcium chloride, etc.) and chloride salts (sodium chloride, potassium chloride, Friedel salt) inside the fly ash particles are continuously exposed to the reaction system through mechanical force, thereby achieving efficient deep carbon fixation and dechlorination of the fly ash; in addition, under the action of mechanical force, the heavy metals on the surface and inside the fly ash particles can fully react with the heavy metal stabilizer and carbon dioxide to achieve efficient stabilization of the heavy metals; after treatment, the fly ash particles are fully homogenized, the particle size is significantly reduced, the specific surface area is greatly increased, the hydration reaction activity and compatibility are also significantly increased, and it has good quality for building material utilization. The mechanical properties of the prepared unburned brick products are better than the current level on the market. It is a fly ash desalination, detoxification and quality improvement utilization technology with great commercial application prospects.

[0102] Obviously, those skilled in the art may make various subsequent applications, supplements, modifications, and variations to the present invention without departing from the spirit and scope of the present invention. If the various applications, supplements, modifications, and variations based on the present invention fall within the scope of the claims of the present invention and their equivalents, the present invention is intended to include such applications, supplements, modifications, and variations.

Claims

1. A method for efficiently detoxifying, upgrading and reusing fly ash from waste incineration, characterized in that: By using a stirred ball mill reactor, a secondary water washing unit, a tertiary water washing unit and a fired-free brick preparation unit arranged in sequence, and coupling a wet mechanochemical process with carbonation, multi-stage water washing and fired-free pressing, the waste incineration fly ash can be detoxified, upgraded and reused; The mechanochemical method coupled with carbonation treatment unit includes a stirred ball mill reactor, a primary centrifuge and multiple material conveying pipelines; a fly ash / additive inlet, a secondary water wash liquid inlet and an exhaust gas outlet are provided at the top of the stirred ball mill reactor, and a flue gas inlet and a primary slurry outlet are provided at the bottom of the reactor; The secondary water washing unit includes a secondary water washing stirring kettle, a secondary centrifuge and multiple material conveying pipelines; a primary water washing fly ash inlet and a tertiary water washing liquid inlet are provided at the top of the secondary water washing stirring kettle, and a secondary slurry outlet is provided at the bottom of the kettle; The three-stage water washing unit includes a three-stage water washing stirring kettle, a three-stage centrifuge and various material conveying pipelines; a secondary water washing fly ash inlet and a clean water inlet are provided on the upper part of the three-stage water washing stirring kettle, and a three-stage slurry outlet is provided at the bottom of the kettle; The unburned brick preparation unit includes a three-stage water-washed fly ash storage bin, a mixer, a pressing machine and a curing bin arranged in sequence; the centrifuges at each stage are each provided with a slurry inlet, a water-washed fly ash outlet and a washing liquid outlet; the slurry inlet is connected to the slurry outlet at the bottom of the kettle in the unit through a pipeline, the water-washed fly ash outlet is connected to the next-stage water-washed stirring kettle or fly ash storage bin through a pipeline, and the washing liquid outlet is connected to the previous-stage water-washed stirring kettle, ball mill reactor or external evaporation and salt extraction equipment through a pipeline; based on this arrangement, the conveying direction of the washing liquid is opposite to the conveying direction of the fly ash; that is, the washing liquid of each stage is conveyed in the order of the three-stage water-washed stirring kettle, the second-stage water-washed stirring kettle and the stirring ball mill reactor, and the washed fly ash of each stage is conveyed in the order of the stirring ball mill reactor, the second-stage water-washed stirring kettle and the third-stage water-washed stirring kettle; The method specifically comprises the following steps: (1) Adding waste incineration fly ash, sodium hydroxide, heavy metal composite stabilizer and secondary water washing liquid into a stirred ball mill reactor, first starting stirring to perform wet mechanical ball milling pretreatment; then continuously introducing flue gas into the reactor and maintaining stirring to perform wet mechanical chemical coupling carbonation reaction; after the reaction is terminated, a first-level slurry is obtained; the heavy metal composite stabilizer is a mixture of sodium hydrogen phosphate and trithiomethyl-s-triazine trisodium salt, and the mass ratio of the two components is 5-9:1; the mass ratio of waste incineration fly ash, sodium hydroxide and heavy metal composite stabilizer is 100:5-10:2-5; the liquid-solid ratio of the reaction materials in the stirred ball mill reactor is 2-5:1, unit L / kg; the flue gas introduced into the reactor is waste incineration flue gas, and the amount ratio of carbon dioxide in the flue gas to waste incineration fly ash is 60L:1kg; (2) The first-stage slurry is subjected to a centrifugal solid-liquid separation operation to obtain a first-stage water wash liquid and a first-stage water-washed fly ash. The first-stage water wash liquid is sent out of the system for evaporation and salt extraction, and the second-stage water-washed fly ash is sent to a second-stage water-washing stirring kettle. The third-stage water wash liquid is added to the second-stage water-washing stirring kettle, and stirring is started to perform water washing. After the water washing is completed, the second-stage slurry is obtained. (3) performing a centrifugal solid-liquid separation operation on the secondary slurry to obtain a secondary water wash liquid and a secondary water-washed fly ash, the former of which is fed into a stirred ball mill reactor, and the latter is fed into a tertiary water-washing stirred tank; adding clean water into the tertiary water-washing stirred tank, starting stirring and performing water washing, and completing water washing to obtain a tertiary slurry; (4) performing a centrifugal solid-liquid separation operation on the tertiary slurry to obtain a tertiary water wash liquid and a tertiary water-washed fly ash. The former is fed into a secondary water-washed stirred tank, and the latter is used to prepare unburned bricks; (5) According to the dry basis mass ratio of 20~35:0~20:0~20:15~25:20~40, take three-level water-washed fly ash, garbage incineration slag, mining tailings, fly ash, and cement; add the three-level water-washed fly ash, garbage incineration slag, mining tailings, fly ash, and cement into a mixer, control the amount of water added so that the water-cement ratio of the materials in the mixer is 0.3~0.5, unit: kg-water / kg-dry basis ash; fully stir to obtain unburned brick slurry; (6) pressing the unburned brick slurry into shape and performing natural curing to finally obtain unburned bricks; In the step (1), the time for wet mechanical ball milling pretreatment is 20 to 40 minutes, and the time for wet mechanochemical coupled carbonation reaction is 30 to 60 minutes; the mass ratio of the grinding balls in the kettle to the dry base material is 1 to 3:1, and the stirring speed during the pretreatment and reaction process is controlled at 500 to 700 rpm.

2. The method according to claim 1, characterized in that In the steps (2) to (4), when performing high-speed centrifugal solid-liquid separation operation on each level of slurry, the speed of the centrifuge is set to 5000-10000 rpm, and the centrifugation time is set to 10-20 minutes.

3. The method according to claim 1, characterized in that In the steps (3) and (4), the liquid-to-solid ratio in the secondary water washing stirring tank and the tertiary water washing stirring tank is 3-6:1, unit L / kg; the stirring rate during water washing is 500-1000 rpm, and the time is 15-30 minutes.

4. The method according to claim 1, wherein In the step (4), the moisture content of the tertiary washed fly ash is controlled to be 20-40%.

5. The method according to claim 1, characterized in that In the step (5), the stirring rate is 200-400 rpm, and the stirring time is 10-30 minutes.

6. The method according to claim 1, characterized in that In the step (5), during the pressing process, the pressure is set to 20-30 MPa; during the natural curing process, the temperature is maintained at 10-40° C., the humidity is maintained at 90-98%, and the curing time is 15-20 days.

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