Method for preparing high-strength stone through high-temperature melting of fly ash and solid waste

Abstract

The invention relates to a method for preparing high-strength stone through high-temperature melting of fly ash and solid waste. The method comprises the following steps: firstly, mixing the fly ash with oil-absorbing diatomite and waste activated carbon, and granulating to obtain a mixture; the silicon content of the mixture is not less than 35%; the average lower calorific value of the mixture is greater than or equal to 2500Kcal / kg; then, the mixture is placed in a vertical smelting furnace to be smelted, and slag is obtained; the slag is placed in a heat preservation mold for 2-4 days, and the high-strength stone is obtained after slow cooling; the smelting temperature is higher than 1300 DEG C. The technical problem to be solved is how to provide the method for preparing the high-strength stone through high-temperature melting of the fly ash and the solid waste, according to the method, water quenching and quenching treatment are not needed, high-temperature slag is directly poured into a heat preservation mold to be slowly cooled, and therefore a stone product with high density and high strength is prepared. The method can be widely applied to the fields of scenic spot grounds, stele stones, hundred-year aisle stone pillar pile foundations and the like.

Description

Technical Field

[0001] This invention belongs to the field of solid waste resource utilization technology, and in particular relates to a method for preparing high-strength stone by high-temperature melting of fly ash and solid waste. Background Technology

[0002] Fly ash from municipal solid waste incineration is a major byproduct of the process. Its composition is complex, containing large amounts of soluble chlorides, heavy metals, and persistent organic pollutants such as dioxins, classifying it as a typical hazardous solid waste. If improperly disposed of, harmful substances in fly ash can easily leach or migrate into the soil and groundwater systems, posing a long-term potential threat to the ecological environment and human health.

[0003] The main technical approach for the harmless and resource-based treatment of fly ash is a combined process of pretreatment with water washing, followed by drying, and finally high-temperature melting. This process first removes soluble chlorides and other impurities from the fly ash through water washing, then dries the washed fly ash before sending it to a high-temperature melting furnace for processing. Under high-temperature conditions, dioxin-like organic pollutants can be completely decomposed, while heavy metals are effectively solidified in the glassy phase structure formed after melting, thus achieving detoxification and stabilization of the fly ash.

[0004] However, in practice, the slag obtained after melting is usually treated by water quenching, which involves using high-pressure water to instantly cool and fragment the high-temperature melt, forming granular glassy slag. While this process facilitates slag collection and transportation to some extent, the rapid cooling process directly leads to the disordered arrangement of atoms within the melt, forming an amorphous glass structure. The resulting glassy slag has a loose structure, is prone to microcracks, and its mechanical strength and chemical stability are significantly lower than those of crystalline materials, making it difficult to meet the application requirements of high-performance building materials. Summary of the Invention

[0005] The main objective of this invention is to provide a method for preparing high-strength stone by high-temperature melting of fly ash and solid waste. The technical problem to be solved is how to provide a method for preparing high-strength stone by high-temperature melting of fly ash and solid waste. This method does not require water quenching and rapid cooling. Instead, the high-temperature molten slag is directly poured into an insulated mold for slow cooling, thereby producing stone products with high density and high strength. These products can be widely used in scenic area ground, stone tablets, and stone pillar foundations for century-old avenues.

[0006] The objective of this invention and the technical problem it solves are achieved through the following technical solution. A method for preparing high-strength stone by high-temperature melting of fly ash and solid waste according to this invention includes: First, fly ash is mixed with oil-absorbing diatomaceous earth and spent activated carbon, and then granulated to obtain a mixture. The silicon content of the mixture is ≥35%. The average lower heating value of the mixture is ≥2500 kcal / kg.

[0007] The mixture is then placed in a vertical melting furnace and melted to obtain slag. The slag is placed in an insulated mold and left to cool slowly for 2–4 days to obtain high-strength stone. The melting temperature is >1300℃; the slag composition includes: SiO2, Al2O3, FeO, Fe2O3, CaO, MgO, and Na2O; the SiO2 content is >45%.

[0008] In one possible implementation, in step S1, the weight ratio of waste activated carbon to oil-absorbing diatomaceous earth and fly ash is 1:9:10.

[0009] In one possible implementation, in step S2, the mixture is fed from the top of the vertical melting furnace. Molten slag flows out from the bottom of the vertical melting furnace. Flue gas is discharged from the top of the vertical melting furnace. The flue gas is treated as follows: First, the flue gas is sent to a high-temperature dust removal system. After dust removal, it is then sequentially sent to the secondary combustion chamber, waste heat boiler, and air preheater to obtain exhaust gas. The inlet temperature of the high-temperature dust removal system is <650℃. The temperature of the secondary combustion chamber is >1100℃. The outlet temperature of the waste heat boiler is <500℃. The temperature of the exhaust gas is <190℃.

[0010] Then, the exhaust gas is subjected to a series of treatments, including primary acid removal, dust removal, secondary acid removal, cooling and water removal, and removal of heavy metals and dioxins, before being discharged.

[0011] In one possible implementation, in step S21, before the flue gas is sent to the high-temperature dust removal system, the mixture is heated with the flue gas until the temperature of the flue gas is <650°C.

[0012] In one possible implementation, in step S21, combustion air is introduced into the air preheater. Combustion is used to exchange heat with the flue gas in the air preheater, and after the heat exchange is completed, the air is introduced into the vertical melting furnace and the secondary combustion chamber.

[0013] In one possible implementation, in step S22, a semi-dry neutralization tower is used for primary acid removal. A bag filter is used for dust removal. A spray tower is used for secondary acid removal. An indirect condenser is used for cooling and water removal. An activated carbon adsorption box is used to remove heavy metals and dioxins.

[0014] In one possible implementation, in step S1, the fly ash includes bagged fly ash and canned fly ash. During mixing, the bagged fly ash is first fed into a bag-breaking pulverizer for crushing, then mixed with oil-absorbing diatomaceous earth, waste activated carbon and canned fly ash, and finally fed into a granulator for granulation.

[0015] In one possible implementation, the waste salt obtained after the high-temperature dust removal system treats the flue gas, the waste salt obtained after the bag filter treats the exhaust gas, the condensate obtained after the secondary acid removal in the spray tower, and the condensate obtained from the indirect condenser are all subjected to water washing and salt separation treatment.

[0016] In one possible implementation, the activated carbon waste generated by the activated carbon adsorption box can be used as waste activated carbon.

[0017] In one possible implementation, the vertical smelting furnace is also equipped with an oxygen production system for introducing oxygen into the vertical smelting furnace.

[0018] By employing the above technical solution, the method for preparing high-strength stone by high-temperature melting of fly ash and solid waste proposed in this invention has at least the following advantages: This application does not use the traditional water quenching process, but instead employs a slow cooling and forming process: high-temperature molten slag is directly injected into a mold wrapped with insulating material, and the entire assembly is placed in an insulated chamber for slow cooling over 2-4 days. During the cooling process, the molten slag has sufficient time to undergo lattice recombination from disordered to ordered, thereby achieving a transformation of the melt structure from an amorphous glassy phase to a dense crystalline phase. This results in stone products with higher density and mechanical strength, exhibiting significantly superior overall performance compared to glassy slag obtained through traditional water quenching.

[0019] The above description is merely an overview of the technical solution of the present invention. In order to better understand the technical means of the present invention and to implement it in accordance with the contents of the specification, the preferred embodiments of the present invention are described in detail below. Attached Figure Description

[0020] Figure 1 This is a schematic flowchart of the method for preparing high-strength stone by high-temperature melting of fly ash and solid waste according to an embodiment of the present invention. Detailed Implementation

[0021] To further illustrate the technical means and effects adopted by the present invention to achieve the intended purpose, the following, in conjunction with the accompanying drawings and preferred embodiments, details the specific implementation, structure, features, and effects of a method for preparing high-strength stone by high-temperature melting of fly ash and solid waste according to the present invention. In the following description, different "embodiments" or "embodiments" do not necessarily refer to the same embodiment. Furthermore, specific features, structures, or characteristics in one or more embodiments can be combined in any suitable manner.

[0022] This invention proposes a method for preparing high-strength stone by high-temperature melting of fly ash and solid waste, the method comprising: First, fly ash is mixed with oil-absorbing diatomaceous earth and spent activated carbon, and then granulated to obtain a mixture. The silicon content of the mixture is ≥35%. The average lower heating value of the mixture is ≥2500 kcal / kg.

[0023] The mixture is then placed in a vertical melting furnace and melted to obtain slag. The slag is placed in an insulated mold and left to cool slowly for 2–4 days to obtain high-strength stone. The melting temperature is >1300℃. The slag composition includes: SiO2, Al2O3, FeO, Fe2O3, CaO, MgO, and Na2O, etc.; among which, SiO2 has the highest content, >45%.

[0024] This application discloses raw materials for preparing high-strength stone, including fly ash, oil-absorbing diatomaceous earth, and spent activated carbon. The oil-absorbing diatomaceous earth originates from solid waste formed after diatomaceous earth is used as a filter aid to adsorb impurities and waste oil. Its main component is silicon dioxide, which can be used as a siliceous conditioning agent to supplement the silicon source required for the molten glass. Simultaneously, the adsorbed waste oil has a high calorific value, providing some heat energy for the melting process. Spent activated carbon, as solid waste, incurs high environmental disposal costs. This application introduces it into co-processing, which can not only replace some fuel to reduce energy consumption but also realize the resource utilization of spent activated carbon, embodying the technical concept of "treating waste with waste."

[0025] This application synergistically combines oil-absorbing diatomaceous earth, spent activated carbon, and fly ash. Utilizing the porous structure of diatomaceous earth and the high reactivity of its amorphous SiO2, it replaces traditional quartz sand as a siliceous conditioning agent. Simultaneously, the spent activated carbon, rich in fixed carbon, rapidly releases its high calorific value during melting. Combined with the impurities adsorbed by the oil-absorbing diatomaceous earth and the calorific value contributed by the waste oil, the average lower heating value of the mixture reaches over 2500 kcal / kg. Therefore, during the smelting process, a melting temperature above 1400℃ can be maintained solely by the heat released from the combustion of the materials themselves, requiring almost no external combustion. This significantly reduces energy consumption and material costs while ensuring effective melting.

[0026] This application discloses the need for smelting in a vertical melting furnace. The vertical melting furnace described herein refers to a counter-current vertical melting furnace, in which solid materials and high-temperature flue gas move in opposite directions within the furnace, transferring heat and matter through contact. Therefore, in this application, the material is fed into the upper part of the vertical melting furnace, allowing the mixture to settle from top to bottom, passing through different temperature zones from low to high, ultimately producing slag at the bottom of the furnace.

[0027] The vertical smelting furnace has a slag outlet at the bottom through which the molten, high-temperature slag is discharged. The discharged slag is directly injected into an insulated mold, and then moved into an insulated chamber by a robotic arm. After slow cooling for 2 to 4 days, a high-strength stone product is obtained.

[0028] To accommodate slag discharge requirements under different operating conditions, the bottom of the vertical smelting furnace is equipped with multiple slag outlets arranged vertically. The bottommost slag outlet is primarily used for furnace shutdown maintenance or periodic cleaning of accumulated molten slag; the upper slag outlets are used for periodic slag discharge during daily production. As a preferred embodiment, the number of slag outlets is three.

[0029] The vertical smelting furnace disclosed in this application requires the introduction of oxygen for smelting. The required oxygen is produced by an oxygen generation system and introduced into the vertical smelting furnace.

[0030] This application discloses the composition of the slag, which mainly includes oxides such as SiO2, Al2O3, FeO, Fe2O3, CaO, MgO, and Na2O; among which, SiO2 has the highest content, greater than 45%. This slag exhibits good fluidity at high temperatures, thus it can be poured into molds of different shapes, and after cooling, stone products of various specifications can be obtained. The resulting stone has a density greater than 2.7 g / cm³, a dense structure, high hardness (Mohs hardness 5-7), and excellent compressive strength, reaching up to 300 MPa. It also possesses good resistance to acid and alkali corrosion and high-temperature resistance (melting point above 1250℃), making it a high-performance inorganic building material.

[0031] In this application, the smelting temperature needs to be controlled above 1300℃. Increasing the smelting temperature can improve the melting effect of fly ash, but excessively high temperatures will significantly increase equipment investment and operating energy consumption. Considering both melting efficiency and cost control, a smelting temperature of 1300-1500℃ is preferred. As a further preferred technical solution, the smelting temperature is 1350℃, which can ensure good melting effect while also taking into account economic efficiency.

[0032] In one possible implementation, in step S1, the weight ratio of waste activated carbon to oil-absorbing diatomaceous earth and fly ash is 1:9:10.

[0033] This application optimizes the weight ratio of waste activated carbon, oil-absorbing diatomaceous earth, and fly ash in the mixture. By precisely controlling the ratio of these three components, a synergistic balance between heat supply and material composition is achieved. On one hand, oil-absorbing diatomaceous earth replaces the traditional silica-based conditioning agent used to form the glass body. Its high content of amorphous SiO2 ensures suitable silicon-to-aluminum ratio conditions during the crystallization transformation of the melt, thereby guaranteeing the quality of the final product. On the other hand, the waste oil adsorbed in the oil-absorbing diatomaceous earth, together with the waste activated carbon, constitutes a high-calorific-value component, providing sufficient heat for the melting process and ensuring that the average lower heating value of the mixture consistently reaches above 2500 kcal / kg. This ratio design satisfies the heat required for self-heating melting while also taking into account the material basis required for melt crystallization, achieving a synergistic balance between heat supply and material composition.

[0034] This application discloses the weight ratio of waste activated carbon to oil-absorbing diatomaceous earth and fly ash in a mixture. By controlling this weight ratio, the heat supply and composition of the mixture can be precisely balanced. On one hand, by using oil-absorbing diatomaceous earth instead of traditional glass-forming ingredients, product quality is ensured. On the other hand, the waste oil and waste activated carbon adsorbed in the oil-absorbing diatomaceous earth can provide sufficient heat, allowing the average lower heating value of the mixture to stably reach above 2500 kcal / kg, thereby achieving a balance between heat supply and composition. As a preferred embodiment, the mixture comprises, by weight percentage: 5% waste activated carbon, 45% oil-absorbing diatomaceous earth, and 50% fly ash.

[0035] In one possible implementation, in step S2, the mixture is fed from the top of the vertical melting furnace. Molten slag flows out from the bottom of the vertical melting furnace. Flue gas is discharged from the top of the vertical melting furnace. The flue gas is treated as follows: First, the flue gas is sent to a high-temperature dust removal system. After dust removal, it is then sequentially sent to the secondary combustion chamber, waste heat boiler, and air preheater to obtain exhaust gas. The inlet temperature of the high-temperature dust removal system is <650℃. The temperature of the secondary combustion chamber is >1100℃. The outlet temperature of the waste heat boiler is <500℃. The temperature of the exhaust gas is <190℃.

[0036] Then, the exhaust gas is subjected to a series of treatments, including primary acid removal, dust removal, secondary acid removal, cooling and water removal, and removal of heavy metals and dioxins, before being discharged.

[0037] In the process of preparing stone, this application requires the treatment of a large amount of toxic fumes generated during fly ash smelting. The treatment method is as follows: Figure 1 As shown, the specific steps are as follows: The flue gas is first sequentially fed into a high-temperature dust removal system, then into the secondary combustion chamber, waste heat boiler, and air preheater to obtain exhaust gas. The high-temperature dust removal system treats the flue gas discharged from the top of the vertical smelting furnace. To ensure the system's normal operation, the temperature of the flue gas entering the system must be controlled below 650℃. This temperature control is crucial because when the flue gas temperature exceeds 700℃, the ash and volatile chlorides carried in the flue gas are in a viscous or gaseous state, easily condensing and adhering to the inner wall of the flue and the surface of the dust collector filter material, leading to flue blockage and dust collector failure. However, when the flue gas temperature drops below 650℃, the ash and chlorides transform into solid particles, which can be effectively intercepted and collected by the dust collector.

[0038] To achieve the above temperature control objectives, this application optimizes the structure of the vertical smelting furnace by appropriately increasing the furnace height and extending the length of the feeding preheating section. By utilizing the countercurrent heat exchange principle between the material and the flue gas, the high-temperature flue gas fully preheats the descending material during its ascent, thereby reducing its own temperature and ensuring that the flue gas temperature at the furnace outlet is stably controlled below 650℃.

[0039] It is worth noting that this invention includes a high-temperature dust removal system at the flue gas outlet of the melting furnace, specifically for collecting impurity salt components in the flue gas. Therefore, precisely controlling the flue gas temperature below 650℃ is not only a necessary condition for ensuring the long-term stable operation of the dust removal system, but also a technical prerequisite for achieving efficient separation and recovery of impurity salts. Furthermore, the vertical smelting furnace disclosed in this application is also connected to an SNCR denitrification unit, capable of performing denitrification treatment on the vertical smelting furnace.

[0040] This application also discloses a waste heat boiler, which recovers waste heat to achieve the tiered utilization of flue gas heat energy, thereby reducing system energy consumption. Specifically, the flue gas (temperature > 1100℃) produced from the secondary combustion chamber enters the waste heat boiler, where heat exchange heats the condensate into saturated steam. The generated saturated steam can be used to generate electricity, which can be used by equipment such as oxygen generators, fans, and water pumps within the plant. The consumed saturated steam is then converted back into condensate for the waste heat boiler and returned to the waste heat boiler, achieving energy self-sufficiency.

[0041] It is worth noting that the exhaust gas disclosed in this application is the gas obtained after the flue gas has been treated by a high-temperature dust removal system, a secondary combustion chamber, a waste heat boiler, and an air preheater.

[0042] In one possible implementation, in step S21, before the flue gas is sent to the high-temperature dust removal system, the mixture is heated with the flue gas until the temperature of the flue gas is <650°C.

[0043] This application discloses a method for cooling the flue gas discharged from the top of a vertical melting furnace to below 650°C. Specifically, before sending the flue gas into a high-temperature dust removal system, the heat carried by the flue gas itself is used to heat the mixture fed into the vertical melting furnace. In particular, this application employs a counter-current vertical melting furnace structure, where the material is added from the top of the furnace and slowly descends, while the high-temperature flue gas flows upwards. During the upward movement, the flue gas comes into full contact with the descending cold material and exchanges heat, transferring heat to the material and gradually reducing its own temperature; the material is preheated, preparing for subsequent melting. By rationally designing the furnace height and the length of the preheating section, it is ensured that the flue gas temperature has been stably reduced to below 650°C by the time it reaches the furnace top outlet.

[0044] This application features a special design for the vertical smelting furnace to reduce the flue gas temperature to 650°C. It improves upon the traditional vertical smelting furnace by increasing its height by one-third and raising the preheating section. This allows for cooling of the flue gas through the introduction of new materials, thereby achieving a temperature reduction to 650°C. Using a conventionally high-height vertical smelting furnace would result in excessively high flue gas temperatures. The viscous, gaseous ash and salt exceeding 700°C in the flue gas would then enter the dust collector and flue, clogging them after cooling and causing the system to malfunction.

[0045] In one possible implementation, in step S21, combustion air is introduced into the air preheater. Combustion is used to exchange heat with the flue gas in the air preheater, and after the heat exchange is completed, the air is introduced into the vertical melting furnace and the secondary combustion chamber.

[0046] The warm flue gas (<500℃) after heat exchange in the waste heat boiler then enters the air preheater to exchange heat with the combustion air. The heated combustion air is then sent to the vertical melting furnace and the secondary combustion chamber as combustion air, further improving combustion efficiency and reducing fuel consumption. The combustion air is supplied to the air preheater via a blower. Additionally, the combustion air can also be used as combustion air in the supplementary combustion system and burners.

[0047] In one possible implementation, in step S22, a semi-dry neutralization tower is used for primary acid removal. A bag filter is used for dust removal. A spray tower is used for secondary acid removal. An indirect condenser is used for cooling and water removal. An activated carbon adsorption box is used to remove heavy metals and dioxins.

[0048] The semi-dry neutralization tower disclosed in this application performs primary acid removal treatment on the waste gas by adding baking soda. The spray tower performs secondary acid removal treatment on the waste gas by adding baking soda and tap water. The indirect condenser collects condensate by circulating cooling water (circulating cooling water inlet and cooling water outlet).

[0049] In one possible implementation, in step S1, the fly ash includes bagged fly ash and canned fly ash. During mixing, the bagged fly ash is first fed into a bag-breaking pulverizer for crushing, then mixed with oil-absorbing diatomaceous earth, waste activated carbon and canned fly ash, and finally fed into a granulator for granulation.

[0050] like Figure 1This application discloses a specific method for preparing the mixture. Although both bagged and canned fly ash are fly ash materials, their packaging and storage conditions differ, requiring differentiated pretreatment methods. Specifically, bagged fly ash is prone to clumping due to compression during transportation and storage, and the packaging bags themselves contain foreign impurities. Therefore, before mixing, it must be unpacked, crushed, and dispersed using a bag-breaking and crushing machine to restore it to a powder state and remove packaging debris. Canned fly ash, on the other hand, is usually introduced into the production line in bulk powder form via a closed pneumatic conveying system, and its state is more uniform, allowing it to be directly mixed.

[0051] The technical solution of this application integrates both bagged and canned fly ash, solving the problems of agglomeration and packaging impurities in bagged fly ash, while fully utilizing the efficiency advantage of canned fly ash's direct usability. Furthermore, through the synergistic combination of oil-absorbing diatomaceous earth and spent activated carbon, precise control of material composition and calorific value is achieved. Specifically, the preparation method of the mixture is as follows: First, the ton-bag fly ash is fed into a bag-breaking crusher for crushing, then fed into a mixer to be mixed with canned fly ash, oil-absorbing diatomaceous earth and waste activated carbon, and finally fed into a granulator for granulation to obtain a mixture.

[0052] In addition, such as Figure 1 As shown, the mixture obtained from the granulator is fed into the conveying system and metering hopper, and then into the vertical smelting furnace through a continuous feeding mechanism. The continuous feeding system is also equipped with a supplementary feeding device, which replenishes material through a supplementary material inlet.

[0053] In one possible implementation, the waste salt obtained after the high-temperature dust removal system treats the flue gas, the waste salt obtained after the bag filter treats the exhaust gas, the condensate obtained after the secondary acid removal in the spray tower, and the condensate obtained from the indirect condenser are all subjected to water washing and salt separation treatment.

[0054] like Figure 1 As shown, this application provides a unified treatment method for materials containing waste salt generated during flue gas treatment. Specifically, this application transports waste salt collected by the high-temperature dust removal system, waste salt collected by the bag filter, salt-containing condensate generated after secondary acid removal from the spray tower, and condensate from the indirect condenser to a water washing and salt treatment system for comprehensive treatment. This unified treatment method can significantly reduce the cost of water treatment, thereby reducing both the investment and operating costs of the water treatment system. Furthermore, centralized treatment of salt-containing materials from different sources simplifies the process flow and improves salt separation efficiency.

[0055] In traditional processes, soluble salts in fly ash are typically removed by washing. However, this process consumes a large amount of water, and the resulting fly ash has a high moisture content, requiring drying to meet the requirements of subsequent processes, leading to a significant increase in drying costs. In contrast, this application abandons the traditional route of pre-washing and salt treatment. Instead, the fly ash is directly fed into a vertical melting furnace for high-temperature melting, causing the salts to volatilize into the flue gas at high temperatures. The salts are then collected by a high-temperature dust removal system, and finally, the collected dry salt powder is centrally washed for desalination. Since only the enriched salt powder needs to be processed, water consumption is significantly reduced, and the fly ash drying step is completely eliminated. Therefore, this application achieves highly efficient desalination while significantly reducing operating costs, demonstrating a clear economic advantage over traditional processes.

[0056] In one possible implementation, the activated carbon waste generated by the activated carbon adsorption box can be used as waste activated carbon.

[0057] The activated carbon adsorption box disclosed in this application is mainly used to remove heavy metals and dioxins generated in gases. The activated carbon itself, after adsorption saturation, is considered waste. This application uses the waste activated carbon generated from the activated carbon adsorption box as raw material, mixing it with fly ash and oil-absorbing diatomaceous earth, thus maximizing resource utilization.

[0058] In one possible implementation, the vertical smelting furnace is also equipped with an oxygen production system for introducing oxygen into the vertical smelting furnace.

[0059] The vertical smelting furnace disclosed in this application requires a continuous supply of oxygen to achieve smelting. This application uses an oxygen production system to produce oxygen and then introduces it into the vertical smelting furnace. Furthermore, the vertical smelting furnace disclosed in this application is also connected to a supplementary combustion system. When the temperature of the vertical smelting furnace is too low, natural gas can be burned through the supplementary combustion system to raise the temperature of the vertical smelting furnace.

[0060] In addition, the secondary combustion chamber disclosed in this application is also connected to a burner, which provides temperature to the secondary combustion chamber by burning natural gas when the temperature of the secondary combustion chamber is too low.

[0061] It is worth noting that the afterburning system and combustion chamber disclosed in this application are mandatory environmental requirements and are required installations. The afterburning system and combustion chamber are optional, but their installation is mandatory.

[0062] This application also discloses an induced draft fan, the main function of which is to discharge the waste gas treated by the activated carbon adsorption box into the atmosphere through an exhaust stack.

[0063] The present invention will be further described below with reference to specific embodiments, but this should not be construed as a limitation on the scope of protection of the present invention. Some non-essential improvements and adjustments made by those skilled in the art based on the above description of the present invention still fall within the scope of protection of the present invention.

[0064] Unless otherwise specified, all materials and reagents mentioned below are commercially available products well known to those skilled in the art; unless otherwise specified, all methods described are methods known in the art. Unless otherwise defined, the technical or scientific terms used should have the ordinary meaning understood by those skilled in the art to which this invention pertains.

[0065] Example 1 The method for preparing high-strength stone by high-temperature melting of fly ash and solid waste in this embodiment includes the following steps: S1. Take fly ash from a municipal solid waste incineration power plant, including bagged fly ash (approximately 40%) and canned fly ash (approximately 60%). First, send the bagged fly ash into a bag-breaking and crushing machine for unpacking, crushing, and dispersing to remove debris from the packaging bags and restore it to a powdery state.

[0066] S2. The treated bagged fly ash, canned fly ash, oil-absorbing diatomaceous earth (waste material that adsorbs waste oil after the use of filter aid), and waste activated carbon are fed into a mixer at a weight ratio of 1:9:10 (waste activated carbon: oil-absorbing diatomaceous earth: fly ash) and mixed thoroughly, i.e. waste activated carbon accounts for 5%, oil-absorbing diatomaceous earth accounts for 45%, and fly ash accounts for 50%.

[0067] S3. The uniformly mixed material is fed into a granulator for granulation to obtain a granular mixture with a particle size of 5-12 mm. Testing revealed that the mixture has a silicon content of 38.2% (≥35%) and an average lower heating value of 2720 kcal / kg (≥2500 kcal / kg).

[0068] S4. The granulated material is first fed into the conveying system and metering silo, and then evenly added from the top of the vertical smelting furnace through a continuous feeding system. An oxygen generation system is installed at the bottom of the smelting furnace, which automatically adjusts the oxygen supply according to the furnace temperature to control the temperature of the melting zone at 1350℃.

[0069] The high-temperature slag formed by melting is discharged from the bottom of the furnace, and the flue gas is discharged from the top of the furnace. There are 3 slag outlets in the vertical direction at the bottom of the furnace. During normal production, the upper slag outlet is opened and slag is discharged 3 times a day at regular intervals.

[0070] The discharged high-temperature molten slag is directly injected into a mold wrapped with a high-temperature resistant flexible insulation material. The mold filled with slag is then transferred by a robotic arm to an insulated chamber for slow cooling for 2-4 days. After demolding, a high-strength stone product is obtained. Testing shows that the resulting stone has a density greater than 2.7 g / cm³, a dense structure, high hardness (Mohs hardness 5-7), and excellent compressive strength, reaching up to 300 MPa. It also possesses good resistance to acid and alkali corrosion and high-temperature resistance (melting point above 1250℃), making it a high-performance inorganic building material suitable for high-value applications such as scenic area paving, stone tablets, and pile foundations.

[0071] S5. The flue gas is treated by preheating the feed material in a counter-current manner, reducing the flue gas temperature at the top outlet of the vertical smelting furnace to 650℃ (<700℃). It then enters a high-temperature dust removal system to collect waste salt. The dust-removed flue gas then enters the secondary combustion chamber, where it is burned at 1150℃ (>1100℃) to completely incinerate organic matter and dioxins. The flue gas then passes through the following stages: Waste heat boiler: generates steam for power generation and self-use, and the outlet flue gas temperature is reduced to 450℃ (<500℃).

[0072] Air preheater: It exchanges heat with the incoming combustion air. The combustion air is heated to 330°C and then sent back to the melting furnace and secondary combustion chamber. The flue gas temperature drops to 160°C (<190°C).

[0073] S6. The exhaust gas after being treated by the air preheater is passed sequentially through: Semi-dry neutralization tower: acid removal by spraying lime slurry.

[0074] Baghouse dust collector: captures reactive salts and dust, and collects dry waste salts.

[0075] Spray tower: secondary deep deacidification, producing saline condensate.

[0076] Indirect condenser: cools down, removes water, and collects condensate.

[0077] Activated carbon adsorption box: Removes trace heavy metals and dioxins to meet emission standards.

[0078] Comparative Example 1 Compared with Example 1, Comparative Example 1 first underwent water washing and desalination treatment.

[0079] The method of this comparative example is as follows: first, the raw fly ash is sent to the pulping system, then it undergoes three-stage countercurrent water washing, then it is sent to the screw press and plate and frame filter press for dewatering, and finally it is sent to the drying unit for drying.

[0080] A comparison of Comparative Example 1 and Example 1 reveals that the process used in Comparative Example 1 involves first washing and desalinating the fly ash. This process requires significant investment in system configuration, including a pulping system, multiple screw presses, plate and frame filter presses, and supporting tank pump sets. After pulping, the raw fly ash undergoes three stages of countercurrent washing and filter press dewatering. The washing volume is substantial, with the dry basis of the washed fly ash being approximately 85%, resulting in a wet fly ash moisture content as high as 38%. Further drying to below 5% moisture content is necessary before it can enter the melting furnace. Notably, the initial moisture content of the raw fly ash is only about 2%, and even after drying to 5%, it remains higher than the initial moisture content, thus increasing the energy consumption cost of the melting process. This process not only involves large equipment investment and a lengthy process but also significant energy consumption in the drying stage, leading to high overall operating costs.

[0081] The method disclosed in this application eliminates the need for pre-treatment with water washing of fly ash. The fly ash is directly fed into a vertical melting furnace for high-temperature melting. The volatilized salts are captured by a high-temperature dust removal system before centralized water washing and desalination. Since only a small amount of water washing is required on the enriched dry salt powder, water consumption and subsequent treatment costs are significantly reduced, and the fly ash drying process is completely eliminated. Therefore, this application achieves highly efficient desalination while significantly reducing equipment investment and operating energy consumption, demonstrating a clear economic advantage over traditional water washing and drying processes.

[0082] In the above embodiments, the descriptions of each embodiment have different focuses. For parts not described in detail in a certain embodiment, please refer to the relevant descriptions in other embodiments.

[0083] The above description is merely a preferred embodiment of the present invention and is not intended to limit the present invention in any way. Although the present invention has been disclosed above with reference to preferred embodiments, it is not intended to limit the present invention. Any person skilled in the art can make some modifications or alterations to the above-disclosed technical content to create equivalent embodiments without departing from the scope of the present invention. Any simple modifications, equivalent changes, and alterations made to the above embodiments based on the technical essence of the present invention without departing from the scope of the present invention shall still fall within the scope of the present invention.

Claims

1. A method for preparing high-strength stone by high-temperature melting of fly ash and solid waste, characterized in that, The method includes: First, fly ash is mixed with oil-absorbing diatomaceous earth and waste activated carbon, and then granulated to obtain a mixture; the silicon content of the mixture is ≥35%; the average lower heating value of the mixture is ≥2500Kcal / kg; Then, the mixture is placed in a vertical smelting furnace and smelted to obtain slag; the slag is placed in a heat-insulating mold and left for 2-4 days, and then slowly cooled to obtain the high-strength stone; the smelting temperature is >1300℃; the composition of the slag includes: SiO2, Al2O3, FeO, Fe2O3, CaO, MgO and Na2O; the content of SiO2 is >45%.

2. The method for preparing high-strength stone by high-temperature melting of fly ash and solid waste according to claim 1, characterized in that, In step S1, the weight ratio of the waste activated carbon to the oil-absorbing diatomaceous earth and the fly ash is 1:9:

10.

3. The method for preparing high-strength stone by high-temperature melting of fly ash and solid waste according to claim 1, characterized in that, In step S2, the mixture is fed from the top of the vertical smelting furnace; the molten slag flows out from the bottom of the vertical smelting furnace; flue gas is discharged from the top of the vertical smelting furnace; the flue gas is treated as follows: First, the flue gas is sent to a high-temperature dust removal system. After dust removal, it is then sequentially sent to the secondary combustion chamber, the waste heat boiler, and the air preheater to obtain exhaust gas. The inlet temperature of the high-temperature dust removal system is <650℃; the temperature of the secondary combustion chamber is >1100℃; the outlet temperature of the waste heat boiler is <500℃; and the temperature of the exhaust gas is <190℃. Then, the waste gas is subjected to a series of treatments, including primary deacidification, dust removal, secondary deacidification, cooling and dehydration, and removal of heavy metals and dioxins, before being discharged.

4. The method for preparing high-strength stone by high-temperature melting of fly ash and solid waste according to claim 3, characterized in that, In step S21, before the flue gas is sent to the high-temperature dust removal system, the mixture is heated with the flue gas until the temperature of the flue gas is <650°C.

5. The method for preparing high-strength stone by high-temperature melting of fly ash and solid waste according to claim 3, characterized in that, In step S21, combustion air is introduced into the air preheater; the combustion is used to exchange heat with the flue gas in the air preheater, and after the heat exchange is completed, it is introduced into the vertical melting furnace and the secondary combustion chamber.

6. The method for preparing high-strength stone by high-temperature melting of fly ash and solid waste according to claim 3, characterized in that, In step S22, a semi-dry neutralization tower is used for primary acid removal; a bag filter is used for dust removal; a spray tower is used for secondary acid removal; an indirect condenser is used for cooling and water removal; and an activated carbon adsorption box is used to remove heavy metals and dioxins.

7. The method for preparing high-strength stone by high-temperature melting of fly ash and solid waste according to claim 1, characterized in that, In step S1, the fly ash includes bagged fly ash and canned fly ash. During mixing, the bagged fly ash is first fed into a bag-breaking pulverizer for crushing, then mixed with the oil-absorbing diatomaceous earth, the waste activated carbon and the canned fly ash, and finally fed into a granulator for granulation.

8. The method for preparing high-strength stone by high-temperature melting of fly ash and solid waste according to claim 6, characterized in that, The waste salt obtained after the high-temperature dust removal system treats the flue gas, the waste salt obtained after the bag filter treats the exhaust gas, the condensate obtained after the secondary acid removal in the spray tower, and the condensate obtained from the indirect condenser are all subjected to water washing and salt separation treatment.

9. The method for preparing high-strength stone by high-temperature melting of fly ash and solid waste according to claim 7, characterized in that, The activated carbon waste generated by the activated carbon adsorption box can be used as the waste activated carbon.

10. The method for preparing high-strength stone by high-temperature melting of fly ash and solid waste according to claim 1, characterized in that, The vertical smelting furnace is also equipped with an oxygen generation system for introducing oxygen into the vertical smelting furnace.

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