Method and system for quickly desalting and detoxifying fly ash

Abstract

The invention belongs to the technical field of dangerous solid waste treatment, and discloses a quick desalting and detoxifying method and system for fly ash. The rapid desalination and detoxification method for the fly ash comprises the following steps: melting a conductive solid material to form a high-temperature molten metal layer, adding a solid mineral waste material, melting to form a slag layer, and controlling the temperature of the slag layer to be 1200-1450 DEG C; feeding fly ash, melting the fly ash under the heating of the slag layer to form slag and separate out fused salt, forming a material layer by the fly ash which is not completely molten, and controlling the thickness of the material layer to be greater than or equal to 0.5 m; due to the density difference, the material layers form a metal layer, a slag layer, a material layer and a molten salt layer which are sequentially distributed from bottom to top, and the material layers are suspended between the molten salt layer and the slag layer; the temperature of the molten salt layer is controlled within the range of 800-950 DEG C; and respectively recycling the discharged molten salt and slag. The rapid desalting and detoxifying method for the fly ash has the advantages that the technological process is simplified, the quality of saline water is improved, energy is saved, and consumption is reduced. The invention further correspondingly provides a rapid desalting and detoxifying system for the fly ash.

Description

Technical Field

[0001] The invention belongs to the technical field of hazardous solid waste treatment, and in particular relates to a method and system for rapid desalination and detoxification of fly ash. Background Art

[0002] Fly ash from the incineration of domestic waste is a fine powdery secondary pollutant produced during the incineration process. Although fly ash contains dioxins and heavy metal harmful substances, it is mainly composed of mineral elements such as Si, Al, Ca, Na, K, Mg, and Cl, and has good resource properties. High-temperature melting is the most thorough way to harmlessly treat fly ash. Under high temperature conditions of 1200~1500℃, dioxins are completely decomposed, and components such as Si, Al, and Ca are reconstructed into an amorphous reticular glass structure. Heavy metals are firmly fixed in the reticular structure. At the same time, the formed glass can also be used to make high-value products such as thermal insulation cotton and glass products. However, due to the high content of chlorine in fly ash, the mass fraction can reach 15~25%, and the melting temperature of Na, K, Ca, Pb, and Zn salts in the form of chloride salts is low (700~800℃). When heated above 1000℃, they are very easy to volatilize. These salts enter the back-end system with the tail gas and cause serious corrosion to the equipment, greatly reducing the service life of the equipment and forming secondary pollution.

[0003] Therefore, before the fly ash enters the melting process, it is usually necessary to add a pretreatment process to remove the chloride salts in it. Water washing is a common method to remove chloride salts from fly ash. After multi-stage water washing, the chlorine content of fly ash can be reduced to less than 1%. At the same time, the chloride salts can be recycled and reused, with good resource utilization effect. However, the wet ash after washing cannot be directly put into the high-temperature furnace, and supporting ash drying equipment is required, resulting in a long process flow, large equipment investment, and high operating costs.

[0004] In the related art, CN115138658A discloses a method and device for harmless reduction of fly ash from a waste incineration power plant. The method adopts a method of directly adding fly ash. Although the water washing pretreatment process is omitted, there are still some shortcomings: on the one hand, under the uniform temperature condition of 1200°C, the salt is very volatile and cannot be collected in the furnace; on the other hand, there may be a pollution problem that dioxins volatilize before they are completely decomposed. Summary of the invention

[0005] In order to solve the above-mentioned problems, the object of the present invention is to provide a method and system for rapid desalination and detoxification of fly ash.

[0006] In the first aspect, the present invention provides a method for rapid desalination and detoxification of fly ash, which specifically adopts the following technical scheme: A method for rapid desalination and detoxification of fly ash, comprising the following steps Step 1: heating and melting the conductive solid material to form a molten metal layer; Step 2: Add solid mineral waste to melt and form a slag layer, and control the temperature of the slag layer to 1200-1450°C; Step 3: Add fly ash, which melts under the heating of the slag layer to form slag and precipitates molten salt. The fly ash that has not been completely melted forms a material layer, and the thickness of the material layer is controlled to be ≥0.5m; due to the density difference, each material layer forms a conductive liquid layer, a slag layer, a material layer and a molten salt layer distributed from bottom to top, wherein the material layer is suspended between the molten salt layer and the slag layer; under the heat insulation effect of the material layer, the temperature of the molten salt layer is controlled in the range of 800-950°C; Step 4: Discharge the molten salt from the molten salt layer and the slag from the slag layer separately for recycling.

[0007] By adopting the above technical solution, the conductive solid material, solid mineral waste and fly ash are added in order. Due to the density difference, each material layer is naturally stratified to form a conductive liquid layer (density 7.1 g / cm 3 )、Slag layer (density 2.3~2.5 g / cm 3 )、Material layer(1.7~1.9g / cm 3 )、molten salt layer(1.3~1.5g / cm 3 ); fly ash gradually melts under the heating of the slag layer to form slag and precipitate molten salt, dioxins are quickly decomposed into non-toxic small molecules, and heavy metals sink with the slag and are fixed. The fly ash layer has a good heat insulation effect, which can block part of the heat conducted upward from the slag layer. By controlling the feed rate of fly ash, its thickness can be controlled, and the upper heating temperature can be reduced to 850-950°C. At this temperature, the molten salt is in a molten state and will not volatilize in large quantities, and with the continuous addition of fly ash, it continues to accumulate to form a molten salt layer; the slag layer is maintained at a high temperature of 1200-1450°C, which is conducive to the full decomposition of organic pollutants such as dioxins. The method of the present invention does not need to pre-wash and dry the fly ash, and can solve the problem of the difficult balance between the volatilization of molten salt and the incomplete degradation of organic pollutants such as dioxins.

[0008] Furthermore, in step three, the fly ash is granulated and has a particle size of 2-3 cm.

[0009] Furthermore, in step 2, the thickness of the slag layer is ≥ 0.5 m.

[0010] Furthermore, in step one, the conductive solid material input is steel slag.

[0011] Furthermore, in step 2, the solid mineral waste input is one or more of silica, slag, and waste glass.

[0012] Furthermore, in step 4, the discharged molten salt is introduced into water, stirred and dissolved, and the solution temperature is controlled to be ≤80°C to obtain a salt solution that can be used industrially. The main components of the discharged molten salt are sodium chloride, potassium chloride, calcium chloride and other salts, the temperature is about 850°C, it is in a molten state, and has good fluidity. The molten salt flows into the water through the salt discharge pipe. Under the action of high temperature and stirring, the chloride salt is quickly cooled and dissolved. By controlling the inlet and outlet water volume and the heat exchange device, the salt water concentration can be increased to a near saturation concentration, and the water temperature is controlled to be ≤80°C. The obtained salt solution can directly enter the back-end process for resource utilization.

[0013] Furthermore, in step 4, the discharged slag is cooled to obtain a glass body that can be used in industry. The glass body can be used as a building material aggregate, or directly enter the resource recovery process in a high-temperature molten state to make high-value products such as thermal insulation cotton.

[0014] In the second aspect, the present invention provides a fly ash rapid desalination and detoxification system, which specifically adopts the following technical solutions: A fly ash rapid desalination and detoxification system, used for the aforementioned fly ash rapid desalination and detoxification method, comprising: A melting furnace, wherein the top wall of the melting furnace is provided with an exhaust gas outlet, the side wall is provided with a molten salt outlet for discharging molten salt from the molten salt layer, and the bottom side wall is provided with a slag outlet for discharging slag from the slag layer and which is higher than the metal layer; A feed hopper is arranged above the melting furnace and is used to add materials into the melting furnace; a feed pipe is connected to the bottom of the feed hopper, and the lower end opening of the feed pipe is lower than the molten salt discharge port; and a heating device for heating the material in the melting furnace.

[0015] Furthermore, the feed hopper is provided with several groups.

[0016] Furthermore, the heating device comprises a bottom electrode and a heating electrode which are arranged relatively at intervals, and the bottom electrode is arranged at the bottom of the melting furnace.

[0017] Furthermore, it also includes a molten salt water quenching and dissolving device connected to the molten salt discharge port through a salt discharge pipe.

[0018] Furthermore, the molten salt water quenching and dissolving device comprises: A dissolving tank having a water vapor outlet, a water inlet, a water outlet, and a molten salt inlet connected to a molten salt discharge port; A stirring device, used to stir the materials in the dissolving tank; and a heat exchanger for heating the material in the dissolving tank.

[0019] Furthermore, the heat exchanger is a tubular heat exchanger.

[0020] Furthermore, the dissolving tank is provided with an observation port.

[0021] The present invention has the following beneficial effects: ① The process flow is simplified. The present invention can realize fly ash desalination in the furnace and simultaneously decompose dioxins and fix heavy metals through process control. There is no need for pre-water washing and wet ash drying systems, which greatly simplifies the fly ash disposal process flow.

[0022] ② The quality of brine is improved. In order to achieve the dechlorination effect, the fly ash washing needs to ensure a certain amount of washing water (the water-ash ratio is usually 2:1~3:1), so the washing brine concentration is relatively low. In addition, due to the low solid-liquid phase density difference of the fly ash washing, the impurity content of the solid-liquid separated brine is high, and the cost of brine purification before evaporation is high. The present invention directly precipitates the chloride salt in the fly ash by high-temperature melting and directly dissolves it in water. The obtained brine has a high concentration, and the solid-liquid phase density difference of the fly ash particles relative to the molten salt in the melting process is large, the separation effect is good, and the desalination purity is high.

[0023] ③ Saving energy consumption. The fly ash desalination method proposed in the present invention has high brine purity and nearly saturated brine concentration. The rear-end evaporation and crystallization process evaporates less water and has low energy consumption. BRIEF DESCRIPTION OF THE DRAWINGS

[0024] Figure 1 It is a schematic diagram of the structure of the ash rapid desalination and detoxification system in the embodiment; Figure 2 Schematic diagram of the structure of the melting furnace in the embodiment (top view).

[0025] Description of reference numerals: 1. Melting furnace; 11. Feed hopper; 111. Feed pipe; 12. Heating electrode; 13. Bottom electrode; 14. Exhaust gas outlet; 15. Molten salt outlet; 16. Slag outlet; 2. Molten salt water quenching and dissolving device; 21. Dissolving tank; 211. Molten salt inlet; 212. Water vapor outlet; 213. Observation port; 214. Water inlet; 215. Water outlet; 22. Stirring device; 23. Heat exchanger; α, metal layer; β, slag layer; γ, material layer; δ, molten salt layer. DETAILED DESCRIPTION

[0026] In order to enable those skilled in the art to better understand the technical solutions of the present invention, the present application will be further described in detail below in conjunction with the accompanying drawings.

[0027] A fly ash rapid desalination and detoxification method is implemented based on an ash rapid desalination and detoxification system.

[0028] Reference Figure 1 and Figure 2The ash rapid desalination and detoxification system includes a melting furnace 1, a feed hopper 11, a heating device and a molten salt water quenching and dissolving device 2. The melting furnace 1 is used to heat the added materials. The top wall of the melting furnace 1 is provided with an exhaust gas outlet 14, the side wall is provided with a molten salt outlet 15 for discharging the molten salt of the molten salt layer δ, and the bottom side wall is provided with a slag outlet 16 for discharging the slag of the slag layer β and higher than the metal layer α. The feed hopper 11 is arranged above the melting furnace 1, and the bottom of the feed hopper 11 is connected to a feed pipe 111 for adding materials into the melting furnace 1. The lower end opening of the feed pipe 111 is lower than the molten salt outlet 15. In this embodiment, three groups of feed hoppers 11 are provided. The heating device is used to heat the materials in the melting furnace 1, and includes a heating electrode 12 and a bottom electrode 13 arranged at a relative interval. The heating electrode 12 is arranged in the center of the top wall of the melting furnace 1, and its bottom end extends downward, and the bottom electrode 13 is arranged in the center of the bottom of the melting furnace 1.

[0029] Reference Figure 1 The molten salt water quenching and dissolving device 2 includes a dissolving tank 21, and a molten salt inlet 211 is opened at the top of the dissolving tank 21. The molten salt inlet 211 is connected to the molten salt outlet 15 of the melting furnace 1 through a salt discharge pipe. A water vapor outlet 212 and an observation port 213 are also provided at the top of the dissolving tank 21. The water vapor outlet 212 is used to discharge excess water vapor in the dissolving tank 21, and the observation port 213 is used to check the state of the material in the dissolving tank 21. The side wall of the dissolving tank 21 is provided with a water inlet 214 and a water outlet 215 lower than the water inlet 214, which are respectively used to inject dissolving water into the dissolving tank 21 and discharge salt solution. The dissolving tank 21 is also equipped with a stirring device 22 for stirring the material in the dissolving tank 21 and a heat exchanger 23 for heating the material in the dissolving tank 21. In this embodiment, the stirring device 22 is a paddle stirrer and the heat exchanger 23 is a tubular heat exchanger 23.

[0030] The specific steps of the fly ash rapid desalination and detoxification method are as follows: 1. Conductive solid material melting: The conductive solid material is added into the melting furnace 1 by means of the feed hopper 11 and the feed pipe 111. The conductive solid material is heated and melted under the cooperation of the heating electrode 12 and the bottom electrode 13 to form a high-temperature molten metal layer α. In this embodiment, steel slag is selected as the conductive solid material, and the conductive liquid layer α formed is a molten steel liquid layer with a thickness of 0.1m and a density of about 7.1 g / cm 3 .

[0031] 2. Melting of solid mineral waste: Continue to add solid mineral waste into the melting furnace 1, heat and melt to form a slag layer β, and control the temperature of the slag layer β to be 1200-1450°C and the thickness ≥0.5m. At this temperature, the fly ash added in the subsequent steps can be melted. In actual operation, the temperature can fluctuate around 1300°C. In this embodiment, the solid mineral waste is selected from silica, slag and waste glass, and the slag layer β formed has a thickness of 0.6m and a density of 2.3~2.5 g / cm3 .

[0032] 3. Fly ash melting: Continue to feed granulated fly ash into the melting furnace 1. The particle size of the granulated fly ash is 2-3cm. Under the heating of the slag layer β, the fly ash melts to form slag and precipitates molten salt. The slag has a large density and sinks to the slag layer β, while the molten salt has a small density and floats to the molten salt layer δ. Dioxins are rapidly decomposed into non-toxic small molecules, and heavy metals sink and are fixed with the slag. The fly ash that has not been completely melted forms a material layer γ. By adjusting the fly ash feeding speed, the thickness of the material layer γ is controlled to be ≥0.5m. In this embodiment, the thickness of the material layer γ is 0.6m and the density is 1.7~1.9g / cm 3 Due to the density difference of each material in the melting furnace 1, a metal layer α, a slag layer β, a material layer γ and a molten salt layer δ (thickness 1m, density 1.3~1.5g / cm 3 ), and the temperature of each layer of material presents a gradient distribution. Among them, the material layer γ is suspended between the molten salt layer δ and the slag layer β, partially overlapping with the molten salt layer δ and the slag layer β, and the molten salt layer δ is kept about 0.5m clear from the top wall of the melting furnace 1. With the continuous addition of fly ash, the thickness of the fly ash material layer γ gradually increases. Fly ash has a good thermal insulation effect and can slow down the upward transfer of heat. Under the thermal insulation effect of the material layer γ, the temperature of the molten salt layer δ is controlled in the range of 800-950℃ by adjusting the thickness of the material layer γ. The temperature of the top molten salt layer δ makes the molten salt molten but not easy to volatilize, which reduces the generation of molten salt-containing tail gas discharge and thus causes equipment corrosion, and is not easy to form secondary pollution.

[0033] Material resource utilization: The molten salt of the molten salt layer δ and the slag of the slag layer β are discharged separately for recycling. The discharged molten salt is introduced into the molten salt water quenching and dissolving device 2, and the solution temperature in the dissolving tank 21 is controlled to be ≤80°C. The discharged molten salt is dissolved under the stirring of the stirring device 22 to obtain a salt solution that can be used industrially. The main components of the discharged molten salt are miscellaneous salts such as sodium chloride, potassium chloride, and calcium chloride. The temperature is about 850°C, in a molten state, and has good fluidity. The molten salt flows into the water through the salt discharge pipe. Under the action of high temperature and stirring, the chloride salt is quickly cooled and dissolved. By controlling the inlet and outlet liquid volume and the heat exchange device, the salt water concentration can be increased to a near saturation concentration, and can be directly used in the back-end process for resource utilization. The slag is discharged from the slag outlet 16 at the bottom of the melting furnace 1, and after cooling, it forms a glass body, which can be used as a building material aggregate, or directly enters the resource utilization process in a high-temperature molten state to make high-value products such as thermal insulation cotton.

[0034] The subsequent operation status of the furnace is maintained by flexibly adjusting the feeding and discharging speeds according to the situation, which can achieve continuous feeding, continuous slag discharge, and intermittent salt discharge.

[0035] The above are all preferred embodiments of the present application, and the protection scope of the present application is not limited thereto. Therefore, any equivalent changes made according to the structure, shape, and principle of the present application should be included in the protection scope of the present application.

Claims

1. A method for rapid desalination and detoxification of fly ash, characterized in that: The steps include: Step 1, heating and melting the conductive solid material to form a molten metal layer (α); Step 2: adding solid mineral waste to melt and form a slag layer (β), and controlling the temperature of the slag layer (β) to be 1200-1450° C.; Step 3: Add fly ash, which melts under the heating of the slag layer (β) to form slag and precipitate molten salt. The fly ash that has not been completely melted forms a material layer (γ), and the thickness of the material layer (γ) is controlled to be ≥0.5m; due to the density difference, each material layer (γ) forms a metal layer (α), a slag layer (β), a material layer (γ) and a molten salt layer (δ) distributed from bottom to top, wherein the material layer (γ) is suspended between the molten salt layer (δ) and the slag layer (β); under the heat insulation effect of the material layer (γ), the temperature of the molten salt layer (δ) is controlled in the range of 800-950°C; Step 4: Discharge the molten salt in the molten salt layer (δ) and the slag in the slag layer (β) respectively for recycling.

2. A method for rapid desalination and detoxification of fly ash according to claim 1, characterized in that: In step three, the fly ash is granulated to a particle size of 2-3 cm.

3. The method for rapid desalination and detoxification of fly ash according to claim 1, characterized in that: In step 2, the thickness of the slag layer (β) is ≥ 0.5 m.

4. A method for rapid desalination and detoxification of fly ash according to any one of claims 1 to 3, characterized in that: In step 1, the conductive solid material input is steel slag.

5. A method for rapid desalination and detoxification of fly ash according to any one of claims 1 to 3, characterized in that: In step 2, the solid mineral waste input is one or more of silica, slag, and waste glass.

6. A method for rapid desalination and detoxification of fly ash according to any one of claims 1 to 3, characterized in that: In step 4, the discharged molten salt is introduced into water, stirred and dissolved, and the solution temperature is controlled to be ≤80° C. to obtain a salt solution that can be used industrially.

7. A method for rapid desalination and detoxification of fly ash according to any one of claims 1 to 3, characterized in that: In step 4, the discharged slag is cooled to obtain a glass body that can be used in industry.

8. A fly ash rapid desalination and detoxification system, used for implementing the fly ash rapid desalination and detoxification method according to any one of claims 1 to 7, characterized in that include, A melting furnace (1), wherein the top wall of the melting furnace (1) is provided with an exhaust gas outlet (14), the side wall is provided with a molten salt outlet (15) for discharging molten salt from a molten salt layer (δ), and the bottom side wall is provided with a slag outlet (16) for discharging molten slag from a slag layer (β) and which is higher than the metal layer (α); A feed hopper (11) is arranged above the melting furnace (1) and is used to add materials into the melting furnace (1); a feed pipe (111) is connected to the bottom of the feed hopper (11), and the lower end opening of the feed pipe (111) is lower than the molten salt discharge port (15); And a heating device for heating the material in the melting furnace (1).

9. The fly ash rapid desalination and detoxification system according to claim 8, characterized in that: The heating device comprises a bottom electrode (13) and a heating electrode (12) which are arranged at a relative interval, and the bottom electrode (13) is arranged at the bottom of the melting furnace (1).

10. The fly ash rapid desalination and detoxification system according to claim 8 or 9, characterized in that: It also includes a molten salt water quenching and dissolving device (2) connected to the molten salt discharge port (15) through a salt discharge pipe.

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