Harmless recycling method for waste incineration fly ash

Abstract

The invention relates to a harmless recycling method for waste incineration fly ash, which belongs to the technical field of harmless treatment of fly ash, and comprises the following steps: uniformly mixing fly ash and auxiliary materials to obtain a mixture; the auxiliary materials comprise a heavy metal stabilizer, a fluxing agent, a diagenesis agent and a metal-based auxiliary material; the heavy metal stabilizer is phosphate; the diagenesis agent is a silicon-based compound; the metal-based auxiliary material is one or more of a magnesium compound and an aluminum compound; the mixture is subjected to forming granulation, heat treatment, leaching desalination and drying, and a harmless recycling product is obtained. According to the harmless recycling method for the fly ash, fixation of heavy metal and decomposition of dioxin at the low temperature can be achieved, the harmless recycling treatment process is high in efficiency and low in energy consumption, and the obtained harmless recycling product is lasting in heavy metal stabilizing effect, low in dioxin content and low in heavy metal leaching concentration and soluble chlorine content.

Description

Technical Field

[0001] The invention relates to the technical field of harmless treatment of fly ash, and in particular to a harmless resource utilization method for fly ash from garbage incineration. Background Art

[0002] Waste incineration fly ash is a substance produced during the incineration of municipal domestic waste and enters the flue gas purification system along with the flue gas, and is eventually captured in the dust collector. The output of waste incineration fly ash of the grate furnace type waste incinerator is about 2-5% of the total amount of waste entering the furnace. According to statistics, the total annual output of waste incineration fly ash in my country in 2023 has exceeded 10 million tons. Since waste incineration fly ash is enriched with heavy metals such as Hg, Pb, Cd, Cu, Cr and Zn, and also contains carcinogens such as dioxins, fly ash is listed as hazardous waste. At present, the disposal method of fly ash in domestic waste incineration power plants still remains at the stage of adding cement and stabilizer solidification landfill, and resource utilization has not yet reached a scale. Fly ash also contains rich calcium and silicon resources, and the resource utilization of fly ash is of great significance. Fly ash water washing cement kiln synergy is a relatively mature means of fly ash resource utilization, but the whole process disposal process is complicated and costly. Fly ash sintering heat treatment can achieve dioxin detoxification of fly ash and is an effective means to realize fly ash resource utilization. However, the current fly ash sintering heat treatment process generally has problems such as low fly ash content and high sintering temperature, resulting in disposal costs that are still far higher than landfill disposal costs. Therefore, the development of efficient and cost-effective fly ash resource utilization technology is of great value and significance. Summary of the invention

[0003] In view of one or more technical problems existing in the prior art, the present invention provides a method for harmless resource utilization of fly ash from waste incineration. The method for harmless resource utilization of fly ash provided by the present invention can achieve the fixation of heavy metals and the decomposition of dioxins at low temperatures. The harmless resource disposal process has high efficiency and low energy consumption. The obtained harmless resource product has a long-lasting heavy metal stabilization effect, low dioxin content, and low heavy metal leaching concentration and soluble chlorine content.

[0004] The present invention provides a method for harmless resource utilization of fly ash from garbage incineration, the method comprising the following steps:

[0005] The fly ash and auxiliary materials are mixed to obtain a mixture; the auxiliary materials include a heavy metal stabilizer, a flux, a diagenetic agent and a metal-based auxiliary material; the heavy metal stabilizer is a phosphate; the diagenetic agent is a silicon-based compound; the metal-based auxiliary material is one or more of a magnesium compound and an aluminum compound;

[0006] The mixed material is subjected to molding and granulation, heat treatment, elution and desalination, and drying to obtain a harmless resource product.

[0007] Preferably, the amount of phosphate is 1-3% of the mass of fly ash; and / or

[0008] The phosphate is one or more of potassium dihydrogen phosphate, potassium monohydrogen phosphate, and potassium phosphate.

[0009] Preferably, the amount of the flux is 2-10% of the mass of the fly ash; and / or

[0010] The flux is at least one of glass powder and fluorite powder.

[0011] Preferably, the amount of the silicon-based compound is 10-60% of the mass of the fly ash; and / or

[0012] The silicon-based compound is one or more of fly ash, steel slag powder, silica gel, tailings powder, silica ash, and fumed silicon dioxide.

[0013] Preferably, the amount of the metal-based auxiliary material is 1-5% of the mass of the fly ash; and / or

[0014] The metal-based auxiliary material is one or more of magnesium hydroxide, magnesium oxide, magnesium carbonate and aluminum hydroxide.

[0015] Preferably, the pressure of the molding granulation is not less than 20 MPa; and / or

[0016] The size of the particles after the molding and granulation is 2 to 8 mm.

[0017] Preferably, the heat treatment is carried out under an inert atmosphere, wherein the concentration of the inert gas in the inert atmosphere is not less than 99.2 vol%; and / or

[0018] The heat treatment temperature is 500-900° C. and the time is 20-60 minutes.

[0019] Preferably, the elution desalination is achieved by an elution device, which comprises: a porous conveyor belt for conveying materials, a plurality of spraying areas and draining areas alternately arranged above the porous conveyor belt, and a plurality of liquid tanks for containing elution liquid below the porous conveyor belt;

[0020] The spraying area is provided with a liquid atomizing component for uniformly spraying the eluent on the surface of the material to elute the material;

[0021] The draining area is provided with a high-pressure gas spray gun for sweeping the liquid on the surface of the material. Preferably, the width of the spraying area is 8 to 12 times the width of the draining area; and / or

[0022] The number of the liquid tanks 24 is 3 to 10.

[0023] Preferably, the amount of the elution liquid used in the elution desalination process is 1.5 to 2.5 times the mass of the fly ash, and the elution time is 10 to 40 minutes.

[0024] Compared with the prior art, the present invention has at least the following beneficial effects:

[0025] The present invention firstly mixes fly ash and auxiliary materials, and forms and granulates the mixed materials to obtain particles with a certain size; then, low-temperature heat treatment is carried out under the action of the auxiliary materials to form a high-strength new phase, which effectively stabilizes the heavy metals in the fly ash and decomposes dioxins, and then soluble chloride salts are removed by elution and desalination to obtain a harmless resource product with higher added value.

[0026] The fly ash harmless resource utilization method provided by the present invention can achieve the fixation of heavy metals and the decomposition of dioxins at low temperature. The harmless resource utilization disposal process has high efficiency and low energy consumption. The obtained harmless resource utilization product has high strength, lasting heavy metal stabilization effect, low dioxin content, and low heavy metal leaching concentration and soluble chlorine content. BRIEF DESCRIPTION OF THE DRAWINGS

[0027] In order to more clearly illustrate the embodiments of the present invention or the technical solutions in the prior art, the drawings required for use in the embodiments or the description of the prior art will be briefly introduced below. Obviously, the drawings described below are some embodiments of the present invention. For ordinary technicians in this field, other drawings can be obtained based on these drawings without paying creative work.

[0028] Figure 1 A schematic structural diagram of a heating treatment device provided by the present invention;

[0029] Figure 2 A schematic structural diagram of a rinsing device provided by the present invention.

[0030] Figure numerals: 11-cylinder, 12-cylinder bracket; 13-heating medium; 111-material inlet; 112-material inlet cover; 113-material outlet; 114-material outlet cover; 115-gas inlet; 116-gas outlet; 14-material conveying component; 21-porous conveyor belt; 22-spraying area; 221-liquid atomization assembly; 23-draining area; 231-high-pressure gas spray gun; 24-liquid tank; 3-material. DETAILED DESCRIPTION

[0031] In order to make the purpose, technical solutions and advantages of the embodiments of the present invention clearer, the technical solutions in the embodiments of the present invention will be clearly and completely described below. Obviously, the described embodiments are part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without making creative work are within the scope of protection of the present invention.

[0032] The present invention provides a method for harmless resource utilization of fly ash from garbage incineration, the method comprising the following steps:

[0033] The fly ash and auxiliary materials are mixed to obtain a mixture; the auxiliary materials include a heavy metal stabilizer, a flux, a diagenetic agent and a metal-based auxiliary material; the heavy metal stabilizer is a phosphate; the diagenetic agent is a silicon-based compound; the metal-based auxiliary material is one or more of a magnesium compound and an aluminum compound;

[0034] The mixed material is subjected to molding and granulation, heat treatment, elution and desalination, and drying to obtain a harmless resource product.

[0035] The present invention firstly mixes fly ash and auxiliary materials, and forms and granulates the mixed materials to obtain particles with a certain size; then, low-temperature heat treatment is carried out under the action of the auxiliary materials to form a high-strength new phase, which effectively stabilizes the heavy metals in the fly ash and decomposes dioxins, and then soluble chloride salts are removed by elution and desalination to obtain a harmless resource product with higher added value.

[0036] The fly ash harmless resource utilization method provided by the present invention can achieve the fixation of heavy metals and the decomposition of dioxins at low temperature. The harmless resource utilization disposal process has high efficiency and low energy consumption. The obtained harmless resource utilization product has high strength, lasting heavy metal stabilization effect, low dioxin content, and low heavy metal leaching concentration and soluble chlorine content.

[0037] According to some preferred embodiments, the amount of phosphate used is 1-3% of the mass of the fly ash.

[0038] According to some preferred embodiments, the phosphate is one or more of potassium dihydrogen phosphate, potassium monohydrogen phosphate, and potassium phosphate.

[0039] According to some preferred embodiments, the amount of the flux is 2-10% of the mass of the fly ash.

[0040] According to some preferred embodiments, the flux is at least one of glass powder and fluorite powder.

[0041] According to some preferred embodiments, the silicon-based compound is used in an amount of 10 to 60% of the fly ash mass.

[0042] According to some preferred embodiments, the silicon-based compound is one or more of fly ash, steel slag powder, silica gel, tailings powder, silica fume, and fumed silica.

[0043] According to some preferred embodiments, the amount of the metal-based auxiliary material is 1-5% of the mass of the fly ash.

[0044] According to some preferred embodiments, the metal-based auxiliary material is one or more of magnesium hydroxide, magnesium oxide, magnesium carbonate, and aluminum hydroxide.

[0045] The present invention achieves local melting by adding flux to fly ash, reduces the temperature of heat treatment, and cooperates with diagenetic agent and metal-based auxiliary material to improve the strength of the new phase after heat treatment. If flux, diagenetic agent and metal-based auxiliary material are not added, the strength of the new phase after heat treatment is low and it is easy to be dispersed in the subsequent leaching process.

[0046] According to some preferred embodiments, the pressure of the molding and granulation is not less than 20 MPa.

[0047] According to some preferred embodiments, the size of the particles after molding and granulation is 2 to 8 mm.

[0048] According to some preferred embodiments, the heat treatment is carried out in an inert atmosphere, and the concentration of the inert gas in the inert atmosphere is not less than 99.2 vol%. The present invention ensures efficient decomposition of dioxins by performing heat treatment in an inert atmosphere. If the content of the inert gas is too low, the decomposition efficiency of dioxins will be affected.

[0049] According to some preferred embodiments, the heat treatment is performed at a temperature of 500 to 900° C. and for a time of 20 to 60 minutes.

[0050] According to some preferred embodiments, the heat treatment is achieved by a heat treatment device, which includes: a cylinder 11, a cylinder support 12 and a heating medium 13 for heating the cylinder; a material inlet 111 and a material outlet 113 are respectively provided at both ends of the cylinder 11; a material inlet cover 112 and a material outlet cover 114 are respectively provided at the material inlet 111 and the material outlet 113; a gas inlet 115 and a gas outlet 116 connected to the cylinder 11 are provided on the side wall of the cylinder 11; the gas inlet 115 is close to the material outlet 113 and opens downward; the gas outlet 116 is close to the material inlet 111 and opens upward; the cylinder support 12 is height-adjustable to facilitate taking out the material after the heat treatment; a material conveying component 14 for accommodating the heat-treated material is provided below the material outlet. The heating medium 13 is one of a resistance wire heating medium, an electromagnetic heating medium, a high-temperature gas heating medium, and a high-temperature liquid heating medium.

[0051] Before heat treatment, first close the material outlet cover, introduce gas into the cylinder through the gas inlet, discharge the air in the cylinder from the gas outlet, add material into the cylinder, close the material inlet cover, heat the cylinder with a heating element, and perform heat treatment. After the treatment, open the material outlet cover, adjust the height of the cylinder bracket so that the height of the material inlet is greater than the material outlet, allow the material to flow out of the cylinder, and transport it to the elution device through the material conveying component for elution and desalination.

[0052] The present invention adds heavy metal stabilizers, fluxing agents, diagenetic agents and metal-based auxiliary materials to the fly ash, so that the temperature requirement of the mixture for heat treatment is not so strict, and harmless resource treatment can be achieved under the heat treatment condition of 500-900°C. Therefore, the use of the above-mentioned heat treatment device can achieve a high filling amount of the mixture (the material in the cylinder can be fully filled) and a small footprint, which can effectively solve the problem of small filling amount and large footprint of the existing rotary kiln for fly ash treatment.

[0053] According to some preferred embodiments, the elution desalination is achieved by an elution device, such as Figure 2 As shown, the elution device includes: a porous conveyor belt 21 for conveying material 3, a plurality of spray areas 22 and drain areas 23 alternately arranged above the porous conveyor belt 21, and a plurality of liquid boxes 24 for containing elution liquid below the porous conveyor belt 21; the porous conveyor belt 21 is used to convey material 3; the spray area 22 is provided with a liquid atomization component 221 for uniformly spraying the elution liquid on the surface of the material 3 to rinse the material 3; the drain area 23 is provided with a high-pressure gas spray gun 231 for blowing the liquid on the surface of the material 3.

[0054] According to some preferred embodiments, the width of the spraying area 22 is 8 to 12 times the width of the draining area 23; and the number of the liquid tanks 24 is 3 to 10.

[0055] The rinsing device provided by the present invention is provided with a plurality of spraying areas and draining areas arranged alternately. The rinsing liquid is atomized in the rinsing area by a liquid atomizing component, so that the rinsing liquid can be evenly sprayed on the surface of the material, so that the material is fully rinsed, and the rinsing effect is significantly better than the rinsing method using an ordinary nozzle. Then the high-pressure gas spray gun blows the liquid on the surface of the material, which can effectively remove the salt solution on the surface of the material after rinsing. Repeating rinsing-draining multiple times can effectively improve the efficiency of rinsing and desalting.

[0056] According to some preferred embodiments, the material conveying component 14 in the heat treatment device is connected to the porous conveying belt 21 of the elution device; the material conveying component 14 is used to convey the heat-treated material to the elution device.

[0057] According to some preferred embodiments, the amount of the elution liquid used in the elution and desalination process is 1.5 to 2.5 times the mass of the fly ash, and the elution time is 10 to 40 minutes.

[0058] According to some preferred embodiments, after leaching and desalination, a step of removing heavy metals from the brine is also included, specifically including: introducing a gas containing carbon dioxide into the brine after leaching and desalination, and then adding a heavy metal treatment agent; the heavy metal treatment agent is at least one of phosphate and sulfide. The phosphate is one or a mixture of sodium phosphate, sodium pyrophosphate, and sodium phytate; the sulfide is one or a mixture of sodium sulfide and potassium sulfide. The amount of phosphate is 0.01-0.1% of the mass of the brine after leaching and desalination. The amount of sulfide is 0.05-0.2% of the mass of the brine after leaching and desalination. The present invention uses a heavy metal treatment agent to remove heavy metals from the brine after leaching and desalination to ensure that the treated brine can meet the discharge standards and be discharged from the system.

[0059] In order to more clearly illustrate the technical solutions and advantages of the present invention, the present invention is further described below in conjunction with the examples. The present invention does not specifically limit the sources of the reagents used in the examples and comparative examples, and the reagents can be directly purchased or synthesized by themselves.

[0060] Example 1

[0061] Fly ash, heavy metal stabilizer (potassium phosphate, used in an amount of 2% of the fly ash mass), flux (glass powder, used in an amount of 8% of the fly ash mass), diagenetic agent (fly ash, used in an amount of 40% of the fly ash mass) and metal-based auxiliary material (magnesium hydroxide, used in an amount of 3% of the fly ash mass) are mixed to obtain a mixture;

[0062] The mixed material is shaped into granules and heat treated (using Figure 1 heat treatment device under inert atmosphere, the concentration of inert gas in the inert atmosphere is not less than 99.2 vol%, the heat treatment temperature is 800 ℃, the time is 40min), elution and desalination (using Figure 2 The ash is washed and desalted using a washing device, with the amount of water being twice the mass of the ash and the washing time being 30 min), and dried to obtain a harmless resource product.

[0063] Example 2

[0064] The fly ash, heavy metal stabilizer (potassium monohydrogen phosphate, the amount of which is 1% of the fly ash mass), flux (fluorite powder, the amount of which is 2% of the fly ash mass), diagenetic agent (steel slag powder, the amount of which is 60% of the fly ash mass) and metal-based auxiliary material (aluminum hydroxide, the amount of which is 1% of the fly ash mass) are mixed to obtain a mixture;

[0065] The mixed material is shaped into granules and heat treated (using Figure 1 heat treatment device under inert atmosphere, the concentration of inert gas in the inert atmosphere is not less than 99.2 vol%, the heat treatment temperature is 500 ℃, the time is 60 min), elution and desalination (using Figure 2 The ash is washed and desalted using a washing device, the amount of water used is 2.5 times the mass of the ash, the elution time is 40 min), and dried to obtain a harmless resource product.

[0066] Example 3

[0067] The fly ash, heavy metal stabilizer (potassium dihydrogen phosphate, the amount of which is 3% of the fly ash mass), flux (glass powder, the amount of which is 10% of the fly ash mass), diagenetic agent (silica fume, the amount of which is 40% of the fly ash mass) and metal-based auxiliary material (magnesium oxide, the amount of which is 5% of the fly ash mass) are mixed to obtain a mixture;

[0068] The mixed material is subjected to molding and granulation, heat treatment (under an inert atmosphere, the concentration of the inert gas in the inert atmosphere is not less than 99.2 vol%, the heat treatment temperature is 900°C, and the time is 20 min), elution and desalination (using Figure 2 The ash is washed and desalted using a washing device, the amount of water used is 1.5 times the mass of the ash, the elution time is 10 min), and dried to obtain a harmless resource product.

[0069] Example 4

[0070] The fly ash, heavy metal stabilizer (potassium phosphate, the amount of which is 2% of the fly ash mass), flux (glass powder, the amount of which is 6% of the fly ash mass), diagenetic agent (fumed silica, the amount of which is 10% of the fly ash mass) and metal-based auxiliary material (magnesium carbonate, the amount of which is 5% of the fly ash mass) are mixed to obtain a mixture;

[0071] The mixed material is subjected to molding and granulation, heat treatment (under an inert atmosphere, the concentration of the inert gas in the inert atmosphere is not less than 99.2 vol%, the heat treatment temperature is 900°C, and the time is 40 min), elution and desalination (using Figure 2 The ash is washed and desalted using a washing device, the amount of water used is 2.5 times the mass of the ash, the elution time is 40 min), and dried to obtain a harmless resource product.

[0072] Example 5

[0073] It is basically the same as Example 1, except that: a traditional rotary kiln is used for heat treatment, the heat treatment is carried out under an inert atmosphere, the concentration of inert gas in the inert atmosphere is not less than 99.2 vol%, the heat treatment temperature is 800°C, and the time is 40 min.

[0074] Comparative Example 1

[0075] The method is basically the same as Example 1, except that no flux is added.

[0076] Comparative Example 2

[0077] It is basically the same as Example 1, except that no diagenetic agent is added.

[0078] Comparative Example 3

[0079] The method is basically the same as Example 1, except that no metal-based auxiliary material is added.

[0080] Comparative Example 4

[0081] It is basically the same as Example 1, except that the rinsing device does not include a draining area.

[0082] Comparative Example 5

[0083] It is basically the same as Example 1, with the only difference being that the rinsing device is a conventional liquid spray head.

[0084] The performance data of the harmless resource recovery products of the embodiments of the present invention and the comparative examples are shown in Table 1. The test methods of each performance are as follows:

[0085] Dioxin content test: refer to HJ 77.3-2008 standard for testing;

[0086] Heavy metal leaching concentration: tested in accordance with HJ / T 300-2007 standard;

[0087] Soluble chlorine content test: silver nitrate volumetric method; the soluble chlorine content refers to the mass fraction of soluble chlorine in the harmless resource product.

[0088] Compressive strength: Tested in accordance with GB / T 17431.2-1998 standard.

[0089] Table 1. Performance data of harmless resource recovery products of the embodiments of the present invention and the comparative examples

[0090]

[0091] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention, rather than to limit it. Although the present invention has been described in detail with reference to the aforementioned embodiments, those skilled in the art should understand that they can still modify the technical solutions described in the aforementioned embodiments, or make equivalent replacements for some of the technical features therein. However, these modifications or replacements do not deviate the essence of the corresponding technical solutions from the spirit and scope of the technical solutions of the embodiments of the present invention.

Claims

1. A method for harmless resource utilization of fly ash from garbage incineration, characterized in that: The method comprises the following steps: The fly ash and auxiliary materials are mixed to obtain a mixture; the auxiliary materials include a heavy metal stabilizer, a flux, a diagenetic agent and a metal-based auxiliary material; the heavy metal stabilizer is a phosphate; the diagenetic agent is a silicon-based compound; the metal-based auxiliary material is one or more of a magnesium compound and an aluminum compound; The mixed material is subjected to molding and granulation, heat treatment, elution and desalination, and drying to obtain a harmless resource product.

2. The method according to claim 1, characterized in that: The amount of phosphate is 1-3% of the fly ash mass; and / or The phosphate is one or more of potassium dihydrogen phosphate, potassium monohydrogen phosphate, and potassium phosphate.

3. The method according to claim 1, characterized in that The amount of the flux is 2-10% of the fly ash mass; and / or The flux is at least one of glass powder and fluorite powder.

4. The method according to claim 1, characterized in that: The amount of the silicon-based compound is 10-60% of the fly ash mass; and / or The silicon-based compound is one or more of fly ash, steel slag powder, silica gel, tailings powder, silica ash, and fumed silicon dioxide.

5. The method according to claim 1, characterized in that The amount of the metal-based auxiliary material is 1-5% of the mass of the fly ash; and / or The metal-based auxiliary material is one or more of magnesium hydroxide, magnesium oxide, magnesium carbonate and aluminum hydroxide.

6. The method according to claim 1, characterized in that The pressure of the molding and granulation is not less than 20MPa; and / or The size of the particles after the molding and granulation is 2 to 8 mm.

7. The method according to claim 1, characterized in that The heat treatment is carried out in an inert atmosphere, wherein the concentration of the inert gas in the inert atmosphere is not less than 99.2 vol%; and / or The heat treatment temperature is 500-900° C. and the time is 20-60 minutes.

8. The method according to claim 1, characterized in that The elution and desalination is achieved by an elution device, which includes: a porous conveyor belt for conveying materials, a plurality of spraying areas and draining areas alternately arranged above the porous conveyor belt, and a plurality of liquid tanks for containing elution liquid below the porous conveyor belt; The spraying area is provided with a liquid atomizing component for uniformly spraying the eluent on the surface of the material to elute the material; The draining area is provided with a high-pressure gas spray gun for blowing away the liquid on the surface of the material.

9. The method according to claim 8, characterized in that The width of the spraying area is 8 to 12 times the width of the draining area; and / or The number of the liquid tanks 24 is 3 to 10.

10. The method according to claim 1, characterized in that The amount of the elution liquid used in the elution and desalination process is 1.5 to 2.5 times the mass of the fly ash, and the elution time is 10 to 40 minutes.

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