A Low-Temperature-Based Method for Harmless Resource Utilization of Waste Incineration Fly Ash

Abstract

This invention relates to a low-temperature-based method for the harmless resource recovery of waste incineration fly ash, belonging to the technical field of fly ash harmless treatment. The method includes: mixing fly ash, auxiliary materials, and a catalyst to obtain a mixture; the auxiliary materials include phosphates; the catalyst is obtained by reacting a mixture containing titanium oxysulfate, ammonium metavanadate, sodium acetate, and sodium hydroxyethyl sulfonate; the mass ratio of titanium oxysulfate, ammonium metavanadate, sodium acetate, and sodium hydroxyethyl sulfonate is 100:0.5-3:5-10:3-6; and subjecting the mixture to mechanical alloying, extrusion molding granulation, and heat treatment to obtain a harmless resource recovery product. The fly ash harmless resource recovery method provided by this invention can achieve the fixation of heavy metals and the decomposition of dioxins at low temperatures. The harmless resource recovery process is highly efficient and energy-saving, and the obtained harmless resource recovery product exhibits long-lasting heavy metal stability, low dioxin content, and low heavy metal leaching concentration.

Description

Technical Field

[0001] This invention relates to the field of fly ash harmless treatment technology, and in particular to a method for harmless resource utilization of waste incineration fly ash based on low temperature. Background Technology

[0002] The incineration process of municipal solid waste generates 3% to 5% fly ash (based on mainstream grate-type incinerators). In 2022, the national output of fly ash from waste incineration exceeded 10 million tons. Waste incineration fly ash is a special type of solid waste, characterized by high salt content and rich in pollutants such as heavy metals and dioxins. It is listed in the National Hazardous Waste List, therefore, the safe disposal of waste incineration fly ash requires high attention.

[0003] Waste incineration fly ash contains abundant recyclable components. Cement kiln co-processing of incineration fly ash can achieve fly ash resource utilization to a certain extent, while saving land resources occupied by landfills. However, the added value it achieves is low, the process is complex, and the cost of fly ash disposal is much higher than that of landfilling. Furthermore, my country currently faces problems such as overcapacity in the cement industry and the uneven distribution of cement production, which limit the sustainable development and widespread application of this technology.

[0004] Heating fly ash can decompose organic compounds such as dioxins and stabilize heavy metals, making it a current research hotspot. High-temperature melting of fly ash can achieve complete harmlessness, volume reduction, and resource recovery, yielding higher value-added products. However, high-temperature melting requires heating the fly ash to 1300℃~1600℃, resulting in high energy consumption and disposal costs far exceeding those of cement kiln co-processes. High-temperature sintering of fly ash mostly requires temperatures of 1100℃, also consuming significant energy. Therefore, reducing the heat treatment temperature of fly ash, lowering process energy consumption, and improving the economic efficiency of fly ash disposal have become urgent scientific and technological challenges in the field of fly ash resource recovery. Developing low-temperature heat treatment technologies for fly ash to achieve detoxification and resource recovery will undoubtedly become an important future direction for waste incineration fly ash disposal technology. Summary of the Invention

[0005] To address one or more technical problems existing in the prior art, this invention provides a method for the harmless resource utilization of fly ash from waste incineration based on low temperature. The method for the harmless resource utilization of fly ash provided by this invention can achieve the fixation of heavy metals and the decomposition of dioxins at low temperature. The harmless resource utilization process is highly efficient and energy-saving. The harmless resource utilization products obtained have a long-lasting effect of heavy metal stability, low dioxin content, and low heavy metal leaching concentration.

[0006] The present invention provides a method for the harmless resource utilization of fly ash from waste incineration based on low temperature, the method comprising the following steps: Fly ash, auxiliary materials, and catalyst are mixed to obtain a mixture; the auxiliary materials include phosphates; the catalyst is obtained by reacting a mixture containing titanium oxysulfate, ammonium metavanadate, sodium acetate, and sodium hydroxyethyl sulfonate; the mass ratio of titanium oxysulfate, ammonium metavanadate, sodium acetate, and sodium hydroxyethyl sulfonate is 100:0.5~3:5~10:3~6. The mixture is subjected to mechanical alloying, extrusion molding and granulation, and heat treatment to obtain a harmless resource-based product.

[0007] Preferably, the amount of phosphate used is 1-3% of the fly ash mass; and / or The phosphate is one or more of sodium phosphate, potassium dihydrogen phosphate, potassium phosphate, and sodium pyrophosphate.

[0008] Preferably, the excipients further include silicon-based excipients and metal-based excipients; The metal-based auxiliary material is one or more of magnesium hydroxide, aluminum hydroxide, bauxite powder, aluminum slag powder, magnesium oxide, and magnesium carbonate. The silicon-based auxiliary material is one or more of the following: fly ash, steel slag powder, tailings powder, silica fume, and fumed silica.

[0009] Preferably, the amount of the silicon-based auxiliary material is 10-50% of the fly ash mass; and / or The amount of the metal-based auxiliary material is 5-25% of the fly ash mass.

[0010] Preferably, the amount of catalyst used is 0.01~0.1% of the fly ash mass; and / or The particle size of the catalyst is no greater than 100 nm.

[0011] Preferably, the reaction temperature is 120~150℃ and the time is 8~12h.

[0012] Preferably, the mechanical alloying treatment employs at least one of ball milling and extrusion.

[0013] Preferably, the ball-to-material ratio of the ball mill is 1:2~3, the ball milling speed is 1000~3000 rpm, and the ball milling time is 15~30 min.

[0014] Preferably, the extrusion pressure is 80~300MPa and the time is 15~30min.

[0015] Preferably, the pressure of the extrusion granulation is not less than 20 MPa; and / or The heat treatment is carried out in an inert atmosphere at a temperature of 225-325°C for 30-120 minutes; preferably, the inert gas content in the inert atmosphere is not less than 98 vol.

[0016] Compared with the prior art, the present invention has at least the following beneficial effects: This invention first enhances the interfacial reaction activity between solid materials by mechanically alloying a mixture of fly ash, auxiliary materials, and catalyst, which is beneficial for the stability of heavy metals in fly ash. Then, the mechanically alloyed material is extruded and granulated to obtain particles of a certain size. Finally, the particles are heat-treated, and the temperature of the heat treatment is lowered by using a self-made catalyst, which can achieve the fixation of heavy metals and the decomposition of dioxins at low temperatures, greatly reducing the cost of the treatment process, while obtaining harmless resource products with higher added value.

[0017] The fly ash harmless resource utilization method provided by this invention can realize the fixation of heavy metals and the decomposition of dioxins at low temperatures. The harmless resource utilization process is highly efficient and energy-saving. The harmless resource utilization product has a long-lasting effect of heavy metal stability, low dioxin content, and low heavy metal leaching concentration. Attached Figure Description

[0018] To more clearly illustrate the technical solutions in the embodiments of the present invention or the prior art, the drawings used in the description of the embodiments or the prior art will be briefly introduced below. Obviously, the drawings described below are some embodiments of the present invention. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0019] Figure 1 This is a schematic diagram of the extrusion device provided by the present invention; Reference numerals: 11-Feeding hopper; 12-Double roller extrusion roller; 13-Crusher; 14-Perforated screen plate; 15-Material conveying components. Detailed Implementation

[0020] To make the objectives, 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 some embodiments of the present invention, but not all embodiments. All other embodiments obtained by those skilled in the art based on the embodiments of the present invention without creative effort are within the scope of protection of the present invention.

[0021] The present invention provides a method for the harmless resource utilization of fly ash from waste incineration based on low temperature, the method comprising the following steps: Fly ash, auxiliary materials, and catalyst are mixed to obtain a mixture; the auxiliary materials include phosphates; the catalyst is obtained by reacting a mixture containing titanium oxysulfate, ammonium metavanadate, sodium acetate, and sodium hydroxyethyl sulfonate; the mass ratio of titanium oxysulfate, ammonium metavanadate, sodium acetate, and sodium hydroxyethyl sulfonate is 100:0.5~3:5~10:3~6. The mixture is subjected to mechanical alloying, extrusion molding and granulation, and heat treatment to obtain a harmless resource-based product.

[0022] This invention first enhances the interfacial reaction activity between solid materials by mechanically alloying a mixture of fly ash, auxiliary materials, and catalyst, which is beneficial for the stability of heavy metals in fly ash. Then, the mechanically alloyed material is extruded and granulated to obtain particles of a certain size. Finally, the particles are heat-treated, and the temperature of the heat treatment is lowered by using a self-made catalyst, which can achieve the fixation of heavy metals and the decomposition of dioxins at low temperatures, greatly reducing the cost of the treatment process, while obtaining harmless resource products with higher added value.

[0023] The fly ash harmless resource utilization method provided by this invention can realize the fixation of heavy metals and the decomposition of dioxins at low temperatures. The harmless resource utilization process is highly efficient and energy-saving. The harmless resource utilization product has a long-lasting effect of heavy metal stability, low dioxin content, and low heavy metal leaching concentration.

[0024] According to some preferred embodiments, the amount of phosphate used is 1 to 3% of the fly ash mass (e.g., it can be 1%, 1.2%, 1.5%, 1.6%, 2%, 2.2%, 2.5%, 2.8% or 3%).

[0025] According to some preferred embodiments, the phosphate is one or more selected from sodium phosphate, potassium dihydrogen phosphate, potassium phosphate, and sodium pyrophosphate. The phosphate of the present invention is a heavy metal stabilizer used to stabilize heavy metals in fly ash.

[0026] According to some preferred embodiments, the excipients also include silicon-based excipients and metal-based excipients; The metal-based auxiliary material is one or more of magnesium hydroxide, aluminum hydroxide, bauxite powder, aluminum slag powder, magnesium oxide, and magnesium carbonate. The silicon-based auxiliary material is one or more of the following: fly ash, steel slag powder, tailings powder, silica fume, and fumed silica.

[0027] This invention improves the mechanical strength of the harmless resource-based products by adding silicon-based and metal-based additives to the auxiliary materials, thus broadening their application scenarios.

[0028] According to some preferred embodiments, the amount of the silicon-based auxiliary material is 10-50% of the fly ash mass.

[0029] According to some preferred embodiments, the amount of the metal-based auxiliary material is 5-25% of the fly ash mass.

[0030] According to some preferred embodiments, the amount of catalyst used is 0.01~0.1% of the fly ash mass (for example, it can be 0.01%, 0.02%, 0.03%, 0.04%, 0.05%, 0.06%, 0.07%, 0.08%, 0.09% or 0.1%).

[0031] According to some preferred embodiments, the particle size of the catalyst is no greater than 100 nm.

[0032] According to some preferred embodiments, the reaction temperature is 120~150°C (e.g., 120°C, 125°C, 130°C, 135°C, 140°C, 145°C or 150°C), and the time is 8~12h (e.g., 8h, 9h, 10h, 11h or 12h).

[0033] According to some preferred embodiments, the preparation method of the catalyst includes: mixing titanium oxysulfate, ammonium metavanadate, sodium acetate, sodium hydroxyethyl sulfonate and water, reacting at 120~150℃ for 8~12h, and obtaining the catalyst by solid-liquid separation and drying.

[0034] This invention involves reacting titanium oxysulfate and ammonium metavanadate with additives (sodium acetate and sodium hydroxyethyl sulfonate) to obtain a vanadium-doped modified titanium dioxide catalyst with small and uniform particle size and excellent catalytic performance. The addition of additives (sodium acetate and sodium hydroxyethyl sulfonate) is beneficial for controlling the catalyst morphology and improving its catalytic activity. The amount of vanadium doping in the catalyst can be controlled by adjusting the amounts of titanium oxysulfate and ammonium metavanadate.

[0035] According to some preferred embodiments, the amount of water used is 20 to 40 times the mass of titanium oxysulfate (e.g., 20, 25, 30, 35 or 40 times).

[0036] According to some preferred embodiments, the mechanical alloying treatment employs at least one of ball milling and extrusion.

[0037] According to some preferred embodiments, the ball-to-material ratio of the ball mill is 1:2~3, the ball milling speed is 1000~3000 rpm, and the ball milling time is 15~30 min.

[0038] According to some preferred embodiments, the extrusion pressure is 80~300MPa (for example, it can be 80MPa, 100MPa, 150MPa, 200MPa, 250MPa or 300MPa), and the time is 15~30min.

[0039] According to some preferred embodiments, mechanical alloying is achieved by extrusion using an extrusion device. This device includes, from top to bottom, a feeding hopper 11, a double-roller extrusion roller 12, a crusher 13, a perforated screen plate 14, and a material conveying component 15 communicating with the perforated screen plate 14 and the feeding hopper. The double-roller extrusion roller 12 is used to extrude the material; the crusher 13 is used to crush the extruded material; the perforated screen plate 14 is used to screen the extruded material; and the material conveying component 15 is used to return the screened material to the feeding hopper, repeating the extrusion-crushing-screening steps. The material conveying component 15 is preferably a bucket elevator or a tubular chain conveyor. The pressure of the double-roller extrusion roller 12 is 80~300MPa, and the size of the crushed particles is less than 5mm. This device utilizes the pressure of the double-roller extrusion roller to achieve mechanical alloying of the material.

[0040] According to some preferred embodiments, the extrusion granulation pressure is not less than 20 MPa; preferably, the size of the granules after extrusion granulation is 2~8 mm. This invention does not specifically limit the shape of the granules after extrusion granulation; for example, they can be spherical, ellipsoidal, or cylindrical.

[0041] According to some preferred embodiments, the heat treatment is carried out in an inert atmosphere at a temperature of 225~325℃ (e.g., 225℃, 250℃, 275℃, 300℃, or 325℃) for 30~120 minutes; preferably, the inert gas content in the inert atmosphere is not less than 98 vol%. This invention ensures efficient dioxin decomposition by performing heat treatment in an inert atmosphere; if the inert gas content is too low, the dioxin decomposition efficiency will be affected.

[0042] To more clearly illustrate the technical solution and advantages of the present invention, the present invention will be further described below with reference to embodiments. The present invention does not specifically limit the source of the reagents used in the embodiments and comparative examples; they can be directly purchased or synthesized in-house.

[0043] Example 1 Catalyst preparation: Titanium oxysulfate, ammonium metavanadate, sodium acetate, sodium hydroxyethyl sulfonate and water were mixed and reacted at 130℃ for 10 h. After solid-liquid separation and drying, the catalyst was obtained. The mass ratio of titanium oxysulfate, ammonium metavanadate, sodium acetate and sodium hydroxyethyl sulfonate was 100:2:6:5, and the amount of water was 30 times the mass of titanium oxysulfate. The fly ash, auxiliary material (sodium phosphate, 2% of the fly ash mass), and catalyst (0.06% of the fly ash mass) are mixed to obtain a mixture. The mixture is subjected to mechanical alloying treatment (using...) Figure 1The product is extruded using an extrusion device at a pressure of 150 MPa for 20 min, then extruded into granules and heat-treated at 300℃ for 60 min to obtain a harmless resource-based product.

[0044] Example 2 Catalyst preparation: Titanium oxysulfate, ammonium metavanadate, sodium acetate, sodium hydroxyethyl sulfonate and water were mixed and reacted at 120℃ for 12h. After solid-liquid separation and drying, the catalyst was obtained. The mass ratio of titanium oxysulfate, ammonium metavanadate, sodium acetate and sodium hydroxyethyl sulfonate was 100:0.5:5:3, and the amount of water used was 20 times the mass of titanium oxysulfate.

[0045] The fly ash, auxiliary material (potassium dihydrogen phosphate, 1% of the fly ash mass), and catalyst (0.01% of the fly ash mass) are mixed to obtain a mixture. The mixture is subjected to mechanical alloying treatment (using...) Figure 1 The product is extruded using an extrusion device at a pressure of 300 MPa for 15 minutes, then extruded into granules and heat-treated at 325°C for 120 minutes to obtain a harmless resource-based product.

[0046] Example 3 Catalyst preparation: Titanium oxysulfate, ammonium metavanadate, sodium acetate, sodium hydroxyethyl sulfonate and water were mixed and reacted at 150℃ for 8 hours. After solid-liquid separation and drying, the catalyst was obtained. The mass ratio of titanium oxysulfate, ammonium metavanadate, sodium acetate and sodium hydroxyethyl sulfonate was 100:3:10:6, and the amount of water was 20 times the mass of titanium oxysulfate.

[0047] The fly ash, auxiliary material (sodium pyrophosphate, 3% of the fly ash mass), and catalyst (0.1% of the fly ash mass) are mixed to obtain a mixture. The mixture is subjected to mechanical alloying treatment (using...) Figure 1 The product is extruded using an extrusion device at a pressure of 80 MPa for 30 minutes, then extruded into granules and heat-treated at 225°C for 30 minutes to obtain a harmless resource-based product.

[0048] Example 4 The process is basically the same as in Example 1, except that mechanical alloying is performed by ball milling at a speed of 2800 rpm for 20 minutes.

[0049] Example 5 The process is basically the same as in Example 1, except that the auxiliary materials include silicon-based auxiliary materials (fly ash, accounting for 40% of the fly ash mass), metal-based auxiliary materials (magnesium oxide, accounting for 12% of the fly ash mass), and phosphates (sodium phosphate, accounting for 2% of the fly ash mass).

[0050] Example 6 It is basically the same as Example 1, except that it includes silicon-based auxiliary materials (fly ash, with an amount of 40% of the fly ash mass), metal-based auxiliary materials (magnesium oxide, with an amount of 12% of the fly ash mass) and phosphates (potassium dihydrogen phosphate, with an amount of 1% of the fly ash mass).

[0051] Example 7 It is basically the same as Example 1, except that it includes silicon-based auxiliary materials (fly ash, accounting for 40% of the fly ash mass), metal-based auxiliary materials (magnesium oxide, accounting for 12% of the fly ash mass), and phosphates (sodium pyrophosphate, accounting for 3% of the fly ash mass). Example 8 The process is basically the same as in Example 1, except that the auxiliary materials include silicon-based auxiliary materials (tailings powder, used at 20% of the fly ash mass), metal-based auxiliary materials (magnesium oxide, used at 15% of the fly ash mass), and phosphates (sodium phosphate, used at 2% of the fly ash mass).

[0052] Examples 5-8 demonstrate how introducing silicon-based and metal-based excipients into the additives can improve the compressive strength of the resulting harmless resource-based products (tested according to GB / T 17431.2-1998 standard) without affecting heavy metal stability and dioxin decomposition. Specifically, the compressive strength of the harmless resource-based product obtained in Example 5 is 2.8 MPa, in Example 6 it is 2.7 MPa, in Example 7 it is 2.4 MPa, and in Example 8 it is 1.9 MPa. In summary, this invention can obtain harmless resource-based products with different compressive strengths by controlling the type and amount of silicon-based and metal-based excipients added, thus meeting diverse needs.

[0053] Comparative Example 1 It is basically the same as Example 1, except that no catalyst was added.

[0054] Comparative Example 2 It is basically the same as Example 1, except that sodium acetate and sodium hydroxyethyl sulfonate were not added in the catalyst preparation process.

[0055] Comparative Example 3 The process is basically the same as in Example 1, except that the mass ratio of titanium oxysulfate, ammonium metavanadate, sodium acetate, and sodium hydroxyethyl sulfonate in the catalyst preparation process is 100:0.4:6:5.

[0056] Comparative Example 4 The process is basically the same as in Example 1, except that the mass ratio of titanium oxysulfate, ammonium metavanadate, sodium acetate, and sodium hydroxyethyl sulfonate during catalyst preparation is 100:3.5:6:5.

[0057] Comparative Example 5 It is basically the same as Example 1, except that titanium dioxide is used as the catalyst.

[0058] Comparative Example 6 It is basically the same as Example 1, except that no excipient (sodium phosphate) was added.

[0059] Comparative Example 7 It is basically the same as Example 1, except that the amount of excipient (sodium phosphate) is 0.5%.

[0060] The performance data of the harmless resource-based products of the embodiments and comparative examples of the present invention are shown in Table 1. The test methods for each performance are as follows: Dioxin content testing: The test shall be conducted in accordance with the HJ 77.3-2008 standard; Heavy metal leaching concentration: Tested in accordance with HJ / T 300-2007 standard.

[0061] Table 1. Performance data of the harmless resource-based products of the embodiments and comparative examples of the present invention. Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention, and not to limit them; although the present invention has been described in detail with reference to the foregoing embodiments, those skilled in the art should understand that modifications can still be made to the technical solutions described in the foregoing embodiments, or equivalent substitutions can be made to some of the technical features; and these modifications or substitutions do not cause the essence of the corresponding technical solutions to deviate from the spirit and scope of the technical solutions of the embodiments of the present invention.

Claims

1. A method for the harmless resource utilization of fly ash from waste incineration based on low temperature, characterized in that, The method includes the following steps: Fly ash, auxiliary materials, and catalyst are mixed to obtain a mixture; the auxiliary materials include phosphates; the catalyst is obtained by reacting a mixture containing titanium oxysulfate, ammonium metavanadate, sodium acetate, and sodium hydroxyethyl sulfonate; the mass ratio of titanium oxysulfate, ammonium metavanadate, sodium acetate, and sodium hydroxyethyl sulfonate is 100:0.5~3:5~10:3~6. The mixture is subjected to mechanical alloying, extrusion molding and granulation, and heat treatment to obtain a harmless resource-based product.

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

3. The method according to claim 1, characterized in that, The auxiliary materials also include silicon-based auxiliary materials and metal-based auxiliary materials; The metal-based auxiliary material is one or more of magnesium hydroxide, aluminum hydroxide, bauxite powder, aluminum slag powder, magnesium oxide, and magnesium carbonate. The silicon-based auxiliary material is one or more of the following: fly ash, steel slag powder, tailings powder, silica fume, and fumed silica.

4. The method according to claim 3, characterized in that, The amount of the silicon-based auxiliary material used is 10-50% of the fly ash mass; and / or The amount of the metal-based auxiliary material is 5-25% of the fly ash mass.

5. The method according to claim 1, characterized in that, The catalyst is used in an amount of 0.01~0.1% of the fly ash mass; and / or The particle size of the catalyst is no greater than 100 nm.

6. The method according to claim 1, characterized in that, The reaction is carried out at a temperature of 120-150°C for 8-12 hours.

7. The method according to claim 1, characterized in that, The mechanical alloying process employs at least one of ball milling and extrusion.

8. The method according to claim 7, characterized in that, The ball-to-material ratio of the ball mill is 1:2~3, the ball milling speed is 1000~3000 rpm, and the ball milling time is 15~30 min.

9. The method according to claim 7, characterized in that, The extrusion pressure is 80~300MPa, and the time is 15~30min.

10. The method according to claim 1, characterized in that, The pressure of the extrusion granulation is not less than 20 MPa; and / or The heat treatment is carried out in an inert atmosphere at a temperature of 225-325°C for 30-120 minutes.

11. The method according to claim 10, characterized in that, The inert gas content in the inert atmosphere is not less than 98 vol.

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