A method for preparing ceramsite by using zinc-containing sludge and sludge incineration fly ash and a product thereof

Abstract

The application discloses a method for preparing ceramsite by using zinc-containing sludge and sludge incineration fly ash and a product thereof, and the method comprises the following steps: uniformly mixing the zinc-containing sludge, the sludge incineration fly ash and iron tailings, high-speed grinding, mixing and stirring with water, and microwave treatment; after the end, granulating and drying to obtain green balls; sintering under air atmosphere, and obtaining ceramsite after cooling. Based on the chemical composition and characteristics of waste, the method combining high-speed grinding, microwave treatment and sintering is adopted, so that the synergistic resource utilization and harmless disposal of heavy metal sludge and sludge incineration fly ash are realized; meanwhile, the leaching concentration of zinc in the obtained ceramsite is at least 35.32+ / -0.04 mg / L, the highest fixed amount of zinc is 96.2%, the ceramsite has no dangerous characteristics, and has high strength. The application not only eliminates the environmental risk of the zinc-containing sludge and the sludge incineration fly ash, but also converts the zinc-containing sludge and the sludge incineration fly ash into available building materials, so that the double benefits of environment and economy are achieved.

Description

Technical Field

[0001] This invention relates to a method for preparing ceramsite using zinc-containing sludge and sludge incineration fly ash, and the product thereof, belonging to the field of harmless and resource-based disposal of hazardous waste. Background Technology

[0002] Zinc-containing sludge is a type of highly toxic hazardous waste generated during wastewater treatment in metal surface treatment enterprises. Currently, the main processes for the harmless disposal of zinc-containing sludge include chemical stabilization, co-processing in cement kilns, and high-temperature sintering. After chemical stabilization, the chromium-containing waste still needs to be safely landfilled, but landfill capacity is limited and cannot continuously receive such waste. Co-processing in cement kilns requires strict control over the characteristics and quantity of chromium-containing sludge entering the kiln to ensure cement quality. High-temperature sintering is energy-intensive and can also lead to some zinc volatilization into the flue gas, increasing the difficulty of flue gas treatment and consequently increasing treatment costs.

[0003] Sludge incineration fly ash is the fly ash produced after incinerating sludge generated from domestic sewage treatment. Currently, the main method for disposing of sludge incineration fly ash is solidification or stabilization followed by landfilling. However, landfilling occupies a large amount of land resources, and pollutants in sludge incineration ash can migrate due to long-term weathering, erosion, rainwater leaching, and soaking, causing serious environmental pollution.

[0004] Iron tailings, a major industrial solid waste generated after mineral processing, are composed of closely associated quartz and magnetite. Their complex mineral composition makes reprocessing technically challenging, and even with magnetic separation, the reduction in tailings grade is limited, resulting in minimal improvement in economic value. Consequently, industrial production shows little incentive to reprocess and utilize them, and they are often directly dumped as waste. Large quantities of iron tailings accumulate in tailings ponds, occupying significant amounts of agricultural and forestry land, and requiring substantial funds for daily maintenance and repair.

[0005] Therefore, there is an urgent need for a simple, efficient, and resource-efficient method for the treatment of hazardous waste containing zinc sludge, sludge incineration fly ash, and iron tailings. Summary of the Invention

[0006] Purpose of the invention: The technical problem to be solved by the present invention is to provide a simple and efficient method for resource-based treatment of zinc-containing sludge and sludge incineration fly ash to prepare ceramsite and the product thereof.

[0007] Technical Solution: To solve the above-mentioned technical problems, this invention provides a method for preparing ceramsite using zinc-containing sludge and sludge incineration fly ash, comprising the following steps: (1) Mix fine zinc-containing sludge, sludge incineration fly ash and iron tailings powder evenly, grind them to obtain the grinding product; (2) The grinding material obtained in step (1) is mixed with water to prepare a slurry, and then microwaved. After the slurry is finished, it is granulated and dried to obtain raw material balls. (3) The raw material balls obtained in step (2) are sintered in an air atmosphere and then cooled to obtain ceramsite.

[0008] The dry basis mass ratio of the fine zinc-containing sludge, sludge incineration fly ash and iron tailings in step (1) is 8~15:12~20:65~80.

[0009] The grinding rate in step (1) is 460-560 revolutions per minute, and the grinding time is 10-24 hours.

[0010] In step (2), the microwave processing power is 800~900W and the time is 5~10 minutes.

[0011] In step (2), the solid phase mass percentage of the slurry is 45% to 55%.

[0012] In step (2), the particle size of the granulated pellets is 10~16mm.

[0013] The moisture content of the raw material balls mentioned in step (2) is 4% to 5.5%.

[0014] In step (3), the roasting temperature is 950~1100℃ and the time is 15~25 minutes.

[0015] The present invention also provides a type of ceramsite prepared by the method, wherein the zinc leaching concentration in the ceramsite is as low as 35.32 ± 0.04 mg / L, the zinc fixation is as high as 96.2%, the compressive strength is as high as 6.64 MPa, and the bulk density is as high as 824 kg / m³. 3 .

[0016] The principle of this invention is as follows: Through the mechanochemical force generated by high-speed ball milling, the ordered crystalline morphology with low chemical reactivity in zinc-containing sludge, sludge incineration fly ash, and iron tailings is transformed into a disordered, amorphous, multiphase system with higher chemical reactivity. This process dissociates the large-molecule organic matter in the zinc-containing sludge and eliminates the hazardous dioxin in sludge incineration fly ash, continuously generating active components such as silicates, aluminosilicates, and aluminoferrites. The grinding product is mixed with water to prepare a slurry, which is then microwaved to give the reactant molecules higher energy, increasing the probability of effective intermolecular collisions while lowering the activation energy of the reaction. This promotes hydration reactions, generating silicon-oxygen, aluminum-oxygen, and silicon-aluminum-oxygen network polymer components, which then encapsulate, stabilize, or solidify a large amount of zinc components, achieving zinc stabilization and solidification.

[0017] During the sintering process, the highly reactive zinc, aluminum, iron, calcium, and silicon components in the raw material pellets rapidly form zinc-aluminum spinel and zinc-iron spinel phases, further achieving structural fixation of zinc and strengthening its solidification, significantly reducing zinc volatilization. Simultaneously, a large amount of aluminosilicate and mullite phases are produced, enhancing the structural strength of the ceramsite. Furthermore, the synergistic effect of mechanochemical and microwave processes enhances the solid-phase reaction activity of the materials, reducing the energy supply for solid-phase reactions. This leads to a decrease in sintering temperature and calcination time, significantly reducing zinc volatilization. The organic matter from the mechanochemical degradation of zinc-containing sludge provides some energy, further resulting in a significant reduction in energy consumption during the ceramsite sintering process.

[0018] Beneficial effects: Compared with the prior art, the present invention has the following significant advantages: 1. Based on the chemical composition and characteristics of waste, this invention adopts a combination of high-speed grinding, low-temperature microwave treatment and sintering to achieve the synergistic resource utilization and harmless treatment of fly ash from the incineration of hazardous waste zinc-containing sludge and general solid waste sludge.

[0019] 2. By adjusting the proportion of raw materials and combining the synergistic effects of mechanochemical and microwave treatment, the solid-phase reaction activity of the materials is enhanced, and the energy supply for the solid-phase reaction is reduced. This results in a decrease in the sintering temperature and calcination time of the materials, which greatly reduces the volatilization of zinc. Meanwhile, the organic matter degraded by the mechanochemical action of zinc-containing sludge provides a certain amount of energy, thus achieving a significant reduction in energy consumption during the sintering process of ceramic particles. This is beneficial for energy conservation, emission reduction, and low carbon emissions.

[0020] 3. The zinc leaching concentration in the ceramsite obtained by this invention is as low as 35.32±0.04 mg / L, and the zinc fixation is as high as 96.2%. It has no hazardous characteristics and possesses high strength. This invention not only eliminates the environmental risks of zinc-containing sludge and sludge incineration fly ash, but also transforms them into usable building materials, achieving both environmental and economic benefits. Attached Figure Description

[0021] Figure 1 This is a process flow diagram of the present invention. Detailed Implementation

[0022] The technical solution of the present invention will be further described below with reference to the accompanying drawings.

[0023] The zinc-containing sludge was taken from Rongchang Metal Surface Treatment Co., Ltd. in Suzhou Industrial Park. Its chemical composition was 3.7% SiO2, 5.9% Al2O3, 1.1% Fe2O3, 0.4% MgO, 4.1% CaO, 0.2% K2O, 0.1% TiO2, 43.1% ZnO, 7.6% CuO, 4.4% SO3, 0.2% P2O5, 0.3% Cl, 0.2% MnO2, and 28.7% loss on ignition.

[0024] The fly ash from sludge incineration was obtained from Zhejiang Zhonghe Bicheng Environmental Protection Technology Co., Ltd., with the following chemical composition: SiO2 10.3%, Al2O3 5.1%, Fe2O3 15.4%, CaO 34.1%, TiO2 0.5%, MgO 1.1%, P2O5 2.4%, SO3 27.7%, K2O 0.5%, Na2O 1.3%, BaO 0.4%, MnO2 0.1%, Cl 0.3%, and loss on ignition 0.8%.

[0025] The iron tailings were taken from East China University of Science and Technology Changshu Research Institute Co., Ltd., with the following chemical composition: SiO2 55.4%, Al2O3 15.9%, Fe2O3 10.4%, CaO 1.8%, Na2O 0.5%, K2O 8.3%, MgO 3.2%, and loss on ignition 4.5%.

[0026] Example 1

[0027] 45 g of fine zinc-containing sludge, sludge incineration fly ash, and iron tailings were mixed uniformly at a dry basis mass percentage of 8:12:80 to obtain a mixture. This mixture was then ground in a vertical planetary ball mill for 10 hours at 460 rpm. The ground product was mixed with water to prepare a slurry with a solid content of 55%. The slurry was then microwaved at 800W for 10 minutes. After microwave treatment, granulation was performed. Granulation was completed, and 10 mm pellets were screened and dried in a vacuum drying oven to obtain raw pellets with a moisture content of 4.0%. The raw pellets were then sintered in a high-temperature furnace at 1000℃ for 20 minutes in an air atmosphere. After sintering, the pellets were allowed to cool naturally to obtain ceramsite A1.

[0028] The heavy metal leaching toxicity of ceramsite A1 was tested using the "Leaching Toxicity Method for Solid Waste (Sulfuric Acid and Nitric Acid Method)" (HJ / T299-2007). The zinc leaching concentration of ceramsite A1 was measured to be 35.32 ± 0.04 mg / L, which is lower than the zinc leaching concentration limit (100 mg / L) in the "Identification Standard for Hazardous Waste (Leaching Toxicity Identification)". The zinc fixation amount was 94.8%. The compressive strength and bulk density of ceramsite A1 were tested according to "Lightweight Aggregates and Their Test Methods Part 2: Test Methods for Lightweight Aggregates" (GB / T 17431.2-2010). The results showed that the compressive strength of ceramsite A1 was 6.55 MPa and the bulk density was 845 kg / m³. 3 It meets the requirements of "Lightweight aggregates and their test methods - Part 1: Lightweight aggregates" (GB / T17431.1-2010).

[0029] Example 2

[0030] 45 g of fine zinc-containing sludge, sludge incineration fly ash, and iron tailings were mixed uniformly at a dry basis mass percentage of 15:20:65 to obtain a mixture. This mixture was then ground in a vertical planetary ball mill for 24 hours at 560 rpm. The ground product was mixed with water to prepare a slurry with a solid content of 50%. The slurry was then microwaved at 900W for 5 minutes. After microwave treatment, granulation was performed. Granulation was completed, and 16 mm pellets were screened and dried in a vacuum drying oven to obtain raw pellets with a moisture content of 4.5%. The raw pellets were then sintered in a high-temperature furnace at 1100℃ for 15 minutes in an air atmosphere. After sintering, the pellets were allowed to cool naturally to obtain ceramsite A2.

[0031] The heavy metal leaching toxicity of ceramsite A2 was tested using the "Leaching Toxicity Method for Solid Waste (Sulfuric Acid and Nitric Acid Method)" (HJ / T299-2007). The zinc leaching concentration of ceramsite A2 was measured to be 40.20 ± 0.02 mg / L, which is lower than the zinc leaching concentration limit (100 mg / L) in the "Identification Standard for Hazardous Waste (Leaching Toxicity Identification)". The zinc fixation amount was 94.5%. The compressive strength and bulk density of ceramsite A2 were tested according to "Lightweight Aggregates and Their Test Methods Part 2: Test Methods for Lightweight Aggregates" (GB / T 17431.2-2010). The results showed that the compressive strength of ceramsite A2 was 6.03 MPa and the bulk density was 812 kg / m³. 3 It meets the requirements of "Lightweight aggregates and their test methods - Part 1: Lightweight aggregates" (GB / T17431.1-2010).

[0032] Example 3

[0033] 45 g of fine zinc-containing sludge, sludge incineration fly ash, and iron tailings were mixed uniformly at a dry basis mass percentage of 10:18:72 to obtain a mixture. This mixture was then ground in a vertical planetary ball mill for 18 hours at 500 rpm. The ground product was mixed with water to prepare a slurry with a solid content of 45%. The slurry was then microwaved at 850 W for 8 minutes. After microwave treatment, granulation was performed. Granulation was completed, and 12 mm particles were screened and dried in a vacuum drying oven to obtain raw material balls with a moisture content of 5.5%. The raw material balls were then sintered in a high-temperature furnace at 950℃ for 25 minutes in an air atmosphere. After sintering, the ceramsite A3 was obtained by natural cooling.

[0034] The heavy metal leaching toxicity of ceramsite A3 was tested using the "Leaching Toxicity Method for Solid Waste (Sulfuric Acid and Nitric Acid Method)" (HJ / T299-2007). The zinc leaching concentration of ceramsite A3 was measured to be 46.26 ± 0.04 mg / L, which is lower than the zinc leaching concentration limit (100 mg / L) in the "Identification Standard for Hazardous Waste (Leaching Toxicity Identification)". The zinc fixation amount was 96.2%. The compressive strength and bulk density of ceramsite A3 were tested according to "Lightweight Aggregates and Their Test Methods Part 2: Test Methods for Lightweight Aggregates" (GB / T 17431.2-2010). The results showed that the compressive strength of ceramsite A3 was 6.25 MPa and the bulk density was 822 kg / m³. 3 It meets the requirements of "Lightweight aggregates and their test methods - Part 1: Lightweight aggregates" (GB / T17431.1-2010).

[0035] Comparative Example 1 45 g of fine zinc-containing sludge, sludge incineration fly ash, and iron tailings were mixed uniformly at a dry basis mass percentage of 8:12:80 to obtain a mixture. This mixture was then mixed with water to prepare a slurry with a solid content of 55%. The slurry was then microwaved at 800W for 10 minutes. After microwave treatment, granulation was performed. Granulation was completed, and 10 mm granules were screened and dried in a vacuum drying oven to obtain raw material pellets with a moisture content of 4.0%. The raw material pellets were then sintered in a high-temperature furnace at 1000℃ for 20 minutes in an air atmosphere. After sintering, the pellets were allowed to cool naturally to obtain ceramsite B1.

[0036] The heavy metal leaching toxicity of ceramsite B1 was tested using the "Leaching Toxicity Method for Solid Waste (Sulfuric Acid and Nitric Acid Method)" (HJ / T299-2007). The zinc leaching concentration of ceramsite B1 was measured to be 225.68±0.04 mg / L, which is higher than the zinc leaching concentration limit (100 mg / L) in the "Identification Standard for Hazardous Waste (Leaching Toxicity Identification)". The zinc fixation amount was 52.2%.

[0037] Comparative Example 2 45 g of fine zinc-containing sludge, sludge incineration fly ash, and iron tailings were mixed uniformly at a dry basis mass percentage of 8:12:80 to obtain a mixture. This mixture was then ground in a vertical planetary ball mill for 10 hours at 460 rpm. The ground product was mixed with water to prepare a slurry with a solid content of 55%, which was then granulated. After granulation, 10 mm diameter pellets were screened and dried in a vacuum drying oven to obtain raw pellets with a moisture content of 4.0%. The raw pellets were then sintered in a high-temperature furnace at 1000℃ for 20 minutes in an air atmosphere. After sintering, the pellets were allowed to cool naturally to obtain ceramsite B2.

[0038] The heavy metal leaching toxicity of ceramsite B2 was tested using the "Solid Waste Leaching Toxicity Leaching Method - Sulfuric Acid and Nitric Acid Method" (HJ / T299-2007). The zinc leaching concentration of ceramsite B2 was measured to be 116.24 ± 0.03 mg / L, which is higher than the zinc leaching concentration limit (100 mg / L) in the "Identification Standard for Hazardous Waste - Leaching Toxicity Identification". The zinc fixation amount was 73.5%.

[0039] Comparative Example 3 Following the method in Example 1, ceramsite was prepared under different raw material ratios, grinding conditions, microwave treatment conditions, and sintering conditions. The heavy metal leaching toxicity of the ceramsite was tested using the "Solid Waste Leaching Toxicity Leaching Method: Sulfuric Acid and Nitric Acid Method" (HJ / T299-2007). The results are shown in Table 1.

[0040] Table 1

[0041] The results in Table 1 show that the zinc leaching concentration of the ceramsite sample in Comparative Example 3 is higher than the environmental threshold, which is dangerous.

Claims

1. A method for preparing ceramsite using zinc-containing sludge and sludge incineration fly ash, characterized in that, Includes the following steps: (1) Mix zinc-containing sludge, sludge incineration fly ash and iron tailings evenly, grind them to obtain the grinding product; (2) Water is added to the grinding product described in step (1) to prepare a slurry, which is then microwaved, granulated, and dried to obtain raw material balls; (3) The raw material balls described in step (2) are sintered in an air atmosphere and cooled to obtain ceramsite.

2. The method according to claim 1, characterized in that, The dry basis mass ratio of zinc-containing sludge, sludge incineration fly ash and iron tailings in step (1) is 8~15:12~20:65~80.

3. The method according to claim 1, characterized in that, The grinding time in step (1) is 10~24h, and the speed is 460~560 revolutions / minute.

4. The method according to claim 1, characterized in that, The solid phase mass percentage of the slurry in step (2) is 45%~55%.

5. The method according to claim 1, characterized in that, The microwave processing in step (2) has a power of 800~900W and a duration of 5~10 minutes.

6. The method according to claim 1, characterized in that, The granules after granulation in step (2) have a particle size of 10~16mm.

7. The method according to claim 1, characterized in that, The moisture content of the raw material balls mentioned in step (2) is 4%~5.5%.

8. The method according to claim 1, characterized in that, The sintering temperature in step (3) is 950~1100℃ and the time is 15~25 minutes.

9. A type of ceramsite prepared by the method according to any one of claims 1 to 8.

Images