Method for co-processing of waste incineration fly ash with hot blast furnace slag

Abstract

This invention discloses a method for co-processing waste incineration fly ash with hot blast furnace slag, relating to the field of hazardous waste disposal and utilization. The proposed method involves controlling the amount of waste incineration fly ash added and using a flux to lower the melting temperature. The fly ash is mixed with boron oxide, crushed, and granulated. This granulation is then simultaneously fed with freshly extruded molten blast furnace slag into a fly ash melting tank, reacted for a certain period, and then water-quenched to prepare water-quenched slag. The waste heat of the hot blast furnace slag is used for high-temperature treatment of the waste incineration fly ash. The high Ca, Si, and Al content of the blast furnace slag has an excellent effect on fixing heavy metal components in the fly ash, thereby immobilizing these heavy metals into the water-quenched slag. This method fully utilizes the valuable components in solid waste, increases the added value of solid waste products, and broadens the utilization pathways of waste incineration fly ash.

Description

Technical Field

[0001] This invention relates to the field of hazardous waste disposal and utilization, specifically to a method for co-processing waste incineration fly ash with hot blast furnace slag. Background Technology

[0002] Fly ash from waste incineration is a harmful byproduct generated during the waste-to-energy incineration process. It primarily originates from flue gas purification equipment such as baghouse dust collectors, as well as deposits at the bottom of flues and chimneys. Its composition is complex and diverse, containing oxides of metals such as calcium, sodium, and potassium, as well as heavy metal ions such as lead, cadmium, and mercury, and chlorides. Fly ash is characterized by high toxicity and high chloride content, making it difficult and costly to treat.

[0003] Currently, the main methods for treating fly ash from waste incineration are cement solidification landfill, chemical stabilization, and thermal treatment. However, these methods all have significant limitations. Cement solidification landfill significantly increases the volume of fly ash, consuming large amounts of land resources, and heavy metals are difficult to stabilize, posing a risk of leaching. Chemical stabilization faces challenges in stabilizing multiple heavy metals and is relatively weak in stabilizing other pollutants. Among thermal treatment technologies, cement kiln co-processing is limited in its application because the chlorine in waste incineration fly ash can easily corrode the kiln body and affect cement quality.

[0004] The co-processing of waste incineration fly ash faces two major challenges: first, ensuring the complete fixation or removal of harmful substances in the fly ash to achieve harmlessness; and second, minimizing the impact on the original process. For example, while cement kiln co-processing can decompose organic pollutants and solidify heavy metals, soluble chloride salts (such as NaCl and KCl) in waste incineration fly ash are difficult to completely remove, easily leading to scaling, blockage, and corrosion within the kiln. Furthermore, water washing pretreatment is costly and complex, limiting its large-scale application. Other processes, such as high-temperature melting and sintering, suffer from technical complexity, difficulty in exhaust gas treatment, and the potential generation of secondary fly ash. Therefore, developing an environmentally and economically feasible method for the resource utilization of waste incineration fly ash remains an urgent problem to be solved. Summary of the Invention

[0005] To address the aforementioned shortcomings of existing technologies, this invention provides a method for co-processing waste incineration fly ash with hot blast furnace slag. This method increases the amount of waste incineration fly ash that can be disposed of, effectively solidifies heavy metals, reduces the leaching toxicity of the fly ash, and minimizes the impact on the original process, thereby reducing the cost of waste incineration fly ash treatment.

[0006] To achieve the above-mentioned objectives, the technical solution adopted by this invention is as follows:

[0007] A method for co-processing waste incineration fly ash with hot blast furnace slag is provided, comprising the following steps:

[0008] S1: Ball mill the fly ash from waste incineration with boron oxide together;

[0009] S2: After ball milling, granulation and drying are used to obtain mixed particles;

[0010] S3: The molten blast furnace slag and mixed particles are fed into the fly ash bag melting pot and waited for the reaction to obtain the melt;

[0011] S4: The molten material is treated by cold water flushing to obtain water-quenched slag.

[0012] Furthermore, the contents of heavy metals Zn, Cu, Pb and Cr in the fly ash from waste incineration are 0–6.00%, 0–5.50%, 0–0.24% and 0–1.00%, respectively.

[0013] Furthermore, the mass ratio of waste incineration fly ash to boron oxide is 10:1.

[0014] Furthermore, the particle size of the mixed particles is 1.0–3.0 mm.

[0015] Furthermore, the mass ratio of the mixed particles to the molten blast furnace slag is 1:10.0 to 10.3; and the melting reaction time of the mixed particles and the molten blast furnace slag is 7 to 10 minutes.

[0016] Furthermore, the molten blast furnace slag is freshly produced slag at 1450–1550°C.

[0017] Furthermore, the cold water flushing pressure is 0.2–0.4 MPa, and the flushing water spray volume is 8–12 m³ / h. 3 / t.

[0018] Furthermore, in step S1, the ball milling time is 10-15 minutes, and the particle size of the ball-milled particles is ≤3 mm.

[0019] The beneficial effects of this invention are as follows:

[0020] This invention proposes a method for co-processing waste incineration fly ash with hot blast furnace slag. By controlling the amount of fly ash added and combining it with boron oxide as a flux to lower the melting temperature, the fly ash is mixed with boron oxide, crushed, and granulated. This granulation is then simultaneously fed into a fly ash melting tank with freshly extruded molten blast furnace slag, reacting for a certain period before water quenching to prepare water-quenched slag. This method utilizes the sensible heat of the blast furnace slag to melt and process the fly ash. Simultaneously, the high Ca, Si, and Al content in the blast furnace slag has an excellent effect on immobilizing heavy metal components, thus fixing the heavy metal components in the incineration fly ash into the water-quenched slag. This method fully utilizes the valuable components in solid waste, increases the added value of solid waste products, and broadens the utilization pathways of waste incineration fly ash.

[0021] The fly ash treatment method provided by this invention has significant beneficial effects. Through an innovative co-processing technology, a single treatment can consume approximately 10% of the fly ash mass of blast furnace slag, greatly improving fly ash treatment efficiency. Simultaneously, leveraging my country's vast annual blast furnace slag resources and the advantages of large-scale processing, it enables large-scale, continuous disposal of fly ash. The combination of these two aspects allows this method to achieve economies of scale in terms of total fly ash treatment volume, effectively solving the problems of fly ash accumulation and environmental pollution, while reducing treatment costs and creating significant economic and environmental benefits. It possesses extremely high industrial application value and market promotion potential. Attached Figure Description

[0022] Figure 1 SEM image of the water-quenched slag prepared in Example 1;

[0023] Figure 2 XRD pattern of the water-quenched slag prepared in Example 1;

[0024] Figure 3 The image shows a comparison of infrared measurements of water-quenched slag prepared with different preparation parameters in Example 6. Detailed Implementation

[0025] The specific embodiments of the present invention are described below to enable those skilled in the art to understand the present invention. However, it should be understood that the present invention is not limited to the scope of the specific embodiments. For those skilled in the art, various changes are obvious as long as they are within the spirit and scope of the present invention as defined and determined by the appended claims. All inventions utilizing the concept of the present invention are protected.

[0026] In the embodiments of the present invention, fly ash from a waste incineration plant was used. Testing revealed that its main components were CaO, SiO2, and Al2O3. Typical heavy metals Zn, Cu, Pb, and Cr, calculated as ZnO, CuO, PbO, and Cr2O3, had contents of 0–6.00%, 0–5.50%, 0–0.24%, and 0–1.00%, respectively.

[0027] Example 1

[0028] The following steps are used to treat fly ash from waste incineration:

[0029] S1: Ball mill the fly ash from waste incineration with boron oxide (analytical grade) at a mass ratio of 10:1; the ball milling time is 10-15 minutes, and the particle size of the ball milled particles is ≤3mm.

[0030] S2: After ball milling, granulation and drying yield mixed particles with a particle size of 1.0–3.0 mm;

[0031] S3: Molten blast furnace slag discharged from the blast furnace slag outlet at 1450-1550℃ and mixed particles are fed together into the fly ash bag melting pot at a mass ratio of 10.0-10.3:1, and the reaction is allowed to proceed for 7-10 minutes to obtain the molten material;

[0032] S4: The cold water flushing method is adopted with a water pressure of 0.2-0.4 MPa and a flushing water volume of 8-12 m³ / h. 3 / t processes the molten material to obtain water-quenched slag.

[0033] SEM and XRD tests were performed on the water-quenched slag. SEM tests are as follows: Figure 1 As shown, the XRD test results are as follows: Figure 2 As shown. Among them. Figure 1 The right side is Figure 1 An enlarged view of the area selected in the left-hand box. Figure 1 The magnification on the left is 500x. Figure 1 The magnification on the right is 2000x. Figure 1 It can be seen that the reconstructed water-quenched slag has a smooth surface with flaky small particles, exhibiting an amorphous and dispersed state with distinct edges and corners. Combined with... Figure 2 XRD analysis results show that the original crystal structure of fly ash in the reconstructed water-quenched slag has changed, basically forming an amorphous glassy structure, which can reduce the exposure of heavy metals in the water-quenched slag and further reduce the leaching concentration of heavy metals. Compared with the original blast furnace slag, the mineral phase composition of the reconstructed water-quenched slag is basically similar to that of industrial blast furnace slag, and no other significant changes were found.

[0034] Example 2

[0035] The difference between this embodiment and Embodiment 1 is that, in step S1, the mass ratio of waste incineration fly ash to boron oxide is 11:1.

[0036] Example 3

[0037] The difference between this embodiment and Embodiment 1 is that, in step S1, the mass ratio of waste incineration fly ash to boron oxide is 9:1.

[0038] Example 4

[0039] The difference between this embodiment and Embodiment 1 is that, in step S3, the mass ratio of molten blast furnace slag to mixed particles is 10.4:1.

[0040] Example 5

[0041] The difference between this embodiment and Embodiment 1 is that, in step S3, the mass ratio of molten blast furnace slag to mixed particles is 9:1.

[0042] Example 6

[0043] The heavy metal content and leaching concentration in the water-quenched slag prepared in Examples 1-5 were detected, and the results were converted into heavy metal solid solubility. Where R F c represents the solid solution ratio. o The concentration of heavy metals in the sample before melting is expressed in mg·kg⁻¹. -1 ;m o c1 is the mass of the sample before melting, in kg; c2 is the concentration of heavy metals in the molten product, in mg·kg⁻¹. -1 m1 represents the mass of the molten product, in kg. The results are shown in Table 1 below.

[0044] Table 1

[0045]

[0046] As shown in Table 1, the water-quenched slag prepared by the method of the present invention has significantly reduced leaching toxicity of typical heavy metals Zn, Cu, Pb and Cr compared with untreated waste incineration fly ash, proving that typical heavy metals in waste incineration fly ash can be fixed by molten blast furnace slag.

[0047] Compared to Example 1, Example 2 reduced the amount of boron oxide. The solid solubility of Zn, Cu, Pb, and Cr in the resulting water-quenched slag was lower than in Example 1. This may be because the reduced boron oxide content resulted in some heavy metals in the waste incineration fly ash failing to melt successfully, leading to insufficient heat and preventing the fly ash from being fixed by the molten blast furnace slag. In contrast, Example 3 increased the amount of boron oxide compared to Example 1, but the leaching toxicity and solid solubility of heavy metals in the water-quenched slag did not change significantly. This demonstrates that a mass ratio of waste incineration fly ash to boron oxide of 10:1 is sufficient to melt the heavy metals. Therefore, a mass ratio of waste incineration fly ash to boron oxide of 10:1 is optimal for cost control.

[0048] Compared to Example 1, Example 4 reduced the amount of mixed particles, resulting in a similar reduction in the leaching toxicity of heavy metals in the water-quenched slag, but a decrease in the solid solution rate. In Example 5, compared to Example 1, the amount of mixed particles increased, but the leaching toxicity of heavy metals in the water-quenched slag increased simultaneously with the solid solution rate. This may be because excessive mixed particles caused the temperature to drop too quickly upon contact with the molten blast furnace slag, preventing the heavy metals in the mixed particles from completely melting and being fixed by the blast furnace slag, thus reducing the heavy metal content in the water-quenched slag. Therefore, a mass ratio of molten blast furnace slag to mixed particles of 10.0–10.3:1 is optimal.

[0049] The water-quenched slags prepared in Examples 1-5 were subjected to infrared spectroscopy. Specifically, 2.0 mg of 200-mesh water-quenched slag and 200 mg of KBr were uniformly mixed, and then the mixture was pressed into a disc with a diameter of 13 mm. The infrared spectroscopy results were obtained at 4000–400 cm⁻¹. -1Record samples within a range with a resolution of 1 cm. -1 Each sample was collected and scanned 20 times. The test results are as follows: Figure 3 As shown in Table 1, the water-quenched slag prepared by the method of the present invention has a similar structure to the untreated industrial blast furnace slag, does not change the original material properties of the blast furnace slag, and still has potential hydration activity, which meets the requirements for subsequent utilization of blast furnace slag in building materials.

Claims

1. A method for co-processing hot blast furnace slag with waste incineration fly ash, characterized in that, Includes the following steps: S1: Ball mill the fly ash from waste incineration with boron oxide together; S2: After ball milling, granulation and drying are used to obtain mixed particles; S3: The molten blast furnace slag and mixed particles are fed into the fly ash bag melting pot and waited for the reaction to obtain the melt; S4: The molten material is treated by cold water flushing to obtain water-quenched slag; The contents of heavy metals Zn, Cu, Pb, and Cr in the waste incineration fly ash are 0~6.00%, 0~5.50%, 0~0.24%, and 0~1.00%, respectively. The mass ratio of the waste incineration fly ash to boron oxide is 10:1; The mass ratio of the mixed particles to the molten blast furnace slag is 1:10.0~10.3; and the melting reaction time of the mixed particles and the molten blast furnace slag is 7~10 min. The molten blast furnace slag is freshly produced slag at 1450~1550℃; Cold water flushing pressure: 0.2~0.4MPa; flushing water spray volume: 8-12m³ / h 3 / t.

2. The method for co-processing waste incineration fly ash with hot blast furnace slag according to claim 1, characterized in that, The particle size of the mixed particles is 1.0~3.0 mm.

3. The method for co-processing hot blast furnace slag with waste incineration fly ash according to claim 1, characterized in that, In step S1, the ball milling time is 10~15min, and the particle size of the ball milled particles is ≤3mm.

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