Method for high-temperature melting and solidification of household garbage incineration fly ash with reduced erosion of refractory materials

Abstract

The application discloses a household garbage incineration fly ash high-temperature melting solidification method for reducing the erosion of refractory materials, which realizes the solidification of fly ash and the reduction of the erosion of fly ash to refractory materials while the heavy metal leaching toxicity reaches the standard by reducing the quartz sand addition amount in fly ash and assisting in the proportion regulation of Al2O3 and CaO. The raw material components and mass percentages are as follows: the fly ash is 40-50%, the Al2O3 is 20-40%, the limestone is 10-15%, and the quartz sand is 0-5%; the melting temperature is 1400-1600 DEG C. The fly ash melting solidification is realized by regulating the content of CaO and Al2O3 and reducing the addition amount of quartz sand, the heavy metal leaching reaches the standard, the erosion of fly ash to refractory materials is reduced, and the service life of the lining is improved.

Description

Technical Field

[0001] This invention relates to the field of waste treatment technology, specifically to a method for high-temperature melting and solidification of fly ash from municipal solid waste incineration to reduce the erosion of refractory materials. Background Technology

[0002] Municipal solid waste incineration fly ash is the ash collected by the flue gas purification system and settles at the bottom of the flue and chimney, typically accounting for about 2% to 5% of the incineration volume. Incineration fly ash contains large amounts of heavy metals, dioxins, and other toxic and harmful substances. Once released into the environment, it will seriously endanger human survival and health. Therefore, the safe and effective treatment of waste incineration fly ash has become an urgent ecological and environmental problem to be solved. High-temperature melting technology can melt fly ash into a stable glassy structure. The dense crystalline structure of the glassy structure firmly seals the fly ash within, effectively solidifying the heavy metals in the fly ash. This is one of the important methods for the harmless treatment of fly ash. Refractory materials are key structural materials for high-temperature melting furnaces. During the high-temperature melting process, the inner refractory lining is corroded by various media in the fly ash, resulting in a shortened service life and affecting stable production.

[0003] Currently, the vitrification of municipal solid waste incineration fly ash requires the addition of large amounts of Si sources such as quartz sand to adjust the fly ash alkalinity, thereby promoting the melting effect and forming a glassy substance. For example, patent 201810517444.0 discloses a method for plasma melting and vitrification of fly ash, which involves adjusting the mass percentage of the main auxiliary materials to 60-75% SiO2, 5-17% Al2O3, and 8-30% CaO to form a glassy slag. Another patent, 202010332134.9, discloses a method for preparing microcrystalline glass from waste incineration fly ash and its large-scale production, which involves adding 20-60 parts of waste fly ash, 5-45 parts of quartz sand, 10-30 parts of limestone, and 5-12 parts of kaolin to produce microcrystalline glass via electrofusion. Meanwhile, numerous studies have shown that adding SiO2 to fly ash helps form a glassy substance and improves the melting effect. However, the presence of SiO2 (quartz sand) in fly ash will aggravate the erosion of refractory materials by fly ash, and react with the main components in refractory materials to generate various silica compounds, causing the inner lining refractory material to expand in volume, accelerate its wear, reduce its service life, and thus increase the cost of smelting treatment.

[0004] Therefore, there is an urgent need to invent a high-temperature melting and solidification method for municipal solid waste incineration fly ash that can reduce the erosion of refractory materials. This method would achieve fly ash solidification, ensure that heavy metal leaching meets standards, and reduce the erosion of refractory materials by reducing the amount of SiO2 added, thereby improving the service life of the lining and reducing the melting and treatment costs of incineration fly ash. Summary of the Invention

[0005] The purpose of this invention is to provide a high-temperature melting and solidification method for municipal solid waste incineration fly ash that reduces the erosion of refractory materials. On the one hand, it achieves fly ash solidification to form solid slag, and heavy metal leaching meets the standards. On the other hand, it also reduces the erosion of furnace lining refractory materials by fly ash by reducing the amount of SiO2 added, thereby improving the service life of the lining.

[0006] The specific technical solution for achieving the objective of this invention is as follows:

[0007] A method for high-temperature melting and solidification of municipal solid waste incineration fly ash to reduce refractory material erosion, comprising using municipal solid waste incineration fly ash as the main raw material and Al2O3, limestone, and quartz sand as auxiliary materials, wherein the mass percentage of the raw material components is: fly ash 40-50%, Al2O3 20-40%, limestone 10-15%, and quartz sand 0-5%; the melting temperature is 1400-1600℃; the specific solidification process includes:

[0008] Step 1: Weigh the fly ash from municipal solid waste incineration, limestone, Al2O3 and quartz sand according to the specified proportions to form a mixture, and then dry it. The drying temperature is 80-110℃ and the drying time is 15-45 minutes.

[0009] Step 2: Put the mixture into a high-temperature melting furnace for melting at a temperature of 1400-1600℃;

[0010] Step 3: After complete melting, cool to obtain solid fly ash slag.

[0011] Furthermore, the Al2O3 is aluminum oxide powder, and the limestone is calcium oxide powder.

[0012] Furthermore, the refractory material is a magnesium-chromium refractory material and a high-alumina refractory material.

[0013] In summary, this invention provides a high-temperature melting and solidification method for municipal solid waste incineration fly ash to reduce the erosion of refractory materials. By controlling the content of CaO and Al2O3 and reducing the amount of quartz sand added, the fly ash can be melted and solidified. While achieving the leaching of heavy metals, the erosion of refractory materials by fly ash is reduced, thereby improving the service life of the lining. Attached Figure Description

[0014] Figure 1 This is a schematic diagram showing the observation results after high-temperature melting in comparative examples and Examples 1-3;

[0015] Figure 2 This is a schematic diagram showing the percentage of erosion area and penetration area of ​​refractory materials during the fly ash melting and solidification process in comparative examples and Examples 1-3;

[0016] Figure 3XRD patterns of different parts (penetrating layer, eroded layer, ash) of refractory material after erosion during the fly ash melting and solidification process in comparative examples and Examples 1-3. Detailed Implementation

[0017] To further understand the technical content, features, and effects of the present invention, the following description, in conjunction with embodiments, is provided but does not constitute a limitation of the present invention. Detailed description follows:

[0018] A method for high-temperature melting and solidification of municipal solid waste incineration fly ash to reduce refractory material erosion is characterized by using municipal solid waste incineration fly ash as the main raw material and Al2O3, limestone and quartz sand as the main auxiliary materials. The mass percentage of the raw material components is as follows: fly ash 40-50%, Al2O3 20-40%, limestone 10-15%, and quartz sand 0-5%; the melting temperature is 1400-1600℃.

[0019] Comparative Example 1

[0020] A large amount of quartz sand is added to adjust the alkalinity of the fly ash. The raw material composition by mass percentage is: 45% fly ash, 30% quartz sand, 20% Al2O3, and 5% CaO. The method for high-temperature melting and solidification of fly ash from municipal solid waste incineration specifically includes the following steps:

[0021] S1 weighs the waste incineration fly ash, limestone, Al2O3 and quartz sand according to the above proportions and prepares a mixture, which is then dried at 110℃ for 30 minutes.

[0022] S2 feeds the mixed materials into a high-temperature melting furnace lined with magnesium-chromium refractory material for melting treatment. The high-temperature melting furnace is heated from room temperature to 1600℃ at a heating rate of 5℃ / min and the melting time is 120min.

[0023] After S3 has completely melted, cool it and observe the melting process.

[0024] Example 1

[0025] The raw material components in this embodiment are as follows (by weight percentage): 50% fly ash, 35% Al2O3, 10% CaO, and 5% quartz sand. The method for high-temperature melting and solidification of fly ash from municipal solid waste incineration specifically includes the following steps:

[0026] S1 weighs the waste incineration fly ash, limestone, Al2O3 and quartz sand according to the above proportions and prepares a mixture, which is then dried at 100℃ for 30 minutes.

[0027] S2 feeds the mixed materials into a high-temperature melting furnace lined with magnesium-chromium refractory material for melting treatment. The high-temperature melting furnace is heated from room temperature to 1600℃ at a heating rate of 5℃ / min and the melting time is 120min.

[0028] After S3 has completely melted, cool it and observe the melting process.

[0029] The differences between the formulations added in the fly ash melting and solidification of Examples 2-3 and Example 1 are shown in Table 1, while the other parts are the same as in Example 1.

[0030] Table 1 Formulation parameters for Comparative Example 1 and Examples 1-3

[0031]

[0032] The observation results after high-temperature melting of Comparative Example 1 and Examples 1-3 are as follows: Figure 1 .

[0033] according to Figure 1 It can be seen that no solid slag was generated in Comparative Example 1, and observation of the refractory material cross-section revealed a loose surface structure and obvious erosion. In contrast, solid slag was generated in Examples 1-3, and no obvious erosion was observed in the cross-section.

[0034] To more intuitively visualize the erosion of refractory materials, Adobe Photoshop software was used to statistically analyze and calculate the percentage of pixels in the eroded and penetrated layers relative to the original solid portion of the cross-section. This yielded the percentage of eroded and penetrated areas of the refractory materials in Comparative Example 1 and Examples 1-3, as shown below. Figure 2 As shown.

[0035] observe Figure 2 It can be seen that the percentage of erosion area and the percentage of penetration area of ​​fly ash on refractory materials during the melting and solidification process of the comparative examples and the embodiments differ significantly. The percentage of erosion area and the percentage of penetration area after fly ash erosion in Comparative Example 1 are the highest, indicating that the fly ash in Comparative Example 1 has the strongest erosion effect on refractory materials. The percentage of erosion area and the percentage of penetration area in Examples 1-3 are not significantly different, and are all much lower than those in Comparative Example 1. This indicates that reducing the amount of silica sand (SiO2) added will greatly reduce the erosion of refractory materials by fly ash.

[0036] To further investigate the erosion of refractory materials by fly ash in Comparative Example 1 and Examples 1-3, samples were taken from different areas of the eroded refractory materials (original brick, bottom permeation layer of the crucible, eroded layer, and residue) for XRD analysis. The results are as follows: Figure 3 As shown.

[0037] Figure 3(a) Comparative Example 1; (b) Example 1; (c) Example 2; (d) Example 3; Original brick #1; Penetration layer #2 after fly ash erosion; Erosion layer #3 after fly ash erosion; Residue #4 after fly ash erosion; Figure 3 (a) It was found that, compared with the original brick in Comparative Example 1, during the fly ash melting and solidification process, Mg2SiO4 compounds were generated in both the erosion layer and the penetration layer of the refractory material, leading to aggravated refractory material erosion. However, observation... Figure 3 (b) It was found that no magnesium silicate phase was generated in either the penetration layer or the erosion layer in Example 1. Only the Mg2SiO4 phase was seen in the slag. This may be because the SiO2 added to the fly ash reacted with the generated MgCr2O4 to generate Mg2SiO4 in the slag. Figure 3 (c) It was found that no magnesium silicate phase was formed in the penetration layer, the erosion layer, or the ash in Example 2, further demonstrating that not adding quartz sand greatly reduces the erosion of refractory materials by fly ash. Similarly, observations were made... Figure 3 (d) It was found that no magnesium silicate phase was formed in the penetration layer, the erosion layer, or the ash residue in Example 3. This indicates that reducing the amount of SiO2 added will greatly reduce the formation of magnesium silicon compounds, thereby reducing the erosion of refractory materials by fly ash.

[0038] The original fly ash and the solid slag generated in Examples 1-3 were digested using the hot plate digestion method in HJ781-2016 "Determination of 22 Heavy Metal Elements in Solid Waste by Inductively Coupled Plasma Emission Spectrometry" for heavy metal analysis. Heavy metal leaching was performed using acetic acid buffer solution as the leaching agent in HJ / T300-2007 "Leaching Toxicity Method for Solid Waste - Acetic Acid Buffer Solution Method". The heavy metal leaching concentrations of the original fly ash and the slag from Examples 1-3, and their test results and indicators (mg / L), are shown in Table 2.

[0039] Table 2. Test results and indicators (mg / L) of heavy metal leaching concentration in the original fly ash and the slag from Examples 1-3.

[0040]

[0041]

[0042] As can be seen from the data in Table 2, the original fly ash contained a high content of heavy metals, with Pb and Cd leaching concentrations of 0.38 and 0.27 mg / L, respectively, both exceeding the limits of GB16889-2008 (0.25 and 0.15 mg / L). However, after the fly ash was melted and solidified under three different formulations, the leaching concentrations of Pb and Cd in the fly ash slag obtained in Examples 1-3 decreased to 0.14-0.15 mg / L and 0.10-0.12 mg / L, respectively. The leaching concentrations of all heavy metals were lower than their limits, achieving the effect of harmless treatment of fly ash.

[0043] In summary, the method of the present invention can achieve fly ash solidification, heavy metal leaching meets the standards, and at the same time reduce the erosion of refractory materials by fly ash and improve the service life of the lining.

[0044] Although the present invention has been described above in conjunction with preferred embodiments, the present invention is not limited to the specific embodiments described above. The specific embodiments described above are merely illustrative and not restrictive. Those skilled in the art can make many other forms under the guidance of the present invention without departing from the spirit and scope of the claims, and all of these are within the scope of protection of the present invention.

Claims

1. A method for high-temperature melting and solidification of municipal solid waste incineration fly ash to reduce refractory material erosion, characterized in that, The main raw material is fly ash from municipal solid waste incineration, with Al2O3 and limestone as auxiliary materials. The mass percentage of the raw material components is: fly ash 50%, Al2O3 40%, and limestone 10%. The specific solidification process includes: Step 1: Weigh the fly ash from municipal solid waste incineration, limestone, and Al2O3 according to the specified proportions to form a mixture, and then dry it. The drying temperature is 80~110℃, and the drying time is 15~45min. Step 2: Put the mixture into a high-temperature melting furnace for melting at a temperature of 1400~1600℃; Step 3: After complete melting, cool to obtain solid fly ash slag; By controlling the content of limestone and Al2O3, fly ash is melted and solidified, achieving heavy metal leaching standards while reducing fly ash erosion of refractory materials. Specifically: The Al2O3 is aluminum oxide powder, and the limestone is calcium oxide powder; The refractory materials are magnesium-chromium refractory materials and high-alumina refractory materials.

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