A method for promoting the chlorination and volatilization of heavy metals by synergistic melting of fly ash from incineration of domestic waste and riverbed sludge

Abstract

The invention discloses a method for promoting the chlorination volatilization of heavy metals by synergistically melting fly ash from incineration of domestic waste and riverbed sludge. Mixing and melting fly ash from incineration of domestic waste and riverbed sludge can significantly promote the chlorination volatilization of heavy metals. The chlorination volatilization rates of Cu, Zn, Pb and Cd reach 82.67%, 100%, 100% and 100% respectively, and are enriched in secondary ash. Compared with the single melting treatment of incineration ash from domestic waste, the volatilization rate of Cu is increased by 135.12%, the volatilization rate of Zn is increased by 7.96%, and the overall volatilization rate of heavy metals is increased by 10.72%. The invention has the advantages of not adding any additives, effectively promoting the chlorination volatilization of heavy metals, reducing the heavy metal residues in glass products, zero leaching of heavy metals in glass products, and efficient recovery of heavy metals in fly ash, laying the foundation for subsequent high-value utilization of resources, having environmental benefits and economic benefits, and being suitable for large-scale promotion and use.

Description

Technical Field

[0001] The invention belongs to the field of hazardous waste disposal and resource utilization, and specifically relates to a method for promoting the chlorination and volatilization of heavy metals by synergistically melting fly ash from the incineration of domestic waste and riverbed sludge. Background Art

[0002] With the rapid development of my country's economy and urbanization, the living standards of residents have been greatly improved, and the output of domestic waste has increased year by year. Incineration has attracted widespread attention and has developed rapidly due to its excellent volume reduction, weight reduction and resource utilization effects. However, a large amount of domestic waste incineration fly ash is produced with incineration, which contains a large amount of heavy metals, soluble chloride salts, dioxins and other toxic and harmful components, which are extremely harmful and are included in my country's "List of Hazardous Wastes (2021 Edition)". It is urgent to develop large-scale harmless and resource-based disposal technology for domestic waste incineration fly ash.

[0003] At present, water washing, acid washing, chelating solidification landfill and high temperature sintering are all used for the disposal of fly ash from the incineration of domestic waste. However, the water washing and acid washing methods have problems such as secondary pollution of water resources, poor removal of heavy metals, and the need for other methods to further treat the residues after disposal; the chelating solidification landfill method has the problem of requiring additional addition of chelating agents, and the solidified body landfill disposal occupies a large amount of land resources; the high temperature sintering method has poor heavy metal solidification effect and still has the risk of heavy metal leaching.

[0004] Compared with the above methods, the melting treatment of incineration fly ash has the advantages of significant volume and weight reduction, high removal efficiency of organic pollutants such as dioxins, and high value of molten vitrified products. Invention patents CN114804589A, CN201910900547.X, CN202011308513, etc. propose to add additives (quartz sand, sodium carbonate, and feldspar, etc.) to reduce the melting point of waste incineration fly ash and achieve fly ash melting and vitrification, but the additional addition of additives greatly increases the cost of melting treatment and reduces the benefits of enterprises; while a small number of invention patents CN109734307B, CN202110031619.9, CN109516700B, etc. mix waste incineration fly ash with auxiliary materials, waste incineration ash or other solid waste for melting treatment to achieve waste incineration fly ash melting and vitrification. The above methods can achieve the melting disposal of waste incineration fly ash and prepare glass products by adding additives or other solid wastes, but all of them aim to increase the solidification rate of heavy metals, which not only causes a waste of valuable metal resources in fly ash, but also the long-term stability and safety of glass products with high heavy metal residues in practical applications are still questionable.

[0005] Therefore, it is an urgent problem to develop a melting treatment technology that does not add any additives, can effectively promote the chlorination and volatilization of heavy metals, reduce the heavy metal residues in glass products, achieve zero leaching of heavy metals in glass products, and efficiently recover heavy metals in fly ash, so as to achieve large-scale disposal, harmless treatment and resource utilization of waste incineration fly ash. Summary of the invention

[0006] In view of the above problems, the present invention discloses a method for promoting the chlorination and volatilization of heavy metals by synergistically melting fly ash from incineration of domestic waste and riverbed sludge. The method does not add any additives, can effectively promote the chlorination and volatilization of heavy metals, reduce the heavy metal residues in glass products, and achieve zero leaching of heavy metals in glass products. The volatilized heavy metals are enriched in the secondary ash, thereby achieving the harmlessness and resource utilization of fly ash from incineration of domestic waste.

[0007] In order to achieve the above technical objectives, the technical solution of the present invention is as follows:

[0008] A method for promoting the chlorination and volatilization of heavy metals by synergistically melting fly ash from the incineration of domestic waste and riverbed sludge, comprising the following steps:

[0009] (1) Sample mixing treatment: The fly ash from the incineration of domestic waste is mixed with the riverbed silt to obtain a mixed sample;

[0010] (2) Melting treatment: melting the mixed sample obtained in step (1) to obtain a vitrified product with low heavy metal residue and zero heavy metal leaching;

[0011] (3) Secondary ash collection: The flue gas generated by the melting in step (2) is subjected to tail gas treatment to obtain secondary ash rich in heavy metals.

[0012] Preferably, the mixing ratio of the domestic waste incineration fly ash and the riverbed sludge in step (1) is 1.5:1 to 9:1 by mass.

[0013] Preferably, the mixing ratio of the domestic waste incineration fly ash and riverbed sludge in step (1) is 4:1 by mass.

[0014] Preferably, the riverbed sludge in step (1) is riverbed dredging sludge or riverbed sediment.

[0015] Preferably, the melting treatment conditions in step (2) are: melting temperature of 1000-1300° C., melting time of 10-50 min, and melting treatment atmosphere of air.

[0016] Preferably, the melting treatment conditions in step (2) are: melting temperature of 1200° C. and melting time of 40 min.

[0017] Preferably, the vitrified product with low heavy metal residue and zero heavy metal leaching generated by the melting treatment in step (2) is cooled by air cooling.

[0018] Preferably, the secondary ash collected from the tail gas treatment in step (3) contains significantly enriched heavy metals and can be used as raw material for metal smelting.

[0019] Compared with the prior art, the present invention has the following obvious advantages and beneficial effects:

[0020] (1) The present invention can significantly improve the chlorination volatilization rate of heavy metals without adding any exogenous additives. The chlorination volatilization rates of heavy metals Cu, Zn, Pb, and Cd in the fly ash from the incineration of domestic waste reach 82.67%, 100%, 100%, and 100%, respectively. Compared with the single disposal of the incineration ash from domestic waste, the chlorination volatilization rate of Cu is increased by 135.12%, the chlorination volatilization rate of Zn is increased by 7.96%, and the overall volatilization of heavy metals is increased by 10.72%;

[0021] (2) The vitrified product produced by the melting treatment of the present invention has low heavy metal residues, which solves the risk of heavy metal leaching in the actual application process of the vitrified product from the source;

[0022] (3) The vitrified product produced by the melting treatment of the present invention has stable properties and zero heavy metal leaching toxicity, which is far lower than the "Hazardous Waste Identification Standard - Leaching Toxicity Identification" (GB5085.3-207);

[0023] (4) During the smelting treatment process of the present invention, heavy metals in fly ash from the incineration of domestic waste and riverbed sludge are enriched in secondary ash, which can be used as raw materials for metal smelting. BRIEF DESCRIPTION OF THE DRAWINGS

[0024] Figure 1 The chlorination volatilization efficiency of heavy metals Cu, Zn, Pb and Cd at different mixing ratios in Example 1.

[0025] Figure 2 This is the XRD analysis of the melt products with different mixing ratios in Example 1.

[0026] Figure 3 The chlorination volatilization efficiency of heavy metals Cu, Zn, Pb and Cd at different melting temperatures in Example 2.

[0027] Figure 4 The chlorination volatilization efficiency of heavy metals Cu, Zn, Pb and Cd at different melting times in Example 3.

[0028] Figure 5 The chlorine content of the molten glass products with different mixing ratios in Example 4 (a) and the proportion of non-bridging oxygen bonds in the molten glass products with different mixing ratios (b) are shown.

[0029] Figure 6 This is the heavy metal content of fly ash from the incineration of domestic waste, riverbed sludge and secondary ash in Example 5.

[0030] Figure 7 This is the heavy metal content of the stabilized product when the fly ash from the incineration of domestic waste in Example 6 is melted at 1200°C and the mixing ratio is 4:1. DETAILED DESCRIPTION

[0031] In order to facilitate the understanding of the present invention, the present invention will be further described in detail below in conjunction with preferred implementation cases, but the implementation methods of the present invention are not limited thereto.

[0032] In order to compare the changes in the chlorination volatilization efficiency of heavy metals in fly ash from municipal solid waste incineration and melted riverbed sludge, the heavy metal chlorination volatilization rate (R) was introduced and defined as follows:

[0033]

[0034] Where W 2 is the content of heavy metals in the sample before melting, mg / kg; m 2 is the mass of the sample before melting, g; W 1 is the content of heavy metals in the vitrified product after melting, mg / kg; m 1 is the mass of the stabilized product after melting, g.

[0035] In order to better compare the overall volatilization effects of heavy metals Cu, Zn, Pb and Cd in fly ash from municipal solid waste incineration and melted riverbed sludge, the overall volatilization rate of heavy metals (A) was proposed and defined as follows:

[0036]

[0037] Where W 2,Zn,Cu,Pb,cd is the content of heavy metals in the sample before melting, mg / kg; m 2 is the mass of the sample before melting, g; yij(t) 1,Zn,Cu,Pb,Cd is the content of heavy metals in the vitrified product after melting, mg / kg; m 1 is the mass of the vitrified product after melting, g.

[0038] Comparative Example 1

[0039] Without adding riverbed silt, the fly ash from the incineration of domestic waste was directly melted at a melting temperature of 1200°C and a melting time of 40 min. Natural air cooling was performed to obtain a melt-stabilized product. The heavy metal content in the product was analyzed to obtain the heavy metal chlorination volatilization efficiency, as shown in Table 1.

[0040] The chlorination volatilization rates of heavy metals Cu and Zn are 35.16% and 92.63%, respectively. The overall volatilization rate of heavy metals is 89.12%, and the chlorination volatilization rate of heavy metals is relatively low.

[0041] Table 1

[0042]

[0043] Example 1

[0044] Effects of different mixing ratios of fly ash from municipal solid waste incineration and riverbed sludge on the chlorination volatilization of heavy metals. The specific components of riverbed sludge and fly ash from municipal solid waste incineration are shown in Table 2.

[0045] Table 2

[0046]

[0047] The riverbed silt was crushed and pre-treated. The fly ash and riverbed silt were mixed evenly in a mass ratio of 9:1, 7:1, 5:1, 4:1, 3:1, 2:1, and 1.5:1. The mixed sample was put into a smelting furnace with a melting temperature of 1200°C and a melting time of 40 min. The mixture was treated in an air atmosphere and naturally cooled to obtain a molten vitrified product. The heavy metal content in the vitrified product was analyzed to obtain the chlorination volatilization efficiency of heavy metals Cu, Zn, Pb, and Cd in samples with different mixing ratios, such as Figure 1 When the mixing ratio of fly ash to riverbed silt was 4:1, the chlorination volatilization efficiencies of heavy metals Cu, Zn, Pb, and Cd were 81.92%, 100.00%, 100.00%, and 100.00%, respectively, and the overall volatilization rate of heavy metals was 98.61%.

[0048] Figure 2 This is the XRD analysis of the molten vitrified products of different mixing ratios of fly ash from the incineration of domestic waste and riverbed sludge. When the ratio of fly ash to sludge decreases from 9:1 to 5:1, the proportion of amorphous in the vitrified products gradually increases. When the ratio of fly ash to sludge is less than 5:1, the proportion of amorphous exceeds 98%. The results are shown in Table 3.

[0049] Table 3

[0050]

[0051] Example 2

[0052] The influence of different melting temperatures on the chlorination and volatilization of heavy metals. The riverbed sludge was crushed and pre-treated, and the fly ash and riverbed sludge were mixed evenly at a mass ratio of 4:1. The mixed sample was put into a smelting furnace, the melting time was 40 minutes, the melting temperature was 1000℃, 1100℃, 1200℃, and 1300℃, and the air atmosphere was treated. The molten vitrified product was obtained by natural cooling. The heavy metal content in the vitrified product was analyzed, and the chlorination and volatilization efficiency of heavy metals Cu, Zn, Pb, and Cd at different melting temperatures was obtained, such as Figure 3At 1300℃, the chlorination volatilization rates of heavy metals Cu, Zn, Pb and Cd in the mixed sample were 87.52%, 100%, 100.00% and 100.00% respectively, and the overall volatilization rate of heavy metals was 99.11%.

[0053] Example 3

[0054] The influence of different melting times on the chlorination volatilization effect of heavy metals. The riverbed sludge was crushed and pre-treated, and the fly ash and riverbed sludge were mixed in a mass ratio of 4:1. The mixed sample was put into a smelting furnace with a melting temperature of 1200℃ and a melting time of 10min, 20min, 30min, 40min, and 50min. The mixture was treated in an air atmosphere and naturally cooled to obtain a molten vitrified product. The heavy metal content in the vitrified product was analyzed to obtain the chlorination volatilization efficiency of heavy metals Cu, Zn, Pb, and Cd in different proportions, such as Figure 4 At 40 minutes, the chlorination volatilization efficiency of heavy metals Cu, Zn, Pb, and Cd in the mixed sample reached the maximum of 82.67%, 100%, 100%, and 100%, respectively, and the overall volatilization rate of heavy metals was 98.67%.

[0055] Example 4

[0056] Chloride ion leaching solutions of glass product samples with a mixing ratio of 5:1, 4:1, 3:1, 2:1, and 1.5:1 of fly ash from the incineration of domestic waste and riverbed sludge were prepared, and the chloride ion content of glass products with different ratios was tested using anion chromatography. The results showed that as the proportion of fly ash from the incineration of domestic waste increased, the chlorine content in the glass product increased significantly, such as Figure 5 (a) Using X-ray photoelectron spectroscopy to analyze the internal structure of the glass product, it was found that by adjusting the ratio of fly ash to sludge, the ratio of non-bridging oxygen bonds in the glass product increased from 6.8% to 54.73%, as shown in Figure 5 (b) The increase in the proportion of non-bridging oxygen bonds helps to increase the solubility of chlorine in the melt during the melting process, thereby promoting the chlorination and volatilization of heavy metals.

[0057] Example 5

[0058] When the mass ratio of fly ash to riverbed silt was 4:1, the melting temperature was 1200℃, the melting time was 40min, and the air atmosphere was used for treatment, the secondary ash was obtained by flue gas treatment, and the heavy metal content in the secondary ash was analyzed. Figure 6 It can be seen that the heavy metal content in the secondary ash is significantly enriched, among which the content of Cu, Zn, Pb and Cd is 2.68, 4.07, 2.97 and 1.57 times that of the original domestic waste incineration fly ash, among which the Zn content is as high as 18845.46 mg / kg.

[0059] Example 6

[0060] The heavy metal content in the vitrified product was analyzed under the conditions of fly ash to riverbed sludge mass ratio of 4:1, melting temperature of 1200℃, melting time of 40min, and air atmosphere treatment. Figure 7 It can be seen that the heavy metal contents of Cu, Zn, Pb and Cd in the glass products have all dropped significantly, and the heavy metal contents of Zn, Pb and Cd have not been detected.

[0061] Example 7

[0062] The fly ash and riverbed silt were mixed evenly in a mass ratio of 9:1, 7:1, 5:1, 4:1, 3:1, 2:1, and 1.5:1, the melting temperature was 1200°C, the air atmosphere was melted for 40 minutes, and the molten vitrified product was obtained by natural cooling. The vitrified product was subjected to heavy metal leaching toxicity test, as shown in Table 4. After melting treatment, the heavy metal leaching toxicity of the glass product was zero, which was far lower than the "Hazardous Waste Identification Standard-Leaching Toxicity Identification" (GB5085.3-207).

[0063] Table 4

[0064]

[0065] The above embodiments are preferred implementation modes of the present invention, but the implementation modes of the present invention are not limited to the above embodiments. Any other changes, modifications, substitutions, combinations, and simplifications that do not deviate from the spirit and principles of the present invention should be equivalent replacement methods and are included in the protection scope of the present invention.

Claims

1. A method for promoting the chlorination and volatilization of heavy metals by synergistic melting of fly ash from the incineration of domestic waste and riverbed sludge, characterized in that: The following steps are involved: (1) Sample mixing: Mix the fly ash from the incineration of domestic waste with the riverbed silt to obtain a mixed sample; (2) Melting treatment: melting the mixed sample obtained in step (1) to obtain a vitrified product with low heavy metal residue and zero heavy metal leaching; (3) secondary ash collection: treating the flue gas generated by the melting in step (2) to obtain secondary ash rich in heavy metals; The mixing ratio of the fly ash from the incineration of domestic waste and the riverbed sludge in step (1) is 4:1 by mass; The domestic waste incineration fly ash contains: 39.82% CaO, 5.24% SiO2, 1.77% Al2O3, 13.39% Na2O; the riverbed silt contains: 0.57% CaO, 68.13% SiO2, 19.31% Al2O3, 0.46% Na2O; The melting treatment conditions in step (2) are: melting temperature of 1000-1300°C, melting time of 40-50 min, and melting treatment atmosphere of air.

2. The method according to claim 1, characterized in that: The riverbed sludge in step (1) is riverbed dredging sludge and / or riverbed sediment.

3. The method according to claim 1, characterized in that: The melting treatment conditions in step (2) are: melting temperature of 1200° C. and melting time of 40 min.

4. The method according to claim 1, characterized in that: The vitrified product with low heavy metal residue and zero heavy metal leaching generated by the melting treatment in step (2) is cooled by air cooling.

5. The method according to claim 1, characterized in that: The heavy metals in the secondary ash collected from the tail gas treatment in step (3) are significantly enriched and can be used as raw materials for metal smelting.

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