Method for synergistically melting and vitrifying household garbage incineration fly ash and coal gasification slag and efficiently recycling metal and glass ceramics

Abstract

The invention provides a household garbage incineration fly ash and coal gasification slag collaborative melting vitrification and efficient metal recovery method, which comprises the following steps: uniformly mixing dried household garbage incineration fly ash and coal gasification slag to obtain a mixture, melting, and cooling to obtain a glass product and an alloy. The raw material cost is low, vitrification of a eutectic system and alloying recovery of metal are achieved, and the alloy recovery rate is high. The invention also provides the microcrystalline glass which is obtained by heat treatment of the glass product prepared by the method, and the obtained microcrystalline glass has high Vickers hardness, low water absorption and good acid and alkali corrosion resistance.

Description

Technical Field

[0001] This application relates to the field of waste resource utilization technology, and in particular to a method for the co-melting and vitrification of municipal solid waste incineration fly ash and coal gasification slag, and the efficient recovery of metals and microcrystalline glass. Background Technology

[0002] With socio-economic development and urbanization, the amount of municipal solid waste generated is continuously increasing. In the field of municipal solid waste treatment, incineration, with its advantages of volume reduction (approximately 70%), volume reduction (approximately 90%), and energy recovery through incineration power generation, is gradually replacing traditional landfill methods and becoming an important development direction for the harmless treatment of municipal solid waste. Since 2018, China's municipal solid waste treatment volume has maintained an average annual growth rate of approximately 6%, reaching 262 million tons by 2024, while the proportion of incineration treatment will increase from 45.1% to 78.9%. However, the waste incineration process generates secondary solid waste, namely incineration fly ash, accounting for 3-5% of the total incinerated material. Due to its high content of harmful components such as heavy metals, chlorides, and organic matter, it is classified as hazardous waste. The harmful elements in municipal solid waste incineration fly ash (MSWI FA) pose potential hazards to the ecological environment and human health, requiring effective methods for its safe disposal.

[0003] Currently, vitrification is a highly efficient heat treatment technology that, through a high-temperature melting process, can simultaneously achieve the stable solidification of heavy metals in municipal solid waste incineration fly ash, the complete decomposition of organic pollutants, and volume and weight reduction of the system. However, the high CaO content in municipal solid waste incineration fly ash results in a high melting temperature, leading to increased energy consumption during the vitrification process. Existing research indicates that adjusting the CaO, SiO2, and Al2O3 content in the municipal solid waste incineration fly ash system can effectively lower the melting glass transition temperature. Furthermore, municipal solid waste incineration fly ash contains a large amount of heavy metals, which can serve as an important secondary metal resource. During the heat treatment process, introducing reducing substances or increasing the chloride content can effectively achieve the recovery of these metal resources. Summary of the Invention

[0004] To address at least one of the aforementioned technical problems, this application provides a method for the co-melting and vitrification of municipal solid waste incineration fly ash and coal gasification slag, and the efficient recovery of metals and microcrystalline glass. The method involves melting a mixture of municipal solid waste incineration fly ash and coal gasification slag to transform it into glass products and metal alloys. This method not only solves the potential harm of harmful elements in municipal solid waste incineration fly ash to the ecological environment and human health, but also effectively achieves the recovery of metal resources.

[0005] In a first aspect, this application provides a method for the co-melting vitrification and efficient metal recovery of municipal solid waste incineration fly ash and coal gasification slag, comprising: uniformly mixing dried municipal solid waste incineration fly ash and coal gasification slag to obtain a mixture, melting, cooling, and obtaining a glass product and an alloy; wherein, based on 100% by mass, the municipal solid waste incineration fly ash comprises 31-33 wt% CaO, 21-23 wt% SiO2, 10-12 wt% Al2O3, 4-6 wt% Na2O, 5.5-7 wt% Fe2O3, 0.5-1.5 wt% C, 0.05-0.15 wt% S, and 11-13 wt% Cl; and, based on 100% by mass, the coal gasification slag comprises 17-20 wt% CaO, 41-44 wt% SiO2, and 16-18.5 wt% Cl. % Al2O3, 2-4wt% Na2O, 12-15wt% Fe2O3, 6-7.5wt% C, 0.5-1.2wt% S, 0.02-0.06wt% Cl.

[0006] By adopting the above technical solution, this application provides a method for the synergistic melting and vitrification of municipal solid waste incineration fly ash and coal gasification slag, and the efficient recovery of metals. This method can reduce the environmental harm caused by municipal solid waste incineration fly ash and recover alloys, thus offering certain economic benefits. This is likely because SiO2 forms the basic framework for glass matrix formation and plays a crucial role in the formation of amorphous structures during the melting process. CaO is another key component that can regulate the melting process through its interaction with silicon and aluminum phases. Coal gasification slag (CGS) is a typical byproduct of the coal chemical industry, rich in SiO2 and Al2O3, and also contains a certain amount of residual carbon. Introducing CGS into the municipal solid waste incineration fly ash melting system can lower the melting point through chemical species regulation, thereby promoting the glassization of municipal solid waste incineration fly ash. Furthermore, the residual carbon in CGS can play a thermal reduction role during the melting process, which is beneficial for achieving the synergistic melting and vitrification of municipal solid waste incineration fly ash and coal gasification slag, and the recovery of metal alloys.

[0007] Both municipal solid waste incineration fly ash and coal gasification slag require the addition of additives for melting to obtain glass. This application melts municipal solid waste incineration fly ash and coal gasification slag to obtain glass products and alloy products, which is low-cost. The preparation of glass products and alloy products from municipal solid waste incineration fly ash and coal gasification slag has a synergistic effect in improving the performance of glass products and metal recovery efficiency.

[0008] Optionally, the mass ratio of the municipal solid waste incineration fly ash to the coal gasification slag is (0.5-8):1.

[0009] By adopting the above technical solutions and optimizing the mass ratio of municipal solid waste incineration fly ash to coal gasification slag, the relative content of non-bridging oxygen bonds (NBO) can be increased, promoting the conversion of bridging oxygen bonds (BO) into NBO to achieve depolymerization of the melt network. This depolymerization process transforms the structure from long-range order to disorder, resulting in an amorphous glass product and enhanced melt flow characteristics.

[0010] Optionally, the melt viscosity is 1.8-42.4 Pa·s.

[0011] Optionally, the melting time is 10-50 min.

[0012] Optionally, B2O3 and Ga2O3 are also added to the mixture, with the total added mass of B2O3 and Ga2O3 being 6-10% of the total mass of municipal solid waste incineration fly ash and coal gasification slag.

[0013] Optionally, the mass ratio of B2O3 to Ga2O3 is (2.33-9):1.

[0014] In a second aspect of this application, a microcrystalline glass is provided, which is obtained by heat treatment of a glass product prepared by the method described in the first aspect of this invention.

[0015] Optionally, the heat treatment temperature is 900℃ and the time is 1.5-2.5h.

[0016] In summary, this application includes at least one of the following beneficial technical effects: 1. This application provides a method for the co-melting and vitrification of municipal solid waste incineration fly ash and coal gasification slag, and for the efficient recovery of metals. This method reduces the environmental harm caused by municipal solid waste incineration fly ash and recovers alloys, offering certain economic benefits. SiO2 forms the basic framework for glass matrix formation and plays a crucial role in the formation of amorphous structures during the melting process. CaO is another key component that can regulate the melting process through interactions with silicon and aluminum phases. Coal gasification slag (CGS) is a typical byproduct of the coal chemical industry, rich in SiO2 and Al2O3, and also contains a certain amount of residual carbon. Introducing CGS into the municipal solid waste incineration fly ash melting system can lower the melting point through chemical species regulation, thereby promoting the glassization of municipal solid waste incineration fly ash. Furthermore, the residual carbon in CGS can play a thermal reduction role during the melting process, which is beneficial for achieving the co-melting and vitrification of municipal solid waste incineration fly ash and coal gasification slag, and the recovery of metal alloys.

[0017] 2. This application provides a microcrystalline glass, obtained by heat treatment of the glass product prepared by the above method. The resulting microcrystalline glass exhibits stable heavy metal residues, and its heavy metal leaching toxicity and total chlorine content are significantly lower than the standard limits set by the "Technical Requirements for Vitrification Products of Solid Waste" (GB / T 41015-2021) and the "Technical Specification for Pollution Control of Fly Ash from Municipal Solid Waste Incineration" (HJ 1134-2020). Its Vickers hardness, water absorption, acid corrosion resistance, and alkali corrosion resistance are 7.53 GPa, 0.07%, 99.56%, and 99.60%, respectively. Attached Figure Description

[0018] Figure 1 Images of fly ash and gasification residue from municipal solid waste incineration; in, Figure 1 (a) fly ash from the incineration of municipal solid waste; Figure 1 (b) refers to coal gasification slag; Figure 2 XRD patterns of fly ash and gasification slag from municipal solid waste incineration; in, Figure 2 (a) XRD pattern of fly ash from municipal solid waste incineration; Figure 2 (b) is the XRD pattern of coal gasification slag; Figure 3 The recovery rates of Ni, Cu, Zn, Pb and Fe in mixtures of different proportions of municipal solid waste incineration fly ash and coal gasification slag were determined after melting for 30 min at a molten viscosity of 4.4 Pa·s, and the distribution patterns of Ni, Cu, Fe, Zn and Pb recovered in different phases were studied. in, Figure 3 (a) The recovery rates of metals Ni, Cu, Zn, Pb and Fe in mixtures of different proportions of municipal solid waste incineration fly ash and coal gasification slag after melting for 30 min at a molten viscosity of 4.4 Pa·s; Figure 3 (b) The distribution of metallic Ni recovered in different phases after melting for 30 min at a molten viscosity of 4.4 Pa·s in mixtures of fly ash from municipal solid waste incineration and coal gasification slag in different proportions. Figure 3 (c) The distribution of recovered metallic Cu in different phases after melting for 30 min at a molten viscosity of 4.4 Pa·s in a mixture of fly ash from municipal solid waste incineration and coal gasification slag with different proportions. Figure 3 (d) The distribution of metallic Fe recovered in different phases after melting for 30 min at a molten viscosity of 4.4 Pa·s in a mixture of fly ash from municipal solid waste incineration and coal gasification slag with different proportions. Figure 3 (e) The distribution of metallic Zn recovered in different phases after melting for 30 min at a molten viscosity of 4.4 Pa·s in a mixture of fly ash from municipal solid waste incineration and coal gasification slag with different proportions. Figure 3 (f) The distribution of metallic Pb recovered in different phases after melting for 30 min at a molten viscosity of 4.4 Pa·s in a mixture of fly ash from municipal solid waste incineration and gasification slag in different proportions. Figure 4 XRD patterns of the glass phase and alloy phase in glass products made from a 1:1 mixture of municipal solid waste incineration fly ash and coal gasification slag. in, Figure 4 (a) XRD pattern of the glass phase in glass products made from a 1:1 ratio of fly ash from municipal solid waste incineration to gasification slag. Figure 4 (b) XRD pattern of the alloy phase in glass product with a 1:1 ratio of fly ash from municipal solid waste incineration to gasification slag. Figure 5 High-resolution XPS spectra of O 1s in glass products made from fly ash and gasification slag of municipal solid waste incineration at different ratios were obtained, along with fitted O 1s spectra and the relative content of NBO in the glass products. in, Figure 5 (a) High-resolution XPS spectra of glass products made from fly ash from municipal solid waste incineration and coal gasification slag in different proportions; Figure 5 (b) Fitted O1s high-resolution XPS spectra of glass products made from municipal solid waste incineration fly ash and coal gasification slag in different proportions. Figure 5 (c) The relative NBO content of glass products under different mixing ratios of fly ash from municipal solid waste incineration and coal gasification slag; Figure 6 High-resolution XPS spectra of Al 2p and relative content of [AlO4] were obtained for glass products made from fly ash and gasification slag of municipal solid waste incineration at different ratios. in, Figure 6 (a) High-resolution XPS spectra of Al2p of glass products made from municipal solid waste incineration fly ash and coal gasification slag in different proportions; Figure 6 (b) The relative content of [AlO4] in glass products of municipal solid waste incineration fly ash and coal gasification slag in different proportions; Figure 7The recovery rates of Ni, Cu, Zn, Pb and Fe metals in a 1:1 mixture of municipal solid waste incineration fly ash and coal gasification slag at different melting viscosities and the distribution patterns of Ni, Cu, Fe, Zn and Pb metals recovered in different phases were studied. in, Figure 7 (a) Recovery rates of metals Ni, Cu, Zn, Pb and Fe at different melting viscosities for a mixture of municipal solid waste incineration fly ash and coal gasification slag in a 1:1 ratio; Figure 7 (b) The distribution of recovered metallic Ni in different phases at different melting viscosities for a mixture of municipal solid waste incineration fly ash and coal gasification slag in a 1:1 ratio; Figure 7 (c) The distribution of recovered Cu metal in different phases at different melting viscosities for a mixture of municipal solid waste incineration fly ash and coal gasification slag in a 1:1 ratio; Figure 7 (d) shows the distribution of recovered metallic Fe in different phases at different melting viscosities in a 1:1 mixture of municipal solid waste incineration fly ash and coal gasification slag. Figure 7 (e) The distribution of recovered metallic Zn in different phases at different melting viscosities in a 1:1 mixture of municipal solid waste incineration fly ash and coal gasification slag. Figure 7 (f) shows the distribution of recovered metallic Pb in different phases at different melting viscosities of a 1:1 mixture of municipal solid waste incineration fly ash and coal gasification slag. Figure 8 The study investigated the recovery rates of Ni, Cu, Zn, Pb, and Fe metals and their distribution patterns in different phases of a 1:1 mixture of municipal solid waste incineration fly ash and coal gasification slag at a molten viscosity of 4.4 Pa·s, while maintaining different melting times. in, Figure 8 (a) The recovery rates of metals Ni, Cu, Zn, Pb and Fe at different melting times for a mixture of municipal solid waste incineration fly ash and coal gasification slag in a 1:1 ratio at a molten viscosity of 4.4 Pa·s; Figure 8 (b) The distribution of recovered metallic Ni in different phases at different melting times for a mixture of municipal solid waste incineration fly ash and coal gasification slag with a 1:1 ratio and a molten viscosity of 4.4 Pa·s. Figure 8 (c) The distribution of recovered metallic Cu in different phases at different melting times for a mixture of municipal solid waste incineration fly ash and coal gasification slag with a 1:1 ratio at a molten viscosity of 4.4 Pa·s. Figure 8 (d) The distribution of recovered metallic Fe in different phases at different melting times for a mixture of municipal solid waste incineration fly ash and coal gasification slag with a ratio of 1:1 at a melting viscosity of 4.4 Pa·s. Figure 8 (e) The distribution of recovered metallic Zn in different phases at different melting times for a mixture of municipal solid waste incineration fly ash and coal gasification slag with a ratio of 1:1 at a molten viscosity of 4.4 Pa·s. Figure 8 (f) shows the distribution of recovered metal Pb in different phases at different melting times for a mixture of municipal solid waste incineration fly ash and coal gasification slag with a 1:1 ratio and a molten viscosity of 4.4 Pa·s. Figure 9 The distribution of heavy metal speciation in the original sample (the original mixed sample before melting) and the glass product; in, Figure 9 (a) shows the speciation of heavy metals in the original sample (the original mixed sample before melting); Figure 9 (b) The speciation of heavy metals in the obtained glass product; Figure 10 The images show the DSC curves of the vitrified products, the XRD patterns of the vitrified products and glass-ceramics, and the crystal phase distribution of the glass-ceramics. in, Figure 10 (a) DSC curves of the vitrified products; Figure 10 (b) XRD patterns of the vitrification products and glass-ceramics; Figure 10 (c) shows the crystal phase distribution of the glass-ceramic. Detailed Implementation

[0019] The embodiments of the present invention will be described in detail below with reference to the examples. However, those skilled in the art will understand that the following examples are only for illustrating the present invention and should not be regarded as limiting the scope of the present invention. Specific conditions not specified in the examples shall be carried out according to conventional conditions or conditions recommended by the manufacturer. Reagents or instruments whose manufacturers are not specified are all conventional products that can be purchased commercially.

[0020] The fly ash sample from municipal solid waste incineration was taken from a municipal solid waste incineration treatment company in Zhejiang Province, and the coal gasification slag sample was taken from a coal chemical company in Anhui Province.

[0021] The municipal solid waste incineration fly ash (MWSI FA) sample appeared as a fine powder. After drying at 105℃ for 12 hours, it was mixed evenly to obtain the municipal solid waste incineration fly ash, which was stored in a sealed bag for later use. The coal gasification slag (CGS) sample was hard and coarse-grained. After drying at 105℃ for 12 hours, it was processed using a planetary ball mill, followed by sieving to obtain coal gasification slag, which was then sealed and stored for later use. Photos of the municipal solid waste incineration fly ash and coal gasification slag are shown below. Figure 1 As shown. Among them, Figure 1 (a) fly ash from the incineration of municipal solid waste, Figure 1 (b) is coal gasification slag.

[0022] The chemical composition of fly ash from municipal solid waste incineration and coal gasification slag was analyzed using XRF and carbon-sulfur analyzers, and the content of relevant metal elements was determined using ICP-OES. The relevant data are shown in Tables 1 and 2.

[0023] Table 1. Chemical composition (mass percentage) of different samples (unit: %)

[0024] Table 2. Main heavy metal content (mass percentage) of different samples (unit: mg / kg)

[0025] The XRD patterns of municipal solid waste incineration fly ash and gasification slag after drying, ball milling, and screening pretreatment are shown below. Figure 2 As shown, where, Figure 2 (a) XRD pattern of fly ash from municipal solid waste incineration. Figure 2 (b) shows the XRD pattern of the coal gasification slag; from Figure 2 (a) It can be seen that the fly ash from municipal solid waste incineration has a high degree of crystallinity, and the crystalline phase is composed of various calcium-containing phases such as CaSO4 (PDF#37-0184), SiO2 (PDF#43-0596), Ni7S6 (PDF#25-0583), CaO (PDF#28-0775), and Al3Ni (PDF#02-0416), as well as heavy metal phases. Figure 2 (b) It can be seen that the coal gasification slag is in an amorphous glassy state. Apart from the weak crystallization peaks of SiO2 (PDF#47-1300) and C (PDF#06-0675), no other obvious crystalline phases were observed.

[0026] The methods for measuring and calculating the recovery rates of metals (Ni, Cu, Fe, Zn, and Pb) are as follows: Acid digestion was used to determine the heavy metal content of solid samples. The specific steps were as follows: Approximately 0.1 g of solid sample was weighed and placed in a 50 mL polytetrafluoroethylene (PTFE) digestion tube. Then, 10 mL of HNO3, 5 mL of HClO4, and 10 mL of HF were added sequentially. The digestion tube was then sealed and placed in a graphite digester. The temperature was raised to 195 °C for 30 min and maintained at 195 °C for 270 min. After digestion, the state of the digest was observed: if there was no remaining solid in the solution and the color was colorless and transparent or light yellow, the digestion was complete; if not, HNO3, HClO4, and HF were added again in the same proportion, and the same digestion procedure was used until the solution was clear and free of solid residue. After complete digestion, the resulting digest was cooled to room temperature, filtered through a 0.45 μm filter membrane, transferred to a 50 mL volumetric flask, and diluted to volume with deionized water. Finally, the obtained sample solution was placed into a 50 ml centrifuge tube, sealed, and stored for the determination of relevant heavy metal content.

[0027] The recovery rates of metals (Ni, Cu, Fe, Zn, and Pb) are calculated as shown in Equation 1:

[0028] in, m 1 and m 2 The values ​​are the mass (g) of the original sample and the alloy product, respectively. c 1 and c 2 The contents (mg / kg) of metals Ni, Cu, Fe, Zn and Pb in the original sample and alloy product are respectively.

[0029] Example 1

[0030] Example 1 investigated the effects of different mass ratios of municipal solid waste incineration fly ash (MWSI FA) and coal gasification slag (CGS) on the metal recovery efficiency and metal separation of glass products, metal alloys and volatile products.

[0031] Municipal solid waste incineration fly ash and coal gasification slag were mixed evenly at different mass ratios (0.5:1, 1:1, 2:1, 4:1, 6:1 and 8:1) to obtain mixtures of municipal solid waste incineration fly ash and coal gasification slag with different mass ratios. The fly ash from municipal solid waste incineration alone and the mixtures of municipal solid waste incineration fly ash and coal gasification slag with different mass ratios were placed in crucibles and heated in a medium-frequency melting furnace. The melting viscosity was maintained at 4.4 Pa·s and the melting time was 30 min. The mixture was then naturally cooled to room temperature to obtain glass products, metal alloys and volatile phase products.

[0032] Single municipal solid waste incineration fly ash and mixtures of municipal solid waste incineration fly ash and coal gasification slag in different mass ratios (0.5:1, 1:1, 2:1, 4:1, 6:1 and 8:1) were used to recover glass products, metal alloys and volatile products. The recovery rates of metals Ni, Cu, Zn, Pb and Fe were as follows: Figure 3 As shown in (a), the recovery rates of Ni, Cu, Zn, Pb, and Fe reached their maximum values ​​when the ratio of municipal solid waste incineration fly ash to coal gasification slag was 1:1, at 68.65%, 100%, 100%, 100%, and 91.43%, respectively. Under different ratios, Zn and Pb maintained a 100% recovery efficiency. The distribution patterns of Ni, Cu, Fe, Zn, and Pb recovery in different phases are shown in Figure (a). Figure 3 As shown in (bf), under different mixing ratios, Zn and Pb are both separated and recovered as volatile phases, while Cu, Ni, and Fe are recovered as alloy phases and volatile phases, respectively. With the increase in the proportion of gasification slag, the proportion of Cu, Ni, and Fe recovered as alloy phases increases. When the mixing ratio of municipal solid waste incineration fly ash to gasification slag is 1:1, the alloy phase separation efficiency of Cu, Ni, and Fe reaches 43.92%, 27.91%, and 37.68%, respectively. This may be because the thermal reduction of residual carbon in the gasification slag promotes the transformation of metals into alloy phases. Therefore, a mass ratio of 1:1 between municipal solid waste incineration fly ash and gasification slag is selected as the preferred mixing ratio.

[0033] XRD was used to analyze the glass phase and alloy phase in glass products made from a 1:1 mixture of municipal solid waste incineration fly ash and coal gasification slag. The results are as follows: Figure 4 As shown in (ab). From Figure 4 (a) shows that the glass product exhibits a completely amorphous state. From Figure 4 As shown in (b), the alloy phase contains a variety of metal compounds, including Cu, Ni and Fe, with the main phases being Cu7S4 (PDF#33-0489), Cu4Ti (PDF#20-0370), Fe3P (PDF#19-0617), Ni (PDF#04-0850), Ni5P2 (PDF#17-0225) and Cu2S (PDF#46-1195).

[0034] Meanwhile, the inventors conducted theoretical research on the better effect of mixing municipal solid waste incineration fly ash and coal gasification slag at a mass ratio of 1:1.

[0035] The structures of different glass products were characterized using XPS. The variations in O 1s binding energy of different glass products are shown below. Figure 5As shown in (a), the O 1s binding energy of the glass products from a single municipal solid waste incineration fly ash is 531.9 eV. As the proportion of municipal solid waste incineration fly ash decreased with the addition of gasification slag, the O 1s binding energy of the glass products gradually decreased, from 531.9 eV for a single municipal solid waste incineration fly ash melt to 531.4 eV when the ratio of municipal solid waste incineration fly ash to gasification slag was 2:1. Notably, when the proportion of municipal solid waste incineration fly ash was further reduced to 1:1, the O 1s binding energy of the glass products remained at 531.4 eV. However, when the proportion of municipal solid waste incineration fly ash was further reduced to 0.5:1, the O 1s binding energy of the glass products increased to 531.7 eV. Subsequently, the high-resolution XPS spectra of the O 1s of different glass products were fitted and analyzed. The peak with a binding energy of 532.0 eV was attributed to bridging oxygen bonds (BO), while the peak with a binding energy of 531.0 eV was attributed to non-bridging oxygen bonds (NBO). Figure 5 (b) Quantitative analysis of BO and NBO showed that the molten viscosity of municipal solid waste incineration fly ash was 4.4 Pa·s, and the NBO content in the glass products was 22.53%. The NBO content reached its highest level of 61.15% when the ratio of municipal solid waste incineration fly ash to coal gasification slag was reduced to 2:1. However, when the proportion of municipal solid waste incineration fly ash was further reduced to a ratio of 0.5:1, the NBO content decreased to 33.46% ( Figure 5 (c) This is because the reduction in the proportion of municipal solid waste incineration fly ash in the molten system leads to a decrease in CaO content, which in turn weakens the depolymerization of the glass network and reduces the NBO content.

[0036] Furthermore, the Al 2p high-resolution XPS spectra of different glass products were analyzed to elucidate the reasons for the increased NBO content in glass products made solely from municipal solid waste incineration fly ash and in glass products with a fly ash to gasification slag ratio of 8:1, 6:1, 4:1, and 2:1. The Al 2p high-resolution XPS spectra of different glass products are fitted as follows: Figure 6 As shown in (a), the peaks with binding energies of 73.4-74.5 eV are attributed to [AlO4] structural units, while the peaks with binding energies of 74.1-75.1 eV are attributed to [AlO6] structural units. Generally, [AlO4] structural units play a role in forming the glass network, while [AlO6] structural units play a role in modifying the glass network. The relative contents of [AlO4] structural units in different glass products are shown in Figure 1. Figure 6As shown in (b), the relative content of [AlO4] structural units in the glass products from municipal solid waste incineration fly ash is as high as 70.16%, while the relative content of [AlO4] structural units in the glass products with a 2:1 ratio of municipal solid waste incineration fly ash to coal gasification slag decreases to 38.34%. The [AlO4] structural units are similar to the [SiO4] tetrahedral structural units; their combination forms complex Al-O-Si structural groups, enhancing the polymerization degree of the glass network. This indicates that the appropriate reduction of CaO chemical species promotes the depolymerization of the glass network structure, resulting in an increase in the NBO content in the glass products. The depolymerization of the complex network structure promotes the transformation of the system towards disorder, enhancing the melting characteristics of the melt. In conclusion, by controlling the compatibility of municipal solid waste incineration fly ash and coal gasification slag to change the chemical species composition of the system, the transformation of bridging oxygen (BO) in the melt to non-bridging oxygen (NBO) can be effectively promoted, thereby inhibiting the formation of a dense glass network structure and facilitating the separation and recovery of the metal phase.

[0037] Example 2

[0038] Example 2 investigated the effect of melt viscosity on the metal recovery efficiency and metal fractionation of glass products, metal alloys and volatile products from municipal solid waste incineration fly ash and coal gasification slag.

[0039] Municipal solid waste incineration fly ash and coal gasification slag were mixed evenly at a 1:1 ratio to obtain a mixture of municipal solid waste incineration fly ash and coal gasification slag. The mixture was then placed in a crucible and heated in a medium-frequency melting furnace. The melting was carried out at different melt viscosities (42.4 Pa·s, 12.4 Pa·s, 4.4 Pa·s and 1.8 Pa·s) for 30 minutes. The mixture was then allowed to cool naturally to room temperature to obtain glass products, metal alloys and volatile phase products.

[0040] The effects of different melt viscosities (42.4 Pa·s, 12.4 Pa·s, 4.4 Pa·s, and 1.8 Pa·s) on the recovery rates of metals Ni, Cu, Zn, Pb, and Fe are as follows: Figure 7 As shown in (a), the recovery rates of Ni, Cu, Zn, Pb, and Fe reached 68.65%, 100%, 100%, 100%, and 91.43%, respectively, at 4.4 Pa·s. The distribution patterns of the recovery of metals Ni, Cu, Fe, Zn, and Pb in different phases are shown in Figure (a). Figure 7 As shown in (bf), the figure shows that at a melt viscosity of 4.4 Pa·s, further decreasing the viscosity enhances the thermodynamic reactivity of the metal reduction and chlorination reactions, resulting in an overall upward trend in the alloy phases and volatile phases of Ni, Cu, Fe, and Zn. Therefore, a melt viscosity of 4.4 Pa·s is preferred for the metal fractionation system.

[0041] Example 3

[0042] Example 3 investigated the effects of melting time on the metal recovery efficiency and metal fractionation of glass products, metal alloys and volatile products from municipal solid waste incineration fly ash and coal gasification slag.

[0043] Municipal solid waste incineration fly ash and coal gasification slag were mixed evenly at a 1:1 ratio to obtain a mixture of municipal solid waste incineration fly ash and coal gasification slag. The mixture was then placed in a crucible and heated in a medium-frequency melting furnace to melt it. The melt viscosity was 4.4 Pa·s. The melting was maintained at different melting times (10, 20, 30, 40 and 50 min). The mixture was then naturally cooled to room temperature to obtain glass products, metal alloys and volatile phase products.

[0044] The effects of different melting times (10, 20, 30, 40, and 50 min) on the recovery rates and metal fractionation of Ni, Cu, Zn, Pb, and Fe are as follows: Figure 8 As shown in (af), the extended melting time is beneficial for metal separation and recovery. With the extension of melting time, the metal recovery rate in the system gradually increases, and the proportions of volatile metal phase and alloy phase also increase simultaneously, remaining relatively stable after 30 minutes of melting.

[0045] In summary, under the conditions of a 1:1 ratio of municipal solid waste incineration fly ash to coal gasification slag, a molten viscosity of 4.4 Pa·s, and a melting time of 30 min, the recovery rates of metals Ni, Cu, Zn, Pb, and Fe were 68.65%, 100%, 100%, 100%, and 91.43%, respectively. A co-melting and simultaneous metal separation and recovery system using municipal solid waste incineration fly ash and coal gasification slag was effectively constructed.

[0046] The glass products prepared under optimal conditions (a 1:1 ratio of municipal solid waste incineration fly ash to coal gasification slag, a melt viscosity of 4.4 Pa·s, and a melting time of 30 min) were subjected to the following tests: Detection 1): Analysis of the chemical speciation of heavy metals in the sample. A modified BCR sequential extraction method was used to analyze the chemical speciation of heavy metals in glass product samples. The specific procedure is as follows: 1.0 g of glass product sample was accurately weighed, and four sequential extraction steps were performed. The heavy metal content in the extract and the final residue of each step was determined by ICP-OES. The first step was the extraction of the acid-extractable form of metal (F1): 40 mL of 0.11 mol / L acetic acid solution was added to the sample, and the mixture was shaken at 30 rpm for 18 hours at room temperature. After the reaction, the mixture was centrifuged, and the supernatant was filtered through a 0.45 μm filter membrane. The resulting filtrate was the F1 extract. The remaining residue was washed with 15 mL of deionized water and centrifuged again. The washings were discarded, and the residue was retained. The second step was the extraction of the reducible form of metal (F2): 40 mL of 0.5 mol / L hydroxylamine hydrochloride solution was added to the residue obtained in the previous step, and the mixture was shaken for 18 hours under the same conditions (room temperature, 30 rpm). The same centrifugation, filtration, and washing procedures as in step one were then performed. The F2 extract was collected, and the washed residue was retained. The third step was the extraction of the metal-oxidizable state (F3): First, 10 mL of 30% hydrogen peroxide solution was added to the residue from the previous step, and the mixture was allowed to stand at room temperature for 1 hour. Then, the mixture was heated in an 85°C water bath until the volume decreased to 2-3 mL. After cooling, another 10 mL of 30% hydrogen peroxide was added, and the heating and evaporation process was repeated. Finally, 40 mL of 1.0 mol / L ammonium acetate solution was added to the cooled residue, and the mixture was shaken at 30 rpm on a rotary shaker for 18 hours at room temperature. Similarly, after centrifugation, filtration, and washing, the F3 extract was collected, and the final residue was retained. The fourth step was the determination of the metal residue state (F4): The residual solid obtained in step three was dried at 105°C for 12 hours, and then digested. After digestion, the residual heavy metal content was determined using ICP-OES.

[0047] Furthermore, the Risk Assessment Code (RAC) and the Potential Ecological Risk Index (RI) were used to assess the individual ecological risks of heavy metals in the samples and the overall potential ecological risks of heavy metals, respectively. The RAC value was calculated as shown in Equation 2:

[0048] in, C F1 It is the acid-extractable content (mg / kg) of a single metal Cu, Ni, Fe, Zn, Pb and Cr in the sample. C Total It is the total content of the metal in the sample (mg / kg).

[0049] RI represents the overall potential ecological risk of heavy metals in the sample, and its calculation is shown in Equation 3:

[0050] in, A i This represents the proportion of the active forms (F1 + F2 + F3) of the metals Cu, Ni, Fe, Zn, Pb, and Cr in the sample. D i The proportion of its residual state (F4) in the sample. T i The values ​​for the metals are 5, 5, 2, 5, and 1, respectively. The evaluation criteria for RAC and RI are shown in Table 3.

[0051] Table 3 Evaluation Criteria for RAC and RI

[0052] In this application, most of the metals in the co-melting system of municipal solid waste incineration fly ash and coal gasification slag are recovered through alloying, while the remaining heavy metals are solidified in the glass product. The speciation of heavy metals in the original sample (a 1:1 mass ratio of municipal solid waste incineration fly ash to coal gasification slag) and the glass product (prepared under optimal conditions: a 1:1 mass ratio of municipal solid waste incineration fly ash to coal gasification slag, a melt viscosity of 4.4 Pa·s, and a melting time of 30 min) was analyzed using the improved BCR continuous extraction experiment described above to evaluate the solidification and stabilization effect of heavy metals in the glass product. The speciation of heavy metals in the original sample and the glass product is shown below. Figure 9 As shown, Figure 9 (a) shows the speciation of heavy metals in the original sample. Figure 9 (b) The distribution of heavy metal speciation in the obtained glass product. As shown in the figure, compared with the original mixed sample before melting, most of the heavy metal elements in the glass product exist in stable forms. In the original sample, the unstable forms (F1+F2) of Cu, Zn, and Pb accounted for 26.59%, 42.59%, and 10.87%, respectively, indicating poor stability of the heavy metals. Under the dual effects of metal separation and vitrification during melting, most of the metals Cu, Ni, and Fe in the glass product were fixed in the glass product as residues (F4). Since metals Zn and Pb were completely enriched in the volatile phase product through chlorination volatilization, their distribution in the glass product was not detected. Figure 9 (b) Further, based on the proportion of each chemical form of heavy metal in the original sample and the glass slag, the RAC value and RI value were calculated respectively (Table 4).

[0053] Table 4. RAC and RI values ​​of the original sample and the glass product

[0054] As shown in Table 4, the RAC values ​​of Cu and Zn in the original sample were 24.68% and 34.22%, respectively, which are in the medium and high risk ranges. In the glass product, the heavy metals all exist in a stable residual state (F4), and there is almost no heavy metal risk.

[0055] Test 2): Analysis of leaching toxicity and total chlorine content of glass products According to the "Solid Waste Leaching Toxicity Method - Sulfuric Acid and Nitric Acid Method" (HJ / T 299-2007), a heavy metal leaching toxicity test was carried out on the molten glass product, and the measured heavy metal content of the leaching solution was compared with the standard limit in the "Technical Requirements for Vitrified Solid Waste Products" (GB / T 41015-2021). The experimental steps are as follows: (1) Prepare the leaching solution: mix sulfuric acid and nitric acid at a mass ratio of 2:1, then dilute with deionized water and adjust the pH to 3.20±0.05; (2) Leach the glass product with a liquid-solid ratio of 10:1, maintain the temperature at 23±2℃, oscillate at a frequency of 30±2 rpm / min, and oscillate for 18±2 h; (3) After the reaction, put the solid-liquid mixture into a centrifuge and centrifuge at 4000 rpm for 5 min, collect the supernatant and seal it for storage, and use it for heavy metal content determination.

[0056] The total chlorine content leaching test was conducted as follows: First, the leaching solution was prepared by adding approximately 500 mL of deionized water to a 1 L beaker, followed by slowly adding 63 mL of concentrated nitric acid and stirring until well mixed. After the solution cooled to room temperature, it was quantitatively transferred to a 1 L volumetric flask, and diluted to the mark with deionized water. 1.000 g of the sample to be tested was accurately weighed and placed in a 50 mL centrifuge tube. 20 mL of the above leaching solution was added and the tube was sealed. The centrifuge tube was placed in a constant-temperature shaker and shaken at 30 rpm for 30 min at the specified temperature. After shaking, the centrifuge tube was transferred to a preheated 100 °C water bath and allowed to stand for 5 minutes, then removed and allowed to cool naturally at room temperature. Next, the centrifuge tube was placed in a centrifuge and centrifuged at 4000 rpm for 5 minutes, collecting the supernatant. 20 mL of deionized water was added to the solid residue in the centrifuge tube, and the mixture was shaken again to redisperse the residue. This process was repeated three times. Finally, the supernatant obtained from the first leaching and the supernatants obtained from the other three rinsings were all transferred to a 50 mL volumetric flask, diluted to the mark with deionized water, mixed well, sealed and stored for subsequent analysis.

[0057] To verify the harmlessness effect of the glass products, leaching toxicity and total chlorine content were tested, and the results are shown in Table 5.

[0058] Table 5. Leaching toxicity and total chlorine content analysis of glass products

[0059] Note: ND indicates not detected. As shown in Table 4, no heavy metal leaching was detected in the glass product samples, and the total chlorine content was 0.06%, which is far below the standard limits of "Technical Requirements for Vitrification Products of Solid Waste" (GB / T 41015-2021) and "Technical Specification for Pollution Control of Fly Ash from Municipal Solid Waste Incineration" (HJ 1134-2020). The glass products meet the requirements for harmless treatment.

[0060] Example 4

[0061] Different addition amounts of B2O3 and Ga2O3 were studied.

[0062] Experimental Group 1: Municipal solid waste incineration fly ash and coal gasification slag were mixed evenly at a mass ratio of 1:1 to obtain a mixture of municipal solid waste incineration fly ash and coal gasification slag. The mixture was placed in a crucible and heated in a medium-frequency melting furnace to melt it. The melt viscosity was maintained at 4.4 Pa·s and the melting time was 30 min. The mixture was then naturally cooled to room temperature to obtain glass products, metal alloys and volatile phase products.

[0063] Experimental Group 2: Municipal solid waste incineration fly ash and coal gasification slag were mixed evenly at a mass ratio of 1:1. 8% of the total mass of municipal solid waste incineration fly ash and coal gasification slag, containing B2O3 and Ga2O3 in a mass ratio of 4:1, was added and mixed evenly to obtain a mixture of municipal solid waste incineration fly ash, coal gasification slag, B2O3, and Ga2O3. The mixture was placed in a crucible and heated in a medium-frequency melting furnace until melted. The melt viscosity was maintained at 4.4 Pa·s, and the melting time was 30 min. The mixture was then allowed to cool naturally to room temperature to obtain glass products, metal alloys, and volatile phase products.

[0064] Experimental Group 3: Municipal solid waste incineration fly ash and coal gasification slag were mixed evenly at a mass ratio of 1:1. 8% of the total mass of municipal solid waste incineration fly ash and coal gasification slag, containing B2O3 and Ga2O3 in a mass ratio of 7:3, was added and mixed evenly to obtain a mixture of municipal solid waste incineration fly ash, coal gasification slag, B2O3, and Ga2O3. The mixture was placed in a crucible and heated in a medium-frequency melting furnace until melted. The melt viscosity was maintained at 4.4 Pa·s, and the melting time was 30 min. The mixture was then allowed to cool naturally to room temperature to obtain glass products, metal alloys, and volatile phase products.

[0065] Experimental Group 4: Municipal solid waste incineration fly ash and coal gasification slag were mixed evenly at a mass ratio of 1:1. 8% of the total mass of municipal solid waste incineration fly ash and coal gasification slag, containing B2O3 and Ga2O3 in a mass ratio of 9:1, was added and mixed evenly to obtain a mixture of municipal solid waste incineration fly ash, coal gasification slag, B2O3, and Ga2O3. The mixture was placed in a crucible and heated in a medium-frequency melting furnace until melted. The melt viscosity was maintained at 4.4 Pa·s, and the melting time was 30 min. The mixture was then allowed to cool naturally to room temperature to obtain glass products, metal alloys, and volatile phase products.

[0066] Experimental Group 5: Municipal solid waste incineration fly ash and coal gasification slag were mixed evenly at a mass ratio of 1:1. 8% of the total mass of municipal solid waste incineration fly ash and coal gasification slag was added and mixed evenly to obtain a mixture of municipal solid waste incineration fly ash, coal gasification slag, and B2O3. The mixture was placed in a crucible and heated in a medium-frequency melting furnace. The melting viscosity was maintained at 4.4 Pa·s, and the melting time was 30 min. The mixture was then naturally cooled to room temperature to obtain glass products, metal alloys, and volatile phase products.

[0067] Experimental Group 6: Municipal solid waste incineration fly ash and coal gasification slag were mixed evenly at a mass ratio of 1:1. 8% of the total mass of municipal solid waste incineration fly ash and coal gasification slag, along with Ga2O3, was added and mixed evenly to obtain a mixture of municipal solid waste incineration fly ash, coal gasification slag, and Ga2O3. The mixture was placed in a crucible and heated in a medium-frequency melting furnace. The melting viscosity was maintained at 4.4 Pa·s, and the melting time was 30 min. The mixture was then allowed to cool naturally to room temperature to obtain glass products, metal alloys, and volatile phase products.

[0068] Application Example 1 Microcrystalline glass was prepared by heat treatment using the glass product obtained in Experimental Group 1 of Example 4. The heat treatment conditions were set at 900°C for 2 hours.

[0069] The DSC test results of the glass product obtained in Experimental Group 1 of Example 4 are as follows: Figure 10 As shown in (a), the DSC curves show an endothermic peak at 745℃ and a distinct exothermic peak at 860℃, which correspond to the glass transition temperature (Tg) and crystallization temperature (Tc) of the glass product, respectively.

[0070] The XRD pattern of the microcrystalline glass sample prepared under heat treatment at 900℃ for 2 hours is shown below. Figure 10 As shown in (b), XRD analysis revealed that its main crystalline phases were SiO2, CaAl2Si2O8, CaSiO3, and Ca2SiO4, with a high crystallinity of 82.60%. Simultaneously, SEM images clearly showed the distribution of the crystalline phases within the glass-ceramic matrix. Figure 10 (c)).

[0071] Application Example 2 The glass products obtained in experimental groups 1-6 of Example 4 were heat-treated to prepare microcrystalline glass. The heat treatment conditions were all 900℃ and 2h.

[0072] The obtained microcrystalline glass underwent performance testing. Vickers hardness testing was conducted according to the "Test Method for Room Temperature Hardness of Fine Ceramics" (GB / T 16534-2009), using an MH-6 Vickers hardness tester. The microcrystalline glass was held under a load of 196 N for 10 seconds, and the corresponding Vickers hardness was measured. Acid and alkali corrosion resistance testing was conducted according to the "Test Method for Acid and Alkali Corrosion Resistance of Fine Ceramics" (JC / T 2138-2012), using 3 mol / L H₂SO₄ solution and 6 mol / L NaOH solution to test the corrosion resistance of the samples. Water absorption was determined according to the "Test Methods for Ceramic Tiles Part 3: Determination of Water Absorption, Apparent Porosity, Apparent Relative Density and Bulk Density" (GB / T 3810.3-2016). The test results are shown in Table 6 below.

[0073] Table 6. Effects of different amounts of B2O3 and Ga2O3 on the quality of glass-ceramics

[0074] Based on experimental groups 1-4 and Table 6, it can be seen that when B2O3 and Ga2O3 are added simultaneously in experimental group 2, and the addition ratio of B2O3 and Ga2O3 is optimized to 4:1, the Vickers hardness, water absorption, acid corrosion resistance and alkali corrosion resistance of the microcrystalline glass can be improved better.

[0075] Based on experimental groups 2, 5, and 6 and Table 6, it can be seen that in experimental groups 5 and 6, after replacing B₂O₃ and Ga₂O₃ with each other by equal mass, the Vickers hardness, water absorption, acid corrosion resistance, and alkali corrosion resistance of the microcrystalline glass were all worse than those in experimental group 2. This may be because adding only B₂O₃ may result in an overly loose glass network, while adding only Ga₂O₃ may result in an overly dense glass network, affecting the fluidity and uniformity of the glass, leading to an incomplete glass network structure and an imbalance in performance.

[0076] The above are all preferred embodiments of this application and are not intended to limit the scope of protection of this application. Therefore, all equivalent changes made to the products, methods and principles of this application should be covered within the scope of protection of this application.

Claims

1. A method for the co-melting and vitrification of fly ash from municipal solid waste incineration and gasification slag, and for the efficient recovery of metals, characterized in that... include: The dried fly ash from municipal solid waste incineration is mixed evenly with coal gasification slag to obtain a mixture, which is then melted and cooled to obtain glass products and alloys. Based on the mass of municipal solid waste incineration fly ash as 100%, the municipal solid waste incineration fly ash includes 31-33 wt% CaO, 21-23 wt% SiO2, 10-12 wt% Al2O3, 4-6 wt% Na2O, 5.5-7 wt% Fe2O3, 0.5-1.5 wt% C, 0.05-0.15 wt% S, and 11-13 wt% Cl; Based on the mass of the coal gasification slag (100%), the coal gasification slag comprises 17-20 wt% CaO, 41-44 wt% SiO2, 16-18.5 wt% Al2O3, 2-4 wt% Na2O, 12-15 wt% Fe2O3, 6-7.5 wt% C, 0.5-1.2 wt% S, and 0.02-0.06 wt% Cl.

2. The method for co-melting and vitrifying municipal solid waste incineration fly ash and coal gasification slag and efficiently recovering metals according to claim 1, characterized in that, The mass ratio of fly ash from municipal solid waste incineration to coal gasification slag is (0.5-8):

1.

3. The method for co-melting and vitrifying municipal solid waste incineration fly ash and coal gasification slag and efficiently recovering metals according to claim 1, characterized in that, The melt viscosity is 1.8-42.4 Pa·s.

4. The method for co-melting and vitrifying municipal solid waste incineration fly ash and coal gasification slag and efficiently recovering metals according to claim 1, characterized in that, The melting time is 10-50 min.

5. The method for co-melting and vitrifying municipal solid waste incineration fly ash and coal gasification slag and efficiently recovering metals according to claim 1, characterized in that, The mixture also contains additives B2O3 and Ga2O3, with the total added mass of B2O3 and Ga2O3 being 6-10% of the total mass of municipal solid waste incineration fly ash and coal gasification slag.

6. The method for co-melting and vitrifying municipal solid waste incineration fly ash and coal gasification slag and efficiently recovering metals according to claim 5, characterized in that, The mass ratio of B2O3 to Ga2O3 is (2.33-9):

1.

7. A microcrystalline glass, characterized in that, The microcrystalline glass is obtained by heat treatment of the glass product prepared by the method according to any one of claims 1-6.

8. The microcrystalline glass according to claim 7, characterized in that, The heat treatment temperature is 900℃ and the time is 1.5-2.5h.

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