Method for preparing microcrystalline glass through one-step heat treatment by ash melting method

Abstract

The invention discloses a method for preparing microcrystalline glass from ash. The method comprises the following steps: by taking ash as a raw material, crushing, uniformly mixing, screening, carrying out ball milling, calcining and removing carbon, uniformly mixing the treated ash with added powder, carrying out high-temperature melting to obtain glass slag, and carrying out nucleation and crystallization one-step heat treatment on the obtained base glass to obtain the microcrystalline glass. According to the invention, the ash is used as the main raw material to prepare the green microcrystalline glass, the content of the ash is 50% or above, the ash can be effectively utilized, the problem of difficult disposal of the ash can be solved, good economic benefits can be obtained, and a sustainable development thought is provided for coal chemical industry.

Description

Technical Field

[0001] This invention relates to the field of inorganic non-metallic materials technology, and in particular to a method for preparing microcrystalline glass from ash slag. Background Technology

[0002] Gasification ash is a solid waste produced in industry, consisting of SiO2, metal oxides, and unburned residual carbon. In recent years, with technological advancements, the amount of ash accumulated has increased year by year, leading to serious environmental pollution and resource waste. Currently, research on the utilization of ash is relatively scarce, mainly focusing on carbon-based / silicon-aluminum-based materials and ceramics. However, the components of ash have poor activity and high residual carbon content, making it difficult to achieve large-scale engineering applications.

[0003] Glass-ceramics are high-performance inorganic materials composed of a glassy phase and a crystalline phase. They possess advantages such as high mechanical strength, corrosion resistance, and good thermal stability, and are widely used in construction, electronics, and military industries. Utilizing ash residue to prepare glass-ceramics not only achieves high-value utilization of solid waste but also reduces raw material costs (components such as SiO2, Al2O3, and CaO in ash residue can serve as network formers and modifiers for glass-ceramics), aligning with the sustainable development concept of "replacing materials with waste."

[0004] The limited application of existing ash and slag disposal technologies has led to resource waste. Summary of the Invention

[0005] To address the problems of difficult carbon removal and low component activity in existing technologies, this invention utilizes ball milling and calcination, component compatibility design, and other methods to improve the performance of glass-ceramics and achieve the harmless and resource-based disposal of ash. Therefore, one objective of this invention is to provide a technical method for preparing glass-ceramics from ash, wherein the ash utilization rate is greater than 50%.

[0006] This technical method is achieved through a one-step heat treatment process using ash slag melting to prepare microcrystalline glass, which includes the following steps:

[0007] (1) The ash and slag are crushed, mixed and screened to obtain ash and slag powder with a predetermined particle size;

[0008] (2) The ash powder is calcined until the weight of the ash no longer changes;

[0009] (3) The calcined ash powder and the additive powder are mixed in a predetermined ratio and ball-milled to obtain a uniformly mixed powder.

[0010] (4) The powder is placed in a muffle furnace for melting, and the base glass is obtained by naturally cooling the furnace to room temperature.

[0011] (5) The base glass is calcined and annealed to room temperature to obtain microcrystalline glass.

[0012] As described above, through crushing, mixing and sieving in step (1), the configuration of the ash residue containing a large amount of unburned and highly graphitized residual carbon is destroyed, thereby improving its reactivity; through calcination in step (2), the residual carbon in the ash residue is effectively removed; through ball milling in step (3), the components of the powder are mixed evenly, preventing the components with large density differences from stratifying in the crucible during the melting process; through melting in step (4), the components of the powder are fully mixed in the molten state, avoiding premature or uneven crystallization that would lead to a deterioration in the performance of the microcrystalline glass; then, the glass is rapidly cooled to room temperature in the furnace to obtain the base glass, and the rapid cooling ensures that uncontrollable crystallization will not occur prematurely, affecting the quality of the finished product.

[0013] In one embodiment of the method of the present invention, the crushing method in step (1) is ball milling, the ball milling speed is 400~600 rpm, the ball milling time is 8~10 h, and the predetermined particle size is ≤150 μm.

[0014] In one embodiment of the method of the present invention, the calcination temperature in step (2) is 850°C and the calcination time is 12h.

[0015] In one embodiment of the method of the present invention, the ratio of the ash powder to the additive powder in step (3) is 50wt%-90wt% ash powder and 10wt%-50wt% additive powder.

[0016] In one embodiment of the method of the present invention, the additive powder in step (3) is a mixture of CaO and CaF2.

[0017] In one embodiment of the method of the present invention, the mass ratio of CaO to CaF2 in the additive powder is 15:1 to 15:4.

[0018] In one embodiment of the method of the present invention, the ball milling speed in step (3) is 400~600 rpm and the ball milling time is 2h.

[0019] In one embodiment of the method of the present invention, the melting process in step (4) involves heating the powder to 1400℃-1500℃ at a rate of 10℃ / min and then holding it at that temperature for 3 hours.

[0020] In one embodiment of the method of the present invention, the calcination process in step (5) involves heating the base glass to 1000°C at 10°C / min, holding it at that temperature for 2 hours, and then annealing it at a rate of 2°C / min.

[0021] Another object of the present invention is to provide a microcrystalline glass obtained by any of the methods described above.

[0022] The method of this invention enhances the reactivity of residual carbon in the ash slag through mechanical activation via ball milling, thus avoiding porosity defects and reducing the various properties of the glass-ceramic. The glass body is activated by alkaline oxide activation; SiO2 and Al2O3 in the glass slag react with the alkaline activator to form Al-O([AlO4)) 5- Tetrahedron and Si-O tetrahedron ([SiO4]) 4- The crystallization process of glass slag, which is an amorphous to semi-crystalline aluminosilicate polymer, can be divided into two stages: crystal nucleation and crystal growth under the action of added nucleating agent (CaF2). The nucleating agent can effectively reduce the energy barrier for crystal formation and effectively reduce the crystallization temperature.

[0023] Compared with the prior art, the method of the present invention has the following specific advantages:

[0024] (1) Using ash slag as raw material to prepare microcrystalline glass provides a sustainable development approach for coal chemical industry;

[0025] (2) The proposed ball milling and calcination method for removing residual carbon is simple to operate and has a significant effect on removing residual carbon;

[0026] (3) The SiO2 content in the ash exceeds 40%, which is the silicon source for glass-ceramics. The alkaline oxide CaO is the calcium source for glass-ceramics, which meets the composition requirements of glass-ceramics. The TiO2, Fe2O3, added CaF2 and heavy metals in the ash act as nucleating agents for glass-ceramics, increasing the nucleation driving force and promoting crystallization, which meets the requirements of glass-ceramics for nucleating agents.

[0027] (4) The compounded alkali activator (CaO) can reduce the viscosity of the glass, promote the formation and melting of the glass, and at the same time reduce the crystallization activation energy of the glass, which is beneficial to promote crystallization in the one-step heat treatment process, so that the microcrystalline glass can form a crystalline phase at a relatively low temperature, shorten the process flow and reduce energy consumption.

[0028] (5) The glass slag contains sufficient SiO2 and Al2O3, eliminating the need to add other components and reducing the difficulty of the composition adjustment process. The SiO2 and Al2O3 in the glass slag undergo an activation reaction with the alkali activator (CaO) to form Al-O([AlO4]) 5- Tetrahedron and Si-O tetrahedron ([SiO4]) 4- Amorphous to semi-crystalline aluminosilicate polymers;

[0029] (6) The present invention has a simple process, low cost, low pollution, strong operability, and is easy to industrialize.

[0030] The foregoing content of this application will become more readily understood in the following description of several embodiments with reference to the accompanying drawings. Attached Figure Description

[0031] The following are accompanying drawings of this application. These drawings are provided only to illustrate the application in a more intuitive form. They are exemplary and are not intended to limit the scope of this application.

[0032] Figure 1 This is the XRD pattern of ash powder in the method embodiment of the present invention;

[0033] Figure 2 These are scanning electron microscope images of ash residue from embodiments of the method of the present invention;

[0034] Figure 3 This is the XRD pattern of the microcrystalline glass prepared in Example 1 of this invention;

[0035] Figure 4 These are scanning electron microscope images of the microcrystalline glass prepared in Example 1 of this invention. Detailed Implementation

[0036] To make this application easier to understand, specific embodiments are described below to further illustrate this application. Unless otherwise specified, the experimental methods described in this application are conventional methods; the materials described, unless otherwise specified, are all commercially available. Unless otherwise defined, all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art to which this application pertains. In case of any inconsistency, the meaning as described in this specification or derived from the content described in this specification shall prevail. Furthermore, the terminology used herein is for the purpose of describing embodiments of this application only and is not intended to limit this application.

[0037] The terms "one embodiment" or "implementation" as used in this specification mean that a particular feature, step, or characteristic described in conjunction with that embodiment is included in at least one embodiment of the invention. Therefore, the terms "in one embodiment" or "in an embodiment" appearing throughout this specification do not necessarily refer to the same embodiment, but may refer to the same embodiment. Furthermore, in one or more embodiments, the particular features, steps, or characteristics can be combined in any suitable manner, as will be apparent to those skilled in the art from this application.

[0038] Example 1

[0039] (1) The ash residue was crushed and mixed to ensure uniformity and stability; the ash residue was then placed in a ball mill and ball-milled at 500 rpm for 8 hours, and passed through a 150 μm sieve to obtain ash residue powder. The XRD pattern of the ash residue powder is shown in [reference needed]. Figure 1 The scanning electron microscope image of the ash powder is shown below. Figure 2 . Figure 1 XRD patterns show that the main crystalline phase of the ash is a complex aluminosilicate (Al2O3) with stoichiometric non-uniform phases.4.54 Si 1.46 O 9.73 The presence of a small amount of incompletely reacted SiO2 and newly formed magnesium metasilicate (MgSiO2) indicates that the raw material minerals underwent a complex transformation reaction at high temperatures. Figure 2 The SEM images visually demonstrate that its microstructure is characterized by irregular blocky shape, sharp particle edges, and loose and porous structure. This heterogeneous structure formed by the rapid cooling of molten droplets corroborates the results of multi-phase XRD analysis, together defining the nature of this ash slag as an amorphous-crystalline composite material.

[0040] (2) The ash powder was calcined at 850℃ for 12 hours until the weight of the ash powder no longer changed. The residual carbon was removed and the powder was passed through a 150μm sieve. The calcined ash powder contained the following components:

[0041] CaO 6.6%, SiO243.76%, Al2O339.71%, Fe2O34.2%, MgO 0.17%, TiO2 2.37%, SO31.83%, K2O 0.24%;

[0042] (3) Weigh 20g of calcined ash powder from step (2), add powder (8g CaO, 0.8g CaF2), mix the ash powder and the added powder, and mix in a ball mill at 500rpm for 2 hours.

[0043] (4) Place the mixed powder in a muffle furnace and heat it to 1400℃ at 10℃ / min for 3 hours to melt it. Then let it cool naturally to room temperature in the furnace to obtain the base glass.

[0044] (5) The base glass obtained in step (4) is heated to 1000℃ at 10℃ / min and held for 1h, then annealed to room temperature. The annealing cooling rate is 2℃ / min.

[0045] The XRD pattern of the microcrystalline glass prepared in this embodiment is as follows: Figure 3 As shown, by Figure 3 It can be seen that the main crystalline phases precipitated in the microcrystalline glass prepared in this embodiment are anorthite and spinel, and the secondary crystalline phases are diopside, nepheline, and albite; its scanning electron microscope (SEM) images are shown below. Figure 4 As shown, the microstructure of glass-ceramics is a dense polycrystalline structure formed by the interweaving of multiple crystalline phases—ammonia feldspar in the form of plates, diopside in the form of short columns, and spinel in the form of needles. These crystals are bonded together by the residual silicate glass phase, forming a multiphase ceramic body with high mechanical strength and stability.

[0046] Example 2:

[0047] As described in Example 1, the difference is that 15.2g of CaO is added in step (3) and no CaF2 is added.

[0048] Example 3:

[0049] As described in Example 1, the difference is that 19.4g of CaO is added in step (3) and no CaF2 is added.

[0050] Example 4:

[0051] As described in Example 1, the difference is that 20.6g of CaO is added in step (3) and no CaF2 is added.

[0052] Example 5:

[0053] As described in Example 1, the difference is that 0.56g of CaF2 is added in step (3).

[0054] Example 6:

[0055] As described in Example 1, the difference is that 1.68g of CaF2 is added in step (3).

[0056] Example 7:

[0057] As described in Example 1, the difference is that 2.8g of CaF2 is added in step (3).

[0058] Comparative Example 1

[0059] (1) Take the ash residue, crush and mix it to ensure that the ash residue is uniform and stable; put the ash residue into a ball mill and ball mill at 500 rpm for 8 hours, and pass it through a 150 μm sieve.

[0060] (2) The ash powder was calcined at 850℃ for 12 hours until the weight of the ash powder no longer changed. The residual carbon was removed and the powder was passed through a 150μm sieve. The calcined ash powder contained the following components:

[0061] CaO 6.6%, SiO243.76%, Al2O339.71%, Fe2O34.2%, MgO 0.17%, TiO2 2.37%, SO31.83%, K2O 0.24%;

[0062] (3) Weigh 20g of the calcined ash residue from step (2) and grind it for 2 hours at 500rpm in a ball mill.

[0063] (4) The abrasive material in step (3) is placed in a muffle furnace and heated to 1400℃ at 10℃ / min for 3 hours. The base glass is obtained by naturally cooling the furnace to room temperature. The obtained glass body is not microcrystalline glass.

[0064] Performance testing

[0065] The microcrystalline glass frits prepared in Examples 1-7 and the glass body prepared in Comparative Example 1 were subjected to hardness, acid resistance, alkali resistance and heavy metal TCLP tests.

[0066] (1) Hardness test

[0067] The experiment used an HV-50A Vickers hardness tester. The test conditions were a load of 1.96 N, which was applied and held for 15 s before the load was released. The test method was the five-point method, and the sample size was 20 mm × 20 mm × 5 mm.

[0068] (2) Acid resistance test

[0069] A standard sample measuring 20mm × 20mm × 5mm was ultrasonically cleaned and dried, then weighed and recorded (G1). It was then sealed in a 20% sulfuric acid solution and corroded for 16 hours. After corrosion, the sample was ultrasonically cleaned, dried, and weighed again (G2). The chemical stability (C) was determined by calculating the mass loss rate of the sample before and after corrosion, using the following formula:

[0070] C = (G1 - G2) / G1 × 100%

[0071] In the formula: C - chemical stability;

[0072] G1 - Mass of the sample before corrosion (mg);

[0073] G2 - Mass of the sample after corrosion (mg).

[0074] (3) Alkali resistance test

[0075] A standard sample measuring 20mm × 20mm × 5mm was ultrasonically cleaned and dried, then weighed and recorded (G1). It was then sealed in a 20% sodium hydroxide solution and corroded for 16 hours. After corrosion, the sample was ultrasonically cleaned, dried, and weighed again (G2). The chemical stability (C) was determined by calculating the mass loss rate of the sample before and after corrosion, using the following formula:

[0076] C = (G1 - G2) / G1 × 100%

[0077] In the formula: C - chemical stability;

[0078] G1 - Mass of the sample before corrosion (mg);

[0079] G2 - Mass of the sample after corrosion (mg).

[0080] (4) Heavy metal TCLP detection

[0081] Acetic acid solution (pH = 2.88±0.05) was used as the extraction solvent. A certain mass of sample was weighed and extracted with the extraction solvent (liquid-to-solid ratio 20 mL: 1 g), followed by continuous leaching at 25 °C for 18 h. The sample was filtered through a 0.45 μm pore size membrane, and the clear leaching solution was collected for analysis. The concentration of the target metal in the sample was determined using ICP-OES.

[0082] The hardness, acid resistance, alkali resistance and heavy metal TCLP test results of the microcrystalline glass prepared in Examples 1-7 and the glass prepared in Comparative Example 1 are shown in Tables 1 and 2 below.

[0083] Table 1. Performance analysis results of the microcrystalline glass prepared in the examples and the glass prepared in the comparative examples.

[0084]

[0085] As shown in Table 1, adding alkali activator CaO and nucleating agent CaF2 in a predetermined ratio can effectively reduce the weight loss rate of acid and alkali solutions in glass-ceramics / glass bodies, proving that adding alkali activator CaO and nucleating agent CaF2 in a predetermined ratio can effectively promote crystallization, thereby forming a glass-ceramic with stable performance.

[0086] Table 2. TCLP analysis results of heavy metals in the microcrystalline glass prepared in the examples and the glass prepared in the comparative examples.

[0087]

[0088] Table 2 shows that the heavy metal TCLP leaching data of the microcrystalline glass prepared in Examples 1-7 and the glass prepared in Comparative Example 1 indicate that the overall environmental risk of heavy metals in both materials is relatively low: except for Mn, the leaching concentrations of Cr, Cu, Pb, and Zn are all in the μg / L range (≤0.07 mg / L), far below the leaching toxicity standard limit for hazardous waste, indicating that both materials have good stabilizing effects on most heavy metals. However, there are significant differences in Mn leaching among different samples: the Mn leaching concentration in Examples 2-4 reaches 3.11~4.28 mg / L, and the Mn leaching in Comparative Example 1 is as high as 7.46 mg / L, while the Mn leaching in the other examples is only 0.02~0.55 mg / L. This difference may be related to the Mn content in the raw materials and the occurrence state of Mn under the influence of the material preparation process—some formulations or processes failed to stabilize Mn in the difficult-to-leach crystalline / glassy phase, making it easier to leach.

[0089] The above description is merely a preferred embodiment and the technical principles employed in this application. Those skilled in the art will understand that this application is not limited to the specific embodiments described herein, and various obvious changes, readjustments, and substitutions can be made without departing from the scope of protection of this application. Therefore, although this application has been described in detail through the above embodiments, this application is not limited to the above embodiments, and may include many other equivalent embodiments without departing from the concept of this application, all of which fall within the scope of protection of this application.

Claims

1. A method for preparing microcrystalline glass in one step by ash melting and heat treatment, characterized in that, Includes the following steps: (1) The ash and slag are crushed, mixed and screened to obtain ash and slag powder with a predetermined particle size; (2) The ash powder is calcined until the weight of the ash no longer changes; (3) The calcined ash powder and the additive powder are mixed in a predetermined ratio and ball-milled to obtain a uniformly mixed powder. (4) The powder is placed in a muffle furnace for melting, and the base glass is obtained by naturally cooling the furnace to room temperature. (5) The base glass is calcined and annealed to room temperature to obtain microcrystalline glass.

2. The method according to claim 1, characterized in that, The crushing method in step (1) is ball milling, with a ball milling speed of 400~600 rpm, a ball milling time of 8~10 h, and a predetermined particle size of ≤150 μm.

3. The method according to claim 1, characterized in that, The calcination temperature in step (2) is 850℃ and the calcination time is 12h.

4. The method according to claim 1, characterized in that, The ratio of ash powder to additive powder in step (3) is 50wt%-90wt% ash powder and 10wt%-50wt% additive powder.

5. The method according to claim 1, characterized in that, The additive powder in step (3) is a mixture of CaO and CaF2.

6. The method according to claim 5, characterized in that, The mass ratio of CaO to CaF2 in the additive powder is 15:1 to 15:

4.

7. The method according to claim 1, characterized in that, In step (3), the ball milling speed is 400~600 rpm and the ball milling time is 2 hours.

8. The method according to claim 1, characterized in that, The melting process in step (4) involves heating the powder to 1400℃-1500℃ at 10℃ / min and then holding it at that temperature for 3 hours.

9. The method according to claim 1, characterized in that, The calcination process in step (5) involves heating the base glass to 1000°C at 10°C / min, holding it at that temperature for 2 hours, and then annealing it at a rate of 2°C / min.

10. A microcrystalline glass, characterized in that, It is prepared by any one of the methods described in claims 1 to 9.

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