KR100465460B1 - Method for Making Crystallized Glass Using Urban Fly Ash - Google Patents

Abstract

Fly ash among incineration ashes in Korea contains transition oxides that are easy to be vitrified and can be crystallized and vitrified after melting without additives. However, since a large amount of chlorine (Cl) is contained in the incineration ash, the present invention introduces a washing method as a pretreatment of the incineration ash. In the case of Al ₂ O ₃ , SiO ₂ and CaO, the incinerated ash was washed with water, and its content was increased after washing, so it was easily vitrified by the main ternary system of CaO-Al ₂ O ₃ -SiO ₂ . Na and K decreased significantly with Cl after washing with water.

Therefore, after washing with water, the melting point was greatly reduced, resulting in a decrease in viscosity during glass manufacturing. As a result of thermal analysis, homogeneous internal crystallization was induced when the glass was subjected to one step heat treatment at 850 to 950 ° C. The appearance of crystal phase with heat treatment significantly increased the modulus of elasticity, hardness and wear resistance in terms of physical properties. By recycling the waste (incineration ash), the present invention has shown the possibility of being used as a landfill solution for waste and a high value-added building material.

Description

Method for Making Crystallized Glass Using Urban Fly Ash}

The present invention relates to a method for producing crystallized glass using urban incineration ash, and in particular, urban incineration ash can be vitrified at low cost by washing with water as a pretreatment process, at the same time lowering the melting temperature and vitrification without additives even at low temperatures. In addition, the present invention relates to a method for producing crystallized glass that can be used as a building material having high strength, high toughness, and high wear resistance by one-step heat treatment.

In recent years, attempts have been made to create high value-added materials by manufacturing crystallized glass (glass-ceramic) by designing and casting a composition for melting using fly ash as the main raw material in urban incineration. At the present time, the hazards of municipal incineration emissions from Korea are very serious. In Korea, it is mainly used as a mixture with cement raw materials, and it is used for ondol flooring for construction, geotechnical soil for road construction, and road construction.

There are four known methods for treating incineration ashes: cement solidification by cement, melt solidification by firing, pharmaceutical treatment by chemical input, and acid extraction by acid and other solvents.

In the double melt solidification method, the incineration material introduced into the reactor is pyrolyzed and melted at a high temperature of about 1,400 ° C., and the structure is discharged as a very dense and harmless slag, which can be recycled as a building material.

Melt solidification method is a problem because the treatment cost, etc., because the treatment at high temperature as described above, but it is difficult to secure the landfill site, when thorough reduction is required and stabilization, such as the scattering of incineration ash and prevention of leaching of heavy metals is required to be. In addition, this method is melted and solidified by using a melting facility, and the slag is melt-stabilized as the incinerator is heated at a high temperature. Heavy metals in the incinerator are stabilized in the slag network and become glassy.

However, low melting point metals are volatilized into gas at the time of melting, so countermeasures are required, and the processing cost is expensive, so it is a technology that can be widely spread only when it is recycled. In other words, the melt solidification method is a method of stabilizing or reducing the incineration ash by heating the incineration ash at a high temperature by using fuel or electricity as a heat source and stabilizing it. The disadvantages are high installation and operating costs.

The content of _{SiO 2 Journal of Hazardous Materials B91 (} 2001) 83-93 Introduction to the ash handling is generally left in the ash is in a small amount and then the SiO ₂ and MgO to the vitrification of ash, so the melt is poor if the just processed Glass was prepared by the addition, and crystallized glass was manufactured through a one-step nucleation process and a two-step crystal growth process.

In Japanese Patent Application Laid-Open No. 8-310834, the composition of SiO ₂ CaO Al ₂ O ₃ was melted at a relatively high temperature of 1400-1500 ° C., and one-step heat treatment at 900 ° C. for 2 hours to produce crystallized glass. A flux other than alkali and alkali was added to lower the melting temperature to obtain the effect of coloring. However, considering the results shown that the crystallized glass thus produced has a bending strength of 76 MPa and a hardness of 5.5 GPa, the high temperature heat treatment process and the low strength and hardness of the material have many problems in actual applicability and process.

In Korean Patent Laid-Open No. 2000-13143, clay is mixed with municipal incinerator ash as a caking additive for plasticity enhancement, limestone is added as a sintering agent, kneaded, stirred, and molded, and then calcined at 1000 to 1300 ° C for 10 to 30 hours. Although a technique for making ceramic products is proposed, the physical properties of the manufactured material are not measured, and thus the practical application range of the material cannot be predicted in terms of mechanical and thermal aspects.

The inventors found that incineration materials that can cause environmental pollution are composed of CaO-Al ₂ O ₃ -SiO ₂ system as the main component, and when it is vitrified and recycled into crystallized glass, it can be applied to building materials, vitrified and crystallized. By developing a heat treatment process that can be made, the inventors invented materials for building materials with high toughness and wear resistance.

Therefore, the present invention has been devised in view of the problems of the prior art, and its purpose is to change the urban incineration ash into a composition that can be vitrified at low cost by washing with water as a pretreatment process, at the same time lowering the melting temperature and vitrification without additives even at low temperatures. It is also possible to provide a method for producing crystallized glass which can be used as a building material having high strength, high toughness and high wear resistance by one step heat treatment.

Another object of the present invention is to prepare a crystallized glass having an aesthetic color on the surface as a structure in which the internal fine crystal phase is uniformly distributed according to the heat treatment by casting after melting for a predetermined time based on CaO-Al ₂ O ₃ -SiO ₂ system To provide a way.

1 is a heat treatment timing diagram illustrating a crystallized glass manufacturing process according to the present invention.

In order to achieve the above object, the present invention comprises the steps of washing the incineration ash to lower the content of chlorine contained in the municipal incineration ash, and heat-treating the glass obtained after melting the washed incineration ash to obtain a crystallized glass It provides a method for producing crystallized glass using urban incineration ash.

According to the X-ray diffraction analysis, the urban incinerator is mainly composed of CaCl ₂ , γ-CaSO ₄ , Ca (OH) ₂ , CalCl ₂ · Ca (OH ₂ ) · H ₂ O crystal phases, and other crystal phases are very It exists in small quantities. The analytical values are described in Table 1 below by measuring by XRF for component analysis to identify the chemical properties of the incineration ash.

As can be seen from Table 1, the main component of the double incinerator ash contains a large amount of CaO, K ₂ O, Na ₂ O, Cl and the like. In general, the current incinerator discharged from domestic incinerators has a high melting point, so it is not easy to solidify after melting, and there is a problem of chlorine gas generation during the vitrification process because it contains a large amount of chlorine. It is necessary to have an inexpensive pretreatment process to lower it.

In the present invention, a method of washing with water was used as a pretreatment step. When the method of washing with water is applied in the present invention, the component changes before and after washing with respect to the incineration ash are investigated and shown in Table 2 below. The incineration ashes washed with pretreatment brought about significant changes in composition. For example, Al ₂ O ₃ changed its content from 3.2 wt% to 9.5 wt% before washing with water, SiO ₂ from 7.3 wt% to 21.7 wt%, and CaO from 19.5 wt% to 25.9 wt%. .

The present invention is to reduce the viscosity of SiO ₂ (20 ~ 30wt%), Al ₂ O ₃ (5 ~ 15wt%) to improve the chemical durability, the glass structure when melting the incineration ash when the water washing process It contains CaO (25-35wt%), MgO, etc., which improves chemical durability, as a main component, and contains Fe ₂ O ₃ , TiO ₂ , P ₂ O _5, etc., which can induce crystallization after glass manufacturing. do.

In the present invention, a method of washing with water is applied to remove chlorine present in a large amount in the incineration ash, which may have obtained the same composition as the calcination method by removing chlorine present in the ash. As described above, the melting point of the incineration ash was also lowered.

In addition, the incineration ash was found to have a large amount of Na ₂ O and K ₂ O as a result of washing, the reason seems to have been removed by dissolving in water in the form of NaCl and KCl in the incineration ash during washing.

This flushing method is economical in minimizing the corrosion of furnaces and facilities during the subsequent melting process by removing the large amounts of Cl contained in the incineration ash.

Based on the crystallized glass composition of CaO-Al ₂ O ₃ -SiO ₂ system having the above composition, after melting for 3 hours at 1400 ℃ to obtain a glass after heat treatment, the internal microcrystalline phase is uniformly distributed in the structure aesthetically on the surface Crystalline glass with color is obtained.

Therefore, the preferred method for producing the crystallized glass according to the present invention using the composition described above for 48 hours by mixing the incineration ash with distilled water in a ratio of 1: 3 in order to remove the chlorine components present in the incineration ash and lower the melting point of the incineration ash. After washing with water, drying in an electric oven at 100 ° C. for 24 hours to obtain vitrified incineration ash, firstly heating the obtained incineration ash at 1400 ° C. for 3 hours, and for 20 to 240 minutes near the maximum exothermic temperature. Characterized in that it comprises a step of obtaining the crystallized glass through the secondary heat treatment.

Since the incinerator itself contains a crystallization agent of TiO ₂ , Fe ₂ O ₃ , MgO can induce internal crystallization without the addition of a separate crystallization agent, the crystallization state is shown as one of the internal and surface crystallization state. In this case, since the surface crystallization state still has amorphous glass inside the material, the surface crystallization state exhibits physical properties that are relatively inferior in hardness, strength, toughness, and abrasion resistance to the material in the internal crystallization state. do.

In this case, in the step of obtaining the crystallized glass through the heat treatment, if the crystallization degree is less than the maximum exothermic start temperature in the material, the crystallization degree is insignificant, and there are many residual glass in the material. When the temperature is higher than the temperature at which is completed, crystallization deeply occurs in the material, which is not preferable because cracks and micropores are formed. Therefore, the heat treatment temperature for the internal crystallization is preferably in the range of 850 ℃ to 950 ℃.

The heat treatment time for obtaining the crystallized glass was 80-90% of the crystallization degree even in a short time of 20 minutes in the molten incinerator glass, and as the heat treatment time was increased to 240 minutes or more, cracks and pores due to severe crystallization were formed, resulting in hardness. The range of 20 to 240 minutes is preferable because it causes a decrease in strength, toughness and wear resistance.

(Example)

Hereinafter, a method of manufacturing crystallized glass according to the present invention will be described in detail with reference to Examples. However, the present invention is not limited to the following examples.

A. Composition of incineration ash

The results of analyzing the incineration ash by XRF are shown in Table 1. The composition is assumed to be an oxide.

Chemical composition of urban incineration ash (% by weight) Furtherance K1 Y1 N1 Na ₂ O 3.06 4.91 13.07 MgO 2.08 1.47 2.61 Al ₂ O ₃ 1.54 0.76 3.20 SiO ₂ 3.15 1.82 7.31 P ₂ O ₅ 0.69 0.29 1.72 K ₂ O 4.61 4.86 11.21 CaO 52.17 54.79 19.51 TiO ₂ 1.21 0.66 2.78 Fe ₂ O ₃ 2.56 0.69 1.39 ZnO 1.16 1.06 3.02 SO ₃ 3.32 4.67 9.76 Cl 23.23 23.17 21.99 T _l (melting point) 1400 ℃ or more 1400 ℃ or more 1350 ℃ Molten state Bad Bad Good (glass)

In Table 1, K1 and Y1 are obtained by using a large amount of Ca (OH) ₂ during the incineration ash treatment in an incinerator, and the amount of CaO is about two times higher than that of N1. In addition, K1 and Y1 showed an unstable range of glass formation because the amount of SiO ₂ was relatively small compared to N1. Therefore, incinerators with high CaO and low SiO ₂ composition were difficult to dissolve at low temperatures under the conditions of 1400 ° C. or lower using an electric furnace. Therefore, in order to apply the present invention, it is necessary to consider the limitations of CaO and SiO ₂ .

B. Incineration Material Pretreatment and Glass Composition

The incineration ash components before and after washing with respect to the composition of N1 in the incineration ashes of Table 1 were compared in Table 2 below. As a result, it was found that the incineration ashes pretreated with water were removed without a calcination process.

Comparison of composition of incineration ash and glass before and after washing (assuming oxide) (wt%) ingredient Before washing After washing Incineration ash Molten Incinerator Glass Incineration ash Molten Incinerator Glass Na ₂ O 13.1 2.2 2.1 2.0 MgO 2.6 7.2 8.2 6.8 Al ₂ O ₃ 3.2 11.0 9.5 13.1 SiO ₂ 7.3 23.4 21.7 25.8 P ₂ O ₅ 1.7 4.3 5.7 5.3 SO ₃ 9.8 0.1 11.9 0.1 Cl 22.0 0.1 0.8 0.1 K ₂ O 11.2 0.3 0.8 0.3 CaO 19.5 36.1 25.9 33.0 TiO ₂ 2.8 6.5 3.8 5.7 MnO 0.2 0.7 0.5 0.5 Fe ₂ O ₃ 1.4 3.4 2.1 2.8 ZnO 3.0 3.6 4.7 3.6 PbO 0.9 0.1 1.1 0.2 BaO 0.6 0.4 0.5 0.3 Total 100 99.4 99.3 99.6

The incineration ash was analyzed by thermal analyzer, and the incineration ash before washing had a melting point of about 1350 ℃ and the incineration ash after washing was about 1263 ℃. As shown in Table 2, the introduction of the water washing method changed the composition of the incineration ash into a vitrifiable composition, and also changed the melting point of the incineration ash.

As described above, in the present invention, the incineration material obtained through the washing method was made of glass at a low temperature, and then crystal growth was induced through heat treatment. The produced glass can be used for other purposes, but is brittle, and thus, in the present invention, the main purpose is to produce crystallized glass by inducing crystallized glass in order to improve hardness, strength, toughness, wear resistance, and the like.

C. Molten Glass Fabrication

The first step is to remove the chlorine content contained in the incineration ash to make the ash ash glass and dilute the ash in 1: 3 with distilled water to wash for 48 hours to reduce the melting temperature. Dry for 24 hours.

In the second step, the above-described raw powder was melted in an electric furnace using a platinum crucible. At this time, the temperature increase rate was maintained for 3 hours to sufficiently melt up to 1400 ℃ at 10 ℃ / min to obtain a molten glass. The glass thus obtained was measured for heat treatment temperature using a thermal analyzer. At this time, it heated up to 1400 degreeC at the temperature increase rate of 10 degreeC / min. The measured heat treatment temperature, that is, the glass transition temperature (T _g ), the maximum exothermic start temperature (T _o ), the maximum exothermic temperature (T _p ), the melting temperature (T _l ) is shown in Table 3.

Thermal Characteristics and Crystallization State of Molten Incinerator Glass After Washing sample T _g (℃) T _o (℃) T _p (℃) T _l (℃) Crystallization Molten incinerator glass after washing 700 885 895 1263 Internal crystallization

In the third step, the glass obtained after melting is heat-treated for 20 to 240 minutes near the maximum exothermic onset temperature for crystallization treatment, and it is examined whether the crystallization state after the heat treatment for each specimen is internal or surface crystallization. Indicated.

In a fourth step, the crystallized glass obtained by the above was analyzed by the powder X-ray diffraction method. At this time, after using the agate induction to make a powder for each specimen was measured in the range of (2θ) 10 ~ 70 ° using a Cu target.

In a fifth step, in order to observe the crystal phase of the crystallized glass, it is corroded in an aqueous 2% hydrofluoric acid (HF) solution, and further treated in an aqueous 15% hydrochloric acid (HCl) solution and washed with water using a scanning electron microscope (SEM). Microstructure was observed to observe the surface and internal crystallization state. (See Table 3 results)

D. Heat Treatment for Manufacturing Crystallized Glass

Referring to Table 3, the crystallization state after the heat treatment was prepared as a test piece for tiles using molten incinerator glass showing internal crystallization as follows.

The incineration ash was mixed with distilled water 1: 3, washed with water for 48 hours, dried in an electric oven at 100 ° C for 24 hours, and then melted for 3 hours at 1400 ° C using a platinum crucible and preheated at a maximum heating temperature near the graphite mold. Was injected into the furnace and cooled in a furnace to obtain crystallized glass.

Figure 1 shows the heat treatment temperature of the crystallized glass according to the heat treatment time to be divided into three stages of melting, crystallization treatment, thermal stress removal. In this case, in order to manufacture the crystallized glass, heat treatment was performed at 800, 850, 900, and 950 1000 ° C. for 20, 60, and 240 minutes, respectively, based on the maximum heating start temperature (T _o ) of the glass.

As a result of investigating the crystal phase analysis using the X-ray diffractometer, the heat-treated specimens were rhoenite ((Mg ₄ Ti ₂ ) Ca ₂ (Al ₄ Si). ₂ O ₂₀ )) appeared to be columnar, and as the heat treatment time became longer, the crystallinity increased as the low-enite formed crystal growth. Also, when heat treatment was performed for 4 hours at each temperature, lozenite was shown as the main phase as the initial crystal phase, but as the heat treatment temperature was increased, pyroxene was shown as the main phase at 900 ° C.

In addition, the test piece was prepared in 30 × 30mm ² and then heat-treated at 800, 850, 900, 950, and 1000 ° C. for 20, 60, and 240 minutes, using a Vickers hardness tester (load: 0.3 kg), Fracture toughness was measured, and the wear resistance evaluation was carried out using a drop type wear tester according to KS F 2182. The test specimen for abrasion test was made in square shape, and then the weight of the test specimen was inclined at an angle of 45 ° to the horizontal plane. At a height of 1100 mm, the particle size 20 of the silicon carbide abrasive C specified in KS L 6508 was dropped by 10 kg. , The powder attached to the test body was removed well, and the weight of the test body was measured to reduce the weight as abrasion loss. The weight was measured to 0.01 g.

In order to measure the elastic modulus of the crystallized glass, the size of the specimen was 10 × 10 × 5 mm. The roughness of the end face of the specimen was 3.2S or less specified in KS B 0161, and the parallelism of the end face was The longitudinal wave vibrator and the shear wave vibrator were fixed to the test piece with an adhesive at 0.02 mm or less, and the longitudinal wave velocity ( V _l ) and the transverse wave velocity ( V _t ) were measured and calculated from the pulse propagation velocity.

In addition, the mechanical properties of the glass and the crystallized glass evaluated in this way were Vickers Hardness of about 6.3 GPa, fracture toughness of 0.84 MPa m ^1/2 (K _1C ), 10.6 (× 10 ^-3 g / The wear rate of cm ² ) and the modulus of elasticity of 105 GP are shown, but the crystallized glass heat-treated at 900 ° C. for 20 minutes in the crystallization state after heat treatment has a hardness of 8.23 GPa and fracture toughness of 1.71 MPa m ^1/2 , 2.12 A wear rate of (× 10 ⁻³ g / cm ² ) and an elastic modulus of 142 GPa were shown. The results of hardness, fracture toughness and wear rate of the crystallized glass according to the heat treatment conditions are shown in Table 4 below.

As can be seen from Table 4, the crystallization degree was less than 850 ° C. below the maximum heat generation starting temperature (T _o ) of the heat treatment conditions, so that there was a large amount of residual glass in the material. The over-crystallization treatment was performed at such a temperature that mechanical properties were undesirable. In addition, in terms of heat treatment time, as the heat treatment time became longer than 240 minutes, the appearance of excessive crystal phases caused micropores inside the high crystallinity, resulting in a decrease in hardness and strength.

On the other hand, in order to measure the coefficient of thermal expansion (glass coefficient of thermal expansion) of the glass and crystallized glass in terms of thermal characteristics evaluation, after the test piece is manufactured to 5 × 5 × 10mm, the temperature increase rate is 5 ℃ / min to raise the room temperature to 800 ℃ Was measured. The coefficient of linear expansion was in the range of about 10.5 to 11.5 × 10 ^-6 / K, which was larger than 9.8 × 10 ^-6 / K of glass and decreased with increasing heat treatment time at high temperatures (900, 950 ℃). In addition, the coefficient of linear expansion of the crystallized glass after heat treatment with the glass was measured and shown in Table 4 below.

The color of the crystallized glass was changed according to the heat treatment temperature. The color of the crystallized glass surface with temperature and time is described in Table 5. This color change is regarded as the effect of the oxidation number change of metal ions by oxidation reaction at high temperature by Fe ₂ O ₃ and TiO ₂ contained in the constituents of the incineration ash.

Comparison of Properties by Heat Treatment Conditions (Temperature and Time) Sample No. Heat treatment temperature (℃) Heat treatment time (min) Vickers Hardness (GPa) Wear rate (10 ^-4 g / cm ² ) Coefficient of linear expansion (10 ^-6 / K) Modulus of elasticity (GPa) K _{1C (MPam} ^1/2 ₎ One Glass 0 6.27 10.48 9.86 104 0.84 2 800 240 6.3 5.28 9.91 110 0.97 3 850 20 7.47 2.95 10.4 139 1.36 4 60 8.13 2.24 11.4 145 1.42 5 240 8.03 2.35 10.7 147 1.27 6 900 20 8.23 2.12 11.5 142 1.71 7 60 7.76 4.14 11.3 143 1.64 8 240 7.44 4.42 11.1 126 1.50 9 950 20 8.07 2.40 11.4 146 1.39 10 60 7.64 4.35 10.8 - - 11 240 6.81 4.76 10.7 - - 12 1000 60 6.65 4.94 10.1 - -

Color of Crystallized Glass Surface According to Heat Treatment Condition Change of time Glass Crystallized Glass Treatment Temperature (℃) 800 850 900 950 1000 in 1 hour black Dark brown Dark brown purple Mauve Taupe More than 1 hour - Dark brown partridge partridge Taupe -

As described above, in the present invention, municipal incineration ash, which is a large amount of environmental pollutants generated in Korea, is removed by inexpensive method to remove chlorine gas, which is a secondary pollutant that may be generated during melting by the washing method, and without addition of a crystallization agent. By heat treatment at low temperature for a short time, it was possible to efficiently recycle resources by manufacturing with construction materials with high hardness, high toughness, high wear resistance and thermal characteristics.

In the above, the present invention has been illustrated and described with reference to specific preferred embodiments, but the present invention is not limited to the above-described embodiments, and the present invention is not limited to the spirit of the present invention. Various changes and modifications can be made by those who have

Claims (4)

Washing the incineration ash to lower the content of chlorine in the municipal incineration ash, High temperature utilizing urban incineration ash, characterized in that consisting of the step of obtaining a crystallized glass by heating the glass obtained after melting the washed incinerator for 20 to 240 minutes at a temperature in the range of 850 to 950 ℃ without adding an additional additive Also, a method for producing crystallized glass having high toughness and wear resistance. delete The composition of the incineration ash according to claim 1, wherein the composition of the incineration ash is lowered in viscosity of the molten glass and improved in chemical resistance, such as SiO ₂ , which forms a skeleton of the glass during melting of the incineration ash, and the chemical durability of Al ₂ O ₃ . A method for producing crystallized glass having high hardness, high toughness, and abrasion resistance using an urban incineration material, which contains CaO and MgO as a main component, and further contains a crystallizing agent capable of inducing crystallization after glass production. In order to remove the chlorine components present in the municipal incineration ash and to lower the melting point of the incineration ash, washing the incineration ash and then drying to obtain the vitrification material which can be vitrified; The incineration ash thus obtained is first heated at 1400 ° C. for 3 hours without additional additives, A method for producing crystallized glass having high hardness, high toughness and wear resistance, comprising: obtaining crystallized glass through secondary heat treatment for 20 to 240 minutes near a maximum exothermic temperature.