KR101377067B1 - Method for stabilizing heavy metal by encapsulation effect using accelerated carbonation of municipal solid waste incineration bottom ash - Google Patents

Abstract

The present invention provides a heavy metal stabilization method by the carbon dioxide immobilization and encapsulation according to an accelerated carbonation reaction in a state of low moisture content in bottom ash from incineration of municipal sold waste. The heavy metal stabilization method in the present invention comprises the steps of: incinerating municipal solid waste and then generating incineration bottom ash; mixing the incineration bottom ash with water in a solid-liquid ratio(water/bottom ash, dm^3/kg) of 0.3; and performing an accelerated carbonation reaction by injecting 30 vol% carbon dioxide gas at a speed of 0.5-2 L/min at a reaction temperature of 20-40°C for 20-240 min without mixing a reducing agent to the incineration bottom ash mixed with water. Through the method, provided is a technique enabling the recycling of the whole bottom ash by performing the high-speed carbonation of fine powder bottom ash in a particle diameter of 0.15 mm or less which has become a problem in the recycling of the whole bottom ash. The stabilization method for heavy metals in bottom ash from incineration of municipal solid waste according to the present invention, is capable of recycling incineration bottom ash safely by stabilizing heavy meals due to the recovery of CO_2 in incineration bottom ash having separated particle sizes through a carbonation reaction and due to the encapsulation by high-speed carbonation, thereby being an environmentally-friendly method. In addition, the method is capable of stabilizing and recycling incineration bottom ash without using a reducing agent separately. Through the method, provided is a technique enabling the recycling of the whole bottom ash by performing the high-speed carbonation of fine powder bottom ash in a particle diameter of 0.15 mm or less which has become a problem in the recycling of the whole bottom ash. [Reference numerals] (AA) Incinerating municipal sold waste; (BB) Selecting bottom ash from incineration ash; (CC) Separating the particle size of the selected bottom ash; (DD) Mixing water with bottom ash of 0.15 mm or less; (EE) Injecting the mixed bottom ash into a high-speed carbonation reactor; (FF) Injecting carbon dioxide for carbonation reaction

Description

Method for Stabilizing Heavy Metal by encapsulation effect using accelerated carbonation of Municipal solid Waste Incineration Bottom Ash}

The present invention relates to a method for stabilizing heavy metals by immobilizing and encapsulating carbon dioxide according to accelerated carbonation reaction in a low moisture content state of domestic waste incineration bottom ash, and more particularly, to encapsulate a highly alkaline living waste incineration bottom ash through accelerated carbonation reaction. To prevent the fixation of CO ₂ and the elution of harmful heavy metals, in particular chromium (Cr). Through this method, the 0.15mm particle size flooring material is very unstable in the environment, so that the problem of the whole flooring material is improved, and after the separation of the particle size, carbonation treatment of the flooring material having a particle size of 0.15mm or less is made possible. It is about.

As industrial development and economies grow in size, the proper disposal of various wastes, which are inevitably generated, is not limited to regional problems, but is also emerging as a global problem. In general, waste can be classified into household waste generated from each household and domestic waste generated from industrial sites, and the municipal waste has a variety of components and is discharged in large quantities. There is a danger of causing environmental pollution. In particular, wastes such as slag, dust, wastewater treatment sludge, and plated sludge contain various heavy metals. If these materials are left outdoors without stabilization, heavy metals may be eluted from rainwater and pollute the environment. In addition, in the past, the treatment of waste has been mainly dependent on landfill, but the treatment is not perfect and a method of incineration and recycling has been proposed. Incineration of domestic waste has advantages such as waste reduction, sanitation, and energy recovery, and it is economical by recycling incineration. However, incinerated municipal waste is high alkali, which is a large amount of calcium (Ca) oxide, sodium Since alkali metal components such as (Na) and potassium (K) are contained, many problems are generated when recycling as aggregate, and it has become a new environmental problem such as secondary environmental pollution due to re-dissolution of heavy metals. Therefore, the addition of a chemical insolubilizer (chelating agent) that does not elute by stably fixing the heavy metal component has been proposed. As a chemical insolubilizer, a substance having a dithiocarbamate linking group is mainly used. It is not enough to handle it stably. As such, municipal waste incinerators can be largely divided into fly ash and floor ash, and fly ash is designated waste, which cannot be recycled, but floor ash is recycled through pretreatment, which is economically effective. .

As a prior art for stabilizing floorings, Japanese Patent Laid-Open No. 2009-195791 discloses that the amount of environmentally regulated substances from incineration materials including calcium, fluorine, and hexavalent chromium is suppressed to less than the environmental standards of the Soil Pollution Measures Act. The present invention relates to a treatment method using a furnace, including a step of generating an incineration bottom ash, mixing water and an incineration ash, and injecting carbon dioxide gas to neutralize the pH of the incineration bottom ash, granulation, and drying. have. However, the treatment method of the incineration ash has a disadvantage in that the treatment cost is high due to the use of a reducing agent simultaneously with or after carbonization treatment.

In addition, it has been pointed out that the problem of the entire flooring material because the flooring material having a particle diameter of 0.15mm or less is very unstable environmentally.

Therefore, the inventors of the present invention incinerated flooring after incineration of the domestic waste and the step of separating the incineration flooring by particle size and mixing the flooring material of 0.15mm or less separated with water and a certain high-cost ratio and the incineration flooring mixed with the water Recycling problem by stabilizing household waste incineration flooring without mixing and treating reducing agent through stabilization method of domestic waste incineration flooring, comprising the step of carbonizing the carbon dioxide gas at a certain weight% at an optimized injection rate and time. It has been confirmed that the entire flooring material can be recycled by recycling the flooring material having a particle diameter of 0.15 mm or less, and thus, the present invention has been completed.

It is an object of the present invention to provide a method for efficiently fixing CO ₂ gas generated after incineration of domestic waste and efficiently stabilizing harmful heavy metals contained in a fine powder incineration bottom material having a particle diameter of 0.15 mm or less.

In order to achieve the above object, the present invention is to incinerate household waste and then to generate an incineration bottom ash and mixing the incineration bottom ash with water and solid ratio (water / floor ash, dm ³ / kg) 0.3 and the water and Accelerated carbonization at low water content in a municipal waste incineration bottom ash comprising the step of accelerating carbonization reaction of 30 vol% carbon dioxide gas at a rate of 1 L / min for 20 to 240 minutes without mixing and processing a reducing agent in the mixed incinerator. It provides a method for stabilizing heavy metals by immobilization and encapsulation of carbon dioxide according to the reaction, and through this method it is possible to recycle the entire flooring material by high-speed carbonization of fine powder flooring having a particle diameter of 0.15mm or less, which has been a problem for recycling the entire flooring material To provide technology.

The method for stabilizing heavy metals of municipal waste incineration bottoms according to the present invention is to stabilize the heavy metals by recovering CO ₂ and encapsulation by high-speed carbonation in the particle size separated incineration bottoms through a carbonation reaction, thereby safely recycling the incineration bottoms. It is not only a method but also stabilization and recycling of incinerated flooring without the use of a separate reducing agent. Through this method, the fine powder flooring having a particle size of 0.15mm or less, which has been a problem for the recycling of the entire flooring material, can be quickly carbonized. It is to provide a technology that enables recycling.

1 is a flowchart illustrating a method of stabilizing heavy metals through encapsulation through accelerated carbonation according to the present invention.
Figure 2 is a graph showing the XRD pattern of the municipal waste incineration bottom ash according to the particle size.
3 is a graph showing the content ratio of poorly soluble salts and soluble salts in domestic waste incineration bottom ash according to particle size.
Figure 4 is a graph showing the water content and the elution amount of chromium (Cr) of household waste flooring.
Figure 5 shows the XRD graph before and after the accelerated carbonation reaction.
6 is a graph showing the dissolution behavior of chromium in the accelerated carbonation reaction.
FIG. 7 is a graph showing the effect of temperature on the accelerated carbonation reaction rate of municipal waste incineration bottom ash and high CO2 capacity.
8 shows the encapsulation mechanism by accelerated carbonation.
9 is a graph showing the results of the encapsulation effect on the dissolved amount of chromium.
10 is a view of an accelerated carbonation reactor for obtaining the encapsulation effect.

Unless defined otherwise, 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 invention belongs. In general, the nomenclature used herein and the experimental methods described below are well known and commonly used in the art.

The heavy metal stabilization method of the municipal waste incineration flooring according to the present invention is solid-liquid 0.6mm or less, preferably 0.15mm or less separated from the step of generating the incineration flooring and incineration of the incineration flooring after burning the municipal waste Mixing (water / solid: dm3 / kg) at 0.1 to 1, preferably 0.3, and 15 to 40% by volume of carbon dioxide, preferably 30, without including a separate reducing agent in the incineration bottom ash mixed with water. It is characterized in that it comprises the step of accelerated carbonation reaction for 20% to 240 minutes at a rate of 0.5 ~ 2L / min, preferably 1L / min, by volume% gas. The condition range refers to a range in which the accelerated carbonation reaction is possible, the preferred condition refers to the optimum accelerated carbonation reaction conditions, and the critical meaning of each condition is based on the description of each component below.

In the present invention, the household waste refers to food waste, household goods and other wastes prescribed by the Ministry of Health and Social Affairs, which are generated in urban life.

Ash incinerated at incinerators can be roughly divided into fly ash and bottom ash. Fly ash discharged by scattering to the top of the incinerator has a high content of dioxins and is landfilled in designated waste landfills, while the bottom ash has a merit that the content of dioxins and the amount of heavy metal leaching are lower than those of fly ash. Therefore, in the present invention, the incineration flooring is intended.

Hereinafter, the present invention will be described in detail with reference to the drawings.

1 is a sequential diagram illustrating a method of stabilizing heavy metals through the fixing and encapsulation effect of CO ₂ through accelerated carbonation according to the present invention. As shown in Figure 1, the present invention incineration of household waste, select the bottom ash of the incineration ash, particle size separation of the selected bottom ash, 0.15 mm or less of flooring material and water mixing, mixed flooring material is injected into the high-speed carbonation reactor, As a procedure of carbonation reaction by injecting carbon dioxide, heavy metal stabilization method by immobilization and encapsulation of carbon dioxide by accelerated carbonation reaction at low moisture content is performed in municipal waste incineration bottom ash.

The present invention is characterized in that the incineration ash is divided into fly ash and incineration ash at a consistent point, and after the particle size is separated for the floor ash to select a flooring material of less than 0.15mm.

Figure 2 is a graph showing the XRD pattern of household waste flooring according to the particle size. In the drawings teulring ZUID by Friedel 1897 _{nyeon: (ettringite: Ca 6 Al 2} (SO 4) 3 (OH) 12 · 26H 2 O), dihydro Kalou mite (hydrocalumite: Ca6Al2 (OH) 12Cl · 7 H 2 O The first common names of friedel's salts are hydrocalumite) and XRD peaks of portlandite (Ca (OH) ₂ ). The material showing the XRD peak is a main material that easily reacts with CO ₂ and is involved in high-speed carbonization of the flooring material. As shown in FIG. 2, the smaller the particle size, the more numerous these materials are present.

3 is a graph showing the total capacity of chlorine and the content of poorly soluble salts and soluble salts in the household waste floor according to the particle size. On the other hand, Figure 3 shows the amount of Friedel's salt (Friedel's salt) according to the particle size. Friedel's salt is a poorly soluble salt that is insoluble in water. As shown in FIG. 3, it can be seen that the content of total chloride (the sum of poorly soluble chloride and soluble chloride) increases at a small particle size, and the ratio of poorly soluble chloride also increases.

Figure 4 is a graph showing the total content and elution of chromium (Cr) of household waste flooring according to the particle size. The water content is not strongly related to the size of the particle size, but it can be seen that the amount of elution increases as the particle size decreases.

Floor materials with a particle size of 0.15mm or less are unstable chemically, which is an obstacle to floor recycling, and is likely to cause heavy metal contamination. Therefore, the flooring can be recycled by stabilizing the flooring having a particle size of 0.15 mm or less.

Combining Figure 3 and Figure 4, the flooring material having a particle size of 0.6mm or less of the incineration flooring material may be the accelerated carbonation incineration flooring material of the present invention.

In the present invention, the incineration ash is characterized in that the mixture of water and solids ratio (water / solid: dm 3 / kg) 0.1 to 1, preferably 0.3. Mixing water and incineration affects the formation of portlandite in the incineration, as in the following equation.

(1) CaO + H ₂ O-> Ca (OH) ₂

The mixing of water and incineration (water cooling process) also affects the production of etlingite and hydrocalumite. The morphology and properties of ettlingite produced under various pH conditions are described in D. Damidot and FP Glasser: Cement Concrete Res. 22 (1992) 1179-1191 and D. Damidot and FP Glasser: Cement Concrete Res. 23 (1992) 1195-1204 and RB Perkins and CD Palmer: Geochim. Cosmochim. Acta. 63 (1999) reported in 1969-1980. As reported in the prior document, the stabilized range of ettringite is at pH 10.5 to 13. In addition, the formation of the ettringite is promoted through monosulfate at a relatively low temperature of 50 ° C. or below, as shown in the following equation.

^{(2) 6Ca 2 + + 2Al} 3 + + 3SO 4 2 - + 38H 2 O → 12H + + Ca 6 Al 2 (SO 4) 3 (OH) 12 · 26H 2 O

Hydrocalumite is produced as shown in Equation (3) under conditions of pH 11.5 or more when the Ca-Al-Cl system is 65 ° C.

^{(3) 2Ca 2 + + Al} 3 + + Cl - + 13H 2 O → 6H + + Ca 6 Al 2 (OH) 12Cl · 7H 2 O

8 shows an encapsulation mechanism.

In the present invention, the moisture content (dm ³ / kg) means a ratio between water and a household waste flooring material having a particle size of 0.15 mm or less as a temporary example. Is made of a thin water layer. When CO ₂ gas is injected, CO ₂ is dissolved in the water layer, and the melted CO ₂ reacts with etlingite, Friedel's salt and Portlandite in the bottom ash. do. As the three substances are decomposed by the carbonation reaction, calcite (CaCO ₃ ), gypsum (CaSO ₄ 2H ₂ O), and an amorphous aluminum compound (Al-compound) are formed in the water layer. The capsule film is formed on the surface of the household waste floor material. That is, the encapsulation effect can be obtained due to the formed amorphous aluminum compound.

9 is a graph showing the results of the encapsulation effect on the elution amount of chromium.

In the present invention, the effect of encapsulation by adjusting the high liquid ratio, that is, the water content of 0.3, shows a significant stabilizing effect compared to the amount of heavy metals eluted at a high water content.

The present invention is characterized in that the incineration ash mixed with water does not include a separate reducing agent, and accelerates carbon dioxide (30%) gas for 20 minutes to 240 minutes at a rate of 1 L / min.

5 is a graph showing the XRD pattern (Pattern) of the domestic waste flooring material before and after the carbonation reaction according to the reaction time. At this time, the reaction temperature is 20 ℃, the solid-liquid ratio (water / solid: dm 3 / kg) is 0.3 and the particle size of the incineration ash is 0.15mm or less. The carbonization reaction occurs in the incubation chamber with 30% carbon dioxide by 15 minutes after the reaction time of ettringite, portlandite and Friedel's salt peaks. Disappears, and the formation of calcite is found to be accelerated.

That is, the peak of calcium hydroxide (Ca (OH) ₂ ), which was the solubility equilibrium in the alkaline solution of the bottom ash, decreased through the carbonation process, in particular, decomposition of hydrocalumite occurred between 30 minutes and 60 minutes. On the other hand, non-existent crystalline gypsum CaSO ₄ was formed after 30 minutes of reaction time and increased with increasing carbonation time.

Figure 6 is a graph showing the elution concentration and pH of Al, Ca, Cl and Cr of household waste floors according to the carbonation reaction time. That is, the data telling the dissolution behavior of Cr. Ettringite present in the flooring has a very high substitution rate with chromium. There is a large amount of chromium in ettringite because it replaces a large amount of chromium when ettringite is produced in the bottom ash. In the graph, the elution of Ca and Al increases in the initial carbonation reaction, indicating that the etlingite is decomposed. As ettringite decomposes, the substituted chromium is released and the elution amount is increased. This results in an increase in the elution of chromium during the weathering treatment. However, the accelerated carbonation in the present invention causes the carbonation reaction rate very fast, so that the amount of chromium elution increases initially but decreases later. Looking at the graph, it can be seen that the elution amount of chromium (Cr) rapidly increases but decreases gradually. This is because the amorphous aluminum compound (Al-compound) generated after decomposition of ettrigite has very high adsorption characteristics, and the adsorption capacity of chromium is also very high, so that the elution amount of heavy metals gradually decreases.

Therefore, the ettringite reacted with CO ₂ until 15 minutes of carbonation is rapidly decomposed and increases the elution amount of chromium. However, the elution amount of chromium decreases after 30 minutes of the fast carbonation reaction. The stabilization of chromium can be thought of in two ways. First, the pH is reduced by the carbonation reaction, so that the solubility is lowered or forms poorly soluble chromium carbonate. Second, the most influential reason is that the amorphous aluminum compound (Al-compound) formed by the carbonation reaction has a high affinity with chromium and thus has a very high adsorption property. In particular, the encapsulation effect makes this effect more effective. Because it can increase.

Figure 7 is a graph showing the effect of temperature on the carbonization reaction rate of domestic waste flooring. In Example 2, specific experimental results are described.

10 is a view of an experimental method of accelerated carbonation for obtaining an encapsulation effect. The incineration bottom ash containing water was spread in the carbonation reactor at the ratio of the thickness (b) and the carbonation reactor diameter (a) at a ratio of 3> b / a> 2, and the carbon dioxide gas having a concentration of 30% was 0.1L / min, and the temperature is adjusted to 20-40 ° C. through a temperature vessel, characterized in that the reaction for a predetermined carbonation reaction time.

Hereinafter, the present invention will be described in more detail with reference to Examples. It is to be understood by those skilled in the art that these embodiments are only for illustrating the present invention and that the scope of the present invention is not construed as being limited by these embodiments.

The elution amount of calcium (Ca), aluminum (Al), and chromium (Cr) was checked according to the particle size of the household waste flooring material. Especially, the content of hydrocalcium calcium (Ca), ecklingite, and portlandite, which are poorly soluble salts, It was confirmed that the particles were also separated. The elution and pH of aluminum (Al), chromium (Cr), and chlorine (Cl) were measured using a flooring material of 0.15 mm or less, the most environmentally problematic and suitable particle size for the carbonation reaction.

The household waste flooring material is immersed in 60% by weight of water recovered from the Gwangmyeong-si area of Korea, and the entire household waste floor material is cooled with moisture, dried at 105 ℃ for 24 hours, and then made of metal components such as iron through magnetic separator. Then, the sieve was separated into particle sizes of 4.75 mm, 2.36 mm, 1.18 mm, 0.6 mm, 0.3 mm, and 0.15 mm, and the results as shown in the following table were obtained.

As shown in Table 1, it can be seen that silicon (Si), calcium (Ca) and aluminum (Al) are rich. Silicon (Si) increases as the particle size of the household waste flooring increases, but calcium (Ca) and aluminum (Al) decrease as the particle size of the household waste flooring increases. That is, it can be confirmed that calcium (Ca) and aluminum (Al), which are involved in carbonation, are distributed at a small particle size.

The municipal waste flooring material was used before and after the high-speed carbonization treatment, the solid waste ratio including the municipal waste flooring is 0.3 dm ³ / kg and the liquid is injected by CO 2 gas to a pH value of 5.8 to 6.3 by carbonation reaction Adjusted to. After the carbonation reaction, the domestic waste floor was filtered from the leachate into a membrane filter having a microstructure of 0.5 μm. The concentration and pH of calcium (Ca), aluminum (Al), chromium (Cr) and chlorine (Cl) in leachate were measured by inductively coupled plasma, atomic emission spectrometry (OPTIMA 5300DV, Perkin Elmer) and ion chromatography (ICS-1500). , Dionex), and pH electrode (SN5135011).

Figure 4 is a graph showing the total content and elution of chromium (Cr) of household waste flooring according to the particle size. The water content is not strongly related to the size of the particle size, but it can be seen that the amount of elution increases as the particle size decreases.

5 is CO ₂ for the municipal waste flooring having a particle size of 0.15 mm or less. Put into incubation chamber and 30% CO ₂ In the atmosphere, samples were taken at different reaction times from 0 to 240 minutes at different reaction temperatures of 20 ° C, 30 ° C and 40 ° C, and the samples taken according to the reaction time were measured to determine the mineral form of the bottom ash. This graph shows the results measured using a ray diffractometer (PW3040 / 00, Philips).

In addition, Figure 7 is CO ₂ in the carbonized household waste flooring Thermal properties were analyzed using thermo gravimetric / differential thermal analysis (TG / DTA, Shimadzu, DTG-60H) before and after carbonation. CO ₂ from the analysis of domestic waste flooring before and after carbonization High dose was estimated. It is also a graph showing the effect of temperature on the carbonization reaction rate of domestic waste flooring. That is, the amount of CO ₂ solidified according to the temperature and reaction time is shown. As shown in FIG. 7, as the temperature increases, the rate of carbonation reaction increases as the temperature increases, and the rate of solidification of CO ₂ increases with increasing temperature at the beginning of the carbonation reaction, but the amount of CO _{2 that} solidifies over time is The most solidification was shown at 20 ° C. This accelerates the surface reaction as the reaction rate increases at higher temperatures, increases the encapsulation effect, and inhibits CO ₂ diffusion into the particles faster because of the rapidly encapsulated surface. Therefore, when the temperature is 20 ℃, the amount of CO ₂ solidified in the household waste floor material of 0.15 mm or less shows a value of 35.4 g / kg after 240 min. This is close to the value of about 38.4 g / kg, the ANC value at 20 ° C. For reference, the ANC value is the maximum amount of municipal waste floor that can capture CO ₂ . In the present invention, ANC is an acid neutralization volume experiment in which the amount of the material reacted with hydrochloric acid is calculated by adding hydrochloric acid until the bottom ash reaches pH 7. The reacted material is defined here as ettringite, Friedel's salt and Portlandite.

The specific parts of the present invention have been described in detail above, and for those skilled in the art, these specific descriptions are merely preferred embodiments, and the scope of the present invention is not limited thereto. Will be obvious. Thus, the substantial scope of the present invention will be defined by the appended claims and their additives.

No explanation of the sign

Claims (4)

A method of stabilizing heavy metals by encapsulating a municipal waste incineration bottom ash in an accelerated carbonation reaction at low water content, comprising:
(a) generating an incineration ash after incineration of domestic waste;
(b) dividing the incineration ash into fly ash and bottom ash, and then separating the particle size from the bottom ash and selecting a floor ash of 0.6 mm or less;
(c) mixing the flooring material having a thickness of 0.6 mm or less at a water / solid ratio of 0.3 dm ³ / kg (water / solid);
(d) The thickness (b) of the bottom ash mixed with water and the diameter (a) of the reactor are expanded in a ratio of 3> b / a> 2 in a high-speed carbonation reactor without including a separate reducing agent in the bottom ash mixed with water. After the carbonation reaction of carbon dioxide gas having a concentration of 15 to 40% by volume at a reaction temperature of 20 to 40 ° C. for 20 to 240 minutes at a rate of 0.5 to 2 L / min.
(e) Ettlingite (ettringite: Ca ₆ Al ₂ (SO ₄ ) ₃ (OH) _{12 ·} 26H ₂ O) contained in the bottom ash in the step (d) carbonation reaction, hydrocalumite: Ca ₆ Al ₂ (OH ) 12Cl _· 7H ₂ O), amorphous aluminum compound (Al-compound) formed by decomposition of portlandite (Ca (OH) ₂ ), gypsum (CaSO ₄ 2H ₂ O) and calsite (calcite: CaCO ₃ ) to form a capsule film on the flooring particle surface.
2. The method of claim 1, wherein the particle size of the flooring material is 0.15 mm or less.
The method of claim 1, wherein the bottom ash comprises heavy metal Cr to stabilize the heavy metal by encapsulating the municipal waste incineration bottom ash by an accelerated carbonation reaction.
The method of claim 1, wherein the incineration ash in step (a) is contained by 60% by weight of water and then dried for 24 hours at a temperature of 105 ℃ by incineration encapsulated living waste incineration bottom ash by accelerated carbonation reaction How to stabilize heavy metals.

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