KR20110091162A - Removal of toxic material in municipal solid waste incineration bottom ash using ultrasonication - Google Patents

Abstract

PURPOSE: A method for eliminating toxic materials from the incineration bottom ash of municipal solid wastes is provided to effectively eliminate dioxins and chlorides from the incineration bottom ash through a mechanical-chemical processing process, a washing process, and a carbonating process. CONSTITUTION: The incineration bottom ash of municipal solid wastes is dried. Granulated blast-furnace slag is added to the dried incineration bottom ash. The incineration bottom ash with the granulated blast-furnace slag is activation-pulverized in order to eliminate dioxins. The incineration bottom ash without the dioxins is stirred with distilled water in which the pH thereof is between 5 and 7 in order to eliminate soluble chlorides. Carbon dioxide gas is injected into the incineration bottom ash without the soluble chlorides in order to carbonate the non-soluble chlorides, and the carbonated non-soluble chlorides are eliminated.

Description

Removal of Toxic Material in Municipal Solid Waste Incineration Bottom Ash Using Ultrasonication

The present invention relates to a method for removing toxic substances from municipal waste incineration flooring, and more particularly, by adding blast furnace slag to incineration flooring of domestic waste, performing mechanical chemical treatment, washing and carbonizing process, and included in the incineration flooring. A method for removing dioxins and chlorides.

In the field of household waste treatment, about 50 incinerators are installed and operated in Korea, and 100 more incinerators are planned to be installed in the future. As a result, the generation of secondary pollutants is another social problem. Among secondary pollutants generated in incinerators during household waste treatment, incinerators are particularly problematic.

In general, incinerators from waste incinerators emit about 10-15% of the waste incineration, and there are two kinds of flooring and fly ash, in which many heavy metals and dioxins are concentrated. 85%) is flooring. The flooring is mainly composed of 30-40% silicon oxide (SiO2), 12-17% calcium oxide (CaO), 6-10% aluminum oxide (Al2O3), 1-5% iron (Fe) and 3-7. % Sodium oxide (Na2O), 2-3% unburned fraction, trace amounts of dioxins, and the like, and in particular, such flooring materials include chromium (Cr), tin (Sn), copper (Cu), lead (Pb), and the like. In addition to containing a large amount of heavy metal oxides, incineration floorings contain about 10 to 20% of the metal components.

Such incineration flooring material is entirely buried without any post-treatment, but there are problems in that dust is generated, and a large amount of dioxins and heavy metals remaining by leaching are dissolved.

On the other hand, in order to solve such a problem, recently, as a method of reducing the volume and removing harmful components, a method of solidifying an incineration bottom material, a melting method, a chemical treatment method, a method of stabilizing by acid and other solvents, etc. are employed. It is becoming.

In addition, there is a problem that the method of solidification, drug treatment or stabilization by acid or other solvent is a stabilization method that does not decompose dioxins.

Among them, the solidification method includes a method of solidifying an incineration bottom material with cement, which increases the volume while solidifying, reducing the waste reduction effect due to incineration, and releasing harmful substances such as dioxins. There are many problems.

In addition, one of the methods for minimizing the volume is to melt the incineration bottom ash in a high temperature furnace to minimize the volume of the incineration ash and to decompose dioxins. This method is expensive in melting facilities and consumes a lot of energy. , Secondary melt dust, and so on.

On the other hand, the characteristics of incineration flooring materials vary depending on the type of waste material, incinerators, and the like. In particular, in the case of a stoker type furnace, 90% of the ash is discharged to the flooring material.

Moreover, since the alkali agent for flue-gas treatment generally becomes about twice the quantity of scattering dust, the generation ratio of a flooring material and a fly ash is about 3-4: 1. In the fluidized bed, about 30-40% of the ash is incinerated bottom ash, about 30% of the remaining fly ash is collected at the bottom of the cooling tower and 70% is collected in the dust collector.

On the other hand, in order to produce pig iron (pig iron) in general, when iron ore, coke, limestone, etc., which are raw materials of molten iron, are put into the blast furnace, iron ore is a by-product during the reduction and melting process, and blast furnace slag is produced.

Blast furnace slag discharged from blast furnace is classified into slow cooling (lumped) slag and quenching (water) slag according to the treatment process.

The generated slag is changed according to the time of pressurized water injection and the regeneration temperature in the regeneration plant. When the regeneration temperature is 1200 ° C or higher and nitrogen in the molten slag is increased, the slag is expanded and has a foam structure. White or yellowish-white softwood slag is produced, and when the rehydration temperature is low, hardwood slag of dark brown particles is produced. Only soft wood slag is produced in Korea. Rapidly cooled blast furnace slag is used as a hydraulic material that is stimulated by alkali and expresses latent hydraulic properties.In particular, as a result of the development of high-molecular-weight products due to the advancement of decomposition and classification techniques, new blast furnace slag is newly developed. It is generated as an application field, and fine powder is widely used because of emulsification as concrete mixed material. In addition, in Korea, a method of manufacturing a friction material using a reinforcement material (published number 1999-0053898) using reinforcement slag, a reinforcing steel reinforcement material using registration reinforcement slag (registered 10-0237331) and a reinforcement slag by the present inventors (publication number 10- 1998-002198). Therefore, the inventors of the present invention have devised the present invention while paying attention to the fact that the potential hydraulic properties of the ash slag are absolutely necessary for incineration ash treatment.

In addition, the flooring material is different depending on the type of incineration waste, but contains 1 to 3% by weight of chlorine components, which makes it difficult to use the flooring material for some recycling purposes. For example, when the flooring material is recycled as a cement raw material, the material of the flooring material should be the same as cement, but the composition of the flooring material is different due to the chlorine contained in the flooring material.

Therefore, it is necessary to remove the chlorine component from the flooring material and to treat it at an appropriate concentration of chlorine ion of 1,000 mg / kg or less. To this end, some treatment companies are using a method of spraying water from the top after depositing the flooring, but the treatment capacity is limited, the efficiency is low, the economy is low, and the environment has problems.

Accordingly, the present inventors have found that when the sludge waste incineration bottom ash is treated by a mechanical chemical method including blast furnace slag and washed with water and carbonated, dioxins and chlorides can be effectively removed, thereby completing the present invention. It became.

An object of the present invention is to provide a method for efficiently removing dioxins and chlorides from the bottom ash of incineration waste.

In order to achieve the above object, the present invention comprises the steps of (a) drying the domestic waste incineration bottom ash; (b) adding blast furnace slag and then activating and grinding to remove dioxins; (c) a washing step of removing the soluble chloride by mixing the incinerated bottom material from which the dioxins have been removed with distilled water of pH 5 to 7; and (d) injecting CO ₂ gas into the washed floor material to carbonate the poorly soluble chloride. It provides a method for removing harmful substances in domestic waste incineration flooring, including the step of igniting.

According to the present invention, it is possible to effectively remove the harmful substances contained in the floor incineration ash of domestic waste, it is possible to smoothly recycle the floor incinerator as a raw material of cement or road substrate.

1 is a process chart showing a process for removing harmful substances in the incineration bottom ash according to the present invention.

The present invention comprises the steps of (a) drying the domestic waste incineration bottom ash; (b) adding blast furnace slag and then activating and grinding to remove dioxins; (c) a washing step of removing the soluble chloride by mixing the incinerated bottom material from which the dioxins have been removed with distilled water of pH 5 to 7; and (d) injecting CO ₂ gas into the washed floor material to carbonate the poorly soluble chloride. The present invention relates to a method for removing toxic substances from municipal waste incineration flooring comprising the step of igniting.

In the present invention, the municipal waste incineration bottom ash of step (a) may be characterized in that the metal is removed, it is preferable to remove the metal using a magnetic separator.

A feature of the present invention is that when crushing household waste incineration bottom ash, the crushing by the mechanochemistry method, chlorine (Cl) ions generated during the crushing by inputting the blast furnace slag which is a by-product of steelmaking which is a material containing CaO It is introduced at the stabilization and grinding stage. In particular, in the case of waste living flooring material, it is recommended to use a vibration mill, a vibration centrifugal mill, or a planetary mill to activate the mechanical chemical method when energizing and activating in the grinding process. It features.

Particularly, in order to make a safe substance by reacting with chlorine which becomes free from harmful compounds and reacts with active chlorine in the treatment of untreated harmful compounds using the above mechanochemical technology, in order to pioneer the effective use method for all substances after detoxification treatment, CaO Ingredients are indispensable. Therefore, the inventors of the present invention considered that it is more efficient to use wood slag among steel slag having the following characteristics from the practical point of view.

In particular, dechlorination reactions in mechanochemical techniques generally require activated calcium (calcium radicals Ca) and activated calcium oxide (CaO) to stabilize active chlorine (chlorine radicals C1) released from the compound. However, quicklime (CaO group) is an amorphous material with strong Ca = O bonds, whereas Ca in the blast furnace slag is -Ca-Si- and -Ca-O-Si The energy to activate by crushing is low, and in -Si-O network, Ca atom exists, so that the wave surface which can be obtained by physical energy is generated, and the active calcium surface is easy to be expressed. Although CaO component is network-linked with SiO2, CaO is not simply absorbing moisture and becoming Ca (OH) 2. Therefore, the CaO component has low heat generation and is easy to transport and store.

In the present invention, the water used in the water washing step is preferably pH 5-7, more preferably using distilled water of pH 5.8 ~ 6.3.

In the present invention, the washing and carbonation treatment were selected as a method for removing chlorides from municipal waste incineration bottom ash.

In order to effectively provide the chloride contained in the municipal waste incineration bottom ash, as shown in FIG. 1, after separating the dry calcined bottom ash by particle size, and then washing with water to remove soluble chloride, poorly soluble chloride is removed. It is characterized by passing through a carbonation process to remove.

In one aspect, the present invention is to heat the municipal waste incineration bottom ash having a water content of about 30-50% to a temperature of 100 ℃ to dry until the decrease in water content is less than 0.1% and using a magnetic separator to remove the iron metal in the floor Particle size separation to remove and classify by particle size using a standard body, distilled water of pH 5.8 ~ 6.3 into the Erlenmeyer flask and the solid-liquid ratio (L / S) to 5 and mixed with the flooring material to be measured and stirred; It is composed of carbonation step by artificially injecting CO ₂ to remove friedel salt which is poorly soluble chloride.

In the present invention, the removal of poorly soluble chloride in the incineration bottom ash through the carbonation process is considered to occur by the following reaction:

_{3CaO · Al 2 O · CaCl ·} 10H 2 O + 3CO 3 2- → 3CaCO 3 + Al 2 O 3 + CaCl 2 + 10H 2 O (1).

Through the washing process according to the present invention, it was possible to effectively remove about 80% of the soluble salts in the form of KCl and NaCl out of the total chloride contained in the bottom incineration ash, the remaining 20% of poorly soluble salt not removed by washing In the case of (Friedel salt), it was confirmed that the final treatment through the carbonation treatment.

Hereinafter, the present invention will be described in more detail with reference to Examples. These examples are intended to illustrate the present invention more specifically, but the scope of the present invention is not limited to these examples.

Example

The municipal waste incineration bottom ash having a water content of about 30-50% was placed in an oven and heated to a temperature of 100 ° C., and dried (about 1 day) until the decrease in water content was less than 0.1%. The dried flooring material was removed by using a magnetic separator to remove the ferrous metals contained in the flooring material.

The reclaimed slag used in this example was used after drying for about 5 hours at 200 ° C. to prevent hydration. These two types of incineration ash samples were collected and mixed according to the following method in order to maintain the uniformity of the sample was used as a complete sample. For sampling, the floor of 0.1m 3 loaded with a crane was divided into four parts, one of them was selected, mixed, and then divided into four parts again, and mixed and divided in the same manner until the sample became about 0.5 l.

Using centrifugal vibration mills used in the mechanical chemistry method, two types of flooring materials obtained from large-scale incinerators were mixed at a ratio of 1: 1 in weight ratio with hand slag, respectively, and the treatment time (1 hour, 2 hours, 4 hours, respectively). , 8 hours, 16 hours, 20 hours) was investigated.

Therefore, the dioxin content of the sample obtained from the dioxin decomposition experiment of the incinerated bottom material treated in this example was investigated, and dioxin / furan (PCDD / F) isotope lime method using GC / MS according to VDI 3499 Sheet 1 Analyzed by. 13C12-2.3.7.8-T4CDD / F of dioxins was used as the internal standard added before the purification process of the sample, and this internal standard was quantified by correcting the loss occurring during the extraction and purification process before GC / MS analysis. Was used. As a result, dioxins remained less than 20% at 2 hours after treatment, and hardly remained at 8 hours.

In order to remove the soluble chlorides from the bottom ash with the iron metal removed, a washing process was performed. In the washing method, 200 mL of distilled water having a pH of 5.8-6.3 was placed in a 500 mL Erlenmeyer flask, and the solid solution ratio (L / S) was set at 5, mixed with the bottom ash (40 g) to be measured, and stirred at 200 rpm for 20 hours. After the stirring sample and the leaching solution were separated from each other using a micro filter, the concentration of K, Na, Ca and Cl for the leaching solution separated from the sample was measured using an X-ray diffractometer.

As a result, 80.1% of chloride was removed after about 30 minutes of washing, and there was no change in removal rate after 30 minutes.

XRD after the washing treatment of the bottom ash with a particle size before and -0.15mm analysis result, the floor before the water washing treatment soluble compound, KCl, NaCl, and I is the peak of the soluble chlorides of Friedel salt _{(3CaO · Al 2 O · CaCl} · 10H 2 O) appear. On the other hand, the XRD of the flushed floor showed no peaks of KCl and NaCl but remained of Friedel salts.

Based on the above results, it was confirmed that the soluble salts were removed but the poorly soluble salts were not removed. The soluble salts were mostly in the form of KCl and NaCl, and the poorly soluble salts were in the form of Friedel salt. there was.

In addition, about 80% of the Cl compounds contained in the incineration bottom ash were soluble chlorides, and about 20% were poorly soluble chlorides.

In order to remove poorly soluble chloride from the soluble salt-free flooring material, the solid-liquid ratio (L / S) of water and incineration flooring material was set to 10, and CO ₂ was artificially blown by using a gas pipe to carry out carbonation. After that, the concentration of chloride was measured using an X-ray diffractometer .

 As a result, it was confirmed that the soluble salts present in the municipal waste incineration bottom ash could be decomposed by carbonation. These results are considered to be caused by the following reaction.

_{3CaO · Al 2 O · CaCl ·} 10H 2 O + 3CO 3 → 3CaCO 3 + Al 2 O 3 + CaCl 2 + 10H 2 O (1)

Having described the specific part of the present invention in detail, it is obvious to those skilled in the art that such a specific description is only a preferred embodiment, thereby not limiting the scope of the present invention. something to do. Thus, the substantial scope of the present invention will be defined by the appended claims and their equivalents.

Claims (2)

How to remove hazardous substances from municipal waste incineration flooring, including the following steps:
(a) drying the domestic waste incineration bottom ash;
(b) adding blast furnace slag and then activating and grinding to remove dioxins;
(c) a washing step of removing the soluble chloride by mixing and stirring the incinerated bottom material from which the dioxin has been removed with distilled water of pH 5-7; and
(d) injecting CO ₂ gas into the washed bottom ash to carbonize the poorly soluble chloride.
The method of claim 1, wherein the waste incineration bottom ash of step (a) is characterized in that the metal is removed.

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