JP2000051645A - Method for treating exhaust gas and fly ash - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a method which can simply materialize the removal of acidic gas and dioxins generated in urban refuse incineration facilities and others and the prevention of the elution of heavy metals from recovered fly ash and of the scattering of treated materials. SOLUTION: A treating agent obtained by incorporating hydrated lime, magnesium oxide, a porous inorganic oxide, amorphous aluminum hydroxide, and active carbon or active coke in accordance with purposes is charged into the flue of an incinerator, recovered fly ash is added with a magnesium chloride aqueous solution, and the mixture is mixed or kneaded. By the addition of a chemical agent and the magnesium chloride aqueous solution, acidic gas and dioxins in exhaust gas are removed, the elution of heavy metals from fly ash is prevented, and the solidification strength of the kneaded substances is improved to prevent the scattering of the substances.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an incinerator used for treating an exhaust gas containing an acidic gas, harmful organic substances such as dioxins, and harmful heavy metals discharged from an exhaust gas treatment facility of an incineration facility for municipal waste. The present invention relates to a method for treating exhaust gas and fly ash using a flue blowing agent.

[0002]

2. Description of the Related Art In recent years, environmental pollution by dioxins has been regarded as a problem. This is compared to other pollutants,
This is because the toxicity of dioxins is extremely high. For example, the LD50 of 2,3,7,8-dioxin, which is said to be the most toxic, in guinea pigs is 2 μm / kg.
Furthermore, dioxins have very strong acute toxicity and have been confirmed to be powerful carcinogens and teratogenic substances. For example, in the case of 2,3,7,8-dioxin, 0.01 to 0.07 μm / kg / d
There is a report that a small amount of ay is carcinogenic. In addition, it has been confirmed that administration of 1 to 10 µm / kg of 2,3,7,8-dioxin to the mother of a pregnant rat causes malformation, and is a unique teratogen. It turns out that there is.

[0003] Sources of dioxins include industrial processes such as municipal solid waste incineration facilities, steel mills, and metal refining industries.
Automobile exhaust gas, chlorine bleaching process in the pulp and paper industry,
Manufacturing process of chemical products such as pesticides. However, in Japan, it is said that most waste is generated from municipal solid waste incineration facilities. In Japan, most of the general refuse is landfilled after being incinerated because of its small land area and extremely high waste generation. For this reason, the amount of dioxin generated in Japan is high.

[0004] In Japan, about 48 million tons (1988)
Municipal waste and about 310 million tons (1985) of industrial waste. In the year 2000, municipal waste is expected to reach about 80 million tons and industrial waste to reach about 600 million tons. About 70% of general waste is incinerated, and about 30% is disposed of directly. About 40% of industrial waste is recycled, about 30% is incinerated, and about 30% is disposed of directly. It has been clarified that a large amount of dioxin is generated during these incineration treatments, and emission regulations for these substances will be greatly strengthened in the future.

[0005] In the case of municipal solid waste treatment, various organic substances and chlorides such as plastic, garbage, and wood are contained in the garbage. When these wastes are incinerated, some of the organic matter is not completely decomposed to carbon dioxide, and the unburned organic matter is discharged to an exhaust gas treatment facility, and becomes a precursor of dioxins.
On the other hand, it is said that chlorine in chloride becomes a gaseous component such as chlorine or hydrogen chloride and reacts with the precursor through a complicated reaction route to form dioxins. Further, it is said that metal salts such as copper chloride contained in fly ash blown up into the exhaust gas treatment facility serve as a catalyst to further promote the generation of dioxins. Generally, it is considered that unburned organic matter is converted into a precursor in an incinerator, and dioxins are synthesized in a low-temperature region such as a boiler or a dust collector.

Research on dioxin countermeasures has only just begun, and the technology has not yet been established. However, countermeasures in incineration facilities currently considered are classified into the following five. That is, A) removal of the causative substances in the refuse, B) suppression of generation under combustion conditions, C) suppression of generation during heat recovery and cooling, D) suppression and removal of generation during exhaust gas treatment, and E) fly ash It is harmless. Of these, in recent years, D)
The suppression of generation and removal during exhaust gas treatment is being actively studied. An important measure in the exhaust gas treatment process is to reduce the temperature of the dust collector. According to the guidelines for preventing the generation of dioxins, the temperature of the dust collector is 250 to 280 ° C in the existing furnace, and 200 ° C or less in the new furnace. It is shown that However, the electric precipitators that have been widely used in existing incinerators cannot reduce the temperature much, and it has been found that dioxins are generated by corona discharge. Dust collector is installed. Recent technologies include oxidation of dioxins by introducing an oxidizing agent or an oxidation catalyst into an exhaust gas treatment process, and furthermore, H ₂ S, NH
_3. Injection of an agent that suppresses the catalytic activity of fly ash, such as triethanolamine, in the exhaust gas treatment process is also being studied.

[0007] In addition to the problem of dioxins, the problem of heavy metals has become a major environmental problem. Cadmium (Cd), lead (Pb), chromium (Cr), and mercury (H) include color-printed paper and cellophane contained in the garbage.
g), arsenic (As), copper (Cu), etc., and plastics include cadmium, lead, zinc (Zn), chromium, mercury, arsenic, etc., and heavy metals are concentrated by incineration. The resulting ash is obtained. At refuse incineration plants, this ash is often separated into main ash composed of garbage and fly ash collected by a bag filter or the like.
Although both the main ash and the fly ash contain heavy metals, heavy metals are particularly easy to elute in the fly ash.

That is, in a refuse incineration plant, slaked lime or quick lime is blown in the middle of an exhaust path (flue) to capture hydrogen chloride gas generated during incineration. These react with the hydrogen chloride gas to form calcium chloride, and the concentration of the hydrogen chloride gas in the exhaust gas is reduced. However, since unreacted slaked lime and quick lime remain in the fly ash, the fly ash exhibits a high alkalinity of pH 12 or more. However, lead contained in fly ash at a high concentration has the property of becoming water-soluble as a plumbate in a high alkali region, so that when fly ash is discarded as it is, lead is eluted.

Therefore, in order to prevent such harmful heavy metals from being eluted, municipal solid waste incineration plants include, for example, chelating agents such as dithiocarbamic acid compounds, soluble sulfides such as sodium sulfide and sodium hydrosulfide, and porous sulfides. A heavy metal stabilizing agent such as an inorganic adsorbent is mixed with fly ash, added with water, kneaded, solidified, and then discarded (landfill disposal). However, since facilities such as a storage tank and an addition device for the heavy metal stabilizing agent are required, there are many municipal solid waste incineration plants that do not implement the above stabilization treatment method.

[0010] The fly ash also contains dioxins. Dioxins may be diffused due to scattering of fly ash-treated materials containing dioxins discarded in landfills. Therefore, further improvement of the solidification strength of the processed ash is expected from the viewpoint of preventing the fly ash from scattering. Therefore, at the municipal waste incineration plant,
For example, in addition to a heavy metal stabilizer, cement is added and kneaded to cure and solidify, thereby improving the solidification strength of the treated product. However, there are many municipal solid waste incineration plants where cement solidification cannot be carried out because facilities such as a cement storage tank are required. In addition, since cement is alkaline, elution of lead is not suppressed when added in large amounts,
Secondary pollution may occur.

[0011]

DISCLOSURE OF THE INVENTION The present invention is directed to the removal of acid gases and dioxins generated in such municipal waste incineration facilities, the suppression of elution of heavy metals from recovered fly ash, and the treatment of treated products. An object of the present invention is to provide a method capable of easily improving the solidification strength with one drug.

[0012]

The present invention is obtained by blending slaked lime and magnesium oxide with a porous substance of inorganic oxide, amorphous aluminum hydroxide, and activated carbon or activated coke according to the purpose. The incinerator flue blowing agent is blown into the incinerator flue to remove acid gases and dioxins from the exhaust gas, and to stabilize heavy metals in the fly ash by adding and mixing the recovered fly ash with an aqueous magnesium chloride solution. And a method for improving the solidification strength of the treated product.

[0013]

DESCRIPTION OF THE PREFERRED EMBODIMENTS In the present invention, slaked lime, magnesium oxide, a porous substance of inorganic oxide and / or amorphous aluminum hydroxide are used as incinerator flue blowing agents. The slaked lime used in the present invention is not particularly limited, and those conventionally used for absorbing and neutralizing acidic gas such as hydrogen chloride gas contained in exhaust gas can be used.
The slaked lime used in the present invention is usually in the form of powder, but it is desirable that the surface area is large in order to effectively remove acid gas. Specifically, it is preferably slaked lime having a specific surface area of at least 10 m ² / g measured by the BET method.
More preferably, it is 0 m ² / g or more. Examples of slaked lime having such a specific surface area include slaked lime obtained by adding water to quick lime and digesting it. In particular,
The use of JIS special lime slaked lime (specific surface area of about 15 m ² / g), which is usually used for exhaust gas treatment, is preferable, but JIS No. 1 slaked lime which is inexpensive in cost may be used. Special slaked lime ("Tamacalc" manufactured by Okutama Kogyo Co., Ltd. "Uesuraimu" manufactured by Ueda Lime, "Kalmu" manufactured by Yoshida Lime, Chichibu Lime manufactured by the treatment such as adding alcohol or amines during the digestion reaction) It is more effective to use "Alock", "Hishikoru" made by Ryoko Lime, etc.).

The inorganic oxide porous material of the present invention will be described. The inorganic oxide porous material has a high adsorption capacity, and adsorbs harmful heavy metals such as lead and dioxins. Based on this adsorption action, it is possible to stabilize heavy metals and remove dioxins.

The stabilization mechanism of heavy metals in the present invention will be described. Low-boiling metals such as lead, cadmium and mercury evaporate from the incinerator and are discharged together with the exhaust gas.
Most of the evaporated heavy metal is condensed or adsorbed on the fly ash surface when the fly ash in the exhaust gas is collected by an electric dust collector or a bag filter, and is collected. However, these heavy metals collected in a state of being adsorbed on the fly ash are ionized and dissolved in the water when the fly ash is exposed to water.
Next pollution occurs. The porous substance of the inorganic oxide used in the present invention is characterized in that it is a substance having a hydrophilic property, and thus effectively adsorbs ionized heavy metals. Further, by injecting the porous material of the inorganic oxide used in the present invention into the incinerator flue or by disposing it in the incinerator flue as a filter, it is possible to effectively collect the heavy metal vapor in the exhaust gas. it can.

The dioxin removal mechanism in the present invention will be described. The generation of dioxins in incineration equipment is organic chloride generated by reacting unburned organic substances with chlorine gas or hydrogen chloride gas. These dioxins are very hydrophobic substances, and are known to be adsorbed by hydrophobic substances such as carbon and activated carbon.
The porous substance of the inorganic oxide used in the present invention is inferior in the performance of adsorbing dioxins to activated carbon, but is less expensive (1/10 to 1/5) than activated carbon, and is used in a large amount. Therefore, the emission concentration of dioxins can be further reduced by using it alone or in combination with activated carbon.

The porous substance of the inorganic oxide of the present invention is a hydrophilic substance other than activated carbon, such as silicate or aluminum silicate. Further, the ability to adsorb dioxins and heavy metals depends on the specific surface area of the porous substance of the inorganic oxide, and the larger the specific surface area, the higher the ability to adsorb dioxins and heavy metals. Usually, a porous substance of an inorganic adsorbent having a specific surface area of 50 m ² / g or more is used for effectively adsorbing dioxins and heavy metals.
Those having a specific surface area of at least 100 m ² / g measured by the T method are preferred. However, if the specific surface area is too large,
Since the average pore diameter becomes too small and the inside of the pores is filled with water molecules when water is kneaded, the heavy metal cannot diffuse into the inside. Therefore, there is an optimum upper limit for the specific surface area of the inorganic oxide porous material, and it is preferable that the specific surface area be 800 m ² / g or less.

The inorganic porous material used in the present invention may be either a synthetic porous inorganic oxide or a natural porous inorganic oxide. Examples of the synthetic substance include synthetic silicic acid, synthetic aluminum silicate, synthetic magnesium silicate, synthetic aluminum hydroxide, and synthetic zeolite. Examples of natural substances include activated clay, acid clay, allophane, bentonite, diatomaceous earth, natural zeolite, and the like.Also, by treating these substances with acids, impurities such as aluminum and magnesium were removed, and the specific surface area was further increased. Substances and the like are preferred.

It is desirable that the inorganic oxide porous material used in the present invention be blended in a large amount since heavy metals are sufficiently adsorbed when the amount thereof is increased. However, if the mixing ratio of slaked lime is too small, the efficiency of removing the acidic gas decreases, which is not preferable. Therefore, the compounding amount of the inorganic oxide porous material of the present invention is preferably 10 parts by weight or more and 200 parts by weight or less, and more preferably 20 parts by weight or more and 100 parts by weight or less with respect to 100 parts by weight of slaked lime. More preferred.

The amorphous aluminum hydroxide of the present invention will be described. Normally, incinerators blow a large amount of powdered slaked lime into a flue to neutralize acid gas. However, since a saturated aqueous solution of slaked lime shows high alkalinity of pH 12 or more, if unreacted slaked lime remains in fly ash, when fly ash is dispersed in water, it becomes alkaline of pH 12 or more. In such a high alkali region, amphoteric metals such as lead dissolve, and the amount of lead eluted from fly ash increases. Therefore, in order to prevent the elution of heavy metals, it is desirable that the pH of fly ash be lower than the pH of slaked lime. Therefore, in the present invention, the pH of the saturated aqueous solution is 1
The pH of fly ash is reduced by adding powdery amorphous aluminum hydroxide of 1.5 or less. By adding such amorphous aluminum hydroxide, the amount of slaked lime can be reduced and the pH of fly ash can be reduced. Furthermore, the larger the specific surface area of the amorphous aluminum hydroxide, the higher the reactivity with the acidic gas. Therefore, the specific surface area measured by the BET method is preferably 15 m ² / g or more, more preferably 30 m ² / g or more. It is more preferred that there be.

The amorphous aluminum hydroxide used in the present invention can be obtained in various forms, but the one obtained by drying and pulverizing the sludge waste of the amorphous aluminum hydroxide generated in the alumite treatment step is obtained. Since there is no other utilization method industrially and it is originally discarded, it is preferable because it is cost-effective.

The amount of the amorphous aluminum hydroxide of the present invention will be described. When the amount of the amorphous aluminum hydroxide used in the present invention is increased, the pH of fly ash tends to decrease, so that it is preferable to mix a large amount from the viewpoint of neutralization. However, if the amount of slaked lime is too small, the efficiency of removing acidic gas may be reduced. Therefore, the amount of the amorphous aluminum hydroxide of the present invention is preferably 10 parts by weight or more and 200 parts by weight or less, more preferably 20 parts by weight or more and 100 parts by weight or less with respect to 100 parts by weight of slaked lime. preferable.

The effect of using a porous inorganic oxide material and amorphous aluminum hydroxide together will be described. Fly ash pH
The amount of lead eluted greatly increases or decreases due to fluctuations in the amount of lead. However, depending on the variation in fly ash properties, the fly ash pH when aluminum hydroxide is added cannot always be reduced as intended, and there is a risk that lead elution from the fly ash cannot be completely suppressed. Therefore, by using an inorganic oxide porous substance that is a lead adsorbent that does not depend only on the pH adjustment function,
That danger can be avoided. Although the reason is not clear, it has been confirmed that by using both of them, the solidification strength of the treated product is improved.

The magnesium oxide and magnesium chloride used in the present invention will be described. Normally, fly ash collected by a dust collector contains a silica component and a compound derived from calcium hydroxide, so if water is added and kneaded,
The solidification reaction proceeds, and a lump of processed material is obtained. However, the solidification strength typified by the compressive strength of the processed product is not very high. For this reason, the mass is likely to be divided and refined due to physical collision or the like, and the risk of scattering at a landfill site or the like increases. The mechanism for improving the solidification strength of the treated fly ash in the present invention is based on the entanglement of the hydrated double salt 3MgO · MgCl ₂ · 11H ₂ O generated by the reaction between magnesium oxide and magnesium chloride in the treated product. Progresses.

The magnesium oxide and magnesium chloride used in the present invention may be either synthetic or natural products. The amount of magnesium oxide and the amount of magnesium chloride of the present invention will be described. When the amount of magnesium oxide used in the present invention is increased, the formation of a double hydrate salt is promoted. Therefore, it is preferable to add a large amount of magnesium oxide from the viewpoint of improving the solidification strength of the treated product. However, if the amount of slaked lime is too small, the efficiency of removing acidic gas may be reduced. Also,
Insufficient inorganic oxide porous material or amorphous aluminum hydroxide to stabilize heavy metals may reduce the heavy metal stabilizing ability. Therefore, the amount of the magnesium oxide of the present invention is preferably from 10 to 200 parts by weight, more preferably from 20 to 100 parts by weight, per 100 parts by weight of slaked lime.
On the other hand, magnesium chloride is added as a solid in a molar ratio of 1/2 to 1/4 based on the amount of magnesium oxide blown into the fly ash. It is efficient from the viewpoint of. Therefore, the amount of magnesium chloride of the present invention is preferably 60 parts by weight or more and 120 parts by weight or less based on 100 parts by weight of magnesium oxide as a solid content.

Although magnesium chloride is used as an aqueous solution, it is preferable to use a 10 to 35% aqueous solution.
A magnesium chloride aqueous solution can be added to the collected fly ash, and water can be added as needed.

In the present invention, a carbon-based adsorbent may be used to adsorb and remove harmful organic substances such as dioxins. Activated carbon and activated coke are preferred as the carbon-based adsorbent used in the present invention, and activated carbon is particularly desirable because of its high adsorption capacity. Activated carbon is classified into coal-based, coconut-shell-based, and wood-based, depending on the origin of the raw material. Activated carbon activation methods include steam activation and chemical activation. The activated carbon used in the present invention may be of any type, regardless of the raw material and activation method. However, a coal-based material is preferred because a coal-based material generally has a high ignition temperature and ensures safety when it is blown into a flue. Activated coke is a carbon-based adsorbent using coke as a raw material. Unlike activated carbon, activated coke is activated or not activated. Generally, activated coke is inferior in adsorption capacity to activated carbon, but is inexpensive and can be used in the same manner as activated carbon in consideration of economic efficiency. The particle size of the carbon-based adsorbent such as activated carbon and activated coke is preferably 100 μm or less, and more preferably 70 μm or less, in consideration of blowing the agent of the present invention into a flue or mixing with other powders. Is more preferable. In order to adsorb substances having a large molecular weight such as dioxins, a carbon-based adsorbent such as activated carbon or activated coke having a large pore volume is preferable. In particular, pores having a pore diameter in a region of 10 nm or more are effective pores for adsorbing dioxins. FIG. 2 shows an example in which the distribution of the pore volume of activated carbon was measured by the BET method. Generally, there are several peaks in the pore size distribution. Therefore, according to the present invention, it is preferable that the maximum value of the pore volume in a region of 10 nm or more when the pore size distribution of the pore volume is measured is 0.01 cc / g or more. For example, in FIG. It is preferable to use a carbon-based adsorbent such as activated carbon or activated coke shown in 2-4.

The amount of the activated carbon used in the present invention will be described. By increasing the amount of activated carbon used in the present invention, the ability to remove organic pollutants such as dioxins is increased. However, if the amount is too large, it may cause a dust explosion. In addition, if the amount is excessively increased, the blowing amount of the entire medicine increases, which is disadvantageous in terms of cost. Therefore, the amount of the activated carbon is preferably 1 part by weight or more and 20 parts by weight or less based on 100 parts by weight of slaked lime.

The specific surface area and pore volume in the present invention will be described. In the present invention, the specific surface area is B
It was measured by the ET method. The BET method is a method generally used as a method for measuring the specific surface area of a porous substance such as activated carbon, a catalyst alone, and zeolite. In this method, after a gas molecule such as nitrogen is adsorbed on the surface of a substance, the specific surface area is calculated from the amount of desorption of the adsorbed gas molecule by raising the temperature of the sample. Nitrogen, argon, or the like is used as the type of gas molecules to be adsorbed, and nitrogen gas is used in the present invention.

In the BET method, the measured value depends on the pretreatment of the sample.
Use a sample that has been dried at ℃ for 3 hours or more. If the sample is sufficiently dried in this way, the adsorbed molecules such as moisture in the pores are released, and the specific surface area and the pore volume can be accurately measured. The gas molecules to be adsorbed have different desorption temperatures and pressures depending on the size of the adsorbed pores.
For this reason, in the BET method, the pore size distribution of the specific surface area and pore volume corresponding to each pore region can be measured by gradually changing the temperature, pressure, and the like in the measurement system. Such data of the pore diameter distribution of the specific surface area and the pore volume is important information for determining the adsorption performance for a substance having a large molecular weight such as dioxins.

The method for producing the treating agent of the present invention will be described. In preparing the drug of the present invention, it is only necessary to physically mix the raw material powder. Mixing is desirably performed in a dry manner, and care must be taken to reduce the water content in the raw materials. It is desirable to dry before mixing. The pulverization may be carried out after mixing the bulk or coarse-grained raw materials at a predetermined mixing ratio. Further, another heavy metal stabilizer such as a chelating agent or a phosphate or a treating agent for dioxins may be mixed.

The exhaust gas treatment method of the present invention will be described. The most general method of the exhaust gas treatment method of the present invention is a method of blowing a powdered treatment agent into a flue of an exhaust gas treatment step of an incinerator. For example, the treatment agent silo shown in FIG. 1 is filled with the treatment agent, and is blown into the flue using a powder feeder and a pneumatic transporter. Furthermore, fly ash collected after injecting the treating agent of the present invention into the flue, as the treating agent of the present invention has a heavy metal stabilizing ability, so long as an appropriate amount of treating agent is blown, However, elution of heavy metals is prevented.
By adding and kneading the recovered fly ash with water, the heavy metals can be more effectively stabilized.If necessary, other heavy metal stabilizers such as chelating agents and phosphates may be used in combination. Is also effective.

Further, since the treating agent of the present invention has a solidification enhancing ability, the recovered fly ash is kneaded by adding an aqueous solution of magnesium chloride and, if necessary, water, to thereby solidify the treated product. Shows a remarkable increase, and scattering of the processed material is prevented. The solidification strength at that time is a value higher than that of the treated material obtained by adding about 20 parts by weight of ordinary cement as a solidifying agent to the fly ash collected after blowing the flue blowing agent consisting of slaked lime alone and kneading with water. Become.

[0034]

The present invention will be described below with reference to examples.
This does not limit the content of the present invention. (Examples 1-1 to 2-2) The substances described below were blended and mixed at the blending ratios shown in Table 1 to obtain treating agents. As the special slaked lime, “Tamacalc” (specific surface area: 38 m ² / g) manufactured by Okutama Kogyo was used. An industrial grade (manufactured by Ako Kasei) was used as magnesium oxide and magnesium chloride. As the porous substance, a substance obtained by treating acid clay with sulfuric acid and washing and removing impurities such as Al and Mg (SiO ₂ content: 90% by weight or more, specific surface area: 230 m ² / g) ) Was used. As activated carbon,
96% of the sample passed through a 100 μm sieve, and the pore size distribution was as shown in FIG. A powdery material corresponding to No. 3 was used. As the amorphous aluminum hydroxide, a product (specific surface area: 25 m ² / g) obtained by drying and pulverizing the amorphous aluminum hydroxide waste generated by the alumite treatment was used.

Further, as a comparative agent, a treatment agent consisting of only a special name slaked lime (specific surface area: 15 m ² / g), a special slaked lime +
A treating agent consisting of a porous material and amorphous aluminum hydroxide was used.

[0036]

[Table 1]

Using this treating agent, an experiment was performed in the following municipal solid waste incinerator. Type: Stalker method Acid gas treatment method: Dry method (method of blowing slaked lime into the exhaust gas treatment process) Dust collection method: Bag filter method Gas emission: 30,000 Nm ³ / hr Blowing amount: 25 kg / hr in slaked lime conversion Fly ash emission : 50 kg / hr This treatment agent was blown into the flue of the incinerator. The blowing rate was 25 kg / hr. The emission concentration of dioxins at the bag filter outlet and the amount of heavy metal (Pb, Cd, Cr ⁶⁺ ) eluted from fly ash collected by the bag filter were measured (according to the “Environment Agency Notification No. 13” method). The results are shown in Table 2.

[0038]

[Table 2]

As is clear from Table 2, it can be seen that the use of this treating agent significantly reduces the concentration of dioxins discharged from the bag filter outlet. Further, it can be seen that the amount of heavy metal eluted from the collected fly ash is suppressed to the regulated value or less.

In the fly ash collected by the bag filter, 25
Table 3 shows the measurement results of the solidification strength (compression strength) of the treated product obtained by adding and kneading 25 parts of a 25% aqueous magnesium chloride solution and 25 parts of water. The compressive strength is as follows.
The columnar solidified product which was poured into a columnar mold for cement mortar having a size of 10 cm × 10 cm and cured at room temperature for 3 days was subjected to an autograph (manufactured by Hitachi, Ltd.) at a loading speed of 0.2 c.
It is the strength (kgf / cm ² ) obtained by dividing the load at the time of compressing and breaking at m / min by the sectional area. As a comparative example, about 20 parts by weight of a treated material kneaded only with water and a normal cement as a solidifying agent were added to fly ash collected when the comparative agent 1-1 (only the special slaked lime) was blown. The compressive strength of the treated product kneaded with water was measured. The compressive strength of a processed material obtained by kneading the fly ash repaired when blowing Comparative Example 1-2 with only water was measured.

[0041]

[Table 3]

As is evident from Table 3, the compressive strength of the treated product is increased only by adding the aqueous magnesium chloride solution and water to the recovered fly ash and kneading the treated fly ash. . It can be seen that the value exceeds the value of the treated material obtained by adding about 20 parts by weight of ordinary cement as a solidifying agent to the fly ash that has been blown and collected with slaked lime alone and kneaded with water.

[0043]

According to the present invention, the treating agent of the present invention is blown into an incinerator flue to remove acidic gases and dioxins from incineration exhaust gas, and to knead the recovered fly ash by adding an aqueous magnesium chloride solution. By this, heavy metal in fly ash is efficiently stabilized and the amount of elution of heavy metal decreases,
In addition, the solidification strength of the processed material is improved, and scattering of the processed material at the landfill site is prevented.

[Brief description of the drawings]

FIG. 1 is an outline of an exhaust gas treatment process in an incineration plant.

FIG. 2 is a view showing a pore size distribution of activated carbon or activated coke used in the present invention.

Continued on the front page F term (reference) 4D002 AA21 AB01 AC04 BA03 BA13 BA14 CA11 DA05 DA06 DA08 DA11 DA12 DA41 DA47 EA07 GA01 GB08 GB12 4D020 AA08 AA10 BA01 BA02 BA06 BA08 BB01 CA08 CD02

Claims (15)

[Claims] An incinerator flue blowing agent comprising slaked lime, magnesium oxide, a porous substance of inorganic oxide and / or amorphous aluminum hydroxide is blown into the flue gas of the incinerator, and then collected. A method for treating flue gas and fly ash in which fly ash is separated using a duster, and an aqueous magnesium chloride solution is added to the collected fly ash and kneaded. 2. An incinerator flue blowing agent comprising slaked lime, magnesium oxide, a porous substance of inorganic oxide and / or amorphous aluminum hydroxide, is blown into the flue gas of the incinerator, and then collected. A method for treating exhaust gas and fly ash, in which a fly ash containing the blowing agent is separated and collected using a duster, and a heavy metal stabilizer and an aqueous solution of magnesium chloride are added thereto and kneaded. 3. The heavy metal stabilizer comprises a chelating agent, a phosphate, sodium silicate, potassium silicate, an inorganic adsorbent, iron sulfate,
The exhaust gas treatment method according to claim 2, wherein the method is at least one selected from the group consisting of iron chloride, aluminum sulfate, and aluminum chloride. 4. The incinerator flue blowing agent according to claim 1, wherein the porous material of the inorganic oxide contains at least one selected from the group consisting of silicic acid and aluminum silicate. The method for treating exhaust gas and fly ash described in the above. 5. The incinerator flue blowing agent according to claim 1, wherein the porous material of the inorganic oxide contains at least one selected from the group consisting of synthetic silicic acid and synthetic aluminum silicate. 4. The method for treating exhaust gas and fly ash according to 3. 6. The inorganic oxide porous material is a clay mineral such as acid clay, activated clay, kaolin, bentonite, allophane and diatomaceous earth, and a treatment of these clay minerals with an acid to remove impurities such as aluminum and magnesium. The method for treating exhaust gas and fly ash according to any one of claims 1 to 3, wherein the method comprises using an incinerator flue blowing agent containing at least one selected from the group consisting of removed substances. 7. An incinerator flue blowing agent characterized in that the inorganic oxide porous substance has a specific surface area of 100 to 800 m ² / g as measured by the BET method. The method for treating exhaust gas and fly ash according to any one of claims 1 to 3. 8. An incinerator flue blowing agent characterized in that the amorphous aluminum hydroxide is obtained by drying and pulverizing amorphous aluminum hydroxide waste generated in the alumite treatment step. The method for treating exhaust gas and fly ash according to any one of claims 1 to 3. 9. The incinerator flue blowing agent according to claim 1, wherein the amorphous aluminum hydroxide has a specific surface area defined by a BET method of 15 m ² / g or more. 4. The method for treating exhaust gas and fly ash according to 3. 10. An incinerator flue blowing agent to which activated carbon and / or activated coke is added.
4. The method for treating exhaust gas and fly ash according to any one of Items 1 to 3. 11. The activated carbon or activated coke having a particle size of 100
The method for treating exhaust gas and fly ash according to any one of claims 1 to 3, wherein an incinerator flue blowing agent, which is a powder having a particle size of not more than μm, is used. 12. The activated carbon or activated coke has a pore volume distribution of 10 n when measured by a BET method.
0.01cc as the maximum value of the pore volume in the region
The method for treating exhaust gas and fly ash according to any one of claims 1 to 3, wherein an incinerator flue blowing agent is used, which is a powder defined as not less than / g. 13. The incinerator flue blowing agent according to claim 1, wherein the slaked lime is a powder having a specific surface area of at least 30 m ² / g as measured by the BET method. Exhaust gas and fly ash treatment method. 14. A mixture of slaked lime (100 parts by weight) and magnesium oxide (20 to 100 parts by weight), an inorganic oxide porous material and / or amorphous aluminum hydroxide (20 to 100 parts by weight).
Using an incinerator flue blowing agent characterized in that it is added in parts by weight, and magnesium oxide 10 in the incinerator flue blowing agent is used.
The exhaust gas and fly ash treatment method according to claim 1, wherein 60 to 120 parts by weight of magnesium chloride is added to 0 parts by weight. 15. To 100 parts by weight of slaked lime, 20 to 100 parts by weight of magnesium oxide, 20 to 100 parts by weight of a porous substance of inorganic oxide or amorphous aluminum hydroxide, and activated carbon and / or activated coke. Using an incinerator flue blowing agent characterized by adding 1 to 20 parts by weight, and adding 60 to 120 parts by weight of magnesium chloride to 100 parts by weight of magnesium oxide in the incinerator flue blowing agent The exhaust gas treatment method according to claim 1, wherein: