JP2001205047A - Method for treating waste gas and soot dust - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a new treating method which efficiently catches acid gas in waste gases generated in the course of burning waste and stably immobilizes harmful heavy metals in soot dust. SOLUTION: This method is characterized in that (1) a waste gas treating agent, which comprises calcium silicate hydrate fine-grains of 40-100% by weight and calcium hydroxide fine-grains of 0-60% by weight, and of which the specific surface area is not less than 60 m2/g, is brought into contact with the waste gases to be treated, that (2) a dust collector collects the soot dust generated by treating the waste gases, and that (3) the collected soot dust is added with iron salt and is kneaded in the wetting state.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION The present invention relates to an exhaust gas treatment device attached to a waste incineration plant and the like, which is used for treating hydrogen chloride gas (hereinafter abbreviated as "HCl") and sulfur oxides (hereinafter "SOx") contained in the exhaust gas. Abbreviated as ") and a method for treating soot and dust generated during exhaust gas treatment and collected by a dust collector, particularly containing a high concentration of harmful heavy metals such as Pb. Regarding soot and dust, the present invention relates to an effective method for stably immobilizing the heavy metal.

[0002]

2. Description of the Related Art Incineration facilities for general garbage are usually incinerators,
Heat exchanger or water spray for cooling high temperature exhaust gas, HCl
It consists of a slaked lime blowing device (blowing into exhaust gas guide tube) and a dust collector for neutralizing acidic gases such as SOx, nitrogen oxides (hereinafter abbreviated as "NOx"), and removal of harmful components such as dioxins. Devices or devices may be added.

[0003] Dust generated when incinerating waste using such incineration equipment includes dust, reaction products of slaked lime with an acidic gas such as HCl, unreacted slaked lime residue, and Pb. Low boiling compounds containing harmful heavy metals such as
It contains cyanide and the like. At present, when disposing of industrial waste containing these harmful heavy metals, cyanide, etc., mix with cement, add water, knead, cure and solidify to remove harmful heavy metals, cyanide, etc. Methods have been implemented to prevent and stabilize elution. However, the conventional method for treating industrial waste which is simply solidified with cement has various problems, and there is a risk that secondary pollution will occur unless the treatment products are strictly controlled.

For example, soot and dust collected in an incinerator for municipal waste includes lead (Pb), cadmium (Cd), mercury (H
g), harmful heavy metals such as chromium (Cr) and copper (Cu). At present, such dusts are buried by mixing with main ash or solidified with cement, but there is a risk that Pb or the like is eluted even if solidified with cement. In particular, recently, HCl generated during incineration,
Slaked lime or quick lime is blown through the exhaust path to capture acidic gases such as SOx, but these unreacted components remain in the fly ash, so the collected dust will have a high pH of 12 or more. It has become alkaline. In general, among the heavy metals contained in dust, Pb, which is the most problematic, is an amphoteric metal, and it is known that a soluble salt is formed and re-dissolved at pH 11 or higher. If not properly treated, Pb elution causes a major problem.

In the method of landfilling soot and dust, landfilling of untreated soot and dust is legally regulated, and a treatment method in which a chelating agent is added to the soot to prevent the elution of Pb or the like. And iron salts are added. However, in recent years, due to the necessity of reducing dioxin emissions, etc., instead of the conventional incinerator type, a melting furnace type in which waste is heated at a temperature above its melting point and collected as glassy slag has been adopted. In this case, low-boiling heavy metals are volatilized and contained in high concentrations in the exhaust gas generated from the melting furnace,
Soot and dust containing such heavy metals in high concentration, so-called fly ash, is collected in the dust collection path and discharged. When Pb contained in the melting furnace fly ash is chelated, one molecule of the chelate compound corresponds to one atom of Pb atom, so that the fly ash containing a high concentration of heavy metal is chelated. In the treatment, the amount of the chelating agent added becomes enormous, and the chelating agent is expensive, which imposes a heavy burden on the operation cost.

In the treatment method in which an iron salt is added, the iron salt used is inexpensive as compared with the chelating agent. However, if the iron salt contains a large amount of slaked lime or unreacted lime, P
In order to lower the pH to a pH range where the elution of b can be suppressed, a huge amount of addition is required, which is not practical,
As in the case of using a chelating agent, there is a great burden in terms of operating costs.

Therefore, it is extremely difficult to simultaneously efficiently capture acidic gases such as HCl and SOx generated during incineration of waste such as municipal waste and stably fix harmful heavy metals at low cost. That is the current situation.

[0008]

SUMMARY OF THE INVENTION The present invention has been made in view of the state of the prior art as described above, and its main objects are to incinerate industrial waste and municipal garbage, melt furnaces and the like. It is intended to provide a method for treating exhaust gas (hereinafter simply referred to as "exhaust gas") generated at the same time as treating dust and soot generated during exhaust gas treatment. To provide a novel treatment technology that can efficiently capture acidic gases such as HCl and SOx in exhaust gas generated during incineration and stably fix harmful heavy metals in dust and soot during the treatment of furnace fly ash. It is.

[0009]

Means for Solving the Problems The present inventor has made intensive studies in order to achieve the above object. As a result, an exhaust gas treatment agent comprising calcium silicate hydrate fine particles having a specific specific surface area, or an exhaust gas comprising a mixture having a specific specific surface area in which calcium silicate hydrate fine particles and calcium hydroxide fine particles coexist. It has been found that by using the treating agent, it is possible to efficiently collect the acidic gas in the exhaust gas, and at the same time, it is possible to fix the heavy metals in the dust without increasing the generation amount of the dust. The dust generated when the exhaust gas is treated with the exhaust gas treating agent is further added with an iron salt and kneaded in a wet state, so that even dust containing a large amount of heavy metals is harmful. They have found that heavy metals can be more stably immobilized, and have completed the present invention.

That is, the present invention provides the following method for treating exhaust gas and dust. 1. (I) An exhaust gas treating agent comprising 40 to 100% by weight of fine particles of calcium silicate hydrate and 0 to 60% by weight of fine particles of calcium hydroxide and having a specific surface area of 60 m ² / g or more is brought into contact with the exhaust gas to produce an exhaust gas. And (ii) collecting dust and soot generated by the exhaust gas treatment with a dust collector,
i) A method for treating exhaust gas and dust, wherein an iron salt is added to the collected dust and kneaded in a wet state. 2. Item 2. The method for treating exhaust gas and dust according to Item 1, wherein the exhaust gas treating agent comprises 40 to 98% by weight of calcium silicate hydrate fine particles and 2 to 60% by weight of calcium hydroxide fine particles. 3. Item 1 or 2 above, wherein the average particle diameter of the calcium silicate hydrate fine particles contained in the exhaust gas treating agent is 0.1 to 4 μm, and the average particle diameter of calcium hydroxide is 4 μm or less.
2. A method for treating exhaust gas and soot as described in 1. above. 4. An exhaust gas treating agent is a slurry obtained by adding water to a raw material containing a calcium silicate-containing raw material or a raw material containing a calcium silicate-containing raw material and a calcium hydroxide-generating raw material, and performing a hydration reaction under wet grinding. 4. The method for treating exhaust gas and dust according to any one of the above items 1 to 3, which is an exhaust gas treating agent or a powdery exhaust gas treating agent obtained by drying and classifying the slurry exhaust gas treating agent. 5. Ferrous sulfate, ferrous sulfate, ferrous chloride,
Item 5. The method for treating exhaust gas and dust according to any one of Items 1 to 4, which is at least one compound selected from ferric chloride and iron polysulfate. 6. When the amount of the iron salt added is such that the pH of the liquid phase during kneading is 7 to 12
Item 6. The method for treating exhaust gas and soot according to any one of Items 1 to 5 above. 7. 7. The method for treating exhaust gas and dust according to any one of the above items 1 to 6, wherein an iron salt is added to the dust and the mixture is kneaded without heating in a wet state or in a paste-like wet state. 8. Item 8. The method for treating exhaust gas and soot according to any one of Items 1 to 7, wherein the exhaust gas is an exhaust gas generated from an incinerator or a melting furnace.

[0011]

BEST MODE FOR CARRYING OUT THE INVENTION In the treatment method of the present invention, calcium silicate hydrate fine particles 40-10
It is necessary to use an exhaust gas treating agent comprising 0% by weight and 0 to 60% by weight of calcium hydroxide fine particles and having a specific surface area of 60 m ² / g or more.

The fine particles of calcium silicate hydrate contained in the exhaust gas treating agent preferably have an average particle diameter of about 0.1 to 4 μm, more preferably about 0.2 to 3 μm. The average particle diameter of the calcium hydroxide fine particles is preferably 4 μm or less, more preferably about 0.2 to 3 μm. In this specification,
The average particle diameter is a median diameter measured by a laser diffraction / scattering method.

[0013] The exhaust gas treatment agent has a specific surface area of the entire exhaust gas treatment agent composed of calcium silicate hydrate particles with calcium hydroxide fine particles, it must be at 60 m ² / g or more, 70m ² / g or more, and more preferably 100 m ² / g or more. In this specification, the specific surface area is a specific surface area determined by the BET method based on the amount of adsorbed N ₂ gas.

As described above, the exhaust gas treating agent used in the method of the present invention consists of calcium silicate hydrate fine particles alone or a mixture of calcium silicate hydrate fine particles and calcium hydroxide fine particles. Oh, 6
It has a large specific surface area of 0 m ² / g or more. Since the exhaust gas treating agent is fine and has a large specific surface area as described above, the contact area with the exhaust gas is large and the acid gas can be efficiently neutralized and removed. In particular, with respect to calcium silicate hydrate contained in the exhaust gas treating agent, due to its large specific surface area, the effect of capturing harmful metals is large, the elution thereof can be suppressed, and the reactivity with acid gas is less than that of calcium hydroxide. Although a little lower, the specific surface area of itself is large, so that the reaction proceeds to the inside in a short time, and the reactivity with the acidic gas is good.

On the other hand, when the specific surface area of the exhaust gas treating agent is less than 60 m ² / g, both the treating ability for acidic gas and the immobilizing ability for harmful metals are not sufficient, which is not preferable. If the particle size of the calcium hydroxide fine particles is too large, the neutralization performance of the acidic gas is reduced, and particles in an unreacted state remain. If the particle size of the calcium silicate hydrate fine particles and the calcium hydroxide fine particles is too small, there is no problem in performance, but the production cost becomes high and handling becomes difficult, so there is a practical disadvantage. Becomes

The proportion of calcium silicate hydrate fine particles and calcium hydroxide fine particles in the exhaust gas treating agent should be about 40 to 100% by weight of the former and about 0 to 60% by weight of the latter. It is preferable to use about 98% by weight and the latter about 2 to 60% by weight.
More preferably, the content is about 80 to 80% by weight and the latter about 20 to 60% by weight. When the calcium silicate hydrate fine particles and the calcium hydroxide fine particles coexist in the exhaust gas treating agent within such a range of the mixing ratio, that is, when the calcium hydroxide fine particles are contained in an amount of 2% by weight or more,
The acidic gas can be neutralized by both the calcium silicate hydrate fine particles and the calcium hydroxide fine particles, and the acidic gas can be efficiently removed. Also, when the calcium hydroxide fine particles increase, the alkali abundance increases,
The amount of acidic processing gas per unit weight increases. On the other hand, if the amount of calcium silicate hydrate increases, the effect of trapping harmful heavy metals increases. Therefore, the content of the calcium hydroxide fine particles may be selected from the above range according to the acid gas concentration in the exhaust gas and the heavy metal concentration in the discharged dust. That is, when the acid gas concentration in the exhaust gas is high, the ratio of the calcium hydroxide fine particles is increased, while when the heavy metal concentration in the dust is high, the ratio of the calcium silicate hydrate fine particles is increased. I just need.

The exhaust gas treating agent used in the present invention is not particularly limited as long as it satisfies the above-mentioned conditions, and its production method is not particularly limited. Water is added to the raw material including the calcium-containing raw material and the calcium hydroxide generating raw material,
It is preferable to produce by a method of performing a hydration reaction under wet grinding. Hereinafter, this manufacturing method will be described in detail.

As the calcium silicate-containing raw material, various cements, granulated blast furnace slag, fly ash and the like can be used. In these raw materials,
Usually, calcium sulphate, calcium aluminate, ferrite and the like are contained, and these also form hydrates by a hydration reaction in the same manner as calcium silicate, but no problem occurs. As the calcium silicate-containing raw material, Portland cement, its clinker, and the like are particularly advantageous in that an inexpensive and stable quality exhaust gas treating agent can be produced.

As a raw material for producing calcium hydroxide, calcium oxide, calcium hydroxide, dolomite plaster and the like can be used. Dolomite plaster usually contains magnesium compounds such as magnesium hydroxide and magnesium carbonate in addition to calcium compounds, but does not cause any particular problem.

[0020] For example, cements and the like are materials that can themselves be a source of calcium silicate and a source of calcium hydroxide. In this specification, the term "a raw material containing calcium silicate and a raw material for producing calcium hydroxide" is used. This includes the case where a material such as cement, which can itself be a calcium silicate source and a calcium hydroxide source, is used alone.

Further, if necessary, siliceous raw materials can be used as raw materials. The siliceous material, for example, when using cements with a high calcium content as a raw material, increases the production amount of calcium silicate hydrate and acts to reduce the production amount of calcium hydroxide. It is. Specific examples of the siliceous raw material include silica fume and diatomaceous earth.

The mixing ratio of the raw materials, that is, the mixing ratio of the calcium silicate-containing raw material, the calcium hydroxide-forming raw material, and the siliceous raw material is determined by the desired fine particles of calcium silicate hydrate and fine particles of calcium hydroxide in the exhaust gas treating agent. May be determined according to the ratio of.

The amount of water to be added is 100 to 2000 parts by weight based on 100 parts by weight of a raw material component comprising a calcium silicate-containing raw material, a calcium hydroxide-forming raw material, and a siliceous raw material.
It is preferable that the amount be about 100 parts by weight, more preferably about 100 to 1000 parts by weight.

In the wet pulverization and hydration reaction of the raw material, usually, the raw material and water are charged into a pulverizer, and at a temperature of about 40 to 100 ° C. (preferably about 50 to 80 ° C.), a predetermined requirement (average particle diameter, This may be performed until particles satisfying the specific surface area are formed.

In the production of the exhaust gas treating agent, the slurry is formed in a form in which the concentration and the fluidity of the produced solids (calcium silicate hydrate fine particles + calcium hydroxide fine particles) are different depending on the ratio of water to the raw material. Is obtained. The obtained slurry is used as an exhaust gas treating agent as it is,
Can be used.

Alternatively, the obtained slurry is dried at about 80 ° C. or higher (preferably 100 to 200 ° C.), crushed if necessary, and classified to a predetermined particle size, thereby treating powdery exhaust gas. Agent can be obtained.

In this production method, the “average particle diameter”
Means the “average particle size” of the particles in the slurry immediately after the completion of the hydration reaction performed under wet pulverization. When the slurry is dried to form powdery particles, secondary particles are formed by agglomeration of the primary particles. Average particle diameter of the particles after the control ”.

In the case where a mixture of calcium silicate hydrate fine particles and calcium hydroxide fine particles is produced by the above-mentioned production method, water is added to a raw material containing a calcium silicate-containing raw material and a raw material containing calcium hydroxide to form a hydrate. By performing the reaction, crystals of calcium hydroxide are precipitated together with calcium silicate hydrate. By performing the pulverizing operation at the same time as the hydration reaction, the crystal growth is suppressed by the impact and friction between the medium (pulverized balls and the like) and the objects to be pulverized, so that extremely fine calcium hydroxide particles are consequently produced. It is formed. Also, when a silicon dioxide raw material is present, it reacts with fine calcium hydroxide precipitated to form fine calcium silicate hydrate. According to such a method, it is a mixture of calcium silicate hydrate fine particles and calcium hydroxide fine particles satisfying the above conditions, and fine calcium hydroxide is formed on the surface of the fine particles of calcium silicate hydrate. A structure having the attached structure can be easily obtained.

On the other hand, for example, in the method of pulverizing slaked lime by pulverizing slaked lime, it is difficult to pulverize crystalline slaked lime to a sufficiently fine particle size.
In addition, general powdery hydrate particles obtained by the reaction between the raw material and water also usually have an average particle size of about 5 μm or more, and calcium silicate hydrate fine particles and calcium hydroxide satisfying the above conditions. A mixture of fine particles cannot be easily produced.

For this reason, as a method for producing an exhaust gas treating agent comprising a mixture of calcium silicate hydrate fine particles and calcium hydroxide fine particles, the desired calcium silicate hydrate fine particles and calcium hydroxide From the viewpoint that a mixture of fine particles can be produced, a method in which water is added to a raw material containing a calcium silicate-containing raw material and a raw material containing calcium hydroxide, and wet pulverization and a hydration reaction are simultaneously performed is preferable. Furthermore, the exhaust gas treating agent obtained by this method is:
Since fine calcium hydroxide adheres to the surface of calcium silicate hydrate, fine calcium hydroxide is dispersed without agglomeration, and the contact area between calcium hydroxide and acid gas is large, It is particularly advantageous in that the gas can be treated more efficiently.

In order to treat exhaust gas using the above-described exhaust gas treating agent, the exhaust gas treating agent may be brought into contact with the exhaust gas to be treated. In contrast, the exhaust gas treating agent according to the present invention may be blown. The blowing amount of the exhaust gas treating agent may be appropriately set according to the scale of the incinerator (the amount of waste incineration), the concentration of the acidic gas in the exhaust gas, and the like, similarly to the conventional exhaust gas treating agent. Usually, the amount of the active ingredient in the exhaust gas treating agent, that is, the total amount of calcium silicate hydrate and calcium hydroxide becomes about 1 to 3 times equivalent to the amount of acidic gas contained in the exhaust gas. Is common.

Next, after treating the exhaust gas in this way, the soot and dust generated by the exhaust gas treatment is collected using a dust collector. Even when the exhaust gas treating agent is used in the form of a slurry, the moisture in the slurry evaporates due to contact with the exhaust gas, so that the same dust as when the powdered exhaust gas treating agent is used is formed.

Thereafter, an iron salt is added to the collected dust and kneaded in a wet state.

According to the treatment method of the present invention, the iron salt to be added to the dust is generally a salt of a weak base and a strong acid, and the aqueous solution is acidic. In addition, the pH of dust can be lowered. Furthermore, it is considered that the gelled iron hydroxide formed when the iron salt is added to the dust also functions to adsorb heavy metals. According to the treatment method of the present invention, it is considered that the elution of heavy metals such as Pb from the solidified soot can be remarkably suppressed by the pH lowering effect and the adsorbing effect by the addition of the iron salt.

Further, in the treatment method of the present invention, the treatment agent used in the treatment of exhaust gas contains a highly alkaline substance and has high reactivity, so that the reaction with an acid gas such as HCl is performed efficiently. . For this reason, the amount of the exhaust gas treating agent used can be reduced, and the amount of generated dust can be suppressed. Moreover, the soot and dust collected after the exhaust gas treatment has a small amount of unreacted alkali substance and a low pH. Therefore, the elution of heavy metals can be sufficiently prevented only by adding a relatively small amount of iron salt.

As the iron salt to be added to the dust, an aqueous solution
What is necessary is just to exhibit acidity when, for example,
Ferrous sulfate (FeSO_Four ), Ferric sulfate (Fe_Two(SO
_Four)_Three), Ferrous chloride (FeCl_Two), Ferric chloride (Fe
Cl_Three), Iron polysulfate (｛Fe _Two(OH) n (SO_Four)
_{3-n / 2}Pickling and oxidation of ferrous metal surface in addition to chemicals such as｝ n)
Ferrous chloride and sulfur, by-products produced in large quantities during titanium production
Ferrous acid can be used.

The amount of the iron salt to be added depends on the components of the waste and the types and amounts of the heavy metals contained therein, and should be determined in advance by experiments. However, the pH at the time of addition and kneading should be in the range of 7 to 12. It is appropriate to add. Usually, 1 to 3 parts by weight of Fe with respect to 100 parts by weight (dry weight) of waste
The addition amount may be in the range of about 00 parts by weight. The iron salt can be used in either a solution state or a solid state. In the case of the solid state, it is necessary to add a small amount of water for kneading. The pH at the time of addition and kneading in the present specification refers to the pH of the liquid phase when a slurry of 10% by weight is added with about 10 times the amount of water to the mixture of dust and iron salt.
It is.

When the dust and the iron salt are kneaded, water is appropriately added to bring the mixture into a wet state or a paste-like wet state. The amount of water at the time of kneading, the kneading time, and the like do not have a great effect on the immobilization performance of heavy metals, and the moisture may be about 10 to 40% in terms of wet weight based moisture content, and the kneading time is 5 minutes to 5 minutes. About 20 minutes is enough.

When kneading the dust and the iron salt, it is preferable to knead the mixture at room temperature without heating from the viewpoint of cost. If the iron salt is added in the form of an aqueous solution,
The iron salt is desirably prepared in a state as dense as possible. When the iron salt is added as a dilute solution, the amount of liquid entrained when adding the desired iron ions becomes excessive, and there is a risk that the liquid component will be separated and flow out of the kneaded material. In a state where separation or outflow occurs, iron salts are not used effectively, and it is necessary to take measures such as filtration after the treatment, which deviates from the original purpose, and the treatment of the filtrate becomes a problem. Therefore, it is desirable to prepare the iron salt in a solution maintained at a state of saturation or more. For example, ferrous sulfate (FeSO ₄ ) is made at 20% or more at room temperature, and ferric chloride (FeCl ₃ ) is made at 48% or more at room temperature. Further, powdered ferrous sulfate and ferric chloride were dissolved in a commercially available aqueous ferric polysulfate solution (11.0% or more of Fe ³⁺ ) or an aqueous ferric chloride solution (37% of FeCl ₃ ), It is also possible to use a solution maintained at a state of saturation or higher. As described above, if the liquid is added as concentrated as possible, the volume of the liquid can be reduced, so that separation and outflow can be suppressed. In this case, when the amount of liquid is too small to be in a wet state, it can be adjusted by adding water separately.

When kneading dust and iron salt,
If necessary, a harmful metal stabilizing or fixing agent may be added. Known materials can be used as the harmful metal stabilizing or fixing agent. More specifically, for example, a neutralizing agent (aluminum hydroxide, phosphoric acid, aluminum sulfate, etc.),
Reacts with harmful metal compounds such as inorganic adsorbents (silica gel, alumina gel, etc.), chelating agents (dimethyl dithiocarbamate, etc.), water glass, phosphates, and Pb to produce hardly soluble or insoluble compounds. One or two selected from compounds (sulfides, phosphates, etc.)
More than species are illustrated. The addition amounts of these components are not particularly limited, and may be appropriately set within a range that does not adversely affect the treatment method of the present invention.

By mixing the dust and the iron salt in a wet state by the above-mentioned method, harmful heavy metals such as Pb can be stably immobilized.

The dust treated in this manner is P
The harmful heavy metals such as b are stably immobilized, and can be treated by a method such as landfill.

The treatment method of the present invention is not limited in terms of the object to be treated.
It can be applied as a method for treating exhaust gas generated when the treatment is performed in a melting furnace or the like. In particular, the method of the present invention is a method that can effectively prevent the elution of heavy metals such as Pb, and is a preferred method for treating so-called melting furnace fly ash containing heavy metals in a high concentration.

[0044]

According to the present invention, the following remarkable effects are achieved. (1) An exhaust gas treating agent used for exhaust gas treatment contains a highly alkaline substance and has high reactivity, so that the reaction with an acidic gas such as HCl is efficiently performed. Therefore, after the reaction is completed, the alkali is reduced in alkali, so that the elution of Pb and the like from the solidified particulates can be significantly suppressed. (2) Since the calcium silicate hydrate particles contained in the exhaust gas treating agent have a large specific surface area, the effect of capturing harmful heavy metals is large, and the elution thereof can be suppressed. (3) Since the calcium silicate hydrate particles contained in the exhaust gas treating agent have high reactivity, a small amount of the exhaust gas treating agent may be used, and the amount of generated dust can be suppressed. In addition, the amount of unreacted alkaline substances contained in the dust is small,
Will also be lower. Therefore, elution of heavy metals can be prevented only by adding a relatively small amount of iron salt. (4) It is not necessary to perform any special treatment such as heating during the treatment of dust, and the elution of heavy metals can be prevented by a simple treatment such as stirring and kneading by adding an inexpensive iron salt. (5) As a result of the above, when treating exhaust gas from various waste incineration facilities, it is possible to efficiently capture acidic gases while reducing the amount of soot generated, and stably fix harmful heavy metals. it can.

[0045]

EXAMPLES Hereinafter, the present invention will be described in more detail with reference to examples. Example 1 100 parts by weight of ordinary Portland cement and 600 parts by weight of 70 ° C. hot water were put into a grinder, hydrated while pulverizing for 2 hours, and the obtained slurry was dried at 150 ° C. for 24 hours, and then pulverized. As a result, an exhaust gas treating agent was obtained.

The obtained exhaust gas treating agent has an average particle size of 2 μm.
m, specific surface area was 130 m ² / g, and contained 58% by weight of calcium silicate and 26% by weight of calcium hydroxide.

This exhaust gas treating agent was blown into the flue of a municipal waste incinerator and collected by a bag filter to obtain soot and dust. The incinerator used was a stoker furnace with a treatment amount of 20 t / day, the exhaust gas treatment method was dry, and the amount of exhaust gas was 11,500.
m ³ N / hr, the exhaust gas temperature was 200 ° C., and the injection amount of the exhaust gas treating agent was 10 kg / hr. Regarding HCl gas concentration and removal rate at inlet and outlet of bag filter, JIS
The results measured according to K0107 are shown in Table 1 below.

For 200 g of this dust, 200 g of water
g and 100 g of polyiron sulfate were added, kneaded, and molded to prepare a test specimen (diameter: 50 mm × length: 100 mm). Pb specified in Notification No. 13 of the Environment Agency for specimens after 7 days
A dissolution test was performed. The results are shown in Table 2 below. Comparative Example 1 For 200 g of soot and dust obtained in the same manner as in Example 1,
200 g of water was added, kneaded, molded and tested (diameter 50
mm × length 100 mm). The Pb elution test specified in Notification No. 13 of the Environment Agency was performed on the specimen after 7 days. The results are shown in Table 2 below. Comparative Example 2 Special lime slaked lime was blown into the flue of a municipal solid waste incinerator and collected by a bag filter to obtain soot and dust. The incinerator used was a stoker furnace with a treatment amount of 20 t / day, the exhaust gas treatment method was dry, the exhaust gas amount was 11,500 m ³ N / hr, the exhaust gas temperature was 200 ° C., and the blowing amount of the special slaked lime was 10 kg / day.
hr. Table 1 below shows the results of measuring the HCl gas concentration and the removal rate at the entrance and exit of the bag filter according to JIS K 0107.

For 200 g of the dust, 200 g of water
g was added, kneaded, and molded to prepare a test specimen (diameter: 50 mm × length: 100 mm). The Pb elution test specified in Notification No. 13 of the Environment Agency was performed on the specimen after 7 days. The results are shown in Table 2 below. Comparative Example 3 For 200 g of soot and dust obtained in the same manner as in Comparative Example 2,
200 g of water and 100 g of iron polysulfate were added, kneaded, and molded to prepare a test specimen (diameter 50 mm × length 100 mm). After 7 days, the test specimen was subjected to the Pb elution test specified in the Environment Agency Notification No. 13. The results are shown in Table 2 below. Comparative Example 4 For 200 g of soot and dust obtained in the same manner as in Example 1,
200 g of water and sulfuric acid 100 with a concentration of 2.7 mol / l
g was added, kneaded, and molded to prepare a test specimen (diameter: 50 mm × length: 100 mm). After 7 days, the test specimen was subjected to the Pb elution test specified in the Environment Agency Notification No. 13.
The results are shown in Table 2 below.

[0050]

[Table 1]

[0051]

[Table 2]

Continued on the front page (72) Inventor Koichi Yukitake 7-55 Minamienkajima, Taisho-ku, Osaka-shi, Osaka Sumitomo Osaka Cement Co., Ltd. Cement and Concrete Research Laboratory (72) Inventor Hiroaki Suzuki Taisho-ku, Osaka-shi, Osaka 7-55 Minamienkajima Sumitomo Osaka Cement Co., Ltd. Cement and Concrete Research Laboratory (72) Inventor Takanori Yamamoto 7-55 Minamienkajima, Taisho-ku, Osaka City, Osaka Sumitomo Osaka Cement Co., Ltd. Cement and Concrete Research In-house (72) Inventor Mitsuru Kaneko 11-1 Haneda Asahi-cho, Ota-ku, Tokyo F-term in Ebara Corporation (reference) 4D002 AA02 AA15 AA19 AA28 AC04 BA03 BA14 CA11 DA05 DA12 DA26 DA70 EA02 GA01 GB08 GB12 4D004 AA37 AB03 BB03 CA15 CA35 CB21 CC11 DA03 DA10 DA20

Claims (8)

[Claims] (I) calcium silicate hydrate fine particles 40
An exhaust gas treating agent having a specific surface area of not less than 60 m ² / g, comprising 100 wt% and calcium hydroxide fine particles of 0 to 60 wt%, and performing exhaust gas treatment by contacting the exhaust gas;
(Ii) A method for treating exhaust gas and dust, which comprises collecting dust and soot generated by exhaust gas treatment with a dust collector, (iii) adding an iron salt to the collected dust and kneading in a wet state. 2. An exhaust gas treating agent comprising 40 to 98% by weight of calcium silicate hydrate fine particles and calcium hydroxide fine particles 2 to 2.
2. The method for treating exhaust gas and soot according to claim 1, comprising 60% by weight. 3. The method according to claim 1, wherein the average particle diameter of the calcium silicate hydrate fine particles contained in the exhaust gas treating agent is 0.1 to 4 μm, and the average particle diameter of the calcium hydroxide is 4 μm or less. Waste gas and soot treatment method. 4. An exhaust gas treating agent comprising: adding water to a raw material containing a calcium silicate-containing raw material or a raw material containing a calcium silicate-containing raw material and a calcium hydroxide-generating raw material to cause a hydration reaction under wet grinding; The exhaust gas treating agent according to any one of claims 1 to 3, which is a slurry-type exhaust gas treating agent obtained by drying or a powdery exhaust gas treating agent obtained by drying and classifying the slurry exhaust gas treating agent. . 5. The method according to claim 1, wherein the iron salt is at least one compound selected from ferrous sulfate, ferric sulfate, ferrous chloride, ferric chloride, and polyferrous sulfate. 2. A method for treating exhaust gas and soot as described in 1. above. 6. The amount of the iron salt to be added when the pH of the liquid phase during kneading is 7
The method for treating exhaust gas and soot according to any one of claims 1 to 5, which is in a range of from 1 to 12. 7. The method for treating exhaust gas and dust according to claim 1, wherein an iron salt is added to the dust and kneaded without heating in a wet state or in a paste-like wet state. 8. The method for treating exhaust gas and soot according to claim 1, wherein the exhaust gas is an exhaust gas generated from an incinerator or a melting furnace.