JP3476192B2 - Steelmaking dust slurry purification method and soil purification agent - Google Patents

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an iron fine particle slurry soil purifying agent suitable for use in removing pollutants from soil contaminated with organic halides, hexavalent chromium, and the like, and this iron. The present invention relates to a method for refining a steelmaking dust slurry that can be advantageously used to obtain a fine particle slurry.

[0002]

2. Description of the Related Art A large amount of organic halides such as trichlorethylene have been used for industrial cleaning such as removal of oils from machinery. From the viewpoint of environmental pollution, the use of such organic halides has recently been regulated. However, since a large amount of organic halides have already been used, soil pollution or water pollution is also progressing. That is, organic halides such as trichlorethylene are stable and difficult to be decomposed by microorganisms, and organic halides dumped in the natural environment not only pollute the soil but eventually pollute rivers and groundwater, which is a beverage. It may become raw water, which is a problem. It is known that such pollution of the natural environment also occurs due to hexavalent chromium left on the site of a factory such as a plating factory.

As a method of purifying soil contaminated with volatile organic compounds such as the above organic halides, a soil gas suction method, a groundwater pumping method, a soil excavation method and the like are known. The soil gas suction method is to forcibly suck the target substance existing in the unsaturated zone.The suction well is installed in the ground by boring, and the inside of the suction well is decompressed by the vacuum pump to vaporize the organic matter. The compound is collected in a suction well, introduced underground, and treated by a method of adsorbing an organic compound in soil gas onto activated carbon. When contamination by the above-mentioned organic compounds extends to the aquifer, a method of installing a submersible pump in the suction well and pumping and treating with soil gas is adopted.

The underground pumping method is a method in which a pumping well is installed in soil and contaminated groundwater is pumped and treated. Furthermore, the soil excavation method is a method in which contaminated soil is excavated, and the excavated soil is subjected to wind drying and heat treatment to remove and recover organic compounds.

However, these methods are not methods for directly purifying soil, but methods for purifying contaminated water collected by the soil gas suction method, groundwater pumping method, or the like, or contaminated water such as rivers and groundwater. However, the target is extremely large, and the processing often takes a long time. Another drawback is that the treatment process is often complicated. For this reason,
There is a demand for a method of directly and simply purifying soil, which is a pollution source.

As described above, the conventional method for purifying soil contaminated with organic halides is to collect contaminated water from the contaminated soil and purify it, or collect and purify the soil itself. It is not a method of directly and easily purifying the contaminated soil itself.

In WO-01 / 08825, iron particles are pulverized to increase the surface area of iron to increase the treatment capacity of pollutants, and in addition to atomization, the shape of the particles is made spherical. Disclosed is a soil purification agent comprising a slurry of spherical iron fine particles having a particle size of less than 10 μm, which enables rapid penetration of iron into the soil.

[0008]

DISCLOSURE OF THE INVENTION Problems to be Solved by the Invention WO-01 / 08
The soil purification agent for iron fine particle slurry described in No. 825 is far superior in the permeability into the soil as compared with the conventional amorphous ones, and it is caused by pollutants such as organic halides and hexavalent chromium. It is possible to detoxify the polluted soil by directly and efficiently reducing this pollutant, or to remove it after detoxification. However, the iron fine particle slurry utilizes steelmaking dust discharged from the converter in the above publication, but such steelmaking dust is mixed with fluorine atoms contained in the raw iron ore or the like, or iron ore. It is clear from the study by the present inventors that it contains a fluorine atom-containing ion such as a fluoride ion derived from fluorspar (CaF ₂ ) and the like, which may cause environmental pollution (secondary pollution). Became. In particular, when the pollutant is an organic halide, a chlorofluorocarbon material may be formed, for example, by a reaction with a fluoride ion.

The object of the present invention is to directly and directly from soil contaminated with pollutants such as organic halides and hexavalent chromium.
It is advantageous to obtain a soil purification agent of iron fine particle slurry that can be detoxified by efficiently reducing this pollutant, or can be removed after detoxification, and there is almost no risk of secondary pollution, and this iron fine particle slurry. Another object of the present invention is to provide a method for refining a steelmaking dust slurry that can be used for

[0010]

[Means for Solving the Problems] The inventors of the present invention have conducted extensive studies in order to obtain a soil purifying agent for iron fine particle slurry that is free from the risk of secondary contamination by fluorine. From many studies, iron fine particle slurry (generally steelmaking dust slurry)
It was found that it is extremely effective to use hydrotalcite to remove a trace amount of ions containing at least a fluorine atom (hereinafter also referred to as a fluorine atom-containing ion) contained in, and has reached the present invention. . That is, iron ore or the like as a raw material for steelmaking contains fluorine atoms, and this is contained in the steelmaking dust slurry in the form of soluble fluorine (that is, fluorine atom-containing ions such as fluoride ions). It is possible to transfer this to hydrotalcite by ion exchange, whereby the fluorine atom-containing ions can be removed from the steelmaking dust slurry.

[0011] Therefore, the above-mentioned object is to produce a steelmaking dust in the form of an aqueous slurry discharged during steelmaking, and a steelmaking dust slurry.
Add 0.2-5 mass% hydrotalcite
The steelmaking dust slurry may be contacted with hydrotalcite to remove ions containing at least fluorine atoms contained in the steelmaking dust slurry. The ion containing at least a fluorine atom in the present invention includes all ions containing a fluorine atom.
That is, fluoride ion (also called fluorine ion), Cl
It includes ions containing all fluorine atoms such as F ₄ ⁻ and IF ₄ ⁻ .

In the above refining method, in general, the fluorine atom-containing ions contained in the steelmaking dust slurry are removed by
It is performed by moving fluorine-containing ions into hydrotalcite. Also, the hydrotalcite is
It is preferable to contact in the presence of a hydrophilic resin. The presence of the hydrophilic resin stabilizes the dispersed state of the iron fine particles, so that the number of times of contact between the steelmaking dust (iron fine particles) and hydrotalcite is improved, and the fluorine atoms can be quickly removed. The contact with hydrotalcite is preferably carried out by mixing steelmaking dust and hydrotalcite, or mixing steelmaking dust with hydrotalcite and a hydrophilic resin. Mixing is simple and preferable. The hydrophilic resin is a polyacrylate (eg, sodium salt),
It is preferably at least one selected from polyacrylamide and polyvinyl alcohol. It is particularly effective in preventing steelmaking dust from settling, and has a great effect in removing fluorine atoms.

Further, it is preferable that the slurry-like steelmaking dust discharged during steelmaking is obtained by collecting exhaust gas generated during refining from an oxygen blowing converter for steelmaking and removing the gas. . Generally, dust collection is performed by wet dust collection;
After the dust collection, steelmaking dust is collected by sedimentation with a thickener.

For the iron fine particles of steelmaking dust in the above-mentioned refining method, the following preferred embodiments of the soil purifying agent can be applied.

The above object can also be achieved by a soil purifying agent for purifying contaminated soil, which is an iron fine particle slurry made of the steelmaking dust slurry obtained by the above refining method.

In the soil purifying agent of the present invention, the iron fine particles preferably have an average particle size of less than 10 μm, particularly 0.1 to 6 μm, and the shape thereof is preferably spherical.

The soil purifying agent generally further contains an antioxidant and preferably has a solid content of 20 to 80% by mass.

The pollutants of the polluted soil are generally organic halides and / or hexavalent chromium, especially organic halides.

Further, the above-mentioned object is a soil purifying agent for purifying contaminated soil, wherein the elution amount of fluorine atoms is
It can also be achieved by a soil purifying agent of an iron fine particle slurry having a solid content of 3 ppm or less. Thus, the elution amount is measured by the method described in Examples below. Such iron fine particles have a solid content of 10 ppm.
It is estimated to have the following fluorine atom content.

The iron fine particle slurry is preferably a steelmaking dust slurry obtained by the above refining method. Further, the preferred embodiments of the soil purifying agent described above can also be applied to this purifying agent.

These soil remediation agents consist of infiltrating contaminated soil with pollutants (eg,
It is used for a method of detoxifying or detoxifying and removing organic halides, hexavalent chromium and the like, particularly organic halides.

[0022]

BEST MODE FOR CARRYING OUT THE INVENTION The steelmaking slurry treated by the method for purifying a steelmaking dust slurry of the present invention is an iron fine particle slurry containing almost no fluorine atom-containing ions, and can be advantageously used as a soil cleaning agent.

The above-mentioned steelmaking dust slurry before refining generally collects steelmaking dust in exhaust gas generated during refining (preferably wet dust collection) from an oxygen blowing converter for steelmaking, and removes gas such as carbon dioxide gas. A slurry of steelmaking dust obtained by removing the slurry, and in the present invention, for example, hydrotalcite (preferably more hydrophilic resin) is added thereto and mixed, for example, at least fluorine atoms in the steelmaking dust. The fluorine atom-containing ion is removed by adsorbing an ion containing (for example, a fluoride ion) on hydrotalcite.

Usually, the steelmaking dust slurry before refining is obtained by collecting the above-mentioned steelmaking dust into a slurry of iron powder sludge by a thickener. If desired, the obtained steelmaking dust may be further added with a high-grade iron powder for a specific application (for example, for toner) to prepare a slurry.

A method for producing the steelmaking dust slurry before refining will be described with reference to FIG.

In the oxygen blowing converter for steelmaking, C, S
Pig iron containing impurities such as i, P, and F is charged, and oxygen is rapidly blown from above while stirring. In this state, a reaction occurs between the pig iron containing impurities and oxygen,
C, Si, P, etc., become oxides and form slag with calcium in fluorspar, and at this time, some of the fluorine compounds are taken into pig iron (such a reaction is considered to occur in the blast furnace during pig iron production). ). During this period, the exhaust gas containing fine iron powder generated by blowing oxygen is collected by wet dust collection through the gas recovery hood.
In wet dust collection, a gas such as CO is sent to a gas recovery tank. The steelmaking dust obtained by collecting the exhaust gas is in the form of an aqueous slurry, and the slurry is coarse-grained (at 60 μm), the coarse one is recovered as coarse iron powder, and the fine one is concentrated with a thickener. Finally, fine particles of iron powder (that is, iron fine particle slurry) can be obtained by selecting only fine particles by a filter press.

The iron fine particles thus obtained also contain iron oxides at various oxidation stages, but since such iron oxides are also in a reducing state in dust captured in a gas combustion state, they have a reducing action leading to a purifying action. It is considered to indicate. Therefore, even if the metallic iron does not account for 30% by mass or more, the iron fine particles can often exhibit a high reducing action.

An example of the particle size of 97 mass% Fe in the coarse iron powder is as follows.

[Table 1] 97 mass% Fe total amount / metal Particle size distribution (unit: T / M (production amount per month)) ≦ 70 μm 50 60 to 70 μm: 5% ≦ 80 μm 100 60 to 90 μm: 10% A composition example of the fine iron powder is as follows.

[Table 2] Slurry Water Wet powder Water SS Metallic iron Wet powder Metallic iron (Unit: T / D (production amount per day)) (Unit: T / M (production amount per month) After filter press 35% 150 53 98 20 4200 546 Slurry 70 70% 325 228 98 25 9100 683 (Product) Meaning of the above abbreviations: SS: Floating substance, wet powder: Iron powder containing water.

The range of components of the fine iron powder is as follows.

[Table 3] Slurry iron iron FeO Fe ₂ O iron total amount CaO SiO ₂ After filter press 11-18 − − 67-71 3-5 0.4-1.0 Slurry 70 29-44 32-38-67-75 --- (Product) All the units of the numerical values in Table 3 above are% by mass.

In the refining method of the present invention, steel dust slurry before thickening with a thickener, or thickening with a thickener, and finally with a filter press to select fine particles only, fine iron powder with hydrotal Sites are added and generally refined by mixing. It is particularly preferable to treat fine iron powder.

In the steelmaking dust slurry to be treated,
The iron fine particles (steel making fine particles) preferably have an average particle diameter of less than 10 μm, more preferably 0.1 to 6 μm, and particularly 0.1 to 3 μm, and the shape thereof is preferably spherical. The solid content of the slurry is 20 to 70% by mass.
(In particular, 20 to 50% by mass) is preferable. Further, the slurry preferably contains an antioxidant. This keeps the iron from being oxidized. In solids,
90 mass% or more is metallic iron and an iron-containing compound. Metallic iron accounts for 30 mass% or more in the solid content.

The hydrotalcite added above is
[M ²⁺ _1-x M ³⁺ _x (OH) ₂ ] [A ^n- _{x / n} z
H ₂ O] (where ^{M 2+} is a divalent ^{metal, M 3+} is a trivalent metal, x is a number less than 1, x and n is any number) formula, in particular _Mg 6 _A l2 (OH ) ₁₆ CO ₃ · _4H 2 O
It is a layered compound having the chemical formula: Anions are generally exchanged between layers. Surprisingly, in the present invention, fluorine atom-containing ions can be effectively exchanged and removed. The migration of the fluorine ions into the hydrotalcite is chemically bonded to the hydrotalcite by the ion exchange between the layers of the hydrotalcite as described above.

The hydrotalcite used in the present invention is generally a powder and has an average particle size of 0.01 to 1.0 μm.
m is preferable, and 0.2 to 0.8 μm is particularly preferable. The addition amount is generally 0.1 to 10% by mass, preferably 0.2 to 5% by mass, and particularly preferably 0.5 to 5% by mass with respect to the steelmaking dust slurry. With respect to the solid content of the steelmaking dust slurry, the addition amount thereof is generally 0.4 to 40% by mass, preferably 0.8 to 20% by mass, and particularly preferably 2 to 20% by mass.

The contact between the steelmaking dust slurry and hydrotalcite is generally carried out by mixing them. Hydrotalcite is added as it is or as dispersed in water. As a mixing method, stirring,
It can be performed by a bead mill, a roll, a homogenizer or the like. From the viewpoint of dispersibility, it is preferable to use a bead mill, a roll or a homogenizer. It is preferable to add hydrotalcite in two or more steps.

The mixing temperature is generally 4 to 95 ° C., 10 to 4
0 ° C. is preferred, the mixing time is generally 0.1 to 1 hour,
0.1 to 0.5 hours is preferable.

At the time of contact (mixing) between the steelmaking dust slurry and hydrotalcite, it is preferable to use a hydrophilic resin. As the hydrophilic resin, various known ones can be used. -Soluble acrylic resins such as acid salts and polymethacrylates (sodium salts are generally used as salts); water-soluble fibrin resins such as methyl cellulose and hydroxyethyl cellulose; polyacrylamide; polyvinyl alcohol; guar gum; xanthan gum; sodium alginate; sucrose And sucrose derivatives and the like, especially polyacrylate,
Polyacrylamide and polyvinyl alcohol are preferred. These hydrophilic resins preferably have a high molecular weight in order to stabilize the dispersion of iron fine particles, preferably have a number average molecular weight of 1,000,000 or more, particularly preferably in the range of 1,000,000 to 100,000,000. Further, the addition amount thereof is generally 0.001 to 1 mass% with respect to the steelmaking dust slurry, and
0.1 mass% is preferable.

The method for refining the steelmaking dust slurry can be carried out by treating the steelmaking dust slurry obtained by utilizing the by-products of iron refining as described above without using any special method or apparatus. Simple and economical.

Further, since it is obtained in the form of a slurry, it is possible to prevent the oxidation of the surface of the iron particles, and hence the oxidation during transportation. During transportation, it is preferable to stir so that the iron particles do not precipitate and solidify. In addition, it is preferable to add an antioxidant to the slurry in order to prevent the surface of the iron particles from being oxidized. Examples of the antioxidant include organic acids (eg, ascorbic acid (vitamin C), citric acid, malic acid, especially ascorbic acid) and salts thereof, and the addition amount thereof is 0. 01 to 10 mass% is general, and 0.1 to 3 mass% is preferable. Further, since it is in the form of slurry, it has an advantage that it can be easily mixed with other materials when producing the soil purifying agent.

The soil purifying agent of the present invention is a soil purifying agent for iron fine particle slurry composed of the steelmaking dust slurry obtained by the above-described refining method. Since the fluorine atom-containing ions are removed, the fluorine atom content is extremely high. Low. still,
The soil purifying agent of the present invention is also a soil purifying agent of iron fine particle slurry which is advantageously obtained by the above-mentioned purification method and has a fluorine atom elution amount of 3 ppm or less based on the solid content. Such a soil purification agent for a fine iron particle slurry having a low fluorine content has not been obtained so far and is a novel soil purification agent.

The iron fine particles preferably have an average particle diameter of less than 10 μm, more preferably 0.1 to 6 μm, and particularly 0.1 to 3 μm, and preferably contain iron fine particles having a spherical shape. And the soil purification agent containing this slurry is useful for detoxifying pollutants from contaminated soil by reduction or the like, or useful for removing after detoxification, further soil, fluorine atom-containing ions such as fluorine ions eluted in groundwater. Since there is almost no such thing, there is no concern about secondary pollution.

As a pollution source to be purified by the present invention,
Examples thereof include organic halides, hexavalent chromium, and cyanides. Organic halides and hexavalent chromium are suitable, and organic halides are particularly suitable. Examples of organic halides include 1,1-dichloroethylene, 1,2
-Dichloroethylene, trichloroethylene, tetrachloroethylene, dichloromethane, carbon tetrachloride, 1,2-dichloroethane, 1,1,1-trichloroethane, 1,
1,2-trichloroethane, 1,1,2,2-tetrachloroethane, dichlorodifluoroethane and the like can be mentioned. It is considered that these organic halides lose halogens and become corresponding hydrocarbons by the dehalogenation action (reduction action) of iron, and are removed from the soil.
The organic halide is particularly effective for organic chlorides (organic chlorine-substituted compounds). Hexavalent chromium can be efficiently reduced to trivalent chromium by the effective reducing action of iron over a long period of time, and can be subsequently removed from the soil if necessary. Further, cyanide (cyan ion) is detoxified by forming a complex with iron ion.

The iron fine particles contained in the slurry used for the soil purifying agent of the present invention are generally extremely fine particles, and therefore, when directly applied to the contaminated soil, they rapidly penetrate into the soil. By using such ultrafine iron powder, the cleaning power can be greatly improved. Further, the iron fine particles are ultrafine particles as described above, and particularly when the shape is a sphere, when they are applied to the contaminated soil, they penetrate into the soil extremely quickly and exhibit a purifying action.

The solid content of the slurry is 20 to 70.
Mass% (particularly 30 to 50 mass%) is preferable. Further, the slurry preferably contains an antioxidant. This keeps the iron from being oxidized. In the solid content, 90 mass% or more is metallic iron and an iron-containing compound.
Metallic iron accounts for 30 mass% or more in the solid content.

The soil purifying agent of the present invention containing the above-mentioned iron fine particle slurry can further use metals other than iron, such as Mn, Mg, Zn, Al and Ti, which are metals having a reducing action. These metals too. The average particle size is preferably as small as possible.

The fine iron powder has a large surface area and is easily oxidized (passivated) on the surface. Therefore, in the present invention, it is preferable to use a hydrophilic binder and / or a metal halide together in order to prevent this.

Metal halides include NaCl, KCl,
MgCl ₂ , CaCl _{2 and the} like can be mentioned, and especially N
aCl is preferred. The metal halide has a function of reducing iron hydroxide or oxide to metallic iron. The amount used is generally 0.5 to 200 mass% with respect to the solid content,
0.5 to 50 mass% is preferable.

When a hydrophilic resin is used in the purification method of the present invention, it is naturally included in the soil purifying agent of the present invention.

Further, the soil purifying agent of the present invention may contain a hydrophilic resin. It may be contained with or without a hydrophilic resin in the purification method. The hydrophilic resin is
It has a function of covering the surface of the iron fine particles and protecting the organic halide from being oxidized until it exhibits a reducing action.
Examples of such hydrophilic resins include disaccharides such as sucrose, sucrose derivatives (eg, sucrose higher fatty acid ester), monosaccharides such as glucose, alginic acid; pullulan, PVA (polyvinyl alcohol), CMC (carboxyl methyl cellulose), Water-soluble resins such as polyacrylamide, guar gum, methyl cellulose and hydroxyethyl cellulose can be mentioned. Pullulan (which has a low viscosity when made into an aqueous solution and is particularly preferable), hydroxyethyl cellulose, sucrose, glucose, and PVA are preferable. Use of a biodegradable polymer as the hydrophilic resin is particularly effective against secondary environmental pollution. The amount used is generally 0.01 to 200% by mass, and preferably 0.01 to 100% by mass, based on the solid content.

The soil purifying agent of the present invention is generally prepared by suspending the purified steelmaking dust slurry by adding an antioxidant, a metal halide or a hydrophilic resin, or a metal halide and a hydrophilic resin, if desired. , Or obtained by dispersing. Further, water can be appropriately added to obtain a desired concentration. If necessary, a surfactant can be used at the time of dispersion. The use of a biodegradable polymer (eg, biodegradable polycaprolactone) in place of the hydrophilic binder is particularly effective against secondary environmental pollution.

The soil purifying agent preferably further contains a metal sulfate (especially ferrous sulfate) as a reducing agent. Since this reacts with oxygen in the air, it is possible to prevent the surface of the metallic iron fine particles from being oxidized.

The soil purifying agent preferably further contains an inorganic carbonate or a carbonate mineral. Examples of these are calcium carbonate, precipitated calcium carbonate,
Mention may be made of magnesium carbonate, coral fossil limestone, limestone and dolomite, with precipitated calcium carbonate being particularly preferred. Since the soil purifying agent of the present invention uses fine particles of iron, it can be injected into the gap between soil particles in the soil. However, since the possibility of elution into groundwater and the like increases when the particles are made into fine particles, in the present invention, it is preferable to fix the eluted iron ions by using the carbonate to prevent it.

As described above, the soil purifying agent of the present invention is generally suspended by adding the purified steelmaking dust slurry and optionally a hydrophilic resin, a metal halide or a metal halide and a hydrophilic resin. , Or obtained by dispersing. At that time, as water used for dispersion,
From the viewpoint of suppressing iron oxidation as much as possible, reducing electrolyzed water (pH
= 7 to 12 are preferable). As the dispersant, a surfactant such as a naphthalene sulfonic acid type may be used. The amount of the dispersant used was 0.
01 to 10 mass% is general, and 0.1 to 5 mass% is preferable. Further, the above-mentioned antioxidant may be further used within the above range.

The soil purifying agent of the present invention can be used to purify contaminated soil as follows. For example, it is carried out by applying the soil purifying agent so as to permeate soil (soil) contaminated with an organic halide. Preferably, a method (1) of infiltrating the soil purification agent by spraying the soil purification agent; or inserting an injection pipe for supplying the soil purification agent into the soil contaminated with the organic halide. A method (2) consisting of injecting the soil purifying agent into the injection pipe can be mentioned.

The above method (2) can be performed, for example, as follows.

An injection pipe for supplying a soil cleaning agent by boring is provided on the surface contaminated with the organic halide. If necessary, a plurality of injection tubes can be provided at intervals. Pour the soil remediator into the supply injection tube. As a result, fine iron particles and the like penetrate into the contaminated soil and gradually come into contact with the organic halide to decompose and remove the organic halide. Before injecting with the injection pipe, groundwater may be discharged from the injection pipe, and then the soil cleaning agent may be injected. The soil surface may be covered with an impermeable sheet (eg, bentonite sheet) so that the injectate does not overflow from the soil surface. Alternatively, the sheet may be embedded in the soil.

The above cleaning method may be performed as follows, for example. That is, as shown in FIG.
Block with the impermeable layer 12 that reaches the impermeable ground 11 in the basement,
An injecting pipe 9, an air-permeable columnar portion 2 and a horizontal air-permeable layer 4 are installed in the soil inside thereof, covered with an air-impermeable sheet 6 on these, and the peripheral portion is glued outside the air-impermeable layer. It can be blocked by the impermeable layer 7 made of backfilled earth mixed with wood. In the horizontal ventilation layer 4, an intake pipe 5, which is a porous pipe having a large number of holes that do not penetrate the breathable material 3, is embedded.

In the purification treatment, for example, the water is drained through a water injection pipe, the cleaning agent of the present invention is injected from an injection tube, and if necessary, the pressure is reduced to disperse the cleaning agent and remove the substance generated by the reducing action of iron. Can be removed.

Covering the surface of soil contaminated with organic halides with an impermeable sheet, as in the above method (generally the sheet cover is installed after injecting the cleaning agent).
However, if necessary, an air-permeable columnar portion (useful for removing the generated substance) can be provided.

Soil contaminated with pollutants other than organic halides can be used in the same manner as above. In addition, contaminated soil (especially soil contaminated with hexavalent chromium)
It is also possible to put the excavated soil into a reaction tank or the like by the soil excavation method and treat with the soil purifying agent of the present invention, and it may be advantageous to remove the treated chromium compound or the like.

The concentration of steelmaking dust in the soil purifying agent to be injected into the soil is generally 0.1 to 50% by mass, preferably 1 to 30% by mass. Further, the injection amount is generally 1 to 400 kg of iron fine particles per 1 m ³ of soil, and preferably 10 to 200 kg.

[0064]

Examples [Examples 1 to 16 and Comparative Examples 1 to 4] (a) Steelmaking dust slurry Using the method shown in FIG. 1, steelmaking dust slurry before refining was obtained under the following production conditions.

Manufacturing conditions: Manufacturing with an upper-bottom blowing converter equipped with an OG (oxygen gas) gas processing system Capacity of converter: 350 T / cycle (T: Corresponding to the mass of steel in the converter, indicated by capacity) Amount to be added) Input pig iron: Hot metal ratio 70 to 96% Oxygen blowing amount: Blowing time about 20 minutes Slurry production rate: 250 t / D (days) The following steelmaking dust slurry before refining was obtained by the above method. Its composition is as follows.

[Table 4] Slurry Water Wet powder Water SS Metallic iron Wet powder Metallic iron (Unit: T / D (production amount per day)) (Unit: T / M (production amount per month) After filter press 35% 150 53 98 20 4200 546 Slurry 70 70% 325 228 98 25 9100 683 (Product) The components of the fine iron powder are as follows.

[Table 5] Slurry iron iron FeO Fe ₂ O iron total amount CaO SiO ₂ After filter press 18 − − 71 4.8 0.4 Slurry 70 29 38 − 67 − − (Product) (Unit: mass%)

The iron fine particles contained in the slurry after the above filter pressing was confirmed to be spherical by observation with an electron microscope (20,000 times). The particle size distribution was as shown in FIG. The average particle size was 1.3 μm.

The particle size distribution of the iron fine particles was measured under the following conditions.

[0070] Measuring instrument: SK laser micron sizer 7000S Dispersion medium: 0.2% NaHMP Dispersion condition: Ultrasonic wave (U.S. WAVE) 5 minutes Table 6 shows the volume fraction of each particle size in the particle size distribution of FIG.

[0071]

The filter-pressed slurry (solid content: 65% by mass) was reduced to about 26% by mass by adding reducing electrolyzed water in a stirring tank, and further hydrotalcite ((powder having an average particle size of 0.2 μm) slurry). 0% by mass, 0.5% by mass, 1.0% by mass, 2.0% by mass,
3.0% by mass of 5 kinds), and 0.01% by mass of sodium polyacrylate, 0.05% by mass of polyacrylamide and 0.01% by mass of polyvinyl alcohol as hydrophilic resins with respect to the respective addition amounts. % And no hydrophilic resin were added, and the mixture was stirred at room temperature for 30 minutes to refine the steelmaking dust slurry to obtain a soil purification agent of iron fine particle slurry.

The composition and the amount of fluorine atom elution of the soil purifying agent obtained above are shown in Table 7 below.

[Table 7] Example Hydrotalcite Hydrophilic resin Fluorine atom elution amount (mass%) (mass%) (mg / L) Comparative Example 1 0 0 1.23 Comparative Example 2 0 PA: 0.01 1.23 Comparative Example 3 0 PAM : 0.05 1.23 Comparative Example 4 0 PVA: 0.01 1.23 Example 1 0.5 0 1.22 Example 2 0.5 PA: 0.01 1.03 Example 3 0.5 PAM : 0.05 1.15 Example 4 0.5 PVA: 0.01 1.21 Example 5 1.0 0 1.05 Example 6 1.0 PA: 0.01 0.79 Example 7 1. 0 PAM: 0.05 0.92 Example 8 1.0 PVA: 0.01 0.87 Example 9 2.0 0 0.93 Example 10 2.0 PA: 0.01 0.13 Example 11 2.0 PAM: 0.05 0.21 Example 12 2.0 PVA: 0.01 0.36 Example 13 3.0 0 0.56 Example 14 3.0 PA: 0.01 0.05 Example 15 3.0 PAM: 0.05 0.08 Example 16 3.0 PVA: 0.01 0.07 Remarks ) PA: sodium polyacrylate PAM: polyacrylamide PVA: four times the value of the fluorine atom elution amount (mg / L) in the polyvinyl alcohol slurry liquid is the fluorine atom content (pp) relative to the solid content.
hit m).

The fluorine atom content is JIS-K-
It was measured by the lanthanum-alizarin complexone absorptiometry described in No. 0102.

From the above results, it is understood that the fluorine-containing ions in the slurry are reduced by the mixing treatment with hydrotalcite, and the fluorine-containing ions are remarkably reduced when the hydrophilic resin is used in combination. This fluorine ion is chemically bound to hydrotalcite and is not considered to be eluted in soil or water.

[Purification test] Next, the soil purification agent obtained in Example 14 was continuously introduced into a bead mill (dispersion device), and after dispersion, HCl was added to a pH meter described below so as to have a pH of 4, After mixing with a line mixer, the pH is measured with a pH meter after mixing (this adjusts the amount of HCl to be added), and then NaOH is added with a pH meter described below so as to have a pH of 7, and further 20% by mass is added. Nitric acid first
An aqueous dispersion containing iron and 0.1% by mass of ascorbic acid (in the same amount as the soil cleaning agent) was added, mixed with a line mixer, and after mixing, the pH was measured with a pH meter to obtain a dispersion.
This dispersion was produced continuously and the resulting dispersion was continuously poured into trichlorethylene-contaminated soil.

The contaminated soil is a soil having a layer of crushed stone at a depth of 30 cm from the ground, a silt layer up to a depth of 2 m, and a clay layer up to a depth of 30 m. I laid a floor slab on top. The floor slab has a total of 25 holes (diameter: 10 cm), 5 on each side and 3 on every 3 m.
Then, the dispersion liquid was injected from there. Injection volume is 4m
^It was carried out for 48 hours at ³ / hour.

As a result, the concentration of trichlorethylene at 5 points (randomly set) in the soil changed as follows 1 month after the injection.

[0080]   Silt layer (before injection → 1 month later (unit: ppm)):   1) 1.85 → less than 0.0005, 2) 0.01 → less than 0.0005,   3) 3.22 → less than 0.0005, 4) 1.97 → less than 0.0005,   5) 0.08 → less than 0.0005.

[0081]   Clay layer (before injection → 1 month later (unit: ppm)):   1) 5.06 → less than 0.0005, 2) 1.03 → less than 0.0005,   3) 3.08 → less than 0.0005, 4) 1.53 → less than 0.0005,   5) 2.93 → less than 0.0005.

Further, of the five places in the soil, the farthest position from the injection port was a horizontal distance of 5 m and a depth of 2 m, and the purifying agent effectively acted even at this position. It can be seen that it has good permeability to soil.

Similarly, a purification test was conducted using the soil purifying agent of Comparative Example 1, and almost the same results as in Example 14 were obtained.

Therefore, it was found that the soil purifying agent of the present invention exhibits an excellent purifying action comparable to that of the untreated fine iron particle slurry, although the concentration of fluorine atoms is reduced.

[0085]

EFFECT OF THE INVENTION By the method for purifying a steelmaking dust slurry of the present invention, fluorine atom-containing ions can be easily removed from the steelmaking dust slurry, and by using the steelmaking dust slurry having a reduced fluorine content, When soil that has been contaminated with pollutants such as halides and hexavalent chromium (especially soil that has been contaminated with organic halides) has been purified, secondary contamination is caused by the elution of fluorine atom-containing ions in the cleaning agent into the soil. There is almost no fear of causing
Therefore, it can be said that the soil purification agent of the present invention is environmentally friendly even after purification of contaminated soil.

[Brief description of drawings]

FIG. 1 is a flow chart showing an example of an embodiment of a method for refining a steelmaking dust slurry of the present invention.

FIG. 2 is a cross-sectional view showing an example of an embodiment of a purification method that can be used in the present invention.

FIG. 3 is a graph showing the particle size distribution of iron fine particles in the steelmaking dust slurry obtained in the examples.

[Explanation of symbols]

2 Breathable column 3 Breathable material 4 Horizontal ventilation layer 5 intake pipe 6 impermeable sheet 9 injection tubes 11 Underground impermeable ground 12 Impermeable layer

Continuation of front page (51) Int.Cl. ⁷ identification code FI C02F 11/00 ZAB B09B 3/00 304K // C22B 1/00 601 (58) Fields investigated (Int.Cl. ⁷ , DB name) A62D 3 / 00 B09C 1/08 C02F 1/42 C02F 11/00 C22B 1/00-9/00

Claims (15)

(57) [Claims] 1. Steelmaking dust in the form of an aqueous slurry discharged during steelmaking has a quality of 0.2 to 5 with respect to the steelmaking dust slurry.
% Of hydrotalcite was added to the steelmaking dust slurry.
A method for purifying a steelmaking dust slurry, comprising removing ions containing at least fluorine atoms contained in the steelmaking dust slurry by contacting the metal with hydrotalcite . 2. Purification of the steelmaking dust slurry according to claim 1, wherein the ions containing at least fluorine atoms contained in the steelmaking dust slurry are removed by moving the ions containing at least fluorine atoms into hydrotalcite. Method. 3. The method for purifying a steelmaking dust slurry according to claim 1, wherein the hydrotalcite is contacted in the presence of a hydrophilic resin. 4. The hydrophilic resin is polyacrylate,
The method for purifying a steelmaking dust slurry according to claim 3, wherein the method is at least one selected from polyacrylamide and polyvinyl alcohol. 5. The method for purifying a steelmaking dust slurry according to claim 1, wherein the contact with the hydrotalcite is performed by mixing. 6. The slurry-like steelmaking dust discharged during steelmaking is obtained by collecting exhaust gas generated during refining from an oxygen blowing converter for steelmaking and removing the gas. 6. The method for purifying a steelmaking dust slurry according to any one of 5 to 5. 7. The wet dust collection is performed as the dust collection.
The method for refining a steelmaking dust slurry according to 1. 8. The method for refining a steelmaking dust slurry according to claim 6, wherein the steelmaking dust is settled and collected by a thickener after the dust collection. 9. A steelmaking dust slurry having a solid content of 20 to 7
It is 0 mass%, The steel making da in any one of Claims 1-8
Method for purifying straw slurry . 10. A soil purifying agent for purifying contaminated soil, soil purifying agent of the iron fine particle slurry consisting of steelmaking dust slurry obtained by the purification method according to any one of claims 1-9. 11. The soil purifying agent according to claim 10 , wherein the iron fine particles have an average particle size of less than 10 μm. 12. The method of claim 11, wherein the iron particles, according to claim 1, which is a spherical
The soil purifying agent according to 0 or 11. 13. The method according to claim 10, further comprising an antioxidant.
The soil purification agent according to any one of 2. 14. The soil purifying agent according to claim 10, which has a solid content of 20 to 80 mass%. 15. The soil purifying agent according to claim 10 , wherein the pollutant of the contaminated soil is an organic halide.