JP2005320230A - Environmental preservation material for water area and its using method - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a preservation material for water areas where a mineral component can be eluted from the inside of a slag to its outside and having a high capability to fix hydrogen sulfide or phosphorus. <P>SOLUTION: The environmental preservation material for water areas is characterized that it contains the slag from a steel making process where a film consisting of a carbonate is not formed on its surface. The environmental preservation material is used as a sand covering material, a recovery material for recessed sea bottoms, a seashore maintenance material, a tidal flat material, a shoal material, a sea weed bed material, a fishery material or the like. <P>COPYRIGHT: (C)2006,JPO&NCIPI

Description

  The present invention relates to maintenance of aquatic environment using steel slag.

  In recent years, water environments such as seas, rivers, lakes, and tidal flats have been studied as uses of steel slag generated in the steel manufacturing process.

Steel slag generated at steelworks, especially steelmaking slag generated from refining furnaces such as converters, pretreatment furnaces, and secondary refining furnaces (torpedo cars in the case of refining in torpedo cars) is hydrated with CaO and MgO components. It has a sex component as free CaO or free MgO. When these hydratable components come into contact with moisture, the hydratable components are eluted in water and the pH increases, and in the case of seawater, Mg ²⁺ contained in the seawater reacts with OH ⁻ from the steelmaking slag. Therefore, the problem that white turbidity occurs due to precipitation of Mg (OH) ₂ occurs. For this reason, when using steel slag for a water environment, it is desirable to treat so that these problems may not occur.

  As a countermeasure against the problems caused by these components, insolubilization by soluble carbonation treatment has been proposed. For example, Patent Documents 1 to 5 disclose techniques for carbonating steel slag.

Patent Document 1 discloses a method in which slag is granulated and solidified, then held in a temperature range of 800 to 300 ° C. in a CO ₂ atmosphere, and free CaO is carbonated into CaCO ₃ to suppress expansion. Has been.

In Patent Document 2, a bulk slag having a particle size of 40 mm or less is aged in a water vapor atmosphere under atmospheric pressure to stabilize the expansibility, and then is mixed for one hour in a mixed atmosphere of water vapor and CO ₂ gas. A method of carbonation by holding the above is disclosed.

  Patent Document 3 discloses a method of carbonation by blowing carbon dioxide gas into a pile or packed bed of granular or coarse granular slag.

Patent Document 4 discloses a carbonated slag that is used as a stone for submerging. The slag is composed of at least one of granular slag, coarse granular slag, or small slag, and the slag is agglomerated using CaCO ₃ produced by the carbonation reaction, or CaCO ₃ and MgCO ₃ as a binder. . As a production method, a method of carbonation by blowing carbon dioxide gas into a pile or a packed bed is disclosed as in Patent Document 3.

In Patent Document 5, the slag surface is covered with CaCO ₃ or MgCO ₃ generated by carbonation of the Ca component or Mg component contained in the slag, and the elution of the components from the slag is suppressed by the coating covering the slag surface. Technology is disclosed.

However, when the carbonation treatment is carried out according to the conventional production method, there is a problem that the usefulness of the slag as a water environment conservation material is reduced due to the cured film made of carbonate such as CaCO ₃ formed on the slag surface. That is, when a soluble component is carbonized to form a cured film on the slag surface, as specified in Patent Document 5, elution of the component from the slag is suppressed. As a result, the increase in pH in the surrounding water area and the white turbidity due to the precipitation of Mg (OH) ₂ are suppressed. However, since the cured film formed on the surface of the slag reduces the water permeability inside and outside the slag, the elution of minerals from the slag is also inhibited. In addition, the ability to fix hydrogen sulfide and phosphorus by slag is also suppressed.
JP-A-52-129672 JP-A-8-259282 Japanese Patent Application Laid-Open No. 11-21115 JP-A-11-71160 JP 2001-26470 A

As described above, when a film made of carbonate such as CaCO ₃ or MgCO ₃ is formed on the surface of the slag, the slag inherent in the slag such as elution of minerals and hydrogen sulfide and phosphorus fixing ability is formed by the formed cured film. The effect of. If slag is utilized in the water environment, it is preferable to utilize these characteristics that are beneficial to the water environment.

  Accordingly, the object of the present invention is to provide a water area conservation material that does not cause problems such as an increase in pH or white turbidity in the water area, and is capable of eluting minerals from the inside of the slag to the outside of the slag, and has a high ability to fix hydrogen sulfide and phosphorus. Is to provide.

The present invention
(1) Aquatic environment conservation, characterized in that a part or all of the aquatic environment conservation material is a steel slag that has been carbonized and is not formed with a carbonate film on its surface. material,
(2) The water area environmental conservation material according to (1), further including dredged soil in addition to the carbonized steel slag,
(3) The water area according to (1) or (2), characterized in that it is used as a sand-capping material, a water bottom recess backfill material, a beach nourishing material, a tidal flat material, a shallow field material, a seaweed field material, or a fishing ground material Environmental conservation materials,
(4) In any one of (1) to (3), the total content of free CaO and Ca (OH) ₂ contained in the steel slag is 0.9% by mass or less. The water area environmental conservation materials listed,
(5) Aquatic environmental conservation material, which is a steel slag in which some or all of the aquatic environmental conservation material is carbonized steel slag and no film of carbonate is formed on the surface, is placed in the aquatic area. A water environment conservation method, characterized by
(6) The water area environmental conservation method according to (5), wherein the water area environmental conservation material further includes dredged soil or local sediment in addition to the carbonated steel slag,
(7) The water area according to (5) or (6), wherein the water area where the water area environmental conservation material is disposed is a bottom of a water bottom, a beach nourishment, a tidal flat, a shallow field, a seaweed pond, or a fishing ground. Maintenance method,
(8) The total content of free CaO and Ca (OH) ₂ contained in the steel slag is 0.9% by mass or less, according to any one of (5) to (7) The water area environmental conservation method described,
It is.

  The steel slag used for the water environment conservation material of the present invention has no film formed of carbonate on the surface, so that minerals can be eluted from the slag to the outside of the slag, and the ability to immobilize hydrogen sulfide and phosphorus Is expensive. For this reason, the water environment is effectively preserved.

  The first of the present invention is characterized in that a part or all of the water area environmental conservation material is a steel slag that has been carbonized, and is a steel slag on which a film made of carbonate is not formed. It is a water area environmental conservation material.

  First, the water area environmental conservation material of the present invention will be described with reference to the drawings. 1 and 2 are schematic cross-sectional views of carbonized steel slag. FIG. 1 is a schematic cross-sectional view of a steel slag 10 used in the present invention, and FIG. 2 is a schematic cross-sectional view of a conventional steel slag 11.

Steel slag 11 subjected to conventional carbonation treatment is covered with a hard coating 30 formed by changing soluble components deposited on the surface of the slag into hard carbonates, and soluble components from the inside of the slag to the outside of the slag. Elution is suppressed. For example, soluble components such as Ca (OH) ₂ change to hard CaCO ₃ . However, the cured film 30 made of carbonate such as CaCO ₃ formed on the surface of the slag also reduces the water permeability inside and outside the slag, and inhibits the elution of minerals contained inside the slag to the outside of the slag. End up. Moreover, although slag has the function to fix the hydrogen sulfide and phosphorus which exist in a water area with the component in slag, if there is no water permeability inside and outside slag, these functions will not be expressed. Thus, although the steel slag having the structure shown in FIG. 2 can prevent pH increase and white turbidity in the surrounding water area due to the slag, the characteristics of the slag cannot be fully utilized.

  In addition, it is covered not only that the surface of the slag is completely covered but also the part where the film is not partially formed, but the water permeability inside and outside the slag is reduced. This includes cases where

In the steel slag 10 used in the present invention, soluble components present in the slag are carbonated, but a film made of carbonate is not formed on the surface. The carbonated soluble component 20 is present free in the steel slag. The degree of dispersion of the carbonated soluble component 20 is determined according to the particle size, porosity, and carbonation treatment method of the steel slag. If the steel slag has a high porosity, the soluble component of the entire slag is carbonated, and the steel slag in which the carbonated soluble component 20 is dispersed throughout the slag can be produced. Conversely, in the case of steel slag having a low porosity, a soluble component in a portion close to the outer periphery of the slag is carbonated, and a steel slag in which the soluble component 20 that is carbonated is dispersed within a certain distance from the outer periphery can be produced. . Even steel slag in which the carbonated soluble component 20 is dispersed only in the vicinity of the outer periphery is sufficiently effective in preventing the increase in pH and the occurrence of cloudiness in the surrounding water area. Since the water environment protection material containing the steel slag of the aspect shown in FIG. 1 has been subjected to carbonation treatment, pH increase and white turbidity in the surrounding water area due to elution of alkali components from the slag are suppressed. In addition, the inherent characteristics of slag such as mineral elution from slag and chemical fixation of compounds in slag can be utilized. The carbonated soluble component is a carbonate such as CaCO ₃ or MgCO ₃ .

  The water area environmental conservation material of the present invention can be used in various water areas, and the effect of the present invention varies slightly depending on the water area. “Water area environmental conservation material” means a material that contributes to the conservation of the water area environment, and “water area environmental conservation” is a broad concept that means that it has a positive effect on the water area environment. The term “water environment conservation” includes concepts such as improvement of the water environment, maintenance of the water environment, and prevention of deterioration of the water environment. If it has at least one of these effects, it corresponds to water environment conservation. In addition, “water area” refers to water regardless of whether it is seawater or freshwater, bottom or underwater, whether it is submerged, whether on the ground or in the ground. It is a concept that means a place to do. Examples of water areas include seas, rivers, lakes, tidal flats, and bottom mud that has been dug from the seabed and stacked on land. However, the present invention is not limited only to these water areas.

  Hereinafter, specific uses and effects of the water environment protection material of the present invention will be described. However, the technical scope of the present invention is not limited to the specific applications listed below. For reference, FIG. 3 shows a concept of specific uses of the water area environmental conservation material. FIG. 3 is a conceptual diagram showing a state in which water environment protection materials are arranged in sand-covering, water bottom recess backfilling, beach nourishment, tidal flats, shallow fields, seaweed beds, and fishing grounds. In FIG. 3, the site | part to which the dot was attached | subjected is an area | region where the water area environmental conservation material is arrange | positioned.

  The water area environmental conservation material of the present invention is used as a sand covering material. The sand covering material is a material that is dropped onto the bottom mud (local sediment) and used to physically contain the bottom mud. If the bottom mud is soft, part or all of the sand covering material may sink into the bottom mud, but such a case is also included in the technical scope of the present invention. Steel slag, in particular steelmaking slag, has a specific gravity greater than that of sand generally used as a sand-capping material, and is therefore stably present on the bottom of the water without being swept away by tidal currents. In addition, hydrogen sulfide and phosphorus generated in the bottom mud can be chemically fixed by steel slag. In addition, it has the effect of inhibiting sulfate reduction of sulfides by sulfate-reducing bacteria (see "FY531 Red Sea tide countermeasure technology development test report, Sediment improvement test using lime", March 1979, Mie Prefecture Hamashima Fisheries Experiment Station) . By these effects, the occurrence of red tide and blue tide is suppressed. Chemical fixation of hydrogen sulfide or phosphorus is effective when steelmaking slag is used as the steel slag. Therefore, when the water area environmental conservation material is used as a sand covering material, it is preferable to use a steelmaking slag as the steel slag.

  The following mechanism has been proposed as a mechanism for chemical fixation of hydrogen sulfide ("Report on research and research on applied technology of steelmaking slag as sand-capping material in 1995 and 1996", March 1997, Coastal Development Technology Research Center (see Japan Steel Slag Association).

  The following mechanism has been proposed as a mechanism for chemical fixation of phosphorus (see above).

  In the following description, the mechanism of chemical fixation of hydrogen sulfide and the mechanism of chemical fixation of phosphorus are the same as described for the sand-capping material, and thus the description thereof is omitted in the following description.

  The water area environmental conservation material of the present invention is also used as a water bottom recess backfill material. The water bottom concave portion backfilling material is a material used to fill a concave portion generated in the water bottom by a flaw or the like as shown in FIG. By physically filling the recess, generation of hydrogen sulfide from the recess is prevented. Moreover, when a recessed part is filled up using the water body environment conservation material of this invention, the sulfate reduction reduction | restoration of the sulfide by a sulfate reduction bacterium and the chemical fixation of hydrogen sulfide are possible.

The water area environmental conservation material of the present invention can also be used as a beach nourishing material. The beach nourishment material means a material used when returning sand by hand again to the beach where the beach sand has been scraped off by waves. There are two purposes for beach nourishment. One is to restore the sandy beach's “breaking waves” function and the habitat for animals and plants by returning sand to the shore where the sand has been scraped. The other is to create new marine recreation such as sea bathing and a new place for hydrophilicity. Although the water environment protection material of the present invention can be used for any purpose, the feature of the present invention is that minerals such as SiO ₂ , P ₂ O ₅ , and Fe are easily eluted from steel slag (particularly steelmaking slag). Considering this, it is particularly effective in providing a function as a habitat for animals and plants. Since the water area environmental conservation material of the present invention is rich in mineral elution from steel slag, the biological productivity in and around the water area environmental conservation material is increased, and the water quality is purified by the living organisms. Eventually, the entire coastal organisms can be increased through the food chain.

  The water environment protection material of the present invention is also used as a tidal flat material. Tidal flat material means a material that is used to create a water area that is flooded when the tide is high, but is visible when the tide is pulled. Since the water area environmental conservation material of the present invention is rich in mineral elution from steel slag, the biological productivity in and around the water area environmental conservation material is increased, and the water quality is purified by the living organisms. Eventually, the whole of the tidal flat can be increased through the food chain.

  The water environment protection material of the present invention is also used as a shallow field material. The shallow field usually means a shallow sea having a water depth of 5 m or less, and the shallow field material means a material used for creating a shallow field. Since the water area environmental conservation material of the present invention is rich in mineral elution from steel slag, the biological productivity in and around the water area environmental conservation material is increased, and the water quality is purified by the living organisms.

  The water area environmental conservation material of the present invention is also used as a seaweed bed material for the creation of sea forests and restoration of firewood burning. The seaweed field means a place where large aquatic plants grow in a community on the bottom of the water, and the seaweed field material means a material used for constructing the seaweed field. Examples of seaweed beds include eelgrass beds, arame-kajime fields, and garamo fields. The Amamo field is a seaweed field that consists of Amamo and Corea. Alame Kajime ground is a seaweed ground consisting of Alame Kajime and Kombu. The garamo field is an algae basin made up of Honda walla such as sawtooth mock and bark. Since the water area environmental conservation material of the present invention is rich in mineral elution from steel slag, the biological productivity in and around the water area environmental conservation material is increased, and the water quality is purified by the living organisms. This chain creates a sea forest rich in biological resources.

  The water area environmental conservation material of the present invention is also used as a fishing ground material. A fishing ground means a water area where fishery is carried out, and a fishing ground material means a material used for creating a place where fish lay eggs and live. Since the water area environmental conservation material of the present invention has abundant mineral elution from steel slag, biological productivity in and around the water area environmental conservation material is increased, and a rich fishing ground is formed.

  Next, the aspect of the steel slag of this invention is demonstrated in detail.

  As steel slag, blast furnace slag and steelmaking slag may be used. Examples of the blast furnace slag include blast furnace slow-cooled slag and blast furnace granulated slag. Examples of steelmaking slag include converter slag, pretreatment slag, decarburization slag, dephosphorization slag, desulfurization slag, desiliconization slag, electric furnace reduction slag, electric furnace oxidation slag, secondary refining slag, and ingot slag. . Two or more of these may be used as steel slag.

In the steel slag used in the present invention, a film made of carbonate such as CaCO ₃ or MgCO ₃ is not formed on the surface. Here, “a film made of carbonate is not formed” means that a carbonate film that prevents elution of minerals present therein is not formed. In addition to the embodiment in which the carbonate film is not formed at all, the embodiment in which a slight amount of carbonate is deposited on the surface but has a substantial influence on the elution of minerals is the “film is formed” in the present invention. Not applicable. Although the manufacturing method of the steel slag used by this invention is not specifically limited, Preferably the manufacturing method based on the knowledge mentioned later is employ | adopted.

In the steel slag used in the present invention, a film made of carbonate is not formed on the surface, but in the inside, carbonation of soluble calcium component and magnesium component has progressed, and carbonation such as CaCO ₃ and MgCO ₃ has progressed. Salt is present free in the slag. Water permeability inside and outside the slag is ensured by allowing carbonation to proceed inside the slag without depositing carbonate on the slag surface. The degree of carbonation in the steel slag is, from the viewpoint of preventing adverse effects due to elution of calcium, the total content of free CaO and Ca (OH) ₂ contained in the steel slag is preferably 0.9% by mass or less. . In addition, "free CaO and Ca (OH) ₂ " here means CaO and Ca (OH) ₂ that are dispersed and present inside the steel slag. The content of free CaO and Ca (OH) ₂ is measured using a measuring means such as an ethylene glycol method or a tribromophenol method.

  The particle size of the steel slag may be determined according to the use and the speed of the tidal current in the water area to be arranged. Generally, the particle size of steel slag is about 100 μm to 300 mm. When arranging in a water area where the tidal current is fast, it is preferable to use slag having a large particle size so that the steel slag is not flushed by the tidal current. On the contrary, when it is arranged in a water area where the tidal current is slow, slag having a small particle diameter may be used. The effect of the present invention is great when a slag having a large surface area per unit mass and a small particle diameter is used.

  The aquatic environment conservation material of the present invention includes at least the above-described steel slag, but may include a material other than steel slag depending on circumstances. Materials other than steel slag include coal ash such as fly ash and bottom ash, crushed waste concrete, waste brick, and waste refractory, municipal waste slag, dredged soil, and dredged soil. Two or more of these may be used in combination, or materials other than these may be used. When mixing steel slag with other components, the mixing ratio of the steel slag is such that some effects due to steel slag such as mineral elution from slag, hydrogen sulfide fixation, and phosphorus fixation are secured to some extent. The content is preferably 20% by mass or more. In particular, sludge dredged soil, dredged soil, and local sediments with low strength are useful as water environment conservation materials by fixing phosphorus and hydrogen sulfide by mixing with slag and increasing physical or chemical strength. It becomes. The increase in chemical strength involves, for example, caking due to a hydration reaction. The dredged soil can be mixed with steel slag not only on land such as a residual soil treatment plant but also on the water such as on a ship.

  Next, the manufacturing method of the steel slag used in this invention is demonstrated. Steel slag used for water area environmental conservation materials is produced by carbonating steel slag. Carbonation treatment of steel slag is also called stabilization treatment. By carbonizing the steel slag, it is possible to prevent elution of alkali components when the steel slag is disposed in the water area.

  When stabilizing steel slag, first, steel slag as a raw material is prepared. The steel slag may be pre-aged. Carbonated water or water is added to the steel slag according to the particle size distribution. For smooth carbonation, it is preferable to add carbonated water. Carbon dioxide-containing gas is supplied around the steel slag, and carbonation of the steel slag proceeds. When the stabilization process of steel slag is performed on an industrial scale, for example, the steel slag is supplied to an apparatus in which carbon dioxide-containing gas is blown from the bottom or side. When the steel slag stabilization process is continuously performed, the slag may be disposed on a net-like movable conveyer or the like capable of ensuring air permeability and gradually moved in the facility.

  When manufacturing steel slag used in the present invention, it is important to control the amount of carbonated water added. Specifically, the range is preferably less than the moisture value at which free water begins to exist and at least 10 mass% less than the moisture value, more preferably 2 to 9 mass% less than the moisture value at which free water begins to exist. The amount of carbonated water added is adjusted so that the range is more preferably 5 to 8% by mass less than the moisture value at which free water begins to exist.

  When the present inventors investigated the relationship between the amount of carbonated water added and the carbonation rate, almost no change occurred without the addition of carbonated water. When carbonated water was added, carbonation was smooth immediately after the gas began to flow. I found out that Moreover, although the rate of carbonation increased with the increase in the amount of carbonated water added, it was confirmed that the rate of carbonation decreased when the amount of carbonated water added exceeded a certain value. That is, it has been clarified that there is a certain optimum amount of carbonated water added.

  According to the study by the present inventors, it is speculated that this phenomenon is related to free water retained by slag. As water is added to the powder, the powder absorbs water for a while. From the viewpoint of powder engineering, the water in this state is called restrained water. When the amount of added water exceeds a certain level, the powder cannot absorb water, and water is present around the powder. This state of water is called free water. When free water is present, the powder group has a paste-like fluidity. When slag was measured, it was found that the aggregate of slag showed fluidity when it exceeded a certain amount of water addition, that is, free water was present above a certain amount of water addition. If such free water is present, it is considered that the carbon dioxide-containing gas does not easily enter the slag, and the carbonation rate becomes slow.

  Even in the method described in Patent Document 3 or Patent Document 4, the importance of moisture and the optimum amount of water are shown. However, according to these conventional techniques, slag particles are solidified to form a solid mass. Therefore, it is described that “an arbitrary amount of water equal to or higher than the water absorption rate (the water absorption rate of fine aggregate or coarse aggregate defined in JIS A1109 or A1110)” is added. This clearly results in the presence of free water, and the carbonation efficiency decreases.

  The water value at which free water begins to exist in the slag varies depending on the particle size of the slag, but in an actual system, the particle size of the slag is not uniform, and slags of various particle sizes of about 40 mm or less are gathered. This particle size distribution also varies depending on the process in which slag is generated, such as a refining process, a cooling process, and a metal processing removal process. About the moisture value at which free (carbonated) water begins to exist, according to the particle size distribution of each slag, if there is a lot of powdered or fine slag, the “flow value” (JIS R2521 refractory alumina cement Measurement method of physical test method or JIS R5201 cement physical test method) and measurement method of “slump value” (JIS A1101 concrete slump test method) when coarse granular slag of about 40 mm or less is included Can be obtained.

As carbonated water added to steel slag, commercially available carbonated water (soda water, carbon dioxide dissolution amount of about 3 g / l-H ₂ O under 1 atmosphere, 20 ° C.) can be used in the laboratory. In the case of industrial production, various types of industrial carbonated water production equipment or various types of exhaust gas discharged at the factory are blown into normal water to dissolve the CO ₂ component in the exhaust gas. Carbonated water produced in this way can be used. Preferably, as the carbonated water, it is preferable to use water containing at least 0.5 times the saturated solubility of the carbon dioxide gas at 1 atmosphere at the temperature of the carbonated water and containing the carbon dioxide gas. If the amount of carbon dioxide dissolved is lower than that, it is difficult to obtain the effect of sufficiently shortening the carbonation reaction. In order to carry out the carbonation reaction more efficiently, those having a large amount of carbon dioxide dissolved in the carbonated water (high degree of supersaturation) are preferred.

Carbonation proceeds by supplying carbon dioxide-containing gas to steel slag to which a predetermined amount of moisture has been added. As the carbon dioxide-containing gas, commercially available carbon dioxide, or carbon dioxide mixed with air, commercially available nitrogen gas, or commercially available argon gas can be used in the laboratory. Industrially, for example, it is efficient to use exhaust gas discharged from various factories in the steelworks. Typical exhaust gases include exhaust gas from a kiln factory that burns lime (approximately 20% by volume as the CO ₂ concentration), exhaust gas from the heating furnace (approximately ₂ % by volume of CO ₂ ), and exhaust gas from the power plant (approximately 15% by volume of CO ₂ concentration). ) And the like.

If the carbon dioxide gas concentration in the carbon dioxide containing gas is low, the carbonation rate naturally decreases, but it has been confirmed from experiments that the efficiency used for carbonation increases as the CO ₂ concentration decreases. It is considered that there is no particular effect other than the increase in the carbonation time.

  The relative humidity of the carbon dioxide-containing gas is preferably controlled in the range of 75 to 100%. From the viewpoint of continuously supplying moisture from the carbon dioxide-containing gas to the slag, the relative humidity of the flowing gas is preferably 75% or more. More preferably, it is 90% or more from the viewpoint of supplying water to the partially dried slag based on the drying theory. Control of the relative humidity can be easily adjusted by blowing carbon dioxide-containing gas into a multi-stage water tank or the like to saturate the water vapor or to mix it with mist-like water vapor in a dedicated container.

  Ideally, the ambient temperature around the steel slag is not lower than normal temperature and not higher than 80 ° C. Moreover, it is preferable to control the ambient temperature around the steel slag by adjusting the flow rate of the carbon dioxide-containing gas. The ambient temperature around the steel slag can be measured with a thermocouple or a commercially available temperature sensor. It is preferable to increase the flow rate of the carbon dioxide-containing gas when the ambient temperature including the steel slag is less than room temperature, and to decrease the flow rate of the carbon dioxide-containing gas when the temperature exceeds 80 ° C. When the gas flow rate is increased, an exothermic reaction proceeds, and when the gas flow rate is decreased, the reaction rate decreases and the temperature decreases.

  The present inventors investigated the relationship between the temperature around the steel slag, the gas flow rate, and the carbonation rate. When the gas is not flown (when left in a carbon dioxide-containing gas atmosphere), it is extremely carbonated. However, it was found that carbonation progresses by flowing gas, and the carbonation rate increases with increasing flow rate. It was also found that the carbonation rate decreased when the gas flow rate exceeded a certain flow rate. In other words, it has become clear that there is an optimum amount of gas flow.

  In order to clarify this cause, the carbonation behavior when the gas flow rate is large is examined. The carbonation rate at the beginning of carbonation is faster as the gas flow rate is larger, but the carbonation may gradually stagnate. all right. It was also found that the ambient temperature around the slag increased as the gas flow rate increased.

  Regarding the temperature at the time of slag treatment, Patent Document 2 describes that when the temperature of the atmosphere is lowered to 80 ° C. or less, carbonation is hardly promoted. In addition, Patent Document 3 and Patent Document 4 have a description that it is advantageous because if the gas is at a temperature higher than room temperature, the reactivity increases accordingly. However, the present inventors have found that the rate of carbonation decreases conversely even if the temperature is simply increased.

  As the cause, first, the following two factors can be considered. First, since the carbonation reaction is an exothermic reaction as described above, a low temperature is considered advantageous from a thermodynamic point of view. Secondly, an influence on the amount of carbon dioxide dissolved in the carbonated water contained in the slag can be considered. The solubility of carbon dioxide (ion) in water is actually larger at low temperatures and exponentially decreases with increasing temperature, so the rate of dissolution of carbonate ions, which decrease with reaction, is considered to be faster at low temperatures. It is done.

  Another concern was the slag drying due to the gas flow itself. In order to verify this, when steam saturated nitrogen gas was flowed instead of carbon dioxide containing gas under the same conditions, the slag mass decreased again when the gas flow rate was high, and the gas itself took carbonated water from the slag. It was. In other words, when a large amount of carbon dioxide-containing gas is flowed, heat generation due to carbonation that occurs in the early stage of the reaction and simultaneously drying of the slag by the gas flow itself progresses, depriving carbonated water from the slag, and the carbonation reaction stagnates. Resulting in.

  Based on the drying theory, there is a knowledge that if the wind speed around the powder is 20 cm / sec or more, the powder can be dried stably. For this reason, in the present invention, the gas flow rate around the slag grains is preferably controlled to 20 cm / sec or less, and from the viewpoint of supplying carbonated water from the gas, to 10 cm / sec or less. However, in practice, it is very difficult to control the gas flow rate due to the pressure loss accompanying the slag filling situation and the non-uniformity of the gas flow. For this reason, the temperature of the atmosphere containing the slag during the stabilization treatment is measured, and this temperature is not lower than normal temperature and not higher than 80 ° C., and preferably 40 ° C. or lower in terms of the solubility of carbon dioxide gas in carbonated water. It is realistic to control the gas flow rate. Here, room temperature varies depending on the region and throughout the seasons, but is usually about 25 ° C., below 10 ° C. in freezing in cold regions, and below 40 ° C. in warm regions.

  In the manufacturing process, it is preferable to periodically measure the ambient temperature including the steel slag and other conditions, and control the temperature so as to obtain the optimum conditions. For example, if the temperature of the surrounding atmosphere containing steel slag increases, one or both of the gas flow rate and relative humidity of the carbon dioxide-containing gas can be controlled, or carbonated water or moisture can be sprayed on the slag to To control the carbonated water content. It is possible to stabilize steel slag in a short time by controlling so that the particle | grains of steel slag do not consolidate through such means.

Each grain of steel slag that has been carbonized according to the above description is embedded in resin, and this is polished and the cross section is observed. The slag containing free CaO or Ca (OH) ₂ having a relatively high porosity. Almost all of the soluble calcium components were stabilized with calcium carbonate. Even in a slag having a relatively low porosity, a soluble calcium component was reacted with calcium carbonate in a layered region of about 0.5 to 2 mm from the outer periphery to the inside. This result indicates that the carbonation reaction has progressed through carbonated water penetrating into the interior. If free CaO or Ca (OH) ₂ is changed to calcium carbonate up to such a state, the total of free CaO and Ca (OH) ₂ after the stabilization treatment is 0.9 mass% or less. With such a steel slag, even if a considerable amount is added to water or seawater, a rise in pH and white turbidity are unlikely to occur.

  Moreover, in the steel slag manufactured by the said manufacturing method, there is little content of slag of a fine particle size. When there is little slag of a fine particle size, generation | occurrence | production of the dust during conveyance will be suppressed and the suspension at the time of throwing into water will end quickly.

  The second aspect of the present invention relates to a method for preserving the water environment using the first water environment protecting material of the present invention. In order to preserve the water environment using the water environment conservation material, as shown in FIG. 3, the water environment conservation material may be disposed in a water area where conservation of the water environment is required. Examples of water areas include bottom mud, bottom depressions, beach nourishment, tidal flats, shallow fields, seaweed beds, fishing grounds, and bottom mud dug up from the sea floor and stacked on land. Note that “arranging in these water areas” does not need to be in these water areas when the water environment conservation material is arranged. In other words, when creating a new tidal flat or a seaweed bed, it is not yet a tidal flat or a seaweed bed at the time of placing the water environment conservation material. However, when water area environmental conservation materials are arranged with the intention of creating a tidal flat or a seaweed bed, the water area corresponds to a tidal flat or a seaweed bed.

  Since the effects when the water area environmental conservation material of the present invention is applied to each water area are as described above, the description thereof is omitted here. Moreover, since the water environment protection material used is also as having demonstrated regarding the 1st of this invention, description is abbreviate | omitted here.

Example 1
As Example 1, an iron and steel slag that was brought into contact with carbon dioxide gas and on which a film made of carbonate was not formed was prepared. Moreover, as a comparative example with respect to Example 1, a steel slag having a film made of carbonate formed on the surface thereof and a steel slag not brought into contact with carbon dioxide gas were prepared. About these three types of steel slag, bio-growth evaluation experiment when each was used for shallow field material was conducted.

  In the experiment method, first, three types of steel slag shown in Table 1 were laid in a 1 m square container with a thickness of 30 cm, and seawater was poured on the slag so as to have a depth of 30 cm. As the steel slag, steel slag having a maximum particle size of 5 mm and a median particle size of 1.6 mm was used.

During the evaluation period, fresh seawater was injected at 200 cm ³ / sec and circulated. In addition, one month after the start of the experiment, 100 eel seeds were sprayed. Table 1 shows the results of the biological growth and the appearance of the shallow-field material at 6 months and 12 months after the start of the test.

  In Example 1 of the present invention, no clouding phenomenon or consolidation occurred on the surface of the shallow-field material, and a clear difference in the amount of Meioventus was observed with the comparative example. There were also differences in other survey items, confirming high biological productivity.

Example 2
As Example 2, a mixed material of steel slag (20% by mass) and a clay (80% by mass) in which a film made of carbonate is not formed on the surface, similar to that used in Example 1, was prepared. did. Moreover, clay was prepared as a comparative example for Example 2. And about the mixed material of Example 2, and the dredged material of a comparative example, the evaluation experiment at the time of using each as a shallow place and tidal flat formation material was done.

  In the experiment, first, a container having a width of 0.5 m, a length of 1 m, and a depth of 0.5 m was installed in the tidal zone. Next, using the mixed material (Example 2) or clay (Comparative Example) prepared above, a slope with a height of 50 cm and a slope of 1: 2 was provided in the container. As the steel slag, one having a maximum particle size of 25 mm and a median particle size of 5.3 mm was used.

  At 1, 7, 28, 90, and 180 days after the start of the test, material strength, change in top height (slope stability), phosphorus concentration in pore water, and macropentos population per 200 cc of material were evaluated. did. The evaluation results are shown in Table 2. The material strength was measured with a Yamanaka type soil hardness meter.

  In Example 2 of the present invention, the material strength increases according to the number of days after the start of the experiment, the top height indicating the stability of the shape, the phosphorus concentration of pore water indicating the degree of chemical purification, and The long-term macropentos population also showed a clear difference from the comparative example.

  The water area environmental preservation material of the present invention is used for preserving water areas such as eutrophic bottom mud, water bottom recesses, beach nourishment, tidal flats, shallow fields, seaweed beds, and fishing grounds. The present invention improves the water environment and creates a rich natural environment.

It is a cross-sectional schematic diagram of the steel slag 10 used in this invention. It is a cross-sectional schematic diagram of the conventional steel slag 11. It is a conceptual diagram which shows the state by which the water area environmental conservation material was arrange | positioned in a sand cover, a bottom refill of a water bottom, a beach nourishment, a tidal flat, a shallow place, a seaweed place, an ammo place, and a fishing ground.

Explanation of symbols

10 ... steel slag,
11 ... steel slag,
20 ... a carbonated soluble ingredient,
30: Cured film.

Claims (8)

  An aquatic environment conservation material characterized in that a part or all of the aquatic environment conservation material is a steel slag that has been carbonized and has no film formed of carbonate on the surface.   The water area environmental conservation material according to claim 1, further comprising dredged soil in addition to the carbonized steel slag.   The water area environmental conservation material according to claim 1 or 2, which is used as a sand-capping material, a water bottom recess backfill material, a beach nourishing material, a tidal flat material, a shallow field material, a seaweed field material, or a fishing ground material. The water area environmental conservation according to any one of claims 1 to 3, wherein a total content of free CaO and Ca (OH) ₂ contained in the steel slag is 0.9 mass% or less. material.   A part or all of the aquatic environment conservation material is a steel slag that has been carbonized, and the aquatic environment conservation material that is a steel slag on which no film of carbonate is formed is placed in the aquatic area. A feature of the water environment conservation method.   The water area environmental conservation method according to claim 5, wherein the water area environmental conservation material further includes dredged soil or local sediment in addition to the carbonized steel slag.   The water area environmental conservation method according to claim 5 or 6, wherein the water area where the water area environmental conservation material is disposed is a bottom of a water bottom, a beach nourishment, a tidal flat, a shallow ground, a seaweed ground, or a fishing ground. The water area environmental conservation according to any one of claims 5 to 7, wherein the total content of free CaO and Ca (OH) ₂ contained in the steel slag is 0.9 mass% or less. Method.

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