JP2007075716A - Method for sinking carbonated/solidified body in water - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To effectively elute an effective component such as iron and silica from the carbonated/solidified body, which is obtained by solidifying an uncarbonated calcium-containing raw material by a carbonation reaction, when the carbonated/solidified body is sunk in the water. <P>SOLUTION: A microbe for producing an acid in the water is stuck to the carbonated/solidified body and the microbe-stuck carbonated/solidified body is sunk in the water. The effective component of the carbonated/solidified body is dissolved by a very small quantity of the acid to be produced by the microbe stuck to the carbonated/solidified body and eluted effectively into the water. Since the effective component is eluted little by little over a long period of time by the acid to be produced by the microbe, the supply of the effective component to the water is continued over a long period of time. <P>COPYRIGHT: (C)2007,JPO&INPIT

Description

  The present invention relates to a method for precipitating a carbonized solid obtained by solidifying an uncarbonated Ca-containing raw material by a carbonation reaction in water.

As one of the methods for making slag generated in the steel manufacturing process, carbonaceous solidified slag in granular form using uncarbonated Ca (CaO and / or Ca (OH) ₂ ) contained therein A method of obtaining a carbonated solidified body (stone) is known (for example, Patent Documents 1 and 2). In this method, for example, powdery slag to which moisture is added is filled into a mold, and a carbonation reaction is caused to uncarbonated Ca contained in the slag by blowing a carbon dioxide-containing gas into the slag filling layer, The slag filling layer is consolidated using calcium carbonate produced by this carbonation reaction as a main binder to obtain a blocked carbonated solidified body. The carbonic acid solidified body thus obtained is used as a material for underwater sedimentation for algal reefs and fish reefs in Patent Document 1 and as a material for sedimentation of freshwater bodies such as rivers in Patent Document 2, respectively. Is.

Japanese Patent No. 3175694 Japanese Patent No. 3175710

  The carbonic acid solidified body production technology is very useful from the viewpoint of resource recycling because slag and other CaO-containing waste materials can be used as raw materials. In addition, when the carbonated solid produced is used as a material for submerging in water, it is found that it has superior performance compared to concrete products in terms of providing a favorable environment for seaweed growth and aquatic life. ing.

  Patent Documents 1 and 2 include a carbonated solid body produced from a raw material containing an iron source and a soluble silica source (one originally contained in an uncarbonated Ca-containing raw material or added as an additive). When submerged in water, iron and silica (silicic acid) elute from the iron source and soluble silica source inside the carbonate solidified body, and this elution component (active ingredient) becomes a nutrient source for aquatic organisms such as seaweeds. It has been shown that it effectively acts on their growth.

However, if a carbonic acid solid body containing an iron source, a soluble silica source, or the like is simply deposited in water, the amount of elution is limited, although some iron and silica are eluted.
Therefore, the object of the present invention is to solve such problems of the prior art and provide an underwater settling method capable of effectively eluting active components such as iron and silica when the carbonated solid is set in water. There is to do.

  The present inventors are effective in the action of an acid with respect to a method for effectively eluting active components (iron, a component of nutrients for aquatic organisms such as seaweeds, silica, etc.) from a carbonate solidified in water. Based on the idea of increasing the elution of the components, the following studies were conducted. The carbonized solid body has countless fine through-holes (pores existing inside the carbonized solid body and having two or more continuous pores open to the surface of the carbonized solid body). In general, the through porosity is about 20 to 60% (volume ratio). And, liquids such as water can be easily permeated into the fine through-holes, and since the pores are fine, the liquid once permeated is held inside the solidified carbonate by the action of surface tension. Therefore, first, a method for increasing the elution of an active ingredient with the acid by impregnating a solidified carbonic acid product (through pores) with an aqueous acid solution was investigated. However, it has been found that since this method uses acid directly in the carbonated solid, the active ingredient is eluted rapidly, and a long-term elution effect cannot be expected. Therefore, the present inventors have produced acid-producing microorganisms (acids in water) as means for allowing a small amount of acid to act on an active ingredient source (iron source, soluble silica source, etc.) over a long period of time in a carbonated solid. The idea was to use microorganisms and investigated its effectiveness. As a result, by attaching acid-producing microorganisms such as nitrifying bacteria to the carbonic acid solidified body, the active ingredient is appropriately eluted by a small amount of acid generated by the acid-producing microorganisms, and the elution action is prolonged over a long period of time. It was found to last.

The present invention has been made based on such findings, and the gist thereof is as follows.
[1] A feature is that microorganisms that generate acid in water are attached to a carbonated solid obtained by solidifying an uncarbonated Ca-containing raw material by a carbonation reaction, and the carbonated solid is deposited in water. A method for submerging carbonic acid solidified bodies.
[2] The method for submerging a carbonated solid in water according to the above [1], wherein the carbonated solid contains an iron source and / or a soluble silica source.

[3] In the submerged method of [1] or [2] above, the solidified carbonic acid product is characterized in that the microorganism that produces acid in water is at least one selected from nitrifying bacteria and sulfur oxidizing bacteria. Submergence method.
[4] In the submerged method according to any one of [1] to [3], the carbonate solidified body is characterized in that the microorganism is adhered to the carbonized solidified body by impregnating the carbonated solid solution with the microorganism. Submergence method.

  A small amount of acid generated by the acid-producing microorganisms attached to the carbonate solidified body dissolves the active ingredients (iron, silica, etc.) of the carbonate solidified body, and these can be effectively eluted in water. Moreover, since the elution of the active ingredient occurs little by little by the acid generated by the acid-producing microorganism over a long period of time, the supply of the active ingredient into water can be maintained for a long period.

  In the method of the present invention, microorganisms that produce acid in water (hereinafter referred to as “acid-producing microorganisms”) are attached to the carbonated solid obtained by solidifying a powdery uncarbonated Ca-containing raw material by a carbonation reaction. This carbonic acid solidified body is submerged in water. The acid-producing microorganism attached to the carbonate solidified body survives and propagates on the surface and inside of the carbonized solidified substance to produce an acid. The acid effectively dissolves the active ingredients such as iron and silica contained in the carbonate solid (what was originally contained in the raw material as an iron source or soluble silica source or / and added as an additive). And elutes in water. Here, the amount of acid produced by the acid-producing microorganism is very small. On the other hand, since new acid is constantly generated, elution of the active ingredient as described above occurs little by little and over a long period of time. The supply of active ingredients will last for a long time. In this way, active ingredients such as iron and silica eluted in water serve as nutrient sources for aquatic organisms such as seaweeds.

Examples of the acid-producing microorganism attached to the carbonate solidified body include nitrifying bacteria (Nitrosomonas genus, Nitrobacter genus, etc.), sulfur-oxidizing bacteria (thiobacillus genus, etc.), and the like.
Here, in the case of nitrifying bacteria (nitrite bacteria, nitrate bacteria, etc.), the following reaction (nitrification action) occurs to produce nitrous acid and nitric acid.
[Nitrite]
NH ₄ ⁺ (: ammonia) + 3 / 2O ₂ → NO ₂ ⁻ (: nitrite) + H ₂ O + 2H ⁻
[Nitric acid bacteria]
NO ₂ ⁻ (: Nitrite) + 1 / 2O ₂ → NO ₃ ⁻ (: Nitric acid)
In the case of sulfur-oxidizing bacteria, the following reaction occurs to produce sulfuric acid.
S ⁰ + H ₂ O + O ₂ → SO ₃ ²⁻ + 2H ⁺
SO ₃ ²⁻ + H ₂ O → SO ₄ ²⁻ (: sulfuric acid) + H ₂
Nitrifying bacteria, as described above, have the effect of converting ammonia into nitrous acid and nitric acid to reduce ammonia, which is highly toxic to living organisms, and the nitric acid produced by the action is a nutrient source for seaweeds. It becomes.

  Carbonated solids to which acid-producing microorganisms are attached contain, as their constituents, active ingredients such as iron sources, soluble silica sources, phosphorus and potassium (that is, ingredients that serve as nutrient sources for aquatic organisms such as seaweeds). It is. Here, the solubility of the soluble silica source refers to solubility in water. The active ingredient may be originally contained in a raw material (uncarbonated Ca-containing raw material) such as slag, or may be added separately as an additive. Details thereof will be described later.

  As described above, the carbonic acid solidified body has innumerable fine through pores as a whole, but water can easily penetrate into the fine through pores, and the surface of the carbonic acid solidified body and The pH of the water inside the fine through-holes is a neutral region of about 8 to 9, and does not increase as high as concrete. Therefore, the surface of the carbonate solidified body and the inside of the fine through pores are very suitable as a habitat environment for acid-producing microorganisms such as nitrifying bacteria.

  The method for adhering the acid-producing microorganism to the carbonic acid solidified body is arbitrary, but the method of impregnating the carbonic acid solidified body with a solution (usually an aqueous solution) containing the acid-producing microorganism is the simplest. In general, microorganisms tend to form aggregates. For example, a method of immersing a solidified carbonate in a solution containing acid-producing microorganisms (preferably a solution containing acid-producing microorganisms in a high concentration), or acid-producing microorganisms are included. If the solution (preferably a solution containing acid-producing microorganisms in a high concentration) is applied to the carbonated solid, the solution is quickly absorbed into the fine through-pores. Can be easily adhered (impregnated). Further, the solution may be given a suitable viscosity by, for example, gelling the solution. In order to give viscosity to the solution, for example, polysaccharides such as starch, gelling agents such as gelatin and agar can be used.

Further, a method may be employed in which acid-producing microorganisms are mixed with a gel-like polymer (eg, starch, gelatin, agar, etc.) and rubbed on the surface of the carbonated solid. In particular, when the acid-producing microorganism is a nitrifying bacterium, since the nitrifying bacterium has a slow growth rate, it takes time to sufficiently attach (reproduce) to the carbonate solidified body, so this method is effective.
In order to increase the survival rate of acid-producing microorganisms, the work of attaching acid-producing microorganisms to the carbonate solidified body is performed immediately before submerging in water, or moisturizing until the carbonized solid body with acid-producing microorganisms adhered is submerged in water. It is preferable to do.

  When impregnating the carbonated solid with the solution containing the acid-producing microorganism, the carbonated solid as it is may be impregnated with the solution, but a considerable amount of carbonic acid solidified inside the carbonized solidified is contained inside. Since water (water necessary for carbonation treatment) is contained, in order to sufficiently impregnate a large amount of solution inside the carbonized solidified body, the carbonized solidified body is dried and a part of or a substantial amount of water inside It is desirable to evaporate all of the water and then impregnate the solution. The carbonic acid solidified body may be dried by allowing it to stand for a suitable period of time in a place where it is not exposed to rain water or the like, and to dry it naturally by heating, or a method of forcibly drying it by heating or the like.

In addition to the acid-producing microorganisms described above, the carbonate solidified body can be impregnated with a solution containing a nutrient salt. Examples of nutrient salts include phosphates, sulfides (eg, iron sulfide), nitrogen compounds, and the like.
As a method for impregnating the carbonated solid with a solution containing a nutrient, an appropriate method such as a method of immersing the carbonated solid in the solution or a method of spraying the solution onto the carbonated solid can be employed.

In the present invention, the carbonate solidified body to which the acid-producing microorganisms are attached as described above is submerged (installed) in the sea as a seaweed aggregating material (base), water / sediment purification material, fishing reef material, construction material, etc. As a result, the active ingredient is effectively eluted from the carbonated solid body over a long period of time as described above.
In addition, the water area in which the carbonate solidified body is set may be a seawater area, a freshwater area (including rivers, lakes, etc.), and a brackish water area.

  The method for obtaining the carbonate solidified body may be a conventionally known method. By causing a carbonation reaction in the presence of carbon dioxide gas to an uncarbonated Ca-containing raw material containing moisture, the uncarbonated Ca-containing raw material is consolidated. Carbonated solid. In general, a raw material filling layer is formed by filling an uncarbonated Ca-containing raw material containing appropriate moisture in a mold, and a carbon dioxide-containing gas is blown into the raw material filling layer so that the raw material filling layer is carbonated. Solidify by reaction to obtain a solidified carbonate.

Hereinafter, preferable production conditions for the carbonated solid will be described.
The uncarbonated Ca contained in the uncarbonated Ca-containing raw material, that is, CaO and / or Ca (OH) ₂ suffices to be contained at least as a part of the composition of the solid particles, and therefore CaO as a mineral. In addition to Ca (OH) ₂ , 2CaO · SiO ₂ , 3CaO · SiO ₂ , glass, and the like that are present in solid particles as part of the composition are also included.

  The uncarbonated Ca-containing raw material is not particularly limited as long as it contains uncarbonated Ca as at least a part of the composition as described above, but the content of uncarbonated Ca is high, and recycling of resources is also possible. Slag, concrete (for example, waste concrete) and the like generated in the steel manufacturing process are particularly preferable in that they can be achieved. Generally, the CaO concentration of slag generated in the steel manufacturing process is about 13 to 55 mass%, and the CaO concentration of concrete (for example, waste concrete) is about 5 to 15 mass% (CaO concentration in cement: 50 to 60 mass%). In addition, since these are easily available, it can be said that they are extremely suitable materials as uncarbonated Ca-containing raw materials. Therefore, it is preferable that at least a part of the uncarbonated Ca-containing raw material, and particularly preferably, the main raw material is slag and / or concrete.

Slag generated in the steel manufacturing process includes blast furnace slag, blast furnace granulated slag, blast furnace slag, decarburization slag, dephosphorization slag, desulfurization slag, Examples include steel slag such as silica slag and cast slag, ore reduction slag, and electric furnace slag. However, the present invention is not limited to these, and a mixture of two or more slags can also be used. .
Moreover, although a considerable amount of iron content (iron content such as granular iron) is included in the slag generated in the steel manufacturing process, the slag may be used after the recovery of this iron content (bullion).

Moreover, as concrete, the waste concrete etc. which were produced by the demolition of a building or a civil engineering structure etc. can be used, for example.
Examples of the non-carbonated Ca-containing material include mortar, glass, alumina cement, CaO-containing refractories, etc., in addition to the above slag and concrete, and one or more of these may be used alone or in combination, or slag And / or mixed with concrete.
These materials are crushed into fine particles as necessary and used as raw materials.

The uncarbonated Ca-containing raw material does not need to be solid particles whose entire amount contains uncarbonated Ca. That is, if the carbonation of the uncarbonated Ca contained in the uncarbonated Ca-containing raw material produces a sufficient amount of CaCO ₃ as a binder for the solidified carbonic acid, the uncarbonated Ca-containing raw material is uncoated Solid particles not containing may be contained.
In general, slag and the like contain active ingredients such as an iron source and a soluble silica source, but solid particles that serve as an active ingredient source such as an iron source and a soluble silica source may be blended as an additive. Examples of the additive include soluble silica sources (such as fly ash and clinker ash), iron sources (such as metallic iron and iron oxide), phosphorus sources, and potassium sources. In addition to these, an arbitrary component (particle) can be contained in an appropriate amount, that is, as long as the strength of the carbonated solid is not reduced.

There is no particular restriction on the particle size of the uncarbonated Ca-containing raw material, but it is preferable that the particle size is fine to some extent in order to secure the contact area with CO ₂ and increase the reactivity. In addition, when the particle size of the uncarbonated Ca-containing raw material is too large, Ca that cannot be carbonated remains inside the raw material particles, so that the raw material particles in the produced carbonized solidified body expand and collapse, causing cracks and the like. In some cases. In view of the above, the uncarbonated Ca-containing raw material has a particle size of substantially 10 mm or less, more desirably 5 mm or less, and particularly desirably 3 mm or less, substantially (that is, excluding inevitably contained solid particles having a large particle size). preferable.

Examples of the carbon dioxide gas or carbon dioxide-containing gas used for causing a carbonation reaction in an uncarbonated Ca-containing raw material include, for example, exhaust gas from a lime burning factory (usually around CO ₂ : 25%) discharged in an integrated steelworks ) and the furnace exhaust gas (normally, CO 2: Although _6.5% before and after) and the like are preferred, but the invention is not limited thereto. In addition, if the CO ₂ concentration in the gas is too low, there arises a problem that the processing efficiency is lowered, but other problems are not exceptional. Therefore, the CO ₂ concentration is not particularly limited, but it is preferable to set the CO ₂ concentration to 3% or more for efficient treatment.

Moreover, there is no special restriction | limiting in the supply amount of a carbon dioxide gas, However, As a general guideline, the gas supply amount of about 0.004-0.5m < ³ > / min * t (raw material ton) should just be ensured. Moreover, there is no special restriction on the gas supply time (carbonation treatment time), but as a guideline, when the supply amount of carbon dioxide gas becomes 3% or more of the weight of the uncarbonated Ca-containing raw material, that is, the gas amount Convert to the raw material 1t per 15 m ³ or more, preferably it is preferable to carry out the gas supply to 200 meters ³ or more carbon dioxide is supplied.

The supplied carbon dioxide gas or carbon dioxide-containing gas may be at room temperature. However, if the gas is at a temperature higher than room temperature, the reactivity increases accordingly, which is advantageous. However, if the temperature of the gas is excessively high, moisture of the mixed raw material is dried or CaCO ₃ is decomposed into CaO and CO ₂ , so that such decomposition does not occur even when a high temperature gas is used. It is necessary to use this gas.
Further, the carbon dioxide gas or the carbon dioxide-containing gas is preferably supplied to the mixed raw material in a humidified state in order to prevent the raw material from being dried. For this reason, when supplying gas to the mixed raw material, it is preferable to supply carbon dioxide gas or carbon dioxide-containing gas into water once to humidify or saturate H ₂ O, and then supply the raw material, thereby drying the mixed raw material. Can be prevented to promote the carbonation reaction.

In order for the uncarbonated Ca-containing raw material to come into contact with carbon dioxide and solidify by the carbonation reaction, as described above, water (water adhering to the surface of the raw material particles) is necessary. Add water. Usually, the water content of the raw material is 3 to 12%, preferably about 5 to 10%.
The carbonate solidified body can also be produced by placing a preformed body of an uncarbonated Ca-containing raw material in a carbon dioxide gas atmosphere and allowing carbon dioxide gas to permeate into the interior from the outer surface of the preformed body. In this case, an uncarbonated Ca-containing raw material is preformed by compression molding or the like, and the preformed material is placed in a carbon dioxide atmosphere to be solidified by carbonation.

  The shape of the carbonate solidified body is arbitrary, in addition to the cube or rectangular shape, for example, the cross-sectional shape is a circle, ellipse, triangle, quadrilateral or more, star shape, etc., or the overall shape is spherical, elliptical A tetrahedron or more polyhedron shape, a cone shape, a columnar shape, a tetrapot shape, or the like can be used. Further, a solidified carbonic acid product produced using a mold or the like may be crushed to an appropriate size.

(B) Test conditions
(1) Three types of test bodies were used: carbonized solidified steel slag (invention example), zeolite (comparative example 1), and no molded product (comparative example 2). The carbonate solid (invention example) and zeolite (comparative example 1) were immersed for 1 week while aerated in an aqueous solution containing nitrifying bacteria. In the case of no molding (Comparative Example 2), an aqueous solution of nitrifying bacteria was used as it was.
(2) 50 mL (volume) of the test specimen after immersion treatment (however, in Comparative Example 2 an aqueous solution of nitrifying bacteria) was transferred to a 1 L beaker.
(3) A 500 ml aqueous ammonia solution (500 mg / L) having a dissolved oxygen amount of 6 mg / L was added to the beaker of (2) above, and a nitrification test was performed at a constant temperature of 25 ° C.

(4) The changes over time in the ammonia concentration and nitric acid concentration in the circulating aqueous ammonia solution were measured, and the effect of each specimen on the nitrification reaction was evaluated.
(5) The ammonia concentration was measured by the indophenol method, and the nitric acid concentration was measured by the high performance ion chromatography (HPLC) method.
(B) Test results The test results are shown in FIG. According to this, it can be seen that the nitrification reaction is the fastest when the carbonated solid is used (invention example), and the growth of nitrifying bacteria is progressing in the carbonated solid.

The graph which shows the time-dependent change of the ammonia concentration and nitric acid concentration in the aqueous ammonia solution in Example 1

Claims (4)

  Carbonation solidification characterized by adhering microorganisms that generate acid in water to a solidified carbonate obtained by solidifying an uncarbonated Ca-containing raw material by a carbonation reaction, and depositing the carbonate solidified in water How the body is submerged.   The method for submerging a carbonated solid in water according to claim 1, wherein the carbonated solid contains an iron source and / or a soluble silica source.   3. The method according to claim 1 or 2, wherein the microorganism that produces acid in water is at least one selected from nitrifying bacteria and sulfur oxidizing bacteria. The method for depositing a carbonated solid in water according to any one of claims 1 to 3, wherein the microorganism is adhered to the carbonated solid by impregnating the carbonated solution with a solution containing microorganisms.

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