JP7299502B2 - SLAG MOLDED PRODUCT AND METHOD FOR MANUFACTURING THE SAME - Google Patents

Description

TECHNICAL FIELD The present invention relates to a slag compact containing steelmaking slag for use in an aquatic environment, and a method for producing the same.

In recent years, in sea areas near coastal areas, (i) seaweed has stopped growing on rocky areas, causing rocky areas to be covered with lime algae (isoyake), (ii) deterioration of water quality, and (iii) muddy bottom sediments. Disappearance of seaweed beds due to erosion, etc. has become a problem. And the problem of declining marine resources is becoming more serious.

The phenomenon of (iii) muddying of the bottom sediment is caused by factors such as changes in seawater flow accompanying artificial changes in coastal topography, inflow of organic matter from domestic wastewater, and collection of sea sand. occurs over a wide range of sea areas. Areas near the muddy sediments are likely to become hypoxic, and in such areas, highly toxic hydrogen sulfide is produced by anaerobic sulfate-reducing bacteria. Hydrogen sulfide poses a great obstacle to living organisms in the vicinity of bottom sediments.

Developing an environmental repair material that can solve the problems caused by the generation of hydrogen sulfide is an important issue in securing marine resources. Utilizing the reaction between hydrogen sulfide and iron is known as one of effective means for reducing hydrogen sulfide in the environment.

Specifically, as exemplified in the chemical reaction formula below, bivalent iron (Fe ²⁺ ) or trivalent iron (Fe ³⁺ ) reacts with hydrogen sulfide ions or hydrogen sulfide to form iron sulfide (FeS) or It produces elemental sulfur ( ^SO ).
HS ⁻ +Fe ²⁺ →FeS+H ⁺
HS ⁻ +2Fe ³⁺ →S ⁰ +2Fe ²⁺ +H ⁺
H ₂ S+Fe ²⁺ →FeS+2H ⁺
H ₂ S+2Fe ³⁺ →S ⁰ +2Fe ²⁺ +2H ⁺ .

One of the causes of the disappearance of seaweed beds is that the influx of iron (an element necessary for the growth of algae) into the coastal waters has decreased due to the devastation of forests and the construction of dams. It is also mentioned that there are In order to maintain and recover fishery resources in sea areas near coastal areas, it is important not only to solve the above-mentioned problems related to hydrogen sulfide generation, but also to supply iron to the water environment. By forming a seaweed bed, it is possible to provide a place where various organisms can live.

Steelmaking slag is a by-product produced in large amounts in the ironmaking process (steelmaking process), and is mainly recycled for use on land, such as roadbed materials and construction materials. Steelmaking slag is required to be used more for recycling, and the development of technologies for using it in marine areas is underway.

Since steelmaking slag contains iron, attention has been paid to it as a material that can solve the problem related to the generation of hydrogen sulfide and promote the formation of seaweed beds. However, since iron in steelmaking slag exists mainly as iron oxide, it is difficult to elute into the water environment. Therefore, even if the steelmaking slag is put into the water environment as it is, the iron elution amount is poor. Therefore, a technique for efficiently eluting iron from steelmaking slag is desired. In addition, steelmaking slag in a pulverized state tends to generate dust during transportation or when thrown into a water environment, which may significantly deteriorate workability. Therefore, steelmaking slag is required to have a shape that is easy to handle.

For example, as a method of supplying iron to an aquatic environment using steelmaking slag, there is a known method of packing steelmaking slag and humus into a bag made of coconut fiber and throwing the bag into a sea area (for example, Patent Document 1). This method is characterized in that dusting of the steelmaking slag is prevented by being enclosed in the bag, and iron can be supplied from the steelmaking slag to the water environment by the iron chelating action of the components generated from the humus.

Also, as an effective method for applying steelmaking slag to the seabed in a shape that is easy to handle, it is known to use a slag compact formed by granulating steelmaking slag (see, for example, Patent Document 2). The slag molded body described in Patent Document 2 is characterized in that it generates little dust and is easy to transport because it is molded. In addition, it contains ligninsulfonic acid as a binder for molding, and a large amount of iron can be supplied from the steelmaking slag into the water environment by the iron chelating action of the ligninsulfonic acid.

For example, a method is known in which iron is eluted from an iron-containing material into an aquatic environment by contacting the iron-containing material with fruit acid or polyphenol (see, for example, Patent Documents 3 and 4).

JP-A-2005-34140 JP 2014-200195 A JP 2012-75398 A JP 2016-195579 A

However, the methods disclosed in Patent Documents 1 to 4 have room for improvement in the following points.

For example, in the method described in Patent Document 1, iron contained in steelmaking slag forms a complex with humic substances produced by fermentation or the like inside the bag, thereby eluting iron into the water environment. However, the form of humic substances for stably eluting iron has not been completely clarified, and depending on the conditions for generating humic substances, iron supply into the water environment may become unstable.

In the method described in Patent Document 2, the surface of the slag molded body is formed with a coating portion containing ligninsulfonic acid and mainly made of acidic soil, thereby suppressing the increase in pH caused by the elution of free lime into the water environment. While suppressing it, it promotes the elution of iron into the water environment. In this method, if the amount of functional groups contained in lignosulfonic acid is small, it may be difficult to stabilize the iron elution amount.

In the methods described in Patent Literatures 3 and 4, the elution of iron in an aquatic environment is accelerated by contacting an iron-containing material with fruit acid or polyphenol. However, from the viewpoint of stabilizing and improving the efficiency of iron elution from steelmaking slag, the knowledge about how much fruit acid or polyphenol should be included in the slag compact according to the type of fruit acid or polyphenol is Documents 3 and 4 do not disclose this.

In view of the above circumstances, an object of one aspect of the present invention is to provide a slag compact that is easy to handle and is capable of stably and efficiently eluting iron into a water environment.

In order to solve the above problems, a slag compact in one aspect of the present invention has a steelmaking slag and an acidic functional group, and a reaction between the acidic functional group and iron contained in the steelmaking slag produces a slag compact in an aquatic environment. and an auxiliary substance that assists the elution of the iron in the above, and contains 50 μmol/g or more of the acidic functional group.

Further, in order to solve the above problems, a method for producing a slag compact according to one aspect of the present invention includes steelmaking slag, having an acidic functional group, and combining the acidic functional group with iron contained in the steelmaking slag. and an auxiliary material containing an auxiliary substance that assists the elution of the iron in a water environment by a reaction, wherein the amount of the acidic functional group contained in the auxiliary material is based on , a calculating step of calculating the mixing ratio of the steelmaking slag and the auxiliary material so that the amount of the acidic functional group per 1 g of the slag molded body is 50 μmol / g or more, and and a mixing step of mixing the auxiliary material and the steelmaking slag at a mixing ratio.

ADVANTAGE OF THE INVENTION According to one aspect of the present invention, it is possible to provide a slag compact that is easy to handle and is capable of stably and efficiently eluting iron into a water environment.

1 is a schematic diagram showing the configuration of a slag molded body in Embodiment 1 of the present invention; FIG. It is a flow chart which shows an outline of an example of a manufacturing process of the above-mentioned slag compact. It is a schematic diagram showing the configuration of a slag molded body in Embodiment 2 of the present invention.

[Embodiment 1]
BEST MODE FOR CARRYING OUT THE INVENTION Embodiments of the present invention will be described below. The following description is for better understanding of the gist of the invention, and does not limit the invention unless otherwise specified.

In the following description, in order to facilitate the understanding of the slag compact in the present embodiment, first, the novel knowledge found by the present inventors will be briefly described.

<Brief description of the findings of the invention>
In the present specification, a substance that has the effect of assisting the elution of iron in an aquatic environment is referred to as an auxiliary substance. The water environment is not particularly limited as long as it is an environment to be reformed by introducing the slag compact, and examples thereof include seawater, freshwater, brackish water near the mouth of a river, lake water, swamp water, and the like.

The auxiliary substance reacts with the iron contained in the steelmaking slag in a water environment and assists the elution of iron as follows. That is, in an aquatic environment, the auxiliary substance binds with iron ions and disperses in the aquatic environment. There are various types of auxiliary substances that can cause such reactions, and there are also various types of functional groups that form bonds with elements such as iron.

It is not easy to investigate the details of the reactions between the auxiliary substances and various elements, and the susceptibility to the reaction that elutes iron from the steelmaking slag into the water environment may differ for each type of auxiliary substance. Therefore, conventionally, when a specific type of substance (for example, fruit acid, polyphenol) is used in combination with steelmaking slag, the amount of the substance added is set on an ad-hoc basis, and depending on the amount of the substance added, In some cases, the amount of iron eluted into was insufficient. Also, the amount of iron elution can vary, for example due to variations in the quality of the material containing the auxiliary substances. Therefore, iron could not be stably eluted in some cases.

The inventors of the present invention have extensively studied the factors affecting the iron elution amount in producing a mixture (slag compact) of steelmaking slag and auxiliary substances. As a result, the concentration of the acidic functional groups contained in the slag molded body is increased to a predetermined value or higher, using the acidic functional groups of the auxiliary substance as an indicator, thereby stably and efficiently eluting iron into the water environment. The inventors have found that it is possible to achieve the invention of the present application.

A slag compact and a method for producing the same according to the present embodiment based on the above findings will be described in detail below.

<Slag molding>
A slag compact according to one embodiment of the present invention will be described with reference to FIG. FIG. 1 is a schematic diagram showing the configuration of a slag compact 1 in this embodiment. Although FIG. 1 shows the slag compact 1 in a spherical shape, the slag compact 1 actually has an irregular shape.

As shown in FIG. 1 , the slag compact 1 of this embodiment includes steelmaking slag 2 , auxiliary material (first auxiliary material) 3 , and binder (second auxiliary material) 4 . Auxiliary material 3 and binder 4 contain auxiliary substance 5 .

(Steelmaking slag)
The steelmaking slag 2 is a large amount of by-product generated in the steelmaking process. The steelmaking slag 2 is, for example, converter slag, electric furnace slag, pretreatment slag, decarburization slag, desulfurization slag, dephosphorization slag, desiliconization slag, electric furnace oxidation slag, electric furnace reduction slag, secondary refining slag, and ingot-making slag. slag and the like. The steelmaking slag 2 may be a mixture of these slags.

The steelmaking slag 2 contains elements such as iron (Fe), manganese (Mn), calcium (Ca), magnesium (Mg), silicon (Si) and phosphorus (P). By containing the steelmaking slag 2, the slag compact 1 not only elutes iron in the water environment, but also elutes components other than iron among the above elements from the slag compact in order to repair the water environment. may In particular, Mn and P can effectively contribute as nutrients to algae.

Steelmaking slag 2 preferably has an iron content of 10.0% by mass or more in terms of total iron in order to ensure the amount of iron eluted in a water environment. Among the Ca contained in the steelmaking slag 2, unreacted soluble CaO (free lime) may elute hydroxide ions, raise the pH of the water environment, and deteriorate the biological environment. Therefore, the soluble CaO may be carbonated by subjecting the steelmaking slag 2 to atmospheric aging or treatment with carbon dioxide before and after forming the steelmaking slag 2 .

(auxiliary material)
The auxiliary material 3 is a material containing a relatively high concentration of the auxiliary substance 5 having an acidic functional group, and is preferably a recycled material (recycled material) in consideration of cost. Unlike new materials that are manufactured and sold according to their intended use, recycled materials are materials that utilize disused materials or waste materials (so-called waste materials). Examples of such auxiliary material 3 include citrus peel, coffee grounds, compost , and bamboo charcoal. By using not only the steelmaking slag 2 but also the recycled material as the auxiliary material 3, the slag molded body 1 can be made of a recyclable material that gives great consideration to the environment.

The auxiliary material 3 may be one or more selected from the group consisting of the materials exemplified above, that is, may be a combination of a plurality of materials. Depending on the availability of each material, the concentration of acidic functional groups in the material, or for the purpose of cost reduction, the mixing ratio of each material in the auxiliary material 3 may be appropriately changed.

The auxiliary material 3 is contained in the slag compact 1 in a dried and pulverized state. The particle size of the auxiliary material 3 contained in the slag compact 1 in one aspect of the present invention may be adjusted as appropriate, and is not particularly limited. As the temperature rises, it becomes easier to generate dust. Therefore, it is preferable that the particle size of the auxiliary material 3 is 100 μm or more. Also, if the particle size of the auxiliary material 3 is too large, the strength of the slag molded body 1 may decrease, and the amount of the auxiliary material 5 (that is, the amount of the acidic functional groups) that can be effectively used in the water environment may decrease. . Therefore, the particle size of the auxiliary material 3 is preferably 5 mm or less.

(binder)
The binder 4 contains an auxiliary substance 5 having an acidic functional group, and is added to the slag molded body 1 in order to improve the yield during molding of the slag molded body 1 and to increase the strength after molding.

For the slag molded body 1 according to one aspect of the present invention, the type and amount of the binder 4 to be added may be appropriately determined in consideration of the amount of acidic functional groups, the cost, the strength of the slag molded body 1, and the like. Binders 4 include, for example, ligninsulfonic acid, metal salts of ligninsulfonic acid, molasses, and starch. When adding ligninsulfonic acid or molasses, the amount of binder 4 added is based on the total weight of steelmaking slag 2 and auxiliary material 3, considering the balance between cost, strength of slag compact 1, and iron elution amount. , preferably in an amount of 2% by mass or more and 10% by mass or less.

Lignin sulfonic acid and its metal salts are excellent in dispersibility and caking properties, and therefore are preferably used as a caking agent. Ligninsulfonic acid and its metal salts have an iron chelating action, and therefore have an action of increasing the amount of iron eluted from the slag compact 1 in a water environment.

In addition, although the pH of lignosulfonic acid can be adjusted as necessary, it is preferably non-alkaline from the viewpoint of suppressing the pH increase and clouding of seawater in the slag molded article 1 . In particular, when the ligninsulfonic acid is acidic, it is more preferable because the effect of preventing or alleviating the pH increase of seawater is likely to be exhibited.

When using a metal salt of ligninsulfonic acid, the type of metal element may be selected as appropriate, for example, sodium (Na), potassium (K), etc. Metal may be used. Considering ease of handling and cost, Mg, Ca or Na are preferred.

The form of ligninsulfonic acid and its metal salt can be selected as appropriate, and can be added in the form of powder or aqueous solution during the production process.

(acidic functional group)
The auxiliary substance 5 contained in the auxiliary material 3 and the binder 4 may be a substance having one type of acidic functional group, or a substance having a plurality of types of acidic functional groups. The auxiliary substance 5 having many acidic functional groups forms a chelate complex with iron ions, adsorbs iron ions, and is dispersed in the water environment to increase the iron elution amount.

Types of acidic functional groups possessed by the auxiliary substance 5 include, for example, a hydroxyl group, a carboxyl group, a carbonyl group, a sulfo group, and the like. The acidic functional group possessed by the auxiliary substance 5 is not limited to these, and may be an acidic functional group of a type that reacts with sodium hydroxide by neutralization titration using sodium hydroxide. This neutralization titration will be specifically described later, but the slag molded body 1 in the present embodiment is produced based on the amount of acidic functional groups contained in the auxiliary material 3 and the binder 4. 4 is adjusted.

As the auxiliary substance 5, a wide variety of organic substances are practically conceivable, and it is not realistic to specifically list them, and it is of little significance. It is conceivable that the auxiliary substance 5 may react relatively easily (rapidly) with elements other than iron (for example, Ca) present as various oxides in the steelmaking slag 2 . It is difficult to elucidate the reaction between the steelmaking slag 2 and the auxiliary substance 5 in detail.

By focusing on the amount of acidic functional groups contained in the slag compact 1, the present inventors made it possible to quantitatively estimate the amount of iron elution caused by the complex reaction between the steelmaking slag 2 and the auxiliary substance 5, We have achieved stable and efficient elution of iron into the water environment.

That is, the slag molded article 1 in the present embodiment contains 50 μmol/g or more of acidic functional groups per 1 g of the slag molded article 1 . In the reaction between the steelmaking slag 2 and the auxiliary substance 5 in a water environment, the elements other than iron in the steelmaking slag 2 can react with the auxiliary substance 5 to reduce the amount of iron complexes produced. However, the slag compact 1 can effectively elute iron in the steelmaking slag 2 by containing 50 μmol/g or more of acidic functional groups. Iron is adsorbed to the auxiliary substance 5 dispersed in the water environment, or the auxiliary substance 5 and iron form a complex and are dispersed, so that iron can be dispersed in the water environment without precipitating. . Therefore, iron can be stably and efficiently eluted from the steelmaking slag 2 into the water environment.

In the present specification, the iron elution amount refers to the total amount of iron eluted into the water environment, and the iron ions that bind to acidic functional groups and are eluted into the water environment are divalent iron with high bioavailability. may be trivalent iron. The trivalent iron eluted into the water environment effectively acts to reduce hydrogen sulfide, and can be reduced to divalent iron by seaweed or microorganisms and effectively utilized in the water environment.

In the slag molded article 1 of the present embodiment, the more the amount of acidic functional groups in the slag molded article 1, the greater the amount of iron elution in the water environment. It is also possible to adjust the iron elution amount (elution rate) in the water environment.

In addition, for example, when the slag molded body 1 is used for reforming a water environment contaminated with hydrogen sulfide, the iron elution amount may be controlled according to the hydrogen sulfide concentration. When used, the iron elution amount may be controlled according to the fertilization effect. It is desirable that the lower limit of the content of the acidic functional groups in the slag compact 1 is set according to the target iron elution amount. However, in order to obtain a clear effect of iron elution for both the purposes of reducing hydrogen sulfide and creating a seaweed bed, the slag molded body 1 preferably contains at least 50 μmol/g of acidic functional groups, and the effect is immediate. In order to improve the properties, it is preferable to contain 100 μmol/g or more of acidic functional groups.

If the iron elution amount in the water environment is too small, the supply of iron to the water environment may be insufficient at the initial stage when the slag compact 1 is introduced into the water environment. On the other hand, if the iron elution amount in the water environment is too large, iron will be excessively supplied into the water environment. Here, the greater the amount of acidic functional groups in the slag compact 1, the greater the proportions of the auxiliary material 3 and the binder 4, and as a result, the proportion of the steelmaking slag 2 becomes smaller. Therefore, the total amount of iron that can be eluted from the slag compact 1 into the water environment can be reduced. Moreover, the more the amount of the auxiliary material 3 and the binder 4 added, the higher the manufacturing cost of the slag compact 1 can be.

Therefore, the upper limit of the content of the acidic functional groups in the slag molded body 1 is preferably 1000 μmol/g or less. Thereby, the iron elution amount per unit time from the slag compact 1 in the water environment can be adjusted to an appropriate amount (that is, an appropriate elution rate). As a result, it is possible to increase the probability that iron will be stably eluted from the slag compact 1 into the water environment continuously over a long period of time. In addition, it is possible to reduce the influence on the pH in the water environment. Further, since the auxiliary material 3 and the binder 4 may be appropriately added to the slag molded body 1, the manufacturing cost of the slag molded body 1 can be relatively reduced.

(Other configurations)
The slag molded body 1 has higher production efficiency and strength as its grain size or overall length increases. Therefore, the slag compact 1 preferably has a particle size or overall length of 10 mm or more. If the particle diameter or the total length is less than 10 mm, dust is likely to be generated and the handleability may deteriorate.

Moreover, since the iron elution amount per weight increases as the specific surface area of the slag molded body 1 increases, the slag molded body 1 preferably has a particle size or overall length of 40 mm or less. If the particle diameter or the total length exceeds 40 mm, the specific surface area of the slag molded body 1 becomes small, and the amount of eluted iron is reduced.

The slag molded body 1 has a particle diameter or a total length of 10 mm or more and 40 mm or less, so that the manufacturing efficiency of the slag molded body 1 and the handling during transportation can be improved, and the specific surface area is increased to make it suitable for use in a water environment. It is possible to make it easier to increase the iron elution amount.

The slag compact 1 of the present embodiment can be put into an aquatic environment to efficiently create a seaweed bed by eluting iron and effectively improve the bottom sediment. Also, the slag molded article 1 may be used as an environment repair material by being charged into a container having an opening.

<Manufacturing method>
Next, a method for manufacturing the slag compact 1 according to this embodiment will be described with reference to FIG.

As shown in FIG. 2, the method for manufacturing the slag compact 1 in this embodiment includes a measurement step S1, a raw material preparation step S2, a ratio calculation step (calculation step) S3, a mixing step S4, and a forming step S5. The measurement step S1 and the raw material preparation step S2 may be performed in the opposite order to each other, or may be performed in parallel. Moreover, each of the above-described steps in the method for manufacturing the slag molded body 1 may be performed at different locations. For example, the measurement step S1 may acquire the results of measurements performed at a remote location.

In the measurement step S1, the amount of acidic functional groups contained in the auxiliary material 3 and the binder 4 is measured by neutralization titration using NaOH, for example. Measurement of acidic functional groups by neutralization titration is carried out, for example, as follows.

That is, the auxiliary material 3 is dried at a temperature of 80° C. or 100° C., for example, and then pulverized into a powder having an average particle size of 1.0 mm or less. After mixing the dried and pulverized auxiliary material 3 with water having a weight of 10 times or more of the dry weight of the auxiliary material 3 and stirring for 1 hour or more to elute the auxiliary substance 5 from the auxiliary material 3, The supernatant obtained by removing solids by filtration or centrifugation is used as an extract. Here, if the extract from the auxiliary material 3 contains substances that interfere with titration analysis, such as mineral acids or metal salts, organic substances having acidic functional groups should be separated in advance using a strongly basic ion-exchange resin. A neutralization titration may be performed from

NaOH adjusted to about 0.1 to 1.0 mol/L depending on the concentration of the acidic functional group is added dropwise to the obtained extract, and the change in pH is measured to obtain a titration curve. The substance amount (mol) of NaOH corresponding to the inflection point of the obtained titration curve is obtained as the amount of the acidic functional group contained in the auxiliary material 3 . By measuring the binder 4 in the same manner as described above, the amount of acidic functional groups contained in the binder 4 can be obtained.

The amount of acidic functional groups measured in the measurement step S1 corresponds to the amount of the auxiliary substance 5 that is eluted from the auxiliary material 3 or the binder 4 and contributes to various reactions in the water environment. It can be said that it is the amount of The content of the acidic functional groups in the slag molded article 1 can also be expressed as the content of effective acidic functional groups.

In the raw material preparation step S2, the steelmaking slag 2, which is an iron-containing raw material, has an average particle diameter of 0.5 mm or more and 25 mm or less from the viewpoint of formability during production of the slag molded body 1 and strength of the slag molded body 1 after manufacturing. Grind into granules. Alternatively, the steelmaking slag 2 is, for example, granular slag that has been sieved to a size of 5 mm or less in length. When granular steelmaking slag is used, depending on its size and shape, it may be used as it is in the next step without being processed.

Alternatively, in the raw material preparation step S2, the granular slag may be pulverized into powdery slag having an average particle size of 0.01 mm or more and 0.2 mm or less. Reactivity between the auxiliary substance 5 and the steelmaking slag 2 is likely to be improved by miniaturization.

Further, if necessary, steelmaking slag 2 whose expansion is suppressed by aging treatment or the like may be used, or steelmaking slag 2 subjected to carbonation treatment or immersion treatment in hydrochloric acid or sulfuric acid may be used.

Next, in the ratio calculation step S3, based on the amount of the acidic functional group contained in the auxiliary material 3, the steelmaking slag 2 and the , auxiliary material 3 and binder 4 are calculated. Here, after determining the mixing ratio of the steelmaking slag 2 and the auxiliary material 3, it is preferable to calculate the mixing ratio of the binder 4 with respect to the total weight of the steelmaking slag 2 and the auxiliary material 3.

In the mixing step S4, the auxiliary material 3, the binder 4, and the steelmaking slag 2 are mixed using, for example, a kneader, using the mixing ratio calculated in the ratio calculating step S3. In the ratio calculation step S3 and the mixing step S4, both the auxiliary material 3 and the binder 4 can be collectively expressed as an auxiliary material containing the auxiliary substance 5.

In the molding step S5, the equipment used for molding the slag molded body 1 is not specifically limited, but can be appropriately selected and used from, for example, a briquette machine, a pan pelletizer, a drum mixer, a rotary mixer, a compression molding press, and the like. . Considering the production efficiency and the strength of the slag compact 1, it is preferable to use a briquette machine.

As described above, in the ratio calculation step S3, the amount of "effective acidic functional groups" contained in the auxiliary material 3 and the binder 4 measured in the measurement step S1 is used. Here, when the slag molded body 1 is put into a water environment, the amount of acidic functional groups from the auxiliary material 3 or the binder 4 is actually greater than the amount of "effective acidic functional groups" measured in the measurement step S1. may be supplied into the aquatic environment. This is because, for example, the acidic functional groups remaining inside the solid matter removed in the measurement step S1 may have an effect.

On the other hand, when the slag compact 1 is introduced into the water environment, the amount of acidic functional groups supplied from the auxiliary material 3 or the binder 4 to the water environment is actually larger than the amount of "effective acidic functional groups". Decrease is unlikely to occur.

Therefore, the slag molded body 1 manufactured by the manufacturing method of the present embodiment has an amount of acidic functional groups per 1 g of the slag molded body 1, which is calculated from the added amount of the auxiliary material 3, or the auxiliary material 3 and the binder 4. is, for example, X μmol/g (X≧50), the following can be said.

That is, when the slag molded article 1 is put into a water environment, the amount of acidic functional groups obtained by multiplying at least X μmol/g by the weight of the slag molded article 1 (more specifically, such an amount of acidic An amount of auxiliary substance 5) corresponding to the functional groups can be provided in the water environment. This is because it is considered that more acidic functional groups (in other words, the auxiliary substance 5) can actually be supplied into the water environment than the above calculated amount. Therefore, the slag molded body 1 can supply at least a predetermined amount of acidic functional groups to the water environment, and stably and efficiently elute iron into the water environment. can be done.

(Modification)
A slag molded body in a modified example of the present embodiment may be manufactured by combining the steelmaking slag 2 and the auxiliary material 3 , and in this case, may be configured without the binder 4 . Even if the binder 4 is not included, it is sufficient that it is molded in the molding step S5 and the amount of the acidic functional group is 50 μmol/g or more.

[Embodiment 2]
Other embodiments of the invention are described below. For convenience of description, members having the same functions as those of the members described in the above embodiments are denoted by the same reference numerals, and description thereof will not be repeated.

The slag compact 10 in this embodiment includes a covering portion 12 covering at least part of the surface of the mixture 11 of the steelmaking slag 2 and the auxiliary substance 5 . The covering portion 12 is mainly made of acidic soil and contains at least one of lignosulfonic acid and its metal salt.

In general, when alkali components derived from the steelmaking slag 2 are eluted in a water environment, the pH around the slag compact 10 may be increased. Therefore, the slag molded body 10 having the covering portion 12 can increase the elution amount of the iron component in the water environment and can suppress the increase in pH.

Acidic soil is, for example, red soil, Kanuma soil, humus soil, peat, etc., as long as it causes a decrease in pH when put into seawater, and does not cause deterioration of water quality of seawater or elution of harmful components. good. The red soil is reddish-brown or yellow-brown clay soil containing a large amount of iron oxide, such as the Kanto loam layer.

When acidic soil is put into seawater, not only does the pH drop, but ammonia nitrogen, nitrate nitrogen, phosphate phosphorus, and the like, which serve as nutritional components for phytoplankton and algae, are eluted. In particular, red soil and humus soil are preferable as a raw material for forming the coating portion because they are likely to exhibit the pH lowering effect due to the ion exchange described above.

Moreover, the covering part 12 may be formed so as to cover a part of the surface of the mixture 11, or may be formed so as to cover the entire surface.

In addition, by containing at least one of ligninsulfonic acid and a metal salt thereof, the covering portion 12 can increase the strength of the covering portion 12 and the iron elution amount. Since the coating portion 12 may peel off in a water environment and impair the iron elution effect at an early stage, the iron content and acidic functional groups contained in the coating portion 12 are not specified in the present invention, but the iron elution amount The iron content and the acidic functional group of the covering portion 12 may be adjusted as appropriate in consideration of the influence of .

[Additional notes]
The present invention is not limited to the above-described embodiments, but can be modified in various ways within the scope of the claims, and can be obtained by appropriately combining technical means disclosed in different embodiments. is also included in the technical scope of the present invention.

Examples of the slag compact according to one aspect of the present invention will be described below, but the present invention is not limited to these examples.

Table 1 shows the chemical compositions of steelmaking slag, auxiliary materials, and binders used as raw materials. The chemical composition was measured in the dry state for various adjuvants and binders.

Further, the steelmaking slag used as a raw material was pretreated as shown in Table 2. Then, various auxiliary materials and binders were pretreated as shown in Table 2, and the amount of acidic functional groups was measured by performing neutralization titration using NaOH as described in Embodiment 1. .

Steelmaking slag after pretreatment and various auxiliary materials and binders were mixed at the mixing ratio of each sample shown in Table 3, and mixed for 5 minutes using a kneader while adding water as appropriate.

Each mixed sample was granulated to a particle size of about 30 mm using a briquette machine, and the obtained granules were dried at 105° C. for 24 hours to produce a slag compact.

An iron elution test was performed on the produced slag compacts as follows.

100 g of the slag compact was immersed in 1000 ml of artificial seawater in a 2 L beaker and stirred for 1 hour at a rotational speed of 100 rpm using a stirrer. After stirring, the iron concentration in the solution obtained by suction filtration was measured by acid decomposition-inductively coupled plasma mass spectrometry. The detection limit for iron in this assay is less than 5 μg/L. Table 3 shows the results.

As shown in Table 3, in the examples in which the amount of acidic functional groups in the slag compact was 50 μmol/g or more, Fe was detected in the elution test (that is, the iron concentration in the solution was 5 μg/L or more). rice field). It can be seen that iron is eluted in the artificial seawater at the time when the slag compacts of the examples are placed in the artificial seawater and stirred for 1 hour (that is, at the initial stage of the introduction into the water environment). Moreover, iron was not eluted excessively. In general, the higher the amount of acidic functional groups, the higher the iron elution amount, and it was shown that the amount of iron elution can be adjusted by adjusting the amount of acidic functional groups. It can be seen that the slag compacts of the examples can stably and efficiently elute iron into the water environment.

On the other hand, in the comparative example in which the amount of acidic functional groups in the slag compact was less than 50 μmol/g, Fe was not detected in the elution test, and the iron concentration in the solution was less than 5 μg/L.

Reference Signs List 1, 10 slag compact 2 steelmaking slag 3 auxiliary material (first auxiliary material)
4 Binder (second auxiliary material)
5 auxiliary substance 11 mixture 12 coating

Claims (6)

steelmaking slag;
an auxiliary substance that has an acidic functional group and assists the elution of the iron in a water environment by a reaction between the acidic functional group and the iron contained in the steelmaking slag;
including a first auxiliary material containing the auxiliary substance;
The first auxiliary material is one or more selected from the group consisting of coffee grounds, compost, and bamboo charcoal,
A slag molded body characterized by containing the first auxiliary material at a rate of containing 50 μmol/g or more of the acidic functional group based on the amount of the acidic functional group contained in the first auxiliary material . steelmaking slag;
an auxiliary substance having an acidic functional group and assisting the elution of the iron in a water environment by a reaction between the acidic functional group and the iron contained in the steelmaking slag;
a first auxiliary material containing the auxiliary substance;
a second auxiliary material that combines the steelmaking slag and the first auxiliary material and contains the auxiliary material;
The first auxiliary material is one or more selected from the group consisting of coffee grounds, compost, and bamboo charcoal,
The second auxiliary material is one or more selected from the group consisting of ligninsulfonic acid, metal salts of ligninsulfonic acid, molasses, and starch,
Based on the amount of the acidic functional group contained in the first auxiliary material and the second auxiliary material, the first auxiliary material and the second auxiliary material contain the acidic functional group at a rate of 50 μmol/g or more. A slag molded body characterized by containing an auxiliary material . 3. The slag molded article according to claim 1 , wherein the slag molded article has a particle size or a total length of 10 mm or more and 40 mm or less. steelmaking slag;
an auxiliary substance that has an acidic functional group and assists the elution of the iron in a water environment by a reaction between the acidic functional group and the iron contained in the steelmaking slag;
containing 50 μmol/g or more of the acidic functional group,
further comprising a coating portion that coats at least a portion of the surface of the mixture of the steelmaking slag and the auxiliary substance;
The slag molded body, wherein the covering part is mainly made of acidic soil and contains at least one of lignosulfonic acid and a metal salt thereof. steelmaking slag;
a first auxiliary material having an acidic functional group and containing an auxiliary substance that assists the elution of the iron in a water environment by a reaction between the acidic functional group and the iron contained in the steelmaking slag; A method for manufacturing a molded body,
The first auxiliary material is one or more selected from the group consisting of coffee grounds, compost, and bamboo charcoal,
Based on the amount of the acidic functional group contained in the first auxiliary material, the steelmaking slag and the first A calculation step of calculating the mixing ratio with the auxiliary material of
and a mixing step of mixing the first auxiliary material and the steelmaking slag at the mixing ratio calculated in the calculating step. steelmaking slag;
a first auxiliary material containing an auxiliary substance having an acidic functional group and assisting the elution of the iron in a water environment by a reaction between the acidic functional group and the iron contained in the steelmaking slag;
A method for producing a slag compact, which combines the steelmaking slag and the first auxiliary material and includes a second auxiliary material containing the auxiliary material,
The first auxiliary material is one or more selected from the group consisting of coffee grounds, compost, and bamboo charcoal,
The second auxiliary material is one or more selected from the group consisting of ligninsulfonic acid, metal salts of ligninsulfonic acid, molasses, and starch,
Based on the amount of the acidic functional group contained in the first auxiliary material and the second auxiliary material, the above-mentioned a calculating step of calculating a mixing ratio of the steelmaking slag, the first auxiliary material, and the second auxiliary material;
a mixing step of mixing the first auxiliary material, the second auxiliary material, and the steelmaking slag at the mixing ratio calculated in the calculating step. .

Images