JP2018053304A - Sintered compact and method for producing the same - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a material capable of continuously, safely eluting divalent iron ions at a high concentration in the environment over a long period without generating a new environmental load in seawater.SOLUTION: Provided is a sintered compact 10 being a porous sintered compact comprising a plurality of iron grains 1 and a carbonaceous matter 3. In the sintered compact 10, a plurality of the iron grains 1 are stabilized by the carbonaceous matter 3. The carbonaceous matter 3 functions as a structure of carrying the iron grains 1, and further forms a local battery by contact with the iron grain 1. In the sintered compact 10, the ratio between the iron grains 1 and the carbonaceous matter 3 is 95:5 to 5:95 by the weight ratio between the iron element and the carbon element (iron element:carbon element), apparent specific gravity is 1.1 to 4.0, open porosity is 20 to 70%, and a collapse load is 50 N or more.SELECTED DRAWING: Figure 1

Description

  The present invention improves biological activity including microorganisms that inhabit the water area by eluting high-concentration divalent iron ions stably in seawater for a long period of time. It is related with the material for improving the bottom sediment environment.

  The bottom sediment of the closed water area, such as the inner part of the bay facing the metropolitan area, has become sludge due to the eutrophication progressed due to the inflowing domestic wastewater and industrial wastewater. Therefore, especially in the summer, bad odors such as hydrogen sulfide generated by the eutrophic bottom layer becoming hypoxic, and blue tides caused by the inversion of the upper and lower layers by agitation by the wind frequently occur. Deterioration and damage to fisheries are major problems.

  In order to improve the sediment environment and reduce the generation of odors and blue tides, measures such as dredging and aeration are being implemented. However, since sludge contains a lot of water and may contain heavy metals, final disposal is difficult, and there is a problem that the environment is further deteriorated by dredging work. The forced aeration process has a problem of high cost because it is necessary to continuously turn on the power.

  In addition, a method of covering the sediment is also performed, and a method of improving the sediment environment by physicochemical action by spraying magnesium hydroxide, lime, blast furnace slag, or the like (for example, Patent Document 1). ) Has been implemented so far. Moreover, in recent years, by improving the microbial activity of phosphorus, sulfur traps, bottom beds, and water areas by spraying materials that elute divalent iron ions (for example, Patent Documents 2 to 4) Has also been proposed.

However, the spraying of blast furnace slag as in Patent Document 1 mainly involves physical containment using the hydraulic properties of the slag, and the amount of iron eluted from the slag is considered to be not so large, so it has immediate effect. I can't expect it.
Moreover, about materials like patent document 2 and 3, although the amount of iron elution is large in order to utilize the local battery effect | action of iron and carbon, water-soluble organic substances, such as starch and shochu, are used as a binder. Therefore, once the lump has actually collapsed, the contact between iron and carbon tends to be insufficient, and there is a question about long-term bottom sediment improvement. Further, there is a problem that the water-soluble organic substance used as the binder increases the biological oxygen requirement (BOD) and chemical oxygen demand (COD) of the sediment environment.
Furthermore, since Patent Document 4 uses organic matter mainly organic industrial waste to sinter iron, it is reduced by the elution efficiency of iron or new due to harmful heavy metals contained in waste. There is a possibility of serious contamination.

Japanese Patent No. 443095 Japanese Patent No. 4710036 Japanese Patent No. 5258171 JP 2012-161799 A

  An object of the present invention is to provide a material that can continuously elute divalent iron ions in the environment stably over a long period of time without generating a new environmental load in seawater. It is.

  As a result of intensive studies to achieve the above-mentioned problems, the present inventors can solve the above-mentioned problems by granulating and sintering a mixture of carbonaceous materials such as iron particles and coke powder using an organic binder. As a result, the present invention has been completed.

That is, the sintered body of the present invention is a porous sintered body containing iron particles and a carbonaceous material,
The ratio between the iron particles and the carbonaceous material is 95: 5 to 5:95 in terms of the weight ratio of iron element to carbon element (iron element: carbon element),
The apparent specific gravity is 1.1 to 4.0,
The open porosity is 20-70%,
And,
The crushing load is 50 N or more.

  In the sintered body of the present invention, the crushing load after being immersed in salt water having a concentration of 5% by weight for 10 days may be ½ or more of the crushing load before being immersed in salt water.

Further, the sintered body of the present invention may have an elution amount of divalent iron (Fe ²⁺ ) ions in salt water after being immersed in salt water having a concentration of 5% by weight for 10 days.

  Moreover, the sintered body of the present invention is made from a steel material or iron oxide whose iron particles contain at least one element of carbon (C), nickel (Ni), and manganese (Mn), and carbon. 50% by weight or more of the material may be pitch coke powder.

  The sintered body of the present invention may be used as an environment improving material, and is preferably used as a bottom environment improving material.

The method for producing a sintered body according to the first aspect of the present invention is a method for producing any one of the above-mentioned sintered bodies,
A step of heating and kneading an iron raw material, a carbonaceous raw material and an organic binder to produce a composite thereof;
Sintering the composite at 500 ° C. or higher in an inert or reducing atmosphere to obtain a sintered body;
It is characterized by including.

The method for producing a sintered body according to the second aspect of the present invention is a method for producing any one of the above-mentioned sintered bodies,
Mixing and kneading an iron raw material, a carbonaceous raw material, an organic binder and water or an organic solvent to obtain a mixture thereof;
Granulating the mixture;
Sintering the granulated product at 500 ° C. or higher in an inert or reducing atmosphere to obtain a sintered body;
It is characterized by including.

  Since the sintered body of the present invention is a sintered body of iron and carbon, the strength of the granulated product is high, and it is difficult to collapse while having a low bulk density and a high open porosity. For this reason, since the favorable contact of iron and carbon continues continuously, it is possible to continue eluting high concentration of divalent iron ions into the sediment environment by the local battery effect.

  In addition, since the sintered body of the present invention is obtained by sintering an iron raw material and a carbonaceous raw material using an organic binder, it is an inexpensive and safe material and can be dispersed in a large amount. Moreover, there are no concerns such as contamination with heavy metals, increased BOD, and COD due to use, and no new environmental load is generated.

It is a schematic diagram which shows the external appearance structure of the sintered compact which concerns on one embodiment of this invention. It is explanatory drawing which expands and shows the principal part of the sintered compact shown in FIG.

Embodiments of the present invention will be described below with reference to the drawings as appropriate. FIG. 1 is a diagram schematically showing an external configuration of a sintered body according to an embodiment of the present invention. FIG. 2 is an explanatory view showing an enlarged main part of the sintered body shown in FIG.
As shown in FIG. 1, the sintered body 10 of the present embodiment is a porous sintered body containing a plurality of iron particles 1 and a carbonaceous material 3. In the sintered body 10, the plurality of iron particles 1 are fixed by the carbonaceous material 3. The carbonaceous material 3 functions as a structure that supports the iron particles 1 and forms a local battery by contact with the iron particles 1. As will be described later, the sintered body 10 is a porous body having a predetermined apparent specific gravity and open porosity, and a plurality of pores 5 are formed. As illustrated in FIG. 2, the carbonaceous material 3 may be present in a state in which a carbonaceous raw material-derived portion 3 a such as coke can be distinguished from an adhesive portion 3 b derived from an organic material such as an organic binder, or The carbonaceous material 3 may be formed substantially integrally in a state where the two cannot be distinguished from each other.

<Composition>
The weight ratio between the iron particles 1 and the carbonaceous material 3 in the sintered body 10 can be adjusted according to the persistence of divalent iron ion elution in water. For example, iron particles 1: carbonaceous material 3 = 95: 5. It is the range of -5: 95, Preferably it is 20: 80-80: 20, More preferably, it is 50: 50-80: 20. When the weight ratio of the iron particles 1 to the carbonaceous material 3 is less than 5% by weight, the carbonaceous material 3 is too much, the contact area with water is small, the supply capacity of divalent iron ions is low, and the sustainability is deteriorated. On the other hand, if the weight ratio of the iron particles 1 to the carbonaceous material 3 exceeds 95% by weight, a local battery is formed and sufficient iron ion supply capability is provided, but it becomes brittle as an integrated material due to low carbon content, Therefore, the iron particles 1 are lost or the sintered body 10 is easily collapsed. The sintered body 10 contains oxygen (10% by weight or less) and other trace elements (Ni, Mn, etc.) in addition to iron and carbon, but the weight ratio is simply that of the iron element and the carbon element. Say ratio. Further, the carbonaceous material 3 includes carbon obtained by firing and carbonizing an organic material such as an organic binder in addition to a carbonaceous material such as coke to be blended in advance.

<Apparent specific gravity / open porosity>
The sintered body 10 of the present embodiment is preferably a porous sintered body having an apparent specific gravity (bulk density) of 1.1 to 4.0 and an open porosity of 20 to 70%. Here, the apparent specific gravity is more preferably 1.3 to 3.5. If the apparent specific gravity is less than 1.1, it will float in the water and the sintered body 10 will easily flow out of the spray area. If it exceeds 4.0, the internal voids will decrease, so the amount of divalent iron ions eluted. Will decrease. Further, the open porosity is more preferably 30 to 60%. If the open porosity is less than 20%, the elution amount of divalent iron ions decreases, and if it exceeds 70%, the strength of the material is lowered and the material tends to collapse, which is not preferable.

<Crushing load>
In the sintered body 10 of the present embodiment, the crushing load is preferably 50 N or more, and more preferably 80 N or more. When the crushing load is less than 50 N, particles are brought into contact with each other by peristalsis caused by a water flow at the time of spraying or after spraying, and the sintered body 10 is easily broken. Thus, when the sintered compact 10 is destroyed by a water flow, the effect of a local battery will lose | disappear because iron and carbon isolate | separate, and there exists a possibility that the elution of bivalent iron ion may decrease. From such a viewpoint, the sintered body 10 of the present embodiment has a crushing load after 50 days of immersion in 5% by weight salt water of 50 N or more, and maintains 1/2 or more of the crushing load before immersion in salt water. More preferably, it is. The effect of the local battery can be maintained for a long period of time when the crushing load after 10 days of immersion in 5% by weight salt water is ½ or more of the crushing load before immersion in salt water.

<Elution amount of iron ions>
Further, in the sintered body 10 of the present embodiment, the elution amount of divalent iron ions after 10 days of immersion in 5% by weight salt water is preferably 2 ppm or more, more preferably 5 ppm or more, and further preferably 10 ppm or more. It is desirable to be. In this way, by supplying a high concentration of divalent iron ions into the sediment environment, hydrogen sulfide and phosphorus can be trapped and a water quality improvement effect can be obtained in a short period of time. It becomes possible to raise the activity and raise the higher water quality improvement effect.

<Thermal weight reduction rate>
Furthermore, in the sintered body 10 of the present embodiment, the weight reduction rate of the sintered body 10 at a temperature from room temperature to 500 ° C. in thermogravimetric analysis in an inert atmosphere is preferably 3% or less. A weight reduction rate from room temperature to 500 ° C. of 3% or less indicates that the organic binder and coke powder are completely carbonized. For this reason, the sintered body 10 is unlikely to collapse when sprayed in water, and an organic compound that is harmful to the environment does not elute from the sintered body 10, so that no new environmental load is caused by this material.

<Iron particles>
The sintered body 10 of the present embodiment is eluted as divalent iron ions into water due to the formation of a local battery by contact of zero-valent metallic iron with carbon, and the bad odor (sulfurization) particularly in anoxic conditions in summer. In addition to suppressing red tides (abnormal plankton generation), it also contributes to the regeneration of seaweed beds by firewood. For this reason, the iron particles 1 may be iron oxide at the stage of the iron raw material as long as it is metallic iron in the final product after firing, but preferably carbon (C ), Manganese (Mn), nickel (Ni) at least one or more steel material containing 0.5 wt% or more is preferably used as a raw material. Examples of the iron particles 1 include cast iron, carbon steel, and stainless steel, but are not limited thereto.

  Since the iron particles 1 constituting the sintered body 10 of the present embodiment are released into the water as divalent ions due to the local battery effect with the carbon sintered in the seawater, the iron particles 1 gradually become smaller. Therefore, the particle size of the iron particles 1 to be used is preferably 200 to 5 mesh according to JIS standards. If the particle size is too small, such as less than 200 mesh, the contact period with water is shortened, and there is a risk of ignition or dust explosion during production. On the other hand, if it is too large to exceed 5 mesh, mixing, kneading and granulation become difficult. The shape of the iron particles 1 may be a granular shape such as a sphere, for example, and may be an irregular lump shape. In FIG. 1 and FIG. 2, for convenience of explanation, the iron particles 1 are drawn in a polyhedral shape having a regular hexagonal shape in plan view, but the present invention is not limited to this.

<Carbonaceous material>
In the present invention, the carbonaceous material 3 is necessary for forming a local battery with iron, and contact with iron is very important. As a raw material (carbonaceous raw material) of the carbonaceous material 3 for forming a local battery, for example, coke, charcoal, coal powder, graphite, coal tar pitch, organic compounds, polymerized carbides, and the like can be used. These may be used alone or in combination of two or more. The shape of the carbonaceous raw material is not limited, but it is preferably a granular shape or a lump shape in which the number of contact points with the iron particles 1 is increased after sintering and a local battery function is easily exhibited, and may have an irregular appearance shape. . 50% by weight or more of the carbonaceous raw material to be blended with the iron raw material is preferably a solid carbonaceous material that melts at a high temperature and does not exhibit fluidity. Examples of such a solid carbonaceous material include graphite, coke powder, and the like. In particular, pitch carbon coke powder having a temperature history of 450 ° C. or higher and having conductivity is more preferable.

  Pitch coke powder with a temperature history of 450 ° C or higher does not melt and flow at high temperatures like coal tar pitch and polymer materials, so it is easy to maintain a granulated shape and is a porous sintered body 10 is easy to obtain. The particle size of the carbonaceous raw material represented by coke powder is, for example, in accordance with JIS standards in order to increase the number of contact points with the iron particles 1 after sintering so as to improve the local battery function and improve granulation. 300-5 mesh is good. If the particle size is larger than 5 mesh, the number of contact points for forming the local battery with the iron particles 1 is decreased, and the elution efficiency is lowered. If the particle size is smaller than 300 mesh, the bulk specific gravity is too small, and the mixing property and granulating property are reduced. In addition to worsening, there is a risk of fire and dust explosion.

  As the coke powder, any coke obtained from petroleum-based or coal-based heavy oil can be used. Among these, coke obtained from coal-based heavy oil is likely to become mesophase rich and needle coke, so it has high conductivity, and as a result, current as a local battery easily flows and iron ions are likely to be generated. preferable.

<Binder>
The sintered body 10 according to the present embodiment is a sintered body of carbon having conductivity that is not an organic substance and iron, and an organic binder is used in the manufacturing process. By using an organic binder, the agglomeration of powdery raw materials is promoted to increase the granulation speed, the yield is improved, and the physical properties (strength, surface state, collapse resistance, etc.) of the sintered body 10 are improved. Furthermore, the adhesion between the iron particles 1 and the carbonaceous material 3 can be strengthened. From such a viewpoint, the organic binder has a fixed carbon content of 20% by weight or more, and includes a pitch containing a large amount of aromatic rings, a phenol resin, lignin, or a lignin sulfonate having a phenol component as a main component. Among these, coal tar pitch excellent in fixed carbon and binding force is most preferable. As the organic binder, water-soluble or non-water-soluble organic binders that can obtain only a weak adhesive state that allows water to easily penetrate between the iron particles 1 and the carbonaceous material 3 are not preferable.

In the coal tar pitch, hydrogen, oxygen, nitrogen, sulfur and the like other than fixed carbon are decomposed and volatilized by firing at 500 ° C. or higher in an inert or reducing atmosphere, and substantially 95% or more of the fired product becomes carbon. In addition, coal tar pitch releases hydrogen, oxygen, nitrogen, sulfur, and the like during firing, thereby forming voids, increasing the contact area between water and iron, and efficiently contributing to iron ion generation. Furthermore, since the coal tar pitch becomes a strong carbide having conductivity, it becomes a good binder for fixing the iron particles 1 and the carbonaceous material 3.
Of the coal tar pitches, those having a fixed carbon amount of 50% or more are preferable from the standpoint of maintaining the shape during firing. Examples of such coal tar pitches include BP and IP manufactured by Seachem Corporation (both Product name).

  The organic binder is preferably blended within a range of, for example, 5 to 20% by weight with respect to 100 parts by weight of the mixture of the iron raw material and the carbonaceous raw material. When the organic binder is less than 5% by weight, there is no effect as a binder. When the organic binder exceeds 20% by weight, the organic binder melts during firing, and a desired shape, suitable apparent specific gravity, and open porosity cannot be obtained. In addition, when a composite is formed only with an iron raw material and an organic binder such as coal tar pitch, the organic binder melts during firing, and the shape of the composite cannot be maintained.

The organic binder typified by coal tar pitch is preferably a granular material so as to be uniformly mixed with the iron raw material and the carbonaceous raw material. As a particle size of this granular material, 200-32 mesh is good, for example. If the particle size of the organic binder is too small, the apparent specific gravity will be too small and the mixing and kneading properties will deteriorate, and if it is too large, the mixing, heating and melting and the inside of the granulated product may become non-uniform.
Further, the coal tar pitch preferably has a softening point at 30 to 150 ° C., for example. The use of coal tar pitch with such a softening point is very convenient for granulation methods using intermolecular forces such as briquette machines that form (granulate) mixtures while heating and dry granulation such as melt granulation. Is good. After granulation by them, the sintered body 10 can be efficiently manufactured because it can be fired as it is.

  Moreover, in addition to coal tar pitch, a phenol resin, etc., you may add the granulation adjuvant for improving granulation property to an organic binder. The granulation aid is not particularly limited as long as it becomes the carbonaceous material 3 during sintering. As examples of the granulation aid, gelatin, starch paste, molasses, lignin sulfonate, konjac flying powder, sodium alginate, polyvinyl alcohol, dextrin, ethyl cellulose, carboxymethyl cellulose, polyacrylamide and the like are suitable. In the case of using a granulation aid, the weight blending ratio of the organic binder and the granulation aid (organic binder: granulation aid) is preferably, for example, 100: 0 to 30:70. By adjusting the blending ratio of the granulation aid so as to be within such a range, the sintered body having a desired shape can be obtained without adversely affecting the apparent specific gravity, open porosity, crushing strength, etc. during sintering. 10 can be manufactured easily.

  In the sintered body 10 of the present embodiment, in addition to iron and carbon, for example, silicon as long as it does not hinder elution of divalent iron ions due to physical properties such as crushing load, apparent specific gravity and open porosity, and local battery effect. Further, it may further contain a mineral-based inorganic substance containing an element such as aluminum, magnesium, calcium, phosphorus, sodium, or potassium.

[Production method]
In the sintered body 10 of the present embodiment, an organic binder is blended with a mixture of an iron raw material and a carbonaceous raw material, granulated into a desired shape as necessary, and then heated to 500 ° C. or higher in an inert or reducing atmosphere. Manufactured by sintering at temperature.

An example of a preferred method for producing the sintered body 10 is as follows:
A step of heating and kneading iron particles or iron oxide particles, a carbonaceous raw material and an organic binder as an iron raw material to produce a composite thereof;
Sintering the composite at 500 ° C. or higher in an inert or reducing atmosphere to obtain a sintered body 10;
A step of cooling the obtained sintered body;
Can be included.

Another example of a preferable manufacturing method of the sintered body 10 is as follows.
A step of mixing and kneading iron particles or iron oxide particles as an iron raw material, a carbonaceous raw material, an organic binder, and water or an organic solvent to obtain a mixture thereof;
A step of granulating the mixture to obtain a granulated product;
Sintering the granulated product at 500 ° C. or higher in an inert or reducing atmosphere to obtain a sintered body 10;
A step of cooling the obtained sintered body;
Can be included.

  The blending order of the iron raw material, carbonaceous raw material, and organic binder is not particularly limited. The mixture of the iron raw material and the carbonaceous raw material may be prepared first, and then the organic binder may be blended, or all raw materials may be blended at once. May be. The same applies when other additives are blended.

  As for the blending method, general mixers and kneaders such as various blenders, mixers and kneaders can be used.

The mixture in which various raw materials are blended is granulated so as to have an arbitrary shape as necessary. The granulated shape is not particularly limited, and may be, for example, spherical, spheroid, cylindrical, or indefinite shape. Among these, when used as a sediment environment improving material, a contact area with seawater or the like becomes large, and thus a spherical shape or a spheroid shape is preferable. Further, the size of the granulated product is not particularly limited because the preferred shape varies depending on the environment used as the bottom sediment environment improving material, but in the case of a sphere, the diameter is 5 mm or more, preferably A diameter of about 5 to 100 mm is preferable. Moreover, when the shape of a granulated material is other than a spherical shape, it is preferable to make it the magnitude | size which becomes a volume comparable as a sphere with a diameter of 5-100 mm.
Although granulation can be performed manually, it is preferable to use a granulator such as a pelletizer or a briquette machine in terms of workability, safety, shape control, and the like.

The granulated raw material mixture is dried at 60 ° C. or higher when water or an organic solvent is used during granulation, and then sintered in an inert or reducing atmosphere at 500 ° C. or higher. For sintering, for example, equipment such as a lead hammer furnace, a top charge furnace, a shuttle furnace, a tunnel furnace, a rotary kiln, a roller hearth kiln, or a microwave can be used, but is not particularly limited thereto. Further, the calcining treatment may be either a continuous type or a batch type. The sintering temperature is more preferably 700 ° C., further preferably 900 ° C., and most preferably 1000 ° C. or higher. By sintering in an inert or reducing atmosphere at 500 ° C. or higher, the organic binder can be reliably carbonized and the iron oxide contained in the iron raw material can be reduced. The sintered body 10 obtained by firing can be used as a bottom environment improving material having no environmental load that expresses rapid divalent iron ion elution and high crushing strength.
The firing may be performed a plurality of times, and the sintered material once sintered may be immersed in an aqueous solution of a compound such as iron or manganese and then fired again.

  The sintered body 10 that has undergone the sintering process is then gradually cooled in an inert or reducing atmosphere, or after being gradually cooled, and then allowed to cool to a temperature at which it can be handled in an air atmosphere. Can be used as

EXAMPLES Hereinafter, although the content of this invention is demonstrated concretely based on an Example, this invention is not limited to the range of these Examples. In the following examples, various measurements and evaluations are as follows unless otherwise specified.

[Apparent specific gravity measurement]
A value (= W1 / V) obtained by dividing the volume (V) of the granulated product by the weight (W1) of the granulated product dried at 105 ° C. was regarded as an apparent specific gravity, and an average value of 5 granulated products was adopted.

[Open porosity measurement]
The granulated product dried at 105 ° C. is immersed in pure water, degassed for 2 hours at 25 ° C. under vacuum (−0.88 MPa), taken out, and the water adhering to the surface of the granulated product is removed with a paper waste. Wipe off and measure the weight of the granulated product containing water (W2). The weight increase due to water content was regarded as the volume increase, and (W2-W1) / V was defined as the open porosity, and an average value of 5 granulated materials was adopted.

[Crushing load measurement]
The load at which the granulated material collapses (the buckling load) was taken as the crushing load. For the load measurement, a hydraulic REH type 100 kN tensile-compression tester manufactured by Shimadzu Corporation was used, a compression load was applied to the sample, the maximum load was set as a crushing load, and an average value of five granulated materials was adopted.

[Thermal weight reduction rate measurement]
The granulated material was pulverized in a mortar, and thermogravimetric analysis (TGA) was performed in a nitrogen atmosphere to measure the thermogravimetric reduction rate. For the measurement, a rapid heating differential thermobalance R-TG-DTA / H8120 manufactured by Rigaku Corporation was used, and the rate of temperature increase was 15 ° C./min. The rate of weight loss when the temperature was raised from 100 ° C. to 500 ° C. was measured. did.

[Measurement of iron content of fired body]
The baked granulated product was pulverized in a mortar and measured by ICP emission spectroscopy.

[Fixed carbon measurement]
It measured based on JIS K-2425.

[Salt water immersion test and measurement of divalent iron ion concentration and COD]
A sodium chloride aqueous solution having a concentration of 5% by weight was prepared, treated with ultrasonic waves for 10 minutes, and then degassed at 25 ° C. under vacuum (0.88 MPa) for 60 minutes, and used for the salt water immersion test. The salt water immersion was performed in a desiccator in a nitrogen atmosphere.
A 20-fold amount of a sodium chloride aqueous solution is placed in a glass sample bottle with respect to the weight of the granulated product (for example, when the granulated product is 5 g, it is immersed in a 100 g sodium chloride aqueous solution). This is deaerated in a vacuum desiccator for 60 minutes under vacuum (0.88 MPa), and nitrogen gas is sealed until atmospheric pressure is reached. After standing for 10 days, the supernatant liquid was measured for divalent iron ion concentration and COD by a pack test (registered trademark; Kyoritsu Riken Co., Ltd.).

[Granulation method]
・ Granulation method A
A predetermined amount of raw materials (iron powder, carbon powder, organic binder) were measured, mixed and kneaded by a kneader at 150 ° C., and spherical particles having a diameter of about 1 cm were prepared manually (rounded with a palm to be spherical).
・ Granulation method B
Measure a specified amount of raw materials (iron powder, carbon powder, organic binder), mix in an alumina mortar, add 10-20% by weight of water with respect to the solid content, and manually add spherical particles with a diameter of about 1 cm (palm) To create a spherical shape. Regarding Example 6, water was not added because the binder was water-insoluble and was already in solution.
・ Granulation method C
A predetermined amount of raw materials (iron powder, carbon powder, organic binder) are measured, mixed with a V blender, and using a bread granulator (model 1237-S-3 Yoshida Seisakusho), an inclination angle of 45 ° C, At a rotation speed of 40 rpm, 20 parts by weight of water was sprayed on 100 parts by weight of the raw material to produce spherical particles having a diameter of about 1 cm.
・ Granulation method D
After measuring a specified amount of raw materials (iron powder, carbon powder, organic binder, water), mixing and kneading with a mixing stirrer, using Briquetta (BGS IN type Shinto Kogyo Co., Ltd.), pocket: 18 × 14 × Rugby ball-like particles were produced under the conditions of a depth of 3.3 mm, roll rotation: 8 rpm, and roll pressure: 12 KN.
In the granulation methods B, C, and D, when water was used, the water was removed by drying at 70 ° C.

[Baking method]
The granulated product was put in a reducing atmosphere firing furnace packed with coke powder, heated at 100 ° C./hour, and fired at 400 ° C., 900 ° C., and 1200 ° C. for 2 hours, respectively. After firing, it was allowed to cool naturally, and the granulated product was taken out when it became 50 ° C. or lower.

[Raw materials]
Iron powder Cast iron powder (Takeuchi Kogyo Co., Ltd., 28 mesh under product, carbon: 2 to 4% by weight, Si: 4% by weight or less, Mn: 0.5 to 1.5% by weight, P: 0.03% by weight or less, S: 0.03% by weight or less)
・ Coke powder Pitch coke powder (Nippon Steel & Sumikin Chemical Co., Ltd. 200 mesh under, 50-200 mesh, 6-9 mesh)
・ Organic binder (1) Coal tar pitch (manufactured by Nippon Steel & Sumikin Chemical Co., Ltd., softening point: 85 ° C., fixed carbon content: 58% by weight, 50 mesh under)
(2) Gelatin (fixed carbon content: 16.2% by weight, manufactured by Wako Pure Chemical Industries)
(3) Soluble starch (fixed carbon content: 9.3% by weight, manufactured by Wako Pure Chemical Industries)
(4) Magnesium lignin sulfonate (manufactured by Nippon Paper Industries Co., Ltd., trade name Sun Extract P321, magnesium lignin sulfonate: 59% by weight, reducing saccharide: 17% by weight, sugar modified product: 18% by weight, inorganic salts: 6% by weight Ash content: 12% by weight, fixed carbon content obtained by subtracting ash content in advance: 25% by weight)
(5) Ethyl cellulose (trade name EC vehicle EC-100 manufactured by Nisshin Kasei Co., Ltd. Solid content concentration 9% by weight Fixed carbon content of ethyl cellulose powder: 1% by weight or less)

Examples 1-9, Comparative Examples 1-7
The sintered bodies of iron particles and carbonaceous materials, which are examples and comparative examples, are prepared by the blending and granulation methods shown in Tables 1 to 3, and the respective crushing loads and the shape of the granulated material after 10 days of salt water immersion and crushing. The load, the crushing load maintenance rate, the iron ion generation concentration, and the COD were measured and evaluated as a sediment environment improving material.
The results are also shown in Tables 1-3.

  Although the sintered bodies of Examples 1 to 9 are porous sintered bodies containing iron particles and a carbonaceous material, since the iron particles and the carbonaceous material are firmly bonded, salt water imitating seawater It does not collapse or the crushing strength does not decrease even if it is immersed in, and has excellent characteristics as a bottom environment improving material as compared with the sintered bodies of Comparative Examples 3 to 6. That is, the sintered bodies of Examples 1 to 9 can continue to release a high concentration of divalent iron ions by a local battery action while maintaining the shape for a long period of time. Moreover, since the organic binder which sinters iron and carbon is fully carbonized, the sintered compact of Examples 1-9 does not produce new environmental burdens, such as a raise of COD.

  As described above, the sintered body 10 of the present embodiment is excellent as an environment improving material, and is particularly excellent as a bottom environment improving material in a closed sea area.

  As mentioned above, although embodiment of this invention was described in detail for the purpose of illustration, this invention is not restrict | limited to the said embodiment, A various deformation | transformation is possible.

  DESCRIPTION OF SYMBOLS 1 ... Iron particle, 3 ... Carbonaceous material, 3a ... Carbonaceous raw material origin part, 3b ... Adhesion part, 5 ... Pore, 10 ... Sintered body

Claims (8)

A porous sintered body containing iron particles and a carbonaceous material,
The ratio between the iron particles and the carbonaceous material is 95: 5 to 5:95 in terms of the weight ratio of iron element to carbon element (iron element: carbon element),
The apparent specific gravity is 1.1 to 4.0,
The open porosity is 20-70%,
And,
A sintered body having a crushing load of 50 N or more.   2. The sintered body according to claim 1, wherein a crushing load after being immersed in 5% by weight of salt water for 10 days is ½ or more of a crushing load before being immersed in salt water. 2. The sintered body according to claim 1, wherein an elution amount of divalent iron (Fe ²⁺ ) ions in the salt water after being immersed in a salt water having a concentration of 5% by weight for 10 days is 2 ppm or more.   The iron particles are made from a steel material or iron oxide containing at least one element of carbon (C), nickel (Ni), manganese (Mn), and 50% by weight or more of the carbonaceous material is pitch coke powder. The sintered body according to claim 1, wherein the sintered body is made from a raw material.   The sintered body according to any one of claims 1 to 4, which is an environmental improvement material.   The sintered body according to any one of claims 1 to 4, which is a bottom environment improving material. A method for producing a sintered body for producing the sintered body according to any one of claims 1 to 6,
A step of heating and kneading an iron raw material, a carbonaceous raw material and an organic binder to produce a composite thereof;
Sintering the composite at 500 ° C. or higher in an inert or reducing atmosphere to obtain a sintered body;
The manufacturing method of the sintered compact characterized by including this. It is a manufacturing method of a sintered compact which manufactures a sintered compact given in any 1 paragraph of Claims 1-5,
Mixing and kneading an iron raw material, a carbonaceous raw material, an organic binder and water or an organic solvent to obtain a mixture thereof;
Granulating the mixture;
Sintering the granulated product at 500 ° C. or higher in an inert or reducing atmosphere to obtain a sintered body;
The manufacturing method of the sintered compact characterized by including this.

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