JP2000334496A - Soil-base inorganic material and its use method - Google Patents

Abstract

PROBLEM TO BE SOLVED: To obtain a soil-base inorganic material which lens itself to high-grade civil engineering and construction materials, vegetation afforestation, or the like, at a low cost by treating mudsoil, such as building sludge and dredging mud, and to provide its use method. SOLUTION: The soil-base inorganic material consists of mudsoil powder obtained by drying mudsoil to a dispersed state and at least a solidifying material. The mudsoil powder may be mainly composed of the powder of silt or clay. The solidifying material essentially consisting of the fine powder of blast furnace granulated slag may be utilized for the solidifying material as well. This solidifying material may be used simply by adding it together with water to the soil-base inorganic material and solidifying the same.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION The present invention relates to mud such as construction sludge and dredged mud (including muddy and muddy mud depending on the water content). ), Especially in mud, especially difficult to treat,
The present invention relates to a soil inorganic material which can be used for civil engineering construction materials, vegetation revegetation, etc., obtained by treating silt or clay consisting of fine particles, most of which are discarded, and a method of using the same.

[0002]

2. Description of the Related Art A large amount of construction sludge containing water is generated during tunnel excavation work, building work, and the like, and a large amount of dredging sludge containing water is also discharged during harbor construction and dredging of bottom soil of lakes and marshes. Is done. Its emissions amount to over a thousand million tons per year.

[0003] Most of these mud are composed of fine particles having a particle size of several tens of µm and a large amount of water, and cannot be piled up on a dump truck, and are difficult-to-treat materials that cannot be walked on by humans. Has become. Therefore, it cannot be reused as it is, and most of it has conventionally been landfilled as sludge of industrial waste. However, recycling is being performed, albeit slightly, and in particular, in recent years, development of technologies for recycling such mud has been actively pursued in various fields.

For example, for construction sludge, technical guidelines for recycling are compiled by the Ministry of Construction, and technical standards for sediment separation, dehydration treatment, stabilization treatment, and the like are set forth. As the dewatering method, various techniques such as centrifugal filtration (screw decanter), pressure filtration (filter press), pressure squeezing filtration (roll press), and high-pressure thin layer dehydration can be applied. I have.

[0005] The above-mentioned stabilization treatment is a treatment for chemically improving the properties of construction sludge by mixing an improving material. The improving materials include cement and cement-based improving materials, lime (quick lime, slaked lime).
And lime-based improving materials are applied.

[0006] Regarding the dredged soil as well, solids are settled and separated in a raw mud tank, and the settled mud is extracted by a pump and added with a dehydration aid, then concentrated and dewatered, and used or used as residual soil. It has been landfilled. In some cases, a solidifying agent is added to the dewatered cake and used as cover soil. In addition,
The treated water discharged in the above-mentioned steps of concentration and dehydration is discharged after being subjected to treatments such as coagulation sedimentation and neutralization.

[0007] These recycled products are also being used as embankments, backfill materials, etc., when they exhibit strength enough to be used for embankments.

[0008]

In the prior art described above, dewatering by a screw decanter or filter press used in dewatering mud, roll dewatering,
In high-pressure thin-layer dehydration or the like, mud solidifies during dehydration and does not turn into a powdery state, so that it is difficult to uniformly mix with an improving material when performing a stabilization treatment. Therefore, the performance (strength) of the recycled material obtained by the treatment for improving the properties of the sludge by mixing the above-mentioned improving material is low, and in order to enhance the performance, a large amount of the improving agent must be added, which increases the cost. become. Also,
There is a limit in the strength itself of the obtained reclaimed soil, and there is a problem that high value-added products cannot be manufactured.

[0009] The present invention, as a part of the technology for positively promoting the recycling of mud such as construction sludge and dredging mud, treats these muds and uses them at low cost for high-grade civil engineering building materials and vegetation greening. An object of the present invention is to provide a usable soil inorganic material and a method for using the same.

[0010]

Means for Solving the Problems In treating mud containing a large amount of water, such as construction sludge and dredging mud, the present inventors have conducted various studies on pretreatment of mud.
As a result, the mud is subjected to a drying treatment so as to be in a state in which the particles of the mud are small and the particles of the mud are dispersed, thereby forming a fine-grained mud. ) Or uniform mixing with additives for imparting functions such as water permeability and pH adjustment, and the performance (eg, strength) of the resulting product (soil-based inorganic material)
Have been found, and the present invention has been accomplished.

The gist of the present invention resides in the following (1) a soil-based inorganic material and (2) a method of using the same.

(1) A soil-based inorganic material comprising mud powder obtained by drying mud in a dispersed state and at least a solidified material.

[0013] The mud powder may be mainly composed of silt or clay powder.

It is also possible to use a solidified material mainly composed of granulated blast furnace slag powder.

In addition to the solidifying material, at least one of a neutralizing material and a ventilation material may be added.

(2) A method of using a soil-based inorganic material which solidifies by adding water to the soil-based inorganic material according to the above (1).

Here, the “mud” is, as described above,
This refers to construction sludge with a large amount of moisture generated by construction work (excluding dredging) such as tunnel excavation work and building work, dredged mud generated by harbor work and dredging of the bottom soil of lakes, and other mud-like inorganic powder. Further, soil generated in a specific area (for example, “red soil” in Okinawa Prefecture) is also included in “mud”. This is because when treated, water is added to show properties similar to construction sludge and dredging mud.

The term "silt or clay" refers to mud from which relatively coarse-grained gravels and sand have been removed, and most of which are mud having a particle size of 75 μm or less. In addition, exceeding 5 μm and 75
Silt up to μm is clay and 5 μm or less is clay. Also, 7
Sand exceeding 5 μm and up to 2 mm is called sand, and sand exceeding 2 mm is called gravel.

Further, "drying the mud in a dispersed state" means performing a drying treatment so that the mud particles are not aggregated but in a dispersed state. Specifically, the water content is reduced to 70% by weight (hereinafter, “%” means “% by weight”) by a drying method described below (pulse jet engine, spray dryer or medium fluidized bed type dryer).
It means to dry below. The mud is originally composed of fine particles except for relatively coarse gravels and sand, and can be made into fine-grained mud by drying the mud in a dispersed state.

[0020]

BEST MODE FOR CARRYING OUT THE INVENTION Hereinafter, the present invention will be described in detail.

The soil-based inorganic material of the present invention is a material for civil engineering construction materials comprising mud powder obtained by drying mud in a dispersed state and at least a solidified material as described above.

The mud powder is a finely divided mud powder having a water content of 70% or less as described above.

The mud powder may be a powder mainly composed of silt or clay powder, that is, a powder obtained by drying mud mainly composed of silt or clay in a dispersed state. Sand and gravels separated from mud are easy to use effectively as civil engineering and construction materials, and are still used relatively frequently after being classified with a sieve, but silt and clay remaining after separation are difficult to reuse, Practical use of soil-based inorganic materials, in which the mud powder is mainly composed of silt or clay powder, is particularly important in promoting the reuse of mud because it is disposed of. The term “mainly composed of silt or clay” refers to mud containing 50% or more silt or clay.

The solidifying material has a function of solidifying the mud powder by adding it to fine-grained mud powder, adding water and mixing, and generally uses cement (eg, Portland cement) as a solidifying material. Just use it. However, it is desirable to use fine powder of granulated blast furnace slag or one containing it as a main component.

The granulated blast furnace slag powder has excellent hydraulic properties and high long-term strength. Portland cement is obtained by finely pulverizing raw materials such as limestone, clay and silica stone, calcining them to form a hydraulic mineral phase (calcium silicate, etc.), and then finely pulverizing again. This is because the crushed slag fine powder is obtained by subjecting a molten blast furnace slag, which is a by-product generated during the production of pig iron, to water granulation and finely pulverizing the obtained granulated slag, and is extremely inexpensive as compared with Portland cement or the like.

The granulated granulated blast furnace slag powder may be used alone as a solidifying material, or the granulated granulated blast furnace slag powder may be used as a main component, that is, at least 50% is granulated blast furnace slag powder. A mixture of (quick lime) powder may be used. Since dihydrate gypsum discharged from flue gas desulfurization equipment and lime powder discharged as dust from a lime burning kiln can be used, it is an inexpensive, high-strength, and desirable solidifying material.

In addition to the solidifying material, at least one of a neutralizing material and a ventilation material may be added.

For example, when an improved material (cement-based or lime-based solidified material) is mixed with a conventional dewatered cake of construction sludge to be used for embankment or cover soil, the water penetrates and the calcium contained in the solidified material is increased. Alkaline components such as eluted into water, the surroundings become alkaline, which may adversely affect the growth of crops, trees, flowers and the like. In addition, poor water permeability and poor drainage sometimes hinder plant growth and the like. In such a case, if the neutralizing material and / or the ventilation material are previously mixed with the soil-based inorganic material, these adverse effects can be prevented or reduced.

Examples of the neutralizing material that can be used for this purpose include acid soil (soil containing iron, Kanuma soil, etc.), sulfuric acid, hydrochloric acid, etc., which have been impregnated with dry mud powder in advance, and as aeration material. Is a porous material of coral soil,
Zeolite and the like can be mentioned.

The method for producing the soil-based inorganic material of the present invention will be described below.

First, mud powder obtained by drying mud in a dispersed state is prepared as a base material.

The method of the drying treatment is not particularly limited. However, as described above, in the dewatering by a screw decanter or a filter press, a roll press dewatering, a high-pressure thin-layer dewatering, etc., which are conventionally used in the dewatering of the mud, the mud is solidified at the time of dewatering, and the mud particles are dispersed. It cannot be dried and powdery mud is not obtained.

One of the recommended methods is a method in which hot air accompanied by a shock wave is blown onto a flow of slurry-like mud to evaporate water, and can be carried out, for example, by a drying apparatus equipped with a pulse jet engine. . According to this method, since the evaporation of water is remarkably promoted, the mud containing a large amount of water is dried in a state in which the particles are dispersed without going through a dehydration step, and directly into fine-grained mud powder. Can be.

In carrying out this method,
According to the average particle size and shape of the soil particles contained in the mud, the water content of the mud is adjusted to an appropriate water content (that is, the dispersion state of the soil particles in the mud is good, and the mud is subjected to smooth and smooth drying treatment. It is preferable to carry out a pretreatment for adjusting the water content to fall within the range of a water content ratio which can be obtained in advance.

Next, hot air accompanied by a shock wave is blown to the flow of the mud whose water content has been adjusted. In order to create a flow of mud, for example, slurry mud may be continuously flowed from a nozzle having a circular or elliptical cross section. A plurality of nozzles may be used, or a thin strip-shaped flow may be formed using a slit-shaped nozzle.

The slurry-like mud is blown off by blowing hot air accompanied by a shock wave on the flow of the mud, and at the same time, the water and the soil particles in the slurry are finely dispersed by the action of the shock wave, and the water (liquid) inside the soil particles is dispersed. Oozes out on the surface of the particles and is blown off by the shock wave, and evaporates quickly because it is in a high temperature air stream. A pulse jet engine may be used as a device for generating hot air accompanied by shock waves, and slurry containing mud may be supplied into the exhaust of the pulse jet engine.

Further, a method of evaporating water by a drying device equipped with a spray dryer or a medium fluidized bed type dryer may be used.

In a spray drier, slurry-like mud is jetted out in a mist state, and hot air is blown there, and the mud is dried by the heat. In a medium fluidized bed dryer, a medium (ball) is present in the fluidized bed.
The supplied slurry-like mud is dried by the heat of the hot air while being crushed by the balls. In any case, the slurry-like mud can be directly converted into mud powder in a state where particles are dispersed.

The water content of the mud powder is preferably not more than 70%. If the water content exceeds 70%, the mud becomes sticky and hardly dispersed, and it is difficult to adjust the water content to an optimum water content for a hydration reaction described later. It is preferably at most 50%, more preferably at most 40%.

The soil-based inorganic material of the present invention can be produced by adding the above-mentioned solidifying material to the thus obtained mud powder as a base material and mixing the same. At that time, if necessary, at least one of the neutralizing material and the ventilation material may be added.

The amount of the solidifying material to be used and the amount to be mixed with the soil-based inorganic material may be appropriately determined according to the use of the obtained soil-based inorganic material.

The mixing method is not particularly limited. Various general blenders and mixers for powder can be used. Since the mud is mud powder that has been dried in a dispersed state,
As described below, uniform mixing can be easily performed.

Here, the necessity of drying the mud in a dispersed state when producing the soil-based inorganic material will be described.

1) Effect of drying itself The purpose of mixing the solidified material with the mud powder is to form a hydrate by utilizing the hydration reaction of the solidified material and to solidify the hydrate with the mud powder. However, by drying the mud, it is possible to adjust the amount of water added to the soil-based inorganic material to the optimum amount of water for the hydration reaction, and to improve the performance (strength) of the obtained soil-based inorganic material. Can be.

That is, if the mud is insufficiently dried and contains excess moisture, when water is added and solidified, the portion where the excess moisture is present becomes voids due to natural drying after solidification. As a result, structural defects are likely to occur, so that the strength of the structure tends to decrease. However, in the soil-based inorganic material of the present invention, the water content can be adjusted to the optimum water content, so that such strength reduction does not occur.

2) Effect of drying into a dispersed state When the particles constituting the mud are fine, the adsorbing force between the particles is increased due to the presence of a certain amount of water outside the particles, and the particles are dispersed even when an external force is applied. It becomes difficult to do. This is because if the mud is mainly silt or clay,
Especially remarkable.

When the conventional mud containing a large amount of water is forcibly dewatered by a conventional mechanical dehydrator such as a filter press, the water can be removed to some extent, but the water is limited to about 80%, and the mud particles are aggregated. After the solidification material is added to the dewatered mud, a considerable amount of mechanical energy is required to mix it uniformly. In addition, uniform mixing cannot be guaranteed.

On the other hand, since the mud dried in a dispersed state is a fine-grained mud powder, the added solidifying material can be easily and uniformly mixed. This homogeneity is extremely important and is the dominant factor for strength development when a reaction between each particle is required, such as a hydration reaction.

When using the above-mentioned soil-based inorganic material of the present invention, it is only necessary to add water. In other words, after transporting this material to the site of use, add the necessary water, mix and mold, and cure according to the usual method, or mold this material before adding the water, and then What is necessary is just to add sufficient moisture and to cure.

The amount of water to be added depends on the content (mixing ratio) of the solidifying material in the soil inorganic material, the particle size of the solidifying material and the inorganic material,
Although it differs depending on the kind and the like, the strength is not exhibited when the amount is too small, and the strength decreases when the amount is too large. If the amount is too small, the hydration reaction does not proceed sufficiently.If the amount is too large, excess water eventually evaporates and dehydrates, but the portion where the excess water was present becomes voids. This is because the strength as a structure is reduced.

The strength of the soil-based inorganic material of the present invention is remarkably improved as compared with a soil obtained by adding a solidifying material to mud after dewatering with a mechanical dehydrator such as a filter press.
Furthermore, there is a possibility that a high-performance soil-based inorganic material having added value by mixing various kinds of additives can be obtained.

The above-mentioned soil-based inorganic material of the present invention includes construction sludge, dredging mud generated by harbor construction and dredging of the bottom soil of lakes and marshes, mud such as dam sediment (inflow sediment, settling mud), and other mud-like forms. A material for civil engineering and construction materials consisting of mud powder obtained by drying inorganic powder and at least solidified material, with high strength, embankment, earth covering, backfilling material, etc.
It is suitable for use in civil engineering construction materials such as riverbed improvement materials, roadbed materials, roadbed materials, etc., revetment vegetation materials, vegetation greening and the like. In addition, since a large amount of water contained in the mud is removed, there is an advantage that transportation costs can be significantly reduced.

When using this soil type inorganic material, it is only necessary to add water.

[0054]

EXAMPLE Mud generated at the time of dredging of a lake is dried by a drying device equipped with a pulse jet engine into mud powder, and the blast furnace granulated slag fine powder (about 400
0 brane), a dihydrate gypsum discharged from a flue gas desulfurization facility, and a solidifying material comprising lime powder, which is dust of a lime burning kiln, were mixed to produce an earth-based inorganic material of the present invention. The mixing ratio of mud powder, granulated blast furnace slag powder, gypsum and lime powder is 50%, 3
5%, 7.5% and 7.5%.

FIG. 1 shows the configuration of the drying equipment used.

As shown in the figure, the drying device includes a sieve 11 for removing dust and coarse particles 13 from raw mud (as-generated mud) 12 and a water content adjusting tank provided immediately below the sieve 11. 10, a raw material supply tank 9 for supplying the raw mud 12 having the adjusted water content to the powder drying chamber 5, and a powder drying chamber 5 on which a pulse jet engine 1 for supplying hot air with a shock wave is mounted on the upper part. And a cyclone 7 and a powder drying chamber 5 provided adjacent thereto and dry powder recovery tanks 14a and 14b attached immediately below each of the cyclones 7. The pulse jet engine 1 includes a fuel supply pipe 2 and a combustion air supply pipe 3.

After the dirt and coarse particles 13 are removed from the raw mud 12 by the sieve 11, the water content is adjusted in the water content adjusting tank 10 so as to have an appropriate water content determined in advance.
The powder is supplied to the powder drying chamber 5 through the control valve 8 and the raw material supply pipe 4. The tip of the raw material supply pipe 4 is located in the exhaust of the pulse jet engine 1, and the exhaust of the pulse jet engine 1 becomes hot air due to the combustion of the fuel supplied to the engine 1 via the fuel supply pipe 2. Therefore, the supplied raw mud 12 is dispersed by the shock wave and heated while being blown off by the hot air, and the water is evaporated to be in a dry state. In order to completely burn the fuel, the secondary air for combustion is supplied from the secondary air supply pipe 6 attached near the position (height) of the tip of the raw material supply pipe 4 on the side wall of the powder drying chamber 5. Supplied.

The mud having a relatively large particle diameter in the mud dried in the powder drying chamber 5 is collected in a dry powder collecting tank 14a attached immediately below the powder drying chamber 5, and the one having a small particle diameter is exhausted. Enters the cyclone 7 where it is separated from the exhaust gas and collected in the dry powder recovery tank 14b.

The drying capacity of the apparatus was 20 kg / h, and kerosene was used as fuel for the pulse jet engine. For comparison, dehydration was performed using a filter press,
A dehydrated cake was obtained. The water content of this dehydrated cake was 300% in terms of the water content ratio (the ratio of water content to solid content).

Table 1 shows the characteristics of the mud (raw mud) used.
In the treatment, the properties of the raw slurry obtained by adjusting the water content of the raw mud are shown in Table 2, and the drying conditions of the raw slurry are shown in Table 3. In addition, adjustment of the water content of the raw mud, the range of the appropriate water content of mud generated during dredging of lakes and marshes,
I went so that it was within that range.

The properties (moisture content) of the obtained mud powder were as shown in Table 4. The water content of the mud powder collected in the dry powder collecting tank 14a immediately below the powder drying chamber 5 shown in FIG. Are shown in the column of "Cyclone".

[0062]

[Table 1]

[0063]

[Table 2]

[0064]

[Table 3]

[0065]

[Table 4]

Water is added to the above-mentioned soil-based inorganic material of the present invention while changing the water content in a wide range, and JIS A121
The uniaxial compressive strength was measured according to the method specified in 6.

FIG. 2 shows the measurement results. As shown,
10 kgf / cm ^{2 when the} water content is in the range of 20 to 80%
It showed a high degree of strength.

On the other hand, for the dewatered cake for comparison, the solidified material consisting of the granulated blast furnace slag powder, gypsum and lime powder was used in the same ratio as above (ie, with the solid content weight of the dewatered cake being 50%). In addition, the water content is 60%
When the uniaxial compressive strength was measured as 2.5 kgf /
cm ² . When a solidifying material is similarly added to slurry-like mud whose water content is adjusted to 80%,
It was about kgf / cm ² .

From these results, it can be seen that the soil inorganic material of the present invention has excellent performance (strength).

[0070]

The soil inorganic material of the present invention can be used for construction sludge,
It is a material for civil engineering construction materials consisting of mud powder obtained by drying mud such as dredge mud and at least solidified material, has high strength, and is suitable for applications such as civil engineering construction materials and vegetation greening.
When using this soil-based inorganic material, it is only necessary to add water.

[Brief description of the drawings]

FIG. 1 is a diagram showing a configuration of an example of a drying apparatus that can be used for producing a soil-based inorganic material of the present invention.

FIG. 2 is a view showing a test result of a uniaxial compressive strength of a soil-based inorganic material of the present invention.

Claims (3)

[Claims] An earth-based inorganic material comprising mud powder obtained by drying mud in a dispersed state and at least a solidified material. 2. At least one of a neutralizing material and a ventilation material.
2. The soil-based inorganic material according to claim 1, comprising a seed. 3. A method of using a soil-based inorganic material according to claim 1 or 2, wherein the soil-based inorganic material is solidified by adding water.