JP4375586B2 - Method for producing and using soil-based inorganic material - Google Patents

Description

【００６２】
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【００６４】
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【００６５】
上記本発明方法により得られた土質系無機材料、および乾燥処理のみを施した材料に対し、それぞれ水分含有量が５５％になるように水を加え、ＪＩＳ Ａ１２１６に規定される方法に準じて一軸圧縮強度を測定した。さらに、土壌汚染の分析等で用いられている方法、すなわち、固化後の試料を粒径１ｍｍ以下に粉砕した後、水に浸漬してｐＨの変化を測定する方法により溶出アルカリ量（ｐＨ）を求めた。
【００６６】
測定結果を表５に示す。この結果から明らかなように、本発明方法により得られた土質系無機材料では、乾燥処理のみの材料に比べて、強度が著しく高く、溶出アルカリ量も顕著に低下した。
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【表５】

【００６８】
【発明の効果】
本発明方法によれば、建設汚泥、浚渫泥などの泥土を、強度が高くかつアルカリ溶出の少ない、土木建材用、植生緑化用等の用途に好適な土質系無機材料とすることができる。また、泥土に多量に含まれている水分が除去されているので、輸送コストを大幅に低減できるという利点も有している。この土質系無機材料は、使用に際し、水を加えるだけでよい。[0001]
BACKGROUND OF THE INVENTION
The present invention treats mud such as construction sludge and dredged mud (they are mud and mud depending on the water content, but these are also referred to herein as “mud”) and The present invention relates to a method for producing a soil-based inorganic material that can be used for building materials, vegetation greening, and the like, and a method for using the soil-based inorganic material.
[0002]
[Prior art]
A large amount of construction sludge containing moisture is generated by tunnel excavation work, building construction, etc. In addition, a large amount of moisture sludge is also discharged in port construction and dredging of lake bottom soil. The amount generated is in the thousands of tons per year.
[0003]
Most of these muds are fine particles containing a large amount of water with a particle size of several tens of μm, so they cannot be piled up on dump trucks and are difficult to handle on humans. Yes. Therefore, it cannot be reused as it is, and most of them have been landfilled as sludge for industrial waste. However, there is a small amount of recycling, and in recent years, in particular, development of these mud recycling technologies has been actively promoted in various fields.
[0004]
For example, for construction sludge, technical guidelines for recycling are compiled by the Ministry of Construction, and technical standards for sediment separation, dewatering treatment, stable treatment, etc. are shown. A method of applying the dehydrated cake obtained in this way to a backfill material or stabilizing it with an improving material and applying it to embankment has been studied. As the dehydration treatment method, various methods such as centrifugal filtration (screw decanter), pressure filtration (filter press), pressure squeeze filtration (roll press), and high pressure thin layer dehydration can be applied. Yes.
[0005]
The above-mentioned stabilization treatment is a treatment to improve the properties of construction sludge by mixing improvement materials. Cement and cement-based improvement materials, lime (quicklime, slaked lime), lime-based improvement materials, etc. are applied to the improvement materials. Has been.
[0006]
As for dredged soil, solid matter is settled and separated in the raw mud tank, and the settled mud is extracted with a pump and added with dehydration aid, then concentrated and dewatered, and used as residual soil or landfilled. ing. In some cases, a solidifying agent is added to the dehydrated cake and used as covering soil. The treated water discharged in the steps such as concentration and dehydration is subjected to treatment such as coagulation precipitation and neutralization, and then discharged.
[0007]
In addition, for dredging that is necessary due to the need for environmental purification of lakes and marshes, dredged mud is expelled to vast farmland that has been borrowed over a long period of time and then naturally dried over several years.
[0008]
[Problems to be solved by the invention]
In the conventional technology described above, in the dewatering with a screw decanter or filter press used in the mud dewatering process, roll press dewatering, high pressure thin layer dewatering, etc., the mud does not solidify during dehydration and does not become a powder, so stable treatment is performed. It is difficult to uniformly mix with the improved material. Therefore, the performance (strength) of the recycled material obtained by the process of improving the properties of sludge by mixing the above-mentioned improving materials is low, and if it is attempted to improve the performance, a large amount of an improving agent must be added, resulting in high cost. become. In addition, the strength of the regenerated soil itself is limited, and it can be used only for backfilling and embankment, and has not yet provided a material with higher added value.
[0009]
Furthermore, in the material solidified by the conventional method, alkaline components such as calcium contained in cement, cement-based improvement material, lime (quick lime, slaked lime), lime-based improvement material, etc. are contained in water due to water permeation during use. Since it elutes, the surroundings become alkaline. For example, the problem is that the pH rises to about 12 and adversely affects the growth of crops, forests, flowers, etc. that require a pH of 10 or less, preferably pH 6.5 to 8.5, and often die. There is.
[0010]
The present invention treats mud soil as part of a technology for actively reusing mud such as construction sludge and dredged mud, and has high strength and low alkali elution (low alkali elution). An object of the present invention is to provide a method for producing a soil-based inorganic material that can be widely used for vegetation, vegetation and the like, and a method for using the same.
[0011]
[Means for Solving the Problems]
The present inventors have made various studies on pretreatment of mud when treating mud containing a large amount of water such as construction sludge and dredged mud. As a result, the mud is subjected to a drying treatment so that there are few aggregated particles and the mud particles are dispersed, and further, a solidified material (including what is referred to as an improving material here), water permeability, After mixing with additives to give functions such as pH adjustment, mechanical performance such as impact force is applied to significantly improve the performance (for example, strength) of the resulting product (soil-based inorganic material). I found out that I could make it.
[0012]
By adding mechanical energy to a substance, it is possible to change the physical and chemical properties of the substance or to cause a chemical reaction, which is generally known as a mechanochemical reaction. It is also possible to cause a synthesis reaction or a decomposition reaction by mechanochemical reaction.For example, after mixing a plurality of metal powders, a method of synthesizing an alloy by adding mechanical energy is called mechanical alloying, which can be put into practical use. Has been. Further, an invention has been made on a method for obtaining a hydraulic substance by mixing an inorganic material containing calcium with a mineral containing alumina (see , for example , JP-A-8-91831).
[0013]
The present invention is an application of this mechanochemical reaction to the treatment of mud (reaction of mud with a solidifying material or other additive), the gist of which is the following (1) method for producing a soil-based inorganic material, and ( 2) in its usage.
[0014]
(1) A method for producing a soil-based inorganic material in which mud is dried in a dispersed state, mixed with inorganic powder that forms a hydrate, and mechanical energy is added to the mixture.
[0015]
(2) A method of using a soil-based inorganic material that is solidified by adding water to the soil-based inorganic material produced by the method described in (1) above.
[0016]
The mud may be mainly composed of silt or clay powder.
[0017]
Examples of inorganic powders that produce hydrates include cement (for example, Portland cement), limestone powder, or limestone powder mixed with gypsum powder, and blast furnace granulated slag fine powder. What has a main component, or what has blast furnace granulated slag fine powder, gypsum powder, and limestone powder as a main component can be used.
[0018]
The mechanical energy may be any of compression, impact, friction and shear, or a combination of two or more.
[0019]
Here, “mud” refers to construction sludge with a lot of water generated by construction work (excluding dredging) such as tunnel excavation work and building work, as well as dredging of port work and dredged soil in the lake. It means dredged mud and other mud-like inorganic powder. Furthermore, soil generated in a specific area (for example, “red soil” in Okinawa Prefecture) is also included in “muddy soil”. This is because, when handling, it shows properties similar to construction sludge and dredged mud by adding water.
[0020]
“Silt or clay” refers to mud soil having a particle size of 75 μm or less, with relatively coarse gravel and sand removed from the mud soil. Note that silt is more than 5 μm and up to 75 μm, and clay is 5 μm or less. Further, sand exceeding 75 μm and up to 2 mm is sand, and sand exceeding 2 mm is called gravel.
[0021]
Further, “drying mud in a dispersed state” means performing a drying process so that mud particles are not aggregated and are dispersed. Specifically, the moisture content is reduced to 70% by weight (hereinafter “%” means “% by weight”) or less by a drying method (pulse jet engine, spray dryer or medium fluidized bed type dryer) described later. It means drying. The mud is originally composed of fine particles except for gravel and sand having a relatively coarse particle size, and can be made into a fine-grained mud by drying the mud in a dispersed state.
[0022]
DETAILED DESCRIPTION OF THE INVENTION
Below, the manufacturing method (henceforth "the method of this invention") of the soil type inorganic material of this invention and the usage method of the material are demonstrated in detail.
[0023]
First, mud soil dried in a dispersed state is prepared as a base material.
[0024]
The method for the drying treatment is not particularly limited. However, as described above, in the conventional dewatering process of mud, dehydration with a screw decanter or filter press, roll press dehydration, high pressure thin layer dehydration, etc., the mud solidifies during drying and can be dried in a dispersed state. It is not possible to obtain a powdery mud.
[0025]
One of the recommended methods is a method of spraying hot air accompanied by a shock wave to the slurry-like mud flow to evaporate the water. For example, it can be carried out by a drying apparatus equipped with a pulse jet engine. According to this method, evaporation of water is remarkably promoted, so that mud containing a large amount of water is dried in a dispersed state without going through a dehydration step, and directly made into fine mud powder. Can do.
[0026]
In carrying out this method, depending on the average particle size and shape of the soil particles contained in the mud, the water content ratio of the mud is an appropriate water content ratio (that is, the dispersion state of the soil particles in the mud is good). Thus, a pretreatment is performed to adjust the water content ratio so that it can be smoothly supplied to the drying process without any trouble.
[0027]
Next, hot air with a shock wave is blown to the mud flow adjusted in water content. In order to create a mud flow, 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 slit-like nozzle may be used to form a thin belt-like flow.
[0028]
The slurry-like mud is blown away by blowing hot air with shock waves on the mud flow. At the same time, water and soil particles in the slurry are finely dispersed by the action of the shock waves, and the moisture (liquid) inside the soil particles is dispersed. It exudes to the surface and is blown away by shock waves, and evaporates quickly because it is in a hot air stream. A pulse jet engine may be used as a hot air generating device with a shock wave, and slurry containing mud may be supplied into the exhaust of the pulse jet engine.
[0029]
Alternatively, a method of evaporating moisture using a drying apparatus equipped with a spray dryer or a medium fluidized bed type dryer may be used.
[0030]
In the spray dryer, slurry-like mud is ejected in the form of a mist, hot air is blown there, and the mud is dried by the heat. In the medium fluidized bed type dryer, the medium (ball) is present in the fluidized bed, and the supplied slurry-like mud is dried by the heat of the hot air while being crushed by the balls. In either case, the slurry-like mud can be directly made into a mud powder in which particles are dispersed.
[0031]
The moisture of the mud powder is 70% or less. If the water content exceeds 70%, the mud becomes sticky and does not become dispersed, and it becomes difficult to adjust the water content to an optimum amount for the hydration reaction described later. Preferably it is 50% or less, More preferably, it is 40% or less.
[0032]
The mud may be mainly composed of silt or clay. Sand and gravel separated from mud are easy to use effectively as civil engineering and construction materials and are still used relatively well after being classified with a sieve etc., but silt and clay remaining after separation are difficult to reuse, Since it is disposed of, if mud is mainly made of silt or clay, it is particularly important to promote the recycling of mud. The “mainly composed of silt or clay” refers to mud containing 50% or more of silt or clay.
[0033]
The inorganic powder that forms a hydrate is mixed with the mud as the base material dried in the dispersed state thus obtained.
[0034]
The inorganic powder that produces hydrate has the function of reacting with water to form a hydrate by adding water to the fine-grained mud, mixing it, and solidifying the mud. As described above, cement, limestone powder, or limestone powder mixed with gypsum powder can be used as a main component. These inorganic powders are conventionally used for solidification of mud, but when used in the method of the present invention, a remarkable effect is recognized as compared with the case of using in the conventional solidification method.
[0035]
In addition, as an inorganic powder for producing a hydrate, a powder mainly composed of granulated blast furnace slag, or a powder mainly composed of granulated blast furnace slag, gypsum powder and limestone powder is used. desirable.
[0036]
Blast furnace granulated slag fine powder has excellent hydraulic properties and high long-term strength. Portland cement is made by pulverizing raw materials such as limestone, clay, and silica, calcining them into a mineral phase (calcium silicate, etc.) having hydraulic properties, and pulverizing again. This is because the pulverized slag fine powder is obtained by subjecting molten blast furnace slag, which is a by-product produced during the production of pig iron, to water granulation, and then pulverizing the resulting granulated slag, which is significantly less expensive than Portland cement and the like.
[0037]
Blast furnace granulated slag fine powder may be used alone as a solidifying material, or as a main component, that is, at least 50% blast furnace granulated slag powder, and gypsum (dihydrate gypsum) or lime (quick lime). The powder may be mixed. Since dihydrate gypsum discharged from the flue gas desulfurization facility and lime powder discharged as dust from the lime kiln can be used, it is an inexpensive, high strength and desirable solidification material.
[0038]
What is necessary is just to determine suitably the solidification material to be used, and the mixing amount to a soil type inorganic material according to the use of the soil type inorganic material obtained.
[0039]
In addition to the above solidifying material, at least one of a neutralizing material and a ventilation material may be added. As will be described later, the soil-based inorganic material of the present invention has little alkali elution, but is completely neutralized by adding a neutralizing material (for example, acid soil, sulfuric acid previously impregnated with dry mud powder). It becomes possible to do. In addition, since the soil inorganic material used has low water permeability and poor drainage, it may cause problems in plant growth and others. However, a ventilation material (for example, porous zeolite) should be mixed in advance. Thus, these adverse effects can be prevented or alleviated.
[0040]
The mixing method is not particularly limited. Various general blenders and mixers for powder can be used. Since the mud is a mud powder that has been dried in a dispersed state, it can be easily mixed uniformly, and there is a mixing effect in the device itself used in the subsequent process of applying mechanical energy. What is necessary is just to mix to some extent uniformly in a process.
[0041]
Then, the process (mechanochemical process) which adds mechanical energy to the mixture of the mud and the inorganic powder which produces | generates a hydrate is given, and a soil type inorganic material is manufactured.
[0042]
Mechanical energy is usually applied by applying a compressive force, impact force, frictional force, shearing force, and the like to the above mixture. Any force or a combination of two or more of these forces may be applied.
[0043]
As a method or apparatus for that purpose, a ball mill, a planetary ball mill, an attritor or the like that can give relatively strong energy is suitable. Many of these are devices in which balls are filled. By rotating the entire device at high speed, the powder is mixed and mechanical energy is imparted (transmitted) to the powder.
[0044]
For example, when a ball mill is used, a mechanochemical reaction occurs in the mud soil to be treated by the method of the present invention when the rotational speed is set to several hundred rpm and the treatment is performed for several hours.
[0045]
Here, when producing a soil-based inorganic material by the method of the present invention, it is necessary to dry the mud in a dispersed state, and the mixture of the mud and an inorganic powder (hydratable inorganic powder) that produces a hydrate. The reason for adding mechanical energy is described.
[0046]
(1) Necessity of drying mud in a dispersed state a. When the particles constituting the uniformly mixed effect mud become fine, the adsorbing force between the particles becomes strong due to the presence of a certain amount of water on the outside of the particles, and it becomes difficult to disperse even if an external force is applied. This tendency is particularly remarkable when the mud is mainly composed of silt or clay.
[0047]
When the mud containing a large amount of water is forcibly dewatered with a conventional mechanical dehydrator such as a filter press, for example, the water can be removed to some extent, but the water content is limited to about 80%, and the mud particles are agglomerated. After adding the solidifying material to the dewatered mud, considerable mechanical energy is required to uniformly mix it. Moreover, uniform mixing cannot be guaranteed.
[0048]
On the other hand, since the mud dried in a dispersed state is a fine-grained mud powder, it can be easily and uniformly mixed. This homogeneity is extremely important when a reaction needs to occur between particles, such as a hydration reaction, and becomes a dominant factor for the development of strength.
[0049]
b. Moisture control effect The purpose of mixing hydrated inorganic powder into mud that has been dried in a dispersed state is to produce hydrate using the hydration reaction of this inorganic powder and integrate it with dried mud However, by drying the mud, it becomes possible to adjust the amount of water added to the soil-based inorganic material to an optimal amount of water for the hydration reaction, and the performance (strength of the soil-based inorganic material obtained) ) Can be improved.
[0050]
In other words, if the mud is not sufficiently dried and contains excess moisture, when water is added to the mud and solidified, the excess moisture remains as pores due to natural drying after solidification, Since it becomes a structural defect, the strength as a structure is reduced, but in the soil-based inorganic material of the present invention, the moisture can be adjusted to the optimum moisture content, and thus such strength reduction does not occur.
[0051]
(2) Reason for adding mechanical energy to the above mixture Since the particles of mud and hydratable inorganic powder are physically broken by mechanical energy to form a highly active molecular surface, activity such as hydration is likely to occur. It will be in the state of becoming Therefore, when water is added to the obtained soil-based inorganic material, the hydration reaction is remarkably accelerated as compared with the case where mechanical energy is not applied, and the effect of improving the performance (strength) of the soil-based inorganic material is great. Further, the hydration reaction is promoted and solidified firmly, so that the elution of alkali is suppressed.
[0052]
When using the soil-based inorganic material obtained by the method of the present invention described above, after transporting this material to the site, it is molded by adding necessary moisture, and is cured according to a normal method, or moisture This material may be formed before adding, and then necessary moisture may be added and cured. As a result, functions such as strength appear.
[0053]
The amount of water added varies depending on the solidified material content (compounding ratio) in the soil-based inorganic material, the particle size and type of the solidified material and the inorganic material, etc. Go down. If the amount is too small, the hydration reaction does not proceed sufficiently. If the amount is too large, the excess moisture will eventually evaporate and dehydrate, but the portion where the excess moisture was present becomes pores. This is because the remaining strength as a structure is lowered.
[0054]
According to the above-mentioned method of the present invention, construction sludge, dredging mud generated from dredging of harbor construction and lake bottom soil, mud such as dam sedimentary sediment (inflow sediment, sediment mud), and other mud-like inorganic powders are strengthened. It is possible to obtain a soil-based inorganic material having a high alkali content and little alkali elution. This soil-based inorganic material has higher strength, such as riverbank foundation materials, riverbed improvement materials, roadbed materials, roadbed materials, building construction foundation materials, bridge foundation materials, subsidence prevention materials for underground buried objects, etc. It is suitable for uses such as civil engineering and building materials that are required, or vegetation greening. In addition, since the water | moisture content contained in mud in large quantities is removed, it also has the advantage that transportation cost can be reduced significantly.
[0055]
The soil-based inorganic material obtained by the method of the present invention only needs to be added with water in use.
[0056]
【Example】
The mud generated at the dredging of the lake is dried with a drying device equipped with a pulse jet engine (drying capacity: 20 kg / h), and the granulated blast furnace slag fine powder (about 4000 branes), Dihydrate gypsum discharged from the flue gas desulfurization facility and inorganic powder (solidifying material) that produces a hydrate consisting of lime powder that is dust of the lime-fired kiln were mixed. The mixing ratio of the mud powder, ground granulated blast furnace slag, gypsum, and lime powder was 50%, 35%, 7.5%, and 7.5%, respectively, in terms of solid content weight excluding moisture.
[0057]
The mixture was subjected to mechanochemical treatment at 500 rpm for 2 hours with a ball mill (processing capacity: 10 kg / charge) to give mechanical energy to produce a soil-based inorganic material.
[0058]
For comparison, only a drying process was performed, and a material without a mechanochemical process (a material only with a drying process) was obtained.
[0059]
Table 1 shows the characteristics of the used mud (raw mud). Table 2 shows the characteristics of the raw material slurry obtained by adjusting the water content ratio of the raw mud, and Table 3 shows the drying conditions of the raw material slurry. In addition, the adjustment of the moisture content of the raw mud was carried out so that the range of the appropriate moisture content was determined for the mud produced at the dredging of the lake, and it was within that range.
[0060]
The properties (water content) of the mud after the drying treatment were as shown in Table 4. In Table 4, the moisture content of the dry powder recovered in the recovery tank attached immediately below the powder drying chamber of the drying equipment used is shown in the “Powder Drying Chamber” column and adjacent to the powder drying chamber. The moisture content of the dry powder collected by the cyclone attached in the above manner is shown in the “Cyclone” column.
[0061]
[Table 1]

[0062]
[Table 2]

[0063]
[Table 3]

[0064]
[Table 4]

[0065]
Water was added to the soil-based inorganic material obtained by the above-described method of the present invention and the material subjected only to the drying treatment so that the water content was 55%, respectively, and uniaxially according to the method defined in JIS A1216. The compressive strength was measured. Furthermore, the amount of eluted alkali (pH) is determined by the method used in soil contamination analysis, that is, after the solidified sample is pulverized to a particle size of 1 mm or less and immersed in water to measure the change in pH. Asked.
[0066]
Table 5 shows the measurement results. As is clear from this result, the soil-based inorganic material obtained by the method of the present invention has a significantly higher strength and a significantly reduced amount of eluted alkali as compared with the material only subjected to the drying treatment.
[0067]
[Table 5]

[0068]
【The invention's effect】
According to the method of the present invention, mud such as construction sludge and dredged mud can be made into a soil-based inorganic material having high strength and low alkali elution and suitable for applications such as civil engineering and building materials and vegetation greening. Moreover, since the water | moisture content contained in mud in large quantities is removed, it also has the advantage that transportation cost can be reduced significantly. In order to use this soil-based inorganic material, it is only necessary to add water.

Claims (2)

A method for producing a soil-based inorganic material comprising drying mud in a dispersed state, mixing an inorganic powder that forms a hydrate with the mud, and applying mechanical energy to the mixture. A method for using a soil-based inorganic material, wherein water is added to the soil-based inorganic material produced by the method according to claim 1 to solidify it.