JP6765661B1 - Soil conditioner - Google Patents

Abstract

PROBLEM TO BE SOLVED: To eliminate adhesion of soil in a short time by mixing a soil conditioner, eliminate agglomerate state of highly viscous soil, prevent adhesion to equipment, and perform continuous sorting in a short time. To provide a soil conditioner that enables treatment. SOLUTION: The soil mixed with a soil conditioner can reduce the adhesiveness in a short time, eliminate the aggregated state of the soil, and improve the particle size so that continuous sorting treatment by sieving is possible. It is a soil conditioner and contains a powdery acrylate-based highly water-absorbent resin having a particle size of 150 μm or less. [Selection diagram] None

Description

The present invention relates to a soil conditioner, in particular, improves highly adherent soil, reduces adhesion to equipment, facilitates sorting and classification work with a sieve in the improved soil, and continuously treats the soil in a short time. It is about a soil conditioner that makes it possible.

Since mixed waste generated from construction and construction work and disaster waste and soil generated by disasters contain combustible materials such as plants and wood and incombustible materials such as earth and sand and concrete waste, they are treated. In some cases, it is generally necessary to carry out sorting work to separate the waste into those to be disposed of and those to be recycled. For example, disaster waste is transported to an intermediate treatment facility, where it is sorted, crushed, processed in an incinerator, etc., and then finally disposed of or recycled.

However, once a disaster waste is generated, it is a huge amount depending on the degree of disaster, so if combustibles and incombustibles cannot be separated quickly, there will be a cost problem due to shortening the life of incineration facilities and increasing the amount of waste. In addition, there was a case where there was a problem in storage or diversion due to the softening of earth and sand due to the decay of the contained organic matter.

In addition, in the treatment of contaminated soil containing radioactive substances (hereinafter referred to as "removed soil"), in the intermediate storage facility, in order to reclaim the removed soil and store it in the soil storage facility, in the removed soil. Organic substances such as plant roots and incombustible substances such as metals are being separated and the volume of removed soil is reduced. Combustibles such as separated plant roots and flexible container pieces are incinerated and screened according to a predetermined particle size. Specifically, soil classified under 20 mm (hereinafter referred to as "treated soil") is a soil storage facility. Will be buried in. In particular, in order to efficiently carry out this classification and classification treatment, it is generally necessary to mix a soil modifier with the removed soil and perform the reforming treatment. Here, the modifier is generally a combination of a polymer-based material such as a superabsorbent polymer or a polymer flocculant that acts on the pore water of the soil, and various other inorganic minerals. The polymer-based material is characterized in that it reacts rapidly with pore water and has an action of agglomerating or absorbing soil particles to reduce the adhesiveness of soil. In particular, some superabsorbent polymers have a water absorption ratio of several hundred times, and theoretically absorb all the water in the soil with a small addition rate, but when the amount of soil becomes enormous, the entire soil is efficiently absorbed. In addition, it is difficult to stir the soil, and it is difficult to disperse and splinters are likely to be generated, so that the water absorption performance is lowered. Therefore, by using inorganic minerals together, the inorganic minerals become a dispersant and play a role of dispersing the polymer-based materials throughout the soil.

In addition, when cement for the purpose of imparting strength to the improved soil or quicklime for the purpose of dehydration effect is used for the inorganic mineral, the pH of the improved soil is changed to 12 or more strong alkaline soil, and after landfill. Considering the recycling of improved soil, the soil cannot be suitable for plant growth. In addition, gypsum and the like are also used, but depending on the type, the soil may not be suitable for diversion because it increases the electrical conductivity and generates harmful gas. Here, the improved soil refers to soil that has been improved by mixing a soil conditioner and soil.

For example, in Patent Document 1, calcium carbonate having a specific surface area of 1,500 cm ² / g or more, inorganic powders such as zeolite and bentonite, thickening materials, acrylamide-based polymer flocculants, and acrylate-based high water absorption. Additives for soil granulation containing sex resins have been proposed. Here, it is described that cement and slag are used in combination as a material for obtaining the strength of the soil after the improvement treatment, but these are materials that release divalent or higher metal ions such as calcium ion and magnesium ion. Therefore, it is incompatible with the acrylate-based superabsorbent polymer, and there is a problem that it becomes a factor that hinders water absorption such as discharging the absorbed water.

On the other hand, Patent Document 2 proposes a soil modification composition and a soil modification method in which a powdered polymer flocculant and gypsum are used in combination. This method has an advantage of using a powdery polymer flocculant, and is considered to be compatible with gypsum described as being used in combination. On the other hand, when considering a modifier in which an acrylate-based superabsorbent polymer and gypsum are used in combination, which is not described in Patent Document 2, divalent calcium ions such as hemihydrate gypsum and type III anhydrous gypsum are released. Similar to the previous stage, there is a problem that the gypsum is not compatible with the acrylic acid superabsorbent polymer. There is also a concern that hydrogen sulfide will be generated by using gypsum.

In recent years, large-scale disasters have occurred frequently, and a large amount of disaster waste and earth and sand mixed with organic matter have been generated each time. Therefore, there is a need for a method and means for separating and treating such waste quickly and efficiently. There is.

JP-A-2019-137763 Japanese Unexamined Patent Publication No. 2009-263583

By the way, in the field of construction where separation work is carried out, specifically, in the separation treatment of soil and waste mixed with combustibles generated by construction work and large-scale disasters, the soil contains water and has high adhesiveness and viscosity. As a result, it easily adheres to the equipment of the processing facility, and since it is agglomerated into agglomerates, the sorting work takes time, which may make continuous processing difficult. Therefore, if combustibles and incombustibles cannot be separated efficiently, the progress of construction will be affected.

INDUSTRIAL APPLICABILITY The present invention is a soil improvement that enables a short-time and continuous separation treatment while preventing the soil from adhering to equipment by eliminating the agglomerated state of highly viscous soil in which the soil loses its adhesiveness in a short time. The purpose is to provide the agent.

By the way, although studies have been made on the pulverization of inorganic minerals and polymer flocculants related to soil improvers, there is a technique that mentions the particle size of acrylate-based superabsorbent polymers. Not.

In order to achieve the above object, the present invention focused on the particle size of the superabsorbent polymer, evaluated the water absorption performance, and then selected the range of the particle size suitable for soil improvement.
The soil conditioner of the present invention is a soil conditioner that can be mixed with soil to lose its adhesiveness in a short time, eliminate the aggregated state, and produce improved soil having a particle size smaller than the specified particle size by sieving. It is characterized by containing a powdery acrylate-based highly water-absorbent resin having a particle size of 150 μm or less.
Here, examples of the highly water-absorbent resin include (meth) acrylic acid-based homopolymers or copolymers such as starch, vinyl acetate, maleic acid, polyvinyl alcohol-based, and CMC-based copolymers as monomers. Acrylate-based crosslinked polymers, which are inexpensive and highly versatile, preferably sodium acrylate, but are generally used acrylate-based high water absorption as long as the effects of the present invention are not deviated. A resin can be used.
In addition, "(meth) acrylic acid" means acrylic acid or methacrylic acid.
By the way, since a superabsorbent polymer is generally used as a water-absorbent material for disposable diapers, the required performance is focused not on the water-absorbing rate but on the water-absorbing capacity, but the soil conditioner of the present invention is a soil conditioner. Since a reaction in a shorter time is required after mixing with, we are pursuing the ability to absorb water in a short time. Therefore, the "short time" in the present invention is specifically 90 as the time until the target soil can be mechanically continuously treated, the soil is no longer adherent, and the aggregated state can be eliminated. It was set to about seconds to 180 seconds.

In this case, as the acrylate-based superabsorbent polymer, an acrylate-based superabsorbent polymer having a water absorption ratio of 150 to 400 times and a water absorption rate of 40 to 80 g / g / s can be used.

Further, as the soil conditioner, one containing a porous substance having a particle size of 10 to 50 μm and a pH adjusting agent having a particle size of 10 to 80 μm can be used.

Further, the powdered superabsorbent polymer used in the soil conditioner of the present invention is a powdery superabsorbent polymer when only the superabsorbent polymer comes into contact with soil, specifically soil containing a large amount of cohesive soil. May cause problems such as water absorption inhibition or slowing of water absorption rate, so it is mixed with inorganic minerals and dispersed so that the powdered resins do not come into contact with each other as much as possible. Is desirable. For this reason, powdered inorganic minerals that do not swell and do not affect water absorption are desirable, and in consideration of the case where the water in the soil contains a large amount of minerals, the water absorption performance of the highly water-absorbent resin is impaired. It is desirable that the porous substance can adsorb minerals so as not to prevent it, and a substance having a high base substitution capacity (also referred to as a cation exchange capacity, hereinafter referred to as "CEC") is more desirable.
Here, as an example of the porous substance, the particle size is in the range of 10 to 80 μm and the CEC is high, specifically, the CEC is in the range of 100 to 300 meq / 100 g, more preferably 150 to 200 meq / 100 g. Examples thereof include zeolite, smectite, vermiculite, and activated carbon.

Further, since the powdery acrylate-based superabsorbent polymer has a reduced water absorption in acidic soil with a soil of 5.9 or less, the weak alkaline side (neutral or weak alkaline, specifically, the pH is 6). It is desirable that an inorganic mineral whose pH can be adjusted is mixed with (about .0 to 9.0).
Here, examples of the inorganic mineral whose pH can be adjusted include pH adjusters such as carbonate, clay, bentonite, and PS ash.

Further, the soil conditioner used contains 5 to 30% by mass of an acrylate-based superabsorbent polymer, 30 to 60% by mass of a porous substance, and 30% to 60% by mass of a pH adjuster. Can be done.

The soil conditioner of the present invention is an improved soil that can reduce the adhesion of soil, eliminate the aggregated state, and reduce the adhesion to mechanical devices by mixing the soil conditioner with the soil, for example, particle size 9. By making the improved soil with low adhesion of .5 mm or less, it has the effect of preventing clogging of the classifier and the agglomeration of the improved soil, and enables continuous mechanical improvement in a short time. Here, the mesh to be passed is not limited to this, and can be determined by the builder according to the treatment method specified for the target soil.

Hereinafter, embodiments of the soil conditioner of the present invention will be described based on specific examples.

Table 1 shows the test results of the water absorption rate and the water absorption ratio of the granular acrylate-based superabsorbent polymer, specifically, sodium acrylate, which is an acrylate-based crosslinked polymer, crushed and classified.
Here, the soil conditioner of the present invention attaches great importance to the water absorption rate, but since the amount of the superabsorbent polymer used increases and the cost increases when the water absorption rate is below a certain level, the water absorption rate can be set in a short time. In order to confirm the amount of water absorbed by the superabsorbent polymer contained in the improved soil for 3 minutes and for a long period of time, the amount of water absorbed by 180 minutes was confirmed.

From Table 1, the superabsorbent polymer having a particle size of 75 μm or less had a very high water absorption rate, and the water absorption rate was slightly reduced when immersed for 180 minutes, but the actual treatment time. It was found that the water absorption ratio was remarkably reduced when the immersion was carried out for 3 minutes. Further, it was clarified that most of the water-absorbent resins having a particle size of 150 μm or more have a water absorption ratio of 350 times or more, but the water absorption rate is significantly lower than that of 150 μm or less.

Table 2 shows the evaluation of the improved performance of the acrylate-based superabsorbent polymer shown in Table 1 in each particle size range, specifically, the classification test results for simulated soil. A predetermined amount of superabsorbent polymer was added to the simulated soil and stirred, and the sieve passing rate of the obtained improved soil was confirmed. Here, it is shown that the particle size range of the sieve having a pore size of 19 mm and the sieve passing rate of 9.5 mm reduces the adhesion of the improved soil, has a high classification effect, and has preferable properties as a soil conditioner.

[Test conditions]
-Simulated soil: 900 g of mixed soil of red soil and black soil (moisture content of about 49%)
・ Addition amount: 0.1% (0.9 g) of acrylate-based superabsorbent polymer with respect to 900 g of soil ・ Stirring time: 30 seconds with Hobart mixer ・ φ20 mm pore size 19 mm and 9.5 mm sieves are stacked. Approximately 300 g of improved soil is added from the top, and each sieve passage rate is calculated from the residual soil on the sieve after shaking for 20 seconds with an automatic shaker (mean value of N = 3).

From Table 2, the superabsorbent polymer having a particle size of 75 to 150 μm had the highest sieve passing rate, and the sieve passing rate tended to decrease as the particle size increased from 150 μm. On the other hand, since the superabsorbent polymer of 75 μm or less has a high water absorption rate, it reacts with water immediately after the addition of soil and often forms a sieving powder before dispersion by agitation operation. Was low, and it was confirmed that the sieve passage rate was the lowest.

Table 3 shows the evaluation of the improved performance of the acrylate-based superabsorbent polymer determined from Tables 1 and 2 at each particle size (in the order of ⊚, ◯, and Δ, the performance is higher).

From the evaluation of the improved performance shown in Table 3, it can be said that the particle size range of 150 μm or less, preferably 75 to 150 μm, that is, the one obtained by removing 75 μm or less from the one of 150 μm or less is the most balanced particle size range as the improving agent. .. That is, it has been found that the soil conditioner of the present invention is required to have a high water absorption amount and a high water absorption rate, which are affected by the particle size of the acrylate-based superabsorbent polymer. Since the water absorption rate increases as the particle size decreases, 150 μm or less is suitable, and further, as the particle size decreases, the amount of water absorption per unit weight decreases, so it can be said that 75 to 150 μm is preferably suitable. ..

Table 4 shows the results of the compounding test carried out to determine the compounding of the soil conditioner of the present invention. A predetermined amount of each of the improving agents 1 to 6 in which the constituent materials shown in Table 4 were combined was added to the target soil and stirred, and the properties of the improved soil were visually confirmed.
Here, in the constituent material, the powdery superabsorbent polymer is an acrylate-based superabsorbent polymer having a particle size of 75 to 150 μm, specifically, sodium acrylate, which is an acrylate-based crosslinked polymer. As the porous material, zeolite having a particle size of 20 μm was used, and as a pH adjuster, calcium carbonate having a particle size of 75 μm or less was used. In contrast to the powdered superabsorbent polymer contained in the soil improving agent of the present invention, a powdered anionic polymer flocculant, specifically, a linear acrylate having a particle size of 150 μm or less. An acrylamide copolymer was used.
In addition, in the formulation of the improvers 1 and 2, neutral magnesium oxide whose pH was adjusted was used in combination in consideration of performance such as strength development.
[Test conditions]
-Target soil: Mixed soil of 70% river sand and 30% rural soil (moisture content of about 24.5%)
・ Addition amount: 30 kg / m ³
-Stirring time: 60 seconds-As for the evaluation, those with a small particle size and low adhesiveness of the improved soil were regarded as good, and those with a large particle size and high adhesiveness were regarded as defective.

In Table 5, the improving agents 1 and 6 for which better evaluation was obtained from the test results in Table 4 were mixed and stirred with the target soil, and the obtained improved soil was measured through a sieve having a pore size of 9.5 mm. The test results confirming the classification effect are shown. Here, the one having a high 9.5 mm sieve passing rate indicates that the classification effect is high.
[Test conditions]
・ Target soil 1: River sand 70% + rural soil 30% (moisture content about 20%)
・ Target soil 2: 100% rural soil (water content about 20%)
・ Addition amount: 30 kg / m ³
・ Stirring time: 90 seconds with Hobert Mixer

From the test results shown in Table 5, the improving agent 6 containing an acrylate-based superabsorbent polymer having a particle size of 75 to 150 μm was more effective than the improving agent 1 containing a powdered anionic polymer flocculant. It was confirmed that the target soil had a high sieving rate in sorting and showed a high improvement effect that was not affected by the soil quality.
Further, from the test results shown in Table 4, in consideration of economy, workability, and efficiency, 5 to 30% by mass of acrylic acid salt-based highly water-absorbent resin and 30 to 60% by mass of porous substances were used as soil conditioners. , It was found that those containing 30% by mass to 60% by mass of the pH adjuster are preferable.

The soil conditioner of the present invention has been described above based on the examples thereof, but the present invention is not limited to the configuration described in the above examples, and the configuration is appropriately modified without departing from the spirit thereof. Is something that can be done.

The soil conditioner of the present invention causes the soil to lose its adhesiveness in a short time and quickly eliminates the aggregated state of the soil while preventing the soil from adhering to the equipment, so that the soil can be separated in a short time by continuous improvement. Therefore, it can be suitably used as a material for modifying the soil to improve the sieving efficiency when sieving to remove wood chips and dust from soil mixed with wood chips and dust generated in the event of a disaster. ..

Claims (3)

The soil mixed with the soil conditioner loses its adhesiveness with a short stirring of 90 to 180 seconds, eliminates the aggregated state of highly viscous soil that tends to become agglomerates, and is short when sieving the soil. A soil conditioner that can filter organic substances from non-combustible substances and soil over time and can improve the particle size to enable continuous classification by sieving, and is a powder with a particle size of 75 to 150 μm . A soil conditioner comprising 10 to 20 parts by mass of a form of sodium acrylate and 40 to 50 parts by mass of a porous substance having a particle size of 10 to 50 μm. Soil conditioner according to claim 1, wherein the sodium acrylate, water absorption capacity 150 to 400 times, sodium acrylate absorption rate 40~80g / g / s. The soil improving agent, soil improvement agent according to claim 1 or 2, characterized in that it contains a pH adjusting agent particle size 10 to 80 [mu] m.