JP7128495B1 - soil conditioner - Google Patents

Abstract

[Problem] To recycle soil containing fine particles, which has been difficult to reuse until now, by preparing the soil into a property that is easy to handle while ensuring safety during soil modification work and stability of the modified soil. To provide a soil conditioner that is easy to use. [Solution] The soil conditioner for improving fine particle-containing soil forms sievable granular soil within 80 seconds when mixed with fine particle-containing soil and stirred, and the granular soil is fine Substantially no change in pH and no increase in temperature for particulate-containing soils. [Selection figure] None

Description

TECHNICAL FIELD The present invention relates to a soil conditioner for modifying soil containing fine particles such as clay (hereinafter referred to as "fine particle-containing soil") to make it reusable.

Waste soil generated from civil engineering work, construction work, soil decontamination work, and the like contains soil components such as clay, sand, and gravel, as well as foreign substances such as metal pieces, glass pieces, and plastic pieces. Also, viscous soil such as sludge generated in sewage treatment plants and the like is generally treated as waste soil. Therefore, in order to reuse the waste soil, it is necessary to separate and remove foreign substances in the waste soil and then improve the properties of the soil. Here, the separate removal of foreign substances in the waste soil is generally performed by sieving using a classifier, but if the properties of the waste soil are problematic, it becomes difficult to perform accurate separation. For example, if the waste soil is highly viscous, the soil components may adhere to the mesh of the classifier, causing clogging.

Therefore, various soil conditioners have been developed to improve the properties of waste soil. For example, there is a mud modifier containing an inorganic coagulant compound and a water-soluble polymer compound (see, for example, Patent Document 1). The mud modifier of Patent Document 1 is particularly aimed at modifying alkaline mud generated in construction using alkaline civil engineering chemicals, and by suppressing the fluidity of mud with a high water content, it is easy to transport. This is an attempt to make it easier.

There is also a soil improver in which sodium alginate powder is blended with inorganic mineral powder (see, for example, Patent Document 2). The soil conditioner of Patent Document 2 is intended to reuse the treated soil as plant-growing soil. It is intended to be neutralized by mineral powder.

JP-A-10-165998 JP-A-2002-371279

In the modification of waste soil, it is required to have safety such that a sudden temperature rise does not occur during soil modification work and stability that pH change (alkalization) does not occur in the modified soil. In addition, in order to facilitate the reuse of the modified soil, it is also necessary to prepare the soil in an easy-to-handle property that can be sieved (viscosity is suppressed and the texture is flaky).

Regarding this point, the mud modifier of Patent Document 1 is intended to reduce the fluidity of mud, but it is merely intended to facilitate transportation, and the modified soil can be reused. Not what we assumed. In addition, since the soil treated with a highly alkaline civil engineering chemical is targeted for treatment, the pH of the resulting modified soil is inevitably high, and the situations where such alkaline soil can be reused are limited.

The soil improver of Patent Document 2 uses sodium alginate powder as the main component, and is intended to be reused as plant-growing soil. is not easy. In addition, Patent Document 2 mentions slag, gypsum, and coal ash as inorganic mineral powders to be mixed with sodium alginate powder. There is a problem with gypsum, and gypsum has a problem in terms of safety due to heat generation, and there is room for improvement.

The present invention has been made in view of the above problems. An object of the present invention is to provide a soil conditioner that facilitates the reuse of soil containing fine particles, which has been difficult to reuse.

The characteristic configuration of the soil conditioner according to the present invention for solving the above problems is
A soil conditioner for improving soil containing fine particles,
When mixed with the fine particle-containing soil and stirred, within 80 seconds, a sievable granular soil is formed, the granular soil having a substantially unchanged pH relative to the fine particle-containing soil, And the temperature does not rise.

According to the soil conditioner of this configuration, even if the fine particle-containing soil containing clay or the like that is difficult to handle is highly viscous, the soil conditioner of this configuration can be easily mixed with the fine particle-containing soil and stirred. Soil containing fine particles can be made into granular soil that can be rapidly sieved. This granular soil does not substantially change in pH and does not rise in temperature compared to the fine particle-containing soil before modification, so that it is highly safe and stable and easy to handle.

In the soil conditioner according to the present invention,
It is preferable that 85% or more of the granular soil, on a weight basis, pass through a sieve with an opening of 9.5 mm.

According to the soil conditioner of this configuration, the granular soil obtained after modification is prepared so that 85% or more on a weight basis passes through a sieve with an opening of 9.5 mm, making it easier to handle. becomes.

Furthermore, the characteristic configuration of another soil conditioner according to the present invention for solving the above problems is
A soil conditioner for improving soil containing fine particles,
a superabsorbent polymer;
crystalline calcium carbonate;
is to contain

According to the soil conditioner of this configuration, the crystalline calcium carbonate acts on the point where the superabsorbent polymer absorbs water contained in the fine particle-containing soil and becomes swollen while entraining the fine particle-containing soil. Then, fine particles aggregate with crystalline calcium carbonate as a nucleus, promoting soil granulation. Here, crystalline calcium carbonate exhibits weak acidity and does not generate heat even in contact with water. Therefore, since the modified soil does not substantially change in pH and does not rise in temperature, it is highly safe and stable and easy to handle.

In the soil conditioner according to the present invention,
It is preferable that the weight ratio of the superabsorbent polymer and the crystalline calcium carbonate is set to 10/90 to 40/60.

According to the soil conditioner of this configuration, the blending ratio of the superabsorbent polymer and the crystalline calcium carbonate is set within the above-mentioned appropriate range, so granulation of the fine particle-containing soil is further promoted. At the same time, granular soil that is highly safe and stable and easy to handle can be obtained.

In the soil conditioner according to the present invention,
It is preferable to modify the fine particle-containing soil into plant-growing soil.

According to the soil conditioner of this configuration, by modifying fine particle-containing soil into plant-growing soil, it can be reused in the agricultural field.

FIG. 1 is a photograph showing over time how soil containing fine particles mixed with a soil improver according to an example becomes granulated as it is agitated.

The soil improver of the present invention will be explained. However, the present invention is not limited to the configurations described in the embodiments and examples described below.

The soil conditioner of the present invention improves fine particle-containing soil generated by civil engineering work, construction work, soil decontamination work, etc., and fine particle-containing soil including sludge generated in sewage treatment plants, etc. These are reused as plant growing soil and the like. Here, in this specification, fine particle-containing soil means soil containing particles having an average particle size of approximately 2 mm or less, and mainly includes sand (average particle size is approximately 2 to 0.6 mm), silt ( 0.6 to 0.004 mm in average particle size), soil containing clay (approximately 0.004 mm or less in average particle size), and the like. However, even if the soil contains particles with a relatively large particle size, such as gravel, if it contains fine particles, it is treated as soil containing fine particles. In particular, soil containing fine particles, which contains a large amount of clay, becomes more viscous when it absorbs water, making it difficult to sieve with a classifier, so it has often been discarded without being reused. However, in some cases, fine particle-containing soil is rich in minerals such as iron, manganese, and zinc, as well as nutrients such as leaf mulch and excrement. If possible, not only can disposal costs be reduced, but new value can be created. Therefore, the present inventors have recognized that it is necessary to improve the properties of the fine particle-containing soil in order to enable the reuse of the fine particle-containing soil, and the soil conditioner of the present invention is used. came to create.

The soil conditioner of the present invention contains a superabsorbent polymer and crystalline calcium carbonate. Examples of superabsorbent polymers include polyacrylic acid-based polymers, polymethacrylic acid-based polymers, polyvinyl acetate-based polymers, polyvinyl alcohol-based polymers, carboxymethylcellulose-based polymers, and the like. Among these, a preferred superabsorbent polymer is sodium polyacrylate, which is a typical polyacrylic acid-based polymer. As the crystalline calcium carbonate, commercially available industrial chemicals can be used, but crushed marble containing crystalline calcium carbonate as a main component may also be used.

When the soil conditioner of the present invention containing superabsorbent polymer and crystalline calcium carbonate is blended with fine particle-containing soil and stirred, sievable granular soil can be formed within 80 seconds. Here, "80 seconds", which is the formation time of the granular soil, is a sufficiently quick time to perform the work before and after the agitation of the soil as a batch process without delay, and is industrially or commercially available. It looks highly practical.

The phenomenon of rapid granulation of fine particle-containing soil by using the soil conditioner of the present invention has not yet been clarified, but the superabsorbent polymer absorbs the water contained in the fine particle-containing soil. As a result of the action of crystalline calcium carbonate on the swollen state involving the fine particle-containing soil, the fine particles are aggregated with the crystalline calcium carbonate as a core, and the granulation of the soil is promoted. Conceivable.

It should be noted that crystalline calcium carbonate exhibits weak acidity and has the property of not generating heat even in contact with water. Therefore, the granular soil obtained by the modification does not substantially change in pH and does not rise in temperature with respect to the fine particle-containing soil before modification. Therefore, it can be said that the soil conditioner of the present invention has high safety and stability and is easy to handle.

In the soil conditioner of the present invention, the blending ratio of the superabsorbent polymer and the crystalline calcium carbonate is preferably set to 10/90 to 40/60 by weight. If the blending ratio of the superabsorbent polymer and the crystalline calcium carbonate is set to 10/90 to 40/60, granulation of fine particle-containing soil is further promoted, and safety and stability are high. A granular soil that is easy to handle can be obtained.

In improving the fine particle-containing soil using the soil conditioner of the present invention, the fine particle-containing soil is granulated to a particle size in which 85% or more of it passes through a sieve with an opening of 9.5 mm on a weight basis. It is preferable to convert This makes it easier to handle the obtained granular soil, and makes it particularly suitable for reuse as plant-growing soil.

The soil improver of the present invention can also contain other components, if necessary. Other components include antifoaming agents, pH adjusters, solvents, thickeners, stabilizers, colorants, deodorants, antibacterial agents, antioxidants, and the like.

<Granulation Test (1)>
In order to confirm the performance of the soil conditioner of the present invention, a granulation test was conducted in Example 1 and Comparative Examples 1 to 8 below, in which various chemicals were blended in simulated soil. As a control, a similar test was also conducted on simulated soil containing no chemicals. Mixed soil of red soil and black soil was used as the simulated soil. The main components of red clay and black soil are sand (average particle size is approximately 2 to 0.6 mm), silt (average particle size is approximately 0.6 to 0.004 mm), and clay (average particle size is approximately 0.004 mm or less). , which corresponds to soil containing fine particles. In addition, the various drugs used are the following products.
・Sodium polyacrylate (super absorbent polymer): manufactured by Nippon Shokubai Co., Ltd. ・Crystalline calcium carbonate: manufactured by Nitto Funka Kogyo Co., Ltd. ・Amorphous calcium carbonate: manufactured by Yakusen Lime Co., Ltd. ・Quicklime: Kashino Lime Industry Co., Ltd. Company-made Slaked lime: Yakusen lime Co., Ltd.

[Example 1]
30 g of the agent (soil conditioner of the present invention) in which the mixing ratio of sodium polyacrylate and crystalline calcium carbonate was set to 20/80 by weight per 1 kg of simulated soil (water content of about 40% by weight). and agitated in a Hobart mixer for 100 seconds. Then, the pH and temperature of the soil (hereinafter referred to as "treated soil") immediately after the stirring was completed were measured. Further, the treated soil was sieved (sieve size: mesh opening 9.5 mm, mesh opening 4.75 mm) to confirm the granulation state.

[Comparative Example 1]
30 g of a drug in which the mixing ratio of sodium polyacrylate and amorphous calcium carbonate was set to 20/80 by weight was blended with 1 kg of simulated soil (water content of about 40% by weight), as in Example 1. was stirred. Then, the same measurement and confirmation as in Example 1 were performed on the obtained treated soil.

[Comparative Example 2]
30 g of a chemical in which the mixing ratio of sodium polyacrylate and quicklime was set to 20/80 by weight was blended with 1 kg of simulated soil (water content of about 40% by weight), and the mixture was stirred in the same manner as in Example 1. rice field. Then, the same measurement and confirmation as in Example 1 were performed on the obtained treated soil.

[Comparative Example 3]
To 1 kg of simulated soil (water content of about 40% by weight), 30 g of an agent in which the mixing ratio of sodium polyacrylate and slaked lime was set to 20/80 by weight was blended, and the mixture was stirred in the same manner as in Example 1. rice field. Then, the same measurement and confirmation as in Example 1 were performed on the obtained treated soil.

[Comparative Example 4]
6 g of sodium polyacrylate was added as a chemical agent to 1 kg of simulated soil (water content: about 40% by weight), and the mixture was stirred in the same manner as in Example 1. Then, the same measurement and confirmation as in Example 1 were performed on the obtained treated soil.

[Comparative Example 5]
80 g of crystalline calcium carbonate was added as a chemical agent to 1 kg of simulated soil (water content: about 40% by weight), and the mixture was stirred in the same manner as in Example 1. Then, the same measurement and confirmation as in Example 1 were performed on the obtained treated soil.

[Comparative Example 6]
80 g of amorphous calcium carbonate was added as a chemical agent to 1 kg of simulated soil (water content: about 40% by weight), and the mixture was stirred in the same manner as in Example 1. Then, the same measurement and confirmation as in Example 1 were performed on the obtained treated soil.

[Comparative Example 7]
80 g of quicklime was added as a chemical agent to 1 kg of simulated soil (water content: about 40% by weight), and the mixture was stirred in the same manner as in Example 1. Then, the same measurement and confirmation as in Example 1 were performed on the obtained treated soil.

[Comparative Example 8]
80 g of slaked lime was added as a chemical agent to 1 kg of simulated soil (water content: about 40% by weight), and the mixture was stirred in the same manner as in Example 1. Then, the same measurement and confirmation as in Example 1 were performed on the obtained treated soil.

〔Control〕
The same agitation as in Example 1 was performed with respect to 1 kg of the simulated soil (water content of about 40% by weight) without adding any chemicals. Then, the same measurement and confirmation as in Example 1 were performed on the obtained treated soil.

The test results of Example 1, Comparative Examples 1 to 8, and the control in granulation test (1) are shown in Table 1 below. The evaluation was made on a three-grade scale from A to C, from the best to the best, comprehensively considering the pH, temperature and granulation state of the treated soil.

In Example 1, which contains sodium polyacrylate and crystalline calcium carbonate, the pH and temperature of the treated soil are almost unchanged from the control in which the chemical is not used, and the safety and stability are high. Met. In addition, 97% of the treated soil on a weight basis can pass through a sieve with an opening of 9.5 mm, and further 77% can pass through a sieve with an opening of 4.75 mm. formed the soil.

On the other hand, in Comparative Example 1, in which sodium polyacrylate and amorphous calcium carbonate were blended, there was almost no change in the pH and temperature of the treated soil. The passage rate of the sieve with an opening of 4.75 mm was slightly inferior to that of Example 1. In fact, the treated soil of Comparative Example 1 was insufficiently granulated and slightly sticky, making it difficult to handle compared to Example 1.

Comparative Example 2, in which sodium polyacrylate and quicklime were blended, showed an increase in pH and temperature, and had problems in safety and stability. In addition, the passing rate of the sieve with a mesh size of 9.5 mm and the passing rate of the sieve with a mesh size of 4.75 mm were inferior to those of Example 1.

Comparative Example 3, in which sodium polyacrylate and slaked lime were blended, showed an increase in pH and temperature, and had problems in safety and stability. In addition, the passing rate of the sieve with a mesh size of 9.5 mm and the passing rate of the sieve with a mesh size of 4.75 mm were considerably inferior to those of Example 1.

Regarding Comparative Example 4 containing only sodium polyacrylate and Comparative Examples 5 to 8 containing only various calcium compounds, the soil was not sufficiently granulated and was difficult to handle. In addition, in Comparative Examples 7 and 8, an increase in pH and temperature was observed, and there were problems with safety and stability.

<Granulation test (2)>
Next, in the soil improver of the present invention, a granulation test was carried out using an agent in which the compounding ratio of sodium polyacrylate and crystalline calcium carbonate was changed.

[Example 2]
30 g of the agent (soil conditioner of the present invention) in which the mixing ratio of sodium polyacrylate and crystalline calcium carbonate is set to 10/90 by weight per 1 kg of simulated soil (water content of about 40% by weight). and agitated in a Hobart mixer for 100 seconds. Then, the pH and temperature of the soil (hereinafter referred to as "treated soil") immediately after the stirring was completed were measured. Further, the treated soil was sieved (sieve size: mesh opening 9.5 mm, mesh opening 4.75 mm) to confirm the granulation state.

[Example 3]
30 g of the agent (soil improver of the present invention) in which the mixing ratio of sodium polyacrylate and crystalline calcium carbonate was set to 40/60 by weight per 1 kg of simulated soil (water content of about 40% by weight). and stirred in the same manner as in Example 2. Then, the same measurement and confirmation as in Example 2 were performed on the obtained treated soil.

The test results of Examples 2 and 3 in granulation test (2) are shown in Table 2 below. Table 2 also shows the test results of Example 1 and the control in the previous granulation test (1). As in the granulation test (1), the pH, temperature, and granulation state of the treated soil were comprehensively examined, and the evaluation was performed on a three-grade scale from A to C from the best.

Example 2 in which the mixing ratio of sodium polyacrylate and crystalline calcium carbonate was 10/90 by weight, and Example 3 in which the mixing ratio was 40/60 by weight were 20/20 by weight. As in Example 1, which was 80, the pH and temperature of the treated soil were almost unchanged from the control in which no chemicals were used, indicating high safety and stability. In addition, the sieve passage rate of the treated soil with an opening of 9.5 mm and the sieve passage rate with an opening of 4.75 mm were both high, forming an ideal granular soil that was easy to handle.

<Granulation test (3)>
Next, the granulation of the fine particle-containing soil mixed with the soil conditioner of the present invention was observed over time as it was agitated, and the time required to form granular soil was confirmed. In this granulation test (3), a soil conditioner (equivalent to Example 1) with a mixing ratio of sodium polyacrylate and crystalline calcium carbonate of 20/80 by weight was used, and the stirring time with a Hobart mixer was was set to 0 to 100 seconds, and the condition of the soil was visually observed every 10 seconds.

FIG. 1 is a photograph showing over time how fine particle-containing soil mixed with a soil conditioner is granulated with agitation. The granulated state of the soil was evaluated on a four-grade scale from A to D from the best.

From FIG. 1, the granular soil begins to form 40 seconds after the start of stirring, the granular soil is almost completely formed after 70 to 80 seconds, and thereafter the shape of the formed granular soil is maintained stably. It was confirmed that As described above, it has become clear that by using the soil conditioner of the present invention, fine particle-containing soil can be reformed into granular soil that can be sieved and easily handled within 80 seconds. rice field.

The soil conditioner of the present invention can be used to improve waste soil generated by civil engineering work, construction work, soil decontamination work, etc., and viscous soil such as sludge generated in sewage treatment plants and the like. In addition, the granular soil obtained after modification can be suitably used as plant-growing soil.

Claims (5)

A soil conditioner that improves waste soil generated from civil engineering work, construction work, or soil decontamination work, or cohesive soil generated at a sewage treatment plant, as fine particle-containing soil,
a superabsorbent polymer;
crystalline calcium carbonate;
contains
A soil conditioner, wherein the blending ratio of the superabsorbent polymer and the crystalline calcium carbonate is set to 10/90 to 40/60 by weight . The soil conditioner according to claim 1, wherein the superabsorbent polymer is sodium polyacrylate. The soil conditioner according to claim 1 or 2 , wherein the fine particle-containing soil is modified into a plant-growing soil. 4. Any one of claims 1 to 3, wherein when blended with the fine particle-containing soil, 85% or more of the fine particle-containing soil is granulated on a weight basis to a particle size that can pass through a sieve with an opening of 9.5 mm. The soil conditioner as described in . 5. The soil conditioner according to claim 4, wherein the granulated soil does not increase in pH and temperature compared to the fine particle-containing soil before granulation.

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