Dust scattering suppression method

Abstract

To facilitate falling of dust which has been scattered already to a ground surface, and to suppress re-scattering of fallen dust.SOLUTION: A dust scattering suppression method comprises: a first step of spraying a solution 2 including polycation by a sprayer 4, capturing dust 1 floating in the air and falling the dust to a ground surface; and a second step of spraying a solution 3 including polyanion by an automobile sprinkler 5, to the ground surface, mixing the sprayed solution with the solution 2 including polycation thereby forming a polyion complex and solidifying soil. By spraying the solution 2 including polycation, a positive charge of the polycation and negatively charged dust 1 are coupled electrically, and falling the dust to the ground surface. Then, by spraying the solution including polyanion to the ground surface, the polycation having captured the dust and polyanion react thereby forming a polyion complex, and after drying the formed polyion complex, the polyion complex and the soil are entangled and solidified, thereby suppressing re-scattering of the fallen dust.SELECTED DRAWING: Figure 2

Description

[Technical field]

[0001] The present invention relates to a method for suppressing the scattering of dust caused by construction vehicles such as dump trucks traveling on temporary roads at construction sites such as housing development sites and tunnel construction sites. [Background technology]

[0002] In the past, workers at construction sites inhaled dust kicked up by construction vehicles traveling on unpaved temporary roads, which caused respiratory disorders and pneumoconiosis, and this had become a major social issue. During the peak of construction, construction vehicles came and went many times a day with almost no break, which increased the amount of dust being dispersed.

[0003] One method of preventing dust from scattering is to sprinkle water on the construction site or on temporary roads to moisten the surface layer, but this method of sprinkling water causes quick drying, especially in summer, and the frequency of water sprinkling increases, placing a heavy burden on the work.

[0004] Another widely used method is to lay multiple steel plates on the site and have construction vehicles run over them to prevent dust from scattering. This method is often used in urban areas and other sites surrounded by residential areas. However, this method of laying steel plates has an issue in that it takes time to replace the steel plates at sites such as construction sites where the driving route changes daily.

[0005] Another method is to spray commercially available dust suppressants on the construction site or temporary roads. However, such dust suppressants are expensive, and there is a problem that it is very costly to spray them over a wide area.

[0006] In recent years, a technique has been proposed for solidifying soil and suppressing dust using a polyion complex, as disclosed in, for example, the following Patent Documents 1 to 3. A polyion complex is a gel-like substance that is produced by mixing polycations and polyanions, as shown in Figure 1, and does not dissolve in water. By spraying this on soil, hydrophilic parts consisting of ion-binding sites of cations and anions and hydrophobic parts forming polymer chains are unevenly dispersed in the soil, and after drying, the polyion complex and soil particles are entangled and fixed. [Prior art documents] [Patent documents]

[0007] [Patent Document 1] JP 2013-185941 A [Patent Document 2] JP 2019-56075 A [Patent Document 3] JP 2015-199057 A Summary of the Invention [Problem to be solved by the invention]

[0008] The methods described in the above Patent Documents 1 to 3 involve spraying a solution containing a polyion complex on the soil surface to solidify the soil and prevent dust from scattering from the ground due to wind or the passage of construction vehicles, but they were ineffective against dust that had already been scattered. That is, they were ineffective against dust generated by the repeated passage of construction vehicles causing the soil solidified by spraying the polyion complex to peel off and expose the underlying soil, or against the large amount of dust generated by excavation work near the face in tunnel construction.

[0009] Therefore, a main object of the present invention is to provide a method for suppressing scattering of dust, which makes it easier for already scattered dust to fall to the ground and suppresses the fallen dust from being re-scattered. [Means for solving the problem]

[0010] In order to solve the above problem, the present invention according to claim 1 comprises: Use a sprayer to spray into the air where dust is suspended. The aqueous solution containing the polycation The diameter of the water particles is set to 5 to 200 μm so that the sprayed water particles can remain suspended for a certain period of time. The first step is to spray and capture the dust suspended in the air and let it fall to the ground; Before the aqueous solution containing the polycation is dried, The present invention provides a method for suppressing dust dispersion, which comprises a first step of spraying an aqueous solution containing a polyanion onto the ground, mixing the aqueous solution containing the polycation to form a polyion complex, and a second step of solidifying the soil.

[0011] In the invention described in claim 1, as a first step, Use a sprayer to spray into the air where dust is suspended. The aqueous solution containing the polycation The diameter of the water particles is set to 5 to 200 μm so that the sprayed water particles can remain suspended for a certain period of time. By spraying, the positive charge of the polycation electrically bonds with the negatively charged dust particles such as clay and silt, and the aqueous solution containing the polycation sprayed into the air captures the floating dust particles and causes them to fall to the ground, making it easier for the dust particles that have already been dispersed to fall to the ground. After that, in the second step, Before the aqueous solution containing the polycation is dried, By spraying an aqueous solution containing polyanions on the ground, the polycations that capture the dust react with the polyanions to form a polyion complex. After drying, the polyion complex becomes entangled with the soil and is fixed, preventing the fallen dust from being scattered again.

[0012] As the present invention according to claim 2, The sprayer for spraying the aqueous solution containing polycations is adapted to use a combination of a plurality of nozzles each having different particle sizes for the water droplets that are sprayed. A method for suppressing scattering of dust according to claim 1. A method for suppressing scattering of dust according to claim 1 is provided.

[0013] In the invention described in claim 2, The sprayer for spraying an aqueous solution containing a polycation is configured to use a combination of a plurality of nozzles each having different particle sizes for the sprayed water particles.

[0014] According to a third aspect of the present invention, there is provided a method for suppressing scattering of dust according to either one of the first and second aspects, in which the amount of polyanion dispersed is greater than that of polycation.

[0015] In the invention described in claim 3, even if the amounts of polycation and polyanion to be sprayed are not equal, by spraying more polyanion than polycation, approximately the same dust dispersion suppression effect can be obtained. Effect of the Invention

[0016] As described above in detail, according to the present invention, dust that has already been scattered is made more likely to fall to the ground, and the fallen dust is prevented from being re-scattered. [Brief description of the drawings]

[0017] [Figure 1] FIG. 2 is a schematic diagram showing a state in which soil particles are immobilized by a polyion complex. [Diagram 2] 1 is a schematic diagram showing a dust scattering suppression method according to the present invention. [Diagram 3] FIG. 1 is a schematic diagram of the experimental setup. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0018] Hereinafter, an embodiment of the present invention will be described in detail with reference to the drawings.

[0019] As shown in FIG. 2, the dust dispersion suppression method according to the present invention comprises a first step of spraying an aqueous solution 2 containing a polycation into the air while dust 1 is suspended in the air, and allowing the water particles of the aqueous solution 2 containing a polycation sprayed into the air to capture the suspended dust 1 in the air and cause it to fall to the ground; and a second step of spraying an aqueous solution 3 containing a polyanion on the ground and mixing it with the aqueous solution containing a polycation to form a polyion complex and solidify the soil.

[0020] The dust 1 is a fine particle material such as clay or silt that floats in the air when soil on the ground is stirred up by the passage of construction vehicles or the wind, or scattered by excavation work of a tunnel face, etc. This dust 1 is generally negatively charged, and the particle size of fine dust that is particularly harmful to the human body is approximately 10 μm or less.

[0021] The aqueous solution 2 containing the polycation is produced by dissolving a polycation (positively charged cation) in water. The polycation may be of natural or synthetic origin, and examples thereof include dicyandiamide-formaldehyde resin, diethylenetriamine-dicyandiamide-ammonium chloride condensate, (meth)acryloyloxyalkyltrialkylammonium chloride polymer, dimethyldiallylammonium chloride polymer, ethyleneimine polymer, diallylamine polymer, ammonia-epichlorohydrin-dimethylamine copolymer, polyacrylamide resin, polymethacrylate resin, polyacrylate resin, and cationized cellulose.

[0022] The aqueous solution 3 containing the polyanion is produced by dissolving a polyanion (a negatively charged anion) in water. The polyanion may be of natural or synthetic origin, and examples thereof include carboxymethyl cellulose, carboxymethyl amylose, carboxymethylated starch, lignin sulfonic acid and its salts, (poly)acrylic acid and its salts, and polysulfonic acid and its salts.

[0023] The water constituting the aqueous solutions 2 and 3 may be water such as tap water, or an aqueous medium containing water as the main component. The aqueous medium containing water as the main component used in the present invention is a medium containing water at 80% by mass or more, preferably 90% by mass or more, and more preferably 95% by mass or more. In addition to water, a small amount of water-soluble alcohols such as methyl alcohol, ethyl alcohol, and 2-propanol, ethers such as diethyl ether and tetrahydrofuran, or ketones such as acetone, methyl ethyl ketone, and cyclohexanone may be mixed and used. These solvents are used to adjust the viscosity of each of the aqueous solutions 2 and 3, or when other components other than polycations and polyanions are used in combination as necessary, it is necessary to dissolve those components. Among these solvents, ethyl alcohol is preferred in order to reduce the impact on the human body and the environmental load.

[0024] To prepare the aqueous solution 2 containing the polycation, the polycation is mixed with a solvent so that the content of the polycation is 0.5 to 5 mass%, preferably 0.7 to 2 mass%. If the content of the polycation is too high, the viscosity of the aqueous solution increases, making it difficult to spray into the air. On the other hand, if the content is too low, it becomes difficult to capture dust suspended in the air, and the effect of solidifying the soil decreases.

[0025] In order to spray the aqueous solution 2 containing the polycation into the air, it is preferable to use a sprayer 4 as shown in FIG. 2. The sprayer 4 ejects the aqueous solution 2 pumped by a pump into the air as a fine artificial mist from a nozzle provided at the tip. The size (diameter) of the water particles sprayed from the nozzle is not particularly limited as long as the water particles sprayed in the air can float for a certain period of time, but is preferably 5 to 200 μm, and more preferably 5 to 30 μm. The nozzle of the sprayer 4 is installed at a predetermined height from the ground and is arranged with the tip facing horizontally or above horizontally, so that the aqueous solution 2 containing the polycation is efficiently sprayed into the air. The water particles of the aqueous solution 2 sprayed into the air capture dust 1 floating in the air, or fall to the ground as water particles alone. Note that a shower nozzle, a sprinkler, or the like may be used as long as it can eject fine water particles into the air.

[0026] The smaller the particle size of the water particles sprayed from the sprayer 4, the greater the chance that they will float in the air and come into contact with the dust 1, but there is a risk that the amount of water that falls to the ground will decrease. For this reason, it is possible to use a combination of multiple nozzles that spray water particles with different particle sizes, for example by providing a nozzle capable of spraying small water particles at a position high above the ground and a nozzle capable of spraying large water particles at a position low above the ground.

[0027] To prepare the aqueous solution 3 containing the polyanion, the polyanion is mixed with a solvent so that the content of the polyanion is 0.5 to 5 mass %, preferably 0.7 to 2 mass %. If the content of the polyanion is too high, the viscosity of the aqueous solution increases, making it difficult to spray. On the other hand, if the content is too low, the effect of solidifying the soil decreases.

[0028] In order to spray the aqueous solution 3 containing a polyanion on the ground, a sprinkler truck 5 can be used as shown in Fig. 2. The sprinkler truck 5 is a vehicle that can be driven and is equipped with a sprinkler device, and sprays the aqueous solution 3 containing a polyanion in a tank onto the ground from a hose or nozzle provided at the rear of the vehicle. Note that a method in which an operator operates a hose to spray water may also be used without using the sprinkler truck 5.

[0029] The procedure for spraying the aqueous solutions 2 and 3 is as follows: the aqueous solution 2 containing a polycation is sprayed into the air to cause the dust 1 suspended in the air to fall to the ground, and then the aqueous solution 3 containing a polyanion is sprayed onto the ground.

[0030] In this way, in the first step, the aqueous solution 2 containing polycations is sprayed into the air, whereby the positive charges of the polycations electrically bind with the negatively charged dust particles 1 such as clay or silt, and the aqueous solution 2 containing polycations sprayed into the air captures the floating dust particles 1 and causes them to fall to the ground, making it easier for the already scattered dust particles 1 to fall to the ground. In other words, the positively charged polycations and the negatively charged dust particles 1 are reliably bound in the air by electrostatic force, and the aggregation of the dust particles suspended in the air is promoted, forming large flocs that fall to the ground by gravity.

[0031] Then, in the second step, an aqueous solution 3 containing a polyanion is sprayed on the ground, whereby the polycations that capture the dust 1 and fall to the ground, or the polycations that are sprayed into the air and fall to the ground as they are, react with the polyanion to form a polyion complex, which becomes entangled with the soil and fixed after drying, thereby preventing the fallen dust from being re-scattered. The polycations and polyanions are mixed on the surface of the ground and in an area slightly below the ground level by spraying the aqueous solution 3 containing the polyanion toward the ground at high pressure.

[0032] The timing of spraying the polyanion-containing aqueous solution 3 is preferably after the polycation-containing aqueous solution 2 is sprayed into the air, the polycation sprayed into the air captures the dust 1 suspended in the air and falls to the ground, and before the polycation-containing aqueous solution 2 that has fallen to the ground is completely dried. Specifically, it is preferable to spray the polyanion-containing aqueous solution 3 within half a day to a day at the latest after the polycation-containing aqueous solution 2 is sprayed into the air.

[0033] It is preferable that the polycation and polyanion are sprayed in approximately equal amounts, or that the polyanion is sprayed in a larger amount than the polycation. As a result of an experiment described later, when the polyanion is sprayed in a larger amount than the polycation, the dust scattering suppression effect is roughly equivalent to that when the polycation and polyanion are sprayed in approximately equal amounts. On the other hand, as a result of an experiment described later, when the polycation is sprayed in a larger amount than the polyanion, the amount of dust scattering tends to increase, which is not preferable.

[0034] Next, an experiment to verify the effect of suppressing dust scattering will be described. In the experiment, as shown in FIG. 3, a container (inner dimensions: length 166 mm × width 106 mm × height 86 mm) was filled with test soil 10 made of Kanto loam, and each test sample (concentration 1 mass%) shown in Table 1 was sprayed on the surface of the test soil 10 at 5 L / m. 2 The soil was uniformly spread at a ratio of 10 to 150 mm, and then the soil was cured for two days under conditions of a temperature of 20°C and a humidity of 60%. Then, air was blown onto the surface of the test soil 10 for five minutes at a speed of 15 m / s using a blower 11. The amount of soil scattered was measured based on the weight of the test soil 10 before and after the air blowing.

[0035] As a result, as shown in Table 1, the amount of soil scattering was the smallest when a polyion complex with approximately equal amounts of polycation and polyanion was sprayed, followed by a polyion complex with an excess of polyanion mixed in comparison to polycation. In contrast, when a polyion complex with an excess of polycation mixed in comparison to polyanion was sprayed, the amount of soil scattering was greater than when water was sprayed alone, and the dust scattering suppression effect tended to be lower.

[0036] [Table 1] In Table 1, PIC: polyion complex, DAAMAC: polydiallyldimethylammonium chloride (positive charge), CMC: carboxymethylcellulose (negative charge), and PAAcNa: sodium polyacrylate (negative charge). [Explanation of symbols]

[0037] 1...dust, 2...aqueous solution containing polycation, 3...aqueous solution containing polyanion, 4...sprayer, 5...watering truck, 10...test soil, 11...blower

Claims

1. A first step of spraying an aqueous solution containing polycations using a sprayer into the air containing suspended dust, with the water particles being 5 to 200 μm in diameter so that the water particles can remain suspended for a certain period of time, thereby capturing the suspended dust in the air and allowing it to fall to the ground; A method for suppressing dust dispersion, comprising a second step of spraying an aqueous solution containing a polyanion onto the ground before the aqueous solution containing the polycation dries, mixing the aqueous solution containing the polyanion with the aqueous solution containing the polycation to form a polyion complex, and solidifying the soil.

2. A method for suppressing dust dispersion as described in claim 1, wherein the sprayer for spraying an aqueous solution containing a polycation is configured to use a combination of multiple nozzles each having a different particle size for the water particles ejected.

3. 3. The method for suppressing scattering of dust according to claim 1, wherein the amount of polyanion dispersed is greater than the amount of polycation dispersed.

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