Spraying Method

Abstract

To provide a spraying method using bentonite, wherein the clogging of piping is prevented.SOLUTION: The present invention discloses a method for air-pumping a bentonite to a spraying position through the piping of a sprayer with a spraying hose 20, wherein the bentonite is made up of a material containing a bentonite mixture and a dispersant with a specified quantity of water added thereto, giving adhesion to it. Preferably, the dispersant is primarily composed of polycarboxylate.SELECTED DRAWING: Figure 1

Description

[Technical field]

[0001] The present invention relates to a spraying method. [Background technology]

[0002] As a method of disposing of radioactive waste, it is planned to use a dedicated tunnel to transport the radioactive waste to an underground facility. When closing such an underground facility, it is necessary to backfill the tunnel that was used. Here, when backfilling, it is being considered to form a low-permeability layer in the tunnel to prevent the outflow of radioactive waste by groundwater.

[0003] In order to form such a low-permeability layer, a spraying method using a material containing bentonite has been considered. There are two types of spraying methods: wet and dry. The wet method is a method in which bentonite that has been given adhesiveness by adding a certain amount of moisture is air-pressurized using a spraying hose. The dry method is a method in which dry bentonite is air-pressurized using a spraying hose, and moisture is supplied while spraying it just before spraying.

[0004] Patent Document 1 discloses a wet spraying method using bentonite. [Prior art documents] [Patent documents]

[0005] [Patent Document 1] JP 2008-223359 A Summary of the Invention [Problem to be solved by the invention]

[0006] By the way, bentonite swells when it absorbs moisture. When using a wet spraying method, the swollen bentonite gradually adheres to the inner surface of the spraying hose or nozzle, which may result in clogging of the spraying hose or nozzle.

[0007] An object of the present invention is to provide a method for suppressing blockage of pipes in a spraying method using bentonite. [Means for solving the problem]

[0008] The present inventors have found that when a dispersant is added to a material containing bentonite, the viscosity of the material decreases, making it possible to spray the material without clogging the spray hose or nozzle. The present invention is based on this finding.

[0009] Specifically, one embodiment of the present invention is a spraying method in which a material containing a bentonite mixture and a dispersant is sprayed onto a spraying location through a piping of a spraying device. Effect of the Invention

[0010] According to the present invention, in a spraying method using bentonite, clogging of pipes can be suppressed. [Brief description of the drawings]

[0011] [Figure 1] FIG. 1 is a diagram showing a spraying device according to an embodiment. [Diagram 2] FIG. 13 is a diagram showing material adhered to the inside of a pipe in an embodiment. [Diagram 3] FIG. 2 is a diagram showing the spraying state (without dispersant) in an example. [Figure 4] FIG. 1 is a diagram showing the spraying state (with dispersant) in an example. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0012] The objectives, features, advantages, and ideas of the present invention will be clear to those skilled in the art from the description of this specification, and those skilled in the art can easily reproduce the present invention from the description of this specification. The embodiments and specific examples of the invention described below show preferred embodiments of the present invention, and are shown for illustrative or explanatory purposes, and do not limit the present invention thereto. It is clear to those skilled in the art that various modifications and alterations can be made based on the description of this specification within the intent and scope of the present invention disclosed in this specification.

[0013] The materials used in the spraying method according to this embodiment include a bentonite mixture and a dispersant.

[0014] ==Bentonite Mixture== The bentonite mixture includes at least bentonite and water.

[0015] Bentonite is a powdered or granular material produced from bentonite ore. It has high viscosity and water absorption properties. It swells when it absorbs water and has low water permeability in the solid state.

[0016] Specifically, the bentonite may be Na-type bentonite or Ca-type bentonite. For example, Kunigel V1 ("Kunigel" is a registered trademark, manufactured by Kunimine Kogyo Co., Ltd.) may be used as powdered Na-type bentonite.

[0017] Moreover, it is preferable that the water content of the bentonite mixture is about ±2% of the optimum water content defined in JIS A 1210. By setting the water content of the bentonite mixture in this way, the density of the low-permeability layer (described later) can be increased.

[0018] The bentonite mixture may contain sand (for example, silica sand), gravel, soil, etc. as solid components other than bentonite.

[0019] ==Dispersant== The dispersant is used to reduce the viscosity of the bentonite mixture. The dispersant is preferably one whose main component is a sulfonate, more preferably one whose main component is a polycarboxylate or a polyphosphate. The dispersant contains water.

[0020] The proportion of the dispersant used in the spraying method according to this embodiment is preferably 0.1 to 0.5 mass% in terms of the weight ratio of the bentonite mixture. If the proportion of the dispersant is lower than 0.1 mass%, the dispersant is not mixed sufficiently with the entire material. If the proportion of the dispersant is higher than 0.5 weight%, the bentonite mixture may aggregate.

[0021] In addition, the moisture content of the entire material (bentonite mixture and dispersant) used in the spraying method according to this embodiment is preferably within ±2% of the optimum moisture content specified in JIS A 1210.

[0022] ==Other Additives== The material used in the spraying method according to this embodiment may contain appropriate additives within the range that does not affect the performance of the bentonite mixture and the dispersant.

[0023] ==Spraying method== In the spraying method according to the present embodiment, a material containing a bentonite mixture and a dispersant is sprayed onto a spraying position via a piping of a spraying device.

[0024] The spraying position is the part where the material is sprayed. For example, when filling a tunnel for transporting radioactive waste to an underground facility, the spraying position is the inside of the tunnel. In this case, the material is used as backfill material for the tunnel.

[0025] The spraying device applies the material to the spray location and may be a standalone device or may be attached to other equipment such as heavy machinery.

[0026] 1 shows a spraying device 1 according to this embodiment. The spraying device 1 has a main body 10, a hose 20, and a nozzle 30.

[0027] The main body 10 includes a storage section for storing the materials, a compressor for pneumatically feeding the materials (neither of which is shown), etc. The materials may be mixed in advance in an external mixer device and then supplied to the storage section of the main body 10, or the materials may be mixed within the main body 10 by providing a mixer in the main body 10.

[0028] The hose 20 is a long pipe connected at one end to the main body 10 and for guiding the pneumatically-fed material to the nozzle 30. The hose 20 may be flexible or rigid. The nozzle 30 is a pipe provided at the other end of the hose 20 (the end opposite to the end connected to the main body 10) for discharging the material. In the case of a spraying device used for filling a tunnel, the length of the hose 20 and the nozzle 30 is preferably about 15 m to 30 m. In addition, the inner diameter of the hose 20 is preferably about 60 to 80 mm, and the inner diameter of the nozzle 30 is preferably about 30 to 60 mm. The inner diameters of the hose 20 and the nozzle 30 may be the same or different. As a specific example, the diameter of the tip of the nozzle 30 may be smaller than the diameter of the tip of the hose 20. The hose 20 and the nozzle 30 are examples of "piping".

[0029] In addition, the spraying device is not limited to the configuration in Fig. 1 as long as it has a configuration including piping for spraying the material to the spraying position. On the other hand, since the tunnel for transporting the radioactive waste to the underground facility is narrow (for example, about 4 m in diameter), it is preferable that the spraying device used for filling the tunnel is smaller than a general spraying device.

[0030] The addition of a dispersant to the bentonite mixture reduces the viscosity of the bentonite mixture, making the material less likely to stick as it passes through the piping of the spraying device, meaning that the bentonite mixture and the material containing the dispersant can be sprayed at the spraying location without clogging the piping.

[0031] The material sprayed at the spraying position solidifies to form a low-permeability layer. The low-permeability layer is a layer that suppresses the outflow of groundwater, etc. The permeability coefficient of the low-permeability layer is, for example, 1.0 x 10 -8 m / s or less.

[0032] == Example == Spraying experiments were carried out using materials with and without dispersants.

[0033] (Materials used) The materials used are as follows: Bentonite: Kunigel V1 (Na-type bentonite, manufactured by Kunimine Kogyo Co., Ltd.) Silica sand: Mixture of No. 3 and No. 5 (dry weight ratio 50:50. Kashima-produced) Dispersant: Polycarboxylate-based dispersant

[0034] (How to prepare materials for spraying) Silica sand No. 3 (wet mass 125.3 kg) and silica sand No. 5 (wet mass 125.6 kg) were added to the mixer and stirred for 30 seconds. Bentonite (wet mass 276.8 kg) was then added and stirred for 30 seconds. The mixer was a twin-shaft forced mixing mixer (capacity 0.5 m 3 ) was used.

[0035] The aqueous solution of the dispersant was then added to the mixer and stirred for 300 seconds to prepare the material for spraying. On the other hand, when no dispersant was included, only water was added. The amount of water was adjusted so that the water content of the entire material was 15.8%.

[0036] (Spraying of materials) The material prepared by the above-mentioned method that passed through a 50 mm sieve was put into a spraying device, and spraying was started. The spraying device used had a material pumping distance (length of piping) of 20 m, a hose with an inner diameter of 75 mm, and a spray nozzle with an inner diameter of 40 mm. The amount of air sprayed in the spraying device was set to 12 m. 3 / h and the rotor speed was 5 rpm. The discharge amount of the material was determined by the amount of air sprayed and the rotor speed.

[0037] (Experimental Results) When a material without dispersant was used, the discharge rate dropped significantly one minute after spraying began, and the spraying equipment was stopped. When the inside of the pipe was checked, lumps of material were formed as shown in Figures 2 (a) and (b). It is believed that these lumps were material containing bentonite that had swelled with moisture and adhered to the inside of the pipe, causing the pipe to become clogged. Furthermore, when a material without dispersant was used, dust from the bentonite mixture was generated during work, as shown in Figure 3.

[0038] On the other hand, when the material containing the dispersant was used, all the material (500 kg for one patch) could be discharged without stopping the operation of the spraying equipment. Also, as shown in Figure 4, almost no dust was generated by the bentonite mixture during the work.

[0039] This result can be attributed to the following reasons, for example. That is, in the case of a material that does not contain a dispersant, bentonite in a state of swelling with moisture and bentonite in a state of not swelling are mixed in the material. And, because there is further moisture between the particles of swollen bentonite, the viscosity of the bentonite increases, and it becomes easy to adhere to the inside of the pipe. Also, since the non-swollen bentonite is in a dry state, it becomes easy to scatter when sprayed. On the other hand, by adding a dispersant, the moisture becomes uniform in the material, and most of the bentonite becomes in a swollen state. That is, since there is almost no dry bentonite, it does not scatter when sprayed. Also, it can be considered that the viscosity decreases due to the electrostatic repulsion between the swollen bentonite particles, and it becomes possible to discharge the bentonite without adhering to the inside of the pipe.

Claims

1. A spraying method in which a material containing a bentonite mixture, water, and a dispersant mainly composed of a polycarboxylate is sprayed onto a spraying position through a piping of a spraying device, A spraying method characterized in that the moisture content of the material is within ±2% of the optimum moisture content specified in JIS A 1210.

2. A spraying method as described in claim 1, wherein the material further contains silica sand.

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