Powder mixture transport method and exothermic body manufacturing method

Abstract

To provide a powder mixture transport method which can stably pneumatically transport a powder mixture containing inorganic powder and can suppress piping wear.SOLUTION: In a method for pneumatically transporting a powder mixture 3, in which air is flowed inside a pipe 20 containing stainless steel material, and a powder mixture containing inorganic powder is transported by entraining air, an inner surface 20a of the pipe 20 has a hardness higher than that of an outer surface 20c of the pipe 20 through hardening treatment, the hardness of the inner surface 20a of the pipe 20 is at least 10 times that of the hardest inorganic powder contained in the powder mixture 3, the hardest inorganic powder has a hardness of at least 30 HV and an average particle size of at most 200 μm, the flow rate of the air flowing inside the pipe 20 is at least 200 m / min and at most 500 m / min, and the ratio of mass of the powder mixture 3 against the area S of the inside of the pipe 20 in a cross section perpendicular to the axial direction of the pipe 20 is at least 1.0×104 kg / m2 and at most 5.0×104 kg / m2.SELECTED DRAWING: Figure 1

Description

[Technical field]

[0001] The present invention relates to a method for transporting a powder mixture and a method for producing a heating element. [Background technology]

[0002] Conventionally, a method of pneumatically transporting powder through a pipe is known. When pneumatically transporting powder through a pipe, the powder being transported may collide with the inner surface of the pipe, causing the inner surface of the pipe to be worn. Therefore, a technology for suppressing the wear of the inner surface of the pipe when pneumatically transporting powder through the pipe has been developed. For example, Patent Document 1 describes a method of transporting ash using an ash transport pipe of a pressurized fluidized bed boiler. The ash transport pipe in this document is formed of an inner pipe and an outer pipe, and a wear prevention device is disposed inside the inner pipe. The wear prevention device in this document is formed by an insert made of a steel material containing 9% or more of chromium. This document describes that the wear prevention device in this document can prevent the inner pipe from being worn by the transported ash, and can extend the life of the ash transport pipe. Furthermore, Patent Document 2 describes a method of nitriding the surface of an austenitic stainless steel for the purpose of hardening the surface. [Prior art documents] [Patent documents]

[0003] [Patent Document 1] Japanese Patent Application Publication No. 10-87072 [Patent Document 2] Japanese Patent Application Publication No. 7-78224 Summary of the Invention [Problem to be solved by the invention]

[0004] To explain the wear of the pipe in more detail, when powder is pneumatically transported through the pipe, the powder repeatedly collides with the inner surface of the pipe, causing the wear of the pipe. In the case of serious wear, for example, wear powder generated by the wear of the pipe surface may be mixed into the powder being pneumatically transported. In addition, damage such as holes opening in the pipe may occur during the transport of the powder. In order to suppress or prevent these, it is necessary to frequently replace the pipe. For example, when powder is used to manufacture a certain product, if the frequency of replacing the pipe increases, problems such as a deterioration in production efficiency and high costs will occur. Therefore, it is important to suppress the wear of the inner surface of the pipe. On the other hand, it is also important to be able to transport the powder stably. Although the technology of Patent Document 1 aims to prevent wear of the pipe, the document does not consider at all about stably transporting the powder. Moreover, Patent Document 2 does not disclose anything about pneumatic transportation of powder. As described above, neither of the techniques of Patent Documents 1 and 2 is able to stably transport powder while suppressing wear on the piping at the same time.

[0005] The present invention relates to a method for transporting a powder mixture, which can stably pneumatically transport a powder mixture containing an inorganic powder and can suppress abrasion of piping. [Means for solving the problem]

[0006] The present invention provides a method for pneumatically transporting a powder mixture. In one embodiment, it is preferable to flow air inside a pipe containing a stainless steel material and transport the powder mixture containing the inorganic powder by entraining it in the air. In one embodiment, the inner surface of the pipe is preferably made harder than the outer surface of the pipe by a hardening treatment. In one embodiment, the hardness of the inner surface of the pipe is preferably 10 times or more the hardness of the hardest inorganic powder contained in the powder mixture. In one embodiment, the hardest inorganic powder preferably has a hardness of 30 HV or more and an average particle size of 200 μm or less. In one embodiment, the flow rate of the air flowing through the piping is preferably 200 m / min or more and 500 m / min or less. In one embodiment, the ratio of the mass of the powder mixture to the area of ​​the inside of the pipe in a cross section perpendicular to the axial direction of the pipe is 1.0×10 4 kg / m 2 Above 5.0×10 4 kg / m 2 It is preferable that:

[0007] The present invention also provides a method for producing a heating tool having a heating element. In one embodiment, the method for manufacturing the heating tool includes a transporting step of transporting the powder mixture by a pneumatic transport method for the powder mixture, a heat generating composition forming step of mixing the powder mixture with water to form the heat generating composition after the transporting step; It is preferable that the method further comprises the step of producing a heat generating element by applying a heat generating composition to one side of a base sheet to produce the heat generating element. In one embodiment, the powder mixture preferably contains one or more of a powder of a carbon material, a silicate, and a halide salt. Effect of the Invention

[0008] According to the present invention, a powder mixture containing an inorganic powder can be stably pneumatically transported, and wear of piping can be suppressed. [Brief description of the drawings]

[0009] [Figure 1] FIG. 1 is a schematic diagram showing an outline of a transport device used in a preferred embodiment of the method for transporting a powder mixture of the present invention. [Diagram 2] FIG. 2 is a cross-sectional view perpendicular to the axial direction of a pipe relating to the transportation device shown in FIG. [Diagram 3]3(a) to (c) are schematic diagrams showing how the powder mixture is transported entrained in air when the powder mixture is transported using the transport device shown in FIG. [Figure 4] FIG. 4 is a schematic diagram for explaining a method for measuring the radius of curvature. [Diagram 5] FIG. 5 is a schematic cross-sectional view of a heating tool produced by a preferred embodiment of the method for producing a heating tool of the present invention. [Figure 6] FIG. 6 is a schematic diagram showing an outline of a preferred embodiment of the method for producing a heating tool of the present invention. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0010] The present invention will be described below based on preferred embodiments with reference to the drawings. Figure 1 shows an outline of a conveying device 100 used in a preferred embodiment of the method for pneumatically conveying a powder mixture of the present invention. The conveying device 100 conveys air through a pipe 20 made of a material including stainless steel, and conveys a powder mixture 3 including inorganic powder by entraining the air.

[0011] The transport device 100 has an air source 10, a pipe 20 containing a stainless steel material, a powder supply unit 30, and a transport destination 40. The transport device 100 transports the powder mixture 3 supplied from the powder supply unit 30 through the pipe 20 to the transport destination 40 by compressed air supplied from the air source 10.

[0012] The air source 10 is connected to the pipe 20 so as to be able to supply compressed air into the pipe 20. As the air source 10, for example, a compressor or the like can be used. The powder supplying unit 30 supplies the powder mixture 3 into the pipe 20. In this embodiment, the powder supplying unit 30 has a powder storage unit 31 and a supply flow path 32. The powder storage unit 31 is capable of storing the powder mixture 3 therein. The powder storage unit 31 is connected to the pipe 20 via the supply flow path 32, and the powder mixture 3 in the powder storage unit 31 can be supplied into the pipe 20 via the supply flow path 32. The powder supplying unit 30 may supply the powder mixture 3 continuously or discontinuously.

[0013] In the pneumatic transportation method of this embodiment, first, the powder mixture 3 is supplied from the powder supply unit 30 into the piping 20. Next, the air source 10 is operated to supply compressed air into the inside of the piping 20. At this time, from the viewpoint of preventing the powder mixture 3 inside the piping 20 from being transported to the powder supply unit 30 side through the communication hole with the supply flow path 32 of the powder supply unit 30 in the piping 20, it is preferable that the communication hole with the supply flow path 32 of the powder supply unit 30 in the piping 20 is closed. In addition, instead of closing the communication hole in the piping 20, it is also preferable to provide a check valve that allows the inflow of air from the supply flow path 32 of the powder supply unit 30 into the inside of the piping 20 and prevents the outflow of air from the inside of the piping 20 to the supply flow path 32 of the powder supply unit 30. The compressed air may be supplied continuously or intermittently.

[0014] Then, the powder mixture 3 is transported by being entrained in the compressed air supplied inside the pipe 20. After all of the powder mixture 3 supplied inside the pipe 20 has been transported to the destination 40, the operation of the air source 10 is stopped. Thereafter, the powder mixture 3 may be supplied again inside the pipe 20, and the pneumatic transport method of this embodiment may be performed again. In the pneumatic transportation method of this embodiment, the powder mixture 3 may be transported in a batch manner or a continuous manner. For example, the air source 10 may be operated in advance to flow air inside the pipe 20, and then the powder mixture 3 may be supplied into the pipe 20.

[0015] The powder mixture 3 contains an inorganic powder. Examples of the inorganic powder include powder of an oxidizable metal. Examples of the oxidizable metal include metal particles such as iron, aluminum, manganese, magnesium, zinc, and calcium. These may be used alone or in combination of two or more. Among these, iron powder is particularly preferred from the viewpoints of ease of handling, safety, and production costs. Examples of the iron powder include one or more types selected from reduced iron powder and atomized iron powder.

[0016] The inorganic powder having the highest hardness contained in the powder mixture 3 (hereinafter, also referred to as the "hardest inorganic powder") preferably has a hardness of 30HV or more and an average particle size of 200μm or less. In general, when an inorganic powder having a hardness of 30HV or more is transported through a pipe, the inorganic powder collides with the inner surface of the pipe, causing the inner surface of the pipe to be worn. In this embodiment, however, the average particle size of the hardest inorganic powder is set to 200μm or less, so that the wear of the inner surface of the pipe can be effectively suppressed. From the viewpoint of achieving this effect more significantly, the average particle size of the hardest inorganic powder is preferably 150μm or less, more preferably 100μm or less, and even more preferably 50μm or less. The hardness of the hardest inorganic powder may be 50HV or more, 80HV or more, or 100HV or more. The upper limit of the hardness of the hardest inorganic powder can be, for example, 130HV. In this embodiment, the inner surface 20a of the pipe 20 is subjected to a hardening treatment, which also contributes to suppressing wear of the inner surface of the pipe. The hardening treatment will be described later.

[0017] The hardness of the hardest inorganic powder can be measured by the following method. [Method for measuring hardness of the hardest inorganic powder] After mixing a curable resin such as epoxy resin with inorganic powder, the resin is cured to obtain a plate-shaped cured product measuring 1 cm in length, 1 cm in width, and 0.5 cm in thickness. At least one surface of the obtained cured product is polished to form a measurement plane. In this way, a measurement sample having a measurement plane is prepared. The ratio of the curable resin to the inorganic powder in the measurement sample is set so that the filling level of the inorganic powder in the measurement sample is as high as possible. The surface of the cured product is polished to such an extent that irregularities or foreign matter are not visible on the surface, so that the indentation depth can be accurately measured in the measurement of the indentation depth described below. A triangular pyramidal diamond indenter is pressed into the measurement plane of the obtained measurement sample with a test force of 49 mN for 5 seconds using a hardness tester (e.g., Dynamic Ultra-Micro Hardness Tester DUH-211S (Shimadzu Corporation)) to measure the indentation depth D. Measurements are taken at 20 arbitrary locations on the measurement plane. Then, for each of the obtained measured values ​​D, the hardness HR is calculated using the following formula (1), and the maximum hardness among the calculated hardness values ​​HR is defined as the hardness of the hardest inorganic powder. In the following formula (1), F1 is the force (49 mN) used when pressing the diamond indenter into the test piece.

[0018]

number

[0019] The average particle size of the hardest inorganic powder can be measured by the following method. [Method for measuring the average particle size of the hardest inorganic powder] The average particle size of the hardest inorganic powder can be the volume-based median size measured by a laser diffraction particle size distribution analyzer. The median size can be measured using a HORIBA LA-950V2 made by HORIBA, Ltd., a standard dry cell, and a refractive index set to 3.5 for the real part and 3.8i for the imaginary part, according to a conventional method.

[0020] The pipe 20 includes a stainless steel material. The pipe 20 may be made of only a stainless steel material. The pipe 20 may have a two-layer structure or a multi-layer structure of three or more layers, and the innermost surface may be made of a stainless steel material. As the stainless steel material, various known materials may be used, and it is preferable to use, for example, SUS304 or the like.

[0021] The pipe 20 has its inner surface 20a hardened. The inner surface 20a of the pipe 20 has a higher hardness than the outer surface 20c. Examples of hardening treatments include nitriding, shot peening, sulfurizing, plating, boronizing, and diffusion penetration, and these can be used alone or in combination of two or more. For example, it is preferable to perform both the nitriding and shot peening simultaneously or in any order. An example of a hardening treatment that includes both the nitriding and shot peening is a combined treatment of the nitriding and shot peening. The pipe 20 used in this embodiment is preferably subjected to a hardening treatment to form a hardened layer on its inner surface 20a. The hardened layer can be formed, for example, by subjecting the inner surface 20a of the pipe 20 to a nitriding treatment and immersing the inner surface 20a in nitrogen.

[0022] In this embodiment, the hardness of the inner surface 20a of the pipe 20 is preferably 10 times or more, more preferably 11 times or more, and even more preferably 11.5 times or more of the hardness of the inorganic powder with the highest hardness contained in the powder mixture 3 (hereinafter, also referred to as the "hardest inorganic powder"). By doing so, it is possible to suppress abrasion of the inner surface 20a of the pipe 20 when the powder mixture 3 is pneumatically transported. The upper limit of the hardness of the inner surface 20a of the pipe 20 is not particularly limited, but can be, for example, 20 times or less of the hardness of the hardest inorganic powder. The hardness of the inner surface 20a of the pipe 20 and the hardness of the hardest inorganic powder can be measured by the following method.

[0023] [Method of measuring hardness of inner surface 20a of pipe 20] A test piece is cut out from the pipe so as to include the inner surface of the pipe. The test piece is cut out so as to penetrate the pipe 20 in the thickness direction. The hardness of the cut out test piece is measured in accordance with JIS Z 2244. Specifically, a square pyramid diamond indenter is pressed into the surface of the test piece that corresponds to the inner surface of the pipe (hereinafter also referred to as the "measurement surface") with a force of 2.94 N for 15 seconds. Thereafter, the diagonal length d of the indentation left on the measurement surface is measured. The value calculated by the following formula (2) is the hardness HV of the inner surface of the pipe. In the following formula (2), F2 is the force (2.94 N) when the diamond indenter is pressed into the test piece.

[0024]

number

[0025] In this embodiment, the flow rate of the air flowing through the pipe 20 is preferably 200 m / min or more, more preferably 230 m / min or more, and even more preferably 250 m / min or more, from the viewpoint of stably transporting the powder mixture 3. The flow rate of the air flowing through the pipe 20 is preferably 500 m / min or less, more preferably 480 m / min or less, and even more preferably 450 m / min or less, from the viewpoint of suppressing the impact when the transported powder mixture 3 collides with the inner surface 20a of the pipe 20 and suppressing wear of the inner surface 20a of the pipe 20.

[0026] In this embodiment, the cross-sectional area S of the inside of the pipe 20 and the mass M of the powder mixture 3 to be transported are in a specific ratio. This also contributes to stable pneumatic transport of the powder mixture containing inorganic powder and suppression of wear of the pipe. The cross-sectional area S of the inside of the pipe 20 is the area of ​​the inside 20b of the pipe 20 in a cross section perpendicular to the axial direction of the pipe 20 (see FIG. 2). Here, the mass M of the powder mixture 3 to be transported is the mass of the powder mixture 3 transported in one transport when the powder mixture 3 is transported in a batch manner. When the powder mixture 3 is transported in a continuous manner, it is the mass of the powder mixture 3 fed into the pipe in one minute. The ratio M / S of the mass M of the powder mixture 3 to the cross-sectional area S of the inside of the pipe 20 is preferably 1.0×10 4 kg / m 2 More preferably, 1.3×10 4 kg / m 2 More preferably, 1.5×10 4 kg / m 2 That is all. By setting the lower limit of the ratio M / S within this range, it is possible to increase the transport efficiency. This point will be described in detail below.

[0027] In the pneumatic transport method of this embodiment, air is flowed inside the pipe 20 and the powder mixture 3 is transported by being entrained by the air. The inventors consider that the behavior of the powder mixture 3 inside the pipe 20 is as follows. At the initial stage when air starts to flow through the piping 20, there is sufficient space within the piping 20 for the air to pass through (see FIG. 3(a)). At this stage, the pressure of the compressed air is relatively small, so the powder mixture 3 transported along with the compressed air may accumulate along the transport path. In FIG. 3, the symbol R indicates the direction in which the compressed air flows. When a location where the powder mixture 3 accumulates occurs within the piping 20, the powder mixture 3 transported subsequently accumulates at that location. When the amount of powder mixture 3 accumulated along the transport path increases, the powder mixture 3 begins to clog the inside of the piping 20 (see FIG. 3(b)). As a result, the gaps through which the compressed air passes within the piping 20 become smaller, and the pressure of the compressed air becomes relatively higher. The inventors consider that when the pressure of the compressed air increases to a level where the compressed air can push out the powder mixture 3 blocking the inside of the pipe 20, the powder mixture 3 is pushed out all at once by the compressed air, and the powder mixture 3 is transported along with the compressed air (see Figure 3(c)). By setting the lower limit of the ratio M / S within the above-mentioned range, the powder mixture 3 is more likely to clog the inside of the pipe 20, and the time it takes for the powder mixture 3 to be pushed out all at once by the compressed air is shortened, so that the powder mixture 3 can be transported efficiently.

[0028] The ratio M / S is preferably 5.0×10 4 kg / m 2 Less than or equal to 4.5×10 4 kg / m 2 More preferably, 4.0×10 4 kg / m 2 By setting the upper limit of the ratio M / S within this range, it is possible to prevent the inner diameter of the pipe 20 from becoming too large. As a result, it is possible to improve the transport efficiency, for example, by making it possible to transport the powder mixture with a small amount of air. In addition, it is also possible to reduce the space required for the transport device 100.

[0029] In this embodiment, the inner diameter of the pipe 20 may or may not be constant in the axial direction. From the viewpoint of stably transporting the powder mixture 3, it is preferable that the pipe 20 has a portion with a constant inner diameter in the axial direction, and it is more preferable that the inner diameter is constant in the axial direction. When the pipe 20 has both a portion with a constant inner diameter and a portion with a non-constant inner diameter, it is preferable that the ratio M / S is within the above-mentioned range in the portion of the pipe 20 with a constant inner diameter.

[0030] In this embodiment, in addition to the air source 10, compressed air may be supplied into the pipe 20 using an auxiliary air source other than the air source 10. The supply of compressed air by the auxiliary air source can be performed at any position in the axial direction of the pipe 20. In this embodiment, the flow rate of the air flowing into the pipe 20 is preferably within the above-mentioned range, and when compressed air is supplied into the pipe 20 using the auxiliary air source, the flow rate of the air flowing into the pipe 20 is preferably within the above-mentioned range upstream of the position where the compressed air is supplied by the auxiliary air source.

[0031] If the true density of the powder is high, the impact energy with the pipe will be high even if the powder size is the same, which will affect the wear of the inner surface of the pipe. From this point of view, the true density of the hardest inorganic powder is preferably 5 g / cm 3 More preferably, 6 g / cm 3 More preferably, 7 g / cm 3 In the above range, the effects of the present invention are significantly exhibited. In addition, the true density of the hardest inorganic powder is set to 10 g / cm3 from the viewpoint of suppressing the increase in the collision energy of the powder with the pipe and further suppressing the wear of the inner surface 20a of the pipe 20. 3 Less than 9g / cm 3 More preferably, 8 g / cm 3 The following is the result.

[0032] The true density of the hardest inorganic powder can be measured by the following method. [Method for measuring true density of hardest inorganic powder] The true density of the hardest inorganic powder can be measured by a density measuring method using a pycnometer in accordance with JIS Z 8807. Specifically, first, the masses of W0 to W3 below are measured. W0: Mass of empty pycnometer W1: Mass of the empty pycnometer when the measurement object, i.e., the hardest inorganic powder, is placed in the pycnometer. W2: Mass of an empty pycnometer when pure water is poured up to the mark W3: The mass of the pycnometer used to measure W1 when pure water is poured into the pycnometer up to the marked line. The true density D of the hardest inorganic powder is calculated by the following formula (3): T In the following formula (3), 1.00 g / cm 3 is the density of pure water.

[0033]

number

[0034] When the content of the hardest inorganic powder in the powder mixture 3 is high, the collision energy with the pipe also increases, which affects the wear of the inner surface of the pipe. From this viewpoint, the effect of the present invention is remarkable when the content of the hardest inorganic powder is preferably 60 mass% or more, more preferably 67 mass% or more, and even more preferably 75 mass% or more. Moreover, from the viewpoint of suppressing the increase in the collision energy of the powder with the pipe and further suppressing the wear of the inner surface 20a of the pipe 20, the content of the hardest inorganic powder in the powder mixture 3 is 100 mass% or less, more preferably 96 mass% or less, and even more preferably 92 mass% or less.

[0035] In this embodiment, as described above, it is preferable that a hardened layer is formed on the inner surface 20a of the pipe 20. From the viewpoint of further suppressing wear of the inner surface 20a of the pipe 20, the thickness of the hardened layer is preferably 5 μm or more, more preferably 10 μm or more, and further preferably 15 μm or more. The upper limit of the thickness of the hardened layer is not particularly limited, but can be, for example, 40 μm or less.

[0036] The thickness of the cured layer can be measured by the following method. [Method of measuring the thickness of the cured layer] A test piece is cut out from the pipe so as to include the inner surface of the pipe. The test piece is cut out so as to penetrate the pipe in the thickness direction. The inner surface of the cut pipe is cut from the surface side of the inner surface in the thickness direction at a constant speed or with a constant external force, while measuring the external force required for cutting and the depth of the cut in the thickness direction. Alternatively, instead of this, the inner surface of the pipe is scraped off while applying a constant external force to the inner surface of the pipe by shot blasting or the like. In this way, the external force required for cutting or scraping off from the inner surface of the pipe to a position 100 μm in the thickness direction is measured. Based on the measurement result, a correlation is obtained between the external force applied to the pipe and the depth of the pipe cut or scraped off. Based on the correlation, a continuous strength distribution is obtained from the inner surface of the pipe in the thickness direction. In the strength distribution, the distance from the inner surface of the pipe in the thickness direction to the point where the strength changes can be the thickness of the hardened layer.

[0037] The hardened inner surface 20a of the pipe 20 has a hardness of preferably 800 HV or more, more preferably 1000 HV or more, and even more preferably 1200 HV or more, from the viewpoint of further suppressing wear of the inner surface 20a of the pipe 20. The upper limit of the hardness of the inner surface 20a of the pipe 20 that has been hardened is not particularly limited, but may be, for example, 2000 HV or less.

[0038] From the viewpoint of further suppressing wear of the inner surface 20a of the pipe 20, the inner surface 20a of the pipe 20 that has been subjected to the hardening treatment has a friction coefficient of preferably 0.5 or less, more preferably 0.45 or less, and further preferably 0.4 or less. The lower limit of the friction coefficient of the inner surface 20a of the pipe 20 that has been subjected to the hardening treatment is not particularly limited, but may be, for example, 0.01 or more.

[0039] The friction coefficient of the inner surface 20a of the pipe 20 can be measured by the following method. [Method of measuring the friction coefficient of the inner surface 20a of the pipe 20] Conduct a friction and wear test (ball-on-disk method) in accordance with JISR1613:2010 to measure the friction force. Specifically, first, a disk test piece is prepared from the same material as the inner surface of the pipe to be measured. The disk test piece is 30 mm in diameter and 3 mm thick. One side of the disk test piece is subjected to the same hardening treatment as the inner surface of the pipe to be measured. The hardened side of the disk test piece is the surface to be measured. Then, the disk test piece is attached to the disk holder of the ball-on-disk method tester so that the surface to be measured of the test piece faces upward. Next, a spherical test piece is gently brought into contact with the measurement target surface of the disk test piece, and then the spherical test piece is pressed against the measurement target surface with a load of 5 N. The spherical test piece is made of cemented carbide and has a diameter of 3 / 8 inch. After that, the disk test piece is rotated at 400 rpm for 600 seconds while the spherical test piece is still pressed against the surface to be measured. The friction force is measured from the start to the end of the rotation of the disk test piece. The friction force is measured using a multi-function friction and wear tester, UMT TriboLab (manufactured by Bruker Japan Co., Ltd.). Then, the average value F3 of the measured frictional forces is calculated. The friction coefficient μ calculated by the following formula (4) is defined as the friction coefficient of the inner surface of the pipe. In the following formula (4), P is the load (5 N) when the spherical test piece is pressed against the measurement target surface.

[0040]

number

[0041] The pipe 20 may have a curved portion 21 in which the axis is curved in a part of the axial direction (see FIG. 1), or may not have such a curved portion. In general, when a powder mixture is pneumatically transported using a pipe having a curved portion, the powder mixture is likely to collide with the inner surface of the curved portion, so that the inner surface of the curved portion is likely to be worn. That is, the problem to be solved by the present invention becomes prominent. However, according to the pneumatic transport method of this embodiment, even when the pipe 20 has the curved portion 21, the wear of the inner surface 20a of the pipe 20 can be further suppressed. When the pipe 20 has the curved portion 21, it is preferable that at least the inner surface 20a of the curved portion 21 is subjected to a hardening treatment.

[0042] The radius of curvature of the axis of the pipe 20 at the curved portion 21 is preferably 200 mm or more, more preferably 230 mm or more, and even more preferably 260 mm or more. The radius of curvature is preferably 1000 mm or less, more preferably 900 mm or less, and even more preferably 800 mm or less. The radius of curvature can be measured by the following method. [Method of measuring radius of curvature] First, select three arbitrary points on the axis of the pipe in the curved portion. In other words, select three arbitrary points P1, P2, and P3 from the range from the curve start point Ps to the curve end point Pe on the axis L of the pipe (see FIG. 4). An imaginary circle C passing through the three points P1, P2, and P3 is assumed, and the radius r of the imaginary circle C is set as the radius of curvature.

[0043] The method for pneumatically transporting a powder mixture of the present invention can be suitably used in a method for manufacturing a heating tool. The present invention includes a method for manufacturing a heating tool, which includes a step of transporting a powder mixture by the above-mentioned method for pneumatically transporting a powder mixture. The method for producing the heating tool of the present invention will be described below by taking a preferred embodiment as an example. 5 shows a schematic cross-sectional view of a heating tool 50, which is a preferred embodiment of a heating tool manufactured by the manufacturing method of a heating tool of the present invention. The heating tool 50 comprises a heating element 60 and a covering sheet 51 that covers the heating element 60. The heating element 60 has a base sheet 61 and a heating composition 62 applied to one side of the base sheet 61.

[0044] A preferred embodiment of the manufacturing method of the heating tool of the present invention will be described below by taking as an example a manufacturing method of the heating tool 50. Figure 6 shows an outline of the manufacturing method of the heating tool 50 of this embodiment. The manufacturing method of the heating tool 50 of this embodiment includes a transporting step, a heat generating composition forming step, and a heating element manufacturing step. In this embodiment, a transporting step is first performed. In the transporting step, the powder mixture 3 is transported to a destination 40 by the pneumatic transport method of the powder mixture of this embodiment described above. In the manufacturing method of the heating tool 50 of this embodiment, the destination 40 is a mixing section 40 that mixes the powder mixture 3 with water. Next, a heat generating composition forming step is performed. In the heat generating composition forming step, the powder mixture 3 and water are mixed to form a heat generating composition. In this embodiment, a water tank (not shown) for holding water is connected to the mixing section 40, and water is supplied from the water tank (not shown) to the mixing section 40. In the mixing section 40, the powder mixture 3 and water are mixed to form a heat generating composition 62.

[0045] In the manufacturing method of the heating tool 50 of this embodiment, the powder mixture 3 preferably contains the above-mentioned oxidizable metal powder as the inorganic powder. The oxidizable metal powder generates heat through an oxidation reaction with oxygen in the air, and has the function of providing heat to the object to be heated. The powder mixture 3 may contain components other than the oxidizable metal. Examples of components other than the oxidizable metal include powder of a carbon material, silicate and halide salt, thickener, etc. Among these, the powder mixture 3 preferably contains at least one of powder of a carbon material, silicate and halide salt. The powder of a carbon material is used to promote the oxidation reaction of the oxidizable metal and generate heat efficiently. The silicate has a function of increasing the heat generation efficiency by supplying water as a medium to the reaction system when the powder of a carbon material and the salt of a halide promote the oxidation reaction of the oxidizable metal. The silicate is preferably used in the form of a powder. Furthermore, the water mixed with the powder mixture 3 has the function of facilitating the generation of an interaction between the powder of the oxidizable metal and the carbon material or the like that serves as a catalyst for the oxidation reaction. The heating element preferably contains all of an oxidizable metal, a powder of a carbon material, diatomaceous earth, a halide salt, and water.

[0046] In this embodiment, the heat generating composition forming step is followed by the heat generating element manufacturing step. In the heat generating element manufacturing step, the heat generating element is manufactured by applying the heat generating composition to one side of a base sheet. In this embodiment, the heat generating composition 62 formed in the mixing section 40 is applied to one side of the base sheet 61 by the application section 41 connected to the mixing section 40. Then, the continuous body of base sheet 61 coated with heat generating composition 62 is cut by first cutting section 70 to obtain individual heat generating elements 60. It is not essential that the continuous body of base sheet 61 coated with heat generating composition 62 is cut by first cutting section 70. For example, in the heat generating element forming step, the heat generating composition may be applied to each of the base sheet 61 sheets cut in advance to produce individual heat generating elements 60. Next, the surface of the heating element 60 facing the base sheet 61 and the surface facing the heating composition 62 are covered with a cover sheet 51. Thereafter, the continuous body of heating tools 50 is cut by a second cutting section 80 to obtain individual heating tools 50. In the manufacturing method of the heating tool 50 of this embodiment, the powder mixture 3 is transported by the pneumatic transport method of the powder mixture of this embodiment. This allows the powder mixture 3 to be transported stably, so that the heating tool 50 can be efficiently manufactured. In addition, wear of the piping 20 can be suppressed, so that the maintenance cost of the equipment used in manufacturing the heating tool 50 can be reduced, and the manufacturing cost of the heating tool 50 can be reduced.

[0047] The base sheet 61 and the cover sheet 51 may be, for example, a fiber sheet such as a nonwoven fabric, a woven fabric, or paper, a resin foam sheet, a metal sheet, or a combination of these. The base sheet 61 and the cover sheet 51 may have a single structure consisting of only one sheet material, whether single-layered or multi-layered, or may have a layered structure in which two or more types of sheet materials are layered on top of each other.

[0048] Although the present invention has been described based on the preferred embodiment, the present invention is not limited to the above-described embodiment and can be modified as appropriate. For example, the hardening treatment may be performed on the entire area of ​​the inner surface 20a of the pipe 20 in the axial direction, or may be performed on only a part of the inner surface 20a of the pipe 20 in the axial direction. Furthermore, the pipe 20 may be generally straight, or may be curved, for example, in an arc shape in the entire axial direction. The pipe 20 may have a plurality of curved portions 21. The curved portions 21 may be curved in the vertical direction, may be curved in the horizontal direction, or may be curved in a direction intersecting both the vertical direction and the horizontal direction.

[0049] 1 has straight portions on both sides of curved portion 21 in the axial direction of pipe 20, where the axis of the pipe extends linearly, and in the straight portions, the axis may extend along the vertical direction, may extend along the horizontal direction, or may extend along a direction intersecting both the vertical direction and the horizontal direction. The straight portions located on one side of curved portion 21 in the axial direction and the straight portions located on the other side may extend in the same direction or different directions. EXAMPLES

[0050] The present invention will be described in more detail below with reference to examples, but the present invention is not limited to the following examples.

[0051] [Evaluation of pneumatic transport performance] <Transport device> A transport device having the same configuration as the transport device 100 shown in FIG. 1 was prepared. The piping of the transport device had a curved portion on its axis, and the length along the axis was 60 m. The distance of the piping from the connection portion with the supply flow path of the powder supply portion to the curved portion of the piping was 11 m. The radius of curvature of the axis at this curved portion was 280 mm. The internal cross-sectional area S of the piping was 9.62×10 -4 m 2 The hardness of the outer surface of the pipe was 200HV. The pipe was made of stainless steel only.

[0052] <Shipping conditions and methods> Using the above-mentioned conveying device, the powder mixture was conveyed under the conditions of Examples 1 and 2 and Comparative Examples 1 to 3 shown in Table 1. Specifically, first, the entire amount of the powder mixture was supplied from the powder supply unit into the pipe. Next, the air source of the conveying device was operated to supply air into the pipe at the flow rate shown in Table 1, and the powder mixture was conveyed by being entrained by the air. The hardness of the inner surface of the pipe in Examples 1 to 3 and Comparative Examples 1 and 2, which were subjected to a hardening treatment, was more than 11 times that of iron powder, which is the hardest inorganic powder, while the hardness was less than twice that of the inner surface of the pipe in Comparative Examples 3 and 4, which were not subjected to a hardening treatment.

[0053] [Table 1]

[0054] <Evaluation> The pneumatic transport performance when the powder mixture was transported under each of the conditions in Examples 1 and 2 and Comparative Examples 1 to 3 was evaluated according to the following criteria. The results are shown in Table 1. ○: The powder mixture can be transported through the pipe to the destination, and the transport time can be measured. ×: The powder mixture stagnates midway through the piping, and the powder mixture cannot be transported to the destination, so the transport time cannot be measured. Here, the transportation time means the time from when the air source of the transportation device is turned on after the powder mixture is supplied into the pipeline to when the entire amount of the powder mixture supplied into the pipeline is transported to the destination.

[0055] [Evaluation of wear suppression effect] <Transport device> The same transport device as in the above-mentioned [Evaluation of pneumatic transport performance] was used. <Shipping conditions and methods> Except for the following points, the transportation conditions and transportation method are the same as those in the above-mentioned [Evaluation of pneumatic transportation performance]. The transportation of the powder mixture was repeated under each of the conditions of Examples 1 and 2 and Comparative Examples 1 to 3. Specifically, after the entire amount of the powder mixture was transported to the destination, the transported powder mixture was accommodated again in the powder accommodation section of the powder supply section. Thereafter, the powder mixture was again supplied from the powder supply section into the piping, and the powder mixture was transported again while being entrained by air. In this manner, the transportation of the powder mixture was repeated, and the powder mixture was transported a total of more than 1000 times for each of Examples 1 and 2 and Comparative Examples 1 to 3.

[0056] <Evaluation> For each of the conditions of Examples 1 and 2 and Comparative Examples 1 to 3, the number of transports was divided into several hundred, and the thickness of the pipe was measured at any number of transports as follows. First, the curved portion of the pipe was taken as the measurement area. Specifically, the portion from the start Rs of the curve in the length direction of the pipe to the end Re was taken as the measurement area. The measurement area was continuous over the entire area in the circumferential direction of the pipe. Then, in the measurement area, the thickness of the pipe was measured by an ultrasonic thickness gauge. Specifically, the measurement area was divided into 8 in the circumferential direction of the pipe and 20 in the longitudinal direction of the pipe, resulting in a total of 160 sections. Then, for each section, the thickness of the pipe was measured at any 10 sections within the section, and the average value of the thicknesses was taken as the thickness of the section. Next, for each of the 160 sections where the thickness of the pipe was measured for each divided number of transports, the wear coefficient of the pipe was calculated as follows. Specifically, the change in the thickness of the pipe measured for each divided number of transports was plotted for each of the 160 sections, linear approximation was performed, and the reduction in the thickness of the pipe was calculated. The calculated reduction was divided by the total number of transports of the powder mixture to obtain the wear coefficient. In this system, the region in which the reduction in the thickness of the pipe was the greatest among the divided numbers was used for evaluation. The abrasion suppression effect was evaluated according to the following criteria for each of the conditions in Examples 1 and 2 and Comparative Examples 1 to 3. The results are shown in Table 1. In Table 1, the "-" in the "Abrasion suppression effect" column for Comparative Example 1 means that the powder mixture stagnated midway through the piping, and the powder mixture could not be transported to the destination in the first place. 〇: Wear coefficient is 7×10 -5 mm / times or less ×: Abrasion coefficient is 7×10 -5 mm / times

[0057] As shown in Table 1, in both Examples 1 and 2, the transportation performance and wear suppression effect were evaluated as "good," indicating that both the transportation performance and wear suppression effect could be achieved. In comparison with Comparative Example 1 in which the flow velocity of the air flowing through the pipe is 146 m / min, in Examples 1 and 2 in which the flow velocity is faster than this, as shown in Table 1, the transportation performance is evaluated as excellent. In comparison with Comparative Examples 2 and 3, in which the inner surface of the pipe was not subjected to a hardening treatment and the ratio of the hardness of the inner surface of the pipe to the hardness of the hardest inorganic powder was less than 2, the examples in which a combined treatment of nitriding and shot peening was performed and the ratio was greater were evaluated as having excellent wear inhibition effects. Therefore, it can be seen that the method for pneumatically transporting a powder mixture of the present invention enables stable pneumatic transport of a powder mixture containing inorganic powder, and also makes it possible to suppress wear on piping. [Explanation of symbols]

[0058] 100 Transport equipment 10 Air Source 20 Piping 3 Powder mixture

Claims

1. A method for pneumatically transporting a powder mixture, comprising flowing air through a pipe containing stainless steel material and transporting a powder mixture containing inorganic powder accompanied by the air, The inner surface of the aforementioned pipe has been hardened to be harder than the outer surface of the pipe. The hardness of the inner surface of the aforementioned pipe is 10 times or more the hardness of the hardest inorganic powder with the highest hardness contained in the aforementioned powder mixture. The hardest inorganic powder has a hardness of 30 HV or more and an average particle size of 200 μm or less. The airflow velocity in the aforementioned pipe is 200 m / min or more and 500 m / min or less. The ratio of the mass of the powder mixture to the internal area of ​​the pipe in a cross-section perpendicular to the axial direction of the pipe is 1.0 × 10 ４ kg / m ２ The above 5.0 x 10 ４ kg / m ２ The following is a method for pneumatically transporting powder mixtures.

2. The hardening treatment applied to the inner surface of the aforementioned pipe includes nitriding and shot peening. The air transport method according to claim 1, wherein the inner surface subjected to the hardening treatment has a hardened layer thickness of 5 μm or more and 40 μm or less, a hardness of 800 HV or more and 2000 HV or less, and a coefficient of friction of 0.01 or more and 0.50 or less.

3. The aforementioned pipe has a curved section in which the axis of the pipe is curved, The pneumatic transport method according to claim 1, wherein the radius of curvature of the shaft in the curved portion is 200 mm or more and 1000 mm or less.

4. The true density of the aforementioned hardest inorganic powder is 5 g / cm³ ３ 10g / cm or more ３ The following is the pneumatic transport method according to claim 1.

5. The pneumatic conveying method according to claim 1, wherein the content of the hardest inorganic powder in the powder mixture is 60% by mass or more and 100% by mass or less.

6. The pneumatic conveying method according to claim 1, wherein the hardest inorganic powder is one or more selected from the group consisting of iron, aluminum, manganese, and magnesium.

7. A method for manufacturing a heating device equipped with a heating element, A transport step of transporting the powder mixture by the pneumatic transport method described in any one of claims 1 to 6, After the aforementioned transport step, a heat-generating composition formation step is performed in which the powder mixture and water are mixed to form a heat-generating composition, The process includes a heating element manufacturing step, in which the heating element is manufactured by coating one side of a base sheet with the heating composition, A method for manufacturing a heating device, wherein the powder mixture comprises, in addition to the hardest inorganic powder, one or more of the following: powder of a carbon material, silicate, and salt of a halide.

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