JP2010285641A - Thermal spraying material, structure having thermal sprayed layer and rotary disk type drier apparatus - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a rotary disk type drier apparatus capable of drying highly corrosive waste liquid such as waste liquid containing a rare metal, by improving corrosion resistance performance of a thermal sprayed layer. <P>SOLUTION: The rotary disk type drier apparatus (1) is operated as follows: a heated disk is rotated; an object to be dried is discharged onto a surface of the disk (4) and dried thereon; and a deposit, which is attached onto the surface of the disk (4) by drying of the object to be dried, is scraped off with a scraper (10) pressed onto the surface. The thermal sprayed layer is formed by spraying a thermal spraying material onto the surface of the disk (4), wherein the thermal spraying material essentially is composed of a tungsten carbide powder and has a Hastelloy powder mixed therein. The Hastelloy powder has a metallic film formed on its surface. <P>COPYRIGHT: (C)2011,JPO&INPIT

Description

  The present invention relates to a thermal spray material, a structure in which a thermal spray layer is formed on the surface of a base material using the thermal spray material, and a rotating disk type drying apparatus in which the thermal spray layer is formed on the disk surface with the thermal spray material.

  Conventionally, liquid waste, liquid sludge, and the like have been subjected to a drying process with a drying device to reduce the water content in order to facilitate disposal or to effectively use as feed or fertilizer.

  Various drying devices have been developed as drying devices for drying such liquid waste and liquid sludge. Among them, the drying materials are dried in a short time in a small space. Rotating disk type dryers that can be used have been used.

  This rotating disk type drying device rotates a heated disk, discharges the material to be dried onto the surface of the disk, dries the material to be dried on the surface of the disk, and adheres to the surface of the disk by drying the material to be dried. The adhered material is scraped off with a scraper pressed against the surface (see, for example, Patent Document 1).

JP 2006-220371 A

  The above conventional rotating disk type drying apparatus can dry a liquid to-be-dried material in a short time in a space-saving manner, and easily collects the dried material generated by drying the to-be-dried material as a deposit on the disk. It is something that can be done.

  Therefore, it is desired to utilize the rotating disk type drying device as a solid-liquid separation device for recovering and effectively reusing rare metal from industrial waste liquid containing rare metal.

  However, the rare metal-containing waste liquid is a waste liquid containing a rare metal used as a semiconductor product, and is a highly corrosive waste liquid such as an etchant used in manufacturing a semiconductor product.

  Therefore, when the rare metal-containing waste liquid is treated using the conventional rotating disk type drying apparatus, the surface of the disk that comes into contact with the rare metal-containing waste liquid may be corroded.

  Therefore, the present inventor aims to improve the corrosion resistance performance of the disk used in the conventional rotating disk type drying apparatus and to apply it to the treatment of the waste liquid containing rare metal, and sprayed layer on the surface of the disk. Research and development have been conducted on a thermal spray material for forming the film, and the present invention has been achieved.

  In the present invention according to claim 1, in the thermal spray material in which the tungsten carbide powder is the main material and the hastelloy powder is mixed, the hastelloy powder having a metal film formed on the surface is included.

  Moreover, in this invention which concerns on Claim 2, the thermal spray material of the said Claim 1 was sprayed on the surface of a base material, and it decided to form a thermal spray layer on the surface of the base material of a structure.

  According to the third aspect of the present invention, the heated disk is rotated, the material to be dried is discharged onto the surface of the disk, and the object to be dried is dried on the surface of the disk. In a rotating disk type drying apparatus configured to scrape off deposits adhered to the surface with a scraper pressed against the surface, the sprayed material according to claim 1 is sprayed on the surface of the disk to form a sprayed layer. did.

  In the present invention, it is possible to improve the corrosion resistance performance of the sprayed layer formed on the surface of the base material, and by forming the sprayed layer on the surface of the disk of the rotating disk type drying apparatus, strong corrosion resistance such as rare metal-containing waste liquid The waste liquid can also be dried.

FIG. 3 is a front sectional view schematically showing a rotating disk type drying apparatus. FIG. Explanatory drawing which shows a test method.

  The specific configuration of the present invention will be described below with reference to the drawings. In the following description, a case will be described in which the thermal spray material according to the present invention is applied to a disk of a rotary disk type drying apparatus as a structure in which a thermal spray layer is formed.

  The rotary disk type drying apparatus 1 is known to have various structures. As schematically shown in FIGS. 1 and 2, a hollow cylindrical rotary shaft 3 is rotatably attached to the casing 2, A hollow disk-shaped disk 4 is attached to the rotating shaft 3 so that the hollow portion of the rotating shaft 3 communicates with the hollow portion of the disk 4. Thereby, the rotating disk type drying apparatus 1 heats the surface of the disk 4 by convection of the heating steam from the hollow part of the rotating shaft 3 to the hollow part of the disk 4.

  In the rotary disk type drying apparatus 1, a drive motor 5 is linked and connected to the rotary shaft 3. Thereby, the rotary disk type drying apparatus 1 rotates the disk 4 clockwise in FIG.

  Further, the rotary disk type drying apparatus 1 attaches the charging pipe 6 to the casing 2, forms a storage tank 7 at the inner lower part of the casing 2, and connects the charging pipe 6 and the storage tank 7 in communication with each other. A nozzle 9 is connected via a pump 8, and the nozzle 9 is arranged facing the surface of the disk 4. As a result, the rotating disk type drying apparatus 1 pumps up the material to be dried supplied from the input pipe 6 to the storage tank 7 by the pump 8 and discharges (sprays) it from the nozzle 9 toward the surface of the disk 4. The material to be dried that has flowed down from the disk 4 is collected in the storage tank 7.

  Further, the rotary disk type drying apparatus 1 is disposed in a state where the scraper 10 is pressed against the surface of the disk 4, a recovery hopper 11 is formed below the scraper 10, and a discharge pipe 12 is connected to the recovery hopper 11 in communication. Yes. Thereby, the rotating disk type drying apparatus 1 scrapes off the dried material (adhered material) adhering to the surface of the disk 4 with the scraper 10 as the material to be dried dries on the surface of the disk 4 and collects it from the discharge pipe 12. I am doing so.

  As described above, in the rotating disk type drying apparatus 1, the heated disk 4 is rotated, the material to be dried is discharged onto the surface of the disk 4, and the material to be dried is dried on the surface of the disk 4. The deposit attached to the surface of the disk 4 by drying is scraped and collected by a scraper 10 pressed against the surface of the disk 4.

  Conventionally, a thermal spray material (for example, WC-17Cr-17Ni) containing tungsten carbide powder as a main material and containing chromium powder and nickel powder is sprayed on the surface of the disk 4 with a high-speed gas spraying device. A sprayed layer was formed on the surface of the film.

  If it is a general liquid waste, even the above-mentioned sprayed layer has corrosion resistance, and there is no practical problem. However, in recent years, in order to recover rare metals from rare metal-containing waste liquids and to effectively reuse them, it has been desired to use the rotating disk type drying apparatus 1, and in the case of drying highly corrosive rare metal-containing waste liquids. It is necessary to further improve the corrosion resistance of the sprayed layer of the disk 4.

  Therefore, a test was conducted on the corrosion resistance performance of the sprayed layer of the disk 4.

  As a test for corrosion resistance, a 65% nitric acid solution, which is a corrosion test solution for stainless steel specified in JIS G0573, was used. Also, the 65% nitric acid solution has a large difference from the waste liquid containing the rare metal to be treated. Therefore, as a test solution closer to the rare metal-containing waste solution, a mixed acid solution in which typical hydrochloric acid, nitric acid, and sulfuric acid that corrode metals are mixed (Here, a mixture of 10% hydrochloric acid, 5% nitric acid, 5% sulfuric acid, and 6% ferric chloride) was used. Further, in the rotary disk type drying apparatus 1, since the material to be dried is treated with alkaline pH adjustment, both nitric acid solution and mixed acid solution are adjusted to pH 9 by adding caustic soda.

  Further, in the normal corrosion resistance test, the test piece is tested in an unstressed state without applying an external force. In the rotating disk type drying apparatus 1, the scraper 10 is pressed against the surface of the disk 4. 4 is in a state where stress is applied.

  Therefore, as a corrosion resistance test, as shown in FIG. 3, a titanium test piece 14 having a sprayed layer 13 formed on the surface is sandwiched between a pair of upper and lower clamping tools 16 and 17 via a support bar 15, A predetermined stress was applied to the test piece 14 by tightening with the bolt 18 and the nut 19. The stress to be applied is a stress that generates a strain of 2000 με that is used when determining the mechanical properties of a general material. Specifically, the relationship between the strain of the test piece 14 and the tightening torque was measured, and the test piece 14 was tightened with a tightening torque (here, a tightening torque of 4 Nm) that generates a strain of 2000 με. As a comparative test, a test was conducted with a tightening torque of 0 Nm (no stress) and a tightening torque of 2 Nm.

  In the present invention, as a test for corrosion resistance, the test piece 14 is immersed for 20 days in a state where a predetermined stress is applied to a test solution made of a 65% nitric acid solution or a mixed acid solution. The amount of decrease in weight (corrosion weight) was measured, and the ratio (reduction ratio) was evaluated. As for the evaluation, when the reduction ratio exceeds 300 ppm, it is evaluated as x because there is a practical problem, and when the reduction ratio is 300 ppm or less, it is evaluated as ○ because there is no practical problem. When the content was 200 ppm or less, it was evaluated as ◎ because the corrosion resistance was remarkably excellent.

  First, a thermal spray material (WC-17Cr-17Ni) containing tungsten carbide powder as the main material and containing 17% chromium powder and 17% nickel powder is sprayed onto the surface of the test piece 14 using a high-speed gas spraying device. The layer 13 was formed, and this was used as a sample No. 1 to test the corrosion resistance.

  As a result, as shown in Table 1, the reduction ratio of the sprayed layer 13 exceeded 300 ppm in any case, and it was evaluated that there was a practical problem.

  Therefore, the present inventor has used tungsten carbide powder as a main material and hastelloy powder as a thermal spray material considered to have corrosion resistance performance compared to a thermal spray material containing tungsten carbide powder as a main material and containing chromium powder and nickel powder. Attention was focused on thermal spraying materials containing. Here, Hastelloy (registered trademark of Haynes Co., Ltd.) is an alloy containing nickel as a main component and containing molybdenum, chromium, iron, or the like. Here, it is referred to as Hastelloy B or Hastelloy C. Represents a generic name.

  Thermal spraying is performed by spraying a thermal spray material (WC-30HST) containing tungsten carbide powder, which is known as a thermal spraying material with excellent corrosion resistance, and containing 30% Hastelloy powder on the surface of the test piece 14 with a high-speed gas spraying device. The layer 13 was formed, and this was used as a sample No. 2 to test the corrosion resistance.

  As a result, as shown in Table 1, although the corrosion resistance performance is improved in the no-stress state with a tightening torque of 0 Nm, the reduction ratio of the sprayed layer 13 is 300 ppm when the tightening torque is 4 Nm close to the operating state. It was exceeded and was evaluated as having practical problems.

  Therefore, the present inventor has repeatedly studied a thermal spray material containing the above-mentioned tungsten carbide powder as a main material and containing hastelloy powder, and covering the surface of the hastelloy powder with a metal film to make the surface of the hastelloy powder smooth without unevenness. I tried using a spherical surface.

  In other words, a spray material (WC-22.2HST + 10HST) containing tungsten carbide powder as the main material and containing 22.2% hastelloy powder and 10% metal film coated with high-speed gas spray on the surface of test piece 14 The thermal spraying layer 13 was formed by thermal spraying with an apparatus, and this was tested as a sample No. 3 for corrosion resistance.

  As a result, as shown in Table 1, the reduction ratio of the thermal spray layer 13 was 300 ppm or less even when the tightening torque was close to 4 Nm, and it was evaluated that there was no practical problem. In addition, if the metal-coated Hastelloy powder is 5% or more of the whole, almost the same result is obtained, and all of the contained Hastelloy powder may be coated with the metal film, or a part of the contained Hastelloy powder may be coated with the metal film. It may be coated with.

  As described above, in the present invention, the corrosion resistance performance of the thermal sprayed layer can be improved by using the thermal spray material containing the Hastelloy powder having a metal film formed on the surface. Therefore, by forming a sprayed layer on the surface of the disk 4 of the rotating disk type drying apparatus 1, it is possible to dry a highly corrosive waste liquid such as a rare metal-containing waste liquid.

DESCRIPTION OF SYMBOLS 1 Rotating disk type drying apparatus 2 Casing 3 Rotating shaft 4 Disk 5 Drive motor 6 Input pipe 7 Storage tank 8 Pump 9 Nozzle 10 Scraper
11 Recovery hopper 12 Discharge pipe
13 Thermal spray layer 14 Specimen
15 Support rod 16,17 Clamp
18 bolt 19 nut

Claims (3)

  A thermal spray material comprising a tungsten carbide powder as a main material and having a metal film formed on a surface thereof, the thermal spray material being mixed with hastelloy powder.   A structure having a thermal spray layer, wherein the thermal spray material according to claim 1 is sprayed on a surface of a base material to form a thermal spray layer.   While rotating the heated disc, the material to be dried was discharged onto the surface of the disc, the material to be dried was dried on the surface of the disc, and the deposit adhered to the surface of the disc was pressed against the surface by drying the material to be dried. A rotating disk type drying apparatus configured to be scraped off by a scraper, wherein the sprayed material according to claim 1 is sprayed on the surface of the disk to form a sprayed layer.

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