Cleaning tool for pressure vessel detection hole and cleaning method for detection hole using the same

Abstract

To provide a cleaning tool capable of efficiently removing a solid matter which closes a space of a backside of a plate made of an anticorrosive abrasion-proof material covering a welded place of a pressure container body lined on the inner surface or a detection hole bored in the welded place.SOLUTION: This cleaning tool for a detection hole 6 bored in a welded place of a pressure container body made of clad steel 3 lined on the inner surface with a covering 1 comprises: an emission pipe 11 having an outer diameter finer than the inner diameter of the detection hole 6 and provided, at the tip, with an outlet for emitting a cleaning liquid in a radial direction; and a discharge pipe 12 coaxially and axially installed outside a non-insertion part of the emission pipe 11 not inserted into the detection hole 6 so as to discharge the emitted cleaning liquid.SELECTED DRAWING: Figure 4

Description

[Technical Field]

[0001] The present invention relates to a cleaning tool for cleaning a detection hole for detecting liquid leakage in a lining provided in a pressure vessel such as an autoclave, and a method for cleaning the detection hole using the cleaning tool. [Background technology]

[0002] One known hydrometallurgical method for producing nickel oxide ores is the HPAL (High Pressure Acid Leaching) method, in which low-grade nickel ore is added to water to prepare a slurry of nickel ore, and the resulting slurry is acid-leached with sulfuric acid at high temperature and pressure, and the resulting leachate containing valuable metals such as nickel and cobalt is sulfidized to recover these valuable metals in the form of sulfides. The HPAL method uses a pressure vessel equipped with an agitator, generally known as an autoclave, and the ore slurry is charged into the autoclave together with sulfuric acid, where it is agitated under high-temperature and high-pressure conditions by injecting high-pressure steam.

[0003] As described above, since the interior of an autoclave is exposed to harsh conditions, it is desirable to fabricate the autoclave body from a highly corrosion-resistant and wear-resistant material, such as titanium. However, titanium is more expensive than carbon steel, so titanium is commonly used as a lining (coating) material. For example, Patent Document 1 discloses a technology in which carbon steel is used as the base material for the autoclave body and the inside is coated with titanium. This makes it possible to fabricate an autoclave that is highly corrosion-resistant and wear-resistant while maintaining strength against high temperatures and pressures, without incurring significant costs.

[0004] As mentioned above, methods for coating carbon steel base materials with titanium include build-up welding, strip lining, and cladding, but explosive bonding, a type of cladding method, has become popular in recent years. Explosive bonding is a cold metallurgical bonding method that utilizes the instantaneous high energy generated when an explosive explodes to join dissimilar metals together, and has the advantage of low residual stress and excellent corrosion resistance.

[0005] When a large pressure vessel, such as an autoclave, is fabricated using plates made of so-called explosively bonded clad steel produced by the explosive bonding method, multiple plates made of the explosively bonded clad steel are prepared, each bent to fit the shape of the pressure vessel, and then butt-welded to adjacent plates. During this welding, grooves are prepared at the joints to increase joint strength. In particular, for plates with a wall thickness exceeding 100 mm, such as those used in autoclaves, grooves are prepared on both sides of the plates, and the coating material is removed from the welded area. Therefore, the welded area is covered with a strip of titanium plate, and fillet welds are made around the entire periphery of the titanium plate to prevent the processing liquid inside the vessel from contacting the base carbon steel. [Prior art documents] [Patent documents]

[0006] [Patent Document 1] Japanese Patent Publication No. 2020-067165 Summary of the Invention [Problem to be solved by the invention]

[0007] When a stirrer is used to stir the treatment liquid inside the pressure vessel to increase the reaction efficiency, as in the autoclave described above, the titanium plates protruding inward and their welded joints are prone to wear, which can result in holes being formed in the titanium plates or cracks in the welded joints of the titanium plates. If a hole is formed in the coating material or a crack occurs in the welded joint, the treatment liquid inside the pressure vessel will leak from that part and come into direct contact with the carbon steel base material, causing rapid corrosion, and the high-temperature, high-pressure treatment liquid inside the pressure vessel may spray out, leading to problems such as a shutdown of operations.

[0008] Therefore, to enable early detection of holes or cracks in the welded portions of the cladding, a leak detection hole, known as a "warning hole," is provided in the welded portion of the base metal on the back side of the cladding. By inspecting the detection hole, for example, during scheduled maintenance, it becomes possible to determine whether a leak has occurred in the cladding. This warning hole can also be used as an inspection port during airtightness testing to check the sealing of the welded portions after the pressure vessel is manufactured or repaired.

[0009] If the processing liquid were to spray out of the detection hole during operation of the autoclave, this could result in the entire plant shutting down. Therefore, it is desirable to be able to detect the presence or absence of a liquid leak from the detection hole as quickly and reliably as possible. However, if the processing liquid inside the autoclave leaks out, its temperature will drop due to evaporation or the influence of the outside air temperature, causing it to crystallize, which could block the space behind the titanium plate or the detection hole.

[0010] As described above, if the space behind the titanium plate or the detection hole is clogged with crystallized matter, there is a risk that the occurrence of a liquid leak will be overlooked. It also makes it difficult to accurately perform an airtightness test after repair. The present invention has been made in consideration of the above circumstances, and aims to provide a cleaning tool that can efficiently remove solid matter that clogs the space behind the plate made of a corrosion-resistant and abrasion-resistant material that covers the welded parts of the pressure vessel body whose inner surface is lined, and the detection hole drilled in the welded parts. [Means for solving the problem]

[0011] In order to achieve the above object, the detection hole cleaning tool according to the present invention is a tool for cleaning the welded portion of the pressure vessel body whose inner surface is lined. the space behind the plate covering the welded area a cleaning tool for a detection hole drilled in a pipe, the cleaning tool having an outer diameter smaller than the inner diameter of the detection hole and a tip end opening a discharge pipe part having a discharge port for discharging the cleaning liquid in a radial direction of the detection hole, and a discharge pipe part concentrically provided on the outside of a non-inserted part of the discharge pipe part that is not inserted into the detection hole, thereby discharging the discharged cleaning liquid, The tip opening is closed with the back side of the plate. The length of the insertion portion of the discharge pipe section that is inserted into the detection hole is the same as the depth of the detection hole, and the discharge pipe section has an outer diameter that is larger than the inner diameter of the detection hole. [Effects of the Invention]

[0012] According to the present invention, it is possible to efficiently clean the space behind the plate covering the welded portion of the pressure vessel body having a lined inner surface, and the detection hole drilled in the welded portion. [Brief explanation of the drawings]

[0013] [Figure 1] 1 is a schematic partial cross-sectional view of a welded portion of an autoclave body in which a detection hole to be cleaned by the cleaning jig of the present invention is drilled. FIG. [Figure 2] FIG. 2 is a front view of the cleaning jig according to the embodiment of the present invention. [Figure 3] FIG. 3 is a perspective view of the tip of the cleaning jig of FIG. 2. [Figure 4] 1. FIG. 4 is an explanatory view showing the flow of cleaning liquid when the detection hole in FIG. 1 is cleaned using the cleaning jig in FIG. [Figure 5] FIG. 3 is a vertical cross-sectional view of the cleaning jig of FIG. 2. [Figure 6] FIG. 10 is an explanatory diagram showing the flow of cleaning liquid when cleaning the detection hole using a conventional cleaning method. DETAILED DESCRIPTION OF THE INVENTION

[0014] Below, we will explain in detail an embodiment of a detection hole cleaning jig according to the present invention, which is used to clean the space behind the plate covering the welded portion of a pressure vessel body whose inner surface is lined, and the detection hole drilled in the welded portion, as well as a cleaning method using the cleaning jig, taking as an example the case where the pressure vessel is an autoclave used when performing acid leaching treatment by the HPAL method. An autoclave is generally a roughly cylindrical container placed on its side, and its interior is divided by partitions into multiple compartments, each equipped with an agitator.

[0015] In the HPAL process, an ore slurry prepared by adding water to nickel oxide ore is charged into the autoclave together with sulfuric acid, and high-pressure steam is then blown in to carry out acid leaching under high-temperature, high-pressure conditions of approximately 230-270°C and approximately 3-5 MPa. In this acid leaching process, in order to leach not only valuable metals such as nickel and cobalt contained in the nickel oxide ore but also iron, an excess of sulfuric acid is added to maintain the pH of the leachate at approximately 0.1-1.0. This leaching process leaches the valuable metals as sulfates and fixes the leached iron sulfate as hematite, producing a leachate containing the valuable metals together with impurities, and a leach residue containing hematite and other impurities.

[0016] As described above, the inside of the autoclave is exposed to harsh conditions that make corrosion and wear likely, so the body of the autoclave is made of clad steel 3, which has a structure in which a base material 2 made of carbon steel is covered with a coating material 1 made of titanium, as shown in Figure 1. In addition, at the welded locations 4 where the base materials 2 of adjacent clad steel pieces 3 are joined, the coating material 1 is removed by groove preparation, and instead a strip-shaped titanium plate 5 is welded. This makes it possible to coat the entire liquid-contacting part inside the autoclave body with titanium.

[0017] However, as shown in Figure 1, the titanium plate 5 protrudes into the inside of the vessel, and is therefore susceptible to wear by the ore slurry and leaching slurry, which can cause holes to form in the titanium plate 5 itself or cracks in the seal welds between the titanium plate 5 and the covering material 1 of the clad steel 3, which can cause leakage of the leachate inside the autoclave. Therefore, to check for the occurrence of leakage, a detection hole 6 is drilled through the weld 4 between the base materials 2 in the thickness direction.

[0018] The inner diameter of the detection hole 6 is preferably about 6 to 12 mm, and more preferably about 8 mm. The detection hole 6 can be drilled with a general drill. A container-side female thread 7 is provided at the outlet of the detection hole 6 on the outside of the container for connection to a cleaning jig, which will be described later. The container-side female thread 7 is preferably, but not limited to, a tapered female thread for a pipe with a nominal diameter of 1 / 8 inch.

[0019] 2 shows a cleaning jig according to an embodiment of the present invention for cleaning the detection hole 6 and the space on the back surface 5a side of the titanium plate 5. The cleaning jig 10 according to this embodiment of the present invention is composed of a discharge pipe section 11 having an outer diameter smaller than the inner diameter of the detection hole 6 and having a plurality of discharge ports 11a at its tip that discharge cleaning liquid in the radial direction, and a discharge pipe section 12 that is concentrically arranged outside the non-inserted portion of the discharge pipe section 11 that is not inserted into the detection hole 6 and that discharges the cleaning liquid discharged from the plurality of discharge ports 11a.

[0020] More specifically, the discharge pipe 11, which is one of the components of the cleaning jig 10, has a plurality of discharge ports 11a at its tip, spaced equally apart in the circumferential direction, and at the end opposite to this tip, has a female threaded portion 11b for introducing cleaning liquid, which has a threaded through-portion at its central axis for threaded engagement with and communication with a cleaning liquid supply tube (not shown). The non-inserted portion of this discharge pipe 11, which is not inserted into the detection hole 6, and the discharge pipe 12, which will be described later, form a double-pipe structure.

[0021] The shape and number of the multiple discharge ports 11a of the discharge pipe portion 11 are not limited, but it is preferable to provide, for example, four approximately rectangular cutout portions at equal intervals in the circumferential direction as shown in Fig. 3. In this way, by inserting the discharge pipe portion 11 into the detection hole 6 and blocking its tip opening with the back surface 5a of the titanium plate 5, the cleaning liquid can be diffused in four directions perpendicular to the axial direction of the discharge pipe portion 11, as shown by the white arrows in Fig. 3. As a result, it is possible to more efficiently clean the space on the back surface 5a of the titanium plate 5.

[0022] The other component of the cleaning jig 10, the discharge pipe 12, has a female threaded portion 12a for collecting cleaning wastewater, which has a threaded flow path in its central axis, and a male threaded portion 12b at its tip, which threadably engages with both the female threaded portion 12a and the container-side female threaded portion 7 to connect these two female threaded portions and has a flow path in its central axis that communicates with both female threaded portions. The female threaded portion 12a for collecting cleaning wastewater and the male threaded portion 12b are collectively referred to as the engaging portion. The end of the discharge pipe 12 opposite the tip is closed by a ring-shaped member, and a female threaded portion 12c for discharging cleaning wastewater is provided on the side adjacent to the ring-shaped member, which has a threaded through-portion in its central axis for threading with and communicating with a cleaning wastewater discharge tube (not shown).

[0023] When the above-described cleaning jig 10 is used to clean the detection hole 6 of the autoclave body, the insertion portion of the discharge pipe 11 of the cleaning jig 10 is inserted into the detection hole 6, as shown in FIG. 4, and the male thread 12b provided at the tip of the discharge pipe 12 is threaded into the container-side female thread 7 at the outlet of the detection hole 6. At this time, it is preferable to abut the tip of the discharge pipe 11 against the back surface 5a of the titanium plate 5. For this reason, it is preferable to measure the depth of the detection hole 6 in advance, and then temporarily align the length of the inserted portion of the discharge pipe 11 so that it matches the depth of the detection hole 6, and then weld the female thread 12a for collecting cleaning wastewater to the tip of the discharge pipe 12. Alternatively, the female thread 12a for collecting cleaning wastewater may not be welded to the tip of the discharge pipe 12, but the degree of threading may be adjustable, which makes it possible to adjust the length of the inserted portion of the discharge pipe 11 to some extent to match the depth of the detection hole 6.

[0024] Next, the male thread 8a of the cleaning liquid supply tube 8 is threaded onto the female thread 11b for introducing the cleaning liquid of the discharge pipe 11, and the male thread 9a of the cleaning liquid discharge tube 9 is threaded onto the female thread 12c for discharging the cleaning liquid of the discharge pipe 12. Then, by opening a valve for, for example, an industrial water supply source connected to the end of the cleaning liquid supply tube 8 opposite the male thread 8a, the cleaning liquid is discharged from the outlet 11a at the tip of the discharge pipe 11. This allows the cleaning water to be sprayed directly onto solids such as leachate crystallization and scale accumulated in blocked areas in the space on the back surface 5a of the titanium plate 5, thereby enabling the solids to be efficiently removed. The solids removed in this way are discharged together with the cleaning water through the discharge pipe 12 and the cleaning liquid discharge tube 9, as indicated by the black arrows in Figures 4 and 5.

[0025] In this way, by using the cleaning jig 10 of an embodiment of the present invention to clean the space behind the plate 5 and the detection hole 6 using a cleaning method consisting of the steps of inserting the discharge pipe portion 11 into the detection hole 6 until its tip contacts the back surface 5a of the titanium plate 5 and introducing cleaning liquid from the end opposite the tip of the discharge pipe portion 11, it is no longer necessary to perform ultrasonic cleaning while sweeping or modulating the frequency of ultrasonic vibrations, as in the conventional method, or to prepare multiple preparation tanks for multiple types of cleaning liquid and clean over a long period of time, and it is possible to easily and efficiently remove solid matter such as crystallized matter and scale that has accumulated in the detection hole 6.

[0026] While the cleaning tool for a liquid leak detection hole and the cleaning method for a liquid leak detection hole using the same of the present invention have been described above based on the embodiments, the present invention is not limited to the above embodiments and can include various modifications and alternative examples within the scope of the present invention. In other words, the rights of the present invention extend to the scope of the claims and their equivalents. [Example]

[0027] The main body of the autoclave was made by joining together several plates of explosively bonded clad steel with a thickness of approximately 130 mm, each having a structure in which a base material of carbon steel is coated with titanium. In order to clean the space on the back surface 5a of the titanium plate 5 provided so as to cover the welded portion 4 between adjacent plates of explosively bonded clad steel 3 as shown in Figure 1, and the detection hole 6 with an inner diameter of 8 mm drilled in the welded portion 4 to communicate with said space, a cleaning jig 10 with the structure shown in Figures 2 and 5 was made.

[0028] Specifically, a carbon steel pipe with an inner diameter of 4 mm and an outer diameter of 6 mm was used for the discharge pipe 11, and a carbon steel pipe with an inner diameter of 8 mm and an outer diameter of 10 mm was concentrically installed on the outside of the non-inserted portion of this pipe that was not inserted into the detection hole 6, creating a double-pipe structure as the discharge pipe 12. An NPT 1 / 8 female thread was screwed into the tip of this discharge pipe 12 as the female thread 12a for recovering cleaning wastewater, and an NPT 1 / 8 male thread was screwed into this as the male thread 12b. Note that the female thread 12a for recovering cleaning wastewater is not welded to the discharge pipe 12, so that the length of the portion of the discharge pipe 11 inserted into the detection hole can be adjusted by plus or minus a few mm from 130 mm.

[0029] Four rectangular cutouts, each 2 mm wide and 4 mm deep, were provided at equal intervals in the circumferential direction as discharge ports 11a at the tip of this discharge pipe section 11. The insertion portion of the discharge pipe section 11 was then inserted into the detection hole 6, and the male thread section 12b was screwed into the NPT1 / 8 female thread section 7 on the container side that had been provided in advance at the outlet of the detection hole 6. When screwing the male thread section 12b into the female thread section 7 on the container side, sealing tape was wrapped around the male thread section 12b to prevent liquid leakage.

[0030] The male thread at one end of the cleaning liquid supply tube 8 was then screwed onto the female thread portion 11b for introducing the cleaning liquid of the discharge pipe portion 11, and the other end was attached to a tap for tap water. Furthermore, the male thread at one end of the cleaning waste liquid discharge tube 9 was screwed onto the female thread portion 12c for discharging the cleaning waste liquid of the discharge pipe portion 12, and the other end was hung down into the drainage groove.

[0031] In this state, the tap for tap water was opened, and tap water with a water pressure of approximately 300 to 400 kPaG was introduced into the detection hole at a flow rate of approximately 5 L / min as a cleaning liquid. As a result, it was possible to visually confirm that cleaning liquid mixed with solid matter, presumably crystallized matter, was being discharged from the other end of the cleaning liquid discharge tube 9. When the presence of this solid matter could no longer be visually confirmed, cleaning was deemed complete. Using the above procedure, three workers took eight-hour shifts to clean all of the detection holes 6 on the autoclave body, spending a total of 24 hours per day, and the cleaning process took approximately five days.

[0032] For comparison, the space on the back side of the titanium plate and the detection holes of the autoclave body similar to the above were cleaned using the method shown in Figure 6. Specifically, instead of using the cleaning jig 10, the cleaning method shown in Figure 6 involved directly threading the male thread 8a of the cleaning liquid supply tube 8 into the female thread 7 of the container. This cleaning method required the laborious removal of the cleaning liquid supply tube 8 to drain the cleaning wastewater from the detection holes 6. Furthermore, as shown by the arrows in Figure 6, the cleaning water only flows in one direction and does not circulate, resulting in poor cleaning efficiency. It was necessary to attach and detach the cleaning liquid supply tube 8 approximately three to five times per detection hole 6 to introduce the cleaning liquid and drain the cleaning wastewater until solid matter was no longer mixed in the cleaning wastewater. Therefore, it took approximately 10 days for three workers to clean all of the detection holes 6 in an autoclave, working in 8-hour shifts for a total of 24 hours per day. [Explanation of symbols]

[0033] 1 Covering material 2 Base material 3 Clad steel 4 Joints 5 Titanium Plate 5a Back 6 Detection hole 7 Container side female thread 8 Cleaning solution supply tube 8a Male thread 9. Washing drainage tube 9a Male thread 10 Cleaning jig 11 Discharge pipe section 11a Discharge port 11b Female thread for introducing cleaning fluid 12 Exhaust pipe section 12a Female thread for collecting wastewater from cleaning 12b Male thread 12c Female thread for draining cleaning fluid

Claims

1. A cleaning jig for the space behind a plate covering a welded portion of a pressure vessel body having a lined inner surface, and for a detection hole drilled in the welded portion, comprising: a discharge pipe section having an outer diameter smaller than the inner diameter of the detection hole and having an outlet at its tip opening for radially discharging cleaning liquid; and a discharge pipe section concentrically arranged outside a non-inserted portion of the discharge pipe section that is not inserted into the detection hole, thereby discharging the released cleaning liquid, wherein the length of the inserted portion of the discharge pipe section that is inserted into the detection hole to block the tip opening with the back side of the plate matches the depth of the detection hole, and the discharge pipe section has an outer diameter greater than the inner diameter of the detection hole.

2. The detection hole cleaning jig described in claim 1, characterized in that the discharge pipe portion has an engaging portion that is fixed to the pressure vessel body, and the engaging portion is capable of adjusting the length of the portion of the discharge pipe portion that is inserted into the detection hole.

3. 3. The detection hole cleaning jig according to claim 1, wherein the discharge ports are a plurality of notches provided at the tip of the discharge pipe portion at equal intervals in the circumferential direction.

4. A method for cleaning the space behind the plate covering the welded portion of a pressure vessel body having a lined inner surface and a detection hole drilled in the welded portion using a detection hole cleaning tool described in any one of claims 1 to 3, characterized in that the method comprises the steps of: inserting the discharge pipe portion into the detection hole until its tip opening abuts the back surface of the plate; and introducing cleaning liquid into the end of the discharge pipe portion opposite the tip portion.

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