Temperature measurement method inside a high-pressure vessel

Abstract

To provide a temperature measurement device that can detect, in an early stage, a hole of a temperature indicator protection tube or entrance of water from a joint opening unit of an end part of the temperature indicator protection tube, and a method for measuring a temperature, using the device.SOLUTION: The temperature measurement device includes: a temperature indicator 11 made of a sheath-type thermo-couple for measuring the temperature of liquid in a high-pressure container such as an autoclave; a bottomed and practically cylindrical protection tube 12 with the temperature indicator 11 inserted therein; and a pressure detector 13 connected to a nozzle 12c leading to the inside of the protection tube 12 by a valve 14, the valve 14 and the pressure detector 13 being desirably connected together by a connection unit 15 with a pressure branch tube. A discharge valve 16 is provided at the top end of the branch tube.SELECTED DRAWING: Figure 3

Description

[Technical Field]

[0001] The present invention relates to a temperature measuring device to be attached to a high-pressure vessel, typically an autoclave, which performs leaching treatment under high temperature and pressure, and a method for measuring the temperature inside the high-pressure vessel using the same. [Background technology]

[0002] A known hydrometallurgical process for nickel smelting, which uses nickel oxide ore as a raw material, is the high-pressure acid leaching (HPAL) method. This method involves adding water to raw ore of uniform particle size to prepare an ore slurry, which is then charged into a reaction vessel together with sulfuric acid. High-pressure steam is then injected into the ore to carry out acid leaching at high temperatures and pressures of approximately 200-270°C and 1.8-5.8 MPaG. This process makes it possible to efficiently recover valuable metals such as nickel and cobalt from low-grade ore.

[0003] In addition, in the manufacturing process of nickel sulfate crystals, a slurry is prepared by adding water to nickel-cobalt mixed sulfide (also referred to as MS), which is a recovered product of nickel and cobalt produced in the above-mentioned nickel smelting process, and the slurry is charged into a reaction vessel, and compressed air is further blown in to perform an oxidation leaching treatment under high temperature and high pressure conditions of a temperature of about 140 to 200°C and a pressure of about 1 to 2 MPaG, thereby producing an aqueous nickel sulfate solution.

[0004] Furthermore, trinickel disulfide (Ni3S2) and nickel (Ni 0 In the manufacturing process for nickel sulfate crystals using nickel matte, which is a solid solution of nickel and MS as the raw material, water is added to crushed nickel matte to prepare a slurry, which is then charged into a reaction vessel together with a small amount of sulfur that is stoichiometrically insufficient. Then, pressurized air is blown in to carry out an oxidation leaching treatment under high temperature and pressure similar to that when MS is used as the raw material, thereby producing an aqueous nickel sulfate solution.

[0005] The reaction vessel used for the leaching treatment under high temperature and pressure as described above is generally a so-called autoclave, which is a high-pressure vessel equipped with a stirrer and which is a cylindrical vessel placed on its side and divided into sections by partitions. In leaching treatment using this autoclave, the temperature of the treatment liquid inside is not only an important state quantity that affects the quality of the product, but is also one of the important parameters for confirming that the reaction is proceeding normally, so it is necessary to be able to measure the temperature accurately over a long period of time.

[0006] For this reason, in high-pressure vessels such as autoclaves, temperature measuring devices are used in which a sheathed thermocouple thermometer, in which a thermocouple element wire is covered with a metal sheath, is further housed in a metal protective tube (thermowell). For example, Patent Document 1 discloses a technology in which a thermometer protective tube (hereinafter simply referred to as a protective tube) is installed so that its tip contacts the object to be measured, and the temperature of the object to be measured is measured using a thermocouple contained in a metal sheath inserted into the protective tube. Note that, although temperature measuring devices in which a sheathed thermocouple thermometer is housed in a protective tube are generally used, temperature measuring devices in which, for example, a resistance temperature detector is housed in a protective tube are also sometimes used. [Prior art documents] [Patent documents]

[0007] [Patent Document 1] Japanese Patent Application Laid-Open No. 2017-96911 DISCLOSURE OF THE INVENTION [Problem to be solved by the invention]

[0008] Because the temperature measuring device is exposed to corrosion and abrasion in the autoclave, there is a risk of a hole being formed in the protective tube of the temperature measuring device. If a hole is formed in the protective tube of the temperature measuring device, the treatment liquid leaking through the hole can corrode, for example, the metal sheath, causing a change in the resistance value of the thermocouple and resulting in inaccurate temperature measurement. This can cause the leaching reaction in the autoclave to become unstable, and if the reaction is particularly poor, this can have a negative impact on quality and cause scaling, known as dents, on the agitator blades.

[0009] In this case, the thermometer reading will deviate significantly from the past trend data, allowing the operator to notice that some kind of abnormality has occurred in the temperature measuring device. However, it takes some time for the abnormality in the temperature measuring device to be noticed after a hole has formed in the protective tube, and during that time there is a risk of safety or environmental problems developing. That is, even if a hole has formed in the protective tube and high-temperature, high-pressure processing liquid in the autoclave leaks into the protective tube, the processing liquid simply comes into contact with, for example, a sheath-type thermocouple thermometer, so the displayed value of the thermometer often shows almost no change, making it difficult for the operator to notice the hole in the protective tube at this point.

[0010] On the other hand, even if the protective pipe does not have a hole, moisture may enter the protective pipe through the flange opening at the end where the thermometer is inserted during periodic inspections of the temperature measuring device or during thermometer replacement. Rainwater may also enter the protective pipe through the flange opening, passing through gaps in the flange seal surface at the end of the protective pipe due to aging degradation of the packing. Furthermore, rainwater may also enter the protective pipe through the thermometer penetration hole in the upper flange, which is generally threaded, due to deterioration of the sealing material. In this specification, the flange opening when the flange at the end of the protective pipe is opened, the gaps in the flange seal surface at the end of the protective pipe, and the thermometer penetration hole in the upper flange are collectively referred to as the "joint opening at the end of the protective pipe." When moisture enters the protective pipe through the joint opening, for example, when operation is stopped, the moisture is removed by blowing air directly into the protective pipe. However, when the protective pipe is long, it is sometimes difficult to remove all the moisture accumulated at the bottom.

[0011] As a result, moisture accumulated at the bottom of the protective tube can cause erroneous temperature readings, and similar to the case where a hole is formed in the protective tube, this can have adverse effects on quality due to poor reaction and can cause scaling on the blades of the stirrer. Furthermore, when a hole is formed in the protective tube or moisture enters through the joint opening at the end of the protective tube, for example, rust occurs in the metal sheath, causing the metal sheath to corrode and form a hole. Insulators such as alumina powder and magnesium oxide powder leak from the inside, causing the metal sheath to adhere to the inside of the protective tube, making it difficult to remove the sheathed thermocouple thermometer from the protective tube when replacing it alone.

[0012] The present invention has been made in consideration of the problems associated with the above-mentioned conventional temperature measuring devices, and has an object to provide a temperature measuring device and a temperature measuring method using the same that can detect holes in thermometer protective tubes and the intrusion of moisture into the thermometer protective tubes from joint openings at an early stage, which can cause equipment trouble in the equipment in which the temperature measuring device is installed and adversely affect the operation of the equipment. [Means for solving the problem]

[0013] In order to achieve the above object, the inventors discovered that by providing a nozzle communicating with the inside of a long, thin protective tube, into which a thermometer for measuring the temperature of the treatment liquid in a high-pressure vessel is inserted, at a portion located outside the high-pressure vessel, and by constantly measuring the pressure inside the protective tube with a pressure detector via the nozzle, it is possible to detect early any holes in the protective tube or the intrusion of moisture through a joint opening, and thus completed the present invention.

[0014] That is, the temperature measuring device according to the present invention is characterized by comprising a thermometer for measuring the liquid temperature in a high-pressure vessel, a protective tube having a bottom and an approximately cylindrical shape into which the thermometer is inserted, and a pressure detector connected via a valve to a nozzle communicating with the inside of the protective tube.

[0015] Further, the temperature measurement method according to the present invention includes: Sheathed thermocouple A protective tube consisting of a bottomed, approximately cylindrical body into which a thermometer is inserted is attached to the high-pressure vessel so that its tip is immersed in the treatment liquid in the vessel, and the temperature of the treatment liquid is measured. At the same time, a pressure detector is connected to a nozzle communicating with the inside of the protective tube via a normally open valve, and the pressure inside the protective tube is constantly measured. When the measured pressure exceeds a threshold value, The temperature measured by the sheathed thermocouple thermometer exhibits a pattern of change over time that regularly fluctuates between a certain upper limit temperature and a certain lower limit temperature at a certain cycle. When Before It is determined that moisture has entered through the opening of the joint at the end of the protective tube. When the measured pressure exceeds a threshold value and the temperature measured by the sheathed thermocouple thermometer does not show a pattern of change over time that regularly fluctuates between a certain upper limit temperature and a certain lower limit temperature at a certain cycle, it is determined that a hole has occurred in the protective tube. It is characterized by: [Effects of the Invention]

[0016] According to the present invention, pressure fluctuations inside a protective tube that occur when a hole is made in the protective tube of a temperature measuring device or when moisture enters through a joint opening can be quickly detected, allowing appropriate measures to be taken quickly for the equipment in which the temperature measuring device is installed. [Brief explanation of the drawings]

[0017] [Figure 1] 1 is a schematic vertical cross-sectional view of an autoclave in which the temperature measuring device of the present invention is preferably installed. [Figure 2] FIG. 2 is a cross-sectional view of the autoclave of FIG. 1 as seen from the II-II direction. [Figure 3] 1 is a front view showing an embodiment of a temperature measuring device of the present invention. [Figure 4] FIG. 4 is a perspective view of a protective tube that constitutes the temperature measuring device of FIG. [Figure 5] 4 is a cross-sectional view showing a specific example of a method for attaching a thermometer to a penetration part of an upper flange located at an end of a protective tube that constitutes the temperature measuring device of FIG. 3. FIG. [Figure 6] FIG. 10 is a front view showing another embodiment of the temperature measuring device of the present invention. DETAILED DESCRIPTION OF THE INVENTION

[0018] 1. Autoclave A temperature measuring device according to an embodiment of the present invention will now be described. First, an autoclave in which a temperature measuring device according to an embodiment of the present invention is preferably installed will be described with reference to FIG. 1. The autoclave shown in FIG. 1 is composed of a horizontally long can body 1 in which a substantially cylindrical pressure vessel having hemispherical or other shaped end plates is installed horizontally, and its interior is divided into a plurality of reaction chambers 3A to 3E by a plurality of partition walls 2 arranged at approximately equal intervals in the longitudinal direction (four partition walls are shown in FIG. 1). Each of these plurality of reaction chambers 3A to 3E is provided with an agitator 4 for carrying out an acid leaching reaction or an oxidation leaching reaction, and the partition walls 2 are notched at the top to allow overflow.

[0019] With this configuration, the raw material slurry is charged through the inlet nozzle 5 into the most upstream reaction chamber 3A located at the left end of the drawing, and is transferred successively to the adjacent downstream reaction chambers toward the most downstream reaction chamber 3E located at the right end of the drawing, overflowing the upper end of the partition wall 2. In this way, the raw material slurry is gradually subjected to leaching treatment in each reaction chamber, and is finally withdrawn as leached slurry from the most downstream reaction chamber 3E through the outlet nozzle 6.

[0020] In order to control the temperature of the leaching treatment, the autoclave having the above structure is provided with a temperature measuring device 10 according to an embodiment of the present invention, as shown in Fig. 2. For the sake of simplicity, Fig. 1 shows an example in which one temperature measuring device 10 is provided in the reaction chamber 3A, which is the most upstream of the autoclave, but generally, at least one temperature measuring device 10 is provided in each of the reaction chambers 3A to 3E.

[0021] 2.Temperature measuring device Next, a temperature measuring device 10 according to an embodiment of the present invention will be described in detail. As shown in FIG. 3 , the temperature measuring device 10 according to the embodiment of the present invention includes a sheath-type thermocouple thermometer 11 for measuring the temperature of a treatment liquid in a high-pressure vessel, such as an autoclave, a bottomed, substantially cylindrical protective tube 12 into which the thermometer 11 is inserted, and a pressure detector 13 connected via a valve 14 to a nozzle 12c that communicates with the interior of the protective tube 12. As also shown in FIG. 4 , the nozzle 12c is provided in a portion of the protective tube 12 located outside the autoclave body 1, i.e., between a large flange 12a for connection to the autoclave and a small flange 12b for connection to the thermometer 11. While the embodiment shown in FIG. 3 illustrates a case in which the thermometer is a sheath-type thermocouple thermometer 11, the temperature measuring device 10 of the present invention is not limited to the sheath-type thermocouple thermometer 11 and can be applied to any rod-shaped or long electric thermometer, such as a resistance thermometer.

[0022] As described above, by connecting the pressure detector 13 to the protective tube 12 via the nozzle 12c and valve 14 that communicate with the inside of the protective tube 12, it becomes possible to constantly measure the pressure inside the protective tube 12. This makes it possible to quickly detect a pressure increase inside the protective tube 12 that occurs when a hole is made in the protective tube 12 or when moisture enters through the joint opening at the end of the protective tube 12.

[0023] Specifically, as described above, the protective tube 12 is exposed to the corrosive and abrasive environment inside the autoclave, and therefore may develop a hole over long periods of use. In this case, the high-pressure treatment liquid being leached inside the autoclave leaks into the inside of the protective tube 12 from the part of the protective tube 12 that is immersed in the treatment liquid, and the pressure inside the protective tube 12 increases due to the evaporation of the leaked treatment liquid or due to being pushed in by the pressure inside the autoclave. As shown in Figures 3 and 4, the tip of the protective tube 12 that is immersed in the treatment liquid is tapered to match the shape of the sheath-type thermocouple thermometer 11, but the shape of the protective tube 12 is not limited to this, and a structure that does not tapered may also be used.

[0024] Furthermore, thermometer 11 is typically attached to the end of protective tube 12 by flange connection or threading. The sealing performance of these joints is easily affected by temperature changes due to the ambient temperature at the location where the temperature measurement device is installed and pressure fluctuations within protective tube 12. This, combined with aging deterioration of the sealing material, can impair the sealing function. Specifically, as shown in Figure 5(a), thermometer 11 is attached by threading the male thread of thermometer 11 into a through-hole in upper flange 12d, which is flange-connected to small flange 12b located at the end of protective tube 12. Alternatively, as shown in Figure 5(b), thermometer 11 is attached by tightening nipple-type fitting 12e into a through-hole in upper flange 12d. For this reason, as shown in Figure 3, rainwater and other contaminants can enter the inside of protective tube 12 through flange connection portion A or threaded portion B. Furthermore, during periodic inspection of the temperature measurement device or replacement of thermometer 11, moisture can enter the inside of protective tube 12 directly through flange opening C of small flange 12b.

[0025] In this way, rainwater or other moisture that has entered the protective tube 12 evaporates when heated by the treatment liquid or gas inside the autoclave. For example, if the temperature inside the autoclave is around 200°C, the saturated vapor pressure of water at 200°C is 1.55 MPaA according to the steam table, so if we assume that the air inside the protective tube 12 is completely replaced with water after the entry, the pressure inside the protective tube 12 will rise to a maximum of 1.55 MPaA. Therefore, if a hole is developed in the protective tube 12, or if moisture enters the protective tube 12 from the fitting opening even if there is no hole, the pressure inside the protective tube 12 will rise, making it possible to detect this early using the pressure detector 13.

[0026] Note that, according to Boyle's law, the pressure measured by pressure detector 13 during normal operation of the autoclave will only rise from atmospheric pressure of 0.10 MPaA to approximately 0.16 MPaA when the temperature inside the autoclave is, for example, 200°C. Even at approximately 270°C, where leaching is performed using the HPAL method, the pressure will only be approximately 0.2 MPaA. Furthermore, since protective tube 12 is not generally designed to withstand high pressures, it will not be maintained at 1.55 MPaA. Therefore, it is preferable to issue an alarm via a DCS (distributed control system) or the like when pressure detector 13 detects a pressure above a threshold value of, for example, approximately 0.3 to 0.5 MPaG.

[0027] When moisture has entered the protective tube 12 from the joint opening at the end of the protective tube 12, unlike when a hole has opened in the protective tube 12 and the treatment liquid has leaked in, the temperature trend showing the change in temperature over time measured by the thermometer 11 will show a characteristic pattern of regularly fluctuating between a certain upper limit temperature and a certain lower limit temperature that is about 5°C lower than this upper limit temperature at a certain period. This is thought to be because, since the long and slender protective tube 12 is exposed to the low temperature outside air only in the part of the protective tube 12 that is located outside the autoclave can body 1, this situation acts like a distillation column, causing the moisture inside to repeatedly evaporate at the bottom and condense at the top.

[0028] That is, moisture that has entered protective tube 12 from the joint opening at the end of protective tube 12 falls by gravity toward the tip of protective tube 12 and evaporates. During this evaporation, heat of vaporization is taken from the surrounding area, causing the temperature measured by thermometer 11 to temporarily drop. The vapor generated by this evaporation then rises inside protective tube 12, causing the temperature measured by thermometer 11 to return to its original temperature. Meanwhile, the vapor that reaches the upper part of protective tube 12, where the temperature is relatively low, is cooled and condensed there. It then turns into moisture, falls, and evaporates again at the tip of protective tube 12. In this way, moisture that has entered protective tube 12 from the joint opening repeats a cycle of evaporation at the bottom and condensation at the top. If this evaporation and condensation were to occur evenly over time, the temperature measured by thermometer 11 would continue to be slightly lower than the true value, but it can be assumed that this cycle is repeated intermittently as water droplets drip.

[0029] When moisture has entered protective pipe 12 from the joint opening as described above, it is preferable to appropriately drain the moisture from inside protective pipe 12. This can be done, for example, by using the configuration shown in Figure 6. That is, valve 14 and pressure detector 13 are connected via connection part 15 having a branch pipe such as a T-joint, and a normally closed release valve 16 is provided at the end of this branch pipe, and further, release piping 17 is provided at the end of this release valve 16 as needed.

[0030] With this configuration, when moisture enters the protective tube 12 from the joint opening, the pressure inside the protective tube 12 increases as described above, and the characteristic temperature pattern described above appears on the temperature trend. Once these changes in both pressure and temperature are confirmed, the release valve 16 can be switched from "closed" to "open" as described above. This allows the moisture and steam inside the protective tube 12 to be released to the outside of the system using their own pressure as a driving force. At this time, the normally open valve 14 is naturally left in the open position. This normally open valve 14 is closed when, for example, replacing the pressure detector 13.

[0031] If a hole is formed in the protective tube 12, there is a risk of high-pressure processing liquid blowing out, so it is not preferable to open the release valve 16 immediately when the internal pressure measured by the pressure detector 13 exceeds the above-mentioned threshold. In other words, even if the internal pressure measured by the pressure detector 13 exceeds a predetermined threshold, if the temperature trend measured by the thermometer 11 does not show the above-mentioned characteristic pattern of regular fluctuations, it is preferable to keep the release valve 16 closed and quickly plan an emergency shutdown or shutdown of the equipment.

[0032] As described above, by using the temperature measuring device according to the embodiment of the present invention, an operator can immediately detect a hole in the protective tube or the intrusion of moisture through the joint opening at the end of the protective tube. This eliminates the problems associated with conventional temperature measuring devices, such as high-temperature, high-pressure slurry leaking through the hole in the protective tube and leaking out from the connection between the protective tube and the thermometer, which can cause safety and environmental issues, or the processing liquid leaking through the hole corrodes the metal sheath, changing its resistance and causing erroneous thermometer readings. Furthermore, the problem of the metal sheath adhering to the protective tube due to rust caused by moisture or other factors is eliminated. This stabilizes the reaction, improving product quality, preventing problems such as scaling on the agitator blades, and allowing the equipment to be shut down before a hole in the protective tube develops into a serious malfunction, thereby improving equipment availability and improving productivity. The present invention has extremely high industrial value. [Explanation of symbols]

[0033] 1 can body 2 Bulkhead 3A~3E Reaction chamber 4. Mixer 5 inlet nozzle 6 outlet nozzle 10 Temperature measuring device 11 Thermometer 12 Protection tube 12a Large flange 12b small flange 12c nozzle 12d Upper flange 12e Nipple type fitting 13 Pressure detector 14 Valves 15 Connection 16 Release valve 17 Discharge piping A flange connection B Threaded part C flange opening

Claims

1. A protective tube consisting of a bottomed, approximately cylindrical body into which a sheathed thermocouple thermometer is inserted is attached to a high-pressure vessel so that its tip is immersed in the treatment liquid in the vessel, and the temperature of the treatment liquid is measured, and a pressure detector is connected to a nozzle communicating with the inside of the protective tube via a normally open valve, so that the pressure inside the protective tube is constantly measured, when the measured pressure exceeds a threshold value and the temperature measured by the sheathed thermocouple thermometer exhibits a pattern of time-dependent changes that regularly fluctuate between a certain upper limit temperature and a certain lower limit temperature at a certain cycle, it is determined that moisture has entered through the joint opening at the end of the protective tube, A method for measuring temperature inside a high-pressure vessel, characterized in that it is determined that a hole has occurred in the protective tube when the measured pressure exceeds a threshold value and the temperature measured by the sheathed thermocouple thermometer does not show a pattern of change over time that regularly fluctuates between a certain upper limit temperature and a certain lower limit temperature at a certain period.

2. 2. The method for measuring the temperature inside a high-pressure vessel according to claim 1, wherein the valve and the pressure detector are connected by a connection having a branch pipe, a normally closed release valve is provided at the tip of the branch pipe, and the release valve is opened when it is determined that moisture has entered through the joint opening.

3. A method for measuring temperature inside a high-pressure vessel as described in claim 1, characterized in that when it is determined that a hole has occurred in the protective tube, an emergency shutdown or shutdown of equipment related to the high-pressure vessel is carried out.

4. The method for measuring a temperature inside a high-pressure vessel according to any one of claims 1 to 3, characterized in that the high-pressure vessel is an autoclave that performs a leaching treatment on the charged raw material slurry under conditions of a temperature of 140 to 270°C and a pressure of 1.8 to 5.8 MPaG while stirring the raw material slurry.

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