Temperature measuring device and method for draining the protective tube thereof

Abstract

To provide a temperature measurement device that can detect, in an early stage, entrance of water from a joint opening unit into a protection pipe and can remove the intruding water.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; a pressure detector 13 connected to one of two nozzles leading to the inside of the protection tube 12 by a valve 14; and a sucking unit 20 connected to the other nozzle by a second valve 22 and a tube 21. The top end part of the tube 21 reaches the bottom part of the protection pipe 12.SELECTED DRAWING: Figure 3

Description

Technical Field

[0001] The present invention relates to a temperature measuring device attached to a high-pressure vessel typified by an autoclave that performs leaching treatment under high temperature and high pressure, and a method for draining water from its protection tube.

Background Art

[0002] In the nickel smelting process using nickel oxide ore as a raw material, a wet smelting method by the high-pressure acid leaching method (HPAL method) is known. In this smelting method, an ore slurry prepared by adding water to raw ore with uniform particle size is charged into a reaction vessel together with sulfuric acid, and high-pressure steam is further blown in to perform acid leaching treatment under high temperature and high pressure of about 200 to 270 °C and a pressure of about 1.8 to 5.8 MPaG. It becomes possible to efficiently recover valuable metals such as nickel and cobalt from raw ore with low nickel grade.

[0003] Also, in the manufacturing process of nickel sulfate crystals, a slurry 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 nickel smelting process, is charged into a reaction vessel, and high-pressure air is further blown in to perform oxidation leaching treatment under high temperature and high pressure of about 140 to 200 °C and a pressure of about 1 to 2 MPaG, thereby producing an aqueous nickel sulfate solution.

[0004] Furthermore, in the manufacturing process of nickel sulfate crystals using nickel matte, which is a solid solution of nickel trisulfide (Ni3S2) and nickel (Ni 0 ), a slurry prepared by adding water to the pulverized nickel matte is charged into a reaction vessel together with a slightly stoichiometrically insufficient amount of sulfur, and high-pressure air is further blown in to perform oxidation leaching treatment under high temperature and high pressure similar to the case using the above MS as a raw material, thereby producing an aqueous nickel sulfate solution.

[0005] As the reaction vessel for performing the leaching treatment under high temperature and high pressure as described above, a so-called autoclave, which is a high-pressure vessel with a stirrer, in which a cylindrical vessel is placed horizontally and its interior is partitioned by a partition wall, is generally used. In the leaching treatment using this autoclave, the temperature of the internal treatment liquid is not only an important state quantity that affects the quality of the product, but also one of the important parameters for confirming that the reaction is proceeding normally. Therefore, it is required to be able to accurately measure the temperature over a long period of time.

[0006] Therefore, for high-pressure vessels such as autoclaves, a temperature measuring device having a structure in which a sheathed thermocouple thermometer in which a thermocouple wire is covered with a metal sheath is further housed in a metal protective tube (thermowell) is used. For example, in Patent Document 1, a thermometer protection tube (hereinafter also simply referred to as a protection tube) is installed such that its tip contacts the measurement object, and the temperature of the measurement object is measured by a thermocouple built in a metal sheath inserted into this protection tube. Generally, a temperature measuring device having a structure in which a sheathed thermocouple thermometer is housed in a protection tube is used. However, in addition, for example, a temperature measuring device having a structure in which a resistance thermometer is housed in a protection tube may also be used.

Prior Art Documents

Patent Documents

[0007]

Patent Document 1

Disclosure of the Invention

Problems to be Solved by the Invention

[0008] In the temperature measuring device with the above structure, moisture might intrude into the interior from the flange opening at the end of the protective tube into which the thermometer is inserted during regular inspections or when replacing the thermometer. Also, due to the aging deterioration of the packing or the like, rainwater might intrude into the protective tube from the flange opening through the gap on the flange sealing surface at the end of the protective tube. Furthermore, rainwater might intrude into the protective tube from the penetration part of the thermometer in the upper flange which generally has a screw-in structure due to the deterioration of the sealing material or the like. In this specification, the flange opening at the time of opening the flange at the end of the protective tube, the gap on the flange sealing surface at the end of the protective tube, the penetration part of the thermometer in the upper flange, etc. as described above are collectively referred to as the "joint opening at the end of the protective tube". When moisture intruded into the protective tube from the joint opening as described above, for example, when the operation was stopped, air was directly blown into the protective tube to remove the moisture, but when the protective tube was long, the moisture accumulated at the bottom might not be completely removed.

[0009] As a result, an incorrect indication might occur in the measured temperature due to the moisture accumulated at the bottom, and variations might occur in the quality of the product. That is, due to moisture, for example, the metal sheath corrodes, so the resistance value of the thermocouple changes, and as a result, the temperature measurement becomes inaccurate. Therefore, the reaction of the leaching treatment becomes unstable in the autoclave, and especially when a reaction failure occurs, this might have an adverse effect on the quality or cause scaling called "beco" on the blade part of the stirrer. Furthermore, when moisture intrudes from the joint opening at the end of the protective tube, for example, when rust occurs on the metal sheath and the metal sheath corrodes and forms a hole, the insulator such as alumina powder or magnesium oxide powder leaks out from the inside, causing the metal sheath to adhere to the inside of the protective tube, and it might not be possible to pull out only the sheath-type thermocouple thermometer from the protective tube when replacing it.

[0010] The present invention has been made in view of the problems of the above conventional temperature measuring device, and aims to provide a temperature measuring device capable of early detecting the intrusion of moisture from the joint opening into the thermometer protective tube and reliably removing the intruded moisture, and a method for draining water from its protective tube.

Means for Solving the Problem

[0011] In order to achieve the above object, a temperature measuring device according to the present invention includes a thermometer for measuring the liquid temperature in a high-pressure vessel, a protective tube having a bottomed substantially cylindrical shape into which the thermometer is inserted, and a pressure detector connected to one of two nozzles communicating with the inside of the protective tube via a first valve, and a suction device connected to the other nozzle via a second valve and a tube. The temperature measuring device is characterized in that the tip of the tube reaches the bottom of the protective tube.

[0012] Further, a method for draining water from a protective tube according to the present invention is to attach a protective tube having a bottomed substantially cylindrical shape into which a thermometer is inserted to the high-pressure vessel so that the tip thereof is immersed in the processing liquid in the high-pressure vessel, and connect a pressure detector to one of two nozzles communicating with the inside of the protective tube via a normally open first valve to constantly measure the pressure inside the protective tube. When the measured pressure exceeds a threshold value, a suction device connected to the other nozzle via a second valve and a tube is driven, so that moisture that has entered the protective tube from the joint opening at the end of the protective tube is sucked and removed from the tip of the tube that reaches the bottom of the protective tube.

Advantages of the Invention

[0013] According to the present invention, when moisture enters the protective tube of the temperature measuring device from the joint opening, it can be quickly detected, and the moisture can be surely drained from the protective tube.

Brief Description of the Drawings

[0014]

Figure 1

Figure 2

Figure 3

Figure 4

Figure 5

Embodiments for Carrying Out the Invention

[0015] 1. Autoclave Hereinafter, the temperature measuring device according to the embodiment of the present invention will be described. First, the autoclave in which the temperature measuring device according to the 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 mirror plates such as hemispherical shapes at both ends is installed horizontally. The inside thereof is partitioned into a plurality of reaction chambers 3A to 3E by a plurality of partition walls (four partition walls are illustrated in FIG. 1) 2 arranged at substantially equal intervals in the longitudinal direction. In each of these plurality of reaction chambers 3A to 3E, a stirrer 4 is provided for performing an acid leaching reaction or an oxidative leaching reaction. Further, the upper part of the partition wall 2 is cut out so that it can overflow.

[0016] With such a configuration, the raw material slurry charged into the most upstream reaction chamber 3A located at the left end of the drawing through the inlet nozzle 5 overflows the upper end portion of the partition wall 2 toward the most downstream reaction chamber 3E located at the right end of the drawing and is sequentially transferred to the adjacent downstream reaction chamber. In this way, the raw material slurry is gradually subjected to a leaching treatment in each reaction chamber and is finally withdrawn as a leached slurry from the most downstream reaction chamber 3E through the outlet nozzle 6.

[0017] In order to perform temperature control of the leaching treatment on the autoclave having the above structure, as shown in FIG. 2, the temperature measuring device 10 of the embodiment of the present invention is provided. In FIG. 1, for the sake of simplicity, the case where one temperature measuring device 10 is provided in the most upstream reaction chamber 3A of the autoclave is illustrated. Generally, at least one temperature measuring device 10 is installed in each of the reaction chambers 3A to 3E.

[0018] 2. Temperature Measuring Device Next, the temperature measuring device 10 according to the 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 thermocouple thermometer 11 that measures the temperature of the processing liquid of the object to be temperature-measured in the autoclave, which is a high-pressure vessel, a protective tube 12 having a bottomed substantially cylindrical body into which the thermometer 11 is inserted, a pressure detector 13 connected to a first nozzle 12c communicating with the inside of the protective tube 12 via a first valve 14, and a suction device 20 connected to a second nozzle 12d communicating with the inside of the protective tube 12 via a second valve 22 and a tube 21. The tip of the tube 21 reaches the bottom of the protective tube 12. In the embodiment shown in FIG. 3, the case where the thermometer is the sheath thermocouple thermometer 11 is shown, but the temperature measuring device 10 of the present invention is not limited to the sheath thermocouple thermometer 11 and can be applied to all rod-shaped or long-shaped electric thermometers such as resistance temperature detectors.

[0019] As also shown in FIG. 4, these first nozzle 12c and second nozzle 12d are provided at a portion of the protective tube 12 located outside the can body 1 of the autoclave, that is, between the large flange 12a for joining with the autoclave and the small flange 12b for joining with the thermometer 11, so as to project in a direction perpendicular to the axial direction of the protective tube 12.

[0020] As described above, by connecting the pressure detector 13 to the first nozzle 12c side communicating with the inside of the protective tube 12, it becomes possible to constantly measure the pressure inside the protective tube 12. As a result, it is possible to quickly detect an increase in the pressure inside the protective tube 12 that occurs when moisture enters the protective tube 12 from the joint opening at the end of the protective tube 12. Further, by connecting the suction device 20 to the second nozzle 12d side communicating with the inside of the protective tube 12, it is possible to remove the moisture that has entered the protective tube 12.

[0021] Specifically, the thermometer 11 is generally attached to the end of the protection tube 12 by means of flange connection, screwing, etc. The sealing performance of these joint parts is susceptible to temperature changes due to the outside air temperature at the location where the temperature measuring device is installed and pressure fluctuations inside the protection tube 12, and the sealing function may be impaired due to the aging deterioration of the sealing member. For example, as shown in Fig. 5(a), it can be attached by screwing the male screw part of the thermometer 11 into the through hole provided in the upper flange 12e that is flange-connected to the small flange 12b located at the end of the protection tube 12, or as shown in Fig. 5(b), it can be attached by tightening the nipple-shaped joint 12f into the through hole of the upper flange 12e. Therefore, as shown in Fig. 3, rainwater or the like may enter the inside of the protection tube 12 from the above flange connection part A or screwing part B. Furthermore, moisture may directly enter the inside of the protection tube 12 from the flange opening C of the small flange 12b during the regular inspection of the temperature measuring device or when replacing the thermometer 11.

[0022] In this way, the moisture such as rainwater that has entered the protection tube 12 evaporates by being heated by the treatment liquid or gas in the autoclave. For example, when the temperature in the autoclave is about 200 °C, according to the steam table, the saturated steam pressure of water at 200 °C is 1.55 MPaA. Therefore, assuming that the inside of the protection tube 12 is completely replaced from air to water after intrusion, the pressure inside the protection tube 12 will rise to a maximum of 1.55 MPaA. Therefore, when moisture intrusion occurs in the protection tube 12 from the joint opening as described above, the pressure inside the protection tube 12 will rise, so it is possible to detect it early with the pressure detector 13.

[0023] During normal operation of the autoclave, the pressure measured by the pressure detector 13 only increases from about 0.10 MPaA to about 0.16 MPaA of the atmospheric pressure according to Boyle's law when the temperature inside the autoclave is 200°C, and even in the case of about 270°C for leaching treatment by the HPAL method, it is at most about 0.2 MPaA. Also, since the protective tube 12 is generally not designed for high pressure resistance, it will not be maintained at 1.55 MPaA. Therefore, for example, when a pressure equal to or higher than a threshold value of about 0.3 to 0.5 MPaG is detected by the pressure detector 13, it is preferable to issue an alarm via a DCS (Distributed Control System) or the like.

[0024] In addition, when moisture enters the protective tube 12 from the joint opening at the end of the protective tube 12, a characteristic pattern that regularly moves up and down between a certain upper limit temperature and a certain lower limit temperature about 5°C lower than this upper limit temperature appears in the temperature trend indicating the change over time of the measured temperature by the thermometer 11. This is because only the portion of the elongated protective tube 12 located outside the can body 1 of the autoclave in the protective tube 12 is exposed to the low-temperature outside air, and this situation is considered to act like a distillation column, causing the internal moisture to repeat evaporation at the lower part and condensation at the upper part.

[0025] That is, the moisture that has entered the protective tube 12 from the joint opening at the end of the protective tube 12 falls toward the tip inside the protective tube 12 by gravity and evaporates. During this evaporation, since it takes the latent heat of vaporization from the surroundings, the measured temperature of the thermometer 11 temporarily drops. Thereafter, since the vapor generated by this evaporation rises inside the protective tube 12, the measured temperature of the thermometer 11 returns to the original temperature. On the other hand, the vapor that has reached the upper part of the relatively low-temperature protective tube 12 is cooled and condensed here. Then, it falls as moisture and evaporates again at the tip inside the protective tube 12. Thus, the moisture that has entered the protective tube 12 from the joint opening repeats a cycle consisting of evaporation at the lower part and condensation at the upper part. If this evaporation and condensation are leveled out in time series, the measured temperature of the thermometer 11 will continue in a state slightly lower than the true value, but it can be estimated that it is intermittently repeated in accordance with the dripping of water droplets. As shown in FIGS. 3 and 4, the tip of the protective tube 12 that is immersed in the processing liquid has a reduced diameter in accordance with the shape of the sheathed thermocouple thermometer 11, but the shape of the protective tube 12 is not limited to this, and a structure without a reduced diameter may be used.

[0026] In the temperature measuring device according to the embodiment of the present invention, when moisture enters the protective tube 12 from the joint opening as described above, the moisture can be extracted from the protective tube 12 by driving the suction device 20. It is preferable to use an ejector, which is a type of vacuum pump, for this suction device 20. This is because an ejector sucks gas based on Bernoulli's principle using a high-speed fluid, has a simple structure without a movable part, and thus can suppress costs.

[0027] Specifically, the ejector is composed of a nozzle section that injects driving fluid at high speed, a suction section that sucks in gas under a reduced-pressure atmosphere by the injected driving fluid, and a diffuser section that discharges the sucked-in gas together with the injected driving fluid. One end of a tube 21 is connected to this suction section. The other end side of the tube 21 is inserted inside the protective tube 12 through the second nozzle 12d described above, and its tip reaches the bottom of the protective tube 12. A second valve 22 is provided at a portion of the tube 21 that is located outside the second nozzle 12d. Further, the tube 21 is attached to the second nozzle 12d by airtightly penetrating a blind flange that is flange-connected to the second nozzle 12d.

[0028] With such a configuration, by introducing a driving fluid such as compressed air or steam into the nozzle section of the ejector to drive the suction device 20, almost all of the moisture in the protective tube 12 can be sucked out. The material of the tube 21 is not particularly limited as long as it can withstand the temperature of the high-pressure container. For example, a Teflon tube or a metal tube can be used. In the case of a metal tube, a copper tube or a stainless-steel tube with an outer diameter of about 3 mm can be preferably used.

[0029] In order to smoothly suck out the moisture in the protective tube 12 described above, it is preferable that the first nozzle 12c side is open to the atmosphere. This can be achieved, for example, by connecting the first valve 14 and the pressure detector 13 via a connection portion 15 having a branch pipe such as a T-shaped joint and opening a normally closed adjustment valve 16 provided at the tip of this branch pipe. In addition, an introduction pipe 17 may be provided at the tip of this adjustment valve 16 as needed.

[0030] When moisture enters the protective tube 12 from the joint opening, as described above, the pressure inside the protective tube 12 becomes high pressure, and the above-described characteristic temperature pattern appears on the temperature trend. Therefore, when changes in both of these pressure and temperature are confirmed, both the adjustment valve 16 and the second valve 22 are changed from "closed" to "open", and the suction device 20 is driven to remove the moisture inside the protective tube 12. At this time, the first valve 14 that is always open remains open as a matter of course. This always-open first valve 14 will be closed, for example, when the pressure detector 13 is replaced.

[0031] In addition, an alarm may be automatically issued when the above-described characteristic temperature pattern appears on the temperature trend. This can be achieved, for example, by capturing the above temperature trend in the DCS, calculating the differential value of the temperature, and issuing an alarm when the frequency of exceeding a predetermined threshold value in the calculated differential value is equal to or greater than a predetermined number per unit time. Alternatively, an alarm may be automatically issued when the temperature difference between the measured temperatures of adjacent reaction chambers of the autoclave becomes equal to or greater than a predetermined threshold value.

[0032] In addition, the suction of moisture inside the protective tube 12 by the suction device 20 may be performed after stopping the operation of the autoclave and cooling the can body 1 to a certain extent. In this case, since almost all of the moisture that has entered the protective tube 12 has condensed, the moisture can be removed more reliably. Also, when the protective tube 12 has a hole due to corrosion, wear, etc., there is a risk that the high-pressure processing liquid will blow out. Therefore, it is not preferable to immediately open the adjustment valve 16 when the internal pressure measured by the pressure detector 13 exceeds the threshold value. That is, even if the internal pressure measured by the pressure detector 13 exceeds a predetermined threshold value, if the above-described characteristic pattern of regularly rising and falling does not appear in the temperature trend measured by the thermometer 11, it is preferable to quickly plan for an emergency stop or shutdown of the equipment without driving the suction device 20 or opening the adjustment valve 16.

[0033] As described above, by using the temperature measuring device according to the embodiment of the present invention, it is possible to immediately notice when moisture has entered the protective tube from the joint opening at the end of the protective tube, and the entered moisture can be surely removed. As a result, problems such as adhesion of the metal sheath to the protective tube due to rust caused by moisture do not occur. In addition, since the leaching treatment can be stably performed in the autoclave over a long period of time, variations in the quality of the product are less likely to occur. Therefore, the industrial value of the present invention is extremely high.

Explanation of Signs

[0034] 1 Can body 2 Partition wall 3A - 3E Reaction chamber 4 Agitator 5 Inlet nozzle 6 Outlet nozzle 10 Temperature measuring device 11 Thermometer 12 Protective tube 12a Large flange 12b Small flange 12c First nozzle 12d Second nozzle 12e Upper flange 12f Nipple joint 13 Pressure detector 14 First valve 15 Connection part 16 Adjustment valve 17 Introduction pipe 20 Suction device 21 Tube 22 Second valve A Flange connection part B Screw-in part C Flange opening

Claims

1. A temperature measuring device comprising a thermometer for measuring the liquid temperature inside a high-pressure vessel, a protective tube of a bottomed substantially cylindrical body into which the thermometer is inserted, a pressure detector connected via a first valve to one of two nozzles communicating inside the protective tube, and a suction device connected via a second valve and a tube to the other nozzle, wherein the tip of the tube reaches the bottom of the protective tube.

2. The temperature measuring device according to claim 1, wherein the first valve and the pressure detector are connected via a connecting portion having a branch pipe, and an adjustment valve is provided at the tip of the branch pipe.

3. The temperature measuring device according to claim 1 or 2, wherein the thermometer is a sheathed thermocouple thermometer.

4. A method for draining water from a protective tube, comprising attaching a protective tube made of a bottomed substantially cylindrical body into which a thermometer is inserted to a high-pressure vessel such that the tip thereof is immersed in a processing liquid inside the high-pressure vessel, connecting a pressure detector via a normally open first valve to one of two nozzles communicating inside the protective tube to constantly measure the pressure inside the protective tube, and when the measured pressure exceeds a threshold value, driving a suction device connected via a second valve and a tube to the other nozzle to suck and remove moisture that has entered the protective tube from a joint opening at the end of the protective tube to the tip of the tube that reaches the bottom of the protective tube.

5. The method for draining water from a protective tube according to claim 4, wherein the pressure detector is connected to the one nozzle via a connecting portion having a branch pipe, and when driving the suction device, an adjustment valve normally closed provided at the tip of the branch pipe is opened.

6. The method for draining water from a protective tube according to claim 4 or 5, wherein the thermometer is a sheathed thermocouple thermometer.

7. The method for draining water from a protective tube according to claim 6, wherein the suction device is driven only when the temperature measured by the sheathed thermocouple thermometer shows a pattern of regular up-and-down changes over time within a certain period between a certain upper limit temperature and a certain lower limit temperature.

8. The method for draining water from a protective tube according to any one of claims 4 to 7, wherein the high-pressure vessel is an autoclave that performs a leaching process under conditions of a temperature of 140 to 270°C and a pressure of 1.8 to 5.8 MPaG while stirring the charged raw material slurry.

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