Repair method for electrolyte concentration equipment

Abstract

To provide a method for repairing an electrolyte condensation facility which can prevent mixing of steam into an electrolyte without needing the facility to stop for a long time.SOLUTION: An electrolyte condensation facility includes: a heating can for heating an electrolyte of copper; and a vacuum evaporation can for evaporating moisture in the electrolyte to condense the electrolyte. The heating can 20 has: a shell and tube type heat exchange part 22 comprising a shell 22a into which high pressure steam is introduced, and multiple heat transfer pipes 22b each of which is formed by a carbon straight tube and allows the electrolyte to be introduced into the tube to conduct heat exchange with the high pressure steam; an upper liquid chamber 23 which is connected to the upper part side of the heat exchange part and where the heated electrolytes discharged from upper opening ends of the respective heat transfer pipes join; and a lower liquid chamber 24 which is connected to the lower part side of the heat exchange part and receives the electrolyte supplied from a steam can to divide the electrolyte into lower opening ends of the respective heat transfer pipes. A method of repairing the electrolyte condensation facility is characterized in that carbon plugs 30 are inserted into the upper opening end and the lower opening end of the heat transfer pipe to seal each opening end when the heat transfer pipe is damaged.SELECTED DRAWING: Figure 3

Description

Technical Field

[0001] The present invention relates to a repair method for electrolyte concentration equipment comprising a heating can for heating a copper electrolyte and a vacuum evaporation can for concentrating the electrolyte by evaporating moisture in the electrolyte.

Background Art

[0002] In the copper electrolytic refining process, to obtain a smooth electrodeposit on a cathode, electrolytic refining is performed in a copper sulfate-sulfuric acid aqueous electrolyte with a copper concentration of 40 to 55 g / L and a free sulfuric acid concentration of 150 to 200 g / L. However, in this process, trace amounts of copper oxides such as CuO and Cu₂O and metallic copper contained in the crude copper used for the anode dissolve in the sulfuric acid serving as the electrolyte, so the amount of copper eluted from the anode is greater than the amount of copper electrodeposited on the cathode. The excess amount of copper, which depends on conditions such as the oxygen concentration in the anode, is usually about 1 to 2% of the amount of copper electrodeposited on the cathode.

[0003] If electrolytic refining is continued without removing excess copper, the copper concentration in the electrolyte will increase, causing a phenomenon called passivation that inhibits the elution of copper from the anode and making it impossible to continue electrolytic refining. For this reason, conventionally, acid-regenerating electrolysis, acid-producing electrolysis, decopperizing electrolysis or dearsenizing electrolysis processes, in which copper is electrowon from a copper sulfate-sulfuric acid aqueous solution using lead or a lead-containing alloy as an insoluble anode, are carried out to recover excess copper as an electrodeposit. Furthermore, in this process, by further electrowinning the electrolyte from which copper ions have been completely removed, advantage is taken of the feature that impurities such as bismuth, arsenic and antimony can be recovered as electrodeposits, and removal of the aforementioned impurities contained in these electrolytes is also carried out (see Patent Document 1).

[0004] Incidentally, in the removal of impurities, the electrodeposition potentials of arsenic, bismuth, and antimony are lower than those of copper. Therefore, when removing these impurities from the electrolyte used in the electrolytic refining of copper, a large amount of electrolyte needs to be processed to adequately remove the impurities. In other words, because the impurity concentration in the electrolyte used in the electrolytic refining of copper is low, a large amount of electrolyte needs to be processed to maximize the effect of impurity electrodeposition, and to perform such electrodeposition, it is necessary to set up a separate electrolytic facility of the same scale as that used for the electrolytic refining of copper. However, setting up such an electrolytic facility is not practical. Therefore, a portion of the electrolyte used in the electrolytic refining of copper is withdrawn from the electrolytic cell, and the withdrawn electrolyte is concentrated to increase the impurity concentration. This concentrated electrolyte is then sent to a re-acid electrolysis, acid-forming electrolysis, copper-removal electrolysis, or arsenic-removal electrolysis process to improve the efficiency of impurity removal.

[0005] As equipment for concentrating the electrolyte, for example, an electrolyte concentration apparatus like the one shown in Figure 1 is used. Specifically, this electrolyte concentration apparatus comprises a vacuum evaporator 10 and a heating vessel 20. The vacuum evaporator 10 and the heating vessel 20 are connected to an electrolyte supply pipe 11 that supplies electrolyte from the vacuum evaporator 10 to the heating vessel 20, and a heated electrolyte supply pipe 21 that supplies heated electrolyte from the heating vessel 20 to the vacuum evaporator 10, respectively, thus forming an electrolyte circulation system by thermal convection.

[0006] Here, the vacuum evaporator 10 is an electrolyte evaporation system that efficiently evaporates water from the electrolyte by utilizing the fact that water in the electrolyte evaporates at a liquid temperature of 100°C or lower. The vacuum evaporator 10 is kept at or below atmospheric pressure, receives electrolyte (liquid phase) from an electrolytic cell (not shown) via a liquid inlet 12 (for example, electrolyte partially withdrawn from a liquid inlet line supplying an electrolytic cell for refining electrolytic copper is introduced into the vacuum evaporator 10), and receives heated electrolyte supplied via a heated electrolyte supply pipe 21 of a heating vessel 20 (described later). The evaporated water is discharged from the exhaust port 14 of the vacuum evaporator 10 by gas extraction.

[0007] By using such a vacuum evaporator 10, the electrolyte can be efficiently concentrated. Therefore, by sending the concentrated electrolyte through the outlet 13 to the next process of repeated acid electrolysis, acid formation electrolysis, copper removal electrolysis, or arsenic removal electrolysis, efficient removal of impurities can be achieved in the electrolysis equipment. The capacity of the vacuum evaporator 10 is 11.1 m³. 3 (The normal usage level is about 50% of the total capacity, so 5m 3 In this case, the amount of electrolyte supplied to the vacuum evaporator 10 and the amount discharged from the vacuum evaporator 10 are, for example, 0 to 130 liters / min for the supply amount and 0 to 65 liters / min for the discharge amount.

[0008] Furthermore, the heating can 20 comprises a shell 22a into which high-pressure steam is introduced through a steam inlet 20a, a shell-and-tube type heat exchange section 22 consisting of a plurality of carbon straight tubes arranged inside the shell 22a, and a plurality of heat transfer tubes 22b into which electrolyte is introduced and heat exchange with the high-pressure steam, and an upper section connected to the upper side of the heat exchange section 22 that combines the heated electrolyte discharged from each upper opening end of the heat transfer tubes 22b. The heat exchange unit has a liquid chamber 23 and a lower liquid chamber 24 connected to the lower side of the heat exchange unit 22, which receives the electrolyte supplied from the vacuum evaporator 10 via the electrolyte supply pipe 11 and distributes it to the lower open ends of the heat transfer tubes 22b. The upper and lower ends of each heat transfer tube 22b are configured to be held in place by being fitted into tube holes 22d of the tube sheet 22c (see Figure 2), which are located on the upper liquid chamber 23 side and the lower liquid chamber 24 side of the shell 22a, respectively. Reference numeral 20b indicates a drain discharge pipe for removing the drain after heat exchange.

[0009] Incidentally, in the electrolyte concentration equipment described above, the electrolyte flowing through the heat transfer tubes 22b has the property of easily corroding metals such as iron, so carbon is usually used as the material that makes up the heat transfer tubes 22b. Although carbon is a material with high corrosion resistance, its strength is inferior to that of metal-based materials, so the heat transfer tubes 22b sometimes break during long-term use. When the heat transfer tubes 22b break, the high-pressure steam inside the shell 22a enters the heat transfer tubes 22b from the point of damage, and the electrolyte in the vacuum evaporator 10 is diluted by the steam, making it difficult to concentrate the electrolyte.

[0010] To prevent steam from entering the heat transfer tubes 22b, it is necessary to either replace the damaged heat transfer tubes 22b with new ones or replace the heating boiler 20 itself with a new one. However, replacing it with a new one is not practical because it would require a long period of equipment downtime and would be very expensive. [Prior art documents] [Patent Documents]

[0011] [Patent Document 1] Japanese Patent Application Publication No. 11-229171 [Overview of the project] [Problems that the invention aims to solve]

[0012] This invention was made in view of these problems, and its objective is to provide a method for repairing electrolyte concentration equipment that enables the equipment to be restored without requiring a long period of downtime, by preventing the ingress of vapor into the electrolyte. [Means for solving the problem]

[0013] In other words, the first invention according to the present invention is, It comprises a heating vessel for heating the copper electrolyte and a vacuum evaporator for evaporating the water in the electrolyte to concentrate it, and, The above-mentioned heated can is A shell-and-tube type heat exchanger consisting of a shell into which high-pressure steam is introduced, and a plurality of heat transfer tubes made of carbon straight tubes arranged inside the shell, in which an electrolyte is introduced inside the straight tubes to exchange heat with the high-pressure steam, An upper liquid chamber is provided on the upper side of the heat exchange section and collects the heated electrolyte discharged from each upper opening end of the heat transfer tubes. An electrolyte concentration apparatus having a lower liquid chamber connected to the lower side of the heat exchange section and which receives the electrolyte supplied from the vacuum evaporator and distributes it to the lower open ends of the heat transfer tubes, When a part of the heat transfer tube in the heat exchange section is damaged to A repair method for electrolyte concentration equipment, which involves inserting carbon plugs into the upper and lower open ends of the damaged heat transfer tubes to seal each open end. In , The specific gravity of the concentrated electrolyte discharged from the vacuum evaporator is measured, and the measured specific gravity value of the concentrated electrolyte is compared with the control value to detect whether or not there is damage to the heat transfer tube. It is characterized by the following:

[0014] Furthermore, the second invention according to the present invention is, In the method for repairing an electrolyte concentration apparatus described in the first invention, The method is characterized by first inserting a temporary plug having an outer diameter approximately the same as the inner diameter of the heat transfer tube at a position deeper than the insertion depth of the plug inside the damaged heat transfer tube, applying adhesive to the tip of the plug and the outer surface of the plug to be inserted, and then inserting carbon plugs into the upper and lower open ends of the heat transfer tube to connect the temporary plug and the plugs. The third invention is, In the method for repairing an electrolyte concentration device described in the second invention, The above-mentioned temporary stopper is characterized by being composed of a silicone temporary stopper or a temporary stopper coated with Teflon®.

[0015] Next, the present invention 4 The invention is The 1 In the method for repairing an electrolyte concentration device described in the invention, The method is characterized in that the introduction of high-pressure steam into the shell of the shell-and-tube heat exchange section is stopped, and the closed shell is filled with water to identify the damaged heat transfer tube. [Effects of the Invention]

[0016] According to the repair method for an electrolyte concentration facility according to the present invention, Carbon plugs are inserted into the upper opening end and lower opening end of the damaged heat transfer tube to seal each opening end. Therefore, even if high-pressure steam in the shell enters the heat transfer tube from the damaged portion of the heat transfer tube, mixing of the high-pressure steam into the vacuum evaporator can be prevented.

[0017] Furthermore, the method of the present invention, in which repair is performed by inserting carbon plugs into the upper opening end and lower opening end of the damaged heat transfer tube, significantly simplifies the work compared to methods of replacing the damaged heat transfer tube with a new heat transfer tube or replacing the heating can itself. Therefore, the method has the effects that a long-term shutdown of the facility is not required and repair costs can be reduced. [Brief Description of the Drawings]

[0018] [Figure 1] A configuration explanatory diagram of an electrolyte concentration facility including a heating can and a vacuum evaporator. [Figure 2] A plan view of tube sheets respectively arranged on the upper liquid chamber side and lower liquid chamber side of a heat exchange section, the tube sheets holding the upper ends and lower ends of each heat transfer tube. [Figure 3] An explanatory diagram showing a heating can with a partially damaged heat transfer tube and a repair method therefor. [Figure 4] An explanatory diagram showing a state where a plug is inserted and fixed into the opening end of a damaged heat transfer tube. [Figure 5] An explanatory diagram showing a state where a temporary plug having an outer diameter substantially equal to the inner diameter of the heat transfer tube is first fitted into the damaged heat transfer tube, then a plug coated with an adhesive is inserted into the opening end of the heat transfer tube, and the temporary plug and the plug are connected. [Mode for Carrying Out the Invention]

[0019] Embodiments of the present invention will be described in detail below.

[0020] (1) Heating can Figure 3 is an explanatory diagram showing a heating vessel 20 with a damaged heat transfer tube 22b and a method for repairing it. An upper liquid chamber 23 is located on the left side of the paper, and a lower liquid chamber 24 is located on the right side of the paper. A shell-and-tube type heat exchanger 22 is provided in the area between the upper liquid chamber 23 and the lower liquid chamber 24. The shell 22a, which constitutes the outer shell of the shell-and-tube type heat exchanger 22, has a steam inlet 20a for introducing high-pressure steam into the interior and a drain outlet pipe 20b for draining condensate after heat exchange on its side. Inside the shell 22a, several (several dozen in this example) straight carbon tubes (which constitute the heat transfer tubes 22b described above) are installed along its longitudinal direction and are approximately the same length as the shell 22a. Furthermore, both ends of the heat transfer tubes 22b are open, the upper end of the heat transfer tube 22b located on the left side of the paper is connected to the upper liquid chamber 23, and the lower end of the heat transfer tube 22b located on the right side of the paper is connected to the lower liquid chamber 24. The upper and lower ends of each heat transfer tube 22b are fitted into and held in the tube holes of the tube sheet (see Figure 2) located on the upper liquid chamber 23 side and the lower liquid chamber 24 side, respectively.

[0021] (2) Repair method By the way, in a copper electrolyte concentration apparatus equipped with a vacuum evaporator 10 and a heating chamber 20, if a heat transfer tube 22b of the heat exchange section 22 is damaged, a carbon plug 30 is inserted into the upper and lower open ends of the damaged heat transfer tube 22b to seal it (see Figure 3). For example, as shown in Figure 4, an adhesive 31 can be applied around the insertion portion of the carbon plug 30 and to the tip of the plug 30, which is formed so that the insertion portion into the heat transfer tube 22b is slightly smaller than the inner diameter of the heat transfer tube 22b, and then fitted into the heat transfer tube 22b.

[0022] In this case, as shown in Figure 5, it is preferable to first insert a temporary plug 40 having an outer diameter approximately the same as the inner diameter of the heat transfer tube 22b at a position deeper than the insertion depth of the plug 30 inside the heat transfer tube 22b, and then apply adhesive 31 to the tip of the plug 30 and the outer surface of the plug (around the insertion part), and then insert the carbon plug 30 into the upper and lower open ends of the heat transfer tube 22b, and fill the gap between the temporary plug 40 and the plug 30 with adhesive 31 to connect them. By adopting this method, the temporary plug 40 can block the adhesive 31 from descending due to gravity until the adhesive 31 hardens, and the presence of the temporary plug 40 makes it difficult for atmospheric pressure to act on the adhesive 31 between the plug 30 and the temporary plug 40, thus preventing the adhesive 31 from falling off on the side of the plug 30 and reducing the bonding area. As a result, it is possible to effectively avoid the problem of the plug coming loose during long-term use.

[0023] The material of the temporary stopper is not particularly limited as long as it can properly block the adhesive, but as an example, a silicone temporary stopper or a temporary stopper coated with Teflon® can be preferably used.

[0024] (3) Detection of damage and identification of damaged heat transfer tubes (3-1) Detection of damage In this type of electrolyte concentration equipment, the amount of concentrated electrolyte sent from the outlet 13 of the vacuum evaporator 10 to the next process is usually adjusted so that the specific gravity of the concentrated electrolyte in the vacuum evaporator 10 reaches a predetermined value (control value), and the amount of water discharged from the vacuum evaporator 10 (i.e., the amount of water evaporated in the vacuum evaporator 10 + the amount of water in the concentrated electrolyte sent to the next process) is adjusted so that the amount of water supplied into the vacuum evaporator 10 (i.e., the amount of water in the electrolyte supplied into the vacuum evaporator 10) is approximately equal.

[0025] However, if the heat transfer tube 22b of the heating vessel 20 is damaged, the high-pressure steam inside the shell 22a will enter the heat transfer tube 22b through the damaged area, and the electrolyte inside the vacuum evaporator 10 will be diluted by the steam, causing the specific gravity of the concentrated electrolyte to fall below a predetermined value (control value).

[0026] Therefore, by measuring the specific gravity of the concentrated electrolyte discharged from the vacuum evaporator 10 and comparing the measured specific gravity value of the concentrated electrolyte with the predetermined value (control value), it becomes possible to detect that a part of the heat transfer tube 22b is damaged if the measured specific gravity value of the concentrated electrolyte is lower than the predetermined value (control value).

[0027] (3-2) Identification of damaged heat transfer tubes By stopping the introduction of high-pressure steam into the shell 22a of the shell-and-tube type heat exchanger 22, and closing the steam inlet 20a and drain outlet 20b of the heat exchanger 22, the inside of the shell 22a is filled with water. As a result, water will flow into the heat transfer tube 22b at the damaged location, making it possible to identify the damaged heat transfer tube 22b by visually inspecting it. [Examples]

[0028] below, Reference example I will explain this in detail.

[0029] [ Reference example 1] Due to damage to the heat transfer tubes in the heating tank of the electrolyte concentration equipment, carbon plugs were inserted into the upper and lower open ends of the damaged heat transfer tubes to seal them.

[0030] Specifically, as shown in Figure 4, a carbon plug 30 was used, formed such that the portion inserted into the heat transfer tube 22b was slightly smaller than the inner diameter of the heat transfer tube 22b. Adhesive (SGL Carbon Technique Japan Co., Ltd.: Tokabait Adhesive) 31 was applied around the insertion portion and tip of the plug 30, and it was fitted into the heat transfer tube 22b and sealed.

[0031] [ Reference example 2] Due to damage to the heat transfer tubes of the heating tank in the electrolyte concentration equipment, Reference example The damaged heat transfer tube was sealed using the carbon plug and silicone temporary stopper used in step 1.

[0032] Specifically, as shown in Figure 5, a temporary plug 40 having an outer diameter approximately the same as the inner diameter of the heat transfer tube 22b was first fitted into the heat transfer tube 22b at a position deeper than the insertion depth of the plug 30. Then, adhesive (Tohkabait adhesive, manufactured by SGL Carbon Technique Japan Co., Ltd.) 31 was applied to the tip and outer surface of the plug 30 (around the insertion part). After that, the carbon plug 30 was inserted into the upper and lower open ends of the heat transfer tube 22b, and the temporary plug 40 and the carbon plug 30 were connected by filling the gap between the temporary plug 40 and the plug 30 with adhesive 31.

[0033] [evaluation] (1) Reference example In experiment 1, the plug sealing process took three days (one day for pre-processing drying, one day for plug installation, and one day for drying). However, it was confirmed that this method was less expensive and allowed for recovery with a shorter equipment shutdown compared to replacing the damaged heat transfer tubes with new ones, or replacing the vacuum evaporator itself with a new one.

[0034] (2) On the other hand, Reference example In 2 Reference example In addition to the advantages related to point 1, it was confirmed that the plug can be prevented from coming loose over a long period of time.

[0035] In other words, Reference example In case 1, the plug came loose after about 3 months, and steam entered the heat transfer tubes. Reference example In case 2, no plug disconnection occurred even after approximately 8 months. [Industrial applicability]

[0036] The method for repairing electrolyte concentration equipment according to the present invention reduces repair costs without requiring prolonged equipment downtime, thus having industrial applicability for use in the electrolytic refining of copper. [Explanation of Symbols]

[0037] 10 Vacuum Evaporator 11 Electrolyte supply pipe 12 Fluid supply port 13 Outlet 14 Exhaust vents 20 heated cans 20a Steam Inlet 20b Drain discharge pipe 21 Heating electrolyte supply pipe 22 Shell-and-tube type heat exchanger 22a Shell 22b Heat transfer tube 22c tube sheet 22d Tube hole 23 Upper liquid chamber 24 Lower liquid chamber 30 plugs 31 Adhesive 40 Temporary plug

Claims

1. It comprises a heating vessel for heating the copper electrolyte and a vacuum evaporator for evaporating the water in the electrolyte to concentrate it, and, The above-mentioned heated can is A shell-and-tube type heat exchanger consisting of a shell into which high-pressure steam is introduced, and a plurality of heat transfer tubes made of carbon straight tubes arranged inside the shell, in which an electrolyte is introduced inside the straight tubes to exchange heat with the high-pressure steam, An upper liquid chamber is provided on the upper side of the heat exchange section and collects the heated electrolyte discharged from each upper opening end of the heat transfer tubes. An electrolyte concentration apparatus having a lower liquid chamber connected to the lower side of the heat exchange section and which receives the electrolyte supplied from the vacuum evaporator and distributes it to the lower open ends of the heat transfer tubes, In a repair method for an electrolyte concentration facility, in which a part of a heat transfer tube in the heat exchange section is damaged, carbon plugs are inserted into the upper and lower open ends of the damaged heat transfer tube to seal each open end, A method for repairing an electrolyte concentration system, characterized by measuring the specific gravity of the concentrated electrolyte discharged from the vacuum evaporator, and comparing the measured specific gravity value of the concentrated electrolyte with a control value to detect whether or not there is damage to the heat transfer tube.

2. A method for repairing an electrolyte concentration equipment according to claim 1, characterized in that a temporary plug having an outer diameter approximately the same as the inner diameter of the heat transfer tube is first fitted into the damaged heat transfer tube at a position deeper than the insertion depth of the plug, adhesive is applied to the tip of the plug and the outer surface of the plug to be inserted, and then carbon plugs are inserted into the upper and lower open ends of the heat transfer tube to connect the temporary plug and the plugs.

3. The method for repairing an electrolyte concentration facility according to claim 2, characterized in that the temporary stopper is made of a silicone temporary stopper or a temporary stopper coated with Teflon (registered trademark).

4. A method for repairing an electrolyte concentration facility according to claim 1, characterized by stopping the introduction of high-pressure steam into the shell in the shell-and-tube type heat exchange section and filling the closed shell with water to identify the damaged heat transfer tube.

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