JP7608765B2 - Method for dispersing release agent slurry and anode casting method using the same - Google Patents

Description

The present invention relates to a method for spraying a release agent slurry onto an anode mold used when casting anodes, which are handled as intermediate products in non-ferrous metal smelting processes such as copper smelting, and a method for casting anodes using the same.

In non-ferrous metal smelting processes, the grade of molten non-ferrous metals is gradually increased through dry processing, and then electrolytic refining is finally performed to produce high-purity non-ferrous metals. For example, in the electrolytic refining of copper, molten refined blister copper with a purity of about 99.5% is produced by oxidizing and reducing blister copper in a previous refining furnace, and cast into a roughly rectangular plate. The resulting anode (hereafter referred to as "anode") made of multiple copper plates and multiple separately prepared cathodes (hereafter referred to as "cathode") are arranged alternately one by one and immersed in the electrolyte in an electrolytic cell, and a voltage is applied to them to produce electrolytic copper.

The above-mentioned electrolytic refining of copper can be classified into the permanent cathode method (hereinafter referred to as the "PC method") and the conventional method (hereinafter referred to as the "seed plate method") depending on the type of cathode used. In the former PC method, a stainless steel thin plate is used as the cathode, and the electrolytic copper electrodeposited on the thin plate is peeled off from the thin plate in a subsequent peeling process and shipped as a product, and the thin plate is reused. On the other hand, in the latter seed plate method, a thin plate-shaped seed plate made of high purity copper is used as the cathode, and the electrolytic copper electrodeposited on the seed plate is shipped as a product together with the seed plate.

In the above-mentioned copper electrolytic refining, the anode and cathode are placed as close to each other as possible in the electrolytic cell to increase productivity, so if there are irregularities on the surface of the anode's body, the anode and cathode may come into contact with each other and cause a short circuit. If a short circuit occurs in the electrolytic cell, the electrolytic efficiency decreases, so in casting the above-mentioned refined blister copper, it is desirable to mold a smooth anode with no irregularities on its surface.

One of the reasons for the unevenness of the anode surface is thought to be that the anode sticks to the mold during casting. As a countermeasure to this, Patent Document 1 discloses a technique for forming a layer of a mold release agent made of clay powder and water glass on the inner surface of the anode mold before pouring the molten metal. It is described that this prevents the anode from sticking during casting and allows the molding of a smooth anode with no unevenness on the surface.

Patent No. 2896764 specification

As shown in the above Patent Document 1, by forming a layer of a release agent (hereinafter referred to as "release layer") on the inner surface of the anode mold, it is possible to prevent problems such as seizure during casting and the resulting unevenness of the anode surface. However, since the release layer is formed by spraying a release agent slurry prepared by adding water to the release agent onto the anode mold, water may evaporate during casting, resulting in the formation of a blister-like convex portion (hereinafter referred to as "blister") formed by a thin film with a hollow interior on the surface of the anode. If such a blister occurs on the surface of the anode, the current is preferentially consumed in the blister during electrolysis, and as a result, some of the blister may break or peel off, causing the above-mentioned short circuit problem. In order to suppress the occurrence of this blister, it is desirable to spray an optimal amount of release agent slurry onto each anode mold.

The optimal amount of the release agent slurry to be sprayed can be determined based on criteria such as the releasability of the anode from the mold. Such criteria can include, for example, the condition of the mold, such as the degree of wear on the inner surface of the mold and the mold temperature when the release agent slurry is sprayed, and the optimal amount to be sprayed is adjusted based on these. However, it is generally difficult to flexibly change the amount to be sprayed once it has been designed.

For this reason, the amount of release agent slurry sprayed onto the mold was prone to excess or deficiency. For example, if an excess of release agent slurry was sprayed onto the mold, it took too long for the moisture to evaporate from the inner surface of the mold, leaving some of it behind, which could boil during the casting of the molten blister copper poured into the mold, causing voids or the above-mentioned swelling in the anode. Conversely, if the amount of release agent slurry sprayed onto the mold was insufficient, the anode could not be properly peeled off from the mold, and the anode could be deformed if it was forcibly peeled off. The present invention was made in consideration of the above circumstances, and aims to provide a method for spraying release agent slurry that allows the amount of release agent slurry sprayed to be freely changed.

The release agent slurry to be sprayed onto the mold is usually prepared by adding water to a release agent made of clay powder in a preparation tank equipped with a stirrer so that the solids concentration (i.e. the mass of the release agent per unit volume of the release agent slurry) is about 30 to 60 g/L. In order to spray the release agent slurry having such a relatively high solids concentration onto the mold as uniformly as possible, it is preferable to pressurize the release agent slurry extracted from the bottom of the preparation tank, where the suspension state is maintained by stirring, to a predetermined pressure by a pressure boosting means such as a slurry pump, and spray it over a wide area through a spraying means such as a nozzle. In this case, when the pressure boosting by the pressure boosting means stops, part of the release agent slurry flowing in the supply pipe from the pressure boosting means to the spraying means is sprayed from the spraying means as it is due to inertia, but the remainder remains in the supply pipe due to a pressure drop caused by friction with the inner wall of the supply pipe or adhesion to the inner wall surface.

The inventors have noticed that the amount of release agent slurry sprayed from the spraying means after the pressure increasing means is stopped is not constant and varies. The factors (disturbances) that cause the variation in the amount of release agent slurry sprayed after the pressure increasing means is stopped include fluctuations in the liquid level of the release agent slurry in the preparation tank, fluctuations in the pressure of the utility air used for operating various devices in the factory, and a drop in the pressure of the release agent slurry due to adhesion of the release agent in the supply pipes. After extensive research into methods to suppress the adverse effects of these disturbances, the inventors have found that the amount of release agent slurry sprayed on each anode mold can be stabilized by devising a method for spraying the release agent slurry, and have completed the present invention.

That is, the method for spraying a release agent slurry of the present invention comprises a step of circulating the release agent slurry by an external circulation system which pressurizes the release agent slurry extracted from the bottom of a storage tank of the release agent slurry and returns the release agent slurry to the storage tank, and a step of spraying the release agent slurry extracted into a supply pipe branching from the external circulation system onto a mold from a spraying means provided at the tip of the supply pipe. The method is characterized in that the amount of the release agent slurry to be sprayed is adjusted depending on the time during which an automatic valve provided on the supply pipe is in an open state, and after the automatic valve is closed, a purge gas is introduced downstream of the automatic valve to spray the release agent slurry in the supply pipe from the spraying means, and the release agent slurry is sprayed onto the mold by introducing the purge gas into the supply pipe .

According to the present invention, the amount of release agent slurry sprayed can be changed as desired.

FIG. 1 is a schematic flow diagram of a release agent slurry supply facility to which a release agent slurry spraying method according to an embodiment of the present invention is suitably applied. FIG. 2 is a schematic diagram of a specific example of a mechanism for scanning the nozzle for spraying the release agent slurry in FIG. 1. 1 is a timing chart showing the opening and closing operations of various valves of a release agent slurry supplying facility performed in accordance with a method for spraying a release agent slurry according to an embodiment of the present invention, and the corresponding operation modes. FIG. 11 is a timing chart showing the opening and closing operations of various valves of a release agent slurry supplying facility performed in accordance with a method for spraying a release agent slurry according to another embodiment of the present invention, and the corresponding operation modes.

Hereinafter, a method for spraying a release agent slurry according to an embodiment of the present invention will be described. First, with reference to FIG. 1, a release agent slurry supplying facility to which the method for spraying a release agent slurry according to an embodiment of the present invention is suitably applied will be described. The release agent slurry supplying equipment shown in Fig. 1 is composed of a storage tank 10 equipped with an agitator 10a that receives a release agent such as clay powder together with industrial water, adjusts the solid content concentration to preferably 20 to 120 g/L, more preferably 40 to 60 g/L, and stores the same, a slurry pump 12, preferably an air-driven diaphragm pump, that pressurizes the release agent slurry extracted from an extraction pipe 11 at the bottom of the storage tank 10, a return pipe 13 that returns the release agent slurry pressurized by the slurry pump 12 to the storage tank 10, a supply pipe 14 that branches off from a branch point P of the return pipe 13 in order to extract the release agent slurry pressurized by the slurry pump 12, and a nozzle 15 that is provided at the tip of the supply pipe 14 in order to spray the release agent slurry on the inner surface of a mold C on a turntable of an anode casting device (not shown). The release agent slurry may be prepared in a preparation tank separate from the storage tank 10. In this case, the release agent slurry prepared in the preparation tank is transferred to the storage tank 10 using a slurry pump, gas pressure pumping, head differential, etc.

The nozzle 15 is preferably a two-fluid nozzle that sprays a mixture of the release agent slurry and the dispersion gas. This allows the release agent slurry, which has a higher solids concentration than a normal nozzle, to be sprayed almost uniformly on the inner surface of the mold, making it possible to mold a high-quality anode with little bulging. This two-fluid nozzle consists of a roughly cylindrical mixing section and a roughly truncated cone-shaped spray section provided at the tip of the mixing section, where the release agent slurry introduced from the side inlet and the dispersion gas introduced from the end inlet are mixed. For example, utility air is used as the dispersion gas, which is supplied via the spray gas supply pipe 17 branching off from the air header 16.

The nozzle 15 is preferably moved unilaterally along the bottom surface of the recess of the mold C. This can be achieved, for example, by the mechanism shown in FIG. 2. Specifically, one end of a shaft portion 23 is supported so as to be freely swingable at the tip of a piston 22 that extends and retracts from a cylinder 21 by the operation of a servo motor 20, a nozzle 15 is provided at the other end of the shaft portion 23, and the central portion of the shaft portion 23 in the longitudinal direction is supported by a fixed shaft. This makes it possible to spray the release agent slurry over almost the entire inner surface of the mold C by reciprocating the piston 22 with the servo motor 20.

As described above, in the release agent slurry supply equipment, the release agent slurry extracted from the bottom of the storage tank 10 is circulated using an external circulation system consisting of the extraction pipe 11, the slurry pump 12, and the return pipe 13. This prevents the release agent contained in the release agent slurry from settling and separating due to gravity and accumulating at the bottom of the storage tank 10 in cooperation with the agitator 10a, and the solids concentration of the release agent slurry in the storage tank 10 can be kept uniform. This makes it possible to keep the solids concentration of the release agent slurry sprayed onto the anode mold uniform through the supply pipe 14 branching off from the branch point P of this external circulation system and the nozzle 15 provided at the tip of the supply pipe 14.

Meanwhile, on the disk-shaped turntable that constitutes the above-mentioned anode casting device, multiple molds C are arranged at equal intervals in the circumferential direction, and as the turntable rotates intermittently, a cycle is repeated in each of the multiple molds C, consisting of pouring molten blister copper, cooling and solidifying the poured molten blister copper, peeling off the anode formed by the solidification, and spraying a release agent slurry onto the mold C after peeling off.

Therefore, the release agent slurry needs to be sprayed intermittently in sequence to the multiple molds C, and for this reason, the supply pipe 14 is provided with a spray valve 14a that opens and closes automatically. This allows the release agent slurry to be sprayed in accordance with the timing of the intermittent rotation of the turntable. In addition, the amount of release agent slurry extracted from the external circulation system can be adjusted by opening and closing the spray valve 14a, so the amount of release agent slurry introduced into the nozzle 15 through the supply pipe 14 can be adjusted depending on the length of time the spray valve 14a is open. In order to stabilize the extraction of the release agent slurry from the external circulation system, a circulation cutoff valve 13a is provided downstream of the branch point P in the return pipe 13 that constitutes the external circulation system, as shown in FIG. 1.

In order to stably inject the release agent slurry from the nozzle 15, the inlet pressure of the nozzle 15 may be maintained higher than a predetermined lower limit by setting the discharge pressure of the slurry pump 12 to an appropriate pressure. In this case, even if the spray valve 14a is switched from open to closed, the injection of the release agent slurry from the nozzle 15 does not immediately stop. However, after the spray valve 14a is switched from open to closed, the pressure and kinetic energy of the release agent slurry flowing through the supply pipe 14 gradually decrease due to friction with the inner wall surface of the supply pipe 14, so that the pressure eventually decreases and the flow rate slows down, and the release agent slurry is no longer injected from the nozzle 15. As a result, a part of the release agent slurry remains in the supply pipe 14. In other words, the amount of release agent slurry injected from the nozzle 15 after the spray valve 14a is closed is smaller than the amount of release agent slurry present in the supply pipe 14 immediately after the spray valve 14a is closed in one cycle.

If the part of the release agent slurry remaining in the supply pipe 14 after the spray valve 14a is closed is not discharged, it will be carried over to the spraying to the adjacent subsequent mold C on the turntable. In other words, the amount of release agent slurry sprayed to the subsequent mold C is the amount obtained by adding the amount of release agent slurry supplied to the supply pipe 14 from the external circulation system by opening the spray valve 14a when spraying to the subsequent mold C, and the amount of release agent slurry carried over from the spraying to the preceding mold C, minus the amount remaining in the supply pipe 14 after the spray valve 14a is closed in the same manner as above.

The amount of release agent slurry remaining in the supply pipe 14 after the spray valve 14a is closed is largely dependent on the degree to which the kinetic energy and pressure of the release agent slurry flowing through the supply pipe 14 immediately after the spray valve 14a is switched from open to closed, due to pressure loss in the supply pipe 14, as described above. Therefore, the amount of release agent slurry sprayed onto multiple molds C may vary from mold C to mold C. In order to suppress this variation, the method for spraying release agent slurry according to the embodiment of the present invention introduces a purge gas into the supply pipe 14, so that the release agent slurry extracted from the external circulation system into the supply pipe 14 is sprayed onto the molds C through the nozzle 15.

Specifically, a purge gas supply pipe 18 for introducing a purge gas is connected to the supply pipe 14 immediately adjacent to the secondary side (downstream side) of the spray valve 14a. As a result, for example, in accordance with the timing when the spray valve 14a goes from open to closed, the purge gas valve 18a provided on the purge gas supply pipe 18, which opens and closes automatically, is opened from closed to open to introduce the purge gas into the supply pipe 14. As a result, most of the release agent slurry remaining in the supply pipe 14 after the spray valve 14a is closed can be sprayed from the nozzle 15 onto the mold C.

As described above, by introducing a purge gas into the supply pipe 14, the amount of release agent slurry introduced from the external circulation system into the supply pipe 14 and the amount of release agent slurry sprayed from the supply pipe 14 through the nozzle 15 onto the mold C during one cycle of each mold C can be made substantially equal, so that the amount of release agent slurry sprayed onto each mold C can be prevented from varying. In addition, the open time of the spray valve 14a can be made directly proportional to the amount of release agent slurry sprayed onto each mold C, so that the amount of release agent slurry sprayed (sprayed) can be precisely adjusted by simply increasing or decreasing the open time of the spray valve 14a.

In one cycle of pouring, cooling and solidifying, stripping, and spraying for each mold C described above, the amount and pressure of the purge gas introduced into the supply pipe 14 after the spraying may be such that almost all of the release agent slurry in the supply pipe 14 can be pushed out from the nozzle 15. In addition, the timing of introducing the purge gas into the supply pipe 14 to purge the release agent slurry in the supply pipe 14 is preferably such that the extraction of the release agent slurry from the external circulation system to the supply pipe 14 is not hindered or a backflow occurs, and it is desirable to open the purge gas valve 18a when the spray valve 14a is closed.

Specifically, as shown in the timing chart of Figure 3, which shows a series of steps performed when spraying the release agent slurry in each mold C, the spray valve 14a is first opened from closed to extract the release agent slurry from the external circulation system to the supply pipe 14 (steps No. 1 to 3). At this time, in order to perform more stable extraction, it is preferable to temporarily switch the external circulation valve 13a of the external circulation system from open to closed (step No. 2). In addition, when a certain amount of the release agent slurry has been extracted, the injection gas valve 17a is switched from closed to open (step No. 3).

Next, the spray valve 14a is switched from open to closed and the purge gas valve 18a is switched from closed to open at the same time. This causes the release agent slurry to be sprayed from the nozzle 15 (Steps No. 4-5). It is preferable to operate the cylinder 21 for the nozzle 15 a short time after the purge gas valve 18a is switched from closed to open (Step No. 5). It is also preferable to keep the spray gas valve 17a and the purge gas valve 18a open for a while after almost all of the release agent slurry in the supply pipe 14 has been sprayed from the nozzle 15, so as to clean the inside of the supply pipe 14 and the nozzle 15 (Step No. 6). Finally, the spray gas valve 17a and the purge gas valve 18a are switched from open to closed, completing the spraying of the release agent slurry to one mold C (Step No. 7).

There are no particular restrictions on the composition of the gas used for the purge gas, so long as it does not substantially cause a chemical reaction with the material of the liquid-contacting parts such as the supply pipe 14 and the mold release agent slurry. For example, compressed air or compressed nitrogen can be used, with compressed air being more suitable from the viewpoint of low cost. Note that FIG. 1 shows a case in which the purge gas supply pipe 18 branches off from the miscellaneous gas air header 16, similar to the dispersion gas described above.

As shown in FIG. 3, the supply pipe 14 is cleaned after each cycle of spraying the release agent slurry in each mold C, so that the problem of clogging due to the release agent in the supply pipe 14 can be prevented. As described above, when general purpose air is used as the dispersion gas or purge gas, it is preferable to provide a filter-equipped pressure regulator in each of the injection gas supply pipe 17 and the purge gas supply pipe 18 as shown in FIG. 1 in order to further stabilize the amount of release agent slurry sprayed in each cycle of spraying the release agent slurry in each mold C. Similarly, when the slurry pump 12 is an air-driven diaphragm pump, it is preferable to provide a filter-equipped pressure regulator in the drive air pipe 19 as well.

In the above-mentioned release agent slurry supply equipment, the supply pipe 14 is structured to branch off from the external circulation system, but the supply pipe may be directly connected to the storage tank 10 and a supply slurry pump different from the slurry pump 12 of the external circulation system may be provided on the supply pipe, thereby introducing pressurized release agent slurry into the nozzle 15. In addition, since the introduction of the release agent slurry into the supply pipe 14 is performed intermittently, it is preferable that the position of the spray valve 14a provided on the supply pipe 14 is as close as possible to the branch point P so that the release agent in the release agent slurry does not settle and separate in the supply pipe 14 and clog the pipe.

In addition, instead of providing the sparge valve 14a and the circulation cutoff valve 13a in the supply pipe 14 and the return pipe 13, respectively, as described above, a three-way valve serving both functions may be provided at the branch point P between the return pipe 13 and the supply pipe 14. The opening and closing of the circulation cutoff valve 13a, sparge valve 14a, injection gas valve 17a, and purge gas valve 18a is generally controlled by a control means 30 such as a CPU (central processing unit) or a PLC (programmable logic controller).

When relatively heavy particles such as barium sulfate are used as the release agent used as the raw material for the release agent slurry, or when the solids concentration of the release agent slurry is high (i.e., when the ratio of the release agent to the dispersion medium such as water is high), the fluidity of the release agent slurry decreases and it is likely to remain in the piping. However, even in such cases, problems caused by the above-mentioned decrease in fluidity can be prevented by selecting a slurry pump with an appropriate pump head (water head) and capacity, and by appropriately setting the supply pressure of the purge gas.

As described above, in the method for spraying release agent slurry according to an embodiment of the present invention, the release agent slurry introduced from the storage tank 10 to the supply pipe 14 by the slurry pump 12 is sprayed from the nozzle 15 using the pressure of the purge gas rather than the discharge pressure of the slurry pump 12, making it possible to extremely accurately control the amount of release agent slurry sprayed in one cycle of spraying the release agent slurry on each mold C.

Furthermore, various release agents can be used with various solids concentrations. For example, a release agent that has the property of adhering to the inner wall of the pipe over time can be used, or a release agent slurry with a relatively high solids concentration can be used. Specifically, it becomes possible to significantly expand the range of solids concentration of the release agent slurry from the conventional range of about 30 to 60 g/L to about 20 to 160 g/L. Also, the range of spray amount of the release agent slurry can be significantly expanded from the conventional range of about 1500 to 2200 mL to about 500 to 3600 mL.

As described above, the use of release agent slurries with a wide range of solid content concentrations allows for greater freedom in the spraying method, and the spraying conditions of the release agent slurry can be optimized for various casting equipment, making it possible to reduce the operating costs required for casting and improve the quality of the anode. For example, instead of the two-fluid nozzle that sprays the release agent slurry together with the above-mentioned dispersion gas, it becomes possible to use a general nozzle that sprays only the release agent slurry without dispersion gas.

Furthermore, because the amount of release agent slurry sprayed can be precisely adjusted, the spraying conditions for these release agent slurries can be optimized according to various conditions during the casting of the anode, resulting in the production of high-quality anodes with almost no unevenness such as bulges. For example, in cases where the temperature of mold C is lower than usual and the water is unlikely to evaporate before pouring, it is possible to use a release agent slurry with a high solids concentration.

In addition, the pressure of compressed air (plant air) available in a general factory may fluctuate due to intermittent use by other equipment in the factory. Conventionally, this pressure fluctuation could change the amount of release agent slurry sprayed. In contrast, in the release agent slurry supply equipment shown in FIG. 1, for example, the measured value of a pressure gauge installed in the air header can be input to the control means 30 to control the opening and closing times of various automatic valves according to the pressure fluctuation of the compressed air, making it possible to keep the spray amount almost constant. This eliminates the need to deal with the fluctuations in the spray amount by spraying more than the amount required in the past, but this makes it possible to improve anode quality and reduce the amount of release agent consumed.

Although the method for spraying slurry according to the embodiment of the present invention has been described above, the present invention is not limited to the above embodiment, and various modifications and alternatives can be included within the scope of the present invention. For example, in the method for spraying slurry according to the above embodiment, when the spray valve 14a is open, the release agent slurry is not sprayed from the nozzle 15 and all of it temporarily stays in the supply pipe 14, and the release agent slurry is sprayed from the nozzle 15 by introducing a purge gas into the supply pipe 14 after the spray valve 14a is switched from open to closed. However, the present invention is not limited to this, and as shown in FIG. 4, the release agent slurry may be sprayed from the nozzle 15 by switching the spray valve 14a from closed to open, and the release agent slurry remaining in the supply pipe 14 may be discharged from the nozzle 15 by introducing a purge gas into the supply pipe 14 after the spray valve 14a is switched from open to closed.

(Example)
In a copper electrolytic anode casting apparatus that repeats a cycle of pouring molten blister copper into a plurality of molds provided at equal intervals in the circumferential direction on an intermittently rotating turntable, cooling and solidifying the molten blister copper, stripping the anodes solidified by cooling from the molds, and spraying a release agent slurry onto the molds after stripping, a release agent slurry supplying facility as shown in Fig. 1 was used to spray the release agent slurry. The solid content concentration of the release agent slurry was changed in various ways within a range of 20 to 160 g/L, and the quality of the stripped anodes was visually confirmed.

The slurry pump 12 was an air-driven diaphragm pump, the nozzle 15 was a two-fluid nozzle, and the driving air for the diaphragm pump, the dispersion gas introduced into the nozzle 15, and the purge gas introduced into the supply pipe 14 were all general-purpose air whose pressure in the air header was constantly kept at about 500 kPa or more. The circulation cutoff valve 13a, the spray valve 14a, the injection gas valve 17a, and the purge gas valve 18a were opened and closed based on the timing chart in FIG. 3. As a result, it was found that even if the solids concentration of the release agent slurry was changed within the range of 20 to 160 g/L, a high-quality anode without blistering on the surface could be molded by appropriately adjusting the opening time of the spray valve 14a and the injection gas valve 17a.

(Comparative Example)
The release agent slurry was filled into the suction cup only by the head pressure of the preparation tank of the release agent slurry, and then the release agent slurry was sprayed onto the mold of the casting device for the electrolytic anode similar to the above-mentioned embodiment by pressure-feeding it with air. As a result, the spray amount fluctuated due to the fluctuation of the water level in the release agent tank. In addition, since the spray amount was determined by the volume of the suction cup, it was impossible to increase the spray amount beyond the volume of the suction cup. Furthermore, since the release agent was pressure-fed by air, it was not possible to pressure-feed all of the release agent in the suction cup to the mold when the air pressure decreased, and the spray amount of the release agent varied.

REFERENCE SIGNS LIST 10 Storage tank 11 Withdrawal piping 12 Slurry pump 13 Return piping 13a Circulation shutoff valve 14 Supply piping 14a Spray valve 15 Nozzle 16 Air header 17 Injection gas supply piping 17a Injection gas valve 18 Purge gas supply piping 18a Purge gas valve 19 Drive air piping 20 Servo motor 21 Cylinder 22 Piston 23 Shaft portion 30 Control means C Mold P Branch point

Claims (4)

A method for spraying a release agent slurry, comprising the steps of: circulating the release agent slurry extracted from the bottom of a storage tank of the release agent slurry by an external circulation system which pressurizes the release agent slurry and returns the release agent slurry to the storage tank; and spraying the release agent slurry extracted into a supply pipe branching from the external circulation system onto a mold from a spraying means provided at the tip of the supply pipe, characterized in that the amount of the release agent slurry to be sprayed is adjusted depending on the time during which an automatic valve provided in the supply pipe is in an open state, and after the automatic valve is closed, a purge gas is introduced into the downstream side of the automatic valve to spray the release agent slurry in the supply pipe from the spraying means, and the release agent slurry is sprayed onto the mold by introducing the purge gas into the supply pipe . The method for spraying release agent slurry according to claim 1, characterized in that the external circulation is stopped while the automatic valve is open. 3. The method for spraying a release agent slurry according to claim 1 , wherein a spray flow rate of the release agent slurry is controlled by a pressure of the purge gas. 4. A method for casting an anode, comprising the steps of: spraying a release agent slurry onto the mold by the method for spraying a release agent slurry according to claim 1; pouring molten blister copper into the mold; cooling and solidifying the molten blister copper in the mold; and peeling off the anode molded by the solidification.

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