KR20200015021A - Apparatus and method of separating incompletely reduced oxide - Google Patents

Abstract

According to an embodiment of the present invention, an unreduced oxide separation device comprises: a reactor; a dispersion plate which is disposed on a lower portion inside the reactor, and in which a metal conversion body containing unreduced oxide is placed on an upper portion; an anode filtration membrane which is disposed on an upper portion of the dispersion plate inside the reactor, ionizes the metal conversion body when power is applied, enables an electrolyte in which the ionized metal conversion body is dissolved to pass therethrough, and has unreduced oxide attached to a lower surface thereof; a cathode filtration membrane which is disposed on an upper portion of the anode filtration membrane inside the reactor, reduces and electrodeposits the first metal of the ionized metal conversion body on a lower surface thereof when power is applied, and enables an electrolyte in which the second metal of the ionized metal conversion body is dissolved to pass therethrough; the electrolyte filled inside the reactor so that the dispersion plate, the anode filtration membrane and the cathode filtration membrane are immersed; and a power supply device with an anode of a power source connected to the anode filtration membrane and a cathode of the power source connected to the cathode filtration membrane. According to the present invention, process efficiency can be increased by reducing excess oxide.

Description

Unreduced oxide separation apparatus and method {APPARATUS AND METHOD OF SEPARATING INCOMPLETELY REDUCED OXIDE}

The present application relates to an unreduced oxide separation apparatus and method.

Pyroprocessing is the process of separating and recovering uranium and ultrauranium elements, which are effective components in spent nuclear fuel. This process is mainly composed of pretreatment, electrolytic reduction, electrolytic refining, electrolytic refining, and waste treatment, and the linkage between each unit process greatly affects the efficiency and economic efficiency of the entire process.

The electrolytic reduction process converts spent nuclear fuel in the form of an oxide into metal and supplies it to the subsequent electrolytic refining process. In this case, when the unreduced oxide is mixed in the supplied metal converter, it may act as an electrical resistance to the anode basket of the electrolytic refining process, and thus application of a desired current may not be possible. This limit of the applied current imposes a limit on the capacity increase of the electrolytic refining apparatus.

In addition, in the electrolytic refining process, as the anode dissolution of the metal converter in the anode basket occurs, the unreduced oxide particles flow out of the anode basket and accumulate on the bottom of the electrolytic refining apparatus. In the current electrolytic refining apparatus configuration, there is a problem in that it is difficult to recover a mixture (slurry form) of an oxide and an oxide and an electrolyte stacked on the bottom.

In addition, in the existing electrolytic reduction process and the electrolytic refining process, spent nuclear fuel is charged into a dedicated transport container corresponding to each process and transferred to a corresponding processing device to perform the process. The spent nuclear fuel, which has completed the pretreatment process, is charged to the transport container for the electrolytic reduction process and transferred to the electrolytic reduction apparatus. At this time, the electrolytic reduction process is performed in a state where the spent nuclear fuel is charged into the transport container for the electrolytic reduction process. In the electrolytic reduction process, the transport container for the electrolytic reduction process is used as the cathode. After the electrolytic reduction process is completed, the spent nuclear fuel is withdrawn from the transport container for the electrolytic reduction process. Then, it is charged to the transport container for the electrolytic refining process and transferred to the electrolytic refining apparatus. At this time, the electrolytic refining process is performed in a state where the spent nuclear fuel in which the electrolytic reduction process is completed is charged into a transport container for the electrolytic refining process. In the electrolytic refining process, the transport vessel for the electrolytic refining process is used as the positive electrode. Most of the electrolytic refining product is recovered from the negative electrode of the electrolytic refining apparatus, but the positive electrode residues remain in the transport vessel for the electrolytic refining process used as the positive electrode, and a separate recovery operation for this residue is required. In order to perform the electrolytic smelting process, which is a subsequent process of the electrolytic refining process, the electrolyte used in the electrolytic refining process is transferred to the electrolytic refining apparatus. In order to transfer the electrolyte from the electrolytic refining apparatus to the electrolytic refining apparatus, a separate electrolyte transfer apparatus is required. As described above, in each unit process constituting the conventional pyro processing, there is a problem in that it is difficult to link between three different electrolytic processes such as electrolytic reduction, electrolytic refining, and electrolytic refining. In addition, the complexity of the linkage between the unit processes adversely affects the efficiency and economics of the entire process.

Korea Patent No. 1733383 (“Recovery device and recovery method of residual electrolyte of metal converter”, registered date: April 28, 2017)

The present invention can increase the capacity and process efficiency by improving the applied current of the electrolytic refining process and at the same time, the unreduced oxide which can solve the problem of accumulation of unreduced oxides and mixtures of electrolytes at the bottom of the electrorefining apparatus. It is to provide a separation device and method.

In addition, the present invention is to provide an unreduced oxide separation device and method that can be built in one process system by connecting three different electrolytic processes such as electrolytic reduction, electrolytic refining, electrolytic refining, which are existing unit processes. .

According to one embodiment of the present invention, a reactor; A dispersion plate disposed at the bottom of the reactor and having a metal converter including an unreduced oxide thereon; An anode filtration membrane disposed above the dispersion plate in the reactor, and when power is applied, ionize the metal converter and pass the electrolyte in which the ionized metal converter is dissolved; The reactor is disposed above the anode filtration membrane, and when the power is applied, the first metal of the ionized metal converter is reduced and electrodeposited on the lower surface thereof, and the second metal of the ionized metal converter is dissolved. The electrolyte is passed through a cathode filtration membrane; The electrolyte filled in the reactor such that the dispersion plate, the anode filtration membrane, and the cathode filtration membrane are immersed; And a power supply device to which the anode of the power source is connected to the cathode filtration membrane, and the cathode of the power source is connected to the cathode filtration membrane.

According to another embodiment of the present invention, a dispersion plate, an anode filtration membrane, and a cathode filtration membrane are sequentially provided from the bottom to the top of the inside of the reactor, and through the plurality of through holes formed in the dispersion plate, the gas is directed upward in the reactor. A fluidization step of fluidizing the metal converter containing the unreduced oxide on the dispersion plate and the electrolyte by blowing into the dispersing plate; By supplying power to the anode filtration membrane and the cathode filtration membrane, the anode filtration membrane ionizes the metal converter and passes through an electrolyte in which the ionized metal converter is dissolved, and the unreduced oxide is attached to a lower surface thereof. A microoxide separation step of reducing and depositing a first metal of the ionized metal converter on the lower surface thereof and passing an electrolyte in which the second metal of the ionized metal converter is dissolved; When the reaction is completed, the gas is blown into the lower surface of the anode filtration membrane to remove the unreduced oxide attached to the lower surface of the anode filtration membrane, and then the removed unreduced oxide is recovered and supplied to the electrolytic reduction apparatus. The gas is blown into the lower surface to remove the first metal deposited on the lower surface of the cathode filtration membrane, and then the removed first metal is recovered and supplied to the electrolytic refining apparatus. There is provided a method for separating unreduced oxides, comprising recovering unreduced oxides, products, and electrolyte salts, which are then condensed in powder form and recovered and fed to an electrolytic smelter.

According to one embodiment of the present invention, by increasing the reduction current by increasing the applied current of the electrolytic refining process can be expected to increase the capacity by separating the non-reduced oxide in the electrolytic reduction process by supplying a metal conversion body with improved reduction rate to the subsequent electrolytic refining process have. In addition, it is possible to improve the process efficiency by reducing the excess oxide, there is an advantage that can solve the problem of the accumulation of the unreduced oxide and the mixture of the electrolyte on the bottom of the electrolytic refining apparatus.

In addition, the electrolyte in which the metal is dissolved is condensed in powder form, recovered, and supplied to the electrolytic smelting process, so that the electrolyte may be supplied in powder form to the electrolytic smelting apparatus without a separate electrolyte transfer device. Using the present invention, it is possible to overcome the complexity of the linkage between the existing electrolytic process, each of the electrolytic process apparatus is connected to one can be built as a process system having a continuity. In particular, the non-reduced oxide separation apparatus and method provided by the present invention can play the role of an electrolytic refining apparatus and an electrolytic refining process by itself, and thus, by using the present invention, a separate electrolytic refining process is omitted, and Electrolytic smelting process can be linked directly.

1 is a conceptual diagram of an unreduced oxide separation device according to an embodiment of the present invention.
2 is a view showing a dispersion plate according to an embodiment of the present invention.
3A to 3C are views for explaining the operation of the unreduced oxide separation device according to one embodiment of the present invention.
4 is a flowchart illustrating an unreduced oxide separation method according to an embodiment of the present invention.

Hereinafter, with reference to the accompanying drawings will be described embodiments of the present invention. However, embodiments of the present invention may be modified in various other forms, and the scope of the present invention is not limited to the embodiments described below. Shapes and sizes of the elements in the drawings may be exaggerated for clarity, elements denoted by the same reference numerals in the drawings are the same elements.

1 is a conceptual diagram of a non-reduced oxide separation device 100 according to an embodiment of the present invention.

As shown in FIG. 1, the unreduced oxide separation apparatus 100 according to an embodiment of the present invention includes a reactor 110 and a non-reduced oxide disposed at a lower portion of the reactor 110 and included at an upper portion thereof. The dispersing plate 111 on which the metal converting body is placed, and the upper part of the dispersing plate 111 inside the reactor 110, when power is applied, ionizes the metal converting body and passes the electrolyte in which the ionized metal converting body is dissolved. The first surface of the metal conversion body ionized on the lower surface of the anode filtration membrane 112 to which the unreduced oxide is attached, and the upper portion of the anode filtration membrane 112 inside the reactor 110, is applied to the lower surface thereof. The metal is reduced and electrodeposited, so that the cathode filtration membrane 113 and the dispersion plate 111, the anode filtration membrane 112, and the cathode filtration membrane 113 which pass the electrolyte in which the second metal is dissolved in the ionized metal converter are immersed. Filled inside the reactor Be may include (L) and a cathode membrane (112) power supply 115 is connected to the negative electrode of the power source and the anode of the power supply connection, a negative electrode membrane 113 in. Here, the first metal may be uranium (U), and the second metal may be ultra uranium including plutonium (Pu).

The reactor 110 described above has a cylindrical structure having a circular cross section, for example, and can accommodate the electrolyte L in a liquid state therein. The electrolyte L may include a LiCl-KCl molten salt. In addition, UCl ₃ may be additionally added to promote the reaction. It is to be noted that the structure of the reactor 110 described above is merely to aid the understanding of the invention, but is not limited thereto.

In addition, the reactor 110 may be made of a material having mechanical stability and corrosion resistance in the high temperature electrolyte (L). For example, the reactor 110 may be made of nickel-based superalloy such as Inconel, stainless steel, tantalum metal, or ceramic, but the material of the reactor 110 is not limited thereto.

The above-described positive electrode filtration membrane 112 and the negative electrode filtration membrane 113 may be disposed to be inclined inside the reactor 110 in a plate shape, and a plate having a plurality of through holes H as shown in FIG. 2 will be described later. It may be shaped. In particular, since the anode filtration membrane 112 is disposed to be inclined, the first metal may be easily recovered. When metal is used as the material of the anode filtration membrane 112, the filtration membrane itself may be dissolved, and a carbon material may be used to prevent this.

In addition, the size (diameter) of the plurality of through holes H formed in the anode filtration membrane 112 is determined in consideration of the size of the unreduced oxide, and should be small enough that the unreduced oxide cannot pass therethrough. On the other hand, the cathode filtration membrane 113 is determined in consideration of the diameter of the reduced metal (first metal), and should be small enough that the first metal cannot pass therethrough.

In addition, a condenser 116 may be further formed on the reactor 110 to condense the electrolyte in which the second metal is dissolved in the ionized metal converter in powder form. For example, the second metal may be ultra uranium including plutonium (Pu). The condensation unit 116 may correspond to a space located above the upper portion of the electrolyte L in the reactor 110. On the other hand, in order to improve the efficiency of the condensation unit 116 may be further provided with a cooling fin on the upper portion of the reactor (110).

In addition, a heater (not shown) may be provided outside the reactor 110 to maintain the electrolyte L inside the reactor 110 at a constant temperature. For example, the electrolyte L may be heated and maintained at a temperature of approximately 500 ° C. In the case where LiCl molten salt is to be used as the electrolyte L, the electrolyte L may be heated and maintained at a temperature of approximately 650 ° C. The type of molten salt used as the electrolyte (L) is not limited, and may include one kind of salt or two or more kinds of salt mixtures. The role of the molten salt may serve to promote or control the reaction as well as the role of the electrolyte. In this case, the electrolyte L inside the reactor 110 may be heated and maintained at a temperature above the melting point.

On the other hand, the above-described non-reduced oxide separation device 100 may include a cyclone 117 for separating the gas from the powder-type electrolyte condensed by the condensation unit 116.

Meanwhile, as illustrated in FIG. 2, the dispersion plate 111 may have a circular plate shape in which a plurality of through holes H are formed. 2 described above may be applied to the anode filtration membrane 112 and the cathode filtration membrane 113 in addition to the dispersion plate 111.

In addition, the reactor 110 is blown into the upper direction of the inside of the reactor 110, the high-pressure gas (G) formed through the plurality of through holes (H) formed in the lower portion of the distribution plate 111 formed in the dispersion plate 111. As a result, the metal converter including the unreduced oxide on the dispersion plate 111 and the carrier gas supply passage P3 and the valve V3 for fluidizing the electrolyte may be formed.

In addition, in the reactor 110 described above, a first gas inflow passage for removing unreduced oxide adhering to the lower surface of the anode filtration membrane 112 by blowing a high-pressure gas G into the lower surface of the anode filtration membrane 112. A non-reduced oxide recovery flow path P8 and a valve V8 for recovering the non-reduced oxide (Metal Oxide, MO) removed from the P6 and the anode filtration membrane 112 may be formed. The non-reduced oxide (MO) recovered through the above-described unreduced oxide recovery channel P8 may be supplied to the electrolytic reduction apparatus.

On the other hand, in the above-described reactor 110, the second gas inflow passage for removing the first metal electrodeposited on the lower surface of the cathode filtration membrane 113 by blowing a high-pressure gas (G) to the lower surface of the cathode filtration membrane 113. And a product recovery flow path P9 and a valve V9 formed at positions opposite to the valve V7 and the second gas inflow flow path P7 to recover the first metal removed from the cathode filtration membrane 113. Can be formed. The first metal may be uranium (U).

In addition, the above-described unreduced oxide separation device 100, the salt recovery passage (P10) and the valve (V10) for recovering the electrolyte in the form of condensed powder, and the electrolyte in the form of condensed powder into the reactor 110 It may further include a salt supply flow path (P5) and the valve (V5) for introducing again. The powdered electrolyte (powder salt) recovered through the salt recovery passage P10 may be supplied to the electrolytic smelting apparatus.

In addition, the non-reduced oxide separation device 100 according to an exemplary embodiment of the present invention may further include a cyclone 117 for separating the gas from the electrolyte in the form of powder condensed by the condensation unit, separated The gas G may be discharged to the outside. The cyclone 117 described above may be connected to one side of the reactor 110 through a flow path P4 and a valve V11.

Meanwhile, reference numeral P1, which is not described in FIG. 1, is a reactant supply flow path for supplying a reactant, that is, a metal converter containing an unreduced oxide, into the reactor 110, and reference numeral P2, which is not described, denotes a gas G of a high pressure. A flow path for blowing into the reactor 110, and V2 is a valve. Unexplained reference numeral P12 and the valve V12 blow the high pressure gas G in the lower direction inside the reactor 110 from the top to deposit the source oxide or cathode filtration membrane 113 attached to the lower surface of the anode filtration membrane 112. A flow path for removing the first metal attached to the lower surface of the). In addition, by using the carrier gas supply flow path P3 and the valve V3, the carrier gas supply flow path P12, and the valve V12, the high pressure gas G is simultaneously simultaneously carried out in the upper direction and the lower direction of the reactor 110, respectively. Blowing may control the residence time of the materials present in the reactor 110. Meanwhile, the first region Z1 is a region between the dispersion plate 111 and the anode filtration membrane 112 within the reactor 110, and the second region Z2 is a portion of the anode filtration membrane 112 within the reactor 110. The region between the cathode filtration membrane 113 and the third region Z3 refers to an electrolyte region above the cathode filtration membrane 113 in the reactor 110.

In the present invention, the high pressure gas (G) to the carrier gas may be used argon gas in consideration of reactivity.

As described above, according to one embodiment of the present invention, by separating the oxides that are not reduced in the electrolytic reduction step, and supplying a metal conversion body having an improved reduction rate to an electrolytic refining step, which is a subsequent step, Capacity increase can be expected. In addition, it is possible to improve the process efficiency by reducing the excess oxide, there is an advantage that can solve the problem of the accumulation of the unreduced oxide and the mixture of the electrolyte on the bottom of the electrolytic refining apparatus.

3A to 3C are views for explaining the operation of the unreduced oxide separation device according to one embodiment of the present invention, and FIG. 4 is a flowchart illustrating a method for separating unreduced oxide according to an embodiment of the present invention. to be.

Hereinafter, an unreduced oxide separation method method according to an embodiment of the present invention will be described with reference to FIGS. 3A to 4. However, for simplicity of the invention, descriptions duplicated with those described in FIGS. 1 to 2 will be omitted.

First, the fluidization step is started (S401). The fluidization step, as shown in Figure 3a, by blowing the high-pressure gas (G) in the upper direction inside the reactor 110 through a plurality of through holes (see H in Figure 2) formed in the distribution plate 111 It may be a process of fluidizing the electrolyte and the metal converter containing the unreduced oxide on the dispersion plate 111.

Next, the unreduced oxide separation step is started (S402). The non-reducing oxide separation step, as shown in Figure 3b, by supplying power to the anode filtration membrane 112 and the cathode filtration membrane 113 in the power supply 115 to ionize the metal converter in the anode filtration membrane 112 and The ionized metal converter passes through the dissolved electrolyte, and an unreduced oxide is attached to the lower surface thereof. In the cathode filtration membrane 113, the first metal of the ionized metal converter is reduced and electrodeposited on the lower surface thereof. The electrolyte in which the second metal is dissolved in the body may be a process of passing through.

Finally, an unreduced oxide, product and electrolyte salt (powder salt) recovery step is started (S403). As shown in FIG. 3C, when the reaction is completed, the recovery step removes the unreduced oxide adhering to the lower surface of the anode filtration membrane 112 by blowing a high-pressure gas G to the lower surface of the anode filtration membrane 112. Thereafter, the removed unreduced oxide is recovered and supplied to the electrolytic reduction apparatus, and the first metal deposited on the lower surface of the cathode filtration membrane 113 is removed by blowing a high-pressure gas G into the lower surface of the cathode filtration membrane 113. The removed first metal may be recovered and supplied to the electrolytic refining apparatus, and the electrolyte in which the second metal is dissolved in the ionized metal converter may be condensed in a powder form and then recovered and supplied to the electrolytic refining apparatus.

As described above, according to one embodiment of the present invention, by separating the oxides that are not reduced in the electrolytic reduction step, and supplying a metal conversion body having an improved reduction rate to an electrolytic refining step, which is a subsequent step, Capacity increase can be expected. In addition, it is possible to improve the process efficiency by reducing the excess oxide, there is an advantage that can solve the problem of the accumulation of the unreduced oxide and the mixture of the electrolyte on the bottom of the electrolytic refining apparatus.

In addition, the electrolyte in which the metal is dissolved is condensed in powder form, recovered, and supplied to the electrolytic smelting process, so that the electrolyte may be supplied in powder form to the electrolytic smelting apparatus without a separate electrolyte transfer device. Using the present invention, it is possible to overcome the complexity of the linkage between the existing electrolytic process, each of the electrolytic process apparatus is connected to one can be built as a process system having a continuity. In addition, since the unreduced oxide separation apparatus and method provided by the present invention can serve as an electrolytic refining apparatus and an electrolytic refining process, by using the present invention, a separate electrolytic refining process is omitted, and Electrolytic smelting process can be linked directly.

The present invention is not limited by the above-described embodiment and the accompanying drawings. It is intended that the scope of the claims be defined by the appended claims, and that various forms of substitution, modification, and alteration can be made without departing from the spirit of the invention as set forth in the claims. Will be self explanatory.

100: unreduced oxide separation device
110: reactor
111: dispersion plate
112: anode filtration membrane
113: cathode filtration membrane
115: power supply
116: condensation
117: cyclone
P1 to P12: flow path
V1 to V12: valve
G: high pressure gas
H: through hole
MO: unreduced oxide
Z1 to Z3: region inside the reactor
L: electrolyte

Claims (11)

Reactor;
A dispersion plate disposed at the bottom of the reactor and having a metal converter including an unreduced oxide thereon;
An anode filtration membrane disposed above the dispersion plate in the reactor, and when power is applied, ionize the metal converter and pass the electrolyte in which the ionized metal converter is dissolved;
The reactor is disposed above the anode filtration membrane in the reactor, and when the power is applied, the first metal of the ionized metal converter is reduced and electrodeposited on the lower surface thereof, and the second metal of the ionized metal converter is dissolved. The electrolyte is passed through a cathode filtration membrane;
The electrolyte filled in the reactor such that the dispersion plate, the anode filtration membrane, and the cathode filtration membrane are immersed; And
A power supply device to which the anode of the power source is connected to the anode filtration membrane and the cathode of the power source is connected to the cathode filtration membrane;
Non-reducing oxide separation device comprising a.
The method of claim 1,
The dispersion plate is formed with a plurality of through holes,
In the reactor,
Fluidized the metal converter containing the unreduced oxide and the electrolyte on the dispersion plate by blowing a gas upwardly in the reactor through a plurality of through holes formed in the dispersion plate to form a lower portion of the dispersion plate. A carrier gas supply flow path to be used;
A further reduced, non-reduced oxide separation device.
The method of claim 1,
The anode filtration membrane and the cathode filtration membrane,
Unreduced oxide separation device having a plate shape, disposed inclined inside the reactor.
The method of claim 3,
In the reactor,
A first gas inflow passage for removing unreduced oxide adhering to the lower surface of the anode filtration membrane by blowing gas into the lower surface of the anode filtration membrane; And
An unreduced oxide recovery flow path for recovering the unreduced oxide removed from the anode filtration membrane;
A further reduced, non-reduced oxide separation device.
The method of claim 4, wherein
The unreduced oxide separation apparatus recovered through the unreduced oxide recovery unit is supplied to an electrolytic reduction apparatus.
The method of claim 3,
In the reactor,
A second gas inflow passage for removing the first metal electrodeposited on the lower surface of the cathode filtration membrane by blowing gas into the lower surface of the cathode filtration membrane; And
A product recovery flow path for recovering the first metal formed at an opposite position of the second gas inflow flow path and removed from the cathode filtration membrane;
A further reduced, non-reduced oxide separation device.
The method of claim 1,
At the top of the reactor,
A condenser for condensing the electrolyte in which the second metal is dissolved in the ionized metal converter in powder form;
A further reduced, non-reduced oxide separation device.
The method of claim 7, wherein
The non-reduced oxide separation device,
A cyclone for separating gas from an electrolyte in powder form condensed by the condenser;
Further comprising, a non-reduced oxide separation device.
The method of claim 8,
The non-reduced oxide separation device,
A salt recovery passage for recovering the condensed electrolyte in powder form and supplying it to an electrolytic smelting apparatus; And
A salt supply flow path for introducing the condensed electrolyte in the form of powder back into the reactor;
Further comprising, a non-reduced oxide separation device.
The method of claim 1,
The first metal is uranium,
And the second metal is superuranium.
A dispersion plate, an anode filtration membrane, and a cathode filtration membrane are sequentially provided from the bottom to the inside of the reactor, and the gas placed on the dispersion plate by blowing gas upward in the reactor through a plurality of through holes formed in the dispersion plate. A fluidization step of fluidizing the metal converter and the electrolyte containing the reducing oxide;
By supplying power to the anode filtration membrane and the cathode filtration membrane, the anode filtration membrane ionizes the metal converter and passes through an electrolyte in which the ionized metal converter is dissolved, and the unreduced oxide is attached to a lower surface thereof. A microoxide separation step of reducing and electrodepositing a first metal of the ionized metal converter on a lower surface thereof and passing an electrolyte in which the second metal of the ionized metal converter is dissolved; And
When the reaction is completed, the gas is blown into the lower surface of the anode filtration membrane to remove the unreduced oxide adhering to the lower surface of the anode filtration membrane, and the removed unreduced oxide is recovered and supplied to the electrolytic reduction apparatus, and the lower portion of the cathode filtration membrane The gas is blown into the surface to remove the first metal electrodeposited on the lower surface of the cathode filtration membrane, and then the removed first metal is recovered and supplied to the electrolytic refining apparatus. The electrolyte in which the second metal is dissolved in the ionized metal converter is powdered. And recovering the unreduced oxide, product and electrolyte salt, which are condensed into a form and then recovered and supplied to the electrolytic smelter.

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