JP2023131572A - Operation method of electric oven - Google Patents

Abstract

To provide a method capable of stably dissolving a raw material through applying a stable electric power, in an operation of dissolving the raw material containing a lithium-ion battery waste using an electric oven.SOLUTION: An operation method of an electric oven having an electrode is for recovering a valuable metal from a raw material containing a lithium-ion battery waste. At a beginning of an operation, the electrode is dropped at a speed that allows the metal contained in the raw material charged into the electric oven to melt before making contact with the metal, and the raw material is processed by arc heating.SELECTED DRAWING: None

Description

The present invention relates to a method for operating an electric furnace for recovering metals containing valuable metals by reducing and melting raw materials containing at least waste lithium ion batteries.

For example, in an operation that uses an electric furnace equipped with three-phase AC electrodes to recover valuable metals from raw materials such as waste lithium-ion batteries, when starting the operation, after charging the raw materials into the electric furnace, By lowering an electrode such as a graphite electrode provided in the electric furnace and generating an arc between the raw material and the electrode, melting of the raw material is started by arc heating.

However, if the lowering of the electrodes at the start of operation is automatically controlled by keeping the current value constant, the resistance between the electrodes will vary greatly from time to time. If the resistance at this time becomes small, an overcurrent will occur, cutting off the electricity supply and stopping the current flow.

For this reason, there is a need for technology that can stably apply electric power and stably start melting of raw materials when starting operations.

Patent Document 1 describes that a DC voltage is applied between a main electrode and a bottom electrode inserted in a furnace, and plasma arc heat generated between the electrodes and Joule heat of a current flowing between the electrodes are used to generate A technology related to a waste plasma melting furnace for melting waste such as incineration ash, fly ash, and residue has been disclosed. Specifically, the voltage between the main electrode and the bottom electrode, the current flowing between the electrodes, the insertion position of the main electrode, the supply status of the material to be melted, the furnace wall temperature, the cooling water temperature, the exhaust gas concentration, the furnace At least two signals of internal temperature, furnace pressure, cooling water flow rate, exhaust gas flow rate from the furnace, and exhaust gas concentration are captured, and the melting operation state in the furnace is grasped by the combination of signal changes, and the furnace control device A furnace operation control method that performs predetermined operation control is disclosed.

However, Cited Document 1 does not disclose how to stably apply electric power and stably melt the raw material when melting the raw material including the waste lithium ion battery.

Japanese Patent Application Publication No. 2000-2411

The present invention was proposed in view of the above circumstances, and is designed to stably apply electric power and stably melt raw materials in an operation that uses an electric furnace to melt raw materials including waste lithium-ion batteries. The purpose is to provide a method that can be melted.

As a result of intensive studies by the present inventor, at the start of operation, the electrode installed in the electric furnace is lowered little by little at a speed that allows the metal contained in the charged raw material to melt before it comes into contact with the metal contained in the charged raw material. The inventors have discovered that the above-mentioned problems can be solved by performing arc heating, and have completed the present invention.

(1) A first aspect of the present invention is a method for operating an electric furnace equipped with an electrode for recovering valuable metals from raw materials including waste lithium ion batteries, wherein at the start of operation, the electrode is This is a method of operating an electric furnace, in which the raw material charged into the electric furnace is lowered at a speed that allows the metal contained in the raw material to be melted before it comes into contact with the metal, and the raw material is treated by arc heating.

(2) In the second invention of the present invention, in the first invention, the waste lithium ion battery is crushed and sieved, a foil-like material obtained as a sieve is prepared, and the foil-like material is used as an additional raw material. This is a method of operating an electric furnace, in which the electric furnace is further charged into the electric furnace.

(3) A third invention of the present invention is a method of operating an electric furnace according to the first or second invention, wherein the electric furnace is a three-phase AC electric furnace.

According to the present invention, it is possible to provide a method that can stably apply electric power and stably melt raw materials in an operation using an electric furnace to melt raw materials including waste lithium ion batteries. .

Hereinafter, a specific embodiment of the present invention (hereinafter referred to as "this embodiment") will be described. Note that the present invention is not limited to the following embodiments, and various changes can be made without departing from the gist of the present invention.

In the method according to the present embodiment, using an electric furnace equipped with electrodes such as a three-phase AC electric furnace, a reduction melting process is performed on a raw material containing at least a waste lithium ion battery, and the This is a method of operating an electric furnace to recover valuable metals.

In this operating method, raw materials including waste lithium ion batteries charged into an electric furnace are heated and reduced by applying voltage to the electrodes to melt them, and metals composed of valuable metals contained in the raw materials are removed. A mixed melt consisting of slag and impurity components is produced. Due to the difference in specific gravity, the resulting mixed melt separates slag with a lower specific gravity into an upper layer and metal with a higher specific gravity into a lower layer. The separated slag is then discharged and recovered by tilting the electric furnace or by tapping from the slag hole. Further, the metal containing valuable metals in the lower layer is discharged and recovered by tapping from a metal hole provided at the bottom of the electric furnace.

Here, the waste lithium ion battery contained in the raw material contains nickel (Ni) and cobalt (Co) as oxides. Therefore, by heating raw materials including waste lithium-ion batteries in an electric furnace and performing a reduction melting process, metals (alloys) composed of valuable metals such as nickel, cobalt, and copper (Cu) and impurities can be removed. It is possible to produce a molten body (melt) consisting of a slag constituted by the components.

The waste lithium-ion batteries contained in the raw material are pretreated before being charged into the electric furnace, at least through crushing treatment and sieving of the crushed product.After these treatments, the raw material becomes. Through such pretreatment, waste lithium ion batteries used as raw materials have a uniform shape to some extent, but compared to various concentrates that are used as raw materials in metal smelting, they contain many different shapes.

Therefore, when raw materials including waste lithium-ion batteries are charged into an electric furnace and electrodes such as graphite electrodes are lowered under automatic control with a constant current value to melt the raw materials, a sufficient amount of molten slag is formed. Therefore, when the electrode is submerged into the unmelted material, the timing at which the current flows and the timing at which the current does not flow intersect, resulting in extremely large current hunting, which exceeds the upper limit of the current. There is. This is thought to be due to the fact that the raw material contains irregularly shaped metal foil or the like.

Therefore, in the method according to the present embodiment, instead of lowering the electrode by controlling the current value to be constant, the electrode is lowered at the start of operation before it comes into contact with the metal contained in the raw material charged into the electric furnace. The metal is lowered at a speed that allows it to melt, and the raw material is treated by arc heating. Here, "lowering the electrode at a speed that allows the metal to melt before it comes into contact with the metal" means that the current value remains within the current value range allowed by the electric furnace. This refers to lowering the electrode.

That is, the electrode is lowered little by little while maintaining a minimum distance so that arc heating occurs continuously and stably on the metal part contained in the raw material. At this time, it is preferable that the lowering of the electrode be performed manually and gradually lowered while arc heating is being performed, rather than automatic control with a constant current value. This makes it possible to effectively suppress the hunting amplitude of the current value.

In the method according to the present embodiment, molten metal and molten slag are gradually formed from the raw material by performing arc heating on the raw material based on the lowering operation of the electrode, and the upper molten slag layer and the molten slag layer are separated. A molten layer consisting of a lower molten metal layer is formed. When the molten slag layer is formed, the molten slag layer is uniform and has a resistance value that allows Joule heating, so that it becomes possible to immerse an electrode in the molten slag layer. Therefore, it is possible to shift from the above-mentioned operation using arc heating to operation using Joule heating, which can automatically control the descent of the electrode with a constant current value.

Furthermore, in such an electric furnace, a solidified metal layer, which is the solidified metal layer that remained at the bottom of the furnace without being discharged during the previous operation, may adhere and form. In such a case, when the next operation starts, if the electrode is automatically lowered to a constant current value, when the electrode is lowered too far, current will flow through the solidified metal layer, effectively blocking the raw material. It may become impossible to apply power. In this respect as well, the method according to the present embodiment is preferable because electric power can be stably applied to the raw material from the start of operation.

Furthermore, in the method according to the present embodiment, a waste lithium ion battery is crushed and sieved, and a foil-like material obtained as a sieve is prepared, and then Preferably, the foil-like material is further charged into the electric furnace as an additional raw material.

The foil-like material obtained by crushing waste lithium-ion batteries has an irregular shape and contains metals such as copper (Cu) and carbon powder, but it also contains aluminum (Al), which has a relatively low melting point. It is. Therefore, when the electric furnace starts operating and the material begins to melt and the temperature around the electrode rises, if the foil-like material is charged as an additional material, a molten material containing aluminum will be easily formed. As this oxidizes to become alumina, a molten slag layer is stably and quickly formed, and the hunting amplitude of the current value can be suppressed more effectively.

Note that the copper contained in the foil-like material is also a metal with a relatively low melting point, and after becoming a molten material, it will constitute a molten metal layer without being oxidized.

Further, the electric furnace to be operated is not particularly limited, but for example, a three-phase AC electric furnace equipped with a graphite electrode can be exemplified. An example of a three-phase AC electric furnace is a submerged arc furnace. A submerged arc furnace has a plurality of electrodes buried (submerged) in the object to be heated, and utilizes Joule heat (electrical resistance heat) as well as heating by arc discharge.

Specifically, in a submerged arc furnace, arc discharge occurs between an electrode tip and an object to be heated, and the object to be heated (raw material) is heated by the arc. At the same time, a current flows between the electrodes (between the electrodes, the object to be heated, and the electrodes) via the object to be heated, and the object to be heated (slag) also generates heat due to Joule heat. In a submerged arc furnace, continuous heating of the slag is possible, and the metal located below the slag is heated by heat transfer from the slag. In this way, the submerged arc furnace has the advantage of being able to heat efficiently with less input power.

EXAMPLES Hereinafter, the present invention will be described in more detail by showing examples, but the present invention is not limited to the following examples.

[Example 1]
The raw materials containing waste lithium-ion batteries are pulverized, and then sieved to separate the powdered raw materials under the sieve (powder) and the foil-shaped raw materials on the sieve. (2) were prepared separately without mixing.

A submerged arc furnace, which is one of three-phase AC electric furnaces, was used as a melting furnace to perform reduction melting treatment on the raw materials.

Specifically, first, as a preheating operation, raw materials were charged into the electric furnace over a period of 3 hours at a charging rate of 30 kg in total (24 kg of powdered raw materials, 6 kg of foiled raw materials) per hour. (Total raw material charge: 90 kg) was subjected to reduction melting treatment. When charging raw materials, first, 6 kg of foil-shaped raw materials and 24 kg of powdered raw materials are charged out of a total of 30 kg of raw materials, and after charging 1 kg of carbon powder on top of this, electricity is started. did. After confirming the formation of a puddle, the rotary furnace lid was closed, and then the foil-shaped raw material and powdered raw material were charged through the charging port provided on the side of the electrode. This process was repeated over a period of 3 hours to carry out the reduction melting process.

At this time, when starting energization, the graphite electrode is gradually lowered at a speed that allows the metal contained in the raw material charged into the electric furnace to melt before it comes into contact with it, so that the raw material is heated by an arc. Processed. In this way, by lowering the graphite electrode little by little and performing arc heating, the applied current value does not exceed the current upper limit value, and hunting is within the range of approximately 20% to 80% of the current upper limit value. It was settled.

Next, 30 kg of raw materials including 6 kg of foil-like material were additionally charged from raw material charging chutes provided on the left and right sides of the electric furnace. As a result, the degree of hunting was within a range of approximately 30% to 60% of the upper limit of the current, and the degree of hunting was further reduced. Thereafter, 30 kg of raw material was additionally charged and melted.

Thereafter, it was confirmed that a molten slag layer had been formed, the graphite electrode was immersed in the slag layer, and the operation was shifted from arc heating to Joule heating. Then, after 21 hours of preheating operation in that state, steady operation was started.

[Comparative example 1]
Example 1 was carried out in the same manner as in Example 1, except that the graphite electrode provided in the electric furnace was lowered so that the raw material charged into the electric furnace was heated by Joule.

As a result, because the graphite electrode was lowered so that it came into contact with the metal contained in the raw material before it melted, a large current flowed when it came into contact with the metal, but the current value rapidly decreased when it was separated from the metal. As shown in the figure, the hunting amplitude of the current value was large, the current flowed at a current exceeding the upper limit value, and the electricity supply was cut off. As a result, we had no choice but to turn off the electricity.

Claims (3)

A method for operating an electric furnace equipped with electrodes for recovering valuable metals from raw materials including waste lithium ion batteries, the method comprising:
At the start of operation, the electrode is lowered at a speed that allows the metal contained in the raw material charged into the electric furnace to melt before it comes into contact with the raw material, and the raw material is treated by arc heating.
How to operate an electric furnace. Crushing and sieving the waste lithium ion battery, preparing a foil-like material obtained as a sieve,
further charging the foil-like material into the electric furnace as an additional raw material;
The method of operating an electric furnace according to claim 1. The electric furnace is a three-phase AC electric furnace,
The method of operating an electric furnace according to claim 1 or 2.