JP2000192128A - Furnace operation method - Google Patents

Abstract

(57) [Problem] To provide a furnace operation method capable of completely separating zinc and iron from electric furnace dust when separating and recovering the same. A method for operating a solid-reductant-packed-bed furnace having two-stage tuyeres in upper and lower stages and filling a carbon-based solid reducing agent, wherein the temperature in front of the upper-stage tuyere is 1500 ° C or higher; Furnace top temperature T (° C) and furnace top oxygen potential Po ₂
With (atm) as a region set under the following conditions, zinc, which is a highly volatile metal, is made into a vapor state, and at the same time, a very high-calorie fuel gas is extracted. Then, the zinc vapor in the exhaust gas is wet-cooled and recovered as a slurry. On the other hand, iron is a low-volatile metal and is melt-reduced in the furnace and accumulates in the hearth. T ≧ 730 (° C.) log (Po ₂ ) ≦ −48138 / (T + 273) +25.3
5

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a solid material for producing a highly volatile metal such as zinc as steam from dust of an electric furnace or a blast furnace, or for producing a fuel gas by burning waste plastic or shredder dust. The present invention relates to an operation method of a reducing material packed bed type smelting reduction furnace.

[0002]

2. Description of the Related Art In recent years, the amount of generated iron scrap containing zinc, such as surface-treated steel sheets for automobiles, has been increasing. In an electric furnace or the like using this iron scrap as a main raw material, dust containing zinc and iron as main components is generated. This dust is currently
Due to the high cost of collection, after collection, they are detoxified and then landfilled.

[0003]

However, the content of zinc contained in the electric furnace dust is 20 to 30%, and the same amount of iron is contained. These forms are oxides and hydroxides, but the amount of dust generated is as large as 15 kg per ton of steel making,
There is a need for a technology for recovering each of them in a completely separated state at low cost and without waste. At the same time, it is considered that a large amount of fuel gas is generated when these are recovered in the solid reducing agent packed bed type smelting reduction furnace, and it is desired to recover this fuel gas as much as possible in calories. Further, in such a solid reduction material packed bed type smelting reduction furnace, for example, it is supposed that a combustible material such as waste plastic or shredder dust is charged and burned. In such a case, so-called dioxin is used. I want to completely burn without generating.

The present invention has been developed to solve the above-mentioned problems, and comprises a highly volatile metal oxide or hydroxide such as zinc and a low volatile metal oxide or hydroxide such as iron. It is an object of the present invention to provide a method for operating a solid-reduction-material packed-bed smelting reduction furnace that can collect and combust combustibles without generating dioxin, while collecting and recovering high calorie fuel gas. Things.

[0005]

In order to solve the above-mentioned problems, a method for operating a furnace according to claim 1 of the present invention is a method for operating a solid reduction material packed bed type smelting reduction furnace, comprising: The temperature of the region is set to 1500 ° C. or higher, and the temperature T (° C.) of the entire furnace and the top of the furnace excluding the smelting reduction region and the oxygen potential Po ₂ (atm) of the furnace top are defined as the regions set under the following conditions. It is characterized in that either one of a highly volatile metal vapor and a fuel gas is produced.

T ≧ 730 (° C.) log (Po ₂ ) ≦ −48138 / (T + 273) +24.7
4. The present inventors have paid particular attention to the point of completely separating and recovering zinc and iron from electric furnace dust containing zinc, and have intensively studied to solve various problems that occur specifically. At this time, the most problematic reaction is a reaction in which zinc gas is combined with oxygen in carbon dioxide to form solid zinc oxide. If zinc before recovery becomes solid zinc oxide, it will adhere to exhaust gas ducts etc. and cannot be recovered, and if the adhesion becomes significant, the duct will be blocked,
Operation cannot be continued. The present inventors have found that the above-mentioned reaction is affected by the temperature inside or at the furnace top of the solid-reduction material packed bed type smelting reduction furnace and the oxygen potential of the atmosphere. That is, the reaction is promoted even when the furnace top temperature is low and the oxygen potential of the atmosphere is high. Here, the oxygen potential is an index indicating the degree of oxidizing property of the atmosphere. Since the atmosphere at the furnace top is almost exclusively carbon dioxide and carbon monoxide, the oxygen potential is specifically CO 2
+ ／ O ₂ = free energy change of reaction of CO ₂ ΔG ° = −67150 + 20.37 (T + 273) (ca
l) is defined by the following equation obtained from

Log (Po ₂ ) = 2 log (Pco ₂ / Pco) − 29386 / (T + 273) +8.914 (1) By defining the temperature and the oxygen potential in the furnace or at the top of the furnace as described above, , Zinc and other highly volatile metals can be maintained in a vapor state to facilitate subsequent recovery. Also, the high temperature gas at the furnace top with a small oxygen potential can be a high calorie fuel gas. In addition,
The reason why the temperature of the smelting reduction region is set to 1500 ° C. or higher is to secure a temperature for causing a smelting reduction reaction and to secure a temperature of a generated melt to realize a good tapping slag. Further, the temperature of the raw material supply portion is desirably 1700 ° C. or higher to promote melting of the raw material.

On the other hand, when powder material such as electric furnace dust is blown from the tuyere, the temperature in front of the tuyere is set so that the powder material is not blown off by the rising airflow in the furnace as described later. It must be at a temperature at which the input material melts immediately,
It was specified as 1500 ° C. or higher as described above. Also,
A method of operating a furnace according to a second aspect of the present invention is characterized in that, in the first aspect of the present invention, at least two upper and lower tuyeres are provided.

In the present invention, by blowing the raw material from the upper tuyere, the region where the raw material is melted and the region where the raw material is reduced can be separated, and a larger smelting region can be secured, so that the productivity is improved. be able to. The method for operating a furnace according to claim 3 of the present invention is the method according to claim 1 or 2.
In the invention of (1), when producing the fuel gas, the fuel gas has a gas calorie of 1500 kcal / Nm ³ or more.

The method of operating a furnace according to claim 4 of the present invention is the method according to any one of claims 1 to 3, wherein any one of a metal oxide, a metal hydroxide, a combustible material, and a mixture thereof is used. One or more are used as charging materials. The present invention specifies raw materials that can be charged according to the first to third aspects of the present invention, and specifically includes oxides, hydroxides, and the like of low volatile metals such as iron, chromium, and nickel.
And ores, dust and sludge containing them, and oxides and hydroxides of highly volatile metals such as zinc and lead, and ores, dust and sludge containing them and combustible materials such as plastic, paper and oil; and Waste plastics, shredder dusts and the like containing them are listed.

The method of operating a furnace according to a fifth aspect of the present invention is characterized in that, in the first to fourth aspects of the present invention, the powdery granular material is blown from a tuyere. According to the present invention, by blowing the powdery and granular charge that is easily blown off due to its light weight from the tuyere, the powdery and granular charge is exposed to the high temperature in front of the tuyere and immediately melts, burns, reduces, By evaporating, by defining the charging method, it is possible to prevent the ascending airflow in the furnace from blowing off to the furnace top.

Further, the method of operating a furnace according to a sixth aspect of the present invention is characterized in that, in the first to fifth aspects of the present invention, the bulk charge is charged from the furnace top. In the present invention, the bulk charging material which is heavy and is not easily blown away is not blown off by the rising airflow in the furnace even if it is loaded from the furnace top, so the charging method is specified.

[0013] A method of operating a furnace according to claim 7 of the present invention is characterized in that, in the invention of claim 6, the bulk charge is continuously charged from the furnace top. is there. When a large amount of the above-described bulk charge is charged from the furnace top, if a large amount is charged at once, the temperature of the furnace top decreases. According to the present invention, in order to satisfy the regulation of the furnace top temperature in the invention of the first aspect, it is specified that the bulk charge is continuously charged from the furnace top, so that the temperature of the furnace top is too low. That is not to be.

The method of operating a furnace according to claim 8 of the present invention is the method according to any of claims 1 to 7, wherein the tuyere blowing gas is any one of hot air, oxygen-enriched hot air, and pure oxygen. Or the use of It is well known that hot air or hot air enriched in oxygen is used as the tuyere blowing gas, but in this invention, the use of pure oxygen further increases the furnace temperature, especially when pure oxygen is blown from the lower tuyere. Therefore, the present invention focuses on the point that it is easy to satisfy the requirements of the first aspect of the present invention.

The method of operating a furnace according to claim 9 of the present invention is the method according to any one of claims 1 to 8, wherein when the highly volatile metal vapor is produced, the gas discharged from the furnace top is subjected to wet cooling. And recovering the highly volatile metal. According to the present invention, when the temperature and oxygen potential at the furnace top of the first aspect of the present invention are satisfied, highly volatile metals such as zinc remain completely in a vapor state. Rapidly solidifies conductive metals,
This is for recovering as a slurry.

A method of operating a furnace according to a tenth aspect of the present invention is characterized in that, in the first to eighth aspects of the present invention, the high-temperature gas discharged from the furnace top is rapidly cooled. This invention is different from the invention of claim 9 only in that the high-temperature gas discharged from the furnace top is quenched only. For example, when combustibles are burned at a high temperature, dioxin is hardly generated. When the combustion exhaust gas is gradually cooled, dioxin may be re-synthesized again. Therefore, it is an object of the present invention to rapidly cool a high-temperature gas at the top of the furnace to prevent the gas from being suppressed.

[0017]

Embodiments of the present invention will be described below. FIG. 1 shows a vertical furnace to which the furnace operating method of the present invention is applied. This vertical furnace 1 is filled with a solid reducing material 2 such as coke, and constitutes a solid reducing material packed bed type smelting reduction furnace as a whole. The vertical furnace 1 is provided with at least two upper and lower tuyeres. As the vertical furnace 1 provided with the tuyeres 3 and 4 in the upper and lower stages in this way, for example, a furnace developed for efficiently melting and reducing chromium ore can be applied. In other words, the upper tuyere 3
When sufficient heat is not obtained for smelting reduction alone, the calorie is supplemented from the tuyere 4 at the lower stage, and the smelting reduction is sufficiently performed during that time.

Hot air, oxygen-enriched air, or pure oxygen as necessary is blown into these tuyeres 3 and 4 through a hot air generator 6 from a blower 5. This is because oxygen is required to burn the solid reducing material 2 in the furnace and use the combustion heat for melting, burning, evaporating, reducing, etc. the raw material, and also heats the blown gas. In this case, the sensible heat of the blown gas can be used as a form of heat input into the furnace. Also, among these, as the proportion of oxygen in the hot air supplied to the lower tuyere 4 increases, the amount of heat up to the upper tuyere 3 increases as described above, and when it becomes pure oxygen, The furnace temperature can be significantly increased. In the present embodiment, the tuyere front temperature and the furnace top temperature must be set high as described later, and in view of these, the ratio of oxygen in the supplied hot air may be adjusted.

On the other hand, a raw material is blown into the upper tuyere 3 from a raw material blowing device 7. The raw material blown from the tuyere 3 at the upper stage is basically limited to a granular material, and melts, burns, reduces and evaporates immediately after blowing. Of this raw material,
Oxides and hydroxides of low-volatile metals such as molten iron are reduced in the process of dropping the packed bed of the solid reducing material, and accumulate in the hearth. The vapor of the highly volatile metal such as zinc that evaporates rises to the furnace top through the gap of the solid reducing material 2 and is discharged together with the furnace gas as described later.

Powdery and granular raw materials such as electric furnace dust are blown from the tuyere 3 in the upper stage in principle. This is because the raw material in powder form is light, so the low-volatile metal is sufficiently melted and blown off by the ascending airflow in the furnace before dropping in the packed bed of the solid reducing material 2 as described above, for example. This is for preventing and suppressing the discharge from the furnace top. On the other hand, since the massive raw material has a large weight, it does not blow off even if it receives a rising air current in the furnace. In addition, since this kind of bulk raw material does not need to be instantaneously melted in front of the tuyere as described above, the raw material is charged from the furnace top by the furnace top charging device 8 in principle. In addition, as described later, in the present embodiment, it is necessary to maintain the temperature of the furnace top at a high temperature, but if a large amount of bulk material is charged at once, the temperature of the furnace top may be too low. Therefore, the bulk material is charged continuously in principle, so that the temperature at the furnace top does not decrease. More specifically, it is preferable to charge continuously by a charging pipe system from the furnace top. Of course, even if a large amount of bulk material is charged at once, a sufficient amount of heat can be obtained and the furnace top temperature can be maintained high,
Doing so would increase the unit fuel consumption, so we want to avoid it. Also, when the bulk material is pulverized into powder and granules,
It should be blown from the tuyere 3 in the upper row.

In this embodiment, in order to keep the temperature of the furnace top high, the secondary combustion gas is supplied to the space of the furnace top and intentionally burned in the furnace top. The secondary combustion gas is also supplied to the inside of the duct for discharging the exhaust gas from the furnace top and burned in the duct. However, when the secondary combustion gas is burned, carbon dioxide is generated. In the present embodiment, the furnace top is included, and exhaust gas cooling and cooling is performed from the furnace top.
It is necessary to reduce the oxygen potential in the duct leading to the cleaning device in accordance with the temperature. For this purpose, it is necessary to measure the gas temperature and the composition and strictly control the supply amount of the secondary combustion gas.

The exhaust gas discharged from the furnace top in this way is sent into the exhaust gas cooling / cleaning device 9. The exhaust gas cooling / cleaning device 9 is specifically a wet cooling device, that is, a liquid is sprayed in the exhaust gas to lower the temperature of the exhaust gas, to cool and solidify a substance in a vapor state, and to drip together with the liquid. Precipitation is performed so that it can be separated and recovered as a slurry, and gas that does not liquefy or solidify is collected as a gas. In this embodiment,
As described later, a highly volatile metal such as zinc is solidified and separated and recovered from the exhaust gas, and the discharged exhaust gas is obtained as a high-calorie fuel gas containing a carbon monoxide gas. In addition, by rapidly cooling such high-temperature exhaust gas, re-synthesis of dioxin which is a harmful substance contained in the raw material can be prevented.

Next, in the solid reduction material packed bed type smelting reduction furnace described above, iron oxides and hydroxides, which are low volatile metals, and zinc oxides and hydroxides, which are high volatile metals, are mainly used. The following describes the conditions for using a powdered material such as electric furnace dust containing a material as a charging material, separating and recovering it into iron and zinc, and simultaneously extracting a high-calorie fuel gas. Here, an example of the composition of the raw material is shown in Table 1. As is clear from the table, it contains a considerable proportion of iron and zinc, and also contains calcium oxide, silica, alumina and the like.

[0024]

[Table 1]

Next, the operating conditions are shown in Table 2. here,
The oxygen-enriched hot air is blown from the tuyere together with the powdery and granular material.

[0026]

[Table 2]

As described above, the powdery and granular charge material is blown from the tuyeres (the upper tuyeres when there are at least two tuyeres). If the temperature in front of the tuyere is low, the iron component to be separated and collected by melting and dropping is not sufficiently melted,
It is blown off by the rising air current in the furnace, discharged from the furnace top, and taken out by the exhaust gas cooling / cleaning device. In other words, iron will be mixed into the slurry in the exhaust gas cooling / cleaning apparatus where only zinc is to be separated and recovered. It has been found that the temperature before the tuyere, especially the temperature before the tuyere for blowing the powdery and granular raw materials, greatly contributes to this. FIG. 2 shows the relationship between the temperature in front of the injection tuyere and the concentration of iron contained in the slurry in the exhaust gas cooling / cleaning device (in the figure, the concentration of iron in the solid content).

As is clear from the figure, the concentration of iron contained in the slurry was such that the temperature before the injection tuyere was 1500 ° C.
In the above region, the size becomes smaller. In other words, the tuyere temperature is 15
If the temperature is set to 00 ° C. or higher, the iron content in the powdery granular material is immediately melted and dropped in front of the tuyere, and therefore, it is considered that a small percentage of the iron is blown off by the rising airflow in the furnace.
Further, by setting the temperature before the blowing tuyere to 1700 ° C. or higher, the melting can be further promoted. Once melted in this way, the molten iron drops into the solid reducing material layer, is reduced during that time, and accumulates in the hearth. Therefore, if it is taken out, high-purity iron can be separated and recovered.

On the other hand, when gaseous zinc reacts with carbon dioxide, solid zinc oxide and carbon monoxide are produced. This reaction is a reversible reaction. As the temperature is lower or the oxygen potential is higher, solid zinc oxide is easily generated. When the temperature in the furnace and from the furnace top to the exhaust gas duct is low, or the oxygen potential is large, solid zinc oxide cannot reach the exhaust gas cooling / manufacturing device and adheres to the furnace wall or duct wall. If the amount becomes extremely large, the duct or the furnace may be closed, and the operation may not be continued.

The factors governing the reaction are temperature and oxygen potential. As the oxygen potential, the atmosphere is almost only carbon monoxide and carbon dioxide, the oxygen potential was defined by the above equation (1). When the relationship between the oxygen potential and the temperature of the furnace top is examined by substituting the reaction heat necessary for the reaction, a single curve (substantially a straight line) shown in FIG. 3 is obtained. In the region where the oxygen potential is lower or the temperature is higher than this, gaseous zinc is stable. That is, the zinc state of the gas can be maintained in the lower left region of the curve in the figure. This area is given by the following two equations.

Log (Po ₂ ) ≦ −48138 / (T + 273) +25.35 (2) where T: ambient temperature in the furnace or at the furnace top (° C.) Po ₂ : oxygen potential (atm) The temperature of the atmosphere at the furnace top was set to 730 ° C. or higher as a temperature condition under which zinc is stable as a gas. Further, it is desirable that the gas temperature T (° C.) and the oxygen potential Po ₂ (atm) at the furnace top before the secondary combustion are in the region surrounded by the following three equations. The reason for this is that the adhesion of zinc oxide is reduced even in the part near the charging surface at the furnace top, the adhesion of zinc oxide in the furnace is eliminated, and there is no need to perform secondary combustion. This is because, even in the case of performing combustion, excessively high-temperature combustion gas is not generated, and it is not necessary to excessively reduce the oxygen potential.

T ≧ 730 ° C. log (Po ₂ ) ≦ −29386 / (T + 273) +6.51 (3) When operating while satisfying these conditions, zinc oxide adheres from the furnace top to the exhaust gas duct. In addition, it is possible to separate and recover zinc and iron as described above, and at the same time, it is possible to collect high-calorie fuel gas. On the other hand, if the conditions were not satisfied, the zinc oxide adhering to the furnace wall clogged the furnace in about one to two weeks, and the operation could not be continued. In order to control these conditions, the amount of air blown from the tuyere, the amount of oxygen enriched, the coke ratio changed by adjusting the feed rate of the raw material, the execution of secondary combustion at the furnace top and duct, and the secondary combustion The main means was gas conditioning.

The present invention is not necessarily limited to a solid reducing agent packed bed type smelting reduction furnace having two upper and lower tuyeres, but can also be widely applied to one having one or one tuyeres. The specific configuration of the furnace in that case is as shown in FIG. Except for the number of tuyere stages, it is the same as the above embodiment.

[0034]

As described above, according to the furnace operating method of the first aspect of the present invention, the temperature of the smelting reduction zone of the solid reduction material packed bed type smelting reduction furnace is set to 1500 ° C. or more and the melting temperature is raised Temperature T of the entire furnace and the top of the furnace excluding the reduction zone
(° C.) and the oxygen potential Po ₂ (atm) at the furnace top (T
≧ 730 (° C.), log (Po ₂ ) ≦ −48138 / (T + 2
73) +25.35) As at least one of the highly volatile metal vapor and the fuel gas is produced as the region set by +25.35), the highly volatile metal such as zinc contained in the electric furnace dust and the like volatilizes. It becomes steam, rises to the furnace top, and low-volatile metals such as iron are melted and flow down to the hearth, so that both can be completely separated, and the highly volatile metals such as zinc are converted into a vapor state. While maintaining and facilitating subsequent recovery, high-temperature gas at the furnace top can be recovered as high-calorie fuel gas.

According to the furnace operating method of the present invention, the raw material is melted by blowing the raw material from the upper tuyere of the furnace having at least two upper and lower tuyeres. Since the region and the region to be reduced can be separated and a larger smelting region can be secured, productivity can be increased. Further, according to the method of operating the furnace according to claim 3 of the present invention, the gas calorie of the fuel gas to be produced is 1500 kcal / Nm ³ or more, so that a high calorie fuel gas containing carbon monoxide is used. Can be collected.

According to the method of operating a furnace according to claim 4 of the present invention, a metal oxide, a metal hydroxide, a combustible material,
And any one or more of these mixtures were used as the charging material, so that various charging materials were melted, reduced,
It can burn, evaporate, separate, recover, and produce high calorie fuel gas. According to the method of operating a furnace according to claim 5 of the present invention, the powdery and granular charge is blown from the tuyere. Melting, burning, reducing and evaporating immediately upon exposure to the high temperature of the furnace, and it can be prevented from being blown to the top of the furnace by the rising air current in the furnace.

According to the method of operating a furnace according to claim 6 of the present invention, the bulk charge is charged from the top of the furnace. It will not be blown off by the updrafts in the furnace. According to the method of operating a furnace according to claim 7 of the present invention, since the bulk charging material is continuously charged from the furnace top, it is possible to prevent the temperature of the furnace top from being excessively reduced and to prevent the furnace top from being excessively lowered. Thus, the regulation of the furnace top temperature in the first aspect of the invention can be satisfied.

According to the furnace operating method of the present invention, any one of hot air, oxygen-enriched hot air, and pure oxygen is used as the tuyere blowing gas. When pure oxygen is blown from the lower tuyere, the temperature in the furnace can be remarkably increased, thereby easily satisfying the requirement of the first aspect of the present invention. According to the method of operating a furnace according to claim 9 of the present invention, when producing a highly volatile metal vapor, the gas discharged from the furnace top is wet-cooled to recover the highly volatile metal. Therefore, the highly volatile metal such as zinc which is completely in a vapor state by the provision of the temperature and the oxygen potential at the furnace top according to the first aspect of the present invention is wet-cooled, whereby the highly volatile metal is rapidly solidified. , Can be recovered as a slurry.

According to the furnace operating method of the present invention, since the high-temperature gas discharged from the furnace top is quenched, recomposition of dioxin can be prevented.

[Brief description of the drawings]

FIG. 1 is a schematic configuration diagram of a furnace to which a method for operating a furnace according to the present invention is applied.

FIG. 2 is an explanatory diagram showing a relationship between a tuyere front temperature and a concentration of iron collected and contained in exhaust gas from a furnace top.

FIG. 3 is an explanatory diagram of a region controlled by a furnace top temperature and an oxygen potential.

FIG. 4 is a schematic configuration diagram showing another example of a furnace to which the method for operating a furnace according to the present invention is applied.

[Explanation of symbols]

 1 is a vertical furnace 2 is a solid reducing agent 3 is an upper tuyere 4 is a lower tuyere 5 is a blower 6 is a hot air generator 7 is a raw material injection device 8 is a furnace top charging device 9 is an exhaust gas cooling / cleaning device

 ──────────────────────────────────────────────────続 き Continued on the front page (72) Yoshiaki Hara 1st Kawasaki-cho, Chuo-ku, Chiba City, Chiba Prefecture Inside the Technical Research Institute of Kawasaki Steel Co., Ltd. 4K001 AA30 BA14 DA01 DA06 DA06 EA08 GA01 GB03 4K012 CB04

Claims (10)

[Claims] 1. A method for operating a solid-reduction-material packed-bed smelting reduction furnace, wherein the temperature of a smelting reduction zone in a furnace is set to 1500 ° C. or higher, and the temperature T ( C.) and an oxygen potential Po ₂ (atm) at the top of the furnace as a region set under the following conditions to produce at least one of a highly volatile metal vapor and a fuel gas. T ≧ 730 (° C.) log (Po ₂ ) ≦ −48138 / (T + 273) +25.3
5 2. The method for operating a furnace according to claim 1, wherein
A furnace operating method comprising at least two upper and lower tuyeres. 3. The method for operating a furnace according to claim 1, wherein when producing the fuel gas, the gas calorie of the fuel gas is 1500 kcal / Nm ³ or more. 4. The method for operating a furnace according to claim 1, wherein at least one of a metal oxide, a metal hydroxide, a combustible, and a mixture thereof is used as a raw material. A method of operating a furnace, characterized in that: 5. The furnace operating method according to claim 1, wherein the powdery and granular material is blown from a tuyere. 6. The furnace operating method according to claim 1, wherein the bulk charge is charged from the furnace top. 7. The method for operating a furnace according to claim 6, wherein
A method for operating a furnace, comprising continuously charging the bulk charging material from the furnace top. 8. The furnace operating method according to claim 1, wherein any of hot air, oxygen-enriched hot air and pure oxygen is used as the tuyere blowing gas. Operating method. 9. The method for operating a furnace according to claim 1, wherein when the highly volatile metal vapor is produced, the gas discharged from the furnace top is wet cooled to recover the highly volatile metal. A method of operating a furnace, characterized in that: 10. The furnace operating method according to claim 1, wherein the high-temperature gas discharged from the furnace top is rapidly cooled.