JP3513832B2 - Operating method of movable hearth furnace and movable hearth furnace - Google Patents

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a moving hearth furnace operating method and apparatus suitable for producing reduced iron from iron ore, iron-making dust, and sludges and also for recovering valuable metals. is there.

[0002]

2. Description of the Related Art Blast furnaces are roughly classified into crude steel production systems.
The converter method and the electric furnace method are known. Of these, the electric furnace uses scrap or reduced iron as an iron raw material, heats and melts them with electric energy, and in some cases, refines them into steel. At present, scrap is the main raw material,
In recent years, the use of reduced iron is increasing due to the tight supply and demand of scrap and the trend of manufacturing high-grade products by the electric furnace method.

As one of the processes for producing reduced iron, for example, in Japanese Patent Laid-Open No. 63-108188, a layer consisting of iron ore and a solid reducing material is stacked on a horizontally rotating hearth and radiated from above. A method for producing reduced iron by heating and reducing iron ore by heat transfer is disclosed. This method has the advantages that the construction cost of the equipment is relatively low and the operation troubles are relatively few. In many cases, the horizontally moving hearth takes the form of a rotary hearth as shown in FIG. 1 and FIG. 2 showing its AA cross section.

[0004] On the rotary hearth 1, a layer t made of iron ore and solid reducing material carried in through a charging port a is stacked. The hearth 1 is covered with a furnace body 2 covered with a refractory material. A burner 3 as a heat source is installed in the upper part of the inside of the moving bed furnace 1 to reduce the iron ore. The temperature inside the furnace is usually around 1300 ° C, and after the reduction treatment is completed, a cooler is installed on the rotary hearth to prevent oxidation after discharging it from the furnace and to improve the ease of handling. After the reduced iron is cooled, it is discharged and collected from the discharge port b.

In such a conventional manufacturing method, gangue and ash contained in the raw ore and carbonaceous material remain in the reduced iron as a product as they are, and the electric furnace (melting furnace) in the next step is used.
However, when the gangue and ash contained in the raw ore or coal enter the electric furnace, the following problems occur.

(1) In order to reduce the sulfur contained in the hot metal, it is necessary to increase the CaO / SiO ₂ ratio in the generated slag, but with the increase of SiO ₂ derived from gangue and ash, a large amount of CaO is produced. The source must be supplied in the form of limestone, dolomite.

(2) Addition of a large amount of CaO and dolomite requires compensation for decomposition heat and sensible heat, which inevitably raises the electric power consumption of the electric furnace, and minimizes the amount of slag entering the electric furnace. In order to keep the above, it is necessary to use beneficiated ultrafine ore and low ash coal with low gangue content.

As described above, in the production of steel through an electric furnace, high-quality ore and coal suitable for a moving bed furnace are required, but the cost tends to increase, and the resource reserves also increase. The current situation is that the production capacity has reached the limit, and as a result, there is a growing need to supply iron sources suitable for electric furnaces based on large amounts of ordinary Australian ore and ordinary coal. There is.

It is easily conceivable that the reduced iron containing gangue and ash can be maintained in a high temperature state and brought into a molten state to remove the slag, but in the conventional method, it can be realized by the following restrictions. Absent.

(1) A slag metal can be separated by maintaining a high temperature until the metal and slag are completely melted in a bath-type melting furnace such as a smelting reduction furnace. It's difficult. Operating conditions such as minimum temperature and holding time for separating slag metal in a radiant heating furnace such as a moving hearth furnace, and the melting behavior that determines it have not been clarified.

(2) In order to raise the temperature of the radiant furnace, it is necessary to generate a high temperature combustion flame. In order to raise the temperature of the combustion flame, it is required to preheat the combustion air and burn it in the vicinity of the theoretical air ratio. On the other hand, in order to prevent reoxidation of reduced reduced iron, it is necessary to maintain a very strong reducing gas atmosphere, but it is difficult to obtain a high temperature combustion flame under this gas condition.

(3) When melted in a moving bed furnace, a thin molten iron layer and a slag layer are separated and exist on the moving bed.
Erosion of the hearth of the moving bed furnace due to molten slag containing O and sticking of the slag to the hearth pose problems.

In this regard, US Pat. No. 3,442,931
In the specification, the maximum temperature of the moving bed furnace is 1260 to 1
A technique is disclosed in which a semi-molten state is obtained by adjusting to an atmosphere containing a combustible gas of 426 ° C. and 10% or more. However, although shrinkage and oxidation resistance can be secured by this, separation of gangue is difficult. there were.

The present invention is an ore rich ore of the Australian system,
We are proposing an operation method and a mobile hearth furnace that can efficiently obtain a reduction product and can effectively recover valuable metals even when using ordinary coal.

[0015]

The present invention solves the problems of the prior art by the following method. That is, according to the present invention, a layer composed of a mixture of an oxide such as powdered iron ore and a solid reducing agent in powder form is loaded on a horizontally moving hearth, and the oxide is reduced by radiative heat transfer from the upper part of the hearth. In the moving hearth furnace, the product obtained by the reduction treatment is melted at 1450 ° C. or higher until reaching the discharge port, and the slag component in the reduced product is aggregated and separated. In the present invention, the oxygen partial pressure of the gas phase in contact with the reduction product is adjusted to a reducing atmosphere, and a layer different from the layer of the mixture is stacked below the layer of the mixture. You can As the oxide, those containing iron oxide containing highly volatile impurities in a high temperature reducing atmosphere, or those containing valuable metals such as chromium and nickel are advantageously suitable.

Further, according to the present invention, there is provided a hearth for placing and moving a layer made of a mixture of an oxide such as powdered ore and a powdery solid reducing agent, and preheating and reducing the layer during the movement, and this hearth. Is a moving hearth furnace consisting of a furnace body surrounding the above and having a burner in the upper part of the inside thereof, the hearth furnace forming a product in a region leading to a discharge port for discharging the product after the reduction treatment. It is a moving hearth furnace characterized by having a melting zone for melting a substance to aggregate and separate a slag component existing therein.

[0017]

BEST MODE FOR CARRYING OUT THE INVENTION When a mixture of an oxide such as powdery iron ore and a powdery solid reducing agent is externally heated, the formula (1)
The reaction of formula (2) proceeds continuously and the reduction reaction proceeds.

CO + FeO → Fe + CO ₂ (near oxide particles) ---- (1) CO ₂ + C → 2CO (carbonaceous material surface) ---- (2)

The reduction reaction of the above formula (1) is generally 600
Although the reaction proceeds at a temperature of not less than 0 ° C, the reaction of the formula (2) does not proceed unless the temperature is higher than that of the reaction of the formula (1). Further, in order for the reaction to proceed continuously, CO
_It is necessary that the diffusion of 2 into the carbonaceous material particles and the diffusion of the generated CO of the equation (2) into the oxide particles occur smoothly.

In the case of ordinary iron ore and powdery solid reducing agent, it is possible to proceed by maintaining the temperature in the furnace at 1100 to 1300 ° C.

The reduction reaction according to the equations (1) and (2) basically proceeds by the reaction between solid iron oxide and gas, and the produced reduced iron becomes porous solid metallic iron. Solid reducing material and ash and gangue contained in iron ore powder are also solid at this temperature and are finely mixed in the reduced iron, making it difficult to separate them by physical means such as crushing and sieving. Is.

According to the present invention, the product subjected to the reduction treatment is melted on the moving hearth to agglomerate slag and metal,
It promotes separation, removes slag by crushing and magnetically separating after cooling, and this makes it relatively efficient even in operations using ore or normal coal rich in gangue. Reduction products can be obtained.

FIG. 3 is a small electric furnace having the structure shown in FIG. 4 using ores and coal having the compositions shown in Table 1 in order to examine the conditions necessary for the aggregation and removal of slag and metal components. It shows the results of experiments conducted with (sample cross-sectional area of 50 × 50 mm).

Here, in this experiment, when the heating time was set to 6 minutes, a layer made of only carbonaceous material was not provided in the lower part of the mixture, and the surface gas atmosphere was made to be near the theoretical air ratio, only carbonaceous material was made in the lower part of the mixture. 3 layers are provided and the surface gas atmosphere is close to the theoretical air ratio, and a layer of carbonaceous material is provided below the mixture and the surface gas atmosphere is a reducing atmosphere. The amount of carbonaceous material was set so that there was a sufficient margin in consideration of reduction and subsequent carburization reaction.
The surface gas atmosphere is the ratio of the sum of the concentrations of all reactive gases to the reducing components in the gas, reducing gas concentration = (CO + H ₂ ) /
Defined as (CO + H ₂ + H ₂ O + CO ₂ ) × 100 (%), the composition near the theoretical air ratio is about 3% of reducing gas concentration, and the reducing atmosphere is about 90% of reducing gas concentration. I decided.

An electric heater h was provided on the upper surface of the electric furnace used in the experiment, and the radiant heat thereof heated the mixture t of the carbonaceous material and the powdery ore provided on the bed s. In order to adjust the gas atmosphere on the surface of the sample, a nozzle n is provided at a position 10 mm above the surface of the sample, an atmosphere adjusting gas is blown from here, and exhausted from n ₁ . The temperature of the furnace was adjusted based on the furnace temperature measured by the thermometer i.

The reduced iron and slag produced were -10 m.
The slag removal temperature was evaluated based on the concentration of slag mixed in the obtained metallic iron after pulverization and magnetic separation.

[0027]

[Table 1]

As shown in FIG. 3 above, the mixed slag concentration can be arranged as a function of temperature regardless of the experimental conditions, and the mixed slag concentration sharply decreases at the furnace atmosphere temperature of 1450 ° C., metal, It became clear that the separation of slag proceeded.

In order to investigate the cause of such rapid separation of metal and slag, microscopic observation of a sample at 1400 ° C. revealed the following characteristics. (1) Carburization of metal is progressing. As a result of carburization, the melting point is lowered, and since it is molten, the initial ore particle shape is not maintained. Moreover, since the surface tension of the metal is very large, many particles were spherical particles.

(2) The carbonaceous material is scattered on the observation surface, but no appearance of hindering the aggregation of the metal is observed. (3) A part of the slag component derived from carbonaceous material was melted, but an unmelted part was also present. (4) Agglomeration between molten metal particles is hindered by
It is a flow of slag derived from highly viscous carbonaceous material that is partially melted. At 1500 ° C., which was observed as a comparison target, not only the metal but also the slag was melted, moved, and agglomerated.

From the above results, if the metal is only melted, if the melting point of carburized iron is raised to 100 ° C. higher than 100 ° C., the separation of the slag should start, but the melting movement of the slag is a constraint condition. The heating furnace atmosphere temperature to 1450 ° C.
It became clear that the above needs to be maintained. 14
50 ° C means Al ₂ O ₃ -S which is the main component of coal ash.
It is the temperature at which the iO ₂ -CaO slag melts, the viscosity decreases, and it becomes possible to aggregate and move.

FIG. 5 shows the structure of a moving bed furnace according to the present invention capable of separating slag and metal devised based on the above basic experiment. In the drawing, 4 is a hearth, 5 is a furnace body, and 6 is a furnace body. Is a layer of carbonaceous material loaded on the hearth 4, 7 is a layer of mixture loaded on the layer 6 of carbonaceous material, 8 is a hearth 5
Is a combustion burner disposed on the upper part of the heating device, and 9 is a heating device for melting the product obtained by the reduction. The heating device 9 uses the burner 9a and the exhaust gas g ₁ for combustion air g ₂
Is composed of a heat exchanger 9b for raising the temperature.

In the moving type hearth furnace having the above-mentioned structure, the raw material charging port is not shown, but the region from the charging port to L ₁ is the preheating zone, the subsequent L ₂ region is the reducing zone, and The region L ₃ is the melting zone, and the region L ₄ is the cooling zone.

The reduction zone L ₂ is heated by burning a combustion burner using a reducing gas generated from a layer of a mixture of powdery ore and carbonaceous material as a main heat source. The layer of the mixture having a reduction rate of 80% or more in the reduction zone L ₂ is heated at 1450 ° C. or more in the melting zone L ₃ , and the slag is removed from the produced reduced iron layer. Then, after being cooled and recovered in the cooling zone L ₄ , it is crushed by the recovery device 10 and discharged from the discharge port b. In the present invention, since the melting zone L ₃ having a high temperature of 1450 ° C. or higher is formed, the heating method of the melting zone L ₃ is different from other zones. The exhaust gas in the melting zone L ₃ is heat-exchanged with the combustion air through the high temperature heat exchanger 9b.

By burning the air preheated to about 900 ° C. and the fuel supplied separately at a substantially theoretical air ratio,
A high-temperature melting zone L ₃ of 1450 ° C. or higher can be formed. Further, since the gas atmosphere of the melting zone L _{3 and} the gas atmosphere of the surface of the reduced iron are controlled independently, the cooling zone L 3
_The gas supply nozzle 11 is provided between the boundary ₄ and the melting zone L _3.
Is preferably provided to supply the atmosphere adjusting gas.

By using the moving bed furnace configured as described above, it is possible to produce a reduced iron from which a mixed layer of powdery ore and carbonaceous material has been reduced and slag has been removed. A mixed layer of powdered ore and carbonaceous material is the cheapest to use a layer in which both are simply mixed in terms of production cost, but the layers that have undergone granulation and other processing in advance are stacked, reduced and melted. You may do it.

In addition to the case of using iron ore as the powdery ore,
According to the present invention, iron-making dust and sludge generated in an electric furnace, a blast furnace, or a stainless smelting furnace can be used, and there are advantages that industrial waste can be reduced from the iron mill and valuable metals can be recovered.

Iron-making dust generated in an electric furnace or a blast furnace contains volatile metals such as Zn and Pb. When recycled to the blast furnace, the volatile Zn circulates in the blast furnace to reach the blast furnace wall. It is treated as ordinary industrial waste because it causes deposits and destabilizes operations. Although a process has been developed in which iron dust is reduced by using a rotary kiln at a low temperature to recycle iron, the amount of Zn removed is still insufficient and the amount recycled to the blast furnace was limited.

In the present invention, it is possible to recover such valuable metals, and when dust or sludge containing volatile metals such as Zn and Pb is charged in the moving hearth furnace, the following will occur. A reaction occurs.

(1) Reduction zone Iron oxide: Fe ₂ O ₃ + 3C = 2Fe + 3CO Zn oxide: Zn + C = Zn (g) + CO Pb oxide: PbO + C = Pb (g) + CO At the same time when the reduction of iron oxide proceeds. ZnO and Pb are reduced as described above and removed from the layer as metal vapor. After that, it is exposed to a high temperature oxidizing atmosphere and finally ZnO, P
It is recovered as a bO powder in a dust collection system. Z in the reduction zone
Although the removal rate of n and Pb reaches 90%, a part of them is present as non-reducing ZnFe ₂ O ₄ .

(2) Melting zone Iron oxide: FeO (l) + C = Fe (l) + CO Zn oxide: ZnO (l) + C = Zn (g) + CO Pb oxide: PbO (l) + C = Pb ( g) + CO Since the whole iron oxide melts and forms slag, the direct reaction between the molten slag and C proceeds, and iron is reduced, Zn and Pb are almost removed (removal rate about 99.5%). Zn and Pb are removed by applying and melting
It will be possible to fully recycle iron.

Further, smelting dust or sludge generated in a stainless smelting furnace can be used to recover valuable metals contained therein. When charged into the moving hearth furnace in accordance with the present invention including C _r dust so that the following reaction takes place.

[0043] (1) the reduction zone iron _{oxide: Fe 2 O 3 + 3C =} 2Fe + 3CO Ni oxide: NiO + C = Ni + CO C r _{oxides: C r2 O 3 + 3C =} 2C r + 3CO iron, reduction of nickel oxide is relatively Although it proceeds even in the low temperature reduction zone, on the other hand, _{Cr 2} O ₃ is difficult to reduce and the reduction by CO gas does not proceed, and the reaction shown in the above equation proceeds only in a part in contact with carbonaceous material. To do. Further, since _{Cr 2} O ₃ has a high melting point, it is difficult to melt it at the temperature of the reduction zone.

[0044] (2) melting zone iron oxides: FeO (l) + C = Fe (l) + CO Ni oxides: NiO (l) + C = Ni (l) + CO C r _{oxides: C r2 O 3 + 3C =} 2C _{In the r} (l) + 3CO melting zone, low melting point iron oxide, SiO ₂ , CaO,
A molten slag containing Al ₂ O ₃ as a main component is formed, and the high melting point _{Cr 2} O ₃ is dissolved therein. The reaction occurs between the molten slag and carbonaceous material, also C _r2 O ₃ of irreducible melt as C _r (l) in the reduced molten iron. Further, by forming the molten slag, the reduction of NiO proceeds, the reduction rate of Ni in the melting zone becomes 98% or more, and the expensive Ni can be almost completely recovered.

In the present invention, a carbonaceous material layer may be stacked below the mixture layer separately from the mixture layer , but by providing such a carbonaceous material layer, the melting zone L ₃
There is an advantage that it is possible to prevent the molten material melted in step 1 from contacting the hearth. The size of the powdery iron ore and the powdery solid reducing agent is 10 mm or less in the sieve mesh from the viewpoint of reducibility and reactivity with CO ₂ .
It is preferably 8 mm or less, particularly preferably 3 mm or less.

[0046]

EXAMPLES Example 1 A rotary hearth having an alumina-based refractory material having a diameter of 2.2 m was provided, and the refractory material in the melting zone was made of a high alumina and highly refractory brick-laying structure. Using a moving hearth furnace as shown in (the specific internal structure is the same as the furnace in Fig. 5), the operation is performed as follows, and the yield of the final product (reduced iron) is changed by changing the temperature in the melting zone. The effect on it was investigated.

A screw type recovery device was arranged at the outlet of the furnace, and a layer 7 of a mixture of fine iron ore and a fine solid reducing agent and a layer 6 of carbonaceous material were stacked at the inlet as shown in FIG. In addition, the powdered iron ore and the powdered solid reducing agent used had a sieve size of 3 mm or less.

The iron ore and carbonaceous material used had the composition shown in Table 1. The furnace temperature in the reduction zone was controlled to 1300 ° C. by burner combustion control, and the residence time in the standard melting zone was 6 minutes. The operation pattern is that when a carbonaceous material layer is not provided below the mixture and the surface gas atmosphere is close to the theoretical air ratio, a carbonaceous material layer is provided below the mixture and the surface gas atmosphere is changed to the theoretical air ratio. Three patterns were used, one in the vicinity and one in which a carbonaceous material layer was provided below the mixture and the surface gas atmosphere was a reducing atmosphere.

FIG. 7 shows the relationship between the temperature of the melting zone and the yield of reduced iron under each condition. At a low temperature below 1450 ° C. at which melting did not occur, the yield of reduced iron did not change regardless of the presence or absence of the lower carbonaceous material layer. If there is no carbonaceous material layer below the mixture, the molten iron and slag produced at 1450 ° C or higher where melting occurs contact the moving hearth surface,
It adhered and reduced the yield of reduced iron significantly. On the other hand, in the case where the carbonaceous material layer was provided in the lower part of the mixture, as the melting
Since the open pores of the porous reduced iron are blocked, oxidation by the atmospheric gas is suppressed, and the reduced iron yield increases once,
As the temperature increased, iron was oxidized by the combustion gas in the vicinity of the theoretical air ratio that was oxidizable, and it was discharged as FeO into the slag. As a result, the yield of reduced iron decreased significantly.

A reducing gas having a reducing gas concentration of 90% is supplied by blowing in an atmosphere adjusting gas on the outlet side of the melting zone,
If the gas atmosphere on the surface of the reduced iron is a reducing atmosphere, reoxidation by the atmosphere gas can be prevented, so that the reduced iron yield at low temperature is confirmed to be stable at a high value of 97% or more. To remove the slag from the reduced iron, the temperature of the melting zone should be 1450 ° C or higher, and to improve the yield of the reduced iron, a carbonaceous material layer should be provided at the bottom, and
It was confirmed that it is important to adjust the reduced iron surface gas atmosphere to a reducing atmosphere.

[0051]

[Table 2]

Experiment Nos. 1 to 3 in Table 2 are the results of the case where the melting zone temperature was low and the operation was performed without providing the carbonaceous material in the lower layer (comparative example), but this example shows that the metal recovery rate is high. Separation of slag, which is the main object of the invention, was insufficient.

Experiment Nos. 4 to 7 are examples in which the influence of the melting zone temperature was observed (adapted examples according to the present invention), and the slag concentration was significantly reduced at 1450 ° C. or higher. In addition, experiment number 8,
Reference numeral 9 is an example (fitting example) in which the effect of heating time is observed, and the longer the time, the more the slag separation proceeds. In Experiment No. 10, the atmosphere on the surface of the layer was changed to a reducing atmosphere, and the yield of reduced iron was remarkably improved. Further, in Experiment Nos. 11 and 12, the carbonaceous material layer was not provided in the lower part, and although the separation of slag, which is the main object of the present invention, was achieved, the yield of reduced iron was slightly higher than that of the optimum condition. Low. Further, although Experiment Nos. 13 to 16 are the results of changing the type of carbonaceous material to char and coke, the same results as for coal were obtained.

Example 2 The same moving type hearth furnace as in Example 1 is applied, and dust and sludge containing volatile metals such as Zn and Pb (electric furnace dust:
t-Fe 54.9 wt%, SiO ₂ 1.3 wt%, Al ₂ O ₃ 1.1 wt%, CaO 1.
5wt%, MgO 0.8wt%, TiO ₂ 0.1wt%, S 0.02wt%,
P 0.04 wt%, Zn 12.5 wt%, Pb 1.1 wt%, C 0.3 wt%,
SUS smelting dust: t-Fe 56.2wt%, SiO ₂ 1.1wt%, Al
₂ O ₃ 0.98 wt%, CaO 1.98 wt%, MgO 0.93 wt%, TiO ₂
0.1wt% S 0.01 wt%, P 0.05 wt%, Ni 0.69 wt%, C
r 5.8wt%, Zn 0.2wt%, Pb 0.1wt%, C 3.8wt%) was investigated for reduction and volatilization behavior. The results are shown in Tables 3 and 4. In this example, the temperature of the reduction zone was set to two levels of 1100 ° C. and 1300 ° C., and the temperature of the melting zone was 1400 ° C. (no melting) and 14 ° C.
Two levels of 80 ° C (with melting) were set.

[0055]

[Table 3]

[0056]

[Table 4]

Table 3 shows the removal rates of Zn and Pb in the reduction zone and the melting zone for the electric furnace dust. The removal of Zn and Pb was achieved by increasing the temperature of the reduction zone from 1100 ° C to 1300 ° C. It was confirmed that the rate increased from the 60% level to the 80 to 90% level and was able to be removed by 99% or more by melting.

Table 4 shows the removal rates of Ni and Cr in the SUS smelting dust having the above composition. Smelting dust of SUS is 0.69% of expensive Ni and 5.8% of Cr.
However, the recovery itself is economically important, and the dumping of dusts containing Cr as industrial waste is not allowed from the viewpoint of environmental pollution.
By increasing the temperature of the reduction zone from 1100 ° C to 1300 ° C, the reduction rate of Ni is reduced from 80% to 90%.
% (There is no significant improvement in the reduction rate of Cr under the condition of no melting even at the exit of the melting zone), and Cr increased from the 10% level to the 20% level. The melting rate of Ni reduces the Ni reduction rate to 98
%, And the reduction rate of Cr could be 95% or more.

[0059]

According to the present invention, since slag can be efficiently separated from reduced iron in a moving hearth furnace, it is possible to reduce the lime basic unit and the electric power basic unit in the electric furnace of the next step. It is possible, and at the same time, it has the advantage that high gangue and high ash, which are the most reserves and cheapest ores and coal, can be used. Further, not only iron ore as powdered ore, but also electric furnace, blast furnace, iron smelting dust generated from stainless smelting furnace, it is possible to recover valuable metals present in it by using sludge, It is possible to significantly reduce the amount of industrial waste emitted from steelworks.

[Brief description of drawings]

FIG. 1 is a diagram showing a configuration of a rotary hearth furnace.

FIG. 2 is a diagram showing a cross section taken along the line AA of FIG.

FIG. 3 is a diagram showing a relationship between a mixed slag concentration and a heating furnace atmosphere temperature.

FIG. 4 is a diagram showing a configuration of an electric furnace used in an experiment.

FIG. 5 is a diagram showing a configuration of a furnace according to the present invention.

FIG. 6 is a view showing a cross section of a mixture and a layer of carbonaceous material loaded on the hearth.

FIG. 7 is a diagram showing the relationship between the yield of reduced iron and the ambient temperature of the heating furnace.

[Explanation of symbols]

1 hearth 2 hearth 3 heating burner 4 hearth 5 hearth 6 layer of carbon material 7 layer of mixture 8 combustion burner 9 heating device 10 recovery device 11 gas supply nozzle t layer of mixture a inlet b outlet h heater n nozzle n ₁ exhaust gas nozzle s PET

─────────────────────────────────────────────────── ─── Continuation of the front page (56) Reference JP-A-10-147806 (JP, A) JP-A-11-106816 (JP, A) JP-A-11-106815 (JP, A) JP-A-11- 106814 (JP, A) JP 11-106813 (JP, A) JP 11-92833 (JP, A) (58) Fields investigated (Int.Cl. ⁷ , DB name) C21B 13/10 F27B 9 / 16

Claims (4)

(57) [Claims] 1. A layer composed of a mixture of an oxide such as pulverized iron ore and a solid reducing agent in powder form is loaded on a horizontally moving hearth, and the oxide is reduced by radiative heat transfer from the upper part of the hearth. The product obtained by the reduction treatment is
A method for operating a mobile hearth furnace, which comprises melting at 1450 ° C. or higher to aggregate and separate a slag component in a reduction product. 2. The method of operating a mobile hearth furnace according to claim 1, wherein the oxygen partial pressure of the gas phase in contact with the reduction product is adjusted to a reducing atmosphere. 3. A layer of the mixture different from the layer of the mixture
The method of operating a mobile hearth furnace according to claim 1, which is loaded below . 4. A layer composed of a mixture of an oxide such as powdered ore and a solid reducing agent in powder form is placed and moved, while preheating the layer,
A moving hearth furnace consisting of a hearth for reduction and a furnace body surrounding the hearth and equipped with a burner in the upper part of the inside of the hearth. A moving hearth furnace characterized by having a melting zone for melting the product and aggregating and separating the slag component present therein in a region up to the outlet.