JPH042643B2 - - Google Patents

Description

[Detailed description of the invention]

[Industrial Application Field] The present invention relates to a method for producing molten metal by melting and reducing powdered ore. [Prior art] A vertical furnace having two stages of upper and lower tuyere. Carbonaceous solid reducing material (hereinafter referred to as carbon material) is charged into the furnace from the top of the furnace, and oxygen-containing gas is introduced from the tuyere. is blown into the furnace to form a fluidized bed of carbonaceous material (hereinafter referred to as the carbonaceous material fluidized bed), and a packed bed of carbonaceous material (hereinafter referred to as the carbonaceous material packed bed) below this fluidized bed of carbonaceous material. ) and supplying powdered ore into the furnace from the upper tuyere to produce molten metal is known. In this process, the powdered ore fed into the furnace is melted all at once in a very hot area in front of the tuyere. The molten powder ore settles in the carbonaceous packed bed region. On the other hand, the ore that has not been completely melted in the high temperature region in front of the tuyeres is fluidized together with the carbonaceous material in the carbonaceous fluidized bed region, where the temperature rise and reduction proceed. The density of the fluidized ore increases as the reduction progresses, and at the same time, the reduced ore repeats alternate fixation and fusion, and as the particle size gradually increases, it settles in the carbonaceous packed bed region. The ore completes its final reduction while descending through this carbonaceous packed bed region. In this final reduction process, the temperature is raised to the tapping temperature, while metalloid components such as Si and Mn are absorbed, and further separated into metal and slag, which are separated into molten metal and slag and accumulate in the lower part of the furnace. become. In this way, the temperature of the carbonaceous packed bed plays an extremely important role in determining the temperature and composition of the molten metal produced, and in this way stable operation can be maintained and high quality molten metal produced. In some cases, it is extremely important to properly control the temperature of the carbonaceous packed bed. A method for producing molten metal from powdered ore by forming a carbonaceous fluidized bed and a carbonaceous packed bed is disclosed in JP-A-62-56537.
Disclosed by No. With this method, the temperature of the packed bed of carbonaceous material cannot be actively controlled during long-term continuous operation, so there is a problem that fluctuations in the temperature of the packed bed directly appear as fluctuations in the composition and temperature of the molten metal. . Furthermore, with this method, dust containing a large amount of carbonaceous material and flux for adjusting slag components is emitted along with the exhaust gas, and since this is not actively collected and reused, the carbonaceous material cannot be used effectively. As part of the flux turned into dust, the slag composition fluctuated, making it difficult to maintain stable slag discharge. [Problems to be Solved by the Invention] The present invention uses a vertical melting reduction furnace having two stages of upper and lower tuyeres, and forms a carbonaceous material packed bed in the lower part of the furnace, and also forms a carbonaceous material packed bed above the carbonaceous material packed bed. This invention relates to an improvement in a method for producing molten metal by forming a fluidized bed and supplying powdered ore into a furnace from an upper tuyere,
Provides a method to prevent fluctuations in the composition and temperature of molten metal caused by temperature fluctuations in the packed bed of carbonaceous material, especially during long-term continuous operation.Effectively recycles carbonaceous material that would otherwise be lost as dust in the exhaust gas of a smelting reduction furnace. It is an object of the present invention to provide a method for stabilizing slag components and maintaining stable slag drainage by reusing flux lost as dust components. [Means for Solving the Problems] The present invention provides a method for producing molten metal using a vertical smelting reduction furnace as described above, in which (a) ore and flux are The dust mainly containing (b) Dust containing mainly carbonaceous matter is blown into the furnace from the lower tuyere. In the above method, by classifying the dust containing the smelting reduction furnace exhaust gas into a fraction smaller than a certain value within the particle size range of 0.1 to 0.5 mm and a fraction larger than a certain value, the dust containing mainly ore and flux, It can be divided into dust that mainly contains carbonaceous matter. The process of separating the dust in the smelting reduction furnace exhaust gas into dust mainly containing ore and flux and dust containing carbonaceous components can be easily and accurately separated if carried out after dust collection. In addition, if the process of separating the dust in the smelting reduction furnace exhaust gas into dust containing mainly ore and flux and dust containing carbonaceous components is carried out during dust collection, air separation can be used, and the separated material can be immediately collected. This is advantageous because it can be returned to the tuyere and circulated at a high temperature. [Operation] In a vertical furnace in which a carbonaceous material packed bed and a carbonaceous material fluidized bed are formed in the furnace, there is a fluidization critical particle size determined by the gas flow rate in the furnace, and carbonaceous material smaller than this particle size exists. is fluidized, and carbonaceous material larger than this critical particle size settles to form a packed bed. As a result, the particle size distribution of the charged carbon material changes,
If the ratio of oxygen-containing gas injected from the upper and lower tuyeres changes, the ratio of the amount of fluidized carbonaceous material to the amount of carbonaceous material forming a packed bed of carbonaceous material changes, and heat transfer in the fluidized bed of carbonaceous material changes. Condition changes. Due to this change, the temperature of the carbonaceous material packed bed cannot be stably maintained, and the composition and temperature of the molten metal produced fluctuate. In other words, as the average particle size of the charged carbonaceous material becomes smaller, the ratio of carbonaceous materials with large particle sizes that should form the carbonaceous material packed bed decreases, and the temperature of the carbonaceous material packed bed decreases and the temperature of the molten metal produced increases. If the components cannot be secured, the consumption rate of the carbonaceous material with large particle size consumed by the oxygen-containing gas blown from the lower tuyere is reduced, and the residence time of the carbonaceous material with large particle size in the furnace is reduced. It is necessary to increase the temperature of the carbonaceous packed bed by increasing the length of time. Conversely, the average particle size of the charged carbonaceous material increases, the ratio of carbonaceous materials with large particle sizes forming the carbonaceous material packed bed increases, the temperature of the carbonaceous material packed bed increases, and the temperature of the molten metal produced increases. When the temperature is too high and the components cannot be secured, the rate of consumption of carbonaceous material consumed by the oxygen-containing gas blown from the lower tuyere can be increased, and the residence time of carbonaceous materials with large particle sizes in the furnace can be shortened. It is necessary to lower the temperature of the carbonaceous packed bed. On the other hand, the present inventors have studied various means for preventing fluctuations in the temperature and composition of the molten metal produced due to the change in particle size of the charged carbonaceous material. During this study, it was discovered that there is a close relationship between changes in the particle size of the charged carbonaceous material and changes in the amount and composition of dust discharged outside the furnace together with the smelting reduction furnace exhaust gas. In other words, components derived from ores and fluxes in the dust are concentrated in fine particles of 0.5 mm or less, and the amount strongly depends on the temperature and oxygen content of the oxygen-containing gas blown in from the tuyere. It does not depend on the particle size of the carbonaceous material, and furthermore, the carbonaceous material in dust is overwhelmingly present in dust with a particle size of 0.1 mm or more, and the amount strongly depends on the change in the particle size of the charged carbonaceous material. It was discovered that the temperature and oxygen content of the oxygen-containing gas blown in from the tuyere are not affected much. In particular, we found that the amount of carbon material in dust increases as the particle size of the charged carbon material becomes smaller, and conversely decreases as the particle size of the charged carbon material becomes smaller. Figure 2 shows the relationship between the particle size of dust and the content of carbonaceous material and the content of components derived from ore and flux. The present inventors determined that the dust should be 0.5 to 0.1 mm based on the relationship between the amount of dust generated, its components, and the particle size of the charged carbon material.
Classified with a constant particle size between, preferably 0.3mm,
We came up with the idea that all of the problems with conventional technology could be solved by injecting dust of 0.3 mm or more, which contains a lot of carbonaceous material, from the lower tuyere, and by blowing dust of less than 0.3 mm, which contains a lot of ore and flux, from the upper tuyere. Originally, the dust was classified according to the above particle size, and the fine-grained dust was blown into the upper tuyere.Ore and flux should be blown into the upper tuyere and melted in the packed bed of carbonaceous material. This is because blowing from the tuyere has the effect of lowering the temperature of the packed bed in the lower part of the furnace, so if it is necessary to raise the temperature of the packed bed of carbonaceous material, it will have the opposite effect. In other words, if the present invention is implemented, even if the temperature of the carbonaceous packed bed decreases due to a decrease in the particle size of the charged carbonaceous material, the amount of dust of 0.3 mm or more that contains a large amount of carbonaceous material will increase overwhelmingly. Since this gas is injected from the lower tuyere, the consumption rate of large particle size carbonaceous materials consumed by the oxygen-containing gas blown from the lower tuyeres decreases, and the residence time of large particle size carbonaceous materials in the furnace is reduced. extends. Therefore, it becomes possible to raise the temperature of the carbonaceous material packed bed, and the temperature and composition of the produced molten metal can be maintained stably. On the other hand, when the particle size of the charged carbonaceous material becomes smaller, the temperature and composition of the molten metal produced can be stably maintained by the completely opposite effect. Furthermore, with this method, all the carbonaceous material supplied to the furnace is not lost due to dust consumed in the furnace.
Carbon material consumption can be reduced. In addition, since all the flux components can be effectively utilized within the furnace, there is almost no fluctuation in the slag components, and stable slag can be maintained. [Example] A vertical smelting reduction furnace 1 shown in Fig. 1 with an inner diameter of 1.2 m, a height of about 5 m, a hot metal production capacity of about 10 tons/6 days (in the case of ferrochrome, the production capacity is about 5 tons/day) was used. Powdered ore was melted and reduced. Carbonaceous material is supplied to the vertical smelting reduction furnace 1 from a carbonaceous material supply port 16 provided above, while high-temperature gas is supplied from an oxygen-containing gas supply pipe 9 through a distribution device 8 to an upper tuyere 6 and a lower tuyere 7. Oxygen-containing gas is blown into the furnace to form a carbonaceous fluidized bed 2 and a carbonaceous packed bed 3. A slag layer 4 and a molten metal layer 5 are formed at the bottom of the furnace, and these are discharged from the tapping slag port 17 at a timely manner. Powdered ore was supplied into the furnace together with oxygen-containing gas from the upper tuyere 6 through the ore supply pipe 14, and coal as a carbon material was continuously supplied into the furnace from the carbon material supply port 16. As powdered ores, iron ore from Australia and chromium ore from South Africa shown in Table 1 were used to produce pig iron and ferrochrome, respectively. Exhaust gas duct 1 for dust in smelting reduction furnace exhaust gas
Collected by a high-temperature dust collector 10 installed in the middle of 5,
After classifying this by 0.3mm using dust classifier 11,
Dust of less than 0.3 mm is supplied to the dust transport pipe 12 to the upper tuyere, and dust of 0.3 mm or more is supplied to the transport pipe 13 to the lower tuyere, and the dust is transported into the furnace from the upper tuyere 6 and lower tuyere 7, respectively. The effect of the present invention was confirmed by blowing into the tank and operating for two consecutive weeks. Table 2 shows the operating conditions of Examples 1 and 2 and Comparative Examples 1 and 2. Comparative Examples 1 and 2 show conventional examples in which no dust is supplied to the tuyeres when producing pig iron and ferrochrome using iron ore and chromium ore, respectively. This figure shows the cases in which each of these was manufactured. In Comparative Examples 1 and 2, the actual tapping temperature did not match the target value, and the fluctuation range of the Si concentration and slag basicity was also extremely large. In Examples 1 and 2, the tapping temperature matched the target value and the fluctuation range was small, and Si
Concentration and slag basicity also varied within a narrow range surrounding the target values. Furthermore, the amount of carbon material consumed was also reduced by the present invention. In the above example, the dust was collected, classified, and blown into the upper and lower tuyeres, but the coarse dust was collected using a cyclone or the like, and then finely divided using equipment suitable for fine dust collection, such as a ceramic filter or bag filter. It is clear that the same effect as in the above embodiment can be obtained even if the grain dust is collected and blown into the lower and upper tuyeres.

【table】

〔Effect of the invention〕

By implementing the present invention, it is possible not only to prevent fluctuations in the temperature and composition of molten metal due to changes in the charged carbon material, but also to reduce the amount of carbon material consumed.
Furthermore, stabilization of slag components can be achieved.

[Brief explanation of drawings]

FIG. 1 is a schematic vertical cross-sectional view of a vertical smelting reduction furnace;
FIG. 2 is a graph showing the relationship between the particle size of dust and the content of carbonaceous material, and the relationship between the content of components derived from ore and flux. 1... Vertical melting reduction furnace, 2... Carbonaceous fluidized bed, 3
... Charcoal material packed bed, 6 ... Upper tuyere, 7 ... Lower tuyere, 10 ... Dust collector, 11 ... Classifier.

Claims (1)

[Claims] 1. A vertical melting reduction furnace having two upper and lower tuyere stages is used, and a packed bed of carbonaceous solid reducing material is formed in the lower part of the furnace, and a carbonaceous solid reducing material is placed above the packed bed. In a method of manufacturing molten metal by forming a fluidized bed and supplying powdered ore from the upper tuyere, the dust contained in the exhaust gas of the smelting reduction furnace, which mainly contains ore and flux, is fed into the furnace from the upper tuyere. A method for producing molten metal from powdered ore, characterized by blowing dust containing mainly carbonaceous matter into the furnace from the lower tuyere. 2 Particle size of dust contained in smelting reduction furnace exhaust gas
A patent claim characterized in that the dust is divided into dust mainly containing ore and flux and dust mainly containing carbonaceous components by classifying into a fraction smaller than a certain value in the range of 0.1 to 0.5 mm and a fraction larger than a certain value. A method for producing molten metal from powdered ore according to scope 1. 3. Claims 1 or 2, characterized in that the process of separating the dust in the exhaust gas from the smelting reduction furnace into dust mainly containing ore and flux and dust containing carbonaceous matter is carried out after collecting the dust. The method for producing molten metal from powdered ore described in . 4. Claims 1 or 2, characterized in that a process of separating the dust in the exhaust gas from the smelting reduction furnace into dust mainly containing ore and flux and dust containing carbonaceous components is carried out at the time of dust collection. A method for producing molten metal from powdered ore as described in .