JPS6047887B2 - Sintered ore manufacturing method - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a sintered ore production method for suppressing the decrease in air permeability due to overmelting during the sintering process and obtaining highly reducible sintered ore. FeO in the sintered ore is reduced by selecting an ore brand located in the lower layer of the mixed raw materials supplied on the pallet of the sintering machine, and preventing a decrease in air permeability due to overmelting of the ore during the sintering process. The present invention relates to a method for producing sintered ore having good reducibility by reducing the porosity and increasing the porosity.

In order to stabilize the furnace condition and reduce the fuel ratio during blast furnace operation, it is important that the charged raw material has good reducibility.

The main iron sources for blast furnace charging are lump iron ore, sintered ore, and pellets, but in recent years the charging ratio of sintered ore has increased to 80 to 90%.
%, and it is no exaggeration to say that the quality of the sintered ore influences the operational performance of the blast furnace. Therefore, it is desired to produce highly reducible sintered ore. As shown in Figure 1, the conventional method for producing sintered ore is that iron ore, limestone, MgO-containing mineral powder, etc. stored separately in a yard IA are transferred to an ore storage layer 4A by a belt conveyor 3A. The coke stored in the storage layer 4 from the yard 1 through the rod mill 2 and the coke stored in the ore storage layer 4 by the belt conveyor 3 are simultaneously cut out onto the belt conveyor 5, and are fed into the primary mixer 6 and secondary mixer 7. After adding moisture, mixing, and granulation, the ore is charged into the pallet 11 on the sintering machine 10 via the feed hopper 8, and then the surface layer of the blended raw materials is ignited in the ignition furnace 9, and after ignition, the raw materials are granulated downward. By inhaling air, the sintering reaction within the blended raw materials proceeds continuously from the upper layer to the lower layer, and the reaction is completed at about 15 to 2 particles, yielding sintered ore.

In this case, the heat of coke combustion in the upper layer is sequentially stored in the lower layer, and the melting rate of the ore in the lower layer is higher than that in the upper layer, so the amount of melt produced in the lower layer is large.

The larger the amount of melt produced in the lower layer, the lower the bed passing wind speed in the latter half of sintering, and compared to high wind speed J, as shown in Table 1, the porosity is high and Fe0) is low, and the porosity is as shown in Table 2. The rate of return will also be lower. The main reason for this decrease in the reduction rate is that the lower layer becomes excessively molten, which obstructs ventilation, lowers the oxygen partial pressure, and creates a dense structure mainly composed of magnetite and amorphous slag. be.

During actual operations and sintering pot tests, it is often seen that when a large amount of a particular brand of ore is blended, overmelting occurs and air permeability decreases. This shows that there are differences in meltability depending on the brand. However, until now, the melting characteristics of each brand have not been quantitatively understood, and therefore,
In order to prevent overmelting of ore, it is first necessary to clarify the melting characteristics of ore. Therefore, the melting characteristics of each brand of ore were measured under the following conditions. For each brand's 7 to W particles (top size of sintered raw materials), -1? of the blended raw materials? The reagents shown in Table 3 approximate the slag composition of the parts, that is, the melting during sintering is thought to start from the fine powder part and gradually dissolve the coarse ore, so the fine? The surface was coated with 20% by weight of a finely powdered reagent prepared according to the composition of the part, dried, and then rapidly heated to 1300°C (heating rate 650°C Imin) in an electric furnace (in the atmosphere).2. After holding the dispute,
The ore was cooled in air, and the molten state of each ore was measured by observing the cross section of the ore.

The results are shown in Figure 2. As shown in Figure 2, there is a correspondence between the crystal water contained in the ore and the melting rate, and ores that contain more crystal water are extremely soluble after the crystal water content reaches 2.0%. I understand. This result is in good agreement with the fact that in actual operation, ore containing 2% or more of crystallization water has a low probability of remaining as the original ore. This is thought to be because crystal water rapidly escapes around 400 to 900° C. during the heating process, making it porous, increasing the reaction area with the slag, and reacting well with the melt. From this measurement result, the crystal water was 2.0
Ores containing 2.0% or more are easily meltable ores, while crystalline water is 2.0% or more.
% ore can be classified as refractory ore.

In order to suppress overmelting after sintering, it is possible to limit the amount of easily melted ore used, but among the brands currently used, ores containing 2.0% or more of crystallized water account for The ratio is high, and it is impossible in daily operations to use a large amount of refractory ore with less than 2.0% crystallization water. Furthermore, if only a refractory ore is used, the reaction time is short from the surface layer to the center of the sintered bed, so that the reaction does not occur sufficiently and remains as a dense base ore, reducing the reducibility from the surface layer to the center. From the above, it has become desirable to develop a technology for producing sintered ore that has excellent reducibility by preventing overmelting of the lower layer while using a large amount of ore containing 2.0% or more of crystallization water. Ivy.

The present invention was made in view of the above circumstances, and is a method for producing sintered ore using a Dwight Lloyd sintering machine, which uses mixed raw materials containing a large amount of easily meltable ore containing crystal water of 2.0% or more. The method is characterized in that the raw materials are supplied onto a pallet and sintered so that the raw materials containing a large amount of refractory ore of less than 2.0% are in the upper layer and the raw materials are in the lower layer.

The method of the present invention will be explained in detail below based on the drawings.

In the present invention, as shown in FIG. 3, easily soluble molten ore containing 2.0% or more of crystallization water is stored in an ore storage layer 4A from a yard 1A via a belt conveyor 3A.

On the other hand, refractory ore containing crystal water of less than 2.0% is stored in the ore storage layer 4B from the yard 1B via the belt conveyor 3B. Thereafter, it is cut onto belt conveyors 5 and 5A together with ore, limestone coke, etc., and fed into ore feed hoppers 8A and 8B via separate primary mixers 6A and 6B and secondary mixers 7A and 7B, respectively. When charging onto a pallet, the raw materials from the ore feed hopper 8B are charged into the lower layer, and the raw materials from the ore feed hopper 8A are charged into the upper layer. By doing this, easily meltable ore is present in the raw material in the upper layer where there is less heat storage, and difficult to melt ore is present in the lower layer where there is a large amount of heat storage, so that both the upper layer and the lower layer are sufficiently heated during the sintering process. The reaction will proceed. In this case, the proportion of easily meltable ore in the blended raw materials in the upper layer (above the center of the sintered layer) is 70 to 100%.
The proportion of easily meltable ore in the blended raw materials in the lower layer (below the center of the sintered layer) is in the range of 0 to 20% (the remainder is hardly meltable ore). Furthermore, since the heat storage in the sintered layer increases sequentially from the top to the bottom, in addition to the method of dividing the sintered layer into two stages as described above, it is also possible to charge the sintered layer by dividing it into three or four stages. good.

In this case, the proportion of easily meltable ore in the blended raw materials in the surface layer of the sintered raw material layer (10c!rl depth from the surface) should be 70% or more, and the blended raw materials in the bottom (10c1n above the grade surface) should be 70% or more. The proportion of easily meltable ore in the mixture is set to 20% or less, and the content of easily meltable ore is gradually reduced from the top to the bottom along the blending gradient between the surface layer and the bottom. EXAMPLE The following tests were conducted to clarify the comparison between the conventional method and the method of the present invention.

The proportions of easily melting ore and hardly melting ore having the chemical compositions shown in Table 4 are shown in Table 5, that is, test 1 is the conventional method in which the whole layer is uniformly charged, and test 2 is the easy melting method of the present invention. In test 8, in order to further clarify the effect of test 2, a large amount of easily meltable ore was blended in the upper layer (above the center of the sintered raw material layer) in a concentrated manner. Sintered ore was produced under three conditions, although the sintered ore was concentrated in the lower part of the center.

In addition, the blended raw materials CaO/SiO2, SiO2, MgO,
Moisture was kept constant.

However, regarding AI2O3, in general, easily melting ores have higher Al2O3 than difficultly melting ores, and due to uneven charging, the upper layer of Tests 2 and 3 had a value of "0.A12".
03 levels are different.

However, the average value of the total amount is the same as Test 1.
Figure 4 shows the wind speed passing through the sintering bed during the sintering process of each of these tests, and Figure 5 shows the velocity of the wind passing through the sintering bed during the sintering process, and
Indicates porosity and reduction rate.

As is clear from FIG. 4, in the method of test 2, in which a large amount of the easily meltable ore according to the present invention is concentrated in the upper layer, the conventional method of test 1 and the method of test 3, in which a large amount of the easily meltable ore is concentrated in the lower layer. Compared to the above method, the passing air velocity during the latter half of the sintering reaction process is higher.

As shown in Fig. 5, the test 2 was not inferior to Tests 1 and 3 in terms of FeO, porosity, and reduction rate in the upper and middle layers, and the FeO porosity in the lower layer was the same as the value in the middle layer. It shows better values compared to Tests 1 and 3, and the return rate is also higher than the conventional method. Based on the above results, the method of the present invention is effective in actually using a large amount of easily melted ore while suppressing the excessive amount of solution produced in the latter half of the sintering process. reduce harm,
As a result, it can be said that this method has the important advantage of being able to produce sintered ore with a higher reduction ratio than conventional methods.

In addition, the sintered ore production method according to the present invention has little heat accumulation and melts easily in the upper layer, which tends to be fragile due to insufficient melting reaction! The melting reaction is accelerated due to the presence of a large amount of carbonaceous ore, which eliminates the brittleness and improves the ventilation rate in the lower layer.
Since the crystallization time can be shortened, it also has the advantage of improving the product yield, cold strength, and production rate, as shown in FIG. 6.

As described above, according to the present invention, both the easily melting ore and the hardly melting ore currently in use can be sufficiently activated, and the product yield, cold strength, and productivity are higher than that of sintered ore produced by conventional methods. This enables highly reducible sintered ore to be produced while maintaining the yield rate, and enables stable blast furnace operation.

[Brief explanation of the drawing]

Figure 1 is a diagram of the conventional sintered ore production process, Figure 2 is a diagram of the relationship between crystal water in ore and meltability, Figure 3 is a diagram of the sintered ore production process according to the present invention, and Figure 4 is the sintering time. Figure 5 shows the relationship between the velocity of air passing through the sintered PET and the FeOl porosity within the sintered layer.
FIG. 6 is a diagram showing the distribution of the reduction rate, comparing the properties of sintered ore produced by the conventional method and the method of the present invention. 1, 1A, 1B... Yard, 2... Rod mill, 3, 3A, 3B... Belt conveyor, 4, 4A, 4B... Ore storage tank. ,5,5A...
...Belt conveyor, 6, 6A, 6B...
Primary mixer, 7, 7A, 7B... Secondary mixer, 8, 8A, 8B... Feed hopper, 9...
...Ignition furnace, 10...Sintering machine, 11...
palette.

Claims (1)

[Claims] 1 In a method for producing sintered ore using a Dwight Lloyd sintering machine, a blended raw material containing a large amount of easily meltable ore containing 2.0% or more of crystallization water is added to the upper layer, and a refractory ore containing less than 2.0% water of crystallization is added to the upper layer. A method for producing sintered ore, characterized in that mixed raw materials are fed onto a pallet and sintered so that the mixed raw materials containing a large amount of ore are in the lower layer.