JPH0156127B2 - - Google Patents

Description

[Detailed description of the invention]

The present invention relates to a sintering operation method for producing sintered ore for iron manufacturing. Sintered ore is widely used as a raw material for blast furnaces for iron manufacturing. Criteria for determining the quality of sintered ore include chemical composition, particle size distribution, cold strength, reduction pulverizability, etc. These are extremely important factors when operating a blast furnace, so they are constantly managed. By the way, it is known that the porosity of sintered mineral products has an important effect on the quality of the product. here,
The sintered mineral porosity refers to the porosity measured based on the provisions of JISM8716-1977. Now, regarding the sintered ore cold strength TI (%), the pores in the sintered ore become strength defects, and the higher the porosity of the sintered ore product, the lower the strength. On the other hand, since the reduction reaction of sintered ore proceeds through contact with reducing gas, the greater the reaction surface area, that is, the higher the porosity of the sintered ore product, the better its reducibility will be. Reduction pulverizability RDI (%)
As for sintered mineral products with higher porosity, reduction progresses and the strength is weaker, so they tend to be worse. These relationships are shown in FIG. With conventional sintering operation methods, it is impossible to quickly measure the porosity of sintered ore products, so quality tests are conducted on directly manufactured products without knowing the porosity of sintered ore products. , until a satisfactory quality value is obtained, the raw material mixture ratio or operational conditions (sintering blower rotation speed, wind box damper opening, cut-off plate angle, raw material layer height, moisture content of raw material in the surge hopper)
I had to repeat the changes. Therefore, it not only takes a huge amount of time to obtain the quality target value, but also requires wasteful mixing of raw materials and manufacturing of sintered ore. This also increases the variation in product quality. Therefore, an object of the present invention is to streamline sintering operations and stabilize the quality of sintered mineral products by quickly estimating the porosity of sintered mineral products. Next, the method of the present invention will be explained with reference to FIG. First, determine the porosity of the raw material packed bed with a diameter of 0.5 mm or less (1). At the same time, the fluidity index within the sintered layer is determined (2). Next, the porosity of the sintered ore product is estimated based on these porosity and fluidity index (3). The blending ratio of raw materials is controlled (4) or the operating conditions are controlled so as to obtain the target porosity from this estimated porosity (5). The pores in the sintered cake can be classified into large-diameter pores that form the apparent surface of the product particles when crushed to obtain sintered ore of a predetermined particle size, but disappear during the crushing process, and The remaining pores can be classified into small diameter pores measured by the JISM8716 method. If these pores were to be classified by size, since the JIS measurement method uses mercury, it is determined by the penetrating power of mercury, and it is possible to classify them based on the limit of approximately 0.5 mm. Now, in the actual production of sintered ore, various pores exist in the state filled with raw materials, and some of these pores are large in diameter and some are small in diameter, but sintered ore is produced during the production process. The particles are melted, and the melt flows and cools, bonding the ores together. Expressing this from the pore side, it can be said that as the ore particles melt and the melt fluidizes, small pores gather and larger pores are generated. As a result, the entire sintered layer shrinks. As the sintered layer melts in this way, smaller pores are integrated into larger ones, and the apparent pore size grows larger. The present inventors paid attention to changes in these pores and found that these changes in pores can be predicted by the following method. The porosity of sintered ore products is the small pores that remain during the sintering and melting process among the small pores that exist in the initial raw material filling state, and this is due to the solid-liquid phase fluidity of the sintered packed bed. Therefore, it can be calculated as shown in equation (1) below. ε=ε′−ε′η ……(1) ε: Porosity of sintered mineral product (%) ε′: Porosity of the initial (before firing) raw material packed bed with a diameter of 0.5 mm or less (%) η: Sintered Fluidity index during interlayer melting. Here, the initial small pores can be roughly classified into the following three types. As shown in FIG. 3, in the raw material packed bed 6, pores 7 within the ore particles, small pores 8 among the pores between the particles, ie those surrounded by fine powder,
Portion 9 occupied by water (in the raw material state, it is not a void pore, but during the firing process, water evaporates and becomes a pore. Also, since water is small and crowded, small pores are generated). It will be done. These quantities are determined by the following equations (2) to (7). ε ₃ = w・ρ ₁ …(2) E=100−ε ₃ −(100−w)・ρ ₁ /ρ ₂ …(3) ε ₁ =0.01×(100−E)× 〓 ⁱ (AiWi ) ……(4) ε ₂ = R・E・(R _0.5 ) ……(5) ε ₀ = ε ₁ + ε ₂ + ε ₃ ……(6) ε′={ε ₀ / (100−E+ε ₂ )} ×100 ……(7) ε ₀ : Porosity of the initial (before firing) raw material packed bed with a diameter of 0.5 mm or less (% per container volume) ε′: Pores with a diameter of 0.5 mm or less of the initial (before firing) raw material packed bed (% per container volume excluding voids with a diameter of 0.5 mm or less) E: Porosity of all interparticle voids when filling raw materials (% per container volume) ε ₁ : Porosity within ore particles (% per container volume) ε ₂ : Porosity of the raw material packed bed with a diameter of 0.5 mm or less (% per container volume) ε ₃ : Volume ratio occupied by water (% per container volume) ρ ₁ : Bulk density of the packed bed (g/cm ³ ) ρ ₂ : Average apparent density of ore particles (g/ ^cm3 ) Ai: Intra-particle porosity of branded ore (% per particle volume) Wi: Mixing ratio of branded ore (-) R _0.5 : 0.5 mm or less in the particle size distribution of raw ore R: Constant w: Weight percentage of water content in the raw material (wt%) Equation (2) calculates the volume ratio of water per container volume from the weight percentage of water content of the raw material and the bulk density of the raw material. Equation (3) calculates the porosity of all interparticle voids in the raw material packed bed from the water content weight component ratio of the raw material, the packed bulk density of the raw material, and the apparent density of the particles. Equation (4) integrates the intraparticle porosity and converts it per container volume. Equation (5) calculates the porosity of interparticle voids with a diameter of 0.5 mm or less in the raw material packed bed using the raw material particle size distribution from the porosity of all interparticle voids in the raw material packed bed. Equation (6) is calculated by integrating the pores with a diameter of 5 mm or less that exist in the raw material packed bed in the initial state.
Equation (7) calculates the initial raw material filling porosity from % per container volume according to the meaning of porosity shown in the JIS method.
This is a formula that converts it back to % per volume excluding pores of 0.5 mm or larger. Regarding equation (5), ε ₂ and E
The relationship with R _0.5 is shown in Figure 4. In Figure 4, the x mark is
When R _0.5 = 75%, the ● mark indicates the case when R _0.5 = 50%, and the ○ mark indicates the case when R _0.5 = 25%. On the other hand, the index η representing the fluidity of the sintered layer including solid and liquid can be determined from the actually measured shrinkage rate of the sintered cake or the chemical composition of the raw material and the melting rate.
Here, the melting rate will be described in detail later, but is generally defined as the volume ratio in the sintered cake of something that has a history of melting during the sintered ore manufacturing process. This is shown in equations (8) and (9). η=a ₁ SR+a ₂ E+a ₃ ...(8) η=b ₁ Q+b ₂ [CaO]+b ₃ [SiO ₂ ]+b ₄ [Al ₂ O ₃ ]+b ₅
[MgO] + b ₄ [FeO]...(9) SR: Shrinkage rate of sintered cake (layer height after sintering/layer height before sintering) x 100 (%) E: Between all particles when filling raw materials Void porosity (% per container volume) [ ]: Components in the raw material (wt%) represented by symbols in [ ] Q: Melt rate of raw material particles in the sintered layer (%) a ₁ ~ a ₃ : Constant b ₁ ~ b ₆ : Constant As mentioned above, the fluidity within the sintered layer has a great influence on the shrinkage of the entire sintered layer and is closely related to it.Conversely, by actually measuring the shrinkage rate of the sintered cake, it is possible to Fluidity within the stratum can be determined. The term E is included in equation (8) to compensate for the fact that the initial interparticle voids in the packed bed also have a large effect on the shrinkage of the sintered cake. Now, the shrinkage rate of the sintered cake can be easily and quickly determined by measuring the layer height before and after firing, and the porosity of all the interparticles when filling the raw material can be determined by calculating the density of the raw material particles measured in advance.
It can be accurately calculated from values such as the moisture content of the raw material measured with a moisture meter and the bulk density of the raw material packed bed obtained by dividing the weight of the raw material charged by the container volume. The present inventors discovered that the fluidity index η can also be determined from the melting rate and the raw material chemical composition values, in addition to equation (8).
Shown in No. That is, as a result of experiments, the present inventors found that the melting phenomenon of ore particles during the production of sintered ore occurs at 1100℃.
At this point, CaO in the raw material reacts to form calcium ferrite, creating an initial melt, and the melt progresses as the melt gradually erodes from the outer periphery of the ore particles inward. I found that. Therefore, the holding time t at 1100° C. or higher and the melting rate Q of the blended raw materials are expressed by the following equation (10). moreover,
The melting rate of the blended raw materials when held at 1100℃ or higher for 6 minutes is the melting rate qj of each single ore brand.
(1100°C or higher for 6 minutes) is expressed as equation (11) by taking a weighted average. Q=・(t/6)n ……(10) = 〓 ^j (qj・wj) ……(11) Where, t: Holding time over 1100℃ (minutes) n: Constant j: Indicates various brands of raw materials Index qj: Melting rate for ore brand j (excluding pores and voids) wj: Volume proportion of ore brand j in the blended raw materials Melting rate qj for each single ore brand when held at 1100℃ or higher for 6 minutes can be determined experimentally in the laboratory when raw materials arrive. An example of the measurement results is shown in the first section.
Shown in the table.

【table】

[Table] To summarize above, the method of the present invention uses pre-measured raw material physical property values (R _0.5 , Ai, ρ ₂ ), raw material blending ratio wi,
Moisture content w, filling bulk density ρ ₁ to initial diameter 0.5mm
Find the following porosity ε′, then the sintered cake shrinkage rate
The fluidity index η in the sintered layer is determined from the actual measurement of SR or the prediction of the raw material composition in the layer and the melting rate Q. From these values, the sintered ore product porosity ε is calculated, and this value is set to the target value. The raw material blending ratio or operating conditions are controlled accordingly. Next, an example in which the method of the present invention is applied to the DL type sintering machine shown in FIG. 5 will be described. Example 1 In this example, the raw material blending ratio was set freely, and the operating conditions were controlled so that the estimated sintered ore product porosity (ε) reached the target value. The rotation speed of the sintering blower 12 of the DL type sintering machine 10,
The operation was controlled by selecting the wind box damper 13, the angle (raw material layer height) of the cut-off plate 14, and the moisture content of the material in the surge hopper 15. The results of this operation are shown in FIGS. 6 and 7. FIG. 6 shows the results of determining the porosity ε of the sintered mineral product using equations (1) to (7) and controlling the operating conditions. Figure 7 is
The porosity ε of the sintered ore product was calculated from equations (1) to (7) and equation (9), and the results of controlling the operating conditions are shown. It can be seen that highly accurate control results are obtained in both cases. Example 2 In this example, the operating conditions were kept constant and the raw material blending ratio was controlled so that the estimated sintered ore product porosity ε was at the target value. Based on the physical properties of the raw materials shown in Table 2, the blending ratio of ores D and E, limestone, coke breeze, and return ore is determined so that the estimated sintered ore product porosity ε becomes the target value, and the sintering operation is started. was carried out. The results of this operation are shown in Figure 8. Furthermore, Table 3 shows a comparison between the conventional method and the method of the present invention. It can be seen that in this case as well, highly accurate operation results were obtained and variations in product quality were reduced.

【table】

【table】

【table】 [Brief explanation of drawings]

FIG. 1 is a graph showing the relationship between sintered ore product porosity and sintered ore quality. FIG. 2 is a process diagram showing the method of the present invention. FIG. 3 is a longitudinal cross-sectional view of the raw material packed bed. FIG. 4 is a graph showing the relationship between all pores and small pores in the raw material packed bed. Figure 5 shows the method of the present invention being applied.
Schematic diagram of the DL type sintering machine. FIG. 6 is a graph showing an embodiment of the method of the present invention. Figure 7 is a graph similar to Figure 6. FIG. 8 is a graph showing another embodiment of the method of the present invention. 10: DL type sintering machine, 12: Sintering blower, 1
3: Wind box damper, 14: Cut-off plate,
15: Sarge Hotupa.

Claims (1)

[Claims] 1. In the manufacturing process of sintered ore, the porosity of the raw material packed bed with a diameter of 0.5 mm or less is determined, the fluidity index of the sintered bed is determined, and the sintered ore is determined based on the porosity and fluidity index. Estimate the porosity of the finished product, and adjust the raw material blend ratio, firing blower rotation speed, wind box damper opening, cut-off plate angle, raw material layer height, or surge hopper so as to obtain the target porosity from the estimated porosity. A sintering operation method consisting of controlling the moisture content of the raw materials within.