JPH0742520B2 - Sintered ore manufacturing method - Google Patents

Description

TECHNICAL FIELD The present invention relates to a method for producing a sinter. More specifically, regarding the quality of sinter ore that has a large effect on the stability of the blast furnace operation and fuel ratio, such as low-temperature reduction powderability and reducibility, even if the raw material composition changes, etc. The present invention relates to a method for producing a sintered ore in which quality characteristics are controlled to fall within a desired range.

[Conventional technology]

Since most of the iron ore loaded into the blast furnace is sinter, the low-temperature reductive pulverizability and reducibility of sinter greatly affect the stability of the blast furnace operation and the fuel ratio. That is, if the low-temperature reductive pulverization of the sinter is remarkable, it is reduced and pulverized in the low-temperature region of the blast furnace (the region of the shaft upper layer of 300 to 700 ° C), and this sintered ore powder impairs the air permeability in the furnace. It causes unstable furnace conditions such as slipping and hanging. In addition, if the reducibility is low, the amount of gas reduced in the bulk state is reduced,
This means that the gas utilization rate of the blast furnace decreases, which in turn increases the blast furnace fuel ratio. Therefore, the low-temperature reductive pulverization property and the reducibility of sinter are important quality characteristics for blast furnace operation, and operation has been conventionally performed by setting the control target value.

Conventionally, in order to know whether or not this control target value is satisfied, a part of the produced sinter is periodically sampled, and the low temperature reduction powderability is the low temperature reduction powdering index (hereinafter referred to as RDI). Also, the reducibility is the rate of reduction (hereinafter referred to as RI)
We are conducting a test to measure as. In this case, the low temperature reduction dusting index (RDI) was calculated as follows: 500g of sinter ore sample was treated with reducing gas containing 30% of CO and the balance of N ₂ after reducing treatment at 550 ° C for 30 minutes.
It is placed in a barrel of 30 mmφ x 200 mmL, rotated at 30 rpm for 30 minutes to be pulverized, and its -3 mm (%) is measured.
The reduction rate (RI) has been tested in accordance with JIS M 8713.

[Problems to be solved by the invention]

Conventional control of low-temperature reductive pulverization property and reducibility of sinter is based on the measured value of the produced sinter, that is, the target value is compared with the measured value. If the difference deviates from the threshold value, feedback control is performed so that the manufacturing conditions of the sintered ore are adjusted so as to be close to the target value. Therefore, there is a large time delay, and the measured value is also obtained. It takes time and effort. For example, since many steps such as raw material mixing, mixing, sintering, crushing, and cooling are performed in the production of sinter, even if the process is adjusted at the time when the actual measurement value is obtained, there is a time delay. In addition, defective products will be generated during that period, and the yield will decrease, and it will be difficult to make accurate adjustments. In addition, even in the measured values of the low temperature reduction powdering index and the reduction rate, many tests must be performed to know whether they are abnormal values. Therefore, the conventional control of low-temperature reductive pulverization property and reducibility of sinter is a very complicated and labor-intensive task, and moreover, there have been many problems in terms of production yield and accuracy of the sinter.

The object of the present invention is to solve such a problem.

[Means for solving problems]

In order to achieve the above-mentioned object, the present invention predicts the RDI value and RI value of the product sintered ore at the stage of manufacturing the sintered ore, and operates by making the predicted values approach the target values. The present invention aims to achieve the above-mentioned object, and provides a method for producing a sintered ore by feed-forward control using a mixing ratio of sintering raw materials and an amount of water at the time of granulation as an operation amount.

That is, in the present invention, the sintering raw material is loaded into a predetermined sintering machine,
When manufacturing iron ore sinter while maintaining operating conditions such as the pallet speed of the sinter, suction air volume, and sintering raw material loading layer thickness within the set range, (1) mixing ratio of sintering raw materials The pseudo-particle size after granulation was calculated from the water content during granulation, the high temperature holding time during sintering was predicted from this pseudo-particle size, and the mixing ratio and chemical composition of the sintering raw materials were used to predict the sintering temperature. The Al ₂ O ₃ / SiO ₂ ratio of the molten part is calculated, and the low temperature reduced powdering index of the sinter is predicted from the high temperature holding time and the Al ₂ O ₃ / SiO ₂ ratio. Of the sintering raw material and / or the amount of water at the time of granulation are adjusted so that the value of the sintering raw material approaches the target value. The pseudo particle size after granulation was calculated from the water content at the time of granulation, and the maximum temperature during sintering was calculated from this pseudo particle size. The porosity after sintering was predicted from the relationship with the amount of void reduction, and the area ratio of the calcium ferrite phase and the area ratio of primary hematite in the sinter mineral were calculated from the mixing ratio of the sintering raw materials. Predict the reduction rate of sinter from the porosity, the area rate of the calcium ferrite phase in the sintered ore mineral, and the area rate of primary hematite, and mix the sintering raw materials so that the predicted reduction rate approaches the target value. The present invention provides a method for producing a sinter, which is characterized by adjusting the ratio and / or the water content during granulation.

The contents of the present invention will be specifically described below based on the tests conducted by the present inventors.

FIG. 1 shows the sintering pot apparatus used for the test. Reference numeral 1 denotes a sintering pot, in which a sintering raw material 3 is loaded on a rostrur 2 and is sucked by an air blower 4 from below the rostrur 2. At that time, a damper 6 is provided in the air chamber 5 below the rustle 2, and the suction air volume is adjusted by the device of the damper 6. In sintering, the coke existing on the upper surface of the sintering raw material 3 is ignited by propane gas, and the sintering raw material is fired and solidified while being sucked downward by driving the exhaust fan 3. As a result of conducting many sintering tests with such a test apparatus, first, the low temperature reduction powdering index (RDI) was determined by the sintering temperature holding time during sintering and the Al ₂ O ₃ / SiO ₂ ratio of the molten part. It was found to have a close relationship.

Figure 2 shows the results of examining the relationship between the high temperature holding time during sintering and RDI with the mixing conditions of the sintering raw materials kept constant. That is, by keeping the mixing conditions of the sintering raw materials the same and changing the suction air volume by the operation of the damper 6 and the granulation conditions (pseudo grain size of the sintering raw materials), the sintering raw materials are maintained at a high temperature of 1100 ° C or higher. Time (below, + 1100 ℃
(Holding time) is changed and this + 1100 ° C holding time
It is a plot of the relationship with RDI (-3 mm% by the above-mentioned test). It can be seen from Fig. 2 that RDI increases with a certain relationship as the holding time (min) of + 1100 ° C increases.

FIG. 3 shows the measurement results of the melting ratio at the time of sintering for each grain size of each iron ore brand in the sintering raw material. As can be seen in Fig. 3, the melting ratio differs depending on the particle size, and the degree of melting also differs depending on the brand. Usually, the generation of the melt in the high temperature region during sintering starts from the surface layer surface of the sintering raw material, and even if the fine particles are completely melted, the coarse particles are not melted in the central part and the sintering is completed. The results in Fig. 3 show that the finer particles increase the melting rate, and the melting rate of each brand varies depending on the cause of the composition such as the density of the ore and the difference in the content even if the grain size is the same. Shows that they are different. The present inventors calculated the chemical composition of the fusion part at the time of sintering from the melting ratio and the chemical composition for each particle size of various sintering raw materials used in the test, and detailed the relationship between the calculated chemical composition and RDI. As a result, it was found that RDI has a close relationship with the Al ₂ O ₃ / SiO ₂ ratio in the fusion zone. FIG. 4 shows the relationship.

As can be seen in Fig. 4, when various sintering raw materials were sintered at a constant + 1100 ° C holding time, the RDI of the sintered material had a constant relationship as the Al ₂ O ₃ / SiO ₂ ratio in the melt increased. Increase with. Therefore, from the relationship between this FIG. 4 and the above-mentioned FIG. 2, the low temperature reduction powdering index (RDI) of the sinter is
It is possible to make a prediction based on the + 1100 ° C holding time and the Al ₂ O ₃ / SiO ₂ ratio of the fusion zone.

On the other hand, the + 1100 ° C holding time has a correlation with the pseudo grain size of the sintering raw material if the sintering conditions such as the air flow rate and layer thickness are unchanged. FIG. 5 shows this correlation. Here, the pseudo particle size after the mixing and granulation of the sintering raw material can be obtained by the following procedure.

In the grain size composition of the sintering raw material obtained from the mixing ratio, the −0.25 mm portion and the 0.25 to 0.5 mm portion that adhere can be empirically expressed by the following equations (1) and (2), respectively.

Proportion (%) = 0.49X + 2.69 of -0.25 mm part in sintering raw material due to mixed granulation. (1) 0.25 to 0.5 mm part in sintering raw material becomes adhering powder due to mixed granulation. The ratio (%) = 1.79X−285.04 (2) where X = 190 + 19a−11a ² and Is.

The particle size composition of the core particles in the sintering raw material = the particle size composition of the sintering raw material-the particle size composition of the adhering powder (3), and the pseudo particle size is the pseudo particle size = the average diameter of the core particles + 18.13 x nuclei. Adhesion amount of particles per unit surface area (g / cm ² ) ...
(4) can be obtained by

Therefore, the pseudo particle size can be calculated from the mixing ratio of the sintering raw materials and the water value at the time of the mixed granulation, and the + 1100 ° C holding time can be calculated from this pseudo particle size. RDI can be predicted from the Al ₂ O ₃ / SiO ₂ ratio.

On the other hand, regarding the reducibility, which is another quality characteristic of sinter,
As a result of diligent research on means for predicting this, it was found that RI can be described by the mineral phase and porosity of sinter. That is, the present inventors have found that RI can be described by the following equation (5) as a result of detailed tests and analyzes of various sintered ores.

RI (%) = a + bx + cy + dz (5) where x: area ratio of calcium ferrite in the mineral phase of the sintered ore (%) y: area ratio of primary hematite in the mineral phase of the sintered ore (%) Z : Porosity (%), a = 15.246, b = 0.193, c = -0.303, d = 0.967.

Therefore, if the independent variables x, y, and z can be estimated by the manipulated variables such as the mixing ratio of sintering raw materials and the moisture value during granulation,
RI values will be predictable.

According to a number of tests conducted by the present inventors, the area ratio of calcium ferrite in the mineral phase of the sintered ore (hereinafter referred to as cf (%)) and the area ratio of primary hematite in the mineral phase of the sintered ore (hereinafter pr It has been found that (%) is estimated by the following procedure.

Figure 6 shows that using only a single brand of iron ore in the sintering raw material, adding silica sand and limestone so that SiO ₂ = 5.5% and basicity = 1.6, and further mixing 4% of powder coke and firing. It shows the cf (%) and pr (%) of the sintered ore obtained by binding each brand. As seen in Figure 6, cf
(%) And pr (%) of mineral phases have a certain value that varies depending on the iron ore brand. Therefore, when blending iron ore of these various brands, a predetermined amount according to the blending ratio of that brand is specified. By adding weight, cf (%) in sinter
And pr (%) can be calculated.

Regarding the porosity, since a melt is generated during sintering and this melt penetrates into the voids, the voids in the sintered ore are smaller than when the sintering raw material was charged. The porosity at the time of charging the raw material can be calculated from the charging amount (volume, weight) and the true specific gravity of the raw material. To estimate the porosity of the sintered ore after sintering, it is necessary to use the melt generation during sintering. It is necessary to quantify the amount of void reduction.

FIG. 7 shows an outline of the apparatus used by the present inventors for the actual measurement in the void. This equipment is for heating the standard sample 11 and the sample under test 12 installed inside the electric furnace 10 while applying a constant load, and comparatively measuring the amount of void reduction with temperature rise. A support tube that holds the
Is a micrometer, 16 is a balance weight, 17 is a weight, 18
Indicates the core, and 19 indicates the differential transformer field.

Fig. 8 shows that this tester used SiO ₂ = 5 for each iron ore brand.
The results of measuring the amount of void reduction at each temperature by mixing silica sand and limestone so that the basicity is 5% and 1.6 are shown. As shown in FIG. 8, the amount of void reduction with sintering temperature varies depending on the origin of the ore such as the density of the ore and the difference in the content of the ore, but shows a constant value for each brand. Therefore, when compounding various ores, the amount of void reduction during sintering can be calculated by adding weights according to the compounding ratio of the ore brand, and the porosity during raw material charging and voids during sintering described above can be calculated. The porosity of the sintered ore can be estimated from the amount of decrease.

The maximum temperature during sintering is estimated as shown in Fig. 9,
A certain correlation is observed with the pseudo particle size at the time of mixed granulation of the sintering raw materials. Therefore, as described above, since the pseudo particle size can be calculated from the mixing ratio of the sintering raw material and the water content, the maximum temperature during sintering can be estimated from this pseudo particle size.

From the above, also for RI, the cf (%) and pr (%) obtained from the mixing ratio of the sintering raw materials, and the maximum temperature during sintering calculated from the mixing ratio and the water content during mixed granulation were used. It can be predicted by using the porosity of the sintered ore obtained by using.

Example 1 A sintering raw material having a mixing ratio shown in Table 1 was granulated with a water content of 6.0%,
The RDI and RI of the sintered ore that would be obtained by sintering this are predicted and compared with the measured values of the RDI and RI of the sintered ore obtained by actual sintering.

The saturated moisture content of the sintering raw material is calculated by weighted average using the saturated moisture content and the blending ratio of each brand that was obtained in advance (6)
Calculated according to the formula, 12.80% is obtained.

Therefore, when the value of a in equations (1) and (2) in the text is calculated from this saturated moisture value, it becomes -0.4, and
The value of X becomes 180.6. Therefore, the proportion (%) of the −0.25 mm portion in the sintering raw material according to the equation (1) that becomes the adhering powder by the mixed granulation is 91.20%, and the 0.25 to 0.5 mm portion in the sintering raw material according to (2) is The ratio of adhering powder due to mixed granulation is calculated to be 49.14%.

The particle size composition (true particle size) before granulation with the compounding ratios in Table 1 was obtained by measurement, and is as shown in Table 2. Since the ratio of the adhering powder due to the mixed granulation is known, the part excluding the adhering −0.25 mm and 0.25 to 0.5 mm parts from the true particle size in Table 2 becomes the core particle. Therefore, the particle size composition of the core particle is It can be expressed as in Table 3. Then, the harmonic mean particle size of the core particles is calculated as 1.116 mm from the following equation (7).

Now, assuming that 100 g of the sintering raw material is mixed and granulated with 6.0% moisture, the amount of the attached −0.5 mm portion and the surface area of the core particles are 24.3 g and 1 from the following equations (8) and (9), respectively.
It can be calculated as 017.7 cm ² .

-0.5mm adhesion amount = 8.9 x 0.492 + 21.8 x 0.912 = 24.3 (g) ... (8) Surface area of core particles = πd ² n ≈ 1017.7cm ² ...... (9) where n (number) = 6W / (πd ³ ρ), W (weight) = 1
00-24.3, ρ (specific gravity) = 3.9, d (particle size) = 0.1116 cm.

Therefore, the adhered amount per unit area is 24.3 / 1017.7 = 0.0
It becomes 23 g / cm ² , and the pseudo particle size after granulation can be calculated as 1.116 + 0.43 = 1.546 mm from the formula (4) in this text, and using this pseudo particle size, hold + 1100 ° C from Fig. 5 and Fig. 9. Time is about 1.52
The maximum temperature can be estimated to be 1260 ℃.

On the other hand, Al ₂ O ₃ / in the fusion zone when the sintering materials in Table 1 were sintered
The SiO ₂ ratio was 0.293 by analysis. Al _{2 in} this fusion zone
From the O ₃ / SiO ₂ ratio and the above + 1100 ° C holding time, the following (1
The RDI is calculated as 32.96 by the equation (0).

RDI = (Al ₂ O ₃ / SiO ₂ ) × 27.7 + 27.0 + 2.9 × (+ 1100 ° C holding time −2.25) (10) = 32.96 Next, predict RI.

First, the estimation of cf (%) and pr (%) of sinter is (11)
Equation (12) and equation (12).

cf (%) = a x 0.458 + b x 0.346 + c x 0.341 + d x 0.287 + e x 0.222 ...... (11) pr (%) = a x 0.038 + b x 0.044 + c x 0.032 + d x 0.117 + e x 0.211 ...... (12) However, a, b, c, d, and e are the proportions of each brand of iron ore, which is the main raw material, in the main raw material.

The maximum temperature of the sintering raw material is 1260 ° C from the pseudo grain size as described above.
Therefore, if the void reduction amount is calculated from the relationship between the sintering temperature and the void reduction amount in Fig. 8 using the values of a, b, c, d, and e in Eq. (11), the void reduction amount is It becomes 5.21%. On the other hand, the porosity when charging the sintering raw material was 55.5% by actual measurement. Therefore, it can be estimated that the porosity of the sinter is 50.3%.

Therefore, cf (%) = 32.567, pr (%) =
7.864, RI = 67.7 by substituting porosity = 50.3%
A predicted value of 9% is obtained.

RDI and RI of the product sinter obtained by actually manufacturing sinter
The measured value of RDI = 33.4%, the measured value of RI = 6
It was 8.2%.

Example 2 The same procedure as in Example 1 was repeated except that the mixing conditions of the sintering raw materials and the water content at the time of granulation were changed to obtain the predicted values of RDI and RI, and the obtained sintered ore was obtained. The measured values of RDI and RI were measured. These predicted and measured values are shown in Figs. 10 and 11
As shown in the figure. As is clear from these results, the predicted value agrees very well with the actual value. Therefore, according to the present invention, the mixing ratio of the sintering raw material and the water content at the time of granulation are used as the manipulated variables for the feed value. Target RD by word control
It can be seen that it is possible to produce sintered mineral products with I and RI values.

[Brief description of drawings]

Fig. 1 is a schematic cross-sectional view of a sintering pot device used in the test of the method of the present invention, and Fig. 2 is a holding time at + 1100 ° C and low temperature reduction powdering index (RD).
Fig. 3 is a diagram showing the melting ratio at the time of sintering of iron ore brands for each grain size, and Fig. 4 is the Al ₂ O ₃ / SiO ₂ ratio and low-temperature reduction powdering index of the molten part. Fig. 5 is a relational diagram with (RDI), Fig. 5 is a relational diagram between pseudo particle size and + 1100 ° C holding time during granulation of sintering raw material,
Fig. 6 shows the cf (%) and pr (%) for each brand when the iron ore in the sintering raw material is a single brand, and Fig. 7 is the heat used to measure the void reduction during sintering. A schematic cross-sectional view of a mechanical analyzer, FIG. 8 is a relationship diagram between the sintering temperature and the amount of void reduction for each iron ore brand, and FIG. 9 is a relationship diagram between the pseudo grain size and the maximum temperature during sintering, Figure 10 shows the relationship between the predicted RDI value and the measured RDI value, No. 11
The figure shows the relationship between the predicted RI value and the measured RI value.

 ─────────────────────────────────────────────────── ─── Continuation of the front page (72) Inventor Harumi Ishii 11-1 Showa-cho, Kure City, Hiroshima Prefecture Nisshin Steel Co., Ltd. Kure Research Institute (72) Inventor Susumu Kamio 11-11 Showa-cho, Kure City, Hiroshima Prefecture Kure Research Institute, New Steel Co., Ltd.

Claims (2)

[Claims] 1. A sintering machine is loaded with a sintering raw material, and the operating conditions such as the pallet speed of the sintering machine, the suction air volume, and the thickness of the sintering raw material loading layer are maintained within a set value range. In producing a sinter, the pseudo particle size after granulation is calculated from the mixing ratio of sintering raw materials and the water content at the time of granulation, and the high temperature holding time during sintering is predicted from this pseudo particle size. Then, determine the Al ₂ O ₃ / SiO ₂ ratio of the molten part during sintering from the mixing ratio and chemical composition of the sintering raw material, and from the high temperature holding time and the Al ₂ O ₃ / SiO ₂ ratio, the low-temperature reduced powder of the sintered ore. Of the sintering index and predict the low-temperature reduction powdering index to approach the target value.
Alternatively, a method for producing a sintered ore, which comprises adjusting the amount of water during granulation. 2. The sintering raw material is loaded into a predetermined sintering machine, and the operating conditions such as the pallet speed of the sintering machine, the suction air volume, the thickness of the sintering raw material loading layer, etc. are maintained within a set value range. In producing sinter, the pseudo particle size after granulation was calculated from the mixing ratio of the sintering raw materials and the water content during granulation, and the maximum temperature during sintering was calculated from this pseudo particle size. The porosity after sintering was predicted from the relationship between the maximum temperature and the amount of void reduction during sintering, and the area ratio of the calcium ferrite phase and the area of primary hematite in the sintered ore mineral were estimated from the mixing ratio of the sintering raw materials. The reduction ratio of the sintered ore is calculated from the porosity, the area ratio of the calcium ferrite phase in the sintered ore mineral, and the area ratio of the primary hematite so that the predicted value of this reduction ratio approaches the target value. Adjust the mixing ratio of sintering raw materials and / or the water content during granulation Method for producing sintered ore according to claim and.