JPH0328331A - Pretreatment of raw material for sintering - Google Patents

Abstract

PURPOSE:To reduce the amt. of a binder, etc., used and to improve the productivity of sintering by rolling and briquetting raw materials for sintering flaked after compacting and kneading under vibration and by sintering the resulting minipellets and other raw materials with a sintering apparatus. CONSTITUTION:Raw materials for sintering on a belt conveyor 3 and a compacting medium are charged to a compacting, plasticizing and kneading space 30, where the raw materials are kneaded under 3-10g vibrating force (g is acceleration of gravity) and flaked. The resulting flakes are fed into a granulator 40, rolled and briquetted under 3-6g vibrating force to obtain tough minipellets. These mini-pellets are mixed with other raw materials and fed into a sintering apparatus 17, where a layer of the raw material mixture is dried with hot exhaust air fed from a preheating hood 50.

Description

[Detailed description of the invention]

[Industrial Field of Application] The present invention relates to a method for pre-processing sintering raw materials when iron ore or the like is fed to a DL sintering machine to form sintered ore.

[Conventional technology 1] Figure 17 is an overall flowchart of a conventional DL type sintering machine. The sintering raw material blending tank l stores sintering raw materials (sintered ore, limestone, coke, quicklime, and return ore), and after being cut out in a fixed amount by the constant feeder 2 installed at the bottom of the blending tank. , are stacked and blended in multiple layers on belt conveyor 3. The raw materials are mixed in drum mixer 4.
Add 4 to 5% moisture and mix and granulate. The granules are conveyed to the ore feed hopper l4, and then transferred to the lower drum feeder 15j.
5 and the feed shoe 1-16 to the pallet 18 of the sintering machine 17. Thereafter, the coke in the raw material is ignited by the ignition burner 19, and sintering progresses. In addition, a preheating hood 23 is disposed in front of the ignition burner l9, and 2 liters of exhaust gas from the sintering cooler 20 is supplied via a booster blower 22, and the raw material before sintering is preheated and dried by the 2 liters of exhaust gas. There are also examples. In this case, fine iron ore (hereinafter referred to as PF) is also used, in which 60% or more of the particles are less than 60 μm. The problem in this case is that if PF is used in a ratio of 10% or more to the main raw material, ventilation of the sintering bed will be inhibited and productivity will decrease. Or a binder to improve ventilation (
There are drawbacks such as a large amount of lime (quicklime, slaked lime, etc.) being required, and a rise in binder costs. In order to solve the above problems, PF (approximately 60%) and the core raw material (return ore or iron ore approximately 40%) are pre-granulated using a drum mixer or disc pelletizer, and then normal sintering raw materials are used. A nuclear granulation method of PF has been proposed, in which the mixture is mixed with iron, charged into a drum mixer, and mixed and granulated (iron and w4:vo
l. 71. NalO (1985)? Granulation of sintering raw materials and its role”). In this case, since a core raw material is required, a mixer with a capacity 1.4 times larger is required for the same PF blending ratio, resulting in high equipment costs. As yet another method, approximately 40% by weight of PF is blended into a normal sintering raw material (60% by weight of fine ore), and the mixture is fed to a disk-shaped beretizer and mixed and granulated to form a pellet of 5 to 10 mm. After that, fine coke is added, and the outer periphery of the pellet is sprinkled with exterior coke, which is then transported to the feed hopper.
A method of sintering is presented (Iron and Steel: vol. 73
, Ikll (1987) li'Basic research on production conditions and quality evaluation of new agglomerated ore for blast furnaces'). The disadvantage of this method is that the apparent density of the green balls is low and the crushing strength of the balls is low, so they are easily broken during the transportation process to the sintering bed, which impedes the air permeability of the bed. Also,
If the average particle size of the finished product is 8 to 10 mm and requires a carbon coating, or if the coating coke does not adhere uniformly to the outer periphery of the pellet, the inside of the ball may not melt and become a single pellet during the crushing process or return ore. There are drawbacks that can easily occur. On the other hand, although it is an old technology, the wet-type grinding and kneading method of granulation and molding (Japanese Patent Publication No. 43-6256) is known. After crushing, moisture adjustment, and mixing, the green pellets are granulated using a vertical, cylindrical, or other type of granulator. This method accomplishes the traditional wet or dry grinding process and moisture adjustment mixing process in one step in a wet state.
This method involves transferring rods or balls by rotating a rod mill or ball mill, and the production volume is low considering the size of the equipment, the power consumption is high, and it is currently not economical. [Problem to be Solved by the Invention J] In view of the above-mentioned circumstances, the present inventors have conducted various studies and found that a large number of consolidation media are given circular motion vibrations and strongly vibrated, and the sintering raw material is placed in the gaps between the consolidation media. High efficiency by supplying
Vibration consolidation plasticization and kneading can be performed at high production volumes, and then this raw material is subjected to vibration tumbling agglomeration, making it possible to produce strong mini-pellets in the desired particle size range with high efficiency. I discovered that. Furthermore, according to this method, even PF containing 60% by weight or more of particles less than 60 gm can be firmly milled to a desired particle size. The present invention further provides that when the mini-pellets obtained as described above are mixed with other sintering raw materials and sintered, a preheating step is added to the raw materials to reduce the moisture content of the raw materials on the surface layer of the bed and form pseudo particles. We have discovered that productivity can be significantly improved by preventing the collapse of the material and improving breathability. It is an object of the present invention to provide the above method. [Ten Steps to Solve the Problems] The present invention pre-processes the sintering raw material to be supplied to the DL sintering machine. (1) Charge the sintering raw material together with a consolidation medium into a consolidation plasticization kneading space, The first step is to apply a vibration force of 3 g to Log (g is the acceleration of gravity) and perform vibration consolidation kneading to form flakes; a second step of dynamic agglomeration and granulation into strong mini-pellets; (1) mixing other raw materials with the raw materials granulated in the li3 and second steps and supplying the mixture to a sintering machine; This method of pre-processing sintered raw materials is characterized by the third step of drying the raw material layer with hot air supplied from a preheating hood provided in front of the ignition furnace. Furthermore, the preheating hoods are installed in multiple stages so that they can slide freely in the same extension storage direction, the number of movable preheating hoods is adjusted according to the moisture content of the mixed raw materials, and the position of the ignition furnace is moved closer to the preheating hood side to improve ventilation. Improvements can be made. [Operation] In the first step of the present invention, by applying an excitation force that causes a strong circular motion to a large number of consolidation media housed in a container, the consolidation media rotate in the same rotational direction, and this When the sintering raw material is charged into a container, the particles of the sintering raw material existing between the consolidation media are consolidated, sheared, transferred, compressed, kneaded, etc. due to the relative movement of the surfaces of adjacent consolidation media in opposite directions.
It provides a comprehensive effect such as crosstalk, squeezes out the internal moisture of the particles, and uniformly spreads the surface moisture. As a result, the particles adhere to each other in the form of flakes and become plasticized. This will be explained using Figure 7. (a) shown in Figure 7
As shown in the figure, it is known that when a fine powder raw material with a certain moisture content is stored in a container and an excitation force is applied in the direction of compressing it, the density of the fine powder inside the container increases. At this time,
The filling state of the particles changes depending on the moisture content of the fine powder raw material in the container and the magnitude of the applied vibration energy, and the density increases according to this filling state. The graph in Figure 7 shows this. When the water content of the fine powder raw material is low, air spaces exist between the powder particles, and the powder is in the state of a dry mixture. When the water content of the fine powder raw material is increased and it is vibrated, the water is uniformly spread over the surface of the particles, the air gap disappears, and the entire granule becomes sticky and plasticized.
The dry density of the fine powder raw material approaches the curve with zero porosity. As the water content increases further, the powder becomes a mushy slurry. This slurry state has less moisture and is empty.
The plastic state with the least amount of voids in the gas layer is called the cavillary region, where the dry density of the plastic body is the highest and forms a dense flake. Powder in this cavity region can be obtained by applying vibrational compression with the most appropriate water content ratio and appropriate energy depending on the properties of the granules. The first step of the present invention utilizes this principle, and involves first processing the body formed into flakes in the cavity region by performing vibration consolidation plasticization kneading, and then processing the structure into flakes in the second step. Powder is transferred and granulated. Therefore, in the first step, the optimum water content ratio and optimum excitation force according to the characteristics of the fine powder raw material are applied to the fine powder raw material, so that the water droplets on the particle surface are uniformly dispersed on the particle surface, and a thin water film is formed on the particle surface. The particles are made to be in an elongated state, and the porosity due to air between the particles is reduced to form a densely packed state, so that the filled state becomes a cavillary region and a densely packed compacted and plasticized flake is formed. Next, in the second step, the packing density is increased by applying transfer by strong vibration to the 5-consolidated and plasticized raw material.
Moisture seepage to the surface, adhesion due to this moisture, and particle size growth occur. The amount of water added should be the difference between the water content of the raw material and the optimum water content ratio for granulation, which is 0 to 2%. That is, when the entire amount of sintered raw materials having a wide particle size range is subjected to vibration consolidation, the optimum water content ratio is adjusted to 5 to 7% compared to the moisture content of the raw materials of 5 to 6%. In addition, when granulating only PF, PF is 8 to 11%.
The optimum moisture content is 9 to 12%. Furthermore, Fig. 13 shows the relationship between the excitation force of the granulator and the yield for the optimum particle size of the sintering raw material, 2 to 8 mm. It can be seen that rolling agglomeration is better. In other words, in order to obtain a yield of 60% or more, it is necessary to granulate with an excitation force of 3 g or more.
At 6 g or more, the granulation effect is saturated. In addition, in the first and second steps, the moisture content of the raw materials is
The added moisture exceeds the appropriate content for sintering operations. Therefore, a drying process for the raw materials is added as a third process, in which the raw materials supplied to the sintering machine are preheated and dried before the ignition furnace.The function of this drying process is as follows. That is, from the upper layer of the sintering bed raw material, for example, 200°C
When the hot air of It moves from point A to point B along the road and is humidified. At the same time, the gas temperature drops from 200°C to 50°C, and the humidity reaches saturation at the point where it intersects the saturation curve. If the raw material temperature and gas temperature are further lowered than point B, moisture will condense and the pseudo particles will collapse, impeding air permeability. Therefore, by pre-drying the surface layer of the raw material with hot air before ignition, it is possible to reduce the amount of condensed water and improve air permeability. [Example J FIG. 1 shows a process diagram showing the first, second and third steps and sintering step of the present invention. The raw material that is quantitatively cut out onto the belt conveyor 3 by the constant feeder 2 from the sintering raw material blending tank 1 is turned into mini pellets via the vibrating kneader 30 and the vibrating granulation rock 40, and is mixed with other sintering raw materials. are mixed and transported to the feed hopper l4, and charged to the pallet l8 of the sintering machine 17. The sintering raw material on the pallet 18 is dried to a predetermined moisture content in a preheating hood 50 disposed in front of the ignition burner 19, and then sintered. Note that, as in the conventional example, the exhaust gas 21 from the sintering cooler 20 is supplied to the preheating hood 50 via the booster blower 22. Each of these steps will be explained below. FIG. 2 shows an example of an apparatus that can suitably carry out the first and second steps of the method of the present invention. In this embodiment, the vibration kneader 30 right and the vibration granulator 40 are both drum-type in shape, and the vibration kneader 30 houses a large number of rods as the consolidation medium 3L. The sintering raw material conveyed by the belt conveyor 3 is supplied to the vibrating kneader 30. As shown in FIG. 3, the vibrating kneader 30 has a large number of rods (consolidation body 34) in a drum 3l.
is housed, and a vibrator 32 is attached to both sides of the drum 3l, which is placed on a spring 33. The vibrator 32 is attached to both sides of the drum 3l so as to be balanced and rotate synchronously.
The motor has variable speed. The vibrator 32 can apply circular vibrations to the drum 31 and the consolidation medium 34 in a wide range of accelerations in cooperation with the spring 33. The relationship between the rotational speed of the motor and the acceleration is determined from α = ω2゛x = (2π/60)'N' x, and is as shown in Fig. 8. However, α: Vibration acceleration ω: Angular velocity X: Amplitude N: Number of rotations. As shown in FIG. 4, the vibration granulator 40 is a vibration kneader 30.
A sintering raw material that has been consolidated, plasticized, and kneaded is supplied from the machine, which is then vibrated and granulated by rolling to form mini-pellets with a uniform particle size of 2 to 8 mm. The specifications of the vibrating kneader and vibrating granulator in this example are as follows. Vibration kneading machine specifications Drum: Horizontal cylindrical vibration method: Circular vibration Excitation force: 3 to tog (g is acceleration of gravity) Amplitude: Stroke 5 to 20 mm Frequency: 500 to 200 rpm Rod amount: drum internal volume lO%~50% Rod diameter:
10mm - 100mm Powder residence time: 20 seconds or more Vibration granulator specifications Vibration method Two-circle vibration Excitation force: 3 to 6 g (g is the acceleration of gravity) Amplitude Two strokes 5 to 15 mm Frequency: 500 to 1,500 rpm Residence time of powder: 20 seconds or more Figures 5 and 6 show side views of an example of an apparatus that can suitably carry out the third step of the present invention.
In this embodiment, three stages of preheating hoods are provided, and FIG.
Figure 6 shows an example in which three hoods are used, with hood B and hood C stored in hood A and used as one preheating hood. FIG. 6 shows that after the telescopic tube 53 is contracted by the cylinder 52 and the B hood and hood C are pulled up and retracted, the B hood and the C hood are stored in the A hood. Only one burner is shown, and the ignition burner l9 mounted on the truck is shown close to the A hood. In this way, the preheating hood is a moving hood type that can be changed according to the moisture content of the raw material, and the amount of blown gas is also controlled by using the booster blower 22 as V V V F (variable
voltage variable frequency
y inverter ) is made variable by control.
Furthermore, the temperature of the blown gas is 300-350℃ when using the gas at the inlet of the exhaust heat boiler of the sintering cooler, and 200-250℃ when using the gas at the fan outlet of the cooling zone.
It can be varied within the range of ~350°C. As shown in Figures 5 and 6, the ignition furnace is mobile, so in the example in Figure 5 the preheating hood can be moved sufficiently for drying, and in the example in Figure 6, the preheating hood can be moved sufficiently for drying. It becomes possible to ignite the sintering raw material immediately after the drying process using a single preheating hood, making it possible to perform sintering operations with high productivity. Next, examples of the method of the present invention will be described. Inner diameter 194 mm $ x length 494 mm I2 (diameter length ratio 2.5
)． Steel rods of 30 mm diameter were charged into a cylindrical drum with an internal volume of 15 I2 so that the filling rate was 25 to 30% of the internal volume of the drum, and L2 t/h of sintering raw material was supplied, with an amplitude of 7 m.
m. Consolidation, plasticization, and kneading were performed by applying a circular motion with an excitation force of 6 g, and then the raw materials were fed into a cylindrical drum of the same size, and granulation was performed by applying a circular motion with an amplitude of 7 mm and an excitation force of 4 g. Figure 9 shows the particle size distribution of the finished product when the entire amount of raw material for sintering with a normal particle size distribution is granulated. As a comparative example, Figure 9 shows a comparison of the particle size distribution of granules produced using a drum mixer using the same raw materials. Note that in this example, the water content was 6.2%, crosstalk, and the total granulation time was 1 minute, and in the comparative example, the water content was 6.5%, and the granulation time was 5 minutes. Next, among the raw materials for sintering, fine powder raw materials (-125 μm is 90
% by weight or more) was mixed in advance by the method of the present invention, granulation time was 1 minute, water content was 9.5%, and lO. Figure 10 shows the particle size distribution when granulated at 5%. FIG. 10 shows, as a comparative example, the particle size distribution of granulated products granulated using the same raw material using a disc veretizer for 5 minutes and water content ratios of 10.5% and 11.5%. Next, when the raw material having the pre-granulation particle size of curve A shown in FIG. 11 was granulated using a disc veretizer, the particle size distribution after granulation was curve B. In the example of the present invention, curve C was obtained. It is clear from FIGS. 9 to 11 that according to the present invention, granules with a particle size of 2 to 8 mm can be obtained with a high yield. Next, Figure 12 shows the apparent density and crushing strength of the granules when the excitation force of the consolidated plasticized mixture was varied.
In addition, the density and crushing strength of the granules of the comparative example are also
It is shown in Figure 2. The bulk density of the raw material before granulation was 2-5 g/crd, and the dry apparent density of the granulated product granulated with a disc veretizer was 3.1. On the other hand, in the examples, the apparent density was very dense, ranging from 4.4 to 5.6, depending on the vibration acceleration. In addition, the crushing strength of the granules (wet balls) granulated with the disk pelletizer was approximately 70 g/piece, whereas in the examples, the crushing strength was approximately 130 to 150 g depending on the vibration acceleration.
/ pieces, which was extremely strong. From Figure 12, it can be seen that when the excitation force of the consolidation plasticization kneader is less than 3g, the consolidation granulation effect is small, and when it exceeds 1Og, it becomes saturated. Next, the third step, the drying step, will be explained. When hot air temperature tg + pallet speed V raw material layer thickness ventilation speed pallet width H is hot air humidity (kg/water = 200°C p = 2.5 cm + win = 700mm = l/sec = 5m/kg/air), Figure 15 shows the behavior of moisture in the bed at the exit of each constant drying zone (T, = 4m, 6m, 8m). It can be seen that the rate of decrease in moisture is greatest when L = 8 m. Table 1 is obtained by calculating the amount of moisture loss by graphically integrating FIG. 15. The results of the pot test in Table 1 show that when the sintered raw material was air-dried before ignition, the effect of improving the ventilation of the sintering bed as shown in FIG. 16 was obtained. In the drying zone L = 8 m, Table 1 shows that the amount of moisture decrease is Δ1.84, and it is possible to significantly reduce binder and fuel costs. These improvements in sintering productivity are approximately 1
It is 7%. [Effects of the Invention] In the method of the present invention, the sintering raw material is vibrated, compacted, plasticized and kneaded, and then granulated by vibratory rolling, so that the following excellent effects are achieved. ■Water is uniformly dispersed during the consolidation, plasticization, and kneading process, so
Can be granulated with low moisture content. ■Since the raw materials are compacted, plasticized, and kneaded, it has become possible to granulate strong mini-pellets with a uniform particle size and high packing density. ■Moisture rises to the surface due to vibration and can be effectively used for granulation. ■It equalizes the moisture content and makes the particle size distribution of the granules uniform. ■Pelletization time is shortened due to forced granulation. For this reason,
The equipment can be made smaller and consume less power than before because it processes the same amount. Furthermore, preheating hoods are installed in multiple stages, and the number of preheating hoods that can be moved is adjusted according to the moisture content of the mixed raw materials, and the ignition furnace is positioned close to the preheating hood, thereby preventing pseudo particles from collapsing in the humid zone. Air permeability is improved, and therefore fuel consumption and binder costs are reduced, and sintering productivity can be significantly improved.

[Brief explanation of drawings]

Figures 1 to 6 are explanatory diagrams of an apparatus that can suitably carry out each step of the present invention. FIG. 3 is a cross-sectional view of the vibration consolidation plasticization mixer that carries out the first step, and FIG. 4 shows a partially cutaway perspective view of the device that carries out the second step. Figures 5 and 6 are side views including a partial cross section of the dryer that carries out the third step, and Figure 5 is an example in which each hood is extended. , 6th
The figure shows an example in which the hood is shrunk into one unit, Figure 7 is an explanatory diagram explaining the principle of the present invention, Figure 8 is a graph showing the relationship between the rotational speed of the motor and the acceleration of vibration, and Figures 9 to 11. The figure is a graph showing an example of the particle size distribution of Examples and Comparative Examples, Figure 12 is a graph showing the apparent density and crushing strength of the products of Examples and Comparative Examples, and Figure 13 is a graph showing the excitation force of the granulator and the sintering force. Figure 14 is a humidity diagram, Figure 15 is a graph showing moisture behavior in the sintering bed at the exit of the drying zone, Figure 16 is a graph showing the relationship between the yield and the optimum particle size of the sintering material, 2 to 5 mm. A graph showing the relationship between the amount of moisture reduction in the sintering bed and the sintering time reduction rate, and FIG. 17 is a process diagram showing a conventional sintering process.

Claims (1)

[Claims] 1. In pre-processing the sintering raw material to be supplied to the DL type sintering machine, the sintering raw material is charged into the consolidation plasticization kneading space together with the consolidation medium, and the excitation force is 3 g to 10 g (g is The first step is to form flakes by applying force (acceleration of gravity) and vibrating compaction, and then applying an excitation force of 3 g to 6 g to the flake-shaped sintered raw material to roll and agglomerate it into a strong mini. A second step of granulating pellets, mixing other raw materials and the raw materials granulated in the first and second steps and supplying the mixture to a sintering machine, and a preheating hood provided in front of the ignition furnace. A method for pre-processing a sintering raw material, comprising a third step of drying the raw material layer with hot air supplied from the sintering raw material. 2. A claim in which the preheating hoods are provided in multiple stages so as to be slidable in the same extension storage direction, the number of movable preheating hoods is adjusted according to the moisture content of the mixed raw materials, and the ignition furnace position is brought close to the preheating hood side. Item 1. A method for pre-processing a sintering raw material according to item 1.