JPH0438809B2 - - Google Patents

Description

[Detailed description of the invention]

[Industrial Field of Application] The present invention relates to a raw material for pre-treatment of hot metal such as dephosphorization and desiliconization, which is made by effectively utilizing iron oxide-containing collected dust discharged from iron-making related equipment. [Prior art] Collection of exhaust gas from iron-making equipment, such as dust collected from grate exhaust gas from iron ore pellet manufacturing equipment, dust collected from main exhaust gas from iron ore sintering equipment, dust collected from flue gas from hot metal pretreatment equipment, etc. Dust contains a large amount of iron oxide, as shown in Table 1. Therefore, in the past, it was considered to reuse this as an iron source. However, these collected dusts have a large amount of impurity elements to be used as blast furnace charging raw materials, and if mixed into sintered ore or pellets, their quality will deteriorate and the stability of blast furnace operation will be hindered, so they are hardly used at present. Most of the waste is dumped without being put to good use.

【table】

[Table] On the other hand, among the additives used in hot metal pretreatment (desulfurization, dephosphorization, etc.), iron oxide, which serves as an oxygen source, is mainly the primary scale produced during the ingot making and soaking process of hot metal and molten steel. In addition, secondary scale crushed materials produced during rolling and wire drawing are used. However, even though these scales are powder, they are extremely hard, so if they are conveyed at high speed and pressure through gas transportation piping or injection lances using powder transport technology, these scales and injection lances will break down. There is a problem in that the filling nozzle and the like are significantly worn out. In addition, fine pulverization to enhance the pretreatment effect is time-consuming.
On the other hand, if it is ground too finely, it will absorb moisture and become agglomerated during storage, so measures to prevent this will also be needed. In order to avoid this problem of abrasion of the tube body and nozzle, the scale is usually diluted with an appropriate amount of fine iron ore powder to alleviate the mechanical impact force. However, with respect to the above-mentioned iron oxide-containing collected dust, no research has been conducted to date to effectively utilize it as an iron oxide source for a hot metal pretreatment agent. [Problems to be Solved by the Invention] The present inventor focused on the above-mentioned circumstances, and the purpose is to collect the iron oxide dust, which is available as a very fine particle. The purpose is to effectively utilize dust as a part of the iron oxide source to solve the various problems mentioned above and to reduce the cost of the iron oxide source. [Means for Solving the Problems] The configuration of the present invention that has solved the above problems is that the iron oxide-containing collected dust discharged from iron-making related equipment is treated under the condition that the following powder properties are satisfied. The gist is that it is mixed with powdery scale and/or iron ore. Particle size structure: 150 μm or less and 105 μm or less account for 80 to 90% by weight of the total. Fluidity index: 35-40 Jetability index: 79-90 [Function] Based on the above-mentioned knowledge, the present inventors used fine iron oxide-containing dust as a source of iron oxide for hot metal pretreatment agent. We first tried to replace all the iron oxide sources with collected dust. However, the collected dust discharged from steelmaking-related equipment is very fine, as shown in Table 2 below, so it is difficult to flow from the accumulated state in the storage tank etc. towards the discharge outlet, and due to moisture absorption. If the entire amount is replaced with collected dust, the amount and speed of cutting from the storage tank will become unstable, and the composition of the entire hot metal pretreatment agent will become non-uniform, resulting in the effect of pretreatment. I learned that it becomes unstable.

[Table] For example, Figures 1A and 1B are cross-sectional explanatory diagrams showing the situation when the powder P is discharged from the bottom outlet 2 of the storage tank (or hopper, etc.) 1 (the on-off valve is omitted for the sake of understanding). ), and Figure 1A is
This is a case where the powder or granule material P has appropriate fluidity, and the powder or granule material P flows out smoothly from the entire surface of the opening of the discharge port 2. On the other hand, FIG. 1B shows the situation when the powder P is too fine and deteriorates. In other words, if the powder P is too fine, a part of the powder P will adhere to the vicinity of the discharge port 2 as a lump P _B due to the accumulation pressure of the powder P itself, which will eventually lead to the bridging phenomenon. It may even become impossible to discharge.
Furthermore, when the nodule P _B collapses due to an external impact, the opening area immediately after that collapses and the outflow amount temporarily increases, but it eventually returns to its original state. Therefore, the amount of powder P that flows out always fluctuates. Applying this outflow situation of granular powder to the collected dust as described above, the collected dust is extremely fine and has poor fluidity as mentioned above, so when cutting out a fixed amount from the storage tank, it is difficult to The outflow situation as shown in Fig. 1B occurs, which in turn has an adverse effect on hot metal pretreatment. It was confirmed that this tendency occurs not only when the collected dust is used alone, but also when a small amount of collected dust is mixed with powdered scale or iron ore. For example, in Figure 2, powdered scale and pig iron ore and collected dust (3 types) with the particle size composition shown in Table 2 are used, and the blended amount of collected dust is 0 to 20.
This figure shows the results of examining the granular properties of mixtures when the weight percentage was changed. However, the particle size structure of the scale and iron ore used was as follows, and the powder characteristic values were determined by the following method. [Scale and particle size composition of iron ore]: See Table 3 [Powder characteristic values] Fluidity index: Measure the angle of repose, degree of compaction, angle of spatula, and degree of agglomeration of each raw material mixture, and measure according to the standards shown in Table 4. Therefore, the liquidity index is determined. Jetability index: The disintegration, difference angle, and dispersion degree of each raw material powder are measured, and the fluidity index shown in Table 4 is taken into account to determine the jetability index according to Table 5.

【table】

【table】

【table】

[Table] As is clear from FIG. 2, the amount of the collected dust mixed in when the collected dust is used together with scale and iron ore significantly influences the particle characteristics of the mixture. As mentioned earlier, such fluctuations in powder properties lead to fluctuations in the cutting speed and amount when preparing the hot metal pretreatment agent, and the fluctuations in the composition of the hot metal pretreatment agent make the pretreatment operation unstable. .
Therefore, in order to be able to utilize collected dust as an iron oxide raw material for hot metal pre-treatment agents, when collected dust is used in combination with scale and iron ore, it is necessary to accurately cut out a quantitative amount of the mixture. Management indicators need to be clarified. The present invention has been completed as a result of further research in pursuit of such circumstances, and in the present invention, the above-mentioned management index of mixed granules consisting of scale and/or iron ore powder and collected dust is used. The particle size structure is as follows.
Three types are defined: a fluidity index and a flowability index. The reasons for establishing these management indicators are explained below. Particle size structure: 150 μm or less and 105 μm or less account for 80 to 90% by weight of the total. This index affects the hot metal pretreatment effect, fluidity during raw material cutting, and transport stability during gas transport and injection into the hot metal. Coarse particles exceeding 150 μm have a specific surface area. Since this is small, the hot metal pretreatment effect and jetting properties are poor. This tendency is the same even when particles with a diameter of 105 μm or less account for 80% by weight or less of the total, in other words, coarse particles with a diameter of 105 μm or more account for 20% by weight or more. However, if the amount of particles with a diameter of 105 μm or less exceeds 90% by weight of the total weight, not only will the fluidity during cutting out of the raw material deteriorate as explained in FIG. Fluidity index: 35-40 Mainly used as an index to maintain stable fluidity when cutting a fixed amount of raw material from the storage tank and to maintain a uniform composition of hot metal pretreatment agent.
If it is less than 20%, the precision of quantitative cutting will decrease and the hot metal pretreatment effect will become unstable. Incidentally, Figure 3 shows that a mixture of scale and/or iron ore powder and collected dust is used as an iron oxide source for hot metal dephosphorization,
This figure shows the results of investigating the number of troubles that occurred during dephosphorization when the fluidity index was varied. When using products with a liquidity index of 35 or higher, the number of troubles that occur is almost zero. Although there is no upper limit to the fluidity index from the perspective of "ensuring quantitative cutting performance," the fluidity index of a general iron oxide source (scale and/or iron ore powder) that does not contain dust collection is approximately 40. From there,
In the present invention, which aims to utilize collected dust, the upper limit of the fluidity index is set at 40. Jet property index: 79 to 90 This is an index of feeding stability during transportation using carrier gas and during injection. If this value is less than 79, it may be due to, for example, a part of the transportation piping sinking. The amount of transportation fluctuates and the stability of the pretreatment effect is inhibited. By the way, Figure 4 has the same scale and / as in Figure 3.
Or, it shows the results of investigating the number of troubles that occur during dephosphorization when a mixture of iron ore powder and collected dust is used as an iron oxide source for hot metal dephosphorization, and the jet property index is varied. The number of troubles that occur when using a product with a jet property index of 79 or higher is almost zero. From the perspective of "ensuring the stability of fluid transport," there is no upper limit to the jet property index, but common iron oxide sources that do not contain collected dust (scale and/or
Since the jetability index of iron ore powder (or iron ore powder) is 90, the upper limit of the jetability index is 90 for the same reason as above.
It was set at 90. In the present invention, the specific means for adjusting the particle size structure, fluidity index, and jetability index are not limited at all, but the most common methods are exemplified as follows. A method in which granules made of scale and/or iron ore are mixed with an appropriate amount of collected dust, and pulverized so that the particle size composition of the mixture falls within a specified range. A method in which the particle size structure, etc. of scale and/or iron ore and collected dust are determined in advance, and the blending amount is adjusted according to those values so that the particle size structure, etc. of the mixture falls within a specified range. Mix scale and/or iron ore and collected dust in an appropriate ratio, and measure the particle size composition of the mixture so that the values fall within the specified range.
A method of additionally mixing scale and/or iron ore or dust collection. Next, an example will be shown in which hot metal pretreatment (dephosphorization or desiliconization) is performed using the present invention. FIG. 5 is a flowchart for dephosphorizing hot metal, and the steps will be explained in detail as follows. (1) Dust D _a collected from pellet production equipment, D b collected from sinter production equipment, D _c collected from hot metal pretreatment equipment _, It is stored together with scale S and iron ore O in each booth of raw material popper 3. (2) Each raw material is cut out from the raw material hopper 3 so as to have a particle size composition and iron oxide content suitable for dephosphorization operation, and sent to the intermediate storage hopper 6 via belt conveyors 4 and 5. (3) Next, the powder mixture is cut out from the intermediate storage hopper 6 and sent from the conveyor 7 to the air separator 9 via the bucket elevator 8. (4) The powder mixture sent to the air separator 9 is dried by the hot air sent from the hot air generator 10 and then classified, and the coarse particles are crushed by the ball mill 11 and then sent from the bucket elevator 8. The air is circulated to the air separator 9. On the other hand, fine particles are fed from the air slider 12 to the silo 13. Further, the dust discharged from the air separator 9 is sent to the electrostatic precipitator 15 via the duct 14, and the collected dust is sent to the silo 13 after being combined with the fine particles sent by the air slider 12. In the silo 13, mixing and drying are constantly carried out using high pressure air. (5) In preparing the hot metal dephosphorizing agent, the mixture cut out from the silo 13 is loaded from the hopper 16 into the jet pack vehicle 17 and transported to the dephosphorizing agent preparation site, and the iron oxide in the dephosphorizing agent raw material hopper 18 is loaded. Transfer to source hopper. Other hoppers store dephosphorizing agent materials such as burnt coal and fluorite. (6) Iron oxide source, burnt lime, and fluorite are cut out from the hopper 18 in the mixing ratio required for hot metal dephosphorization, and conveyed to the conveyor 1.
9 and stored in the dephosphorizing agent storage hopper 20,
The dephosphorizing agent is sent to a dephosphorizing agent supply hopper 22 by a jet bag truck 21. 22 is a bug filter. (7) The dephosphorizing agent stored in the dephosphorizing agent hopper 22 is
After passing through the relay hopper 24 and the like, the dephosphorizing agent is sucked into the hot metal through the suction lance 25, and a dephosphorizing operation is performed. Although the illustrated example shows an example in which dephosphorization is performed in the pig iron mixer 27, it is of course possible to apply the method to dephosphorization in a ladle, etc. (8) The oxidation-containing exhaust gas discharged from the dephosphorization site is introduced into the electrostatic precipitator 28 through the duct 26, and the collected dust is sent from the hopper 29 to the raw material hopper 3 by the jet pack vehicle 30. Note that FIG. 5 and the steps (7) to (8) above show the case where the present invention is used for dephosphorization treatment, but when it is used for desiliconization treatment, it may be carried out in accordance with this,
It can be similarly applied to ladle desiliconization and hot metal sluice desiliconization. Also, even when used for dephosphorization, the fifth
The process shown in the figure is merely an example, and can be modified and implemented as appropriate depending on the situation at the site. In the above flow diagram, there is no restriction on the timing of measuring and adjusting the particle size structure etc. in accordance with the management index of iron oxide raw materials, and it can be performed at any stage from silo 13 to hopper 17 depending on the site situation. The powder is extracted, its particle size composition, fluidity index, and jetability index are measured, and depending on these values, the separation conditions by the air separator 9 are changed, or each raw material powder is supplied from the raw material hopper 3. By changing the ratio, etc., each management index may be adjusted so that it falls within the above-mentioned specified range. [Example] The results of a hot metal dephosphorization operation according to the above method using scale, iron ore, and dust collection are shown below.
The results are shown in Tables 6 and 7 together with the results when no dust collection was used. FIG. 6 shows the content of phosphorus and sulfur contained in the collected dust used, and it can be seen that the contents are almost constant. As is clear from the results in Tables 6 and 7, according to the present invention, a dephosphorization effect comparable to that obtained when only scale and iron ore are used as iron oxide sources is obtained.

【table】

【table】

【table】

[Table] [Effects of the Invention] The present invention is configured as described above, and enables the effective use of collected dust, as well as stabilizing the particle size structure, fluidity index, and jetability index of the hot metal pretreatment agent. Therefore, the pretreatment effect can also be stabilized at a high level. Moreover, since the collected dust is originally very fine and does not require any pulverization, the energy required for pulverization is also reduced compared to when only scale or iron ore powder is used.

[Brief explanation of drawings]

Figures 1A and B are explanatory diagrams showing the fluidity and outflow situation of powder and granules, Figure 2 is a graph showing the influence of the amount of collected dust on powder characteristic values, and Figures 3 and 4 are oxidation Figure 5 is a graph showing the influence of the blastability index and fluidity index on the number of troubles during hot metal dephosphorization operations when dust collection is used together with scale and iron ore as iron sources. FIG. 6 is a flowchart showing a preparation example of a hot metal dephosphorizing agent, and a graph showing changes in phosphorus and sulfur content in collected dust. 3...Raw material hopper, 4,5,7,19...Conveyor, 12...Air slider, 6,16,2
0,22...hopper, 9...air separator,
13... Silo, 17, 21, 30... Jetpack car, 27... Mixed iron car.

Claims (1)

[Scope of Claims] 1. Dust containing iron oxide discharged from iron-making related equipment is mixed with granular scale and/or iron ore under the condition that the following powder characteristics are satisfied. A raw material for hot metal pre-treatment material characterized by: Particle size composition: 150 μm or less, and 80-90% by weight of the total particle size: Fluidity index: 35-40 Jetability index: 79-90