JP2009114515A - Method for operating blast furnace - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a method for operating a blast furnace, which can effectively utilize a conventional sieve facility as it is, improves the performance of removing deposited powders of raw materials for the blast furnace such as iron ore, at a comparatively low cost, and can reduce an amount of a fine powder to be brought into the blast furnace. <P>SOLUTION: The method for operating the blast furnace includes the steps of: preparing the raw material 1 in a wet condition for the blast furnace; adding a surface active agent 2 to the raw material and mixing them; and charging a material 6 remaining on a sieve after having been sieved into the blast furnace. It is preferable to use a fatty acid or an alkylbenzene sulfonic acid as the surface active agent, add the surface active agent 2 onto the raw material for the blast furnace on a belt conveyor 3 with a spray method, and mix the raw material 1 for the blast furnace with the surface active agent 2 by using an impact given in a connection fall 3a of the belt conveyor 3. <P>COPYRIGHT: (C)2009,JPO&INPIT

Description

  The present invention relates to a method for efficiently performing blast furnace operation by sieving blast furnace raw materials such as iron ore and removing fine powder in advance in an iron making process.

  In ironmaking processes using vertical furnaces such as blast furnaces, it is necessary to circulate reducing gas in the packed bed to reduce iron ore. It is desirable to remove fine powder in advance for the charging materials such as iron ore, coke, and sintered ore. For this reason, each steelworks has a sieving facility (vibrating sieving) for removing fine powder from these ironmaking raw materials. However, the raw material stored in the yard has not been sufficiently removed by conventional sieving since the adhesion of fine powder increases when the moisture content increases due to rain or the like during storage of the raw material. In particular, iron ore has a high affinity with moisture, and it is very difficult to remove fine powder when wet. In addition, the clay-like raw material adheres to the screen of the sieve and becomes a factor causing clogging. For this reason, in a raw material sieving equipment having a high moisture adhesion, a sieving having a large mesh has been used. For example, even in the same blast furnace raw material, since the sintered ore sent directly from the sintering plant contains almost no water and fine powder easily falls, a sieve with an opening of 4 to 6 mm is usually used for fine powder removal. In the case of iron ore, which contains water and often has fine powder adhered thereto, a sieve having an opening of about 10 mm is usually used in order to improve the removal performance of the powder and suppress clogging. That is, the raw material in the range of 4 to 10 mm that can be used as it is as a normal blast furnace raw material is also screened out, which is a factor for greatly reducing the yield. Further, even when a sieve having an opening of 10 mm is used, a part of fine powder of 1 mm or less still adheres to ore of 10 mm or more and does not fall, and the powder removal efficiency is not significantly improved.

  As a sieving means that can improve the powder removal efficiency of wet raw materials such as iron ore, an expandable sieve mesh and a movable mechanism that conveys the raw material while deforming it in conjunction with up and down and left and right A special screen having, for example, a jumping screen (registered trademark) is known. With Jumping Screen (registered trademark), it is possible to expect the effect of dispersing the adhered powder by the impact force at the time of dropping, by applying the repetitive movement of pulling and loosening to the mesh made of urethane. Further, since the mesh is always deformed, clogging is unlikely to occur even when a wet raw material is used.

As a method for removing adhering powder of raw materials in a wet state other than sieving, a method is known in which iron ore to which fine powder has adhered is washed with a screen-type jet washer to remove the adhering powder (see, for example, Patent Document 1). .). It is said that the iron ore adhering powder is washed cleanly because the washing water is jetted on the screen vigorously, and the cleaning liquid containing the adhering powder can be efficiently processed by the screen-type dehydrator and the liquid cyclone.
Japanese Patent No. 3255775

  As mentioned above, blast furnace raw materials with a large amount of adhering powder when wet have been classified with a sieve having a large mesh opening, but the yield is greatly reduced, but the adhering powder is still mixed on the sieve. The adhering powder removal effect was not great.

  In addition, the sieving method using a special screen can be expected to separate the adhering powder of the raw material in the wet state, but the screen material is made of a resin material such as urethane, and is constantly deformed and stretched. When using a hard material with a large specific gravity such as stone, there is a problem in durability. If the durability of the screen is low, not only the running cost associated with the screen replacement becomes high, but also the frequency of stopping the line for replacement becomes high, which may be a major factor in the deterioration of productivity. In addition, since the screen is very different from the vibrating screen used in the conventional steelworks, it is necessary to remove the conventional screen and construct a new special screen facility, which is expected to require enormous facility costs. The Therefore, the method using a special screen is not very popular as a sieving method for iron making raw materials.

  Furthermore, in the method of washing iron ore with a screen jet washer, a huge construction cost is required to newly construct equipment such as a screen jet washer, a screen dehydrator, and a hydrocyclone. . Further, particularly in water treatment containing iron ore fine powder, there is a problem in that maintenance costs are high due to severe equipment wear. Furthermore, the moisture brought into the blast furnace due to the water adhering to the iron ore after washing may increase, lowering the blast furnace top temperature and destabilizing the operation.

  Therefore, in the present invention, it is possible to effectively utilize the conventional sieving equipment as it is, and improve the performance of removing adhered powder from blast furnace raw materials such as iron ore at a relatively low cost, and reduce the amount of fine powder brought into the blast furnace. The purpose is to provide a method for operating a blast furnace.

  In order to solve the above-mentioned problems, the present inventors have studied a method for efficiently removing adhering powder due to moisture in a blast furnace raw material using a conventional general-purpose vibration sieve. When using the existing sieving equipment to improve the attached powder removal performance, the vibration energy that can be given to the blast furnace raw material is constant, so it is considered necessary to weaken the adhesive force itself due to moisture. Regarding the adhesion between particles due to the cross-linking effect of the liquid, a relationship as shown in the following formula (a) is generally known.

F = 2πrσ / (1 + tan (θ / 2)) (a)
(F: adhesion force, σ: surface tension of liquid, r: particle radius, θ: contact angle of liquid bridge to particle)
According to the above formula (a), it is shown that the adhesion due to the cross-linking effect of the liquid is proportional to the surface tension of the liquid. Since water has a polar molecular structure, water attracts each other and is known as a liquid having a large surface tension. When a surfactant is added to water, surfactant molecules are dispersed on the liquid surface, and the surface tension can be greatly reduced.

  Among the surfactants, particularly fatty acid salts have the property of changing the ore surface from hydrophilic to hydrophobic. For this reason, in the flotation process, a method of adding as a surfactant and performing aeration on the surface of the ore where the ore surface has changed to hydrophobic to float and separate is used. When the ore surface is changed from hydrophilic to hydrophobic, it becomes difficult for moisture to adhere and liquid cross-linking itself hardly occurs.

Due to the above effect, the adhesion effect due to moisture is greatly weakened, so that it is possible to greatly enhance the effect of removing the adhered powder even when vibration energy equivalent to the conventional one is given. The characteristics of the present invention obtained from the above findings are as follows.
(1) A method of operating a blast furnace, comprising adding a surfactant to a wet blast furnace raw material, mixing the mixture, and charging the sieved sieve into the blast furnace.
(2) The method for operating a blast furnace according to (1), wherein fatty acid or alkylbenzenesulfonic acid is used as the surfactant.
(3) A surfactant is sprayed and added onto a blast furnace raw material on a belt conveyor, and the blast furnace raw material and the surfactant are mixed using an impact at a transfer drop of the belt conveyor. A method for operating a blast furnace according to (1) or (2).

  According to the present invention, while using a conventional sieving facility, sieving of wet blast furnace raw materials such as iron ore exposed to rainwater and the like can be easily performed. As a result, it is possible to sufficiently suppress the fine powder material charged into the blast furnace, ensuring air permeability in the blast furnace and improving operational stability. Moreover, since the surface of the blast furnace raw material is hydrophobized, the amount of moisture falling under the sieve increases, so the amount of moisture brought into the blast furnace as the sieve is reduced compared to the conventional case. In recent years in blast furnace operation, the temperature at the top of the blast furnace decreases due to the reduction of the amount of coke, and moisture is agglomerated and dust discharge tends to be hindered. Since the amount of heat is reduced, it is easy to secure a necessary temperature (100 ° C. or higher) at the top of the furnace, and there is an effect that dust discharge performance is improved and air permeability is easily secured.

  According to the present invention, by adding a surfactant to a blast furnace raw material such as iron ore that is in a wet state due to the presence of moisture, the adhesion of fine powder can be weakened, so a surfactant is added to the blast furnace raw material. By mixing and sieving, the fine powder can be easily removed even in the conventional sieving equipment. Then, the top of the sieve, which is the raw material of the blast furnace from which fine powder has been removed by sieving, is charged into the blast furnace and operated to produce pig iron.

  The wet state is a state in which moisture exists on the surface of particles such as iron ore. The effect of surfactants on the moisture content of raw materials such as iron ore varies depending on the pore distribution inside the raw material particles (because the moisture on the particle surface after the moisture is absorbed by the pores inside the target particles becomes a problem) ), The effect is large when the water content of the raw material is 5 mass% or more.

  The present invention is most effective when used for iron ore as a blast furnace raw material, but is also effective when used for coke, coal, sintered ore, limestone, and the like.

  As the surfactant used in the present invention, basically any type of surfactant can be used, but those that dissolve and diffuse easily in water are particularly desirable. This is because when the dissolution rate in water is low, stirring power and time are required for dissolution. Further, those having the effect of converting hydrophilicity to hydrophobicity by adhering to the surface of blast furnace raw materials such as ores are more desirable. Specifically, oleic acid such as sodium stearate, lauric acid, stearic acid It is preferable to use various fatty acids such as sodium salt and potassium salt, sodium linear alkylbenzene sulfonate, and the like. This is because an effect of weakening the adhesion between the ore and the water can be expected by deteriorating the wettability of the surface of the ore and the like with water.

  As a method of adding a surfactant, a method of adding on a yard and mixing with a heavy machine, or a method of adding on a blast furnace raw material such as ore on a belt conveyor and mixing using a drop impact on a transfer chute of the belt conveyor However, if the mixing effect is sufficient, the latter method is desirable because it is less expensive. Further, the position where the surfactant is added on the belt conveyor is preferably as far as possible from the sieve, and is preferably close to the raw material yard side. This is because it becomes easier for the surfactant to reach the entire ore if it passes through the connecting drop more and is transported over a longer time.

  FIG. 1 is a flowchart showing an embodiment of the present invention. When using the iron ore 1 to which fine powder adheres as a blast furnace raw material, the surfactant 2 is added to the iron ore 1 on the conveyor belt conveyor 3 by spraying from above. When the iron ore 1 to which the surfactant 2 is added falls at the connecting chute portion 3a of the conveyor belt conveyor 3, the surfactant and the iron ore are mixed. In this state, the iron ore 1 is screened using the sieving equipment 4 used for screening the iron ore before charging the blast furnace, so that the iron ore 1 has the iron ore fine powder 5 and the iron ore after the fine powder is removed. By separating the iron ore 6 on the sieve into the blast furnace, it is possible to charge the iron ore with a small proportion of fine powder into the blast furnace.

  In order to confirm the effect of the present invention, a sieving test was conducted under the following conditions.

  1. Iron ore with high powder adhesion due to moisture was prepared, and sieved by applying about 5T to a vibrating sieve having a width of 2 m, a length of 3.5 m, and a mesh opening of 7 mm. It was 3.9 mass% when the moisture content of the iron ore was measured by the drying method.

  2. After water was sprinkled on the same iron ore as in 1 above, it was mixed well using an excavator and allowed to stand for several hours in order to allow the water to blend into a wet state. Here, when the water content of the iron ore was measured again by the drying method, it was 9.3 mass%. The wet iron ore was subjected to about 5 T on the above-mentioned vibrating screen and sieved.

  3. Add 0.5 mass% of mixed fatty acid sodium to iron ore to the same wet iron ore as 2 above, sprinkle water, stir well with an excavator, then use about 5T for the above vibrating sieve and screen went. The added mixed fatty acid sodium was milky white solid powder having a particle size of 1 mm or less.

  4. Finally, 0.5 mass% of linear alkylbenzene sulfonate (LAS Na) is added to the wet iron ore of 2 above, and after stirring well with an excavator, about 5T is applied to the above vibration sieve. And sieved. The added sodium alkylbenzene sulfonate was in the form of a white solid powder having a particle size of 1 mm or less.

  Table 1 shows the measurement results of “mass ratio under sieving” after sieving 1 to 4 above and “recovery rate under particle size of 5 mm or less (−5 mm)”.

  When the wet iron ore obtained by adding moisture to the iron ore is sieved, the mass ratio under sieve (mass under sieve ÷ mass of sieve feed × 100) is greatly reduced. Therefore, when the sieving -5 mm recovery rate (under sieving -5 mm mass ÷ sieving supply -5 mm mass x 100) is calculated, the recovery rate is also greatly reduced, and a large amount of -5 mm powder adheres to the sieving sample. It was confirmed that Under the condition where the mixed fatty acid sodium was added and mixed, the weight ratio under the sieve was greatly increased as compared with the case of only the wet iron ore. The sieving -5 mm recovery was also restored to a level close to that before the addition of water, and the effect of sieving the adhered powder by the surfactant was confirmed. Moreover, the same result was shown also in the conditions which added and mixed sodium linear alkylbenzenesulfonate, and the adhering powder removal effect was shown.

The flowchart which shows one Embodiment of this invention.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Iron ore 2 Surfactant 3 Conveyor belt conveyor 3a Transfer chute part 4 Sieve equipment 5 Iron ore fine powder 6 Iron ore after fine powder removal

Claims (3)

  A method of operating a blast furnace, comprising adding a surfactant to a wet blast furnace raw material, mixing the mixture, and charging the sieved sieve into the blast furnace.   The method for operating a blast furnace according to claim 1, wherein fatty acid or alkylbenzene sulfonic acid is used as the surfactant.   2. A surfactant is sprayed and added onto a blast furnace raw material on a belt conveyor, and the blast furnace raw material and the surfactant are mixed using an impact at a transfer drop of the belt conveyor. Or the operating method of the blast furnace of Claim 2.

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