JP2009019241A - Method for operating blast furnace using non-fired agglomerated ore - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a method for operating a blast furnace using a non-fired agglomerated ore, capable of realizing a stable operation of the blast furnace by preventing deterioration in permeability when using the non-fired agglomerated ore in the blast furnace. <P>SOLUTION: The method for operating the blast furnace using the non-fired agglomerated ore comprises a step of charging the non-fired agglomerated ore into a peripheral part of the furnace at a radius location corresponding to 0.7-1.0 by a non-dimensional radius when using the non-fired agglomerated ore 1 as a raw material for iron manufacture in the bell-less blast furnace, provided that the non-fired agglomerated ore 1 is obtained by agglomerating an iron oxide raw material with an inorganic binder such as cement 4. <P>COPYRIGHT: (C)2009,JPO&INPIT

Description

  The present invention relates to a method for operating a blast furnace when an unfired agglomerated ore is used as a raw material for iron making.

  In the pig iron manufacturing process using a blast furnace, it is important to maintain the space ratio in the packed bed above a certain value in order to allow the reducing gas to flow through the packed bed formed by the charge charged in the blast furnace. It is desirable that the particle size of the charge forming the packed bed is large. Therefore, it is necessary to increase the strength of the charge and suppress its pulverization. Especially in large blast furnaces, sintered ore obtained by baking powdered ore with the combustion heat of carbonaceous materials, or powdered ore with a pelletizer, etc. A sintered agglomerate such as a baked pellet that is heat-cured at a high temperature of 1000 ° C. or higher after being formed into a wide shape is widely used.

  On the other hand, studies on non-fired agglomerated minerals that are not subjected to high-temperature heat treatment have been made especially for the purpose of energy saving. Non-calcined agglomerated minerals are cured for a certain period of time at a relatively low temperature of several hundred degrees or less using room temperature or waste heat, etc. using powdered iron ore or iron-making dust as a binder with a hydraulic binder such as cement. Manufactured.

  When cement-based binders are used in the production of non-fired agglomerated minerals, sufficient cold strength can be obtained, and therefore the transfer from the production site to the blast furnace can be easily performed, up to several hundred degrees Celsius in the upper part of the blast furnace. In this area, the shape can be maintained. However, it has been pointed out for a long time that the cement is thermally decomposed in a higher temperature range, so that the strength is remarkably reduced, and the strength is lowered in the middle and lower parts of the blast furnace, and the air permeability is deteriorated accordingly.

On the other hand, if an unfired agglomerated mineral is produced using an adhesive hydrocarbon mixture such as asphalt or pitch as a binder, the volatile matter in the binder evaporates from about 200 ° C., and the viscosity of the binder increases, increasing the strength. In addition, non-calcined agglomerates with improved high-temperature strength are also known (for example, the strength is further increased because glassy carbon binds iron ore particles at about 800 ° C., and the evaporation of volatile components is almost complete.) , See Patent Document 1).
Japanese Patent Publication No. 3-64571

  Although patent document 1 is a technique which improves the high temperature intensity | strength of a non-baking agglomerated mineral, when a volatile matter starts evaporation from 200 degreeC, it will be discharged | emitted from a blast furnace upper part accompanying a reducing gas. The gas discharged from the blast furnace is generally recovered and used because it contains a combustible component such as CO gas. However, if volatile components are accompanied by this recovery process, it will be used as a tar component when cooled to a temperature below the aggregation point. Stick. Therefore, exhaust gas cannot be recovered from the blast furnace, so that there is a problem that the blast furnace cannot be used in actual operation.

  The present invention aims to solve such problems of the prior art, and when using unfired agglomerated ore in a blast furnace, it prevents non-fired deterioration and realizes stable operation of the blast furnace. It was made to provide a method for operating a blast furnace using agglomerates.

  In order to solve such problems, in the present invention, in a bell-less blast furnace, when an unfired agglomerated material agglomerated with an inorganic binder is used as a raw material for iron production, The operation method of the blast furnace which is charged in the periphery of the furnace having a dimensionless radius of 0.7 to 1.0 is used.

  According to the present invention, an unfired agglomerated ore can be used as a blast furnace raw material without deteriorating the air permeability of the blast furnace. Thereby, the manufacturing cost of pig iron can be reduced. Further, the efficiency of blast furnace operation can be improved, and the reduction of the reducing material ratio and high productivity can be obtained.

  The present invention is characterized in that when a non-calcined agglomerated ore is used as a raw material for iron making in a bell-less blast furnace, the non-calcined agglomerated ore is charged in the periphery of the furnace having a dimensionless radius of 0.7 to 1.0. It is what. The non-fired agglomerated ore used in the present invention is obtained by agglomerating an iron oxide raw material together with a binder, and guarantees the strength at a low temperature with an inorganic binder such as cement. By using an inorganic binder, no volatile matter is generated from the binder even when heated in a blast furnace, and no tar content is contained in the recovered gas.

  At a high temperature at which the strength of the inorganic binder is reduced, a pure iron layer is generated as the raw iron oxide is reduced in the furnace. This is because when the raw material descends in the blast furnace, the concentration of CO gas having a strong reducing power increases and the temperature rises. The present inventors considered that the reduction in agglomerate strength could be compensated by the joining effect due to the formation of the pure iron layer, and studied the method. As a result, the raw iron oxide is rapidly reduced by charging the non-fired agglomerated ore into the outer peripheral portion in the blast furnace, the dimensionless radius in the furnace within a range of 0.7 to 1.0, It was found that the strength of the agglomerate was suppressed by the joining effect of the pure iron layer, and that the unfired agglomerate could be used in a blast furnace, and the present invention was completed.

  The reason why the unfired agglomerated ore is charged into the outer peripheral portion in the blast furnace will be described in detail below.

The reduction of the raw material in the blast furnace is a gas-solid reaction with CO gas, and the reaction rate is the movement rate of CO between the gas phase and the raw material surface and the CO ₂ gas generated by the reduction, the reduction reaction on the raw material surface. It is determined by the diffusion rate of CO and CO ₂ gas inside the raw material particles.

  Assuming that there is a product phase of the outer shell and an unreacted phase in the center inside the particles during the reaction, and there is a non-thickness interface at the boundary between them, the above process proceeds sequentially. Since the velocity is sufficiently smaller than the gas moving velocity, it can be regarded as a quasi-steady state, and the reaction velocity is given by the following equation (1) (see “Metallurgy Reaction Engineering”, Yokendo, Tokyo, p. 50). .)

In the formula (1), R _A : overall reaction rate, C _A0 : CO gas concentration, C _Ae : CO gas equilibrium concentration, r ₀ : particle radius, r _i : radius of _{intraparticle} reaction interface, k _fA : CO gas Transfer coefficient in the film, D _s : diffusion coefficient in particles, k: rate constant, K: equilibrium constant.

The intramembrane transfer coefficient k _fA is obtained from the following equation (2) (Ranz-Marshall equation).

In the equation (2), D _p : particle diameter, D _A : molecular diffusion coefficient of CO component in mixed gas, y _A : mole fraction of CO gas, Re: Reynolds number = D _p ρρ / μ, Sc: Schmitt number = μ / ρD _A.

  From the above formulas (1) and (2), it is effective to increase the rate of CO gas in contact with the raw material in order to accelerate the reduction of the raw material and accelerate the joining effect due to the formation of the pure iron layer. Recognize.

  In the operation of a bell-less blast furnace, it is important to secure a predetermined air flow while maintaining a smooth unloading of raw materials and coke. It is also important to control dust discharge and heat loss from the furnace. For this purpose, charging into the furnace is performed while appropriately controlling the ratio of the raw material and coke in the radial direction of the furnace.

  At that time, in the range from the center of the furnace or near the furnace wall, the ratio (heat flow ratio) of the falling material, the heat flux of the coke and the heat flux of the rising gas is reduced, compared with the middle part. Therefore, the operation to increase the amount of gas is relatively large. That is, since the gas flow rate is increased in the vicinity of the furnace wall on the outer periphery of the furnace, it is possible to increase the efficiency of blast furnace operation by charging a highly reducible raw material in this area.

  The present inventors have found that a raw material for iron making obtained by adding a binder to an iron oxide raw material and agglomerating it without firing is excellent in reducibility. The iron oxide raw material here is an iron oxide raw material containing iron ore, iron ore powder, roasted iron oxide powder, pellet raw material powder, blast furnace dust, steelmaking dust, sintered dust, etc., and the binder is heat treated at high temperature It is an inorganic binder containing hydraulic binders such as various cements, blast furnace slag, etc., which can produce agglomerates by molding powdered iron ore, ironmaking dust and the like without any problems.

As described above, by introducing the non-fired agglomerated ore into the outer periphery of the blast furnace, it is possible to prevent pulverization and at the same time increase the efficiency of blast furnace operation. As an example showing the effect of the present invention, iron ore pulverized product 76 mass%, 10 μm or less and iron oxide powder 6 mass% containing Fe ₂ O ₃ of 90 mass% or more, ordinary cement 2 mass%, blast furnace slag fine powder 6 mass% are kneaded. After the granulation, the reducibility of the uncalcined agglomerated mineral cured in steam for 24 hours was measured. The reducibility was measured according to JIS M8713. A sample having a particle size of 12 mm ± 1 mm was dried, charged into a reaction tube, heated to 900 ° C., and reacted in 30 mass% CO-70 mass% N ₂ gas for 3 hours. A predetermined reduction rate was calculated from the mass before and after the reaction and the iron component value. As a result, the reducibility of ordinary sintered ore and the like was about 65%, while the reducibility of the unfired agglomerated mineral was 74%, which proved to be excellent in reducibility. When using such agglomerated minerals with excellent reducibility in a blast furnace, the efficiency of blast furnace operation is improved by charging the outer periphery of the agglomerate.

  When the charging position of the unfired agglomerated ore in the blast furnace is less than 0.7 in dimensionless radius, the joining effect by the pure iron layer is not sufficient, the unfired agglomerated ore is pulverized, and the air permeability is It may get worse. If the dimensionless radius is in the range of 0.7 to 1.0, the air permeability can be maintained well, but the effect is higher as the charging is performed at a position closer to the outer peripheral portion of the dimensionless radius 1.0. If the charging position of the non-fired agglomerated mineral in the blast furnace is within the above range, the raw material other than the non-fired agglomerated mineral is charged within the range of 0.7 to 1.0 in dimensionless radius. There is no problem.

  Hereinafter, an embodiment of a method for producing an unfired agglomerated mineral used in the present invention will be described with reference to the drawings. FIG. 1 is a schematic view showing a method for producing a non-fired agglomerated mineral 1 used in the present invention. Cement 4, iron ore 5 and hematite powder 6 charged in a hopper (raw material storage tank) 3 with a quantitative cutting device 2 are introduced into the humidification mixer 8 by a predetermined material cutting device conveying device 7. Here, regarding the cement 4, the iron ore 5 and the hematite powder 6, each hopper is illustrated one by one, but it is not always necessary to have one, and a plurality of types can be mixed in the hopper. It may be used. Although not shown, if necessary, there may be a pulverization step for adjusting the particle size in advance, a step for removing foreign matters, and the like. Although there is no restriction | limiting in particular about the humidification mixer 8, the thing with a high mixing stirring ability is desirable. In the case where a low mixing and stirring ability is employed, the mixing time becomes long, so that there is a demerit that productivity is lowered.

  The humidified and mixed raw material is transported to the granulator 10 by the raw material transport device 9 and granulated. Although the dish type rolling granulator was shown in the example of FIG. 1, there is no big restriction | limiting in the kind of granulator.

  The main granulation methods include a rolling granulation method using a disk pelletizer or a drum type granulator, and a compression granulation method using a briquetting machine. Since the briquetting machine mechanically compresses the particle group, the filling rate of the molded product is increased and the green strength (strength immediately after molding. On the other hand, the cold strength is a binder after a certain curing period after molding. Is a tendency to increase, but the cold strength after curing depends largely on the quality and quantity of the binder, and is large in the rolling granulation method and the compression granulation method. There is no difference. In addition, the compression granulation method is characterized in that it is easy to produce a uniform particle size and properties as compared with the rolling granulation method, but has high equipment costs and repair costs. Furthermore, when a dish type rolling granulator is used, an agglomerate close to a spherical diameter is produced. On the other hand, according to the compression granulator, various shapes such as almond type and bean charcoal mold can be manufactured. Therefore, a preferable method may be selected as appropriate for the granulation method in view of such circumstances.

  The agglomerated product after granulation is conveyed to the stationary yard 12 by the raw material conveyance device 11. After curing for a predetermined time in a stationary yard, the agglomerated material becomes unfired agglomerated mineral 1 that can be used in a blast furnace, and is charged into the blast furnace and used as a raw material for iron making.

  The particle size of the unfired agglomerated mineral 1 in a normal temperature atmosphere is preferably about 8 mm to 30 mm. This is because if it is smaller than this, the air permeability as the packed layer is deteriorated, and if it exceeds this, the reducibility is deteriorated.

  The binder is not particularly limited as long as it can exhibit sufficient strength in the cold, and the best one may be used in consideration of easy availability and market price, such as blast furnace cement and Portland cement. .

  In addition, fine and high-purity hematite powder can also be used as a raw material for the agglomerate. For example, in the cold rolling step of the steel manufacturing process, the iron oxide layer on the surface is removed with hydrochloric acid before rolling, and iron is eluted as iron chloride in this hydrochloric acid. By roasting this iron chloride, high-purity and fine-grained hematite powder (pickling line recovered powder) is recovered. This hematite powder can be used as a raw material for the unfired agglomerated ore used in the present invention.

  Next, the usage method of the said unbaking agglomerated mineral in a blast furnace is demonstrated.

  First, the blast furnace used in the present invention is a bell-less blast furnace as shown in FIG. This is a type of blast furnace in which the raw material is charged into the top of the furnace by continuously rotating the tilt angle (angle with respect to the vertical direction) of the turning chute 20 and is excellent in controllability of the charge distribution. In FIG. 2, as an example, a structure in which three furnace top bunkers 21 are arranged in parallel may be two to four or more, or may be a structure arranged in series above.

  First, the raw material is charged into the furnace top bunker 21. The raw materials are iron-containing raw materials including coke and unfired agglomerated minerals, such as sintered ore, pellets, iron ore, and reduced iron. These are compounded and mixed in a blast furnace storage tank. The raw material is charged into the top of the furnace through the turning chute 20 to form a raw material layer 22 in the furnace.

  In order to charge non-fired agglomerated ore within a range of 0.7 to 1.0 of the radius of the blast furnace furnace, the charging method to the top bunker 21 and the tilt pattern of the swivel chute 20 are appropriately selected. To do. For example, the iron-containing raw material is divided into two batches of charge (here, divided by a mass ratio of 55:45), and the non-fired agglomerate is mixed with the iron-containing raw material to be charged later. The coke, the first batch of iron-containing raw material, and the second batch of iron-containing raw material are charged while tilting the swivel chute 20 from the outer peripheral side to the inner peripheral side in the following tilt pattern.

Coke: 54 ° × 2 turns, 53.5 ° × 2 turns, 53 ° × 2 turns, 52 ° × 2 turns, 51.5 ° × 2 turns, 51 ° × 2 turns, 50 ° × 3 turns, 49 ° × 1 turn, 48 ° × 1 turn, 45 ° × 1 turn, 42 ° × 1 turn, 25 ° × 2 turn, 20 ° × 1 turn Iron-containing material (first batch): 50 ° × 1 turn, 49 ° × 1 turn, 48 ° × 2 turns, 46.5 ° × 2 turns, 45.5 ° × 1 turn, 44.5 ° × 1 turn, 43.5 ° × 1 turn, 42.5 ° × 1 turn, 41 ° × 1 turn Iron-containing material (2nd batch): 51 ° × 1 turn, 50 ° × 1 turn, 50 ° × 2 turns, 49 ° × 2 turns, 48 ° × 1 turn Then, after the first batch of iron-containing material is charged, it becomes a deposited shape in which a flat portion is formed from 0.7 to a furnace wall with a dimensionless radius. The second batch has a pattern in which the raw material falls on the flat part, so that the non-fired agglomerated ore can be formed on the outer peripheral side without forming a stable deposit shape without flowing into the center. .

  In order to confirm the effect of the present invention, a non-fired agglomerated use test was conducted in an actual blast furnace. The uncalcined agglomerated ore used is composed of 73 mass% of iron ore A having the components shown in Table 1, 13 mass% of iron ore B, 6 mass% of hematite powder, and 8 mass% of cement, and the production method shown in FIG. It was produced by the same granulation process.

The tested blast furnace is a bellless blast furnace similar to that shown in FIG. 2 having an inner volume of 5153 m ³ , a furnace port diameter of 11.4 m, a hearth diameter of 15.0 m, and 40 tuyere. The blast furnace was charged with the charging amount and the charging position, charged with unfired agglomerated ore, and operated, and the amount of tapping and reducing material ratio were measured. The amount of unfired agglomerated charge was shown as a ratio to the total iron-containing raw material (total amount of sintered ore, pellets, massive iron ore, and unfired agglomerated ore). The charging position of the unfired agglomerated ore is 0 to 0.5 (the center of the furnace with a dimensionless radius of less than 0.5), 0.5 to 0.7 (0.5 or more, 0). The rotation and tilt patterns of the swivel chute were adjusted so that there were three types, an intermediate position of less than 0.7) and 0.7 to 1.0 (outer peripheral portion of the furnace having a dimensionless radius of 0.7 or more).

  The test results are shown in Table 2. In the present invention examples 1 and 2 in which the unfired agglomerated ore was charged at a position having a dimensionless radius of 0.7 to 1.0, compared with the case where the unfired agglomerate was not used (comparative example 1). In the comparative examples 2 to 5 in which the non-fired agglomerated ore was charged to 0 to 0.5 or 0.5 to 0.7 with a dimensionless radius, The amount decreased and the reducing agent ratio increased. From this result, it can be seen that the present invention makes it possible to stably use non-fired agglomerated minerals and realize high-efficiency blast furnace operation.

Schematic which shows the manufacturing method of a non-baking agglomerated mineral. Schematic of a bell-less blast furnace.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Unbaking agglomerate 2 Fixed quantity cutting device 3 Hopper 4 Cement 5 Iron ore 6 Hematite powder 7 Raw material conveyance device 8 Humidification mixer 9 Raw material conveyance device 10 Granulator 11 Raw material conveyance device 12 Standing yard 20 Turning chute 21 Top Bunker 22 Raw material layer

Claims (1)

  In a bell-less blast furnace, when using a non-fired agglomerated agglomerated iron oxide raw material together with an inorganic binder as a raw material for iron making, the non-fired agglomerated mineral has a dimensionless radius of 0.7 to 1.0. A method of operating a blast furnace using unfired agglomerated ore, which is charged in the periphery of the furnace.

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