JP2023128269A - Blowing lance for blast furnace and blast furnace operation method - Google Patents

Abstract

To prevent an excessive rise in furnace temperature in a blast furnace operation method in which a charcoal material having a large combustion speed is blown into the blast furnace.SOLUTION: In an operation method of a blast furnace in which a blast furnace blowing lance 5 is inserted into a blow pipe, pulverized coal containing 50 mass% or more of a charcoal material having a combustion speed of 3.0 (mg/min) or higher is blown from an inner tube 51 by a carrier gas while a hydrogen-based reducing gas is blown from an outer tube 52, and the blast furnace is operated so as to satisfy the condition of X1/X2≥0.5 where a flow rate of the hydrogen-based reducing gas is set to X1 and a flow rate of the carrier gas is set to X2. The blast furnace blowing lance has double-tube structure, and the tip opening of the inner tube is inclined by 55 degrees or more to a plane perpendicular to the axial direction of the inner tube. A distance W between the inner tube and the outer tube in the longitudinal direction is limited to a predetermined range.SELECTED DRAWING: Figure 2

Description

The present invention relates to a blast furnace injection lance for blowing pulverized coal or the like into a blast furnace, and a blast furnace operating method.

In blast furnace operation, pig iron is produced by charging iron raw materials (lump ore, sintered ore, pellets, etc.) and coke (reducing material) alternately in layers from the top of the furnace. As a cost reduction method in blast furnace operation, a method is known in which the amount of coke charged is reduced and pulverized coal is injected from a blast furnace injection lance installed in the tuyere. Furthermore, a method of operating a blast furnace is known in which hydrogen-based reducing gas is blown into the tuyere for the purpose of reducing the reducing agent ratio in the blast furnace, reducing carbon dioxide emissions, and the like.

Here, if the pulverized coal blown in from the tuyeres contains a large amount of volatile matter (hereinafter also referred to as VM), the blowing pressure will fluctuate and stable operation of the blast furnace will be inhibited. Therefore, semi-anthracite coal or the like (hereinafter also referred to as conventional carbon material) having a low VM is used as the pulverized coal injected into the blast furnace. However, in recent years, it has become difficult to secure carbonaceous materials with low VM due to resource depletion. Therefore, a method of injecting modified coal (hereinafter also referred to as char) obtained by carbonizing biomass or lignite as a carbon material is being considered. However, char derived from biomass or lignite has weaker carbon bonds than conventional carbon materials, so it is easier to burn (in other words, it burns at a higher rate). Therefore, when the above-mentioned char is used as the blowing carbon material, there is a risk that the combustion position (combustion focus) will shift toward the tuyere side and the furnace body temperature will rise excessively.

Patent Document 1 discloses a blast furnace blowing lance with a double tube structure configured to blow a gaseous reducing agent from an inner tube and circulate cooling air between an outer tube and an inner tube. , the above-mentioned issues have not been considered.
Patent Document 2 describes a double pipe lance in which the tip of the inner pipe has a cutout shape for the purpose of preventing wear of the tuyere.

Japanese Patent Application Publication No. 2006-312757 Utility Model Publication No. 62-97154

An object of the present invention is to prevent an excessive rise in the temperature of the furnace body in a method of operating a blast furnace in which carbonaceous material having a high combustion rate is injected into the blast furnace.

In order to solve the above problems, a blast furnace blowing lance according to the present invention provides (1) a blast furnace blowing lance having a double pipe structure having an outer tube and an inner tube, in which the tip opening of the inner tube is connected to the inner tube; The tube is inclined by a predetermined angle θ of 55 degrees or more with respect to a plane perpendicular to the axial direction of the tube, and is connected to the most extreme end of the tip opening of the inner tube and the tip opening of the outer tube for blowing into the blast furnace. A lance for blast furnace injection, characterized in that when the distance in the longitudinal direction of the lance is W, the distance W satisfies the following formula (1).
W≦tanθ×D・・・・・・Formula (1)
However, D is the diameter of the inner tube.

(2) The most distal end of the inner tube is located at any one of a protruding position on the outside of the outer tube, a position in the pipe line inside the outer tube, and a position flush with the tip opening of the outer tube. The blast furnace blowing lance according to (1) above, characterized in that the lance is disposed in a straight line.

(3) The blast furnace injection lance according to (1) or (2) above, wherein the tip opening of the outer tube is perpendicular to the axial direction of the inner tube.

(4) In the method of operating a blast furnace in which the blast furnace blowing lance according to any one of (1) to (3) above is inserted into a blow pipe, combustion is performed while blowing hydrogen-based reducing gas from the outer pipe. Pulverized coal containing 50% by mass or more of carbonaceous material at a speed of 3.0 (mg/min) or more is blown into the inner tube by a carrier gas, and the flow rate of the hydrogen-based reducing gas is set to X1, and the flow rate of the carrier gas is A method of operating a blast furnace characterized by satisfying the blowing conditions shown in the following formula (2) when X2 is taken as X2.
X1/X2≧0.5...Formula (2)

According to the present invention, in a method of operating a blast furnace in which carbonaceous material having a high combustion rate is injected into the blast furnace, the temperature of the furnace body can be increased by adjusting the amount of hydrogen-based reducing gas injected and the tip angle of the inner tube of the blast furnace injection lance. It is possible to prevent an excessive rise in

It is a schematic diagram of a blast furnace. FIG. 2 is an enlarged view of the tip of a blast furnace injection lance. This is a test device that simulates the lower part of a blast furnace. It is a graph showing the relationship between the tip inclination angle θ and the rate of increase in the number of carbonaceous particles. It is a graph showing the relationship between the hydrogen-based reducing gas flow rate (X1)/carrier gas flow rate (X2) and the rate of increase in the number of carbonaceous particles.

Embodiments of the present invention will be described below with reference to the drawings. FIG. 1 is a schematic diagram of a blast furnace (bellless blast furnace) according to the present embodiment. In the blast furnace 1, iron raw materials such as sintered ore, pellets, and lump ore are used as main raw materials, and coke, pulverized coal, and hydrogen-based reducing gas are used as reducing agents. Iron raw material and coke are charged into the blast furnace 1 from the top of the furnace in alternating layers. As a result, inside the blast furnace 1, a lump zone, a cohesive zone where the iron raw material melts and changes from solid to liquid, and a drip zone where liquid molten iron and molten slag drip onto the coke layer are formed. .

The blast furnace 1 in this embodiment includes a tuyere 2, an annular pipe 3, a blow pipe 4, a blast furnace blowing lance 5, a tap hole 6, and the like. The annular tube 3 is arranged so as to surround the lower part of the blast furnace 1. The blow pipes 4 are provided intermittently in the circumferential direction of the annular pipe 3, and are each connected to a different tuyere 2. The blast furnace blowing lance 5 is inserted through each blow pipe 4, and the tip of the blast furnace blowing lance 5 extends into the inside of each blow pipe 4. The tap hole 6 is provided to discharge hot metal accumulated at the bottom of the furnace. In the above-described configuration, the blast furnace blowing lance 5 blows pulverized coal and hydrogen-based reducing gas into the blow pipe 4 . The blown pulverized coal and hydrogen-based reducing gas are blown into the blast furnace 1 through the tuyeres 2 together with the hot air blown from the annular pipe 3 to the blow pipe 4.

The hot air is generated, for example, in a hot air stove (not shown). For example, a cylindrical furnace including a heat storage chamber in which silica bricks are arranged in a lattice shape can be used as the hot blast furnace. The temperature of the hot air is adjusted by detecting the temperature of the hot air and controlling the amount of heat stored in the hot air stove and the amount of air supplied based on the detection result. The above equipment configuration of the blast furnace 1 is an example, and the present invention is not limited to these configurations. That is, the present invention can also be applied to, for example, a bell-type blast furnace.

The pulverized coal contains 50% by mass or more of carbonaceous material having a high combustion rate when the total amount of pulverized coal to be blown is 100% by mass. That is, in the blast furnace operating method of the present embodiment, the operating condition is to inject pulverized coal rich in carbonaceous materials with a high combustion rate from the tuyeres 2. The definition of burning rate is as follows. First, carbon material (mass 10 mg) is heated to 900 (°C/ The combustion rate (mg) is calculated by increasing the temperature from room temperature to 1000°C at a heating rate of /min) can be obtained. Note that the end point at which the change in the mass of the carbonaceous material ends is the point in time when the slope of the curve of the temporal change in the mass of the carbonaceous material deviates from the linear relationship.

Furthermore, in this specification, "charcoal material with a high burning rate" refers to a carbon material with a burning rate of 3.0 (mg/min) or more. A carbonaceous material with a burning rate of 3.0 (mg/min) or more is easier to burn than conventional carbonaceous materials. As a carbon material having a combustion rate of 3.0 (mg/min) or more, char obtained by carbonizing biomass or lignite can be used. Biomass includes, for example, agricultural biomass (wheat straw, sugarcane, rice bran, plants, coconut kernels, etc.), forestry biomass (paper manufacturing waste, lumber waste, thinned wood, firewood forests, etc.), and livestock biomass (livestock). Biomass from fisheries (fisheries processing residues), biomass from waste products (garbage, RDF (Refused Derived Fuel) garden trees, construction waste, sewage sludge), etc. can be used. . Regarding lignite, there are no particular restrictions on the production area. Furthermore, char is a carbonaceous substance that is produced when a carbon material is heated without being softened or molten (see JIS0104 Coal Utilization Technical Terminology).

Note that the particle size of the pulverized coal used in this embodiment is not particularly limited, but can be set to, for example, 75 μm or less.

The configuration of the blast furnace injection lance 5 will be described in detail with reference to FIG. 2. FIG. 2 is an enlarged view of the tip of the blast furnace injection lance of this embodiment. The blast furnace blowing lance 5 has a double tube structure consisting of an inner tube 51 and an outer tube 52, and pulverized coal is blown into the inner tube 51, and the outer tube 52 (in other words, the inner tube 51 and the outer tube 52) Hydrogen-based reducing gas is blown in from the gap formed between the two. An inert gas such as nitrogen gas can be used as a carrier gas for blowing the pulverized coal. The hydrogen-based reducing gas is a reducing gas containing at least hydrogen as an element, and may be a hydrogen-containing gas such as natural gas, COG, LPG, or methane gas, or may be hydrogen gas itself.

The distal end surface 51A of the inner tube 51 is formed in a notch shape, and is inclined by θ (hereinafter referred to as the distal end inclination angle θ) with respect to a plane perpendicular to the longitudinal axis 5a of the inner tube 51 and the outer tube 52. are doing. Details of the tip inclination angle θ will be described later. The distal end surface 52A of the outer tube 52 is perpendicular to the longitudinal axis 5a, and does not have a cutout shape like the inner tube 51. Here, when the distance (separation distance) in the direction of the longitudinal axis 5a between the distal end of the distal end surface 51A of the inner tube 51 and the distal end surface 52A of the outer tube 52 is W, the distance W is calculated by the following formula ( 1) must be satisfied.
W≦tanθ×D・・・・・・Formula (1)
However, D is the diameter of the inner tube 51.
FIG. 2 illustrates a state in which the distal end of the inner tube 51 and the distal end surface of the outer tube 52 are flush with each other (that is, distance W=0), but within the range of formula (1), the inner tube 51 is 52 (see "Protruding position" in FIG. 2), or may be retracted inside the outer tube 52 (see "Pipe line position" in FIG. 2).

The present inventor discovered that it is possible to prevent an excessive rise in the temperature of the furnace body by simultaneously satisfying condition A regarding the amount of hydrogen-based reducing gas blown into the blast furnace, and conditions B and C regarding the structure of the blast furnace injection lance 5. did.
Condition A: When the flow rate of the hydrogen-based reducing gas flowing through the outer tube 52 is X1, and the flow rate of the carrier gas flowing through the inner tube 51 is X2, X1/X2≧0.5.
Condition B: The tip inclination angle θ of the tip surface 51A of the inner tube 51 is set to 55 degrees or more (less than 90 degrees).
Condition C: W≦tanθ×D
Note that the condition C has been described above, so the explanation will not be repeated.

By satisfying condition A and condition B at the same time, with condition C being satisfied as a precondition, the pulverized coal discharged from the inner tube 51 becomes dense and difficult to come into contact with oxygen, so the combustion focus is shifted to the inside of the furnace. can be done. Thereby, excessive temperature rise in the furnace body temperature can be prevented. That is, by setting the tip inclination angle θ to 55 degrees or more, the pulverized coal particles discharged from the inner tube 51 can be dispersed once. By satisfying the injection condition of condition A, the dispersed pulverized coal particles are surrounded by the hydrogen-based reducing gas and cannot be dispersed, but instead become densely packed, so that the dense state can be maintained until they are blown into the furnace. . In other words, the pulverized coal particles once dispersed collide with the hydrogen-based reducing gas traveling straight in a ring shape and are bounced back toward the center of the ring, so that the pulverized coal particles can be densely packed. On the other hand, when the tip inclination angle θ is lowered to less than 55 degrees, the pulverized coal particles discharged from the inner tube 51 do not disperse and are less likely to collide with the hydrogen-based reducing gas, so that the above-mentioned crowding effect can be fully expressed. I can't.

Next, the present invention will be specifically explained by showing examples.
(Test 1)
Using a test device simulating the lower part of a blast furnace shown in FIG. 3, the rate of change in furnace body temperature (%) was evaluated while varying the flow rates of the carbonaceous material used as pulverized coal and the hydrogen-based reducing gas. Note that the furnace body temperature was measured by a temperature sensor 15, which will be described later. The experiment was conducted under constant standard conditions, and the temperature at which almost no change in the temperature sensor 15 was observed was defined as the furnace body temperature under the standard conditions. Next, the conditions were changed and the experiment was continued until the measured value of the temperature sensor 15 stopped changing, and the temperature was measured when the value stopped changing. The temperature difference between the two was divided by the furnace body temperature under the standard conditions to obtain the furnace body temperature change rate under the changed conditions. The time required to stabilize the conditions after changing them was about 3 hours. In the test furnace 10 in FIG. 3, 12 is a tuyere, 13 is a blow pipe that supplies hot air to the tuyere 12, and 14 is a double tube structure test furnace lance (hereinafter referred to as a double tube test furnace lance). 15 is a temperature sensor. Note that the number of double tube lances 14 for the test furnace is one.

The test furnace 10 was a vertical rectangular parallelepiped with a length of 1.2 m, a width of 1.2 m, and a height of 2.4 m, and the furnace wall had a two-layer structure with refractory bricks pasted on the inside of the iron shell. A thermocouple was used as the temperature sensor 15, and this thermocouple was placed 600 mm above the central axis of the tuyere 12 between the furnace brick and the iron skin.

The test furnace 10 was filled with coke having a particle size of 9 to 13 mm. The blowing temperature of the hot air was set to 1200° C., and the blowing amount was set to 0.8 (m ³ /min). The amount of pulverized coal injected was made to match the blowing conditions of a typical actual furnace: 200 (kg/pig-ton).
In addition, pulverized coal particles (75 μm or less) used in an actual blast furnace were used.

Table 1 shows the type and properties of the carbon material used as pulverized coal in this test. Char 1 is a char obtained by carbonizing brown coal, and Char 2 is a char obtained by carbonizing biomass (wood). Ash is ash and FC is fixed carbon. Since the VM has been described above, the description thereof will not be repeated.

Table 2 shows the injection ratio of each carbon material blown from the test furnace double tube lance 14, tip inclination angle θ, flow rate ratio of hydrogen-based reducing gas and carrier gas (X1/X2), furnace body temperature change rate, and evaluation. Show the results. In addition, the blowing ratio of each carbon material was shown as a mass fraction when the total amount of pulverized coal injected in each comparative example and example was set to 100% by mass. The rate of change in furnace body temperature in each Example and Comparative Example was calculated by setting the rate of increase in furnace body temperature in the Reference Example as 100%. When the furnace body temperature change rate was 100% or less, the evaluation was given as "○", and when the furnace body temperature change rate was more than 100%, the evaluation was given as "x". As a hydrogen-based reducing gas, a gaseous reducing agent containing hydrogen that simulates the components of coke oven gas (in mass %, H ₂ : about 59%, CH ₃ : about 29%, CO: about 6%, N ₂ : about 6 %)It was used.
By comparing and referring to the reference example, comparative example 1, and comparative example 2 in which the tip inclination angle θ is unified to 0 degrees, the content ratio of semi-anthracite coal A with a combustion rate of less than 3.0 (mg/min) is 100% by mass. By reducing the amount from 50% by mass and switching to Char 1 or Char 2, which has a combustion rate of 3.0 (mg/min) or more, the rate of change in furnace body temperature (%) increased. It is thought that the inclusion of carbonaceous material with a combustion rate of 3.0 (mg/min) or higher caused the combustion focus to be near the tuyeres, and the rate of change in furnace body temperature (%) increased.

In Examples 1 to 4, the furnace body temperature change rate was comparable to that of the reference example (100%), and the evaluation was "○". It is presumed that by satisfying conditions A and B, an effect of crowding the pulverized coal was produced, and the combustion focus was shifted to the inside of the furnace. In addition, comparing Examples 1 and 2 with Examples 5 and 6, even if X1/X2 is lowered from 1.0 to 0.5, the furnace body temperature change rate (%) is almost the same as that of the reference example. It was found that it was maintained to a certain extent. Comparing Examples 5 and 6 and Comparative Examples 3 and 4, by lowering X1/X2 from 0.5 to 0.4, the furnace body temperature change rate (%) was significantly lower than that of the reference example. It was found that it increases. It is presumed that as X1/X2 decreased to 0.4, the effect of maintaining the dense state of pulverized coal decreased, and the combustion focus shifted to the tuyere side.

(Test 2)
In order to investigate the reason why the rate of change in temperature of the furnace body improves by setting the tip inclination angle θ to 55 degrees or more, we varied the tip inclination angle θ and determined the rate of increase in the density of carbonaceous particles. . The rate of increase in the degree of density of carbonaceous particles was evaluated by the rate of increase (%) in the number of carbonaceous particles existing within a predetermined area. Specifically, we used general-purpose fluid analysis software (FLUENT) to calculate the state of motion of particles injected into the blowpipe from the blast furnace injection lance, and calculated the following results at a position 100 mm from the tip of the blast furnace injection lance toward the inside of the furnace. A snapshot of carbon particles inside the blowpipe was output. From the output snapshot results, the number of carbonaceous particles within a circular area (an area corresponding to 6.25% of the cross-sectional area of the blow pipe) centered on the center point of the cross-section of the blow pipe was counted. As the carbon material particles, pulverized coal particles (particle size: 75 μm or less) that are blown into an actual blast furnace were used. Note that the flow rate ratio (X1/X2) of the hydrogen-based reducing gas and the carrier gas was set to 1.2.

Based on this tabulation result, the rate of increase (%) in the number of carbonaceous particles was calculated, with the number of carbonaceous particles within the circular region when the tip inclination angle θ was 0 degrees as 100%. FIG. 4 is a graph summarizing the calculation results. Referring to the figure, as the tip inclination angle θ increased, the rate of increase in the number of carbonaceous particles (that is, the rate of increase in the degree of density of carbonaceous particles) increased. In particular, when the tip inclination angle θ was set to 55 degrees or more, the rate of increase in the degree of density of carbonaceous particles increased significantly. That is, it was found that by setting the tip inclination angle θ to 55 degrees or more, the pulverized coal discharged from the blast furnace injection lance was sufficiently dense.

(Test 3)
In order to evaluate the influence of the amount of hydrogen-based reducing gas blown on the dispersion of carbonaceous materials, the rate of increase in the degree of density of carbonaceous material particles was investigated by changing the flow rate of hydrogen-based reducing gas. The degree of density of carbonaceous particles was calculated using the same method as Test 2. The tip inclination angle θ was unified to 55 degrees. The graph in FIG. 5 is a test result, and the flow rate of the hydrogen-based reducing gas is expressed as X1/X2 (flow rate of hydrogen-based reducing gas/flow rate of carrier gas for pulverized coal) described in the embodiment.

As shown in the figure, it was found that when X1/X2 reached 0.5, the rate of increase in the degree of density of carbonaceous particles increased rapidly.

In addition, under the blowing conditions of When the rate of increase in the degree of density of material particles was investigated, they were "13.1%", "13.5%", "13.3%", and "12.9%", respectively. It was confirmed that the rate of increase in the density of carbonaceous particles hardly changes depending on the direction of the cut surface. The direction of the cut surface was defined as ``top'', ``right'', ``bottom'', and ``left'' in the clockwise order of the direction in which the cut surface faces when the tuyere is viewed from inside the furnace. .

1: Blast furnace 2: Tuyere 3: Annular tube 4: Blow pipe 5: Blast furnace blowing lance 6: Tapping port 51: Inner tube 52: Outer tube

Claims (4)

In a blast furnace blowing lance with a double pipe structure having an outer pipe and an inner pipe,
The distal end opening of the inner tube is inclined by a predetermined angle θ of 55 degrees or more with respect to a plane perpendicular to the axial direction of the inner tube, and the distal end of the distal opening of the inner tube and the outer tube A blast furnace blowing lance, characterized in that, where W is a distance in the longitudinal direction of the blast furnace blowing lance from the tip opening of the blast furnace blowing lance, the distance W satisfies the following formula (1).
W≦tanθ×D・・・・・・Formula (1)
However, D is the diameter of the inner tube. The distal end portion of the inner tube is located at any one of a protruding position outside the outer tube, a position inside the outer tube within the conduit, and a flush position flush with the distal end opening of the outer tube. The blast furnace blowing lance according to claim 1, wherein the lance is provided with a lance. The blast furnace blowing lance according to claim 1 or 2, wherein the tip opening of the outer tube is perpendicular to the axial direction of the inner tube. A method of operating a blast furnace in which the blast furnace blowing lance according to any one of claims 1 to 3 is inserted into a blow pipe,
While blowing hydrogen-based reducing gas from the outer tube,
Injecting pulverized coal containing 50% by mass or more of carbonaceous material with a combustion rate of 3.0 (mg/min) or more through the inner tube with a carrier gas,
A method for operating a blast furnace, characterized in that the blowing conditions shown in the following equation (2) are satisfied, where the flow rate of the hydrogen-based reducing gas is X1 and the flow rate of the carrier gas is X2.
X1/X2≧0.5...Formula (2)