JPH02182813A - Method for operating blast furnace - Google Patents

Abstract

PURPOSE:To keep the temp. at raceway constant by beforehand detecting furnace heating condition at lower part of the furnace with the temp. near the raceway and controlling relative descending velocity of charged material near furnace wall in the bosh part with the specific equation based on the detected temp. CONSTITUTION:Surface temp. of the charged material near the raceway 7 in the blast furnace is continuously measured, and when this measured value is varied by TR from the setting temp. near the raceway 7, variation VS of the relative descending velocity for the charged material near the furnace wall within 2m from the furnace wall in the bosh part A or a shaft part B is made as a function of the temp. near the raceway 7 and calculated by using the equation VS=(a)X TR and the relative descending velocity of the charged material near the furnace wall in the bosh part A or the shaft part B is adjusted by VS. Then, in the equation, (a) is factor and in the case of adjusting the relative descending velocity of the charged material in the bosh part A, this is made to the value in the range of 3.6-4.5X10<-4>, and in the case of adjusting the relative descending velocity in the shaft part B, this is made to the value in the range of 2.2-2.8X10<-4>. By this method, the stable and efficient blast furnace operation can be executed.

Description

DETAILED DESCRIPTION OF THE INVENTION [Industrial Field of Application] The present invention relates to a method for operating a blast furnace under stable conditions.

[Conventional technology]

When operating a blast furnace, the goal is to operate efficiently (low fuel ratio, high iron production ratio, etc.) under stable furnace conditions. In order to achieve this operation, it is required to precisely control the furnace thermal state, especially in the lower part of the furnace. Methods for detecting the furnace thermal condition in the lower part of the furnace include methods that estimate the furnace thermal condition in the lower part of the furnace using a mathematical model, methods that directly measure the furnace thermal condition using various detection ends, hot metal temperature, Sl content, etc. There are known methods for estimating the furnace thermal state from

The method of estimating the furnace thermal state in the lower part of the furnace using a mathematical model has been introduced in almost all blast furnaces, although there are some problems with estimation accuracy. Recently, methods for directly measuring furnace thermal conditions such as tuyere tip temperature and furnace wall temperature using various detection ends have been applied to blast furnaces.

On the other hand, although the method of estimating the furnace thermal state from the temperature of hot metal or Si 2 content has good estimation accuracy, it has the disadvantage that action tends to be delayed.

In addition, these detection methods also become effective for stable operation of a blast furnace by combining them with means for controlling furnace heat. For example, in Japanese Patent Application Laid-open No. 55-104406,
Charge control, air blow control, fuel injection control, furnace top pressure control, etc. are performed so that the heat flow ratio calculated from the gas temperature and rate of fall measured by the detection end matches the set reference heat flow ratio. Furthermore, in Japanese Patent Publication No. 63-31523, when there is a protrusion of 100 mm or more on the wall of the blast furnace under the furnace wall, the layer thickness ratio of ore/coke near the furnace wall is adjusted to the average layer thickness ratio. The charging of raw materials is controlled so that the amount increases by 10% or more.

[Problem to be solved by the invention]

However, in the method of JP-A-55-104406 mentioned above, the method for setting the reference heat flow ratio is not clarified;
Therefore, the standards for action are not clear. Also,
The method disclosed in Japanese Patent Publication No. 63-31523 is an extremely effective method when erosion of the refractories constituting the blast furnace progresses and disturbances occur in the furnace wall, but it It cannot be applied to profiles with little erosion and unevenness of the furnace wall bricks.

Therefore, an object of the present invention is to perform stable and efficient blast furnace operation by controlling the relative descending speed of the charge near the furnace wall.

[Failure to solve the problem]

The present invention detects the furnace thermal state in the lower part of the furnace in advance at the temperature near the raceway, and uses a specific relational expression based on the detected temperature to determine the relative position of the charge near the furnace wall in the morning glory section or the shaft section. Maintain a constant raceway temperature by controlling the rate of descent. As a result, the furnace thermal condition in the lower part of the furnace is controlled, resulting in stable and efficient blast furnace operation (low fuel ratio,
This is to achieve a high iron output ratio).

That is, the present invention measures the temperature near the raceway of a blast furnace, and when the measured temperature fluctuates from a preset temperature near the raceway, the relative drop of the charge near the furnace wall within 2 m from the furnace wall is measured. The method is characterized in that the speed change amount Δvs is calculated as a function of the furnace wall temperature using the following equation (1), and the relative descent speed near the furnace wall is adjusted and controlled by ΔVS. Here, the relative descending speed V is a value obtained by dividing the descending speed by the average descending speed of the blast furnace calculated from the amount of iron tapped and the amount of coke burned.

ΔVs=aXΔT3...(1) Here, Δv
5 is the amount of change in relative descent speed (dimensionalless variable), and ΔT@ is the amount of change in temperature near the raceway (° C.). a is a coefficient, which is in the range of 3.6 to 4.5X10-' when adjusting the relative descending speed of the charge in the bosh section, and from 2.2 to 4.5 x 10-' when adjusting the relative descending speed of the shaft section. 2.8X10-
Takes values in the range '.

[Effect]

The above-mentioned formula (1) was obtained from the experimental results described below.

In this experiment, a model having a structure as shown in FIG. 2 and having a size of about 1/20 of an actual blast furnace was used. The hearth diameter of this model is 345 mm, the hearth diameter is 378 mm,
The effective height from the tuyere to the top of the shaft is 1217mm.
Met. In addition, at the front of the equipment, coke and pseudo-ore (a mixture of easily melted metal and stearic acid whose solid-liquid flow rate ratio and packing density are adjusted to approximate the conditions in the actual blast furnace) are deposited. A heat-resistant glass was attached so that the melting behavior could be observed.

Coke 1 and pseudo ore 2 were charged alternately in layers from a bell 3 at the top of the device via a movable armor 4. On the other hand, heated air at 180°C is passed through 18 tuyeres 5 at the bottom of the device.
The pseudo ore 2 was molten and dripped. The molten material was collected in the hearth and then discharged from the tap hole 6. The coke was conveyed to a lower hopper by six row reef feeders 8 installed directly below the raceway 7, and further discharged into a closed storage by a chiny bra conveyor 9. In addition, in this blast furnace model, the temperature state inside the furnace is 0.

A thermometer, pressure gauge, and hot wire anemometer were installed to detect the stress state and gas flow near the wall.

We then determined the relationship between the temperature near the raceway, which represents the furnace thermal state in the lower part of the furnace, and the relative descending speed of the charge near shaft section B. As shown, it was found that a linear functional relationship was established. This relational expression can be expressed by the following equation, where the temperature near the raceway to the morning glory section is T8, and the relative descending speed of the charge near the shaft section B is v5.

Tl1 = -263,3x V, +272.2 Therefore, the amount of variation ΔT in the temperature TI near the raceway and the amount ΔVS of variation in the relative descent speed ■3 have the following relationship, and the variation 9 in the temperature T1 near the raceway In order to make 8T as zero as possible, it is necessary to control the amount of change ΔVs in the relative descending speed Vs so as to satisfy the following equation.

ΔTl=263.3XΔVs The vicinity of the raceway in the present invention is a range of 1 m from the periphery of the raceway space that is closely related to the furnace heat in the lower part of the furnace. In addition, the reason why the relative descending velocity V is taken as the relative descending velocity of the charge located near the furnace wall within 2 m from the furnace wall is that the
This is because this model experiment revealed that the relative descending speed of the charge within the range of m or less has a large effect.

When converting the above equation to an actual furnace based on the Stanton number, the following equation (2) is obtained. Note that the Stanton number is the ratio of the heat transfer between gas and solid to the amount of heat stored in the charge, and the blowing temperature for this model experiment was determined so that the Stanton number in the actual reactor and the Stanton number in the model matched. has been done. Therefore, by assuming that the Stanton number is constant, it is possible to calculate the actual reactor conversion value based on the Stanton number from the temperature measurement value of this model experiment.

ΔT*=350XΔVS...(2) Therefore, from the cutting, ΔVS=aXΔTII...(1) is obtained, and this relational expression is used to calculate the variation ΔT@ of the coke surface temperature T near the raceway. When the amount of change ΔVs in the relative descending speed V5 of the charge is controlled based on V5, operation under stable furnace conditions becomes possible.

That is, when the amount of variation ΔT1 becomes larger on the plus side, the operation is performed such that the amount of change Δvs in the relative descending speed V becomes larger on the plus side. Further, when the amount of variation ΔT□ becomes large on the negative side, an operation is performed such that the amount of change ΔVs in the relative descent speed Vs becomes large on the negative side. As a result, the furnace heat condition is always kept within a stable range, and efficient operation is performed.

Note that as means for varying the amount of change Δv5, there is a method of controlling fuel injection conditions, charge distribution conditions, air blowing conditions, and the like. For example, fuel injection reduces coke combustion and slows the relative rate of descent of the charge. Also,
The relative rate of descent can also be controlled by controlling the combustion of coke by adjusting the flow rate of the injected liquid fuel. Furthermore, when the ore/coke layer thickness ratio near the furnace wall is increased, the relative rate of descent increases.

Note that the above-mentioned equation (1) is a relational equation derived to control the relative descending speed V of the charge in the shaft section B, but the temperature T near the raceway 7 is It was found from similar experiments that there is a relationship expressed by a linear function with respect to the relative descending speed of the charge. Therefore, by adjusting the relative rate of descent of the charge into the bosh section, the furnace thermal state can also be controlled. In this case, the coefficient a in equation (1) is expressed in a slightly modified range as follows.

a=3.6~4.5X10-' In this way, by adjusting the relative falling speed of the contents in the furnace, the furnace thermal state is controlled, and the blast furnace can be operated under stable barking conditions. . Further, according to the present invention, the time required for taking a predetermined response after detecting the temperature inside the furnace and for the result to appear in the furnace heat is short, making it possible to control the furnace condition quickly and with high precision.

〔Example〕

Example 1 During actual operation of a blast furnace, an optical thermometer was installed near the raceway 7 of the blast furnace, and the surface temperature of coke near the raceway 7 was continuously measured. The surface temperature of the coke near the raceway 7 from the start to the end of the measurement fluctuated upward and downward in a range of about 300°C, centered around an average of 1700°C. Therefore, when the amount of variation ΔT11 in the surface temperature of the coke in the raceway 7 exceeded +200° C., the fuel injection was stopped and the amount of coke burned was increased. As a result, the descending speed of the charge at the end of the shaft increased from 5 m/hour to 5.3 m/hour, and the coke surface temperature Til near raceway 7 returned to the target temperature of 1700° C. in 20 minutes. In addition, in an example using an actual reactor, the actual descending speed will be used instead of the above-mentioned relative descending speed.

Furthermore, when the amount of variation ΔT in the surface temperature of the coke near the raceway 7 reached 1,200° C., the amount of fuel blown was increased to suppress the amount of coke burned. This results in
The descending speed of the charge in shaft part B decreased from 5 m/h to 4.7 m/h, and in 20 minutes raceway 7
The surface temperature T of the nearby coke returned to the target temperature of 1700°C.

-Example 2- Similarly, an optical thermometer was installed near the raceway 7 of the blast furnace, and the surface temperature of the coke near the raceway 7 was continuously measured. The surface temperature of the coke near the raceway 7 from the start to the end of the measurement fluctuated upward and downward in a range of about 300°C, centered around an average of 1700°C. Therefore, the amount of variation ΔT in the surface temperature of coke near raceway 7
When R exceeds +200℃, stop fuel injection and
Increased the amount of coke burned. By this, morning glory m
The rate of descent of the charge at A is from 6 m/hour to 6.5 m
/ hour, and the coke surface temperature T near raceway 7 returned to the target temperature of 1700°C in 20 minutes.

Furthermore, when the amount of variation ΔTIl in the surface temperature of coke near raceway 7 reached -200° C., the amount of fuel blown was increased to suppress the amount of coke burned. As a result, the descending speed of the charge in the morning glory section A is increased from 6 m/hour to 5 m/hour.
．． The surface roar T of the coke near raceway 7 decreased by 5 m/h in 20 seconds.

The temperature returned to the target temperature of 1700°C.

〔Effect of the invention〕

As explained above, in the present invention, the temperature near the raceway, which typically represents the furnace thermal state, is controlled by adjusting the relative descending speed of the charge that descends inside the blast furnace. be able to. Therefore, it is possible to always maintain the furnace condition in a stable state and efficiently operate the blast furnace with a low fuel ratio and high iron production ratio.

[Brief explanation of the drawing]

FIG. 1 is a graph showing the relationship between the relative descending speed of the charge and the temperature near the raceway, and FIG. 2 shows the blast furnace model used in the present invention. 1: Coke 2: Pseudo ore 3: Bell
4: Movable armor 5: Tuyere
6: Tapping lower: Raceway 8: Rotary feeder 9: Chiny bra conveyor A: QB face part B: Shaft part Patent applicant Nippon Steel Corporation Representative Mr.
Masu Kobori (and 2 other people) Sum of the charges vs. descending speed 1 (-) Fig.

Claims (1)

[Claims] 1. When the temperature near the raceway of the blast furnace is measured and the measured value fluctuates by ΔT_R from the preset temperature near the raceway, 2 m from the furnace wall of the morning glory section or the shaft section.
The amount of change Δ in the relative descending speed of the charge near the furnace wall within
A blast furnace operating method characterized in that V_S is calculated as a function of the temperature near the raceway using the following equation, and the relative descending speed of the charge near the furnace wall in the morning glory section or the shaft section is adjusted by ΔV_S. ΔV_S=a×ΔT_R [However, a is a coefficient, and when adjusting the relative descending speed of the charge in the morning glory section, it is 3.6 to 4.5×10^-^4
In the case of adjusting the relative descending speed of the shaft part, the value is in the range of 2.2 to 2.8 x 10^-^4. ]