JPH02182814A - Method for operating blast furnace - Google Patents

Abstract

PURPOSE:To keep the temp. at raceway constant by beforehand detecting furnace heat condition at lower part of the furnace with the temp. near the raceway and controlling heat flow rate near furnace wall in a shaft 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 preset temp. near the raceway 7, variation HFR of the heat flow rate near the furnace wall within 2m from the furnace wall in a bosh part A or the shaft part B is made as a function of the temp. near the raceway 7 and calculated by using the equation HFR=(a)X TR, and the heat flow rate near the furnace wall in the bosh part A or the shaft part B is adjusted by HFR. Then, in the equation, (a) is factor and in the case of adjusting the heat flow rate in the bosh part A, this is made to the value in the range of 1.2-1.5X10<-3>, and in the case of adjusting the heat flow rate in the shaft part B, this is made to the value in the range of 4.8-5.9X10<-4>. By this method, the stable and efficient blast furnace operation is 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, Si 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 can also be effective for stable operation of blast furnaces 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 below the belly of the furnace, the layer thickness ratio of ore/coke near the furnace wall is compared with 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 operate a blast furnace stably and efficiently by controlling the heat flow ratio near the furnace wall.

[Means 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 controls the heat flow ratio near the furnace wall of the shaft part using a specific relational expression based on the detected temperature. Maintain a constant temperature in the way. As a result, the furnace thermal condition in the lower part of the furnace is controlled, and stable and efficient blast furnace operation (lower fuel consumption, higher iron output) is achieved.

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 amount of change ΔI in the heat flow ratio near the furnace wall within 2 m from the furnace wall (It is characterized in that pi is calculated as a function of the temperature near the raceway using the following equation (1), and the heat flow ratio near the furnace wall is adjusted and controlled by ΔHF11.

ΔHFa=aXΔT1 (1) Here,
Δ)(pil) The amount of change in the heat flow ratio HF R (dimensionless variable), ΔT, is the amount of change in temperature near the raceway (1). And, a is the coefficient, and the heat flow ratio of the morning glory part is When adjusting the heat flow ratio of the shaft part, it is in the range of 1.2 to 1.5X10-3, and when adjusting the heat flow ratio of the shaft part, it is 4.8 to 5.9.
Takes a value in the range of X 10-'.

Note that the heat flow ratio HF,l is expressed by the following formula.

C1×G, C1×ρ, × However, CS is the specific heat of the charge C1 is 1 heat of gas G, is the mass velocity of the charge G is the mass velocity of the gas ρ5 is the bulk density of the charge ρ9 is the density of the gas Vs is the rate of descent of the charge v9 is the rising speed of gas V.

kcal/(kg-k) kcal/(kg-k>kg/(m''・sec)kg/(m''・sec)kg/m'kg/m' m7 seconds m7 seconds [action] The above formula [1 ) were obtained from the experimental results described below.

In this experiment, a model of an actual blast furnace approximately 1×20 in size and having the structure shown in FIG. 2 was used. The hearth diameter of this model is 345 cm, and the hearth diameter is 378 ll1m.
, the effective height from the tuyere to the top of the shaft is 1217
It was mm. 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 alternately charged 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 rotary 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 9 air permeability.

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

When we determined the relationship between the coke surface temperature near raceway 7, which represents the furnace thermal state in the lower part of the furnace, and the heat flow ratio near shaft section B, there was a relationship between the two as shown in Figure 1. It was found that a linear functional relationship holds true. This relational expression can be expressed by the following equation, where the coke surface temperature near the raceway 7 is TRs and the heat flow ratio near the shaft portion B is HPI.

T* −−125, Ox H, +225.2 Therefore, the amount of variation ΔTR in the surface temperature T of coke near raceway 7 and the amount of variation ΔHF 11 in the heat flow ratio HF1 have the following relationship, and In order to make the furnace temperature T, as low as possible, it is necessary to control the amount of change in the heat flow ratio ΔHF l so as to satisfy the following equation.

Δ”r, = 125, OXΔHF 1 In the present invention, the vicinity of the raceway is a range of 1 m from the periphery of the raceway space in the lower part of the furnace, which is closely related to the furnace heat. The reason for setting the heat flow ratio of the charge near the furnace wall within 2 m from This is because it was found in this model experiment that the

When converting the above equation to an actual furnace based on the Stanton number, the following equation (2) is obtained. The Stanton number is the ratio of the amount of heat transfer between gas and solid to the amount of heat accumulated in the charge, and the blast temperature in this model experiment was determined so that the Stanton number in the actual furnace and the Stanton number in the model matched. ing. 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.

Δ T ll ;; +875 x Δ T □
・ ・ ・ (2) So,
From the abrasion, ΔHPa=aXΔTR'''m is obtained, and using this relational expression, the change in heat flow ratio I (pi When controlling the amount ΔHFR, operation under stable furnace conditions becomes possible. That is,
When the amount of variation ΔTl increases to the positive side, an operation is performed such that the amount of change ΔHFR of the heat flow ratio HF& increases to the positive side. Furthermore, when the amount of variation ΔTR increases to the negative side, the operation is performed such that the amount of change ΔHFR of the heat flow ratio Hpx increases to 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 Δ)lpm, there is a method of controlling fuel injection conditions, charge distribution conditions, air blowing conditions, etc. For example, by changing the particle size or amount of ore or coke charged near the furnace wall, the gas flow velocity or descent rate near the furnace wall can be changed, and the heat flow ratio near the furnace wall can be controlled.

Note that the above-mentioned equation (1) is a relational equation derived for controlling the heat flow ratio ΔHPI at the end of the shaft portion.

However, similar experiments have revealed that the temperature TR in the vicinity of the raceway 7 also has a relationship expressed by a linear function with respect to the heat flow ratio HF1l in the morning glory section Δ. Therefore, by adjusting the heat flow ratio HPI in this morning glory section A, the furnace heat state can also be controlled. In this case, the coefficient a in equation (1) is expressed in a slightly modified range as follows.

a = 1.2 to 1.5X10-' In this way, by adjusting the heat flow ratio HPa, the furnace thermal state is controlled, and the blast furnace can be operated under stable 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 - In 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 ΔTIl in the surface temperature of coke near raceway 7 exceeds +200°C,
Fuel injection was stopped to increase the amount of coke combustion, and at the same time, the particle size of the ore charged within 2 m from the furnace wall was reduced to reduce the gas flow rate near the furnace wall. This increases the heat flow ratio at the shaft end from 0.70 to 0.7.
8, and the coke surface temperature Ti near raceway 7 returned to the target temperature of 1700°C in 20 minutes.

In addition, when the amount of variation ΔT in the surface temperature of coke near raceway 7 reaches 1200°C, the amount of fuel injection is increased to suppress the amount of coke combustion, and at the same time, the amount of variation ΔT in the surface temperature of coke near raceway 7 is increased to suppress the amount of coke combustion. The particle size of the charged ore was increased to increase the amount of gas flowing near the furnace wall. As a result, the heat flow ratio in the shaft portion B decreased from 0.70 to 0.62, and the surface temperature T of the coke near the raceway 7 returned to the target temperature of 1700° C. in 20 minutes.

Example 2 - Similarly, an optical thermometer was installed near the raceway 7 of the blast furnace, and the surface temperature of the charge near the raceway 7 was continuously measured. The furnace wall temperature from the start to the end of the measurement was on average 1
It fluctuated within a range of approximately 300°C above and below 700°C. Therefore, when the amount of variation ΔTQ in the coke surface temperature near raceway 7 exceeds +200°C, the fuel injection is stopped and the amount of coke combustion is increased. The particle size of the incoming ore was reduced to reduce the amount of gas flowing near the furnace wall. This increases the heat flow ratio to the morning glory from 0.70 to 0.89.
The coke surface temperature TI near raceway 7 returned to the target temperature of 1700° C. in 20 minutes.

In addition, when the amount of variation ΔT in the surface temperature of coke near raceway 7 reaches 1200°C, the number of fuel injection bases is increased to suppress the amount of coke combustion, and at the same time, the fuel injection base is increased within a range of 2 m from the furnace wall. The particle size of the charged ore was increased to increase the amount of gas flowing near the furnace wall. As a result, morning glory part A
The heat flow ratio at T11 decreased from 070 to 0.51, and the surface temperature of coke near Raceway 7 decreased in 20 minutes.
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, can be controlled by adjusting the amount of change in the heat flow ratio in the blast furnace. Therefore, the furnace condition is always maintained in a stable state,
It becomes possible to operate the blast furnace efficiently 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 temperature near the raceway and the heat flow ratio, and FIG. 2 shows the blast furnace model used in the present invention. 1: Coke 2: Pseudo ore 3; Bell 4: Movable armor 1
5: Tuyere 6: Tapping lower: Raceway 8: Raw cliff feeder 9: Tubular conveyor A: Morning glory section B: Shaft section

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 in the heat flow ratio near the furnace wall within ΔH_F_R is calculated as a function of the temperature near the raceway using the following formula, and the heat flow ratio near the furnace wall in the morning glory part or the shaft part is adjusted by ΔH_F_R. Blast furnace operation method. ΔH_F_R=a×ΔT_R [However, a is a coefficient, which is in the range of 1.2 to 1.5 × 10^-^3 when adjusting the heat flow ratio of the morning glory part, and when adjusting the heat flow ratio of the shaft part 4.8~5.9×10
Takes a value in the range ＾-＾4. ]