JPH0317209A - Method for operating blast furnace - Google Patents

Abstract

PURPOSE:To control blast furnace condition with high accuracy and to maintain good operating condition in the blast furnace by predicting variation of softening fused-sticking zone based on difference between the calculated descending velocity of the softening fused-sticking zone and the actual measured value of descending velocity of charged material and the calculated value of heat flow ratio. CONSTITUTION:Temp. and gas component distribution in the furnace diameter direction are measured with a gas sampler set just above the charged material at the upper part of the blast furnace. From the above measured values and the operational condition, shape and position of the softening fused-sticking zone is obtd. by quantitatively calculating as iso-thermal line distribution at 1400 deg.C the temp. of charged material in furnace diameter direction. On the other hand, the descending velocity of the charged material is actually measured with a micro wave profile meter reflecting the micro wave on surface of the charged material at the furnace top. Based on the calculated descending velocity of the above softening fused- sticking zone, the actual measured value of the descending velocity of the charged material and heat flow ratio at the blast furnace operation separately calculated, the future position and shape of the softening fused-sticking zone are predicted. The furnace top charging condition, tuyere blasting condition, etc., are controlled so that the prediction of this changing direction comes in the adequate range. By this method, the control with the high accuracy can be executed, the good blast furnace operating condition is maintained and the productivity is improved.

Description

[Detailed Description of the Invention] [Industrial Application Field] The present invention relates to a method of operating a blast furnace, in particular, a method for controlling the charge or air blowing conditions assuming the future shape and position of the softened cohesive zone. This article relates to an operation method for stable operation with a good h rate. [Conventional technology] In a blast furnace, ores and coke are charged in layers from the top of the furnace.
Heat and smelt by blowing air from the grain.

The ores charged from the top of the furnace descend through the furnace and are heated and reduced by the gas above, and begin to soften and fuse at around 1,250°C, and melt and drip at around 1,400°C. This softening cohesive zone has extremely poor ventilation, so in order to ensure ventilation in the furnace in this area, the height of the softening cohesive zone temperature range should be different in the furnace radial direction, and the ore It is necessary to allow gas to flow into the coke layer between the minerals and the ores. Furthermore, if the position of the softening cohesive zone in the furnace is too low, the furnace heat will fluctuate due to poor reduction, and if it is too high, the high temperature area will expand and the ventilation will deteriorate, so it is important to keep the blast furnace stable. In order to operate efficiently, it is necessary to appropriately control the height of this softening and cohesive zone temperature range within the furnace.

In response to this, the present applicant first indexed the gas composition and temperature distribution in the radial direction of the furnace obtained with an in-furnace gas sampler installed at the top of the furnace and kept this within an appropriate range. Japanese Patent Laid-Open No. 60-404 describes a method for stabilizing and increasing the efficiency of blast furnace operation by grasping the isothermal distribution in the radial direction of the furnace at 1400°C, which is representative of the settling zone, and controlling this within an appropriate range.
This is proposed by No. 82. [Problem to be solved by the invention 1 The indexing of the gas composition and temperature distribution in the radial direction of the furnace obtained by a gas sampler is qualitative information about the height of the softened cohesive zone in the furnace, which is intertwined with other factors. In many cases, this was not appropriate as it provided only a limited amount of information, which in turn hindered the stability and efficiency of operations.

In addition, in calculating the isothermal distribution in the radial direction inside the furnace at 1400°C, the amount of reaction in the furnace is calculated based on the mass balance and heat balance from the furnace top gas temperature and components obtained as the operation results, and the operating conditions such as combined air blowing conditions. is calculated, and the temperature distribution in the furnace height direction is calculated from the reaction temperature and heat transfer rate. However, this calculation is performed under the condition that the inside of the furnace is maintained in a steady state, and the calculation is performed under an unsteady state. In other words, in many cases, calculations based on short-term operating results or calculations during periods where the conditions inside the reactor are undergoing significant changes cannot be applied because material balance and heat balance cannot be taken. Therefore, this method has the disadvantage that it is not possible to know how the shape of the softened cohesive zone and its position are changing. [Means for Solving the Problems] The present invention solves the above-mentioned problems, and the temperature in the radial direction of the furnace and the temperature in the radial direction of the furnace determined by the gas sampler installed directly above the charge in the upper part of the blast furnace. CO, CO2. H2. From the distribution of gas components such as N2 and the operating conditions, the shape and position of the softened cohesive zone are quantitatively determined as a 1400°C isothermal line segment of the charge in the radial direction of the furnace. The following methods were explored to be applied to the operating method of blast furnaces that perform control. That is,
Based on the difference between the falling speed of the softened cohesive zone and the actual value of the falling speed of the charge, and the separately calculated heat flow ratio of blast furnace operation,
This is a blast furnace operating method characterized by determining the future position and shape of the softened molten t-zone and controlling the distribution of the top charge or the conditions for blowing air from the slats.

[Effect J] As a result of applying the conventional isotherm distribution calculation in the radial direction inside the furnace at 1400°C (hereinafter referred to as model calculation) to various cases, we found that the There were cases where the actual descent speed measured by the sensor did not match. Furthermore, when examining these results, the heat flow ratio calculated separately, and changes in the position and shape of the cohesive zone after the period covered by the calculation, it became clear that there was a certain relationship between them. . The relationship is shown below. (1)
A period of 5 days or more is selected as the period covered by the model calculation, and calculations are performed using the average operating results.The actual falling speed data to be compared is the latest daily average during the period covered by the model calculation. Use values. (2) Comparison of the actually measured falling rate distribution (linear approximation) and the model calculated falling rate distribution shows that if the slope in the actual measurement is larger, the difference in level between the core and the wall of the cohesive zone will increase. It shows that it is growing. (See Figure 1) (3) At that time, how the cohesive zone of the furnace wall and the furnace core will change can be determined by comparing the heat flow ratio for the same period as the measured descent rate data and the heat flow ratio for the period covered by the model calculation. Determined by comparison. Figure 1 shows the situation of this change. Heat flow ratio T
FR is defined by the following formula. VTOX RTQ ・-(1) However, 2 Wore (Wcoke): Ore (coke) charging rate (t/hr)R
ore (Rcoke): Ore (coke) specific heat (kca″l/t・℃) V TG: Furnace top gas N (Nrn’/hr)
RTG: Furnace top gas specific heat (k ca I/N
rrr'-'C) The heat flow ratio generally indicates the average height of the cohesive zone in the furnace, and it agrees well with the relationship of changes in the cohesive zone shown in FIG.

In Figure 1, ■TFRM is the average heat flow ratio for the period covered by the model calculation, TFRR is the heat flow ratio for the same period as the actually measured rate of descent data, and ■The broken line in the cohesive zone is the model at this time. The shape of the cohesive zone obtained by calculation is shown, and the solid line shows the direction of change of the cohesive zone predicted by the present invention. Furthermore, there are various methods for measuring the descending speed of the top charge, but here, the value measured by a top charge profile meter using microwaves is applied. In other words, Section 3 provides an overview of the 6-microwave profile meter, which measures the charge profile at regular time intervals and calculates the rate of descent from the amount of change.
As shown in the figure. This is a method in which microwaves from a microwave oscillator are emitted onto the surface of the charge at the top of the furnace, the reflected waves are received by a receiver, and the distance to the charge is calculated from the microwave propagation time. be. By performing this operation in the radial direction of the furnace, the profile of the charge can be obtained. The specifications of the profile meter are: Measurement time: 120 seconds Measurement accuracy: ±130 mm Measurement range: One direction in the radial direction.

Furthermore, it is important that the difference between the descending speed calculated by the model and the actually measured descending speed be below a certain value, otherwise the above relationship will not be obtained. This value varies depending on the size of the blast furnace, etc., but is usually around 20 mm/min. If the difference is very large, the above relationship cannot be obtained because the deviation from the steady state inside the furnace is extremely large, and the model calculation results do not represent the inside situation at all. It is estimated to be. As shown above, the shape of the softened cohesive zone obtained as the isothermal distribution in the furnace radial direction at 1400℃ of the charge, the rate of descent of the charge obtained in the calculation process, and the rate of descent of the charge obtained during the same period as the model calculation. It is possible to predict changes in the cohesive zone by using the heat flow ratio, the actually measured charge fall rate 5, and the heat flow ratio for the same period as the actual measurement. By taking cohesive zone control actions in response to this prediction result, it becomes possible to control the cohesive zone with higher precision than before, contributing to the stabilization and efficiency of blast furnace operations.

The processing flow of the present invention will be explained with reference to FIG. Based on the daily blast furnace operation results, the average operation results from the present to five days ago are created, and using this as input data, the isothermal distribution in the radial direction inside the furnace at 1400°C, which represents the softened cohesive zone, is determined. The details of this method are as shown in the aforementioned Japanese Patent Publication No. 60-40482.

? The in-furnace radial distribution of the charge descending speed when . Also, calculate the heat flow ratio during this same period using equation (1). Next, find the average heat flow ratio for 1 day during the 5 day period of the target day. In addition, the average actually measured load descending speed during the same period is calculated from the microwave profile meter measurement results.

From these results, we predict how the current (5-day average) cohesive zone position and level will change in the future according to the classification shown in Figure 1. Based on the results, the operational actions necessary to control the softened cohesive zone within an appropriate range are determined. The action is the air blowing temperature from the tuyeres,
Temperature, air flow rate, etc., and raw material charging conditions at the furnace are 1.
The method is selected based on control factors such as the amount of coke or ore charged per batch, the height of the charging line, the charging order, the location of the movable armor, and the chute angle in a bellless blast furnace.

[Example] The present invention was applied to a furnace with an internal volume of 4500 rr? The blast furnace has an iron output ratio of 1.9.
An example of application during the period of operation (3 months) is shown below.

The isothermal distribution calculation in the radial direction of the furnace at 1400°C, which represents the softened cohesive zone, was calculated based on the average operating results for 5 days, and the actual rate of descent was calculated from the average operating results for the most recent 1 day. The series of predictions shown in Figure 3 was carried out every five days, and based on the results, actions were taken according to predetermined standards. 15mm/min or less, and the difference between the two is L5mm
/min or more, the process is interrupted and no prediction of changes in the cohesive zone is required.

Table E shows operation data to which the present invention was applied in comparison with operational data before application of the present invention. This shows the fluctuations in the rate of descent of the contents in the reactor, and the fluctuations are larger. According to Table I, which has a large value, as a result of improving the accuracy of cohesive zone control,
As the burden descent situation was improved and the furnace heat fluctuation was reduced, the ventilation resistance, density index, and hot metal composition variation f [si
], [S1) were greatly improved.

[Effects of the Invention] According to the present invention, it is possible to predict the direction of change in the softened cohesive zone in the furnace based on information based on various operational results, and it is possible to perform more precise control to keep the softened cohesive zone within an appropriate range. , it is possible to maintain the operating condition of the blast furnace in good condition and improve productivity.

[Brief explanation of the drawing]

Fig. 1 is a schematic diagram showing the classification of the prediction of changes in cohesive zone shape according to the present invention, Fig. 2 is a processing flow diagram for implementing the present invention, and Fig. 3 is an explanatory diagram of a microwave profile meter. Inside the small f-zoto furnace

Claims (1)

[Claims] 1. Temperature in the radial direction of the furnace and CO, CO_2 in the radial direction of the furnace, measured with a gas sampler installed directly above the charge at the top of the blast furnace.
, H_2, N_2, etc. from the gas component distribution and operating conditions,
The shape of the softened cohesive zone and its position are determined by the 1400°
In a blast furnace operating method that quantitatively determines the isothermal distribution of °C and controls the charge or air blowing conditions, the difference between the falling speed of the softened cohesive zone and the actual value of the falling speed of the charge The method is characterized in that the future position and shape of the softened cohesive zone is assumed based on the heat flow ratio of the blast furnace operation, which is calculated separately, and the distribution of the top charge or the air blowing conditions from the tuyere are controlled. How to operate a blast furnace.