JPH0118963B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention proposes a method for estimating the internal situation of a blast furnace in an unsteady state such as during firing operation, particularly the position of the cohesive zone.

In a blast furnace, pig iron is manufactured by charging coke carbonized in a coke oven and sintered ore fired in a sintering machine into the blast furnace. In order to ensure stable operation, it is important to understand the situation inside the blast furnace.

Conventionally, the condition inside a blast furnace has been a black box, but in recent years, dismantling investigations of blast furnaces have begun to be conducted, and analysis of the condition inside a blast furnace is progressing. According to the results of many studies, the conditions inside a blast furnace are: a lumpy zone where the raw material exists as a lump just as it was before charging; a cohesive zone where the raw material has become semi-molten due to heat and load; and molten pig iron. It has been found that the coke can be roughly divided into five areas: a drip zone where the coke and slag descend between the coke, a raceway where the coke burns and moves due to the air blowing from the tuyere, and a tundish where the molten product accumulates. . Among these, the temperature and pressure inside the furnace change rapidly at the cohesive zone, so it is important to understand the position of the cohesive zone to understand the temperature rise in the furnace wall and prevent spalling of the furnace wall bricks. It is particularly important to prevent the rise in pressure loss in the furnace to below a certain value and to prevent shelving, slipping, etc.

However, in the steady state of blast furnace operation, analyzes have been performed on both the blast furnace cross-sectional uniform model and the blast furnace radial direction model, whereas in the unsteady state of blast furnace operation, the blast furnace cross-sectional uniform model has been analyzed. However, an analysis of the blast furnace radial model has not yet been performed. Therefore, in an unsteady state such as during a blast furnace firing operation, it is not possible to fully grasp the situation inside the furnace.

The present invention has been made in view of the above circumstances, and it is an object of the present invention to provide a method for estimating the internal condition of a blast furnace in an unsteady state during blast furnace operation, particularly the position of a cohesive zone.

The method for estimating the position of the cohesive zone in a blast furnace according to the present invention is as follows:
During unsteady operation of the blast furnace, the radial distribution of the charge unloading rate, gas composition in the furnace, and temperature in the furnace is actually measured at the top of the charge layer, and the measured values are used to calculate the temperature distribution in the furnace. The method is characterized in that it is applied to a predetermined mathematical model that has been set in advance to perform arithmetic processing, and the position of the cohesive zone is determined based on the result.

First, the mathematical model used in the present invention will be explained. This mathematical model is the following three equations. Basic equation regarding heat: D/Dt (c _j ρ _j E _j H _j ) + c _j ρ _j T _j ∂/
∂zV _j =− 〓 ^k h _kj / δ(T _j −T _k )＋Q _j ……(1) However, D/Dt≡∂/∂t+v∂/∂z c _j : Heat capacity of j phase ρ _j : J phase Density E _j : Let g, s, and l be the gas phase, solid phase, and liquid phase, respectively,
If ε and ε _l are the vacancy rate and liquid retention rate of the packed layer, respectively, Eg: ε (1-ε _l ), Es: 1-ε, E _l : ε ε _l T _j : J phase temperature T _k : Temperature of k phase V _j : Superficial equivalent flow rate of j phase h _kj : Heat transfer coefficient between k phase and j phase δ : Representative length Q _j : Reaction heat and heat loss in j phase t, z : Time and furnace Coordinates of height Basic equation for reaction: D/Dt (E _j ρ _j ξ _i ) + ξ _i ρ _j ∂/∂zV _j = R _i M _i ...(2) where, ξ _i : mass fraction of i component M _i : Molar weight of component i R _i : Reaction rate of component i Basic equation regarding the law of conservation of mass: D/Dt(E _j ρ _j )+ρ _j ∂/∂zV _j = 〓 ⁱ R _i M _i ……(3 ) In the case of a blast furnace, the rising speed of gas V _g is fast, so ∂T _g ／∂t≪V _g ∂T _g ／∂z ...(4). Since it can be assumed to be the same as the steady state, the unsteady behavior of the blast furnace is considered to be caused by the solid, ie, the charge. Therefore, we actually measured the distribution of the charge unloading speed in the blast furnace radial direction, estimated the charge unloading trajectory from the results, and based on the unloading trajectory,
By performing calculations using the above-mentioned basic equations (1), (2), and (3), the temperature distribution in the furnace in an unsteady state can be determined. However, the temperature of the cohesive zone is 1100~
Since the cohesive zone exists in the range of 1400°C, the position of the cohesive zone in the unsteady state and its formation process can be estimated by determining the temperature distribution in the furnace in the unsteady state as described above.

FIG. 1 is a flowchart showing the procedure for carrying out the method of the present invention. As shown in Fig. 2, the distribution of the charge unloading speed in the blast furnace radial direction was actually measured by moving the in-furnace raw material detection device 1 in the blast furnace radial direction and measuring the behavior of the top of the in-furnace charge layer over time. In addition, the blast furnace radial distribution of gas composition and temperature inside the furnace is actually measured using a sonde 2 inserted into the top of the charge layer. Also, from the operating conditions, the (ore/coke) ratio and gas flow rate distribution in the blast furnace radial direction are assumed. Based on these measured values and assumed values, the basic formula
Using a mathematical model consisting of equations (1), (2), and (3),
Estimating and calculating the situation inside the furnace. Then, the estimated calculation results regarding the gas flow are calculated sequentially from the top of the layer toward the bottom of the furnace, and when the radial gas mass flow rate distribution in the upper part of the cohesive zone does not match a predetermined value, the assumed value of the gas flow rate is changed, Further, when the estimated calculation result regarding the amount of unloading in the furnace does not match the actual amount of unloaded at the top of the layer, the above-mentioned (ore/coke) ratio assumption value is changed and the estimated calculation is performed using the mathematical model. Then, this procedure is repeated until the estimated calculation result matches the above-mentioned actual results, thereby increasing the (ore/coke) ratio and the gas flow rate distribution in the blast furnace radial direction at the top of the layer.

As a result of research, it has been found that the radial gas mass flow rate distribution in the upper part of the cohesive zone described above has the relationship shown in Figure 3 with respect to the shape of the cohesive zone, and that The radial gas flow velocity distribution in the upper part of the cohesive zone was determined from the following: Figure 3 shows the relationship between the cohesive zone shape and the radial gas mass flow rate at the top of the cohesive zone. The difference between the height of the furnace core and the height of the furnace wall is 1.5m (solid line), 3.0m (dot-dashed line), and 4.5m, respectively.
(Dotted line) is illustrated.

Furthermore, by paying attention to the descending behavior of the charge and performing the calculations shown in equations (5) and (6) below, it is possible to estimate the unsteady behavior in the furnace, and to estimate the temporal change of the cohesive zone in the unsteady state. can be found.

(c _j T _j ) _z=z0 −Vsdt− (c _j T _j ) _z=z0 =∫ ^t=t0+ 〓 ^t _t=t0 F(T _j )dt ……(5) (ξ _i ) _z=z0 − Vsdt−(ξ _i ) _z=z0 =∫ ^t=t0+ 〓 ^t _t=t0 G(ξ _i )dt ……(6) However, V _s : Solid unloading speed Here F(T _j ) is the basic equation From equations (1) and (3), the following
In equation (7), G(ξ _i ) is given by equation (8) below from basic equations (2) and (3).

F(T _j )=1/E _j ρ _j {− 〓 ^k h _kj /δ(T _j −T _k )＋Q _j −c _j T _j 〓 ⁱ R _i M _i } ……(7) By using such a method, it is possible to estimate the situation inside the furnace in an unsteady state during blast furnace operation, especially the temperature distribution inside the furnace, and determine the position of the cohesive zone. If you can understand the situation inside the furnace, especially the position of the cohesive zone, you can understand the temperature rise in the furnace wall, and use the temperature rise in the furnace wall and the predefined spalling area to determine the temperature of the furnace wall. It is possible to prevent the occurrence of brick spalling. Furthermore, since the increase in pressure loss within the furnace can be estimated, it is possible to suppress it below a certain value and prevent the occurrence of shelf hanging, slipping, etc.

Next, examples of the method of the present invention will be described. Figures 4a, b, and c show the formation of a cohesive zone and the furnace wall static pressure distribution during the firing operation, which were determined using the method of the present invention. In the figure, the shaded area indicates the position of the cohesive zone in the blast furnace, and the polygonal lines indicate how the static pressure on the furnace wall changes with respect to the height of the blast furnace. Also a
b is for 12 hours after the start of burning operation, b is for
The values shown in c are the values after 16 hours have elapsed, and c represents the values after 20 hours have elapsed. These results correspond well to the results of separate measurements, such as changes in furnace pressure, and it was confirmed that the method of estimating the inside condition of a blast furnace according to the method of the present invention is effective.

As shown in Figure 4c, if the cohesive zone rises to the shaft part, the pressure loss inside the furnace will increase and it is expected that shelving, slipping, etc. will occur, so the blowing pressure should be adjusted. This allows the occurrence of shelf hanging, slips, etc. to be avoided in advance.

As described in detail above, the present invention uses the radial distribution of the charge unloading speed, the gas composition in the furnace, and the temperature in the furnace, which are actually measured at the top of the charge layer, during unsteady operation of the blast furnace. The situation inside the furnace, especially the position of the cohesive zone, is estimated by applying calculations to a mathematical model that has been set in advance to find the temperature distribution. This means that the situation inside the reactor can also be grasped. Therefore, the present invention has excellent effects such as being able to prevent abnormalities in an unsteady state in advance.

[Brief explanation of drawings]

Figure 1 is a chart showing the method according to the present invention, Figure 2 is a schematic diagram showing the method for measuring the state of the top of the furnace charge layer, and Figure 3 is a diagram showing the cohesive zone shape and the top part of the cohesive zone. Distribution diagrams showing the relationship with the radial gas mass flow rate, and FIGS. 4a, b, and c are explanatory diagrams showing the conditions inside the furnace determined by the method of the present invention. 1...Furnace raw material detection device, 2...Sonde.

Claims (1)

[Claims] 1 During unsteady operation of the blast furnace, the charge unloading speed,
The radial distribution of the blast furnace gas composition and temperature in the furnace was actually measured at the top of the charge layer, and the measured values were
1. A method for estimating the position of a cohesive zone in a blast furnace, characterized by performing arithmetic processing on a predetermined mathematical model set in advance to obtain the temperature distribution in the furnace, and determining the position of the cohesive zone based on the result.