JPS6277413A - Method for controlling position of welded zone of blast furnace - Google Patents

Abstract

PURPOSE:To form a stable softened and welded zone and to make a smooth blast furnace operation by inserting sondes into the barrel part of a blast furnace, determining the into the barrel part of a blast furnace, determining the upper and lower positions of the welded zone from the values actually measured therewith and controlling the layer thickness distribution in the radial direction of charge in accordance therewith. CONSTITUTION:>=1 Pieces of the sondes are inserted into the blast furnace from the belly part 2 thereof. The results of the measurement therewith are fed via a mechanism 10 for measuring gas conc. and a mechanism 11 for measuring gas. solid temp. to an arithmetic unit 12, by which the upper and lower positions of the welded zone are determined. The mode of the charging quantity analysis of the ore and coke is determined by a mechanism 13 for distributing O/C in accordance with the result thereof. As a result, the distribution of the layer thickness ratio in the radial direction of a coke layer 7 and ore layer 8 at the furnace top and the grain size distribution thereof are controlled by operating a device 14 for controlling the charging of the raw material. The shape of the welded zone meeting the operation at the present point of the time is thereby created and a smooth blast furnace operation is realized.

Description

Detailed Description of the Invention (Industrial Application Field) The present invention forms a stable softened cohesive zone even when conditions inside the furnace change due to fluctuations in the quality and production volume of pig iron produced in a blast furnace. The present invention also relates to a method for controlling the position of the cohesive zone for smooth blast furnace operation.

(Prior art) Generally, iron ore charged into a blast furnace reaches a high temperature while undergoing reduction, begins to soften and shrink, and then further descends, and when it enters a high temperature region, the melt falls off, but from the start of this softening, the melt falls off. The series of ore layers in a semi-molten state up to the point where the ore layer is in a semi-molten state is defined as a cohesive zone.

Since this cohesive zone has very high gas flow resistance, the part of the blast furnace where the cohesive zone is located is considered to be a part that resists gas flow. Therefore, how to control the shape of the cohesive zone viewed from the radial direction has a big impact on the stability and productivity of the blast furnace (
act.

In order to control the shape of the cohesive zone in this way, it is necessary to know the shape, but it is impossible to directly observe it. Therefore, in recent years, attempts have been made to insert a sonde into a blast furnace and estimate the shape of the cohesive zone using various measurement data obtained.

For example, "Tetsu to Hagane J 67 (1981) S69 or "Tetsu to Hagane J 69 (1983) S 5 has TD
A voltage pulse is sent to a flexible conductive cable inserted into the blast furnace, called the R method or TDR melting zone sensor, and the length of the cable is determined by the length of the cable until the reflected wave that is generated when the cable melts in the melting zone returns. A method for measuring body position is shown. Another method is to simultaneously insert several flexible vertical probes with thermocouples in the radial direction of the furnace and track the temperature pattern to determine the shape of the cohesive zone.

However, inside the blast furnace, the rate of descent of the charge differs between the upper and lower parts due to the slope of the shaft. For example, the descending speed is 7 m/hour in the upper part of the furnace, but it decreases to 4 m/hour in the lower part of the furnace. Therefore, in the above case where a flexible cable is used, the cable is bitten by the charge at the top of the furnace and descends with the same particles, but the falling speed is different between the tip and the biting position, causing the cable to fall into the sonde. This causes deflection, causing a problem in the accuracy of the tip position.

In addition, "Tetsu-to-Hagane J 66 (1980) 3685 describes a system that estimates the shape of the cohesive zone using information on the gas temperature and gas composition of two sondes, upper and lower, installed horizontally in the shaft of a blast furnace. is disclosed.

This method estimates the shape of the cohesive zone by defining the line at which the solid temperature is 10'0℃ and the CO2 in the gas is 0 as the upper shape of the cohesive zone while maintaining consistency between the measured values and the calculated values. There is. However, with this method, since the position of the horizontal sonde is located in a low-temperature region well above the actual cohesive zone, there is a possibility that a considerable error may occur in estimating the shape of the cohesive zone at the bottom, which is far away from that position. be.

Furthermore, a common problem with the methods using these sensors is that although it is possible to estimate the upper shape of the cohesive zone, it is impossible or impossible to estimate the lower shape.

(Problems to be Solved by the Invention) The present invention solves the above-mentioned problem, that is, it is impossible or inaccurate to estimate the position of the cohesive zone, especially the lower shape.

(Means for solving the problem) By the way, the cohesive zone is an ore layer between the softening start temperature (Tms) and the melt drop temperature (Tmd), but Tll
l5 and T+++d are not constant, but vary depending on the type of ore and the reduction rate of the ore until reaching it. In other words, it has become clear that when the reduction rate is low, the material softens at low temperatures and the melt melts at low temperatures. Therefore, the position of the cohesive zone cannot be determined only from the temperature information obtained by the sonde, and an estimation system is required that also takes into consideration information on the gas concentration representing the reduction situation. Furthermore, if the sonde penetrates both the upper and lower sides of the cohesive zone at the same time, the position of the cohesive zone can be determined accurately, but in other cases, the temperature distribution and reduction rate distribution in the vicinity must be estimated using some method. There is a need to.

The present invention allows estimation of the position of the cohesive zone and control of the cohesive zone based on the estimation to suit the operating conditions of the blast furnace.

That is, the present invention involves inserting one or more sondes into the blast furnace from the belly or lower part of the blast furnace, and determining the upper side of the cohesive zone from the actual measured values of gas/solid temperature and gas composition obtained from the sondes. and the lower position, and so that the position of the cohesive zone occupies the optimum position for blast furnace operation.
This method is characterized by controlling the distribution of the ratio of ore layer thickness to coke layer thickness in the radial direction of the blast furnace. The method of the present invention will be explained in detail below with reference to the drawings.

FIG. 1 is an explanatory diagram of the present invention, where ■ is a blast furnace, 2 is a blast furnace, and 3 is a sonde inserted into the furnace from the furnace belly, which is connected to a gas concentration measuring mechanism 10 and a gas/solid temperature measuring mechanism 11. . 4 is a cohesive zone, 5 is an upper side thereof, and 6 is a lower side thereof. 7 is a coke layer charged from the top of the furnace, 8 is an ore layer, and 9 is a tuyere. 12 is the gas concentration measuring mechanism 10 and the gas concentration measuring mechanism 10;
A calculation device for estimating the shape of the cohesive zone from the measured value from the solid temperature measuring mechanism 11, and a setting mechanism 13 for setting the distribution of ore and coke ratios based on the output from the calculation device
(hereinafter referred to as 0/C distribution setting mechanism), 14 is the setting mechanism 1
This is a raw material charging control device whose operation is controlled by 3.

In order to control the position of the cohesive zone by the method of the present invention, the blast furnace 1
One or more probes 3 are inserted into the reactor horizontally or inclined at an arbitrary height of the reactor belly 2 or lower. This sonde detects the gas/solid temperature at any position of the inserted trajectory, CO, CO2, H2, H2O,
Since the concentration of gases such as N2 can be measured, these measurement results can be obtained using the gas concentration measurement mechanism 10 and the gas/solid temperature measurement mechanism 1.
1, the data is sent to an arithmetic unit 12 for estimating the cohesive zone shape, and the cohesive zone shape is estimated by the device, which will be described later. Further, based on the results, the O/C distribution setting mechanism 13 determines the mode of analysis of the amount of ore and coke charged,
As a result, the raw material charging control device operates, and the radial layer thickness distribution of the charge at the top of the furnace is controlled. Therefore, we create an efficient cohesive zone shape that best suits the current operating conditions.
Smooth blast furnace operation can be realized.

Next, a method for estimating the cohesive zone position in the present invention will be explained. First, a method for estimating the temperature distribution and reduction rate distribution near the cohesive zone will be explained.

First, the inside of the blast furnace is divided in the height direction and the radial direction by a square lattice whose negative side has a minute length of DL. On each grid point, gas flow rate U, reaction amount kc due to chemical reaction, reduction rate RR1 solid fall rate Us, gas concentration F1 gas temperature Tg, solid temperature Ts
It has a mechanism for calculating.

The gas temperature Tg and the solid temperature Ts can be expressed from the heat balance as follows.

Heat storage rate = (heat input - heat output) rate due to bulk flow; heat transfer rate based on temperature gradient; heat generation (or heat absorption) rate due to reaction heat; heat transfer rate from (and to) other phases; heat loss; It can be expressed as From now on, assuming that the model is in a steady state and using the basic heat transfer equations (1) and (2) obtained with the heat storage rate = 0, -Qr
(1-η) ha (Tg -Ts) 2 0
... River (1) Basic formula for solid temperature % formula %) r: Radial distance (m), Z: Height distance (m),
ha: Heat transfer coefficient (kcal/cd-s ・'C)
Subscript “g”: gas “S”; solid “r”: radial direction “Z”: height direction The basic equation for gas concentration distribution F is a function of position and is calculated from mass balance by Equations (3) to (7). It is expressed as follows.

・・・・・・(3) ・・・・・・(4) ・・・・・・(5) ・・・・・・(6) Gr, Gz, and G are the calculated gas mass velocity. r direction,
The components in two directions and the absolute value, FCO=FN2, are gas concentrations expressed in MOL fraction.

Increment in gas amount per unit volume due to FRCO-FRN2 S reaction (mol/g bed-s) Increment in total gas amount per unit volume due to TFRS reaction (
mol/rr? bed -s ) TVML ; Total MOL flow rate of gas (mol/rd -s) dTVML ; Increment of total MOL flow rate of gas (+nol
/Bo・S) Next, the reduction rate at each position is the solid flow rate Usr.

It is related to Usz and the flow direction. Iron ore is reduced from hematite to magnetite (RRI) at each reduction stage.

The reduction rate from magnetite to wustite (RR2) and from wustite to iron (RR3) is expressed by the following equations (8).

U Srl U sz is the velocity component (m/s) of the solid at each position found from the solid flow model. ■1~V4 is 1
This is the reaction rate (mol Co/s·co, mol H2/s·co) of each stage of coparticles.

Wo is the weight of one particle (g/co) + dog-do4
is the amount of reduced oxygen in the ore at each reduction stage (gmolo 2
/g). The total reduction rate (RR) of ore is (11)
It is expressed by the formula.

RR=0.111 RRI +0.1871RR,2+
0.7017RR3 (11) The reduction rate at each position is calculated by integrating equations (8) to (11) along the direction of solid flow from the top of the furnace.

For example, the gas/solid temperature at a certain point on the lattice point is us R
Because it is affected by R% Us, kc, F, etc.
These are calculated simultaneously.

A calculation method for obtaining the optimal temperature distribution and gas concentration distribution in the vicinity of the actual measurement value (minimizing the error) using the temperature information and gas concentration information measured by the sonde as input conditions is as follows.

l) First, select the target sonde. This is one or more sondes installed below the belly of the reactor.

2) Determine the grid point closest to the in-furnace measurement point of each sonde.

3) The temperature at each grid point is determined by converting the differential equation developed from the local heat balance that takes into account heat conduction, convective heat transfer between particle fluids, reaction heat, sensible heat changes, etc. into differences, and using the relaxation method. The problem is solved by repeated convergence calculations, but when the grid points match the measurement points, the actual value is given instead of the calculation of the differential equation system. Since the heat balance is calculated at other grid points, the influence of the actual measured temperature gradually spreads to the surrounding area each time it is repeated, and in the end, the heat balance is taken into account near the actual measurement point, and the result is the most suitable for the actual measurement value. It is possible to converge to the gas/solid temperature distribution.

Next, a method for estimating the position of the cohesive zone from the estimated gas/solid temperature distribution and reduction rate distribution will be explained. As explained at the beginning, the cohesive zone is defined as the area where the ore softens and contracts. The conditions under which the ore undergoes softening and shrinkage are determined by the solid temperature, layer reduction rate, and type of ore, as shown in Figure 5. The softening start temperature (T
ms) and the falling temperature (Tmd) of the melt. When the temperature on a grid point near the cohesive zone is given, it is determined whether the temperature is between the two, and if it is between the two, it can be defined as a cohesive zone.

The softening start temperature Tms regarding the sintered ore can be expressed as a function of the reduction rate RR as shown in equation (12).

Tm5=1140-153.6 RR+244.7 R
R-(12) Also, the melting temperature Tmd of the sintered ore is (13
), expressed by equation (14).

Tmd=129 RR+1291 (0<RR<0.7
)・・・・・・(13) Tmd-230X (RR-0,7) +1381(R
R>0.7) (14) If it is a cohesive zone, the shrinkage rate of the cohesive zone is calculated from the difference between the temperature on the lattice point and the softening start temperature. The shrinkage rate sR of sintered ore is the lattice point (I
, J) as a function of the dimensionless temperature T expressed by the solid temperature Ts, the softening start temperature Tms, and the reference temperature To (=1000° C.).

The dimensionless temperature T is T=(Ts-Tms)/To''...(15)
Shrinkage rate SR is SR=0.02-0.2517+26.7T-12,I
T3... (16) In this way, the cohesive zone is determined, the temperature, and the shrinkage rate are calculated at all grid points near the cohesive zone, so the current distribution of the cohesive zone can be estimated. It is possible to do so.

In fact, it goes without saying that the accuracy of estimating the shape of the cohesive zone improves as the actual measurement point approaches the cohesive zone.

Next, a method of controlling the O/C distribution to control the shape of the cohesive zone will be explained. The reason why the O/C distribution influences the cohesive zone shape is explained by the gas permeability, the transferability of gas sensible heat, the degree of progress of the reaction, and the radial distribution of the amount of oxygen to be reduced.

The ore layer has a smaller particle size and layer void ratio than the coke layer, so gas permeability is poor in areas where the ore layer is relatively thick in the radial direction of the blast furnace. The flow rate and gas flow rate decrease.A decrease in gas flow rate affects various aspects.In terms of heat transfer, it causes a decrease in the amount of sensible heat of the gas flowing through a unit cross-sectional area, and worsens heat transfer to solids.In terms of reactions, Since a sufficient amount of gas is not supplied to reduce the gas, the concentration of the reducing gas decreases, and the driving force for reduction weakens, resulting in a relative decrease in the reduction rate.

From the above, a portion with high O/C in the radial direction brings about a decrease in the reduction rate and a decrease in gas/solid temperature.

Therefore, for example, in order to achieve a high cohesive zone in the center, it is necessary to supply sufficient heat to the center of the lower part of the furnace. For this purpose, it is necessary to increase the supply of gas to the center of the furnace, that is, to reduce the O/C in the center.

Moreover, in order to realize a high cohesive zone in the peripheral part, the 0/C of the peripheral part may be reduced for the same reason.

(Example) Examples of this invention are shown below.

Figure 2 (B) shows a direct observation of the conditions inside the blast furnace at each position using a fiberscope mounted on a blast furnace probe that can be inserted up to 4 meters into the blast furnace at an angle of 25 degrees. . The tunnel portion in the figure corresponds to the cohesive zone. In this case, the cohesive zone has been penetrated.

FIG. 2(A) shows a comparison between the cohesive zone shape estimated by calculation with the given O/C distribution and the position of the tunnel portion. Direct observation using a fiberscope and the estimated results show good agreement.

FIG. 3 is an example of estimating the temperature in the vicinity using the temperature of each part obtained by the furnace belly sonde as an input condition. In this figure, information on the sonde installed above the reactor belly is also entered at the same time. Black positions indicate actual measured values. The shape of the cohesive zone in FIG. 2(A) is based on this temperature distribution, and it can be seen that the surrounding temperature also converges to a substantially appropriate value based on this actual measurement value.

Figure 4 (al) is estimated based on the actually measured O/C distribution (layer thickness distribution) during operation with low O/C in the center and the solid temperature information measured from the furnace belly sonde. It has a cohesive zone shape.In this case, the thinner ore layer at the center is thicker at the periphery, and as a result, the periphery of the cohesive zone enters the combustion zone, indicating a bad situation. The temperature measured in the reactor was also relatively low and the furnace conditions were unstable.

On the other hand, in Figure 4 (bl), where the O/C layer thickness distribution in the radial direction is made relatively uniform by proper control of the O/C distribution, a furnace condition with a uniform gas flow distribution is achieved, and the The measured solid temperature also increased, and we were able to achieve the desired cohesive zone shape.

(Effect of the invention) The effect of stabilizing the shape of the cohesive zone is due to the reduction of Si in hot metal and the effect of Si
This appears in variations in concentration. With this invention, 5 in hot metal
It showed a decrease of i-0.1%, and the stabilization effect of the furnace condition resulted in a decrease of the blast furnace fuel ratio by 3 kg/tpig.

Furthermore, by managing the stable cohesive zone shape through fine-grained O/C distribution control, it was possible to maintain stable blast furnace operation even in the unstable phase of increasing or decreasing production.

[Brief explanation of drawings]

Fig. 1 is an explanatory diagram showing the overall configuration of the present invention, including signal processing flow and control method. Fig. 2 shows an embodiment of the present invention, and Fig. 2 (A) shows the installation in the belly of the blast furnace in which it was implemented. Figure 2 (B) shows the position of the sonde, the position of the cohesive zone observed by the fiberscope, and the shape of the cohesive zone estimated by the present invention. Figure 2 (B) shows the distribution of the furnace charge observed by the fiberscope. An explanatory diagram showing the comparison between the state and the observation position. Fig. 3 is a graph showing the gas temperature at each position in the furnace calculated by the present invention and the gas temperature measured at the actual measurement point. Fig. 4 is a graph showing the gas temperature at each position in the furnace calculated by the present invention. Figure 5 shows a comparison of two types of cohesive zone shapes after controlling the distribution and estimating them using measurement information from a sonde installed in the reactor belly. FIG. Applicant: New Japan! ! Tetsu Corporation Patent Attorney Minoru Aoyagi (A) Figure 2 (B)

Claims (1)

[Claims] One or more sondes are inserted into the blast furnace from the belly or lower part of the blast furnace, and the upper and lower positions of the cohesive zone are determined from the actual measured values of gas/solid temperature and gas composition obtained from the sonde. and controlling the distribution of the ratio of the ore layer thickness to the coke layer thickness and the particle size distribution in the radial direction of the blast furnace so that the position of the cohesive zone occupies an optimal position for blast furnace operation. Method for controlling cohesive zone position.