JPS626721B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION (Industrial Application Field) The present invention relates to an improvement in a blast furnace operating method, and in particular provides a blast furnace operating method capable of stably maintaining furnace conditions.

(Conventional technology) Conventionally, as a blast furnace operating method to maintain stable furnace conditions, the CO and CO ₂ concentrations in the furnace top gas are detected, and the gas utilization rate of the entire furnace η _cp = CO ₂ / (CO + CO ₂ ) is detected. At the same time, the CO and CO ₂ concentration distribution in the radial direction of the furnace is detected on the raw material in the furnace or on the upper part of the charging material layer in the furnace, and the gas utilization rate in the radial direction of the furnace η _cp = CO ₂ / (CO +
There is a blast furnace operation method that detects the CO ₂ ) distribution, determines the gas utilization rate distribution in the furnace radial direction that maximizes the gas utilization rate of the above-mentioned furnace top gas, and adjusts the Ore/Coke distribution to achieve that gas utilization rate distribution. be.

In this operating method, if the gas utilization rate of the furnace top gas is maximum, the indirect reduction rate in the furnace is maximum, the direct reduction rate is minimum, and the endothermic reaction due to direct reduction is minimized, resulting in a decrease in furnace heat and a ventilation load. The idea is to effectively prevent the abnormality of the temperature drop and stabilize the furnace condition.

In other words, reactions shown in equations (1) and (2) occur in the blast furnace, and the independent reaction in equation (2) (occurring at the upper part of the shaft) is called an indirect reduction reaction, and the reaction shown in equation (1) is called an indirect reduction reaction. ), the simultaneous reaction of equation (2) (occurring at the bottom of the shaft part) is called a direct reduction reaction, and equation (1) is an endothermic reaction, and the smaller the proportion of direct reduction reaction in the reduction reaction, the more
It is said that a decrease in furnace heat is effectively prevented and the furnace condition is stabilized.

C+CO ₂ →2CO (1) CO+O ^* →CO ₂ (2) Equation (1) is the carbon gasification reaction equation, and O ^* in equation (2) is ore (lump ore, sintered ore, pellets). ) indicates oxygen bonded to Fe in

The above-mentioned furnace top gas utilization rate η _cp increases as the amount of CO ₂ increases.
The less CO there is, the bigger it becomes. A small amount of CO (a large amount of CO ₂ ) indicates that the amount of reaction in equation (1) is small. Therefore, the idea is that the higher the furnace top gas utilization rate η _cp is, the higher the indirect reduction rate and the lower the direct reduction rate, and the more stable the furnace condition will be.

(Problems to be Solved by the Invention) However, with this conventional method, it was not possible to maintain stable furnace conditions. The reason for this is that the CO and CO ₂ concentration in the furnace top gas detected by conventional methods and the CO and CO ₂ concentration distribution in the furnace radial direction on the raw material charged in the furnace or at the top of the charging material layer in the furnace are This is the result of the total reaction, and it is not possible to detect what kind of reaction is occurring at which level in the direction of the furnace height. In other words, the conventional method does not detect the situation inside the furnace in the direction of the furnace height, and operates without grasping the situation inside the furnace in the direction of the furnace height, which is closely related to the furnace situation as determined by the present inventors. It's in being.

(Means/effects for solving the problem) As a result of various investigations into the relationship between the inside situation of the furnace in the direction of the furnace height and the furnace condition, the present inventors found that The amount of carbon change in the furnace wall in the middle of the blast furnace shaft, which is calculated from the detected values of CO, CO ₂ and H ₂ concentrations in the lower and upper parts of the gas, is extremely closely related to the stability of blast furnace operation. If the amount shows the carbon precipitation reaction shown in equation (3), the furnace condition is unstable, while if the above carbon change amount shows the carbon gasification reaction, the furnace condition is stable. I found it.

2CO→C+CO ₂ (3) If a carbon precipitation reaction is detected on the furnace wall in the middle of the blast furnace shaft, the fuel ratio should be increased to lower the O/C in the entire radial direction of the furnace, or, for example, a bell type In the case of a blast furnace, if the O/C of the furnace wall is lowered by increasing the amount of protrusion of the movable armor into the furnace when charging ore and reducing the amount of ore deposited on the furnace wall, the heat flow on the furnace wall is reduced. It has also been found that as the ratio decreases, the gas temperature at the furnace wall in the upper middle part of the shaft part increases, and the carbon precipitation reaction can be changed to a carbon gasification reaction in the furnace wall part in the middle part of the blast furnace shaft part.

The present invention has been made based on the above-mentioned new findings, and provides a blast furnace operating method that stably maintains the furnace condition, and the gist thereof is as follows.

The CO, CO ₂ and H ₂ concentrations in the lower and upper parts of the furnace gas rising up the furnace wall in the middle of the blast furnace shaft are detected, and based on these detected concentrations, carbon changes in the furnace wall in the middle of the blast furnace shaft are detected. If the carbon change amount indicates a carbon precipitation reaction, the O/C of the furnace wall is lowered so that the carbon change amount indicates a carbon gasification reaction. Operating method.

Hereinafter, the blast furnace operating method of the present invention will be explained in detail.

First, I will explain how the above new findings were obtained.

The present inventors have discovered that CO in the furnace height direction of the furnace gas,
We investigated the CO ₂ and H ₂ concentration distribution and the carbon change distribution based on this concentration distribution. Collect the furnace gas in the direction of the furnace height, and collect CO, CO ₂ and H ₂ in the furnace gas in the direction of the furnace height.
In order to detect the concentration distribution, horizontal sondes were placed in multiple stages in the direction of the furnace height. Specifically, in a blast furnace 3 with a height H = 25.3 m between the tuyere 1 and the stock line 2 shown in Fig. 1, an oblique sonde 4 is placed at a relative height of 1.00 of the height H, a relative height of 0.77, Horizontal sondes 5, 6, 7, and 8 are placed at each position of 0.62, 0.48, and 0.32 to collect gas in the furnace at the center, middle, and periphery (furnace wall) in the radial direction of each stage in the furnace height direction. By analyzing the gas composition, we can determine the concentration of CO, CO ₂ and H ₂ in the furnace gas in the furnace height direction along the gas flow lines at the center, middle and periphery (furnace wall) in the radial direction of the furnace. The distribution was determined.

Based on the CO, CO ₂ and H ₂ concentration distribution of the furnace gas in the furnace height direction, the carbon change amount distribution in the furnace height direction was determined. This is basically to determine the reaction in the furnace from the change in the gas composition in the furnace, and for this purpose it is necessary to determine the change in the gas composition along the gas flow line in the furnace. Therefore, the direction of the furnace height using the horizontal sonde is
When measuring the CO, CO ₂ , and H ₂ concentration distribution, the gas flow lines in the furnace are measured using the well-known He tracer method, and the radial gas sampling position of the sonde at each stage is determined to be at the center or middle of the radial direction. The gas sampling position was determined so as to align with the gas flow line in the peripheral area (furnace wall).

The method for determining the in-furnace reaction, that is, the amount of carbon change, from the change in the in-furnace gas component along the gas flow line is as follows.

(1) Obtain CO, CO ₂ and H ₂ [%] from furnace gas analysis.

(2) Since the amount of _N2 inside the furnace does not change, the amount of CO and _CO2 gas at each location in the furnace is determined from the _N2 balance, Q _cp , Q _cp2
[Nm ³ /Nm ³ −Blast] is as shown in equations (4) and (5). (However, if there is no enrichment of O ₂ , N ₂ etc.) Q _cp = 0.79Nm ³ /Nm ³ -Blast x CO%/10
0%-(CO%+ _CO2 %+ _H2 %) (4) Q _cp2 = ^0.79Nm3 / ^Nm3 -Blast× _CO2 %/
100% - (CO% + CO ₂ % + H ₂ %) (5) (3) From equations (4) and (5) above, the gas in the furnace moves along the streamline from arbitrary position A to B in the height direction inside the furnace. The amount of change in gas composition during the rising process can be expressed as in equations (6) and (7).

ΔQ _cp =Q _cp (B)−Q _cp (A) (6) ΔQ _cp2 =Q _cp2 (B)−Q _cp2 (A) (7) (4) From equations (6) and (7) above, A− The in-furnace reaction amount between B, ie, the carbon change amount IC, can be expressed as in equation (8).

IC [Kgmole-C/Nm ³ -Blast] = - (ΔQ _cp + ΔQ _cp2 ) / 22.4 (8) If the above carbon change amount IC is a positive value, it is the precipitated carbon amount, and if it is a negative value, it is the gasified carbon Indicate quantity.

The relationship between the carbon change distribution in the furnace height direction investigated using the above method and the furnace condition is that if the carbon change IC in the furnace wall between sonde 7 and 5 is a positive value, the furnace condition is unstable. On the other hand, when the amount of carbon change IC in the furnace wall between sondes 7 and 5 was a negative value, the furnace condition was stable.

Furthermore, the carbon change distribution in the furnace height direction in the center and middle areas shows the carbon change distribution between all sondes.
IC was a negative value.

If the amount of carbon change IC in the furnace wall between sonde 7 and 5 is a positive value, in other words, if a carbon precipitation reaction occurs in the furnace wall in the middle of the blast furnace shaft,
The reasons why the furnace condition becomes unstable are as follows.

Since indirect reduction does not occur in the zone where the carbon precipitation reaction occurs, the ore reaches the lower part of the blast furnace shaft without being reduced. Since most of the ore reduction in the lower part of the blast furnace shaft is direct reduction, the amount of direct reduction increases in this case. As a result, a decrease in furnace heat and an abnormality in ventilation loading occur.

Further, the reason why the carbon precipitation reaction does not occur in the furnace center and the furnace middle part but occurs in the furnace wall is as follows. Carbon precipitation reactions tend to occur in regions where the heat flow ratio increases and the gas temperature decreases. Generally, in a blast furnace, the position of the cohesive zone in the center is raised to lower the ventilation resistance of the cohesive zone. For this reason, the basics of operation are to maintain the central flow by lowering the O/C of the center than the O/C of the periphery and lowering the heat flow ratio of the center than the heat flow ratio of the periphery. In principle, O/C distribution control is also performed within the range of maintaining the central flow, and the peripheral heat flow ratio will not become lower than the central heat flow ratio.

Therefore, even if the radial heat flow ratio distribution changes due to some undetectable cause, such as a change in O/C distribution due to a change in raw material particle size, and the carbon precipitation reaction of equation (3) occurs, First, it occurs on the furnace wall.

On the other hand, the results of investigating the relationship between the amount of carbon precipitation reaction on the furnace wall in the middle of the blast furnace shaft and the charge distribution are as follows.

The amount of carbon deposition reaction on the furnace wall in the middle of the shaft depends largely on the temperature distribution and gas composition distribution in the middle of the shaft, but if the O/C is changed in the entire radial direction or at a specific position, As the heat flow ratio changes, the temperature distribution and gas composition distribution in the entire radial direction or in the furnace height direction at a specific position change, and the amount of carbon precipitation reaction on the furnace wall in the middle of the shaft portion changes.

Therefore, if a carbon precipitation reaction is detected on the furnace wall, increase the fuel ratio and apply O/O to the entire radial direction.
O/C of the furnace wall can be reduced by lowering the C or, in the case of a bell-type blast furnace, increasing the amount of protrusion of the movable armor into the furnace when charging ore to reduce the amount of ore deposited on the furnace wall. decrease. As a result, the heat flow ratio on the furnace wall where the carbon precipitation reaction is occurring decreases, and the gas temperature on the furnace wall in the middle of the shaft increases, causing the carbon precipitation reaction in the furnace wall in the middle of the shaft to turn into carbon gas. change into a reaction. As a result, indirect reduction also progresses on the furnace wall in the middle of the shaft, reducing the amount of direct reduction at the lower part of the shaft and stabilizing the furnace condition.

(Example) Hereinafter, an example of the blast furnace operating method of the present invention will be described.

Figures 3, 4, and 5 show sonde 4, as shown in Figure 1.
5, 6, 7, and 8 are placed in the direction of the furnace height,
The CO ₂ and H ₂ concentration distribution was detected, and the carbon change distribution in the furnace height direction could be calculated from equations (4) to (8). The changes in the measured and calculated values of the amount of carbon change in the radial peripheral area (relative radius 0.95) of the blast furnace 3 in the shaft upper part U, shaft part middle M, and furnace lower part L in the furnace height direction are shown in FIG. FIG. 6 shows the number of occurrences of drops and slips in the blast furnace during the carbon change change display period shown in FIGS. 3 to 5.

The amount of change in the upper part U of the shaft part in Figure 3 is based on CO, CO 2 , and CO detected by sondes 5 and ₄ in Figure 1, respectively.
Using H ₂ % and equations (4) to (8), the amount of change in the middle part M of the shaft section in Fig. 4 can be calculated using CO, CO ₂ , H ₂ % and (4 ) to (8). Furthermore, the amount of change in the lower part L of the furnace in Figure 5 was determined using the CO, CO ₂ and H ₂ % detected by sonde 7, the theoretical gas composition at the tuyere 1 level, and equations (4) to (8). It is.

Further, the vertical axes in FIGS. 3 to 5 indicate the monthly average value obtained by performing the detection of the gas composition and calculation of the amount of carbon change at a rate of (once/1 to 2 days). Furthermore, the number of drops indicates the number of small drops of 0.5 to 1.0 m of the raw material packed in the furnace, and the number of slips indicates the number of abnormal large drops of 1 meter of the raw material packed in the furnace. shows the average number of occurrences.

As shown in Figure 4, from May to June S56, there was a carbon precipitation reaction equivalent to 20 to 30 Kg/T-p in the middle part M of the shaft, and 140 Kg/T-p in the lower part L of the furnace.
A considerable amount of carbon gasification reaction (endothermic reaction) occurred, resulting in poor unloading as shown in Figure 6, but in July the ore base was increased from 80T/ch to 84T/ch.
As a result of trying to lower the peripheral (furnace wall) O/C by increasing ch to The load was reduced to below T-p, and as shown in FIG. 6, the load drop was improved. During this period, the total amount of carbon gasification reaction in the upper shaft part, middle part, and lower part of the furnace did not change much, but the O/C of the furnace wall part was lowered, and the carbon precipitation reaction in the middle part M of the shaft part was changed to a carbon gasification reaction. By changing the temperature, the furnace conditions could be stabilized. Calculating the amount of carbon change in the middle part of the blast furnace shaft and the furnace wall in this way, if the amount of carbon change indicates a carbon precipitation reaction, reduce the O/C of the furnace wall and make sure that the amount of carbon change is equal to the amount of carbon gas. It is clear that making the reactor exhibit a chemical reaction is extremely effective for stabilizing the furnace condition.

Figure 7 shows the drop per day showing the stability of the furnace condition when the conventional method (furnace top gas utilization distribution management method) and the present invention method (method for controlling the amount of carbon change in the furnace wall in the middle of the shaft) were implemented. It is clear that the furnace condition can be maintained stably according to the method of the present invention.

In the present invention, the two gas sampling positions (upper and lower) on the gas flow line of the furnace wall in the middle of the blast furnace shaft, that is, the positions of the CO, CO ₂ and H ₂ concentration detection points, are important, and this depends on the furnace conditions. It is necessary to investigate and select the upper and lower two points on the gas flow line of the furnace wall in the middle of the blast furnace shaft where the amount of carbon change that shows a sufficient correlation with stability and instability can be detected.

(Effects of the Invention) As detailed above, according to the blast furnace operating method of the present invention, the furnace can be operated while stably maintaining the furnace condition, and its value in blast furnace operation is great.

[Brief explanation of the drawing]

The drawings are all explanatory diagrams of the blast furnace operating method of the present invention, FIG. 1 is an explanatory diagram of the method of detecting the gas composition distribution in the direction of the furnace height, and FIGS. 2 to 7 are explanatory diagrams of the embodiments of the blast furnace operating method of the present invention. It is a diagram. 1...tuyere, 2...stock line, 3...blast furnace, 4-8...sonde.

Claims (1)

[Claims] 1 Detect CO, CO ₂ and H ₂ concentrations in the lower and upper parts of the furnace gas rising up the furnace wall in the middle of the blast furnace shaft, and based on the degree of detection, detect the carbon in the furnace wall in the middle of the blast furnace shaft. The amount of carbon change is determined, and if the amount of carbon change indicates a carbon precipitation reaction, the O/C of the furnace wall is lowered so that the amount of carbon change indicates a carbon gasification reaction. Blast furnace operating method.