JPH04268005A - Method for operating fine powdered coal blowing blast furnace - Google Patents

Abstract

PURPOSE:To maintain the replacing ratio of coke, to improve the productivity and to reduce a fuel ratio by quickly detecting the lowering of reaction efficiency to fine powdered coal and controlling the blowing quantity of the fine powdered coal and blasting condition according to the lowered quantity in the large quantity of fine powdered coal blowing operation in a blast furnace. CONSTITUTION:In the operating method for blowing the fine powdered coal from a tuyere part in the blast furnace, existence ratio of unburnt char from the fine powdered coal to carbon contained in dust is measured by microscopic observation of the dust in exhaust gas at a furnace top and the dust in the furnace core, and any one kind among blowing quantity of the fine powdered coal and/or blasting temp., oxygen quantity in blasting or blasting humidity is adjusted so as to be in the preset reference value or lower. The inferior condition of the blast furnace operation due to lowering of reaction efficiency to the fine powdered coal can be avoided and a molten iron can stably be supplied.

Description

[Detailed description of the invention]

0001

[Industrial Application Field] The present invention injects a large amount of pulverized coal from the tuyere of a blast furnace, ensures its reactivity, maintains a high replacement rate with coke, improves productivity, and improves fuel ratio. This invention relates to a blast furnace operating method that reduces the

0002

BACKGROUND OF THE INVENTION A technique for injecting auxiliary fuel through the tuyeres in blast furnace operation is disclosed in Japanese Patent Publication No. 40-23763 for the purpose of reducing hot metal manufacturing costs and improving productivity. In particular, the injection of pulverized coal from the blast furnace tuyeres is not only a means of stabilizing blast furnace operation, but also an effective means of reducing costs by substituting a portion of expensive coke with inexpensive pulverized coal. Recently, it has been implemented in many blast furnaces. In addition, we will take countermeasures against the aging of coke ovens and
A further increase in the amount of pulverized coal injected is also required from the perspective of expanding the degree of freedom in energy selection.

The pulverized coal injected from the tuyeres reacts in place of some of the coke in the blast furnace, and because of its reactivity and high calorific value, it generates a large amount of reducing gas at high temperatures. Not only can heat be maintained at a high level, but it also makes the reduction reaction of iron ore more efficient. Therefore, by injecting pulverized coal from the tuyeres, it is possible to enjoy the effects of improving the economic efficiency and productivity of the blast furnace.

0004

[Problem to be solved by the invention] By the way, in conventional blast furnace operation, the amount of pulverized coal injected is not large, so all of the injected pulverized coal reacts in the blast furnace. As a result, there is a possibility that not all of the pulverized coal will react in the blast furnace. If all of the pulverized coal does not react, some unburned char will be generated. Since this unburned char is discharged from the top of the furnace along with the rising gas flow, the substitution rate of pulverized coal for coke decreases, causing an increase in the fuel ratio and a decrease in production. In addition, this unburned char forms a layer of coke in the center of the lower part of the blast furnace (
When trapped and deposited in the furnace core (called the furnace core), it impedes the liquid permeability of the hot metal slag flowing down this area and the gas permeability of this area, resulting in an increase in blast pressure and the occurrence of slips. The fall of the burden becomes unstable and the production volume decreases further. If the entire amount of pulverized coal does not react as described above, not only the effects of the pulverized coal injection operation described above cannot be enjoyed, but also stable operation of the blast furnace cannot be achieved.

[0005] The reaction efficiency of pulverized coal is generally judged by the change in the substitution rate of pulverized coal for coke.If the substitution rate decreases, the fuel ratio increases and the production volume decreases. Increase the amount of pulverized coal injected to the extent that it can be maintained. However, when this decrease in replacement rate is detected, an increase in blast pressure indicates a deterioration in the liquid permeability and air permeability of the furnace core, and slip/drop occurs, indicating a failure in the descent of the charge inside the blast furnace. It is often accompanied by an increase in the number of cases, and it will not recover unless significant action is taken over a long period of time.
Losses due to lower production will become even greater. this is,
Since this substitution rate does not directly indicate the reaction efficiency of pulverized coal; in other words, it is an index that includes other fluctuation factors, it is possible to detect the aforementioned operational fluctuations caused by the generation of unburned char at an early stage. and by being unforeseeable. Therefore, there is a need for a method that can directly detect the reaction efficiency of pulverized coal and take immediate action.

Therefore, the present invention measures the proportion of unburned char in the dust contained in the exhaust gas at the top of the furnace or the carbon in the dust in the furnace core when a large amount of pulverized coal is blown into the furnace. The purpose is to avoid a decrease in production volume due to an increase in fuel ratio or poor ventilation by changing the amount of air flow and/or air blowing conditions.

[0007]

[Means and effects for solving the problems] In order to achieve the object, the operating method of the present invention is an operating method in which pulverized coal is injected from the tuyere of a blast furnace. The presence ratio of unburned char derived from pulverized coal to the carbon in the dust in the core is measured, and the amount of pulverized coal injected and/or the blowing temperature is adjusted so that the presence ratio is below a preset value. It is characterized by adjusting either the amount of oxygen or the humidity of the air. Below, a method for detecting unburned char and a method for changing the amount of pulverized coal injected and the blowing conditions according to the present invention will be explained.

[0008] The dust contained in the furnace top exhaust gas or the dust in the furnace core contains unburned char derived from pulverized coal, fine coke, and ore powder, and in ordinary chemical analysis, unburned char and fine coke are found in the dust. Exists as carbon,
It is impossible to distinguish between the two. Therefore, we created a sample by removing as much ore powder as possible from the collected dust, embedding it in resin, and polishing the surface.
Optically identified by microscopic observation. The pulverized coal injected through the tuyere undergoes rapid thermal decomposition, releasing a large amount of volatile matter as gas and producing char. When the entire amount of char does not react in the blast furnace and remains as unburned char, the shape of the particles is porous particles with a rounded shape close to a spherical shape and a developed pore structure, as can be inferred from the char generation conditions. It is. On the other hand, coke powder is generated by mechanical shock due to swirling of coke in a raceway, and the pore structure of the coke itself does not change much even when subjected to sudden thermal shock.
It exhibits an angular, less-porous particle morphology. Therefore, the abundance ratio of unburned char is measured by observing the embedded and polished sample under a microscope and counting the number of particles based on the difference in particle form between the two. The measurement method may be a method using a normal point counter, or a method in which several dozen points of view are selected and the number of unburnt char and coke breeze is counted and totaled in each field of view.
In either method, it is desirable that the sum of both numbers is 100 or more. Furthermore, if the particle diameter is also measured when counting the number of particles, it is also possible to estimate the weight ratio of unburned char to the carbon in the dust. The dust to be collected from the top of the furnace can be collected directly from the exhaust gas at the top during operation or from the dry dust collector, and the dust in the furnace core can be collected from the tuyere during operation or during a break. A common method is to insert a probe into the body and collect the sample. Furthermore, it is desirable to collect dust not only when changing pulverized coal injection conditions or air blowing conditions, but also periodically as part of daily operational management.

Now, the standard value of the proportion of unburned char in the carbon in the furnace top exhaust gas or the dust in the furnace core, which is used as a reference for operation by determining the reaction efficiency of pulverized coal, depends on the type of pulverized coal. Even for the same type of coal, it varies depending on the charging conditions of the blast furnace. In addition, the standard value for dust in the furnace top exhaust gas compared to dust in the furnace core is based on the fact that the residence time of dust in the blast furnace is longer and the reactivity of unburned char is higher than that of coke breeze. It is necessary to take this into consideration when setting. Normally, the dust in the furnace top exhaust gas is set at 3 to 6%, and the dust in the furnace core is set at around 8 to 12%, but the optimum value should be determined based on the operating results such as the replacement rate of pulverized coal for coke in the blast furnace. Bye. If the ratio of unburned char to the carbon in the furnace top exhaust gas or the dust in the furnace core is greater than the standard value, the amount of pulverized coal injected and/or the blowing conditions are adjusted so that it is below the standard value. change.

[0010] When the amount of pulverized coal injected is reduced, the following air ratio increases, the reaction efficiency of the pulverized coal increases, and the generation of unburned char is suppressed.

(Air ratio) = (Air blown from the tuyeres, pure oxygen, amount of oxygen in pulverized coal)/(Amount of oxygen required to burn C and H in pulverized coal to CO2 and H2O) ) Therefore, as shown in FIG. 1, the amount of pulverized coal injected is reduced in accordance with the amount of increase in the proportion of unburned char in the carbon in the furnace top exhaust gas or the dust in the furnace core relative to the reference value.

[0012]In order to reduce the proportion of unburned char in the carbon in the dust contained in the furnace top exhaust gas, it is effective to simply adjust the amount of pulverized coal injected and the blowing conditions, but as mentioned above, In cases where a large amount of unburned char accumulates in the furnace core, resulting in poor ventilation or a drop in temperature within the furnace core, it is more effective to combine them. That is, this method not only suppresses the generation of unburned char, but also eliminates the unburned char trapped in the furnace core to eliminate poor ventilation and increase the temperature inside the furnace core.

[0013] When the air blowing temperature or the oxygen concentration in the air is increased, the temperature of the gas blown into the raceway from the tuyeres (flame temperature) increases, so the reactivity of the pulverized coal improves and unburnt char is removed. This can suppress the occurrence and also increase the temperature inside the furnace core. In addition, by increasing the amount of steam being blown, the amount of char reaction increases in the reducing atmosphere in and around the raceway, suppressing the generation of unburned char, and eliminating unburned char trapped in the furnace core. can. Therefore,
As shown in FIGS. 2, 3, and 4, the blowing temperature, oxygen concentration during blowing, Increase any kind of steam during blowing. Therefore, if the proportion of unburned char in the carbon in the furnace top exhaust gas or the dust in the furnace core based on microscopic observation is larger than the standard value, the amount of pulverized coal injected should be adjusted according to Figures 1 to 4. By lowering and/or increasing any one of the blowing temperature, the amount of oxygen during blowing, and the blowing humidity, the blast furnace operation can be made below the standard value, and the blast furnace operation becomes stable.

[0014]

[Examples] The features of the present invention will be explained in detail with reference to Examples below. As shown in Table 1, in Example 1, the proportion of unburned char in the carbon in the dust contained in the furnace top exhaust gas increased from the standard value of 5% to 8%, so pulverized coal was injected. This is an example of operation in which the amount was reduced to 5%.

In Example 2, since the proportion of unburned char in the carbon in the dust contained in the furnace top exhaust gas increased from the standard value of 5% to 9%, the blowing temperature was increased to 5%.
This is an example of operation in %.

In Example 3, the proportion of unburned char in the carbon in the dust contained in the furnace top exhaust gas increased from the standard value of 5% to 8%, so the amount of oxygen in the blast was increased to 5%. This is an example of operation in %.

In Example 4, the proportion of unburned char in the carbon in the dust contained in the furnace top exhaust gas increased from the standard value of 5% to 8%, so the steam being blown was increased to 5%. This is an example of operation.

In Example 5, the proportion of unburned char in the carbon in the dust contained in the furnace top exhaust gas increased from the standard value of 5% to 11%, so the amount of pulverized coal injected was reduced. This is an example of operation in which the air temperature was increased to 5%.

In Example 6, the proportion of unburned char in the carbon in the dust contained in the furnace top exhaust gas increased from the standard value of 5% to 10%, so the amount of pulverized coal injected was reduced. This is an example of operation in which the amount of oxygen during blowing was increased to 5%.

In Example 7, the proportion of unburned char in the carbon in the dust contained in the furnace top exhaust gas increased from the standard value of 5% to 9%, so the amount of pulverized coal injected was reduced. This is an example of operation in which the amount of steam being blown was increased to 5%.

In Example 8, the proportion of unburned char in the carbon in the dust in the furnace core increased from the standard value of 10% to 13%, so the amount of pulverized coal injected was reduced to 10%.
This is an example of operation in %.

Example 9 is an operation example in which the proportion of unburned char in the carbon in the dust in the furnace core increased from the standard value of 10% to 15%, so the blowing temperature was increased to 10%. be.

In Example 10, the proportion of unburned char in the carbon in the dust in the furnace core increased from the standard value of 10% to 14%, so the amount of oxygen in the blast was increased to 10%.
This is an example of operation in %.

In Example 11, since the proportion of unburned char in the carbon in the dust in the furnace core increased from the standard value of 10% to 13%, the steam being blown was increased to 10%.
This is an example of operation.

In Example 12, the proportion of unburned char in the carbon in the dust in the furnace core increased from the standard value of 10% to 17%, so the amount of pulverized coal injected was lowered and the blowing temperature was lowered. This is an example of an operation in which the amount increased to 10%.

In Example 13, the proportion of unburned char in the carbon in the dust in the furnace core increased from the standard value of 10% to 15%, so the amount of pulverized coal injected was reduced, and the This is an example of operation in which the amount of oxygen was increased to 10%.

In Example 14, the proportion of unburned char in the carbon in the dust in the furnace core increased from the standard value of 10% to 14%, so the amount of pulverized coal injected was reduced, and the This is an example of operation in which steam was increased to 10%.

In either case, the fuel ratio is lower and the pig iron output is larger than in the comparative example.

The comparative example is a case in which it is assumed that the reaction efficiency of pulverized coal is reduced and the replacement rate for coke is reduced, and the ratio of the amount of iron ore charged from the furnace top/the amount of charged coke (O/
C), the fuel ratio is high, and the amount of iron output is low.

[0030]

[Table 1]

[0031]

[Table 2]

[0032]

As explained above, in the present invention, the reduction in the reaction efficiency of pulverized coal is caused by the proportion of unburned char derived from pulverized coal in the dust contained in the top exhaust gas or the carbon in the dust in the furnace core. The amount of pulverized coal blown into coke and/or the blowing temperature, the amount of oxygen in the blowing, and the blowing humidity are adjusted according to the amount of increase in the abundance ratio. By avoiding a decrease in replacement rate and poor ventilation in the furnace core, it is possible to improve productivity, lower the fuel ratio, and provide a stable supply of hot metal.

[Brief explanation of the drawing]

[Figure 1] Existence ratio of unburned char derived from pulverized coal to carbon in dust contained in the furnace top exhaust gas or dust in the furnace core of the present invention (hereinafter referred to as the existence ratio of unburned char)
FIG. 3 is a diagram showing the relationship between the amount of increase in the amount of pulverized coal and the amount of decrease in the amount of pulverized coal injected with respect to the reference value.

FIG. 2 is a diagram showing the relationship between the amount of increase in the abundance ratio of unburned char with respect to a reference value and the amount of increase in blowing temperature.

FIG. 3 is a diagram showing the relationship between the amount of increase in the abundance ratio of unburned char with respect to a reference value and the amount of increase in oxygen during blowing.

FIG. 4 is a diagram showing the relationship between the amount of increase in the abundance ratio of unburned char with respect to a reference value and the amount of increase in steam during blowing.

Claims (1)

[Claims] Claim 1: In an operating method in which pulverized coal is injected from the tuyere of a blast furnace, the abundance ratio of unburned char derived from pulverized coal to the dust contained in the top exhaust gas or the carbon in the dust in the furnace core is measured. and adjusting any one of the amount of pulverized coal injected and/or the temperature of the pulverized coal, the amount of oxygen in the blast, and the humidity of the blast so that the abundance ratio is equal to or less than a preset value. .