JP3077691B1 - Blast furnace operation method - Google Patents

Abstract

An object of the present invention is to operate a blast furnace without causing a stairwell for a long period of time. SOLUTION: The gas density in the standard state is ρ ₀ , the furnace top gas flow rate in the standard state is V ₀ , the furnace top temperature is T, the standard state temperature is T ₀ , the furnace top pressure is P, and the standard state pressure is P. ₀ , when the area of the furnace port is S, the gas energy E in the furnace at the furnace port of the blast furnace is calculated by the following equation, and the calculated value is obtained in advance when the blow-through actually occurs based on the operation results of the blast furnace. The operation is performed by adjusting at least one of the coke ratio, the pulverized coal ratio, the blowing conditions, and the furnace top pressure of the blast furnace so as to be smaller than the minimum value E ₀ of the furnace port gas energy. E = ρ ₀ (V ₀ / S) ² × T / T ₀ × P ₀ / P Effect When the operating conditions are not changed, and even when the operating conditions are largely changed, the equipment at the top of the blast furnace is not changed. The blast furnace can be operated without causing blow-through for a long period of time, because the flow of gas and gas can be stabilized.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a blast furnace operating method capable of preventing a blow-by at a blast furnace opening and stably operating the blast furnace.

[0002]

2. Description of the Related Art In recent years, it has become difficult to maintain stable operation for a long period of time due to deterioration of the furnace body due to extension of the life of the blast furnace and deterioration of air permeability in the blast furnace due to high pulverized coal injection operation. I have. In particular, if a stairwell occurs, there is a danger that the furnace condition will fall due to shortening of the life of the furnace, etc.Continuing stable operations for a long period of time without causing a stall will lead to the productivity and economic More very important matter.

As a method for preventing blow-by, Japanese Patent Publication No.
In -10407, the pressure drop level is measured and calculated,
There is disclosed a ventilation control method for controlling the air flow and the like so that the pressure loss level is always equal to or lower than the dangerous pressure loss level. In Japanese Patent Application Laid-Open No. 9-78111, the particle size distribution and density distribution of the charge and the flow velocity distribution of the gas in the furnace are measured. A blow-by prevention method for adjusting the distribution and the amount of hot air is disclosed.

[0004]

However, the methods disclosed in Japanese Patent Publication No. 59-10407 and Japanese Patent Application Laid-Open No. Hei 9-78111 detect the sign just before a blow-by occurs,
This is a method of adjusting the blowing amount or the like (usually greatly reducing the blowing amount) to prevent blow-through, and is an emergency evacuation method for preventing blow-through, rather than achieving stable operation for a long time. Further, a large change in the amount of air blow during the normal operation leads to a change in the furnace condition of the blast furnace, which is not preferable for a long-term stable operation.

SUMMARY OF THE INVENTION The present invention has been made in view of the above-mentioned problems, and is intended to reduce the in-furnace gas energy at the furnace opening by designing a fuel ratio, a blowing condition, and the like so as not to cause blow-by for a long period of time. It is intended to provide a method by which a blast furnace can be operated.

[0006]

In order to achieve the above-mentioned object, a method for operating a blast furnace according to the present invention comprises the steps of reducing the gas energy in the furnace at the mouth of the blast furnace from the amount of the top gas, the top gas temperature, and the top pressure. The coke ratio of the blast furnace and the pulverized coal are calculated so that the calculated value is smaller than the previously determined minimum value E ₀ of the furnace port gas energy when the blow-through actually occurs due to the operation results of the blast furnace. At least one of the ratio and the blowing condition is adjusted. By doing so, the charge and the gas flow at the blast furnace mouth can be stabilized.

[0007]

DESCRIPTION OF THE PREFERRED EMBODIMENTS In a blast furnace operation, a force F1 due to a raw material load from above and a pushing force F2 from below by gas are compared, and the pushing force F2 from below is smaller than the force F1 due to the raw material load. If, for example, the charge moves downward, the operation is normal. And when both become equal, the charge stops moving, and conversely, when the pushing force F2 from below becomes greater than the force F2 due to the raw material load,
A blow-through (upward movement of the charge in the furnace by the gas) causes operation failure.

Therefore, the blow-by is determined in advance when the blow-through actually occurs due to the gas energy in the furnace (hereinafter referred to as "furnace gas energy") E at the mouth of the blast furnace during operation and the actual operation of the blast furnace. By managing the minimum value (hereinafter, referred to as “blow-through limit furnace energy”) E ₀ of the furnace gas energy set in advance, the sign can be predicted in advance.

The method of operating a blast furnace according to the present invention is based on the above-mentioned knowledge, and calculates the furnace gas energy E by the following equation 1, and the calculated value is smaller than the blow-through limit furnace energy E _0. The operation is performed by adjusting at least one of the coke ratio, the pulverized coal ratio, the blowing conditions, and the furnace top pressure of the blast furnace.

[0010]

E = ρ ₀ (V ₀ / S) ² × T / T ₀ × P ₀ / P where ρ ₀ : gas density in standard condition (kg / Nm ³ ) V ₀ : furnace in standard condition Top gas flow rate (Nm ³ / s) T: furnace top temperature (K) T ₀ : standard state temperature (K) (= 273) P: furnace top pressure (kg / cm ² ) P ₀ : standard state pressure (kg / cm ² ) (= 1.03) S: Furnace opening area (m ² )

It is needless to say that at least one point, preferably the lowest value among a large number of data, is used as the blow-through limit furnace energy E ₀ employed in the blast furnace operating method of the present invention.

In the blast furnace operating method of the present invention described above,
A method of calculating the furnace port gas energy E by the above-described formula 1 will be described. The furnace top gas flow rate, furnace top gas temperature, and furnace top pressure required to calculate the furnace port gas energy E are determined by, for example, the following method.

The blast furnace is vertically divided into, for example, five sections, and a pre-tropical zone, a gas reduction zone, a solution loss zone, a fusion zone, and a dripping zone are formed from above. Among them, in the pre-tropical zone, the evaporation of water in the charge and the thermal decomposition reaction of limestone, the reduction reaction of iron oxide in the gas reduction zone, the solution loss reaction in the solution loss zone, and the ore in the cohesive zone. Reaction of sinter and ore, carburization, Si, M
It is assumed that a reduction reaction of n and P occurs.

As described above, by limiting the reaction in each stage and giving the solid temperature in each stage as a precondition, the solid flow rate in the upper stage and the change in the solid flow rate due to the reaction are added to obtain the solid flow rate. From the mass balance equation, the sum of the gas flow rate in the lower stage and the amount of change in the gas flow rate due to the reaction is the gas flow rate. The total reaction amount, the gas flow rate in each stage, and the solid flow rate are obtained.

[0015] Further, three values obtained by multiplying the gas temperature, the gas specific heat, and the gas flow rate in the lower stage, multiplying the solid temperature, the solid specific heat, and the solid flow rate, and multiplying the total reaction amount and the reaction heat, are added. The heat input of the product is equal to the product of the product of the gas temperature, the specific heat of the gas, and the gas flow rate, the product of the solid temperature, the specific heat of the solid component, and the solid flow rate in the lower stage, and the heat output of the product obtained by adding the three values of the furnace body heat dissipation , The gas temperature at each stage is determined.

Then, the gas temperature and gas flow rate in the pre-tropical zone of the gas flow rate at each stage determined by the above-described mass balance equation and the gas temperature at each stage determined by the heat balance equation are determined by the furnace top. Gas temperature and furnace top gas flow rate. Further, the furnace top pressure is set to an arbitrary pressure depending on the facility capacity, operating conditions, and the like.

Using the thus obtained top gas temperature, top gas flow rate, and top pressure, a furnace port gas energy E is calculated, and the calculated furnace gas energy E is calculated as the blow-through limit furnace port energy. to be smaller than E _0, the coke ratio, pulverized coal ratio, blowing conditions i.e. hot air volume and oxygen flow amount, and furnace top the pressure is to adjust the, increasing the hot air volume and oxygen flow volume, The gas flow rate will increase, resulting in an increase in the top gas temperature and an increase in the top gas flow rate. Then, the furnace port gas energy E eventually increases.

Further, assuming that all the pulverized coal is burned in the dropping zone, when the pulverized coal ratio is increased, the furnace gas energy E increases as in the case where the amount of hot air and the amount of oxygen blown are increased. Will be.

When the coke ratio is increased, the solids flow rate is increased and the furnace top gas temperature is lowered. Also, an increase in the coke ratio leads to a decrease in the pulverized coal ratio. as a result,
If the coke ratio is increased, the furnace gas energy E will decrease.

From the above, it can be seen that there are the following three control means as a method of reducing the furnace port gas energy E. One of them is to reduce the gas flow rate in the blast furnace. For example, there is a method in which the oxygen enrichment rate is increased in the amount of hot air and the amount of oxygen blown from the tuyere of the blast furnace, and the amount of gas blown into the blast furnace is reduced. Since nitrogen in the hot air does not contribute to the reaction, increasing the oxygen enrichment rate reduces the amount of gas in the furnace without lowering the tapping rate, and reduces the furnace gas energy E
Can be reduced.

The second is to lower the furnace top temperature. For example, reducing the amount of pulverized coal used per tapping amount (hereinafter, referred to as “pulverized coal ratio”) and increasing the amount of coke used (hereinafter, referred to as “coke ratio”). Increasing the coke ratio to increase the amount of charge from the top of the furnace per tapping rate, and increasing the heat flow ratio (heat of charge / heat of gas in the furnace) to lower the furnace top temperature Can be. As a result, the furnace port gas energy E can be reduced.

Third, the furnace top pressure is increased. By raising the furnace top pressure, the furnace top gas flow rate can be reduced, and as a result, furnace port gas energy E can be reduced.

By the way, the value of the blow-through limit furnace port gas energy E ₀ differs depending on, for example, the furnace port profile of the blast furnace. Even in the blast furnace having the same furnace port profile, the gas flow in the furnace port becomes uneven due to damage to the furnace port during operation of the blast furnace, for example, refractory falling off the furnace port, and the blow-through limit furnace gas energy E _0. Varies. Therefore, when the shape of the throat portion has changed, it is necessary to obtain the blow-limit furnace inlet gas energy E ₀ again.

In this case, for example, there is a furnace port refractory temperature as an index for knowing a change in the furnace port profile. Therefore, in the blast furnace operating method of the present invention described above, the degree of damage to the furnace mouth refractory is detected from the temperature of the blast furnace furnace wall, and the value of the blow-through limit furnace mouth energy E ₀ is determined in accordance with the degree of damage. It is desirable to correct it.

In this case, for example, when the refractory temperature is ΔT (° C.)
If it rises, it is determined that the furnace refractory has fallen off. Due to the fall of the refractory at the furnace opening, a space is created in the furnace,
If it becomes blow easy state, the value of the blow-limit furnace inlet gas energy E ₀ is reduced. Accordingly, if the furnace port refractories fall off and the blow-through limit furnace port gas energy E ₀ decreases and the operation is continued in a state where the furnace port gas energy E becomes smaller than the furnace port gas energy E, blow-through occurs.

[0026]

DESCRIPTION OF THE PREFERRED EMBODIMENTS The results of experiments conducted to confirm the effects of the blast furnace operating method of the present invention will be described below. Internal volume is 2
In a blast furnace with 700 m ³ , tapping ratio of 2.0 ton / m ³ / day and furnace top pressure of 1.75 kg / cm ² , the relationship between the furnace gas energy E and blow-through was investigated for three months. In the healthy period, as shown in FIG. 1, when the furnace mouth gas energy E is 2.85 kg / m / sec ² or more, and when the furnace mouth portion is damaged, it is omitted from the drawing. When the energy E was 2.55 kg / m / sec ² or more, it was found that blow-by occurred. Therefore, the blow-through limit furnace port gas energy E ₀ in this blast furnace is 2.8.
And 5 kg / m / sec ^2, also at throat injury ([Delta] T is 100
℃ blow limit furnace inlet gas energy E ₀ when) exceeding was 2.55 kg / m / sec ^2.

FIG. 2A shows the operation history before the blast furnace operation method of the present invention is carried out. Internal volume of 2700 m ^3, in blast furnaces tapping ratio 2.0ton / m ³ / day, the hot air amount 3900Nm ³ / min, oxygen flow amount is 6400Nm ³ /
When the plant was operated for hours, there was a request for an increase in production of 100 tons per day. When the plant was operated with the amount of hot air increased by 100 Nm ³ / min, blow-through occurred frequently. When the operation analysis was performed later, the furnace port gas energy E was found to be lower than the blow-through limit furnace gas energy E ₀ (= 2.85 kg / m / sec ² ).
Was bigger than.

On the other hand, in a blast furnace having an inner volume of 2700 m ³ and a tapping ratio of 2.0 ton / m ³ / day, the hot air volume is 3850 Nm ³ / min and the oxygen blowing volume is 6600 Nm ^3.
/ Hour, calculated furnace gas energy is 2.71 kg / m /
During the operation at ² seconds, there was a request to increase the production by 100 tons per day, the hot air flow rate was 50 Nm ³ / min, and the oxygen flow rate was 600
When the operation was designed with the amount increased by Nm ³ / hour, the calculated reactor gas energy was 2.84 k in the above-described model calculation.
It became g / m / sec ^2.

Therefore, it is determined that the furnace port gas energy can be maintained at a value smaller than the blow-through limit furnace port gas energy E ₀ , and the hot air flow rate is 50 Nm ³ / min, and the oxygen blowing rate is 60.
The operation was performed by increasing the amount by 0 Nm ³ / hour, and thereafter, the actual furnace gas energy E was traced, and the furnace gas energy E was increased to 2. It became the 84kg / m / sec ^2. At this time, it is determined that the possibility of blow-by is large, and
0 Nm ³ / min is reduced to 3850 Nm ³ / min, while the oxygen injection is increased by 400 Nm ³ / h to 7
When the operation was designed at 600 Nm ³ / hour, the calculated furnace gas energy was 2.73 kg / m / sec ^2. Thereafter, when the operation was performed under these conditions, no blow-by occurred. This process is shown in FIG.

FIG. 3A shows another example of the operation history before the method of operating the blast furnace according to the present invention. In a blast furnace with an inner volume of 2700 m ³ and a tapping ratio of 2.0 ton / m ³ / day, the hot air flow was 3900 Nm ³ / min, and the oxygen blowing rate was 6400 Nm ³ / hour, and continuous blow-through occurred. did. At that time, the temperature of the furnace refractory was 300 ° C.
To 410 ° C. When the furnace mouth was visually inspected after the wind was shut off, the furnace mouth refractory was damaged or dropped off. When the operation analysis was performed later, the furnace gas energy E was found to be lower than the blow-through limit furnace gas energy E when the furnace port was damaged.
₀ (= 2.55 kg / m / sec ² ).

On the other hand, in a blast furnace having an inner volume of 2700 m ³ and a tapping ratio of 2.0 ton / m ³ / day, the amount of hot air is 3850 Nm ³ / min and the amount of oxygen blown is 6600 Nm ^3.
/ Hour, calculated furnace gas energy is 2.71 kg / m /
After operating for ² seconds, the furnace refractory temperature was 300
Temperature rise from 410 ℃ to 410 ℃.
It was determined that there was a dropout. Therefore, the blow-through limit furnace gas energy E ₀ (= 2.55 kg /
m / sec ² ), the hot air flow rate is 3700 Nm ³ / min.
When the operation was performed at an oxygen injection rate of 8500 Nm ³ / hour and a calculated furnace gas energy of 2.51 kg / m / sec ² ,
No stairwell occurred. This process is shown in FIG.

FIG. 4 (a) shows still another example of the operation history before the method of operating the blast furnace according to the present invention. In a blast furnace having an inner volume of 2700 m ³ and a tapping ratio of 2.0 ton / m ³ / day, a coke ratio of 326 kg / ton · p
ig, pulverized coal ratio was 180 kg / ton · pig. When the coke ratio was changed to 314 kg / ton-pig and the pulverized coal ratio was changed to 195 kg / ton-pig, the run-through occurred frequently. When the operation analysis was performed later, it was found that the furnace port gas energy E was larger than the blow-through limit furnace port gas energy E ₀ (= 2.85 kg / m / sec ² ).

On the other hand, the inner volume is 2700 m^Three , Out
Pig ratio is 2.0 ton / m^Three / Day in a blast furnace
326 kg / ton ・ pig, pulverized coal ratio is 180
kg / ton-pig, calculated furnace gas energy is 2.
73kg / m / sec^Two Had been operating. Then coke
The ratio is 318 kg / ton ・ pig, and the pulverized coal ratio is 190 k.
Operation to change the specifications to g / ton ・ pig
As a result of the design, the model
Gas energy is 2.83 kg / m / sec^Two It became. Obedience
The gas energy E₀ (= 2.85
kg / m / sec^Two) Calculation furnace gas energy is smaller than
And the coke ratio is 318.
kg / ton ・ pig, pulverized coal ratio is 190kg / ton
・ Pig operation, and then actual furnace gas energy
E was performed by tracing. As a result, the furnace gas temperature
As a result, the furnace port gas energy E was 2.85 kg / m /
Second ^Two It became. At this time, if the possibility of
Judge and set the coke ratio to 321kg / ton-pig, fine
Designed for operation with a pulverized coal ratio of 185 kg / ton ・ pig
At this time, the calculated furnace gas energy was 2.78 kg / m / sec.
^Two Since then, operations have been carried out under these conditions.
Of course, no stairwell occurred. FIG. 4 (b) shows this process.
Show.

[0034]

As described above, according to the blast furnace operating method of the present invention, not only when the operating conditions are not changed, but also when the operating conditions are largely changed, the charge at the top of the blast furnace does not change. The gas flow can be stabilized.
Therefore, according to the blast furnace operating method of the present invention, it is possible to operate the blast furnace without causing blow-by for a long time.

[Brief description of the drawings]

FIG. 1 is a diagram showing an operation example (relation between gas energy and blow-by frequency) of the present invention.

FIG. 2 is a diagram showing the operation history of a blast furnace at the time of increasing production.
(A) is a diagram showing a case where the method of the present invention is not performed, and (b) is a diagram showing a case where the method of the present invention is performed.

3A and 3B are diagrams showing the operation history of a blast furnace at the time of furnace opening damage, wherein FIG. 3A shows a case where the method of the present invention is not performed, and FIG. 3B shows a case where the method of the present invention is performed.

FIGS. 4A and 4B are diagrams showing the operation history of a blast furnace when the pulverized coal ratio is increased by reducing the coke ratio, wherein FIG. 4A shows a case where the method of the present invention is not performed, and FIG. 4B shows a case where the method of the present invention is performed. FIG.

Claims (2)

(57) [Claims] 1. The furnace gas energy E at the blast furnace furnace opening is calculated by the following equation, and the calculated value is the furnace gas energy previously determined when blow-through actually occurs based on the operation results of the blast furnace. A blast furnace operating method by adjusting at least one of a coke ratio, a pulverized coal ratio, a blowing condition, and a furnace top pressure of the blast furnace so as to be smaller than a minimum value E ₀ of the blast furnace. E = ρ ₀ (V ₀ / S) ² × T / T ₀ × P ₀ / P where ρ ₀ : gas density in standard condition (kg / Nm ³ ) V ₀ : furnace top gas flow rate in standard condition ( Nm ³ / s) T: Furnace top temperature (K) T ₀ : Standard state temperature (K) (= 273) P: Furnace top pressure (kg / cm ² ) P ₀ : Standard state pressure (kg / cm ² ) ( = 1.03) S: Furnace opening area (m ² ) 2. The method according to claim 1, wherein the degree of damage of the refractory at the furnace mouth is detected from the temperature of the furnace wall of the blast furnace furnace, and the minimum value E ₀ of the furnace gas energy is corrected according to the degree of damage. The blast furnace operating method according to claim 1, wherein