JP3844858B2 - Blast furnace operating method with pulverized coal fuel injection. - Google Patents

Description

[0001]
[Industrial application fields]
The present invention relates to a method for operating a blast furnace with high operational efficiency by blowing pulverized coal fuel from a tuyere of a blast furnace.
[0002]
[Prior art]
In integrated steelmaking, improving the operating efficiency of the blast furnace is one of the most important issues in reducing the cost of steelmaking. In addition, since the oil shock, in order to reduce heavy oil consumption and reduce ironmaking costs, pulverized coal fuel injection operation has been adopted in which pulverized coal is injected into the furnace instead of heavy oil.
However, the deposit may suddenly grow on the furnace wall of the blast furnace due to the disturbance of the thermal load balance of the furnace body. When deposits grow on the furnace wall, the gas flow in the blast furnace is significantly disturbed, which tends to increase the fuel ratio and decrease the operation efficiency. As a result, the ironmaking cost increases and sometimes triggers the furnace condition.
[0003]
As a means for removing deposits, a cleaning operation (cas operation) for temporarily reducing the operation efficiency in order to increase the fuel ratio for a short period of time and lower the pulverized coal ratio to ensure the air permeability of the blast furnace, Is used to reduce the level of the charge in the furnace, and mechanically remove the deposits adhering to the furnace wall in the blast furnace.
As means for removing deposits in the furnace while maintaining the operation efficiency, controlling the flow rate of hot air in the circumferential direction of the furnace is introduced in Japanese Patent Laid-Open No. 6-256821. In this method, a hot air control valve was provided in the hot air branch pipe connected to each tuyere of the blast furnace, and when the temperature decreased due to the formation of deposits on the furnace wall at the top of the tuyere during blast furnace operation, the temperature dropped. The opening degree of the hot air control valve of at least two or more hot air branch pipes corresponding to the location is increased.
[0004]
[Problems to be solved by the invention]
However, in order to improve the operation efficiency of the blast furnace, it is more important to operate the blast furnace under conditions where there is no adhesion or growth of deposits on the furnace wall, rather than removing deposits generated on the furnace wall in the blast furnace. It is. In this regard, the current cleaning operation is based on the assumption that deposits adhere and grow on the furnace wall in the blast furnace, and only removes the deposits that have adhered and grown. Moreover, in the method of removing the deposits adhering to the furnace wall in the blast furnace by the mechanical means by resting wind, the operation efficiency of the blast furnace is lowered during the period until resting wind.
On the other hand, the method of Japanese Patent Laid-Open No. 6-256821 that controls the flow rate of hot air in the circumferential direction by a hot air control valve is advantageous because it can suppress the growth of deposits while maintaining the operation efficiency of the blast furnace. It can be said. However, since it is necessary to provide a hot-air control valve in the hot-air branch pipe connected for every tuyere, the cost concerning a hot-air control valve and its control mechanism becomes high.
The present invention has been devised to solve such problems, and by controlling the amount of pulverized coal fuel injected in the circumferential direction of the furnace body according to the circumferential distribution of the temperature in the furnace, The purpose is to operate the blast furnace with high efficiency while suppressing the generation of deposits on the furnace wall and reducing and removing deposits.
[0005]
[Means for Solving the Problems]
In order to achieve the object of the blast furnace operating method of the present invention, pulverized coal fuel is introduced into the furnace from a blowing lance inserted into a down pipe connected to a tuyere provided in the blast furnace along the circumferential direction. When blowing, temperature information in the circumferential direction of the furnace is taken out by temperature detection means embedded in the furnace wall of the blast furnace at a plurality of stages in the height direction and at equal intervals in the circumferential direction, and the circumference of the furnace temperature is obtained. The amount of deviation regarding the direction is obtained, and the amount of pulverized coal fuel injected into the furnace from each injection lance is calculated based on the amount of deviation. Thus, in the tuyere in the direction where the temperature is low, conversely, the amount of blowing is controlled to be small .
The index of deviation that controls the amount of pulverized coal fuel injected in the circumferential direction of the furnace body is a weight for each height level to the temperature information obtained by the temperature detection means embedded in the furnace wall at each height level. The temperature data is obtained by multiplying the coefficient, and the temperature data in the height direction in each direction obtained by dividing the circumferential direction of the furnace body into a plurality of equal intervals is summed to obtain an index of the deviation of the furnace temperature distribution.
[0006]
[Action]
Under blast furnace operation where the amount of pulverized coal fuel is increased, if an unbalanced situation occurs where the amount of pulverized coal fuel injected is low in only one direction, the carbon supply before tuyere per unit ore in that direction In other words, the carbon consumption before the tuyere decreases. According to the results of a model experiment assuming an actual blast furnace (“Iron and Steel” Vol. 73 (1987), p. 1996), if the consumption of carbon in front of the tuyere in a certain direction (I) is completely stopped, It is said that the descending speed distribution of objects is large in the direction (II) where carbon is consumed as usual in the lower part of the furnace, but conversely, in the upper part of the furnace, it becomes larger in the direction (I) where carbon consumption is completely stopped. Therefore, the residence time from the upper part of the furnace to the lower part of the furnace becomes large in the direction (I) in which the carbon consumption is completely stopped.
From these results, in the direction (I) where the amount of pulverized coal fuel injected is small, the heating time of the solid becomes longer according to the long residence time, and the total amount of heat dissipated from the upper part of the furnace to the lower part of the furnace becomes large. However, when viewed locally, a situation where heat is insufficient at the upper part of the furnace where the descending speed is large occurs, and a tendency for deposits to be generated and grown on the wall of the furnace body is predicted.
[0007]
Therefore, in the present invention, based on the circumferential balance of the furnace body temperature, the amount of pulverized coal fuel is increased at the tuyere in the high temperature direction, and conversely in the tuyere at the low temperature direction. Reduce the amount. The injected pulverized coal fuel generates a local gas flow around the deposit, and the deposit is removed from the furnace wall by reduction and melting by this peripheral gas flow. In this way, by controlling the amount of pulverized coal fuel injected in the circumferential direction of the furnace body, the carbon consumption before the tuyere per unit ore is increased, and the circumferential distribution of the descent speed is set to an appropriate state. Correct it.
[0008]
Embodiment
In the equipment configuration according to the present invention, a thermocouple thermometer 2 is provided in a plurality of stages in the height direction in the blast furnace 1 so that all furnace temperatures of the blast furnace 1 are detected. A plurality are provided in the circumferential direction.
A plurality of tuyere 3 are provided along the circumferential direction at the lower part of the blast furnace 1, and each tuyere 3 is connected to the annular pipe 5 through the blower branch pipe 4. A down pipe 6 for blowing pulverized coal fuel that opens near the tuyere 3 is fed into the blower branch pipe 4. The down pipe 6 is connected to a distributor 8 through each branch pipe 7 for blowing pulverized coal fuel. The distributor 8 is provided with a measuring device 9 for measuring the flow rate of the pulverized coal fuel. The distributor 8 is connected to the feed tank 11 by a pipe 10, and a carrier gas supply pipe 13 having a flow rate regulator 12 is opened in the middle of the pipe 10.
[0009]
The pulverized coal is fed into the feed tank 11 from the reservoir tank 14 through the pulverized coal supply pipe 15. The feed tank 11 is connected to a pressurized nitrogen gas supply pipe 17 provided with a flow rate regulator 16 in order to maintain the inside in an atmosphere in which pulverized coal does not burn and to send the pulverized coal from the inside through the pipe 10. .
The pulverized coal sent out from the feed tank 11 is sent through the pipe 10 by a carrier gas such as air sent from the carrier gas supply pipe 13, sent into the distributor 8, and each branch pipe 7 for blowing pulverized coal fuel. Distributed to. The flow rate of the pulverized coal fuel distributed to each branch pipe 7 is measured by the measuring device 9, and the flow rate of the pulverized coal fuel passing through the branch tube 7 is adjusted by the flow rate regulator 18. Then, the pulverized coal fuel is blown into the blower branch pipe 4 from the blower lance 19 through the down pipe 6 and blown into the blast furnace 1 together with hot air.
[0010]
The temperature detected by the thermocouple thermometer 2 is input to the temperature management system 20. The temperature management system 20 calculates 8-hour average value temperature data from the input temperature information, and determines the deviation of the thermal load in the circumferential direction of the furnace body based on the 8-hour average value temperature data. The determination result is output from the temperature management system 20 to the pulverized coal injection amount management system 21. In the pulverized coal injection amount management system 21, the flow rate of the pulverized coal fed through each branch pipe 7 is adjusted.
Next, a method of determining the deviation amount of the temperature distribution in the furnace for the blast furnace 1 provided with a plurality of thermocouple thermometers 2 in three stages in the height direction will be described. Divided into 90 degree azimuths at each height level of the furnace body, and temperature information detected by a plurality of thermocouple thermometers 2 provided in the furnace body of each azimuth as 1 minute data for 8 hours per 90 degree azimuth Averaged. The average values obtained are shown in FIGS.
[0011]
(A) is an average value obtained from the temperature indication value of the thermocouple thermometer 2 installed at the S-3 stave level at a height of 25620 mm from the ground level. (B) is an average value obtained from the temperature indication value of the thermocouple thermometer 2 installed at the S-1 stave level at a height of 20425 mm from the ground level. (C) is an average value obtained from the temperature indication value of the thermocouple thermometer 2 installed at the B-2 stave level at a height of 17810 mm from the ground level. The average values of (a) to (c) are linked with the temperature information obtained by the thermocouple thermometer 2 embedded in the furnace body, and are constantly at intervals of 8 hours or based on data of the past 8 hours. Updated.
[0012]
Specifically, the numbers 1, 2,... Clockwise from the 0 degree side of the furnace body to 12 thermocouple thermometers 2 embedded at equal intervals in the circumferential direction inside the furnace body at the S-3 stave level. The average value for 8 hours is taken from the 1-minute data of No. 1 to 3 in the direction from 0 to 90 degrees, and the average value of the three of No. 1 to 3 is taken as TS-3-1.
Similarly, 90 degrees to 180 degrees are set to TS-3-2, 180 degrees to 270 degrees are set to TS-3-3, and 270 degrees to 0 degrees are set to TS-3-4. FIG. 2A is a graph of the four average values TS- 3-1 to TS- 3-4 obtained in this way. 2 (b) and 2 (c) similarly show the four average values TS-1-1-1 to TS-1-4, TB obtained at the S-1 stave level and the B-2 stave level. 2-1 to TB-2-4 are graphed.
[0013]
When the average values are multiplied by weighting factors A, B, and C of (0.5 to 1.0) and the height directions in the respective directions are summed, the result shown in FIG. 2D is obtained. This is an index of the circumferential distribution of the furnace temperature. The weighting factors A to C mean the rate at which the temperature distribution in the height direction of the furnace body affects the temperature distribution in the circumferential direction during blast furnace operation. For example, the coefficient is 1 at the S-3 stave level at the high position. For the S-1 stave level and the B-2 stave level, which have a large fluctuation, the sensitivity is lowered using a coefficient close to 0.5. Specifically, t ₁ is defined as 0 to 90 degrees, and t ₁ = (TS−3-1) * A + (TS−1-1) * B + (T−B−2-1) * Find t ₁ as C. Similarly, 90 ° to 180 ° is t ₂ , 180 ° to 270 ° is t ₃ , and 270 ° to 0 ° is t ₄ .
[0014]
The temperature management system 20 calculates the circumferential distribution of the indexed furnace temperature based on the temperature information detected by the thermocouple thermometers 2 arranged in plural in each stage in this way, and the furnace temperature distribution. The average value of the indices in each of the four directions is output to the pulverized coal injection amount management system 21. In the pulverized coal injection amount management system 21, the flow rate regulator 18 is adjusted to an opening degree proportional to the deviation of the index of each direction with respect to the input average value of the index of each four direction. Thereby, the flow volume of the pulverized coal fuel which flows through each branch pipe 7 is controlled according to the furnace temperature balance.
Specifically, if the total amount of pulverized coal fuel injected into the blast furnace 1 is M _pc and the flow rate of the pulverized coal fuel passing through the branch pipe 7 in the range of 0 ° to 90 ° azimuth of the blast furnace 1 is M _pc1 ,
M _pc1 = M _pc * t ₁ / (t ₁ + t ₂ + t ₃ + t ₄ )
It becomes.
[0015]
Similarly, the flow rate M _pc2 of the pulverized coal fuel passing through the branch pipe 7 in the range of 90 ° to 180 ° of the blast furnace 1 and the pulverized coal fuel passing through the branch pipe 7 of the blast furnace 1 in the range of 180 ° to 270 ° azimuth. The flow rate M _{pc3 of} the blast furnace 1 and the flow rate M _pc4 of the pulverized coal fuel passing through the branch pipe 7 in the range of 270 ° to 0 ° direction of the blast furnace 1 are obtained by the following equations, respectively.
M _pc2 = M _pc * t ₂ / (t ₁ + t ₂ + t ₃ + t ₄ )
M _pc3 = M _pc * t ₃ / (t ₁ + t ₂ + t ₃ + t ₄ )
M _pc4 = M _pc * t ₄ / (t ₁ + t ₂ + t ₃ + t ₄ )
In this manner, the pulverized coal fuel is blown into the blast furnace 1 while controlling the flow rate of the pulverized coal fuel that passes through each branch pipe 7 according to the circumferential distribution of the furnace temperature. For example, if the flow rate of the pulverized coal fuel in the period 2 of FIG. 3 is controlled as shown in FIG. 2F, the temperature distribution of the furnace body is improved. Moreover, adhesion and growth of the deposits on the furnace wall are prevented and the deposits are removed without reducing the operation efficiency of the blast furnace 1.
[0016]
The pulverized coal fuel injection amount control according to the present invention is particularly effective for blast furnace operation in which a large amount of pulverized coal fuel injection amount exceeding 150 kg / ton is injected. With such a high blowing amount, the entire amount of pulverized coal blown into the blast furnace cannot be burned by the oxygen contained in the hot air being blown, and deposits tend to adhere and grow on the furnace wall. Therefore, the adhesion / growth status of deposits is determined from the temperature balance along the circumferential direction in the furnace, and the amount of pulverized coal fuel injection is controlled according to the determination result, so that the balance of temperature distribution is good. Improve in direction. As a result, the inactivation of the furnace body and the generation of deposits on the furnace wall are prevented without lowering the operation efficiency of the blast furnace, and the deposits adhering to the furnace wall of the blast furnace are also removed. In this regard, in blast furnace operation where the pulverized coal injection rate is less than 150 kg / ton, the entire amount of pulverized coal injected is maintained in the furnace environment where combustion occurs. The effect of controlling in the direction is reduced.
[0017]
【Example】
A blast furnace operation was performed while blowing pulverized coal fuel using a blast furnace 1 in which 12 thermocouple thermometers 2 were embedded in the furnace wall at equal intervals in the circumferential direction in three stages in the height direction. FIG. 3 shows the transition of the index for each of the four directions and the blast furnace operation index obtained by indexing the furnace temperature distribution at this time.
Period 1 shows a state before controlling the injection amount of pulverized coal fuel according to the present invention, and the injection amount of pulverized coal fuel was controlled from November 18, 1996. In the period 2, the flow rate of the pulverized coal fuel passing through the branch pipe 7 was controlled based on the index for each of the four directions obtained by indexing the furnace body temperature distribution. As a result of the control, the index of 0-90 degrees azimuth and the index of 90-180 degrees azimuth with a small index indexed by the temperature management system 20 increased, and the indices of 180-270 degrees and 270-0 degrees azimuth with large indices decreased. . From this, it can be seen that the deviation of temperature distribution in the circumferential direction of the furnace body decreases. It can also be seen that there is no decrease in production or increase in fuel ratio in the process of improving the temperature distribution deviation. From this, it is confirmed that the temperature distribution is made uniform in the circumferential direction of the furnace body and the entire interior of the furnace is activated without reducing the operation efficiency of the blast furnace.
[0018]
【The invention's effect】
As described above, in the blast furnace operating method of the present invention, by controlling the amount of pulverized coal fuel injected in the circumferential direction of the furnace body, the circumferential deviation of the furnace body temperature distribution is reduced, and Therefore, it becomes possible to stably maintain the operation efficiency at a high level for a long period of time. Even when deposits are generated on the furnace wall, the deposits can be removed without the need for a wind or the like to stop the operation of the blast furnace and without significantly reducing the operation efficiency as in the cleaning operation. In addition, since the generation and growth of deposits on the furnace body are prevented, the occurrence of slips and blowouts that cause malfunctions in the blast furnace are suppressed, and the operation of the blast furnace is stabilized and the life of the furnace body is extended. .
[Brief description of the drawings]
FIG. 1 is an overall view of an equipment configuration for carrying out the present invention. FIG. 2 is a diagram for explaining an example of managing the circumferential balance of the flow rate of pulverized coal fuel passing through a branch pipe in an actual furnace. Showing that the balance of the furnace body temperature in the circumferential direction has been improved by controlling the flow rate of the pipe in the circumferential direction.
1: blast furnace 2: thermocouple thermometer 3: tuyere 4: blower branch pipe 5: annular pipe 6: down pipe 7: branch pipe for supplying pulverized coal fuel 8: distributor 9: measuring instrument 10: piping 11: feed tank 12 16, 18: Flow rate regulator 13: Carrier gas supply pipe 14: Reservoir tank 15: Pulverized coal supply pipe 17: Pressurized nitrogen gas supply pipe 19: Blowing lance 20: Temperature management system 21: Pulverized coal blowing amount Management system

Claims (2)

When the pulverized coal fuel is blown into the furnace from the blowing lance inserted into the down pipe connected to the tuyere provided in the blast furnace along the circumferential direction, the pulverized coal fuel has a plurality of stages in the height direction and is circular in each stage. Temperature detection means embedded in the furnace wall of the blast furnace at equal intervals in the circumferential direction retrieves the temperature information in the circumferential direction of the furnace , obtains a deviation amount in the circumferential direction of the furnace temperature, and determines each blow based on the deviation amount. The amount of pulverized coal fuel that is blown into the furnace from the lance lance is reversed when the tuyeres at low temperatures are used, so that the amount of pulverized coal fuel increases at the tuyeres with higher temperatures. A method for operating a blast furnace with pulverized coal fuel injection, characterized in that the amount is controlled to be small .   The temperature information obtained by the temperature detection means embedded in the furnace wall of each height level is multiplied by a weighting factor for each height level to obtain temperature data, and the furnace body circumferential direction is divided into a plurality at equal intervals. The temperature data in the azimuth direction and the height direction are summed to index the deviation amount of the furnace temperature distribution, and the amount of pulverized coal fuel injected from each injection lance into the furnace is controlled based on the obtained index. The blast furnace operating method according to claim 1.

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