JP2019157148A - Pulverized coal injection method to blast furnace - Google Patents

Abstract

To provide a method enabling stable pulverized coal injection into a blast furnace to maintain a good thermal balance in a blast furnace circumferential direction by removing with a relatively short purge a deposition of pulverized coal before the pulverized coal adheres firmly to a piping.SOLUTION: In a pulverized coal injection method to the blast furnace that the pulverized coal to be injected into the blast furnace is sent by air using a plurality of pulverized coal injection lines and is injected into the furnace through a pulverized coal injection lance disposed in a tuyere at an end of the pulverized coal injection line, an operation in which a purge gas is blown for at least 15 minutes within 24 hours from an end of a previous purge is repeated for all the pulverized coal injection lines when supplying the purge gas to each of the pulverized coal injection lines.SELECTED DRAWING: Figure 1

Description

  The present invention relates to a pulverized coal blowing method for blowing pulverized coal into a blast furnace, and more particularly to a pulverized coal blowing method effective for stably blowing pulverized coal into a blast furnace from a pulverized coal blowing line.

  In blast furnace operation, pulverized coal injection operation is performed in which pulverized coal is injected from a blast furnace tuyere instead of coke as a reducing material. The operation of injecting pulverized coal into the blast furnace is excellent in cost reduction effect because pulverized coal is less expensive than blast furnace coke. In addition, by increasing the amount of pulverized coal injected into the blast furnace, it is possible to reduce the load on the coke oven, which is a blast furnace coke manufacturing facility, and contribute to the extension of the life of the coke oven. Therefore, in the conventional blast furnace operation, development of an operation technique for injecting more pulverized coal has been demanded, and at present, a large amount of pulverized coal injection operation of 150 kg / t-molten or more is also performed.

  When performing blast furnace operation with such a high ratio of pulverized coal injection, it is important to improve the flammability of the pulverized coal in the blast furnace and prevent deterioration of air permeability in the furnace. It is known to use a material having a ratio of less than 74 μm of 75 mass% or more (Patent Document 1).

  On the other hand, in order to blow pulverized coal into the furnace of a blast furnace, it is necessary to pass through several piping systems, valves, blowing devices, and the like. However, if the pulverized coal is excessively pulverized, the problem arises that the pulverized coal adheres to the inside of the piping system and is blocked. For example, it is known that pulverized coal easily adheres to a bend portion having a relatively small diameter and a large curvature in the case of a plurality of branch pipes after the distributor in the transport pipe (Patent Document 2). If the piping is closed due to the adhesion of pulverized coal, the amount of pulverized coal injection varies in the circumferential direction in the blast furnace, causing hot metal component fluctuations and furnace condition failure. In particular, in the case of blast furnace operation where the amount of pulverized coal injection is large, if a blockage occurs in a part of the piping, it is forced to reduce or stop wind, resulting in a significant reduction in production and other problems.

JP 2002-194408 A Japanese Patent Laying-Open No. 2015-187294

  In the prior art as disclosed in Patent Documents 1 and 2, even if the particle size of the pulverized coal is strictly controlled, blockage in the piping cannot be completely prevented. For example, in these techniques, when a pipe is blocked, it takes at least “3 hours” and, on average, “5 hours” or more to remove pulverized coal firmly adhered in the pipe. A stop was necessary. As a result, there is a difference in the temperature of the tuyere tip in the furnace between the tuyere that continues blowing and the tuyere that stops blowing, and deviation in unloading speed occurs, etc. There was a problem that deterioration in the balance of directions was unavoidable, resulting in an increase in coke ratio and cost.

  The purpose of the present invention is to remove the adhesion of pulverized coal by a relatively short time purge before the pulverized coal adheres firmly in the pipe, to maintain a good thermal balance in the blast furnace circumferential direction, It is intended to propose a method that enables stable pulverized coal injection.

  As a result of diligent research to solve the above-mentioned problems of the prior art and realize the above-mentioned object, the inventors have developed a new method for injecting pulverized coal into a blast furnace as described below. It was.

  That is, the present invention uses a plurality of pulverized coal injection lines to feed the pulverized coal injected into the blast furnace, and the pulverized coal injection disposed at the tuyere at the end of each pulverized coal injection line. In the method of injecting pulverized coal into the blast furnace through the lance into the blast furnace, when supplying the purge gas to each pulverized coal injection line, the operation of flowing the purge gas for 15 minutes or more within 24 hours from the end of the previous purge is performed. This is a method for injecting pulverized coal into a blast furnace, which is repeated for all the injection lines.

In the method for injecting pulverized coal into the blast furnace according to the present invention configured as described above,
(1) The pulverized coal is injected into a large blast furnace having 30 or more tuyere at an amount of 150 kg / t-molten iron or more. (2) The pulverized coal has a particle size of 74 μm or less and 70 mass%. Having a particle size distribution of 90 mass% or less,
(3) The purge gas is nitrogen gas or a gas in which nitrogen gas is adjusted to 8 vol% or less with dry air,
Is considered to be a more preferable solution.

  According to the method for injecting pulverized coal into the blast furnace according to the present invention, the purge gas (nitrogen gas or a mixed gas thereof) is supplied to all of the pulverized coal injection lines for at least 15 minutes within 24 hours from the end of the previous purge. By repeating the operation, the pulverized coal blowing line can be periodically purged. Therefore, when blowing pulverized coal into the furnace from the pulverized coal blowing line, the blockage of the pulverized coal blowing line is suppressed without significantly reducing the amount of pulverized coal blowing while maintaining the circumferential balance. Charcoal can be stably injected to produce low-cost blast furnace hot metal.

  In addition, according to the present invention, it is possible to remove the pulverized coal piping by nitrogen, its mixed gas or air one by one, so that stable pulverized coal can be blown in the long term, and the adverse effects due to equipment troubles can be kept small. Can do.

It is the figure which showed typically the injection equipment to the suitable blast furnace used for implementing this invention. It is a figure for demonstrating an example of the order which purges a pulverized coal blowing line in implementing this invention. In the example shown in FIG. 2, it is a figure for demonstrating an example of the pulverized coal injection line which purges simultaneously.

Hereinafter, the present invention will be described more specifically with reference to the drawings.
FIG. 1 is a diagram schematically showing a pulverized coal injection facility (pulverized coal injection line) suitable for use in carrying out the present invention (in a blast furnace having an internal volume of 5000 m ³ , an output ratio of 2. This is an example in which the target PCR (pulverized coal injection ratio) in 3 is 175 kg / t.) In this example, two pulverized coal injection lances 12 and 13 are provided at 38 tuyere 11 respectively, and pulverized coal injection lines 9 and 10 are provided for each lance as an example.

  Reference numerals 1 and 2 in FIG. 1 are blowing tanks for storing pulverized coal. The blowing tanks 1 and 2 are provided for each blowing system, and are an example in which two sets are set as one set (one set is used as a reserve tank). Reference numerals 3 and 4 denote distributors that distribute the pulverized coal fed from the blowing tanks 1 and 2 into a predetermined amount. Further, 5 and 6 are supply pipes connecting the blowing tanks 1 and 2 and the distributors 3 and 4 respectively. The feeding pipes 5 and 6 are provided with mixers 7 and 8 for mixing nitrogen gas with pulverized coal. The mixer 7 includes a first mixer 7a and a second mixer 7b, and the mixer 8 includes a first mixer 8a and a second mixer 8b. Furthermore, 9 and 10 are pulverized coal injection lines connected on the downstream side (blast furnace side) of the distributors 3 and 4. The pulverized coal blowing lines 9 and 10 are branched in the same number as the tuyere provided in the blast furnace, and a predetermined amount of pulverized coal distributed by the distributors 3 and 4 is blown into the blast furnace tuyere.

  Also, 11 shown in the figure is a blast furnace tuyere (one of a plurality of tuyere arranged around the blast furnace) provided on the blast furnace peripheral wall, and 12 and 13 are blast furnace tuyere. 11 is a blowing lance disposed in the air passage 11. The blowing lances 12 and 13 are respectively connected to pulverized coal blowing lines 9 and 10 having different feeding paths, and individually blow the pulverized coal pumped from the blowing tanks 1 and 2 individually. Is something that can be done. The pulverized coal injection lines 9 and 10 are further provided with pressure regulators 14 and 15, pulverized coal cutoff valves 16a and 17a, tuyere cutoff valves 16b and 17b, and injection cocks 18 and 19, respectively.

  The above equipment has a double lance structure in which two blowing lances 12 and 13 are arranged for one blast furnace tuyere 11. Since the blowing lances 12 and 13 are connected to the pulverized coal blowing lines 9 and 10 having different feeding paths, the blowing lances 12 and 13 can be blown.

  As an example, when the present invention is carried out in the above equipment, one of 76 pipes of two systems is stopped from blowing pulverized coal. When stopping the blowing, the pulverized coal shutoff valves 16a, 17a are closed to stop the blowing of pulverized coal. Next, for example, nitrogen gas, which is a purge gas, is blown from the nitrogen purge valves 20, 21, and the pulverized coal adhering to the inner wall of the pulverized coal blowing lines 9, 10 together with the nitrogen gas from the pressure relief cock pipes 22, 23. Is discharged outside the tube. The flow rate of the purge gas (nitrogen) is preferably 2 to 6 times the carrier gas flow rate during normal pulverized coal blowing. The reason is that if the amount of purge gas is less than twice the carrier gas, the adhering pulverized coal cannot be removed, while if it exceeds six times, the piping is deformed and risks such as pulverized coal leakage occur. The purge gas is more preferably discharged to the outside, but the purge gas can also be discharged into the blast furnace. Nitrogen gas is preferably used as the purge gas for the purpose of preventing abnormal combustion of pulverized coal, but a gas in which nitrogen gas is mixed with dry air and the oxygen concentration is adjusted to 8 vol% or less can also be used.

  When clogging occurs in the pulverized coal blowing line and the thinning operation is performed, the PCR decreases as the number of thinning lines increases. And the range of the tuyere tip (raceway) temperature is expanded between the thinned tuyere and the tuyere that has been blown with a predetermined amount of pulverized coal, resulting in a bias in the circumferential state in the blast furnace. Problems such as lowering of the level occur. On the other hand, in the pulverized coal injection method suitable for the present invention, the pulverized coal injection stop time due to purge is short, and clogging of the pulverized coal injection line is difficult to occur. Thus, stable operation over the long term is possible.

  In addition, as an installation for implementing the present invention, the above-described installation has been described in accordance with an example of a double lance structure in which two pulverized coal feeding paths are provided and a blowing lance is disposed at the most advanced portion thereof. However, the number of blowing lances installed, the opening diameter, the number of pulverized coal feeding paths and the cross-sectional area may be appropriately changed, and this point is not particularly limited. Further, in the present invention, the pulverized coal injection line is blocked by appropriately selecting and blowing pulverized coal of different types and brands (semi-anthracite, non-slightly caking coal, etc.) in consideration of the operation status and the like. Can be prevented more efficiently.

  FIG. 2 is a diagram for explaining an example of the order of purging the pulverized coal blowing line when actually implementing the pulverized coal blowing method of the present invention in the above-described facility. In the example shown in FIG. 2, the blast furnace tuyere 11 is provided at 38 locations (# 1 to # 38) at equal intervals along the peripheral wall at the bottom of the blast furnace wall. As shown in FIG. 1, each blast furnace tuyere 11 is provided with a pulverized coal injection line capable of performing pulverized coal injection and a purge operation for each lance.

  FIG. 3 is a diagram for explaining an example of a pulverized coal blowing line that performs purging simultaneously in the example shown in FIG. 2. Here, the two pulverized coal injection lines that can be purged are classified into right and left, for example, the right line of the blast furnace tuyere 11 at the location # 1 is shown as right- # 1, and the blast furnace feather at the location # 1. The left line of the mouth 11 is shown as left- # 1. In the example shown in FIG. 3, an example of purge rotation in the case where the number of pulverized coal blowing lines that perform purging at the same time is two is shown. In the example shown in FIG. 3, when purging with two pulverized coal blowing lines in the order of 1 to 38, for example, the pulverized coal blowing lines that are purged simultaneously are set to right- # 1 and right- # 20. Thus, it is comprised so that it may purge simultaneously with the two pulverized coal blowing lines of the symmetrical position on the circumference. By doing so, even if the pulverized coal blowing line is sequentially purged while the pulverized coal is being blown, the circumferential balance during the pulverized coal blowing can be maintained well.

  In the pulverized coal injection method of the present invention described above, all the operations of stopping the pulverized coal injection from a part of the pulverized coal injection lance and purging the corresponding pulverized coal injection line, The pulverized coal injection line is repeated in order. At this time, the purge operation may be performed continuously or at intervals. However, in any case, the purge operation is repeated in order so that the purge gas can be continuously flowed for 15 minutes or more within 24 hours from the end of the previous purge for all the pulverized coal injection lines. There is a need.

<Experimental example 1>
Using the equipment (pulverized coal injection line) shown in FIG. 1, the number of simultaneous purges, the purge interval, the type of pulverized coal, the particle size, the amount of pulverized coal injected per line, and the purge conditions are constant. The purge effect was evaluated by changing the purge time. The effect of the purge was evaluated by measuring the pressure loss of the blowing line before the pulverized coal adhered and before and after the purge. And, it is effective when the pressure loss is reduced to the level before the pulverized coal adheres after purging (○), but the effect is insufficient when the pressure loss before and after the purge does not return to the level before the adhesion (△) ), The case where no drop in pressure loss was observed before and after purging was regarded as ineffective (x). The results are shown in Table 1 below.

  From the results in Table 1, when the purge time was 5 minutes, the pressure loss did not decrease before and after the purge, and the attached pulverized coal could not be removed. When the purge time was 10 minutes, the pressure loss decreased before and after the purge, but the pressure loss before the adhesion could not be fully restored. It has been found that when the purge time is 15 minutes or longer, the pressure loss before the pulverized coal adheres after the purge can be recovered.

  On the other hand, if the purge time for one time is lengthened, the time for purging all the pulverized coal blowing lines becomes longer, and the purge interval corresponding to the time from the end of the previous purge to the start of the current purge becomes longer. If the purge interval was within 24 hours, the pressure loss before the pulverized coal adhered after the purge could be recovered, but if the purge time became longer, the adhesion of the pulverized coal to the pulverized coal blowing line became stronger and the pressure loss before the adhesion It turned out that it may not be able to return to the end.

  Further, if the number of pulverized coal injection lines to be purged simultaneously is set to 2 or more, the purge interval can be reduced, but the effective amount of pulverized coal injection is reduced accordingly. Therefore, it was found that the number of pulverized coal blowing lines to be purged simultaneously is preferably 1 to 4, more preferably 2 or 3. If there are two or more pulverized coal injection lines to be purged at the same time, it is not always necessary to start and end the purge at the same time. For example, the second purge starts when half of the scheduled purge time has elapsed. At the time when the first purge is completed, it is possible to take a procedure in which half of the scheduled time for the second purge has elapsed and the third purge is started.

  From the above, in the method of injecting pulverized coal into the blast furnace according to the present invention, the operation of flowing purge gas for 15 minutes or more within 24 hours from the end of the previous purge is repeated for each pulverized coal injection line. It has been found that it is necessary to prevent clogging of the charcoal blowing line.

<Experimental example 2>
The pulverized coal injection amount per line is 1.1 t / hr and the feed ratio 2.3 (174 kg / t-molten iron) as standard conditions. The number of clogged pipes when charcoal was injected was investigated. In addition, the kind of pulverized coal of an Example, a particle size, and charcoal type property are charcoal type: Jerimbah charcoal, particle size: mass ratio of 74 micrometers or less, 80 mass%, charcoal type property (VM: 14.9, Ash: 10.3, FC) : 74.8, TS: 0.56, HGI: 92.7). The results are shown in Table 2.

Pulverized coal injection amount (effective) = (Set injection amount) x (Integration of injection time for each line)
/ ((Operating hours) x (Total number of pulverized coal injection lines))

From the results in Table 2, the following were found. First, Comparative Example 1 is a normal blowing condition in which repeated purge is not performed. Due to 7.2 pipe clogging per day and deterioration of furnace conditions such as air permeability and circumferential temperature balance, the output ratio was 2.3 t / day · m ³ at the beginning. It decreased to 1 t / day · m ³ . In Comparative Example 2, when one purge time was purged one by 10 minutes, the clogging of piping decreased to 3.4 pipes per day, but it was 2.3 t / day · m ³ at the beginning. The ratio dropped to 2.2 t / day · m ³ .

On the other hand, in Example 1, the purge time for one purge was 15 minutes, and the pipe clogging decreased to 1.5 pipes per day, and the output ratio was 2.3 t / day · m ^3. The operation to keep it as it was. In Example 2, the purge time for one purge is 30 minutes, and two purges are performed. Between the end of the previous two purges and the start of the next two purges, pulverized coal is removed from the total number of lines. The operation was carried out with the blowing time in between, and the time until one round of purge was set to 23.5 hours.

From the above, in the present invention, it is not always necessary to continuously perform the purge, and by clogging the purge gas continuously for 15 minutes or more again within 24 hours from the end of the previous purge, the pipe clogging is 0.2 per day. It was found that the operation of maintaining the output ratio at 2.3 t / day · m ³ could be achieved. Therefore, it became clear that long-term stable pulverized coal injection becomes possible by using the pulverized coal injection method of the present invention.

  The method of injecting pulverized coal into the blast furnace of the present invention is not limited to simply injecting pulverized coal into the blast furnace, and is also applicable to cases where piping is clogged by injecting powder in other furnaces. Is possible.

1, 2 Blow tank 3, 4 Distributor 5, 6 Feed pipe 7, 8 Mixer 8a First mixer 8b Second mixer 9, 10 Pulverized coal blow line 11 Blast furnace tuyere 12, 13 Blow lance 14, 15 Pressure regulators 16a, 17a Pulverized coal shutoff valve 16b, 17b Tuyere shutoff valve 18, 19 Blowing cock 20, 21 Nitrogen purge valve 22, 23 Pressure relief cock piping

Claims (4)

  Pulverized coal to be blown into the blast furnace is aired using a plurality of pulverized coal blowing lines, and blown into the furnace through pulverized coal blowing lances arranged at the tuyere at the end of each pulverized coal blowing line. In the method of injecting pulverized coal into the blast furnace, when supplying the purge gas to each pulverized coal injection line, the operation of flowing the purge gas for at least 15 minutes within 24 hours from the end of the previous purge is performed on the total number of pulverized coal injection lines. A method of injecting pulverized coal into a blast furnace, which is performed repeatedly.   The method for injecting pulverized coal into a blast furnace according to claim 1, wherein the pulverized coal is injected into a large blast furnace having 30 or more tuyere at an amount of 150 kg / t-molten or more. .   The method of injecting pulverized coal into a blast furnace according to claim 1 or 2, wherein the pulverized coal has a particle size distribution in which a particle size of 74 µm or less is 70 mass% or more and 90 mass% or less.   The pulverized coal for a blast furnace according to any one of claims 1 to 3, wherein the purge gas is nitrogen gas or a gas in which nitrogen gas is adjusted to 8 vol% or less with dry air. Blowing method.