JP5141214B2 - How to operate a vertical furnace - Google Patents

Description

  The present invention relates to a vertical furnace operating method for efficiently performing vertical furnace operations such as blast furnaces and cupolas by sieving metallurgical coke as a raw material in a steelmaking process or the like and removing powder in advance.

  In refining processes using vertical furnaces such as blast furnaces and cupolas, it is necessary to circulate reducing gas in the packed bed to reduce iron ore, etc., so reducing gas circulates for efficient operation. It is necessary to secure possible voids, and it is desirable to remove in advance the powder contained in the charging materials such as iron ore, coke and sintered ore. For this reason, each steelworks has a sieve facility (vibrating sieve) for removing powder from these ironmaking raw materials. However, the raw material stored in the yard has been difficult to remove with a conventional sieve because the adhesion of fine powder increases when the water content increases due to rain or the like during storage of the raw material. Furthermore, when the moisture content of the raw material is high, the clay-like raw material adheres to the screen of the sieve and becomes a factor causing clogging. For this reason, a sieve having a large opening has been used in a raw sieve apparatus having high moisture adhesion. For example, even with the same blast furnace raw material, coke sent directly from a coke plant via CDQ (coke dry fire extinguishing equipment) contains almost no water and powder easily falls. Therefore, a sieve with an opening of about 8 mm is usually used to remove the powder. However, in the case of coke, which has been stored in the yard and often contains moisture and powder, a sieve having an opening of about 10 mm is used to improve the powder removal performance and suppress clogging. Yes. In other words, the raw material in the range of 8 to 10 mm that can be used as it is as a normal blast furnace raw material is also screened, which is a factor of reducing the yield. Further, even if a sieve having an opening of 10 mm is used, a part of the powder of 1 mm or less still adheres to the raw material of 10 mm or more and does not fall, and the powder removal efficiency is not significantly improved.

  As a sieving means for improving the powder removal efficiency of the wet raw material, a special screen having a movable screen that can be expanded and contracted and transported the raw material while being deformed in conjunction with the upper and lower and left and right, such as a jumping screen (registered trademark) It has been known. With Jumping Screen (registered trademark), it is possible to expect the effect of dispersing the adhered powder by the impact force at the time of dropping by giving the repetitive movement of pulling and loosening to the urethane mesh. Further, since the mesh is always deformed, clogging is unlikely to occur even when a wet raw material is used.

  As a method for removing powder adhering to iron making raw materials other than sieving, a method is known in which iron ore to which powder adheres is washed with a screen-type jet washer to remove the adhering powder (see, for example, Patent Document 1). It is said that the iron ore adhering powder is washed cleanly because the washing water is jetted on the screen vigorously, and the cleaning liquid containing the adhering powder can be efficiently processed by the screen-type dehydrator and the liquid cyclone.

Although it is not a technique for removing powder from raw materials, as a method for reducing the moisture content of field deposits, a water absorbent molded product made of a water-absorbent resin is used when a bulk raw material is stacked on or discharged from an outdoor storage yard. A method of mixing is known (for example, see Patent Document 2). The water-absorbent molded product has a size larger than that of the raw material when swollen so that it can be separated from the raw material by sieving.
Japanese Patent No. 3255775 Japanese Patent Laid-Open No. 61-60784

  As mentioned above, blast furnace raw materials with a large amount of adhering powder when wet have been classified with a sieve having a large mesh opening, but the yield is greatly reduced, but the adhering powder is still mixed on the sieve. The adhering powder removal effect was not great. Among them, coke, which is a raw material for blast furnace, has a porous surface and is easily mixed with adhering powder. Especially, coke produced by the wet fire extinguishing method, and coke once temporarily stored in a yard, etc. have a And the adhering powder easily mixed on the sieve, and the adhering powder removing effect was not great.

  In addition, the sieving method using a special screen can be expected to separate the adhering powder of the raw material in a wet state, but the screen material is made of a resin material such as urethane, and since it constantly deforms and expands, When a hard material such as metallurgical coke is used, there is a problem in durability. If the durability of the screen is low, not only the running cost associated with the screen replacement becomes high, but also the frequency of stopping the line for replacement becomes high, which may be a major factor in the deterioration of productivity. In addition, since the screen is very different from the vibrating screen used in the conventional steelworks, it is necessary to remove the conventional screen and construct a new special screen facility, which is expected to require enormous facility costs. The Further, when water-containing resin or the like adheres to the sieving equipment and the sieve mesh is blocked, it is necessary to stop the line for cleaning the screen, which is a major factor in the deterioration of productivity. Therefore, special screens are not very popular as a sieving method for steelmaking raw materials.

  Furthermore, in the method of washing a raw material with a screen-type jet washer, a huge construction cost is required to newly construct equipment such as a screen-type jet washer, a screen-type dehydrator, and a liquid cyclone. In particular, when treating water containing iron ore or coke fine powder, there is a problem that the equipment is heavily worn and maintenance costs are high. Furthermore, moisture brought into the blast furnace due to moisture adhering to the raw material after cleaning may increase, lowering the blast furnace top temperature and destabilizing the operation.

  On the other hand, in the method described in Patent Document 2, when it rains during the period of storage in the yard, the amount of water that can be absorbed even by high-performance water-absorbing resin is sufficient, although it can temporarily absorb rainwater. There is a problem that the effect is limited because it is limited, and the moisture content once absorbed is difficult to dissipate, so that the water content is increased in some cases. In addition, when sieving this piled up deposit, the water-absorbent resin used as the water-absorbent molded product is used, so the clogging of the sieving at the time of sieving with the swollen resin and the raw material on the screen There is a problem of contamination.

  Therefore, in the present invention, it is possible to effectively utilize the conventional sieving equipment as it is, it is possible to improve the adhesion powder removal performance of the metallurgical coke relatively inexpensively, and the clogging of the sieving in the sieving equipment, etc. It is an object of the present invention to provide a method for operating a vertical furnace that is less likely to cause trouble and that can stabilize the operation of the vertical furnace.

  In order to solve the above-mentioned problems, the present inventors have studied a method for efficiently removing the adhering powder due to moisture of the metallurgical coke using a conventional general-purpose vibration sieve. The adhering powder is considered to adhere to the metallurgical coke due to the cross-linking effect of moisture. Therefore, if moisture can be removed, the number of moisture crosslinks may be reduced, and the amount of powder removed may increase. Then, it experimented about the adhesion powder removal effect by the amount of moisture. Dried coke was prepared, blended so as to have a constant particle size distribution, water having a coke mass ratio of 5% to 20% was added, respectively, and a sieving test was performed with a 20 cmφ round sieve with a mesh of 9.5 mm. In each test, the coke mass was 300 g. Further, when sieving, a low-tap type vibration sieve was used, and the same vibration was applied for 30 seconds. The generated sieve was sufficiently dried and the mass was measured. The results are shown in Table 1.

  It is considered that the smaller the mass ratio under sieve (mass under sieve ÷ initial mass × 100), the more adhering powder to the coke on the sieve, but according to the results in Table 1, the water addition rate is 5 mass% to 20 mass% (moisture content) Content ratio: 4.8 mass% to 16.7 mass%), it was shown that the greater the amount of water added, the lower the sieving mass ratio and the greater the amount of adhered powder on the sieving. Table 1 also shows the powder ratio (the powder (−9.5 mm) mass with a particle size of 9.5 mm or less on the sieve / mass on the sieve × 100) that should fall as the sieve among those remaining on the sieve. . According to Table 1, when the water content of the coke charged into the sieve is high, the ratio of the powder in the coke separated on the sieve increases, and the amount of the powder brought into the vertical furnace such as a blast furnace is increased. It turns out that it will increase.

  In order to efficiently remove the adhering powder at all moisture concentrations, a moisture absorbent that has a high moisture absorption capability that can quickly absorb a large amount of moisture even under high moisture content conditions and bring it close to a dry state. It is effective to add before sieving. As the water absorbent having these characteristics, a polymer water-absorbing material or silica gel can be considered.

  If a moisture absorbent is added before sieving, the water content of the coke is reduced, and the number of water bridges that bind the powder and lumps is reduced during sieving, so that the coke powder can be separated efficiently. Become. Therefore, the coke on the sieve has a reduced powder rate as compared with the case where no water absorbent is added, so that a reduction in pressure loss in the operation of a vertical furnace such as a blast furnace can be expected.

The present invention has been made based on such findings, and the features thereof are as follows.
(1) Metallurgical coke on a sieve obtained by adding and mixing a powdery moisture absorbent having a particle size that passes through a sieve used in a state after moisture absorption to a wet metallurgical coke and mixing the mixture. A method of operating a vertical furnace characterized by charging the vertical furnace into a vertical furnace.
(2) The method for operating a vertical furnace according to (1), wherein a polymer water-absorbing material is used as the moisture absorbent.
(3) The method for operating a vertical furnace according to (1) or (2), wherein the water absorbent has a particle size of ½ or less of a sieve mesh.
(4) was added by spraying the water absorbent on metallurgical coke on the belt conveyor, mixed with pre Ki冶 gold coke and the moisture absorbent by using a shock in transit drop of the belt conveyor that The operation method of a vertical furnace as described in any one of (1) to (3).

  ADVANTAGE OF THE INVENTION According to this invention, while using the conventional sieving equipment, the sieving of the coke in a wet state can be easily performed due to the influence of exposure to rainwater or the like. This makes it possible to sufficiently suppress the powdery portion of coke charged into the vertical furnace, ensuring air permeability in the vertical furnace and improving operational stability.

  In addition, the amount of water brought from the coke into the vertical furnace can be reduced.

  Furthermore, when sieving wet raw materials in the past, sieving powder containing moisture may adhere to the belt and cause a failure of the belt conveyor. However, using the method of the present invention, moisture is absorbed by moisture. Since it is supplemented by the agent, the adhesiveness of the sieving powder is reduced, and these troubles can be avoided.

  In the present invention, a powdery water absorbent is added to the metallurgical coke and mixed, and sieving is performed to remove moisture from the metallurgical coke in a wet state due to the presence of moisture, and Since the adhesion can be reduced, the powder can be easily removed while using a conventional sieving equipment. And the top of the sieve from which the powder has been removed by sieving is placed in a vertical furnace and operated to produce pig iron and the like. The present invention is applicable to all metallurgical coke in a wet state.

  The wet state is a state in which moisture is present on the particle surface of the metallurgical coke. The effect of the moisture absorbent on the moisture content of metallurgical coke varies depending on the pore distribution inside the coke particles (because the moisture on the particle surface after moisture is absorbed by the pores inside the coke becomes a problem) The effect is great when the water content of the material is 5 mass% or more.

  As the water absorbent used in the present invention, a substance that has a very high water absorption rate and does not exhibit adhesiveness by trapping water in the molecular structure after water absorption is desirable. Examples of these substances include silica gel and various polymer water-absorbing materials, but especially polymer water-absorbing materials can take in water several hundred times more than their own weight, and the water absorption rate is remarkably fast, More suitable. It is also particularly preferable to use zeolite or activated carbon. Since the moisture absorbent must be removed from the metallurgical coke as a sieve after absorbing moisture, it must be in the form of a powder having a particle size that passes through the sieve mesh used in the state after moisture absorption.

  In addition, as shown in Table 1, if the coke in a wet state contains water in an amount of about 5 mass% or more, it is considered that the effect can be obtained by reducing the crosslinking due to moisture. It is effective when applied to coke with a lot of moisture. Moreover, since powder is often generated by handling during storage, it is preferably applied to coke stored in a yard or the like. Furthermore, coke for yard storage has a tendency to contain a large amount of moisture due to rain water in addition to a large amount of generated powder, and it is particularly preferable to apply it to yard storage coke.

  The moisture absorbent is preferably added at any location on the conveying line until the wet coke is screened. For example, in the case of coke stored in the yard, the moisture absorbent is added from the cutting out of the yard to the sieve, and in the case of coke that has been wet extinguished, from the fire extinguisher to the sieve. . When a moisture absorbent is added when stored for a long time in a yard or the like, it will be affected by subsequent rainfall, etc. Therefore, when adding a moisture absorbent in the yard, the moisture absorbent is added when cutting out from the yard. Thus, after adding the water absorbent, it is not exposed to rain in the yard or the like, the influence of the wet coke other than the water can be reduced as much as possible, and the effect of the water absorbent can be sufficiently exhibited. In addition, there is usually a sieve under the storage tank that is a hopper for storing coke to be charged in the vertical furnace. This is preferable because coke and a water absorbent are mixed in the storage tank to secure time for water absorption.

  As a method of adding the moisture absorbent to the metallurgical coke, add it at the time of cutting on the yard and mix it with heavy machinery, or add it to the blast furnace raw material on the belt conveyor, and drop impact on the connecting chute of the belt conveyor There is a method of using and mixing, but the latter method is desirable because of its lower cost. Further, the position where the moisture absorbent is added on the belt conveyor is preferably as far as possible from the sieve, and is preferably close to the raw material yard side. This means that it is easier for the moisture absorbent to reach the entire metallurgical coke and more time is required for water absorption if it passes through the transit drop more and is transported over a longer period of time. Because.

  Furthermore, as a method for cutting out the water absorbent when adding the water absorbent to the metallurgical coke, various powder quantitative cutting methods such as cutting with a vibration feeder can be applied. Therefore, it is desirable to be in a sealed state that is blocked from outside air until just before the addition to the metallurgical coke. Therefore, from the above point of view, the most suitable method is to pneumatically convey the inside of the piping by pressure from the sealed storage tank and to spray the metallurgical coke using the pressure. After adding and mixing the moisture absorbent, sieving is carried out with a conventional sieving equipment, but the sieving equipment can be operated under the same operating conditions as before and does not require any special operation.

  In addition, in order to prevent the moisture absorbent that has absorbed moisture from entering the coke on the sieve, and to prevent the moisture absorbent from adhering to the sieving equipment and blocking the sieve mesh, The diameter is preferably ½ or less of the sieve mesh, and more preferably, the water absorbent has a particle diameter of 1 mm or less in order to uniformly disperse the water absorbent on the wet coke surface. With such a particle size, it is possible to pass through the sieve sufficiently even after moisture absorption, so it is recovered as sieving together with the coke powder adhering to the wet coke, to the coke used in the vertical furnace on the sieve. Can be prevented.

  FIG. 1 is a flowchart showing an embodiment of the present invention. When the wet coke 1 to which the powder is attached is used as a raw material for the blast furnace, the moisture absorbent 2 in the storage tank in a sealed state is added to the wet coke 1 by spraying from the upper part through the air feed line 3. When the moisture coke 1 to which the moisture absorbent 2 is added is conveyed by the belt conveyor 4 and dropped at the transfer chute portion 4a of the belt conveyor 4, the moisture absorbent and the wet coke are mixed. In this state, the wet coke 1 is sieved using the sieving equipment 5 that is conventionally used for sieving the raw material before charging the blast furnace, so that the wet coke 1 goes to the blast furnace after the sieving powder 6 and the powder are removed. By separating the coke 7 into the blast furnace and charging the blast furnace coke 7 into the blast furnace, it becomes possible to charge the blast furnace with a raw material with a small proportion of powder.

  In order to confirm the effect of the present invention, a sieving test was conducted under the following conditions.

  Coke to be used in a blast furnace was prepared, and about 5 tons was applied to a vibrating sieve having a width of 2 m, a length of 3.5 m, and an opening of 8 mm, and sieved. It was 3.9 mass% when the moisture content of coke was measured by the drying method.

  After water was sprinkled on the same coke, it was mixed well using an excavator, and left to stand for several hours in order to allow the water to blend into a wet state. Here, when the moisture content of the coke was measured again by the drying method, it was 9.3 mass%. About 5 tons of this wet coke was applied to the above-mentioned vibrating sieve and sieved.

  Furthermore, a polyacrylic acid-based polymeric water-absorbing material is added to the remainder of the wet coke in a mass ratio of 0.01, 0.1% to the coke, or silica gel is added in a mass ratio of 1.0% to the coke. After stirring well with an excavator, about 5 tons were subjected to the above-mentioned vibrating sieve and subjected to a sieving test.

  Table 2 shows the measurement results of “mass ratio under sieving” after sieving and “recovery rate under particle size of 5 mm or less (−5 mm)” after sieving.

  When wet coke in which moisture was added to coke was sieved, the mass ratio under sieve (mass under sieve ÷ sieve feed mass × 100) was greatly reduced. Therefore, when the sieving -5 mm recovery rate (sieving -5 mm mass ÷ sieving supply -5 mm mass x 100) is calculated, the recovery rate is also greatly reduced, and a large amount of -5 mm powder adheres to the sample on the sieving It was confirmed that Furthermore, under the conditions in which a polymer water-absorbing material, which is a moisture absorbent, was added and mixed, the mass ratio under the sieve was greatly increased as compared with the case of only wet coke. The recovery rate under sieving −5 mm was also greatly recovered, and the effect of adhering powders off by the polymer water-absorbing material could be confirmed. The coke entering the sieve was sampled, sieved with a 5 mm sieve, and the moisture content of the coke on the sieve was measured by a drying method. As a result, it was 4.9 mass% when 0.1 mass% of the polymer water-absorbing material was added. Since the added polymer water-absorbing material had a particle diameter of -1 mm, it was considered that the water content in the coke portion was reflected because it was hardly mixed in +5 mm. When silica gel was used as the moisture absorbent, although the effect was small compared to the polymer water-absorbing material, the mass ratio under the sieve and the -5 mm recovery rate was increased compared to the case without the moisture absorbent. Although the powder separation efficiency is improved as the amount of the additive is increased, the running cost is increased.

  Coke stored in the yard was mixed with coke that is normally used at a mass ratio of 30 mass%, and an operation test was performed in which it was used as a blast furnace raw material. Furthermore, an operation test was performed in which a polyacrylic acid-based polymer water-absorbing material was added to and mixed with coke as a moisture absorbent, followed by sieving, and a comparison with the operation using ordinary coke was performed.

  When using a water absorbent, use the same equipment as shown in Fig. 1 and sprinkle the polymer water-absorbing material on the coke at the belt conveyor connecting part at a rate of 0.1 mass%, and then transport it further by the belt conveyor. After passing through the belt conveyor connecting portion, sieving was performed with a sieve having a sieve size of 10 mm. Blast furnace output is 12,000 tons / day, coke ratio is 380 kg / tp, pulverized coal (PC) ratio is 120 kg / tp, coke strength, grain size and sintered ore strength, grain size is almost constant The operation was carried out under as constant conditions as possible except for the amount of yard coke used and whether or not the additive was used before sieving. Yard coke was used, and each day was operated with and without the use of the additive before sieving and when no yard coke was used.

  When the moisture content of the coke at the yard was measured by a drying method, it was 9.7 mass%, and the moisture content of ordinary coke was 3.5 mass%. When a moisture absorbent is used when using yard coke, the mass ratio under the sieve is 19.9 mass%, the sieving -5 mm recovery rate is 76.7 mass%, and when the moisture absorbent is not used, the mass ratio under the sieve is It was 15.5 mass%, under-sieving -5 mm recovery rate 59.8 mass%. Table 3 shows the daily average blast furnace upper pressure loss value during each operation.

  According to Table 3, when yard coke with a high water content is used, the pressure loss at the upper part of the blast furnace increases as compared with when not using it. Although the pressure loss in the entire blast furnace showed the same increasing tendency as the upper pressure loss shown in Table 3, most of the pressure loss could be explained by the change in pressure loss at the upper part. On the other hand, when a moisture absorbent (polymer water-absorbing material) is used in front of the sieve, it can be seen that the increase in pressure loss is greatly suppressed.

The flowchart which shows one Embodiment of this invention.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Wet coke 2 Moisture absorbent 3 Pneumatic feed line 4 Belt conveyor 4a Transfer chute part 5 Sieving equipment 6 Sieving powder 7 Blast furnace coke

Claims (4)

Add a powdery water absorbent with a particle size that passes through the sieve mesh to be used in a state after moisture absorption to wet metallurgical coke, mix and siege the metallurgical coke on the sieve. A method of operating a vertical furnace characterized by being charged in a furnace.   The method for operating a vertical furnace according to claim 1, wherein a polymer water-absorbing material is used as the moisture absorbent.   The method for operating a vertical furnace according to claim 1 or 2, wherein the water absorbent has a particle size of 1/2 or less of the mesh. It was added by spraying the water absorbent on metallurgical coke on the belt conveyor, and characterized by mixing the front Ki冶 gold coke and the moisture absorbent by using a shock in transit drop of the belt conveyor A method for operating a vertical furnace according to any one of claims 1 to 3.

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