JP4830728B2 - Method for producing sintered ore - Google Patents

Description

  TECHNICAL FIELD The present invention relates to a method for producing sintered ore used in a blast furnace, specifically, producing a sintered ore by charging a raw material composed of fine ore and miscellaneous raw materials into a pallet from a surge hopper with a roll feeder. The present invention relates to a method for producing a sintered ore that can improve the productivity by mixing coarse pseudo particles in a blended raw material and can maintain the yield of the sintered ore product.

A sintered ore used as an iron source for a blast furnace is generally manufactured as follows. The unloaded powdered iron ore raw material, the auxiliary material containing CaO, and the auxiliary material containing SiO ₂ are piled up in the yard for each brand. Also, some powdered iron ore raw materials, iron-containing dust, charcoal materials, etc. are mixed and piled in the yard as blending powder. These raw materials loaded in the field are sent to a raw material tank, cut out from the raw material tank in accordance with a pre-planned mixing ratio, kneaded and granulated with water in a drum mixer together with a coagulant, and 0.25. A blended raw material consisting of an aggregate of various raw materials (hereinafter also referred to as “pseudo particles”) having a particle size distribution of about ˜5 mm is supplied to the sintering machine.

  More specifically, after the raw material is charged into the surge hopper, it is cut out from the lower part of the surge hopper by a roll feeder, and placed on the grate in the pallet through the sloping chute, and is a layer of a floor sinter ore. It is loaded on top. At this time, the distance from the great surface to the upper surface of the sintered raw material packed layer composed of pseudo particles (hereinafter also referred to as “layer thickness of the raw material packed layer”) is usually within a range of about 400 to 750 mm. It is adjusted to become the value of. Then, in the ignition furnace, by igniting the upper surface of the sintered raw material packed layer, the condensed material contained in the pseudo particles existing on the packed layer surface starts to burn, and the sintering reaction starts.

  The sintered material packed bed is sucked from below the pallet while moving from the supply side to the discharge side, so air flows in from the upper part of the sintered material packed layer and passes through the layer toward the lower part. To do. As a result, the combustion part of the aggregate forms a high-temperature combustion zone, and the combustion zone moves from the upper part to the lower part of the sintered raw material packed bed. Since the heat generated in the combustion zone is accumulated as it moves from the upper part to the lower part, generally, the upper part of the raw material packed bed tends to be insufficient in heat and the lower part is likely to be excessive in heat. Along with this movement of the combustion zone, the surrounding pseudo particles are heated by the heat generated in the combustion zone, undergo melting and assimilation reactions, and sintered, and finally the sintered raw material packed layer forms a sintered cake. . And the sintered cake formed in this way is discharged from the discharge section of the sintering machine.

By the way, in recent years, with increasing use of limonite containing a large amount of goethite (Fe ₂ O ₃ .H ₂ O: Goethite), deterioration of the air permeability of the sintered raw material layer and reduction of the product yield are regarded as problems. Yes. This is due to the fact that voids that effectively act for ventilation are blocked, despite the fact that the sintered layer has many pores. Because limonite has a higher content of crystallization water than hematite (Fe ₂ O ₃ : Hematite) and becomes porous after decomposition of crystallization water in the temperature rising process, it is easy to assimilate with the melt. As a result, the viscosity of the melt increases.

  When a large amount of limonite is used, it is considered that a highly viscous melt is generated in the lower part of the packed bed where excess heat is generated and the voids are easily blocked, resulting in deterioration of air permeability and product yield. ing. In addition, the increase in the amount of moisture brought into the sintered raw material packed bed by limonite promotes the enlargement of the water agglomeration layer formed in the lower part of the combustion zone and the collapse of the pseudo particles in that part, so that air permeability It is thought to cause deterioration.

  Therefore, conventionally, various techniques for ensuring air permeability during firing have been studied by controlling the void structure of the sintered raw material packed layer.

  As a method for controlling the porosity of the sintered raw material packed layer that has been conventionally performed, for example, as disclosed in Patent Document 1, there is a control method by mechanically changing the structure of the packed layer. In this document, a plurality of breathable control plates (hereinafter also referred to as “ventilating plates”) horizontally arranged at intervals in the width direction of the pallet are directed toward the pallet traveling direction, and the bed deposit hopper of the raw material accumulation layer is formed. A method for producing a sintered ore is disclosed in which a raw material slope is formed on the side, a plurality of ventilation grooves are formed by cutting from a middle layer to a lower layer portion of the raw material deposition layer, and then the raw material deposition layer is sintered. According to the method disclosed here, the water evaporated in the upper part of the raw material filling layer escapes from the slit-like high porosity portion formed in the lower layer, so that the condensation of the water in the lower part of the raw material filling layer can be prevented. , Breathability is improved. This improvement in air permeability increases the rate of lowering the combustion zone, shortens the sintering time, and improves the productivity of the sintered ore.

  However, according to the method disclosed in Patent Document 1, the gas passing through the packed bed is selected by the presence of a portion having a intermittently high porosity in the width direction of the sintering machine formed by the ventilation plate. Flow, thus creating a drift. As a result, the shape of the combustion zone does not become horizontal in the width direction, and only the periphery of the portion with a high porosity is burned off quickly. In general, in a sintered raw material packed layer, if the time for which the temperature is maintained at a high temperature of 1000 ° C. or higher is short, sintering becomes insufficient, and the yield and strength of the sintered product decrease. Therefore, even in the method disclosed in the above-mentioned document, since the porosity is high, the firing rate is high and the temperature is kept at a high temperature, and the product yield and product strength are significantly reduced, contributing to the improvement of productivity. There is a problem that the number of sintered cake portions that do not increase.

  On the other hand, due to the above-mentioned gas drift, in the low porosity portion sandwiched between the high porosity portions, the gas passage amount decreases, so the combustion zone lowering speed also decreases. As a result, the combustion zone does not reach the lowermost layer of the raw material packed layer at the time of exhausting, and there is a possibility that an unfired part remains, which may cause a decrease in product yield and product strength. As a countermeasure, increasing the number of vent plates will alleviate gas drift and make the lowering rate of the combustion zone uniform, but there is a lower limit on the interval between the vent plates, so the lowering rate of the combustion zone There is a limit to homogenization.

  Furthermore, there is a problem of adhesion of raw materials to the ventilation plate. When a ventilation plate whose thickness is substantially increased by the adhesion of the raw material is used, the width of the portion having a high porosity is expanded from the original operation plan value. This variation in the width of the portion having a high porosity promotes the variation in the gas flow, and causes a nonuniformity in the lowering speed of the combustion zone. As a countermeasure, it is necessary to increase the frequency of cleaning the ventilation plates, which increases the man-hours for maintenance and management of the equipment.

  As described above, with the technique disclosed in Patent Document 1, although it is possible to increase the productivity of sintered ore, it is difficult to achieve both increase in productivity and maintenance of product yield, and frequent facility maintenance. Is required and the operating efficiency is also reduced.

  By the way, conventionally, it is known that mixing a small amount of particles coarser than the pseudo particle size constituting the sintered raw material packed layer improves the air permeability in the packed layer, increases the firing rate, and decreases the product yield. It has been.

  For example, Non-Patent Document 1 shows an increase in production rate and a decrease in product yield due to mixing coarse pseudo particles (that is, pseudo particles having a large particle size). It has been pointed out that the mixing of coarse pseudo-particles results in the formation of a region with a low packing density around the coarse particles, improving air permeability and increasing the firing rate.

  In addition, the inventors previously described a method for improving the productivity of sintered ore by adding limonite having a particle size of 5 to 40 mm to improve the air permeability of the sintered raw material packed layer in Patent Document 2. Proposed.

  Furthermore, Patent Document 3 discloses a method of forming a sintered ore by mixing up to 80% by mass of raw pellets in a sintered raw material and firing it with a sintering machine. Conventionally, in order to prevent bursting due to rapid expansion of water vapor in the pellet, the mixing ratio of the fine powder material in the pellet raw material powder is suppressed to 30 to 70%, so that the diffusion of water vapor in the pellet proceeds smoothly. Was considered to be. On the other hand, in the method disclosed in the same document, by mixing raw pellets into the sintered raw material, the pellet pieces can be fused with the sintered ore even when bursting occurs. It becomes possible, and the restriction | limiting of the mixture ratio of the fine powder in a pellet raw material can be removed. In addition, since the pellet drying and firing steps can be consolidated in the sintering machine, the fuel consumption rate can be reduced, and the mixed pellets can improve the air permeability, thus improving the productivity. It is said that.

  In Patent Document 4, anthracite is granulated in advance to a particle size of 5 to 40 mm, and then coated and granulated with a fine powder raw material in which fine ore, a melting point adjusting material, and a binder are mixed, and charged into a sintering machine. In addition, there is disclosed a method for producing a sintered ore that produces fine coke and uses a large amount of fine ore without impairing air permeability.

  On the other hand, as a means to prevent the product yield from decreasing, the method of increasing the maximum temperature in the raw material packed bed by increasing the amount of powdered coke as a fuel, or increasing the raw material layer thickness to increase the heat retention time due to its heat storage effect Methods for extending are known.

  Non-Patent Document 1 also describes that the decrease in product yield due to the blending of coarse particles is suppressed by increasing the blending amount of the powder coke. Although there is no specific description in Patent Document 2, it is described that the amount of powder coke is increased when blending ores. Also, in Patent Document 3, it is necessary to add 3 to 5% of the granular solid fuel of the pellet mass in addition to the granular solid fuel necessary for firing the sintered raw material for heating and firing the raw pellets. There is a description that when the amount added is 3% or less, an unfired part or an unmelted part is generated, while when it is 5% or more, the molten part of the sintered raw material becomes excessive.

  And as a manufacturing method of coarse quasi-particles, for example, in addition to the pellet processing method disclosed in Patent Document 3, Patent Document 5 discloses a method of screening powder ore with a sieving machine, Kneading while adding water using a kneader such as a high-speed agitating mixer, granulating to a diameter of 2 to 5 mm using a granulator such as a pan pelletizer, and sieving powder ore and other sintering raw materials using a drum mixer A method of mixing and granulating is disclosed. Further, in Patent Document 6, when sintering a sintered raw material in which the sinter feed is replaced with a pellet feed, bentonite and water are added to the sinter feed to form mini-pellets having a particle diameter of 2 to 7 mm. A method of mixing or mixing granulation is disclosed.

  Furthermore, Patent Document 7 discloses a method of granulating by adding moisture and a binder in advance before charging a compounding tank installed in front of the primary mixer, and Patent Document 8 includes a die. A method of extruding with an extruding machine, and Patent Document 4 discloses a method of granulating anthracite coal as described above and coating and granulating with a fine powder raw material in which fine ore, a melting point adjusting material and a binder are mixed. Has been.

  However, none of these methods are sufficient techniques to improve the productivity of sintered ore and to secure the yield of sintered ore products, and there are still problems to be solved in order to achieve both. It is left.

Japanese Patent Laid-Open No. 9-184022 (Claims and paragraphs [0012] to [0017]) JP 2003-113426 A (claims, paragraphs [0012] and [0013]) JP-A-5-287391 (Claims [0004] and [0006]) JP-A-8-199250 (claims, paragraphs [0011] to [0015]) JP 60-138020 A (claims, etc.) Japanese Patent Laid-Open No. 61-213328 (claims) Japanese Examined Patent Publication No. 59-33646 (Claims and column 2, line 34 to column 3, line 11) Japanese Patent Laying-Open No. 2005-290525 (claims, etc.) Koji Jojo, Masaru Matsumura, Sonzo Kawaguchi: CAMP-ISIJ Vol. 17 (2004) 586-589 pages

  As described above, the following problems remain in the prior art. That is, (1) as disclosed in Patent Document 1, improvement in mechanical air permeability by forming a ventilation groove in a raw material deposition layer using a ventilation plate tends to lower the product yield, and maintenance management of the apparatus. Man-hours also increase. (2) Even in the method for improving ventilation by mixing coarse particles disclosed in Non-Patent Document 1, Patent Document 2, Patent Document 3, and the like, a decrease in product yield is unavoidable and countermeasures are necessary. (3) In the technique disclosed in Patent Document 4 for the purpose of collecting fine coke, the powder coke must be collected from the pellets mixed in the sintering raw material. It cannot be used as a blast furnace charge, and therefore the product yield is inevitably lowered.

  The present invention has been made in view of the above problems, and the problem is that the particle diameter and the mixing ratio of the coarsened particles are adjusted by adjusting the layer thickness of the raw material packed layer while coarsening a part of the raw materials. It is providing the manufacturing method of the sintered ore which can make productivity improvement and maintenance of a product yield compatible by optimizing.

  In order to solve the above-mentioned problems, the present inventors have conducted various tests and studies to improve the air permeability by coarsening a part of the raw material rather than by controlling the mechanical porosity. And the method which can ensure a product yield by optimizing the layer thickness of a raw material packed layer, the particle diameter of the coarse particle, and a mixing ratio was discovered.

According to the present invention, while maintaining a high production rate obtained by mixing coarse particles, it is possible to achieve maintenance of a product yield that could not be realized by the prior art. In addition, it is possible to avoid a reduction in production rate that is unavoidable when the product yield is improved by increasing the thickness of the raw material packed layer. Air permeability is improved by optimizing the granulation of raw materials and the mixing ratio of coarse particles after granulation, thus avoiding problems in equipment maintenance and maintaining high equipment availability. be able to. The reason why the product yield reduction prevention measures by increasing the blending amount of the powder coke is not adopted is because of the recent CO ₂ emission regulations.

  The present inventors have further obtained the following findings (a) to (c) and completed the present invention with respect to the action and mechanism of the production rate improving means and the product yield improving means.

  (A) Improving the air permeability of the sintered raw material packed layer is effective as a means for improving the production rate. The reason is that if the air permeability in the sintered raw material packed layer is improved, the lowering speed of the combustion zone is increased and the sintering time is shortened. On the other hand, an increase in the thickness of the sintered raw material packed layer is effective as a means for improving the product yield. Since the amount of heat accumulated in the raw material packed layer increases due to the increase in the layer thickness, the time that is maintained at 1000 ° C. or more is lengthened, the sintering reaction is promoted, and a strong sintered cake is produced. It is.

  (B) However, each of these improvement means has the following drawbacks.

  1) When the firing rate is increased by improving the air permeability, even if the temperature in the layer rises to 1000 ° C or higher due to the arrival of the combustion zone, the combustion zone immediately passes and cooling starts. Therefore, a sufficient sintering time cannot be secured, and a strong sintered structure is hardly formed.

  2) On the other hand, when the layer thickness of the raw material packed layer is increased, the airflow resistance in the packed layer is increased, so that the air permeability is lowered and the firing rate is decreased. Further, the increase in the temperature in the layer causes an increase in the flow velocity of the gas passing through the layer, the pressure loss in the layer increases, the air permeability decreases, and the lowering speed of the combustion zone becomes slow.

  3) As described in the above 1) and 2), the increase in production rate and the improvement in product yield are contradictory via air permeability, and it is difficult to achieve both. This is because the improvement in air permeability shortens the holding time of 1000 ° C. or more, while the decrease in air permeability extends the sintering time.

  (C) Therefore, the present inventors have solved the above problem based on a completely new idea of achieving both high productivity and high product yield by mixing coarse pseudo particles (that is, pseudo particles having a large particle size). Solved. The idea is to improve the air permeability of the raw material packed bed with coarse quasi-particles with a particle size of 3 mm or more, and collect coarse quasi-particles as sintered ore with a particle size of at least the coarse quasi-particles or larger. This is a method of ensuring a high product yield.

  1) Pseudo particles granulated to a size equal to or larger than the particle size of the sintered ore after being sintered under good air permeability by mixing coarse pseudo particles and then charged into the blast furnace. Can be recovered and used as a sintered ore product with a particle size as it is or larger than that, a decrease in the yield of sintered ore products can be suppressed. Furthermore, if the pseudo particles present around the coarse pseudo particles are recovered as a sintered ore of 5 mm or more at the same ratio as before the coarse pseudo particles are mixed, a high product yield can be reliably maintained.

  2) In order to maintain a high product yield, it is necessary to secure a temperature and time for sufficient sintering of the coarse quasiparticles and the surrounding quasiparticles. Increase layer thickness. If we can grasp the rise limit of the layer thickness within the range that does not impair the improvement of air permeability obtained by coarse pseudo particles and the lower limit of the layer thickness so that the product yield does not decrease excessively, high production rate and high Compatibility with product yield is possible.

  3) As a result of the investigation test described in detail later, it was found that the range of the layer thickness of the raw material packed layer capable of achieving both a high production rate and a product yield is 530 to 730 mm. It was also found that the proper range of the particle size of the coarse pseudo particles is 3 mm or more and 20 mm or less, and the proper range of the mixing ratio of the coarse pseudo particles is 22% by mass or less of the total blended raw materials. The mixing ratio of coarse pseudo particles is preferably 6% by mass or more.

This invention is completed based on said knowledge, The summary exists in the manufacturing method of the following sintered ore. That is,
In the manufacturing method of sintered ore, which comprises granulating a raw material containing iron ore including limonite, secondary raw material, limestone, returning ore and a coagulating material, and then supplying and firing it on a pallet of a sintering machine A part of the mixture is granulated in a separate system so that the particle diameter is 3 mm or more and 20 mm or less, which is larger than the granulated particles obtained by granulating the remaining blended raw materials, and then the remaining blending The mixing ratio of the granulated particles having a large particle diameter in the total blended raw materials of the granulated particles obtained by granulating the raw material and the particles after granulating the large particle diameter is 22% by mass or less. , And charging and sintering on a sintering machine pallet so that the layer thickness of the blended raw material packed layer is not less than 530 mm and not more than 730 mm. It is.

  In the present invention, “limonite” means iron ore containing a large amount of water of crystallization, for example, pisolite ore and maramamba ore. These structures contain 5.0% by mass or more of crystal water.

  “Sub-material” means a raw material containing a fossil component such as serpentine and quartzite, and “condensation material” means powdered coke, powdered coal and the like. In addition, miscellaneous raw materials such as blast furnace dust may be blended in the blended raw materials.

  “Layer thickness of the raw material packed layer” means the distance from the surface of the sintering machine pallet's great surface to the upper surface of the sintered raw material packed layer. The height of the packed bed consisting of a group of pseudo particles charged in the upper part of the sintered ore.

  In addition, “mm” representing the particle diameter (particle diameter) means a representative diameter of the sieve mesh. For example, a particle having a particle diameter of 20 mm or less means a particle diameter under a sieve when the sieve is sieved with a 20 mm sieve, and a particle having a particle diameter of 3 mm or more and 20 mm or less is a sieve having a sieve diameter of 20 mm. It means a particle having a particle diameter under the sieve when sieved with a sieve and having a particle diameter on the sieve when the sieve mesh is sieved with a sieve of 3 mm.

  In the description of the present specification, “particles after granulation” are also referred to as “pseudo particles”, and “particles after granulation having a large particle diameter” are also referred to as “coarse pseudo particles”.

  According to the method of the present invention, coarse pseudo particles having an appropriate particle size are mixed in an appropriate mixing ratio in the packed layer of the sintered raw material, and the operation for optimizing the layer thickness of the raw material packed layer is performed. It is possible to achieve a high product yield that cannot be achieved by the conventional technology while ensuring the effect of improving the production rate by mixing the two. Also, since the air permeability is improved by optimizing the mixing ratio of raw material granulation and coarse pseudo particles, maintenance management of equipment that occurs in the case of forming a ventilation groove using an air permeability control plate, etc. This avoids this problem and maintains a high facility utilization rate. Therefore, the present invention can be widely applied in a slag-making raw material manufacturing process as a method for manufacturing a sintered ore that can achieve both high productivity and good product yield.

  As described above, the present invention relates to a sintered ore that is granulated from a raw material containing iron ore, a secondary material, limestone, a return mineral, and a coagulated material, and then fed onto a pallet of a sintering machine and fired. In the production method, a part of the blended raw material was granulated in a separate system so that the particle diameter was 3 mm or more and 20 mm or less, which was larger than the granulated particles obtained by granulating the remaining blended raw materials. Thereafter, the granulated particles obtained by granulating the remaining blended raw material and the granulated particles having a large particle size are mixed with the granulated particles having a large particle size in the total blended raw material. In the method for producing sintered ore, the mixture is mixed so that the ratio is 22% by mass or less, and charged on the sintering machine pallet so that the layer thickness of the mixed raw material packed layer is 530 mm or more and 730 mm or less. is there. Hereinafter, the method of the present invention will be described in more detail with test results.

(1) Effect of Raw Material Layer Thickness on Production Rate and Product Yield when Coarse Pseudoparticles Mixed (1) -1 Test Method for Confirming Effect by Coarse Pseudoparticle Mixing Production when Coarse Pseudoparticles are Mixed into Sintered Raw Material The effect of the layer thickness of the raw material packed layer on the rate and product yield was confirmed by a sintering pot test.

  Table 1 shows the blending conditions of the pan test and the packed layer thickness of the raw material.

  Unsieved and undried maramamba fine ore and blast furnace dust are mixed at the mixing ratio described in the column of coarse pseudo particles in Table 1, and mixed with water using a high-speed stirring mixer (trade name: Eirich mixer). After kneading, it was granulated using a pan pelletizer. FIG. 1 is a diagram showing the particle size distribution of coarse pseudo-particles obtained as described above.

  Next, the raw materials described in the powder raw material column in Table 1 were weighed and collected so as to have the mixing ratio as described, and granulated by a drum mixer. The granulated powder material and the coarse pseudo particles were placed in a vat and mixed manually. As shown in Table 1, the mixing ratio of the coarse pseudo particles at this time was 0% by mass or 21.4% by mass of the total blended raw materials. In the above process, the powder ore transported from the yard in the sintering factory is kneaded with water by a high-speed stirring mixer, granulated by a pan pelletizer, and raw materials other than coarse pseudo-particles granulated in another system, This is a test that simulates mixing in the transport process to the surge hopper.

  The blended raw material in which the coarse pseudo particles were mixed was placed in a sintering pot test apparatus having a height of 750 mm and an inner diameter of 300 mm, and subjected to a pot test. In the pan test, after igniting with an LPG burner for 1 minute while sucking under a pan pressure of about 20 kPa, firing was performed at a constant pan bottom pressure of 9.8 kPa, and suction was performed 3 minutes after the exhaust gas temperature reached the maximum temperature. Was stopped and the test was terminated.

  After completion of the test, the sintered cake was immediately removed from the pan test apparatus and allowed to cool until the temperature of the sintered cake dropped to room temperature. After completion of cooling, the produced sintered cake was dropped from a height of 2 m four times, and then the sieve mesh was sieved with a 5 mm sieve to measure the mass on the sieve to determine the product yield and the production rate. . Here, the production rate means a value obtained by dividing the mass on the sieve sieved by a 5 mm sieve by the effective area of the sintering machine and the sintering time, and is calculated by the following formula (1). In the case of the pot test, the cross-sectional area of the sintering pot was used as the effective area of the sintering machine. In addition, the product yield was evaluated in percentage by using the following equation (2) by dividing the mass of sintered ore on the sieve sieved by the above-mentioned 5 mm sieve by the mass of the original sintered cake.

Production rate (t / m ² / d) = [mass of sintered ore having a particle size of 5 mm or more (t) / {effective area of the sintering machine (m ² ) × sintering time (min)}] × 60 × 24 ・ ・ ・ ・ (1)
Product yield (mass%) = {mass of sintered ore having a particle size of 5 mm or more (t) / mass of sintered cake (t)} × 100 (2)
The production rate and product yield in each test when the production rate and product yield of Test No. 1 which is a test for a comparative example with a layer thickness of 500 mm without mixing coarse pseudo particles were set to 100%, Indexed as production rate and relative product yield. Then, the case where the relative production rate was 102% or more and the relative product yield was 96% or more was judged to be effective.

  The reason that the relative production rate is effective is more than 102%, based on the empirical rule that if the results of the above level can be achieved in the pan test, considering the fluctuation of the data in the pan test, the actual sintering machine is also effective. Is based. In addition, the case where the relative product yield is 96% or more is regarded as effective because the limit of accepting a decrease in the product yield accompanying the increase in the production rate is 96% based on past experience. That is, even when the production rate is high, the average particle size of the product sintered ore often decreases when the product yield is low. Since a decrease in the particle size of the sinter may adversely affect the air permeability in the blast furnace, a state in which the product yield of the sinter is excessively decreased should be avoided. Therefore, in the present invention, the lower limit value of the relative product yield is set to 96%.

(1) -2 Appropriate Layer Thickness of Raw Material Packed Layer FIG. 2 is a diagram showing the effect of the layer thickness of the raw material packed layer on the relative production rate and relative product yield obtained by the above test. In the figure, test number 4 is a test for the inventive example, and test numbers 1 to 3 and 5 are tests for the comparative example.

  Test number 1 (circle mark in the figure), which is a test of the comparative example, is a test of the base condition described above. Test No. 2 (□ in the figure), which is a test of the comparative example, is a test in which the thickness of the raw material packed layer is increased to 625 mm without mixing coarse pseudo particles. As the effect of the raw material layer thickness on the production rate and product yield described above, the relative product yield increased to a little less than 101%, while the relative production rate decreased to 95%. Also, in test number 3 (marked with ● in the figure), which is a test of a comparative example in which coarse pseudo particles are mixed while the layer thickness of the raw material packed layer is kept at 500 mm, the relative production rate is greatly improved to 140%. However, the relative product yield decreased to 96% or less.

  Therefore, when the test No. 4 (marked with ■ in the figure), which is the test of the present invention example in which the layer thickness of the raw material packed layer was increased to 600 mm, was performed, the relative production rate increased to 126%, Yield was also 97.5%. Furthermore, when test number 5 (marked with ▲ in the figure) for the comparative example in which the layer thickness of the raw material packed layer was increased to 750 mm was performed, the relative product yield was 102%. The production rate has dropped to 96%.

  From these series of tests, it was found that when coarse pseudo particles were mixed, the relative production rate decreased linearly and the relative product yield increased linearly as the layer thickness of the raw material packed layer increased. . This phenomenon is caused by the fact that the air permeability is improved by mixing coarse pseudo-particles, the layer thickness of the raw material packed layer is increased, the air resistance is increased, and the excessive increase in the firing rate is suppressed. It shows that the amount of increase in ventilation resistance per layer thickness is balanced with the amount of decrease in firing rate associated therewith. Therefore, when the layer thickness of the raw material packed layer is 530 mm, the relative production rate is improved to 135%, and the relative product yield is secured to 96%. In addition, when the thickness is 675 mm, the production rate is improved to 110%, and the relative product yield is improved to 100%.

  That is, it has been clarified that a high production rate can be achieved while maintaining the product yield by simultaneously mixing coarse pseudo particles and increasing the layer thickness of the raw material packed layer. From the above results, when the thickness of the raw material packed layer is increased to 730 mm, the relative production rate is 102%. This means that in the present invention, the improvement in the air permeability of the raw material packed layer due to the mixing of coarse pseudo particles is 730 mm when the layer thickness is completely offset by the increase in the thickness of the raw material packed layer. ing.

  From the above test results and considerations, it was confirmed that the appropriate layer thickness of the raw material packed layer capable of obtaining the effects of the present invention is in the range of 530 mm to 730 mm, and the preferred range is 675 mm to 730 mm.

  In addition, it is guessed that the effect similar to this invention is possible also by the method of forming a ventilation groove | channel in a raw material filling layer with a mechanical means as shown, for example as patent document 1. FIG. However, as long as the method for improving the air permeability by mechanical means is adopted, as described above, the adhesion of the raw material to the device such as the air permeability control plate is inevitable, and the gas flow distribution in the sintered raw material packed bed is made uniform. Equipment maintenance to maintain is required. On the other hand, the present invention is excellent in that a high equipment operation rate can be stably maintained without requiring such equipment maintenance man-hours at all.

(2) Formation of coarse pseudoparticles and appropriate particle size (2) -1 Formation of pseudoparticles In the present invention, the raw material constituting the coarse pseudoparticles uses maramamba fine ore with a high fine powder ratio in the particle size configuration. It is preferable to do. In addition, as a result of improving the air permeability by blending coarse pseudo particles, carbon sources such as powder coke and carbon-containing dust can be used so that coarse particles can be sufficiently sintered even if the holding time of 1000 ° C. or higher is shortened. It is good to mix. As a result of tests by the present inventors, it was confirmed that 1 to 2% by mass of the coarse pseudo particles is sufficient as the C content to be blended. Moreover, in order to produce | generate calcium ferrite, you may mix | blend CaO sources, such as limestone.

  The method for forming the coarse pseudo-particles is not particularly defined, but a granulation method using a generally used dish-type granulator, and manufacturing of briquettes using an extruder or a briquette machine as disclosed in Patent Document 8 above. A method or the like may be adopted. Moreover, as shown in Patent Document 7, a method of adding water and a binder in advance and granulating the raw material before it is charged into a blending tank installed in front of the primary mixer may be used. In addition, a melting point adjusting material or a binder as described in Patent Document 4 may be used. However, it is not necessary to granulate anthracite in advance as described in Patent Document 4.

  Further, after adding water and a binder, it may be solidified while being piled, and coarsely pulverized for use. Furthermore, if means such as adding moisture and a binder at the mountain mine (mine) and solidifying in the ship being transported is adopted, it is not necessary to secure the time required for curing in the steelworks, which is efficient. Note that the same effect as the productivity improvement effect obtained in the present invention can be obtained by blending block ore as disclosed in Patent Document 2 instead of forming coarse pseudo particles. However, in the invention disclosed in Patent Document 2, it is necessary to stably secure a lump ore that is more cost-effective to be charged in a sintering machine than directly charged in a blast furnace. Depending on supply and demand trends, there may be economic disadvantages. Therefore, the method according to the present invention, in which coarse pseudo particles are formed by granulating limonite fine ore, which is expected to increase in the future supply and demand balance of ores, is more advantageous in terms of economy.

  Further, as shown in the above test, when obtaining the effects of the present invention, it is not necessary to screen the fine iron ore. In other words, the method of the present invention is similar to the method described in Patent Document 3 using pellets or Patent Document 5 in which pseudo-particles of 2 to 5 mm are manufactured using a sieve of powder ore. Compared to other methods that require a sieving step, there is an advantage in that it is a simple process with no steps.

(2) -2 Appropriate particle size of coarse pseudo particles The effect of the particle size of coarse pseudo particles mixed in the sintered raw material on the production rate and product yield was confirmed by conducting the same pan test.

  Table 2 shows the blending conditions of the pan test including the particle size of the coarse pseudo particles and the packed bed thickness of the raw material.

  Coarse pseudo particles are sieved, the mixing ratio of coarse pseudo particles is constant at 21.4% by mass, and mixed raw materials are prepared by mixing coarse pseudo particles of various particle sizes, and pot tests are conducted using these mixed raw materials. Carried out. In addition, the pan test was performed by the same method as described in the above (1) -1, and the relative production rate and the relative product yield were compared. In the table, test numbers 7 to 11 are tests for the examples of the present invention, and test number 6 is a test for the comparative examples.

  FIG. 3 is a diagram showing the effect of the particle size of coarse pseudo particles in the blended raw material on the relative production rate and the relative product yield.

According to the results in the figure, the relative production rate becomes the maximum when the particle size (particle size range) of the coarse pseudo particles is 8 to 10 mm, and the relative production rate is almost constant when the particle size is 5 to 8 mm or more. It was. The relative product yield was 96% or more when the coarse pseudo particle diameter was 3 to 20 mm, and 99% or more when the coarse pseudo particle diameter was 5 to 15 mm.
The reason why the relative product yield is reduced to 96% when the particle size of the coarse pseudo particles is in the range of 15 to 20 mm is that the firing rate is increased by improving the air permeability of the raw material packed layer, and the packed layer is maintained at 1000 ° C. or higher. This is because the sintered cake was discharged from the sintering pot without being sufficiently sintered due to the shortened time. Furthermore, when coarse quasi-particles having a particle diameter of 20 mm or more are mixed, it is estimated that the relative product yield is further reduced to less than 96%. On the other hand, the relative product yield decreased to less than 96% when the particle size of the coarse pseudo particles was less than 3 mm because the pseudo particles having relatively small particle sizes were densely arranged around the coarse pseudo particles. It is presumed that this is due to a decrease in firing, hindering firing and a decrease in relative product yield.

  From the above test results and consideration based thereon, it was confirmed that the range of the appropriate particle size of the coarse pseudo particles in the present invention is 3 mm or more and 20 mm or less. Moreover, the range of a preferable particle size is 5 mm or more and 15 mm or less.

(3) Appropriate mixing ratio of coarse pseudo particles Furthermore, the effect of the mixing ratio of coarse pseudo particles mixed in the raw material on the production rate and product yield was confirmed by conducting the same pan test.

  Table 3 shows the conditions of the pan test including the mixing ratio of coarse pseudo particles.

  As shown in Table 3, in the mixing ratio change test for coarse pseudo particles, the coarse pseudo particles having a particle size (particle size range) of 15 to 20 mm have a mixing ratio of about 21 to 36% by mass with respect to the total raw material mass after mixing. The pan test was conducted. The method of the pan test is the same as that described above.

  FIG. 4 is a graph showing the effect of the mixing ratio of coarse pseudo particles in the blended raw material on the relative production rate and the relative product yield. According to the results shown in the figure, the relative production rate showed the maximum value when the mixing ratio of coarse pseudo particles was 28.6% by mass. On the other hand, it has been found that the relative product yield sharply decreases when the mixing ratio of coarse pseudo-particles exceeds 22% by mass.

  The reason why the relative product yield decreases when the mixing ratio of the coarse pseudo particles exceeds 22% by mass is that the mixing ratio of the coarse pseudo particles is excessively increased and the air permeability is excessively improved. This is because a sufficient time during which the temperature is maintained at 1000 ° C. or more cannot be secured, and an unfired portion increases in the layer of the packed layer. In addition, the relative production rate decreased when the mixing ratio of coarse pseudo particles was 35.9% by mass, although the firing time could be shortened by improving the air permeability, but the particle size of 5 mm or more due to the decrease in the relative product yield described above. It is inferred that the decline in sinter production yielded a dominant effect.

  According to the above test results and consideration, the appropriate range of the mixing ratio of coarse pseudo particles in the present invention is 22% by mass or less. The mixing ratio of coarse pseudo particles is preferably 6% by mass or more.

  According to the method of the present invention, coarse pseudo particles having an appropriate particle size are mixed in an appropriate mixing ratio in the packed layer of the sintered raw material, and the operation for optimizing the layer thickness of the raw material packed layer is performed. It is possible to maintain the high product yield that could not be realized by the conventional technology while securing the effect of improving the production rate by mixing the two. Also, since the air permeability is improved by optimizing the mixing ratio of raw material granulation and coarse pseudo particles, maintenance management of equipment that occurs in the case of forming a ventilation groove using an air permeability control plate, etc. This avoids this problem and maintains a high facility utilization rate. Therefore, the method of the present invention can be widely applied in the field of raw material production of sinter as a method for producing sintered ore that can achieve both high productivity and good product yield.

It is a figure which shows the particle size distribution of the coarse pseudoparticle used for the test. It is a figure which shows the effect of the layer thickness of the raw material packed layer on a relative production rate and a relative product yield. It is a figure which shows the effect of the particle size of the coarse pseudoparticle in a mixing raw material on a relative production rate and a relative product yield. It is a figure which shows the effect of the mixing ratio of the coarse pseudoparticle in a mixing raw material on a relative production rate and a relative product yield.

Claims (1)

In the manufacturing method of sintered ore, which comprises granulating a raw material containing iron ore, sub-raw material, limestone, return ore and coagulating material, and supplying and firing it on a pallet of a sintering machine. Part of the remaining blended raw material is granulated in a separate system so that a part thereof has a particle diameter of 3 mm or more and 20 mm or less, which is larger than the granulated particles formed by granulating the remaining blended raw material. The mixing ratio of the particles after granulation having a large particle diameter and the particles after granulation having a large particle diameter, which are obtained by granulating the particles, is 22% by mass or less. A method for producing a sintered ore, comprising mixing so that the layer thickness of the blended raw material packed layer is 530 mm or more and 730 mm or less on a sintering machine pallet.

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