JP5375742B2 - Granulation method of sintering raw material - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a method of granulating raw material for sintering capable of easily and inexpensively improving productivity of sintered ore even when a fine powder proportion of the raw material for sintering increases. <P>SOLUTION: The method of granulating raw material for sintering includes the steps of: forming pseudo-particles by granulating a part of the raw material for sintering containing powder iron ore, auxiliary material, and carbonaceous material; forming other pseudo-particles by granulating the remainder of the raw material for sintering in another system; and subsequently mixing the pseudo-particles constituted by granulating a part of the raw material for sintering and the other pseudo-particles constituted by granulating the remainder of the raw material for sintering, wherein, when forming the pseudo-particles by granulating a part of the raw material for sintering, powder containing 3.5 mass.% or less T.C. (total carbon) and 67.5 mass.% or more T.Fe (total iron) with the ratio of particles with 10 &mu;m or smaller particle size being 20 mass% or less is added to form pseudo-particles with 5 mm or larger particle size. <P>COPYRIGHT: (C)2012,JPO&amp;INPIT

Description

  The present invention relates to a method for granulating a sintered raw material in the production of a sintered ore used in a blast furnace, and more specifically, even when the fine powder ratio of the sintered raw material is increased, the productivity of the sintered ore is inexpensive. The present invention relates to a method for granulating a sintered raw material that can be improved greatly.

  The manufacture of sintered ore used as an iron source in a blast furnace is generally performed by the following method. Powdered iron ore, auxiliary materials, and carbon materials are blended at a predetermined ratio to obtain a sintered raw material. The sintered raw material is added with moisture, mixed, humidified and granulated, and becomes pseudo particles having a particle diameter of about 2 to 4 mm (hereinafter also abbreviated as “pseudo particles”). The granulated sintered raw material is charged on a pallet of a sintering machine to form a sintered raw material packed layer (hereinafter also abbreviated as “filled layer”) on the pallet.

  The thus formed packed bed is ignited on the upper surface thereof in the ignition furnace of the sintering machine, combustion of the carbonaceous material existing in the packed bed is started, and the combustion part of the carbonized material forms a combustion zone. Since the packed bed is sucked from below, the combustion zone gradually moves from the upper part to the lower part of the packed bed. In the combustion zone, the surrounding pseudo particles are heated by the combustion heat, the pseudo particles are partially melted, and the pseudo particles are crosslinked and sintered by the melt, and the packed layer is finally sintered cake It becomes. The sintered cake is discharged from the sintering machine and is crushed to a predetermined particle size by a crusher to become a sintered ore.

  In recent years, high-quality fine iron ore has been depleted, so the ratio of fine powder has increased due to low grade, and the use of high-quality fine iron ore as an alternative to high-quality fine iron ore has increased. Along with this, the ratio of fine powder in the sintered raw material is increasing. The high-grade fine powdered iron ore referred to here has a ratio of 80% by mass (hereinafter referred to as “particle size” of 0.25 mm or less) when sieving with 0.25 mm sieve in running water. mass%) or higher, and T.W. It refers to iron ore with Fe (total iron) of 60 mass% or more, and specific examples include pellet feed ore from South America. Such a high-grade finely divided iron ore is hereinafter referred to as pellet feed fine ore.

Now, the iron grade of sintered ore is deeply related to the operating results of the blast furnace, and considering the recent situation where reduction of CO ₂ emitted from the blast furnace is required due to increased environmental awareness, high grade pellet feed Future production forms of sintered ores are expected to be directed to the production of high-quality sintered ores using a large amount of fine ore. However, in the production of sintered ore, if the amount of pellet feed powder ore is increased, the fine powder ratio increases in the sintered raw material, and the granulated pseudo particles are raw materials that remain fine without being granulated. The ratio of so-called ungranulated powder increases.

  The non-granulated powder rate mentioned here is obtained by drying pseudo particles obtained by granulating a sintered raw material at 105 ° C. for 2 hours in an air atmosphere, and then shaking for 15 seconds using a sieve having a mesh size of 0.25 mm. The particle diameter obtained by classification is a ratio (mass%) of 0.25 mm or less. The ungranulated powder rate is an index used for evaluating the productivity of sintered ore because it shows a good correlation with the air permeability of the packed bed when firing pseudo particles with a sintering machine. When the ratio of ungranulated powder increases, when the granulated pseudo particles are charged onto the pallet of the sintering machine, the voids formed in the packed bed are blocked with the remaining fine powder without being granulated. Therefore, the air permeability of the filling layer is hindered. As a result, the firing rate, which is the rate at which the combustion zone moves from the upper part toward the lower part, decreases, and the productivity of the sintered ore deteriorates.

  Conventionally, for example, as described in Non-Patent Document 1, the increase in the fine powder ratio in the sintered raw material has been dealt with. However, as described in the same document, the effect of reducing the rate of ungranulated powder due to quick lime is remarkable up to 2% of the quick lime blending ratio, but even if blended beyond that, ungranulated The amount of reduction in the powder rate hardly changes. Moreover, since quick lime is as expensive as 5,000-12,000 yen per ton, it wants to suppress the usage-amount as much as possible.

  Then, technical development corresponding to the pulverization of the sintering raw material which does not rely on quick lime is performed, for example, there exist nonpatent literature 2 and patent documents 1-3.

  In Non-Patent Document 2, a maramber ore from Australia with a high fine powder ratio is granulated to form a green ball which is a pseudo particle having a particle diameter of about 15 mm, and this green ball is placed in the packed bed to ventilate the packed bed. A MEBIOS method has been proposed that secures the properties and improves the productivity of sintered ore.

Moreover, in patent document 1, the fine iron ore and carbon | charcoal material which are a part of sintering raw material are mixed previously, and a high-density prefabrication with an apparent density of 2.7 g / cm ³ or more and a particle size of 5 mm or more. A granulation method is described in which a granulated product is granulated and then the remaining sintered raw material is added to the pre-granulated product, mixed, granulated, and supplied to a sintering machine.

  In the granulation method of the sintering raw material described in Patent Document 2, granulated iron ore is granulated to produce mini-pellets having a particle diameter of 2 to 5 mmφ and a crushing strength of 100 to 150 g / 5 mmφ balls, and the remaining firing The raw materials are mixed, conditioned and granulated in a separate system to make pseudo particles. The mini pellets and pseudo particles are separately supplied, mixed on a sintered material sloping plate, and supplied to a sintering machine.

  Patent Document 3 describes a pretreatment method of a sintered raw material in which a sintered raw material containing iron ore is compressed and crushed by a roller press crusher, and then granulated by adding a binder. In Patent Document 3, by treating the sintered raw material with a roller press crusher, a large amount of ultrafine particles having a particle size of 45 μm or less can be obtained, and pseudo-particle formation can be efficiently performed during granulation, It is said that the strength of the granulated product is improved.

  Here, in particular, the strength of the granulated material is noted in Patent Document 2 and Patent Document 3 because it is concerned that the pseudo-particles collapse when firing. That is, when firing the pseudo-particles in which the packed layer is formed by a sintering machine, the firing proceeds from the upper part of the packed layer toward the lower part, so the lower part is loaded from the upper part while the upper part is melted and sintered. It is necessary to endure. For this reason, when low-strength pseudo particles are placed in the lower part of the packed bed, the upper part collapses while it melts and sinters, the porosity decreases, the air permeability of the packed bed is hindered, and the productivity deteriorates. There is a danger to do.

Takeo Sato, Shinichiro Nakano, Shinichi Kurosawa, Hideomi Tanaka, Seiki Nagano: Floating, 32 (1985) p. 84-90 Eiki KASAI, Sergey KOMAROV, Koichi NUSHIRO, Masanori NAKANO: ISIJ International, Vol. 45 (2005) p. 538-543 Toru Murase and Naoto Hirai: Iron and Steel, Vol 79 (1993), p. 1129-1137

JP 2009-114537 A JP-A-4-198427 JP 2007-162127 A JP 2008-57028 A

  The conventional methods for granulating sintered raw materials described in Non-Patent Document 2 and Patent Documents 1 to 3 have the following problems.

  Since the non-patent document 2 does not describe a specific granulation method, it is necessary to separately examine a granulation method capable of reducing the above-mentioned ungranulated powder rate. For this reason, the granulation method described in Non-Patent Document 2 is not a method that can be immediately applied to the production of sintered ore.

Patent Document 1 describes a method of granulating a sintered raw material to improve the strength of sintered ore by high-density pseudo particles. For example, since the above-mentioned pellet feed powder ore has a high density, the pellet feed powder When ore is used as a sintering raw material, it is easy to set the apparent density of the preliminary granulated product to 2.7 g / cm ³ or more. However, even if the apparent density of the pre-granulated material containing the difficult-to-granulate pellet feed powder ore is 2.7 g / cm ³ or more, the pre-granulated material has sufficiently high strength, It is not always possible to reduce the rate.

  Patent Document 2 describes that in order to produce mini-pellets with high crushing strength, a pan pelletizer is not suitable, and a granulation facility for charging a sintered raw material into a compacted plasticization kneading space is required. . However, since such a granulation facility is generally expensive, it is difficult to achieve a reduction in the ungranulated powder rate at a low cost by the method for granulating a sintering raw material described in the same document.

  In the granulation method of the sintered raw material described in Patent Document 3, it is necessary to crush the sintered raw material with a roller press, and equipment cost is required for introducing the roller press. Moreover, although adding polyacrylic acid type | system | group dispersing agent and quicklime as a binder is described, the cost deterioration by use of a dispersing agent cannot be avoided. Furthermore, as described above, there is a problem that there is an upper limit to the effect of reducing the ungranulated powder rate by quick lime. For these reasons, it is difficult to achieve a reduction in the ungranulated powder rate at a low cost by the method for granulating a sintered raw material described in the same document.

  The present invention has been made in view of the above problems. Even when the fine powder ratio of the sintering raw material is increased, the air permeability of the packed bed can be secured, and the sintered ore productivity can be maintained at a low cost. It aims at providing the granulation method of a raw material.

  The present inventors suppressed the increase in the ratio of ungranulated powder and increased the air permeability of the packed bed even when the fine powder ratio of the sintering raw material increased with increasing the amount of pellet feed powder ore used. Therefore, an inexpensive method that can maintain the productivity of sintered ore was examined. As a result, the present inventors have reached the conclusion that it is most effective to rely on the sintering raw material granulation method previously proposed in Patent Document 4 by the present inventors.

  Specifically, a part of the sintering raw material is granulated by a pan pelletizer into pseudo particles (hereinafter also abbreviated as “green balls”) having a particle size larger than general pseudo particles of 5 mm or more. This is a granulation method of a sintered raw material in which the remainder of the sintered raw material is granulated into pseudo particles by a system, and then the green ball and the pseudo particles obtained by granulating the remaining sintered raw material are mixed.

  Therefore, when a large amount of pellet feed powder ore was used, a method that can increase the strength of the green ball at a low cost was examined, and it was found that the fine powder having a particle size of 10 μm or less affects the strength of the green ball. .

  The mechanism by which ultrafine powder having a particle size of 10 μm or less affects the crushing stress of pseudo particles or green balls is as follows. In the granulation of the sintering raw material, particles smaller than the core particles of 1 mm or less, called adhering powder, surround the relatively large particles of about 3 to 5 mm called core particles to form pseudo particles. The binder that binds the core particles and adhering powder plays the role of moisture added during the granulation process, and enters and mixes between the core particles and the adhering powder during the mixing, stirring, and granulating processes. To do.

  On the other hand, the ultrafine powder having a particle diameter of 10 μm or less contained in the sintering raw material is suspended in the water and can move freely with the water, so that it enters between the core particles and the adhering powder together with the water. In this way, the ultrafine powder having a particle size of 10 μm or less fills the space between the pseudo particles and the adhering powder to form a crosslink, thereby increasing the strength of the pseudo particles. The strength increase by this mechanism is manifested not only in the pseudo-particles granulated in the process of producing ordinary sinter, but also in green balls with large particle sizes, as well as the sintering raw material for granulating green balls Even when only the pellet feed powder ore is granulated, it is expressed in the same manner.

  However, not all of the ultrafine powder having a particle diameter of 10 μm or less contributes to the development of the strength of pseudo particles or green balls. For example, an ultrafine powder containing C (carbon) does not show an effect of developing strength even when added to a sintering raw material. This is because C has poor wettability with water and is difficult to suspend in water.

  The present inventors, who confirmed the above phenomenon from experiments, investigated low-cost raw materials containing ultrafine powder having a particle size of 10 μm or less, and focused on dusts generated in the steelworks. This is because dusts must be processed in steelworks and are inexpensive. As a result, powdered iron oxide by-produced from the steel plate hydrochloric acid pickling waste liquid was converted to T.P. C. Was found to contain 20 mass% or more of ultrafine powder having a particle size of 0 mass% and a particle size of 10 μm or less.

Further, the powdered iron oxide by-produced from the steel plate hydrochloric acid pickling waste liquid has an angular particle shape and T.P. Since the ratio of Fe ₂ O ₃ to Fe is about 96.5 mass% (the content of T.Fe is 67.5 mass% or more), it is a high-grade material that does not contain C and is found in other iron-making dusts. We noticed that there was little variation in quality. Then, the powdered iron oxide was added to a part of the sintering raw material to granulate a green ball and subjected to a compression fracture test. As a result, it was found that the crushing strength of the green ball was increased.

  Here, the powdered iron oxide by-produced from the steel sheet hydrochloric acid pickling waste liquid is, for example, the steel sheet hydrochloric acid pickling waste liquid used in the pickling process of hot-rolled steel sheets as described in Non-Patent Document 3. It is obtained by roasting and is often used as a raw material for ferrite, which is a composite oxide and magnetic material. Hereinafter, powdered iron oxide by-produced from the steel plate hydrochloric acid pickling waste liquid is referred to as pickling sludge.

The reason why the strength of the granulated green ball is increased by adding the pickled sludge to a part of the sintered raw material is considered to be due to the following reasons (a) to (c).
(A) Pickling sludge has good wettability with water because it does not contain C in addition to containing 20 mass% or more of fine powder having a particle size of 10 μm or less.
(B) The particle shape is angular, and the fine powders are entangled well when entering between the core particles and the adhering powder to form a bridge.
(C) T.W. Since the ratio of Fe ₂ O ₃ to Fe is 95 mass% or more, the specific gravity is large, and once the crosslinks are formed, they do not move easily.

  In addition, since pickling sludge is iron oxide powder byproduced simultaneously with hydrochloric acid, it contains about 1000 ppm of chlorine. In the manufacturing process of sinter, chlorine easily forms chlorides and volatilizes. Since the volatilized chloride is recovered together with other dust generated in the manufacturing process of the sintered ore, the amount of dust generated increases. For this reason, it is more preferable to use pickled sludge subjected to dechlorination treatment as powder.

  The present invention has been completed on the basis of the above findings, and the gist of the method (1) to (4) below is a granulation method for a sintered raw material.

  (1) A part of a sintered raw material containing fine iron ore, auxiliary raw material and carbonaceous material is granulated into pseudo particles, and the rest of the sintered raw material is granulated into pseudo particles by another system, A method of granulating a sintered raw material by mixing pseudo particles obtained by granulating a part of a sintering raw material and pseudo particles obtained by granulating the remainder of the sintering raw material, wherein a part of the sintering raw material is granulated. When making pseudo-particles, T.W. C. (Total carbon) of 3.5% by mass or less, T.I. Fe (total iron) is contained in 67.5% by mass or more, a powder having a particle size of 10 μm or less in a proportion of 20% by mass or more is added, and granulated into pseudo particles having a particle size of 5 mm or more. A method for granulating a sintered raw material.

  (2) At least one brand among the fine iron ores contained in a part of the sintered raw material is T.P. Fe fine iron ore containing 60% by mass or more of Fe and having a particle size of 0.25 mm or less is 80% by mass or more, and this fine iron ore is the total amount of fine iron ore and auxiliary materials in all of the sintered raw materials The granulation method of the sintering raw material according to (1) above, wherein the proportion of the sintering raw material is 10% by mass or more.

  (3) The method for granulating a sintered raw material according to (1) or (2) above, wherein powdered iron oxide obtained by roasting a hydrochloric acid pickling waste liquid is used as the powder. .

  (4) The method for granulating a sintered raw material according to (3) above, wherein the powdered iron oxide obtained from the steel plate hydrochloric acid pickling waste liquid has been dechlorinated.

In the present invention, the “auxiliary raw material” is a raw material excluding fine iron ore and charcoal, and includes, for example, raw materials containing quicklime and SiO ₂ and raw materials containing MgO. Further, “carbon material” is a raw material containing free carbon, for example, powder coke, anthracite, C-containing dust, and the like.

  In the granulation method of the sintered raw material of the present invention, when a part of the sintered raw material is granulated into pseudo particles, a powder containing ultrafine powder having a particle diameter of 10 μm or less is added, and the particle diameter By granulating into pseudo particles having a diameter of 5 mm or more, the pseudo particles obtained by granulating a part of the sintered raw material have high strength, and even when the fine powder ratio in the sintered raw material is increased, the pseudo particles are placed on the pallet of the sintering machine. When charged, the air permeability of the packed bed can be ensured, and the productivity of the sintered ore can be improved at a low cost.

It is a figure which shows an example of the manufacturing process flow of a sintered ore. It is a figure which shows the relationship of the crushing strength of the powder added to a part of sintering raw material, and a green ball. It is the figure which shows the relation between the blending rate of the pellet feed fine ore and the relative production rate when all of the sintering raw materials are mixed and granulated without mixing and granulating a part of the sintering raw materials in another system is there. It is a figure which shows the relationship between the crushing strength of a green ball at the time of granulating by adding powder to a part of sintering raw material, and a relative production rate.

  Below, the granulation method of the sintering raw material of this invention is demonstrated based on drawing.

  FIG. 1 is a diagram showing an example of a manufacturing process flow of a sintered ore, and shows a manufacturing process flow of a sintered ore to which the method for granulating a sintered raw material of the present invention can be applied. In the manufacturing process flow of the sintered ore shown in the figure, in the granulation system A, water 4 and powder 5 are added to the fine iron ore 1a, the auxiliary raw material 2a and the carbonaceous material 3a which are part of the sintered raw material, After mixing and conditioning using a high-speed stirring mixer 6, granulation is performed using a pan pelletizer 7 to obtain green balls which are pseudo particles having a particle diameter of 5 mm or more. On the other hand, in the granulation system B, water 4 is added to the powdered iron ore 1b, the auxiliary raw material 2b, and the carbonaceous material 3b, which are the remainder of the sintered raw material, and mixed using the primary drum mixer 8 and the secondary drum mixer 9, Condition and granulate to make pseudo particles.

  The green balls granulated by the granulation system A and the pseudo particles granulated by the granulation system B are mixed in the conveying process up to the surge hopper 10 and charged onto the pallet of the sintering machine 11 to form a packed bed. Form. The green balls and pseudo particles on which the packed layer is formed on the pallet of the sintering machine 11 are fired to become a sintered cake and are discharged from the sintering machine. The discharged sintered cake is crushed to a predetermined particle size by a crusher (not shown) to obtain a sintered ore.

  The method for granulating a sintered raw material of the present invention involves granulating a part of a sintered raw material including fine iron ore, auxiliary raw material and carbonaceous material into pseudo particles, and granulating the remainder of the sintered raw material in another system. A method of granulating a sintered raw material by mixing pseudo particles obtained by granulating a part of the sintering raw material and pseudo particles obtained by granulating the remainder of the sintering raw material. When granulating the part to make pseudo particles, C. (Total carbon) of 3.5% by mass or less, T.I. Fe (total iron) is contained in 67.5% by mass or more, a powder having a particle size of 10 μm or less in a proportion of 20% by mass or more is added, and granulated into pseudo particles having a particle size of 5 mm or more. And

  The ultrafine powder having a particle diameter of 10 μm or less can be suspended in water and freely moved together with water when it is added to a part of the sintering raw material and granulated. For this reason, it enters between the core particles and the adhering powder together with moisture, and the fine powder fills between the pseudo particles and the adhering powder to form a bridge, thereby increasing the strength of the granulated green ball. When the ratio of the particle diameter contained in the powder is 10 μm or less is less than 20 mass%, the amount of crosslinking formed by filling the fine particles between the adhering powder and the fine powder is insufficient, and when firing with a sintering machine The green ball collapses in the packed bed due to insufficient strength and impairs the air permeability of the packed bed.

  In addition, even if it is a fine powder with a particle size of 10 μm or less, C has poor wettability with water, and it is difficult to suspend in water. Does not form crosslinks. For this reason, the T.V. When C (total carbon) exceeds 3.5 mass%, it is not possible to sufficiently form a cross-link by the fine powder, so when firing with a sintering machine, the green balls collapse in the packed bed due to insufficient strength, and the packed bed Impairs breathability.

Further, T.I. contained in the powder. If Fe (total iron) is less than 67.5 mass%, it means that the ratio of Fe ₂ O ₃ is less than 96.5 mass%, and the specific gravity is reduced accordingly, and after the formation of cross-links, it moves easily. The property of disappearing is reduced.

  From these, in the granulation method of the sintered ore of the present invention, the powder added to a part of the sintering raw material is T.P. C. (Total carbon) is 3.5 mass% or less; Fe (total iron) is contained in an amount of 67.5 mass% or more, and the ratio of the particle size of 10 μm or less is set to 20 mass% or more.

  Part of the sintering raw material is mixed to obtain particles having a particle diameter of 5 mm or more (green balls). The pseudo particles granulated by the usual sintering raw material granulation method are about 2 mm to 4 mm. By making the particle size of the green balls coarser than the pseudo particles obtained by granulating the remaining sintering raw materials, moderate voids are created in the packing layer formed from the green balls and the pseudo particles, and the air permeability of the packing layer is ensured. Because it can be done.

  As described in Patent Document 4, the ratio of a part of the sintered raw material granulated in the green ball to the entire sintered raw material is preferably 22 mass% or less. If the ratio of a part of the sintering raw material granulated into the green ball exceeds 22 mass%, when the packed layer is formed by the sintering machine, excessive voids are generated by the green ball having a coarse particle diameter, and the sintering time is increased. This is because the product yield is reduced as a result. Moreover, it is preferable that the ratio of a part of the sintering raw material granulated into the green ball is 6 mass% or less.

  As described above, in the granulation method of the sintering raw material of the present invention, since the fine powder contained in the powder fills the space between the pseudo particles and the adhering powder to form a bridge, a part of the sintering raw material is granulated. Increased strength of the green ball. Strength increase due to this mechanism is that the sintering raw material for granulating green balls does not contain core particles, as shown in the examples described later, only pellet feed fine ore is blended as part of the sintering raw material as fine iron ore And when it is granulated, it is expressed similarly.

  For this reason, in the method for granulating a sintered raw material of the present invention, at least one brand among the fine iron ores contained in a part of the sintered raw material is T.P. Fe fine iron ore containing 60 mass% or more of Fe and having a particle size of 0.25 mm or less is 80 mass% or more, and the fine iron ore accounts for the total amount of fine iron ore and auxiliary raw materials in all of the sintered raw materials. Even when the ratio is 10 mass% or more, it can be granulated into a high-strength green ball, and the air permeability of the packed layer can be ensured when firing with a sintering machine.

  In the granulation method of the sintering raw material of the present invention, it is preferable to use powdered iron oxide (pickling sludge) obtained by roasting a steel plate hydrochloric acid pickling waste liquid as a powder. Pickling sludge is inexpensive because it is a dust produced as a by-product from the steel plate hydrochloric acid pickling waste liquid generated at the steelworks, and the strength of the green balls granulated for the reasons (a) to (c) described above. Because it rises.

  In the method for granulating a sintered raw material of the present invention, it is preferable to use a dechlorinated treatment as pickling sludge. Chlorine contained in pickled sludge volatilizes by forming chlorides in the sinter production process, and is collected along with other dust generated in the sinter production process, suppressing the increase in dust generation At the same time, when the dust is recovered, the chlorides are less likely to corrode the piping of the recovery device. Pickling sludge can reduce the chlorine concentration to about 100 ppm by applying a desalting treatment.

  In order to confirm the effect of the granulation method of the sintered raw material according to the present invention, the following test was performed to verify the effect of the present invention.

  Prior to the pot test, the strength of the green ball having a granulated particle diameter of 5 mm or more was investigated by simulating the granulation system A in the manufacturing process flow of the sintered ore shown in FIG. The green balls were granulated using a pan pelletizer after adding moisture and powder to a sintered raw material containing fine iron ore, auxiliary materials and carbonaceous materials, mixing and conditioning using a high speed stirring mixer.

  In this test, only the pellet feed fine ore was used as the sintered raw iron ore. This is because if the condition is such that the strength of the green ball mainly composed of the difficult-to-granulate pellet feed powder ore is increased, the strength can be surely increased even when other fine iron ores are used.

  Table 1 shows the blending amount of the sintering raw material when the green ball is granulated in this test. In addition, the T.P. Table 2 shows the ratio of Fe content and particle size of 0.25 mm or less. In the steelmaking dust added to the sintering raw material as a powder, T.W. Fe content, T.I. C. Table 3 shows the content ratio and particle diameter ratio of 10 μm or less (hereinafter also abbreviated as −10 μm ratio).

  The -10 μm ratio of the powders shown in Table 3 is measured by a method based on JIS R1629.

  As shown in Table 1, in Conventional Example 1, no powder containing ultrafine powder having a particle size of 10 μm or less was added to the sintering material. In the present invention example 1, the pickled sludge is added to the sintered raw material as a powder with the same particle size without crushing, and in the present invention example 2, the pickled sludge is crushed to obtain a -10 μm ratio of 100 mass%. After that, it was added to the sintering raw material as a powder. In Comparative Example 1, the -10 μm ratio was 55 mass%, and T.W. C. Was used as a powder. In Comparative Example 2, the -10 μm ratio was 18 mass%, and T.W. C. Used as a powder.

  Green balls discharged from the pan pelletizer with a particle size of 5 mm or more were collected and sieved with a sieve mesh of 6 mm, and 10 green balls were arbitrarily collected from under the sieve to measure the crushing strength.

  FIG. 2 is a diagram showing the relationship between the powder added to a part of the sintering raw material and the crushing strength of the green balls. In Conventional Example 1 in which no powder was added, the crushing strength was 1.0 N. In Example 1 of the present invention, pickling sludge having a -10 μm ratio of 20 mass% was added, and the crushing strength was 1.5 N. Became. In Invention Example 2, crushed pickling sludge having a -10 μm ratio of 100 mass% was added, and the crushing strength further increased to 3.0N.

  On the other hand, in Comparative Example 1, the -10 μm ratio is 55 mass%. C. Is added, and the crushing strength becomes 1.0 N. In Comparative Example 2, the −10 μm ratio is 18 mass%, and T. C. Was added, and the crushing strength became 0.9N. From this result, in order to granulate a high-strength green ball, the powder added to the sintering raw material has a ratio of the particle diameter of 10 μm or less of 20 mass% or more, and T.I. C. It has been found necessary that the content of is less than 4.0 mass%.

  Next, a pan test was conducted using the green balls granulated in Invention Example 1, Invention Example 2 and Comparative Example 1. The composition of the sintering raw material in the pan test, the -10 μm ratio of the added powder, and the T.P. C. Table 4 shows the content and the crushing strength of the green balls granulated by the granulation system A.

  As shown in Table 4, Conventional Example A is a case that does not include pellet feed fine ore. Comparative Example A is a case in which 10 mass% of pellet feed powder ore is added to Conventional Method A, and Comparative Example B is a case where 1.5 mass% of quicklime is added to Comparative Example A. Invention Example A is a case using the green ball of Invention Example 1 shown in Table 1. Invention Example B is a case using the green ball of Invention Example 2 shown in Table 1. Comparative Example C is a case using the green ball of Comparative Example 1 shown in Table 1.

  In the conventional example A, the comparative example A, and the comparative example B, only the granulation system B in the production process flow of the sintered ore shown in FIG. 1 is used, and the granulation process in the general production process of the sintered ore is simulated. . Specifically, in the conventional example A, the comparative example A, and the comparative example B, the primary drum mixer 8 and the secondary drum mixer 9 are used, and moisture is contained in all of the sintered raw materials including fine iron ore, auxiliary raw materials, and carbonaceous materials. Was added, mixed, conditioned and granulated to obtain pseudo particles.

  In Invention Example A, Invention Example B and Comparative Example C, according to the manufacturing process flow of the sintered ore shown in FIG. After the remaining sintered raw material was granulated into pseudo particles in the grain system B, the green balls of the granulation system A and the pseudo particles of the granulation system B were mixed. As shown in Table 4, the amount of pellet feed fine ore used in Comparative Examples A to C and Invention Examples A and B was all 10 mass%. In any case, granulation system B was granulated by adding powdered coke as a carbonaceous material to the sintered raw material at a ratio of 4 to 4.5 mass% as an external number.

  Pseudoparticles granulated in the granulation system B, or pseudoparticles mixed with green balls were charged into a sintering pot test apparatus having a height of 500 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 cooling is completed, the manufactured sintered cake is dropped four times from a height of 2 m, and the sieve mesh is screened with a 5 mm sieve to measure the mass on the sieve to evaluate the productivity of the sintered ore. The production rate was calculated as an index. 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.
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)

Fig. 3 shows the relationship between the ratio of the pellet feed powder ore ratio and the relative production rate when all of the sintered raw material is mixed and granulated without mixing a part of the sintered raw material in a separate system and granulating. FIG. The relative production rate in the figure represents the production rate (t / m ² / d) in each test as a percentage when the production rate of the conventional method A is 100%. In Comparative Example A in which 10 mass% of pellet feed fine ore was blended, the relative production rate was reduced to 93%, but in Comparative Example B in which 1.5 mass% of quicklime was blended, the relative production rate was recovered to 100%.

FIG. 4 is a diagram showing the relationship between the crushing strength of a green ball and the relative production rate when a powder is added to a part of the sintered raw material and granulated. The relative production rate in the figure represents the production rate (t / m ² / d) in each test as a percentage when the production rate of the conventional method A is 100%. In Invention Example A, a green ball having a crushing strength of 1.5 N was blended, and the relative production rate increased to 102%. Furthermore, in the present invention example B containing green balls having a crushing strength of 3.0 N, the relative production rate increased to 108%. However, in Comparative Example C, a green ball having a crushing strength of 1.0 N was blended, and the relative production rate was reduced to 93%.

  In the present invention example A and the present invention example B containing the pellet feed powder ore, the production rate was improved from the conventional example A in which the pellet feed powder ore was not blended. The high strength green produced by the granulation system A This is because, by adding the balls, the air permeability of the filling layer is ensured when firing, and the firing speed is increased. On the other hand, the relative production rate of Comparative Example C similarly blended with pellet feed fine ore was 93%, which was lower than that of Conventional Example A, because when the green balls with low crushing strength were fired, they collapsed and filled the voids. This is because a portion in which the air permeability is hindered is generated and the firing becomes non-uniform.

  From this result, by increasing the strength of the green ball at a low cost, when increasing the amount of pellet feed powder ore used to reduce the production rate of sintered ore because granulation is difficult in the past In order to improve the production rate of the sintered ore than that of the conventional example A in which the pellet feed powder ore is not blended, it is judged that the crushing strength of the green ball is preferably 1.5 N or more.

  From the above test results, when a part of the sintered raw material is granulated by the method of granulating a sintered ore of the present invention, the ratio of the particle diameter of 10 μm or less is 20 mass% or more, C. Is added to a green ball having a particle diameter of 5 mm or more, and the remainder of the sintering raw material is granulated into a pseudo particle by another system. It was revealed that the production rate of sintered ore can be improved by mixing the pseudo particles obtained by granulating the remainder of the sintered raw material to produce sintered ore.

  In the granulation method of the sintered raw material of the present invention, when a part of the sintered raw material is granulated into pseudo particles, a powder containing ultrafine powder having a particle diameter of 10 μm or less is added, and the particle diameter By granulating into pseudo particles having a diameter of 5 mm or more, the pseudo particles obtained by granulating a part of the sintered raw material have high strength, and even when the fine powder ratio in the sintered raw material is increased, the pseudo particles are placed on the pallet of the sintering machine. When charged, the air permeability of the packed bed can be ensured, and the productivity of the sintered ore can be improved at a low cost.

  If the granulation method of the sintered raw material of the present invention is applied to the production of sintered ore, high-quality sintered ore can be produced at low cost even when the pellet raw material that is difficult to granulate is blended with the sintered raw material. Since it can be produced, it is a very useful technique for producing sintered ore used in a blast furnace.

1a: Fine iron ore, 1b: Remaining fine iron ore, 2a: Auxiliary raw material,
2b: remaining auxiliary material, 3a: carbon material, 3b: remaining carbon material, 4: moisture,
5: Powder, 6: High-speed stirring mixer, 7: Pan pelletizer,
8: primary drum mixer, 9: secondary drum mixer, 10: surge hopper,
11: Sintering machine

Claims (4)

After granulating a part of the sintered raw material containing fine iron ore, auxiliary raw material and carbonaceous material to make pseudo particles, the rest of the sintered raw material is granulated to make pseudo particles in another system, A method for granulating a sintered raw material in which pseudo particles obtained by granulating a part and pseudo particles obtained by granulating the remainder of the sintering raw material are mixed,
When granulating a part of the sintering raw material to obtain pseudo particles, C. (Total carbon) of 3.5 mass% or less, T.I. Fe (total iron) is contained in 67.5% by mass or more, a powder having a particle size of 10 μm or less in a proportion of 20% by mass or more is added, and granulated into pseudo particles having a particle size of 5 mm or more. A method for granulating a sintered raw material.   Among the fine iron ores contained in a part of the sintering raw material, at least one brand is selected from T.P. Fe fine iron ore containing 60% by mass or more of Fe and having a particle size of 0.25 mm or less is 80% by mass or more, and this fine iron ore is the total amount of fine iron ore and auxiliary materials in all of the sintered raw materials The granulation method of the sintering raw material according to claim 1, wherein the proportion of the sintering raw material is 10% by mass or more.   The method for granulating a sintering raw material according to claim 1 or 2, characterized in that powdered iron oxide obtained by roasting a hydrochloric acid pickling waste liquid is used as the powder.   4. The method for granulating a sintered raw material according to claim 3, wherein the powdered iron oxide obtained from the steel plate hydrochloric acid pickling waste liquid has been dechlorinated.

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