JP2018048390A - Manufacturing method of carbon-containing non-burned agglomerated ore for blast furnace - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a manufacturing method of a carbon-containing non-burned agglomerated ore for blast furnace capable of providing a carbon-containing non-burned agglomerated ore having stable quality simply at low cost by reducing variation of strength of an agglomerate in an upper layer part and a lower layer part of a mountain when mound agglomerate is primary cured.SOLUTION: There is provided a manufacturing method of a carbon-containing non-burned agglomerated ore for blast furnace including a process for mounting agglomerate which is molded after moisture adjusting a blending raw material containing a fine powdery iron-containing raw material, a fine powdery carbon material and a hydraulic binder in a treatment pit surrounded by a side wall, covering the same with a heat insulation sheet, injecting steam of prescribed amount from a floor surface of the treatment pit and primary curing the agglomerate while heating, heating of the agglomerate by injecting stream from the floor surface of the treatment pit is initiated during mounting a raw pellet by inputting and laminating the same from upper part of the treatment pit.SELECTED DRAWING: Figure 3

Description

  This invention relates to a method for producing a carbon-containing unfired agglomerate for blast furnaces. The agglomerate formed by adjusting the moisture content of the blended raw material is piled up in the treatment pit, and steam is generated from the floor surface of the treatment pit. The present invention relates to a method for producing a carbon-containing unfired agglomerated blast furnace for blast furnace by primary curing of the agglomerate while spraying and heating.

  The iron raw materials for blast furnaces in the current iron making process are mainly iron-containing raw materials containing powdered iron ore with an average particle size of about 2 to 3 mm, and these are auxiliary materials such as limestone and silica and carbon materials such as powdered coke and anthracite. Are mixed and granulated while adjusting the moisture to make pseudo-granulated particles (granulated products with fine particles of 0.5 mm or less attached to the surface of core particles of 1 mm or more), and then with a sintering machine Sintered sinter dominates.

  On the other hand, iron-containing dust collection dust collected from a large amount of sintered dust, blast furnace dust, etc. in the iron making process, fine dust such as sludge and scale powder (these are generally called iron making dust), pellet feed Fine iron ore such as (pellet raw material) is also agglomerated and used as a blast furnace iron raw material. Since these are finely divided iron-containing raw materials in which fine particles having a particle size of 0.25 mm or less occupy 80% or more of the whole, when granulating and sintering by the sintered ore process as described above, A thing collapse | crumbles, the air permeability of a raw material packed layer deteriorates, and productivity will fall.

  Therefore, in the case of agglomerating such a finely divided raw material as a main iron-containing raw material by firing, a higher mixing / granulating function is required than the above-mentioned sintered ore process. After adding and mixing water to the contained raw material and the auxiliary raw material, and using a granulator such as a disk pelletizer having a higher granulation ability than a drum mixer, mainly fine particles having a particle size of 0.25 mm or less are mainly used. It has been practiced to produce spherical pellets. Moreover, since such pellets are granulated products having a higher density than the pseudo-granulated particles in the sintering process, an external heating type firing machine using a combustion gas or the like as a heat source is used when firing the pellets. Since it is used, enormous manufacturing energy and manufacturing cost will be required.

  On the other hand, the fine powdered iron-containing raw material in which fine particles having a particle size of 0.25 mm or less occupy 80% or more of the whole is added with a binder (binder) such as cement, and granulated to agglomerate such as pellets. After being molded into a blast furnace, it has been used for a long time as an iron raw material for a blast furnace by using a non-calcined agglomeration process in which the strength is increased to obtain agglomerates.

  According to such a non-fired type agglomeration process, it becomes possible to add a large amount of carbonaceous material into the agglomerated mineral, which is impossible in the fired type agglomeration process to obtain sintered ore and fired pellets. Therefore, in recent years, for the purpose of reducing the reducing material ratio during blast furnace operation, a method for producing a carbon-incorporated non-fired agglomerated mineral using this process has been studied.

For example, the theory necessary to reduce iron oxide ore's reduced oxygen to metallic iron to iron ore or iron-containing raw materials containing various types of iron-containing and carbon-containing dust collected from steelworks. After blending carbon-based carbonaceous material corresponding to 80 to 120% of the carbon content (C content in all raw materials: about 10 to 15 mass%), kneading and molding by adding early strong Portland cement A method of producing a carbon-incorporated unfired agglomerated mineral with a crushing strength at room temperature of 7850 kN / m ² (corresponding to 80 kg / cm ² ) or more by curing for 7 days has been proposed (see Patent Document 1).

However, in the carbon-containing uncalcined agglomerated mineral as in Patent Document 1 above, in order to maintain the cold crushing strength of 85 kg / cm ² or more required as a blast furnace raw material, the carbon content ratio (TC) in all raw materials Must be limited to less than 15% by mass (corresponding to 1.2 in terms of carbon equivalent). Therefore, although direct reduction of iron oxide in coal-containing unfired agglomerated minerals has progressed, reduction of major blast furnace iron-containing raw materials such as sintered ore charged into the blast furnace in addition to coal-containing unfired agglomerated ore is reduced. It cannot be promoted sufficiently.

  Therefore, in obtaining the carbon-containing unfired agglomerated mineral, the particle size of all raw materials is set to 2 mm or less, and the blending ratio of the fine powdered carbon material is set so that the carbon content ratio (TC) in all the raw materials is 15 to 25 mass% A method for producing a blast furnace carbon-containing unfired agglomerated mineral that is adjusted and has a median diameter of pulverized carbonaceous material of 100 to 150 μm has been proposed (see Patent Document 2). According to the carbon-containing non-calcined agglomerated mineral obtained by this method, when used in a blast furnace, not only the carbon-containing non-calcined agglomerated mineral but also the reduction rate of other iron-containing raw materials such as sintered ore. It is possible to improve the ratio of reducing material during blast furnace operation.

  However, carbon-containing unfired agglomerated minerals have lower agglomerate strength immediately after molding than non-fired agglomerated minerals that do not contain carbon, and carbon is hydrophobic and porous. For this reason, the amount of added water necessary for maintaining the strength of the agglomerate also increases compared to the case where no carbon is contained. Therefore, as the carbon content increases, the moisture content in the carbon-containing unfired agglomerates to maintain cold crushing strength increases, and curing after forming into pellets (acceleration of cement hydration reaction) In addition, there is a problem that the time until the strength development in drying is prolonged.

  Thus, the carbon-containing unfired agglomerated mineral has a relatively low cold crushing strength and requires a relatively long curing time in order to develop the necessary strength. These tendencies become particularly prominent when the carbon content is increased as in Patent Document 2 described above. Then, when curing the agglomerate which shape | molded the mixing | blending raw material, the method of flowing steam and promoting a curing process is known (for example, refer patent documents 3 and 4).

  By the way, in the non-firing type agglomeration process as described above, generally, a raw material containing fine powdered iron, a fine powdered carbon material, a hydraulic binder or the like is cut out from a hopper or the like so as to have a predetermined blending amount. , Pulverize blended raw materials (or pulverize and blend each raw material in advance), knead while adjusting the amount of water using a kneader, for example, granulate with a granulator and sieve To obtain pellets (agglomerates).

  And the pellets obtained by granulation are cured so as to be strong as iron raw materials for blast furnaces. At that time, when piled up in the processing pit surrounded by the side wall and primary curing, the upper part of the processing pit The pellets are supplied by connecting a belt conveyor or the like to a feed cart that runs on a pedestal installed so as to straddle the stack, and the pellets are dropped from the feed cart into the processing pit and loaded. For example, the pellets are piled up in a processing pit having an area of about 26 m × 13 m at a height of about 3 to 5 m, covered with a heat insulating sheet such as a blue sheet, and subjected to primary curing for about 2 days. At this time, when curing by flowing steam, a steam ejection pipe is provided on the floor surface of the processing pit, and after stacking pellets and applying a heat insulating sheet, steam is directed upward from below the processing pit. Water and heat are applied from the lower layer to the upper layer of the blown-up and piled pellets (from the lower layer part to the upper layer part of the mountain). After the primary curing, the treated pellets are discharged from the processing pits, taken out to the raw material yard (secondary curing yard), left in the atmosphere for about 8 to 12 days, and then subjected to secondary curing, and a carbon-containing carbon that has developed strength. An unfired agglomerated mineral is obtained.

  However, when agglomerates such as pellets are piled up for primary curing, the strength (cold strength) varies between the lower layer and the upper layer of the mountain. If there is a variation in strength in the agglomerate after the primary curing, the agglomerate with insufficient curing will be pulverized during the transshipment work for the secondary curing, or the carbon-containing unburned lump after the secondary curing. The yield of the ore is reduced.

  Regarding the presence of low-strength agglomerates, increasing the blending amount of hydraulic binders such as cement increases the amount of slag generated when the obtained carbon-containing unfired agglomerated ore is used in a blast furnace. The dehydration endotherm of the hydraulic binder in the blast furnace becomes obvious, and adverse effects such as the reduction effect of the reducing material ratio being impaired are caused. Further, if the pile height of the agglomerates is lowered in order to suppress variation, a correspondingly large processing pit area is required, and work efficiency is deteriorated.

  Therefore, for such a problem of variation, for example, the amount of binder added is increased in the lower layer portion of the pile where the agglomerates are piled up, and the amount of hydraulic binder added is decreased in the upper layer portion of the mountain. A method for reducing the variation has been proposed (see Patent Document 5). Moreover, the method of suppressing dispersion | variation is also known by mounting a raw pellet on a mountain-shaped inclined surface and curing (refer patent document 6). However, in the former method, the composition of the agglomerate must be adjusted according to the timing of loading, and in the latter method, it is necessary to configure a special apparatus and the agglomerate deposition. Since the thickness of the layer is smaller than in the case of stacking, the productivity is lowered, and there is room for examination in terms of workability and cost in either method.

JP 2003-342646 A JP 2008-95177 A JP 2001-348624 A JP 2009-161791 A JP-A-6-145824 JP 2013-79433 A

  Therefore, as a result of earnestly examining the variation in strength when the piled agglomerates are primarily cured in the non-fired agglomeration process as described above, the present inventors have found the agglomerates from above the processing pits. In the middle of stacking while dropping and stacking, by injecting steam from the steam jet pipe and starting the heating of the agglomerate, the dispersion of the strength of the agglomerate in the upper and lower parts of the mountain is reduced. The present invention has been completed by finding out that it is possible.

  Therefore, the object of the present invention is to reduce the variation in strength of the agglomerates between the upper layer and the lower layer of the pile when the piled agglomerates are primarily cured, and to provide a stable quality carbon-containing unfired agglomerated ore. Is to provide a method for producing a coal-containing non-fired agglomerated blast furnace ore that can be obtained simply and at low cost.

That is, the gist of the present invention is as follows.
(1) The agglomerate formed after adjusting the water content of the compounded raw material containing finely divided iron-containing raw material, finely divided carbonaceous material, and hydraulic binder is piled up in a processing pit surrounded by side walls, A method for producing a coal-containing non-fired agglomerated blast furnace for a blast furnace, including a step of first curing the agglomerate while covering and heating a predetermined amount of steam from the floor of the treatment pit, The blast furnace carbon-containing non-fired ingot is characterized by injecting steam from the floor of the treatment pit and starting the heating of the agglomerate while the agglomerate is charged and stacked from above Method for producing ore.
(2) With respect to the pile height H of the agglomerate piled up in the processing pit, the stacking height h of the agglomerate is 50 to 70% (0.5H ≦ h ≦ 0.7H). The method for producing a carbon-containing non-fired agglomerated blast furnace for blast furnace according to (1), wherein heating of the agglomerate is started by injecting steam from the floor surface.
(3) The method for producing a carbon-containing non-fired agglomerated blast furnace for blast furnace according to (1) or (2), wherein the pile height H of the agglomerate piled in the treatment pit is 3 to 5 m.
(4) The method for producing a carbon-containing unfired agglomerated blast furnace for a blast furnace according to any one of (1) to (3), wherein a carbon content ratio (TC) in the blended raw material is 15 to 25% by mass.
(5) The method for producing a carbon-containing non-fired agglomerated blast furnace for blast furnace according to any one of (1) to (4), wherein the time for curing by jetting steam in the primary curing is 15 to 30 hours.
(6) The method for producing a carbon-containing non-fired agglomerated blast furnace for a blast furnace according to any one of (1) to (5), wherein the amount of steam used in the primary curing is 13 to 17 tons per ton of agglomerates.

  ADVANTAGE OF THE INVENTION According to this invention, when the agglomerate piled up in the non-baking type | mold agglomeration process is primary-cured, the dispersion | variation in the intensity | strength of the agglomerate in the upper layer part of a pile and a lower layer part can be reduced. Therefore, a stable quality carbon-containing non-fired agglomerated ore can be obtained easily and at low cost.

FIG. 1 is a schematic explanatory view showing an example of a curing treatment apparatus that primarily cures agglomerates. Fig.2 (a) is a graph which shows the relationship between carbon (carbon) content and crushing strength of a carbon-containing non-baking agglomerated ore, and FIG.2 (b) is the pellet (aggregate) before curing. It is a graph which shows the relationship between the additional water content required for intensity | strength maintenance, and carbon content. FIG. 3 is a schematic diagram showing the location of a mountain where the temperature history and the strength of the pellets were measured in the primary curing of the following production experiment I. FIG. 4 is a graph showing a temperature history in the primary curing of the following production experiment I, where (a) shows curing conditions 1, (b) shows curing conditions 2, and (c) shows curing conditions 3. FIG. FIG. 5 is a graph showing the relationship between peak height and pellet strength due to the difference in primary curing of the following production experiment I, (a) shows the average strength of pellets in each layer of the height of the mountain, (b) Indicates the percentage of low-strength products in the pellets in each layer at the height of the mountain.

The present invention will be described in detail below.
In the method for producing a carbon-containing unfired agglomerated ore for a blast furnace according to the present invention, after the moisture content of a blended raw material containing a finely divided iron-containing raw material, a finely powdered carbonaceous material, and a hydraulic binder is formed into an agglomerated material. In the processing pit, when piled up in the processing pit surrounded by the side wall and covered with a heat insulating sheet, the agglomerates are primarily cured while being heated by spraying a predetermined amount of steam from the floor surface of the processing pit. In the middle of stacking while agglomerates are loaded and stacked from above, steam is injected from the floor of the treatment pit to start heating the agglomerates.

  In general, when agglomerates piled up in a non-baking type agglomeration process are primarily cured, the temperature of the agglomerates becomes about 40 to 60 ° C. due to the hydration reaction (exothermic reaction) of the hydraulic binder. At this time, the agglomerate at the position corresponding to the lower layer of the mountain loses heat to the floor surface of the processing pit, whereas the agglomerate at the position corresponding to the upper layer of the mountain has its own heat generation and is transmitted from the lower layer side. Since it is preheated by heat, a temperature difference occurs in the agglomerate between the lower layer portion and the upper layer portion. This is the same even when heating by injecting steam from the floor surface of the processing pit, and the upper layer side becomes higher than the lower layer part due to heat transfer from the lower layer part side, so the upper layer part of the mountain It is considered that the strength of the agglomerates in the lower layer part varies.

  In addition, in actual production, it takes about 24 hours from the start of stacking of the agglomerate into the processing pit to the completion of the stacking. This is different from the case of slag steam aging in which slag stored in the yard is collected into a processing pit by heavy machinery, and in the production of coal-free unfired agglomerated ore for blast furnaces, it is obtained by blending and molding raw materials. This is because the agglomerates thus formed are sequentially loaded from above the processing pits and stacked. For this reason, there is a difference in the curing time between the agglomerate located in the lower part of the mountain and the agglomerate located in the upper part, and it is considered that this may cause variations in the strength of the agglomerate.

  In general, when obtaining a carbon-containing unfired agglomerate, when agglomerates are piled up in treatment pits for primary curing, blended raw materials such as pulverized iron-containing materials, pulverized carbon materials, hydraulic binders, etc. are specified. Cut out from the hopper so that the blended amount becomes, pulverized with a pulverizer such as a ball mill, and kneaded using a kneader such as a Redige mixer or Eirich mixer while adjusting the moisture content (moisture content) Is about 9 to 14% by mass). Then, for example, it is granulated with a granulator such as a pan pelletizer, and further sieved with a vibration sieve or the like to obtain granulated pellets (as agglomerates). At this time, after pulverizing each raw material which comprises a mixing | blending raw material, it is good also as a mixing | blending raw material. Also, instead of granulating the kneaded blended raw material with a granulator into an agglomerate, for example, briquetting with a compression molding machine or extrusion molding with an extrusion molding machine, etc. An agglomerate may be obtained.

  Then, for example, as shown in FIG. 1, the agglomerates obtained in the processing pits 1 surrounded by the side walls are piled up. That is, in this example, a processing pit 1 is formed in a building 10 with a roof surrounded by three sides by a side wall 2 made of a concrete retaining wall or the like, and the mount 3 is installed so as to straddle the processing pit 1. ing. Further, the gantry 3 can move the processing pit 1 in the lateral width direction (x direction) along the rail provided on the upper end surface of the side wall 2 (in the example of FIG. 1, one end of the gantry 3 is the wall of the building 10). The mine cart (loader) 4 is loaded on the gantry 3, and the mine cart 4 moves in the depth direction (y direction) of the processing pit 1. be able to. In addition, the agglomerate produced by connecting the belt conveyor 5 is supplied to the feed cart 4, and the agglomerate is formed from above the processing pit 1 by the movement of the gantry 3 and the feed cart 4. The agglomerate piles 6 are formed by stacking the agglomerates in the processing pit.

  Here, in the conventional method, after the agglomerates are piled up in the treatment pit 1 of the curing treatment apparatus as shown in FIG. 1, the agglomeration is performed using the hoist type crane 7 installed on the ceiling of the building 10. The pile 6 is covered with a heat insulating sheet 8 such as a blue sheet, and steam is injected from a vapor jet pipe 9 provided on the floor surface of the treatment pit 1, so that the lower portion of the pile 6 of agglomerated piles Water and heat are applied from the top to the upper layer portion to promote the hydration reaction of the hydraulic binder to express the strength of the agglomerate (hereinafter referred to as “conventional method”). This is to eliminate the waste of steam injected from the steam jet pipe 9, and after covering the pile 6 of the agglomerate with the heat insulating sheet 8, steam is sent from the steam jet pipe 9 on the floor surface of the processing pit 1. It has been thought that by injecting the heat and moisture from the steam as much as possible, the curing of the agglomerates can be promoted more efficiently.

  However, as a result of repeated trial and error by the present inventors, steam injection was started from the steam discharge pipe in the middle of stacking the agglomerates, and the remaining agglomerates were stacked while injecting steam. When the process is completed and covered with a heat insulating sheet, surprisingly, the strength variation of the agglomerates in the upper and lower layers of the mountain is suppressed compared to the conventional method, and the amount of steam used is reduced. Even if it is the same as in the case of the conventional method (that is, in the case of the present invention, the steam is not covered with the heat insulating sheet while the remaining agglomerates are stacked after the start of the jet of steam. It was found that the average strength of the agglomerates obtained after the primary curing (average of the primary cured mountains) is higher than that of the conventional method. One reason for this is considered to be that the strength of the agglomerates located in the lower part of the mountain is improved and the difference in strength from the upper part is eliminated.

  Preferably, the agglomerate stacking height h is 50 to 70% (0.5H ≦ h ≦ 0.7H) with respect to the pile height H of the agglomerate piled in the processing pit. It is preferable to start heating the agglomerates by injecting steam from a steam outlet pipe or the like installed on the floor of the pit. If the steam injection timing is outside this range, the average strength of the agglomerate obtained after primary curing (average of the primary cured mountain) may be the same as or lower than the conventional method. In some cases, variations in the strength of the agglomerates between the upper layer portion and the lower layer portion of the mountain cannot be sufficiently suppressed.

  Of course, it is also possible to improve the strength of the agglomerate located in the lower part of the mountain by starting the jet of steam from the floor surface of the processing pit at an earlier timing, such as simultaneously with the agglomerate loading. However, it is not practical to use steam that is relatively expensive to manufacture, and if the amount of steam increases too much, the agglomerate swells due to the influence of coagulated water, rather the agglomerate. There is a risk that the strength of the material decreases and the variation becomes large. Therefore, in the present invention, considering the use of a predetermined amount of steam as in the conventional method, it is advantageous in terms of cost balance to set the timing as described above.

  Here, FIG. 2 (a) shows the effectiveness of steam curing in obtaining a carbon-containing unfired agglomerated ore. In general, when there is no steam, the strength (crushing strength) of the carbon-containing non-fired agglomerate decreases linearly as the carbon (carbon) content increases. There are two possible causes for this. One is that the carbonaceous material is porous, and a hydraulic binder such as cement is trapped in the pores, so that it does not work effectively for bonding. The other is that the charcoal material is hydrophobic and porous, so the amount of water added to maintain the strength of the agglomerates such as pellets is higher than when no charcoal material is contained. This is because the variation in the product (carbon-containing unfired agglomerated mineral) is promoted due to the moisture variation between the agglomerates. Therefore, when steam curing is performed, not only the cement hydration reaction is promoted, but also the variation in moisture is eliminated and the average product strength is improved. The effect is more prominent for agglomerates with a higher carbon content. However, even if steam curing is performed, since the carbonaceous material is porous, the hydraulic binder is trapped in the pores, does not work effectively for bonding, and the adverse effect is not eliminated, and there is an upper limit on the carbon content. If the carbon content is 15 to 25%, it is possible to produce an agglomerate having a predetermined strength that can withstand the use of a blast furnace while maximizing the effect of steam curing. FIG. 2B shows the relationship between the amount of added water and the carbon content necessary for maintaining the strength of the pellet (agglomerated material).

The strength required for the blast furnace carbon-containing uncalcined agglomerated minerals is required not to collapse at the time of transportation and charging to the blast furnace, and varies depending on the method of transportation and charging, but is generally 85 kg / cm. A strength of about ² or more is required. In general, the crushing strength of a carbon-containing unfired agglomerated ore according to JIS M8718 “Iron Ore Pellet Crushing Strength Test Method” is obtained by applying a compressive load to a measured sample at a specified pressure rate. The load value at the time of destruction is measured, and the load value per unit cross-sectional area (kg / cm ² ) is usually used as the strength index. Further, instead of this strength index, the load value itself (kg / Piece) for one measured sample may be expressed as the strength index for convenience. Incidentally, the cold crushing strength of pellets produced by firing is generally about 150 kg / cm ² .

In the present invention, there is no particular limitation other than the timing of jetting steam, and it can be the same as a known method for obtaining a carbon-containing unfired agglomerated ore.
For example, the blended raw material of the carbon-containing non-fired agglomerated mineral is not particularly limited as long as it contains a finely divided iron-containing raw material, a finely powdered carbonaceous material, and a hydraulic binder, and known materials can be used. Especially, as described in Patent Document 2, if a blended raw material having a carbon content ratio (TC) in the total raw material of 15 to 25% by mass is used, the reduction ratio of the reducing material during blast furnace operation can be reduced. it can. In the case of a blended raw material having a high carbon content as described above, it is generally difficult to develop strength, but by using the method of the present invention, a carbon-containing unfired agglomerated mineral that can reduce the reducing material ratio is obtained. It becomes possible to stably supply quality while suppressing variations in quality. In addition, there is no restriction | limiting in particular also about the means for obtaining an agglomerate from a mixing | blending raw material, and its procedure, A well-known method as mentioned above can be used.

  Here, the pulverized iron-containing raw material is one in which fine powder particles having a particle size of 0.25 mm or less occupy 80% or more of the whole. For example, iron-containing dust such as sintered dust and blast furnace dust generated in the iron making process is used. First, fine powdered iron ore used as pellet feed (raw material for pellets), or powdered iron ore previously pulverized with a crusher can be used. In addition, examples of the fine powdery carbon material include blast furnace primary ash, coke dust, powder coke, coal, and the like. Among them, a fine powdery carbon material having a mass-based median diameter (d50) of 100 to 150 μm. It is good. Furthermore, examples of the hydraulic binder include an aging binder composed of fine powder mainly composed of blast furnace granulated slag and an alkali stimulant, Portland cement, bentonite, quicklime, and the like.

  In addition, as for the treatment pit used for primary curing, conventional ones used for steam curing of steelmaking slag can be used as they are, and agglomeration is carried out in the same manner as the conventional method. Can do. At this time, the pile height H of the agglomerate piled in the processing pit is generally 3 to 5 m, and the same applies to the present invention. If it is too high, the agglomerate may collapse due to the load, and if it is too low, the work efficiency may be reduced.

  In the present invention, the injection of steam from the floor surface of the processing pit is started after the agglomerate is stacked in the processing pit until the stacking is completed, and the stacking is completed by injecting steam in a certain time. Place a heat insulation sheet at the place. Here, the time for injecting the steam can be the same as in the conventional method, and in particular, when using a blended raw material having a carbon content ratio (TC) in the total raw material of 15 to 25% by mass, Is 15 to 30 hours, and the amount of steam used at that time is 13 to 17 tons per ton of agglomerates.

  Further, in the present invention, similarly to the conventional method, the primary curing is continued with the heat-insulating sheet covered even after the injection of the predetermined amount of steam is finished. Specifically, it is preferable to continue the curing for about 42 to 50 hours after covering the piled agglomerates with a heat insulating sheet. That is, the primary curing time after starting the agglomeration stacking is about 64 to 74 hours. After the primary curing is completed, the agglomerates are taken out from the processing pits and sieved using a vibrating sieve if necessary, and then loaded into the raw material yard (secondary curing yard) to the atmosphere. Then, secondary curing is carried out for about 5 to 8 days, and a carbon-containing non-fired agglomerated mineral that exhibits strength as an iron raw material for blast furnace can be obtained.

  The present invention will be specifically described based on examples. The present invention is not limited to these contents.

(Production Experiment I)
While adjusting the blending ratio so that the carbon content (TC) in the total raw material becomes 20% by mass to the fine iron-containing raw material consisting of sintered dust and fine iron ore, In addition, Portland cement is added as a hydraulic binder, pulverized with a ball mill so that the maximum particle size of these blended raw materials is 2 mm or less, and then the water content is 12% by mass. The pellets having an average particle diameter of 14 mm were produced by granulation using a pan pelletizer while adjusting the pressure to be. In addition, the manufacturing capacity of the pellet at this time is about 60 t / hour.

  While producing pellets as described above, the pellets are stacked in the treatment pit 1 using the curing treatment device shown in FIG. 1, and the primary curing is performed according to the following curing conditions 1 to 3, Then, the manufacturing experiment (Comparative Examples 1-2, this invention 1) which carries out secondary curing was performed. Here, the processing pit 1 is surrounded on three sides by a side wall 2 made of a concrete retaining wall having a height of 4 m, and has an area of 26 m width × 13 m depth. Then, the pedestal 3 and the feed trolley (loading machine) 4 installed above the processing pit 1 are driven to throw in the pellets for loading, and the height (26 m in the width direction, 13 m in the depth direction, height ( H) A pile 6 of 4 m pellets was piled up. At this time, it took 24 hours (from the start to the end of the stacking) to complete the stacking.

First, as curing condition 1 according to Comparative Example 1, when the stacking of pellets was completed, a resin-made blue sheet (heat insulating sheet) 8 was covered so as to cover all of the pellets 6 and spraying of water vapor was performed at all. Without curing, it was cured until 48 hours had passed since the sheeting of the blue sheet.
Further, as curing condition 2 according to Comparative Example 2, as in curing condition 1, after completion of the stacking of pellets, the resin blue sheet 8 is covered and steam is discharged from the steam ejection pipe 9 installed on the floor surface of the processing pit 1. The water vapor was stopped after 24 hours had elapsed from the injection, and was cured until 48 hours had passed since the blue sheet was hung.
On the other hand, as curing condition 3 according to the present invention 1, when the stacking height (h) of the pellets reaches 2 m during the stacking (12 hours from the start of the stacking), steam is injected from the steam discharge pipe 9. When the stacking of pellets was completed (the height of the peak was 4 m), the blue sheet 8 was put on when the stacking of the pellets was completed, and the steam was stopped when 24 hours had elapsed from the injection, Cured until time passed.

  Then, each pellet that has finished primary curing under these conditions is discharged with a shovel loader, transported to the yard with a dumper, loaded again into the yard via a stacker, and subjected to secondary curing for 8 days. Comparative Example 1 (curing condition 1 (primary curing), secondary curing), Comparative Example 2 (curing condition 2 (same), secondary curing), Invention 1 (curing condition 3 (same), secondary curing) The carbon-containing unfired agglomerated minerals according to each production experiment were obtained. The amount of water vapor used under curing conditions 2 and 3 is 15 tons per ton of pellets (water vapor consumption of 15 tons / ton product).

  During the primary curing in each of these production experiments, as shown in FIG. 3, temperature measurement was performed at different heights of the piles of the stacked pellets. In the measurement, the height h = 80 cm (layer height ratio h / H = 0.2), h = 200 cm (layer height ratio h / H = 0.5) at the substantially central position in both the width direction and the depth direction of the pellet peak 6. Three temperature histories at h = 320 cm (layer height ratio h / H = 0.8) were measured. The results are shown in FIG.

Regarding “curing condition 1 without using steam” shown in FIG. 4 (a), the temperature exceeds 65 ° C. around 50 hours from the start of stacking (start of curing) in the upper layer of the mountain with a layer height ratio of 0.8. After that, it descended slightly and finally reached about 60 ° C. In the middle part of the mountain with a layer height ratio of 0.5, the temperature rose to 60 ° C. around 36 hours from the start of curing, then dropped, and finally reached about 52 ° C. In addition, in the lower layer part of the mountain having a layer height ratio of 0.2, the temperature rose to 55 ° C. around 24 hours after the start of curing, but continued to fall after the sheet was hung, and finally reached 45 ° C. .
Further, in “curing condition 2 for injecting water vapor after stacking” shown in FIG. 4B, the water vapor is injected into both the upper layer of the mountain having a layer height ratio of 0.8 and the middle layer of the mountain having a layer height ratio of 0.5. The temperature rose in the upper part of the mountain, reaching a maximum of 85 ° C. (42 hours after the start of curing) and a maximum of 72 ° C. (after 48 hours). On the other hand, in the lower layer portion of the mountain having a layer height ratio of 0.2, the temperature was maintained at about 55 ° C. during the water vapor injection, but after that it descended to finally reach 50 ° C., and at the end of curing, the lower layer of the mountain A large temperature difference of 50 to 75 ° C. was formed between the upper part and the upper layer part, and the temperature difference widened as compared with the case of curing condition 1 (45 to 60 ° C.) without using water vapor.

On the other hand, in “curing condition 3 for injecting water vapor in the middle of stacking” shown in FIG. 4C, the temperature rise in the middle layer (maximum 72 ° C.) and upper layer (maximum 80 ° C.) of the mountain Although the temperature is lower than in curing condition 2 ″, the time during which the temperature of the lower layer of the mountain is maintained at 55 ° C. is extended, and at the end of curing, the temperature difference between the lower and upper layers of the mountain (50 to 70 ° C.) was reduced compared to “curing condition 2”.
Note that the outside air temperature was 20 ° C. under any of these curing conditions. The temperature rise immediately after the pellets are stacked is due to cement hydration (exothermic reaction).

Therefore, for the pellets of each production experiment obtained by secondary curing after curing conditions 1 to 3 as described above (carbon-containing unfired agglomerated ore), the crushing strength for each position of the mountain height in the primary curing Was measured. Here, pellets located in the lower layer (layer height ratio h / H = 0.2), middle layer (layer height ratio h / H = 0.5), and upper layer (layer height ratio h / H = 0.8) during primary curing 100 were selected at random, the crushing strength was measured for these 100 samples (pellets), and the average value was determined for each curing condition. The result is as shown in FIG. Moreover, the ratio of the sample from which crushing strength becomes 50 kg / cm < ² > or less was calculated | required among 100 samples selected for every position of the height of a peak above. The result is as shown in FIG. The crushing strength is measured by applying a compressive load at a specified pressure rate to one sample to be measured according to JIS M8718 “Iron ore pellet crushing strength test method”. The load value per unit cross-sectional area (kg / cm ² ) was taken as the crushing strength.

As shown in FIG. 5 (a), as compared with Comparative Example 1 that was primarily cured under curing condition 1 that does not use steam, Comparative Example 2 that was primarily cured under curing condition 2 and curing condition 3 that use steam. In the case of the present invention 1, the crushing strength of the pellets was high throughout the lower layer portion, middle layer portion, and upper layer portion of the mountain. At that time, in Comparative Example 1 where the primary curing was performed under the curing condition 1, the difference in strength between the pellet located in the upper layer part of the mountain and the pellet located in the lower layer part was approximately 75 kg / cm ² (150-75 = 75 kg / cm ² ). There is also 100 kg / cm ² (180-80 = 100 kg / cm ² ) in Comparative Example 2 where the primary curing was performed under the curing condition 2, whereas in the present invention 1 where the primary curing was performed under the curing condition 3, the upper layer of the mountain The difference in strength between the pellets located in the lower part and the pellets located in the lower part is approximately 60 kg / cm ² (170-110 = 60 kg / cm ² ), and the quality difference of the mountain in the primary curing compared to Comparative Examples 1 and 2 Was relaxed. Moreover, according to FIG.5 (b), especially the ratio which the pellet located in the lower layer part of a mountain | pipe has insufficient intensity | strength is reduced significantly (in Comparative Example 1, it is 30% and Comparative Example 2 is 25%) On the other hand, 15% in the present invention 1), it was found that homogenization was achieved when the entire mountain was made into a carbon-containing unfired agglomerated ore. In addition, the pellet finally obtained by this invention 1 (carbon-containing non-baking agglomerated ore) is the whole which totaled each 100 samples of the lower layer part of the mountain in the case of primary curing, an intermediate | middle layer part, and the upper layer part. The average crushing strength was 130 kg / cm ² , and among these total samples, the proportion of samples with a crushing strength of 50 kg / cm ² or less was 7.8%.

(Production Experiment II)
Timing of starting the injection of steam (stacking layer height ratio at the start of steam), amount of steam used per ton of pellets (steam intensity), time to spray steam (steam curing time), and stacking height of pellets Was changed as shown in Table 1, and the primary curing was performed, and the carbon-containing unfired agglomerated minerals according to the present invention 2 to 16 were obtained in the same manner as in Production Experiment I. And about each obtained carbon-containing unbaking agglomerated ore, the average crushing strength (average product crushing strength) and the ratio of crushing strength 50 g / cm < ² > or less were calculated | required similarly to the manufacture experiment I. The results are as shown in Table 1, and the present inventions 1 to 16 were all intended to homogenize the crushing strength of the entire mountain compared to Comparative Example 1 and Comparative Example 2, but the conditions for primary curing The following considerations can be made from the viewpoint of optimizing the above.

First, the timing at which the steam is injected can be compared in the present inventions 1 to 5, and the pellet stacking height h is 0.6 relative to the pellet stacking height H (layer height ratio 0.6). ) (Invention 3), the obtained carbon-containing unfired agglomerated mineral had the highest average crushing strength, and the ratio of crushing strength of 50 g / cm ² or less was the smallest. In other words, there is a possibility that the strength expression of the middle and upper layers of the mountain will be insufficient if the steam ejection timing is advanced, and that the strength expression of the lower layer of the mountain may be insufficient if the steam ejection timing is delayed. It is done.

Further, the amount of water vapor used can be compared and examined in the present inventions 1 and 6 to 9, and the case of the present invention 1 is the most effective. If the amount of steam is small, the overall strength expression may be insufficient. On the other hand, if the amount of steam is excessively large, the pellets may swell and the strength may decrease.
Further, the steam curing time can be compared in the present inventions 1 and 10 to 13, and the case of the present invention 1 is the most effective. Here, since the amount of water vapor used is the same (15t / t product), if the steam curing time is shortened, the amount of steam per unit time will be excessive, and excessive pellets may cause swelling of the pellets. It is done. On the other hand, if the steam curing time becomes too long, the amount of steam per unit time decreases, and it is considered that the effect of the present invention is limited.
Furthermore, the stacking height when stacking the pellets can be compared in the present inventions 1 and 14 to 16, and the present invention 1 is the most effective. If the stacking height is too low, the effect of the present invention may be limited. In addition, when the stacking height becomes too high, the pellet may collapse due to the stacking load as described above.

  As described above, according to the present invention, when primary agglomerates such as pellets piled up in the non-fired agglomeration process are primarily cured, the variation in strength in the stacking height direction is reduced, and the average strength is reduced. improves. Therefore, it becomes possible to obtain a carbon-containing unfired agglomerated mineral with stable quality. In addition, according to the present invention, it becomes possible to stably supply a carbon-containing non-calcined agglomerated ore with a high carbon content ratio while suppressing variation in quality. It is advantageous in planning. Furthermore, it is possible to ease the management of the agglomerate strength index in the primary curing, and to reduce the amount of hydraulic binder used such as cement. You can get it at a cost.

1: treatment pit, 2: side wall, 3: mount, 4: feed cart (loading machine), 5: belt conveyor, 6: pile of agglomerates, 7: hoist crane, 8: heat insulation sheet, 9: Steam ejection pipe, 10: building.

Claims (6)

  The agglomerate formed after adjusting the moisture content of the finely divided iron-containing raw material, the finely powdered carbonaceous material, and the blended raw material containing the hydraulic binder is piled up in the processing pit surrounded by the side wall, and covered with a heat insulating sheet, A method for producing a coal-containing unfired agglomerated blast furnace for a blast furnace, which includes a step of primary curing of the agglomerate while injecting a predetermined amount of steam from the floor surface of the treatment pit and heating. The blast furnace carbon-containing uncalcined agglomerated ore is characterized by injecting steam from the floor of the processing pit and starting the agglomerate heating while the agglomerates are being loaded and stacked. Production method.   From the floor of the processing pit at a timing when the stacking height h of the agglomerate is 50 to 70% (0.5H ≦ h ≦ 0.7H) with respect to the pile height H of the agglomerate piled in the processing pit. The method for producing a carbon-containing unfired agglomerated blast furnace according to claim 1, wherein heating of the agglomerate is started by jetting steam.   The method for producing a carbon-containing non-fired agglomerated blast furnace for blast furnace according to claim 1 or 2, wherein a pile height H of the agglomerate piled in the treatment pit is 3 to 5 m.   The carbon content rate (T.C) in the said compounding raw material is 15-25 mass%, The manufacturing method of the carbon-containing unbaking agglomerated mineral for blast furnaces in any one of Claims 1-3.   The method for producing a coal-containing unfired agglomerated blast furnace for a blast furnace according to any one of claims 1 to 4, wherein a time for curing by jetting steam in the primary curing is 15 to 30 hours. The method for producing a carbon-containing unfired agglomerated blast furnace according to any one of claims 1 to 5, wherein the amount of steam used in the primary curing is 13 to 17 tons per ton of agglomerates.

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