JP6680167B2 - Method for producing coal-free uncalcined agglomerated ore for blast furnace - Google Patents

Description

  The present invention relates to a method for producing a coal-containing non-calcined agglomerated ore for a blast furnace, in which agglomerates formed by adjusting the water content of a raw material mixture are piled up in a processing pit, and steam is generated from the floor surface of the processing pit. The present invention relates to a method for producing a coal-containing non-calcined agglomerated ore for a blast furnace by first curing an agglomerate while injecting and heating.

  The iron raw material for the blast furnace in the current iron making process mainly uses powdered iron ore with an average particle size of about 2 to 3 mm as an iron-containing raw material. And are mixed together while adjusting the water content, and granulated to form pseudo-granulated particles (granulated product in which fine powder particles of 0.5 mm or less are attached to the surface of core particles of 1 mm or more), and then using a sintering machine. Sintered ore sinters dominate the mainstream.

  On the other hand, in addition to iron-containing dust collected by a dust collector that collects a large amount of sintering dust, blast furnace dust, etc. generated in the iron-making process, fine dust such as sludge and scale powder (these are generally called iron-making dust), and pellet feed. Finely powdered iron ore such as (raw material for pellets) is also used as an iron raw material for a blast furnace by agglomerating. Since these are fine-powdered iron-containing raw materials in which fine powder particles having a particle diameter of 0.25 mm or less account for 80% or more of the whole, they are granulated by the above-described sinter ore process, and when granulated, they are granulated. The material collapses, the air permeability of the raw material packed layer deteriorates, and the productivity decreases.

  Therefore, when agglomerated by firing such a finely powdered raw material as a main iron-containing raw material, a higher mixing / granulating function than that of the above-mentioned sinter process is required. After adding and mixing water to the raw material and the auxiliary raw material, further using a granulating machine such as a disc pelletizer having a higher granulating ability than a drum mixer, mainly fine powder particles having a particle diameter of 0.25 mm or less Spherical pellets are manufactured. Further, since such a pellet is a granulated material having a higher density than pseudo-granulated particles in the sintering process, when firing the pellet, an external heating type firing machine using combustion gas as a heat source is used. Since it is used, enormous manufacturing energy and manufacturing cost are required.

  On the other hand, a fine powdery iron-containing raw material in which fine powder particles having a particle diameter of 0.25 mm or less occupy 80% or more of the whole is agglomerated such as pellets by granulating by adding water together with a binder (binder) such as cement. It has been used for a long time as a raw material for iron for a blast furnace by using a non-calcining type agglomeration process in which the agglomerated ore is obtained by curing after being molded into an agglomerate.

  According to such a non-fired agglomeration process, it becomes possible to add a large amount of carbonaceous material into the agglomerated ore, which is not possible in a fired agglomeration process such as obtaining sintered ore or fired pellets. Therefore, in recent years, for the purpose of reducing the reducing material ratio during the operation of the blast furnace, a method for producing a carbon-containing non-calcined agglomerated ore utilizing this process has been studied.

For example, iron ore, or iron-containing iron oxide raw material consisting of various types of iron-containing, carbon-containing dust collected in iron mills, the theory necessary for reducing oxygen to be reduced of iron ores to metallic iron After mixing carbon-based carbonaceous material corresponding to the carbon content of 80 to 120% of the carbon content (C content in all raw materials: about 10 to 15 mass%), kneading and molding by adding early strength Portland cement , A method for producing a carbon-containing non-calcined agglomerate having a crushing strength at room temperature of 7850 kN / m ² (corresponding to 80 kg / cm ² ) or more by curing for 7 days (see Patent Document 1).

However, in the carbon-containing non-calcined agglomerated ore as disclosed in Patent Document 1, in order to maintain the cold crushing strength of 85 kg / cm ² or more required as a raw material for the blast furnace, the carbon content ratio (TC) in the total raw material Had to be limited to less than 15% by mass (corresponding to 1.2 in terms of carbon equivalent). Therefore, even if direct reduction of iron oxide in coal-containing non-calcined agglomerates proceeds, reduction of major iron-containing raw materials for blast furnaces such as sinter ore charged into blast furnaces other than carbon-containing non-calcined agglomerated ores It cannot be promoted enough.

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

  However, the non-calcined agglomerated ore containing carbon has a lower agglomerate strength immediately after forming as compared with the non-calcined agglomerated ore containing no carbon, and the carbon is hydrophobic and porous. Therefore, the amount of added water required to maintain the strength of the agglomerate becomes larger than that in the case where carbon is not contained. Therefore, as the carbon content increases, the water content in the coal-containing non-calcined agglomerated ore for maintaining the cold crushing strength increases, and curing after molding into pellets (acceleration of hydration reaction of cement And drying), there is a problem that it takes a long time to develop strength.

  As described above, the coal-containing non-calcined agglomerated ore has a relatively low cold crushing strength and requires a relatively long curing time in order to develop the required strength. These tendencies become more remarkable especially when the carbon content ratio is increased as in Patent Document 2. Therefore, when curing an agglomerate obtained by molding a blended raw material, a method of flowing steam to accelerate the curing treatment is known (see, for example, Patent Documents 3 and 4).

  By the way, in the non-firing type agglomeration process as described above, generally, the finely powdered iron-containing raw material, the finely powdered carbonaceous material, and the blended raw materials such as the hydraulic binder are cut out from the hopper or the like so that each has a predetermined blending amount. , The compounded raw materials are crushed (or each raw material is crushed and compounded in advance) and kneaded while adjusting the water content using a kneader, for example, granulated by a granulator and sieved , Pellets (agglomerates) are obtained.

  Then, the pellets obtained by granulation are cured so as to have the strength as the iron raw material for the blast furnace. At that time, when piled up in the processing pit surrounded by the side wall for primary curing, the upper part of the processing pit is used. Pellets are supplied by connecting a belt conveyor or the like to a feed truck that runs on a pedestal installed so as to straddle the pellets, and the pellets are dropped from the feed truck into the processing pit for loading while loading. For example, 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 primary curing is performed for about 2 days. At this time, when steaming is used for curing, a steam jetting pipe is provided on the floor surface of the processing pit, piles of pellets are placed on the heat insulating sheet, and then steam is directed upward from below the processing pit. Water and heat are applied from the lower layer to the upper layer of the piled pellets (from the lower layer to the upper layer of the pile). After the primary curing, the treated pellets are discharged from the processing pit, carried out to the raw material yard (secondary curing yard) and left in the atmosphere for about 8 to 12 days to carry out the secondary curing. An unfired agglomerated ore is obtained.

  However, when agglomerates such as pellets are piled up for primary curing, the strength (cold strength) varies between the lower and upper layers of the mountain. If the agglomerates after primary curing have variations in strength, the agglomerates with insufficient curing will be pulverized during the transshipment work for secondary curing, or non-fired coal-containing agglomerates after secondary curing. The yield of the ore will decrease.

  Regarding the inclusion of low-strength agglomerates, increasing the blending amount of hydraulic binder such as cement increases the amount of slag generated when the obtained coal-containing uncalcined agglomerates are used in a blast furnace. However, the dehydration endotherm of the hydraulic binder in the blast furnace becomes apparent, which causes adverse effects such as impairing the reducing agent ratio reducing effect. Further, if the pile height of the agglomerates is reduced in order to suppress the variation, a correspondingly large processing pit area is required and the work efficiency is deteriorated.

  Therefore, with respect to such a problem of variation, for example, the binder addition amount is increased in the lower layer portion of the pile of agglomerates and the hydraulic binder is reduced in the upper layer portion of the pile to improve the strength. A method for reducing variations has been proposed (see Patent Document 5). In addition, a method is also known in which raw pellets are placed on a mountain-shaped inclined surface and cured to suppress variations (see Patent Document 6). However, in the former method, the agglomeration of the agglomerate must be adjusted according to the timing of packing, and in the latter method, it is necessary to configure a special device and the agglomeration of the agglomerate. Since the layer thickness is smaller than in the case of piles, the productivity is reduced, and there is room for study in terms of workability and cost in any 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 diligent studies on the variation in strength when primary curing of piled agglomerates in the non-firing type agglomeration process as described above, the present inventors found that agglomerates were formed from above the processing pits. By dropping steam and injecting steam to start heating of the agglomerates while piled up while dropping and loading, variation in strength of agglomerates between the upper and lower layers of the mountain is reduced. The present invention has been completed by finding that it can be done.

  Therefore, an object of the present invention is to reduce the variation in the strength of the agglomerates in the upper and lower layers of the mountain when the piled agglomerates are first cured, and to obtain a stable quality coal-free uncalcined agglomerated ore. The object is to provide a method for producing a coal-containing uncalcined agglomerated ore for a blast furnace, which can be obtained easily and at low cost.

That is, the gist of the present invention is as follows.
(1) Finely powdered iron-containing raw material, finely powdered carbonaceous material, and a compounded raw material containing a hydraulic binder, after adjusting the water content, formed agglomerates, piled up in a processing pit surrounded by side walls, and used a heat insulating sheet. A method for producing a coal-containing non-calcined agglomerated ore for a blast furnace, which includes a step of covering and covering a primary surface of an agglomerate while injecting a predetermined amount of steam from the floor surface of the processing pit to heat it. The coal-containing non-calcined lump for a blast furnace characterized by injecting steam from the upper part of the blast furnace to start heating the agglomerate while injecting steam from the floor surface of the processing pit during the pile process. Method for producing ore.
(2) The stacking height h of the agglomerates is 50 to 70% (0.5H ≦ h ≦ 0.7H) with respect to the stacking height H of the agglomerates stacked in the processing pit. The method for producing a coal-containing non-calcined agglomerated ore for blast furnace according to (1), wherein steam is injected from the floor surface to start heating the agglomerate.
(3) The method for producing a carbonized non-calcined agglomerated ore for blast furnace according to (1) or (2), wherein the pile height H of the agglomerates piled up in the processing pit is 3 to 5 m.
(4) The method for producing a carbonized non-calcined agglomerated ore for blast furnace according to any one of (1) to (3), wherein the carbon content ratio (TC) in the blended raw material is 15 to 25 mass%.
(5) The method for producing a coal-containing non-calcined agglomerated ore for blast furnace according to any one of (1) to (4), in which steam is injected and cured in the primary curing for 15 to 30 hours.
(6) The method for producing a coal-containing non-calcined agglomerated ore for 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 agglomerate.

  According to the present invention, when the agglomerates piled up in the non-firing type agglomeration process are subjected to primary curing, it is possible to reduce variations in the strength of the agglomerates in the upper layer portion and the lower layer portion of the mountain. Therefore, a stable quality coal-free non-calcined agglomerated ore can be easily obtained at low cost.

FIG. 1 is a schematic explanatory view showing an example of a curing treatment device for primary curing an agglomerate. FIG. 2 (a) is a graph showing the relationship between the carbon (carbon) content and the crushing strength of a coal-containing non-calcined agglomerated ore, and FIG. 2 (b) is a graph of pellets (agglomerates) before curing. It is a graph which shows the relationship between the amount of added water required for strength maintenance, and carbon content. FIG. 3 is a schematic diagram showing the locations of peaks where the temperature history and the strength of pellets were measured in the primary curing of the following Production Experiment I. FIG. 4 is a graph showing the temperature history in the primary curing of the following manufacturing experiment I, where (a) is the curing condition 1, (b) is the curing condition 2, and (c) is the curing condition 3. FIG. 5 is a graph showing the relationship between the mountain height and the pellet strength due to the difference in the primary curing in the following manufacturing experiment I, (a) shows the average strength of the pellet in each layer of the mountain height, (b) Indicates the proportion of low-strength products in the pellet in each layer at the mountain height.

Hereinafter, the present invention will be described in detail.
In the method for producing a coal-containing non-fired agglomerated ore for a blast furnace according to the present invention, finely powdered iron-containing raw material, finely powdered carbonaceous material, and a blended raw material containing a hydraulic binder are water adjusted to form agglomerates. Then, when piled up in the processing pit surrounded by the side wall and covered with a heat insulating sheet, a predetermined amount of steam is jetted from the floor surface of the processing pit to heat the agglomerates for primary curing of the agglomerates. In the middle of loading and stacking the agglomerates from above, steam is injected from the floor surface of the processing pit to start heating the agglomerates.

  Generally, when primary curing of piled agglomerates in the non-baking type agglomeration process, the temperature of the agglomerates is about 40 to 60 ° C. due to the hydration reaction (exothermic reaction) of the hydraulic binder. At this time, the agglomerates in the lower layer of the mountain lose heat to the floor surface of the processing pit, while the agglomerates in the upper layer of the mountain generate their own heat and are transferred from the lower layer side. Since it is preheated by heat, a temperature difference occurs in the agglomerates between the lower layer portion and the upper layer portion. This is also the case when heating by injecting steam from the floor of the processing pit, and the heat transfer from the lower layer side causes the upper layer side to have a higher temperature than the lower layer portion. It is considered that the strength of the agglomerate varies between the lower layer and the lower layer.

  In addition, in the actual manufacturing, it takes about 24 hours from the start of the agglomeration of the agglomerates in the processing pit to the completion of the pile. This is different from the case of steam aging of slag that is stored in a yard and put into a processing pit with a heavy machine, and in the production of coal-containing non-fired agglomerated ore for blast furnace, it is obtained by blending raw materials and molding. This is because the agglomerates thus obtained are sequentially loaded from above the processing pit to be stacked. Therefore, it is considered that the curing time inevitably differs between the agglomerates located in the lower part of the mountain and the agglomerates located in the upper part, which causes variations in the strength of the agglomerates.

  In general, when obtaining a coal-containing non-calcined agglomerated ore, when agglomerates are piled up in the processing pit and primary curing is performed, raw materials containing fine iron powder, fine carbonaceous materials, hydraulic binders, and other raw materials are specified. Cut out from the hopper so that the compounding amount becomes, and crush with a crusher such as a ball mill, and knead while adjusting the water content using a kneader such as a Loedige mixer or an Eirich mixer (water content Is about 9 to 14% by mass). Then, for example, it is granulated with a granulating machine such as a pan pelletizer, and further sieved with a vibrating sieve or the like to obtain granulated pellets (as agglomerates). At this time, each raw material constituting the blended raw material may be crushed and then blended to obtain a blended raw material. Further, instead of granulating the compounded raw material adjusted with water content with a granulator to form an agglomerate, for example, a briquette using a compression molding machine or extrusion molding with an extrusion molding machine is performed. Agglomerates may be obtained.

  Then, for example, as shown in FIG. 1, the obtained agglomerates are piled up in the processing pit 1 surrounded by the side wall. That is, in this example, a processing pit 1 surrounded on three sides by a side wall 2 made of a concrete retaining wall or the like is formed in a building 10 having a roof, and a pedestal 3 is installed so as to extend over the processing pit 1. ing. Further, the pedestal 3 can move 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 pedestal 3 is a wall of the building 10). Of the ore), and the ore feeding dolly (loading machine) 4 is loaded on the gantry 3, and the ore feeding dolly 4 moves in the depth direction (y direction) of the processing pit 1. be able to. Further, the agglomerates produced by connecting the belt conveyor 5 to the ore feeding dolly 4 are supplied, and the agglomerates are produced from above the processing pit 1 by the movement of the gantry 3 and the ore feeding dolly 4. Is charged and the agglomerates are stacked in the processing pit, so that the piles 6 of piled agglomerates are formed.

  Here, in the conventional method, after agglomerating the agglomerates 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 of objects is covered with a heat insulating sheet 8 such as a blue sheet, and steam is jetted from a steam jet pipe 9 provided on the floor surface of the processing pit 1 to form a lower layer portion of the pile 6 of piled agglomerates. To the upper layer, water and heat are applied to accelerate the hydration reaction of the hydraulic binder to develop the strength of the agglomerate (hereinafter, referred to as "conventional method"). This is to eliminate waste of the steam ejected from the steam ejection pipe 9, and after covering the mountain 6 of the agglomerate with the heat insulating sheet 8, the steam is ejected from the steam ejection pipe 9 on the floor surface of the processing pit 1. It has been thought that by injecting, the heat and water from the steam are not released as much as possible, and the agglomeration of the agglomerate is promoted more efficiently.

  However, as a result of repeated trial and error by the present inventors, steam injection was started from the steam ejection pipe in the middle of stacking the agglomerates, and while the steam was being injected, the remaining agglomerates were stacked and piled up. After the completion of the procedure and covering with a heat insulating sheet, surprisingly, the variation in the strength of the agglomerates in the upper and lower layers of the mountain was suppressed compared to the conventional method, and the amount of steam used was reduced. Even if it is the same as 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 during the loading of the remaining agglomerates after the start of the steam injection, It was found that the average strength of the agglomerates obtained after primary curing (released between the agglomerated agglomerates) (average of primary cured piles) was higher than in the conventional method. It is considered that one of the reasons for this is that the strength of the agglomerates located in the lower layer of the mountain is improved and the strength difference from the upper layer is eliminated.

  It is preferable that the agglomeration height h of the agglomerates is 50 to 70% (0.5H ≦ h ≦ 0.7H) with respect to the heap height H of the agglomerates of the agglomerates piled in the processing pit. It is advisable to start the heating of the agglomerates by injecting steam from a steam injection pipe or the like installed on the floor surface of the pit. If the timing of injecting steam is outside this range, the average strength of the agglomerates obtained after primary curing (the average of the primary cured mountains) may be the same as or lower than that of the conventional method. In some cases, it is not possible to sufficiently suppress the variation in the strength of the agglomerate between the upper layer portion and the lower layer portion of the mountain.

  Of course, it is also possible to improve the strength of the agglomerates located in the lower layer of the mountain by starting the injection of steam from the floor surface of the processing pit at an earlier timing, such as simultaneously with the agglomeration of the agglomerates. Although it is possible, it is not practical to use steam that requires a relatively high manufacturing cost as much as possible, and if the amount of steam increases too much, the agglomerates swell due to the influence of coagulated water, and rather the agglomerates There is a risk that the strength will decrease and the variation will increase. Therefore, in the present invention, it is advantageous in terms of cost balance to set the timing as described above in consideration of using a predetermined amount of steam in the same degree as in the conventional method.

  Here, FIG. 2 (a) shows the effectiveness of steam curing in obtaining a coal-containing non-calcined agglomerated ore. Generally, in the absence of steam, the strength (crush strength) of a coal-containing uncalcined agglomerate decreases linearly with an increase in carbon content. There are two possible causes for this. One is that since the carbonaceous material is porous, a hydraulic binder such as cement is trapped in the pores and does not work effectively for bonding. Second, since carbonaceous materials are hydrophobic and porous, the amount of added water required to maintain the strength of agglomerates such as pellets is greater than when carbonaceous materials are not included. This is because variation in water content among agglomerates promotes variation in products (non-calcined agglomerated ore). Therefore, when steam curing is carried out, not only the cement hydration reaction is promoted, but also variations in water content are eliminated and the average product strength is improved. The effect is more remarkable in the agglomerates having 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 binding and the adverse effect is not eliminated, and the carbon content has an upper limit. If the carbon content is 15 to 25%, it is possible to produce the agglomerate having a predetermined strength that can withstand the use of the blast furnace by maximizing the effect of steam curing. Note that FIG. 2B shows the relationship between the amount of added water and the carbon content necessary to maintain the strength of pellets (agglomerates).

The strength required for a coal-containing uncalcined agglomerated ore for a blast furnace is such that it does not collapse at the time of transportation to the blast furnace or charging, and it depends on the method of transportation or charging, but it is generally 85 kg / cm. A strength of about ² or more is required. Generally, the crushing strength of a coal-containing uncalcined agglomerated ore is determined by applying a compressive load at a specified pressing speed to one measured sample in accordance with JIS M8718 "Iron ore pellet crushing strength test method". The load value at the time of breaking 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 represented as a strength index for convenience. By the way, 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 except for the timing of ejecting steam, and the same method as a known method for obtaining a coal-containing non-calcined agglomerated ore can be used.
For example, the compounded raw material of the coal-containing non-calcined agglomerated ore is not particularly limited as long as it contains the finely powdered iron-containing raw material, the finely powdered carbonaceous material, and the hydraulic binder, and known materials can be used. Among them, as described in Patent Document 2, if a blended raw material in which the carbon content ratio (TC) in all raw materials is 15 to 25 mass% is used, it is possible to reduce the reducing material ratio during blast furnace operation. it can. In the case of such a blended raw material having a high carbon content ratio, strength is generally difficult to develop, but by using the method of the present invention, a coal-containing non-calcined agglomerated ore capable of reducing the reducing agent ratio can be obtained. It is possible to suppress the variation in quality and to supply stably. There are no particular restrictions on the means or procedure for obtaining the agglomerates from the blended raw materials, and the known methods described above can be used.

  Here, the finely powdered iron-containing raw material means that fine powder particles having a particle size of 0.25 mm or less occupy 80% or more of the whole, and for example, iron-containing dust such as sintering dust or blast furnace dust generated in the iron-making process is used. First, there may be mentioned finely powdered iron ore used as a pellet feed (raw material for pellets) and powdered iron ore previously crushed by a crusher. Examples of the fine carbonaceous materials include blast furnace primary ash, coke dust, coke dust, coal, and the like. Among them, the mass-based median diameter (d50) is 100 to 150 μm. Is good. Further, examples of the hydraulic binder include an aging binder composed of fine powder containing generally used ground granulated blast furnace slag as a main component and an alkali stimulant, Portland cement, bentonite, quick lime and the like.

  Regarding the treatment pit used for primary curing, the conventional one used for steam curing of steelmaking slag can be used as it is, and the agglomeration of agglomerates can be performed in the same manner as the conventional method. You can At this time, the pile height H of the agglomerates piled in the processing pit is generally 3 to 5 m, and the same is true in 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 from the time when the agglomerates are stacked in the processing pit to the time when the stacking is completed, and the steam is injected at a fixed time to complete the stacking. At that point, cover it with a heat insulating sheet. Here, the time for injecting steam can be the same as in the conventional method, and in particular, when using a blended raw material in which the carbon content ratio (TC) in the total raw material is 15 to 25 mass%, Is 15 to 30 hours, and the amount of steam used at that time is 13 to 17 tons per ton of agglomerate.

  Further, in the present invention, similarly to the conventional method, the primary curing is continued with the heat insulation sheet being covered even after the injection of the predetermined amount of steam is completed. 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 time for primary curing after starting to load agglomerates is about 64 to 74 hours. Then, after the primary curing is completed, the agglomerate is taken out of the processing pit, sieved using a vibrating sieve, etc., if necessary, and then reloaded in the raw material yard (secondary curing yard) and put into the atmosphere. Secondary curing for about 5 to 8 days can be carried out to obtain a coal-containing non-calcined agglomerated ore showing strength as an iron raw material for blast furnace.

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

(Manufacturing experiment I)
From the blast furnace primary bye and coke dust while adjusting the blending ratio so that the carbon content (TC) in the total raw material is 20 mass% in the pulverized iron-containing raw material composed of sintered dust and fine pulverized iron ore. Finely powdered carbonaceous material is further added, and Portland cement is added as a hydraulic binder, and the mixture is crushed with a ball mill so that the maximum particle size of these raw materials is 2 mm or less, and then the water content is 12% by mass. Granulation was performed using a pan pelletizer while adjusting so that pellets having an average particle diameter of 14 mm were produced. The pellet production capacity at this time is approximately 60 t / hour.

  While manufacturing the pellets as described above, the pellets are stacked in the treatment pit 1 using the curing treatment apparatus shown in FIG. 1, and the primary curing is performed under the following curing conditions 1 to 3, Then, the manufacturing experiment (Comparative Examples 1 and 2 and Invention 1) of 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 width 26 m × depth 13 m. Then, the gantry 3 and the ore feeding trolley (loading machine) 4 installed above the processing pit 1 are driven to load and pellet the pellets, 26 m in the width direction, 13 m in the depth direction, and the height ( H) A pile of 4 m pellets 6 was piled up. At this time, it took 24 hours (from the start to the end of the stacking) until the stacking was completed.

First, as a curing condition 1 according to Comparative Example 1, when piles of pellets are completed, a resin blue sheet (heat insulating sheet) 8 is covered so as to cover all the piles 6 of pellets, and no steam is injected. Instead, it was cured until 48 hours passed after the blue sheet was hung.
Further, as the curing condition 2 according to the comparative example 2, similarly to the curing condition 1, after the pile of the pellets is completed, the resin blue sheet 8 is covered, and the steam is discharged from the steam ejection pipe 9 installed on the floor surface of the processing pit 1. The injection was started, the water vapor was stopped 24 hours after the injection, and the steam was cured until 48 hours after the blue sheet was hung.
On the other hand, as the curing condition 3 according to the first aspect of the present invention, when the stacking height (h) of pellets reaches 2 m during stacking (12 hours from the start of stacking), injection of steam from the steam ejection pipe 9 is performed. Start, and while continuing to flow steam, cover the blue sheet 8 when the pile of pellets is completed (the height of the pile is 4 m), stop the steam 24 hours after the injection, and stop it from the seating of the blue sheet. I was cured until time passed.

  Then, for each pellet that has undergone the primary curing under these conditions, the pellets are discharged by a shovel loader, transported to the yard by a dumper, loaded again into the yard via a loading machine, and then subjected to the 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) Coal-free uncalcined agglomerated ore according to each manufacturing experiment was obtained. The amount of water vapor used under curing conditions 2 and 3 is 15 tons per ton of pellets (amount of water vapor used is 15 tons / ton product).

  During the primary curing in each of these manufacturing experiments, as shown in FIG. 3, the temperature was measured at different heights of the piles of the piled 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 a position approximately in the center in both the width direction and the depth direction of the pellet mountain 6. The temperature history was measured at three points of h = 320 cm (layer height ratio h / H = 0.8). The results are shown in Fig. 4.

Regarding "curing condition 1 without using steam" shown in Fig. 4 (a), in the upper part of the mountain with a layer height ratio of 0.8, the temperature exceeds 65 ° C about 50 hours after the start of packing (start of curing). After that, it dropped slightly and finally reached about 60 ° C. In the middle part of the mountain with a bed height ratio of 0.5, the temperature rose to 60 ° C. about 36 hours after the start of curing, then dropped, and finally reached about 52 ° C. In the lower part of the mountain with a bed height ratio of 0.2, the temperature rose to 55 ° C 24 hours after the start of curing, but continued to drop after seating, and finally reached 45 ° C. .
Further, under the "curing condition 2 of injecting steam after pile-up" shown in FIG. 4B, steam is injected into both the upper layer part of the mountain with a bed height ratio of 0.8 and the middle layer part of the mountain with a bed height ratio of 0.5. The temperature rose to a maximum of 85 ° C in the upper part of the mountain (42 hours after the start of curing) and 72 ° C in the upper part of the mountain (48 hours after the same). On the other hand, in the lower part of the mountain with a bed height ratio of 0.2, the temperature was maintained at about 55 ° C. during the steam injection, but after that, it decreased to 50 ° C., and at the end of curing, the lower part of the mountain A large temperature difference of 50 to 75 ° C. was formed between the upper part and the upper part, and the temperature difference was widened as compared with the case of curing condition 1 (45 to 60 ° C.) where steam was not used.

On the other hand, under the "curing condition 3 in which steam is injected during pile-up" shown in FIG. 4C, the temperature rise in the middle layer (maximum 72 ° C.) and the upper part (maximum 80 ° C.) of the mountain is the same as in the previous case. Although it is lower than the case of curing condition 2 ", the temperature of the lower part of the mountain is maintained at 55 ° C for an extended period of time, and at the end of curing, the temperature difference between the lower and upper parts of the mountain (50-70 ° C) was reduced as compared with "curing condition 2".
The outside air temperature was 20 ° C under any of these curing conditions. The temperature rise immediately after the pellets are loaded is due to the hydration reaction (exothermic reaction) of the cement.

Therefore, for the pellets (coal-containing non-calcined agglomerate) of each production experiment obtained by secondary curing after the above curing conditions 1 to 3, crushing strength for each position of the mountain height in primary curing Was measured. Here, the 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 randomly selected, and the crushing strength of these 100 samples (pellets) was measured to obtain an average value for each curing condition. The result is as shown in FIG. In addition, the ratio of the samples having a crushing strength of 50 kg / cm ² or less was calculated from the 100 samples selected for each position of the mountain height. The result is as shown in FIG. In addition, the crushing strength is measured according to JIS M8718 “Iron ore pellet crushing strength test method”, when one sample to be measured is crushed by applying a compressive load at a specified pressing speed. The load value per unit cross-sectional area (kg / cm ² ) was measured as the crush strength.

As shown in FIG. 5 (a), as compared with Comparative Example 1 in which primary curing was performed under Curing Condition 1 without using steam, Comparative Example 2 in which primary curing was performed under Curing Condition 2 using steam and Curing Condition 3 and In the case of the present invention 1, the crush strength of the pellet was high in all of the lower layer portion, the middle layer portion, and the upper layer portion of the mountain. At that time, in Comparative Example 1 in which primary curing was performed under curing condition 1, the strength difference between the pellets located in the upper layer and the pellets located in the lower layer was approximately 75 kg / cm ² (150-75 = 75 kg / cm ² ). Similarly, in Comparative Example 2 which was primary cured under curing condition 2, it was 100 kg / cm ² (180-80 = 100 kg / cm ² ), whereas in Invention 1 which was primary cured under 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 layer is about 60 kg / cm ² (170-110 = 60 kg / cm ² ), and the quality difference of the mountain in the primary curing is higher than in Comparative Examples 1 and 2. Was relaxed. Further, according to FIG. 5 (b), the ratio of insufficient strength of the pellets located in the lower layer of the mountain is remarkably reduced (30% in Comparative Example 1 and 25% in Comparative Example 2). On the other hand, in the present invention 1, 15%), it was found that homogenization can be achieved when the whole mountain is a coal-containing non-calcined agglomerated ore. In addition, the pellet finally obtained in the present invention 1 (non-calcined agglomerated ore) is a total of 100 samples of the lower layer, the middle layer and the upper layer of the mountain during the primary curing. The average crush strength was 130 kg / cm ² , and the proportion of the samples having a crush strength of 50 kg / cm ² or less was 7.8% of the total samples.

(Manufacturing experiment II)
Timing of starting steam ejection (ratio of stacking layer at steam start), amount of steam used per ton of pellets (steam basic unit), time to eject steam (steam curing time), and stacking height of pellets Was carried out in the same manner as in Production Experiment I except that the primary curing was carried out by changing as shown in Table 1 to obtain a coal-containing non-calcined agglomerated ore according to the present invention 2 to 16. Then, with respect to each of the obtained coal-containing non-calcined agglomerated ores, the average crush strength (average product crush strength) and the ratio of the crush strength of 50 g / cm ² or less were obtained in the same manner as in Production Experiment I. The results are as shown in Table 1. In all of the present inventions 1 to 16, compared to Comparative Example 1 and Comparative Example 2, the crush strength in the entire mountain was homogenized, but the condition of primary curing was used. The following considerations can be made in the sense of optimizing.

First, the timing of injecting steam can be compared and examined in the present inventions 1 to 5, and the timing at which the pellet stacking height h is 0.6 with respect to the pellet stacking height H (layer height ratio 0.6 )) (Invention 3), the obtained coal-containing non-calcined agglomerated ore had the highest average crush strength, and the crush strength of 50 g / cm ² or less was the lowest. That is, if the steam ejection timing is early, strength development in the middle and upper layers of the mountain may be insufficient, and if the steam ejection timing is delayed, strength development in the lower layer of the mountain may be insufficient. To be

Further, the amount of steam used can be compared and examined in Inventions 1 and 6 to 9, and the case of Invention 1 is most effective. When the amount of steam is small, strength development as a whole may be insufficient. On the contrary, if the amount of steam becomes too large, the pellets may swell and the strength may be lowered.
Further, steam curing time can be compared and examined in Inventions 1 and 10 to 13, and Invention 1 is most effective. Since the amount of steam used is the same (15t / t product), it is thought that the amount of steam per unit time becomes excessive when the steam curing time is shortened, resulting in swelling of pellets due to excess water content. To be On the other hand, if the steam curing time becomes too long, the amount of steam per unit time will decrease, and the effect of the present invention may be limited.
Furthermore, the stacking height when stacking the pellets can be compared and examined in Inventions 1 and 14 to 16, and the case of Invention 1 is most effective. If the stacking height becomes too low, the effect of the present invention may be limited. If the loading height becomes too high, the pellets may collapse due to the loading load as described above.

  As described above, according to the present invention, when primary curing of agglomerates such as piled pellets in the non-firing type agglomeration process, variation in strength in the stacking height direction is reduced, and the average strength is improves. Therefore, it becomes possible to obtain a coal-containing non-calcined agglomerated ore with stable quality. Further, according to the present invention, since it becomes possible to stably supply a coal-containing non-calcined agglomerated ore having a high carbon content while suppressing variations in quality, it is possible to reduce the reducing agent ratio when using a blast furnace. It is advantageous in trying. Furthermore, the management of the strength index of the agglomerates in the primary curing can be eased, and the amount of hydraulic binder such as cement used can be reduced, making it easy and low to use coal-containing non-calcined agglomerates. You will be able to get it at cost.

1: Processing pit, 2: Side wall, 3: Stand, 4: Feeding cart (loading machine), 5: Belt conveyor, 6: Pile of agglomerates, 7: Hoist type crane, 8: Heat insulation sheet, 9: Steam ejection pipe, 10: Building.

Claims (6)

  Finely powdered iron-containing raw material, finely powdered carbonaceous material, and an agglomerate formed after adjusting the water content of the blended raw material containing a hydraulic binder, 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 non-calcined agglomerated ore for a blast furnace, which includes a step of primary curing an agglomerate while injecting a predetermined amount of steam from the floor surface of the treatment pit to heat it, and During the process of loading and stacking agglomerates, steam is injected from the floor surface of the processing pit to start heating of the agglomerates. Production method.   With respect to the pile height H of the agglomerates piled up in the processing pit, the agglomeration height h of the agglomerates is 50 to 70% (0.5H ≦ h ≦ 0.7H) from the floor of the processing pit. The method for producing a coal-containing non-calcined agglomerated ore for blast furnace according to claim 1, wherein steam is injected to start heating of the agglomerate.   The method for producing a coal-containing non-calcined agglomerated ore for blast furnace according to claim 1 or 2, wherein a pile height H of the agglomerates piled up in the processing pit is 3 to 5 m.   The method for producing a carbonized non-calcined agglomerated ore for blast furnace according to any one of claims 1 to 3, wherein a carbon content ratio (T.C) in the blended raw material is 15 to 25 mass%.   The method for producing a coal-containing non-calcined agglomerated ore for blast furnace according to any one of claims 1 to 4, wherein the steam is injected and cured in the primary curing for 15 to 30 hours. The method for producing a coal-containing non-calcined agglomerated ore for blast furnace according to claim 1, wherein the amount of steam used in the primary curing is 13 to 17 tons per 1 ton of agglomerate.

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