JP2021091965A - Method for producing molding sintering raw material, and method for producing sintered ore - Google Patents

Abstract

To provide a method for producing a high-strength molding sintering raw material by adding a binder at least comprising organic fiber to a blended sintering raw material, and a method for producing sintered ore for steelmaking with excellent productivity and high strength at low cost by using the molding sintering raw material.SOLUTION: When a molding sintering raw material is produced by adding a binder to a blended sintering raw material comprising iron ore, carbonaceous material, and auxiliary material for molding, an aggregate comprising iron ore base powder and cellulose nanofiber is used as the binder to produce the molding sintering raw material. There is also provided a method for producing sintered ore by sintering the molding sintering raw material thus obtained, with a sintering machine.SELECTED DRAWING: Figure 1

Description

The present invention relates to a method for producing a molded sintered raw material used when producing a sintered ore by a DL sintering machine, and a method for producing a sintered ore for iron making using this molded sintered raw material.

In the operation of the DL sintering machine, when the surface of the sintered raw material charging layer (hereinafter, simply referred to as “charging layer”) is ignited by the ignition furnace arranged on the pallet, the surface layer of the charging layer is ignited. The carbonaceous material in the charging layer is burned by the action of the suction gas sucked from the portion to the lower layer portion. Then, the combustion of the carbonaceous material gradually proceeds to the lower layer and forward as the pallet moves. At the same time, it is known that the water generated in the upper layer portion of the charging layer is cooled and condensed in the lower layer portion having a low temperature in the process of being sucked into the lower layer portion. Therefore, a layer having a high water content called a wet zone is formed in the lower layer of the charging layer. When the concentration of this wet zone is increased, water fills the voids between the raw material particles, which are the flow paths of the suction gas, and the ventilation resistance is increased. In particular, it is known that the ventilation resistance of the wet zone occupies about half or more of the ventilation resistance of the charging layer. In such an environment, in order to improve the productivity of the sinter, it is considered effective to reduce at least the aeration resistance associated with the condensation of water in this wet zone.

In response to this problem, in the conventional step of granulating a compounded sintered raw material to produce a molded sintered raw material, the water content of the compounded sintered raw material is adjusted (for example, less than 8 mass%), and moreover. At the time of molding (granulation), high-temperature exhaust gas is introduced into the molding machine (granulator) to dry it, and the final moisture content is 4 mass% or less. A technique for suppressing the influence of the wet zone of the charged layer by charging the molded sintered raw material having a low water content thus obtained onto a pallet has been proposed (Patent Documents 1 to 4). ). However, these methods have a problem that the obtained molded sintered raw material is insufficiently dried, and the actual situation is that they have not been sufficiently put into practical use.

On the other hand, in order to solve the above problems, a new method has been developed in which not only fresh lime but also an organic binder is used when granulating the compounded sinter raw material, and the production efficiency of the sinter is improved and the sinter is baked. A technique has been proposed that makes it possible to reduce the amount of carbonaceous material required for the production of sinter (Patent Document 5).

However, the method disclosed in Patent Document 5 was effective in preventing pulverization of the granulated particles and destruction during drying. However, this method increases the cost of the sinter that is finally produced as compared with the manufacturing technology of ordinary molded sinter raw materials, and the effect of using an organic binder (improvement of production efficiency by improving air permeability). There was a problem that the economic effect of reducing the amount of carbonaceous materials) was diminished. On the other hand, it is conceivable to use fiber materials such as cellulose nanofibers that can reinforce and strengthen fibers, but quality (strength) can be improved by using ready-made products that have already been processed into the form of cellulose nanofibers as they are. There was a problem that it did not contribute to the cost and the cost was high.

JP-A-58-199827 Japanese Unexamined Patent Publication No. 60-089526 Japanese Unexamined Patent Publication No. 61-238925 Japanese Unexamined Patent Publication No. 3-215629 Japanese Unexamined Patent Publication No. 2007-169760

An object of the present invention is to overcome the above-mentioned problems of the prior art, and by examining the type and usage of the binder used at the time of molding the compounded sintered raw material, high-strength and inexpensive molding is performed. The purpose is to propose a method for producing a sinter raw material, and to propose a method for inexpensively producing a high-strength sinter for iron making with excellent productivity by using the molded sinter raw material. ..

The first method of the present invention, which was developed to solve the above-mentioned problems of the prior art and achieve the above-mentioned object, adds a binder to a compounded sintered raw material containing iron ore, a carbonaceous material, and an auxiliary raw material. A method for producing a molded sintered raw material by molding, which comprises using an aggregate containing iron ore raw material powder and cellulose nanofibers as the binder.

In addition, the second method of the present invention is a method for producing sinter, which is produced by using a molded sinter raw material produced under the first method.

In each of the above-mentioned production methods of the present invention,
(1) As the aggregate containing the iron ore raw material powder and the cellulose nanofibers, the one obtained by co-crushing the iron ore and the cellulose fibers shall be used.
(2) The aggregate containing the iron ore raw material powder and the cellulose nanofibers shall be aggregated in the range of 99.9 / 0.01 to 80/20 in terms of the mixed mass ratio of the iron ore and the cellulose fibers. ,
(3) The total solid concentration of the iron ore raw material powder and the cellulose fiber shall be 10 mass% to 80 mass%.
(4) The amount of the aggregate containing the iron ore raw material powder and the cellulose nanofibers added to the compound sintered raw material corresponds to the amount of the cellulose nanofibers added in the range of 0.01 mass% to 2.00 mass%. To be a quantity,
However, it is considered that each of them becomes a more preferable embodiment.

(1) According to the present invention relating to the above-mentioned configuration, at the time of molding a compound sintered raw material obtained by mixing an auxiliary raw material such as raw lime powder with an iron ore raw material powder (hereinafter, in the example of "granulation"). By using an aggregate containing iron ore raw material powder and plant-derived cellulose nanofibers as the binder (described), a high-strength molded sintered raw material can be produced at low cost.
(2) Further, according to the present invention, since sinter is produced using the molded sinter raw material, high-strength sinter can be produced at low cost with high productivity.

It is a schematic diagram of a sinter manufacturing process. It is a transmission electron micrograph (TEM photograph) of an aggregate containing iron ore raw material powder and cellulose nanofibers. It is a figure which shows the particle size distribution of the iron ore before co-grinding and the co-grinding thing after co-grinding.

Generally, the sinter, which is the main raw material of the blast furnace, is produced through the process as shown in FIG. As shown in FIG. 1, various sintering raw materials are first stored in a plurality of hoppers 1. The sintered raw material contains, for example, iron ore powder having an average particle size of about 1.0 to 5.0 mm, miscellaneous iron sources such as various dusts generated in a steel mill, and CaO such as limestone, quicklime, and steelmaking slag. Auxiliary raw materials such as raw materials, coagulants such as coke breeze and smokeless charcoal, MgO-containing raw materials made of refined nickel slag, dolomite, serpentine, etc. as optional compounding materials, SiO _2- containing raw materials made of refined nickel slag, iron ore, etc. There is. Then, the compounded sintered raw material obtained by cutting out and blending a predetermined amount of each of the above-mentioned sintered raw materials on a conveyor at a predetermined ratio from the raw material storage hopper 1 is then subjected to a molding device such as a drum mixer 2, that is, a product. While supplying to a granulator or the like and stirring and mixing, humidity control is added as necessary, and an organic / inorganic binder is added for molding (granulation). As a result, a molded (granulated) sintered raw material which is a pseudo particle having an average particle size of about 3.0 to 6.0 mm can be obtained.

The average particle size is the arithmetic mean particle size of the major axis, and is Σ (Vi × di) (however, Vi is the abundance ratio of particles in the i-th particle size range, and di is the i-th particle size range. It is a particle size defined by).

As an example of a molding apparatus for molding (granulating) the compound sintered raw material, that is, a granulator, it is preferable to mold using one or more drum mixers, pelletizers, and the like.

The molded sintered raw material (pseudo-particles) thus obtained is then charged from a surge hopper (not shown) arranged on the sintering machine via a charging device 3 including a drum feeder and a cutting chute. , It is charged and deposited on the sintering machine pallet 4 so as to have a thickness (height) of about 400 to 600 mm. Next, with respect to the raw material deposition layer charged on the sintering machine pallet 4, that is, the charging layer, the carbonaceous material contained in the charging layer is provided by the ignition furnace 5 installed above the charging layer. Ignite. As a result, the charcoal material in the charging layer is sequentially burned by the downward suction by the wind box 6 arranged under the pallet 4, and the charging raw material (molding firing) is generated by the combustion heat generated at this time. Sintering is completed by sequentially burning and melting the raw material).

After that, the sintered layer (sintered cake) on the pallet 4 of the sintering machine is sized by a sieve 9 through a crusher 7 and a sintering machine cooler 8, and is a massive adult sintered ore of 5.0 mm or more. And -5 mm return ore are separated and recovered.

When the air in the charging layer is sucked downward through the wind box 6, gas fuel, liquid fuel, oxygen or the like may be blown from above the charging layer. The gaseous fuel is selected from blast furnace gas, coke furnace gas, blast furnace / coke furnace mixed gas, linz-donaw gas, city gas, natural gas, methane gas, ethane gas, propane gas, shale gas and their mixed gas. One or more flammable gases are used. Further, as the liquid fuel, heavy oil, rapeseed oil and the like are used.

As described above, in the first method proposed in the present invention, iron ore raw material powder, coke powder, auxiliary raw material powder and the like are mixed, and a required amount of water is added to the compounded sintered raw material thus obtained. Further, granulation and molding are carried out by adding a characteristic binder described later, and then drying is performed to produce a molding and sintering raw material having a water content of about 4.0 mass% or less. In this method, the water content of the compounded sintered raw material is adjusted to be larger than the general water content suitable for granulation (8 to 10 mass%). Further, in order to exert the binder action even after the water evaporates, the compounded sintered raw material is granulated and molded by adding an organic binder or a mixed binder of the organic binder and an inorganic binder added as needed. To obtain the desired molded sintered raw material.

In the present invention, in adjusting the water content (humidity control) of the compounded sintered raw material, water is added after adding a powdery organic binder or an inorganic binder to the compounded sintered raw material, or an organic binder or It is preferable to add it at the same time as or before the inorganic binder such as bentnite or water glass.

The present invention includes, as the binder, particularly an organic binder, not a powdery organic binder such as a gum-based substance or a cellulosic thickener, but a fibrous organic binder, particularly an iron ore raw material powder and a cellulose nanofiber (CNF). It is characterized by paying attention to the aggregate and using it.

The cellulose nanofiber used in the present invention is considered to be a completely new material in the technical field of light weight and high strength, but has been conventionally used as a functional material such as a deodorizing material. As the cellulose nanofibers that can be used in the present invention, the cellulose fibers constituting the plant are produced by mechanical defibration such as homogenizer or grinder treatment, or chemical treatment such as decomposition by cellulase or chemical treatment. Any of the manufactured fibers can be used. The cellulose nanofibers preferably used as a binder in the present invention are fine fibers having a fiber diameter of 3 to 100 nm and a length of 100 nm to several μm, and can be dispersed in water or a solvent. Fibers characterized by points are preferred. The cellulose fibers can be defibrated to the smallest unit, microfibrils, and are provided in a state of being dispersed in water at a high concentration. These are also produced by, for example, a TEMPO-catalyzed oxidation method. It is possible. In this respect, general cellulose nanofibers are sold that are manufactured by using 90 mass% or more of water as a dispersion medium, but have not received much attention in the ironmaking field so far.

Therefore, in the present invention, while paying attention to the characteristics of the cellulose nanofiber as a binder, in order to solve the above-mentioned problem of using the cellulose nanofiber alone, as a more preferable embodiment, the cellulose nanofiber is used. Is not used as a single substance, but as an aggregate containing the iron ore raw material powder and the cellulose nanofibers (hereinafter, abbreviated as iron ore raw material powder / cellulose nanofiber aggregate). That is, by mixing the iron ore raw material powder and the cellulose fiber which is the raw material of the cellulose nanofiber and co-pulverizing them, it was decided to use this as the above-mentioned aggregate. The reason is that iron ore was originally used in the blast furnace method, while cellulose fibers are plant-derived fiber aggregates used in pulp production, such as inexpensive pulp, paper, and used paper. It is easy to use as a sintering raw material because it can be used, and it can be provided at a lower cost than the use of other binders, and it is effective in improving the strength as a molding sintering raw material. It is.

Here, the co-grinding method may be any co-grinding method. For example, in order to pulverize iron ore and pulverize cellulose fibers such as pulp which is a raw material of cellulose nanofibers, water is used. A wet pulverization method using a solvent such as the above is also one of the effective methods. In particular, a crusher 10 such as a ball mill, a roller mill, or a bead mill having a grinding function is preferably used. In addition, a wet tower mill that grinds by rotating a screw is also preferably used because it can perform continuous processing. In the treatment with a wet tower mill, a slurry having a concentration in which the weight of the iron ore to be crushed is 0.25 or more with respect to the weight 1 of water as a solvent is obtained, and the linear velocity on the outer circumference of the screw is 1.5 m /. It is preferably sec or more, more preferably 3 m / sec, and according to this method, a grinding effect similar to that of a ball mill, a roller mill, or a bead mill can be obtained, so that the efficiency is further improved.

The above-mentioned iron ore raw material powder / cellulose nanofiber aggregate can be applied as a mixture of iron ore and cellulose fiber in the range of 99.9 / 0.01 to 80/20, and can be pulverized. From the viewpoint of efficiency and increase in viscosity, those assembled in the range of 99.9 / 0.1 to 90/10 are preferable. Further, the total solid concentration of iron ore and cellulose fiber can be used from 10 mass% to 80 mass%, and is preferably 20 mass% to 60 mass% from the viewpoint of pulverization efficiency and viscosity increase.

The iron ore raw material powder / cellulose nanofiber aggregate used in the present invention has the property of returning to the same viscosity as before drying when water is added after drying, so that the amount of water during transportation is significantly reduced. It is possible to do. Further, the aggregate is formed and sintered by adding the binder to the mixed (blended) sintering raw material obtained by mixing raw lime, powdered coke, and other auxiliary raw material powders in addition to the iron ore raw material powder. When producing a raw material, it is possible to adopt a molding method such as granulation or briquette molding as a molding method.

According to the research by the present inventors, an aggregate containing iron ore raw material powder and cellulose nanofibers is added to a compound sintered raw material composed of iron ore powder or the like, and humidity control is performed (granulation) as necessary. In the case of the molded sintered raw material thus obtained, it has been confirmed that the crushing strength is improved as compared with that produced by the conventional method. In the case of the conventional molded sintered raw material, since a general organic binder is used, the maximum crushing strength is controlled only by the intermolecular force of the binder itself that is interposed between the particles of the sintered raw material powder. Has been decided. However, in the case of the method of the present invention, since an aggregate containing iron ore raw material powder and cellulose nanofibers is used as a binder, the cellulose nanofibers contained in this aggregate are dispersed and adhered to the surface of the iron ore powder. Will exist. Therefore, the hydroxyl group of the cellulose nanofibers is bonded more strongly by hydrogen bonding with the oxide on the surface of the iron ore powder, so that the particles of the iron ore powder are fiber-reinforced by the cellulose nanofibers. is there.

Further, in the case of the iron ore raw material powder / cellulose nanofiber aggregate, the crushing strength is caused by the large fiber diameter of the cellulose nanofibers and the interaction between the fracture surface of the iron ore generated by co-grinding and the cellulose nanofibers. Is expected to improve.

Furthermore, in those used in the form of an aggregate containing the iron ore raw material powder and the cellulose nanofibers as described above, the cellulose nanofibers are localized as compared with the case where the cellulose nanofibers are added alone to the blended sintered raw material. It is considered that higher crushing strength can be obtained because uneven distribution can be suppressed.

The amount of the iron ore raw material powder / cellulose nanofiber aggregate as the binder added to the compound sintered raw material is preferably about 0.01 mass% or more and 2.00 mass% or less as the addition amount of the cellulose nanofibers. More preferably, it is 0.10 mass% or more and 1.00 mass% or less. The reason is that if the amount added as cellulose nanofibers is 0.01 mass% or more, the crushing strength is improved, while even if the amount added as cellulose nanofibers exceeds 1.00 mass%, the strength is further increased. This is because the improvement effect of

Further, in addition to the iron ore raw material powder, even if a solid content such as dust is mixed and co-crushed, a certain strength improving effect can be obtained, so that these can also be used. However, in the case of iron ore raw material powder with large undulations, its surface texture has the effect of promoting the conversion of cellulose nanofiber raw material into cellulose nanofibers. Regarding the blending, it is desirable to blend the iron ore raw material powder in an equal amount or less and co-crush it.

Further, the appearance shape of the molded sintered raw material is more stable with the addition of the iron ore raw material powder / cellulose nanofiber aggregate without collapsing. It is considered that this is because the cellulose nanofibers crosslink the particles of iron ore powder with each other, and it is presumed that this also leads to the improvement of the sinter productivity. Therefore, the addition amount of the iron ore raw material powder / cellulose nanofiber aggregate is preferably 0.01 mass% or more and 1.00 mass% or less in terms of the addition rate as the cellulose nanofiber.

Further, in order for the cellulose nanofibers to sufficiently crosslink the iron ore powder particles, it is desirable that the size of the voids between the iron ore powder particles is equal to or less than the length of the cellulose nanofibers. The reason is that even if the coarse particles of iron ore powder have large voids, it is sufficient that there are fine particles that enter the large voids. For example, assuming that the typical length of the cellulose nanofibers after co-grinding is 1 μm, it is desirable that the proportion of the co-crushed products after co-grinding having a particle size of 20 μm or less is 20% or more of the total.

First, iron ore (-2.38 mm) and pure pulp (5 mm) were used under the conditions of screw rotation speed of 700 rpm and 1 hour using a NE008 tower mill manufactured by Nippon Eirich Co., Ltd. under the compounding conditions shown in Table 1. , Sanyo Kasei) was crushed to obtain an iron ore raw material powder / cellulose nanofiber aggregate. As for the obtained aggregate, as is clear from the transmission electron micrograph shown in FIG. 2, iron ore powder and cellulose nanofibers having a diameter of about 100 nm have been confirmed.

An example of the particle size distribution of the iron ore before co-grinding and the co-crushed product after co-grinding is shown in FIG. The particle size changed in the smaller direction by co-grinding, and the weight ratio of the particles having a particle size of 20 μm or less after co-grinding was 49%.

Next, the obtained iron ore raw material powder / cellulose nanofiber aggregate was used as a cellulose nanofiber with respect to a mixture of fresh lime (4 mass%) and a compound sintered raw material (96 mass%), and the concentration thereof was 0.5 mass%. , 1.0 mass% was added and granulated, and then dried at 105 ° C. for 1 hour to obtain a molded sintered raw material (Examples 1 and 2).

Further, the obtained iron ore raw material powder / cellulose nanofiber aggregate was filtered, dried (105 ° C.), and dehydrated for 24 hours as a binder under the same conditions as in Example 1. A molded and sintered raw material was obtained (Example 3). For the obtained molded sintered raw material, the crushing strength was determined using a uniaxial compression tester, and this is shown in Table 2. As the organic binder of the comparative example, powdered CMC (carboxymethyl cellulose Na salt, AS ONE physics and chemistry product) was added to the compounded sintered raw material, and then the water content was adjusted. Then, a crushing strength test was conducted in the same manner as in the examples. The measurement results are shown in Table 2.

From the results shown in Table 2, comparing Examples and Comparative Examples (CMC), which are examples produced under the conditions conforming to the present invention, when iron ore raw material powder / cellulose nanofiber aggregate was used as a binder ( It can be seen that in Examples 1 and 2), higher crushing strength was obtained than in the case of using CMC (Comparative Example). Further, the dried iron ore raw material powder / cellulose nanofiber aggregate (Example 3) also showed the same performance as that of Example 1 which was not dried.

Next, using the molded sintered raw material obtained as described above, the same binder species as in Examples 1 to 3 and Comparative Example 1 were used to produce a sinter under the conditions shown in Table 3. The results are shown in Table 3 as Examples 4 to 6 and Comparative Example 2. The amount of coke shown in Table 3 is shown as an outside value of the total amount of iron ore powder and auxiliary raw materials shown in Table 1.

The yield, sintering time, productivity and pseudo-particle size of the sinter shown in Examples (4 to 6) and Comparative Example 2 were determined and shown in Table 3. The operation was carried out with the thickness of the charging layer of the molding and sintering raw material on the pallet of the sintering machine set to 400 mm. As is clear from Table 3 showing the results, the examples (4 to 6) produced under the conditions conforming to the method of the present invention are the examples of the present invention in terms of yield, sintering time, and productivity as compared with Comparative Example 2. It was confirmed that all of them showed better results.

In particular, as can be seen from Table 3, when the iron ore raw material powder / cellulose nanofiber aggregate was used as the binder (Examples 4 to 6), the sintering time was shortened and the productivity was improved as compared with Comparative Example 2. You can see that it is improving. It is considered that this is because the average wind speed is higher than that of Comparative Example 2 and the air permeability is improved.

1 Hopper 2 Drum mixer 3 Loading device 4 Sintering machine Pallet 5 Ignition furnace 6 Windbox 7 Crusher 8 Sintering machine Cooler 9 Sieve 10 Crusher

Claims (6)

In a method of producing a molded sintered raw material by adding a binder to a compound sintered raw material containing iron ore, a carbonaceous material, and an auxiliary raw material, an aggregate containing iron ore raw material powder and cellulose nanofibers is used as the binder. A method for producing a molded sintered raw material, which is characterized by being used. The method for producing a molded sintered raw material according to claim 1, wherein the aggregate containing the iron ore raw material powder and the cellulose nanofibers is a co-crushed iron ore and the cellulose fibers. The aggregate containing the iron ore raw material powder and the cellulose nanofibers is characterized in that it is assembled in the range of 99.9 / 0.01 to 80/20 in terms of the mixed mass ratio of the iron ore and the cellulose fibers. The method for producing a molded sintered raw material according to claim 1 or 2. The method for producing a molded sintered raw material according to any one of claims 1 to 3, wherein the total solid concentration of the iron ore raw material powder and the cellulose fiber is 10 mass% to 80 mass%. The amount of the aggregate containing the iron ore raw material powder and the cellulose nanofibers added to the compound sintered raw material shall be an amount corresponding to the range of 0.01 mass% to 2.00 mass% in terms of the amount of the cellulose nanofibers added. The method for producing a molded sintered raw material according to any one of claims 1 to 4, wherein the molded sintered raw material is produced. A method for producing a sintered ore, which comprises sintering a molded sintered raw material produced by the method for producing a molded sintered raw material according to any one of claims 1 to 4 with a sintering machine.

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