JP2012072486A - Method for manufacturing sintering raw material - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a method for manufacturing a sintering raw material used for manufacturing a sintered ore, wherein air permeability of a raw material packed bed is improved when operating a sintering machine, thereby effectively improving productivity of the sintering ore without deteriorating strength and yield thereof.SOLUTION: The method comprises: when granulating a sintering raw material into a granulated sintering raw material in a pseudo-particle form, adding excess moisture to the sintering raw material so as to achieve a moisture value higher than an appropriate moisture value for granulating the sintering raw material, thereby granulating large-diameter pseudo-particles having larger particle size than those formed under the appropriate moisture value; and subsequently subjecting the pseudo-particles to a drying treatment, thereby reducing the moisture value of the large-diameter pseudo-particles after the drying treatment to the appropriate moisture value without increasing the diameter of the particles.

Description

  The present invention provides a raw material for producing a sintered ore that is useful in securing stable and high productivity and high strength of the sintered ore when the sintered ore is produced by a dweroid type sintering machine. It relates to the manufacturing method.

In recent years, in the steel industry, a large amount of carbon dioxide gas is emitted in the production of iron, so the influence on global warming has been regarded as a problem, and reduction of CO ₂ emissions has become an important issue. In response to such a problem, in recent blast furnace operation, operation with a low reductant ratio (total amount of tuyere-injected fuel and furnace top-charged coke used to produce 1 ton of hot metal, hereinafter referred to as “RAR” Say) is recommended. In order to perform low RAR operation of a blast furnace, in general, the raw material particle size is reduced to increase the heat receiving efficiency and the reaction interface area with the reducing gas, the raw material properties are improved to improve the reducibility, and the blast furnace operation. It is considered that methods such as suppressing the ambient gas flow to improve the gas utilization rate or reducing the amount of heat removed from the blast furnace furnace body are effective.

  However, during low RAR operation, the ratio of ore raw material to coke in the furnace (Ore / Coke) increases, resulting in deterioration of air permeability in the upper part of the furnace, ventilation in the lower part of the furnace due to deformation and enlargement of the fused body. It was pointed out that it would be difficult to perform stable blast furnace operation due to the deterioration of performance. Therefore, in order to realize a stable low RAR operation, the properties of sintered ore, which accounts for about 70% of the iron ore raw material, are very important.

In general, sintered ore used as a raw material for a blast furnace is generally manufactured through a treatment as described below. That is, first, in addition to iron ore powder having a particle size of 10 mm or less, a SiO ₂ -containing material composed of silica, serpentine, various smelting slags, a secondary material composed of a limestone-based material containing CaO such as limestone, and powder A solid fuel-based powder raw material serving as a heat source such as coke or anthracite is added with an appropriate amount of water, mixed in a drum mixer, and granulated to produce a granulated sintered raw material.

  The granulated and sintered raw material thus obtained, that is, the granulated compounded and sintered raw material, has an appropriate thickness on the pallet of a Dwytroid (DL) sintering machine, for example, about 500 to 700 mm. After being charged, the solid fuel in the surface layer is ignited, and after ignition, the solid fuel is combusted using the air sucked downward, and the sintering raw material is sintered with the combustion heat to sinter the cake. To do. Next, the sintered cake is crushed and sized, and a product having a certain particle size or more is used as a product sintered ore. In addition, the thing with a small particle size after sizing is reused as a sintering raw material as a return ore.

  In general, as one of the factors that influence the operation of the blast furnace, there is a problem of reducibility of the product sintered ore (hereinafter simply referred to as “sintered ore”). The reducibility of the sinter is related to the gas utilization rate in the blast furnace and has a good negative correlation with the RAR. When the reducibility of the sinter is improved, the RAR in the blast furnace decreases. . In the case of sintered ore, the cold strength is also an important factor for ensuring air permeability in the blast furnace, and each blast furnace is operated with a lower limit standard for the cold strength.

In order to improve the cold strength of the sintered ore, it is important to uniformly fill the sintering pallet with the sintering raw material, secure a sufficient sintering time, and sinter gently. However, in recent years, blast furnaces have increased the use of sintered ore due to the operation of high dip ratio, and the quality of raw materials has decreased (increased high crystal water ore, increased Al ₂ O ₃ ore, increased fine ore. As a result, it is difficult to ensure good air permeability in the packed layer of the deposited sintered material on the sintering pallet (hereinafter referred to as “raw material packed layer”) and to ensure sufficient sintering time. There is a concern that the productivity of the sintering machine, the yield, and the cold strength of the sintered ore may be reduced due to this.

  Conventionally, in order to improve the air permeability of the raw material packed layer, a method for granulating a sintered raw material has been studied in order to solve such problems. For example, in Patent Document 1, before adding water to one or more blends of sintered raw materials containing coarse particles and fine powder, the moisture content is determined from the water absorption rate of the sintered raw materials and the particle size distribution before granulation. The lower limit moisture concentration at which the sintered raw material after the addition shows the adhesion force, that is, the critical moisture concentration is calculated, and the added amount of moisture in the granulation mixer is set so that the moisture concentration of the pseudo particles is equal to or higher than the critical moisture concentration. A method for producing pseudo particles by granulating while controlling is disclosed.

  With respect to this point, it was difficult to control the moisture content in the granulation mixer by determining the appropriate moisture content in advance according to the change of the sintering raw material in the granulation method of the sintered ore before that. However, according to the method described in Document 1, since the amount of fine powder that does not adhere to the coarse particles can be minimized, the average particle size of the pseudo particles is increased and the air permeability is improved. It explains that the productivity of the ore is improved.

  Moreover, in patent document 2, from the saturated water absorption rate and the particle size distribution before granulation of each sintering raw material individually accommodated in a plurality of sintering raw material tanks, A critical moisture concentration that is a lower limit value is calculated in advance for each sintering material, and among the sintering materials accommodated in the plurality of sintering material tanks, at least the sintering material having a large saturated water absorption rate. Add moisture to the water to achieve a water concentration equal to or higher than the saturated water absorption rate, and then blend multiple types of the above-mentioned sintered raw materials and granulate while adding water to achieve a water concentration equal to or higher than the critical moisture concentration. Thus, a method for granulating pseudo particles is disclosed. According to this method, the amount of water added to the sintering raw material charged into the DL sintering machine can be easily controlled, and the operation can be performed without reducing productivity and yield.

  Further, Patent Document 3 discloses a method of performing a drying process after granulation. However, since the powder is pulverized in the course of the drying process, a product having a large pseudo particle size cannot be produced.

  Furthermore, Non-Patent Document 1 discloses the relationship between the amount of moisture added to the pseudo particles, the air permeability of the packed bed, and the particle size of the pseudo particles in FIG. According to the content disclosed in Non-Patent Document 1, when the moisture content is 0 to 7.5 mass%, the absorption of moisture into the pseudo-particles is gradually saturated, and the moisture that wets the particle surface produces a binder effect. It is reported that the granulated particle diameter of the granulated particles is increased and the air permeability is improved.

  However, when the water content exceeds 7.5 mass%, the particles continue to increase, but the voids between the particles are filled with excess water, so the flow of air passing through the packed bed is reduced. The problem of being disturbed arises.

JP 11-61281 A JP 2000-1725 A JP 2006-336064 A “Iron and Steel” Japan Iron and Steel Institute 68 (1982), p. 2174

The methods disclosed in Patent Documents 1 and 2 are methods for predicting appropriate moisture in advance before manufacturing pseudo particles, and for quickly dealing with fluctuations in the quality of sintered raw materials. However, the deterioration of the quality of the sintered raw material in recent years is remarkable, and the permeability of the deposited layer (hereinafter referred to as “sintered packed layer”) of the sintered raw material is reduced due to the increase in fine powder, and the flow due to the increase in Al ₂ O _3. Just setting the proper water content to prevent a decrease in productivity due to a decrease in productivity is not a fundamental solution.

  Therefore, the object of the present invention is to solve the above-mentioned problems of the prior art and improve the air permeability of the raw material packed layer during the operation of the sintering machine, without causing a decrease in strength or yield. Another object of the present invention is to propose a method for producing a sintered raw material used for producing sintered ore, which is effective in improving the production rate of sintered ore.

  In order to solve the above-mentioned problems, in the present invention, in a method for producing a granulated sintered raw material obtained by mixing and granulating a sintered raw material containing coarse or fine particles of iron ore under water addition and granulating the raw material, In the case of the above granulation, first, by adding and granulating an excess moisture than the appropriate moisture value for granulating the sintered raw material, the particle size formed under the appropriate moisture value Granulate particles with a larger diameter (hereinafter referred to as “expanded diameter pseudo-particles”), and subsequently dry the particles so that the moisture value after drying of the expanded diameter pseudo-particles is equivalent to the original appropriate moisture value. The manufacturing method of the sintering raw material characterized by reducing is proposed.

  That is, in the present invention, when producing a granulated and sintered raw material (pseudo particle) to be charged into a DL sintering machine, first, an appropriate moisture value suitable for mixed granulation (granulated sintered raw material is sintered). When it is deposited on the machine pallet, the moisture value is higher than the moisture amount suitable for granulating the sintered raw material without deteriorating the air permeability of the raw material packed layer, that is, This is a method for granulating expanded diameter pseudo particles by adding excess water beyond an appropriate water value. As a result, it is possible to obtain expanded pseudo particles in which the particle size of the obtained pseudo particles is larger than that obtained when the moisture content is appropriate.

  In the present invention, in particular, it is important to heat-dry the swelled pseudo-particles immediately without performing curing or the like until the moisture value of the swelled pseudo-particles becomes equivalent to the original appropriate moisture value. . By performing such a drying treatment, the particle size of the obtained pseudo particles is increased, while the moisture can be reduced to an appropriate moisture value by drying without incurring the expanded diameter of the particles. . As a result, the size of the pseudo particles can be maintained while adsorbing the surrounding fine powder to be expanded.

  In this way, in the case of pseudopores in a multi-porous state that has been dried and removed, the influence of excessive moisture for increasing the diameter as in the past is also affected during the sintering operation. On the other hand, only the effect of increasing the particle diameter can be enjoyed without being affected, that is, without causing deterioration of air permeability. In addition, this makes it possible for the product sintered ore to improve the productivity of the sintered ore without causing a decrease in cold strength or yield.

And this invention becomes more preferable embodiment by setting it as the following structures further.
(1) The moisture value after drying of the expanded diameter pseudo-particle is set within an appropriate moisture value ± 1 mass%,
(2) The moisture value of the expanded diameter pseudo particles at the time of granulation is increased by 10 to 50% from the appropriate moisture value.
(3) The expanded diameter pseudo-particles have a water-containing fine powder layer composed of moisture and agglomerated fine powder in the outer layer,
(4) The proper moisture content of the pseudo particles means granulated moisture that maximizes the cold air permeability of the raw material packed layer, and is within a range of about 4.0 to 9.5 mass% depending on the blended raw material. It must be a thing.

  According to the present invention having the above-described configuration, once the pseudo-particle size is increased and expanded to obtain an expanded pseudo particle, and then the expanded pseudo particle is not put in between after granulation, Or, by drying so that the pseudo particles do not break even if there is a gap, excess moisture that contributed to expansion is removed, so sintering expected when excess moisture is added Only the effect of increasing the diameter of the expanded pseudo particles can be enjoyed without deteriorating the air permeability of the packed bed.

  By adopting such a configuration, in the present invention, the air permeability of the raw material packed layer is improved, and as a result, the sintering time can be shortened, so the cold strength and yield of the product sintered ore are reduced. The production rate of sintered ore can be improved without incurring.

It is a figure which shows the outline | summary of the sintering test process according to a conventional method. It is a figure which shows the relationship between granulation water | moisture content and air permeability. It is a figure which shows the outline | summary of the sintering test process according to this invention method. It is a figure which shows the relationship between granulated water | moisture content and the harmonic mean diameter of a pseudo particle. It is a figure which shows the relationship between granulation moisture and the particle size distribution of a pseudo particle. It is the cross-sectional photograph of the expanded diameter pseudo-particle granulated by appropriate water | moisture content +3.0 mass%, and it is the schematic diagram. It is the cross-sectional photograph of the expanded diameter pseudo-particle granulated by appropriate water | moisture content +5.0 mass%, and it is the schematic diagram. It is a figure which shows the relationship between granulation moisture and sintering time. It is a figure which shows the relationship between granulation moisture and a production rate. It is a figure which shows the relationship between granulated moisture and a yield.

  First, in order to elucidate the mechanism of improving the air permeability of the raw material packed bed on the sintering machine pallet and the production rate of the sintered ore, the inventors simulated the actual machine sintering process as shown in FIG. Grain and sintering tests were performed. In this granulation test, first, iron ore raw materials including coarse iron ore (8 mm or less) and fine iron ore (0.125 mm to 0.063 mm) are used to adjust the basicity from silica, quick lime, limestone, etc. The obtained mixed sintered raw material 1 is mixed with a disk mixer 2, and then the mixed sintered raw material after mixing is transferred to the drum mixer 3, and the drum mixer 3 is added while adding water. Was rotated and granulated to obtain pseudo particles.

  Next, in order to estimate the appropriate moisture value at which the cold air permeability of the packed bed is maximized, the inventors first granulated the two types of ore types and their blending ratios as shown in Table 1. The relationship between moisture and air permeability index was measured. FIG. 2 shows the relationship between the measured granulated moisture and the air permeability index. As can be seen in this figure, the air permeability of the packed bed varies greatly depending on the blending ratio of the sintering raw materials to be used. At level 1 it is 7.6% and at level 2 it is 5.5%. I found out that

  Generally, the appropriate moisture is granulated moisture that maximizes the cold breathability index in the raw material packed bed, and is 4.0 depending on the type of raw material used (determined by the properties of the ore and the mixing rate). It is in the range of ˜9.5 mass%.

  Furthermore, in order to investigate the superiority of the present invention, a sintering raw material production test was conducted in which the excess moisture was added to the appropriate moisture and granulated, followed by drying immediately. In this test, the amount of water to be added to the drum mixer 3 shown in FIG. 1 is determined based on T1: 7.6 mass% corresponding to the above-mentioned appropriate moisture for the sintered blend raw materials having the component compositions shown in Table 2. On the other hand, T2: 8.6 (+1) mass%, T3: 9.6 (+2) mass%, T4: 10.6 (+3) mass%, T5: 11 The test was conducted at six levels of 0.6 (+4) mass% and T6: 12.6 (+5) mass%.

  In a normal sintering operation, the granulated particles immediately after granulation by the drum mixer 3 are directly charged into a sintering machine as shown in FIG. However, in this test, as shown in FIG. 3, pseudo particles obtained by granulation are placed in the vat 4 and immediately put in the dryer 5 set at 200 ° C. for a predetermined time (5 to 20). Min) decided to dry. However, it is not preferable to completely dry the particles more than necessary, for example, because the particles are ruptured. Desirable drying time is measured in advance with the time-dependent change in the amount of water evaporated from the raw material, and the moisture content of the pseudo particles after drying is about the initial appropriate moisture value ± 1 mass% (around the vicinity of 7.6 mass%). Value). The value of the proper moisture ± 1 mass% is a range in which the swollen pseudo-particles can be dried to such an extent that they do not break even when dried.

  Table 2 shows the composition of the compounded sintering raw material used in this test, and Table 3 shows the ratio of moisture added during granulation and the moisture content of the pseudo particles after drying measured immediately before the sintering test.

  FIG. 4 shows the harmonic mean diameter of the granulated particles (expanded pseudo particles granulated by adding excessive water) after granulation by the drum mixer 3, and FIG. 5 shows the original proper granulated water content. : Shows the particle size distribution of granulated particles granulated by adding water in excess of the proper water amount of 10.6 mass% or 12.6 mass%, that is, swelled pseudo particles. As a result, as shown in FIG. 4, for those having a moisture value of 7.6 to 11.6 mass% at the time of granulation, the harmonic mean diameter of the particles is increased in accordance with the increase of the granulated moisture. The reason for this is that, when moisture is added excessively, when moisture absorption into the pseudo-particles is saturated, the excess moisture stays on the particle surface to form a water film, and the moisture exerts a binder action. It is considered that fine powder aggregates in the water film portion, and forms a hydrous fine powder layer to increase the granulated particle diameter.

  As can be seen from FIG. 5, when the particle size distribution ratios at 7.6 mass%, 10.6 mass%, and 12.6 mass% are compared, the water content during granulation increases. In the case of granulated moisture of 10.6 mass%, the ratio of coarse particles of 8.0 to 1.0 mm is increased, and the ratio of fine powder of -1 mm is decreased. On the other hand, as shown in FIG. 4, in the region exceeding 11.6 mass%, the harmonic average particle size of the pseudo particles decreases as the granulated water increases. That is, it can be seen from the results shown in FIGS. 4 and 5 that an excessive water addition of 12.6 mass% corresponding to +5 mass% causes the core particle part to collapse rather than a proper moisture value of 7.6 mass%, and rather does not aggregate. It can be seen that the fine powder ratio increases. Therefore, in the case of the present invention, it is understood that the amount of water added excessively is preferably within a range of about 10% (8.4 mass%) to 50% (11.6 mass%) from the appropriate moisture value. .

  FIG. 6 shows that a hemispherical sintered raw material corresponding to a swelled pseudo particle size is placed on a preparation, granulated by giving water more than the appropriate water, and then equivalent to the appropriate water (7.5 mass%). It is the cross-sectional photograph of this raw material which shows the condition when it is made to dry-dehydrate until, and its explanatory drawing.

  In the figure, the upper photo shows the excess particles within the scope of the present invention on the surface of the quasi-particles (nuclear particles) riding on the convection generated by the decrease of the moisture that is reduced in the drying process. The phenomenon of adhering and increasing the pseudo particle size can be observed. As a result, the expanded pseudo particles as shown in the middle photograph and the schematic diagram on the right side are obtained.

  On the other hand, the lowermost figure shows that when adding excess moisture within the scope of the present invention to granulate and drying it, it does not return to the level equivalent to the proper moisture, but exceeds the scope of the present invention. However, in this case, the fine particles fall around the quasi-particles (core particles), and the diameter of the quasi-particles (core particles) is not increased, but instead the diameter decreases. It has been confirmed that the effects of the present invention do not occur.

  Next, FIG. 7 shows an example in which water is added in excess of the appropriate moisture value, adjusted to an appropriate moisture value +5.0 mass%, granulated, and then dried. In this example, as shown in the middle photo and schematic diagram in the figure, the fine powder that exists around the quasi-particles (nuclear particles) has a large amount of water loss during the drying process, so it cannot catch up with the convection of water, It can be seen that fine powder that cannot be contained in the water-containing fine powder layer by the water film + aggregated fine powder as shown in FIG. 6 is generated and does not contribute to the increase of the pseudo particle diameter. As shown in the lowermost photograph and schematic diagram, it becomes clearer when dried out of the range of the present invention (-3 mass%).

  Next, FIG. 8 and FIG. 9 show the relationship between the moisture after the granulation before and after drying, the drying time, the sintering time, and the production rate when the method conforming to the method of the present invention is performed. . As shown in FIG. 8 and FIG. 9, the appropriate moisture value for granulation: 7.6 mass%, while the granulated moisture value is excessively added to 10.6 mass% and 11.6 mass%, It can be seen that the settling time is shortened and the production rate is improved. On the other hand, if this moisture value exceeds 11.6 mass% to 12.6 mass%, that is, if the excess moisture content exceeds 50%, the air permeability deteriorates due to the influence of the average particle size, and the sintering time increases, resulting in production. The rate is also falling.

  FIG. 10 shows the effect on the yield of sintered mineral products of +10 mm investigated after the sintering test. As can be seen from this figure, at least in the range of excess water value of about 10% (+1 mass%) to about 50% (+4 mass%) carried out according to the method of the present invention, no decrease in yield was observed, but 50% If it exceeds (11.6 mass%), the yield decreased.

  As described above, according to the present invention, when the pseudo-particles of the compound sintering raw material charged into the sintering machine are granulated while adding water using a drum mixer, It is desirable to form an expanded pseudo particle having an increased diameter by granulating the pseudo particle by adding excess moisture than the original proper moisture value required for the Immediately, that is, without drying or curing, the sintered raw material is dried and removed to a moisture equivalent to the original proper moisture value. This improves the air permeability of the raw material packed bed on the pallet during the operation of the sintering machine and improves the productivity of the sintered ore without causing a decrease in the cold strength and yield of the sintered ore. It becomes possible to do.

Example 1
This example was tested for the method according to the invention in the operation of a downward suction DL sintering machine with an effective grate area of 410 m ² and a production rate of 1.5 t / h · m ² . In this test, two drum mixers were used, granulated by adding 10.6 mass% (appropriate moisture value: + 40% relative to 7.6 mass%) corresponding to the excess moisture amount to the primary drum mixer, and the appropriate moisture value. The quasi-particles obtained by squeezing the harmonized average particle diameter of 1.08 mm to 1.25 mm, and then blowing hot air at 300 ° C. in the secondary drum mixer, Was dried, and dehydration was controlled by drying to a moisture value of 7.9 mass% corresponding to an appropriate moisture value. At this time, the average particle size of the pseudo particles was improved by about 15%, the air permeability of the sintered packed layer was improved, and the sintering production rate was improved by about 6%. From this, the method of the present invention improves the air permeability of the raw material packed layer on the sintering machine pallet, and can improve the sintering productivity without reducing the cold strength and yield of the sintered ore. I knew it would be possible.

  The technique of the present invention can be applied not only to the production of pseudo particles by the exemplified drum mixer but also to the case of granulation using another granulator, and agglomeration techniques such as pelletizing other than the sintering raw material. Application to is also possible.

1 Sintering raw material 2 Mixer 3 Drum mixer 4 Butt 5 Sintering machine

Claims (5)

In a method for producing a granulated sintered raw material obtained by mixing and granulating a sintered raw material containing coarse or fine particles of iron ore under water addition and granulating the raw material,
At the time of the above granulation, first, by adding excess moisture than the appropriate moisture value for granulating the sintered raw material and granulating, than the particle size formed under the appropriate moisture value Sintering characterized by granulating swelled pseudo particles having a large diameter and subsequently drying the particles to lower the moisture value after drying of the swelled pseudo particles to the equivalent of the original proper moisture value Raw material manufacturing method. The method for producing a sintered raw material according to claim 1, wherein the moisture value after drying of the expanded pseudo particles is set within an appropriate moisture value of ± 1 mass%. 3. The method for producing a sintered raw material according to claim 1, wherein the moisture value of the expanded pseudo particles at the time of granulation is increased by 10 to 50% from the appropriate moisture value. The method for producing a sintered raw material according to any one of claims 1 to 3, wherein the swollen pseudo particles have a water-containing fine powder layer composed of moisture and agglomerated fine powder in the outer layer. The method for producing a sintered raw material according to any one of claims 1 to 4, wherein the proper water content of the pseudo particles is granulated water that maximizes the cold air permeability of the raw material packed layer.

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