JP5803540B2 - Method for producing unfired carbon-containing agglomerated mineral - Google Patents

Description

  The present invention relates to a method for producing a non-fired carbon-containing agglomerated mineral.

  Conventionally, steel mills have been blended with various iron oxides, added with cement-based aging binders, kneaded and molded to produce unfired pellets and briquettes, which have been used as blast furnace raw materials.

  These unfired carbon-containing agglomerated ores for blast furnaces must have a certain cold crushing strength to withstand transportation to the blast furnace and pulverization during blast furnace charging. Therefore, when granulating iron oxide with a granulator, adjust the particle size distribution of dust to an appropriate range, add moisture to binders such as limestone and cement, granulate, and then cure and harden The strength has been secured.

  In addition, these unfired carbon-containing agglomerated ores for blast furnaces cause a reduction reaction in the blast furnace due to the carbon contained in the blast furnace, resulting in an improvement in the reduction rate. The amount of carbon has been increased.

  From the above, it is desired that the unfired carbon-containing agglomerated ore for blast furnace has a large amount of interior carbon and high cold crushing strength.

As a method of increasing the cold crushing strength of unfired carbon-containing pellets for blast furnaces, “addition of a hydraulic binder to a finely divided iron-containing raw material and finely divided carbonaceous material, and a carbon content ratio in all raw materials (TC) Is adjusted to a blending ratio of the pulverized carbonaceous material so that it is 15 to 25% by mass, further mixed and granulated while adjusting the moisture, and then subjected to a curing treatment to obtain a cold crushing strength of 85 kg / cm ^2. (8300 kN / m ² ) A method for producing unfired carbon-containing pellets for blast furnaces, wherein the curing treatment is performed after the pellets after granulation are left in the atmosphere for 12 to 48 hours in a primary curing yard. The pellet is charged into a shaft furnace for secondary curing, and steam blowing treatment is performed in the shaft furnace at a temperature of 60 to 90 ° C. and a treatment time of 5 hours or more. And before the steam blowing process The total processing time of the drying process should be within 8 hours "is the invention (Patent document 1).

In addition, for the purpose of reducing the ratio of reducing material in blast furnace operation, “in-carbon non-fired agglomerated minerals that are kneaded, molded, and cured by blending iron-containing raw material and carbon-based carbonaceous material and adding a binder. The binder is selected so that it contains 80 to 120% of the theoretical carbon required to reduce the reducible oxygen of stones to metallic iron, and the crushing strength at room temperature is 7850 kN / m ² or more. An invention of a carbon-incorporated non-fired agglomerated blast furnace for a blast furnace characterized by being kneaded, molded and cured is proposed (Patent Document 2).

  In addition, for the purpose of reducing the strength after reduction of unfired briquette used in the blast furnace method and DR method (direct reduction method), “carbon interior with a porosity of 15 to 25% after molding and drying” There is a proposal of “non-fired briquette” (Patent Document 3).

In addition, by adjusting the particle size of all iron raw materials, the blending ratio of fine powdered carbon materials, and adjusting the median diameter of fine powdered carbon materials, 50 kg / cm ² (4900 kN / m) required as raw material pellets for blast furnaces ² ) While maintaining the above cold strength, it has a sufficient carbon content to greatly reduce the ratio of reducing material during blast furnace operation, and the crushing strength after reduction is 7 kg / cm ² (690 kN / m ² ) or more A non-fired carbon-containing pellet manufacturing method has been proposed (Patent Document 4).

JP 2009-161791 A JP 2003-342646 A JP 62-290833 A JP 2008-95177 A

The unfired carbon-containing agglomerated ore for blast furnace is desired to have a large amount of interior carbon and high cold crushing strength.
According to the invention described in Patent Document 1, the amount of carbon contained in the non-fired carbon-containing pellets for blast furnaces is large, and a non-fired carbon-containing pellet with high cold crushing strength can be obtained. Furthermore, in the secondary curing shaft furnace, there is a problem that steam blowing curing and subsequent drying treatment are required, resulting in high equipment costs and treatment costs.

  According to the invention described in Patent Document 2, a cement binder such as early-strength Portland cement is used instead of quick lime in order to maintain the cold crushing strength of the unfired agglomerated mineral with carbonaceous materials. Therefore, increasing the amount of binder added not only reduces the rate of temperature rise at the shaft in the blast furnace due to the endothermic cement dehydration reaction, but also generates a reduction stagnation zone (low temperature thermal storage zone) at low temperatures. The problem is that it promotes the reduction pulverization of the sintered ore charged as the iron raw material for the blast furnace in the blast furnace.

According to the invention described in Patent Document 3, it can be expected to some degree that the strength reduction during reduction in the blast furnace of the carbonaceous material-incorporated unfired briquette can be suppressed.
However, the porosity after molding and drying of the carbonaceous material-incorporated non-fired briquette is affected by the properties and particle size of the raw material and the carbonaceous material, and it is difficult to control the porosity within the range of 15 to 25%. There is a problem of receiving.

According to the invention described in Patent Document 4, the blending ratio of the finely powdered carbon material is set so that the particle size in all raw materials is 2 mm or less and the carbon content ratio (TC) in all raw materials is 15 to 25% by mass. By adjusting and setting the median diameter of the carbon material to 100 to 150 μm, producing a non-fired carbon-containing agglomerated mineral having good cold crushing strength and post-reduction crushing strength and having a high reducing material ratio reduction effect. Can do.
However, in this method, the particle size in all the raw materials must be 2 mm or less, the median diameter of the carbonaceous material must be 100 to 150 μm, there are restrictions from both the raw material and the carbonaceous material, and 10 If the amount of non-fired carbon-containing agglomerated mineral used in the blast furnace is increased, the amount of slag charged into the blast furnace also increases. In addition, since the early strong cement undergoes a dehydration reaction (endothermic reaction) at 400 to 500 ° C., excessive use of the carbon-containing agglomerated mineral with 10% added cement lowers the temperature in the blast furnace, There is a problem that a temperature rise delay and a reduction delay occur.

  The present inventor has selected a non-fired carbon-containing agglomerated mineral with a high amount of interior carbon and high cold crushing strength by using a small hydraulic binder by selecting and optimizing the binder in accordance with the characteristics of the iron oxide raw material. The manufacturing method of was examined.

  An object of the present invention is to provide a method for producing a non-fired carbon-containing agglomerated mineral with a high amount of interior carbon and high cold crushing strength by using a small hydraulic binder.

  The present inventor has found that by changing the hydraulic binder to pregelatinized starch, it is possible to produce a non-fired carbon-containing agglomerated ore for blast furnace with high cold crushing strength.

  The present invention has been made to solve the above-mentioned problems based on this finding, and the gist thereof is as follows.

(1) the upper limit of the particle size on at least one solid carbon pellet feed and fine iron ore which is the particle size adjusted to 250 [mu] m, and mixed and kneaded adding a binder containing α-starch which is particle size control limit to 200μm particle size step When,
The mixed and kneaded product is molded into an agglomerated ore by a briquette method or an extrusion molding method , and granulated ;
Curing and drying the molded agglomerate,
The manufacturing method of the non-baking carbon-containing agglomerated mineral characterized by implementing.
(2) When the total amount of the hydraulic binder is replaced with the pregelatinized starch so as not to include the hydraulic binder, the amount of the pregelatinized starch is at least one of the pellet feed and fine iron ore and solid carbon The method for producing a non-fired carbon-containing agglomerated mineral according to (1), wherein the content is 0.3% by mass or more and 1.0% by mass or less with respect to the total mass of the pregelatinized starch.
(3) The amount of the solid carbon is 20% by mass or more and 30% by mass or less with respect to at least one of the pellet feed and fine iron ore, and the total mass of the solid carbon and pregelatinized starch ( The manufacturing method of the non-baking carbon-containing agglomerated mineral in any one of 1) and (2).

  The present invention can provide a method for producing an unfired carbon-containing agglomerated mineral having a high cold crushing strength.

The figure which shows a coke mixture ratio and a reducing material ratio reduction effect.

The test results of the carbon-containing agglomerated agglomerated by various molding methods are shown below. The molding method was agglomerated by the rolling granulation method, the compression molding method, and the extrusion molding method, and the volume of the agglomerate was unified to 5 cm ³ . In the rolling granulation method, a granulation test was performed using a pan pelletizer having a diameter of 1 m. In the compression molding method, a briquette machine having a roll diameter of 500 mm was used and compression molding was performed at a linear pressure of 4 t. In the extrusion molding method, the molding test was performed with the extrusion speed (speed at which the raw material passes through the holes) set to 40 mm / s.
The agglomerated carbon-containing agglomerated minerals were cured in an atmosphere of 30 ° C. for 14 days, dried at 105 ° C. for 2 hours, and then subjected to a crushing strength test.
In addition, as a pretreatment, a predetermined amount of raw materials including a binder were mixed, kneaded for 6 minutes with a kneader, added with a predetermined amount of water, and then kneaded for 4 minutes to agglomerate.

  The crushing strength was measured in accordance with JIS M8718 “Iron Ore Pellet Crushing Strength Test Method” by applying a compressive load to one sample at a specified pressure rate to measure the load value when it was broken. .

Table 1 shows the post-curing strength of a molded product molded by the briquette method under the condition of blending powder ore adjusted to a particle size of 250 μm or less and blending 25% by mass of −1 mm powder coke. In the case of riodose pellet feed, MBR pellet feed, MUSA pellet feed, and lobe river powder ore, the early strength Portland cement was entirely replaced with pregelatinized starch in response to the early strength Portland cement addition conditions. Strength was developed when 0.3% or more of pregelatinized starch was added.
The pregelatinized starch becomes a gel when water is added, reducing the frictional force between the particles. By performing compression molding or extrusion molding in this state, rearrangement of particles is promoted, and the packing density becomes dense.
When compression molding is performed using an ore-based raw material with a single particle and few voids, such as lump ore or pellet feed, the gelatinized pregelatinized starch is efficiently diffused between the particles without being buried in the irregularities of the particles, and dried. Since a strong network is formed later, the strength of the molded body is improved.
Although a slight improvement in strength is observed under the condition where 1.5% of pregelatinized starch is added, no significant improvement effect is observed. Therefore, considering the strength and cost, the amount of pregelatinized starch added is 0.3. It is desirable to set it to -1.0%.
On the other hand, when the pregelatinized starch was less than 0.3%, the strength was almost the same as when 5% of early strong Portland cement was blended.
Moreover, when powder sintering is mix | blended, the intensity | strength improvement effect by addition of pregelatinized starch is hardly recognized. This is presumably because the sintered iron source has many irregularities of single particles and many voids, and the pregelatinized starch was buried in the particles of the sintered dust.

  Table 2 shows the strength of carbon-containing agglomerated minerals obtained by adding 1.0% pregelatinized starch to carbon-containing agglomerated minerals containing 25% by mass of -1 mm coke powder in ore raw material of each particle size and molding by briquette method. Indicates. When the particle size of the ore-based raw material exceeds 250 μm, it has been found that the strength of the agglomerate is greatly reduced and the effect of the binder is lost. This can be attributed to the fact that the strength decreased due to the cracking of the ore having a large particle size by compression molding, and that the filling structure became rough as the cause of the strength decrease.

Table 3 shows the results of the molding test under the condition where 200 μm or more pregelatinized starch was added.
If the particle size of the pregelatinized starch is too large, it is not well mixed with the ore powder at the time of kneading, and the strength development effect is low, so the particle size of the pregelatinized starch is preferably 200 μm or less.
In the case of pregelatinized starch having a particle size of 200 μm or more, it is considered that the addition efficiency was lowered because the starch was not well mixed with the raw material during kneading.

FIG. 1 shows the blast furnace use test results when the coke mixing ratio is changed. The carbon-containing agglomerated mineral used in this test is 1% of pregelatinized starch and uses a riodose pellet feed. The reducing material ratio reducing effect shows the effect when using 100 kg / tpig of carbon-containing agglomerated ore in a blast furnace.
It was found that when a carbon-containing agglomerated mineral blended at a coke blending ratio of 20 to 30% was used in a blast furnace, the reduction efficiency was improved and the reducing material ratio reduction effect was maximized. On the other hand, when the coke blending ratio is less than 20% and when blending more than 30%, the reducing material ratio reducing effect is lowered, so that the coke addition amount is desirably 20% to 30%. At all levels, regardless of the coke powder blending ratio, the strength of the carbon-containing agglomerated mineral added with 1% pregelatinized starch satisfied 1000 kN / m ² or more.

Table 4 shows that riodose pellet feed is used as an ore-based raw material with 1% pregelatinized starch added and 25% coke powder is added. The strength after drying of the carbon-containing agglomerated mineral produced is shown (molding conditions are the same as described above).
From Table 4, it can be seen that the effect of pregelatinized starch is low in the rolling granulation method without compression. The pregelatinized starch diffuses due to the compaction between the particles and improves the strength between the particles at the time of drying. Therefore, it is considered that the briquette method and the extrusion molding method accompanied by compression at the time of molding improved the strength.
Therefore, the briquette method and the extrusion molding method are desirable in order to obtain the maximum effect of improving the cold strength of the carbon-containing agglomerated mineral using pregelatinized starch. However, the strength improvement effect is recognized also by the rolling granulation method.

  By using a small hydraulic binder, it is possible to provide a method for producing a non-fired carbon-containing agglomerated mineral with a large amount of interior carbon and high cold crushing strength.

Claims (3)

The upper limit of the particle size on at least one solid carbon of particle size control pellet feed and fine iron ore in 250 [mu] m, and mixing and kneading adding a binder containing α-starch which is particle size control limit to 200μm particle size,
The mixed and kneaded product is molded into an agglomerated ore by a briquette method or an extrusion molding method , and granulated ;
Curing and drying the molded agglomerate,
The manufacturing method of the non-baking carbon-containing agglomerated mineral characterized by implementing. When the total amount of hydraulic binder is replaced with the pregelatinized starch so as not to include a hydraulic binder, the amount of pregelatinized starch is at least one of the pellet feed and fine iron ore, solid carbon, and pregelatinized. It is 0.3 mass% or more and 1.0 mass% or less with respect to the mass total of starch, The manufacturing method of the non-baking carbon-containing agglomerated mineral of Claim 1 characterized by the above-mentioned.   The amount of the solid carbon is 20% by mass or more and 30% by mass or less with respect to at least one of the pellet feed and fine iron ore, and the total mass of the solid carbon and pregelatinized starch. The manufacturing method of the non-baking carbon-containing agglomerated mineral in any one of Claims 2.

Images