WO2012026542A1 - Method for producing carbon-material-containing metal oxide agglomerates - Google Patents

Abstract

In the present invention: water and a sufficient quantity of a binder (D) for caking a metal oxide (A), which is the main component, and a carbonaceous material (B), are added to a powdered raw material (C) containing the metal oxide (A) and a sufficient quanity of the carbonaceous material (B) to reduce the metal oxide (A), and a mixed raw material (F) is formed using a mixer (1); and when carbon-material-containing metal oxide agglomerates (H) are produced by agglomerating the mixed raw material (F) using an agglomerating means, and drying the raw agglomerates (G) that are obtained in a drier (3), a starch-containing substance containing 2 to 13 mass % of protein is used as the binder (D), and when the temperature of the raw agglomerates (G) in the drier (3) has reached the gelatinization temperature of the starch-containing substance, the raw agglomerates (G) are dried in such a manner that the moisture in the raw agglomerates (G) remains at not less than 6 mass %, thereby producing the carbon-material-containing metal oxide agglomerates. Consequently, when using the starch-containing substance as a binder, the strength of the agglomerates after drying can be ensured and cost reductions can be achieved without using organic substances, and without carrying out pre-treatment.

Description

Method for manufacturing carbon oxide-incorporated metal oxide agglomerates

The present invention relates to a method for producing a carbonaceous material-containing metal oxide agglomerate that is reduced in a rotary hearth furnace or the like.

The reduced iron production method using a shaft reduction furnace represented by the MIDREX method and the HyL method produces reduced iron from iron ore and iron oxide pellets using natural gas. However, the present method has a problem that the location condition of the plant is limited to the area where the natural gas is produced because the high-cost natural gas is reformed into the reducing gas.

Therefore, in recent years, a method of producing reduced iron using a coal material such as coal as a reducing agent in place of natural gas has attracted attention. For example, a mixed raw material of powdered iron ore and coal is used as raw pellets or raw briquettes. After agglomerating into a (general agglomerate) and drying this raw agglomerate into a carbonaceous iron-incorporated iron oxide agglomerate, this carbon-internalized iron oxide agglomerate is placed on the rotary hearth Thus, a method of producing reduced iron by heating and reducing while moving in the furnace has been developed (for example, Patent Document 1).

Also, after the dried carbonaceous material-incorporated iron oxide agglomerate is placed on the rotary hearth and heated while moving in the furnace, the iron oxide in this carbonaceous material-incorporated iron oxide agglomerate is solid-reduced and then produced. A method for producing high-purity granular metallic iron by further heating and melting the metallic iron to be melted and aggregating while separating from the slag component has been developed (for example, see Patent Documents 2 and 3).

These methods have advantages such that coal can be used as a reducing agent, powdered iron ore can be used directly, reduction is fast, and the carbon content in the product can be adjusted. . In particular, the method for producing the granular metallic iron has the advantage that the slag component can be removed from the product in advance and the carbon content in the product can be further increased as compared with the method for producing the reduced iron. Yes.

However, since carbon materials such as coal have a water-repellent surface, there is almost no effect of bonding the agglomerate grains to each other. The strength of the product is lower than that of the agglomerate not containing carbonaceous material. In particular, if the strength of the iron oxide agglomerates after drying is low, the iron oxide is destroyed and pulverized when charged into the reduction furnace, leading to a reduction in the yield and quality of the reduced iron, and in addition, the powder enters the hearth. Adhering may cause operational troubles.

Therefore, the applicant of the present application has advanced earnestly research and development on means for improving the strength after drying of the carbonaceous iron-incorporated iron oxide pellets which are a kind of carbonaceous iron-incorporated iron oxide agglomerates, and completed the invention disclosed in Patent Document 4. (Prior art 1). This prior art 1 is characterized in that an organic binder such as starch and an inorganic flocculant such as bentonite are used in combination as a binder. Carbonaceous iron-incorporated iron oxide pellets granulated using such a binder have the advantage of excellent strength after drying and a small amount of inorganic material remaining as impurities after reduction.

In addition, the applicant of the present application has also studied a means for producing a metal oxide agglomerate using a metal refining dust containing a high concentration of an alkali metal element as a raw material, and in Patent Document 5, an acidic substance such as lignin is used as a binder. It was also disclosed that a metal oxide agglomerate having excellent strength after drying can be produced by using a starch-containing substance such as wheat flour (Prior Art 2).

Patent Document 6 also discloses that pregelatinized starch is used as an agglomeration binder in order to agglomerate steelmaking dust and reuse it as a converter raw material (prior art 3).

In all of the above prior arts 1 to 3, a starch-containing substance is used as a binder, but it is necessary to use it together with other substances or to pre-gelatinize starch, which increases the cost of the binder. The problem remains. Furthermore, in prior art 1, even if the addition amount is small, an inorganic substance such as bentonite is used together. Therefore, when producing reduced iron in a rotary hearth furnace, the inorganic substance is contained in the obtained reduced iron as a slag component. The residual energy increases in the process of producing hot metal and molten steel using reduced iron as a raw material, and when granular metal iron is produced in a rotary hearth furnace, the amount of slag separated from the granular metal iron increases. There is also a problem that the energy intensity of the rotary hearth furnace increases.

As described above, when using a starch-containing substance as a binder, further reducing the cost while ensuring the strength of the agglomerate after drying without using an organic substance or the like and without pretreatment. There has been a demand for the development of a method for producing an agglomerated carbon oxide agglomerate that can be realized.

US Pat. No. 3,443,931 Japanese Laid-Open Patent Publication No. 2002-339909 Japanese Unexamined Patent Publication No. 2003-73722 Japanese Patent No. 3040978 Japanese Patent No. 3944378 Japanese Unexamined Patent Publication No. 2001-214222

Therefore, the present invention, when using a starch-containing substance as a binder, without using an organic substance together and without performing pretreatment, while further ensuring the strength of the agglomerate after drying, further cost reduction An object of the present invention is to provide a method for producing a carbonaceous material-containing metal oxide agglomerate that can be realized.

In order to solve the above problems, the present inventors first granulated raw pellets containing carbonaceous materials using only various starch-containing substances as binders, and variously changed the drying conditions of the raw pellets to produce carbonaceous materials. A test for producing interior iron oxide pellets was conducted, and the effects of the properties of the starch-containing substance and the drying conditions on the strength of the carbonaceous interior iron oxide pellets after drying were investigated.

As a result, the protein content and gelatinization temperature of the starch-containing substance and the drying conditions were found to be closely related to the strength expression of the carbonaceous iron oxide pellets after drying. It came to complete.

According to the first aspect of the present invention, the metal oxide and the carbonaceous material are bonded to a powdery raw material containing a metal oxide as a main component and a carbonaceous material in an amount sufficient to reduce the metal oxide. A sufficient amount of binder and water are added to form a mixed raw material, and the raw agglomerate obtained by agglomerating the mixed raw material is dried with a dryer to form a carbonaceous metal oxide mass. In manufacturing the composition, only the starch-containing material containing 2 to 13% by mass of protein is used as the binder as it is, and the temperature of the raw agglomerate in the dryer reaches the gelatinization temperature of the starch-containing material. The carbonaceous material-incorporated metal oxide agglomerate is characterized by drying so that moisture remains in the raw agglomerate in an amount of 6% by mass or more.

The invention according to claim 2 is the method for producing a carbonaceous material-incorporated metal oxide agglomerate according to claim 1, wherein a heat pattern in the dryer is set in accordance with a gelatinization temperature of the starch-containing substance.

Invention of Claim 3 selects the thing which has the gelatinization temperature suitable for the heat pattern in the said dryer as said starch containing substance, The manufacturing method of the carbonaceous material interior metal oxide agglomerate of Claim 1 It is.

The invention described in claim 4 is the method according to any one of claims 1 to 3, wherein the addition amount of the starch-containing substance is increased by 0.075 mass% or more per 0.1 mass% increase in the ash content in the starch-containing substance. It is a manufacturing method of the carbonaceous material interior metal oxide agglomerate of 1 item | term.

According to the present invention, a starch-containing substance containing 2 to 13% by mass of protein is used as the binder, and when the temperature of the raw agglomerate in the dryer reaches the gelatinization temperature of the starch-containing substance, By allowing 6% by mass or more of moisture to remain in the raw agglomerated material, it has become possible to ensure the strength of the agglomerated material after drying without increasing the cost of the binder.

It is a flowchart explaining the outline | summary of the manufacturing method of the carbonaceous material interior metal oxide agglomerate which concerns on implementation of this invention. It is a graph which shows the heat gelatinization curve (amylogram) of various starch. It is a graph which shows the relationship between pellet temperature and the residual moisture in a pellet in the drying test of the raw pellet by a pot great furnace.

Hereinafter, embodiments of the present invention will be described in more detail with reference to the drawings.

FIG. 1 is a flowchart for explaining an outline of a method for producing a carbonaceous material-containing metal oxide agglomerate according to an embodiment of the present invention. Here, reference numeral 1 indicates that the metal oxide A and the carbonaceous material B are added to the powdery raw material C containing the metal oxide A as the main component and the carbonaceous material B in an amount sufficient to reduce the metal oxide A. A mixer for adding and mixing a sufficient amount of binder D and water E for caking, 2 is an agglomeration means for agglomerating the mixed raw material F mixed in the mixer 1. As an example of the converting means 2, reference numeral 21 denotes a pelletizer that granulates the mixed raw material F to produce raw pellets G ₁ , 22 denotes a briquette machine that press-molds the mixed raw material F to produce raw briquettes G ₂ , reference numeral 3 Is a dryer for drying raw pellets G ₁ or raw briquettes G ₂ (generically referred to as raw agglomerates G) to produce dry pellets H ₁ or dry briquettes H ₂ (generically referred to as dry agglomerates H).

As the metal oxide A, not only iron oxide but also non-ferrous metal oxides such as Ni, Cr and Mn can be used. Specifically, as iron oxide sources, powdered iron ore, mill scale, iron making dust (blast furnace dust, converter dust, sintered dust, electric furnace dust, mill sludge, pickling sludge, etc.), non-ferrous metal oxides As a source, dust containing non-ferrous metal oxides such as powdered non-ferrous metal ore, alloyed iron production, non-ferrous metal refining, and the like can be used. A mixture of two or more types can also be used.

Further, as the carbonaceous substance B, for example, coal, coke powder, petroleum coke, char, charcoal, pitch, and the like can be used, and these can be used alone or in combination of two or more.

The mixing ratio of the carbonaceous material B to the metal oxide A may be an amount sufficient for the metal oxide A to be reduced to metallize by the carbonaceous material B. The actual blending ratio varies depending on the quality of the target reduced metal or granular metal, such as the quality of the metal oxide A, the amount of fixed carbon in the carbonaceous material B, the metallization rate after reduction, and the amount of residual carbon.

Then, a sufficient amount of binder D and water E are added to the powdery raw material C containing the metal oxide A and the carbonaceous material B, and the metal oxide A and the carbonaceous material B are caking together, and mixed. Mix in the vessel 1 to obtain a mixed raw material F.

As the binder D, a starch-containing substance containing 2 to 13% by mass of protein is used.

Here, the reason why the protein content of the starch-containing substance is in the range of 2 to 13% by mass is as follows. That is, when the protein content is less than 2% by mass, the amount of protein that becomes an aggregate after cooling is insufficient even when the raw agglomerate G is heated in the dryer 2 and the starch-containing material as a binder is gelatinized. This is because the strength of the dry agglomerated product H cannot be obtained sufficiently. On the other hand, when the protein content exceeds 13% by mass, the starch-containing substance becomes too viscous when mixed with water in the mixer 1 or when the mixed raw material F is granulated with the pelletizer 21, and the protein content becomes uniform. This is because mixing becomes impossible or granulation becomes difficult. A more preferable range of the protein content is 3 to 12% by mass.

As starch-containing substances containing 2 to 13% by mass (more preferably 3 to 12% by mass) of protein, wheat flour and rye flour can be used. Tapioca and corn starch (corn flour) have a protein content of 2 Since it is less than mass%, it cannot be used for the present invention (see Example 1 below).

The addition amount of the binder D may be an amount sufficient for caking the metal oxide A and the carbonaceous material B, and is usually 1 to 2% by mass with respect to the powdery raw material C in consideration of economy. It is a suitable range. Further, the amount of water E added is adjusted so that the water content of the raw agglomerate G is 11 to 14% by mass from the viewpoint of easy agglomeration of the raw agglomerate G and prevention of flattening. preferable.

The mixed material F at pelletizer 21 which is a means of agglomeration means 2 and granulated, and green pellets G _1. As the pelletizer 21, a known disk-type pelletizer or drum-type pelletizer can be used. During granulation, a part of the water E added to the powdery raw material C may be added here. The diameter of the green pellets G ₁ is preferably in the range of 6 ~ 30 mm in consideration of the surface of the reduction rate in terms of handling and reducing furnace, and more preferably in the range of 9 ~ 19 mm.

Alternatively, pressure molding in briquette machine 22 is a mixed raw material F is another means of agglomerating means 2 may be a raw briquette G _2. As the briquette machine 22, for example, a known twin-roll briquette machine with excellent productivity is recommended, but an extruder, a cylinder brace, or the like may be used. The size of the raw briquettes G ₂ is, or equal to that of the raw pellets G ₁ equivalent of about volume.

The raw agglomerate G (raw pellet G ₁ or raw briquette G ₂ ) agglomerated in this way has a moisture content of 1% by mass using a dryer 3 such as a known moving great dryer. Dry agglomerate H (dry pellet H ₁ or dry briquette H ₂ ) is obtained by drying to the following. This dry agglomerated material H corresponds to the “carbon material-containing metal oxide agglomerated material” in the present invention.

Here, in drying in the dryer 3, when the temperature of the raw agglomerate G reaches the gelatinization temperature of the starch-containing substance D as a binder, the moisture content in the raw agglomerate G is 6% by mass. It is important to dry so that it remains.

When the temperature of the raw agglomerate G reaches the gelatinization temperature of the starch-containing substance D, the reason why the moisture remaining in the raw agglomerate G is 6% by mass or more is as follows.

That is, when starch is heated to a temperature higher than a certain temperature with water added, gelatinization starts and the viscosity increases. FIG. 2 shows the heat gelatinization curves (amylogram) of various starches published (Nippon Chemical Co., Ltd. homepage, [July 30, 2010 search], Internet <URL: http: //www.nicidene. com / kkh / b / b-1.htm>). Here, the temperature at which the viscosity starts to increase is called the gelatinization temperature. As shown in the figure, the gelatinization temperature is distributed in the range of 60 to 90 ° C., and the temperature varies depending on the kind of starch, which is 67 ° C. for tapioca, 85 ° C. for corn, and 90 ° C. for wheat flour.

As described above, since gelatinization of starch is a phenomenon that occurs in the presence of moisture, the present inventors have determined that the temperature of the raw agglomerate G is the glue of the starch-containing substance D during drying in the dryer 3. It was considered that a predetermined amount of moisture needs to remain in the raw agglomerate G in order for gelatinization of the starch-containing substance D to proceed sufficiently when reaching the crystallization temperature.

Therefore, in order to grasp the drying behavior of the green agglomerate G in the dryer 3, a drying test simulating the drying behavior of raw pellets by a moving great dryer was performed. Specifically, hematite ore as a metal oxide (−44 μm, 60% by mass or more) and bituminous coal (−80 μm, 80% by mass or more) as a carbonaceous material in a mass ratio of 81.7: 18.3. 1% by weight of flour as a binder (protein content: 3.1% by mass) was added thereto, and raw pellets having a diameter of 18 mm and a water content of about 13% by mass were granulated. 30 kg of this raw pellet was filled in a pot grate having an inner diameter of 300 mm, and a drying test was conducted by passing heated air at 130 ° C. or 180 ° C. through the raw pellet packed bed at a flow rate of 300 Nm ³ / h. Then, thermocouples were installed at two locations on the left and right sides in the raw pellet packed layer to measure the raw pellet temperature during the drying test, and the drying time was sequentially changed to measure the residual moisture content in the raw pellet.

The measurement results are shown in FIG. 3 in relation to the raw pellet temperature and the water content in the raw pellet. For example, “180 (L)” in the figure means a temperature measurement result by a thermocouple installed on the “left” side in the raw pellet packed bed in a drying test with heated air of “180 ° C.” “130 (R)” means a temperature measurement result by a thermocouple installed on the “right” side in the raw pellet packed bed in the drying test with heated air of “130 ° C.”.

As shown in the figure, as the raw pellet temperature rises, the moisture content (residual moisture amount) in the raw pellet decreases, but the lower the heated air temperature (130 ° C), the same raw pellet temperature. By comparison, it can be seen that the amount of residual moisture is small.

That is, when the temperature of the heated air is lowered, it takes a longer time to reach the same raw pellet temperature, which means that the evaporation of moisture has progressed during this time. Considering kinetics, it means that the higher the temperature is heated, the higher the temperature of the raw pellets is, which is preceded by the heat transfer in the raw pellets, but the evaporation is delayed. In an extreme example, when the temperature of the heated air is set to 90 ° C., the flour does not gelatinize and only drying proceeds. Therefore, the raw pellets are dried with hot air as high as possible without causing bursting (explosion due to rapid evaporation of moisture), leaving much moisture in the raw pellets to promote gelatinization of the flour and then proceeding with drying Is better.

As shown in FIG. 3, when the raw pellet temperature reaches 90 ° C., which is the gelatinization temperature of the flour added as a binder, the residual moisture content in the raw pellet is about when dried with heated air at 180 ° C. When dried with heated air at 7.0 ° C. and 130 ° C., it is about 3.0 to 5.5% by mass.

On the other hand, when the drop strength of the dried pellets dried to a residual moisture content of 1.0% by mass or less was measured by the above drying test, the target 15 times was secured when dried with heated air at 180 ° C. When dried with heated air at 130 ° C., the target of 15 times could not be secured.

Therefore, when dried with heated air at 180 ° C., when the raw pellet temperature reaches 90 ° C., which is the gelatinization temperature of flour, a sufficient amount of moisture remains in the raw pellet, and the flour As the gelatinization progressed, sufficient strength was developed in the dried pellets, but when dried with heated air at 130 ° C, the raw pellet temperature reached 90 ° C, the gelatinization temperature of flour. Sometimes, it is assumed that residual moisture in the raw pellets is insufficient, and gelatinization of the flour does not proceed sufficiently, so that the dried pellets do not have sufficient strength.

Based on the above results and considerations, in order to develop sufficient strength in the dried pellets, when the raw pellet temperature reaches 90 ° C., which is the gelatinization temperature of wheat flour, at least 6% by mass in the raw pellets It is assumed that water (more preferably 7% by mass) needs to remain.

In the above drying test, only the case where wheat flour having a gelatinization temperature of 90 ° C. was used as a binder is illustrated, but even when a starch-containing substance other than wheat flour is used, the raw pellet temperature is gelatinized of the starch-containing substance. When 6% by mass or more (more preferably 7% by mass or more) of water remains in the raw pellet when the temperature is reached, it is naturally assumed that the starch-containing substance is gelatinized.

From the above, when drying in the dryer 3, when the temperature of the raw agglomerate G reaches the gelatinization temperature of the starch-containing substance D, the moisture in the raw agglomerate G is 6% by mass or more ( More preferably 7 mass% or more).

As is clear from the above, a starch-containing material containing 2 to 13% by mass (more preferably 3 to 12% by mass) of protein is used as the binder, and the agglomerates are formed during drying in the dryer 3. When the temperature of the product G reaches the gelatinization temperature of the starch-containing material D, which is a binder, drying is performed so that moisture remains in the raw agglomerate G by 6 mass% or more (more preferably 7 mass% or more). Thus, it is possible to produce a dry agglomerated material (carbon material-containing metal oxide agglomerated material) H having excellent strength after drying at low cost (see Examples 1 and 2 below).

In order to realize the drying behavior commensurate with the gelatinization temperature of the starch-containing substance D as described above, when there is no choice in the starch-containing substance used as the binder D, the starch-containing substance is gelatinized. What is necessary is just to set the heat pattern in the dryer 3 according to temperature. The heat pattern in the dryer 3 can be easily adjusted, for example, by changing the temperature and / or flow rate of the heated air, the drying time (= the residence time of the raw agglomerate G in the dryer 3), etc. Can do.

On the other hand, when it is difficult to change the heat pattern in the dryer 3 due to productivity restrictions, etc., the starch-containing material used as the binder D has a gelatinization temperature suitable for the heat pattern in the dryer 3. Just choose one.

As starch-containing substances that can be used as binder D, there are various types of bread-making, feed-use, and industrial-use, but it is desirable that they can be obtained at low cost and in large quantities for industrial use as in the present invention. It is. Generally, the lower the degree of purification (ie, the purity) of starch-containing materials, that is, the higher the ash content, the lower the price and the greater the availability of starch-containing materials.

However, if the ash content in the starch-containing material increases, the net starch content in the starch-containing material decreases, so even if the same amount is added, the ability as a binder decreases.

Therefore, although it is cheaper and can be obtained in large quantities, when a starch-containing material with low purity is used, the addition of the starch-containing material per 0.1% by mass increase in the ash content in the starch-containing material The amount may be increased by 0.075% by mass or more (see Example 3 below).

In order to confirm the effect of the present invention, the following granulation / drying tests were conducted.

[Example 1] Effect of protein content of starch-containing substance First, the influence of the protein content of starch-containing substance on the granulation property of raw pellets and the drop strength of dried pellets was investigated.

Similar to the above-described drying test for grasping the drying behavior, hematite ore (44 μm, 60% by mass or more) as a metal oxide and bituminous coal (−80 μm, 80% by mass or more) as a carbonaceous substance in a mass ratio of 81.7: It mix | blended in the ratio of 18.3. Then, 1.0% by mass of various starch-containing substances as a binder was added thereto, and raw pellets having a diameter of 18 mm and a water content of about 13% by mass were granulated. Then, 30 kg of the raw pellets are filled in a pot grate having an inner diameter of 300 mm, and a drying test is performed by passing heated air at 180 ° C. through the raw pellet packed bed for 1 hour at a flow rate of 300 Nm ³ / h. The drop strength of the pellet (dry pellet) was measured. The drop strength was defined as the number of drops until breakage when the sample was repeatedly dropped from a height of 45 cm. In the test of this specification, measurement was performed with 15 dry pellets, and the average value was displayed.

The results of this granulation / drying test are shown in Table 1 below. The gelatinization temperature shown in the table is a value estimated using the amylogram of FIG. 2 without performing direct measurement. Here, wheat flour (thin flour in Table 1 and strong flour is also a kind of wheat flour) is considered to change the gelatinization temperature depending on the production area and type, but 90 ° C. obtained from the amylogram of wheat in FIG. 2 contains starch. Since the maximum value of the gelatinization temperature of the substance is assumed, all of them were set to “90 ° C. or less”. Further, the residual moisture content when the gelatinization temperature is reached shown in the table is a value obtained from the drying curve of the heated air temperature of 180 ° C. in FIG. In addition, the granulation properties shown in the table are ◎ when granulation is easy, and granulation is possible even when irregularly shaped small particles are formed during granulation or raw pellets slip and rolling becomes unstable. Cases were marked with ◯ and cases where granulation was difficult and granulation could not be made with x, respectively. Moreover, the fall strength of the dry pellet made the pass 15 times or more. And the case where granulation property is (double-circle) or (circle), and drop strength is a pass was made into the invention example, and it was set as the comparative example in the case other than that.

As is clear from the table, in Test Nos. 1, 4, and 5, which are invention examples, the protein content of the starch-containing substance added as a binder is in the range of 2 to 13% by mass, and the temperature of the raw pellet is When the gelatinization temperature of the starch-containing substance is reached, the residual moisture content in the raw pellet is 6% by mass or more, which satisfies the requirements of the present invention, and is excellent in granulation properties and dry pellet drop strength. .

In contrast, Test Nos. 2 and 3, which are comparative examples, show that when the temperature of the raw pellet reaches the gelatinization temperature of the starch-containing substance, the residual moisture content in the raw pellet becomes 6% by mass or more. Since the protein content of the starch-containing substance added as a binder is too low, the requirements of the present invention are not satisfied, and although the granulation property is excellent, the falling strength of the dried pellets is inferior.

Moreover, test number 6 which is a comparative example was added as a binder although the amount of residual moisture in the raw pellet was 6% by mass or more when the temperature of the raw pellet reached the gelatinization temperature of the starch-containing substance. Since the protein content of the starch-containing substance is too high, it does not satisfy the requirements of the present invention, and the granulation property and the drop strength of the dried pellet are inferior.

[Example 2] Influence of heating air temperature Next, in order to investigate the influence of the heating air temperature on the drop strength of the dried pellets, in the test number 4 in Table 1 above, the carbonaceous material was lignite (-74 μm, 80 mass). %) And the binder addition amount was increased to 1.5 mass%, and a test in which the heating air temperature was changed to 105 ° C. was added (test number 7). The drying time was 1 hour, the same as in Example 1 above. The results of this test are shown in Table 2 below together with the test number 4 in Table 1 above.

As shown in the table, in test No. 7 in which the heated air temperature was lowered to 105 ° C., the drop strength of the dried pellets was greatly reduced despite the increase in the binder addition amount to 1.5% by mass. This is presumably because the raw pellet temperature did not reach the gelatinization temperature of wheat flour during the drying time of 1 hour, and the strength was not sufficiently developed. Even if the drying time is extended, the heated air temperature is too low, so when the raw pellet temperature reaches the gelatinization temperature of the flour, it is determined that the residual moisture content in the raw pellet is significantly less than 6% by mass. It is presumed that strength is not developed.

[Example 3] Effect of ash content of starch-containing material Furthermore, in order to investigate the effect of ash content of starch-containing material on the drop strength of dry pellets, two types of rye flour with high ash content were used as binders. A granulation / drying test was carried out using various amounts of these additives. The test conditions were the same as in Example 1 except for the binder type and amount added.

Table 3 shows the test results. As shown in the table, when rye flour having a low grade for foods and a high ash content is used as a binder, a target drop strength of 15 times can be secured at a binder addition amount of 1.0% by mass. However, it was found that the drop strength increased as the binder addition amount was increased, and the target of 15 times or more could be achieved. And by comparing the test number 9 and the test number 11 that have a drop strength of 15 times or more and the same level, the ash content of the starch-containing substance as a binder is 0.4 mass. % (1.6-1.2 = 0.4) increases, it is necessary to increase the amount of binder added by 0.3 mass% (1.5-1.2 = 0.3) in order to maintain the drop strength. I understand that there is.

Therefore, even if a starch-containing substance having a high ash content is used as a binder by increasing the added amount of the starch-containing substance by 0.075 mass% per 0.1 mass% increase in the ash content in the starch-containing substance. It is clear that the drop strength of the dried pellet can be reliably ensured 15 times or more.

Although the present invention has been described in detail and with reference to specific embodiments, it will be apparent to those skilled in the art that various changes and modifications can be made without departing from the spirit and scope of the invention.

This application is based on a Japanese patent application filed on August 27, 2010 (Japanese Patent Application No. 2010-190718), the contents of which are incorporated herein by reference.

According to the present invention, in producing a carbonaceous material-containing metal oxide agglomerate, when using a starch-containing substance as a binder, no organic substance is used in combination, and no pretreatment is performed, so that the cost can be reduced. realizable.

DESCRIPTION OF SYMBOLS 1 ... Mixer 2 ... Agglomeration means 21 ... Pelletizer 22 ... Briquette machine 3 ... Dryer A ... Metal oxide B ... Carbonaceous material C ... Powdery raw material D ... Binder E ... Water F ... Mixed raw material G ... Raw agglomeration Product G ₁ … Raw pellet G ₂ … Raw briquette H… Carbonized metal oxide agglomerates (dried agglomerates)
H ₁ ... dry pellet H ₂ ... dry briquette

Claims (4)

1. A binder in an amount sufficient for caking the metal oxide and the carbonaceous material to a powdery raw material containing a metal oxide as a main component and a carbonaceous material in an amount sufficient to reduce the metal oxide. When the raw material agglomerate obtained by agglomerating the mixed raw material is dried with a dryer, a carbonaceous material-containing metal oxide agglomerate is produced.
   As the binder, only a starch-containing material containing 2 to 13% by mass of protein is used as it is, and when the temperature of the raw agglomerate in the dryer reaches the gelatinization temperature of the starch-containing material, the raw agglomerate is used. A method for producing a carbonaceous metal-incorporated metal oxide agglomerate, characterized in that drying is performed so that water remains in an amount of 6% by mass or more.
2. The method for producing a carbonaceous material-containing metal oxide agglomerate according to claim 1, wherein a heat pattern in the dryer is set in accordance with a gelatinization temperature of the starch-containing substance.
3. The method for producing a carbonaceous metal-incorporated metal oxide agglomerate according to claim 1, wherein a material having a gelatinization temperature that matches a heat pattern in the dryer is selected as the starch-containing substance.
4. The carbonaceous material internal oxidation according to any one of claims 1 to 3, wherein the addition amount of the starch-containing material is increased by 0.075 mass% or more per ash content increase of 0.1 mass% in the starch-containing material. A method for producing metal agglomerates.
   

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