JPH0364571B2 - - Google Patents

Description

[Detailed description of the invention]

<Technical field> The present invention is aimed at preventing scattering of the powder when charging iron ore powder or iron oxide powder in a blast furnace, and maintaining air permeability in the furnace to allow the refining reaction to proceed smoothly. Regarding the preliminary treatment of raw material iron ore powder. <Prior art> In recent years, the grain size of iron ore charged into blast furnaces has tended to become smaller due to demands such as increasing the pig iron production ratio or reducing the coke ratio. The amount of iron ore powder used will continue to increase due to the increasing amount of iron ore handled due to necessity, and the strengthening of dust collection to prevent dust pollution at pig iron factories. There is a tendency. If these iron ore powders are charged into a blast furnace as they are, they will cause poor and uneven ventilation, an increase in the amount of gas ash generated, and poor unloading. Iron ore powder must be agglomerated using an appropriate method because it has a significant negative impact on operations. The following methods are currently used industrially to agglomerate raw materials such as iron ore powder or iron oxide powder. (1) Sintering method Iron ore powder of approximately 5 mm or less is mixed with coke of an appropriate particle size and limestone powder as needed, and fired on a grid at a temperature of 1,200 to 1,400 degrees Celsius. A method in which the parts are melted and sintered, and after cooling, they are crushed into suitable particles. (2) Peitzizing - Calcination method An appropriate amount of water and, if necessary, bentonite, lime, etc. are added to finely ground iron ore powder, and it is granulated using a rotating drum or rotating plate, and then fired and sintered in a rotary kiln. How to obtain sufficient strength by (3) Pelletizing - Cold hardening method A suitable amount of water is added to a mixture of finely pulverized iron ore powder and Portland cement or Portland cement clinker powder using what is commonly called the cold bond method. A method of obtaining sufficient strength by granulating and then curing. These methods can be roughly divided into the three methods mentioned above, but methods (1) and (2) both involve adding strength to the iron ore powder granules or pellets by using some method. It is being fired. This firing not only requires large-scale equipment, but also
There is a problem that SOx, NOx, dust, etc. generated from the kiln become a source of pollution. For this reason, the method (3) above has been developed as a non-fired agglomeration method, but the method (3) has the following drawbacks and is still not sufficient. (b) It takes a long time (usually 7 to 10 days) to develop strength, so large-scale curing equipment is required. (b) Since pellets are spherical, their angle of repose is small, and when they are introduced into a blast furnace, they are unevenly distributed in the center of the furnace, making blast furnace operation extremely unstable. To avoid this, the amount used is limited to very small amounts (usually 10-20% by weight). (c) In order to achieve sufficient strength, it is necessary to add a large amount of cement (usually 7% or more), which increases the slag ratio during blast furnace operation. Sexuality becomes worse. (d) Since the pellets are spherical and the reduction reaction proceeds topochemically, unreduced FeO tends to remain inside the pellets. (e) Due to the presence of hydration water (bound water) in cement, the fuel ratio increases and condensation occurs at the top of the furnace, which is inconvenient for operation. (F) The bonds of cement hydrate are destroyed by heating, and therefore the hot strength at 500 to 800°C is significantly reduced. <Objective of the invention> The present invention develops strength in a short time after forming without sintering in advance, has water resistance, has excellent reducibility in a blast furnace, and has iron ore powder at a melting temperature. It is an object of the present invention to provide a method for producing uncalcined agglomerated ore having sufficient strength to maintain its shape until it reaches . <Configuration of the Invention> In order to achieve the above object, the configuration of the present invention is characterized in that a sticky hydrocarbon mixture is added and mixed with iron ore powder, and then the mixture is compression molded and hardened. The iron ore powder used in the present invention is hematite-based,
Either magnetite type or limonite type may be used. In the present invention, a predetermined amount of a sticky hydrocarbon mixture is added to the iron ore powder. Here, the viscous hydrocarbon mixture refers to one consisting of one or more of asphalt, pitch, or solvent extracted carbon (SRC). All of these are sticky and hydrocarbon-based mixtures that are solid or semi-solid at room temperature and usually melt when heated to 100°C or higher.
Further heating in a neutral or reducing atmosphere evaporates the volatile components and increases the viscosity, eventually turning into glassy carbon and graphite. The amount of these sticky hydrocarbon mixtures added is preferably 1% to 6% by weight. If it is less than 1% by weight, the strength of the molded product will be low;
If the amount exceeds 50°C, the adhesive hydrocarbon may ooze out onto the surface of the molded product and cause them to stick to each other.
This is preferable because the molded product softens when heated to a higher temperature. In order to add the sticky hydrocarbon mixture to the iron ore powder, it is preferable to add the molten hydrocarbon mixture by spraying or the like, and mixing is preferably carried out using a pug mill or the like. It is preferred that the time from addition of the binder to the iron ore powder to compression molding be as short as possible. If this time is too long, the binder will solidify and the moldability will deteriorate, which is not preferable. In such a case, it is necessary to heat the iron ore powder. When the above sticky hydrocarbon mixture is added to iron ore powder, the sticky hydrocarbon mixture acts as a binder, and when cooled to room temperature after compression molding, the molded product develops strength due to the solidification effect of the binder and exhibits high strength. At this time, granulation using a rotating plate type or rotating drum type granulator is not preferred because granulation cannot be achieved unless the amount of binder is increased, and as a result, a softening phenomenon occurs when heated to 50° C. or higher. On the other hand, compression molding using rolls is preferred because not only can the amount of binder added be reduced, but also the strength of the molded product is high, molding unevenness is small, and large-scale processing is possible. When performing compression molding with a roll, a hopper with a vibration plate attached to the top of the roll gives vibration to the molding material in the hopper, which improves the biting of the raw material into the roll and also deaerates the air in the raw material. This is preferable because it improves moldability and also increases the strength of the molded product. Another advantage is that by applying vibration to the raw material, the phenomenon of hanging of the raw material in the hopper can be prevented. In addition, during roll forming, if the particle size of the iron ore powder is too large, it will be difficult to bite into the forming roll, resulting in a decrease in formability. Therefore, the maximum diameter of the particles is preferably smaller than the gap between the forming rolls, and is usually preferably 5 mm or less. The thickness of the flakes (molded product) is preferably 7 mm or more and 15 mm or less, and the thickness of the flakes can be controlled by changing the roll gap. The obtained flakes are crushed to the required particle size (usually 10 to 50 mm) using a crusher as necessary. Next, when the molded body is heated in a neutral or reducing atmosphere, the volatile content in the binder evaporates from about 200°C and the viscosity of the binder increases, so the strength of the molded body increases, and the strength of the molded body increases until it reaches about 800°C. At this point, the evaporation of volatile matter is almost completed and the glassy carbon binds the iron ore particles, further increasing the strength of the compact. Since carbon is very chemically inert and has high hot strength in a neutral or reducing atmosphere, the hot strength of the molded article does not decrease under heating during the above-mentioned molding. On the other hand, during smelting, the carbon remaining in the compact ultimately chemically reacts with the iron ore powder to reduce the iron ore and disappear. <Effects of the Invention> The manufacturing method of the present invention described above has the following effects. (1) Since the cold strength of the compact is achieved by solidifying the binder, agglomerates with high strength can be produced immediately after compaction. That is, it does not require post-forming firing equipment or curing equipment and exhibits a cold drop strength of 80% or more within 30 minutes after molding, so it can be immediately charged into a blast furnace and has excellent hot strength.
Therefore, high-quality molded bodies can be manufactured in large quantities easily and inexpensively. (2) Since cement is not used as a binder, it is possible to obtain agglomerated ore without a high slag ratio. (3) Since the agglomerate produced by the compression molding method using rolls is in the form of flakes, it has a larger angle of repose and better reducibility than conventional uncalcined pellets. (4) Since the carbon remaining in the compact reduces iron ore, it has the advantage of reducing the coke ratio during blast furnace operation. <Experimental Example> Next, an experimental example of the present invention will be shown below. Experimental example 1 Iron ore (hematite type) powder from Rio Doce, Brazil, crushed to 1 mm or less, was heated to 150℃,
After adding 1.0% to 8.0% by weight of straight asphalt melted at °C and mixing in a pug mill,
It was compression molded into flakes using a pair of pressure molding rolls. After the molded product was allowed to cool to room temperature, the cold drop strength was measured according to JISM8711, and the results shown in FIG. 1 were obtained. The conditions for forming the roll are as follows. Roll diameter: 450mm Roll width: 300mm Molding pressure: 800-1000Kg/cm ^2- roll rotation speed: 2rpm Flake thickness: 10mm As is clear from Figure 1, the amount of cement added to iron ore powder is 2% to 6% by weight. It turns out that weight % is preferred. When it is less than 2% by weight, the strength is low;
Moreover, when the amount is 6% by weight or more, not only the effect of improving strength is small, but also excess asphalt oozes out onto the surface of the molded product, making it more likely to solidify. Experimental Example 2 The iron ore powder from Rio Doce used in Experimental Example 1
4% by weight of straight asphalt melted at 150°C was added and mixed in a pug mill. Using the same roll machine as used in Experimental Example 1, flakes of various thicknesses were formed by changing the roll gap. After the flakes were allowed to cool to room temperature, the cold drop strength was measured according to JIS M8711, and the final reduction rate was measured according to JIS M8713, and the results shown in Figure 2 were obtained. As is clear from FIG. 2, it is preferable that the thickness of the molded flakes is 6 mm or more and 15 mm or less.
That is, when it is less than 6 mm, the drop strength is low, and when it is more than 15 mm, the reducibility of the flakes becomes poor, which is not preferable. Experimental example 3 Australian Hasmalay iron ore (hematite type) powder of 3 mm or less heated to 140-150℃
After adding 4% by weight of tar pitch heated and melted at 180 to 210°C and mixing in a pug mill, vibration was applied to the forming raw material using a hopper equipped with a vibrating plate on the top of the roll of the pressure forming roll machine used in Experimental Example 1. Compression molding was performed using a roll while degassing the air. The molding conditions were as follows. Roll gap: 6 mm, molding pressure: 900 Kg/cm ² After cooling the flakes to room temperature, the yield and cold drop strength were measured, and the results shown in Table 1 were obtained. For comparison, measurements were also taken on molded products made from the same raw materials using a briquetting machine.

[Table] From the results in Table 1, it can be seen that the roll forming of the present invention is superior to the conventional briquette machine forming in terms of product yield and strength of the molded product. In addition, in the roll forming of the present invention, when the raw material hopper above the roll is vibrated to separate the air in the raw material and then roll formed, the biting of the raw material into the roll is improved, resulting in improved product yield and molded product strength. It is clear that the results are improved. Experimental Example 4 In Experimental Example 3, the raw material was vibrated and the flakes formed with a roll were cooled to room temperature, heated in an electric furnace with _N2 gas atmosphere at a specified temperature for a specified period of time, allowed to cool in the furnace, and then processed according to JIS M8711. The cold drop strength was measured and the results shown in Figure 3 were obtained. The amount of heating per level of flakes was 25 kg, the heating temperature was 300 to 900°C, and the heating time was 5 hours. From the results shown in FIG. 3, it can be seen that the strength of the molded product of the present invention does not decrease due to heating. Experimental Example 5 5% by weight of asphalt heated and melted at 150-170°C was added to Australian Robe River iron ore powder of 1 mm or less heated at 150-170°C, mixed in a pug mill, and then mixed in the roll forming machine used in Experimental Example 1. Compression molding was performed at a molding pressure of 600 kg/cm ² while applying vibration to the raw material. After cooling the flakes, the cold drop strength, final reduction rate, and blistering index were measured according to JIS, and the following results were obtained. The thickness of the flakes was 8 mm. Cold drop strength 91% Final reduction rate 97% Blistering index 3.5% As is clear from the above results, the agglomerate of the present invention has high cold strength and final reduction rate, and is excellent as a raw material for blast furnace charging. I understand. Experimental example 6 2% by weight of 88μ limestone powder was added to Canadian Tatsusu iron ore powder of 1 mm or less heated to 140-150℃.
After addition and mixing, 3% by weight of tar pitch heated and melted at 180-210°C was added and mixed in a pug mill.
Compression molding was performed at a molding pressure of 900 kg/cm ² using the roll molding machine equipped with a rolled copper plate used in Experimental Example 1. After cooling the flakes to room temperature, the cold drop strength, final reduction rate, and blistering index were measured according to JIS, and the following results were obtained. Cold drop strength: 88% Final reduction rate: 97% Blistering index: 3.7% As is clear from this experimental example, in the manufacturing method of the present invention, there is no problem even if limestone powder is mixed and molded. Ore can be produced. Experimental Example 7 7% by weight of coke powder of 1 mm or less was mixed with the iron ore powder from Rio Doce, Brazil used in Experimental Example 1.
After heating to 180-200℃, 6% by weight of SRC (ash content 0.6% by weight, volatility 49.7% by weight) heated and melted at 290-310℃ was added and mixed in a pug mill. Molding pressure 500 with roll forming machine
Compression molded at kg/ ^cm2 . After cooling the flakes to room temperature, the cold drop strength, final reduction rate, and blistering index were measured according to JIS, and the following results were obtained. Cold drop strength: 92% Final reduction rate: 98% Blistering index: 3.8% As is clear from this experimental example, in the production method of the present invention, there is no problem even if coke powder is mixed and molded, but rather good unburned agglomerate ore is produced. Can be manufactured.

[Brief explanation of drawings]

Figures 1 to 3 are graphs showing the properties of molded products produced by the manufacturing method of the present invention. Figure 1 is a graph showing the relationship between cement addition amount and cold drop strength, and Figure 2 is a graph showing the relationship between flake thickness and cold drop strength. A graph showing the relationship between cold drop strength and final reduction rate, and FIG. 3 is a graph showing the relationship between cold drop strength and heating temperature.

Claims (1)

[Scope of Claims] 1. A method for producing non-calcined agglomerate ore, which comprises adding and mixing a sticky hydrocarbon mixture to iron ore powder, and then compression molding and hardening the mixture. 2. Claim 1, characterized in that one or more of asphalt, pitch, or solvent-extracted charcoal is used as the sticky hydrocarbon mixture.
A method for producing uncalcined agglomerated ore as described in Section 1. 3. The method for producing uncalcined agglomerate ore according to claim 1, wherein the amount of the sticky hydrocarbon mixture added is 1% to 6% by weight.