JPH0365412B2 - - 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 coal stone powder as needed, and fired on a grid at a temperature of 1,200 to 1,400°C to sinter the iron ore. A method of melting a portion, sintering it, cooling it and then crushing it into suitable particles. (2) Pelletizing - Calcining method An appropriate amount of water and, if necessary, bentonite, coal, etc. are added to finely ground iron ore powder, and the pellets are granulated using a rotating drum, rotating plate, etc., 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;
When it is introduced into the blast furnace, it is 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) It is necessary to add a large amount of cement (usually 7% or more) to achieve sufficient strength.
Since the slag ratio increases during operation of the blast furnace, the tap ratio, coke ratio, furnace front workability, etc. deteriorate. (d) Since the pellets are spherical and the reduction reaction proceeds topochemically, unreduced FeO tends to remain inside the pellets. (e) Since the raw material iron ore needs to be pulverized in the manufacturing process, the power cost for pulverization is high. <Objective of the invention> The present invention develops strength in a short period of 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 . <Structure of the Invention> In order to achieve the above object, the structure of the present invention is characterized in that a mixture of iron ore powder, cement, and water is compressed into flakes using a pressure forming roll, and then cured. The iron ore powder used in the present invention is hematite-based,
Either magnetite-based or limonite-based cement may be used, and the cement used may be portland cement, mixed cement, alumina cement, or portland cement clinker powder. The particle size of the iron ore powder is preferably smaller than the roll gap of the roll forming machine used, and is usually preferably 5 mm or less. Next, the smaller the amount of cement added to the iron ore powder as a binder, the better; however, if it is less than 2% by weight, the cold drop strength will decrease, and if it is less than 2% by weight, it is not preferable, and if it is more than 8% by weight, it may not be added. The strength is not improved so much, so the amount added is preferably 2% by weight or more and less than 8% by weight. The iron ore powder, cement, and water may be mixed at the time of crushing the iron ore, or may be mixed using an ordinary concrete mixer or the like. The amount of water added to the mixture of iron ore powder and cement varies depending on the fineness of the iron ore powder, but it is usually preferably 4% by weight or more and less than 8% by weight. The cold drop strength is low, and if it exceeds 8% by weight, the amount of water added will leak out of the molded product during molding, which is not preferable. When the mixed raw material is compression molded using a pair of pressure molding rolls, a molded product is continuously produced in the form of flakes. Also, the thickness of the flakes can be controlled by changing the roll gap. The thickness of the flakes is preferably 6 mm or more and less than 15 mm. If it is less than 6 mm, the cold drop strength will be low, while if it is more than 15 mm, the reducibility of the uncalcined agglomerate will be poor, so these are not preferred. The molded product is crushed to a predetermined particle size using a crusher as necessary.
It is usually crushed to 10 to 50 mm and then cured. For curing of the molded product, steam curing is preferable when charging the molded product into a blast furnace after curing for less than one day, and room temperature curing may be used when curing for more than one day. In addition, in either case of steam curing or room temperature curing, it is preferable to perform forced drying at 100°C or higher after curing. Forced drying is preferred because it increases the strength of the molded product and also reduces the amount of moisture entering the blast furnace. <Effects of the Invention> The present invention described above has the following advantages. B. Because iron ore powder is cold agglomerated, SOx,
There is no need to take measures to prevent air pollution such as NOx and dust. Since it is manufactured in the form of flakes, it has a larger angle of repose than conventional unfired pellets, and can prevent uneven distribution during charging into the blast furnace. c) The curing time can be significantly shortened compared to conventional non-fired pellets. D. The amount of cement used can be reduced compared to conventional unfired pellets, and the slag ratio during blast furnace operation can be suppressed. E) Grinding power costs can be reduced compared to conventional non-fired pellets. F. It has excellent reducibility and improves the smelting effect. <Experimental Examples> Experimental examples of the present invention are shown below. Experimental Example 1 One level of 150 kg of iron ore (hematite type) powder from Rio Doce, Brazil, which had been dried at 105°C and then ground to 1 mm or less, was mixed with 1% to 10% by weight of early-strength Portland cement. Thereafter, 100 parts by weight of the mixture and 6 parts by weight of water were mixed using a concrete mixer, and compression molded into flakes using a pair of pressure molding rolls. Moldings at 20℃ relative humidity
JIS M8711 after curing for 1 day and 7 days at 80% or more
The drop strength was measured according to the method and the results shown in Figure 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% by weight to 8%. It turns out that weight % is preferred. Experimental Example 2 After mixing 94 parts by weight of Riodoce iron ore powder used in Example 1, 6 parts by weight of early-strength Portland cement, and 5 parts by weight of water in a pug mill, the same roll machine as used in Experimental Example 1 was used. , flakes of various thicknesses were formed by changing the roll gap. After curing the flakes for one day at room temperature, the falling strength was measured according to JIS M8711, and the final reduction rate was measured according to JIS M8713, and the results shown in Figures 2 and 3 were obtained. It can be seen from FIGS. 2 and 3 that the thickness of the molded flakes is preferably 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 reduced quality of the flakes becomes poor, which is not preferable. Experimental Example 3 Iron ore (hematite type) from Hamasley, Australia was crushed to 5 mm or less, then 6wt% of ordinary Portland cement and 6wt% of water were added, mixed in a pug mill, and then crushed in the forming roll machine used in Experimental Example-1. Compression molded. The flakes were cured under various conditions, and then the angle of repose, falling strength, final reduction rate, and maximum pressure drop value were measured, and the results shown in Tables 1 to 4 were obtained. For comparison, briquette machine molded products and unfired pellets (ordinary Portland cement 10wt%)
88μ sieve residue after adding to Hammersley iron ore
Grind to 1.2% and granulate into 13-15mm diameter using a dish granulator)
were also prepared and tested.

[Table] It is clear that the roll forming according to the present invention has a significantly higher product yield.

[Table] The test was discontinued due to several occurrences.
From Table 2, it can be seen that the cold drop strength of the roll compression molded product of the present invention is significantly higher than that of other molded products. On the other hand, the effect of accelerated curing or long-term curing is small for molded products made using a briquette machine. This is thought to be because the non-uniformity of the molded product caused by the molding pressure not acting uniformly on the molded product is not eliminated by curing. In addition, unfired pellets made of dish-shaped granules require 7 hours of curing at room temperature to achieve 95% drop strength.To shorten this time, steam curing at 80℃ for 3 hours results in cracks on the surface. There are problems that can occur and damage the product. However, the molded product of the present invention is steam cured at 80°C.
Over time, the drop strength reaches 91%, making it possible to develop strength in a short period of time.

[Table] Next, looking at the reducibility, compared to the briquette machine molded product or the conventional dish-shaped granulated product, the final reduction rate of the molded product according to the present invention is as clear from Table 3. It can be seen that it is 95%, which is a significant improvement. This is thought to be due to the fact that the molded product of the present invention has a flake shape and is as thin as 10 mm, so that the reduction reaction progresses to the inside. Moreover, the swelling index of the molded product of the present invention is also the same as that of the conventional molded product, and it can be seen that there are no disadvantages in this respect.

[Table] The angle of repose was measured after the cylinder was pulled out.
Furthermore, the angle of repose was measured for the molded product of the present invention and the molded product of the comparative example. The results are shown in Table 4. Table -
As is clear from 4, the angle of repose of the molded product of the present invention is larger than that of the conventional molded product, and it is found that it is convenient when charged into a blast furnace. Experimental example 4 1 iron ore (magnetite type) from Tatsusu, Canada
Mixed with 7% by weight of ordinary Portland cement and 5% by weight of coke powder after pulverized to less than mm.
6 parts by weight of water was added to 100 parts by weight, mixed in a pug mill, and then molded using the roll molding machine used in Experimental Example 1 at a molding pressure of 1500 kg/cm ² . The thickness of the flakes was 13 mm. Curing the molded product at room temperature for 1 day,
After 4 hours of steam curing at 80℃ and 4 hours of steam curing at 50℃
After curing at each level of drying at 250°C for 2 hours, the cold drop strength, final reduction rate, and blistering index were measured according to JIS, and the results shown in Table 5 were obtained.

[Table] As is clear from Table 5, the final reduction rate was 91 to 92% in all of the experimental examples.
As in case 3, it can be seen that the reducibility is greater than that of the conventional one. Example 5 Iron ore (limonite type) from Robe River, Australia was crushed to 3 mm or less, and then 25% by weight of early strength Portland cement and 5% by weight of 88μ solid coal powder were added and mixed, based on 100 parts by weight of the mixture. After mixing 7 parts by weight of water in a pug mill, using the roll forming machine used in Experimental Example 1, the molding pressure was 500 kg/
Molded in cm ² . The flake thickness was 8.0 mm. Curing the molded product at room temperature for 1 day, steam curing at 90℃ for 2 hours,
After steam curing at 90℃ for 2 hours and drying at 200℃ for 2 hours, the cold drop strength was determined according to JIS.
The final reduction rate and blistering index were measured and the results shown in Table 6 were obtained.

[Table] As is clear from Table 6, the final reduction rates in this experimental example were all 95% to 96%, and as in the case of Experimental Example 3, it can be seen that the reducibility is greater than that of the conventional example. I understand. It is also clear that short-term strength can be achieved by steam curing.

[Brief explanation of drawings]

1 to 3 relate to the molded product of the present invention,
Figure 1 is a graph showing the relationship between cement addition amount and falling strength, Figure 2 is a graph showing the relationship between flake thickness and falling strength, and Figure 3 is a graph showing the relationship between flake thickness and final reduction rate. be.

Claims (1)

[Scope of Claims] 1. A method for producing non-calcined agglomerate ore, which comprises compression molding a mixture of iron ore powder, cement and water into flakes using pressure molding rolls, and then curing the mixture. 2. The non-calcined agglomerated ore according to claim 1, characterized in that in the mixture, the amount of cement added is 2% to 8% by weight, and the amount of water added is 4% to 8% by weight. manufacturing method.