JPH01116035A - Method for molding of reserve reducing ore into mass - Google Patents

Abstract

PURPOSE:To reduce the using amt. of a binder and to permit the molding of the above ores into a mass at relatively low temp. in a good yield by kneading the charcoal material of powdery reserve reducing ores having specific metallizing ratio thereto and subjecting the same to pressure molding. CONSTITUTION:The charcoal material such as coal and coke breeze is kneaded to the reserve reducing ore powder having 30-80% metallizing ratio at a high temp. About 3-15% binder such as soft pitch and asphalt is added thereto, is subjected to pressure molding at <=300 deg.C and is molded into mass. In this way, the molded material having high strength can be manufactured in high yield by using reduced amounts of binder.

Description

Detailed Description of the Invention (Field of Industrial Application) The present invention is a method for melting and reducing iron ore that does not rely on a blast furnace process, in which fine ore is pre-reduced, and carbonaceous materials such as coal and coke are added to the pre-reduced ore. This is an agglomeration technology for mixing slag material such as limestone, agglomerating it in a molding machine, and charging it into a smelting reduction furnace, and relates to a method for agglomerating pre-reduced ore.

(Prior Art) Iron ore smelting reduction methods are generally divided into a preliminary reduction step and a smelting reduction step in terms of reduction functional efficiency and equipment characteristics. However, in the preliminary reduction process, a fluidized bed is used for powder or granular ore. In addition, electric furnaces or special smelting reduction furnaces have been developed for smelting reduction, but the pre-reduced ore obtained in the pre-reduction process has a pre-reduction rate of 30-98% metallization rate obtained at a reduction temperature of 600-900°C. -95%, the process of economically and stably charging this into a melting reduction furnace has become a very important technology.

In other words, pre-reduced ore has a high temperature and is highly reoxidizable, so if it is left in powder form, it is likely to be easily reoxidized and difficult to charge into a smelting reduction furnace, resulting in agglomeration.

Some iron oxide remains in the pre-reduced ore, and it is necessary to add a reducing agent such as coal or coke to melt and reduce it.
It would be advantageous in terms of the process if a carbonaceous material such as coke or a lime-forming slag agent were combined and used as a raw material for melt reduction.

Generally, when such raw materials are agglomerated, the usual method is to cool the molding material to a temperature of 100° C. or lower, add a binder, and then agglomerate it with a molding roll.

However, this method requires a cooling process for cooling, and also causes heat loss, which is not economical. In addition, when agglomeration is carried out at high temperatures, if the process contains 80-90% or more reduced iron and the temperature is 650°C or higher, no binder is required, as in the known process using only reduced iron. It is well known that it can be agglomerated into products,
In this case, when the metallization rate is high as in the above-mentioned process for reduced iron cars, and when the total amount of reduced iron or the addition of single materials is as low as a few inches, agglomeration is carried out using the thermoplasticity of iron. can.

However, agglomeration of raw materials with a low preliminary reduction rate used in the melt reduction process by mixing a large amount of carbonaceous materials such as coal and coke is difficult because the carbonaceous materials themselves function as exfoliating materials.
Agglomeration is difficult, and with conventional reduced iron forming technology, it was not possible to form the reduced iron unless the pre-reduced ore was cooled. (
Reference technology JP-A No. 12712) (Problems to be solved by the invention) The present invention solves the problem of metallization at a high temperature of 3 while retaining sensible heat.
It is possible to agglomerate by mixing 0-80% powder pre-reduced ore with carbonaceous materials such as coal, coke powder, or different types of powders such as lime slag, without reducing the metal content. High-strength molded products can be agglomerated with a lump yield of 80 ts or more without installing cooling equipment or using a large amount of binder. Particularly in order to avoid reducing the metallization rate, which is the quality of the product during the molding process, it is possible to reduce the water content by pre-drying the coal.

(Means for Solving the Problems) The present invention involves mixing pre-reduced ore with a high temperature metallization ratio of 30-80% and coal, and then adding a hydrocarbon-based material such as 3-15% soft pitch or asphalt. Add binder and press mold.

(Function) When coal is added to the high-temperature pre-reduced ore, the coal is carbonized by the sensible heat of the pre-reduced ore, producing a substance that is compatible with the binder on the surface of the coal, and at the same time, the temperature decreases and the amount of binder added can be reduced. By raising and pre-treating the material to be molded in this way, a molded material with high strength can be produced at a high yield. Generally, when coal is heated, water evaporates at 100℃.
Releases storage gases such as CH+, Co□ at 100-200°C, 2o.

At -300°C, coal begins to decompose. 300-400℃
Then the decomposition becomes intense and H2O, CO2□, Co,
Gaseous components such as CmHn and tar with low viscosity begin to be generated. Tar generation is most active at 400-500°C. At 500-800°C, CrnHn decomposes to produce CH, +, etc., and tar decomposes to become gas.

When prereduced ore at 700-900°C and coal at room temperature are mixed, the above-mentioned decomposition reaction occurs. The carbonization reaction of coal is endothermic and shows an endothermic reaction of 550-600 kcal/'p. Therefore, when coal is mixed at the point where the hot pre-reduced ore is discharged, the coal undergoes the above-mentioned reaction and the temperature of the pre-reduced ore and the coal mixture decreases. - e.g. 900°C, l
When KP's pre-reduced ore is mixed with 0.3 of room temperature coal, the temperature will eventually drop to around 300°C. Coal undergoes carbonization in the preliminary reduction ore to generate tar. When a binder is added in this state, the binder and the coal with tar on the particle surface are in a state where they are likely to bond, so when pressurized, the pre-reduced ore is completely wrapped in this group of bonds,
A mixed molded product with high strength can be obtained.

(Example) When a large amount of coal is added to the pre-reduced ore at once, the temperature decreases greatly due to the carbonization reaction, resulting in little decomposition of the coal and insufficient tar formation, resulting in low strength.

If you want to make a high-strength molded product with a high yield, you need to mix the pre-reduced ore and coal uniformly, and you need to know where, which coal to add, how much to add, and how long to knead it. The method of mixing is extremely important. 50 as an example
70% pre-reduced ore at 0-900℃, 0-30% bituminous coal, lignite, anthracite at room temperature, 0-12% soft pitch at 150℃ and asphalt as a binder, and 5-10 tons/- using a double roll molding machine. An example is shown in which a molded and manufactured product is sieved and the sieved results are displayed as +108 lump index.

(1) Figure 1 shows the influence of crosstalk time.

The results of looking at the effect of mixing time are shown in Figure 1. In order to increase the product yield, it is important to thoroughly mix the mixture and binder, and it is necessary to ensure an appropriate mixing time.

(2) Figure 2 shows the effects of coal ratio and binder content.

Although bituminous coal was used in this test, the product yield tends to decrease as the coal content decreases.

In this case, the product yield can be ensured by increasing the amount of binder blended. The reason why the yield decreases as the coal ratio decreases is presumed to be because the number of bonds decreases.

(3) Figure 3 shows the influence of coal brands.

Next, tests were conducted with different brands of coal, but as the brands of coal changed to bituminous coal, lignite, and anthracite, the product yield tended to gradually decrease. This seems to be related to the amount of tar generated when coal is heated, but if the amount of tar generated is small, the product yield is low, so it is possible to secure the yield by increasing the amount of binder added. I can do it.

(4) Effects of one type of binder We tested two types of binders, soft pitch and asphalt, to determine the difference in product yield, and found that soft pitch had a slightly higher yield. However, no particularly large difference was observed.

(5) Relationship between coal moisture content and product reoxidation rate When pre-reduced ore is mixed with coal, in the early stage of mixing, the moisture contained in the coal comes into contact with the thermal pre-reduced ore and steam is generated, which is absorbed by the pre-reduced ore. The higher the temperature of the mixture, the lower the metallization rate. The decrease in metallization rate varies depending on factors such as temperature and moisture content, but at temperatures above 200°C, pre-reduced ore has a large specific surface area and is easily reoxidized, so if there is room in the process, pre-drying the coal can help retain moisture. It is desirable to reduce the amount of

To explain with reference to FIG. 4, the powdered pre-reduced ore discharged from the pre-reduction furnace (not shown) is sent to the forming bag f12 via the container 1 storage bin 3 and supplied to the mixing section M. On the other hand, powdered coal is supplied to the hopper 11 of the coal supply device 10, the constant feeder 12, the screw conveyor 13, and the chute 14.
is supplied to the mixing section M, where it is mixed with the pre-reduced ore, applied with extra pressure by the screw feeder 4, and force-fed to the forming roll 5 made of a smooth roll. The plate-shaped molded product rolled by the molding roll 5 is cut into a predetermined size by a separator 6 that is synchronized with the molding roll 5 and subjected to shearing force, and is cooled by dropping it into a cooling tank 8. After that, it is carried out via a photographing conveyor 7 and then carried out to a predetermined location by a carry-out conveyor 9.

After agglomeration, it is not cooled and is supplied hot to the next process such as a melting reduction furnace.

[Brief explanation of the drawing]

Figure 1 is a diagram of the influence of kneading time, Figure 2 is a diagram of the influence of mixing time, coal ratio, pine,
Figure 3 shows the influence of coal brand, Figure 4 shows the influence of coal blending amount.
The figure is a schematic explanatory diagram of a preconcentration reduction furnace showing one example of implementing the present invention. 1 is a container, 2 is a compression molding device, 3 is a storage bin, 4
1 is a screw feeder, 5 is a forming roll, 6 is a separator, 7 is a vibrating conveyor, 8 is a cooling tank, 9 is an unloading conveyor, 10 is a carbon material supply device, 11 is a hopper, 12 is a constant feeder, 13 is a huskscrew conveyor , 14
Hashiyu), MH mixed! Patent Applicant Nippon Steel Co., Ltd. Agent Patent Attorney Fuku Kumagai i(%) pie〉72yaaiai(%)

Claims (1)

[Claims] A method for agglomerating pre-reduced ore, which involves adding carbonaceous material to pre-reduced ore with a metallization rate of 30-80%, kneading it, adding a binder at a temperature of 300°C or less, and press-molding it.