JPH07150260A - Method for dehydrating bound water in pisolite ore - Google Patents

Abstract

(57) [Abstract] [Purpose] Bound water in pisolite ore is dehydrated without pulverizing the ore itself. [Configuration] Pisolite ore is supplied from the ore hopper 1 onto the belt conveyor 2. The electromagnetic wave generator 4 is installed in the central part of the belt to irradiate the moving ore with electromagnetic waves,
Heat to a temperature of 300-500 ° C.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for dehydrating bound water in iron ore, which is a raw material for ironmaking in a blast furnace.

[0002]

2. Description of the Related Art When a pisolite ore is directly sintered,
Yield of sinter from its mineral properties, especially the pisolite structure,
Strength is reduced. This is because when the mineral called goethite (Fe ₂ O ₃ · 2H ₂ O) contained in pisolite ore is heated, the combined water is decomposed and a large crack is generated at the goethite part, and the melt generated in the crack is generated. This is because the liquid permeates and a large amount of coarse pores are generated in the mineral structure of the sinter.

As a countermeasure, the bound water in the pisolite ore may be dehydrated in advance before firing and then fired. The decomposition temperature of the bound water in pisolite ore is about 25
Since the temperature is 0 ° C. and the temperature is about 450 ° C., the bound water can be dehydrated by heating at a temperature in this range or higher. For example, Japanese Unexamined Patent Publication No. 1-316427 describes a method of directly heating ore at 1200 ° C. or higher as a method for dehydrating bound water in iron ore, but it has not been put into practical use yet. At present, the heat treatment of ores including pisolite ore is not performed before the production of sinter.

[0004]

DISCLOSURE OF THE INVENTION Problems to be Solved by the Invention
As described in Japanese Patent No. 7, the conventional method for dehydrating bound water in ore requires a high temperature of 1200 ° C. or higher, which is industrially difficult. Further, if the heating is carried out at a temperature lower than that, the problem that large cracks occur in the goethite part during dehydration of bound water cannot be solved. These cracks form voids in the ore and are surrounded by the melt during sintering to generate coarse air holes. The coarse air holes significantly reduce the yield and strength of sintering.

The present invention makes it possible to dehydrate the bound water in the pisolite ore without requiring a high temperature heat source and without causing the thermal cracking of the goethite portion in the ore.

[0006]

The gist of the present invention is a method for dehydrating bound water in pisolite ore, characterized by irradiating the pisolite ore with electromagnetic waves to heat it to a temperature of 300 to 500 ° C. In response, electromagnetic waves are emitted while continuously moving the pisolite ore horizontally.

[0007]

The present invention dehydrates the bound water by utilizing the fact that electromagnetic waves having a specific frequency excite the OH bond due to the resonance of water molecules to generate heat, which is the same as the heating principle of a microwave oven. Is.

The bound water of pisolite ore is goethite (F
e ₂ O ₃ · 2H ₂ O). Conventionally, the bound water was dehydrated by directly heating it above the decomposition temperature of the bound water, but direct heating causes a temperature distribution on the surface and inside of the ore, so large cracks occur in the goethite part during dehydration, and the sintered ore It was a cause of lowering the yield and strength. On the other hand, when electromagnetic waves are used, heating can be performed evenly inside the ore, and dehydration can be performed without causing cracks. If the heating temperature is lower than 300 ° C, the bound water cannot be sufficiently dehydrated, and since the dehydration of the bound water is completed at 500 ° C, it is not necessary to heat above the temperature.

The present invention will be described in detail with reference to FIG.
Dewatering of bound water of pisolite ore is done by conveyor belt 2
Productivity can be improved by irradiating electromagnetic waves while moving the ore above.

The raw material pisolite ore is supplied from the ore hopper 1 onto the belt conveyor 2. The belt speed is determined by the electromagnetic wave irradiation time. The supplied ore moves to the mine ore side, and the height is adjusted by the cutoff plate 3. The electromagnetic wave generator 4 is installed in the center of the belt and irradiates the electromagnetic wave in the range from the electromagnetic wave irradiation start position P ₁ to the electromagnetic wave irradiation end position P ₂ . The ore after irradiation is sent to the ore storage layer as it is.

The amount cut out from the ore hopper 1 is adjusted according to the production amount. It is preferable that the width of the belt is 500 mm and the thickness of the ore layer to be stacked is 100 mm or less. This is because the irradiation time required for dehydration becomes significantly longer when the amount is longer than this. Electromagnetic wave output is 300W / t-or
It may be more than e and 30 kW / t-ore or less. This is because the former is the lowest output comparable to the decomposition start temperature of bound water, and the latter is the output that can completely remove bound water in a short time. The irradiation time is preferably more than 5 minutes and 60 minutes or less. This is because the ore weight loss due to dehydration does not start in 5 minutes or less and the bound water is almost dehydrated in 60 minutes or more. Further, it is desirable that the distance between P _{1 and} P ₂ indicating the irradiation distance is 50 to 100 cm. If it is less than 50 cm, the dehydration efficiency will decrease, and if it exceeds 100 cm, installation will be difficult due to equipment restrictions.

When the pisolite ore is held at a temperature of 300 to 500 ° C., the ore moving speed is 5 to ₁ for P _{1 to} P ₂ .
It is desirable to move at 0 cm / min. This is because if the speed is higher than this, the dehydration efficiency is lowered, and if the speed is below this range, the production rate is lowered. The distance between the irradiation device and the ore is preferably 20 to 30 cm. This is 20 cm
If it is less than the above value, the entire ore cannot be uniformly irradiated with electromagnetic waves, so that the dehydration efficiency decreases, and if it exceeds 30 cm, the irradiation density becomes small and the dehydration efficiency decreases.

Further, about 6% of water is added to an ore of 10 mm or less used for producing a sintered ore, and particles of 1 mm or less are granulated into particles of 1 mm or more to form a granular ore aggregate. This is called a pseudo particle. It is necessary to change the dehydration rate because the amount of added water required to produce these pseudo particles needs to be changed slightly depending on the ore used. The amount of coke for combustion during sintering is the water content of the entire pseudo particle (including bound water)
This is because it is important to secure the optimum amount of bound water in view of the balance with other ores.

The particle size of the irradiated pisolite ore is 10 m
m or less. This is because the pisolite ore contains about 8% bound water over the entire grain size.

The frequency of the electromagnetic wave used in the present invention is 245.
At 0 MHz, it is similar to a microwave oven that is generally used.

The dewatering effect is the bound water reduction rate (%) = (1-
(Bound water content of ore before electromagnetic irradiation (wt%)-Bound water content of ore after irradiation (wt%)) / Bound water content of ore before electromagnetic irradiation (wt%)) x 100 The larger the value, the greater the effect of electromagnetic wave irradiation.

[0017]

Example 1 A typical Australian pisolite ore (average grain size =
3.3 mm, bound water content = 8.5 wt%) was used. The sample is a 500 cc beaker containing 500 g of the ore.

FIG. 2 shows the bound water loss rate and the ore temperature with respect to the electromagnetic wave output when the electromagnetic wave was irradiated for a fixed irradiation time of 10 minutes. The higher the electromagnetic wave output, the higher the ore temperature and the higher the bound water loss rate. FIG. 3 shows the bound water loss rate and the ore temperature with respect to the irradiation time when the irradiation output was kept constant at 800 W. The ore temperature began to rise 5 minutes after the irradiation, reached about 700 ° C. 10 minutes after the irradiation, and the bound water loss rate reached about 90% and reached 100% after 60 minutes. Table 1 shows the results of comparing the difference in the bound water loss rate when dehydration by heating at 500 ° C. and the present invention and the difference between the average particle diameters of the ores before and after the experiment. Difference in particle size when heated directly to 500 ° C under the same bound water loss rate 0.54
In the present invention, the combined water was 0.09 mm, and the bound water could be dehydrated without causing pulverization. FIG. 4 shows the results when the irradiation width was changed while moving the ore layer at 10 cm / min. The dehydration rate showed the maximum at a position of 50 to 100 cm.

[0019]

[Table 1]

[0020]

[Embodiment 2] In FIG. 5, 10 cm /
The operation results when a sinter experiment is conducted by irradiating the pisolite ore, which has been moved for a minute, with an electromagnetic wave having an output of 1000 W for 10 minutes are shown. The amount of pisolite ore used at this time was 3 in the blended raw materials.
At 0%, the bound water loss rate is 95%. The product yield of the sintered ore was improved by 4% by the irradiation of electromagnetic waves, the sintering time was shortened from 26 minutes to 22 minutes, and the production rate was improved by 3%. Also,
The amount of coke for thermal compensation at the time of dehydration of bound water was reduced by 2 kg / t-sinter.

[0021]

According to the present invention, it is possible to improve the sintering operation result by dehydrating the bound water in the pisolite ore without pulverizing the ore.

[Brief description of drawings]

FIG. 1 shows an example of a device for implementing the invention.

FIG. 2 is a diagram showing a relationship among an electromagnetic wave output, a bound water loss rate, and an ore temperature when irradiation time is constant.

FIG. 3 is a diagram showing a relationship between an irradiation time, a bound water reduction rate, and an ore temperature when the irradiation output is constant.

FIG. 4 is a diagram showing a relationship between an irradiation distance and a bound water reduction rate when the irradiation output and the ore moving speed are constant.

FIG. 5 is a diagram showing a result of a sintering operation using pisolite ore dehydrated by electromagnetic wave irradiation.

[Explanation of symbols]

1 ore hopper 2 belt conveyor 3 cut-off plate 4 electromagnetic wave generator P ₁ electromagnetic wave irradiation start position P ₂ electromagnetic wave irradiation end position

Claims (2)

[Claims] 1. A method for irradiating a pisolite ore with an electromagnetic wave to obtain 30
A method for dehydrating bound water in pisolite ore, which comprises heating to a temperature of 0 to 500 ° C. 2. The method for dehydrating bound water in pisolite ore according to claim 1, wherein the pisolite ore is continuously moved in a horizontal direction and the electromagnetic wave is applied thereto.