JPH09157761A - How to adjust the water content of cold pellets - Google Patents

Abstract

(57) Abstract: To provide a method for promoting the utilization of cold pellets, thereby increasing the recycling amount of dust, and supplying a cheap raw material to the ironmaking process, thereby reducing the water content in the cold pellets. . SOLUTION: The cold pellet 4 is irradiated with microwaves and heated to 100 to 150 ° C to reduce the water content in the cold pellet 4 to 1 wt% or less.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a water content adjusting method for optimizing the water content contained in cold pellets for iron making in a blast furnace or the like.

[0002]

2. Description of the Related Art The amount of dust generated in steelworks is increasing year by year, and it is difficult to dispose of it in landfills. This dust is T. Since it is a high Fe raw material with 40 to 50 wt% of Fe, its resource utilization is inevitable. However, since the particle size of the generated dust is as fine as 50 to 100 μm, cement or quick lime is added as a binder, and this is mixed and granulated to obtain a cold pellet (CP) processed into particles having a diameter of about 10 to 15 mm. , This is for blast furnace raw material,
It is used for converters and for cold iron source melting methods that do not rely on blast furnaces.

However, when granulating dust,
Some amount of water must be added. as a result,
The moisture content of the finished CP is, for example, 8 wt immediately after granulation.
% After the first curing (3 days), it usually becomes about 6 wt%, and if it rains during the curing period, it becomes about 7 wt%. When this CP is used in a blast furnace, the surface is usually wet with water, which reduces the efficiency of the sieving work carried out before charging the blast furnace, and when the water contained therein evaporates. Since heat is taken away, a low temperature heat preservation zone is formed at the shaft interruption, which triggers the pulverization of the raw material in the furnace. Therefore, the amount of CP used is limited to about 3% of the charged raw material. Further, when this CP is used in a converter, it is used together with ore and scrap as one of the coolants for desiliconizing molten steel. However, if it contains water, fumes will be generated when charged, and 100 kg per charge
It produces a certain amount of dust. Therefore, the amount used is limited to about 2% of molten steel.

When the amount of use is limited in this way, the amount of dust in the place increases. Therefore, reducing the water content of CP can secure the production amount of CP and reduce the amount of iron ore by using inexpensive dust, which leads to the reduction of the material cost.

[0005]

Therefore, if dehydration is required, it is necessary to install a large dryer at the end of the CP transfer process, which is a great disadvantage in terms of equipment cost and power consumption. Therefore, at present, the amount of binder such as quick lime added is increased to enhance the granulation ability and reduce the CP-containing water. However, since the binder is expensive, the amount used is limited, and the water content is 5 to 7 wt% at the most immediately before use.

On the other hand, JP-A-7-150260 discloses a method of irradiating iron ore with microwaves to dehydrate the bound water in the iron ore. But this is 300
This is a method of heating an ore to a combined water decomposition temperature of ˜500 ° C., and does not evaporate the carried-in water as represented by the wetting of the CP surface.

It is an object of the present invention to provide a method for reducing the water content in CP in order to promote the utilization of CP, thereby increasing the amount of dust recycled, and supplying an inexpensive raw material to the ironmaking process. To do.

[0008]

[Means for Solving the Problems] The method for adjusting the water content of CP of the present invention is to irradiate the CP with microwaves to obtain a temperature of 100 to 150 ° C.
It is a method for adjusting the water content of CP, wherein the water content in the CP is reduced to 1 wt% or less by heating to 1.

[0009]

BEST MODE FOR CARRYING OUT THE INVENTION As for the content of water contained in CP, 15% is water of crystallization of a binder, and the remaining 85% is attached water. Water hydrate is present in the form of water of crystallization, adherent water unlike, decomposing be irradiated with microwaves, the dehydration is hardly found as shown in FIG. ₂ Ca (OH) 2
It has been clarified by experiments using reagents. Therefore, if 85% of the water content is dehydrated, almost all the attached water content is dehydrated.

Next, the microwave irradiation conditions suitable for removing the moisture adhering to CP by evaporation will be described.

First, the irradiation output is preferably 10 kW / CP-t or more and less than 30 kW / CP-t. This is because, as shown in FIG. 3, the dehydration rate does not reach 85% below 10 kW / CP-t, and the temperature rises rapidly and the CP explodes above 30 kW / CP-t. Is.

Next, as shown in FIG. 4, the irradiation time is preferably 1 minute / CP-t or more and 3 minutes / CP-t or less. This is because the dehydration rate does not reach 85% at less than 1 minute / CP-t, and even if the dehydration rate exceeds 3 minutes / CP-t, there is almost no decrease in water content.

The irradiation efficiency is highest when the irradiation area is adjusted to the surface area of the raw material layer.

As shown in FIG. 5, it is desirable that the irradiation position is such that the irradiation is performed with a distance of 100 mm or more and 150 mm or less from the surface of the raw material layer. Irradiation efficiency becomes higher as it gets closer to the surface of the raw material layer, but if it gets too close to the distance of less than 100 mm, the evaporated water enters the waveguide, and the condensed water absorbs microwaves, which reduces the dehydration ability for the irradiated object. Resulting in. Further, if the irradiation position exceeds 150 mm, it is too far away, and the irradiation efficiency decreases, so the dehydration rate also decreases.

The thickness of the raw material layer is 10 as shown in FIG.
If it is 0 mm or less, the temperature is raised almost uniformly by microwave irradiation and the dehydration rate shows a constant value. On the other hand, the layer thickness is 100m
If it exceeds m, the heating temperature will be low and the dehydration rate will also be low. This is because microwaves cannot sufficiently penetrate layers thicker than 100 mm.

The frequency of the microwave used in the present invention is 2450 MHz, which is the same as the general frequency used in, for example, household microwave ovens.

Under the irradiation conditions as described above, CP is applied to the microwave.
By irradiating the surface with CP, the CP is uniformly 100 to 150 ° C.
When heated to at least 8 of the water in CP
Adhesive water equivalent to 0% or more evaporates and the amount of water is 1 wt.
The CP is less than or equal to%.

[0018]

EXAMPLES The batch type microwave irradiation apparatus as shown in FIG. 1 was used to remove the adhering water from the CP for the blast furnace and the CP for the converter, and each CP was used to carry out an actual machine test.
As the dehydration condition, microwave irradiation output is 10 kW / CP
-T, irradiation time 1 minute / CP-t, the surface area of the raw material layer was 1 m ² , and the sample thickness was 100 mm. as a result,
CP was heated to 110 ° C. and the water content became 1 wt% or less, and a dehydration rate of 83% was obtained. As a result of using this CP in an actual machine, as shown in FIG. 7, even when the amount of CP for blast furnace used exceeded 3%, the temperature in the middle stage of the blast furnace shaft did not decrease. Further, as shown in FIG. 8, with regard to the CP for converter as well, almost no fumes were generated even when used in an amount of 2% or more, and generation of dust could be suppressed.

[0019]

According to the present invention, the water content of CP is 1 wt% or less (the dehydration rate is 83%), and the amount of CP used can be increased. As a result, it is possible to increase the effective amount of dust used, so that it becomes possible to supply the ironmaking raw material at a lower cost.

[Brief description of the drawings]

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

FIG. 2 is a diagram showing a relationship between irradiation time and dehydration rate when a Ca (OH) ₂ reagent is irradiated with microwaves.

FIG. 3 is a diagram showing the relationship between microwave irradiation output and CP dehydration rate.

FIG. 4 is a diagram showing a relationship between microwave irradiation time and CP dehydration rate.

FIG. 5 is a diagram showing a relationship between a microwave irradiation position and a dehydration rate of CP.

FIG. 6 is a diagram showing a relationship between a material layer thickness, a dehydration rate, and an in-layer temperature at the time of microwave irradiation.

FIG. 7 is a diagram showing a relationship between a CP blending ratio and a blast furnace shaft middle stage temperature.

FIG. 8 is a diagram showing a relationship between a CP blending ratio and a dust generation amount.

[Explanation of symbols]

 1 Microwave oscillator 2 Waveguide 3 Heating oven 4 CP

Claims (1)

[Claims] 1. A method for adjusting the water content of a cold pellet, which comprises irradiating the cold pellet with microwaves and heating it to 100 to 150 ° C. to reduce the water content in the cold pellet to 1 wt% or less.