JPS62107032A - Two-stage-ignition sintering method - Google Patents

Abstract

PURPOSE:To obtain a high-strength sintered product by limiting the proportion of coke fines as raw material, in sintering the raw materials for sintering laid into two layers, the upper and lower layers, by a two-stage-ignition system, so as to prevent incomplete combustion of coke fines. CONSTITUTION:The proportion of above-mentioned coke fines in the raw materials for sintering in which iron-ore fines, coke fines, limestone, etc., are blended is limited to 2-3.5wt%. The above raw materials for sintering are laid on the pallet of a sinter machine into two layers, the upper and lower layers. Then each layer is ignited independently to allow each combustive reaction to proceed.

Description

DETAILED DESCRIPTION OF THE INVENTION (Industrial Application Field) The present invention relates to a method for sintering a sintering raw material such as powdered iron ore using a two-stage ignition method.

(Prior Art) Powdered iron ore, which is used for iron ore manufacturing, is agglomerated by sintering and then charged into a blast furnace.

In general, D is a method of agglomerating raw materials for sintering (hereinafter simply referred to as "raw materials" or "sintering raw materials"), which are made by blending coke, limestone, etc. with ironmaking raw materials such as powdered ore.
-L type (dry 1-roid type) sintering machines have been used. As shown in Fig. 1, bedding ore and sintering raw materials are sequentially supplied from a hopper 3.4 onto a large number of pallets 2 which are rotated around a sintered strand l.
The surface of the sintered raw material is ignited in the process of passing through the ignition furnace 5, and air is circulated from above the raw material downward by suctioning it with the blower 7 from the air 'R6 placed below the valent movement area.
This is a method in which the raw material is sintered from above to the bottom while the pallet moves toward the ore discharge end, and the firing is completed just before the ore discharge end to obtain agglomerated sintered 2J1:.

The progress of sintering during this period is as shown in Figure 2, with reference numeral 8.
indicates the raw material, the shaded area indicates the sintering reaction zone 9, and the symbol 1o located above the sintering reaction zone indicates the sintered completed zone. The raw material is mixed with coke as a fuel in advance, and as shown in Fig. 1, after being ignited in the ignition furnace 5,
- Air is vented from above at a temperature of 0.24 degrees and 21% to burn the coke, thereby melting and sintering the ore. After ignition, sintering progresses to the lowest layer in about 30 minutes. The combustion exhaust gas is exhausted through the wind box 6, and at this time, 08 in the exhaust gas is about 11%, and the average temperature is 100℃.
It is about °C. Gas at this oxygen concentration level still has enough oxidizing power to burn coke, and therefore it is desirable to reuse the exhaust gas.

As one of such exhaust gas reuse technologies, the 'd&ring technology for the exhaust gas sintering process, as exemplified in [Tetsu to Hagane J Vol. 69, page 4.72], has been implemented. This involves extracting the exhaust gas from the latter half of the sintering process and spraying it onto the raw material surface again to reuse it as sintering gas.
It is effective in reducing the amount of gas released into the atmosphere, reducing nitrogen oxides, and increasing the amount of waste heat recovered.

However, the coke combustion and sintering reaction that occur within the sintered layer are similar to those in the conventional sintering method shown in FIG. 2, and therefore the productivity improvement effect by increasing the sintering progress rate cannot be achieved.

In order to use the exhaust gas again to promote the sintering reaction and to speed up the sintering progress, it is necessary to allow the sintering reaction to proceed simultaneously in the raw material layer.

As a method to specifically realize this, Japanese Patent Application Laid-Open No. 47-263
There is a method shown in No. 0.1. In this method, a plurality of raw material supply devices and ignition furnaces are provided at different positions in the pallet traveling direction, and the surfaces of each supplied raw material are ignited in sequence to advance the sintering reaction.
This makes it possible to reuse waste gas and significantly increase the sintering reaction rate, resulting in improved productivity. Figure 3 schematically shows the progress of sintering in the case of the two-stage ignition type. In the figure, the symbols are the same as those in FIG. The exhaust gas that has passed through the upper layer is used again for combustion in the lower layer.

(Problems to be Solved by the Invention) However, in the above-mentioned publication, the coke blending ratio was not disclosed, nor was there any suggestion regarding its criticality. In addition, in this two-stage ignition sintering method, the gas flowing from the upper layer to the lower layer during the sintering process has a low oxygen concentration, so the coke breeze blended in the lower layer tends to be incompletely combusted, causing combustion heat generation. The amount will decrease. Furthermore, the temperature of the gas flowing from the upper layer to the lower layer is mostly 100° C. or lower, and no preheating effect can be expected in the lower layer. As a result, the temperature within the layer decreases, making it impossible to achieve sufficient melting and sintering, leading to deterioration in the strength of the finished sintered ore, which is a drawback of the two-stage ignition sintering method.

As described above, although the conventional two-stage ignition sintering method is superior in productivity to the one-stage sintering method, it has a practical problem in that the strength of the product is significantly reduced.

In addition, increasing the blending ratio of coke powder, which has traditionally been done as a strength improvement measure, actually resulted in a decrease in the strength of the product.

Thus, an object of the present invention is to provide a method for producing high-strength sintered products by preventing incomplete combustion of coke breeze in a two-stage ignition sintering method.

(Means for Solving the Problems) In order to achieve the above object, the present inventors conducted various investigations and found that in the two-stage ignition sintering method, combustion occurs in two places, so if the coke blending ratio is too high, the lower layer It was found that incomplete combustion occurs when the parts are burned, resulting in a decrease in strength. Therefore, after further consideration, we found that by setting a limit on the blending ratio of coke, we were able to prevent the decline in product strength, which is an adverse effect of the two-stage ignition sintering method, and achieve a high production rate without reducing the strength of the sintered product. The present invention was completed after learning that the operation could be carried out using

Here, the gist of the present invention is to spread the sintering raw material charged on a pallet in two stages, upper and lower, and to ignite each layer to cause the combustion reaction to proceed independently in each layer.
This is a two-stage ignition sintering method characterized by limiting the blending ratio of coke powder to 2.0 to 3.5 wt% in each layer.

Above 2￥S1. The pyrotechnic sintering method and its operating method are already known and there are no particular restrictions, but the thickness of each layer is preferably equal. Furthermore, there are no particular restrictions on the size of the coke powder.

(Function) As mentioned above, the two-stage ignition sintering method is superior in terms of productivity because combustion occurs at two locations, but on the other hand, it has a major problem in that the strength of the finished sintered ore decreases. The present invention contributes to the knowledge of the following matters in solving such problems.

That is, in general, the combustion of coke breeze in the sintered layer occurs due to the oxidation reaction of the fixed carbon contained therein by oxygen in the passing gas, and if there is sufficient oxygen, the following (
1) A state of complete combustion is reached as shown in equation 1, and the calorific value is 94 k.
cal/oxygen mole. On the other hand, if there is a lack of oxygen, incomplete combustion will occur as shown in equation (2) below, and the calorific value at this time will be 53 kcal/mole of oxygen. The calorific value is reduced by 44% compared to that during complete combustion.

C+0. -,=CO□...Equation (1) (heat generation 1=93
．． 989 kcal/oxygen mol)2C+0□ =2CO
...Equation (2) (heat generation Mt - 52,796 kcal/oxygen mol) And the lower layer strength decrease during the above-mentioned two-stage ignition type sintering is due to the low Ot after burning the upper layer powder coke? This is because the combustion reaction of the coke in the lower layer progresses in the f4 degree gas, and too many operations in the mixing of the coke in the upper layer further induce incomplete combustion of the coke powder in the lower layer, leading to an extreme drop in strength.

Similarly, mixing too much coke in the lower layer also causes a decrease in the strength of the lower layer.

In other words, in the one-stage ignition sintering method, there is only one combustion zone, and when the blending ratio of coke breeze is about 4%, oxygen becomes excessive, and most of the heat is generated by the reaction according to equation +11 above. It is determined by the blending ratio of Therefore, as the coke blending ratio is increased, the heat generation (2) increases and the strength is improved.

On the other hand, in the two-stage ignition sintering method, there are two combustion sections, and when the blending ratio of coke breeze is about 4%, the overall combustion reaction is oxygen-deficient, and the combustion reactions are as shown in equations +11 and (2) above. In addition, the calorific value at this time is determined by the amount of oxygen (concentration) and the distribution ratio of the combustion reaction equation +11 and equation (2). In this case, the incomplete combustion reaction of equation (2) above becomes more dominant, resulting in a decrease in calorific value, contrary to the one-stage ignition sintering method.

To explain in more detail, in the case of the two-stage ignition sintering method, if the blending ratio of coke breeze in the upper layer exceeds 3.5 wL%, the oxygen concentration supplied to the lower layer will be less than 11%, and the The combustion reaction increases incomplete combustion regardless of the coke breeze blending ratio. Furthermore, even if the oxygen concentration supplied to the lower layer is 11% or more, the coke blending ratio in the lower layer is 3.5 wt.
%, incomplete combustion will similarly increase. Therefore, in the two-stage ignition sintering method that assumes atmospheric suction,
In order to maintain good combustion of blended coke, it is important to keep the blending ratio of coke breeze in the lower layer to 3.5 wt% or less, which prevents incomplete combustion in the lower layer and improves strength. Deterioration can be prevented. In addition, in the method of the present invention, the lower limit of the blending ratio of ζ coke powder is 2. Owt% is defined as less than 2.0wt%, which is necessary for developing strength.
This is because they cannot obtain .

The invention will now be further explained with reference to the accompanying drawings.

First, the sintering pallet apparatus will be explained. FIG. 4 shows a partial cross section of a sintering test machine for carrying out the present invention. In the figure, reference numeral II indicates the main body, which has a height of 6
It has a cylindrical shape with an inner diameter of 00m+ and an inner diameter of 300m-.
A grate 12 made of grids at intervals is provided at the bottom, and a wind box 13 is provided below the grate 12, which is designed to suck in air by exhaust air a (not shown). Ignition is performed by a C gas combustion burner 14 installed on the pallet body. Using this Tes I-machine, bedding ore 15 is spread on the grate plate 12, and a predetermined amount of raw material 16.16 is charged thereon in two stages.
The surface of this filled raw material is ignited and fired.

Next, to explain the 1st grade during the firing test, first the layer height was 3.
A raw material equivalent to 0.001 mm was charged and ignited, and immediately after the ignition was completed, another raw material was charged in an amount equivalent to a layer height of 300 mm, and after ignition was performed again, firing was carried out by atmospheric suction. The coke powder added to the raw materials is adjusted to a preset amount before use.

Next, the present invention will be further described in detail in connection with Examples, but these are ii'L illustrations of the present invention, and the present invention is not limited thereby.

Example In this example, two-stage ignition sintering was carried out using the apparatus shown in FIG. The raw material method blending ratio is shown in Table 1, and the blending ratio of coke powder in each of the upper and lower layers is 1.5 wt% to 5 wt%.
The test was conducted by changing Q up to 5 wL% intervals.

Table 1 (wt%) The test results are summarized in a graph in Figure 5, and as is clear from the results, the coke powder blending ratio of the upper and lower layers was set at 2.0 to 3.54%. By limiting the amount, the strength of the sintered product can be improved.

As a reference example, the results obtained when one-stage sintering (layer height 300 mm, blending ratio shown in Table 1, coke powder blending ratio 3.OwL%) were carried out using the apparatus shown in Figure 4, and 2 according to the present invention. Stage ignition sintering (coke powder blending ratio: upper layer 3.
5 wt%, lower layer 3.5 wt%) are summarized in Table 2.

From the above comparison in Table 2, it can be evaluated that the method of the present invention is an excellent method that can significantly improve the production rate while having the same strength as the one-stage sintering method.

[Brief explanation of drawings]

Figure 1 is a schematic illustration of a conventional DL type sintering machine; Figure 2 is a graph showing the progress of sintering in the one-stage sintering method; Figure 3 is a graph showing the progress of sintering in the two-stage sintering method; Similar graphs; FIG. 4 is a schematic illustration of the sintering test machine utilized in the present invention; and FIG. 5 is a graph showing the results of an example of the present invention. 12 Nigerate board, 13: Wind box, 14: Burner, 15: Bed ore, 16: Raw material

Claims (1)

[Claims] In the two-stage ignition sintering method, the sintering raw material charged on a pallet is spread in two stages, upper and lower, and each layer is ignited to allow the combustion reaction to proceed independently in each layer. A two-stage ignition type sintering method characterized in that each sintering method is limited to 2.0 to 3.5 wt%.