JPS61204346A - Operating method for sintering where emission of nitrogen oxide is controlled - Google Patents

Abstract

PURPOSE:To sharply reduce the quantity of NOx emitted, while maintaining high productivity, by pelletizing sintering material with specific water content by use of limestone having grains with <=1mm grain size in higher weight percentage than usual and by feeding the pelletized material into a continuous downward suction-type sintering machine so as to supply during combustion the surface of a sintering bed with a specific amount of water. CONSTITUTION:In the process of sintering operation, the limestone having >=60wt.% grains with <=1mm grain size is used with 4-6% water for pelletization to pelletize the sintering material. This sintering material is fed into the continuous downward suction-type sintering machine so that surface of the sintering bed where coke combustion reaction is in progress is supplied with water by 5-90L/t-(raw material).

Description

DETAILED DESCRIPTION OF THE INVENTION (Industrial Application Field) The present invention relates to a method for producing sintered ore in the steel industry.

(Prior Art) As is well known, in the blast furnace method, the iron ore to be charged into the blast furnace is preferably sintered ore, which is currently widely practiced.

In addition, the sintered ore manufacturing method involves mixing a predetermined amount of iron ore raw materials, coke, limestone powder, etc., adding water to form pseudo-granules, and then using a continuous downward suction sintering machine. It is also well known that sintering is a common practice.

By the way, when manufacturing sintered ore, NOx exists in the combustion exhaust gas of t-coke mixed with the sintering raw material, which poses a major environmental problem. It is now necessary to carry out additional sintering work.

As a method to suppress the generation of NOx, sintering raw material C
; JP-A-55-107739 discloses that the limestone powder to be mixed and sweetened is finely granulated and quicklime or slaked lime is used.
has been disclosed.

(Problems to be solved by the present invention) Although the above-mentioned method of making limestone into finer particles reduces the amount of NOx generated, the particle size of the raw material becomes smaller, resulting in poor air permeability and, as a result, productivity decreases. It will drop. Also, if you combine quicklime and slaked lime, you can certainly avoid a drop in productivity, and
Although the Ox suppression effect is helpful, quicklime and slaked lime are relatively expensive, and as a result, there is a problem in that they increase the cost of producing sintered ore.

(Means and effects for solving the problems) The present invention uses three technical means to advantageously solve the above problems. Namely, the first point is that iron ore, limestone, and coke are When adding limestone to create pseudo-granules, it is common to use limestone with a grain size of 30 to 50X with a weight distribution of 1 square or less in normal sintering operations.
However, it is necessary to adjust this 'i'''L to a range of 4.0 to 6.OX.The third point is that during the sintering reaction, 5.0 to 9Q, 0l/ t- To supply moisture to the raw material.

That is, the present invention relates to a sintering operation method.

Limestone with a particle size of 1.04 or less and a weight of 60 or more is used.

The sintering raw material is granulated with a granulation moisture content of 4.0 to 6.0, and the sintering raw material is fed to a continuous downward suction sintering machine (; and the sintering material is fed to the surface of the sintering bed where the coke combustion reaction is in progress. ~90,0l/
t- Supplying moisture to raw materials? This is a sintering operation method that suppresses the generation of nitrogen oxides.

and n et al. describe the interaction of the three means. First, when the moisture supplied from above the sintered layer, that is, water or steam, reaches the combustion zone, it undergoes the following two reactions (2) to generate H2.

Q + H, O→OO+ H3 O0+ H20→002+H2 Produced in this reaction and due to the reduction action of fF-H2 j) NO
In addition, the use of all limestone with small grain size promotes the above-mentioned HS production reaction and thereby increases the NOx reduction effect of H2. The moisture supplied from above the bed becomes condensed moisture in a zone of moisture that forms below the combustion zone.
The voids between pseudo-particles are blocked, and the pseudo-particles coalesce and fluidize due to excess moisture, which reduces air permeability, inhibits the coke combustion reaction, and increases the amount of NOx generated. By reducing the moisture in the n1 moisture condensation zone (which is supplied from above the sintering bed) by an amount corresponding to the moisture that condenses, inhibition of the coke combustion reaction is prevented.
Combined with the NOx reducing effect of H2 mentioned above, this significantly reduces NOx.

The present inventors conducted an experiment to reduce the amount of NOx generated by the above means, and found that the upper limit for the amount of moisture supplied from above the sintering bed was 901/ml per raw material; Because the O3 concentration in the coke decreases and inhibits coke combustion (2), the amount of NOx generated increases on the contrary, and if the amount is less than 5L per raw material, NOx
It turns out that no reduction effect can be obtained. In addition, the upper limit of granulation moisture is 6X, and if it is higher than this, the condensed moisture in the wet zone will increase, and the reduction in NOx generation will be smaller due to the above reason (=).The lower limit is specified as 4N. The reason for this is that below that n, the pseudo-granulation of the raw material does not proceed, and not only does the amount of NOx generated increase, but the productivity and yield are also extremely deteriorated.

Regarding the limestone particle size (=), by increasing the particle size to 14 or less or more than 60 in terms of weight ratio, the amount of NOx reduction increases.

Figure 2 shows the relationship between the weight ratio of limestone insects and the amount of NOx generated.
By increasing the temperature to 0X or more and spraying water vapor, it is possible to reduce NOx significantly more than simply reducing the particle size of limestone (2).The reason for this is that fine limestone has a catalytic effect on the combustion of coke, It is thought that by promoting the generation of H2, the NOx reduction effect (2) will suppress the amount of NOx generated.

Moisture, ie, water and/or water vapor, may be supplied by any means capable of uniformly supplying, such as spraying or coating. For example, a mixture of water and steam or spraying may also be used. It is not very effective in the part where the internal temperature of 1 is not sufficiently high at the beginning of sintering, and it is effective to supply H2O only in the part where it reacts with 0 or 00, that is, during coke combustion.

(Example) As raw material conditions, iron ore 56.2N, return ore 30.0,
Serpentine 2.1X and the present invention (- limestone 11.7Xf adjusted to the particle size within the specified range, coke 3.6X
The raw material granulated with moisture in the range specified in the present invention in addition to the outside number of
At 0, water or steam is sprayed from the top surface of the sintered ore bed in an amount within the specified range. , 3 is the sintering completion zone. Combustion zone: 4 f moisture supply nozzles were installed in the width direction of the sintering machine on the upper surface of the electric zone, and the water was evenly sprayed. The results are shown below, and as a comparative example, conventional granulation moisture and Table 1 shows the results of spraying water on the top surface of the sinter bed with limestone particle size.

As is clear from Table 1, the limestone particle size and granulation water content are adjusted to the range specified in the present invention, and water or steam is sprayed during sintering (= water or steam is sprayed during sintering). Compared to what I did.

It was possible to significantly suppress NOx f and improve productivity.

(Effects of the Invention) As explained above, according to the method of the present invention, it is possible to significantly reduce the amount of NOx generated and to improve productivity.

[Brief explanation of the drawing]

FIG. 1 is a diagram illustrating the moisture supply method in the example, and FIG. 2 is a diagram showing the relationship between limestone particle size, granulation moisture, the amount of moisture supplied during sintering, the amount of NOx generated, and the combustion zone movement speed. 1... Moist zone, 2... Combustion zone, 3... Sintering completion zone, 4... Moisture supply nozzle. Agent: Patent attorney Masamitsu Akizawa and 2 others

Claims (1)

[Claims] (1) In the sintering operation method, the particle size of 1.0 mm or less is 6
Using 0% by weight or more of limestone, the granulation moisture content is 4.0-6.
The sintering raw material is granulated as 0%, and the sintering raw material is supplied to a continuous downward suction type sintering machine, and the moisture content of 5.0 to 90.0 l/t of the raw material is delivered to the surface of the sintering bed during the coke combustion reaction. A sintering operation method that suppresses the generation of nitrogen oxides.