JPS62297421A - Multi-stage ignition type sintering method - Google Patents

Abstract

PURPOSE:To prevent the quality degradation of sintered ore of 2nd and subsequent layers by using fuel having a fine grain size and/or high reactivity for the 2nd and subsequent layers with respect to the uppermost layer for the fuel to be added to and mixed with the granular iron ore raw materials which are divided to plural layers and are supplied to a sintering machine. CONSTITUTION:The grain size of coke as the fuel to be added to the lower layer raw material B in a multi-stage ignition type sintering method is selected at the size smaller than the grain size of the coke to be added to the upper layer raw material A so that the product yield and strength of the upper and lower layers are made approximately equal to each other. The reactivity of the coke to be added to the lower layer raw material B is selected at the reactivity larger than the reactivity of the coke to be added to the upper layer raw material A so that the product yield and strength of the upper and lower layers are made approximately equal to each other. As a result, the advantages including the increased productivity of the multi- stage ignition type sintering method, decreased air flow rate for calcination per ton of the sintering raw materials, the reduced electric power consumption of the main exhaust an and the decreased generation of NO2 are best utilized without degrading the quality and yield of the lower layer sintered ore. The respective records of the above-mentioned embodiment and comparative example are shown in Table 2.

Description

Detailed Description of the Invention 3. Detailed Description of the Invention (Field of Industrial Application) The present invention relates to a method for producing P:f8 botanical ore in the steel industry. This relates to the so-called multi-stage ignition sintering method, in which the raw material is divided into multiple stages and charged into a sintering machine, and then the surface layer of the raw material in each stage is ignited to form multiple combustion zones and sinter. It is.

(Prior art) The multi-stage ignition sintering method is a method in which sintering is performed by forming multiple combustion zones within the raw material layer, as described in, for example, Japanese Patent Application Laid-Open No. 47-26304. In addition, since the proportion of oxygen involved in combustion increases, the amount of sintering air per ton of sintered raw material decreases, reducing the power consumption per ton of sintered raw material. It has the characteristic of being able to Furthermore, JP-A-53-48904
As per the title, the second row and below (counting from the top) are 1.
The combustion shell gas of the coke breeze added to the 1-+ is the exhaust gas of the first stage, so it has a low oxygen content and has the characteristic that the amount of iN Ox generated can be suppressed to a low level.

(Problems to be Solved by the Invention) However, in the above multi-stage ignition sintering process, the composition of the sintering gas in the second and subsequent stages is 1.120 and C.
Since the gas with high O□儑 and low oxygen content is used, the combustion of coke breeze is not carried out sufficiently, which has the disadvantage of deteriorating the quality of the first stage coke in the second stage and below. Was.

As a conventional technique to solve these drawbacks, a method has been proposed in which, for example, dry return ore, sand, fine ore, or quicklime powder is charged as a heat-absorbing and water-agglomerating material between each raw material charging layer. There is. (Unexamined Japanese Patent Publication No. 57-137413)
However, although this method can remove H20 to some extent, it does not solve the adverse effect of high CO2 concentration resistance. In addition, the charging device and the device for separating the water agglomerated material from the finished sintered ore in the product processing system are complicated, and the composition of the finished sintered ore has a large variation.

The present invention solves these problems, prevents deterioration of the quality of sintered ore in the second stage and below in the multi-stage ignition sintering method, and achieves this with simple equipment. It provides:

(Means for Solving the Problems) The present invention divides powdered iron ore raw material into multiple stages and charges the raw material into a sintering machine, and then ignites the surface layer of the raw material in each stage to create multiple combustion zones. When forming and sintering, the particle size of the fuel to be added and mixed with the raw materials in the second stage and below is such that the fuel to be added and mixed with the raw materials in the uppermost stage is also fine-grained and/or 2
This method is characterized in that the reactivity of the fuel added to and mixed with the raw materials in the lower stages is higher than that of the fuel added and mixed with the raw materials in the uppermost stage.

The coke powder added to and mixed with the raw materials for the second stage and below may be obtained by strengthening the crushing of ordinary coke powder, or by
It is also possible to use fine dust-collected coke generated in CDQ equipment or the like.

The highly reactive coke may be produced by low-temperature carbonization, or anthracite may be used. Alternatively, coke powder or coke dust collected in fine powder may be granulated or pseudo-granulated with cement/quicklime, and the reactivity may be increased by the combustion promoting action of CaO.

(Function) In the normal one-stage ignition sintering method, the exhaust gas composition directly under the pallet truck is 02 = 10 to 15%, C0 = 1 to 2%,
CO2 = 5 to 10, and 20 = around 10. The raw materials for the second stage and below are sintered using a gas with such a composition. It has the characteristics of

(1) 0□ concentration is low. Therefore, the combustion rate of coke becomes slower.

(2) Contains CO2 and H2O. CO2, H2O are the third
As shown in the figure, s 02+ has a large specific heat compared to N2. In order to clarify the cause of the quality deterioration of sintered ore from the second stage onwards, the inventor investigated the As a result of extensive research into the determinants of heat and heat patterns, it was discovered that the moving speed Su of the front surface of the high temperature zone and the moving speed Su' of the rear surface of the high temperature zone are expressed by the following equation. That is, V: Gas flow rate (m/hr) ゛Cg: Gas specific heat (kcol/Nm3℃) Cp: Raw material specific heat (kcol/kg ℃) ρ,: Raw material density (kg
/m3) to: Overall thermal conductivity (kcaI/m-h "・℃) γ:
Coke burning rate per unit volume (kxoI/m3)
ρU: Coke density From these equations, Su and Su' depend on the specific heat of the gas. Considering the formation of the high-temperature zone in the second stage and below in the multi-stage ignition sintering method from this point of view, it is found that At the rear surface, due to the magnitude of the specific heat of CO□, T (20), the rear surface movement speed Su' of the high temperature zone becomes small. , because the 02 concentration in the gas is low, the coke combustion rate γ
is small, the moving speed Su of the front of the high temperature zone is
On the contrary, it becomes smaller.

As a result, the shape of the high-temperature zone in the second stage and below in the multi-stage ignition sintering method is such that the front surface of the high-temperature zone is chased by the rear surface of the high-temperature zone, as shown in FIG. 2 (a) K. It exhibits a sharp shape with a narrow high temperature zone and a high maximum temperature. In such cases, the sintered ore to be fired has a short residence time in the high temperature region and a slow cooling rate, resulting in a decrease in quality, especially strength and yield, as mentioned above in the problems of the conventional technology. That's why I'm coming.

In order to eliminate such adverse effects, as is clear from the above discussion, it is sufficient to increase the combustion rate γ of coke, and a concrete means for achieving this is to make the fuel particles finer. Alternatively, the reactivity of the fuel may be increased, or both may be combined.

If the fuel particles are made finer or the fuel becomes more reactive, the second
As shown in (b) of the figure, the shape of the high-temperature zone becomes sound, and a decrease in strength and yield can be prevented.

Additionally, the moving speed of the high temperature zone becomes faster for the same gas flow rate, resulting in a further increase in productivity.

(Example) Of the present invention, the two-stage ignition sintering method will be explained using drawings and tables as an example.

The raw materials used are as shown in Table 1.

Table 1: Raw Material Blending Ratio In one embodiment of the present invention, as shown in FIG. After dividing into two parts, mixed raw material A and mixed raw material B, powdered coke from coke powder hoppers 4A and 4B is added by weight, mixed and granulated while adding water to secondary mixers 5A and 5B, and further Surge hoppers 6A and 6B,
It is fed through drum feeders 7A and 7B to a pallet truck 10 on which bedding ore 9 is laid, and then 1 ignition furnace 8A's and 8B.
This is followed by ignition, forming two stages of combustion zones 11A+ and IIB, and sintering.

Examples and comparative examples of the present invention are shown in Table 2.

As a comparative example, when the particle size and reactivity of the coke added to the lower layer raw material B are the same as those of the coke added to the upper layer raw material A, the product yield and strength of the lower layer are both lower than those of the upper layer. decreased.

On the other hand, in Example 1, in which the particle size of the coke added to the lower layer raw material B was smaller than the particle size of the coke added to the upper layer raw material A, the product yield and strength of the upper and lower layers were almost the same. became.

Furthermore, in Example 2, in which the reactivity of the coke added to the lower layer raw material B was made greater than the reactivity of the coke added to the upper layer raw material A, the product yield and strength of the upper and lower layers were almost the same. .

Furthermore, if the particle size of the coke added to the lower layer raw material BK is made smaller than the particle size of the coke added to the upper layer raw material A, and the reactivity is also increased, the product yield and strength of the lower layer will be
O is almost the same as that of the upper layer. Here, we take the two-stage ignition sintering /f:, as ψ'1:
As explained above, the concept is the same in the case of ignition in three or more stages, and it goes without saying that the effects of the same aircraft can be obtained.

(Effects of the Invention) As explained above, according to the method of the present invention, the production volume of the multi-stage ignition sintering method can be increased without degrading the quality and yield of the lower layer sintered ore, and the sintering raw material tons can be fired. It is possible to take full advantage of the characteristics of lower air volume, lower power consumption for main exhaust air, and lower NOx generation.

[Brief explanation of drawings]

Fig. 1 is a fuel and raw material supply system diagram in an embodiment, Fig. 2 is an explanatory diagram of the operation of the present invention, and Fig. 3 is a temperature distribution diagram in the layer height direction. It is a relationship diagram. l... Raw material hopper 2... Mixer 3... Division damper 4A and 4B... Coke powder hopper 5A and 5B... Secondary mixer 6A and 6B... Surge hopper 7A and 7B... Drum Feeders 8A and 8B, ignition furnace 9... bedding ore lO... pallet truck 11
A and IIB... Combustion zone applicant Nippon Steel Corporation @1llffl Figure 2 $1 Figure 3 L/L (°C'

Claims (1)

[Claims] (1) In a multi-stage ignition sintering method in which powdered iron ore raw material is divided into multiple layers and supplied to a sintering machine, each layer is ignited to form multiple combustion zones and proceed with sintering. The fuel added to and mixed with the powdered iron ore raw material is
A multi-stage ignition sintering method characterized by using particles with fine diameter and/or particles with high reactivity in the layers below.