JPS5884931A - Manufacture of sintered ore - Google Patents

Abstract

PURPOSE:To enhance the yield, strength and reduction powdering index (RDI) of sintered ore obtd. by a sintering method using air sucked downward by adjusting limestone in starting materials including fine iron ore to a prescribed grain size and vibrating the surface of sintered ore in the early stage of sintering. CONSTITUTION:Limestone as a starting material is adjusted so that fine granules having <=0.25mm. grain size are contained by <=19% of the total amount of the limestone, and the adjusted limestone and other blended starting materials are charged into a sintering machine using air sucked downward. After firing the starting materials on the pallet of the sintering machine, vibration load is applied to the surface of sintered ore. Thus, the yield, strength and RDI of the resulting sintered ore are enhanced.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention improves the yield and strength of sintered ore produced by a downward suction sintering machine, such as a DL type sintering machine, particularly in the upper layer, and also improves the reduction of sintered ore. The present invention relates to a method for sintering fine ore that improves the reduction index (RDI), which is one of its properties.

The sintered ore, ie, kunter cake, produced by the downward suction sintering machine has different physical strengths in its upper layer, middle layer, and lower layer. This difference is significant between the upper and middle layers. The yield and physical strength of the upper layer of sinter cake are medium,
Various reasons can be considered for the remarkable inferiority compared to the lower layer, but the main ones are thought to be as follows. That is, (1) Even if the material is charged evenly and fluffy, the middle and lower layers will be compressed due to the overlapping of the raw material itself in the upper layer, and the density of the material will increase, resulting in lower yield and strength. will rise, but this will not happen to the upper management.

(2) In the upper layer, sufficient thermal retention is not obtained compared to the middle and lower layers, and the development of the semi-molten layer of fine ore particles is relatively incomplete, and the fused layer of each particle is not sufficiently developed. What you can't do.

(3) If the upper layer is in a semi-molten state than the middle and lower layers, the trunk will not be compressed. However, during sintering, the middle and lower layers are compressed by the load of the sintered ore itself in the upper layer, compressing the pores, improving physical strength and dramatically increasing yield. There is a strong possibility that

One purpose of the present invention is to improve the condition (porosity) of the sinter cake, especially in the upper layer, to improve strength and yield, and to achieve uniform physical properties of sintered ore throughout the entire layer. The aim is to obtain the following.

Generally, when sintering raw materials are charged into a sintering machine without segregation,
The density change in the lower layer becomes larger as you go to the lower layer, and the density in the lower layer increases by 20 to 25% compared to the upper layer. Therefore, it is not possible to make the porosity uniform in each section of the sintered layer. As sintering of the raw material particles between the layers progresses, semi-melting progresses, and the lower layer is compressed under the influence of the load of the sintered ore above that portion. The pores are therefore reduced. The state of the pores in each part of the sintered layer directly affects the yield and strength of each part of the sintered layer.

As a result of various studies, the inventor Go has found that if the same loading conditions as in the lower layer are applied to the upper layer during the progress of melting, almost uniform yield and strength can be obtained over the entire cross section of the sintered layer. Ta.

The formation of pores in sintered ore is thought to be due to the gap between the raw material grains that form the charge layer remaining as is, or due to generated gas, but these changes in pores are caused by the fact that the part forming the peripheral wall of the pore is half This is easiest when in the molten state. In other words, when the semi-molten zone is progressing through the upper layer, by applying a load with vibration that does not affect the unsintered zone, the purpose of improving the physical properties of the upper layer is to It can be achieved.

When the target layer is in a semi-molten state, in order to apply an efficient load to it without affecting the unsintered part, it is necessary to apply not only a simple load but also a small load by applying vibration to it. The most distinctive feature is that it can produce an effect comparable to that of a large load, and that vibrations are absorbed by the semi-molten zone, making it possible to prevent them from affecting the unsintered part.

The above is intended to improve the strength and yield of the upper layer of the sinter cake, but RDI, which is one of the reducing properties of sintered ore, can be applied by applying a vibration load as described in the example below. However, the current situation is that there is not much improvement. Therefore, I would like to discuss the technical philosophy regarding improvement measures regarding this RDI.

Reduction pulverization index (RDI), which is one of the reduction properties of sintered ore
is generally low in the upper layers, and tends to change in the lower layers, resulting in high values. This is thought to be due to two main reasons: the packing density of the raw materials differs between the upper and lower layers, and the thermal history that the raw materials receive during the sintering process differs due to the downward intake sintering with top ignition. ing.

The present inventors placed importance on the fact that the thermal history differs between the upper layer and the upper layer, and conducted various investigations and studies from the viewpoint of the mineral structure generated in the sintered ore, and as a result, the following became clear. That is, because the upper layer receives less heat from the coke combustion exhaust gas during sintering and the sinter cake layer-1 is thin, rapid heating and cooling occur, and the structure members are either appropriate or insufficient.
In the lower layer, the degree of utilization of the combustion exhaust gas from the upper layer increases, so the maximum temperature of the sintered layer increases and the time for maintaining the oxidizing atmosphere at high temperature increases. As a result, it was revealed that the crystals of the formed minerals in the lower layer structure became coarse, and in particular, the crystal grains of secondary hematite, which is the mineral responsible for the deterioration of RDI, became coarse.

Therefore, the present inventors began research on suppressing the growth of hematite crystals in the lower layer, and as a result of investigating and examining the behavior of melt formation during the sintering process using basic experiments and test sintered steel, etc.
It has been found that the formation or growth of secondary hematite can be controlled by delaying the reaction of limestone in the sintering compound raw material during the sintering process.

This is an attempt to suppress the formation of secondary hematite by actively reacting Fe, O, and CmO to generate calcium ferrite when the internal atmosphere becomes oxidizing in the latter half of the sintering process. It is. For this purpose, the reaction of CaO in the first half of the sintering process, for example FeO-8i0. It is necessary to suppress the reaction of CaO in the -CaO-based melt, and for this purpose it is attempted to cut or limit the fine particle size of the limestone added.

This is because fine limestone has good contact with other fine ores, and reacts in the reducing atmosphere in the latter half of the sintering process.
810. This is to facilitate the generation of -CaO-based slag. Therefore, regarding the improvement of RDI, the limestone particle size of -0,25-
Either the method of sintering is carried out by adjusting the particle size so that the fine particles are 19 mm or less, particularly preferably 17 mm or less, based on the total amount of limestone, or the above-mentioned method is applied only to the lower layer of the raw material layer of the pot or R-let. This is an attempt to apply a method to limit limestone particles.

In addition to adjusting the particle size of the applied limestone, vibration load is applied to a level that does not affect the unsintered part during the sintering process when the semi-molten layer (sintered zone) is progressing through the upper layer of the raw material layer. The purpose is to produce sintered ore with good physical properties and reducing properties.

The reason for applying the method of restricting limestone fine particles only in the lower layer of the raw material layer is that the RDI of the upper layer is as described above.
Compared to the lower layer, the value is normally low and good. Therefore, if the charging material can be charged in two stages by means such as two-stage charging, by applying it only to the lower layer, the R
This is because the DI can be averaged.

The content of the present invention will be described below based on examples.

Example 1 The distribution of limestone, which is currently generally added to sintering compound raw materials, is as shown in Table 1. In this-
The amount of 0.25 mm is varied from 30 mm to 15 mm by a crushing method or particle size adjustment method, and charged into a sintering device along with other blended raw materials, and after ignition, the sintered forming layer is 10 to 15 mm When the load became 100 Y/-, the amplitude was
A sintering test was conducted while applying a vibrating load of a13o cycle, RDI was measured, and the influence of the amount of limestone fine particles on RDI was investigated. For comparison, a normal sintering test was also conducted.

The results are shown in FIG. This results in a limestone particle size of -
0.25mW! It has been found that the smaller the amount of RDIK, the better the improvement effect, and it is quite effective at 19 inches or less, and especially noticeable at 17 inches or less.

Table 1 Particle size distribution of limestone The blending ratios of the raw materials are shown in Table 2.

Table 2 Example 2 Similar to Example 1, the amount of -0.25m in limestone was changed to four levels, and the mixture was charged into a sintering device together with the other blended raw materials shown in Table 2, and after ignition. Sintered formation layer is 1011135m
At this time, a sintering test was conducted by varying the load while applying vibrations with an amplitude of 1° and 3°, and the particle size distribution of limestone and the properties of the sintered ore when changing the vibration load were investigated.

This formulation contains a large amount of easily softened ore and is effective with a relatively light vibration load, so the load is 50
Return to town ~ 200 kl? /, up to 4 levels. Note that the amplitude and load of the vibration load need to be changed as appropriate since the softening properties differ depending on the brand of ore to be blended. The results are shown in Figure 2. By successively increasing the vibration load,
When yield and strength improve to normal levels, RDI tends to deteriorate, albeit slightly, by adding a vibration load; RDI is improved by adjusting.

It was also confirmed that the reduction rate (RI) of the sintered ore was improved.

Example 3 FIG. 3 shows test results when particle size adjustment of limestone was applied only to limestone mixed in the lower layer and a vibration load was applied. The reason why the limestone particle size is adjusted only in the lower layer is as described above (this is because the RDI of the lower layer of the sinter cake is inferior to that of the upper layer).

In the case of only the lower layer, the strength tended to improve compared to the whole layer, and RIDI slightly deteriorated, but the second
The limestone particle size shown in the figure is not adjusted (-0.25 aum is 23
．． 99b) A significant improvement effect is recognized when compared with case F).

FIG. 4 is a route map showing an example of a vibration load applying device used when carrying out the present invention.・ is arranged on the upper surface of the charging surface 2 and the rear surface of the ignition furnace 3, and the roll 1
．． 1', f... are vibration devices 4, 4', l
Although we have manufactured a device that is connected to ..., it is not limited to this, and in short, any device that can obtain the required pressurized vibration will suffice. Layer ventilation 41 - Care must be taken not to obstruct and prolong the sintering time.

[Brief explanation of the drawing]

Figure 1 shows the amount of limestone fine particles (-0,25Ilm) and R
Diagram showing the relationship with DI, '? Figure 2 shows the relationship between yield, strength, and general DI when vibration load is applied at the mixing ratio shown in Table 1 and the limestone particle size is adjusted. Figure 3 shows the relationship between limestone particle size adjustment in the lower layer. A diagram showing the relationship between yield, strong 1117, I'LT)I when applied only to
Figure 4 is a diagram showing one example of a vibration load applying device used in the present invention. Representative patent attorney Masaaki Akizawa Mitsugai 2 people j! r1 figure 3 queen 155, hit. Potato 4M

Claims (5)

[Claims] (1) In the downward suction sintering method for fine iron ore, the particle size of the limestone added to the disposed raw material is adjusted so that -0.25M fine particles are 19 or less with respect to the total amount of limestone, and the sintering A sintered ore manufacturing method characterized by applying a vibration load to the surface of the sintered ore after ignition on a sintering machine. (2) A patent that adjusts only the particle size of the limestone added to the lower layer of the raw material layer on the sintering machine pallet so that -0.25 m fine particles are 19 mm or less in the downward suction sintering method of powdered iron ore. A method for producing sintered ore according to claim (1). (3) *In the downward sintering method for iron ore, the scope of the patent claims is to apply h-vibration load when the sintering zone is moving through the upper layer of the raw material layer after igniting the raw material on the sintering machine) mouth),
or the method for producing sintered ore described in section 1). (4) In the downward suction sintering method for powdered iron ore, a vibration load is applied to the surface of the sintered ore from the time when the sintered formation layer reaches 10 to 15 cm after igniting the charged raw material (1) )
, The sintered ore manufacturing method described in (2) or (3). (5) Claims (1), (2), (3) in which the vibration load is appropriately adjusted depending on the softening properties of the sintering raw material used.
, or the method for producing sintered ore described in item (4).