JPH0610313B2 - Pretreatment method for sintering raw material - Google Patents

Description

TECHNICAL FIELD The present invention relates to a pretreatment method for raw materials used for self-fluxing sinter.

(Prior Art) The self-fluxing sinter used as a blast furnace raw material is generally manufactured by the method described below. First, the powdered ore loaded from the ship is piled up in the powdered ore yard for each brand. After that, various powdered ores that have been piled up are mixed by a bedding method at a preset ratio to obtain blending powder.
This blending powder and each raw material such as limestone, powder coke and return ore are put in separate mixing tanks, and a predetermined amount of each raw material is continuously cut out from each mixing tank. This is sent to a primary mixer for water addition and granulation. If necessary, further granulate with a secondary mixer. The raw material (pseudo particles) thus granulated is continuously supplied from the hopper onto the pallet of the sintering machine, and the powder coke on the surface layer of the raw material is ignited by the ignition furnace. Forced ventilation with the air box. By the above operation, a self-fluxing sintered ore as a blast furnace raw material is manufactured.

On the other hand, there are SI (normal temperature strength), RDI (reducing powdering index), RI (reducibility index), etc. as criteria for indicating the quality of the sinter. These qualities have a great influence on the fuel ratio, productivity, operability, etc. in a blast furnace using these sinters as raw materials. Therefore, various techniques have been studied conventionally. For example, a method has been proposed in which the CaO weight content ratio / SiO ₂ weight content ratio (hereinafter, the weight content ratio is omitted and simply referred to as “CaO / SiO ₂ ”) of the sinter is increased. However, CaO / SiO ₂ of the sintered ore needs to be uniquely determined depending on the operating conditions of the blast furnace, and cannot be applied in practice. The _Al 2 _{O 3} weight content / SiO ₂ weight content of fines portion due to miniaturization of the SiO ₂ source (hereinafter, simply by omitting the weight proportion "Al ₂
It is abbreviated as "O ₃ / SiO ₂ ". ), Or a method of preliminarily granulating easily meltable ore powdered ore (especially powdered ore containing a large amount of fine powder) from Australia or India, which has gangue such as clay, by pre-granulating with a reduced CaO source content. However, none of them have been practically applied industrially because no clear effect was obtained despite the increase in manufacturing cost.

(Technical problem to be solved by the invention) The present invention provides a high {Al ₂ O ₃ weight content ratio / (Al ₂ O ₃
Weight content + Fe ₂ O ₃ weight content)}, (hereinafter,
Omitting the weight content ratio, simply saying “Al ₂ O ₃ / Al ₂ O ₃
+ Fe ₂ O ₃ ”. ) Powder ore is CaO / SiO
_The composition of ₂ suppresses the formation of strip-shaped calcium ferrite which is inferior in reducibility, and at the same time promotes the formation of amorphous slag which is excellent in room-temperature strength and resistance to reduction pulverization. It is an object of the present invention to provide a method for producing a sintered ore having excellent convertibility and reducibility with a good yield.

(Means for Solving the Technical Problem) The present invention is based on the chemical composition and the compounding ratio of various powdered ores to be mixed as a sintering raw material, {average Al ₂ O ₃ weight content ratio / (average Al ₂ O ₃ weight) of all powdered ores. Content ratio + average Fe ₂ O ₃ weight content ratio) value, (hereinafter, the weight content ratio is omitted and simply referred to as "average Al ₂ O ₃ / average Al ₂ O ₃ + average Fe ₂ O ₃
It is abbreviated as "value". ) Is calculated, various powdered ores are classified based on this average value, and Al ₂ O ₃ /
The average CaO / S of all the sintering raw materials is the CaO source compounded as a solvent for powdered ores with Al ₂ O ₃ + Fe ₂ O ₃ values.
It is a pretreatment method for a sintering raw material, which is characterized in that it is blended so as to have a value lower than the iO ₂ value, and this mixture is mixed and granulated prior to mixing all the sintering raw materials and granulating.

(Detailed Description of the Invention) Sintered ore is composed of various mineral structures. That is, the quality of the sintered ore is determined by the quality (physical property value) and the composition ratio of these various structures. Therefore, first, various structures constituting the sintered ore were classified according to phase and morphology, and strength and reducibility of each structure were measured. As a result, the amorphous slag, which is a silicate compound, has a high strength, and the strip-shaped calcium ferrite (abbreviated as strip-shaped CaF hereinafter) present in the amorphous slag is reduced compared to other mineral structures. It was found that the sex was extremely poor. That is, if strip-shaped CaF is produced as another mineral structure (for example, acicular or fine-type calcium ferrite) and formation of amorphous slag that does not contain strip-shaped is promoted, a highly reducible sinter having high strength is obtained. Can be manufactured.

Therefore, the conditions for producing strip-shaped CaF existing in the amorphous slag were examined next. First, elemental analysis was performed on the strip-shaped CaF existing in the sintered ore using XMA.
This measurement revealed that the strip-shaped CaF had a higher Ca / Si fire than the surrounding amorphous slag phase. Next, various powdered ores, limestones, and silica stones were used to carry out synthetic tests of sintered structures with various composition. As a result, in order to generate strip-shaped CaF, higher Al ₂ O ₃ / Al ₂ O ₃ + Fe ₂ O ₃ and higher CaO / S than the current raw material composition are used.
It has been found that this is the case when an iO ₂ composition is required and is fired at high temperature. That is, the actual sinter has a microscopic component segregation, and therefore has a higher Al ₂ than the average composition of the sinter.
O ₃ / Al ₂ O ₃ + Fe ₂ O ₃ and high CaO / SiO
_There is a region of _2, and strip-like CaF exists in the actual sinter. Therefore, this high Al ₂ O ₃ / Al ₂ O
The generation of strip-like CaF is suppressed by reducing the region where ₃ + Fe ₂ O ₃ and high CaO / SiO ₂ are formed.

Therefore, high Al ₂ O ₃ / Al ₂ O ₃ + Fe ₂ O ₃ and high Ca
As a method of reducing the O / SiO ₂ region, a method is considered in which all the sintering raw materials are finely pulverized and uniformly mixed to obtain the average composition of the sintered ore microscopically. However, this method is not industrially applicable because it causes a large increase in manufacturing cost.

Therefore, the present invention provides high Al ₂ O ₃ content among powdered ore for sintering raw materials.
/ Al ₂ O ₃ + Fe ₂ O ₃ powder ore is mixed with a CaO source in a small amount and granulated outside the system, so that high Al ₂ O ₃ / Al ₂ O ₃ + Fe _{2 is obtained under the} same raw material mixing conditions. O
_{The area of 3} and high CaO / SiO ₂ composition was reduced.

(Effects of the Invention) Therefore, according to the present invention, strip-shaped Ca having inferior reducibility is inferior.
It suppresses the formation of F and promotes the formation of amorphous slag that is excellent in room temperature strength and resistance to reduction pulverization, and produces a sintered ore that is excellent in room temperature strength, reduction pulverization property, and reducibility with good yield. be able to.

(Example) Next, the Example of this invention is described.

FIG. 1 shows an example in the case of making a process. First, the main sintering raw material powder ore 1, the return ore 3, the limestone 4, the silica stone 5, and the powder coke 6 are mixed and granulated from the main sintering raw material line 7 into a granulating machine 8
High Al ₂ O ₃ / containing less CaO source
Al ₂ O ₃ + Fe ₂ O ₃ powdered ore 2, limestone 4, silica stone 5,
The powder coke 6 is supplied to the mixing granulator 10 through the external granulation line 9. The mixture mixed in the mixing granulators 8 and 10 is mixed in the mixer 11 if necessary, and then the sintering machine 12 is used.
Sintered with. If the amount of decrease in CaO / SiO ₂ is fixed, if a low SiO ₂ powder ore is used as the powder ore for external granulation, the CaO source to be compounded in the external granulation can be small.

Next, an example in which the effect of the present invention is confirmed will be described.

Sintering pot test Sintering pot conditions Raw material mixture Powder ore: 10 brands shown in Table 1 (A to D are South American powder ores,
(E to J are powdered ores from Australia, India) Silica: Compounded so that SiO _{2 in the} product sintered ore will be 5.5%.

Limestone: Compounded so that CaO / SiO ₂ in the product sinter becomes 1.6.

Return ore: 20% for new raw material Powder coke: 4.5% for new raw material Firing condition Ignition: 1 minute Negative pressure: 1200 mmH ₂ O (constant) External granulation condition 1) No external granulation ( Conventional method) 2) Method of the present invention 3) Comparative method (1) ... Total amount of powdered ore from Australia and India (E ~)
J) is granulated outside the system 4) Comparison method (2) ... Granulation of powdered ore (I, J) from Australia, India, which contains a large amount of fine powder. , According to the mixing ratio of each sintering condition.

Sintering Pot Test Results As shown in Table 2 and FIG. 2, it can be seen that the sinter produced by the method of the present invention is superior in quality and productivity to the conventional method in all respects. Furthermore, when the results of the present invention are examined in detail, the reducibility is improved as the amount of CaO source (CaO / SiO ₂ ) in the external granulation is reduced, but the productivity, strength, etc. are CaO / SiO ₂ values. It can be seen that it has a peak value near 0.5. This is because the amount of strip-shaped CaF continuously decreases as the amount of CaO source mixed with the external granulation decreases, and the reducibility improves and CaO /
When SiO ₂ is less than 0.5, the amount of amorphous slag also decreases,
It is considered that productivity and strength have decreased.

On the other hand, the comparative method (1) in which all ore from Australia and India was granulated outside the system improved the reducibility as the amount of CaO source mixed with the outside granulation decreased, but the productivity, strength, etc.
/ SiO ₂ has a peak at around 1.0 and significantly lowers below 0.5. It is considered that this is because the amount of powdered ore that is granulated outside the system is so large that the melt during the sintering reaction is significantly reduced. Further, the productivity and the peak value of strength when CaO / SiO ₂ is around 1.0 are lower than those of the method of the present invention. It is considered that this is because the average ordinary Al ₂ O ₃ / Al ₂ O ₃ + Fe ₂ O ₃ value of the powdered ore subjected to the external granulation was lower than that of the method of the present invention, and the effect was reduced. Also in Australia,
In the comparative method (2) in which the powdered ore of Indian fine powder and a large amount of fine powder was granulated outside the system, the effects on the productivity and quality with respect to the amount of CaO source compounded outside the system were similar to those of the method of the present invention. As shown, its effect is small. This shows only the same tendency because the ore measured by the method of the present invention happened to contain the ore defined by the comparison method (2). Further, this comparison method (2) uses the high Al content specified in the method of the present invention.
_It is considered that the effect was small because only ₂ O ₃ / Al ₂ O ₃ + Fe ₂ O ₃ powder ore was contained. In addition, productivity and strength peak values are outside system granulation compound Ca
It is considered that the reason why the amount of O source (CaO / SiO ₂ ) moved to the smaller one was due to the above reason.

The test was carried out by changing the powder coke blending amount, the powder coke blending ratio to the external granulation, the silica stone blending amount, the limestone blending amount, and the like, and the same effects as those in the above-described examples were obtained. Further, the smaller the average CaO / SiO ₂ value of the sintered ore, the greater the effect.

[Brief description of drawings]

FIG. 1 is a block diagram showing one embodiment of the present invention, and FIG. 2 is an explanatory diagram showing the results of a sintering pot test in the embodiment of the present invention. 1 ... Main powder ore for sintering raw material, 2 ... Powder ore for external granulation,
3 ... Return ore, 4 ... Limestone, 5 ... Silica, 6 ... Powder coke, 7
... Main sintering raw material line, 9 ... External granulation line, 8,1
0 ... Mixing granulator, 11 ... Mixing machine, 12 ... Sintering machine

Claims (1)

[Claims] 1. From the chemical composition and the compounding ratio of various powdered ores blended as a sintering raw material, {average Al ₂ O ₃ weight content ratio / (average Al ₂ O ₃ weight content ratio + average Fe ₂ O ₃
Weight content ratio)} value is calculated, and various powdered ores are classified based on this average value, and higher than the above average value {Al ₂ O ₃
Weight content ratio / (Al ₂ O ₃ weight content ratio + Fe ₂ O ₃
For a powdered ore having a value of (weight content ratio)}, a CaO source compounded as a solvent is blended so as to be lower than the average (CaO weight content ratio / SiO ₂ weight content ratio) value of all sintering raw materials, 2. A pretreatment method for a sintering raw material, which comprises mixing and granulating all the sintering raw materials prior to mixing and granulating.