JPS6123726A - Production of uncalcined lump ore - Google Patents

Abstract

PURPOSE:To produce uncalcined lump ore at a high molding yield with good efficiency by pelletizing preliminarily a mixture composed of powder ore and cement then subjecting the pellets to roll molding thereby forming lump ore. CONSTITUTION:The above-mentioned mixture is preliminarily pelletized prior to rolling molding of said mixture in the stage of subjecting the mixture to roll molding to form the lump ore. The density of the molding is made higher than the density of the untreated mixture by the preliminary pelletization, by which the bite to rolls in the subsequent roll molding and the interaction among the particles as well as the strength and molding yield of the molding are improved. The above-mentioned preliminary pelletization is executed by pseudopelletization in which the molding is simply pelletized by a mixer, etc. or minipelletization in which the molding is made into small pellets sized about 5mm. by a pelletizer. The raw material having poor moldability is efficiently lumped by the above-mentioned method.

Description

DETAILED DESCRIPTION OF THE INVENTION <Industrial Field of Application> The present invention relates to a method for agglomerating fine ore without sintering, and is an improvement to particularly improve the molding yield.

<Background technology and its problems> When fine ore is charged into a reed-1 blast furnace, it causes poor or uneven ventilation, an increase in the amount of gas ash generated, and poor unloading, resulting in an increase in coke ratio or It is known that this has a significant negative impact on blast furnace operations, such as a decrease in the pig iron production ratio. Therefore, it is currently being industrially practiced to agglomerate and use fine ore. This method is classified as shown below.

(1) Sintering method Mix coke with a particle size suitable for fine ore of class 5 or less and limestone powder as necessary,
A method in which iron ore is fired at a temperature of °C to melt and sinter a portion of the iron ore, and after cooling, it is crushed into suitable granules.

(2) Beretstyzing - Calcination method A suitable amount of moisture and, if necessary, bentonite, lime, etc. are added to the crushed ore powder and granulated into pellets using a rotating drum or plate, and then fired in a rotary kiln. A method of obtaining sufficient strength by sintering.

(3) Pelletizing - cold hardening method. This is a method commonly referred to as cold bonding method, in which finely pulverized ore powder is mixed with portland cement or portland cement clinker.
Add appropriate amount of water to the powder mixture and place it in a rotating drum.
- A method of granulating into pellets using a rotating plate, etc., and curing the edges to obtain sufficient strength.

Of the above three methods, methods (11 and (2)) both require large-scale firing equipment because the granules or reddish are fired, and they also reduce SOx and NOx generated from the firing furnace. In addition, there is a fundamental flaw in that powder gardens become a source of pollution.For this reason, the method (3) above is expected to be used as a non-fired agglomeration method;
) method has the problems of primitive methods as shown below3.
(a) Since it takes a long time (usually 7 to 10 days) to develop strength, large-scale curing equipment is required.

(b) Because pellets are spherical, their angle of repose is small, and when they are put into a blast furnace, they are unevenly distributed in the center of the furnace, making blast furnace operation extremely unstable. To avoid this, the amount used is limited to a very small amount (usually 10 to 20% by weight).

el Because it is necessary to add a large amount of cement (usually 7% or more) to K to achieve sufficient strength, the slag ratio increases during blast furnace operation, resulting in a decrease in the tap iron ratio.

The coke ratio and furnace workability deteriorate.

) Because the reduction reaction proceeds in a spherical and topochemical manner, unreduced FeO tends to remain inside the pellet.

(e) Since it is necessary to finely crush the raw material iron ore during the manufacturing process, the power cost for crushing is high.

The present inventor has already invented a method of agglomerating by roll forming as a method to solve the above problems (%Application No. 59-4
No. 0398). The present invention is characterized in that a mixture of fine ore, cement and water is compressed into flakes using a pressure forming roll and then cured. According to this roll forming method, since it can be produced in the form of flakes, the angle of repose is large compared to conventional unfired pellets, and the phenomenon of uneven distribution during loading into the blast furnace can be prevented, and the curing time is significantly shorter than that of conventional unfired pellets. This has various effects such as being able to shorten the time. However, even with this roll forming method,
Under certain raw material conditions, there was melting that caused a decrease in yield. For example, if a large amount of ore such as Brazilian speculite, which has poor formability, is mixed, the strength immediately after roll forming (hereinafter referred to as
The green strength of the molded product was low, resulting in the molded product collapsing in subsequent steps and resulting in a decrease in yield.

<Means for Solving the Problems> The present invention has been made in view of the above-mentioned actual situation, and it is an object of the present invention to provide a method that can efficiently assemble even raw material ores with poor formability. The structure of the present invention which achieves this object is characterized by pre-granulating the mixture of fine ore and cement before roll-forming and agglomerating the mixture. Pre-granulation here refers to granulating the above mixture by some means in the VC prior to roll forming to increase the density of the formed product compared to that of the unprocessed mixture, for example. This can be carried out by methods such as , pseudo-granulation, mini-pelletization, or roll forming. Pseudo-granulation refers to the state in which powder particles are aggregated and granulated before being pelletized by simple granulation performed with a mixer or pelletizer, and mini-pelletization refers to the state in which powder particles with a diameter of 5 This refers to controlling the grains so that they become like small pellets with a grain size of about 100 ml or less.

<Function> The molding yield during roll forming is determined by the magnitude of the green strength, and if this is small, the molded product will collapse during subsequent steps, especially during transportation of the molded product, and the yield will decrease. The green strength of molding depends on molding conditions (roll gap, pressing force, pretreatment, etc.)
) and raw material conditions (ore name, particle size, moisture, etc.), so if the raw material conditions are poor, this can be covered by the molding conditions - for example, if a large amount of Brazilian iron ore is blended. If the fine ore has a unique shape, the bonding strength of the fine part of the raw material tends to be insufficient, but this can be compensated for by increasing the molding conditions, for example by increasing the packing density of the molded product. This is possible. Therefore, in the present invention, in order to make the molded product well-compacted and to improve the green strength of the molded product, preliminary granulation is carried out before agglomeration by roll forming. By doing this, the density of the molded product is improved by preliminary granulation, and as a result, in the subsequent roll forming, the biting into the roll and the interaction between particles are improved, and the molded product is tightly compacted. Therefore, the green strength of the molded product is improved, leading to an improvement in yield. In addition, when performing roll forming as preliminary granulation, in order to improve the forming conditions, after the first roll forming, part or all of the formed product may be crushed into small particles and then roll formed. A part of the mixture may be separately mixed with the raw materials and roll-formed.

<Example> An appropriate amount of water was added to the raw materials of the composition shown in Table 1 above, and after thoroughly mixing with a roller mixer, the mixture was molded by the following four-pass method. In addition, the roll forming machine is equipped with a vibrating plate, and the roll size is 450 + m x 350 mm.
The number of roll rotations is 2 r, p, m.

(1) Put it through a roll forming machine.

(After being granulated and pseudo-granulated using a drum mixer, it is applied to a roll forming machine.

(II) After being granulated into smudged pellets using a Hough W heretizer, the pellets are applied to a roll forming machine.

υn After passing through the shredder and roll forming machine, further
1. Place the other part on a roll forming machine.

The green strength of the molded products agglomerated by these four methods was measured as follows.

[Measurement method for molded product green strength]

Molded product immediately after molding (particle size 10w or more)] OK.

was placed in an iron box (30 cy++ cubic) and dropped 5 times from a height of 2 m onto a 10 crn thick printing plate, and the percentage of the molded product that did not collapse was defined as the green strength of the molded product. The measurement results are shown in the figure. As shown in the figure, the molded green strength of the molded product according to the method of the present invention according to CD) (III) (IV) is higher than that of the molded product according to (1) K, and (ff) (III) It can be seen that the method (A') has a higher yield than the method CI). Regarding this,
This is more noticeable in raw material B, which contains more Brazilian wrought iron ore, which has poor formability, than raw material A.

<Effects of the Invention> As explained above in detail based on the examples, the present invention performs preliminary granulation prior to roll forming, so the green strength of the molded product improves, and therefore a large amount of raw material with poor moldability can be used. Even when it is blended into the above, it can be efficiently produced without reducing the yield.

[Brief explanation of drawings]

The figure is a graph showing the relationship between the green strength of molded products and the processing method.

Claims (2)

[Claims] (1) A method for producing non-calcined agglomerate ore, which comprises pre-granulating the mixture of fine ore and cement before roll-forming and agglomerating the mixture. (2) A method for producing non-calcined agglomerate ore, which is characterized in that a pseudo-granulation method, a mini-pelletization method, or a roll-forming method is employed as the preliminary granulation method as set forth in claim 1.