JPH04318109A - Method for improving strength in powdery coal pressurized compact - Google Patents

Abstract

PURPOSE:To provide the manufacturing method for powdery coal pressurized compact, which does not pulverize in storing and conveying processes up to charging into a smelting reduction furnace for executing stable smelting reduction operation and at the time of rapid heating in the smelting reduction furnace. CONSTITUTION:At the time of pressurize-compacting the powdery coal containing >=15% volatile matter, powdery iron oxide-containing material is mixed at >=5% and <=40%, or further additionally, <=20% powdery material made-up to have <=3% volatile matter by heating the coal is mixed at >=5% and <=40%. In the smelting reduction process for producing iron by using the powdery ore and general powdery coal, without using expensive binder, efficient supply of the powdery coal is executed and problem of crack due to rapid heating of the coal is solved, and large industrial and economical effects are obtd.

Description

[Detailed description of the invention]

0001

[Industrial Application Field] The present invention is a method for improving the strength of pulverized coal compacted products for effectively using pulverized coal in a method for producing molten iron alloy from iron ore or its pre-reduced product by smelting reduction. It is related to.

0002

BACKGROUND OF THE INVENTION At present, the blast furnace method is used as a mass production iron manufacturing method. The blast furnace method is an excellent process in terms of productivity and thermal efficiency, but the problem is that iron ore requires an agglomeration process such as sintering, and coal requires a coking process. That's true. In particular, in order to obtain the high-strength coke required by the blast furnace method, resource-constrained coal with excellent caking properties called so-called coking coal must be carbonized in an indoor coke oven. Must be. Moreover, since the indoor coke oven is a very expensive piece of equipment, a huge amount of money is required to update it.

On the other hand, the smelting reduction method is a new process that has been developed to solve the problems inherent in the current blast furnace method as described above. As one of the smelting reduction methods, a method is being developed that uses a metallurgical furnace that can blow gas from the top and bottom, and utilizes the large amount of slag that exists in the furnace, and some problems have already been solved. Only the issue of coal remained.

[0004] In other words, it is desired to develop a process that uses inexpensive steam coal and does not require a coking process as a smelting reduction method to solve the problems inherent in the blast furnace method. Until now, it has been difficult to solve this problem for the following reasons. First, coal is sieved to select lumps (approximately 10 mm or more), and when these are fed into a melting and reduction furnace, coal cracks due to the rapid vaporization of volatile matter due to rapid heating, and the average particle size becomes fine particles of about 3 mm. As a result, the following two problems arise.

(2) The scattering rate of carbonaceous materials is 10% or more (carbonaceous materials with a diameter of 2 mm or less are scattered at a certain rate (for example, 15% of carbonaceous materials with a diameter of 2 mm or less). ■As the carbon material becomes finer, its specific surface area increases, making it less likely to get caught up in the slag, which delays carburization into the metal, making stable operation impossible. On the other hand, when powdered coal is supplied to a smelting reduction furnace, the following problem occurs.

[0006] In the method of adding powdered coal from above, the proportion of coal that is discharged out of the system along with the exhaust gas from the smelting reduction furnace is close to 30%. ■With the method of blowing powdered coal into metal, the metal is agitated too strongly as a result of the blowing, resulting in an increase in the amount of iron-based dust generated. ■Those made by adding a binder to powdered coal and forming it (for example, into briquettes),
When rapidly heated in the furnace, the binder becomes a source of gas and breaks into small pieces.

[0007]Also, powdered coal formed without adding a binder is less likely to break when rapidly heated in a furnace, but its cold strength is weak, so it is difficult to store and transport the coal until it is put into the melting reduction furnace. Re-pulverization occurs. As described above, there are many problems with the use of powdered coal. As described above, in the conventional method, coal pulverization is an unavoidable problem, and as a result, stable melting and reduction operations cannot be performed.

[0008] Generally, coal is purchased in the form of a powder mixture, which contains 30 to 40 pieces of powder coal with a particle size of 4 mm or less.
%include. For this reason, a major challenge in the smelting reduction iron manufacturing method is to effectively utilize powdered coal, which has many problems in use for the above reasons.

[0009]

[Problems to be Solved by the Invention] Based on the above knowledge, the present invention provides the following steps in order to perform stable melting reduction operation.
Provides a method for producing pressed coal powder that does not become powdered during the storage and transportation process before being put into a smelting reduction furnace, and also does not become pulverized when rapidly heated in a smelting reduction furnace. The purpose is to

0010

[Means for Solving the Problems] The present invention supplies oxygen gas to a metallurgical furnace in which gas can be blown from the top and bottom, as shown in FIG. The volatile content of 1
When rolling powdered coal containing 5% or more, 5 to 40% of powdered iron oxide-containing material is mixed or further added, and the coal is heated to reduce the volatile content to 3% or less. The subject matter is a method for improving the cold strength of a press-molded product of pulverized coal, which is characterized by mixing 20% or less of pulverized coal.

[0011]

[Operation] First, Figure 2 shows powdered coal of various brands dried in an air-dried state, pulverized to 0.3 mm or less, and then compressed and molded using a roll compactor, the size of which is 3 to 10 mm.
The influence of the coal volatile content on the powder generation rate is shown when the I-type drum test is conducted on the molded product. The powder generation rate is expressed as the weight percentage of 200 g of molded product having a particle diameter of 2 mm or less after 60 revolutions using an I-type drum. It can be seen that the powder generation rate increases when the volatile content is less than 15%. The reason why the strength of the press-formed product changes depending on the volatile content of the coal used when powdered coal is pressurized without adding a binder is considered to be as follows. Coal contains functional groups such as carboxyl groups, quinone groups, and hydroxyl groups, and the amount of these groups generally increases as the volatile content increases. Functional groups also exist on the coal surface. The number of these surface functional groups increases as the coal particle size becomes smaller (because the specific surface area becomes larger). When pulverized coal is compressed under pressure and the distance between adjacent coal particles becomes very small, van der Waals forces occur between the functional groups of adjacent particles. It is thought that this force causes the coal particles to stick together. Volatile content is 15%
The reason why the strength of the molded product decreases in the case of coal with less than .

Next, FIG. 3 shows powdered coal (volatile content 36%) with a particle size of 0.3 mm or less and powdered iron oxide containing material (T.Fe: 61.5%, with a particle size of 0.2 mm or less). M.Fe:7
．． 6%, FeO: 27.6%, C: 4.5%), and the effect of the blending ratio of powdered iron oxide-containing substances on the powder generation rate according to the I-type drum test of the molded product that was pressure-formed with a roll compactor. Show the impact of It can be seen that the powder generation rate can be suppressed to a lower level when the powdery iron oxide containing material is blended at a ratio of 5% or more and 40% or less, compared to when the powdery iron oxide containing material is not blended. This is because the porosity of the powdered coal/iron oxide-containing mixture is reduced by blending the powdered iron oxide-containing material, which is finer than the particle size of powdered coal and has a different particle size structure, so that the compacting pressure is applied to each particle. On the other hand, if the content of iron oxide-containing substances is too large, the number of surface functional groups on the pulverized coal will be relatively reduced, increasing the strength of the molded product. This is determined by the combination of two effects: that it becomes impossible to maintain the

FIG. 4 shows pulverized coal (volatile content 36%) with a particle size of 0.3 mm or less and 30% powdered iron oxide containing material with a particle size of 0.2 mm or less (same composition as in FIG. 3 above). , and a powder material of 0.2 mm or less (hereinafter abbreviated as powder heated coal) made by heating coal to a volatile content of 3% (hereinafter abbreviated as powdered heated coal) was added, and the molded product was press-formed using a roll compactor. The influence of the blending ratio of heated charcoal powder on the powder generation rate is shown in the mold drum test. If the mixing ratio of powdered heated coal is within a range of 20% or less, the powder generation rate can be kept low compared to the case of a molded product made of only powdered coal without any addition.

FIG. 5 shows pulverized coal (volatile content 36%) with a particle size of 0.3 mm or less, 30% of powdered iron oxide containing material with a particle size of 0.2 mm or less, and powder heating to a particle size of 0.2 mm or less. This figure shows the influence of the volatile content of heated charcoal powder on the powder generation rate in an I-type drum test of a molded product containing 20% charcoal and pressure-molded using a roll compactor. The reason why the strength of molded products increases when powdered heated carbon is added is as follows.
Coal heated to reduce the volatile content to 3% or less is
It is thought that this is because the irregularities on the grain surface become complex, and when mixed into the coal grains, they create a wedge effect in the molded product.

FIG. 6 shows pulverized coal with a particle size of 0.3 mm or less (volatile content 36%) mixed with 30% powdered iron oxide containing material with a particle size of 0.2 mm or less (same composition as in FIG. 3). , 0.2m in which the coal was further heated to reduce the volatile content to 3% or less.
This figure shows the influence of the thickness of a molded product on the powder generation rate in an I-type drum test of a molded product that is pressure-molded using a roll compactor after blending powdered heated coal of less than m. Thickness of molded product is 3-8m
m, the powder generation rate can be suppressed to the lowest level.

[0016] As such powdered iron oxide-containing material and/or powdered heated coal, dust generated in the melting reduction process can be used. As mentioned above, powdered coal formed under appropriate conditions has improved cold strength,
In addition, it is difficult to powder even when put into a smelting reduction furnace and subjected to rapid heating. Therefore, by implementing the present invention, coal problems that have been problems in the development of conventional smelting reduction methods, namely scattering and carburization delay, can be solved. , and the problem of effective supply of powdered coal can now be solved.

[0017]

EXAMPLE FIG. 1 shows an example of the equipment of a melting reduction furnace used to carry out the present invention. In a container lined with a refractory 1, a bottom blowing tuyere 2 is provided at the bottom for blowing a gas such as nitrogen into the molten metal to stir it. The top blow lance 3 is for supplying oxygen gas into the furnace. Ore is supplied into the furnace from a fine ore input port 4 provided on the furnace shoulder. A large amount of molten slag 5 exists in the furnace,
It is necessary that the bottom-blown agitated metal bath 6 be isolated from the top-blown oxygen jet. The required amount of slag is 3
When the metal 6 and slag 5 generated are discharged by tilting the furnace at 50 kg/t metal or more, the amounts of remaining metal and remaining slag are adjusted.

Table 1 shows the main operating conditions of the smelting reduction furnace.

[0019]

[Table 1]

[0020] Pre-reduced ore was used as the ore. The component conditions are shown in Table 2. This was conveyed into the furnace through a fine ore inlet 4 on the shoulder of the smelting reduction furnace using nitrogen gas.

[0021]

[Table 2]

On the other hand, in the operation of this example, carbonaceous material roll-formed under various conditions as shown in Table 3 was used. In both cases, the material was introduced into the furnace through the furnace opening 7. As a result, the operational results when changing the type of carbon material were as shown in Table 4. Therefore, according to the present invention, more preferable results can be obtained when using a powdered iron oxide-containing material or a carbon material formed by mixing powdered heated coal in addition to a carbon material formed from only powdered coal. It was done.

[0023]

[Table 3]

[0024]

[Table 4]

[0025]

[Effects of the Invention] As described above, the present invention is a smelting reduction process for producing iron using powdered ore and powdered coal, which are the cheapest raw materials, without using an expensive binder. This solution solves the problems of effective supply of powdered coal and pulverization due to rapid heating cracking of coal, and has great industrial and economical effects.

[Brief explanation of drawings]

FIG. 1 is an explanatory diagram showing an example of melting reduction equipment used to carry out the present invention.

FIG. 2 is a diagram showing the influence of the volatile content of pulverized coal on the powder generation rate of pulverized coal press-molded products.

FIG. 3 is a diagram showing the influence of the blending ratio of powdered iron oxide-containing substances on the powder generation rate of pulverized coal press-molded products.

FIG. 4 is a diagram showing the influence of the blending ratio of heated pulverized coal on the powder generation rate of a pulverized coal press-molded product.

FIG. 5 is a diagram showing the influence of the volatile content of pulverized heated coal on the powder generation rate of pulverized coal press-molded products.

FIG. 6 is a diagram showing the influence of the thickness of the press-molded product on the powder generation rate of the press-molded product.

Claims (2)

[Claims] Claim 1: When press-molding powdered coal containing 15% or more of volatile matter, powdered iron oxide-containing material is added to 5% or more of 4
A method for improving the strength of a press-molded product characterized by mixing pulverized coal in an amount of 0% or less. 2. In the method according to claim 1, 20% of the powdered material is obtained by further heating the coal to reduce the volatile content to 3% or less.
A method for improving the strength of a press-molded product of pulverized coal, characterized by mixing the following: