JPH0931469A - Preliminary treatment of coal charged to coke oven - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a method for preliminary treating coal charged to a coke oven, capable of surely preventing the generation of dust, etc., by firmly granulating the fine powdery coal. SOLUTION: This method for preliminary treating coal charged to a coke oven is constituted by separating dried coal to coarse grain coal and fine powdery coal, adding 5-30wt.% heavy oil and water to the fine powdery coal to form an aqueous slurry, then granulating it to granulated coal having a particle diameter over a separating point by a wet granulation, then performing a dehydrating treatment and blending with the coarse grain coal.

Description

Detailed Description of the Invention

[0001]

TECHNICAL FIELD The present invention relates to a method for pretreatment of coal charged in a coke oven.

[0002]

2. Description of the Related Art As a manufacturing method for improving the quality of coke for iron making, it is known to dry coal to improve the coal packing density in a coke oven. At this time, it is also known that fine powder is separated due to decrease in water content of coal and causes dust during transportation of coal, which adversely affects the environment.
Therefore, the dry coal is separated into coarse coal and fine coal, and the coarse coal is fed into the coke oven as it is and is carbonized to obtain coke. On the other hand, pulverized coal becomes a dust source at the transfer section of the transfer conveyor when it is transferred to the coke oven, and also mixes in the gas generated by the coke oven when it is charged into the coke oven, and enters the tar, ammonium sulfate, etc. to be recovered. Therefore, it is also known to carry it into a coke oven by carrying out a treatment such as granulation to increase the diameter so that it does not become a dust source and the like.

However, as a pretreatment method for coal which can improve the strength of the granulated coal as described above and prevent it from collapsing during transportation, heavy oil is added to the coal,
Dry granulation is disclosed in JP-B-49-28241.

[0004]

In the method of dry granulation of coal as described above, the strength of the coke does not improve so much, and after granulation, when the conveyor is transferred to the coke oven for transfer, it collapses at the transfer section. As a result, a large amount of pulverized coal is generated and dust is generated, deteriorating the environment. Furthermore, when charging the coke oven, the fine coal is mixed into the coke oven gas, and the tar and ammonium sulfate recovered from the coke oven gas are mixed with the fine coal. There is a problem that quality will be deteriorated. In particular, in recent years when it is necessary to consider the environment, the dust collection tends to be strengthened, which is a big problem. The method of the present invention has been made in order to advantageously solve such a problem, and provides a pretreatment method for coke-charged coal that can reliably and stably improve the strength of coke. The purpose is.

[0005]

The feature of the method of the present invention lies in that dry coal is separated into coarse coal and fine coal, and 5 to 40% of heavy oil and water are added to the fine coal to prepare a water slurry. The pretreatment of the coal charged into the coke oven, which is characterized in that the coal is granulated into a granulated coal having a particle size exceeding the separation point by wet granulation, and then subjected to dehydration treatment and mixed with coarse coal. Is the way.

[0006]

BEST MODE FOR CARRYING OUT THE INVENTION Coal drying is carried out by adding a coal water content of about 5% in order to increase the bulk density during charging into a coke oven.
Since the bulk density is not improved so much even if dried to less than 2%, the lower limit is preferably 2%. In this way, the dried coal is separated into coarse coal and fine coal, as the particle size of the fine coal to be separated, the height of the conveyor transfer section, the height of the coke oven, the coke oven generated gas due to the capacity of the coke oven, etc. The particle size (weight) of the pulverized coal mixed in the dust generation source or the gas generated by the coke oven changes depending on the amount of emissions, etc. Therefore, it is decided according to these conditions. If the capacity of the furnace and the height of the connecting part of the conveyor are 0.1
It will be any value within the range of 0.4 mm (average particle size).

Heavy oil, for example, tar, waste oil of steel rolling oil, or a mixed oil thereof is added to the pulverized coal separated as described above. In particular, tar is separated from coal when carbonized, and is advantageous in strength during granulation because it has affinity with coal. However, 5 to 40% is sufficient as the amount of the heavy oil added, and if it is less than 5%, the function as a binder for reliably granulating the pulverized coal becomes insufficient, and it easily collapses. If so, the granulated coal becomes soft, which is not preferable. As an aspect of adding such a heavy oil, for example, pulverized coal is introduced into a slurry tank to add the heavy oil, and at the same time water is added in an amount of 10 to 40.
%, Add it to a water slurry, guide it to a granulator, and use the added water as a medium to roll the fine coal and heavy oil in water while applying centrifugal force to compress and granulate, so-called wet granulation To do. Since such wet granulation does not include gas in the granulated coal unlike the dry granulation, the granulated coal becomes extremely dense granulated coal and the strength can be surely improved.

Thus, before adding the heavy oil and water to the fine coal to form a water slurry, the fine coal is introduced to, for example, a kneader in advance, the heavy oil is added and kneaded, and then the slurry tank as described above. It is possible to prevent water entrapment in the pulverized coal during granulation by introducing water into a water slurry by adding water and performing wet granulation, thereby further improving the strength of the granulated coal. The granulated coal particle size for granulating the pulverized coal in this manner is a particle size exceeding the separation point of the pulverized coal separated into the coarse coal and the fine coal as described above.
That is, if the granulated coal particle size is less than the separation point of the pulverized coal,
As described above, it is not preferable because it becomes a dust source at the transfer section of the conveyor.

After the granulated coal is formed as described above, it is dehydrated by a sieve bend, hot air blowing, centrifugal dehydrator and the like. It is preferable that this dehydration treatment is stopped by dehydration of the water content of the dry coal (coarse coal) or more. That is, some fine coal is also mixed in the coarse coal separated after drying as described above, when the coarse coal and granulated coal are mixed and conveyed to the coke oven, Moisture (water) can moisten fine coal in coarse coal to prevent dust generation, and also prevent fine coal from mixing in the coke oven generated gas when it is charged into the coke oven. be able to. In addition, by leaving water in the granulated coal, the amount of dehydration is reduced so much that there is no need for drainage, and therefore wastewater treatment equipment is also unnecessary, which is extremely advantageous. For example, if the water content of normal coke oven charged coal is dried to about 2% and the separated coal particle size is 0.3 mm, coarse coal is about 70% and granulated coal is about 30%. Fine powder of less than 0.3 mm, which was contained in about 5% in the coarse coal, will adhere to the granulated coal after it is mixed with the granulated coal and before charging into the coke oven, thus reliably preventing dust generation. can do.

As described above, the coarse coal and the granulated coal are mixed, conveyed and charged into the coke oven, and carbonized to produce coke.

[0011]

EXAMPLES Next, examples of the method of the present invention will be given together with comparative examples.

[Table 1] Note 1: Dry coal is the water content of coal after drying. Note 2: Heavy oil A is tar, B is 50% tar, and residual steel strip rolling waste oil. Note 3: In Examples 1 to 4, pulverized coal and water were introduced into a slurry tank to form a water slurry, and then wet granulation. In Examples 5 to 8, pulverized coal and heavy oil were introduced into a kneader and kneaded, and then water was added in a slurry tank to prepare a water slurry, and then wet granulation. Note 4: Granulated coal strength indicates the collapse rate when granulated coal is repeatedly dropped 20 times from a height of 2 m. Note 5: Conveyance conditions were determined by visually observing the state of dust generation at the transfer section of a conveyor with a transfer height of 2 m (“no” for almost no dust generation, and “yes” for clear dust generation).

[0012]

According to the method of the present invention, it is possible to stably improve the strength of granulated coal made of pulverized coal, and prevent dust generation during transportation to a coke oven or the like to prevent environmental deterioration. it can. Further, since it is possible to avoid mixing of fine coal into the gas generated in the coke oven during charging into the coke oven, it is possible to avoid deterioration of quality because there is almost no inclusion in the recovered tar, ammonium sulfate, etc. Therefore, the quality of coke can be improved by drying the coal without major modification of the existing coke oven and incidental equipment, and great effects such as stabilization of blast furnace operation can be achieved.

 ─────────────────────────────────────────────────── ─── Continuation of the front page (72) Inventor Yoshihiro Serizawa 5-3 Tokai-cho, Tokai-shi, Aichi Nippon Steel Co., Ltd. Nagoya Steel Works (72) Inventor Masa Sato 5-3 Tokai-cho, Tokai-shi, Aichi Nippon Steel Co., Ltd. Nagoya Steel Works

Claims (3)

[Claims] 1. Dry coal is separated into coarse coal and fine coal, 5 to 40% of heavy oil and water are added to the fine coal to form a water slurry, and then wet granulation is performed to separate the particles above the separation point. A method for pretreatment of coal charged in a coke oven, which comprises granulating granulated coal having a diameter, then subjecting it to dehydration treatment and mixing with coarse coal. 2. The method for pretreatment of coal charged in a coke oven according to claim 1, wherein a heavy oil is added to the pulverized coal and the mixture is kneaded to produce a water slurry. 3. The water content of the granulated coal is dehydrated to a value higher than that of the dry coal.
The pretreatment method for the coal charged in the coke oven described in.