JP2003055718A - METHOD FOR TREATING Cr-CONTAINING SLUDGE, AND PELLET FOR STEELMAKING BY USING THE METHOD - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a method for treating Cr-containing sludge by which effective components can be recycled and also to provide pellets for steelmaking using the method. SOLUTION: In the method for treating Cr-containing sludge, the Cr- containing sludge of high water content is mixed with dry sintering dust and the resultant mixture of about 10% water content is mixed with iron-containing zinc dust and a binder and pelletized into green pellets, and these green pellets are cured and dried into the pellets for steelmaking. The pellets for steelmaking can be obtained by treating the Cr-containing sludge above. The pellets for steelmaking have a specific gravity higher than that of the molten slag in a converter into which they are to be thrown and are dried to <=4% decreasing drying rate region.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for treating Cr-containing sludge in which active ingredients can be reused, and a steelmaking pellet obtained by the method.

[0002]

2. Description of the Related Art For example, in steel mills or other factories, there is a case where a high water content Cr-containing sludge is generated after a plating process, a pickling process and a wet dust collecting process. In this case, conventionally, the generated Cr-containing sludges are normally landfilled as industrial waste.

However, recently, the acceptable capacity of the landfill site has been reduced, and the cost of outsourcing for landfill processing is also high, which causes a problem of cost increase. Further, sludge contains effective components such as iron, and if it is disposed of, it causes a waste of resources.

On the other hand, the applicant of the present invention aims to reduce the amount of industrial waste by pelletizing iron-zinc sludge, which is not a Cr-containing sludge, and introducing it into a converter.
A method for reusing an active ingredient such as iron present in sludge has been developed, and was previously proposed as Japanese Patent Laid-Open No. 56-139633. However, according to this method, there is a problem that the dehydration equipment is large, the equipment cost is high, and the drying time is long. In addition, when the pellets are put into a converter, the amount of water in the pellets is large and an explosion occurs in the furnace. Therefore, when this technique is directly applied to the Cr-containing sludge, the dispersion of Cr becomes uneven and the slag However, there was a problem in that the non-uniform mixing with the steel and the yield of pellet iron were significantly reduced.

[0005]

DISCLOSURE OF THE INVENTION The present invention solves the above-mentioned problems of the prior art, and provides a steelmaking pellet capable of reusing an active ingredient from a Cr-containing sludge in a short time with a simple facility. C that can be produced at low cost
A method for treating r-containing sludge, and a method obtained by the method, which can evenly disperse without introducing in-furnace explosion even when it is charged into a converter, has a high iron yield, and has a Cr standard value or less. The present invention has been completed for the purpose of providing pellets for steelmaking which can enable the converter operation in the above.

[0006]

Means for Solving the Problems The present invention, which has been made to solve the above-mentioned problems, is obtained by mixing a high-moisture Cr-containing sludge with a sintered dry dust to obtain a mixture having a water content of about 10%. After mixing the mixture with iron-containing zinc dust and binder, granulate to form raw pellets,
Then, the raw pellets are cured and then dried to be used as steelmaking pellets.

Further, in order to solve the same problem, it is preferable to dry the raw pellets to a reduction rate dry region of 4% or less to obtain steelmaking pellets, which is an invention according to claim 2. Furthermore, the present invention made to solve the above-mentioned problems is a steelmaking pellet obtained by treating Cr-containing sludge, and the specific gravity thereof is larger than the specific gravity of the molten slag of the converter, and 4 The steelmaking pellets are characterized by being dried up to a reduction rate dry region of not more than%.

[0008]

BEST MODE FOR CARRYING OUT THE INVENTION Preferred embodiments of the present invention will be described below with reference to the drawings. The drawing is an overall flow chart showing an example of a manufacturing process of steelmaking pellets according to the present invention, in which 1 is a source of sintered dry dust, 2 is a source of Cr-containing sludge, and 3 is a source of iron-containing zinc dust. The source 4 is a hopper for storing each raw material supplied from these supply sources and cutting out a fixed amount.

The Cr-containing sludge contains a high water content of 50 to 60%, and if it is stored in the hopper 4 as it is, it cannot form a bridge and be accurately cut out and blended. Therefore, in the present invention, the Cr-containing sludge is mixed with the sintered dry dust in advance to form a mixture having a water content of about 10%, and the mixture is stored in the hopper 4 to prevent the occurrence of bridges.

Iron-containing zinc dust and a binder are stored in the hopper 4. The iron-containing zinc dust is for imparting a sufficient mass to pass through the slag layer and enter the molten pig iron when the steelmaking pellets produced as described below are put into the converter. That is, it is for adjusting the specific gravity of the steelmaking pellets, and is prepared and added so as to be larger than the specific gravity of the in-furnace slag. As the binder, for example, granulated blast-furnace slag fine powder called “mentoment” made of silica and CaO can be used.
Note that quick lime necessary for granulation is also stored in the hopper 4.

As the iron-containing zinc dust, it is preferable to use two types of high zinc dust and low zinc dust.
Here, high zinc dust means a zinc content of about 2%, and low zinc dust means a zinc content of about 0.5%.
Refers to the following: Since the high zinc dust is a fine particle, it may not be possible to form a nucleus when pelletizing in the subsequent step and a pellet for steelmaking having a desired shape may not be obtained, and in the present invention, a low zinc dust that is a coarse particle dust having a large diameter. By adding, it is used as a core during granulation.

As described above, the high-moisture Cr-containing sludge stored in the hopper 4 is mixed with the sintered dry dust to have a moisture content of about 10%, and a predetermined amount of iron-containing zinc dust, binder and quick lime is cut out. Then, they are mixed by a mixing device 5 such as a ball mill. Next, the obtained mixture is granulated by a granulating device 6 such as a pan pelletizer to form raw pellets having a particle size of about 20 to 30 mm and a water content of about 10%.

After that, the green pellets are cured in the curing yard 7, so that the strength is exhibited by the hydration reaction of the binder. Then, it is dried by a drying device 8 such as a band dryer to obtain pellets for steelmaking. At this time, the water content is 1
Dry pellets of about 0% are dried to a reduction drying area of 4% or less to obtain steelmaking pellets. In this way, by removing the free moisture in the pellets and drying them to a reduced rate drying area of 4% or less, it is possible to eliminate the rapid evaporation of moisture when the pellets are put into the converter and to prevent the explosion in the reactor. Can be prevented.

Thereafter, the obtained steelmaking pellets are transported by truck to a ground bunker and conveyed to the furnace hopper 9 of the converter 10. Then, the steelmaking pellets in the hopper are put to use by charging the blast furnace hot metal together with the auxiliary raw material.

The Cr-containing sludge treatment method thus obtained and the steelmaking pellets thus obtained have a particle size of about 10 to 30 mm and a specific gravity larger than that of the molten slag in the furnace ( In-furnace slag specific gravity 2.5-
3.0 has a specific gravity of 3.0 to 3.5),
Also, the water content is sufficiently dried up to a rate-reduced dry area of 4% or less. Therefore, when the pellets are put into the converter, the pellets can enter the molten pig iron without floating in the slag layer due to the large specific gravity. In addition, since free water is removed and the product is dried to a rate-reduced dry area of 4% or less, there is no explosion in the furnace due to rapid water evaporation, and the iron components in the pellets are uniformly dispersed in the slag and hot metal. It is possible to secure a good yield (iron yield is about 90%). Moreover, since there is no explosion in the furnace, Cr does not adhere to the furnace wall and corrode the furnace material, and since Cr is not unevenly distributed in the hot metal and is uniformly dispersed, it is below the Cr standard value (hot metal component regulation value (0.055% or less). In addition, in the pellets that have not been dried to a reduction rate of 4% or less, the iron yield is as low as 40%,
It has been confirmed that the pellet of the present invention can secure an iron yield of 90% or more even if 20 to 40 kg per ton of molten pig iron and molten steel can be charged, while only 5 kg or less per ton of molten steel can be charged. It should be noted that zinc can be circulated as ZnO together with the generated dust, gradually increasing the Zn concentration in the dust, and reused as high-zinc concentrated dust.

[0016]

As is clear from the above description, the method for treating Cr-containing sludge of the present invention is capable of reusing the effective components from the Cr-containing sludge in a short time with a simple facility. , And that can be produced at low cost, and the pellets for steel making obtained by this, even when thrown into the converter does not cause in-furnace explosion, can be uniformly dispersed and have a high iron yield, and Cr
It is possible to enable converter operations below the standard value. Therefore, the present invention greatly contributes to industrial development as a method for treating Cr-containing sludge that eliminates the conventional problems and a steelmaking pellet obtained by the method.

[Brief description of drawings]

FIG. 1 is an overall flow chart of a manufacturing process showing an embodiment of the present invention.

[Explanation of symbols]

1 Source of sintered dry dust 2 Cr-containing sludge supply source 3 Source of iron-containing zinc dust 4 hopper 5 mixing equipment 6 granulator 7 curing yard 8 dryer 10 converter

   ─────────────────────────────────────────────────── ─── Continued front page    (72) Inventor Kenji Hashimoto             5-3 Tokai-cho, Tokai-shi, Aichi Nippon Steel Corporation             Ceremony Company Nagoya Steel Works (72) Inventor, Wataru Sakai             5-3 Tokai-cho, Tokai-shi, Aichi Nippon Steel Corporation             Ceremony Company Nagoya Steel Works (72) Inventor Shu Matsumoto             5-3 Tokai-cho, Tokai-shi, Aichi Nippon Steel Corporation             Ceremony Company Nagoya Steel Works F-term (reference) 4K001 AA10 BA24 CA26

Claims (3)

[Claims] 1. A high-moisture Cr-containing sludge is mixed with sintered dry dust to obtain a mixture having a moisture content of about 10%, and the obtained mixture is mixed with iron-containing zinc dust and a binder, and then granulated. A method for treating Cr-containing sludge, which comprises forming pellets, curing the raw pellets, and then drying the pellets for use as steelmaking pellets. 2. The method for treating Cr-containing sludge according to claim 1, wherein the raw pellets are dried to a rate-decreasing dry area of 4% or less to obtain pellets for steelmaking. 3. A pellet for steelmaking obtained by treating Cr-containing sludge, the specific gravity of which is higher than the specific gravity of molten slag in a furnace, and which is dried to a reduction rate dry region of 4% or less. Steelmaking pellets characterized by being