JPH05125459A - Method for dezincificating scrap galvanized steel sheet - Google Patents

Abstract

PURPOSE:To evaporate and liberate deposited Zn and to use scrap galvanized steel sheet as the iron source by heating the scrap in nonoxidizing nitrogen gas. CONSTITUTION:An inert gas such as N2 is passed through a heat exchanger 10 from a pipeline 9, heated and supplied into an externally heated rotary kiln 1 provided with a burner 3 as the external heating means. When O2 gas as the inevitable impurity is contained in the N2 gas, a stoichiometrical excess of H2 gas over the O2 gas is added to the N2 gas and supplied into the kiln 1. The scrap galvanized steel sheet in a closed vessel 8 is supplied into the kiln 1 by a feeder 7, the scrap in the kiln 1 is heated to 800-1200 deg.C by the external heating means 2, hence the Zn depositing on the scrap is evaporated, liberated, cooled by a waste gas treating device 13, solidified and recovered, and the scrap freed of Zn is collected and recovered in a closed vessel 12 as an iron source.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for dezincing galvanized steel scrap, which enables reuse of galvanized steel scrap whose use is restricted as a cold iron raw material or a cast iron raw material. It is something to do.

[0002]

2. Description of the Related Art As a method for dezincing galvanized steel scrap while heating, for example, JP-A-51-126911, JP-A-57-85916, or JP-A-Hei-2.
There is one disclosed in Japanese Patent Publication No. 298225 and the like.

In Japanese Patent Laid-Open No. 51-126911, steel scrap is heated to 1090 to 1250 ° C. in an atmosphere having a CO ₂ / CO molar ratio of 0.004 or less to remove impurities such as copper and tin. A method is disclosed in which zinc is vaporized by dropping the liquid and then separated and removed. This method uses a reducing gas having an extremely high reducing ability, specifically, a reducing gas having a high reducing ability obtained by burning a solid reducing agent such as coke with air. Since a large amount of exhaust gas used for this dezincification process contains evaporated zinc, it is difficult to reuse the reducing component of exhaust gas or recover sensible heat unless zinc is separated and removed from exhaust gas. ..
Moreover, since the separation of zinc targets a large amount of exhaust gas, a large separation / recovery device is required.

Japanese Patent Application Laid-Open No. 57-85916 discloses a method of heating galvanized steel scrap to a temperature near the boiling point of zinc to evaporate and separate zinc. Specifically, this is a technology that uses a rotary kiln to control the amount of excess air in a gas burner that generates heat to suppress the oxidation of steel plate scraps. However, even if the amount of excess air is regulated, the generation of an oxidizing atmosphere is unavoidable, so that oxidation of plated zinc is caused and the dezincification rate is unavoidably lowered. Also, since a large amount of exhaust gas used for this dezincification process contains evaporated zinc, it is necessary to separate and remove zinc from the exhaust gas before reusing the reducing components of the exhaust gas or recovering sensible heat. Is difficult. Moreover, since the separation of zinc targets a large amount of exhaust gas, a large separation / recovery device is required.

Japanese Unexamined Patent Publication (Kokai) No. 2-298225 discloses a method in which zinc-attached scrap is heated to 500 ° C. or higher and is contacted with an oxidizing gas containing oxygen of 1 vol% or more to evaporate and separate. However, in an oxidizing gas atmosphere, oxidation of the plated zinc is caused, so that dezincification of oxidized zinc cannot be expected so much, which results in higher temperature and longer heating time. Also, since a large amount of exhaust gas used for this dezincification process contains evaporated zinc, it is necessary to separate and remove zinc from the exhaust gas before reusing the reducing components of the exhaust gas or recovering sensible heat. Is difficult.
Moreover, since the separation of zinc targets a large amount of exhaust gas, a large separation / recovery device is required.

[0006]

In all of the conventional methods for heating zinc galvanized steel scraps for dezincing treatment, the separated zinc is present in the gas used in the treatment system in the form of zinc or zinc oxide. Therefore, there is a problem that the separation / recovery device for separating inclusions from the large amount of gas has a large capacity, and the gas cannot be reused or sensible heat cannot be collected unless the inclusions are separated from the gas. .. The present invention solves this problem.

[0007]

The gist of the present invention is as follows.

In a dezincing furnace equipped with heating means, galvanized steel scrap is heated to 800 to 1200 ° C. in an inert gas atmosphere partitioned from the heating means to evaporate galvanized zinc on the scrap steel surface. -A method for dezincification of galvanized steel scrap, which is characterized by scattering.

A dezincification method for scraps of galvanized steel sheet, wherein the dezincification furnace equipped with the heating means is an externally heated rotary kiln.

Nitrogen gas is used as the above-mentioned inert gas atmosphere, or a dezincification method for scraps of galvanized steel sheet.

A dezincification method for scraps of galvanized steel sheet, characterized in that an excess amount of hydrogen gas is added to the oxygen inevitably contained in the nitrogen gas in an amount equal to or greater than the oxygen content.

[0012]

The present invention heats galvanized steel scrap to 800 to 1200 ° C. in a dezincing furnace equipped with heating means under an inert gas atmosphere partitioned from the heating means, and Since the plated zinc is vaporized and dissipated without being oxidized, the required amount of the inert atmosphere gas for achieving the evaporation and separation of zinc is smaller than that of the conventional undivided atmosphere gas. It is only necessary to separate and recover zinc from the intervening inert gas, so that the capacity of the exhaust gas treatment device can be reduced. In addition, the inert gas after separating and recovering zinc can be used again as a dezincing atmosphere gas, and the oxidation of steel plate scraps during the dezincing treatment is suppressed.

Further, according to the present invention, by using the external heating type rotary kiln as the dezincing furnace equipped with the above heating means, the heating operation of the galvanized steel plate waste and the heating operation of the inert atmosphere gas and the distillation operation of zinc can be performed. Since it is carried out in a partitioned atmosphere, each atmosphere gas can be reused.

In the present invention, when nitrogen gas is used as the inert gas atmosphere, the handling operation is easy.

Further, in the present invention, when hydrogen gas in excess of an equivalent amount to oxygen inevitably present in the nitrogen gas is added, the treatment in a substantially inert gas atmosphere is achieved.

[0016]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS The present invention will be specifically described below based on the embodiments shown in the drawings.

FIG. 1 is an explanatory view showing the outline of an external heat type rotary kiln type dezincing apparatus for scrapping galvanized steel plates for carrying out the method of the present invention. The heating means 2 is arranged on the outer circumference of the body of the rotary kiln body 1. The temperature of the inert gas atmosphere supplied to the inside of the rotary kiln body 1 by means described later is 800 to 1200 ° C. by the heating means 2.
The temperature is raised to. When the temperature of the inert gas atmosphere is lower than 800 ° C., the evaporation rate of zinc becomes slow and the processing time is extended. Further, if it exceeds 1200 ° C, it is not economical from the viewpoint of equipment load.

In this example, as the heating means 2, a plurality of burners 3 are provided on the outer peripheral portion. Pipe lines 4 for supplying fuel and supporting gas to these burners 3, respectively.
The fuel or supporting gas passing through the pipe 4 can replace the heat of the exhaust gas that has heated the rotary kiln body 1. This heat exchange is carried out by the heat exchanger 6 provided in the middle of the exhaust gas pipe 5. As another aspect of the heating means 2, an electric heating device may be arranged on the outer periphery of the body of the rotary kiln body 1.

On the upstream side of the rotary kiln body 1, a galvanized steel plate scrap supply device 7 as a material to be treated is arranged.
For the galvanized steel scrap, for example, shredder scraps cut into a predetermined size range are used. It is preferable that the galvanized steel plate scrap supply device 7 is provided with a mechanism for blocking the invasion of outside air. The regenerated inert gas used for the treatment is used as a purge gas to purge the inside of the airtight container 8 and supply it to the supply device 7.

Further, on the upstream side of the rotary kiln body 1, an inert gas supply pipe line 9 for keeping the material to be treated in an inert atmosphere is provided. In the present invention, nitrogen gas, argon gas or the like can be used as the inert gas, but nitrogen gas is economically preferable. When nitrogen gas is used, the inclusion of unavoidable components is unavoidable depending on the conditions under which the gas is generated,
When an oxygen component is contained as an inclusion and becomes a disturbance of the dezincification treatment, it is possible to prevent the disturbance by adding hydrogen gas in excess of the oxygen equivalent amount.

A heat exchanger 10 for replacing the heat of the exhaust gas used for heating the rotary kiln body 1 is provided in the middle of the inert gas supply pipe 9. As another aspect, an inert gas preheated to, for example, 500 to 800 ° C. is supplied by supplying an inert gas to be supplied to the sealable container 12 described later to the inert gas supply pipe line 9 or a combination thereof. Can be supplied as an atmosphere gas.

The atmosphere of this inert gas may be controlled under the condition that the partial pressure of zinc is such that the evaporation of zinc in the main body 1 of the rotary kiln is positively achieved. This can be achieved by supplying the gas from the upstream side and discharging it as exhaust gas on the downstream side of the rotary kiln main body 1. The supply and discharge amount are determined by the conditions such as the capacity of the rotary kiln main body 1, the processing temperature and the processing time.

On the downstream side of the rotary kiln body 1, there is provided a dezincing steel plate waste discharging device 11. At the time of discharging the steel plate scraps to the outside of the system, it is preferable to prevent the atmospheric gas from flowing out, and for example, a sealable container 12 provided with a pressure equalizing means is provided. The sealable container 12 stores steel plate scraps which have been heated to 800 to 1200 ° C. and are hardly oxidized during dezincification treatment. When this steel plate waste is not used immediately for melting or the like, it is desirable to cool it in the atmosphere to a temperature at which oxidation does not proceed actively. The steel plate scraps in the sealable container 12 can be cooled by, for example, supplying an inert gas used for the dezincing treatment atmosphere from the lower part of the sealable container 12, performing heat replacement, and then discharging from the upper part of the sealable container 12. .. On the other hand, the heated inert gas is used as a dezincing treatment atmosphere gas.

On the downstream side of the rotary kiln body 1, there is provided an exhaust gas treatment device 13 for the atmospheric gas used for dezincification treatment. The dezincification method according to the present invention, that is, the method of heating galvanized steel scraps and the inert atmosphere gas that contributes to the evaporation of zinc by a separately prepared heating means, directly galvanizes with heated gas as in the prior art. Since the amount of the inert atmosphere gas used is 1/10 to 1/3 as compared with the method of heating the steel plate scraps and evaporating zinc, the exhaust gas treatment device 13 can be downsized. The exhaust gas treatment device 13 is for separating and collecting the exhaust gas with a bag filter after cooling the exhaust gas to, for example, 300 ° C. or lower. The exhaust gas from which zinc has been separated and removed, that is, the recycled inert gas, can be reused.

The present invention has been described above with respect to the case of the external heating type rotary kiln. However, in addition to the continuous dezincing method, for example, galvanized steel plate scraps are stored in a specific batch container,
A mode in which the container is closed, an inert gas is supplied while being discharged, the inside of the container is maintained in an inert atmosphere, and the container is externally heated to 800 to 1200 ° C. for dezincing treatment can also be adopted. In this case, the galvanized steel scraps may have irregular shapes as long as they can be accommodated in the container.

As described above, according to the present invention, as shown in FIG.
Dezincification treatment is achieved at a high rate of 5% or more.

[0027]

INDUSTRIAL APPLICABILITY According to the present invention, since the dezincification treatment of galvanized steel scrap is carried out in an inert atmosphere gas which is divided from the heating means, the generated gas or the used gas can be treated independently, and heat exchange, Recyclable and economically superior.

[Brief description of drawings]

FIG. 1 is an explanatory view showing an outline of an external heat type rotary kiln type dezincing apparatus for scraps of galvanized steel sheet for carrying out the method of the present invention.

FIG. 2 is a diagram showing a dezincification rate in the present invention.

[Explanation of symbols]

 1 Rotary Kiln Main Body 2 Heating Means 3 Burner 4 Pipeline 5 Exhaust Gas Pipeline 6 Heat Exchanger 7 Galvanized Steel Plate Waste Supply Device 8 Sealable Container 9 Inert Gas Supply Pipeline 10 Heat Exchanger 11 Steel Plate Waste Discharge Device 12 Sealable Container 13 Exhaust gas treatment equipment

Claims (4)

[Claims] 1. A dezincification furnace equipped with heating means,
Dezincification of galvanized steel scraps, characterized in that galvanized steel scraps are heated to 800 to 1200 ° C. in an inert gas atmosphere partitioned from heating means to evaporate and dissipate the galvanized zinc on the surface of the scraps. Method. 2. The dezincification furnace equipped with the heating means is an externally heated rotary kiln.
A method for dezincing scrap of galvanized steel sheet as described. 3. The dezincification method for scraps of galvanized steel sheet according to claim 1, wherein nitrogen gas is used as the inert gas atmosphere. 4. The method for dezincing galvanized steel scrap according to claim 3, wherein an excess amount of hydrogen gas relative to oxygen inevitably present in the nitrogen gas is added.