JP2009161845A - Method for pretreatment of scrap - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a method for pretreatment of low grade scrap by which, when using low grade scrap containing organic matters in the scrap as a main charging raw material for a steelmaking furnace, flame initiation at steelmaking furnace charging can be prevented and the organic matters contained in the scrap can be reused as a resource and treatment can be carried out inexpensively. <P>SOLUTION: This invention relates to a method for pretreating, before charging, the scrap to be charged into a steelmaking furnace and characterized in that the scrap is heated using superheated steam to melt or pyrolyze the organic matter contained in the scrap. It is preferable that the temperature of the superheated steam is 300 to 800°C. A melt or pyrolysis gas, resulting from the melting or pyrolysis of the organic matter, is separated from the scrap. It is preferable that the superheated steam is produced by using steam generated from dust collecting equipment for exhaust gas from a steelmaking furnace and further heating it. <P>COPYRIGHT: (C)2009,JPO&INPIT

Description

  The present invention relates to a pretreatment method before charging a scrap to be charged into a steelmaking furnace, and more particularly to a pretreatment method for low-grade scrap containing organic matter in the scrap.

  As one of the iron sources used as the main raw material in steelmaking furnaces, scrap iron generated in-house or in the city is used. Most of the scrap iron (city scrap) generated in the city contains many impurities such as plastics other than metal like scrap car scraps of automobiles. When scrap metal with many impurities is used to separate impurities and use only the metal content as the main raw material for the steelmaking furnace, it is difficult and expensive to separate the metal and impurities. There were many cases. However, in order to effectively use resources, scrap iron containing a large amount of these impurities is required to be recycled as a main raw material for steelmaking. When using scrap car scraps of automobiles as the main raw material for steelmaking furnace charging, dismantle the automobile and collect the things that are easy to separate from the iron part except for iron, and then, as shown in FIG. 1 (b) , Press and store it in a scrap yard, and load it into a steelmaking furnace as needed.

  Waste scraps of automobiles still have around 5% of impurities such as plastics other than iron, coated vinyl for wiring, and oil, which is called low-grade scrap. If scrap iron containing a large amount of plastic components is charged into a steelmaking furnace, for example, a converter without removing impurities, the plastic component contains a large amount of volatile components. Therefore, it is charged into a high-temperature steelmaking furnace. As soon as the volatile matter evaporates and burns at once, a violent flame is ejected from the inlet. When the flame was intense, problems such as burning of ducts around the steelmaking furnace or deterioration of the environment due to fumes occurred. Therefore, when it is used as a main raw material for steelmaking without removing impurities from low-grade scrap such as scrap car scraps of automobiles, the amount of low-grade scrap charged per time must be limited in terms of safety and environment. Is in the situation.

  In the method of removing impurities other than metal from scrap automobile scraps, the car body from which valuable parts such as engines, missions, batteries, tires, liquids and other hazardous materials or pollutants have been removed is first shredded. After being cut by a machine, various kinds of sorting means (magnetic separation, specific gravity sorting, visual sorting) are used to separate into iron, non-ferrous metal and non-metal. In addition to separation and collection by a time-consuming method, combustibles mainly made of plastics, vinyl chloride, rubber, and fibers are called shredder dust and have to be incinerated.

  Patent Document 1 describes a method for thermally decomposing a scrap car in which the entire body is steamed and burned as it is when scraping ferrous and non-ferrous metals from the body from which valuable parts and hazardous materials have been removed. Steaming is to heat the vehicle body in a state where oxygen is blocked as much as possible to generate a thermal decomposition product. The waste car body with the engine removed is placed in a steaming furnace. In the case of the direct heating method, combustion exhaust gas generated by burning fuel gas is blown into the furnace chamber, and the furnace atmosphere is maintained at a temperature of 500 to 650 ° C. Since the firing is steaming, the generated gas is less than that of a normal heating furnace, but some gas is generated by the combustion and thermal decomposition of plastics, vinyl chloride and rubbers. Since the oxygen concentration in the atmosphere is 10% by volume or less, the metals do not receive so much oxidation. An indirect heating type radiant tube or an electric heating type may be used.

  Patent Document 2 relates to a method of recovering a metal by treating a metal composite waste plastic in which metal and plastic are complicated, such as a scrap car. , A method is described in which a plastic component is gasified and carbonized, a carbonized component containing metal is separated and charged into a melting furnace together with coke, and the coke is used as a heat source and refined with an oxygen-containing gas to produce hot metal. .

  Patent Document 3 relates to an apparatus for recovering valuable materials from a composite waste consisting of a thermoplastic and a metal, and does not relate to a pretreatment method for scraps charged into a steelmaking furnace. In this document, a heating furnace is used to heat a waste of a composite material composed of a thermoplastic and a metal in the absence of oxygen by using a heated inert gas or superheated steam as a heat source, and a cracked gas generated in the carbonization furnace is combusted. An apparatus for recovering molten plastic and non-oxidized metal is described which comprises a combustion furnace. By supplying superheated steam, the thermoplastic metal composite waste is heated in the absence of oxygen using this as a heat source. The thermoplastic is melted and dropped while being partially pyrolyzed and taken out of the system. The organic gas generated by pyrolysis when the thermoplastic is melted is completely burned in the combustion furnace. The molten plastic taken out of the system has increased hardness due to thermal decomposition. In this way, it can be separated into thermoplastic and non-oxidized metal.

Japanese Patent Laid-Open No. 10-47635 Japanese Patent Laid-Open No. 11-80844 JP-A-11-76979

  In the method described in Patent Document 1, when combustion exhaust gas is used as a heat source by direct heating, there is a slight amount even if the oxygen concentration in the atmosphere is low, and organic substances such as plastics contained in the lower scrap are burned. Therefore, these organic substances cannot be reused as a heat source. In addition, in order to raise the scrap to a predetermined temperature, a large amount of combustion exhaust gas is required, and most of the sensible heat of the combustion exhaust gas is discharged without being used for heating the scrap, resulting in poor thermal efficiency. Moreover, it is difficult to transmit heat to every corner of the scrap with the indirect heating radiant tube, and there is a problem that the cost is high with electric heating.

  In the method described in Patent Document 2, it is necessary to immerse scrap in a molten liquid of 280 ° C. or higher, for example, a molten salt bath, and complicated equipment is required to form a high-temperature molten salt bath, and the process is complicated. There is also a need for cleaning to remove the melt from the plastic pulled up from the melt.

  In the method described in Patent Document 3, the thermoplastic contained in the composite material is melted and dropped while partially pyrolyzing and taken out of the system, and the remaining valuable metal is attached to the thermoplastic or oxidized on the surface. It is necessary to collect it in the absence of Therefore, it is necessary to control the temperature so that the plastic does not carbonize and melt and fall, and an electric heater is indispensable for temperature control, which increases both the equipment cost and the maintenance cost. Further, since the process is performed at a low temperature, the process takes a long time. Therefore, it is not suitable for a process in which a large amount of scrap car waste is used as a charging raw material for a steelmaking furnace.

  The present invention, when using a low-grade scrap containing organic matter in the scrap as a main raw material for steelmaking furnace, prevents the generation of flame at the time of steelmaking furnace charging, and makes it possible to reuse the organic matter contained in the scrap as a resource, An object is to provide a method for pre-processing low-grade scrap that can be processed at low cost.

That is, the gist of the present invention is as follows.
(1) A pretreatment method before charging scraps to be charged into a steelmaking furnace,
A scrap pretreatment method, characterized by heating scrap with superheated steam and melting or pyrolyzing organic substances contained in the scrap.
(2) The scrap pretreatment method according to (1) above, wherein the temperature of the superheated steam is equal to or higher than a thermal decomposition temperature of the organic matter.
(3) The scrap pretreatment method according to (2) above, wherein the temperature of the superheated steam is 300 to 800 ° C.
(4) The scrap pretreatment method according to any one of (1) to (3), wherein a melt or pyrolysis gas generated by melting or pyrolyzing the organic substance is separated from the scrap.
(5) Any one of the above (1) to (4), wherein a portion other than the melt or pyrolysis gas generated by melting or pyrolysis of the organic matter is left as a carbide together with scrap. The scrap pre-processing method described in 1.
(6) The scrap prior to any one of (1) to (5) above, wherein the superheated steam is obtained by further heating the steam generated from the steel furnace exhaust gas dust collector. Processing method.
(7) The pre-scraping according to any one of (1) to (6) above, wherein the pyrolysis gas generated by the pyrolysis is burned and used to heat the steam to generate superheated steam. Processing method.
(8) The scrap pre-treatment method according to any one of (1) to (7), wherein the scrap is heated by superheated steam and then pressed.
(9) The scrap pretreatment method according to any one of (1) to (7) above, wherein after the scrap is heated with superheated steam, the scrap is charged into a steelmaking furnace without press forming.
(10) The scrap pretreatment method as described in (9) above, wherein the scrap container used when heating the scrap with superheated steam also serves as a scrap charging container for charging the scrap into the steelmaking furnace.

  In the present invention, among the organic substances contained in the lower scrap, volatile components are separated as pyrolysis gas, so that no flame is generated during charging into the steelmaking furnace. The portion of the organic matter adhering to the scrap as carbide is effectively used as a heat source in the steelmaking furnace. The part separated as pyrolysis gas or melt from the organic substance can be effectively used as a heat source.

  Since superheated steam that does not contain oxygen is used for heating the scrap, the organic matter in the scrap does not burn and the scrap surface does not oxidize and can be used effectively as a resource. Since the superheated steam has a larger specific heat than combustion exhaust gas, the temperature of the scrap can be raised with a small amount of gas, and there is little sensible heat loss discarded without being used for heating the scrap.

  When the exhaust gas dust collector of a steelmaking furnace has a steam recovery facility, the steam recovered in the steelmaking furnace can be used as a raw material for the superheated steam of the present invention, so that it is possible to obtain superheated steam at a low cost. it can.

  The present invention is a pretreatment method before charging a scrap to be charged into a steelmaking furnace, characterized in that the scrap is heated by superheated steam, and an organic substance contained in the scrap is melted or pyrolyzed. Superheated steam means steam that has a high temperature above the saturation temperature at that pressure (in this case atmospheric pressure). By heating the scrap with superheated steam and melting or pyrolyzing the organic matter contained in the scrap, the volatile matter in the organic matter can be separated from the scrap, so the scrap after pretreatment is charged into the steelmaking furnace. At that time, there is no flame from the entrance.

  As shown in FIG. 1 (a), the processing flow of the method of the present invention is as follows. The scrap is heated by superheated steam, then pressed or not pressed, stored in a scrap yard, or not stored. Charged into a steelmaking furnace.

  According to the method described in Patent Document 1, in the case of the direct heating method, the combustion exhaust gas is used as the heating gas, and even though the oxygen concentration is low, it contains some oxygen, so the organic matter contained in the scrap Part of it burns. On the other hand, in the present invention, since the superheated steam not containing oxygen is used, the organic matter is not burned during the pretreatment, and the organic matter can be effectively used as a heat source. Further, since the specific heat of the superheated steam has a value twice that of the combustion exhaust gas, the scrap can be heated with a smaller amount of gas than the combustion exhaust gas. Concerning heat transfer, the convective heat transfer of superheated steam is 10 times or more that of air, and also has a combined heat transfer effect that transfers heat by radiant heat transfer. Further, regarding the sensible heat remaining in the gas discharged after the scrap heating, if it is superheated steam, the sensible heat loss can be reduced as compared with the combustion exhaust gas.

  In the present invention, the temperature of the superheated steam is preferably a temperature equal to or higher than the thermal decomposition temperature of the organic matter. Thereby, the organic substance contained in scrap can be thermally decomposed by heating with superheated steam, and can be separated into pyrolysis gas and residual carbide. The thermal decomposition temperature of the organic substance is 200 to 500 ° C.

  The temperature of the superheated steam is preferably 300 to 800 ° C. If it is 300 degreeC or more, a plastic can be thermally decomposed. On the other hand, if the temperature of the superheated steam exceeds 800 ° C., the equipment cost such as heat resistance measures of the steam heating equipment becomes too large, which is not preferable.

  It is preferable that the scrap or pyrolysis gas generated by melting or pyrolyzing the organic substance is separated from the scrap by heating the scrap with superheated steam. As shown in Fig. 2, the scrap is placed in the scrap heating device, the superheated steam generated by the superheated steam generator is introduced into the scrap heating device, the generated pyrolysis gas is separated, and the molten organic matter is separated. Then, the processed scrap is charged into a steelmaking furnace. By separating the pyrolysis gas from the scrap, no flame is ejected from the charging inlet when the scrap after the pretreatment is charged into the steelmaking furnace. Further, the melt and pyrolysis gas separated from the scrap can be recovered and used as a heat source.

  In the present invention, among the organic substances contained in the scrap, it is preferable that the parts other than the melted or pyrolyzed gas generated by melting or pyrolysis remain as a carbide together with the scrap. The carbide remaining with the scrap is charged into the steel making furnace together with the scrap, and can be effectively used as a heat source in the steel making process. Therefore, in the present invention, when the scrap is heated with superheated steam, it is necessary to separate the volatile matter in the organic matter as a pyrolysis gas, but it is preferable to leave the volatile matter as a carbide in the scrap as much as possible. In order not to melt the organic substance and separate it from the scrap as a melt, but to leave it as a carbide in the scrap, it is preferable that the heating temperature of the scrap with superheated steam is 400 ° C. or higher.

  About the superheated steam used by this invention, water can be heated to saturated steam, and also saturated steam can be heated and temperature can be raised, and it can be set as superheated steam. As a superheated steam generator, in addition to a burner or an electric heater method, a method by induction heating can be selected.

  On the other hand, in a steelmaking furnace exhaust gas dust collector such as a converter OG exhaust gas dust collector, steam is generated using heat recovered by an exhaust gas duct. Therefore, if the superheated steam used in the present invention can be obtained by using the steam generated from the steel furnace exhaust gas dust collector, it is not necessary to newly consume energy and generate superheated steam.

  A preferred processing flow of the present invention is shown in FIG.

  In the example shown in FIG. 3, steam generated in a steam generator, steam generated in a steel furnace exhaust gas dust collector (OG boiler), and waste steam after scrap heating are used as raw material for superheated steam. . These raw material vapors are used as superheated steam in a superheated steam generator. The superheated steam generated by the superheated steam generator is used to heat the scrap disposed in the scrap heater.

  Pyrolysis gas generated by pyrolyzing organic substances by heating the scrap is contained in the steam and recovered. The steam immediately after heating the scrap has not yet dropped to the saturation temperature, and is in the state of superheated steam. Steam and pyrolysis gas can be separated by the pyrolysis gas treatment device, and the separated steam can be recycled as a raw material of the superheated steam generator. The separated pyrolysis gas is further subjected to hydrogen chloride treatment in a pyrolysis gas treatment apparatus. The pyrolysis gas that has been processed can be used as a heat source for a superheated steam generator, stored in a gas holder and used as various heat sources, or directly supplied to a power generator and used as a fuel for power generation.

  As the side wall of the scrap heating device used when heating the scrap with superheated steam has a double wall structure, the steam that has finished scrap heating is introduced between the double walls, and used for preheating the scrap heating device. Also good. As for the steam whose temperature has further decreased due to the preheating of the container and has reached the saturation temperature, only the pyrolysis gas can be recovered by condensing the steam and separating it as water. This pyrolysis gas can be used as a heat source. In the present invention, it is preferable that the pyrolysis gas generated by pyrolysis is burned and used for heating the steam to generate superheated steam. Thereby, superheated steam can be produced | generated cheaply.

  About the scrap used for the heating using superheated steam, it is preferable to shred and give it in advance. By subdividing, heating with superheated steam is uniformly performed on the entire scrap, so that iron and other components can be easily separated, organic materials such as plastics are easily decomposed, and the heating time can be shortened.

  It is preferable to perform press molding after heating the scrap with superheated steam and melting or thermally decomposing the organic matter contained in the scrap, since the handling of the scrap becomes easy.

  On the other hand, after the scrap is heated with superheated steam and the organic matter contained in the scrap is melted or pyrolyzed, press molding may not be performed. In this case, it is preferable that the scrap container used when heating the scrap with superheated steam also serves as a scrap charging container for charging the scrap into the steelmaking furnace.

  Using the apparatus shown in FIG. 4, pretreatment was performed before charging the scrap to be charged into the steelmaking furnace 11. As the raw material for the superheated steam, steam generated in a steelmaking furnace exhaust gas dust collector (not shown) is used and supplied with steam from a steam pipe. This raw material steam is used as superheated steam in the superheated steam generator 1. The scrap 2 disposed in the scrap heating device 3 is heated using the superheated steam generated by the superheated steam generator 1. A system for blowing the atmosphere control gas 13 is also prepared.

  The scrap 2 is prepared in the charging hopper 7, supplied to the transporting conveyor 9 by operating the charging gate 8 disposed at the bottom of the charging hopper 7, transferred by the transporting conveyor 9, and supplied to the scrap heating device 3. In the scrap heating device 3, organic substances contained in the scrap are thermally decomposed by heating with superheated steam, and then transferred from the scrap heating device 2 to the scrap chute 10 by the transport conveyor 9. The scrap 2 that has been processed is charged into the steelmaking furnace 11 from the scrap chute 10. A converter was used as the steel making furnace 11.

  The pyrolysis gas generated by pyrolyzing the organic matter by heating the scrap 2 is contained in the steam and recovered by the waste steam processing apparatus 5. The waste steam treatment device 5 separates the steam and the pyrolysis gas. The dissolved organic matter is collected in a waste liquid tray 6 in the scrap heating device 3 and separated into organic matter and water by the waste liquid treatment (separation) device 4, and the organic matter is collected. Water is discharged into the side groove 12.

  Using the above apparatus, automobile scraps (approximately 450 kg) pressed to 500 mm square were heated with steam at 800 ° C. at 150 kg / hr for 30 minutes, and reached 400 ° C. at the center of the scraps. Three scraps treated in this way were charged into the converter, but the flame from the furnace opening was not a problem.

It is a figure which shows the flow until it inserts recycling scrap iron into a smelting furnace, (a) shows the example of this invention, (b) shows a prior art example. It is a figure which shows the flow until it inserts the recycled scrap iron of this invention into a smelting furnace. It is a figure which shows the flow until it inserts the recycled scrap iron of this invention into a smelting furnace. It is one Example which shows the pre-processing method of the scrap of this invention.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Superheated steam generator 2 Scrap 3 Scrap heating apparatus 4 Waste liquid processing (separation) apparatus 5 Waste steam processing apparatus 6 Waste liquid receptacle 7 Input hopper 8 Input gate 9 Transport conveyor 10 Scrap chute 11 Steelmaking furnace 12 Side groove 13 Gas for atmosphere control

Claims (10)

A pre-treatment method for charging scrap to be charged into a steelmaking furnace,
A scrap pretreatment method, characterized by heating scrap with superheated steam and melting or pyrolyzing organic substances contained in the scrap.   The scrap pre-treatment method according to claim 1, wherein the temperature of the superheated steam is equal to or higher than a thermal decomposition temperature of the organic matter.   The scrap pretreatment method according to claim 2, wherein the temperature of the superheated steam is 300 to 800 ° C.   The scrap pretreatment method according to any one of claims 1 to 3, wherein a melt or pyrolysis gas generated by melting or pyrolyzing the organic substance is separated from the scrap.   The scrap in advance according to any one of claims 1 to 4, wherein a part other than the melt or pyrolysis gas generated by melting or pyrolysis of the organic matter is left as a carbide together with the scrap. Processing method.   The scrap pretreatment method according to any one of claims 1 to 5, wherein steam generated from a steel furnace exhaust gas dust collector is used to further heat the steam to obtain the superheated steam.   The scrap pretreatment method according to any one of claims 1 to 6, wherein the pyrolysis gas generated by the pyrolysis is burned and used to heat the steam to generate superheated steam.   The scrap pretreatment method according to any one of claims 1 to 7, wherein the scrap is press-molded after being heated by superheated steam.   The scrap pretreatment method according to any one of claims 1 to 7, wherein after the scrap is heated by superheated steam, the scrap is charged into a steelmaking furnace without press forming.   The scrap pretreatment method according to claim 9, wherein the scrap container used when heating the scrap with superheated steam also serves as a scrap charging container for charging the scrap into the steelmaking furnace.

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