Title of Invention: METHOD AND DEVICE FOR REFINING

METAL MATERIAL

Technical Field Technical Field

The invention relates to a method for refining metal material produced in processing waste tires under which the metal material is heated for distilling off non-metallic constituents. Further, the invention relates to a device for carrying out this method. The metal material represents a significant component of the material produced in the process for recycling of steel cord from waste tires. Background Art Background Art

The continuing growth of the car industry is accompanied by a problem of disposal of accumulated waste tires from discarded cars. While the reclamation of waste rubber appears to be resolved, the waste steel cord as a reinforcing component of the tire, due to the presence of rubber and textile fiber residuals, has resulted into a worldwide problem since such a type of waste is not suitable for recycling and consequently for use in manufacturing new tires. The problem consists in removing rubber and/or textile residuals as a source of carbon, which is known as an element adversary affecting the quality of the reclaimed metal, specifically its elasticity. The final product is too brittle and therefore unsuitable for further use. At the present time, the following methods for processing waste rubbers to obtain their individual constituents such as rubber, steel and textile cord are used. According to one method, the tire is crushed into small pieces to obtain rubber in the form of flakes containing textile material, metal reinforcing material in the form of resilient, mostly steel cord, which is subsequently isolated in the following stage. To eliminate difficulties accompanying the crushing of resilient rubber, the tires are first steeply cooled down, for example by liquid nitrogen and in such a fragile frozen condition the tire rubber may be easily crushed. Various alternatives of this method are described in RU2299804, RU2299807, DE10357968, DE102006028563 and WO2007091876. According to another method, as disclosed in LT5422 and EP0816035, ozone is used to cause partial rubber destruction and thus to enable its ease fragmentation. The combination of both methods, i.e. application of ozone and the cryogenic process teaches LT5521. The separation of the steel cord from the rubber by using a magnetic separator is described in DE10357968 and WO0069610. In the process of recycling the steel cord, conventional heating is applied at a temperature of 100 up 600 ⁰ C under which the waste material is subjected to partial pyrolysis to produce volatile substances, which may be condensed or directly combusted as shown in JP2004298829, RU2322347, RU2004128978 and WO2006038899. The second product is carbon black which can be again used for tire production. In general, the above described methods of steel cord recycling encounter certain disadvantages. First, said methods require high energy consumption in connection with freezing or application of ozone and further, as stated above, the metal material obtained by their application fails to show properties which would enable it to be used for recycling. As a result, the problem of accumulation of the waste steel cord has not been successfully overcome and consequently, at the present time, the Europe Union may register about 115 000 tons of accumulated waste steel cord in landfill. Only recently, efforts have been made to replace the standard heating methods by microwave heating based on the knowledge that that rubber containing carbon efficiently absorbs microwaves and this phenomenon may be used for processing the waste rubber. The application of this method, for example in the production of tires or other rubber materials in the process of vulcanization, is described in EP0661149, EP0640470 and DE4420198 and in connection with appropriate microwave devices is disclosed in FR2562833, UK1278062, JP56078963, CA1209309 and CA1205964. The microwave heating used for production of active carbon by pyrolysis of waste tires is further disclosed in WO8808871, WO8904355, WO9105818, WO0103473, CN1229055 and UK1513656. Methods and devices for conducting pyrolysis by microwave heating of uncrushed or crushed tires are disclosed in JP2006349224, WO2005073344 and US2007102279. Nevertheless, the refining of steel wire material separated mechanically from tire fragments, which contains undesired admixtures such as rubber and textile cord and which is therefore not suitable for further processing by standard metal processing methods has not been disclosed and resolved satisfactorily. Disclosure of Invention Technical Problem

The primary object of this invention is to avoid deficiencies of the prior art and to provide an inexpensive and effective method for recovering waste steel cord from recycling tires. Another object of this invention is to produce a metal raw material on the basis of waste steel cord, which is substantially free from detrimental admixtures and thus suitable for further processing for example by crushing, pressing or melting. Technical Solution

The object of the present invention may be achieved and the described deficiencies overcome by a method for refining metal material separated from crushed waste tires by heating and distilling off a portion of non-metallic constituents wherein the fragments of metal material comprising 82 - 98 % by mass of steel cord are exposed in a closed space to microwave radiation with a frequency of 890 MHz to 2450 MHz to reach a temperature of 100 to 700 ⁰ C of the metal material at which the volatile fraction of the non-metal constituents is distilled off and separated by cooling and condensation and the solid constituents comprising mixture of steel cord and carbon black are cooled and the steel cord isolated. Advantageously, the refining process using the microwave radiation may be performed under inert atmosphere. In order to improve the ductility of the final product,- a pure steel wire, and thus to make the processing of the steel cord for example by pressing easier the refining process is conducted up to the temperature of the steel cord of 600 to 700 ⁰ C. The device for performing of the process according to the invention may comprise a batch reactor, a continuous reactor equipped with an endless conveyor or rotary kiln. In an advantageous embodiment the continuous reactor comprises a microwave heating chamber provided with microwave generators and including an endless conveyor for transport of a treated material throughout the heating chamber, the heating chamber being associated at its entrance with a preheating zone supplied by the treated material and by a cooling zone at its exit thereof, the cooling zone having an upper outlet for gases and distilled off components connected to a condenser and a lower outlet for solid components connected to a separator. Advantageous Effects

The process for refining metal material produced in processing waste tires for recycling purposes according to the invention is based on a selective microwave heating of impurities present in the waste steel wire such as rubber and textile cord. Under the effect of microwaves, first of all the residual rubber resulting from separation of individual waste tire constituents is heated while the steel wire is highly resistant to the effect of microwaves and remains relatively cold or only slightly heated. In this way, said non-metallic impurities adhered to the waste steel cord may be removed and suitable metal raw material with a purity exceeding 99 % is so produced without the necessity to employ other energy consumption procedures for the tire fragmentation. After removing the rubber or textile cord residuals, a highly pure metal free from carbon is obtained. The raw metal material produced under this method is due to its purity suitable for further processing such as crushing, pressing or melting. The removed impurities in the form of gaseous and volatile inflammable substances are separated by condensation as by-products and if appropriate they may be used for conventional heating or pre-heating processes. Accordingly, the low energy consumption characterizing this process may be further reduced. The steel cord recycling process based on the application of microwave radiation may be performed as a continuous process on a continuous device provided with the means for avoiding leakage of the microwaves and for safe withdrawing gaseous and volatile substances. The recycling process may be advantageously performed under an inert atmosphere. Description of Drawings

The attached drawing shows a scheme of a continuous device for performing the method. Mode for Invention

Example 1

1 kg of waste steel cord in the form of steel wire fragments of length from several centimeters to tenths centimeters and obtained by crushing waste tires and separating the metal material containing 5.6 % rubber and 1.4 % textile cord was put into a microwave batch reactor. Under the nitrogen inert atmosphere, the material was exposed to a microwave radiation with a frequency of 2450 MHz so that the residual rubber was selectively heated up to 600 ⁰ C and volatile products were distilled off. The volume temperature of the batch did not exceed 300 ⁰ C. After completion of the distillation process by which the rubber and textile were pyrolysed and products were distilled off the remaining solid constituent containing steel cord and carbon black was cooled down and the steel cord was easily separated from the carbon black. The resulting product - steel cord had the following composition: Fe - 98.580 %; Ni - 0.180 %; Cr - 0.090 %; Cu - 0.050 %; Co - 0.020 %; P - 0.012 %; Si - 0.240 %. The produced by-product, i.e. gaseous and liquid substances were condensed by cooling and used as a fuel oil for conventional heating.

Example 2

Steel cord raw material comprising 2 - 15 % rubber was supplied into a continuous microwave reactor at a rate of 20 kg per hour. Inside the microwave radiation zone of the reactor having an output of 8 kW and frequency 915 MHz the rubber was removed in the form of gaseous and liquid substances that were separated by condensation in the form of fuel oil. The resulting product leaving the reactor and separated from carbon black was a steel cord suitable for further processing by pressing, crushing or melting.

Example 3

1 kg steel cord raw material containing up to 15 % rubber and textile cord was placed into a microwave batch reactor. Under inert atmosphere, the material was exposed to a microwave radiation for one hour with a frequency 896 MHz thus heated up to 700 oC. The ruber and textile cord were removed from wire raw material by selective microwave heating as volatile substances, oil and gas. Main products steel cord and black carbon are obtained in high quality and were convenient for further recycle processing.

Example 4

One preferred embodiments of a device for performing the method according to the invention is shown in the attached drawing. The drawing illustrates a continuous microwave reactor comprising a microwave heating chamber 4 provided with four magnetrons 5 - microwave generators. The heating chamber 4 includes an endless belt conveyor (not shown in the drawing) for transport of the material treated throughout the heating chamber 4. At the entrance end, the heating chamber 4 is associated with a preheating zone 3 fitted with a hopper 1 for material supply. Further, the preheating chamber comprises a conventional heater and a dosing device for continuous supplying the endless belt conveyor with the preheated material. At the exit end, the heating chamber 4 is followed by a cooling zone 6. The cooling zone 6 has an upper outlet for distilled off gaseous and liquid components connected to a condenser 7 and a lower outlet for solid components, steel cord and carbon black, connected to a separator 10. Outlets of the condenser 7 are connected to a condensed liquid product tank 9 and to a residual volatile product retainer 8. Outlets of the separator 10 are connected to a steel cord recipient 11 and carbon recipient 12. For higher treatment temperatures, at which the metal was heated up to 600 to 700 ⁰ C, the use of magnetrons with a frequency of 2450 MHz were preferred. By exposing the steel cord to this temperature for certain time a metal tempering process improving the ductility of the final pure metal product was accomplished. The higher ductility enabled the final product to be easily processed, for example by pressing. Industrial Applicability

The invention may be used in recycling waste tire containing steel wire for obtaining a product in the form of refined steel cord free of undesired impurities and suitable for further processing such as crushing, pressing and more specifically, melting.