WO2005073344A1

WO2005073344A1 - The waste rubber or waste tire resolution method and system by avail of microwave

Info

Publication number: WO2005073344A1
Application number: PCT/KR2004/000207
Authority: WO
Inventors: Tae Jin Kim
Original assignee: Tae Jin Kim
Priority date: 2004-01-31
Filing date: 2004-02-04
Publication date: 2005-08-11
Also published as: KR100469161B1; KR20040015782A

Abstract

Disclosed is a method and a device for resolving waste rubber or waste tires using microwaves to preserve the environment and to economically and conveniently recover resources, such as oil, carbon black, or steel cord, which are mainly imported, thereby effectively regenerating them. Recently, most of the increasingly generated waste tires have been fed into a cement kiln and used as a heat source therein. However, this use is gradually declining because of environmental pollution. Conventionally, based on the judgment that a regeneration method of pyrolyzing the waste rubber or the waste tires to recover them as energy and resources is most effective, many pyrolysis devices have been developed. However, the method of regenerating the waste tires through simple pyrolysis is disadvantageous in that since the resolution time is long and since heat efficiency is a very low 10 %, the treatment cost is high, thus it is economically inefficient. The device for resolving the waste rubber or the waste tires using the microwaves is characterized in that the waste rubber or the waste tires is selectively heated, a resolution rate is rapid, the device has a simple structure, operation is simple, and it is possible to achieve uniform heating, thus recovering superior oil, carbon black, and steel cord, resulting in preservation of the environment, contribution to the state economy, and realization of profit.

Description

DESCRIPTION

THE WASTE RUBBER OR WASTE TIRE RESOLUTION METHOD AND SYSTEM BY AVAIL OF MICROWAVE

Technical Field The present invention relates to a method and a device for resolving waste rubber or waste tires using microwaves to recover oil, carbon black, and steel cord. The rubber is a general term for natural rubber which is produced from vegetation and synthetic rubber ( cis- polyisoprene; IR, butadiene rubber; BR, styrene-butadiene rubber; SBR) which is produced in a petrochemical plant, and. frequently used as material that is essential in everyday life or in every industry.

Background Art: With respect to tires which are a representative rubber product, production of tires and generation of waste tires increase continuously in accordance with an increase in the number of automobiles. The number of waste tires generated in the year 2002 is estimated to be about 24 millions as described in Table 1 (the number of generated and reused waste tires each year / unit: thousands) .

TABLE 1 Waste tires generated and reused each year (unit: thousands)

(Data: Korea Tires Manufacturers Association) Methods of treating the waste tires may be roughly classified into three categories : an original form utilization method employed in engineering works, a process utilization method of regenerating the rubber and the tire, and a heat utilization method of using them as a heat source in a cement kiln or of incinerating them through pyrolytic incineration. Conventionally, the original form utilization method and the process utilization method were used, but, recently, the heat utilization method, which employs the high energy (8,000 kcal/kg) of the waste rubber/waste tires, is frequently used. Perfect chemical resolution must be assured to prevent environmental pollution in the course of regenerating waste rubber/waste tires through the original form utilization method and the process utilization method, thus the heat utilization method is considered as the best method. The method of using the waste tires as the heat: source for a cement kiln occupies 84 % of the total treatment amount, but the pyrolytic incineration method, occupies merely 3 %. However, dust, generated when the waste tires is incinerated in the cement kiln, and harmful dioxins, aromatic hydrocarbons, chlorine compounds or the like, generated during an uncontrollable operation period of the kiln, which forms 4.9 % of the total operation time , are exhausted, thus contaminating the environment . Hence , the use of this method is gradually being limited in advanced countries, such as the USA or Japan. For reference, if the waste rubber is pyrolyzed under oxygen-free conditions, about 60 % of carbon black and inorganics and about 40 % of gas and regenerated oil are obtained even though the composition may slightly vary according to the reaction condition. Furthermore, the composition of the waste tires depends on compounds used during production of the tire, and the compositional ratio depending somewhat on its use is as described in Table 2.

Table 2 Compositional ratio of waste tire

Data: Wastes Pyrolysis Research Center of Korea Institute of Energy Research

As described in Table 2, the amount of natural rubber and synthetic rubber is 22 % and 25 %, respectively, and. the amount of carbon black is about 24 %. The amount of the steel cord used to support tires and to increase its strength is 14 %, and the amount of the inorganic additive or the process oil is about 15 %. In other words, it is possible to recover 45 - 50 % of regenerated oil through pyrolysis . Various technologies with respect to the pyrolytic incineration method, that is, the pyrolysis method, which, is currently considered to be the most ideal waste rubber/waste tires treatment method, have been developed and many related patents have been filed and registered. Although much effort and many attempts have been made, it is difficult to commercialize this method because the following problems have not been overcome. Since the waste rubber/waste tires must be indirectly- heated under oxygen-free conditions, a heating time is long, and cooling to room temperature must be conducted after the resolution is finished so as to reduce the risk; of explosions or fire. Thus, a great quantity of energy is consumed. For reference, from the experimental data of Korean Patent No. 10-0335012, it can be seen that heat capacity required to pyrolize the waste tires is 167 kcal/kg, it takes 2.5 hours to achieve the resolution when 6000 kg of waste tires are heated using a reactor having a heat capacity of 1800000 kcal/h, and heat efficiency is a very low 11 %. FIG. 1 schematically illustrates a device for pyrolyzi g the waste rubber/waste tires using a conventional indirect heating process. As shown in the drawing, according to the mechanism of pyrolyzing the waste rubber or the waste tire, when waste rubber pieces are charged in a reactor having a nitrogen atmosphere and indirectly heated so as to be maintained at 400 - 500^°C, the carbon black and the steel cord remain in the reactor and distillate is transferred into a quenching bath or a cooling bath, thereby producing oil. In the above device, it is necessary to conduct a continuous process in order to treat a great quantity of waste rubber, thus the carbon black and the steel cord are continuously accumulated therein and there is the risk of fire when the waste rubber pieces are fed into the reactor at high temperatures. Since the reactor for pyrolysis is operated at high temperatures, there is a high possibility that explosions or fire may occur if oxygen is supplied along with the waste tires. Additionally, since the steel cord is wound around a transferring device, such as a screw, which is required in the continuous process, it is difficult to desirably conduct the continuous process, thus a batch-type reactor for pyrolysis is frequently used. It is necessary to increase the volume of the reactor in order to increase the treatment amount, thus the device inevitably becomes large. Accordingly, the time required for heating and cooling for resolving the waste tires, is lengthened, thus it is difficult to operate it twice or more per day. Furthermore, if the waste tires are not cut, they must be fed into the reactor in small amounts because of their high volume. Hence, they must be cut into small pieces, thus an additional cost is required. The waste rubber or the waste tires have relatively low thermal conductivity. However, since batch-type pyrolysis employing indirect heating is conducted in an external indirect heating manner, the temperature of the waste tires that are located near a wall of the reactor is locally increased, thus coking is formed on the wall of the reactor and thermal conductivity is rapidly reduced. As well, if the waste tires are locally heated to a high temperature, cracking of crude rubber material significantly occurs, resulting in increased yield of non- condensable gas components. Accordingly, oil recovery is reduced, and the quality of carbon black and steel cord is reduced.

Brief Description of Drawings FIG. 1 schematically illustrates a device for pyrolyzing waste rubber/waste tires using a conventional indirect heating process; FIG. 2 illustrates a basic system according to the present invention; FIG. 3 is a perspective view of a resolution device as a main part, according to the present invention; and FIG. 4 illustrates a sectional structure and incidental facilities of the resolution device according to the present invention. ^ Description of reference numerals for main parts in the drawings 100: reactor 200: magnetron 300: oil condensing vessel 400: boiler 500: oil storage tank 600: control panel 700: nitrogen feeding pipe 800: means for discharging carbon black and steel cord 900: feeding means 10: desulfurizing unit 20: distillation unit 30: nitrogen high pressure bomb 40: flow meter 50 : valve 60 : Vacuum recovering unit 70: pulverizer 80: assortment and packing 90 : carbon black

Detailed description of Invention

Technical Problem As described above, the present invention aims to avoid the disadvantages of a conventional batch-type reactor in which the volume of reactor must be large because it is impossible to continuously supply waste tires or waste rubber and in which it is impossible to recover carbon black and steel cord until the temperature of the reactor is reduced to room temperature after a reaction has finished, thus a great quantity of energy is unnecessarily consumed. Additionally, the present invention aims to avoid other disadvantages in which, since a temperature gradient in the reactor is significant because of physical properties of the waste tires or the waste rubber having low thermal conductivity, cracking increases if a local temperature is high during pyrolysis of the waste rubber, thus increasing the generation of non-condensable gas, resulting in reduced recovery of oil. Therefore, the present invention adopts a method using microwaves instead of a direct heating method in order to avoid the above disadvantages . The microwaves have a frequency corresponding to a middle region between radio waves and infrared light, and are frequently used in communication frequency, microwave ovens, or industrial heating furnaces. At the present time, industrially allowable frequencies in Korea and the USA are 2.45 GHz (wavelength: 12 cm) and 915 MHz (wavelength: 32 cm) , and these frequencies are used in the present invention. For reference, industrially allowable frequencies in other countries are different. A process of heating material using microwaves is based on the rapid rotation of polar and dielectric molecules, such as water, after they absorb the microwaves, or an ionic conduction phenomenon. A heating rate depends on dielectric properties of an object. Of the dielectric properties, a dielectric constant ( ε ' ) of material denotes an ability to store electric energy, and a dielectric loss factor ( ε " ) denotes an ability to convert electric energy into heat energy and to consume it. When these values are high, heating is easily achieved. Furthermore, the microwave has the advantage of having very high energy conversion efficiency. The waste rubber or the waste tires has a low dielectric constant and a low dielectric loss factor, thus it may be considered that heating using the microwave is not effective. However, an antioxidant, zinc oxide, cobalt, and a sulfur compound are uniformly added in order to increase the adhesion strength or improve the physical properties during the production of the rubber tire. It was mistakenly thought that metal components do not absorb the microwaves but reflect them. However, in practice, the microwaves penetrate metal to a micrometer depth from a surface of metal and are absorbed by the metal . Hence, if the metal components exist in the micrometer size range, they may absorb the microwaves, thus instantaneously being heated. The metal components, particularly cobalt salts, which are uniformly distributed in the waste rubber/waste tires, absorb the microwaves and thus act as hot sites, thereby uniformly and rapidly heating the waste rubber/waste tires. Microwaves of 915 MHz and 2.45 GHz both permeate through the waste rubber/waste tires to increase the internal temperature. Since the energy of 915 MHz microwaves is relatively weak, they can easily permeate through the rubber/tires, but a heating time is long. The 2.45 GHz microwaves have a lower permeation ratio than the 915 MHz microwaves. However, the waste rubber or the waste tires can be still more effectively resolved by properly combining the two wavelengths. The microwaves heat material by rapidly rotating polar dielectrics, such as water molecules. Based on the above mechanism, they are extensively used in many industries, such as sterilization, dyeing, cooking, heating, and wood processing, and in all of daily life. An object to be heated by microwaves must be a polar dielectric. However, as described in Table 3, it is very difficult to conduct heating using microwaves because most organic compounds are non-polar and have very low dielectric constants unlike water which has a very high dielectric constant of 78.54 at 2.45 GHz. Furthermore, when using rubber, it is considered almost impossible to conduct heating using microwaves because the dielectric constant of the rubber at 1 GHz is similar to the dielectric constant of 2.27 of benzene at 2.45 GHz.

TABLE 3 Dielectric constant

Data: Food Science and Industry, Vol. 31, No. 1 (1998), CRC Handbook Technical Solution However, a small amount of ferromagnetic material, such as an antioxidant, zinc oxide, cobalt salt, or a sulfur compound, is uniformly distributed among waste rubber or waste tires so as to increase the adhesion strength to an steel cord or to improve physical properties. The material absorbs microwaves and thus acts as a uniform hot site, thereby uniformly and selectively heating the waste rubber or the waste tires to resolve the rubber or tire. If the waste rubber or the waste tires is resolved using the microwave, it is possible to achieve very rapid resolution in comparison with a heating method, and it is possible to prevent energy from being wasted. As described above, in the present invention, the waste rubber or the waste tires is resolved by heating the inside of the rubber using microwaves so that the waste rubber is explosively resolved. Accordingly, a device is very simple compared to a heating device and pollutants are not generated because combustion gas is not generated.

Advantageous Effects As described above, a method employing microwaves is more economical than a resolution method employing fossil fuels because conversion efficiency of electricity to heat is a very high 80 % or so and because it is possible to selectively heat only waste rubber or waste tires . Results of resolution of the waste rubber/waste tires through an indirect heating method and the method employing microwaves are described in the following Table 4.

As described in Table 4, in the course of resolving waste rubber/waste tires through the method using microwaves, energy consumption is twice as low or less, a cost is three times as low, and a resolution time is six times as low as those of the indirect heating method. As well, since the oil recovery amount is relatively large, the resolution time is shortened, thus operation is convenient and economic efficiency is significantly increased. Considered the most reasonable, the regeneration method of pyrolyzing the waste rubber or the waste tires has not been commercialized because of the high treatment cost and the inconvenient operation. However, as in the present invention, if the waste rubber or the waste tires are resolved through the technology of resolving the waste rubber or the waste tires using microwaves, the following advantages are assured in comparison with the indirect heating resolution method. The resolution time is significantly reduced, resolution operation is convenient, installation cost is reduced because it is possible to miniaturize a reaction device, and unnecessary energy waste is prevented because only the waste rubber or the waste tires are selectively heated, thus an energy cost required in the resolution is significantly reduced. Furthermore, an oil recovery amount is increased because heating is constantly conducted at relatively low temperatures, it is possible to recover superior carbon black and steel cord, environmental pollution due to combustion gas can be prevented because clean energy, that is, electricity, not fossil fuel, is used to conduct resolution, and the risk of explosions or fire is reduced. In addition, the output and irradiation time of the microwaves are properly controlled to produce a rubber powder product while the waste rubber/waste tires is not completely resolved, thus it is possible to apply the method of the present invention to this field. Furthermore, since it is possible to achieve miniaturization, the waste rubber/waste tires is directly treated in each district which discharges the rubber or: tires, thus it is possible to develop state and locaL economies and to prevent environmental pollution.

Best Mode for Carrying Out the Invention To accomplish the above objects, examples of the present invention will be described in detail, referring to the accompanying drawings .

EXAMPLE 1: Basic system

As shown in FIG. 2 which illustrates a basic system according to the present invention, the basic system of the present invention comprises heating waste rubber or waste tires using microwaves of a magnetron 200 provided on an internal wall of a tower-type reactor 100 into which nitrogen gas is fed, collecting gas generated through pyrolysis in an oil condensing vessel 300, storing oil which is extracted from the oil condensing vessel 300 in an oil storage tank 500, and completely combusting gas which is not condensed in the oil condensing vessel 300 in a. boiler 400. The tower-type reactor 100 is provided with means 900 for supplying the waste rubber or the waste tires at an upper part thereof and means 800 for discharging" carbon black and steel cord at a lower part thereof. The reactor 100 according to the present invention may be made solely of stainless steel. However, since sparks may occur when the steel cord of the waste tires comes into contact with stainless steel, it is economical and preferable that an internal part of the reactor be made of ceramic absorbing a small amount of microwaves, a middle part be made of stainless steel reflecting the microwaves, and an external part be made of insulating material . It is possible to design the reactor 100 so that it has various shapes, such as a cylinder or a hexahedron, but it is preferable that the shape be a cylinder optimized to maximize the efficiency of the microwaves. The magnetron 200 for generating the microwaves is attached to a wall of the reactor 100, and one or a plurality of magnetrons which has an output from 500 W - 30 kW may be selectively used depending on the size of the reactor or the amount of waste rubber or waste tires to be treated. The magnetron generating 2.45 GHz or 915 MHz may be selectively employed. The means 900 for supplying the waste rubber or the waste tires are provided at the upper part of the reactor 100, and the means 800 for discharging the carbon black and the steel cord generated after the resolution are provided in conjunction with a switching device preventing leak of the microwaves and oil gas at the lower part of the reactor. The nitrogen feeding pipe 700 for feeding nitrogen into the reactor so as to remove oxygen from the reactor and to rapidly exhaust the oil gas, and an oil gas exhaustion pipe 300a for exhausting the oil gas from the reactor therethrough, is also provided. A control panel 600 capable of controlling the state of the reactor 100 and the magnetron 200 is provided so as to control the temperature of the reactor, the output of the magnetron, the operation time, and a safety device for blocking power. In the oil condensing vessel 300 connected to the oil gas exhaustion pipe 300a, it is possible to control the composition (composition depending on a boiling point) of recovered oil by controlling the temperature of cooling water within a range from -10^°C to room temperature. The collected oil is stored in the oil storage tank 500, and non-condensable gas components which are not condensed at the above temperature are transferred through a non- condensable gas exhaustion pipe 300b into the boiler 400 and then converted into heat energy therein, thus being economically used. Gas completely combusted into carbon dioxide and water in the boiler is exhausted through a combustion gas exhaustion pipe 400a to the atmosphere. A detailed description will be given of the reactor 100 in the basic system as described above, with reference to FIG. 3 which is a perspective view of a resolution device as a main part according to the present invention and FIG. 4 which illustrates a sectional structure and incidental facilities of the resolution device according to the present invention.

EXAMPLE 2

A device for resolving waste rubber or waste tires using microwaves comprises a tower-type reactor 100 which has an internal wall made of ceramic material, a middle part made of stainless steel, and an external part made of insulating material, an oil pan lOOe which has a hopper lOOf at a center thereof and is provided at an upper part of an internal part of the tower-type reactor, an oil exhaustion pipe 500a which is provided at an upper part of the external part of the tower-type reactor, an oil gas exhaustion pipe 300a which is provided over the oil pan lOOe and on which a cooling oil trap 300c is installed, a conical dome 130 on which cooling water pipes lOOg are provided and which seals the tower-type reactor, a door 100a provided on the wall of the middle part of the tower- type reactor 100, a worktable 100b wh±ch is provided beneath a bottom of the door and on which rails 100c are mounted so that a net-type waste tires pile unit 110 is mounted on sliders 110a on the rails 100c, a nitrogen feeding pipe 700 which is introduced into the middle part of the tower-type reactor 100, a plurality of magnetrons 200 provided on an internal wall of the middle part of the tower-type reactor 100, a cylindrical carbon black recovering vessel 120 having an iron net 120a at a bottom thereof and a circular rail 120b at a circumference of the bottom thereof in the tower-type reactor 100, on which two rows of carbon black recovering vessel upper rails 121 are mounted and which rotates using a pulley 12Od connected to a vibrator 120e and a motor 120c mounted on an upper end of a dustpan 140 provided at the bottom of the tower-type reactor, a carbon black recovering pipe 10Od extending from the dustpan 140 outside the tower-type reactor 100, and a vacuum recovering unit 60 which transfers carbon black 90 into a pulverizer 70 therethrough. In the basic system in which the waste rubber or the waste tires are resolved using the microwaves in the reactor 100, as in example 1, the oil gas exhaustion pipe 300a which is provided on the conical dome 130 is connected to the boiler 400, and the oil exhaustion pipe 500a of the oil pan lOOe is connected to an oil storage tank 500, a desulfurizing unit 10, and a distillation unit 20. Nitrogen is supplied from a high pressure nitrogen bomb 30 through a flow meter 40 and the nitrogen feeding pipe 700, and controlled using a valve 50. Cooling water controlled to a temperature range from -10^°C to room temperature circulates through the cooling water pipes lOOg to condense the oil gas which is generated by resolving the waste rubber or the waste tires using the microwaves and a concentration gradient of which exists in the reactor at the upper part of the reactor, thereby collecting the oil gas on the oil pan lOOe. The collected oil is transferred through the oil exhaustion pipe 500a into the oil storage tank 500, stored therein, and passed through the known desulfurizing unit 10 and the distillation unit 20, thereby producing regenerated oil. Meanwhile, the oil gas that is not condensed while it passes through the oil gas exhaustion pipe 300a provided on an upper side of the conical dome 130 and the cooling oil trap 300c, is recovered, and non-condensable gas components are completely combusted in the boiler 400 and then exhausted to the atmosphere. The waste rubber or the waste tires are stuffed in the waste tires pile unit 110 which is capable of moving a heavy body using the rails 100c xaounted on the worktable 100b, and then transferred into the reactor 100. The carbon black recovering vessel 120 rotates at a predetermined speed using the pulley 120d wh ch is connected to the vibrator 120e and the motor 120c on the dustpan 140 on the bottom of the reactor 100 so that the microwaves uniformly irradiates the waste rubber or the waste tires in the waste tires pile unit 110 moved on the carbon black recovering vessel upper rails 121 on the carbon black recovering vessel 120. The carbon black recovering vessel 120 is vibrated with the vibrator 120e on the dustpan 140 so that pyrolyzed carbon black 90 is thoroughly exhausted through the iron net 120a. Furthermore, carbon black 90 dropped on the dustpan 140 is drawn by the vacuum recovering unit 60 and exhausted outside the reactor 100, pulverized using the pulverizer 70 into predetermined particles, assorted and packed 80, thereby creating a product.

Claims

1. A method of resolving waste rubber or waste tires using microwaves, comprising: heating the waste rubber or the waste tires using the microwaves of a magnetron 200 provided on an internal wall of a tower-type reactor 100 into which nitrogen gas is fed; collecting gas generated through pyrolysis in an oil condensing vessel 300; storing oil which is extracted from the oil condensing vessel 300 in an oil storage tank 500; and completely combusting gas which is not condensed in the oil condensing vessel 300 in a boiler 400, wherein the tower-type reactor 100 is provided with means 900 for supplying the waste rubber or the waste tires at an upper part thereof and means 800 for discharging carbon black and steel cord at a lower part thereof.

2. A device for resolving waste rubber or waste tires using microwaves, comprising: a tower-type reactor 100 which has a wall made of ceramic material, a middle part made of stainless steel, and an external part made of insulating material; an oil pan 100e which has a hopper lOOf at a center thereof and is provided at an upper part of an internal part of the tower-type reactor; an oil exhaustion pipe 500a which is provided at an upper part of the external part of the tower-type reactor; an oil gas exhaustion pipe 300a which is provided over the oil pan lOOe and on which a cooling oil trap 300c is installed; a conical dome 130 on which cooling water pipes lOOg are provided and which seals the tower-type reactor; a door 100a provided on the wall of the middle part of the tower-type reactor 100; a worktable 100b which is provided beneath a bottom of the door and on which rails 100c are mounted so that a net-type waste tires pile unit 110 is mounted on sliders 110a on the rails 100c; a nitrogen feeding pipe 700 which is introduced into the middle part of the tower-type reactor 100; a plurality of magnetrons 200 provided on an internal wall of the middle part of the tower-type reactor 100; a cylindrical carbon black recovering vessel 120 having an iron net 120a at a bottom thereof and a circular rail 120b at a circumference of the bottom thereof in the tower-type reactor 100, on which two rows of carbon black recovering vessel upper rails 121 are mounted and which rotates using a pulley 120d connected to a vibrator 120e and a motor 120c on a dustpan 140 on a bottom of the tower- type reactor; a carbon black recovering pipe lOOd extending from the dustpan 140 outside the tower-type reactor 100; and a vacuum recovering unit 60 which transfers carbon black 90 into a pulverizer 70 therethrough.