Method for Recovering Carbon Black from Waste Tires

Abstract

To efficiently recover high purity carbon black from a waste tire and reutilize the same to save resources and reduce a greenhouse gas load.SOLUTION: A method of recovering carbon black includes: a dry distillation step of drying a waste tire in a dry distillation apparatus (1); and a heating step of gasifying a fixed carbon content to allow the carbon black to remain in a solid state by disposing a carbonized residue (C) remaining after drying under a high temperature environment higher than a first set temperature (T1) at which the fixed carbon content of a rubber carbonized matter starts to gasify, for example 800°C, and lower than a second set temperature (T2) at which the carbon black starts to gasify, for example 1,400°C.SELECTED DRAWING: Figure 4

Description

Technical Field

[0001] The present invention relates to a method for recovering carbon black from waste rubber tires.

Background Art

[0002] Waste rubber tires used in various vehicles such as automobiles contain about 25% carbon black by weight. Here, carbon black is produced by incomplete combustion of fossil fuels at high temperatures, and the environmental load during production is very high. Furthermore, among the total greenhouse gas emissions (228 kg_CO2 / tire) of the raw materials constituting a passenger car tire (for example, a 195 / 65R / 15 tire), the greenhouse gas emissions 68.4 (kg_CO2 / tire) attributed to the carbon black added to the passenger car tire account for about 30%. From these facts, as one of the measures against global warming, a technology for recovering carbon black from waste rubber tires with high purity has become an urgent need.

[0003] In addition, waste rubber tires used in various vehicles such as automobiles are generally incinerated at recycling facilities and recycled. However, simply incinerating them results in a low recycling rate. Therefore, recently, a method of improving the recycling rate by using a pyrolysis oilification process (process) for recycling waste tires has been utilized. For example, waste tires are filled into a retort and heated in an oxygen-free atmosphere to pyrolyze the waste tires. The retort gas generated at this time is cooled and recovered as an oil component. The recovered oil component is reused as fuel for the retort, and the non-gasified residue is recovered and reused as carbide. A technology for reusing the recovered oil component as fuel is disclosed in, for example, Patent Document 1.

Prior Art Documents

Patent Documents

[0004]

Patent Document 1

Summary of the Invention

Problems to be Solved by the Invention

[0005] However, in the recycling process of waste tires described in Patent Document 1, the carbonized residue after the carbonization process is recovered in a state containing rubber carbide and carbon black. That is, in the carbonization in the range of 300°C to 800°C, only the volatile components are gasified, and a mixture of the fixed carbon content of the rubber and carbon black remains, and it cannot be said that high-purity carbon black is recovered.

[0006] An object of the present invention is to provide a method for recovering carbon black from waste tires that can efficiently recover high-purity carbon black from the carbonized residue of waste tires.

Means for Solving the Problems

[0007] To solve the above problems, a method for recovering carbon black from waste tires according to the present invention includes a carbonization step of carbonizing waste tires in a carbonization apparatus, and the carbonized residue remaining after carbonization is placed in a high-temperature environment exceeding a first set temperature (T1) at which the fixed carbon content of the rubber carbide in the carbonized residue starts to gasify and less than a second set temperature (T2) at which the carbon black starts to gasify, thereby gasifying the fixed carbon content and leaving the carbon black in a solid state, including a heating step.

[0008] In one aspect of the above invention, the first set temperature (T1) at which the fixed carbon content starts to gasify is set to 800°C, and the second set temperature (T2) at which the carbon black starts to gasify is set to 1400°C.

[0009] One aspect of any of the above inventions includes a pulverization step of pulverizing the carbonized residue obtained by carbonization between the carbonization step and the heating step.

[0010] One aspect of any of the above inventions is to add trace oxygen with a weight concentration of 5% or less in the high-temperature environment.

[0011] One aspect of any of the above inventions utilizes, as a heat source for maintaining the high-temperature environment, the heat obtained by burning the pyrolysis gas generated in the pyrolysis process.

[0012] One aspect of any of the above inventions utilizes, as a heat source for maintaining the high-temperature environment, the heat obtained by burning the pyrolysis oil obtained by cooling the pyrolysis gas generated in the pyrolysis process.

[0013] One aspect of any of the above inventions includes an iron classification step of separating iron components from carbon black remaining as a solid in the heating step.

[0014] One aspect of any of the above inventions includes an ash classification step of separating ash from carbon black remaining as a solid in the heating step.

Advantages of the Invention

[0015] According to the present invention, high-purity carbon black can be efficiently recovered from the carbonized residue of waste tires. Furthermore, the recovered carbon black can be reused during the production of new tires, making it possible to reduce the greenhouse gas load caused by carbon black during tire production.

Brief Description of the Drawings

[0016]

Figure 1

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Figure 10

Mode for Carrying Out the Invention

[0017] [Embodiment] (Recycling Equipment for Waste Tires) With reference to FIGS. 1 to 3, the recycling equipment for waste tires will be described. FIG. 1 is an overall schematic view of the recycling equipment for waste tires. The recycling equipment of FIG. 1 includes a carbonization furnace 1, a primary cooler 2, a secondary cooler 3, a cooler-side safety device 4, a crude oil tank 5, a filter 6, a refined oil tank 7, a flow meter 8, an excess gas incinerator 9, a kerosene tank 10, and a residual oil tank 47.

[0018] The carbonization furnace 1 includes a cylindrical body 21, a heating furnace 22 provided below the body 21, a lid 23 provided on the upper side of the body 21 so as to be openable and closable, and a cartridge container 25 detachably mounted inside the body 21. The lid 23 has a carbonization gas outlet 27. The body 21 has a combustion exhaust gas outlet 28 for discharging the combustion exhaust gas generated by the heating furnace 22. The heating furnace 22 uses the regenerated refined oil and the cooled carbonization gas for combustion.

[0019] The white arrows 31, 32, 33, 34, 35 indicate the air supply passages through which the pyrolysis gas generated in the pyrolysis apparatus 1 flows. The thick solid arrows 36, 37 indicate the exhaust passages through which the combustion exhaust gas generated in the excess gas incinerator 9 and the heating furnace 22 flows. The thin solid arrows 41, 42, 43, 44, 45 indicate the oil supply passages through which the pyrolysis oil separated from the pyrolysis gas in the primary cooler 2 and the secondary cooler 3 flows. The thin solid arrow 46 indicates the oil supply passage through which kerosene flows from the kerosene tank 10 to the excess gas combustion furnace 9. The air supply passages 31, 32, 33, 34, 35, the exhaust passages 36, 37 and the oil supply passages 41, 42, 43, 44, 45, 46 are composed of air supply pipes, exhaust pipes, oil supply pipes and other passage members.

[0020] The pyrolysis gas outlet 27 of the pyrolysis apparatus 1 is connected to the gas inlet of the primary cooler 2 via the air supply passage 31. The gas outlet of the primary cooler 2 is connected to the gas inlet of the secondary cooler 3 via the air supply passage 32. The gas outlet of the secondary cooler 3 is connected to the cooler side safety device 4 via the air supply passage 33. The gas outlet of the cooler side safety device 4 is connected to the heating furnace 22 via the air supply passage 35 and is also connected to the excess gas incinerator 9 via the air supply passage 34. The fuel inlet of the excess gas incinerator 9 is connected to the kerosene tank 10 via the oil supply passage 46. The exhaust gas outlet of the excess gas incinerator 9 is connected to an exhaust treatment unit (not shown) via the exhaust passage 36.

[0021] The oil outlets of the primary cooler 2 and the secondary cooler 3 are connected to the crude oil tank 5 via the oil supply passages 41, 42. The oil outlet of the crude oil tank 5 is connected to the filter 6 via the oil supply passage 43. The oil outlet of the filter 6 is connected to the refined oil tank 7 via the oil supply passage 44. The oil outlet of the refined oil tank 7 is connected to the heating furnace 22 via the oil supply passage 45 and the flow meter 8. The fuel exhaust gas outlet 28 of the pyrolysis apparatus 1 is connected to the exhaust treatment unit via the exhaust passage 37.

[0022] Next, the operation of the entire pyrolysis system will be briefly described.

[0023] The waste tire T is put into the cartridge container 25 and heated in the heating furnace 22 of the carbonization apparatus 1. Thereby, carbonization gas is generated. The generated carbonization gas is sequentially sent from the carbonization gas outlet portion 27 to the primary cooler 2 and the secondary cooler 3 through the air supply passages 31 and 32 and cooled. Thereby, the oil component in the carbonization gas is separated and sent to the crude oil tank 5 as carbonization oil. On the other hand, the carbonization gas from which the oil component has been separated is sent to the cooler side safety device 4 through the air supply passage 33, a part of which is sent to the heating furnace 22 of the carbonization apparatus 1 through the air supply passage 35, and the rest is sent to the excess gas incinerator 9 through the air supply passage 34.

[0024] The essential oil in the essential oil tank 7 is sent to the heating furnace 22 through the oil supply passage 45 and the flow meter 8 and reused for combustion. The exhaust gas generated in the excess gas incinerator 9 is sent to the exhaust gas treatment unit together with the combustion exhaust gas discharged from the combustion exhaust gas outlet portion 28 of the carbonization apparatus 1.

[0025] FIG. 2 shows a longitudinal sectional view of the carbonization apparatus 1. FIG. 3 shows a longitudinal sectional view of the cartridge container 25. As shown in FIG. 2, a protective can 26 that forms a cartridge container storage chamber 24 is provided in the body 21. A convex portion 25a that protrudes upward is formed on the bottom wall of the cartridge container 25. Further, an intrusion portion 26a that intrudes from below into the convex portion 25a is formed at the center of the bottom wall of the protective can 26. The canopy 23 is detachably fastened to the cartridge container 25 or the body 21 by a plurality of clamps 48. The combustion exhaust gas outlet portion 28 communicates with the heating furnace 22 through an annular gap between the protective can 26 and the body 21.

[0026] The basket-shaped middle shelf 30 can be mounted at approximately the middle of the vertical width inside the cartridge container 25. In this embodiment to in the carbonization process related thereto, this middle shelf 30 is not used.

[0027] As shown in FIG. 3, the convex portion 25a is formed at substantially the center of the bottom wall of the cartridge container 25 and has a height of approximately 1 / 3 to 1 / 2 of the vertical width of the cartridge container 25.

[0028] (Carbonization process) The carbonization process of waste tire T will be described. In Fig. 1, the waste tire T is put into the cartridge container 25 and heated in an oxygen-free atmosphere by the heating furnace 22 of the carbonization device 1. Thereby, carbonization gas is generated. The generated carbonization gas is sequentially sent from the carbonization gas outlet 27 through the air supply passages 31 and 32 to the primary cooler 2 and the secondary cooler 3 and cooled. Thereby, the oil component in the carbonization gas is separated and sent to the crude oil tank 5 as carbonization oil. On the other hand, the carbonization gas from which the oil component has been separated is sent to the cooler side safety device 4 through the air supply passage 33, a part of which is sent to the heating furnace 22 of the carbonization device 1 through the air supply passage 35, and the rest is sent through the air passage supply 34 to the excess gas incinerator 9.

[0029] The essential oil in the essential oil tank 7 is sent to the heating furnace 22 through the oil supply passage 45 and the flow meter 8 and reused for combustion. The exhaust gas generated in the excess gas incinerator 9 is sent to the exhaust gas treatment unit together with the combustion exhaust gas discharged from the combustion exhaust gas outlet 28 of the carbonization device 1.

[0030] Fig. 4 is a flowchart of the carbonization process of waste tire and the carbon black recovery method. Steps S1 to S6 show the carbonization process. Regarding the carbonization process, since it has already been described with reference to Fig. 1, it will be briefly described. In step S1, the waste tire is put into the carbonization device 1, and in step S2, the waste tire in the carbonization device 1 is heated and carbonized in an oxygen-free state. The carbonization gas in step S3 is generated by the heating and carbonization. In step S4, the carbonization gas is cooled to produce recycled oil. In step S5, the recycled oil is reused as fuel for the heating furnace 22 of the carbonization device 1. On the other hand, in step S6, after the carbonization process, the carbonized residue C and the metal wire W remain in the carbonization device 1.

[0031] (Crushing and carbon black recovery process) In Fig. 4, the steps from step S6 to step S17 surrounded by the two-dot chain line R show the process for separating and recovering carbon black, ash, and the metal wire W from the carbonized residue C after carbonization. The carbonized residue C and the metal wire W in step S6 are pulverized by a pulverizer in step S7 and become a mixture of the pulverized carbonized residue C and the metal wire W shown in step S8.

[0032] Figs. 5 and 6 illustrate a stirrer 51 which is an example of a pulverizer. The stirrer 51 includes a pedestal 56 supported on the upper end surface of the convex portion 25a, a rotating shaft 58 rotatably supported on the pedestal 56 via a bearing 57, a plurality of support members 59 integrally rotatably attached to the rotating shaft 58, and a plurality of stirring rods 60 fixed to each support member 59. Each stirring rod 60 extends downward and is set to have different lengths from each other. In this embodiment, in the case of four stirring rods 60, two are short and two are long. However, the present invention is not limited to this.

[0033] Fig. 6 is a bottom view (underside view) of the stirrer 51. As shown in Fig. 6, the support member 59 is formed in a cross shape, and four stirring rods 60 are provided at the ends of each support member 59. Also, an annular reinforcing member 61 for reinforcing the support member 59 is provided so as to connect each support member 59.

[0034] Figure 7 shows an example of a specific pulverization operation by the stirrer 51. As shown in Figure 7, the stirrer 51 is inserted into the cartridge container 25, and the pedestal 56 of the stirrer 51 is abutted and supported on the upper end surface of the convex portion 25a. The rotating shaft 58 projects upward from the cartridge container 25 and is connected to a driving device (not shown). Each stirring rod 60 penetrates into the carbonized residue C. The mounting table 54 on which the cartridge 25 is placed is rotatable, but is used in a fixed state. When the rotating shaft 58 of the stirrer 51 rotates in the direction of arrow A1, the stirring rod 60 orbits in the same direction as the rotating shaft 58 to stir the carbonized residue C. As a result, the fixed carbonized residue C is pulverized into powder. Further, the carbonized residue C adhering to the metal wire W is peeled off. It should be noted that it is also possible to stir and pulverize the carbonized residue C by fixing the stirrer 51 and rotating the mounting table 54 in the direction of arrow A2.

[0035] In addition, as a pulverization operation, a mixture of the carbonized residue C and the metal wire W can be discharged from the cartridge container 25 and pulverized by a stamping type rolling pressure device.

[0036] Returning to Figure 4, in step S8, the finely pulverized carbonized residue C contains rubber carbide and carbon black. Here, the rubber carbide contains fixed carbon, volatile components, and ash. Carbon black is manufactured by incompletely burning fossil fuels at high temperatures and has a strong crystal structure. The gasification temperature of carbon black is 1400 °C or higher. That is, the second set temperature (T2) at which carbon black starts gasification is set to 1400 °C. The crystal strength of the fixed carbon in the rubber carbide is weaker than that of carbon black, and the gasification temperature of the fixed carbon is 800 °C. The volatile components of the rubber carbide are mainly highly viscous liquid components, and the gasification temperature of the volatile components is 600 °C or higher. The metal wire is iron and is treated as a substance that does not gasify. Ash is not gasified.

[0037] The mixture of the carbonized residue C containing components with the above-described properties and the metal wire W is fed into the dry distillation apparatus 1 or another heating apparatus, and is heat-treated in step S9. In this case, a trace amount of oxygen is fed. A trace amount of oxygen is a small amount of oxygen relative to the combustion equivalent oxygen ratio of the carbonized material. In this embodiment, for example, 5% or less by weight of oxygen is fed. The oxygen is fed in the form of an oxidizing agent containing oxygen molecules, such as oxygen elemental, enriched oxygen, air, water vapor, or carbon dioxide.

[0038] In step S9, which is the heating step, the temperature is raised to a high-temperature environment in the range of more than 800°C and less than 1400°C, and the mixture is heat-treated in an atmosphere containing a trace amount of oxygen of 5% or less, as described above. That is, the mixture is heat-treated in a high-temperature environment above 800°C, which is the first set temperature (T1) at which fixed carbon begins to gasify, and below 1400°C, which is the second set temperature (T2) at which carbon black begins to gasify.

[0039] As the temperature rises, moisture first evaporates at about 100°C, then hydrogen is released, and the volatile components gasify at 600°C or higher. As the temperature rises further and exceeds 800°C, the fixed carbon gasifies. The carbon monoxide or carbon dioxide produced by gasification is discharged as in step S10, and the carbon black, ash, and metal wire W remain in the dry distillation apparatus (heating apparatus) 1 as in step S11.

[0040] The metal wire W contained in the mixture in step S11 is taken out by a metal wire take-out machine in a metal wire take-out process (iron classification process) in step S12. That is, the iron content is classified. The classified metal wire W in step S13 is recycled as scrap iron in step S14.

[0041] The mixture of carbon black and ash obtained by classifying the metal wire W in step S12 is separated by an ash classifier in step S15. That is, it is separated into ash shown in step S16 and carbon black shown in step S17. As a result, high-purity carbon black is finally recovered.

[0042] Figure 8 is a graph showing the temporal change in temperature and the temporal change in the mass (thermogravimetry) of carbon residue C during the heat treatment. The upper graph G1 shows the mass change when the oxygen concentration is 5%. The middle graph G2 shows the mass change when the oxygen concentration is greater than 5% and less than or equal to 10%, for example, when it is 10%. The lower graph G3 shows the mass change when the oxygen concentration is greater than 10%, for example, when it is 20%. The graph X1 indicated by the dashed line is the change in temperature.

[0043] In graph G1, as the temperature rises, first, water evaporates at 100 °C, then hydrogen is released, and above 600 °C, volatile components are gasified. As the temperature further rises and exceeds 800 °C (the first set temperature), the fixed carbon component is gasified. Carbon monoxide or carbon dioxide generated by gasification is discharged, and carbon black and ash that are not gasified remain. That is, the first set temperature (T1) at which the fixed carbon content starts to gasify is set at 800 °C.

[0044] As in graphs G2 and G3, when the oxygen concentration is increased, combustion even starts with carbon black, and the recovery rate of carbon black becomes lower than that in the case of graph G1.

[0045] Figure 9 is a schematic diagram of a metal wire extractor (iron classifier). As shown in Figure 9, the metal wire extractor (iron classifier) is configured to include a rod-shaped electromagnet 52 and a suspension member 62. By adsorbing the metal wire W with the electromagnet 52, the metal wire W is separated from the carbon residue C.

[0046] Figure 10 is a schematic diagram of an ash classifier that separates carbon black and ash. The ash classifier in Figure 10 is configured to include a cyclone type classifier main body 53 having a filter, a hose 53a, and a nozzle portion 53b. The mixture of carbon black and ash is sucked by the nozzle portion 53b, and the ash and carbon black are separated using the centrifugal force within the classifier main body 53.

[0047] [Effects of the Embodiment] (1) High-purity carbon black can be efficiently recovered from waste tires, and the recovered carbon black can be reused in tire manufacturing. This enables effective utilization of resources, eliminates the environmental burden associated with newly manufacturing carbon black, and reduces the greenhouse gas load.

[0048] (2) During the heating process, a small amount of oxygen (5% or less) is introduced, which promotes the gasification of rubber carbide. In particular, by using a small amount, while promoting the aforementioned gasification, it is possible to prevent even carbon black from burning and maintain a high recovery rate of carbon black.

[0049] [Other Embodiments] (1) In the above embodiment, the carbonized residue was heat-treated in a high-temperature environment in the range exceeding 800°C and less than 1400°C. However, by heat-treating in a high environment in the range exceeding 900°C and less than 1400°C, the gasification of fixed carbon is further promoted.

[0050] (2) As the crusher, in addition to the stirrer 51 shown in Fig. 5, a stamping type rolling pressure device that continuously strikes the mixture of carbonized residue and metal wire can also be used.

[0051] (3) As the iron classifier, in addition to the electromagnet as shown in Fig. 9, a cyclone type classifier can also be used.

[0052] (4) As the ash classifier, for example, a classifier that separates by specific gravity difference can also be used.

[0053] Although several embodiments of the present invention have been described, each of the above embodiments is presented as an example and is not intended to limit the scope of the invention. These novel embodiments can be implemented in various other forms, and various omissions, replacements, and changes can be made without departing from the gist of the invention. These embodiments and their modifications are included in the scope and gist of the invention, and are included in the invention described in the claims and the equivalent scope thereof.

Explanation of Signs

[0054] 1 Carbonization apparatus (an example of a heating apparatus) 51 Stirrer (an example of a crusher) 52 Electromagnet for extracting metal wire (an example of an iron classifier) 53 Cyclone classifier (an example of an ash classifier) W Metal wire C Carbonized residue

Claims

1. A carbonization step of carbonizing waste tires charged into a cartridge container detachably attached to a carbonization apparatus within the carbonization apparatus; a pulverization step of removing the carbonization residue remaining after carbonization in powder form and removing the carbonization residue adhering to the metal wire by pulverization using a pulverizer attached to the cartridge container after taking out the cartridge container from the carbonization apparatus; a heating step of attaching the cartridge container containing the pulverized carbonization residue to the carbonization apparatus and placing it in a high-temperature environment where the fixed carbon content of the rubber carbide in the pulverized carbonization residue exceeds the first set temperature of 900°C at which gasification occurs and is less than the second set temperature of 1400°C at which carbon black begins to gasify, thereby gasifying the fixed carbon content and leaving the carbon black in a solid state; A method for recovering carbon black from waste tires, comprising the steps of:

2. The method for recovering carbon black from waste tires according to claim 1, wherein trace oxygen with a weight concentration of 5% or less is added in the high-temperature environment.

3. The method for recovering carbon black from waste tires according to claim 1, wherein the heat obtained by burning the carbonization gas generated in the carbonization step is used as a heat source for maintaining the high-temperature environment.

4. The method for recovering carbon black from waste tires according to claim 1, wherein the heat obtained by burning the carbonization oil obtained by cooling the carbonization gas generated in the carbonization step is used as a heat source for maintaining the high-temperature environment.

5. The method for recovering carbon black from waste tires according to claim 1, further comprising an iron classification step of separating iron components from the carbon black remaining as a solid in the heating step.

6. The method for recovering carbon black from waste tires according to claim 1, further comprising an ash classification step of separating ash from the carbon black remaining as a solid in the heating step.

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