Method for preparing pyrolysis carbon black through cascade pyrolysis of waste tires

Abstract

The invention discloses a method for preparing cracked carbon black through stepped pyrolysis of waste tires, which fully controls the cracking process through a stepped cracking method of slow heating cracking, rapid heating cracking and rapid cooling. The slow heating enables organic matters to be fully decomposed, the generation of gaseous products is reduced, the rapid heating and rapid cooling change the structure of the cracked carbon black and the main components of impurities, and the cracked carbon black is prevented from being converted into graphite carbon. Through the cascade pyrolysis technology, the yield balance of three-phase pyrolysis products is maintained, the stability and efficiency of the pyrolysis process are considered, side reactions and colloid residues are reduced, and the existence of amorphous carbon in a carbon black structure is ensured. Compared with the cracked carbon black obtained by the traditional cracking method, the carbon black prepared by the method disclosed by the invention has the advantages that the content of a surface adhesive layer is low, the hydrophilic performance is excellent and the surface activity is good according to a contact angle test, the reinforcing performance of the cracked carbon black is greatly improved, and the economic benefit of the product is maximized.

Description

Technical Field:

[0001] The present invention relates to the technical field of solid waste treatment, and particularly relates to a method for preparing pyrolytic carbon black by stepwise pyrolysis of waste tires. Background Art:

[0002] Waste tires contain valuable resources such as rubber, steel wires, carbon black, and zinc, and belong to precious secondary resources. Their full recovery and reuse can help alleviate the shortage of rubber resources and reduce "black pollution". Currently, the treatment of waste tires mainly includes tire retreading, recycling of reclaimed rubber, recycling of rubber powder, pyrolysis, etc. With the increasing attention of all sectors of society to carbon emission reduction, the harmless and resourceful utilization ways of waste tires have developed rapidly.

[0003] The high-temperature pyrolysis recovery treatment method of waste tires has gradually attracted extensive attention and in-depth research. Pyrolysis technology is one of the methods to realize the energy conversion and resource utilization of solid waste. The pyrolysis method can convert solid waste energy into various chemical products and gas products, which can alleviate the energy shortage and reduce pollutant emissions. Waste tires undergo pyrolysis in a high-temperature and inert gas environment, mainly generating solid, liquid, and gas phase products, specifically including pyrolysis gas, pyrolysis oil, and pyrolytic carbon black, etc. Among them, the pyrolytic carbon black in the pyrolysis products has potential economic value, and high-quality carbon black has fewer impurities and excellent reinforcing properties.

[0004] Currently, the preparation of tire pyrolytic carbon black fails to consider the influence of its surface gum layer. The gum layer generated during the pyrolysis process will cover the surface of the pyrolytic carbon black, resulting in the masking of its surface active sites, causing poor hydrophilicity, low surface activity, and lack of reinforcing properties of the pyrolytic carbon black, thereby reducing its economic value. Although the further activation and modification of pyrolytic carbon black can reduce or remove the gum layer on the carbon black surface, this method increases the process complexity and economic cost. Therefore, there is an urgent need to develop a simple pyrolysis method for waste tires to reduce the generation of gum layer impurities during pyrolysis and recover pyrolytic carbon black with high hydrophilicity and high reinforcing properties. Summary of the Invention:

[0005] The present invention provides a method for preparing pyrolytic carbon black by stepwise pyrolysis of waste tires. By adopting a stepwise temperature control process of slow heating pyrolysis, rapid heating pyrolysis, and rapid cooling, the pyrolysis process is fully controlled, the generation of gum layer impurities during pyrolysis is reduced, and the hydrophilicity of carbon black is enhanced, solving the problems of poor hydrophilicity and low reinforcing properties of the pyrolytic carbon black obtained by the prior art tire pyrolysis.

[0006] The present invention is realized through the following technical solutions:

[0007] A method for preparing pyrolytic carbon black by stepwise pyrolysis of waste tires, the method comprising the following steps:

[0008] (1) Under an inert atmosphere, the waste tire particles are slowly heated from room temperature at a heating rate of 10 - 30 °C / min, preferably 20 - 30 °C / min, to 350 - 550 °C, preferably 400 - 500 °C, and maintained at this temperature for 5 - 8 min, preferably 7 - 8 min;

[0009] (2) The product of step (1) is rapidly heated to 650 - 850 °C, preferably 680 - 750 °C at a heating rate of 40 - 60 °C / min, preferably 50 - 55 °C / min and maintained at this temperature for 0.5 - 2 min, preferably 0.5 - 1 min;

[0010] (3) The pyrolysis product of step (2) is rapidly cooled to room temperature by water spraying on the product and its carrier, and pyrolytic carbon black is obtained after vacuum drying at 100 °C for 20 - 24 h.

[0011] Preferably, in step (1), the inert gas is selected from one of nitrogen, argon, and helium;

[0012] Preferably, in step (1), the waste tire particles are solid particles with a particle size of 2 - 3 mm obtained by washing, magnetic separation, and crushing of scrapped automobile tires.

[0013] Preferably, in step (3), deionized water is used for water spraying.

[0014] Preferably, in step (3), the carrier is a silicon nitride crucible.

[0015] The present invention adopts temperature - gradient pyrolysis. The waste tire particles are first slowly heated from room temperature at a rate of 10 - 30 °C / min, which is equivalent to gradually preheating, and then pyrolyzed at 350 - 550 °C for 5 - 8 min to ensure the balance of the gas - liquid - solid three - phase yields in the pyrolysis process, promote the sequential and full pyrolysis of natural rubber and synthetic rubber in waste tires, generate organic substances distributed between C1 and C16 and pyrolytic carbon, reduce the residue of side - reaction products and gums, thereby improving the yield and quality of carbon black; then it is rapidly heated to 650 - 850 °C at a heating rate of 40 - 60 °C / min and maintained for a short time of 0.5 - 2 min. The rapid heating changes the structure of pyrolytic carbon black and the main components of impurities. When the temperature is in the range of 650 - 850 °C, the impurities of pyrolytic carbon black are more single and the ash content is lower. Maintaining for a short time prevents the conversion of pyrolytic carbon black into graphite carbon; then it is rapidly cooled by water spraying, which can greatly reduce the existence of graphitized carbon black in pyrolytic carbon black, enhance the hydrophilicity and surface activity of pyrolytic carbon black, and improve its reinforcing performance.

[0016] The beneficial effects of the present invention are as follows:

[0017] 1) The present invention controls the cracking process fully through a stepped cracking method of slow heating-up cracking, rapid heating-up cracking, and rapid cooling. Slowly heating up to 350 - 550 °C enables the full decomposition of organic substances, and can also maximize the solid-phase and liquid-phase yields to the greatest extent, reduce the generation of gaseous products, reduce side reactions and the residue of gum. Rapid heating-up and rapid cooling can not only quickly remove the gum layer on the surface of carbon black, but also prevent the graphitization of the carbon structure caused by long-term high temperature by rapidly heating up to 650 - 850 °C, obtaining carbon black with better reinforcement performance, thereby increasing the output and quality of carbon black, and taking into account the yield balance of the three-phase pyrolysis products as well as the stability and efficiency of the pyrolysis process.

[0018] 2) Compared with the carbon black obtained by traditional cracking methods, the carbon black obtained by the method of the present invention has less gum layer content on its surface. Through contact angle testing, it is found that it has excellent hydrophilic properties and good surface activity, thus greatly improving the reinforcement performance of the cracked carbon black. Description of the drawings:

[0019] Figure 1 It is the static contact angle test result of the cracked carbon black prepared in Example 1. Detailed implementation manners:

[0020] The following are only the preferred implementation manners of the present invention. It should be noted that the following preferred implementation manners should not be regarded as a limitation of the present invention. The protection scope of the present invention should be subject to the scope defined by the claims. For those of ordinary skill in the art in this technical field, without departing from the spirit and scope of the present invention, several improvements and retouches can also be made, and these improvements and retouches should also be regarded as within the protection scope of the present invention.

[0021] Example 1:

[0022] (1) Weigh 4 g of waste tire particles as reaction raw materials and place them in a silicon nitride crucible. Under a nitrogen atmosphere, slowly heat up from room temperature to 450 °C at a heating rate of 20 °C / min and maintain for 7 min; then rapidly heat up to 750 °C at a heating rate of 50 °C / min and maintain for 0.5 min, and then quickly cool the silicon nitride crucible and the product by water spraying. Finally, place the silicon nitride crucible and the product carbon black in a vacuum drying oven and bake at 100 °C for 24 h to obtain cracked carbon black.

[0023] (2) Conduct a sessile drop method static contact angle test on the cracked carbon black obtained in step (1), and the result is as Figure 1 shown. The time required for water to completely immerse into the cracked carbon black prepared by this method is only 5 s. It can be seen that the cracked carbon black prepared by this method has good hydrophilicity. The content of gum layer impurities on the surface of the cracked carbon black prepared by this method is reduced, the hydrophilic property of the carbon black is increased, the surface activity of the carbon black is improved, and further the reinforcement performance of the cracked carbon black is enhanced.

[0024] Comparative Example 1:

[0025] A reference example, the difference being that step (1) is different. Step (1) is as follows: Weigh 4 g of waste tire particles as reaction raw materials and place them in a silicon nitride crucible. Under a nitrogen atmosphere, slowly heat from room temperature to 420 °C at a heating rate of 20 °C / min and maintain for 7 min; then quickly heat to 550 °C at a heating rate of 50 °C / min and maintain for 0.5 min. Subsequently, perform water spraying to quickly cool the silicon nitride crucible and the product. Finally, place the silicon nitride crucible and the product carbon black in a vacuum drying oven and bake at 100 °C for 24 h to obtain pyrolytic carbon black.

[0026] Perform a sessile drop method static contact angle test on the pyrolytic carbon black obtained in step (1). The time required for water to completely immerse in the pyrolytic carbon black prepared by this method is 14 s.

[0027] Comparative Example 2:

[0028] A reference example, the difference being that the cooling method in step (1) is different. Step (1) is as follows: Weigh 4 g of waste tire particles as reaction raw materials and place them in a silicon nitride crucible. Under a nitrogen atmosphere, slowly heat from room temperature to 450 °C at a heating rate of 20 °C / min and maintain for 7 min; then quickly heat to 750 °C at a heating rate of 50 °C / min and maintain for 0.5 min. Subsequently, naturally cool to obtain pyrolytic carbon black. Perform a sessile drop method static contact angle test on the obtained pyrolytic carbon black. The time required for water to completely immerse in the pyrolytic carbon black prepared by this method is 12 s.

[0029] Example 2

[0030] (1) Weigh 5 g of waste tire particles as reaction raw materials and place them in a silicon nitride crucible. Under a nitrogen atmosphere, slowly heat from room temperature to 400 °C at a heating rate of 15 °C / min and maintain for 6 min; then quickly heat to 800 °C at a heating rate of 40 °C / min and maintain for 2 min. Subsequently, perform water spraying to quickly cool the silicon nitride crucible and the product. Finally, place the silicon nitride crucible and the product carbon black in a vacuum drying oven and bake at 100 °C for 24 h to obtain pyrolytic carbon black.

[0031] (2) Perform a sessile drop method static contact angle test on the pyrolytic carbon black obtained in step (1). The results show that the time for water to completely immerse in the pyrolytic carbon black prepared by this method is 9 s.

[0032] Example 3

[0033] (1) Weigh 6 g of waste tire particles as reaction raw materials and place them in a silicon nitride crucible. Under a nitrogen atmosphere, slowly heat from room temperature to 450 °C at a heating rate of 25 °C / min and maintain for 7 min; then quickly heat to 850 °C at a heating rate of 45 °C / min and maintain for 1 min. Subsequently, perform rapid cooling of the silicon nitride crucible and the product by water spraying. Finally, place the silicon nitride crucible and the product carbon black in a vacuum drying oven and bake at 100 °C for 24 h to obtain pyrolytic carbon black.

[0034] (2) Perform sessile drop method static contact angle measurement on the pyrolytic carbon black obtained in step (1). The results show that the time for water to completely immerse into the pyrolytic carbon black prepared by this method is 11 s.

[0035] Example 4

[0036] (1) Weigh 3 g of waste tire particles as reaction raw materials and place them in a silicon nitride crucible. Under a nitrogen atmosphere, slowly heat from room temperature to 350 °C at a heating rate of 10 °C / min and maintain for 8 min; then quickly heat to 650 °C at a heating rate of 60 °C / min and maintain for 1 min. Subsequently, perform rapid cooling of the silicon nitride crucible and the product by water spraying. Finally, place the silicon nitride crucible and the product carbon black in a vacuum drying oven and bake at 100 °C for 24 h to obtain pyrolytic carbon black.

[0037] (2) Perform sessile drop method static contact angle measurement on the pyrolytic carbon black obtained in step (1). The results show that the time for water to completely immerse into the pyrolytic carbon black prepared by this method is 10 s.

[0038] Example 5

[0039] (1) Weigh 4 g of waste tire particles as reaction raw materials and place them in a silicon nitride crucible. Under a nitrogen atmosphere, slowly heat from room temperature to 500 °C at a heating rate of 30 °C / min and maintain for 5 min; then quickly heat to 700 °C at a heating rate of 55 °C / min and maintain for 1.5 min. Subsequently, perform rapid cooling of the silicon nitride crucible and the product by water spraying. Finally, place the silicon nitride crucible and the product carbon black in a vacuum drying oven and bake at 100 °C for 24 h to obtain pyrolytic carbon black.

[0040] (2) Perform sessile drop method static contact angle measurement on the pyrolytic carbon black obtained in step (1). The results show that the time for water to completely immerse into the pyrolytic carbon black prepared by this method is 8 s.

[0041] Example 6

[0042] (1) Weigh 2 g of waste tire particles as reaction raw materials and place them in a silicon nitride crucible. Under a nitrogen atmosphere, slowly heat from room temperature to 550 °C at a heating rate of 30 °C / min and maintain for 8 min; then quickly heat to 680 °C at a heating rate of 55 °C / min and maintain for 2 min. Subsequently, perform water spray cooling on the silicon nitride crucible and the product quickly. Finally, place the silicon nitride crucible and the product carbon black in a vacuum drying oven and bake at 100 °C for 24 h to obtain pyrolytic carbon black.

[0043] (2) Perform sessile drop method static contact angle measurement on the pyrolytic carbon black obtained in step (1). The results show that the time for water to completely immerse into the pyrolytic carbon black prepared by this method is 7 s.

[0044] Example 7

[0045] (1) Weigh 4.5 g of waste tire particles as reaction raw materials and place them in a silicon nitride crucible. Under a nitrogen atmosphere, slowly heat from room temperature to 480 °C at a heating rate of 28 °C / min and maintain for 6 min; then quickly heat to 720 °C at a heating rate of 40 °C / min and maintain for 1 min. Subsequently, perform water spray cooling on the silicon nitride crucible and the product quickly. Finally, place the silicon nitride crucible and the product carbon black in a vacuum drying oven and bake at 100 °C for 24 h to obtain pyrolytic carbon black.

[0046] (2) Perform sessile drop method static contact angle measurement on the pyrolytic carbon black obtained in step (1). The results show that the time for water to completely immerse into the pyrolytic carbon black prepared by this method is 8 s.

Claims

1. A method for preparing pyrolytic carbon black by stepwise pyrolysis of waste tires, characterized in that, the method comprises the following steps: (1) Under an inert atmosphere, the waste tire particles are slowly heated from room temperature to 350 - 550 °C at a heating rate of 10 - 30 °C / min and maintained at this temperature for 5 - 8 min; (2) Then the product of step (1) is rapidly heated to 650 - 850 °C at a heating rate of 40 - 60 °C / min and maintained at this temperature for 0.5 - 2 min; (3) The pyrolysis product of step (2) is rapidly cooled to room temperature by spraying water on the product and its carrier, and pyrolytic carbon black is obtained after vacuum drying at 100 °C for 20 - 24 h.

2. The method according to claim 1, characterized in that, in step (1), the inert gas is selected from one of nitrogen, argon, and helium.

3. The method according to claim 1, characterized in that, in step (1), the waste tire particles are solid particles with a particle size of 2 - 3 mm prepared by cleaning, magnetic separation, and crushing of scrapped automobile tires.

4. The method according to claim 1, characterized in that, in step (1), the waste tire particles are slowly heated from room temperature to 400 - 500 °C at a heating rate of 20 - 30 °C / min and maintained at this temperature for 7 - 8 min.

5. The method according to claim 1, characterized in that, in step (2), the product of step (1) is rapidly heated to 680 - 750 °C at a heating rate of 50 - 55 °C / min and maintained at this temperature for 0.5 - 1 min.

6. The method according to claim 1, characterized in that, in step (3), deionized water is used for the water spraying.

7. The method according to claim 1, characterized in that, in step (3), the carrier is a silicon nitride crucible.

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