Investigation Of Waste Tire Pyrolysis In Rotary Kiln And The Application Project

Generation of used tires is increasing rapidly with economic development. The disposal of used tires has become an important issue worldwide and represents a major environmental problem. Pyrolysis is a process with production of liquid oil, solid char and gas, in addition to the steel chord, all of which have the potential to be recycled. Pyrolysis processing of used tires is considered to be an environmentally acceptable and promising disposal method with its high-energy recovery and low pollution emission.A pilot-scale rotary kiln pyrolyzer was designed and used to study the pysolysis of waste tires. Characteristics and the potential applications of pyrolytic products were investigated. On this basis, the optimization and the flow chart of pyrolysis system were proposed.Pyrolysis temperature plays most important role in pyrolysis reaction. As results of the second reaction of pyrolytic products, the yield of pyrolytic oils and chars decreased, while the pyrolytic gases increased with increasing pyrolytic temperature. Between 500℃ to 550℃, the yield of oils and chars were much higher.The properties of derived oil were studied in detail, and the potential application approaches of oil were recommended. The gross calorific value of oil is high, and the viscidity is relatively low, and the content of sulfur as well as density of oil is high. The weight percentage of the light fraction below 200℃ amounted to as much as 33%~40% and the increasing of pyrolytic temperature helps raise the amount of light fraction. Aromatic substance is the main component of pyrolytic oil, and the percentage of aromatic increased from 40% to 60% with increasing temperature. Aromatic is mainly composed of single-ring aromatic, such as BTX (benzene, toluene, xylene), etc. And then is the 2 to 4 ring PAH, in which the content of naphthyl- and phenanthryl- substance is more than 70%. Aliphatic in light fraction is mainly alkene and cycloalkyl substance. In the fraction above 200癈, alkyl of C13--C32 is the primary component. Some substance contains N, O, S were also examined, such as ketone, nitrile, etc. Pyrolytic oil then can be used as fuel after proper treatment. Furthermore, it may also be used after distillation. Light aromatic can be extracted from light fraction, such as BTX, etc. The fraction above 200℃ may have different application, for example, diesel oil, processing oil for rubber, bitumen, and this fraction can also be used to obtain BTX with cracking processing under hydrogen.The component and porosity of pyrolytic char were investigated. Devolatilizing reaction completed in 500-550℃. The GCV of char is high. Pyrolytic char contains relatively high content of ash and sulfur, which can be remarkably reduced after acid washing. And the sulfur contained in pyrolytic char is over 60% of which exists in raw tires. Carbon black in tire is the main component of pyrolytic char. The surface area of pyrolytic char increased before 550℃, whereas the pore volume and porosity of pyrolytic char increased with pyrolysis temperature and reached the maximum at 550℃, then decreased. The mecro- and macropore structure of char are more developed than micropore, and the mean pore diameter is about 50 nm. Pyrolytic char can be used as fuel, which is close to blind coal. However, the sulfur in char is a disadvantage. Pyrolytic char could be used to produce activated carbon. Both pyrolytic char and the derived activated carbon show excellent aqueous adsorption capacity for organic large molecular waste, such as methylene blue. Furthermore, the pyrolytic char also exhibits satisfying adsorptioncapacity for heavy metal (Pb, Cr). Carbon black is another potential application approach for pyrolytic char. The carbon black properties and vulcanizate characteristics of pyrolytic char is lower than N330 with high performance, but is closed to lower N660, which is commonly used for sidewall or inner tube of tire.Pyrolysis of tire in rotary kiln is governed by movement, heat and mass transfer between solid and gas and kinetic parameters of thermal decompos...