| Companied with the development of auto industry, the problem caused by waste tires has become a sever social and environmental issue. It is the key point to find a way disposing them energy-savingly, efficiently and environmental-friendly. By pyrolysis, waste tires can get degraded into gas, liquid and solid products that can be used in various applications, making it a good choice for the treatment of waste tires.This paper investigates the microwave pyrolysis of waste tires. The polar rubber and carbon black contained inside the tires are good microwave absorbent that can make the temperature of feedstock rise very fast. In turns the pyrolysis progress can be shorten. The steel wires inside of tires can also react with microwave to become heating point, stimulating the pyrolysis. Furthermore, there are only a few essays concerning about this issue, making this article rather a prospective study.Firstly, experiments are done to investigate temperature-rise and weight-loss during the pyrolysis. The pyrolysis of rubber powder can divided into three stage. In the first stage, temperature rise from25℃to125℃slowly. Water is separated out from rubber powder. Weight-loss in this period is less than1%. The second stage can finish within2-3min. Temperature rise from125℃to350℃quickly. Non-compressible gas and oil vapour are generated in this period. Weight-loss is about45-50%. In the last stage, temperature keeps among300-350℃and no further weight-loss takes place. A high microwave power can bring forward the pyrolysis. For example, it takes10min for weight-loss to reach to50%when power of700W is applied, but it is21min when300W is applied.Secondly the pyrolytic products are investigated systemically. For gas products, H2, CH4, and CO are the main compositions, accounting for nearly90vol%. In liquid products, the main compositions are benzene, toluene, o-xylene, m-xylene and limonene. The concentration of limonene is the highest that can reach to10wt%, much higher than that of traditional pyrolysis. But when a higher power is applied, the concentration of limonene decreases. For pyrolytic char, the ratio of different elements hardly change when different powers are applied. C is the main element taking place about78wt%.95wt%of total S remains in solid pyrolytic product. Although the specific pore surface area of pyrolytic char is only about50m2/g, it may be a better absorbent than commercial activated carbon in absorbing larger molecules.At last microwave pyrolysis experiments are done with steel wires inside of the feedstock to investigate how mental will influence the pyrolysis. By comparing the results of non-steel pyrolysis and the ones with steel under different power, it is found the steel wire can make pyrolysis possible under a low power. For example when adding steel wire into feedstock under500W, the weight-loss can reach the level that under700W and the pyrolysis can finish completely. The position of steel wire in feedstock and its adding ratio can also influence the result with some regular. It is found a lower adding ratio(1:10) and the position of upright in the feedstock are more effectively to stimulate pyrolysis. The fluid of carrier gas can change the ratio of gas and liquid products. When a higher fluid is applied, there are more liquid products and less gas products. |
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