Microwave pyrolysis commercial processes

Microwave pyrolysis of plastic (or plastic-containing) wastes is a relatively new area that has been studied only in the last decade or so. Because of this, there is considerably less information in the scientific literature compared with other approaches to the pyrolysis of plastics. Also, there is a substantial amount of information contained in patents, which suggests that the development of microwave pyrolytic processes has been more intuitive rather than strictly scientific. This chapter will summarize the developments in this area that are described both in scientific and commercial literature. 

Mixing carbon with microwave-transparent materials, particularly plastics, and subjecting the mix to microwave radiation, is a very efficient way to heat up such materials, increasing their bulk temperature to a point where pyrolysis occurs. In this chapter the main characteristics of a number of microwave pyrolysis processes, for plastics and other materials, have been introduced, showing that these processes combine the advantages of microwave heating with the commercial and environmental opportunities intrinsic to the pyrolysis of wastes. 

Scientific studies have found that the differences between microwave and conventional pyrolysis go beyond the obvious difference in the source of heat. Other differences arise from the very high rates of heat transfer from the microwave-absorbent to the waste, the amount heat received by the primary pyrolytic products once they leave the absorbent bed and the highly reducing environment. These three aspects have been shown to have an important effect in the final products since they modify the extent of secondary and tertiary reactions. Moreover, the scientific studies have shown that a nonthermal microwave effect in these processes is unlikely to exist. Tests have showed the potential of the microwave-induced pyrolysis process for the treatment of real plastic-containing wastes and it is believed that a commercial process could be developed, for example, to recover clean aluminium from plastic/aluminium laminates. Other materials, in particular tyres, coal and medical wastes are very good candidates to be treated/recycled using microwave pyrolysis and there have been a considerable number patents filed with this goal in mind. 

The research and development carried out so far in has shown that, even though microwave pyrolysis will not be the solution to the whole problem of plastic disposal, it certainly has the potential to help reducing the number of resources currently committed to landfill. Evidence of this potential is the number of companies interested in the development of the process and that are currently active, trying to commercialize proprietary microwave pyrolysis processes. However, this chapter has shown that in order to accomplish a more widespread utilization of this kind of processes a better communication between the commercial and scientific communities is needed. The companies with their patents would be able provide many innovative ideas that may help to increase processes efficiency and the scientific community would provide explanations for the improvements, that would in turn generate even more ideas in a self-sustaining cycle of improvement. 

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