Microwave Heating Applied to Pyrolysis

Abstract

The use of microwaves for heating is well established in society, being used in domestic and some industrial processes. However, there is potential for this technology to be introduced and applied to many other industrial heating processes, which offers unique advantages not attained with conventional heating. In this sense, microwave technology is being explored as one method to assist in waste management. Currently, significant quantities of hazardous wastes are generated from a multitude of products and processes. The increase in both the quantity and of the diversity of waste production is now posing significant problems for their effective management. New technologies are being investigated to develop systems which shall support the safe handling, transportation, storage, disposal and destruction of the hazardous constituents of this waste. The recent interest in microwave technologies appears to offer the best solution to waste management, whereby a variety of microwave systems can be designed, developed and tailored to process many waste products. It is possible that microwave technologies shall provide for: (i) a reduction in waste volume, (ii) rapid heating, (iii) selective heating, (iv) enhanced chemical reactivity, (v) the ability to treat waste in-situ, (vi) rapid and flexible processes that can also be controlled remotely, (vii) ease of control, (viii) energy savings, (ix) overall cost effectiveness, (x) portability of equipment and processes, (xi) cleaner energy source compared to some more conventional systems, etc. From existing processes for the harnessing of energy and raw materials from waste, thermochemical conversion routes are suitable candidates for the application of microwave technology. One of the thermochemical processes which is rapidly gaining in importance in this field is pyrolysis. This process not only allows for higher energy recovery from the waste, but it also generates a wide spectrum of products. Hitherto, most published work on the pyrolysis process has dealt with conventional heating systems, although recent interest in microwave-assisted pyrolysis (MP) has highlighted its unique advantages, not within the scope of traditional methods. The aim of this chapter is to emphasize the principles of MP and to show recent research on the application of this technology to waste treatment. As an introduction to the topic, a brief background on the pyrolysis process and the fundamentals of microwave irradiation as an energy source are presented.