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152 Advances in Eco-Fuels for a Sustainable Environment

reduces the viscosity of the pyrolysis oil being produced of the pyrolysis oil has a low
hydrocarbon chain length. Temperature plays a primary role in the variation of the
viscosity of the pyrolysis oil produced. If the temperature rose over 350 °C, the vis-
cosity of the pyrolysis fuel increased due to the evaporation of the heavier and longer
hydrocarbon chain in the engine waste oil.

5.16 Conclusions

The following conclusions were drawn from this investigation.

The microwave pyrolysis with SiC was an energy-efficient process compared to the elec-
trical pyrolysis and microwave pyrolysis without a microwave absorber.
The time taken for reaching pyrolysis temperature in microwave pyrolysis without an
absorber was 4.7% and 9.5% faster than electrical pyrolysis. In microwave pyrolysis with
an absorber, it was 61.9% and 71.4% faster than electrical pyrolysis.
Microwave-assisted pyrolysis with silicon carbide susceptors with 1.1 and 2.2kW consumes
32% and 38% less specific power consumption value compared to electrical pyrolysis.
The optimum temperature was found in the range of 350–400°C for microwave pyrolysis
with a nitrogen flow rate of 2–3L/min. The maximum pyrolysis oil obtained in the micro-
wave pyrolysis with 1.1 and 2.2kW power was 3% and 10% less than electrical pyrolysis,
respectively.
The microwave with 1.1kW power was more suitable compared to the microwave with
2.2kW power rating.
Higher heating rate increases the noncondensable gas yield and decreases the pyrolysis oil
yield and char yield due to secondary cracking and higher kinetic energy.
The GC-MS results indicate that the pyrolysis oil obtained by the electrical and microwave
pyrolysis was nearly the same alkane percentage, but alkenes and other elements are slightly
higher in the microwave pyrolysis oil.
FT-IR spectrum confirmed the same alkane present in the electrical and microwave pyrol-
ysis processes.
The calorific value obtained in the microwave pyrolysis with 2.2kW power was 2% higher
than electrical pyrolysis.
The study recommended for the future research can refer to different hazardous
wastes, which result from a microwave pyrolysis operated by solar energy, in order
to achieve a maximum energy recovery during the pyrolysis process. Extensive
research will be carried out on microwave susceptors to find the suitable and highest
efficiency microwave absorber for the pyrolysis process. Microwave susceptors pre-
pared with the addition of different ceramics and metals will enhance the process effi-
ciency and fuel quality. The future research will be focused on better utilization of
pyrolysis yields such as liquid, char, and noncondensable gases for various applica-
tions to increase the efficiency.

Acknowledgments

The authors would like to acknowledge the Department of Science and Technology—Science
and Engineering Research Board (DST-SERB) for providing valuable support and sanctioning