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Associate Professor TSUBAKI Shuntaro and his research group achieved "ultra" rapid pyrolysis of biomass by spatially separating the microwave electric and magnetic fields
-Contributing to the Utilization of Organic Resources such as Lignocellulose and Food Waste-
POINT
- Effective utilization of organic resources such as biomass is desired to achieve a carbon-neutral society.
- "Ultra" rapid pyrolysis of biomass was achieved using microwaves*1 with spatially separated electric and magnetic fields.
- This work contributes to the effective utilization of organic carbon resources such as lignocellulose and food waste.
SUMMARY
Unused biomass resources, such as lignocellulose, agricultural wastes, and food waste are expected as a source to produce biofuel and functional materials. Carbon materials derived from biomass (biochar) can store carbon in solid form for long periods, contributing to decarbonization.
A research group led by Associate Professor TSUBAKI Shuntaro from Kyushu University, Assistant Professor FUKUSHIMA Jun from Tohoku University, Research Department Director YAMAGUCHI Aritomo from the National Institute of Advanced Industrial Science and Technology, Dr. NISHIOKA Masateru from Minamo Co., Ltd., and Professor Emeritus WADA Yuji from Tokyo Institute of Technology (currently Institute of Science Tokyo), has achieved "ultra" rapid pyrolysis of biomass through the microwave heating. Efficient heating of biomass was achieved during pyrolysis by using a semiconductor microwave oscillator*2 and a cavity resonator with separated electric and magnetic fields. As biomass undergoes carbonization, its microwave absorption properties significantly change from dielectric to conductive materials. Carbonized biomass reflects microwaves and generates plasma so that it cannot be heated by dielectric heating*3 under the microwave electric field. Then, an efficient heating of carbonized biomass was enabled by applying inductive heating*4 under a microwave magnetic field. Furthermore, we improved process efficiency by scaling up the cavity resonator using 915 MHz and a flow-type magnetic field heating device operating at 2.45 GHz.
This work was published online in Chemical Engineering Journal (Elsevier) on September 28, 2024 (Japan Standard Time).
Comment from the researcher
Microwave heating is widely used as kitchen microwave ovens, enabling the efficient and rapid heating of materials. Carbon materials are heated extremely quickly by microwaves; however, the suppression of plasma during heating is still challenging. Combining induction heating by magnetic fields, which is also used in IH cooking, successfully suppressed plasma formation and efficiently heated biochar. Additionally, we achieved a continuous magnetic field heating system for heating biochar.
GLOSSARY
*1 Microwaves
Electromagnetic waves with frequencies ranging from 300 MHz to 30 GHz, widely used in telecommunication (such as mobile phones and WiFi) and radar. Specific frequencies such as 2.45 GHz are also used in household microwave ovens and industrial heating devices. However, 915 MHz is effective for scaling up. In addition, lower frequencies below 300 MHz are referred to as radio frequencies.
*2 Semiconductor microwave oscillator
Conventional microwave ovens use magnetron, where the phase, frequency, and output fluctuate over time. On the other hand, solid-state microwave oscillators can precisely control these parameters, enabling delicate microwave heating control that cannot be achieved with conventional microwave ovens. In recent years, high-power semiconductor-based microwave heating devices have been increasingly adopted.
*3 Dielectric Heating
A phenomenon where heating occurs due to the rotational relaxation of dipoles, such as water, under microwave or radio frequency electric fields.
*4 Induction Heating
A phenomenon where a magnetic field induces eddy currents on the surface of conductors such as metals and carbon, resulting in Joule heating.
Paper Information
Publication: Chemical Engineering Journal
Title: Process intensification of the ultra-rapid pyrolysis of bamboo by spatially separated microwave electric and magnetic fields
Authors: Shuntaro Tsubaki, Jun Fukushima, Aritomo Yamaguchi, Masateru Nishioka, Yuji Wada
DOI：10.1016/j.cej.2024.156260
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