Chemical Engineering for Improvement of the Efficiency of Microwave Energy Use in Processing of Plant Biomass

Abstract

Combined coaxial-circular waveguide equipped with protective module allowing the transmission of microwave energy of three magnetrons with the output of 0.9 kW per each into the pressurized reaction chamber and capable of operating at temperatures of up to 250 °C and a pressure of up to 10 bars was designed and tested. Choke flange junction of the waveguide sections was used instead of contact flange connection. The developed waveguide construction allows to place the radio transparent partition inside the free space volume of a choke flange junction performing protection of emitters and summing of microwave energy of three magnetrons with an efficiency close to 100% that was proven by tests with fresh water as a microwave energy absorber. The extraction set-up equipped with the above-mentioned waveguide has demonstrated the stable and safety operation of the transmitting block and the accurate automatic control of the temperature and pressure inside the reaction chamber in the presence of a strong electromagnetic field. The construction of the microwave extraction set-up allows to use the impact of the combination of temperature and pressure on the cell wall, promoting the high rate isolation of secondary metabolites from biomass that was demonstrated by water extraction of black alder bark.