16th International Conference
on Microwave and High Frequency Heating

18-21 September 2017, Delft, The Netherlands
11:00   Biomass and waste processing
Chair: Ioan CALINESCU
11:00
15 mins
BIO-OIL FROM MICROWAVE ASSISTED PYROLYSIS OF SEWAGE BIOSOLIDS
Graham Brodie, Alex Duan, Augustine Doronila
Abstract: Although biosolids, derived from stockpiled sewerage sludge, can be used as a nutrient source, pyrolysis of the biosolids yields: syngas; bio-oil; and biochar. The high processing temperature also ensures the products are sterile, reducing the hazard which is normally associated with the conventional use of biosolids. Twenty-three, 2 kg samples of biosolids were treated in a 6 kW, multi-magnetron, multi-mode microwave chamber, operating at 2.45 GHz. Because dry biosolids have very low dielectric properties, The samples were thoroughly mixed with 10 % by mass of biochar that was produced from earlier experiments. This biochar acted as a microwave susceptor to initiate the pyrolysis process. Samples were placed into a 4-litre fused quartz crucible with a close fitting lid, to reduce exposure of the sample to oxygen. The resulting pyrolysis oil was analysed in a Varian 3800 Gas Chromtograph with a 30-m long, 0.25-mm diameter fused silica column connected to a Varian 1200L quadrupole Mass Spectrometer operated in 40-500 total ion chromatogram scan mode and a Varian FID. The bio-oil consisted of approximately 40% phenols and carboxylic acids; however, a total of 36 chemical compounds have been identified in the bio-oil, from various mass spectra (One sample’s spectrum shown in Fig. 1).
11:15
15 mins
DIELECTIC HEATING OF A SIC CATALYST FOAM CARRIER USING MICROWAVES AND RADIO WAVES
Markus Kraus, Ulf Trommler, Ingo Hartmann, Michael Frieß, Frank Holzer, Christian Hoyer, Ulf Roland
Abstract: Thanks to new catalysts, off-gas cleaning processes for the removal of hazardous organic compounds from air streams are established and efficient in operation today. Nevertheless, for small biomass furnaces (4 to 100 kW heat output) operating in a non-continuous mode, the initial as well as the burn out combustion phases are still problematic in terms of contaminants in the effluent. Due to low temperatures in the combustion chamber, an incomplete combustion takes place in these phases leading to the emission of CO and volatile organic compounds such as methane. The temperature of the off-gas from boiler systems is solely not sufficient for a thermal activation of the catalyst preventing an adequate post-treatment. In this study, a noble metal catalyst coated on a SiC foam carrier was placed in the off-gas stream and additionally heated either by microwaves (with a frequency of 2.45 GHz) or by radio waves (f = 13.56 MHz). For a pilot-scale experimental setup, the resulting temperature distributions of the catalyst carrier and the heating efficiencies were investigated. Temperature was continuously measured by means of fiber optic sensors and through-glass infrared thermography. Finally, the results were compared with simulation data showing a good correlation (Fig. 1). In principle, both frequencies can be used for heating the catalyst/SiC system. Applying radio waves, the temperature distribution within the catalyst carrier is more homogeneous. Alternatively, the microwave heating leads to higher power input efficiency and, therefore, higher final mean temperatures.
11:30
15 mins
PILOT SCALE APPLICATIONS OF MICROWAVE HEATING FOR SOIL REMEDIATION
Jiří Kroužek, Václav Durďák, Jiří Hendrych, Pavel Mašín, Jiří Sobek, Pavel Spacek, Petra Kubínová
Abstract: Thermal remediation technologies are very efficient methods for the removal of volatile or semi-volatile lipophilic contaminants from solid materials. Compared with inefficient conductive heating, microwaves bring several benefits that could increase the potential for soil remediation which remains low due to high energy and material demands. We developed three different microwave technologies for direct soil heating including vacuum and off-gas treatment system. The innovative configurations were based on material heating in microwave furnace and in-situ heating of contaminated surfaces and subsurface soil environment. Pilot remediation tests were performed at conditions close to full technology application using 6 kW microwave generator, our results confirmed laboratory experiments that had showed high contaminant removal efficiency at relatively low temperatures. Applying open microwave setup for in-situ soil heating, we measured spatial temperature and contaminants mass distribution in soil. The results suggested the principles of microwave heat transfer a decontamination process in soil and they helped pose and validate the numerical model of in-situ microwave soil heating. This research set the limits of technology for full scale application.