16th International Conference
on Microwave and High Frequency Heating

18-21 September 2017, Delft, The Netherlands
13:30   Break - Posters
DESIGN OF A NEW SYSTEM FOR MEASURING THE COMPLEX PERMITTIVITY OF CHEMICAL SOLUTION
Yang Yang, Kama Huang
Abstract: A cylindrical cavity for permittivity measurement is designed (as shown in Fig. 1), and it was made into a whole system with the vector network analyze. The FDTD (finite-difference time-domain) and neural network algorithm is used to calculate the dielectric constant of chemical solution at the frequency of 2.45GHz. The real part and loss angle tangent of permittivity is put into a same neural network, which improves the accuracy of calculation. The solution of known permittivity is used to correct calculation error of the neural network and improve the accuracy of inversion. Matlab is used to realize the serial data communication between the device and the computer. In addition, we also design the man-machine interface to make the system easy to operate and convenient to use. As shown in Fig. 2, the computational results are in good agreement with the experimental results, where the maximum relative error is less than 10% and the average error is 5%, which means the proposed system can serve as an effective tool for measuring the complex permittivity of chemical solution.
A SIMPLE METHOD TO MEASURE COMPLEX PERMITTIVITY FOR VARIABLE TEMPERATURE MATERIALS
Xiaoqing Yang, Zhanwei Liu, Yang Yin
Abstract: Complex permittivity (CP) measurement of variable-temperature is difficult and complicated in microwave heating applications. A simple and convenient method was employed for measuring CP of material over variable temperature in the paper. This method utilized experimental temperature rising of samples to obtain the function between CP and temperature by genetic algorithm (GA). We choose agar solution (sample) and Yangshao reactor (microwave heating system) validated the reliability and feasibility of this method, which showed the accuracy.
VEGETABLE BLANCHING
David Mclean, Joel Mclean
Abstract: Extensive microwave blanching trials were undertaken on corn, carrots and broccoli. These trials confirmed, by sensory and textural analysis, that microwave blanching returned superior quality vegetables than conventional techniques. The trials demonstrated that complete enzyme inactivation was possible using microwave energy in times between 10 and 30 seconds, and established that no dwell time was required to achieve this. Inactivation was achieved at temperatures around 80° C. It was found during trial work that a “hybrid” system which utilized microwave energy with some additional steam achieved the best quality vegetables with the most uniform heat distribution. The trials were conducted on a scaled version of a potential commercial system to ensure smooth up-scaling.
MICROWAVE WOOD MODIFICATION APPLICATION FOR NEW MATERIAL PRODUCTION (TECHNICAL-ECONOMIC ASSESSMENT)
Alexandra Leshchinskaya
Abstract: MICROWAVE WOOD MODIFICATION APPLICATION FOR NEW MATERIAL PRODUCTION (TECHNICAL-ECONOMIC ASSESSMENT) A. Leshchinskaya.. National University of Science and Technology "MISIS", 4 Leninskiy Pr., Moscow, 119049 Russia. E-mail: alixfl@mail.ru Keywords: microwave wood modification, Torgvin, Vintorg material, specific cost. Many wood species have low mechanical properties, which limit their use in industry. One of the plantation fast growing hardwood species Paulownia (Paulownia fortunei) has low density and low strength properties. These limit the industrial use of this species. High intensity microwave (MW) modification converts Paulownia wood to highly porous material “Torgvin”, which is used for manufacturing new composite material “Vintorg” with high mechanical and physical properties. The technology of the new material manufacturing includes MW wood modification, drying, impregnation by resin, hot pressing, and finishing. Economic study of the Vintorg manufacturing process in mills with output range 6300 to 18600 m3/year showed required capital costs from US$3,982,000 to $7,782,000. Estimated Vintorg production costs fluctuate in the range from US$255 to $448/m3 depending on mill output and resin costs. MW processing costs comprises 24 to 34% of the total specific production costs. A significant advantage of Vintorg production process is an opportunity to use it for low grade timber and in small scale mills. The specific costs of Vintorg manufacturing are acceptable for industry and economic advantages provide good opportunities for commercialization of the new MW technology.
SIMULATION OF RF FIELDS FOR WOOD GLUING APPLICATIONS
Nyle Parker
Abstract: Dielectric heating has clearly shown itself to be beneficial to the timber industry due to the benefits obtained from volumetric heating [1]. A RF dual electrode induction heating system is numerically modelled using the FEA package COMSOL to determine the heating rate and variation within a material load. The important effect of the material loading of the applicator and its interactions with the established fields is demonstrated. A comparison is then established between the simulation and physical process. Field uniformity is very important to establish uniform heating of a material in batch processing. The applicator establishes a strong electric field between two separate electrodes and a ground plate. 15kV is applied to each electrode at 13.56 MHz by a RF Generator. Dielectric heating is observed more readily at the glue lines, demonstrating the higher dielectric loss of the material. Comparison between the simulated electric field interaction with the material and IR photos of actual heating show the variation of heating and the effect of material loading of the field. Strategies to improve uniformity will be posed. Additionally material permittivities are measured using the broad band coaxial probe method and included in the electromagnetic model to yield a well modelled problem.
IMPROVEMENT OF HEATING PERFORMANCE VIA THE COMBINATION OF TURNTABLE ROTATING AND FREQUENCY SELECTING
Zhengming Tang, Tao Hong, Yinghong Dr Liao, Huacheng Zhu, Kama Huang
Abstract: Microwave heating has attracted extensive attention of the public because of its convenience and high efficiency. However, it usually leads to non-uniform temperatures. In this paper, a novel combination method of rotating turntable and optimal selected frequencies is proposed to improve the heating performance. On the basis of integral equation theory, the heating uniformity on small changes in microwave frequency is studied [1].The results show that the heating performance depends highly on microwave frequencies. Due to the fact that some frequencies should contribute more to improving heating performance than others and rotating can improve heating uniformity [2], the rotating turntable and optimal selected frequencies are both employed in the heating process. The Finite Element Method (FEM) is used to simulate the heating process and assess the performance. It shows that the proposed method can improve heating uniformity and heating efficiency effectively, which is also verified by experiment.
RADIO-FREQUENCY HEATING AS AN EFFICIENT OPTION FOR PVC-P COATINGS
Andreas Lehm, Bernd Morgenstern, Michael Stoll
Abstract: The use of dielectric heating grants a lot of advantages which the PVC-P processing and coating industries have not explored yet. So radio-frequency processes are efficient in heating through dielectric loss all over the substrate’s volume and can be much faster than conventional processes used in common PVC-P processing (conduction and convection). Results obtained within a FILK research project by using a 50 Ω solid state generator, a frequency at 27.12 MHz and a stray field applicator, as it is recommended for flat products [1], proof an efficient usage of radio-frequency heating for processing PVC-P coatings. Furthermore, it was shown that the dielectric heating of PVC-P leads to a perfect fusion of compact and foamed films, composites and foamed artificial leather. The results of the mechanical tests shown in Table 1 confirm this. So all in all there will be new fields for applications using radio-frequency heating for processing plastisols to floor coverings, interior of automobiles or wallpapers and many more. The advantages are of the much shorter process time (app. 50 % faster), the need of less energy (up to 86 % electrical) or the much less needed space for radio-frequency applicators. These facts may increase the industries’ productivity, product’s quality and energy saving potential compared to other heating processes.
INFLUENCE OF MICROWAVE HEATING ON THE PROPERTIES OF GLYCEROL
Hui Shang, Hanmo Wang, Wenhui Zhang
Abstract: Glycerol and glycerol-water system were investigated with external electromagnetic field operated at 2.45GHz. Different microwave power levels, treatment time were applied to glycerol and glycerol-water system in the laboratory work. It was found that after microwave treatment, the viscosity of glycerol increased especially at high microwave power level. From the analysis of infrared, the formation of hydrogen bond was found after microwave treatment. For the mixture of glycerol and water, the dielectric properties of the solution extremely changed compared to pure glycerol and pure water due to the formation of hydrogen bond, with the increase of microwave power, the energy input to the solution increases, thus lead to severe molecular motion and the dielectric properties can be improved to some extent, whereas for more microwave energy input into the system, the hydrogen bond can be destroyed, thus making the whole system’s polarity decrease.
INFLUENCE OF WATER CONTENT ON THE VISCOSITY REDUCTION OF HEAVY CRUDE OIL VIA MICROWAVE IRRADIATION
Hui Shang, Lu Liu, Tianye Wang, Wenhui Zhang
Abstract: With the trend of higher yield of heavy crude oil, transporting and refining this kind of oil becomes the key issue in oil industry due to the high viscosity and bad fluidity. Microwave heating can change crude oil's properties according to reported researches due to its special mechanism. Liaohe heavy oil was investigated for this purpose. Samples were prepared by adding different amount of water using emulsification machine. It was found that the oil viscosity can be highly reduced at higher water content via microwave irradiation, whilst for the fresh oil samples, the viscosity increased after microwave treating. It is clear that for the crude oil with additional water inside, when the water and oil form O/W emulsion, microwave can highly reduce the system’s viscosity, however, if the formation of water and oil as W/O, the viscosity of the oil will increase after microwave treatment.
STUDIES ON MICROWAVE CHEMICAL PROCESSES TOWARDS PRODUCTION IN CHEMICAL INDUSTRY
Takeko Matsumura
Abstract: Various microwave reactions are common in laboratory. However, there are significant hurdles to overcom to apply microwave technic in Large scale microwave synthesis of metal oxide and metal complexes are examined. Microwave synthesis of ZnO was carried out with various microwave reactors, 50ml, 2l, and 20l with 2.45 GHz microwave frequency. The result is shown in Fig.1and Table1. Fig. 1. Scale up microwave synthesis of ZnO (A):20l Microwave Reactor, (B):Profile of microwave reaction, C: Product References 1)Hasegawa, N., T. Mitani, N. Shinohara, M. Daidai, Y. Katsura, H. Sego, T. Watanabe, IEICE Transactions on Electronics E97.C, 986-993, 2014. 2)A. Kaiho, M. Kogo, R. Sakai, K. Saito, T. Watanabe, Green Chem., 17, 2780-2783, 2015.
STUDY ON MICROWAVE REACTION OF PLATINUM METAL COMPLEXES, DIELECTRIC PROPERTIES, MICROWAVE REACTORS, AND MOLECULAR REACTION MECHANISM WITH DENSITY FUNCTION THEORY.
Takeko Matsumura
Abstract: Platinum metal complexes are important functional materials as phosphor illuminants. These metals, rarely occurring in nature, are very hard against chemical reaction. That means, it is hard process to dissociate M-Cl bond of MCl3 (M; Ir or Ru) to form new N-M or C-M bonds with organic ligands. Microwave dielectric effect was focused to dielectric property of reaction media. The dielectric loss factor, ε”, and conductivity, σ, of metal ions take important roles of microwave thermal effect. The microwave chemical effect on these platinum metal complexes are discussed in view of molecular orbital theory with density function theory. Fig.1. Real-time monitoring of MW synthesis for Ru(II) complex References 1. T.Matsumura-Inoue,M.Tanabe, Chem. Lett.,1994,443 2. T. Matsumura-Inoue, Y. Yamamoto, N. Yoshikawa, M. Terashima, Y. Yoshida, A. Fujii , K. Yoshino, Optical Materials, ,27(2004)187-191
EVALUATION OF MICROWAVE SUSCEPTORS PERFORMANCE THROUGH IN SITU DIELECTRIC CHARACTERIZATION UP TO 1100ºC
Beatriz García-Baños, José D. Gutiérrez, Julian Jimenez-Reinosa, Jose F. Fernández
Abstract: It is well-known that the heating process of materials with low microwave absorption (i.e. quartz) can be improved with the addition of microwave susceptors [1]. Candidate materials to be used as susceptors are typically selected depending on their dielectric properties (mainly their loss factor) at room temperature. However, big changes are observed in their loss factor as temperature increases. Due to these changes, some susceptors are better suited to certain heating processes than others, leading to more efficient processes and/or higher quality products. Thus, the dielectric characterization of microwave susceptors with temperature gives important information for the determination of the best candidate depending on the desired heating process. For example, susceptors that perform very well for slow heating rates can be distinguished from other susceptors more adequate for very fast heating processes. However, there is a lack of dielectric characterization data under microwave heating at high temperature [2]. In this work, the dielectric properties of quartz samples with a small quantity (1%) of different additives (graphite, potassic humate, carbon black, etc.) have been measured with temperature up to >1000ºC [3]. The results show how the heating processes are very different depending on the additive, and their use as susceptors is assessed.
DEVELOPMENT OF HIGH-TEMPERATURE MULTI-MAGNETRON MICROWAVE FURNACE FOR PREPARATION OF HIGH EFFICIENCY THERMOELECTRIC MATERIALS
Direk Boonthum, Mudtorlep Nisoa, Chesta Ruttanapun
Abstract: In this paper, we have successfully developed multi-magnetron high-temperature microwave furnace for heating materials at high rate and high temperature more than 1000 °C. The development of microwave were carried out by modelling, design, fabrication and experimental testing. Distribution of electric field in the waveguide and in the cavity were calculated by Comsol multi-physics, therefore furnace cavity was optimized to be 28x28x28 cm3. The waveguides and magnetrons are mounted on the four sides of the cavity. Each two waveguides on the opposite sides are placed at 90 degree to each other. Therefore, electric fields were maximized at the center of the cavity and minimized in the waveguides. To suppress the microwave leakage within safety standards, choke parameters are 2.7mm < d < 3.7 mm, 0 < h < 7.5 mm, w > 6 mm. The experimental heating of SIC crucible in the furnace have shown that crucible’s temperature can be increased from room temperature to 1000o C within only about a few minutes. Synthesis of thermoelectric Al-doped ZnO in a microwave furnace took less than 20 times the time of a conventional furnace, and the electric power of Al-doped ZnO, synthesized in the microwave furnace, was higher. Heat energy in the furnace depends on the number of operating magnetrons.
THE CAVITY PERTURBATION METHOD: IMPLEMENTATION LIMITS FOR “CLASSICAL” AND “ADVANCDED” NUMERICAL APPROACHES
Guido Link, John Jelonnek
Abstract: The cavity perturbation technique, whose theoretical background was given by Bethe and Schwinger in 1943 [1], is intensively used for more than 50 years for materials dielectric characterization. Till now, it is one of most convenient and precise methods for permittivity measurements. The implementation of this analytical method, however, is limited to material samples much smaller than the resonator itself. This originates from the fundamental condition on a negligible perturbation of the overall field pattern in the cavity. Moreover, it imposes the restrictions on the maximal loss factor of tested material. With the development of powerful computers and improved numerical algorithms, nowadays many electromagnetic problems can be solved numerically. In particular, an application of the numerical modelling to the cavity perturbation problem allows to extend the “classical” limits imposed on the geometry and permittivity of measured material samples. By solving the inverse problem the measurement system may be pre-calibrated in that way that the resonance frequency and the quality factor are directly converted into the complex permittivity of the material [2]. This presentation focuses on the aspects of the overall applicability, limits and uncertainties for the dielectric characterization based on the numerically assisted cavity perturbation technique.
MEASUREMENT OF DIELECTRIC PERMITTIVITY OF VERMICULITE AT HIGH TEMPERATURA USING A OPEN-ENDED COAXIL PROBE
João Rubens Alves Zacarias, Fabricio Ferreria Batista, Raymundo de Amorim Junior, Glauco Fontgalland
Abstract: In microwave heating processes is always important to know the dielectric permittivity value of the material to be heated. There are already study about the measurement of the dielectric permittivity of the vermiculite, for the frequency of 2.45 GHz, using the transmission line method in a microstrip line [1]. However, it is necessary to observe the behavior of the dielectric permittivity for high temperature in the frequency of 2.45 GHz. In this work, the measurement of the dielectric permittivity is made using a open-ended coaxial probe. The open-ended coaxial probe uses the reflection method to characterize the dielectric permittivity of the material [2]. The sample vermiculite sample is heated in a convection oven, and measurements will be taken afterwards. The vermiculite sample is heated from room temperature (25 ºC) to approximately 200 ºC. the measurement of the dielectric permittivity is done in a range of 25 ºC. Figure 1 shows the permittivity measurement in relation to temperature. The results obtained are important to optimize the microwave heating of vermiculite.
CANNABIS SATIVA ECOSUSTAINABLE MICROWAVE ASSISTED EXTRACTION FOR COSMETIC AND PHARMACEUTICAL APPLICATIONS
Carla Villa, Eleonora Russo
Abstract: Hemp (Cannabis sativa L.) is a C3 crop native to Central-Northeast Asia but it is well adapted to the soil and climate in Europe and it can generally be grown without the aid of chemical crop protection agents. Despite the great interest on Cannabis for its main cannabinoid tetrahydrocannabinol (THC), the fiber grade (with a very low content of THC) is cultivated for industrial purposes to manufacture foodstuffs and cosmetics. Taking into account these statements and our interest in green microwave extractions, the aim of this work was the development of new ecofriendly methods to obtain industrial hemp extracts of cosmetic and pharmaceutical interest. Different solventless microwave extractions, such as SFME (solvent-free microwave extraction), MHG (microwave hydro-diffusion and gravity) and innovative microwave extractions with alternative green solvents were performed. The results were compared to conventional methods in terms of efficiency and quality. The microwave applicator consists of a multipurpose prototype equipped with two optical fibers and a control unit which allows managing different parameters such as power and temperature. The furnace presents two holes on the walls allowing its use for several applications. The green extracts were characterized and evaluated for their biological potential and safety.
MICROWAVE-ASSISTED SYNTHESIS OF ZnSe NANOPARTICLES WITH HIGH LUMINESCENCE
Katarzyna Matras-Postolek, Svitlana Sovinska, Adam Zaba, Dariusz Bogdal
Abstract: Keywords: ZnSe nanoparticles, microwave irradiation, high quantum yield In the last few years inorganic nanocrystals (NCs) due to tunable luminescence and absorption spectra are attracting much interest in various fields of science and engineering, such as light emitting devices, photovoltaics and catalysis [1]. Zinc selenide (ZnSe) NCs belonging to II-VI group with a wide band-gap energy of 2.8 eV is one of promising materials with high luminescence in blue-green region [2]. In this work, zinc selenide nanoparticles were synthesized by microwave technique using zinc stearate, and selenourea as a precursors and dimethylformamide (DMF) as a solvent. Synthesis was carried out in the temperature range of 150 to 210°C and variable molar composition of zinc to selenium. The obtained nanomaterials were characterized with different techniques including XRD, EDX and TEM spectroscopy. Nanoparticles characterized by small size about 10 nm and intensive blue emission with a maximum band at 435 nm. This work was financially supported by National Centre for Research and Development under Lider Program, contract no. LIDER/009/185/L-5/13/NCBR/2014. References 1. Talapin D. V., Lee J. S., Kovalenko M. V., Shevchenko E. V., Chemical Reviews, 2010, 110, 389–458. 2. Hao L., Bai Z., Huang Z., Liao S., Zhang Z., Applied Physics A, 2016, 122, 967.
MICROWAVE DRIVEN PLASMA GASIFIER-SOLID OXIDE FUEL CELL SYSTEM FOR HUMAN WASTE PROCESSING
P Aravind, Guido Sturm, J Diehl, Georgios Stefanidis, Wieberen de Jong
Abstract: A community based sanitation system that processes human waste at an omnigasification plant is presented. The concept aims to destroy pathogens and generate energy from waste. The waste is dried, converted to syngas in a microwave assisted plasma gasifier and the gas produced is fed into a solid oxide fuel cell to produce electric power. In addition, a front-end for the process has also been developed with the design of a water diverting toilet and a community sanitation centre as well as the recognition of women empowerment, branding and sustainable business modeling. Plasma gasification has been demonstrated to be feasible at the small scale required for the application and the concept of energy recovery has been proven by integrating a gasifier, a gas cleaning unit, and SOFC test station. With thermodynamic calculations, it is shown that such a plant can be energy self-sufficient