Ampere 2019

The 17th International Conference on Microwave and High Frequency Heating: AMPERE 2019 is the largest event in Europe dedicated to scientific and industrial applications of microwave and radiofrequency power systems.

The conference presents the status and trends in the multidisciplinary fields of microwave and radiofrequency heating, dielectric properties, material processing, high power systems and technologies.

The AMPERE conference is a unique opportunity for the presentation and discussion of the most recent advances in the microwave technology and its applications. The conference provides many opportunities to researchers and engineers from academia and industry to exchange innovative ideas, networking, discuss collaborations and to meet with international experts in a wide variety of specialities of microwave and high frequency technologies at both scientific and industrial scale.

URI permanente para esta colecciónhttps://riunet.upv.es/handle/10251/129319

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Elucidation of electromagnetic wave effect and outgoing of future trend in microwave Chemistry and Biology
(Editorial Universitat Politècnica de València, 2019-10-15) Horikoshi, Satoshi
[EN] Can we use microwaves as electromagnetic energy in the chemical and biological fields? We have been researching this question in many aspects and in a bird's-eye view. In response to this question, in some chemical reactions, it turned out that the advantage of microwaves is heat. Note that we also found that this efficient thermal energy transfer method is useful in the chemical field. On the other hand, it was found that electromagnetic waves other than thermal energy can be used in limited chemical reactions (mainly radical reactions). On the other hand, in biological use, there are not many things that require more heat energy than the atmosphere in the first place. However, we have found that depending on the microwave irradiation conditions, it can be activated as a stimulus other than heat. In other words, we discovered a phenomenon that would not have appeared without microwaves. In this paper, it will explain the electromagnetic wave effects of microwaves using photocatalysts, enzymes, and plants as examples. Furthermore, the importance of microwave control will be explained from the development of intelligent cooker.
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Experimental study of microwave slow wave comb and ceramic applicators for soil treatment at frequency 2.45 GHZ
(Editorial Universitat Politècnica de València, 2019-10-15) Brodie, Graham; Torgovnikov, Grigory
[EN] In many cases in industry it is required to heat or treat surface layers of different material (soil, timber, concrete, plastics and so on) with microwaves (MW). Traditional MW irradiators (antennas) cannot provide heating only to the surface areas and energy penetrates deep into the material, where it decays exponentially due to normal attenuation. To reduce energy losses it was required to develop special MW applicators for surface treatment to increase process efficiency. To address this problem, a slow wave ("surface wave") comb and ceramic applicators were designed, built and studied. The main property of slow waves is that the energy concentration is very near impedance electrode – comb or ceramic plate surface. Comb and ceramic slab applicators for frequency 2.45 GHz operation were designed for the soil treatment and studied using soil with moisture content range 32-174% and density range 590-1070 kg/m3 . 30 kW MW plant was used for experiments. Results of the experiments showed that a ceramic applicator provides better uniformity of energy distribution across the width of the applicator. It reduces overheating of the soil surface and energy losses. The depth of energy penetration provided by ceramic applicator is lower compared with the comb applicator. It means that the ceramic applicator provides better energy localization and more energy absorption in the soil surface layers compared with the comb applicator. The ceramic applicator is more effective for MW treatment of the soil surface areas and is recommended for practical use in machines for thermal treatment and sterilization of surface layers of the soil and other materials.
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Developing microwave chemistry under process engineering principles
(Editorial Universitat Politècnica de València, 2019-10-15) Tioni, Estevan; Breysse, J.; Rousseaux, Pascal
[EN] It is nowadays admitted that microwaves are frequently used in organic chemistry labs [1] (even if not as much as it was predicted 20 years ago, one must say [2]). On the other side it is also certain that this technology has not yet found its place in chemical industry: application at a production scale are very scarce [3][4] and this despite the potential advantages of the technology (selective heating, high heating rate, low thermal inertia…). The point is that mastering all the aspects of microwaves assisted synthesis at industrial scale demands a lot of different skills to work together: chemistry, process engineering, microwave engineering, materials science. This is so challenging that tools and methodologies for quantification of industrial microwave interest and scaling-up of lab results are missing. In this work we present our contributions to the deployment of microwaves for synthesis in the chemical industry which are mainly The development of small pilot reactors (1 L) in stainless steel, capable to withstand temperature and pressureThe application of a chemical engineering methodology to microwave assisted synthesisAn example of intensification (see table) of an industrially interesting reaction using microwave to access NPW (high temperature and pressure)A tentative of rationalization of process criteria to identify a priori the interest of microwave heating for a specific application [1]. Diaz-Ortiz et al., Chem. Rec. 2019, 19, 85–97 [2]. Kappe, Chem. Rec. 2019, 19, 15–39 [3]. Aldivia, brevet WO2004/066683A1 [4]. https://cen.acs.org/articles/94/i36/Microwaving-ton.html
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Do a science experiment for future scientists
(Editorial Universitat Politècnica de València, 2019-10-15) Kanematsu, Y.; Matsumura, Takeko
[EN] It has been realized that various chemical reactions are accelerated under irradiation of MW. Such Microwave chemistry is known as time-saving, clear and eco-friendly. MW ovens are world-wide domestic tools for cooking which can serve meals quickly. Regardless of its convenience, few understand the essential mechanism of MW ovens. For better understanding of MW chemistry, authors think it is necessary for to introduce elementary knowledge by holding a 1-day program of experiments by using microwave (MW) ovens.“Science with microwave oven”, 1-day program which we developed and named “Hirameki Tokimeki Science” was supported by Japan Society for the promotion of Science, has been performed over four years.More than 100 students of elementary and junior-high school have joined the program.Here we report the program, response from students.Program of experiments: “1: Dyeing handkerchief with onion peer (*1), 2: Cooking of pizza quickly yeast-leavened, 3: Preparation of shining slime with fluorescein dye synthesized in nonsolvent reaction. 4. Plasma in MW oven (*2), etc.”Students realized how MW accelerated chemical reactions and that dyeing under MW was faster and more fixed compared with the conventional methods. Besides, they could enjoy lunch with pizza and dealing with the slime, both they made. They had a good time with a bit of scientific knowledge. Through 1-day program, we can make science more familiar with students, and it will cause young students to become more interested in science, lead them to future research workers.In addition to the “Hirameki Tokimeki (Inspiration and Spark) Program, we have doneVolunteer activities at Ishinomaki, one of the most damaged cities at the Higashi Nihon Big Earthquake, in 2011.“Science with microwave oven” program surely gives students mysterious interest anddream for Science. That is “Inspire and Spark!” (*1) (*2)
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On the possibilities of permittivity calculation in a certain bandwidth from single frequency results
(Editorial Universitat Politècnica de València, 2019-10-15) Lozano-Guerrero, Antonio; Monzó-Cabrera, Juan; Díaz-Morcillo, Alejandro
[EN] The permittivity of a material can be obtained from resonant measurements in an accurate way [1] at a single frequency (where the resonance occurs). In figure (1) results for the Debye Model at 298K temperature can be seen in the 10MHz-50GHz frequency band for distilled water. In this work we explore the possibilities of obtaining the permittivity of materials from resonant measurements in a certain frequency bandwidth around the resonance frequency. With this purpose a Debye model jointly with a certain conductivity useful for polar liquids [1], are studied to evaluate this possibility jointly with inverse techniques.
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In-situ spectroscopy and two-color thermography during microwave irradiation in materials processing
(Editorial Universitat Politècnica de València, 2019-10-15) Fukushima, Jun; Takizawa, Hirotsugu; Japan Society for the Promotion of Science
[EN] Concentration of microwave E-field between material particles is considered to cause the enhancement of sintering1 and chemical reaction under microwave irradiation. For example, it is usually required 1700 °C to synthesize AlN by carbothermal reduction method using Al2O3 as a starting material, but microwave processing can proceed this process at 1200 °C2. To understand this phenomenon, it is necessary to understand an occurrence behavior of plasma and a chemical reaction related to radical species generated by a local E-field concentration. In addition, in material synthesis using a raw material powder of several mm, it is suggested that a selective heating in the powder scale occurs. However, to discuss this selective heating behavior on this scale, it is necessary to realize a quantitative temperature measurement system with independent of the emissivity of the material and several mm spatial resolution. In this study, we conducted an in-situ spectroscopy and two-color thermography to verify these non-equilibrium effects during microwave irradiation. For example, in the iron making process, it was investigated that CN plasma was generated, and this CN radical contributed to the reduction reaction (Fig. 1(a))3. In addition, the developed two-dimensional two-color thermography system with a high resolution of 8.8 mm/pixel was enable to discuss local temperature gradients quantitatively (Fig. 1(b)).
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Scalable microwave waste-to-fuel conversion
(Editorial Universitat Politècnica de València, 2019-10-15) Robinson, Megan; Popovic, Zoya; U.S. Department of Defense
[EN] This paper presents an efficiency study for scalable microwave waste management. When waste with carbon content is subjected to volume power densities on the order of 0.25W/cm3 at GHz frequencies, it converts to solid coke fuel with oil and gas bi-products that can further be processed for fuel, leaving no trace. For an efficient process, a well-controlled uniform RF field should be maintained in a non-uniform and time-variable material. We are developing a 2.45-GHz active microwave cavity with solid-state (GaN) spatially power combined sources for lower volumes, Fig.1. In the energy balance calculations, the input energy into the system consists of the waste chemical energy and the DC electrical energy used to obtain the RF power with an efficiency that can reach 70% for kW power levels. The efficiency of RF power conversion to heat in the waste mass is calculated from full-wave simulations for typical waste mixtures and ranges from 10 to 90% depending on the material and cavity filling. The output energy estimates are collected from various pyrolysis process descriptions, e.g. [1], with the total energy being that of the solid fuel (35MJ/kg) and oil caloric values, e.g. 40MJ/kg for plastics and about 10-15MJ/kg for nonplastics [2]. A byproduct is flue gas which can be converted to Syngas [3]. The total worse-case carbon footprint balance (0.3-3) calculations will be presented. Fig. 1. Block diagram of active microwave cavity for waste to fuel conversion. References D. Czajczyńska, “Potential of pyrolysis processes in the waste management sector,” Thermal Science and Engineering Progress, vol. 3, p. 171. Sept., 2017. J.A. Onwudili, “Composition of products from the pyrolysis of polyethylene and polystyrene in a closed batch reactor: effects of temperature and residence time,” Journal of Analytical and Applied Pyrolysis, vol. 86 p. 293–303. Nov., 2009. S. Chunshan, "Tri-reforming of methane: a novel concept for synthesis of industrially useful synthesis gas with desired H2/CO ratios using CO2 in flue gas of power plants without CO2 separation." Prepr. Pap.-Am. Chem. Soc., Div. Fuel Chem 49, no. 1 (2004): 128.
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Growth of nannochloris algae in the presence of microwaves (continuous reactor)
(Editorial Universitat Politècnica de València, 2019-10-15) Calinescu, Ioan; Vintila, Alin; Diacon, Aurel; Vinatoru, Mircea; Chipurici, P.; Galan, Ana Maria; Velea, Sanda; European Regional Development Fund; Government of Romania
[EN] Algae are very effective in capturing the sun's energy, carbon dioxide from the atmosphere, and nutrients to turn them into useful substances (carbohydrates, oils, proteins, etc.). Besides the main metabolites, there are also secondary metabolites, such as carotenoids (astaxanthin, β-carotene, lutein, lycopene, and canthaxanthin [1]). Both major and compounds existing in small amounts in algae are useful. Oils and carbohydrates could provide biofuels, proteins can get products with nutritional value and from carotenoids can be prepared food supplements. Obtaining biofuel from algae has not yet proved to be economically viable [2, 3]. A much higher interest might be getting food supplements from algae. To increase their value as ingredients for food supplements, algal oils should have a higher degree of unsaturation (rich in omega 3) and an increased carotenoid content to be an important additional benefit in over all processing of algae. There are studies that refer to the influence of environmental factors on algae composition [2], but the microwave influence on algae growth, especially algal metabolites composition change is very poor studied. In this paper, besides the experiments for the activation of algal growth in discontinuous reactors [4] additional work was conducted in a continuous photobioreactor. The goal was checking not only the growth of microalgae but also their content in polyunsaturated oil and in carotenoids. By microwave-controlled irradiation of the nutrient and algae flux, which is recirculated through the photobioreactor and through a glass reactor located in a TE-type monomod cavity, the lipid content of the algae increased, but only, the modification of the lipid fraction content was significantly increased in the concentration of polyunsaturated acids with 16 and 18 carbon atoms. As far as carotenoids are concerned, the algae nannochloris has a higher carotenoid content over many known vegetables holding carotene or lycopene (carrots or tomatoes). Besides oil increasing microwave treatment produced a significant increase in carotenoid content of algae. They can be extracted together with omega-3-rich algal oil and are the basis of very valuable dietary supplements.
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Faster plasticizers production by microwave irradiation
(Editorial Universitat Politècnica de València, 2019-10-15) Jermolovicius, Luiz; Pouzada, Eduardo; Castro, Edmilson; Nascimento, Renata; Senise, José; Instituto Mauá de Tecnologia, Brasil; Fundação de Amparo à Pesquisa do Estado de São Paulo
[EN] In this work the microwave effect of enhancing chemical reactions was applied to maleic anhydride esterification with 2-ethylhexanol-1 catalyzed by p-toluene sulfonic acid. The analysis of this reaction was simplified considering the industrial practice of withdrawn the reaction water, which makes the whole reaction act as a pseudo irreversible one. A statistical design of experiments was applied to determine an empirical chemical kinetics equation with three levels of catalyst concentration and two levels related to the kind of heating (microwave and conventional); six chemical kinetics equations (three for microwave heating and three for conventional heating) were determined. A batch/plug flow simulation was done and a spreadsheet developed for the reactor’s behavior. The most interesting result was the confirmation of a synergic effect between microwaves and acid catalysis that accelerated this esterification reaction, transforming it in a fast reaction.
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Continuous industrial-scale microwave-assisted extraction of high-value ingredients from natural biomass
(Editorial Universitat Politècnica de València, 2019-10-15) Radoiu, Marilena; Splinter, Steven; Popek, T.
[EN] An innovative technology for the continuous extraction of bioactive compounds from a wide range of biological materials has been developed, scaled up and successfully demonstrated at commercially-relevant scales. The technology, known as MAPTM, or “Microwave-Assisted Process”, robustly transfers from laboratory to continuous, industrial scale operation. In wide-ranging trials, MAPTM has comprehensively demonstrated its ability to outperform many KPIs of conventional extraction processes, while offering biomass throughput, product consistency and low operational costs not attainable by other emerging technologies. Radient’s proprietary continuous-flow MAPTM extractor, Figure 1, was designed for continuous processing of up to 200 kg/h of biomass material. Verification of the mechanical integrity of the system was confirmed by flow testing of biomass / solvent slurries. Testing and verification of the efficiency of microwave energy transfer to the extractor cavity was completed at various microwave power settings using flowing water at 870 kg/h. The microwave energy transfer to the system was verified to be >95 % in each case. As an example of performance, continuous flow MAPTM extraction of the antioxidant SDG from flax biomass was performed using 70 % ethanol / water as the solvent at two different conditions: - 75 kg/h flax / 5 L/kg solvent / 15 kW microwave power / extractor residence time 24 min; - 110 kg/h flax / 5 L/kg solvent / 20 kW microwave power / extractor residence time 16 min. The industrial-scale conditions for these runs were determined by extrapolating from optimized conditions previously obtained from batch lab-scale MAPTM experiments. The continuous flow approach eliminates the requirement for having geometric similarity between scales, i.e the equipment shape and dimensions do not have to scale proportionately.
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Microwave pretreatment of lignocellulosic biomass to release maximum phenolic acids
(Editorial Universitat Politècnica de València, 2019-10-15) BICHOT, Aurélie; Radoiu, M.; Bernet, Nicolas; Mechin, Valérie; Delgenès, J.P.; García Bernet, D.
[EN] The objectives fixed by world’s governments concerning energy transition have aroused interest on lignocellulosic biomass utilization for bioenergy and green chemistry applications. However, due to their resistant structure, deconstructive pretreatments are necessary to render possible biological conversions of these lignocellulosic residues. Microwave (MW) treatment has been reported as efficient in many biotechnology fields; biomass pretreatment for biorefinery purposes is another possible application. This work presents the effects of MW pretreatment on underexploited natural agri-food biomass of economic interest: wheat bran, miscanthus stalks and corn stalks. Various parameters were studied including solvent, power density, treatment duration, pressure. Effects were evaluated by a complete biomass characterization before and after treatment, with main focus on phenolic acids release. In the tested conditions and when compared to the high NaOH consumption reference extraction method for phenolic acids, the atmospheric pressure (open vessel) microwave treatment did not allow attaining high acid yields (Fig.1). The most important parameters for improving treatment efficiency were power density and solvent. In order to increase yields, microwave treatments under pressure were carried out to reach higher temperatures while taking care as to not exceed the acid denaturation temperature (150°C) and to avoid the formation of inhibitors. Phenolic acids yields and biomass composition are currently being processed and will be discussed.
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Low temperature degradation behaviour of 10Ce-TZP/Al2O3 bioceramics obtained by microwave sintering technology
(Editorial Universitat Politècnica de València, 2019-10-15) Gil-Flores, Lorena; Salvador Moya, Mª Dolores; Penaranda-Foix, Felipe L.; Rosa, Roberto; Veronesi, Paolo; Leonelli, Cristina; Borrell Tomás, María Amparo; Escuela Técnica Superior de Ingeniería de Telecomunicación; Instituto Universitario de Tecnologías de la Información y Comunicaciones; Departamento de Comunicaciones; Departamento de Ingeniería Mecánica y de Materiales; Escuela Técnica Superior de Ingeniería Industrial; Instituto Universitario de Investigación de Tecnología de los Materiales de la UPV; Ministerio de Economía y Competitividad; Generalitat Valenciana
[EN] Zirconia is one of the most used ceramics, especially for biomedical applications, due to its exceptional mechanical properties. However, it is commonly known that its properties can be diminished owing to a low temperature degradation (LTD). This phenomenon consists on a spontaneous phase transformation, from tetragonal to monoclinic, under certain conditions, which is accelerated when the samples are exposed under high levels of humidity at a temperature range between 20-300 ºC. In addition to the fact that the monoclinic phase presents worse mechanical properties than the tetragonal one, there is a volume change of 4% between phases that gives rise to defects in the material as microcracks. Due to this reason, zirconia prostheses failed catastrophically inside the human body between 1999 and 20011. Previous researches reveal that Al2O3 addition suppress the propagation of phase transformation2. Thus, the aim of the present work is to study the hydrothermal ageing of zirconia doped with ceria and toughened with alumina (10Ce-TZP/Al2O3) composite, which has been sintered by microwave employing two different frequencies: 2.45 and 5.8 GHz. Microwave heating technology is based on the absorption of electromagnetic radiation by the material, which allows the sample to be heated. So far, most microwave heating equipments use 2.45 GHz; accordingly, the novelty of this study is to employ a frequency of 5.8 GHz and to investigate its effect on LTD. LTD is carried out in an autoclaved in steam at 120 ºC and 1.2 bar, because these conditions accelerate the hydrothermal aging process3. In order to characterize the degraded samples, micro-Raman spectroscopy, AFM, nanoindentation technique and electronic microscopy have been performed. References 1. Norton, M. R., Yarlagadda, R., Anderson, G. H. J. Bone Joint Surg. Br., 2002, 84–B, 631–635. 2. Fabbri, P., Piconi, C., Burresi, E., Magnani, G., Mazzanti, F., Mingazzini, C. Dent. Mater., 2014. 3. Presenda, Á., Salvador, M. D., Moreno, R., Borrell, A. J. Am. Ceram. Soc., 2015, 98, 3680–3689.
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Generalisation and evaluation of macroscopic models for microwave susceptors in contact with heated foods
(Editorial Universitat Politècnica de València, 2019-10-15) Celuch, Malgorzata; Wilczynski, Konrad; Olszewska-Placha, Marzena
[EN] Introducing a thin conductive layer into a finite-mesh (as inherent in e.g. finite difference time domain (FDTD) and finite element (FEM) methods) typically requires a dedicated equivalent macroscopic model allowing for computationally effective and accurate electromagnetic (EM) and thermal simulations. Thin conductive layers, such as microwave susceptors, characterised by their surface resistance (Rs), are adequately represented with a dielectric surrogate layer of higher thickness and proportionally scaled conductivity, maintaining the value of Rs. Systematic evaluation of macroscopic models of microwave susceptors used for enhancing the heating efficiency of microwavable food packages has been reported in [1]. Our studies therein focus on validity, accuracy and practical application limits of the proposed macroscopic models of thin metallic layers, in terms of power dissipated in susceptor placed in free space and irradiated by EM wave, at all angles of incidence. In this work we extend our studies to real-life simulation scenarios, in which microwave susceptor is in contact with food. We first consider a four-layer model as in Fig. 1(left) and conduct both analytical and numerical conformal FDTD calculations. The accuracy and application limit of the macroscopic model are investigated for all incidence angles and both, TE and TM polarisations of the impinging EM wave, for different foods. We aim to determine a range of optimum, in terms of power dissipated in the susceptor, values of the susceptor’s surface resistance in all those cases. The results of our canonical calculations with the four-layer model of Fig.1(left) are validated in the 3D FDTD modelling scenario of Fig.1(right), representative of a real-life domestic oven. While for normal incidence our results are in overall agreement with some of the previously published observations [2], they are formalised and generalised to constitute reliable guidelines for microwave oven and food packaging designers and manufacturers. We also show cases where some of the earlier rule-of-the-thumb guidelines fail.
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A high-power source of optical radiation with microwave excitation
(Editorial Universitat Politècnica de València, 2019-10-15) Churyumov, Gennadiy; Denisov, Oleksandr; Frolova, Tetyana; Wang, Nannan; Qiu, Jinghui
[EN] For more than 50 years, interest to the microwave heating technology has not weakened. In addition to the traditional areas of its application, which described in detail in [1], recently there has been an expansion of technological possibilities for the use of microwave energy associated with the impact of electromagnetic waves of the microwave range on various materials (sintering of metal and ceramic powders) and media, including plasma [2]. One such new direction is the creation of high-power and environmentally friendly sources of optical radiation on the basis of an electrodeless sulfur lamp with microwave excitation [2, 3]. The purpose of this paper is to the further development of the theory and practice of microwave excitation by the electrodeless sulfur lamps, improvement the energy efficiency during energy conversion into the optical radiation and widening the application of new light sources in real practice. The results of the computer modeling of conversion process of the microwave energy into optical radiation energy are presented. The simulation results are compared with experimental data. It is shown that additional use of the solar panels for the reverse conversion of the optical radiation into DC energy with follow-up its using in the circuits of secondary power supply allows improving the energy efficiency of the light source. References Microwave Power Engineering. Edited by E.C. Okress. V. 1, 2. Academic Press, New York & London. 1968.A.N. Didenko, SVCh-energetika. Teoriya i praktika. – Moscow: Nauka. 2003.- 445 s.G. Churyumov, T. Frolova, “Microwave Energy and Light Energy Transformation: Methods, Schemes and Designs. Microwave Energy and Light Energy Transformation: Methods, Schemes and Designs” // In book “Emerging Microwave Technologies in Industrial, Agricultural, Medical and Food Processing.” Edited by Kok Yeow You, IntechOpen, 2018. pp. 75-91.
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Microwave treatment of materials in low pressure
(Editorial Universitat Politècnica de València, 2019-10-15) Ryszard, Parosa; Brożynski, Andrzej; Grzeskowiak, Piotr; Kowalczyk, Krzysztof; Natoński, Marek; Ziętek, Piotr; Zytkiewicz, Janusz
[EN] Ryszard Parosa, Andrzej Brożyński, Piotr Grześkowiak, Krzysztof Kowalczyk, Marek Natoński, Piotr Ziętek and Janusz Żytkiewicz PROMIS-TECH Poland Keywords: microwave treatment, low pressure heating, microwave drying Uniquely favourable characteristics of biological product can be obtained through the use of the microwave method in vacuum heating process. Microwave-vacuum drying is superior to other methods in terms of dried products' structure, flavour, colour and biological active compounds contents. But applications of such a methods seems to be much wider: drying of fruits and vegetables for consumption, drying of herbs for extraction of valuable biological compounds, for modification of seed structure (sunflowers seeds, pumpkin seeds), for pasteurisation etc. A universal system was designed for testing such processes in laboratory scale and several industrial scale system have been developed. Process of thermal treatment can be carried out with plastic drum installed inside of multi-mode microwave cavity and cavity which is connected by microwave line with reflectometer and circulator - to microwave generator. In laboratory unit generator 2.45 GHz with controlled power (from 50W to 800W) was applied. System was equipped with vacuum pump with pressure control and is controlled by computer. Most important technical parameters, like: microwave power, time of treatment, pressure inside of drum, temperature of steam – are controlled and recorded. Laboratory scale unit is shown below. Basing on laboratory scale test several technologies in industrial scale was developed. Industrial scale unit equipped with 8 generators of 3 kW (2.45 GHz) was constructed and for last 8 years has been successfully used for “production” of crispy chips which are now popular in Polish marked. Exemplary industrial scale installation is shown in photo below. Multi – drum microwave drier. Two cavity microwave industrial drier Another system for modification od seed is now constructed – ordered by big industrial producer of batons and sweet snacks. Process will be carried our inside of dielectric drum in low pressure and reactor will be equipped with 8 generators of 3 kW (2.45 GHz). Treatment time will be reduced to 3-4 minutes and next material (seeds) will be cooled down. Last project which now realized is connected with drying of wood flour applied in composite material production. System will work continuously with two airlocks and with dielectric drum and will be connected with 4 microwave generators (3 kW, 2.45 GHz). In next step planed installation will be equipped with microwave high power generator ca. 60 kW with frequency 915 MHz.
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Subcritical hydrothermal conversion (SHC) process supported by microwaves
(Editorial Universitat Politècnica de València, 2019-10-15) Ryszard, Parosa
[EN] Ryszard Parosa PROMIS-TECH, Poland Subcritical Hydrothermal Conversion (SHC) process can be used for utilization of wet biomass with recovery of energetic gases and diesel-like fluids. Process is carried out in high pressure (over 200 Barr) and wet biomass is heated up to 350°C. In our research we have apply microwave system to heat wet biomass in high pressure vessel – with control of the most important process parameters like temperature, pressure, microwave power and reflection coefficient. In the first stage process was tested with use of small metallic vessel connected to microwave line (rectangular waveguide) by special ceramic window. Microwave generator 2.45 GHz with controlled output power in range of 200 W to 3 kW was applied. Sewage sludges with moisture content up to 60% were heated by microwaves to temperature from 250°C to 350°C with pressure ca 300 Barr. After heating by 15 - 20 minutes inside of vessel fluid like oil was obtained with solid particles in form of carbon black. Fluid after separation of water contains hydrocarbons – with biodiesel structure. The similar process with conventional heating by metallic walls of vessel needs much longer time – about 40 minutes, and higher energy consumption.In the next stage a semi-industrial system was designed with process reactor in form of ceramic tube located inside of metallic cavity with two single mode microwave radiators connected to microwave generators of 2.45 GHz and with output power 3 kW (CW) each.Heating process is provided in stop/flow system: biomass inside of high pressure cavity is heated by microwaves to adjusted temperature (280 -350°C) and product is transported by heat exchanger to separator. At the same time next portion of biomass is injected to the cavity. During the process reflected microwave power was recorded. When treated material was in very high pressure, close to subcritical state, specific fluctuations of reflected power level ware observed. Water in subcritical condition lose polar structure and dielectric constants change, but in the hydrothermal conversion process another chemical compounds are formed (for example diesel like hydrocarbons) and treated material still effectively absorb microwaves. In the described system ca 60 – 80 kg of wet biomass (with 50 – 55% of water) was treated and ca 8 – 15 kg of diesel – like fluid was obtained. Basing on the preliminary results a new industrial scale system was designed and actually is under construction. In industrial scale installation a microwave heating system of 60 kW, 915 MHz is planned, with two radiators installed along ceramic tube. Estimated efficiency of the system is in range of 200 to 400 kg of biomass treated in hour.
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Sintering of MLCC’S barium titanate with microwaves
(Editorial Universitat Politècnica de València, 2019-10-15) Aguilar-Garib, Juan; Tijerina-García, Osvaldo; Garza-Guajardo, Javier
[EN] A comparison of microwave and conventional, in an electric resistance furnace, sintered layers of dielectric base barium titanate (BaTiO3) of the kind employed for multilayer ceramic capacitors (MLCC) was performed. Two kinds of samples were used for each processing method; the layers alone without electrodes, and the green MLCC with the layers and electrodes interdigitated. Samples were exposed to microwaves for 20 minutes and heated up to 1050°C and 1150°C for sintering in a crucible with graphite that acted as reduction agent and microwave susceptor. Conventional sintering was performed in the same arrangement but lasted 120 minutes since it was found that 20 minutes was not enough time to achieve sintering. Heating rate in both cases was 10 °C/min. It was observed that the layers without the electrodes achieve about the same densification for both processes, while in the case of the green MLCC’s the results were variable, ranging from sample that became dust, to cracked samples and some well sintered ones. At least in the microwave case, it is possible that the variability of the results is due to the importance of the location of the sample in the cavity that in turn affects the electric field pattern, especially because the presence of the electrodes that can cause overheating around them.
Access status: Abierto ,
Microwave Generated Plasma Railway Track Treatment
(Editorial Universitat Politècnica de València, 2019-10-15) Swan, Julian; Candy, Matt; Radoui, Marilena; Richardson, Gareth
[EN] Braking conditions are a fundamental issue for the railway and have been a limiting factor in network capacity & timetabling. This work was focused on taking high power microwave generated plasma out of the laboratory into a railway environment. The Imagination Factory with no experience in microwave generated plasma has partnered with experts in this field to develop a mobile system which delivered 15kW 2.45GHz microwave generated plasma – Fig.1. The plasma was created within a dielectric tube placed in a monomode microwave cavity; the atmospheric plasma sustained in different inert gases (nitrogen, argon) gases as well as mixtures of inert gases with reactive molecules was jetted directly onto the railhead as to change the conditions for the wheel-rail interface. This technology is hoped to be a game changer in enabling predictable & optimized braking on the railway network. Challenges encountered during the demonstration phase will be discussed.
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Experimental Investigations of Microwave Effects on Rock Breakage Using SEM Analysis
(Editorial Universitat Politècnica de València, 2019-10-15) Teimoori, Khashayar; Hassani, Ferri; Sasmito, Agus; Madiseh, Ali; Natural Sciences and Engineering Research Council of Canada
[EN] Preconditioning of hard rocks by microwave energy has recently been considered a potentially effective technology in mechanical rock breakage for civil and mining engineering. To obtain the amount of mechanical damage that a single-mode microwave treatment produces in rocks, it is necessary to analyze and evaluate the thermal cracking process by microwave heating at different power levels, exposure times, and distances from the antenna. The current study employs the scanning electron microscopy imaging technique to capture images from surfaces of irradiated rock specimens and to compare them with a nontreated specimen. To evaluate and quantify the amount of cracking (i.e. crack density, crack size, etc.) in a rock specimen after microwave irradiation with different microwave input operating parameters, the following steps were evaluated. First, several experiments of single-mode microwave treatments with different operating parameters were performed on rectangular specimens of basalt. Then, cylindrical core samples with a dimension of r = 0.5 cm, h = 2cm, were drilled from the center of the irradiated specimens and prepared for image processing. The results of the present study show that there are significant differences between the number of microcracks present in samples irradiated at different power levels and distances from the antenna. Also, longer exposure times result in more severe cracks.
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Numerical investigation on the effects of single-mode microwave treatment on rock breakage system
(Editorial Universitat Politècnica de València, 2019-10-15) Teimoori, Khashayar; Hassani, Ferri; Sasmito, Agus; Madiseh, Ali; Natural Sciences and Engineering Research Council of Canada
[EN] In this study, a rock model which consists of a conceptual block (host rock and ore sample) is numerically modeled by using the finite element method. The rock model is subjected to several single-mode microwave treatments with different power levels, distances from the antenna, and exposure times in order to calculate and compare the corresponding effects including temperature distribution and mechanical stress/damage profiles. The main objective of the present study is to analyze the distribution of temperature and mechanical stress at the boundary of two different attached rocks when exposed to microwaves. This enables comparing the intensity of the distribution with respect to the applied microwave input operating parameters and, consequently, understanding rock preconditioning. The results of the present study verify that an increase in temperature by microwave treatment facilitates the rock weakening process. Also, a more efficient selection of the distance from the antenna and the power level can maximize the overall impact of the microwave treatment on rock preconditioning which ultimately helps with the rock breakage mechanism.

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