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Mitani T.,Kyoto University | Mitani T.,Japan Science and Technology Agency | Hasegawa N.,Kyoto University | Hasegawa N.,Japan Science and Technology Agency | And 10 more authors.
Chemical Engineering Journal | Year: 2016

A wideband microwave reactor with an output that includes the 915 MHz and 2.45 GHz ISM (Industrial, Scientific and Medical) bands was designed and fabricated. The reactor structure incorporated a coaxial cable, and a liquid sample was placed in the space between the inner and outer conductors. Insertion of a truncated cone-shaped polytetrafluoroethylene (PTFE) device was used as a method to reduce microwave reflection over a wide frequency range. The reactor had a volume of 360 ml and was designed employing a 3D electromagnetic simulation. Ultrapure water and a 0.1 M NaOH solution were selected as the liquid samples and experimentally measured permittivity data for these liquids were employed during the reactor simulations. The measured reflection ratio exhibited the same trend as the simulation results between 800 MHz and 2.7 GHz. The reflection ratio was especially low in the case of the NaOH solution (less than 2%), although this value increased to more than 40% upon removal of the PTFE insert. Microwave heating tests demonstrated that this reactor was able to heat liquid samples at 915 MHz, 1.7 GHz and 2.45 GHz, with estimated microwave absorption efficiencies varying between 28% and 66% depending on the frequency, sample type and heating duration. The reflection ratio and heating data demonstrated that this reactor functioned over a wide frequency range between 800 MHz and 2.7 GHz. A non-uniform temperature distribution in the sample remained a challenge that must be addressed in future work. © 2016 The Authors. Source

Mitani T.,Kyoto University | Oyadomari M.,Kyoto University | Suzuki H.,Kyoto University | Yano K.,Kyoto University | And 4 more authors.
Nihon Enerugi Gakkaishi/Journal of the Japan Institute of Energy | Year: 2011

Efficient pretreatment prior to enzymatic saccharification process is essential for profitable bioethanol production from woody biomass. Microwave pretreatment is expected as an efficient and energy-cost-saving method to enhance enzymatic susceptibility. The objective of the present study is to develop an efficient, high-volume, and continuous microwave pretreatment system toward commercially-based bioethanol production. As a feasibility study, we developed prototypes of a continuous-flow-type microwave pretreatment system for bioethanol production from woody biomass. A unit of the microwave irradiation sections of a continuous-flow-type microwave pretreatment system was designed with a 3D electromagnetic simulator. Prototype experiments and quantitative estimation of energy balance were also conducted. Microwave pretreatment provided 45.9% of the total saccharide yield woody biomass weight by electric consumption of 552 kJ; whereas conventional heating pretreatment provides 43.6 % of the total saccharide yield by 498 kJ, when the mixture was composed of 70 g of woody biomass (Japanese cedar sapwood chips) and 770 g of solvents (ethylene glycol: phosphoric acid = 95:5). We estimated 14.8g of bioethanol and 439 kJ of bioethanol energy could be produced by the prototype microwave pretreatment. Although heat dissipation from the metal pipe to the air and the ratio of solvents to woody biomass are immediate problems, microwave is a future potential energy-saving pretreatment method without loss of the saccharide yield. Source

Hasegawa N.,Kyoto University | Mitani T.,Kyoto University | Shinohara N.,Kyoto University | Daidai M.,Japan Chemical Engineering and Machinery Co. | And 3 more authors.
IEICE Transactions on Electronics | Year: 2014

A simple, low reflection, and highly-efficient pilot-plant scale microwave irradiation reactor for woody biomass pretreatment was fabricated. Pretreatment is an essential process for effective bioethanol production. The fabricated reactor consists of 8 microwave irradiators which are attached to a metal pipe. The woody biomass mixture which contains water and organic acid flows through the metal pipe and is heated by microwaves at a total power of 12kW. To design the microwave irradiators, we used a 3D Finite Element Method (FEM) simulator, which was based on the measured complex permittivity data of the woody biomass mixture. The simulation results showed that the reflection coefficient |S 11| from the reactor was less than -30 dB when the woody biomass mixture temperature was between 30°C and 90°C. Finally, we experimentally confirmed that the fabricated irradiation reactor yielded a microwave absorption efficiency of 79%. Copyright © 2014 The Institute of Electronics, Information and Communication Engineers. Source

Jin T.,Japan National Institute of Advanced Industrial Science and Technology | Ma Y.,Japan National Institute of Advanced Industrial Science and Technology | Matsuda W.,Japan National Institute of Advanced Industrial Science and Technology | Masuda Y.,Japan National Institute of Advanced Industrial Science and Technology | And 5 more authors.
Nippon Seramikkusu Kyokai Gakujutsu Ronbunshi/Journal of the Ceramic Society of Japan | Year: 2011

Pervaporation of ethanol from ethanol/water mixture solution using surface-modified mesoporous silica membranes has been carried out. The mesoporous silica layers were prepared on commercially available porous alumina tubes by dip-coating in a series of silica sols. Subsequently, organosilane compounds with different alkyl chain lengths [C nH 2n+1(CH 3) 2SiCl; n = 1, 3, 8, 12, and 18] were covalently reacted to the surface of these mesoporous layers with high coverage. Surface-modified mesoporous silica membranes showed ethanol permselectivity and the total flux increased with increasing ethanol concentration in feed composition and feed temperature. Ethanol separation factors in the range from 7.90 to 8.24 and total flux of 2.762.89 kg·m -2·h -1 were obtained by pervaporation at 323K and at 5 wt % ethanol feed composition using surface modified membranes. In the presence of 1 wt % acetic acid in a ternary model fermentation (5 wt % ethanol-94 wt % water-1 wt % acetic acid), separation factor and total flux were decreased, and this tendency was minimized by increasing pH above pK a ⊖ (pK a ⊖= 4.74 at 298 K) and changing HOAc to OAc - ions in the feed solution. © 2011 The Ceramic Society of Japan. Source

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