Experimental study on the heating effects of microwave discharge caused by metals

Wang, Wenlong; Liu, Zhen; Sun, Jing; Ma, Qingluan; Ma, Chunyuan; Zhang, Yunli

doi:10.1002/aic.13766

Cited by 63 publications

(35 citation statements)

References 36 publications

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“…As a direct consequence of these discharges, considerable heat is produced, leading to the formation of high-temperature local hotspots. Wang and co-author reported the heat produced by discharge can melt the metal terminals (as shown in Figure 4 ) and the energy conversion efficiency from the electric energy to heat by microwave-metal discharge can amount to 20%–60% during the microwave irradiation process, as shown in Figure 5 [ 96 , 97 ]. One the other hand, at a microscopic level, these discharge are actually plasma [ 12 ].…”

Section: Effects Of Microwave-metal Interactionsmentioning

confidence: 99%

Review on Microwave-Matter Interaction Fundamentals and Efficient Microwave-Associated Heating Strategies

2016

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Microwave heating is rapidly emerging as an effective and efficient tool in various technological and scientific fields. A comprehensive understanding of the fundamentals of microwave–matter interactions is the precondition for better utilization of microwave technology. However, microwave heating is usually only known as dielectric heating, and the contribution of the magnetic field component of microwaves is often ignored, which, in fact, contributes greatly to microwave heating of some aqueous electrolyte solutions, magnetic dielectric materials and certain conductive powder materials, etc. This paper focuses on this point and presents a careful review of microwave heating mechanisms in a comprehensive manner. Moreover, in addition to the acknowledged conventional microwave heating mechanisms, the special interaction mechanisms between microwave and metal-based materials are attracting increasing interest for a variety of metallurgical, plasma and discharge applications, and therefore are reviewed particularly regarding the aspects of the reflection, heating and discharge effects. Finally, several distinct strategies to improve microwave energy utilization efficiencies are proposed and discussed with the aim of tackling the energy-efficiency-related issues arising from the application of microwave heating. This work can present a strategic guideline for the developed understanding and utilization of the microwave heating technology.

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Section: Effects Of Microwave-metal Interactionsmentioning

confidence: 99%

Review on Microwave-Matter Interaction Fundamentals and Efficient Microwave-Associated Heating Strategies

2016

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“…Our research group has studied the heating effects associated with microwave-metal discharges and found that the energy conversion ratio from electrical energy to heat can reach as high as 30% [28]. Based on the unique material characteristics of WPCBs and the discharge properties of metals, we have previously established that microwave-induced pyrolysis holds promise as a way to process WPCBs [26][27][28][29][30].…”

Section: Introductionmentioning

confidence: 99%

Kinetic Study of the Pyrolysis of Waste Printed Circuit Boards Subject to Conventional and Microwave Heating

et al. 2012

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This paper describes a kinetic study of the decomposition of waste printed circuit boards (WPCB) under conventional and microwave-induced pyrolysis conditions. We discuss the heating rates and the influence of the pyrolysis on the thermal decomposition kinetics of WPCB. We find that the thermal degradation of WPCB in a controlled conventional thermogravimetric analyzer (TGA) occurred in the temperature range of 300 °C-600 °C, where the main pyrolysis of organic matter takes place along with an expulsion of volumetric volatiles. The corresponding activation energy is decreased from 267 kJ/mol to 168 kJ/mol with increased heating rates from 20 °C/min to 50 °C/min. Similarly, the process of microwave-induced pyrolysis of WPCB material manifests in only one stage, judging by experiments with a microwave power of 700 W. Here, the activation energy is determined to be only 49 kJ/mol, much lower than that found in a conventional TGA subject to a similar heating rate. The low activation energy found in microwave-induced pyrolysis suggests that the adoption of microwave technology for the disposal of WPCB material and even for waste electronic and electrical equipment (WEEE) could be an attractive option.

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“…However, there are also some natural drawbacks of microwave heating: (a) When heating materials by microwave, there exist "hot spots" and thermal runaway problems in the system temperature [7], which will cause degradation of the processing materials [8][9][10][11] and even cause burning and explosion of the microwave reactor and reactants [12,13]. (b) When dealing with numerous solid materials, their stacking in the heating cavity can easily result in some sharp edges, tips or submicroscopic irregularities, which may lead to electric sparks or electric arcs [14,15]. These electric discharges will affect the heating process and the product composition, and lead to safety problems when dealing with materials that have a low flashing point or in high temperature conditions [16,17].…”

Section: Introductionmentioning

confidence: 99%

“…For studies on the electric discharge phenomena, related research has focused on microwave discharges in sintering of powdered metals. Attention is mainly paid to factors that influence the intensity and frequency of microwave discharges, such as the magnetron output power [14,33], the size, amount, conductivity, morphology and surface conditions of the metal [14,[33][34][35] and the dielectric properties of the surrounding medium [15,[35][36][37]. The lack of comprehensive consideration of the heating uniformity and safety of microwave heating solid stack materials has hindered the further application of microwave heating.…”

Section: Introductionmentioning

confidence: 99%

Impact of Filled Materials on the Heating Uniformity and Safety of Microwave Heating Solid Stack Materials

et al. 2018

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Microwave heating of solid stack materials is common but bothered by problems of uneven heating and electric discharge phenomena. In this paper, a method introducing fluid materials with different relative permittivity is proposed to improve the heating uniformity and safety of solid stack materials. Simulations have been computed based on the finite element method (FEM) and validated by experiments. Simulation results show that the introducing of fluid materials with proper relative permittivity does improve the heating uniformity and safety. Fluid materials with the larger real part of relative permittivity could obviously lower the maximum modulus value of the electric field for about 23 times, and will lower the coefficient of variation (COV) in general, although in small ranges that it has fluctuated. Fluid materials with the larger imaginary part of relative permittivity, in a range from 0 to 0.3, can make a more efficient heating and it could lower the maximum modulus value of the electric field by 34 to 55% on the whole studied range. However, the larger imaginary part of relative permittivity will cause worse heating uniformity as the COV rises by 246.9% in the same process. The computed results are discussed and methods to reach uniform and safe heating through introducing fluid materials with proper relative permittivity are proposed.

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Experimental study on the heating effects of microwave discharge caused by metals

Cited by 63 publications

References 36 publications

Review on Microwave-Matter Interaction Fundamentals and Efficient Microwave-Associated Heating Strategies

Review on Microwave-Matter Interaction Fundamentals and Efficient Microwave-Associated Heating Strategies

Kinetic Study of the Pyrolysis of Waste Printed Circuit Boards Subject to Conventional and Microwave Heating

Impact of Filled Materials on the Heating Uniformity and Safety of Microwave Heating Solid Stack Materials

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