Microwave dielectric characterization of hay during pyrolysis

Abstract:Microwave technology has a potential application in the extraction of zinc from sulphide ores, knowledge of the dielectric properties of these ores plays a major role in the microwave design and simulation for any process. The dielectric properties of zinc sulfide concentrate for two different apparent densities-1.54 and 1.63 g/cm 3 -have been measured by using the resonance cavity perturbation technique at 915 and 2450 MHz during the roasting process for the temperature ranging from room temperature to 850 • C. The variations of dielectric constant, the dielectric loss factor, the dielectric loss tangent and the penetration depth with the temperature, frequency and apparent density have been investigated numerically. The results indicate that the dielectric constant increases as the temperature increases and temperature has a pivotal effect on the dielectric constant, while the dielectric loss factor has a complicated change and all of the temperature, frequency and apparent density have a significant impact to dielectric loss factor. Zinc sulfide concentrate is high loss material from 450 to 800 • C on the basis of theoretical analyses of dielectric loss tangent and penetration depth, its ability of absorbing microwave energy would be enhanced by increasing the apparent density as well. The experimental results also have proved that zinc sulfide concentrate is easy to be heated by microwave energy from 450 to 800 • C. In addition, the experimental date of dielectric constant and loss factor can be fitted perfectly by Boltzmann model and Gauss model, respectively.

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Section: Dielectric Properties Modelingmentioning

confidence: 99%

Dielectric Properties of Zinc Sulfide Concentrate during the Roasting at Microwave Frequencies

Guang-jun

Yang

et al. 2017

Minerals

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“…To date, there are only a small number of publications which report the dielectric properties of a small selection of biomass types. These include sorghum [178], oil palm [179][180][181], Australian wood-based biomass [182], wood pellets [183], Tobacco stems [184], hay [185], switchgrass [186] and corn stover [187]. However, the majority of these studies have only acquired dielectric property measurement information at temperatures up to ca.…”

Section: Dielectric Properties Of Biomassmentioning

confidence: 99%

“…50°C. It is known that the dielectric properties of biomass change nonlinearly with temperature [183], however only a limited number of studies have determined the dielectric properties of biomass at elevated temperatures (within the 100°C -900°C temperature range) [176,185,186,188,189]. Considering that the pre-treatment of biomass may require temperatures that exceed 100°C (for example biomass torrefaction requiring temperatures up to 300°C), further work is required to determine the dielectric responses of different biomass feedstocks at higher temperatures.…”

Section: Dielectric Properties Of Biomassmentioning

confidence: 99%

The application of microwave heating in bioenergy: A review on the microwave pre-treatment and upgrading technologies for biomass

Kostas

Beneroso

Robinson

2017

Renewable and Sustainable Energy Reviews

253

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Bioenergy, derived from biomass and/or biological (or biomass-derived) waste residues, has been acknowledged as a sustainable and clean burning source of renewable energy with the potential to reduce our reliance on fossil fuels (such as oil and natural gas). However, many bioenergy processes require some form of pre-treatment and/or upgrading procedure for biomass to generate a modified residue with more suitable properties and render it more compatible with the specific energy conversion route chosen. Many of these pre-treatments (or upgrading procedures) involve some form of substantive heating of the biomass to achieve this modification. Microwave (MW) heating has attracted much attention in recent years due to the advantages associated with dielectric heating effects. These advantages include rapid and efficient heating in a controlled environment, increasing processing rates and substantially shortening reaction times by up to 80%. However, despite this interest, the growth of industrial MW heating applications for bioenergy production has been hindered by a lack of understanding of the fundamentals of the MW heating mechanism when applied to biomass and waste residues. This article presents a review of the current scientific literature associated with the application of microwave heating for both the pre-treatment and upgrading of various biomass feedstocks across different bioenergy conversion pathways including thermal and biochemical processes. The fundamentals behind microwave heating will be explained, as well as discussion of the imperative areas which require further research and development to bridge the gap between fundamental science in the laboratory and the successful application of this technology at a commercial scale.

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“…These models can fit the experimental curves perfectly in predicting the variations of dielectric properties. The first model is called Boltzmann model, it is based on a sigmoidal function, which can be given by [14,15]: (3) where is dielectric properties (dielectric constant and dielectric loss), and temperature (°C) is the lone independent variable, , , and are the regression coefficients. The second model is Gauss model and can also be expressed as exponential form [15,16]: (4) where is dielectric properties (dielectric constant and dielectric loss), and (°C) is the temperature, , , and are the regression coefficients.…”

Section: Dielectric Properties Modelingmentioning

confidence: 99%

Dielectric properties of zinc sulfide concentrate during the roasting at microwave frequencies

Guang-jun¹,

Li²,

Yang³

et al. 2017

Preprint

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Abstract:Microwave technology has a potential application in the extraction of zinc from sulphide ores, knowledge of the dielectric properties of these ores plays a major role in the microwave design and simulation for any process. The dielectric properties of zinc sulfide concentrate for two different apparent densities-1.54 and 1.63 g/cm 3 -have been measured by using the resonance cavity perturbation technique at 915 and 2450 MHz during the roasting process for the temperature ranging from room temperature to 850 °C. The variations of dielectric constant, the dielectric loss factor, the dielectric loss tangent and the penetration depth with the temperature, frequency and apparent density have been investigated numerically. The results indicate that the dielectric constant increases as the temperature increases and temperature has a pivotal effect on the dielectric constant, while the dielectric loss factor has a complicated change and all of the temperature, frequency and apparent density have a significant impact to dielectric loss factor. Zinc sulfide concentrate is high loss material from 450 to 800 °C on the basis of theoretical analyses of dielectric loss tangent and penetration depth, its ability of absorbing microwave energy would be enhanced by increasing the apparent density as well. The experimental results also have proved that zinc sulfide concentrate is easy to be heated by microwave energy from 450 to 800 °C. In addition, the experimental date of dielectric constant and loss factor can be fitted perfectly by Boltzmann model and Gauss model, respectively.

show abstract

Microwave dielectric characterization of hay during pyrolysis

Cited by 38 publications

References 44 publications

Dielectric Properties of Zinc Sulfide Concentrate during the Roasting at Microwave Frequencies

Dielectric Properties of Zinc Sulfide Concentrate during the Roasting at Microwave Frequencies

The application of microwave heating in bioenergy: A review on the microwave pre-treatment and upgrading technologies for biomass

Dielectric properties of zinc sulfide concentrate during the roasting at microwave frequencies

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