Influence of frequency, grade, moisture and temperature on Green River oil shale dielectric properties and electromagnetic heating processes

Hakala, J. Alexandra; Stanchina, W.E.; Soong, Yee; Hedges, Sheila W.

doi:10.1016/j.fuproc.2010.08.016

Cited by 35 publications

(19 citation statements)

References 55 publications

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“…Water played an important role in affecting the pore structure, forming the jet flow pressure on the pores due to the evaporation of the water. This effect of jet flow caused by microwave heating was more significant than that leaded by conventional heating, because water with high dielectric constant resulting in high absorption of microwave energy could be quickly vaporized . Therefore, three kinds of data (specific surface area, cumulative pore volume, and average pore diameter) shown in Figure were all increased at first especially for the average pore diameter.…”

Section: Resultsmentioning

confidence: 98%

Evaluation of different microwave heating parameters on the pore structure of oil shale samples

Zhu

Yang

et al. 2018

Energy Science & Engineering

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The pore structure of oil shale during microwave heating significantly determines the flow behavior, the transformation products and the ultimate recovery regardless of ex situ retorting or in situ development methods. In this experimental study, the effects of microwave heating parameters including heating time, reaction temperature and output power on the heating behavior, surface morphology and pore roughness of oil shale were investigated based on the nitrogen adsorption/desorption and scanning electron microscope (SEM) experiments. Fractal dimension D1 and D2 (at relative pressures of 0‐0.5 and 0.5‐1, respectively) were calculated according to the fractal Frenkel‐Halsey‐Hill model. The relationships between specific surface area, cumulative pore volume, average pore diameter, and fractal dimension have been studied. The results demonstrated that the pore structure of oil shale was greatly influenced by microwave heating parameters due to the decomposition of kerogen, the internal pressure caused by the steam and volatiles, the complicated reactions and the thermal stress induced by microwave. Moreover, fractal dimension also changed correspondingly with different heating parameters. The variations of fractal dimension D1 was consistent with the evolvement of specific surface area and the changes in fractal dimension D2 showed negative correlation with average pore volume. The relationships between D1 and surface roughness, D2 and pore structure were verified based on the comparison of SEM images. The fractal theory is reliable to describe the surface morphology and pore structure of oil shale and thus supports the application of microwave heating on the oil shale development.

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Section: Resultsmentioning

confidence: 98%

Evaluation of different microwave heating parameters on the pore structure of oil shale samples

Zhu

Yang

et al. 2018

Energy Science & Engineering

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“…In conclusion, the coal permittivity usually decreases with the rise of test frequency (Hakala et al 2011;Cai 2013; Boykov 2006). As a result of the intrinsic composition and structure of coal and the complexity of reactions during heating, the effect of temperature on dielectric properties are very complicated thus leading to a slight difference in the test results obtained by different scholars (Feng and Chen 2007;Li et al 2012;Peng et al 2012).…”

Section: Test Of Complex Dielectric Constant Of Coalmentioning

confidence: 91%

“…Generally speaking, coal with a low rank has a greater e 0 and e 00 ; e 0 and e 00 decreased gradually with the increase of coalification and reached the smallest for bituminous coal with a medium metamorphic degree; subsequently, e 0 and e 00 started to increase again with the increase of metamorphic degree (Misra et al 1991;Meng 2001;Zubkova and Prezhdo 2006;Hakala et al 2011). For dry coal samples, e 0 and e 00 varies little from lignite to young anthracite and subsequently increased rapidly with the rising coal ranks (Chatterjee and Misra 1990;Wang 1982).…”

Section: Test Of Complex Dielectric Constant Of Coalmentioning

confidence: 99%

Progress of the technique of coal microwave desulfurization

Tao

Xie

et al. 2014

Int J Coal Sci Technol

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With the advantages of its fast speed, effective and moderate controllable conditions, desulfurization of coal by microwave has become research focus in the field of clean coal technology. Coal is a homogeneous mixture which consists of various components with different dielectric properties, so their abilities to absorb microwaves are different, and the sulfur-containing components are better absorbers of microwave, which makes them can be selectively heated and reacted under microwave irradiation. There still remain controversies on the principle of microwave desulfurization at present, thermal effects or non-thermal effects. The point of thermal effects of microwave is mainly base on its characters of rapidly and selectly heating. While, in view of non-thermal effect, direct interactions between the microwave electromagnetic field and sulfur containing components are proposed. It is a fundamental problem to determine the dielectric properties of coal and the sulfur-containing components to reveal the interaction of microwave and sulfur-containing compounds. However, the test of dielectric property of coal is affected by many factors, which makes it difficult to measure dielectric properties accurately. In order to achieve better desulfurization effect, the researchers employ methods of adding chemical additives such as acid, alkali, oxidant, reductant, or changing the reaction atmosphere, or combining with other methods such as magnetic separation, ultrasonic and microorganism. Researchers in this field have also put forward several processes, and have obtained a number of patents. Obscurity of microwave desulfurization mechanism, uncertainties in qualitative and quantitative analysis of sulfur-containing functional groups in coal, and the lack of special microwave equipment have limited further development of microwave desulfurization technology.

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“…7,8 Many researchers have already proposed and investigated microwave heating to overcome the difficulties in reservoir development. 7,8 Many researchers have already proposed and investigated microwave heating to overcome the difficulties in reservoir development.…”

mentioning

confidence: 99%

“…microwave apparatus: A, real image of experimental setup; B, schematic diagram of experimental setup, in which (1) represents the wave generator, (2) represents the sample holder made from quartz glass,(3) represents the digital display board, (4) represents the thermocouple, (5) represents the pressure gauge, (6) represents the liquid receptor, (7) represents the condensation loop device,(8) represents the gas flow meter, and (9) represents the vacuum bag…”

mentioning

confidence: 99%

The experimental study of microwave heating on the microstructure of oil shale samples

Zhu

Yang

Liu

et al. 2019

Energy Science & Engineering

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The microstructure of oil shale plays a vital role in the seepage and production of shale oil and gas and can be modified by microwave irradiation. In this study, the experimental work aims to visualize and analyze the microstructure of oil shale under microwave heating with different heating parameters by traditional two‐dimensional (optical microscope and scanning electron microscope) and advanced three‐dimensional (micro‐CT) methods. Volumetric reconstructions of oil shale before and after microwave heating were completed to directly visualize the pore structure and fracture network of the samples. The similarities and differences between microwave heating and conventional heating were also investigated. Finally, based on the three‐dimensional CT data, the porosity and the degree of anisotropy of the samples were calculated. Traditional two‐dimensional imaging methods showed that microwave heating led to more pores and fractures due to the differential thermal stress caused by rapid heating, which differed from conventional heating. Porosity calculations based on the CT image data indicated that a long heating time and a high output power could lead to a large porosity value. Oil shale obtained by drilling horizontally into the bedding plane showed the largest porosity and lowest heterogeneity of pore distribution after heating and had a different fracture morphology. The results from this study are important for the exploitation of oil shale using microwave heating, and the application of these analytical techniques is useful for the evaluation of the flow behavior of transformation products.

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Influence of frequency, grade, moisture and temperature on Green River oil shale dielectric properties and electromagnetic heating processes

Cited by 35 publications

References 55 publications

Evaluation of different microwave heating parameters on the pore structure of oil shale samples

Evaluation of different microwave heating parameters on the pore structure of oil shale samples

Progress of the technique of coal microwave desulfurization

The experimental study of microwave heating on the microstructure of oil shale samples

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