Microwave assisted coal conversion

Singh, Surinder; Neculaes, V.B.; Lissianski, Vitali; Rizeq, George; Bulumulla, S.B.; Subia, Raul; Jeff, Manke,

doi:10.1016/j.fuel.2014.09.108

Cited by 46 publications

(19 citation statements)

References 17 publications

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“…Microwave irradiation technology has the characteristics of high thermal efficiency, strong penetrating power, and selective heating. It is used for drying coal [20], pyrolysis [21], improving grindability [22], coking [23], flotation [24], and other aspects. Some studies have reported on the improvement in CBM extraction by microwave irradiation.…”

Section: Introductionmentioning

confidence: 99%

Mechanism of Increasing the Permeability of Water-Bearing Coal Rock by Microwave Steam Explosion

Guan

et al. 2021

Geofluids

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Microwave heating of water-bearing coal can promote pore water evaporation. The pores are broken under the action of steam pressure, increasing the permeability of the coal. This study is aimed at investigating the mechanism of permeability improvement of water-bearing coal rock by microwave steam explosion. First, a microwave oven was used to irradiate and heat five groups of coal rock with different water contents; the NMR test was then conducted on the heated sample. Second, the internal vapor pressure and temperature changes during the heating process were obtained through the T-connector for samples with different water contents. Finally, a numerical experiment was used to explore the deformation characteristics of pores under three filling conditions. The experimental results showed that the total porosity increased significantly when the water content of coal increased from 0% to 8%, while the permeability increased by nearly 4.78 times. The extreme value of gas pressure inside the sample showed an increasing trend. The gas pressure and temperature were in line with the equation of state for an ideal gas during the rising phase. Numerical experiments showed that the pore boundary shrunk inward under vacuum conditions, and compressive stress appeared at the tip. The saturated humid air and liquid water conditions expanded the pore boundaries outward and caused tensile stress at the tip, with the latter being nearly 2.3 times larger than the former, making it more conducive to the development of pores. The findings of this study can be used as a reference value for the expansion of coalbed methane extraction technology.

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Section: Introductionmentioning

confidence: 99%

Mechanism of Increasing the Permeability of Water-Bearing Coal Rock by Microwave Steam Explosion

Guan

et al. 2021

Geofluids

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“…With these unique properties, the microwave has been applied in coal processing operations such as cleaning, drying/dewatering, coking, floatation, grinding, and desulfurization. 19 − 21 …”

Section: Introductionmentioning

confidence: 99%

Experimental Research on the Influence of Microwave Radiation on Coal Permeability and Microstructure

Wang

Gao

et al. 2021

ACS Omega

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At present, there is limited information available about the effects of microwave radiation on desorption characteristics, microstructures, and functional groups of coal. This research focuses on the influence of microwave radiation on coal sample desorption and examines the changes in pore structures and oxygenic groups of different coal samples using liquid nitrogen adsorption, nuclear magnetic resonance, and X-ray photoelectron spectroscopy. Results prove that the methane desorption capacity and desorption rate are proportional to the increase in microwave energy; the initial dynamic diffusion coefficient is also proportional to microwave energy but negatively proportional to the attenuation coefficient. As a result of microwave radiation, the Brunauer–Emmett–Teller (BET) surface area, pore size, and Barret–Joyner–Halenda (BJH) pore volume decreased. The specific surface area of BET decreased and then increased as microwave energy increased, while the average pore size increased and then decreased. However, the change in the BJH cumulative adsorption pore volume was complicated. The microwave radiation decreases the volume and number of micropores while increasing the volume and number of medium pores. With the increase in microwave energy, the number and volume of micropores continue to decrease, while the number and volume of medium pores continue to increase. An increase in microwave energy increased the surface area of oxygenic groups with the increasing relative content of COO–, C–O, and C=O bonds; however, the relative content of C–C/C–H bonds decreased. These findings deepen the understanding of the antireflection effects of microwaves on coal.

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“…In recent years, microwave heating has gained widespread popularity in coal drying, desulphurization, pyrolysis, grinding, and coal bed methane [20,[26][27][28][29]. Among these, the research results in the field of grinding and coal bed methane showed that microwave treatment can lead to the formation of new cracks and promote the expansion of the original cracks in coal mass [30].…”

Section: Introductionmentioning

confidence: 99%

Modification of Coal Samples with Bursting Liability Subjected to Microwave Irradiation

Wen

Guan

Zhao

et al. 2021

Shock and Vibration

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This paper introduces the innovative technique to release the bursting liability of coal seam via microwave irradiation. To verify the feasibility of this environment-friendly technique, a series of laboratory tests incorporating acoustic emission (AE) investigation were carried out. Test results indicated that both the uniaxial compressive strength (UCS) and bursting energy index of raw and water-soaked coal samples were significantly reduced. In particular, the bursting liability was reduced by one level when the values of UCS were compared, the evidence of which is the variation of wave velocities of tested coal samples. It can also be found from the events and hits in the complete stress-strain curve and the cumulative curve of acoustic emission that the elastic modulus of the raw and water-soaked coal samples subjected to microwave irradiation decreased by 58.42% and 29.63%, respectively. This facilitates the entry into the stage of stable crack propagation more quickly, the growth rate and size of the cracks were slower and more uniform, and there were no smaller coal fragments ejecting during the failure process of the coal samples. Meanwhile, the proportion of high-energy events released in coal samples experienced a decline after the treatment of the microwave. Moreover, microwave heating principally promoted the initiation and expansion of microcracks in coal samples under the influence of microwave power of 1 kW and a heating time of 120s, which may cause the overall damage of large fractures to break into multiple small and medium cracks. Based on the experimental results, the conceptual process of using microwave in weakening the bursting liability of coal seam was then proposed, which will be the meaningful reference for microwave-assisted oil recovery and coal bed methane production.

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Microwave assisted coal conversion

Cited by 46 publications

References 17 publications

Mechanism of Increasing the Permeability of Water-Bearing Coal Rock by Microwave Steam Explosion

Mechanism of Increasing the Permeability of Water-Bearing Coal Rock by Microwave Steam Explosion

Experimental Research on the Influence of Microwave Radiation on Coal Permeability and Microstructure

Modification of Coal Samples with Bursting Liability Subjected to Microwave Irradiation

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