Experimental study and energy analysis on microwave-assisted lignite drying

Li, Longzhi; Jiang, Xiaowei; Qin, Xuzhen; Yan, Keshuo; Chen, Jian; Feng, Tai; Wang, Fumao; Song, Zhanlong; Zhao, Xinbing

doi:10.1080/07373937.2018.1480494

Cited by 18 publications

(9 citation statements)

References 29 publications

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“…P real is the real output power of microwave (W), P 1 is the latent heat required for water evaporation (W), and P 2 is the sensible heat required for the rise in sludge temperature (W). The real output power P real is measured according to GB/T18800-2017 [36]; detailed measurement steps and results can be found in Table A2. Energy consumption is defined as the electric energy consumed by the evaporation of moisture per unit mass:…”

Section: Energy Transfer Process Analysismentioning

confidence: 99%

“…Drying kinetics are crucial for gaining insights into the underlying drying mechanism. Based on research findings from conventional hot air drying, the microwave drying process of materials, such as lignite [36][37][38] or sludge [39,40], can be divided into three stages: preheating, constant-rate, and decreasing-rate stages. Some researchers [41][42][43] have further divided the decreasing-rate stage of lignite into two stages to account for the shrinkage effect observed during the drying process.…”

Section: Introductionmentioning

confidence: 99%

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Microwave Drying of Sewage Sludge: Process Performance and Energy Consumption

Wang,

Zhang,

Huang

et al. 2024

Processes

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The microwave drying of sewage sludge is characterized by its speed and safety. A novel method for identifying free and bound water is proposed in this study. Experiments were performed to investigate the process performance and energy consumption in a microwave drying unit. The results indicate that the microwave drying process can be described in three stages, i.e., the preheating stage, constant-rate stage, and decreasing-rate stage. The preheating and constant-rate stages mainly remove free water, while the decreasing-rate stage mainly removes bound water. The Linear model effectively describes the kinetic processes in the constant-rate stage, and the modified Page I model is suitable for describing the decreasing-rate stage. The energy conversion process in microwave drying is explored, revealing that heat efficiency and energy consumption are consistent with microwave power changes. The heat efficiency in the constant-rate drying stage ranges from 60.33% to 71.01%, lower than that in the preheating stage but higher than that in the decreasing-rate stage. Energy consumption in the constant-rate stage ranges from 3.84 kJ/g to 8.20 kJ/g, significantly lower than in the other two stages. These results provide fundamental data for the industrial application of microwave drying of sludge and contribute to the advancement of microwave drying technology.

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Section: Energy Transfer Process Analysismentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

Microwave Drying of Sewage Sludge: Process Performance and Energy Consumption

Wang,

Zhang,

Huang

et al. 2024

Processes

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“…Meanwhile, the steam pressure generated after steamization and the thermal stress caused by the thermal expansion of mineral particles accumulate continuously, leading to the development and expansion of pores, which opens channels for the subsequent migration of coalbed methane [ 7 , 16 ]. Briefly, the thermal effect of microwave is the rationale of coal seam degassing, and it is also the root cause why microwave technology can be applied to other coal engineering (e.g., microwave drying of lignite [ 17 , 18 ] and microwave pyrolysis of low-rank coal [ 19 , 20 ]).…”

Section: Introductionmentioning

confidence: 99%

Effect of moisture on microwave ignition of bituminous coal

et al. 2023

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The interaction between water and microwave is of vital importance to reveal the microwave ignition mechanism of water-bearing coal. This study used two group of bituminous coal after drying and water saturation treatment, for experimental testing and contrastive analysis. During the experiment, permeability of coal samples was obtained based on nuclear magnetic resonance(NMR) test, then different power of microwaves were applied to coal samples, and the occurrence of hot spots within coal samples was regarded as a sign of microwave ignition. Microwave ignition of water-saturated coal is mainly affected by microwave power and coal permeability. The pore water in low permeability coal is conducive to microwave ignition, while the pore water in high permeability coal will prolong the ignition time. There is a permeability threshold, above which the average ignition time of water-saturated coal samples is longer than that of dry coal samples, but below which the opposite is true. These insights can be used to evaluate the safety of microwave technology when applied to coal engineering.

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“…Second, the moisture absorbs a large amount of heat in the combustion process, reducing the heat release and flame temperature. , However, this problem can be alleviated by dewatering, and the physical and chemical properties of lignite are improved to some extent in this process. Moreover, the calorific value of lignite increases after drying . Dehydration has become the key issue for the full utilization of lignite resources …”

Section: Introductionmentioning

confidence: 99%

“…Moreover, the calorific value of lignite increases after drying. 12 Dehydration has become the key issue for the full utilization of lignite resources. 13 Microwave heating technology has been widely used in various industries.…”

Section: Introductionmentioning

confidence: 99%

The Influence of Anionic Additives on the Microwave Dehydration Process of Lignite

Liu

Feng

et al. 2020

Energy Fuels

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Different anionic additives were added to lignite to enhance the effect of microwave heating on the dehydration and upgrading processes. The dehydration kinetics and moisture diffusion coefficient as well as the physical and chemical properties of solid and liquid products were studied in detail. During the microwave heating process, the enhancement effect of each additive was in the order of Na2CO3 < Na2SO4 < NaCl < NaNO3. The dehydration process of lignite was well fitted by the logarithmic model. For the solid products, as the promotion effect on the dehydration process of lignite increased, the structure tended to be stable, the content of harmful gas released by combustion was reduced, and the surface hydrophobicity was enhanced. At the same time, for the liquid products, the total organic carbon, chemical oxygen demand, and electrical conductivity increased, the pH decreased and the surface tension increased first and then decreased. With an increasing additive enhancement effect, moisture loss was supplemented by the loss of inorganics and then organics.

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Experimental study and energy analysis on microwave-assisted lignite drying

Cited by 18 publications

References 29 publications

Microwave Drying of Sewage Sludge: Process Performance and Energy Consumption

Microwave Drying of Sewage Sludge: Process Performance and Energy Consumption

Effect of moisture on microwave ignition of bituminous coal

The Influence of Anionic Additives on the Microwave Dehydration Process of Lignite

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