Kinetic analysis on the microwave drying of different forms of water in lignite

Li, Chao; Liao, Junjie; Yang, Yin; Mo, Qiong; Chang, Liping; Wang, Bao

doi:10.1016/j.fuproc.2018.03.017

Cited by 33 publications

(12 citation statements)

References 41 publications

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“…In addition, there are a great deal of hydrophilic oxygen-containing groups in the lignite. Therefore, the apparent activation energy is higher during the second falling rate period [26].…”

Section: Effective Diffusion Coefficient and Activation Energymentioning

confidence: 97%

“…In addition, the drying rate curves present several different stages between 100- During the warm-up period, mostly bulk water evaporates, resulting in massive mass loss and, therefore, the drying rate increases significantly. This is due to the high dielectric constant and loss factor of the water [26]. The drying rate is a short constant in the (B) period, which could be attributed to the sufficient supply of bulk water and the balance between the water evaporation energy and the thermal energy generated by microwave energy [12].…”

Section: The Effect Of Temperature During Microwave Dryingmentioning

confidence: 99%

“…Compared to the first falling rate period, the absorbed water is being removed in the second falling rate period, and the drying rate decreases slightly, which can be attributed to the amount of the absorbed water being relatively less and having a lower dielectric loss factor than the capillary water. In addition, the desorption of absorbed water, which is in the state of multilayer and monolayer adsorption, needs to break down the stronger hydrogen bonds [26], therefore, a further reduction of the drying rate can be detected in the second falling rate period.…”

Section: The Effect Of Temperature During Microwave Dryingmentioning

confidence: 99%

“…During the first falling rate period, the mass loss can be mainly attributed to the removal of capillary water compared to absorbed water during the second falling rate period. Capillary water, which exists in the pore channels of lignite, was removed through overcoming the Van der Waals forces and hydrogen bond resistance, which exists among the water molecules [26]. However, the amount of absorbed water is relatively less and it is tightly bounded to the solid particles.…”

Section: Effective Diffusion Coefficient and Activation Energymentioning

confidence: 99%

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Effect of Temperature and Microwave Power Levels on Microwave Drying Kinetics of Zhaotong Lignite

Zhao

Liu

et al. 2019

Processes

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Microwave drying is a promising and effective way to drying and upgrading lignite. The influence of temperature (100-140 • C) and microwave power levels (500-800 W) on thin-layer drying characteristics of Zhaotong lignite under microwave irradiation were investigated. Fourteen thin-layer drying models were used to analyze the microwave drying process while six thin-layer drying models were used to analyze the hot-air drying process. The microwave drying processes at all temperature (100-140 • C) or low microwave power levels (500-700 W) exhibited four periods: a warm-up period, a short constant period, the first and second falling rate period, while one falling rate period was found during hot-air drying. The effective diffusion coefficient of lignite were calculated and it increases with increasing temperature and microwave power levels. During microwave drying, the two-term exponential model is the most suitable model for all applied conditions, while the Modified Page model is the most suitable model to describe the hot-air drying experiments. The apparent activation energy were determined from Arrhenius equation and the values for the first and second falling rate period are 3.349 and 20.808 kJ·mol −1 at different temperatures, while they are 13.455 and 19.580 W·g −1 at different microwave power levels. This implies the apparent activation energy is higher during the second falling rate period, which suggest that the dewatering of absorbed water is more difficult than capillary water. The value of apparent activation energy in hot-air drying is between the first and second falling rate period of microwave drying. Results indicate that microwave drying is more suitable to dewatering free water and capillary water of lignite.Processes 2019, 7, 74 2 of 18 high reactivity, and low pollution impurities [3], it will be used more widely in the future. Thus, moisture removal is the first essential step to improve the quality of lignite by drying technologies in downstream utilization, such as pyrolysis, gasification, liquefaction, and combustion.Various lignite dehydration technologies have been developed and researched by evaporation or non-evaporation methods [4]. Solar drying [5], steam-fluidized bed drying [6], and flue gas drum drying [7] are based on evaporation drying, while mechanical thermal expression [8,9] and hydrothermal dewatering [10,11] are based on non-evaporation drying. In traditional drying technologies, heat is transferred from the surface to the interior of the material by convection and conduction while the moisture transferred from the inside of the material to the surface. Most of thermal drying process are operated with combustion gas or superheated water vapor and the configuration of the drying reactor are complicated, which induces high costs of construction. In addition, traditional methods will lead to heating inhomogeneity, which is not beneficial for lignite upgrade. Among these dehydration technologies, microwave drying of low-rank coal is a very promising method due to its unique he...

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“…In addition, there are a great deal of hydrophilic oxygen-containing groups in the lignite. Therefore, the apparent activation energy is higher during the second falling rate period [26].…”

Section: Effective Diffusion Coefficient and Activation Energymentioning

confidence: 97%

Section: The Effect Of Temperature During Microwave Dryingmentioning

confidence: 99%

Section: The Effect Of Temperature During Microwave Dryingmentioning

confidence: 99%

Section: Effective Diffusion Coefficient and Activation Energymentioning

confidence: 99%

See 2 more Smart Citations

Effect of Temperature and Microwave Power Levels on Microwave Drying Kinetics of Zhaotong Lignite

Zhao

Liu

et al. 2019

Processes

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“…To ensure high-intensity drying of iron (II) sulfate heptahydrate, it is necessary to study the influence of the process parameters (rate of filtration of the thermal agent), the geometric dimensions of the layer on the nature of the change in moisture content over time [30]. Generalization of the results of the kinetics of drying and determination of kinetic coefficients will allow calculating the main dimensions of the drying unit, substantiating the optimal technological parameters of the process, depending on the required productivity [31,32]. Despite the fact that there is practically no information in the literature on the kinetic regularities of drying of iron (II) sulfate heptahydrate during the implementation of the process by the filtration method, the goal of the work is formulated.…”

Section: Proposed Solution To the Problemmentioning

confidence: 99%

Study of the Kinetics of Drying Iron (Ii) Sulfate Heptahydrate by Filtration Method

Tsiura

Кіндзера

Huzova

et al. 2021

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The object of research: kinetics of filtration drying process of iron (II) sulfate heptahydrate. Solved problem: to obtain the calculated dependence of the kinetics of filtration drying, which predicts the nature of the change in the moisture content of the material in time during the period of complete saturation of the thermal agent with moisture in the range of heights of the material layer 30.10-3–120.10-3 m and the speeds of the thermal agent 0.46–1.61 m/s. Main scientific results: The kinetics of filtration drying of iron (II) sulfate heptahydrate was investigated at different heights of the material layer and pressure drops over dry material, which means at different speeds of movement of the thermal agent. A certain critical moisture content, which is Wcr=0.065 kg H2O/kg dry mat and the time it reaches at different heights of the material layer and the speeds of movement of the thermal agent. Based on the solution of the system of differential equations of material balance in the layer and the kinetics of drying, the kinetic coefficients for iron (II) sulfate heptahydrate a=15.75 1/m, α=3.03.10-3 1/s were determined, which made it possible to obtain the calculated dependence of the kinetics drying, which predicts the nature of the change in the moisture content of the material over time during the period of complete saturation of the thermal agent with moisture in the range of heights of the material layer H=30.10-3–120.10-3 m and the velocities of the thermal agent υ=0.46–1.61 m/s. The area of practical application of the results: enterprises for the production of titanium (IV) oxide with the production of iron (II) sulfate heptahydrate as a by-product and enterprises specializing in the manufacture of pigments based on iron (II) sulfate heptahydrate. Innovative technological product: iron (II) sulfate tetrahydrate (FeSO4•4H2O, rosenite), obtained as a result of drying by the filtration method. Scope of application of the innovative technological product: in the production technology of iron oxide pigments.

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Optimization on Drying of Acid Leaching Slag by Microwave Heating Using Response Surface Methodology

Zheng

Gao

et al. 2019

The Minerals, Metals &Amp; Materials Series

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Kinetic analysis on the microwave drying of different forms of water in lignite

Cited by 33 publications

References 41 publications

Effect of Temperature and Microwave Power Levels on Microwave Drying Kinetics of Zhaotong Lignite

Effect of Temperature and Microwave Power Levels on Microwave Drying Kinetics of Zhaotong Lignite

Study of the Kinetics of Drying Iron (Ii) Sulfate Heptahydrate by Filtration Method

Optimization on Drying of Acid Leaching Slag by Microwave Heating Using Response Surface Methodology

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