Effect of temperature and microwave power levels on microwave drying kinetics of zhaotong lignite

Pengfei Zhao, Chenhui Liu, Wenwen Qu, Zhixiu He, Jiyun Gao, Lijuan Jia, Siping Ji, R. R Ruan

Research output: Contribution to journalArticle

Abstract

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.

Original languageEnglish (US)
Article number74
JournalProcesses
Volume7
Issue number2
DOIs
StatePublished - Feb 1 2019

Fingerprint

Coal
Lignite
Drying
Microwaves
Kinetics
Temperature
Water
Activation energy
Dewatering
Air
Microwave irradiation

Keywords

  • Apparent activation energy
  • Effective diffusion coefficient
  • Hot-air drying kinetics
  • Lignite
  • Microwave drying kinetics

Cite this

Effect of temperature and microwave power levels on microwave drying kinetics of zhaotong lignite. / Zhao, Pengfei; Liu, Chenhui; Qu, Wenwen; He, Zhixiu; Gao, Jiyun; Jia, Lijuan; Ji, Siping; Ruan, R. R.

In: Processes, Vol. 7, No. 2, 74, 01.02.2019.

Research output: Contribution to journalArticle

Zhao, Pengfei ; Liu, Chenhui ; Qu, Wenwen ; He, Zhixiu ; Gao, Jiyun ; Jia, Lijuan ; Ji, Siping ; Ruan, R. R. / Effect of temperature and microwave power levels on microwave drying kinetics of zhaotong lignite. In: Processes. 2019 ; Vol. 7, No. 2.
@article{1577d476f65d44d689ba27302b0c8544,
title = "Effect of temperature and microwave power levels on microwave drying kinetics of zhaotong lignite",
abstract = "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.",
keywords = "Apparent activation energy, Effective diffusion coefficient, Hot-air drying kinetics, Lignite, Microwave drying kinetics",
author = "Pengfei Zhao and Chenhui Liu and Wenwen Qu and Zhixiu He and Jiyun Gao and Lijuan Jia and Siping Ji and Ruan, {R. R}",
year = "2019",
month = "2",
day = "1",
doi = "10.3390/pr7020074",
language = "English (US)",
volume = "7",
journal = "Processes",
issn = "2227-9717",
publisher = "MDPI AG",
number = "2",

}

TY - JOUR

T1 - Effect of temperature and microwave power levels on microwave drying kinetics of zhaotong lignite

AU - Zhao, Pengfei

AU - Liu, Chenhui

AU - Qu, Wenwen

AU - He, Zhixiu

AU - Gao, Jiyun

AU - Jia, Lijuan

AU - Ji, Siping

AU - Ruan, R. R

PY - 2019/2/1

Y1 - 2019/2/1

N2 - 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.

AB - 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.

KW - Apparent activation energy

KW - Effective diffusion coefficient

KW - Hot-air drying kinetics

KW - Lignite

KW - Microwave drying kinetics

UR - http://www.scopus.com/inward/record.url?scp=85062774478&partnerID=8YFLogxK

UR - http://www.scopus.com/inward/citedby.url?scp=85062774478&partnerID=8YFLogxK

U2 - 10.3390/pr7020074

DO - 10.3390/pr7020074

M3 - Article

VL - 7

JO - Processes

JF - Processes

SN - 2227-9717

IS - 2

M1 - 74

ER -