Analysis of moisture re-adsorption behavior of dried lignite: Inherent and extrinsic factors

Abstract

This work aimed to clarify the influencing factors and mechanism of the moisture re-adsorption characteristics of dried lignite through a combination of experiment and simulation. By using the self-built experimental system, the effects of extrinsic environment and lignite’s inherent properties on moisture re-adsorption characteristics were investigated. Mercury intrusion method was used to determine the pore structure and Fourier transform infrared spectroscopy was used to analyze the distribution of surface functional groups. Then, based on the quasi second-order kinetic model, the rate constant of moisture was calculated. Experimental results revealed that pore size and oxygen-containing functional groups are the main influencing factors. A close correlation between porosity and rate constant was observed. With the help of molecular dynamics simulation, moisture is found to be more easily adsorbed on carboxyl groups compared to hydroxyl groups. In the light of thermodynamics analysis and Dent model, the effect of extrinsic environment on moisture re-adsorption was examined. In low-humidity environment, humidity is the decisive factor for moisture equilibrium content, while it is temperature in high-humidity environment. The result of this paper will provide a systematic understanding of moisture re-adsorption of dried lignite.

Keywords:

• moisture re-adsorption
• pore structure
• particle size
• thermodynamic analysis
• dried lignite

Additional information

Funding

This work is supported by the National Natural Science Foundation of China (51974308, 51974312), National key R&D Program of China (2019YFE0100100), Major Science and Technology Project of Shanxi Province (20181102017), the open sharing fund for the large-scale instruments and equipments of China University of Mining and Technology (CUMT) (DYGX-2020-001).