Modeling and experiments for transient diffusion coefficients in the desorption of methane through coal powders. (July 2017)

• Record Type: Journal Article
• Authors: Zhao, Wei; Cheng, Yuanping; Jiang, Haina; Wang, Haifeng; Li, Wei
• Is Part Of: International journal of heat and mass transfer. Volume 110(2017)
• Page Start: 845
• Page End: 854
• Publication Date: 2017-07
• Subjects: Unipore diffusion -- N2 adsorption -- Mercury intrusion porosimetry -- Capillary mechanics; UDM unipore diffusion model -- UDMD unipore diffusion model with D(t) -- UDMS unipore diffusion model simplification -- UDMS unipore diffusion model with D(t) simplification -- NMR Nuclear Magnetic Resonance; Heat -- Transmission -- Periodicals; Mass transfer -- Periodicals; Chaleur -- Transmission -- Périodiques; Transfert de masse -- Périodiques; Electronic journals; 621.4022
• DOI: 10.1016/j.ijheatmasstransfer.2017.03.065
• Languages: English
• ISSNs: 0017-9310

Abstract

Highlights: Measure the transient diffusion coefficients with a limit approximation method. Analyze the factors affecting transient diffusion coefficients in the desorption of methane. Propose a new model to describe the transient diffusion coefficients variation with time. Develop a new desorption model by introducing transient diffusion coefficients. Abstract: Diffusion is widely thought to be the key factor that controls the desorption of gas through porous media. However, the classical diffusion model with a constant Fick diffusion coefficient is inadequate for describing desorption from coal over the entire timescale. In this study, a new model to describe the time-dependent diffusion coefficients during desorption was developed. Experiments including proximate analyses, isothermal adsorptions, mercury intrusions, N2 adsorptions and methane desorptions were conducted to verify its validity. The results demonstrated that the Fick diffusion coefficients decreased over the desorption period first sharply and then slowly. By introducing the time-dependent relationship into the general unipore model, we obtained a unipore diffusion model with D (t) (UDMD), which had a better degree of fit with the laboratory desorption than that of the original. Moreover, the simplification for the UDMD was acquired for engineering applications.