Water Adsorption and Desorption of Upgraded Brown Coal. Part 1: Isotherms of Adsorption and Desorption

Abstract

Isotherms of water adsorption and desorption of upgraded brown coal (UBC) were compared to those of its feedstock coals, dried and not dried. The shape of isotherms showed that UBC was exposed to an irreversible collapse of capillaries by losing its original water, as was dried feedstock coal. By analyzing isotherms from the viewpoint of heat of adsorption and heat of wetting, the affinity of UBC to its adsorbed moisture was found to be smaller than that of its dried feedstock coal. This may be caused by the oil adsorbed onto its surface during slurry dewatering of the UBC process. The heat of wetting of UBC was smaller than those of its feedstock coals, which were dried. As far as UBC has the equilibrium moisture under normal ambient conditions, the risk of hot pile because of heat of wetting seems to be reduced.

Effect of Hydrothermal Treatment Coupled with Mechanical Compression on Equilibrium Water Content of Loy Yang Lignite and Mechanism

“…As reported by Shigehisa et al 6) and Charrière et al 15) , adsorption process includes three steps. (1) Adsorption on active adsorption sites; (2) formation of water clusters; and (3) pore lling of water clusters and capillary condensation in narrow pores.…”

“…These studies showed that there are many factors (e.g., oxygen-containing functional groups, RWC, pore volume, and RH) that affect EWC of dewatered lignite [6][7][8][9][10][11][12][13] . Early work was based on the measurement of adsorption-desorption isotherms of water, and water in lignite can be categorized into free, capillary, multilayer, and monolayer water, which is the basis for the scienti c studies today 7,8) .…”

“…Numerous studies showed that dewatered lignite with different RWCs either re-adsorb or evaporate water at various RHs [6][7][8][9][10][11][12][13][14][15] . As reported by Shigehisa et al 6) and Charrière et al 15) , adsorption process includes three steps.…”

Analysis of the tempo‐spatial effects of hydraulic fracturing by drilling through underground coal mine strata on desorption characteristics

“…Tests of gas adsorption-desorption were carried out with the self-designed laboratory simulation testing device, which was slightly modified according to the experimental devices. [42][43][44][45][46] The laboratory tests: the vacuum degree of the sealed coal sample is less than 10 Pa, stable for 48 hours, and filled with high-purity test methane (99.99%). The tests of gas adsorption equilibrium were concluded when the gas pressure change was no more than 0.05 MPa for 2 hours.…”

“…Four groups, the coal samples with the grain size range of 1‐3 mm and the weight of 1000 g were screened and immediately put into a glass container with a sealing grinding port to maintain its original moisture state. Tests of gas adsorption‐desorption were carried out with the self‐designed laboratory simulation testing device, which was slightly modified according to the experimental devices …”