Experimental Study on the Wettability of Tectonic Soft Coal in Huaibei Mining Area, China

Abstract

This study investigated the wettability of tectonic soft coal by analyzing the relationship between proximate analysis indexes, oxygencontaining functional groups, pore characteristics, hardness, gas adsorption capacity, and contact angles. Results show that coal was more hydrophilic with the increase of gas adsorption capacity, moisture content, ash content, and the content of Si−O−Si functional groups and was more hydrophobic with the increase of the fixed carbon content and coal hardness, while the correlation between volatile matter and wettability was not obvious. The isothermal adsorption/desorption curves of coal obtained from a lowtemperature nitrogen adsorption experiment show that the greater the number of open pores and the better the connectivity of pores, the better the coal wettability. The pore fractal characteristic was analyzed with respect to two aspects: the coal surface roughness represented by the surface fractal dimension D 1 and the pore irregularity and complexity represented by the structure fractal dimension D 2 . The relationships between D 1 , D 2 , and the contact angle show that with the increase of D 1 and D 2 , the coal wettability becomes better, which indicates that the rougher the coal surface and the more complex the pore structure, the better the coal wettability.

Wetting Behavior of CO2–H2O–coal with Different Metamorphic Degrees under In Situ Thermophysical Conditions

“…From the Lambert–Beer law, the normalized peak area percentage was used to represent the relative content of functional groups . According to the polynomial curve fitting shown in Figure , hydroxyl groups rapidly decreased, and oxygen-containing functional groups steadily decreased with coal rank, while aromatic hydrocarbons increased.…”

“…82 From the Lambert−Beer law, the normalized peak area percentage was used to represent the relative content of functional groups. 83 According to the polynomial curve fitting shown in Figure 15, hydroxyl groups rapidly decreased, and oxygen-containing functional groups steadily decreased with coal rank, while aromatic hydrocarbons increased. The fitted curve of aliphatic hydrocarbons showed a semicircular trend of first increasing and then decreasing with coal rank, consistent with Sun et al 5 Breakage of aliphatic hydrocarbon chains under acidic environments or complex reactions (e.g., dissociation, addition, substitution) generates free radicals, 84,85 which could be responsible for the reduction of the aliphatic hydrocarbons in GHS and PDS coals.…”

Experimental Study on the Wettability of Coal with Different Metamorphism Treated by Surfactants for Coal Dust Control

“…However, because the contact angle decreases with the increase in hydroxyl, quartz, moisture, and ash content, 51 eq 4 was used to initialize them …”

Effect of Sodium Carboxymethyl Cellulose on the Dynamic Wetting Characteristics of the Dust Suppression Droplet Impacting the Coal Surface

“…At present, scholars mainly evaluate the wetting ability of droplets on coal by observing the static or slow wetting characteristics of droplets on the coal surface. The commonly used evaluation methods are the sessile drop method, sink test method, capillary rise method, infiltration method, and so on. − The sessile drop method is a common experimental method to measure the contact angle, which forms three-phase contact by slowly dropping droplets on the solid surface. A contact angle less than 90° means high wettability, while a contact angle greater than 90° means low wettability.…”