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

The dynamic wetting behavior of droplets impacting the coal surface directly affects the efficient application of water-based dust suppression materials in coal-related industrial production. In this paper, ultrapure water, Tween-80, and sodium carboxymethyl cellulose are taken as the research objects. Using high-speed photography technology, the spreading, oscillation process, and splash morphology of many kinds of droplets during impacting the coal surface are captured. The effects of viscosity, surface tension, and impact velocity on dynamic wetting characteristics were studied. The results show that with the decrease of surface tension, the retraction and oscillation of droplets are significantly reduced. For the same kind of droplets, the greater the impact velocity, the faster the droplet spread, and the dimensionless maximum spreading coefficient (ßmax) and dimensionless steady-state spreading coefficient (ße) of droplets are bigger. With the increase of velocity, the time for different kinds of droplets to reach the ßmax increases. At the same impact velocity, ßmax and ße of droplets (0.2% Tween-80 + 0.1% sodium carboxymethyl cellulose) are the largest, indicating that adding a small amount of sodium carboxymethyl cellulose can promote droplet spreading. With the increase of sodium carboxymethyl cellulose content, ßmax and ße decreased gradually. The results have a great significance to the research, development, and scientific utilization of water-soluble polymer dust inhibitors.

Wetting behavior during impacting bituminous coal surface for dust suppression droplets of fatty alcohol polyoxyethylene ether.

The wetting behavior of droplets during impacting coal surface widely exists in the dust control process. Understanding the effect of surfactants on the diffusion of water droplets on coal surface is critical. To study the effect of fatty alcohol polyoxyethylene ether (AEO) on the dynamic wetting behavior of droplets on bituminous coal surface, a high-speed camera is used to record the impact process of ultrapure water droplets and three different molecular weight AEO solution droplets. A dynamic evaluation index, dimensionless spreading coefficient ([Formula: see text]), is used to evaluate the dynamic wetting process. The research results show that maximum dimensionless spreading coefficient ([Formula: see text]) of AEO-3, AEO-6, and AEO-9 droplets is greater than that of ultrapure water droplets. With the increase of impact velocity, the [Formula: see text] increases, but the required time decreases. Moderately increasing the impact velocity is conducive to promoting the spreading of droplets on the coal surface. Below the critical micelle concentration (CMC), the concentration of AEO droplets is positively correlated with the [Formula: see text] and the required time. When the polymerization degree increases, the Reynolds number ([Formula: see text]) and Weber number ([Formula: see text]) of droplets decrease, and the [Formula: see text] decreases. AEO can effectively enhance the spreading of droplets on the coal surface, but the increase in polymerization degree can inhibit this process. Viscous force hinders droplet spreading during droplet interaction with the coal surface, and surface tension promotes droplet retraction. Under the experimental conditions of this paper ([Formula: see text], [Formula: see text]), there is a power exponential relationship between [Formula: see text] and [Formula: see text].

Spreading Behavior and Wetting Characteristics of Anionic Surfactant Droplets Impacting Bituminous Coal.

Spraying water-based materials on the coal surface is a common means of coal dust suppression. There are obvious dynamic wetting behaviors during droplets impacting coal. To explore the spreading behavior and wetting characteristics of anionic surfactant droplets on bituminous coal, three anionic surfactants, which are sodium dodecyl sulfate (SDS), sodium dodecyl sulfonate (SDDS), and sodium dodecyl benzene sulfonate (SDBS), were used for the droplet impact experiment and molecular dynamics (MD) simulation. The results show that the addition of anionic surfactants can promote the wetting behavior of the droplet, and the difference between the head group and the tail group of the surfactant molecules can affect the wettability of the droplet. The dimensionless spreading coefficient shows the rule of SDBS > SDS > SDDS. When the concentration does not reach critical micelle concentration (CMC), the surface tension decreases and the dimensionless spreading coefficient of droplets increases with the increase of concentration. When the droplet concentration reaches the CMC, surface tension is no longer an effective indicator to evaluate the wettability of droplets. The dimensionless spreading coefficient can effectively evaluate the macroscopic spreading wetting behavior of droplets, and it is better than the surface tension. MD simulation results show that the interaction between anionic surfactants and coal molecules can affect the adsorption behavior, and the interaction energy and adhesion work are shown as the rule of SDBS < SDS < SDDS. The results of MD simulation and the impact experiment show that the intermolecular adsorption behavior has a significant influence on the spreading process. The results of MD simulation further explain the results of the droplet impact experiment.