Polymer-augmented aqueous foams for suppression of respirable coal dust

Study on Crust-Shaped Dust Suppressant in Non-Disturbance Area of Open-Pit Coal Mine-A Case Study

Dust pollution in open-pit coal mines severely restricts the green development of mines. Therefore, dust control has become an important requirement for the sustainable development of the mining industry. With the goal of dust pollution prevention and control in open-pit coal mines, this paper puts forward the concept of a non-disturbance area of an open-pit coal mine. It clarifies the characteristics of dust generation, the coverage area, and the dust particle size distribution characteristics of the non-disturbance area. Taking the dust control at the dump site as an example, the study comprehensively utilizes indoor tests and field tests to develop a dust suppressant for the dump site and determine its dust suppression efficiency and effective service cycle. The results show that the D10, D50, and D90 particle sizes of dust in the non-disturbance area are smaller than those in the disturbance area, and the difference in particle size of D90 is the most obvious. Gelatinized starch and non-ionic polyacrylamide, as the main components of the dust suppressant, can effectively reduce dust pollution in the dump; the optimal concentration is 1.0%, and the dust suppression service cycle is more than one month. The developed dust suppressant does not contain corrosive, toxic, or heavy metal elements. Although the application of a dust suppressant will cause plant growth to lag, it does not affect plant health. The research findings serve as a reference for the zoning treatment of dust in open-pit mines.

Effects of Surfactant Compounding on the Wettability Characteristics of Zhaozhuang Coal: Experiment and Molecular Simulation

It is important to study the mechanism of wettability of Zhaozhuang coal with surfactant compoundings in order to prevent dust disaster in the process of coal seam mining. By means of molecular simulation, the amounts of water absorbed by different systems, which are composed of monomer surfactant molecules and Zhaozhuang coal molecules or compounding surfactant molecules and Zhaozhuang coal molecules, were compared in this paper. The simulation results show that the system composed of 0.2% sodium dodecyl benzene sulfonate (SDBS) and 0.3% alcohol polyoxyethylene ether (AEO3) had the maximum water absorption amount of 479, which is significantly better than that of other compounding methods and of each monosurfactant system. Analysis results show that the interference of non-ionic surfactant can greatly reduce the electrostatic repulsion between ionic surfactants and make the adsorption sites on the Zhaozhuang coal molecule more compact. The experimental results show that the decreasing percentage of the contact angle of this type of compounding solution on Zhaozhuang coal was 83.74%, which is the best of the six compounding methods. It has a high degree of consistency with the simulation results, and the molecular simulation method applied in this paper shows that it is convenient and accurate. This research plays a guiding role in dustproof work in Zhaozhuang coal mining.

Interaction of Particles with Surfactant Thin Films: Implications for Dust Suppression

Understanding the interaction of particles with foams is important in antifoaming applications and dust suppression. In the former, the aim is for the particles to break the foam, whereas in the latter it is desirable that the stability of the foam is maintained or enhanced. The interaction of particles of different wettabilities with thin surfactant films is investigated with a Sheludko cell, enabling the thinning and rupture of the films to be studied in the presence and absence of a particle, using white-light interferometry. The films were prepared from the surfactant cetyltrimethylammonium bromide and a commercial dust suppression foaming agent. The film lifetimes are extended upon the addition of hydrophilic particles and reduced upon the addition of hydrophobic particles with advancing contact angles >90°. The Laplace pressure in the film surrounding a particle is calculated as a function of the contact angle and particle size, revealing that the meniscus surrounding hydrophilic particles has a positive Laplace pressure, which increases the lifetime of the film.

Foam property tests to evaluate the potential for longwall shield dust control

Tests were conducted to determine properties of four foam agents for their potential use in longwall mining dust control. Foam has been tried in underground mining in the past for dust control and is currently being reconsidered for use in underground coal longwall operations in order to help those operations comply with the Mine Safety and Health Administration's lower coal mine respirable dust standard of 1.5 mg/m³. Foams were generated using two different methods. One method used compressed air and water pressure to generate foam, while the other method used low-pressure air generated by a blower and water pressure using a foam generator developed by the U.S. National Institute for Occupational Safety and Health. Foam property tests, consisting of a foam expansion ratio test and a water drainage test, were conducted to classify foams. Compressed-air-generated foams tended to have low expansion ratios, from 10 to 19, with high water drainage. Blower-air-generated foams had higher foam expansion ratios, from 30 to 60, with lower water drainage. Foams produced within these ranges of expansion ratios are stable and potentially suitable for dust control. The test results eliminated two foam agents for future testing because they had poor expansion ratios. The remaining two foam agents seem to have properties adequate for dust control. These material property tests can be used to classify foams for their potential use in longwall mining dust control.