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Foam dust suppression is an efficient method to control dust hazards, in which the foam morphology is closely related to its dust-suppression performance. As a commonly used foaming agent auxiliary, water-soluble polymer (e.g. carboxymethyl cellulose) is believed to be able to change foam morphology. To explore the effect of carboxymethyl cellulose (CMC) on the foam morphological characteristics, CMC was added in alpha-olefin sulfonate (AOS) solution at different concentrations and tested for the influence on bubble size, distribution and uniformity of AOS foams. The results showed that both during the foam formation and decay, the average bubble size decreased, and the foam uniformity simultaneously increased with an increase of AOS concentration, and furthermore, the size and uniformity gradually stabilized when the AOS concentration was higher than 0.1 %. After CMC addition, there is an optimal turning point (0.1 % AOS) where the effect of 800 mg/L CMC addition on foam morphology is most pronounced, the average radius of bubbles could reach a minimum of 0.13 mm, and the uniformity reaches the highest. Adding CMC of 800 mg/L in 0.1 % AOS solution is an effective way to optimize the morphology of dust-suppression foam. This study provides important reference for using water-soluble polymer to improve the performance of dust-suppression foam in engineering.

To reveal the influence of pore structure of coal on the characteristics of coal dust generation during roadheader cutting, a self-developed coal cutting system was used to generate dust. A low field nuclear magnetic resonance was utilized to measure the pore system of coal. Results show that the porosity had negative correlations with the cumulative proportions of both respirable dust and fine particulate matter (PM2.5), but the positive influence on the mass ratio of dust generation (MRD) of total dust and slight effect on MRD of respirable dust and PM2.5 were observed. The correlations of the fractal dimension (Df) of pore structure on dust generation were inverse compared with that of porosity. The negative relationship between porosity and Df was the reason for the opposite correlations. This study can provide basic support for the estimate of dust hazard and the development of dust control technologies.

As dust is one of the main hazards generated by coal cutting, understanding the properties of dust generation is essential for preventing and controlling its propagation. This paper therefore aims to investigate the influence of coal brittleness on dust generation. A system was devised to produce dust and the density, uniaxial compressive strength, and Brazilian tensile strength of dust samples were then measured. The results showed that the cumulative proportions of fine particulate matter and respirable dust increased with brittleness, while a declining trend was observed from the mass ratio of total dust to coal sample. B14 (half of the product of compressive and tensile strength) had the strongest correlation with the properties of dust generation, and accounted for more than 95% of B15 (half of the sum of compressive and tensile strength).

To investigate the characteristics of coal dust generation when cut by a roadheader, a system was designed for performing cutting experiments. The aerodynamic diameter distribution of dust was tested by a laser particle size analyzer. Correlations between the coal proximate compositions and the characteristics of dust generation were studied. Results showed that fixed carbon had significantly positive correlations with the cumulative proportion of respirable dust and the rate of dust generation. The bonded high-density pulverized core could be responsible for reducing the correlation with fine particulate matter. The presence of moisture had inhibitory effects on dust generation. Volatile matter had a slightly negative influence on dust generation, and ash was considered to have no effect. More attention should be focused on heading faces with high fixed carbon and low moisture. This study provides essential guidance for understanding the characteristics of dust generation and improving dust reduction technologies.

Water spray is the most widely used means of wet dust reduction, and its atomization parameters are directly related to the effect of dust reduction. In order to obtain the atomization properties of solid-cone spray for dust reduction, the paper used droplet velocity and particle size to characterize its atomization characteristics. The Phase Doppler Particle Analyzer (PDPA) was used to precisely measure droplet sizes and velocities of a solid-cone spray at distances of 15 cm, 25 cm and 45 cm horizontally from the nozzle outlet, using low and medium spray pressures. The results show that the droplet size was fluctuant before spray pressure increasing to 2.0 MPa and then decreased gradually with the increasing of spray pressure. The droplet velocity increased with the raising spray pressure and the velocity at 45 cm is the minimum. The droplet size measurements taken 45 cm from the nozzle exhibited more complex slope changes in particle size curve that were not existed at the closer distances spray of 15 cm or 25 cm, which implies that the near-field spray is more stable than far-field spray. This study is of important significance for further understanding the characteristics of solid-cone spray and guiding its application in dust reduction.

Foam dust suppression is an important way to control dust hazards. Polymers are believed to be able to change foam properties. To investigate the effect of polymers addition to foaming agent solution on the key dust-suppression performance of the foam, tests were conducted by measuring and comparing the contact angle, viscous modulus and foam-drainage rate of several different surfactant/polymer solutions, which can characterize the wettability, surface viscosity and stability of foam. The results show that the polymer (HEC, HPAM, PVA) addition increased the contact angle between the liquid and coal dust by increasing the surface tension of the surfactant solution. The variation is more obvious with an increase in polymer concentration (especially over 0.3 wt.‰); simultaneously, the polymer increases the surface viscosity of the foaming agent solution significantly, and slows down the foam-drainage rate, which is advantageous for increasing the foam stability. Because of the variation, the low concentration of polymer (0.1–0.3 wt.‰) has a weak influence on the wetting ability of the foaming agent while improves the surface viscosity and stability of foam significantly, which is an improvement in terms of the dust-suppressing ability of foams.

Foam dust suppression is an effective technique for controlling dust at its source. Dilatational interfacial rheology is an important property of aqueous foam. It characterizes the strength and toughness of liquid film and acts on the foaming process and drainage, affecting foaming capacity (FC) and foam stability (FS). The interfacial viscoelastic properties of anionic and nonionic surfactants commonly used were studied by testing the viscoelastic properties with different foaming agent concentrations (FAC) and their effects on foam performance were investigated. The results show that increasing FAC from 0.1 wt. ‰ to 1.0 wt. ‰ generally decreased the viscoelastic modulus, which was negatively correlated with FC: 6501 had a highly linear relationship between FC and viscoelastic modulus. The viscoelastic modulus of K12 and AES were positively correlated with FC in the low-modulus range, then negatively correlated at higher viscoelastic modulus values; the turning point was defined as the optimal viscoelastic modulus. The viscoelastic modulus had a significant positive effect on FS. The surface viscoelasticity contributed greatly to improving FS before the critical micelle concentration (CMC) was reached. After reaching CMC, micelle properties of bulk phase mainly affected the foam life.

Spray dust reduction is widely used in dust pollution control. The spray effect directly affects dust reduction efficiency, hence it is important to understand spray atomization and differential characteristics for typical water-based dust reduction media: tap water, magnetized water, surfactant solution, and magnetized surfactant solution. This study selected five measuring points 10, 15, 20, 25, and 40 cm from the nozzle to measure spray velocity and droplet size using a Phase Doppler Particle Analyzer at 1.5, 2.0, and 2.5 MPa. The results shown that the spray velocity of the other three media was generally larger than that of tap water. From 20 cm to 25 cm, the spray velocity of magnetized water and surfactant solution water decreased rapidly, with 35.53% and 49.78% reduction, respectively. The droplet size of tap water spray at 40 cm increased, whereas the sprays of other water-based media continuously decreased. The change amplitude of Sauter mean diameter (D32) was lower trend with pressure. Magnetized surfactant solution maintained the largest ratio of particles

Safe mining is the premise and guarantee of sustainable development of coal energy. Due to the combination of excellent properties of polymers and traditional soft matters, polymer-containing soft matters are playing an increasingly important role in mine disaster and hazard control. To summarize the valuable work in recent years and provide reference and inspiration for researchers in this field, this paper reviewed the recent research progress in polymer-containing soft matters with respect to mine dust control, mine fire control, mine gas control and mine roadway support. From the perspective role of polymers in a material system, we classify mine polymer-containing soft matters into two categories. The first is polymer additive materials, in which polymers are used as additives to modify fluid-like soft matters, such as dust-reducing agents (surfactant solution) and dust-suppressing foams. The second is polymer-based materials, in which polymers are used as a main component to form high performance solid-like soft matters, such as fire prevention gels, foam gels, gas hole sealing material and resin anchorage agent. The preparation principle, properties and application of these soft matters are comprehensively reviewed. Furthermore, future research directions are also suggested.