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The unsteady foaming-agent mixing ratio in traditional foam-dust-suppression technology limited the dust suppression efficiency. Recent studies proved that the steady mixing ratio could be guaranteed by keeping the jet pumps or Venturis working under cavitation conditions, but the pressure loss of the current devices was over 50%. To decrease the pressure loss under cavitation conditions, we proposed a new mixing device by introducing a spoiler in the Venturi structure. Through computational fluid dynamics (CFD) simulation, the spoiler structure influence on the downstream flow field and the cavitation cloud structure, which affected the total pressure loss of the device, were revealed. For structure optimization, the effect of the other geometric parameters, including the throat length and divergent angle, on the pressure loss was also studied. The proposed device enhanced the cavitation on the suction tube side of the throat; meanwhile, the cavitation in other parts of the device was avoided. Therefore, the cavitation zone in the proposed device was much smaller than that in current devices, and the pressure loss was reduced significantly. When the flow ratio was 0.5-1%, the critical pressure ratio of the proposed mixing device was 0.71-0.68, which indicated that the pressure loss was only 29%-32%. The laboratory experiment verified that when the proposed device worked under cavitation conditions, the accurate and steady mixing ratio was guaranteed. The field experiment indicated that due to the reduced pressure loss of the proposed device, the required water inlet pressure decreased to 0.29 MPa, and the dust suppression rate increased dramatically. This study was of important value in manipulating cavitation cloud structure using a spoiler, clarifying the influence of the cavitation cloud structure on the liquid mixing performance and expanding the application field of the cavitating mixing method.

Wet dust removal is one of the main technical measures in coal dust control, and coal dust wetting is the key factor to determine the effect of wet dust removal. In order to explore the micro-wetting process of coal dust, this paper uses molecular dynamics simulation to study the micro-wetting process of coal dust in different simulation conditions. The molecular dynamics simulation was carried out under different ensemble, thermodynamic states as well as relaxation pretreatment methods, then the H2O molecular layer and coal dust molecular layer in each simulation were quantitatively analyzed by relative concentration. The research results show that a method for establishing molecular model of lignite is proposed and the 2D periodic surface structure is more reasonable. The surface system of coal-H2O molecule is established by NVT aeration method, where the simulation result is close to the actual coal dust wetting process. The simulation effect of medium and large coal dust-H2O molecular system is better than that of small coal dust-H2O molecular system. This study provides a new solution for changing the empirical method of molecular dynamics simulation of coal system wetting and oversimplification of coal system.

Methane-air explosions are the most fatal accidents in underground coalmines. To understand its destruction, a worst-case full-scale methane-air explosion at a longwall coalface was simulated and a...

To investigate the overpressure of methane-air explosions in straight large-scale tunnels, the computational fluid dynamics (CFD) code of Flame Accelerator Simulator (FLACS) was used and validated against experiments conducted at three different scales, and the effects of the volume concentration of methane in air, the blockage ratio (BR), the tunnel length, and the cross-section were studied. When analysed using the GaussAmp mathematical model, the maximum peak overpressure appears at a volume concentration of 10.30 % of methane in air. Blockage ratios (BR) of 0.15 and 0.3 resulted in the combustion of methane-air mixtures with the volume concentration of 6.5 % and 14.0 % of methane in air, producing a fatal overpressure of 21 kPa. When the BR increases up to 0.75, both the lean and rich mixtures cause a peak overpressure of over 60 kPa. Combustion of the same methane-air mixture produces the same overpressure, which decays approximately linearly at the same slope owing to a smooth wall roughness before travelling near the outlet, independent of the specific tunnel length. A method to characterise the cross-sections was proposed, and the maximum peak overpressure of different lengths of methane-air mixtures in different cross-sectional tunnels was found, presenting various regimes from a hump shape to a wave-like uplift and bowl shape. The cross-section parameters determine the degree of confinement and further control the maximum peak overpressure in the modelled tunnels. An exponential asymptotic model can be used to conveniently obtain the maximum peak overpressure. These phenomena indicate that approximately square-shaped cross-sections should be selected to avoid an extremely high overpressure in large-scale tunnels with the potentially significant accumulation of methane-air mixtures.

Sodium dodecyl benzene sulfonate (SDBS) was mixed with alkyl polyglycoside (APG) and fatty alcohol ether sulfate (AES) and a FoamScan foam analyzer and a proposed coal dust wetting method were used to test the foaming and wetting properties of various compound solutions. The foaming and wetting properties of the SDBS/AES and SDBS/APG compound solutions were optimal at the mass ratios of 0:1 and 1:2 respectively as the total mass concentration of the compound solution was 0.2%. Besides, the properties of optimal SDBS/APG compound solutions is better than optimal SDBS/AES compound solution. In addition to hydrophilic head, AES contains ether groups (C-O-C) which have lone electron pairs, it can form hydrogen bonds with water molecules and improve the water locking ability of the liquid film. Therefore, the pure AES solution has a better foaming performance than the SDBS/AES compound solution. For the SDBS/APG compound solution, the head groups of the SDBS (SO3−) have a better hydrophilicity than those of the APG ( OH); therefore, the SDBS molecules are closer to water phase and the APG molecules are closer to the air phase. This arrangement could slow the diffusion of air and decrease the loss of water molecules, which ensures better foaming properties. Because the surface of the coal dust is electronegative, there is no electrostatic repulsion force between APG and coal dust surface, so APG molecules can be absorbed on the surface of coal dust more easily than SDBS. Since the anionic surfactant SDBS can carry more water molecules, the synergistic effects of the SDBS and APG molecules made the dust wetted in the shortest time.

The influence of a poly(vinyl alcohol) (PVA) molecule on the air/water interfacial structure of adsorbed sodium lauryl ether sulfate with one polyethylene oxide group (SLE1S) was investigated using molecular dynamics simulations. Increasing SLE1S surface density increases the interface thickness and forces both SLE1S and PVA molecules to migrate towards the air (actually vacuum) to different degrees. While most surfactants, when dilute, align parallel with the interface, increasing surfactant surface density forces tail groups gradually to align more perpendicularly to the interface. The three types of oxygen atoms in the SLE1S head group, i.e. the ionic, ester and ether oxygen atoms, form three distinct hydration shells, with PVA monomers appearing both within these shells and between the second and third shell due to its own hydrogen bonding with water and excluded volume of surfactant and water. The ionic oxygen atoms form more hydrogen bonds with water molecules and PVA than do the ester and ether oxygen atoms. The addition of PVA decreases slightly the number of hydrogen bonds between the surfactant oxygen atoms and the water molecules, as PVA chains form new hydrogen bonds with both of them. With increasing surfactant concentration, the PVA is pushed away from the bulk water, decreasing the number of the hydrogen bonds between it and water. These results are relevant to the use of polymers to aid surfactant in aqueous foaming applications.

Large-scale coalmine accidents have occurred occasionally with great impact on society. To assess the characteristics of large-scale coalmine accidents, a database involving 782 Chinese accidents from 1950 to 2016 was built and analysed. The historical change of large-scale coalmine accidents was divided into four stages according to the accident number per year. Explosions and fires were the primary causes and deemed to be thermodynamically driven accidents due to their identical thermochemical essence of combustion, interchangeability and producing similar gaseous hazards. By constructing an analysis framework, some useful features were derived from the database. About 55% of the gas explosions occurred in coalmines with low methane-gas emission rates. Coal dust explosions were responsible for about 59% of the fires and explosions with over 100 casualties. The interchangeability of fires and explosions led to 79% of the large-scale coalmine fires and explosions in recent years. As ignition sources, blasting work, self-heating and friction and impact caused 86% of the fires and explosions from 2007 to 2016. About 44% of fires and explosions happened in coalmines with central ventilation systems. About 85% of fires and explosions concentrated on the locations of coalface, heading face and roadway.

To better understand the coal dust wetting ability of anionic surfactants with different structures, sodium dodecyl sulfate (SDS), sodium dodecyl sulfonate (SDDS), and sodium dodecyl benzene sulfonate (SDBS) were selected. The surface tension, wetting time, and infrared spectra of coal dust were tested. The hydrophilic-lipophilic balance (HLB) values of the surfactants were calculated. Results showed that the decrease in the surface tension could shorten the wetting time at low surfactant concentrations. But the decrease in the wetting time was no longer related to the constant surface tension that was lower than 45 mN/m. The adsorption density depends on the hydrophobic interactions and electrostatic repulsions between the surfactant molecules and the coal dust. During the dynamic immersion process, the surfactants with high HLB values could bring the coal dust into the bulk solution rapidly. The wetting time of coal dust for SDBS with a high adsorption density and low HLB or SDS with a small adsorption density and high HLB was relatively longer. The adsorption density and HLB value of SDDS were intermediate between those of SDS and SDBS. Under the combined action of these two factors, the wetting time of SDDS was shorter than those of SDS and SDBS.

Aqueous foam is widely used in fire extinguishing and dust suppression technologies. Improving the foaming ability is the key to reducing the added concentration of foaming agents as well as the economic cost. In this work, the effect of a water-soluble polymer (polyvinyl alcohol, PVA) on the foaming ability of anionic surfactant (sodium dodecyl ether sulfate, SDES) was studied by an experiment and molecular dynamics simulation. The experimental results showed that PVA greatly improves the foaming ability of SDES solutions when the surfactant concentration is less than 0.1%, which is attributed to the fact that the polymer can enhance the stability of bubble films and reduce the bubble rupture rate during the foam generation process. The simulation results indicate that PVA can enhance the hydration of surfactant head groups and contribute to the formation of a three-dimensional hydrogen bond network between surfactants, polymers, and water molecules, thus greatly improving the stability of bubble liquid films. The above results suggest that water-soluble polymers can be used to improve the foaming ability of surfactant solutions by enhancing the bubble film stability, which is beneficial as it reduces the added concentration of foaming agents in aqueous foam applications.

To increase the operating range for cavitating quantitative mixing devices, a new jet pump is proposed. The distribution of pressure, velocity, turbulent dissipation rate, and vapor bubbles were studied numerically, and the influence of geometric parameters and flow ratio on the operating range were investigated experimentally. The proposed jet pump overlaps the high turbulence and low pressure regions at the nozzle exit, causing significant cavitation. When the cross section near the diffuser inlet is filled with vapor bubbles, the jet pump reaches its operating limit. Since the structure of suction chamber remains the same as conventional jet pumps, increasing secondary flow deforms the axisymmetric cavity cloud, which leads to quick reduction of the critical pressure ratio. Empirical curves are proposed to optimize the area ratio for given flow ratios, based on experimental tests of nine jet pumps. When the critical flow ratio 0.8, which is significantly higher than current jet pumps. Reliability of the proposed jet pump was examined when operating as quantitative mixing device and flow meter simultaneously. When the flow ratio

The solution and foam properties of systems composed of sodium alcohol ether sulfate (AES) and partially hydrolyzed polyacrylamide (HPAM) at different concentrations were investigated. The addition of HPAM could increase the surface tension of AES solutions caused by the decrease of surfactant adsorption density at the air-water surface. The viscosity of the AES/HPAM systems were determined by the HPAM concentration. With the increase in AES concentration, the foam generation time and bubble size first decreased and then reached a plateau, while the initial liquid volume of the foam increased first and then reached a plateau. The inflection occurred at an AES concentration of 0.1 wt%, which is higher than the critical micelle concentration (CMC). This is because the air-water surface area increased dramatically during foam generation, which makes surfactant surface density unsaturated at the CMC. Only a higher surfactant concentration could maintain the saturation of surface adsorption density. The addition of HPAM could improve the foamability and enlarge the bubble size at low AES concentrations, because the increased bulk viscosity and the hydrogen bonds between AES molecules and HPAM chains stabilized bubble films and reduced the breakdown of large bubbles. The increase of HPAM concentration would always improve the liquid-carrying capacity and decrease the drainage rate of the foam. These findings indicate that it is possible to use low concentrations of foaming agents and improve foam properties by adding water-soluble polymer in field applications.

To improve accuracy and stability of mini quantitative liquid adding, a new cavitating venturi device is proposed and investigated experimentally. Cavity cloud initiates at the throat exit where the velocity gradient is the highest and the local pressure is the lowest. Since the suction inlet is set at the throat exit, it is easily covered by the cavity cloud in which the pressure remains at saturation vapor pressure. Once cavity cloud dominates the suction inlet, both working and suction flow rate remains constant and independent of downstream pressure. Therefore, the proposed device can be used as an adding device and a flow meter simultaneously when it is under cavitation condition. The critical pressure ratio exceeds 0.6 when flow ratio is below 2%, which is over 50% higher than present jet pumps. The critical pressure ratio rises with the decreasing of adding ratio, which makes the proposed adding device especially applicable for mini quantitative adding. Moreover, the working range of the proposed device is hardly changed when sucked water is replaced by high-viscosity foaming agent.

The relationship between coal dust chemical composition and its wettability was analyzed in detail using the Walker test method. The wetting rate of coal dust was also investigated. Results show that the wetting time of coal dust is negatively correlated with moisture content. Increased moisture content improves the wettability, while the content of ash, volatile matter and fixed carbon in the coal dust has no effect on wettability. Surface hydroxyl is the main factor that determines the wettability of coal dust. The wetting time decreases linearly (R2 = 0.81) with increasing hydroxyl functional group content. The increase of carbonyl group content improves coal dust wettability, but there is no obvious relationship between carboxyl group content and the wetting time. Increased quartz content leads to decreased wettability, which indicates that quartz on the coal dust surface associated with organic composition may be hydrophobic. Compared to bulk chemical composition, the wettability of coal dust is more closely related to the surface hydroxyl functional group. In addition, the wetting time increases linearly with increasing coal dust mass, but the wetting rate differs for different coal dust samples. Coal dust with high hydroxyl content has a faster wetting rate than dust with lower hydroxyl content.

Foamability, liquid holdup, and foam appearance are key factors that determine dust control efficiencies. As the foam production method of the FoamScan instrument is similar to foaming device used for dust control, and its measurement means can satisfy the requirements of precise measuring, the FoamScan technology is adopted to explore the influence of xanthan gum (XG) and partial hydrolytic polyacrylamide (HPAM) on dust-related foam properties of sodium dodecyl benzene sulfonate (SDBS). It was found that with the increase of the polymer mass fraction, the liquid volume in the foam gradually increased. Additionally, the foaming time t200 of the foaming agent decreased at first, then remained almost constant for both polymers, which indicated that the foamability and liquid holdup were enhanced by the addition of polymers into SDBS. In addition, the efficiencies of XG are higher than that of HPAM. The image analysis using the CSA software revealed that the mean radius formed by XG was smaller than ...

The interactions of sodium carboxymethylcellulose (SCMC) and a superabsorbent polymer (SA) with aqueous solutions of active surfactants such as sodium dodecylbenzenesulfonate (SDBS) and alkyl polyglycoside were investigated in terms of surface tension, sink time, and foam liquid fraction. An SA is a more suitable surfactant than SCMC for wetting coal dust, and SDBS and an SA additive in an SA:SDBS weight ratio of 1:4 is the best coal dust suppressant.

To investigate the characteristics of methane-air explosions in large-scale tunnels with different structures, the CFD code for gas explosion modelling of FLACS was validated and used to model the explosions in tunnelling faces, coalfaces and crosscuts, where explosions mostly occurred in coalmines. The maximum overpressures were obtained as about 150–1400 kPa but varied for places with different cross-sections. The confinement degree and combustible mixture volume compete for controlling the overpressures, the space congestion degree influences the competition. For the tunnelling faces and crosscuts with low congestions, the increase of confinement degree caused by reducing cross-sections takes the dominant effect, which makes the overpressure in 3 m × 2 m cross-section tunnels higher. However, the 6 m × 4 m coalface produces the largest overpressure as the highly congested coalface strengthens the effect of increasing the mixture volume on pressure rise. Since the pressure reflection results from space constraints, a higher confinement degree causes a greater reflection. In crosscuts with both ends closed, the delayed combustion of the unburnt rich mixture after the seal’s failure generates a high pressure than assumed. Because of containing the same volume combustible mixtures in the crosscut modelling with the same cross-section, little difference exists in the overpressure regardless of sealing conditions. The flame is more inclined to propagate towards free spaces, and the flame of a larger volume combustible mixture fills a longer tunnel more comprehensively. In straight tunnelling faces, the flame length can be calculated as the product of the equivalent side length of the cross-section and its corresponding simulated constant.

Improving the foamability of anionic surfactants in hard water is essential to reduce the adding concentration and economic cost of foaming agents for dust control. In this work, sodium dodecyl sulfate (SDS) and sodium dodecyl ether sulfate (SDES) were selected to explore the mechanism of polyethylene oxide (EO) groups improving the foamability of anionic surfactants in hard water by experiments and molecular dynamics simulations. The experimental results show that SDES containing EO groups has better foaming performance in hard water compared with SDS. The simulation results indicate that the presence of EO groups can inhibit the combination of SO4− groups and Ca2+ ions at the air/water interface, which makes part of Ca2+ ions migrate from the interface layer to the bulk water. In addition, EO groups attract some Ca2+ ions to distribute around them, thereby further reducing the number of Ca2+ ions combined with SO4− groups, which helps to improve the surface activity and foamability of anionic surfactants in hard water. An increase in the number of EO groups can enlarge the interfacial thickness and the number of hydrogen bonds between surfactants and water molecules, enhancing the strength of bubble film. Moreover, the farther the EO group is from the SO4− group, the smaller the contribution to the hydration of anionic surfactants.

A sustained release type of inhibitor (PS-C) prepared with poly(acrylic acid)/sodium alginate super absorbent (PS), ascorbic acid (VC), and water was developed, which exhibited a not only highly efficient but also sustained inhibition performance on the spontaneous combustion of coal. The impact of PS hydrogel on coal oxidation was examined thermodynamically by TGA–DSC tests, and the variations of functional groups on coal surface under the influence of VC were in situ monitored by an FT-IR technique. The inhibition performance was evaluated with a parameter defined as the emitted carbon monoxide concentration decay rate during coal oxidation. The results show that the PS hydrogel and VC perform distinctive inhibition characteristics by physically removing the accumulated heat and chemically interrupting the free radical chain reaction of coal oxidation, respectively. The composite PS-C is capable of combining the inhibition characteristics of PS hydrogel and VC as well as further realizing a dramatic syn...

Foamability, foam initial liquid volume, and bubble size of fatty alcohol sodium polyoxyethylene ether sulfate (AES) surfactant solution were studied with and without the addition of sodium carboxymethylcellulose (CMC) at different gas flow rates, using a sparging method. The generation time decreased with increasing gas flow rate. At low gas flow rates, the added CMC greatly enhanced the foamability by preventing bubble collapse. The initial liquid volume of the foam first increased rapidly, and then gradually decreased. Increasing the CMC concentration increased the initial liquid volume of the foam. The mean bubble diameter first clearly decreased, then increased slowly with increasing gas flow rate. CMC showed different effects on bubble size at high and low gas flow rates. Adsorption of CMC on AES molecules forms a network structure and improves bubble film stability, which can explain the above results. These findings provide guidelines for generating foam with excellent properties suitable ...

Studies have shown that palmatine (PAL) has anti-cancer effects. However, the activity and potential mechanisms of PAL against colorectal cancer remain elusive. The results showed that PAL significantly inhibited the proliferation of colon cancer cells in vitro and in vivo without significant effect on non-tumorigenic colon cells. Target prediction and clinical sample database analysis suggested that PAL may contribute to colon cancer cells phase arrest and apoptosis by targeting aurora kinase A (AURKA). Inhibition and overexpression of AURKA proved that PAL induces G2/M phase arrest and apoptosis in colon cancer cells by targeting AURKA. Moreover, PAL promoted intracellular Reactive oxygen species (ROS) production and decreased mitochondrial membrane potential (ΔΨm). PAL reduced the levels of AURKA, Bcl-xl and Bcl2 proteins, and promoted the expression of pro-apoptotic proteins P53, P73, Caspase3 and Caspase9, as well as the increase of cytochrome c (cyt. c) in cell lysates in vitro and in vivo. Together, our study confirmed that PAL induced G2/M phase arrest and mitochondrial-associated pathway apoptosis in colon cancer cells by targeting AURKA. PAL may provide a novel solution for the treatment of colon cancer by serving as a new AURKA inhibitor.

Due to large energy loss, current foam technology for dust suppression requires high inlet water pressure, but performance is poor where ventilation volume is high. This paper proposes modifying key foam device components, including the agent mixing device, foam generator, and nozzle, to address these problems. A cavitating jet pump was simultaneously employed for accurate agent mixing and flow meter, guaranteeing accurate agent flow and low energy loss. A vertical foam generator was designed to increase foam volume and ensure even foam distribution among the foam nozzles. The two-layered foam nozzles were designed and fabricated using 3D printing to ensure even and thick foam impact area on the dust source, effectively blocking dust escape passages. Experiments were performed in the laboratory and on a real heading face. Ventilation volume was 560–570 m3/min for the field experiment with initial total dust concentration 589–679 mg/m3. The proposed system reduced required inlet water pressure to 0.87 MPa, while achieving 86.8% average total dust suppression efficiency and reducing long-term time average respirable dust concentration to 3.9–5.7 mg/m3. This study will help improve performance and expand application fields for foam dust suppression technology.

The authors described a short and highly enantioselective route to (R)-salmeterol involving asymmetric synthesis of cyanohydrin followed by nucleophilic substitution with 6-(4-phenylbutoxy) hexyl methanesulfonate.

A synthetic method for 2-formylcyclopent-2-enecarboxylic acid is described. This procedure comprises two steps. The first step is a [2 + 2] cycloaddition reaction, and the second step is a hydrolysis and ring-opening reaction. A plausible mechanism of the hydrolysis and ring-opening reaction was supposed. Then, the effects of different solvents, base mol ratio, concentration of base, and reaction temperature on the yield of the second step were studied. Finally, under the obtained optimized conditions, the product was achieved and isolated in 59.4 % yield, which was more than double the ones reported previously. An improved and efficient procedure for the synthesis of 2-formylcyclopent-2-enecarboxylic acid has been developed.