Influence of coal properties on dust suppression effect of biological dust suppressant

In order to study the effect and influencing factors of biological dust suppressant on secondary dust of coal dust, the biological dust suppressant was prepared with bacillus pasteurii and 0.6 mol/L urea-CaCl₂ solution. The experimental result shows that the yield of mineralized products of CC is the highest, reaching 81.11%, in bonding solutions with different calcium source and different concentration. For 5.0 g coal dust, 8 mL is the suitable spraying amount of bacteria solution and bonding solution. Biological dust suppressant has the best secondary dust suppression effect on coal dust with particle size above 200 μm. Moreover, it has the strongest effect on inhibiting secondary dust emission of lignite, and the weight loss rate of coal dust about 200 μm is only 0.84%. At the same time, the proportion of calcite crystals with the strongest thermal stability in mineralized products produced by MICP is higher. When the coalification degree of coal is lower, the effect of biological dust suppressant on secondary dust emission is better.     

Experimental and molecular dynamics simulation research on compound dust suppressant based on locust bean gum

To solve the problem of coal dust pollution, this paper used experiments and molecular dynamics simulations to develop a new composite dust suppressant with locust bean gum as the binder, fatty alcohol polyoxyethylene ether as the wetting agent, and glycerol as the water-retaining agent. Through a single factor analysis of the effects of each material, the appropriate concentrations of each were selected for an orthogonal experiment. The best composition of dust suppressant was obtained from an anti-wind erosion experiment. Then, scanning electron microscopy and energy-dispersive X-ray spectroscopy were performed on a coal sample sprayed with dust suppressant to observe that the dust suppressant had good adsorption on and binding to low-rank coal. Finally, an on-site experiment was conducted on the developed composite dust suppressant. The dust reduction rate reached 92.3%. Materials Studio software was used to simulate the interaction between dust suppressants and coal dust, with pure water as a control group for comparison. By analyzing the electrostatic potential of the dust suppressant and low-rank coal molecules, as well as the relative concentration distribution curves of both molecules, the water molecule mobility, and the heat of adsorption, the micro-action between dust suppressants and coal could be understood.     

Preparation of microbial dust suppressant and its application in coal dust suppression

To promote the application of microbially induced carbonate precipitation (MICP) technology for coal dust suppression, two urease-producing bacteria (SZS1-3 and SZS1-5) in a coal mine soil were screened. 16 s rDNA sequencing of these bacteria indicated sequences similar to those of Acinetobacter guillouiae CIP 63.46 and Staphylococcus caprae ATCC 35538, respectively. Strains SZS1-3 and SZS1-5 had their largest urease activity at the initial urea concentration of 0.5 mol/L, under slightly alkaline (pH = 9) and neutral (pH = 7) initial pH levels, respectively. Their final mineralized products were vaterite-type and calcite-type calcium carbonate. Although dust suppression results indicated that both bacteria can effectively bind coal dust particles, consolidated coal dust treated with SZS1-5 had a stronger resistance to wind and rain. The screening, mineralization and dust suppression potential analysis of these two urease-producing bacteria can provide reference for the application of MICP technology in coal dust suppression.     

A study on the dust control effect of the dust extraction system in TBM construction tunnels based on CFD computer simulation technology

In order to control dust in a tunnel boring machine (TBM) construction tunnels, this paper, in combination with field measurements, applies CFD computer simulation technology to study the dust control effect of TBM construction tunnels under different dust extraction flow rates. Firstly, the dust extraction system is closed, and the result of the simulation show that the dust diffuses to the entire TBM working area within 181 s, indicating the necessity of having a dust extraction system in the tunnel. Secondly, the dust extraction system is open and under the original dust extraction flow rate of Q_e = 8 m³/s, the overall dust diffuses to the entire working area L_o = 130 m, and the full-face dust diffusion distance is L_f = 47.54 m. Then the study was carried out with the setting of 2 m³/s ≤ Q_e ≤ 14 m³/s. The results show that: when Q_e ≤ 8 m³/s, the full-face dust diffuses to 47.54–71.84 m; when Q_e > 8 m³/s, the full-face dust can be controlled at 42.81–46.34 m; and when Q_e = 8 m³/s, the full-face dust control effect is better, and the average dust concentration in the tunnel is as low as 12.25 mg/m³, indicating that the original dust extraction system has a better design. The field measurement results verify that the CFD computer simulation results are accurate.     

Investigation of lag on ignition of coal dust clouds under varied experimental conditions

Lag on ignition (LOI) of coal dust cloud greatly influences the initiation and propagation of coal dust explosion. This paper investigates the effects of coal dust particle size, dust concentration, ignition temperature, and dust dispersion pressure on LOI of coal dust clouds using Godbert-Greenwald furnace along with a high-speed camera. LOI of coal dust cloud significantly decreased by 1/13 times from 959 to 77 ms with increase in the ignition temperature from 600 to 1000 °C, demonstrating greatest influence of ignition temperature on LOI. LOI increased by 60% with increase in dust concentration from 500 to 4000 g/m³. Optimum dust dispersion pressure at which LOI was found minimum is determined 70 kPa. Empirical relations are established between LOI of coal dust cloud and particle size, ignition temperature, dust concentration, and dispersion pressure. The results are analysed in terms of the occurring physical processes, which led to a better understanding of the variation of LOI, ignition behavior, and explosion propagation of coal dust clouds at varied experimental conditions.     

Experimental investigation of the performance of a novel foam generator for dust suppression in underground coal mines

Dust in underground coal mines is a serious threat to workers’ health and safety. Foam is used as an efficient means of dust suppression in these confined workplaces. A novel foam generator has been designed to overcome the problem of bottlenecks due to the complex operation and high cost of existing foam technology. Experimental performance testing and evaluation showed that a 20–40 m³/h gas source for generating foam is produced by a small 0.4–0.6 m³/h flow-rate jet, and the device consumes as little as 4–6 kg/h of foaming agent. It requires only a normal pipeline water pressure, eliminating the need for a compressed air supply (compressor, pipelines and/or hoses). Its simplified structure combines the advantages of safe, reliable and convenient operation with compact size. The marked reduction in the consumption of water and foaming agent significantly reduces foam production cost. The foam generator was tested at a coal face and successfully controlled dust produced by a longwall double-drum shearer.     

An investigation on the aluminum dustexplosion suppression efficiency and mechanism of a NaHCO3/DE composite powder

A NaHCO₃/diatomaceous earth (DE) composite powder suppressant with unique clustered structures is prepared by high-pressure impact method, using DE as the carrier and NaHCO₃ as the loaded chemical suppressant. The purpose is to obtain affordable, environmentally friendly, high-efficiency power explosion suppression materials. The suppression efficiencies of the NaHCO₃/DE composite powder suppressant on aluminum dust propagation and explosion pressure are tested. The results show that as the content of the NaHCO₃/DE composite powder suppressant increases, the maximum flame length gradually reduces and the suppression efficiency gradually increases. Addition of 60 wt% of the NaHCO₃/DE composite powder suppressant suppress aluminum dust flame propagation and addition of 100 wt% of the NaHCO₃/DE composite powder suppressant can fully suppress aluminum dust explosion. Comparison with pure NaHCO₃ and pure DE reveals that NaHCO₃/DE composite powder suppressant is more effective in suppressing aluminum dust flame propagation and aluminum dust explosion pressure than either of the two powders alone. The suppression mechanism of the NaHCO₃/DE composite powder suppressant is established: On the one hand, reaction is suppressed by the decomposition of NaHCO₃ and the product of this decomposition; on the other hand, as DE is rich in porous structures, when the loaded NaHCO₃ powder separates from DE, the porous structures will not only limit flame propagation, but will also well adsorb the substances generated from explosion reaction.     

Experimental investigation of the wetting ability of surfactants to coals dust based on physical chemistry characteristics of the different coal samples

To select suitable surfactant as water-spray additive to improve dust suppression efficiency, six types of coal sample (lignite, long flame coal, non-caking coal, gas coal, coking coal, and anthracite) were selected from some typical mining areas in China, the influence of the physical chemistry characteristics of coal samples on the wetting ability of surfactants to the coals dust was investigated. Their proximate composition, ultimate content, chemical structure, surface morphology, pore structure parameters, and contact angle were determined. Three kinds of anionic surfactants – Sodium Alcohol Ether Sulphate (AES), Sodium Alpha-Olefin Sulfonate (AOS), Fatty Acid Methyl Esters Ethoxylate Sulfonate (FMES) – and one kind of nonionic surfactant – Coco Diethanolamide (CDEA) – were selected to carry out sedimentation experiments on the coal samples dust, to explore the main factors influencing the wettability of the coal samples dust. Among these factors, pore size is the main factor determining the wettability of coal dust, the contact angle decreases linearly (R² = 0.96) with pore size increase. The experimental results demonstrate that the following factors produce correspondingly increased wettability: higher moisture content, lower carbon content, higher oxygen content, more oxygen-containing functional groups, and increased pore size. In addition, the wettability of the six types of the coal samples dust shows a high-low-high trend with metamorphic degree increase, lignite has the strongest wettability, and the coking coal with the highest degree of metamorphism in the selected bituminous coal sample has the weakest wettability. Moreover, compared with nonionic surfactants, anionic surfactants have stronger wetting ability, but the same anionic surfactants have different wetting abilities to coal dust with different metamorphic degrees. AOS has stronger wetting ability to the dust of long flame coal, non-caking coal, and anthracite; AES has stronger wetting ability to the dust of lignite and coking coal; and FMES has stronger wetting ability to the dust of gas coal. The research results provide a theoretical basis for different coal mines to select suitable surfactants as water-spray additives to improve dust suppression efficiency.     

Study on the preparation of green suppressors and their characteristics in coal dust flame propagation inhibition

The properties of a green waste molecular sieve-based powder suppressor in inhibiting the flame propagation of coal dust were studied. Waste molecular sieve (S) was pretreated and selected as the carrier, potassium oxalate (K) and ferric citrate (T) as the active components. The reverse dissolution crystallization method was adopted and S@K/T, S@T/K, S@T-K suppressors with different core–shell structure were prepared by different loading sequences. Their particle size, morphology and thermal pyrolysis behavior were compared. The results showed that the particle distribution of three powders is uniform and the dispersity of them is good. The active components of explosion suppression are evenly loaded on the waste molecular sieve carrier and they have different coating structure. The thermal desorption heat of them is 44.64 J/ g, 66.95 J/g and 92.9 J/g, respectively. Furthermore, the flame propagation characteristics of coal dust were tested by the Hartmann flame propagation device. The results showed that all powders had the effect of inhibiting the flame propagation of coal dust and the inhibition effect is S@T-K, S@T/K and S@K/T from strong to weak. Combined with characterization results, the influence mechanism of the difference in the flame propagation inhibition effect of three suppressants was investigated.     

Research on law and mechanism of dust explosion in bag type dust collector

The bag type dust collector will accumulate dust during long-term operation, and the high temperature during operation will cause dust explosion. In this paper, with the dust removal system involved in the “8·2” Kunshan dust explosion accident taken as the research background, the minimum ignition temperature and lower explosion limit experiments are carried out on aluminum powder with different particle sizes (10–60 μm) by using the lowest ignition temperature test device and the 20 L near-spherical explosive device. The dust concentration distribution and temperature field in the bag type dust collector are analyzed through the CFD-FLUENT software. Through the analysis of the experimental results, it is found that when the particle size of aluminum powder is 19 μm, the minimum ignition temperature is 585 °C, and the lower explosion limit of concentration is 0.04 kg/m³. The simulation results indicate that the dust particles gather in the dust collecting bucket, and the aluminothermic reaction occurs in the dust collecting bucket. The temperature of the upper and right parts in the dust collecting bucket is above 600 °C, which exceeds the minimum ignition temperature. At the interface between the dust hopper and the dust collecting bucket, the concentration of aluminum powder reaches 0.126 kg/m³, which exceeds the lower explosion limit of aluminum powder.     

氧化石墨烯与甲基丙烯酸和烯丙基磺酸钠共聚物的制备与性能

通过氧化和超声波作用制备了氧化石墨烯(GO)纳米相片层分散液,再与甲基丙烯酸(MAA)和烯丙基磺酸钠(SAS)进行自由基共聚反应制备了氧化石墨烯与甲基丙烯酸和烯丙基磺酸钠的共聚物P(GOMAA-SAS),各组分的质量比为m(MAA)∶m(SAS)∶m(GO)=13∶6∶1。FT-IR检测结果表明GO与单体之间发生了共聚反应,AFM检测结果表明共聚物中GO片层的厚度为4 nm、长宽在5~10 nm范围。应用结果表明用10%的P(GO-MAA-SAS)鞣制皮革的收缩温度为84℃,GO的鞣制作用与GO的纳米效应和与胶原纤维的键合作用及其二者之间的协同作用有关,研究结果 GO纳米片层可以鞣制皮革并且GO的分散状态是影响鞣制效果的主要因素。     

Electric arc furnace filter dust: Influence of organic material on the bulk density and flowability

In this study, the influence of condensed organic matter on the flowability and the bulk density of electric arc furnace (EAF) dust was investigated. The properties of the original dust samples containing some organic matter were compared with the properties of these samples after the removal of the condensed organic compounds by a deoiling procedure. The particle size distribution and the density of the three investigated dust samples were quite similar but the content of organic matter (TOC) was different. The values for the bulk density were lower for the original dust compared to the deoiled dust samples. The higher the TOC content, the higher the difference in the bulk density. Thus, the storage capacity of the dust silo was reduced by 9–17%. The flowability of all deoiled dust samples was very similar, whereas the flowability of the original dust was worse. The higher the TOC content, the worse the flowability. The average reduction of ff_c in comparison to the deoiled dust samples was 48, 38, and 17% for EAF dust samples with 0.65, 0.46, and 0.26% TOC, respectively. Evidently, the condensed organic matter on the dust particles reduces the flowability of the material. Therefore, the bulk density for dust with a higher TOC content is also lower.     

Effects of radial air flow quantity and location of an air curtain generator on dust pollution control at fully mechanized working face

To better understand the effects of radial air flow quantity and the location of air curtain generator on dust pollution control, the 2–109₂ fully mechanized working face in Xinzhi coal mine (Huozhou Coal Electricity Group Co., Ltd., Shanxi, China) was numerically simulated in the present study. A full-scale physical model of the working face was established; then, based on airflow-dust particle two-phase flowing characteristics, the k-ε-Θ-k_p mathematical model was constructed. The comparison between simulation results and field measurements validated the model and the parameter settings. Furthermore, the effects of ventilation parameters on airflow migration and dust diffusion were numerically investigated using FLUENT. The results show that the increase of the radial air flow quantity (denoted as φ) and the distance of the air curtain generator from working face (denoted as d_w) is beneficial to the formation of a dust-control air curtain. At a constant d_w, the dust diffusion distance (denoted as D) decreases with the increase of φ. At a constant φ, D decreases with the increase of d_w when a dust-control air curtain is formed; otherwise, the increase of d_w leads to the increase of D. By analyzing the simulation results, the optimal ventilation parameters for 2–109₂ fully mechanized working face and those working faces under similar production conditions are determined as: φ = 240–270 m³/min and d_w = 20–30 m.     

The effect of the trapping of dust grains on the sheath structure and the charging in a plasma

A model of the trapping of dust grains is shown in a plasma for the first time. The multiple sheath potential, the space charge density and the multiple electric field associated with our model are simulated. Our result explains the confinement of the dust grains observed in the experiment.     

The effect of the trapping of dust grains on the sheath structure and the charging in a plasma

A model of the trapping of dust grains is shown in a plasma for the first time. The multiple sheath potential, the space charge density and the multiple electric field associated with our model are simulated. Our result explains the confinement of the dust grains observed in the experiment.     

预处理方式对透明质酸发酵液的超滤膜污染影响的研究

叙述了透明质酸（HA）发酵液经5种不同预处理方法处理后,所获得清液在超滤过程中通量J的变化规律,通过比较预处理前后发酵液中透明中质酸浓度和分子量的变化;超滤前后膜通量的变化及酶液处理后膜通量的变化,探讨了膜超滤过程中污染规律及预防方式。     

Preparation of hierarchical CdS structures and effect of sodium dodecyl benzene sulfonate (SDBS) on the morphologies

Dendritic-like CdS and flower-like CdS structures have been prepared by hydrothermal method. The as-prepared CdS have been analyzed by X-ray diffraction, field emission scanning electron microscopy (FESEM), ultraviolet–visible and room temperature photoluminescence (PL). And the photocatalytic activities also have been investigated. FESEM results indicate the role of SDBS is to make the CdS crystals assemble together. The optical energy band gap of dendritic-like CdS is 2.46 eV, and flower-like CdS is 2.48 eV. PL results show that dendritic-like CdS and flower-like CdS emit both blue and green fluorescence. Photocatalysis results show that the catalytic efficiency of dendritic-like CdS is better than flower-like CdS.     

Effects of [Bmim][Cl] ionic liquid with different concentrations on the functional groups and wettability of coal

In view of high dust concentration in coal mining and difficulty of traditional water injection in coal wetting, the effects of [Bmim][Cl] (1-butyl-3-methylimidazole chloride) ionic liquid with different concentrations on wetting performance and functional groups of coals have been studied. Optical droplet morphology analysis system and FTIR (Fourier transform infrared spectrometer) were used. The results showed that coal samples treated with [Bmim][Cl] ionic liquid had a significant change in the content of aliphatic groups. In the coal samples treated with 0% concentration [Bmim][Cl], the content of CH₂ groups was 77.86%, CH₃ groups was 14.07%. When [Bmim][Cl] concentration was 4%, the content of CH₂ groups decreased to 24.55%, CH₃ groups increased to 61.25%. Besides, the contact angle is the minimal of a 41.1° at 4% ionic liquid concentration. The relationship between contact angles and contents of functional groups were analyzed. Results showed that the content of CH₃ groups and CH₂ groups had the greatest effect on the contact angle and 4% [Bmim][Cl] ionic liquid treatment can effectively reduce the contact angle and improve the coal wettability. It is of great significance to increase coal wettability and reduce dust generation by changing the contents of functional groups.     

The effect of the curing time and temperature on final properties of flexible PVC with an epoxidized fatty acid ester as natural-based plasticizer

One of the most useful polymeric materials at industrial scale is plasticized polyvinyl chloride (P-PVC) or PVC plastisol. This is characterized by optimum balance among processing conditions, overall properties, cost, and versatility; however, it has some problems related to plasticizer migration (generally phthalates derivatives) with toxicity problems. As a consequence of the appearance of new regulations which restrict the use of phthalates, the study of new plasticizers with low toxicity and low migration has become a very interesting research field. In this study, the optimum curing conditions of vinyl plastisols with a natural-based epoxidized fatty acid ester as plasticizer have been investigated by the following mechanical properties: thermal behavior, color changes, solvent migration, and microstructure changes in terms of the curing conditions. This study was carried out with a plasticizer content of 70 phr (per hundred resin); different isothermal curing conditions ranging from 160 to 220 °C, and curing times in the 6–10 min range were used. The results revealed that the best curing conditions are 200 and 220 °C for curing times near to 14 and 10 min, respectively, which are similar to those used for other commonly used plasticizers.     

褐煤煤尘爆炸火焰传播特性及燃烧热分解机理研究

煤尘爆炸是矿井安全开采的主要危险源之一。以褐煤煤尘为研究对象,探究煤尘粒径对煤尘火焰传播过程的影响。用高速摄影装置记录火焰的传播过程,进而分析不同粒径下煤尘爆炸火焰传播的高度和速度。为进一步分析煤尘燃烧过程中的化学反应机理,借助反应分子动力学方法对煤分子燃烧中的初始热分解过程进行了模拟。研究结果表明:爆炸火焰传播高度呈先增加、后稳定的趋势,传播速度呈先增大、后减小的趋势;随着煤尘粒径的减小,火焰传播高度和传播速度均呈增大的趋势;当煤尘粒径为10.5 μm时,火焰传播高度和传播速度的峰值分别为623 mm和4.3 m/s;煤尘热分解主要产物为H₂、H₂O、CO₂和CH₂O,这些产物进一步与氧气的结合会促进煤尘燃烧和火焰传播过程,使得整个体系燃速加快。为煤尘热分解和燃烧提供了较为充分的数据基础。