Semi-coke powder filtration experiments using a dual layer granular bed filter

The separation of semi-coke powders from tars and gases during coal pyrolysis is of crucial importance to the coal chemical industry. This work describes an experimental study on semi-coke powder filtration using an experimental dual layer granular bed filter with an inner diameter of 100?mm. With an initial filtration velocity of 0.2?m/s, the dual layer granular bed filter had a filtration efficiency of 99.943% and a pressure drop across the filter of only 1456?Pa. When the initial filtration velocity was increased to 0.25?m/s, the filtration efficiency was 99.937% and the pressure drop was 1834?Pa. Our results indicated that the dual layer granular bed filter we developed and tested showed significant promise as a high-temperature dust collector in low-temperature coal pyrolysis.     

密闭空间煤粉爆炸特性的实验研究

为了探明煤粉在密闭空间中的爆炸特性参数,利用20 L球形爆炸装置进行实验测试,实验研究了不同点火能量对煤粉爆炸行为的影响,对比CaCO_3和Al(OH)_3两种惰性介质的抑爆效果及惰性介质的抑爆效力随点火能量的变化规律进行了重点探讨。结果表明:随着点火能量的增加,爆炸压力随着煤粉浓度的增加呈现先上升后下降的趋势,在同一浓度下,粉尘最大爆炸压力和最大升压速率呈线性上升,在高浓度下,粉尘爆炸压力受点火能量的影响更显著;添加CaCO_3和Al(OH)_3能够降低煤粉的爆炸压力,相对于CaCO_3的物理抑爆而言,Al(OH)_3的物理-化学抑爆效果更佳;惰性介质抑爆效力随点火能量增加而下降,建议采用5~10 k J点火能量考察惰性介质对煤粉爆炸的抑制效力。     

An investigation of the nozzle’s atomization dust suppression rules in a fully-mechanized excavation face based on the airflow-droplet-dust three-phase coupling model

In order to suppress the diffusion of high concentrations of dust towards the operating area in a fully-mechanized excavation face effectively, this study constructed a mathematical model that describes the interactions among droplets, dust and airflows, and then validated the accuracy of the established model. Finally, under single-forced ventilation conditions, the dust suppression rules when different nozzles were used at different spraying pressures were investigated in detail. The results reveal that when different spraying schemes were used, the dust mass distributions in different regions along the tunnel were basically the same; they all first decreased, then increased and finally decreased. At a spraying pressure of 2–8?MPa, the spraying pressure and dust suppression efficiency followed a logarithmic function; however, with an increase in the spraying pressure, the dust suppression efficiency increased gradually at a declining rate. Under a spraying pressure of 8?MPa, the dust clusters in which the dust concentration exceeded 110?mg/m³ in the fully-mechanized excavation face were reduced significantly. Out of all the spraying schemes, the one using K2.0 nozzles at a spraying pressure of 8?MPa achieved the most favorable dust suppression performance, and the dust suppression efficiency in a fully-mechanized excavation face was as high as 86.1%; meanwhile, the proportion of respirable dust with a diameter smaller than 7?μm increased gradually from 16% to 27%.     

Study on coupling diffusion of composite dust and cloud-mist dedust technology in fully mechanized driving face of mixed coal-rock roadway

Aiming at addressing the problem of coal dust and rock dust mixed pollution in mixed coal-rock roadways, this study conducted a CFD numerical simulation on the coupling migration and pollution of coal dust and rock dust in the fully mechanized driving face of mixed coal-rock roadway (i.e., roadway section with both coal seam and rock stratum). Research findings: Small coal dust particles mainly migrate backward along the upper space of the roadway, while large coal dust particles mostly diffuse backward along the bottom of the air return side and settle evidently, with the concentration being higher than 1,000 mg/m³. The concentration of rock dust starts to decline significantly to about 350–800 mg/m³ in the middle and rear of the roadway. The concentration of coal dust is relatively high (200–500 mg/m³) in the front of the roadway, and it decreases gradually to around 175 mg/m³ in the middle and rear sections. With the increase of diffusion time T of rock dust and coal dust, the diffusion distance L_D shows a linear increasing trend. Both rock dust and coal dust conform to the linear equation L_D = 0.82 T + 11. After the application of the cloud-mist dedust technology, all the measuring points in the mixed coal-rock roadway witnessed a dust removal efficiency of above 75 %, which is a mark of effectiveness of the technology in improving the underground working environment.     

气吸输送系统的分离除尘装置的设计研究

针对气吸输送系统的分离、除尘装量压损高、占地面积大问题，提出了一体化的结构设计。它显著地减少了系统压力损失达１３００Ｐａ以上．并在生产运行中得到了验证。文中对分离除尘装置的设计有关问题进行了分析和研究。     

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.     

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。     

Simulation analysis and engineering application of distribution characteristics about multi-stage atomization field for cutting dust in fully mechanized mining face

To improve the dust suppression efficiency of the external spray systems of shearers, a dust reduction method consisting of shearer external multi-stage atomization and dust removal fan was proposed. Computational fluid dynamics-based numerical simulation was combined with atomization experiments to analyze the migration and distribution of the cutting dust and multi-stage atomization field under airflow at the 2307 fully mechanized mining face of the Tangkou mine. The results show that with adding dust removal fan and multi-stage atomization points, the peak area of wind speed appeared on both sides of the shearer, and the wind speed was greater than 2.7 m/s, the dust concentration on the downside side of the shearer decreased, the spray coverage area increased significantly, and the droplet concentration at the shearer drum was the largest, exceeding 0.05 kg/m³. According to the research results, the multi-stage atomization arrangement of single-fluid water nozzles of shearer was put forward, and the field application was carried out. Compared with the engineering application results of the single-stage atomization dust suppression system, the total dust reduction rate of the synergistic effect of multi-stage atomization external spray with dust removal fan for the shearer is 87.12%, which is 38.59% higher than that of the conventional single-stage atomization dust suppression system.     

无人机静电喷雾治理开放性粉尘的数值模拟

将静电喷雾技术与无人机技术相结合用于治理开放性粉尘,使用Fluent对粉尘的扩散模型进行数值模拟.模拟得出无人机工作高7m,喷雾压力为0.2MPa时,无人机静电喷雾的平均降尘效率能达到85.87％,并在自然风速为1m/s、空气相对湿度为70％时,局部区域的降尘效率高达95.93％.本文提出的无人机静电喷雾控制开放性粉尘...     

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.     

新型铁路隧道落煤吸尘装置吸煤特性仿真分析与试验验证

由于空气扰动,运煤专用列车途经隧道进出口时会出现大面积落煤现象,针对长距离清理隧道落煤面临的人工清理效率低、成本高等难题,设计了一种由1根主输送煤料管和多根吸煤支管组成的新型铁路隧道落煤吸尘装置,用于清理颗粒小、质量轻的铁路隧道落煤。在对主输送煤料管设计中,首先利用欧拉-拉格朗日法建立了输煤管道中的气固两相流模型;其次基于Fluent有限元仿真研究了煤粒入射角和定长管道上多个支管间距对主输送煤料管内流场的影响,分析煤粒最佳入射角以及主输送煤料管上安装吸煤支管数量的最优值;最后通过现场试验对有限元仿真结果进行了验证。仿真和试验结果表明:煤粒入射角α在小于45°时主输送煤料管压降小,颗粒流可获得较大的水平输送速度;支管间距在750mm附近时,水平输送速度波动范围小且煤料的输送量明显大于其余各组,更加利于铁路隧道落煤的输送。研究结果对改进主输送煤料管结构形式、提高输送隧道落煤效率以及优化铁路隧道落煤吸尘装置具有重要意义。     

A study on coatability of marble dust on metal substrates

Marble dust is a hazardous construction/industrial waste generated during the extraction, cutting and polishing of marble-producing rocks. The present work explores the potential of marble dust to be used as a coating material on metal substrates. For this, the high-velocity oxy-fuel (HVOF) spraying route is adopted to deposit marble dust coatings on four different metallic substrates: mild steel, inconel, aluminum, and copper. Liquefied petroleum gas is used as the fuel and nitrogen as the carrier gas while the coating deposition is performed by varying the spray distance over a range from 50 mm to 250 mm. The coating microstructure is studied using a scanning electron microscope (SEM) and the developed phases are identified using an x-ray diffractometer. The developed coatings are characterized in terms of deposition efficiency, coating thickness and adhesion strength. It is found that the coatings exhibit fairly good interfacial adhesion and thickness values that varied quite significantly with the spray distance. Maximum deposition efficiency of about 68 % is obtained for the copper substrate when the deposition is performed at a spray distance of 100 mm. This experimental investigation thus shows that despite being a waste, marble dust is eminently coatable on several metallic substrates.     

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.     

Investigation to rectangular flat pleated filter for collecting corn straw particles during pulse cleaning

This work investigated the amounts of dust residual of a rectangular flat pleated filter for collecting corn straw particles during pulse cleaning and attempted to explore the causes of incomplete cleaning. In this study, dust residual, filter’s pressure drops and static peak pressures were obtained across flat pleated filter during the pulse cleaning. The optimum parameters were obtained that the pulse electromagnetic valve size was one inch, the pulse pressure was 0.2–0.3?MPa, and the filtration velocity was 0.6?m/min for the nozzle type with 7 holes with a diameter of 7?mm (7?×?Ф7?mm). Under this condition, the experimental results show that the dust residuals were 198.4 (64%), 52.7 (17%), 58.9 (19%)?g for initial collected dust residual 310?g at top, middle and bottom areas of the filter panel, respectively. The dust residuals were major on the top area of the filter panel, especially on the gap locations between the two-adjacent pulse airflows. Meanwhile, the more pulse interval or dust concentration was increased the dust residuals of the filter panel and the pressure drops of the filter were increased. Moreover, the static peak pressure distribution can give guidance to the dust residual distribution.     

Preparation of monodisperse charged droplets via electrohydrodynamic device for the removal of fine dust particles smaller than 10 μm

Electrohydrodynamic (EHD) device is utilized in various applications and could be useful for the suppression of particulate matter in ambient conditions. In this study, we focused on the ejection of charged droplets containing electrolytes in a microdripping mode and with high charge density. Several different electrolytes with different physical and electrical properties were tested for our EHD process in order to produce the charged droplets stably. Results from series images by high-speed camera represented that droplet size and frequency were dependent on the applied voltage and flow rate, and showed different behaviors in various EHD modes such as dripping, microdripping, mixed dripping, and unstable dripping. Consecutive experimental data for charge density showed that 15?wt% KCl solution was proper to obtain highly charged droplets with the size from 50 to 100?μm. For this solution, the suppression of the fine dust particle was tested for the removal of PM10, PM2.5, and PM1 at various applied voltages. The droplet formation in microdripping mode was effective for the removal of smaller dust particles and could be applicable for the air remediation in indoor or domestic environment.     

粒径对煤粉云最低着火温度特性的影响

为了研究粒径对煤粉云最低着火温度特性的影响,采用粉尘云最低着火温度测试装置测试了不同粒径下煤粉云的最低着火温度,并结合ReaxFF分子动力学对其反应机理进行了微观层面的探讨。结果表明:当煤粉中位径在34 μm时,煤粉云的最佳着火质量浓度为750 g/m³,最低着火温度为550 ℃;随着煤粉粒径的增加,煤粉云最低着火温度逐渐增大,当煤粉中位径达到124 μm,煤粉云最低着火温度上升至650 ℃。通过ReaxFF分子动力学对煤粉热解过程的计算结果表明:随着反应的进行,大分子煤结构逐步分解,芳香环、C—C键、C—O键和C—H键等断裂,产生更小的分子结构,其中,H₂、H₂O、CO₂和CH₂O等小分子产生的数量逐渐增多;H·自由基和OH·自由基在反应初期有明显的数量变化,且其含量对于最终稳定产物有重要影响。     

Study on the combined dust suppression effect of sodium alginate and sodium fatty acid methyl ester sulfonate

To further improve the effect of dust control in coal mines and protect the health of workers, the effect of sodium alginate (SA) on the dust suppression ability of sodium methyl ester sulfonate (MES) was studied using molecular dynamics simulation. Scanning electron microscopy and X-ray photoelectron spectroscopy analyses were performed to compare the dust suppression effect of the SA/MES dust suppressant compound to MES by itself. The results show that when SA is present, the coal dust bonds together more, agglomerates into large particles, and settles. This finding is also consistent with the results of molecular dynamics simulations. In the analysis of relative concentrations and mean square displacement, the presence of SA can reduce the water diffusion on the coal surface, making it easier for coal dust to agglomerate. In addition, we analyzed the mode of action of SA through radial distribution and electrostatic potential, and determined that SA forms a unique networking chain structure to capture and retain water molecules. SA increases the probability of interaction between water and surfactant, thus increasing the amount of adsorption. This study provides a more in-depth understanding of the dust suppression mechanism of mixed dust suppressants.     

Investigation on the atomization characteristics of a solid-cone spray for dust reduction at low and medium pressures

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.     

Inhibition characteristics of coal dust explosion at the gasification atmosphere

The risk of coal dust explosion threatens the safety of coal gasification process. To reveal the inhibition of carrageenan dry-water material (CDM) on coal dust explosion, a 20 L spherical explosive device was adopted to compare with SiO₂ and NH₄H₂PO₄ at the atmosphere of coal gasification. The thermal decomposition behavior and chemical structures of the explosion residues were characterized by synchronous thermal analyzer, X-ray photoelectron spectroscopy and FTIR. The results indicate that the CDM showed the optimal inhibiting effect on 300 mesh and the maximum explosion pressure of anthracite coal dust was reduced to 0.02 MPa with the percentage of 97.53%. At the same concentration, the inhibiting effect of CDM on the coal dust explosion was better than that of SiO₂ and weaker than that of NH₄H₂PO₄. Through the residues analysis, the CDM mainly prevented the volatilization of C-H and consumption of oxygen-containing groups and sulfur-containing groups contributing to the inhibition of coal dust explosion.     

CFD simulations of air curtain dust removal effect by ventilation parameters during tunneling

During coal mining, the fully-mechanized tunnel is always under high-concentration of dust pollution. This brings not only the potential risk of dust explosion but also makes the tunnel workers suffer from coal mine pneumoconiosis (CWP), a systemic disease featured by pulmonary fibrosis. Therefore, it is extremely important to establish a theory and optimal parameters for dust control over fully-mechanized excavating tunnels. In this study, we analyzed the dust diffusion under several parameters, including the distance between the forced air opening and the cutting face (L_Y), the height of the forced air cylinder above the floor (L_H), and the distance between the center of the forced air cylinder and the nearest coal wall (L_J). The optimal dust control parameters were determined as: L_Y = 20 m, L_H = 3 m and L_J = 0.6 m. Under this condition, the airflow can effectively suppress the diffusion of dust particles. At the same time, the operating environment of the roadheader driver was remarkably improved and the requirements on miners’ occupational health and safe production were satisfied. The present study proposed a new approach for occupational health of the workers in the excavating tunnel and clean production management.