首页 | 本学科首页   官方微博 | 高级检索  
相似文献
 共查询到20条相似文献,搜索用时 989 毫秒
1.
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-kp 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 dw) is beneficial to the formation of a dust-control air curtain. At a constant dw, the dust diffusion distance (denoted as D) decreases with the increase of φ. At a constant φ, D decreases with the increase of dw when a dust-control air curtain is formed; otherwise, the increase of dw 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 dw = 20–30 m.  相似文献   

2.
A high concentration of dust in a fully-mechanized excavation face is a serious threat to the safety of production underground and miners’ health. This paper discusses the use of a novel air curtain generator and proposes a novel dust control and prevention technique. Based on the k-ε two-equation turbulence model, Hertz-Mindlin model and the CFD-DEM coupled interface compiled with C++ language, this paper firstly constructs a simulation model of the coupling between airflows and dust in a fully-mechanized excavation face, and then simulates the airflow fields and dust fields under forced/exhaust ventilation conditions with and without a novel air curtain generator being utilized. The results show that when only the forced/exhaust ventilation was used, a high concentration of dust spread throughout the entire tunnel space and no effective air curtain was formed. Furthermore, after the air curtain generator was turned on, as the radial-to-axial forced air ratio (PFQ) increased, the horizontal vortex in the front of the head-on section weakened gradually, and the originally disordered airflows behind the heading machine moved uniformly towards the head-on section. As the PFQ further increased, the distance (d) between the formed air curtain and head-on section decreased overall; through a curve fitting, this relationship can be written as: d = ?5.247 ln(PFQ) + 13.569. When the PFQ > 5:5, the average negative-pressure-induced dust-exhaust capacity increased, the distance between the formed air curtain and the head-on section decreased, and the re-entrainment of dust did not take place in a straightforward manner. Finally, some field measurements were carried out in order to validate the simulated results, with the subsequent comparison showing that the numerical simulated results were basically accurate.  相似文献   

3.
《Advanced Powder Technology》2019,30(11):2600-2615
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.  相似文献   

4.
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...  相似文献   

5.
To investigate the effects of the air volume ratio parameters (axial-to-radial flow ratio of the wall-attached air cylinder “δ” and the forced-to-exhaust ratio of the ventilation system “β”) on the air curtain dust suppression in a rock tunnel’s fully-mechanized working face, the eastern belt fully-mechanized working face in Huipodi mining company (Shanxi Mineral Group Co., Ltd., China) was numerically simulated by CFD software in this study. First, a mathematical model for describing the airflow-dust migration in a fully-mechanized working face was established using the Euler-Lagrange method. A full-scale geometrical model of the tunnel was also developed. The effectiveness of the established models and the related parameter settings were then verified by making comparisons between the field measured values and the numerical simulation results. Finally, the airflow migration and dust dispersion rules under different ventilation conditions (δ?=?5:5–1:9 and β?=?0.5–1.5) were simulated. According to the simulation results, a decrease in δ and β contributed to the formation of an effective axial dust-suppression air curtain in the fully-mechanized excavating region. For eastern belt fully-mechanized working face and those under similar production conditions, an effective axial dust-suppression air curtain can be formed when δ?=?1:9–2:8 and β?=?0.5–0.75. When δ?=?1:9 and β?=?0.5–0.75, the high-concentration dust were blocked in the space in front of the driver of heading machine (i.e., within 7?m from the head-on section), which achieved a better dust suppression effect.  相似文献   

6.
《Advanced Powder Technology》2020,31(6):2456-2468
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 (LY), the height of the forced air cylinder above the floor (LH), and the distance between the center of the forced air cylinder and the nearest coal wall (LJ). The optimal dust control parameters were determined as: LY = 20 m, LH = 3 m and LJ = 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.  相似文献   

7.
曹伟  刘海军  王聪 《工程力学》2013,30(9):288-292
气幕发射方式是一种新型的航行体水下垂直发射方式。采用数值模拟的方法,研究了不同射流速度情况下航行体水下垂直发射过程中气幕形态、航行体表面压力及阻力特性等的变化规律,得到了在出筒过程中,不同气体射流速度情况下,航行体均可顺利通过气幕的最小半径处,气体射流马赫数越大,航行体总阻力系数越大;在出水过程中,航行体总阻力系数单调降低,与气体射流马赫数无关等结论。  相似文献   

8.
Metal dust has explosion risk in wet dust removal system. In this study, a gas–liquid dual phase explosion hydrogen inhibition method (EHIM) is proposed. The inhibitory effect of KH2PO4 on Al dust explosion in a dust removal pipe (gas phase) and Al dust hydrogen generation in a wet dust collector (liquid) is discussed separately and collectively. Adding 70% KH2PO4 totally inhibits the formation of Al dust explosion flames while inhibiting Al–water reaction in the wet dust collector at the same time. Inside the dust removal pipe, KH2PO4 acts in the initial stage of Al dust combustion and works as a pyrolysis endothermic coolant under 220℃–380℃; inside the aqueous solution of the dust collector, it generates AlPO4 with water and creates a film over the surface of the Al particles, which isolates water from Al, thus blocking Al–water reaction. Our new method offers a novel way of protecting the safety of wet dust removal systems.  相似文献   

9.
Preparation of microcrystalline cellulose (MCC) beads with a laboratory-scale centrifugal granulating apparatus was studied, and the pharmaceutical quality of the beads was characterized with respect to the subsequent drug layering. Five process parameters of potential importance, including rotor rotation speed X1, slit air X2, spray air pressure X3, spray air rate X4, and height of nozzle setting X5, were evaluated using a fractional factorial design (FFD 25-2) as the experimental design. The responses evaluated were expected yield, mean size, size distribution, shape characteristics (including roundness, circularity, elongation, rectangularity, and modelx), and friability. All five process parameters studied were found to have an influence on the selected properties of the beads, but the effects of rotor rotation speed, slit air flow rate, and spray air rate were statistically significant (p <. 05). The effect of the rotor rotation speed was found to be the most potent on all the responses studied. The results also show some significant interactions between the parameters tested. The most significant interactions were between rotor rotation speed and slit air, rotor rotation speed and spray air, and slit air and spray air.  相似文献   

10.
针对传统风幕控尘装置设备多、空间小、掘进机移动不便等诸多不足之处,⌒进行了优化设计。为确保新型风幕控尘装置的实际应用效果,指导现场防尘系统设计,确定抽出式风机风筒安设位置,依(山西某矿掘进巷道工作面1:1建立了物理几何模型,并利用计算流体动力学(CFD)进行模拟。根(湍流模型特性及流体运动特点,选取拉格朗日法离散相模型对掘进巷道粉尘浓度分布进行了模拟分析并进行现场实践。结果显示,所选物理几何模型参数设置合理,拟合精度达到预测要求;加装新型风幕控尘装置前后,粉尘浓度下降对比明显;距底板2.1 m处安设抽出式风机风筒时,系统降尘效果显著。  相似文献   

11.
In this article the analysis of steady state and transient gas sensing characteristics of undoped and Pd surface doped SnO2 films, deposited by spray pyrolysis, is described. The influence of parameters such as air humidity (2-50% RH), operation temperature (25-500 °C) and Pd surface concentration (0-1% ML Pd) on gas response to CO and H2 (0.1-0.5%), response time, shape of sensitivity S(T) curves and activation energy of τ(1/kT) dependencies are discussed. A mechanism based on a chemisorption model is proposed to explain how Pd influences the gas sensing characteristics of SnO2 films.  相似文献   

12.
确保喷雾液滴在接触烟道壁面前完全蒸发,是保障电站脱硫废水在锅炉尾部烟道内蒸发处理安全运行的关键。喷雾液滴的破碎、聚并等动力学行为,以及液滴群的粒径分布和速度等因素的影响机制,是喷雾蒸发的主要特性。设计搭建了热态风洞实验台,利用激光粒度分析仪和粒子图像测速仪(particle image velocimeter,PIV),在不同的引射空气压力、喷嘴水流量,以及风速、加热空气温度等条件下,对喷雾液滴群的粒径变化和速度变化进行了测量和分析。实验结果表明:以大液滴形态离开喷嘴的射流在引射气流的携带作用下,因破碎而形成小液滴,而后液滴间聚并效果会显现出来。液滴初始粒径仅与引射气体压力和水流量有关;风速的提高一定程度上会促进液滴间的聚并。提高高压气体压力、温度、风速以及减小水流量均有助于提高液滴群速度,其中提高风速对液滴群的增速效果最为明显。研究结果为喷雾的数值模拟及工程应用改进方向提供了参考。  相似文献   

13.
In order to enhance the spray for dust suppression performance in a fully-mechanized mining face, based on orthogonal test, comparison test, numerical simulation and field application, the Venturi negative-pressure secondary dedust device was developed. Meanwhile, the local spray closure technique was proposed, which can not only effectively prevent the escape of coal dust from entering the footway space, but also remove coal dust around the respiratory zone from the footway space successfully. The results demonstrated that, under spray pressure of 6?MPa, the Sauter mean droplet size, negative pressure suction flow rate and effective spray distance of the novel dedust device with a throat-to-nozzle distance and throat diameter of 20?mm and 65?mm were 47.37?µm, 11.21?m3/min and 5.4?m respectively. Moreover, the novel dedust device produced droplets to a smaller scale than a single-nozzle. Additionally, the negative pressure and airflow velocity in the negative pressure suction inlet of novel dedust device were within the range from ?0.97?Pa to ?541.04?Pa and from 2.96?m/s to 27.29?m/s respectively. Finally, compared with the original dust suppression measures, the local spray closure technique can enhance the removal ratio of respiratory dust by an average of 44.3%.  相似文献   

14.
The loss of contact between the vane tip and cylinder wall was proven to cause a serious leakage and inefficient operation of the rotary vane expander, which was developed to replace the throttling valve in the trans-critical CO2 refrigeration system. An improved structure was suggested by introducing high-pressure gas into the vane slots. This paper presents the experimental investigation of the improved prototype expander. By comparing the improved prototype with the original, focusing on the expander performance and the p-θ diagram as well as the vane movement, the effects of introducing high-pressure gas into the slots on the thermodynamic processes and performance were analyzed. The results showed that, by introducing the high-pressure gas into the vane slots, the volumetric efficiency was increased from 17% to 35%, and the isentropic efficiency improved from 15% to 45%, resulting in a maximum COP improvement of 27.2% compared to the throttling cycle under the same working conditions.  相似文献   

15.
The dry dense medium separation of iron ore based on floating and sinking of ore particles in a gas–solid fluidized bed was investigated using zircon sand as the fluidized medium. The float-sink of ore particles with mean size Dave = 23.6 mm was investigated as the fluidizing air velocity and the float-sink time were varied. It was found that gangue with density less than 2850 kg/m3 which float is able to be separated from valuable ore with density greater than 2850 km/m3 which sink. The set point (density where half the particles float and half the particles sink) decreases with increasing the air velocity, and that the float-sink separation is completed within 2 min. The influence of different sized ore particles in the float-sink experiments was also investigated. As a result, the iron ore with Dave ? 17.6 mm are successfully separated. As Dave decreases below 17.6 mm, the ore particles with density near the set point tend to scatter in the fluidized bed without floating or sinking, resulting in separation efficiency which decreases with decreasing Dave. This indicates that the size of the ore particles is one of the major factors to achieve high separation efficiency.  相似文献   

16.
The spray drying process consists of a fast convective drying of liquid droplets by hot air. Initially, the water activity (aw) of a drop is close to 1. During drying, the drop surface aw decreases while viscosity increases until reaching a sticky rubbery state before further drying. This can be observed for products such as carbohydrates, leading to particles sticking on walls (product losses) or to adhesion between particles leading to agglomeration. In this study, particle stickiness was investigated in a cocurrent pilot spray dryer by measuring drying air properties (temperature and relative humidity) at different positions. This allowed describing the evolution of temperature and mean water content of the drying drops. Two model products (maltodextrin DE12 and DE21) were spray dried varying process parameters liquid flow rate (1.8, 3.6, and 5.4 kg/h), air temperature (144°, 174°, and 200°C), airflow rate (80–110 kg/h), and rotary atomizer speed (22,500–30,000 rpm). The two products exhibit different drying behaviors in relation to their affinity towards water (sorption isotherms) and glass transition temperature evolution with aw (stickiness). Depending on drying conditions and product, the drop stickiness was observed very rapidly, close to the atomizer, or later, along the chamber. This approach can be used to identify conditions and positions corresponding to sticky particles.  相似文献   

17.
The purpose of this research was to simultaneously evaluate the removal efficiency of acid gases and PAHs from the flue gas emitted by a laboratory incinerator. This flue gas contained dust, acid gases, organics and heavy metals. A spray dryer combined with a fabric filter was used as the air pollution control device (APCD) in this study. The operating conditions investigated included different feedstock additives (polyvinyl chloride (PVC) and NaCl) and spray dryer additives (SiO2, CaCl2 and NaHCO3).The removal efficiency for SO2 could be enhanced by adding inorganic additives, such as SiO2, CaCl2 and NaHCO3. The presence of PVC in the incinerator feedstock also increased the removal efficiency of SO2in the spray dryer. The improved removal of PAHs could be attributed to the addition of feedstock additives (PVC and NaCl) and spray dryer additives (SiO2, CaCl2 and NaHCO3).  相似文献   

18.
Nozzle arrangement in the nozzle spray system has a significant impact on the gas-droplet flow characteristics and the temperature distribution within the circulating fluidized bed flue gas desulphurization (CFB-FGD) tower, which is critical to the SO2 removal efficiency. The effects of spray direction, nozzle number and nozzle spray angle on gas-droplet distribution and temperature distribution inside the FGD tower are investigated with numerical simulation based on a Eulerian-Lagrangian mathematical model. An optimal nozzle arrangement scheme is proposed to improve the contact between gas and water droplets and the flue gas temperature distribution. Results show that upward spray direction is beneficial to the interaction between water droplets, improving gas-droplet flow characteristics and spray evaporation process, and water droplets number trapped by tower wall could be reduced in the water droplets evaporation. With the increase in nozzle number, it is conducive to the contact between flue gas and water droplets to increase the evaporation efficiency of water droplets, as well as the uniformity of temperature distribution inside the tower. With nozzle spray angle increases from 30° to 120°, flue gas velocity decreases, water droplets number trapped by the tower wall increases. The temperature distribution at different cross-section is the most uniform when the nozzle spray angle is 60°.  相似文献   

19.
The ignition temperature in the air atmosphere at the separating line between an explosion and no explosion in a dust cloud, Tib, has been investigated for mixtures of fine and coarse dusts of the same material. The minimum ignition temperature, Tim, which is the lowest temperature at which an explosion is obtained has also been determined. Measurements were made in a Godbert-Greenwald Furnace apparatus. The results obtained indicated that the ignition temperature is dependent on the particle size, and an admixture of fine dust of 30% to coarse dust is sufficient to reduce the Tim values significantly.  相似文献   

20.
A gas–solid fluidized bed has been used to separate particulate iron ore (+250–500 μm in size) by segregating the particles by density. The ore particles were put into a cylindrical column of inner diameter of 100 mm and bed height of 50 mm, and were fluidized at a given air velocity u0/umf = 1.2–3.2 for 10 min. u0 and umf are the superficial air velocity and the minimum fluidization air velocity, respectively. The bulk density of the ore particles after fluidization was measured as a function of height through the bed in 5 mm increments (the 50 mm height was divided into 10 layers) to investigate the density-segregation. The size of the particles in each of the 10 layers was also measured to investigate size-segregation. It was found that both density-segregation and size-segregation occurred as a function of height through the bed after fluidization at u0/umf = 2.0. However, the segregation did not occur near the bottom of the bed for lower u0/umf and did not occur near the top of the bed for larger u0/umf. The origin of the segregation-dependence on the air velocity was discussed considering the air bubbles size and the fluidizing intensity at upper and lower sections of the bed. The Fe content of the 10 layers at u0/umf = 2.0 was measured to calculate the Fe-grade and Fe-recovery. The ore-recovery was also calculated using the weight of ore particles as a function of height through the bed. The feed Fe-grade (before separation) was 52.1 wt%. If the ore particles in the bottom half of the bed were regarded as the product, the Fe-grade was 59.0 wt%, and the Fe-recovery and the ore-recovery were 68.5 wt% and 60.5 wt%, respectively.  相似文献   

设为首页 | 免责声明 | 关于勤云 | 加入收藏

Copyright©北京勤云科技发展有限公司  京ICP备09084417号