大浓度范围内PV型旋风分离器粒级效率的计算方法

探讨了旋风分离器入口含尘浓度对其分离性能及粒级效率的影响机理。对旋风分离器内部气固两相运动进行了相似分析,得到了包括入口含尘浓度在内的一系列影响分离性能的相似准数。通过相似试验及试验数据的多元回归分析,建立了各相似准数与粒级效率的关系,得出了能精确估计大浓度范围内PV型旋风分离器粒级效率的计算公式。     

CFD Analysis of Dust Explosion Relief System in the Counter-Current Industrial Spray Drying Tower

The aim of the paper was to evaluate the performance of venting devices in an industrial counter-current spray tower during dust explosion using a CFD model and EN14491:2006 standard. Three-dimensional CFD simulations of dust explosion in the spray tower for six different configurations of safety vents located at the top and side walls of the dryer were carried out. In the calculations, in which dust was replaced with a flammable gas-air mixture, the following parameters of dust explosion were analyzed: reaction progress, maximum and average gas temperature, gas velocity, and pressure. Reduced pressures calculated according to EN 14991:2006 standard are close to maximum pressure obtained from CFD simulations for all analyzed spatial configurations of the safety vents, which proves that the CFD model can be used both to design explosion mitigation systems and to describe the mechanism of explosion propagation in the drying chamber. Results of the calculations allowed us to evaluate the performance of analyzed venting devices, to determine the spatial configuration and parameters of venting devices that should be installed to minimize damages of the dryer construction.     

Das elektrische Verhalten hochohmiger Stäube

Highly resistive dusts show markedly non‐ohmic properties. The property known as specific resistivity is strongly dependent on the dust layer thickness and on the polarity of the high voltage. The current transport occurs by excess charges of both polarities, which leads to high space charge densities and induces strong electrostatic fields. The theory of electrets provides a consistent explanation of the phenomena observed so far. To investigate the electrical properties, highly resistive dusts were exposed to an electrical field with interfering corona discharges within a tip‐plate arrangement.     

SEPARATION OF AIRBORNE DUST IN ELECTROSTATICALLY ENHANCED FIBROUS FILTERS

The removal of small charged dust particles from a gas stream using an external electric field is common in many industrial applications. In the present paper, the feasibility of using electrostatically enhanced fibrous filters (EEFFs) to separate high concentration dusts from a contaminated gas stream is studied and models to predict both the pressure drop through the filter and the collection efficiency in the dust laden filter are proposed and these models are confirmed by experiments.     

Effectiveness of coal mine dust control: A new technique for preparation and efficacy of self-adaptive microcapsule suppressant

This study aims to make full use of the agricultural waste peanut shells to lower material costs and achieve cleaner production at the same time. Cellulose nanofibrils (CNF) extracted from peanut shells were mixed with acrylic acid (AA) and dimethyl diallyl ammonium chloride (DMDAAC) to prepare a new type of capsule core (dust suppressant). Then, the self-adaptive AA-DM-CNF/CA microcapsules were prepared under the action of calcium alginate. The infrared spectroscopy and X-ray diffraction analysis results suggest that AA, DMDAAC and CNF have experienced graft copolymerization which leads to the formation of an amorphous structure. The scanning electron microscopy analysis results demonstrate that the internal dust suppressant can expand and break the wall after absorbing water, featuring a self-adaptive function. Meanwhile, the laser particle size analysis results show that the microcapsules, inside which the encapsulated dust suppressant can be observed clearly, maintain a good shape. The product performance experimental results reveal that the capsule core and the capsule wall achieve synergistic dust suppression, thus lengthening the dust suppression time. The product boasts good dust suppression, weather resistance, degradation and synergistic combustion performances. Moreover, this study, as the first report on the development and analysis of dust-suppressing microcapsules, fills in the research gap on the reaction mechanism between dust-suppressing microcapsules and coal by MS simulation. The proposed AA-DM-CNF/CA dust-suppressing microcapsules can effectively lower the dust concentration in the space and protect the physical and mental health of coal workers. In general, this research provides a new insight into the structure control and performance enhancement of dust suppressants. Expanding the application range of microcapsules is of crucial economic and social benefits.     

The wettability of coal and its relevance to the control of dust during coal mining

Water sprays are used on longwall mining machines to help control respirable coal dust during underground mining operations. Surfactant reagents added to the sprays, if properly selected, can improve the coal dust wettability and capture efficiency of water droplets. Combining water-soluble polymers with a surfactant can improve dust suppression further by altering the adhesion-cohesion properties of water droplets. The mechanism of coal dust control using a surfactant-polymer reagent is discussed. The Bureau of Mines tested an anionic surfactant-polyethylene oxide polymer water spray additive in the laboratory and in an underground longwall coal-mining operation. The results were encouraging but anomalously high headgate dust concentrations were consistently observed when the surfactant-polymer reagent was injected during the longwall tests. A hypothesis, based on rheological considerations and an adaptation of the Good-Islam liquid bridge model, is suggested to explain the phenomenon. A brief example of the method for correcting the mine dust concentration data for the excess headgate dust is given.     

高温除尘技术综述

介绍了高温除尘技术的特点,综述了国内外高温除尘设备的现状、水平以及发展趋势,并对该技术在各行业中的应用前景进行了展望。     

电弧炉粉尘球团直接还原的热传导模型

对电弧炉炼钢粉尘加上还原剂碳混合制粒成的球团还原过程的热传导行为进行了研究,根据实验推导了球团导热模型的结构参数,并试图建立热传导模型。     

发动机铸件的清理技术成功案例潍柴缸体清理线

大马力发动机缸体铸件清理一直是铸件生产中的关键,铸件清理生产效率、职工劳动强度、铸件清理质量、环境污染、生产自动化水平是清理生产中的焦点。潍柴动力股份有限公司铸造二期项目大件清理工部采用新的清理流程及技术装备,经生产检验可靠地解决了以上清理生产中的难点。