Characteristics of centrifugal separator

An approximate method is proposed for the calculation of the integral separational characteristics of a centrifugal separator.Translated from Inzhenerno-Fizicheskii Zhurnal, Vol. 43, No. 1, pp. 124–131, July, 1982.     

二元颗粒的旋风分离效率

为了揭示二元颗粒的分离特性,以较难分离的沥青和滑石粉为母体粉料,以容易分离的煤粉和石油焦为添加粉料,两两形成4种差异二元颗粒体系,并以直径300 mm的PV型旋风分离器为模型,比较分离效率。结果表明:沥青颗粒、煤粉和石油焦的加入均能促进其分离效率,添加比例越大,效率提高越明显,且煤粉的促进作用比石油焦的更大;滑石粉、煤粉和石油焦的加入降低其分离效率,添加比例越大,分离效率降低越明显,且煤粉的抑制作用也更大;提出稳定团聚促进颗粒分离的观点,建议采用团聚相对稳定度来判断添加颗粒的促进或抑制作用,且采用团聚相对稳定度可从定性和定量两方面解释二元颗粒旋风分离的特殊现象。     

Theory of centrifugal sedimentation of large particles

The motion of particles of finite size in rotating viscous liquids is investigated. On the basis of the properties of centrifugal sedimentation described, its possible technical applications are discussed.Translated from Inzhenerno-Fizicheskii Zhurnal, Vol. 32, No. 5, pp. 865–869, May, 1977.     

Characterization of the graded distribution of primary particles and wear behavior in the A390 alloy ring with various Mg contents fabricated by centrifugal casting

Three kinds of functionally graded rings using A390 as a base alloy and containing 0, 6 and 12 wt%Mg were prepared by centrifugal casting, and their microstructure and mechanical properties were investigated and compared. It is shown that the A390 ring without Mg content takes a characteristic of the primary Si particles distribution in the inner and outer layers. The 6%Mg ring reinforced by Si/Mg₂Si particles has a different performance with its particles distribution only in the inner layer. Regarding the 12%Mg ring, the Mg₂Si reinforced particle is distributed near the entire cross-section. It is demonstrated that the existence of the light in situ Mg₂Si particles with lower density rather Al liquid makes changes to the gradient distribution of particles across the cross-section. Characteristics and distribution of the primary particles were assessed by the optical microscopy (OM), scanning electron microscopy (SEM), energy dispersive spectrum (EDS) and image analyzer software. The hardness and wear rate along the thickness of samples were measured to investigate the variation in the mechanical properties corresponding to the variation in microstructure. Also, the worn surfaces of the material were examined by scanning electron microscopy (SEM) to study the dominant wear regime.     

Analysis of the motion of suspended particles in a rotor separator

We discuss a method for the calculation of the efficiency of a rotor-ring separator which includes a rotor made up of a set of plane rings and blades to form channels. The calculation reduces to an analysis of the motion engendered by the primary forces of the suspended particles in the channel between the blades and is based on the solution of differential equations by a numerical method. The research results have been generalized in the form of a relationship linking dimensionless complexes, this relationship suitable for engineering calculations.Translated from Inzhenerno-Fizicheskii Zhurnal, Vol. 60, No. 3, pp. 449–453, March, 1991.     

Hygroscopic behavior of substrate-deposited particles studied by micro-FT-IR spectroscopy and complementary methods of particle analysis

The application of microscopic Fourier transform infrared (micro-FT-IR) spectroscopy combined with complementary methods of particle analysis is demonstrated here for investigations of phase transitions and hygroscopic growth of micron-sized particles. The approach utilizes the exposure of substrate-deposited, isolated particles to humidified nitrogen inside a sample cell followed by micro-FT-IR spectroscopy over a selected sample area. Phase transitions of NaCl, sea salt, NaNO3, and (NH4)2SO4 particles are monitored with this technique to evaluate its utility and applicability for particle hydration studies. The results are found in excellent agreement with literature data in terms of (a) reliable and reproducible detection of deliquescence and efflorescence phase transitions, (b) quantitative measurements of water-to-solute ratios in particles as a function of relative humidity, and (c) changes in the IR spectra resulting from phase transitions and changing relative humidity. Additional methods of particle analysis are employed to complement and assist in the interpretation of particle hygroscopicity data obtained from micro-FT-IR measurements. The analytical approach and the experimental setup presented here are relatively simple, inexpensive, readily available and therefore may be practical for hydration studies of environmental particles collected in both laboratory and field studies.     

Analysis of fluid flow in centrifugal casting

Centrifugal casting process is a fast process with melt, cast and moulds being opaque. It is almost impossible to observe the melt behavior during casting. Cold modeling experiments were conducted using horizontal transparent moulds and transparent fluids of different viscosities to study the effect of different process variables on the flow pattern. Effects of the thickness of fluid cylinder, viscosity of the fluid, diameter of the mould, and rotational speed of the mould on the formation of complete hollow fluid cylinder are investigated. The influence of rotational speed has been studied in aluminum casting. The cylinders are cast at different rotational speed with varying thickness. It is observed that the speed required to form uniform cylinder increases with the increase in thickness of a fluid cylinder. As rotational speed is increased the hardness of the cast cylinder also increases. The flow patterns seen in cold modeling experiments and actual castings agree reasonably well.     

The removal of particles from the matrix of a high-gradient magnetic separator

The desorption of hematite particles from the matrix of a magnetic separator was studied experimentally as a function of the pH value and flowrate of the water used for flushing. It was found that the removal of particles was strongly dependent on the pH value of the flushing water, the optimum being at pH 11. A model based on Derjaguin-Landau-Verwey-Overbeek (DLVO) theory was developed, and the experimental results were analyzed in terms of this model, which offers a good explanation of the residual forces hampering the removal of particles from a matrix.     

螺旋导流膜分离器中流体流动特性研究

为减少膜分离中的浓差极化和膜污染,提出了一种新型的膜分离组件,螺旋导流膜分离器.通过数值模拟确定了螺旋导流膜分离器的最小工作状态,并从螺旋导流膜分离器中流体流动的轴向速度、周向速度、壁面剪切应力和压力等流场特性分析,对其分离机理有了较为全面、深入的认识.     

Fluidization behavior of nano-particles by adding coarse particles

Fluidization behaviors of SiO₂ and TiO₂ nano-particles by adding coarse particles of FCC, ordinary Al₂O₃ and heat-resistant Al₂O₃, has been investigated experimentally. The effect of size and inventory of coarse components on the fluidization behavior of nano-particles has been studied. The results reveal that the fluidization quality of the mixture systems can be improved with increasing the amount of the coarse particles. For SiO₂ nano-particles, the optimum of FCC, ordinary Al₂O₃ and heat-resistant Al₂O₃ are 30%, 40% and 50%, respectively. Similarly, the optimal amount of FCC, ordinary Al₂O₃ and heat-resistant Al₂O₃ is about 30% for TiO₂ nano-particles. Fluidization quality is almost the best for all these three coarse additives of 65–80 μm. The analysis performed from the standpoint of the Richardson–Zaki (R–Z) equation reveals that the apparent terminal velocity derived through scaling experimental data to R–Z equation affects the expansion index of the mixture systems.     

采出液中固相颗粒对三相分离器性能的影响

为研究采出液中固相颗粒对气液固三相分离器性能的影响,基于计算流体力学软件Fluent,模拟分析三元驱采出液内所含的固相颗粒粒度及含量变化对三相分离旋流器处理固相体积分数分布、速度场和除砂分离效果的影响。结果表明:入口固相颗粒粒度变化对其径向速度影响较大,呈线性影响关系,颗粒粒径越大,流向旋流器器壁的径向速度越大,粒径不同对切向速度和轴向速度影响较小;固相含量增加,旋流器固相质量分离效率呈先增大后减小的趋势。     

Buildup of particles on fibers in a high field-high gradient separator

In previous publications the performance of a high field-high gradient magnetic filter was calculated using a particle trajectory model to obtain the capture cross section of the fibers. The configuration of the particle buildup was assumed to be constant without considering the forces on the particle after impinging on the fiber. We now calculate the equilibrium configuration of particle buildup on the edge of a flat ribbon considering only the magnetic and viscous forces and including the effect of the fluid boundary layer. The configurations obtained as a function of field and flow are consistent with the few approximate direct observations reported in the literature. The performance of the filter, calculated using the particle trajectory model, now modified by this equilibrium buildup configuration, is compared to previously reported experimental results on separation of CuO from Al2O3slurries. A somewhat better fit is now obtained over the entire range of fluid velocity and fields, but an adjustable parameter affecting the viscous drag on the collected particles is required.     

Impact of grade separator on pedestrian risk taking behavior

Pedestrians on Delhi roads are often exposed to high risks. This is because the basic needs of pedestrians are not recognized as a part of the urban transport infrastructure improvement projects in Delhi. Rather, an ever increasing number of cars and motorized two-wheelers encourage the construction of large numbers of flyovers/grade separators to facilitate signal free movement for motorized vehicles, exposing pedestrians to greater risk. This paper describes the statistical analysis of pedestrian risk taking behavior while crossing the road, before and after the construction of a grade separator at an intersection of Delhi. A significant number of pedestrians are willing to take risks in both before and after situations. The results indicate that absence of signals make pedestrians behave independently, leading to increased variability in their risk taking behavior. Variability in the speeds of all categories of vehicles has increased after the construction of grade separators. After the construction of the grade separator, the waiting time of pedestrians at the starting point of crossing has increased and the correlation between waiting times and gaps accepted by pedestrians show that after certain time of waiting, pedestrians become impatient and accepts smaller gap size to cross the road. A Logistic regression model is fitted by assuming that the probability of road crossing by pedestrians depends on the gap size (in s) between pedestrian and conflicting vehicles, sex, age, type of pedestrians (single or in a group) and type of conflicting vehicles. The results of Logistic regression explained that before the construction of the grade separator the probability of road crossing by the pedestrian depends on only the gap size parameter; however after the construction of the grade separator, other parameters become significant in determining pedestrian risk taking behavior.     

Properties of magnetic fluid particles

Very fine particles of magnetite, nickel ferrite, and cobalt ferrite were produced by grinding coarser powders in a ball mill with a carrier fluid and a surfactant. The particles were examined by means of chemical analysis, electron microscopy, x-ray diffraction, magnetic measurements, and Mössbauer spectroscopy. Properties were determined before and after removing the surfactant coating. The most significant observation was that in some systems a large fraction of the spins was pinned in extremely high anisotropy fields as a result of bonding to the surfactant molecules. Anomalous magnetic hysteresis behavior was also noted when the surfactant coating was present.     

用于聚合物颗粒回收的旋风分离器的结构改进

针对某聚丙烯酰胺流化床干燥器旋风分离器排料困难、颗粒回收效率低等问题,指出其原因在于灰斗结构不合理,造成排料口负压过大,导致返料风机难以将分离下的颗粒送回干燥器;提出在灰斗内增加新型内构件,以减小排料口压降的改进措施;通过冷态对比实验,对新型内构件的效果进行检验。结果表明:增设新型内构件后,排料口压降降幅达60%以上,分离效率和压降变化较小;排料口静压大幅提高,返料效果得到显著改善。     

尖劈状磁场中磁流体磁性微粒的受力分析

通过有限元方法对尖劈形磁场中磁流体磁性微粒所受的磁场力进行了数值分析,分别给出了磁场气隙处磁通量和磁场强度随不同气隙宽度和夹角的变化规律.在此基础上,利用虚位移法和麦克斯韦应力张量法计算磁流体磁性微粒在气隙上方所受的磁场力.结果表明,随着气隙宽度的减小,磁通量、磁场强度和磁场力明显增加;随着气隙夹角的增加,磁通量、磁场...     

Theoretic model and computer simulation of separating mixture metal particles from waste printed circuit board by electrostatic separator

Traditionally, the mixture metals from waste printed circuit board (PCB) were sent to the smelt factory to refine pure copper. Some valuable metals (aluminum, zinc and tin) with low content in PCB were lost during smelt. A new method which used roll-type electrostatic separator (RES) to recovery low content metals in waste PCB was presented in this study. The theoretic model which was established from computing electric field and the analysis of forces on the particles was used to write a program by MATLAB language. The program was design to simulate the process of separating mixture metal particles. Electrical, material and mechanical factors were analyzed to optimize the operating parameters of separator. The experiment results of separating copper and aluminum particles by RES had a good agreement with computer simulation results. The model could be used to simulate separating other metal (tin, zinc, etc.) particles during the process of recycling waste PCBs by RES.     

The motion of small paramagnetic particles in a high gradient magnetic separator

The force balance equation describing the motion of a small paramagnetic particle near a cylindrical ferromagnetic collector is presented in general form. The capture cross-section for a particle approaching a bare wire is found to be a function of the coefficient of magnetic force and the magnetization of the cylinder. Calculations show that the assumption of potential flow versus creeping flow is a critical one which can change the capture cross-section by as much as a factor of three.     

Hygroscopic behavior of individual submicrometer particles studied by X-ray spectromicroscopy

A novel application of single particle scanning transmission X-ray microscopy (STXM) and near edge X-ray absorption fine structure (NEXAFS) spectroscopy is presented for quantitative analysis of hygroscopic properties and phase transitions of individual submicrometer particles. The approach utilizes the exposure of substrate-deposited individual particles to water vapor at different relative humidity followed by STXM/NEXAFS spectromicroscopy analysis. The hygroscopic properties of atmospherically relevant NaCl, NaBr, NaI, and NaNO(3) submicrometer particles were measured to evaluate the utility of the approach. An analytical approach for quantification of a water-to-solute ratio within an individual submicrometer particle during hydration and dehydration cycles is presented. The results for the deliquescence and efflorescence phase transitions and quantitative measurements of water-to-solute ratios are found in excellent agreement with available literature data. Oxygen K-edge NEXAFS spectra of submicrometer sodium halide droplets are reported along with a unique experimental observation of the formation of the halide-water anionic complex in NaBr and NaI microdimensional droplets. The analytical approach provides a unique opportunity for spectromicroscopy studies of water uptake on environmental particles collected in both laboratory and field studies.