Gravity Separation of Particulate Solids in Turbulent Fluid Flow

The separation characteristics of particles' settling velocity, size, density, and shape are introduced, and the equivalent settling condition for laminar, transition, and turbulent flow are explained. A similarity model of particle transport in a turbulent flow field is briefly discussed. Typical operation principles in separation devices for counter current and cross-flow separation are presented. The separation function, cut point, sharpness, and separation stage utilization coefficient are determined to assess the efficiency for process sequences for multistage turbulent cross-flow separation. Satisfactory to very good results were achieved in the difficult separation of a partially liberated aggregate consisting of hardened cement paste rubble with sharpness from 0.66 to 0.94 at separation stage utilization coefficients of 7 to 87%. Specific mass flow rates of 3 to 16 t/(m² · h) and mass related energy consumption of 0.2 to 8 kWh/t were obtained.     

联箱-小孔型气液分离器的CFD数值模拟

在冷凝过程中采用气液分离(分液冷凝)能同时实现强化传热和降低压降.高效的气液分离是提升分液冷凝器性能的关键.本文针对联箱-小孔型气液分离器,建立了三维数值模型,研究了其气液分离特性.基于实验结果对模型进行了验证,分析了分液孔径(0.5～2.0 mm)和分液孔位置(居中、不居中)对联箱内工质流动特性的影响.结果表明:在入...     

斜窄上升流内沉渣/浮油过程及其应用

研究了钢厂污水通过拉美拉斜浅层时,斜窄(上升)流内微细固渣沉降及油滴漂浮的机理。为重钢高线厂的浊环水二次净化,设计和制作了占地20×30=600m2的斜窄流沉渣浮油池,有效工作面积达3000m2。投产1年的测试结果平均为:进水量1800~2200m3/h,含固及油分别为61·25g/m3及150g/m3;出水含固3~7·5g/m3,含油5~9·3g/m3;底流渣泥含水42%~52%;底流渣泥含水64·5%;撇除的油经分离除水后含水<10%;达到了实用要求。已推广到济南钢厂等企业。     

卫星重力梯度数据用于精化地球重力场的研究

确定厘米级大地水准面和发展超高阶地球重力场模型是现代物理大地测量的主要科学目标之一。卫星重力梯度测量的实现将为这一目标做出重大贡献。文章着重评述这一领域的研究进展，并讨论利用卫星重力梯度数据精化地球重力场的若干理论和方法问题。     

退役汽车有色金属涡电流分选的发展现状和展望

涡电流分选自20世纪70年代以来,共经历了5个发展阶段,目前已广泛应用于退役汽车破碎料等固体废弃物中有色金属的回收与再利用.目前,国内外对涡电流分选开展了深入研究,主要研究内容包括分选力模型、分选效率、细粒物料分选及计算机控制等4个方面.简述了报废汽车回收利用现状、破碎料分选流程及涡电流分选的重要作用,并对涡电流分选在上述4个方面的国内外研究进展及应用现状进行了总结;同时展望了涡电流分选的前景和未来发展的趋势.     

Assessment of Mechanical Properties of Cohesive Particulate Solids. Part 2: Powder Flow Criteria

The fundamentals of cohesive particulate solids' consolidation and flow properties using a reasonable combination of particle and continuum mechanics by means of micro/macrotransition of the "characteristic particle contact" are explained. The adhesion force models of Tomas (2001a) are used to derive the stationary, instantaneous T S1 time yield loci and consolidation loci. Next, the uniaxial compressive strength σ c ( σ 1 ), effective angle of internal friction } e ( σ 1 ), and bulk density 𝜌 b ( σ 1 ) are obtained as powder constitutive functions. The approach has been shown to be effective for the data evaluation of cohesive powder flow properties, like a very cohesive titania nanopowder (surface diameter d s = 200 nm, solid density 𝜌 s = 3870kg/m 3 ) with the fit r 2 xy > 0.95. Finally, these models in combination with accurate shear cell test results are used as constitutive functions for computer-aided silo design for reliable flow.     

Variational Multiscale Large Eddy Simulation of Turbulent Flow in a Diffuser

In the present study, variational multiscale large eddy simulation (LES) is applied to turbulent flow in a diffuser, which represents a challenging test case due to the appearance of flow separation and subsequent reattachment. Two different scale-separating operators based on multigrid operators are used for separating large and small resolved scales. Dynamic as well as constant-coefficient-based subgrid-scale modeling are employed in the variational multiscale LES. The results show that the variational multiscale LES with a simple constant-coefficient Smagorinsky model using a projective scale-separating operator yields a very good prediction of most of the crucial flow features. Furthermore, it turns out to be by far the most computationally efficient approach, resulting in a computing time reduction of about 18% compared to the traditional LES with a dynamic Smagorinsky model. The variational multiscale LES with a dynamic Smagorinsky model does not prove to be a superior approach.     

不同重力条件对 PbO-B2O3玻璃分相的影响

研究了PbO—B2O3在不同重力条件下的分相现象，并分析了不同实验条件下试样的成分均匀性以及试样不同部位的显微结构．结果发现，玻璃发生分相后形成连续的富硼相和分散的富铅相．对于分相在高重力阶段发生的试样，顶部富铅相的尺寸远远小于试样的底部，试样顶部的含铅量远远低于试样的底部，因此该试样的成分均匀性最差，其次是在正常重力下发生分相的试样．     

富铁相形态对电磁净化效率的影响

研究了Al-2％Fe初生富铁相形貌的改变对电磁分离效率的影响。以Mn作为变质剂来改变富铁相形态，当摩尔比Mn／Fe=1．3～1．5时，富铁相由针状转变为规则的块状或球状。分别在变质前后进行电磁分离试验，并且分析了试样不同部位的微观组织，试验表明：变质后，富铁相的形貌有利于在熔体中迁移，并且电磁净化的效率比变质前提高了20％，可达到90％以上。     

Turbulent Fluid Flow and Heat Transfer Calculation in Mold Filling and Solidification Processes of Castings

Based on the time-averaging equations and a modified engineering turbulence model, the mold filling and solidification processes of castings are approximately described. The algorithm for the control equations is briefly introduced, and some problems and improvement methods for the traditional method are also presented. Both calculation and tests proved that. comparing with the laminar fluid flow and heat transfer, the simulation results by using the turbulence model are closer to the real mold filling and solidification processes of castings.     

Separation of matrix alloy and reinforcement from aluminum metal matrix composites scrap by salt flux addition

Separation of matrix alloy and reinforcements from pure Al-SiC_p composite scrap by salt flux addition has been theoretically predicted using interface free energies. Experiments performed confirm the theoretical prediction. Complete separation of matrix aluminum and reinforcement from metal matrix composites (MMCs) scrap has been achieved by addition of 2·05 wt% of equimolar mixture of NaCl-KCl salt flux with a metal and particle yield of 84 and 50%, respectively. By adding 5 wt% of NaF to equimolar mixture of NaCl-KCl, metal and particle yield improved to 91 and 73%, respectively. Reusability of both the matrix aluminum and the SiC separated from Al-SiC_p scraps has been analysed using XRD, SEM and DTA techniques. The matrix alloy separated from Al-SiC_p scraps can be used possibly as a low Si content Al-Si alloy. However, the interfacial reaction that occurred during the fabrication of the composites had degraded the SiC particles.     

Separation characteristics of different size and density fractions in batch coal flotation

Batch flotation experiments were carried out using two coal samples to study the behaviour of each size and the density fractions in coal flotation. Different size fractions obtained from sizing of concentrates and tailing were subjected to float and sink analysis using organic liquids. The distribution curve technique was adopted to evaluate the performance of flotation. The results show that selectivity of flotation decreases with decrease in particle size. The specific gravity of separation is influenced more by the level of the frother dosage than by the collector dosage. The specific gravity of separation increases with increase in flotation time. The maximum value attained at infinite flotation time increases with decrease in particle size but the rate at which it is reached decreases.     

Separation of flocculated ultrafine coal by enhanced gravity separator

The separation of ultrafine coal is inefficient due to the low settling velocity in centrifugal field. The feasibility of increasing particle size by flocculation to increase the separation efficiency is verified. The effect of flocculant on the size distribution of ultrafine coal was tested. The effect of flocculant dose on deash and desulfurization efficiency was studied to determine the appropriate dosage. Further, influence of the main operating parameters of the concentrator, including centrifugal force and water counter pressure on the separation performance, was studied. In addition, a comparative test was designed to verify the stability of the flocs. Results showed that the size of ultrafine coal particles could be effectively increased by the addition of flocculant, and the yield of ?0.045 µm fraction was decreased from 50% to 17% when the flocculant dosage was 10 g/t. The combustible material recovery of clean coal increased from 58% to 66%; meanwhile, the ash content reduced from 16.7% to 14.6%. In addition, combustible matter recovery and desulphurization efficiency decreased with the increase of centrifugal force, while they increased with the water counter pressure. Results of comparison tests of ultrafine coal with flocculant pretreatment and artificial coal with the same size composition showed that the latter had greater combustible recovery and desulfurization efficiency.     

基于收益分享合同的垃圾源头分类激励机制

通过建立两阶段的Stackelberg动态博弈模型,研究了固定不可燃垃圾处置费和变动垃圾处置费2种情况下,垃圾发电厂如何制订收益分享合同相关条款,促使居民实行垃圾源头分类,并提高可燃垃圾燃烧热值。结果表明:存在唯一的最优分享比例使得发电厂的收益最大,消费者的选择存在最优的可燃垃圾回收数量和最低垃圾燃烧热值水平。     

高压静电分选技术在回收废旧电路板中的研究进展

高压静电分选是利用物质的导电特性、介电常数差异,使静电力、重力、离心力等有效地作用在所有粒子上而实现分选,具有高效、低耗、环境友好等显著优点,是废旧电路板无害化处理和资源化利用的先进技术之一。分析了高压静电分选机的工作原理,结合对电场及空间电荷分布的研究和颗粒荷电及动力学过程研究的新进展,总结了应用于废旧电路板回收的高压电选机设备及工艺流程,并提出了该技术在废旧电路板回收再利用方面的一些新动向。     

双膜分离器的研究

本文以He-CH_4二元混合气体及He-CH_4-N_2三组元混合气体为被分离体系,对由中空纤维型醋酸纤维素膜(CA)与毛细管硅橡胶膜(SR)构成的单膜和双膜渗透器进行了实验研究,测试与分析了有关参数及操作条件对分离性能的影响;建立并验证了适用于双膜渗透器的数学模型;对非对称膜渗透行为的数学计算模型作了进一步的探讨。     

倾角与冷却水温度对新型闭式重力热管换热器传热性能影响

本文以丙酮为工作流体,设计了一套新型重力热管换热器,该装置由五根底部连通的垂直蒸发管共用一根水平同心套管冷凝管构成。采用理论和实验相结合的研究方法,分析了装置的传热性能,并对其结构参数进行优化。研究了当倾斜角度为15°~90°、操作温度为40~80℃、冷却水温度为10~30℃时装置的传热性能。结果表明:新型重力热管换热器具有良好的等温性能及操作稳定性;当充液率为15%、倾斜角度为60°、冷却水温度为30℃时,换热器达到最佳工作状态;最大传热量可达1 700 W左右,此时平均热阻为0.042℃/W。     

双膜分离器的研究

本文以He-CH_4二元混合气体及He-CH_4-N_2三组元混合气体为被分离体系,对由中空纤维型醋酸纤维素膜(CA)与毛细管硅橡胶膜(SR)构成的单膜和双膜渗透器进行了实验研究,测试与分析了有关参数及操作条件对分离性能的影响;建立并验证了适用于双膜渗透器的数学模型;对非对称膜渗透行为的数学计算馍型作了进一步的探讨。     

铁路站房大门空气幕阻隔特性分析

基于不可压缩流体N-S方程及k-ε两方程湍流模型,采用有限体积法,对铁路站房大门空气幕的夏季阻隔特性进行了研究,得到了车站室内外流场分布特性。     

Separation of zinc and nickel ions in a strong acid through liquid-liquid extraction

Many solid wastes contain both zinc and nickel at the same time. For recycling or recovery of metals, it is essential to separate materials. Among those materials, zinc and nickel are very difficult to be separated because there is not so much difference in the chemical and physical properties. This paper focuses on the separation of zinc and nickel ions in a diluted aqua regia solution. Liquid-liquid extraction by TBP, Cyanex 272 and Cyanex 301 was used and a distribution coefficient (D), a separation factor (S) and a relative purity (R) were induced to evaluate the degree of separation. All of the extractions were proportional to the concentration of the extractants, and zinc ions were extracted more easily than nickel ions. Among the extractants, Cyanex 301 showed the best characteristics regarding Zn/Ni separation. In particular, the extraction of zinc ions in the range of pH相似文献