Adhesion forces for water/oil droplet and bubble on coking coal surfaces with different roughness

Surface roughness plays a significant role in floatability of coal. In the present paper, coking coal surface was polished by three different sandpapers and the surface properties were characterized by contact angle and roughness measurements. The effect of surface roughness on floatability was investigated by adhesion force measurement system for measuring interaction forces between droplets/bubbles and coking coal surfaces with different roughness. The results showed that the contact angle decreased with increasing roughness yet the adhesion force between the water droplet and coal surface increased owing to the increased contact line and the appearance of line pinning. Maximum adhesion forces between water and surfaces were 111.70, 125.48, and 136.42 μN when the roughness was 0.23, 0.98, and 2.79 μm, respectively. In contrast, under a liquid environment, the adhesion forces between air bubble/oil droplet and coal surfaces were decreased with increasing roughness because of the restriction by water. Maximum adhesion forces of increasing roughness were 97.14, 42.76, and 17.86 μN measured at interfaces between air bubble and coal surfaces and 169.48, 145.84, and 121.02 μN between oil droplet and surfaces, respectively. Decreasing roughness could be beneficial to the spreading of oil droplets and the adhesion of bubbles which is conducive to flotation separation.     

Prospects of utilization of waste dumped low-grade limestone for iron making: A case study

Low grade dumped limestone sample having high silica of 8.1%, 36.8% CaO, and 3% Al_2O_3 has been studied with the aim to reduce the silica level to below 3% for its utilization in iron making. Beneficiation study of the sample was initiated with desliming of the feed sample of -100 μm to remove the siliceous ultrafine particles and to improve the feed quality. Flotation study was carried out by column flotation technique varying the collector dosage, superficial air flow velocity and froth depth to assess their effect on silica reduction and CaO recovery. It was observed that increased collector dosage and superficial air velocity increases the recovery of CaO, and increase in the froth depth reduces the mass flow and silica content in the concentrate. The best result was found at 1.25 cm/sec superficial air velocity, 25 cm froth depth, 1.25 kgpt collector dosage and concentrate assayed 47.3% CaO, 2.8% silica with 72% CaO recovery.     

煤泥浮选泡沫层中气泡特征的提取

利用图象处理的方法来突出浮包沫表面的气泡与图象背景的对比,并提取气泡的边界,为建立泡沫精神与图象中泡沫表面气泡个体统计特征间的关系模型提供依据。在对泡沫表面各种气泡形态的分析中,提出了气泡提取在煤泥浮选泡沫图象分析的可行性。通过对实验室浮选柱所采集的51组泡沫图象进行处理分析,认为图象灰度直方图的均衡化和中值滤波算法对提高图象的动态对比范围,突出气泡的亮度有明显的效果。最后还分析了适合于气泡提取的阈值分割算式法以及气泡的边缘检测算法,从而描述泡沫层图象中气泡的大小和形状等个体特征,达到识别煤泥浮选泡沫图象的目的。     

Study on Non-Collision Mineralizing Mechanism of Froth Cyclone

On the basis of the mineralizing mechanism of froth cyclone, this paper expounds that the froth cyclone flotation process is accomplished in a limited centrifugal field. The main feature of air bubble mineralizing in the froth cyclone is a synthetic mineralizing process, of which the non-collision mineralization of minute air bubble separated out dominates, supplemented with the collision mineralization. Moreover, this paper points out that the hydrophobic separated out and centrifugal force strengthen the selectivity of fine coal particle, accelerate the flotation speed and improve the slime recovery.     

新型多功能材料泡沫铝的结构性能及前景展望

泡沫铝按结构分为泡状铝和多孔铝两类，它是一种新型的多功能泡沫材料，同时具有金属和气泡的多种优良性能．被广泛地应用在建筑、交通运输等行业中。今后应加大对泡沫铝力学性能的研究，深入探讨其结构形态与阻尼特性之间的关系，研究具有大内耗和功能结构一体化的新型阻尼泡沫铝材料。     

Droplet creator based on electrowetting-on-dielectric for lab on a chip

With the development of micromachining technology, the micro total analysis system (μTAS) or lab on a chip (LOC) is becoming an interdisciplinary research area, involving the micromechanical system (MEMS), biotechnology, analysis chemistry and others, and has been widely applied to many fields, such as chemical analysis, biochemical sensing, drug delivery, molecular separation, amplification, sequencing and synthesis of nucleic acids, environmental monitoring, and others. The manipulation …     

Nanobubble generation and its applications in froth flotation(part Ⅳ): mechanical cells and specially designed column flotation of coal

Coal is the world's most abundant fossil fuel.Coal froth flotation is a widely used cleaning process to separate coal from mineral impurities.Flotation of coarse coal particles,ultrafine coal particles and oxidized coal particles is well known to be difficult and complex.In this paper,the nanobubbles' effects on the flotation of the varying particle size,particle density and floatability coal samples were evaluated using a bank of pilot scale flotation cells,a laboratory scale and a pilot scale specially designed flotation column.The parameters evaluated during this study include the flow rate ratio between the nanobubble generator and the conventional size bubble generator,the superficial air velocity,collector dosage,frother concentration,flotation feed rate,feed solids concentration,feed particle size,and the superficial wash water flow rate,etc.The results show that the use of nanobubbles in a bank of mechanical cells flotation and column flotation increased the flotation recovery by 8%～27% at a given product grade.Nanobubbles increased the flotation rate constants of 600～355,355～180,180～75,and 75～0 microns size coal particles by 98.0%,98.4%,50.0% and 41.6%,respectively.The separation selectivity index was increased by up to 34%,depending on the flotation feed characteristics and the flotation conditions.     

Rheological investigations of the improved fine scheelite flotation spiked with agitation medium

The fine scheelite flotation using garnet and glass beads as agitation medium was investigated through slurry rheology and froth property analysis. The apparent viscosity of fine scheelite, calcite and quartz (?20 μm) slurry were measured and the corresponding scheelite flotation behaviours, froth water recovery and froth height were studied. It was found that calcite slurry could aggregate into network structures and exhibit much higher apparent viscosity at the vicinity of pH 8.5–9.0 than scheelite and quartz (scheelite, calcite, and quartz slurry at 20.34, 38.66, and 14.58 mPa·s, respectively). Agitation medium containing garnet and glass beads could reduce the slurry apparent viscosity by effectively dispersing the calcite network structures in flotation slurry, and improve the fine scheelite flotation selectivity. As the apparent viscosity was reduced, the froth water recovery decreased from 24.33% to 6.37% and initial froth height of the flotation froth decreased from 69.6 to 8.7 mm, and finally results in increase in separation efficiency from 23.10% to 31.96%. The results could be potentially used in flotation of fine minerals by applying agitation medium to improve the process selectivity.     

气泡增强型水力旋流器的数值模拟研究

采用欧拉模型与离散相模型相结合的方法对气泡增强型水力旋流器中油-气-水三相流场进行数值模 拟,分析了速度场和油滴粒子的运动轨迹,并且对比了油滴粒径、工作流量、含油浓度3种不同因素对注气后水力旋 流器与常规水力旋流器分离效率的影响。数值模拟结果表明,注气后水力旋流器内流场的切向速度和轴向速度较 常规水力旋流器更高,油滴分离所需的时间更短,对30μm 以上油滴的分离效率比常规水力旋流器高出约20%。从 数值模拟的角度验证了入口注气可以提升水力旋流器的分离性能。     

Nano-microbubble flotation of fine and ultrafine chalcopyrite particles

As is well known to mineral processing scientists and engineers, fine and ultrafine particles are difficult to float mainly due to the low bubble-particle collision efficiencies. Though many efforts have been made to improve flotation performance of fine and ultrafine particles, there is still much more to be done. In this paper, the effects of nano-microbubbles (nanobubbles and microbubbles) on the flotation of fine (−38 + 14.36 μm) and ultrafine (−14.36 + 5 μm) chalcopyrite particles were investigated in a laboratory scale Denver flotation cell. Nano-microbubbles were generated using a specially-designed nano-microbubble generator based on the cavitation phenomenon in Venturi tubes. In order to better understand the mechanisms of nano-microbubble enhanced froth flotation of fine and ultrafine chalcopyrite particles, the nano-microbubble size distribution, stability and the effect of frother concentration on nanobubble size were also studied by a laser diffraction method. Comparative flotation tests were performed in the presence and absence of nano-microbubbles to evaluate their impact on the fine and ultrafine chalcopyrite particle flotation recovery. According to the results, the mean size of nano-microbubbles increased over time, and decreased with increase of frother concentration. The laboratory-scale flotation test results indicated that flotation recovery of chalcopyrite fine and ultrafine particles increased by approximately 16–21% in the presence of nano-microbubbles, depending on operating conditions of the process. The presence of nano-microbubbles increased the recovery of ultrafine particles (−14.36 + 5 μm) more than that of fine particles (−38 + 14.36 μm). Another major advantage is that the use of nano-microbubbles reduced the collector and frother consumptions by up to 75% and 50%, respectively.     

十字交叉型微通道内液滴形成的数值模拟研究

基于Fluent软件的流体体积分数（Fluid Volume Fraction,VOF）模型,针对十字交叉型微通道内液滴的形成过程开展了三维数值模拟研究,分别研究了连续相黏度、分散相黏度、两相界面张力系数、壁面接触角对液滴形成的影响,为实际应用提供参考。研究表明随着连续相流速的增加,液滴生成直径减少,生成频率增大;增加连续相黏度时,液滴生成直径变小,生成频率的变化则相反;当分散相黏度超过连续相黏度时,出现射流现象而不能生成液滴;液滴生成直径随两相界面张力系数的增加而增大,生成频率降低;增大壁面接触角有利于液滴的产生,且两相流速为0.01 m/s和0.02 m/s时,接触角应分别取到150°和120°才能正常生成液滴。     

Rapid monotectic solidification under free fall condition

Thesolidificationprocessofmonotecticalloyhasbeenofgreatinterestformanyyears.Onereasonisthatmonotectictransformation,inwhichoneparentliquidphaseL1decomposessimultaneouslyintoonesolidphaseSandanotherliquidphaseL2,playsanimportantroleintheresearchofphaseseparationandcrystalgrowthkinetics[1—5].Anotherreasonisthatmanyapplicationsofmonotecticalloysinindustry,suchasCu-Pb,Al-Pb,Al-Bi,Al-SnandAl-Inareself-lubricatingbearingalloysorhigh-temperaturesuperconductorsiftheyhavehomogeneouslydispersedmic…     

DFS⁃1有机硅油型消泡棒的研发

泡排是目前长庆气田的主体排水采气工艺,部分泡沫到达地面管线后仍然未能消泡,需要辅助消泡剂以降低泡沫对污水处理系统造成的危害。由于液体消泡剂作用时间短、消泡效果差、自动化程度低,近年来长庆气田加大了固体消泡装置应用,但与之配套的固体消泡棒成本高、适用性差,导致消泡效果不明显,严重制约了工艺的推广应用。根据长庆气田水质特征,以二甲基硅油与气相SiO₂颗粒为原料制得硅膏,并辅以固化剂蔗糖及乳化剂S?185,通过熔融反应,冷却后制成固体消泡剂DFS?1。采用Q/SY 17001-2016《泡沫排水采气用消泡剂技术规范》对其进行室内测试,消泡时间小于等于12.1 s,抑泡时间大于10 min,采用模拟地层水对比评价,各项性能参数均符合要求,可满足长庆气田现场应用需求。     

化学药剂在引气浮选中的作用

在引气浮选中，影响除油效率的因素主要是油粒直径、气泡直径和油粒表面的化学性质．加入表面活性剂、聚合物及无机物凝聚剂，可以降低气泡直径、增大油粒直径、降低油粒表面的电位，从而提高除油效率．     

Topology Chemical Process Research on the Condensing and Growing Phase Multi Micro Oil Droplets Based on Hydrodynamics

The hydrodynamic research about the droplet condensing of the multi phase liquid state on the surface of the coal glass and water discusses the deepening process of convex shape curve and the formation of S shape,and puts emphasis on describing the diagram formation method of the later.In the induction period the active diagram of the micro droplet is decided by pH value forming as convex shape diagram or S shape diagram.When pH value is above 4.0,the damage of convex shape diagram cannot be recovered,in that case produce S shape activity diagram.When pH value is equal to or above 12.0,the hard surface with alkali liquid state loses adhesion,so that the micro droplet condensing of the multi phase liquid state stops completely.The research result shows that the water cleaning conditions of getting rid of the oil micro droplets can be decided by the pH value.     

Clustering-driven watershed adaptive segmentation of bubble image

In order to extract froth morphological feature, a bubble image adaptive segmentation method was proposed. Considering the image’s low contrast and weak froth edges, froth image was coarsely segmented by using fuzzy c means (FCM) algorithm. Through the attributes of size and shape pattern spectrum, the optimal morphological structuring element was determined. According to the optimal parameters, some image noises were removed with an improved area opening and closing by reconstruction operation, which consist of image regional markers, and the bubbles were finely separated from each other by watershed transform. The experimental results show that the structural element can be determined adaptively by shape and size pattern spectrum, and the froth image is segmented accurately. Compared with other froth image segmentation method, the proposed method achieves much high accuracy, based on which, the bubble size and shape features are extracted effectively.     

高含水旋转湍流场中油滴分散特性的数值模拟

旋转湍流场中液滴的分散特性是流体机械设计优化过程中的难题。采用新型同心旋转圆筒装置获得了均匀分布的旋转湍流场，在Hinze模型的基础上考虑了分散相黏度对油滴分散特性的影响，对旋转湍流场和油滴分散特性的关系进行了初步探讨，获得了雷诺数为5.5×104~2.4×105，相对离心力为21.9~643.3时，流场特性与油滴分散特性的经验关系式，完善了旋转湍流场内油水分散特性的研究，为旋转湍流场内液⁃液分散特性提供新的研究思路。     

水中油滴在不同润湿性表面上的铺展行为研究

通过高速显微实验与理论推导相结合的方式,从微观角度研究了水中油滴在光滑铜板基底的铺展行为;通过物理和化学修饰,实现了黄铜表面水下超亲油到超疏油的可控调节,观察了油滴浮升到修饰黄铜表面后铺展长度随时间变化的差异。与空气中液滴撞壁铺展不同,水中油滴的铺展需要同时考虑液滴铺展过程中周围流体对液滴铺展的黏性作用,其在基底表面的铺展过程十分复杂。采用能量守恒方法,得到了油滴在水中基底表面上的特征值之间的定量关系,建立了基于能量守恒方法的油滴在不同润湿性固体基底表面的铺展模型,用以指导新型油水分离设备的制备。     

荷电液滴联合声波捕集颗粒物的过程和特性

搭建显微可视化平台,观测以半山电厂灰为代表的颗粒物在电场及声场作用下相对于悬垂荷电单液滴的运动和捕集特性,利用激光粒度仪对颗粒物的凝并效果进行验证. 实验结果显示：对液滴进行荷电,可以将以惯性捕集为主要作用的灰颗粒绕流运动变为以静电力（介电泳力、库仑力）为主导的吸引作用,颗粒物在液滴表面的沉积状态由树枝状变为紧密堆积状态,而增加声场后,在颗粒初始轨迹之上叠加了往复的振动. 荷电液滴引入的静电力和液桥力强化了团聚体内部的黏附作用. 进一步的粒径分布表征实验发现,荷电液滴和声波的加入均可以有效促进颗粒的团聚长大.     

表征煤泥浮选泡沫图象特征的最佳色彩方案

针对煤泥浮选泡沫图象的表征方法问题 ,进行了实验室浮选柱试验 ,采集了 5 1组煤泥浮选泡沫图象 ,研究了煤泥泡沫图象的三种色彩表示系统 ( RGB,YCb Cr,灰度 ) ,分析了泡沫图象的亮度、色调及 RGB三分量的分布规律 .结果表明 ,精煤泡沫图象是灰色的 ,且色彩信息量非常少 ,在进行煤泥泡沫图象处理和识别时 ,可以采用图象的 RGB三个单独分量进行计算 ,也可以用平均灰度和公式法亮度进行计算 ,这样可以减少三分之二的数据传输量和计算量 ,加快图象处理速度 .