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1.
工程渣土在水洗砂过程中产生的洗砂泥浆存在脱水效果差、不稳定的问题,这与泥浆的脱水性能密切相关。通过模拟现场洗砂工艺获得不同脱水性能的洗砂泥浆,开展了改进滤失试验及模拟压滤试验,研究了洗砂泥浆脱水性能受洗砂工艺的影响规律,获得了一种能够快速表征泥浆脱水性能的指标,用以指导优化渣土洗砂工艺。结果表明：洗砂泥浆脱水性能受洗砂粒径和加水量影响明显,滤失量及渗透系数与脱水性能有较好的相关关系;而30 min滤失量与最终滤失量、最终泥饼含水率呈现较好的相关性,能够较准确地反映泥浆脱水性能;经模拟压滤试验进一步验证,30 min滤失量可以作为洗砂泥浆脱水性能的快速表征指标。基于此提出了一套洗砂泥浆脱水性能的快速检测及工程渣土洗砂工艺优化方法,能够及时为洗砂工艺参数调整提供指导,以获得脱水性能较优的洗砂泥浆,最终使脱水效果得以改善和稳定。 相似文献
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《Russian Geology and Geophysics》2007,48(7):558-574
Destruction of geomaterials and geomedia material, as well as general brittle and ductile materials, have been treated theoretically and experimentally using the general approach of nonlinear dynamic systems. The process of destruction in loaded solids (inelastic deformation, damage accumulation, fracture) is presented as a space-time evolution of a nonlinear dynamic system, which allows interpreting all deformation and fracture within the limits of a single theory. The space-time hierarchies of nonlinear systems were found out to undergo collective effects and self-organization. The experimental and theoretical studies of the evolution of loaded solids revealed their universal fractality and showed brittle fracture and plastic deformation to be self-similar processes at different scales, for which scaling parameters have been estimated. The evolution of inelastic strain and destruction of solids is modeled numerically in terms of hierarchic systems. 相似文献
3.
S.W. Ihle B.B. Johnson T.A. Raven G.J. Sparrow 《International Journal of Mineral Processing》1983,11(4):239-253
Previous laboratory work indicated that the dewatering of suspensions of kaolin and fine quartz on a sand bed could be described by a simple two-term equation with one term for the drainage component and one for the evaporation component.Field tests have been carried out at three sand-washing operations in Victoria to determine if the equation is applicable in practice.The thickened suspensions were dewatered to a solid when they were ponded in shallow depths onto a sand bed. The changes in solids content during the dewatering confirmed that the dewatering equation could be used in practice.The dewatering equation is potentially very useful since it can be used to calculate optimum ponding depths, and therefore the area required to dewater a given production of tailing. 相似文献
4.
基于某真空井点降水综合试验,建立了三维地下水流数值模拟模型,将模型模拟预测数据与试验观测数据进行对比,研究真空负压和井点间距对真空井点降水效果的影响,得出了真空井点周围渗流场的变化性状,提出了真空井点周围真空及重力场耦合区、耦合场与重力场过渡区和重力场区3个区的概念。得出了不同负压在不同井点深度条件下对地下水渗流场的影响变化。对比结果表明,建立的真空井点降水模拟分析方法,能够较好的模拟真空井点周围观测井水位与出水量的相关关系;分析方法可用于真空井点降水试验分析,且为真空井点降水设计提供了依据。 相似文献
5.
The results of experiments on a 40 cm × 40 cm grate-discharge ball mill have been analysed for variation of mill hold-up weight of solids with solids feed rate, weight percent solids, mean feed particle size, material specific gravity and work-index. It is shown that mill hold-up weight is independent of the material specific gravity and mean feed particle size, and it varies linearly with solids feed rate and weight percent solids, at least over the range of practical interest. The variations in the transport behaviour of different materials have been attributed to the differences in the size distribution of the mill hold-up solids. It is shown that work-index can be used as the material characteristic for the development of an empirical correlation. Variation of mean residence time of solids with solids feed rate and weight-percent solids is also discussed. 相似文献
6.
Carl P. Beitelshees C.Judson King Hugo H. Sephton 《International Journal of Mineral Processing》1981,8(2):97-110
An experimental study was made to identify surfactants which are effective for removal of copper from dilute aqueous solution (100–500 ppm) by precipitate flotation as the sulfide, and which at the same time can be recovered from the CuS product for recycle. Batch flotation experiments confirmed that a cationic surfactant was necessary for flotation of CuS from such dilute suspensions; however, no satisfactory way could be found for recovering cationic surfactants from the CuS. This led to consideration of amphoteric surfactants, which are cationic at low pH and anionic at high pH. It was found that a change to negative, rather than simply neutral, charge was required for efficient surfactant recovery. It was further found, through the assistance of experiments in which the CuS suspension was agitated with solvents, that certain functional groups which interact chemically with the CuS surface should also be absent from the surfactant molecule. Following this logic, Amphoterge K-2 (Lonza Chemical Co.) was identified as a suitable surfactant, provided CuS was precipitated with S2? in excess. Tests established that 95% of adsorbed Amphoterge K-2 could be recovered by raising the pH to 11 and boiling the suspension for one hour, followed by decanting. Surfactant thus recovered was effective in a second flotation test. Foamate solids settled rapidly; such behavior would help reduce the consumption of chemicals for the pH change.Column flotation studies were made using Amphoterge K-2 for removal of Cu2+ present at 100 ppm and pH = 2. High removals of CuS could be obtained at concentrations of surfactant above about 25 ppm, for which conditions a substantial fraction of the surfactant remains in solution rather than being adsorbed onto the CuS. The recovery of CuS would be improved by introducing the surfactant in a separate feed, below the feed of CuS suspension. Adding some surfactant in the CuS feed, as well as in a lower feed, gave an even better recovery of CuS (99.8%) at sufficiently high surfactant loadings. 相似文献
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The management of uranium tailings, generated as a by-product of ore processing, is particularly important to minimize the environmental footprint of the industry. A clear understanding of tailings slurry behavior is required at the time of deposition to help evaluate the storage capacity and life span of the containment facilities. The main purpose of this study was to investigate the segregation and self-weight settling properties of uranium tailings. Detailed laboratory investigations were conducted on tailings from 4, 5, and 6 % nominal mill feeds (high-grade McArthur River ores blended with special wastes on site) from the Cameco Key Lake operation. The results indicate that the three uranium tailings can be characterized as a sandy silt material with a negligible amount of clay. Their depositional behavior is governed by the initial solids content of the slurry. The investigated tailings showed insignificant segregation between 25 and 40 % initial solids content. The initial hydraulic conductivity during settling was about 10?4 m/s at a void ratio of 4 and was increased by half an order of magnitude for the 4 % mill feed, and by almost two orders of magnitude for the 5 and 6 % mill feeds at a void ratio of 8. Over the same range of initial void ratio, the settling potential increased threefold: from 8 to 24 % for the 4 % mill feed and from 12 to 36 % for the 5 and 6 % mill feeds. The better rate and amount of dewatering of future high mill feed tailings as compared to the current low mill feed tailings means that the onsite containment facility can store more tailings thereby supporting a longer life span of the mill. 相似文献
9.
An extensive test programme has been conducted on 10.2-, 25.4- and 38.1-cm “Krebs” hydrocyclones in order to study the effects of some design and operating variables on their volume capacities.For a given pressure the capacity of a cyclone was found to rise sharply with the addition of solid particles to water until the solids content was about 15% by weight. Further increase in solids caused a decrease in throughput. The effect of vortex finder diameter on the throughput was found to be non-linear. A general equation which relates inlet and outlet diameters, operating pressure and feed solids content to the volume capacity is presented. This equation is independent of hydrocyclone diameter. 相似文献
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A technique is presented by which the cut size of a classifier can be estimated without size analyses of the coarse and fine products. Using the corrected solids recovery and the classifier feed size distribution, an indicated d50 size can be determined which is usually within ± 10% of the actual cut size.By computer simulation of the classification process, actual/indicated cut size ratios were determined for a variety of operating conditions. Through the application of these ratios, it has been demonstrated that the d50 of a classifier can be estimated with an accuracy comparable to that obtained through the use of classification curves. The main limitations of this technique are that accurate measurement of the solids content in the slurry streams is required and that no information is obtained concerning the sharpness of separation. 相似文献
12.
R.J. Wakeman 《International Journal of Mineral Processing》1979,5(4):379-393
The process of dewatering incompressible filter cakes by vacuum pumps which cannot maintain vacuum (low-capacity suction systems) has been examined experimentally, and a theoretical model is proposed for interpretation of the results. Application of the model requires relative permeability and capillary pressure information which are obtained by applying empirical data combined with a mathematical model for permeability. The concepts of modified threshold pressure and pore size distribution index are utilised in the model, and their effects on dewatering dynamics are assessed. 相似文献
13.
The flotation cell is quantified as a mixing device for one, two, and three phase systems using combinations of water, air, and solids. To do this, power consumption was measured as a function of impeller speed, rate of aeration, and solids concentration. Initial suspension of solids and dispersion of suspended solids throughout the water or water/air system were also studied as influenced by impeller speed, particle size and solids concentration. The power number and air flow number were used to correlate the data.Flotation studies with a zinc ore using three sizes of cells of the same design, showed that aeration had to be controlled in the smaller cells to duplicate the results in the cell of commercial size. For optimum results the flow number range in the smallest cell was less than the critical value for suspension of coarse particles. Operating flow numbers for the three cell sizes under optimum conditions were close; commercial cells of the same size operating elsewhere appear to have two to three times higher flow numbers.The general relationships among air flow, impeller speed, particle suspension and flotation are discussed with particular reference to scale-up problems and coarse particle flotation. Both impeller speed and aeration should be considered as variables requiring systematic study and independent adjustment. 相似文献
14.
在数值计算成果的基础上,对阻力圆盘浮力射流的流场进行了分析和总结,基于轴线流速的变化规律将盘后流场分为3个区域:回流区、过渡区和自相似区.得到了回流区的长度随弗劳德数F0、孔口直径D/d以及盘离孔口的距离H/d的变化规律,并得到了工况为H/D=1,D/d=2,6和H/D=3,D/d=2在不同弗劳德数F0条件下的横截面上的流速分布和达到自相似区的最小长度;结果表明弗劳德数F0的大小是决定绕流流态的主要因素;同时分析了由正常绕流发展到非正常绕流的压力场变化,发现由于弗劳德数F0的增大而导致流场中出现的第三个负压中心的大小和位置与绕流是否能正常发生存在密切的关系. 相似文献
15.
The stratigraphic record and processes of turbidity current transformation across deep‐marine lobes 
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下载免费PDF全文 Ian A. Kane Anna S. M. Pontén Brita Vangdal Joris T. Eggenhuisen David M. Hodgson Yvonne T. Spychala 《Sedimentology》2017,64(5):1236-1273
Sedimentary facies in the distal parts of deep‐marine lobes can diverge significantly from those predicted by classical turbidite models, and sedimentological processes in these environments are poorly understood. This gap may be bridged using outcrop studies and theoretical models. In the Skoorsteenberg Formation (South Africa), a downstream transition from thickly bedded turbidite sandstones to argillaceous, internally layered hybrid beds, is observed. The hybrid beds have a characteristic stratigraphic and spatial distribution, being associated with bed successions which generally coarsen and thicken‐upward reflecting deposition on the fringes of lobes in a dominantly progradational system. Using a detailed characterization of bed types, including grain size, grain‐fabric and mineralogical analyses, a process‐model for flow evolution is developed. This is explored using a numerical suspension capacity model for radially spreading and decelerating turbidity currents. The new model shows how decelerating sediment suspensions can reach a critical suspension capacity threshold beyond which grains are not supported by fluid turbulence. Sand and silt particles, settling together with flocculated clay, may form low yield strength cohesive flows; development of these higher concentration lower boundary layer flows inhibits transfer of turbulent kinetic energy into the upper parts of the flow ultimately resulting in catastrophic loss of turbulence and collapse of the upper part of the flow. Advection distances of the now transitional to laminar flow are relatively long (several kilometres) suggesting relatively slow dewatering (several hours) of the low yield strength flows. The catastrophic loss of turbulence accounts for the presence of such beds in other fine‐grained systems without invoking external controls or large‐scale flow partitioning and also explains the abrupt pinch‐out of all divisions of these sandstones. Estimation of the point of flow transformation is a useful tool in the prediction of heterogeneity distribution in subsurface systems. 相似文献
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在数值计算成果的基础上,对阻力圆盘浮力射流的流场进行了分析和总结,基于轴线流速的变化规律将盘后流场分为3个区域:回流区、过渡区和自相似区。得到了回流区的长度随弗劳德数F0、孔口直径D/d以及盘离孔口的距离H/d的变化规律,并得到了工况为H/D=1,D/d=2,6和H/D=3,D/d=2在不同弗劳德数F0条件下的横截面上的流速分布和达到自相似区的最小长度;结果表明弗劳德数F0的大小是决定绕流流态的主要因素;同时分析了由正常绕流发展到非正常绕流的压力场变化,发现由于弗劳德数F0的增大而导致流场中出现的第三个负压中心的大小和位置与绕流是否能正常发生存在密切的关系。 相似文献
17.
Axisymmetric consolidation of multi-layered soils induced by groundwater extraction from a dewatering well is studied with consideration of the anisotropic permeability and the well length. Laplace-Hankel transforms are utilized to solve the governing equations. The analytical layer-element method is used to build relationships between displacements, stresses, excess pore pressure and seepage velocity in the transformed domain. The real solutions can be obtained by the inversion of Laplace-Hankel transforms. A series of parametric studies, especially the length of a dewatering well and the combined effect of pumping and recharging, are conducted to analyze the consolidation behaviors of layered soils. 相似文献
18.
R.J. Wakeman 《International Journal of Mineral Processing》1979,5(4):395-405
The dynamic dewatering model is extended to systems where the total pressure loss across the cake is constant (that is dewatering is effected by a pump which is able to maintain the vacuum). Using the model, prediction of dewatering characteristics is facilitated when a representative value is assigned to the pore size distribution index. The effects of altering process variables on the decreasing cake saturation and increasing air flow rate are quantified and discussed. The methods presented may be a useful tool for assessing changes in process variables or in the initial sizing of filters. 相似文献
19.
现有基坑相关研究主要关注土方开挖过程引起的变形,认为围护结构变形起点是土方第1次开挖。然而,一些工程实测表明,基坑开挖前降水阶段即可引起围护结构及周边地层发生厘米级的变形。显然,未考虑开挖前变形的基坑监测数据将低估基坑施工的环境效应。为了研究基坑开挖前降水引发基坑变形的机制,开展了室内模型试验,对基坑开挖前降水过程进行了缩尺精细化模拟。通过微型降水井的设置与调控,模型试验真实再现了实际基坑降水过程中井流效应对围护结构受力变形的影响。试验过程中发现,随着降水的进行,坑外降水漏斗不断扩展,围护结构悬臂式侧移及坑外拱肩式地面沉降也随之产生。另外,降水导致墙前水压力明显减小,并诱发墙前侧向总压力重分布（以减小为主）,围护结构为此发生指向坑内的悬臂式运动以寻求新的受力平衡,并通过墙后土体损失诱发坑外地层变形。 相似文献
20.
Yosry A. Attia 《International Journal of Mineral Processing》1983,10(3):173-181
One of the main usages of ball clays is in the pottery industry. However, in order to transport the clay suspensions from the mine site, some distance away from the consumer, dewatering of the clay suspension must be performed. The main restriction is that any dewatering treatment must not interfere in obtaining deflocculated, free flowing suspensions required by the pottery manufacturer.Investigations in the flocculation/deflocculation of these clay suspensions, resulted in finding a technique capable of achieving both requirements. The technique employs flocculation by an anionic flocculant in the presence of 10 mM of magnesium sulfate, thus achieving the dewatering step. When the magnesium sulfate was removed from the flocculated suspensions by simply washing the filter cake, good deflocculation of the clay suspension was achieved at alkaline pH. The role of MgSO4 in the flocculant adsorption/flocculation, and subsequently in the flocculant desorption/deflocculation, was discussed. 相似文献