The air flow number in flotation machine scale-up

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.     

Studies in the selective flocculation of hematite from gangue using high molecular weight polymers. Part 2: Physical factors

Having previously established a system of hematite and silica which can be separated effectively using long-chain polyacrylamide flocculants (Part 1) a stirred tank system was chosen to enable physical variables of flocculant concentration, impeller speed, time of flocculation, slurry concentration, ratio of hematite to quartz in the feed and particle size distribution to be studied.It was concluded that the time of flocculation allowed should be kept short and that there is an optimum of impeller speed though not a sharp one. Slurry concentration must be kept to 1% w/w to prevent serious performance deterioration. A clear optimum flocculant concentration was not found under present circumstances though very low concentrations (< 1 ppm) gave poor results while high concentrations gave no improvement on the results at about 2 ppm.Comparison between an impeller and a propeller of the same diameter and location in the tank pointed to the possibility of critical agitation configurations and the need for caution in scaling up results.The grade of material settling from a selective aggregation process is heavily dependent on the particle size distributions of the mineral species. Larger flocculated minerals produce richer flocs.     

明渠水流自掺气发展区水气结构分析

为研究明渠水流自掺气发展区内水气结构特征,采用针式掺气流速仪对自掺气发展区内气泡尺寸与数量进行了试验研究,比较了气泡尺寸与数量随自掺气发展的变化规律,结果显示,同一水流断面上,随着掺气浓度的减小,气泡弦长尺寸分布范围与弦长平均值逐渐减小,掺气区内小尺寸气泡在数量上占有较大的比例,而大尺寸气泡则在含气量上占有较大的比例,分析认为从水面附近高掺气浓度区至自掺气区域底缘低掺气浓度区,明渠自掺气水流水气结构发展过程为“水面变形为主—水面变形与个体空气泡共存—个体空气泡”,为进一步研究明渠自掺气形成机理提供了一定的参考。     

气动试验法测定渗透系数的可行性分析

基于竖管法测定沉积物渗透系数的原理,设计一种以空气作为流体测定沉积物渗透率的试验方法—气动试验法,将沉积物的空气渗透率(k_a)转换成用水当做流体时测定的渗透系数(K_w)。利用气动试验法和竖管法分别测定3组沙漠砂样和7组河漫滩砂样的渗透系数。试验结果表明,气动试验法测定沉积物的渗透系数可行,与竖管法相比更加方便、快捷,可以解决竖管法耗水、耗时的局限性,可应用于干旱-半干旱地区野外沉积物渗透系数的测定。     

Lateglacial and early Holocene tephrostratigraphy and sedimentology of the Store Slotseng basin,SW Denmark: a multi‐proxy study

The history of the Lateglacial and Preboreal sedimentary succession from the Store Slotseng kettle hole basin, SW Denmark is presented. A tephrostratigraphical and multi‐proxy investigation of the sediments, including stable isotope geochemistry, reveals small‐ and large‐scale changes in the surrounding environment through time. Three distinct tephra horizons are observed. Two of them are identified as the Preboreal Hässeldalen Tephra and the Younger Dryas Vedde Ash. The third was deposited around the Pre‐Bølling/Bølling transition. The Preboreal sediments record two significant decreases in authigenic carbonate content. Using tephrostratigraphy the lower one is identified as occurring during the Preboreal Oscillation, while the upper one is contemporaneous with the Rammelbeek Phase, which by some is recognised above the Preboreal Oscillation. This period has not previously been observed in this region. The discovery of the Hässeldalen Tephra in the Store Slotseng basin expands the known southwestern limit of the ash cloud, and increases the area for potential future observations. The Hässeldalen Tephra (c. 11.3 cal. ka BP) was deposited just prior to the Preboreal Oscillation and as such has a large potential for precise correlation and characterization of this short climatic perturbation.     

Nanobubbles,hydrophobic effect,heterocoagulation and hydrodynamics in flotation

It has been shown in recent years that the long-range attractive interaction forces between hydrophobic surfaces in aqueous systems are caused by the capillary forces of gas bridges which form at the coalescence of nanobubbles adhering on the surfaces. The coalescence of nanobubbles on selectively hydrophobized particles with coarser bubbles initiates the jump into the three-phase contact at the attachment events in flotation. Therefore, one should no longer speak of hydrophobic forces in these events but of hydrophobic effects because they are caused by capillary forces. However, in the selective hydrophobization of particles by long-chain collectors (surfactants), there is another situation. Here, the association of nonpolar groups in the adsorption layers plays an important role in the energy balance of adsorption. This association is caused by “truly” hydrophobic interactions, which support the spotty distribution of the adsorbed collector ions on the particle surfaces and promote the formation of nanobubbles. This paper is intended to show to what extent the results obtained by basic research on the nanobubble formation as well as the force–distance dependence of collision events can be applied to flotation processes. This particularly requires the consideration of the highly turbulent flow conditions in the impeller stream of the flotation machines, in which the attachments almost exclusively occur. Various phenomena which occur in these machines and affect the reagent regime and the hydrodynamics point to the fact that nanobubbles can form, exist and even grow into microbubbles in that region. Therefore, so-called combined attachment events should predominate as already imagined several decades ago. The highly turbulent pressure fluctuations in the impeller stream in addition to the dispersion of the bubbles effect also their oscillations in size and shape, so that adsorption equilibria in the interfaces liquid/gas cannot be supposed. However, the pressure fluctuations present the possibility to overcome potential barriers in the wetting films at attachment events.     

自进式直旋混合射流钻头结构优化与钻孔能力分析

自进式射流钻头作为水力喷射径向钻井技术开采煤系气的核心部件,对钻井效率有决定性影响。为获取直旋混合射流钻头结构的最优参数,采用Fluent数值模拟与室内钻进试验相结合的办法,分析不同钻头结构参数下三维流场的速度特性,给出优化准则,并通过钻进试验加以验证,得到钻头的最优参数:中心孔孔径1.2 mm,叶轮槽槽宽0.7 mm,叶轮长度4.5 mm,叶轮径向长度3.5 mm,倾角45°,混合腔腔长6 mm。并通过理论分析解释了不同参数对钻头钻进速度产生变化的原因,主要是通过影响直旋混合射流中直射流与旋转射流的通量,进而引起射流三维的变化。采用灰色关联分析法得出各参数结构对钻进位移的敏感性系数由高到低依次为:中心孔孔径、叶轮槽宽、叶轮径向长度、混合腔腔长、叶轮倾角、叶轮长度。室内钻进试验结果表明:优化后的射流钻头具有更高的钻进效率,在关联分析中对钻进效率影响最大的是直射流与旋转射流通量,且直旋通量比在0.54时,射流能量分配较合理。研究成果对径向钻井煤层气、天然气开采中钻头的设计与结构优化具有指导意义。      

The effect of bubble size on the rate of flotation of fine particles

Flotation experiments have been carried out in a cell in which bubbles of known size could be generated independently of the turbulence levels, which could be controlled by varying the impeller speed. The mean bubble size ranged from 75 μm to 655 μm.Results are reported for the flotation rates of fine particles, less than 50 μm diameter. The materials floated were polystyrene latex particles, quartz and zircon. These were chosen to give a wide range of specific gravity.It was found that the flotation rate was very strongly affected by the bubble size, there being an increase of up to one hundred-fold when the bubble size was reduced from 655 μm to 75 μm. Effects of particle density and impeller speed are also reported.     

The Effects of Operational Parameters on a Mono-wire Cutting System: Efficiency in Marble Processing

Mono-wire block cutting machines that cut with a diamond wire can be used for squaring natural stone blocks and the slab-cutting process. The efficient use of these machines reduces operating costs by ensuring less diamond wire wear and longer wire life at high speeds. The high investment costs of these machines will lead to their efficient use and reduce production costs by increasing plant efficiency. Therefore, there is a need to investigate the cutting performance parameters of mono-wire cutting machines in terms of rock properties and operating parameters. This study aims to investigate the effects of the wire rotational speed (peripheral speed) and wire descending speed (cutting speed), which are the operating parameters of a mono-wire cutting machine, on unit wear and unit energy, which are the performance parameters in mono-wire cutting. By using the obtained results, cuttability charts for each natural stone were created on the basis of unit wear and unit energy values, cutting optimizations were performed, and the relationships between some physical and mechanical properties of rocks and the optimum cutting parameters obtained as a result of the optimization were investigated.     

上海越江隧道工程场地地层波速测试及其工程应用

该文利用单孔波速测试技术,对上海越江隧道工程场地作稳定性地质调查与评价。剪切波测试成果表明,工程场地属软弱场地土,场地类别为Ⅳ类;不需要考虑土层的液化现象;Ⅶ度地震烈度条件下,工程场地不会发生震陷问题;场地地脉动卓越周期为0．60～0．81s。     

Meteorological factors affecting the speed of movement and related impacts of extratropical cyclones along the U.S. east coast

The speeds of historical cool-season extratropical cyclones along the U.S. east coast, hereafter East Coast Winter Storms (ECWS), occurring during the period from 1951 to 2006 were computed. Average storm speed was 13.8 ms⁻¹ with stronger storms generally moving faster than weaker storms and faster storms forming during the midwinter months (December–March). There was no clear trend in ECWS speed during the time period, although considerable season-to-season variability was present. The monthly and seasonal variations in storm speed could not be attributed to the El Ni?o-Southern Oscillation or North Atlantic Oscillation (NAO) alone. However, the speed of ECWS was considerably slower when both El Ni?o and the negative phase of NAO occurred simultaneously. Characteristic patterns in the upper levels of the atmosphere, specifically 300 hPa zonal winds and 500 hPa geopotential heights, were present during periods when ECWS speeds were among the slowest (and separately fastest). For slow storm speed, these patterns also prevailed during months in which El Ni?o and negative NAO phase occurred. These patterns were also present during months with extended runs of high oceanic storm surge. This provides a qualitative link between the atmospheric conditions associated with slow storms and potentially high coastal storm surge impacts. Among the prime consequences of ECWS speed are extended periods of high storm surge, mainly due to slow-moving storms. The sustained high tidal levels often lead to substantial damage caused by coastal flooding, overwash, and beach erosion.     

Surface Miners: Evaluation of the Production Rate and Cutting Performance Based on Rock Properties and Specific Energy

The purpose of this research was to evaluate the production rate (PR) and cutting performance of surface miners (SM) based on rock properties and specific energy (SE). We use data from equipment manufacturers and experimental data in this study and propose a new method and equations to determine both the PR and the cutting speed of SM. The unconfined compressive strength (UCS) of the rock, its abrasivity, and the machine’s engine power are the three most important factors influencing the PR. Moreover, the cutting depth, UCS, and engine power have a significant impact on the cutting speed. We propose a new method and equations to determine the energy required to cut a volume unit and a surface unit, i.e., specific energy, and establish the relationship between SE, UCS, and PR. The results of this study can be used by surface miner operators to evaluate the applicability of the machines to a specific mine site.     

天山南坡台兰河流域冰川物质平衡变化及其对径流的影响

应用控制流域的径流及相关降水资料,通过模型重建了台兰河流域平均冰川物质平衡序列.结果显示,1957—2000年流域冰川平均年物质平衡为-287mm,累计冰川物质平衡-12.6m;44a来由于气温升温引起的冰川净消融相当于每年补给河流径流1.24×10⁸m³,占河流年径流量的15%.1982年以后,流域冰川物质平衡一直呈负平衡,1957—1981年平均物质平衡为-168mm·a^-1,1982—2000年平均为-445mm·a^-1.随着气候由暖干向暖湿转型,降水量增加,但冰川对气温的敏感性更大,冰川消融加快,冰川融水量持续增加.气温和降水量的变化与北大西洋涛动和北极涛动变化一致,其突变年份都在1986—1988年左右.     

Groundwater and geotechnical aspects of deep excavations in Hong Kong

Consideration of groundwater is a key element in almost every construction project. The design of deep excavations for basements or underground railway station concourses below the water table require that the water pressures are taken into account. Whilst these can be considered to be hydrostatic in soil, the decreasing permeability of rock with depth and the fact that groundwater flow is invariably along discrete fractures means that the water pressure is unlikely to be hydrostatic at depth.

Groundwater control for deep excavations can be achieved by a number of methods such as grouting, pumping or structural walls or a combination of these. For tunnelling projects grouting is extensively used, but the development of sophisticated tunnelling machines has led in many cases to the demise of compressed air as a means of groundwater control.     

敞开型测压管水位监测的滞后时间问题研究

分析了敞开型测压管在水位监测时产生滞后现象的机理,提出了一种简单新方法估算滞后时间,并与Hvorslev解答进行了对比。参数分析结果表明,所提出方法估算的滞后时间约为Hvorslev解答的1/5～1/10。当测压管进水段的长度足够时,敞开型测压管可以应用于渗透系数为10-5甚至10-6 cm/s的土体当中,而不会产生显著的滞后现象。通过28根敞开型测压管的现场注水试验,检验了测压管的灵敏度,并验证了分析结果的合理性。     

珠江口伶仃洋ZK1钻孔的磁性地层学研究

伶仃洋地区年代格架的建立对区域古环境的重建及海陆交互作用的研究具有重要意义.利用磁性地层学和AMS 14C测年对珠江口伶仃洋ZK1钻孔(113°40′E、22°34′N,孔深100.3 m)0～32 m岩心进行了系统的年代学研究.5个样品的AMS 14C测试年龄为(486±120)～(2268±149)a BP.岩心的...     

华南武功山中生代花岗岩体热史及隆升机制研究

根据全岩Rb－Sr和黑云母、钾长石、全岩K－Ar、磷灰石裂变径迹同位素年龄测定结果,结合地质构造证据,分析了华南武功山花岗岩体的冷却历史。假定岩体冷却和地温梯度降低同步,估算出武功山中生代岩体的原始侵位深度为6km。在岩浆冷却过程中,岩体冷却上升速率逐渐降低。该岩体在180．8Ma。热侵位结晶,以较快的速率冷却上升,冷却速率为10．7C／Ma。,上升速率为0．11mm／a。经过28Ma后,岩体上升至地下约3km深处,转为缓慢冷却,平均冷却速率为1．7C／Ma,平均上升速率为0．02mm／a。最后对武功山地区晚中生代构造演化过程、热演化模式及其大地构造意义进行了讨论。     

Pre-eruptive conditions revealed by mega- and pheno-cryst compositions from the Quaternary Erzincan Volcanics, Eastern Turkey: Insights into the magma processes

Quaternary Erzincan Volcanics (QEVs) from the Erzincan Basin consist of mega- and pheno-cryst-bearing high-K calc-alkaline dome lavas. Fourteen nearly phenocrystic domes, with a range of basaltic-andesite, andesite, dacite and rhyolite compositions, were emplaced in the North Anatolian Fault Zone. The emplacement ages yielded by the unspiked K–Ar technique range from 102 to 140 ka. The andesitic domes (each less than 3 km in diameter) contain amphibole megacrysts. Amphibole compositions show a linear variation from ferro-edenite, edenite to pargasite from rhyolite to andesite. Pargasitic amphibole megacrysts scattered into the groundmass are very similar in composition to the microlites. All plagioclases are 53 mol%. Oscillation types are An₃₂₋₅₀ whose variations range from 10 to 16 mol% An and have 10–150 μm in thickness. Pre-eruptive conditions, calculated from mega- and pheno-cryst composition, using pyroxene and two oxide thermometers and the Al-in-hornblende barometer, ranged from 918 to 837 °C and 6.6 to 4.3 kbar for andesitic magma, 824–755 °C and 4.6–4.2 kbar for dacitic magma to 803–692 °C and 4.3–3.9 kbar for rhyolitic magma, which correspond to a depth of >10 km for storage region of the crust. The fO₂ values vary from −14.25 to −15.35 log units which are plotted just below nickel–nickel oxide (NNO) buffers. The systematic decrease in thermobarometric results from andesite to rhyolite is consistent with a single magma reservoir moving upward through the crust followed by fractional crystallization. Textural and compositional relationships of mega- and pheno-crystic phases suggest that magma mixing, fluid input to the reservoir and fractional crystallization processes, with a small amount crustal contamination play key role in evolution of the QEVs.     

遂渝线无碴轨道桩板结构路基动力响应现场试验研究

通过遂渝线现场实测,对CRH2动力分散型机车在桩板结构路基试验段高速行车条件下的动响应规律进行了研究,分析路基动力响应和列车速度的关系以及动应力沿路基深度方向的变化规律等。结果表明：随车速的增大,动位移、加速度及动应力均有不同程度的增加,并在临界速度附近先增大后减小;动应力随路基深度的增加衰减很快,并且随着深度的增加,动应力值和静态应力值越来越接近;桩底土动应力较大,桩基加深了路基的动力影响范围,改善了路基土体部分的受力状态。     

高海拔冻土区通风管路基管内风速及影响因素研究

在多年冻土地区,路基工程的修筑将对下伏多年冻土的热力稳定性产生显著的影响.为保护多年冻土,保证路基的长期稳定性,通风管作为一种对流换热类主动冷却降温措施被广泛应用.通风管内的对流换热强度与管内风速密切相关,针对这一问题,采用现场监测与数值模拟相结合的方式开展了通风管内风速特征及影响因素的研究.结果表明:随通风管管径的增...