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1.
Batch flotation tests on low- and high-rank Australian coals showed that it was difficult to reduce the original ash yield substantially whilst maintaining high recovery. The ash yield of the flotation concentrates was found to be mainly the result of the recovery of composite coaly grains containing both carbonaceous matter and mineral matter. Even 50 μm grains were composite in nature, the mineral matter being very finely disseminated. Separation of the flotation products using the heavy-liquid density-gradient technique showed that flotation recovery of coaly grains of a given size decreased with increasing relative density of the grains. The effect was much greater for coal of low rank. The fall in recovery correlated with an increase in the proportion of hydrophilic mineral matter in the composite grains, rather than with the changing proportions of the macerals vitrinite and inertinite. 相似文献
2.
《International Journal of Mineral Processing》2005,75(1-2):83-90
The effect of three most important reagents for coal flotation namely sodium meta silicate, collector (kerosene) and frother (MIBC) was studied using 23 full factorial design. The regression models were developed using factorial experiment data to quantify the effect of sodium meta silicate, collector and frother and to predict grade and recovery of combustible material for different reagent conditions. The addition of sodium meta silicate increased the recovery without affecting the grade significantly. The MIBC addition reduce the surface tension at the liquid–vapor interface, which results in the production of finer bubble size distribution and thus improves flotation rates and recovery values. However, a finer bubble size distribution also increases water recovery, which results in a greater recovery of entrainable ash bearing particles and thus degradation of the product grade. The interaction between OH group of MIBC and hydrated mineral matter improves flotability of high ash coal particles and degrades the product grade further. The negative effect of kerosene and MIBC interaction on both grade and recovery could be due to the recovery of high ash coal particles in preference to low ash coal particles. The highest possible grade of product is 94.19% combustibles with 25.33% recovery. A product with 91.11% combustibles grade at 95.58% recovery was obtained at 0.1 g/kg sodium silicate, 0.4 g/kg collector and 0.075 g/kg frother from the coal fines tested. 相似文献
3.
W.J. Trahar 《International Journal of Mineral Processing》1981,8(4):289-327
From the examination of data from detailed plant surveys and associated laboratory batch testing, the principal effects of particle size in flotation have been identified. The current state of knowledge concerning the role of this variable is discussed in terms of the evidence presented. It is concluded that the minimum degree of hydrophobicity necessary for the flotation of a particle depends upon its size and as a result, recovery-size curves are a valuable diagnostic aid to the assessment of flotation performance. Entrainment is shown to be an important contributory mechanism to the recovery of fine particles which, when coupled with a low rate of genuine flotation, can account for much of the observed behaviour of such fines. The significance of particle size and its consequences in flotation research, in plant operations and in control schemes has been under-rated. The separate conditioning or flotation or both of separate size fractions seems inevitable as ores become increasingly difficult to concentrate. 相似文献
4.
Coal flotation studies were carried out in ultrasonically assisted flotation cells. Representative hard coal slime samples from Prosper-Haniel Coal Preparation Plant located in Bottrop, Ruhr Region of Germany were used for this purpose. A Wemco type flotation cell was fitted with transducers and tests were carried out at variable frequency and power. The reagent for coal flotation was Ekofol-440 with variable dosages during conventional and ultrasonic flotation experiments. The results showed that ultrasonic coal flotation yields more combustible recovery and lower ash values in concentrates than conventional flotation by using similar reagent dosages. These results are explained on the basis of efficient surface cleaning of the coal particles. 相似文献
5.
Leonard J. Warren 《International Journal of Mineral Processing》1985,14(1):33-44
Laboratory batch flotation tests were carried out on a deslimed (+6 μm) sulfiderich cassiterite ore, an ultrafine fraction (?6 μm) of a cassiterite ore and a bituminous coal. Chemical conditions were kept constant but the water recovery was varied by changing the height of the froth column and the rate and depth of froth removed. The recovery of the floatable mineral in each system was then found to be linearly related to the weight of water recovered. The intercept of the regression line on the mineral recovery axis, where the water recovery is zero, was interpreted as the recovery due to true flotation. The entrainment contribution was proportional to the slope of the line. In this way the contributions of entrainment and true flotation to overall recovery were separated. 相似文献
6.
S. Kelebek U. Demir O. Sahbaz A. Ucar M. Cinar C. Karaguzel B. Oteyaka 《International Journal of Mineral Processing》2008,88(3-4):65-71
The effects of dodecylamine (DDA), kerosene and pH on the recovery of combustible matter and ash content of a lignitic coal from Tuncbilek, Turkey have been studied using a three-variable and two-level (23) factorial experimental design. The coal sample responded favourably to batch flotation with high recoveries in excess of 95% using both kerosene and DDA respectively. The main effects of all three factors on the recovery are positive. Significance of DDA as a collector, is somewhat greater than that of kerosene, but its selectivity for ash reduction is not significant at the 95% confidence level. The pH-dependence of recovery by these collectors is opposite to each other. The DDA-induced flotation recovery is lowest at pH 9.4, an effect which has been related to precipitation of cationic species of this collector. The kerosene-induced recovery and grade of combustible matter increases with pH and this has been attributed to a better dispersion of coal and its associated clays. The two-way interaction effects are all negative at a smaller level. The main and interaction effects have been discussed on the basis of adsorption at most favourable surface sites, different modes of orientation of DDA species, competition with kerosene, and probable collecting properties of the frother used. The simultaneous effects of the two collectors on the recovery of combustible matter have been discussed at each pH value used. 相似文献
7.
An attempt at flotation of fine grains of zinc carbonate using potassium ethylxanthate as the collector and sulphydryl and copper ions as the activators has been undertaken. Results of the flotation tests have been interpreted in terms of the adsorption of activating agents as well as the grain size effect. 相似文献
8.
Electro-flotation tests were conducted on chalcopyrite particles with a modified Hallimond tube designed for electro-flotation, using platinum anode—copper cathode and graphite anode—copper cathode systems. Flotation tests were carried out for fines of chalcopyrite of size below 20 microns with potassium ethylxanthate as collector. Studies were done on flotation with hydrogen and oxygen separately with the usual variables. Dissolution of chalcopyrite at various current densities, with reagent at optimum conditions and without reagent was also studied. It is observed that electro-flotation particularly with oxygen, is effective in the flotation of fine particles of chalcopyrite. 相似文献
9.
Ashiwani Kumar Gupta P.K. Banerjee Arun Mishra P. Satish Pradip 《International Journal of Mineral Processing》2007
The frothers of alcohol family (MIBC and Alpha-terpineol) were compared with polyglycol ethers (DF-1012) in terms of two phase characterization parameters like foamability, foam stability, surface activity and bubble size distribution. In this research, fundamental two phase frother characterization parameters were linked with three phase coal flotation behavior. 相似文献
10.
水泥土搅拌桩复合地基的试验和数值模拟分析 总被引：1，自引：0，他引：1
水泥土搅拌桩处理软土地基可以提高地基承载力并减小沉降量。针对珠海地区的淤泥质土,进行了4种垫层厚度的水泥土搅拌桩复合地基现场静载荷试验,并在现场试验的基础上采用FLAC3D对水泥土搅拌桩复合地基进行了数值模拟分析。将数值模拟得到的4种垫层厚度复合地基的沉降曲线与现场试验的沉降曲线进行了比较,两者基本吻合。采用此模型计算了不同桩径和桩距复合地基的承载力和沉降量,研究了桩径、桩距的改变对复合地基承载力和沉降量的影响,并对改变桩径和桩距两种方案进行了比较,为水泥土搅拌桩复合地基的设计提供了参考。 相似文献
11.
Hallimond tube flotation experiments have been carried out on the two calcium minerals scheelite and calcite using dodecylammonium chloride as collector. The main variables studied were the calcium ion concentration and the pH.In the case of scheelite, addition of calcium chloride markedly lowered the flotation recovery. Recovery was also lowered when the pH was reduced below about 10. Since it is known that the zeta potential of scheelite is almost independent of pH this confirms that co-adsorption of un-ionized amine is necessary for good flotation. Other un-ionized long-chain molecules can replace the amine; thus it was shown that excellent flotation can be obtained event at about pH 7 by adding dodecanol together with dodecylammonium chloride. With the completely ionic trimethyldodecylammonium chloride recoveries were poor and were independent of pH.In the case of calcite, calcium chloride had no immediate effect on flotation recovery, but at low collector concentrations marked depression occurred after many hours standing in the presence of calcium ions. The effect of pH on flotation of calcite was anomalous and there appear to be two pH regions in which recoveries are high.The results are discussed and attention is drawn to the need for more thorough studies of the calcium carbonate/water interface. 相似文献
12.
《矿物学报》2013,(Z1)
Effects of particle size and chain length on flotation of quaternary ammonium salts (QAS) onto kaolinite have been investigated by mico-flotation tests. The two kinds of quaternary ammonium salts [RN(CH3)3] with different chain lengths, dodecyltrimethylammonium chloride (DTAC) and cetyltrimethylammonium chloride (CTAC) were used as collectors for kaolinite in different particle size fractions (0.075–0.01 mm, 0.045–0.075 mm, 0–0.045 mm). The anomalous flotation behavior of kaolinite have been further explained based on crystal structure considerations by adsorption tests and molecular dynamics (MD) simulation. The results show that the flotation recovery of kaolinite in all different particle size fractions decreases with an increase in pH when DTAC and CTAC are used as collectors. As the concentration of collectors increases, the flotation recovery increases. The longer the carbon chain of QAS is, the higher the recoveries of coarse kaolinite (0.075–0.01 mm and 0.045–0.075 mm) are. But the flotation recovery of the finest kaolinite (0–0.045 mm) decreases with chain lengths of QAS collectors increasing, which is consistent with the flotation results of unsifted kaolinite (0–0.075 mm). It is explained by the froth stability related to the residual concentration of QAS collector. In lower residual concentration, the froth stability becomes worse. Within the range of flotation collector concentration, it's easy of CTAC to be completely adsorbed by kaolinite in the particle size fraction (0–0.045 mm), which led to lower flotation recovery. Moreover, it is interesting that the particle size of kaolinite is coarser, the flotation recovery is higher. The anomalous flotation behavior of kaolinite is rationalized based on crystal structure considerations. The results of MD simulations show that the (001) kaolinite surface has the strongest interaction with DTAC, compared with the (001), (010) and (110) surfaces. On the other hand, when particle size of kaolinite is altered, the number of basal planes and edge planes is changed. It is observed that the finer kaolinite particles size become, the greater relative surface area of edges is, and the more the number of edges is. It means that fine kaolinite particles have more edges to adsorb less cationic colletors than that of coarse kaolinite particles, which is responsible for the poorer floatability of fine kaolinite. 相似文献
13.
为研究不同围压下深部复合地层岩体变形和破坏特征,结合地质赋存条件制作了类层状复合岩石试样,通过开展不同围压下的三轴压缩试验,研究了围压对水平层状复合岩体变形破坏特征的影响。试验结果表明：随着围压的不断增加,峰后偏应力-应变曲线的降低速率逐渐变缓,应变软化程度逐渐减弱;随着围压的增大,水平层状复合岩石的破坏形态呈现出明显差异,整体上破坏形态逐渐由脆性破坏向延性破坏过渡;在一定围压状态下,围压对软岩膨胀变形的约束效果相对硬岩较弱,导致水平层状复合岩石试样的软、硬分层之间的膨胀变形不协调,在层间黏结力作用下,软、硬分层之间发生相对错动现象。该研究成果对于施工单位预防深部复合地层隧道掘进机（TBM）工程灾害具有一定的指导意义。 相似文献
14.
Single bubble velocity profile (velocity vs. distance) has been measured for a 1.45 mm diameter bubble to try to explain reported differences in gas holdup in two systems: F150 vs. 1-pentanol, and MIBC vs. NaCl. It was found that in F150 the bubble slowed rapidly to reach the terminal velocity stage of the profile while in 1-pentanol the bubble remained in the deceleration stage and was consequently moving faster, at almost twice the speed. The lower rise velocity in F150 means longer bubble residence time and corresponding higher gas holdup than with 1-pentanol, as reported. In the second system, the bubble in MIBC reached terminal velocity more rapidly than in NaCl which agrees with the reported higher gas holdup in MIBC compared to NaCl. An implication for gas holdup evaluation is that the value may depend on the part of the velocity profile over which it is measured. Possible exploitation of this reagent effect on bubble rise velocity in flotation is considered. 相似文献
15.
16.
Yang Xiao Minqiang Meng Ali Daouadji Qingsheng Chen ZhijunWu Xiang Jiang 《地学前缘(英文版)》2020,(2):375-388
Strength and deformation behaviors of rockfill materials,key factors for determining the stability of dams,pertain strongly to the grain crushing characteristics.In this study,single-particle crushing tests were carried out on rockfill materials with nominal particle diameters of 2.5 mm,5 mm and 10 mm to investigate the particle size effect on the single-particle strength and the relationship between the characteristic stress and probability of non-failure.Test data were found to be described by the Weibull distribution with the Weibull modulus of 3.24.Assemblies with uniform nominal grains were then subjected to one-dimensional compression tests at eight levels of vertical stress with a maximum of 100 MPa.The yield stress in one-dimensional compression tests increased with decreasing the particle size,which could be estimated from the single-particle crushing tests.The void ratio-vertical stress curve could be predicted by an exponential function.The particle size distribution curve increased obviously with applied stresses less than 16 MPa and gradually reached the ultimate fractal grading.The relative breakage index became constant with stress up to 64 MPa and was obtained from the ultimate grading at the fractal dimension(a?2:7).A hyperbolical function was also found useful for describing the relationship between the relative breakage index and input work during one-dimensional compression tests. 相似文献
17.
E. Burdukova J.S. Laskowski G.R. Forbes 《International Journal of Mineral Processing》2009,93(1):34-40
Long-chain amines, used in potash ore flotation as collectors, are insoluble in NaCl–KCl saturated brine. In commercial applications, these amines are melted at 70–90 °C, dispersed in acidic solution of hydrochloric or acetic acids, and such emulsions are then introduced to the flotation pulp.To model the commercial potash ore flotation process, dodecyl amine, used in this study, was melted at 70 °C, dispersed in hydrochloric acid aqueous solution and was added to a KCl–NaCl saturated brine at room temperature. This results in the precipitation of the amine. The present study summarizes the influence of the conditions on the particle size and morphology of the precipitating amine particles. Methyl isobutyl carbinol (MIBC), common frother in flotation processes, was shown to affect amine dispersion when added into a hot amine emulsion prior to mixing with a saturated brine. This study demonstrates that the precipitating amine particles are selectively abstracted by KCl particles, but not by NaCl particles. 相似文献
18.
The effect of operating parameters on the hydrodynamics of three geometrically similar Rushton turbine flotation cells with volumes of 2.25, 10 and 50 dm3 was determined. The operating parameters investigated were superficial gas velocity (Jg), impeller rotational speed (N), and frother (methyl isobutyl carbinol, MIBC) concentration. 相似文献
19.
泥岩遇水易崩解泥化,特别是耦合荷载作用后,其力学性能衰减更加明显。为掌握泥岩在环境因素和外部荷载作用下的性能演化规律,开展了干湿循环与上覆荷载共同作用下的压缩特性试验。发现初次浸水后压实泥岩发生膨胀,但随着干湿循环作用的进行,泥岩试样发生压缩变形。然后,对压实泥岩试样进行孔隙分析,结果表明,泥岩孔隙分布呈现双峰特征,峰值大约位于0.3 ?m和10.0 ?m孔径处,干湿循环和荷载的作用引起孔隙体积减小,特别是对大孔径孔隙的影响最显著。最后,依据泥岩的膨胀、压缩和孔隙分布特征,提出了压实泥岩的孔隙-荷载-水分相互作用模型,将压实泥岩的孔隙体积分为团粒内孔隙和团粒间孔隙两类;分析了荷载-干湿循环引起泥岩团粒崩解破碎和充填团粒之间孔隙的演变过程。揭示了泥岩孔隙-水分-荷载的相互作用机制,为泥岩路基的填筑提供了理论参考。 相似文献
20.
翠湖湿地软土触变性试验研究 总被引：1，自引：0，他引：1
利用自行研制的微型十字板剪切仪对翠湖湿地软土的触变性进行了试验研究。观测了湿地软土扰动后由不同静置时间引起的抗剪强度的变化,确定了扰动后湿地软土的抗剪强度恢复时间、恢复程度、灵敏度以及触变强度比率。对湿地软土的触变性进行了3个不同深度处的试验研究,得到了深度和静置时间对扰动后土体抗剪强度恢复的耦合影响。对湿地重塑土样进行了不同含水率的试验研究,得到了湿地软土含水率和抗剪强度的对应曲线。试验结果可为深入研究湿地软土工程力学性质提供依据,也可为沼泽湿地的合理开发利用提供参考。 相似文献