Developing critical coalescence concentration curves for industrial process waters using dilution

Critical coalescence concentration (CCC) is commonly used to characterize frothers. The CCC is determined from a plot of Sauter mean bubble size (D₃₂) vs. frother concentration, referred to here as the ‘addition’ method. Industrial flotation systems can encounter a number of naturally occurring surfactants and salts that also influence bubble size. In effect there is a ‘system’ CCC. This paper introduces a dilution method to identify the system CCC. The study verifies the dilution technique using the commercial frother DF-250. It is shown that the system CCC can be expressed as an equivalent DF-250 concentration to provide context and a means of comparing water samples. The viability of using gas holdup to provide an estimate of process water D₃₂ is also explored. To illustrate the procedure three samples of process water from the Albian Sands bitumen processing plant were examined. They proved to be similar and yielded a system CCC equivalent to about 20 ppm DF-250. It is concluded that the dilution and frother equivalent techniques can be used to help identify system hydrodynamic properties.     

Critical coalescence concentration of inorganic salt solutions

Critical coalescence concentration (CCC) was determined in a laboratory-scale mechanical flotation cell for a series of coalescence inhibiting inorganic salts (KCl, NaCl, Na₂SO₄, CaCl₂ and MgSO₄) compared to two commercial frothers (methyl isobutyl carbinol, Dowfroth 250C). The salt CCC values ranged from 0.07 M (MgSO₄) to 0.31 M (KCl and NaCl) and correlated with ionic strength. The CCC values are compared to transition concentrations in the literature. The effect of salts on gas dispersion in flotation systems is discussed.     

Zircon mineral solids concentrated from Athabasca oil sands froth treatment tailings: Surface chemistry and flotation properties

Zircon mineral solids concentrated from Athabasca oil sands froth treatment tailings were compared by X-ray photoelectron spectroscopy, infrared spectroscopy, and collector-assisted froth flotation before and after surface cleaning in a low temperature, radio-frequency oxygen plasma. Plasma cleaning was effective at removing a surface bound layer of organic matter having chemical markers consistent with bituminous fractions. Specifically, the observation of long-chain aliphatics, ester and ether linkages, aromatic indicators, and hydroxyls in the absence of carboxylic acid groups, suggested the surface organic layer was representative of asphaltene or resin. Supporting this interpretation was the identification of pyrrolic and thiophenic chemical states. Plasma degradation of the hydrocarbon component transformed the zircon particles from hydrophobic to hydrophilic as evidenced by their recovery in water/ethanol froth flotation tests. The cleaned zircon particles were subsequently collected in the froth using dodecylamine. This work explains the surface conditions responsible for the reporting of zircon to the froth treatment tailings and demonstrates the efficacy of plasma cleaning as a means to condition zircon for coupling with collector agents. A physical model of surface adsorption is discussed and process implications are considered.     

Examination of NaCl and MIBC as bubble coalescence inhibitor in relation to froth flotation

With scarcity of fresh water resources, flotation plants are increasingly under pressure to supply their water needs from other sources such as bore water, seawater or recycled plant water. This water generally contains a high concentration of inorganic electrolytes which may have a substantial influence on the performance of the flotation operation. In this study, the stabilisation mechanism of bubbles by salt was investigated using a specifically designed experimental set-up. Two bubbles of approximately the same size were produced at the tip of two adjacent capillaries in concentrated solutions of an inorganic electrolyte (NaCl). Their coalescence behaviour was recorded using high speed video imaging in which information such as coalescence time and deformation of the resultant bubble upon coalescence could be extracted. The results were then compared against a similar system using MIBC. It was found that delayed coalescence in NaCl required a relatively concentrated solution in the order of 0.1-0.5 M to achieve coalescence times comparable to MIBC. Unlike NaCl, it appears that a small amount of MIBC, in the order of 10⁻⁵ M, is sufficient to delay the coalescence of bubbles, which reach a maximum at a concentration of 3 × 10⁻³ M. The analysis of oscillation patterns during the coalescence process revealed that the oscillation is noticeably damped in the presence of MIBC at high concentrations, although this is not the case in NaCl solutions. Results are discussed in terms of bubble stability, froth stability and their possible implications on particle recovery.     

Study of the local critical coalescence concentration (l-CCC) of alcohols and salts at bubble formation in two-phase systems

The acoustic emissions generated by bubbles when they form are well understood and can be easily measured using a hydrophone and amplifier. Bubbles emit an audible sound not only when they form, but also when two or more coalesce. In this case, however, the amplitude of the sound is higher than after bubble formation. The difference in amplitude is enough to tell between bubble formation and bubble coalescence. Based on this property, the capability of alcohols and salts to prevent coalescence right after bubble formation at a capillary tube was studied. In general, the higher the gas flow rate through the capillary the more intense the collisions between subsequent bubbles, which eventually leads to coalescence, hence a higher reagent concentration in the system is needed to protect the bubbles against it. The reagent concentration at which coalescence is prevented can be seen as a local critical coalescence concentration (l-CCC) at the gas flow rate tested. This allows generating a curve of l-CCC vs. gas flow rate that can be used for comparison between different reagents. The paper presents results of l-CCC curves for alcohols and salts. The l-CCC curves show a comparable effect on coalescence prevention between 0.4 M NaCl and 8 ppm MIBC (a common frother), which is in agreement with the literature (Quinn et al., 2007).     

Breakup and re-formation of bubble clusters in a flotation cell

This study is concerned with the behavior of bubble clusters in a well-controlled turbulent flow. We used a specially designed cell where the bubble aggregates could be formed and exposed to breakage by a rotating impeller. The effects of impeller speed and the concentration of collector on cluster behavior were studied. It was found that the size of the clusters increases with the concentration of collector used. We also found that although the clusters could easily be destroyed under the action of impeller, they could reform, especially at lower impeller speeds. It was observed that the size of the bubbles arriving into the impeller region in the absence of particles before breakage was considerably higher than the size of the clusters formed at the same impeller speed. It appears that both cluster breakage and re-formation take place simultaneously, and the extent of formation and regrowth is mainly determined by the hydrophobicity of the particles and the impeller speed.     

Froth flotation of sphalerite: Collector concentration,gas dispersion and particle size effects

This experimental work on sphalerite flotation investigated the effect on flotation performance of three particle size fractions, namely, coarse (d₈₀ = 100 μm), medium (d₈₀ = 39 μm) and fine (d₈₀ = 15 μm), bubble size distribution, superficial air velocity, and collector dosage. Bubble size distributions were characterized with the image analysis technique. The two-phase (liquid–gas) centrifugal pump and frother addition (MIBC, 5–30 ppm) allowed generating bubble diameters between 150 and 1050 μm, and air holdup ranging from 0.2% and 1.3%. Main results showed that each particle-size distribution required an optimal bubble-size profile, and that sphalerite recovery proceeded from mechanisms involving true flotation (when J_g = 0.04 cm/s and 1.9 × 10⁻⁴ M SIPX). However, cluster-flotation occurs at high collector dosage (when J_g = 0.04 cm/s and d₃₂ between 285 and 1030 μm), and requiring further investigation.     

Removal of Phormidium sp. by positively charged bubble flotation

The objectives of this study were to investigate the behavior of Phormidium sp. during flocculation and negatively or positively charged bubble flotation in order to optimize algal removal processes and identify mechanisms underlying the efficiency of flotation with positively charged bubbles. The nuisance of Phormidium sp. significantly decreases water quality in natural watershed and clogs filter bed in water treatment plant. Although dissolved air flotation has been recently adopted for algae removal, the best method has not been fully investigated. According to theories on dissolved air flotation, the operational conditions affect removal of the process and in this study, the optimum bubble generations was also investigated for better algal removal. Bubbles were generated at two levels of saturated pressure and measured at different bubble concentrations (10%, 20% and 30%), in the absence and presence of coagulants. Bubbles forming at 6 bars and 3 bars were observed at zeta potentials of −30 mV to + 27 mV. The chain-like algae were cultured in the laboratory for 20 days. At the stationary phase, Phormidium sp. sizes ranged from 2 μm to 10 μm in diameter and about 100–200 μm in length. Over a pH range of 4.0–7.0 (increments of 0.5), the negative zeta potentials were −4 mV to −12 mV. Algal removal by flocculation was determined by jar tests and by the batch dissolved air flotation (BDAF) method with bubble generation and flotation. We obtained optimal Phormidium sp. removal with positively charged bubble flotation at a 30% bubble rate at >16 mV and a bubble formed at 6 bars, with removal of up to 85% and 93% of cells and chlorophyll a, respectively. We also demonstrated the efficacy of using positively charged bubbles to remove Phormidium sp. cells and the importance of positively charged bubbles in the rarely reported interaction between bubbles and chain-like algae.     

煤泥柱浮选的承载能力与气含率轴向分布

为优化柱浮选设备的处理能力和分选效果,采用压差法测定柱体内部的气含率,同时通过调整入料浓度和流速,分析煤泥柱浮选承载能力和气含率轴向分布的变化规律,并探索两者之间的内在联系及对煤泥分选效果的影响。结果表明：入料流速小于临界流速时,气含率在轴向上从底部到顶部依次增大;流速达到临界流速或以上时,气含率轴向分布发生逆变;临界流速随入料浓度的升高逐渐减小。承载能力随入料流速的增大先增大后减小,拐点为气含率轴向分布逆变的临界流速;一定范围内浓度的升高有利于提高承载能力和可燃体回收率。建立了煤泥柱浮选的承载能力预测模型,线性拟合的相关系数R 2=0.873,达到了较高的预测精度。     

Effect of gas rate and impeller speed on bubble size in frother-electrolyte solutions

In a flotation cell, bubble size is a function of both coalescence and breakup phenomena. Two phase tests, conducted in a conventional 5.5 L Denver mechanical flotation cell, studied the effect of impeller speed, gas flow rate and frother concentration on bubble size in various electrolyte-frother solutions. The addition of frother to a synthetic sea salt did reduce the measured bubble size (at certain mechanical conditions); whereas the effect of frother addition to NaCl was too small (when compared to measurement errors) to make significant conclusions. This led to more detailed CCC curves (0–50 ppm MIBC) for NaCl, NaCl + MgCl₂, NaCl + CaSO₄, and NaCl + KCl solutions, at constant electrolyte concentrations, to be conducted. They showed an increase in bubble size with the addition of MIBC. This was attributed to the saturation of frother at the air-water interface, reducing local surface tension gradients that help produce smaller bubbles. This occurrence is typically masked in traditional CCC curves due to the dominance of coalescence effects at low frother concentrations.     

硫化铜镍矿浮选尾矿处理工艺探索

利用重选一浮选一磁选联合工艺对硫化铜镍浮选尾矿进行进一步处理,综合回收尾矿中的镍、铁等有价金属.该项研究开拓了硫化铜镍矿山浮选尾矿综合利用的新思路,为金属矿山在资源综合回收与利用方面提供了一种有益的尝试.     

某卡林型金矿浮选工艺试验研究

某金矿石金品位为3.20g/t,是主要的回收元素,其中伴生的锑可作为综合回收的对象。原矿中金主要被硫化物包裹,占80.51%,其次被氧化物包裹,占11.58%,单体金和连生金较少,只占4.24%。针对该矿石性质,在原有工艺流程和药剂制度基础上,开展浮选条件试验,获得最佳工艺参数,磨矿细度-0.074mm占84.6%、碳酸钠用量为2000g/t、硫酸铜用量为200g/t、硝酸铅用量为150g/t、丁基黄药用量为150g/t。当磨矿细度-0.074mm占84.6%时,采用最佳药剂制度,通过一粗三精二扫,中矿循序返回工艺流程,获得精矿金品位46.14%,金回收率90.91%,尾矿品位为0.29g/t。尾矿工艺矿物学表明,尾矿中流失的金主要是硅酸盐包裹金、单体及连生体金,尤其是硅酸盐包裹的金未能回收。尾矿中+0.044mm粒级的金占30.90%,可探讨重选工艺回收的可能,-0.025mm粒级的金占60.07%,粒度过细,很难通过浮选工艺回收。     

浮选精煤中水的存在形式与脱除

通过研究浮选精煤中水的形式 ,分析了浮选精煤的理论脱水方法 ,并通过对浮选精煤脱水技术设备应用现状分析 ,得出应用高效、低能耗新型脱水设备 ,以及添加一定的助滤剂 ,是一种有效的脱水途径     

改造浮选尾煤工艺 实现洗水闭路循环

介绍了滴道盛和煤矿洗煤厂通过对浮选尾煤处理系统进行改造,降低浮选尾煤浓度,来实现洗水闭路循环.     

Estimation of the bubble size and bubble loading in a flotation froth using electrical resistance tomography

Flotation process is widely used in mineral industry for the separation of valuable minerals from low-grade ore slurry. There are several parameters such as the bubble size and bubble loading that predict the efficiency of the flotation process. These parameters can be used for the control of the flotation process. There are already some techniques that can be used for online monitoring of these parameters, for example, the high-speed video imaging and a probe sensor based on electrical resistance tomography (ERT). These methods, however, suffer for some limitations. The high speed video imaging gives information only on the surface of the froth and in the previously proposed ERT based techniques the conductivity of the froth is typically modeled to be smoothly varying. However, in reality the froth is composed of different size of bubbles having highly conductive surface and very low conductive interior which configuration cannot be modeled with smoothly varying conductivity distribution. In this paper, we propose a computational approach in which the structure of the froth is modeled and both the bubble size and the conductivity of the boundary of the bubbles are estimated. The proposed approach utilizes data measured with the standard ERT probe. The estimated bubble size and conductivity of the boundary of the bubbles are compared to online measured camera based estimates of the bubble size and bubble loading. The proposed approach is evaluated with simulated measurements and real data from Pyhäsalmi Mine. The results show that there is a high correlation between the camera based and the ERT based estimates of the bubble size. Furthermore, some of the parameters obtained from the ERT based method correlate well with the camera based estimate of the bubble loading.     

调浆气氛对黄铁矿浮选电化学性质影响研究

基于氧气在黄铁矿浮选电化学反应中的作用,考察了p H为4.00、6.86、9.18、10.01和10.96五种缓冲溶液浮选体系下,矿浆溶氧量(DO)对黄铁矿浮选矿浆电位(Eh)和回收率的影响。研究表明,五种缓冲溶液体系下,Eh均随着DO的增加而增加,碱性条件下DO对Eh的影响较小;浮选回收率随DO的增加呈下降趋势,碱性条件下回收率的变化较大。     

浮选柱在某选矿厂铜镍分离作业中的应用实践

为改善某选矿厂一期和二期生产线浮选过程能耗高、指标波动大、自动化程度低的现状,将在工业试验阶段运行良好的浮选柱应用到三期新建浮选系统中。针对浮选柱系统投产后存在的问题,进行了合理地适应性工艺改进,将铜镍分离浮选工艺优化为一次粗选、三次扫选、四次精选的柱机联合流程,使铜镍互含指标基本达标,同时降低了电能消耗,提高了浮选生产效率,为浮选柱在铜镍分离作业中的进一步推广运用奠定了基础。     

某低品位铜镍硫化矿浮选工艺流程试验研究

针对某低品位铜镍硫化矿矿石的性质和特点,进行了浮选工艺流程的试验研究。试验结果表明:原矿中镍和铜的品位分别为0.87%和0.28%,在"快速浮选+一次粗选、两次精选、两次扫选"工艺条件下,得到了镍品位为7.47%、回收率为83.41%,铜品位为2.30%、铜回收率为80.51%的混合精矿,与常规浮选流程相比,该工艺流程的工艺指标较好,可实现该矿石的充分回收与利用。     

浮选柱串联处理高浓度煤泥水效果初探

分析了浮选作业现状,阐述了浮选入料性质特别是入浮浓度对浮选柱分选效果的影响,提出了采用浮选柱串联解决高浓度浮选的新方法,并通过试验论证了该方法的可行性,对工业现场的浮选作业具有一定的指导意义.     

氯化钠强化煤泥浮选过程的机理探讨

煤泥浮选是选煤厂提质增效的重要环节,以无机盐离子为基本要素的溶液化学环境对煤泥.浮选过程具有重要影响。文章以溶液体系中常见的无机盐一NaCl为调控因素,研究了NaCl对无烟煤煤泥浮选过程的影响。采用气泡尺寸检测、气泡破裂时间检测、聚焦光束反射测量等技术手段研究了NaCl对浮选体系气泡尺寸和颗粒聚集行为的影响。结果表明:NaCl可以显著降低气-液两相体系的气泡尺寸,0.4mol/L的NaCl对气泡尺寸的降低作用与9 mg/L的仲辛醇相当;NaCl促进了矿浆体系中的颗粒聚集,0.6mol/L NaCl溶液的加入使矿浆中颗粒的平均弦长由28.5μm增大至40μm;NaCl对气泡尺寸和颗粒聚集行为的调控作用对煤泥浮选过程具有显著的促进作用,在氯化钠浓度为0.6 mol/L条件下,浮选精煤可燃体回收率可从26.32%提高至74.04%.