煤泥盐水浮选技术

盐水对浮选体系下颗粒与气泡行为的影响规律进行了综述。浮选矿浆中的无机盐电解质在提高精煤可燃体回收率的同时也增加了脉石矿物的回收。反电荷阳离子在煤粒表面吸附改善颗粒疏水性,颗粒-气泡间的液膜排液速度因双电层被压缩而加快;同时电解质兼有起泡剂的效果,能有效阻止气泡兼并聚合。另一方面,盐水浮选体系下细粒脉石颗粒的水流夹带和聚合截留现象严重,可燃体回收与脉石颗粒非选择性上浮之间的矛盾激增。     

复配起泡剂强化低阶煤浮选的试验研究

为了探究复配起泡剂对低阶煤浮选的强化效果,选取正戊醇、MIBC、仲辛醇和聚乙二醇(PEG)进行浮选动力学试验,通过表面张力和泡沫稳定性试验,揭示了复配起泡剂强化低阶煤浮选的作用机理。浮选结果表明:起泡剂单独使用时,PEG浮选精煤产率最高,浮选速率最快,正戊醇浮选效果最差;三种短链醇和PEG复配后,浮选精煤产率随着复配药剂中PEG含量的增加而增加,显著高于短链醇单独使用,其中正戊醇和PEG复配后浮选效果最好。通过测试不同起泡剂表面张力和泡沫稳定性可知,复配起泡剂表面张力更接近于PEG,表明混合溶液中PEG的性能占主导;正戊醇和PEG复配后降低表面张力的能力最强,起泡能力和泡沫稳定性最好,这是由于长链与短链协同吸附,在气-液界面形成了紧密结合的吸附层,增强了Gibbs-Ma-rangoni效应,从而提高了泡沫稳定性。     

电解浮选中气泡尺寸对精煤产率的影响

细粒煤的分选一直是选煤业的难点。鉴于电解浮选已成功应用于高岭石等细粒矿物的浮选,采用自制的小型电解浮选槽中,在不同电解质种类及不同电解质浓度条件下探索电解浮选处理细粒煤的效果。试验结果证明,不同的电解质对精煤产率的影响都有最优的电解质浓度,精煤产率最高的电解质是Na2SO4,能达到70.139%;随着电解质浓度的增加,马兰矿8#煤精煤产率最大时气泡尺寸含量最多的粒级范围逐渐减小。     

浮选起泡剂对气泡大小和泡沫稳定性的影响

为了研究起泡剂对气泡大小的影响，采用单孔气泡发生器，多孔气泡发生器和浮选槽进行了试验。试验发现只有使用多孔气泡发生器（或在浮槽中）测定时，气泡大小主要依赖于起泡剂的浓度，起泡剂浓度低时（C＜CCC），气泡大得多，这说明此时气泡兼并是决定气泡大小的主要机理，起泡剂浓度超过临界兼并浓度（CCC）时，气泡兼并可以被阻止。起泡剂起泡性能试验指出，在动力学条件下泡沫的稳定性决定于气泡兼并作用。     

浮选柱泡沫层检测控制系统的研究

针对浮选柱泡沫层检测控制系统的2种方式加以阐述。液位和气含率都是影响矿物浮选指标的因素。液位控制简单直接,但不精确;气含率控制更具体,但成本高于液位控制。利用压差法检测浮选柱气含率进行煤泥浮选试验,并研究循环压力、进气量和起泡剂浓度对气含率的影响以及气含率对煤泥浮选效果的影响。结果表明,起泡剂浓度对气含率的影响最大,进气量次之,循环压力最小。在一定范围内,随着气含率的增大,精煤产率增大,精煤的灰分也随之增大;随着循环压力增大,精煤产率增大,但精煤灰分有所下降。     

浮选柱气含率及其影响因素对煤泥分选的研究

利用压差法检测浮选柱气含率,通过正交设计和煤泥浮选实验,研究循环压力、进气量和起泡剂浓度对气含率的影响以及气含率对煤泥浮选效果的影响.结果表明,起泡剂浓度对气含率的影响最大,进气量次之,循环压力最小.在一定范围内,随着气含率的增大,精煤产率增大,精煤的灰分也随之增大,精煤质量下降.当气含率为24.17%时,精煤产率为87.35%,精煤灰分为10.02%.随着循环压力增大,精煤产率增大,但精煤灰分有所下降.分析指出气含率大小可作为调节浮选柱矿物分选指标的一个参考标准.     

含磁黄铁矿的硫化铜镍矿石浮选时起泡剂作用效率的研究

起泡剂的种类、用量和选择性是优先浮选基本工艺参数之一。起泡剂在液一气界面上吸附，使气泡具有稳定性、牢固性和分散性。浮选中所形成的泡沫应牢固地粘附于浮矿粒上，同时，从浮选槽中刮出时泡沫易于破裂。但泡沫太稳定，使得泡沫产品的输送过程、浓密和过滤大为复杂，降低净化作业的效率。由于混合浮选精矿的分离效果决定于混合浮选回路中形成的泡沫的稳定性和起泡剂的选择性，所以，制定混合一优先浮选流程时对起泡剂的质量和选择性提出了特殊要求。作者研究了RSTron、MHBR、乙醇和oflflF－3起泡剂对含磁黄铁的硫化银镍矿浮选招标…     

不同胺类捕收剂泡沫性能及其机理研究

为了研究十二胺、十四胺、十六胺与癸醚胺中不同的分子结构对泡沫浮选性能的影响，借助高速摄像机等检测设备，对气-液两相体系下气泡大小，气-液-固三相体系下捕收剂的起泡性、单位体积泡沫带矿量和泡沫水回收率等参数进行测量。结果表明：① 在15 ℃、pH=6.0及药剂用量低于临界兼并浓度的条件下，达到临界兼并浓度时气泡索特直径由小到大依次为：十二胺＜癸醚胺＜十四胺＜十六胺；② 随药剂用量的增加，十二胺、十四胺、癸醚胺与石英作用后产生的泡沫体积先增大后减小，十六胺产生的泡沫体积随药剂用量的增加而减小；③ 十二胺的单位体积泡沫带矿量几乎不随药剂用量的改变而改变，十四胺、十六胺、癸醚胺单位体积泡沫带矿量呈先增加后下降的趋势，其中十六胺的变化速率最快，明显高于十二胺和十四胺；④ 随着药剂用量的增加，十二胺、十四胺、十六胺与石英矿物颗粒形成的泡沫水回收率逐渐增加，癸醚胺逐渐下降。⑤ 碰撞几率Pc随气泡索特直径的减小而增加，减小气泡直径是增加浮选回收率的有效手段，但泡沫水回收率随之增加，使得脉石夹带现象严重。     

电解质强化煤泥浮选效果的机制

对电解质强化煤泥浮选效果的机理进行了综述。电解质的添加可以薄化矿物颗粒表面的水化膜,压缩气泡与颗粒表面的双电层,降低气泡与颗粒表面的静电斥力,有利于气泡的矿化。同时电解质有利于阻止气泡的兼并,降低气泡的尺寸,增加浮选体系中微小气泡的数量,提高浮选的动力学,并在一定浓度范围内增加浮选泡沫的稳定性。     

旋流微泡浮选柱提高精煤回收率的试验研究

针对煤炭试样细粒级含量高的特性,依据浮选机试验确定的最优试验工艺条件,利用旋流微泡浮选柱进行了提高精煤回收率的试验,取得了精煤灰分7.78％、产率70.78％的良好分选指标.比较柱浮选和常规浮选试验,结果表明,在精煤灰分相接近的情况下,柱浮选的精煤产率要高9.32％.     

无机盐阳离子对粉煤灰浮选泡沫稳定性的影响研究

粉煤灰中矿物组成的自然属性使得浮选脱炭体系的泡沫稳定性较差,从而影响了未燃炭的有效脱除。通过添加无机盐阳离子的方式来改变粉煤灰浮选矿浆体系的液相性质,研究了不同离子种类和含量对两相泡沫和粉煤灰浮选三相泡沫稳定性的影响,并进行了浮选验证。研究结果表明：无机盐阳离子的添加提高了泡沫的稳定性,阳离子价态越高,这种稳定作用就越明显。利用泡沫稳定性调节中的离子效应,对采自湖北黄石的粉煤灰样品进行了浮选脱炭的验证试验,结果表明：Fe3+对泡沫的稳定作用有效提高了粉煤灰的浮选脱炭效果,与空白浮选体系相比,在Fe3+浓度为3 mmol/L的条件下,浮选低炭灰烧失量由8.85%降低至5.57%,炭脱除率由41.94%提升至74.55%;与添加Fe3+的浮选体系相比,Mg2+和Na+对浮选指标的提高作用依次减弱。     

Case studies on the performance and characterisation of the froth phase in industrial flotation circuits

This paper deals with two separate case studies investigating the froth phase performance and characterisation of two industrial rougher/scavenger flotation circuits. Froth phase performance was quantified using a mass balance approach to estimate froth zone recovery. Measured characteristics of the froth phase included frother solution concentration determined by gas chromatography, and the time taken for an equilibrium froth sample to decay to one-half of its original froth height. The latter measurement is referred to as the ‘froth half-life’ and is strongly linked to froth stability. Special methods and techniques developed to preserve frother in solution and to measure froth half-life are briefly described. The frother type in the first case study was a mixture of straight and branched alcohols, whilst the frother type in the second case study was a mixture of alcohols, aldehydes and triethoxybutane. The first case study focussed on a flotation circuit treating a low grade ore containing only a small fraction of floatable copper sulphide minerals, while the second case study focussed on a flotation circuit treating a higher grade complex sulphide ore containing significant quantities of chalcopyrite, galena, sphalerite and pyrite.It was found that froth zone recovery of valuable mineral generally decreased down-the-bank of the two industrial rougher/scavenger circuits. Moreover, decreases in froth zone recovery significantly limit the overall cell recovery of valuable mineral achievable from the plant scavenger cells. However, the decrease in froth zone recovery could not be linked to the removal of frother from the pulp solution to the concentrate product in the preceding rougher flotation stages. Measurements of residual frother in solution suggested that, approximately, only 5–10% of the added frother was removed into the rougher/scavenger concentrate, with the remainder appearing in the scavenger tailings. This finding suggested there was apparently adequate frother in solution in the scavenger stages.There was, however, a correlation to the froth half-life, with the froth half-life also generally decreasing down-the-bank. A simple, empirical model, based on the froth half-life and froth residence time of gas, is proposed here to predict froth zone recovery. Further, it is proposed that the froth stability, as measured by the froth half-life, is strongly linked to the presence of particles in the froth, with poorly mineralised scavenger froth characterised by a short half-life and, potentially, a low froth zone recovery. The importance of particles on froth stability was confirmed in separately conducted laboratory experiments. These experiments also demonstrated the wide variation in froth stability behaviour between different frother types.     

Dynamic froth stability in froth flotation

A new measure for froth stability is introduced in this work, based on a dynamic stability test for non-overflowing froth columns. The dynamic stability factor represents the lifetime of a bubble in the froth, and is defined as the ratio of the total volume of froth at equilibrium to the volumetric gas rate introduced into the system. Experiments have been carried out at laboratory scale to measure the dynamic stability factor under different operating conditions. Air flowrate and frother concentration were the key operating variables. It was found that the equilibrium height and the dynamic stability factor depend significantly upon both the air flowrate and the frother concentration. Also, the dynamic stability factor and the fraction of air overflowing as unbroken bubbles in batch flotation tests were related and can be used to establish a stability criteria. These measurements will also allow a clearer quantitative link to be formed between froth stability with froth structure and flotation performance.     

Influence of coal particles on froth stability and flotation performance

Solid particles have significant effect on flotation froth. In this research, the effects of coal particles of different size and hydrophobicity on froth stability and flotation performance were studied. The froth stability was measured in both the froth formation and froth decay processes by maximum froth height, froth half-life time and water recovery. The results show that fine particles of moderate hydrophobicity contributed most to maximum froth height in the froth formation process and were most favorable for flotation. Fine hydrophilic particles stabilized the froth in the froth formation process but the froth half-life time was very short due to the high water solid ratio. High hydrophobic particles of both fine and coarse size fractions greatly increased the froth half-life time in the froth decay process. But the froths were very rigid and the maximum froth heights were very low. The presence of fine hydrophobic particles was very unfavorable for the recovery of coarse particles.     

Hydrodynamic theory of rising foam

There is a large body of literature that tries to model flotation based on froth properties with little or no experimental verification of the underlying features. These models adopt the so called channel-dominated theory of foam drainage. There is no experimental evidence to support this foam drainage theory. Instead the new, simple and experimentally validated foam drainage equation of Stevenson (2006a) [Stevenson, P. 2006a. Dimensional analysis of foam drainage. Chem. Eng. Sci. 61, 4503–4510] has been extended to describe the liquid flux and liquid profile in columns of pneumatic froth. The condition for the maximum value of gas rate for froth stability has been described and this shows that there is a maximum volumetric liquid fraction that a foam can exhibit. It is shown that the numerical calculations of liquid profile of Neethling et al. (2003a,b) [Neethling, S.J., Lee, H.T., Cilliers, J.J. 2003a. The recovery of liquid from flowing foams. J. Phys.: Cond. Matter 15, 1563–1576; Neethling, S.J., Lee, H.T., Cilliers, J.J. 2003b. Simple relationships for predicting the recovery of liquid from flowing foams and froths. Miner. Eng. 16, 1123–1130] are incorrect, and this may mean that all of their later simulations of the flotation process are similarly deficient. Instead a simple and accessible method of calculated liquid fraction profiles, both with and without added washwater is shown. In addition, a model for the effect of surface and internal bubble coalescence on the hydrodynamic condition of the froth is presented. It is recognised that the gas–liquid systems considered in the current work are dissimilar to practical mineralised flotation froths and these differences are discussed.     

Influence of gas flow rate and frothers on water recovery in a froth column

Froth plays an important role in the froth flotation separation of minerals. In froth and foam liquid drains away due to gravity until equilibrium is reached and at the same time is carried upwards by the moving gas phase. This paper aims at better understanding of the influence of the superficial gas velocity and frothers on the liquid drainage in foam and liquid recovery rate from the froth column. The obtained experimental data shows that the available standard drainage theory does not properly describe the influence of gas flow rate and Dowfroth 250 frother on the liquid recovery rate. The theory overpredicts the liquid recovery rate from the froth column. The improvement of the standard theory by inclusion of the contribution of the vertex geometry to the liquid drainage in foam does not resolve this problem. It appears that the liquid drainage process in the froth column is controlled by the interfacial properties of the adsorbed surfactants at the gas–liquid interface.     

基于均匀试验设计优化煤泥浮选药剂制度

为了研究浮选药剂制度对煤泥浮选的影响,以水峪选煤厂的煤泥为研究对象,基于均匀试验设计方法建立浮选效果与药剂用量之间的数学模型,考察捕收剂和起泡剂用量对浮选效果的影响。研究结果表明:捕收剂在一定的用量范围内,煤泥浮选效果只与起泡剂用量存在相关关系; 最佳的起泡剂用量为75 g/t,适宜的捕收剂用量为130 g/t; 与现场药剂用量捕收剂257 g/t和起泡剂143 g/t相比,在保证精煤灰分不变的情况下,浮选精煤产率提高0.49 %,可燃体回收率提高0.50 %,浮选完善指标提高0.17 %,捕收剂用量降低127 g/t,起泡剂用量降低68 g/t; 当捕收剂用量在一定范围内时,起泡剂用量是影响浮选效果的关键因素,适宜的起泡剂用量可显著提高煤泥分选效果。     

浮选过程中的泡沫夹带研究进展

细粒矿物浮选过程中,亲水的脉石矿物泡沫夹带进入精矿中,导致精矿品位降低。揭示泡沫排液及排脉石过程中的相关理论,可以为浮选泡沫结构及泡沫夹带行为的研究提供理论基础。浮选过程中的脉石泡沫夹带是一种普遍现象,脉石夹带回收率与精矿水回收率呈线性关系;两相泡沫排液受重力、毛细作用力(表面张力)、黏滞力控制,不同含液率的两相泡沫排液遵循不同的排液公式;三相泡沫的排脉石过程遵循对流—扩散模型,脉石的夹带回收率受三相泡沫排液速率及脉石颗粒浓度分布控制。浮选操作条件、亲水脉石的特性、矿浆特性以及泡沫结构是影响泡沫夹带的主要因素;优化浮选操作条件,改变浮选流程结构和改变药剂制度可以有效降低脉石的泡沫夹带,提高浮选选择性。未来,还需开发表征浮选三相泡沫特征的方法、装置或仪器,三相泡沫的结构及形态、疏水矿物颗粒与亲水脉石颗粒在泡沫中的运动路径及分布规律、浮选三相泡沫排液及排脉石的数学模型还需要进一步的细致研究。另外,降低脉石泡沫夹带的技术对于部分浮选体系虽有一定效果,但脉石的泡沫夹带尚难以消除,须开发一些革命性的技术。     

Flotation frother mixtures: Decoupling the sub-processes of froth stability,froth recovery and entrainment

The flotation process consists of two distinct phases: the pulp and froth phase. One of the main roles of the froth phase is to create a suitable environment for the separation of floatable, valuable minerals from non-selectively recovered, entrained gangue minerals. As a result the froth phase plays a significant role in the metallurgical performance of industrial flotation cells. Froth stability is important for the recovery of valuable minerals. However, a stable froth may contribute to increased entrainment and, consequently, a lower grade.This study compares the effect of frother mixtures with that of their single component frothers on the froth stability, froth recovery and entrainment of a platinum-bearing UG2 ore using polyglycol and alcohol frothers. The study showed that frother mixtures resulted in a greater froth stability than either of their component frothers. The increased froth stability was reflected in increased froth recoveries and greater overall recoveries. However, the important aspect in the use of frother blends was that they altered the froth structure and resulted in a lower degree of entrainment. This, together with the increased recovery, resulted in higher grades of valuable mineral recovered to the concentrate when using the frother mixtures.