Fine coal circuitry considerations in treatment of soft coal with difficult washabilities

A typical process used in Chinese metallurgical coal preparation plants employs heavy-media separation to treat the coal coarser than 0.5 mm. The − 0.5 mm fine coal is treated with froth flotation. A major disadvantage of this process is that a large quantity of fine coal is recycled in the heavy-media cyclone circuit, which results in high magnetite losses. The − 0.5 mm fine coal in the media is a result of poor raw coal deslime screen efficiency and the continuous breakage associated with the processing of soft coal. Another disadvantage of this typical process is that some coarse clean coal particles are lost to the froth flotation tailings. This investigation focuses on the simulation of processing fine soft coal with water-only cyclone (WOC) and spirals. WOCs and spirals have become popular devices for treating fine coal. WOCs can operate at low specific gravity cut points to produce low ash clean coal while spirals tends to operate at high specific gravity cut points and act as a scavenger to rewash the underflow (refuse) from WOCs. The combination of WOCs and spirals can compete with a heavy-media cyclone with respect to both efficiency and clean coal yield when treating 1 mm × 100 Mesh fine coal. This fine coal processing circuit can subsequently increase the bottom size of the heavy-media cyclone feed from 0.5 mm to 1 mm which will reduce the loading of the heavy-media cyclone circuit. This change in circuitry thus reduces magnetite consumption without scarifying separation efficiency of the 1 mm × 0 size fraction. Furthermore, the reduction of the nominal top size of the froth flotation feed from 0.5 mm to 0.15 mm will greatly decrease or eliminate the loss of clean coal to flotation tailings.     

浮选药剂联合使用及其在煤泥浮选中的应用研究

由于药剂协同作用的存在,在将高活性的芳烃MA捕收剂和高选择性的煤油捕收剂混合使用的时候,完善指标最高可超过53,在MA含量为0.4的时候精煤产率和灰分可达为81.8%和11.85%,相对于单一使用MA或煤油在保持高产率的同时,起到了降低灰分,提高完善指标的作用。     

Influences of Jameson flotation operation variables on the kinetics and recovery of unburned carbon

The purpose of this study was to investigate the influences of Jameson flotation operation variables on the recovery and kinetics of unburned carbon (UC). The waste sample of petroleum coke, filter powder or fly ash, used in the experiments was collected from lime calcination plant tailings. The effect of Jameson flotation parameters on the recovery and kinetics efficiencies of UC was systematically studied. The feasibility of separating unburned carbon and refuse was determined from the combustible recovery (CR) and ash reduction (AR) (%) curves. Within the range studied, the optimum diesel oil dosage was 3500 g/tonne, pine oil dosage was 2500 g/tonne, pulp density was 15%, wash water rate was 0.17 cm/s and downcomer immersion depth was 50 cm. The results indicate that the Jameson flotation technique is effective in removing the UC from waste filter powder. Furthermore, the classical first-order kinetic flotation model (R = R_∞ [1 − exp (− k ? t)]) was applied to data from the tests. The model was evaluated by statistical technique, after non-linear regression on the model parameters. It is found that the classical first order flotation kinetic model, most extensively used among flotation models, fits the tests data very well.     

Enhanced desulfurizing flotation of high sulfur coal by sonoelectrochemical method

Enhanced desulfurizing flotation of high sulfur coal was investigated using the sonoelectrochemical method. The supporting electrolyte used in this process was calcium hydroxide and the additive was anhydrous ethanol. The effects of treatment conditions on desulfurization were studied by a single-factor method. The conditions include anhydrous ethanol concentration, sonoelectrolytic time, current density, and ultrasound intensity. For the coal sample with a particle size of − 0.076 mm, the optimal experimental conditions achieved for anhydrous ethanol, sonoelectrolytic time, current density, and ultrasound intensity are 2.1 mol/L, 20 min, 15 × 10^− 3 A/cm², and 1.2 W/cm², respectively. Optimal conditions cause a sulfur reduction of up to 75.4%. The raw and treated coals were analyzed by infrared spectroscopy and a chemical method. Pyritic sulfur, organic sulfur, and ash are partially removed. Compared with enhanced flotation by ultrasound or electrochemistry, desulfurizing flotation of high sulfur coal by sonoelectrochemistry is an effective technology.     

提高细粒煤分选回收的策略研究

分析了某矿小于0.5 mm粒级煤样的粒度和密度组成;分别采用单一浮选工艺流程和"TBS+浮选"的工艺进行对比实验;结果表明,单一浮选实验精煤产率只有41.74%,而窄粒级的粗煤泥在TBS中能够得到较好的分选,与浮选的综合精煤产率高达64.91%。     

Optimization of some parameters in column flotation and a comparison of conventional cell and column cell in terms of flotation performance

In this study, a comparative evaluation was made between column and mechanical flotation cells for fine coal cleaning. In addition, the optimum values of operating parameters were examined, which are important to achieve a desired separation performance in column flotation, such as the frother concentration, the collector dosage, the froth thickness, the wash water rate, the air rate and the feeding rate. The coal sample was collected from a classifying cyclone overflow stream consisting of nominally −130 μm material. Ash, volatile mater, fixed carbon and total sulfur contents of the sample were found to be 47.50%, 20.80%, 31.70% and 0.75%, respectively. Comparison of the column and mechanical flotation results indicated that column flotation was considerably more efficient than mechanical flotation for fine coal cleaning. High froth thickness and wash water addition during column flotation made it possible to obtain cleaner coals. The column flotation produced a 15.60% product ash with a 50.92% clean coal yield and 81.85% combustible recovery.     

Enhancement in hydrophobicity of low rank coal by surfactants — A critical overview

The flotation of fine (− 0.5 mm) low rank or oxidized coal is difficult to achieve with the common coal flotation collectors like kerosene, fuel oil or diesel oil (oily collector). The presence of small amounts of oxygen is enough to cause oxidation. The oxidation of coals starts with the physical adsorption of oxygen on the surface to form an oxycomplex followed by chemical adsorption of oxygen to form polar phenolic-OH, carbonyls, phenols and peroxide type oxygenated moieties by the rupture of cyclic rings. The addition of promoter, surfactant or oxygenated functional groups to the collector molecule markedly enhances the flotation of lower rank and oxidized coals due to the hydrogen bonding with the polar part of the coal surface and the reagent. The performance of these reagents is compared with that of oily collectors, namely kerosene, dodecane, nonylbenzene and polar part of the surfactant having an oxygen atom. The mode of addition of non-ionic surfactant with oily collector also has a major role in the flotation response. The addition of non-ionic surfactant after the oily collector has shown a positive effect on yield and grade.     

细粒难浮煤泥浮选试验研究

分析了内蒙古能源中心选煤厂煤泥性质,说明试验煤泥是以高灰细泥为主的极难浮煤;高灰细泥在浮选过程中容易因夹带、黏附作用而进入精煤,影响精煤质量。通过探索试验发现,煤浆质量浓度为40∥L,捕收剂、起泡剂用量均为1．0kg／t时,煤泥浮选效果最好,此时精煤产率为53．53％,灰分为13．92％,但仍未达到厂家要求。为将精煤灰分降至11％以下,对煤泥进行二次浮选试验。当煤浆质量浓度为50g／L,捕收剂、起泡剂用量均为1．5kg／t,搅拌时间为1min时,二次浮选效果最好,此时精煤产率为52．78％,精煤灰分为10．14％,中煤产率为6．57％,中煤灰分为57．30％,尾煤产率为40．65％,尾煤灰分为76．81％,中煤可直接出售。二次浮选工艺可有效降低精煤灰分,提高精煤产率,解决了煤泥难浮问题,满足了生产需求。     

望峰岗选煤厂煤泥可浮性研究

通过对望峰岗选煤厂煤泥性质的分析,说明入浮平均粒度较粗,各粒级煤泥灰分均在30％以上,嵌布较均匀,单体解离度低,为浮选降灰带来困难;煤泥表面接触角较小为50．06。,说明其天然可浮性较差,经捕收剂十二烷或柴油处理后,煤泥接触角增大,煤的可浮性提高;若要求精煤灰分为14％,则标准浮选精煤产率约为65％。通过单因素试验确定煤浆质量浓度为80g／L,捕收剂用量为800∥t,起泡剂用量为128g／t时,煤泥浮选效果较好,浮选完善度最高为66．94％,精煤灰分符合要求,精煤产率较高为71．67％。最后以捕收剂、起泡剂和煤浆质量浓度为正交因素设计正交试验,考察各因素对煤泥可浮性的影响,并得出最佳浮选药剂制度。结果表明：当捕收剂用量为1000g／t,起泡剂用量为42g／t,煤浆质量浓度为60g／L时,煤泥浮选效果最好,此时精煤产率为71．59％,精煤灰分为14．30％,达到高产降灰的目的。     

煤泥可浮性曲线的绘制及应用

介绍了依据煤炭H-R可选性曲线的基本形式绘制煤泥可浮性曲线的步骤:根据煤泥分步释放浮选试验结果,分别绘制出精煤曲线β、尾煤曲线θ、灰分特性曲线λ、产率曲线γ和精煤灰分±0.5%含量曲线ε;在A选煤厂的应用实践表明,该曲线可较好的预测煤泥浮选效果。     

Comparative study of the performance of conventional and column flotation when treating coking coal fines

Investigations were carried out on coking coal fines by conventional cell and column flotation techniques. The effects of different operating parameters were evaluated for both conventional and column flotation. The coal fines were collected from Bhojudih washery, India. These coal fines averaged 24.4% ash, 19.8% volatile matter and 53.8% fixed carbon on a dry basis. A commercial grade sodium silicate, light diesel oil and pine oil were used as depressant, collector and frother respectively. The flotation performance was compared with release analysis. The conventional flotation results indicated that a clean coal with 14.4% ash could be obtained at 78.0% yield with 88.4% combustible recovery. The ash of the clean coal could be further reduced to 10.1% at 72.0% yield with 85.6% combustible recovery by using column flotation. The column flotation results were close to those obtained by release analysis.     

Flotation response of coal washery reject fines: Characteristics,process optimization,and oxidation

The present paper outlines the characterization, electrokinetic behaviour, and flotation response of rejected coking coal fines with 32.5% ash generated in a coal washery in Eastern India. The response methodology and central composite rotatable design (RSM-CCRD) were used for the process modelling and optimization of the flotation process using diesel, methyl isobutyl carbinol (MIBC), and sodium hexametaphosphate as a collector, frother, and depressant to maximize ash reduction, yield, and combustible recovery. At optimum condition, a 9.7% clean ash coal was achieved with a 63% yield at collector, frother, and depressant dosages of 0.78, 0.31, and 0.80 kg/ton, respectively. The model prediction and experimental data corroborated sufficiently. Subsequently, within 1 year, the fines oxidized and did not float with the collector. Fourier-transform infrared spectroscopy (FTIR) confirmed surface oxidation on oxidized coal. The oxidized coal responded favourably to acid oil, a vegetable oil refinery waste. With acid oil as a collector, the oxidized coal can upgrade to 12% clean ash coal with a 60% yield; the combustible recovered is 80%. The work indicates successful upgradation of fresh and oxidized coal using the froth flotation process.     

Rationalization of the up-grading circuit of celestite for advanced applications

The conversion of celestite into other strontium compounds, mainly strontium carbonate, is a necessary step for many industrial applications. However, the impurities need to be removed to achieve a suitable celestite grade (> 90% SrSO₄) for the conversion process.Therefore, this paper is aimed at celestite separation from calcite using gravity separation (i.e., jig and shaking table). The jig was used to deal with coarse sizes (− 15 + 2.0 mm) while shaking table was used to deal with finer sizes (− 0.5 + 0.080 mm) or cleaning the jig tailings after further regrinding to − 0.5 mm. Moreover, the shaking table separation was evaluated in terms of its operating parameters using statistical design of experiments. Starting from the primary crushed − 0.5 + 0.080 mm fraction contains 44.91% SrO (79.58% SrSO₄), a celestite concentrate 51.88%SrO (91.93% SrSO₄) was produced at optimum conditions; i.e., 25%, 3 cm, 25 l/min, and 6 degree for pulp density, stroke length, water flow rate, and table slope, respectively.     

应用射流浮选柱分选微细煤泥的试验研究

介绍了细粒煤分选技术的发展现状和射流浮选柱具有的浮选速度快、分选精度高、综合性能显著优于传统机械搅拌式浮选机的特点。试验表明 ,在精煤灰分相近的情况下 ,射流浮选柱浮选微细煤泥的精煤产率明显高于机械搅拌式浮选机 ;在精煤产率相近的情况下 ,前者的精煤灰分比后者的低 2 0 %～ 3 0 %。     

FCSMC-3000旋流—静态微泡浮选柱运行实践

兴华焦化厂采用静态微泡浮选柱技术回收煤泥中的精煤,当入料矿浆浓度为８０ｇ／Ｌ,灰分为１１％～１４％时,精煤回收率可达８０％,精煤灰分稳定在６％左右;回收的精煤掺入炼焦精煤中,生产的焦炭仍能达到出口焦炭质量标准。     

Direct measurement of entrainment in large flotation cells

A key response variable to describe the metallurgical performance in a flotation cell is the concentrate grade. The mineral feed characteristics and conditioning determine the grade of the particles attached directly to the surfaces of the bubbles by true flotation, while the operating conditions, such as gas rate, bubble size, froth depth and others, determine the amount of gangue recovered by entrainment, which finally decreases the concentrate grade.In this paper, the recovery of liquid and solids by entrainment was evaluated by direct measurement of the fraction of liquid and solids reported to the concentrate in a 130 m³ mechanical flotation cell.The liquid and solids entrainment, per size classes (+ 150; − 150 + 45; − 45 µm), was measured by the radioactive tracer technique. The procedure consisted of introducing a tracer impulse at the cell feed entrance. The tracer time response was monitored on-line at the concentrate overflow and at the tailings discharge. Also, in order to obtain the quantitative distribution of the feed, samples were taken periodically from the concentrate and tailings streams, for a period of 4 residence times, during the tracer tests. This allowed the quantification of the mass of tracer reporting to both streams.Experimental results confirmed that solids entrainment with the froth was strongly dependent on particle size, and that the entrainment factor (EF = solid/water recovery ratio) was similar to that reported for smaller size cells under similar operations conditions.     

表面改质机与微泡浮选机在东曲矿选煤厂的应用

东曲矿选煤厂因入浮煤泥可浮性差、浮选设备能力不足,使浮选作业效率低;通过增设表面改质机,并用两台微泡浮选机替换了两台旧的浮选机,明显改善了分选效果;在浮选精煤灰分变化较小的情况下,浮选精煤产率提高约8%~10%,总精煤产率提高约1.6%~2.0%,取得了可观的经济效益。     

唐家河选煤厂煤泥水系统改造

分析了唐家河选煤厂煤泥水系统工艺流程,并在此基础上进行了煤泥水采样试验研究。结果表明:中矸煤泥水灰分高于原生煤泥灰分,直接进入浓缩机会造成精煤损失,降低尾煤灰分;进入中煤和矸石段的悬浮液较多,悬浮液中-0.3 mm粒级未得到有效分选;浮选尾矿灰分高于压滤煤泥灰分;中矸浓缩旋流器溢流、中矸高频筛筛下水直接进入浓缩机是造成唐家河选煤厂尾煤灰分偏低的主要原因。通过将中矸浓缩旋流器溢流、中矸高频筛筛下水导入浮选系统,在浮选机原有一、二室通道基础上增加通过面积,即一、二室小流量短路改造,实现了尾煤灰分、精煤产率和入浮煤泥量的提高。改造后,在精煤灰分相近的情况下,唐家河选煤厂浮选尾煤灰分提高了7.28%,每年增加精煤销售收入555.98万元。     

新华含稀土磷矿浮选实验研究

采用反浮选工艺,研究了抑制剂种类及用量、捕收剂WF-01用量、浮选时间、矿浆浓度和磨矿细度等因素对新华含稀土磷矿浮选效果的影响,并对较佳浮选条件下获得的磷精矿和尾矿进行了稀土分析. 结果表明,浮选剂选用WF-01,工业硫酸不适宜单独作为此矿样浮选时磷矿物的抑制剂,而采用工业磷酸作为抑制剂和矿浆pH值调整剂,在磷酸用量9 kg/t、捕收剂WF-01用量0.8 kg/t、浮选时间9 min、磨矿细度82%为-74 mm、矿浆浓度35%的浮选条件下,可获得较好的浮选和稀土富集效果,磷精矿的P2O5品位可从原矿的21.71%增加到32%以上,回收率达到90%;在浮选过程中稀土主要富集在磷精矿中,富集比为1.56,在精矿中的含量为87.09%.     

Beneficiation of fine coal by using the free jet flotation system

The free jet flotation system was developed at the Berlin Technical University in 1985. This system was able to treat ultrafine particles of about −53 μm. In the present study, the fine size fraction of the coal (−0.5 mm) containing 45% ash taken from the Zonguldak Central Washery Plant (ZCWP) of Turkish Hard Coal was beneficiated by using the free jet flotation system. In the flotation tests, the best results were obtained in the case of using a mixture of 90% kerosene and 10% iso-octanol in the amount of 400 g/ton as a collector. Also, the optimum system parameters of a 30 l free jet type flotation (FJFT) cell used in this study were determined from the results of systematic tests. In the optimum free jet flotation conditions, the floating coal containing 18.73% ash with a combustible recovery of 72.4% was obtained.