Automatic control of a laboratory flotation column

The operation of industrial flotation columns requires the control of at least two variables, the interface position and the bias rate, by manipulation of some appropriate operating variables. Problems arise due to the reliability of existing methods of measuring the bias (i.e bias = tailings water - feed water), a situation which has often forced the industry to disregard this control loop. Moreover, when using such a measuring approach, the identification of the process dynamics is impossible. A second problem arises from the possible interaction between both control loops that might call for the use of a more complex multivariable control strategy.Recent work done at Laval University has demonstrated the feasibility of an independent sensor for bias, which models the relation between the conductivity profile across the interface and the bias value using a neural network algorithm. A 250 cm height, 5.25 cm diameter Plexiglas laboratory column was equipped with a series of conductivity electrodes in its uppermost part (across the interface) to measure both interface position and bias rate. Using such equipment, the flotation column dynamics was identified. The results thus obtained permitted the design and implementation of a distributed PI control strategy, where bias was associated to wash water rate and froth depth to tails rate. Both PI controllers were tuned using a frequency-response tuning method. Results of both identification and process control are presented and discussed.     

浮选柱自动控制技术的发展与应用

针对当前浮选柱自动控制的研究现状,考虑到传统的人工操作系统的局限性与当前自动化的不足之处,以浮选柱的控制机理为出发点,提出其工作原理及其控制的可实施性.主要从加药量控制、液位控制、给矿浓度控制、进气量控制4个方面着重分析控制过程原理及检测仪器的应用情况.其中,加药量控制主要探讨了给定加药量与矿浆流量以及矿浆浓度的关系;...     

浮选柱及其控制技术的研究进展

针对细粒、复杂、低品位的物料分选,浮选柱以其结构简单、占地小和易自动控制等优点倍受青睐。简述了浮选柱的分选特征、性能优势和研究进展,比较了几种常见浮选柱的分选机理、特征和各自的性能优势,重点阐述了浮选柱过程控制参数的特点、控制途径和控制算法的研究进展及存在的不足,展望了浮选柱未来的发展方向。     

Cyclonic-static micro-bubble flotation column

A cyclonic-static micro-bubble flotation column (FCSMC) was developed for mineral separation, particularly for whole flotation circuits. The FCSMC featured multiple mineralisation steps, including countercurrent mineralisation, cyclone mineralisation and pipe flow mineralisation in a single column, through which the mineralisation energy, mineralisation rate and dynamic turbulence intensity gradually increased to compensate for the decrease in the floatability of mineral particles. It thus led to highly efficient mineralisation as well as a sufficient retention time fine mineral recovery. The usability and performance of the FCSMC was assessed and further confirmed by lab-, pilot- and industrial-scale units based on magnetite ore. The iron concentrate grade reached 69% with a recovery of 95%.     

Arsenopyrite enrichment by column flotation

Arsenic-rich, gold-bearing pyrite concentrates may be further enriched in arsenic to assist subsequent Au beneficiation. Among several amines tested in refloating a local Chalkidiki pyrite concentrate, 2-coco 2-methyl ammonium chloride proved successful by raising the grade from 9% to 22%, although total solids recovery was low. The use of a froth-stabilizing frother was also benefecial to the process. Optimum hydrohynamic conditions were: intermediate pulp flowrate, low wash water and gas flowrate; the latter abated the mixing/dispersion process in the collection zone.     

Selectivity in phosphate column flotation

The objective of this work was the study of the selectivity of apatite flotation in a column by means of kinetic analysis. The recovery and apatite content in the concentrate were correlated to the collector dosage, depressant dosage and air flow rate. The test results were subjected to statistical analysis aimed at identifying the experimental conditions producing the best P₂O₅ content and recovery.     

浮选机－浮选柱联合分选某硫铁矿尾矿试验研究

以广东云浮某硫铁矿选矿厂的浮选尾矿为样品,采用浮选机-浮选柱联合分选工艺进行分选,充分利用浮选机和浮选柱两种设备的特性,在保证粗颗粒回收的同时强化了微细颗粒的回收。对原矿样品的粒度和硫含量进行了分析,结果表明硫主要分布于+74 μm和-10 μm两个粒级中。通过浮选机两次粗选、两次扫选、粗精矿再磨后两次精选流程的闭路试验,可从含硫6.91%的浮选入料中获得品位为33.42%、回收率为63.82%的硫精矿。在相同的药剂用量下,通过浮选机-浮选柱联合分选,可获得品位为32.68%、回收率为70.84%的硫精矿。粒级回收率分析表明,与单一浮选机工艺相比,浮选机-浮选柱联合分选后,-54 μm细粒级的回收率明显提高,尤其是-20 μm粒级,回收率提高了将近10个百分点。     

浮选柱液位自动控制系统设计探讨

浮选柱液位的控制是直接影响回收率及精矿质量的一个重要因素.本文从控制策略的确定、液位探测与传感装置的比较、执行机构的选择、管路的设计等方面对浮选柱矿浆液位自动控制系统进行了初步研究,并分析了两种较为典型的浮选柱液位自动控制系统.     

旋流微泡浮选柱和机械搅拌式浮选机工艺效果对比

简要介绍了邢台矿选煤厂煤泥处理工艺流程,详细分析了浮选柱与浮选机各自的分选原理和特点,并根据邢台矿选煤厂工艺流程和入浮煤泥性质,通过对选前脱泥与不脱泥重介条件下旋流微泡浮选柱和机械搅拌式浮选机浮选工艺效果的分析,对比了两种浮选设备的分选工艺效果。     

Bubble spargers in column flotation: Adaptation to precipitate flotation

The limiting factor for metal-organic precipitate flotation in a column is the level of aggregate stability under the turbulence created by the rising bubbles. The hydrodynamic conditions in a 75 mm diameter pilot column were optimised by using different bubble spargers (Microcel, Flotaire, Imox) and by varying the gas flow rate into the bubble sparger, feed flow rate in the column, type and concentration of frother and recirculating pump flow rate. With the bubble spargers used, the average bubble diameter ranges from 0.30 and 1.10 mm, with up to 25% gas hold-up. The parameters influencing average bubble diameter are the superficial gas velocity and the recirculating pump flow rate. For optimal concentrations (10 to 20 mg/1), the type of frother has a negligible role.Strong interaction occurs between superficial gas and feed velocities and recirculating pump flow rate for bubble size control. The optimum operating conditions must accordingly be maintained to prevent carryover of small bubbles into the recirculating pump or the purified solution. An example of the Mo precipitate flotation confirms the assumption made for the effect of bubble size and dissipation energy on the separation results. reserved.     

Dynamic model of a flotation column

A linear multivariable model for a flotation column is derived from process analysis and experimental data. The data have been taken from a pilot-scale column (height 720 cm; diameter 5.1 cm) with all necessary instrumentation installed. The flotation column was operated in a water-air system. The model has been derived aimed at utilisation in the design of the control system. The model describes the relationship between controlled variables (froth layer height, bias and air holdup in the recovery zone) and manipulated variables (wash water, air and non-floated fraction flowrates). It has been validated comparing the experimental data with those obtained from simulations. Finally, the conditions under which the model is applicable are presented.     

炼焦中煤柱浮选试验研究

以山西新裕选煤厂重介中煤为研究对象,通过破碎、细磨释放中煤有机组分,利用旋流和无旋流两种进气结构的浮选柱进行了浮选对比试验,研究结果表明:旋流进气结构的浮选柱在大充气量时,中煤可燃体回收率可达66.67%;无旋流进气结构的浮选柱在较小的充气量时,中煤浮选产品灰分可降至10.31%。在此基础上,针对中煤特点提出了"重选+粗选+精选"的中煤再选工艺。     

基于PID参数模糊自整定的浮选床液位控制研究

针对浮选床液位这种大滞后、大惯性且难以建立精确的数学模型的控制对象,采用模糊自整定PID复合控制,根据浮选柱内的液位变化迅速由模糊控制策略调整自身的PID参数,从而快速稳定浮选床的液位值。结果表明,对于浮选床液位的控制,采用该算法的控制精度高,响应速度快,可满足浮选生产工艺过程中对浮选床液位的调节要求。     

Assessment of expert fuzzy controllers for conventional flotation plants

Many undesirable dynamic characteristics are present in conventional flotation plants that hinder the design and implementation of control systems. New expert and fuzzy control strategies for these processes are presented and assessed here via simulation. The algorithms are based on previous work, and they emulate current operating practices in an active copper flotation plant in Chile. The new controllers were able to achieve high recoveries and also avoid control saturation despite severe disturbances in the feed flowrate.     

浮选柱泡沫层厚度自动控制系统的设计和实现

为解决邢台矿选煤厂FCMC旋流微泡浮选柱液位波动较大、控制精度低、调整不及时的问题,设计了一套泡沫层厚度自动控制系统。该系统上位机采用研华工控机,触摸屏选用西门子SMART1000,控制器为西门子S7-200PLC,传感器为超声波液位计,执行机构为电控液动推杆。通过合理设计,该厂浮选柱泡沫层厚度实现了闭环控制,液位稳定性得到了提高,保证了产品数质量指标。     

Selective detachment process in column flotation froth

The selectivity in flotation columns involving the separation of particles of varying degrees of floatability is based on differential flotation rates in the collection zone, reflux action between the froth and collection zones, and differential detachment rates in the froth zone. Using well-known theoretical models describing the separation process and experimental data, froth zone and overall flotation recovery values were quantified for particles in an anthracite coal that have a wide range of floatability potential. For highly floatable particles, froth recovery had a very minimal impact on overall recovery while the recovery of weakly floatable material was decreased substantially by reductions in froth recovery values. In addition, under carrying-capacity limiting conditions, selectivity was enhanced by the preferential detachment of the weakly floatable material. Based on this concept, highly floatable material was added directly into the froth zone when treating the anthracite coal. The enriched froth phase reduced the product ash content of the anthracite product by five absolute percentage points while maintaining a constant recovery value.     

Recovery of coal fines using column flotation

Tests carried out on 100mm dia × 2300mm high flotation column using coal fines from the coking coal washeries at Sudamdih, Patherdih, Kathara and Moonidih (India) have shown that the performance of the column is superior to that of the conventional cells with respect to the grade and recovery of the product. The column is found to operate efficiently both on coarse and fine fractions in the feed. The reasons for the superior performance of the flotation column have been analysed.     

浮选柱充填方式及其优化

分析了最常用的填料充填与筛板充填两种方式对浮选环境的作用,并指出：筛板充填整合了浮选柱内的流态和矿化环境,具有稳定气泡、提高浮选和矿化效率的作用.试验结果表明,柱体灰分梯度由充填前的1.62%/m提高到6.80%/m;填料充填可“清洗”泡沫层,降低精煤灰分,稳定泡沫层.提出了在浮选柱中下部采用筛板充填和精选泡沫区采用填料充填的混合充填方式,使浮选柱内真正形成符合矿物分选过程非线性变化的两种分选环境.通过充填方式的优化,提出了筛板充填和蜂窝管充填的混合充填方式.模拟结果表明：蜂窝管的强制性抑制使浮选柱内第2筛板高度处流体的径向分散完全消失,轴向速度已经基本平稳,实现了在较短距离内流体从紊流迅速过渡到“塞流”.     

单相混合级联整流器新型控制策略研究

针对单相混合级联整流器两种功率模块的不同能量传输特性,对电路拓扑的工作原理进行了详细分析,并且基于数学模型,提出了一种新型控制策略。在此基础上,解决了无桥整流器的电流过零点畸变问题。并与传统控制策略进行了对比,重点对直流侧电压波动与无功功率的关系进行了理论分析和数学推导,并进一步对负载突变时的动态响应速度进行了对比分析,仿真验证了理论分析的正确性和控制策略的有效性,为不同应用场合下选取合适的控制策略提供了重要的理论依据。     

Level control strategies for flotation cells

Flotation is a difficult process to run efficiently. One way to make flotation performance better is to improve cell level control. However, controlling pulp levels in flotation cells is a complex control task because of strong interactions between the levels in flotation cells. Therefore advanced controllers are needed to give good level control. This paper deals with a model of six flotation cells in series. Simulations are performed to compare different control strategies. Four control strategies are considered: one SISO controller and three different MIMO controllers including a new multivariable controller. It is shown that level control performances of the MIMO controllers are significantly better than that of the classical SISO controller.