Air-sparged Hydrocyclone Flotation Research Articles

Air bubble and oil droplet interactions in centrifugal fields during air-sparged hydrocyclone flotation

The interactions of air bubbles and oil droplets in centrifugal flotation have been considered with respect to process conditions present during Air-sparged Hydrocyclone (ASH) flotation. Encounter efficiency of oil droplets with air bubbles has been found to be significantly smaller when compared to encounter efficiency of mineral particles. Collision and sliding contact times have been determined. Collision has been found to be insufficient for successful contact between oil droplets and air bubbles while sliding allows for film rupture depending on specific system conditions. Although the tenacity of oil droplet attachment to an air bubble is believed to be greater than the tenacity of a mineral particle, emulsification makes oil flotation in centrifugal devices with large dissipation of energy inefficient and hence requires the use of high molecular weight polymeric flocculants.

Recovery of coke fines from fly ash by air sparged hydrocyclone flotation

Fly ash from a power plant in Gdansk, Poland is stockpiled at two dump sites and contains an average of 15 wt% combustible residue, in the form of very fine coke particles. If recovered, the coke could serve as environmentally friendly fuel or as a source of carbon-derived materials, and the ash could be utilized in the production of construction materials. Since the fly ash material is already wet, a flotation technique was proposed for separation and product recovery. The flotation tests were carried out in a 1-l Denver-type flotation cell and in a 2-inch diameter air-sparged hydrocyclone (ASH). The flotation concentrate from the air-sparged hydrocyclone contained 35% coke by weight on a dry basis, with a coke recovery to the concentrate of 54%. Experimental results are discussed with respect to particle characteristics.

97/01602 Axial flow reversal and its significance in airsparged hydrocyclone (ASH) flotation

In recent years the potential of air-sparged hydrocyclone (ASH) flotation for fine coal cleaning has been demonstrated both in pilot plant testing and in a plant-site demonstration program. Further improvements in the ASH technology will depend, to some extent, on improved understanding of the complex multiphase fluid flow. Froth transport plays a very important role in determining the efficiency of fine coal cleaning by ASH flotation. It should be noted that the surface of zero axial velocity is of particular significance in froth transport because the location of this surface actually accounts for the amount of froth being transported to the overflow. In this regard, the axial flow reversal has been examined based on specially designed tracer experiments. On the basis of these experimental results, modeling efforts were made to characterize the flow pattern in the ASH. The theoretical predictions based on turbulent fluid dynamic considerations were found to describe experimental observations regarding the surface of zero axial velocity. These results that define the surface of zero axial velocity together with froth phase features established from X-ray CT measurements provide an excellent description of the flow characteristics in ASH flotation and explain the effect of various process variables, such asmore » dimensionless area (A*), dimensionless flowrate (Q*), inlet pressure, percent solids, etc., on flotation recovery. On this basis it is expected that further advances in the design and operation of the ASH system can be made, leading to more efficient use of the ASH technology for fine coal cleaning.« less

Swirl flow characteristics and froth phase features in air-sparged hydrocyclone flotation as revealed by X-ray CT analysis

The time-averaged multiphase flow characteristics of air-sparged hydrocyclone flotation have been studied using X-ray computed tomography. Criteria of froth stability and the relationship between froth phase features and flotation response have been established. Quantification of the spatial extent of the different flow regimes has been done in order to characterize the flow behavior during steady-state operation of a nominal 2-inch diameter air-sparged hydrocyclone (ASH-2C). The influence of different operating and design variables on multiphase flow characteristics has also been established.

Bubble generation in swirl flow during air-sparged hydrocyclone flotation

Air-sparged hydrocyclone (ASH) flotation is a new, promising technology, and, since its conception, numerous applications have been successfully tested. Nevertheless, research and development efforts have continued to improve the technology with respect to operating conditions and design considerations.

Flow phenomena and its impact on air-sparged hydrocyclone flotation of quartz

Fluid flow phenomena and therefore the flotation efficiency of air-sparged hydrocyclone (ASH) flotation are strongly dependent on operating and design variables such as air and slurry flow rates, underflow and overflow opening areas, percent solids of the feed, reagent levels, particle size and ASH length. Time-averaged multiphase flow characteristics, as determined by X-ray CT (described in a previous publication), are used to understand and explain the steady-state ASH flotation of quartz. A detailed parametric study of quartz flotation by a nominal 2-in. diam. air-sparged hydrocyclone (ASH-2C) revealed the influence of these variables on the flotation response, which is discussed in terms of the multiphase flow characteristics. Thus, a phenomenological description of quartz flotation has been established to assist in the further development and utilization of the ASH technology.

Removal of insoluble slimes from potash ore by air-sparged hydrocyclone flotation

The presence of insoluble mineral components, typically clay minerals, in potash ores has always been a problem to the potash industry, particularly in the processing of low grade sylvinite ores. The insoluble slimes must be removed prior to potash flotation because of their high affinity for amine collectors used in the subsequent flotation of sylvite. In this regard, air-sparged hydrocyclone (ASH) flotation was examined as a process alternative for the removal of such insoluble slimes from potash ores. The effects of reagent concentration and ASH operating variables on the recovery of insolubles were studied for a typical plant feed from the Saskatchewan potash field. Results indicate that, for single stage ASH flotation, over 70% of the insolubles could be floated from a potash feed containing about 7% insolubles with salt recoveries in the underflow product exceeding 92%. These results with a 2-inch air sparged hydrocyclone suggest that high specific capacity ASH flotation, 100 times the specific capacity of conventional flotation, is a viable process alternative for the removal of insoluble slimes from potash ores.

Peculiar process of coal tar pitch carbonization (textural and physicochemical characterization)

The presence of insoluble mineral components, typically clay minerals, in potash ores has always been a problem to the potash industry, particularly in the processing of low grade sylvinite ores. The insoluble slimes must be removed prior to potash flotation because of their high affinity for amine collectors used in the subsequent flotation of sylvite. In this regard, air-sparged hydrocyclone (ASH) flotation was examined as a process alternative for the removal of such insoluble slimes from potash ores. The effects of reagent concentration and ASH operating variables on the recovery of insolubles were studied for a typical plant feed from the Saskatchewan potash field. Results indicate that, for single stage ASH flotation, over 70% of the insolubles could be floated from a potash feed containing about 7% insolubles with salt recoveries in the underflow product exceeding 92%. These results with a 2-inch air sparged hydrocyclone suggest that high specific capacity ASH flotation, 100 times the specific capacity of conventional flotation, is a viable process alternative for the removal of insoluble slimes from potash ores.

Dimensionless Analysis of Process Variables in Air-Sparged Hydrocyclone ( ASH ) Flotation of Fine Coal

Abstract Fine coal cleaning by froth flotation in a 2-inch air-sparged hydrocyclone (ASH) has been investigated and the effects of important design and operating variables on separation efficiency examined. In order to reduce the complexity of the analysis, the flotation performance of the air-sparged hydrocyclone was studied by dimensionless analysis. As a result of these efforts, an empirical model was derived to predict the flotation effectiveness of the air-sparged hydrocyclone unit of various levels of design and operating variables, thus allowing for optimization of the flotation separation. Since the model is based on dimensionless analysis, it is anticipated that subsequent development efforts to scale-up the ASH flotation system for industrial utilization will be facilitated

4838434 Air sparged hydrocyclone flotation apparatus and methods for separating particles from a particulate suspension: Jan Miller, Y Yi assigned to University of Utah

Material balance packages are used to estimate unmeasured variables and upgrade the measured ones in mineral processing plants. The reliability of such estimates strongly depends on the data structure. Their variance-covariance matrix is here derived to evaluate the reliability of estimated flowrates, dilutions, particle size distributions and chemical assays. A relationship is shown to relate estimates reliability to the degree of redundancy of data. An illustration is given for a flotation plant.

Froth Characteristics in Air-sparged Hydrocyclone Flotation

Abstract Air-sparged hydrocyclone flotation is a new technology that has been under development during the past decade. This technology combines froth flotation principles together with the flow characteristics of a hydrocyclone such that the air-sparged hydrocyclone system can perform flotation separations in a matter of seconds or even less. The most important feature of the air-sparged hydrocyclone is its high specific capacity which corresponds to significant savings in capital cost (equipment and floor space). In air-sparged hydrocyclone flotation, the slurry is in swirl flow having high tangential and axial velocities. Both concentrate product (froth) and tailings are formed and discharged at high velocities. These unique fluid-flow features have a significant effect on the nature of the froth phase created and the corresponding transport properties. Froth characteristics and froth control as currently understood are emphasized in this chapter which reviews the state-of-the-art in air-sparged hydroc...