Mark S. Klima

Dense-medium separation of heavy-metal particles from soil using a wide-angle hydrocyclone

Abstract Wide‐angle hydrocyclone tests were conducted to separate fine (‐150 μm) particles based on differences in particle density. Mixtures of ferrosilicon (FeSi) and quartz or lead and soil of similar size ranges were separated in a 25.4 mm diameter hydrocyclone under various test conditions. Separations were made in dense‐medium suspensions of fine magnetite and water to improve the overall separation efficiency compared to water‐only separations. For the FeSi/quartz mixture, when the suspension relative density was raised to 1.4, FeSi recoveries exceeding 89% with quartz recoveries over 90% were obtained in a single pass through the hydrocyclone. For the lead/soil mixture, lead recoveries exceeding 97% with soil recoveries over 95% were possible at a suspension relative density of 1.3.

Multi‐stage wide‐angle hydrocyclone circuits for removing fine, high density particles from a low density soil matrix

Abstract Simulations were performed for various hydrocyclone staging arrangements using experimental results from single‐stage wide‐angle hydrocyclone separations when processing fine (‐150 μm) particles in a 25 mm diameter hydrocyclone. Mixtures of fine quartz and magnetite or ferrosilicon of similar size ranges were used to represent low density (e.g., soil) and high density (e.g., heavy metal contaminant) particles, respectively. The staging arrangements included re‐treating the overflow and/or underflow streams in both once‐through and recirculating circuits. The results indicated that heavy metal recoveries greater than 95% with soil rejections over 90% could be obtained for the ferrosilicon/quartz system using a three‐stage circuit. Lower metal recoveries were obtained when processing the lower density magnetite.

Using Model Discrimination to Select a Mathematical Function for Generating Separation Curves

A statistical technique, known as model discrimination, is presented for selecting a mathematical function to fit separation data in order to estimate the characteristic parameters — the relative density of separation and the probable error. Some of the more commonly used functions are compared by their goodness of fit and their parameters evaluated statistically using a sensitivity analysis approach in order to determine the function with the best fit and the maximum parameter sensitivity. Application of this technique is demonstrated using sets of separation data from actual heavy media cyclone operations. For separator data exhibiting apparent bypassing, i.e., a fraction of feed apparently exiting with the clean coal and/or a fraction of feed apparently exiting with the refuse, a modelling technique is given whereby an existing function can be expanded to incorporate the bypass parameters.

Evaluation of a Pilot-Scale, Plate-and-Frame Filter Press for Dewatering Thickener Underflow Slurries from Bituminous Coal-Cleaning Plants

Laboratory testing was conducted to evaluate the performance of a pilot-scale, plate-and-frame filter press for dewatering bituminous coal slurries. The fully automated filter press is manufactured by T.H. Minerals and is equipped with a hydraulic system, which operates the plate and diaphragm feed pumps. The filter press is capable of achieving an operating pressure of up to 1035 kPa. The unit contains a single set of plates having a filtration area of 0.45 × 0.45 m. Thickener underflow samples were collected from two bituminous coal-cleaning plants located in Pennsylvania. The first sample (Plant 1) was nominal −840 µm and had an ash value of 39.2%. It contained approximately 34% of −25 µm material with an ash value of 64.5%. The second sample (Plant 2) was nominal −150 µm and had an ash value of 17.5%. It contained approximately 65% of −25 µm material with an ash value of 20.9%. Testing was conducted to evaluate the effects of filter time, air-drying time, and air-blow pressure on filtrate flow, filtrate solids content, final cake moisture, and filter press unit capacity. For Plant 1, product moistures ranged from 23.5% to 25.6% with filtrate solids content ranging from 1% to 2% solids by weight. The unit capacities ranged from 45 kg/hr/m2 to 70 kg/hr/m2. For Plant 2, product moistures ranged from 16.1% to 21.6% with filtrate solids less than 0.1% by weight. The unit capacities ranged from 117 kg/hr/m2 to 168 kg/hr/m2. In both cases, low cake moistures were associated with lower unit capacities. The results indicate that the filter press is capable of producing handleable filter cakes without the use of additional flocculants.

An Interpolation Methodology for Washability Data

A methodology for the interpolation of washabilily data is presented. This procedure provides a means whereby the washability data for both the weight and the attributes (e.g., ash, sulfur, etc.) can be interpolated for any size and/or relative density interval desired. Unlike some techniques which rely on the interpolation of interval values, this technique involves the interpolation of cumulative values. Since point values are used, there is no ambiguity as to what size or relative density corresponds to which interval value.

Dense-medium cycloning of fine coal refuse material

Laboratory testing was carried out to evaluate the performance of a dense-medium cyclone for treating fine coal refuse. The tested material was obtained from the feed stream to a water-only cyclone circuit treating nominal −0.6 mm bituminous coal refuse material obtained from an existing waste pile. A 76.2 mm (3 in) diameter cyclone was used for all tests, which were carried out at three medium relative densities, with and without ultrasonic treatment. Fractional recovery (partition) curves were generated for several size fractions (g) from which the characteristic performance parameters (relative density of separation and probable error) were determined. In addition, the corresponding magnetite size selectivity parameters (cut size, sharpness index, and apparent bypass) were also determined. The results indicated that the dense-medium cyclone was capable of cleaning down to 0.037 mm. Ultrasonic treatment appeared to have only minimal impact on the overall separation of the coal and magnetite.

Application of an Unsteady-State Pulp-Partition Model to Dense-Medium Separations

Abstract Since there has been a growing interest in using gravity concentration techniques for the processing of fine coal (less than about 0.5 mm in size), it is important that a performance prediction procedure is used which is capable of showing differences in the operating conditions of the separator. The generation of fractional recovery or partition curves is one such procedure. A fractional recovery curve is a plot of the fraction of or probability that a given size feed material of a given density reports to the product against the density. This paper derives a mathematical model, based upon the physics of the separation process, from which fractional recovery values can be obtained. The heart of this derivation is the convection-diffusion equation which takes into account both the settling and the mixing of particles within a free-settling-type separator. The fractional recovery curve can be obtained by fitting these values to an appropriate mathematical function. Although the fractional recovery...

Effect of Hydroacoustic Cavitation Treatment on the Spiral Processing of Bituminous Coal

Testing was conducted to evaluate the effects of hydroacoustic cavitation (HAC) treatment on spiral separation when processing nominal −1500 µm Illinois-basin bituminous coal. Cavitation was produced either by flow through an ultrasonic resonator chamber or enhanced cavitation by initial flow through a cavitation box followed by flow through the ultrasonic chamber. After treatment, the slurry was passed through a hydrocyclone for desliming, and the underflow stream was used as spiral feed. Spiral tests were carried out using a two-stage spiral at three volumetric flow rates for different HAC treatment conditions. HAC treatment reduced the overall size distribution of the spiral feed material. Likewise, desliming of the treated material led to a reduction in the ash values for each size interval. For example, after HAC treatment, the ash value of the deslimed material was reduced to 25% compared to 41% for the untreated deslimed material. Subsequent spiral separation of the treated material produced clean coal with an ash value of 15% at a yield of 79% compared to an ash value of 18% at a yield of 59% for the untreated material. HAC treatment had only a minimal effect on sulfur reduction.

An Evaluation of a Two-Stage Spiral Processing Ultrafine Bituminous Coal

Testing was conducted to evaluate the performance of a multistage Multotec SX7 spiral concentrator treating ultrafine bituminous coal. This spiral mimics a two-stage separation in that the refuse is removed after four turns, and the clean coal and middlings are repulped (without water addition) and then separated in the final three turns. Feed samples were collected from the spiral circuit of a coal cleaning plant located in southwestern Pennsylvania. The samples consisted of undeslimed cyclone feed (nominal − 0.15 mm) and deslimed spiral feed (nominal 0.15 × 0.053 mm). Testing was carried out to investigate the effects of slurry flow rate and solids concentration on spiral performance. Detailed size and ash analyses were performed on the spiral feed and product samples. For selected tests, float-sink and sulfur analyses were performed. In nearly all cases, ash reduction occurred down to approximately 0.025 mm, with some sulfur reduction occurring even in the − 0.025 mm interval. The separation of the + 0.025 mm material was not significantly affected by the presence of the − 0.025 mm material when treating the undeslimed feed. The − 0.025 mm material split in approximately the same ratio as the slurry, and the majority of the water traveled to the clean coal stream. This split ultimately increased the overall clean coal ash value. A statistical analysis determined that both flow rate and solids concentration affected the clean coal ash value and yield, though the flow rate had a greater effect on the separation.

Effects of Desliming and Hydroacoustic Cavitation Treatment on the Flotation of Ultrafine Bituminous Coal

ABSTRACT Testing was conducted to evaluate the effects of desliming in combination with hydroacoustic cavitation (HAC) treatment on flotation when processing nominal -150 μm Illinois-basin bituminous coal, which was obtained from a refuse stream at an operating coal-cleaning plant. Cavitation was produced either by flow through an ultrasonic resonator chamber or enhanced cavitation by initial flow through a cavitation chamber followed by flow through the ultrasonic unit. Desliming was carried out using a 102 mm diameter hydrocyclone. Flotation tests were conducted using a laboratory flotation cell for different reagent amounts and flotation times. The results indicated that desliming improved flotation substantially. Moreover, in some cases, HAC treatment provided an additional benefit by liberating ultrafine inorganic material prior to desliming.