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Ozer C.E.,Julius Kruttschnitt Mineral Research Center
Minerals Engineering | Year: 2016

A convenient apparatus for density fractionating finely sized coal samples has been developed. It is inexpensive compared with the apparatus used in current methods. The apparatus and method are described, and a possible use of the test results in conjunction with ash content of coal matter is discussed. © 2015 Elsevier Ltd. All rights reserved. Source


Leigh G.M.,Julius Kruttschnitt Mineral Research Center
IEEE Transactions on Signal Processing | Year: 2013

New algorithms for the continuous wavelet transform are developed that are easy to apply, each consisting of a single-pass finite impulse response (FIR) filter, and several times faster than the fastest existing algorithms. The single-pass filter, named WT-FIR-1, is made possible by applying constraint equations to least-squares estimation of filter coefficients, which removes the need for separate low-pass and high-pass filters. Non-dyadic two-scale relations are developed and it is shown that filters based on them can work more efficiently than dyadic ones. Example applications to the Mexican hat wavelet are presented. © 2012 IEEE. Source


Peng Y.,University of Queensland | Bradshaw D.,Julius Kruttschnitt Mineral Research Center
Minerals Engineering | Year: 2012

In this work, the flotation of ultrafine pentlandite and its separation from lizardite in de-ionized water, and bore water of high ionic strength were studied. In de-ionized water, the flotation separation was poor due to low pentlandite recovery and high lizardite entrainment. However, bore water increased pentlandite flotation recovery while reducing lizardite entrainment. The possible mechanisms responsible for the improved flotation separation in bore water were investigated by electrokinetic studies, Scanning Electronic Microscopy (SEM) analysis and settling tests. It was found that the reduction of electrical double layer forces between particles in bore water might mitigate the coating of lizardite particles on pentlandite surfaces resulting in the improved pentlandite flotation. The reduction of electrical double layer forces might also induce the aggregation of lizardite particles and therefore enhance lizardite rejection. This study provides a new direction to address slime coating and high gangue entrainment in ultrafine mineral flotation by electrolytes. © 2012 Elsevier Ltd. All rights reserved. Source


A new method was developed to infer the HGI (Hardgrove Grindability Index) values from the product fineness indicator, t10, predicted by the multi-component breakage model. A total of 41 sets of JKFBC (JK Fine-particle Breakage Characteriser) tests, on coals from Australia and China, plus ores containing various minerals and a clinker, were used to validate this method. The JKFBC and the multi-component breakage model have the potential to improve or replace the traditional HGI test. A new coal grindability index can be generated from the multi-component model parameters. As the major error sources associated with the traditional HGI test have been removed in this new approach, superior repeatability and reproducibility can be expected. More work is recommended in this area to validate this novel approach and to identify its limitations. Simulations were conducted by employing the multi-component breakage model to demonstrate the effects of particle size and density on pulverised fuel (PF) grinding; to troubleshoot the PF production problems related to the coal properties; and to elucidate the observed trend of the non-linear phenomenon of the HGI effect on the PF milling capacity; whereby a 10 unit reduction in HGI from 50 to 40 requires four times more energy than a 10 unit HGI reduction from 90 to 80 in order to achieve the same PF production rate. © 2013 Elsevier Ltd. All rights reserved. Source


Shi F.,Julius Kruttschnitt Mineral Research Center
Fuel | Year: 2014

A multi-component breakage model has been developed at the Julius Kruttschnitt Mineral Research Centre (JKMRC) to describe the energy-size reduction in relation to particle size and density for coal breakage characterisation. The model takes the following form: t10=M/(RD/ RDmin)c ·{1-exp[-fmat·x·E]}. The model incorporates four parameters and fits 60 JKFBC (JK Fine-particle Breakage Characteriser) test data for each of the Australian coal and Chinese coal samples, with R2 = 0.982 and 0.978 respectively. The multi-component model can be switched into a single component model by setting c = 0. A set of tn-family of curves for coals ground in the JKFBC are presented. It was found that the data from various particle sizes and densities of the two coal samples, collected from the Australian and Chinese power stations, all fall on similar tn-curve trend lines. These tn-family of curves can be used in the multi-component model to estimate the product size distribution from the predicted t10 values. A procedure has been developed to calibrate the multi-component model with seven tests based on a combination of various particle sizes, coal densities and grinding energy levels, using the JKFBC device. Over 100 sets of data have been used to validate the calibration procedure. © 2013 Elsevier Ltd. All rights reserved. Source

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