Measurement of magnetic susceptibility in titanium minerals processing

Cavanough, Gary (2004). Measurement of magnetic susceptibility in titanium minerals processing PhD Thesis, School of Engineering, The University of Queensland.

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Author Cavanough, Gary
Thesis Title Measurement of magnetic susceptibility in titanium minerals processing
School, Centre or Institute School of Engineering
Institution The University of Queensland
Publication date 2004
Thesis type PhD Thesis
Supervisor Dr. Peter Holtham
Dr Toni Kojovic
Total pages 151
Collection year 2004
Language eng
Subjects L
290702 Mineral Processing
640300 First Stage Treatment of Ores and Minerals
291301 Process Metallurgy
640205 Other non-ferrous ores (e.g. copper, zinc)
Formatted abstract
Magnetic separation is routinely used in the processing of titanium minerals, and the efficiency of these operations can be determined by measuring the magnetic properties of the process streams. The valuable components in the feed to a titanium minerals plant have specific magnetic susceptibilities ranging from -10-9 m3kg-1(zircon) to 10-6 m3kg-1 (ilmenite). However, in an industrial environment, in which the mineral temperature may range from 20 to 120°C, it is difficult to measure susceptibilities lower than about 10-7 m3kg-1. Hence laboratory testing of spot samples from magnetic separators is currently required to obtain accurate performance data. This is an inherently slow process and where feed grades are variable, optimum performance of separators is generally not achieved.

This thesis describes the development of an inductance-based instrument for measuring down to low levels of magnetic susceptibility online in harsh plant environments. The major difficulties in developing this device were temperature induced changes in the resistance/ capacitance of the inductance coil and phase stability of the inductance coil excitation current. Coil temperature problems were solved by using a physical small coil in batch operation. Phase stability was overcome by designing a phase extraction system that used the coil excitation phase information as part of the phase extraction algorithm.

Investigations were made into calibration and measurement error of the instrument. Calibration at low levels of magnetic susceptibility was performed using a range of chemical salts. For higher susceptibilities no well defined calibration standards were found and a method to measure high levels of susceptibility was formulated. The method relies on diluting the highly magnetic material with salt to prevent magnetic interaction between particles. It was found that the resolution of the electronics was the most significant error and the homogeneity of the sample the least significant.

Plant samples were tested and the device was able to determine the zircon content in a zircon magnetics circuit, determine the TiO2 content in the non-mag stream of a magnetic circuit, determine the iron content in the mag stream of a magnetic circuit and determine the metallic iron content of reduced ilmenite.

The device has also been used in a system to determine the mass distribution of the magnetic properties of a titanium mineral sample in less that 1 minute. Previously, the distribution was determined using a laboratory scale magnetic separator (e.g. an Ore Sorters Permroll), with it taking approximately 40 minutes to process each sample. The system is best described as an hourglass with mineral flowing from a hopper through a small inductance coil. The impedance of the coil is proportional to the mean magnetic susceptibility of the number of particles within the coil (i.e. each measurement is the mean magnetic susceptibility of a fixed size group of particles). An algorithm has been developed to determine the percentage of the feed material at each level of magnetic susceptibility. Hence the results are identical to those determined using a laboratory magnetic separation. Accuracy of the device has been proven by simulation and by testing of plant samples using the new system and comparing the results with measurements made using a Permroll separator.

The thesis also presents recommendations for future work and future potential applications of magnetic susceptibility measurement to mass flow of titanium minerals, measurement of moisture content and jigging operations.
Keyword Titanium metallurgy

Document type: Thesis
Collection: UQ Theses (RHD) - UQ staff and students only
Citation counts: Google Scholar Search Google Scholar
Created: Fri, 24 Aug 2007, 18:28:02 EST