THE NATURE OF LITHIUM MINERAL PHYSICAL PROPERTIES IN SELECTING CALCINATION AND ROASTING EQUIPMENT

摘要

Until recently, Talison was essentially the sole supplier of spodumene concentrate to the world. The bulk of the spodumene concentrate had a grade of 6 wt% Li_2O and still remains the bench mark for chemical grade. In addition, the combined spodumene and quartz content comprised roughly 90 wt% and other minerals only 10wt%. The newer spodumenes being offered to the market typically have a lower amount of spodumene and quartz and behave differently in the calcination and/or roasting operations which are typically the first steps in the processing of lithium concentrate to extract the lithium. Furthermore, many of the new ores require flotation of a significant portion of the ore in order to achieve the grade and this results in a finer concentrate. Similarly, the secondary lithium mineral concentrates, such as lithium micas and clays, are also fine (compared with the median particle size of the Talison SC6.0) and contain a larger percentage of other minerals. They are generally more reactive, for example to acids at low temperature. There are a suite of tests that can be performed on a lithium concentrate to determine which equipment is the most suitable for the calcination and or roasting of the ore. The tests that can be considered include elemental analysis, mineralogy, PSD (particle size distribution), TGA (thermogravimetric analysis), DSC (Differential Scanning Calorimetry) and the Heating Microscope Dilatometer. Based on the physical properties a selection of the best equipment can be made for the application with the melting point and PSD of the concentrate being the two main factors to consider. Typically, the range of calciners and roasters available include rotary kilns, fluidised bed kilns, flash calciners, tunnel kilns and multiple hearth furnaces. This paper provides guidance for the selection of the most suitable equipment based on the physical properties of the lithium concentrate.