A principal component of the Project is the processing plant required to refine the friable sandstone resource. In order to ensure the integrity of the surrounding environment, SCM has decided to process the resource off-site, rather than on-site, as is the case with conventional operations of this nature. In opting to process this way, SCM eliminates the need for the overflow-prone settling dams that are a feature of other similar sand extraction operations. This section provides an overview of the proposed off-site processing plant.
SCM has held commercial discussions with landholders of three sites within the Greater Sydney Area for locating a sand washing and kaolin processing facility. These sites are currently undergoing feasibility analysis and are not yet the subject of commercial confidentiality agreements. As such, they cannot be made public at this stage.
Conceptual Process Flowchart
A basic flow-chart describing the process for production of the various construction sand, specialty sand and kaolin products is shown in the figure below.
The friable sandstone will be washed in attrition cells to remove the kaolin and silt matrix from the loosely bound quartz sand and gravel fraction (particle size <75 μm), and passed through screens to remove the pea gravel (particle size >2 mm). The next process involves hydro-cyclone sizers in which sand (particle size >75 μm), kaolin (particle size <20 μm), and remaining quartz silt (particle size 75 μm-20 μm) are separated.
The specialty sand components are passed through a series of screens to separate into the various grades. Depending on the end product, some of the sands are dried and bagged, whereas others are stockpiled for bulk delivery to end customers.
The kaolin component is passed to a thickening tank where it settles to produce a slurry containing 20% solids. Investigations are underway to determine the feasibility of bacterial beneficiation to further reduce the already very low iron content (see Kaolin spec sheet). If this process is to be implemented, it would occur at this stage. If bacterial beneficiation is not implemented, the kaolin will pass through magnetic separators to remove the lower-grade magnetic component.
The magnetic component, although low in iron content, is not white enough for the higher-value products, and so would be passed through a filter press to significantly lower the moisture content, before being sold as an additive for low value building products (light coloured bricks, tiles, and pavers).
The non-magnetic kaolin component will be passed through a filter press, before proceeding into one of two processes. The first involves drying and crushing to produce white firing kaolin for higher-value bricks, pavers, tiles, ceramics (including sanitaryware), plasterboards, refractory clays, and hydrous rubber fillers. The second involves calcining (heating to between 500°C and 1200°C depending on final application) and crushing to produce a range of products including functional plastics filler, metakaolin for pozzolans (cement additive) or paper and paint fillers (opacifiers).
These processes have been designed in conjunction with Roger Smith and Associates and Stratum Resources, following significant processing and product investigations.
As the proposed Project will employ off-site processing, it will be necessary to obtain approval for an off-site processing facility separately from the extraction site approval. To ensure extraction does not commence without the ability to process the resource, it is anticipated that approval for the Newnes Junction Project will be conditional on SCM securing the relevant consents for a processing facility.
© Sydney Construction Materials 2010