In conjunction with geotextile experts MMS has developed a simple and low cost method of dewatering and drying mineral concentrates using geotextile tubes called Contubes. Contubes are made from high strength woven multifilament pervious polymeric yarn. The nature and size of the pores in the Contubes allows the free flow of clear filtrate out of the tube whilst retaining even the smallest particles inside the tube. Contubes, when dewatered, can be left for a determinate length of time to air dry by evaporation through the pores of the geotextile to a dryness that allows easy further handling. The materials of manufacture allow the outward filtering of water from inside the tube but are impervious to water, such as rainfall, from outside the tube. Contubes can be manufactured to widths of 7m, obtain heights of 5m when full and can be up to 200m in length depending on the hourly and daily feed flow rate requirements.
The mode of operation is to construct Contube Farms on an impervious base (similar to gold heap leach operations). Whilst some tubes are being filled with mineral concentrate, others are passively dewatering and drying and the remainder are being “harvested” i.e. opened and the dry mineral concentrate removed for onward transportation. The process works best in temperate to tropical climates where evaporation rates are higher. There is also the necessity to have available relatively flat land space to locate the Contube Farms. The process can handle dilute to concentrated pulp slurries and, depending on the feed material, can produce a product containing a few percent of moisture that can easily be handled by standard methods. Typically, a mineral slurry feed will dewater and dry down to below 5% moisture in about 15 to 20 days and can then be harvested. The filtrate produced has low suspended solids (< 30ppm) and water recovery is high for recycle back into the process plant.
The process has a very low capital component, mostly incurring operational costs. It replaces the requirement for high capital equipment such as concentrate thickeners, belt or pressure filters and concentrate drying and storage. The used Contube geotextiles can be recycled or can be re-used as an excellent road base for haul roads etc.