Klinkau filter elements are being used in treatment plants within the mining industry. Their most frequent application is for dewatering coal and coal-fine tailings as well as ore concentrates such as zinc, iron, copper and noble metals. These concentrates emerge from the flotation process where they then undergo dewatering to reach the required maximum permissible water content (TMC) for transportation. High-capacity processing is required so quick cycle times are necessary. Filtration times are reduced to a minimum resulting in high flow rates combined with abrasion in the fill channels and inlets/outlets. This is also the case for drying at the end of the filtration cycle where the water in the cake’s pores is blown out. Metals from the ore concentrates are solubilized using mineral acids and then chemically dissolved before being separated in a precipitation process. Membrane filter plates are preferred here to achieve high yields during cake washing. The filter material used here needs to have a high level of chemical resistance as well being able to cope with high temperatures.
Specific examples of mining applications
Copper ore concentrate
A flotation process separates ground copper ore from its mineral by-products. The size of the ore particles requires the use of chamber filter plates and squeezing using membrane filter plates. Residual water in the filter cake is easily extracted in a subsequent blow drying procedure. The filter elements are therefore equipped with replaceable inserts at the filtrate drainage outlets. Filter cloths are then protected and their service lives extended.
Iron ore concentrate
To reduce flow rates and the anticipated abrasion at the inlets and outlets, Klinkau membrane filter plates are made with the largest possible inlet/outlet sizes. If required, the elements can also be equipped with multiple inlets which substantially reduce flow rates and help the elements to perform securely. Cycle times can then be shortened to a minimum and major filter press capacities achieved.
Coal tailings are being increasingly used as fuel. Tailings in coals fines are separated from other minerals during the flotation process and then dewatered in a membrane filter press. The Klinkau membrane filter plates used here have all the required design features such as enlarged inlet/outlet sections and replaceable inserts, as well as using moveable filter cloths to provide fully automated cake release.
Zinc ore concentrate
To achieve a high level of TS content in the filter cake, a process of intense blow drying takes place following filtration and squeezing. The filter plate's outlet areas therefore have cross sections that are as large as possible to reduce air speed and keep abrasion to a minimum. The filter elements are also equipped with wear plates at the filter drainage outlets to protect the filter cloths.
Metal refineries use membrane filter presses not only for the different processing areas but also for dewatering process sludges, e.g. for filtering the goethite and gypsum residues which are products of zinc smelting and contain high levels of iron. The cake is eventually deposited in landfills. The dewatering efficiency of Klinkau membrane filter plates is therefore crucial. TS values required for landfill disposals can already be achieved at filtration pressures of 8 bar and squeeze pressures of 16 bar.
Quarzite sand is an important raw material within the chemicals and glass industries. The sand undergoes wet classification with the separate fractions undergoing dewatering using membrane filter presses. Profitable dewatering results can already be achieved with filtration pressures of up to 10 bar and squeezing at 15 bar. The overhang version of Klinkau's replaceable membrane filter plates has major benefits due to a robust design and easy to replace membranes.
Kaolin varies greatly in its filtering depending on grain-size distribution. Coarse types of kaolin can therefore be adequately dewatered with chamber filter presses, usually at filtration pressures of 8 or 15 bar. Dewatering of fine types of kaolin is more profitable using membrane plate technology due to the much shortened filtration times. The membranes also enable extra squeezing of residual water despite the highly malleable filter cake. Thermal drying of kaolin is costly so membrane filter plates are gradually added until a squeeze pressure of up to 30 bar is reached. Thermal drying (TCD: see products and technologies) of the kaolin cake within the membrane filter press offers an interesting business option.