Globally, mining operators focus increasingly on tailings filtration to recover process water and store tailings more safely. Generally, required water contents below 20-w% are reached by using filter presses. To maintain high efficiency, complete cake detachment is needed because incomplete discharge reduces plant performance. However, filter cake discharge can occur in different ways, mainly influenced by adhesion of the filter cake to the filter cloth as well as by cohesion of the cake. Therefore, this study points out different major detachment behaviors and a theoretical approach to describe them. Furthermore, investigations on iron ore tailings filtrations were carried out to show the influences of different filter media, different filtration pressure and cake post-treatment on adhesion and cohesion.
The global growth in demand for raw materials is leading to a continuous increase in the mining of ores and thus to an expanding volume of tailings to be stored. To ensure safer storage and an optimized recovery of process water, the tailings slurry is often thickened followed by filtration in filter presses and dry stacking. However, an increasing blinding effect during the time of operation requires cleaning or replacement of the filter media. Cloth washing using spray nozzles is a possible solution, but there is insufficient quantitative data published on the performance. For this reason, this article examines the cleaning of an iron ore cloth from tailings filtration by continuous water spraying. Water flux, spray time and direction (front- and back-wash) variation were investigated by evaluating cleaning performance using flow resistance measurement and comparison to the unused and industrially used state where blinding has occurred. Sufficient cleaning and achieving the flow rate of the unused cloth is possible. However, excessive spray cleaning should be avoided, as damage to the fibers may occur. Spray cleaning can be stated to be economically reasonable since a water demand of 2.5 m3 m−2 and an energy consumption of 391 kWh m−2 is necessary for a sufficient regeneration. Furthermore, the spray cleaning is assumed to cost USD 39 m−2, which is approximately similar to replacing the fabric but reduces plastic waste.
Currently, the storage of ore processing residues is a major challenge in the mining industry. These tailings are increasingly filtered in advance of disposal using filter presses to make storage safer and to recover water effectively. However, the falling of the detached filter cakes between the individual filtration cycles results in the abrasive wear of the filter cloths at specific points of the chamber geometry and is a main reason for the necessity of a regular replacement. Improved filter media selection through abrasion testing replicating this specific load case increases plant economics by reducing the risk of unplanned downtimes. Therefore, this article explains a test procedure adapted to the direction-specific wear. A brush apparatus is presented, which abrasively loads filter fabrics stretched over an exchangeable edge geometry uniaxially in one direction. The effects of important apparatus setting parameters (sample clamping torque, brush overlap, and brush speed) are shown. Furthermore, the resistances of three different filter media typical for tailings filtration were compared and different edge geometries investigated. Thereby, significant differences were found with regard to filter media type, filter media material, and edge geometry. Depending on the edge geometry used, the polypropylene fabric withstands a load amount by a factor of 3.3 to 8.9 higher than the nonwoven polypropylene, the nylon fabric withstands a load amount by a factor of 3.6 to 5.3 higher than the polypropylene fabric and the nylon cloth withstands a load amount by a factor of 16.1 to 31.8 higher than the nonwoven polypropylene.
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