No abstract

Devices in process engineering often include permeable components. As shown in our recent work for planar components, laser-beam powder bed fusion offers the opportunity to integrate permeable sections into complex monolithic metal parts in one go. This paper extends the approach to components with curved surfaces. Different scan strategies were investigated for their effects on surface morphology and permeability of tubular samples. It was found that in order to ensure consistent properties of a permeable tube, different starting points or rotation of the scan vectors have to be used.

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.

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.

By offering an opportunity to fulfil environmental and process water recovery specifications, filtration of tailings has received increasing attention. In the process, complete cake detachment is required to maintain high throughputs. Incomplete discharge represents a bottleneck in the process. Therefore, a deeper understanding of cake detachment behaviour is a key to success. Experimental studies on adhesion forces between filter cake and cloth are a first step towards detachment prediction. Filtrations using an FLSmidth lab filter press and subsequent adhesion measurements with iron ore tailings and two different filter media show the influence of filtration pressure on adhesion.