Screen blinding is one of the most common operations failures in mineral processing, and this phenomenon entails screen aperture clogging by particles. Vibrating screens are electromechanical equipment used for separation of heterogeneous aggregates into size fractions. In the case of processing wet, sticky ores, which have a high amount of surface moisture and contain clay slime, fine particles are attached to the wire mesh, forming a barrier layer (Geng et al., 2023).
In this regard, the main reason for such a process can be found in the presence of strong cohesive forces produced by external moisture. With the rise of ore moisture content, there occur capillary and surface effects creating adhesive connections between mineral particles and screening deck. These particles form agglomerations that block the holes on a deck; then, new material comes through these areas, causing even quicker blinding of the whole screening deck.
Blinding of screens poses serious problems for overall process efficiency. The more the apertures become clogged, the smaller the area of effective openings of the screen becomes, thus greatly decreasing the efficiency of the machine. In result, fine particles cannot penetrate through the screen to be transferred to the undersize product and get trapped in the oversize product stream. Such poor sorting creates problems in further crushing and grinding processes causing energy waste and low efficiency of mineral recovery (Ortega-Rivas, 2016).
For the solution to these issues, the mining industry utilizes vibrating flip-flow screens (VFFS). Instead of a rigid screen, a VFFS employs an extremely elastic polyurethane sieve mat in the two-mass system. Tremendous acceleration of particles is caused by the elastic vibrations of the polyurethane mat due to the motion of the primary frame against the floating one; therefore, the particles are thrown out, and the agglomerates are divided into wedge-shaped pieces (Geng et al., 2023).
Apart from flip-flow technique, modern materials used for the construction of the screen deck provide secondary solutions. In the case of rigid-flexible coupled screen surface, the structural integrity is complemented with very flexible components in order to provide the screen with the optimal vibration frequency that would help get rid of sticky coatings. Moreover, the use of electrically heated screen decks is possible; in these units the layer of the moist material that touches the wires is dried out, thus breaking the moisture tension, after which the normal vibrations will shake off the stuck particles.
In summary, dealing with sticky ore calls for specific mechanical measures due to the continuous danger of screen blinding. Using the mentioned technologies and applying proper screen deck materials allows preventing the blockage of apertures.
References
Geng, R., Yu, C., Wang, Y., Wang, X., Zhang, X., & Li, R. (2023). Effect of external moisture content on screening performance of vibrating flip-flow screen and circular vibrating screen. Minerals, 13(5), 585. https://doi.org/10.3390/min13050585
Ortega-Rivas, E. (2016). Unit operations of particulate solids. CRC Press. https://doi.org/10.1201/b11059
