High solids concentration agitation for minerals process intensification

Abstract

in Wiley Online Library (wileyonlinelibrary.com).By using mixing intensification involving high solids concentration as a means to achieve process intensification for the mineral process industry is discussed here. Improving agitator energy efficiency is essential for operating at high solids concentrations. It is shown that improved agitator energy efficiency can be achieved by removing baffles and using higher power number impellers at high solids loadings. Power consumption (50-80%) reductions were demonstrated in the experiments. It is also suggested that slurry stratification in tanks can be used to boost either solids residence time or slurry mass flow. Basic equations related to solids residence time and solids throughput are presented for guidance toward minerals process intensification. An example on doubling throughput via intensification is presented.

Reduced IMRs in a mixing tank via agitation improvement

“…in slurries such as that made of sand and water, the mixing is not an issue. The mixing time in this regime is so short in comparison with the process time scale that achieving good mixing is not normally an issue (Wu et al, 2011). Other process condition could be more important, e.g.…”

“…It is useful to alert to the readers that removal of baffles is more energy efficient for solids suspension at high Reynolds numbers, contrary to the low Reynolds number situations in this paper. Refer to Wu et al (2011) and Wang et al (2012) for more detailed information on this topic. …”

“…Mixing vessels are critical for bulk materials chemical slurry processing such as leaching, digestion, crystallization, adsorption, ion-exchange and polymerization (Nienow, 1994;Wu et al, 2011). Homogeneous mixing is vital for product blending consistency and purity of the reaction products.…”

Process Intensification in Stirred Tanks

“…A key issue with this approach is elevated agitation power consumption. The agitator power tends to increase rapidly with the solids concentration at high solids loadings, particularly as the solids concentration approaches the solids packing condition [6,16,17]. One solution to this problem is to remove the baffles, which are traditionally used in stirred tanks.…”

“…Large-scale mechanically stirred slurry tanks are used extensively in the minerals processing industry, where a large number of them are employed for continuous hydrometallurgical operations such as leaching, digestion, oxidation, and precipitation due to the long residence time required and the large ore material flux involved [6]. New minerals refineries built in recent years show a trend of increasingly large tanks being used for ore processing.…”