Quantitative determination of modal content and morphological properties of coal sulphides by digital image analysis as a tool to check their flotation behaviour

An efficient depression of coal sulphides in the flotation process means a healthier environment and may be essential for the sustainability of a coal operation. Nitric and ferric oxidative pre-treatment of coal pyrite have been tested to improve pyrite depression, and the results are compared with those from the process of raw, not pre-treated coal. The removal indexes point to nitric pre-treatment as the best, but depression is still low. The microscopic study of feed and products, coupled to Digital Image Analysis (DIA) in all the cases, provide important clues to understand the behaviour of pyrite, which can be related to quantitative parameters, such as the exposition ratio (ER), and to qualified interpretation of the textures. Pyrite shows in the first float an unexpected hydrophobic behaviour, which is due to its occurrence as framboids, or porous particles which may be intergrown with organic matter and behave as coal. In general, the flotation results can be predicted from the DIA-data, e.g. depression of liberated pyrite into the tailings, increased by oxidative pre-treatments by 300% (ferric) or by > 400% (nitric); or concentration of middlings with lower pyrite ER in the floats. DIA is an efficient tool to obtain some important quantitative informations which otherwise would be inaccessible (e.g. the morphological data on > 1,000,000 pyrite particles for this study), and its use should be enhanced to check ore processing

Investigation of exergy ratios of a solar pond

In this paper, we present an experimental and theoretical investigation for exergetic assessment of a rectangular solar pond (with dimensions of 2 m × 2 m × 1.5 m) at various reference temperatures. The experimental solar pond was designed and built at Cukurova University in Adana, Turkey. The system was filled with salty water to form three zones (namely, Upper Convective Zone (UCZ), Non-Convective Zone (NCZ), and Low Convective Zone (LCZ)) accordingly. A data acquisition device was used to measure the temperatures hourly at various locations in the pond. An exergy model was developed to study the exergetic performance of the pond for its three zones in terms of exergy efficiencies. The lowest and highest reference environment temperatures for various days in the months were considered. The results show that the efficiency ratios of the LCZ are found to be higher than the corresponding the NCZ and also the UCZ. © Springer International Publishing Switzerland 2014