| Potassium chloride (KCl) is an important kind of potassium fertilizers and is the raw materials to product potassium sulfate (K2SO4) and potassium nitrate (KNO3). KCl is mainly produced by normal flotation and reverse flotation methods. And normal flotation technique is the one which is widely used in the potash industry in China (over80%plants) because of its capacity of utilizing low-grad ores and reducing energy consumption. Qinghai region is the largest area of KCl prodution in China. There are still many problems in KC1production in this area, such as excessive water consuming in ore decomposition process, high KC1content in tail liquid, serious NaCl entrainment of products, low flotation recovery of the whole process and serious impact of temperature especially the low temperature on octadecylamine collctor (ODA) used to flotate KCL. The first four problems mentioned above have been solved to some extent by our group currently. However, the influence of low temperature on collectors has not yet been solved. Many problems have been caused by this negative influence, such as decreasing the yearly production time and reducing the full utilization of production apparatus. However, there is few related research on this problem reported at home and abroad. So, it is important to develop a new collector suitable for normal flotation at low temperature. This study aimed at searching a collector of mixed amine by combining different amine collectors, consisting primarily of ODA which has been commonly used in China. The following contents have been completed in this paper:(1) Effect of different amine collectors on the hydrophobicity of KCl crystal surface in KCl saturated brine:Contact angle is an important parameter to characterize the wetting relationship between solids and liquids, which can be used to measure the effect of collector on the strength of hydrophobicity at the crystal surface. Contact angles were examined to fix the compositions and ratios of the mixed amine preliminarily. The results show that the mixed amine collector with the mole ratio of DDA-20%, ODA-60%and C20-20%produces the most excellent hydrophobic state at the KC1crystal surface, which benefits KCl flotation.(2) Effect of different amine collectors on the surface tension of KCl saturated brine:The surface tension tests were performed to indirectly determine the distribution and aggregation state of collectors in the solution, and to fix the compositions and ratios of the mixed amine collector furthermore. The results show that the mixed amine collector with the mole ratio of DDA-20%, ODA-60%and C20-20%has better surface chemical properties which is conducive to improve the flotation behavior of KCl particles in theory.(3) Effect of mixed amine on the flotation recovery of KCl at temperatures of5℃and23℃:The micro-flotation tests were carried out to directly examine the effect of mixed amine collector with the definite compositions on the recovery of KCl particles in KCl saturated solution system. The results show that KC1can be more effectively floated by the mixed amine collector with the composition of DDA-20%, ODA-60%and C20-20%, as suggested by the average15%increase of KC1recovery ratio compared to ODA. The recovery of KCl by using the mixed amine collector is higher than that by using ODA at low temperature. Therefore, it obviously demonstrate that this mixed amine collector can be used at both room temperature and low temperature.(4) Studies of the mechanism of mixed amine collector:According to the related theories on the amine collectors in KCl flotaion process, the theoretical model, turbidity measurements and particle size experiments were performed to interpret the action principle of mixed amine collector at high or low concentration respectively. The results illustrate that with the addition of C20, the precipitation amount of mixed amine collector increases, meanwhile, with the addition of DDA, the dispersion of collector in the brine is improved. These changes all benefit the increase of the flotation recovery of KCl particles. In brief, this study provides an experimental basis for solving the collector problem from using ODA only at low temperature. At the same time, the mixed amine collector obtained by this work is a new collector choice for the KC1production in Qinghai, China. |
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