Study On The Increasing Of KCl Recovery In Industrial Flotation Process

Potassium chloride (KCl) is one important kind of potassium fertilizers, and is produced mainly by normal flotation and/or reverse flotation techniques. The normal flotation technique has been widely used in Chinese potash industry (over 80% plants) because of its capacity of utilizing low-grade ores and reducing energy consumption. The normal flotation technique is mainly composed of decomposition process or crushing process, flotation process and centrifugal process in series with the general recovery of KCl approximate 40%(product purity KCl>90%). The lower recovery and small capacity production may restrict its further application. However, with the rapid consumption of high-grade ores and the increase of low-grade ores, the demand of potash industry for the normal flotation technique increases. So, the research for enhancing the KCl recovery of this technique is of great significance.This paper aims at the lower recovery of potassium chloride in the industrial practice. Based on the survey of production status and theoretical analysis, the key of increasing recovery is to reduce the loss of KCl in the tailings and tail liquid. The tail liquid is from the decomposition process and crushing process, and the tailings are from the flotation process. According to the above mentioned processes, the obtained results are as follows:(1) Research of the decomposition process of carnallite. According to the phase diagram of KCl-NaCl-MgCl2-H2O quaternary system, the effects of washing liquor, temperature and mother liquor composition on the decomposition process were studied. The results show that the recycling of washing liquor can improve the ore grade. The consumption of fresh water is larger at the lower temperature than that at the higher temperature. The ore consumption, fresh water consumption, liquor quantity and pulp quantity decreased rapidly with the increasing of the content of magnesium chloride in the mother liquor; meanwhile, the recovery of potassium chloride and the pulp concentration sharp increased. The decomposition recovery can reach 85.33%. Compared with the original production, the recovery can increase by 19.19%.(2) The impact of adding magnesium chloride to brine on the sylvite processing. According to the sylvite processing, two procedures were designed to add magnesium chloride in the processes, and the effect of magnesium chloride on the potassium chloride production were studied. The results show that adding magnesium chloride can decrease the dissolvability of KCl particles in the wet crushing process of potash ore, resulting in the increasing of KCl recovery without introducing more sodium chloride into the plant.(3) The results on the flotation and washing processes are as follows:On the conditions that the octadecylamine concentration＞8E-5mol/L, the time of rougher flotation≥7min, and pulp concentration being 15～25%, the potash recovery can reach 94.63%. Simultaneously, when washing time of coarse sylvite controled in 8 minutes, and washing water quantity being the 1.0～1.1 times of theoretical value, a good washing efficiency is obtained, and the potash recovery is about 85% with the purity over 96%.(4) Effects of high Mg2+ concentration on KCl flotation. The effects of hydrated Mg2+ on the nature of the solution, the dispersion of octadecylamine, and the flotation of KCl were investigated by combining micro-flotation test, absorption spectroscopy and molecular dynamics simulations (MDS). The results show that the hydration of magnesium ion increases the solution viscosity, and decreases the dispersion of octadecylamine in solution, the adsorption of octadecylamine on KCl surface, as well as the KCl recovery. However, the KCl recovery will be improved by increasing the air flow rate in high Mg2+ concentration brine.(5) Plant experiments for 72-hours. Results of plant experiments show that the recoveries of the normal flotation technique from 39.53% (normal period) and 35.95%(other times) to 48.50% and 47.35% in annual output of 200,000 tons of production line by increasing the recoveries of decomposition process and flotation process with carnallite as raw material in industrial production. Compared with the original production, the water consumption reduced 40.43%(normal period) and 39.61%(other times), tail liquid decreased 34.03%(normal period) and 38.82%(other times), with the content of potassium chloride decreasing from 4.80%～5.28%to 4.29%-4.34%. Similarly, using sylvite as raw material, the normal flotation recovery increased from 41.22%～51.53% to 56%～62% in the production line with 60,000 tons annual output by adding magnesium chloride to brine. The increase of recovery is not less than 10%, and the product qualities reach the standards of industrial grade KCl and agricultural grade KCl.Briefly, this study achieved the goals of optimizing the production process and increasing the KCl recovery. Therefore, it can provide a guidance to certain extent for the industrial application.