Process Optimization And Flotation Mechanism Analysis Of KCl Preparation From Complex Minerals Of Sodium, Potasium And Magnesium

Thanks to the great efforts from workers and researchers over30years, the technology of the potassium chloride production has been neck by neck with or even exceeded the ones in Israel and other advanced countries, the output capacity of potassium chloride has stood on the way of stable growth, the level of the self sufficiency of potassium chloride has increased gradually as well. According to statistics, potassium chloride production was3.2million tons and potassium sulfate production was1million tons in2011, which lead to the outstanding self-sufficiency rate of40%. However, China is still under resources scarcity in soluble potassium, which is of about0.7billion tons potassium resources. To ensure the national agricultural security, transformation technology of carnallitite in salt lake and insoluble potassium resources, seeking oversea potassium resources and meeting the growing demand of domestic potash resources have become China’s potash fertilizer industry’s inevitable choices.Process optimization and flotation mechanism analysis of KCl preparation from complex minerals of sodium, potassium and magnesium from overseas inorganic potassium-abundent ore were discussed in this paper.Firstly, the concentration of the soluble and insoluble substance in potash mineral was studied. Furthermore, the form, characteristics and particle size distribution of potassium ore was investigated in detail. NaCl, KCl, MgCl2, CaCl2, a small amount of Na2SO4and clay were the main compositions of the ore. Judging from the mineral composition, KCl existed mainly in the form of carnallite and grew adhesively with the growth of MgCl2. Meanwhile, sylvine ore (KCl-NaCl) was mixed in the mineral. NaCl was in cubic crystal structure and aparted from carnallite. The surface of carnallite was covered with a few ultrafine grained sodium chloride.To seperate the sodium salt, the best process was flotation. The adsorption properties of octadecylamine hydrochloride(ODH) on KCl and NaCl surfaces were studuied by density functional theory. The simulation results showed that N atom of ODH was the active spot with strong negative charge, K top and Na top were the best adsorption spots of KCl(100) with oxygen defect and NaCl(100) with F color. The most favorable adsorption position of ODH was A3-K-top, of which the adsorption energy was-157.38kJ/mol. The lowest energy position of ODH on NaCl(100) surface was B3-Na-top, of which the adsorption energy was -23.24kJ/mol. When ODH was absorbed on KC1(100) surface, the atomic charge of N varied from-0.258e to-0.406e. Consequently, KC1can be floated with ODH collectors. However, halite cannot be floated with ODH.Based on the mineral characteristics analysis and theoretical calculation, the optimization of cold decomposition-flotation process was further discussed. The effects of temperature, solid content and washing condition on the property of the product were studied in details. Potassium chloride with high purity and recover rate could be obtained at the temperature of25℃, solid content was30%, dosage of ODH was33.5g/t minerals, dosage of2#oil was25g/t minerals, cold decomposition time was30minute and time of flotation was10minute. Final output contained96.05%KC1and KC1recovery rate could be up to83.47%. The tailing contained98.84%NaCl after being washed. Flotation process under high temperature was explored. At35℃, the product contained98.53%KC1and KC1recovery rate was84.65%. Aiming at potassium salt ore with lower percent of MgCl2which may consists of KC1and NaCl, secondary flotation combinational process was developed. The product contained95.06%KC1and KC1recovery rate increased from59.79%to84.41%correspondingly.