Abstract: To better make use of sparingly soluble K-bearing ore and extract potassium chloride, halite and limestone were chosen as the composite additive for the calcination of sparingly soluble K-bearing ore.The influence of Na/K mol ratio, calcination temperature and time, limestone amount, volatility of K and Na on the potassium extraction rate was investigated.K extraction rate of 84.6% is obtained for the sample with Na/K mol ratio of 4 and limestone amount of 12.5wt%, calcined at 900 ℃ for 90 min.The phase analysis of the filter slag from leaching the calcined product was analyzed by XRD and the mechanism of NaCl and CaCO3 for the decomposition of potassium feldspar was discussed.The mass ratio of the NaCl-CaCO3 composite additive to sparingly soluble K-bearing ore is 0.73.Compared with other systems, the additive amount is largely reduced.

Key words: sparingly soluble K-bearing ore;K-feldspar;additive;K extraction rate;NaCl;CaCO3