Laboratory and Pilot Scale Studies of Potassium Extraction from K-feldspar Decomposition with CaCl2 and CaCO3

Processes for potassium extraction from abundant K-feldspar have recently attracted interest to ensure potash self-sufficiency for developing countries. Concurrently, distiller waste and soda residue formed in the ammonia-soda process (Solvay method) have resulted in serious pollution. A method of potassium extraction from K-feldspar with distiller waste and soda residue as additives is proposed. The effects of roasting temperature, particle size of K-feldspar and the amount of additive on potassium extraction for the K-feldspar-CaCl2-CaCO3 system were studied. The reaction kinetics of the system with mass ratios of K-feldspar (106-160 mu m) : CaCl2 : CaCO3 = 1 : 2 : 2 at 750-850 degrees C were modeled by the diffusion-based Ginstling-Brounshtein equation. The apparent activation energy was approximately 111 kJ.mol(-1). On the basis of the XRD and SEM-EDS analysis, two different reaction mechanisms were proposed below and above the melting point of CaCl2 (772 degrees C). A pilot test was carried out at a roasting temperature of 850 degrees C and the recovery of potassium was approximately 82%. The encouraging results obtained in the laboratory were replicated at the pilot scale.