Abstract:In order to examine the leaching rate of potassium chloride from the sintering dust by water, surface morphology and inner structure of the dust, especially the existing state of potassium chloride, were observed by scanning electron microscopy (SEM) and linear scanning technique via energy dispersive spectroscopy (EDS). The characterization shows that the sintering dusts are mostly porous composites or agglomerates of the fine dust particles with size less than 10 μm, and the potassium chloride and sodium chloride particles are partly covered by other water insoluble matters in the dust which consist of elements iron, calcium and etc. Exposure of potassium chloride in the agglomerated dust matrix of this kind suggests that the leaching can be simply perceived as the dissolution of water soluble matters in the dust. On-line monitor of specific electrical conductivity of the leaching system verifies the prediction that leaching kinetics of potassium chloride from the sintering dust fits dissolution model well. Leaching equilibrium can be reached within 5 min with potassium leaching ratio more than 95%.

Key words: potassium chloride; sintering dust; leaching; kinetics; surface exposure