Extraction of Si from Alkaline-Roasted Boron Ore Concentrate

The process of alkali roasting boron ore concentrate was proposed for the problems existing in the process of boron ore concentrate smelting. In the paper the influencing factors included molar ratio of alkali to boron ore concentrate, roasting temperature, and roasting time were investigated. The single experiment and orthogonal experiments show the optimal conditions for roasting under the conditions evaluated include a temperature of 550oC, roasting time of 60 min, and a molar ratio of alkali to ore of 3:1. In the roasting process, the Si extraction correlated with the shrinking core model assuming a solid product layer according to XRD and SEM. Thus, the kinetics is controlled by diffusion through the product layer. The apparent activation energy for Si extraction was 13.47kJ•mol-1, and the roasting rate can be expressed as: 1-(2/3α)-(1-α)2/3=1.428×10-2exp(-13470/RT)t