Investigation of the moisture classification and moisture removal behavior of diamond wire saw silicon powder waste cake

Abstract

When processing silicon wafers for photovoltaic power generation, approximately 35 % of high-purity silicon is lost as a diamond wire saw silicon powder (DWSSP) waste cake with a high moisture content. The high moisture content of DWSSP results in the oxidation of high-purity silicon, which hinders the recovery and utilization of silicon resources. Disappointingly, a method for the removal of moisture from the DWSSP waste cake, which is crucial for silicon recovery, has not yet been revealed. In the present study, a novel investigation was conducted to determine the moisture classification of a DWSSP waste cake and to reveal the moisture removal behavior. The results indicate that the moisture content in the DWSSP waste cake can be divided into two distinct categories: surface adsorbed water and capillary water. Moreover, the kinetics analysis and simulation demonstrated that the elimination of moisture predominantly takes place during the constant-rate period and the falling-rate period. Increasing the drying temperature and reducing the equivalent diameter of the DWSSP waste cake will contribute to improving the efficiency of moisture removal. The application of the findings of this study can help to reduce the harmful environmental impacts of DWSSP and achieve the efficient recovery of silicon resources.