Continuous recycling of diamond wire sawing silicon powder – electron beam melting coupled with continuous feeding technology

Abstract

Diamond Wire Sawing Silicon Powder (DWSSP), as the current major photovoltaic solid waste, how to achieve large-scale recycling has become the focus of the industry’s attention. In this work, a novel approach characterized by enhanced purification, reduced energy consumption, and large-scale recycling capacities was proposed. Focusing on the secondary oxidation of powder, which is difficult to be solved by traditional methods, it was proposed to utilize the electron beam melting technology to achieve rapid melting by its higher energy density and vacuum degree, and reduced the oxygen impurity by 98.4 %. Then, through the prefabricated molten pool and continuous feeding technology, substantially increased the yield of high-purity silicon (91 %) and reduced the energy consumption per unit of production (19.01 kW/kg). Finally, for the purified silicon ingot, the content of major metal impurities was reduced to less than 5 ppmw, and the content of some volatile metal impurities was reduced to less than 1 ppmw. This research demonstrate the feasibility of electron beam melting coupled with continuous feeding technology in realizing low-energy, large-scale and high-purity recycling of DWSSP.