Distribution behavior of valuable elements in oxygen-enriched top-blown smelting process of waste printed circuit boards

Oxygen-enriched top-blown smelting is a promising technology for processing waste printed circuit boards (WPCBs). The distribution behavior of valuable elements in WPCBs during smelting was investigated by varying the oxygen-enriched concentration, oxygen volume, CaO/SiO2 (mass ratio), and Fe/SiO2 (mass ratio). The optimal operating conditions were obtained by implementing a one-factor-at-a-time method. X-ray diffractometer, scanning electron microscopy-energy dispersive spectrometer, and inductive coupled plasma-atomic emission spectroscopy methods were utilized to detect the chemical composition, occurrence state as well as elemental contents of alloy and slag. It is found that the elements of Cu, Sn and Ni are mainly accumulated in the alloy while Fe is mainly oxidized into the slag. The direct yields of Cu, Sn and Ni are 90.18%, 85.32% and 81.10% under the optimal conditions of temperature 1250 °C, oxygen-enriched concentration 30%, oxygen volume 24 L, CaO/SiO2 mass ratio 0.55, and Fe/SiO2 mass ratio 1.05. The results show that the valuable metals are mainly lost in the slag through mechanical entrainment. © 2024 The Nonferrous Metals Society of China