Study On Recovery Of Valuable Metal During High Temperature Smelting Process Of Waste Printed Circuit Board

The valuable metals in the waste printed circuit board are rich in variety and of high economic value,and the organic matter and heavy metal in the waste circuit board are easy to cause harm to the environment,so the recycling of waste printed circuit board has become a hot issue to be solved urgently.The waste circuit board was treated by high temperature melting with industrial waste slag as slag-making agent,it can not only efficiently recover valuable metal,but also effectively deal with industrial waste slag,realize the treatment and use of industrial solid waste,reduce the treatment cost of industrial waste slag and the cost of smelting experiment cost.This paper aims at efficient recovery of valuable metals from waste printed circuit boards,and the research results are as follows:（1）Thermodynamic study of slag system based on Al₂O₃-Si O₂-Fe O-Ca O-1.5Mg O.Based on the selected Al₂O₃-Si O₂-Fe O-Ca O-1.5%Mg O slag system,the slag type of high temperature oxygen-rich top blow smelting process of waste circuit board was selected,and the effects of Ca O content,Mg O content and Fe/Si O₂ on the melting temperature and viscosity of slag were investigated.With the increase of Ca O content,the melting temperature of slag decreases first and then increases,and the viscosity of slag decreases.With the increase of Mg O content,the melting temperature of slag increases and the viscosity of slag decreases.The increase of Fe/Si O₂ will increase the melting temperature of slag and decrease the viscosity of slag.The results showed that the Ca O content is between 9.5%～17.5%,Mg O content is about1.5%,Fe/SiO₂ is between 0.75～1.15,which is the theoretical better slag type range.（2）Experimental study during high temperature Oxygen-enriched top blow smelting of waste printed circuit board.Based on the optimal slag type range obtained from the previous thermodynamic theoretical study,the high temperature oxygen-rich top blow smelting experiment of waste printed circuit board was carried out at 1250℃.The results show that metal recovery is best when oxygen concentration is 30%,oxygen concentration is 24 L,Ca O content is 14.5%and Fe/Si O₂ is 1.05,the yield of Cu,Sn and Ni was 90.18%,85.32%and81.09%respectively.（3）Study on distribution behavior of main elements in high temperature Oxygen-enriched top blow smelting of waste circuit board.The occurrence forms of Cu,Sn,Ni and Fe in the alloy and slag were investigated under different experimental conditions based on the high temperature oxygen-rich top blow smelting experiment of waste printed circuit board.The results showed that the alloy and slag obtained under different smelting conditions were examined by SEM-EDS and XRD.In the process of high temperature oxygen-rich top blow smelting of waste circuit board,metal mainly enters into smelting slag by means of mechanical entraining and chemical loss.Mechanical entraining is the main way of metal entering into smelting slag,and a small part of metal enters into slag by means of chemical loss.The results show that the valuable metals are more easily lost in slag at low oxygen concentration than at high oxygen concentration.With the increase of oxygen content,the metal enters into the slag phase,as the CaO content increases,viscosity decreases,which is beneficial to reduce metal mechanical entraining loss;The increase of Fe/SiO₂ will promote the valuable metals from alloy phase to slag phase in the form of oxidation loss.Under the same conditions,Fe can easily enter into smelting slag than Sn and Ni.