Roasting At Low Temperature-smelting At High Temperature To Recycle Value Metals From Waste Printed Circuit Board

In recent years, with the development of Chinese economic and technology,people's living standards improves gradually. The amount of the electronic equipment which has closely relationship with our lives has become more and more larger. This has also lead the number of electronic scrap increased drastically. Electronic waste has the characteristics of high yield, high value metal content, high hazard and so on.This makes electronic waste become a non-general "garbage", we must find the most appropriate way to deal with electronic scrap, so we can get the highest economic and environmental benefits. At present, the recycling of electronic waste has become a major issue all over the world. Our country has disposed the most electronic scrap in the world, so how to solve the problems of electronic waste is a major challenge in China.Printed circuit board is the core parts of electronic equipment. And the printed circuit board contains a higher content of valuable metals, also has more recovery value. This paper takes the waste printed circuit board as the research object. The experiment was carried out by pyrometallurgy, and the experimental process was divided into two steps: roasting and smelting. In this experiment, the mixture of copper slag/zinc volatile slag and Ca O is the fluxing agent, using ability for the collection of precious metals of Cu-Sn alloy to recover valuable metals?Cu?Sn?Au?Ag?Pt?Pd? in the circuit board, and finally obtain the following conclusions:?1?The effects of roasting temperature and time on the weight loss rate were investigated. Temperature at 800-1100 degrees, the time in the 330min-380 min range,the weight loss rate of material change is not obvious, the average weight loss rate was 45%, So the most suitable roasting temperature is 800 degrees, the roasting time is 60 min.?2?In this experiment the Ca O-Fe O-Si O₂-Al₂O₃ quaternary slag type was adopted,and the analog computation was used by thermodynamic simulation software Factsage. Recovery of metals and the slag composition range under optimal test condition condition was predicted. The predicted optimal test conditions were:oxygen partial pressure = 10-9-10-8.5atm, slag former agent was 2 or 3 times to the roasting materials, Ca O amount was 0.1 times to roasting materials, temperature is lower then 1400?, the recovery of Cu?Sn under these conditions were more then90%, slag composition range was Fe O/Si O₂=1.35-1.55, Ca O/Si O₂=0.13-0.46,Al₂O₃=10%-15%.?3?The optimal conditions of smelting is: copper slag experiment: The amount of copper slag is 2.5 times to roasting materials, Ca O amount is 0.1 time to roasting materials, smelting temperature is 1350 ?, smelting time is 30 min. Under these conditions the recovery of Cu?Sn is 97.29% and 98.20% respectively, the recovery of Au?Ag?Pt?Pd is 99.42%?98.27%?98.75%,99.62% respectively.?2?Zinc volatile residue experiment: the smelting temperature and time of the test were consistent with the previous experiment, the main research is the amount of zinc volatile slag and Ca O. Optimal experiment conditions is the amount of zinc volatile slag is 1.5 times to the electronic waste after roasting, and the amount of Ca O is 10% of the roasting materials. Under these conditions the recovery of Cu?Sn?Au?Ag?Pd?Pt is 95.45%?96.55%?95.93%?99.32% respectively.?4?Based on the theoretical analysis and experimental results, the reasonable slag composition of recovery of value metals from waste printed circuit board by pyrometallurgy is Fe/Si O₂=1.07-1.23?w/w?, Ca O/Si O₂=0.15-0.37?w/w?, and Al₂O₃=8.48%¹0.53%.