Study On The Metal Recovery Process In The Waste Printed Circuit Board

With the rapid growth of waste electrical and electronic equipment(WEEE) in our country, the quantity of waste printed circuit board(PCB) is increasing sharply in recent years.Lots of precious metals were contained in the PCB and can be recycled as resources,at the same time, large amounts heavy metal and other toxic substances were contained in the PCB and may pollute environmental severely without appropriate treatment.There are three kinds of recycling techniques in recent:heat treatment,chemistry processing and mechanical treatment. Lower recycling efficiency was feature in these techniques.This paper studies three main parts of the metal recovery process in the PCB:the PCB dissociation,flow separation of broken materials,remove the organic components of separated products.For each part of the experiment,all of the experimental conditions for recycling metals have been optimized,and the recycling efficiency was heightened significantly,the experimental results provide theoretic foundation for industrialization in the future.Liberation experimental results show that:the crushed materials mainly concentrated in the size of 0.074 to 0.125 mm,0.125～0.25mm,0.42mm to 0.25,0.42 to 0.84mm;The metal and non-metallic in the material smaller than 0.84 mm are basically separated;At different broken time.as the time increases,metal liberation degree also will be increased gradually,but at a certain period of time(130 s),the liberation degree change little;In the minimum speed, metal liberation is not in expectation,when the rotate speed is over 2000r/min,can reach an ideal separation results.Dealing with the printed circuit board scrap by using air separation technology have achieved separation enrichment effectively,different size can be identified by calculating the optimum operation of gas velocity:in the size of 0.074 to 0.125mm,0.125～0.25mm,0.42mm～0.25,0.42 to 0.84mm,the better separation gas velocity is 0.24 m/s,0.28m/s,0.57m/s and 0.71 m/s,copper recovery rates were 90.56%,85.34%,86.28%,80.33%respectively.The fire experimental results show that:burning can effectively remove organic compounds in the separated material,which produced poisonous gas component in smelting technology:the copper concentrated at the size of 0.42～0.84mm,0.25-0.42mm.In the same heating time(60 min),600℃is the ideal heating temperature;under the same temperature(600℃),materials were fully burned over the time of 40 min.