Case Study: Leaded Glass Separation

 


Background

Most glass we encounter daily does not contain lead. However, older TVs and computers with CRT displays as well as crystal housewares can contain up to 40% lead oxide. It’s encouraging that we’ve moved away from producing leaded glass; however, there is still a significant amount in the economy that needs to be collected and properly disposed of.

Challenges

  • When glass is collected in bulk, it can be easy to confuse leaded glass with unleaded glass. 
  • When it’s time to recycle the glass, leaded and unleaded glass particles need to be processed separately for health and safety reasons.
  • Because we’re trying to separate leaded glass for safe disposal, traditional glass sorting methods can be too expensive.

Solutions

  • Because leaded glass has a density of three and unleaded glass has a density below 2.8, Sepro was able to develop a dense media process to separate the two types of glass. 
  • Initial heavy liquid tests indicated that a density cut point between 2.85 and 2.90 would provide the best results.
  • Sepro’s Condor Dense Media Separator was used for the pilot scale testwork. Approximately two-tonnes of crushed glass split into -10mm/+2mm and -2mm/+1mm size fractions was used for the pilot testwork.

Results

  • Despite crushing some particles were not fully liberated and contained a mixture of leaded and unleaded glass (as seen in the photo). These unliberated particles proved difficult to separate because of their intermediate density.
  • Despite these challenges, the separation was over 70% efficient which was considered successful given the amount of unliberated particles.

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