Environmental Performance Comparison Of The Traditional Pyrometallurgical Process And A Novel Hydrometallurgical Process To Recover Lead From Spent Lead-acid Batteries

Within the main application areas of the metallic lead, the lead-acid battery is theproduct that consumes most of the lead produced worldwide; more than70%of the globalproduction is used in lead-acid batteries. In China alone, the consumption of refined leadin2010was4.21million tons,80%of which was used to produce lead-acid batteries.The recovering process of lead from spent lead-acid batteries has a long history.Recovery rates higher than90%have reached since more than ten years ago and currentlylead-acid batteries are the commercial products with the highest recovery ratio. Anaverage-size spent lead-acid battery contains typically48-50wt%of lead paste which inturn is composed by PbSO4(~60%), PbO2(~28%) and PbO (~9%) in mass percentage.The reduction of lead sulfate requires the intervention of higher temperatures and thereforelead paste commonly decomposes through an energy-intensive process, i.e.pyrometallurgical process. In general, this method represents over90%of the globallyinstalled technology despite the tough criticism behind it. In this approach, lead pasteoften smelts in a furnace at temperatures of over1000°C using coke or coal as fuel andthus generating large amounts CO2, lead particulate, and SO2emissions.Considering the size of the market, the toxicity of the product and the apparentimpact potential of the traditional recovering process, it results strongly necessary toassure the ecological efficiency of the implemented process for the recycling andrecovering of lead from spent lead acid batteries. In response to this challenge, newapproaches are being developed at different scales using hydrometallurgical mechanismsthat provide allegedly cleaner and more efficient procedures to recover lead. A researchscale process recently has been developed and still under adjustments is used to recoverlead as ultra-fine lead oxide through a hydrometallurgical process. This new methodologyis believed to have a substantial reduction of pollution, with a higher material recoveryratio and less energy-intensive consumption.As part of the development of this new methodology, this research aims to make acomparison of the environmental performance of both the pyrometallurgical and thehydrometallurgical processes from a Life-Cycle perspective to assess the potential environmental benefit of the new technology. This entails the consideration of all theresources and energy consumption, emissions and treatment of discarded material relatedto the lead oxide recovering process. Through the definition of comprehensive boundaries,the selection of a representative functional unit and a thorough compilation of data,holistic environmental impacts of both processes are identified and analyzed.This study shows that the main contributors to the environmental impacts of thesecondary lead production process vary from one methodology to another. On one side,the energy consumption (in the form of coal burning) in the pyrometallurgical processshares the largest proportion of environmental impact for the study.