Battery paste desulfurisation

The TBRC is represented by the Kaldo process, developed and operated by Boliden in Sweden and detailed in Chapter 7. This process is suitable for both primary and secondary smelting and can accept whole batteries if required. The Kaldo system at the Ronnskar smelter has adequate facilities for the capture of sulfur and paste desulfurisation is unnecessary. 

In this case batteries are fully separated, metallic components are simply melted and drosses from that operation together with desulfurised battery pastes are subjected to hydrometaUurgical extraction of lead followed by electrowinning from the leach solution. As detailed in Chapter 9, solutions used for lead electrolytes are fluosilicates as used in the Betts refining process, fluoborates and chlorides. 

After desulfurisation, battery paste material contains PbO, Pb(OH)2, PbC03, Pb02 and some fine metallic Pb. A common problem with hydrometaUurgical extraction is that both metallic lead and Pb02 are not soluble in the leaching solutions. A common approach is to make use of the reaction shown in Equation 11.16, by the addition of lead powder as required under acidic conditions. 

The Ginatta process also uses a fluorborate electrolyte and is based on the leaching of battery pastes which have been desulfurised with ammonium carbonate. The electrowinning process is licensed to MA Industries, who promote it in conjunction with their battery breaking technology (Ginatta, 1984). 

As an example, indicative costs are provided for the treatment of scrap lead-acid automotive batteries to produce refined lead using battery breaking and paste desulfurisation, followed by melting and reduction in a short rotary furnace, as described in Chapters 10 and 11. A typical small scale unit handling 35 000 tonnes per year of batteries is considered with a lead production of around 19 000 tonnes per year. Relevant production data is as follows ... 

The primary smelting stage feed varies from whole drained batteries to disintegrated whole batteries, mixed paste and metaUics after separation of plastics, pastes only after separation of metallics and plastics, and pastes after desulfurisation. Some processes are unsnited to different types of feeds. 

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