THE SODA ASH SMELTING OF LEAD-ACID-BATTERY RESIDUE

A pyrometallurgical process for the recovery of lead from battery resi due was investigated. The process involved pelletizing the residue wit h sodium carbonate followed by a carbothermic smelting operation. The overall reaction in the process is as follows: PbSO4(s) + Na2CO3(s) C(s) = Pb(1) + CO(g) + CO2(g) + Na2SO4 The sulphur dioxide emissions a re minimal since the sulphur is fixed in the slag as sodium sulphate. Lead emissions are considerably reduced due to the use of pellets and a lower smelting temperature. The optimum conditions for the maximum r ecovery of lead were determined. These were: a smelting temperature of 1223 K, a charcoal addition of 3 mass% and a sodium carbonate additio n of 20 mass percent. A moisture addition of 10 mass% during pelletizi ng was found to be sufficient to complete the sulphate-carbonate excha nge reaction and to produce a strong green pellet. Sintering of the gr een pellets prior to reduction was found to have no effect on the lead recovery. However, a minimum in the strength and abrasion resistance of the pellets occurred at 773K. Lead recoveries of 96-98% were achiev ed and the lead content of the slag was in the range of 1-2 mass%.