Reverberatory and rotary furnaces are widely used for recovery lead from battery scrap. This scrap consists of pure metallic lead and antimonial lead from battery plate grids, connectors and terminals. Also contained in the batteries is the paste (a mixture of lead sulfate and oxide) resulting from electrolytic action during the life of battery. Up to 98% lead may be recovered from the metallic charged into the furnace.
Prior to recycling, batteries are usually broken up and sorted into constituent products. Fractions of cleaned plastic (such as polypropylene) are recycled into battery cases or other products. The dilute sulfuric acid is either neutralized for disposal or recycled to the local market. Most domestic battery scrap is processed in rotary furnaces or reverberatory furnaces, a furnace more suitable for processing fine particles.
C + PbO + PbSO4 > Pb + PbS + CO2
PbS + Fe > Pb + FeS
C + PbS + 2 Na2CO3 > 2Pb + @Na2S +3CO2
Connectors, grids and battery paste containing lead sulfate and lead oxide are desulfurized with a mixture of soda ash, coke and cast iron turnings or fine scrap. The carbothermic reduction of the sulfate-oxide fraction releases the lead values and results in sodium-iron sulphide eutectic matte by- product preventing the emission of shulphur dioxide.
Magnesia Chrome refractories are best suited for use in both these types of furnaces.
In some areas of reverberatory furnaces, the addition of excess soda ash to enhance effective desulfurization will demand refractories with higher content of magnesia. Here, an 80% magnesia-chrome products has been found to the best lining material. In high production rotary furnaces where abrasion at the charging end of the vessel results in the uneven wear of the lining, a dense 60% magnesia-chrome fused grain containing product has been found to be the most effective.
Herman Santoso is a graduate of the Mechanical Engineering University of Tarumanagara in Jakarta, Indonesia. He has technical expertise in glass melting furnaces and the application of refractories in the recycling of non-ferrous materials that include lead scrap. In 2015, after 21 years working for various manufacturers of refractory products, he became the Sales Group Manager for PT. Harbison Walker Indonesia