Pyrometallurgical Processing of Spent Lead Acid Batteries
The pyrometallurgical processing of spent lead-acid batteries (LABs) mainly involves three types of processes: after simple treatments such as acid removal and casing separation, the batteries undergo mixed smelting; after crushing and sorting, the metallic and paste components are separated and smelted individually; or after separating the metallic and paste parts, the paste is desulfurized and then both parts are smelted separately. In developed countries, mechanical crushing technology and rotary short kiln smelting are primarily used. In moderately developed countries, saw-cutting pretreatment technology is predominantly applied, with reverberatory and blast furnaces being the main smelting methods. In developing countries, most of the time, only manual disassembly, casing removal, and acid draining are performed, and small reverberatory and makeshift furnaces are typically used for smelting.
In China, the main furnace types for pyrometallurgical smelting include reverberatory, rotary short, and blast furnaces. The energy consumption ranges from 400 to 600 kg of standard coal per ton of lead, with dust concentrations in flue gases reaching 10-20 g/m³ and SO₂ concentrations at 0.075 kg/kg of metal feed. The metal recovery rate generally reaches only 80%-85%, and the slag contains over 10% lead. Manual feeding is often employed, which results in high labor intensity, leading to high energy consumption and significant pollutant emissions.
Lead Acid Battery Recycling Line process
Desulfurization pretreatment combined with pyrometallurgy is gradually becoming a popular method for lead paste treatment. This process involves initially subjecting the lead paste to wet desulfurization, followed by pyrometallurgical smelting of the desulfurized paste. To overcome the high energy consumption, high metal volatilization loss, and high pollution emissions associated with pyrometallurgical recycling, many researchers have focused on the development of lead paste desulfurization and conversion processes. Common desulfurizing agents include Na₂CO₃, NaOH, and NaHCO₃, which convert PbSO₄ in the lead paste into soluble Na₂SO₄ and insoluble PbCO₃ or Pb(OH)₂ precipitates. The by-products recovered from the filtrate can be sold. As PbCO₃ decomposes into PbO at around 340 ℃, the desulfurized and converted PbCO₃ can be smelted at lower temperatures, usually at least 100-150 ℃ lower than the smelting temperature of untreated lead paste.
