Pyrometallurgical extraction of metals, such as smelting and roasting, from sulfur containing ores and spent catalyst typically generate large amounts of SO₂ emissions. Gases produced by primary smelting activities are typically directed to sulfuric acid plants for capture of the SO₂ and conversion to a marketable by-product. Stricter environmental regulations are now targeting secondary smelting gases and are posing new challenges to mining companies world-wide.

Secondary smelting activities produce gases that are particularly challenging since they are highly variable in nature, such as gases from Pierce-Smith converters and batch smelters. These gases are either too dilute or variable in SO₂ concentration to be suitable for direct feed to an acid plant.

Integration of the Cansolv SO₂ Scrubbing System Load Leveling design enables the treatment of these difficult gases. By varying inventories of lean and rich absorbents, the Cansolv SO₂ Scrubbing System has been engineered to uncouple absorption and regeneration processes. In operation, the lean absorbent flow to the absorber is modulated according to inlet concentration while the rich amine is pumped to the regenerator at a constant flowrate, creating a steady stream of pure SO₂ from a variable or dilute stream of SO₂ laden gas. The pure concentrated SO₂ can be converted to sulphuric acid (without further gas cleaning), dried and liquefied or in some cases, reduced to elemental sulfur.

Key benefits of applying the Cansolv SO₂ Scrubbing System to treat metallurgical offgases include:

• Ability to convert variable and dilute smelter gases into steady pure SO₂ gas stream;
• Less gas cleaning requirements;
• Ease of integration with existing acid plant or simplified design of new sulfuric acid plant

Case Study

Hindustan Zinc Ltd Lead Smelter

Reference Literature

Leveille, V., (2009). Cansolv SO₂ scrubbing system: review of commercial applications for smelter SO₂ emissions control. Presented at SAIMM 2009