Smelter Gases and Dust

Immense quantities of sulphur dioxide are produced when sulphide ores are oxidized during the smelting stage. If the sulphur dioxide goes up the smokestack of a smelter, it can react with the water vapor in the air to create sulphuric acid, the acid you can find in acid rain or snow. It is estimated that an average of about 60% of all sulphur emitted to the atmosphere comes from smelting and other industrial activity. Ores that can be treated by hydrometallurgical methods do not produce air emissions, but process waters might have to be treated before they can be discharged.

Many smelters now trap their sulphur dioxide to make sulphuric acid, which is a useful product in itself. A large smelter can produce thousands of tonnes of sulphuric acid per day. The gases are drawn through a catalytic oxidation process that turns the sulphur dioxide into sulphur trioxide. this chemical reacts to form sulphuric acid which can be sold to the general bulk chemical trade or used to make agricultural fertilizers when dissolved in water.

Dusts in the smelter exhausts can be recuperated by passing them through cyclones and electrostatic precipitators. These units can recover up to 95% of particulate dusts, returning them for processing to recover their metal content.

After Mining Ends
Mining is always only a temporary use of land, and an important goal of the operating company is to return the mine site to a natural and stable state, thereby making it available for other uses.

Towards this end, the industry has accepted mine reclamation techniques that consist of removing, relocating or demolishing buildings and physical infrastructure; closing pits and shafts; stabilizing underground workings, soil and slopes; treating tailings and waste water appropriately; and revegetating land.

Reclamation can be carried out at many stages of mining activity — after exploration; after surface or underground mining; or after treatment and processing facilities have been closed.