Sulphuric Acid Plants

All the process gas, containing SO₂ , from the Roasters and the Lead Smelter is treated by three single contact Monsanto Plants, ranging in capacity from 410 t/d to 820 t/d. These plants convert 95% of the contained SO₂ in the process gas to a marketable 93% sulphuric acid and acid battery acid. The remaining SO₂ in the acid plant tail gas is removed by a Cominco-designed ammonia crubbing process that reduces the SO₂ to less than 500 ppm in the tail gas. This gas passes through a Brinks plume eliminator before discharging to a 125-m stack.

The ammonia scrubbing system produces an ammonium bisulphite solution that is subsequently acidified with sulphuric acid to produce a pure SO₂ gas and ammonium sulphate solution. The SO₂ gas is dried, compressed and condensed to a liquid for direct sales. This scrubber solution and residual sulphuric acid that is not sold is pumped to the Fertilizer Plant to produce an ammonium sulphate fertilizer.

Sulphuric acid is recovered from the sulphur gases from the Roasters and the Lead Smelter.

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