Removal of sulphur dioxide from flue gases

Mixtures of Ca(OH)₂ and different siliceous materials such as fly ash, bentonite, silica fume, and diatomite were hydrated to produce reactive SO₂ sorbents. It was observed that these sorbents showed a better reactivity toward SO₂ than the Ca(OH)₂ itself. This behavior is closely related to the pozzolanic nature of the hydrated sorbents and to the greater surface area. The reactivity of the sorbents was strongly influenced by the source of siliceous material and the hydration conditions. The total sulphation capacities of the sorbents were determined at 338 K with a synthetic gaseous mixture containing 5,000 ppm SO₂ and 55% relative humidity. Depending on the chemical and physical properties of the sorbents, the SO₂ captures ranged from 1.20 to 5.58 mmol SO₂/g sorbent. The amount of SO₂ capture increased with the increasing surface area of the sorbent. The utilization of Ca(OH)₂ with SO₂ improved significantly when Ca(OH)₂ was hydrated with siliceous materials first and later exposed to SO₂.