Activation of ca(oh)2 using different siliceous materials

Siliceous materials such as silica fume, bentonite and diatomite were mixed with Ca(OH)₂ and hydrated at different conditions to produce reactive SO₂ sorbents. Two different hydration methods were used; namely atmospheric and pressure hydration. The effects of the hydration temperature, time and siliceous material/Ca(OH)₂ weight ratio on the physical properties of the activated sorbents were investigated. A statistical design technique was applied by use of a two-level factorial design matrix to interpret experimental results. In atmospheric hydration, it was found that increasing the temperature and hydration time caused an increase in the total surface area of the sorbents. But, increasing the siliceous material/Ca(OH)₂ weight ratio caused a decrease in the total surface area of the sorbents. The relative surface area increments of sorbents are also influenced by the chemical composition of the siliceous material. In pressure hydration, mathematical analysis showed that the surface area of the activated sorbents was positively affected by the hydration variables. The activated sorbents were characterized by using thermogravimetry, x-ray diffractometer and scanning electron microscope. Thermogravimetric measurements showed that increasing the amount of reacted Ca(OH)₂ during hydration, which was presumably converted to Ca-containing reactive speciesies caused an increase in the surface area of the sorbent. X-ray diffraction studies also indicated that calcium silicate hydrates were the principal Ca-containing species formed during hydration.