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High surface area and porous CaCO 3 particles were produced by absorption of CO 2 in aqueous suspensions of Ca(OH) 2 with the addition of a suitable additive at 27 °C and 1 bar. The CaCO 3 surface area was determined mainly by the shape and size of the constituting primary particles. In the absence of any additive, the CaCO 3 surface area varied with the initial Ca(OH) 2 concentration and reached a highest value (19.6 m 2 /g) at 2.4 wt.% Ca(OH) 2 . The CaCO 3 surface area was affected little by the CO 2 flow rate (1.0–3.5 L/min) and decreased with increasing solution temperature (27–45 °C). The CaCO 3 surface area was affected markedly by the kind of additive, the amount of additive, and when to add the additive. The optimal conditions for maximizing the CaCO 3 surface area were identified for each additive. Among the six additives tested (Dispex A40, Dispex N40, sodium bis (2-ethylhexyl) sulfosuccinate, Disponer 926, ammonium stearate, and stearic acid sodium), Dispex A40 and N40 were more effective. An effective additive in raising the CaCO 3 surface area and pore volume was to enhance the formation of fine CaCO 3 primary particles and the loose aggregation of them. High surface area CaCO 3 was obtained when an effective additive was added after bubbling CO 2 into the Ca(OH) 2 suspension. The CaCO 3 with the highest surface area (57 m 2 /g) was obtained by adding 0.25 wt.% Dispex A40 to a 2.4 wt.% Ca(OH) 2 suspension when the solution pH dropped to 6.5–6.2. The high surface area CaCO 3 was highly reactive toward SO 2 , and the reactivity increased with increasing surface area in general. A conversion of 0.87 was achieved when the CaCO 3 with the highest surface area was sulfated at 950 °C and 4000 ppm SO 2 for 1 min. |
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