The cyclic sorption ability of two Greek limestones for CO2 and SO2 was investigated aided by thermogravimetric analysis. Effects of CO2 on the sulfation and of SO2 on carbonation were also determined by simultaneous sulfation and car-bonation.
The time required for the chemically controlled CO2 capture stage was unaffected by the number of carbonation/calcination cycles. On the other hand, the time needed to calcine the samples decreased with an increase in the number of cycles. Increasing the particle size resulted in a reduction in the CO2-sorption capacity of both limestones. Reducing the reaction temperatures caused a reduction in the capture capability of the limestones due to the reduced calcium utilization.
Florina limestone sulfated according to an unreacted core sulfation mode, whereas Megalopolis limestone followed a uniform sulfation mode. Periods of calcination during sulfation resulted in higher SO2 capture efficiencies than continuous sulfation of the limestone. Simultaneous carbonation/sulfation tests showed that each one of these processes is affected by the other. The CO2 capture capacity of the limestones was significantly reduced by the presence of SO2, whereas SO2 capture can be increased by slow carbonation, and sulfation remains unaffected by the presence of CO2 for longer time periods. Florina limestone presents increased tolerance to sulfation compared with Megalopolis limestone. Overall the Florina limestone is superior to the Megalopolis limestone.
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