ENHANCEMENT OF REACTIVITY OF CAO PRODUCED FROM LIMESTONE BY MEANS OF HYDRATION-DEHYDRATION

To achieve high reactivity of CaO particles produced from calcined limestone, the influences of calcination temperature on reactivity of CaO for recarbonation (which is a reverse reaction of calcination) and sulfurization were experimentally studied by use of thermogravimetric analysis. The CaO particle structure was studied by measurement of pore size distribution and SEM photographs. Furthermore, enhancement of CaO reactivity and change of CaO particle structure were achieved by water or steam vapor hydration/dehydration treatment, and the effect of hydration/dehydration treatment on reactivity was studied. It was found that the calcination temperature influenced the reactivity as well as the reaction capacity. By increasing the calcination temperature, both reactivity and capacity were decreased because of the growth of CaO crystal and also of pore plugging. The calcined limestone treated by hydration/dehydration was remarkably enhanced in terms of reactivity by increasing the specific surface area caused by the formation of small crystals and the change of crystal shape. It was therefore suggested that a highly reactive CaO could be produced by hydration/dehydration treatment even though the CaO calcined at high temperature was of low reactivity.