Pore distribution changes of calcium‐based sorbents reacting with sulfur dioxide

Changes in the pore structure of calcium oxide sorbents derived from calcium carbonate (c‐CaO) and calcium hydroxide (h‐CaO) reacting with sulfur dioxide are determined. Results show that the pore shape of c‐CaO approximates a cylinder while that of h‐CaO appears to be slit‐ or platelike. The pore volume of c‐CaO is located in much smaller pores than that of h‐CaO when compared on the basis of an equivalent pore shape model. The effect of sintering was to reduce surface area through coalescence of smaller pores, while only minor effects were observed upon pore volume and conversion from calcium oxide to calcium sulfate. Both sorbents expand to allow greater reaction than is possible given the initial porosity and formation of a larger volume product. The h‐CaO reacts to higher levels of conversion than the c‐CaO because the pore shape of the h‐CaO allows for greater particle expansion and, therefore, reaction beyond the limits of the initial porosity.