For dissociation of limestone in the slag zone of the blast furnace. The reaction is:

For dissociation of limestone in the slag zone of the blast furnace, the reaction is endothermic accompanied by an increase in entropy.
 $CaC{O}_{3_{(s)}}\to Ca{O}_{(s)}+C{O}_{2_{(g)}}\Delta H=+QKJ$
Heat is absorbed for the decomposition hence endothermic, entropy increases during the reaction as a gaseous product are obtained.