HIGH-TEMPERATURE REACTION BETWEEN SULFUR-DIOXIDE AND LIMESTONE .1. COMPARISON OF LIMESTONES IN 2 LABORATORY REACTORS AND A PILOT-PLANT

Twenty-three different limestones were studied with respect to their capacity for reaction with sulphur dioxide, and were found to differ markedly. Geologically young limestones have the highest capacity, and geological old limestones the lowest. The presence of ferric oxide affected the sulphur dioxide capacity of limestones adversely, but otherwise no general relationship was observed between chemical composition and sulphur dioxide capacity. A negative correlation exists between the time required for calcination and the sulphur dioxide capacity. Experiments were carried out in three different reactor systems: a laboratory recycle reactor, a laboratory fluidized-bed reactor, and a coal-fired fluidized-bed pilot plant. Qualitatively, the rankings of limestones with respect to sulphur dioxide capacity were identical for the three reactor systems, and laboratory experiments may thus be used for the determination of such a ranking. The pilot plant was less efficient with respect to limestone utilization than the other reactor systems, elutriation from the bed or locally reducing conditions in the bed being assumed to be the major cause of this difference.