AbstractThe rate of calcium sulfite dissolution in slurry scrubbers and hold tanks for flue gas desulfurization affects SO2absorption, limestone utilization and sulfite oxidation. The dissolution rates of calcium sulfite were measured by the pH‐state method. A mass transfer model was developed assuming that calcium sulfite particles behave as spheres in an infinite stagnant solution. The model combined with the Bechtel‐modified Radian solution equilibrium program successfully predicts calcium sulfite dissolution rates at pH 3.5 – 5.5, 23 and 55°C, 0.001 – 0.3 M Ca++and 2 – 25 mM dissolved sulfite. The effects of sulfate content in solids and liquids and particle size/shape were also studied.At conditions typical of flue gas desulfurization processes calcium sulfite dissolution was controlled by mass transfer, not surface reaction kinetics. Dissolution was fast at low pH and slowed near the equilibrium pH determined by dissolved Ca++and SO3=concentrations in the aqueous solutions, Kspof the CaSO3· 1/2H2O solids, and temperature. The presence of dissolved Mg++increased the equilibrium pH and enhanced the disolution rate. The presence of dissolved sulfate reduced the dissolution rate and the equilibrium pH. The effect of sulfate was not adequately described by the mass tra