UNCATALYZED HETEROGENEOUS OXIDATION OF CALCIUM BISULFITE

Wet limestone scrubbing is the most common flue gas desulfurization pr ocess for control of sulfur dioxide emissions from combustion of fossi l fuels. Forced oxidation in the scrubber loop improves the dewatering properties of the sludge, leading to the formation of gypsum (Ca50 . 2H(2)O). A literature analysis revealed that uncertainties on the mech anisms of the oxidation reaction and on the values of the kinetic para meters still remain. In the present work the oxidation rate was experi mentally studied by contacting pure oxygen or mixtures of oxygen and n itrogen with a calcium bisulfite solution. The experiments were carrie d out in a well-mixed bubbling reactor varying temperature, oxygen par tial pressure and sulfite concentration, in the absence of solid calci um sulfite and of catalytic species. It was shown that the rate of the process is controlled by reaction kinetics, and that the reaction rat e is zero order in dissolved oxygen and 3/2-order in bisulfite ion. Co pyright (C) 1996 Elsevier Science Ltd