Thiosulfate as an Oxidation Inhibitor in Flue Gas Desulfurization Processes: A Review of R and D Results

摘要

The article describes the pilot-plant testing of sodium thiosulfate (Na2S2O3) as an oxidation inhibitor in flue gas desulfurization by lime and limestone slurry scrubbing with and without MgO and adipic acid additives. The effectiveness of thiosulfate is proportional to the inhibitor product, defined as the product of thiosulfate concentration (M), calcium concentration (M), and the moles of SO2 absorbed per hour per liter of hold tank volume. Gypsum saturation was less than 100% and scaling was eliminated when the inhibitor product exceeded 0.3 times 10 to the minus 6 times M to the 3rd power/hr. Thiosulfate was relatively more effective in systems with chlorides and less effective in systems promoted by MgO. An inhibitor product greater than 10 to the minus 6 times M to the 3rd power/hr significantly enhanced dewatering of solids from limestone scrubbing. SO2 removal and/or limestone utilization were increased in systems that started with less than 10 mM dissolved calcium.