Laboratory flames of H2/CO/O2/N2 will be studied over a range of stoichiometries seeded with sulfur and sodium species to determine the nature of the chemistry controlling the formation of deposits of sodium sulfate and carbonate on cooled substrate materials. With measurements of temperature using Na-D reversal, atomic Na and OH profiles using LIF, and the surface deposit composition using in-situ Raman scattering, a kinetic model for the deposition process can be developed. Effects of substrate material and temperature, and the composition of the gas phase species will be determined. In particular, the reversibility of the Na2SO4 and Na2CO3 layer build-up will be examined as a function of flame conditions. This program will resolve the nature of the chemistry controlling the formation of deposits of sodium sulfate and carbonate from flames on cooled substrates. It will establish which species in the gas phase are involved in the heterogeneous surface production of these salts. Such knowledge will be needed to develop combustion modification strategies to minimize high temperature corrosion and deposition in sulfur and sodium containing systems.
