Laboratory studies of binary salt CVD in combustion gas environments

Abstract

Abstract A flash‐evaporation technique is used to obtain vapor deposition characteristics for the binary alkali sulfates K 2 SO 4 + Na 2 SO 4 at 1 atm above 1, 100 K. This technique gives results of immediate engineering interest, such as dewpoint temperatures, condensate composition and rates of vapor deposition as well as useful data on the system's thermodynamic characteristics. It is concluded that alkali sulfate deposition and vaporization in combustion environments are inevitably influenced by chemical reactions such as hydroxide formation. It is also concluded that solution nonideality is important even for homologous alkali‐salt mixtures. Predictions are made using convective‐diffusion mass transfer theory, accounting for chemical reactions by means of effective volatilities, and assuming regular, nonideal condensate solutions. The predicted dewpoints, condensate compositions and deposition rates are quantitatively consistent with experimental observations. This approach, validated here, can be extended to more extreme conditions of engineering interest, including turbulent, high‐temperature/pressure systems.