Alkali Vapor Condensation on Heat Exchanging Surfaces: Laboratory-Scale Experiments and a Mechanistic CFD Modeling Approach

Abstract

Inorganic vapors and their condensation can lead to severe operational problems in pulverized fuel systems such as integrated gasification and combined-cycle power plants or a conventional pulverized fuel combustion system. In order to understand these phenomena, a laboratory-scale cooling line for hot gases is used to measure and quantify the deposition of alkali vapors caused by heterogeneous condensation on a horizontal probe. The cooling line consists of two zones, an isothermal evaporation zone for the vaporization of alkali salts and a condensation zone. A condensation probe equipped with steel rings is placed inside the condensation zone with a gradually decreasing temperature. Different concentrations of inorganic vapors are studied under controlled conditions, and condensation rates on a probe, maintained at different temperatures, are quantified. A computational fluid dynamics model is developed and used to validate a heterogeneous condensation model based on Ficks’ law of diffusion. Numerical m...