Calculation of mass transfer coefficients for corrosion prediction in two-phase gas-liquid pipe flow

摘要

Internal corrosion in industrial environments involving gas-liquid flow can be a serious concern. For example, in the oil and gas industry, corrosive water phase is usually transported in tubes and pipes along with hydrocarbon and gas phases. These gas-liquid flows develop complex flow patterns where the liquid phase can distribute in quite different ways (as stratified layers, intermittent slugs, annular film, etc.) depending on the gas and liquid flow rates and pipe inclination. In these circumstances, the water phase can flow at very high velocities compare to either single-phase water flow or two-phase hydrocarbon-water flow. High water velocities usually lead to high mass transfer rates that can accelerate corrosion of the metallic pipe surface. In general, proper calculation of corrosion rates via mechanistic electrochemical models requires the knowledge of the mass transfer rate of corrosive species. However, there are very few studies in the open literature that show specific experimental data or propose ways to compute mass transfer rates in gas-liquid flow; particularly, for large pipe diameters. This study introduces a methodology for the estimation of mass transfer rates in gas-liquid flow based on the Chilton-Colburn analogy, eddy diffusivity, and mechanistic gas-liquid flow modeling. The proposed mechanistic models covers a wide range of fluid's properties and flow rates, different flow regimes and pipe inclinations, and show good agreement with mass transfer experimental data from large-scale gas-liquid flow.