Prediction and Assessment of Corrosion in Sulfuric Acid Alkylation Units

摘要

Sulfuric acid alkylation (SAA), the conversion of olefins and butane to high-octane alkylate using highly concentrated sulfuric acid as a catalyst, is a very profitable refinery operation with powerful incentives to maximize throughput. However, until recently there were only minimal corrosion data available upon which to assess the possible equipment damage resulting from changes in SAA unit operating conditions. Thus, a joint industry program (JIP) entitled "Prediction of Corrosion in Sulfuric Acid Alkylation Units" was launched in January 2006 and completed in January 2010, to develop an empirical, predictive, data-based computer model for quantification/prediction of corrosion rates of carbon steel and selected stainless steels and nickel-base alloys under SAA conditions. This model encapsulates results of an extensive experimental corrosion program that generated hundreds of corrosion rate data points in sulfuric acid alkylation as a function of temperature, wall shear stress, and variation in sulfuric acid and acid soluble oil (ASO) concentrations. The experimental setup developed for generating corrosion rate data is described alongside important data / parametric insights from the JIP and the significant technical challenges encountered during the experimental simulation phase. An overview of the corrosion prediction software model is also given.