Fine Tune the Design of Sour-water Strippers Using Rate-based Simulation

Sour-water strippers (SWSs) are common in petroleum refineries, as well as gas-processing and gasification plants, and are used to remove ammonia, hydrogen sulfide and carbon dioxide from contaminated process waters. The design of these units is typically done using the equilibrium or theoretical stage method. The actual number of trays is determined from the required theoretical stages, using tray efficiencies. The tray efficiencies are not based on actual tray performance, but on experience-based rules of thumb. These rules of thumb are usually conservative to compensate for reduced tray efficiency — due to tray malfunction, foaming or plugging — and to add some design margin for future capacity expansion. Reliable rate-based process simulators are now available for the design of SWS units, and can be used for improved estimation of tray efficiency and for estimating the actual number of trays for optimal design of these units. For existing columns, this approach can be useful for troubleshooting and evaluating available spare capacity. Equilibrium-stage models, which form the basis for rate-based calculations, are first evaluated by looking at the impact of sour-water feed H2S and NH3 content, stripper column equilibrium…