TOOLS AND STRATEGIES FOR THE OPTIMIZATION OF H2S SCAVENGING IN RESIDUAL FUELS: A CASE HISTORY.

摘要

It is well known that on July 1st 2012 a H2S specification was implemented to the revision of the ISO 8217. The limit of 2 mg/Kg in the liquid phase was established for all marine diesel and residual grades. We present here a year-long case history on the application of a H2S scavenger for residual marine fuel in a major European refinery. We can show here how the accurate monitoring as well as the optimization of the dosage rates based on the specific system configuration assure a great cost saving (more than 40% in comparison with the previous treatment) and the required specifications. This significant improvement was possible firstly through the identification of the operative conditions affecting the H2S content in the residual fuel and also the enhanced scavenging action of the additive. Laboratory tests based on real conditions, especially in terms of contact time and mixing degree, allowed us to determine the minimum dosage ratio (scavenger vs. H2S) necessary to reduce the hydrogen sulfide below the specification limit. Thanks to the know-how acquired during our application and the study of the historical data, our technicians applied an additive dosage management based on the process parameters and able to predict the H2S content in the untreated residual fuel. Once optimized, this treatment management had a major impact on the reduction of both the overdosages and the off-specs risk. Moreover, to further improve the prediction accuracy, we developed a mathematical model that was used under the supervision of our experts and gave additional benefits, in terms of efficiency and cost reduction.