Sistema automático de controle de corrosão em topo de destilação atmosférica

Abstract

Pre-salt oil processing brought many challenges for refineries in Petrobras. Pre-salt oil contains short chain carboxylic acids, which reduce the distillation overhead water pH, moreover theres is a higher difficulty in desalting those oils, what makes chloride to increase in distillation tower overhead, affecting corrosion rates substantially. For these reasons, the replacement of ammoniacal water by amine as a neutralizer, in addition to the distillation tower overhead automatic corrosion control system was identified as a possible solution to reduce corrosion. The corrosion control project in distillation tower overhead system was conducted in Capuava Refinery through the research and development (R&D) project called Pre-Salt Petroleum Processing in Refining. The automatic tracking control equipment was used for online measurement of pH, iron and chloride and control of neutralizer, filmer and caustic flows, respectively. It was observed that, regardless of the automatic control and processed oil, there was a significant increase in corrosion because of neutralizing amine injection in the system. Items such as spray nozzles, quick-response corrosion probes and high wash water flowrate are critical to the success of the overhead corrosion control, especially when using amine as neutralizers.