Study On Erosion Corrosion And Their Failure Mechanism In A Refinery Air Cooler

Petrochemical and oil refinery plants have suffered continuous economic loss and human casualties due to carbon steel corrosion in H2S containing environment.Hydrocracking is a very important process in the petrochemical industry,through which naphtha,diesel liquefied gas and other products can be obtained.The formation of corrosive aqueous solution whose chemical composition consist of hydrogen sulfide(H2S),can be effected by crude oil which has sulfides and chlorides compounds.It is very useful to know the mechanism of action of different corrosive agents on metallic materials in oil refinery environment.This aqueous solution acids are among the most aggressive media to cause varied damages on carbon steel during plant operation in hydrocracking.The research object of this work is to study the failure mechanism of air cooler tubes in fractionator tower of hydrogenation unit by visualization method and color indicator technique to observe the multiphase flow behavior.In case of air cooler failure,the results of CFD simulation describe the fact that erosion by fluid plays a leading role in the entire process of erosion and corrosion,and the influence of electrochemical corrosion is relatively small.Bias flow is a significant reason for the damage of air-cooler tube.Based on results of simulation,this work simulates the fluid flow according to the real operating conditions in the field.After the scheme of experiment design,process simulation,equipment design and selection,a pipe flow loop is designed for the experimental set up of erosion corrosion which is suitable for air cooler.Based on this set up,the visual experiment of air cooler tube is designed and completed.The experimental results show that the flow of distribution in the entrance of each section of pipe is different due to deflection angle,but there is no significant difference in the flow behavior and distribution of fluid in the fourth section of the pipeline.Through the transparent glass tube,it can observe the flow behavior of the experimental medium and the distribution and the flow of droplets in the gas-liquid two phase flow.The results of visual experiment and CFD simulation are compared,and are in good agreement between simulation and experimental results.According to experimental phenomena,the flow behavior of the fluid under the actual operating conditions was summarized.For the flow behavior of the experimental medium,distribution and the flow of droplets in multiphase flow of air-cooler tubes,a color indicator technique is used in this work.Before it can be used in the experimental set up,a small scale experiment is designed to observe the performance of indicator on experimental medium.The results shows that the denser the droplet is,the more obvious the color change is,and the place where there are no bubbles has almost no color change.When indicator react with experimental medium it changes the color due to acidic or basic nature.When the gas-liquid two phase flow in the pipe,the distribution phenomena and behavior of two phase flow is more obvious in the vicinity of small droplets by color change near the inlet of walls.The visualization indicator research work shows multiphase flow behavior and distribution in real time that provides innovative research to promote the advancement of chemical engineering,multiphase flow transportation,chemical safety and other disciplines.