Research On Naphthenic Acid Corrosion Under High Temperature And High Flow Rate

Naphthenic acid corrosion is common corrosion form in oil refining equipments and a problem needed to be solved in high sulfur and high acid crude oil refining process.Despite the high acid crude oil refining enterprises has been carried out for improving the adaptability of equipment, process improvement, adding corrosion inhibitors or used mixed refining method to reduce corrosion, but naphthenic acid corrosion is still serious in existing high-speed turbulent regions such as the elbow, tee. Therefore, the research on refining device structure design, life prediction and long period of safe operation has the practical significance.Naphthenic acid corrosion rate under different temperature, velocity of flow conditions were measured through naphthenic acid corrosion testing under high temperature and high velocity in this paper. The influence of temperature on the naphthenic acid corrosion was cleared by analysis of corrosion test data, and drew the corresponding diagram through the Origin software. Finally the main influence of velocity and turbulent state of naphthenic acid corrosion was confirmed through comparison and analysis between the results of theoretical FLUENT simulation and the practical analysis results of samples by using 3D corrosion morphology analyzer. Main conclusions are as follows:(1) The analysis of controlling mechanism of naphthenic acid corrosion kinetics showed that naphthenic acid corrosion rate was mainly controlled by corrosion reaction;the reactant, mass transfer of the product and adsorption and desorption processes were not the control process of naphthenic acid corrosion. And the theoretical analysis showed that the corrosion rate and temperature was in accordance with Arrhenius formula.(2) The analysis of API581 and corrosion test data showed that the corrosion rate V and temperature T matched the linear rule that lnV was proportional to(-1/T), in accordance with the theoretical analysis. In order to realize the accurate prediction of naphthenic acid corrosion rule, the linear law lnV was proportional to(-1/T) should be applied.(3) Turbulence intensity on specimen surface would decrease with increasing of distant from specimen center distance R under high-speed direct injection flow flushing.Highest turbulence intensity value existed in the center of the specimen which was about9.5%. Meanwhile, the intensity of turbulence has a significant effect on the local maximum corrosion depth and the average corrosion depth, and the influence degree is enhanced with the increase of turbulence intensity. And specimens had the highest corrosion rate in strong turbulent zones, local corrosion depth was 4 times of the average corrosion depth in strong turbulent zones.