High Temperature Naphthenic Acid Flow-induced Corrosion Behavior And Preventive Measures Of Petrochemical Unit

Naphthenic acid is a general term of various organic acids in petroleum,and is very corrosive.Naphthenic acid corrosion is a key factor that affects the safe production of petrochemical plant.In this paper,with respect to the problem that the influencing law and mechanism of fluid flow on high temperature naphthenic acid corrosion are not clear,and the corrosion detection and evaluation is not accurate enough,etc.,by the means of experiment and numerical simulation,etc.,researches are conducted on high temperature naphthenic acid flow-induced corrosion of carbon steel at different impact angles,the influencing law and mechanism of hydrodynamic factors such as impact angle,flow velocity and flow pattern,etc.on naphthenic acid flow-induced corrosion are revealed,the detection and evaluation improvement method of naphthenic acid corrosion that uses impact angle,flow velocity and flow pattern as the correction parameter is proposed,thus improving the accuracy of naphthenic acid corrosion detection and predictive evaluation of petrochemical plant.The main research contents and achievements are as follows:(1)Researches on experiment and numerical simulation of naphthenic acid flow-induced corrosion at different impact angles that cover all impact angles are carried out for the first time,and the flow-induced corrosion law of naphthenic acid at different impact angles and the influencing mechanism of hydrodynamic factors are revealed.The results show that the scouring angle has an important influence on the flow-induced corrosion behavior of naphthenic acid,and different corrosion rate and corrosion morphology are exhibited at different impact angles.Corrosion rate of carbon steel first rises with increasing impact angle,then decreases and then increases again,there are maximum and minimum values,forming a curve similar to sinusoidal curve,where the values at 0o and 60 o scouring angle are the two minimum values of corrosion rate;and the values at 30 o and 90 o impact angle are the two max.values of corrosion rate.(2)It is found that the flow-induced corrosion of naphthenic acid at different impact angles is jointly controlled by surface shear stress and near-wall turbulence intensity.At small impact angle of less than 60o(inclusive of 60o),the corrosion rate and variation law of surface shear stress at different impact angle are basically consistent,the surface shear stress is the main control factor for corrosion;at bigscouring angle of over 60o(excluding 60o),near-wall kinetic energy of turbulent flow increases,and corresponding to high corrosion rate,the near-wall turbulence intensity is the main control factor for corrosion.(3)The analysis is carried out on the influence of flow velocity and gas-liquid two-phase flow on naphthenic acid corrosion,and the influencing mechanism of flow velocity and gas-liquid two-phase flow on naphthenic acid flow-induced corrosion is revealed.(4)In combination with the results of corrosion experiment and the simulation analysis,the influencing mechanism of hydrodynamic factors on naphthenic acid flow-induced corrosion is analyzed,and the fluid-solid coupling action mechanism of naphthenic acid flow-induced corrosion is explained.In the flow-induced corrosion system of naphthenic acid,corrosion is caused by the combined action of fluid erosion and naphthenic acid corrosion,and the synergistic effect between them yields a corrosion rate higher than the sum of erosion and naphthenic acid corrosion.Hydrodynamic factors such as flow velocity,flow pattern,impact angle and multiphase flow,etc.influence the magnitude of scouring intensity and change mass transfer process generally by changing the magnitude of surface shear stress and near-wall turbulence intensity,thus affecting the severity of corrosion.(5)The detection and evaluation improvement method of naphthenic acid corrosion with scouring angle,flow pattern and flow velocity as the correction parameters is proposed,and the corrosion detection and evaluation system for the petrochemical process plant that processes high acid crude oil is established,which provides a more reasonable method for improving the detection and predictive evaluation accuracy of naphthenic acid corrosion.