Erosion Corrosion Laws Of 20# Carbon Steel Under The Conditions Of Gas-liquid Equilibrium

20# carbon steel is the commonly used material of equipment and piping in oil refining industry.The corrosive medium mainly includes NH4 HS and NH4 Cl formed during the refining process,resulting in serious erosion corrosion under a certain flow velocity,which threating the nature security and causing serious financial loss due to the high-sulfur,high-chlorine and high-nitrogen poor crude oil quality.Erosion corrosion is the principal failure pattern as the flow form corrosion,coupling with obvious riskiness and locality especially in acidic water system.The influence factor of erosion corrosion refers to chemical process,equipment structure,medium concentration,velocity,temperature,pressure,operating conditions and etc.The present researches are short of systematic prediction method and control technology,thus the corrosion failure accidents occur frequently.In this paper,the erosion corrosion failure of acidic water system was investigated based on one petrochemical enterprise and the erosion corrosion laws of typical material of 20# carbon steel was studied under gas-liquid equilibrium conditions.The distribution law of different corrosive medium both in gas phase and liquid phase,and the pH values were obtained in view of gas-liquid balance,ionic equilibrium and chemical counterpoise model according to the Aspen simulation software.Meanwhile,the Computational Fluid Dynamics(CFD)simulation was applying to research the flow characteristics in the acidic water pipelines.The result shows that the corrosive gas mole fraction in water was increasing with the reducing temperature and the higher liquid phase fraction location the more serious erosion corrosion failure.The reasonable water injection could raise the pH value and slow down corrosion rates.The rotary erosion experiment device was used to analyze the different factors for corrosion rates of the typical material 20# carbon steel in NH4 Cl solution,including concentration,temperature,velocity and static conditions.Moreover,the surface morphology of the corrosive specimens was observe by the scanning electron microscope(SEM)technology to discuss the erosion corrosion mechanism,which in favor of learning more factors about the 20# carbon steel corrosion leakage and perforation failure in the petrochemical industry.The study results could provide a theoretical basis for reducing the corrosion failure of acidic water system pipes.The innovation of this paper depends on the actual operation conditions of the acidic water pipes.The chemical process was comprehensive analyzed and the numerical simulation calculation combining with the erosion corrosion experiment research methods were applying to establish the gas-liquid equilibrium corrosion conditions,which was aimed at exploring the characterization test and critical discipline of the erosion corrosion.The comprehensive analysis could provide the optimization design,material selection and corrosion failure analysis for the pipelines in the petrochemical industry.