Research On Corrosion Behavior Of Q345R Steel In MDEA Mixed Amine Solution

The alcohol amine method for removing CO₂ is most widely used in natural gas pretreatment because of its economical efficiency.In the actual production process of the factory,the decarbonized amine solution that has absorbed CO₂ is corrosive,and the accumulation of impurity ions and degradation products in the amine solution will also increase the corrosivity of the amine solution,affecting the long-term smooth operation of the device,and improving the factory Production costs,and even lead to safety accidents.A receiving terminal natural gas amine decarburization system uses MDEA-PZ mixed amine liquid as the absorbent,and the main material of the absorption tower is Q345R low alloy steel.Based on this,this paper uses three test methods:electrochemical polarization curve method,electrochemical impedance spectroscopy,and weight loss method,supplemented by surface analysis technology,to study the corrosion characteristics and corrosion behavior of Q345R steel in MDEA-based mixed amine solution.The corrosion characteristics of Q345R under different total amine concentration and amine ratio,and the influence of temperature and CO₂ loading on corrosion were studied.The corrosion mechanism of the lean and rich MDEA-PZ mixed amine liquid on Q345R was discussed.In the MDEA-PZ mixed amine liquid lean solution,the corrosion cathode reaction is mainly the reduction of water,and in the semi-lean and rich liquids containing CO₂,the corrosion cathode reaction is mainly the reduction of HCO₃^-.In addition,water,hydrogen ions,and protonated amines participate in the reduction reaction,and the main corrosion product is Fe CO₃.The corrosion characteristics of MDEA-PZ mixed amine liquids with different concentrations of oxalate,formate,acetate,sulfate and four kinds of heat-stable salts and chloride ions were carried out.It is obtained that oxalate has the greatest effect on the corrosion promotion of Q345R in the MDEA-PZ mixed amine solution,followed by chloride ions,and sulfate has less effect on corrosion.Using the weight loss test data,based on the BP neural network,the corrosion rate prediction model of Q345R in the MDEA-PZ mixed amine solution was established,and the corrosion rate prediction distribution map was drawn.The predicted data has a good match with the experimental data,which provides a scientific basis for corrosion monitoring during equipment operation.