Research On The Analysis And Controlling For Corrosion Of Natural Gas Centrifugal Compressors

Sulfur corrosion is a common phenomenon in petrochemical industry which has negative impact on production and safety. The wear of the compressor shaft caused by the sulfur corrosion poses a serious threat to product safety in Dongying compression station. A special issue of corrosion prevention and controlling was raised to deal with the problem.Site investigation has been carried out, which including the composition analysis of samples collected in several parts of the oil gas compressor system. Samples were analyzed with EDS, AAS, IR,etc. The results indicated that the wear of the compressor was caused by the chemical and also electrochemical corrosion of sulfur. Developing a new kind of corrosion inhibitor has been performed to deal with the wear in the next work.Inhibitors are frequently used for controlling sulfur corrosion in oil and gas production due to its low cost, easy operation and significant effects. In the Lab. work, a corrosion inhibitor TD-02 was prepared, and the inhibition properties of TD-02 were investigated by weight loss, SEM and electrochemistry measurements in saturated hydrogen sulfide solution. The results show that significant inhibition effect was achieved by adding TD-02 as inhibitor, which has a high inhibitive efficient more than 90% in lab experiment. A protective film is formed by adsorption of inhibitor molecules on the matrix and inhibition achieved by geometry covering.A series of field tests were carried out in Dongying compression station. The results show that significant inhibition effect was achieved by adding TD-02 as inhibitor. The sample surface was shiny black after field test, and the morphology is very close to the situation before the test. The EDS results show that the content of S can be ignored basically and the loss weight results are not obvious also. The field test results indicated that the wear of the compressor shaft was significantly inhibited, which achieves the desired results.An inducement passivation effect of normal-butylamine (nBA) was discovered in our work. The effect of inhibitor present during potentiodynamic scanning in 3%NaCl solution was investigated by electrochemistry measurement methods. The inducement of passivation is caused by the difference between the differential coefficient of anodic and cathodic currents to inhibitor coverage ratio.A numerical analysis method is proposed and applied to study passivation kinetics of low carbon steel in sodium nitrate solution. Curve of passive film coverage against time is obtained and discussed. A maximum growth rate is found at initiating passive potential during the film forming process. A 77% film coverage ratio is obtained at the initiating passive potential, which indicated that the film has already begun forming before the initiating passive potential arrived.