The Research Of Corrosion Of The Circulating Water System In Yanchang Refinery

Circulating water system is an important system in refinery. Its equipment or pipeline will leak caused by corrosion.It makes the overhaul period of atmospheric pressure device, catalyst unit, reforming hydrogenation device in Yan chang refinery shorter than abroad refinery.The production safety and economic benefits of Yan chang refinery has been threatened seriously. So it makes it a concerned subject for the researchers to improve the level of corrosion guard automatic control,to relieve the corrosion situation of the circulating water system,to extend its service life and to find out the relationship between influence factors and corrosion rate.Through the field investigation and the systemic analysis about corrosion situation of Yan chang refinary circulating water system, the main corrosion effect factors is found. They are Chloride ion, temperature, PH value and calcium ions.And their fluctuation ranges are as follow:Chloride ion300～500mg/L, temperature30～60℃,PH value7.2-9.4and calcium ions50-150mg/L. According to the actual situation of each factor, the test solution is simulated.The tests are designed by orthogonal experiment method.And each test includes four effect factors, meanwhile each factors have tree levels. During some tests the electrochemical polarization are used to get the polarization curves.And the corrosion rate is worked out.At first the effect situation about corrosion rate is studied by using the method of comparing the size of D-value.Then the relationships between the effect factors and the corrosion rate is worked out by using the ASA software. During some tests the electrochemical impedance test method are used to get the EIS curve.The impedance will be found by analysing the Nyquist diagram and the the EIS curve.It will explain the system corrosion process in microcosmic angle by analysis the relationship between the value of the impedance,the change of the capacitive arc,the fit of the equivalent circuit and the corrosion effect factors.Through studying the corrosion of circulating water system in Yan chang refinery,it makes some improve in the corrosion mechanism study and corrosion model study.Meanwhile it has worked out the corrosion relationship model.That will provide the relevant parameters to the system corrosion guard and the information fuse technical in the refinery industry and make a good foundation of the all automatic corrosion guard in the refinery in the future.