某天然气处理厂回注水处理系统腐蚀防护方法研究

Study on corrosion protection method of reinjection water treatment system in a natural gas processing plant

为了考察回注水系统的腐蚀情况,针对陕北某天然气处理厂含甲醇污水显酸性、Cl^-和硫化物含量高、腐蚀性强的特点,通过分析污水组成性质,研究污水对20#钢、Q235B钢和L316钢的腐蚀情况,并利用灰色系统理论建模软件3.0研究各腐蚀因素对Q235B钢腐蚀速率和腐蚀深度的影响程度大小。研究结果表明:L316钢更耐腐蚀,腐蚀速率为0.0015 mm/a,达到国标0.0760 mm/a以下,最大腐蚀深度为47.63μm,为3种材质中最低;以腐蚀速率和腐蚀深度作为母因素,在硫化物、Cl^-、矿化度和pH值4种因素当中,硫化物对应的灰关联度分别是0.75和0.80,是造成腐蚀的最主要因素;采用抗硫缓蚀剂保护法,通过电化学法从3种缓蚀剂中筛选出TS-792C,阻抗数据模拟软件ZSimpWin模拟出等效电路图,其所对应Q235B钢的阻抗最大,Tafel极化曲线拟合下腐蚀速率为0.0130 mm/a,缓蚀率可达90.26%,抗硫效果最好。在80℃和硫化物含量为300 mg/L时,Q235B钢的腐蚀速率均低于0.0760 mm/a,在TS-792C投加量为100 mg/L时,回注污水的腐蚀电流密度和腐蚀速率分别为0.462 m A/cm^2和0.0505 mm/a,均处于最低值,具有良好的耐温、抗硫性能。

In order to investigate the corrosion situation of the reinjection water system,in view of the characteristics of the methanol-containing sewage of a natural gas processing plant in northern Shaanxi such as high acidity,high Cl^-and sulfide content,high salinity and strong corrosivity,on-site material 20#steel,Q235 B steel and L316 steel were used to study the current corrosion status of reinjection water system through analyzing the composition of the sewage.The influence of different factors on the corrosion rate and corrosion depth of Q235 B steel was studied using gray system theory modeling software 3.0.The study results showed that,L316 steel had better anti-corrosion capability,the corrosion rate was 0.0015 mm/a,which below the national standard requirement(0.0760 mm/a),the maximum corrosion depth was 47.63μm,which was the lowest among the said three materials.The corrosion rate and corrosion depth are the parent factors,among the four factors of sulfide,Cl^-,salinity and p H value,the ash correlation of sulfides are 0.75 and 0.80 respectively,which are the key factors causing corrosion.Using sulfur corrosion inhibitor protection method,by electrochemical method,TS-792 C was selected from the above three corrosion inhibitors,and the equivalent circuit diagram was then simulated by impedance data simulation software ZSimpWin,it was indicated that,Q235 B steel had the best impedance performance,the corrosiong rate fitted by Tafel polarization curve was 0.0130 mm/a,and the inhibition rate reached 90.26%,which showed the best anti-sulfur effect also.Under the condition that the temperature was 80℃,the mass concentration of sulfide was 300 mg/L,the corrosion rate of Q235 B steel was lower than 0.0760 mm/a,when the TS-792 C dosage was 100 mg/L,the corrosion current density and corrosion rate of the reinjection sewage were both at their lowest values:0.462 mA/cm^2 and 0.0505 mm/a respectively,that means,the reinjection sewage had good temperature and sulfur resistance ability.