高含硫净化厂硫磺成型装置的湿气腐蚀机理

国内某高含硫气田净化厂采用水造粒硫磺成型工艺,硫磺成型单元大气呈酸性且湿度大,因而生产设施的大气腐蚀成为不可忽视的安全隐患。为此,通过在该净化厂硫磺成型单元硫磺颗粒成型罐的中部和顶部及硫磺产品传送带周围进行现场挂片试验,采用扫描电镜和能谱仪分析了腐蚀产物的微观形貌和化学成分,并分析了酸性湿气对结构钢腐蚀的原因及其主控因素。结果表明,硫磺成型单元大气腐蚀不可忽视,尤其在硫磺成型罐周围,因温度较高、空气湿度较大,发生了中度腐蚀,失重腐蚀速率高达0.117 0mm/a,超出了净化厂腐蚀控制指标,腐蚀产物膜呈片状疏松堆积,其元素组成主要为Fe、O、S,腐蚀产物的主要成分可能是FeOOH、FeSO4、Fe2O3和Fe3O4,腐蚀进程的主控因素为湿度和酸度。结论认为,高含硫气田净化厂硫磺成型单元大气腐蚀较严重,对关键设备及承力结构钢应采取有效的防护措施。

Moist atmosphere corrosion of sulfur forming unit in high sulfur natural gas purification plants

The water granulation sulfur forming process is adopted by a high sulfur containing natural gas purification plant. The atmosphere around the sulfur forming unit in this plant is acidic and wet so that atmospheric corrosion has been a potential safety hazard that should not be neglected. In view of this, the coupons test was conducted around the sulfur formation vessel and the conveyor belts, and the microstructure and chemical components of corrosion products were studied through the SEM/EDS analysis. On this basis, the corrosion causes and main controlling factors were also discussed. The following findings were concluded. The atmosphere corrosion on the sulfur forming unit should never be overlooked, especially due to high temperature and large humidity around the sulfur forming unit vessel, the coupons there were corroded moderately with a corrosion rate of 0.1170 mm/a, which exceeds such a plant’s prescribed limit. The corrosion product membranes were found to be schistose aggregated loosely and mainly composed of the elements of Fe, S, O. A further integrated analysis implied that the corrosion products could be FeOOH，FeSO₄，Fe₂O₃ and Fe₃O₄. Humidity and acidity are the two major controlling factors of the atmosphere corrosion. The atmosphere corrosion is rather serious around the sulfur forming unit in such a desulphurization purification plant, so effective measures should be taken to protect those key equipments and the strength bearing structural steel.