海水淡化用薄壁卷焊钛管传热及耐蚀性能

Heat transfer and corrosion resistance experiments of thin-wall curling-welding titanium tube for desalination

采用TIG自动卷焊工艺制备了Φ22mm×0.4mm规格的薄壁卷焊TA2传热管,借助低温多效蒸馏海水淡化中试平台开展了薄壁卷焊钛管在海水应用环境中的传热及耐蚀性能实验研究。采用失重法分析评价了其耐腐蚀性能,并与标准规格Φ22mm×0.5mm无缝钛管在耐腐蚀性能、投资经济性方面进行了对比。结果表明:在低温多效海水淡化实际应用条件下,薄壁卷焊钛管总传热系数可达3400W/(m^2·K)以上;在降膜蒸发喷淋冲刷及浓海水高温高湿腐蚀环境中,薄壁卷焊钛管与无缝钛管具有同等优良的耐海水腐蚀性能,年平均腐蚀速率小于0.0003mm/a,焊缝处也未发现点蚀现象,能满足实际海水淡化工程对材料的应用要求。相比于传统无缝钛管,同等传热面积条件下,薄壁卷焊钛管能使海水淡化传热材料投资降低25%以上,在海水淡化、石油化工等领域应用前景广阔。

One type of Φ22 mm×0.4 mm thin-wall welded titanium tube was developed using Tungsten Inert Gas(TIG) curling-welding technology. Heat transfer and corrosion resistance experiments on this kind of tube were conducted in the circumstance of practical desalination operating conditions based on the LT-MED pilot scale test platform. Weight loss method was adopted to evaluate the resistance to seawater corrosion of titanium tube. The Φ22 mm×0.4 mm thin-wall welded titanium tube was compared with Φ22 mm×0.5 mm rolled seamless titanium tube in terms of corrosion resistance and service economy.The results indicated that the total heat transfer coefficient of falling film evaporator with thin-wall welded titanium tube would be over 3400 W/(m^2·K) in the LT-MED experimental conditions, and the thin-wall welded titanium tube had the same excellent corrosion resistance as rolled seamless titanium tube in the operating environment of falling film flow of seawater and high temperature and high humidity corrosion of brine. The annual mean corrosion rate was less than 0.0003 mm/a. No pitting corrosion was found at welded seams during the testing process. The utilization requirements validity of thin-wall welded titanium tube for desalination was verified. Comparing with the usual rolled seamless titanium tube, the spread application of thin-wall curling-welding titanium tube in the LT-MED device can greatly decrease investment cost of heat transfer tube by more than 25% under the same heat transfer area. The research results show that thin-wall welded titanium tube have an extensive application prospect in the field of thermal desalination and petrochemical engineering.