LNG工厂停产状态下循环冷却水腐蚀性研究

为了研究停产状态下循环冷却系统特性,以便更好地控制循环水水质,防止循环系统腐蚀、结垢。结合LNG工厂停产情况下循环系统药剂控制实例及配套工艺操作,通过更换药剂种类、优化加药方案,依据水质化验数据分析和挂片腐蚀实验结果,表明药剂控制方案可行。研究表明,停工状态下沉积在管道中的黏泥和腐蚀产物等污垢较多,易产生垢下腐蚀并阻碍了缓蚀药剂与金属表面的接触,影响了缓蚀效果。浓缩倍数是影响药剂效果的关键因素。高浓缩倍数状态时,药剂在水中的停留时间会更长,应选用稳定性优良,不易分解的药剂。若浓缩倍数发生大幅降低,则必须立即更换相应药剂。

Study on the corrosivity of the recirculating cooling water during shutdown in LNG plant

In order to better control the water quality so as to inhibit the corrosion and scaling, the characteristics of the recirculating cooling system during shutdown state were studied. Related to chemical dosing cases and operating procedures, chemicals were screened and chemical dosing program were optimized. The designed chemical scheme were proved to be feasible by analyzing the water quality data and coupon corrosive test results. The study showed that since there were more dirts such as slime and corrosion products depositing in the pipeline under the shutdown state, under-deposit corrosion is prone to occur and the effects of corrosion inhibitors are degraded by reducing the contact between the metal surfaces and inhibitors. Cycles of concentration (CoC) is the key factor for the function of the corrosion inhibitors. Considering the high residence time of the chemicals in water at high CoCs, it would be better to choose the stable and persistant chemicals. Correspondingly, the chemicals need to be replaced when the CoC is reduced significantly.