为了缓解换热通道壁面金属催化结焦,在温度为800℃,时间为2 h条件下,实现了内径为2 mm,长度700 mm的304不锈钢管道内表面TiN涂层的化学气相沉积(CVD);进一步,在700℃的氧化气氛中,将TiN涂层氧化得到TiO2涂层。采用扫描电子显微镜(SEM)、能量散射X射线谱(EDS)和X射线衍射(XRD)仪等分别检测了涂层的形貌、元素组成和晶型结构。检测结果表明,CVD法制备的TiN、TiO2涂层表面均匀完整,粒子结合紧密,其组成基本符合化学计量比;其中TiN为立方晶相结构,TiO2为金红石相结构。以某种碳氢燃料A为原料采用自制的超临界裂解装置对TiN、TiO2涂层的抑制结焦效果进行了初步评价。结果表明,与304空白管相比,TiN涂层管和TiO2涂层管高温稳定运行时间明显延长,其中TiN涂层管抑焦效果更加显著。
In order to inhibit the metal catalytic coking, a TiN coating was deposited on the inner surface of stainless steel oil duct with the internal diameter of 2 mm and the length of 700 mm by chemical vapor deposition(CVD), in the process of which the deposition temperature was set as 800 ℃ for 2 h.Furthermore, the TiN coating turned into TiO2 coating in oxidizing atmosphere at 700 ℃.The coating's morphological features and textures were characterized by SEM, EDS and XRD.As shown in SEM, the surface of the TiN and TiO2 coating prepared by CVD, is continuous, close-packed and homogeneous.According to the observation of EDS, both of them are stoichiometric.The results from XRD indicate that the TiN in the coating has cub phase and the TiO2 has rutile phase.A supercritical cracking system was set up for preliminary evaluating of the coking inhibition characteristic of two kinds of inhibitors and with some hydrocarbon fuel A as feedstock.The results show that compared with the 304 blank tube, the duration time of fuel cracking at high temperature is enhanced obviously in TiN and TiO2 coating tubes, and the anti-coking performance of TiN is more significant.