SiO_2/S涂层与乙酸钾抗结焦性能的对比

Comparison Between the Anti-Coking Properties of SiO_2/S Coating and Potassium Acetate

以石脑油为裂解原料,在850℃下对退役HP40炉管内表面进行结焦试验,并对比了SiO2/S涂层与乙酸钾的抗结焦性能。采用场发射扫描电子显微镜(FE-SEM)和透射电镜(TEM)表征了焦炭形貌,采用热重(TGA)、元素分析和拉曼光谱考察了焦炭结构。结果表明,由于退役HP40炉管内表面状态的改变,加剧了催化结焦。SiO2/S涂层可以有效地抑制催化结焦,其结焦抑制率达到65%,但是SiO2/S涂层剥落后,焦炭以催化焦为主,同时夹杂着部分热裂解焦。当乙酸钾质量分数为400μg/g时,抑焦率达到60%。当乙酸钾质量分数分别为0、100、200和400μg/g时,丝状焦直径分别为100、60、45和35nm。SiO2/S涂层与乙酸钾对焦炭结构影响较小,退役HP40炉管内表面焦炭为高沸点、缩合度较高的大分子,石墨化程度较低。

Coking tests were carried out on the inner surface of after-service HP40 cracking tube at 850℃ with naphtha as feed.The anti-coking properties of SiO2/S coating were compared with that of potassium acetate addition.The morphologies of cokes deposited on the surface were characterized by field emission scanning electron microscopy（FE-SEM） and transmission electron microscope（TEM）,and the structure of cokes was analyzed by TGA,elemental analysis and Raman spectroscopy.The results showed that the changes of the inner surface conditions of after-service HP40 cracking tube led to the accelerated catalytic coking.SiO2/S coating could inhibit catalytic coking,and coke deposition was reduced by 65%.Cokes deposited on the coating-spelled region were mainly catalytic coke mixed up with some pyrolytic coke.Coke deposition was reduced by 60% when potassium acetate was added with the mass fraction of 400 μg/g.The diameters of filamentous coke were about 100,60,45 and 35 nm when potassium acetate was added with the mass fraction of 0,100,200 and 400 μg/g,respectively.SiO2/S coating and potassium acetate had little effect on the structure of cokes deposited on the inner surface of after-service HP40 cracking tube.The coke was the substances with a high molecular mass,very condensed structure,high boiling point,and presented a low graphitization degree.