Abstract Delayed coking is one of the most widely used residue upgradation process in crude oil refining where vacuum residue is thermally cracked and converted into distillates and petroleum coke. During heating of vacuum residue in coker furnace, coke is continuously deposited in furnace tubes which is removed at regular intervals by one of the three methods namely (i) pigging, (ii) steam air decoking or (iii) online spalling (OLS). OLS is one of the preferred methods of coke removal from coker furnace tubes. We have noticed very effective as well as “not so effective” OLS in a commercial delayed coker furnace. In present article, the changes in composition and properties of furnace coke during effective and ineffective OLS were systematically analyzed by various analytical tools such as Dilatometer, TGA, HRSEM, SEM-EDX and XRD. Based on these analyses, it was found that inorganic deposits such as iron sulphides and tube metal corrosion products play a major role in failure of OLS. Higher total acid number (TAN) of vacuum residue may be promoting the formation of iron sulfide deposits in furnace tube.

中文翻译：

---

延迟焦化炉管沉积焦炭成分对在线剥落的影响

摘要 延迟焦化是原油精炼中应用最广泛的渣油提质工艺之一，将减压渣油热裂解转化为馏分油和石油焦。在焦化炉中加热减压渣油期间，焦炭连续沉积在炉管中，焦炭通过三种方法之一定期清除，即 (i) 清管、(ii) 蒸汽空气除焦或 (iii) 在线剥落 (OLS)。OLS 是从焦化炉管中去除焦炭的首选方法之一。我们已经注意到在商业延迟焦化炉中的 OLS 非常有效和“不太有效”。在本文中，通过膨胀计、TGA、HRSEM、SEM-EDX 和 XRD 等各种分析工具系统地分析了有效和无效 OLS 期间炉焦的成分和性质的变化。基于这些分析，发现无机沉积物如硫化铁和管金属腐蚀产物在 OLS 失效中起主要作用。减压渣油的较高总酸值 (TAN) 可能会促进炉管中硫化铁沉积物的形成。