催化裂化装置沉降器结焦与防治对策

Study on coking in settler of FCCU and prevention countermeasures

通过对催化裂化装置沉降器结焦原因分析,提高对结焦问题的再认识,认为反应油气中存在未气化和未转化的重油组分以及从汽提段汽提出来的"软焦炭"都是沉降器结焦的主要前身物。提出了抑制和减缓沉降器结焦的对策:合理设计原料雾化系统并与提升管优化匹配,最大限度消除"液雾生成区";采用降低油剂接触前催化剂温度来提高催化剂循环量,建议催化剂温度不小于630℃;合理应用高油剂混合能量技术以实现"大剂油比、强返混、短时间接触"的操作模式;合理控制反应深度,控制油浆密度(20℃)大于1 050 kg/m3时不回炼,降低反应油气中重油(油浆)组分含量;建议适宜的汽提段操作温度为500℃,进一步促进待生催化剂上携带的重质烃类转化。通过有效地采取上述措施,对抑制和减缓沉降器结焦能够起到积极作用。

The understanding of coking has been deepened through the analysis of the causes of coking in FCCU settler. It is concluded by the author that the main precursors of coke are the unevaporized and uncon- verted heavy oil component in reactor oil vapor and ＂soft coke＂ from stripping section. The following counter- measures are proposed to control and mitigate the coking in the settler： the design of feed atomizing system and riser reactor is optimized to eliminate the ＂ liquid mist formation zone＂ ; the temperature of catalysts is reduced before they contact with oil and appropriate temperature of catalyst is above 630 ℃ ; advanced catalyst and oil mixing technology is applied to realize the operation of ＂large catalyst to oil ratio, strong back mixing and short contact time＂ ; The reaction depth is properly controlled and slurry is not recycled when its density （20 ℃） is greater than 1 050 kg/m3 so as to lower the slurry in reactor oil vapor; 500 ℃ operating temperature is recom- mended for stripping section to further promote the conversion of heavy hydrocarbons carried over with the spent catalysts. The taking of above measures can inhibit and mitigate the coking in FCCU settler. Key Words： FCC, settler, liquid-phase heavy oil, eoking, high oil and catalyst mixing energy, stripper temperature