延迟焦化工艺弹丸焦形成原因和对策

延迟焦化工艺生产过程中有时会产生弹丸焦，通过对渣油生焦机理和形成弹丸焦时的渣油性质进行分析，得出渣油的沥青质含量、金属（V+ Ni）含量高是产生弹丸焦的原因。采取渣油合理掺炼，控制渣油中的沥青质含量不大于9.3%、稳定因子不大于0.30、金属（V+ Ni）含量不大于244μg/g，可以避免弹丸焦产生，另外通过降低加热炉温度，提高循环比和反应压力等优化操作手段，也可以抑制弹丸焦的生成。

CAUSES OF SHOT COKE FORMATION IN DELAYED COKING UNIT AND COUNTERMEASURES

Shot coke was formed in delayed coking unit when processing poor quality crude oils.By reviewing coke formation mechanism and analyzing the properties of residue feedstock which shot coke was formed,it was found that high in asphaltene and metals(Ni+V)contents of feedstock was the main cause of shot coke formation.Measures,such as proper adjusting the blending ratios of various residue feeds to control the feedstock properties including asphaltene content,metals content and stable factor not more than 9.3%,244μg/g and 0.30,respectively,could significantly reduce the chance of forming shot coke.Furthermore,when processing poor quality residue feedstock,optimizing operation parameters,such as decreasing furnace outlet temperature,increasing recycle ratio and reaction pressure,could suppress the formation of shot coke as well.