石油馏份蒸汽裂解结焦动力学

Kinetics of Coke Deposition in Steam Pyrolysis of Oil Fractions

在可连续测量石油烃水蒸汽热裂解结焦速度的流动积分反应装置上,研究了石脑油和轻柴油结焦速度与温度、烃分压和动力学裂解深度的关系,小试与工业炉的结焦过程,给出了结焦模型。结果表明,同小试一样,工业炉的结焦反应也为反应控制。结焦反应的活化能随原料的芳烃指数增大而变小。结焦速度与结焦母体随裂解深度的变化表明,在低裂解深度下,原料和焦油中的芳烃是主要结焦母体,在高裂解深度下,二次反应生成的“缩聚物”是主要结焦母体。

With equipment specially designed and assembled for studying coke deposition in pyrolysis of hydrocarbons, kinetics of coke deposition during pyrolysis of naphtha and light gas oil was studied at temperatures of 1033—1223K, KSF of 0.6—8 and under hydrocarbon partial pressure of 0.2—0.7atm. The effect of run time on coking rates showed that kinetics of coking reaction was a limiting step in coking. In naphtha pyrolysis an activation energy of coke formation of 88—100kJ/mol was consistent with an activation energy of commercial pyrolysis furnaces of 104kJ/mol. And during gas oil pyrolysis an activation energy of coke formation of 142kJ/mol was consistent with an activation energy of commercial pyrolysis furnaces of 151kJ/mol. This showed that kinetics of coking reaction was also a limiting step in coking in commercial pyrolysis furnaces. An activation energy of coke formation in highly dependent on the BMCI of feedstock, the higher the value of BMCI, the lower will be the value of activation energy. The existence of a minimum coking rate with KSF, and composition of pyrolysis product showed that oil atmospheric distillate with multi-alkyl substituted aromatics in gas oil were highly active coking precursors.