Abstract: The n-d-M method, E-d-M method and hydrocarbon group (PONA) analysis method were used to analyze the composition and properties of the existing delayed coker feedstocks(vacuum residue,FCC slurry) and ethylene tar. The conductivity and thermal weight loss (including TGA and DTA) of feedstocks were measured, and the influence of blending ethylene tar on the stability and pyrolysis process of delayed coker feedstocks colloid was studied. The results showed that blending ethylene tar in the existing delayed coker feedstock would lead to a decrease in the saturation and an increase in the aromatic content of the feedstock. In the case at 35 oC, the colloidal stability parameters of delayed coker feedstocks increased with the increase of the ethylene tar blending ratio, and the colloidal stability was improved in a certain range. In addition, the mixing ethylene tar would lead to the coking reaction trend in advance and higher coke yield, and the yield of each distillate in the product would change significantly. It proves that the pyrolysis process and the pyrolysis products compositions are complicated after mixing ethylene tar.

Key words: ethylene tar, delayed coking, colloidal stability, pyrolysis