Carbon Residue Removal Of Heavy Oil By Thermal Cracking In Supercritical Water

Carbon residue removal behavior of heavy oil thermal cracking was investigated under supercritical water(SCW)with reaction temperature of 390℃,water to oil ratio of 2:1～4:1(wt)and water density of 0.15～0.25 g/cm3,and compared with thermal cracking under supercritical benzene.At high water to oil ratio and high water density,thermal cracking of heavy oil can be transferred from oil phase to SCW phase.Compared with thermal cracking in oil phase,heavy oil cracking in SCW phase is significantly accelerated.Due to the coke-like structure self-assembly and accelerated condensation coking of resin and asphaltene rich in carbon residue under SCW,cracking liquid products with low carbon residue content,low molecular weight and relatively high H/C ratio can be obtained.Although the intervention of supercritical benzene can accelerate thermal cracking of heavy oil from the perspective of diffusion improvement,the acceleration of the condensation of heavy oil components is not selective.Carbon residue content of the liquid cracking products under supercritical benzene has decreased,but carbon residue removal efficiency is not as good as reaction under SCW environment.In order to quantitatively study the relationship between carbon residue content and internal properties of cracking products,quantitative relationship between carbon residue content and H/C ratio,asphaltene,SARA components were established by multiple regression.Calculation results show that asphaltene contributes the most to carbon residue,followed by resin.According to molecular dynamics simulations,different structures of condensed ring aromatic hydrocarbons have different thermal cracking behaviors and have different contributions to carbon residue.