| The viscous oil is characterized by high density,high asphaltene content and poor mobility,which brings great challenges to its transportation and process.How to choose the appropriate process to upgrade the viscous oil is a big question which the related departments are confronted with and is also the corresponding hot of technology development.In this paper,fundamental study on visbreaking（VB）of oil sands bitumen vacuum residue（OSVR）and thermal cracking of OSVR with CO+H2/H2O were carried out,which laid the basis for the development of thermal cracking technology with CO+H2/H2O.The influences of different hydrogen source on the upgrading of OSVR were analyzed.This paper reveals the possibility of CO+H2/H2O system as potential hydrogen for the visbreaking process.A five-parameter dynamic model is established by a simplified reaction network.The results show that under the same reaction conditions,the viscosity and density of the oil produced with CO+H2/H2O are higher than that of the conventional visbreaking reaction,but its stability is better.Compared with conventional visbreaking,the coke induction period of thermal visbreaking with CO+H2/H2O extends 34 min at the same coke yield,the spot test rate reduces by 12 grades,the viscosity reduction rate is more than 29%,oAPI is slightly increased.The presence of H2-H2O,CO-H2O,CO+H2/H2O,N2-H2O can inhibit the coke formation and improve colloidal stability in the thermal modification of oil sand vacuum.For the four systems of this study,the order of inhibition of the coke formation capacity was H2-H2O>CO+H2/H2O>CO-H2O>N2-H2O.Compared with pure thermal visbreaking processing,the induction period of coke was respectively prolonged by 6 min,2.5 min,4 min,1 min in the system of H2/H2O,CO/H2O,CO+H2/H2O,N2/H2O.The use of CO+H2/H2O as potential hydrogen source for the thermal conversion of inferior viscous oil is similar to the case with pure hydrogen in improving product distribution,inhibiting condensation and the ability of providing hydrogen.It shows that the thermal conversion of inferior viscous oil using CO+H2/H2O as hydrogen source is effective and feasible.Compared with the pure VB process,the distillate yield in the CHVB process was raised by about 4.3 percentage at the same coke yield 0.1wt%.Under the same reaction conditions,the yield of each product component in the CHVB process was lower than that of pure VB process.The kinetic results showed that the thermal reaction of the OSVR with CO+H2 and the hydrovisbreaking reaction of OSVR are followed by the first order reaction kinetics.Compared with VB process,the reaction rate constants of oil sand vacuum to gas,distillate,diesel and vacuum gas oil was lower and the corresponding activation energy was higher,which revealed the reason why CO+H2/H2O system mitigated the thermal cracking of oil sand vacuum and improved its reaction severity. |
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