Abstract: The direct catalytic cracking technology of crude oil can realize a one-step leap from crude oil to olefins and aromatics, which is of great significant implications for the transformation and upgrading of the refining industry in China. Using total fractions of paraffin-base crude oil (159-780 ℃) as raw materials, the modeling strategy of the structure of mixed fractions and molecular composition lumped-block was used to model and calibrate the process parameters of direct catalytic cracking of crude oil to olefin (UPC). The accuracy of this method was validated by using industrial test data. In order to produce more olefin and control coke formation, the model was optimized by using the NSGA-Ⅲ multi-objective optimization algorithm, and the optimized operational parameters were obtained. The optimized operating conditions were as follows: first-stage preheating flash temperature at 194.32 ℃, second-stage preheating flash temperature at 228.16 ℃, first-stage riser reactor outlet temperature at 615.73 ℃, and second-stage riser reactor outlet temperature at 622.59 ℃. The total yield of ethylene and propylene by UPC process was 53.367%, and that of coke was 8.311%. In addition, due to the fact that the tax contribution of fuel-based process was obviously higher than that of chemical process, the olefin yield was greatly increased and the fuel oil yield was greatly decreased after the optimization of UPC process parameters, and the gross value of crude oil production decreased by RMB 44.30 Yuan/t.

Key words: whole fraction, paraffin-base crude oil, direct catalytic cracking of crude oil, molecular lumping, process simulation, multi-objective optimization