Research On Catalytic Cracking Of VR/VGO Blending With Waste Grease Based On Structure-Oriented Lumping Method

It is necessary to select a proper method to optimize the composition of catalytic cracking feedstocks and the process conditions aiming at increasing the light oil yield as the crude oil is getting worse and worse. At the same time, it’s a good way to broaden the range of catalytic cracking feedstocks. In the context of that, the structure-oriented lumping method is taken to establish the catalytic cracking kinetic model of VR/VGO blending with waste grease, and the model is taken to optimize the blending ratio of waste grease and the process conditions.In order to take advantages of the structure-oriented lumping method to describe the multi-core molecular in catalytic cracking materials, four structural increments are added into the original structure-oriented lumping method. And then a material molecular matrix containing686single-core molecules,623multi-core molecules and36waste grease molecules is used to describe the molecular composition of vacuum gas oil, residue and waste grease. A set of analysis technologies,including True-Boilling Points Distillation, GC-MS, GPC and IR, is taken to make a detail analysis to the composition, structures and properties of catalytic cracking materials. And the relative content of every molecular lump is acquired with the nonlinear regression method.126reaction rules of single-and multi-core molecules and6reaction rules of waste grease molecules are established based on the carbon ion reaction mechanism, completing the establishment of reaction net. And the basic reaction rate constants of different reaction rules are acquired with genetic algorithms according to the product distribution of typical catalytic cracking materials. At last, the SOL model software package is built with MATLAB.The experimental results of lab-scale unit indicates that the SOL model could predict the product distribution and some typical molecular contents accurately, and the relative errors between the calculating and experimental values are less than10%.Taking theVR/VGO as feedstock, and considering light oil yield and olefin content in gasoline, the optimized result given by the model shows as follows:the proper blending ratio of VR=40%,T=505～525℃. C/O ratio=4.5～7, residence time=1.5～2s. The SOL model also says the proper blending ratio of waste grease is5%, and the proper process conditions are: T=500℃, C/O ratio=6.25. And the experimental results show that gasoline yield and conversion rate increase by0.64%and0.82%. but coke yield decreases0.49%after blending with waste grease. And the properties of gasoline and dissel are not changed, but the sulphur content decreases. The experimental results show that the relative errors between calculating and experimental contents of typical molecules in gas are less than8%.