This work aims to develop a molecular-level process model framework for simulating the FCC process. The process model consists of the riser, regenerator, and separation models. A complex molecular-level kinetic model, containing 3,652 molecules and 8,202 reactions, was developed for the heavy oil FCC process. The kinetic model was coupled with the riser model, and the model parameter was tuned by a set of systematic experimental data from a pilot-scale plant. After that, a two-zone and two-phase regenerator model was built. The regenerator was combined with the riser model, and the coupled modeling and process simulation for the riser-type FCC unit was developed. The results show that the calculated value of fraction yields and key bulk properties agrees well with the experimental data. Moreover, the molecular distribution of the product and temperature profile was also predicted.

The molecular conversion of complex mixture involves a large number of species and reactions. The corresponding kinetic model is consist of a series of ordinary differential equations (ODEs) with severe stiffness, leading to an exponentially growing computational time. To reduce the computational time, we proposed a mass-temperature decoupled discretization strategy for a large-scale molecular-level kinetic model. The method separates the mass balance and heat balance calculations in the rigorous adiabatic reactor model and divided the reactor into several isothermal segments. After discretization, the differential equations for heat balance can be replaced by algebraic equations between nodes. We used a molecular-level diesel hydrotreating kinetic model as the case to validate the proposed method. We investigated the effects of temperature estimation methods and node number on the accuracy of the model. A good agreement between the discretization model and rigorous model was observed while the computational time was significantly shortened