Integrated FCC riser—regenerator dynamics studied in a fluid catalytic cracking pilot plant

Abstract

In this paper a dynamic simulator of the FCC pilot plant, operated in Chemical Process Engineering Research Institute (CPERI), is presented. The simulator was developed and verified on the basis of steady-state and dynamic experiments. The operation of the pilot plant permits the execution of case studies for recording of the dynamic responses of the unit, by imposing substantial step changes in a number of the manipulated variables. The comparison between the dynamic behavior of the unit and this predicted by the simulator, arise useful conclusions on both the similarities of the pilot plant to commercial units along with the ability of the simulator to depict the main dynamic characteristics of the integrated system.The simulator predicts the wt% feed conversion, the wt% coke yield and the heat consumed by the catalytic reactions in the FCC riser on the basis of semi-empirical models developed in CPERI and simulates the regenerator according to the two-phase theory, with a dilute phase model in account for post-combustion reactions. The riser and regenerator temperature, the stripper and regenerator pressure drop and the composition of the regenerator flue gas are measured on line and are used for verification of the ability of the simulator to predict the dynamic transients between steady states in both open-and closed-loop unit operation. All the available process variables such as the reaction conversion, the coke yield, the carbon on regenerated catalyst and the catalyst circulation rate are used for the validation of the steady state performance of the simulator. The results reveal the ability of the simulator to predict accurately the operation of the pilot plant in both steady state and dynamic conditions. The dynamic simulator can serve as the basis for the development of a model based control structure for the pilot plant, besides its use as a tool for process optimization studies.

Feed conversion targeting in an FCC pilot plant using a non-linear MPC strategy

“…In general, the process model should be accurate enough to maintain good prediction properties over the range of operating conditions of interest. The ability of the PP model to simulate accurately the dynamics of the PP has been demonstrated previously [1][2][3].…”

“…The pseudo-steady state and dynamic sub-models that constitute the PP dynamic simulator have been presented in the literature [1][2][3]12] and are not the subject of this paper. However, it is needed to clarify that the catalyst characteristics were represented by indices [2].…”

“…Practically, the system of equations (1)-(5) concisely describes the mass and energy balances of the riser section [3]. The operational variables (unknowns) in this system are 14, namely the conversion (y x ), the coke yield (y c ), the feed, inert and catalyst rates ( F W , N , C ), the pressure ( ) and the temperature ( ) of the reactor, the feed preheat temperature ( ), the temperature at the regenerator dense section ( ), the feed vaporization enthalpy (…”

“…In previous work [1][2][3] a dynamic mathematical model has been developed and verified on the basis of steady state and dynamic experimental data of the CPERI FCC PP. The effective manipulated variables in the PP (and its simulator) are the catalyst circulation rate, feed preheat temperature, combustion air flow rate (and temperature), and gas-oil feed flow rate, whereas the gas-oil composition and the catalyst quality are considered as disturbances.…”

FCCU simulation based on first principle and artificial neural network models

“…[9,10] One very important reason for this complexity is given by the kinetics of the process, because the feedstock consists of thousands of components. The estimation of intrinsic kinetic constants is extremely difficult in this case.…”