Modelling and simulation of FCC riser reactors: An heterogeneous approach

The present dissertation considers an in-depth study of Fluidized Catalytic Cracking (FCC). It is postulated that advanced FCC reaction models require the determination of relevant parameters for both adsorption and reaction. With this in end two series of experimental runs are developed in a novel CREC Riser Simulator.; The first series of experimental tests, 17 in total, is addressed to study thermal cracking. These tests show that thermal cracking at 560{dollar}spcirc{dollar}C and above is important even in catalytic cracking runs. From these experiments and besides the kinetic parameters, the molecular weights for various product lumps and a reaction order, for gas oil thermal cracking, are determined.; The second series of experimental runs, 26 in total, are valuable for assessing catalytic cracking kinetics and adsorption phenomena. Adsorption parameter estimation provides insights regarding the limits of "b" and {dollar}gamma{dollar} adsorption parameters. For each "b" value there is at least one region for {dollar}gamma{dollar} which produces K{dollar}rmsp{lcub}o{rcub}{dollar} and Ea parameters satisfying expected adsorption trends: It is shown that K{dollar}rmsb{lcub}i{rcub}{dollar} (T, MW{dollar}rmsb{lcub}i{rcub}){dollar} decreases with temperature and molecular weight. Using the estimated adsorption parameters the amount of adsorbed hydrocarbons is calculated to be between 8 and 36wt% (coke included) and these values are compatible with published literature data.; On this basis a novel heterogeneous catalytic cracking model, including reaction and adsorption, is developed. This task also considers a parameter estimation procedure. Given the satisfactory prediction of the experimental data it is concluded that both the parameter estimation and the heterogeneous model are most adequate. Moreover, taking into account the complexity involved and the large number of estimated parameters, 38 in total, it is judged that the development of the proposed model and of the related parameter estimation procedure is accomplished successfully.; Given the importance of riser hydrodynamic simulation, a multidimensional multiphase flow hydrodynamics model is examined for isothermal ambient conditions (cold model). With this in end, a commercial CFD code is employed. It is shown that the two-phase Navier-Stokes equation with turbulence and phase viscosity correction functions do not reproduce experimental data reported in the technical literature. This is particularly true for the particulate volume fraction profiles. However, if additional forces, like the Saffman lift force, are included in the model, experimental radial velocities and volume fractions profiles are obtained and this applies to both the particulate phase and the gas phase.; Moreover, in addition to the multidimensional multiphase isothermal model, a one-dimensional non-isothermal heterogeneous model is investigated. This new model accounting for the endothermicity of the cracking reactions and incorporating realistic kinetics shows that adsorption is a very important phenomenon in FCC. In fact, combined adsorption and reaction influences significantly both the riser hydrodynamics and the riser performance.