Fluid catalytic cracking (FCC) is one of the most important conversion processes in petroleum refineries. In modern FCC units, the risers have served as the major commercial reactor, where the low value heavy hydrocarbons were cracked into more valuable products such as gasoline and light olefinic compounds. And a regenerator is used for recovering catalysts' reactivity. These two reactors collaborate with each other to crack the feed oil and realize the recycle of the expensive and considerable quantity of catalyst in FCC units. In this thesis, CFD (Computational Fluid Dynamics) has been used to simulate three-dimensional multi-phase, multi-species, turbulent reacting flow in fluid catalytic cracking (FCC) process. In the regenerator, a three dimensional multiphase model which used to simulate the gas-solid two phases flow hydrodynamics and inter phase reactions was presented. A modified drag model used to describe the gas-solid two phases interaction was developed. The results obtained from numerical iterations have a good agreement with the field data. Parametric studies on operation parameters such as air flow rate and oxygen enrichment were conducted based on the real operation experiences. In the riser, FCC catalyst, oil, and air were used as the solid, liquid, and gas three phases, respectively. A hybrid technique for coupling chemical kinetics and hydrodynamics computations was employed, where the simulation was divided into two parts, one is reacting flow hydrodynamic simulation with a small but sufficient number of lumped reactions to compute flow filed properties, and the other is reacting flow hydrodynamics with many subspecies where complex chemical reactions occur. A four-lump kinetic model was used for the major species simulation and a fourteen-lump kinetic model was used for the subspecies simulation. The results were validated against measurements. And the effect of catalyst temperature on the cracking reactions was evaluated.
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