Usage of CFD modelling for improving an FCC riser operation

The homogeneity of the regenerated catalyst flow upstream of the feed injectors at the bottom of an industrial FCC (Fluid Catalytic Cracking) riser was thoroughly investigated using several techniques (sampling, temperature and gamma -scan survey). It appeared that marked maldistribution was taking place, due to a bend at the bottom of the riser, which could not be corrected by the existing steam injection system. The situation was analysed by use of CFD (Computational Fluid Dynamics) modelling with an approach adapted to circulating fluidised beds, which was able to describe the catalyst flow pattern and viodage distribution. A new steam injection layout was then designed using the CFD model and implemented. Field observation subsequent to the implementation revealed that the goal had been achieved, as demonstrated by the temperature map above the feed injectors. The better homogeneity of the catalyst flow resulted in an improved catalyst/feed contacting and better performance of the unit.