A two‐zone model for fluid catalytic cracking riser with multiple feed injectors

Abstract

Developments in modeling of the fluid catalytic cracking (FCC) process have progressed along two lines. One emphasizes composition-based kinetic models based on molecular characterization of feedstocks and reaction products. The other relies on computational fluid dynamics. The aim is to develop an FCC model that strikes a balance between the two approaches. Specifically, we present an FCC riser model consisting of an entrance-zone and a fully developed zone. The former has four overlapping, fan-shaped oil sprays. The model predicts the plant data of Derouin et al. and reveals an inherent two-zone character of the FCC riser. Inside the entrance zone, cracking intensity is highest and changes rapidly, resulting in a steep rise in oil conversion. Outside the entrance zone, cracking intensity is low and varies slowly, leading to a sluggish increase in conversion. The two-zone model provides a computationally efficient modeling approach for FCC online control, optimization, and molecular management.

Dispersion of feed spray in a new type of FCC feed injection scheme

“…In an ideal condition, the atomized feed oil should contact with the catalysts rapidly and uniformly so that the maximum yield in gasoline, LPG and diesel are obtained. However, the actual flow and contact of oil with catalysts in the traditional FCC feed injection scheme are quite different from the ideal because of the very complex hydrodynamics of gas‐solid flow in that zone . Extensive work has been done to explore the effects of feed injection on the hydrodynamic behavior in the feed mixing zone, and it included both experimental research and numerical simulation.…”

Review of Research Related to Fluid Cokers

“…A diverging tip results in spray jets that expand with a larger angle, which seems to help improve the liquid distribution ,,, by promoting the entrainment of bed particles into the spray jet cavity. ,,, More sophisticated nozzle tips, such as cloverleaf attachments, ,,, help achieve a larger interfacial area between the jet cavity and the fluidized bed and usually improve liquid distribution (Figure ). In the FCC process, nozzles that provide a fan-shaped jet have successfully increased the interfacial area between the jet and bed. , Adding a solid surface on which the spray impacts can significantly improve the liquid distribution, , but the erosion of the strike surface would be a concern.…”

“…103 In the FCC process, nozzles that provide a fan-shaped jet have successfully increased the interfacial area between the jet and bed. 130,144 Adding a solid surface on which the spray impacts can significantly improve the liquid distribution, 140,145 but the erosion of the strike surface would be a concern. Gas and liquid properties affect the spray characteristics.…”

Physicochemical Processes Occurring inside Clusters Consisting of FCC Catalyst Particles

“…Fluid catalytic cracking (FCC) is widely applied in the oil refining industry. In the riser reactor of the FCC unit, vacuum gas oil (VGO), when in contact with hot regenerated catalyst particles, can be converted into lighter products through catalytic cracking . The FCC riser is a typical gas‐solid reaction system, in which complicated transport phenomena and chemical reactions occur on multiscale structures, including two boundary‐scale structures (microscale structure, such as individual catalyst particles and macroscale structure, such as the whole gas‐solid mixture in the FCC riser), and the intermediate or mesoscale structure (cluster consisting of a number of FCC catalyst particles) .…”