摘要:

Downward feed injection scheme is more promising than traditionally upper feed injection scheme for FCC riser reactors, however, its effects on the whole riser performance have not been elaborated. This study aims at CFD modeling of hydrodynamics and chemical reactions in an industrial-scale riser reactor, with focus on the influence of downward feed injection scheme. For this purpose, a CFD model, verified earlier in a real industrial riser reactor, is extended to the present work. The hydrodynamics, temperature profile and species concentration distribution in the riser reactor with the downward feed injection scheme are numerically studied and compared to those in the upper feed injection scheme. The results indicate that different from the smooth evolution in the upward feed injection scheme, the gas velocity, particle content and riser temperature in the downward injection scheme exhibit local maximum value in the feed injection zone. In the middle and upper zones of the riser reactor, the downward 45° and 60° injections show lower gas velocity and riser temperature than the upward 60° injection while the downward 30° injection shows an opposite trend. The downward feed injection scheme with an angle of 45° and a velocity of 60 m/s is optimal for the present industrial-scale riser reactor. Compared to the traditionally upper feed injection scheme, the new downward feed injection scheme could enhance the yields of the diesel and gasoline species by 0.93 and 0.29% point and reduce the yields of the dry gas and coke species by 0.61 and 0.96 unit.

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