Development and application of counter‐current feed injection technology in riser reactors

A counter‐current feed injection scheme is proposed to improve the jet‐solid mixing and reaction in the injection zone of riser reactors. By analyzing the characteristics of the coupled flow field, combined with experiments and numerical simulation, the advantages of the new injection technology are investigated. Experimental results show that the particles distribute more uniformly when the feed is injected downward, which is good for the mixing and reaction of the jet with particles. By simulating the reaction in an industrial fluid catalytic cracking (FCC) riser, it is found that the yields of gasoline and liquefied petroleum gas (LPG) are increased significantly by using the counter‐current feed injection structure. Simultaneously, the formation of coke is reduced considerably. On this basis, a riser‐fluidized bed coupled reactor was designed by adopting the proposed counter‐current feed injection technology to solve the coking problem in an industrial pyridine synthesis system. Results from the side‐stream sampling show that the carbon content of the catalyst reduces significantly, indicating a decrease in coke formation. By now, the improved industrial reactor has been in stable operation for 2 years, showing good reliability.