Fluidized catalytic cracking with novel emulsified feeding for increasing light oil yield and reducing additional CO₂ emission

The fluid catalytic cracking unit (FCCU) is widely used in the processing of heavy oil. Fast and sufficient vaporization of heavy oil can maximize the light oil yield and reduce the coke yield. However, the inferior quality generally makes the heavy oil difficult to be vaporized. Unvaporized oil remaining on the catalyst surface will lead to high coke yield and subsequently high carbon dioxide emissions in the regenerator. The novel emulsified feeding technique can achieve secondary atomization of oil droplet through micro-explosion, which can reduce the droplet diameter and enhance the droplet vaporization. Computational Fluid Dynamics (CFD) simulation was performed to investigate the effect of emulsified feeding on the droplet vaporization and cracking reaction in the FCC riser reactor. It was found that when the reaction temperature is constant, the emulsified feeding can promote the droplet vaporization and cracking reaction. The average vaporization ratio can be improved by 1.2%-1.7%, and the light oil yield can be improved by 0.6%-0.8% compared to the conventional atomized feeding. The volume fraction of droplet near the side wall is largely reduced. The additional carbon emissions produced by unvaporized oil can therefore be reduced in the regenerator. In addition, the emulsified feeding technique will not have great impact on solids fluidization and pressure balance in the riser. The probability of micro-explosion of emulsion droplets is further discussed with respect to its effect on the vaporization and cracking reaction. The maximum light oil yield can be obtained with micro-explosion probability of 85%.