This paper describes many structural issues which are endemic to the FCC operation resulting in limitations in operational flexibility with subsequent negative impact on economics including items such as incomplete combustion of spent catalyst within the regenerator commonly referred to as the “salt and pepper” appearance of regenerated catalyst, erosion of reactor or regenerator hardware leading to unscheduled shutdowns or reduced cycle length, and poor aeration at the inlets of regenerated catalyst hoppers and along the length of the standpipes leading to poor fluidization and reduced catalyst circulation rates.
The CFD, coupled with spent catalyst regeneration kinetic model, is used is to evaluate the regenerator performance of a commercial regenerator. The results were used as basis to recommend hardware and operational modifications. The proposed modifications were subsequently modeled using the CFD kinetic tool to quantify the benefits.
A prominent refinery located in the eastern half of North America recently formed a team of FCC experts with the goal of identifying the root cause and delivering a solution to an exceptionally challenging case of maldistribution within their FCC regenerator. The result was a measurable reduction in the maldistribution resulting in a more stable operation with lower NOx, CO and particulate emissions. This approach may be an excellent model for other refineries facing similar issues within their FCC units.
This paper provides an overview of how afterburn presents itself in various operations describing both the stable and unstable forms of general or localized afterburn.
This work was originally presented at the 2016 AFPM Annual Meeting.
This project delivered an excellent outcome, giving us confidence that specific hardware changes would restore the operation of our Cracker to the level we expect – which it did. Our team’s collaborative approach brought together CPFD’s expertise and our refinery knowledge.
— Thys Heyns, Viva Energy Australia, General Manager of Refining
