Experimental validation of a new heat transfer intensification method for FCC external catalyst coolers

Abstract

In petroleum refining industry, external catalyst cooler is a key device in FCC units processing heavy residue feedstock. In this study, a new heat transfer intensification method was proposed for FCC external catalyst coolers, which aims to increase their bed-to-wall heat transfer coefficient by enhancing the internal solids mixing and thus the particle renewal on heat tube surface by a double-distributor design. To validate this idea, a large cold model with similar heat tube design and heat transfer mechanism to industrial catalyst coolers was built. Heat transfer coefficient and axial profiles of particle concentrations were measured under different operating conditions. The experimental results proved the feasibility of this heat transfer intensification idea. Higher bed-to-wall heat transfer coefficient, smaller fluidizing gas usage and higher adjustment flexibility are realizable in the new catalyst cooler. It is also learned from this study that uniform gas distribution, limited wall effect, good fluidization state are necessary to achieve good heat transfer performance in FCC external catalyst coolers. An effective height was speculated from the axial tube wall temperature distributions, within which the heat transfer intensification of the new catalyst cooler is effective. This effective height is also found to rise with increasing superficial gas velocity.