(28b) Tower Internals Modifications Improve Performance of Atmospheric Crude Tower

ENAP Refinerias operates a crude unit topping column at the Bio Bio refinery in Talcahuano, Chile. The refinery engineers expressed concern with discoloration of the atmospheric gas oil (AGO) product, which could be symptomatic of entrainment of heavy reduced crude into the AGO draw collector. Plugging of the liquid distributor above the stripping section was observed during previous shut-downs and this was considered to be a major contributor to the poor AGO product quality. Koch-Glitsch performed a detailed hydraulic analysis of the existing equipment below the AGO draw collector using process simulations of the current topping unit operation. Based on this analysis, the wash tray weirs were modified, down-pipes were added below the bottom wash tray seal pan and the stripping section liquid distributor was replaced. The new equipment was designed, fabricated and installed within a three week period. After the column was put back into service the atmospheric gas oil color improved and its metals content decreased significantly. This paper describes the details of this revamp.