Additional Feedstock for Fluid Catalytic Cracking Unit

Abstract

Fuel refineries are configured with Fluid Catalytic Cracking Unit (FCCU) to convert Vacuum Gas Oils (VGO) into higher value gasoline and middle distillates. But such refineries also generate 8–12% of heavy oils known either as decant oil or clarified oil (CLO), which has to be downgraded as furnace oil. The recycling of the decant oil into FCCU along with VGO feed is restricted to maintain the coke formation within design limits so that there is no decrease either in conversion or yield of liquid products from FCC operations. The condensed aromatic ring compounds present in CLO makes it undesirable feedstock for cracking, as it promotes heavy coke formation on the catalyst. Hence, CLO is disposed by absorbing in the residual fuel oils.

Of late, FCC units are being operated with higher severity to maximize gasoline, and this has resulted in much higher concentration of condensed aromatics in CLO. Hence, better utilization of CLO depends on separating its saturated hydrocarbon components as a good feedstock for recycling into FCCU with the simultaneous production of extract with enriched poly condensed aromatics as a value added product, namely Carbon Black Feed Stock (CBFS). This article describes several extraction studies carried out on CLO to obtain raffinate for which cracking studies were carried out in automated Micro Activity Test (MAT) unit. The quality of extract phase from each of the above studies was evaluated for its suitability as feedstock for carbon black.