Corrosion and aging risk assessment of an injection system for FCC/Bio-oil co-feed

Abstract

Fast pyrolysis oil (FPO) is a renewable biocrude with high corrosivity and poor thermal stability. Co-processing FPO with petroleum intermediates in existing fluid catalytic cracking (FCC) units is one of the most applicable methods for transforming low-quality biocrudes into drop-in fuels. Although FPO is immiscible with petroleum intermediates, co-processing can be achieved using two separate feeding lines for FCC injection instead of the premixture. However, the corrosion of structural materials and the thermal stability of FPO pose significant challenges to the co-processing feed injection system, as the feedstocks are usually preheated to 100–300 °C prior to injection. This study focuses on the corrosion of stainless steel (SS) 316L and evaluates the aging risk of FPO at a temperature range of 80–220 °C. SS 316L experienced noticeable degradation with increasing temperature. Corrosion rates of 0.06, 0.62, and 1.77 mm/y were observed at 80, 150 and 220 °C, respectively. The experimental observation also reveals phase separation (liquid and solid phase) of FPO at the experimenting temperatures. However, the change in the physicochemical properties of the phases becomes more significant as temperature increases. Furthermore, a critical temperature of about 80 °C was identified, which signifies both the onset of active corrosion of SS 316 L in FPO and the fast aging of FPO.