Feasibility study of a process for the reduction of sulfur oxides in flue gas of fluid catalytic cracking unit using the riser reactor

In this work, a new process for achieving the recovery of elemental sulfur by utilizing a fluidized catalytic cracking (FCC) riser reactor for SO_x treatment (FCC-DeSO_x) is proposed. The process leverages the high temperatures and hydrocarbon concentrations in the FCC riser reactor to convert SO_x into H₂S. Subsequently, H₂S, along with the cracked gas, is processed downstream to produce sulfur. Thermodynamic analysis of the key reduction reactions in the FCC-DeSO_x process revealed that complete conversion of SO_x to H₂S is feasible in the dry gas (hydrogen-rich) prelift zone, as well as the upper and lower zones of the riser, upon achieving thermodynamic equilibrium. Experimental studies were conducted to replicate the conditions of these reaction zones using a low concentration of hydrogen gas as the reducing agent. Through process optimization, investigation of the minimum reaction time, and kinetic studies, the potential of this method for the complete reduction of SO_x was further confirmed.