Design, optimization and controllability analysis of an improved sulfur recovery unit based on SuperClaus process

To meet stricter environmental regulations, the SuperClaus process has been proposed to enhance sulfur recovery in Claus sulfur recovery units (SRUs). SuperClaus modifies the traditional Claus process by adding a catalytic bed for direct hydrogen sulfide oxidation after the Claus beds. This study begins with a steady-state simulation of the Claus process using AspenPlus, with results closely matching industrial data-showing relative errors of 5.56% for SO₂, 8.10% for H₂S, and 0.84% for sulfur recovery. The SuperClaus process is then designed, optimized, and simulated under steady-state conditions. Unit operations, such as the reaction furnace, heat recovery boiler, and catalytic reactors, were modeled as plug-flow reactors (PFRs). Simulation results show sulfur recovery increases from 95.9% to 98.5% using SuperClaus process. In addition to considering the detailed reaction kinetics and design of an optimized SuperClaus reactor, the main novelty of this work is the dynamic simulation of the SuperClaus unit performed using AspenPlus Dynamics. The control system is tested under step changes in feed temperature (±20%), pressure (±10%), and concentration (±5%). Results indicate that concentration changes have the most significant impact on overshoot in the control loop. Despite disturbances, the control system effectively maintains desired setpoints, demonstrating the robust performance of the SuperClaus configuration under varying operating conditions.