A Model-Driven Digital Twin Framework Development for Sulfur Dioxide Conversion Units Simulation

Abstract

In the phosphate industry, sulfuric acid is a key compound in phosphoric acid and fertilizer production. Industrially, the sulfuric acid H2SO4 is made generally in a sequence of three main steps: burning liquid sulfur with air, catalytic oxidation of sulfur dioxide SO2 to sulfur trioxide SO3, and formation of H2SO4 by the reaction of H2O with the SO3. The catalytic conversion of the SO2 into the SO3 is considered as the crucial reaction that affects the gas emissions and the performance of the process. In this paper, an industrial SO2 conversion unit of four catalytic beds reactors with vanadium pentoxide as a catalyst, and three heat exchangers were modeled. The model was based on heat transfer, energy and mass balance equations, and the kinetic reaction of the SO2 catalytic conversion was proposed and calibrated using the experimental plant data. The simulation of the four catalytic beds was carried out in steady-state and dynamic mode using Unisim Design R451 simulator. The proposed model was tested and validated using the studied plant measurements, and the accuracy of the model has exceeded 97%. A graphical interface of the SO2 conversion unit was integrated to make it suitable for industrial use and operator training. Finally, a digital twin (DT) of the studied conversion unit was developed based on an architecture integrating the plant, the virtual system, and the communication part in a Distributed Control System (DCS) context. The developed DT in this work makes it possible to simulate in real-time the SO2 conversion unit, predict the process performance, and optimize the unit efficiency.