Simulation and optimization of sulfuric acid plant

Abstract

The current legislation imposes tighter restrictions in order to reduce the impact of chemical process industry on the environment. In this context, this study presents the steady state model, simulation and optimization results for an industrial sulfuric acid plant. The model, implemented in Aspen-Hysys includes a catalytic reactor (four pass converter), heat exchangers, mixers, splitters and reactive absorption columns. The kinetic parameters were estimated for the degenerated form of Hougan-Watson kinetics considering a catalyst consisting of V2O5, while the remaining model parameters were estimated using classical correlations. Catalyst specification, bed height and diameter were conducted to avoid excessive pressure drop in each converter bed. The optimum heatup path with maximum %SO2 oxidized was determined for each bed using the Microsoft Excel Goal seek operation. Aspen-Hysys V7.1 has been successfully used to design every sub-process of the sulfuric acid plant in one integrated environment. The simulation of sulfuric acid process included automatic chemistry generation and the capacity of handling electrolyte reactions for all unit models. Aspen-HYSYS provides specialized thermodynamics models and built-in data to represent the non-ideal behavior of liquid phase components in order to get accurate results. The simulation results agree very well with the real plant data and theoretical data for maximum %SO2 oxidized in each bed. The SOx emission was reduced nearly 80% from the existing plant with this simulation model and 650 psi steam was generated in waste heat boiler using the heat of the exothermic reactions. Material and energy flows, sized unit operations blocks can be used to conduct economic assessment of each process. The simulation model developed can also be used as a guide for understanding the process and the economics, and also a starting point for more sophisticated models for plant designing and process equipment specifying.