Modification of Claus Sulfur Recovery Unit by Isothermal Reactors to Decrease Sulfur Contaminant Emission: Process Modeling and Optimization

Abstract

Abstract Due to environmental limitations and issues, the main goal of this research is modification of conventional Claus sulfur recovery process to decreases sulfur contaminant emission. In this regard, two environmentally friendly alternatives are proposed based on the isothermal concept in reactors. Since Claus reaction is exothermic and reversible, the adiabatic fixed bed reactors in the catalytic section of Claus process are substituted by the isothermal reactors. The furnace and catalytic reactors are modeled based on the mass and energy conservation laws at steady state condition. To prove accuracy of the developed model, the simulation results of conventional process are compared with the available plant data. Then, the optimal condition of modified processes are calculated considering sulfur recovery as the objective function using the Genetic algorithm as a useful method in global optimization. The attainable decision variables are inlet temperature of furnace and reactors, coolant temperature, feed split fraction and air flow rate in the furnace. The simulation results show that H2S conversion in the proposed cases increases about 1.87 % and 1.78 % compared to the conventional process. Generally, the main advantages of proposed structures are higher sulfur recovery and lower sulfur contaminant emission such as COS and CS2 emission.