The feed properties and physical dimensions of SRU were obtained from an industrial SRU plant. The optimization range for fuel gas flow rate was from 29 to 2034 nm 3/hr, air temperature from 180 to 360☌ and for acid gas temperature, 180 to 230☌ was considered. As a constraint, total BTEX at waste heat boiler outlet (WHB) was maintained below 1ppm. The objectives of optimization were to 1) Maximize sulfur recovery, 2) Minimize fuel gas consumption to furnace, 3) Minimize air and acid gas preheating temperature. Optimization was performed in MATLAB using genetic algorithm.
MATLAB was used as a platform to link Chemkin Pro with Aspen Hysys. Claus furnace was modelled using Chemkin Pro, while catalytic section (including condensers, re-heaters and incinerator) was modelled using Aspen Hysys (Sulsim). A well validated model for Claus furnace from previous studies was used for furnace simulations. A multi-objective optimization approach is deployed to minimize feed preheating temperature and fuel gas co-firing, while maintaining high BTEX destruction. However, temperatures above 1050☌ is not required when BTEX concentration is low. High temperatures are achieved through feed preheating and co-firing acid gas with fuel gas.
BTEX can be oxidized at the recommended temperatures above 1050☌. Benzene, Toluene, Ethylbenzene and Xylene (BTEX) present in feed gases to Sulfur Recovery Units (SRU) cause frequent catalyst deactivation.