Numerical Analysis of Preheating Furnace Performance in Razi Petrochemical's Ammonia Processing Unit Considering the Effects of Hydraulic and Geometric Variables

This study investigates the combustion of natural gas within a three-dimensional preheating ammonia furnace at the Razi Petrochemical Company (RPC) in Mahshahr, Iran. The furnace geometry is modeled assuming non-premixed fuel and air. We present a model of steady-state compressible chemical-turbulence combustion, incorporating conductive, convective, and radiative heat transfers. Zeldovich and Fenimore mechanisms are utilized to address thermal and prompt pollutant emissions in the presented computational fluid dynamics (CFD) simulations. Furnace performance was evaluated based on hydraulic parameters and geometric parameters. Results indicate that excess air (inverse of equivalence ratio) significantly influences combustion within the furnace. For instance, pollutant emissions increase by 50.62%, 53.27%, and 56.2%, respectively with the addition of 20%, 40%, and 60% excess air at a constant fuel mass flow rate of 0.0557 kg/s.