REACTING TURBULENT FLOW SIMULATION TO IMPROVE THE MIXING PROCESS IN AN OIL REFINERY INCINERATOR

摘要

Combustion emission is one of the most important issues in the design of industries. Todays' strict environmental standards have limited the productions of CO, NO_x, SO_x, and other hazardous pollutants from the related industries. In this work, we study a typical oil refinery incinerator, which is used to burn waste gases residue produced during bitumen production process. The waste gas mainly includes a mixture including N_2, H_2O-vapor, and O_2 species. Additionally, there are significant amounts of CO species and C_xH_y droplets in the waste gas composition. The measurements show that the CO emission becomes so crucial in high flow rate of feeding waste gas to the incinerator. Here, we numerically simulate the combustion process in this incinerator by solving the full turbulent reacting flow equations. In this regard, we use the finite-volume method to solve the RANS equations. For turbulence modeling purposes, we use the two-equation k-ε model along with standard wall functions. The non-premixed combustion is simulated by solving the mixture fraction equations for both fuel and waste gas streams. The interaction between turbulence and combustion is properly considered in the current modeling. We use the P_1 method to solve the radiation transfer equation in emitting and absorbing medium of combustion gasses. The WSGG model is used to consider the absorption coefficient variation. The set of governing equations are solved using a SMPLE-based algorithm. The current solutions provide good knowledge about the mixing pattern of flue gas and air-fuel streams in the incinerator. The improper mixing in the incinerator suggests we present a new design to re-design the waste gas inlet to the incinerator. Our simulation shows that the new design would result in substantial improvement in mixing process of these two streams. We find that this new design would effectively reduce the CO ppm at the exit of incinerator's stack.