(72p) A CFD Model-Based Optimization of a Process Burner Geometry

Burner design and placement in process heaters, crackers, and reformers continues to be an active area of study, as the temperature and heat flux distribution from the resulting flames can vary significantly between designs. It has become even more important in the recent times due to design adjustments necessary at existing cracker plants to adapt to the new feed types emerging from the booming shale gas industry.  The lower gas prices offer a significant cost advantage to the US industry. Burner designs play an important role in product mix and over performance of the crackers.  It also directly impacts the process efficiency, emissions control, and the mechanical durability of the equipment and its components.

 In this paper, the flow, heat, and chemistry taking place on the fire box side of a process heater is modeled using STAR-CCM+, a computational fluid dynamics software code. The flow distribution is simulated using the steady RANS approach, and the gas phase combustion is modeled using the fast chemistry assumption, with the Presumed Probability Distribution Function (PPDF) and equilibrium approach. The heat transfer to the process tubes and walls takes into account both convective and radiative modes, with the radiation being modeled using the discrete ordinates method (DOM). 

The most significant part of this work is that the baseline geometry of the process burner is then optimized using the SHERPA Optimization algorithm to obtain a design that gives the maximum flame length along the tube walls, and uniform temperature distributions on the fire box side. The whole optimization process is automated.  This CFD Model-based optimization of the burner geometry requires minimal user input for the Sherpa Optimization algorithm, which uses a blend of search strategies to adapt itself to the design space and reach a final optimized design based on a given set of objectives and/or constraints. The CFD results from the optimized burner geometry are then compared with those from the original geometry. 

This optimization methodology can save significant time in developing new burner designs or optimizing the operating conditions and configurations of existing heaters.