(98ag) CFD-Based Enhancement of Temperature Uniformity in Industrial Furnaces With Self-Recuperative Burners

Natural gas used in industrial furnaces amounts for an important portion of the fuel global consumption. As much as 50% of the energy released by combustion inside hot enclosures is lost through the exhaust. A necessary and sustainable proposal is to seek the recovery of some of this energy, but centralized heat exchangers are severely limited in their effectiveness by sizing and temperature constraints. An alternative is to use a self-recuperative burner that merges a casing to create a premixed flame with a heat exchanger. In this process, up to 95% of the hot flue gases produced immediately preheat incoming combustion air with a recovery of up to 70% of the energy, that else would be lost. This approach ideally increases furnace efficiency and air preheat temperature, but also poses a design challenge on key specifications for product quality: Such as the pressure distribution, temperature uniformity and furnace fuel requirements. In this work, Computational Fluid Dynamics is employed to characterize turbulent flow and heat transfer profiles for two existing industrial furnaces: One with a self-recuperative setup and another with a traditional burner-exhaust configuration. In the former, profiles related to the burner configuration are investigated as well as the mixing efficiency; whereas in the latter, the conventional furnace is benchmarked against the recuperative setup thoroughly comparing impact of the burner design choice between the current. Relevant changes in design are then proposed for the conventional furnace to be successfully modified to a self-recuperative setup. Results indicate that a furnace with this new configuration, with a sufficiently controlled pressure in the recovery outlets, presents a sufficiently uniform temperature profile. In accordance to this result, the benefit obtained by using a self-recuperative configuration in fuel consumption and quality of heating should then be weighed against the related operative and capital costs of this implementation.