| Natural gas reburning is a NOx reduction strategy in furnaces in which high Reynolds number (turbulent) jets are used to mix reburning fuel and furnace gases. Modeling of the reburning process requires a description of detailed chemical kinetics and the turbulent mixing between the reburn fuel (natural gas) and oxidizer (the product gases from the main combustion chamber of the furnace). Two types of modeling strategies (an integral and differential approach) have been developed and applied to the reburning application.; The one-reactor model (1RM) is a simple mixing model that can incorporate a detailed chemistry scheme without prohibitive computational costs. Within a limited range in process parameters, the integral model yields good predictions of data from various pilot-scale reburn experiments. Based on these strengths, the integral model can serve as an effective reburn design tool. As an integral model, the 1RM requires the coupling effect of the chemical reactions on the turbulent mixing to be known a priori. Another shortcoming of integral approaches is that they yield only a one-dimensional representation of the turbulence-chemistry interaction.; The conditional moment closure (CMC) approach is a state-of-the-art combustion model which gives multi-dimensional details of a turbulent reacting flow. In order to couple detailed hydrodynamic calculations to a comprehensive chemistry set, the quasi-steady assumption must be made to yield computationally tractable solutions. The quasi-steady approximation for the singly-conditional case is validated for various reacting test-case flows, including homogeneous, isotropic turbulence and turbulent reacting jets. As a first step in applying the quasi-steady (singly-conditioned) CMC model to full-scale furnace simulations of reburning, the differential strategy is applied to a simplified reburn problem. |
