Modeling finite-rate mixing effects in reburning using a simple mixing model

Natural gas reburning is a NOx to N-2 conversion technology in which turbul ent jets are used to mix reburning fuel into furnace gases. Modeling of the reburning process requires a description of the detailed chemical kinetics and the turbulent mixing between the reburn fuel (natural gas) and oxidize r (the furnace gases). The simple mixing models developed for the reburning application by Alzueta et al. [1], Cha et al. [2], and Han et al. [3] are able to incorporate the necessarily large chemistry sets with little comput ational overhead. These simple mixing approaches, e.g., the One-Reactor Mod el (1RM), yield good predictive capabilities over the parametric range in r eburn zone stoichiometries [2]. This study investigates the role of finite- rate mixing on reburn performance over the parametric range in temperature. This is done through the application of the 1RM to the reburn pilot-scale data sets of Mereb and Wendt [4, 5]. Results show weaknesses in the simple mixing model at relatively low temperatures. Possible causes for this break down of the 1RM and similar simple mixing model approaches at low temperatu res include uncertainties in the chemistry and/or the influence of the "hom ogeneity assumption" in the mixing model. (C) 2000 by The Combustion Instit ute.