An experimental and computational fluid dynamics (CFD) simulation study of reburning under laboratory turbulent mixing conditions

A combined experimental and computational fluid dynamics (CFD) modeling study of the reburn process under turbulent mixing conditions on a laboratory scale has been performed. The experimental work includes novel laboratory results of reburn under different mixing conditions, and intends to cover the gap between the studies of the reburn process made in ideal reactors and the studies conducted in pilot-scale and full-scale plants that are available in the literature. A model has been developed using the AIOLOS software, together with a reduced description of the chemistry taken from literature, and it allows us to describe the reburn process, reproducing the main features that occur in the experimental system, and thus it can be used as a useful tool for prediction and optimization of the NO reduction by reburn. The results obtained indicate the necessity for considering a detailed description of mixing, because they indicate that simple modeling approaches, such as the plug flow reactor and the Zwietering configuration descriptions, fail to describe, in detail, what occurs experimentally in well-controlled laboratory experiments in which turbulent mixing occurs. In addition, the main effect of mixing between the reburn fuel and the primary combustion gases has been determined to be the modification of the local stoichiometry, which is ultimately responsible for the variation of the NO reduction. A significant synergy between the variables that are influencing the reburn process and the mixing conditions is observed, and this indicates the necessity of riot neglecting any of the variables for the assessment of the NO reduction and for optimization of the reduction process.