Analysis of reburn technology using results from CFD, detailed chemical kinetic scheme and experimental work.

The paper presents the outcome of a comprehensive study analysing results from computational fluid dynamics (CFD) simulation, detailed chemical kinetic scheme and experimental work applied to reburning technology to reduce NOx emissions in pulverised coal fired boilers. These different approaches have advantages and disadvantages when applied to the design of reburn installations for retrofit or new boilers, to optimise the reduction of NOx emission. One of the objectives of the present paper is to show the importance of these three different approaches when they are Used together, to understand and to improve the reburn technology. The other objective is to analyse results arising, in order to better understand the reburn technology. Finally, the work provides some indications for implementation of reburn technology. The influence of stoichiometric ratio, temperature and NOx concentration was studied and results from CFD are presented. These show that NOx reduction efficiency is strongly dependent on the local conditions inside the reburn zone, as well as the average values. This shows the importance of having CFD models coupled with detailed chemical kinetic schemes. Other aspects were also studied: the efficiency of NOx reduction using coal as reburn fuel instead natural gas; the influence of the presence of NH3 (in order to consider advanced reburning technology injecting ammonia in the reburn zone). The work presented in this paper is continuing in order to build an efficient mechanism to couple the CFD model with the detailed chemical kinetic scheme. The combined model and the experimental work can provide powerful tools for the design of clean technologies in pulverised coal fired boilers.