Studio Sperimentale e Modellazione di Processi Selettivi Non Catalitici di Abbattimento di Ossidi di Azoto utilizzando Ammoniaca e Urea come Agenti di Riduzione. Cinetica Chimica e Fluidodinamica. / Experimental and Modelling Study of Selective Non-Catalytic Reduction of Nitrogen Oxides by Ammonia and Urea. Chemical Kinetics and Fluid Dynamics.

AUTOR(ES)
DATA DE PUBLICAÇÃO

1999

RESUMO

Selective non-catalytic reduction (SNCR) process is a post-combustion strategy aimed to reduce the amount of NOx in combustion exhausts through the injection of a reducing compound downstream the main combustion region. The chemical kinetics of the Thermal DeNOx and NOxOUT processes, whose involve the addition of ammonia and urea respectively, was investigated experimentally using a laboratory jet stirred reactor. In particular, the effect of changing the initial reactants concentration and the reaction temperature on the NO reduction was studied. Comparisons with several detailed kinetic models for the Thermal DeNOx process previously presented in the literature evidenced that these models are not able to represent correctly the process behaviour in the conditions investigated. One of these was properly modified in order to reproduce the experimental data so as to provide an effective tool for process simulation in a wide range of operating conditions. The new experimental results were also used for a kinetic modelling study of the NOxOUT process. A first attempt of modelling the chemistry of the nitric oxide reduction with urea is proposed. The potentiality of two different approaches to model the influence of mixing between the reactants was finally investigated. The first approach involves a detailed description of the chemical kinetics linked with a simplified reactor model to describe the fluid dynamic behaviour. In the second one, it was used a simplified kinetic model together with a detailed modelling of the fluid dynamics through a CFD (Computational Fluid Dynamic) code. The reliability of these two different approaches was analysed by comparison with several experimental results previously presented in the literature for the Thermal DeNOx process. As a last step the influence of mixing on the overall NO abatement was discussed with reference to the characteristic mixing and reaction times.

ASSUNTO(S)

engenharia quimica uréia thermal denox redução chemical kinetics experiments Óxidos fluid dynamics noxout amônia

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