• CFD modeling
• combustion
• RNA
• deposition

The present work is aimed for the prediction of gaseous alkali sulphates with RNA approach. In the last year, also FLUENT has developed a version of the reactor network and this thesis focuses mainly on the formation of the reactors and the implementation of the kinetic. The first part of the work was dedicated to the study in the literature of experimental apparatus IPFR and 500 kW, both located at ENEL laboratories in Livorno. It was carried out an analysis of the experimental data with regard to the major pollutants and the production of particulate, with the purpose of being able to derive any tendency for the prediction of particulates by varying the experimental apparatus and the fuel. The second part of the work was dedicated to the CFD modeling of the experimental apparatus KVSA, biomass powered with 500 kW, located at the University of Stuttgart. With the use of package ANSYS 16.0 has built geometry, grid domain and simulations were carried out. This modeling has adopted some strategy to simplify the calculation of the kinetics reaction, such as the decrease of the computational cost, the high number of computation cells (about 106) and equations (neccesary for the description of a multiphase turbulent reactive system) make unworkable adoption of complex kinetic scheme needed to describe the formation of aerosols. The goal is to get the field of temperature, chemical species and density, these data are the input for the RNA models.
The third part of the work was dedicated to the post-processing, that is search in literature and write by FLUENT requested format the kinetic schemes and thermodymanic data. The technique RNA divided the domain into a series of macro-regions almost homogeneous in terms of temperature, density and major chemical species. These regions are treated as perfectly stirred reactors in which the formation of aerosols can be calculated with detailed kinetic, that includes hundreds of species and thousands of chemical reactions. Once obtained the results, varying the number of reactors made a comparison between the varoius chemical species. The last part of the work was dedicated to the formulation of detailed parametric models of depositions the convection zone of the combustion chambers for all examined experimental apparatus, such as IPFR, 500 kW and KVSA. The objective is to be able to study the deposition tendency of alkali on tube bank surfaces by applying a mechanism of condensation. The deposition models can quantify the deposition rate of alakali compounds in specific conditions of the convective pass and give an estimation of the most favourable factors to depositions.