Naslov
Numerical modelling of pollutant formation and removal during fuel combustion
(Numeričko modeliranje nastajanja i uklanjanja polutanata pri izgaranju goriva)

Autori
Bešenić, Tibor

Vrsta, podvrsta i kategorija rada
Ocjenski radovi, doktorska disertacija

Fakultet
Fakultet strojarstva i brodogradnje

Mjesto
Zagreb

Datum
31.03

Godina
2021

Stranica
175

Mentor
Vujanović, Milan

Ključne riječi
flue gas desulfurisation ; seawater desulfurisation ; absorption modelling ; mass transfer coefficient ; droplet absorption ; wall film absorption ; spray scrubbers ; SOx ; pulverised fuel combustion ; nitrogen oxides formation ; fuel nitrogen ; fuel nitrogen partitioning ; NOx

Sažetak
Reduction of harmful impact on the environment caused by rapid development of a fossil fuel- powered society is one of the most significant global challenges. The combustion-related pollutants such as sulfur oxides and nitrogen oxides stand among the most harmful ones due to large amounts of emissions discharged globally. The advanced models that provide insight into pollutant production and removal processes can be useful in designing new, more sustainable technology. Numerical models presented in this work aim to improve the calculation accuracy and efficiency for complex physicochemical processes of nitrogen oxides formation during the combustion of pulverised fuels, as well as the calculation of sulfur dioxide removal from flue gases by seawater absorption in spray droplets and liquid wall film. The chemical processes of absorption in droplets were modelled for pure water by a simplified chemical model accounting for the reactions in the aqueous phase, and additionally for seawater, by introducing the influence of alkalinity that increases the absorption potential. The second part of absorption modelling is the mass transfer dynamics, and it was described by two film theory. It separates the influence of resistances for the interface’s liquid and gas side. For droplets falling in the stream of rising gases, determining the mass transfer can be an issue, and the penetration theory was selected as the most suitable among the implemented models for the dominant liquid side mass transfer coefficient. Furthermore, to account for all of the relevant processes, the absorption of sulfur dioxide in wetted walls was also modelled by adopting an analogous approach. The main difference is in the implementation of the mass transfer model, as the hydrodynamic processes influencing the liquid wall film are different. The used approach is based on dimensionless parameters and hydrodynamic characteristics of wall film. The developed and implemented models were validated against experimental data obtained in the literature for simplified geometries and industrial cases. The comparison showed that the model is capable of replicating experimental results for different geometries, range of sulfur dioxide concentrations and liquid-to-gas ratios. Additionally, the nitrogen oxides’ formation was modelled with the aim of accurately predicting their concentrations in pulverised solid fuel combustion systems. The Euler-Lagrangian approach was also used for describing the multiphase flow of fuel particles, and the combustion model was augmented by addition of a nitrogen oxides’ production model. Thermal and fuel production pathways were included, but the fuel nitrogen pathway was modified by the addition of partitioning factor that accounted for changing influences of different pathways. Then, the experimental analysis of bituminous coal was performed on a TG-MS system and by applying a derived method for quantifying the fuel nitrogen partitioning. Finally, the obtained experimental data was used in numerical simulations of a drop tube test, resulting in nitrogen oxides’ concentrations comparable with the ones reported in the literature.

Izvorni jezik
Engleski

Znanstvena područja
Strojarstvo

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