Fast pyrolysis bio-oil (FPBO) is considered a good substitute for conventional fuel oils in several application, such as boilers, furnaces, and gas turbines. This bio-oil has different physical and chemical properties compared to the one of petroleum and other bio-oils. In fact, as it has been widely demonstrated in many studies, this replacing needs some modifications of the already existing technology to be adapted to work with FPBO. The aim of this thesis is to investigate how to set up a CFD model of a nozzle with FPBO, and to analyse the average size of the spray particles for future applications in gas turbines.