Pollutant emissions of a biomass gasifier inside a multifuel energy plant

Abstract

Several benefits in clean energy and pollutant emissions can be offered from biomass energy application. This research analyzes a biomass gasifier installed at the University of Perugia and presents the description of a multifuel biomass energy plant with all its components: the combustion chamber and the heat exchanger, installed to supply the thermal input to the turbine, with 100 kW electric power and 1 MW thermal power.The application of a Computational Fluid Dynamics (CFD) prediction model can help to better understand the knowledge on chemical and thermofluidodynamic features linked to pollutant emissions. A numerical modelling based on Ansys Fluent code is realized with the aim to reproduce the behaviour of the gasifier. Two different stoichiometric woodchips:air ratios are taken into account in the numerical calculations. Experimental tests have been conducted to validate the results of the numerical analysis.The obtained results show that the experimental and the numerical analysis with the 1:5 stoichiometric ratio are comparable. The influence of the woodchips:air stoichiometric ratio on the temperature distribution that may be reached inside the gasifier is highlighted. The relationship between woodchips:air stoichiometric ratio, temperature and NOx emissions is considered. Furthermore, a comparison between the values of NOx and CO pollutants obtained with the numerical model and experimental tests has been done. The gasification process contributes to the production of renewable energy and it can be combined with other energy cycles (e.g. Organic Rankine Cycle).The novelty of the work consists in the definition and validation of a method for the analysis of the operating temperatures of the gasifier to verify how they can be combined with other heat exchange systems and in the analysis of the pollutants during the gasification process.