| Abstract [eng] |
Following the implementation of strict EU environmental regulations, for medium-sized combustion plants, we are compelled to seek effective technological solutions to reduce emissions. The aim of this final project is to experimentally investigate the potential for reducing NOx emissions from biomass combustion. It was chosen to carry out experiments using air redistribution and flue gas recirculation methods. The first part of the Master's graduation project analyses the National Air Pollution Plan, what are the requirements for Lithuania, and the deadline by which Lithuania has to meet them. It looks at how nitrogen and sulphur oxides are formed and what they can be. In addition to this there is also an overview of the primary and secondary emission reduction measures, the reduction of nitrogen oxides through staged combustion, air staging strategies and the impact of flue gas recirculation on NOx and CO formation. The second part describes the methodology of the study, the specificities of wood combustion, the experimental test stands and the measurement of combustion parameters. The third part presents the results of the experimental tests and the graphical analysis. The work is summarised at the end of the paper with conclusions. A list of references used is also given. The experimental tests were carried out on two stands - the KTU combustion processes laboratory and the laboratory of UAB "Enerstena". The stands are designed to carry out various tests on different types of biomass combustion and to measure pollutant emissions under different combustion conditions. The measurements were carried out in different combustion situations, such as changing the primary and secondary air supply points, connecting the flue gas recirculation to the primary or secondary air and regulating the oxygen concentration in the primary or secondary air. Three types of biomass were used in the experiments: sunflower husk pellets, shredded pine bark and wood pellets. The experimental tests show that different types of biomass give different results and specific conditions are needed to obtain the lowest nitrogen oxide emissions. By recording measurements at different combustion conditions and averaging the emissions at specific conditions, the following lowest nitrogen oxide emissions were found: sunflower husk pellets - 80,9 mg/Nm³, shredded pine bark - 152 mg/Nm³ and wood pellets - 62,62 mg/Nm³. These emissions of nitrogen oxides are influenced not only by the combustion conditions, but also by the fuel characteristics, such as the moisture, the nitrogen content in the dry mass of the fuel. The moistest fuel was shredded pine bark and the lowest nitrogen-containing fuel was wood pellets. |
