## 4 Materials and Methods  
Emissions from the combustion of solid and alternative solid fuels are highly dependent on the design of the combustion equipment. Emissions from biomass combustion can generally be divided into emissions that are primarily influenced by combustion technology and combustion conditions and emissions that are influenced by fuel properties. When burning wood in fireplaces and stoves, water vapor, carbon dioxide (CO\({}_{2}\)), nitrogen (from the air), ash and fly ash, carbon monoxide (CO), organic gaseous carbon (OGC), nitrogen oxides (NOx), and unburned particles (soot) can be emitted. Emissions caused by incomplete combustion are primarily the result of insufficient mixing of combustion air and fuel in the combustion chamber, a total lack of available oxygen, too low a combustion temperature, or too short a time. These parameters are related to each other through the reaction rate for the basic combustion reactions. However, when sufficient oxygen is available, temperature is a very important factor due to its exponential effect on reaction rates. Optimizing these variables generally contributes to reducing emissions from incomplete combustion. The conversion of fuel carbon to CO\({}_{2}\) takes place in several steps and using several reaction pathways. CO is the most important final intermediate. The rate at which CO oxidizes to CO\({}_{2}\) depends primarily on temperature. CO can be considered a good indicator of combustion quality. Nitrogen oxides produced during wood burning are mainly nitric oxide (NO) and nitrogen dioxide (NO\({}_{2}\)). They arise at a high temperature (above 1000 \({}^{\circ}\)C) from the nitrogen in the air (around 80%). As already mentioned in the introduction, there are several constructional arrangements of burners and combustion devices. They differ not only in shape, but also in the arrangement of individual functional parts of the combustion equipment. The heat exchange surfaces are arranged in such a way as to ensure optimal heat transfer from the combustion process to the heat-carrying medium. The burner, which forms the basis of the combustion equipment, must meet not only technical but also emissions parameters. Mandatory environmental standards determine in particular the permitted content of emis  
Figure 4: Secondary-air-controlling aperture. sions in flue gas. Determining the amount of emissions is evaluated on the basis of officially approved methods and procedures for taking samples of flue gas in a device's chimney. Such sampling and measurement work is carried out at a workplace in the University of Zilina's Department of Power Engineering, using the furnace setup shown in Figure 5.  
This workplace allows the connection of any heat source up to 50 kW. The measurement takes place continuously, with computerized recording and evaluation of the measured quantities. The workplace was used for the measurement of emissions from two types of burners--retort and rotary. A standard burner from the Slovak furnaces manufacturer was chosen as the retort burner. This burner has a bottom fuel feed to the center of the burner and an air feed through the burner wall. The second burner chosen was our novel-design burner. This burner is rotary, with the chamber rotating in a rotary motion. The fuel is fed from above into the center of the combustion chamber. The air is led through the wall of the chamber. Both burners were gradually installed in the selected boiler at the workplace, and the performance and emission parameters of combustion in each of the burners were determined. In the case of automatic fuel supply to the boiler, the test must take place for at least 6 h at nominal and minimum heat output.