Flue Gas Recirculation System for Biomass Heating Boilers—Research and Technical Applications for Reductions in Nitrogen Oxides (NOx) Emissions

Abstract

The paper discusses the results of investigations of the change in thermal and emission-related parameters of a heating boiler fueled with biomass after a modification with a proprietary flue gas recirculation system made for this type of equipment. The results provide insight into the combustion process with a multistage flue gas recirculation that materially affected the boiler operation: a reduction in the mass concentration of nitrogen oxides (NOx) by reducing the combustion temperature. The authors also observed a reduction in the emission of particulate matters (PM) and carbon monoxide (CO). For the investigations, the authors used a heating boiler fitted with an automatic fuel feed (timber pellets) and a proprietary patented flue gas recirculation system (Polish patent Pat. 243395) for low power solid fuel heating boilers. Aside from the measurement of the mass concentration of the emitted pollutants, the research focused on the measurements of the temperature inside the combustion chamber, the temperature of the flue gas and the level of oxygen in the flue gas. The aim of the research was to confirm the validity of using the flue gas recirculation technique to reduce emissions of harmful substances from biomass heating boilers, as a technique not previously used for this group of devices. Moreover, the aim of the research was to test an original engineering solution, in the form of a flue gas distribution valve, and investigate its effect on reducing NOx emissions and improving other thermal and emission parameters of the boiler. The obtained research results confirm the validity of the chosen actions and provide a positive premise for the practical use of this technology in solid fuel heating boilers.

Control System Modification of a 5-kW Pellet Stove: Study and Analysis

“…In order to optimize the process, a heat accumulator can be installed. In that sense, different studies have been focused on these subjects, especially concerning the optimization of these stoves at industrial and local level, as in the case of the design of a 4-KW biomass stove to increase its efficiency [11]; the improvement of biomass stoves with low carbon monoxide emissions [12] or biomass cooking stoves with different biomass fuels [13,14]; or the use of biomass stove for heating [15], including flue gas recirculation systems in order to reduce NOX emissions [16].…”

“…Regarding flue gas composition, the following figures (Figures [13][14][15][16] show its evolution over time, being influenced by the working stage. Thus, in the case of carbon monoxide evolution (Figure 13), there was an increase from 0 to approximately 1600 ppm, corresponding to the operating stage.…”

Laboratory Tests of Electrical Parameters of the Start-Up Process of Single-Cylinder Diesel Engines

“…Basically, exhaust emission tests come down to determining the values of four standard exhaust gas components, but there are researchers, e.g., Mikulski et al [43], who use FTIR analysis of exhaust gases where they identify 23 exhaust gas compounds. In order to make heating systems more efficient and to better understand electricity generation, a number of studies have been carried out, of which the following are worth mentioning [44][45][46]. An important area of research when it comes to reducing emissions is also the adsorption and regeneration of the system, which includes the coupling of physical and chemical effects [47].…”