Demonstration of a top-lit updraft based pyrolytic burner with low emission operation and automatic process control

In this study, a small-scale (4.7 kWfuₑl) biomass burner based on “top-lit updraft” (TLUD) technology with automatic process control was developed for process heat generation. The combustion experiments were performed using wood pellets to gain more insights on the process, its repeatability and the behaviors of the emitted gaseous and particulate emissions under different combustion phases. The emission values were compared with similar small-scale combustion technologies as well as the emission limits defined in official regulations. The results showed that the average emissions (based on standardized 13 vol. % O₂ content in the dry flue gas (STP)) over the entire process from start-up to switch-off were 29.4 mg/m³ for CO, 80 mg/m³ for NOₓ, and 3.6 mg/m³ for total particle matter (TPM) measured within the hot gas. These results were below the official limits for wood-fueled small-scale systems. The developed process control approach resulted in very low residual O₂ content in the flue gas (approx. 2 vol. %), high flue gas temperatures and repetition accuracy. Thus, the process offers potential for further development in terms of process control, scale-up, and application in different areas.