Renewable Heat Generation from Waste Gasification: Infrared Thermal Imaging and Flue Gas Emissions Monitoring of Producer Gas Flame

This work investigates the combustion of Producer Gas (PG), composed of 1.90 % CH4, 18.50 % H-2, 8.85 % CO2, 22.20 % CO, 7.40 % H2O, and 41.15 % N-2, obtained from wood packaging waste gasification. Experiments were conducted using a rising co-current stationary fluidized-bed gasifier coupled with a purpose-built combustion test rig. Flame stability and temperature distribution were analysed through thermal imaging in the 7.5-14 mu m spectral range, using a pixel-based correlation method. The flame emissivity was calibrated at multiple points using N-type thin-wire thermocouples and adjusted on the Infrared (IR) thermal camera allowing a simplified dynamic analysis of the flame. Results demonstrate that at an ER (Phi) of 0.85, the PG flame remained stable and uniformly distributed within the combustion chamber. However, at a lower Phi of 0.43, the flame exhibited instability, likely due to reduced flame temperatures, which lower reaction rates and weaken the chemical kinetics governing PG combustion. Additionally, high air-flow rates at this condition contributed to flame perturbation, detachment, and quenching. At ultra-lean conditions (Phi = 0.43 and TL similar to 10 kW), significant flame instability and "neck thinning" were observed. Introducing a small amount of methane (up to 5 %) helped stabilize the flame under these conditions, suggesting a potential strategy for maintaining flame stability during ultra-lean PG combustion. Flue gas emissions were monitored for 0.45 <= Phi <= 0.70 and varied from 53 ppm CO, 10 % CO2 and 55 ppm NOx to 550 ppm CO, 15 % CO2 and 275 ppm NOx. Data analysis highlighted the fuelprompt NOx production mechanism at lower flame temperatures where thermal NOx formation is unlikely to occur. The NOx emissions increased from 200 ppm to 275 ppm as the TL rose from 20 kW to 25 kW but remained nearly constant under increasing lean Phi conditions. This trend revealed the further evidence supporting the predominance of fuel-promt NOx formation.