Influence of kaolinite on the PM emissions from small-scale combustion

In recent years, the use of the renewable and CO₂-neutral energy carrier wood as a fuel for heat supply in domestic households increased. But as a result, the emission of particulate matter rises to a high level. Due to higher mineral content of wood (especially the content of potassium), the formation of particulate matter during combustion is much higher than that during combustion of fossil fuels like oil or gas. Therefore, the objective of the present work was the analysis of the effect of the mineral additive kaolinite on the particulate matter formation during combustion of wood pellets blended with 0, 0.5 and 1 wt% kaolinite. The examinations were conducted in two different small-scale combustion plants in cooperation between the University of Technology Hamburg (TUHH) and the Technology and Support Centre in the Centre of Excellence of Renewable Resources Straubing (TFZ). For the combustion experiments, an 8.6-kW pellet stove and a 12 kW pellet boiler were used. The results show a similar reduction effect of particulate matter emissions for both combustion devices of 46% (pellet stove) and 48% (pellet boiler) using 0.5 wt% kaolinite. The use of 1 wt% shows different results. The total particulate matter emissions of the pellet boiler were reduced of about 69% while the emissions of the pellet stove only slightly decreased about 5%.