Pollutants and their reduction in small-scale wood incinerators

Emissions during thermal utilization of wood residues were studied at two small-scale firing systems. Effects of primary technical measures on reduction of NO sub(x), CO, PCDD/F, and PAH were tested in the flue gases of an underfeed stoker (250 kW). The organic pollutants were also analyzed in the ashes. Chipboards, untreated wood, and wood with preservatives (CrCuB = CCB) were applied. It was shown that an optimization of the combustion parameters for low CO and NO sub(x)-emissions did not necessarily result in the reduction of PCDD/F and PAH. At the second furnace, a pre-oven system (65 kW), effects of full and part load operation were tested without technical modifications. Here, PCDD/F and PAH concentrations in ashes and flue gases mostly increased at part load operation. Due to the decreased temperatures, concentration of CO increased. Unexpectedly NO sub(x) increased at part load operation burning chipboards. Using wood, regardless of whether treated with CCB preservative or not, the load had no effect on the amount of the NO sub(x) emission.