Co-firing of biomass and natural gas and NOx emission from bio dust firing

NO emission can be reduced by means of two-step combustion in a 20 kW burner firing wood, straw and natural gas. A full-scale boiler produces the highest level of NO in connection with oil firing, while the wood share has no impact on emission levels. NO can be minimised by controlling air volumes and wood-powder injection. Rapid heating of wood creates a high share of volatile components and residual coke yield of only 2-7%. Block 2 of the Avedøre Power Station had a wood burnout degree of > 99.8% at O2 levels as low as 1.5%. At co-firing of wood + oil or wood + natural gas, most alkali metals occur as sulphate in coatings, and the K content came to about 11-15%.