Combustion of biomass(straw and wood)and coal was investigated in a drop tube furnace.Moreover

factors like mixing ratio and air staging on emissions of NO and CO along the flue gas flow direction was analyzed.Also

the unburned carbon content in fly ash was investigated.The results show that

along the flue gas flow direction

the NO concentration increased first and then decreased slowly for pure combustion of both biomass and coal

and the NO emission from straw or wood combustion only accounted for about 1/3or 1/2of that from coal combustion.The CO content during coal combustion increased first and then decreased

while that during the biomass combustion reduced gradually.Increasing the staging air quantity had little influence on variations of the NO and CO concentration but can reduce the NO emission dramatically for coal combustion.For co-combustion of the biomass and coal

the NO emission reduced gradually with the increasing mixing ratio

but when the mixing ratio increased to over 40%

increasing the biomass proportion had little effect on NO reduction.When the straw's proportion and the staging air volume reached over 40% and 20%respectively

staging air had little influence on NO emission.