On the basis of laboratory-scale high temperature drop tube furnace

an oxy-fuel combustion experimental apparatus was built up to simulate the real oxy-fuel combustion. Under conditions with three kinds of recycles(no-RFG

de-ash and ash)

ultra fine particle formation experiments for DT bituminous coaland SH bituminous coal were carried out to investigate the influence of recycled ash on formation of ultrafine particle matters. The results show that

compared with the no-RFG condition

under condition with de-ash flue gas recycle

the yields of ultrafine particle matters of the DT and SH coal were both basically invariant

while that under condition with ash recycle decreased by about 12.03%(DT coal) and 7.73%(SH coal)

respectively. Under condition with ash recycle

the silicon aluminate

which was rich in the ash of DT coal

would adsorb the Na and K vapor released during the combustion

and the rich CaO in the SH coal may also adsorb the S element during the combustion to restrain the S from migrating to the ultrafine particles

both of the reactions decreased the formation of the ultrafine particles.