Formation characteristics of ultra fine particles during oxy-coal combustion with flue gas recirculation

A laboratory-scale 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), combustion experiments of DT bituminous coal (rich in Si and Al) and SH bituminous coal (rich in Ca) were conducted 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 absorb the Na and K vapor released during the combustion, and the rich CaO in the SH coal may also absorb 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.