To investigate the effect of high concentration water on coal volatilization

char gasification

char particle burnout and CO generation during wet oxy-coal combustion

the coal pyrolysis and combustion experiments were carried out in simulated flue gas atmospheres on a self-built drop tube furnace

with the particle residence time in the reactor of 0.2s

0.3sand 0.5s.The pyrolysis tests were conducted in pure N2 atmosphere

pure CO2 atmosphere and CO2 with different concentrations of steam atmosphere.On this basis

the combustion tests adopt O2 with volume fraction of 5%

10%

21% and 30%to take place the N2 or CO2in the pyrolysis atmospheres.the residence time of coal particles in the reactor during each test is0.2s

0.3sand 0.5s

respectively.The results indicate that

compared with air combustion

high concentration CO2 during oxy-coal combustion can inhibit the devolatilization of coal.The addition of high concentration H2 O during oxy-coal combustion can enhance the early stage devolatilization of coal

and the gasification reaction between char and H2 O or CO2didn't occur during the pyrolysis.The water nearly had no effect on burnout rate of the coal under conditions with high O2 concentration and long enough residence time

but it did decrease the burnout rate of coal under conditions with low oxygen concentration.The water can enhance the oxidation of CO

thus the CO concentration in the furnace was reduced.