Physical change in coal particle and effect of limestone flux on char reactivity were studied with a laboratory-scale entrained flow gasifier at atmospheric pressure, using a Blair Athor coal at a design flow rate of 2kg/h. Results were obtained from a series of tests at an oxygen-coal ratio of 0.8, a limestone flux-coal ash ratio of 35wt%. The temperature in the gasification zone was in a range of 1400 to 1650°C. A special sample probe was used to collect char samples at three different axial positions in the 670mm long reactor for the observation and measurement of residual char properties.
Devolatilization was initiated very quickly in the forward region of the reactor with particle blowhole formation and fragmentation. During gasification, macropore surface and crack in char particle markedly developed, and, thus, the amount of fragment increased.Several types of fragment such as plate, block, skelton and ball type, were observed after the gasification zone of the reactor.
The observed coal conversion obtained from the flux addition experiments was about 5% higher than that conversion obtained from the flux addition experiments was about 5% higher than that from the non-flux experiments. This suggested that melting ash in char particle was attributed to increases in macropore and fragmentation of char, and, thus, enhanced overall char reactivity.
