(122h) A Gasification Characteristics of Indonesian Kideco Coal in a Segregated Fluidized Bed Gasifier

In fluidized bed coal gasification reaction, coal particles were reacted with oxygen agent (in operating condition), and were being reduced the size and density during converting to char. The hydrodynamic values such as minimum fluidizing velocity and terminal velocity of particle will be reduced. With the increase of outlet gas velocity and the decrease of the hydrodynamic values of particle by gasifying, it is hard to maintain the sufficient particle residence time for complete conversion in the reactor.

If the gasifier was operated with the low gas velocity for preventing the particle elutriation, the mixing and mass transfer will become worse and apparent chemical reaction will be reduced.

To maintaining the sufficient residence time and hydrodynamic operating values in the reactor, the gasifier operate with two flow regimes. One is the turbulent regime with high superficial gas velocity, and large coal particle with high density. The other is the bubbling regime with low superficial gas velocity, small char particle with low density. Its behaviour will be segregated fluidized bed.

The tests were carried out in a fluidized bed with 0.05 m ID and 0.4 m height for turbulent regime, and 0.1 m ID diameter and 0.7 m height for bubbling regime. Coal was fed into the lower part of gasifier by screw feeder up to 2 kg/h. The gas mixture of O2 , air and N2 for adjusting the O2/C ratio and Uo/Umf is injected into bottom of the gasifier. The proximate and ultimate analysis of Kideco coal is volatile matter, fixed carbon, moisture and ash 49.26%, 38.36%, 9.30% and 3.08%, respectively. And C 62.17%, H 4.08%, N 1.32%, S 0.24% and O 19.80%, respectively.

The operating conditions are temperature were between 750 and 850 °C, O/C ratio were between 40 and 70%. The typical gas concentration of CO, H2, CO2 and CH4 in gas outlet was 39.72%, 28.46%, 19.91% and 2.07%, respectively.