Characteristics of Coal Partial Gasification on a Circulating Fluidized Bed Reactor

Experiments of coal partial gasification are conducted on a self-designed circulating fluidized bed (CFB) gasifier. The CFB gasifier system consists of a furnace, coal-feed system, air-feed system, steam generation system, gas–solid separation system, temperature- and pressure-measuring system, and material-returning system. The furnace is surrounded with electric heating wires, and the height and diameter of the furnace are 2600 and 120 mm, respectively. The experiments are conducted at temperatures between 885 and 980 °C. The coal particle size of 0.35–0.9 mm is chosen for experiments. The coal particle is gasified in the mixture of O2 and steam. The effects of different oxygen/coal ratios and steam/coal ratios on the performance of coal partial gasification are studied. As the results show, a higher oxygen/coal ratio leads to a higher gasification temperature and carbon conversion, while a slightly higher steam/coal ratio is better for the quality of syngas. The results show that the volume fraction of combustible gas and the lower calorific value reach as high as 70% and 9.1 MJ/Nm3, respectively. It can be obtained from the results of Raman and Fourier transform infrared spectra that the structure of chars becomes higher ordered as the different functional groups are gradually consumed. The chars become less reactive because higher ordered results in less reactivity.