Research on alkali-catalyzed gasification of coal black liquor slurry cokes made up by five different coals

The black liquor from paper mills contains large quantities of sodium compounds and other organic matter, such as lignin and cellulose. The sodium compounds will provide the catalytic action in coal black liquor slurry (CBLS) gasification, while lignin and cellulose can enhance the heat value in the process of gasification. Five black liquor slurries were made from coals from different regions: Xin Wen, Huang Ling, Zao Zhuang, Shen Mu and Shen Hua. Alkali-catalyzed gasification experiments on the different samples of CBLS and coal water slurry (CWS) were made on a thermobalance and a fixed-bed reactor. The residues of gasification were analyzed by X-ray diffraction (XRD), scanning electron microscopy (SEM) and Fourier transform infrared (FTIR) spectroscopy. The results reveal that many mesopores and micropores exist on the surface of the CBLS coke, which play a key role in the catalytic gasification process, and sodium as a catalyst can quicken the gasification reaction rate. XRD shows that NaCl and sodium silicate are the main crystal components in dry samples of CBLS and CWS. The C-O stretching vibration peak shifting to a lower wavenumber means that the energy for the C-O stretching vibration in the CBLS carbon matrix decreases after partial gasification. Not only the coal rank but also the oxygen-containing groups and minerals influence coal coke's gasification activity. Of the five different CBLS, the gasification reactivity of CBLS made by the Huang Ling coal was found to be higher than that of the others. The higher the degree of coalification, the lower the activity of the coke. (c) 2007 Curtin University of Technology and John Wiley & Sons, Ltd.