To investigate the reasons of high carbon content in bottom ash (BA) and guide the suitable utilization of residual carbon, the physicochemical properties of BA which was obtained from an industrial circulating fluidized bed coal gasifier were primarily studied via Raman spectrometer, N-2 adsorption test and thermogravimetric analysis and compared with raw coal (RC) and fly ash (FA). BA has the lowest combustion reactivity than RC and FA, which is attribute to high degree of carbon deactivation, limited specific surface area, low catalysis elements contents and high ash content. In this study, the carbon content of BA first increases and then decreases with increasing BA particle size and the peak value appears at about 2 mm. The degree of carbon deactivation increases and specific surface area decreases with increasing BA particle size. Furthermore, it was found that some BA particles were covered with compact shell, which probably hindered the adequate conversion of inside carbon. The formation of shell was presumably owing to the re-attachment of volatile matter to the char matrix and the migration of coal ash, based on the results of Ramen spectra and SEM.
Source: JOURNAL OF THE ENERGY INSTITUTE Volume: 95 Pages: 1-7
DOI: 10.1016/j.joei.2020.12.004 Published: APR 2021
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