Characterization of carbonized municipal waste as substitute for coal fuel

Carbonaceous material produced from municipal waste (MW) was studied as a potential substitute for coal energy by evaluating its calorific values, chlorine content, and combustion behavior. The behaviors of calorific values and chlorine content of carbonized MWs (CMWs) during carbonization were investigated to replace the coal CMWs in the supply material of the existing boilers. By comparing the combustion behaviors of the CMWs and coals with various fuel ratios (=fixed carbon/volatile matter), the overall conversions of the combustion of the CMWs and coals were arranged in the order of their fuel ratios. Therefore, it was possible to evaluate their combustion behaviors using the fuel ratios for practical applications. However, strictly speaking, the detailed combustion behavior of the CMWs was different. A detailed investigation of the combustion process revealed that the combustion of fixed carbon at the burnout of the CMWs was slightly slower than that of the coals for the same fuel ratio, while the initial combustion process including the devolatilization of the CMWs was faster. This behavior was considered to be caused by complicated phenomena such as the catalytic effect on the gasification behavior of alkali and alkali earth metals, hindrance effect of ash on gasification reactant, original chemical structure, and transition of pore structure.