Direct melting of municipal solid wastes pyrolysis char and its promotion by the char combustion

The municipal solid wastes pyrolysis char (MSWC) is a mixture of carbon and ash. Its direct melting contributes to the harmless and most weight-reducing disposal of the municipal solid wastes (MSW). To investigate the impact of the MSWC's combustion on its ash melting, in this research direct MSWC melting was investigated, the apparent activation energies and pre-exponential factors of the char combustion and ash melting reactions were obtained experimentally; reaction models of the MSWC's combustion and its ash melting were established for MSWC in a crucible and for a single particle to investigate the important factors affecting the ash melting. Thermodynamic analysis results showed that the presence of carbon can reduce the ash melting temperature by approximately 40 degrees C. The apparent activation energies of combustion and ash melting were 148.06 kJ/mol and 878.79 kJ/mol, respectively; but the MSWC combustion rate was much faster than that of ash melting. The combustion heat promoted its ash melting in a crucible inside furnace. The simulation results for a single MSWC particle showed that both the combustion and ash melting processes can be promoted by increasing the surrounding temperature and O-2 concentration in combustion air; while the higher carbon content in the MSWC only slightly improved ash melting when supplying air for combustion. Moreover, a reduction in the MSWC's particle size can make the carbon combustion faster but does not contribute to higher ash melting ratio due to the increase in specific heat dissipation; and particle radius larger than 1.5 mm would result in incomplete combustion of MSWC. These findings can provide guidance for the application of the MSW pyrolysis and char melting technology.