Effect of alkali and alkaline earth metals on co-pyrolysis characteristics of municipal solid waste and biomass briquettes

To investigate the influence of alkali and alkaline earth metals (AAEMs: K, Na, Ca, and Mg) on the co-pyrolysis of municipal solid waste (MSW) and biomass briquettes (CSBs), the pyrolysis properties and products distribution for the blends of pretreated CSBs and MSW were studied by thermogravimetric analysis with Fourier-transform infrared spectroscopy under N2 and CO2 atmospheres. Results showed that the AAEM salts were effective at reducing the initial temperature during pyrolysis process. The presence of AAEM salts inhibited the volatile release rate of the first pyrolysis stage of the blend, while the alkali and alkaline earth salts separately enhanced the volatile release rates of the second and third pyrolysis stages under both atmospheres. Replacement of N2 with CO2 caused lower residual masses of the blend, which were further reduced by the catalytic effect of the AAEM salts. The CO2 yields were enhanced by adding AAEM salts under the N2 atmosphere. Ca had the most obvious catalytic effect on the CO production in the third pyrolysis stage. Different AAEM salts added to the samples displayed different effects on the emissions of alkyl and carbonyl groups.