Pyrolysis and char reactivity of a poor-quality refuse-derived fuel (RDF) from municipal solid waste

Abstract

The present study focuses on analyzing the pyrolysis and combustion behaviors of a refuse-derived fuel (RDF), which is generated in a MSW treatment plant located in Zaragoza (Spain). Pyrolysis experiments were carried out in a TGA apparatus and a fixed-bed reactor at different peak temperatures (400 and 600°C) and heating rates (5 and 40°Cmin−1). The reactivity towards oxygen of produced chars was also measured in the same TGA device at a heating rate of 10°Cmin−1 and a final temperature of 800°C. Pyrolysis results were significantly affected by peak temperature and heating rate. The found effect of peak temperature on char and fixed-carbon yields as well as on measured properties (H:C and O:C ratios, BET surface area and average pore diameter) was in agreement with previous studies. However, the effect of heating rate, especially on the release rate of volatiles, could be explained by a change in the pyrolysis reaction scheme. The RDF-derived chars obtained at the highest heating rate showed a higher reactivity in air. In addition, an increase in peak temperature also led to a higher reactivity. This result can indicate that the carbon present in the RDF-derived char is dispersed within an ash matrix containing a high number of active sites, the distribution of which could be improved when heating rate (and, to a lesser extent, peak temperature) is increased. The addition of 10wt.% RDF to two-phase olive mill waste prior to slow pyrolysis led to an apparent increase in the carbonization efficiency as well as to an enhancement of the resultant char's reactivity in air.