Pyrolysis of municipal solid waste with iron-based additives: A study on the kinetic, product distribution and catalytic mechanisms

Abstract

To realize highly efficient and environmentally friendly utilization of municipal solid waste (MSW) and iron ore, we proposed a novel method for combining MSW pyrolysis and iron ore reduction. The effects of two iron-based additives (iron ore and iron oxide) on the pyrolysis characteristics of MSW were first investigated by using TGA, and the kinetic results illustrated that the average activation energy of MSW pyrolysis was 180.32 kJ/mol. By adding iron ore and iron oxide, the activation energy decreased to 151.76 and 150.18 kJ/mol, respectively. Then, the product yield and product composition of MSW were analyzed by a fixed-bed reactor, GC-MS and GC. The fixed-bed reactor experiments of MSW pyrolysis indicated that the iron ore and iron oxide acted as catalysts to change the yield and composition of pyrolysis gas and tar, thereby promoting thermal cracking of MSW and showing a high conversion rate for MSW pyrolysis (55.81 and 55.05%). The GC-MS and GC analyses demonstrated that the two additives could significantly reduce the heteroatomic compounds of pyrolysis tar and increase H2, CO and CO2 production. Furthermore, the reduction of iron ore and the catalytic mechanism were analyzed by H2-TPR, XPS and BET. The H2-TPR results showed that compared with the peak of iron oxide, the characteristic peaks of iron ore shifted to a high temperature due to being suppressed by minerals in the iron ore. XPS suggested that the MSW volatiles led to an increase in the binding energy of Fe 2p3/2 and Fe 2p1/2 and a decrease in the binding energy of O 1s during the reduction of iron ore. BET analysis indicated that the high activity of the catalyst might be attributed to its high surface area.