Thermogravimetric analysis and pyrolysis product characterization of municipal solid waste using sludge fly ash as additive

MSW pyrolysis was performed in a fixed-bed reactor at 700 °C and sludge fly ash (SFA) was used as an additive. Only organic fractions of MSW were considered. The yield of the products was compared under three conditions: without SFA, with 5% SFA and with 10% SFA. TG-FTIR was also performed on the single, mixed and SFA fractions of MSW to determine the kinetic parameters of the feedstock. The plastic and rubber fractions were the most useful fractions of MSW. Kinetic analysis showed that addition of SFA resulted in the reduction of the apparent activation energy (E). With SFA pyrolysis, the liquid yield decreased from 20.8% to 6.4% and the gas yield increased from 65.5% to 76.4% with 5% SFA and then, decreased to 73.2% with 10% SFA. The major active species in SFA (CaO, SiO₂ and Fe₂O₃) greatly promoted tar cracking effect, resulting in greater gas and lower liquid yield. Addition of 5% SFA, proved to be the most feasible condition, because of higher H₂ yield, lowest char yield and better quality liquid product. Thus, concentration of SFA additive proved to be an important factor in products formation of MSW pyrolysis. The possible ecological risk valuation of heavy metals in chars showed the RI values, with 5% and 10% SFA, as 49.02 and 65.10, respectively. This work demonstrated that addition of sludge fly ash played a vital role in the pyrolysis of MSW.