Applicability of municipal solid waste incineration (MSWI) system integrated with pre-drying or torrefaction for flue gas waste heat recovery

A system based on pre-drying and torrefaction of raw municipal solid waste (MSW) is proposed in this study to minimize the amount of pollutants and improve the efficiency of the system by recovering flue gas waste heat as heat source for the pre-drying or torrefaction stage. A steady-state model integrated with the mass residual rate and energy coefficient of this novel system is established to evaluate the effect of pretreating solid waste on the performance of the municipal solid waste incineration (MSWI) system comprehensively. Thermodynamic calculation results show that the low heating value (LHV) of the MSW is increased to approximately 9000 kJ/kg at a torrefaction temperature of 533 K for 30 min; the combustion flue gas temperature is approximately 1150 K, thereby satisfying the incineration temperature requirement. Further, pre-drying is conducive for improving the energy utilisation rate; for torrefaction, when the mass residual rate of MSW is greater than 39.25%, the energy coefficient of the pretreatment exceeds 1. For the pre-processing method involving torrefaction, the mass loss and LHV improvement after torrefaction should be considered to select the appropriate torrefaction conditions. This study supplies effective and feasible reference for developing higher performance MSWI system with pre-drying or torrefaction as the pretreatment. •Proposed a model to describe municipal solid waste incineration system.•Suggested a model to predict the specific heat of flue gas.•Posed a method to predict the specific heat of municipal solid waste in China.•Pre-drying of municipal solid waste could optimize its’ incineration.•The impacts of torrefaction depend on operating condition.