Investigation of the combustion behaviors and kinetic modelling of municipal solid waste char under isothermal conditions using a micro-fluidized bed

Abstract

Approaches to the accurate measurement of combustion kinetics are essential for the numerical simulation, reactor design and process optimization of MSW-fired systems. The micro-fluidized bed reaction analyzer (MFBRA), which consisted of a micro-fluidized bed reactor and electrical control devices, was applied in the investigation of the combustion behaviors and kinetic modelling of noodles char (NC) and bamboo chopsticks char (BC). And the kinetics obtained from the thermogravimetric analyzer (TGA) were compared. The results indicated that the TGA might not fully meet the requirement for kinetic study of MSW char combustion due to the temperature deviation and prolonged testing time. Besides, the lower activation energy suggested insufficient heat and mass transfer in TGA. The combustion rate was strongly temperature dependent in MFBRA and BC exhibited around two times higher reactivity than NC. The combustion behavior would transfer from chemically controlled regime into pore diffusion controlled regime at 973 K for NC, and 923 K for BC. Volumetric reaction model (VRM) would overestimate the combustion rate due to the active surface variation during combustion. In contrast, random pore model (RPM) could well predict the conversion process for both samples at high temperatures, which might correspond to the pore enlargement and coalescence. The obtained activation energies of NC and BC combustion in the chemically controlled regime were 56.12 and 48.73 kJ/mol, respectively. Therefore, elevating the oxygen partial pressure and increasing the feeding rate were feasible ways for acquiring fast combustion rate of MSW char as a result of good reactivity in industrial applications.