Multi-objective optimization of biomass-rich MSW pyrolysis using hybrid multiphase lumped compartment-kinetic model

Abstract

Due to fossil fuels depletion, alternate energy sources are of growing interest. Biomass or municipal solid waste is a renewable energy source that can be converted to oils or synthetic gas through pyrolysis or gasification. A better understanding of the mechanism and kinetics of these processes is essential in the design of industrial facilities. In the present work, pyrolysis product components were taken into consideration along with char and oil as lumped parameters in a compartment model, and the kinetic constants for municipal solid waste two-step pyrolysis were identified based on a proposed simplified set of reactions. The experimental data were obtained from the process of two-step pyrolysis using Ni/ZSM-5 catalyst in a laboratory-scale reactor. MATLAB/Simulink software was used to implement the dynamic model and identify the kinetic parameters based on the experimental results. The model was in good agreement with the measured data, having R² value of 0.974. The validated model was further used to find the optimal parameters of the process in two cases. The collected gas had the highest lower heating value at the operating conditions of 830 °C, steam flow rate of 0.123 mL/h, and it required reduced experimental time, while the highest volumetric H₂ percentage was obtained at 941.6 °C temperature and no steam flow rate at similar to original experimental time. According to the multi-objective optimization results, the Pareto front revealed the most advantageous operating point for both heating value and hydrogen content at 774 °C and zero steam flow rate.

Graphical abstract