Combustion optimization of various biomass types to hydrogen-rich syngas: Two-stage pyrolysis modeling, methane addition effects, and environmental impact assessment

Biomass, as a renewable and carbon-neutral energy resource, holds significant potential for advancing sustainable energy systems. The conversion of biomass into hydrogen-rich syngas through the pyrolysis process emerges as a highly promising approach for clean energy production. This study explores the combustion characteristics of various types of pre-mixed biomass fuels and the syngas generated from them. This study investigates the combustion characteristics of pre-mixed various types of biomass fuels and the syngas they produce. The combustion modeling includes a detailed flame structure, covering drying, two-stage pyrolysis, and both heterogeneous and homogeneous reactions. The two-stage pyrolysis process consists of a primary stage that produces hydrogen-rich syngas and a secondary stage that decomposes tar. The associated governing equations and boundary conditions are solved analytically. Furthermore, to enhance combustion performance, the effect of methane addition to biomass-based fuels is analyzed. The findings indicate that an increase in equivalence ratio results in a greater amount of fuel in the reaction zone, leading to elevated flame temperatures and longer flame fronts. Upon examining different types of biomass combustion, plastic exhibited the highest flame temperature, while rice husk recorded the lowest. Additionally, the addition of methane results in higher burning rates and flame temperatures, with approximately 5.9 % and 13.23 % increases, respectively, in dual fuel (50 % biomass and 50 % methane) compared to mono biomass fuel. Finally, to address environmental concerns, a multi-objective optimization using the genetic algorithm method was conducted to maximize flame temperature while minimizing pollutant emissions.