Walnut shell oil-bath torrefaction coupled with fast pyrolysis: Effect of torrefaction heating modes

Area of Science:

• Biomass Conversion and Bioenergy
• Renewable Energy Technologies
• Chemical Engineering

Background:

• Lignocellulosic biomass is a renewable alternative to fossil fuels.
• Low effective hydrogen-to-carbon ratio (H/Ceff) limits biomass applications.
• Torrefaction and co-pyrolysis are promising for upgrading biomass.

Purpose of the Study:

• Investigate the impact of different heating modes on oil-bath torrefaction of walnut shells.
• Evaluate the subsequent fast co-pyrolysis of torrefied biomass.
• Optimize torrefaction for enhanced hydrocarbon production.

Main Methods:

• Evaluated six heating modes for oil-bath torrefaction of walnut shells.
• Utilized a combination of microwave and lightwave heating (Com1: 67% microwave, 33% lightwave).
• Analyzed the resulting torrefied biomass and co-pyrolysis products.

Main Results:

• Com1 heating mode yielded the lowest residual mass (84 wt%) and highest gas production (495.47 mL/g).
• Torrefied feedstock under Com1 exhibited the highest effective hydrogen-to-carbon ratio (H/Ceff).
• Com1 promoted hydrocarbon production while reducing oxygen-containing compounds, with specific trends observed for olefins, acids, phenols, and aromatic hydrocarbons.

Conclusions:

• Decarboxylation and decarbonylation reactions are key during oil-bath torrefaction.
• Optimized microwave and lightwave torrefaction (Com1) enhances hydrocarbon yield from lignocellulosic biomass.
• This approach offers novel strategies for biomass upgrading and biofuel production.