Improving Fast Pyrolysis Bio-Oil Yield and Quality by Alkali Removal from Feedstock

Area of Science:

• Biomass valorization
• Thermochemical conversion
• Chemical engineering

Background:

• Alkali metals in biomass can negatively impact pyrolysis efficiency and bio-oil quality.
• Pre-treatment methods are crucial for optimizing biomass conversion into valuable products.

Purpose of the Study:

• To investigate the effectiveness of water and nitric acid leaching for alkali removal from forest residues, eucalyptus, and wheat straw.
• To optimize leaching parameters and evaluate the impact on fast pyrolysis bio-oil yield and composition.
• To assess the feasibility of acid leaching for different biomass feedstocks at pilot scale.

Main Methods:

• Laboratory-scale optimization of water and dilute nitric acid leaching parameters for various biomass feedstocks.
• Bench-scale fast pyrolysis of leached and untreated biomass in a bubbling fluidized bed reactor.
• Pilot-scale pyrolysis demonstration using acid-leached oat straw.

Main Results:

• Nitric acid leaching significantly reduced alkali content in eucalyptus residues and wheat straw.
• Leaching increased organic liquid yield and sugar content in bio-oils from eucalyptus and wheat straw.
• Acid leaching of forest residues led to bed agglomeration during pyrolysis, hindering the process.
• Pilot-scale pyrolysis of leached oat straw confirmed high organic liquid yield.

Conclusions:

• Nitric acid leaching is a viable pre-treatment for enhancing bio-oil production from certain biomass types like eucalyptus and wheat straw.
• Biomass feedstock characteristics, particularly the presence of catalytic elements, influence the success of acid leaching pre-treatment.
• Further research is needed to address challenges like bed agglomeration for successful acid leaching of diverse biomass feedstocks.