Evaluation on nitrogen conversion during biomass torrefaction and its blend co-combustion with coal

Area of Science:

• * Combustion Science
• * Environmental Chemistry
• * Biomass Energy

Background:

• * Biomass torrefaction and coal co-combustion are key strategies for sustainable energy.
• * Understanding nitrogen transformation during these processes is crucial for emission control.

Purpose of the Study:

• * To investigate the impact of torrefaction atmospheres (CO2, O2) on biomass nitrogen behavior.
• * To analyze nitrogen migration and transformation mechanisms during coal co-combustion.
• * To optimize torrefaction conditions for reduced NOx emissions.

Main Methods:

• * Biomass torrefaction under different atmospheres (CO2, O2, N2/O2).
• * X-ray Photoelectron Spectroscopy (XPS) for nitrogen speciation analysis.
• * Coal co-combustion experiments to evaluate NO emission reduction.

Main Results:

• * CO2 torrefaction suppressed pyrrolic nitrogen (N-5) to quaternary nitrogen (N-Q) conversion.
• * O2 torrefaction showed the opposite trend in nitrogen conversion.
• * NO emission reduction effectiveness shifted from positive to negative with increasing torrefaction temperature.
• * Torrefaction in N2/O2 at 250°C resulted in the lowest NO emissions.

Conclusions:

• * Torrefaction atmosphere significantly influences biomass nitrogen speciation and transformation pathways.
• * The interplay between NCO, NH intermediates, and char-NO heterogeneous reduction governs NO emissions.
• * Low-temperature N2/O2 torrefaction offers a promising method for enhancing biomass properties and minimizing NO emissions in co-combustion.
• * Utilizing power plant effluent as a torrefaction medium is theoretically supported.