The effect of torrefaction, slow, and fast pyrolysis on the single particle combustion of agricultural biomass and lignite coal at high heating rates

Abstract

The present paper studies single particle combustion of olive residue (OR), almond shell (AS), and Tunçbilek lignite (TL) and their thermal pre-treated particles in a vertical wire mesh reactor (WMR) setup. Pre-treatment of the fuels was done via torrefaction, slow, and fast pyrolysis. The particles with different masses were heated to 1000 °C by radiation with a heating rate of 900 °C/s. The combustion process was recorded with a high-speed camera. The time analysis demonstrated that the particle mass and size did not affect ignition delay time; however, slow pyrolysis had a significant effect on the ignition delay time. The ignition delay time was significantly increased for the chars produced from slow pyrolysis compared to raw and other heat-treated particles for all fuels. Burnout times of all fuels increased proportionally with particle mass. Fast and slow pyrolysis generally increased the char combustion and burnout times. The average burnout times for fast and slow pyrolyzed biochars were ∼20 s and ∼29 s, respectively, while those of raw biomass were ∼9 s. The average burnout times for fast and slow pyrolyzed lignite particles was ∼20 s and ∼53 s, respectively, while those of raw lignite was ∼19 s, when 2 mg particles were compared. Fast pyrolyzed biomass particles had similar burnout times compared to those of raw TL particles. This depicts the potential of co-firing TL with biomass chars produced from fast pyrolysis.