Combustion behavior of heavy fuel oil with varying asphaltene contents

Asphaltene is the heaviest fraction of heavy fuel oil (HFO) with complex high-molecular-weight polar compounds of hydrocarbons and heteroatoms. The current study investigates the thermochemical characteristics, gas products, and single droplet combustion behavior of HFO samples with varying asphaltene contents through different combustion experiments. The combustion process involves the release of low-boiling volatile gases during preheating, followed by intense oxidation and coke ignition at the ignition temperature, leading to complete combustion. Results from the experiments reveal that, in comparison to other samples, HFO with 4 % asphaltene content (HFO4) has a promising burnout rate (S = 1.6861 × 10–3%·min-1· °C-1) and the preheating stage only accounts for 72.29 % of the lifetime. Furthermore, visualization analysis of transient images reveals that HFO4 droplets exhibit higher instability and micro-explosion size during combustion. The condensed aromatics in asphaltene modulate reaction intensity by controlling free radical dynamics, while metals like iron and vanadium enhance reactivity through catalytic effects. The formation of fine particles from polyaromatic condensation and metalloporphyrin reactions modifies thermal conductivity, intensifying droplet micro-explosions. High asphaltene content in HFO raises environmental concerns because of smoke and heavy metal emissions during combustion, underscoring the need for efficient, low-pollution strategies in utilizing asphaltene and heavy oil.