Heavy Fuel Oil (HFO) is not homogenous and has an average droplet size of 70 micron and larger.
It contains numerous much larger clusters of asphaltenes and complex long-chain hydro-carbons.
It is a refinery waste stream product with a high BTU content used as fuel oil.
Centrifuges and automated filters are used to clean the fuel. A percentage of the purchased fuel ends up in the slop tank.

HFO needs to be heated and pressurized before it can be used to operated engines or boilers.
Exposing fuel to heat and pressure will unavoidably increase the size and mass of the fuel droplet,
change the physical condition of the oil and negatively impact the combustion process.