Refining

The residues that make up residual fuels come from several refinery processes. In the first instance the fuel is heated and fed into the atmospheric distillation column where the lighter hydrocarbon molecules are distilled off as gases, gasoline, kerosene and gas oil, leaving about 50% of the crude as residue. Some of this residue is fed into the vacuum distillation column where it will be further processed to produce vacuum gas oil, waxy distillates and a residue. This residue can form part of the blend in marine bunkers or can be fed into thermal crackers. Here, under high pressure and temperature more light hydrocarbon molecules form and are removed as light distillates. Also the heavy gas oil from the vacuum distillation column may be subjected to catalytic cracking where as a result of chemical reaction yet more light hydrocarbon molecules are formed and separated into even lighter distillate fractions. The residues from all these processes can be blended with a variety of distillates to make up the specified marine bunkers.