The Production and Processing of Heavy Fuel Oil
Heavy fuel oil, or residual oil as it is also known, is a by-product of the refining of crude oil produced from oil wells/reservoirs both on and offshore.
Offshore, the oil is brought to the oil production platform through risers that connect the reservoir to the platforms. Here it is filtered to remove sand and grit before being pumped through various separators that remove the inherent gas and water. It is then heated and pumped ashore using sub-sea pipelines.
Once at the crude oil refinery, it is processed to remove any remaining water/salts before being heated to over 650°F and passed into a vertical distillation column. Here the various fractions are drawn off, leaving a tarry residue at the bottom of the column. It is here the HFO is drawn off for distribution to ships bunkers that after further on-board treatment use it as engine or boiler fuel.
Recent rules and annexes by the International Maritime Organization (IMO) and MARPOL 73/78 have capped the sulfur content of HFO to 4.5%, being further reduced to 3.5% next year. These "bottoms" therefore have to be further processed by de-sulfurization to reduce the sulfur level to within these limits.
Production of Heavy Fuel Oil for use in Ship's Main Engines/Boilers
The next section deals with the supply and storage of the HFO in the ships bunkers