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Aalborg Solutions No. 12 · January 2009 Changing from HFO to MDO or MGO MARPOL Annex VI "Regulations for the Prevention of Air Pollution from Ships" stipulate that Heavy Fuel Oil (HFO) combustion is not permitted during port stay and in specific areas at sea. The switchover to lighter types like Marine Diesel Oil (MDO) or Marine Gas Oil (MGO) requires monitoring and some modifications to the burner and fuel systems, as outlined by Aalborg Industries in this brief. 1.0 Legislation and compliance Since May 2005, specific environmentally friendly MARPOL regulations have been in force that stipulate that emissions from main and auxiliary machinery are kept within specific limits. They require, for instance, reduction of sulphur oxide combinations (SOx), carbon dioxide (CO2) and nitrogen oxide combinations (NOx). The subsequent EU Marine Fuel Sulphur Directive defines Sulphur Emissions Control Areas (SECAs) slightly different from those agreed by the International Maritime Organization (IMO) under MARPOL Annex VI. The mentioned legislation has substantial impact on existing or future installations of Aalborg Industries’ boilers, burners and fuel systems. This brief covers the cautions and considerations, which should be addressed in connection with switch-overs between the traditional HFO or specified fuels and the lighter grades of fuel such as MDO and MGO. 1.1 Oil selection The regulations limit the traditional use of Heavy Fuel Oil (HFO) for all operating conditions to the extent that combustion of HFO is no longer permissible during port stay and in specific areas at sea. It has become necessary to switch to lighter, “better” fuel oil types like low sulphur fuels. Low sulphur fuels are unfortunately not always readily available in all ports, which can again lead to use of yet other fuel types like MDO or MGO that can achieve the stipulated emission results and comply with legislation. 1.2 Auxiliary boilers and burners Most burner systems have so far been designed to burn HFO as the main fuel, but MDO can usually substitute HFO, and most plants will have no problems with temporary change-over to MDO operation. 2.0 Fuel properties If special fuel such as low-sulphur fuel oil is not available in a port, the obvious choice of fuel would be a good quality Marine Diesel Oil (MDO) or Marine Gas Oil (MGO). ous burner types react differently upon fuel changes/switch-overs, and will consequently be dealt with separately. 1.3 Burner and fuel systems In general, all auxiliary boiler plants are equipped with a burner and an associated fuel system. This often means that the fuel system has been designed for a particular type of burner installation. The components in the fuel systems are generally quite common and will therefore in the following be dealt with in general terms whereas the vari-

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