Fuel oil Blending Fundamentals

International Maritime Organization (IMO) is moving forward with a marked reduction from 3.5% to 0.5% in the maximum sulfur content of marine fuel (bunker fuel oil) on January 1, 2020. This new regulation will cause a dramatic shift in the demand of marine fuels used globally and will have an immediate impact on global refining.

In-line bunker fuel blending can represent an extremely cost effective and accurate method of producing fuel, that meets the quality specification (typically ISO8217) and IMO 2020 environmental rules. According to the CE Delft study, bunker fuels between 0.1% and 0.5% sulfur can easily be met by a wide range of blends, as opposed to traditional marine distillates. Its modelling suggests these blends will contain various residuals, treated light cycle oils, treated light distillates and kerosene etc.

Heavy fuel oils and marine bunker oils are blends of heavy refinery products, distillation residues, visbraking residues, thermal cracked residues, and in many cases diluted with CDU distillates such as kerosene, for viscosity adjustment. A broad range of different types of fuels oils as well as bunker oils are brought on the market. These different types are distinguished by differences in viscosity. These materials are of high viscosity, inferior flow properties and with physicochemical properties that do not comply with required specifications.

Transformation of these materials as fuel oils or as bunker oils requires blending them with lighter, but still low cost petroleum products such as diesel oils and kerosene, with the target to adapt the major specification properties of interest in fuel oil and bunker fuel oils. These are the viscosity, specific gravity, Conradson carbon residue, flashpoint and sulfur to their requested specification.

Fundamentals and optimized functions of effective blending simulation includes :

• Measuring physical properties of component streams to be blended.
• Measuring the blend properties.
• Determination and control of the ratio of blend components to achieve a well-defined blend specification.
• Ratio limits.
• Properties constraint of the blend.
• Constraint limits.
• Check component availability.
• Volumes of final blends required by the consumers (internal and external).

Of special interest in blending fuel and bunker oils is to prevent precipitates caused by blending of incompatible feedstocks.

Efficient blending of fuel oil and bunker oil is conducted in many cases at elevated temperatures to enable flowing of the feedstocks through pipelines. Fast blending is preferred. Re-blending or repair blended batches that are of border-lined or off-spec quality must be eliminated.

The small-scale in-line blending must be monitored closely directly on the ship to meet the IMO-2020 maximum allowed SOx emission. This solution normally requires only two fuels HSFO and LSFO to be blended, in order to reach the required maximum of 0.5% sulfur content of marine fuel.

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