Bad Bunkers -? Surprise! ISO8217 Will Not Save You by Ara Barsamian

2020 will be a mess from fuel oil stability and compatibility point of view. 2020 is clearly price-driven, so the temptation to “cut corners” is great, meaning a set of highly variable number of blend components to manufacture the fuel oil will open a “Pandora’s Box” of  large  numbers of complex and questionable formulations.

1. Fuel Oil Component Order of Blending

Exhaustive studies of the relationship between asphaltene content and aromaticity have shown that the order in which we do the fuel oil blends is critical to obtain compatible and stable fuels.

The order of blending will be one of the concerning issues. Two fuel oil blend components, A and B, each perfectly stable on their own, exhibit a puzzling behavior: when blending fuel A into B, the blended fuel is perfectly stable and compatible. On the other hand, blending fuel component B into A leads to immediate sludging.

Why is that?

By now, most people know that asphaltenes micelles in fuel oil are kept in a colloidal solution by “high” aromaticity of the colloidal “soup” of maltenes. 

Question is, what signifies “high” aromaticity? Some answers are in the various studies [1] and patents [2].

2. Fuel Oil Blend Asphaltene Content and Aromaticity

An extreme case analysis of expected 2020 fuel oil blend categorizes them into paraffinic, aromatic, and hybrid. Before considering the characteristics of these blends, we need to examine some of he typical properties of residual materials and cutters.

Table 1 illustrates some of the properties of Vacuum residue, aka Vacuum Tower Bottoms (VTB) and Visbreaker (VBR) Tar Bottom.

Table 2 illustrates properties of typical cutters in two categories:

Aromatic cutters, typically from FCC units, such as Cycle Oils (Light Cycle Oil, or LCO, Heavy Cycle Oil, or HCO) and Slurries or Clarified Oils (CLO). These are HIGHLY aromatic liquids.

Paraffinic cutters, typically from atmospheric and vacuum distillation  units, such as atmospheric gasoil (AGO), Light and Heavy AGO, and Vacuum Gasoil (VGO).

Credit: D. Stratiev [Reference 1]

3. The 2020 Fuel Oil Blends

The type of 2020-compliant fuel oil blends fall into 3 categories:

Paraffinic blends typically use Vacuum Tower Bottoms and the cheapest cutter, e.g. atmospheric gasoil, such as LAGO, HAGO, or more expensive ULSD. Problem is that while VTB has about 80% aromatics, the gasoils have typically 30 to 40% aromatics, and the resulting blend aromaticity could drop below 40 depending on the blend ratio and the order of blending. The VTB:GO blend becomes  a candidate for sludging depending on the order of blend: GO dropped in VTB is ok because it keeps the aromaticity of the blend high all the time, mostly at or above 50%; the reverse is not true.

Aromatic blends typically use “cracked” blend components, such as VisbreakerTar Bottoms and highly aromatic cutters such as FCC Cycle Oils (LCO, HCO). The aromaticity of Visbreaker tars are in the 47 to 56%.; the aromaticity of cycle oils is in excess of 80%. Any aromatic blend will always have an excess of aromaticity (more than ~50%) and be stable.

Hybrid blends typically use paraffinic blend components such as Atmospheric Tower Bottom, Vacuum Tower Bottoms and mixtures of both paraffinic cutters such as AGO, LAGO, HAGO, and  aromatic cutters such as FCC Cycle Oils (LCO, HCO). The aromaticity of ATB and VTB’s are in the 50 to 60% range; the gasoils 30 to 40% aromatics, and the  cycle oils in excess of 80%. Depending on the blend recipe, any hybrid blend is not guaranteed to  always have an excess of aromaticity (more than ~50%) and be stable.

Typical recipes using components readily available in the Gulf Coast can be found in reference [3]. For example, a hybrid blend recipe might have 70% VTB, 10% LCO, 16% AGO, and 4% Slurry

4. Conclusions

The asphaltene content and aromaticity of fuel oil is critical to it being “fit for use”. And although it was pointed out to ISO and other bunker industry organizations in writing with proposals to add these to ISO8217, nothing was done. They have done a great disservice to all the bunker community, and the bunker users will pay the price buying ISO8217-compliant bunkers that are not fit for use.

For further information or learn more about 2020 bunker blending, please contact the author at ara@refautom.com or attend RAI upcoming 2020 Bunker Blending Course in Houston, March 11-12, 2019.

References:

[1] Stratiev.D., et al, “Investigation on Residual Fuel Oil Stability”, Oil&Gas European Magazine, 2008,

[2] US Patent 9,803,152 B2 Kar et al, assignee: ExxonMobil, ‘Modifications of Fuel Oils for Compatibility”, October 31, 2017

[3] Barsamian, A. et al, “IFO380 recipes can meet 2020 reduced-sulfur bunker regs”, O&GJ, pp.22-24, Dec 2017

The Author

Ara Barsamian is the president and CEO of Refinery Automation Institute LLC (RAI), has over 48 years of experience in bunker, gasoline, diesel, and biofuels blending operations and technology. Among his first experience  at Exxon was computerized bunker blending in Aruba. Lately he has been involved in the IMO 2020 bunker blends, recipes, and ISO 8217 specs. Earlier in his career, he was a group head with Exxon Research & Engineering Co., president of 3X Corp., and vice-president of ABB Simcon, all in the area of fuels blending. Mr. Barsamianis a member of AIChE, ASTM, and IBIA. He holds BS and MS degrees in electrical engineering from City University of New York, and is a professor (adjunct) at NJ Institute of Technology.