(142d) Plausible Pathway to Meet IMO 2020 Global Sulfur Cap

Authors: 
Waturuocha, A., University of Tulsa
Mavarez Nava, G., University of Tulsa
Volk, M., University of Tulsa
Banerjee, D., University of Tulsa
Following the International Maritime Organization’s (IMO) decision to decrease the global limit for sulfur content of marine fuel oil from 3.5 wt% to 0.5 wt% effective January 1 2020, there has been a lot of discussion about how ship owners may comply. Several options have been proposed to meet this new limit for the shipping industry; utilizing on-board scrubbers with the existing high sulfur fuel oils, switching to LNG fuels which are practically sulfur free, or switching to low sulfur fuels by blending. For refiners; another option may be further processing of the high sulfur crude residue through challenging technology such as resid hydroprocessing. These options all have advantages and disadvantages, some require expensive retrofit of the current ships, some come with higher risks due to limited experience, however, the biggest constraint is the time to enforcement. Ultimately refiners as well as the transportation industries are looking for the most economical pathway for immediate solution.

Historically, marine fuel oil, also known as bunker fuel, is the atmospheric tower bottoms (ATB), which is the feedstock for the vacuum tower and is seldom available for fuel oil blending; thus the bunker fuel oil would typically be a blend of any of the following streams- low sulfur ATB, FCC slurry oil, hydrotreated gas oils, coker liquid, visbroken residue, deasphalted oil (DAO) etc. However, other studies indicate that, despite the fact that pricing of the blend components is an issue; the availability of the blend components that could meet the bunker fuel recipe in all geographic areas of the world is a greater problem. As for example, most of the low-sulfur crudes in the world are available outside the United States. Besides that, not all refineries have all the units or plants to produce the blend materials.

Typically, refiners fractionate the crude feed before hydroprocessing the different fractions. The heaviest fractions such as the ATB and vacuum resid (VR) that typically go into the bunker fuel recipe are the most difficult to hydroprocess. In this paper we explored an unorthodox option as a possible solution to meeting the demand of reduced sulfur bunker fuel market targeting the global limit of IMO - crude oil pretreatment through hydrotreating. The most common hydrotreater unit in a refinery may be used to produce low-sulfur blend material directly from whole crudes. This may eliminate the major capital cost of installing a new unit.

At the University of Tulsa Research Campus, we have a state-of-the-art large scale (4 to 4 ½ L) continuous hydroprocessing facility that could be operated up to 540°C and 27.6 MPa pressure. The present paper will discuss the unusual option of hydrotreating and subsequent fractionation of a whole crude oil with focus on the extent of Hydrodesulfurization (HDS) and Hydrodenitrification (HDN) of its ATB and/or VGO fractions. The experimental system was operated at 0.5 h-1 LHSV, 15.2 MPa and H2/oil ratio of 1200 L/L and 3 temperatures (335°C, 348°C and 357°C) using commercially available Nickel-Molybdenum on alumina catalyst. The feed and products were analyzed and bulk conversion of each contaminant as well as the density change is presented. The extent of HSD in the resulting products make them good candidates for blending materials to meet the target <0.5 wt% sulfur. The practicability of this option and other options will also be discussed.

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