Oil sands-derived feed processing
Processing crudes derived from oil sands requires a good understanding of the facility, and of the sources and processing requirements of the available crudes
MAX OVCHINNIKOV, JOSIANE GINESTRA, DORIAN RAUSCHNING, BILL GILLESPIE and KEVIN CARLSON
Criterion Catalysts & Technologies
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The processing of oil sands-
derived feeds presents inherent challenges to refineries. The very nature of heavy feedstocks such as bitumen, coupled with substantive technology and operational issues, often complicates effective, efficient hydroprocessing. Criterion has collaborated with Canadian operators to develop customised catalyst systems and operating strategies to improve days on stream, generate higher yields and facilitate the processing of more challenging feeds. This article details the growing pervasiveness of oil sands as a viable feedstock for global oil processing, and the lessons, challenges and opportunities gleaned by Criterion through its customised research and technical service.
Synthetic oil continues to grow and supplement current oil supplies. The realities of growing global demand, reduced conventional oil supply, increased competition and tighter environmental controls drive oil producers to adapt and optimise their production sites to process synthetics, including extra-heavy or bitumen-derived crudes. While Canada and the Americas are the most abundant sources of bitumen, the raw material is available on every continent, says the US Geological Survey’s Energy Resources Program. Today, many full or partially synthetic crude oils are created by Canadian and Venezuelan producers. Canadian production originates from extra-heavy crudes (Cold Lake) and oil sands (Athabasca bitumen). According to Canada’s Center for Energy, “oil sands deposits are in an area larger than the island of Newfoundland or the state of North Carolina. The Athabasca oil sands area, by far the largest, is the site of all surface mining projects and most in-situ extraction projects.” Venezuelan production originates primarily from extra-heavy crude from the Orinoco region. IHS CERA, an energy consulting firm, projects oil sands production will grow from 1.7 million b/d in 2012 to 3.2 million b/d in 2020. It also says that markets outside of North America, particularly Asia, hold potential for oil sands expansion, with China expected to nearly double its 10 million b/d refining capacity by 2030.
Maximising the opportunities of heavy oil/bitumen
Upgrading these heavy feeds is typically accomplished by employing a combination of hydrogen addition such as hydrocracking, and carbon rejection such as coking, together with many other subsequent hydrotreating steps. As production facilities have been developed and expanded with a variety of technologies, the result is synthetic crudes that typically fall into three categories (see Figure 1):
• Fully synthetic: ranging from light, bottomless sweet crudes to full-range partially treated blends
• Synbit: a combination of synthetic/heavy blends
• Dilbit: simply diluted heavy feeds.
Processing heavy oil and bitumen-derived feeds increases global oil supply, delivers market-ready fuels that are clean and environmentally responsible, and delivers a direct economic benefit to producers. Many facilities have increased the use of these types of feeds in order to maximise asset utilisation and facility margins. This often requires increased process and technology capabilities in a number of refining process units, particularly hydroprocessing assets. The magnitude of impact depends on the feed processed, the inherent flexibility of the facility operations and the ability to offset this increased processing requirement.
Maximising for synthetics: facing the challenges
Processing heavy oil is not always easy. When compared to most conventional crude oil processing and conversion, a bitumen-derived crude is a greater challenge, particularly to hydroprocessing unit operations. Difficulty arises due to inherently higher concentrations of sulphur, nitrogen and aromatic contents; high levels of metal contaminants such as nickel and vanadium, which are detrimental to catalyst performance; and increased levels of asphaltene and arsenic contaminants. Asphaltenes can foul process equipment and lead to an unexpected pressure drop, while arsenic will rapidly deactivate catalysts even if at very low levels.
When it comes to heavy crudes, variations within the crude properties themselves are expansive, usually because of the different technologies and operational practices applied during production and upgrading. In some cases, heavy crude properties may vary from shipment to shipment because of blending approaches or operational changes in their production. While these changes may not seem significant on a bulk property basis, they become quite significant —often problematic — for downstream processing units at a facility. Even within the various types of crude — sweet, sour and bottomless — there may be significant variations, usually caused by how it was produced, blended and upgraded.
Ultimately, one must be aware of the operational impact of these heavy feedstocks. This requires an improved understanding of the streams that are both directly recovered from the fractionation of the refinery feeds and those from upstream units. Major operational adjustments may be required for a facility to maintain targeted operations. As a result of these numerous issues, hydroprocessing becomes a seemingly complex and expensive endeavour that can result in fouling heat exchangers, premature catalyst deactivation and possible complete equipment failure.
Through collaboration with numerous upgrader and refinery operators, Criterion has deciphered the DNA code of bitumen and how refineries — with minimal adaptation and investment — can complement their existing operations with bitumen feedstock processing capabilities. The key is collaboration.
Development of an improved guard catalyst for arsenic removal
Arsenic is naturally present in many petroleum feedstocks. Although the concentration of arsenic is low in most petroleum feeds, some crude oils from Taching (China), Venezuela, certain Russian crudes and Athabasca bitumen contain high levels of arsenic (see Figure 2).1 Some shale oil deposits also exhibit high levels of arsenic, in particular the Green River area of Colorado, Wyoming, and Utah.
Species containing arsenic can be found in a wide distillation range of petroleum feedstocks, but in general the highest concentration of arsenic is found in the naphtha boiling point range. For naphtha feedstocks, it is not uncommon to see arsenic concentration in the 10-50 wppb range, and as high as 600-700 wppb in extreme cases. The predominant types of arsenic- containing species are aryl- and alkyl-partially oxygenated arsines, and the typical structures of these compounds are shown in Figure 3. In some crudes the source of arsenic is purely inorganic, which is sometimes indirectly evidenced by the absence of zinc in a crude.2 The exact molecular composition of arsenic-containing species is highly dependent on the geographical and geological source of crude oil, and the precise molecular mapping of arsenic compounds is often complicated by a low concentration of arsenic compounds with respect to the detection limits of speciation analytical methods.3
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