High-quality products from heavy sour crudes
Application of current and emerging technologies will determine the potential of poor-quality crudes as sources of high-quality products
KBC Advanced Technologies
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Refiners have long faced a major dilemma in designing refineries to produce high-quality products: purchase high-quality crudes to minimise investment or invest in expensive technology to allow low-quality crudes to be upgraded to meet product specifications. This choice is driven by the relative costs and availability of low- versus high-quality feedstocks, as well as the current and anticipated future market demands for products. The continuing depletion of high-
quality crude combined with the world market demand shifting toward higher-quality fuels and other products is putting renewed emphasis on this choice.
Many of the tried and proven technologies that have been employed for decades have seen evolutionary improvements, which will extend their usefulness well into the 21st century. These offer the refiner a viable route to upgrade existing refineries to accept lower-cost feedstocks and/or produce additional high-value products. The emergence of several revolutionary technologies may have a dramatic effect on both the feedstocks to the refinery and the process steps utilised within it.
This article reviews trends in products and product qualities, crude supplies, evolutionary technology developments and some interesting revolutionary developments, all of which will impact investment in future refineries.
Market and environmental demand trends are continuing in the direction of lower sulphur and higher hydrogen content of final products. Refineries are still trying to reduce fuel oil production while increasing diesel and gasoline. At the same time, the quality of available refinery feedstocks is decreasing.
Evolution in crude supplies
A basic fact: unconventional oil production is much more expensive than conventional oil recovery. Options for producing and distributing very heavy crude oils vary, including:
• Selling directly to refineries that can handle less than 10° API crude oils
• Creating a heavy crude oil 20°-25° API, “Maya crude equivalent” to be processed at existing high- conversion refineries
• Creating a higher-quality, sweet 30°-40°+ API crude oil that many refineries can handle
• Producing high-quality finished products.
Historically, prices have favoured sacrificing quality in order to produce as much crude oil as possible. Once a plant is built, recovering some high-value finished products is often desirable, as long as it does not significantly reduce the total amount of heavy crude oil produced. This is a way of effectively using excess heavy oil processing capacity to upgrade unconventional oils. If heavy oil production continues until there is no longer excess heavy oil treating capacity available, it will become necessary for producers to build additional upgrading capacity. Market prices for heavy crude oil might drop and producers and refiners will have an incentive to maximise additional upgrading capacity. Some upgraders may take advantage of price fluctuations to produce a higher-quality product at the expense of production until sufficient demand for synthetic crude matches the upgrading capacity.
If unconventional crudes are still in abundant supply, it may be desirable to expand upgrading facilities with additional residue conversion and hydrocracking capacity, especially if a strong market materialises in China for synthetic crude. Expanding hydroprocessing unit capacity will offer the upgrader the opportunity to produce either higher-quality products or additional lower-quality products based on heavy crude oil and finished product economics.
There is a wide range of crude oil upgrading options that can allow a large selection of upgraded crude oil qualities, ranging from the simple process of diluting with light sweet crude oil (naphtha or natural gas condensates) to produce a Maya crude equivalent, to complex flow schemes that include residue hydrocracking, delayed coking and multiple high-pressure hydrocracking units that generate 100% high-quality finished products.
The market for selling very heavy crude oil directly is extremely limited because very few existing refineries are capable of receiving and/or processing such low-quality crude oils. It is likely that, at most, 50 000 b/d can be sold to these refineries at distressed prices for short periods of time.
Producing Maya crude equivalent is currently an attractive level of upgrading. Target specifications for producing this type of crude are gravity around 20°-25° API and sulphur content around 3-4 wt%. There is currently high demand for this quality crude oil because the production of Maya and other similar heavy crude oils has been declining in recent years. Exports of Maya crude oil have decreased by about 1 million b/d over the past seven years. Capacity of processing heavy oils has increased significantly over the same time period (notably at Reliance, Jamnagar, India; Motiva, Port Arthur, USA; and Marathon Garyville, USA).
Creating a higher-quality sweet, synthetic crude oil with gravity between 30° and 40° API opens up the potential market for upgraded crude oil by an order of magnitude because most refineries are capable of processing crude oils of this quality. At the present time, it may be difficult for the producer to justify the cost of the additional upgrading required. However, this level of upgrading could be phased in, if necessary, to accommodate potential market changes in the future.
Creating high-quality finished products from unconventional crude oils is possible but unlikely to be economically viable unless the refinery is located near a large high-value market for finished products, has very economic logistical options available for product movement or has a unique specification it can meet. For example, ultra-low pour point diesel is a high-value product in western Canada, near the upgrader site, because of the cold winter.
Evolution in processing
For grassroots refineries that depend on a heavy crude oil slate and specific market demands (maximum gasoline or maximum diesel production), there are several traditional configurations that allow flexibility. The following discussion should be considered applicable to a traditional refinery processing heavy crude or a syncrude upgrading site.
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