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DOE - Fossil Energy Techline - Issued on: April 22, 1999 New Research Focuses on Improving Refinery Coking ProcessThe U.S. Department of Energy is entering into a 3-year research project with the University of Tulsa and an 9-member industry consortium to tackle the challenges of reducing energy consumption and upgrading the environmental performance of an oil refinery's coking process. Pound-for-pound, coking - the process of extracting additional liquid and gaseous products from heavy "bottom of the barrel" oil - is the most energy intensive of any operation in a modern oil refinery. Large amounts of energy are required to heat the thick, poor-quality petroleum residuum to the 900 to 950 degrees F required to crack the heavy hydrocarbon molecules into lighter, more valuable products. Reducing the amount of energy consumed by the coking process can improve a refinery's economics and significantly lower the release of greenhouse gases and airborne pollutants. The University of Tulsa's research could also produce another environmental benefit. Today's refineries must contend with increasing amounts of unwanted sulfur, metals and other impurities in crude oil feedstocks. These impurities often remain trapped in the coke, degrading its value and creating disposal problems. Researchers will study ways to reduce the amount of contaminants in coke, making it better suited for commercial use in the metals or chemicals industry. The focus of the research project will be on a process called "delayed coking," a technology first installed in a U.S. refinery in 1929 and now in use at nearly 50 installations around the country. In a delayed coker, after gasoline, diesel, and other lighter products are distilled from the feedstock crude oil, the residuum left behind is fed into horizontal tubes inside a furnace and heated rapidly to cracking temperatures. Since the residuum resides in the furnace tubes for only a short period of time, formation of coke is "delayed" until the feed material reaches large vats, called "coking drums," downstream of the heater. Although the delayed coker has a long history, refineries have relied primarily on handed-down experience of plant engineers to develop and operate the equipment. Very little systematic scientific research has been done to explore the complex chemical reactions that take place inside a delayed coker. The University of Tulsa project will begin to fill in some of the gaps in knowledge about the molecular transformations that occur as petroleum residuum changes into solid coke. The expectation is that, as the fundamental processes become better understood, they can be fine-tuned to improve energy efficiencies and product quality. Guided by an industry-led steering committee, University researchers will conduct experiments, for example, to determine if lower temperatures - perhaps below 900 degrees F - applied in specially modified furnaces or preheaters can effectively crack the residuum into higher quality products and reduce coke formation. Additives - perhaps including certain types of waste plastics - will be studied to determine if the hydrogen they release can prevent coke formation and lead to higher quality products. New types of venturi aspirators and other injection devices will be studied to determine if various approaches to spraying the residuum into the coker can enhance its operation. The research will be conducted with heavily instrumented laboratory- and pilot-scale equipment, and the results are likely to provide one of the most thorough scientific studies of the coking process done to date. As data are collected, researchers will create mathematical and chemical models of the coke formation process as a basis for evaluating chemical and engineering modifications that can be made to the equipment. The project will be conducted in three one-year phases. In Phase I the University of Tulsa will begin a series of base runs using reassembled, customized coking units, one from an earlier DOE project and one provided by industry. In Phase II the researchers will begin detailed analyses of the coking process in the furnace tube under varying temperatures and agitation, studying how liquid yields and quality changes at the different operating conditions and correlating the furnace tube chemistry with coke drum conditions. In Phase III, research will be scaled up and a series of coordinated tests will be conducted in both the stirred batch and flow systems, and process improvements will be evaluated for potential industrial use. The entire 3-year project is expected to total more than $2.5 million. DOE, through its National Petroleum Technology Office in Tulsa, will provide the University with $1,005,000. The University and its eight industrial partners will contribute $1,590,000. The consortium includes: Citgo Petroleum Corp.; Marathon Ashland Petroleum LLC; Chevron Corporation; Conoco, Inc.; Great Lakes Carbon, Inc.; Petrobras, the state-run oil company of Brazil; Suncor Energy, an independent Canadian integrated oil and gas company; Equilon Enterprises LLC, a joint venture petroleum company formed in January 1998 between Texaco Inc. and Shell Oil Company; and Baker-Petrolite. -End of TechLine- For more information, contact: Technical contacts: |