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Unformatted text preview: Copyright © 2010 American Institute of Chemical Engineers (AIChE). On the Horizon Gazing into an Energy Crystal Ball By mid-century, new energy sources could be integrated into the existing chemical-conversion infrastructure, but additional research is needed to fine-tune the technologies and improve efficiencies and economics. Vern W. Weekman, Jr. Princeton Univ. I f we could look into an Energy Crystal Ball and get a peek at the year 2050, what might we see? We would certainly see growth in such non-CO2-producing energy sources as nuclear, wind and solar, as well as growth in CO2-neutral biofuels. We would also see that air transportation still depends on the jet engine and jet fuel; trains, trucks and heavy construction equipment still need diesel fuels; and ships are still powered mostly by heavy fuel oils. Cars and light trucks may still need diesel and gasoline if hybrid vehicles prove to be competitive with fuel-cell and electric cars. At the same time, petrochemicals such as light olefins, benzene and para-xylene will continue to be essential raw materials for a wide range of products. The crystal ball would also reveal that the new energy sources have not displaced all of the existing fossil fuels. Rather, some new equilibrium between the newer and older sources will be established. Many studies have explored the future use of specific new energy sources and some small degree of integration. However, few, if any, have considered how to accomplish a broad integration of the old and new sources to achieve this new equilibrium. The National Academy of Engineering and the National Academy of Sciences recently completed the “America’s Energy Futures” study (1). Administered by the National Research Council and chaired by Harold Shapiro, president emeritus of Princeton Univ., this study should facilitate a productive national discussion of the nation’s energy policy and energy future. The study’s first phase consisted of reports from three panels — one on energy efficiency, another on electricity from renewable sources, and a third on alternative liquid transportation fuels (2). This third panel undertook a study of the economics of integrating chemical conversion technologies for biomass and coal. The second phase of the National Academies’ study focuses on strategic, tactical, and policy issues. Shinnar (3) was among the first to recognize the potential advantages of integrating alternative energy sources with existing chemical-conversion technologies. Williams (4) showed that synergies are possible in the cogasification of coal and biomass when coupled with Fischer-Tropsch (FT) and catalytic (ZSM-5) processing. Our energy crystal ball reveals the efficient and economic integration of energy sources with chemical manuCEP June 2010 23 On the Horizon facturing and processing illustrated in Figure 1. This article suggests overall strategic paths that should be explored in future energy studies in the hope of adding some clarity to the picture. Using electricity to produce hydrogen … Figure 1 demonstrates how electricity and hydrogen can be made from a variety of sources. The advantage of making electricity from nuclear, solar, wind, and geothermal sources is that it is generated without producing CO2 emissions. Some of this electricity is used for electrolysis to make H2, which in turn is used to upgrade fossil fuels or employed in fuel cells to power cars and light trucks. However, due to thermodynamic losses and process inefficiencies, the electrolysis step consumes 20–25% of the electrical energy. Making H2 from fossil fuels may be cheaper, but the associated CO2 emissions must be balanced against the lower cost. The H2 fuel cell is about 60% efficient, so the overall efficiency (with the electrolysis step) is about 45–50%, which is similar to that of an efficient diesel engine (2). Since a combined electric motor and battery is 80–85% efficient, an all-electric car may offer more energy efficiency than a car powered by a hydrogen fuel cell. One alternative is to feed this electricity directly to the grid to charge the batteries in electric cars or plug-in hybrids. An important future study should determine whether the electric car or plug-in hybrid will offer a lower-cost transportation system than H2 fuel cells, since expanding the existing electrical grid may be cheaper than building a new H2 infrastructure (5). Fossil fuels are gasified and the resulting carbon monoxide and hydrogen can be water-gas-shifted to produce more H2, although at the expense of more CO2 production. Cooper (6) recently explored the technologies and economics of gasification for simultaneously producing electricity and methanol from coal. Natural gas is also steam-reformed to produce CO and/or H2. Lighter fractions of crude oil (naphtha) are catalytically converted to higher-octane components as well as H2. Finally, biomass is gasified to CO and H2 or shifted to all H2. Biomass is essentially CO2-neutral, because the resulting CO2 is balanced by increased growth of replacement plant material. 24 June 2010 CEP … for chemical conversion The hydrogen produced by these methods is fed to a variety of processing steps. In the Bergius process, finely divided coal is liquefied catalytically with high-pressure H2, and the resulting heavy coal liquid is upgraded using the high-pressure H2 and various catalysts. For example, some of the same catalytic hydrocracking and catalytic desulfurization and denitrogenation technologies widely used to upgrade coal liquids to conventional fuels are also employed to upgrade heavy oils and tar sands. However, due to the high H2 pressure required, direct liquefaction may be more expensive than the indirect route, i.e., gasification followed by FT synthesis. Coking, another conversion process, has long been used extensively in petroleum refining. Through a thermal soaking process, it converts heavy fractions to lighter olefinic products and solid petroleum coke. These lighter products must be upgraded with H2 processing to reduce the olefin content and increase product quality. The coke produced is either gasified to CO and H2 or disposed of as easily sequestered solid carbon. Since coking with coke sequestration competes directly with gasification, more work is required to assess the relative economics. In shale retorting, another thermal process, shale is partially burned to heat the petroleum-like material locked in the rock and then capture it as shale oil. This liquid must be upgraded by catalytic H2 processing to reduce its high nitrogen content and produce useful fuels. The high-carbon spent shale can then be buried in landfills or in the mines where it originated. In all of these routes, the product has a higher quality and a higher H2 content, so it will create less CO2 when burned as a fuel. During the transition period, fossil fuels continue to be used as the development of alternative energy sources progresses. Some of the H2 produced from the non-CO2 sources is used to upgrade fossil fuels. These H2-upgraded fossil fuels have a lower environmental impact because they produce less CO2 and they are compatible with the existing fuel distribution system. If H2 is made from fossil fuels, then, stoichiometrically, using the H2 in a fuel cell or to upgrade fossil fuels will result in the same overall reduc- Figure 1. Fossil fuel and alternative energy sources can be integrated with chemical manufacturing and processing. Process Heat Electricity To Grid H2 Nuclear H2 Electricity H2 Electrolysis Catalytic H2 Processing O2 Solar PV, Thermal Methanol Production Electricity H2 Methanol Catalytic Liquefaction Wind, Tides, Geothermal Natural Gas H2 Natural Gas Reforming ZSM-5 Catalytic Processing CO2 Thermal Processing Naphtha Conventional Fuels, Petrochemicals, Light Olefins Naphtha H2 Catalytic Reforming Coke Fossil Fuels Gasoline, Petrochemicals FischerTropsch Alcohols, Diesel, Lubes, Waxes, Petrochemicals Coal, Heavy Oils, Shale Oil H2 Wood / Stalks Vegetable Oils Algae H2 & CO Gasification Water Gas Shift Fats Oils CO2 Esterification/ Pyrolysis Biodiesel Ethanol Biomass Grains Cellulosic Material Hydrolysis/ Fermentation Ethanol CEP June 2010 25 On the Horizon tion in CO2 released to the atmosphere. Research is needed to evaluate the overall economic impacts of H2-upgrading of fossil fuels versus the direct use of H2 in fuel cells. A large part of the transportation sector (i.e., over-theroad diesel trucks, heavy construction equipment, airplanes, and trains) still require H2-upgraded hydrocarbon fuels. The manufacture of petrochemicals and polymers also still requires the chemical conversion technologies outlined above (3). lube oils, waxes, and petrochemicals, the combination of FT synthesis and ZSM-5 processing plays a key role in energy integration. The FT process, proven in large-scale plants in Germany during World War II and subsequently used in South Africa, Borneo and Qatar, yields very pure products, because all impurities must be removed from the H2 and CO feed to protect the FT catalyst. For example, according to information gathered after the war, the FTbased fuels used in Germany’s zeppelins were so pure that the exhaust-gas condensate could be used for showers and dishwashing. FT diesel fuel has a very high cetane number and no sulfur, making it an excellent blending stock for conventional diesel. Some of the methanol produced by the methanol process goes directly to market, and some is converted by ZSM-5 to high-octane gasoline and to olefins for petrochemicals manufacturing. This methanol-to-gasoline technology has been demonstrated in a large-scale plant in New Zealand. FT products require fairly extensive upgrading using conventional petroleum refining technology, so, when only gasoline or diesel is required, part or all of the FT effluent can be fed to ZSM-5 processing for conversion directly to high-octane gasoline or high-quality diesel. Depending on process conditions, the ZSM-5 step can Co-processing of biomass and high-carbon fossil fuels Figure 1 shows that the heavier fossil fuels (i.e., coal, tar sands, heavy oils, shale oil) can be integrated with biomass (i.e., wood, plant stalks) through gasification and water-gas-shift technologies. Larson, et al., (4) and Ramage (2) have outlined comparative economics for co-gasification of coal and biomass. All the feed materials are linked to conventional fuels through the CO and H2 produced in gasification and subsequently converted in either the FT process or the methanol process. Huber (7) presented a comprehensive review of various routes to biomass fuels. With the flexibility to make a broad range of products, including conventional fuels, alcohols and oxygenates, Numerous chemical-conversion processes can play a role in energy integration. Process Feed Products Catalytic H2 Liquefaction Coal, biomass, heavy oils, tar sands, shale, peat, H2 All conventional fuels Gasification Coal, biomass, heavy oils, tar sands, shale, peat, natural gas, oxygen, air CO and H2 Thermal Conversion (coking, retorting) Coal, heavy oils, biomass, shale, tar sands, peat Coke, all conventional fuels, C1 to C3 gases, olefins Catalytic Water-Gas Shift CO, H2, H2O H2 Catalytic Reforming of Natural Gas Natural gas, C1 to C5 gases CO2 and H2 Methanol Production CO and H2 Methanol Fischer-Tropsch Process CO and H2 Higher alcohols, paraffins, light olefins, diesel, gasoline, waxes, lubricating oils Conversion of Alcohols to Hydrocarbons (ZSM-5) Methanol, ethanol and higher alcohols, raw Fischer-Tropsch effluents, bioalcohols, bioolefins, biooils All conventional fuels, olefins Catalytic Naphtha Reforming C5 to C20 hydrocarbons High-octane gasoline, H2, petrochemicals Fermentation Grains, cellulosic parts of plants, sugar cane Ethanol Thermal and Catalytic Olefins Production C2 to C40 paraffins C2 to C40 olefins, petrochemicals, H2 Catalytic Methanation CO2, CO, H2 CH4, some higher hydrocarbons Catalytic Hydrocracking Heavy hydrocarbons, H2 Low-sulfur, high-H2-content conventional fuels Catalytic Desulfurization and Denitrogenation Fuels high in sulfur and nitrogen, H2 Low-sulfur conventional fuels 26 June 2010 CEP convert FT effluent and methanol to light olefins for use in polymers and petrochemicals (8). Vegetable oils and animal fats are upgraded to biodiesel by hydrogenation and purification, or fed directly to ZSM-5 processing for conversion to conventional fuels (8). Upgrading these liquid biofuels is expensive, and it may be more cost-effective to use the one-step ZSM-5 route to produce high-quality conventional fuels. Research to find an economical way to ferment cellulosic material to alcohol indicates that gasifying this cellulosic material and using the FT/ZSM-5 route to produce fuels may make economic sense. Because ZSM-5 can convert almost any alcohol, oxygenate, or biodiesel to conventional fuel, converting the bioalcohols to gasoline or diesel and shipping the fuel via existing pipelines may be more cost-effective and have lower environmental impacts than transporting the alcohol cross-country by trains or trucks for blending. In addition, it would allow an unlimited amount of alcohol or biodiesel to be used as a fuel without affecting current engine performance. A path to the future If we are to reach the new energy equilibrium predicted by our energy crystal ball, where energy and environmental needs are met simultaneously, it will be critical that we integrate solar, wind, nuclear, and biomass energy sources into our existing infrastructure for the chemical conversion of fossil fuels. Doing so will translate into the most effi- Literature Cited 1. 2. 3. 4. 5. 6. 7. 8. Shapiro, H. T., et al., “America’s Energy Future: Technology and Transformation,” U.S. National Research Council, National Academies Press, Washington, DC (2009). Ramage, M. P., et al., “America’s Energy Future — Liquid Transportation Fuels from Coal and Biomass,” U.S. National Research Council, National Academies Press, Washington, DC (2009). Shinnar, R., and F. Citro, “A Road Map to U.S. Decarbonization,” Science, 313 (5791), pp. 1243–1244 (Sept. 1, 2006). Larson, E. D., et al., “Co-Production of Synfuels and Electricity from Coal + Biomass with Zero Net Greenhouse Gas Emissions: An Illinois Case Study,” Energy and Environmental Science, 3 (1), pp. 28–42 (2010). Ramage, M. P., et al., “Transitions to Alternative Transportation Technologies — A Focus on Hydrogen,” U.S. National Research Council, National Academies Press, Washington, DC (2008). Cooper, H. C., “Producing Electricity and Chemicals Simultaneously,” Chem. Eng. Progress, 106 (2), pp. 25–32 (Feb. 2010). Huber, G. W., “Synthesis of Transportation Fuels from Biomass: Chemistry, Catalysis and Engineering,” Chemical Reviews, 106 (9), pp. 4044–4098 (2006). Weisz, P. B., “The Remarkable Active Site: Aluminum in Silica,” I&EC Fundamentals, 25 (1), pp. 53–58 (Feb. 1986). Integration of solar, wind, nuclear and biomass sources with the existing chemicalconversion infrastructure for fossil fuels will be key to reaching a new energy equilibrium. cient and economical use of all of our energy resources and ensure that the resulting liquid fuels will be clean-burning with minimal CO2 emissions. Such integration could also enhance the value of alternative energy sources, by promoting their use and increasing our energy independence, while utilizing the sunk cost of the extensive infrastructure of existing chemical-conversion technologies. For instance, hydrogen obtained from sources that do not produce CO2 may be used more economically to chemically upgrade fossil fuels and biofuels. This H2-upgrading route might significantly reduce atmospheric CO2 while reducing the need for a new hydrogen delivery infrastructure. In another example, biofuels may be processed catalytically to conventional fuels, enabling their unlimited use in current engines without incompatibility problems in distribution systems. The bottom line is that the integration of existing chemical-conversion technologies with various energy sources will enable us to use our existing fuels, petrochemicals, and engines more economically, while reaping the benefits of lower carbon impact from new energy sources, such as solar, wind, nuclear, and biomass. CEP VERN W. WEEKMAN, JR., has been a leader in the energy industry. He began his career at Mobil Oil Corp., where he was actively involved in establishing Mobil Oil’s international leadership position in the catalytic processing of petroleum. He held positions as manager of process research and development; president of Mobil Solar Energy Corp.; and director of Mobil Oil’s Central Research Laboratory, where he was responsible for all of the company’s basic and exploratory research in both the upstream and downstream areas. He serves as an industrial lecturer in the Chemical Engineering Dept. at Princeton Univ. Weekman earned a BS and a PhD from Purdue Univ. and an MS from the Univ. of Michigan, all in chemical engineering, and was awarded a doctorate honoris causa at Purdue’s May 2007 graduation. He was elected to the National Academy of Engineering in 1985, and as part of AIChE’s Centennial Celebration in 2008 was named one of the 100 Chemical Engineers of the Modern Era in recognition of his work in chemical reaction engineering, modeling, and catalytic cracking. He has been an active leader of AIChE, including chair of the Government Relations Committee and terms as a director (1989–1992) and president (1998), and is a director of the Chemical Heritage Foundation. His major awards include AIChE Institute Lecturer (1978), Purdue Distinguished Engineering Alumnus Award (1980), AIChE Wilhelm Award in Reaction Engineering (1982), and Amundson Award in Reaction Engineering (2005). Acknowledgments The author wishes to acknowledge the many helpful suggestions of colleagues on the AIChE Government Relations Committee, in particular Dave Gushee, Pete Lederman, and Cawas Cooper, and the encouragement of the GRC Chair, Otis Shelton. Former Mobil colleagues Mike Ramage, Jim Katzer, and Jack Wise also made valuable suggestions. CEP June 2010 27 ...
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