Fuel Processing Technology (v.71, #1-3)
Fuel science in the year 2000: an introduction by Gerald P. Huffman; Irving Wender (1-6).
The current volume contains 15 papers that review the most active research and technology topics in fossil fuel science. This introductory paper contains a brief overview of the material presented in those papers.
Review of advances in combustion technology and biomass cofiring by Everett A. Sondreal; Steven A. Benson; John P. Hurley; Michael D. Mann; John H. Pavlish; Michael L. Swanson; Greg F. Weber; Christopher J. Zygarlicke (7-38).
Advances in combustion technology will be adopted only when they reduce cost and can be implemented with acceptable technical risk. Apart from technical risk, future decisions on new power plants will be principally influenced by trends in fuel cost, the efficiency and capital cost of new generating technologies, and environmental and regulatory policies including possible carbon taxes. The choice of fuel and generating technology for new power plants is influenced by an increasingly complex combination of interrelated factors: (1) current and future governmental polices on restructuring and deregulation of utilities, and environmental regulations that in the future could include taxes on carbon emissions; (2) macroeconomic factors such as proximity to load centers, electrical transmission lines, plant capital investment, delivered fuel cost, and fuel price stability; and (3) the state of development of new generating and environmental control technologies and the associated benefits and risks involved in their deployment, which are strongly related to fuel properties. This paper describes three advanced high-efficiency power systems for which the EERC has performed supporting research and development: (1) a coal-fired supercritical steam boiler with advanced emission controls; (2) an indirectly fired combined cycle using compressed air as the working fluid in a gas turbine (GT), fired either on coal alone or on coal and natural gas; and (3) two versions of a hybrid gasifier-pressurized fluidized-bed combustor (PFBC) system.
Keywords: Combustion technology; Biomass cofiring; Fuel;
Trends in predicting and controlling ash vaporization in coal-fired utility boilers by Eric G. Eddings; Adel F. Sarofim; Christina M. Lee; Kevin A. Davis; James R. Valentine (39-51).
The past decade has seen a dramatic increase in the use of computational fluid dynamics (CFD) in the solution of problems related to the design and operation of pulverized coal-fired utility boilers. These tools have been increasingly used to simulate the performance of utility boilers, primarily for NO x control and associated problems of unburned carbon in fly ash and in water-wall corrosion. These models are extended to calculate the emissions of submicron particles by the vaporization and condensation of ash constituents. A single particle model for the vaporization of minerals in coal was first calibrated with results for vaporization of 14 coals in a laboratory reactor. The calibrated model was then applied in the simulation of the ash vaporization in a 500-MW opposed-wall fired boiler with 12 burners on each of the front and rear walls, and for cases before and after retrofitting the boiler with burner technology to reduce NO x emissions. The simulations showed that the ash vaporization occurred primarily during short intervals along particle trajectories when the particle temperatures increased above 1800 K. The ash vaporization decreased slightly on retrofitting the boiler, and the contributions by different burners to the total amount vaporized varied widely, particularly after the low-NO x retrofit.
Keywords: Ash vaporization; Coal-fired utility boilers; CFD;
Suppression of nitrogen oxides emission by carbonaceous reductants by Akira Tomita (53-70).
The present status of NO x emission from power stations and automobiles is first summarized, and the controlling regulations in respective areas are reviewed. In spite of much progress, we have to further reduce the NO x emission in all the areas. In order to develop more effective technology, the fundamental understanding of the relevant reactions is essential. The heterogeneous reactions, like NO x and N2O formation from coal char, NO x and N2O reduction with carbon, and NO x reduction with hydrocarbon gases over heterogeneous catalysts are not well understood yet. This paper briefly summarizes our recent studies on the heterogeneous reactions of NO x formation and destruction. The importance of surface nitrogen species is emphasized in all the reaction systems. The presence of such surface species plays a very important role, not only in NO x destruction on carbon surfaces, but also in the NO x release during coal char combustion. Finally, future research areas are identified, where we need to understand what actually happens under high-temperature reaction conditions.
Keywords: NO x ; Coal combustion; Diesel; Carbon; Surface species; Mechanism;
Characterization and reactivity of organically bound sulfur and nitrogen fossil fuels by Martin L Gorbaty; Simon R Kelemen (71-78).
Advances in X-ray instrumentation over the last decade have allowed the determination and quantification of organically bound sulfur and nitrogen forms in fossil fuels, which led to deeper understanding of their reactivities. This paper reviews recent technical advances in this area, highlights achievements of significant progress in chemical understanding and areas where further advances will likely occur.
Keywords: Organic sulfur; Organic nitrogen; Characterization; XPS; XANES;
Gasification technologies: the path to clean, affordable energy in the 21st century by Gary J Stiegel; Russell C Maxwell (79-97).
The gasification of carbon-based solid and liquid materials has been around for nearly two hundred years and was used extensively for the production of town gas in the latter part of the nineteenth and twentieth centuries. Although this application has all but vanished, other applications have evolved, thus continuing gasification's important role as a commercial technology. Numerous advancements have been made since its introduction, leading to a more cost-competitive, thermally efficient, and environmentally friendly technology. However, as deregulation of the power industry continues and as increased environmental pressures are placed on industry, opportunities for further technological advances and expanded applications to meet these challenges will be created. In addition, these changes will likely restructure the technology and ownership objectives, placing premiums on efficiency, environmental acceptability, and the ability to utilize multiple feedstocks and produce multiple products. In the twentieth century, gasification will be the heart of a new generation of energy plants, possessing both feedstock and product flexibility, near-zero emission of pollutants, high thermal efficiency and capture of carbon dioxide, and low feedstock and operating and maintenance (O&M) costs.
Keywords: Gasification; Energy plants; Feedstock;
Concerns about climate change and the role of fossil fuel use by Donald J. Wuebbles; Atul K. Jain (99-119).
The greenhouse effect, the ability of certain gases like carbon dioxide and water vapor to effectively trap some of the reemission of solar energy by the planet, is a necessary component to life on Earth; without the greenhouse effect, the planet would be too cold to support life. However, human activities are increasing the concentration of carbon dioxide and several other greenhouse gases, resulting in concerns about warming of the earth by 1–5°C over the next century. Recent increases in global averaged temperature over the last decade already appear to be outside the normal variability of temperature changes for the last thousand years. A number of different analyses strongly suggest that this temperature increase is resulting from the increasing atmospheric concentrations of greenhouse gases, thus lending credence to the concerns about much larger changes in climate being predicted for the coming decades. It is this evidence that led the international scientific community through the Intergovernmental Panel on Climate Change (IPCC) to conclude (after a discussion of the remaining uncertainties) “Nonetheless, the balance of the evidence suggests a human influence on global climate”. More recent findings have further strengthened this conclusion. Computer-based models of the complex processes affecting the carbon cycle have implicated the burning of fossil fuels as a major factor in the past increase in concentrations of carbon dioxide. These models also suggest that, without major policy or technology changes, future concentrations of CO2 will continue to increase largely as a result of fossil fuel burning. This paper reviews the current understanding of the concerns about climate change and the role being played by fossil fuel use.
Keywords: Climate change; Greenhouse effect; Greenhouse gases;
Climate change and energy options: decision making in the midst of uncertainty by Jeffrey I. Steinfeld (121-129).
Understanding the world's natural systems, and how our own activities may be affecting those systems, are crucial for the long-term well-being of our society and of all the inhabitants of this world. One of the most complex of these is the global climate system. The nature and extent of significant alterations to the global climate system due to increasing emissions of greenhouse gases (GHG), resulting from human activity such as energy production and manufacturing processes, is still the subject of considerable uncertainty and, indeed, controversy. However, the possible consequent effects on ecological systems and human society may be of such profound gravity, that continuing research into the causes and effects of climate change, and development of viable technology solutions for mitigation of these effects, are essential. Understanding the global climate system, determining how our activities may be influencing it, and taking responsible actions to protect it for future generations, may be among the greatest challenges that humanity has ever faced.
Keywords: Climate change; Energy; Greenhouse effect;
The bridge from cold facts and hot rhetoric to rational climate policy by William F. O'Keefe (131-137).
The scientific community must expand its role in the political debate over climate change if we are to have wise and smart policies. The current debate is characterized by a cacaphony of competing scientific claims, scare tactics and propaganda. Scientists, particularly those in academia, are badly needed to uphold the principles of scientific inquiry and standards of evidence, upon which rational public policy depends. They should weigh into the conflict heavily, when the bounds of -rational analysis are exceeded. The acid test of analytical rigor must remain a first principle.
Syngas production for gas-to-liquids applications: technologies, issues and outlook by D.J Wilhelm; D.R Simbeck; A.D Karp; R.L Dickenson (139-148).
The main gas-to-liquids (GTL) interest now is in Fischer–Tropsch (F–T) synthesis of hydrocarbons. While synthesis gas (syngas) for GTL can be produced from any carbon-based feedstock (hydrocarbons, coal, petroleum coke, biomass), the lowest cost routes to syngas so far are based on natural gas. Thus, the focus for GTL has been largely on associated gas, so-called stranded or remotely located gas reserves, and larger gas reserves that are not currently being economically exploited. The principal technologies for producing syngas from natural gas are: catalytic steam methane reforming (SMR), two-step reforming, autothermal reforming (ATR), partial oxidation (POX), and heat exchange reforming. The distinguishing characteristics of these technologies and their commercial uses are discussed in this paper. Ongoing R&D efforts to develop lower-cost syngas generation technologies are also briefly discussed.Relevant commercial experience with large-scale syngas generation for GTL is also discussed. As a frame of reference, in terms of syngas flow rates, a 20,000 b/day F–T plant would be comparable to three 2500 mt/day methanol plants. Single-train methanol plants are now producing more than 2500 t/day—and plants approaching 3000 mt/day have been announced. The projected relative economies of scale of the various syngas production technologies indicate that two-step reforming and ultimately, ATR, should be the technologies of choice for large-scale GTL plants. Nevertheless, for a 20,000 b/day F–T liquids plant, capital charges still dominate the manufacturing costs. Syngas production (oxygen plant and reforming) comprises half of the total capital cost of this size GTL plant. While air-blown reforming eliminates the expensive oxygen plant, air-blown reforming is unlikely to be competitive with, or offer the flexibility of, oxygen-blown reforming. The reasons for this conclusion are discussed.The proposed and future GTL facilities should be substantially less costly than their very expensive predecessors—as the result of improvements in FT catalyst and reactor design, the most significant of which have been pioneered by Sasol. In the absence of a breakthrough technology, economy of scale will be the only significant mechanism by which GTL can achieve greater economic viability. However, even with such further cost reductions, the economic viability of GTL plants will remain confined to special situations until crude price levels rise substantially. In the long term, if a ceramic membrane reactor (combining air separation and partial oxidation) can be developed that enables the 20% reduction in GTL investment costs that the R&D effort is targeting, GTL could become economically viable at crude prices below US$20/b.
Keywords: Syngas; Gas-to-liquids; Fisher–Tropsch;
Fischer–Tropsch: a futuristic view by Anton C Vosloo (149-155).
Although the three processing steps that constitute the Fischer–Tropsch based Gas-to-Liquids (GTL) technology, namely syngas generation, syngas conversion and hydroprocessing, are all commercially proven and individually optimized, their combined use is not widely applied. In order to make the GTL technology more cost-effective, the focus must be on reducing both the capital and the operating costs of such a plant. Current developments in the area of syngas generation, namely oxygen transfer membranes and heat exchange reforming, have the potential to significantly reduce the capital cost and improve the thermal efficiency of a GTL plant. Further improvements in terms of the activity and selectivity of the Fischer–Tropsch catalyst can also make a significant reduction in the operating cost of such a plant.
Keywords: Fischer–Tropsch; Natural gas conversion; Liquid fuels;
Fischer–Tropsch synthesis: current mechanism and futuristic needs by Burtron H. Davis (157-166).
Mechanisms for the generation of hydrocarbon and oxygenate products from synthesis gas using the Fischer–Tropsch synthesis are presented. The data generated to date indicate that, while there are similarities between iron and cobalt catalytic synthesis mechanisms, the details differ. For the iron catalyst, it is concluded that an oxygenate mechanism is more appropriate in light of today's data. While less mechanistic data for the cobalt catalyst are available, it appears that a surface carbide mechanism is a better choice.
Keywords: Fischer–Tropsch synthesis; Reaction mechanism; Isotopic tracer studies;
Transportation fuels of the future? by William J. Piel (167-179).
Society is putting more emphasis on the mobile transportation sector to achieve future goals of sustainability and a cleaner environment. To achieve these goals, does society need to jump to a new combination of fuel and vehicle technology or can we just continue to improve on the current fuels and drive train technology that has powered us the past 70 or more years? Do we need to move to more exotic energy conversion technology (fuel cell vehicles?), or can improving fuel properties further allow us to continue using combustion engines to power our vehicles? What fuel properties can still be improved in gasoline and diesel? Besides removing sulfur, should there be less aromatics in fuels? Should aromatics be eliminated? Is there a role for oxygenates in gasoline and diesel? Do blending oxygenates in fuels help or hinder in achieving the environmental goals? Can we and should we reduce our dependency on crude oil for transportation energy? Why have not the previous government-sponsored Alternative Fuel programs displaced crude oil?The marketplace will determine which fuel and vehicle technology combination will eventually be used in the future. Does the information we know today give us insight to this future? This paper will attempt to address some of the key issues and questions on the role fuels may play in that marketplace decision.
Keywords: Transportation; Fuel; Crude oil;
Methane hydrates potential as a future energy source by Sang-Yong Lee; Gerald D. Holder (181-186).
Gas hydrates are crystalline solids that form from mixtures of water and light natural gases such as methane, carbon dioxide, ethane, propane and butane. They are of considerable interest for their potential as an energy resource and for their potential role in global climate change. From an energy resource point of view, the enormous amounts of methane hydrate under the ocean and beneath arctic permafrost represent an estimated 53% of all fossil fuel (coal, oil, natural gas) reserves on earth, about 10,000 gigatons. The difficulty with recovering this source of energy is that the fuel is in solid form and is not amenable to conventional gas and oil recovery techniques.
Keywords: Methane hydrates; Energy source; Global climate;
Biomass and renewable fuels by Helena L. Chum; Ralph P. Overend (187-195).
Biomass is an important contributor to the world economy. Agriculture and forest products industries provide food, feed, fiber, and a wide range of necessary products like shelter, packaging, clothing, and communications. However, biomass is also a source of a large variety of chemicals and materials, and of electricity and fuels. About 60% of the needed process energy in pulp, paper, and forest products is provided by biomass combustion. These processes could be improved to the point of energy self-sufficiency of these industries. Today's corn refinery industry produces a wide range of products including starch-based ethanol fuels for transportation. The biomass industry can produce additional ethanol by fermenting some by-product sugar streams. Lignocellulosic biomass is a potential source for ethanol that is not directly linked to food production. Also, through gasification biomass can lead to methanol, mixed alcohols, and Fischer–Tropsch liquids. The life science revolution we are witnessing has the potential to radically change the green plants and products we obtain from them. Green plants developed to produce desired products and energy could be possible in the future. Biological systems can already be tailored to produce fuels such as hydrogen. Policy drivers for increased use of biomass for energy and biobased products are reviewed for their potential contributions for a carbon constrained world.
Keywords: Biomass; Fuels from biomass; Biological hydrogen production; Sustainable energy systems; Carbon constrained world;
The future of nuclear energy by John I Sackett (197-204).
Nothing will be as important to the people of the world in the next century and beyond as energy to provide clean water and electricity. But how will this need be met with the increasingly recognized need to substantially reduce carbon dioxide emissions? Nuclear power provides a compelling option, but it must meet certain requirements in order to gain public and political support. In this paper, those requirements are examined and the imperative for continued research into advanced nuclear power technologies is discussed.
Keywords: Nuclear; Technology; Energy;
Author Index (209).
Subject Index (211).
Contents of Volume 71 (2001) (213-214).