AN AMERICAN CHEMICAL SOCIETY JOURNAL VOLUME 7, NUMBER 6
NOVEMBER/DECEMBER 1993
0 Copyright 1993 American Chemical Society
Specia 1 Sect ion Role of Combustion Research in the Fossil Energy Industry L. Douglas Smoot* College of Engineering and Technology and Advanced Combustion Engineering Research Center, Brigham Young University, Provo, Utah 84602 Received April 8, 1993. Revised Manuscript Received September 8, 199P
The use of fossil fuels currently dominates world-wide energy production. While there are many alternatives to the use of coal, oil, natural gas, and other fossil fuels, published projections show that fossil fuels will continue to provide the bulk of the world’s expanding energy needs in the foreseeable future. Given its vast reserves and the rapidly developing clean-coal technologies, coal is projected to assume an increasingly important role. Yet increasing use of these fossil fuels presents many challenges of world-wide significance, including control of acid rain, emissions of toxic compounds and trace metals, particulate emissions, and carbon oxide emissions. Further, with the expanding world energy needs, ever-increasingefficienciesfor generation of power and industrial heat are essential. Accomplishments in cleaner and more efficient use of fossil fuels have been substantial. This paper specifically examines the role of fundamental and applied research toward these new developments. Six specific commercial applications of new technology based on prior research are examined: (1) increasing efficiency of utility boilers, (2) reduction in carbon carryover in pulverized coal boilers, (3) coal selection for minimum fouling tendencies, (4) SO, removal through sorbent injection, (5) low NO, burners in large furnaces, and (6) mild gasification of coal. In each specific case, the vital role of research in the current commercial practice is examined and discussed. The rapidly developing new technology of combustion modeling is also explored. Its state of development is summarized and examples of commercialapplication are illustrated. Results of a survey among several international groups active in comprehensive combustion modeling show a rapidly developing level of application of this technology to industrial needs. The future industrial role of this technology is also assessed. On the basis of this foundation of research need and accomplishment in the fossil energy industry, the role and research program of the Advanced Combustion Engineering Research Center, on whose annual conference this special publication of Energy and Fuels is based, is summarized. The Center’s focus on clean and efficient use of fossil energy is identified, and the research program in six related thrust areas is outlined. Recent general research progress is identified.
Center Foundations In 1983, the National Academy of Sciences made a recommendation to the National Science Foundation (NSF) and to the federal government in general that
* Abstract published in Advance ACS Abstracts, October 15, 1993.
research in universities should include focused, interdisciplinary research aimed at the nation’s needs.’ Much of (1) Blum, S. L.; Fossum, R. R.; Lardner, J. F. The New Engineering Research Centers Purposes, Goals and Expectations; National Academy Press: Washington, DC, 1986.
0887-0624/93/2507-0689$04.00/00 1993 American Chemical Society
690 Energy & Fuels,
VoZ. 7, No. 6,1993
the ongoing research was oriented toward the idea of a single principal investigator with a graduate student ortwo. The need for programs at universitiesfor interdisciplinary research with a focus on helping industry in the United States was identified. On the basis of such recommendations, the NSF organized a new program called “EngineeringResearch Centers”. The mission of these Centers has been to improve the competitive position of the United States industry in the international arena in a given technical discipline. Any engineering college could compete for a center, and each was free to identify the research topic. Rationale and justification were required as to whether new advances in this research topic had the potential to help the country toward an improved competitive position. There are currently 18 Engineering Research Centers. The name of our Center is the Advanced Combustion Engineering Research Center (ACERC). ACERC works with a variety of fossil fuels: coal, natural gas, petroleum, slurries,solid wastes, and the like. The principal fuel which ACERC emphasizes is coal. ACERC is the only such engineering research center in combustion. The centers are given grants ranging from about $2 million to $4 million a year by NSF, in addition to other supporting resources. Our center was started in 1986, but we have been doing combustion research at the university since the mid-1960s. Initial combustion research at the university was in the area of rocket propulsion, and combustion of propellants. In the early 19709, work on fossil fuels was initiated. ACERC has been in existence since 1986 and is currently in its eighth year. This special issue of Energy and Fuels contains papers from within and outside ACERC in each of the Center’s six thrust areas. The papers were presented at the SeventhAnnual TechnicalConference in Park City, UT, March 3-4,1993. This paper has two parts. In the first part, the need for combustion-related fossil energy research is identified and some contributions of such research to the fossil energy industry are presented. In the second part, the focus and role of ACERC in combustion research is considered, as an introduction to the sections of this special issue that follow. It must be emphasized that this brief paper does not present a comprehensive review of the vast, international research effort in fossil energy. It is intended to show that the continued use of fossil fuels is essential and that combustion-related research has helped and will help to make the use of these fuels more efficient and environmentally acceptable.
Fossil Energy Importance of Fossil Fuels. About 90 % of the world‘s energy in 1988 was supplied by fossil fuels as shown in Figure 1.2 About 30 % of the total was coal, which has vast reserves, the most extensive of any fossil fuel (Figure 2).3 It is also projected that the use of fossilenergy will increase by an estimated 43 % over the next 15 years.* There does not seem to be any cost-effective alternative to the dominant use of fossil energy for meeting world energy (2) Fulkerson, W.; Judkins, R. R.; Sanghvi, M. K. Sei. Am. 1991,8394. (3) Daman, E. L. Coal Combustion in the 21st Century, 2nd InternationalSymposiumon Coal CombustionScience and Technology;Beijing, China, 1991; pp 1-7. (4) Siegel, J. Clean Coal Technology-Coal’s Link to the Future. Energy World; 1992, 196, Mar., i-vii.
Smoot
1937
Coal (74%) 45 qu
1988
-
Oil (38%)
I Hvdro ( 1 ;I quads
(;as (5%) 3 auads Nuclear (5%) 17 quads
Hydro 22 quads
Figure 1. Fossil fuels-88% of world’s energy use (nobiomass).2
PROVEN
ADDITIONAL SPECULATIVE+
Figure 2. World nonrenewable energy resources.s
needs. Solar energy is currently too expensive and has a low energy density. It has been estimated that to equal the total generating capacity of the U.S. with solar power would require covering approximately 37% of the U.S. land with photovoltaic cells.5 Further, availability and storage technology are in q ~ e s t i o n .Nuclear ~ fission is a viable technical energy source. However, costs are escalating, partly because of the environmental constraints6 while negative public sentiment in the U.S.A. and some other countries is a major issue. We have largely harnessed the water capacity that we have in the U.S.A.7 We have low capacity for geothermal energy use, and geothermal sources are not commonly located where we need the energy.7 Nuclear fusion has no available technology for controlled public energy generation.8 Use of wind is increasingbut is limited to windy areas for electricalenergy production. Consumption of biomass materials may contribute increasinglyto this energy need. In this regard, much of the technology related to fossil fuels can be applied to biomass. On the other hand, fossil fuels are flexible. They are used in various forms for transportation, power generation, industrial/commercial heating, making use of liquids, solids, and gases. And there is a vast infrastructure and delivery system for fossil fuels including home heaters and furnaces, supertankers, service stations, pipelines, boilers, and engines for delivering and consuming these fuels. It takes decades to develop, commercialize and recapitalize for a new energy source. It may take 10-15 years to implement a new energy technology to the commercial stage: but it traditionally requires about 50 (5) Weinberg, C. J.; Williams, R. H. Sei. Am. 1991, 107-118. (6) Balzhiser,R. E. Future Consequencesof NuclearNonpolicy. Energy Production, Consumption,and Consequences;Helm, J. E., Ed.; National Academy of Engineering; National Academy Press: Washington, DC, 1990; Chapter 3, p 188. (7) Mills, R.; Toke, A. Energy, Economics, and the Environment; Prentice-Hall,Inc.: Englewood Cliffs, NJ, 1985. (8) Hafele, W. Energy from Nuclear Power. Sei. Am. 1991,95-106.
Role of Combustion Research years to provide the required infrastructure through enormous capitalized costa of delivering new energy supp1ies.g Role of Coal. Coal must play a significant role in meeting our energy needs. I t is the most abundant fossil reserve: 70% of the world's known fossil reserves, and 94% of the US. reserves are According to Fulkerson et a1.,2 there are about 200 years of known world coal reserves using existing technologies at present consumption rates. Estimated undiscovered resources expands world energy supply from coal to about 1500 years.2 Known recoverable reserves of US. coal could satisfy domestic demands at current consumption rates for nearly 300 years,l0 though depletion time would be substantially reduced if based on projected increasing consumption rates. Coal currently has about a 30% share of the world fossil energy market, while business claimed $21 billion of annual trade in coal in 1988.4 Fossil fuels are declining in known reserves. Natural gas has estimated reserves of 120 years, and oil has 60 years with current technologies at current use rates.2 Even so, these fossil fuels play a vital role in meeting our energy needs. Natural gas is a fuel of choice for power generation in advanced pressurized turbine systems because of very high-efficiency and very low-pollutant emissions levels. According to the 1986 World Energy C~nference,~ coal dominates the proven world nonrenewable resource reserves, with oil, natural gas, and uranium following. Coal also dominates the speculative reserves. Coal is a flexible fuel. It can be combusted, pyrolyzed, used as a chemical feedstock, liquefied directly or indirectly, or gasified. It is difficult to envision just how the world's future energy needs will be met without making substantial use of coal and other fossil fuels. Technology Demonstrations. The Clean Coal Technology (CCT) program has 47 projects now active, with government and private investment around $5 billi~n.~JO Table I provides a brief summary of this extensive US. demonstration effort for coal. Approved projects range from integrated gasification combined cycle systems to pyrolysis systems producing improved products to sulfur and nitrogen control systems. This program has the potential for a major impact on coal use. 60% of the financial resources in CCT is from industrial investment. Federal coal research, development, and demonstration funding in fiscal 1991 was about $675 million? including $415 million for CCT. Coal is an important element in the federal government's program. According to a DOE official, the 1992 and 1993 DOE Coal R&D budget (excluding CCT) was $280 million. Federal research and development funding for coal is substantial, though not increasing. Much of the research and development in coal is driven by increasingly stringent federal Clean Air Act regulations and amendments (1970,1977,1980,1990), which regulate maximum emissions on acid rain precursors (SO,, NO,) on new sources for fossil-fuel-fired units.ll Regulations in other countries (e.g., Japan, Germany) are often more stringent." In addition, regulations are imposed on toxic (9) Penner, 5.5.Assessment of Research Needs for Coal Utilization. US. Department of Energy contract report, ContractNo. DOE DE-FGO382FE-60014,1983;p 94. (10) Clean Coal TechnologyDemonstrationProgram,Program Update 1991; U. S . Department of Energy, Report No. DOE/FE-O247P, Waahington, D.C., 1992. See also: Clean Coal Today,DOE/FE 0215P-9,US. Department of Energy, Washington, D.C., Issue 10, Spring, 1993.
Energy & Fuels, Vol. 7, No. 6,1993 691 metals, particulates, and hazardous organics and based on past trends, further regulations can be anticipated. Coal costs are low and stable, while costa for other fuels are subject to greater fluctuation, depending on embargoes, foreign wars, and extremes in weather. Coal cost has been very steady for about a decade now a t about $3/MMBTU.4 A projection from the World Energy Conference (Figure 313shows that the use of coal will continue to increase well into the next century, becoming the world's most important fossil fuel. While such long-range projections are subject to substantial uncertainty, it is difficult to imagine the circumstances that will allow the world to ignore ita coal reserves. Oil and natural gas will also continue to be important fossil fuels for many years to come. Fossil fuels are going to continue to dominate the world energy picture because there is no economically acceptable and sufficiently flexible alternative on the horizon. It may well be that biomass conversion, solar energy, nuclear fission, and other energy sources will see increasing use in various parts of the world. But current projections support the continuing importance of coal, gas, and oil.
Role of Combustion Research Experimental Research. Combustion research is already vital to fossil energy. Research has already made and is continuing to make a significant difference on clean and efficient fossil energy production by industry. Most of this research has been experimental. Experimental testing has been the basis of the past development of fossil energy technology and remains a vital element in current developments. This section is not intended to provide a comprehensive review of the substantial worldwide experimental research and development program relating to fossil energy. However, three cases have been selected to specifically illustrate commercial energy technologies where experimental research has substantially contributed or is contributing: coal quality, power plant efficiency, and sulfur oxides (SO,) capture. Coal Quality. The first example comes from an applied industrial research effort,12based on data from CONSOL, Inc. This project made use of a pilot-scale research facility to examine coal ash deposition. Minerals in coal are a significant problem in terms of furnace operation and particulate emissions. One of the key questions in a new power plant is the selection of coal. While many factors must be considered (e.g., availability, cost, sulfur level), fouling tendencies are among the most important. The pilot facility was developed to aid in coal selection, to identify poor coal candidates and to identify design parameters. Coal quality has a significant impact on the operation of the system, in such ways as coal pulverization operations, coal ignition, pollutant emissions, particulate removal systems, ash deposition, heat transfer, and erosion/corrosion.ll There are now at least 40 such pilotscale facilities in the world.12 Twenty-three of these are in the United States. CONSOL sought to establish the value of the pilot-scale tests in the coal selection process. In the test procedure, New York State Electric and Gas (11)Smoot, L. D., Ed. Fundamentals of Coal Combustion: For Clean and Efficient Use; Elsevier: New York, 1993.
(12) Harding, N. S., REI, Inc.; personal communication with author, Pittsburgh, PA, Sept 22,1992.
Smoot
692 Energy & Fuels, Vol. 7, No. 6,1993 Table I. Summary of CCT Demonstration Projects by Application CategoryLo sponsor
project Advanced Electric Power Generation Systems ABB Combustion Engineering, Inc. Combustion Engineering IGCC Repowering Project Healy Clean Coal Project Alaska Industrial Development and Export Authority Arvah B. Hopkins Circulating Fluidized-Bed Repowering Project The City of Tallahassee Air-Blown/Integrated Gasification Combined-CycleProject Clean Power Cogeneration Limited Partnership Nucla CFB Demonstration Project Colorado-UteElectric Association, Inc. PCFB Demonstration Project DMEC-1 Limited Partnership Tidd PFBC Demonstration Project The Ohio Power Company PFBC Utility Demonstration Project The Ohio Power Company and the Appalachian Power Company Pinion Pine IGCC Power Project Sierra Pacific Power Company TAMCO Power Partners Toms Creek IGCC Demonstration Project Wabash River Coal Gasification Repowering Wabash River Coal Gasification Repowering Project Project Joint Venture Gasification Combined Cycle with Fuel Cell Duke Energy Corp. Pennsylvania Electric Company Externally-fiied Turbine/Heat Exchanger-Combined Cycle Air Products and Chemicals, Inc. Second Generation Pressurized Fluidized Bed Easton Utilities and Arthur D. Little Advanced Coal Diesel with Scrubber and NO, Control High-Performance Pollution Control Devices SNOX Flue Gas Cleaning Demonstration Project ABB Combustion Engineering, Inc. AirPol, Inc. 10-MW Demonstration of Gas Suspension Absorption Babcock & Wilcox Company Demonstration of Coal Reburning for Cyclone Boiler NO, Control Full-scale Demonstration of Low-NO, Cell Burner Retrofit Babcock & Wilcox Company LIMB Demonstration Project Extension and Coolside Demonstration Babcock & Wilcox Company SOX-NOX-ROX Box Flue Gas Cleanup Demonstration Project Babcock & Wilcox Company Confined Zone Dispersion Flue Gas Desulfurization Demonstration Bechtel Corporation Advanced Cyclone Combuster with Internal Sulfur, Nitrogen, and Coal Tech Corporation Ash Control Energy and Environmental Research Corp. Enhancing the Use of Coals by Gas Reburning and Sorbent Injection Evaluation of Gas Reburning and Low-NO, Burners on a Wall-Fired Energy and Environmental Research Corp. Boiler LIFAC-North America LIFAC Sorbent Injection Desulfurization Demonstration Project Commercial Demonstration of the NOXSO SOz/NO, Removal Flue MK-Ferguson Company Gas Cleanup System New York State Electric & Gas Corp. Milliken Clean Coal Technology Demonstration Project Integrated Dry NO,/S02 Emission Control System Public Service Company of Colorado Pure Air on the Lake, L.P. Advanced Flue Gas Desulfurization Demonstration Project Southern Company Services, Inc. Demonstration of Advanced Combustion Techniques for a Wall-Fired Boiler Demonstration of Innovative Application of Technology for the Southern Company Services, Inc. CT-121 FGD Process Demonstration of Selective Catalytic Reduction Technology for the Southern Company Services, Inc. Control of NO, Emissions from High-Sulfur-Coal-FiredBoilers Southern Company Services, Inc. 180-MWe Demonstration of Advanced Tangentially Fired Combustion Techniques for the Reduction of NO, Emissions for Coal-Fired Boilers Tennessee Valley Authority Micronized Coal Reburning Demonstration for NO, Control on a 175-MWeWall-Fired Unit Demonstration of the Union Carbide CANSOLV System at the Union Carbide Chemicals and Plastics Company, Inc. ALCOA Generating Corporation Warrick Power Plant Coal Processing for Clean Fuels ABB Combustion Engineering, Inc. and CQ, Inc. Development of the Coal Quality Expert Air Products and Chemicals, Inc. Commercial-ScaleDemonstration of the Liquid-Phase Methanol (LPMEOH) Process Cordero Coal Upgrading Demonstration Project Cordero Mining Company Custom Coals International Self-scrubbing Coal: An Integrated Approach to Clean Air ENCOAL Corporation ENCOAL Mild Coal Gasification Project Advanced Coal Conversion Process Demonstration Rosebud SynCoal Partnership Industrial Applications Bethlehem Steel Corporation Blast Furnace Granulated Coal Injection System Demonstration Project Bethlehem Steel Corporation Innovative Coke Oven Gas Cleaning System for Retrofit Applications Passamaquoddy Tribe Cement Kiln Flue Gas Recovery Scrubber ThermoChem, Inc. Demonstration of Pulse Combustion in an Application for Steam Gasification of Coal Centerior Energy Corp. Clean Power from Integrated COREX Directing Iron Making Process
Corp. (NYSEG), working jointly with CONSOL, sought to select a suitable coal for a 625-MW b0i1er.l~ Correlative methods based on coal and Coal minerals properties have been established for estimating fouling tendencies.13 Such correlations relate acidlbase reaction, (13)Harding, N. Mancini,R. Cordner,w.c. Use of a Utility Model CombustionFacilityto Determinethe CombustionCharacteristics of Several Coals and Coal Blends for Potential Use in a 625 MW Boiler. Coal Technology '83; Houston, TX, Nov 1983.
percent sodium, percent iron, ash fusion temperature, and such properties to fouling tendency. The test strategy called for comparing fouling tendency correlations and pilot-scde fouling tendency tests with fouling tests. seven candidate coals were tested for fouling tendency in pilot-scale tests and at full-scale, with a boiler firing rate of 100MW, and a list of coals by foulingtendency from worst to best was established. ~h~ least-fouling cod
Role of Combustion Research
Energy & Fuels, Vol. 7,No. 6, 1993 693
-
coal Gas ....... ..... Uranium .;.:.:.:.:.:::
-
I:/ I I I
1 - 1
'3
11 11 I
5
--4 .wU
NewSources Oil
Hydro Noncommercial
1980
1960
0
/
/
..
2020
ZOO0
0 '
2040
2060
Figure 3. World energy utilization projections into the next ~entury.~ 35
30
f";
15 10
5 I
1910
1
I
I
I
1950
1930
I
I
1970
I
1991
Year
Figure 4. Coal-fired power plant efficiency improvements in this century.'
in the 100-MW boiler test was also least fouling in the pilot-scale tests, and the worst at full-scale was the worst at pilot-scale. Only in one case were two coals rotated by one position in the ordered list of fouling tendency. This outcome clearly increased the confidence that the pilotscale tests would produce a good indication of coal fouling in large-scaleboilers. However, computationswith fouling correlations were wholly inadequate. In fact, the best coal suggested by correlative methodswas the worst performing coal in both the boiler and the pilot furnace, and vice versa.12 Use of these correlative methods was not reliable for coal selection based on fouling tendency. Efficiency. The second experimental case deals with increasing power generation efficiency4 as illustrated in Figure 4. Since 1900, U.S. net coal-fired power plant efficiency has increased from below 5 % to around 33% . This is a remarkable change, though little increase has been observed in the past 30 years. The role of research in this increase is not obvious, and much was likely accomplishedby trial-and-error test methods at large scale. However, newer technologies where research is playing a significant role have been demonstrated for further substantial increases in efficiency. Use of hot-gas cleanup to avoid cooling of the gas between the gasification and the combustion cycles can further increase the efficiency by about 2 % ,4 while use of a high-temperature gas turbine in the combustioncycle will push efficiency toward 45 % .14 These technologies have been or are being demonstrated.1° For further efficiency increases, three alternatives are being investigated beyond combined cycle, high-pressure systems. One is the gasification-fuel cells system where the efficiency projection is 5 0 4 0 %.4 Another is MHD combined with pulverized coal combustion. Coal is seeded with a potassium salt,which is readily ionizable, and energy is first extracted by flowingcombustion products through (14) Holt, N. Highly Efficient Advanced Cycles. EPRI J. 1991, Apr/ May 40-43.
an electromagnet, followed by a steam cycle. Projected efficiency for such a process is reported to be in the range of 55-60 % .15 A third is high-pressure, fuel-lean naturalgas-fired turbines which also seek efficiencies in the range of 55% .16 It is clear from this discussion that research has had and will continue to have a major impact on increasing power generation efficiency. SO, Capture. The third example is SO, capture by sorbents. This technology has been developed and commercialized in fluidized-bed systems for some time." The application discussed here, which is also commercial, is in pulverized coal systems. In the early 1980s,EPA initiated a program called LIMB, for limestone injection and sulfur capture.17 This program was to demonstrate sorbent capture of SO, in pulverized coal furnaces which is the way most of the electrical power is currently generated in the United States. Here, powdered limestone, dolomite, or hydrated lime are injected as very small particles downstreamof the combustionzone where the temperature is within a required range for this capturing process.ll A substantial research effort on rates, modeling, key variables, and optimal sorbents, followed by test and demonstration programs, has been conducted over the past decade.18 Commercial applications of sorbent capture of SO, for four European furnaces have been recently documented.'g Where limestone capture of sulfur dioxide can be made to work, it is far less expensive than down-stream scrubbing, being only about 22% of the plant cost for a 600-MW plant.lg Two to three seconds of residence time were achievedin the temperature window from about 1000 to 1400 K (1300-2100 O F ) with naturally occurring dolomite. As the sorbent heats up, the carbon dioxide or water are released, leaving calcium oxide. Calcium oxide reacts with a sulfur dioxide to produce calcium sulfate. This remains in a solid form and is removed downstream by precipitators or filters. The four, full-scale, European, coal-fired boilers operated on various coals with sulfur contents in the coals ranging from 0.2 to 4.0% with 5090% sulfur recovery by sorbent capture being reported. This technology has been commercial at 600 MW since 1984.19 Comprehensive Modeling Research. Modeling research for combustionand gasificationprocesses in boilers, reactors, gasifiers, and pyrolyzers has been ongoing for about the past 25 years. Commercially applicable capabilities are now at the doorstep of industrial use. Use of this technology has not been substantial in the past, compared to testing. However, because of the potential increase in use of this technology, the role of modeling research is emphasized herein. These models, of which there are several now commercially available, are based (15)Santore, R. R., Ed.; PETC Review, Clean Coal Technology Program Overview; U.S. Department of Energy; Pittsburgh Energy
Technology Center: Pittsburgh, PA, 1992, Issue 6. (16) de Piolenc, M. DOE Firming Plans for AdvancedTurbine System Development Programs. Gas Turbine World; 1992, July-Aug, 23-26. (17) DePero, M. J.; Goots,T. R.; Nolan, P. S. Final Results of DOE LIMB and Coolside Demonstration Projects. First Annual Clean Coal Technology Conference: Cleveland, OH, Sept 22-24,1992. (18) Slaughter, D. M.; Chen, S. J.; Seeker, W. R.; Pershing, D. W.; Kirchgessner, D. A. Increased SO2 Removal with the Addition of Alkali Metals and Chromium to Calcium-based Sorbents. 22nd Symposium (International) on Combustion; The Combustion Institute: Pittsburgh, PA, 1989. (19) Angleys,M.; Lucat, P. Direct Desulfurizationby Lime/Limeatone Furnace Injection in Pulverized-Coal Boilers. 2nd International Symposium on Coal Combustion Science and Technology, Beijing, China, 1991; pp 584-590.
Smoot
694 Energy &Fuels, Vol. 7, No. 6,1993 Table 11. Broad Systems Application Potential of Computerized Combustion Design Models combustion gasification pyrolysis
entrained pulverized fluidized systems fixed bed systems
gases liquids solids slurries
Table 111. Various Objectives for Application of Comprehensive Combustion Models general characteristics test variables feedstocks scaling optimization
retrofitting test program planning study alternatives design trend analysis
on numerical solutions of multidimensional, differential equations for conservation of mass, energy, and momentum, combined with rate process laws or correlations, physical and chemical properties, and coefficients from experimental data.11120 The computer requirements for these codes are now acceptable, and they will improve further through faster computational times per unit cost and through the improved numerical methods. Currently, three-dimensional code solutions for full-scale furnaces with as many as 250 000 grid nodes are being obtained on advanced, high-poweredengineering workstations.” Such solutions on the workstation may require a few days, but at an acceptable cost. The potential uses for this technology are essentially unlimited, and its application can be very cost-effective, compared to costs of full-scale testing. Most fossil energy companies have not had, or do not have, this capability in-house. However, various companies provide these services, or companies can hire qualified professionals such as new doctoral graduates who possess this capability. Some organizations apply this technology through use of consultants. Status and Objectives. What are the objectives of such modeling? Table I1 indicates the various systems and fuels to which such technology can be applied while Table 111 notes several likely objectives. Fuels include gas, liquids, solids, and slurries in combustors, furnaces, gasifiers, or pyrolyzers. Objectives can be for programplanning, study of various alternatives, effects of different fuel feedstocks, or design and optimization. Other objectives might be trend analysis, retrofitting, identification of test variables, or scaling of measurements. This new technology has not been widely applied in the United States or the world among companies who are responsible for energy generation. It is commonly viewed with suspicion or cautious acceptance by many and with enthusiasm by a few, depending on the nature of the company and their level of technology. Table IV provides an illustrative list of typical applications for combustion modeling technology, while Table V notes the kinds of properties that such models can compute. These examples include carbon loss, optimization of low NO, burners, regions of particle impact on walls of furnaces, effects of changes in fuel feedback quality, effects of high pressure, importance of various oxidizers, effects of changes in burner configuration and impacts of larger or smaller coal particle size; an almost limitless list of applications is possible with this technology. These models can calculate temperature distributions, gas composition, velocity, particle trajectories, extent of particle burnout, NO, formation and reduction, SO, formation (20) Smoot,L. D.; Smith, P. J. Coal Combustion and Gasification; Plenum Press: New York, 1985.
Table IV. Some Typical Applications of Combustion Model Technology reduce carbon loss optimize low NO, burner swirl no. find regions of particle impact on wall test effects of feedstock change examine effects of high pressure determine importance of C02 H20,Oz oxidizers evaluate changes in burner configuration calculate impact of larger or smaller coal size optimize furnace size check peak temperatures for materials impact identify peak radiative heat flux zones compute effects of load variation find regions of maximum SO, capture estimate effectiveness of flue-gas recirculation on NO, evaluate impact of high-moisture coals
Table V. Typical Properties That Combustion Models Can Calculate temperature distribution SO, formation and capture gas composition velocities particle trajectories extent of burnout NO, formation and reduction
pressure distribution particle size distribution ash/slag accumulation time variations local variations
and capture, pressure distribution, particle size distribution, ash/slag accumulation, and so forth. Most models of this type will provide spatial variation of such quantities, while some give temporal (Le., time) dependence. Survey. A survey was recently conducted by the author to establish the recent extent of application of this new technology. Responses from 14organizations were sought throughout the world. Two key questions were posed to these professionals. The first question asked was, “in the 1990’s (1990-1992)for how many cases have you applied comprehensive combustion modeling at the specific request of industry?” For those who responded positively, they were asked to provide some details. Twelve responses were received from seven countries (Table VI) and the number of model applications for industry ranged from 1 to 20 per respondee as summarized in Table VII. One group had completed 20 utility applications. Seven of the 12 had completed industrial furnace applications; four of the 12 had completed up to five gas turbine applications, while an equal number had applied the codes to gasifiers. Applications to reactors/combustors, recovery boilers, incinerators, and blast furnaces had also been completed. These applications have been made for 13 different kinds of energy-related industries also illustrated in Table VII. These include the aerospace industry, the pulp/paper industry for consumption of black liquor, utilities, boiler manufacturers, cement kilns, oil refineries, and glass making. The second question asked of these groups was “have your calculations with your comprehensive combustion model, in any of these cases, been a significant factor in an industry having made a substantial commitment of financial resources?” Nine of the 12respondees said “yes,” which was somewhat surprising. Table VI11 provides insight into the indicated purposes of the industrial applications of this comprehensive modeling technology. Nineteen different purposes were identified with nearly all groups surveyed noting that computations of combmtion efficiency, flow patterns, general furnace features, temperature and heat flux distribution, gas compositions, and effects of variables being the most frequently sought quantities. To illustrate the potential of this technology
Role of Combustion Research
Energy & Fuels, Vol. 7, No. 6, 1993 695
Table VI. Combustion Modelers Responding to Survey of 1990s Activity 1. ACERC/BYU Utah; Brewster/Hill 2. Advanced Scientific Computing, - --Ltd. Canada; Knill 3. Babcock & Wilcox Ohio; Fiveland 4. BHP Research Newcastle Laboratories Australia; Truelove 5. Cinar,LTD. England; Lockwood 6. Fluent, INC. Connecticut; Pate1
7. International Flame Research Foundation The Netherlands: Weber Richter Consulting California, Richter 9. Sheffield University England; Swithenbank 10. University of Stuttgart IUD,Germany; Schnell/Hein 11. University of Sydney Australia; Kent 12. Tsinghua University China; Lixing
Table VII. Recent Multidimensional Combustion Model Applications to Industry. system utility boilers gas turbines industrial furnaces gasifiers reactors/combustors recovery boilers fires incinerators blast furnaces
no. of yes 11 4 I 4 I 1 1 1 1
applic range 1-20 2-5 1-12 1-5 1-12 10 2 5 3
fuels coal, oil, gas black liquor, wood, coke, solid wastes
Types of Industries boiler manufacturers cement kilns/gypsum utilities small energy glass power generating metallurgical pulp/paper incinerators aerospace environmental steel oil refineries 0 12 of 14respondees/7Countries [Australia (2), Canada (11, China (I),England (2), Germany (l),Netherlands (l),USA (4)l principal basis for industrial financial resource commitment: 9/12 yes.
Table VIII. Indicated Purposes of Comprehensive Combustion Model Application Most Frequent (>lo) combustion efficiency temperature/heat transfer flow patterns gas composition general features trends analysis Frequent (>5) minerals effects design NO, test planning reactor size configuration change fuel change Less Frequent (>1) pressure distributions so, other pollutants flame shape ignition stability residence times
for industrial application, four specific, commercial application cases are presented here. Carbon Carryouer. The first application is for an Australian utility boiler. The work was presented at the 24th International Combustion Symposium, in Sydney, Australia, in July of 1992.21 The 200-MWe,tangentiallyfired furnace was half of a 410-MWe boiler referred to as the Wallerawang unit. Burners were on six levels, and the unit consumed about 2000 tonslday of coal. Dimensions, in meters, of this large-scale, coal-fired furnace were about 11 m X 9 m X 32 m. The objective of this work was to reduce the percent of carbon carryover in the ash. Lowering carbon in ash is important in increasing power generation efficiency. When firing a t the rate of 2000 tons/ (21) Chen, J.; Mann, A. P.; Kent, J. H. Computational Modeling of Pulverized Fuel Burnout in Tangentially Fired Furnaces. 24th Symposium (International)on Coal Combustion;The Combustion Institute: Pittaburgh, PA, 1992; pp 1381-1389.
I
Test Condidons 2
Measured p r e d i w
1
0
Test 1 Test2 a Comparison with Data 3
Test 3
Common Size (T2)
21 1
0
1
FIOW
Distribution
a Major
Contributor
1.0 1.17 1.32 b. Front Back Flow Distribution
21ur 01
4 5 0 Km s300 pm
90 0.8 L
88
83
1.6
4.6
Effecb of Coal Partide Size
Figure 5. Predicted percentage of carbon in ash from tangentially fired 200-MW. utility boiler.
T2 refers to value for test 2.
day of coal with 10% ash and with 5% carbon carryover in ash, the loss of carbon per day is 10 tons. At $25/ton of coal, annual carbon losses would be over $65000. Cutting carbon loss in half would save over $30 000/year. To this end, comprehensive model computations were compared with three different furnace testa on carbon carryover. In Figure 5a, measured and predicted percent of carbon carryover values are shown to be in quite good agreement. This suggested that the model could be used to identify causes of carbon carryover. Changes in carbon carryover due to changes in flow distribution were predicted as shown in Figure 5b. The flow distribution was changed by varying the tilt angle of the burners. Results show that carbon loss could be reduced by half with this change. Thus, flow distribution was identified as a major contributor to carbon loss, according to predictions. Larger coal particles have commonly been thought to be responsible for carbon carryover. In a standard grind of coal, an average particle size of 70 pm is typical, but up to 2% of the coal by weight can be larger than 400-pm
Smoot
696 Energy & Fuels, Vol. 7,No. 6, 1993 a NOconcentrationsLow NOx burner.
b. GastemperatureStandard cell burner.
c GastemperatureLow NOx buner.
Figure 7. Simplified flow diagram for ENCOAL Corporations' liquid-from-coal mild gasification process.1° B
J
SECTION 1-1
Figure 6. Comparison of predicted and measured properties from a 30-MWetest furnace with OhioNo. 6 coal. Gas (a)nitrogen oxide concentrations; low NO, burner; (b) gas temperature; standard cell burner; (c) gas temperature; low NO, burner.22
particles.22 Thus, the effects of particle size were also investigated with the model. In the first case, a particle size of 90 % less than 150 pm was assumed with only 0.8 % greater than 300 pm. In the second case, 88% less than 150 pm was assumed, while doublingthe amount over 300 pm to 1.6 % For the third case, 83% less than 150pm was assumed with 4.6 % greater than 300 pm. Predicted results surprisingly showed that the carbon carryover was not a strong function of particle size in this analysis. A 6-fold increase in particles greater than 300 pm caused almost no predicted impact on carbon carryover, which remained at near 2%, according to predictions. Reportedly, tests are under way in Australia to evaluate these findings. The types of applicationsof this technology can be many and varied, such as optimizing furnace size, estimating temperatures for materials impact for gas turbines, identifying peak radiative heat flux zones, computing effects of various parameters, or finding regions of maximum SO, capture for injection of sorbents. Low NO, Burner. Applications for estimating NO, control are also of substantial interest, such as effectiveness of flue gas recirculation on NO, reduction, computing effects of coal change on NO, emissions, determining contributions of thermal and fuel NO, to total NO, emissions, optimizing the design of a low NO, burner or investigating the potential for reburning. A recent commercial application for NO, control has been published by Fiveland and Latham,23 based on this technology. They investigated a retrofit for a two-nozzle cell-burner system by comparing NO, predictions from a comprehensive combustion model with test measurements at three different scales: a 1.75-MW small pilot-scale facility,a 30-MW test boiler, and a 605-MW utility boiler. Figure 6 shows predicted temperature distributions of the standard cell burner and the low-NO, cell burner in the
.
(22) Be&,J. M.; Chomiak, J.; Smoot, L. D. h o g . Energy Combust.Sci. 1984,10,177-208.
(23) Fiveland, W. A.; Latham, C. E. Use of Numerical Modeling in the Design of a Low-NO, Burner for Utility Boilers. First International Conference on Combustion Technologies for a Clean Environment, Vilamoura, Portugal, Sept, 1991.
30 MW system. There was not much difference in the temperature distribution for the two alternative burners. However, NO, concentrationsfor the two alternatives were substantially different as also noted in Figure 6. Further, measurements at 30 and 1.75 MW compare very well with predictions and likely better than can be regularly expected. For data at the 30-MW scale with the standard burners and two different coals, the measured NO, concentration was about 970 ppm compared to a predicted value of 900 ppm. For the low NO, cell burner, the investigators measured 310 and predicted 292 ppm. With over-fire air injected downstream, NO, concentrations of 120ppm were measured while the prediction was 155ppm. From several NO, studies on the effects of swirl number, particle size, moisture percentage, coal type, and stoichiometric ratio, trends have consistently been predicted while average differences in measured and predicted NO, concentrations are typically 30 % .ll Model predictions will also provide insight into controlling mechanisms. For example, data for a high moisture coal showed surprisingly that NO, was higher than for a low-moisture coal. Model predictions agreed and showed that use of the high-moisture coal delayed coal ignition, causing more mixing of oxygen from the secondarystream into the primary stream before ignition occurred. When coal ignition did occur, nitrogen evolved from the solid coal particles in the presence of higher oxygen concentrations, leading directly to higher NO, concentrations. Incorrect intuition had suggested that the higher moisture coal would burn at low temperature, leading to lower NO,." Mild Gasification. The third modeling application is for a new mild gasification process, where use of modeling on process development is illustrated. This process, referred to as the LFC (liquid from coal) process, is one of the nation's Clean Coal Technology (CCT) programs, selected in 1989, and whose demonstration is cofunded by the Department of Energy and ENCOAL Corp.l0 In this process, coal is heated and mildly gasified a t temperatures in the range of 800 K (1000 OF) to produce liquid and solid products. In the CCT program, a 1000tons/day plant has been built and is being operated in Gillette, WY, for processing Wyoming subbituminous coal and other test coals. A simplified schematic diagram of the process is illustrated in Figure 7. The heart of the process is a large rotary grate pyrolyzer where a rotating bed of centimeter(24) Boardman, R. D.; Smoot, L. D. AIChE J. 1988,34 (9), 1573-1576.
Role of Combustion Research sized (2 in. X l/g in.) coal is mildly gasified under controlled conditions by a hot recycle gas stream. According to Langan and Friggins,26 inventors developed a working computer model of reaction kinetics at the onset the process to design the process for the desired products and to provide for process control. The model solves a system of nonlinear, coupled, differential equations which combine heat- and mass-transfer rates with coal pyrolysis rates as source terms. The computerized solution reportedly leads directly to a real-time process control system to optimize and tailor products for various coal feedstocks. The method was also reportedly used in the design of the LFC process. The model was calibrated by comparison to pilotscale data and is now being compared to full-scale data. While the details of the process and the model were said to be proprietary, the use of comprehensive modeling in the earliest stages of process development is conceptually well-illustrated by this process development. Utility Boiler. The fourth modeling application to be illustrated is for the coal-fired, 80-MWe, corner-fired Goudey utility boiler of New York State Electric Generating Co. (NYSEG) located in Binghamton, NY. A threedimensional comprehensive combustion model, PCGC-3, has been applied to this system for comparison with recent measurements.Il Figure 1in ref 26 shows a schematic of the Goudey furnace. During the summers of 1989 and 1991,a team of professors and students from ACERC made detailed, in situ boiler measurements with conventional and optical instruments for temperature, gas composition, particle velocity, gas velocity, and turbulence intensity in this large-scale boiler. Figure &19B in ref 11illustrates the flow patterns of the particles. Particle temperatures are illustrated with changes in a color-scale corresponding to a temperature scale. The inlet nozzles are fired downward from four-corner banks on each of four levels. Graphical representations were produced with a licensed software package developed at the ~ n i v e r s i t y . That ~~ figure showed particle trajectories from solution of Lagrangian particle equations, simultaneously solved in a coupled fashion with the combusting Eularian gas-phase flow field. The gas and the coal enter through the primary burners while the combustion air is injected around the outside of each burner in these registers. The particles enter at low temperature, heat up, eventually becoming hot near the burner before they are competely dispersed in the furnace. Some of the particles flow into the lower part of the furnace, then circulating upward in a rotating, tangential flow. Particles exit the furnace at about 1100 K (1500 O F ) . A reliable prediction of this sort requires realistic rates of coal devolatilization, turbulent mixing, radiative transfer, char oxidation, gaseous combustion, and particulate dispersion. Predictions have been compared with measurements,2s as shown elsewhere in this special volume. Future Potential for Combustion Models. Research, development, and application of combustion modeling is progressing a t an accelerated rate, as evidenced by the international survey. Some few industrial organizations have the in-house capability now to apply this technology (25)Langan, W. T.; Friggins, G . R. Overview of Advanced Coal Combustion and Conversion Clean Coal Technology Demonstration Program; ASME paper No. 91-JPGC-FACT-23, 1991. (20) Hill,5.C.; Smoot, L. D. A Comprehensive Code for Simulation of Combustion Systems; PCGC-3. Energy Fuels, this isaue. (27) Zundel, A.; Owen, S.;Sederberg,T. CQUELBYU-Users Manual; Engineering ComputerGraphicsLaboratory: BrighamYoung University, Provo, UT, 1992.
Energy & Fuels, Vol. 7, No. 6, 1993 697 while many others still view the technology with uncertainty. However, based on the rapidly increasing international application of this technology, by at least the turn of the century, it is the author's opinion that use of comprehensive combustion modeling will become an essential engineering tool among the most successful fossil energy companies. Research Needs. Much research remains to be accomplished to ensure clean and efficient use of fossil fuels. Destruction of the ozone layer is an important question. N2O has a very long half-life compared to NO. It is produced in high percentages in certain combustors such as fluidized beds which operate at lower temperatures. It can apparently persist in the atmosphere for thousands of years. Global warming is an important technical issue with political consequences. Control of minerals in conversion of low-quality fossil fuels remains a challenge. Variable-quality feedstocks, increasingly tight environmental regulations, emissions of toxins and trace metals, acid rain control, and clean incineration of wastes add to research needs. Further, research is required to support new technology developments such as IGCC systems, advanced high-pressure turbine systems and conversion of coal to gaseous and liquid products. Significant research is required to contribute to the solution of these problems in areas of energy generation on a worldwide scale.
Role of ACERC ACERC was established in 1986 with a major research grant from the Engineering Centers Division of the US. National Science Foundation. Major participants, who also provide additional research funding, are Brigham Young University, the University of Utah, the University of North Dakota, the State of Utah, about 27 US. industries, the US. Department of Energy, the US. Environmental Protection Agency, and the State of Illinois Geological Survey. The Center is built on 2 decades of combustion research. Currently 22 faculty, 20 professionals, 40 undergraduate students, 60 graduate students, and 10 postgraduate associates participate in the Center. The mission of ACERC is to conduct fundamental, interdisciplinary, experimental, and modeling research work toward the clean and efficient use of fossil fuels including coal, natural gas, and oil, with emphasis on lowquality fuels. The products of the Center include (1)new understanding of combustion mechanisms and their relationships to fuel properties and structure, (2) new computerized, comprehensive combustion models, (3) advanced combustion concepts that can lead to improved combustion or conversion processes, and (4) graduate and undergraduate students educated in the fundamentals of combustion engineering who can solve a wide range of challenging problems. The author readily acknowledges that the ACERC combustion research program is a very small part of the related worldwide research effort. The ACERC program is emphasized here not to suggest that it is the most important work in this area but to show its place and role in combustion research and, in so doing, to introduce the research papers that follow. ACERC authors have recently published a book1' which provides a detailed review of research related to ACERC efforts, which includes over a thousand references to work outside the Center. Research projects in ACERC are focused into six thrust areas: (1)fuel structure and reaction mechanisms; (2) fuel
Smoot
698 Energy & Fuels, Vol. 7,No. 6,1993
Table IX. Summary of Active ACERC Research Projects ( 1993).
I . Computer Aidcd Design Methods 2. New Fundamenul Understanding 3. Process Suetepiea
1 -
~~
II Mechanisms
Model Evaluation (VI)
I
Fvcla
Chmctenwtiod Suuuturc (Submodels) (I)
DotdProcess
Pcrfor"ce(V1)
Comprehensive Modeling (VI
t
no.
1A 1B
1c 1D 1F 1K 1L 1N
2E 2H 21
Figure 8. ACERC research thrust areas and products. Parentheses refer to thrust area numbers of Table IX. minerals, fouling and slagging; (3) pollutant formation/ control and solid-wasteincineration; (4) turbulent, reacting fluid mechanics and heat transfer; ( 5 ) comprehensive model development; (6) model evaluation data and process strategies.11 Relationships among these thrust areas are illustrated in Figure 8. Table IX provides a list of active projects for each thrust area. Thrust area chairs provide technical coordination among projects and organize an annual thrust area review meeting where active researchers in the field inside and outside ACERC discuss results and directions. A key Center objective is the development of advanced, computerized models of combustion processes. Physical and chemical components (submodels) required for computer-code simulation are illustrated in a systems perspective in Figure 9. These components include gaseous turbulence, gaseous reaction, particulate/droplet dispersion, particulate/droplet reaction, radiation, NOJSO, formation, and mineral-matter behavior. Each of these areas, in its own right, is a major research field. ACERC fossil fuels research includes work on coal, natural gas, slurries, and oil, together with solid wastes. Eleven coals from various regions of the US. have been identified for specific study and extensively characterized. Eight of the eleven coals are from the US. Argonne National Laboratory Premium Sample Coal Program.28 Smith et a1.m provided a detailed description of the selection and standard characterization of these eleven coals. Experimental coal research in all six thrust areas makes principal use of these eleven coals. ACERC facilities and equipment include main-frame computers, advanced computer workstations, advanced chemical analysis equipment (NMR, FTIR, MS, SEM, GC), coal particle drop-tube furnaces (atmospheric, high pressure), lab-scalereadors (high-pressure gasifier,control profile reactor (CPR)), and laser diagnostics equipment (pyrometers, CARS, velocimeters). Laser-based diagnostics can be applied to reactors while inlet and outlet flow measurements give mass balances usually within f2 76. ACERC is currently funded by NSF through 1997. In addition to the ongoinginterdisciplinary research program, ACERC has established a workable program to transfer new center technology to industrial and governmental (28) Vorres, K.S. Energy Fuels, 1990,4, 420-426. (29) Smith, K. L.; Smoot, L. D.; Fletcher, T. H.; Pugmire, R. J. The Structure and Reaction Processes of Coal; Plenum Press: New York,in
press.
3c
project title Thrust Area 1: Fuel Structure and Reaction Mechanisms NMR Analysis of Coal and Char Structure Mechanisms and Kinetics of Rapid Devolatilization Chemical Characterization of Coals & Their Combustion Producta Char Oxidation Production of Char/Tar/Gas Samples Fundamental High-pressure Reaction Rate Data Devolatilization Submodel Development Soot in Coal Combustion Thrust Area 2 Fuel Minerals, Fouling and Slagging Behavior of Mineral Matter in Combustion Systems Char Minerals/Surface Properties Minerals Behavior Measurementa for Model Evaluation Thrust Area 3: Pollutant Formation/Control & Waste Incineration Prediction of Hazardous Waste Destruction During
Thermal Incineration Fluidized Bed Incineration Real-TimeMS Monitoring of Combustion Processes 35 Acid Rain Precursor Submodel Development and Evaluation 3F 3G
3K Development of a High Performance Low NO, Coal Combustor 3L CO and NHs Removal from Industrial Offgas Thrust Area 4: Turbulent, Reacting Fluid Mechanics and Heat Transfer 4A Turbulent, Reacting, TwePhiwe Flows 4E Turbulent Mixing and Reaction 4G Radiation in Combustion Systems Thrust Area 5 Comprehensive Model Development 5D Pre- and Postprocessing of Combustion Simulations 5G Parallel Computation for Combustion Engineering 5K 3-D Model Application 5L 3-D Code Advanced Research 5P Transport Reactor Model 5Q Advanced Fixed Bed Model 5s ACERC/FLUENT3-D Combustion Model 5T Second Generation 3-D Model 5U Oil Fired 3-D Model 5V Gaseous Combustion Modeling 5W Gas Turbine Modeling 5X 3-D Code Advanced Development Thrust Area 6: Model Evaluation Data and Process Strategies 6B BYU/ACERC CPR Combustion Testa 6C Development and Application of CARS in Low-Quality Fuel Reactors 6D Large-ScaleFurnace Testa 6E CQIM Application and Comparison 6F Coal/Char Testing
NMR = nuclear magnetic resonance; MS = mass spectroscopy; 3-D = three-dimensional; CPR = control profile reactor; CQIM = coal quality impact model.
participants. Products include technical papers, combustion model software, process strategies, and cooperative technical projects. The Center has had seven years of continuous funding, a stable, strong research team, and substantial industrial participation. The Center produces about 80 publications a year and several research products, including computerized combustion software, have been identified. Brigham Young University and the University of Utah do about 90% of the work, about two-thirds of which is at Brigham Young University, the other third at the University of Utah. The University of Kentucky and the University of North Dakota also participate in the Center. This special issue of Energy and Fuels provides an overview of research in each ACERC thrust area, together with technical details of several of the research projects
Energy & Fuels, Vol. 7, No. 6, 1993 699
Role of Combustion Research
/
\
,
I
,
I
Advanced Comburtion
I Uim Workmp Group
I
Figure9. Elements requiredfor the development of ageneralized model of large-scale furnaces and gasifiers. Related thrust area numbers are shown in parentheses.
in ACERC. Further details can be found in two recently published books and the references therein."Sm
Summary This introductory paper provides a rationale for the value of combustion research in fossil energy and the role of the Advanced Combustion Engineering Research Center. Data and evidence are presented to support the view that there is no current alternative to the substantial worldwide use of fossil fuels as the major source of energy. Information is also provided to indicate the increasingly vital role of coal for energy generation. Key problems and challenges that have resulted and may develop from expanding uses of fossil fuels are discussed, and the role of combustion research in solving these problems is addressed. Some examples of recent combustion research results which have been commercialized are presented to illustrate the continuing contributions of combustion research. These examples include SO, removal through sorbent injection in utility furnaces, modeling of low NO, burners in commercial boilers, scaling data for changing coal feedstocks, devel-
opment of power generation cycles with higher efficiencies, and reduction of carbon loss in utility furnaces. The paper documents the developing and expanding role of comprehensive combustion models in the fossil energy industry. Various types of applications of this technology are illustrated, and the properties that such models calculate are summarized. Results of a worldwide survey on comprehensive combustion model uses illustrate the expanding role of this technology. The paper concludes with a summary of the research mission, focus and program of the Advanced Combustion Engineering Research Center and identifies the Center's six areas of research activity. A review of the research program in each of these thrust areas is included in this special issue, together with several research papers in each thrust area from investigators within and outside ACERC.
Acknowledgment. The author acknowledgesDr. Craig Eatough, Postdoctoral Associate in the Advanced Combustion Engineering Research Center (ACERC)at Brigham Young University for assisting with the literature search and proofing the manuscript. Appreciation is also expressed to Mrs. Marilyn Asay, ACERC Administrative Assistant, and Ms. Charlotte Sellers, ACERC secretary, for preparing the manuscript. The time for preparing this paper was supported by a multiyear grant from the Engineering Centers Division of the National Science Foundation. Our other sponsors include ABB Combustion Engineering, Inc.; Advanced Fuel Research, Inc.; Ahlstrom Pyropower Inc.; Air Products and Chemicals,Inc.; Babcock and Wilcox; CONSOL Inc.; Corning Inc.; Dow Chemical U.S.A.; Eastman Kodak Co.; EG&G; Electric Power Research Institute; Empire State Electric Energy Research Corp.; Environmental Protection Agency; Fluent, Inc.; Foster Wheeler Development Corp.; Gas Research Institute; General Electric Corp.; General Motors Corp.; Geneva Steel; Illinois Clean Coal Institute; Illinois State Geological Survey; Morgantown Energy Technology Center; Pittsburgh Energy Technology Center; Reaction Engineering International, SGI International; Solar Turbines Inc.; South Carolina Energy R&D Center; Southern California Edison Co.; State of Utah; Texaco, Inc.; TRW; Westinghouse Idaho Nuclear Co. Inc.; and Weyerhaeuser Technology Center.
