Energy & Fuels 1993, 7, 906-909
906
Thrust Area 6: Model Evaluation Data and Process Strategies Geoff J. Germane Department of Mechanical Engineering, Brigham Young University, Provo, Utah 84602 Received May 21, 1993. Revised Manuscript Received June 2, 1993"
The mission of ACERC is to conduct advanced experimental and theoretical combustion engineering research and produce useful products that have the promise of improving the technical competitiveness of U.S.industry. The strategic plane of this Thrust Area includes developingadvanced instrumentation for combustion measurements and obtaining detailed combustion data to properly evaluate the predictive and interpretive computational models being developed in ACERC. A cylindrical, downfired reactor (CPR) has been built which allows detailed control of wall temperature, inlet air velocities, and swirl, fuel type, inlet conditions, and complete radial and axial optical and intrusive probe access to the flame. Researchers in the Thrust Area have been involved in obtaining appropriate validation data using advanced instruments such as CARS in natural gas and coal flames in the CPR, where the near field is accessible and inlet conditions are well-characterized, and in full-scale industrial coal-fired boilers where far-field data obtained with advanced particle in situ counting and sizing instrumentation and radioimeters provide valuable information concerning the heat-transfer and combustion products composition essential to model evaluation. Comparison of ACERC comprehensive codes with other coal-quantified models, such as CQIM, is also a research initiative in Thrust Area 6.
Introduction The mission of ACERC is to conduct advanced experimental and theoretical combustion engineering research and produce useful products that have the promise of improving the technical competitiveness of U.S.industry. This includes a focused effort to develop multidimensional computer codes that will adequately describe the complicated chemistry, energetics, and fluid mechanics associated with turbulent coal flames. Evaluation of the code or specific submodels as potential design tools for industrial furnaces involves comparisons of code predictions to turbulent flame data collected in a range of different combustor sizes. The purpose of Thrust Area 6 is to collect combustion data for model evaluation, investigate combustion process strategies for efficient combustion with low pollutants for low-grade fossil fuels such as fuel oil, coal, and gas, and develop advanced instrumentation capability for accurate combustion measurements. Though much of the process data obtained in combustion facilities and reported in the open literature (coldflow mixing data, gaseous combustion data, and coal combustion data) has little value for model validation because the boundary conditions of the flows (flow rates and velocity profiles of the imput fuel and oxidizer streams) to the combustor are not well-known, and the geometry in many instances is uncertain, some of the available data which can be of limited use has been tabulated.lp2 Table I summarizes recent representative sets of available natural gas and comprehensive coal combustion data with suffi*Abstract published in Advance ACS Abstracts, October 15, 1993. (1) Phillips, S. D.; Smoot, L. D. Data Book for Eualuation of ThreeDimensional Combustion Models; Combustion Laboratory, Brigham Young University: Provo, UT, 1989. (2) Christensen, K. R.; Raaband, M. W.; Smoot, L. D. Revised Data Book For Evaluation of Combuetion and Gasification Models; Final Report, Vol. 111, Contract No. DE-AC21-85MC22059, Oct 1987.
0887-0624/93/2507-0906$04.00/0
cient detail for model comparisons. Projects in Thrust Area 6 have been developed as part of a strategic plan to obtain the needed data and evaluate the utility of the codes as furnace design tools.
Strategic Plan Key issues in the strategic plan for Thrust Area 6 include the following. 1. Type of Data Needed. Development of process strategies requires measurements similar to some of those needed for detailed computer code evaluation. Elements that require separate evaluation and verification include prediction of the fluid dynamic flow fields (including mean and root-mean-square velocity distributions), particle dispersion, gas-phase chemical reactions, coal devolatilization, heterogeneous reactions between the gas-phase and the coal/char particles, nitrogen, and sulfur pollutant formation, temperature, and radiation profiles within a combustion system, and slagging and fouling associated with the particles as they impact the walls or boiler tubes in the furnace. The wide range of experiments necessary (3) Eatough, C. N. Controlled Profile Reactor Design and Combustion Measurements; Ph.D. Dissertation, Department of Mechanical Engineering, Brigham Young University, Provo, UT, 1991. (4) Boardman, R. D.; Eatough, C. N.; Germane, G. J.; Smoot, L. D. Comparison of Measurements and Predictions of Flame Structure and Thermal NO, in a Swirling, Natural Gas Diffusion Flame; First International Conference on Combustion Technologies For a Clean Environment, Vilamoura, Portugal, 1991. (5) Costa, M.; Costen, P.; Lockwood, F. C. Pulverized-coal and heavy fuel oil flames: large-scale experimental studies at Imperial College, London. J.Inst. Energy LXIV 1991,64, 64-76. (6) Smooth, L. D.; Bartholomew, C. H.; Pershing, D. W. Sixth-Year Progress Report; Research Program Volume,NSF Advanced Combustion Engineering Research Center, Brigham Young University, Provo, UT, Jan 1992; Vol. 11. (7) Smoot, L. D.; Bartholomew, C. H.; Pershing, D. W. Seventh-Year Progress Report; Research Program Volume,NSF Advanced Combustion Engineering Research Center, Brigham Young University, Provo, UT, Feb 1993; Vol. 11.
0 1993 American Chemical Society
Model Evaluation Data and Process Strategies
Energy &Fuels, Vol. 7, No. 6, 1993 907
Table I. Representative Recent Combustion D a t a Sets cateaow lab-scale natural gas 2-D combustion lab-scale coal and heavy fuel oil 2-D combustion lab-scale coal 2-D combustion full-scale coal 3-Dcombustion
investigator/affiliation
measurements
meas technique
Eatough?~' ACERC/BYU
U,V,W,02,COSCOz, Nz NO, NH3, HCN, T
five-pole Pitot tube, water-quenched sample probe, suction pyrometer
Costa et a1.F Imperial College
CO, COZ,02,CH4, C Z H ~CZHZ, , T, incident radiant flux
water-quenched sample probe, thermocouple, ellipsoidal radiometer
Butler, Bonin, and Sanderson,"lO ACERC/BYU
u (part), no. density (part), size (part, T (gas), T (part), incident total and radiant flux,. CO, . C02.02. _. _. NO, SOz, C, H, N,S u, v (gas), u (part), no. density (part), size (part), T (gas), T (part), incident total and radiant flux, CO, COS,02, NO,SOz, C, H, N, S
PCSV-P, suction pyrometer, two-color pyrometer, water-quenched probe, total heat flux meter.Ie b s.o i d a l radiometer dusty Pitot tube, PCSV-P, suction pyrometer, two-color pyrometer, water-cooled probe, total heat flux meter, ellipsoidal radiometer
Cannon et al.,496JACERC/BYU
ACERCREACTOR
/
I
I
Temporal Tempmure and S p C C l U ConccnlraUon.
pEzzzq
1
EVALUATION
1
INDUSTRIAL SCALE
Some Flow Characranrtlc'r.
for code evaluation referenced in Figure 1 have been conducted, are underway or are planned. 2. Scale of Data Needed. Comprehensive verification of combustion codes requires measurements made in both the near-burner and far fields in a turbulene flame. Figure 2 illustrates the complementary relationship of small-scale, well-controlledcombustors with other, larger scale facilities as sources of evaluation information. Detailed, spaceresolved and temporal data, which can be more readily and inexpensively obtained in small-scale facilities, and more coarse measurements obtained from large, commercial furnaces are both required for process and model development. The main advantages of small laboratory facilities compared with industrial boilers are low operating cost, flexibility, and accessibility, and the ability to carefully control and define the boundary and inlet conditions. They are large enough to give sufficient spatial resolution and to create a near-burner furnace environment while small enough to utilize advanced measurement techniques essential to providing accurate and complete data for model evaluation. Temporal and spatial measurements of species and temperature within or across large flames cannot be easily made using laser-based instruments necessary for such noninstrusive measurements.
LARGE UTILITY SCALE
DATA BOOK
-4000-7500 MBTUhr
TWOANDTKHREE DIMENSIONS
(WBrL)
Figure 2. Interrelation of combustion test scale in process and model evaluation.
The detail and range of possible measurements is generally inversely related to the scale of the furnace facility. ACERC reactors have provided access for detailed flame measurements at about 0.1-1.5 million Btu/h, and the 800 million Btu/h Combustion Engineering facility at the Goudey Station of New York State Gas and Electric has been utilized for far-field testing. In the absence of commonly accepted scaling laws for combustion, it is anticipated that validated computer models can provide scaling strategies for combustion processes. Figure 2 also illustrates the flexibility of a small-scale laboratory facility in a dual role as a tool for combustion process screening or development tests. 3. Required Instrumentation. Historically, intrusive probes such as thermocouples, Pitot tubes, and grab sample probes have been used to characterize the properties of flames. However, use of advanced nonintrusive diagnostic instruments such as laser-based techniques for measuring gas velocity (LDV),particle velocity, and size distributions (e.g., PCSV), gas temperature and species concentrations
Germane
908 Energy & Fuels, Vol. 7, No. 6,1993
air staging can also be accomplished in misymmetric or asymmetric configurations.
Natural Gas Supply
Research Projects wirl Generator/BumerInlet
Figure 3. ACERC/BYU controlled profile reactor (CPR).
(e.g. coherent anti-Stokes Raman spectroscopy (CARS) and laser-induced fluorescence (LIF)), and advanced optical techniques to measure radiative heat flux, can provide accuracy heretofore unobtainable, especially in laboratory-scale combustors such as the BYU/ACERC controlled profile reactor (CPR). 4. Development of a Mobile Instrumentation Capability. A mobile instrumentation capability, developed for on-site tests at industrial facilities, has been used in two sets of full-scale tests a t the Goudey Station of the NYSEG. The mobile probes, instrumentation, and data acquisition system were tested and refined in the CPR prior to the full-scale tests. The mobile instrumentation capabilitiesinclude particle temperature measurement and determination of total and incident radiant heat flux. Data reduction and analysis have been performed on-site with the data acquisition microcomputer. 5. Constructionof Controlled-TemperatureProfile Combustor at BYU. The BUY/ACERC CPR has provided key opportunities for instrumentation development and calibration and unique detailed flame measurements. A wide range of test conditions and control of the operating conditions in the reactor (especially inlet conditions) is possible. The cylindrical CPR is down-fired with a diameter of 0.80 m and a length of 2.5 m (see Figure 3). The reactor consists of six independently water-cooled sections with an interchangeable top section to accommodate different burner types. Two pairs of opposed 9 cm X 28 cm ports in each section allow access for nonintrusive laser diagnostic systems, visual observations, radiometer access, and photography. Refractory plugs are inserted in these ports to reduce heat loss. Wall heat flux and temperature are measured and can be controlled to near isothermal conditions by means of electric heaters. The misymmetric geometry facilitates code comparisons, which results in more efficient computer utilization and experimental programs. The CPR can be easily modified to produce asymmetric combustion and flow conditions by changing the placement of the burner or inlet flows. Combustion
Elements of four selected research projects are summarized: BYU/ACERC CPR Combustion Tests, Development and Application of CARS in the ACERC/ BYU CPR, Large Scale Furnace Tests, and CQIM A p plication and Comparison. BYU/ACERCCPR CombustionTests. The objective of this project was first to develop a new test facility to obtain reliable, advanced spatial, and temporal measurements of particle and gas temperature, species concentration, velocity, particle size, and heat flux, then to produce these additional required data for code evaluation, and to evaluate new processes or strategies for improvement in combustion efficiency or pollutant control. Detailed comprehensivecoal and gas tests have been along with temperature measurements in gas and coal flames with the CARS instrument in the CPR. One of several series of coal combustion tests in the CPR was completed using Utah Blind Canyon HVB coal, the results of which have been analyzed and published by researchers from three ACERC These tests are among the most complete and extensive detailed coal combustion measurements known. Coal feed rate was steady over the duration of the tests within about 1 4 % of the setpoint. Two particle size distributions with mass mean diameters of 22 and 55 pm were used. Wall temperatures varied about 5 % over 24 h. In situ particle size distribution, velocity, and number density were measured with a laser-based PCSV, gas and particle temperature, and wall incident radiation and radiant heat transfer were determined, local gas species concentrations, and pollutants were measured, and solids samples were collected to determine carbon burnout and local particle composition. Each test consisted of up to 36 sets of local measurements throughout the reactor. Reactor thermal and mass flux balances were also conducted to add confidence to the test results.8 Development and Application of CARS in LowRank Fuel Reactors. The primary objective of this project has been to develop the capability in ACERC of making temperature and species concentration measurements in combustorswith the coherent anti-Stokes Raman spectrometer (CARS), to make critical temperature and species concentration measurements in the BYU/ACERC CPR for comprehensivemodel evaluation and verification, and to make correlation of several turbulence properties which could contribute to verification of chemistry turbulence interactions in comprehensivecombustionmodels. The extension of CARS to the CPR involved fabrication of optical tables and support structure, implementation of methods to translate the field lenses to measure radial (8) Sanderson, D. K. Predictions and Measurements of Gas Species Concentrationsand Solids Compositionin a Pulverized Coal Flame. M.S. Thesis, Brigham Young University, Provo, UT, 1992. (9) Bonin, M. P. Optical Measurement of Particle Size,Velocity and Number Density in PulverizedCoal Flames. Ph.D.Dissertation, Brigham Young University, Provo, UT, 1992. (10) Butler, B. W. An Experimental Evaluation of Radiant Energy Transportin ParticleLadenFlames. Ph.D. Dissertation, Brigham Young University, Provo, UT,1992. (11) Butler, B. W.; Denison, M.; Webb, B. W. Radiation Heat Transfer in a Laboratory-Scale,Pulverized Coal-Fired Reactor: Experiment and Analysis. 3rd World Conference on Experimental Heat Transfer, Fluid Mechanics, and Thermodynamics, in press.
Model Evaluation Data and Process Strategies
1500- 1600 K 1400- 1500 K
1300- 1400 K 1200 - 1300 K
0 1100 - 1200 K 1OOO- l l 0 0 K 900-100OK
0
800-900K
Figure 4. Temperature contour plot for natural gas assisted coal/air flame (SR = 0.8).
temperatures, and development of techniques to maintain precise optical alignment for sufficient signal strength while traversing radially in the CPR. Two sets of CARS temperature measurements were made a t 8axial positions and 11 radial locations in a natural gas and natural gas/ pulverized coal flame in the CPR.12 Figure 4 shows an example CPR temperature contour plot for a turbulent natural gas flame at nearly stoichiometric conditions. Large-Scale Furnace Tests. The purpose of this project is to ensure that the ACERC combustion models can be used in simulating, designing, and controlling advanced combustion processes. Full-scale model validationtesting at the 80-MWe (800million BTU/h) Goudey Station, a power plant in Johnson City, NY, was initiated (12) Pyper, D.; Blackham, S.;Warren, D.; Hansen, L.;Christensen, J.; Haslam, J.; Germane, G. J.; Hedman, P. 0. CARS Temperature Measurements in the BYU Controlled Profile Reactor in Natural Gas and Natural Gas-Assisted Coal Flames. Western S t a b Section/The Combustion Institute, Berkeley, CA, 12 Oct 1992.
Energy & Fuels, Vol. 7, No. 6,1993 909 in 1989 and continued during 1991 in cooperation with New York StateGas& Electric (NYSEG)and Combustion Engineering, Inc., with financial assistance from both ACERC and ESEERC0.9J0,13-18The most recent tests in July, 1991, involved measurements by ACERC of gas temperature, total incident radiant flux and total heat flux, particle size distribution, velocity, and concentration, gas and particle composition, and gas velocity and turbulence intensity. The test matrix comprised 28,2-h tests during steady conditions with no wall or soot blowers operating. Sixteen ACERC personnel from two Thrust Areas made measurements which resulted in a data an order of magnitude larger than the 1989 set. The host utility provided the full complement of plant data along with coal particle size and proximate and ultimate analyses. The mobile trailer was used to carry the instrumentation of this facility. CQIM Application and Comparison. This project involves the comparison of results from the Coal Quality Impact Model (CQIM) to ACERC comprehensive combustion codes and furnace test data. Once the differences, similarities and accuracy of the code predictions are established, the possibility of using the comprehensive code to enhance the CQIM will be evaluated. The results of this study will increase ACERC interaction with the utility industry and will facilitate technology transfer.
Acknowledgment. The author recognizes the excellent contributions of Profs. John N. Cannon, Paul 0.Hedman, Brent W. Webb, and Mardson Queiroz; Drs. Craig N. Eatough and Stephen K. Kramer; and many dedicated and able graduate and undergraduate students to the accomplishments in ACERC Thrust Area Six. The financial assistance or participation by the Advanced Combustion Engineering Research Center (ACERC),the Departments of Mechanical Engineering and Chemical Engineering at Brigham Young University, ESEERCO, New York State Gas & Electric, Combustion Engineering, the U.S.Department of Energy, and EPRI is also gratefully acknowledged. (13)Cannon, J. N.; Webb, B. W.; Bonin, M. P. The Effecta of Different Coals on Combustion Parameters Measured in a Full-Scale Utility Boiler. EPRI Heat Rate Improvement Conference: Birmingham, AL, 1992. (14) Hill, S. C.;Cannon, J. N.; Smoot,L. D. Measurementand Prediction of Coal Combustion in a Utility Furnace. Ninth Annual (International) Pittsburgh Coal Conference, Pittsburgh, PA, 1992; p 551. (15) Butler, B. W.; Wilson, T.; Webb, B. W. Measurement of Time Resolved Local Particle-Cloud Temperature in a Full-Scale Utility Boiler. 24th Symposium (International) of Combustion; The Combustion Institute: Pittsburgh, PA, 1992. (16) Bonin, M. P.; Queiroz, M. Local Particle Velocity, Size and Concentration Measurements in an Industrial-Scale Pulverized CoalFired Boiler. Combust Flame 1991,85, 121-133. (17) Butler, B. W.; Webb, B. W. Measurementsof LocalTemperature and Wall Radiant Heat Flux in an Industrial Coal-Fired Boiler. AIAA/ ASME Thermophysics and Heat Transfer Conference,Seattle, WA, 142, 1990, pp 49-56. (18)Cannon,J. N.; Webb, B. W.;Queiroz,M. Resultsof GoudeyStation Boiler Testing 1989; Interim report, ESEERCO Project No. EP-89-09, Empire State Electric Energy Research Co., NY, Jan 1992.
