Progress 09/01/09 to 11/30/13
Outputs
Target Audience: The target audience for this program is the general scientific and technical community reached through technical publications and presentations. Changes/Problems: During the program period, GE closed its facility in Irvine, CA, requiring the program and its related equipment to be transferred to GE’s Global Research Center in Niskayuna, NY. This transfer resulted in GE requesting and being granted a 1-year no cost extension. This had been noted in earlier annual reports. What opportunities for training and professional development has the project provided? This program provided training opportunities for three graduate and ten undergraduate student researchers at Brigham Young University. How have the results been disseminated to communities of interest? The results have been communicated through technical publications and presentations as noted in the products section. What do you plan to do during the next reporting period to accomplish the goals?
Nothing Reported
Impacts
What was accomplished under these goals?
Experimental To support the development of kinetic models of biomass gasification, extensive lab-scale experimental work was conducted on four main experimental apparatus: 1) flat-flame burner (FFB), 2) high pressure flat-flame burner (HPFFB), 3) single-particle reactor (SPR) and 4) bench-scale gasifier (BSG). The FFB was used to measure the pyrolysis yields of poplar sawdust, switchgrass, corn stover, and straw at high particle heating rates (~105 K/s) and atmospheric pressure using particle residence times < 130 ms. The measured biomass volatile yields exceeded their respective ASTM volatiles test value by ~10 wt% (daf). A refractory biomass tar near 1-2 wt% (daf) was measured for each of the biomass feed stocks. The HPFFB was used to measure apparent CO2 gasification rates of poplar sawdust, switchgrass, and corn stover chars using particle residence times < 500 ms at total pressures of 10 and 15 atm. The measured gasification rate of switchgrass char was the slowest, and the rates at which poplar sawdust and corn stover chars gasified were similar. Modifications to the SPR and associated diagnostics allowed this project to generate new data on biomass pyrolysis and gasification rates and mechanisms. Specifically, poplar, switch grass and corn stover biomass particles ranging in size from ¼ to ½ inch nominal diameter reacted in environments with up to 70% CO2 and H2O producing time-resolved measurements of particle mass, surface and center temperature, size, shape, and off-gas compositions. These data provide the framework for new mechanistic and rate measurements for biomass reactivity. Biomass pyrolysis and char gasification experiments were conducted in the BSG to provide additional data for model development as well as validation for the CFD model. The BSG is an entrained flow gasifier operating at atmospheric pressure, having particle heating rates > 104 K/s and particle residence times up to 2-3 s. Pyrolysis experiments were conducted in N2 at temperatures spanning 667 to 915°C. The gasification of biomass-derived chars using both CO2 and steam was done at temperatures of 1000°C and 1200°C. The CO2 gasification rates increased with concentration up to 50% vol. of CO2, above which conversion remained essentially constant. Although low conversion was generally observed, poplar char appeared more reactive during CO2 gasification than either corn stover or switchgrass chars. This differed from the HPFFB results indicating similar reactivity for corn stover and poplar chars. For steam gasification, the concentration of water in nitrogen was fixed at 46% vol. When compared with CO2 gasification, conversion during steam gasification was higher and all chars were found to be similar. Kinetic Models The primary pyrolysis of biomass was modeled using the Chemical Percolation Devolatilization (CPD) model assuming that biomass pyrolysis occurs as a weighted average of its individual components. The CPD model was incorporated into the CFD model described below for the pyrolysis reaction. Thermal cracking of biomass tar into light gas was predicted using a tar-cracking model from the literature. Two theoretical models of biomass gasification derived in this project describe the particle reaction mechanisms and rates at differing levels of detail. The most fundamental model describes the transient, spatially resolved changes in particle temperature and composition and particle off-gas composition in terms of intrinsic reactivities, spatially and temporally resolved transport properties, and particle characteristics. This model draws on work previously done for oxidation kinetics and was entirely rewritten both to incorporate the new kinetic mechanisms for gasification and to improve its numerical performance. The new kinetic mechanisms indicate that the ratio of inherent gasification of H2O compared to CO2 spanned 2 to 7 over the range of particle temperatures and sizes of interest. A simpler model of particle reactivity based on external surface area completed as part of this project provides more computationally efficient but less detailed analyses of particle behavior and was incorporated into the CFD model for char gasification. The experimental data described above provided kinetic parameters for both models. CFD – Advanced Modeling Tool The pyrolysis and gasification of the biomass feedstocks in the BSG were modeled using ANSYS® Fluent® incorporating the simplified kinetic model. Particle tracking was realized by using the Lagrangian approach while the gas flow was modeled with the standard Eulerian method. The simplified kinetics include moisture evaporation, thermal degradation of biomass to char/tar/light gases, tar to light gas conversion, combustion/gasification of char in O2/H2O/CO2, and gas phase reactions. The pyrolysis simulation results showed reasonable agreement with the experimental results obtained from the BSG but gasification simulation results differed significantly. Since the pyrolysis of biomass converts a majority of the carbon into gaseous products, the discrepancy in simulated vs. experimental gasification rate has a lower impact on estimated total conversion than would be the case for coal. The CFD model was then employed to estimate the exit concentrations, biomass conversions and residence times for a commercial scale gasifier in a BTL plant. BTL Process, Economics and LCA A technical model was developed using Aspen Plus® exploring BTL transportation fuel production by gasification in a pressurized, oxygen fed, entrained-flow gasifier. Capital cost and life cycle assessment (LCA) models were developed using the mass and energy balance data from the model. Data from similar existing coal and biomass gasification plant models developed by the DOE and others along with non-proprietary inputs from GE Energy gasification business were utilized. A feedstock of 2,000 Tonne/d with 25 % moisture and a collection radius of 30 miles was considered and a cumulative gasoline and diesel fuel production of ≈40 MGal/yr was estimated. A costing analysis was carried out to evaluate the process economics. The capital cost of the BTL plant as described above was estimated using a number of available literature data. “Biomass Gasification” report from SRI Consulting, Process Economics Program, November 2005 was used. The gasification process was substituted with an entrained flow gasification estimate from “Cost and Performance Baseline for Fossil Energy Plants Volume 1: Bituminous Coal and Natural Gas to Electricity” Revision 2a, September 2013, Revision 2, November 2010, DOE/NETL-2010/1397. The process economics was carried out with poplar as the biomass feedstock in the base case. Two other cases were evaluated with corn stover and switchgrass as the biomass feedstock. Environmental LCA models were completed for diesel and gasoline fuels produced via gasification and subsequent Fischer-Tropschreaction of corn stover, switchgrass, and poplar feedstocks. The impacts for the biomass-based fuels were compared to fossil-based diesel and gasoline on a unit energy (well-to-wheels) basis. The cultivation inputs and emissions for the biomass were obtained from the literature and combined with the inputs and emissions obtained from the above technical models of the BTL plant. The fossil fuel LCA models were based on ecoinvent® 2.2 data for diesel and petrol. The use phases (combustion in a vehicle) for all fuels were based on modified ecoinvent 2.2 vehicle models. The results indicate a substantial reduction in lifecycle greenhouse gas (GHG) emissions for the biomass fuels over the fossil fuels if GHG emissions from land use changes are not included. Fossil fuel and ozone depletion are also significantly reduced for the biomass fuels. Overall, the lifecycle impacts for the biomass fuels decrease in the following order corn stover > switchgrass > poplar.
Publications
- Type:
Theses/Dissertations
Status:
Published
Year Published:
2011
Citation:
Lewis, A. D. (2011). Sawdust Pyrolysis and Petroleum Coke CO2 Gasification at High Heating Rates, M.S. Thesis, Chemical Engineering Department, Brigham Young University
- Type:
Journal Articles
Status:
Published
Year Published:
2012
Citation:
Fletcher, T. H., H. R. Pond, J. Webster and L. L. Baxter (2012). "Prediction of tar and light gas during pyrolysis of black liquor and biomass." Energy & Fuels, 26, 3381-3387.
- Type:
Journal Articles
Status:
Published
Year Published:
2012
Citation:
Mehrabian, R., S. Zahirovic, R. Scharler, I. Obernberger, S. Kleditzsch, S. Wirtz, V. Scherer, H. Lu and L. L. Baxter (2012). "A CFD model for thermal conversion of thermally thick biomass particles." Fuel Processing Technology, 95, 96-108.
- Type:
Journal Articles
Status:
Published
Year Published:
2013
Citation:
Lewis, A. D. and T. H. Fletcher (2013). Prediction of Sawdust Pyrolysis Yields from a Flat-Flame Burner Using the CPD Model, Energy & Fuels, 27, 942-953.
- Type:
Theses/Dissertations
Status:
Other
Year Published:
2014
Citation:
Lewis, A., "Gasification of Biomass, Coal, and Petroleum Coke at High Heating Rates and Elevated Pressure," PhD Dissertation, Brigham Young University (in progress 2014)
- Type:
Conference Papers and Presentations
Status:
Accepted
Year Published:
2011
Citation:
Shawn Maghzi and George Rizeq (2011). Experimental study of biomass pyrolysis in an entrained flow reactor. Technical Meeting of the Western States Section of the Combustion Institute Hosted by the University of California Riverside, Riverside, CA. October 17-18, 2011. Paper # 027RK-0061.
- Type:
Conference Papers and Presentations
Status:
Accepted
Year Published:
2010
Citation:
Lewis, A., S. Goodrich, K. Kolste, G. Sorensen, and T. H. Fletcher (2010). Rapid Pyrolysis and CO2 Gasification of Petroleum Coke and Sawdust in a High Pressure Flat-Flame Burner, presented at the 2010 AIChE Annual Meeting, Salt Lake City, UT.
- Type:
Conference Papers and Presentations
Status:
Accepted
Year Published:
2011
Citation:
Lewis, A. D. and T. H. Fletcher (2011) Predicting Sawdust Pyrolysis Yields Using the CPD Code with a Tar Cracking Model, presented at the 7th US National Combustion Institute Meeting, Georgia Institute of Technology, Atlanta, Georgia.
- Type:
Conference Papers and Presentations
Status:
Accepted
Year Published:
2012
Citation:
Beutler, J. and L. L. Baxter (2012). Biomass and carbon capture as CO2 management techniques. Tsinghua Visiting Lecture Series. Beijing, China.
- Type:
Conference Papers and Presentations
Status:
Accepted
Year Published:
2012
Citation:
Beutler, J. and L. L. Baxter (2012). Biomass particle reactions: Experimental and model results. UC Davis Energy Institute Distinguished Lecture Series. Davis, California: 30.
- Type:
Conference Papers and Presentations
Status:
Accepted
Year Published:
2012
Citation:
Beutler, J. and L. L. Baxter (2012). Black liquor & biomass particle reactions: Experimental and model results. From Molecular Understanding to Industrially Relevant High-Temperature Processes, Turku, Finland. September 14, 2012.
- Type:
Conference Papers and Presentations
Status:
Accepted
Year Published:
2013
Citation:
Lewis, A. D. and T. H. Fletcher (2013). Pyrolysis and CO2 Gasification Rates of Biomass at High Heating-Rate Conditions, presented at the 8th US National Combustion Meeting, The Combustion Institute, Park City, Utah (May 19-22, 2013).
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Progress 09/01/11 to 08/31/12
Outputs
OUTPUTS: Work has progressed on the pyrolysis and gasification of poplar wood, switchgrass and corn stover in the Single-Particle Reactor (SPR), the atmospheric Flat Flame Burner (FFB) and the High Pressure Flat Flame Burner (HPFFB) at Brigham Young University (BYU) this past year. No experiments were performed in the Bench Scale Gasifier (BSG) at General Electric Global Research as that equipment was being relocated from Irvine, CA to Niskayuna, NY. The BSG will be operational for the last program year, performing experiments in char burnout and gasification to generate kinetic data for model development and then validate the gasification kinetic models being generated at BYU. Improvements to SPR experimental set-up When running pyrolysis experiments with only N2 gas flowing through the reactor, it was observed that the poplar particles reacted completely to ash indicating there was likely oxygen getting into the reactor. A gas chromatograph/mass spectrometer (GC/MS) which was purchased to analyze pyrolysis gases from the Single Particle Reactor (SPR) was also able to measure oxygen in the system. After fixing cracks and increasing reactant gas flow rates, approximately 0.5% oxygen remained. Earlier near-spherical poplar particle experiments will be re-run with the now lower oxygen content to reconfirm and/or update results before experiments with corn stover pellets are conducted. Improvements were also made on the mass balance to decrease noise by 90%. FFB and HPFFB Pyrolysis of poplar sawdust, straw, switchgrass, and corn stover was studied in the FFB with particle residence times less than 1 second. Up to 10.6 wt% (dry ash-free) higher volatile yields were measured in the FFB when compared to a standard ASTM volatiles test. Biomass CO2 gasification experiments (40% and 90% CO2) were conducted using fully-pyrolyzed chars in BYU's HPFFB; the chars were generated in GE's BSG. DISSEMINATION: During this reporting period, several presentations and publications were made. Presentations were made at the 20th European Biomass Conference, Tsinghua University, UC Davis and Abo Akademi University, Finland. Publications are listed below. PARTICIPANTS: During this reporting period, project participants from General Electric (prime contractor) included Dr. John McDermott (PI) and Dr. Xiaoying Bao; and from BYU included Prof. Larry Baxter (Co-PI), Prof. Thomas Fletcher and graduate students Aaron Lewis and Jacob Beutler. TARGET AUDIENCES: 1) General scientific community, and 2) Faculty and students at academic institutions. PROJECT MODIFICATIONS: Nothing significant to report during this reporting period.
Impacts
A validated, single particle combustion model has been converted to object-oriented code making it more user-friendly. Some of the code has been re-written and optimized, reducing run-time by an order of magnitude. While it is still too slow to be used as a user-defined function in computational fluid dynamics (CFD) code, it is useful for comparing with experimental data and optimizing gasification kinetic parameters. In CO2 gasification experiments, poplar and corn stover chars appeared to have similar reactivity up until about 150 ms, but corn stover was more reactive from 150-300 ms. The higher reactivity of the corn stover char was likely due to a catalytic effect of the ash, since the ash content of the corn stover char was 84 wt%. Future work will include switchgrass char and use of inductively coupled plasma analysis of the ash to improve understanding of ash vaporization of corn stover and switchgrass chars. The ability to account for differing gasification reactivities as a function of biomass type and particle size & shape in kinetic and CFD models will be critical to developing and designing fuel flexible biomass gasifiers at the scale needed to support liquid biofuel production. This program will add significant new kinetic insights into CFD modeling for biomass gasifiers.
Publications
- Fletcher, T. H., H. R. Pond, J. Webster and L. L. Baxter (2012). "Prediction of tar and light gas during pyrolysis of black liquor and biomass." Energy & Fuels 26: 3381-3387.
- Mehrabian, R., S. Zahirovic, R. Scharler, I. Obernberger, S. Kleditzsch, S. Wirtz, V. Scherer, H. Lu and L. L. Baxter (2012). "A CFD model for thermal conversion of thermally thick biomass particles." Fuel Processing Technology 95: 96-108.
- Beutler, J. and L. Baxter (2012). Biomass gasification and combustion. Energienet.dk Energy Review. Fredericia, Denmark.
- Beutler, J. and L. Baxter (2012). Recent developments in biomass combustion, cofiring, and gasification. 20th European Biomass Conference. Milan, Italy. 1: 17.
- Beutler, J. and L. L. Baxter (2012). Biomass and carbon capture as CO2 management techniques. Tsinghua Visiting Lecture Series. Beijing, China.
- Beutler, J. and L. L. Baxter (2012). Biomass particle reactions: Experimental and model results. UC Davis Energy Institute Distinguished Lecture Series. Davis, California: 30.
- Beutler, J. and L. L. Baxter (2012). Black liquor & biomass particle reactions: Experimental and model results. From Molecular Understanding to Industrially Relevant High-Temperature Processes, Turku, Finland.September 14, 2012
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Progress 09/01/10 to 08/31/11
Outputs
OUTPUTS: OUTPUTS: The current USDA-funded project is conducted in collaboration with Professors Larry Baxter and Tom Fletcher from Brigham Young University (BYU). The BYU team focused on the Detailed Devolatilization Model (CPD), the Char-Gas Model (CBK), and the single particle model (SPM) for biomass gasification. Also, BYU team conducted experiments using BYU's facilities for model calibration and validation. At GE Global Research's Irvine facility an experimental campaign was completed to study biomass pyrolysis at conditions relevant to entrained flow gasification. The experiments were conducted using an atmospheric pressure bench-scale entrained flow reactor capable of varying temperatures, heating rates, and residence times. The feed and sampling systems were substantially modified to reliably feed biomass and collect high tar concentrations respectively. This work, along with other experimental tasks at BYU, will be used for calibration and validation of detailed and simplified biomass gasification kinetic models. This study tested three biomass fuels including energy crop (switchgrass), woody residue (poplar), and agricultural residue (cornstover). Detailed gas, tar, and char yields were measured and correlated. At BYU, the Single Particle Reactor was utilized to gasify and devolatilize corn stover of various particles sizes and shapes. The particle surface and center temperatures were measured during the process which will be used to develop kinetic parameters. This will be used to develop the single particle code and continue to increase the efficiency. Also, progress was made on experimental and modeling activities on PMG program (Particle Modeling GUI). The computation time to process the images from the experiment was decreased by 50 times. The single particle combustion and gasification code was converted to an object-oriented code and made more user friendly. Also, an atmospheric flat-flame burner (FFB) and high pressure flat-flame burner (HPFFB) was used to study the pyrolysis of poplar sawdust, straw, switchgrass, and cornstover. DISSEMENATION: Information dissemination occurred through: (1) presentation at the Technical Meeting of the Western States Section of the Combustion Institute Hosted by the University of California Riverside, Riverside, CA; (2) Graduate seminars at BYU PARTICIPANTS: During this reporting period, project participants from General Electric (GE - prime contractor) included Dr. George Rizeq (PI) and Dr. Hong Lu; and from Brigham Young University (BYU - subcontractor) included Prof. Larry Baxter (Co-PI), Prof. Tom Fletcher, and BYU grad students on this project included Jacob Beutler, Brad Nielsen, and Aaron Lewis. TARGET AUDIENCES: (1) General scientific community, and (2) Western State Section of Combustion Institute. PROJECT MODIFICATIONS: The lab in Irvine, California was closed and the project is being transitioned to GE Global Research Center in Niskayuna, NY.
Impacts
Unlike pulverized coal, biomass particles are neither small enough to neglect internal temperature gradients nor equant enough to model as spheres. Experimental and theoretical investigations indicate particle shape and size influence biomass particle dynamics, including essentially all aspects of combustion and gasification such as drying, heating, pyrolysis, oxidation, and gasification. In essentially all gasifiers, local fuel-rich regions exist, so a comprehensive particle reactivity model must include all of these stages and effects of size and shape on them. This project upon completion will theoretically and experimentally illustrate how these size and shape effects influence particle conversion. Experimental data from a novel single droplet reactor at BYU include simultaneous temporal data on internal temperature, spatially resolved surface temperature, size, shape, images from multiple directions and mass data. These simultaneous data will offer insight into biomass reaction mechanisms and provide computer code verification and validation information. They are especially useful because of accurate furnace characterization (gas flow rates and furnace temperature). These mechanisms include, but are not limited to, particle drying, swelling, devolatilization, heatup, oxidation, and ash formation. Preliminary model predictions agreed with measurements within their uncertainty limits.
Publications
- Baxter, L. L., W. Roberts and H. Lu (2010). Particle conversion rates during biomass combustion. Coal: Rising to New Challenges - The Clearwater Clean Coal Conference - The 35th International Technical Conference on Clean Coal & Fuel Systems. Clearwater, Florida.
- Beutler, J., L. Baxter, S. Clausen, A. Fateev and S. Hvid (2010). Biomass co-firing for CO2 management: Full-scale field test. 2010 AIChE Annual Meeting, 10AIChE, November 7, 2010 - November 12, 2010, Salt Lake City, UT, United states, American Institute of Chemical Engineers
- Shawn Maghzi and George Rizeq. Experimental study of biomass pyrolysis in an entrained flow reactor. 2011 Technical Meeting of the Western States Section of the Combustion Institute Hosted by the University of California Riverside, Riverside, CA. October 17-18, 2011. Paper # 027RK-0061.
- Lewis, A. D., Sawdust Pyrolysis and Petroleum Coke CO2 Gasification at High Heating Rates, M.S. Thesis, Chemical Engineering Department, Brigham Young University (April, 2011).
- Lewis, A., S. Goodrich, K. Kolste, G. Sorensen, and T. H. Fletcher, Rapid Pyrolysis and CO2 Gasification of Petroleum Coke and Sawdust in a High Pressure Flat-Flame Burner, presented at the 2010 AIChE Annual Meeting, Salt Lake City, UT (November 7-12, 2010).
- Lewis, A. D. and T. H. Fletcher, Predicting Sawdust Pyrolysis Yields Using the CPD Code with a Tar Cracking Model, presented at the 7th US National Combustion Institute Meeting, Georgia Institute of Technology, Atlanta, Georgia (March 20-23, 2011).
- Baxter, L. L. (2011). Biomass-coal cofiring: An overview of technical issues. Energy production from solid biofuels towards global warming abatement. P. Grammelis. London, Springer Verlag. 1: 43-74.
- Baxter, L. L., H. E. Garcia and B. Liu (2010). Slag-refractory interactions during coal and biomass combustion and gasification. Coal: Rising to New Challenges - The Clearwater Clean Coal Conference - The 35th International Technical Conference on Clean Coal & Fuel Systems. Clearwater, Florida.
- Baxter, L. L. and H. Lu (2011). Biomass combustion characteristics and implications for renewable energy. Energy production from solid biofuels towards global warming abatement. P. Grammelis. London, Springer Verlag. 1: 95-122.
- Beutler, J., S. Clausen, A. Fateev, S. Hvid, S. Kaer and L. L. Baxter (2010). Cofiring field test in a full-scale 350 mwe power production plant: Near-burner measurements. Coal: Rising to New Challenges - The Clearwater Clean Coal Conference - The 35th International Technical Conference on Clean Coal & Fuel Systems. Clearwater, Florida.
- Beutler, J. B., S. Clausen, A. Fateev, S. Hvid and L. L. Baxter (2010). Biomass co-firing for CO2 management: Full-scale field test and modeling AIChE 2010 Annual Meeting. Salt Lake City, UT, AIChE.
- Hoskisson, J., W. Anderson, R. Reid and L. L. Baxter (2010). Ash and slag spectral emittance measurements. Coal: Rising to New Challenges - The Clearwater Clean Coal Conference - The 35th International Technical Conference on Clean Coal & Fuel Systems. Clearwater, Florida.
- Jenkins, B. M., L. L. Baxter and J. Koppejan (2011). Biomass combustion. Thermochemical processing of biomass: Conversion into fuels, chemicals, and power. R. C. Brown. London, Wiley.
- Li, M., L. Baxter and S. Ghosh (2010). Eddy impaction as an ash deposition mechanism: An theoretical and experimental investigation. 2010 AIChE Annual Meeting, 10AIChE, November 7, 2010 - November 12, 2010, Salt Lake City, UT, United states, American Institute of Chemical Engineers
- Li, M., D. Yeates, S. Ghosh, R. Khadgi and L. L. Baxter (2010). Eddy impaction as an ash deposition mechanism: An experimental and theoretical investigation. AIChE 2010 Annual Meeting. Salt Lake City, UT, AIChE.
- Lu, H., E. Ip, J. Scott, P. Foster, M. Vickers and L. L. Baxter (2010). Effects of particle shape and size on devolatilization of biomass particle. Fuel 89(5): 1156-1168.
- Moore, T. J., D. P. Cundick, M. R. Jones, D. R. Tree, R. D. Maynes and L. L. Baxter (2011). In situ measurements of the spectral emittance of coal ash deposits. Journal of Quantitative Spectroscopy and Radiative Transfer 112(12): 1978-1986.
- Moore, T. J., M. R. Jones, D. R. Tree, R. Daniel Maynes and L. L. Baxter (2011). An experimental method for making spectral emittance and surface temperature measurements of opaque surfaces. Journal of Quantitative Spectroscopy and Radiative Transfer 112(7): 1191-1196.
- Pei, L., G. Jiang, L. L. Baxter and M. R. Linford (2010). Analysis of coal and biomass by static time-of-flight secondary ion mass spectrometry (tof-sims). Surface Science Spectra 17(1): 1-67.
- Romriell, A. S., J. Hoskisson and L. L. Baxter (2010). Ash emittance characterization. AIChE 2010 Annual Meeting. Salt Lake City, UT, AIChE.
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Progress 09/01/09 to 08/31/10
Outputs
OUTPUTS: OUTPUTS: Progress in this first reporting period (during which project initiation was delayed until 2Q-2010 due to funds release/contract signing delays) included a project kickoff meeting held at Brigham Young University (BYU) in Provo, Utah, and attended by Dr. George Rizeq (PI) and Dr. Hong Lu from GE (prime contractor) and Prof. Larry Baxter (Co-PI), Prof. Tom Fletcher, and their grad students on this project from BYU. Discussion topics during the meeting included project objectives, work breakdown structure, tasks and schedule, division of responsibilities between GE and BYU on modeling and experimental tasks, experimental facilities to be used, biomass fuels to be tested, and sample preparation methods. Based on kickoff meeting agreements, a detailed work breakdown structure highlighting work flow between modeling and experimental tasks as well as organizational responsibilities was prepared and disseminated to project participants. Additional progress during this period included revisiting the biomass feeder design for the Bench Scale Gasifier (BSG) at GE's Fuel Conversion Lab (FCL) in Irvine, CA. Along with GE's project team, a group of students from University of California, Irvine (UCI) participated in this redesign effort as part of their senior design class at UCI's Mechanical Engineering department. Other BSG modifications were explored particularly in relation to the main gasification reaction tube, which was altered in length to match the residence time of biomass participles undergoing gasification. Work also progressed at BYU in development and expansion of the single biomass particle gasification model. In short, this is a transient, multi-dimensional model that describes drying, pyrolysis, oxidation, gasification, inorganic reactions, and fly ash formation for particles of arbitrary size, shape, and composition. Other activities at BYU included expansion and application of the Chemical Percolation Devolatilization (CPD) model to biomass. Recent modeling of sawdust pyrolysis has shown promise using a combination of the additivity law, the CPD model, and secondary tar cracking kinetics. The CPD model was used to model the primary pyrolysis of cellulose, hemicellulose, and lignin separately using kinetic and structural parameters. During this project, the biomass CPD model will be evaluated for its ability to predict devolatilization yields for switchgrass, poplar wood, and corn stover. The CPD model will be calibrated and validated using experimental facilities including the High-Pressure Flat-Flame Burner (HPFFB) at BYU. DISSEMENATION: Info dissemination occurred through: (1) presentations at the 2010 AIChE meeting and the 35th International Technical Conference on Clean Coal & Fuel Systems; (2) Graduate seminars at BYU; (3) invited lectures in Beijing and in Xining, China; and (4) biomass workshop held in Provo, Utah, and titled Technical Issues of Biomass Repowering and Co-Firing where Prof. Baxter was the primary instructor. The workshop attendees wanted to gain knowledge about biomass behavior during combustions/gasification and to positively impact their industrial operations. PARTICIPANTS: During this reporting period, project participants from General Electric (GE - prime contractor) included Dr. George Rizeq (PI) and Dr. Hong Lu; and from Brigham Young University (BYU - subcontractor) included Prof. Larry Baxter (Co-PI), Prof. Tom Fletcher, and BYU grad students on this project Jacob Beutler, Brad Nielsen, and Aaron Lewis. TARGET AUDIENCES: (1) General scientific community, (2) AIChE through annual meeting, and (3) Attendees of the 35th International Technical Conference on Clean Coal & Fuel Systems. PROJECT MODIFICATIONS: Nothing significant to report during this reporting period.
Impacts
Unlike pulverized coal, biomass particles are neither small enough to neglect internal temperature gradients nor equant enough to model as spheres. Experimental and theoretical investigations indicate particle shape and size influence biomass particle dynamics, including essentially all aspects of combustion and gasification such as drying, heating, pyrolysis, oxidation, and gasification. In essentially all gasifiers, local fuel-rich regions exist, so a comprehensive particle reactivity model must include all of these stages and effects of size and shape on them. This project theoretically and experimentally will illustrate how these size and shape effects influence particle conversion. Experimental data from a novel single droplet reactor at BYU include simultaneous and temporal data on internal temperature, spatially resolved surface temperature, size, shape, images from multiple directions and mass data. These simultaneous data will offer insight into biomass reaction mechanisms and provide computer code verification and validation information. They are especially useful because of accurate furnace characterization (gas flow rates and furnace temperature). These mechanisms include, but are not limited to, particle drying, swelling, devolatilization, heatup, oxidation, and ash formation. Preliminary model predictions agreed with measurements within their uncertainty limits. A biomass version of the Chemical Percolation Devolatilization (CPD) code was created using parameters for biomass components and combining it with a first-order tar cracking model. It was found that superposition may not be appropriate with high ash content fuel or in predicting individual gas species. The CPD model performed satisfactory in predicting pyrolysis yields for five kinds of sawdust, three different reactors (flat flame burner, fluidized bed, drop tube), and high heating rates. Fuel specific tar cracking kinetics could be used with loss of some generality to the model. Future work includes switchgrass, poplar wood, and corn stover.
Publications
- Baxter, L.L., H.E. Garcia, and B. Liu, Slag-Refractory Interactions During Coal and Biomass Combustion and Gasification, in Coal: Rising to New Challenges - The Clearwater Clean Coal Conference - The 35th International Technical Conference on Clean Coal & Fuel Systems. 2010: Clearwater, Florida.
- Baxter, L.L., W. Roberts, and H. Lu, Particle Conversion Rates During Biomass Combustion, in Coal: Rising to New Challenges - The Clearwater Clean Coal Conference - The 35th International Technical Conference on Clean Coal & Fuel Systems. 2010: Clearwater, Florida.
- Lewis, A., S. Goodrich, K. Kolste, G. Sorensen, and T. H. Fletcher, Rapid Pyrolysis and CO2 Gasification of Petroleum Coke and Sawdust in a High Pressure Flat-Flame Burner, presented at the 2010 AIChE Annual Meeting, Salt Lake City, UT (November 7-12, 2010).
- Lewis, A. D. and T. H. Fletcher, Predicting Sawdust Pyrolysis Yields Using the CPD Code with a Tar Cracking Model, accepted for presentation at the 7th US National Combustion Institute Meeting, Georgia Institute of Technology, Atlanta, Georgia (March 20-23, 2011).
- Lu, H., E. Ip, J. Scott, P. Foster, M. Vickers, and L.L. Baxter, Effects of particle shape and size on devolatilization of biomass particle. Fuel, 2010. 89(5): p. 1156-1168.
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