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Optimum usage and economic feasibility of animal manure-based biomass in combustion systems

ProQuest Dissertations and Theses, 2009
Dissertation
Author: Nicholas Thomas Carlin
Abstract:
Manure-based biomass (MBB) has the potential to be a source of green energy at large coal-fired power plants and on smaller-scale combustion systems at or near confined animal feeding operations. Although MBB is a low quality fuel with an inferior heat value compared to coal and other fossil fuels, the concentration of it at large animal feeding operations can make it a viable source of fuel. Mathematical models were developed to portray the economics of co-firing and reburning coal with MBB. A base case run of the co-fire model in which a 95:5 blend of coal to low-ash MBB was burned at an existing 300-MW e coal-fired power plant was found to have an overall net present cost of $22.6 million. The most significant cost that hindered the profitability of the co-fire project was the cost of operating gas boilers for biomass dryers that were required to reduce the MBB's moisture content before transportation and combustion. However, a higher dollar value on avoided nonrenewable CO 2 emissions could overrule exorbitant costs of drying and transporting the MBB to power plants. A CO2 value of $17/metric ton was found to be enough for the MBB co-fire project to reach an economic break-even point. Reburning coal with MBB to reduce NOx emissions can theoretically be more profitable than a co-fire project, due to the value of avoided NO x emissions. However, the issue of finding enough suitable low-ash biomass becomes problematic for reburn systems since the reburn fuel must supply 10 to 25% of the power plant's heat rate in order to achieve the desired NOx level. A NOx emission value over $2500/metric ton would justify installing a MBB reburn system. A base case run of a mathematical model describing a small-scale, on-the-farm MBB combustion system that can completely incinerate high-moisture (over 90%) manure biomass was developed and completed. If all of the energy or steam produced by the MBB combustion system were to bring revenue to the animal feeding operation either by avoided fueling costs or by sales, the conceptualized MBB combustion system has the potential to be a profitable venture. [PUBLICATION ABSTRACT]

viii TABLE OF CONTENTS Page ABSTRACT......................................................................................................................iii

DEDICATION...................................................................................................................v

ACKNOWLEDGEMENTS..............................................................................................vi

TABLE OF CONTENTS................................................................................................viii

LIST OF FIGURES..........................................................................................................xii

LIST OF TABLES........................................................................................................xxiii

1. INTRODUCTION......................................................................................................1

1.1. Industrialization of Agriculture..........................................................................2 1.2. Coal-fired Power Plants and Their Emissions..................................................10 1.3. Problem Statement...........................................................................................17

2. BACKGROUND INFORMATION.........................................................................18

2.1. Fuel Supply and Properties..............................................................................18 2.1.1. Coal.............................................................................................................18 2.1.2. Dairy Biomass.............................................................................................22 2.1.3. Feedlot Biomass..........................................................................................42 2.1.4. Hog or Swine Biomass................................................................................47 2.2. Manure-based Biomass’s Effect on Emissions from Coal Combustion..........50 2.3. Energy Conversion Technologies....................................................................54 2.3.1. Biological Gasification of Manure-based Biomass.....................................56 2.3.2. Thermal Gasification of Manure-based Biomass........................................63 2.3.3. Co-firing Coal and Manure-based Biomass in Primary Burn Zones..........69 2.3.4. Reburning Coal with Manure-based Biomass.............................................75 2.4. Competing NO x Control Technologies............................................................85 2.4.1. Primary NO x Controls.................................................................................86 2.4.2. Selective Catalytic Reduction.....................................................................89 2.4.3. Selective Non-catalytic Reduction..............................................................92 2.5. Competing Uses for Manure-based Biomass...................................................94

3. LITERATURE REVIEW.........................................................................................95

ix Page

3.1. Previous Economic Studies..............................................................................95 3.1.1. Co-firing Coal with Biomass......................................................................95 3.1.2. Reburning Coal with Biomass....................................................................99 3.1.3. Competing NO x Control Technologies.....................................................101 3.1.4. Dollar Values of Emissions.......................................................................102 3.2. Review of Designs for Small-scale, On-the-farm Manure-based Biomass Combustion Systems......................................................................................103

4. OBJECTIVE AND TASKS...................................................................................113

5. MODELING..........................................................................................................115

5.1. Modeling the Properties of Manure-based Biomass......................................115 5.2. Modeling Biomass Fuel Pre-combustion Processing.....................................118 5.2.1. Drying Manure-based Biomass.................................................................118 5.2.1.1. Conveyor belt biomass dryers........................................................120 5.2.1.1.1 Perpendicular air flow dryer.........................................................125 5.2.1.1.2 Parallel air flow dryer...................................................................133 5.2.1.2. Steam-tube rotary biomass dryers..................................................135 5.2.2. Transporting Manure-based Biomass.......................................................148 5.2.3. Grinding and Processing of Manure-based Biomass................................152 5.2.4. Emissions from Pre-combustion Processing of Biomass..........................153 5.3. General Modeling of Coal and Biomass Oxidation.......................................155 5.3.1. Direct and Complete Combustion of Coal and Biomass Fuels.................155 5.3.2. Partial Oxidation and Gasification of Coal and Biomass Fuels................165 5.4. Modeling Manure-Based Biomass Combustion in Large Utility Coal-Fired Boilers............................................................................................................172 5.4.1. Heat and Fueling Rates of Coal-fired Power Plants..................................173 5.4.2. Coal-fired Power Plant Emissions............................................................174 5.4.2.1. NO x from primary burn zones........................................................174 5.4.2.2. Ash from coal.................................................................................178 5.4.2.3. CO 2 from coal.................................................................................179 5.4.2.4. SO 2 from coal.................................................................................179 5.4.3. Co-firing Coal with Manure-based Biomass.............................................179 5.4.4. Reburning Coal with Manure-based Biomass...........................................184 5.4.5. Comparing Reburning to Other Secondary NO x Control Technologies...187 5.5. Modeling Small-Scale, On-the-farm Manure-Based Biomass Combustion Systems..........................................................................................................189 5.5.1. Combustion System for High Moisture Manure-based Biomass..............190 5.5.2. Combustion System for Scraped Solids and Lower Moisture Biomass...200 5.6. Modeling the Economics of Manure-based Biomass Combustion Systems..202 5.6.1. Drying Cost Estimations...........................................................................205

x Page

5.6.2. Transportation Cost Estimations...............................................................207 5.6.3. Processing and Firing Cost Estimations....................................................208 5.6.3.1. Co-firing.........................................................................................208 5.6.3.2. Reburning and other secondary NO x control technologies............210 5.6.4. Cost of Emissions......................................................................................213 5.6.5. Overall Economic Analysis.......................................................................215 5.6.6. Economics of Small-scale, On-the-farm Systems.....................................223

6. RESULTS AND DISCUSSION............................................................................225

6.1. Biomass Drying Models.................................................................................225 6.2. Biomass Transportation Model......................................................................242 6.3. Economics of Manure-based Biomass Combustion in Large-scale Coal- fired Power Plants..........................................................................................248 6.3.1. Co-firing....................................................................................................249 6.3.1.1. Base case inputs and results...........................................................250 6.3.1.2. Biomass and coal fueling...............................................................262 6.3.1.3. CO 2 , SO x , and ash emissions..........................................................265 6.3.1.4. Biomass drying and transporting....................................................271 6.3.2. Reburning..................................................................................................278 6.3.2.1. Base case inputs and results...........................................................279 6.3.2.2. Biomass and coal fueling...............................................................286 6.3.2.3. CO 2 , NO x , SO x , and ash emissions.................................................289 6.3.2.4. Biomass drying and transporting....................................................294 6.4. Combustion at Smaller-scale, On-the-farm Systems.....................................296 6.4.1. Base Run...................................................................................................296 6.4.2. Flushing Systems and Solids Separation...................................................299 6.4.3. Effect of Drying Solids Before Combustion.............................................302 6.4.4. Combustion of Dried Biomass Solids.......................................................304 6.4.5. Operation of Fire-tube Boiler....................................................................308 6.4.6. Additional Fueling for Complete Wastewater Disposal...........................309 6.4.7. Economic Estimations for Small-scale Manure-based Biomass Systems 310

7. SUMMARY AND CONCLUSIONS....................................................................315

7.1. Drying and Transportation.............................................................................315 7.2. Economics of Co-firing..................................................................................316 7.3. Economics of Reburning................................................................................318 7.4. On-the-farm Combustion...............................................................................318

8. SUGGESTED FUTURE WORK...........................................................................320

xi Page

REFERENCES...............................................................................................................322

APPENDIX A................................................................................................................339

APPENDIX B................................................................................................................345

APPENDIX C................................................................................................................349

APPENDIX D................................................................................................................357

VITA..............................................................................................................................365

xii LIST OF FIGURES Page Figure 1.1 Feedlot cattle on large confined animal feeding operation (FactoryFarm.org, 2007)...............................................................................1 Figure 1.2 Solid manure generated from an animal feeding operation (FactoryFarm.org, 2007)...............................................................................2 Figure 1.3 Change in number of operations with milk cows and growth of large dairy operations in the US from 1997 to 2007 (NASS, 2008)......................4 Figure 1.4 Number of operations with milk cows, milk cow inventory percentage, and milk production percentage in 2007 vs. size category of operation, Total operations in US = 71,510 (NASS, 2008)...........................................4 Figure 1.5 Number of operations with feed cattle and feed cattle inventory percentage in 2007 vs. size category of operation, Total operations in US = 967,540 (NASS, 2008).........................................................................5 Figure 1.6 Number of operations with hogs & pigs and hog & pig inventory percentage in 2007 vs. size category of operation, Total operations in US = 65,640 (NASS, 2008)...........................................................................5 Figure 1.7 Number of total American farms and farm labor workers vs. year (NASS Census, 2002)...................................................................................7 Figure 1.8 CO 2 emissions from all nonrenewable fuels in the US (EIA, 2007a)..........13 Figure 1.9 Top 20 states that emitted CO 2 from coal combustion in 2004 and their respective coal consumption (EIA, 2007c).................................................15 Figure 1.10 NO x and SO x emissions from conventional power plants and combined heat-and-power plants in the US from 1995 to 2006 (EIA, 2007c)............16 Figure 2.1 Coal fields in the United States (EIA, 2005)...............................................19 Figure 2.2 Average numbers of dairy cows in the US (not including heifers) for 2006 (NASS, 2007 and USDA, 2007)........................................................23 Figure 2.3 Current dairy and feedlot manure disposal (adapted from Schmidt et al., 1988)............................................................................................................25

xiii Page Figure 2.4 Higher heating value of cattle biomass vs. moisture and ash percentage (assuming a dry, ash free HHV of 19,770 kJ/kg)........................................32 Figure 2.5 Nitrogen, sulfur, and chlorine contents of DB, FB, Texas lignite, and Wyoming sub-bituminous (adapted from TAMU, 2006 and Arcot Vijayasarathy, 2007)...................................................................................33 Figure 2.6 Manure-based biomass mean dry particle density vs. volatile solids percentage....................................................................................................35 Figure 2.7 Measurements and fitted curves for bulk density of manure-based biomass from various sources.....................................................................36 Figure 2.8 Measurements and fitted curves for specific heat of manure-based biomass from various sources.....................................................................37 Figure 2.9 Measurements and fitted curves for thermal conductivity of manure- based biomass from various sources...........................................................38 Figure 2.10 Particle size distributions of beef cattle and dairy cow manure from various sources plus Rosin-Rammler distribution equations generated by Lawrence (2007) and the current author................................................41 Figure 2.11 Feedlot cattle on large 1,000+ head operations in the US (NASS, 2007 and USDA, 2007)........................................................................................43 Figure 2.12 Feedlot biomass collection at soil surfaced feed yards................................44 Figure 2.13 Feedlot biomass collection at paved surfaced feed yards............................44 Figure 2.14 Higher heating values for cattle ration, raw FB, partially composted FB, finished composted FB, coal, and respective FB+5% crop residue blends (adopted from Sweeten et al., 2003)................................................46 Figure 2.15 Total inventory of hogs and pigs by state in the US in 2007 (NASS, 2007)............................................................................................................48 Figure 2.16 Fuel nitrogen paths to NO and N 2 (adapted from Di Nola, 2007)...............51 Figure 2.17 Stabilization triangles of avoided emissions and allowed emissions (adapted from Pacala et al., 2004)...............................................................52 Figure 2.18 CO 2 emission vs. O/C and H/C ratios, with various fuels indicated (Carlin et al., 2008).....................................................................................52

xiv Page Figure 2.19 Mercury reduction co-benefits from secondary combustion controls (adapted from Arcot Vijayasarathy, 2007)..................................................54 Figure 2.20 Five paths to heat and electrical energy production from MBB (adapted from Annamalai et al., 2007)......................................................................55 Figure 2.21 Simplified anaerobic digestion flow diagram (adopted from Probstein et al., 2006c)....................................................................................................57 Figure 2.22 (a) Mole fraction of methane in biogas vs. H/C and O/C ratios in flushed DB (b) HHV of biogas vs. H/C and O/C ratios in flushed DB (adopted from Carlin, 2005)........................................................................60 Figure 2.23 Cattle manure gasification for corn ethanol production (Panda Energy, 2007)............................................................................................................65 Figure 2.24 Different zones in an updraft, fixed-bed gasifier (adapted from Priyadarsan et al., 2005b)............................................................................66 Figure 2.25 Schematic of 10 kW (30,000 Btu/hr) fixed-bed counter flow gasifier (Gordillo et al., 2008)..................................................................................67 Figure 2.26 Gas species profiles for FB at air flow rate of 45 SCFH (adopted from Priyadarsan, 2002).......................................................................................68 Figure 2.27 Experimental bed-temperature profile for DB at a time interval of 140 minutes with equivalence ratio of 1.8 and ASR of 0.38 (Carlin et al., 2008)............................................................................................................68 Figure 2.28 Schematic of small-scale 30 kW (100,000 Btu/hr) co-firing experimental setup.......................................................................................70 Figure 2.29 NO emission from coal and 90:10 coal-FB blends (adopted from Annamalai et al., 2003b).............................................................................72 Figure 2.30 NO emission for coal, 90:10, and 80:20 blends of coal and FB vs. equivalence ratio (adapted from Arumugam et al., 2005)..........................72 Figure 2.31 Fuel nitrogen conversion efficiency to fuel NO x for coal, 90:10, and 80:20 blends of coal and FB (computed by Carlin et al., 2008 from data found by Arumugam et al., 2005)...............................................................74 Figure 2.32 Elemental Hg reductions while co-firing coal with cattle biomass (adopted from Arcot Vijayasarathy, 2007).................................................75

xv Page Figure 2.33 Simplified schematic of the reburn process.................................................77 Figure 2.34 NO reduction percentage with coal, feedlot biomass and blends of coal and FB from a base level of 600 ppm NO (adopted from Annamalai et al., 2001 and Annamalai et al., 2005).........................................................81 Figure 2.35 Schematic of small-scale 30 kW (100,000 Btu/hr) coal reburn facility......83 Figure 2.36 NO x vs. CO for two reburn fuels from a base NO x level of 340 g/GJ (0.79 lb/MMBtu).........................................................................................83 Figure 2.37 Numerical simulation of Hg oxidation from reburning coal with various fuels (adopted from Colmegna, et al., 2007)...............................................84 Figure 2.38 Delayed fuel-air mixing in low-NO x burners..............................................88 Figure 2.39 Schematic of a SCR application (adapted from Srivastava et al., 2005).....89 Figure 2.40 Comparative costs for different reagents in SCR applications (Salib et al., 2005).....................................................................................................91 Figure 2.41 Schematic of a SNCR application (adapted from Srtivastava et al., 2005)............................................................................................................93 Figure 3.1 Schematic of a blended-feed co-firing arrangement for a pulverized coal boiler (adapted from DOE, 2004)...............................................................98 Figure 3.2 Schematic of a separate-feed co-firing arrangement for a pulverized coal boiler (adapted from DOE, 2004)...............................................................98 Figure 3.3 Design for a wastewater treatment plant for large confined animal feeding operations and drainage of anaerobic treatment lagoons (Kolber, 2001)...........................................................................................105 Figure 3.4 Components of the covered waste processor in the wastewater treatment plant discussed by Kolber (2001)..............................................................105 Figure 3.5 The Elimanure TM System developed by Skill Associates (2005)..............107 Figure 3.6 Black box thermodynamic model of a manure energy conversion system (Carlin, 2005)................................................................................108

xvi Page Figure 3.7 Required manure biomass solids composition needed to completely convert manure waste to combustion gases, water vapor, dry ash, and to maintain a desired system temperature of 373 K (Carlin, 2005)..............108 Figure 3.8 Conceptualized model for manure biomass thermo-chemical energy conversion system for a CAFO (Carlin, 2005).........................................109 Figure 3.9 Waste disposal efficiency of conceptualized manure biomass energy conversion system vs. mass of additional fuel used for combustion (Carlin, 2005)............................................................................................110 Figure 3.10 Schematic of a moving grate manure biomass combustor (adapted from Mooney et al., 2005).................................................................................112 Figure 5.1 Mass and energy flow diagram for conveyor belt dryers (adapted from Kiranoudis et al., 1994).............................................................................121 Figure 5.2 Perpendicular-flow conveyor belt dryer....................................................126 Figure 5.3 Parallel flow conveyor belt dryer...............................................................133 Figure 5.4 Indirect rotary steam-tube dryer for biomass.............................................136 Figure 5.5 Cross-sectional view of rotary steam-tube dryer (adapted from Canales et al., 2001)................................................................................................137 Figure 5.6 Heating and drying zones and assumed temperature and moisture content profiles for rotary steam-tube dryer (adapted from Canales et al., 2001)...................................................................................................138 Figure 5.7 Arrangement of steam tubes in rotary dryer..............................................143 Figure 5.8 Transporting MBB from animal feeding operations to centralized drying facilities and to large power plants............................................................149 Figure 5.9 General combustion process for coal and manure-based biomass.............156 Figure 5.10 Energy conservation for computing adiabatic flame temperature.............161 Figure 5.11 Energy conservation for computing heat lost to an external process.........164 Figure 5.12 Partial oxidation of coal and biomass and subsequent burning of producer gases...........................................................................................166

xvii Page Figure 5.13 Co-firing coal with biomass.......................................................................180 Figure 5.14 Reburning coal with biomass.....................................................................185 Figure 5.15 Selective catalytic reduction modeling......................................................187 Figure 5.16 Selective non-catalytic reduction modeling...............................................188 Figure 5.17 Conceptualized design of MBB thermo-chemical energy conversion system for large free stall dairies or large indoor piggeries with flush waste disposal systems..............................................................................191 Figure 5.18 Mass and energy balance of wastewater in fire-tube boiler.......................195 Figure 5.19 Conceptualized design of MBB thermo-chemical energy conversion system for large feedlot corrals or open lot dairies that produce low moisture manure........................................................................................201 Figure 5.20 Scope of manure-based biomass co-firing economic study.......................203 Figure 5.21 Scope of manure-based biomass reburn economic study..........................204 Figure 5.22 Capital and annual cash flows encountered for manure-based biomass co-fire and reburn operations and retrofit projects....................................216 Figure 5.23 Generating an annual operating income or cost from the addition of individual cash flows for each year in the life of the co-fire or reburn project........................................................................................................217 Figure 5.24 Translation of future capital costs to present dollar values.......................218 Figure 5.25 Integrating capital investment costs with annual operating incomes to generate an overall net present worth of a co-fire or reburn system.........221 Figure 5.26 Generating a overall annualized cost from the net present worth..............222 Figure 6.1 Dryer air flow rate vs. air exit temperature and exit relative humidity at fixed chamber temperature drop, ΔT chamber = 10 K. MBB being dried from 60% to 20% moisture at a rate of 0.56 kg/s (2 metric tons/hour).....227 Figure 6.2 Dryer air flow rate vs. air exit temperature and drying chamber temperature drop at fixed exit relative humidity = 20%. MBB being dried from 60% to 20% moisture at a rate of 0.56 kg/s (2 metric tons/hour)...................................................................................227

xviii Page Figure 6.3 Recycled dryer air flow rate vs. air exit temperature and drying chamber temperature drop at fixed exit relative humidity = 20%. MBB being dried from 60% to 20% moisture at a rate of 0.56 kg/s (2 metric tons/hour)...................................................................................229 Figure 6.4 Dryer heat consumption vs. air exit temperature and exit relative humidity. MBB being dried from 60% to 20% moisture at a rate of 0.56 kg/s (2 metric tons/hour)...................................................................230 Figure 6.5 Dryer heat consumption and air mass flow rate in drying chamber vs. rate of manure-based biomass...................................................................231 Figure 6.6 Comparison of two drying models for perpendicular air flow dryers by monitoring Reynolds number against characteristic biomass particle size and sphericity. Biomass application thickness on conveyor belt = 80 mm.............................................................................................233 Figure 6.7 Comparison of two drying models for perpendicular air flow dryers by monitoring Reynolds number against characteristic biomass particle size and biomass application thickness on conveyor belt.........................235 Figure 6.8 Determination of appropriate manure-based biomass application thickness....................................................................................................236 Figure 6.9 Comparison of fuel consumption between conveyor belt dryer and rotary steam-tube dryer.............................................................................239 Figure 6.10 Temperature of entrained vapor and temperature of biomass solids in the drying zone vs. molar fraction of steam in vapor phase......................240 Figure 6.11 Temperature of entrained vapor vs. characteristic particle size of biomass solids...........................................................................................241 Figure 6.12 The effect of holdup on the slope, biomass residence time, and biomass speed through a rotary steam-tube dryer...................................................242 Figure 6.13 Montone 33.6 m 3 (44 yd 3 ) dump trailer (Montone Trailers, LLC., 2008).243 Figure 6.14 Number of hauling vehicles and hauling weight vs. moisture percentage of transported manure based biomass.......................................................244 Figure 6.15 Total diesel fuel consumption from hauling vehicles vs. moisture percentage of transported manure based biomass.....................................245

xix Page Figure 6.16 Total diesel fuel consumption and number of trucks required vs. biomass transport distance and trailer volume..........................................247 Figure 6.17 Number of trucks required for hauling MBB vs. hauling schedule and annual number of hauling days.................................................................248 Figure 6.18 Flow diagram of computer spreadsheet model for coal/manure-based biomass co-firing system on an exiting coal-fired power plant................249 Figure 6.19 Overall cash flows for the base case run of the manure-based biomass co-fire economics model...........................................................................261 Figure 6.20 Biomass drying and transportation cost and annualized cost/revenue of biomass co-fire system vs. the biomass co-fire rate..................................262 Figure 6.21 Fueling rates for Wyoming sub-bituminous coal and low-ash dairy biomass vs. co-fire rate..............................................................................263 Figure 6.22 Annualized cost/revenue and net present worth vs. year 1 coal price.......264 Figure 6.23 Annualized cost/revenue and net present worth vs. year 1 farmer’s asking price for manure.............................................................................265 Figure 6.24 Annualized cost/revenue and net present worth vs. the value of CO 2 .......266 Figure 6.25 Specific CO 2 reduction cost/revenue vs. the value of CO 2 ........................267 Figure 6.26 Effect of flue gas desulphurization on the annualized cost/revenue of co-firing manure-based biomass with coal................................................268 Figure 6.27 Ash emission vs. co-fire rate when replacing Wyoming sub-bituminous coal with low-ash dairy biomass...............................................................269 Figure 6.28 Ash emission vs. co-fire rate when replacing Texas lignite with low-ash dairy biomass.............................................................................................270 Figure 6.29 Ash emission vs. co-fire rate when replacing Texas lignite with high- ash feedlot biomass...................................................................................270 Figure 6.30 Matching coal-fired power plants and areas with high agricultural biomass densities, adapted from (Virtus Energy Research Associates, 1995) and (Western Region Ash Group, 2006).........................................272

xx Page Figure 6.31 Manure-based biomass co-fire O&M cost components vs. distance between plant and animal feeding operations...........................................273 Figure 6.32 Manure-based biomass co-fire capital cost components vs. distance between plant and animal feeding operations...........................................273 Figure 6.33 Annualized cost/revenue and net present worth vs. manure-based biomass transport distance........................................................................274 Figure 6.34 Annualized cost/revenue vs. natural gas price...........................................275 Figure 6.35 Overall fuel costs for coals and low-ash dairy biomass at different drying requirements...................................................................................276 Figure 6.36 Number of trucks and dryers and manure-based biomass fueling rate vs. power plant capacity..................................................................................277 Figure 6.37 Flow diagram of computer spreadsheet model for reburning coal with manure-based biomass in an exiting coal-fired power plant along with comparisons to SCR and SNCR systems..................................................279 Figure 6.38 Overall cash flows for the base case run of the manure-based biomass reburn economics model...........................................................................285 Figure 6.39 Overall cash flows for the base case run of the SCR economics model....286 Figure 6.40 Drying and transport O&M costs and annualized cost/revenue vs. percentage of plant’s heat rate supplied by manure-based biomass reburn fuel.................................................................................................287 Figure 6.41 Fueling rates of Wyoming sub-bituminous coal and low-ash dairy biomass vs. percentage of plant’s heat rate supplied by the biomass reburn fuel.................................................................................................288 Figure 6.42 Annualized cost/revenue and net present worth of manure-based biomass reburning and SCR vs. coal price................................................288 Figure 6.43 Annualized cost/revenue and net present worth vs. the value of CO 2 .......289 Figure 6.44 Annualized cost/revenue for both MBB reburning and SCR vs. the value of NO x .............................................................................................290 Figure 6.45 Annualized cost/revenue vs. NO x levels achieved by primary NO x

controllers..................................................................................................291

xxi Page Figure 6.46 Specific NO x reduction cost/revenue for manure-based biomass reburning vs. the value of NO x ..................................................................292 Figure 6.47 The effect of sulfur emissions on annualized cost during reburning.........293 Figure 6.48 Ash emission vs. heat rate supplied by biomass reburn fuel for Wyoming sub-bituminous coal being replaced by low-ash dairy biomass......................................................................................................293 Figure 6.49 Annualized cost and net present worth of both reburning and SCR vs. manure-based biomass transport distance.................................................294 Figure 6.50 Number of required trucks and dryers and biomass fueling rate vs. plant capacity......................................................................................................295 Figure 6.51 Sample output from computer spreadsheet model of small-scale on-the- farm manure biomass combustion system................................................298 Figure 6.52 Usable steam produced from combustion system vs. number of animals housed at the feeding operation.................................................................299 Figure 6.53 Usable steam, remaining wastewater, and disposal efficiency vs. moisture percentage of the flushed manure...............................................300 Figure 6.54 Disposal efficiency and steam production vs. moisture content of the separated MBB solids................................................................................301 Figure 6.55 Boiler and disposal efficiency vs. the amount of solids remaining in the wastewater after the solid separator..........................................................302 Figure 6.56 Adiabatic flame temperature and wastewater mass flow vs. moisture percentage of the dried solids....................................................................303 Figure 6.57 Steam production and use vs. moisture percentage of the dried solids.....303 Figure 6.58 Effects of preheating combustion air.........................................................304 Figure 6.59 Boiler efficiency vs. excess air percentage and stack temperature............305 Figure 6.60 Disposal efficiency vs. excess air percentage and stack temperature........306 Figure 6.61 Flame temperature, Steam production, and steam usage vs. ash percentage in the MBB solids...................................................................307

xxii Page Figure 6.62 The effect of ash percentage in the MBB solids on disposal efficiency....307 Figure 6.63 Steam production and disposal efficiency vs. moisture percentage of boiler blow down solids............................................................................309 Figure 6.64 The effect of additional fueling on the disposal efficiency........................310 Figure 6.65 Simple payback period vs. the capital investment of the fire-tube boiler of the small-scale MBB combustion system.............................................314

xxiii LIST OF TABLES Page Table 1.1 Electric coal-fired units, electrical capacity, coal consumption, average coal prices, and average coal heat value in 2006 for each state in the US..11 Table 2.1 Ultimate and heat value analyses of major coals mined in the US (Probsein et al., 2006a)...............................................................................20 Table 2.2 Ultimate, proximate, and heat value analyses of coals modeled in this study (TAMU, 2006)...................................................................................21 Table 2.3 Averaged ultimate, proximate, and heat value analyses of dairy cow feed, as-excreted manure, and aged solids for various dairies in Texas (Mukhtar et al., 2008).................................................................................26 Table 2.4 Averaged ultimate, proximate, and heat value analyses for dairy manure solids collected by various methods for various dairies in Texas (Mukhtar et al., 2008).................................................................................28 Table 2.5 Ultimate and heat value analyses of dairy manure from a dairy in Comanche, Texas (Sweeten and Heflin, 2006)...........................................30 Table 2.6 Measured mean dry particle density for manure-based biomass from various sources............................................................................................34 Table 2.7 Results of sieve analyses of beef cattle manure..........................................39 Table 2.8 Results of sieve analyses for dairy cow manure.........................................40 Table 2.9 Ultimate and heat value analyses of cattle feed ration and feedlot manure from Bushland, Texas....................................................................45 Table 2.10 Ultimate, proximate, and heat value analyses of various hog or swine manures.......................................................................................................49 Table 2.11 Material and thermal balance for anaerobic digestion of cattle manure (adopted from Probstein et al., 2006c)........................................................61 Table 2.12 Reburn systems and experimental results with various reburn fuels..........79 Table 2.13 NO x reduction performance of primary control technology applications on coal-fired boilers (adopted from Srivastava et al., 2005).......................87

xxiv Page Table 3.1 Capital investment costs of installing a biomass co-firing system on an existing coal-fired power plant, taken from various sources......................97 Table 3.2 Capital investment costs of installing a reburning system on an existing coal-fired power plant, taken from various sources..................................100 Table 5.1 Constants for Nusselt number computed in equation (5.83).....................144 Table 5.2 Polynomial equations used to compute specific heats of various species (Annamalai et al., 2006)............................................................................162 Table 5.3 Constants for computing Gibbs free energy, 0 ,,f T i gΔ , in equation (5.162) in kJ/mol, temperature, T, in degrees Kelvin (Probstein et al., 2006b).....170 Table 5.4 Uncontrolled NO x levels for wall and tangentially fired coal-fired power plants, assuming no primary or secondary NO x control technologies are used (USEPA, 2006)......................................................175 Table 5.5 Constants for equation (5.173), used to determine NO x levels, in g/GJ th , attained by primary NO x controls (USEPA, 2006)...................................176 Table 5.6 Cost of primary NO x combustion controls for coal boilers, 300 MW e

size (adopted from USEPA, 2006)............................................................211 Table 5.7 Cost of secondary NO x combustion controls for coal boilers (adopted from USEPA, 2006)..................................................................................211 Table 5.8 MACRS depreciation rates for 5, 10 and 20-year property life classes used for modeling biomass co-fire and reburn systems (adapted from Newnan et al., 2000).................................................................................219 Table 6.1 Empirical constants required for drying constant (k m ) model for perpendicular air flow dryers....................................................................232 Table 6.2 Base case parameters for rotary steam-tube manure-based biomass dryer..........................................................................................................238 Table 6.3 Base case input parameters for coal-fired power plant operating conditions and emissions...........................................................................251 Table 6.4 Base case input parameters for co-firing and SO x controls.......................252 Table 6.5 Base case input parameters for manure-based biomass drying system.....253

xxv Page Table 6.6 Base case input parameters for manure-based biomass transportation system........................................................................................................255 Table 6.7 Base case economics input parameters.....................................................256 Table 6.8 Base case fueling and emissions results for a 300 MW e coal plant operating before any co-firing or reburning system is installed................258 Table 6.9 Base case fueling and emissions results for a 300 MW e coal plant operating while co-firing manure-based biomass (5% by mass)..............259 Table 6.10 Comparison of base case Year 1 costs for power plant operation before and during manure-based biomass co-firing (300 MW e plant, 5% biomass by mass)......................................................................................260 Table 6.11 Additional base case inputs for reburning coal with manure-based biomass......................................................................................................280 Table 6.12 Base case fueling and emissions results for a 300 MW e coal plant operating while reburning coal with manure-based biomass (10% by heat)...........................................................................................................282 Table 6.13 Comparison of base case Year 1 costs of selected NO x control technology arrangements (300 MW e plant, 10% biomass by heat for reburn case)...............................................................................................283 Table 6.14 Base case values for modeling the small-scale on-the-farm MBB combustion system....................................................................................297 Table 6.15 Base case run for the economics of the small-scale MBB combustion system when no additional fuel is burned.................................................312 Table 6.16 Economic results for the small-scale MBB combustion system when additional fuel is used to completely vaporize all waste from the animal feeding operation.......................................................................................313

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Abstract: Manure-based biomass (MBB) has the potential to be a source of green energy at large coal-fired power plants and on smaller-scale combustion systems at or near confined animal feeding operations. Although MBB is a low quality fuel with an inferior heat value compared to coal and other fossil fuels, the concentration of it at large animal feeding operations can make it a viable source of fuel. Mathematical models were developed to portray the economics of co-firing and reburning coal with MBB. A base case run of the co-fire model in which a 95:5 blend of coal to low-ash MBB was burned at an existing 300-MW e coal-fired power plant was found to have an overall net present cost of $22.6 million. The most significant cost that hindered the profitability of the co-fire project was the cost of operating gas boilers for biomass dryers that were required to reduce the MBB's moisture content before transportation and combustion. However, a higher dollar value on avoided nonrenewable CO 2 emissions could overrule exorbitant costs of drying and transporting the MBB to power plants. A CO2 value of $17/metric ton was found to be enough for the MBB co-fire project to reach an economic break-even point. Reburning coal with MBB to reduce NOx emissions can theoretically be more profitable than a co-fire project, due to the value of avoided NO x emissions. However, the issue of finding enough suitable low-ash biomass becomes problematic for reburn systems since the reburn fuel must supply 10 to 25% of the power plant's heat rate in order to achieve the desired NOx level. A NOx emission value over $2500/metric ton would justify installing a MBB reburn system. A base case run of a mathematical model describing a small-scale, on-the-farm MBB combustion system that can completely incinerate high-moisture (over 90%) manure biomass was developed and completed. If all of the energy or steam produced by the MBB combustion system were to bring revenue to the animal feeding operation either by avoided fueling costs or by sales, the conceptualized MBB combustion system has the potential to be a profitable venture. [PUBLICATION ABSTRACT]