ADVANCED HETEROGENEOUS REBURN FUEL FROM COAL AND HOG MANURE

Transcription

1 ADVANCED HETEROGENEOUS REBURN FUEL FROM COAL AND HOG MANURE Final Report (For the period September 24, 2002 September 23, 2003) Prepared for: AAD Document Control U.S. Department of Energy National Energy Technology Laboratory 626 Cochrans Mill Road, MS Pittsburgh, PA Performance Monitor: Andrew O Palko Submitted by: Melanie D. Jensen Ronald C. Timpe Jason D. Laumb September 2003 Award No. DE-FG26-02NT41551 University of North Dakota Energy & Environmental Research Center PO Box 9018 Grand Forks, ND 58202

2 EERC DISCLAIMER LEGAL NOTICE This research report was prepared by the Energy & Environmental Research Center (EERC), an agency of the University of North Dakota, as an account of work sponsored by the U.S. Department of Energy. Because of the research nature of the work performed, neither the EERC nor any of its employees makes any warranty, express or implied, or assumes any legal liability or responsibility for the accuracy, completeness, or usefulness of any information, apparatus, product, or process disclosed, or represents that its use would not infringe privately owned rights. Reference herein to any specific commercial product, process, or service by trade name, trademark, manufacturer, or otherwise does not necessarily constitute or imply its endorsement or recommendation by the EERC. DISCLAIMER This report was prepared as an account of work sponsored by an agency of the United States Government. Neither the United States Government nor any agency thereof, nor any of their employees, makes any warranty, express or implied, or assumes any legal liability or responsibility for the accuracy, completeness, or usefulness of any information, apparatus, product, or process disclosed, or represents that its use would not infringe privately owned rights. Reference herein to any specific commercial product, process, or service by trade name, trademark, manufacturer, or otherwise does not necessarily constitute or imply its endorsement, recommendation, or favoring by the United States Government or any agency thereof. The views and opinions of authors expressed herein do not necessarily state or reflect those of the United States government or any agency thereof.

3 ADVANCED HETEROGENEOUS REBURN FUEL FROM COAL AND HOG MANURE ABSTRACT This study was performed to investigate whether the nitrogen content inherent in hog manure and alkali used as a catalyst during processing could be combined with coal to produce a reburn fuel that would result in advanced reburning NO x control without the addition of either alkali or ammonia/urea. Fresh hog manure was processed in a cold-charge, 1-gal, batch autoclave system at 275 C under a reducing atmosphere in the presence of an alkali catalyst. Instead of the expected organic liquid, the resulting product was a waxy solid material. The waxy nature of the material made size reduction and feeding difficult as the material agglomerated and tended to melt, plugging the feeder. The material was eventually broken up and sized manually and a water-cooled feeder was designed and fabricated. Two reburn tests were performed in a pilot-scale combustor. The first test evaluated a reburn fuel mixture comprising lignite and air-dried, raw hog manure. The second test evaluated a reburn fuel mixture made of lignite and the processed hog manure. Neither reburn fuel reduced NO x levels in the combustor flue gas. Increased slagging and ash deposition were observed during both reburn tests. The material-handling and ash-fouling issues encountered during this study indicate that the use of waste-based reburn fuels could pose practical difficulties in implementation on a larger scale.

4 TABLE OF CONTENTS LIST OF FIGURES... ii LIST OF TABLES... iii INTRODUCTION...1 EXECUTIVE SUMMARY...2 EXPERIMENTAL...3 Feedstocks...3 Equipment...5 Methods...7 Hog Manure Processing...7 Reburn Testing...8 RESULTS AND DISCUSSION...9 Reburn Fuel Production...9 Materials Handling Issues...12 Reburn Tests...13 CONCLUSION...15 REFERENCES...17 i

5 LIST OF FIGURES 1 Schematic of the autoclave system used during hog manure processing Schematic of the CEPS used for the reburn tests Water-cooled probe and feeder used for the reburn fuel Dried raw hog manure Processed hog manure from second test (left), third test (middle), and fourth test (right) 11 6 Flue gas composition during reburn test with lignite dried raw hog manure reburn fuel Flue gas composition during reburn test with lignite-processed hog manure reburn fuel...15 ii

6 LIST OF TABLES 1 Proximate and Ultimate Analyses of Raw Hog Manure and Beulah Lignite Elemental Results of XRFA of Raw Hog Manure Ash Results of XRFA of Beulah Lignite Ash Furnace Conditions During the Reburn Tests Mass Balance Data for the Hog Manure Processing Tests Proximate and Ultimate Analyses of Processed Hog Manure Elemental Results of XRFA of Process Hog Manure Ash Results of Proximate and Ultimate Analyses of Ash Produced During the Reburn Tests Results of XRFA of Ash Produced During the Reburn Tests...17 iii

7 ADVANCED HETEROGENEOUS REBURN FUEL FROM COAL AND HOG MANURE INTRODUCTION A reburn fuel is a prepared fuel used in a combustion system for the purpose of reducing the concentration of NO x in the flue gas. It is introduced downstream of the combustion zone into the fuel-lean section of the boiler. The primary reburn fuel of choice has been natural gas, but other fuels have been examined for this purpose, including biomass, coal pond fines, and Orimulsion. Reburn fuel can also be produced from a renewable feedstock such as hog manure. When properly processed, the protein and cellulosic components in the manure can be converted to an organic material that is sufficiently energy-dense to make its transportation from a farming operation to a coal-fired power plant economically feasible. At a coal combustion site such as a power plant, this processed manure could be mixed with pulverized coal or coal fines in the appropriate proportion to provide a combustible feed with the necessary energy density for reburning. Reburning fuel is typically fed at a rate that provides a heat input of 10% to 20% of the total heat input to the combustor. Maly et al. have shown that reburning can reduce NO x levels by 50% 60% (1). Advanced reburning occurs when alkali and ammonia or urea are introduced with the reburn fuel and can significantly improve NO x control over basic reburning. It is believed that the nitrogen content inherent in hog manure and the alkali used to catalyze its processing could produce a reburn fuel component that would result in advanced reburning NO x control without the addition of either alkali or ammonia/urea. The concept of producing a fuel from manure was investigated by Yokoyama et al. (2) and Itoh et al. (3). During their studies, human sewage sludge was treated under N 2 at temperatures ranging from 250 to 340 C for nominally 60 min in the presence of a sodium carbonate catalyst. Conversions of the sludge to liquid fuel consisting of 40% to 53% of moisture- and ash-free feed were achieved. The product was a heavy oil with a heating value of roughly 35 MJ/kg (about 15,000 Btu/lb). The yield and properties of the heavy oil were found to be strongly dependent on reaction temperature and catalyst loading. Separation of the heavy oil from the aqueous fraction was fairly easily accomplished. The goal of this project was to preliminarily investigate the production of a heterogeneous advanced reburn fuel from processed hog manure and pulverized coal. Following preparation of the reburn fuel, its effectiveness at reducing NO x levels in flue gas was to be evaluated in a pilot-scale combustion unit. Specific project objectives included: Process hog manure to produce an energy-dense material that can be combined with pulverized lignite to form an advanced reburn fuel. Comprehensively analyze the reburn fuel components. Perform two reburn tests to evaluate the NO x removal achieved by reburning. The first test would be performed using a reburn fuel composed of a mixture of coal and raw hog manure to derive a baseline reburn NO x removal level. The second test would be performed using 1

8 a mixture of lignite and the processed hog manure to highlight the NO x -reduction improvements resulting from the hog manure processing. EXECUTIVE SUMMARY A reburn fuel is used in a combustion system for the purpose of reducing the concentration of NO x in the flue gas. It is introduced downstream of the combustion zone into the fuel-lean section of the boiler. Reburning has been shown to reduce NO x levels by 50% 60%, and significantly better NO x control has been achieved with advanced reburning, which occurs when alkali and ammonia or urea are introduced with the reburn fuel. The primary reburn fuel of choice has been natural gas, but other fuels have been examined for this purpose, including biomass, coal pond fines, and Orimulsion. Reburn fuel can also be produced from a renewable feedstock such as hog manure. When properly processed, the protein and cellulosic components in the manure can be converted to an organic material that is sufficiently energy-dense to make its transportation from a farming operation to a coal-fired power plant economically feasible. At a coal combustion site such as a power plant, this processed manure could be mixed with pulverized coal or coal fines to produce a reburn fuel. This study was performed to investigate whether the nitrogen content inherent in hog manure and alkali used as a catalyst during processing could be combined with coal to produce a reburn fuel that would result in advanced reburning NO x control without the addition of either alkali or ammonia/urea. Fresh hog manure was processed in a cold-charge, 1-gal, batch autoclave system at 275 C under a reducing atmosphere in the presence of an alkali catalyst. Instead of the expected organic liquid, the resulting product was a waxy solid material. Three tests were performed in order to produce enough product for characterization and pilot-scale reburn testing. The products from the three tests were combined into a composite sample, which was found to contain 47 wt% volatiles, 7 wt% fixed carbon, and 44 wt% ash. Elemental analysis showed a nitrogen content of 2 wt%. The heating value was found to be about 19,200 kj/kg. Analysis of the composite product ash by x-ray diffraction showed a 12.5 wt% phosphorus content, 22.4 wt% calcium content, and 2 wt% magnesium content. The waxy nature of the material made size reduction difficult. Initial attempts were performed using a hammermill, but some of the material merely agglomerated to form larger waxy lumps. Eventually, the more brittle oversized material was broken up and sized manually using a 1-mm (18-mesh) sieve. Another material-handling issue arose during feeding to the pilot-scale combustor. During feeding tests, it was found that the material was likely to soften as it heated and plug the feeder or port. A water-cooled probe was fabricated and the reburn fuel pneumatically fed through the cooled tube. The size-reduced composite sample of processed hog manure was combined with pulverized Beulah lignite in a 85:15 weight ratio of composite sample to lignite to form the reburn fuel for testing. A second reburn fuel was produced by combining air-dried, size-reduced, raw hog manure 2

9 and lignite in the same proportion. Testing of this reburn fuel provided a comparison to estimate the NO x -reduction improvements that could be obtained by processing the hog manure. Reburn tests were performed in a pilot-scale combustor to determine not only the level of NO x reduction on a more realistic scale than is possible with laboratory- or bench-scale equipment, but also to gain practical information needed for possible scaleup, such as ease of feeding, the occurrence of fouling or slagging, and changes in furnace operating conditions required because of the reburn fuel. Two tests were performed in which the reburn fuel was fed at a rate that provided a heat input equal to about 10% of the total heat input to the combustor. The first was performed with the reburn fuel composed of dried raw hog manure and lignite. During this test, the NO x concentration in the flue gas was not noticeably reduced. The second test was performed using the reburn fuel composed of the composite sample of processed hog manure and lignite. The NO x levels in the flue gas did not change during this test either. Increased slagging and ash deposition were observed during both reburn tests. The deposition was located in both the convective pass and the lower radiant sections of the furnace. The results of this study indicate that fresh hog manure processed in an autoclave system at 275 C under CO and in the presence of an alkali catalyst did not produce a viable reburn fuel, even when combined with lignite. Even if the material had reduced NO x levels in the combustor flue gas, serious material-handling issues (in terms of size reduction and feeding) and increased slagging and ash deposition potential would have required solutions. While the production of viable reburn fuels from animal waste and lignite may be possible, the same difficulties in material handling and ash fouling may occur. Because this type of problem may not be as apparent at a laboratory scale, future studies should include research at a large enough scale to permit adequate evaluation of these potential barriers to practical application. EXPERIMENTAL Feedstocks The coal used in the testing was lignite from the Freedom Mine in western North Dakota. The raw hog manure was procured from EnviroPork, a 5000-sow hog production operation that produces 110,000 piglets each year and is located approximately 30 miles from the Energy & Environmental Research Center (EERC). The manure was less than 24 hrs old when obtained and had not yet entered the sewage treatment process when collected. It is assumed that hog manure from such a large operation will be generally representative of hog manure from other farming locales. Both the lignite and hog manure were characterized by ash, moisture, sulfur, carbon hydrogen nitrogen (CHN), and heat content analyses performed according to the ASTM standards for each. The results are shown in Table 1. Samples of the lignite and hog manure ash also were analyzed using x-ray fluorescence analysis (XRFA) to provide a better understanding of their composition, especially with regard to alkali content. These results are shown in Tables 2 and 3. 3

10 Table 1. Proximate and Ultimate Analyses of Raw Hog Manure and Beulah Lignite Air-Dried Raw Hog Manure Beulah Lignite As-Received Moisture-Free As-Received As-Fed Moisture, wt% 7.22 na a Volatiles, wt% Fixed Carbon, wt% Ash, wt% Carbon, wt% Hydrogen, wt% Nitrogen, wt% Sulfur, wt% Oxygen, wt% b Heating Value, kj/kg c a Not applicable. b By difference. c Not measured. Table 2. Elemental Results of XRFA of Raw Hog Manure Ash Element Raw Hog Manure Ash a Si 4.25 Al 0.05 Fe 1.42 Ti 0.06 P Ca Mg 3.17 Na 1.4 K 2.24 S 0.59 V 0 Ni 0 Ba 0 Sr 0.02 a All values in wt% of ash. 4

11 Table 3. Results of XRFA of Beulah Lignite Ash Oxide Beulah Lignite a Silica, SiO Aluminum Oxide, Al 2 O Ferric Oxide, Fe 2 O Titanium Oxide, TiO Phosphorus Pentoxide, P 2 O 5 0 Calcium Oxide, CaO 19.5 Magnesium Oxide, MgO 7.4 Sodium Oxide, Na 2 O 5.2 Potassium Oxide, K 2 O 0.2 Sulfur Trioxide, SO Vanadium Pentoxide, V 2 O 5 0 Nickel Oxide, NiO 0 Barium Oxide, BaO 0 Strontium Oxide, SrO 0 a All values in wt% oxide on an ash basis. Equipment Processing of the manure fraction of the reburn fuel was carried out in the cold-charge autoclave system at the EERC, which has been described in the literature (4). A schematic of the autoclave system is shown in Figure 1. Reburn testing was performed in the EERC s pilot-scale combustion and environmental processing simulator (CEPS). A schematic of the system is shown in Figure 2. CEPS is designed to topfire nominally 2 kg/hr (4.4 lb/hr) of pulverized coal, although other solid or liquid fuels can be utilized with slight system modifications. A complete description of the CEPS is available on the Internet at Modifications to the CEPS were necessary to facilitate the completion of this project. A provision to inject the reburn fuel approximately 0.46 m (18 in.) below the top of the furnace was added. A 9.52-mm (3/8-in.) water-cooled probe was inserted in the port and connected to a feeder/eductor combination. Cooling of the feed prevented plugging of the feeder because of softening of the reburn fuel. The reburn fuel could then be blown into the CEPS at the appropriate location. The feeder is shown in Figure 3. 5

12 Figure 1. Schematic of the autoclave system used during hog manure processing. Figure 2. Schematic of the CEPS used for the reburn tests. 6

13 Figure 3. Water-cooled probe and feeder used for the reburn fuel. Methods Hog Manure Processing The basic procedure for processing the hog manure for use as a reburn fuel component was as follows. Water was added to bring the hog manure moisture content to 80 wt%, the minimum required for the material to be adequately stirred during processing. Sodium formate was added as a proprietary alkali reaction promoter at a rate of 5 wt% of the moisture- and ash-free (maf) manure. The autoclave was purged with N2 to eliminate any air, and then CO was added at a rate of 10 gmol for each 200 g maf manure. This was done to prevent cracking and the loss of hydrocarbons to the gas phase. While stirring, the cold-charged autoclave was heated at a rate of roughly 8 C per min to the reaction temperature, where it was held for approximately 20 min (this approach was used because prior experience showed that the reactions begin during the heatup phase and that lengthy residence times at the maximum temperature can actually produce undesirable products). Rather than quenching the reaction and losing potentially valuable liquid vapors to the product gas stream, the system was allowed to cool overnight, and the products were collected the next day. Gas produced during the processing was analyzed using gas chromatography analysis. The remaining product was separated into organic and aqueous fractions. The organic fraction was principally solid and was collected by vacuum filtration, air-dried, and stored in a sealed container until particle-size reduction and mixing with coal. The aqueous phase was treated as waste. 7

14 Reburn Testing In preparation for the reburn tests, the processed manure was size-reduced and combined with pulverized Beulah lignite in a weight ratio of roughly 85 wt% processed hog manure to 15 wt% pulverized lignite. It was fed at a rate that provided the equivalent of 10% of the heat input to the combustor. Beulah lignite served as the primary fuel for the reburn tests. The CEPS was operated under standard conditions meant to simulate a full-scale utility boiler. Furnace conditions and feed rates for the tests are presented in Table 4 (note that the Section 4 and 8 thermocouples were malfunctioning during the tests). All of the resulting particulate matter was collected in a baghouse. On-line gas analyzers were used to monitor O 2, CO, CO 2, SO 2, and NO x levels, including both fuel NO x and thermal NO x. Table 4. Furnace Conditions During the Reburn Tests Reburn Test with Dried Raw Manure Reburn Test with Processed Manure Average Coal Feed Rate, kg/hr Average Reburn Fuel Rate, kg/hr , increased to a Furnace Section Temperature, C Temperature, C Preheat Air Secondary Air Section Section Section 4 Open a Open Section Section Section Section Open Thermocouple malfunctioned. 8

15 RESULTS AND DISCUSSION Reburn Fuel Production Four autoclave runs were performed during the course of this research. The first processing test was performed at a reaction temperature of 300 C. The stirrer disconnected during the test and the organic products consisted of a char-like solid and a heavy-oil foam, neither of which were suitable for use as a reburn fuel. The foam, when allowed to stand overnight, resulted in a thin, waxy sheet of material. The foam comprised 88% moisture and 12% other volatiles of which 14 wt% was carbon, 5% hydrogen, 1% nitrogen, and the balance oxygen. When dried, the foam was a dark brown waxy material. The stirrer was repaired, and three additional tests performed to produce a sufficient amount of organic product for analysis and reburn testing. To avoid coking reactions, the reaction temperature for the three production tests was reduced to 275 C. Table 5 presents the mass balance data from all four of the autoclave tests. Mass balances of greater than 90% indicate that all species were sufficiently accounted for and that the products are indeed representative of the reactions that occurred. Table 5. Mass Balance Data for the Hog Manure Processing Tests Autoclave Test Number Feed Material Hog Manure + H 2 O, kg (solids content of manure, kg) (0.277) (0.396) (0.393) (0.401) CO Charged, kg Total Feed Material, kg Product Material Recovered Condensate, kg Foam, kg Residue, kg Product Gas, kg Total Product Recovered, kg Mass Balance, %

16 The product gas was analyzed by gas chromatography and found to contain over 80 mol% CO, 12 to 15 mol% CO 2, and smaller quantities of H 2, N 2, and O 2. Reports from literature and previous EERC experience with biomass processing indicated that a liquid product could be expected as a result of processing the manure (2!4). However, each of the three production runs yielded a predominantly formed product, more waxlike than true solid. Figures 4 and 5 show the dried raw manure and the formed product of the three autoclave production tests, respectively. The manure used in this project was fresh, gathered from the floor of the hog pens rather than partially digested manure from the waste treatment section of the hog production complex. This is thought to be the reason that the conversion of manure to fuel resulted in a formed product rather than a liquid product. The products of the three production tests (Tests 2 through 4) were combined into a composite sample. The results of proximate and ultimate analyses performed on the composite sample of processed material are presented in Table 6. When compared to the raw manure (Table 1), the composite sample can be seen to be enriched in carbon and ash while the concentration of nitrogen, oxygen, and sulfur are decreased from that of the raw manure. As Table 6 shows, the composite material had a heating value of 19,171 kj/kg and a nitrogen content of 2 wt%. These values compare well to those found in the literature for a variety of reburn fuels with heating values ranging from 19,280 to 42,090 kj/kg and nitrogen contents of 0.4% to 1.28 wt% (dry basis) (1). Figure 4. Dried raw hog manure. 10

17 11 Figure 5. Processed hog manure from second test (left), third test (middle), and fourth test (right).

18 Table 6. Proximate and Ultimate Analyses of Processed Hog Manure Composite Sample of Processed Hog Manure As-Received Moisture-Free Moisture, wt% 2.21 na a Volatiles, wt% Fixed Carbon, wt% Ash, wt% Carbon, wt% Hydrogen, wt% Nitrogen, wt% Sulfur, wt% Oxygen, wt% b Heating Value, kj/kg 19,171 c a Not applicable. b By difference. c Not measured. Table 7 presents the results of the XRFA performed on the composite sample ash. The inorganic elemental composition of the raw manure and processed composite sample are similar except for the significantly lower levels of sulfur, sodium, potassium, and magnesium in the processed manure, a benefit to reducing ash fouling and sulfur emissions potentially enhanced by the addition of the reburn fuel. The soluble nature of sodium, potassium, and magnesium suggests that those elements may have partitioned to the water phase and were removed from the formed product during filtration. Materials Handling Issues Owing to the waxy nature of the material, normal means of particle-size reduction, e.g., grinding or milling, were not as effective as expected. While using a hammermill to reduce the particle size of the composite sample, a tarry cylinder formed that jammed the mill. Some of the more friable material passed the mill screen. The remaining material was screened manually, with the more brittle oversized material broken up and forced through the 18-mesh (1-mm) screen. Roughly 14% of the material could not be size-reduced to the necessary size for feeding to the CEPS. The physical nature of the material also contributed to difficulties in feeding the mixture of coal and processed hog manure during the combustion testing. The waxy nature tended to result in softening of the mixture and plugging of the feeder tube. Difficulties were overcome by using an eductor to pneumatically inject the material through a water-cooled feeder with N 2. 12

19 Table 7. Elemental Results of XRFA of Processed Hog Manure Ash Element Processed Hog Manure Ash a Si 3.88 Al 0.11 Fe 1.32 Ti 0.07 P Ca Mg 2.33 Na 0.7 K 0.26 S 0 V 0 Ni 0 Ba 0 Sr 0.02 a All values in wt% of ash. Reburn Tests Two reburn tests were performed. The first test was performed to evaluate the NO x reduction that could be achieved by a wt% mixture of lignite and unprocessed hog manure. A second test was performed with reburn fuel composed of processed hog manure and lignite to permit quantification of the improvements in NO x -reduction ability due to processing the hog manure. The reburn tests were performed in a pilot-scale combustor to determine not only the level of NO x reduction on a more realistic scale than is possible with laboratory- or bench-scale equipment, but also to gain operability information needed for possible scaleup, such as ease of feeding, the occurrence of fouling or slagging, and changes in furnace operating conditions required due to the reburn fuel. Figure 6 shows gas composition data from the test with the reburn fuel containing dried raw hog manure. For ease of viewing, only four gas compositions are shown. The CO level for the run was 45 ppm. Shortly after turning on the reburn feed, the gas-sampling pump overheated and had to be restarted. This can be seen in Figure 6 from approximately 16:00 to 16:16. The NO x concentration for the run ranged from 980 to 1000 ppm. The scatter in the NO x data were similar before and after the reburn fuel was injected. No reduction in the NO x concentration was observed when the reburn fuel containing lignite and dried raw hog manure was fed. 13

20 Figure 6. Flue gas composition during reburn test with lignite dried raw hog manure reburn fuel. Figure 7 plots the gas composition data from the test with the reburn fuel containing processed hog manure. The CO level for this test was 65 ppm. The NO x concentration was highly variable because of inconsistent coal feed rates caused by high relative humidity. The NO x levels varied from 600 to 1000 ppm. The NO x level did not reduce after the reburn fuel containing coal and processed hog manure was injected. Upon observing the lack of reduction in NO x levels, the feed rate of reburn fuel was increased from an average of kg/hr to kg/hr at 14:00. The increased reburn fuel feed rate did not affect the amount of NO x in the exit gas. The ash produced during the reburn tests was analyzed for ash, moisture, sulfur, and CHN contents. Oxygen was determined by difference. Samples of the ashes were also analyzed using XRFA to provide a better understanding of their inorganic composition, especially with regard to alkali content. These results are shown in Tables 8 and 9. Table 8 shows that virtually complete carbon burnout was achieved during the reburn tests. Combustor ash trapped significantly more sulfur than baghouse, ash and that of the processed hog manure trapped 1.6 times as much as that of the raw manure. Table 9 shows that the ash produced from the test of the lignite raw hog manure reburn fuel contained more silicon, magnesium, and potassium and less calcium than the ash produced during the reburn test using lignite processed hog manure reburn fuel. Processing the hog manure increased calcium concentration and decreased potassium concentration in the ash, which should have a positive effect on reducing fouling. The effect of processing on sodium content in ash was inconclusive. Increased slagging and ash deposition were observed during both reburn tests. The deposition was located in both the convective pass and the lower radiant section. 14

21 Figure 7. Flue gas composition during reburn test with lignite processed hog manure reburn fuel. CONCLUSION When fresh hog manure was processed at elevated temperatures under a reducing atmosphere in the presence of an alkali catalyst, the resulting product was not the expected liquid, but was instead a waxy solid material. The fact that fresh manure (rather than partially digested from treatment ponds) was used in this project is thought to be the reason that the formed, waxy solid was produced instead of a liquid. The form of the product created materials-handling issues in terms of size reduction methods and techniques for feeding it into the combustor. When combined with lignite, the resulting heterogeneous reburn fuel did not reduce NO x levels in the flue gas and, in fact, resulted in increased slagging and ash deposition in the pilot-scale combustor. The results of this study indicate that during additional development of reburn fuels from animal waste, other practical issues should be considered and addressed in addition to the reduction of NO x levels. Other animal wastes, when processed according to other methods, may produce reburn fuels that reduce NO x levels. Researchers should make use of appropriately sized equipment so that they can adequately consider and address materials-handling and slagging and ash deposition issues that may arise because of the use of waste-based reburn fuels. 15

22 Table 8. Results of Proximate and Ultimate Analyses of Ash Produced During the Reburn Tests Lignite Raw Hog Manure Reburn Fuel Lignite Processed Hog Manure Reburn Fuel Combustor Ash Baghouse Ash Combustor Ash Baghouse Ash AR a MF b AR MF AR MF AR MF Moisture, wt% 0.08 c Volatiles, wt% Fixed Carbon, wt% Ash, wt% Carbon, wt% Hydrogen, wt% Nitrogen, wt% Sulfur, wt% b Oxygen, wt% d As-received. Moisture-free. Not applicable. d By difference. a c 16

23 Table 9. Results of XRFA of Ash Produced During the Reburn Tests a Baghouse Ash Convective Pass/Combustor Ash Element Raw Manure Fuel Processed Manure Fuel Raw Manure Fuel Processed Manure Fuel a Si Al Fe Ti P Ca Mg Na K S V Ni Ba Sr All values in wt% of ash. REFERENCES 1. Maly, P.M. et al. Alternative Fuel Reburning. Fuel 78, 1999, Yokoyama, S. et al. Liquid Fuel Production from Sewage Sludge by Catalytic Conversion Using Sodium Carbonate. Fuel 66, 1987, Itoh, S. et al. Direct Thermochemical Liquefaction of Sewage Sludge by a Continuous Plant. Wat. Sci. Tech. 26, 1992, Timpe, R.C.; Hetland, M.D. Low-Intensity Treatment of Low-Rank Coals, Lignin Waste, and/or Other Biomass to Obtain Liquid Fuel and Products of Added Value; Final Report (April 1, June, 30, 2001) for U.S. Department of Energy Contract No. DE-FC26-98FT40320; EERC Publication 2001-EERC-06-02; Energy & Environmental Research Center. Grand Forks, ND, April