Powder River Basin Subbituminous Coal Research Articles

Coal Chemical-Looping with Oxygen Uncoupling (CLOU) Using a Cu-Based Oxygen Carrier Derived from Natural Minerals

Chemical-looping with oxygen uncoupling (CLOU) is considered a promising technology to burn solid fuels with improved CO2 capture and has the potential to improve fuel conversion and reaction rates. Cu-based oxygen carriers (Cu-OC) are often used in solid fuel CLOU. This study focused on investigating Cu-OC derived from a natural mineral for solid fuel CLOU because of their potentially lower cost compared to synthetic OCs. Reactivity and recyclability of a natural ore-derived Cu-OC on coal char (Powder River Basin sub-bituminous coal) were studied at 900 °C in Ar and air using TGA-QMS and fixed-bed reactor-QMS for five cycles. Cu-OC was prepared by simply heating chalcopyrite in air. Chalcopyrite is one of the principle copper sulfide ores and one of the primary ores for copper. The prepared Cu-OC had primarily CuO and CuFe2O4 (CuOFe2O3) as active compounds based on XRD analysis and an oxygen capacity 3.3% from oxygen uncoupling. The carbon conversion efficiency Xc was 0.94 for reduction at a ratio of Cu-OC to char ϕ = 75 and the product gas was primarily CO2 with trace O2. The reactivities and the rates were similar for five redox cycles. These results indicate that the natural ore-derived material with low cost has potential as a competitive oxygen carrier in solid fuel CLOU based on its reactivity in this study.

Evolution of Fly Ash Aluminosilicates in Slagging Deposition during Oxy-Coal Combustion Investigated by 27Al Magic Angle Spinning Nuclear Magnetic Resonance

Boiler slagging jeopardizes the safe and economic operation of coal-fired boilers. Aluminosilicates are the most abundant substances in fly ash and boiler slagging deposits. In order to understand the roles of the fly ash aluminosilicates in slagging, studying their evolution in the ash deposition is invaluable. In this work, 27Al magic angle spinning nuclear magnetic resonance (MAS-NMR) and X-ray diffraction were used to measure the aluminum coordination and the phase distribution in fly ash and ash deposit samples of two USA thermal coals [Powder River Basin (PRB) sub-bituminous coal and Illinois coal] and their blended coal prepared in an oxy-coal combustion experiment apparatus. Morphology and constituents of these samples were also analyzed using scanning electronic microscopy. The results show that, for all fly ashes and ash deposits, the aluminum exists only in aluminosilicates and is mainly four-coordinate aluminum [Al(IV)], with a small amount in six-coordinate aluminum Al(VI) (chemical shift: 2....

Enhanced production of secondary biogenic coalbed natural gas from a subbituminous coal treated by hydrogen peroxide and its geochemical and microbiological analyses

Unmineable coal accounts for over 90% of the world’s fossil fuel resources. Fortunately, many coal seams contain indigenous microorganisms capable of utilizing the coal as a carbon source to produce secondary biogenic coalbed natural gas. However, coal bioavailability has been shown to be a significant factor that limits the extent of bioconversion. In this study, we have analyzed the rate and yield of the biogas production and assessed the gas potential, carbon balance, stable carbon isotopes, microbial communities, and microbial pathways changes resulting from the hydrogen peroxide pretreatment with the Wyoming’s Powder River Basin subbituminous coal. The results showed that coal pretreated with hydrogen peroxide can significantly enhance the bioavailability of coal for enhancing the biogas production, with a peak yield of 552.6 μmol/g coal (437.1 Scf/ton coal) at the day 184. The stable carbon isotopic analysis indicated that the δ13C values of the methane and carbon dioxide were much less negative than the published field data. This suggested that the enrichment or depletion of the precursor 13C could contribute to the shift of the carbon isotopic composition in the subsequence processes. Therefore, the data should be used with cautions for interpreting genesis of the thermogenic/biogenic methane and the methanogenic pathways. The methanogenic pathways were also investigated with re-fed experiment and microbial community analysis. The results indicated that the hydrogenotrophic pathway was not active in the original inoculum became activated after the gas production. The microbial community analysis demonstrated that the obligate hydrogenotrophic methanobacterium was the most dominant methanogens in the microcosms after the gas production. This suggested that the chemical treatment of coal has impacts on the microbial structure during the subsequent methane production phase.

Mild degradation of Powder River Basin sub-bituminous coal in environmentally benign supercritical CO2-ethanol system to produce valuable high-yield liquid tar

A novel and environmentally benign binary supercritical fluid system, comprised of supercritical CO2 and ethanol (SCCO2-ethanol), was employed to convert coal, a conventional energy resource, into high-value liquid tar which can be used as feedstock for the production of fuels/chemicals and carbon fibers. The SCCO2-ethanol system shows good performance for producing valuable liquid tar in high yield from Powder River Basin sub-bituminous coal. The results show that the highest yield of liquid tar reaches up to approximate 38 wt% (38 g/100 g raw coal) at 350 °C, and that SCCO2 can promote the liquid tar yield by 5.6 wt% compared to that using pure ethanol due to the synergistic effect between ethanol and SCCO2. The liquid tars are better candidates as clean fuels than the raw coal or even bituminous coal due to their higher heating values and almost free from ash. The liquid tars from degradation in SCCO2-ethanol (liquid tarSCCO2-ethanol) and in ethanol without SCCO2 (liquid tarethanol) at 350 °C were characterized with multiple analytical techniques. Fourier transform infrared analyses indicated that both liquid tars have similar distributions of functional groups. The proportion of volatile and small-molecular species in liquid tarSCCO2-ethanol is higher than liquid tarethanol according to thermogravimetric analysis. Further, gas chromatograph/mass spectrometry analyses show that phenols and aliphatic esters are the dominant volatile compounds in both liquid tars. The 1H and 13C nuclear magnetic resonance analyses reveal that both liquid tars have low aromaticity and liquid tarSCCO2-ethanol contains more aromatic carbons than liquid tarethanol, especially highly condensed aromatic carbons. Methylene and aliphatic and aromatic CH3 are the major aliphatic moieties in both liquid tars. The liquid tars can be separated into light oil and asphaltene fractions by extraction with n-heptane. In addition, the asphaltene fraction has potential to be used as the precursor for fabricating carbon nanofibers via electrospinning. Possible mechanisms for releasing volatile compounds and asphaltene from Powder River Basin sub-bituminous coal by SCCO2-ethanol degradation were also discussed.

Pulverized coal particle ignition in a combustion environment with a reducing-to-oxidizing transition

A reducing-to-oxidizing (RO) environment is characteristic of what a coal particle experiences in the near-burner region of pulverized coal (pc) furnaces. The RO environment can influence early-stage coal combustion processes such as ignition, aerosol formation, and char burnout. However, fundamental studies have focused on either oxidizing conditions (mimicking the post-flame region) or reducing conditions (mimicking the devolatilization region). The effect of this RO environment on early-stage coal combustion has, until now, not been considered. Here, the role of this reducing-to-oxidizing environment on single-particle ignition is evaluated. Powder River Basin (PRB) sub-bituminous coal was used, with a particle size of 125–149 μm and two nominal gas temperatures of 1300 K and 1800 K. The experimental findings for purely-oxidizing conditions with 20 vol% oxygen are compared with those of reducing-to-oxidizing environment. Single particles were tracked using high speed, high resolution videography. Emission intensities of the particles were used to evaluate the prevailing ignition modes, and to determine the characteristic ignition and induction times in both oxidizing and reducing-to-oxidizing environments. Experimental findings show that homogeneous-to-heterogeneous mode of ignition is prevalent for purely oxidizing conditions for both nominal gas temperatures of 1300 K and 1800 K. However, hetero-homogeneous ignition is favored in reducing-to-oxidizing environment at 1800 K and heterogeneous ignition at 1300 K gas flame temperature. The reducing-to-oxidizing environment leads to longer ignition delay times of about 20% and 40% on average for 1300 K and 1800 K nominal gas temperatures respectively but shorter induction times than those of oxidizing condition. The results show that ignition behavior in a reducing-to-oxidizing post-flame environments can be quite different from those in oxidizing environments.

Observations and Assessment of Fly Ashes from High-Sulfur Bituminous Coals and Blends of High-Sulfur Bituminous and Subbituminous Coals: Environmental Processes Recorded at the Macro- and Nanometer Scale

Fly ash was investigated with a variety of chemical, mineralogical, petrographic, and microbeam techniques from three coal-fired units at two Kentucky power plants. Two units burn high-sulfur Illinois Basin high volatile bituminous (hvb) coal, and the third unit burns a ∼70:30 blend of high-sulfur Illinois Basin hvb coal and low-sulfur, relatively high-CaO Powder River Basin subbituminous coal. With high-S, high-Fe coals in all of the blends, spinel (magnetite) is an important constituent in the fly ashes. Overall, the fly ashes are dominated by glass. Portlandite was noted in the high-Ca-coal-derived ash. Concentrations of Ba and Sr are highest in the latter fly ash, a function of the Powder River Basin coal source for a portion of the blend. Rare earth elements do not have a high concentration in any of the fly ashes and do not show any significant partitioning between the electrostatic precipitator (ESP) or baghouse rows in the individual generating units. In contrast to previously studied fly ashes fr...

Selecting and implementing a fuel blend for scrubbed units at a pulverized coal power plant

The DTE Power Plant includes four boilers, each generating up to 5.7millionlbs/h of supercritical steam, and each supporting the generation of up to 800MWe (net) of electricity. At the time of the testing two units were equipped with both scrubber and selective catalytic reduction systems in addition to electrostatic precipitators. Over a two year period, the Plant modeled and tested a wide variety of fuels and fuel combinations with a base fuel of Wyoming Powder River Basin (PRB) subbituminous coal and Central Appalachian bituminous coal. Fuels incorporated into the blend included petroleum coke, northern PRB subbituminous coal, and northern Appalachian bituminous coal. Various blend combinations were considered and/or tested. Operation with 100% PRB was also tested. The objective was to optimize the fuel blend from both technical and economic perspectives. The blend proven to be optimal from both technical and economic perspectives included 10% petroleum coke with PRB coal and, as necessary, Central Appalachian coal. This blend was implemented.

Detection of rare earth elements in Powder River Basin sub-bituminous coal ash using laser-induced breakdown spectroscopy (LIBS)

We reported our preliminary results on the use of laser-induced breakdown spectroscopy to analyze the rare earth elements contained in ash samples from Powder River Basin sub-bituminous coal (PRB-coal). We have identified many elements in the lanthanide series (cerium, europium, holmium, lanthanum, lutetium, praseodymium, promethium, samarium, terbium, ytterbium) and some elements in the actinide series (actinium, thorium, uranium, plutonium, berkelium, californium) in the ash samples. In addition, various metals were also seen to present in the ash samples.

Depolymerization and solubilization of chemically pretreated powder river basin subbituminous coal by manganese peroxidase (MnP) from Bjerkandera adusta

This study evaluated the influence of four chemical pretreatment agents (HNO3, catalyzed H2O2, KMnO4, NaOH) on the subsequent enzymatic conversion of subbituminous coal by a fungal manganese peroxidase (MnP) produced by the agaric white-rot fungus Bjerkandera adusta. The effects of the combined chemical and enzymatic treatments were analyzed by high performance size exclusion chromatography (HPSEC) and 3-dimensional excitation emission matrix fluorescence spectroscopy (3D-EEM). The nature of pretreatment agents and their applied concentrations had significant impacts on subsequent enzymatic conversion of coal. The 3D-EEM spectroscopic analysis provided new insight into the nature of the depolymerized and released coal constituents. Using the fluorescence spectra, it was possible to distinguish among humic-like, fulvic acid-like, protein-like, and aromatic/PAH-like substances. The fungal enzyme MnP had little effect on the untreated coal controls. Nitric acid (HNO3) was the most effective pretreatment agent as indicated by the HPSEC profiles, followed by catalyzed H2O2 and KMnO4. Low molecular weight aromatic fragments with sizes ranging from 1.1 to 6.2kDa were released by all of the pretreatment agents used in combination with MnP. For KMnO4 and HNO3 pretreated coal, all four EEM regions increased after MnP treatment (for example, 307.5/422nm and 232.5/426nm, and 340/448nm and 242.5/484nm for humic and fulvic acid-like fragments, respectively).

Co-pyrolysis of low rank coals and biomass: Product distributions

Pyrolysis and gasification of combined low rank coal and biomass feeds are the subject of much study in an effort to mitigate the production of green house gases from integrated gasification combined cycle (IGCC) systems. While co-feeding has the potential to reduce the net carbon footprint of commercial gasification operations, success of this strategy requires investigation of the effects of coal/biomass co-feeding on reaction kinetics and product distributions. Southern yellow pine was pyrolyzed in a semi-batch type drop tube reactor with either Powder River Basin sub-bituminous coal or Mississippi lignite at several temperatures and feed ratios. Product gas composition of expected primary constituents (CO, CO2, CH4, H2, H2O, and C2H4) was determined by in situ mass spectrometry while minor gaseous constituents were determined using a GC–MS. Product distributions are fit to linear functions of temperature, and quadratic functions of biomass fraction, for use in computational co-pyrolysis simulations.The results are shown to yield significant nonlinearities, particularly at higher temperatures and for lower ranked coals. The co-pyrolysis product distributions evolve more tar, and less char, CH4, and C2H4, than an additive pyrolysis process would suggest. For lignite co-pyrolysis, CO and H2 production are also reduced. The data suggests that rapid pyrolysis of biomass produces hydrogen that stabilizes large radical structures generated during the early stages of coal pyrolysis. Stabilization causes these structures to be released as tar, rather than crosslinking with one another to produce secondary char and light gases. Finally, it is shown that, for the two coal types tested, co-pyrolysis synergies are more significant as coal rank decreases, likely because the initial structure in these coals contains larger pores and smaller clusters of aromatic structures which are more readily retained as tar in rapid co-pyrolysis.

On the use of single-film models to describe the oxy-fuel combustion of pulverized coal char

Computational fluid dynamic (CFD) simulations traditionally rely on the computational efficiency of single-film global kinetic oxidation models to predict char particle temperatures and char conversion rates in pulverized coal boilers. In oxy-fuel combustion with flue gas recirculation (FGR), as is commonly employed, char combustion occurs in the presence of elevated CO2 levels and, frequently, elevated water vapor levels (when employing wet FGR). Furthermore, local oxygen concentrations can be quite high in the vicinity of oxygen injection lances. The suitability of existing approaches to modeling char combustion under these conditions has been unclear. In particular, our previous work has shown that both boundary layer conversion of CO and gasification reactions of steam and CO2 need to be included to give reasonable agreement with the experimental measurements, for particles over 60μm in size. In this paper, we report on the development and application of an extended single-film reaction model that includes both oxidation and gasification reactions. We have systematically interrogated the performance of the model in comparison to experimental data for two US coals (a Powder River Basin subbituminous coal and a low-sulfur, high-volatile bituminous coal) for a variety of model assumptions. While the extended single-film model does not give perfect agreement with the data, reasonably good agreement is achieved for high-temperature environments with 12–36vol.% O2 and 16vol.% H2O in either N2 or CO2 diluent. The analysis shows that, to achieve such agreement with the data while maintaining reasonable values for activation energy of the reactions, incorporation of both steam and CO2 gasification reactions is required.

Thermal Behavior of Coal and Biomass Blends in Inert and Oxidizing Gaseous Environments

Oxy-fuel combustion and gasification (pre-combustion) may have potential for capturing carbon dioxide at lower costs for power generation. Oxy-co-firing and co-gasifying coal with biomass could further reduce effective CO2 emissions and utilize renewable energy resources. A key feature of these two approaches is that they process fuel in concentrated CO2 or O2/CO2 instead of N2 or O2/N2. Accurate predictive models of these processes using blends of coal and biomass can be used in process simulation and could aid in the development and implementation of these technologies. To develop these accurate predictive models, it is important to understand the conversion routes and thermal behavior of these fuels in appropriate gas environments. The objectives of this study are to investigate the impact of inert and oxidative gaseous environments on thermal behavior and reactivity of coal and biomass blends and to study the effect of biomass percentage on coal/biomass blend co-utilization. Fuel samples included a Powder River Basin (PRB) sub-bituminous coal, yellow pine wood sawdust pellets, and mixtures of 10 and 20 weight percent wood in coal. The samples were tested under N2, CO2, and 10% O2 in CO2 by volume using a non-isothermal thermogravimetric method for temperatures up to 1000℃. Fuel weight losses of both coal and wood are essentially the same in CO2 as in N2 in the low temperature range, but higher in 10% O2 in CO2 compared to N2 and CO2. However, total weight losses at 1000℃ under CO2 and 10% O2 in CO2 are similar and higher than in N2 due to char gasification by the CO2 and combustion by O2. The char combustion in 10% O2 in CO2 takes place at lower temperature than char gasification in CO2. Coal and wood blends have higher reactivity compared to coal alone in the lower temperature range due to the high volatile matter content of wood. Interactions of wood and coal in these gas environments and blend percentage are discussed.

High-resolution X-ray computed tomography observations of the thermal drying of lump-sized subbituminous coal

Drying of low-rank coals affects: coal cleaning, combustion, comminution, gasification, liquefaction, and in-seam fluid-flow (water, coalbed methane, and carbon dioxide for sequestration/enhanced coalbed methane). To evaluate the extent of drying-induced transitions, 3 lump-sized (approximately 6 × 2 × 2 cm) Powder River Basin subbituminous coal samples were thermally dried in an air-drying coal oven at 50 °C over two weeks. A high-resolution industrial X-ray computed tomography scanner was utilized to generate (non-destructively) three-dimensional regional volumetric renderings, as-received and over 3-stages of drying. The lumps had cleats, both open and mineral filled, with a degree of fracture diversity along the longitudinal plane. Comparison of the virtual slice surfaces, at identifiable locations, allowed the induced cracking and shrinkage accompanying the transitions during 19% moisture loss to almost dry to be observed. Under these drying conditions, the heat transfer, and thus extent of drying, proceeded radially inward. With increased drying time the fractures extend and become larger in aperture as the coal shrinks. The major fractures mostly followed the existing cleat system. With additional drying, these cleats widened and the aperture increase propagated deeper into the coal extended into the butt cleats. New fractures were located mostly perpendicular to the cleat fracture surface. The external volume of the coal lumps had limited shrinkage. The axial extent of the shrinkage length (lump edge to lump edge) was on the order of 4–6%, the bulk of the shrinkage being accommodated by the internal shrinkage between cleats.

Energy Recycling by Co-Combustion of Coal and Recovered Paint Solids from Automobile Paint Operations

Experiments were carried out in a pilot-scale pulverized coal combustor at the Energy and Environmental Research Center (EERC) burning a Powder River Basin (PRB) subbituminous coal. A scanning mobility particle sizer (SMPS) and an electrical low-pressure impactor (ELPI) were used to measure the particle size distributions (PSDs) in the range of 17 nm to 10 μm at the inlet and outlet of the electrostatic precipitator (ESP). At the ESP inlet, a high number concentration of ultrafine particles was found, with the peak at approximately 75 nm. A trimodal PSD for mass concentration was observed with the modes at approximately 80-100 nm, 1-2 μm, and 10 μm. The penetration of ultrafine particles through the ESP increased dramatically as particle size decreased below 70 nm, attributable to insufficient or partial charging of the ultrafine particles. Injection of nanostructured fine-particle sorbents for capture of toxic metals in the flue gas caused high penetration of the ultrafine particles through the ESP. The conventional ESP was modified to enhance charging using soft X-ray irradiation. A slipstream of flue gas was introduced from the pilot-scale facility and passed through this modified ESP. Enhancement of particle capture was observed with the soft X-ray irradiation when moderate voltages were used in the ESP, indicating more efficient charging of fine particles.

Particle imaging of ignition and devolatilization of pulverized coal during oxy-fuel combustion

Oxy-fuel combustion of coal is a promising technology for cost-effective power production with carbon capture and sequestration that has ancillary benefits of emission reductions and lower flue gas cleanup costs. To fully understand the results of pilot-scale tests of oxy-fuel combustion and to accurately predict scale-up performance through CFD modeling, fundamental data are needed concerning coal and coal char combustion properties under these unconventional conditions. In the work reported here, the ignition and devolatilization characteristics of both a high-volatile bituminous coal and a Powder River Basin subbituminous coal were analyzed in detail through single-particle imaging at a gas temperature of 1700 K over a range of 12–36 vol % O 2 in both N 2 and CO 2 diluent gases. The bituminous coal images show large, hot soot cloud radiation whose size and shape vary with oxygen concentration and, to a lesser extent, with the use of N 2 versus CO 2 diluent gas. Subbituminous coal images show cooler, smaller emission signals during devolatilization that have the same characteristic size as the coal particles introduced into the flow (nominally 100 μm). The measurements also demonstrate that the use of CO 2 diluent retards the onset of ignition and increases the duration of devolatilization, once initiated. For a given diluent gas, a higher oxygen concentration yields shorter ignition delay and devolatilization times. The effect of CO 2 on coal particle ignition is explained by its higher molar specific heat and its tendency to reduce the local radical pool. The effect of O 2 on coal particle ignition results from its effect on the local mixture reactivity. CO 2 decreases the rate of devolatilization because of the lower mass diffusivity of volatiles in CO 2 mixtures, whereas higher O 2 concentrations increase the mass flux of oxygen to the volatiles flame and thereby increase the rate of devolatilization.

Managing slagging at Monroe Power Plant using on-line coal analysis and fuel blending

Monroe Power Plant of DTE Energy is a 3100 MW (net) station in southeastern Michigan. This station consists of four Babcock & Wilcox wall-fired boilers firing blends of southern Powder River Basin (PRB) subbituminous coal along with Central Appalachian bituminous coals. The station manages the coal properties in the various fuel blends using an on-line analyzer. This analyzer measures the complete proximate analysis, the heating value, and the ash chemistry of the coal being loaded into the silos. The on-line analyzer program has been used to control the slagging properties of the coal being burned, with the result being a dramatic reduction in costly slagging incidents at the plant. The on-line analyzer is used to guide modifications to the blend; it is also used to provide guidance to operators concerning the fuel being fed to pulverizers and burners. This paper describes this effort in the context of an overall combustion program and it details the results of that program.

Pilot-Scale Study of the Effect of Selective Catalytic Reduction Catalyst on Mercury Speciation in Illinois and Powder River Basin Coal Combustion Flue Gases

A study was conducted to investigate the effect of selective catalytic reduction (SCR) catalyst on mercury (Hg) speciation in bituminous and subbituminous coal combustion flue gases. Three different Illinois Basin bituminous coals (from high to low sulfur [S] and chlorine [Cl]) and one Powder River Basin (PRB) subbituminous coal with very low S and very low Cl were tested in a pilot-scale combustor equipped with an SCR reactor for controlling nitrogen oxides (NOx) emissions. The SCR catalyst induced high oxidation of elemental Hg (Hg0), decreasing the percentage of Hg0 at the outlet of the SCR to values <12% for the three Illinois coal tests. The PRB coal test indicated a low oxidation of Hg0 by the SCR catalyst, with the percentage of Hg0 decreasing from ∼96% at the inlet of the reactor to ∼80% at the outlet. The low Cl content of the PRB coal and corresponding low level of available flue gas Cl species were believed to be responsible for low SCR Hg oxidation for this coal type. The test results indicated a strong effect of coal type on the extent of Hg oxidation.

Chemistry and petrology of fly ash derived from the co-combustion of western United States coal and tire-derived fuel

Inorganic ash chemistry and petrology was investigated in coal-combustion by-products from the burning of tire-derived fuel (TDF) with a 1:1 blend of Colorado and Utah high volatile C bituminous coal and Powder River Basin subbituminous coal. Both coal components had high vitrinite contents. With the exception of Sr and Ba, the trace-element contents of the coals were not high. The fly ash was enriched in Zn, known to be a constituent of both the rubber and the wire in tires. Cu, also a constituent of the brass coatings of bead wire, was enriched in the same fractions with high Zn concentrations. Zn and Cu, along with several other elements, increased in concentration in the back, cooler row of the electrostatic precipitator. The enrichment of other elements, such as Se, As, and Pb, was more problematical. It is possible that the latter elements have more of a coal source than a tire source.

Advanced high-temperature, high-pressure transport reactor gasification

The U.S. Department of Energy (DOE) National Energy Technology Laboratory Office of Coal and Environmental Systems has as its mission to develop advanced gasification-based technologies for affordable, efficient, zero-emission power generation. These advanced power systems, which are expected to produce near-zero pollutants, are an integral part of DOE's Vision 21 Program. DOE has also been developing advanced gasification systems that lower the capital and operating costs of producing syngas for chemical production. A transport reactor has shown potential to be a low-cost syngas producer compared to other gasification systems since its high-throughput-per-unit cross-sectional area reduces capital costs. This work directly supports the Power Systems Development Facility utilizing the KBR transport reactor located at the Southern Company Services Wilsonville, Alabama, site. Over 2800 hours of operation on 11 different coals ranging from bituminous to lignite along with a petroleum coke has been completed to date in the pilot-scale transport reactor development unit (TRDU) at the Energy & Environmental Research Center (EERC). The EERC has established an extensive database on the operation of these various fuels in both air-blown and oxygen-blown modes utilizing a pilot-scale transport reactor gasifier. This database has been useful in determining the effectiveness of design changes on an advanced transport reactor gasifier and for determining the performance of various feedstocks in a transport reactor. The effects of different fuel types on both gasifier performance and the operation of the hot-gas filter system have been determined. It has been demonstrated that corrected fuel gas heating values ranging from 90 to 130 Btu/scf have been achieved in air-blown mode, while heating values up to 230 Btu/scf on a dry basis have been achieved in oxygen-blown mode. Carbon conversions up to 95% have also been obtained and are highly dependent on the oxygen-coal ratio. Higher-reactivity (low-rank) coals appear to perform better in a transport reactor than the less reactive bituminous coals. Factors that affect TRDU product gas quality appear to be coal type, temperature, and air/coal ratios. Testing with a higher-ash, high-moisture, low-rank coal from the Red Hills Mine of the Mississippi Lignite Mining Company has recently been completed. Testing with the lignite coal generated a fuel gas with acceptable heating value and a high carbon conversion, although some drying of the high-moisture lignite was required before coal-feeding problems were resolved. No ash deposition or bed material agglomeration issues were encountered with this fuel. In order to better understand the coal devolatilization and cracking chemistry occurring in the riser of the transport reactor, gas and solid sampling directly from the riser and the filter outlet has been accomplished. This was done using a baseline Powder River Basin subbituminous coal from the Peabody Energy North Antelope Rochelle Mine near Gillette, Wyoming.

99/00391 Characterization of hot-gas filter ash under PFBC operating conditions

The objective of this program was to perform bench scale dynamic tests of ash formation and long-term ash cake formation in pressurized fluidized bed combustion (PFBC) systems to help in the development of methods to predict possible filter bridging problems and suggest possible strategies for mitigating these problems. During the program, four ash formation tests using a washed coal from the Consol Enlow Fork mine, with two size distributions of Plum Run dolomite at two different temperatures, were completed under conditions simulating the operation of the American Electric Power (AEP) Tidd PFBC. In addition, the same test matrix, plus two tests using no sorbent, was completed with the Belle Ayr Powder River Basin sub-bituminous coal, which will be used at the Southern Company Services (SCS) Wilsonville, Alabama, power systems development facility (PSDF).