Illinois Coal Research Articles

Islands in the Beans: Diversity of Ground Beetles (Coleoptera: Carabidae) Inhabiting West-Central Illinois Coal Mine Remnants

American Entomologist • Winter 2005 Ground beetles (Coleoptera: Carabidae) are common in North American agricultural fields, and can play a beneficial role in suppressing pest insects in these environments (Thiele 1977, Lovei and Sunderland 1996). Ground beetles are also important as bioindicators of habitat conditions, and often have close associations with such environmental variables as soil type, vegetation cover, and microclimate (Niemela et al. 1992). All of these characteristics come into play in the midwestern United States, where agricultural activities dominate much of the landscape and alternative habitats are patchy in nature. In west-central Illinois, coal mine remnants represent distinct habitats within agricultural fields (Murray 1998). Shaft mining was a major industry in this region from the middle 1800s until about 1920, when strip mining became more economically advantageous (Hallwas 1984). Most mines disappeared from the area by 1930, and all were closed by 1960. The shafts were abandoned and filled with refuse and dirt (Monteith 1976). In most cases, the surrounding lands were cultivated. Secondary succession associated with these mine remnants produced patches of habitat diversity in a sea of monocultural cropland (Fig. 1). We undertook a study of the ground beetles inhabiting these coal mine remnants. Our goals were to compare the species diversity among coal mine remnants and surrounding agricultural fields and to identify members of the community that could serve as indicators of the different habitats.

STEEL BELT FILTER: A SUITABLE TECHNOLOGY FOR DEWATERING FINE CLEAN COAL AND TAILINGS

ABSTRACT Many coal preparation plants in the United States continue to discard the minus 150 micron size fraction of their run-of-mine coal without any attempt to recover the clean coal content of this size fraction. This undesirable practice is partly caused by a variety of deficiencies with existing fine coal dewatering technologies, such as high moisture content of the product, loss of significant amounts of ultra-fine clean coal, high capital/operating costs, and operational unfriendliness. This study investigated the suitability of a newly developed fine particle dewatering technology, known as Steel Belt Filter (SBF), for dewatering both fine clean coal and fine tailings materials generated at coal preparation plants in the United States. The unique feature of this new technology is the combined use of mechanical pressure and suction force (vacuum), a combination which is known to provide excellent dewatering performance. A SBF prototype unit having a belt width of 0.6 m was tested at the Illinois Coal Development Park. A factorial experimental design using the response surface methodology was conducted to optimize the dewatering performance of the SBF prototype unit. Two different clean coal slurry samples having mean particle sizes of 400 micron and 50 micron and two fine coal tailings samples having mean particle sizes of 20 and 10 micron were dewatered using the SBF technology. A solid recovery of greater than 99% was achieved by using a suitable flocculant type and dosage for each sample. Surface moisture content of dewatered products varied from nearly 18.5% for coarser clean coal to 31% for finer clean coal and 18% for coarser tailings to 26% for finer tailings. A preliminary economic analysis conducted for a near-term commercialization of the SBF technology in the U.S. coal industry estimates the SBF dewatering cost for combined spiral + flotation product to be $1.09/ton of dry coal.

Exotic Grasslands on Reclaimed Midwestern Coal Mines: An Ornithological Perspective1

The largest grasslands in Indiana and Illinois are on reclaimed surface coal mines, which are numerous in the Illinois Coal Basin. The reclamation goal of establishing a vegetation cover with inexpensive, hardy exotic grass species (e.g., tall fescue, smooth brome) inadvertently created persistent, large grassland bird refuges. We review research documenting the importance of these sites for native prairie birds. On mines, grassland specialist birds (restricted to grassland throughout their range) prefer sites dominated by exotic grasses to those rich in forbs, whereas nonspecialist bird species show no significant preference. Midwestern mine grasslands potentially could be converted into landscapes that include native warm-season grasses and forbs adapted to the relatively dry, poor soil conditions, in addition to the present successful exotic grass stands. A key question is whether native mixtures will resist conversion to forb-rich or woody growth over the long term, as the exotic grasses have done.Nomenclature: Smooth brome, Bromus inermis Leyss.; tall fescue, Festuca arundinacea Schreb.Additional index words: Avian conservation, grassland birds, mine grasslands.

Sintered coal ash/flux materials for building materials

An Illinois coal ash, which has metals and a large amount of iron, is considered to be an especially difficult waster for disposal. In the process described in this paper, the high iron and metal content is used to create a building material with special properties. The metals are sequestered. The metals allow a process that creates valueadded products, building materials.

Advantage of Illinois Coal for FGD Removal of Mercury

An investigation was conducted to characterize and modify mercury speciation in Illinois coal combustion flue gas so that a mercury control strategy can be implemented in conventional flue gas desulfurization (FGD) units. Mercury is readily volatilized during coal combustion and leaves the high-temperature zone as gas-phase elemental mercury (Hg°). As the flue gas is cooled, a portion of the Hg° is converted, primarily to mercuric chloride (HgCl 2 ), in the presence of catalytically active surfaces. Unlike Hg 0 , HgCl 2 is highly soluble in water and has a high affinity for alkaline sorbents; it can, therefore, be easily removed in wet scrubbers and spray dryers (FGD units). This study specifically examined the effect of injection of Illinois coal combustion residues (ICCRs) on the conversion of Hg° to HgCl 2 in coal combustion flue gases. Tests were conducted in two tasks. Task I studied Hg° oxidation using a fixed-bed, bench-scale reactor in a simulated Illinois coal combustion environment. Various types of ICCRs were examined to determine active residues in the oxidation of Hg°. A scrubber sludge and two bottom ash samples were determined to be active Hg° catalysts. The most active ICCR (a bottom ash sample) was chosen for Task II. Task II was performed in two subtasks. In Subtask I, the active bottom ash sample was injected in a pilot-scale combustor while burning natural gas doped with appropriate amounts of Hg°, hydrogen chloride (HCl), nitrogen oxides (NO X ), and sulfur dioxide (SO 2 ). Injection of this bottom ash sample did not contribute to the background gas-phase oxidation of Hg°, indicating that in-flight oxidation of Hg° in the pilot-scale combustor may be mass transfer limited. In Subtask II, a representative Illinois coal was combusted in the pilot-scale combustor. As with most bituminous coals, the combustion flue gas of this coal was dominated by oxidized forms of mercury. Additional Hg° was doped into this flue gas, and significant oxidation of Hg° was observed. It was determined that the fly ash generated from combustion of this coal is very active in oxidation of Hg°. Additional pilot-scale tests were performed to investigate the activity of the Illinois coal fly ash. It was determined that packed-bed flow modes, such as those observed in baghouses, are required to catalytically oxidize Hg° using this Illinois coal fly ash.

Optimization of the Dewatering Performance of a Steel Belt Filter

The main goal of this study was to investigate the suitability of a newly developed fine particle dewatering technology, known as steel belt filter (SBF), for dewatering fine clean coal. The unique feature of this new technology is the combined use of both vacuum (suction force) and pressure (mechanical squeeze) for achieving the desired solid-liquid separation. A continuously operating SBF prototype unit having a belt width of 0.6 m was tested at the Illinois Coal Development Park. A factorial experimental design using the response surface methodology was conducted to optimize the dewatering performance of the SBF prototype unit. The clean coal slurry sample used as the dewatering feed was a combined spiral and flotation product with a mean particle size of 400 micron and an ash content of 19.2%. A solid recovery of greater than 99% was achieved by using a small dosage of an anionic flocculant. The minimum surface moisture content achieved by SBF dewatering was nearly 18.5%, whereas the mass product throughput capacity was 0.92 ton per hour (t/h) for a 0.6 wide SBF.

Methane and CO 2 sorption and desorption measurements on dry Argonne premium coals: pure components and mixtures

Sorption and desorption behaviour of methane, carbon dioxide, and mixtures of the two gases has been studied on a set of well-characterised coals from the Argonne Premium Coal Programme. The coal samples cover a maturity range from 0.25% to 1.68% vitrinite reflectance. The maceral compositions were dominated by vitrinite (85% to 91%). Inertinite contents ranged from 8% to 11% and liptinite contents around 1% with one exception (Illinois coal, 5%). All sorption experiments were performed on powdered (−100 mesh), dry coal samples. Single component sorption/desorption measurements were carried out at 22 °C up to final pressures around 51 bar (5.1 MPa) for CO 2 (subcritical state) and 110 bar (11 MPa) for methane. The ratios of the final sorption capacities for pure CO 2 and methane (in molar units) on the five coal samples vary between 1.15 and 3.16. The lowest ratio (1.15) was found for the North Dakota Beulah-Zap lignite (VR r=0.25%) and the highest ratios (2.7 and 3.16) were encountered for the low-rank coals (VR r 0.32% and 0.48%) while the ratio decreases to 1.6–1.7 for the highest rank coals in this series. Desorption isotherms for CH 4 and CO 2 were measured immediately after the corresponding sorption isotherms. They generally lie above the sorption isotherms. The degree of hysteresis, i.e. deviation of sorption and desorption isotherms, varies and shows no dependence on coal rank. Adsorption tests with CH 4/CO 2 mixtures were conducted to study the degree of preferential sorption of these two gases on coals of different rank. These experiments were performed on dry coals at 45 °C and pressures up to 180 bar (18 MPa). For the highest rank samples of this sequence preferential sorption behaviour was “as expected”, i.e. preferential adsorption of CO 2 and preferential desorption of CH 4 were observed. For the low rank samples, however, preferential adsorption of CH 4 was found in the low pressure range and preferential desorption of CO 2 over the entire pressure range. Follow-up tests for single gas CO 2 sorption measurements consistently showed a significant increase in sorption capacity for re-runs on the same sample. This phenomenon could be due to extraction of volatile coal components by CO 2 in the first experiment. Reproducibility tests with methane and CO 2 using fresh sample material in each experiment did not show this effect.

Mine-mouth power and process steam generation using fine coal waste fuel

The techno-economic feasibility of mine-mouth power generation using processed fine coal refuse fuel has been evaluated. Fine coal processing studies were conducted on the −100 mesh fine coal refuse of a central Illinois coal mine. On-site column froth flotation testing using a 15-cm diameter (7 kg/h) laboratory Jameson cell produced a 30 175 kJ/kg and 2.85% sulfur product at a combustible recovery of 75%. The mean particle size of the product was 60 μm. The product was dewatered in a Technicas Hidraulicas filter press to a 21% total moisture content filter cake from a 27% solids slurry at 6–10 min cycle times and at 99.5% solids capture efficiency. Material handling tests involving pumpability of the fine coal fuel established the feasibility of pumping this fuel to a fluidized bed boiler. For a 44% moisture content slurry, rheological measurements indicated a yield stress ( τ 0) value of 275 Pa and viscosity ( η) of 0.795 Pa s. Based on these measurements a hydraulically driven piston pump was determined to be appropriate for this application. Bench-scale combustion tests, conducted at Canadian Energy Technology Center, using a 100-mm diameter, 5 m high circulating fluidized bed combustor demonstrated the feasibility of achieving sustained combustion of the fine coal slurry containing up to 51% moisture content. High combustion efficiency and low emission levels were achieved for SO 2, NO x , and mercury. CO emissions were high, but in an industrial unit with longer particle residence time and a hotter cyclone, lower emission levels can be expected. Engineering economics for the project indicate feasibility. Conservative estimates of profitability indicate potential to provide a return on investment in the range of 20–25%. A 40% return on investment is projected if the Coal Industrial Park includes production and captive use of process steam.

The significance of Illinois coal and the Illinois State geological survey (ISGS) washer : Khan, L. A. et al. Proceedings of the International Technical Conference on Coal Utilization & Fuel Systems, 2002, 2, (27), 631–638

The significance of Illinois coal and the Illinois State geological survey (ISGS) washer : Khan, L. A. et al. Proceedings of the International Technical Conference on Coal Utilization & Fuel Systems, 2002, 2, (27), 631–638

Predicted CO 2 emissions from maceral concentrates of high volatile bituminous Kentucky and Illinois coals

A large collection of well-characterized coals, documented in the Center for Applied Energy Research's (CAER) database, was used to estimate the CO 2 content of maceral concentrates from Kentucky and Illinois high volatile bituminous coals. The data showed no correlation between CO 2 versus coal ranks and between CO 2 versus maceral content. Subsequently, eight sets of low-ash density-gradient centrifugation (DGC) maceral concentrates from five coal beds were examined, spanning in the high volatile rank range. Heating value was not determined on the concentrates, but instead was calculated using the Mott–Spooner formula. There was a good correlation between predicted CO 2 and maceral content for the individual iso-rank (based on vitrinite reflectance, analyzed on whole (parent) coal) sets. In general, the predicted CO 2 increases from liptinite-rich through vitrinite-rich to inertinite-rich concentrates (note: no “concentrates” are absolutely monomaceral).

A comparative evaluation of new fine particle size separation technologies

The conventional technologies used in industrial operations to achieve fine size separations at 150 μm and below are inefficient. To obtain precise fine size separations, the state of the art fine particle sizing technologies investigated in this study include the newly developed Pansep screen as well as a new design cyclone (gMax TM) with and without an apex water injection system (Cyclowash TM). The performance of a Pansep screen having a screening surface area of 0.5 m 2 is evaluated for size separations at 150 μm and 45 μm particle sizes, whereas a 15 cm diameter gMax cyclone with and without a Cyclowash attachment is studied for particle size separation at 45 μm only. The results of this study indicate that the size separation performance obtained by the Pansep screen is significantly better than the performance obtained from conventional technologies such as, cyclone and sieve bend for classifying the minus 1 mm particle size coal slurry at 150 μm. An excellent overall screening efficiency of 98% is obtained from the Pansep screen in comparison to the 44% obtained from the sieve bend and 57% from the raw coal classifying cyclone operating in an Illinois coal preparation plant. For the 45 μm size separation, a conventional cyclone efficiency of 37% is improved to 68% by the gMax cyclone, 70% with the use of Cyclowash attachment and to nearly 99% by the Pansep screening technology. The oversize throughput capacity of the Pansep screen for a particle size separation at 45 μm can be high as 5 ton/h m 2 without any significant negative effect on the overall size separation efficiency. No significant deterioration in the overall screening efficiency is noticed for the particle size separation at 150 μm while obtaining the same oversize throughput indicating the possibility of obtaining higher throughput rates for coarser size separations.

Properties and rheology of coal–water mixtures using different coals

The properties, settling rates, and the rheology of coal–water mixtures (CWM) made up from different coals were investigated. Test suspensions containing different concentrations of suspended particles were made up from each of four different pulverized parent coals: a Pittsburgh Seam No. 8 coal, an Illinois coal, and the product and feed from a flotation process using an Illinois coal. All the parent coals had broad particle-size distributions. In addition, the Pittsburgh Seam No. 8 coal was classified into four different size fractions using sieving, resulting in three coarser, narrow particle size cuts and the fine residual fraction passing 325-mesh, which had a broad size distribution. The property characterizations for all coals included the following: elemental analyses, heating values, particle size analyses, particle surface areas and pore sizes, solid heat capacities, and thermal conductivities. Tests on the suspensions included detailed supernatant ion analyses, and measurements of pH values and zeta potentials. For each test coal maximum-packing volume fractions were estimated using centrifugation, and the settling rates and directly measured yield stresses, using the vane method, were determined for every concentration of coal–water mixtures (CWM) used. The shear-stress/shear-rate dependences of the test suspensions, covering the shear-rate range from 0.1 to 10 5 s −1, were determined using a capillary rheometer. For some of the test suspensions, correction for a pronounced wall-slip effect was required. Apart from the directly measured yield stresses using the vane method, yield stresses were estimated indirectly by extrapolation and rheological model-fitting. Extrapolation of directly measured yield stresses to infinite limit was used to estimate maximum packing for comparison with those determined from the irreducible sediment volumes using centrifugation. The two-parameter power-law, Bingham plastic and Casson empirical rheological models, and the three-parameter Herschel-Bulkley and Sisko models were used to fit the shear-stress/shear-rate data. In general, the shear-stress/shear-rate dependence was found to be shear-thinning, power-law, over the lower ranges of shear, and to tend to Newtonian limit at high shear; a dependence which is best described by the three-parameter Sisko model.

Corrosivities derived from two Illinois coals with a low and a high Cl content under low NO x conditions

Corrosivities derived from two Illinois coals with a low and a high Cl content under low NO x conditions

Formation and use of coal combustion residues from three types of power plants burning Illinois coals

Formation and use of coal combustion residues from three types of power plants burning Illinois coals

Formation and use of coal combustion residues from three types of power plants burning Illinois coals

Coal, ash, and limestone samples from a fluidized bed combustion (FBC) plant, a pulverized coal combustion (PC) plant, and a cyclone (CYC) plant in Illinois were analyzed to determine the combustion behavior of mineral matter, and to propose beneficial uses for the power plant ashes. Pyrite and marcasite in coal were converted during combustion to glass, hematite and magnetite. Calcite was converted to lime and anhydrite. The clay minerals were altered to mullite and glass. Quartz was partially altered to glass. Trace elements in coal were partially mobilized during combustion and, as a result, emitted into the atmosphere or adsorbed on fly ash or on hardware on the cool side of the power plants. Overall, the mobilities of 15 trace elements investigated were lower at the FBC plant than at the other plants. Only F and Mn at the FBC plant, F, Hg, and Se at the PC plant and Be, F, Hg, and Se at the CYC plant had over 50% of their concentrations mobilized. Se and Ge could be commercially recovered from some of the combustion ashes. The FBC ashes could be used as acid neutralizing agents in agriculture and waste treatment, and to produce sulfate fertilizers, gypsum wall boards, concrete, and cement. The PC and CYC fly ashes can potentially be used in the production of cement, concrete, ceramics, and zeolites. The PC and CYC bottom ashes could be used in stabilized road bases, as frits in roof shingles, and perhaps in manufacturing amber glass.

Chemical and Engineering Properties of Fired Bricks Containing 50 Weight Percent of Class F Fly Ash

The generation of fly ash during coal combustion represents a considerable solid waste disposal problem in the state of Illinois and nationwide. In fact, the majority of the three million tons of fly ash produced from burning Illinois bituminous coals is disposed of in landfills. The purpose of this study was to obtain a preliminary assessment of the technical feasibility of mitigating this solid waste problem by making fired bricks with the large volume of fly ash generated from burning Illinois coals. Test bricks were produced by the extrusion method with increasing amounts (20-50% by weight) of fly ash as a replacement for conventional raw materials. The chemical characteristics and engineering properties of the test bricks produced with and without 50 wt% of fly ash substitutions were analyzed and compared. The properties of the test bricks containing fly ash were at least comparable to, if not better than, those of standard test bricks made without fly ash and met the commercial specifications for fired bricks. The positive results of this study suggest that further study on test bricks with fly ash substitutions of greater than 50 wt% is warranted. Successful results could have an important impact in reducing the waste disposal problem related to class F fly ash while providing the brick industry with a new low cost raw material.

Corrosivities in a pilot-scale combustor of a British and two Illinois coals with varying chlorine contents

Many US boiler manufacturers have recommended limits on the chlorine (Cl) content (<0.25% or<0.3%) of coals to be used in their boilers. These limits were based primarily on extrapolation of British coal data to predict the probable corrosion behavior of US coals. Even though Cl-related boiler corrosion has not been reported by US utilities burning high-Cl Illinois coals, the manufacturer's limits affect the marketability of high-Cl Illinois coals. This study measured the relative rates of corrosion caused by two high-Cl coals (British and Illinois) and one low-Cl Illinois baseline coal under identical pilot-scale combustion conditions for about 1000 h which gave reliable comparisons. Temperatures used reflected conditions in boiler superheaters. The corrosion probes were fabricated from commercial alloy 304SS frequently used at the hottest superheater section of utility boilers. The results showed no evidence of direct correlation between the coal chlorine content and rate of corrosion. A correlation between the rate of corrosion and the metal temperature was obvious. The results suggested that the different field histories of corrosivity from burning high-Cl Illinois coal and high-Cl British coal occurred because of different metal temperatures operated in US and UK utility boilers. The results of this study can be combined into a database, which could be used for lifting the limits on chlorine contents of coals burned in utility boilers in the US

00/00626 Adaptation of a briquetting machine for the dewatering and consolidation of fine coal

The Illinois Clean Coal Institute (ICCI) developed a new coal preparation method to recover the high heating value Illinois coal, containing high amounts of sulfur (in the form of pyrite). Unfortunately, the new cleaning method, consisting of fine grinding the coal to liberate mineral matter, such as the pyrite, produced large amounts of high moisture ultra-fine coal. One of the economically viable alternatives to dewater and recover the fine coal was to adapt a commercially available machine. A roll briquetting machine was chosen for the dual purpose of dewatering and consolidating fine coal. Preliminary results indicated that robust briquettes with low moisture content could be produced under the current configuration. However, two areas of concern were realized during the pilot-scale experiments. First, the arching and caking problems resulted in inconsistent feeding of material. Second, back drainage into the feed hopper resulted in varying the feed moisture. Therefore, to effectively utilize the briquetting machine to dewater fine coal, appropriate mechanical modifications were needed. Design changes were conducted on the feed area of the machine, which resulted in the elimination of the problems encountered. Briquettes with consistent low moisture content and adequate strength characteristics could now be produced under the new configurationmore » of the briquetting machine.« less

Desulfurization of Hot Syngas Containing Hydrogen Chloride Vapors Using Zinc Titanate Sorbents

There is a primary need to increase the use of Illinois coal resources by developing new methods of converting the coal into electricity with highly efficient and environmentally acceptable systems. New coal gasification processes that can generate electricity with high thermal efficiency either in a combined gas-turbine, a steam-turbine cycle (IGCC), or in a fuel cell (MCFC) are being developed. Both of these new coal-to-electricity pathways require that the coal-derived fuel gas be at a high temperature and free of potential pollutants, such as sulfur compounds. Unfortunately, some high-sulfur Illinois coals also contain a significant amount of chlorine, which converts into hydrogen chloride (HCl) in the coal gas. In this study, two simulated gasifier-product streams were contacted with the zinc titanate desulfurization sorbent in a bench-scale atmospheric fluidized-bed reactor at temperatures ranging from 538 to 750 °C (1000−1382 °F). The first set of experiments involved treating a medium-Btu fuel gas (simulating that of a “Texaco” oxygen-blown, entrained-bed gasifier) containing 1.4% H2S and HCl concentrations of 0, 200, and 1500 ppmv. The second set of experiments evaluated the hot-gas desulfurization of a low-Btu fuel gas (simulating the product of the “U-Gas” air-blown gasifier), which had a 0.5% H2S content and with HCl concentrations of 0, 200, and 800 ppmv. These operating conditions were typical of the gas-treatment requirements of gasifier systems fueled by Illinois basin coals containing up to 0.6% chlorine. The results of the experiments at 538 and 650 °C at all the HCl concentrations revealed no deleterious effects on the capability of the sorbent to remove H2S from the fuel-gas mixtures. In most cases, the presence of the HCl significantly enhanced the desulfurization reaction rate. Some zinc loss, however, was encountered in certain situations at 750 °C when low-steam operating conditions were present. Also of interest, a portion of the incoming HCl was removed from the gas stream and was retained permanently by the sorbent.

99/02823 Removal of ash, sulfur, and trace elements of environmental concern from eight selected Illinois coals, USA

99/02823 Removal of ash, sulfur, and trace elements of environmental concern from eight selected Illinois coals, USA