Past Research Funding for FY 1996-1997
Following are descriptions of research activities. The investigators involved are indicated in parenthesis. The contact person information is hyperlinked to the appropriate name.
Froth Flotation for Fine-Coal Cleaning
Work continued on a $lM, four-year contract from the DoE for the scale-up and testing of the CAER-developed dewatering of ultrafine clean coal slurry technology at a proof-of-concept facility at the Powell Mountain Coal Company's Mayflower Preparation Plant in Virginia (B.K. Parekh, J. Groppo). The scale of operation is 1 to 2 tons per hour and uses a clean-coal slurry obtained from the commercial KENFLOTE units employed at Powell Mountain. The process involves modification of the surface properties of coal by treatment with a combination of metal ions and a surfactant mixture. The modified coal slurry is then dewatered using high pressure, centrifuge, or vacuum filter technologies.
Staff also completed the second year of a 5-year effort funded through the KY/ DoE EPSCoR-program (B. K. Parekh) to investigate coal deep-cleaning technologies using column flotation and hydrothermal treatment. The objective is to remove hazardous trace elements from coal while achieving a 90 percent combustible recovery.
In another project sponsored by DoE under the auspices of the Appalachian Clean Coal Technology Consortium (B. K. Parekh), a novel method for destabilizing the column flotation froth product is being investigated. Stable froth leads to inefficiencies in the dewatering of clean coal: chemical and mechanical methods are being investigated to break down highly stable bubbles to de-foam the froth.
In-LineA Dry Coal Cleaning by Triboelectrostatic Processing
Work also continued on a follow-on three-year, $0.54M DoE grant for research on in-line dry coal cleaning of a stream of pulverized coal through tribo-electrostatic processing techniques (J. Stencel). This work focuses on obtaining the engineering and scientific information needed to determine whether it is feasible to place triboelectrostatic separators between the pulverizers and burners of utility-scale combustion units. Measurements have been made at two plants - a 350 MW and a 200 MW plant. The data showed that effective charging of coal and mineral matter occurs during pulverization and classification, the extent of which enables up to 50 percent removal of mineral matter at a BtU recovery of 95 percent. During the next year, the project will involve scale-up work of a bench-scale separator at the CAER and the conceptualization of a process scale-up, including equipment and cost estimates.
Combustion and Emissions Control
Circulating Dry Scrubbing - Flue Gas Emissions Control
Work in coal combustion and emissions control has shifted over the last few years, moving away from a focus on atmospheric pressure fluidized bed combustion towards the control of flue gas emissions. Work over the last two years has been supported primarily by state funds, and also includes a small project for the Tennessee Valley Authority (J. Stencel). The TVA work was concerned with circulating dry scrubbing (CDS) for flue gas emissions control specifically for the simultaneous capture of SO2 and NOx. Using an integrally-staged CDS pilot plant developed at the CAER, it was shown that SO2 could be efficiently scrubbed from coal-combustion gas using lime-based sorbents. The amount of NOx removed from the combustion gas, however, was not greatly enhanced. Neither did the addition of sodium additives, which have been shown to assist NOx capture in other technology applications result in appreciable increases in NOx capture. The TVA is evaluating the need for larger scale testing.
Coal Combustion By-products
The management of coal combustion byproducts is an area of growing concern to the electric power industry. Specific interests are how to use or safely dispose of accumulated ash and flue gas desulfurization materials. A considerable proportion of the Center's current efforts is in investigating wet and dry methods for separating and recovering carbon from ash - the product of incomplete combustion - and for employing and reusing the ash and byproducts in useful applications.
Froth Flotation for Separating Carbon from Fly Ash
The CAER has investigated, for a number of years, froth flotation techniques for the separation of carbon from fly ash (T. Robl, J. Groppo). The initial research focused on the development of a selective flotation reagent that would remove carbon more effectively than could be achieved by available technology. The work resulted in a patent pertaining to the composition of the flotation reagent. This intellectual property has now been licensed to Advanced Pozzolan Technologies (APT) of Atlanta, GA. APT represents several utility clients and has provided funding for pilot-scale development valued at $286K. A continuous pilot-scale facility has been considered at the CAER to process 200 lbs/hr of fly ash, producing a premium low-carbon pozzolan for cement applications and a carbon enriched product for fuel use. Several long-duration tests were completed to verify critical scale-up parameters as well as to produce one ton product samples for customer evaluation. The construction of a commercial-scale facility processing 35 tph of ponded fly ash was started in 1997.
Triboelectrostatic Separation of Carbon from Fly Ash
Applying the expertise developed in the triboelectrostatic separation of mineral matter from coal, a separator was constructed and applied to the separation of unburned carbon from coal fly ash. The separator and associated hardware are the subject of five invention disclosures. Contracts to support research and development were awarded by the Electric Power Research Institute (EPRI) and Asea Brown Boveri (ABB) (J. Stencel, H. Ban) and have examined the efficiencies of particle separations. The EPRI contract examined char-ash separation efficiencies for 20 combustion fly ashes produced in domestic coal-fired electric plants. The ABB work is continuing and involves proprietary technologies of the CAER and this company. During the next year, one focus of the triboelectrostatic separation work will be to find industries interested in scale-up of the process to feed rates as high as 50 tons/hour.
With funding from NASA/ EPSCoR (J. Stencel, A. Rubel) investigations have begun of the triboelectrostatic separation of minerals representative of lunar ores, with the objective of understanding the effects of separating the composites of different physical mixtures and particle size under tribo-charging conditions. A second element of this research is to investigate the use of activated carbons for methane storage. A high pressure balance has been developed to determine methane uptake and porosity in pore-modified carbons at temperatures between 25-150 °C and pressures up to 500 lb/in2.
Mine Haulback of Coal Combustion By-products
Research continued on a $0.9M DoE contract to investigate refilling highwall mine adits with spent ash and scrubber waste (T. Robl). The objective of the project is to demonstrate the economics of emplacing wetted fly ash in mine openings for high-wall stabilization and potentially for the remining of stranded coal. There are about 19,000 miles of abandoned highwalls in the Appalachians, many of them having been augered to recover coal. The successful application of a low-cost technique to stabilize the highwalls could add several billion tons of surface-accessible coal reserves to the region's supply.
The fly ash used in this field experiment is the product of Eastern Kentucky coal mined by Costain Coal, and returned to their Floyd County mine for mine-site disposal. The site for the field emplacement was the Sunny Ridge Mining Job 20. Auger mining in the 1970's left open ±100 foot deep holes in the mine face, effectively preventing further mining with newer technologies. Stabilization of the highwall with low-strength fly ash "cement" could allow deeper mining with a highwall miner - to depths perhaps in excess of 1000 feet. Substantial progress was made in understanding the material properties and the mode of emplacement of coal combustion by-products in the mine openings. Field experiments focused on the emplacement of the fly ash cement and the logistics of delivery from rail loadout to the mine opening. Chemical and mechanical testing of the fly ash and of the derived cement is continuing with the UK Department of Civil Engineering and Transportation Center.
Fuels and Chemicals
In the Fischer-Tropsch research under a second three-year, $4.7 million contract from DoE (B. Davis), efforts have been made to develop, test and scale-up promising iron-based F-T catalysts for pilot plant runs at a LaPorte, Texas plant. The studies involve cooperative work with United Catalyst, Inc., and interactions with a range of industrial organizations, among them, Air Products and Chemicals, Exxon, Shell, and Statoil. The objectives are to develop superior catalysts suitable for use in advanced slurry phase reactors that could be applied to a range of chemical processes. Successful investigations have produced an iron-based catalyst suitable for chemicals production (low alpha catalyst) with high activity and extended catalyst life. Studies now emphasize the development of robust, active catalysts suitable for the production of transportation fuels (high alpha catalysts).
A source of high-octane paraffins is desirable for the production of Reformulated Gasoline (so-called 'clean gasoline'). Acid-catalyzed isomerization is one approach; acid catalyzed alkylation employing low boiling alkane-alkene fractions is another. Current isomerization catalysts operate only at high temperatures with thermodynamic limitations allowing only a limited improvement in octane numbers. Sulfated zirconia offers promise as a catalyst that can operate at low temperature. In work sponsored by DoE/ EPSCoR (B. Davis) research is being carried out on the preparation and activation of sulfated zirconia catalysts, and on the mechanisms of catalytic conversion. These studies will also assess plasma spray coating with zirconia for application to land-based gas turbines - a preferred coating for utilization in high-temperature applications.
Advanced Two-Stage Direct Coal Liquefaction
In direct liquefaction, work has continued on a second three-year, $4.45 million contract from DoE (F. Derbyshire, C. Lafferty) to evaluate process concepts that could effect a reduction in the cost of producing coal liquids in a two-stage liquefaction process. Work accomplished during the first phase of this project is being evaluated in a larger, continuous bench-scale testing program involving collaboration with Hydrocarbon Technologies, Inc., LDP Associates, CONSOL, and Sandia National Laboratories. A first continuous 25-day bench-scale run was completed at HTI in March, 1996 to investigate the effects of coal cleaning by oil agglomeration, and recycle solvent modification by successive dewaxing and hydrotreating. Coals cleaned by oil agglomeration provided exceptionally high (>98 percent) coal conversion. Solvent modification provided high (IBP) distillate yields. A second run was made in November-December 1996 to evaluate dispersed catalysts developed at the CAER.
Novel Chemical Approach to Direct Coal Liquefaction
A novel chemical approach to two-stage direct liquefaction is the subject of other investigations supported by a $.6 million subcontract from CONSOL (F. Derbyshire). The first stage process is being studied by CONSOL, and for reasons of confidentiality, no details of this work can be given. The first stage products have been sent to CAER where high temperature pressure filtration has been successfully employed to effect solid-liquid separation. The catalytic upgrading of these filtrates is also being investigated.
Carbon Fibers and Activated Carbon Fibers
The synthesis of general purpose carbon fibers and activated carbon fibers from noncommercial pitch-like sources is the subject of ongoing research. Fibers are synthesized from various raw materials, with emphasis on coal liquids produced from coals of different rank and by various methods. These studies have resulted in small industrial research contracts to investigate the utility of commercially produced coal tars as fiber precursors (F. Derbyshire).
In a collaborative arrangement with Professor Isao Mochida of Kyushu University, and also supported by an NSF grant, investigations are underway on the use of activated carbon fibers as catalysts for the removal Of SO2 from flue gases and its low temperature conversion to sulfuric acid. Research focuses on understanding the reaction mechanisms and defining the critical catalyst characteristics.
Carbon Fiber Composite Materials
Work continued on the joint development of novel carbon fiber composites, partly sponsored by the Oak Ridge National Laboratory (F. Derbyshire, M. Jagtoyen). In addition, internally-funded work has focused on alternative methods for forming activated carbon fiber composites employing techniques developed at the CAER and resulting in composites with different structures. The unique properties of both types of composite are leading to investigations of their potential for a diversity of applications in air and water treatment.
Activated Carbon Catalysts
A Cooperative Research and Development Agreement (CRADA) with the DoE Federal Energy Technology Center (Malvina Farcasiu) and the CAER (F. Derbyshire, M. Jagtoyen) led to the joint development of activated carbon catalysts for reactions relevant to environmental problems, specifically the hydrode-halogenation of polyaromatic compounds. The catalysts were prepared and characterized at the CAER and tested for their catalytic behavior at FETC's facility in Pittsburgh, PA. The results are very promising and a patent application has now been awarded.
Nanoparticle Catalysts, Fullerenes and Nanotubes
Research into the fundamental limitations of crystalline nano-particles produced by, CO2 laser pyrolysis (Materials Program) continued with emphasis on the production of ideal transition metal carbides, nitrides and sulfides [Fe, Mo, W]. This work is funded by the Consortium for Fossil Fuel Liquefaction Science (CFFLS) and the National Science Foundation (NSF). The CFFLS component focuses on the development of catalyst particles for upgrading coal-derived liquids and plastics waste. The NSF component concerns the development of particles for battery electrodes (Li:MoS2) and gas sensors (Mo2C, Mo2N). In the work on bifunctional catalysts for coprocessing coal and plastic, it was found that Brönsted acid sites play a key role in the conversion of medium density polyethylene to valuable fuel products.
In research on novel carbons (Materials Program), the polymerization of C60 (fullerene) solids is being studied in collaboration with Dr. M. Nunez-Regueiro at CNRS, France. Three new polymeric phases have been isolated and studied. Theoretical modeling to understand the intermolecular bonding was done by Professor K. Subbaswamy and his group (Department of Physics and Astronomy, UK).
Considerable excitement has developed over the discovery, by Professor Richard Smalley, Rice University, of a continuous process to produce perfect carbon nanotubes. Investigations into the physical properties of carbon nano-tubes are being vigorously pursued at CAER, in collaboration with Smalley and also Professor Mildred Dresselhaus, MIT. Comparison of these polymerized products to the photopolymerized products patented by Eklund in 1994 have shown interesting differences in the inter-fullerene bonding.
A number of exchange visits were made between American and Japanese scientists as part of an NSF grant for research in the areas of carbon nanotubes, fullerenes and ultrafine particle catalysts (Materials Program). The research is a collaborative effort of UK, MIT, the University of Electro-Communications (Tokyo), Tokyo Institute of Technology, the Institute of Molecular Science (Okazaki), Shinshu University (Nagano), and Kyushu University (Fukuoka).
Funding to investigate the production of thin films of layered carbon-selenium (tellurium) compounds by chemical vapor deposition (CVD) has been awarded by the Department of Defense, Advanced Research Projects Agency (Materials Program). These intercalation compounds are being investigated for their C-axis thermal and electrical transport properties and for Peltier refrigeration. The CVD method under study promises to produce a wide range of new carbon materials with possible applications in thermoelectricity and magnetic recording.
With NSF funding (Materials Program) investigations are being made to synthesize and evaluate Si clathrate solids which exhibit a regular array of hollow Si polyhedra. The polyhedra are covalently bonded and can be endohedrally doped with electron donors such as Na and Ba. Possible applications in novel semiconductor devices may emerge. The compounds (Ba,Na) Si46) were found to exhibit superconductivity at ~4K, although applications exploiting superconductivity are not envisioned.
Research Services and Crosscutting Applications
The Analytical Services group (G. Thomas) and the Applied Microscopy group (J. Hower) provide support services primarily to other CAER program areas. Nonetheless, there are constant efforts to develop funding sources and to expand the Center's client base to include other faculty and staff, government, and industrial organizations. This effort has been further strengthened by the Center's new Industrial Support Initiative (D. Taulbee), which focuses on performing services for industrial clients who can benefit from the Center's substantial analytical and problem-solving capabilities. The effort basically serves to connect the industrial client with members of our staff who possess appropriate expertise. A description of some of the research services follows.
Paving and Construction Materials
The Applied Microscopy Group carried out a variety of studies on the petrography of fly ash and other coal combustion byproducts. A project sponsored by Monex Resources (T. Robl, R. Rathbone) focused on the characterization of carbon forms in fly ash and the effects of these forms on fly ash performance in Portland cement. Preliminary results suggest that the distribution of these forms exerts a significant influence on their use in concrete applications.
Work sponsored by United Catalyst, Inc. (B. Davis) is investigating the hydrogenation of acetylene and dienes present in polymerization grade ethylene. The objective is to understand the factors that determine the selectivity for the hydrogenation of low concentrations of acetylene that are present in ethylene. The work involves a study of the reaction mechanisms using isotopic tracers and comprehensive characterization of both commercial and model catalysts.
Foundry and Metals Finishing
The low-cost of triboelectrostatic processing and its effectiveness in separating physical mixtures of fine-sized particles suggests its broad applicability to a number of crosscutting areas. In research sponsored by Allison Engines (J. Stencel, H. Ban), efforts are underway to employ tribo-electrostatic processing to remove trace ceramic impurities necessary to upgrade the quality of super alloys used in the manufacture of turbine blades. An analytical technique was developed to characterize the low level of ceramic impurities present in the alloy.
In collaborative work with ZTT Minerals of Calhoun, TX ( D. Taulbee) analytical support and technical assistance was provided in identifying the optimum operating temperatures and feed formulations for ZTT's rotary kilns used in its foundry operation. In the process, coal is pelletized with lime and electric-arc-furnace dust to recover zinc oxide and reduced iron as the primary products.
Work was sponsored by the Hill and Griffith Company ( D. Taulbee), a foundry supplier headquartered in Cincinnati, OH. The CAER investigated improved castings sand formulations which have the potential to substantially reduce benzene emissions. While carbonaceous additives, including coal, in foundry sand cores are essential for the production of quality castings, they are recognized as a major source of benzene. Pending environmental legislation will require the adoptions of maximum achievable control technology for benzene emissions by the year 2000.
Textiles, Paper and Pulp
Research is continuing on using column flotation technology for the treatment of industrial wastewaters where the contaminants can be flocculated prior to separation and removal. Successful investigations have been made for the removal of dye substances from textile manufacturing process waters and waste products from the effluent of the paper and pulp industry (B. K. Parekh).