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Center for Advanced Separation Technologies: Projects

Virginia Tech

Title:

Development of a Novel Method for Cleaning and Dewatering Coal

 PI's:

Roe-Hoan Yoon, Gerald Luttrell

Institution:

Virginia Tech

Phone:

(540) 231-7056

E-Mail:

 ryoon@vt.edu

Abstract:

Fine coal cleaning is the most difficult and costliest part of cleaning coal. Therefore, many coal companies discard fine coal to impoundments or to underground workings, creating environmental concerns. The total value of fine coal being discarded in the U.S. is estimated to be in the range of $1.5-2 billion per year. It is, therefore, proposed to develop an advanced process that can be used to recover coal from fine coal streams and dewater the clean coal products. In addition, a method of dewatering refuse products will also be developed to obviate the need for impoundments in the future. The process will be tested in a bench-scale continuous operation to obtain scale up and cost information.

Status:

In-Progress

Title:

Development of a Novel Method for Cleaning and Dewatering CoalSurface Force Measurement Between Hydrophobic Surfaces

 PI:

Roe-Hoan Yoon

Institution:

Virginia Tech

Phone:

(540) 231-7056

E-Mail:

 ryoon@vt.edu

Abstract:

According to the classical DLVO theory, the stability of the films of water is determined by double-layer force and van der Waals dispersion force. It has recently been shown, however, that these two surface forces alone cannot explain many colloidal phenomena such as stability of oil-in-water emulsions, wetting films, foam films, and aqueous slurry of coal. The Principal Investigator of the proposed work has shown that the stability can be predicted better by using the extended DLVO theory, which includes hydrophobic force. In the proposed work, hydrophobic force measurements will be conducted using the colloidal probe technique with an atomic force microscope (AFM) and the thin film pressure balance (TFBC) technique. The measurements will be conducted at different temperatures to derive thermodynamic information for the thin films of water. The results will be useful for modeling flotation, gas hydrate formation, gas-gas separation, energy (CH4) storage and transportation, and CO2 sequestration.

Status:

In-Progress

Title:

Development of a Model-Based Flotation Simulator

 PI's:

Roe-Hoan Yoon

Institution:

Virginia Tech

Phone:

(540) 231-7056

E-Mail:

 ryoon@vt.edu

Abstract:

Flotation is the most widely used separation process used in the mining industry, and is regarded as the best available technology for fine coal recovery. The process also serves as the primary means of separating bitumen from silica in the oil sands industry. The process is controlled by both hydrodynamic and surface chemistry parameters. However, most of the mathematic models developed and use in industry today are based on hydrodynamic parameters only, while the process is critically dependent on the chemistry of the system. More recently, however, Virginia Tech has developed a flotation model based on both hydrodynamic and surface chemistry parameters. The model is based on first principles and can predict flotation recovery and grade under turbulent flow
conditions. In light of this recent breakthrough, the objective of this project is to develop a comprehensive flotation simulation package that incorporates the phenomenological flotation model developed at Virginia Tech into state-of-the-art reactor and transport models that accurately describe the performance of industrial flotation circuits. The simulator will include a user-friendly graphical interface and an optimization module to assist plant operators and equipment manufacturers in designing high-efficiency circuits at the lowest possible cost. Since the simulation package will make use of modeling expressions developed from first principles, this new simulation tool will also be useful for the scale-up, diagnosis and control of industrial flotation operations.

Status:

In-Progress

University of Kentucky

Title:

Cavitation Pretreatment of a Flotation Feedstock for Enhanced Coal Recovery

 PI:

Rick Honaker

Institution:

University of Kentucky

Phone:

(859) 257 1108

E-Mail:

 rhonaker@engr.uky.edu

Abstract:

For the portion of the feed to a coal preparation plant having a particle size below 150 microns, the most common process used to separate coal particles from the associated mineral matter is froth flotation. The process exploits the hydrophobic nature of the coal surfaces by injecting air bubbles and encouraging the formation of coal particle-bubble aggregates. As a result of a density that is lower than water, the bubble-particle aggregates float to the top of the cell while
the hydrophilic mineral matter follows the water to the underflow reject stream. Approximately 7% to 12% of the plant feed reports to the flotation circuit.

Problems that occur when employing froth flotation in the coal industry include i) coal surfaces that are weakly-to-moderately hydrophobic and ii) flotation systems that are overloaded and limited by insufficient retention time. In both cases, the impact is low flotation recovery and thus significant energy loss. Laboratory tests indicate that a potential solution to both problems is to pre-aerate the flotation feed using a cavitation tube. By injecting feed through a cavitation
system, micron-sized air bubbles nucleate onto the surface of the coal particles. As a result, when the particles interact with bubbles produced from a conventional bubble generator, the attachment process occurs more rapidly. Laboratory tests conducted by two different research groups have found that pre-aeration through a cavitation tube improved coal recovery by as much as 20 absolute percentage points in both batch conventional flotation cells and continuous flotation columns when treating difficult-to-float coals.

A full-scale in-plant test program is proposed to evaluate and quantify the technical feasibility
and economic benefits of using a cavitation system to pre-aerate flotation feed for conventional flotation cells and flotation columns. The research team includes flotation professionals employed by Eriez Manufacturing who are experts in cavitation technologies. Patriot Coal Corporation will provide preparation plant test sites which are located in southern West Virginia. A cavitation system will be installed within an active flotation feed stream and tests performed with and without cavitation treatment to provide the differential separation performances needed to assess the benefits of the proposed concept. The technical and economical findings of the study will be reported and presented to the coal industry at national conferences and meetings.

Status:

In-Progress

Title:

Computational Fluid Dynamics (CFD) Analysis Of An Air-Based Density Separator

 PI:

Rick Honaker

Institution:

University of Kentucky

Phone:

(859) 257 1108

E-Mail:

 rhonaker@engr.uky.edu

Abstract:

Potential benefits of dry coal cleaning technologies to provide significant pre-combustion upgrading of run of mine (ROM) coals are well documented. Benefits include the ability to i) recover coal from pit waste, ii) reduce trace element concentrations that are prevalent in ROM coals, iii) remove pyritic sulfur and iv) reduce ash content and thereby improve the heating value without the use of water.

Fundamental studies scrutinizing the theoretical and technical aspect of dry coal cleaning as a means to comprehend and improve the efficiency of the process have not been previously undertaken. Moreover, few empirical and mathematical modeling approaches have been carried out which have added to the body of knowledge but substantive research by means of state of the art Computational Fluid Dynamics (CFD) have never been undertaken.  The proposed project will continue to develop a workable CFD model and demonstrate the use of a laboratory dry coal cleaning unit to better understand and validate the fundamental elements and study the numerous variables affecting the complex process. The technology employs the use of air table equipment to achieve a density-based separation. An upward movement of air through the table deck suspends the light coal particles while the heavy rock particles remain on the deck and are driven by table vibration in a direction that is opposite of the light suspended particles. The technology has proven to provide efficient high density separations for particles having a particle size greater than 6 mm. Preliminary studies with the laboratory scale unit have demonstrated the applicability with regards to finer size fractions of the range 6 mm to 1 mm. Limited studies using a larger pilot scale unit on Wyoming coal achieved an ash reduction of over 60% and produced coal meeting end user specifications. Similar on-field tests performed on Indian hard-to-clean coals have yielded significant ash reductions of up to 20%. The proposed project will further evaluate coarse coal upgrading using CFD modeling. The developed model can then be applied to implement changes in the existing design to better suit fine coal cleaning which is of greater importance to the industry.

The proposed project will involve a project team consisting of university researchers, a computational software program for developing the CFD model to study the fundamentals of the process and a laboratory scale dry coal cleaner testing unit for validation purposes. A laboratory scale air-table dry coal testing unit will be installed at the state of the art research facility of the University of Kentucky and a detailed statistically-designed test program will be conducted to quantify parametric effects associated with coarse and fine coal cleaning and understand the effect of the process variables and their co-relations. Process efficiencies, CFD model and validation information will be used in a proof-of-concept study that will improve the understanding of the technological process and determine the feasibility of using the technology for upgrading run-of-mine coal.

Status:

In-Progress

Title:

Beneficiation of Fine Size Powder River Basin Coal

 PI's:

D. P. Patil, Rick Honaker

Institution:

University of Kentucky

Phone:

(859) 257 8026

E-Mail:

 dpatil@aldenresources.com, rick.honaker@uky.edu

Abstract:

Powder River Basin (PRB) supplies a significant amount of  coal  for power generation and ranks number one in coal producing states.  The PRB coal being low in ash and sulfur is preferred by utilities, even though it contains high moisture and mercury.   The PRB seams are modestly dipping.  As such, the amount of overburden burden is increasing as mine production progresses. The increased depth of the overburden and seam has caused significant effort to be focused on ensuring stability of the high benches that are created in the extraction process. The second geologic factor is the increased presence of non-coal partings and, in some cases, a complete split in the seam. In addition to impacting the mining practice and increasing extraction cost, both factors increase the amount of coal that is contaminated by the rock in the partings and overburden and thus left in the pit as fill material due to the inability to meet market specifications.  As such a significant amount of fine size ( minus 5 mm) coal is discarded, which amounts to a significant revenue loss for coal producers.   Because of the nature of the coal, dry coal cleaning technology appears to be most promising for beneficiation of the fine size PRB coal.

The main objective of the proposed project is to evaluate a laboratory modified dry table machine for processing  5 x 1 mm size Wyoming coal.  The project will evaluate various operating criteria using  a statistically designed experiments to determine the grade and recovery of clean coal.

Status:

Completed

Title:

Development of Strategies to Minimize the Release of Toxic Metals from Coal Waste Impoundments

 PI:

Frank Huggins

Institution:

University of Kentucky

Phone:

(859) 257 4045

E-Mail:

frank.huggins@uky.edu

Abstract:

A number of trace elements in coal are of significant environmental concern. Such potentially hazardous elements include As, Cr, Se, and Hg, and are principally associated with one or other of two major minerals in coal, namely pyrite and the clay mineral, illite. Coal cleaning is performed principally to minimize the amount of these and other minerals entering pulverized coal combustion. At the same time, hazardous trace elements associated with pyrite and illite are removed from coal combustion and hence their environmental impact during combustion is thereby reduced. However, such trace elements tend to be concentrated in the waste tailings (rejects) from coal separation technologies, and are normally disposed of under water in coal waste impoundments. Here, trace elements may pose other environmental problems because both major and trace elements in such rejects may be leached and mobilized. Consequently, the waters in such impoundments have to be isolated from the local groundwater in order to avoid possible contamination of local drinking water supplies. Despite concerns about solubilized trace elements in coal impoundments, relatively little is known about the rates and concentrations of specific chemical forms of such trace elements that can be leached from coal minerals and mobilized in these waters and how their behavior might be controlled. More data are clearly needed to assess the environmental hazard from mobilized ions in coal tailings impoundments.

In our previous CAST project, we applied a variation of ASTM Standard Test Method D5744 - 07 (Laboratory Weathering of Solid Materials Using a Humidity Cell) to investigate the long-term (~5 months) leaching behavior of major and trace elements in coal rejects from a commercial coal preparation plant. In this work, we established that alkali and alkaline earth elements (Na, Mg, Ca, Sr) in the rejects were readily solubilized and buffered the pH of the aqueous leaching medium and thereby delayed the release of hazardous trace elements from acidic solubilization of pyrite and illite. In the proposed project, we will explore means of controlling the buffering capability of alkali and alkaline earth elements in coal rejects by modification of coal separation processes and also by determining how best to mix coal rejects with fly-ash so as to minimize release of trace metals from both materials.

Status:

In-Progress

Title:

Dewatering of Fine Coal Pellets

 PI:

Darrell Taulbee

Institution:

University of Kentucky

Phone:

(859) 257 4045

E-Mail:

darrell.taulbee@uky.edu

Abstract:

Technologies to recover the fine coal generated during mining operations are known and commercially proven.  However, the marketability and value of the recovered fines suffers from a high and difficult to remove moisture content.  Fluidized-bed dryers are generally considered the method of choice for drying fine coal but fluidized-bed dryers can be problematic to operate, difficult to permit, and pose fire and explosion hazards.  They also create dust-containment issues during drying as well as during subsequent shipping and handling.  Forming pellets from the fine coal in a pan pelletizer can eliminate these obstacles as air or hot gases can be flowed through a pellet bed allowing the pellets to be dried with minimal dust generation.  Not only is pelletization a relatively simple and inexpensive process but, importantly, the wet coal fines recovered from cleaning operations require little if any additional water to initiate pellet nucleation and growth.  Should a more durable or a stoker product be required, the dried coal pellets provide an ideal feedstock for production of briquettes to serve as a high-quality substitute for increasingly expensive stoker coals.  Thermal drying of the clean fine coal also has the potential to allow for greater overall coal-preparation-plant recoveries in the coarse coal cleaning circuits.  Perhaps, more importantly in view of the growing demand for green energy, the dried pellets can be co-briquetted with biomass harvested from the vast acreages of reclaimed surface mines and forests prevalent in the Appalachian and Illinois Basin coal fields.

The proposed project will focus on demonstrating the feasibility and advantages of fixed-bed drying of pellets made from fine coals recovered from spiral cleaning circuits and froth-flotation cells. The coal pellets will be formed both with and without an added binder to determine if  pellets can be produced that are sufficiently durable product to withstand the rigors of shipping and handling briquetting.  In the final task, dried coal pellets will be co-briquetted with biomass to demonstrate the feasibility of using this approach as a vehicle for moving biomass into the utility and industrial-heat markets.  Successful co-briquetting of fine coal and biomass can provide a low-moisture, free-flowing product that does not generate dust during transport, freeze during winter, and that can be transported, stored, and processed in existing infrastructure thereby offering a practical near-term approach to generate green energy without requiring a substantial capital investment.

Status:

In-Progress

Title:

Chemical Stabilization Of Fine Coal Waste: Elimination Of Slurry Impoundments

 PI:

Rick Honaker

Institution:

University of Kentucky

Phone:

(859) 257 1108

E-Mail:

 rhonaker@engr.uky.edu

Abstract:

The fine coal waste generated from the processing of run-of-mine coal through a wet cleaning facility is typically stored in a slurry impoundment. The amount of material reporting to the slurry impoundment varies significantly from operation-to-operation and is largely a function of the amount of material finer than 150 microns in the plant feed, the mineral matter content and the type of fine coal circuit employed. Several environment and safety issues surround the use of impoundments which has made permitting of new impoundments a very difficult and time consuming task.

A novel concept involving the deployment of chemical stabilization has the potential to eliminate the need of slurry impoundments and allow co-storage with the coarse waste. The project will investigate the use of a chemical system involving the addition of sodium silicates, cement, pozzolanic fly ash or other chemicals to the thickener underflow stream material. The result is expected to be a stabilized solidified waste that can be co-disposed with coarse refuse, thereby eliminating slurry ponds. The patented concept was previously successful and commercialized for the treatment of sludge from steel manufacturing and automobile manufacturing plants as well as mine acid waste. The product produced from the chemical stabilization process can be as hard as concrete or rock with the ultimate hardness determined by the chemical mixture and content. Potential pollutants are entrapped within the solidified matrix and thus will render the material non-polluting and acceptable for disposal with coarse reject. The project will optimize the chemical mixture required to be successful for the treatment of conventional thickener underflow (30% solids by weight) and a paste thickener underflow (50% solids by weight).

Status:

Completed

 West Virginia University

Title:

Separation of Mineral Matter from Coal in a Riser System

 PI's:

Eric Johnson

Institution:

West Virginia University

Phone:

(304) 293 3111 x2309

E-Mail:

eric.johnson@cemr.wvu.edu

Abstract:

The goal of this research is to completely evaluate the separation of mineral matter from coal in a dry riser system. At present, there are enormous amounts of small coal particles in waste ponds. These ponds represent a significant amount of available energy as well as an environmental hazard. The interest in recovering this resource is hampered by the fact that this potential fuel contains a significant amount of mineral matter, including pyrite. The amount of coal fines in waste ponds is estimated to be more than 2.5 billion tons. To date, pyrite (sulfur) has been separated from coal fines in a circulating bed type riser system. The purpose of this proposal is to continue this initial, exploratory, success and to extend the process to separate additional mineral matter from the coal. This effort is based on the fact that the separation of mineral matter improves with decreasing size.

Status:

Completed

Title:

Photoactive, Organic-Inorganic Hybrid Porous Structures for Photocatalytic CO2 Reduction

 PI's:

James Lewis

Institution:

West Virginia University

Phone:

(304) 293 3422 x1409

E-Mail:

james.lewis@mail.wvu.edu

Abstract:

One of the greatest challenges of our day is the disturbing temperature increase of the atmosphere and the undesirable acidity of the oceans due to CO2 emissions from burning fossil fuels in automobiles and power plants. The removal of CO2 in the environment is an obstacle for current carbon-capture technology as carbon dioxide is a relatively inert and stable compound. Currently, there are a few technologies available for CO2 capture from coal flue gas or other point sources. We have developed a class of porous materials readily capture CO2 and then can utilize the energy from sunlight to capture and convert CO2 into viable products such as methanol or methane. In this proposal, we will use these materials and develop a device which can be potentially used in coal plant technology to reduce CO2 emissions. In this device, the CO2 is bubbled in a chemical solution through a membrane containing these light sensitive materials. The energy of the light along with a small applied voltage is used to generate the chemical reactions converting the CO2 into viable products. We will use 1st generation materials and devices to improve the efficiencies for 2nd generation materials and devices.

Status:

Completed

Title:

Development of Biochemical Techniques for Extraction of Mercury from Waste Streams Containing Fine Coal Particles

 PI's:

Jay Wiedemann

Institution:

West Virginia University

Phone:

(304) 442-3135

E-Mail:

jmwiedemann@mail.vt.edu

Abstract:

Both elemental (Hg0) and ionic (Hg2+) mercury are distributed widely in the environment:  Hg0 mainly in air, and Hg2+ predominantly in water and soil.  Both occur as a result of natural processes, namely volcanic activity and the leaching of ores, but also as a result of human activities, including the burning of fossil fuels, the incineration of waste, and the use of mercury in industrial processes.  Both forms are subject to conversion by biological processes into methylmercury and other organomercury salts. The amount of Hg released into the biosphere by human activities has increased since the advent of the industrial age and today accounts for approximately 75% of the environmental input (Mason and Fitzgerald 1996). Globally, this figure may be as large as 70,000 tons per year (Robinson and Tuovinen 1984).  A typical soil sample may contain between 20 and 150 parts per billion (ppb) Hg (Von Burg and Greenwood 1991). Appalachian coal typically contains between 150 and 240 ppb. Coal from Northern Appalachia has the highest natural Hg content of all sources of coal in the USA (Telwart et al. 2005). In extreme cases, human activity has discharged enough Hg into the environment to cause large numbers of deaths and birth defects, most notably at Minamata Bay, Japan (Takeuchi et al. 1962).

Most chemical forms of mercury (including Hg2+) are highly toxic.  This toxicity is due to the affinity of Hg for the sulfhydryl group present on the amino acid cysteine. By attacking this sulfhydryl group, Hg is capable of rendering a cell’s enzymes non-functional. Methylmercury and related organic mercury compounds present an even greater danger, in part because they accumulate in food chains.  Despite this potent toxicity, however, some bacteria are capable not only of surviving, but of thriving in the presence of high levels of Hg.  This remarkable capability has been studied extensively over the past thirty years (Barkay et al. 2003; Nascimento and Chartone-Souza 2003; Osborn et al.1997). It is achieved by the protein products of the mer operon.

The seven Mer proteins encoded by this operon work collectively to confer bacterial resistance to multiple forms of Hg. In the case of Hg2+, the Mer proteins transport Hg2+ across the plasma membrane and into the cytoplasm, where a mercury reductase (MerA) carries out the critical step of reducing Hg2+ to the relatively inert elemental form, Hg0.    Each of these steps is accomplished with exquisite sensitivity for Hg2+.  Hg0, due to its high vapor pressure and low solubility in water, diffuses passively out of the cell and, eventually, into the air.

The mer operon is among the most diverse and ubiquitous in bacteria, having been identified in a broad range of species isolated from both environmental and clinical settings.  The mer operons have been identified on plasmids (Clark et al. 1977; Griffin et al. 1987; Summers and Silver 1972), on transposons (Misra et al. 1984; Huang et al. 1999), and in genomic DNA (Inoue et al. 1991; Wang et al. 1987). As with resistance to antibiotics and/or other heavy metals, resistance to Hg can be disseminated through populations of bacteria by natural processes (Bogdanova et al. 1998). The mercury-resistance bacterial populations may be also resistant to various antibiotics and/or other heavy metals.

The research project outlined in this proposal is the extension of exploratory research performed on a previous Center for Advanced Separation Technologies (CAST, DE-FC26-02NT41607) and WV EPSCoR’s Summer/Semester Undergraduate Research Experience (SURE, EPS2005-24) project examining the potential to extract mercury from waste streams containing fine coal particles

Status:

Completed

Title:

Zeta-Potential Approach to Fine Coal Beneficiation

 PI's:

Mohindar Seehra

Institution:

West Virginia University

Phone:

(304) 293 3422 x1473

E-Mail:

mseehra@wvu.edu

Abstract:

An undesirable byproduct of the modern coal preparation plants is the fine coal slurries from which residual fine coals are difficult to recover. Consequently, these slurries are being discarded in settling ponds. In addition to the loss of useful carbons, these settling ponds represent a major hazard to life and environment in the neighboring communities.

The coal slurries are essentially colloidal solutions of water with suspended particles of coal, clays, silica and sometimes other components of ash. The primary goal of the research proposed here is to determine the electrochemical conditions for the selective agglomeration of the fine coal particles in the slurries. If successful, such a process could recover a significant portion of the fine coals from the slurries with minimal contamination from the particles of ash.

The proposed research is based on the concept that particles in a colloidal suspension carry an electrical charge because of the deposition of ionic species from the fluid on the surface of the particles. Since similar particles have similar charges, they experience mutual electrostatic repulsion, thus avoiding agglomeration and creating a suspension. Zeta potential measures the difference between charge on the particles and any charge on the fluid. Measurements of the zeta potential of the slurry as a function of the pH varied by suitable alkaline or acidic additives will be used to determine the conditions for near zero potential usually called IEP (iso-electric point).Near IEP, agglomeration of the particles should occur because charges on the particles have been neutralized by the additives. Systematic experiments are proposed to first investigate water suspensions of particles of pure silica, pure clays (kaolinite), and pure carbons before experiments on coal slurries are undertaken. These experiments are expected to determine whether IEP’s for clays and silica occur at a different pH than that for pure carbon. If so, then selective agglomeration of   particles of fine coals might be possible without significant contamination from the particles of ash assuming that coals and ash particles are separate. Since many previous studies have attempted to recover fine coals through oil agglomeration, we propose to investigate zeta potential measurements in such cases also to determine if such recoveries are indeed based on IEP’s.

Several buckets of coal slurries have already been acquired through the courtesy of Consol Inc. A suitable apparatus for zeta potential measurements is being acquired and it is expected to be in place before the start of the project. Other techniques to be employed in this project include x-ray diffraction and thermo-gravimetric analysis to quantify the carbon and minerals of ash in slurries, and Scanning Electron Microscopy (SEM) and light scattering techniques to determine the particles size distribution of the recovered solids. The proposed project duration is 18 months.

Status:

Completed

Title:

Fine Coal Flotation and Removal of Toxic Trace Elements

 PI's:

Eung Cho

Institution:

West Virginia University

Phone:

(304) 293 9336

E-Mail:

eung.cho@mail.wvu.edu

Abstract:

Huge tonnages of fine coal (e.g., -100 mesh or 0.15 mm) are being discarded to impoundments from coal preparation plants because currently no method is available to treat this fine size effectively. This size is rarely processed with gravity separation. Although it has a high degree of liberation of refuse materials, this fine size tends to cause poor selectivity between coal and refuse materials in the flotation process. This study focuses on further increasing the degree of liberation especially for toxic trace elements of mercury, arsenic and selenium from coal by preconditioning, which might result in higher-grade coal product by flotation.

The preconditioning of fine coal will be conducted with sodium sulfite to liberate the toxic trace elements from coal structure before flotation. The idea is that sodium sulfite combined with oxygen in acidic solution is a strong oxidizing reagent to partially leach the trace elements to enhance the degree of liberation of the trace elements. Since these trace elements are believed to be associated with coal pyrite, they will be liberated additionally when the coal pyrite is partially leached by the same oxidizing reagent.

When the coal is fired, some of these elements are emitted into the atmosphere and pose health hazards. Mercury may be the most toxic trace element in coal. Most of the arsenic vaporize in the flame but condense in the boiler (e.g., 95%). However, the most detrimental effect by arsenic is that its vapor poisons very expensive catalysts for Selective Catalytic Reduction for NOx control. Selenium compounds are five times as toxic as arsenic. Much of the selenium vaporized by coal combustion is emitted to the atmosphere (e.g., 45%). The major environmental concern is that the emission of this element into the arid parts of the U.S. becomes concentrated in the soil and plants sometimes to toxic levels.

After coal is liberated from the pyrite and trace elements, it will be floated using starvation quantities of frother and collector in order to minimize the casual flotation of coal pyrite. Other reagents of pyrite depressants and coal agglomerates will not be used unless they are highly required. The main objective of this study is to determine the technical feasibility of this preconditioning method by measuring the relationship among leaching conversion of pyrite/trace elements, their rejections, and the recovery of carbonaceous materials through the coal flotation.

Status:

Completed

Title:

Polymer Nanocomposites for CO2 Capture

 PI's:

Rakesh Gupta

Institution:

West Virginia University

Phone:

(304) 293 9342

E-Mail:

rakesh.gupta@mail.wvu.edu

Abstract:

It is proposed to develop effective and low-cost, nanoclay-based, polymer nanocomposites to work as high-capacity solid-adsorbents to capture carbon dioxide from post-combustion flue gases. Montmorillonite nanoclay does not by itself adsorb CO2, but it can have a very high specific surface area when properly dispersed in a polymer matrix. If amine groups are attached to the nanoclay surface, however, CO2 can be captured by chemisorption. Subsequently, the nanoclay can be regenerated by the use of a temperature swing method. Our preliminary experiments have shown that an amine compound, 3-aminopropyltrimethoxysilane, can be successfully grafted on the montmorillonite surface, and this treated clay exhibits a very high CO2 capture capacity of ~8wt% CO2 at atmospheric pressure and ~25wt% CO2 at high pressures. In the proposed research, we will increase the density of amine grafting on the nanoclays by additional chemical treatment which makes use of groups not only on the clay edges but also on the faces of the clay platelets. This should lead to a further enhancement in the CO2 capture capacity. Amine-grafted nanoclays will then be dispersed in a suitable polymer matrix to make polymer nanocomposites. The polymer will allow for the full surface area of the nanoclay to be exposed to the CO2, and it will serve to both absorb additional CO2 and also to “filter out” components in the flue gas that might reduce the sorbent activity with repeated adsorption/desorption cycling. Thus, the effect of the large surface area of the nanoclay, the high amine grafting density and the CO2 absorption capacity of the polymer matrix itself should all lend themselves to the formation of polymer nanocomposites that have a truly superior CO2 capture capacity.

Status:

Completed

Montana Tech

Title:

Mercury Removal from Clean Coal Processing Air Stream

 PI's:

Kumar Ganesan

Institution:

Montana Tech

Phone:

(406) 496-4239

E-Mail:

kganesan@mtech.edu

Abstract:

Mercury is at the top of the EPA’s list among the air toxic metals to be controlled.  Mercury is a high-priority regulatory concern because of its persistence and bioaccumulation in the environment and its neurological health impacts.  Mercury is present in three different species upon the combustion of coal:  elemental mercury, divalent mercury (II), and particulate bound mercury.  Elemental mercury is the mercury vapor released during combustion, mercury (II) results from the oxidation of elemental mercury by various elements in the flue gas, and particulate mercury forms when elemental mercury or mercury (II) attaches to solid particles (fly ash) in the flue gas. Currently, there is no effective control technology that removes all three forms of mercury, especially the elemental form, from coal-fired flue gas. Montana Tech has successfully developed, tested, and patented metallic mercury filter that can remove elemental form of mercury at or above 90 % efficiency. However, these metallic filters are expensive because of the high cost of metals that is used to fabricate the filters. To increase the cost effectiveness of the filters, the PI continuously explored novel materials to use in the filtering system. Based on the funding from CAST and the Montana MBRCT programs, the PI has successfully completed some preliminary tests on a new metallic nano particle (MNP) filter. The goal of this research is to develop a cost effective device to remove mercury from clean coal processing air stream.

In general, low rank coals like the Powder River Basin (PRB) sub-bituminous coals have high moisture content and low Btu values. Therefore, the cost of transporting and burning high moisture and low Btu coal is economically not attractive compared to low moisture and high Btu bituminous coal. The clean coal technologies are aimed to reduce the initial moisture content by 30-40% and increase the Btu values of sub-bituminous coal by 30-40%. There are abundant low-rank coal deposits in the United States and through out the world that will be utilized in energy production for decades to come. Clean coal technology seeks to reduce environmental effects by using multiple technologies to clean coal and contain its emissions. A significant co-benefit of clean coal process is that contaminants are eliminated before its combustion. The clean coal technologies that use thermal treatment processes claim mercury removal up to 70 % in addition to the co-benefits of lower sulfur and nitrogen oxide emissions. This elimination of the contaminants at the source, “source reduction” is the best pollution prevention approach that any industry and community would like to accomplish. In addition, the back-end capital costs and maintenance costs of large control equipment involved in reducing mercury emissions is minimized if not completely avoided.

The main objective of this research is to use metallic nano particle filters to remove mercury from pre-combustion low-rank clean coal processing air stream. CAST in 2008, allowed the PI to develop a new metallic nano particle (MNP) filters using ceramic substrates aiming to reduce the over all cost of the filtration system. The objectives of this proposed research are: to assemble filters with maximum metallic nano particles (MNP) by increasing the MNP deposition; to optimize thermal desorption; to generate synthetic gas to simulate the sweep gas stream of clean coal process and to assemble large scale filtration system to test in the lab as well as in the field.

Status:

Completed

University of Utah

Title:

Characterization, Analysis and Simulation of Fine Coal Filtration Second Year of Two Year Project

 PI's:

Jan Miller and C.L. Lin

Institution:

University of Utah

Phone:

(801) 581-5160

E-Mail:

jan.miller@utah.edu

Abstract:

Fine coal filtration and dewatering are of great importance to the coal industry due to its significant impact in the quality, shipping and handling of the coal product. High moisture content in the coal product reduces its heating value, increases costs, and reduces the coke yield in the case of metallurgical coal. In this regard, it is of significant importance to improve our fundamental understanding of water removal from the pore network structures present in filtration cakes.

In order to gain a better understanding of the complex transport phenomena that occur in the porous media, a study of the effect of three-dimensional pore geometry on the effective transport properties of the porous media is necessary. At present, the information from the microscopic pore geometry analysis is not detailed enough to provide an accurate prediction of transport properties from model simulation. Techniques and methodology for a detailed description of the three-dimensional pore geometry analysis of a completely interconnected porous system is needed.

The proposed research work is aimed to study fluid transport phenomena in fine coal filter cake using x-ray microtomography techniques to characterize the complex three-dimensional pore geometry. The 3D porous structure captured by XMT analysis will be coupled with the Lattice Boltzmann Method (LBM) to simulate and to establish a fundamental relationship between pore microstructure and filtration operation variables.

The proposed research program will provide a wealth of new information that will be of benefit to investigators working on fine coal dewatering. Procedures for the determination of a detailed 3-D interconnected pore structure from x-ray microtomography measurements will be established. Analysis of the pore connectivity in a packed bed of particles should allow for a detailed description of fluid flow and transport in the filter cake structure. We expect to be able to study the effect of pressure drop, cake pore geometry, surface tension and contact angle on the cake resistance and the breakthrough pressure which are so significant in the cake cracking phenomena of major importance in fine coal dewatering process.

Status:

Completed