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Biochemical Removal of HAP Precursors from Coal

Description: Column biooxidation tests with Kentucky coal confirmed results of earlier shake flask tests showing significant removal from the coal of arsenic, selenium, cobalt, manganese, nickel and cadmium. Rates of pyrite biooxidation in Kentucky coal were only slightly more than half the rates found previously for Indiana and Pittsburgh coals. Removal of pyrite from Pittsburgh coal by ferric ion oxidation slows markedly as ferrous ions accumulate in solution, requiring maintenance of high redox potentials in processes designed for removal of pyrite and hazardous air pollutant (HAP) precursors by circulation of ferric solutions through coal. The pyrite oxidation rates obtained in these tests were used by Unifield Engineering to support the conceptual designs for alternative pyrite and HAP precursor bioleaching processes for the phase 2 pilot plant. Thermophilic microorganisms were tested to determine if mercury could be mobilized from coal under elevated growth temperatures. There was no evidence for mercury removal from coal under these conditions. However, the activity of the organisms may have liberated mercury physically. It is also possible that the organisms dissolved mercury and it readsorbed to the clay preferentially. Both of these possibilities are undergoing further testing. The Idaho National Engineering and Environmental Laboratory�s (INEEL) slurry column reactor was operated and several batches of feed coal, product coal, waste solids and leach solutions were submitted to LBL for HAP precursor analysis. Results to date indicate significant removal of mercury, arsenic and other HAP precursors in the combined physical-biological process.
Date: May 12, 1997
Creator: Olson, Gregory J.
Partner: UNT Libraries Government Documents Department

Surfactant-Assisted Hydrothermal Synthesis of Single Phase Pyrite FeS2 Nanocrystals

Description: Iron pyrite nanocrystals with high purity have been synthesized through a surfactant-assisted hydrothermal reaction under optimum pH value. These pyrite nanocrystals represent a new group of well-defined nanoscale structures for high-performance photovoltaic solar cells based on non-toxic and earth abundant materials.
Date: March 27, 2009
Creator: Wadia, Cyrus; Wu, Yue; Gul, Sheraz; Volkman, Steven; Guo, Jinghua & Alivisatos, Paul
Partner: UNT Libraries Government Documents Department

Sulfur transformations in early diagenetic sediments from the Bay of Concepcion, off Chile

Description: Despite the recognition that both organic sulfur and pyrite form during the very early stages of diagenesis, and that the amount of H{sub 2}S generated in bacterial sulfate reduction primarily limits their formation, the mechanisms and the active species involved still are not clear. In this study, we quantified the major forms of sulfur distributed in sediments to assess the geochemical mechanisms involved in these transformations. XANES spectroscopy, together with elemental analysis, were used to measure sulfur speciation in the organic-rich sediments from the Bay of Concepcion, Chile. Organic polysulfides constituted the major fraction of the organic sulfur, and occurred maximally just below the sediment surface (1--3 cm), where intermediates from H{sub 2}S oxidation were likely to be generated most abundantly. Sulfonates, which could be formed through the reactions of sulfate and thiosulfate, also showed a sub-surface maximum in the vicinity of the ``oxic-anoxic interface``. These results strongly suggest a geochemical origin for organic polysulfides and sulfonates, and illustrate that intermediates from H{sub 2}S oxidation play a dominant role in incorporating sulfur into organic matter. Pyrite was absent in the surficial layer, and first appeared just below the H{sub 2}S maximum, where organic polysulfides began to decrease in abundance. From these results, we argue, that an iron monosulfide precursor formed first from reactions with H{sub 2}S, and then reacts with organic polysulfides, completing the synthesis of pyrite in the sediment column.
Date: April 1, 1995
Creator: Vairavamurth, M.A.; Wang, Shengke; Khandelwal, B.; Manowitz, B.; Ferdelman, T. & Fossing, H.
Partner: UNT Libraries Government Documents Department

A modified release analysis procedure using advanced froth flotation mechanisms. Final technical report, September 1, 1995--August 31, 1996

Description: Recent studies indicate that the optimum separation performances achieved by multiple stage cleaning using various column flotation technologies and single stage cleaning using a Packed-Flotation Column are superior to the performance achieved by the traditional release procedure, especially in terms of pyritic sulfur rejection. This superior performance is believed to be the result of the advanced flotation mechanisms provided by column flotation technologies. Thus, the objective of this study was to develop a suitable process utilizing the advanced froth flotation mechanisms to characterize the true flotation response of a coal sample. This investigation resulted in the development of a modified coal flotation characterization procedure, termed as the Advanced Flotation Washability (AFW) technique. The apparatus used for this procedure is a batch operated Packed-Column device which provides enhanced selectivity due to a plug-flow environment and a deep froth zone. The separation performance achieved by the AFW procedure was found to be superior to those produced by the conventional tree and release procedures for three nominally -100 mesh coal samples and two micronized samples. The largest difference in separation performance was obtained on the basis of product pyritic sulfur content. A comparison conducted between the AFW and the release procedures at an 80% recovery value showed that the AFW technique provided a 19% improvement in the reduction of pyritic sulfur. For an Illinois No. 5 coal sample, this improvement corresponded to a reduction in pyritic sulfur content from 1.38% to 0.70% or a total rejection of 66%. Micronization of the sample improved the pyritic sulfur rejection to 85% while rejecting 92% of the ash-bearing material. In addition, the separation performance provided by the AFW procedure was superior to that obtained from multiple cleaning stages using a continuous Packed-Column under both kinetic and carrying-capacity limiting conditions.
Date: May 1, 1997
Creator: Honaker, R.Q. & Mohanty, M.K.
Partner: UNT Libraries Government Documents Department

A Silica/Fly Ash-Based technology for Controlling Pyrite Oxidation.

Description: The overall objective of this project is to develop methodologies by which sodium metasilicate or fly ash may produce an effective coating on pyrite surfaces for inhibiting pyrite oxidation. Milestones for the following periods include: First six-months - (1) Characterize pyrite surface reactions for understanding pyrite coating establishment. (2) Start a preliminary outdoor leaching - column experiment using 10 kg mine pyritic spoil treated with silicates to evaluate potential application of coatings on a large scale. Second six-months - (1) Characterize silicate - iron reactions in solution and on pyrite surface for understanding pyrite silica - coating formation. Third six-months - (1) Evaluate pyrite surface deposition of silicate having Na - silicate or fly ash as source. Fourth six- months - (1) Evaluate silicate coating durability in large outdoor columns.
Date: September 21, 1997
Partner: UNT Libraries Government Documents Department

New concept for coal wettability evaluation and modulation. Technical progress report, April 1--June 30, 1995

Description: The objective of this project is to evaluate the surface wettability and flotation of coal and pyrite in order to establish a new separation strategy for advanced coal cleaning for premium fuel applications. During this quarter, mini-cell flotation tests were carried out on Upper Freeport, Pittsburgh No. 8, and Illinois No. 6 coals, and two pyrite samples. Flotation media used were kerosene, benzene, and amyl-xanthate. Test results are given and discussed.
Date: May 1, 1996
Creator: Hu, W.
Partner: UNT Libraries Government Documents Department

Cross flow flotation column for coal and minerals beneficiation

Description: An apparatus and process are disclosed for the separation of coal from pyritic impurities using a modified froth flotation system. The froth flotation column incorporates a helical track about the inner wall of the column in a region intermediate between the top and base of the column. A standard impeller located about the central axis of the column is used to generate a centrifugal force thereby increasing the separation efficiency of coal from the pyritic particles and hydrophilic tailings.
Date: December 1997
Creator: Lai, Ralph W. & Patton, Robert A.
Partner: UNT Libraries Government Documents Department

Pulverization Induced Charge: In-Line Dry Coal Cleaning

Description: The technical feasibility of separating mineral matter and pyrite from coal as it is transported from pulverizers to boilers in pulverized coal combustion units will be examined. The charge imparted on coal during pulverization and transport to pulverized coal (PC) burners in a utility boiler will be quantified. In addition to field charge measurements, an existing computational model will be extended to numerically simulate charged particle motion in a turbulent gas through an electric field. Results from the field tests and numerical modeling will be employed in design and construction of a laboratory scale pulverizer/classifier. This laboratory unit will be used to quantify the magnitude and differential charge imparted on bituminous and subbituminous coals during pulverization and classification at temperatures and with gaseous constituents typical to utility PC units. An electrostatic separator, designed for in-line operation between pulverizers and PC boilers, will be used to clean prepulverized coals. Theoretical and experimental data are to be used in preparing a preliminary design for a full-scale, (15 ton/hr) in-line, electrostatic coal cleaning device. Finally, the economic potential for application to PC units will be assessed.
Date: May 13, 1997
Creator: Schaefer, J.L. & Stencel, J.M.
Partner: UNT Libraries Government Documents Department

Engineering development of advanced physical fine coal cleaning technologies: Froth flotation. Quarterly technical progress report No. 25, October 1, 1994--December 31, 1994

Description: A study conducted by Pittsburgh Energy Technology Center of sulfur emissions from about 1300 United States coal-fired utility boilers indicated that half of the emissions were the result of burning coals having greater than 1.2 pounds of SO{sub 2} per million BTU. This was mainly attributed to the high pyritic sulfur content of the boiler fuel. A significant reduction in SO{sub 2} emissions could be accomplished by removing the pyrite from the coals by advanced physical fine coal cleaning. An engineering development project was prepared to build upon the basic research effort conducted under a solicitation for research into Fine Coal Surface Control. The engineering development project is intended to use general plant design knowledge and conceptualize a plant to utilize advanced froth flotation technology to process coal and produce a product having maximum practical pyritic sulfur reduction consistent with maximum practical BTU recovery. This progress report provides a summary of the technical work undertaken during this period, highlighting the major results. A brief description of the work done prior to this quarter is provided in this report under the task headings.
Date: December 31, 1994
Partner: UNT Libraries Government Documents Department

Electrochemical Evaluation of Thin-Film Li-Si Anodes Prepared by Plasma Spraying

Description: Thin-film electrodes of a plasma-sprayed Li-Si alloy were evaluated for use as anodes in high-temperature thermally activated (thermal) batteries. These anodes were prepared using 44% Li/56% Si (w/w) material as feed material in a special plasma-spray apparatus under helium or hydrogen, to protect this air- and moisture-sensitive material during deposition. Anodes were tested in single cells using conventional pressed-powder separators and lithiated pyrite cathodes at temperatures of 400 to 550 C at several different current densities. A limited number of 5-cell battery tests were also conducted. The data for the plasma-sprayed anodes was compared to that for conventional pressed-powder anodes. The performance of the plasma-sprayed anodes was inferior to that of conventional pressed-powder anodes, in that the cell emfs were lower (due to the lack of formation of the desired alloy phases) and the small porosity of these materials severely limited their rate capability. Consequently, plasma-sprayed Li-Si anodes would not be practical for use in thermal batteries.
Date: September 8, 1999
Creator: GUIDOTTI,RONALD A.; REINHARDT,FREDERICK W. & SCHARRER,GREGORY L.
Partner: UNT Libraries Government Documents Department

Mechanisms of pyrite oxidation to non-slagging species. Quarterly report, January 1, 1995--March 31, 1995

Description: This document is the third quarterly status report on a project conducted at the High Temperature Gasdynamics Laboratory at Stanford University, Stanford, California and concerned with enhancing the transformation of iron pyrite to non-slagging species during staged, low-NO{sub x} pulverized coal (P.C.) combustion. The research project is intended to advance PETC`s efforts to improve our technical understanding of the high-temperature chemical and physical processes involved in the utilization of coal. The work focuses on the mechanistic description and rate quantification of the effects of fuel properties and combustion environment on the oxidation of iron pyrite to form the non-slagging species magnetite. The knowledge gained from this work is intended to be incorporated into numerical codes that can be used to formulate anti-slagging strategies involving minimal disturbance of coal combustor performance.
Date: August 1, 1995
Creator: Akan-Etuk, A.E.J. & Mitchell, R.E.
Partner: UNT Libraries Government Documents Department

A fine coal circuitry study using column flotation and gravity separation. Quarterly report, 1 December 1994--28 February 1995

Description: Column flotation provides excellent recovery of ultrafine coal while producing low ash content concentrates. However, column flotation is not efficient for treating fine coal containing significant amounts of mixed-phase particles. Fortunately, enhanced gravity separation has proved to have the ability to treat the mixed-phased particles more effectively. A disadvantage of gravity separation is that ultrafine clay particles are not easily rejected. Thus, a combination of these two technologies may provide a circuit that maximizes both the ash and sulfur rejection that can be achieved by physical coal cleaning while maintaining a high energy recovery. This project is studying the potential of using different combinations of gravity separators, i.e., a Floatex hydrosizer and a Falcon Concentrator, and a proven flotation column, which will be selected based on previous studies by the principle investigator. During this reporting period, an in-plant Box-Behnken test program of the Floatex hydrosizer has been conducted at Kerr-McGee`s Galatia preparation plant. The results have shown that the Floatex hydrosizer can be successfully used to reject most of coarser ({plus}100 mesh) pyrite and mineral matter in the coal stream to the plant. With a single operation, ash rejection of 63% and total sulfur rejection of 43% have been achieved while maintaining a combustible recovery as high as 90.5%. A long term duration test under the optimum operating conditions determined from Box-Behnken test results has also been conducted. The feed samples for the following enhanced gravity - column flotation studies, which will be carried out in the next reporting period, have been collected.
Date: December 31, 1995
Creator: Honaker, R.Q. & Reed, S.
Partner: UNT Libraries Government Documents Department

Oxidation of coal and coal pyrite mechanisms and influence on surface characteristics. Quarterly technical progress report, December 1, 1993--May 31, 1994

Description: The objective of this research is to develop a mechanistic understanding of the oxidation of coal and coal pyrite, and to correlate the intrinsic physical and chemical properties of these minerals, along with changes resulting from oxidation, with those surface properties that influence the behavior in physical cleaning processes. The results will provide fundamental insight into oxidation, in term of the bulk and surface chemistry, the microstructure, and the semiconductor properties of the pyrite. During the fourteenth and fifteenth quarters, flotation tests were done on Upper Freeport coal from the Troutville No. 2 Mine, Clearfield County, Pennsylvania and on coal samples from the Pennsylvania State Coal Bank. The influence of electrode potential on the surface properties of coal pyrite was tested using contact angle measurements on polarized Pittsburgh coal pyrite electrode.
Date: January 1, 1996
Creator: Doyle, F.M.
Partner: UNT Libraries Government Documents Department

A Silica/Fly Ash-Based Technology for Controlling Pyrite Oxidation

Description: The purpose of our studies during this past six-month period was to evaluate the surface properties of iron-oxide-silicate coatings. The specific objectives were (a) to evaluate the mechanisms and ability of hydrous ferric oxide (HFO) to adsorb silica (Si); (b) to evaluate the effects of Si on the bulk and surface properties of HFO; and (c) to evaluate the effect of Si on heavy-metal adsorption properties by iron-oxides.
Date: April 14, 1997
Creator: Evangelou, V. P.
Partner: UNT Libraries Government Documents Department

Electrochemical Evaluation of Pyrite Films Prepared by Plasma Spraying

Description: Thermally activated batteries use electrodes that are typically fabricated by cold pressing of powder. In the LiSi/FeS2 system, natural (mineral) pyrite is used for the cathode. In an effort to increase the energy density and specific energy of these batteries, flame and plasma spraying to form thin films of pyrite cathodes were evaluated. The films were deposited on a 304 stainless steel substrate (current collector) and were characterized by scanning electron microscopy and x-ray dlfllaction. The films were electrochemically tested in single cells at 5000C and the petiormance compared to that of standard cells made with cold-pressed powders. The best results were obtained with material deposited by de-arc plasma spraying with a proprietq additive to suppress thermal decomposion of the pyrite.
Date: October 30, 1998
Creator: Guidotti, R.A. & Reinhardt, F.W.
Partner: UNT Libraries Government Documents Department

Controlling incipient oxidation of pyrite for improved rejection. Eighth quarterly technical progress report, July 1, 1994--September 30, 1994

Description: The major objectives of this work are (1) to determine the Eh-pH conditions under which pyrite is stable, (2) to determine the mechanism of the initial stages of pyrite oxidation and (3) to determine if the semi-conducting properties of pyrite effects its oxidation behavior. It is known that moderate oxidation of pyrite produces a hydrophobic surface product. This hydrophobic product makes it extremely difficult to depress pyrite in coal flotation circuits. The eventual objective of this work is to prevent pyrite oxidation in order to better depress pyrite in coal flotation circuits. In this work clean, unoxidized pyrite surfaces are being produced by fracturing pyrite electrodes in an electrochemical cell. It has been shown that pyrite assumes a unique potential referred to as the ``stable potential`` at the instance it is fractured and that this potential is several hundred millivolts more negative than the steady state mixed potential of pyrite. It has also been shown that by holding the potential of pyrite at its stable potential during fracture, pyrite undergoes neither oxidation nor reduction. It has also been found that fresh pyrite surfaces created by fracture in an electrochemical begin to oxidize at potentials that are about 200 mV more negative than the potentials reported in the literature for pyrite oxidation. This is attributed to the fact that most work on pyrite has employed polished electrodes that have pre-existing oxidation products on the surface. The existence of a pH dependent stable potential for freshly fractured pyrite electrodes was based on studies conducted mainly on pyrite from Peru.
Date: December 31, 1994
Creator: Yoon, R.H. & Richardson, P.E.
Partner: UNT Libraries Government Documents Department

COMPREHENSIVE INVESTIGATION OF THE LIBERATION CHARACTERISTICS OF PYRITE AND OTHER ASH-FORMING MINERALS FROM COAL

Description: The objective of this project is the development of methods for the measurement, prediction and modeling of the liberation characteristics of mineral matter and pyrite from coal, and to implement these findings in viable computer-simulation systems for coal cleaning plants. The central thrust of the project will be based on using the Andrews-Mika diagram as a convenient and experimentally verifiable model for the liberation characteristics of the constituents of coal during comminution. In order to establish the Andrews-Mika diagram, it is necessary to develop efficient techniques for density fractionation and for the measurement of the liberation spectrum in products obtained from the comminution of narrow composition fractions of coal. Dense-liquid techniques are used to produce fractionated samples, and image-analysis techniques, using linear-intercept analysis, are used to measure the liberation spectrum. The prediction of the liberation of mineral matter and pyrite from coal after comminution is based on a linear stochastic model for the description of the mineralogical texture and the random fracture pattern associated with the comminution process. Stereological correction of the distribution of linear grades is required for both the measurement and prediction of the true distribution of volumetric grades in the particle population.
Date: March 22, 1999
Partner: UNT Libraries Government Documents Department

Engineering development of advanced physical fine coal cleaning technologies: Froth flotation. Quarterly technical progress report No. 26, January 1, 1995--March 31, 1995

Description: A study conducted by Pittsburgh Energy Technology Center of sulfur emissions from about 1,300 United States coal-fired utility boilers indicated that half of the emissions were the result of burning coals having greater than 1.2 pounds of SO{sub 2} per million BTU. This was mainly attributed to the high pyritic sulfur content of the boiler fuel. A significant reduction in SO{sub 2} emissions could be accomplished by removing the pyrite from the coals by advanced physical fine coal cleaning. An engineering development project was prepared to build upon the basic research effort conducted under a solicitation for research into Fine Coal Surface Control. The engineering development project is intended to use general plant design knowledge and conceptualize a plant to utilize advanced froth flotation technology to process coal and produce a product having maximum practical pyritic sulfur reduction consistent with maximum practical BTU recovery. The overall project scope of the engineering development project is to conceptually develop a commercial flowsheet to maximize pyritic sulfur reduction at practical energy recovery values. This is being accomplished by utilizing the basic research data on the surface properties of coal, mineral matter and pyrite obtained from the Coal Surface Control for Advanced Fine Coal Flotation Project, to develop this conceptual flowsheet. This progress report provides a summary of the technical work undertaken during this period, highlighting the major results. A brief description of the work done prior to this quarter is provided in this report under the task headings.
Date: July 1, 1995
Partner: UNT Libraries Government Documents Department

A SILICA/FLY ASH-BASED TECHNOLOGY FOR CONTROLLING PYRITE OXIDATION

Description: The results of pyrite oxidation in mining areas are very low pH and elevated concentrations of iron and sulfate in the groundwater. Pyrite oxidation is therefore the main cause for acid mine drainage production. One approach to prevent AMD production is microencapsulation of pyrite crystals with an iron-oxide/silica coating (Zhang and Evangelou, 1998). Coating prevents diffusion of oxygen and Fe{sup 3+} to the crystal's surface and they are no longer able to oxidize it. The objective of this portion of the study was to test the hypothesis that fly ash is able to provide the necessary silica for iron-oxide/silica coating formation on the pyrite surfaces thus, decreasing pyrite oxidation and diminishing acid mine drainage production.
Date: February 10, 1998
Creator: EVANGELOU, DR. V.P.
Partner: UNT Libraries Government Documents Department

Mechanisms of pyrite oxidation to non-slagging species. Quarterly report, January 1--March 31, 1997

Description: This document is the eleventh quarterly status report on a project that is concerned with enhancing the transformation of iron pyrite to non-slagging species during staged, low-NO{sub x} pulverized coal (P.C.) combustion. The research project is intended to advance PETC`s efforts to improve the technical understanding of the high-temperature chemical and physical processes involved in the utilization of coal. The work focuses on the mechanistic description and rate quantification of the effects of fuel properties and combustion environment on the oxidation of iron pyrite to form the non-slagging species magnetite. Activities during this report period were associated with the numerical encoding of the pyrite combustion model. The computer program resulting from the efforts put forth is intended to provide predictive capabilities with respect to pyrite composition during pulverized coal firing. The subroutines that have been written to track the fate of a pyrite particle of specified size and composition flowing in a gaseous environment of specified oxygen concentration, temperature, and velocity are being debugged and tested.
Date: December 31, 1997
Creator: Akan-Etuk, A. E. J. & Mitchell, R. E.
Partner: UNT Libraries Government Documents Department

Mechanisms of pyrite oxidation to non-slagging species. Quarterly report, October 1--December 31, 1996

Description: This document is the tenth quarterly status report on a project that is concerned with enhancing the transformation of iron pyrite to non-slagging species during staged, low-NO{sub x} pulverized coal (P.C.) combustion. The research project is intended to advance PETC`s efforts to improve the technical understanding of the high-temperature chemical and physical processes involved in the utilization of coal. The work focuses on the mechanistic description and rate quantification of the effects of fuel properties and combustion environment on the oxidation of iron pyrite to form the non-slagging species magnetite. During this report period numerical encoding of a pyrite combustion model was embarked upon. The effort was intended to lead to predictive capabilities with respect to pyrite composition during pulverized coal firing. Many subroutines were written of a FORTRAN computer program to track the fate of a pyrite particle by integrating time-dependent differential equations for species, momentum, and energy conservation. Inputs to the program include fuel-related properties such as particle size and composition, as well as properties of the reactor environment such as oxygen level, temperature, gas velocity, and a set of initial and final positions.
Date: December 31, 1997
Creator: Akan-Etuk, A. E. J. & Mitchell, R. E.
Partner: UNT Libraries Government Documents Department