The Experts below are selected from a list of 7518 Experts worldwide ranked by ideXlab platform
John R. Bunt - One of the best experts on this subject based on the ideXlab platform.
-
Mineralogical, chemical, and petrographic properties of selected South African power stations’ Feed Coals and their corresponding density separated fractions using float-sink and reflux classification methods
International Journal of Coal Preparation and Utilization, 2018Co-Authors: Rudelle Rautenbach, Ratale H Matjie, John R. Bunt, Christien A. Strydom, Q.p. CampbellAbstract:ABSTRACTThree South African Feed Coal samples for the combustion process were beneficiated to produce carbon-rich and mineral-rich fractions. The mineralogical, petrographical, and chemical propert...
-
the impact of particle size and maceral segregation on char formation in a packed bed combustion unit
Fuel, 2013Co-Authors: N Malumbazo, John R. Bunt, Nicola J WagnerAbstract:Abstract Highveld parent Coal was crushed into three size fractions, namely: 5 mm–75 mm, 5 mm–53 mm, and 5–37.5 mm. The crushed samples were subjected as Feed Coals to heating in a packed-bed reactor to investigate the influence of particle size reduction on char formation and reactivity. Coal petrography was utilized to assess the maceral and char formation distribution of the Feed Coal samples and their packed-bed combustion unit’s products. The maceral distribution of the Feed Coal fractions differed from the typical run-of-mine Highveld Coal petrographic composition; the smallest size fractions (−53 mm and −37.5 mm) having the highest vitrinite content. Maceral distribution was further divided into total reactive maceral particles, total inert maceral particles, and total inertinite particles. The −53 mm and −37.5 mm Feed Coal samples had the highest total reactive maceral particle content. Inert char particles dominated in the packed-bed combustion unit samples due to high inertinite maceral group content of the Highveld Coals. Unexpectedly, the −53 mm Feed Coal sample had higher content of total reactive maceral particles and lower content of total inert maceral particles; whereas the −37.5 mm Feed Coal sample had high content of reactive maceral particles and high content of total inert maceral particles. This variation in maceral group content lead to the −53 mm Feed Coal sample being more reactive (producing more devolatilized and porous chars and thus reacting faster with reactant gases) than the −37.5 mm Feed Coal sample. This was due to inert maceral particles restricting the −37.5 mm Feed Coal sample from fully softening and reacting with reactant gas. This was also this was attributed to variation in volatile propagation of the three particle sizes. This confirms that a Feed Coal with smaller particle sizes results in different reactivity, char formation, and better heat transfer during combustion than the Feed Coal with large particle size range. Another important factor that plays a role in combustion is maceral association; it was observed that maceral distribution has a great influence on the char formation and its reactivity more than Coal particle size.
-
Pipe reactor gasification studies of a south african bituminous Coal blend. Part 1 - Carbon and volatile matter behaviour as function of Feed Coal particle size reduction
Fuel, 2009Co-Authors: John R. Bunt, Frans WaandersAbstract:Abstract The Sasol-Lurgi fixed-bed dry-bottom (FBDB) MKIV gasifiers are proven to be robust as far as acceptable Coal properties are concerned, in particular its ability to accommodate a range of particle size distributions (PSD) fractions. Over the years, the findings from a number of studies conducted at Sasol have played a key role in the optimization of the Sasol-Lurgi gasifiers as far as the limited amount of Coal preparation by crushing and screening is concerned. The continued optimization efforts by Sasol over many years have led to a robust and reliable gasification technology for Coal conversion, and more improvements are envisaged for the near future. In this study, gasification profiles inside real Coal beds were investigated experimentally using a pilot scale combustor unit (pipe reactor), where the top size of the Coal blend was systematically reduced from 75 mm, 53 mm and 37.5 mm. The pilot scale combustor has an inside diameter of 400 mm, is approximately 3 m long and the combustion rate is controlled by regulating the oxygen/nitrogen ratio of the gas Feed. Ash is not removed continuously, so the combustion front moves upwards through the Coal bed with time, resulting in a temperature gradient across the bed. The combustion process can be stopped at any point in time by removing all of the oxygen from the Feed gas (i.e. quenching with nitrogen). The combustor was constructed so that it can be tilted onto its side and opened up like a coffin to allow sample taking and visual inspection of the combustion profile. In this case, equivalent sized slices were taken across the length of the reactor bed contents and the samples were analysed for PSD, proximate analysis, ultimate analysis, Fisher assay and Coal char CO 2 reactivity. This paper focuses on the Coal property transformational behaviour (as characterized by the proximate analysis and Fischer tar results) through packed Coal beds of different Feed Coal size distributions. The proximate analysis results showed clear reaction zone profiles to be occurring within the pipe reactor, i.e. drying, pyrolysis, reduction and combustion (ash bed) zones, in agreement with the SL-FBDB MKIV commercial-scale findings. It was found that a decrease in Feed Coal particle size resulted in better heat transfer across the particles with ensuing faster volatile matter and tar evolution.
Paul K S Lam - One of the best experts on this subject based on the ideXlab platform.
-
partitioning and transformation behavior of toxic elements during circulated fluidized bed combustion of Coal gangue
Fuel, 2014Co-Authors: Chuncai Zhou, Guijia Liu, Ting Fang, Paul K S LamAbstract:Abstract A study on toxic elements behaviors from a 330 MW Coal gangue circulated fluidized bed co-combustion power plant equipped with electrostatic precipitators (ESPs) was performed. Simultaneous sampling of Feed Coal, bottom ash, fly ash and flue gas were implemented. Sequential chemical extraction was taken to investigate the transformation behaviors of toxic elements. The relative distribution and partitioning behavior of toxic elements in the power plants were analyzed systemically. The toxic elements can be divided into two groups, Cluster one, whereby high volatile tendencies are represented by As, Cd, Cu, Pb, Se and Sn which have a volatilization ratio more than 20% and are mainly enriched in fly ash. These elements are primarily associated with sulfide minerals. Cluster two, represented by Co, Cr, Mn and V, have low volatilization rate (⩽5%) and are equally distributed between bottom ash and fly ash. In addition, Bi, Ni and Zn may be located between Cluster one and Cluster two. The variation of modes of occurrence of toxic elements could lead to the difference of transformation behaviors during the combustion of Feed Coal. Most toxic elements transformed and partitioned into other fractions from Fe–Mn oxides during combustion.
James C. Hower - One of the best experts on this subject based on the ideXlab platform.
-
Geochemical partitioning from pulverized Coal to fly ash and bottom ash
Fuel, 2020Co-Authors: James C. Hower, Shifeng DaiAbstract:Abstract Fly ash and bottom ash chemistry is a function of the chemistry and mineral assemblages of the Feed Coal in addition to Coal pulverization, boiler type and size, combustion parameters and combustion efficiency, and configuration of the ash collection system. Pulverization eliminates
-
Coal derived unburned carbons in fly ash a review
International Journal of Coal Geology, 2017Co-Authors: James C. Hower, Colin R. Ward, John G Groppo, Uschi M Graham, Irena Kostova, Mercedes M MarotovalerAbstract:Abstract Unburned carbon (UC) in fly ash indicates inefficiency in combustion and may be an impediment to the beneficial use of fly ash or ash products in a variety of applications. The characteristics of the Coal-derived UC are a function of the rank and type of the Coal, as well as the size of the Feed Coal and the combustion conditions. At any Coal rank, inertinite macerals are inherently more difficult to combust than the associated vitrinite, and some will have a tendency to appear in the fly ash more or less unchanged from their appearance in the Feed Coal. The nature of UCs resulting from vitrinite is dependent upon the Coal rank. Low-rank huminite/vitrinite will tend to form an isotropic char; bituminous vitrinite will appear as isotropic and anisotropic cokes; and anthracite vitrinite, naturally anisotropic, is observed as partially combusted vitrinite fragments in the ash. The absorption of air entraining agents by UCs limits the use of high-UC fly ashes as a Portland cement substitute, with both standards organizations and regulatory bodies imposing limits on the acceptable UC concentrations. UC in fly ash can be used to adsorb organic compounds (such as phenols, dyes, herbicides, polychlorinated biphenyls, and petroleum constituents) and to capture trace elements (particularly Hg) from flue gas. UCs can also be used as sources of activated carbons, manufacture of graphite, and cokes in the metallurgical industry, as well as a source of carbon to Feed back into the boiler. Beneficiation of fly ash to segregate relatively UC-free or UC-rich splits for beneficial re-use can be done by size classification, electrostatic separation, and froth flotation, as well as density separation, acid digestion, and incipient fluidization. Thermal processing may also be used to burn off the UC, leaving a relatively UC-free fly ash as the product.
-
mercury capture by native fly ash carbons in Coal fired power plants
Progress in Energy and Combustion Science, 2010Co-Authors: James C. Hower, Constance L, Eric M Suuberg, Robert H Hurt, Jennifer Wilcox, Edwin S OlsonAbstract:Abstract The control of mercury in the air emissions from Coal-fired power plants is an ongoing challenge. The native unburned carbons in fly ash can capture varying amounts of Hg depending upon the temperature and composition of the flue gas at the air pollution control device, with Hg capture increasing with a decrease in temperature; the amount of carbon in the fly ash, with Hg capture increasing with an increase in carbon; and the form of the carbon and the consequent surface area of the carbon, with Hg capture increasing with an increase in surface area. The latter is influenced by the rank of the Feed Coal, with carbons derived from the combustion of low-rank Coals having a greater surface area than carbons from bituminous- and anthracite-rank Coals. The chemistry of the Feed Coal and the resulting composition of the flue gas enhances Hg capture by fly ash carbons. This is particularly evident in the correlation of Feed Coal Cl content to Hg oxidation to HgCl 2 , enhancing Hg capture. Acid gases, including HCl and H 2 SO 4 (at small concentrations) and the combination of HC1 and NO 2 , in the flue gas can enhance the oxidation of Hg. In this presentation, we discuss the transport of Hg through the boiler and pollution-control systems, the mechanisms of Hg oxidation, and the parameters controlling Hg capture by Coal-derived fly ash carbons.
-
Arsenic and Mercury Partitioning in Fly Ash at a Kentucky Power Plant
Energy & Fuels, 2003Co-Authors: Tanaporn Sakulpitakphon, James C. Hower, Alan S. Trimble, William H. Schram, Gerald A. ThomasAbstract:Coal and fly ash samples were collected from a 500-MW unit at a Kentucky power plant, with the objective of studying the distribution of arsenic, mercury, and other trace elements in fly ash. The Coal Feed was low-sulfur, high volatile A bituminous central West Virginia Coal. The plant produced a relatively low-carbon fly ash. In contrast to power plants with high-mercury Feed Coal, the fly ashes from the lower-mercury Feed Coal had low mercury values, generally not exceeding 0.01 ppm Hg. Mercury capture by fly ash varies with both the amount and type of carbon and the collection temperature; mercury capture is more efficient at lower temperatures. Arsenic in the Feed Coal and in the flue gas is of concern to the utility, because of the potential for catalyst poisoning in the selective catalytic reduction system (in the planning stage at the time of the sampling). Arsenic is captured in the fly ash, increasing in concentration in the more-distant (from the boiler) reaches of the electrostatic precipitator...
-
Volcanic ash in Feed Coal and its influence on Coal combustion products
2000Co-Authors: Michael E. Brownfield, Ronald H. Affolter, James D. Cathcart, James C. Hower, Gary D. Stricker, Isabelle K. Brownfield, J.t. O'connorAbstract:The US Geological Survey and the University of Kentucky Center for Applied Energy Research are collaborating with an Indiana Utility to determine the physical and chemical properties of Feed Coal and Coal combustion products (CCPs) from a Coal-fired power plant. The plant utilizes a low-sulfur (.23--.47 weight percent S) Coal from the Powder River Basin, Wyoming. Scanning Electron Microscope (SEM) and X-ray diffraction (XRD) analysis of Feed Coal samples identified two mineral suites. A primary suite (not authigenic) consisting of quartz (detrital and volcanic beta-form grains), biotite, and minor zircon and a secondary authigenic mineral suite containing calcite, alumino-phosphates (crandallite and gorceixite), kaolinite, quartz, anatase, barite, and pyrite. The authigenic minerals are attributed to air-fall and reworked volcanic ash that was deposited in peat-forming mires. The Powder River Basin Feed Coals contain higher amounts of Ba, Ca, Mg, Na, Sr, and P compared to other analyzed eastern Coals. These elements are associated with alumino-phosphate, biotite, calcite, and clay minerals. The element associations are indicative of Coal that incorporated volcanic ash during deposition. XRD analysis of CCPs revealed a predominance of glass, perovskite, lime, gehlenite, quartz, and phosphates with minor amounts of periclase, anhydrite, hematite, and spinel group minerals in themore » fly ash; and quartz, plagioclase (albite and anorthite), pyroxene (augite and fassaite), rhodonite, and akermanite in the bottom ash. Microprobe and SEM analysis of fly ash samples revealed quartz, zircon, monazite, euhedral laths of corundum with merrillite, hematite, dendritic spinels/ferrites, and rounded grains of wollastonite with periclase. The abundant Ca and Mg mineral phases in the fly ashes are related to the presence of carbonate, clay, and phosphate minerals in the Feed Coal. The Ca- and Mg-rich mineral phases in the CCPs can be attributed to volcanic minerals deposited in the peat-forming mire. Dissolution and alteration of these minerals occurred either in the peat-forming sate or during Coalification/diagenesis contributing to the authigenic mineral suite. Additionally, detrital mineral input and epigenetic ground-water flow may have affected the geochemistry of the Feed Coal.« less
Guijia Liu - One of the best experts on this subject based on the ideXlab platform.
-
partitioning and transformation behavior of toxic elements during circulated fluidized bed combustion of Coal gangue
Fuel, 2014Co-Authors: Chuncai Zhou, Guijia Liu, Ting Fang, Paul K S LamAbstract:Abstract A study on toxic elements behaviors from a 330 MW Coal gangue circulated fluidized bed co-combustion power plant equipped with electrostatic precipitators (ESPs) was performed. Simultaneous sampling of Feed Coal, bottom ash, fly ash and flue gas were implemented. Sequential chemical extraction was taken to investigate the transformation behaviors of toxic elements. The relative distribution and partitioning behavior of toxic elements in the power plants were analyzed systemically. The toxic elements can be divided into two groups, Cluster one, whereby high volatile tendencies are represented by As, Cd, Cu, Pb, Se and Sn which have a volatilization ratio more than 20% and are mainly enriched in fly ash. These elements are primarily associated with sulfide minerals. Cluster two, represented by Co, Cr, Mn and V, have low volatilization rate (⩽5%) and are equally distributed between bottom ash and fly ash. In addition, Bi, Ni and Zn may be located between Cluster one and Cluster two. The variation of modes of occurrence of toxic elements could lead to the difference of transformation behaviors during the combustion of Feed Coal. Most toxic elements transformed and partitioned into other fractions from Fe–Mn oxides during combustion.
Chuncai Zhou - One of the best experts on this subject based on the ideXlab platform.
-
partitioning and transformation behavior of toxic elements during circulated fluidized bed combustion of Coal gangue
Fuel, 2014Co-Authors: Chuncai Zhou, Guijia Liu, Ting Fang, Paul K S LamAbstract:Abstract A study on toxic elements behaviors from a 330 MW Coal gangue circulated fluidized bed co-combustion power plant equipped with electrostatic precipitators (ESPs) was performed. Simultaneous sampling of Feed Coal, bottom ash, fly ash and flue gas were implemented. Sequential chemical extraction was taken to investigate the transformation behaviors of toxic elements. The relative distribution and partitioning behavior of toxic elements in the power plants were analyzed systemically. The toxic elements can be divided into two groups, Cluster one, whereby high volatile tendencies are represented by As, Cd, Cu, Pb, Se and Sn which have a volatilization ratio more than 20% and are mainly enriched in fly ash. These elements are primarily associated with sulfide minerals. Cluster two, represented by Co, Cr, Mn and V, have low volatilization rate (⩽5%) and are equally distributed between bottom ash and fly ash. In addition, Bi, Ni and Zn may be located between Cluster one and Cluster two. The variation of modes of occurrence of toxic elements could lead to the difference of transformation behaviors during the combustion of Feed Coal. Most toxic elements transformed and partitioned into other fractions from Fe–Mn oxides during combustion.
-
Distribution of trace elements in Feed Coal and combustion residues from two Coal-fired power plants at Huainan, Anhui, China
Fuel, 2013Co-Authors: Quan Tang, Chuncai Zhou, Guijian Liu, Ruoyu SunAbstract:The rapid expansion of Coal-fired power plants (CFPPs) in China has produced huge volume of toxic elements associated combustion residues, which pose great threat to local environment. In this study, Feed Coal, fly ash, bottom ash and FGD gypsum samples were collected from two different CFPPs at Huainan, Anhui, China. Feed Coal and combustion residues were morphologically and mineralogically characterized by scanning electron microscopy equipped with energy-dispersive microanalyser and X-ray diffraction. Concentrations of thirteen major and trace elements in these samples were determined by inductively coupled plasma atomic emission spectrometry (B, Ti, Mn, Ni and Zn), inductively coupled plasma mass spectrometry (Cd, Co, Cr, Cu, Pb, Sn and V) and atomic fluorescence spectroscopy (As). The results show that most of the trace elements were concentrated in the fly ash, only Fe and Mn were enriched in the bottom ash. The diameters of ash particles removed by the electrostatic precipitator were in an inverse relationship with the enrichment factors of most trace elements. To address possible exposure of combustion residues in the environment, laboratory controlled leaching tests were carried out on fly ash and gypsum to understand the environmental behaviors of these elements. Both fly ash and gypsum were identified as not-hazardous wastes.