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Coal Fly Ash (coal + fly_ash)
Selected AbstractsMechanisms of Submicron and Residual Ash Particle Formation during Pulverised Coal Combustion: A Comprehensive ReviewASIA-PACIFIC JOURNAL OF CHEMICAL ENGINEERING, Issue 3-4 2005D. Yu Coal fly ash has been a traditional concern of utilities since coal was used to generate electricity because it may bring about a number of technical and economic problems such as slagging, fouling, corrosion, erosion, waste disposal and overall boiler efficiency reduction. Moreover, fine particulates that escape the combustion system are recognized to have a negative impact on health and the environment due to the enrichment of the toxic trace elements and being readily inhaled. This work gives a brief review of the studies carried out in the past decades and tries to elucidate those processes that contribute to ash formation. They include the mechanisms that control submicron ash formation and those that are related to residual ash formation. The mechanism of vaporization and condensation is believed to be the major source of submicron ash particles and is discussed in detail in this review. Residual ash formation is the consequence of the competition between ash coalescence and char fragmentation. Moreover, fragmentation of excluded minerals and rotationally induced shedding may also contribute to the residual ash formation. Our literature review has provided a number of experimental and theoretical results describing how the submicron ash and residual ash are formed, Finally we present some recommendations for possible future research topics, including sampling techniques, measurement techniques, experimental studies and modelling efforts. [source] Removal characteristics of some priority organic pollutants from water in a fixed bed fly ash columnJOURNAL OF CHEMICAL TECHNOLOGY & BIOTECHNOLOGY, Issue 12 2005Mitali Sarkar Abstract The efficiency of a coal fly ash (generated from a thermal power plant) adsorption column for the removal of some priority organic pollutants, viz phenol, o -hydroxyphenol, m -hydroxyphenol and 4-nitrophenol from aqueous solution has been studied. The column performance was evaluated from the concept of the formation of a primary adsorption zone and the breakthrough curve. The extent of solute removal obtained from breakthrough curve during column operation was compared with that obtained from the isotherm parameters for batch operation. The loaded solutes in the column were successfully eluted with acetone, achieving 98% recovery. In order to determine the practical applicability of the column operation the process was repeated a number of times and the variation of column capacity with number of operation cycles was evaluated. Even after six successive cycles, the column was found to retain almost 80% capacity. Copyright © 2005 Society of Chemical Industry [source] The use of coal fly ash in sodic soil reclamationLAND DEGRADATION AND DEVELOPMENT, Issue 3 2003D. Kumar Abstract An experiment was conducted for two years in northwest India to explore the feasibility of using coal fly ash for reclamation of waterlogged sodic soils and its resultant effects on plant growth in padi,wheat rotation. The initial pH, electrical conductivity, exchangeable sodium percentage and sodium adsorption ratio of the experimental soil were 9.07, 3.87,dS,m,1, 26.0 and 4.77 (me l),1/2, respectively. The fly ash obtained from electrostatic precipitators of thermal power plant had a pH of 5.89 and electrical conductivity of 0.88,dS,m,1. The treatments comprised of fly ash levels of 0.0, 1.5, 3.0, 4.5, 6.0 and 7.5 per cent, used alone as well as in combination with 100, 80, 60, 40, 20 and 10 per cent gypsum requirement of the soil, respectively. There was a slight reduction in soil pH while electrical conductivity of the soil decreased significantly with fly ash as measured after padi and wheat crops. The sodium adsorption ratio of the soil decreased with increasing fly ash levels, while gypsum treatments considerably added to its favourable effects. Fly ash application increased the available elemental status of N, K, Ca, Mg, S, Fe, Mn, B, Mo, Al, Pb, Ni, Co, but decreased Na, P and Zn in the soil. An application of fly ash to the soil also increased the concentrations of above elements except Na, P and Zn in the seeds and straw of padi and wheat crops. The available as well as elemental concentrations in the plants was maximum in the 0 per cent fly ash,+,100 per cent gypsum requirement treatment except Na and heavy elements like Ni, Co, Cr. The treatment effects were greater in the fly ash,+,gypsum requirement combinations as compared to fly ash alone. Saturated hydraulic conductivity and soil water retention generally improved with the addition of fly ash while bulk density decreased. Application of fly ash up to 4.5 per cent level increased the straw and grain yield of padi and wheat crops significantly in both years. The results indicated that for reclaiming sodic soils of the southwest Punjab, gypsum could possibly be substituted up to 40 per cent of the gypsum requirement with 3.0 per cent acidic fly ash. Copyright © 2003 John Wiley & Sons, Ltd. [source] Determination of refractory elements in atmospheric particulates using slurry sampling electrothermal vaporization inductively coupled plasma optical emission spectrometry and inductively coupled plasma mass spectrometry with polyvinylidene fluoride as chemical modifierRAPID COMMUNICATIONS IN MASS SPECTROMETRY, Issue 14 2006Yuefei Zhang Electrothermal vaporization (ETV) inductively coupled plasma optical emission spectrometry (ICP-OES) and inductively coupled plasma mass spectrometry (ICP-MS) with polyvinylidene fluoride (PVDF) as chemical modifier are critically compared for the determination of refractory elements in coal fly ash and airborne particulates. The atmospheric particulates that collected on a PVDF filter were introduced into the graphite furnace in the form of a slurry by dissolving the filter in dimethylformamide, and the dissolved filter PVDF, along with additional added PVDF powder, was used as a chemical modifier for subsequent ETV-ICP-OES and ETV-ICP-MS determination. The vaporization behaviors of analytes (Ti, Zr, V, Mo, Cr, La) in ETV-ICP-OES/MS were studied in detail, and the optimal ETV operating parameters were obtained. Under the optimized operating conditions, the detection limits of target elements were 0.08,2.7,ng,m,3 for ETV-ICP-OES and 0.5,50,pg,m,3 for ETV-ICP-MS, respectively, with analytical precisions of 3.5,7.3% for ETV-ICP-OES and 3.9,9.6% for ETV-ICP-MS, respectively. The tolerable amounts of matrix elements for ETV-ICP-OES are higher than for ETV-ICP-MS. Both ETV-ICP-OES and ETV-ICP-MS were used to directly determine the trace refractory elements in coal fly ash and airborne particulates and the analytical results are comparable. Copyright © 2006 John Wiley & Sons, Ltd. [source] Natural revegetation of coal fly ash in a highly saline disposal lagoon in Hong KongAPPLIED VEGETATION SCIENCE, Issue 3 2008L.M. Chu Abstract. Question: What is the relationship of the naturally colonizing vegetation and substrate characteristics in fly ash lagoons? Location: West lagoon, Deep Bay, a 13-ha coastal lagoon in Hong Kong in subtropical Southeast Asia. Methods: Vegetation establishment was examined in a coal fly ash lagoon two years after its abandonment to investigate the distribution of vegetation in relationship to the chemical properties of the fly ash in the lagoon. A greenhouse experiment assessed the limits imposed on plant growth in fly ash. Results: The fly ash was saline, slightly alkaline and very poor in organic matter and nitrogen. Ash from bare and vegetated areas differed significantly in their salinity and extractable concentrations of inorganic nitrogen and various metals. Bare ash had a significantly higher conductivity and extractable sodium, aluminum, manganese, potassium, and lead. In total 11 plant species that belonged to seven families were found growing on the fly ash; all species except the shrub Tamarix chinensis were herbaceous. Using discriminant analysis, the most important factors in distinguishing bare and vegetated ashes were conductivity and sodium. Cluster analysis of bare samples gave two distinct groups, one from the periphery of the lagoon, which had lower sodium, conductivity, organic carbon, potassium and copper, and the other from a second group that contained ashes from the central region of the lagoon. Results of the greenhouse experiment showed that the inhibition of plant growth was significantly correlated with the presence of soluble toxic elements in ash. Conclusion: Toxicity and salinity seem to be the major limiting factors to plant establishment in fly ash, and these factors must be ameliorated for the successful reclamation of these fly ash lagoons. [source] | |||||||||||||