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Fly Ash (fly + ash)
Kinds of Fly Ash Selected AbstractsChemical removal of PCBs from water samples under ambient conditionsJOURNAL OF CHEMICAL TECHNOLOGY & BIOTECHNOLOGY, Issue 5 2002Hendrik Nollet Abstract Liquids and sludges containing polychlorinated biphenyls (PCBs) can be treated to concentrate the PCBs in a solid residue. The latter can then be handled to destroy the PCBs. In the first part of this work, procedures are explored by which 2,3,4-trichlorobiphenyl (TCB) and 2,2,,3,3,,4,5,6-heptachlorobiphenyl (HeCB) are insolubilised, flocculated and removed from the water. The results demonstrate that application of Fe(III)-oxyhydroxide precipitation permits effective and reversible co-precipitation of TCB and HeCB. Fly ash from coal-fired thermal powerplants and CaO can be used as well for the rapid removal of TCB and HeCB. In the second part of this work, rapid insolubilisation followed by the degradation of TCB and HeCB by zero-valent iron powder in anaerobic batch systems is presented. Zero-valent iron was also used for the reductive dechlorination/remediation of TCB and HeCB sorbed on the fly ash and CaO particles. Overall, this paper describes a methodology to rapidly concentrate the PCBs from water and to concomitantly detoxify them in the concentrate by a chemical reductive process under ambient conditions of pH and temperature. © 2002 Society of Chemical Industry [source] The Fate of Lead in MSWI-Fly Ash During Heat Treatment: An X-Ray Absorption Spectroscopy Study,ADVANCED ENGINEERING MATERIALS, Issue 6 2009Rudolf Paul Wilhelm Jozef Struis The study focuses on the potential of removing toxifying Pb from a certified, multi-element fly ash (BCR176) by thermal treatment between 300 and 950,°C under different carrier gas compositions (Ar or Ar,+,O2). The treatment was studied by in situ monitoring the evaporation rate of Pb, C, S, Na, and K during heating and by synchrotron X-ray absorption spectroscopy of selected samples collected during vaporization at the Pb L3 -edge. [source] Fly ash concrete subjected to thermal cyclic loadsFATIGUE & FRACTURE OF ENGINEERING MATERIALS AND STRUCTURES, Issue 5 2010M. S. KHAN ABSTRACT The present study describes the behaviour of concrete as well as fly ash concrete when subjected to varying number of high temperature heating cycles. A Concrete mix (1:2.37:2.98) with 340 kg/m3 cement and,w/cm,ratio 0.45 was prepared. Cement was replaced by varying percentages (0%, 20%, 40%, 50% and 60%) of fly ash by weight of cement. The concrete was subjected to a constant temperature of 200°C for 7, 14, 21 and 28 heating cycles. One heating cycle corresponds to 8 h heating and subsequent cooling in 24 h. Subsequently the effect of temperature on the properties of the concrete was investigated and compared with that of the properties of unheated concrete. The compressive strength of plain as well as fly ash concrete increased when it was subjected to thermal cyclic loads. Moreover, the compressive strength increased with an increase in number of heating cycles. Thermal conductivity of concrete was found to decrease with an increase in the fly ash content. [source] Processing of urea-formaldehyde-based particleboard from hazelnut shell and improvement of its fire and water resistanceFIRE AND MATERIALS, Issue 8 2009M. Gürü Abstract The purpose of this study was to manufacture urea-formaldehyde-based particleboard from hazelnut shell and eliminate its disadvantages such as flammability, water absorption, swelling thickness by using fly ash and phenol-formaldehyde. Synthesized urea-formaldehyde and grained hazelnut shells were blended at different ratios ranging from 0.8 to 3.2 hazelnut shell/urea-formaldehyde and dried at 70°C in an oven until constant weight was reached. In addition, other parameters affecting polymer composite particleboard from hazelnut shell and urea-formaldehyde were investigated to be the amount of fly ash, amount of phenol formaldehyde and the effects of these parameters on bending stress, limit oxygen index, water absorption capacity and swelling in the thickness. The optimization results showed that the maximum bending strength was 4.1N/mm2, at urea-formaldehyde ratio of 1.0, reaction temperature of 70°C, reaction time of 25,min, hazelnut shell/urea-formaldehyde resin of 2.4 and mean particle size of 0.1,mm. Although the limited oxygen index and smoke density of composite particleboard without fly ash has 22.3 and 1.62, with fly ash of 16% (w/w) according to the filler has 38.2 and 1.47, respectively. Water absorption and increase in the swelling thickness exponentially decreased with increasing phenol formaldehyde. Copyright © 2009 John Wiley & Sons, Ltd. [source] The lignite electricity-generating sector in Greece: Current status and future prospectsINTERNATIONAL JOURNAL OF ENERGY RESEARCH, Issue 9 2004N. Koukouzas Abstract Lignite plays an important role in Greece's energy sector as it satisfies over 70% of country's needs in electric power. The extraction of lignite takes place mainly in three regions of Greece, namely Ptolemais-Amyndeon, Megalopolis and Florina. The annual production of lignite is around 60 million tons, out of which 48 million tons derive from the coal fields of northern Greece (Ptolemais-Amyndeon and Florina). Almost the entire lignite production is consumed for electricity generation, while small amounts of lignite are used for briquettes and other applications. The Greek coal-fired power plants, which are about 4500 MW, use conventional technology and they are old (an average of 30 years). In the coming years new coal fields will be exploited in Florina,another 2.5 million tons of coal,in order to satisfy the currently under construction 365 MW plant located at Meliti, Florina, Northern Greece. Even though the lignite reserves are widespread in Greece and other areas such as Elassona and Drama could possibly host power plants, it is expected that the Florina power plant will be the last coal-fired plant to be build in the country. Lignite has to compete with natural gas,the construction of the main gas pipeline network has been completed,imported oil and renewable energy sources. The new EU regulations on power plant emissions raise obstacles for the firing of lignite, although it is low in sulphur. It must be shown that lignite produces low cost electricity in a environmentally friendly manner. The utilization of fly ash and land reclamation can improve the situation in lignite mining. In particular, specific attention was paid to further research and potential use of fly ash in road construction, the production of bricks and concrete, and the production of zeolites from lignitic fly ash. The use of clean coal technologies in power plants can solve many emission problems. Specific measures to increase the efficiency of lignite-fired power units might include: identification of the loss sources of every unit, improvement of the cold end of the steam turbines, optimization of the beater wheel mills operation, and the combination of natural gas-fired turbines with the existing boilers. The liberalization of the electricity market needs to be considered seriously from the lignite industry, since the potential electricity producers can freely choose from all kinds of fuels, such as imported coal, oil, gas and renewables. However, Greek lignite meets the requirements for the security of supply, as indicated in the EU's Green Paper. It needs only to be competitive in the new energy sector by improving mining and combustion conditions. Further research on these topics, through the European Commission's ECSC and Framework Programmes, as well as the national programmes, is required. Copyright © 2004 John Wiley & Sons, Ltd. [source] Emission of trace toxic metals during pulverized fuel combustion of Czech coalsINTERNATIONAL JOURNAL OF ENERGY RESEARCH, Issue 13 2003P. Danihelka Abstract A study of the trace elements emission (As, Se, Cd, Co, Cr, Cu, Zn, Hg, Tl, Pb, Ni, Sn, Sb, V, Mn and Fe) from pulverized coal combustion has been made at six heating and power stations situated in the Czech Republic. The amount of chlorine in coal has considerable influence on volatilization of some elements such as Zn, Cu, Pb, Hg and Tl, which is explained by the formation of thermodynamically stable compounds of these elements with chlorine. Generally, the affinities for Cl follows the order Tl > Cu > Zn > Pb > Co > Mn > Sn > Hg. The experimental data indicates enrichment of some of the trace toxic elements in the emissions (Cu, Zn, As, Se, Cd, Sn, Sb, Hg and Pb) and good agreement was obtained by thermodynamic equilibrium calculations with a few exceptions. In the case of Fe, Mn, Co, Cr and Sn calculated values are overestimated in the bottom ash and there are zero predicted amounts of these elements in the fly ash. In comparison, the results from experiments show up to 80% of these elements retained in fly ash. This implies that there exist additional steps leading to the enrichment by Fe, Mn, Co, Cr and Sn of small particles. Such mechanisms could include the ejection during devolatilization of small inorganic particles from the coal of bottom ash particles, or disintegration of the char containing these metals to small particles of fly ash. On the other hand, there are slightly overestimated or similar values of relative enrichment factors for As, V, Cu, Cd, Sb, Tl and Pb in the fly ashes and zero predicted values for bottom ashes. Our experimental results show about 5% or less of these elements are retained in bottom ashes, so they probably remain in the bottom ash inside unburned parts of coal. Copyright © 2003 John Wiley & Sons, Ltd. [source] Silicon-mediated resistance of sugarcane to Eldana saccharina Walker (Lepidoptera: Pyralidae): effects of silicon source and cultivarJOURNAL OF APPLIED ENTOMOLOGY, Issue 8 2006M. G. Keeping Abstract:, The effects of four silicon sources , a USA calcium silicate, a local (South African) calcium silicate, Slagment® and fly ash , on the resistance of sugarcane cultivars (two resistant and two susceptible) to Eldana saccharina Walker (Lepidoptera: Pyralidae) were studied in a potted sugarcane trial. Silicon sources were applied at 5000 or 10 000 kg/ha for the calcium silicates and Slagment; fly ash was applied at 15 000 or 30 000 kg/ha. The greatest increase in plant silicon content (particularly in stalks) was recorded for plants treated with local calcium silicate. Silicon uptake did not vary significantly between the susceptible and resistant cultivars, although the resistant cultivars had inherently higher silicon content than the susceptible ones. Treatment with silicon significantly reduced borer damage and borer performance at the higher treatment level. In general, borer damage and performance decreased with increasing rates of applied silicon and both variables were inversely related with per cent stalk silicon. On average, the higher silicon rate reduced damage by 34% in the susceptible cultivars and by 26% in the resistant cultivars, supporting the argument that susceptible cultivars benefit more from silicon treatments than resistant ones. We propose that calcium silicate amendments could be employed in the integrated, area-wide management of E. saccharina and in the management of soil acidity, both of which are widespread problems in the South African sugar industry. [source] Removal of heavy metals from municipal solid waste incineration (MSWI) fly ash by traditional and microwave acid extractionJOURNAL OF CHEMICAL TECHNOLOGY & BIOTECHNOLOGY, Issue 9 2010Jun Xue Abstract BACKGROUND: Municipal solid waste incinerator (MSWI) fly ash is regarded as hazardous waste because it contains various toxic metals. A previous study has shown that fly ash can be detoxified by removal of heavy metals. In this work, the extractability of heavy metals from MSWI fly ash by traditional and microwave acid extraction were compared. RESULTS: A 24 , 1 fractional factorial experimental design was adopted using acid concentration, extraction time, temperature, and liquid/solid (L/S) ratio as the experimental factors for traditional extraction, and acid concentration, extraction time, liquid/solid (L/S) ratio and microwave power as the experimental factors for microwave extraction. The traditional extraction results show that L/S played an important role in Zn, Cd extraction while L/S ratio and extractant concentration were important for Pb extraction. However, no controlling parameter was determined for Cu and Cr extraction. For the microwave extraction, it was shown that L/S was important for Pb and Zn and extractant concentration was important for Pb, Zn and Cd. The time and the power were not significant for the extractability of heavy metals. CONCLUSION: Hydrochloric acid was an effective extractant. Microwave heating promoted extraction and shortened extraction time. Microwave acid extraction treatment is a potentially feasible method for the removal of heavy metals from MSWI fly ash. Copyright © 2010 Society of Chemical Industry [source] Use of recycled copper slag for blended cementsJOURNAL OF CHEMICAL TECHNOLOGY & BIOTECHNOLOGY, Issue 3 2008M Isabel Sánchez de Rojas Abstract Copper slag is a by-product generated during smelting to extract copper metal from the ore. The copper slag obtained may exhibit pozzolanic activity and may therefore be used in the manufacture of addition-containing cements. In this paper the effect of the incorporation of the copper slag in cement is measured. Blends of copper slag with Portland cement generally possess properties equivalent to Portland cement containing fly ash, but very different to the silica fume incorporation. Copper slag and fly ash reduce the heat of hydration more effectively than silica fume in mortars. The replacement of 30% cement by copper slag reduces the flexural and compressive strength in a similar way to fly ash; however, after 28 days, the reduction is less than the percentage of substitution. Hydrated calcium aluminate phases were analysed using scanning electron microscopy (SEM) and X-ray diffraction (XRD) techniques. The pozzolanic activity of copper slag is similar to that of fly ash and higher than silica fume. In the presence of low water/cement ratios, certain pozzolanic materials produce a very compact cement paste that limits the space available for hydration products, a determining factor in the formation of hydrated calcium aluminates. SEM was found to be a useful analytical technique when aluminates are formed and can be clearly detected by XRD. Copyright © 2008 Society of Chemical Industry [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] Chemical removal of PCBs from water samples under ambient conditionsJOURNAL OF CHEMICAL TECHNOLOGY & BIOTECHNOLOGY, Issue 5 2002Hendrik Nollet Abstract Liquids and sludges containing polychlorinated biphenyls (PCBs) can be treated to concentrate the PCBs in a solid residue. The latter can then be handled to destroy the PCBs. In the first part of this work, procedures are explored by which 2,3,4-trichlorobiphenyl (TCB) and 2,2,,3,3,,4,5,6-heptachlorobiphenyl (HeCB) are insolubilised, flocculated and removed from the water. The results demonstrate that application of Fe(III)-oxyhydroxide precipitation permits effective and reversible co-precipitation of TCB and HeCB. Fly ash from coal-fired thermal powerplants and CaO can be used as well for the rapid removal of TCB and HeCB. In the second part of this work, rapid insolubilisation followed by the degradation of TCB and HeCB by zero-valent iron powder in anaerobic batch systems is presented. Zero-valent iron was also used for the reductive dechlorination/remediation of TCB and HeCB sorbed on the fly ash and CaO particles. Overall, this paper describes a methodology to rapidly concentrate the PCBs from water and to concomitantly detoxify them in the concentrate by a chemical reductive process under ambient conditions of pH and temperature. © 2002 Society of Chemical Industry [source] A comparative adsorption study of copper on various industrial solid wastesAICHE JOURNAL, Issue 10 2004Archana Agrawal Abstract The adsorption behavior of Cu on three solid waste materials,sea nodule residue (SNR), fly ash (FA), and red mud (RM),was investigated. The effects of various parameters, such as pH of the feed solution, contact time, temperature, adsorbate and adsorbent concentration, and particle size of the adsorbent, were studied for optimization of the process parameters. Adsorption of copper increased with increasing time, temperature, pH, and adsorbate concentration, and decreased with increasing initial copper concentration. The equilibrium data fit well with the Langmuir and Freundlich isotherms in the case of SNR, but not on RM and FA, because there was no appreciable effect of temperature on the metal removal on these two adsorbents. The adsorption of copper on SNR followed first-order kinetics involving the surface complex formation mechanism on the charged surface. Under the optimized conditions the adsorption capacity for copper was found to be 19.65 mg/g of SNR, 1.98 mg/g of FA, and 2.28 mg/g of RM. Thus the adsorption capacity of SNR was found to be more than that of activated carbon, thus making it suitable for the treatment of industrial effluents to reduce the level of copper within the permissible limits for its land disposal (3 mg/L) according to ISI guidelines. © 2004 American Institute of Chemical Engineers AIChE J 50: 2430,2438, 2004 [source] Application of water as a solvent in microwave-assisted extraction for analysis of PCBs and CBzs in fly ashJOURNAL OF SEPARATION SCIENCE, JSS, Issue 6 2005Yifei Sun Abstract Polychlorinated biphenyls (PCBs) and chlorobenzenes (CBzs) are two classes of dioxin precursors formed in municipal solid waste incinerators (MSWIs); they produce negative health effects similar to those of dioxins. Reducing the analytical time required for determining the concentrations of these compounds in MSWIs is important for quickly evaluating their importance and assessing associated health risks. In the present study, water is used as a safe and environmentally friendly solvent in microwave-assisted extraction (MAE) for PCB and CBz analyses. MAE is compared with traditional Soxhlet extraction (SE) to determine the extraction efficiencies. The evaluation of extraction efficiencies shows that MAE has a high extraction efficiency compared with that of SE when water content is lower than 60%. Furthermore, the extraction time and organic solvent consumption are reduced with MAE compared with SE. [source] Speciation of zinc in secondary fly ashes of municipal solid waste at high temperaturesJOURNAL OF SYNCHROTRON RADIATION, Issue 4 2009Meijuan Yu The evaporation aerosols produced during the vitrification process of municipal solid waste incinerators (MSWI) fly ash represent a potential environmental risk owing to their high content of heavy metals. In this research, high-temperature heating processes were carried out on fly ashes collected from bag houses in a Chinese MSWI plant and the secondary fly ashes (SFA) were separately collected at three high temperatures (1273,K, 1423,K and 1523,K) below the melting range. Elemental analysis showed that high contents of both zinc and chlorine were present in these SFA samples and, according to the standard of the heavy metals industrial grade of ore, SFAs can be re-used as metallurgical raw materials or rich ore. Moreover, as shown by XAS analysis and for different high temperatures, zinc environments in the three SFA samples were characterized by the same local structure of the zinc chloride. As a consequence, a zinc recycling procedure can be easily designed based on the configuration information. [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] Degradation processes in Al/SiCp/MgAl2O4 composites prepared from recycled aluminum with fly ash and rice hull ashMATERIALS AND CORROSION/WERKSTOFFE UND KORROSION, Issue 11 2007M. I. Pech-Canul The degradation characteristics of Al/SiCp/spinel composites prepared with fly ash (FA) and rice hull ash (RHA) under environmental conditions were investigated. Composite specimens were prepared with recycled aluminum via reactive infiltration in the temperature range 1050,1150,°C for 50,70 min and, in argon atmosphere at a pressure slightly above that of the atmospheric pressure. Results reveal that although both FA and RHA help in preventing SiCp dissolution and the subsequent chemical degradation of the composites, due to the interaction of native carbon in FA with liquid aluminum, FA-composites are susceptible to corrosion via Al4C3. Moreover, this phase accelerates the degradation process and increases the damage severity. The primary corrosion mechanism in both types of composites is attributed to microgalvanic coupling between the intermetallic Mg2Si and the matrix. Accordingly, an appropriate control of the Si/(Si,+,Mg) molar ratio in the aluminum alloy hinders the Mg2Si corrosion mechanism in both types of composites and a proper FA calcination prevents chemical degradation in FA composites. [source] Urinary metal and polycyclic aromatic hydrocarbon biomarkers in boilermakers exposed to metal fume and residual oil fly ashAMERICAN JOURNAL OF INDUSTRIAL MEDICINE, Issue 6 2005Sutapa Mukherjee MBBS Abstract Background Boilermakers are occupationally exposed to known carcinogens. Methods The association of urinary 1-hydroxy-pyrene (1-OHP), a biomarker of polycyclic aromatic hydrocarbon (PAH) exposure, with biomarkers of metal exposure (vanadium, chromium, manganese, nickel, copper, and lead) in boilermakers exposed to metal fume from welding and dust particulates from residual oil fly ash (ROFA) was examined. A repeated measures cohort study was conducted during the overhaul of an oil-fired boiler. Twice-daily urine samples were obtained for 5 days and analyzed for cotinine, 1-OHP, and metals. Generalized estimating equations (GEE) were used to model the multivariate relationship of 1-OHP to the explanatory variables. Results Metal and 1-OHP levels were determined for 165 urine samples from 20 boilermakers and these levels increased during the workweek. However, the 1-OHP level was not significantly associated with any individual metal level at any time point. Conclusion This suggests that boilermakers were occupationally exposed to PAH and metals, but 1-OHP as a PAH biomarker was unable to serve as a surrogate marker of metal exposure for the metals measured in this study. Am. J. Ind. Med. 47:484,493, 2005. © 2005 Wiley-Liss, Inc. [source] Reinforcement of compatibilized NR/NBR blends by fly ash particles and precipitated silicaPOLYMERS FOR ADVANCED TECHNOLOGIES, Issue 5 2009C. Kantala Abstract Effects of precipitated silica (PSi) and silica from fly ash (FA) particles (FASi) on the cure and mechanical properties before and after thermal and oil aging of natural rubber (NR) and acrylonitrile,butadiene rubber (NBR) blends with and without chloroprene rubber (CR) or epoxidized NR (ENR) as a compatibilizer have been reported in this paper. The experimental results suggested that the scorch and cure times decreased with the addition of silica and the compound viscosity increased on increasing the silica content. The mechanical properties for PSi filled NR/NBR vulcanizates were greater than those for FASi filled NR/NBR vulcanizates in all cases. The PSi could be used for reinforcing the NR/NBR vulcanizates while the silica from FA was regarded as a semi-reinforcing and/or extending filler. The incorporation of CR or ENR enhanced the mechanical properties of the NR/NBR vulcanizates, the ENR being more effective and compatible with the blend. The mechanical properties of the NR/NBR vulcanizates were improved by post-curing effect from thermal aging but deteriorated by the oil aging. Copyright © 2008 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] Revegetation of Pb/Zn Mine Tailings, Guangdong Province, ChinaRESTORATION ECOLOGY, Issue 1 2000Z. H. Ye The Lechang lead/zinc mine is located in the north part of Guangdong Province, southern China. The tailings residue from the extraction of lead/zinc ores was permanently stored in tailings ponds, which required revegetation to reduce the environmental impact. A field study was, therefore, conducted to evaluate the effects of different ameliorants, including: (1) pig manure (PM); (2) mushroom compost (MC); (3) burnt coal residue (BC); (4) fly ash (FA); and (5) surface soil on the growth of Agropyron elongatum (tall wheat grass), Cynodon dactylon (Bermuda grass), Lolium multiflorum (Italian ryegrass), and Trifolium repens (clover) in the tailings residue. The results from the core profiles indicated that adding FA (10 cm) or BC (15 cm) as a barrier layer between the cover soil and the tailings could increase pH, compared to the treatment with soil only. C. dactylon grew well and had a high cover (90,100%) in all the treatment plots except the control plots without any amendment. A. elongatum and L. multiflorum had a higher cover when grown in plots covered with a barrier layer using FA or BC (both with surface soil), than those grown in plots covered with surface soil only. Treatment plots receiving a thicker soil cover (30 cm) had a better dry weight yield than those with a thinner soil cover (15 cm), regardless of the barrier layer. The results from this study indicate that the use of either 15 cm BC or 10 cm FA as a barrier layer with surface soil, or the use of 38 tonnes PM/ha and 6 cm MC, were effective for the revegetation of Pb/Zn mine tailings. C. dactylon was the best species among the four species used for revegetation. Key words: reclamation, Pb/Zn mine tailings, burnt coal, mushroom compost, fly ash, Bermuda grass, Italian ryegrass, clover. [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] Influence of oil-atomized air on flow and combustion characteristics in a 300 MWe down-fired boilerASIA-PACIFIC JOURNAL OF CHEMICAL ENGINEERING, Issue 3 2010Zhengqi Li Abstract A method of admitting oil-atomized air into a furnace to adjust coal combustion in a down-fired boiler is described. Experiments with a small-scale furnace simulating a down-fired, pulverized-coal, 300-MWe utility boiler were carried out at a single-phase test facility to investigate the influence of oil-atomized air on the aerodynamic field in the furnace. With the acceleration of oil by secondary air, the primary air/fuel can reach a more distant position with respect to the burner nozzle and the volume of the recirculation zone shrinks. Industrial experiments were also performed in a 300-MWe full-scale boiler. The gas temperature distribution along the primary air/fuel flow in the furnace and the gas components in the near-wall region were measured with the dampers of the oil-atomized air box open and closed. When open, the oil-atomized air does not impede the ignition of the primary air/fuel and can carry the primary air/fuel to a position much deeper in the furnace, resulting in a lowered carbon content in the fly ash. Copyright © 2009 Curtin University of Technology and John Wiley & Sons, Ltd. [source] In-situ catalytic synthesis of ammonia from urea in a semi-batch reactor for safe utilization in thermal power plantASIA-PACIFIC JOURNAL OF CHEMICAL ENGINEERING, Issue 3 2010J. N. Sahu Abstract Urea as the source of ammonia for the flue gas conditioning/NOx reduction system in thermal power plant has the obvious advantages that no ammonia shipping, handling and storage is required. The process of this invention minimizes the risks and hazards associated with the transport, storage and use of anhydrous and aqueous ammonia, as ammonia is a highly volatile noxious material. But no such rapid urea conversion process is available as per requirement of high conversion in shorter time, so here we study the catalytic hydrolysis of urea for fast conversion in a semi-batch reactor. The catalysts used in this study are: TiO2, fly ash, mixture of Ni and Fe and Al2O3. Number of experiments was carried out in a semi-batch reactor at different catalyst doses, temperatures and concentration of urea solution from 10 to 30% by weight and equilibrium study has been made. Copyright © 2009 Curtin University of Technology and John Wiley & Sons, Ltd. [source] Mercury and halides emissions from 200 MW pulverized coal combustion boilerASIA-PACIFIC JOURNAL OF CHEMICAL ENGINEERING, Issue 2 2010Hui Wu Abstract Mercury emission from coal-fired power plants is the major industrial source of mercury pollution in China. For a better understanding about the coal combustion Hg emission in China, a field measurement was conducted on a 200 MW pulverized coal fired boiler. Halides being proved to be mercury transformation participators, the U.S. EPA (Environmental Protection Agency) recommended Ontario Hydro method (OHM) and EPA Method 26A were adopted to determine the speciation of Hg and halides in postcombustion flue gases, respectively. Results indicated that, as the flue gas cooling down, the percentage of oxidized mercury in total gas phase mercury (Hg2+(g)/HgT(G)) increased from 41% to about 74% across the electrostatic precipitator (ESP) outlet. Oxidized mercury (Hg2+(g)) was more apt to be absorbed onto the fly ash. The main halides measured in flue gas were HF and HCl, while the concentrations of Cl2 and HBr were extremely low and no Br2 was detected in flue gas. Analysis indicated that acid flue gas components, such as HCl, HF, SO2 and NO, showed a certain extent of promotion on Hg oxidation. The measured mercury emission factor (EMF) in this test was 5.63 g/1012J (13.1 lb/1012Btu). Copyright © 2009 Curtin University of Technology and John Wiley & Sons, Ltd. [source] Leaching characteristics of heavy metals in fly ash from a Chinese coal-fired power plantASIA-PACIFIC JOURNAL OF CHEMICAL ENGINEERING, Issue 2 2010Xun Gong Abstract China is the largest coal ash producer in the world. Hydraulic ash transport systems are used in most coal-fired power plants, which lead to serious water pollution due to leaching of trace elements. The investigation on the leaching behavior of trace contaminants from coal ash is critical to environmental risk assessments. Batch leaching tests have been performed on the fly ash collected from each field of the electrostatic precipitator (ESP) of a coal-fired power plant to study the leaching characteristics of Cd, Cr, Pb and V. Leaching solutions included HCl solution of initial pH = 4 and NaOH solution of pH = 10. The liquid/solid (L/S) ratio was about 4:1 in all leaching tests. Fourteen leaching time intervals were selected, ranging from 15 min to 7 days. The results show that under studied experimental conditions, Cr has a relatively higher leachability in the acid-leaching solution, while Pb has a higher leachability in the alkaline solution. With the increase of leaching time, the leachability of Cr in each ash sample increases obviously. Within the same time interval, Cr in the ash sample from the last field of ESP has the highest leachability. The concentration of Cd in FA3 is the highest, but the leachability of Cd for FA3 is not the highest among the three ash samples. The concentration of V in FA1 is the highest; no increased trend with leaching time has been found in the experiment. Copyright © 2009 Curtin University of Technology and John Wiley & Sons, Ltd. [source] Response surface modeling and optimization for production of ammonia from urea in a batch reactorASIA-PACIFIC JOURNAL OF CHEMICAL ENGINEERING, Issue 4 2009J. N. Sahu Abstract Ammonia is applied to removal of NOx contaminates contained in a flue gas stream from energy producing boilers and increase of efficiency of an electrostatic precipitator for removal of fly ash from flue gas stream from a boiler using fossil fuel. In this study, urea hydrolysis for production of ammonia, in different application areas that requires safe use of ammonia, was investigated in a batch reactor. The single and combined effects of operating parameters such as initial feed concentrations, temperature, time and stirring speed on the production of ammonia from urea were analyzed using response surface methodology (RSM). A 24 full factorial central composite experimental design was employed. Analysis of variance (ANOVA) showed a high coefficient of determination value (R2 = 0.976) and satisfactory prediction second-order regression model was derived. The optimum production conditions were determined as temperature, 180 °C; initial feed concentrations, 22.24 wt% of urea; time, 74.9 min and stirring speed, 1150 rpm. At optimum conversion conditions, the conversion of urea for production of ammonia was found to be 75.65%. Copyright © 2009 Curtin University of Technology and John Wiley & Sons, Ltd. [source] Partitioning behavior of mercury during coal combustion: the influence of low-NOx burners and operation load of boilerASIA-PACIFIC JOURNAL OF CHEMICAL ENGINEERING, Issue 4 2009Guang-Qian Luo Abstract Two 200 MW, pulverized bituminous coal-fired electric utility boilers each equipped with a five-field cold-side electrostatic precipitator (ESP) as the only air pollution control device (APCD) were investigated on mercury distribution and speciation under various conditions. With the same fuel consumption, both facilities are the same but with different burners, low-NOx type and conventional type. Sampling points of gaseous mercury and chlorine species were at the inlet and outlet of the ESP. The mercury concentrations in various solids, including parent coal, bottom slag, economizer bottom ash and fly ash in different hoppers of ESP, were sampled and analyzed. The Ontario Hydro Method was employed to detect mercury in flue gas, and HCl and Cl2 were detected by the EPA method 26. A series of tests were conducted on the boiler with low-NOx burners under various loads (70, 85 and 100% of full load) and on the other boiler with conventional burners under full load. Results showed that small amount of mercury remained in the solid combustion products and most of mercury was released into the atmosphere. The majority of the released mercury was in oxidized form. Burner types and load variation had effects on Cl species concentration in flue gas. Furthermore, particle diameter and carbon content and specific surface area of fly ash affected speciation and distribution of mercury and mercury removal efficiency of ESP. Copyright © 2009 Curtin University of Technology and John Wiley & Sons, Ltd. [source] Operation of a municipal solid waste co-combustion pilot plantASIA-PACIFIC JOURNAL OF CHEMICAL ENGINEERING, Issue 6 2007V. K. C. Lee Abstract The co-combustion of municipal solid waste (MSW) is a novel and highly integrated design combining cement manufacturing, thermal processing of MSW and energy/electricity production (termed the Co-Co process). This novel design of the Co-Co process was developed in 2003,2004 and a pilot plant with a capacity of 40 tonnes per day was constructed and commissioned in 2005. The pilot plant was operated for a period of 10 weeks during 2005. Various feed protocols, namely, MSW as received and after removal of recyclables, were tested. Stack emissions were monitored either continuously (gas emission) or periodically (dioxins and heavy metal emissions). Solid residues including bottom ash and fly ash were also sampled and analysed for heavy metals and dioxins periodically. It was found that the levels of dioxins in the stack emissions and fly ash were below normal MSW thermal treatment processes, and government environmental and international limits (more than 1000 times less). Other gases, such CO, NOx, SOx and HCl, were also well below government environmental licence limits as defined by a best practical means (BPM). In addition, the materials recovery and recycling facility (MRRF) was tested. It demonstrated that different fractions, including metals, plastics and glass, of the MSW could be separated and recovered. The Co-Co process was successfully demonstrated and its emission levels were well below normal MSW thermal treatment processes. Copyright © 2007 Curtin University of Technology and John Wiley & Sons, Ltd. [source] Mechanisms 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] The Partitioning of Arsenic, Selenium, Cadmium, and Cesium during Pulverized Coal Combustion in a 17 kW Downflow CombustorASIA-PACIFIC JOURNAL OF CHEMICAL ENGINEERING, Issue 3-4 2001Wayne S. Seames The combustion of coal liberates arsenic, selenium, cadmium, and cesium into the environment. These toxic metals, which are discharged with the flue gas or collected with fly ash, may vaporize in the hot portions of the combustor then return to the solid phase in cooler zones of the process downstream. Understanding the mechanisms by which toxic metals partition between the vapor and solid phases is an important step for predicting and mitigating the effect of these metals upon the environment. An investigation of these partitioning mechanisms was performed. The results suggest that the dominant heterogeneous partitioning mechanism for transformation to the solid phase in the post-combustion zone is the reaction of metal vapor on the surface or within the pores of a supermicron ash particle for the Pittsburgh seam and Illinois #6 coals but not for the Ohio blend coal. A relationship between the concentration of supermicron phase arsenic, selenium, and cadmium to calcium was also observed, suggesting the formation of As-Ca, Se-Ca, and Cd-Ca reaction products. Selenium appears to be more reactive than arsenic for the formation of these calcium-based complexes. [source] | ||||||||||||||||||||||