Search Results
Abstract
On irradiation with neutrons, some of the interesting trace elements in coal, coal ash and fly ash produce short-lived nuclides which may be determined—together with some of the matrix elements—by activation analysis. This enables the characterization of samples. To find out the distribution of elements in the gaseous or aerosol exhaust of fossil-fired power plants, we simulated the combustion in a quartz apparatus containing a cold trap, using the combustion temperature (780 °C) employed for the standard ash determination. High Se values were found in the cold trap deposits from black coal from Poland. Halogens were also found in the deposits.
Abstract
The intense 14-MeV neutron facility at Lawrence Livermore National Laboratory was used for fast-neutron activation analysis (FNAA) of standard fly ash, orchard leaves, and bovine liver supplied by the U.S. National Bureau of Standards. The high flux of 14-MeV neutrons allowed concentration determinations of up to 20 elements from the set of Na, Mg, Al, Si, P, K, Sc, Ti, Fe, Co, Ni, Zn, As, Se, Rb, Sr, Y, Zr, Mo, Sb, Ba, Ce, Tl, and Pb. Interferences and steep flux-gradients were problems, but the elemental profile we obtained is the most complete analysis using FNAA to date.
Abstract
The Lawrence Livermore Laboratory program to evalute the trace elements in stack emissions from coal-fired power plants is described. Stack sampling and analysis of fly ash at modern, western U. S. power plants is discussed. Scanning-electron-microscope techniques are shown to be essential for accurate sizing of stack particles sampled with cascade impactors. Particle-size distributions for volatile and nonvolatile trace elements are reported. Comparisons show that the trace elemet enrichment factors of western and eastern U. S. coal-fired power plants are significantly different.
Abstract
Instrumental neutron activation analysis (INAA) was applied to assess element concentrations in eleven samples of mineral supplements/multivitamins acquired in drugstores and pharmacies in São Paulo city, SP, Brazil. Concentrations of Ca, Co, Cr, Cu, Fe, K, Na, Se and Zn were determined. A comparison was made between the results obtained with the labels of the mineral supplents. Certified reference materials, NIST SRM1400 Bone Ash and NIST SRM 1633b Coal Fly Ash were analyzed for quality control of the analytical results.
Abstract
Fired-clay products such as bricks, tiles and pavers, are made in large volumes for use in a variety of construction applications throughout the world. A significant proportion of them ends up being a waste product either during their production process or the demolition of buildings. High pressure steam curing or autoclaving has proven extremely versatile for the manufacture of cement-based building products incorporating waste materials such as fly-ash and blast furnace slag. The nature of hydration products in an autoclaved cement based system incorporating different amounts of finely ground brick waste was investigated by means of thermal analysis and XRD, and is the subject of this paper.
Summary
Modelingand experimental approaches to study reactive transport across chemical gradients in porous media are presented. Particular emphasis is placed on apurposeful experimental setup to obtain information necessary for model calibration and verification. As example, diffusion tube experiments on the layered acidic jarosite/alkaline coal fly ash system have been carried out using radiotracers 3H+, 22Na+, and 59Fe3+. Such radiotracer diffusion tube experiments provide modelers with reliable information incorporatingsome of the complexities observed in the environment such as local heterogeneities.
Abstract
The effect of neutron irradiation on the leachability of elements in solid wastes comprising of coal fly ash, hospital and municipal incinerator ashes was studied. There was a marked increase in leachability in the neutron irradiated wastes compared to non-irradiated wastes especially for elements such as As, Cd, Co, Cr, Sm and Zn. For elements such as Fe and Sm there was no significant difference in the leachabilities in the irradiated and non-irradiated wastes. The possible causes of this scenario and implications are discussed.
Abstract
Epithermal Instrumental Neutron Activation Analysis has been used to measure the concentration of uranium in eutectic salt solutions in support of a research program in which the actinide elements are separated from rare earths and other fission products using high-temperature electo-deposition. The uranium response over three decades in concentration follows a negative power function; and high concentrations of samarium interfere with the determination of uranium but can be accurately corrected. The EINAA method was successfully used to analyze NIST SRM 278 Obsidian and NIST SRM 1566a Fly Ash.
Abstract
The internal standard method coupled with the standard addition method has been applied to the analysis of environmental materials, such as urban particulate matter, vehicle exhaust particulates and coal fly ash by photon activation. High-resolution gamma-ray spectrometry makes possible to use multi-internal standard gamma-rays, in order to crosscheck the analytical results obtained from each internal standard. It was ascertained that this method can provide not only accurate analytical results but also the information of homogeneity of samples, correlation of elements in the sample, loss or contamination in the preparation process.
Abstract
Trace element partitioning was studied at a pulverized-lignite fired power plant in Texas. Concentrations of 41 elements were determined by neutron activation analysis (NAA) for lignite fuel and combustion effluents collected during 10 consecutive days. Elements studied were grouped into three classes according to their enrichment factors and the relationship between their concentrations and particle size. In general, the concentration enhancement in fly ash and the difference in enhancement between elements placed in different classes are shown to be less significant in this study than for other partitioning studies on higher rank coals.
