Search Results

You are looking at 21 - 30 of 52 items for :

  • "coal fly ash" x
  • Refine by Access: All Content x
Clear All

Abstract  

Instrumental neutron activation analysis (INAA) together with scanning electron microscopy (SEM) have been used in the study of fly ash from large electric power and heating plants. Two basic kinds of fly ash originating either from brown coal or heavy-oil combustion can be characterized both by morphology and trace element composition. INAA technique used consisted of both short (1 min) and long (2 h) activations to ensure the determination of 30–40 elements in each fly ash sample. The average composition and determination limits obtained by INAA for coal fly ash produced in several electric power plants burning two kinds of brown coal have been compared with those obtained for fly ash originating from heating plants burning heavy-oil. Coal fly ash showed much higher concentrations of many elements especially of Sc. La, Th, Cs, Ce, Sm, Rb and Al in comparison with oil fly ash. On the other hand, the latter contained relatively high concentrations of V and Ni. The results of INAA of fly ash samples can be used for the projection of efficient separating devices and for the evaluation and prediction of contamination levels in the vicinity of large emission sources.

Restricted access

Summary  

A simple sample decomposition and laser fluorimetric determination of uranium at trace level is reported in certain refractory minerals, like ilmenite, rutile, zircon and monazite; environmental samples viz. soil and sediments; industrial waste materials, such as, coal fly ash and red mud. Ilmenite sample is decomposed by heating with ammonium fluoride. Rutile, zircon and monazite minerals are decomposed by fusion using a mixture of potassium bifluoride and sodium fluoride. Environmental and industrial waste materials are brought into solution by treating with a mixture of hydrofluoric and nitric acids. The laser induced fluorimetric determination of uranium is carried out directly in rutile, zircon and in monazite minerals and after separation in other samples. The determination limit was 1 μg . g-1 for ilmenite, soil, sediment, coal fly ash and red mud samples, and it is 5 μg . g-1 for rutile, zircon and monazite. The method is also developed for the optical fluorimetric determination of uranium (determination limit 10 μg . g-1) in ilmenite, rutile, zircon and monazite minerals. The methods are simple, accurate, and precise and they require small quantity of sample and can be applied for the routine analysis.

Restricted access

Abstract  

Landfills and waste disposal sites are now routinely used for disposal of solid wastes and their incinerator ashes. Trace elements from these ashes are leached by rain and acid rain into nearby waterways providing a pathway for toxic elements to re-enter the food chain and the human life cycle. This paper examines the mechanism and the extent of leaching of 20 elements viz. Ag, Al, As, Ba, Br, Ca, Cd, Co, Cr, Fe, Hg, La, Sb, Sc, Ce, Sm, Ta, V, W and Zn. Instrumental neutron activation analysis (INAA) was used for the assay. The solid wastes studied are municipal refuse incinerator ash, coal fly ash, hospital incinerator ash, raw sewage sludge and its incinerator ash.

Restricted access

Abstract  

Different pattern recognition techniques were applied for classification and characterization of a large number of coal, and coal fly ash samples. Cluster analysis was performed on 116 samples using the concentration data of 40 elements. The effect of the number and type of the elements on the clustering was studied in detail. It was proved that short time activation analysis enables the characterization of these types of samples if139Ba and87Sr are included, these data being obtained by increasing the irradiation and counting times. The two elements and chlorine were found to be necessary for such a classification. The combination between cluster analyses and principal component analysis gives accurate and confirmed results. The statistical analyses of the subgroups are compared.

Restricted access

Abstract  

Knowledge of occurrence and concentration of trace elements in dust particulates from and around industrial establishments is essential to know the source of pollutants and atmosphere quality. Dust particulates from two cement factories in the central part of India were analyzed for 5 minor (Cl, Fe, K, Mg, Na) and 23 trace elements (Ag, As, Ba, Br, Cd, Co, Cr, Cs, Dy, Eu, Ga, Hf, Hg, La, Mn, Sb, Sc, Se, Sm, Sr, Th, W and Zn) by INAA and RNAA techniques. Significant differences have been observed for some toxic trace elements at different locations. Mn content is particularly high in all the dust particulates. Urban particulate (SRM 1648) and Coal fly ash (SRM 1633a) from NIST and Pond sediment (CRM No. 2) from NIES were also analyzed. The data have been analyzed and interpreted in terms of air quality at different locations inside the plant and two factories.

Restricted access

Abstract  

To order to examine experimentally the modified monostandard method implemented in the program MULTINAA, the FRM reactor in Garching (Germany) was calibrated and an INAA of a standard reference material NIST/SRMI1633b Coal Fly Ash was performed. The relative, thek 0-and the modified monostandard standardizations are applied. This work shows that for all of the examined 1/-nuclides the modified monostandard method provides identical analytical results to those determined by thek 0-method. For the non-1/ nuclides177Lu and152Eu the monostandard results are correct. Compared with the certified values of the analysed SRM1633b sample and also with the results of the relative method, it can be concluded that the modified monostandard method performed at our experimental conditions gives analytical results with accuracy better than 5%.

Restricted access

Abstract  

Concentrations of 35 elements in Chinese Standard Rocks (GSR-1 to GSR-3) and Soils (GSS-1 to GSS-8) have been measured with INAA using the SLOWPOKE reactor. At the same time, the U. S. NBS reference standards: SRM-1632a (Bituminous Coal), SRM-1633a (Coal Fly Ash) and SRM-1646 (Estuarine Sediment) were also analyzed in order to cross-check the accuracy of this method. The results obtained indicate that the reproducibility of the method is satisfactory for most of the elements, namely the precision in general, is better than ±10%. Comparison of our values for NBS SRM-1632a, 1633a and 1646 with the certified values of NBS or with values cited in the literature indicates good agreement. The results were found to be accurate within ±10% error of the established results.

Restricted access

Abstract  

The k 0-method of standardisation for instrumental neutron activation analysis (INAA) has been used at the OPAL research reactor to determine the elemental composition of three certified reference materials: coal fly ash (SRM 1633b), brick clay (SRM 679) and Montana soil (SRM 2711). Of the 41 certified elements in the three materials, 88 percent were within five percent of the certified values and all determinations were within 15 percent of the certified values. The average difference between the measured and certified values was 0.1 percent, with a standard deviation of 4.1 percent. Since these reference materials are widely used as standards in the analysis of archaeological ceramics by INAA, it has been concluded that the INAA facility in Australia is particularly well-suited for nuclear archaeometry.

Restricted access

Abstract  

A new Compton suppression system (CSS) for the gamma-ray spectrometer portion of the neutron activation analysis (NAA) was set up at the RPI/ITN. The pneumatic transfer system, SIPRA, for short-lived nuclides and cyclic irradiations was improved. A full calibration procedure of the CSS and SIPRA systems was performed. Two certified reference materials, NIST-SRM-1572 (Citrus Leaves) and NIST-SRM-1633a (Coal Fly Ash) were analyzed using the calibration factors. The CSS was instrumental in lowering the detection limits of Cr, Fe, Hg, Rb, Sr, Th and Zn by reducing background and/or spectral interference considerably. The analytical results were evaluated by comparison to the NIST certified values with deviations ranging from 2% to 8% for the above mentioned elements, except Zn ranging from 10% to 15% for biological and environmental samples, respectively.

Restricted access

Abstract  

The concentration of rare earths and other elements have been determined in the bed sediment samples of Karnafuli estuarine zone in the Bay of Bengal by instrumental neutron activation analysis (INAA). The samples and the standards soil-5, soil-7, coal fly ash and pond sediment were prepared and simultaneously irradiated for short and long time at the TRIGA Mark-II research reactor facility of Atomic Energy Research Establishment, Savar, Dhaka. The maximum themal neutron flux was of the order of 1013 n·cm–2·s–1. After irradiation the radioactivity of the product nuclides was measured by using a high resolution high purity germanium detector system. Analysis of -ray spectra and quantitative analysis of the elemental concentration were done via the software GANAAS, it has been possible to determine the concentration level of 27 elements including the rare earths La, Ce, Sm, Eu, Tb, Dy and Yb and uranium and thorium.

Restricted access