Speciation of heavy metals in street dust samples from Sakarya I. Organized industrial district using the BCR sequential extraction procedure by ICP-OES

This paper focuses on the concentrations of heavy metals (Cd, Co, Cr, Cu, Mn, Ni, Pb and Zn) in 20 dust samples collected from the streets of the Organized Industrial District in Sakarya, Turkey using sequential extraction procedure were determined by ICP-OES. The three-step BCR sequential extraction procedure was used in order to evaluate mobility, availability and persistence of heavy elements in street dust samples. Three operationally defined fractions isolated using the BCR procedure was: acid extractable, reducible, and oxidizable. The mobility sequence based on the sum of the BCR sequential extraction stages: Cd (82.3%) > Mn (80.0%) > Zn (78.8%) > Cu (70.2%) > Ni (65.9%) > Pb (63.8%) > Cr (47.3%) > Co (32.6%). Validation of the analytical results was checked by analysis of the BCR-701 certified reference material. The concentrations of metals in the street dust samples have been shown a decrease after the each extraction stage. KEY WORDS: Heavy metals, ICP-OES, Organized industrial district, Sequential extraction, Dust, Turkey Bull. Chem. Soc. Ethiop. 2013, 27(2), 205-212.DOI: http://dx.doi.org/10.4314/bcse.v27i2.

Numerical Investigation of Turbulent Hydrogen-Methane-Nitrogen Non-Premixed Jet Flame

In this work, the numerical investigation of the two-dimensional axisymmetric turbulent diffusion flame of a composite fuel was performed by using a computational fluid dynamics code to predict flame structure. The composite fuel was an H2/CH4/N2 gas mixture. The amount of H2 and N2 in the fuel mixture varies under constant volumetric fuel flow rate. Fluent, which solves the governing and reaction equations using the finite volume method, was used as the computational fluid dynamics program. The non-premixed model was used for computation of the combustion. The standard k-ε model was used for modeling the turbulent flow. The interaction of the chemistry and turbulence was accounted for by the program with the probability density function model. This model was validated against the experimental data taken from literature. In general, the numerical results of the temperature, velocity, and CO2 concentration distributions were in satisfactory agreement with the experimental results. The numerical results showed that adding H2 to the fuel mixture decreases the flame length and generally increases the maximum temperature of the flame. On the other hand, adding N2 to the mixture decreases both the flame length and maximum flame temperature. The flame length corresponds to the axial position of the peak flame temperature. Keywords: Combustion Modeling; Composite Fuels; Diffusion Flame; H2/CH4/N2 Flame; Flame Length; Emission

Numerical Investigation of the Effect of Different Conical Turbulators on the Performance of a Liquid Fuelled Boiler

The increment in the combustion of fossil fuels for heating and power generation in recent years has led researchers to design more efficient energy conversion systems by increasing the efficiency of the existing systems and by minimizing energy losses. In this study, increasing the efficiency of the liquid fuelled smoke tube boilers used for domestic heating was researched. In this context, turbulators with full conical and frusto-conical geometries placed to smoke tubes of boiler and their effects on flame structure, heat transfer and boiler efficiency were investigated numerically. Calculations were carried out at two dimensional axisymmetric conditions and Fluent was used as the computational fluid dynamics software. In all cases, the standard k-ε model was used for modelling the turbulent flow and the species transport model was used for modelling the combustion. The results obtained by using these turbulators were evaluated for each placement condition of the turbulators. Besides, the temperature and the stream function distribution and the pressure drop in the boiler were investigated according to the type of turbulators. Finally, it was discussed which type of turbulator would be most appropriate at boilers. Keywords: Spray Combustion; Combustion Modelling; Boilers; Conical Turbulator