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Numerical simulation of coal powder distribution along the air-coal mixture channel influenced by various shutter angles

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Zivkovic N. , Stefanovic P. , Zivkovic G. , Cvetinovic D.

Zeszyty Naukowe Politechniki Rzeszowskiej. Mechanika

2006

tom z. 68 [231]

261-268

For implementation of the plasma system for mineral oil free combustion support and start-up on power plant boilers few technical problems have be to solved. One of the key requirements in the implementation process is a regulation of coal powder distibution in the mixture channel in order to achieve adequate concentration in the zone where plasma has to be introduced. Regulation of powder distribution with shutters, positioned in the vertical section of the channel after the mills and prior to plasma generators is proposed solution. The paper represents numerical simulation of this problem using numerical software for modelling of two-phase flow problems, developed in Laboratory of Thermal Engineering and Energy. The model is based on Euler-Lagrangian approach. Continual phase was treated by Euleiran and disperse phase was treated Lagrangian approach. For turbulence modelling a well known k-!!! model was used. The computation results were obtained for three combinations of shutter system positions. The input data were velocity profile of continual phase and concentration profile of disperse phase in the inlet cross section, obtained by experiments. On the basis of the presented results it can be concluded that the positions of groups of shutters has a great influence on flow and concentration field in the burner channels, therefore it should be properly adopted as an adequate regulation method.

Coal powder fractions distribution in thermal power plant mixture channel presented by numerical calculations

100%

Zivkovic N. , Stefanovic P. , Cvetinovic D.

Zeszyty Naukowe Politechniki Rzeszowskiej. Mechanika

2008

tom z. 73 [253]

311-318

One of the problems during exploalation period of thermal power plant is in determine and optimize distribution of various coal powder fractions in the mixture channel. Regulation of distribution with shutters, positioned after the mills, is proposed solution. The paper present distribution of coal powder fractions, obtained by numerical calculations, using numerical software for modelling of two-phase flow problems. The problem is two-dimensional, considering that, transversal dimension of the domain is relatively big compared with the other two dimensions, and volume occupied by solid phase is much less than volume occupied by continual phase. Continual phase is treated by an Eulerian approach, and solid phase is modeled by Lagrangian approach. The model takes in consideration coupling of phases by PSI-CELL method. Turbulence was modeled with standard k-ε model. The model treats particles as an ideal sphere. In order to determine particle movement, all relevant forces, (with continual affect and impulse affect), are incorporated in the model. The results obtained, include velocity field and profiles of continual phase, concentration field and profiles of coal particles and mass flow distribution at the outlet cross section of mixture channel for various coal particle diameters and various angular positions of shutters.

Concentrations of heavy metal cations and a health risk assessment of sediments and river surface water: a case study from a Serbian mine

75%

Zivkovic N. , Takic L. , Djordjevic L. , Djordjevic A. , Mladenovic-Ranisavljevic I. , Golubovic T. , Bozilov A.

Polish Journal of Environmental Studies

2019

tom 28

nr 3

Mining and processing of metal ores are often significant sources of heavy metal contamination of river sediments. Heavy metal contamination of river sediments resulting from mining and smelting represents a major concern due to the potential risk involved. This study was performed to investigate the content of heavy metal (Cd, Cr, Fe, Mn, Ni, Cu, Pb, Hg, As, and Ba) cations in the sediments of the Korbevačka River, the main recipient of all kinds of pollutants from the Pb-Zn Grot Mine, and to estimate the potential health risks of metals to humans. On the basis of the heavy metal cations content, the potential health risk assessment calculated for a lifetime of exposure (ingestion and inhalation), based on the U.S. Environmental Protection Agency (EPA) model, was determined as the cumulative non-carcinogenic and carcinogenic risk for children and adults. The study proved that: a) the heavy metal cations content in the Korbevačka River sediments is significant; b) risk assessment indicates that while carcinogenic risk is completely insignificant, cumulative non-carcinogenic risk is significant – especially for children – as it approaches unacceptable values; and c) metal lead is the main concern in regard to negative influence on human health.