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Homogeneity of the flue gas-flow through the chamber of an electrostatic precipitator is one of the basic influencing parameter on dedusting efficiency. This paper presents results of a multiobjective optimization study of the flue gas controlling devices of electrostatic precipitator of 324 MWe lignite fired Unit A4 of TPP "Nikola Tesla" in Serbia. The aim was to achieve better flow homogeneity in the cross-section of the precipitator compared to the original design. Additional constraints were to maintain the minimum as possible overall weight of the proposed design as well as pressure drop through the precipitator. Numerical simulations based on CFD were used to investigate dependence of the velocity distribution in the ducts and precipitator’s chamber with respect to the geometrical parameters of tested concepts of turning blades. A series of 22 detailed full-scale numerical models of the precipitator with different concepts of turning vanes designs were developed. Assessment of the flow field uniformity for each tested design was performed based on the analysis of several homogeneity parameters calculated for selected vertical cross-sections of the precipitator. After the reconstruction according to optimized design, results of measurements confirmed significant improvements of the velocity distribution in the vertical cross-sections of the precipitator, increase of dedusting efficiency and reduction of PM emission.

The anthropogenic emission of GHG especially CO has to be limited and reduced due to 2 their impact on global warming and climate change. Combustion of fossil fuels in the energy sector has a dominant share in total GHG emissions. In order to reduce GHG emission, European Union established a scheme for GHG allowance trading within the community, and the implementation of the European Union emission trading scheme, which is a key to GHG reduction in a cost-effective way. An important part of emission trading scheme is prescribed methodology for monitoring, reporting, and verification of the emission of GHG including characterization of the local fuels combusted by the energy sector. This paper presents lignite characteristics from open-pit mine Borovica- Pljevlja, which has highest coal production in Montenegro (>1.2 Mt per year), including evaluation of its carbon emission factor based on the laboratory analysis of 72 coal samples. Testing of the samples included proximate and ultimate analysis, as well as, net calorific value determination. In accordance with the obtained results, linear correlations between net calorific value and combustible matter content, carbon content and combustible matter content, hydrogen content and combustible matter content, carbon content and net calorific value, were established. Finally, the non-linear analytical correlation between carbon emission factor and net calorific value for Pljevlja lignite was proposed, as a base for the precise calculation of CO emission evaluation.

Paper presents short review of research problems, applied methods for solving problems and main results obtained by the researchers in Laboratory for Ther-mal Engineering and Energy (LTE) of the "Vinca" Institute of Nuclear Sciences, Belgrade, Serbia dealing with pulverized coal combustion processes and tech-nologies for reduction of pollutions problems at thermal power plants in a period since 2000. The presented results were published in numerous studies realized for different users, Ph. D., Masters, and Specialist thesis, in international and domestic scientific journals and monographs, presented at numerous internation-al and domestic scientific conferences, etc. Presented research projects and re-sults of applied research projects realized at pulverized coal combustion thermal power plants clearly show that LTE team was involved in key activities of reha-bilitation and modernization, including implementation of best available technol-ogies for pollution reduction at thermal power plants, in the region of South East Europe.

The electrostatic precipitator system of the lignite fired 350 MWe unit B1 of Thermal Power Plant Kostolac B has been modernized during 2014. The results of complex in site measurements, performed in the frame of performance control test at the beginning of the exploitation period of the upgraded electrostatic pre-cipitator proved that, under normal and guarantee working conditions of the boiler and precipitator, the emission of particulate matter do not exceed limiting value. After the period of precipitator further adjustments, five series of meas-urements in the frame of acceptance test were performed in accordance with rel-evant standards. This paper presents results of the investigation of particulate matter concentration, laboratory analysis of the lignite, fly and bottom ash sam-ples, working parameters of the unit and upgraded electrostatic precipitator as well as results of the calculations. The averaged mean particulate concentration at the exit of upgraded electrostatic precipitator of the unit B1 during Acceptance test was below guaranteed value. It is confirmed that adjustments of electrostatic precipitator electrical parameters have improved electrostatic precipitator effi-ciency, as well that electrostatic precipitatorcould work highly efficiently in en-ergy save mode with lower power consumption. © 2018 Society of Thermal Engineers of Serbia.

The behavior of the mast is non-linear due to its slenderness and compliant guy-support system, having a tendency to lose stability and even crush suddenly. Wind load is one of the main factors affecting the stability of the structure of the mast. Structural assessment of the different mast configurations has been investigated in the past. Furthermore, European standards EN 1993-3-1:2006 and EN 1993-1-6:2007 already provides some guidelines about the basis of structural analysis of masts and towers. This paper presents the results of numerical simulations of a guyed mast exposed to wind action using finite element method. Structural analyses were performed for three different constant wind loads, modal analysis provides the values of natural frequency and mode shapes, while the stability analysis was performed for the first three buckling load factor values. The motivation for this study is to investigate the contribution of finite element method to structural analysis of a lattice structure such as guyed mast as an alternative and/or improvement to the literature and codes.

New system for start-up and flame support based on coal gasification by low temperature air thermal plasma is planned to supplement current heavy oil system in Serbian thermal power plants in order to decrease air pollutions emission and operational costs. Locally introduced plasma thermal energy heats up and ignites entrained coal particles, thus starting chain process which releases heat energy from gasified coal particles inside burner channel. Important stages during particle combustion, such as particle devolatilisation and char combustion, are described with satisfying accuracy in existing commercial computer fluid dynamics codes that are extensively used as powerful tool for pulverized coal combustion and gasification modeling. However, during plasma coal gasification, high plasma temperature induces strong thermal stresses inside interacting coal particles. These stresses lead to thermal shock and extensive particle fragmentation during which coal particles with initial size of 50-100 mu m disintegrate into fragments of at most 5-10 mu m. This intensifies volatile release by a factor 3-4 and substantially accelerates the oxidation of combustible matter. Particle fragmentation, due to its small size and thus limited influence on combustion process is commonly neglected in modelling. The main focus of this work is to suggest novel approach to pulverized coal gasification under high temperature conditions and to implement it into commercial comprehensive code ANSYS FLUENT 14.0. Proposed model was validated against experimental data obtained in newly built pilot scale direct current plasma burner test facility. Newly developed model showed very good agreement with experimental results with relative error less than 10%, while the standard built-in gasification model had error up to 25%.

A fuzzy approximation concept is applied in order to predict results of coupled computational structure mechanics and computational fluid dynamics while solving a problem of steady incompressible gas flow through thermally loaded rectangular thin-walled channel. Channel wall deforms into wave-type shapes depending on thermal load and fluid inlet velocity inducing the changes of fluid flow accordingly. A set of fluid-structure interaction numerical tests have been defined by varying the values of fluid inlet velocity, temperature of inner and outer surface of the channel wall, and numerical grid density. The unsteady Navier-Stokes equations are numerically solved using an element-based finite volume method and second order backward Euler discretization scheme. The structural model is solved by finite element method including geometric and material non-linearities. The implicit two-way iterative code coupling, partitioned solution approach, were used while solving these numerical tests. Results of numerical analysis indicate that gravity and pressure distribution inside the channel contributes to triggering the shape of deformation. In the inverse problem, the results of fluid-structure interaction numerical simulations formed a database of input variables for development fuzzy logic based models considering downstream pressure drop and maximum stresses as the objective functions. Developed fuzzy models predicted targeting results within a reasonable accuracy limit at lower computation cost compared to series of fluid-structure interaction numerical calculations. Smaller relative difference were obtained when calculating the values of pressure drop then maximal stresses indicating that transfer function influence on output values have to be additionally investigated.

The revised Intergovernmental Panel on Climate Change guidelines for national greenhouse gas inventories recommends that more comprehensive and thus more reliable characteristics of the local fossil fuels should be used for the national greenhouse gas inventory calculations. This paper deal with the carbon emission characteristics of low-calorific lignite recovered from the Kolubara open-pit mine. The samples of coal were carefully selected in order to cover the net calorific value, ash and water content of the broad spectrum of the quality of the raw lignite supplied to the Serbian thermal power plants. Correlation analysis of the laboratory analysis data gave a linear dependency of the net calorific value on the combustible content in the coal samples. Also, linear correlation between the carbon content and the net calorific value was found. The regression analysis of experimentally determined coal characteristics implies that the carbon emission factor is dependent on the net calorific value. For the subset of raw lignite samples with the net calorific value Q(d)(r) = 6-10 MJ/kg, that is most representative for current and near future use for power generation in Serbian thermal power plants, the linear dependency CEFr (tC/TJ) = 34.407 - 0.5891.Q(d)(r) MJ/kg was proposed. Regarding the net calorific ranges of samples examined, the raw Kolubara lignite carbon emission factor is considerably higher than those recommended by Intergovernmental Panel on Climate Change Tier 1 method of 27.6 tC/TJ.

Pulverized coal particles concentration distribution across the burners distribution channels, especially where plasma torches are installed, is one of the key issues for efficient implementation of plasma system for liquid fuel free combustion support at the pulverized coal fired boilers. The possibility of pulverized coal particles concentration increase at the lower burner channels of TPP Nikola Tesla - A1 boiler using regulation shutters is analyzed experimentally and numerically. Subject of present work is two-phase flue gas-particles mixture flow in burners distribution channels with regulation shutters installed at the TPP Nikola Tesla A1 boiler. Aim of this work is to optimize position of implemented system of shutters to achieve desired concentration and velocity distribution in channels with plasma torches, using numerical modelling. Experimental investigation was performed for the verification of proposed mathematical model for the prediction of the analyzed two-phase flow. Based on verified model, numerical parametric analysis was done. Obtained results of gas phase velocity field. coal particles concentration field, velocity and concentration profiles clearly show the dependence between shutters position and the coal particles mass flow rate and concentration distribution at the outlet cross-section of the burners distribution channels. According to the numerical optimization results suitable modification of the shutter system is proposed.

This paper concern the results of software fire spread process prototype in terminal 2 of Belgrade airport using computational fluid dynamics. Numerical simulation of fire for the most critical fire scenario has been performed, primarily obtaining the space and time distribution of: velocity, pressure, temperature, and smoke concentration, assuming that HVAC systems have been switched off and all doors on the evacuation ways have been opened, just as the fire started Also, two simulations have been compared of the smoke ventilation and not ventilation for the same scenario. Within the framework of the results presentation, isosurfaces of constant temperature (100 degrees C) and smoke concentration (4000 ppm) are presented, based on the numerical simulation. Progression of these surfaces along the terminal 2 coincides to the experimental and experience evidence, forming the plume zone just above the fireplace, and spreading in the zone of underground ceiling and stairwell openings.