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The paper presents a possible approach for creating business decisions based on multi-criteria analysis. Seven options for a possible revitalization of the thermal power plant Kolubara-A Unit No. 2 with energy indicators of sustainable development (EISD) are presented in this paper. The chosen EISD numerically express the essential features of the analyzed options, while the sustainability criteria indicate the option quality within the limits of these indicators. In this paper, the criteria for assessing the sustainability options are defined based on several aspects: economic, social, environmental and technological. In the process of assessing the sustainability of the considered options the Analysis and Synthesis of Parameters under Information Deficiency (ASPID) method was used. In this paper, the EISD show that production and energy consumption are closely linked to economic, environmental and other indicators, such as economic and technological development of local communities with employment being one of the most important social parameter. Multi-criteria analysis for the case study of the TPP Kolubara-A clearly indicated recommendations to decision makers on the choice of the best available options in dependence on the energy policy. (C) 2017 Elsevier Ltd. All rights reserved.

Oxy-fuel combustion is the most promising carbon capture and storage technology, which eliminates carbon dioxide emissions into the atmosphere and also decreases nitrogen oxides emissions thereby lowering global warming potential. In order to implement oxy-fuel combustion technology in full scale power plants, its costs, mainly connected with the amount of pure oxygen produced, must be lowered. The main hypothesis is that it is possible to maintain similar velocity and heat transfer distribution while maintaining stable and efficient burner operation during both combustion technologies modifying burner aerodynamics. Excess oxygen is chosen as a representative parameter of burner's performance and investigation is carried out for four different oxy-fuel burner oxygen excess ratios (λ: 0.8, 0.98, 1.07, and 1.24) together with reference air combustion case. This study suggests a workflow, based on semi-industrial experimental investigations and computational fluid dynamics model composed of advanced sub-models for different combustion phases for development of real scale dual-mode coal swirl burners able for efficient operation during both combustion regimes. The results show that the temperature in near-burner zone and nitrogen oxides emissions increase, while carbon monoxide emissions decrease with the increase of burner oxygen excess ratio, and stable combustion with similar velocity and temperature distributions for both combustion modes is achieved for oxygen excess ratio of 1.07, with decrease in nitrogen oxides and carbon monoxide emissions during oxy-fuel combustion. The performed study demonstrates that it is possible to choose the appropriate burner settings regarding nitrogen oxides and carbon monoxide emissions and burner's ability to operate stably in both air and oxy-fuel combustion modes. © 2019 Elsevier Ltd

Despite benefiting from vast fuel reserves, combustion of low-rank coals is commonly characterized by low thermal efficiency and high pollutant emissions, partly due to high moisture content of the coals in question. Thus, removal of moisture from low-rank coals is deemed an important quality upgrading method. The paper provides an overview of the current status of low-rank coal upgrading technologies, particularly with respect to utilization of drying and dewatering procedures. In order to examine the influence of relevant parameters on the moisture removal process, a model of convective coal drying in a packed, as well as in a fluid bed combustion arrangement, is developed and presented. Product-specific data (intraparticle mass transfer, gas-solid moisture equilibrium) related to the coal variety addressed herein (lignite) are obtained through preliminary investigations. Effective thermal conductivity of the packed bed as defined by Zehner/Bauer/Schlunder is used to define heat transfer mechanisms occurring in the packed bed. Similar two-phase fluidization model has been validated for different types of biomaterials. (C) 2014 The Institution of Chemical Engineers. Published by Elsevier B.V. All rights reserved.

The paper addresses results for the case of convective drying of particulate solids in a packed and in a fluid bed, analyzing agreement between the numerical results and the results of corresponding experimental investigation, as well as the differences between packed and fluid bed operation. In the fluid bed simulation model of unsteady simultaneous one-dimensional heat and mass transfer between solids, gas phase and bubble phase during drying process, based on two-phase bubbling model, it is assumed that the gas-solid interface is at thermodynamic equilibrium. The basic idea is to calculate heat and mass transfer between gas and particles (i.e., the drying process) in suspension phase as for a packed bed of particles, where the drying rate (evaporated moisture flux) of the specific product is calculated by applying the concept of a drying coefficient. Mixing of the particles (i.e., the impact onto the heat and mass transfer coefficients) in the case of fluid bed is taken into account by means of the diffusion term in the differential equations, using an effective particle diffusion coefficient. Model validation was done on the basis of the experimental data obtained with narrow fraction of poppy seeds characterized by mean equivalent particle diameter (d(s.d) = 0.75 mm), re-wetted with required (calculated) amount of water up to the initial moisture content (X-0 = 0.54) for all experiments. Comparison of the drying kinetics, both experimental and numerical, has shown that higher gas (drying agent) temperatures, as well as velocities (flow-rates), induce faster drying. This effect is more pronounced for deeper beds, because of the larger amount of wet material to be dried using the same drying agent capacity. Bed temperature differences along the bed height are significant inside the packed bed, while in the fluid bed, for the same drying conditions, are almost negligible due to mixing of particles. Residence time is shorter in the case of a fluid bed drying compared to a packed bed drying. (C) 2012 Elsevier Ltd. All rights reserved.

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 CFD 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 􀈝m disintegrate into fragments of at most 5-10 􀈝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 D.C 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%.

Low-calorific lignite from Kolubara open-pit mines is mainly used for heat and power generation in PE 'Thermal Power Plants Nikola Tesla'. The IPCC methodology suggests that CO2 emissions by fossil fuel combustion shall be calculated as product of fuel mass and standardized (country or even region related) values of lower heating value, carbon emission factor and factor of oxidation of combusted fuel. This approach doesn't take into account the influences of unit thermal efficiency as well as fundamental characteristics of combustion process, the most important influencing factors on overall CO2 emission. This paper presents the results of calculation of specific CO2 emissions by three different approaches: (a) using the observed linear correlation for calculation of carbon emission factor of the raw lignite, (b) based on the level of CO2 in the flue gas measured at 6 different power plant thermal units 'Nikola Tesla' A and B, (c) based on the mass balance of carbon in the coal, flying ash and bot tom ash. Comparing all the results, we conclude that the best solution is obtained by using the observed linear correlation for calculation of the carbon emission factor of the raw lignite. The calculation of specific CO2 emissions based on the measured flow rate and the share of CO2 in the flue gas gives higher, while calculation based on the carbon mass balance gives less values for the specific CO2 emissions. Higher values for specific CO2 emissions and some dissipation of these results is obtained for units A1 and A2 at output power of about 200 MW, than in the case of units whose output power during the test was over 300 MW - units A4 and A6, or over 600 MW - units B1 and B2.

The requirements of the international document Directive 2001/80/EC relating to limitation of the particulate matter emissions from large thermal power plants have been incorporated into relevant regulations of domestic legislation. In accordance with the commitments, since 2005 it was started with reconstruction and modernization of electrostatic precipitator system of all thermal units within the Electric Power Industry of Serbia. The reconstruction and modernization of electrostatic precipitator system of the unit B2 of thermal power plant 'Nikola Tesla B' was done during 2011, while the reconstruction of the electrostatic precipitator system of the unit B1 was conducted in 2012 year. One of the main objectives of performed reconstructions and modernizations, financed by donations of the European Union, was to decrease the emission of particulate matter in the flue gas from these units down to level below 50 mg/Nm3, in normal conditions and under guaranteed operating conditions of the boiler and electrostatic precipitator system. This paper presents results of the measurements of particulate matter concentration performed in accordance with standards ISO 9096 and EN 13284-1, immediately after the reconstruction and shortly before the end of the period of about 1 year after the reconstruction, as a part of control and guarantee investigations of the reconstructed electrostatic precipitators of Thermal Power Plant Nikola Tesla B units. In addition, this paper presents re sults of labosatory analysis of the coal samples taken during test, working parameters of the unit and upgraded electrostatic precipitator system during the tests as well as results of the calculations. The results of the measurements confirm that particulate matter concentration in the flue gas from reconstructed electrostatic precipitators fall down below guaranteed values, thus confirming the effectiveness of the reconstructive operations.

Coal combustion power plant Kolubara A has five thermal units with total installed capacity of 270 MW operates as a part of Public Enterprise which has planned to accept and apply the Clean Development Mechanism (new power plants on lignite and natural gas with higher energy efficiency as well as activities related to the rehabilitation and modernization of existing facilities). Two units were put in operation before more than fifty years and in order to extend the lifetime of these blocks in the process of revitalization, in this paper, beside an existing option which considers coal (lignite) combustion, are analysed possible options of thermal power units with gas and renewable energy sources: biomass, renewable solid fuels, waste materials, wind and sun. Paper presents seven energy system options of the thermal unit status which are described with suitable chosen indicators in respect to different aspects of sustainability: economical, ecological, social and resources indicators. In this paper energy indicators are defined as a tool for the sustainability assessment of energy system options. ASPID method of multi-criteria assessment was used to calculate general index of sustainability and obtained ranking of options. This study presented and analysed cases, with predefined constraints when priority has environmental indicator and different conditions where one of sub-indicators have priority, as an example of applying multi-criteria method. 1st International Conference Multidisciplinary Engineering Design Optimization (MEDO), Proceedings, Sep 14-16, 2016, Univ Belgrade, Elect Engn Inst Nikola Tesla, Belgrade, Serbia