Coal-fired power plants energy efficiency and climate change: Current state and future trends

Termoelektrane na fosilna goriva, pre svega ugalj, emituju velike količine ugljen dioksida, koji se smatra glavnim uzročnikom fenomena globalnog zagrevanja. Smanjenje emisije CO2 u energetskom sektoru je postalo jedan od osnovnih prioriteta svih nacionalnih vlada. Sa druge strane, globalno zagrevanje direktno utiče na proizvodnju energije. Ovaj uticaj se pre svega ogleda u mogućnosti odvođenja otpadne toplote, neophodnog za rad postrojenja. U doglednoj budućnosti efikasnost rada postojećih termoenergetskih postrojenja opadati, ukoliko se ne ulože dodatni napori kako bi se unapredio njihov rad, posebno imajući u vidu optimizaciju rada kondenzacionog dela postrojenja, a ovo opet vodi povećanoj emisiji CO2. Predviđeni porast potrošnje energije dodatno podvlači ovaj problem.U radu je dat pregled današnjih metoda za smanjenje emisije CO2 u atmosferu, ali je osnovni cilj rada da ukaže na mogućnosti povećanja energetske efikasnosti postojećih postrojenja, uz relativno mala ekonomska ulaganja, čime bi se smanjili i ekološki problemi. Prikazan je uticaj porasta temperature rashladne vode i vazduha na energetsku efikasnost termoelektrana u Srbiji sa protočnim i povratnim sistemom hlađenja. Rezultati su dobijeni na osnovu originalnih matematičkih modela i numeričkih simulacija, koje su autori predstavili u drugim radovima. Dobijeni rezultati mogu biti od koristi kako pri revitalizaciji postojećih, tako i pri projektovanju novih termoenergetskih kapaciteta.Coal-fired power plants emit large amounts of CO2, which constitutes one of the largest causes of global warming. Reducing CO2 emissions in the energy sector has become a top priority for national governments. On the other hand, fossil energy production is also affected by air and water temperatures. Local weather conditions affect the capacity of cooling towers and natural water bodies to transfer waste heat from steam condensers to the atmosphere. Without technology-based improvements in cooling system efficiency, the steam-cycle energy efficiency would decrease. This again leads to increased consumption of fossil fuels and thus increasing emissions of CO2. Increasing in global energy demand aggravates this issue. In this paper, the overview of currently actual methods for CO2 reduction is given. The main objective, however, is to find a cost-effective solution for increasing the energy efficiency of existing plants in Serbia. The overview of cooling water temperature increase impact on the energy efficiency in Serbian power plants is given, based on meteorological data and numerical simulation. This study is done for both, power plants with once-through and with closed cycle cooling system. Obtained results could be used as useful guidelines in design of the new power plants and also in improving existing power plants performances

Coal-fired power plants energy efficiency and climate change: Current state and future trends

Termoelektrane na fosilna goriva, pre svega ugalj, emituju velike količine ugljen dioksida, koji se smatra glavnim uzročnikom fenomena globalnog zagrevanja. Smanjenje emisije CO2 u energetskom sektoru je postalo jedan od osnovnih prioriteta svih nacionalnih vlada. Sa druge strane, globalno zagrevanje direktno utiče na proizvodnju energije. Ovaj uticaj se pre svega ogleda u mogućnosti odvođenja otpadne toplote, neophodnog za rad postrojenja. U doglednoj budućnosti efikasnost rada postojećih termoenergetskih postrojenja opadati, ukoliko se ne ulože dodatni napori kako bi se unapredio njihov rad, posebno imajući u vidu optimizaciju rada kondenzacionog dela postrojenja, a ovo opet vodi povećanoj emisiji CO2. Predviđeni porast potrošnje energije dodatno podvlači ovaj problem.U radu je dat pregled današnjih metoda za smanjenje emisije CO2 u atmosferu, ali je osnovni cilj rada da ukaže na mogućnosti povećanja energetske efikasnosti postojećih postrojenja, uz relativno mala ekonomska ulaganja, čime bi se smanjili i ekološki problemi. Prikazan je uticaj porasta temperature rashladne vode i vazduha na energetsku efikasnost termoelektrana u Srbiji sa protočnim i povratnim sistemom hlađenja. Rezultati su dobijeni na osnovu originalnih matematičkih modela i numeričkih simulacija, koje su autori predstavili u drugim radovima. Dobijeni rezultati mogu biti od koristi kako pri revitalizaciji postojećih, tako i pri projektovanju novih termoenergetskih kapaciteta.Coal-fired power plants emit large amounts of CO2, which constitutes one of the largest causes of global warming. Reducing CO2 emissions in the energy sector has become a top priority for national governments. On the other hand, fossil energy production is also affected by air and water temperatures. Local weather conditions affect the capacity of cooling towers and natural water bodies to transfer waste heat from steam condensers to the atmosphere. Without technology-based improvements in cooling system efficiency, the steam-cycle energy efficiency would decrease. This again leads to increased consumption of fossil fuels and thus increasing emissions of CO2. Increasing in global energy demand aggravates this issue. In this paper, the overview of currently actual methods for CO2 reduction is given. The main objective, however, is to find a cost-effective solution for increasing the energy efficiency of existing plants in Serbia. The overview of cooling water temperature increase impact on the energy efficiency in Serbian power plants is given, based on meteorological data and numerical simulation. This study is done for both, power plants with once-through and with closed cycle cooling system. Obtained results could be used as useful guidelines in design of the new power plants and also in improving existing power plants performances

Begov most – Staničenje, zaštitna arheološka iskopavanja u 2014. godini na trasi autoputa E 80, Koridor 10 – istočni krak

Lokalitet Begov most se nalazi u ataru sela Staničenje, u podnožju brda Gradište koje dominira nad dolinom Nišave, jugozapadno od kasnoantičkog i ranovizantijskog utvrđenja na tom uzvišenju. U zoni eksproprijacije na trasi izgradnje autoputa E 80 na ovoj lokaciji arheološki nadzor zemljanih radova konstatovao je kasnoantičko nalazište, koje se manifestovalo većom količinom lomljenog i pritesanog kamena, fragmentima antičkih opeka i ulomcima kasnoantičke grnčarije (sl. 1).2 Osim toga, u zapadnom profilu useka nove trase autoputa uočeni su ukop grobne rake i lobanja pokojnika. Grob je bio orijentisan u pravcu zapad-istok, sa odstupanjem ka jugu, što je ukazivalo na sahranu hrišćanske provenijencije

Numerical computation and prediction of electricity consumption in tobacco industry

Electricity is a key energy source in each country and an important condition for economic development. It is necessary to use modern methods and tools to predict energy consumption for different types of systems and weather conditions. In every industrial plant, electricity consumption presents one of the greatest operating costs. Monitoring and forecasting of this parameter provide the opportunity to rationalize the use of electricity and thus significantly reduce the costs. The paper proposes the prediction of energy consumption by a new time-series model. This involves time series models using a set of previously collected data to predict the future load. The most commonly used linear time series models are the AR (Autoregressive Model), MA (Moving Average) and ARMA (Autoregressive Moving Average Model). The AR model is used in this paper. Using the AR (Autoregressive Model) model, the Monte Carlo simulation method is utilized for predicting and analyzing the energy consumption change in the considered tobacco industrial plant. One of the main parts of the AR model is a seasonal pattern that takes into account the climatic conditions for a given geographical area. This part of the model was delineated by the Fourier transform and was used with the aim of avoiding the model complexity. As an example, the numerical results were performed for tobacco production in one industrial plant. A probabilistic range of input values is used to determine the future probabilistic level of energy consumption

Toxicity Screening after Electrochemical Degradation of Reactive Textile Dyes

The application of various electrodes for in situ degradation of Reactive Yellow 125 (RY125) and Reactive Green 15 (RG15) dyes, as well as ecotoxicity screening test of their degradation products were studied in this paper. The degradation process was performed in a two-electrode cylindrical cell, with Fisher platinum electrode as anode and Pd, Zr, or C electrodes as cathode; in 0.1 M Na2SO4 as supporting electrolyte. The optimal conditions (voltage and pH value) for degradation were determined in a platinum-palladium (Pt-Pd) model system for 200 mg/L of both reactive dyes. Then the electrolysis with other electrodes was conducted under the same conditions. Decolorization was monitored spectrofotometrically (UV-Vis) and the degradation efficiency was confirmed by HPLC technique with a DAD detector. Differences in degradation efficiency were observed between these three electrochemical systems (Pt-Pd, Pt-Zr, and Pt-C). The Pt-Pd system was the most efficient for the degradation of both reactive dyes. Achieved decolorization percentage for RG15 and RY125 were 98% and 97%, respectively. The ecotoxicity assessment of degradation products was performed using Anemia sauna. Toxicity data were compared by Kruskal-Wallis one-way analysis and pair-wise group comparisons with Mann-Whitney U tests. Statistically significant differences (p lt 0.05) in mortality (%) for Pt-Pd and Pt-Zr systems were determined between treated and untreated dye solutions of RG15. System Pt-C had no detectable significance in treatment of solutions of both dyes

Risk of thermal pollution of the danube passing through Serbia due to thermal power plants

A thermal power plant (TPP) uses large amounts of fresh water, mostly for cooling purposes. Among different types of cooling systems, once-through cooling is the most water-intensive and has the greatest environmental impacts. From the view-point of the steam cycle efficiency, this type of cooling still provides the most efficient electricity production, and therefore is widely used. Water is withdrawn from nearby water bodies, absorbs heat from the steam in a condenser, and then discharged back to its original source at higher temperatures causing severe environmental impacts, including fish killing, disturbing ecosystems, and heating-up natural water bodies. The total installed capacity of almost 1100 MW on the right bank of the Danube in Serbia threatens the ecosystem of this large international river due to thermal pollution. This problem will be even more pronounced in the near future, due to an inevitable increase in production capacity for new 350 MW, currently under construction. Herein, analysis of the legal framework for the protection of water from thermal pollution as well as analysis of the actual situation on the site of the TPP "Kostolac" in Serbia are presented. Based on meteorological and hydrological parameters, configuration and operation parameters of the plant, the numerical simulation of the condenser was carried on. The temperature of the water leaving condenser and amount of heat discharged back to the river are obtained. According to those results, the analysis of the existing thermal pollution of the Danube River in the flow through Serbia is given by numerical simulation using software ANSYS CFX. Analysis of thermal discharge into the Danube for the five-year period has been carried out. The cooling water effluent causes a temperature increase in the area of the right bank of the Danube, and this thermal disturbance extends along the right river bank for kilometers. Note that the flow rate of the Danube is currently large enough to compensate this thermal disturbance, but for a smaller river and/or larger electricity production capacities, this influence would have even more significant consequences on the ecosystem, making those results even more useful for further analysis

COAL-FIRED POWER PLANTS ENERGY EFFICIENCY AND CLIMATE CHANGE-CURRENT STATE AND FUTURE

 Coal-fired power plants emit large amounts of CO2, which constitutes one of the largest causes of global warming. Reducing CO2 emissions in the energy sector has become a top priority for national governments. On the other hand, fossil energy production is also affected by air and water temperatures. Local weather conditions affect the capacity of cooling towers and natural water bodies to transfer waste heat from steam condensers to the atmosphere. Without technology-based improvements in cooling system efficiency, the steam-cycle energy efficiency would decrease. This again leads to increased consumption of fossil fuels and thus increasing emissions of CO2. Increasing in global energy demand aggravates this issue.       In this paper, the overview of currently actual methods for CO2 reduction is given. The main objective, however, is to find a cost-effective solution for increasing the energy efficiency of existing plants in Serbia. The overview of cooling water temperature increase impact on the energy efficiency in Serbian power plants is given, based on meteorological data and numerical simulation. This study is done for both, power plants with once-through and with closed cycle cooling system. Obtained results could be used as useful guidelines in design of the new power plants and also in improving existing power plants performances

Study of the Electrochemical Oxidation of Reactive Textile Dyes Using Platinum Electrode

Textile industries are widespread in developing countries. Among the various processes in the textile industry, the dyeing process uses large volumes of water for dyeing, fixing and washing. Textile industry wastewater is characterized by intensive color and high chemical oxygen demand (COD) concentrations that discarding of these toxic wastewaters to the environment will cause a major problem. In this study electrochemical oxidation of reactive textile dyes: Reactive Blue 52, Reactive Black 5, Reactive Green 15, and Reactive Yellow 125, using platinum anode was examined. Electrolysis is carried out in electrochemical cell containing membrane which is standard membrane in industry. Membrane separated anodic and cathodic area. Supporting electrolyte was 0.1M sodium sulfate which is also present in real textile effluents. Applied voltage of 6, 12 and 24V, and influence of membrane on electrolysis were examined on model dye (Reactive Blue 52). Highest degradation degree for model dye was achieved at 12V, so electrolysis of other dyes was done on this voltage. COD value of all dyes dropped after 60 minutes of electrolysis below a measurable level ( LT 30mg/L O-2), except Reactive Black 5 whose COD reduction was 57.95% with membrane and 35.28% without membrane applied. Complete decolorization was achieved after 10 to 60 minutes for all dyes. Degradation products of model dye Reactive Blue 52 were monitored with HPLC, and influence of pH on decolorization was also examined on model dye

Ispitivanje oksidativnog stresa i krvne slike ovaca odgajanih u regiji koja je bila izložena delovanju municije sa osiromašenim urnijumom (DU)

The paper presents the results of several health status parameters of sheep bred in the area exposed to depleted uranium (DU) ammunition during NATO bombing of Serbia and Montenegro in 1999. The blood samples of sheep were collected randomly in the region of Bujanovac, in 2004. Complete blood count was performed according to standard laboratory procedures. Concentration of red blood cells malondialdehyde (RBC MDA) and activity of erythrocyte superoxid dismutase (SOD) were determined spectrophotometrically, while the functional activity of leukocytes was investigated by NBT reduction and adhesion test. The results of complete red blood cells count indicated normocytic hypochromic anaemia. The total number of leukocytes and the differential leukocytes count were within the physiological range. Although the leukocytes adhesiveness was not changed in DU exposed animals, their increased NBT reduction revealed stimulated leukocytes' oxidative burst. This finding, together with significantly increased RBC MDA concentrations, as well as the activity of RBC antioxidant SOD, point to the existence of oxidative stress. Although the results indicated that animals were under oxidative stress, still there are no conclusive data that it was due to the exposure of DU that entered the environment during military operations.U ovom radu su prikazani rezultati ispitivanja zdravstvenog stanja ovaca odgajanih u regionu koji je bio izložen delovanju municije sa osiromašenim uranijumom (DU) tokom bombardovanja Srbije i Crne Gore 1999. godine, od strane NATO pakta. Uzorci krvi su uzeti tokom 2004. godine od ovaca u regionu Bujanovca, metodom slučajnog izbora. Kompletan pregled krvi obavljen je standardnim laboratorijskim procedurama. Koncentracija malondialdehida u ertirocitima (RBC MDA) i aktivnost eritrocitne superoksid dismutaze (SOD) određene su spektrofotometrijski, dok je funkcionalna aktivnost leukocita ispitana NBT testom redukcije i adhezije. Rezultati kompletnog pregleda eritrocita su ukazali na postojanje normocitne hipohromne anemije. Ukupan broj leukocita i leukocitna formula su bili u fiziološkim okvirima. Kod životinja izloženih delovanju osiromašenog uranijuma nije bila izmenjena adhezivnost leukocita, ali je pojačana NBT redukcija ukazivala na to da je bio podstaknut njihov oksidativni prasak. Ovaj nalaz, uz značajan porast koncentracije RBC MDA i aktivnosti eritrocitnog antioksidativnog enzima SOD, ukazivali su na postojanje oksidativnog stresa. Rezultati dobijeni ovim ispitivanjima su upućivali na to da su životinje bile pod oksidativnim stresom, ali nemamo sigurne podatke da je on bio posledica izlaganja dejstvu osiromašenog uranijuma (DU) koji je dospeo u njihovu životnu sredinu tokom vojne akcije u tom regionu