Argyropoulos G.,Aristotle University of Thessaloniki |
Grigoratos T.,Aristotle University of Thessaloniki |
Voutsinas M.,Public Power Corporation of Greece |
Samara C.,Aristotle University of Thessaloniki
Environmental Science and Pollution Research | Year: 2013
Ambient concentrations of PM10 and associated elemental and ionic species were measured over the cold and the warm months of 2010 at an urban and two rural sites located in the lignite-fired power generation area of Megalopolis in Peloponnese, southern Greece. The PM10 concentrations at the urban site (44.2 ± 33.6 μg m-3) were significantly higher than those at the rural sites (23.7 ± 20.4 and 22.7 ± 26.9 μg m-3). Source apportionment of PM10 and associated components was accomplished by an advanced computational procedure, the robotic chemical mass balance model (RCMB), using chemical profiles for a variety of local fugitive dust sources (power plant fly ash, flue gas desulfurization wet ash, feeding lignite, infertile material from the opencast mines, paved and unpaved road dusts, soil), which were resuspended and sampled through a PM10 inlet onto filters and then chemically analyzed, as well as of other common sources such as vehicular traffic, residential oil combustion, biomass burning, uncontrolled waste burning, marine aerosol, and secondary aerosol formation. Geological dusts (road/soil dust) were found to be major PM10 contributors in both the cold and warm periods of the year, with average annual contribution of 32.6 % at the urban site vs. 22.0 and 29.0 % at the rural sites. Secondary aerosol also appeared to be a significant source, contributing 22.1 % at the urban site in comparison to 30.6 and 28.7 % at the rural sites. At all sites, the contribution of biomass burning was most significant in winter (28.2 % at the urban site vs. 14.6 and 24.6 % at the rural sites), whereas vehicular exhaust contribution appeared to be important mostly in the summer (21.9 % at the urban site vs. 11.5 and 10.5 % at the rural sites). The highest contribution of fly ash (33.2 %) was found at the rural site located to the north of the power plants during wintertime, when winds are favorable. In the warm period, the highest contribution of fly ash was found at the rural site located to the south of the power plants, although it was less important (7.2 %). Moderate contributions of fly ash were found at the urban site (5.4 and 2.7 % in the cold and the warm period, respectively). Finally, the mine field was identified as a minor PM10 source, occasionally contributing with lignite dust and/or deposited wet ash dust under dry summer conditions, with the summertime contributions ranging between 3.1 and 11.0 % among the three sites. The non-parametric bootstrapped potential source contribution function analysis was further applied to localize the regions of sources apportioned by the RCMB. For the majority of sources, source regions appeared as being located within short distances from the sampling sites (within the Peloponnesse Peninsula). More distant Greek areas of the NNE sector also appeared to be source regions for traffic emissions and secondary calcium sulfate dust. © 2013 Springer-Verlag Berlin Heidelberg.
Vasile-Pafili S.M.V.,Public Power Corporation of Greece |
Bartzis J.G.,University of Western Macedonia
Applied Thermal Engineering | Year: 2010
This paper presents an experimental investigation of a carbohydrazide application on three Units with mixed metallurgy boilers water-steam cycles in the Power Plant of Ptolemais (Greece). The tests were performed using carbohydrazide as an oxygen scavenger and metal passivation agent, with the parallel application of different alkalization agents on All-Volatile regime, in order to find the most appropriate. The optimization of this carbohydrazide application concerns the adaptation of the final products dosage for the Units needs. The tests that were performed, the measurements, the analyses and other relevant data, the results evaluation and the conclusions, are presented. The results were obtained under real industrial conditions and may provide a general tool for developing the know-how of this kind of treatment. © 2010 Elsevier Ltd. All rights reserved.
Lambropoulos D.C.,Public Power Corporation of Greece
Quarterly Journal of Engineering Geology and Hydrogeology | Year: 2010
Evaluating grout curtains below dams is a difficult task for both geologists and geotechnical engineers because of the nature of the work: problems of the site are obscured and grouting treatment is based, beyond knowledge of the site conditions, on both chance and intuition. The resulting effectiveness of grouting works is in many instances established and confirmed only after the first impounding, when the integrity of the grout curtain can be quantified by leakage measurements, monitoring of piezometers, etc. At Messochora dam, the highest concrete-faced rockfill dam in Greece, remedial treatment and maintenance grouting would be difficult after impounding and therefore, to reduce uncertainty and risks, an effort is made to analyse the adequacy of grouting works before reservoir filling. © 2010 Geological Society of London.
Konidaris D.N.,Public Power Corporation of Greece
Journal of the Air and Waste Management Association | Year: 2010
This paper analyzes the natural desulfurization process taking place in coal-fired units using Greek lignite. The dry scrubbing capability of Greek lignite appears to be extremely high under special conditions, which can make it possible for the units to operate within the legislative limits of sulfur dioxide (SO2) emissions. According to this study on several lignite-fired power stations in northern Greece, it was found that sulfur oxide emissions depend on coal rank, sulfur content, and calorific value. On the other hand, SO2 emission is inversely proportional to the parameter γCO2max, which is equal to the maximum carbon dioxide (CO 2) content by volume of dry flue gas under stoichiometric combustion. The desulfurization efficiency is positively correlated to the molar ratio of decomposed calcium carbonate to sulfur and negatively correlated to the free calcium oxide content of fly ash. Copyright 2010 Air & Waste Management Association.
Trimintzios P.,A+ Network |
Georgiou G.,Public Power Corporation of Greece
Journal of Computer Systems, Networks, and Communications | Year: 2010
Wireless Broadband offers incredibly fast, "always on" Internet similar to ADSL and sets the user free from the fixed access areas. In order to achieve these features standardisation was achieved for Wireless LAN (WLANs) and Wireless Metropolitan Area Networks (WMANs) with the advent of IEEE802.11 and IEEE802.16 family of standards, respectively. One serious concern in the rapidly developing wireless networking market has been the security of the deployments since the information is delivered freely in the air and therefore privacy and integrity of the transmitted information, along with the user-authentication procedures, become a very important issue. In this article, we present the security characteristics for the WiFi and the WiMAX networks. We thoroughly present the security mechanisms along with a threat analysis for both IEEE 802.11 and the 802.16 as well as their amendments. We summarise in a comparative manner the security characteristics and the possible residual threats for both standards. Finally focus on the necessary actions and configurations that are needed in order to deploy WiFi and WiMAX with increased levels of security and privacy. Copyright © 2010 P. Trimintzios and G. Georgiou.