Thermodynamic study of atmospheric corrosion seasonal kinetic, based on Sun photometer data

Zbog ogromnih gubitaka koji nastaju na strojarskim materijalima, atmosferska korozija predstavlja tehnološki, ekonomski, kao i ekološki problem zbog povećanja sadržaja onečišćenja u životnom okolišu. U ovom radu su prikazani rezultati termodinamičke dijagnostike ograničavajućeg stupnja ukupne kinetike korozije uslijed dodira čvrstih površina s vodenom parom, na osnovu podataka dobivenih svakodnevnim promatranjem tlaka vodene pare u Temišvaru 2011., od ožujka do prosinca. Na osnovu sezonskih vrijednosti izračunate su konstante difuzije vodene pare, nastale uslijed gradijenta koncentracije, kao i energije termokemijske aktivacije prvog stupnja korozije, na osnovu Ahrrenijusove jednadžbe. Izračunate relativne sezonske varijacije kemijske polarizacije vodene pare u odnosu na ukupnu promjenu entropije nastale i kondenzacijom na čvrstim površinama, uspoređene su s literaturnim vrijednostima za slobodne Gibbs-energije mogućih produkata relaksacijskih termokemijskih reakcija. Ograničavajući stupanj ukupnog procesa korozije, određen je usporedbom molarnog rada depolarizacije sukcesivnih elektrokemijskih relaksacijskih procesa. Depolarizacijski rad proporcionalan je konstanti brzine sezonski aktiviranih sukcesivnih relaksacijskih procesa u razdoblju koncentracijske depolarizacije vodene pare: elektrokemijske relaksacije kisika i vodika pri pretlaku depolarizacije vodika i standardnom potencijalu indikatora anodnog rastvaranja metala. Podaci rabljeni za izračunavanje tlaka vodene pare u atmosferi dobiveni su pomoću fotometra iz meteorološke stanice na "Politihnici" Sveučilišta u Temišvaru, Rumunjska (45,74 °N; 21,22 °E). Mjerenja su provedena u području valnih duljina 940 nm, uporabom empirijskih modela i podataka o temperaturi, barometarskom tlaku i vlažnosti zraka, a suglasne su s rezultatima 4 različite metode s varijacijama do 2 %.The atmospheric corrosion is a mechanical, technological, economic as well as an ecological problem, due to the enormous losses in corroded vessels material and machine material due to enhanced content of corroded material pollutants in environment. The results of the thermodynamic diagnostic study are given in this paper of the limited step in the water vapor corrosion kinetic based on the monitoring data for the seasonal water vapor pressure measured daily in Timisoara, by 2011, from March to December. Based on the seasonal values of the measured data, the seasonal diffusion rate constants the activation energies of the first chemical corrosion step are determined. The calculated seasonal water vapor chemical surface polarizations relative to the values of equilibrium entropies and also of the condensed water vapor on the solid surfaces are compared with the literature data of the possible products of chemical processes. The thermodynamic diagnostic study of the limited successive relaxation step in overall corrosion kinetic is carried out, based on the comparison of the molar water vapor couple relaxation work. The depolarization work is proportional to the depolarization rate constants of reactants and products activated successively in couple with water vapor concentrations depolarization energy, in the same time period: the electrochemical relaxation for the achievement of oxygen and hydrogen equilibrium in the seasonal activated corrosion cell, hydrogen depolarization energy and oxygen striping indicators standard potential. Data used to calculate the water vapor pressure in atmosphere are based on measurements accomplished by a sun photometer located at the Politechnica University of Timisoara, Romania (45,74 °N; 21,22 °E). The extraction of water vapor amount from sun photometer capacity relies on a measurement in the region of water vapor absorption at 940 nm. In order to apply the empirical models, the temperature, barometric pressure and humidity content have been taken from a weather station. One found that the experimental values of water vapor pressure, obtained using the sun photometer, are comparable with four other methods, and within, the experimental variations is characterized by a relative error of 2 %

Sustainable development of Romanian cities through biogas production from municipal wastes and application in co-combustion processes

Today municipal wastes represent a general problem from multiple points of view: necessary space for depositing, odor, possible soil contamination. In the same time, a large quantity of organic residual material remains unused in terms of energy conversion by potentially producing a biofuel which, in its term, can be used for covering at least partially, the human demand for energy. In this context, the present paper underlines the possible applications of anaerobic fermentation for biogas production by using as main substrate solid municipal waste from city of Timisoara, Romania, inside a pilot installation for determining its potential for further usage at larger scale in firing or co-firing processes; in this context, conclusions will be traced, based on the resulted experiments

Analysis of Surface Water Quality and Sediments Content on Danube Basin in Djerdap-Iron Gate Protected Areas

As water is essential to life and is an indispensable resource for ecosystems and their services and for nearly all human activities, the goal of this research was to evaluate the surface water quality of the Danube as it passes through the Romania–Serbia border in the nature reservations Djerdap and Iron Gate. The study aimed to assess the oxygen regime, nutrients and heavy metals contamination of the surface waters of the Danube on a length of about 240 km, between Bazias and Iron Gate II. Reference sampling and analytical methods (UV-VIS and AAS) were deployed to reach this goal. In addition, sediments were analyzed through back scattered SEM-EDAX for the elemental analysis of the sediment surface. Results obtained show a low environmental impact of heavy metals, while the Danube’s oxygen regime is under stress due to nutrients’ (nitrites and orthophosphates) significant concentration in the Danube surface water in the analyzed sector. Our approach can be applied to other water bodies in the area, to increase available scientific data together with societal awareness of the Danube’s environmental risks