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The Pedersen process is an alumina production process, which combines pyrometallurgical and hydrometallurgical methods. In the pyrometallurgical stage, limestone is calcined and CO2 is generated. This off-gas can be captured with a high CO2 concentration. At the end of the hydrometallurgical process, aluminum hydroxides, like bayerite, are precipitated using CO2. In this paper, experimental work on precipitation of aluminum hydroxides through the addition of a mixture of CO2, O2 and N2 is presented. The parameters varied, as were the percentages of each gas and the temperature. The indicators measured were the time until the beginning of precipitation and the time that the precipitation lasts. These tests simulate the use of a smelter furnace off-gas in the precipitation stage of the Pedersen process and have shown promising results. [ABSTRACT FROM AUTHOR]

In this study, we present the preliminary results of our effort to construct a new high spatial resolution precipitation database (1 km x 1 km) over Greece, on an annual and monthly basis. A variety of spatial parameters (i.e., latitude, longitude, altitude, aspect, distance from water bodies, among others) and ERA5 reanalysis data were used as independent variables in an algorithm combined with the Regression Kriging with a Histogram-Based Gradient-Boosting Regression Tree. The dependent variable in the algorithm was the gauge data covering most of the area studied. Maps were constructed for the ERA5 reanalysis and the modelled mean precipitation totals on an annual and monthly basis for the 1980-2010 study period. The findings of the analysis show that the applied methodology improves the spatial resolution and distribution of the ERA5 reanalysis precipitation totals over Greece. Furthermore, when comparing the modelled high spatial resolution datasets against ERA5 datasets over the gauge precipitation totals, the model achieved an average R² improvement of 31.7%, with the largest improvement recorded on an annual basis, while the RMSE decreased by 16.6% on average and more than 40% on an annual basis. [ABSTRACT FROM AUTHOR]

Dojran Lake is the smallest natural lake in Macedonia, but is very important water resource for population in the region. Main economy in the region is tourism and fishery. Dojran Lake with its hydrological basin is a closed hydrological system with natural inflow of water to the lake, but no natural outflow. Recharge of the lake is from direct surface and underground inflow. In the period 1988-2000, the water level in the lake continuously was declining. Water level declination caused ecological catastrophe for the flora and fauna in the lake and lake's basin. In 2002, the Republic of Macedonia finished a project to build a system for bringing water from Gjavato wells near Vardar River with capacity of 1 m /s. The water level in the lake has recently increased. The reasons for changing the water level in the lake are not clearly identified, and they are located in hydrological conditions or uncontrolled usage the water from the lake. In order to define the causes of changes in the lake requires detailed hydrological and meteorological analysis. This paper will present the results of mathematical-statistical analysis on the basis of historical data of measured water level, precipitation, and air temperature from hydro-meteorological stationNew Dojran for the period 1961-2008. [ABSTRACT FROM AUTHOR]