Lime sludge which is generated in the industrial processes of water softening is a significant environmental and economic burden, due to increasingly stringent of national and international regulations relating to the management of waste streams. The high content of calcium carbonate in this material opens the possibility of its application in the processes of acidic waste water neutralization. In this paper, a research of characteristics of the process of neutralizing the acidity of water in terms of different initial pH value and flow regime, applying lime sludges which are generated in treatment of salt and fresh water, was conducted. Results of research showed that the initial pH value of water and the presence of NaCl have a significant effect on the solubility of calcium carbonate in the process of neutralization, while the examined flow regime (mixing speed of magnetic stirrer) had a negligible impact.

A numerical procedure for deriving the thermodynamic properties , , and of the vapor phase in the subcritical temperature range from the speed of sound is presented. The set of differential equations connecting these properties with the speed of sound is solved as the initial-value problem in domain . The initial values of and are specified along the isotherm with the highest temperature, at a several values of [0.1, 1.0]. The values of are generated by the reference equation of state, while the values of are derived from the speed of sound, by solving another set of differential equations in domain in the transcritical temperature range. This set of equations is solved as the initial-boundary-value problem. The initial values of and are specified along the isochore in the limit of the ideal gas, at several isotherms distributed according to the Chebyshev points of the second kind. The boundary values of are specified along the same isotherm and along another isotherm with a higher temperature, at several values of . The procedure is tested on Ar, N2, CH4, and CO2, with the mean AADs for , , and at 0.0003%, 0.0046%, and 0.0061%, respectively (0.0007%, 0.0130%, and 0.0189% along the saturation line).

Summary: In this paper, based on derived differential equation for the heat transfer and a suitable boundary condition (equation of heat exchange), the appropriate model of cooling of meat stakes in the form of a flat plate is set up. By using theory of similarity, Fourier and Biot criterion is defined, which allowed setting criterial equation of temperature field which included an unnamed temperature and geometric criterion. For solving the obtained criterial equation, existing diagrams of temperature functions were utilized, which were specified by analytical method for the core, the surface and the interior of the observed model. The proposed model is used for analytical solving of a number of practical problems in the cooling process of meat steaks in a gaseous environment. Particular focus has been on the temperature of the surface and core of steak as well as ambient temperature and cooling time. Also, it was shown that proposed model can be used to define temperatures or temperature field along the thickness of steak, depending on the distance from the central plane. Special possibility of applying the model is for the case of preventing freezing steaks, when their temperature is maintained within specified limits.

The used arable land covering in Croatia 882752 ha and in Bosnia and Herzegovina (B&H) 447181 ha or 15.60% (Croatia) and 8.75% (B&H) of the state territory. Main field crops are maize for grain (302266 ha and 189 557 ha and winter wheat (168433 ha and 57480 ha). Annual yields of wheat in the mentioned period were from 4.00 to 5.50 t/ha (Croatia) and from 2.63 to 3.80 t/ha (B&H). Global warming and increasingly experiencing with extreme weather conditions around the globe affecting often adversely on field crop yields. Annual temperature over Europe increased between 0.1 and 0.4% /decade. In our study, average air temperature in 2008-2012 (October-June) were higher from average (19611990) for 0.9 oC (Osijek), 1.5 oC (Zagreb), 0.8 oC (Tuzla) and 1.2 oC (Banja Luka). As both in Croatia and B&H are dominant less permeable soils, the low yields of wheat in the growing season 2009/2010 (4.04 t/ha in Croatia and 2.67 t/ha in B&H: average of the remaining four years 5.30 t/ha and 3.74 t/ha, respectively) are in close connection with excessive precipitation. Precipitation in December-February (mm) were 244 (Osijek), 230 (Zagreb), 296 (Tuzla) and 414 (Banja Luka) or the higher for the referent values for 76%, 57%, 59% and 90%, respectively. Also, loss of yield is partly caused by excess of precipitation in May and June (350 mm in Osijek, 434 mm in Tuzla and 383 mm in Banja Luka (average 19611990: 147 mm, 203 mm and 209 mm, respectively)

In the first part of the study, several mathematical methods for solving differential equations systems describing a process which are most commonly used in engineering theory and practice, were analyzed, for a characteristic example of a complex chemical reaction. The analysis was performed from the aspect of required mathematical knowledge, the time necessary for solving the problem, the possibility of error, as well as accuracy the obtained results. The second part of the study gives a suggestion of a more efficient method for solving the observed problem, which applies the principle of reducing the system to one differential equation which is most conveniently regarded as a nonhomogeneous first order equation with constant coefficients, dependent on time. The study shows that the suggested method is simpler then existing technique.

In this paper supercritical fluid extraction with carbon dioxide at different pressure was investigated and the total yield of the extract was measured. With increasing pressure from 80 to 300 bar extraction yield was increasing. It was due to the fact that supercritical carbon dioxide density increases by increasing pressures. Qualitative and quantitative analyses obtained extracts and essential oils obtained from these extracts were done using GC/MS and GC/FID analyses. Also, investigation of the extraction kinetics in the function of pressure (80, 100 and 200 bar), where every point of kinetic curve with new sample of drug in extractor was obtained is performed. The highest extract yield was obtained at pressure 200bar (4.17g/100g drug). At the end of the extraction process, CO2 – extract has been removed, and content of residual essential oil in the drug was determined. Essential oil content in drug after supercritical extraction was the highest at pressure 80 bar.