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The main problem of hydraulic transport is the resistance generated during the mixture transport through the pipe-line. Testing the flow characteristics of mixtures, shown in this paper, are based on the principles of determining the unit energy losses by a mathematical calculation using the non-linear regression - the Levenberg-Marquardt algorithm. Such obtained results allow determining a transport rate in the horizontal pipe-line, depending on the mixture bulk density and pipe-line diameter. The flotation tailings is mainly used as a filling material in the mine "Trepca" - Stari Trg. According to the grain size distribution, it is a fine-grained material of a size of 0.074 mm to 1.2 mm. It is a multicomponent material containing pyrite, pyrrhotine and other heavy metals, and therefore, has a high bulk mass. The average rate of the hydromixture, in which the energy losses reach the minimum value, depends on the pipe-line diameter and kinetic bulk density of the mixture. For the test interval of change in the pipe-line diameter, shown in this paper (0.168 mm, 0.176 mm, 0.193 mm, and 0.225 mm), and kinetic bulk density of the hydraulic mixture (1-1.6 kg/m(3)), this rate ranges from 3-5.5 m/s. The increase of the energy losses in the hydraulic mixture transport increases proportionality with the increase of its kinetic bulk density. The results, presented in this paper, show that the required bulk density of 1.6 kg/m(3) should be accepted as a limit from a point of view of the hydraulic transport cost-efficiency.

The present study compares the performances of the regression models developed by the response surface methodology combined with the full factorial, Box-Behnken or face central composite designs applied for the ultrasound-assisted KOH-catalyzed methanolysis of sunflower oil. While all models led to similar optimal reaction conditions, the models based on the simpler designs had the smaller corrected Akaike information criterion values, the insignificant lack of fit and the more favorable statistical criteria than the model based on the full factorial design. Including fewer experiments, the Box-Behnken design can be recommended for the optimization of ultrasound-assisted biodiesel production processes., U radu se porede performanse regresionih modela razvijenih na osnovu kombinovanja metodologije površine odziva sa punim faktorijelnim, Boks-Benken-ovim ili centralnim kompozitnim planom kada se primene na ultrazvukom podržanu bazno-katalizovanu metanolizu suncokretovog ulja. Iako su svi modeli dali slične optimalne uslove reakcije, modeli zasnovani na jednostavnijim planovima imali su manje vrednosti Akaike-ovog informacionog kriterijuma, neznačajnu vrednost odstupanja od modela i povoljnije statističke kriterijume u odnosu na model zasnovan na punom faktorijelnim planu. Boks-Benken-ov plan, koji zahteva manji broj eksperimenata, može da se preporuči za optimizaciju proizvodnje biodizela u ultrazvučnom reaktoru.

The present work deals with the modeling of the kinetics of essential oils extraction from plant materials by water and steam distillation. The experimental data were obtained by studying the hydrodistillation kinetics of essential oil from juniper berries. The literature data on the kinetics of essential oils hydrodistillation from different plant materials were also included into the modeling. A physical model based on simultaneous washing and diffusion of essential oil from plant materials were developed to describe the kinetics of essential oils hydrodistillation, and two other simpler models were derived from this physical model assuming either instantaneous washing followed by diffusion or diffusion with no washing (i.e., first-order kinetics). The main goal was to compare these models and suggest the optimum ones for water and steam distillation and for different plant materials. All three models described well the experimental kinetic data on water distillation irrespective of the type of distillation equipment and its scale, the type of plant materials and the operational conditions. The most applicable model is the one involving simultaneous washing and diffusion of the essential oil. However, this model was generally inapplicable for steam distillation of essential oils, except for juniper berries. For this hydrodistillation technique, the pseudo first-order model was shown to be the best one. In a few cases, a variation of the essential oil yield with time was observed to be sigmoidal and was modeled by the Boltzmann sigmoid function., Rad se bavi modelovanjem kinetike ekstrakcije etarskog ulja iz biljnih materijala primenom destilacija vodom i vodenom parom. Eksperimentalni podaci dobijeni su proučavanjem kinetike hidrodestilacije etarskog ulja ploda kleke. Literaturni podaci o kinetici hidrodestilacije etarskog ulja iz različitih biljnih materijala su, takođe, uključeni u modelovanje. Za opisivanje kinetike hidrodestilacije etarskog ulja razvijen je fizički model koji je zasnovan na istovremenom ispiranju i difuziji etarskog ulja iz biljnog materijala. Iz ovog modela izvedena su dva prostija modela od kojih je prvi zasnovan na trenutnom ispiranju praćenim difuzijom a drugi na difuziji bez ispiranja (tj.na kinetici prvog reda). Glavni cilj je bio poređenje ovih modela i predlaganje optimalnog za destilacije vodom i vodenom parom I za različite biljne materijale. Sva tri modela opisuju dobro eksperimentalne kinetičke podatke u slučaju destilacije vodom nezavisno od tipa destilatora i njegove veličine, tipa biljnog materijala i procesnih uslova, ali je najbolji model koji uključuje istovremeno ispiranje i difuziju etarskog ulja. Ovaj model je, međutim, neprimenljiv za vodeno-parnu destilaciju etarskog ulja, izuzev za etarsko ulje ploda kleke. Za ovu destilaciju etarskog ulja najbolji je kinetički model pseudo-prvog reda. U slučaju nekoliko biljnih materijala, promena prinosa etarskog ulja sa vremenom je sigmoidna, pa je modelovana Bolcmanovom sigmoidnom funkcijom.

On construction with dimensions 15 x 5 x 2 m, conditions of temperature transmission and vegetables growth are examined. We have been cultivating pepper, cucumber, small cucumber, tomato, and lattice. Over ground heating has been used, consisting of one bent pipe with radius of 10 mm, in the shape of hairpin along the both sides of the construction. Underground heating consists of six pipes with radius of 20 mm on the depth of 350-400 mm. There have been measured the temperature inside construction, the temperature outside construction, the waterflow, and water temperature flowing into and out of the construction. The approximate heating flow factor K is determined by both the equation: heating balance equation and basic equation for temperature transmition. Vegetable growth has been watching during the period of time from March to November 2005.