Milan Tomić

Significance of the structural properties of CaO catalyst in the production of biodiesel: An effect on the reduction of greenhouse gases emission

The influence of the physicochemical properties of a series of CaO catalysts activated at different temperatures on the biodiesel production was investigated. These catalysts show dissimilar yields in the transesterification of triglycerides with methanol. We have found significant relationships between structural properties (the type of the pore system, the typical CaO crystal phase and the sizes of crystallites (up to 25 nm), the minimal weight percentage of CaO phase, the total surface basicity and potential existence of two types of basic active sites) of CaO prepared and activated by means of thermal treatment at highest temperature and catalytic efficiency. Benefits of this catalyst are short contact time, standard operating temperature and atmospheric conditions, relatively low molar ratios and small catalyst loading. These all together resulted in a very high biodiesel yield of high purity. The properties of different biodiesel (obtained with the use of the prepared CaO catalyst) blends with different diesel and biodiesel ratios indicate that the higher the fraction of biodiesel fuel the better the achieved fuel properties according to the EU standards. A significant reduction of CO2 and CO emissions and only a negligible NOx increase occurred when blends with an increased biodiesel portion was used. The use of biodiesel derived blends, and the eventual complete replacement of fossil fuels with biodiesel as a renewable, alternative fuel for diesel engines, would greatly contribute to the reduction of greenhouse gases emissions. [Projekat Ministarstva nauke Republike Srbije, br. ON 172061 i TR 34008]

The effects of working parameters and tillage quality on rotary tiller specific work requirement

Accepted 31 October, 2011 The aim of this paper was to analyze the influence of rotary tiller rotor rotation direction on specific work requirement (SWPTO). The SWPTO was calculated by measuring the power take-off (PTO) torque, PTO speed, working speed and depth, as well as the working width. The tillage quality was determined by the bulk density and soil structure. Reverse rotor rotation direction concept is characterized by more efficient tillage which provides significantly higher amount of macro-structure aggregates (0.25 to 10 mm) and their better distribution in the soil. Significantly lower SWPTO was observed with the reverse rotor rotation direction. It was within the range of -2.15-27.74% (14.35% on average) depending on the work speed which was 0.29 to 1.08 m s -1 . Multiple linear regression provided new equations for the calculation of SWPTO depending not only on the working parameters, but on the intensity of soil breaking and soil conditions as well. The obtained equations had high values of Coefficients of determination R 2 (0.92 to 0.99 for conventional and 0.84 to 0.93 for reverse rotor rotation direction). Reverse rotor rotation direction had lower SWPTO values which were 20.3 and 15.5% for the working speeds of 0.5 and 1.0 m s -1 , respectively, and were obtained for equal values of tillage intensity parameters.