Džibra - sekundarni proizvod alkoholne fermentacije

Processes of bioethanol production from sugars, starch or cellulose produce enormous amounts of stillage (about 20 dm3 per dm3 ethanol), as a by-product. Chemically, stillage is an aqueous solution of different products obtained by alcoholic fermentation. Stillage has a high chemical oxygen demand (higher than 100 g/dm3) and is considered to be a potentially dangerous pollutant of the environment. For the processes of bioethanol production called "healthy energy", treatment and use of stillage is of great importance. This work reviews treatment processes by which stillage is converted into valuable products or feedstocks. The special attention is paid to the treatment processes which enable reuse of stillage. .U postupku dobijanja bioetanola iz šećernih, skrobnih ili celuloznih sirovina nastaje, kao sporedni proizvod, velika količina džibre (oko 20 dm3 po dm3 etanola). Po sastavu, džibra je vodeni rastvor ostataka nakon destilacije fermentacione komine. Džibra ima veliku vrednost hemijske potrošnje kiseonika (veću od 100 g/dm3) i predstavlja potencijalno opasnog zagađivača životne sredine. Za proizvodnju etanola u procesima za dobijanje "zdrave energije" od značaja je tretman i upotreba džibre. U ovom radu je dat pregled postupaka obrade džibre u cilju njenog iskorišćenja i prevođenja u vredne proizvode ili kao sirovina za različite procese. Posebna pažnja je posvećena tehnološkim postupcima kojima se džibra vraća u proces.

Bioetanol - stanje i perspektive

Processes of bioethanol production currently applied all over the world are reviewed in this paper. Attention is focused on potentially cheap biomass sources, as well as the most important operating factors controlling the progress and result of saccharification and fermentation reactions and affecting the yield of fermentable sugars and ethanol, respectively, such as: the type and concentration of acid, the type of enzyme, the type of working microorganism, operating temperature, duration time and pH. The hydrolysis conditions, namely duration time, temperature and sulfuric acid concentration, were combined in a single parameter, known as the "combined severity" (CS), in order to estimate the efficiency of bioethanol production from biomass. When the CS increases, the yield of fermentable sugars also increases. The decrease in the yield of monosaccharides coincides with the maximum concentrations of by-products, such as furfural and 5-hydroxymethylfurfural, which are well-known as yeast inhibitors. The highest ethanol yields has been obtained using the yeast Saccharomyces cerevisiae. With low oil prices and political reluctance to implement carbon taxes, fuel-ethanol production will remain uncompetitive unless some other form of cost reduction can be made, such as feedstock preparation costs.U ovom radu razmotreni su procesi dobijanja etanola iz biomase. Naglasak je stavljen na polazne sirovine, značajne faktore koji kontrolišu tok i efekte reakcija ošećerenja i fermentacije i utiču na prinos fermentabilnih šećera i etanola, respektivno, kao što su: vrste i koncentracije kiselina, vrste enzima, vrsta proizvodnog mikroorganizma, temperatura, pH i vreme trajanja reakcije. Radi sagledavanja perspektive industrijske proizvodnje bioetanola ocenjena je ekonomičnost celokupnog postupka proizvodnje bioetanola iz biomase

Uticaj operativnih uslova na promenu pritiska na dnu kolone sa vibracionom mesalicom prečnika 16,6 cm

The effects of the intensity of vibration, superficial gas velocity, content of solid particles and rheology of the liquid phase on the total and time-averaged pressure variation at the bottom of a 16.6 cm i.d. reciprocating plate column were studied. The total and time-averaged pressure variation at the column bottom were found to increase with increasing vibration intensity, liquid viscosity and content of solid particles, but to decrease with increasing superficial gas velocity. The pressure variation at the column bottom was greater in the column filled with CMC solutions than in the one with distilled water. The pressure variation at the column bottom was correlated with the vibration intensity and the liquid phase hold-up. The pressure variations at the bottom of columns of different diameter were also compared. The oriffice coefficient for plates of approximately the same free fraction area was found to decrease with increasing column diameter

[Kontinualni postupci dobijanja biodizela]

Continuous biodiesel production on laboratory and industrial scale was analyzed, with focus on their advantages and disadvantages. Attention was paid to specific characteristics of industrial processes in order to point out the advanced technologies. The well-known base-catalyzed continuous biodiesel production processes are related to problems caused by the immiscibility of the reactants (alcohol and oil), application of relatively high operating temperature (usually the boiling temperature of alcohol or one near it) and obtained yield of methyl ester yields lower than desired. One way to overcome these problems is to employ special reactor design favoring the emulsion process and increasing the overall rate of biodiesel production process, even at room temperature and atmospheric pressure. The second way is to apply heterogeneous catalysts in continuous processes, which will probably be the optimal approach to economically justified and environmentally friendly biodiesel production

Утицај концентрације раствора и степена полимеризације карбоксиметилцелулозе на садржај гаса у реактору са вибрационом мешалицом

Gas holdup was investigated in a gas-liquid and gas-liquid-solid reciprocating plate column (RPC) under various operation conditions. Aqueous carboxymethylcellulose (sodium salt, CMC) solutions were used as the liquid phase, the solid phase was spheres placed into interplate spaces, and the gas plase was air. The gas holdup in the RPC was influenced by: the vibration intensity, i.e., the power consumption, the superficial gas velocity, the solids content and the rheological properties of the liquid phase. The gas holdup increased with increasing vibration intensity and superficial gas velocity in both the two- and three-phase system. With increasing concentration of the CMC PP 50 solution (Newtonian fluid), the gas holdup decreased, because the coalescence of the bubbles was favored by the higher liquid viscosity. In the case of the CMC PP 200 solutions (non-Newtonian liquids), the gas holdup depends on the combined influence of the rheological properties of the liquid phase, the vibration intensity and the superficial gas velocity. The gas holdup in the three-phase systems was greater than that in the two-phase ones under the same operating conditions. Increasing the solids content has little influence on the gas holdup. The gas holdup was correlated with the power consumption (either the time-averaged or total power consuption) and the superficial gas velocity

Optimization of oil recovery from oilseed rape by cold pressing using statistical modeling

Cold pressing is frequently used to produce high-quality vegetable oils, especially from seeds with high oil content, such as rapeseeds. But, it encounters a challenge from the industrial demand for high oil yield. Modeling the cold pressing process using experimental and statistical approaches would help to understand the effects of cold pressing conditions on oil yield and process efficacy. Therefore, this work aimed to investigate the effects of nozzle diameter (8–12 mm), screw frequency (40–60 Hz), and press head temperature (40–80 °C) on the oil recovery from rapeseeds by cold pressing using response surface methodology coupled with a 33 full factorial design. An extended quadratic equation fitted the experimental data accurately and reproducibly, as proved by the acceptable coefficient-of-determination (R2 = 0.873), a not significant lack-of-fit (p = 0.872), and a very low mean relative percentage deviation (± 6.7%, 35 data). The ANOVA revealed that nozzle diameter, press head temperature, their interaction, three-factor interaction, and squared nozzle diameter influenced pressed oil yield significantly. The optimal condition for obtaining the highest pressed oil yield (26.7%) within the experimental domain was a nozzle diameter of 10 mm, a screw frequency of 50 Hz, and a press head temperature of 80 °C. The crude oil extraction degree achieved by cold pressing was 60.8% compared to the Soxhlet method. The rapeseed oil contains predominantly oleic, linoleic, linolenic, and palmitic acids, agreeing with other reported rapeseed oils