Browsing by Author "Ljutzkanov L."
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Item Energy efficient SO2 removal from flue gases using the method of Wellman-Lord(2013-11-05) Dzhonova-Atanasova D.; Razkazova-Velkova E.; Ljutzkanov L.; Kolev N.; Kolev D.Investigations are reviewed on development of energy efficient technology for SO2 removal from flue gases of combustion systems by using the method of Wellman-Lord. This method is characterized by absorption of sulfur dioxide with sodium sulfite solution, which reacts to form sodium bisulfite. The absorber is typically a packed column with multiple stages. After evaporation of the solution, SO2 and sodium sulfite are obtained. The latter is dissolved in water from condensation of the steam carrying SO2 from the evaporator. The regenerated solution returns in the absorber. The SO2 removed from the flue gases is obtained as a pure product for use in chemical, food or wine production. Technical and economical assessment of this regenerative method is presented in comparison to the non-regenerative gypsum method, using data from the existing research papers and own experience from investigations on improvement of the Wellman-Lord method and development of innovative gypsum technology.Item Oxidation of sulfide ions in model solutions of sea water using of metal catalysts built in carbon matrix(2013-11-05) Dermendzhieva N.; Razkazova-Velkova E.; Martinov M.; Ljutzkanov L.; Beschkov V.The possibility of catalytic oxidation of sulfide ions from model solutions of seawater in a lab-scale model of fuel cell is studied. Two types of metal-containing catalysts (Mn u Co) incorporated in a matrix of activated carbon are synthesized. The metals are in the form of spinel-type oxides containing about 35 % vol. of the activated carbon. The processes of oxidation occurring in the anode space are considered. Experiments with different initial concentrations of sulfide ions (25-125 mg/dm-3) are carried out. The quantity of catalyst added into the solution volume is varied. The experiments are performed at room temperature and with constant mixing rate. The sulfide ions are oxidized above 90 % in about 3 hours for all initial concentrations by the use of both types of catalysts whereas the process is much slower without a catalyst (40 % in about 3 hours).Item Study of the influence of different catalysts on the rate of oxidation of sulfide ions in model solutions of seawater(2014-01-01) Dermendzhieva N.; Razkazova-Velkova E.; Martinov M.; Ljutzkanov L.; Beschkov V.The possibility for catalytic oxidation of sulfide ions in model solutions of seawater is studied. The catalysts - synthesized metal oxides incorporated in a matrix of activated carbon, are characterized by iodine adsorption. The possibility for using activated carbon as a catalyst is also considered. The influence of the amount of the catalyst is investigated. The experiments are performed at room temperature, with a constant mixing rate and initial concentrations. The oxidation of sulfide ions in the anode compartment of a laboratory scale fuel cell is described. A comparison is made of the oxidation rate into a fuel cell with the catalytical oxidation without electrodes and electrical connections at the same conditions.Item Visible light photocatalytic activity of TiO2 deposited on activated carbon(2013-03-01) Eliyas A.; Ljutzkanov L.; Stambolova I.; Blaskov V.; Vassilev S.; Razkazova-Velkova E.; Mehandjiev D.Four photocatalyst samples, prepared from beech sawdust, were synthesized by an original method, combining pyrolysis and impregnation - two of them: TiO2 + activated carbon and other two - only activated carbon. The pyrolysis process has been carried out at two different temperatures - 680 C and 830 C. The prepared samples were characterized by a series of methods - XRD, BET, SEM and DTA/TG. The most important result was achieving visible light photocatalytic activity with an azo dye pollutant for both materials. The TiO2/AC-680 C sample demonstrated higher activity under visible light illumination than the TiO2/AC-830 C sample. The visible light activity was attributed to the active carbon component in the composite materials, which was evidenced by the photocatalytic tests with bare carbon (without any TiO2) manifesting visible light activity. The AC-680 C carbon was superior to the AC-830 C under visible illumination probably due to its higher specific surface area and porous texture. UV-light testing of the photocatalytic activity revealed that the TiO2/AC-680 C sample was higher than that of the TiO2/AC-830 C under polychromatic UV-A illumination (320-400 nm with a maximum at l = 365 nm). The TiO 2/AC-680 C sample was also more efficient with the monochromatic UV-C illumination (l = 254 nm). © 2012 Versita Warsaw and Springer-Verlag Wien.