Tülay Durusoy

Biodesulfurization of Turkish lignites: 1. Optimization of the growth parameters of Rhodococcus rhodochrous, a sulfur-removing bacterium

Abstract The effects of inoculum percentage, initial pH, growth temperature, shaking rate, substrate type and initial substrate concentration on the growth kinetics of Rhodococcus rhodochrous , a sulfur-removing bacterium, were investigated. The optimum value for each parameter that favoured the maximum specific growth rate was calculated from models established through linear of non-linear regression of the relevant data. Around these optima, biodesulfurization experiments were performed with sterile lignite. An increase in sulfate, pyritic and organic sulfur reduction with increasing reaction time were observed. The highest decreases in the total (30.2%) and organic sulfur (27.1%) contents were obtained with Mengen lignite at 75 h of biodesulfurization.

Effect of heating rate and particle size on the pyrolysis of göynük oil shale

Pyrolysis kinetics of (−210 + 149), (−250 + 210) and (−420 + 250) μm particle size Göynük oil shale was investigated under non-isothermal conditions with a heating rate of 10–60 K/min in the 298–1173 K pyrolysis temperature interval under argon atmosphere. The pyrolysis characteristics of the samples were analyzed using TG/DTG curves. Differential thermogravimetric data were analyzed by a model assuming first order kinetics. Minimum activation energy was obtained as 0.6 kJ/mol with 60 K/min in (−210 + 149) μm. It appears from the results that higher heating rate values have a limiting effect on the behavior of the pyrolysis reaction.

Effects of Heating Rate and Particle Size on Pyrolysis Kinetics of Gediz Lignite

Gediz lignite was pyrolyzed in a thermobalance apparatus at atmospheric pressure in this study. Effects of heating rate and particle size on the pyrolysis kinetics were examined. Experiments were conducted at nonisothermal conditions with a heating rate range of 10 to 90 K/min under an argon atmosphere in the pyrolysis temperature interval of 298 to 1173 K. Two different particle size ranges were tested: 595 > D p > 297 and 53 > D p > 44 w m. Average relative volatile matter yields were calculated as 40.6 and 39.0% of the total volatile matter yields from 678 to 777 K for the linear segments of the thermogravimetric (TG) curves of the larger and smaller size particles, respectively. TG data were analyzed by a reaction rate model assuming first-order kinetics, and lower apparent activation energies were calculated at higher heating rates. Minimum apparent activation energy was obtained as 9.05 kJ/mol at the heating rate value of 90 K/min with 53 > D p > 44 w m size particles.

The factors affecting the growth kinetics of Sulfolobus solfataricus, a sulfur removing bacterium

Abstract The effects of temperature, agitation rate, inoculum size, initial pH and concentrations of glucose and ammonium sulfate of the fermentation medium on the specific growth rate of Sulfolobus solfataricus , a new sulfur utilizing and removing bacterium, was investigated. Growth experiments were designed and arranged in appropriate groups to elucidate the influence of each parameter. The optimum value for each parameter that favored the maximum specific growth rate was calculated from models established through linear or nonlinear regressions of the relevant data. Around these optima, biodesulfurization experiments were performed in glucose or glucose deficient medium with sterilized or unsterilized lignite. Of these, the run with unsterilized coal in glucose medium yielded the maximum removal of total, organic, pyritic and inorganic sulfur forms as 57.79%, 47.81%, 71.43% and 97.73%, respectively. The decrease in organic sulfur content was highly remarkable and has not been reported before with a reduction of more than 2% on a formula base.

Pyrolysis kinetics of blends of Tunçbilek lignite with Denizli peat

Abstract Tuncbilek lignite and Denizli peat and several peat–lignite blends were pyrolyzed in a thermobalance apparatus at atmospheric pressure. Experiments were carried out dynamically by increasing the temperature from 25°C to 900°C with a heating rate of 20°C/min under an argon atmosphere. Differential thermogravimetric data were analyzed by a reaction rate model assuming first-order kinetics. Effect of blending ratio of peat and lignite on the pyrolysis kinetics was investigated. Kinetic parameters were determined and the results was discussed.

Effect of Heating Rate on Pyrolysis Kinetics of Tuncbilek Lignite

Pyrolysis kinetics of the Tuncbilek lignite was investigated by thermogravimetric analysis in the present study. All experiments were conducted at nonisothermal conditions with a heating rate range of 10-80 K/min in the pyrolysis temperature interval 298-1173 K under argon atmosphere. Although some differences were obtained in TG/DTG curves of the lignite samples at different heating rates, the same volatile matter yield of 40.7% of the total weight of the sample was calculated in the same temperature range of 673-873 K of the TG curves. Kinetic parameters were determined with the use of the proposed model. A comparison of the experimental and model values of the weight of lignite at any time was presented. Lower activation energies were calculated at higher heating rates for Tuncbilek lignite. Minimum activation energy was obtained as 24.8 kJ/mol at the heating rate value of 60 K/min. It appears to be the lowest one when compared to those obtained from the literature.Pyrolysis kinetics of the Tuncbilek lignite was investigated by thermogravimetric analysis in the present study. All experiments were conducted at nonisothermal conditions with a heating rate range of 10-80 K/min in the pyrolysis temperature interval 298-1173 K under argon atmosphere. Although some differences were obtained in TG/DTG curves of the lignite samples at different heating rates, the same volatile matter yield of 40.7% of the total weight of the sample was calculated in the same temperature range of 673-873 K of the TG curves. Kinetic parameters were determined with the use of the proposed model. A comparison of the experimental and model values of the weight of lignite at any time was presented. Lower activation energies were calculated at higher heating rates for Tuncbilek lignite. Minimum activation energy was obtained as 24.8 kJ/mol at the heating rate value of 60 K/min. It appears to be the lowest one when compared to those obtained from the literature.

Biodesulfurization of Turkish lignites: 2. Microbial desulfurization of Mengen lignite by the mesophilic microorganism Rhodococcus rhodochrous

Abstract The effects of substrate type in the growth medium, mixing time of lignite into the growth medium and the biodesulfurization time on sulfur removal were studied. Biodesulfurization experiments were carried out with Mengen lignite under optimum growth conditions of Rhodococcus rhodochrous . The highest reduction of organic sulfur forms was 27.1% when sodium acetate was the substrate. Sulfate sulfur could be totally reduced when lignite was added to the culture medium 24 h after incubation. Compared with sodium acetate, glycerol yielded higher sulfate sulfur reduction rates when lignite was added at the time of incubation. The highest organic sulfur removal rates were found when sodium acetate was the substrate.

Effect of Heating Rate on Pyrolysis Kinetics of Göynük Oil Shale

Pyrolysis kinetics of the Göynük oil shale was investigated by thermogravimetric analysis in the present study. All experiments were conducted at nonisothermal conditions with a heating rate of 5-90 K/min in the 298-1173 K pyrolysis temperature interval under argon atmosphere. Differential thermogravimetric data were analyzed by a reaction rate model assuming first-order kinetics. Minimum activation energy was obtained as 3.0 kJ/mol at the heating rate value of 20 K/min. It appears to be the lowest one when compared to those in the literature.

Pyrolysis kinetics of blends of mengen lignite with Denizli peat

Mengen lignite and Denizli peat and several lignite-peat blends were pyrolyzed in a thermobalance apparatus at atmospheric pressure. Experiments were carried out at nonisothermal conditions in the pyrolysis temperature interval of 293-1173 K under argon atmosphere at the heating rate value of 30 K/min. A decrease in both relative volatile matter yields and total conversion percentage of the sample with the increase in the blending ratio of lignite to peat was determined. Thermogravimetry (TG) and derivative thermogravimetry (DTG) data were analyzed by a first-order reaction rate model. Apparent activation energies of the lignite and peat were calculated as 32.42 kJ/mol and 52.09 kJ/mol, respectively. Effects of the peat weight percentage of the blends on kinetic parameters were investigated, and the results were discussed.

Biodesulphurization of turkish lignites. 3. The effect of lignite type and particle size on microbial desulphurization by Rhodococcus rhodochrous

Abstract The effects of lignite type and lignite particle size on the rate of sulphur removal were studied. Biodesulphurization experiments were carried out with Mengen, Elbistan, Tuncbilek and Gediz lignites at the optimum growth conditions of Rhodococcus rhodochrous. The highest decreases in the total (25.3%) and organic sulphur contents (21.4%) were obtained with Gediz and Mengen lignites, respectively. Furthermore, increased desulphurization rates have been observed with smaller particle sizes. Reduction in particle size from 390 to 63 μm resulted in an increase in total sulphur and organic sulphur removal rates by factors of 2.8 and 19, respectively.