Tijen Özbaş Bozdemir

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.

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.

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.

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.

Chemical Desulfurization Kinetics of Mengen Lignite in Aqueous Sodium Carbonate

In the present study the effects of sodium carbonate as a leachant in desulfurization of Mengen lignite were investigated. A kinetic study was also carried out, and the shrinking core model was proposed to describe the kinetic data of pyritic sulfur removal. The highest sulfur removal percentages were observed for total and sulfate sulfur as 36.2% and 97.1%, respectively, with the use of a coal alkali solution volume ratio of 1/70 at 120 degrees C. Desulfurization of Mengen lignite with 100 mL of 0.2 M aqueous sodium carbonate solution at 140 degrees C for 3 hours caused 96% removal of pyritic sulfur. It was also observed that the rate of leaching increased significantly with temperature and alkali solution concentration.

Biodesulfurization of Mengen lignite with Rhodoccocus rhodochrous: Effects of lignite concentration and retreatment

Biodesulfurization of Mengen lignite by a mesophilic bacterium, Rhodococcus rhodochrous ATCC 53968, was investigated in a batch-stirred and aerated reactor. Experiments were carried out at 28°C with the inoculum percentage, initial pH, and initial sodium acetate concentration of the biodesulfurization medium as 8% (v/v), 6.5, and 20 mM, respectively. The effects of the lignite concentration and retreatment on the removal of different sulfur forms from coal were investigated. The highest decreases in the total and organic sulfur contents were obtained as 21.4% and 9.2%, respectively, at the operational conditions of the lignite concentration of 5 g/L at 500 rpm stirring and 0.18 vvm aeration rates. The total and organic sulfur contents of the coal after biodesulfurization were correlated with the coal concentration by using the linear least-squares regression method. In the rebiodesulfurization run that lasted 8 days, the highest organic sulfur-reducing percentage was obtained as 10.2% at the same experimental conditions.