Sadriye Küçükbayrak

Production of fuel briquettes from olive refuse and paper mill waste

Some processes have been widely applied to biomass in order to take advantage of its energy potential. In particular, these processes are based on pyrolysis or gasification. In this study, briquetting was applied to olive refuse and paper mill waste to form fuel briquettes. For this purpose, the particle sizes of both biomass samples were decreased to −250 μm and then they were briquetted in a steel die under pressure between 150 and 250 MPa at ambient temperature. Effects of the moisture content of the biomass samples and briquetting pressure on the shatter index, compressive strength, and water resistance of the briquettes obtained were investigated. This study showed that the mechanical strength of the briquettes produced only from the olive refuse was not high enough. On the other hand, strong briquettes were produced using paper mill waste. When olive refuse was blended with fibrous paper mill waste, briquettes with sufficiently high mechanical strength could be produced. Burning profiles of the samples were derived applying derivative thermogravimetry technique under dynamic dry air atmosphere up to 1273 K with a heating rate of 40 K·min−1 and then combustion characteristics of the briquettes were compared.

Characterization of a glass-ceramic produced from thermal power plant fly ashes

Abstract Glass-ceramic materials were developed from fly ash samples obtained from Cayirhan Thermal Power Plant in Turkey. On the basis of DTA analyses, nucleation experiments were carried out at 680°C for 5, 10 and 15 h whereas crystallization experiments were performed at 924°C for 20 min. Crystallized samples were cooled in the furnace. X-ray diffraction analyses revealed the presence of only the diopside [Ca(Mg,Al)(Si,Al) 2 O 6 ] phase in the produced glass-ceramic samples and scanning electron microscopy (SEM) investigations showed the presence of a homogeneously dispersed phase. The results of the Vickers microhardness tests indicated that the hardness values of the fly ash based glass-ceramic decreased with the increases in holding time at the nucleation temperature. In addition, wear resistance of fly ash-based glass-ceramics decreased with holding time at the nucleation temperature.

FUEL BRIQUETTES FROM BIOMASS-LIGNITE BLENDS

In this study, a western Turkish lignite (Kutahya-Seyitomer) was blended with some biomass samples such as molasses, pine cone, olive refuse, sawdust, paper mill waste, and cotton refuse, and these blends was used in the production of fuel briquettes. Blends were subjected to briquetting pressures between 50 and 250 MPa; the ratio of biomass to lignite was changed between 0 and 30 wt.%. The mechanical strength of obtained briquettes was investigated considering shatter index and compressive strength. Effects of the ratio of biomass to lignite and applied pressure on the strength of the briquettes were examined. This study indicated that the mechanical strength of the briquettes produced from Kutahya-Seyitomer lignite can be improved by adding some biomass samples. For example, the presence of paper mill waste increased the shatter index of the briquettes obtained. Similarly, sawdust and paper mill waste increased compressive strength of the briquettes. Water resistance of the briquettes can be augmented by adding olive refuse, cotton refuse, pine cone or paper mill waste.

Crystallization behaviour of glasses produced from fly ash

Abstract The crystallization behaviour of fly ash based glass samples annealed at 600°C for 2 and 10 h was investigated by DTA, XRD and SEM. On the basis of DTA, nucleation experiments of two glass samples were carried out at 680 and 687°C for 5 h and crystallization experiments were performed at 924 and 892°C for 20 min. The Avrami constant for both glass samples was calculated as 4, which indicates bulk crystallization, predicted by the Ozawa equation. Using the modified Kissinger equation, activation energies of crystal growth were determined as 318 and 312 kJ/mol for samples annealed at 2 and 10 h, respectively. Single peak analysis technique proved that the activation energy is independent of DTA heating rate. SEM observations indicated that the produced glass–ceramic samples have fine grained microstructure. The crystallized phase was identified as diopside [Ca(Mg,Al)(Si,Al)2O6] by X-ray diffraction analysis. The results of Vickers microhardness tests showed that the hardness values of the produced glass–ceramic samples decreased with the increase in holding time at the annealing temperature.

Estimation of calorific values of Turkish lignites

Abstract New formulae have been developed for estimating the calorific values of Turkish lignites from their proximate analyses data. In order to obtain these formulae, 24 Turkish lignites from different areas were analysed to obtain calorific values and proximate analyses. The data of another 26 Turkish lignites obtained from the literature were used to check the developed correlations. All the correlations were obtained using least squares regression analysis. The mean differences between observed and calculated calorific values using the formulae developed range from 3.78 to 7.56%.

Effect of mineral matter on the reactivity of lignite chars

In this study, the effect of mineral matter on the combustion reactivity of chars produced from 25 lignite samples originating from various parts of Turkey was investigated. Char samples were produced from both original and demineralized lignites. Non-isothermal thermogravimetry has been used to determine the combustion reactivity of the samples. The combustion activation energies were calculated by the Coats-Redfern and Zsako methods from their TG data. Burning profiles of the original and demineralized lignite chars were also compared and discussed. The relationship between the carbon contents of the parent lignites and the conversions of their chars at 1273 K was studied as well. It was observed that the mineral species showed an important effect on the combustion reactivity of the char samples.

Effect of lignite properties on reactivity of lignite

The purpose of this study is to relate the combustion reactivity of lignite to its physical and chemical properties. Non-isothermal thermogravimetry, where the sample whose temperature increased at a linear rate (40 K/min) was heated in air, has been used to investigate the combustion reactivities of 25 lignite samples originating from different areas of Turkey. Since combustion reactivity is affected by the chemical and physical properties of coal, the combustion reactivity of the lignites used in this study was related to their proximate and ultimate analysis results and physical properties such as pore structure and surface area. The calculated activation energy values for the combustion reactions of the lignites ranged between 64 and 139 kJ/mol. Definite correlations between the activation energy values and the above-mentioned properties were found.

Combustion characteristics of lignite-water slurries

Coal water slurries have been developed over the last 15 years as an alternative to fuel oil mainly in industry and power station boilers. They are also a considerable potential for gasification applications, blast furnace injection and fluidized bed combustors. Determination and improvement of combustion characteristics of coal-water slurries are as important as the preparation of the suitable slurry. Suspended single droplet combustion technique may be the best of the methods used in the investigation of combustion characteristics of liquid fuel droplets. The main advantage of this technique is that, droplet lifetime history, ignition delay, flame structure, centre and surface temperature of the droplet and burning rate can be investigated and a good comparative result for different fuels under the same conditions can be obtained. Therefore, suspended single droplet combustion technique was used in this study. The effect of droplet size, lignite fraction in the slurry and furnace temperature on slurry combustion were studied systematically.

Desulphurization of some Turkish lignites by pyrolysis

Abstract The purpose of this study was to examine the sulphur removal efficiency of pyrolysis from some Turkish lignites. The parameters tested for their effects were: flow of nitrogen; particle size of coal; time and temperature. Temperature is the most important factor and the total sulphur removed increased up to 900 °C. Pyrolysis is effective in removing all three sulphur-containing groups in lignite. The ultimate and proximate analysis of the lignite samples affect the desulphurization yield of pyrolysis and the sulphur content of the products.

Combustion reactivity of different rank coals

Abstract In this study, the combustion reactivity of different rank coals, such as peat, lignite, bituminous coal and anthracite samples, was investigated. Non-isothermal thermogravimetry has been used to determine the combustion reactivities of the samples. The differences observed in the burning profile of the samples were studied. The calculated activation energy values of the samples were investigated, regarding carbon content, volatile matter content and burning profile peak temperature. The relationship between ignition temperature and carbon content (dmf) of the coal samples was also studied. The weight loss percentages of the different rank coal samples were discussed, depending on temperature.