Reha Yavuz

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.

Factors affecting the adsorption of chromium (VI) on activated carbon.

The aim of this investigation was to determine the adsorption behavior of chromium (VI) on two different activated carbon samples produced from Tuncbilek lignite. The effects of the initial chromium (VI) concentration (250–1000 mg/L), temperature (297–323 K) and pH (2.0–9.5) on adsorption were investigated systematically. The effectiveness of the parameters on chromium adsorption was found to be in the order of pH, the initial Cr(VI) concentration and the temperature. Increasing the pH from 2.0 to 9.5 caused a decrease in adsorption. However, the adsorption was increased by increasing the initial Cr(VI) concentration and temperature. The multilinear mathematical model was also developed to predict the Cr(VI) adsorption on activated carbon samples within the experimental conditions.

Trace-element, rare-earth element and boron isotopic compositions of tourmaline from a vein-type Pb–Zn–Cu ± U deposit, NE Turkey

This paper reports trace-element, rare-earth element (REE) and boron isotopic compositions of tourmaline in the Asarcık granitoid and quartz veins at Şebinkarahisar. Abundant tourmaline occurs in the vein-type Pb–Zn–Cu ± U deposit, within the northeastern Pontide Metallogenic Belt, both within the Late Cretaceous Asarcık granitoid and in associated quartz–tourmaline veins. Tourmaline in the granitoid forms as rosettes up to 1.5 cm in diameter, whereas in quartz–tourmaline veins a few centimetres to a few metres wide, it occurs as black needles and masses that cut the pluton. We present a systematic geochemical study of these tourmalines – all of the schorl-dravite series. Tourmalines from the quartz veins contain high concentrations of ore metals such as Ag, Bi and Zn and have higher Sr, Cr and Sn contents than tourmalines in the Asarcık granitoid. Tourmalines from intensively altered parts of the pluton are characterized by higher concentrations of trace elements such as Ba, Rb, V, Sc, Th and Zr compared with occurrences in the quartz veins and in the fresh and less-altered granitoid. Chondrite-normalized patterns of REEs in tourmalines from the Asarcık granitoid are generally similar to those of tourmalines in the quartz veins. All vein tourmalines, however, are characterized by heavy REE enrichments, in sharp contrast to those in the granitoid. Boron isotopic compositions of tourmalines range from − 14.0 to − 2.2‰ and fall within the δ11B range of this mineral in granite-related settings. Tourmaline rosettes from the Asarcık granitoid show relatively lighter δ11B values ( − 14.0 to − 12.2‰) in comparison with those in the quartz veins ( − 10.4 to − 2.2‰).

Adsorption of an anionic dispersant on lignite

Abstract Since coal is not a homogeneous substance but a mixture of carbonaceous materials and mineral matter, it has a variety of surface properties. Therefore, it is not easy to control the properties of coal suspensions by simply adjusting variables, such as pH and/or electrolyte. A chemical agent needs to be added to control the properties of the coal suspensions. The aim of this investigation is to determine the adsorption behavior of an anionic dispersant in the presence of a wetting agent using some Turkish lignite samples. The presence of a wetting agent in the dispersant adsorption behavior is important, since usage of a wetting agent in the preparation of coal–water slurries which are acceptable for potential industrial users is of great importance. The effects of dispersant concentration, temperature and pH on the dispersant adsorption were studied systematically, and the experimental results are presented. Pellupur B69 as a dispersant, commercial mixture of formaldehyde condensate sodium salt of naphthalene sulphonic acid, and Texapon N25 as a wetting agent, a sodium lauryl ether sulfate, have been used.

Thermal decomposition kinetics of natural Turkish limestones under non-isothermal conditions

Abstract The kinetic parameters for the thermal decomposition of 20 natural Turkish limestones, including the activation energy, pre-exponential factor and mechanism, were determined from their non-isothermal TG data. Thermogravimetric measurements were made in pure N2 and in a mixture of 15% CO2 and 85% dry air, at a constant heating rate of 10 K min−1. A computer program written in basic was used to evaluate the kinetic parameters of the decomposition reactions from experimental TG data. Five different calculation methods were employed in the kinetic analysis of the TG curves of the samples; this analysis also incorporated 14 different model equations reported in the literature concerning solid state rate-controlling mechanisms. It was observed that the values of the kinetic parameters showed differences depending on the method of calculation, the gaseous atmosphere and the sample properties.

Stepwise demineralisation and chemical isolation of the mineral matter of Göynük lignite

The mineral matter of coal contains a number of inorganic constituents, which play an important role in almost all coal utilisation systems. Some techniques have been applied to coal to separate its mineral matter from its organic part. In this study, an alternative method was applied to separate the mineral matter content of a Turkish lignite. For this purpose, Goynuk lignite was treated, in sequence, with acetic acid, ammonia, hydrochloric acid, hydrofluoric acid and nitric acid at 70°C for 60 min in order to remove individual mineral species. After each stage, the lignite was treated with performic acid, the product of reaction between hydrogen peroxide and formic acid, at 50°C. The organic coal matrix was decomposed as a result of performic acid oxidation, and consequently, the recovered mineral species were isolated. Ammonia, which has the potential of chemical comminution, was used to increase the effects of the subsequent reagents and enhance the extent of separation between the organic and inorganic phases. In each mineral matter removal stage, the lignite was treated with the reagents of the previous stage, and then, a new reagent was added to investigate whether the last stage has a different effect on the mineral species. FT-IR and X-ray diffractometry techniques were used to determine the constituents of the isolated mineral matter after each stage.