Muammer Canel

EXTRACTION OF SOLID FUELS WITH SUB- AND SUPERCRITICAL WATER

Abstract Two Turkish lignites and an oil shale were extracted with water in the sub- and supercritical states. With the non-isothermal experimental technique used, it was possible to determine in one experiment the kinetic data as well as conversion degree and yield. A simple reaction-kinetic model was used to obtain the activation energies and the pre-exponential factors for extraction with water.

Hydrogenating supercritical coal extraction with toluene, tetralin, molecular hydrogen and their mixtures

Abstract Hydrogenating extraction of bituminous coal and lignite was investigated using toluene as extracting solvent, and molecular hydrogen and/or tetralin as hydrogenating agent. In non-isothermal experiments a fixed bed of coal was slowly heated from ambient temperature to 550 °C in a stream of pressurized toluene/H 2 /tetralin mixture, and the extraction rates were continuously measured over the entire temperature range. The measured extraction rate profiles showed characteristic differences depending on the combination of solvent and hydrogenating agent. These differences were interpreted and compared with the thermodynamic phase behaviour of the solvent-H 2 system, to understand the physical and chemical steps involved in the complex mechanism of hydrogenating coal extraction. The fact that the addition of hydrogen during extraction had a negative effect on coal conversion and extract yield was also explained.

Comparison of Retorting and Supercritical Extraction Techniques on Gaining Liquid Products from Goynuk Oil Shale (Turkey)

In this study, conversion of Goynuk oil shale to liquid products was investigated. In the first part of the study, pyrolysis of organic compounds called kerogen, which is the majority of organic material in oil shale, was performed and amounts of residue char, tar, water and gas were determined. After that, oil shale samples were extracted by toluene in an Autoclave and an amount of liquid products obtained by extraction and by pyrolysis was compared with each other. In addition asphaltene, oil, residue char and gas yields in the tar and the optimum conditions at which the maximum yields are obtained were determined. In the pyrolysis experiments, the effects of temperature on residue char, tar, gas and water were investigated. In conclusion, supercritical extraction is a more available method than pyrolysis in conversion of Goynuk oil shale to liquid products.

The Pyrolysis of Scrap Tire with Lignite

Abstract Mustafa Kemal Pasa lignite obtained from the Mustafa Kemal Pasa region of Bursa, Turkey was subjected to pyrolysis with scrap tires. Effects of the pyrolysis conditions, such as temperature, weight percent of the scrap tires in the blends, and synergism on the results, was investigated. Tars obtained at the end of pyrolysis were characterized by Fourier transform infrared spectroscopy and gas chromatography mass spectrometry analysis. It is found that synergism between the coal and tire leads to improved tar yields at all temperatures.

Temperature Programmed Pyrolysis and Supercritical Extraction of Turkish Lignites

Abstract The aim of this study was to determine product evolution rate and volatile product distribution with the capillary gas chromatographic detection during temperature programmed pyrolysis of some Turkish lignites. The pyrolysis examinations conducted under non-isothermal conditions at a low heating rate of 2 K/min up to 550°C can show that the typical volatile product evolution begins at about 350°C and reaches its maximum value at approximately 440°C. n-Paraffins and 1-olefins in aliphatic fraction of pyrolysis products were classified as a carbon number. n-Paraffins up to about C30 were observed among the products and these were accompanied by smaller but significant amounts of 1-olefins. Supercritical toluene extraction was also performed on the lignite samples and the conversion degree and the extract yield results were compared with the results of pyrolysis.

Influence of Experimental Conditions on Product Distribution During Pyrolysis of Tuncbilek Lignite (Turkey) at Low Heating Rates

Tuncbilek lignite is subjected to pyrolysis under nitrogen stream of 3.5 L/min. at 0.5, 5, 10 MPa and in the temperature range between 220°C and 950°C. The effect of temperature and nitrogen pressure on the formation rates of evolved products during pyrolysis (tar, total gas and gaseous species [H2, CH4, C2H4, C2H6, CO, CO2, and H2O]) and the yields of tar and gaseous products are also determined. It is found that thermal degradation, radical formation, and decomposition processes play an important role on pyrolysis of Tuncbilek lignite.

Characterization of the Göynük oil shale-derived asphaltenes and pre-asphaltenes by 1H and 13C nuclear magnetic resonance and by gas chromatography

Abstract The oil shale-derived asphaltenes and pre-asphaltenes of the Goynuk oil shale have been studied by means of the nuclear magnetic resonance technique (NMR) and gas chromatography. 1 H and 13 C NMR spectra were obtained on the latter using the inverse gated heteronuclear decoupling pulse sequence. The study and quantitative determination of the different types of hydrogen and carbon atoms present in the samples have shown that the oil shale-derived asphaltenes and pre-asphaltenes are composed basically of aliphatic hydrocarbons, olefins and the contribution, though less important, of aromatic hydrocarbons. Taking into account both the NMR and chromatographic analysis, it can be said that asphaltenes and pre-asphaltenes are formed by similar compounds which mainly differ in the size of the components. These ones are larger in the pre-asphaltenes. It was also observed that with increasing pressure the size of extracted structures increases. The maximum in the recovered aromatic structures obtained under 250 bar and the decrease when the pressure is increased to 300 bar could be explained by rearrangement reactions.

Pyrolysis of a Turkish lignite at high heating rates

Abstract The products of pyrolysis of Tuncbilek lignite at high heating rates were investigated using the Curie-point technique. The effects of final temperature and pressure are discussed.

Behavior of Chars from Bursa Mustafa Kemal Paşa Alpagut and Balıkesir Dursunbey Çakirca Lignite (Turkey) during Non-catalytic and Catalytic Gasification

Abstract The reactivities of chars obtained by pyrolysis of Bursa Mustafa Kemal Paşa Alpagut lignite and Balıkesir Dursunbey Çakırca lignite (Turkey) at different temperatures were determined by CO2 gasification and by combustion with O2. Catalytic effect of Na2CO3 on the CO2 and O2 gasification reactivity of chars was investigated. Gasification tests were performed in the fixed bed reactors operating at ambient pressure. Reactivity of chars during the CO2 gasification reactions was determined by calculating the reaction rate constants and reactivity of chars during the O2 gasification was determined by using ignition temperatures of the samples. Activation energies and Arrhenius constants of the chars on the CO2 gasification reactions were also calculated by the help of Arrhenius curves. The activation energy for CO2 gasification was generally decreased with pyrolysis temperature, due to the different surface characteristics and different nature of carbon atoms gasified as the gasification reactions proceed. Generally, the increase in pyrolysis temperature leads to an increase in gasification reactivity with CO2. The reactivity of chars in catalytic gasification was higher than the corresponding non-catalytic reactivity of the same chars. Ignition temperature increased with increasing pyrolysis temperature.

Sonochemical synthesis and characterisation of lead sulfide nanoparticles using different capping agents

Lead sulfide (PbS) nanoparticles of about 12 nm in diameter and with a single crystalline structure have been prepared by a sonochemical method. The influence of reaction time and different capping agents such as polyethylene glycol (PEG), cetylytrimethylammonium bromide (CTAB), tetraethylortosilicate on the morphology of the synthesised PbS nanoparticles have been investigated. Results revealed polyethylene glycol (PEG) was a useful capping agent to produce PbS nanostructures with a suitable size distribution. Further studies demonstrated that by increasing the polymer chain length of PEG, the size of the PbS nanoparticles decreased remarkably. The nanoparticles were characterised by X-ray diffraction, energy dispersive X-ray spectroscopy, and transmission electron microscopy and the surface areas were determined using the BET method.