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Öğe Adsorption of Co(II) and Hg(II) from water and wastewater onto modified lignin(TAYLOR & FRANCIS INC, 2007) Demirbas, A.In this study, adsorptions of heavy metal ions Co(II) and Hg(II) onto modified lignin from Ailanthus altissima woods by alkali glycerol delignification are presented. The Langmuir isotherm model is only applicable to batch adsorber systems where sufficient time is provided to allow equilibrium between toxic metal ion in solution and the toxic metal ion adsorbed on the media to occur. The maximum adsorption capacities are 7.1 - 7.7 and 4.4 - 5.3 mg per g of the modified lignin for), Co( II) and Hg( II), respectively. The adsorption of the heavy metal ions increases with pH.Öğe Biodiesel production facilities from vegetable oils and animal fats(TAYLOR & FRANCIS INC, 2007) Demirbas, A.; Karslioglu, S.Biodiesel is a renewable fuel that can be produced from vegetable oils, animal fats, and used cooking oil including triglycerides. Biodiesel, an alternative biodegradable diesel fuel, is derived from triglycerides by transesterification with methanol and ethanol. Concerns about the depletion of diesel fuel reserves and the pollution caused by continuously increasing energy demands make biodiesel an attractive alternative motor fuel for compression ignition engines. There are four different ways of modifying vegetable oils and fats to use them as diesel fuel, such as pyrolysis ( thermal cracking), dilution with hydrocarbons ( blending), emulsification and transesterification. The most commonly used process is transesterification of vegetable oils and animal fats. The transesterification reaction is affected by molar ratio of glycerides to alcohol, catalysts, reaction temperature, reaction time and free fatty acids and water content of oils or fats. In the transesterification, free fatty acids and water always produce negative effects, since the presence of free fatty acids and water causes soap formation, consumes catalyst and reduces catalyst effectiveness, all of which result in a low conversion. Biodiesel has over double the price of diesel. The high price of biodiesel is in large part due to the high price of the feedstock.Öğe Boron compounds as hydrogen storage materials(TAYLOR & FRANCIS INC, 2007) Ozturk, T.; Demirbas, A.Hydrogen exhibits the highest heating value per mass of all chemical fuels. Furthermore, hydrogen is regenerative and environmentally friendly. Hence, hydrogen storage is very important for humans. Hydrogen storage in metal hydrides is considered as one of the most attractive methods. In the present work, the hydrogen absorption-desorption behavior of the boron compounds has been compared. We present recent developments in the search for hydrogen-storage capacity of boron. Boron compounds have a very high energy density, much better than that of liquid hydrogen and also a lot safer. LiBH4 is a complex hydride that consists of 18 mass% of hydrogen. It has stability compared with other chemical hydrides and an easy conversion to H-2. Thus, there are a good many reasons that hydrogen-storage materials for LiBH4 will be used in the future at many ranges for power sources. The future warrants further investigations of the B-H system from the viewpoint of hydrogen energy storage.Öğe Carbon dioxide disposal via carbonation(TAYLOR & FRANCIS INC, 2007) Demirbas, A.Carbonation is a solidification/stabilization process. The availability of a carbon dioxide (CO2) fixation technology would serve as insurance in case global warming causes severe restrictions on CO2 emissions. In order to prevent rapid climate change, it will be necessary to stabilize CO2 as carbonate by the carbonation process. Carbonation of the widely occurring mineral olivine (Mg2SiO4) converts CO2 into an environmentally benign mineral magnesite (MgCO3).Öğe Combustion characteristics of 24 lignite samples(TAYLOR & FRANCIS INC, 2008) Sensogut, C.; Ozsen, H.; Demirbas, A.In this study, the combustion characteristics such as thermogravimetric analysis (TGA) and differential thermogravimetric analysis (DTGA), burning profile, ignition temperature, and peak temperature were analyzed for 24 lignite samples from different areas of Turkey. The samples were heated up to 900 degrees C at a constant rate of 10 degrees C/min in a 5 mL/min flow of dry air. The burning profiles of the samples studied, combined with proximate, sulfur analysis and calorimetry results, contribute to a clearer identification of lignite samples' structure and a better understanding of the coalification process. The lignite samples have been tested with particle size of 0-0.05 mm. Ignition temperatures of the samples have been determined from their burning profiles.Öğe Determination and calculation of combustion heats of 20 lignite samples(TAYLOR & FRANCIS INC, 2008) Demirbas, A.; Dincer, K.; Topaloglu, N.In this study, the proximate analyses, such as volatile materials (VM), fixed carbon (FC), and higher heating value (HHV), were determined for 20 lignite samples from different areas of Turkey. The lignite samples have been tested with particle size of 0-0.05 mm. Combustion heats (higher heating values, HHVs) of 20 lignite samples obtained from different Turkish sources were determined experimentally and calculated from both ultimate and proximate analyses. The HHVs (MJ/kg) of the lignite samples as a function of fixed carbon (FC, wt%) or volatile materials (VM, %) was calculated from the following equations: HHV = 0.2997FC + 11.1170 (1) HHV = -0.3225VM + 42.223 (2) The correlation coefficients for Eqs. (1) and (2) were 0.9820 and 0.9686, respectively. The combustion heats calculated from Eqs. (1) and (2) showed mean differences of +0.4% and +0.4%, respectively.Öğe Determination of heavy metal pollution in grass and soil of city centre green areas (Konya, Turkey)(HARD, 2007) Onder, S.; Dursun, S.; Gezgin, S.; Demirbas, A.This research was conducted to determine levels of heavy metal pollution in the years 2003-04. In this research, samples of grass and soil taken from green areas in 8 different areas of Konya city centre were used as material. The samples were obtained from factory gardens, areas experiencing heavy traffic and residential areas. The changes in analysis results of heavy metal levels (Pb, Cu, Zn, Co, Cr, V, Cd and Ni) in the samples were discussed for sampling years and sampling places in both grass and soil samples. The results of the study showed that heavy metal contents in both soil and grass samples were higher in 2004 than in 2003. In this study, some heavy metal content in the samples obtained in areas with heavy traffic and in factory garden areas was over the limit levels (5.67 ppm for Pb in soil and 10.69, 27.51 and 0.19 ppm for Cu, Cr and Cd in grass, respectively) and represents a risk for humans.Öğe Effect of Prussian blue on organic sulfur of coal in aqueous medium(TAYLOR & FRANCIS INC, 2007) Demirbas, A.This study is an attempt to desulfurize organic sulfur from coal samples with ferric hexacyanoferrate (II), Fe-4 [Fe(CN)(6)], as the desulfurization agent. Effect of temperature, particle size and concentration of ferrocyanide ion on desulfurization from the coal samples has been investigated. The temperature and stirring time are the most important parameters for the level of desulfurization of organic sulfur. Removal of organic sulfur content increased continuously with increasing temperature from 298 to 368 K. The organic sulfur removal rate sharply increases from 10 min to 30 min stirring time. After 30 min, it reaches a value of plateau. Particle size between - 100 mesh and - 200 mesh slightly affects the amount of organic sulfur removal. Gradual increase in the concentration of ferric hexacyanoferrate ( II) raised the magnitude of desulfurization, but at higher concentration, the variation is not significant.Öğe Effects of moisture and hydrogen content on the heating value of fuels(TAYLOR & FRANCIS INC, 2007) Demirbas, A.In this work, effects of moisture and hydrogen contents on lower heating value (LHV) of fuels were investigated. The LHV at constant pressure measures the enthalpy change of combustion with and without water condensed, respectively. Moisture in biomass generally decreases its heating value. Moisture in biomass is stored in spaces within the dead cells and within the cell walls. Higher heating value (HHV) of a fuel decreases with increasing of its moisture content. The LHV of a fuel increases with increasing of its hydrogen content. The LHV of a fuel depends on its oxygen content and the LHV of a fuel decreases with increasing of its oxygen content. The LHV of a fuel increases with increasing the hydrogen content due to cause combustion water. Moisture in a fuel generally decreases its HHV. The LHV of a fuel increases with increasing the sulfur content due to cause SOx gases absorbed by water.Öğe Fuel cells as clean energy converters(TAYLOR & FRANCIS INC, 2007) Demirbas, A.A fuel cell is a device in which the energy of a fuel is converted directly into electricity direct current by an electrochemical reaction without resorting to a burning process, rather than to heat by a combustion reaction. The chemical energy of the fuel is released in the form of an electrical energy instead of heat when the fuel is oxidized in an ideal electrochemical cell. Energy conversion by a fuel cell depends largely upon catalytic electrodes, which accomplishes the electrochemical reaction to convert fuel into electric energy without involving the burning process. Efficiencies of fuel cells ( 40 - 85%) are considerable high compared to heat engines. Catalysts are so expensive that electricity from most fuel cells costs about a thousand times more than the same amount derived from conventional sources. The need is to develop the catalysts from the different precursors to succeed in the necessary chemical reactions in an effective way.Öğe The importance of bioethanol and biodiesel from biomass(TAYLOR & FRANCIS INC, 2008) Demirbas, A.The aim of this study is to provide a global approach on liquid biofuels such as bioethanol and biodiesel, a key topic for the future of energy for transportation. The term biofuel is referred to as liquid or gaseous fuel for the transport sector that are predominantly produced from biomass. There are several reasons for biofuels to be considered as relevant technologies by both developing and industrialized countries. They include energy security reasons, environmental concerns, foreign exchange savings, and socioeconomic issues related to the rural sector. Bioethanol is a petrol additive/substitute. It is possible that wood, straw, and even household wastes may be economically converted to bioethanol. Bioethanol is derived from alcoholic fermentation of sucrose or simple sugars, which are produced from biomass by hydrolysis process. Biodiesel is an environmentally friendly alternative liquid fuel that can be used in any diesel engine without modification. There has been renewed interest in the use of vegetable oils for making biodiesel due to less pollution and its renewable nature in contrast to conventional petroleum diesel fuel.Öğe The importance of natural gas as a world fuel(TAYLOR & FRANCIS INC, 2006) Demirbas, A.In recent years, natural gas (NG) is the fastest growing primary energy source in the world. NG is widely available, and it is the cleanest burning petroleum based fuel. The global market for NG is much smaller than for oil because gas transport is difficult and costly due to relatively low energy content in relation to volume. NG uses industrial, residential, electric generation, commercial and transportation sectors. NG is used across all sectors in varying amounts. CO2 emission of NG is lower than all other petroleum derivated fuels which it makes engines favorable also in terms of the greenhouse effect. Very positive contribution of NG on the environmental pollution must also be considered in economical aspects.Öğe Mathematical modeling the relations of biomass fuels based on proximate analysis(TAYLOR & FRANCIS INC, 2007) Demirbas, A.The objectives of this work are to submit the heating value studies related to mathematical modeling of biomass fuels based on experimental data published in the last twenty-five years. There was a linear relationship between parameters that make up the physical composition, proximate analysis, and elemental analysis towards the energy content of biomass. It is possible to build models based on data from physical composition, proximate and elemental analysis using regression analysis. The experimental determination of heating value and ultimate analysis requires special instrumentation, whereas chemical and proximate analysis data from biomass and vegetable oil samples can be obtained relatively easily by using common laboratory equipment.Öğe Modeling higher heating values of lignites(TAYLOR & FRANCIS INC, 2008) Demirbas, A.; Dincer, K.In this work, the elemental analysis results such as carbon (C), hydrogen (H), oxygen (O), nitrogen (N), and sulfur (S) were used for calculated higher heating values (HHVs) of 26 lignite samples from different areas of Turkey. The lignite samples have been tested with particle size of 0-0.05 mm. The HHVs of 26 lignite samples obtained from different Turkish sources were experimentally determined and can be calculated from the equation-based modeling. The HHVs (MJ/kg) of the lignite samples as a function of carbon (C), hydrogen (H), oxygen (O), nitrogen (N), and sulfur (S) was calculated from the following equation: HHV = 31.6(C) + 142.3(H) + 30.8(S) - 15.4(O) - 14.5(N) of which the correlation coefficiens for the equation was 0.9891. HHVs calculated from the equation showed mean deviation of +0.1.Öğe Obtaining of Boron as an Alternative Fuel from Borax with Various Methods(TAYLOR & FRANCIS INC, 2009) Sen, N.; Demir, C.; Demirbas, A.; Kar, Y.This study examined how to obtain elemental boron from borax. For this purpose, first boric acid (H3BO3) was obtained from borax decahydrate with using HCl and H2SO4. The boric was then converted to boron oxide using a dehydration process. It has been studied to reduce the boric acid and the boron oxide into elemental boron with using the elemental magnesium (Mg) and butyl nitrite (C5H9NO2), and also with using sawdust, charcoal, and cellulose. Then, the obtained elemental boron was subject to the burning process to prove its purity. The pure-elemental boron gave a strong green-colored flame when it was burned. Among these, the methods using the elemental magnesium (Mg) and butyl nitrite (C5H9NO2) in order to obtain elemental boron are more reasonable than those of the others.Öğe Sustainable green diesel: A futuristic view(TAYLOR & FRANCIS INC, 2008) Demirbas, A.; Dincer, K.The energy sources have been split into three categories: fossil fuels, renewable sources, and nuclear sources. Energy new and renewable resources will play an important role in the world's future. There are several reasons for biofuels to be considered as relevant technologies by both developing and industrialized countries. They include energy security reasons, environmental concerns, foreign exchange savings, and socioeconomic issues related to the rural sector. The term modern biomass is generally used to describe the traditional biomass use through the efficient and clean combustion technologies and sustained supply of biomass resources, environmentally sound and competitive fuels, heat, and electricity using modern conversion technologies. Modern biomass can be used for the generation of electricity and heat. Biofuels as well as green diesel produced from biomass by Fischer-Tropsch synthesis are the most modern biomass-based transportation fuels. Green diesel is a renewable replacement to petroleum-based diesel. Biomass energy conversion facilities are important for obtaining bio-oil by pyrolysis. Pyrolysis is the most important process among the thermal conversion processes of biomass. There are four different ways of modifying vegetable oils and fats for use as diesel fuel, such as pyrolysis, dilution with hydrocarbons (blending), emulsification, and transesterification.
