Esen Bolat

Chemical demineralization of a Turkish high ash bituminous coal

Demineralization of coal prior to usage offers some technical and cost-effective advantages since one of the most common limitations on coal processes results from high mineral matter content. In this work aimed at reducing the mineral matter content of high ash, low sulfur Amasra bituminous coal from Turkey, since physical methods were of limited use for reducing the ash content of bituminous coals, demineralization was studied using different acids (HF, HCl, HNO3 and H2SO4) alone and 0.5 N aqueous NaOH in combination with either one or two of the acids. The use of extraction with 0.5 N NaOH followed by leaching with 10% HCl was the optimum approach for the chemical cleaning of the coal under study, the maximum degree of demineralization obtained being 46.78%.

The effect of oxidation on the flotation properties of a Turkish bituminous coal

Abstract It is well known that the behaviour of oxidized coal is different than that of original coal during flotation and that the efficiency of flotation differs according to the degree of oxidation. The degree of oxidation of coal particles can be determined based on their surface properties. For this, the electrokinetic potantial measurement is considered to be an efficient method to determine the surface properties of oxidized coal. In this work, based on the zeta potential and flotation data obtained, it can be concluded that the flotability of Amasra coal deteriorates on oxidation but can be increased by using electrolytes at low concentrations in the flotation media.

Supercritical-fluid extraction of essential oil from Turkish lavender flowers☆

Abstract Essential oil was extracted from Turkish lavender flowers by supercritical carbon dioxide. A statistical experimental design based on “Second Order Central Composite Design” was planned fixing the extraction period at four hours. Parameters such as pressure, temperature, carbon dioxide flow rate, and particle size coded as x1, x2, x3, and x4, respectively, were used. These parameters were investigated in five levels (−2, −1, 0, 1, and 2). The dependent variable Y1 was taken as the relative overall essential oil yield. The effects of operating conditions of supercritical fluid extraction on the relative overall yields were calculated with respect to steam distillation. The optimum conditions to obtain Y ≥ 80% were about x1 = 85.77 bar, x2 = 36.58 °C, x3 = 10.11 L h−1, and x4 = −2143 μm, after some modifications for third order-like model. The components of lavender essential oil such as fenchone, camphor, linalool, linalyl acetate, bornyl acetate, and cadinene were detected by GC-MS chromatography. Fenchone and camphor were determined as the major components. Besides, the essential oil samples extracted and trapped in alcohol for each experiment were analyzed qualitatively by gas-liquid chromatography. Then, the same response surface methodology was used for components of essential oil such as fenchone (Y2) and camphor (Y3).

Coprocessing of a Turkish lignite with a cellulosic waste material. 1. The effect of coprocessing on liquefaction yields at different reaction temperatures

Abstract In recent years, the liquefaction potential of waste materials has been investigated to increase the yield of coal conversion processes and the quality of liquid fuels from coal. The results have shown that the coprocessing of coal with biowaste materials increases liquefaction yields. In this study, the effects of liquefaction of Soma lignite with sawdust as a coprocessing agent, on total conversion, oil+gas total yields, asphaltene yields and preasphaltene yields were investigated at five different temperatures, 300, 325, 350, 375 and 400°C, 40 atm initial cold pressure, 1/1 (wt/wt) sawdust/lignite ratio and 3/1 (vol/wt) tetralin/(lignite+sawdust) ratio values.

Coprocessing of a Turkish lignite with a cellulosic waste material: 2. The effect of coprocessing on liquefaction yields at different reaction pressures and sawdust/lignite ratios

Abstract Most of the research works done for alternative energy sources have shown that, in general, coprocessing of coal with biomass-type wastes has a positive effect on the liquefaction yields and these materials are increasingly studied as coliquefaction agents for the conversion of coal to liquid fuels. Addition of biomass waste materials to coal is known to be synergetic in that it improves the yields and quality of liquid products produced from coal under relatively mild conditions of temperature and pressure. This paper reports the coprocessing of a Turkish lignite with sawdust in the category of biomass-type waste material. The experiments have been conducted in a stainless-steel reactor, and temperature and tetralin/(lignite+sawdust) ratio were kept constant at 350 °C and 3:1 (vol/wt), respectively. This is the first time that the influence of reaction pressures on coliquefaction yields was investigated. In addition, the influence of the sawdust/lignite ratios on coprocessing conversion and product distribution was also investigated under the same reaction conditions. The runs were carried out at 10, 25, 40, 55, and 70 atm initial cold hydrogen pressure values and at 0.5:1, 0.75:1, 1:1, 1.25:1, and 1.5:1 sawdust/lignite (wt/wt) ratio values.

Economic analysis and comparison of chemical heat pump systems

Over the last years great interest has been shown in chemical heat pump systems. Chemical heat pumps represent a new technology with great potential to reduce the energy consumption in very different sectors. They can provide the ability to capture the rejected low-grade heat and to reuse it at increased temperature levels in various industrial processes. Heat can be removed from a heat source at low-temperature by an endothermic reaction and can be boosted to a heat sink at high-temperature by an exothermic reaction. Since chemical heat pumps can operate without compression, with less electrical power and at higher temperature levels compared to conventional heat pumps, they can afford high performance advantages. As an additional advantage, energy storage can also be accomplished so that intermittent energy sources can be utilized in a chemical heat pump system. The objective of this work was to study methanol–formaldehyde–hydrogen, ethanol–acetaldehyde– hydrogen, i-propanol–acetone–hydrogen and n-butanol–butyraldehyde–hydrogen chemical heat pump systems based on catalytic dehydrogenation of alcohols at low-temperature and hydrogenation of aldehydes and a ketone at high-temperature. On the base of economic analysis, the quantity of waste-heat that must be supplied to produce the benefits of the process heat and also the improvement in the net gain reached were determined and compared. � 2002 Elsevier Science Ltd. All rights reserved.

Coprocessing of a Turkish lignite with a cellulosic waste material: 3. A statistical study on product yields and total conversion

The objectives of this study were to evaluate statistically the effects of coprocessing parameters on liquefaction yields, to determine the key process variables affecting the oil+gas, oil and asphaltene yields and total conversion. A statistical experimental design based on Second Order Central Composite Desing was planned fixing the liquefaction period at 1 h. Parameters such as temperature, initial cold pressure, tetralin/(lignite+sawdust) and sawdust/lignite ratios coded as x1, x2, x3 and x4, respectively, were used. The parameters were investigated at five levels (−2, −1, 0, 1 and 2). The effects of these factors on dependent variables, namely, oil+gas, oil and asphaltene yields and total conversion were investigated. To determine the significance of effects, the analysis of variance with 99.9% confidence limits was used. It was shown that within the experimental ranges examined, temperature and sawdust/lignite ratio were the variables of highest significance for oil+gas yields, oil yields and total conversion.

Liquefaction of Turkish lignites and asphaltites with a Turkish vacuum residual oil

Abstract Liquefaction studies in a magnetically stirred autoclave were carried out using different types of lignite and asphaltite. Tupras vacuum residue oil was coprocessed with Beysehir, Cayirhan, Goynuk, Keles and Orhaneli lignites, and Silopi and Şirnak asphaltites. Coprocessing was performed under liquefaction conditions of 2:1 solvent:lignite or asphaltite ratio, 440°C, 80 atm hydrogen pressure for 1 hour reaction time. Total conversions ranging from 40.3 to 92.1% (d.a.f.) for both lignites and asphaltites were obtained. A comparison of liquefaction yields obtained in vacuum residue oil with those obtained using tetralin or anthracene and creosote oils as solvent, under the same operation conditions, was made.

The effect of ash and ash constituents on the liquefaction yield of Turkish lignites and asphaltites

Abstract The objective of this work was to study mineral matter effects in coal liquefaction. A suite of 16 lignites and two asphaltites have been liquefied in a batch autoclave under a standard set of reaction conditions. Experiments were performed at 440 °C, 60 min residence time and 8 MPa hydrogen pressure (cold charge). All experiments were carried out in solvents, like anthracene oil, creosote oil, tetralin and TUPRAS vacuum residual oil, at a solvent:lignite ratio of two. The ash content of lignites and asphaltites ranged from 7.73 (dry) to 59.99% (dry). It was found that, generally, as the ash content increased, the total conversion of lignite and conversion to tetrahydrofuran (THF), toluene or hexane solubles increased; total conversion, THF and toluene solubles yields appear to remain constant at high ash contents. Multiple regression analysis was employed to relate yield and conversion data with specific ash minerals.

The Liquefaction of Sunflower Seed Hulls

Liquefaction of a biomass waste material, namely, sunflower seed hulls, was studied in a laboratory scale stainless-steel reactor. The key parameters investigated were temperature, cold hydrogen pressure, and tetralin to solvent mixture ratio within the ranges of 325–375°C, 10–30 atm., and 0/1–1/1, respectively. A Box-Behnken experimental design was used fixing the liquefaction period at 45 minutes. The effects of parameters on dependent variables, namely, oil + gas, asphaltene, and preasphaltene yields and total conversion were evaluated, and the model equations for dependent variables were developed. It was shown that temperature and tetralin to solvent mixture ratio were the variables of highest significance on liquefaction yields. An optimization study was also done by using the desirability function approach.