Hüseyin Karaca

Chemical cleaning of Turkish lignites by leaching with aqueous hydrogen peroxide

Two Turkish lignites (Beypazari and Tuncbilek) were leached with the solutions of hydrogen peroxide in water or in 0.1 N H2SO4. The effects of some process parameters, such as concentration, time and temperature, on the removal of ash and sulphur have been investigated. The rate of ash and sulphur removal are relatively high in the first 30 min, but slow after 60 min of the reaction time. Depending on the type of lignite, the maximum reductions ranged from 30 to 70% in ash, from 70 to 95% in pyritic sulphur, and from 42 to 58% in total sulphur. A relatively small reduction (a maximum of 25%) was estimated for organic sulphur. The optimum process conditions were established as a hydrogen peroxide concentration of 15 wt.%, a temperature of 30 °C and a leaching time of 60 min. High peroxide concentration or high temperature did not result in an appreciable further reduction in ash and sulphur. Due to partial dissolution or oxidation of the lignites, some organic material losses occurred but no heating value loss was estimated. An overall kinetic approach was also applied for pyritic sulphur removal, and the conversion data were analyzed by using both homogenous and heterogeneous reaction models.

Demineralisation of lignites by single and successive pretreatment

In this study, two Turkish lignites (Bolu-Mengen, Kutahya-Tuncbilek) were treated under atmospheric and reflux conditions with 10–30% NaOH, 10% HCl and 10% H2SO4 solutions, singly and/or successive treatments to determine the effects of this treatment on the mineral matter and acidic functional groups. Characterisation of the treated and untreated samples was by Fourier transform infrared spectroscopy. The process of successive pretreatment was found to be more effective than single steps in terms of demineralisation and removal of carboxylate structures. During NaOH treatment, the first of successive steps, salts soluble in acid but not in water were determined. In successive demineralisation steps with 30% NaOH and 10% HCl, a low level of 3.3% ash was obtained for the Tuncbilek lignite. In addition, during the pretreatment, most of the Ca and K were exchanged with Na.

Co-liquefaction of Elbistan Lignite and Biomass. Part I: The Effect of the Process Parameters on the Conversion of Liquefaction Products

Abstract In this study, the liquefaction of Elbistan lignite and the co-liquefaction of Elbistan lignite with the biomass were examined. The biomass type used in this study consists of waste plastic, waste paper, waste mud, and molasses. The dissolution reactions were carried out in tetralin at 350–425°C under nitrogen atmosphere. Mo(CO)6, Cr(CO)6, Fe2O3, and MoO3 were used as the added catalysts. The particle size ranged from 0.25 mm to 1.5 mm, the isothermal extraction periods ranged from 30 to 150 min, and the solvent/lignite ratio ranged from 1/1 to 9/1. The results indicated that total conversion and oil + gas conversion obtained during the liquefaction largely changed according to catalyst type, biomass type, and reaction temperature. It is understood that other process parameters, such as particle size and solvent/solid ratio, did not have any important effects. According to the obtained results, optimum process parameters were determined as particle size of 1.5 mm, solvent/solid ratio of 3/1, reaction time of 90 min, and reaction temperature of 400°C. Fe2O3 was selected as the most suitable catalyst type and waste paper as biomass type. In order to reduce liquefaction cost in liquefaction operations, results of the experimental studies showed that using coal + biomass instead of coal, nitrogen instead of hydrogen, and recycled solvent instead of fresh solvent would be more suitable.

Desulfurization of Fuel by Leaching Using H2O2 and H2SO4

Abstract In this research, different concentrations of H2O2 and H2SO4 solutions were used in order to remove the sulfur from high sulfur contented No. 6 fuel oil. In desulphurization experiments, reaction temperature, reaction time, and the concentration of H2O2 and H2SO4 were varied in a range of 20–50○C, 30–150 min, 5–35%, and 0.05–2.00 N, respectively. The ratio of reagent/fuel oil was taken as 10/1 and the stirring speed as 1,000 rpm. According to the results obtained, considering the desulphurization and the organic structure of the fuel, the most appropriate method was found as the H2O2 leaching method. It was barely determined that the highest desulphurization was achieved by H2O2/0.1N H2SO4 leaching method. The optimum process parameters for H2O2 leaching method were found as a concentration of 15%, reaction temperature of 30○C, and reaction time of 60 min; and for H2SO4 leaching method were found as concentration of 0.1 N, reaction temperature of 30○C, and reaction time of 150 min. It was observed that by increasing the reaction temperature, reaction time, and reagent concentration, the carbon and hydrogen contents of the fuel decreased considerably and on the contrary the oxygen content increased very rapidly. A partial decrease of nitrogen content was also observed.

The characterization of coal liquefaction products obtained under an inert atmosphere and catalytic conditions. Part II: Soluble products

Beypazari and Tunçbilek lignite were liquefied using two different catalyst methods—physically mixing and impregnation. The liquefaction occurred under conditions of inert atmosphere and various process parameters. Solvent to coal ratio, pressure, catalyst type, catalyst concentration, temperature, and time were examined as process parameters. The most appropriate parameters for the total soluble products obtained by liquefaction of both lignites and for elemental analysis of preasphaltenes were determined as follows: 2/1 solvent to coal ratio; from 1.25 MPa to 2.50 MPa initial nitrogen pressure; Fe 2 O 3 and Mo(CO) 6 as catalyst types; 3% as catalyst concentration; 400°C as reaction temperature; and 60 min as reaction time. In general, fuel quality of both preasphaltene and total soluble products decreased as temperature increased above 400°C and reaction time exceeded 60 min. The fuel quality of the preasphaltenes and the total soluble products obtained under the catalytic conditions and in the state of impregnation of catalyst onto coal is higher than under the noncatalytic conditions and in the state of physically mixing of catalyst.

The Co-liquefaction of Elbistan Lignite and Biomass. Part II: The Characterization of Liquefaction Products

Abstract This study examines the effects of various process parameters regarding separately and co-liquefaction in a nitrogen gas medium under catalytic and non-catalytic conditions of Elbistan lignite and various biomass samples, the direct use of which is inconvenient both economically and ecologically. According to the obtained results, the optimum process parameters are as follows: The particle size is 1.5 mm, liquid/solid ratio is 3/1, reaction time is 90 min, and reaction temperature is 400°C. Fe2O3 has been selected as the most suitable catalyst type and waste paper as the most suitable biomass type. At 3/1 liquid/solid ratio, as a result of the liquefaction studies, which are made through using fresh and recycled solvent, the obtained total conversions are 90.2 and 88.4%, oil + gas conversions are 59.3 and 57.6%. Elemental analyses have been made in order to gain information on the structure of the preasphaltene and chars, which are obtained as a result of the liquefaction of Elbistan lignite separately and together with paper under catalytic conditions. According to the results of the elemental analysis, chars and preasphaltenes may not be used as fuel. However, as preasphaltenes have high content of both carbon and hydrogen, their re-liquefaction under catalytic and non-catalytic conditions separately or together with the biomass, and the co-liquefaction of the char with the biomass or burning it in a fluidized bed may be recommended. According to the results of gas chromatography/mass spectrometry analyses of the oils obtained as a result of liquefaction, the oils basically consist of various components, such as naphthalene and its derivatives, tetraline and derivatives, indene, butylated-hydroxytoluen, binaphtalene, and indole.

Effects of coal liquefaction parameters on the removal of oxygen and the higher heating value of the soluble products

In this study, effects of coal liquefaction parameters on the removal of oxygen, the higher heating value of char, and soluble products during the catalyst physically mixing or impregnation of the two Turkish lignites were investigated. According to the results, the effects on the higher heating value of char and the soluble products of the reaction parameters were almost similar for both lignites. In the case of catalysts physically mixing, the higher heating value of total soluble products of Beypazari lignite increased as a result of increase in solvent/coal ratio and temperature. In the case of the catalyst physically mixing and impregnation of Tuncbilek lignite, the higher heating value of char and the soluble products was observed to have increased considerably at 350–400°C of the reaction temperature in 10–60 minutes of reaction time. According to the results of FT-I.R., it was observed that functional groups with oxygen (carboxylic, carbonyl and etheric) were decreased or removed completely, depending on the liquefaction conditions.

Determination of Optimum Process Parameters in Desulphurization of Fuel Oil

Abstract In this research, desulphurization of number 6 fuel oil (residue fuel oil) by chemical methods was studied. Besides, factors like reaction temperature, reaction time, concentration, and stirring speed were examined to determine the effects of various process parameters on desulphurization and on higher heating value. According to the results obtained, the optimum values of process parameters were determined as H2O2 concentration of 15%, reaction temperature of 40○C, reaction time of 60–150 min and stirring speed of 1, 000 rpm. Under these conditions, the sulphur content in the fuel oil sample was reduced from 2.78 to 2.29%–1.54% approximately. The degree of desulphurization increased, but higher heating value decreased seriously at high levels of H2O2 concentration, reaction temperature, reaction time, and stirring speed. Some fuel oil samples that are pretreated with H2O2/0.1 N H2SO4 were extracted successively with acetone, ethanol, ethylene glycol, and hydrogen peroxide. In conclusion, the sulphur content decreased approximately from 2.29 to 1.08%. Partial decrease determined in the higher heating value of the sample at the end of extraction.

Co-liquefaction Behaviour of Elbistan Lignite and Olive Bagasse

In the present study, co-liquefaction potential of Elbistan lignite and Balikesir olive bagasse were investigated by direct coal liquefaction process. The olive bagasse is a cheap and abundant biomass, so it is used to decrease the cost of oil production from the lignite. The effect of blending ratio of the lignite and the olive bagasse on liquefaction conversion and oil yield were investigated. Characterization studies of the starting materials were done using XRD, FTIR, DTA/TG and elemental analysis. Elemental compositions of liquefaction products were also determined and the composition of the obtained oil was identified by GC/MS. DTA and TGA results indicated the synergistic effect of the lignite and the olive bagasse and maximum oil conversion (36 %) was obtained from 1:3 blending ratio of lignite: olive bagasse. The results showed that the obtained oil was paraffinic-low waxy oil with 22.5 MJ/kg of calorific value and 95 g/cm3 density.

Liquefaction Potential of Adiyaman Peat

In the present study, liquefaction potential of Adiyaman peat was studied by direct liquefaction technique to obtain oil as a fuel purposes due to its high carbon and hydrogen content and low sulphur ratio. The peat and liquefaction products, named char, asphaltene, preasphaltene and oil, were characterized by XRD, FTIR, SEM, DTA/TG and elemental analysis. The compositions of the obtained oil were also identified by GC/MS. The results indicated that the obtained oil was paraffinic-low waxy oil with 21.73 MJ/kg of calorific value and 0.93 g/cm3 density and it was composed of naphthalene and phenolic groups. The oil conversion ratio was found to be 29 %.