RELATION BETWEEN SWELLING OF LIGNITES AND THE CHARACTERISTICS OF SWELLING AGENTS

Relation between swelling ratio of lignites and lignite and solvent characteristics was developed using a third level factorial design with three variables; percent carbon content, particle size of the lignite and electron donor number of the solvent. The results indicate that particle size of the lignite does not affect the swelling ratio. While swelling ratio of the lignites decreases slightly with increasing carbon content of the lignites electron donor number of the solvent has a noticeable effect on the swelling ratio.     

A STUDY OF SULPHUR REMOVAL DURING LIGNITE HYDROLIQUEFACTION

ABSTRACT

Samples of Beypazari, Elbistan and Kangal lignites have been liquefied in hydrogen atmosphere in the presence of a solvent (tetralin) in a stainless steel reactor tube at 440^°C. Cobalt/motybdate and iron/sulfide were used as catalysts in all hydroliquefaction experiments. Semi-coke yield and total sulphur content reduction of the lignites were studied. It has been found that the use of a catalyst increased the semi-coke yield considerably. Sulphur content reduction varied depending on the type of catalysts and the lignite used in the experiment. The highest total sulphur content reduction was obtained using 5% iron sulphide catalyst with Elbistan lignite. It has also been observed that the reduction in the total sulphur content exhibits a maximum for increasing percentages of total sulphur in the subject lignites.     

LIQUEFACTION OF ELBI˙STAN AND YATAĞAN LIGNITES I N CARBON MONOXIDE/HYDROGEN GAS MIXTURES

Abstract

Thc effects of experimental parameters on the liquefaction yields of Elbistan and Yatagan lignites vcre investigated by using different solvents, guses and catalysts.

In hydroliquefaction of Elbistan lignite with anthracene and creosote oils, higher oil yields were obtained with anthracene oil. Based on this result, anthracene oil was chosen as solvent for further work done with Elbistan lignite. First the effect of moisture in lignite samples vas observed with synthesis gas as medium gas: then, the effect of carbon monoxide/ hydrogen ratio in liquefaction gas mixture was determined using moist lignite samples. The highest oil yield was obtained with moist lignite sample in 3CO/IH₂gas mixture and it was 57.3 % (daf).

The hydroliquefaction oil yields of Yatagan lignite obtained with creosote oil were higher than those obtained in anthracene ail. On Further work done with Yatagan lignite, creosote oil was chosen as solvent. First, the effects of CoMo and red mud catalysts, then in catalyzed medium, the effects of moisture in lignite samples and at last, using moist lignite samples and red mud catalyst. the effects o f carbon monaxide/hydrogen in synthesis gas medium and also, the increase in the oil yield a s an effect of catalyst presence, increased further: the 3CO/lH, ratio in gas medium was suitable for obtaining higher oil yields; and also for obtaining high oil yields, 440°c could be taken a s the most suitable temperature value and the pressure should be increased a s much as technical and economical conditions permit.     

EXAMINATION OF THE HYDROLIQUEFACTION BEHAVIOR OF CHINESE LIGNITE

ABSTRACT

In order to examine the hydroliquefaction behaviour of Chinese lignites a series of bench scale experiments with four lignites, obtained from Inner Mongolia and province Yunnan, in comparison with three foreign lignites or brown coals were performed under three sets of constant reaction conditions. The results show that Chinese lignites in general are comparable with other lignites and conversion can be precaculatad from analytical data with reasonable accuracy. The H/C-ratio of the organic coal matter is an appropriate characterization parameter for the evaluation of the hydroliquefaction behaviour of lignites. Chinese lignites Shengli and Xun-dian reveal higher hydrogenation reactivity than the other five lignite samples. Under conditions used a maximum conversion of more than 80% with oil yields of 60% are obtained. The influence of temperature, H-transfer potential, catalyst and residence time on the product distribution were also investigated in detail. Each lignite has specific sensivities for these factors. The experimental results provide interesting informations for a perspective on hydroliquefaction of these lignites.     

PYROLYSIS OF SOME TURKISH LIGNITES BETWEEN 200 - 600°C

Abstract

This study was undertaken to examine the effect of pyrolysis between 200-600°C on sulphur content, proximate and ultimate analyses of four (Seyitomer, Tuncbilck, Elbistan and Kangal) lignite samples. A decrease in semi-coke yield and an increase in tar and gas yields with increasing temperature were observed for all samples. Percent reduction of volatile matter was the same up to 400°C for the lignites. It has been observed that total sulphur contents were reduced significantly during carbonization. The highest sulphur reduction, 45%, was obtained with Elbistan lignite. By increasing temperature, hydrogen, carbon dioxide, methane and hydrogen sulphur yields increased notably but ethane and propane yields increased only slightly for all samples. In order to study effect of C, H and O contents of the original lignites on the yield and the distribution of the products, a linear regression analysis has been carried out and the model relations have been obtained. Experimental data and the model values from the relations have been compared. Yield values appear to be in good agreement with the model values for all samples.     

A STUDY OF SULPHUR REMOVAL DURING LIGNITE HYDROLIQUEFACTION

Samples of Beypazari, Elbistan and Kangal lignites have been liquefied in hydrogen atmosphere in the presence of a solvent (tetralin) in a stainless steel reactor tube at 440^°C. Cobalt/motybdate and iron/sulfide were used as catalysts in all hydroliquefaction experiments. Semi-coke yield and total sulphur content reduction of the lignites were studied. It has been found that the use of a catalyst increased the semi-coke yield considerably. Sulphur content reduction varied depending on the type of catalysts and the lignite used in the experiment. The highest total sulphur content reduction was obtained using 5% iron sulphide catalyst with Elbistan lignite. It has also been observed that the reduction in the total sulphur content exhibits a maximum for increasing percentages of total sulphur in the subject lignites.     

EXTRACTION KINETICS OF COALS AT SUBCRITICAL AND SUPERCRITICAL CONDITIONS

ABSTRACT

The extraction kinetics of two lignites and one bituminous coal with benzene, toluene and pyridine were studied at both sub and supercritical conditions in a batch reactor equipped with a coal basket. The time-extract yield data of lignites at supercritical conditions could'nt be treated due to severe thermal decomposition and heating-up effects. The data for Zonguidak coal and those for subcritical extraction of Cizre lignite could be fitted into a first order rate equation with the rate constants changing 0·02-0·05 min^?1 range.     

SUPERCRITICAL FLUID EXTRACTION OF TURKISH LIGNITES AND OIL SHALE WITH TOLUENE MIXTURES

Abstract

Supercritical -Fluid extraction (SFE) of two Turkish lignites and oil shale with toluene mixtures were investigated. Experiments were performed in a batch autoclave at 623 K. Extracts recovered from SFE were fractionated into oils, asphaltenes and preasphal-tenes by solvent extraction.

The conversion of lignites decreased with increasing n-pentane content in the mixture. The extraction yield and the products (oils, AS, PAS) increased with increasing n-pentane content in its range below 15 %

The conversion and the extract yield obtained from Cöynük ail shale is higher with toluene mixture than toluene.     

LIQUEFACTION OF ELB�STAN AND YATAĞAN LIGNITES I N CARBON MONOXIDE/HYDROGEN GAS MIXTURES

Thc effects of experimental parameters on the liquefaction yields of Elbistan and Yatagan lignites vcre investigated by using different solvents, guses and catalysts.

In hydroliquefaction of Elbistan lignite with anthracene and creosote oils, higher oil yields were obtained with anthracene oil. Based on this result, anthracene oil was chosen as solvent for further work done with Elbistan lignite. First the effect of moisture in lignite samples vas observed with synthesis gas as medium gas: then, the effect of carbon monoxide/ hydrogen ratio in liquefaction gas mixture was determined using moist lignite samples. The highest oil yield was obtained with moist lignite sample in 3CO/IH₂gas mixture and it was 57.3 % (daf).

The hydroliquefaction oil yields of Yatagan lignite obtained with creosote oil were higher than those obtained in anthracene ail. On Further work done with Yatagan lignite, creosote oil was chosen as solvent. First, the effects of CoMo and red mud catalysts, then in catalyzed medium, the effects of moisture in lignite samples and at last, using moist lignite samples and red mud catalyst. the effects o f carbon monaxide/hydrogen in synthesis gas medium and also, the increase in the oil yield a s an effect of catalyst presence, increased further: the 3CO/lH, ratio in gas medium was suitable for obtaining higher oil yields; and also for obtaining high oil yields, 440°c could be taken a s the most suitable temperature value and the pressure should be increased a s much as technical and economical conditions permit.     

EXTRACTION OF LIGNITE WITH TOLUENE IN SUB- AND SUPERCRITICAL STATES

Abstract

Nine Chinese lignite samples were extracted with toluene using a nonisothermal experimental technique at sub- and supercritical conditions in a semi-continuous apparatus. The effects of lignite properties, pressure, and H-donor solvent on the yields were investigated.

The results show that the oil yield is about 1.8 to 2.7 times that of Fischer assay and the conversion and extract yield increase linearly with the increase of volatile matter of lignite and pressure. When a H-donor solvent (tetraline) is added to the solvent (toluene), the conversion and extract yield are increased.     

LIQUEFACTION AND THE CHARACTERIZATION OF COAL DERIVED LIQUIDS OF MENGEN LIGNITE

ABSTRACT

The liquefaction characteristics of Mengen lignite has been investigated in the presence of cobalt-molybdenum on alumina catalyst in a 1 lt batch autoclave system with anthracene oil used as solvent. The experiments were carried out in the range of 15–60 atm for initial hydrogen pressure, 360–440°C for reaction temperature, 1–5 for solvent to coal ratio and 0–20% of coal for catalyst loading which were chosen as process variables. Coal particle size and reaction time were kept constant as below 200 mesh and 30 minutes respectively, (Erdem 1987)

The product was analyzed in terms of total conversion, liquid yield and liquid product distribution determined as preasphaltenes, asphaltenes and oils. The oil fraction was further separated by column chromatography while the asphaltenes were separated into basic and acid/neutral fractions. The preasphaltenes were divided into two fractions as carbene (CS₂ solubles) and carboid (CS₂ insolubles). (Inanç 1989)

The oil yield is mostly affected by the catalyst loading which shows to a certain extent that the conversion of asphaltenes to oils is a catalytic step. The selected process variables showed a positive trend with respect to the yield of hexane eluted oil which is the desired product of liquefaction.     

CHARACTERIZATION OF THE STRUCTURAL FEATURES OF OXIDIZED BEYPAZARI LIGNITE USING DECONVOLUTED SOLID STATE 13C NMR SPECTRA

ABSTRACT

The solid state ¹³C NMR method have been used to investigate the structural changes occurred in Beypazari lignite while oxidizing at 150°C in a dynamic air atmosphere. Least squares curve fitting techniques have been used to resolve the overlapping bands in the 0-220 ppm region of the 13_c NMR spectra. Measurements of the relative intensities of the functional groups observed in the oxidized coals were used to follow the progress of air oxidation. Oxidation reactions seemed to decrease the total intensities of both aliphatics and aromatics, though the reduction in aliphatics was more pronounced. The relative intensities of the total aliphatics decreased from 1.0 to 0.9 and 0.6 in the original and lignites oxidized for 12 and 312 hours, respectively. The relative intensities of Ar-C-C in the 130-148 ppm region for the same set of samples were 1.0, 0.9 and 0.8. The least-squares bands resolved in the carbonyl region were at 175 ppm and 190 ppm in the original lignite; at 180 ppm (carboxylic acids), 195 ppm (meta substituted ketones) 210 ppm (di orto substituted ketones) in the lignite oxidized for 12 hours and at 170 ppm (esters), 180 ppm, 200 ppm (aldehydes) and 210 ppm in the lignite oxidized for 312 hr. Carbonyl intensity increased from 1.0 in the original lignite to 2.3 and 3.3 in the oxidized lignites. The intensity of aromatic ethers increased from 1.0 in the original lignite to 1.9 and 1.6 for the oxidized samples. The mechanism of oxidation ether. Aldehydes are easily oxidized to carboxylic acids in the presence of air by the free radical formation of a peroxy acid. The carboxylic acid formed by disproportionation reactions between the peroxy acid and aldehydes might combine with phenols to produce esters as it was observed in the present work. The presence of high free radical concentration in the oxidation atmosphere probably caused to abstract hydrogen atoms from the aromatic structures thus degrading aromatics to produce hydroperoxides which acted later as it was described above. The gradual degradation of aromatic structures observed in the present study indicated that the oxidation reactions of the aromatic rings should less probable when compared to the oxidation of aliphatic structures.     

DISSOLUTION OF COALS NEAR CRITICAL CONDITIONS

ABSTRACT

Two lignites and one bituminous coal were extracted with benzene, toluene and pyridine at both sub and overcritical conditions in a specially designed experimental system which enabled easy solid-liquid separation. Extract yields increased somewhat at overcritical conditions due to more thermal decomposition. The differences between the power of the solvents were not apparent for the lignites, whereas the solubility in pyridine of the bituminous coal was very much higher than those in benzene and toluene. The amounts of oils, asphaltenes and preasphaltenes in the extracts depended on the type of coal and the solvent.     

INVESTIGATION OF THE RELATION BETWEEN CHEMICAL COMPOSITION AND ASH FUSION TEMPERATURES FOR SOKE TURKISH LIGNITES

Abstract

The purpose of this paper was to investigate the relationship between ash composition and ash fusion characteristic temperatures for some Turkish lignites. The lignite samples used are from different areas in Turkey. Regression analysis was used to relate the ash composition to the ash fusion behaviour. The results suggest that the chemical composition has a significant effect on the ash fusion temperatures. To consider Fe₂O₃ as an acidic ash constituent makes the realtionships between the selected ash composition parameters and ash fusion temperatures clearer.     

EXAMINATION OF THE HYDROLIQUEFACTION BEHAVIOR OF CHINESE LIGNITE

In order to examine the hydroliquefaction behaviour of Chinese lignites a series of bench scale experiments with four lignites, obtained from Inner Mongolia and province Yunnan, in comparison with three foreign lignites or brown coals were performed under three sets of constant reaction conditions. The results show that Chinese lignites in general are comparable with other lignites and conversion can be precaculatad from analytical data with reasonable accuracy. The H/C-ratio of the organic coal matter is an appropriate characterization parameter for the evaluation of the hydroliquefaction behaviour of lignites. Chinese lignites Shengli and Xun-dian reveal higher hydrogenation reactivity than the other five lignite samples. Under conditions used a maximum conversion of more than 80% with oil yields of 60% are obtained. The influence of temperature, H-transfer potential, catalyst and residence time on the product distribution were also investigated in detail. Each lignite has specific sensivities for these factors. The experimental results provide interesting informations for a perspective on hydroliquefaction of these lignites.     

PYROLYSIS OF SOME TURKISH LIGNITES BETWEEN 200 - 600°C

This study was undertaken to examine the effect of pyrolysis between 200-600°C on sulphur content, proximate and ultimate analyses of four (Seyitomer, Tuncbilck, Elbistan and Kangal) lignite samples. A decrease in semi-coke yield and an increase in tar and gas yields with increasing temperature were observed for all samples. Percent reduction of volatile matter was the same up to 400°C for the lignites. It has been observed that total sulphur contents were reduced significantly during carbonization. The highest sulphur reduction, 45%, was obtained with Elbistan lignite. By increasing temperature, hydrogen, carbon dioxide, methane and hydrogen sulphur yields increased notably but ethane and propane yields increased only slightly for all samples. In order to study effect of C, H and O contents of the original lignites on the yield and the distribution of the products, a linear regression analysis has been carried out and the model relations have been obtained. Experimental data and the model values from the relations have been compared. Yield values appear to be in good agreement with the model values for all samples.     

TEXAS LIGNITE DESULFURIZATION

ABSTRACT

Texas lignites are a low-Btu, high-ash and moderately high-sulfur fuel that can be readily upgraded before combustion using physical and microbial desulfurization technology. Although physical and chemical processes and some microbial processes are effective in removing pyritic sulfur, they are ineffective for removing organic sulfur. Microbial processing of Texas lignite with sulfur content of up to 15 wt.% was investigated using laboratory shake-flask experiments. Organisms of the genus Thiobucillus ferrooxiduns, Leptospirillum Jerrooxidans and Pseudomonas putidawere investigated. It was found that up to 77% of the sulfur compounds present in the Texas lignite with more than 90% of the pyritic sulfur could be removed by the use of these microbes. Texas lignite samples were pulverized to pass through 149-μim sieve. Thiobucillus ferrooxiduns reduced up to 54% of the total sulfur and 78% of the pyritic sulfur in 14 days and Leptospirillum ferrooxidans removed up to 41% and 60%, respectively. A mixed culture of these two bacteria was also studied for sulfur removal The lignite was retreated with P. putidu which further removed 50% of the total sulfur in 7 days. P. puiidu could successfully remove up to 37% of the organic sulfur in 7 days.     

EFFECT OF PRESWELLING ON SOXHLET AND SUPERCRITICAL GAS EXTRACTION OF A TURKISH LIGNITE

Preswelling of Mugla-Yatagan lignite with THF (Tetrahydrofuran) followed by removal of the swelling agents results in higher extract yields, probably because the solvent molecules had easier access to the expanded pore structure of the swollen lignite. On the other hand, the yields of supercritical THF extract of the same lignite sample indicated that during removal of the swelling agent the expanded pore structure had collapsed. The results show that higher extract yields might have been obtained by the combined effect of the expanded pore structure of the swollen lignite and the solvent power of the mixed solvent,i.e., of the mixture of swelling agent and supercritical extraction fluid.     

SOLVENT EXTRACTION OF COALS THROUGH ATD3 REACTION UNDER AMBIENT PRESSURE CONDITION

ABSTRACT

A novel reaction such as ATD³ reaction which has been recently found to be an attractive reaction for rendering more 50% coal extractable, has been tested on different bituminous coals and a lignite. The reaction has been found to be generally applicable on coals and lignite to render about 50% coal extractable. The reaction proceeds under industrially convenient conditions and involves the use of only coal or petroleum derived solvents. Reaction of % carbon, % volatile matter and atomic O/C ratio of coals with the extractability of coal through ATD³ reaction has been drawn.     

STUDY OF STRUCTURAL FEATURE OF PEAT,LIGNITE AND HUMIC ACID BY SOLID STATEl3C NMR SPECTROSCOPY

Abstract

Four low rank coals (peat and lignite) and their derived humic acids have been investigated by the^l3C CP/MAS/TOSS NMR technique. The NMR analysis indicates that the peat contains a significant amount of unaltered plant components including cellulose, hemicellulose, lignin, waxes, and resins.

Variable contact time and dipolar dephasing experiments were performed on each sample. The data from above experiments, together with normal CP/MAS integration over selected chemical shift range, were used to derive 12 parameters of carbon skeletal structure including the aromaticity.From the ratio of aromatic bridgehead carbons, f_a ^cp, to the aromatic peripheral carbons, f^cpxBp as measured by NMR, the aromatic cluster size may be estimated for each coal.