Properties Of Lignite Research Articles

Petrological and organic geochemical properties of lignite from the Kolubara and Kostolac basins, Serbia: Implication on Grindability Index

The influence of different coal lithotypes on grindability has been investigated using lignite from two of the most important Upper Miocene lignite basins in Serbia (Kolubara and Kostolac). Yellow xylite-rich types demonstrated the most negative impact on Hardgrove Grindability Index (HGI). All different types of xylite-rich coal, as well as total xylite-rich coal from the Kolubara basin have a negative influence on the grindability properties, while only the yellow type of xylite-rich coal from the Kostolac showed a negative impact on HGI. Matrix coal does not show a clear effect on HGI.A negative correlation between textinite content and HGI is observed in both basins, whereas contents of other macerals do not show influence on grindability properties.Content of total organic carbon demonstrated the negative impact on HGI. Correlation analysis indicates that the negative impact of the yellow type of xylite-rich coal and the sum of total xylite-rich coal on the grindability properties partly can be related to content of total organic carbon and high amount of soluble organic matter. Matrix lithotype does not show any significant correlation with bulk geochemical parameters in both basins.The peat-forming vegetation of all samples from both basins were dominated by decay-resistant gymnosperm (coniferous) plants, belonging to one or several of the families Taxodiaceae, Podocarpaceae, Cupressaceae, Araucariaceae, Phyllocladaceae and Pinaceae. Lignite from the Kolubara basin is characterized by a higher contribution of angiosperm vegetation than coal from the Kostolac basin. Peatification of the Kolubara coal occurred under more oxic conditions than the Kostolac one.Analysis of biomarkers indicated that the negative impact of all types of xylite-rich coal from the Kolubara on HGI can be related to the higher proportion of angiosperms, abundance of mid-chain n-alkanes and sesquiterpenoids, aromatization of non-hopanoid triterpenoids and hopanoids, and intense degradation of wood tissues in a more oxic environment. The positive impact of matrix coal on HGI in the Kolubara samples can be attributed to elevated content of non-aromatic hopanoids and low amounts of aromatic non-hopanoid triterpenoids and sesquiterpenoids, which seems to hinder the grindability properties.

Feasibility Studies of the Sequential Dewatering/Dry Separation of Chinese Lignite in a Vibration Fluidized-Bed Dryer: Effect of Physical Parameters and Operation Conditions

The combined dewatering process and dry separation in a vibration fluidized-bed dryer was developed to upgrade Chinese lignite in terms of moisture and ash for effective utilization in power plants. The influence of operational parameters (fluidizing gas velocity, vibration strength, bed height, and drying temperature) and lignite properties (particle size and moisture content) on the drying or separation characteristics of −6–1 mm lignite was examined in a laboratory-scale vibration fluidized-bed dryer. Both operational parameters and lignite properties had a significant effect on the drying and separation performance. The drying and separation behaviors of a vibration fluidized bed were both enhanced in comparison to the case without vibration under the same operating conditions. Moreover, with the change in gas velocity, the drying and separation processes could be combined in the same vibration fluidized-bed dryer. Both processes achieved promising results compared to those of the fixed gas velocity condition, which was confirmed by the low calorific value analysis. A sequential drying and separation system in a vibro-fluidized-bed dryer was also designed on the basis of the separation and drying characteristic results.

Altered transport of lindane caused by the retention of natural particles in saturated porous media

Attachment and straining of colloidal particles in porous media result in their reversible and irreversible retention. The retained particles may either increase the retention of hydrophobic pollutants by sorption onto the particles, or enhance pollutant transport when particles, loaded with the pollutants, are remobilized. The present study examines the effects of retained particles on the transport of the hydrophobic pesticide lindane (gamma-hexachlorocyclohexane) in saturated porous media. The lignite particles used have median diameters of about 3μm, 1μm, 0.8μm, and 0.2μm, respectively. Laboratory column experiments were analyzed by numerical modeling in order to identify and understand the processes involved in the transport of the particles and of lindane. Four scenarios were considered in which the solution containing lindane is injected either during or after the elution of the particles. The results show that lignite particles retained in a sandy porous medium alter the transport of the invading lindane. Particle retention was high in all scenarios and increased with increasing particle size. Remobilization of particles occurred due to a change in solution chemistry, and continuous particle detachment was observed over time. Numerical modeling of particle transport suggests that both reversible attachment and irreversible straining affected the transport of the particles. Lindane was retarded in all scenarios due to the strong particle retention in conjunction with the sorption of lindane onto the sand and onto retained particles, and the limited number of mobile particles carrying lindane. Moreover, it was found that intra-particle diffusion limited adsorption/desorption of lindane onto/from both limestone fragments of the sand and lignite particles. We assume that retention of lindane is reversible even though lindane recovery was incomplete over the duration of the experiments. The analysis of the effluent concentration suggests that retained particles loaded with lindane may become a secondary source of lindane. Models describing the transport of lindane fitted the experimental data very well and indicated the specific contribution of retained particles to the retardation of lindane. Since the properties of lignite also known as brown coal are similar to those of biochar, the results of the present study could be extended to the potential effects of biochar on lindane and other contaminants in soils, which would include both their retention and their enhanced transport. However, while the transport mechanisms of lindane are similar in water-unsaturated soils and saturated porous media considered here, the behavior of particles is more complex, requiring additional studies.

Effect of ammonoxidation on lignite properties

Oxidised lignite is a potential alternative source of N fertilizers. Ammonoxidation is the reaction of a given substrate with oxygen in aqueous ammonia. Lignite ammonoxidation is used for converting low-rank lignite into slowly nitrogen-releasing artificial humic matter. A lignite sample is compared before and after ammonoxidation in terms of geochemical and petrological properties, as well as the acid–base and physical hydrophobic sorptive behavior. The most obvious change caused by ammonoxidation is the decrease of attrinite, texto-ulminite and textinite in favor mainly of densinite and gelohuminite. In general, the ammonoxidative reactions promote the destruction of the structured humic macerals (texto-ulminite, textinite), and the formation of gels, which resulted in the cementation of the freely fine humic particles (attrinite). The pzc values are 3.4 and 4.3 for oxidised and non-oxidised lignite, respectively. After ammonoxidation the contents of carboxylic and free phenolic groups are found to be lower. The oxidised lignite shows a statistically lower sorptive capacity and affinity than the original sample due to a possible decrease in the hydrophobicity of the lignite.

Enhanced-hydrogen gas production through underground gasification of lignite

Underground coal gasification is one of the clean technologies of in-situ coal utilization. Hydrogen production from underground gasification of lignite was investigated in this study based on simulation experiments. Pyrolysis of lignite, gasification activity, oxygen-steam gasification and the effect of groundwater influx were studied. As well, the advantages of lignite for stable underground gasification were analyzed. The results indicate that lignite has a high activity for gasification. Coal pyrolysis is an important source of hydrogen emission. Under special heating conditions, hydrogen is released from coal seams at temperatures above 350 °C and reaches its maximum value between 725 and 825 °C. Gas with a hydrogen concentration of 40% to 50% can be continuously obtained by oxygen-steam injection at an optimum ratio of steam to oxygen, while lignite properties will ensure stable gasification. Groundwater influx can be utilized for hydrogen preparation under certain geological conditions through pressure control. Therefore, enhanced-hydrogen gas production through underground gasification of lignite has experimentally been proved.

Effect of co-combustion on the burnout of lignite/biomass blends: A Turkish case study

Co-combustion of Turkish Elbistan lignite and woody shells of hazelnut was performed in a TGA up to 1173 K with a heating rate of 20 K/min. SEM images of each fuel revealed the differences in their physical appearances. Hazelnut shell was blended with lignite in the range of 2-20 wt% to observe the co-combustion properties. Maximum burning rates (Rmax), temperatures of the maximum burning rates (T(R-max)), and the final burnout values of the parent samples and the blends were compared. The results were interpreted considering lignite properties and the major biomass ingredients such as cellulosics, hemicellulosics, and lignin. Deviations between the theoretical and experimental burnout values were evaluated at various temperatures. Burnout characteristics of the blends up to 10 wt% were concluded to have a synergistic effect so the addition of hazelnut shell up to 8 wt% provided higher burnouts than the expected theoretical ones, whereas addition of as much as 10 wt% led to a decrease in the burnout. However, the additive effects were more favorable for the blend having a biomass content of 20 wt%. Apparent activation energy, Rmax, and T(R-max), were found to follow the additive behavior for the blend samples.

Properties and Reserves of Lignite in the Aydin-Sahinali Field, Turkey

This study focuses on some lignite properties and calculation of lignite reserves with two classical (isopach and polygon) methods in the Aydin-Sahinali field, Turkey, which is located in the western Turkey. This field has been mined by a private coal company since 1960 by open-cast and mainly underground mining methods. The producing lignites are consumed in domestic heating and industrial factories around Aydin. The metamorphic rocks of Palaezoic age form the basement of the coal field. The lignite-bearing unit of Miocene age, from bottom to the top, consists mainly of pebblestone, lignite and clayey lignite, siltstone with sandstone lenses, white colored claystone, clayey limestone and silisified limestone lenses. This unit in the lignite field was unconformably overlain by Pliocene unconsolidated sands and gravels. Three hundred seventy-three borehole data have been evaluated, and this study shows that a relatively thick and lateral extensive lignite seam has a mineable thickness of 1.6–14.4 m. The core samples from boreholes in panels in the lignite field indicate that the coal seam, on an as-received basis, contains high moisture contents (17.95–23.45%, average), high ash yields (16.30–26.03%, average), relatively high net calorific values (3,281–3,854 kcal/kg, average), and low total sulfur contents (1.00–1.22%, average). The remaining lignite potential in the Aydin-Sahinali lignite field was calculated as a 4.7 Mt of measured and a 2.9 Mt of mineable lignite-reserves.

Effect of Various Experimental Parameters on the Swelling and Supercritical Extraction Properties of Lignite

The original lignite sample, the samples swollen in dimethylsulfoxide (DMSO), dimethylformamide (DMF), pyridine, tetrahydrofuran (THF), acetone, ethylenediamine (EDA), N-methyl-2-pyrrolidone (NMP), tetrabutylammonium hydroxide (TBAH), the samples impregnated by ZnCl2 as catalyst and the samples both swollen in the solvents and impregnated by ZnCl2 were subjected to the supercritical toluene extraction and the effects of temperature, pressure, pre-swelling procedure, hydrogen donor solvent (tetralin), and catalyst on the extract yields were investigated.

Mechanical/thermal dewatering of lignite. Part 2: A rheological model for consolidation and creep process

A rheological model is presented for the description of the dynamic behaviour of lignite during mechanical/thermal dewatering (MTE). The dewatering during the MTE-process is described depending on the process parameters time, temperature, pressure and the initial height of the coal filling in a press. The model was verified by comparing the calculations with experimental data in a wide range of process parameters. The comparison for three different lignites shows an excellent agreement. Therefore the model is also applicable for the technical process design. Additional experiments and calculations have been performed for a detailed analysis of the hydraulic pressure drop during the expression of water from lignite. It was found that the differences in geological history result in large variations of the lignite permeability and have remarkable influence on the duration of the primary consolidation (early stage dewatering). The theoretical and experimental results offer a deeper understanding of the influence of process parameters and lignite properties on the consolidation process and the kinetics.

Effect of lignite properties on reactivity of lignite

Effect of lignite properties on reactivity of lignite

Progress of coal gasification technology

Underground coal gasification is one of the clean technologies of in-situ coal utilization. Hydrogen production from underground gasification of lignite was investigated in this study based on simulation experiments. Pyrolysis of lignite, gasification activity, oxygen-steam gasification and the effect of groundwater influx were studied. As well, the advantages of lignite for stable underground gasification were analyzed. The results indicate that lignite has a high activity for gasification. Coal pyrolysis is an important source of hydrogen emission. Under special heating conditions, hydrogen is released from coal seams at temperatures above 350 °C and reaches its maximum value between 725 and 825 °C. Gas with a hydrogen concentration of 40% to 50% can be continuously obtained by oxygen-steam injection at an optimum ratio of steam to oxygen, while lignite properties will ensure stable gasification. Groundwater influx can be utilized for hydrogen preparation under certain geological conditions through pressure control. Therefore, enhanced-hydrogen gas production through underground gasification of lignite has experimentally been proved.

Effect of different binders on the combustion properties of lignite. Part II. Effect on kinetics

In this research kinetic analysis of the Tuncbilek lignite and its mixture with different binders (molasses, CMC, sulphide liquor, heavy crude oil, sodium silicate,cornstarch, lime, peridur, bentonite, cement and poly(vinyl-acetate)) were analysed by thermogravimetric (TG/DTG) methods. Two different kinetic models (Arrhenius and Coats–Redfern) were used to determine the activation energies of the samples studied. The concept of weighed mean activation energy was applied to determine the overall reactivity of the samples. It was observed that molasses, CMC, heavy crude oil, peridur, bentonite and poly(acetate) decreased the activation energy of the coal sample, whereas, all other binders increased the activation energy of the coal sample.

Effect of lignite properties on reactivity of lignite

The purpose of this study is to relate the combustion reactivity of lignite to its physical and chemical properties. Non-isothermal thermogravimetry, where the sample whose temperature increased at a linear rate (40 K/min) was heated in air, has been used to investigate the combustion reactivities of 25 lignite samples originating from different areas of Turkey. Since combustion reactivity is affected by the chemical and physical properties of coal, the combustion reactivity of the lignites used in this study was related to their proximate and ultimate analysis results and physical properties such as pore structure and surface area. The calculated activation energy values for the combustion reactions of the lignites ranged between 64 and 139 kJ/mol. Definite correlations between the activation energy values and the above-mentioned properties were found.

Influence of oxidation in aqueous medium on the structure and properties of lignites

In this paper, the effect of oxygen uptake on the structure and properties of lignites was investigated using five different Turkish lignites. Lignite samples were oxidised in aqueous medium at 423 K under 1.5 MPa partial pressure of oxygen for 60 min. Relations between the oxygen uptake and the elemental compositions of the lignite samples were investigated. FT-i.r. technique was applied to the original and oxidised lignite samples to investigate functional group analyses. Mercury porosimetry analyses of the samples were carried out up to about 220 MPa. Effect of oxygen uptake on the bulk density, apparent density, porosity, and pore radius of the lignite samples were compared. Differential Thermogravimetry (DTG) technique was performed to compare the thermal reactivity of the original and oxidised lignite samples.

98/03502 Laboratory assessment of technological properties of lignites from the Ptolemals and Megalopolis fields, Greece

98/03502 Laboratory assessment of technological properties of lignites from the Ptolemals and Megalopolis fields, Greece

98/02623 Changes of chemical properties of lignite with weathering: Yuan, H. et al. Huanjing Huaxue, 1997, 16, (4), 311–315. (in Chinese)

High pressure sorption experiments with carbon dioxide and methane were carried out at a temperature of 45 °C and at pressures up to 15 MPa with three samples of methane-bearing, medium-rank coals in a moisture-equilibrated state using a manometric method. The samples were taken from selected positions of drill cores from exploration boreholes in the Bohemian part of the Upper Silesian Basin, and were characterized by a narrow range of degree of coalification and markedly different petrographic compositions, including a different mineral matter content. The total porosity of the coal samples was between 9% and 10%. A positive correlation was found between the equilibrium moisture in the coal samples and the total abundance of oxygen functional groups determined by FTIR. The excess sorption capacities ranged from 0.78 to 0.91 mmol g−1 for CO2 and from 0.45 to 0.52 mmol g−1 for CH4, and after recalculation to coal organic matter, the excess sorption capacities increased by up to 14% in the coal with the highest mineral fraction. The highest CO2/CH4 ratio was found in the sample that had the highest inertinite and liptinite content. The experimental isotherm data was fitted by modified Langmuir and Dubinin–Radushkevich sorption isotherms. The parameters obtained by these two methods were in good agreement for carbon dioxide. It was found that the sorption capacity of the organic matter in a coal sample with prevalence of inertinite (63.0 vol.%) was lower only by 14% for CO2 and by 18% for CH4 than the sorption capacity of the organic matter in a coal sample with prevalence of vitrinite (65.3 vol.%). This provided confirmation that the petrographic composition of a coal has an ambiguous effect.

96/06636 The Ion exchange properties of low rank coals on actinides and other heavy metals

The removal of heavy metal and low-level radioactive wastes from the environment and their subsequent immobilization in an appropriate repository is one of the major environmental challenges facing our nation. The scope and magnitude of the contamination at many DOE and Superfund sites are such that successful remediation will require the development of new, inexpensive technologies which remove, in an environmentally acceptable manner, the heavy metal and radioactive wastes from contaminated soil and water. In this paper, we will present the preliminary data on the viability of using low rank coals or lignites as a novel, inexpensive material to remove actinides and other metals from the aqueous system, and the effects of high radiation on ion-exchange properties of lignites.

Geotechnical properties of the Ptolemais lignite

The paper describes an investigation of the geotechnical properties of the Ptolemais lignite (brown coal) and shows that the soil mechanics principles used in the study of natural and cemented soils are applicable. The material has a high and variable void ratio incompatible with its preconsolidation pressure, which may be attributed to the existence of structure (chemical bonding). Bond strength and degradation have been studied and are found to be isotropic, while the stress-strain response in the prevield domain is intensely cross-anisotropic. The shear strength determined from triaxial CU and CD tests is variable but strongly dependent on the in situ moisture content. Tests on high quality intact specimens having a wide range of moisture contents (100–150%) verify a hypothesis that the magnitude of bond strength (expressed by the peak shear strength) is inversely proportional to the moisture content. A Hvorslev-type normalization process shows that the peak shear strength of the material can be estimated from the in situ moisture content with reasonable accuracy, thus facilitating preliminary stability calculations of production cuts in lignite mines. The properties of the Ptolemais lignite are compared with the properties of a lignite from another location in Greece (Megalopolis) and an Australian lignite (Morwell). It is shown that the shear strength characteristics of the lignite types studied are similar and strongly dependent on the in situ moisture content, which seems to be a measure of the magnitude of inter-particle bonding.

Changes of Chemical Properties and Microbiological Succession of Lignites with Weathering.

Changes of chemical properties of lignite, collected from Shenyang Coal Mine, Liao Ning Province, Northeast China, and microbial succession on it with 4 years of weathering in open air were studied. With weathering, the content of total carbon and nitrogen, and C/N ratio decreased, while the ash content and the amount of organic matter which was extracted with 0.1M NaOH increased distinctly. UV-VIS spectra of humic and fulvic acids obtained from lignite samples changed systematically with weathering. Distribution of fulvic acids into adsorbed and nonadsorbed fractions with a cross-linked polyvinylpyrrolidone (PVP), which were regarded as humic and non-humic substances, respectively, was also changed. However, the IR spectra scarcely differed among the humic acids in lignite samples which were recently excavated and those which were weathered. Microbial succession on lignite was observed with weathering; actinomycetes as the first colonizers, followed by bacteria and then fungi. The dominant microorganisms were Actinosynnema sp., Streptomyces sp. and Nocardia sp. among actinomycetes, two Arthrobacter spp. among bacteria and two Aspergillus spp. among fungi.

EFFECTS OF COAL SURFACE CHARGE ON THE ADSORPTION AND GASIFICATION ACTIVITIES OF CALCIUM AND POTASSIUM

ABSTRACT The electrokinetic properties of lignite, subbituminous and bituminous coal particles and their demineralized derivatives have been measured as a function of pH. Compared to the raw coals, demineTalization generally increased the net negative surface charge densities on the coals. Calcium or potassium adsorption (by ion-exchange) onto the demineralized coals was strongly dependent on pH and the surface charge properties of the coals. Metals uptake was very low (0,1-0.4% wt.) in strongly acidic media (∼pHl) but increased dramatically as the net negative charge on the coals was increased by increasing the pHs of the coal suspensions to pH 6 or 10. The reactivities of the calcium- ot potassium-loaded chars in carbon dioxide at 800°C were similarly dependent upon the pHs at which the catalysts were ion-exchanged onto the coals. For the calcium-containing chars, the reactivities increased in the order: pH 6 > “pH 10 > pH 1 while the variation of the gasification rates with potassium loading pH was: pH...