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The objective of the work was testing the suitability of X-ray Diffraction (XRD) and Scanning Electron Microscopy with X-ray microanalysis (SEM/EDS-Energy Dispersive X-ray Spectroscopy) for qualitative assessment of mercury present in coals and furnace wastes (slag, ash). Such information is essential e.g. for determination of the potential effects of waste coal dumps on the environment (mercury compound emissions through leaching and erosion to water and soil). No minerals of mercury, i.e. containing mercury as a necessary and substantial component were identified with the application of the above mentioned techniques in studied hard coal and fly ash samples provided by a heat and power plant. In hard coal, mercury was detected as an impurity only in the alumina silicates. EDS spectra of pure coal grains did not show the emission lines of mercury. In fly ash, the minerals of mercury were also not detected; mercury was present in an amorphous component (mineral glass) and probably as an impurity in hauyne Na 3 Ca(Si 3 Al 3)O 12 (SO 4). [ABSTRACT FROM AUTHOR]

Highlights • The production of expanded clay granulate was investigated in this paper. • Attention was focussed upon the kilning phase for fresh clay cooking and expansion. • Hard coal or Durum wheat (DW) straw was considered to fuel the rotary kiln line. • Life Cycle Assessment was performed for comparison of the two fuel-related plants. • The DW-related plant resulted to be the most environmentally sustainable. Abstract Straw can be valorised through a set of unconventional applications other than the traditional ones being mainly related to livestock breeding. It can be utilised in bioenergy field as renewable feedstock for anaerobic digestion and other biological processes, or as fuel for direct combustion. However, it can also find suitable application in buildings as a multiple-function material (i.e. enveloping and insulation) or for production of other building materials. This paper investigates an Expanded Clay Granulate (ECG) production system in Sicily where straw is used as fuel in the cooking/expansion process, and so contributes both fields: buildings and bioenergy. In this study, the authors carried out a comparative Life Cycle Assessment (LCA) according to the subject International Standards, to environmentally validate shifting from hard coal to Durum Wheat (DW) straw as fuel for cooking and expansion of input fresh clay in a rotary kiln line. Study development provided the definition of the system functional unit and boundaries: the former was represented by the production of thermal energy as required for the making of 1 m3 ECG, depending upon whether the kilning phase is fuelled with hard coal or DW straw. Whilst, the latter were designed to include all processes for which differences were recorded due to the change in the fuel utilised. The study documented that, despite the environmental impacts associated with DW straw production, the hard coal fuelled system is far more impacting than that providing straw utilisation, mainly because of the related huge emissions of carbon dioxide. [ABSTRACT FROM AUTHOR]

The restoration of soil fauna on a spoil heap is a strong indicator of successful reclamation. The studies were conducted on two types of materials: bare rock (BR) and BR with topsoil (TS) which were applied during coal spoil reclamation and three vegetation types. Four variants investigated included natural forest succession on BR (Succession_BR) and TS (Succession_TS), afforestation (Reclamation_TS) and afforestation with Robinia pseudoacacia (Robinia_TS). Soil pH, soil organic carbon (SOC) and total nitrogen (TN) content, and soil texture were measured in 0–10 cm layers. Earthworms were collected using hand sorting method, and enchytraeids were collected using wet extraction with the heating method. The investigated soil had varying pH values from 5.3 in a BR to 7.2 in Robinia_TS. The highest content of SOC and TN were in Successinon_BR, and the lowest was in Succession_TS. Enchytraeids density was in the following increasing order: 275, 2982, 3001 and 4548 ind m−2 for Succession_BR, Robinia_TS, Succession_TS and Reclamation_TS, respectively. Earthworm density ranged from 0 ind. m−2 in the Succession_BR through 116 ind m−2 and 120 ind m−2 in Reclamation_TS and Succession_TS, respectively up to 162 ind m−2 in the Robinia_TS. The reclamation treatment was a major driver for soil fauna development while vegetation type was of secondary importance. Investigated soil fauna was positively related to pH value and clay content. The most stimulating variant for the development of earthworms and enchytraeids was the application of reclamation with various tree species and the planting of Robinia pseudoacacia on the topsoil. [ABSTRACT FROM AUTHOR]

This work presents the results of an experimental study on the properties of tar that originated from underground coal gasification (UCG) trials. Two in situ experiments of UCG were performed using oxygen as the gasification agent under the HUGE and HUGE 2 projects. Trials were conducted using different configurations of the fire channel, gasification time and method of raw gas collection and purification. The obtained tars were analysed over a wide range of parameters that are typical for the assessment of the quality of conventional coke oven tar. The results of the analysis showed that in terms of physical–chemical properties, both tars are highly different from each other, as well as from typical coal tar from a coking plant. One characteristic observation of the UCG-derived tars is a higher content of ash as well as toluene and quinoline insolubles compared with a typical coke oven tar. Both tars are susceptible to thermal destruction and degradation to lighter products, and the characteristics of the coking distillation residue after heating to high temperatures is different from coke oven tar. The tested tars vary in boiling range and fractional composition. The analysis also showed that tars from UCG contain more heterocyclic compounds than does coke oven tar, and the tar from HUGE is heavier than tar from HUGE 2. The content of PAHs in the tar from HUGE is many times higher than in tar from HUGE 2 and at a similar level as coke oven tar; however, the naphthalene content in both UCG tars is many times lower compared to typical coke oven tar. The probable reasons for the differences described in this report include the tar residence time in the sampling point, as well as different extents of tar fractionation phenomena, which resulted from the distinct configurations of the gas transportation and purification systems. [ABSTRACT FROM AUTHOR]

Tests of coal samples collected from a borehole drilled in the surrounding of an underground coal gasification georeactor were conducted. This experiment was conducted for the first time in an active coal mine in Poland. The aim of the tests was to determine the extent of heat penetration around the UCG cavity during a nearly two month gasification process. The method of measuring the mean reflectance of the vitrinite index (R o ), which is more generally used to measure the degree of the coalification of organic substances in coal (macerals) under the influence of temperature, was applied. The method is still used to evaluate the usefulness of coal for producing coke. The mean reflectance of the vitrinite index determined for the collected samples and reflectograms, allowed the inference that when the georeactor was operating, the temperature in the UCG cavity reached approximately 1300 °C. Based on R o , the point in a coal seam surrounding the georeactor corresponding to the temperature of approximately 700 °C was also identified, where there were signs of the initial stage of coal transformation. The point was located 1.94  m from the boundary of the UCG cavity. Then, at the distance of 1.73 m from the boundary of the UCG cavity the point with a temperature of approximately 1000 °C was identified. The tests confirmed that it is possible to use the method of determining the mean reflectance of vitrinite index to measure the distance of influence of georeactor temperature on the rock mass. This is particularly important for underground coal gasification conducted in active mines. In the future the results will be used to predict the time of heating needed for coal deposits to become gasified, based on laboratory tests and coal type. [ABSTRACT FROM AUTHOR]

This letter deals with the in-situ determination of important inorganic gas phase species in high temperature gasification product gas. The fuels are waste wood and German hard coal which were co-gasified at 1500 °C in lab-scale experiments. The release of the vapour species 34 H 2 S + , 36 HCl + , 56 KOH + , 58 NaCl + , 60 COS + , 64 SO 2 + , and 74 KCl + was determined online by a Molecular Beam Mass Spectrometer. The experimentally determined data sets were compared to calculated data sets in order to distinguish the underlying release mechanisms. The release behaviour of the inorganics 34 H 2 S + , 36 HCl + , 60 COS + , 64 SO 2 + and 58 NaCl + cannot be attributed to simple mixing and dilution effect only. Further, it is shown that the release of these inorganics is significantly influenced by secondary reactions, e.g. competitive reaction with S and Cl. [ABSTRACT FROM AUTHOR]

Chemical looping combustion (CLC) is an emerging CO 2 capture technology utilizing two interconnected circulating fluidized beds (CFB). An oxygen carrier is oxidized in the air reactor and reduced in the fuel reactor. In comparison to a classic oxyfuel process, no air separation unit is required to provide the oxygen needed to burn the fuel. The solid fuel, such as coal or biomass, is gasified in the fuel reactor, and the products from gasification are oxidized by the oxygen carrier. This work presents results of 110 h autothermal and partial autothermal CLC operation with ilmenite and iron ore as oxygen carriers. Hard coal and a fuel blend of hard coal and torrefied biomass were used as fuels. The results show that the oxygen demand of the fuel reactor required for a complete conversion of unconverted gases was in the range of 27%. At the same time, the carbon capture efficiency was low in the present configuration of the 1 MW th pilot. This means that unconverted char left the fuel reactor and burned in the air reactor. The reason for this is that no carbon stripper unit was used during these investigations. Some possible modifications like an oxygen carrier with oxygen uncoupling, a lower fuel feeding point or a secondary fluidization of the fuel reactor could significantly enhance the carbon capture efficiency. [ABSTRACT FROM AUTHOR]

A Colombian hard coal was stepwise pyrolyzed from 200 to 800 °C, and the resulting changes in surface and material properties were investigated by thermogravimetric analysis and volumetric adsorption techniques as well as by density, surface area, ATR-IR and GC/MS measurements. It was observed that a loss of volatile compounds occurred up to a pyrolysis temperature of 600 °C. These compounds were identified as CO, CO 2 and H 2 O and mainly large substituted aromatic compounds and long-chain hydrocarbons. The loss of functional groups was also monitored by a decrease of related IR bands. The devolatilization was found to cause an increase in density and surface area; the adsorbed amount of CO 2 and O 2 increased in this temperature region as well. The char pyrolyzed at 600 °C was the only sample with a hydrophobic surface. Increasing the temperature to 800 °C led to no further mass loss, but to a structural reorganization of the char indicated by the reappearance of aromatic IR bands. This high-temperature restructuring resulted in a decrease of density, surface area and adsorbed gas amount. [ABSTRACT FROM AUTHOR]

In this article, the results from a pilot-scale, underground coal gasification (UCG) experiment conducted in an operating coal mine “Wieczorek” were presented. The 60-day gasification trial demonstrated that through the appropriate selection of the test site and by applying all safety standards essential for the coal mining industry, UCG in an active mine can be conducted safely and efficiently. The idea of the technical realization of the UCG process, as well as selected gasification results, such as the primary mass balance parameters, gas production rate, coal consumption rate, coal gasification efficiency and the changes in gas composition, were presented. [ABSTRACT FROM AUTHOR]

The aim of the experimental works presented in this paper was to develop a method using wavelength dispersive X-ray fluorescence spectrometry (WDXRF) in order to determine the content of 16 rare earth elements (REEs) and the concentration of the said elements in 169 samples of combustion ash of coals coming from ten Polish coal mines, as well as to validate the method. It was found out that there is a clear diversity in the levels and ranges of the variability of REEs occurrence in coal ashes. The average content of cerium, lanthanum , and scandium amounts to 198.8 μg ∙ g − 1 , 76.5 μg ∙ g − 1 , and 52.4 μg ∙ g − 1 respectively, whereas for such metals as europium, holmium, lutetium, terbium, and thulium, the average content does not exceed the level of 5 μg ∙ g − 1 (the average content for these metals amounts to 1.2 μg ∙ g − 1 , 1.4 μg ∙ g − 1 , 0.3 μg ∙ g − 1 , 1.3 μg ∙ g − 1 , and 0.6 μg ∙ g − 1 , respectively). In addition, this paper presents an analysis of data obtained by means of hierarchical clustering analysis. Simultaneous interpretation of the dendrogram of objects (coal ash samples) and the color map of the experimental data allowed a more in-depth analysis of the relationships between the clustered coal ash samples from different coal mines and the content of the rare earth elements. [ABSTRACT FROM AUTHOR]

Highlights: [•] Release mechanisms of Na-, K-, S-, and Cl-species for co-gasification of coal and petcoke. [•] Effect of the mode of occurrence of fuel constituents on the release. [•] Dilution effect explains release trends of NaCl and HCl for all fuel blends. [•] Dilution effect explains release of H2S and COS for blends of hard coal/petroleum coke, but not for hard coal/refinery residue. [ABSTRACT FROM AUTHOR]

Fly ash, which is a by-product of combustion in furnaces or boilers, is used in certain materials as an additive for waste recycling. The optical properties of fly ash and the effects on the heat transfer phenomena of materials used in engineering applications differ and depend on the kind of solid fuel and the combustion conditions. The morphological and the radiative properties of fly ash samples of Turkish lignite, biomass, and hard coal that are burned in different thermal power plants were studied herein. The samples, which were collected from cyclones, were morphologically examined using scanning electron microscopy (SEM) images, and their chemical compositions were analysed by energy dispersive x -ray spectroscopy (EDX). Absorbance measurements were made in the wavelength range from 2.5 to 25 μm, and the discrete dipole approximation (DDA) was applied for a numerical assessment of the radiative properties of the samples. The measured absorbance values of all samples for particle diameters of 25 and 75 μm displayed significant differences in the related wavelength range. The most prominent change was observed in the biomass sample, and the hard coal fly ash had the lowest absorbance values in the related spectrum range. Although the particle shapes of lignite and biomass fly ashes are not same, the changes in the measured absorbance values were similar. The effects of the k index of the complex refractive index (CRI) on the radiative properties were examined for values of 0.01, 0.1, 0.3, 0.5 and 1.0. According to the measured absorption values and the calculated absorption efficiency results, the k index may be between 0.3 and 1.0 at the related wavelength range. It was concluded that the effects of the particle size and absorption index of fly ash on the heat transfer properties are important in the specified wavelength range. [Display omitted] • The absorbance properties of lignite (low-rank), biomass and hard coal fly ashes are investigated. • The measured absorbance values of lignite and biomass fly ashes show similarity. • The measured absorbance values of hard coal fly ash are the smallest. • The radiative properties of the samples markedly change in the wavelength range of 2.5–20 μm. • The k index of the complex refractive index (m) of the samples should be defined according to absorbance. [ABSTRACT FROM AUTHOR]

Abstract: Biomass cofiring in coal power plants (with thermal contributions of typically 5–20%) is an interesting option to mitigate CO2 emissions, since the additional costs are relatively minor and a secondary benefit is provided by the increased fuel flexibility. Worldwide, about 150 cofiring plants are in operation. In Germany, the electrical power potential for biomass cofiring in coal plants is about 28 TWh per annum, assuming a 10% replacement of coal combustion by biomass. In this paper, we study the economic potential of biomass cofiring in hard coal power plants in Germany. To this end, we identify suitable biomass input fuels, investment and operating costs, and the profitability of cofiring investments. In a sensitivity analysis, we check for the robustness of the results gained, and in a Monte Carlo simulation (MCS) uncertainties are explicitly taken into account. We find that both regional and international biomass supplies are relevant, and that the cost effectiveness of cofiring is strongly affected by the prices for biomass, coal and CO2 permits, while investment and operating costs only have a modest influence. According to our calculations, electrical power generation costs attributable to biomass combustion for a plant put into operation in 2020 are between 70 and 75 € MWh−1, while the average costs of biomass fuel from various sources and markets are calculated to be around 4.1 € GJ−1. [Copyright &y& Elsevier]

Abstract: The kinetics of polish hard coal and its char gasification using carbon dioxide as gasifying agent was studied at atmospheric pressure between 293 and 1223K at different linear heating rates. Calculations using isoconversional method showed that coal gasification has two separate steps: pyrolysis in the range from 600 to 850K and gasification in the range from 1000 to 1273K. This proves the additivity of pyrolysis and gasification steps. The apparent activation energy calculated using the F1 model for coal char gasification is equal to 245kJ/mol, and log A is equal to 7.41/s, which is similar to the value obtained by the isoconversional method. Coal gasification reaction with carbon dioxide is faster and takes place in a lower temperature range than the gasification process of the char obtained in a separate process. The stabilized and chemically deactivated char is harder to gasify, and the same conversion is achieved at the higher temperature. The estimated shift may be as high as 150K. [Copyright &y& Elsevier]

Abstract: The effect of drainage and outburst elimination are obviously different between soft and hard coal sub-layers under per-drainage of coal seam, and hence, the location of per-drainage borehole related to the soft sub-layer is the key that determines whether the outburst can be eliminated in whole coal seam. This paper discusses the differences between soft and hard coal from fields of pore radius distribution, pore structure, surface area and permeability, and the per-drainage effect was numerical simulated under different distance between per-drainage hole and soft sub-layer. Moreover, the optimum hole arrangement of outburst elimination is given in the paper. The result of research shows that the macro-pore with aperture that is larger than 50,000nm, is dominant at about 50% in hard coal, correspondingly, the micro-pore with aperture less than 100nm accounts for about 41.23% in soft coal. The surface area of soft coal is 1.6 times as that of hard coal. The residual gas content in soft coal sub-layer is obviously more than it in hard coal sub-layer under the same pre-drainage condition. To 5.5m-thick coal seams which top is a soft coal sub-layer of 0.5m-thick, pre-drainage gas can eliminate danger of gas outburst in whole coal seam at the seam time after 455days drainage when the per-drainage holes are 1.0m distances from the soft coal sub-layer. [Copyright &y& Elsevier]

Abstract: Series of modified with vanadium, cobalt, nickel, manganese and copper montmorillonite were compared as additives for desulfurization during combustion of hard coal. Samples of coal with added montmorillonite were subject to a 2h a flow reactor in the air atmosphere, at 1173K. The weight ratio of montmorillonite:coal was 1:500. Changes in sulfur dioxide contents in flue gasses caused by the additive were investigated by means of an exhaust gas analyzer. During the co-combustion of coal with montmorillonite modified with vanadium was removed 58–84% of SO2 from flue gasses. Application of Co and Ni led to a reduction in SO2 emissions by 35–53% and 83–90%, respectively. For additions of Ni, Cu and Mn was observed to reduce emissions of SO2 by 60–73%. As a result of using diversified preparatory procedures on montmorillonite additives DESOX obtained were materials with different physicochemical properties. Sulfate forms obtained after the combustion process with addition of montmorillonite additives are amorphous and very well dispersed. [Copyright &y& Elsevier]

Abstract: In the study the research potential offered by the Scanning Electron Microscope to investigate into the surface of hard coal for mineral substances, especially of chlorine, was utilized. The identification of such substances – basing upon the resulting X-ray spectra and photographs – allowed one to corroborate the usefulness of further investigation step – viz. leaching. Variable parameters in those investigations were: grain size, leaching temperature, time and leaching cycles. Of great importance for the efficiency of the leaching process is granulation. The smaller the grain of coal, the more chlorine was removed because the opening of pores closed in the process of fragmentation increases the carbon surface available for water molecules. [Copyright &y& Elsevier]

Abstract: The main goal of the study presented in the paper was an experimental comparison of the underground lignite and hard coal seams air gasification simulated in the ex situ reactor. In the study lignite and hard coal were gasified with oxygen, air and oxygen enriched air as gasification agents in the 50- and 30-h experiments, respectively, with an intrinsic coal and strata moisture content as a steam source. Application of air as a sole gasification agent was problematic for a resulting rapid decrease in temperatures, deterioration of gas quality and, finally, cessation of gasification reactions. Use of oxygen/air mixture of an optimum ratio led to valuable gas production. In lignite seam gasification with oxygen/air (of 4:2 volume ratio) the average H2 and CO contents in product gas were 23.1vol.% and 6.3vol.%, respectively, and the calorific value was 4.18MJ/m3, whereas in hard coal gasification with the oxygen/air ratio (of 2:3 volume ratio) the average H2 and CO contents in produced gas were 18.7vol.% and 17.3vol.%, respectively, and product gas calorific value equaled 5.74MJ/m3. [Copyright &y& Elsevier]

Abstract: Groundwater pollution is considered the most serious potential environmental risk related to the underground coal gasification technology (UCG). A variety of hazardous water-born contaminants have been identified during different UCG operations conducted so far, and in some locations long-term groundwater contaminations were observed. Characteristic organic UCG-related pollutions are mostly the phenols, benzene with its derivatives, polycyclic aromatic hydrocarbons, and heterocycles. In the inorganic array, ammonia, cyanides, sulphates, and heavy metals are usually identified. Although the fact that the coal rank affects the contaminants’ formation and release processes during the UCG is known, the information is still scarce. The main goal of the study presented in the paper is the comparison of the processes of formation and release of water contaminants produced during UCG simulations on hard coal and lignite. Significant differences in the qualitative and quantitative description of the contamination profiles were identified for both types of coal. From the analysis it follows that the formation of contaminants is the function of coal rank, the elemental composition of coal, and the gasification temperature. In case of hard coal gasification, the total load of inorganic and organic pollutants in the process water is substantially higher in comparison to lignite. It has been identified that the reaction pH is the parameter affecting concentrations of heavy metals in process waters. The macromolecular structure of coal and temperature were recognized as the main factors governing the distribution of organic compounds. The highly aromatised structure of hard coal becomes the source of substantial quantities of aromatic compounds; still the contribution of smaller species (one or two rings) is high. For lignite, the relative contributions of higher aromatics are greater as compared to hard coal. [Copyright &y& Elsevier]

Abstract: The present study investigates the heavy metal content of coal fly ash (FA) samples coming from three different sampling points (secondary cyclone, cooler and filter) of a pilot plant combustion facility. The combustion experiments were carried out in a 0.1MW Circulated Fluidized Bed (CFB) boiler using South African coal, with the addition of limestone for sulfur capture. FA was tested for the presence of selected heavy metals using inductively coupled plasma optical emission spectrometry (ICP-OES); batch leaching tests were conducted as well. The samples were also characterized in terms of their microstructure, chemical and mineralogical composition, total surface area and particle size distribution. Most of the studied metals (Cd, Cr, Cu, Ni, Mn, Zn) showed enrichment in the fine, filter FA particles, while Pb was mostly concentrated in the cooler sample. Regarding leaching characteristics of the examined samples, Cr was found to occur in considerable amounts. Although the use of CFB technology for the combustion of solid fuels steadily gets bigger worldwide, only a very limited number of studies have environmentally assessed CFB-coal FAs to date. Thus, the current study aims to contribute toward building a more integrated knowledge on the environmental impact of this abundant power production by-product. [ABSTRACT FROM AUTHOR]

Abstract: Na-, K-, Cl-, and S-species released during thermal conversion of coal can cause several problems such as fouling, slagging and corrosion, especially in gas turbines and heat recovery systems. To reduce this problems an enhanced understanding of the underlying release mechanisms for Na-, K-, Cl-, and S-species is needed. Therefore, basic investigations have been performed in an atmospheric lab-scale tube furnace at 1400°C under gasification and combustion conditions. Hot gas analysis has been carried out by molecular beam mass spectrometry. The release of H2S, HCl, K+, NaCl, COS, and SO2 has been qualitative and quantitative analysed and correlated with the coal composition. The results show a strong dependence of coal composition and reaction atmosphere on the release of Na-, K-, Cl-, and S-species. Additionally, thermodynamic equilibrium calculations with the software package FactSage 5.4.1 have been undertaken for comparison with the experimental results. [Copyright &y& Elsevier]

Numerous environmental polycyclic aromatic hydrocarbon (PAH) sources have been reported in literature, however, unburnt hard coal/ bituminous coal is considered only rarely. It can carry native PAH concentrations up to hundreds, in some cases, thousands of mg/kg. The molecular structures of extractable compounds from hard coals consist mostly of 2–6 polyaromatic condensed rings, linked by ether or methylene bridges carrying methyl and phenol side chains. The extractable phase may be released to the aquatic environment, be available to organisms, and thus be an important PAH source. PAH concentrations and patterns in coals depend on the original organic matter type, as well as temperature and pressure conditions during coalification. The environmental impact of native unburnt coal-bound PAH in soils and sediments is not well studied, and an exact source apportionment is hardly possible. In this paper, we review the current state of the art. [Copyright &y& Elsevier]

Abstract: The sequestration of CO2 by pumping it into deep coal seams is being investigated. It is therefore worthwhile to gather the information available on the interactions of CO2 with coals and the effects of CO2 on coals'' properties in order to attempt a prediction of the long-term effects of sequestration. In the experiment, the volumetric changes of the coal matrix were monitored for a low-rank coal (Cdaf 84.14; Vdaf 33.4) for mixtures of CO2 and CH4 of different proportions and single gases. In the case of the sorption of a mixture of gases, the course of the kinetics of expansion of the coals studied indicates a lack of visible deformation of the coal structure. The observed phenomenon of a higher affinity to CO2 and displacement of CH4 by this sorbate may, provide one of the reasons for abrupt disturbances in the rock, by changes in the bed permeability, caused by competitive processes of sorption and desorption. [Copyright &y& Elsevier]

Abstract: Turkey becomes more dependent on foreign countries for fulfilling its energy needs day by day. While 77% of the overall primary energy consumption in 1970 was met by the domestic energy sources, this percentage decreased to 28% in 2003. As for the electricity production, while 89% of the produced electricity was produced by using the domestic sources, this percentage decreased to 68% in 1970 and 44% in 2003. The percentage of dependence on foreign countries increased year by year and reached 56% in 2003. The energy sources of Turkey are renewable energy sources and coal. If both of these energy sources are used effectively, Turkey will have a capacity to produce its overall electricity production using its own sources. The incorrect policies applied in Turkey introduced oil as a primary energy source for electricity production in 1970s and Turkey defrayed the cost of this wrong application severely by oil crisis. After 2000, natural gas, which was completely imported, was introduced as an energy source and its share in electricity production reached 45%. It is vital for Turkey to question this situation in order to ensure a sustainable development using reliable energy sources. [Copyright &y& Elsevier]

Abstract: The paper reports the results of experiments concerning the sorption/desorption processes, observed under laboratory conditions, in two types of coal extracted from operational coal-mines in Poland, using CH4 and CO2 to observe their relative inter-reaction with the coal samples when introduced in varying proportions and conditions. Numerous studies concerning the sorption/desorption phenomena have described the operational mechanisms and the relationship of mine gases to the organically-created coal-body in mines. The differences in the behaviour of certain gases is twofold: firstly the essentially different characteristics of CO2 and CH4, and secondly the structure of the coal-bed itself: its degree of metamorphism and content of macerals. From the results yielded, it was observed that the divergence of the isotherms of sorption of CH4 and other gases in comparison with the isotherms of sorption of CO2 and a CO2/CH4 mixture differed and that the curve on the sorption isotherm was more clearly distinct after the introduction of CO2 molecules to the system: coal with a higher degree of metamorphism—CH4, which is closely related to the rigidity of the structure according to the level of metamorphism. Since coals with higher carbon content exhibit lower molecular bonding than low-carbonised coals, the characteristic feature of the bonds in the first case is their mobility. Knowledge of the physical and chemical properties of hard coals, as well as their interaction with mining gases, is of great use in solving problems concerned with the extraction of methane from mines or its storage in goafs. [Copyright &y& Elsevier]

Biological methane production from coal seams through their biological conversion is one of the methods that have been postulated to utilize unmineable resources. Furthermore, energy production from methane is considered less environmentally-harmful than the combustion of coal. In the current study, meta-bituminous coal extracted from the Upper Silesian Coal Basin (USCB) was investigated in terms of its potential for biological methane formation. Both natural and stimulated (by bioaugmentation) methanogenic activity was assayed. Consortia of microorganisms selected from highly methanogenic peat (Moszne peat bog) and sediments (Szczecin subsidence reservoir) were enriched on various media and used for coal bioaugmentation. It was found that both peat- and sediment-derived microbiota are capable of coal degradation, with the latter being more effective. FT-IR revealed changes in the utilization patterns of organic matter by each community that were linked to differences in the stable carbon isotope indices of the gases produced. The ability to cleave aromatic rings was recognized as the most important feature of the microbial community used in the production of methane from the tested coal. • Lake sediment and peat microbiota are able to stimulate coal biogasification. • FT-IR revealed structural changes in coal caused by autochthonous microbiota. • Lake sediment microbiota have an impact on coal dearomatization. • Peat microbiota contribute to the degradation of coal-associated carboxylic groups. • Stable isotopes suggest different utilization of coal fractions by various types of microbiota. [ABSTRACT FROM AUTHOR]

The aim of the study was to analyse the effect of temperature on the sorption and diffusion of CO 2 and CH 4 on hard coal. Four coal samples, characterized by various degrees of coalification, were used in the research. The sorption measurements were carried out in three temperature values: 278 K, 313 K and 353 K and for the consecutive pressure values of 1 bar, 5 bar and 15 bar. Langmuir's sorption capacity in relation to CH 4 and CO 2 was the highest for the coal with the lowest degree of coalification and was 32.15 cm3/g and 76.4 cm3/g respectively. The lowest Langmuir sorption capacity in relation to CH 4 and CO 2 were obtained for medium-rank coal (19.23 cm3/g and 29.26 cm3/g) and high-rank coal (20.33 cm3/g and 32.89 cm3/g). The temperature growth resulted in a reduction of the sorption capacity of coal in relation to CH 4 and CO 2 , and that decline was exponential in relation to temperature. The absolute decreases in the total sorption capacity were from 0.03 cm3/g to 0.21 cm3/g in relation to CH 4 , and from 0.10 cm3/g to 0.51 cm3/g in relation to CO 2 , per 1 K temperature increase. Within the measurement temperature range of 278–353 K, no „critical temperature point", above which there is no reduction in CH 4 and CO 2 sorption, was observed. An increase in the temperature pushed up the values of the effective diffusion coefficients, in relation to CH 4 by more than one order of magnitude, and in relation to CO 2 by approximately four times. A decrease in the selectivity of CO 2 /CH 4 was also observed along with the coal rank. The ratio of effective diffusion coefficient values D e C O 2 / D e C H 4 for all the investigated coal samples declined strongly along with temperature growth. • The temperature relationship between the parameters of sorption CH 4 and CO 2 transport in coal was investigated. • Coal samples with various degrees of coalification were used. • The temperature growth resulted in a reduction of the sorption capacity of coal in relation to CH 4 and CO 2. • The CO 2 /CH 4 selectivity factor decreased with increasing coal rank. [ABSTRACT FROM AUTHOR]

• Simultaneous analysis of heavy pyrolyzates and quantification of light pyrolysis gases. • Deans switch enables time-efficient analysis of broad pyrolysis product spectra. • Hard coal released increased amounts of light hydrocarbons as pyrolysis products. • Lignites mainly released oxygenated pyrolysis gases. • Phenol derivatives and long-chain hydrocarbons identified as condensable pyrolyzates. The pyrolysis of solid fossil fuels and biomass is of great relevance, because it influences the combustion kinetics of these fuels, and the pyrolysis products are potential raw materials for further chemical processing. The aim of this work was to develop a pyrolysis system able to separate the whole variety of pyrolysis products during one pyrolysis experiment without the need to replace GC columns for improved resolution. A conventional pyrolysis system equipped with a coupled gas chromatography (GC)/mass spectrometry (MS) detector was extended by a second GC with a fused-silica capillary column and a thermal conductivity detector (TCD). The coupled pyrolysis–GC/MS–GC/TCD system was used to investigate the evolved pyrolysis products of two lignites and a hard coal enabling the qualitative detection of pyrolyzates (GC/MS) while simultaneously quantifying the light gases (TCD). Benzofuran, catechol, and a preference for even-numbered hydrocarbon pyrolyzates in addition to a higher pristene/heptadecane ratio were found to be characteristic for the two studied German lignites in comparison to the Columbian hard coal as well as a higher release of especially oxygen-containing light gases. [ABSTRACT FROM AUTHOR]

The present work is dedicated to the experimental investigation of the influence of fuel-type and oxidizer composition upon flame structure and behaviour of swirl-stabilized pulverized coal flames. Detailed flame measurements are conducted by employing a combination of flame-intrusive and non-intrusive measurement techniques which can provide complementary data about flow fields, major product species and radiative heat transfer from the flames. Four flames with constant thermal output (60 kW th ) and stoichiometry are employed. While previous studies of the same configuration were limited to one fuel (Rhenish lignite), the influence of fuel type is investigated here by additionally measuring the same set of parameter for Prosper Haniel bituminous coal. Two reactive atmospheres (conventional air and oxy-fuel with an O 2 / CO 2 ratio of 25 / 75 vol %) are employed to investigate the impact of changes in oxidizer. The combined analysis of measurement results show that flame length is predominantly controlled by the effective swirl intensity when the flame ignites and stabilizes in the vicinity of the burner. Further on, measurements from narrow-band flame imaging and heat flux measurements show that the location of peak combustion intensity is determined by the flow inlet conditions (at the burner). This being key parameters, that could be employed to match heat transfer profiles when transitioning from conventional air firing to oxy-fuel in existing power plants. [ABSTRACT FROM AUTHOR]

To increase the efficiency of thermal power plants, we have recently proposed and analyzed a novel exhaust heat recovery process called hot air recirculation (HAR), applied to a brown-coal-fired power unit as a test case. However, the performance of HAR, applied to a hard coal-fired power unit, is not clearly understood yet. In this study, the HAR process was redesigned to match the actual supply air and flue gas layout of a hard-coal-fired boiler. The thermo- and techno-economic performances of HAR, as well as the conventional bypass flue (CBF) process, applied to a 600 MW hard-coal-fired power unit, were analyzed in detail. The results indicate that, when the boiler exhaust heat is recovered from 122 to 90 °C, the net coal savings, initial capital cost, and payoff period of HAR are 3.49 g/(kW·h), $1.473 million, and 1.34 years, respectively, whereas those of CBF are 2.98 g/(kW·h), $2.528 million, and 3.04 years, respectively. Therefore, it is established that HAR can benefit a hard-coal-fired power plant with a greater saving on coal consumption and a more economical project investment, in addition to providing a safe and reliable operation, as compared to similar processes. • >The HAR process was designed for exhaust heat recovery from a hard-coal-fired boiler. • >The techno-economic performance of HAR was analyzed with hard-coal-fired power units. • >HAR exhibits advantages in the thermo- and techno-economic performance over CBF. • >An extra efficiency increase is attained when HAR is used for a hard-coal-fired unit. [ABSTRACT FROM AUTHOR]

Abstract: Coal flotation studies were carried out in ultrasonically assisted flotation cells. Representative hard coal slime samples from Prosper-Haniel Coal Preparation Plant located in Bottrop, Ruhr Region of Germany were used for this purpose. A Wemco type flotation cell was fitted with transducers and tests were carried out at variable frequency and power. The reagent for coal flotation was Ekofol-440 with variable dosages during conventional and ultrasonic flotation experiments. The results showed that ultrasonic coal flotation yields more combustible recovery and lower ash values in concentrates than conventional flotation by using similar reagent dosages. These results are explained on the basis of efficient surface cleaning of the coal particles. [Copyright &y& Elsevier]

The aim of this research was to compare the structure, sorption properties and the kinetics of sorption to CO 2 and CH 4 in nanomaterials with a very orderly structure and in structurally heterogeneous coal. The authors tested synthetic materials such as multiwall carbon nanotubes (MWCNT) and reduced graphene oxide (rGO) as well as natural materials such as coals of various ranks. The value of the surface area of Langmuir and Brunauer, Emmett and Teller, in MWCNTs and rGO was much higher than in the coal. The course of CH 4 and CO 2 sorption of the materials was investigated and the parameters of sorption isotherms in the pressure of 0–2.0 MPa were determined. The nanomaterials reached the sorption equilibria much faster than the coal. The highest total CH 4 sorption capacity was found in low-rank coal. The highest CO 2 total sorption capacity was found in MWCNTs and low-rank coal. The highest relative mean drop in CH 4 and CO 2 sorption capacity resulting from the increasing measurement temperature was found in the MWCNTs and the low-rank coal. The authors analysed the courses of CH 4 and CO 2 sorption kinetics in the materials of highly different structures. The kinetics of CH 4 and CO 2 accumulation in MWCNT and rGO nanomaterials progressed almost instantaneously, and their rate was many times higher than in the case of kinetics on hard coals. • Multi-wall carbon nanotubes, reduced graphene oxide and two types of hard coals were characterized. • The structure, sorption capacity and kinetics of sorption of carbon nanomaterials and coals were compared. • Volumetric and gravimetric sorption methods were used for the analyses. • Nanomaterials had higher surface area and a higher total adsorption capacity. • In nanomaterials, much faster sorption kinetics were obtained. [ABSTRACT FROM AUTHOR]

• The competitive sorption of CO 2 and CH 4 on hard coal where measured. • The value of the effective diffusion coefficient grew along with the content of CO 2. • An increase of CO 2 adsorbate concentration worsens the fit of the Langmuir isotherm model. • Competitive sorption of CO 2 −CH 4 on coal causes a small change of pore structure. This paper presents the results of studies on the competitive sorption using the gas mixtures CO 2 −CH 4 on hard coal from a Polish coal mine. The experiments were conducted at an original research stand under isobaric conditions, for the pressure values of 1, 2, 5, 10 bar, and at the temperature of 313 K. The value of the effective diffusion coefficient D e grew along with the content of CO 2 in the gas mixture, while for the sample saturated with pure CO 2 the value of D e was higher than in the sample saturated with pure CH 4 by more or less one order of magnitude. The Langmuir and Langmuir-Freundlich sorption isotherms were determined. It was observed that an increase in the sorption corresponding to the filling of monolayers in both isotherms occurred along with a growth of the CO 2 concentration in the gas mixture. The total pore volume increased by 19.0–29.7% in a sample saturated with pure CO 2 as compared to a sample saturated with pure CH 4. Pore distribution was similar. At the same time, in the sample saturated with CO 2 , the pore volume was higher than in the case of other samples for almost entire diameter range. [ABSTRACT FROM AUTHOR]