Polish Lignite Research Articles

Petrographic composition of Polish lignite and its possible use in a fluidized bed gasification process

The main objectives of the study include the estimation of the proportion of lithotypes and macerals in lignite deposits and the determination of petrographic criteria for the assessment of quality and possible use of lignite in fluidized bed gasification process. Measures taken to meet the objectives included field research and laboratory studies. The study included results from 293 samples of low-rank coal from Polish deposits. The data used in the study included currently exploited, abandoned and prospective lignite deposits. Lignite deposits were divided into seven regions: A—Western, B—Legnica, C—Wielkopolska, D—Konin, E—Łódź–Bełchatów, F—North, and G—Radom. Polish lignite deposits include mainly humic coal, with four basic lithotypes identified: xylitic coal, xylo-detritic coal, detro-xylitic coal and detritic coal. Dominating lithotypes include detritic coal and xylo-detritic coal. Fibrous xylites, present only in minor amounts in Polish lignite, have a negative influence on coal gasification process (grinding). The highest content of fibrous xylites is observed in the Konin region. Petrographic composition of coal was determined on the basis of maceral group and the sum of gelified macerals. It has been found that the influence of macerals from the huminite group on fluidized bed gasification is significant. The average content of this component in tested coal is 89%. Meanwhile, average content of macerals from the liptinite group in Polish coal is 8%, while for macerals from the inertinite group it is 3%. The content of mineral matter in lignite deposits is a highly variable parameter. According to the proposed scheme, in order to be suitable for fluidized bed gasification, the maceral composition of the coal should contain at least 80% huminite, while the sum of the macerals from the inertinite group and mineral matter should be less than 20%. Taking into account the whole region, it should be noted that petrographic composition of lignite in almost all of the deposits allows its use in the process of fluidized bed gasification. However, limited usefulness in this process can be observed in some of the deposits containing bituminiferous lignite.

Relationship between random reflectance of ulminite B/collotelinite and technological parameters of Polish low-rank coal

The main objective of the study is to determine the correlation between random reflectance of ulminite B/collotelinite and chemical and technological parameters in Polish low-rank coals. The study includes results from 284 samples of humic low-rank coal from Polish deposits tested by the author and supplemented with data from the literature. Research on the properties of different types of coal include: technical analysis, physico-chemical and petrographic analysis. Among the studied deposits, the average random reflectance (Rr) is 0.28, with a standard deviation of 0.06 and the coefficient of variation at 20%. Gross calorific value in the tested coal varies from 7.25MJ/kg to 26.30MJ/kg, with average value of 12.46MJ/kg. Average total moisture in Polish low-rank coal deposits is 47.8% and ranges from 15% up to 60%. Carbon content in the tested coal recalculated to dry ash-free basis varies from 56.4% to 79.0% while on average it is 68.1%. Basic parameters of Polish low-rank coal are characterized by low variability, while gross calorific value and carbon content are of very low variability. The highest variability is observed in case of ash content and sulphur content. The correlation between random reflectance, gross calorific value and carbon content is very high. There is high correlation between moisture, net calorific value and random reflectance. The analysis shows that it is possible to calculate random reflectance of ulminite B/collotelinite from gross calorific value, carbon content and total moisture with a correlation coefficient equal to 0.97. By analyzing the correlation between the measures of the degree of coalification and using multiple regression, it has been found that the suborder of Polish lignite can be determined with use of the random reflectance of ulminite B/collotelinite. Based on the results of multiple regression, it is proposed that the boundary between low-rank C (soft brown coal) and low-rank B (dull brown coal) for Polish low-rank coal should be set at a random reflectance of ulminite B equal to 0.35%.

Changes of the lignite seam architecture — A case study from Polish lignite deposits

The architecture of a lignite seam is not only of great cognitive importance, but it is also important for the planning and exploitation of lignite. Therefore, this paper presents the factors that had or could have an impact on the deformation of lignite seams. All the currently extracted lignite seams in Poland of the Early and Middle Miocene age have been considered. Their development, as indicated by the thickness from a few to nearly 250m, was controlled by intensive subsidence during deposition of the peat reaching a maximum of more than 700m. Most cases that are theoretically possible were supported by data from boreholes and observations in existing opencast mines. Both surfaces bounding the lignite seam, that is, bottom and roof, were taken into account.The following factors could impact on the formation of the bottom of the lignite seam: the paleotopography before the development of peat mires and syn- and post-depositional tectonics. On the other hand, the roof of the lignite seam could be deformed by such geological processes as: the post-depositional tectonics, post-depositional erosion and compaction. The causes of changes in the bottom of the lignite seam deformations are relatively easy to explain. In contrast, the causes of the roof of the lignite seam irregularities are still poorly understood. In the latter case, often overlooked or underestimated, is the impact of compaction with maximum sizes ranging up to 450m. In fact, the compaction of peat/lignite often plays a major role in the folding of the roof of the lignite seam.

On the use of ethanol for evaluating microporosity of activated carbons prepared from Polish lignite

Microporous activated carbons prepared by KOH chemical activation or steam activation from lignite were characterised by adsorption of N2 at 77K and CO2 at 298K. Subsequently, the adsorption of ethanol was carried out and complemented by adsorption of benzene and cyclohexane. The isotherm analysis included application of the αs method using ethanol reference data obtained here by also studying non-porous carbon blacks. The work confirmed that ethanol is an experimentally convenient adsorptive to use and leads to results in overall agreement with those obtained using other probe molecules. Of particular interest was the observation that ethanol can gain access to the whole microporosity even in the case of samples containing constricted micropore entrances. It was also possible to show that certain furnace carbon blacks contain intrinsic microporosity which is more difficult to unambiguously detect by adsorption of N2 at 77K. On the other hand, the results also suggested that the exact shape of the ethanol adsorption isotherm on a non-porous surface is more sensitive to the nature of the surface than has previously been found with other adsorptives.

The influence of demineralisation and ammoxidation on the adsorption properties of an activated carbon prepared from a Polish lignite

The preparation of cheap nitrogen-enriched materials with large adsorptive capacities and selectivity towards volatile organic compounds remains a challenge. Ammoxidation has been used to prepare nitrogen-enriched activated carbons using a demineralised Polish lignite. The lignite samples were demineralised by two different methods before nitrogen-enrichment by ammoxidation and physical activation in steam. The surface chemistry was investigated by elemental analysis, Boehm titration, infrared and XPS spectroscopies and adsorptive properties by a linear solvation energy relationship approach. Results show a quasi-total demineralisation and a higher reactivity towards nitrogen for the demineralised samples. The BET surface is also higher than for the non-demineralised lignite. Active carbons previously ammoxidated and demineralised are more interesting in terms of selective removal of gaseous pollutants.

Influence of minerals and added calcium on the pyrolysis and co-pyrolysis of coal and biomass

AbstractThe pyrolysis behaviour was studied of two types of biomass (pine and wheat) and a Polish lignite (Turow) in the presence of minerals and ion-exchanged calcium using a variety of laboratory-scale methods including pyrolysis–gas chromatography–mass spectrometry (py–GC–MS) and thermogravimetric analysis coupled to a FTIR spectrometer (TGA–FTIR). Ion-exchange worked well for all samples, but particularly for the biomass, and the wt% Ca introduced followed the order wheat (4·17 wt%) > pine (1·74 wt%) > coal (0·80 wt%). The degree of catalysis displayed by the calcium during pyrolysis of the ion-exchanged samples varied with the fuel used. Significant catalysis by calcium was observed in pyrolysis of pine, but only a small effect was seen for wheat and very little for coal. The inherent minerals also play a catalytic role in all the samples studied, but potassium is by far the most important in the pyrolysis of the raw wheat straw. The gases and light volatiles are influenced by the presence of catalyt...

Demonstration of plasma excited atomic resonance line spectroscopy for on-line measurement of alkali metals in a 20 kW bubbling fluidized bed

An instrument based on Plasma Excited Atomic Resonance Line Spectroscopy (PEARLS) was applied to measurements of vapor and aerosol phase Na and K in atmospheric combustion conditions. The PEARLS method is based on dissociation of alkali compounds by a direct current plasma torch and subsequent determination of alkali concentration by atomic absorption spectroscopy. The measurements were carried out in a 20 kW bubbling fluidized bed reactor during co-combustion of biomass and coal. The capability of the instrument to operate under atmospheric high-ash conditions was demonstrated. The analysis was made directly from hot (880 °C) particulate laden sample gas. The fuels were pine bark mixed with South African coal and Finnish forest residue mixed with Polish lignite. Thirty percent addition of coal or lignite to biomass reduced measured alkali concentrations by 44–64%. The reduction is explained by conversion of alkali chlorides and hydroxides to sulfates and silicates.

Identification of Organic Sulfur Compounds in Supercritical Extracts from Polish Lignite

Supercritical fluid extraction (SFE) of a Bełchatów lignite (Ro = 0.26%) was carried out with four different solvents, i.e., a toluene, 2-propanol, toluene/2-propanol, and toluene/THF mixtures, at 360 °C and 10 MPa in an apparatus with continuous flow of solvent. The type of solvent has an influence not only on the extract yield but also on the sulfur extractability. For the 2-propanol/toluene mixture the highest process yield was obtained, 43.1%. The toluene/THF mixture was shown to be the most effective solvent in terms of the extraction of organosulfur compounds (OSC). Gas chromatography−mass spectrometry (GC-MS) was used to study the distribution of OSC in the extract obtained on the SFE process. The results demonstrate that the preparation of a sample prior to GC-MS analysis has a great influence on the OSC distribution of the extract. For the raw extract with solvent, aliphatic and aromatic thiols, aliphatic sulfides, polysulfides, and the C1−C4 alkylthiophenes were detected, whereas only diphenyl sulfide, benzothiophene, and dibenzothiophene were identified after solvent removal by evaporating and final drying of the sample in a vacuum oven. Methyl thiol and methyl mono-, di-, and trisulfides seem to be originally present in the lignite. The presence of thiol and mono-, di-, and trisulfides substituted with an isopropyl group in the extract can be explained as due to the reaction of elemental sulfur with the 2-propanol used for the extraction

Mine drainage treatment in Polish lignite mining

The paper presents volumes and characteristics of water discharged from some Polish lignite open pit mines and discusses methods for its treatment. Results of research work concerned with increase in mine drainage efficiency by using processes of radiation, flocculation and filtration through a set of bog plants, iknown as grass filter are also discussed.