Polish Lignite Research Articles

The Impact of Opencast Lignite Mining on Rural Development: A Literature Review and Selected Case Studies Using Desk Research, Panel Data and GIS-Based Analysis

The future of opencast mining and energy production based on conventional resources is one of the most important issues being discussed in international forums. The whole discussion is becoming increasingly heated and takes on a special significance with the drastic increase in energy commodity prices that has occurred with the outbreak of war in Ukraine. Especially in a country like Poland, these issues are accompanied by heated discussions between miners, the government and citizens. It should be emphasised that Polish lignite mining currently produces about 35% of the cheapest electricity in Poland and also creates many jobs. The aim of this study is to assess the possibility of continuing opencast mining and its impact on rural development—both from an environmental and socio-economic point of view. The study was conducted for two municipalities in Poland where opencast lignite mining plays an important role, namely Kleszczów and Kleczew. As a result, it was found that in the case of the studied municipalities, the presence of opencast mining has contributed to their development, and the application of modern environmental protection technologies and recultivation have reduced the difficulties associated with mining. On the other hand, the decision to start mining should be the result of a comparison between the potential environmental and social benefits and damages. In some cases, mining is beneficial for community development and leads to new opportunities for agriculture and tourism after reclamation. The study is a combination of different methods, i.e., case studies, GIS remote sensing analysis (based on Landsat data) and econometric analysis for selected socio-economic data.

Socio-Economic Resilience of Poland’s Lignite Regions

The article is seeking to analyse the coal transition in three Polish lignite regions as part of the scientific discussion on a just transition, which is a big challenge, especially in the regions and countries dependent on their own coal deposits as the main source of energy. Polish lignite mines are now entering the phase-out of coal, which results from implementing the assumptions of the Green Deal and the Paris climate agreement. The article answers the following question: what is the socio-economic resilience of coal regions in the context of the projected closure of mines in the coming years? The empirical analyses are based on secondary statistical data. The analysis and comparison of basic statistical data, i.e., the level of employment and lignite extraction in three lignite regions in the period from the end of the Second World War to 2017, allowed the authors to determine the phases of the adaptive cycle in which the individual regions are. In the second part of the study, the indicator evaluation method was used in order to calculate the Socio-Economic Resilience Index for individual areas (poviats) included in the coal regions, which made it possible to assess the current resilience and its intra-regional differentiation. The obtained results, which indicate that the regions under analysis are in different phases of the adaptive cycle and reveal their territorial heterogeneity, allow us to assume that the possibilities of a just energy transition of regions depend on the diversity of local conditions and resources, emphasising at the same time the territorial dimension of the issue of the energy transition.

Low-Cost Organic Adsorbents for Elemental Mercury Removal from Lignite Flue Gas

The research presented by the authors in this paper focused on understanding the behavior of mercury during coal combustion and flue gas purification operations. The goal was to determine the flue gas temperature on the mercury emissions limits for the combustion of lignites in the energy sector. The authors examined the process of sorption of mercury from flue gases using fine-grained organic materials. The main objectives of this study were to recommend a low-cost organic adsorbent such as coke dust (CD), corn straw char (CS-400), brominated corn straw char (CS-400-Br), rubber char (RC-600) or granulated rubber char (GRC-600) to efficiently substitute expensive dust-sized activated carbon. The study covered combustion of lignite from a Polish field. The experiment was conducted at temperatures reflecting conditions inside a flue gas purification installation. One of the tested sorbents—tire-derived rubber char that was obtained by pyrolysis—exhibited good potential for Hg0 into Hg2+ oxidation, resulting in enhanced mercury removal from the flue. The char characterization increased elevated bromine content (mercury oxidizing agent) in comparison to the other selected adsorbents. This paper presents the results of laboratory tests of mercury sorption from the flue gases at temperatures of 95, 125, 155 and 185 °C. The average mercury content in Polish lignite was 465 μg·kg−1. The concentration of mercury in flue gases emitted into the atmosphere was 17.8 µg·m−3. The study analyzed five low-cost sorbents with the average achieved efficiency of mercury removal from 18.3% to 96.1% for lignite combustion depending on the flue gas temperature.

Experimental measurements for Polish lignite combustion in a 1 MWth circulating fluidized bed during load changes

The conventional design of circulating fluidized beds mainly focuses on high process efficiency, while electricity markets increasingly target operating flexibility due to the increased penetration of renewable energy sources. In this work, the operational flexibility of the CFB furnace when applied to compensate for the feed-in fluctuations from renewable energies has been investigated experimentally. Employing a 1 MWth CFB test facility, Polish lignite was combusted over a wide range of transient operating conditions. The profiles of temperatures and pressures along the riser, the flue gas concentration and the temperature developments in the bed zone, and the outlet of the cyclone that identify the basis for operational flexibility and scale-up studies were shown. It was found that the circulating fluidized bed furnace can be operated with higher positive and negative load change rates up to ±25%/min, maintaining high combustion efficiency and low emissions. Furthermore, the temperature distribution along the riser was almost homogeneous at higher loads. By reducing the load, the temperature difference in the bed zone and after the cyclone was decreased and heterogeneous temperature distribution along the riser can be observed, resulting in a slight decrease in the combustion efficiency.

Is the Złoczew lignite deposit geologically suitable for the first underground gasification installation in Poland?

Abstract The present study focuses on alternative methods of exploiting lignite in comparison to conventional opencast mining and combustion in power plants for the generation of electricity. In Poland, opencast lignite pits cover large areas, creating social and environmental conflicts. In order to stabilise the production level of electricity and reduce the negative effects of opencast mining, alternative ways of exploiting lignite are suggested, one of these being underground gasification in situ. The Złoczew lignite deposit, which will most likely be exploited in the near future, provides an opportunity to discuss the unconventional method of underground coal gasification (UCG). On the basis of technological and geological criteria that have been established to determine the suitability of Polish lignite for underground gasification, resources to be used this way have been estimated. Through gasification, over 15 million tonnes of lignite can be utilised, which is about 2.5 per cent of resources of the Złoczew deposit intended for opencast mining. With this in mind, we suggest to take action by starting a pilot installation, to be followed by a commercial one for underground gasification after completion of superficial mining. Naturally, any future application of this method will be preceded by assessment of geological conditions at the Złoczew opencast pit.

New Insights Into the Genesis of the “Poznań Clays” – Upper Neogene of Poland

The present study focuses on the upper Neogene deposits, called the “Poznań Clays”, that cover more than 75,000 km<sup>2</sup> of Poland. They are situated between the first mid- Polish lignite seam and the glaciogenic deposits of the Pleistocene age. Lithostratigraphically, the “Poznań Clays” belong to the uppermost portion of the lignite-bearing Grey Clays Member and the whole Wielkopolska Member (Poznań Formation). The examined fine-grained sediments include mud-rich floodplain deposits with palaeosol remnants and large sandy-muddy or muddy palaeochannel bodies. Therefore, taking into account facies analysis, cross-sectional geometry, and the planform of the palaeochannels, it can be stated that the “Poznań Clays” formed in the environment of a late Neogene anastomosing river.

Composition of lipids from the First Lusatian lignite seam of the Konin Basin (Poland): Relationships with vegetation, climate and carbon cycling during the mid-Miocene Climatic Optimum

Samples of detrital lignite have been collected for detailed organic geochemical and carbon isotope analyses from the First Lusatian lignite seam at the Adamów, Jóźwin IIB and Tomisławice opencast mines, deposited after the last peak of the Mid-Miocene Climatic Optimum. Carbon isotopic compositions of biomarkers from Polish lignite are reported for the first time. The aim of the study is to improve the chemotaxonomic value of biomarkers by relating the results to existing paleobotanical data, and to gain information about the influencing factors on δ13C of lignite and lipids. Furthermore, biomarker and isotopic proxies are tested for their applicability in paleoclimate studies.The molecular composition of the extracted lipids is highly variable, including leaf-wax n-alkanes in the C23 to C31 range, diterpenoids, hopanoids, and angiosperm-derived triterpenoids, as well as saturated fatty acids, long-chain n-alkanols and n-alkan-2-ones. The relative abundances of mid-chain (C23, C25) n-alkanes and their 1–2‰ higher δ13C values compared to long-chain n-alkanes (C29, C31) argue for a minor contribution of macrophytes (graminoids, etc.) to peat formation, enhanced during periods of raised water level. The presence of ferruginol and dehydroferruginol testifies the contribution of Taxodiaceae. The abundances of pimarane-type diterpenoids and the presence of non-aromatic abietane-derivatives argue for the contribution of Pinaceae. Based on the presence of lupeol and lupane-type triterpenoids, an input of Betulaceae can be concluded. The contribution of further angiosperms cannot be specified based on the composition of pentacyclic triterpenoids. However, the results indicate mixed vegetation, and are in agreement with paleobotanical data highlighting abundant conifers of the Taxodiaceae/Cupressaceae and Pinaceae families, as well as angiosperms of various families (e.g., Nyssa, Quercus, Fagus), including Betulaceae (e.g., Alnus, Betula, Corylus). Based on the relationship between the carbon preference index of n-alkanes and mean annual air temperatures, obtained from a global database of peatlands, an average temperature of 24.5 °C is obtained. This value is significantly higher as estimated from paleobotanical data (15.7–19.7 °C), probably due to the influence of changes in vegetation on carbon preference index.The relative abundances of diterpenoids versus di- plus angiosperm-derived triterpenoids in detrital lignite samples revealed variable contributions of gymnosperms and angiosperms during the middle Miocene. Consistent with these results, a positive relationship exists between the di-/(di- + tri-) terpenoid biomarker ratios and δ13C of lignite samples, indicating the dominating role of varying gymnosperm/angiosperm contributions on the carbon isotopic composition of lignite. The C-isotope data of long-chain n-alkanes, diterpenoids, and angiosperm-derived triterpenoids co-vary within the profiles, arguing for an overall control of changes in δ13C of atmospheric CO2 on δ13C of plant lipids. Fluctuations in δ13C of individual compounds may also be related to changes in carbon cycling within the peat, humidity and air temperature. The influence of local variations in ambient CO2 (e.g., the canopy effect) cannot be excluded.

The suitability of Polish lignite for gasification

The article discusses the impact of the lithotype of lignite on the suitability for gasification in CO2 atmosphere. The research was aimed at determining the influence of lithotype, petrographic composition, and physical and chemical properties of coal on the composition and release of syngas. The examined coals were humic coals. The first step was to determine the impact of lithotype on the degree of carbon conversion at a temperature of up to 815 °C. The gasification process was conducted in the temperature range of 600–1100 °C. During the experiment, two gas samples, used for determining the chemical content of gas, were collected at 950 and 1050 °C, respectively. What is more, continuous monitoring of the gas density during the gasification was carried out. Depending on the lithotype, the content of ash, moisture, and the degree of coalification, the intensity of gas release is different for different temperatures. In addition, it has been found that coals with a high content of poorly gelified xylite and a low ash content are the fastest reacting and the most responsive. The importance of this research lies in determining that the gasification of coal with a low degree of coalification requires technologies carried out at reactor temperatures above 1000 °C.Graphical abstract

Analysis of the occurrence of critical elements and raw materials in Polish lignite deposits with particular emphasis on coal ashes

Fly ash collected from landfills at power plants using lignite from the following mines: Turów in Bogatynia, Bełchatów in Rogowiec, and Pątnów in Konin was subjected to analysis. Petrographic studies were performed using a reflected light optical microscope. The chemical composition (the presence of minor, trace, and rare elements) was determined using ICP-MS and X-ray spectroscopy. Petrographic examination using a JEOL JXA-8230 electron microprobe analyzer allowed determining critical elements in the selected minerals. Silicate and aluminosilicate enamel, mullite aggregates, magnetite-hematite iron microspheres and fine unburned carbon particles were found in the analyzed fly ash samples; in addition, small amounts of gypsum and anhydrite were also recorded. The results of oxide analyses of fly ash samples, e.g. CaO content higher than 10% wt, suggest their calcium character. In order to present interesting concentrations of the analyzed critical elements, their maximum contents were compared to their Clarke values (for sedimentary rocks and crustal rocks). The comparison to Clarke values of sedimentary rocks, based on calculation of the enrichment factor (EF), has shown that the content of majority of critical elements in lignite and its ashes is similar to the mean values for sedimentary rocks; the contents higher than Clarke value did not exceed the mentioned values and were observed in the case of tungsten (6.2 - the Turów deposit) and silver (5 to 7 in the Turów deposits). In addition, the comparison of analytical content to Clarke values of crustal rocks did not fundamentally alter these relations; the maximum contents higher than the Clarke value were recorded for tungsten (9.4) and silver (9.3) in the Turów deposit. The microanalysis of iron microspheres has revealed the presence of Ga. In the case of the platinum group, the presence of Pd, Pt, In, Nb, V, Cu, and Ti was confirmed.

Tectonic and Glaciotectonic Deformations in the Areas of Polish Lignite Deposits

Abstract This study addresses the complex geology caused mainly by tectonic and glaciotectonic processes in lignite-bearing areas of Poland. Tectonics played a dominant role in the deformation of peat/lignite seams during their deposition. This is especially true for deep grabens where the thickest lignite seams were deposited (e.g., Bełchatów). Conversely, glaciotectonics led to the post-depositional deformation of other deposits (e.g., Sieniawa). The effects of tectonic and glaciotectonic processes in this region are investigated using both simplified geological cross-sections and photography. The size, depth and architecture of the glaciotectonic structures verified in this study demonstrate the importance of their consideration during the exploration and exploitation stages of such lignite deposits, as well as the planning of construction projects in areas strongly transformed by glaciotectonics.

Combustion properties of torrefied biomass obtained from flue gas-enhanced reactor

Torrefaction is the process of thermal treatment that leads to enhanced biomass properties. Specifically, torrefaction of raw biomass can lead to higher energy density, improvement of handling and grinding properties, and other advantages. This work investigates the combustion properties of torrefied biomass obtained from the torrefaction of willow (Salix viminalis) in the presence of flue gas. The properties were compared with other solid fossil fuels such as Polish hard coal and Polish lignite. The comparison was based on proximate and ultimate analyses as well as the combustion of the fuels using an auto-thermal bubbling fluidized bed reactor. The combustion process of torrefied willow was stable, and the most promising result was radically low SO2 emission levels. However, the relatively high NOx emission should be decreased by the application of primary or secondary methods of NOx removal.

The suitability of polish ortho-lignite deposits for clean coal technologies

Abstract The article presents the suitability of polish lignite deposits for clean coal technologies, mainly fluidized bed gasification and underground gasification. One of the key elements in this study, is a detailed diagnosis of the resource base, its analysis on the basis of the established verification criteria and -as a result - the achievement of a reliable assessment of suitability for highly efficient production of fuels and electric energy through lignite gasification in both surface and underground installations, taking into account both sozological conditions and protected geological sites. The analysis has shown that only 10 out of from 166 lignite deposit meet the criteria for the potential development of process underground gasification.

The need for verification of the Polish lignite deposits owing to development and nature conservation protection on land at the surface

Abstract Poland is a country rich in lignite. The area where the lignite occurs occupies approx. 22% of the total surface area of the country. Geological resources of Polish lignite deposits are estimated at 23.5 billion Mg, but in the majority (69%) the accuracy of their identification is poor. Nevertheless the amount of coal in Polish deposits allows - at least in theory - for mining and energy production at the current level for hundreds of years to come. It is an important raw material for the energy security of the country both currently and in the future. Because the vast majority of Polish and foreign mines use an open pit method for lignite extraction the actual amount of mineral available for the extraction depends not only on the properties of the deposit but to a large extent on the method of development of the surface land above the deposit, as well as on the sensitivity of the environment in the vicinity of any future mines. After careful analysis it can be stated that only a few of the lignite deposits may be subject to cost-effective mining operations. These deposits should be subjected to special protection as a future resource base which will ensure the energy security of the country. Some examples of domestic deposits have been presented where due to the conflict resulting from the development of the area should be deleted from the Balance Sheet of Mineral Deposits because their exploitation is irrational and uneconomic. Keeping such deposits in the Balance Sheet, and the use of large numbers in the context of their resource base leads to an unwarranted sense of wealth which consequently does not encourage the protection of these deposits which may actually be subject to rational exploitation in the near future. In summary there is a need to find a compromise in order to adequately protect all natural resources including mineral deposits.

An overview of lithotype associations of Miocene lignite seams exploited in Poland

Abstract Currently, three stratigraphically distinct lignite seams of Early to Middle Miocene age are exploited in Poland, namely the third Ścinawa lignite seam (ŚLS-3), the second Lusatian lignite seam (LLS-2) and the first Mid-Polish lignite seam (MPLS-1). All of these are composed of numerous macroscopically distinguishable layers defined as lignite lithotypes. In the present paper, the lithotypes of Polish lignites are grouped into seven major lithotype associations that originated in various types of mire. Therefore, an approximate reconstruction of mire type can be based on lignite lithotypes. Within the Polish lignite seams examined, the commonest in order of importance are: xylodetritic (XDL), detroxylitic (DXL), detritic (DL) and xylitic (XL) lithotype associations, mostly with a massive (m) or horizontal (h) structure. They are particularly dominant in lignite opencasts belonging to the Konin and Adamów mines. However, in the lowermost seams at the Turów and Bełchatów mines, a substantial part of the seams comprises the bitumen-rich (BL) lithotype association. These seams also lignite lithotypes that in large quantities have a gelified (g) and/or nodular (n) structure. In contrast, lignites from the Sieniawa mine are characterised by an admixture of the best-developed lithotype associations of both fusitic (FL) and weathered (WL) lignites. Moreover, the vast majority of these lignites have a folded (fo) and/or faulted (fa) structure, because they were completely deformed by glaciotectonics.

Towards the improvement of thermal efficiency in lignite-fired power generation: Concerning the utilization of Polish lignite deposits in state-of-the-art IGCC technology

Summary Integrated coal Gasification Combined Cycle (IGCC) is the most advanced technology for coal-fired power generation. The two-stage entrained flow gasification process allows for the use of a wide range of coal, as long as the gasification temperature is above the ash melting point of a used fuel. In this gasification technology, lignite, which often has a low ash melting point, can be preferably utilized. However, ash fluidity is also another importance, because the behaviour of molten slag can diminish a stable ash discharge from a gasifier. As the eligibility of coal ash properties is a considerable factor, water physically and chemically kept in lignite (30 – 60% in mass) attributes to deteriorating gasification efficiency, because it causes significant heat loss and increasing oxygen consumption. Developing a thermal evaporative lignite drying method will be a necessary attempt to apply lignite to the coal gasification process. For those preceded objectives, coal and ash properties and drying characteristics of several grades of Polish lignite, extracted from Belchatow and Turow deposits, have been experimentally investigated in a preliminary study evaluating the applicability and consideration for its utilization in state-of-the-art clean coal technology, IGCC. This paper particularly discusses the eligibility of Polish lignite from the perspective of the fusibility and fluidity of ash melts and the fundamental drying kinetics of lignite in superheated steam in the light of water removal. The viscosity of ash melts is measured at high temperature up to 1700 °C. In the drying tests, the significant influence of structural issues, because of the provenance and origin of lignite on the drying characteristics, was found by applying the method of sensitivity analysis of physical propensity. This paper concludes that the investigated Polish lignite has characteristics favourable for utilization in IGCC technology, once the precautions related to its high moisture have been carefully addressed. Copyright © 2016 John Wiley & Sons, Ltd.

Qualitative and chemical characteristics of mineral matter in the selected lignite deposits in light of their suitability for clean coal technologies

An analysis of the variability of ash content and chemical composition of coal ash is crucial when assessing the possibility of using this raw material in clean coal technologies (CCS). The paper focuses on chemical, technological and quality characteristics of ash from the combustion of lignite from Polish deposits. Ash content on a dry ash-free basis for the samples from 9 deposits varies from 1 to 50%. The most commonly observed ash content in the studied samples of lignite is in the range between 10–20%. The measured ash melting temperatures from the collected lignite samples have shown that the sintering, softening, melting and flow temperatures, determined in an oxidizing atmosphere (air), are higher than those determined in a reducing atmosphere. In the majority of Polish lignite deposits, the dominant component of ash was SiO2 , followed by CaO. When evaluating the suitability of coal in energy production, with particular emphasis on the combustion and gasification processes, it is also necessary to study the behavior of ash at high temperatures and the impact of ash on the gasification and combustion facilities. Ash fouling and slagging processes, which are heavily dependent on the ash content, composition, melting point and the content of chlorine, phosphorus and sulfur in coal, have a negative effect on the combustion process.

Planning for Reliable Coal Quality Delivery Considering Geological Variability: A Case Study in Polish Lignite Mining

The aim of coal quality control in coal mines is to supply power plants daily with extracted raw material within certain coal quality constraints. On the example of a selected part of a lignite deposit, the problem of quality control for the run-of-mine lignite stream is discussed. The main goal is to understand potential fluctuations and deviations from production targets dependent on design options before an investment is done. A single quality parameter of the deposit is selected for this analysis—the calorific value of raw lignite. The approach requires an integrated analysis of deposit inherent variability, the extraction sequence, and the blending option during material transportation. Based on drill-hole data models capturing of spatial variability of the attribute of consideration are generated. An analysis based on two modelling approaches, Kriging and sequential Gaussian simulation, reveals advantages and disadvantages lead to conclusions about their suitability for the control of raw material quality. In a second step, based on a production schedule, the variability of the calorific value in the lignite stream has been analysed. In a third step the effect of different design options, multiple excavators and a blending bed, was investigated.

A113 過熱水蒸気雰囲気におけるポーランド褐炭の乾燥特性の実験的調査 : 炭層深度が乾燥特性に及ぼす影響の調査(OS1 次世代型火力発電システム技術)

A113 過熱水蒸気雰囲気におけるポーランド褐炭の乾燥特性の実験的調査 : 炭層深度が乾燥特性に及ぼす影響の調査(OS1 次世代型火力発電システム技術)

Evaluation of the Effectiveness of an Eco-Friendly Technology for Splicing Steel Cord Conveyor Belts

A new eco-friendly method of splicing steel cord conveyor belts without the use of noxious materials has been developed by the Mining Institute at Wrocław University of Technology in collaboration with the Bełchatów Lignite Mine – the two leaders in implementing state-of-the-art and environment friendly technologies in mining in Poland [1,2,3]. Polish lignite mines use belts with steel cords. Such belts are spliced through high temperature vulcanization, which is not safe for the environment and has an adverse impact on human health. Strength and durability are the two main properties of belt splices, having a bearing on the failure-free operation of the belt conveyors used for the haulage of stripped rock or muck in open pit mines [4,5,6]. This means that properly made steel cord belt splices should have the strength and durability parameters similar to the ones of the belt without splices. Many factors contribute to the quality of the splice, including the ones connected with the splicing technology, workmanship and with the fact that splices are made directly on conveyors in heavy mine conditions.

Selected harmful elements in polish lignite

Streszczenie W węglu brunatnym z polskich złóż występują liczne pierwiastki rzadkie, śladowe i rozproszone, z których część może wywierać niekorzystny wpływ na środowisko naturalne oraz człowieka. Jednak pierwiastki te w większości nie osiągają koncentracji szkodliwych w analizowanym węglu. W pracy zbadano zawartości wybranych pierwiastków szkodliwych w każdym stężeniu i pierwiastków szkodliwych w większym stężeniu. Analizowano udział tych elementów zarówno w próbkach węgla brunatnego, jak i popiołach tego surowca uzyskanych metodą powolnego spalania. Do pierwiastków toksycznych w każdym stężeniu zaliczono Pb, Hg, Cd, Be, As, a w większym stężeniu: Zn, Se, Sb, Cu, Mn. Pierwiastki śladowe oznaczano metodą instrumentalnej neutronowej analizy aktywacyjnej (INAA), ICPMS-Mikrofala i ICP-OES. Ze względu na brak norm określających dopuszczalną zawartość pier- wiastków szkodliwych w węglu brunatnym oparto się na porównywaniu oznaczonej zawartości z dopuszczalnymi dziennymi dawkami dla ludzi i dopuszczalnej zawartości tych pierwiastków w glebach oraz w wodach. Zawartość Hg, Pb, As i Cd w badanym węglu brunatnym jest nieduża, a ich stężenia osiągają maksymalnie: Hg do 2,6 ppm, Pb do 26,22 ppm, As do 19,72 ppm i Cd do 17,76 ppm. Podane koncentracje są bardzo małe w porównaniu do granicznych dopuszczalnych wartości w glebach. Wyjątek stanowi średnia zawartość rtęci w złożu Adamów. Zawartość pierwiastków toksycznych w popiołach jest wyższa w porównaniu z węglem surowym, co świadczy, że składniki te związane są z substancją mineralną węgla. Zawartość innych oznaczonych pierwiastków śladowych (Sb, Zn, Mn i Cu) w badanym węglu jest również nieduża i nie stanowi zagrożenia dla środowiska naturalnego. Jednocześnie pierwiastki takie jak Mn, Pb i Cu mają małą lotność, przez co obserwuje się ich koncentrację w popiele po spaleniu węgla. Z drugiej strony takie pierwiastki jak Cd i Hg ze względu na swoją wysoką lotność ulatniają się w trakcie spalania wraz ze spalinami i dlatego ich zawartość w popiele jest niższa niż w węglu.