Projects / Programmes
Petrology of brown (low-rank) coals as mined and/or used in Slovenia, natural gasses in them, and their gas-sorption properties
| Code |
Science |
Field |
Subfield |
| 2.16.00 |
Engineering sciences and technologies |
Mining and geotechnology |
|
| Code |
Science |
Field |
| P420 |
Natural sciences and mathematics |
Petrology, mineralogy, geochemistry |
| Code |
Science |
Field |
| 2.07 |
Engineering and Technology |
Environmental engineering
|
Coal; lignite; gases CO2, CH4, N2, gas sorption; chemical, maceral and mineral composition of coals; isotope characterization; microtexture and structure; permeability
Researchers (16)
Organisations (4)
Abstract
The objective of our research project will be to determine and explain gas-sorption (adsorption and desorption) characteristics of different types of coal and their varieties (lithotypes), which are mined and / or used in Slovenia. These are the Velenje lignite, Zasavje brown coal and brown coals imported from Indonesia and the Czech Republic. The gas-sorption characteristics of coals will be studied in comparison to their petrology, such as lithotypes, chemical, maceral and mineral composition, as well as microstructure (porosity, fracturing, size, shape, orientation of their components). Some of the project investigations have already been practiced in the past and are not novelties; what is a novelty is that this project will be conducted as a comparison study between petrological and gas - sorption characteristics of coal matrix, which will be made for the first time for the Slovenian coals. A new approach will be also study of isotopic composition of gases, especialy of desorbed ones.
The largest part of our research will be focused on the Velenje lignite, while other coals will be used for comparisons. The majority of our research will comprise measurements and analyses of samples, on which we will in advance determine their in situ spatial geological environment. This will enable us to interpret the obtained results not only for different types of coals, but also, especially for the Velenje lignite, from the spatial point of view. This will connect our applied scientific project with the ongoing investigations in the Velenje lignite mine which deal with possibilities of degasification of the lignite seam by oriented drill-holes and capturing of coal-bed gases. The starting part of the project will be sampling of characteristically and spatially precisely defined groups of coal lithotypes. We intend to collect approximately 30 samples of the Velenje lignite and 5 samples of each of the other three coals. This phase will be followed by the preparation of samples for analyses.
Measurements of adsorption and desorption of gasses CO2, CH4 in N2 will be conducted according to the gravimetrical and volumetrical methods using different pressure levels, on differently prepared samples, in different atmospheres, with different contents of added water. The laboratories in Ljubljana and Velenje have already installed special reaction vessel s– autoclaves, as well as adequate computer programs. Proximate composition (portions of organic and inorganic parts, water, volatile components, sulphur), specific energy value (calorific value), chemical composition (with composition analysis of major, minor and trace elements), isotopic composition of carbon and nitrogen, and, finally, petrographic (maceral and mineral) composition will be determined to all samples that will be gas-sorption investigated. Degree of coalification of different coals will be determined on the basis of relevant chemical and optical parameters of the investigated coal samples.
The above described analytical phase, in which petrographic characterisation with optical and scaning electrone microscopy, and sorption tests will cover the major part, will be followed by the interpretation phase. This will include comparative interpretation of the results of sample investigations and interpretation of petrologically dependent gas-sorption characteristics of different types of lignite within the Velenje lignite seam.
Studying gas sorption of coals at different physico-chemical conditions and in dependence of petrological features is currently one of the major research themes in coal characterization with regard to modern views of the use of coal, especially in the nearest future (see Chapter 11). Therefore, the results of our research will be published in the Slovenian and international scientific journals.
Significance for science
The Velenje lignite is on average a 60 m thick seam, exploited 300 m underground. It is situated in the middle of a 1000 m thick sequence of Pliocene clastics filling the intermontane Velenje basin. The length of the seam is 8.5 km and the width up to2.5 km. The Velenje Lignite Mine is a technologically modern operation. In spite of that, there exist a danger of outbursts of coal and gasses, also known by some tragic events in the past. Gas research activities connected with coals run in many countries, to a greater scale in bituminous coals than lignites. Coalbed methane and CO2 sequestration are the most propulsive activities, especially if combined. Lignites are not very suitable for this, because they are mostly low gaseous. They contain mostly only biogenic gasses, not also thermogenic. Generation of thermogenic gasses is much greater than the production of biogenic gasses. Different-quality lignites and brown coals are used world-wide. They contain more than 40 % water and 10 % ash, “if clean”. The share of organic matter is therefore low. Also due to this explanation, it is clear why lignites are mostly gas-poor coals. They are enriched in CO2 versus methane. It is no problem when such CO2 retains under pressure in the coal structure, but it becomes dangerous when the structure of coal is affected by outer stresses or even broken. That leads to a sudden exhalation of CO2 and braking of surrounding coal having characteristics of an explosion. In the case of the Velenje lignite, many above described gas-features as common for lignites are quite different. First, the Velenje lignite is relatively gas-rich, more than normal for lignites. CO2 mostly prevails over CH4, and the ratio between these two gasses varies greatly. Methane is more mobile than CO2, and a lot of it it migrated upwards to hanging-wall sediments. Maybe the most interesting thing is that also thermogenic CO2 and CH4 gasses are present in this lignite. This was found by carbon isotopic analyses. It is presumed that a part of these two thermogenic gasses originates from “deep geological strata” and came into the lignite seam via fractures of the Šoštanj fault system, and a part of methane could be produced by microbial CO2 reduction activity. Referring to all above described characteristics it comes out that it would be very interesting to find out or better define relations between petrology of coal and gas behaviour within it. It is the fact that the Velenje lignite is heterogeneous composed of inter-beds which could be important carriers of gas properties in regard to their retention and mobility. The answer to these questions may be solved to considerable degree with gas-sorption tests and petrological investigations. Quite a lot of results of such investigations exist world-wide for bituminous coals, but not many for low lignites. To fill this gap a little, we also see one of reasons of our work.
Significance for the country
A direct application of results of this project relies especially to their use at the Velenje Lignite Mine itself. It is also the reason why the Mine is both project partner and co-financing organisation. The results which will explain the role of petrologic composition, structure and texture in the behaviour and occurences of gasses within the lignite seam are expected to be useful at the operative projects which are running at the mine itself. Among them, the closest usage of the results of this project is expected in the case of the drainage project running in the Preloge field - northern wing. Some explanations about different gasses and their amounts in different parts of the whole mine are also expected to be better explained with this project-s results. Further on, the results of detailed petrological characterisation of samples and gas sorption characteristics will serve as source parameters for continuing phases of mathematical modelling (SCA modelling) of dynamical effects in lignite as a reaction to external stresses and at presence of different gasses. Coal mining in Slovenia had a similar historical and economical development as in other countries of industrialised Europe from the mid-18th century onwards. Modern mining in our country started at the very beginning of the 16th century, when Idrija mercury was found some years ago (1492). Miners started to looking for metals also in other places of the country, but it was not before the 19th century when a true mining geology emerged which started to study a wide spectrum of geological phenomena in a real scientific way. In our Alpine-Dinaric-Pannonian basin geological realm not only metal deposits but also coal deposits, mostly found in the 18th and 19th century, were found to occur in mostly quite complicated structures. About 45 coal mines operated in the past on the territory of nowadays Slovenia. All these are documented, the biggest among them, about 20, in the form of elaborations of coal reserves. The main area of coal mining in Slovenia was for a long time the Zasavje area in which the mining will be finished in close next years. Only the Velenje Lignite Mine will operate for maybe 40 years. In the history of this coal mine, from 1875 onwads, several great mining and geological scientific works have been done and even much more applied studies to solve different geotechnological and related problems. Velenje was always a site of modern research and exploration work in mining, geology and also other branches, which also took care on development and education of young generations in a way to be prosperous in the future. Velenje is also a frequent place of professional meetings to exchange knowledge and experiences also in the wider area and world. Each time has its challenges and needs, and tries to find some new issues. To study gasses – being generated, accumulated, recovered, emitted, captured, migrated, as it seems making our planet warmer than it would normally be (or maybe not?) – is for sure one of the challenges of our time. With this project, and in contacts with colleagues internationally and at home, we would like to be active on this domain.
Most important scientific results
Annual report
2011,
2012,
2013,
final report,
complete report on dLib.si
Most important socioeconomically and culturally relevant results
Annual report
2011,
2012,
2013,
final report,
complete report on dLib.si
