Greek Lignite Research Articles

Externalities from lignite mining-related dust emissions

During the last three decades, several studies have been conducted in order to assess the external costs of electricity production from fossil fuels, especially coal and lignite. Nevertheless, these studies usually ignore the impacts generated by the upstream mining works. This paper contributes to existing literature and attempts to fill this gap by exploring the externalities of lignite mining owing to the emission of suspended particulate matter. To this end, a ‘bottom-up’ approach is implemented, using as case study the largest operational lignite surface mine at the Lignite Center of Western Macedonia (Greece). The results indicate that annual air pollution externalities of lignite mining are of the order of 3€/ton of lignite, which corresponds to around 5.0 €/MWh. The estimated costs are significantly lower, i.e. up to 80%, when dust deposition is considered in air dispersion models. In any case, these findings should be seen as a starting point for discussion owing to the lack of specific emission rates for Greek lignite mines.

The Appeal in Greek Lignite: Clarification of the Law or Jumpstarting Article 106 TFEU?

The Appeal in Greek Lignite: Clarification of the Law or Jumpstarting Article 106 TFEU?

Study of slagging and fouling mechanisms in a lignite-fired power plant

A significant proportion of the electrical power requirements of Greece are covered by lignite-fired power plants. Greek lignite is characterized by a high water and ash content and a low heating value. Slagging and fouling are common inside the power units and severely affect the performance of the power plants (reduced efficiency, steam leakage in the superheaters and water walls whereas the high temperature of the exhaust gases leads to the mal-functioning of the electrostatic filters). In addition excessive interior pollution cause the units to stop for cleaning resulting in a reduced production and increased maintenance costs.In this paper the results from a measurement campaign in a steam boiler affected by excessive deposits are presented and compared against the manufacturer's operating data. A number of differences were found between the two sets of data and were attributed to the particulars of excessive amount of deposits in the boiler. In addition, the present study investigates the chemical composition and behavior of the slagging and fouling deposits that occur in units of the Kardia power plant as well as of a bottom ash and a fly ash sampled from the same unit. The steam path of the unit was simulated using the DNA software in order to model the effect of the contamination on the global performance parameters of the power plant and the results were compared against the experienced operational performance parameters. In addition, a number of practices are proposed and assessed for reducing the levels of boiler contamination and extending the time between successive maintenance stoppages.

Evaluation of the long-term environmental performance of Greek lignite-fired power stations

Abstract At national, regional and global level, there is no doubt that the electric generation from fossil fuel-fired power plants is one of the greatest causes of air pollution and climate change. However, fossil fuels contribute more than 70% in the planet electricity generation during the last 30 years. In Greece, lignite is the only proved significant indigenous fossil fuel source, currently representing about 50% of the national electricity generation (a situation which is not expected to change dramatically in the near future). As a result, owed to the use of local lignite reserves (poor quality lignite), the Greek Lignite Thermal Power Stations (LTPSs) are responsible for the production of significant airborne emissions and particle releases (e.g. CO2, SO2, NOX, PM). At the same time, Greece, on top of the Kyoto Protocol, has accepted specific obligations and incorporated into its national legislation several air quality Directives concerning the reduction of various harmful gases and particle releases attributed to fossil fuel combustion. Thus, wide scrutiny of concentration time series of all these airborne emissions constitutes an important indicator of the current technology used, considering at the same time that any violation noted should be the object of serious national concern. Under this argument, the current work presents and evaluates the long-term environmental performance of the Greek lignite-based electricity generation system as far as CO2, NOX, SO2 and PM are concerned up to the year 2011. According to the results obtained, one may rank the operating LTPSs according to their environmental performance giving to the Greek society the necessary tools to determine their utilisation factor on top of the techno-economic criteria used up to now.

Services of General Economic Interest and State Measures Affecting Competition

The last year has been a typical year in this survey of SGEI and state measures affecting competition where the report is a series of ad hoc measures relating to SGEI. Two new soft communications have been published to complement the Almunia Package of measures to regulate compensation for SGEI: a European Commission instrument to determine swap rates and a Commission Staff Working Paper. There are a few European Commission Decisions, particularly in the postal sector, involving financing SGEI that fall outside of the new Almunia Package, but are assessed according to the new methodological approach. The GC has tasked the European Commission to take greater care to analyse the funding of ancillary services to health care schemes; a rebuke that is seen also in applying Article 106 TFEU in the Greek Lignite case. Of a wider significance for EU economic law the CJEU and the European Commission have provided analysis of the definition of ‘economic activity’ which triggers the application of EU law generally. Two cases have considered the application of Article 106 TFEU, with the GC providing greater analysis of when, and how, Article 106 and 102 TFEU may be used together.

Low rank coal – CO2 gasification: Experimental study, analysis of the kinetic parameters by Weibull distribution and compensation effect

Gasification is generally considered as the most effective for low rank coal exploitation and CO2 gasification offers the advantage of upgrading an environmentally detrimental gas. Isothermal CO2 gasification tests of Greek low rank coal were performed in a tubular fixed bed reactor, to study the effect of the various reaction conditions. Greek lignite was quite reactive with CO2, resulting in high conversions even at short reaction times, while the obtained chars remained reactive after devolatilisation, as the continuous increase of conversion indicated. Conversion was very sensitive to temperature due to both pyrolysis and C–CO2 reactions, and for the granulometries studied (up to 1000 μm) the gasification rate was independent of particle size. CO2 partial pressure affected the gasification rate at low CO2 partial pressures, since the reactivity of lignite remained high (conversion ∼85% w/w daf) even for 0.25 atm CO2 partial pressure. The presence of CO retarded the reaction and the gasification rate decreased rapidly as the concentration of CO increased. The first order Volume Reaction Model (VMR) adopted was proven quite effective in describing the experimental results. Experimental results showed that the activation energy (E) varied with time, passing through a wide maximum between 10 and 15 min. The pre-exponential factor (k0) follows the behaviour of the activation energy, however, it exhibits a more sharp maximum at the same time region. The variations of the kinetic parameters with time could be attributed to the different nature of carbon atoms gasified and the changes of the number of active collisions, as the gasification reaction proceeds. As the gasification reaction advanced the Arrhenius parameters (E and k0) increased or decreased simultaneously, exhibiting a compensation effect. The probability density function (pdf) of the Weibull distribution was employed successfully to depict the variations of the kinetic parameters, E and k0.

The prospect of using greek lignite in an energy portfolio related to power generation

The lignite-based power generation contributes 38% towards Greece’s energy independence. Reducing the lignite use while simultaneously importing more expensive natural gas both government deficit and the cost of energy will increase. This surcharge is passed to consumers. Switching to renewable resources invokes an even greater fiscal imbalance, since the costs from the use of wind turbines and solar photovoltaic panels are 87 €/MWh, and 180–284 €/MWh respectively, while natural gas stands at 95 €/MWh and lignite-derived energy is 45 €/MWh.In case of replacing a 300 MW lignite fed power unit with a 300 MW natural gas fed power unit, the loss in income will be 66,540,000 €/year. Coupled with the increased cost of natural gas (31,800,000 €/year) the total is 98,340,000 €/year in addition to the loss of 1235 jobs.Greek authorities intends to replace lignite-fired plants having a total installed capacity of 2531 MW with equivalent natural gas-fired plants resulting in annual total deficit in excess of 787 M€. The targets set by the Greek Ministry of Energy and Climatic Changes to reduce emissions include halving Greek lignite-derived power output from 4800 MW to 2300 MW (>-52%). This move simultaneously increases Greek energy dependence on expensive foreign energy sources and will potentially provoke social unrest at the loss of 12500 jobs with loss of annual income on the order of 670 M€. However, if the existing power output from lignite-fed power plants is maintained, the penalty that PPC (Public Power Corporation) has to pay for the resultant CO2 emissions is significantly smaller (300 M€ at 7.5 €/t of emitted CO2/GWh.Proceeding with the immediate reduction in lignite-fired energy results in economic and social catastrophe (annual income loss:-670 million € + annual CO2 emissions penalty: 348 M€= -322 M€). Lignite-fired plants will become obsolete only when the CO2 emissions penalty exceeds 63.5 €/t of emitted CO2/GWh from a purely economic perspective.

A comparative study on structural differences of xylite and matrix lignite lithotypes by means of FT-IR, XRD, SEM and TGA analyses: An example from the Neogene Greek lignite deposits

The FT-IR spectra for both Neogene xylite and matrix lignite samples from six different Greek lignite deposits (NW Greece) show significant differences. In particular in the aliphatic stretching region (3000–2800cm−1) the intensities of the vibrations are more prominent in the xylite lithotype as in the matrix lignite lithotype. The intense bands in the region 3402–3416cm−1 are attributed to −OH stretching of H2O and phenol groups for both xylite and matrix lignite lithotypes. The bands at ~3697cm−1 and ~3623cm−1 as well as at ~538cm−1 and 470cm−1, which are more evident in the FT-IR spectra of the matrix lignite, are attributed to a higher clay content in the samples of this lithotype. Data resulting from X-ray diffraction analysis (XRD), scanning electron microscopy (SEM) and thermoanalytical methods (TG/DTG and DTA) indicate main differences of the xylite and matrix lignite lithotype as well. Typical peaks in X-ray diagrams confirm the high content of clay minerals in matrix lithotype, and their minor contribution in the xylite lithotype. Scanning electron microscopy (SEM), combined with the FT-IR and XRD results, reveals prevalence of gypsum, pyrite/marcasite, quartz, and clays in the matrix lignite lithotype as compared with the xylite lithotype and also textural differences such as the heterogeneity in the mass of matrix lignite and the homogeneity of the xylite. Compositional differences of the examined lignite materials, as identified by FT-IR, were also confirmed by TG/DTG/DTA. While cellulose decomposition was observed by an endothermic peak of DTA curves, at around 360°C, in the xylite samples, lignin degradation became a prominent process observed in the temperature range from 200°C to 400°C in the matrix lignite samples. This was also observed by an exothermic peak on DTA curves. Each of the heat effects was accompanied with a partial mass loss registered on TG curves. As a whole, the data resulting from the combined research by means of FT-IR, XRD, SEM, and TG/DTG/DTA of both xylite and matrix lignite lithotypes confirm the significant differences between these two lignite lithotypes reflecting their different structure, texture, and maturity stage.

Co-pyrolysis of biodiesel-derived glycerol with Greek lignite: A laboratory study

The study has investigated the potential utilization of crude glycerol, generated from the biodiesel production Greek plants, as potential alternative fuel via co-processing with Greek lignite in existing combustion or gasification plants, looking forward to alleviate biodiesel production cost and to manage by-products by substituting conventional fuels. Fast pyrolysis was performed in this study in order to gain a further insight into the fluidized bed gasification/combustion process. Co-pyrolysis of lignite with crude glycerol performed batch-wise, in a laboratory scale, non-continuous, captive sample, wire mesh reactor, at atmospheric pressure. The process was performed at an average heating rate over the range of 300–1000°C/s and a reaction time of 0.5s, by varying temperature (650, 750 and 850°C) and feedstock composition (15wt% and 20wt%, of crude glycerol in the blend with lignite). Pyrolysis of blends of glycerol with lignite resulted in high hydrogen yield (65.44 v/v%) normalized, for the blend of 20wt% glycerol at 850°C, making evident that co-pyrolysis of crude glycerol with lignite could be a source for H2 production.

Comparative Study of Combustion Properties of Five Energy Crops and Greek Lignite

Solid biofuels from energy crops are widely considered as an attractive alternative for power production in dedicated combustion or cofiring applications. The aim of this work is to present fuel and ash characterization along with thermogravimetric investigations of pyrolysis and combustion behavior for five crops (cardoon, Miscanthus, Paulownia, willow, and poplar) compared with Greek lignite. Devolatilization is well modeled by three independent parallel reactions and reaches higher rates than lignite; char reactivity of woody biomass and Miscanthus was high, whereas cardoon char resembled more closely that of lignite. High potassium concentration and low melting temperatures were found for all biomass ashes; therefore, a severe/high slagging or agglomeration potential is expected. Overall, cardoon appears to be the most problematic of the investigated biomass fuels, due to high ash content, low ash melting temperature, a slower char combustion rate, and risk of chlorine corrosion; cofiring with lignite...

Natural Desulfurization in Coal-Fired Units Using Greek Lignite

This paper analyzes the natural desulfurization process taking place in coal-fired units using Greek lignite. The dry scrubbing capability of Greek lignite appears to be extremely high under special conditions, which can make it possible for the units to operate within the legislative limits of sulfur dioxide (SO2) emissions. According to this study on several lignite-fired power stations in northern Greece, it was found that sulfur oxide emissions depend on coal rank, sulfur content, and calorific value. On the other hand, SO2 emission is inversely proportional to the parameter y CO2max, which is equal to the maximum carbon dioxide (CO2) content by vol ume of dry flue gas under stoichiometric combustion. The desulfurization efficiency is positively correlated to the molar ratio of decomposed calcium carbonate to sulfur and negatively correlated to the free calcium oxide content of fly ash.

Experimental investigation on the combustion behaviour of pre-dried Greek lignite

The present paper includes the results of the combustion tests with Greek dried lignite performed at a 1 MWth semi industrial scale pulverized coal combustion facility. Scope of the campaign is the investigation of the combustion behaviour of Greek lignite, i.e. temperature fields, ignition, burnout, emissions, as well as slagging and fouling tendency, while firing with varying levels of recirculated flue gas. Dry coal co-firing conditions in a large scale boiler are simulated by adjusting the volume flow of recirculated flue gas. Two test series representing different boiler operation modes are performed. During the first series the maximum flue gas temperature increase, when co-firing dry coal, is determined, while in the second test series the needed load decrease, in order to keep constant furnace outlet temperature in dry coal co-firing conditions is recorded. A detailed measurement set is carried out including temperature profiles, emissions, fuel, fly ash sampling and slagging and fouling investigations through the installation of dedicated deposition probes. The anticipated increase of the furnace temperature profiles by decreasing the inserted recirculated flue gas is confirmed by the experimental results. No clear trend of dry coal co-combustion on the emissions' behaviour is noticed, while dry coal firing appears to have a moderate effect on the deposition behaviour of Greek lignite. These preliminary investigations indicate that no significant operational problems are expected during a potential future demonstration of dry lignite co-firing in a Greek large scale boiler.

Numerical investigation on the combustion behaviour of pre-dried Greek lignite

Dry coal firing is expected to play an increasingly important role in future lignite power plants. The planned evolution from the conventional lignite drying concept with hot recirculated flue gas to the “fluidized bed drying with internal heat utilization, WTA”, technology in the next generation of lignite power plants is estimated to bring an additional efficiency increase of 2–4% points compared to the today’s state of the art. In this framework NTUA/LSB and CERTH/ISFTA has performed experimental investigations at a semi industrial scale 1 MWth facility on the characterization of Greek pre-dried lignite’s combustion behaviour in terms of temperature fields, heat transfer, emissions, slagging and fouling tendency and residues quality. The present work focuses on the numerical investigation of Greek dry lignite combustion firstly by post-processing and evaluation of available experimental data and secondly by combustion simulations. Q–T plots describing the heat transfer in the experimental facility are derived and specific cases of the performed tests are simulated with a commercial CFD tool, in order to estimate flow, temperature fields, NOx emissions and compare with the available experimental data. A good agreement between simulated and experimental results will support the further work on large scale boiler simulations in raw and dry coal co-firing mode, where the possibility of validation with experimental data is limited. The obtained Q–T diagrams are used to evaluate the influence of co-firing on the heat transfer in the facility and to further extrapolate the conclusions of the performed semi industrial tests on the large scale. The overall results of the CFD simulations, including predictions of temperature and NOx profiles, are in good agreement with the available experimental data at the reference case, while at the dry coal co-firing cases succeed on reproducing the basic trends of the performed experiments.

Quantitative evaluation of minerals in fly ashes of biomass, coal and biomass–coal mixture derived from circulating fluidised bed combustion technology

The chemical and mineralogical composition of fly ash samples collected from laboratory scale circulating fluidised bed (CFB) combustion facility have been investigated. Three fly ashes were collected from the second cyclone in a 50 kW laboratory scale boiler, after the combustion of different solid fuels. Characterisation of the fly ash samples was conducted by means of X-ray fluorescence (XRF), X-ray diffraction (XRD) and scanning electron microscopy (SEM). Quantitative analysis of the crystalline (mineral) and amorphous phases in each ash sample was carried out using the Rietveld-based Siroquant system, with an added spike of ZnO to evaluate the amorphous content. SiO 2 is the dominant oxide in the fly ashes, with CaO, Al 2O 3 and Fe 2O 3 also present in significant proportions. XRD results show that all three fly ashes contain quartz, anhydrite, hematite, illite and amorphous phases. The minerals calcite, feldspar, lime and periclase are present in ashes derived from Polish coal and/or woodchips. Ash from FBC combustion of a Greek lignite contains abundant illite, whereas illite is present only in minor proportions in the other ash samples.

Uncertainty management of a hydrogeological data set in a greek lignite basin, using BME

The occurrence of chemical pollutants in ground water is an issue of considerable interest. In the case of Ptolemais lignite opencast mining area in Greece, ammonium, nitrites, nitrates, iron total and total manganese concentrations, as well as various other elements have been monitored since the early 2000s through a borehole network. The continuous, though, alteration of the surface topography due to the intensive mining works, limits the life span of the water boreholes and results to irregular spatiotemporal distribution of the samples. Regarding the problem of mapping the water contamination, the coarse and irregular sampling pattern, combined with absence of seasonal variations and temporal trends, does not facilitate spatiotemporal processing of the data. On the other hand, a mere spatial analysis requires the attribution of the whole set of monitored values for each borehole, to a single point in space. The objective of this work is to develop a methodology to cope with the problem of uncertainty caused due to the above assumptions. The proposed solution is based on the consideration of interval data. The Bayesian maximum entropy (BME) theory (Christakos, Modern spatiotemporal geostatistics. Oxford University Press, New York, 2000) is an essential component of this methodology. The main reason for this is that it is the only theory in the framework of Geostatistics that offers powerful tools to merge the uncertainty sources with the rest of conventional measurements. This ability is a result of its generalized view on the problem of estimation that focuses on the knowledge of a natural variable and not the variable itself. The application of the proposed methodology led to sharper posterior distributions, an indication of the increased certainty in estimated values which is induced by the broader utilization of data.

Application of Greek lignite as an additive for controlling rheological and filtration properties of water–bentonite suspensions at high temperatures: A review

This review paper presents the results of an extensive study investigating whether addition of 3% w/w Greek lignite to 6.42% w/w water–bentonite suspensions, after being exposed to high temperatures, can prevent gelation and control filtration characteristics. Two different bentonites and eight lignites from different Greek basins have been used while a commercial lignite product has been used as standard. The lignite-free bentonite suspensions heated to 177 °C for 16 h (thermal aging) thicken considerably, increasing the yield stress and the yield point. Fluid consistency and flow behavior indices also change while no significant change is observed for plastic viscosity. Thermal aging of the suspensions results in unacceptably high fluid loss values. Addition of Greek lignite to water–bentonite suspensions, followed by thermal aging, provided the rheological stability of the suspensions by maintaining the low yield stress/point regardless of the type of bentonite. Some of the lignites performed as well as their commercial counterpart. No specific trends for rheological improvement have been identified with respect to various characteristics of lignites such as contents of humic, fulvic acids, humins and other parameters such as specific surface area and cation exchange capacity. Furthermore, addition of lignite in most cases provided very good filtration control of the water–bentonite suspensions after exposure to 177 °C, with some Greek lignites being superior to the commercial product. The same lignite parameters examined for rheological control, were also examined to determine their effect on fluid loss of these suspensions for both bentonites. The content of humic and fulvic acids of two groups of lignites showed weak inverse correlations with the fluid loss volumes for both bentonites, while all other parameters did not seem to directly correlate with the effectiveness of the lignites.

Evaluation of low-rank coals as raw material for Fe and Ca organomineral fertilizer using a new EDXRF method

A rapid and reliable method for analyzing Fe and Ca in low-rank Greek coals was developed. The presence of Fe and Ca is of importance regarding the potential use of these coals as raw material for organomineral fertilizers. Samples were collected from the main Greek lignite deposits and standards were prepared using Atomic Absorption Spectroscopy (AAS), which were also employed in the Energy Dispersive X-ray Fluorescence (EDXRF) method. The new method offers the advantages of being timesaving, non-destructive and can be easily incorporated in a fertilizer production line. Analysis of low-rank Greek coals demonstrated a significant Fe and Ca content ranging from 0.15 to 1.97 wt.% for Fe and from 0.04 to 2.51 wt.% for Ca. When both EDXRF and AAS techniques were applied, the Fe and Ca concentration values differed less than 5%, demonstrating that both techniques are reliable for low-rank coals in the above concentration range. These EDXRF results may be used as a preliminary test regarding the application of Greek coals in organomineral fertilizer production, given that in these coals iron and calcium are the most abundant metals.

Liberation of volatiles from Greek lignites during open system non-isothermal pyrolysis

Open system non-isothermal (programmed) pyrolysis with on line quantitative gas chromatographic analysis of pyrolysis gases (methane, carbon dioxide, carbon monoxide and molecular nitrogen) was performed on a series of Greek lignite samples. The investigation was aimed at exploring variations in the chemical properties of the samples and correlating them with petrographic data. For reference purposes one lignite sample from NW Germany was studied using the same procedure. The pyrograms of the four gases are sensitive indicators reflecting the chemical composition of the lignites. They represent unique fingerprints and document a greater variability in chemical composition than suggested from the petrographic data and proximate analysis.

Lignite industry in Greece within a world context: Mining, energy supply and environment

Today coal covers 38% of global production and roughly 30% of the EU-25 power output. In 2005 domestic lignite with a share of 60.5% in power generation and accounting about 30% of primary energy consumption is currently the most important indigenous fuel of Greece. Greece, mining 70 Mt annually, is the second lignite producer in the EU and fourth in the world. Approximately 97% of the lignite used to supply the existing lignite-fired power plants of Greece is mined by Public Power Corporation S.A. (PPC). Lignite as the base load fuel gives a competitive strength in PPC's and Greece's fuel mix. Due to lignite consumer prices in Greece are significantly below those in other comparable markets in EU-15. Extraction of lignite has a very long tradition. Significant achievements and large experience which has been gained during many years of mining operations place Greek lignite-mining industry in the leading position in Europe. The paper presents current state of Greek lignite industry, including operating mines, volume of production and other important production indicators as well as improvements in labor productivity and good results in industrial safety. The future of coal and specifically of Greek lignite will be crucially determined by environmentally compatible, i.e. low-CO 2 generation of electricity. Investment in modernization and renewal of the power plant fleet are the key to securing electricity supply and progress in preventing climate change.

Evaluation of an On-Line Ash Analysis System for Low-Grade and Inhomogeneous Greek Lignite

The possibility of using commercial on-line analysis systems for monitoring the ash content of low-grade lignites was investigated by carrying out numerous bench- and pilot-scale trials in the mines of Public Power Corporation SA, Greece. Pilot-scale trials were based on a dual-energy {gamma}-ray transmission analyzer, which was installed on the conveyor belt that transports lignite from the pit to the bunker of Kardia mine, Ptolemais. According to the obtained results, the accuracy of the on-line measurements was not adequate and did not allow lignite quality monitoring in real time. The deterioration of the on-line measurements' accuracy, compared to previous applications in other mining sites, was related to the intense variation of the lignite ash content and ash composition, which distorted the calibration of the analyzer. The latter is based on certain assumptions regarding the average atomic number of the organic and mineral matter contained in the lignite. Further experimental work is needed to investigate solutions for successful implementation of this method to low-grade lignites that exhibit large variation in ash content and composition. 17 refs., 15 figs., 7 tabs.