Lignite Power Plants Research Articles

Thermodynamic analysis and comparison of retrofitting pre-drying concepts at existing lignite power plants

Lignite is considered as a domestic and abundant energy source for several countries. However, its high ash and moisture content have a negative effect on power plant efficiency, on cost of electricity (COE) and consequently on CO2 emissions. The aim of the present work is the investigation and optimization of existing lignite pre-drying concepts and their improvement in terms of overall plant efficiency and integration. The main process parameters examined are the heat source for drying and the respective drying medium. In the conventional lignite drying process, hot recirculating flue gas is used as a heating medium, while in the current state-of-the art pre-drying concepts, a fluidized bed drying system is considered. Different concepts are also examined including a) the utilization of preheated air as heating medium and b) the optimized integration of a heat pump as a heat source for the drying process. Based on the performed thermal cycle calculations, the plant efficiency increase is evaluated. The results of the study indicate that higher plant efficiency is expected, when focussing on the optimized pre-drying process scheme and its integration with the overall steam.

Source-receptor relationships by using dispersion model in a lignite burning area in Western Macedonia, Greece

Quantifying the contribution of individual sources to air pollution in one area is the first essential step in managing air quality in this region. This is of great interest especially in areas with combined urban and industrial emission sources. The area of Western Macedonia is a very complex in terms of air quality management problem because of large and complex pollution sources operating in the region. The emissions from five lignite power plants (LPP) operating in this region, the corresponding opencast lignite mining, as well as the urban activities in the industrial axis, is a complex problem to quantify the contribution of these sources in a spatial and temporal scale in the region. This paper attempts to quantify the contribution of LPP to the particulate pollution of this region, using PM10 concentrations measurements and simulations. Specifically were used: a) suspended particulate PM10 concentration measurements for a two years period (2009-2010) at various locations in the region and b) simulations of atmospheric dispersion. The results showed that the LPPs contribution to the PM10 concentrations of the regions studied ranged from 27-84% when the background was removed. These results were also confirmed by the corresponding Index of Agreement (IOA) between the mean monthly model calculations and the station measurements after removing the background. The LPPs contribution to the PM10 concentrations was a factor of the distance between the receptor area and the LPP, while the presence of other PM10 sources was found also to contribute at a higher or a lesser extent, depending on the area’s activities (e.g. urban, agricultural etc) and seasonal characteristics.

Increasing the renewable energy sources absorption capacity of the Macedonian energy system

Macedonian energy sector is the main emitter of greenhouse gases with share of about 70% in the total annual emissions. Also, 70%–75% of emissions are associated with the electricity generation due to the predominant role of the lignite fuelled power plants. Recently, the government has adopted a strategy for the use of renewable energy sources (RES) which identifies a target of 21% of final energy consumption from RES by 2020. In this paper, analyses are conducted in order to investigate to which extent and in which way the absorption capacity of the power system for RES electricity can be improved. For this purpose, combining various conventional and RES technologies, including pump storage hydro power plant and revitalisation of the existing lignite power plants six scenarios for the power system expansion are developed by making use of EnergyPLAN model. Critical excess of electricity analyses are conducted in order to identify the maximal penetration of wind electricity. The results have shown that in the exiting capacities maximal penetration of wind electricity in 2020 is 13% of total electricity consumption. The revitalization of the existing lignite power plants and building of pump storage power plant would increase the wind penetration. Furthermore, the developed scenarios are comparatively assessed in terms of the associated greenhouse gases emissions and import of electricity.

Calcium looping for CO2 capture from a lignite fired power plant

Calcium looping (CaL) process is considered as a competitive technology for the capture of CO2 emitted from fossil fuel power plants. In this process two fluidized bed reactors are coupled. In the first reactor, i.e. carbonator, CO2 is absorbed by CaO and CaCO3 is produced, while in the second one, referred as calciner, fuel is oxy – fired, so that calcium particles, already having absorbed CO2 in the carbonator in order to produce CO2-rich flue gases, are regenerated. Numerous studies have focused so far on the implementation of this process in coal fired plants. However, little work has been performed in terms of lignite fired plants. Thus here, the knowledge gaps are filled by means of a thorough investigation of the particular technology using a thermodynamic approach. It is worthwhile noticing, that the analysis is conducted on an existing lignite power plant, which is already operating and is located at the wider area of Meliti, Greece (330MWe lignite fired power plant). For a more profound work, a series of parametric scenarios are investigated, for their optimum coupling setup, which subsequently lead to the conclusion that the energy penalty for the sorbent regeneration in cases of lignite combustion is higher than in cases of coal combustion. This is due to the higher moisture content and lower calorific value of lignite compared with coal. Finally, in order to achieve a lower energy penalty, several configurations are presented, resulting that the optimum is to burn pre-dried fuel, utilize solid heat exchanger and insert the fresh limestone inside the calciner instead of the carbonator. All configurations are evaluated in terms of CO2 capture and net efficiency.

Cement mortars hybridized with zeolite and zeolite-like materials made of lignite bottom ash for heavy metal encapsulation

Abstract Bottom ash (BA) from Mae Moh lignite power plant was used to synthesize zeolite and zeolite-like materials. Low temperature synthesis (100–110 °C) was completed using SiO 2 to Al 2 O 3 with molar ratios of 2.94 and 2.92, respectively. Factors investigated that affect synthesis include particle size distribution, pretreatment of BA, concentration of alkali solution and liquid to solid ratio. The synthesized product qualities were characterized by mineralogical composition, morphology, specific surface area, pore size, pore volume and cation exchange capacity. Natrolite-K zeolite (NAT-K) was obtained with a solution of BA and 7 M KOH. Zeolite-like material (potassium aluminosilicate hydrate: KASH) was obtained using very fine BA and 9 M KOH solution. The NAT-K, KASH and BA powders were used to replace type I Portland cement at 0, 5, 10, 20 and 30% by weight to produce composite materials for heavy metal encapsulation. The compressive strength and bulk density of the NAT-K- or KASH-hybridized cement mortars were tested at 1, 7 and 28 days. The heavy metal encapsulation capacity was also tested using the 28-day cement mortar containing either 5 wt% NAT-K or KASH adsorbed with Cr, Ni and Cd ions. The results showed that 5 wt% of NAT-K could improve early strength of cement mortar and the 28-day specimens with 5–10 wt% of NAT-K replacement had compressive strength similar to that of the normal cement mortar. The NAT-K and KASH encapsulate Cr, Ni and Cd ions in the structures of cement mortar matrices more than 97%.

An energy source policy assessment using analytical hierarchy process

Energy resource planning for a district in the built environment is a challenging issue for the authorities. They have to take many criteria into account in order to derive sustainable, robust, and long-term energy policies. Among these criteria authorities have to look at the alternatives from different point of views, such as the environmentalists, industry, local community, and local authorities of that district. In this study, an Analytical Hierarchy Process (AHP) method was developed in order to facilitate energy resource planning activities. This method was applied to the district of Aydin in Turkey. Hypothetical results showed that solar energy investments has the highest priority and can be realized by local residents and government, while industry and government can make investments for geothermal power plants and de-centralized lignite power plants using clean technology.

Investigation of technical and economic aspects of pre-dried lignite utilisation in a modern lignite power plant towards zero CO2 emissions

The pre-drying technology is expected to play an important role in the next generation of brown coal power plants. The integration of the fluidised bed drying system with internal heat utilization (WTA technology) is estimated to bring an efficiency increase of up to 6 percentage points in future brown coal power plants compared to the current state of the art. Furthermore, brown coal pre-drying is considered as an indispensable part in future oxy-fuel brown coal fired boilers. In the present work the potential utilisation of brown coal pre-drying is evaluated based on a realistic reference case scenario. Thermal cycle calculations and economic feasibility studies are carried out for a modern Greek power plant, taken as reference case and for two dry lignite firing cases. In the first co-firing scenario investigated a co-firing share of dry lignite to a thermal share of 25% is regarded. Furthermore, the configuration of a brown coal boiler fired 100% with pre-dried lignite is examined. For all cases, the main economic parameters are calculated including investment costs, cost of electricity, payback period, return on investment. The effect of the CO2 allowances price on the economic feasibility of the considered scenarios is also evaluated.

An economic comparison assessment of lignite and biomass IGCC power plants

Abstract An economic assessment between lignite and biomass integrated gasification combined cycle power plants (IGCC and BIGCC respectively) for power generation was carried out. The two alternative power plants are presented together with the selection of the appropriate equipment. An economic evaluation was carried out for the two power plants, taking into account a net power of 100 MW. The economic evaluation was carried out using the methods of the net present value and the internal rate of return. Finally, a sensitivity analysis was carried out. Calculations have been carried out with an Excel spreadsheet. It was shown that both investments are profitable throughout their economic life. However, because of the difference in the selling price of the MW h between the two power plants and to the cost of CO 2 emissions for the lignite power plant, the biomass plant is more profitable with a net present value up to 417 M€ and an internal rate of return of 23.33%. A threshold price of 27.28 €/t for CO 2 emissions was also determined.

Investigation of pre-drying lignite in an existing Greek power plant

The application of lignite pre-drying technologies in next generation of lignite power plants by utilizing low pressure steam as a drying medium instead of hot recirculated flue gas - combined with thermal utilization of the vaporized coal moisture - is expected to bring efficiency increase of 2-4 percentage points in future lignite power plants compared with today?s state of the art. The pre-drying concept is of particular importance in Greek boilers firing lignite with a high water and ash content. The combustion of Greek predried lignite has been investigated experimentally and via numerical simulations in our previous research. This study focuses on the potential integration of a lignite pre-drying system in an existing Greek power plant with dry lignite co-firing thermal share of up to 30%. The radiative and convective heat fluxes to the boiler and the overall boiler heat balance is calculated for reference and dry lignite co-firing conditions by an in-house calculation code. The overall plant?s thermal cycle is then simulated using commercial thermal cycle calculation software. The net plant efficiency is in this way determined for reference and dry coal co-firing conditions. According to the simulation results the integration of a pre-drying system and the implementation of dry lignite co-firing may bring an efficiency increase of about 1.5 percentage points in existing Greek boilers. It is therefore considered as an important measure towards improving plant efficiency and reducing specific CO2 emissions in existing plants.

Production scheduling of a lignite mine under quality and reserves uncertainty

The effect of uncertainty sources to the stochastic optimization of the combined project of a new surface lignite mine exploitation and power plant operation for electricity generation is investigated. Major sources of uncertainty that were considered are the reserves and the quality of the lignite. Since probability distribution functions for these uncertainties were estimated during the detailed exploration phase of the deposit, the overall goal is then to determine the optimal capacity of the power plant and consequently the optimal production rate of the mine over the time. The optimization objective that was selected is the maximization of the net present value of the project. Emphasis is placed on the sensitivity analysis for the investigation of the effect of quality and reserves uncertainty on project optimization, on the mathematical formulation of risk attitude strategy and on increasing the efficiency of the optimization process by creating a limited set of feasible solutions applying empirical rules. The developed methodology was applied for the determination of the optimal annual production rate of a new surface lignite mine in the area of Ptolemais–Amynteon in Northern Greece.

Serbian energy development based on lignite production

Lignite, as an energy resource, is a mainstay of electricity generation in the Republic of Serbia. Installed capacity of lignite power plants represents 68% of the total installed capacity of Electric Power Industry of Serbia, the only company in Serbia, which manages electricity generation. In the future, with the increase in demand for electricity, both in Serbia and in Europe, we should expect more extensive and effective utilization of lignite as the main energy potential. In addition, due to increased emissions of CO2, NOX and other pollutants, the Republic of Serbia must accelerate the implementation of flexible mechanisms of Kyoto Protocol and the guidelines set by the European Union. Lignite in the future will retain its existential importance in the electricity generation in the Republic of Serbia.

Dry Lignite Cofiring in a Greek Utility Boiler: Experimental Activities and Numerical Simulations

Lignite predrying and dry lignite firing is considered as an important development step for the next generation of lignite power plants. The integration of a predrying system in future lignite power plants, which utilizes low temperature steam for the drying process, combined with the further thermal utilization of lignite’s evaporated moisture, may bring an efficiency increase of four to six percentage points compared with today’s state of the art. Firing predried lignite is however expected to cause certain changes in the combustion behavior of large scale boilers. The investigation of these changes in an existing Greek utility boiler through experimental activities and numerical simulations is the scope of the present work. The investigations take place in a 75 MWth lignite fired Greek boiler. The specific unit is equipped with dedicated dry lignite burners. The measurements are performed with a dry lignite thermal share of 6%. Higher cofiring thermal shares of up to 20% are further simulated and the e...

Sensitivities of injection rates for single well CO 2 injection into saline aquifers

This paper investigates methods to predict potential injection rates of CO 2 into a saline aquifer and analyses the sensitivities of the input parameters. Geological parameters are based on conditions at the European CO 2 Onshore Research Storage and Verification Project in Ketzin, Germany, and varied within an acceptable range. Two injection regimes for CO 2 are analysed: pressure controlled injection and power plant controlled injection, where the CO 2 flux depends on the load curve of a 600 MW net lignite power plant. The results are determined with a numerical model and compared to an analytical solution with constant pressure injection. The injection rates depend mainly on the geological setting and only slightly on technical parameters. Aquifer permeability and thickness show approximately linear sensitivity and have a dominant impact. Depth is also of high importance, but the impact is more complex and is based on geothermal temperature and hydrostatic gradient, which affect viscosity, compressibility and caprock stability. Vertical anisotropy is insensitive. The difference in the mean rate between constant pressure injection and power plant controlled injection is 8%. Peak injection rates are 29% above mean injection rates, which shows that the reservoir can effectively dampen rate variations. The analytical solution predicts the highest injection rates, the lowest temporal variability and decreasing rates with injection duration. The numerical solution predicts a stronger temporal variability and the rates increase with duration. In the initial phase the differences between the methods add up to a factor of 1.45.

The effect of quality and reserves uncertainty to production scheduling of a lignite mine feeding a power plant

The effect of uncertainty sources to the stochastic optimization of the combined project of a new surface lignite mine exploitation and power plant operation for electricity generation is investigated. Major sources of uncertainty that were considered are the reserves and the quality of the lignite. Since probability distribution functions for these uncertainties were estimated during the detailed exploration phase of the deposit, the overall goal is then to determine the optimal capacity of the power plant and consequently the optimal production rate of the mine over the time. The optimization objective that was selected is the maximization of the expected net present value of the project. Emphasis is placed on the mathematical analysis applied for the investigation of the effect of the two main parameters in project optimization.

Monitoring of arsenic in aquatic plants, water, and sediment of wastewater treatment ponds at the Mae Moh Lignite power plant, Thailand

Mae Moh is a risky area for arsenic contamination caused by the effluent from biowetland ponds in Mae Moh lignite-fuelled power plant. The objective of this study was to investigate the arsenic concentrations of Mae Moh biowetland ponds and determine the main factors which are important for arsenic phytoremediation in the treatment system. The result revealed that arsenic concentrations in the supernant were in the range of less than 1.0 microg As L(-1) to 2.0 microg As L(-1) while those in the sediment were in the range of 25-200 microg As kg soil(-1). Both values were below the Thailand national standard of 0.25 mg As L(-1) for water and 27 mg As kg soil(-1) for the soil. Arsenic accumulation in the biomass of 5 aquatic plants at the biowetland ponds ranged from 123.83 to 280.53 mg As kgPlant(-1). Regarding the result of regression analysis (R (2) = 0.474 to 0.954), high concentrations of organic matter and other soluble ions as well as high pH value in the sediment could significantly enhance the removal of soluble arsenic in the wetland ponds. From the regression equation of accumulated arsenic concentration in each aquatic plant, Eichhornia crassipes (Mart.) Solms. (R (2) = 0.954), Ipomoea aquatica Forsk. (R (2) = 0.850), and Typha angustifolia (L.) (R (2) = 0.841) were found to be preferable arsenic removers for wastewater treatment pond in the condition of low Eh value and high content of solid phase EC and phosphorus. On the other hand, Canna glauca (L.) (R (2) = 0.749) appeared to be favorable arsenic accumulator for the treatment pond in the condition of high Eh value and high concentration of soluble EC.

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.

Factors affecting the cost of capture for Australian lignite coal fired power plants

In Australia, one of the challenges in deploying CO2 capture and storage is the cost of implementing capture at the large number of lignite power plants. This study investigates the cost of retrofitting CO2 capture to a typical 500 MW lignite coal-fired power plant in Australia, and includes the costs for CO2 separation and compression of the CO2 in preparation for transport via pipeline to a storage site. The results show that the cost for CO2 capture using MEA solvent is over US$70 per tonne CO2 avoided. Using alternative solvent technology reduces the cost to less than US$30 (approximately A$35) per tonne CO2 avoided.

Life cycle assessment of carbon dioxide capture and storage from lignite power plants

In this article, we present a life cycle assessment (LCA) of CO 2 capture and storage (CCS) for several lignite power plant technologies. The LCA includes post-combustion, pre-combustion and oxyfuel capture processes as well as subsequent pipeline transport and storage of the separated CO 2 in a depleted gas field. The results show an increase in cumulative energy demand and a substantial decrease in greenhouse gas (GHG) emissions for all CO 2 capture approaches in comparison with power plants without CCS, assuming negligible leakage within the time horizon under consideration. Leakage will, however, not be zero. Due to the energy penalty, CCS leads to additional production of CO 2. However, the CO 2 emissions occur at a much lower rate and are significantly delayed, thus leading to different, and most likely smaller, impacts compared to the no-sequestration case. In addition, a certain share of the CO 2 will be captured permanently due to chemical reactions and physical trapping. For other environmental impact categories, the results depend strongly on the chosen technology and the details of the process. The post-combustion approach, which is closest to commercial application, leads to sharp increases in many categories of impacts, with the impacts in only one category, acidification, reduced. In comparison with a conventional power plant, the pre-combustion approach results in decreased impact in all categories. This is mainly due to the different power generation process (IGCC) which is coupled with the pre-combustion technology. In the case of the oxyfuel approach, the outcome of the LCA depends highly on two uncertain parameters: the energy demand for air separation and the feasibility of co-capture of pollutants other than CO 2. If co-capture were possible, oxyfuel could lead to a near-zero emission power plant.

Neutron activation analysis and natural radioactivity measurements of lignite and ashes from Megalopolis basin, Greece

Elemental concentrations and specific activity values of natural radionuclides were measured in lignite, bottom ash and fly ash samples collected from the Megalopolis power plant A in southern Greece, using nuclear analytical techniques. The results show that the elements As, Br, Mo, Sb, Se, and U were enriched in the lignite samples, the elements Mo, Se and U in bottom ash, while fly ash samples were enriched in As, Mo, Sb, Se and U. Specific activity measurements also show that 238U (226Ra) activity values in lignite and both ash samples were high relative to the corresponding data for coal and earth crust given in the literature. As a high quantity of fly ash is produced during the operation of the lignite power plant A, this power plant should be considered as a major source of air particulate pollution and radiation to the population living in the vicinity of lignite burning power plant.

Elemental deposition in the vicinity of a lignite power plant in southern Greece

Bulk deposition samples were collected on a monthly basis in Megalopolis city, located near lignite power plants. A total of 23 elements (As, Br, Ca, Ce, Co, Cr, Cs, Eu, Fe, Hf, La, Mo, Na, Rb, Sb, Sc, Se, Ta, Tb, Th, U, Yb, Zn) were detected in the collected samples using INAA. The coal burning marker elements As and Se were found enriched in the collected samples together with Mo, Br, Sb, U and Zn. Factor analysis permitted the identification of four sources: re-suspended soil/road dust, lignite power plant, sea spray and traffic emissions. A wind direction effect on deposition rates of all elements (except rates of Na, Rb, Sb and Zn) was also found.