Michael Galetakis

A spatial decision support system for the optimal environmental reclamation of open-pit coal mines in Greece

Mine reclamation is an integral part of the mineral development process. The selection of land use after the mine closure is a difficult decision, which is complicated further because of the variety of parameters that must be taken into account trying to provide the local community with a viable development plan. Conventional methods used for reclamation planning are characterised by the lack of data integration and by time-consuming analysis. In this study, we propose a spatial decision-support system (SDSS) that minimises these problems, as data integration and analysis are offered within one computerised environment. A geographical information system and multi-criteria decision-making methods, based on binary integer linear programming models, have been integrated to select the appropriate land use in different parts of a post-mining area taking into account social, technical, economic, environmental and safety criteria. The proposed SDSS was used for the selection of the optimal landscape reclamation strategy of the Amynteon lignite surface mine located at West Macedonia Lignite Centre, Northern Greece. On the basis of developed mine maps, the model variables are assessed and incorporated into the objective optimisation function. Emphasis is placed on the spatial diversification of the model variables. The application demonstrates that the decision-support system allows the mining company to determine in an efficient way the specific land use (agricultural land, forest, recreational area and industrial zone) that is considered the most suitable for every part of the study area.

Study on Catalytic Combustion of Biomass Mixtures with Poor Coals

The effect of catalyst addition on ignition and combustion characteristics of biomass fuels from the Mediterranean region, one lignite and lignite/biomass blends, were investigated. Transition metal oxides and alkali/alkaline earth compounds were used as catalysts. The experiments were conducted in a thermogravimetric analysis system. The performance of the process was evaluated in terms of combustion rate, ignition, and combustion indices. The results showed that metal oxides enhanced the ignition and combustion performance of lignite, showed no catalytic activity to burn off of biomass fuels, but influenced the temperature sensitivity of their reaction in air. The relative activity was in the following order: V2O5>Fe2O3>CaO>NaCl>MgO>CuO>TiO2>LiCl. The combustion characteristics of the blends followed those of parent fuels in an additive manner. Blending lignite with biomass fuels increased its thermochemical reactivity. In terms of burnout, catalyzed combustion of blends was further improved.

Prediction of the Performance of On-line Ash Analyzers Used in the Quality Control Process of a Coal Mining System

Abstract In this article, an analytical method for the prediction of dual energy transmission performance, based on uncertainty analysis, is proposed. Comparison of theoretically computed errors to those estimated during the trial operation of dual energy transmission analyzers installed in the lignite mines of Megalopolis and Ptolemaes (Greece), shows that the developed analytical method for the prediction of dual energy transmission performance is not only accurate but also explanatory, aiding engineers and quality control personnel to realize the capabilities of the analyzer. Also, by taking into consideration the reduced quality variation of mined coal, as a result of the homogenization, which takes place during mining from several benches as well as during transportation, stacking, and reclaiming, the optimal installation position of the analyzer can be selected.

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.

Discrete-Event Simulation of Continuous Mining Systems in Multi-layer Lignite Deposits

Continuous surface mining systems, employing bucket wheel excavators, belt conveyors, and stackers, are used in the exploitation of most of the large lignite mines in northern Greece. One particular characteristic of these mines is that the deposits consist of a series of lignite layers of thickness varying from just a few centimeters up to several meters, with interbedded layers of sandy and clayey waste material. This multi-layer geology dictates frequent changes of the material excavated on each bench, which adds to the complexity of the inherently stochastic mining system and makes material flow a critical performance parameter.

Public acceptance of surface mining projects and the determination of the marginal environmental cost

Surface mining operations can adversely impact the environment. The size and nature of earth-moving works carried out for the exploitation of mineral deposits can cause severe environmental problems unless the mining company plans and implements an effective environmental protection and land reclamation programme. Such a programme starts from the early stages of deposit exploration and continues for many years after the closure of the mine. The type and magnitude of environmental damage associated with surface mining projects are closely related to various site-specific, physical, chemical, ecological, socioeconomic and cultural characteristics, which must be thoroughly identified, analysed and modelled. The goal of this study is to provide decision-makers with information that is necessary for assessing the contribution of a proposed project to national, regional and local development and welfare. Using this approach, project proponents and supervising authorities are able to communicate effectively with public interest groups. Speedy and effective communication between all stakeholders engenders mutual cooperation and collaboration while minimising political damage, all of which will minimise risks that may lead to financial losses or cancellation of the project in its entirely. This article is a review of the main regulatory aspects of public involvement in decision-making involving environmental management of surface mining projects with special emphasis on the Aarhus Convention, an initiative of UN Economic Commission for Europe. The study cites several cases of ‘contract-based’ agreements between mining companies, supervising authorities and the public that have successfully addressed various environmental and socioeconomic issues. Furthermore, this article proposes a methodology for predicting the budget that is required for financing environmental protection and land reclamation works throughout the entire life of the mine, taking into account numerous technical and economic parameters as well as the associated uncertainty. The methodology proposed in this study may be useful during negotiations of environmental management plans for new or for existing mining activities.

Investigation of the Combustion Performance of Residues from Vineyards and Processing Industry via Fluidized Bed Experiments, Factorial Design, and Modeling

ABSTRACT Residues from vineyards and wine/spirits industry, as being abundant in South European countries, were investigated for their application in thermal processes for energy production. The thermal behavior and the reactivity of the fuels and their blends were determined by thermogravimetric analysis tests. The combustion performance of the residues in terms of efficiency and emissions was studied by carrying out experiments in a fluidized bed unit. The effects of excess air ratio, fuel loading, and blending ratio were examined and a factorial design and modeling was developed in order to provide optimal values of process variables for minimizing emissions. The results showed that CO emissions were low, SO2 emissions were negligible, while NOx emissions from grape husks were high. A mitigation of CO and NOx levels could be achieved by decreasing excess air from 50% to 30% or reducing reactor loading. By increasing the percentage of grape husks in the mixtures, flue gas emissions were increased, however, combustion efficiency was maintained at high levels. Factorial design analysis and modeling indicated that the optimum combustion and emission performance was accomplished when the combustor was fed with vine shoots at reduced loading and excess air below 40%.

Reprint of: Production scheduling of a lignite mine under quality and reserves uncertainty

Abstract 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.

Development of an Expert System for the Prediction of the Performance of Bucket-Wheel Excavators Used for the Selective Mining of Multiple-layered Lignite Deposits

The performance of bucket-wheel excavators used for the selective mining of multiple-layered lignite deposits is mainly determined by the physical and mechanical properties of the excavated material (digability parameters), as well as by the thickness and the inclination of the excavated layer. The lack of sufficient information regarding the diggability of the excavated layers during mine design stage results in a poor estimation of the bucket-wheel excavator’s performance. Such inaccurate estimation could lead to inappropriate equipment selection. The possibility of prediction of the bucket-wheel excavator performance by using an expert system was investigated in the present study. The development of the expert system was based on the existing boreholes’ data related to physical and mechanical properties of waste and lignite layers, on their geological descriptions and on the existing experiential knowledge about selective mining by bucket-wheel excavators.

A Multi-objective Response Surface Analysis for the Determination of the Optimal Cut-off Quality and Minimum Thickness for Selective Mining of Multiple-layered Lignite Deposits

For the estimation of grade and tonnage of the multiple-layer lignite deposits a sophisticated evaluation methodology, based on exploitation and quality parameters, is used. These parameters are usually determined empirically and the selected values are not always optimal. For the estimation of the optimal values, a new methodology based on response surface analysis is suggested. The minimum thicknesses for selective excavation of lignite and waste layers, as well as the maximum allowable ash of the mined lignite, were considered as the decisive control parameters, while the recovery of the lignite, the ash of the mined lignite, and the number of the exploitable lignite blocks were selected as the response variables. The developed methodology was applied in the South Field lignite mine in the area of Ptolemais. The estimated optimal values were compared to those currently applied and their impacts to deposit recovery, equipment utilization, and to the quality of the mined lignite were examined.