Case Study
K.M. Tanguturi; R.S. Balusu
Abstract
It is necessary to obtain a fundamental understanding of the goaf gas flow patterns in longwall mine in order to develop optimum goaf gas drainage and spontaneous combustion (sponcom) management strategies. The best ventilation layout for a longwall underground mine should assist in goaf gas drainage ...
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It is necessary to obtain a fundamental understanding of the goaf gas flow patterns in longwall mine in order to develop optimum goaf gas drainage and spontaneous combustion (sponcom) management strategies. The best ventilation layout for a longwall underground mine should assist in goaf gas drainage and further reduce the risk of sponcom in the goaf. Further, in the longwall panel, regulators are installed in the maingate (MG) seals to control the gas migration on the MG side and the mine operators frequently encountered with seals leakage problems leading to abnormal gas contents in the tube bundles. Extensive parametric studies were carried out to investigate the effects of ventilation layouts, regulators, and seals leakages on the goaf gas distribution using the Computational Fluid Dynamics (CFD) techniques. The results of various CFD simulations are presented and discussed in detail in this paper.
Case Study
Sh. Sadat Etemadzadeh; G. Emtiazi; Z. Etemadifar
Abstract
Most studies on sulfur bioleaching from coal depend on an autotrophic microorganism with a low growth and a long leaching time. For this reason, heterotrophic heat and acidic pH-resistant Alicyclobacillus was used as the growing and resting cells for the sulfur and iron removal from coal. The results ...
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Most studies on sulfur bioleaching from coal depend on an autotrophic microorganism with a low growth and a long leaching time. For this reason, heterotrophic heat and acidic pH-resistant Alicyclobacillus was used as the growing and resting cells for the sulfur and iron removal from coal. The results obtained were analyzed by XRF. The data showed that 26.71% of sulfur was removed by Alicyclobacillus in a few days; however, 49.07% of sulfur was removed by Acidithiobacillus in 30 days. This was interesting since the leachings of zinc, strontium, titanium, and iron by Alicyclobacillus, obtained in a few days, were almost the same as the leachings by Acidithiobacillus in 30 days. The results obtained also showed that the Alicyclobacillus cells growing at 55 ˚C removed most of the coal impurities without any change in the carbon content of this fuel. To the best of our knowledge, coal leaching by Alicyclobacillus is reported for the first time.
Case Study
R. Norouzi Masir; R. Khalokakaie; M. Ataei; S. Mohammadi
Abstract
Mining can become more sustainable by developing and integrating economic, environmental, and social components. Among the mining industries, coal mining requires paying a serious attention to the aspects of sustainable development. Therefore, in this work, we investigate the impacting factors involved ...
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Mining can become more sustainable by developing and integrating economic, environmental, and social components. Among the mining industries, coal mining requires paying a serious attention to the aspects of sustainable development. Therefore, in this work, we investigate the impacting factors involved in the sustainable development of underground coal mining from the structural viewpoint. For this purpose, the decision-making trial and evaluation laboratory (DEMATEL) technique, which is a graph-based method, is utilized. To do so, at first, twenty effective factors are determined for three components. Then the hierarchical structure and the systematic approach are used to determine the total exerted influence or total received influence of the components. The results obtained show that the environmental and social components are the most important, and the economic components are the least important among them.
Case Study
B. A. Mert
Abstract
This paper presents the procedures used for determining and defining the tonnage and grade of the coalfields of Kangal basin from the developed GIS-aided block model. In this work, firstly, all the lithological logs of drill holes and chemical analysis data of core in the basin were analyzed with the ...
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This paper presents the procedures used for determining and defining the tonnage and grade of the coalfields of Kangal basin from the developed GIS-aided block model. In this work, firstly, all the lithological logs of drill holes and chemical analysis data of core in the basin were analyzed with the help of geostatistics, and then the digital raster maps of each one of the attributes such as the thickness, calorific value (LCV), ash content (AC%), moisture content (MC%), and surface maps of lignite seams were mapped in GIS environment. In the second stage, quantities of the overburden and resources with different categories were calculated on the basis of field-based quality and volume queries with the help of the digital maps on GIS platform. As a result, it was estimated that the Kalburçayırı field had a tonnage of 116 Mt of lignite with an LCV of 1308 kcal/kg, the Hamal field had a tonnage of 30 Mt of lignite with an LCV of 987 kcal/kg, and the Etyemez field had a tonnage of 48 Mt of lignite with an LCV of 1282 kcal/kg. Also it was estimated that almost 24,278,151 tons of lignite in the Hamal and Etyemez fields had a quality of less than 950 kcal/kg that could be directly fired without the blending process in the power plant. As a consequence, the Hamal and Etyemez fields should go into production as soon as possible and be fired in the power plant after being mixed with the lignite in the Kalburcayırı field so that they can be redounded to economy.
Case Study
Rock Mechanics
M. Zoorabadi
Abstract
Numerical modelling techniques are not new for mining industry and civil engineering projects anymore. These techniques have been widely used for rock engineering problems such as stability analysis and support design of roadways and tunnels, caving and subsidence prediction, and stability analysis of ...
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Numerical modelling techniques are not new for mining industry and civil engineering projects anymore. These techniques have been widely used for rock engineering problems such as stability analysis and support design of roadways and tunnels, caving and subsidence prediction, and stability analysis of rock slopes. Despite the significant advancement in the computational mechanics and availability of high speed computing hardware, the input data and constitutive models remain the main source of errors affecting the reliability of numerical simulations. The problem with the input data has been deepened more by introducing empirical-based methods such as GSI classification to downgrade the rock properties from laboratory scale to field scale. The deformability modulus and strength parameters are the main outputs of these downgrading techniques. Numerical modelling users simply apply these downgrading methods and run the model without considering the real mechanics behind the stress induced failure and deformation around the underground excavations. While to the contrary to the commonly used downgrading methods that produce a constant modulus for rock at all depths, the rock modulus is stress dependent and varies with depth. In addition to this, the mechanism of stress induced displacement is not similar to the deformation of a continuum model simulated with equivalent rock properties. Apart from the mechanical characteristics of rocks, the magnitude and orientation of in-situ stresses are two other important parameters that have significant impacts on stress induced rock fracturing. The impacts of these two parameters have also been neglected in many practical cases. This paper discuss this old fashioned topic in more details with presenting the known facts and mechanics which numerical modelling users ignore them due to the unquestioning acceptance of downgrading methods. It also covers the influence of the stress magnitude and orientation on stress induced rock fracturing.
Case Study
Exploitation
K. Ghanbari; M. Ataei; F. Sereshki; A. Saffari
Abstract
The presence of methane in coal mines is one of the major problems in underground coal mines. Every year, in underground coal mines, a lot of casualties due to outbursts and explosions of methane gas is occurring. Existence of this gas in the mines not only creates a difficult and dangerous situation ...
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The presence of methane in coal mines is one of the major problems in underground coal mines. Every year, in underground coal mines, a lot of casualties due to outbursts and explosions of methane gas is occurring. Existence of this gas in the mines not only creates a difficult and dangerous situation for work but also makes it more expensive. The release of this gas to the air causes a further pollution of the atmosphere and increases the greenhouse gases in the air. Thus Coal Bed Methane (CBM) drainage before, during, and after coal mining is necessary. Accordingly, the CBM drainage can reduce the risks involved in these mines. In the past decade, CBM has offered a significant potential to meet the ever-growing energy demand and can decrease the disastrous events. In this research work, the CBM potential in Eastern Kelariz, Western Razmja, Bornaky, Bozorg, Razzi, and Takht coal mines of Eastern Alborz coal mines company is investigated using the rock engineering systems (RES) based on the intrinsic and geological parameters. Nine main parameters are considered for modeling CBM, and the interactions between these parameters are calculated by a proposed system. Based on the RES method, the parameters that are dominant (depth of cover) or subordinate (gas content) and also the parameters that are interactive are introduced. The proposed approach could be a simple but efficient tool in the evaluation of the parameters affecting CBM, and hence be useful in decision-making. The results obtained show that Razzi coal mine has a good potential to perform CBM drainage.
Case Study
Exploitation
B. Unver
Abstract
The prerequisite of maintaining an efficient and safe mining operation is the proper design of a mine by considering all aspects. The first step in a coal mine design is a realistic geometrical modelling of the coal seam(s). The structural features such as faults and folding must be reliably implemented ...
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The prerequisite of maintaining an efficient and safe mining operation is the proper design of a mine by considering all aspects. The first step in a coal mine design is a realistic geometrical modelling of the coal seam(s). The structural features such as faults and folding must be reliably implemented in 3D seam models. Upon having a consistent seam model, the attributes such as calorific value, ash and moisture contents, volatile matter, and sulfur must be estimated in the block model. Considering the geotechnical and hydrogeological conditions, the most appropriate mine design strategy can be selected and implemented. Application of the above steps to three coal basins in Turkey are presented in this paper. The Soma-Eynez and Tunçbilek-Ömerler basins are the two most important lignite resources having an on-going production and prospect for future underground mining. Comprehensive 3D coal seam modelling is carried out at both basins. As both are extensively faulted due to tectonism, it is a challenging task to realistically model their structures. On the other hand, the Karapınar basin has a considerably different geological, structural, and coal measure rock conditions in comparison to the Eynez-Ömerler basin. The Karapınar basin is a relatively recently explored brown field site suitable mainly for surface mining. Coal seam(s) geometry and quality-related attributes certainly play the most important role for production planning and mining activities. The influence of the inherent characteristics of each site on the modelling and mine design strategy are also briefly discussed. This paper presents the fundamentals of coal seam modelling at various geological and structural conditions. It is believed that the methodology presented in this paper can be considered as a guiding example for a comprehensive 3D modelling and resource estimation of coal seams around the world.
Review Paper
Mineral Processing
I. Kursun Unver; M. Terzi
Abstract
Today coal is among the most important energy sources. In order to meet the world's energy demands, low-calorie lignite with a high ash content is generally used in the large capacity coal-fired thermal power plants. As a result of coal firing, wastes such as fly ash, slag, and flue gas are also produced. ...
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Today coal is among the most important energy sources. In order to meet the world's energy demands, low-calorie lignite with a high ash content is generally used in the large capacity coal-fired thermal power plants. As a result of coal firing, wastes such as fly ash, slag, and flue gas are also produced. Subsequently, toxic trace elements within coal are transferred to wastes such as slag, fly ash, and flue gases. Large amounts of these, which are usually stored in collection ponds or stockpiles, are problematic in terms of environment. Although coal fly ash (CFA) has been utilized in construction and several other industries for decades, its current ratio of utilization is still quite limited. As an important fact, CFA also contains many valuable metals including germanium (Ge), gallium (Ga), vanadium (V), titanium (Ti), and aluminum (Al). In addtion, coal and CFA can be regarded as alternative sources of radioactive elements. Therefore, they also have a great potential in terms of the precious metals and trace elements they contain. In this study, the present literature on the distribution of trace elements in coal and coal ash during firing and ore preparation processes and their recovery possibilities with mineral processing practices are reviewed. While many research works on the subject clearly indicate that the large amounts of the ashes produced from firing of coal could be problematic in terms of environment, many studies and practices also show that coal combustion products also have a great potential in terms of the precious metals and trace elements.
Case Study
Mineral Processing
S. Shahraki; M. Karamoozian; A. Azizi
Abstract
Sulfur is one of the most significant impurities in coal, which reduces the quality of coal and also results in environmental pollution. This work was aimed to investigate the removal of sulfur from coal by the leaching method employing parameters expected to affect the removal rate such as acid concentration ...
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Sulfur is one of the most significant impurities in coal, which reduces the quality of coal and also results in environmental pollution. This work was aimed to investigate the removal of sulfur from coal by the leaching method employing parameters expected to affect the removal rate such as acid concentration (10-30%), temperature (40-80 °C), and reaction time (40-100 min). A response surface methodology using Box-Behnken design was employed to maximize, model, and evaluate the factors affecting the desulfurization process. The results obtained indicated that the desulfurization value increased with increase in the acid concentration, temperature, and reaction time. A quadratic model with a high correlation coefficient (R2=0.98) is proposed and developed for the relationship between the removal value and the influential factors. The modeling results demonstrated that the significance degree of factors was in the order of acid concentration>temperature>reaction time. It was also found that the maximum desulfurization (about 87%) could be obtained under the optimal conditions of acid concentration=25%, temperature=80 °C, and leaching time=84 minutes.
Case Study
Exploitation
M. Mohtasham Seyfi; J. Khademi Hamidi; M. Monjezi; A. Hosseini
Abstract
Methane gas emission, accumulation, and explosion are the most important risk factors in underground coal mines. Hence, having a knowledge of methane gas emission potential in underground coal mines is of crucial importance in preventing the explosion risk, loss of life, and property, and providing miners' ...
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Methane gas emission, accumulation, and explosion are the most important risk factors in underground coal mines. Hence, having a knowledge of methane gas emission potential in underground coal mines is of crucial importance in preventing the explosion risk, loss of life, and property, and providing miners' safety. The purpose of this work is to provide the prediction maps for the C1, C2, and B2 coal seams gas contents, and to identify high gas content panels in the Parvadeh No. 1, Tabas coal mine. For this, the data collected from exploratory boreholes is put into geostatistical analysis in ArcGIS in order to estimate the coal seams gas content in unsampled points using the kriging estimation method. Reviewing the gas content maps has revealed that seams of C1, B2, and C2 have gas contents more than 15 cubic meters per ton in about 84%, 55%, and 22% of the understudied area, respectively. The present work highlights the potential and the need for implementation of a methane pre-drainage system, particularly in deeper longwall panels.
Review Paper
Mineral Processing
S. G. Ozkan
Abstract
Ultrasound can be used both simultaneously or as a pretreatment technique for flotation to produce higher combustible recoveries, higher heat values, and lower ash data from raw hard coals. The recent research works have indicated that modifying coal surfaces, especially physical surface cleaning with ...
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Ultrasound can be used both simultaneously or as a pretreatment technique for flotation to produce higher combustible recoveries, higher heat values, and lower ash data from raw hard coals. The recent research works have indicated that modifying coal surfaces, especially physical surface cleaning with the help of the cavitation process created by power ultrasound at certain frequency and time intervals, might cause significant changes in flotation responses by a thorough adsorption of reagents on coal surfaces. When power ultrasound is applied to a coal slurry that makes the bubbles to collapse near a coal surface, a high-speed jet of liquid is driven into the particles, and this jet may deposit enormous energy densities at the site of impact. The simultaneous ultrasonic treatment also causes significant changes in local temperatures and pressures within the slurry containing coal and a certain number of reagents at variable dosages during flotation. This treatment improves the effectiveness of reagent molecules at coal surfaces and interfaces due to their more uniform distribution in the pulp and also enhancement of the activity of the reagents used. This paper reviews the results of the recent studies and the possible mechanism of simultaneous ultrasound-assisted coal flotation.
Case Study
Rock Mechanics
R. Rafiee; A. Azarfar
Abstract
One of the main concerns of an underground coal mining engineer is the safety and stability of the mine. One way that the safety and stability can be ensured is to know and understand the coal mine geology and how it reacts to the mining process. One technique that has shown a lot of success in the coal ...
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One of the main concerns of an underground coal mining engineer is the safety and stability of the mine. One way that the safety and stability can be ensured is to know and understand the coal mine geology and how it reacts to the mining process. One technique that has shown a lot of success in the coal mining industry for geologic technical evaluation purposes is the coal mine roof rating (CMRR). The CMRR classification is based on geotechnical data taken from the immediate roof layers within the mine. Since the uncertainty exists in geotechnical data, and CMRR process depends on the expert’s idea implicitly, the final value may be inaccurate. In this paper, the fuzzy type 2 is used to overcome this uncertainty. To design the fuzzy system for calculating the CMRR, only quantitative variables (UCS, spacing, and persistence) are considered as fuzzy inputs. Finally, the scores of CMRR and FCMRR for four units of Riccall mine are compared.
Case Study
Rock Mechanics
N. Aziz; A. Mirzaghorbanali; G. Yang; S. Khaleghparast; H. Resekh
Abstract
There is an increasing need to determine accurately the strength properties of tendons for an effective ground control on mines and underground structures as well as on modelling simulations. The strength properties of cables, used as cable bolts, have been evaluated mainly by their ultimate tensile ...
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There is an increasing need to determine accurately the strength properties of tendons for an effective ground control on mines and underground structures as well as on modelling simulations. The strength properties of cables, used as cable bolts, have been evaluated mainly by their ultimate tensile strength, as this kind of test can be carried out in the field as well as in the laboratory. Only recently, there has been a growing interest in cable bolt failures in shear because of the documented field failure evidence. Accordingly, this paper reports various methods of shear testing of rock bolts and cables using different shear testing rigs, some have been developed by the rock bolting research team at the University of Wollongong. A programme of shear testing of a variety of cable bolts marketed in Australia was undertaken, the results of which were reported and conclusions were drawn. It was concluded that plain cable bolts were de-bonded during shearing when compared to spiral cables under the same testing conditions. In addition, both the single shear and double shear testing methodologies will result in the same outcome if there is no de-bonding, and a proper confinement is applied.
Case Study
Exploitation
S. Mohammadi; M. Ataei; R. Khaloo Kakaie; A. Mirzaghorbanali
Abstract
Immediate roof caving in longwall mining is a complex dynamic process, and it is the core of numerous issues and challenges in this method. Hence, a reliable prediction of the strata behavior and its caving potential is imperative in the planning stage of a longwall project. The span of the main caving ...
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Immediate roof caving in longwall mining is a complex dynamic process, and it is the core of numerous issues and challenges in this method. Hence, a reliable prediction of the strata behavior and its caving potential is imperative in the planning stage of a longwall project. The span of the main caving is the quantitative criterion that represents cavability. In this paper, two approaches are proposed in order to predict the span of the main caving in longwall projects. Cavability index (CI) is introduced based on the hybrid multi-criteria decision-making technique, combining the fuzzy analytical network processes (ANP) and the fuzzy decision-making trial and evaluation laboratory (DEAMTEL). Subsequently, the relationship between the new index and the caving span is determined. In addition, statistical relationships are developed, incorporating the multivariate regression method. The real data for nine panels is used to develop the new models. Accordingly, two models based on CI including the Gaussian and cubic models as well as the linear and non-linear regression models are proposed. The performance of the proposed models is evaluated in various actual cases. The results obtained indicate that the CI-Gaussian model possesses a higher performance in the prediction of the main caving span in actual cases when compared to the other models. These results confirm that it is not possible to consider all the effective parameters in an empirical relationship due to a higher error in the prediction.
Original Research Paper
Rock Mechanics
H. Mohammadi; H. Darbani
Abstract
There are various criteria that need to be examined alongside each other when designing a longwall mining system. Challenges such as determination of the supported roof width, support system design, caving height determination, lateral or chain pillar size determination, and optimum support design for ...
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There are various criteria that need to be examined alongside each other when designing a longwall mining system. Challenges such as determination of the supported roof width, support system design, caving height determination, lateral or chain pillar size determination, and optimum support design for the main gate and tail gate roadways have to be tackled for this aim. Three-dimensional analysis would deliver the highest accuracy of induced stresses around the longwall working area. Thus, the main purpose of this paper is to develop a three dimensional geometrical computing model (3GCM) for calculating the induced stresses in both longitudinal and transverse loading orientations of the extraction panel. 3GCM is capable of studying the changes of induced stresses along the longitudinal orientation of working and the lateral pillar as well as the induced stresses ahead and behind of the face. The proposed computational model, for analyzing the vertical induced stresses, was used in one of the longwall workings in the Parvade-2 coal mine of Tabas, Iran. Validation of 3GCM has approved its high efficiency for the analysis of induced stresses within the working as well as surrounding areas.
Case Study
Exploitation
S. Maleki; F. Sotoudeh; F. Sereshki
Abstract
Ventilation is a vital component of an underground mining operation, used to guarantee a safe atmosphere for workers and survive them from the hazardous and toxic gases. In the recent years, engineers have begun to apply new operation research techniques in order to optimize the ventilation systems to ...
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Ventilation is a vital component of an underground mining operation, used to guarantee a safe atmosphere for workers and survive them from the hazardous and toxic gases. In the recent years, engineers have begun to apply new operation research techniques in order to optimize the ventilation systems to assist in achieving a regulatory compliance, reduce ventilation costs, and improve its efficiency. Airflow regulation optimization in mine ventilation networks is described as a minimization model whose objective function is a minimum number of regulators and energy consumption. In this work, all the previously accomplished works were first reviewed. Then a ventilation system was designed for the Western-Razmja coal mine by a manual method, and an axial fan was proposed. Subsequently, the same ventilation system was simulated using the VENTSIM 3D software. The results obtained by computer simulation showed that there was a reliable relation between the manual method and the simulation approach. In the final step, the GAMS software was used to solve a Mathematical Programming (MP) problem to minimize the overall cost of ventilation by determination of the optimum location for the fan and regulators. The final results of this work illustrated that not only the number of regulators were reduced through solving the MP model but also the total resistance of the Western-Razmja coal mine was reduced by 14% from 1.6 to 1.3. Furthermore, it was observed that the total efficiency of the proposed fan was increased.
Case Study
Exploitation
P. Afzal
Abstract
Finding a proper estimation method for ore resources/reserves is important in mining engineering. The aim of this work is to compare the Ordinary Kriging (OK) and Advanced Inverse Distance Squared (AIDS) methods based on the correlation between the raw and estimated data in the East-Parvadeh coal deposit, ...
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Finding a proper estimation method for ore resources/reserves is important in mining engineering. The aim of this work is to compare the Ordinary Kriging (OK) and Advanced Inverse Distance Squared (AIDS) methods based on the correlation between the raw and estimated data in the East-Parvadeh coal deposit, central Iran. The variograms and anisotropic ellipsoids are calculated to estimate the ash and sulfur distributions by the IDS and OK methods. The results obtained by these techniques show that their correlation coefficients are similar for the raw and estimated data. However, the statistical parameters obtained by the AIDS method are better based on the ash and sulfur means, although the variance of these variables is lower according to the OK method. The results obtained indicate that the AIDS method yields more reliable results than the OK method.
Research Note
Exploitation
J. Balaraju; M. Govinda Raj; C.H.S.N. Murthy
Abstract
Reliability estimation plays a significant role in the performance assessment of mining equipment, and aids in designing efficient and effective preventive maintenance strategies. Continuous and random/irregular occurrence of failures in a system could be the main cause for performance drop of machinery. ...
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Reliability estimation plays a significant role in the performance assessment of mining equipment, and aids in designing efficient and effective preventive maintenance strategies. Continuous and random/irregular occurrence of failures in a system could be the main cause for performance drop of machinery. The accomplishment of a projected level of production is possible only by an efficient operation of the equipment. In order to improve the equipment life, a critical analysis of failure/breakdown occurrences is required to be carried out, and appropriate remedial measures need to be designed and implemented to enhance reliability. This paper presents a reliability analysis of Load-Haul-Dumper (LHD) in an underground coal mine. The goodness-of-fit distribution of each LHD was made through the Cramer-Von-Mises statistic test. The parameters involved were estimated using both the maximum likelihood analytical estimation process and the graphical process. Further, an attempt was made to reduce the total cost of operation by estimating the reliability-based preventive maintenance time intervals.
Case Study
Rock Mechanics
H.C. ZHAO; H.J. An; M.S. Gao
Abstract
Both the deformation characters and the failure mode of the large cross-sectional longwall installation roadway under compound roof are becoming an emergent issue than ever before due to the rapid development of modern mining equipment. Various engineering applications have revealed that the insufficient ...
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Both the deformation characters and the failure mode of the large cross-sectional longwall installation roadway under compound roof are becoming an emergent issue than ever before due to the rapid development of modern mining equipment. Various engineering applications have revealed that the insufficient design and inappropriate support technology are the main reasons for the fatal accidents associated with the sudden roof fall attributed to the separation of the overlying compound strata. The present research work, therefore, starts with a case study using the conventional support technology in order to demonstrate the importance of this issue followed by a summarization of the typical failure mode of the longwall installation roadway under compound strata with varied thicknesses. Then a simplified theoretical model is proposed and set up aiming at a better understanding of the distribution of the elastic-plastic zones as well as the effects of different caving procedures. The finite element analysis software program FLAC3D is adopted to evaluate the effect of the caving method and the reinforcement provided by an additional support. Then a case study conducted at a typical coal mine with compound roof condition is presented to verify the advantages of the proposed design. The results obtained show that the optimized design presented in this research work is effective to control the deformation of the surrounding rock, particularly in terms of separation of the overlying compound strata.
