IR@CIMFR - Central Institute of Mining and Fuel Research (CSIR)
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Critical insights from Rock-Eval analysis of vitrains
No full textRock-Eval S2 and S4 curves are commonly used to interpret active source rocks. In this work we report the formation of unusual, uneven, spiky S2 pyrograms from Rock-Eval of manually isolated vitrain bands from Mvb and Lvb coals. The spikes and unevenness in the S2 curves for coking-vitrains are interpreted to form from the release of gases or bubbles bursting from the melt during the pyrolysis stage. Crucible swelling numbers measured for these vitrains were observed to be 3 to 4 times higher than the parent coal from which they were separated. Field Emission Scanning Electron Microscope (FE-SEM) images also document formation of three dimensional bubbles due to bursting of gaseous bubbles, in the pyrolysis-residue (using Rock-Eval) of coking-vitrains. For bulk coal samples and vitrains isolated from HvbA coals, the S2 pyrograms were observed to be smooth. At higher sample weights, the formation of spikes for the vitrains from Mvb and Lvb was observed to increase, irrespective of the heating-rates used, owing to the release of greater amounts of gases or bubbles bursting from the melt. The results indicate the importance of cross-examining S2 pyrograms as it offers clues towards the behavior of coals during pyrolysis, and for better interpretation of results
Broad-spectrum contaminant removal from water using sustainable pressure assisted osmosis
No full textA novel, single-stage Pressure Assisted Osmosis system capable of broad-spectrum removal of anionic and cationic contaminants from water is described in this article. The system has demonstrated a high removal efficiency of over 95 % for anions such as sulfate and cations such as calcium and magnesium. It has also demonstrated a removal efficiency of over 90 % for monovalent anions such as carbonate and chloride. The modular system is characterized by a high degree of process intensification. The portable set-up attempts to merge several parts like feed cells, membrane assembly, and external force media into one compact unit. Another design feature was the operational flexibility of mechanical force addition. The portable device demonstrated sustained solvent flux without the usage of electric power. The proof of the concept of experimental studies with real-time operational aspects like reverse salt diffusion is described in this work
Evaluation of Treatment Techniques for Utilising Acid Mine Water in Agriculture
No full textAcid mine water was treated with fly ash zeolite (FAZ), followed by different active chemicals to know its suitability for crops. Acid mine drainage (AMD) was obtained from Gorbi abandoned opencast mines of Singrauli, Northern Coalfields (NCL), India. The AMD was treated with 20 g/l dosing of fly ash zeolite, followed by different precipitating chemicals, using different doses of Ba(OH)2, BaCO3 and Ca(OH)2. The doses of 1.0 g/l Ba(OH)2, 1.5 g/l BaCO3 and 0.5 g/l Ca(OH)2 were used. The treatment with FAZ, followed by 1.0 g/l of Ba(OH)2, converted the water quality of AMD to the permissible level. The electrical conductivity (EC), percentage of sodium and metals found at the permissible level indicated the suitability of mine water for agriculture use. AMD treated directly with 1.0 g/l of Ba(OH)2 was found unsuitable for agriculture use. The treatment with FAZ and followed by BaCO3 (1.5 g/l) explained that the water quality was not at the permissible level and unsuitable for agriculture use. AMD treated directly with 1.5 g/l of BaCO3 was also found unsuitable for agriculture. The treatment with FAZ, and followed by 0.5 g/l dosing of Ca(OH)2, also showed water quality not at the permissible level. The conductivity, total salt content (as TDS) and sulfate values increased or decreased minimally, and there was an increase in the concentrations of total hardness and calcium hardness in the final treated mine water. The direct dosing with 0.5 g/l of Ca(OH)2 made AMD unsuitable for agriculture use. Treatment with 20 g/l FAZ followed by 1.0 g/l of Ba(OH)2 produced the treated AMD suitable for agriculture use
Design of rock bolt-based goaf edge support for conventional depillaring with stowing
No full textRock bolts have replaced the conventional cog/chock as roof support from underground coal mines working with continuous miner (CM) technology in Bord and Pillar mining method with caving system. Rock bolts installed in the gallery at the goaf edge by aligning the adjacent stable rib during the CM-based mechanised depillaring have proven its potential by restricting goaf encroachment towards the working area. However, conventional depillaring with stowing and caving system still uses skin-to-skincog/chock as goaf edge support in Indian coalfields which poses threat to the safety of miners during its erection and withdrawal. Further, bearing capacity of such goaf edge support also reduces with increase in height of working. Field study found that the adjacent in-bye rib of the working slice remains intact and stable due to less span of hanging roof inside the goaf during conventional depillaring with stowing compared to caving. These field outcomes are also validated during the numerical simulation and observed that the goaf edges are over-supported in a stowing panel as it adopted the similar goaf edge support pattern as that of caving. Further, a parametric study is conducted on numerical models by varying the nature of roof, gallery width, and depth of cover to estimate the rock load height (considering 1.5 safety factor contour) around the goaf edges in stowing panels. Multivariate regression analysis was carried out to establish a relationship among influencing parameters for estimation of rock load height at the goaf edges in stowing panels for a given geo-mining condition. This paper presents a novel design of rock bolts as goaf edge support on the basis of roof-rib interaction in conventional depillaring with stowing panel
Mercury emissions and partitioning from Indian coal-fired power plants
No full textIn India coal combustion is the single largest source of emission of mercury which is a wide-spread persistent global toxicant, travelling across international borders through air and water. As a party to the Minamata convention, India aims to monitor and reduce Hg emissions and stricter norms are introduced for mercury emissions from power plants (30 μg/Nm3 for flue gas in stack). This paper presents the results obtained during the experimental studies performed on mercury emissions at four coal-fired and one lignite-fired power plants in India. The mercury concentration in the feed coal varied between 0.12–0.27 mg/Kg. In the mercury mass balance, significant proportion of feed coal mercury has been found to be associated with fly ash, whereas bottom ash contained very low mercury. 80%–90% of mercury was released to air through stack gas. However, for circulating fluidised bed boiler burning lignite, about 64.8% of feed mercury was found to get captured in the fly ash and only 32.4% was released to air. The mercury emission factor was found to lie in the range of 4.7–15.7 mg/GJ. © 2020 Published by Elsevier B.V. on behalf of The Research Centre for Eco-Environmental Sciences, Chinese Academy of Science
Palaeobotanical and biomarker evidence for Early Permian (Artinskian) wildfire in the Rajmahal Basin, India
No full textThis study provides a combined analysis on the palynology, fossil charcoal and biomarkers of the subsurface coal deposits from a borehole RMB #2 drilled at the Dhulia Coal Block, Rajmahal Basin, India, in attempts to establish the chronology of sedimentation and to propose palaeobotanical as well as geochemical evidence for the occurrence of wildfires in these sediments. The palynological investigation suggests a Scheuringipollenites barakarensis palynoassemblage from the lower Barakar Formation, dated as Artinskian (Early Permian) in age. This assemblage reveals the dominance of Glossopteridales and sub-dominance of taxa belonging to Cordaitales and Coniferales. Fossil charcoal in sediments is usually recognized as a direct indicator for the occurrence of palaeo-wildfires. More data involving the anatomical features of fossil charcoal analyzed by Field Emission Scanning Electronic Microscope broaden our knowledge on Early Permian wildfires from the peninsula of India. The studied macroscopic charcoal fragments exhibit anatomical details such as homogenized cell walls, uniseriate simple and biseriate alternate pitting on tracheid walls and rays of varying heights pointing to a gymnospermous wood affinitity. The excellent preservation of charcoal fragments, shown by their large sizes and almost unabraded edges, suggests a parautochthonous origin. The embedded biomarker study performed for charcoal sediments and its characterization demonstrate the presence of n-alkanes, isoprenoids, terpenoids and aromatic compounds. A bimodal distribution pattern of n-alkanes with a Cmax at n-C25 is identified. Diterpenoids and pentacyclic terpenoids are identified, indicating the input of an early conifer vegetation and bacterial activity, respectively. The identified polyaromatic hydrocarbon (PAH) compounds, together with the charcoal fragments, clearly suggest that repeated wildfire events occurred during the deposition of these Artinskian sediments in the Rajmahal Basin
Extended abstract on empirical Approach Based Estimation of Charge factor and dimensional parameters in underground blasting
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GEOTECHNICAL STUDY TO EVALUTE PIT SLOPE DESIGN OF AN LIMESTONE OPENCAST MINE- A CASE STUDY
No full textThis paper deals with a geotechnical study conducted at a mechanised limestone opencast mine attached to a cement plant in India. The study consists of comprehensive field investigations and detailed slope stability analysis to evaluate pit slope design, which can enable optimum mineral extraction while maintaining pit slope stability. The slope mass at this mine mainly consists of dolomite and limestone overlain by up to 40 m thick soil cover in some slope sections. The Rock Quality Designation across different rocks varies from 76 to 90, which signify very good rock quality. The Uni-axial compressive strength of limestone and dolomitic limestone varies in the ranges of 51 - 78 MPa and 81 - 112 MPa respectively, which signify Strong to Very Strong rocks. The limestone & dolomitic limestone are classified as good to very good rock mass based on Rock Mass Rating classification approach. Detailed stability analysis is carried out to evaluate optimum pit slope designs for different slope sections at this mine for an ultimate pit depth of 140 m. The recommended slope designs include overall pit slope angle, overall slope angles for rock slope and soil slope, bench width, bench height, ramp width and inter-ramp slope angle. Sensitivity analysis is carried out to study the relative influence of the change in cohesion and angle of internal friction on the factor of safety. Further, different remedial and control measures are suggested for implementation during the execution of recommended slope design for optimum mineral extraction along with pit slope stability
Preparation and Certification of Indian Reference Material of Bituminous Coal
No full textCertified reference materials (CRMs) are used for evaluating analytical methods, quality assurance and traceability of analytical results to international standards. Bituminous coal is the medium grade coal with high heating capacity and low moisture content. CRM of bituminous coal powder (BND 5101A) has been developed and certified for ash, gross calorific value (GCV),volatile matter (VM) and total sulphur (S) content as 22.16 ± 0.15%; 6114 ± 44 kcal/kg; 29.2 ± 0.36% and 0.71 ± 0.04%, respectively. The sample of coal selected for the purpose is high-rank bituminous type, which was collected from an opencast mine of Central Coalfields Ltd. The work has been carried out jointly by CSIR-Central Institute of Mining and Fuel Research (CSIR-CIMFR), Dhanbad and CSIR-National Physical Laboratory (CSIR-NPL), New Delhi. Proficiency testing (PT) program was carried out among 28 reputed coal laboratories of the country in accordance with ISO/IEC 17043:2010. Based on the performance of laboratories in the PT program, 8 laboratories were selected for inter-laboratory comparison (ILC) program as per ISO 13528:2015. This paper describes the methodology employed for the preparation of a coal reference material, homogeneity, stability studies and the ILC analytical and statistical work performed for the certification of the contents of ash, GCV, VM and total S