IR@CIMFR - Central Institute of Mining and Fuel Research (CSIR)
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Specific blasting technique for tunnelling in hot zones.
No full textEncountering hot zones while excavating tunnels for hydropower projects in the Himalaya, India, is a challenge for civil engineers. Blasting within the hot rock mass can pose serious threats due to possibility of temperature-induced unintended detonation of explosives. Moreover, the paucity of a suitable rock-blasting method for these hot zones sometimes compels engineers to realign the tunnel. Such a realignment is costly and time-consuming. A temperature of 50–98°C was encountered while excavating the rock mass for head race tunnel of Karchham–Wangtoo Hydro-Electric Project, Himachal Pradesh, India. The Directorate General of Mine Safety, India, suggests that blastholes with temperature greater than 80°C must not be charged and blasted. Similarly, the use of electric or non-electric detonators is discouraged above 70°C because of premature detonation. Hence excavation works were suspended for tunnel construction. A unique drill and blast method has been adopted for blasting the hot strata in the tunnel. The technique described in this study can be easily followed in similar situations for tunnel-rock excavation
Utilization of High Ash, Low Volatile Coking Coals of Jharia Coalfield, India for Coke Making
No full textIndia is having limited resources of coking coal, an essential input for production of iron and steel especially through blast furnace route. The coking coal sources are presently from the lower seams of Jharia coalfield, which are high in ash content and low in volatile matter and difficult to wash. This paper describes the washability characteristics of a typical coking coal from the Eastern and Western Jharia coalfields aiming at 18% ash level in the clean coal mainly to meet the specifications of coke making for blast furnace use. Conventional float-and-sink testing was used to determine the yield of clean coal for the coarser fraction, while the coal fines was subjected to flotation. The theoretical recovery of clean coal for the coal tested from Eastern and Western Jharia coalfields are 27% and 19.7% at the stipulated ash content. The coking propensities and the petrographic analysis of the clean coal strongly support its use for coke making either directly or as a blend with imported coal
Refractive index of different perovskite materials
No full textThe perovskite solar cell technologies are the hope of satisfying the huge demand of tomorrow’s energy requirements. The inorganic, organic and mixed perovskite materials are the backbone of modern solar cells. The energy band gap and refractive index of perovskites help in selecting proper materials for solar cell, solid-state lighting and lasing applications. In this paper, various perovskite materials and different energy band gap–refractive index relations have been studied. A simple empirical relationship between energy gap ‘Eg’ and refractive index ‘n’ for perovskites has been developed and proposed. Using this relationship, refractive indices of 33 different perovskites have been calculated and compared with their reported values. Also, the refractive indexes of about 140 new perovskites have been predicted and reported probably for the first time. The researchers interested in refractive index calculation may use the proposed relation and need not to worry for complex experimental setup
Assessment of hydrological condition in strata associated with old mine working during and post-monsoon using electricalresistivity tomography: a case study
No full textWater management is a strategic factor in old coal mine working areas due to disturbance in the aquifer caused by subsidence resulting in drying of wells and streams. Cavity formation due to underground mining leads to roof fall, heaving of clay floors and collapse of coal pillars in soft clay floors. Logging of water in old mine workings is a common phenomenon especially during
rainy season. Mine water is extensively used in various mining activities, and hence, a study has been conducted in part of Jamadoba 6 and 7 Pits, Jharia coalfield, India, to assess the hydrological condition during and post-monsoon. Initially, a conceptual model has been prepared to identify the possible sources of water including its path entering into old mine workings.
Electrical resistivity tomography (ERT) i.e. Wenner-Schlumberger configuration with quality factor 5 has been adopted as it is effectual and reliable in detecting subsurface cavities at shallow depth and the possible path of transmission of subsurface water into the mine void with season variation. The study helped in identification of abandoned incline, porous and permeable strata conditions. The correlation of the resistivity variations is observed to be in close approximation with working plans and available borehole lithology. This technique proved to be suitable for adopting such studie
Impacts of changes in commercial non-coking coal grading system and other coal policies towards estimation of CO2 emission in Indian power sector
No full textIn India, coal-based electricity is a leading cause for greenhouse gas emissions. However, many uncertainties prevail in the emissions estimation from coal-fired plants due to the dynamics of varying net calorific values (NCV) and carbon emission factors (CEF) associated with different grades of coal coupled with the coal oxidation factors (COF) of power plants. After 2012, a major change in the Indian non-coking coal grading system along with other developments like (a) rising efficiencies of thermal power plants, (b) changes in coal quality due to mining at deeper seams, (c) coal mining and distribution strategy have affected the NCVs, CEFs and COF associated with coal combustion in Indian power plants. These changes are expected to impact the CO2 emissions from coal-based power plants. Our findings suggest that implementation of the newly revised, power sector specific, NCV-CEF-COF-2015 have resulted in reduction of CO2 emission estimates from coal-based electricity generation by about 139 Tera grams (Tg) (12%) and 73 Tg (7%) for the year 2015 as compared to the corresponding emissions calculated using NCV-CEF-COF-1994 and NCV-CEF-COF-2007, respectively. Going forward, these newly estimated factors will provide greater accuracy in emissions estimation from coal-fired power plants in India
Numerical simulation based approach for assessment of blast induced deformation pattern in slot raise excavation
No full textThe excavation of long-hole slot raises in a single lift comes with the difficulties of face jamming, insufficient face movement and boulder formation. The main reasons behind these problems are improper blast design, presence of geological discontinuities or inaccuracy in drilling. The proper blast design to get uniform breakage pattern for slot raise excavation consists of design of drilling, charging and delay parameters. This paper has discussed the numerical simulation based approach for assessment of blast induced deformation pattern in slot raise blasting. The numerical models with different variants of slot raise blast design was made for this purpose in Ansys-Explicit Dynamics. The model was given tested rock mass properties data of Rampura Agucha underground Lead–Zinc mine. The deformation pattern output for these variants were analysed. The analysis of deformation pattern suggests that the ratio of number of reamer holes and blast holes have more impact on deformation pattern. The more uniform deformation contour was observed for the cut hole blast with six reamer holes and five blast holes for the experimental site. The deformation pattern output for excavation of periphery holes were also analysed. The drilling pattern and delay timing for the slot raise blast was decided on the basis of model output. The experimental trials at the mine was taken on the basis of revised blasting pattern. The face jamming has been reduced with revised pattern. The blasting pattern has also been advantageous in reducing overall blasting cost by reducing the number of drill holes in cut portion
Ground vibration generated by hydraulic rock breakers and its impact on the safety of nearby earthfill dam in a graphite mine
No full textA detailed impact analysis on the effects of non-explosive chemicals and hydraulic rock breakers at a graphite mine in India close to an irrigation dam was carried out in this study. The dam was 70 m from the mining lease boundary. When a single hydraulic rock breaker worked on fractured rock mass, the magnitude of ground vibration recorded at 10 m on the same working bench was 2.37 mm s−1 but when it worked on fresh rock surface the ground vibration at 9 m on the same working bench was 4.67 mm s−1. Beyond 35 m on the same bench, no ground vibrations were recorded. Ground vibrations generated by three jack hammer drilling machines operating simultaneously on the same working bench were less than 0.5 mm s−1 when measured at 7.2 m distance. The combined effect on the magnitudes of ground vibrations by two hydraulic rock breakers operating simultaneously on the same bench 6 m apart was found to be negligible. The ground vibrations generated by hydraulic rock breakers and other mining activities were found to be lower than required to cause any structural damage or threat to the stability of the dam
Waste to wealth: Recovery of value-added products from steel slag
No full textSteel slag, a by-product generated during steel production poses a solid waste disposal challenge. The same slag contains valuables such as titanium, nickel, vanadium, iron, aluminum, silica among others. The extracted components can cause productive value addition in diverse realms like wastewater treatment to semiconductor devices. A paradigm shift is required towards waste valorization for developing profitable extraction methods for these constituent elements. In this review, an attempt was made to assimilate such technologies into one concrete and concise compendium. The pros and cons of each method were weighed comparatively with respect to applicability and innovation. An effort was attempted for assessing key design aspects and scale-up potential vis-à-vis the economic analysis for the valorization techniques. It was seen that the leaching technique was the most widely used in the resource recovery domain followed by other techniques like fusion, hydrothermal treatment. Techniques that dominate the exploration of some of the metals from their lean ores or respective mineral slags might also be explored for their recovery from steel slag. Some technologies like slag filter development for phosphate removal has already been tested in real-life conditions while others are in the nascent stages of development. Special focus can be directed towards the simultaneous extraction of multiple components or direct in-situ product formation and its subsequent separation. This paper reviews various technologies for steel slag valorization to guide researchers working in the field of slag resource recovery and sustainable waste utilization
Pore Properties in Organic-Rich Shales Derived Using Multiple Fractal Determination Models Applied to Two Indian Permian Basins
No full textThe pore geometry of shale reservoirs plays an important role in the storage and transportation of petroleum in these unconventional resources. Intrinsic surface roughness, indicated by fractal dimensions and contrasting pore size distributions of shales are primary factors that influence shale’s fluid flow and resource volume characteristics. The Frenkel–Halsey–Hill (FHH) derived fractal dimensions are widely applied for evaluating the pore structural complexities of shales. In this work, for a suite of shales samples collected from two Permian basins, India, with distinct maturities, low pressure nitrogen gas adsorption–desorption has been employed to elucidate the pore structural framework. Three alternative fractal calculation methods (FHH, Neimark, and Wang–Li) are compared to provide further insight into the fractal characteristics of the shales. Ambiguities are revealed in the selection of the most appropriate fractal values. Fractal dimensions calculated by the FHH and Wang–Li methods are in relatively close agreement (ranging between 2.5 and 2.8) and the small systematic differences between their values can be explained in terms of fitting errors and assumptions associated with both methods. However, the Neimark fractal values are unreasonable (>3 for all the samples). Thermal maturity is a key controlling feature of the pore structural facets and fractal dimensions of the Raniganj basin samples (Tmax = 431–463 °C) but not for North Karanpura (Tmax = 434–442 °C) samples. Strong correlations exist between calculated fractal dimensions and specific surface area, pore volume, and average pore radius for all samples. However, systematic differences in these values between the samples from the two basins are most likely explained in terms of their mineralogical differences, specifically the higher kaolinite content of the Raniganj samples
An Experimental Study on Importance of Bushing Used in Flameproof Enclosure for Hazardous Area
No full textThe flameproof (Exd) enclosure is used to make a complete flameproof equipment by putting many non-explosion proof components within it which are intended to be used in explosive atmospheres. A flameproof bushing is interconnected with the common wall of the flameproof enclosures to facilitate the electrical connections. An experimental study was carried out on the Ex d enclosures to understand the importance and effect of bushing on flamepath, gap/clearance, volume of Exd enclosure and explosion reference pressure. The reference pressure tests were carried out to measure the pressure on the Exd enclosures having spigot and threaded joints fitted with and without interconnecting Exd bushing. Results indicated that the reference pressures increased for the enclosures without fitted bush tested with gas group IIB and IIC representative gas mixture. Present study was carried out to explore the importance of the bushing in the flameproof enclosures to enhance the safety of hazardous area