IR@CIMFR - Central Institute of Mining and Fuel Research (CSIR)
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Study of Detection Techniques for Heating of Coal in Underground Coal Mines
No full textIn this paper, fire indices, which assumed to be one of the most prominent ways to determine the extent of underground coal mine fire, along with their limitations have been discussed. The other techniques, which may overcome the limitations of the fire indices such as fire ladder and installation of gas sensors, have also been discussed. Fire ladder can identify the gas present in a locality with respect to temperature and vice-versa. Whereas, gas sensors can measure the available gas concentration in the targeted area of the underground coal mine
Bioprocess technology for coal washer effluent treatment by Lemna minor
No full textDuckweed species are promising macrophytes that can be used in wastewater treatment due to their rapid growth, ease of harvest, low fiber feed potential, and high protein contents. Waste‐water contaminants that are likely to be generated during washing of coal are total suspended solids (TSS), chemical oxygen demand (COD), acidity or alkalinity (pH), and metallic contaminants. Bioprocesses were developed to evaluate the potential of duckweed (Lemna minor) to treat coal washery effluent (CWE) as well as to study the impact on the biochemical changes of the Lemna minor. CWE samples were diluted with distilled water (DW) in different ratios as follows: T1‐CWE:DW(20:80%), T2‐CWE:DW(40:60%), T3‐CWE:DW(60:40%), T4‐CWE:DW (80:20%), T5‐CWE (100%), and Control‐DW(100%). The electrical conductivity of the effluent treated with Lemna minorwas 0.035 deciSiemens per meter (dS/m) in the control at Day 10 and substantially higher at treatment ratios of 100, 80, and 60 percent (1.754, 1.842, and 1.631 dS/m). The highest amount of TSS was observed at test ratio T5 (38,834 mg/L), followed by T4 (28,816 mg/L), T3 (26,970 mg/L), T2 (15,320 mg/L), T1 (4,524 mg/L), and control (424 mg/L). Total hardness was higher (820 mg/L) in T4 compared to the control (220 mg/L). Total hardness of the effluent decreased after 30 days of incubation in all the treatment aliquots. The CWE at 20 percent concentration increased the duckweed population and no adverse impacts on its growth were observed. At higher concentration (T5) total mortality of Lemna minor was observed. The chlorophyll production was determined to be inversely proportional to the effluent concentration. Based on this study, it is concluded that Lemna minor can be used for treating CWE after dilution with fresh water
Exploratory Study of Archaebacteria and their Habitat in Underground, Opencast Coal Mines and Coal Mine Fire Areas of Dhanbad
No full textCoal contains abundant microbial genera which include archaebacteria. The study of archaea kingdom in coal mines is a significant tool for knowing the relationship between coal and archaebacteria, the major role in geochemical cycle and application for further coal bio–beneficiation. The present study related to exploration of archaebacteria and their habitat in coal mining area of Dhanbad with reference to their ecology and nutrient availability that have evolve to grow under extreme conditions. Total six different sites such as two underground coal mines (Sudamdih shaft and Chasnalla underground mine), two opencast coal mines (Chandan project and Bhowra abandoned mine), Jharia mine fire and Sudamdih coal washery of Dhanbad was selected. Seven gram negative obligate anaerobic bacteria were isolated from the selected sites. The isolated species were rod and cocci shaped and the colony was round, smooth, off white in colour and with entire margin and little are cluster of cocci in shape. The isolated species were identified as Methanococcus spp, Methanobacterium spp andMethanosarcina spp. Apart from that two thermoacidophilic sulfur oxidizing bacteriaSulfolobus spp was also isolated from Jharia Coal Mine Fire. The physicochemical and biological characterization of the habitat was also studied for the entire selected area
Influence of Overlying Roof Strata on Rib Design in Mechanised Depillaring
No full textDepillaring of the existing pillars (square or rectangular in shape) by continuous miner provides irregular shaped ribs. An assessment of strength of such a rib becomes a difficult task. Literature review finds a number of approaches for the rib design but the scope of straight forward application of these approaches is limited due to the uniqueness of geo-mining conditions of the Indian coalfields. This review also finds that a wide spectrum of moderate roof conditions is yet to be properly addressed. Field studies at some depillaring operations in Indian coalfields indicated the influence of roof strata over the stability of a rib is considerably high. A systematic study of the roof strata influence on simulated models provided interesting results. A model for rib design is conceived on the basis of the simulation results. Discussing couple of field experiences of rib stability during mechanised depillaring under two different types of roof strata of Indian coalfields, this paper presents some results of the simulation along with the conceived model of a rib design
Detection and delineation of coal mine fire in Jharia coal field, India using geophysical approach: A case study
No full textCoal mine fire is a serious problem in Jharia coal field, India. The coal mine fire can be detected with different techniques such as borehole temperature measurement, thermo-compositional analysis, remote sensing techniques, thermo-graphic measurement and geophysical methods. In this study, various geophysical methods were used to detect the surface and subsurface coal mine fires. Geophysical techniques used in the present study are apparent resistivity, self-potential (SP), magnetic method and thermography. Geophysical anomalies such as low SP value of −60 mV−60 mV, high negative magnetic response and low apparent resistivity value helped us to detect and delineate the fire and non-fire areas laterally as well as depthwise. Furthermore, the thermography survey was carried out in the coal field using thermal imaging camera in order to substantiate the geophysical methods. This integrated approach was found to be more advantageous for the detection and delineation of surface and subsurface fire with respect to use of any specific techniques. Moreover, the level of threat towards the locality, national railway line was also assessed unambiguously using the above techniques. Hence, proper planning and implementation towards the mitigation of hazard can be achieved on the basis of the reported results
Development a modified crossing point temperature (CPTHR) method to assess spontaneous combustion propensity of coal and its chemo-metric analysis
No full textSpontaneous combustion of Indian coals was investigated using sponcomb rig at University of Nottingham, UK to assess their susceptibility. In the present study authors have used eleven coal samples collected from the Jharia coalfield (JCF), India. Both thermal as well as gas profiles from sponcomb rig were studied critically to develop a modified crossing point temperature to assess the spontaneous combustion propensity of coal. The product of combustion gases (CO, CO2, CH4, and H2) emitted from sponcomb rig within the temperature range between ambient and 300°C of these coal samples were studied. The initial product of combustion gas i.e. CO followed by H2indicates propensity towards oxidation of coal in laboratory condition for Jharia coalfield. The temperatures at which CO and H2 releases in the level of 50 ppm (TCO50, TH250), crossing point temperature of coal (CPTCT) (temperature of coal and bath temperature is same) and modified crossing point temperature of coal (CPTHR) (temperature where dT/dt is equal to 2.0 oCmin−1 because heating rate is double of programme temperature 1 oCmin−1) determined from sponcomb rig categorises the coal as per their propensity to spontaneous combustion. The results of these methods have been compared with other standard method i.e. crossing point temperature method – India, which is widely adopted in Indian regulatory bodies to verify the suitability of this method
Insights into the effects of matrix retention and inert carbon on the petroleum generation potential of Indian Gondwana shales
No full textThe Rock-Eval pyrolysis and total organic carbon (TOC) analysis technique is widely used for organic geochemistry screening of source rocks and potential unconventional petroleum reservoirs. The Rock-Eval-derived parameters, the Hydrogen Index (HI), which is the ratio between hydrocarbons released under the S2 curve (hydrocarbon formed by thermal pyrolysis; S2 is an indicator of petroleum generation potential) and total organic carbon (TOC) can be used to infer the type of organic matter present in a rock. However, HI is often under-estimated due to retention of some hydrocarbons included under the S2 curve by the rock matrix, and the presence of inert carbon within the rock. Here we describe and correct the matrix retention and inert carbon effects on hydrocarbon generation from a suite of shale samples from Indian Gondwana shale reservoirs. Removal of the petrographically-identified inert carbon component from the samples tested leads to less scatter in the TOC-S2 relationship obtained. The ratio of volume percentage of organic matter identified through optical microscopy to TOC is calculated, and that ratio was least in the one heat-affected sample, but higher in low-TOC shales (12.5%). With decreasing TOC content in the sample set analyzed, the corrected HI values calculated using the S2-TOC intercept, increase significantly. This correction can therefore lead to false indications about the type of organic matter present. A key novel finding of this work is the need while correcting HI for matrix retention effects, to consider samples with a specific range of TOC contents, and to match them to the kerogen types present (e.g. Types III and IV in the samples analyzed). Filters should also be applied to adjust for the degree of thermal maturity and organic facies
Evaluation of Quartz Reduction by Coal Cleaning for Thermal Utilization of an Indian Coal
No full textIn Indian coals, quartz is abundantly found and its proportion usually varies from 5–20% by weight. Beneficiation of high-ash thermal coals of India has become the prerequisite for improving the overall economics and efficiency of power generation. A detailed survey of literature reveals that no systematic work has been done of beneficiated coal for Indian coals with respect to quartz, as also for correlation with abrasion. Therefore, to understand this effect different sizes of crushed coal were subjected to float-sink treatment at specific gravities in the range of 1.30– 1.80. This study highlights the systematic method of measuring crystalline silica (α-quartz) in bulk coal samples using NIST-SRM 1878a as a calibration standard withmore accuracy by FT-IR as well as distribution of quartz in various screen sizes, float-and-sink fractions, for both the feed and clean coal. The results show that there is a linear relationship between ash % and quartz % with respect to specific gravity for all screen sizes. Characterization of the feed and clean coal with respect to quartz was also done using XRD, SEM, and XRF spectroscopic techniques to evaluate the reduction behavior of quartz during the coal-cleaning process
Modelling of design parameters of intrinsically safe instruments for the safety of oil, gas and coal industries
No full textIntrinsic safety is the safest technique to prevent explosions that might occur in underground coal mines and process industries in the presence of explosive atmosphere. Designing of intrinsically safe equipment require keeping its energy below the minimum ignition energy of the explosive gases. In this work, three empirical relations based on standard IS/IEC 60079-11 have been proposed for the first time and used in the calculation of short circuit current (I), permitted capacitance (C) and inductance (L) of intrinsically safe circuits designed for gas groups IIA, IIB, IIC and I. The calculated values are compared with the available experimental and reported values. A fairly good agreement has been obtained between them. The designers of intrinsically safe circuits can use these relations as a very handy tool especially for the explosive gas atmosphere of underground coal mines and process industries. This research will contribute to the reduction of fatal accidents due to explosive gases
Numerical modeling approach for design of water-retaining dams in underground hard rock mines—a case example
No full textDuring transition from open pit extractions to underground mining of an orebody, often both the open pit and the underground workings operate simultaneously, before the former is closed. To avoid the risk of inundation, the underground workings connecting or driven closer to the open pit are isolated using bulkheads. In this paper, the authors reviewed some of the theoretical equations and norms followed worldwide for determining the safe dimensions of a bulkhead to withstand water pressure. It is found that the theoretical equations are insufficient to represent the actual mode of failure and the ultimate pressure–bearing capacity of a bulkhead, as they were developed based on only one mode of failure of the dam construction material. For better representation of the bulkhead failure and its strength determination, it is found prudent to conduct strain-softening numerical modeling simulating a real mining scenario. Mode of dam failure and effect of parameters such as dam thickness and roadway dimensions on the ultimate pressure–bearing capacity of an arched bulkhead are studied. Numerical modeling studies show that the failure initiates with tensile cracking of the dam surface, but the bulkhead ultimately fails in a combination of tension and shear yielding. On comparison, it is found that the tensile failure theories underestimate the pressure-bearing capacity of a dam, while the shear strength– and crushing strength–based equations overestimate the same. Further, an application of the numerical modeling technique for design of water-retaining dams at an underground mine for its safe isolation from the open pit is presented