IR@CIMFR - Central Institute of Mining and Fuel Research (CSIR)
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Strata behaviour of a wide and deep longwall panel under massive sandstone bed - a case study
No full textLongwall technology is one of the principal underground coal mining methods widely used around the globe which is not fully emerged in India. However, since the introduction of first self-advancing powered roof supports, there has been mixed experience of longwall technology. History of failure of some longwall panels desponded the success stories of others. Majority of longwall downtimes and/or failure had been attributed due to poor cavability of roof, inadequate capacity of supports, lack of knowledge on longwall caving mechanisms, less than adequate strata monitoring systems, etc.
Strata around coal seams in India are dominated by competent beds, which do not normally cave in immediately after face advance, rather it remains in hanging condition for certain length and break into large discrete blocks. This type of caving mechanics is irregular and complex. Fracturing of competent bed in the immediate roof zone is certain to manifest itself on face as heavy load on supports, bleeding of hydraulic legs of supports, aggressive face spall and guttering in gate roads and in worst conditions longwall face stoppage and sometimes even structural failure of supports as the severity may be.
This paper presents a case study of strata behavioural experiences gained while extracting a deep and wide longwall panel overlain by 3.0 to 3.5m coal roof as immediate roof and 20 to 28m thick competent sandstone bed as main roof with high capacity longwall equipment. While extracting the panel the precise strata monitoring and trigger action response plans are prepared and implemented successfully for negotiating all the strata control hindrances
Impact of modified chitosan on pore water bioavailability of zinc in contaminated soils
No full textThe present work examines the utilisation potential of the bio-waste, chitosan for the remediation of soils contaminated with zinc (Zn). The mechanism involved was elucidated via a study of Zn sorption kinetics on pure and modified chitosan beads, the latter containing molybdate and phosphate compounds. The effect of equilibration time on adsorption was explained with reference to chemical sorption and intra-particle diffusion mechanisms. The findings showed that chitosan acts upon freely dissolved zinc in soil pore water. The use of modified chitosan beads resulted in a significant decrease in Zn bioavailability, which may be attributed to a combination of Zn complexation, the sorbent's high surface area and cation exchange capacity (CEC). This study provides an insight into issues associated with zinc contaminated soils and the amelioration of nutrient-deficient soil through modified chitosan amendments
Gasification reactivity of high ash Indian coals in varying concentrations of CO2
No full textOptimisation of coal gasification processes requires a good understanding of coal reactivity of the CO2 and steam gasification reactions. Presently there are very few studies on gasification behaviour of high ash coals. Therefore, present paper investigates the gasification behaviour of char samples in 100, 70 and 30% concentrations of CO2 in the temperature range of 900-1050°C using thermogravimetric analyser. Char samples were prepared from high ash Indian coals in inert atmosphere at 800, 900 and 1,000°C. Effects of coal/char properties, char preparation temperatures, char gasification temperatures and varying concentrations of CO2 on gasification reactivity of high ash char samples have been reported. Higher pyrolysis temperature shows adverse effect on CO2 gasification, whereas higher gasification temperature, CO2 concentration, alkali index, surface area as well as porosity favour CO2gasification reactions
Critical limits of Mehlich 3 extractable phosphorous, potassium, sulfur, boron and zinc in soils for nutrition of rice ( Oryza sativa L.)
No full textWe evaluated the critical limits of P, K, S, B and Zn in Inceptisols and Alfisols for nutrition of rice (Oryza sativaL.) using Mehlich 3 as an extractant. Three levels, each of P (0, 14 and 23 mg kg-1 soil), K (0, 23 and 36 mg kg-1soil), S (0, 4.5 and 9.0 mg kg-1 soil), B (0, 0.5 and 1.0 mg kg1 soil) and Zn (0, 2.3 and 4.5 mg kg-1 soil) were applied separately to 20 Alfisols and Inceptisols each for growing rice in greenhouse. Biomass yield, concentration and uptake of those nutrients by rice were significantly influenced (P ≤ 0.01) by the soil and rate of each of the nutrients (P, K, S, B and Zn), but not by their interactions in both the soil orders. The amount of these five nutrients as extracted from soils by Mehlich 3, alike conventional extractants, showed significant positive correlations (P≤ 0.01) with biomass yield, nutrients concentration and their uptake by rice plant, which indicated suitability of Mehlich 3 in predicting plant available nutrients in soil. The critical levels of Mehlich 3 extractable P, K, S, B and Zn for rice in Inceptisols were 14.7, 51.2, 22.9, 0.65 and 1.27 mg kg-1; while in Alfisols those values were 8.2, 117.3, 21.9, 0.40 and 2.15 mg kg-1, respectively
Influence of organic and inorganic content on fractal dimensions of Barakar and Barren Measures shale gas reservoirs of Raniganj basin, India
No full textThe carbonaceous shale beds of Barren Measures and Barakar Formations of Raniganj basin have been investigated for organic and inorganic content influence on the matrix containing micro, meso, macropores, structures and related fractal dimensions. The significant amount of TOC suggests slow suspension during the consolidation of the sediments in an abundant river channel owing to low energy environmental conditions. The adequate thermal maturity indicates shale beds of both the Formations are good to excellent source rock for dry hydrocarbon genesis.
The plot of ln(ln(P/P0)) versus ln(V) have shown three distinct straight line sections within the whole relative pressure range (0.0000–1.0000), further denoted as Region I (P/P0 = 0.0002–0.0090; D1), Region II (P/P0 = 0.0090–0.3000; D2) and Region III (P/P0 = 0.3000–1.0000; D3) and the linear fitting equations were obtained with different slopes. The values of D1, D2, D3, signifying the complexity of micro-, meso- and macropores, providing supplementary sites for gas adsorption. Fractal dimensions have shown a positive correlation with clay content, whereas negative correlation with total organic content indicates that inorganic content plays a vital role in the rugged surface formation useful for gas storage. The positive linear correlation of fractal dimensions (D1and D2) with Langmuir volume accentuated that smaller pores (micro and meso) contains ideal rugged surfaces suitable for gas adsorption due to heterogeneity, irregular pore surfaces, complex pore openings and structures. Furthermore, D3 shown negligible negative correlation with VL specifies the larger pore size do not provide sites for adsorption space, because of the altered smooth surfaces formed during diagenesis. An empirical method for estimation of sorption capacity (ESC) has been proposed taking into account of the positive and negative influence of the fractal dimensions, clay, minerals and total organic content. The strong positive linear relationship of Langmuir volume (VL) with an empirically estimated sorption capacity (ESC) (R2 = 0.86) and about 90% curves match, signifies the proposed empirical formula can be used as an indirect method for estimation of sorption capacity of shale samples
Assessment of roof convergence during driving roadways in underground coal mines by continuous miner
No full textIn India, a number of coal seams are being extracted by using the continuous miner (CM). There is a need to standardise some of the major parameters like cut-out distance (COD) and the convergence of the roof strata for safe operation of the CM. The production and productivity of this system mainly depend on the COD, i.e. the length of the stable drivage made in the coal seam by the CM at a time without installing any reinforcement/support. This factor is determined by assessing the convergence of the roof strata. Therefore, prior to driving of the roadways by the CM, the estimation of the convergence of the roof strata is necessary for safe and stable driving of the roadways. No suitable empirical relationship is found between the convergence and the COD. This paper deals with the assessment of the roof convergence during development of the coal seams by the CM. Variations of the convergence with the major influencing parameters, i.e. the COD, the rock mass rating and the width of the gallery, are obtained by the parametric study through elasto-plastic numerical modelling. The trend of the convergence data with respect to the input parameters is found non-linear. Thus, a non-linear multivariate model is framed by putting the constant and exponents in the input parameters. These constant and exponents are determined through regression analysis to develop a predictive model. The coefficient of determination of the model is around 0.98. The model is validated with the monitoring data of different mines. This model can be applied for the assessment of the convergence of the roof in underground coal mines for safe driving of the roadways by the CM. Alternatively, optimum COD of the CM can be designed by fixing the threshold limit of the convergence value for a particular geomining condition
Strategies for underground Extraction of the inclined coal seams by continuous miner
No full textLarge-scale machanisation in underground coal mining becomes necessary to meet the gap between the demand and the supply of coal in India by improving the production and productivity. The macanisation becomes difficult when the inclination of the coal seam is high as it involves a number of geotechnical and operational issue. In India, there are huge reserves of the coal where the seams are inclined. Unless, these coal seams are extracted applying proper methodologies, the working would be jeopardized due to the severe geotechnical problems. Therefore, it is important to understand the behavior of the rock mass during the working in the inclined coal seam. In this study, the field investigation and the numerical modeling are carried out to assess the stability of the workings of the inclined coal seams. The effect of the inclination on the stability of surrounding rock masses is evaluated by parametric study through numerical modeling. The variation of the inclined pillar strength, the stress regime and the failure zone are presented in this study. The case study of the shantikhani Mine of singereni Collieries Company Limited are presented where the workingsare carried out in the inclined coal seams
Beneficiation and utilization of low volatile coking coal and non-linked washery Indian coking coals for metallurgical purposes
No full textIndian coal industry is the world’s third largest in terms of production and fourth largest in terms of proven coal resources. Coal deposits are of drift origin, high in ash content but low in sulphur. There are 20 major coalfields located in east and south eastern quadrant of the country. The coking coal reserves are less compared to the non coking coals and the good quality coking coals has been exhausted leaving behind poor quality feed stock for the metallurgical sector. For production of iron & steel through blast furnace route, coking coal is an important raw material. The good quality coking coals of the upper seams are fast depleting leaving behind the inferior quality lower seam coal. The lower seam coals presently being mined are mostly low volatile coking coal (LVC). They constitute about 50% of the total coking coal reserves in India. These coals are characterized by high raw coal ash content and poor washability characteristics. Beneficiation of the lower seam coals in the existing washery circuits (2 or 3 product) does not yield requisite quality demanded by the steel sector of the country and as a result it is termed as Non-Linked Washery (NLW) colas, and the entire production of inferior coals is diverted to the thermal power sector, thus, wasting the scarce coking coal resources. In this paper, an attempt has been made to focus the cost-effective and eco-friendly approach for utilization of the LVC/NLW coking coals illustrating with a case study
Blast induced rock mass damage around tunnels
No full textDrilling and blasting is a preferred method of rock excavation world-wide due to low initial investment, cheap explosive energy, easy acceptability among the blasting engineers and, possibility to deal with different shapes and sizes of openings. Although, drill and blast method has witnessed significant technological advancements, it has inherent disadvantage of deteriorating surrounding rock mass due to development of network of fine cracks in it leading to safety and stability problems. The damage in the peripheral rock mass culminates in the form of overbreak and damaged zone beyond overbreak. In some cases the projects cost has increased more than 15% because of overbreak. Although significant efforts have been made to assess damage to the surrounding rock mass using different methods, the solution based on easily available site parameters is still lacking. Authors have carried out field investigations at five different tunnels located in Himalaya, India to study blast induced damage for wide range of rock mass quality Q values (0.03–17.8). In addition to Q, specific charge, perimeter charge factor, maximum charge per delay, advancement and confinement factors have also been used. Data sets of 113 experimental blasts are collected from the five tunnel sites. All the parameters, easily available to the site engineers, have been used for developing an empirical correlation to estimate the rock mass damage around the tunnel, which is discussed in the paper. The proposed empirical correlation has been validated using ultrasonic tests on rock core samples obtained from one of the experimental location
Prediction of coal ash fusion temperatures using computational intelligence based models
No full textAbstract In the coal-based combustion and gasification processes, the mineral matter contained in the coal (predominantly oxides), is left as an incombustible residue, termed ash. Commonly, ash deposits are formed on the heat absorbing surfaces of the exposed equipment of the combustion/gasification processes. These deposits lead to the occurrence of slagging or fouling and, consequently, reduced process efficiency. The ash fusion temperatures (AFTs) signify the temperature range over which the ash deposits are formed on the heat absorbing surfaces of the process equipment. Thus, for designing and operating the coal-based processes, it is important to have mathematical models predicting accurately the four types of AFTs namely initial deformation temperature, softening temperature, hemispherical temperature, and flow temperature. Several linear/nonlinear models with varying prediction accuracies and complexities are available for the AFT prediction. Their principal drawback is their applicability to the coals originating from a limited number of geographical regions. Accordingly, this study presents computational intelligence (CI) based nonlinear models to predict the four AFTs using the oxide composition of the coal ash as the model input. The CI methods used in the modeling are genetic programming (GP), artificial neural networks, and support vector regression. The notable features of this study are that the models with a better AFT prediction and generalization performance, a wider application potential, and reduced complexity, have been developed. Among the CI-based models, GP and MLP based models have yielded overall improved performance in predicting all four AFTs