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By R. Y. Wan

Newmont Gold Company has advantageously used the capabilities of mineral oxidizing bacteria to develop a process for pretreatment of low grade sulfidic and carbonaceous-sulfidic refractory gold ores. The biooxidation process results in the oxidation of the sulfidic minerals with increased exposure of gold for subsequent gold recovery. The biooxidized carbonaceous-sulfidic ores cannot be heap leached with cyanide because of the "preg-robbing" characteristics of the carbonaceous matters in the ores. An alternative heap leach process using ammonium thiosulfate was developed to extract gold from the "preg-robbing" biooxidized ores. The ammonium thiosulfate leach process has been successfully practiced both in laboratory and pilot plant testing. Satisfactory test results encourage the continuation of process development.

Jan 1, 1996

By K. V. Raj, A. Miller

"Workers at mineral processing facilities are often exposed to high levels of dust generated when ores are processed. Crushing, grinding, screening, and other processes generate large quantities of dust, which can exceed the threshold VALUES (prescribed by the Mine Safety and Health Administration (MSHA). Many ores contain quartz (silica), which has been known to cause serious health problems in workers over time. Given the structure of mineral processing plants, the airflow regime is not coherent inside the building, which may lead to multiple recirculation zones. These recirculation zones can trap dust, and concentrations of dust can then rise over time. Therefore, there is a need to understand the airflow phenomenon that occur inside of mineral processing facilities and how these occurrences interact with the dust generation processes to identify zones of potentially high dust concentration. Computational fluid dynamics (CFD) modeling can give a better understanding of the airflow and help recommend designs and methods to mitigate the high dust concentrations in a mineral processing plant. This paper presents the CFD modeling of airflow inside of a mill building to demonstrate airflow patterns that will affect the generation and subsequent dispersion of dust due to crushing, grinding, and other activities. This study was conducted by researchers from the National Institute for Occupational Safety and Health (NIOSH). INTRODUCTION In a mineral processing facility, minerals go through various mechanical processes in order to reduce their size for separation of economic minerals from gangue minerals to produce a final marketable product. This research, conducted by the National Institute for Occupational Safety and Health (NIOSH), focuses on ore mills in metal and nonmetal mining (MNM) operations, but the applicability of the approach will be valid for any large structure where workers are exposed to airborne contaminants. The processes of crushing, grinding, cleaning, drying, and product sizing in these facilities generate a large amount of dust, creating hazardous conditions for the workers in these facilities. This is highlighted by the fact that MSHA sampling data for the years 1997–2012 indicate that 12.3% and 15.9% of the gathered samples were over 100 µg/m3 for silica for metal and nonmetal mills, respectively [1]. Mineral processing operations typically use some type of engineering control to address their most significant dust sources. Engineering controls include such approaches as bag-house-type dust collectors, scrubbers, and electrostatic precipitation [2]."

Jan 1, 2018

By Nikhil Dhawan, Veeranjaneyulu Rayapudi

This study investigates upgrading of low-grade banded hematite quartzite iron ore (Fe ~31%). Conventional beneficiation was found to be futile. The susceptibility of iron phases to microwave exposure and their selective absorption assists in the liberation of iron values. Microwave exposure of coarse particles at 540 W for 10 min yielded a concentrate with Fe 56.30% and recovery of 50.68%. Conventional carbothermic reduction at 500 °C, 60 min and 9% charcoal yielded a concentrate with Fe 57.6% and iron recovery of 68%. The presence of sufficiently bonded silica leads to an easy formation of a fayalite phase. The microwave reduction design yielded FeG of 57.6%, FeR of 47% and a yield of 24% at an optimal condition of 540 W, 8 min and 6% charcoal. It was found that a small fraction of microwave-irradiated ore-charcoal mixture melted rapidly, and pure ferrite balls were observed within 8 min. An optical micrograph of a ferrite ball reveals the retained austenite and martensite phase.

By K. A. Lewandowski

Heap leaching efficiency is reduced by poor solution flow characteristics (channeling and ponding), which result from compaction and fines migration. Agglomeration of the ore can prevent compaction and immobilize fines, but copper leaching requires an acid-resistant binder to stabilize the agglomerates. Until now, there has not been a satisfactory way to evaluate whether a binder was effective, other than squeezing a handful to see if it ?feels right.? Procedures have been developed to quantitatively determine whether a binder produces agglomerates that can withstand compaction in an acidic solution, and have identified several binders that will provide sufficiently compaction-resistant agglomerates for copper heap leaching. Keywords: Copper heap leaching, Binder performance, Compaction

Jan 1, 2010

By T. A. Lloyd

The use of tank cells over the years has provided a means for low cost, space efficient, extra capacity in existing flotation circuits. In some cases, new plants have selected tank cells as the machine of choice. Typical tank cells use high efficiency impellers for mixing, which results in low power draw. Unfortunately, these mixers have poor aerating characteristics that compromise metallurgical performance. This has all changed with Outokumpu's new flotation concepts. Outokumpu has recently developed the HG or High Grade flotation cell that can provide higher recovery with better selectivity while maintaining the simple operation of conventional cells.

Jan 1, 1993

By Siddhartha Roy, Hemant Agrawal, Ram Madhab Bhattacharjee, Devi Prasad Mishra

Heat stress in underground coal mines is a major threat to the health and safety of the miners. Hence, managing heat and prediction of heat stress in advance is essential for maintaining a safe, healthy, and productive underground mine environment. In this study, an extensive ventilation survey has been carried out in three different deep and mechanized underground coal mines. The ventilation survey data are used to develop 3D simulation models with the VentSim™ software to predict the conditions that could cause heat stress in underground mine workings. The developed 3D models predicted well the wet-bulb globe temperature (WBGT), a recognized indicator of potential heat stress, with a coefficient of determination (R2) of 0.986, 0.994, and 0.993 for Mine-A, Mine-B, and Mine-C, respectively. Moreover, through 3D modelling, the applications of auxiliary ventilation and spot coolers to reduce the wet-bulb globe temperature (WBGT) for improving the underground workplace environment have been explored. The study demonstrated that auxiliary ventilation and spot coolers can help in significant reduction of heat stress conditions in an underground mine environment. By application of auxiliary ventilation, to increase air volumes, and spot coolers, the WBGT index in mining faces is reduced by 1.2–1.4 °C and 3.9–5.4 °C, respectively. Therefore, it is concluded that the spot coolers are more effective in reducing the heat stress conditions in hot and humid underground mine environments in comparison with auxiliary fan that is used to increase the air volume and velocity. This study opens up a new horizon of 3D simulations for heat stress management in underground mines. The outcome of this study will be useful for the researchers, mine operators, and environmentalists understanding the heat stress contributors and their control in underground mine environment.

May 10, 2023

By Shakuntala Tudu, Indrajit Paul, Surajit Sinha, Pulibandla Basaveswara Rao, Shaik Mahaboob Basha, Srinivas Dwarapudi

The iron and steel manufacturing sector directly accounts for 7–9% of global CO2 emissions. Raw material preparation, such as iron ore sintering, pelletizing, and cock making, is the major CO2 emitter. As climate change becomes a bigger concern, steel manufacturers need to lower CO2 emissions without hindering efficiency or increasing costs. In recent years, the percentage of iron ore pellets in blast furnaces has increased due to its uniform size, good reducibility, and high tumbler index. Pelletizing is energy-intensive and emits considerable CO2. Around 20% of CO2 emissions during pellet making come from fluxes. In the present work, the authors established a novel CO2- free flux called wollastonite (CaO.SiO2) for sustainable palletization. Pellets with varying percentages of wollastonite (0–6%) are prepared and tested for chemical, physical, and metallurgical properties. Image analysis through an optical microscope is carried out to quantify the phases of fired pellets. SEM–EDS is performed to evaluate the chemical composition of the melt and slag phases. The results showed that the reducibility index (RI) and swelling index (SI) of pellets decreased with an increase in wollastonite dosage. Pellet strength increases with an increase in wollastonite addition up to 1.2% CaO (2.27% wollastonite), and a decrease in strength is observed thereafter. The increase in strength is attributed to the increase in slag bonds. The decrease in strength beyond 1.2% CaO is mainly because of an increase in low melting eutectics and more magnetite content. Pellets with 2.27% wollastonite to get 1.2% CaO showed good physical and metallurgical properties.

Mar 4, 2024

By J. L. Huiatt

Kerosine, fuel oil No. 2, vapor oil, and fuel oil No. 6 were separated into general hydrocarbon fractions by ion exchange chromatography and adsorption chromatography. The collecting properties of these fractions were evaluated by flotation of molybdenum and copper minerals from a natural chalcopyrite ore. Paraffin fractions and aromatic fractions of low polarity produced the best molybdenum recoveries. Selective flotation of molybdenite from copper sulfide minerals was not possible with any of the chromatographic fractions.

Jan 1, 1972

By Ronald L. Wiegel

In a mineral processing plant there are a number of routine decisions which are based at least in part on the plant's metallurgical performance. Among these are those related to: 1) equipment functioning properly 2) suitable operating conditions 3) reagents achieving desired results 4} determining operating response to changes in ore 5) defining circuits offering potential for improvement A step beyond the routine, are the periodic management evaluations of operating supervision and technical assistance, which are based largely on profit -a direct function of are availability, metallurgical performance and operating costs. The "yardstick", excuse me -"meterstick", by which performance is best measured is the plant metallurgical balance, which tells not only what was produced but how it was produced. Since this metallurgical balance is directly related to both plant profits and individual rewards, it is only reasonable to make that "meterstick" as precise as humanly possible.

Jan 1, 1978

By Wenjun Ju, Xiaodong Sun, Jianwei Zheng, Bingding Yi, Zhaorui Ma, Pengfei Jiang, Lingfu Zhu, Yangfa Zheng

The presence of hard roof poses a significant threat to the safety of underground coal mining. In this study, a mechanical model is established for underground stopes to analyze the overburden structure with the advancing of the mining face. It is indicated that the load-bearing arch structure (LBAS) is formed above the stope for roofs with regular hardness, whereas the reversed-basin bearing structure (RBBS) is formed for hard roofs. Compared with the LBAS, the RBBS can induce an additional pressure at the foot of the bearing structure, and this effect becomes less as the distance between the hard roof and stope increases. The ultra-deep borehole hydro-fracturing technique (UHT) is proposed to weaken the hard roof for pressure release, and the associated equipment and procedures are also presented. The UHT is based on horizontal drilling along the axial direction of the roadway in the roof, and then the receding segmented hydraulic fracturing technique is used to achieve the purpose of fracturing (weakening) of the surrounding rocks. Field tests are carried out in 3022 roadway of Daliangwan coal mine in Yulin to assess the developed technique, equipment, and fracturing procedures. To evaluate the fracturing effect, deep borehole stress-meters are installed at different depths of the fractured and un-fractured zones of the roadway, along with hydraulic support pressure sensors placed at the mining face. The results show that compared with the un-fractured zone, the pressure on the wall and pillar sides is lower than that in the fractured zone, and the associated weighting duration and weighting area ratio of the fractured are reduced by 53.23% and 33.59%, respectively. This indicates that the presented UHT can provide a new solution for the prevention and control of mining disasters induced by hard roof failures in underground coal mining.

Nov 2, 2020

By Kai Koosmen, Mehdi Serati, Tengzhou Wang

Spalling and rockburst are unwanted brittle failures at the boundaries of underground excavations that are commonly observed in hard rock and high-stress environments at significant depths, although, spalling has also been observed in comparatively shallow soft rocks. The crack initiation (CI) stress threshold (representing the stress level at which new micro cracks begin to form in an intact rock) is widely used to establish the in-situ spalling strength, and is generally regarded as the lower limit of the long-term rock strength. This study analyses the evolution of CI and other mechanical properties for a high-porosity sandstone with an average UCS of 38 MPa under unconfined cyclic compressive loading. The results indicate that rock properties are variably affected by cyclic loading with; no significant effect on Youngs Modulus; a moderate increase in Poisson’s ratio and fracture angle; a moderate decrease in UCS; and a major reduction in the CI stress threshold. All of these changes were generally amplified by cyclic loading at higher stresses. From the results, it is concluded that rockburst and spalling limit in underground structures may reduce over time if the rock is subject to repetitive cyclic loading, and that the reductions will be greater for higher cyclic stresses. This may be a significant factor in the design and operation of some deep underground structures.

Apr 26, 2022

By C. Clark, J. Seymour, D. Benton

"National Institute for Occupational Safety and Health NIOSH is conducting research on jackleg use and related accidents in underground metal mines. This paper provides an analysis and overview of jackleg drill usage, accidents, operational characteristics, and alternatives, based on information from injury reports, legacy research, stakeholder input, and published literature. Jackleg drills are involved in more ground fall accidents in underground metal mines than any other drill. Jackleg-related injuries are most prevalent at the face in the course of installing initial ground support. Alternatives to jacklegs for drilling and bolting under incomplete support in narrow underground openings are not yet available. Small mechanized bolting equipment needs to be developed to address jackleg-related accidents and improve safety at mines where jacklegs are being used. JACKLEG DRILL Description The term “jackleg drill” is a generic name for a class of handheld, rotary, percussion rock drills that are equipped with an attached reaction leg to provide stability and thrust for the drill (Figure 1). All of the drill and leg controls are located near the operator’s handle at the rear of the head portion of the drill. Jacklegs are classified according to the bore size of their pneumatic pistons which normally range from 6.03 to 8.26 cm (2.375 to 3.25 in) [Kurt, 1982; Clark, 2012]. Jacklegs typically weigh 460 N (103 lbs), but their weight can approach 535 N (120 lbs) after they are fitted for operation with drill steel and air and water hoses [McKibbin and Clark, 2001]. In underground mines, jackleg drills are commonly used to drill 3.8-cm (1.5-in) diameter holes 1.83 m (6 ft) deep in rock. Application The jackleg drill is primarily used in underground mines when the size of the ore body, the ground conditions, or the mining method do not permit large openings to be mined using mechanized equipment (e.g., narrow vein mining). Jacklegs are used to drill blast-holes for explosives and also holes for installing ground support. These versatile drills are used in nearly all phases of mining including exploration, development, production, and maintenance [Kurt, 1982; Williams et al., 2007; Chen and McKinnon, 2012]. The jackleg is used to drill holes in rock using drill bits attached to hollow steel bars called drill steels (rotary percussion drilling). After the hole is drilled, the jackleg can be used to install different types of ground support components, depending on the ground conditions and the specific ground support measures that are needed. For example, the jackleg can be used to install expansion-anchor rockbolts or resin-grouted rockbolts using the drill’s rotary-motion feature. On the other hand, the jackleg can also be used to install friction-type Split-Set™ rockbolts using the drill’s percussion (hammer-motion) feature. As shown in Figure 1, various washer-like bearing plates can be installed along with these bolts to provide additional ground support and to help secure surface control products, such as wire mesh and shotcrete that are in turn used to retain small, loose material between the bolts [Clark, 2012]."

Jan 1, 2016

By Donald W. Gentry

Introduction The mining industry is perhaps best characterized by the numerous and abnormally high risks associated with the business of mining and by its most basic assets - ore deposits, people and technology. At the most fundamental level, it is the quality and effective utilization of these basic assets that determine a mining company's ability to compete efficiently in the international market place. The gold industry has received much attention in recent years and especially in recent months, for good reason. This commodity serves as an excellent platform for the subsequent discussion of these three basic assets and their role in mining's future. Facets of the gold industry The fate of this noble metal in recent times illustrates some of the various risks associated with the mining industry and the importance of high-quality assets, whether they be ore deposits, people or technologies. The following comments pertaining to the gold industry help place proper focus on subsequent discussions. All monetary amounts given are in US dollars. Throughout 1997, falling gold prices broke record after record: first hitting three-year lows, then a 12-year low in July and finally an 18-year low at year's end. From Jan. 1 through Dec. 31, 1997, the price of gold fell by more than $2.57/g ($80/oz), or some 22%. The decline in gold-mining profitability and stock prices was even more dramatic. At the beginning of 1997, the 20 largest gold producers in North America had a market capitalization of approximately $44.5 billion. At year's end, this market cap had fallen to $26.2 billion, a reduction of 41%. The total market cap of all the world's gold companies fell from $71 billion to $46 billion, a 35% drop (Serwer, 1998). Analyses suggest that, at a spot gold price of $9.65/g ($300/oz), only one, or possibly two, North American gold-producing companies can make money when break-even or "total costs of production" are considered. While strong hedge positions mitigate this situation in the short term, clearly, this is an industry in desperate straits. For example, write-downs for North American producers in 1997 were approximately $2.5 billion. Speculative short positions in 1997 were near historical record highs and generally exceeded long positions by factors of 9:1 or 10:1. Much of this is driven by some US commercial banks, hedge fund managers and commodity speculators who can significantly move gold prices sharply over short periods of time by selling gold they do not own in the expectation they can buy it back at a lower price before they have to deliver. These signifcant short positions are likely to continue as long as central banks are willing to sell or loan gold to financial institutions that in turn make the gold available to speculators who hope to capitalize on price fluctuations. The Far East accounts for approximately 26% of the annual demand for gold. Including India, the region accounts for 43% of total demand. More than 85% of the physical demand for gold is for investment jewelry in Asia and the Middle East. This demand is extraordinarily price sensitive. The fairly recent turmoil in Asian markets and economies, combined with currency devaluations throughout the region, have made gold more expensive (30% to 50% in local currencies) for those peoples most likely to treat gold as a safe investment haven. Higher interest rates also have reduced the amount of money they have to spend on consumer goods such as jewelry. All of these recent Asian events are deflationary in nature. Deflation, if coincident with rising unemployment, could result in significant dishoarding of gold. There is one key fact to remember when analyzing

Jan 1, 1999

"The Ohio River Bridge East End Crossing Tunnel requires a 75-year service life of its cast-in-place reinforced concrete lining. This twin-tube 3-lane (each tube) highway tunnel is about 55-ft wide and 30-ft high. Since unified tunnel service life prediction methodology does not exist in the US, challenges occurred during the design-build phase of this project. These challenges include the methodologies in determining the reinforced concrete’s degradation mode, the lining’s surface chloride concentration level, the reinforcing steel’s critical chloride threshold value for corrosion, how to verify the concrete’s diffusion coefficient, and the durability impact from concrete crack width. This paper presents a methodology in verifying the proposed concrete mix can achieve the service life requirements. This methodology can be adopted for service life prediction for future tunnels to be built in the US. INTRODUCTION The Ohio River Bridge East End Crossing (ORBEE) Tunnel is part of a Public Private Partnership project, which connects transportation network between Louisville, Kentucky and southern Indiana. Located in Louisville, Kentucky, the twin-tube highway tunnel provides northbound and southbound lanes of the Kentucky approach to a new bridge across the Ohio River. Tunnel lengths are approximately 1,675-ft and 1,685 for the northbound tube and the southbound tube, respectively. Connected by two cross-passages, both tubes have a roadway width of 40-ft, for 3-lane traffic, and a vertical clearance of 26.5-ft.The tunnel was constructed by drill and blast method with shotcrete and rock dowels as initial ground supports. The final tunnel lining system includes: •,Nominal 16” cast-in-place reinforced concrete lining, with 2” and 3” concrete covers over reinforcing steel for its extrados and intrados, respectively. •,20” cast-in-place reinforced concrete invert slab, with 4” and 3” concrete covers over reinforcing steel on its top face and bottom face, respectively. •,PVC waterproofing system around tunnel perimeter, excluding invert slab. •,Perforated PVC groundwater collection pipes on both sides of the tubes and one below the invert slab of each tube."

Jan 1, 2016

By J. L. Whitlock

A mutant strain of Pseudomonas paucimobilis is utilized to effectively degrade and or remove 90-98% of cyanide, thiocyanate, toxic heavy metals and ammonia from a cyanidation mill process and mine discharge maximum of 21,000 m3/d (5.5 MGD). Homestake Mining Company?s biological wastewater treatment plant has been in full scale operation for over 2 years at the Homestake Mine in Lead, South Dakota.

Jan 1, 1987

By D. Kruse

Top-down constructed large-diameter (up to 90 m or 300 ft) shaft design and constructability issues present an interesting suite of challenges and opportunities highlighted in this paper. The study covers 2D and 3D finite element models used to analyze various failure modes, evaluate the shaft liner and internal structures' response to seismic loading, assist in segment design and assess final structural design tradeoffs. Efforts to achieve economic advantage over conventional heavy civil practices have prompted innovative solutions for ring and segment design, ring build assembly and annulus backfill grouting. Intended for soft ground conditions, relationships between soil parameters and structure design are also explored. Mining Engineering, 2011, Vol. 63, No. 9, pp. 81-88. Official publication of the Society for Mining, Metallurgy and Exploration, Inc.

Jan 1, 2011

By Tung Vu, Michael Harrington

"The Regional Connector project is a complex subway light-rail project that runs through the heart of downtown Los Angeles, CA. The design-build contract was awarded in April 2014 to the Regional Connector Constructors (RCC), a joint venture between Skanska USA Civil West California District Inc. and Traylor Brothers Inc., and their designer team consisting of Hatch Mott McDonald (HMM) and subconsultants. The project broke ground on Sept. 30, 2014 and is expected to be completed in winter 2021-2022. The main components of the project consist of 6.4-m (21-ft) diameter twin-bored tunnels, three crosspassages, a 87-m (287-ft) long crossover SEM cavern, three new underground stations, and cut-and-cover tunnels along South Flower, Alameda and 1st Streets. The project map is shown in Fig. 1. The design and construction challenges associated with each of these main components are discussed in the following sections.Project designTunnels. The Regional Connector tunnels are located primarily within the Fernando formation consisting predominantly of extremely weak to very weak, massive, clayey siltstone. About 305 m (1,000 ft) of tunnels on the eastern end are in alluvium and mixed face of Fernando formation and alluvium. The tightest curve of the tunnel alignment is 178 m (583 ft) in radius. The tunnels were designed with a reinforced precast concrete tunnel lining (PCTL) to be used with an earth balance pressurized (EPB) tunnel boring machine. The PCTL ring is 5.5 m (18 ft-10 in.) inside diameter, 27 cm (10.5 ft) thick, 1.5 m (5 ft) long, and consists of five segments and a key. The segments were designed with 6,500 psi concrete, 80 ksi yield strength wire rebar, convex joint surfaces to enhance seismic performance, and a dosage of 1.7 lbs polypropylene microfibers per cubic yard of concrete for fire resistance. The rings are designed with a right ring and left ring pattern and a taper of 3.8 cm (1.5 ft) to allow for alignment curve negotiation. Figure 2 shows typical sections of the PCTL. The structural lining design was modeled using FLAC 3D. Four consecutive rings were modeled with 32 dowel connection. Loading considered in the lining design includes temporary ground load during excavation, long-term ground loads, seismic loads and train loads. The seismic loads on the PCTL were simulated with the racking deformation applied at vertical boundaries of the model. Due to variation of geologic condition along the tunnel alignment and different surcharge requirements, three different types of reinforcement (typical, heavy and extra heavy) were designed. The typical type PCTL was required in Fernando formation, the heavy type was required in alluvium or mixed-face condition, and the extra heavy type was required in alluvium and underneath the Japanese Village Plaza where a surcharge of 1,000 psf was required."

Sep 1, 2019

By S. Bhattacharaya, S. Aich, B. K. Nandi

"At present scenario, there has been an increasing demand in the usage of blend coal in power sector; regardless of how, specific knowledge on burning and ignition characteristics and their interactive effects is stingy. In this work a detailed investigation was therefore taken up to study in detail the combustion characteristics of selected coal samples and their blends. Certain parameters were believed to have significant effects on combustion characteristics of individual coal and their blend. Major parameters identified for this purpose included proximate analysis, combustion conditions, heating rate, reaction regions, blending ratios, ignition condition, reactivity (or reaction rate) and burnout temperatures. With the help of these parameters, thermal features and reaction kinetics of the individual and blended samples were investigated through a qualitative and quantitative thermo-gravimetric analysis of two different individual coals and their blend carried out in an oxygen atmosphere from ambient to 800 0C at a constant heating rate of 10 K/min. A significant difference in terms of rate of mass loss with temperature correlated from Arrhenius expression along with coal-coal blend interactions and deviation from their expected behaviour, have been observed between the kinetics of individual and blend samples, the latter showing better ignition performance and comprehensive combustion phase. It was also found that particles having the lowest percentages of volatile matter and ash could possibly be blended with particles having high ash and volatile matter to meet the required burning condition which can be effective in terms of cost savings, improved fuel economy, reduced undesirable exhaust emissions and improved safety of coal burning equipment. Experimental results further indicated that individual samples and coal blend samples have different combustion features in terms of residue left, peak temperatures and activation energies. Thermodynamic activation parameters such as activation energy, pre-exponential factor and order of reaction were computed from the thermal data using the modified form of non-isothermal methods. INTRODUCTION Coal has been the most significant source of energy for India and would remain so at least for the next few decades. About 60-65% of the electricity produced in India is from coal fired power plants. Indian coal is of drift origin and of high ash content. Ash content of the coal burnt in power plants in India is in the range of 30-45%, most of it being Run-of-Mine coal. Most of the power plants in India source their coal from number of mines, most common being multiple sourcing. Usually coal from each source [1] is burnt separately. For various reasons mostly associated with logistics, burning of blended coal is rarely practiced. Blending of coal is practised mainly for improving the quality of available coal and meets the shortage of coal supply. Blending technique is generally practised in power industries to reduce the cost of power generation along with mitigating combustion performance or slagging problem ensuring consistency in as fired coal quality and also for environmental compliance. Blending good quality imported coal can improve coal quality and helps in preserving indigenous coal resources for longer period [2]. Use of blended coal shall reduce load on all boiler components (Mill, CHP, Boiler, AHP) & reduce O&M cost and increase the availability. The main purpose of blending is to get a blended as fired coal having ash, volatile matter and gross calorific value close to design coal and the two coals are to be blended in such ratio proportions that resultant coal blend have desired ash, volatile matter and gross calorific value [3]. For a coal to be blended certain parameters have to be considered to get compatibility with respect to combustibility ( Burn ability) of coal, grindability ( HGI), ash fusion behavior, swelling characteristics of coal, need to be checked"

Jan 1, 2017

By Jogeshwara Sahu, Sapan Kumar Kandi, SANDEEP KUMAR JENA, Sachida Nanda Sahu, Sarada Prasad Das

The present article reports the recovery of potassium from mica scrap using carbide lime waste and NaCl. The acid leaching of mica [4 M H2SO4 at 90 °C] can recover a maximum of 25% potassium. However, in the chlorination roasting (with CLW and NaCl) water leaching process, it was possible to recover potassium to the tune of 94% [900 °C, 50 min roasting; mica:CLW:NaCl 1:0.75:1]. The formation of water-soluble phase like sylvite (KCl) and water-insoluble phases like anorthite ( CaAl2Si2O8) and nepheline ( NaAlSiO4) confirms the complete breakdown of the mica crystal structure. The extraction mechanism proceeds with the formation of a transition state followed by the release of potassium as KCl. The characterisation studies using ICP-OES, XRD, FTIR and FESEM support the proposed extraction mechanism. The salt produced by the evaporation of roast-leached liquor confirms the presence of sylvite and halite only, which can be separated to get the fertiliser grade KCl.

Sep 29, 2021

By Steve Kral

San Francisco, CA will host about 1,500 tunneling and underground construction professionals from around the world during the biannual Rapid Excavation and Tunneling Conference (RETC), June 19-22. These professionals are gathering in a city that has seen much under-ground work throughout its history. And, today, the San Francisco region has more than $4.6-billion in tunneling projects under way. The RETC will include three-and-a-half days of technical programming, complete with proceedings, two short courses, two field trips and a host of social activities. In addition, the accompanying exhibit has attracted 127 exhibitors in 152 booths, an RETC record. The following is a brief list of activities that will take place during the conference. A more complete program is provided in the official showguide that is bound into this issue of Tunneling & Underground Construction.

Jan 1, 2011