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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 Bobby G. Cahoon

The ( ) Tayaaja ( ) . The deposit ( ) 130 kilometers due east of the continental divide and approximately 290 kilometers east-southeast of Lima (Figure 1). Relief in the immediate vicinity of the mine, which lies or the west side of the Mantaro river, is in excess of 2,000 meters, and the elevation varies from a low of 2,000 meters above sea level on the Mantaro River to a high of 4,386 meters at point T-27 (Figure 2). Although the Cobriza deposit was first reported by the Italian Geographer Antonio Raimondi in 1866, only three reports have been published on the deposit, which began production in 1966 (Duefias, 1908; Fernandez Concha and Garcia y Garcia, 1961; Petersen. 1965). Many private reports have, however, been written by geologists employed by the Cerro de Pasco Corporation. These reports and the author's observations, while employed as the Cobriza Division Mine Geologists form the basis of the present paper, which describes the relations between-the ore controls in the Cobriza mine and the regional and local structure.

Jan 1, 1971

By Andrea B. Baldwin

In recent years, federal and state regulatory agencies have tightened air emission standards. Two of the acid gases, hydrochloric acid (HCI) and sulfur dioxide (SO2), are under heavy scrutiny for reduction. . Most traditional scrubbing systems, i.e. wet scrubbers and spray dryers, meet the standards but they typically are high in capital cost, have significant space requirements for equipment, and are difficult to maintain. Dry sodium injection (DSI) is a alternative technology that has been shown to be effective in HCl and SO2 removal while being the inverse to the problems listed with traditional systems. This paper covers the mechanics of dry injection scrubbing using the most effective sorbents, sodium bicarbonate and mechanically-refined trona (natural sodium sesquicarbonate). It presents DSI performance data for Chambers Medical located in Hampton, SC. This facility incinerates local medical and municipal solid waste. Chambers Medical has used mechanically-fined trona for HCl and SO2 removal since late 1991.

Jan 1, 1995

By Odd G. Askilsrud, Steinar Johannessen

New powerplants, tunnels and dams are currently under construction at Meraaker to triple the annual power production of a nearly 100 year old power scheme. A total of 44 km tunnels with cross sections varying from 7 m2 to 32 m2 have been excavated in hard rock formations. Ten kilometers were excavated by a High Performance Tunnel Boring Machine (HP TBM). The remaining tunnels have been completed by the drill and blast method, using modem proven equipment and procedures. This paper gives special attention to the TBM drive and equipment selection, including, planning, site organization and performance.

Jan 1, 1993

By E. Watkins, S. J. Schatzel, K. Ajayi, V. Gangrade

The National Institute for Occupational Safety and Health (NIOSH) has been conducting research related to unconventional gas wells positioned in abutment pillars associated with active longwall mining in Southwestern PA. The Ventilation and Explosion Prevention Team at NIOSH is working toward predicting and characterizing a hypothetical casing breach and its effect on the safety and health of mine workers, gas well workers, and the general public. An important aspect of this research is to distinguish coalbed gas from shale gas in the mine environment as an indicator of a casing breach. Another noncoal gas source exists in the region in the form of underground gas storage fields which also have the potential to migrate towards mine workings. During a potential gas breach, the addition of excess natural gas to coal mine environments will exceed the anticipated ventilation loading and can create a mine explosion hazard. A methodology has been developed to distinguish these gas sources. Gas samples from the three sources were analyzed by gas chromatography, and interpretive methods were applied to distinguish the populations graphically and statistically. Bivariate plots using the hydrocarbon index and the normalized molecular ratios showed that the sources occupy different regions of the graphs. All samples of non-coal gas contained under 2% CO2, and all coal samples included greater than this amount. A multivariate T-squared (T2) test analysis relating comparing data in pairs showed a low p-value (dimensionality parameter) and a high T2 test statistic for all comparisons, indicating that these sources are different and distinct gas populations. Ultimately, stakeholders from the mining and gas production industries can utilize this method to identify gas sources and a potential casing breach.

Mar 2, 2022

By I. Moreno-Ventas, G. Ríos, J. C. Fernández-Caliani, M. Bacedoni

"This paper delves into the constraints on the nature, origin and thermal evolution of the accretions formed in the uptake shaft of the flash smelting furnace operated by Atlantic Copper in Huelva, Spain, outlining recommended practices for preventing accretion buildup. The accretions were investigated using quantitative electron probe microanalysis, X-ray diffraction and digital imaging techniques, and the experimental data on mineral composition, crystal chemistry and textural relationships were interpreted in terms of thermodynamic phase equilibrium in the SiO2-Fe-O-S system. The results suggest that two distinct types of accretions were formed by the fractional crystallization of two coexisting immiscible melts, under changing conditions of oxygen partial pressure (pO2). The type I accretion of magnetite + delafossite ± cuprite ± tridymite ± metallic copper crystallized from a fractionating copper-rich melt at pO2 above about 10-5 atm, while the type II accretion of magnetite + fayalite + metallic copper + chalcocite derived from a melt with lower copper concentration when pO2 levels dropped below that critical level. Phase compositions and textures were consistent with a cooling history of both compositionally contrasting liquids from about 1,250 °C, the liquidus temperature of magnetite, to eutectic or near-eutectic temperatures of around 1,100 °C. The maintenance of appropriate temperatures — above the liquidus temperature of magnetite — and oxygen partial pressure levels may be critical for the prevention of accretion buildup. IntroductionCopper flash smelting with oxygen-enriched air, an autothermal process developed half a century ago by Outotec (Espoo, Finland), formerly Outokumpu, currently accounts for about 50 percent of the world’s primary sulfide-based copper (Schlesinger et al., 2011). The partial reaction of copper sulfide concentrates produces two separate molten streams, copper-iron-sulfide matte and iron oxide-rich slag, and releases sulfur dioxide (SO2) gas. The matte is sent to converters to remove the remaining iron and sulfur, leaving blister copper with grade of about 99.5 percent copper (Cu), which is cast into anodes for electrolytic refining.The SO2-rich gas generated by the oxidation of sulfide feed particles contains a significant proportion of dust that is entrained in the process off-gas. The gas from smelting is transferred into a waste heat recovery boiler, where it is cleared of dust and cooled before it is converted into sulfuric acid. If the process is not operated properly, the dust-bearing gas may form accretions between the uptake shaft of the flash smelting furnace and the waste heat recovery boiler, causing severe problems in the gas handling system (Swinbourne, Simak and Yazawa, 2002; Miettinen, 2008; Stefanova et al., 2012). Removing the dust accretions usually requires a greal deal of time, effort and resources. Understanding the buildup of accretion may help in reducing the problems and optimizing the process"

Jan 1, 2017

By A. S. Winters

INTRODUCTION Homestake Mining Co. owns and operates the Bull¬dog Mountain mine near Creede, CO. Lead-silver con¬centrates are produced from ores extracted from narrow veins which dip from 1.04 to 1.39 rad (60 to 80°). An¬nual mill throughput is approximately 90 700 t (100,000 st). Ore shoots average 2 m (7 ft) in width and the ore is often weak, muddy, and poorly consolidated. Walls can be either strong or highly fractured along the strike of the veins. Cut-and-fill methods were initially selected to mine the deposit and considerable overhand mining occurred during the initial stages of the mine. Because of un¬stable ground conditions, mine management recognized that other methods would have to be employed. Undercut-and-fill mining was adapted to extract the loose ore from narrow veins and is presently the primary method used. Approximately 80% of the annual pro¬duction is extracted by this system. Loading ramps are positioned along the strike of the vein on 90-m (300-ft) intervals to allow for 45-m (150-ft) long cuts in each direction from the extraction raise. This interval was selected for efficient slusher operation and stope cycling. Loading ramps rather than chutes were selected for ore movement into 4.5-t (5-st) Granby-type cars because of extremely sticky ore conditions. Mined-out areas are filled with deslimed mill sands. Sand is pumped from the mill into two mine storage dams where the water is decanted. Each dam has a 544-t (600-st) capacity. Sand is pumped into the mine at a 30 to 40% slurry through 2195 m (7200 ft) of 51-mm (2-in.) thick wall pipe. When called for, sand is reslurried within the dams to a density of 55 to 65% and pumped to the particular mine opening requiring fill. Dry cement is added to the slurry prior to pumping. The capacity of the mine fill system is 20 t/h (22 stph). DEVELOPMENT Vertical development below the main adit level oc¬curs on 61-m (200-ft) intervals from an internal winze. Main haulage drifts or laterals are 2.7 x 2.7 m (9 x 9 ft) in section and driven parallel to the vein structures. Ground conditions generally dictate that better progress can be realized in the footwall than in the hanging wall. A distance of approximately 21 m (70 ft) is maintained between vein and drift openings to accommodate a smooth 18-m (60-ft) radius curve for crosscuts which are driven on 91-m (300-ft) intervals. Approximately 18 m (60 ft) of tail room is driven past the vein inter¬section to accommodate train loading. Ore and waste are hauled using diesel or electric driven locomotives operating over 18-kg (40-Ib) rail [762-mm (30-in.) gage]. Loading ramps are established above each crosscut¬ vein intersection. Scram drifts are then driven in the vein to determine the width and grade of the ore. If a prior decision to mine the block had been reached, then the scram is driven only far enough [about 12 m (40 ft)] to establish a drawpoint and scraper tail room. In most cases, the drawpoint is a 2.1 x 2.1-m (7 x 7-ft) cutout driven about 2.4 m (8 ft) into the footwall. On the level above, a raise bore station is established in the footwall to one side of the crosscut-vein inter¬section. The station is of sufficient size to accommo¬date a Robbins 41R raise boring machine. Support for the station is accomplished with 1.2 and 1.8-m (4 and 6-ft) roof bolts and wire screening. Once completed, a 152-mm (6-in.) concrete slab is poured and the raise drill set in position to center the 1.5-m (5-ft) diam hole approximately 1.8 m (6 ft) from the vein footwall. A 229-mm (9-in.) pilot hole is then drilled to the scram cutout below and reamed back to full diameter (see Fig. 1). STOPING Initial mining in a typical undercut-and-fill stope be¬gins from the top of the borehole. The initial cut can be either immediately beneath the track level or the old scram drift depending upon the particular situation. Cuts vary but are generally 2.4 to 3 m (8 to 10 ft) high. Support is accomplished by square-set timber, overhead caps, or roof bolts and screening depending upon ground conditions. Once the initial cut is removed, underhand timber and screen is installed and cemented sand fill placed. The stope is then ready for undercut mining. Prepara¬tion work begins with sinking 4.5 to 6 m (15 to 20 ft) on the borehole plus cutting a slot to the vein. As sinking progresses, hanging sets are installed to provide man¬way and service facilities. Hanging sets 1.7 m (5 ft 8 in.) long and 1.6 x 2.2 m (5 ft 4 in. x 7 ft 4 in.) in section are installed with steel hangers similar to shaft sets. Framed 203 x 203-mm (8 x 8-in.) timbers are made up in advance and shipped to the stope during sinking operations. When manway and service facilities are completed to the floor of cut to be mined, generally 3.65 to 4.3 m (12 to 14 ft) below the previous sand fill, the ore is removed to the hanging wall plus a round each way along the vein. Levelers or long stringers are then installed over the raise opening to support the work deck, slusher, and grizzly opening. All waste and ore from the sinking process is fed by gravity to the raise (see Fig. 2). Once the stope is equipped, mining pro¬gresses outward in each direction from the grizzly open¬ing. Stope equipment consists of 907 kg (2000 lb) pull air tuggers, timber skips, 11-kW (15-hp) ventilation fans, 15 to 22-kW (20 to 30-hp) electric slushers, 762 to 1270-mm (30 to 50-in.) scrapers, 67-mm (25/a-in. ) jackleg drills, as well as other drilling and blasting supplies. In narrow stopes [generally less than 2 m (7 ft) wide], no support is required for the underhand caps of the previous fill. Where wide sections in the vein occur, segment braces are installed beneath the caps to insure that the sand support cannot slip away from the hanging wall. Sections as great as 6 m (20 ft) wide and 4.5 m

Jan 1, 1982

By Marianne Snedeker

In January we published a questionnaire asking about the content of MINING ENGINEERING and about your interests. At the same time we hired an outside firm, READEX Inc., of St. Paul, MN, to send the same questionnaire to a sampling of about 1000 US members, selected on an nth name basis, so that we could have some preliminary numbers for the Annual Meeting in February. READEX sent us the final results of its survey in March. At that time, 525 responses of the 992 surveys sent out had been returned, for a 52.9% response, an extraordinarily high return for a low-key (no incentive for return) random sampling. On May 7, we cut off on tabulating returns from the magazine so that we could report the results to you in this issue. At that time, we had 594 questionnaires returned. Our 594 and READEX's 525 (we have assumed that relatively few people returned both), represent a 1119 return, about 3.5% of the approximately 32,000 who received the January issue of ME. About ME Through responses to the questionnaire, we were hoping to learn more about you, your interests, and how the magazine could better serve you. Those of you who responded, told us something positive-you look at or read the magazine. Of the 1119 respondents, 1068 or 95.4% indicated that they had read or looked through the November and/or December issues. Those of you who refer to the magazine once are 466 or 42.6%. Those of you who refer to the magazine two or three times are 559 or 51.1%. Those of you who refer to the magazine four or more times are 68 or 6.2%. How much time do you spend reading the magazine? Of those responding to this question: 186 spent up to 1/2 hr 16.6% 590 spent up to 1 hr 52.7% 292 spent 1-2 hr 26.1% 51 spent more than 2 hr 4.6% In an informal survey among our staff, we determined that most people spend 1/2 to 1 hr reading magazines to which they subscribe at home. Does that match your experience? Many of you, 764 or 69.4%, clip your magazine for further reference. Also, many of you, 513 or 64.2%, do not pass your copy on to another reader, indicating perhaps that you are clipping it or receiving the magazine at home. Those magazines that are passed on reach: 2 people - 159 - 20.0% 3-5 people - 95 - 11.9% 5 or more - 31 - 3.9% Answers to what portions of the magazine you find useful indicated that the top three were Industry News, feature articles, and Technical Papers; see Table 1. The "other" category included advertising-display, classified, and employment-Coming Events, product information, Washington Survey, new books, the reader service card, and Engineering Fundamentals. Of those responding, 797 or 75.3% indicated a preference for dual notation of SI (metric) with English units; 228 or 21.5% preferred all SI units; while 34 or 3.2% preferred SI with dual notation of other metric units. Based on the preliminary numbers reported by READEX for this question, the MINING ENGINEERING Committee in February voted to return to a policy of dual notation. This decision has been implemented. We asked for your appraisal of the technical level of the magazine. Of those responding, 78 or 7.4% indicated it is too technical, 147 or 13.8% indicated it is not technical enough, and 836 or 78.8% judged it to have the correct tech¬nical level. In response to the question about whether you like to read an occasional feature that is not technically oriented, 32 said no, but an overwhelming 97% (1024) said yes. Of the specific topics, 785 like history, 558 political or socioeconomic articles, 440 career development, and 373 human interest. Other topics suggested included new disciplines, mineral resources of the world by

Jan 6, 1982

By James R. Jones

It has been 2-1/2 years since the Congress passed the Surface Mining Control and Reclamation Act of 1977 (PL95-87) the Office of Surface Mining every deadline specified in the Act. Hopefully the Congress will begin to realize that specifying unrealistic deadlines does not accomplish the end desire of legislation any sooner -- it only adds to the confusion, and actually hinders orderly, efficient progress. OSM has been sued by all categories of involved parties -- environmental activitist organizations, the states, and the coal operators. This situation has resulted for two reasons: (1) insufficient time was allotted by the Congress to properly develop the regulations and program, and (2) OSM?s philosophy that it must dictate every detail of reclamation operations from Washington, even though many of its people are inexperienced with coal mining. These law- suits are now demonstrating their value. OSM is showing signs of "pulling-in-its horns" and, hopefully, will approach the revised regulations in a more realistic fasion.

Jan 1, 1980

By Robert J. Auber, Thomas R. Scotese

The West Leg Interceptor is part of a new sanitary sewer system in the southwest suburbs of Cleveland. The first two construction contracts were excavated in glacial soils varying from hard tills to pressurized silts and flowing sands. These soil and groundwater conditions were locally problematic during shaft and tunnel excavations and final lining construction. A variety of solutions were developed primarily during construction. During the WLI-1R Contract, subgrade pressures, continued ground losses, and displacements necessitated extra eductor wells and modified inverts for stabilization of shafts. At the WLI-2Contract, one shaft excavation in similar ground required only one extra well. In the WLI-1R tunnel, localized inflows of groundwater, silt, and sand through the geotextile fabric were stopped by cement grouting. In one WLI-2 connector tunnel, damage to the TBM flood doors combined with wet, flowing silt and sand led to ground losses, surface settlements, plugging, patching, and chemical grouting. The concrete lining in the main WLI-2 tunnel required remedial work to improve watertightness at joints.

Jan 1, 1999

By S. Bhagwat

Coals capable of emitting 2 lbs SO2/106 Btu heat input must be defined as high sulfur coals. This is because electric utility plants built after 1971 may not emit more than 1.2 lbs SO2, and those built before 1971, and regulated under the State Implementation Plans (SIP), may exceed the 2 lbs S0 limit only under closely defined restrictions concerning ambient air quality and prevention of air quality deterioration. Coals produced in Kentucky, Illinois, West Virginia, Ohio, Pennsylvania, and Indiana account for 77% of SO2 pollution potential and are, therefore, the subject of this investigation. These coals have suffered market share losses in the 10 years from 1974 through 1984. This is due to their sulfur content as well as their lack of price competitiveness with low sulfur western and imported coals. Kentucky and West Virginia have been able to increase their compliance quality coal production substantially, but other states have largely been unable to do so because of nonavailability of low sulfur coal deposits. Assuming that the current relative productivity and cost competitiveness of coal producing states will not change significantly by 1994, this paper makes two projections of coal production in the selected states. In scenario I, the current clean air regulations are assumed to apply until 1994, and coal production in the selected states is projected to in¬crease by about 6% in 1994 compared to 1984. In scenario II, it is assumed that acid rain legislation will be implemented, which will adversely affect the markets for high sulfur coals. Coal production in the selected states under this scenario is projected to decline about 10% between 1984 and 1994, jeopardizing up to 13,000 mining jobs. The author concludes that better coal quality and greater cost competitiveness are both essential to stem the market losses and to regain strength.

Jan 1, 1988

By J. Hanna, H. R. Gonzalez

Discussion by N.L. Hargett Dear Dr. Hanna: As discussed in our phone conversation, we are enclosing a suggested revision to the paper, "Application of Bentonitic Clays in Suspension Fertilizer Formulations," published in MINERAL & METALLURGICAL PROCESSING, May 1990. The revision will replace the second paragraph in the article. The reason for the revision is that suspensions have decreased in market share since 1984 and at present comprise an estimated 25% to 30% of fluid mixtures. This represents 6% to 7% of all fluids and only 2% to 3% percent of all fertilizers. Based on national surveys conducted by the Association of American Plant Food Control Officials (AAPFCO), suspensions comprised an estimated 25% of all fluid mixtures in 1974, 33% in 1976, 35% in 1980, 40% in 1984, and 36% in 1988. Revision to "Application of Bentonitic Clays in Suspension Fertilizer Formulations." Suspension fertilizers are an important segment of the fertilizer industry in the United States. Suspensions allow higher concentrations of nutrients (N, P2O5, K2O) than clear liquid solution fertilizers. K20 content of solutions is limited to about 10%, while suspensions can contain more than 30% K2O. Suspensions can tolerate greater variations in temperature than solutions. In suspensions, if crystallization occurs, the crystals can remain suspended in a clay jell instead of settling as they would in solutions. Solubility is not a limiting factor in suspensions, since complete solubility of phosphate is not required. This allows a wider range of phosphate materials to be used. Also, materials commonly used in formulating suspensions are less expensive and more widely available than those for clear liquids (Getsiner et al., 1984).

Jan 1, 1992

By Weibai Hu

The flotation separation of wolframite from fluorite and quartz is investigated with chelating agents and neutral oil as synergic collectors. Test results indicated that a-nitroso-ß-naphthol has a strong collectivity for wolframite and selectivity against fluorite and quartz. The 8-hydroxyquinoline has collectivity and selectivity also. They both have a better activity than sodium oleate. However, the cupferron is slightly inferior. The synergism of chelating agents and neutral oil looks promising, especially for fine wolframite particles. The activation effect of Fe2+ and Ca2+ ions on separation of wolframite from fluorite and quartz is slight. The UV absorb-spectra measurements showed that the adsorption of chelating agent on wolframite is multilayer, and flotation behavior is related to chemisorption. The chelating agent which bonds to Fe and Mn sits on the wolframite surface, and the reaction between Mn2+ ion with collector is more significant. The essentials affecting reagent activities are the bonding factor and the hydrophobic factor. These factors are discussed by structure-activity relationship theory. The synergism of neutral oil is a secondary collector likely to lengthen the hydrocarbon chain of chelating agents.

Jan 1, 1985

By Zygmunt Sadowski

Problems encountered in barite flotation from various waste materials such as spent drilling muds are likely to be closely connected with the effect of chemical additives and metal ions present either added or present as contaminants, on the flotation. Fuerstenau and Palmer (1976) have studied in detail the adsorption of multivalent cations onto oxide and silicate minerals. It was observed that the adsorption of a multivalent metal species exhibits a sharp pH dependence which is related to the formation of hydroxy complexes of the metal ions in solution. Investigations on the recovery of barite from tailings ponds and mining wastes (Sullivan and Lamot, 1981) have shown that such barite materials can contain large quantities of carbonate and silicate minerals (including clay minerals). Also iron oxide slimes can be present. From these substances cations such as Ca2+, Mg2+, Fe2+ and A13+ can potentially dissolve and be present in the aqueous phase accompanying the various minerals. These ions and their hydrolysis products can have a substantial effect on any subsequent flotation scheme. The present study investigates the effect of the noted ions on both the stability and electrokinetic behavior of barite suspensions.

Jan 1, 1986

By U. B. Kodukula

The iron ore beneficiation plant at Serra-Azul Mines of ArcelorMittal, Brazil operates at a rated capacity of 3.2 million tons per year. The ore is concentrated using magnetic separation, jigging, hydrocyclones and spiral concentrators. The tailings from the process plant are generated from classifier overflow of 135 tons per hour dry solids and thickener underflow of 48 tons per hour dry solids. A systematic experimental program was carried out using Multi-gravity separator (MGS), and wet high-intensity magnetic separator (WHIMS) for recovering the iron values from both of the tailing streams while minimizing the total quantity of tailings to be discarded. The classifier overflow contained 32.3 percent iron, 49.9 percent silica and 2.18 percent alumina and was 45 percent finer than 45 microns in size. The thickener underflow sample contained 47.3 percent iron, 27.6 percent silica and 2.49 percent alumina and was 16 percent finer than 45 microns in size. Separation results on the classifier overflow sample with the MGS indicated that a concentrate containing 62.1 percent of iron, 10.8 percent silica and 0.36 percent alumina can be achieved with a weight recovery of 24.5 percent. The results with WHIMS at 6500 Gauss indicated that concentrate containing 62.6 percent iron, 8.3 percent silica, and 0.65 percent alumina can be achieved at a weight recovery of 34.7 percent. 4.7 percent. WHIMS studies at 6500 Gauss on thickener underflow sample indicated that a concentrate containing 61.4 percent iron, 8.8 percent silica, and 1.74 percent alumina can be achieved at a weight recovery of 57.2 percent. Based on these results, and further in-house test works, a WHIMS installation was adopted for the recovery of iron values from the tailings in the operating plant at ArcelorMittal Serra Azul Mines, Brazil.

Feb 23, 2014

By J. G. Groppo, A. E. Bland, B. K. Parekh, W. F. Stotts

Many coal preparation plants discard fine coal (generally minus 100 mesh) because it is difficult to beneficiate economically. At the Kentucky Energy Cabinet Laboratory (KECL), the waste streams from several Kentucky preparation plants were evaluated for cleaning with counter-current column flotation. A series of performance evaluations were conducted using a 0.05 m (2 in.) internal diameter (I.D.) 7.9 m (26 ft.) high laboratory column. The objectives of these tests were to assess the performance in terms of recovery and percent ash in clean coal and to optimize the operating parameters relative to combustible recovery and grade. Refuse streams containing 30-50 percent ash were upgraded to 2-8 percent ash with Btu recoveries of nearly 90 percent. A pilot scale column flotation cell was installed at the Bell County Coal preparation plant. This pilot plant utilized a 5.79 m (19 ft.) high and 0.15 m (6 in.) I.D. column to verify the performance data of the 0.05 m (2 in.) I.D. column for two different waste streams. Performance evaluation and pilot plant testing results related to scale-up are discussed.

Jan 1, 1988

Liebherr Mining Equipment Co., of Newport News, VA and Baxter Springs, KS, introduced the T282, a new two-axle, diesel-electric, AC drive haul truck with a payload capacity of 327-t (360-st). The T282 was unveiled at a press briefing in October 1998 at the company's Baxter Springs research and development1 manufacturing facility. In addition to an increase in pay- load capacity, the truck's AC drive system has been de- signed to allow for easy configuration to a trolley-assist system with minimal additional equipment. The T282 provides fuel savings, reduced maintenance requirements, and reduced downtime and maintenance costs, providing the mine operator with increases in productivity. Basic dimensions and weight of the T282 are: ? Overall length, 14.5 m (47.5 ft). ? Overall width, 8.7 m (28.7 ft). ? Loading height, 6.5 m (21.2 ft). ? Height - body up, 13.9 m (45.9 ft). ? Empty vehicle weight, 201 t (221 st). ? Operating weight - loaded, 528.6 t (582.6 st). ?Engine, Detroit Diesel 16V4000 at 2 MW (2,750 hp). ?Electric drive system, Siemens/Liebherr.

Jan 1, 1999

By A. M. Al Taweel, V. K. Kasireddy

Intensive coal cleaning usually necessitates fine grinding of the feed in order to liberate inorganic constituents from the surrounding organic matrix. This however adversely affects the ability of flotation techniques to beneficiate coal. Such difficulties are mainly attributed to the increase of particle population density, the decrease in capture efficiency, and the greater tendency of inorganic components to report with the froth. A three-pronged approach was adopted in an attempt to overcome these difficulties. The aggregative flotation technique was used to reduce particle population densities and improve capture, while unconventional spargers were used to generate a wide range of bubble sizes. Use of unagitated flotation columns allowed for the maintenance of countercurrent flows in both the recovery and washing sections. The combined effect of these parameters enabled the recovery of 92% of the carbon content of coal having an average particle size of 20.5 µ m, while rejecting 85% of the ash. This was accomplished using 2 kg of fuel oil per tonne of coal in a column 2 meters high operating at 2-3 tph/m3, a capacity which compares favourably with conventional cells.

Jan 1, 1989

By Charles Ronkos, Jeffrey Edwards, Brian Brodsky

The Marlin gold-silver deposit is in western Guatemala, 15 kilometers south of a major transform fault that separates the North American and Caribbean plates. A district-scale, northwest-trending graben controlled deposition of a greater than 1200 meter thick upper Tertiary quartz latite to rhyolite volcaniclastic sequence. These volcanics were subsequently intruded and unconformably overlain by a small intermediate, latite to andesite, volcanic complex. Classic low-sulfidation, quartz-calcite-adularia veins and stockwork formed a 2.2 million ounce gold deposit, in association with late-stage andesite dike swarms, along a west-northwest striking normal fault on the eastern flank of the volcanic complex.

Jan 1, 2005

By Claus Becker

The new, 2.600 m long pipe under the river Elbe in Hamburg/Germany required for 2 traffic lanes, emergency lane and space for utilities a boring diameter of 14,20 m(46,6 ft). According the geology (glacial deposits consisting of clay, sand and marl, all containing big boulders) a Slurry-Shield with crusher was selected. With a minimum cover of 7 m and a maximum pressure of 5,6 bar extensive ground treatment was necessary to make the drive feasible. The machine contains a lot of new developments. The drive was finished in spring 2000 so all experiences can be reported. A special risk sharing contract avoided completely litigation.

Jan 1, 2001