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By Pramod C. Thakur

During the past ten years, the US coal industry has experimented with various ways to extract methane from coal seams. Drilling long horizontal boreholes in solid coal from mine workings and vertical gob degas boreholes are becoming standard techniques for methane recovery from coal seams. Prime motivations for such work have always been safety and productivity in mines, but the commercial value of gas so produced is encouraging utilization. The paper reviews various ways to produce methane from coal seams and discusses some utilization projects extant in the industry.

Jan 1, 1984

By O. G. Olvera, L. S. Quiroz-Castillo, P. J. Valenzuela-Guerrero, D. G. Dixon

The effect of sulfuric acid concentration on the extractions of arsenic and copper in the catalyzed batch leaching of an enargite concentrate was studied. The acid concentrations studied were 60, 45, 30 and 15 g/L. The experimental series yields maximum copper extractions of 96 to 98% in an interval of 81 - 185 h leaching time for 60 - 15 g/L initial sulfuric acid concentration; all the copper extractions plateaued after these values; the rates and plateaus of copper extraction are increased with higher acid concentrations. Arsenic extractions reached maximum values of 89% in 57 hours, 57% in 49 hours, 33% in 25 hours, and 25% in 112 hours respectively; these maximum values were followed by a steep decrease in arsenic concentration, which indicates a precipitation event occurs in the process. According to the literature and process conditions, the arsenic precipitates obtained are iron arsenates similar to scorodite. The stability of the residues was tested using the Toxicity Characteristic Leaching Procedure (TCLP) from EPA; the residues for the four concentration levels passed the TCLP test, reporting arsenic leaching values below 1 mg/L.

Jan 1, 2014

By John Loui Porathur

Highwall Mining has been recently introduced in India. The first Continuous Highwall Mining extraction in India started operating at Ramagundem Opencast Project-II (OC-II) of Singareni Collieries Company Ltd. (SCCL) in December 2010. A new hybrid empirical and numerical modelling approach has been devised to design web pillars for the initial Highwall Mining sites in India, considering the complex geology, such as existence of thick seams and multiple seams in close proximity. This paper gives the scientific elucidation of a comprehensive design methodology adopted for the above mentioned Indian Highwall Mining sites. The design technology includes web pillar design for multiple seams using hybrid empirical and numerical methods, slope stability assessment, ground movement monitoring, and recommendations for conducting blasting operations in the vicinity of Highwall Mining extractions.

Aug 1, 2013

By T. Tamagawa

A gaseous chlorination process for hydrometallurgical treatment of a chalcopyrite concentrate was investigated. The overall process is visualized to consist of low temperature chlorination-selective oxidation, followed by aqueous chloride leaching and SX-EW for producing electrolytic copper, elemental sulfur and ferric oxide. In this article, the chlorination phase of the processes is described. Initially, the chlorination behavior of chalcopyrite-concentrate micro-pellets was investigated using a small batch-type fluidized bed reactor. The optimum conditions thereby established was used in continuous chlorination tests. The chlorinated products thus prepared were used in the selective oxidation phase of the investigation.

Jan 1, 1999

By T. Tamagawa, N. S. Fu, I. Iwasaki, M. Kobayashi

A 3-stage fluidizing bed process of chlorination, selective oxidation and sulfur chloride conversion was tested for processing of a chalcopyrite concentrate. It was found that the use of excess oxygen was essential to a stable operation in the oxidation reactor. The oxygen-excess gas will inevitably cause the oxidation of the sulfide concentrate in the chlorination and sulfur chloride conversion reactors. A new flowsheet is proposed to separate the chlorination and the selective oxidation steps with separate flow paths of the fluidizing gases, thereby preventing the passage of oxygen-excess gas in the chlorination and sulfur chloride conversion reactors. The feasibility of the proposed flowsheet was demonstrated in a laboratory-scale fluidizing bed setup.

Jan 1, 2000

By T. Tamagawa

A gaseous chlorination process for hydrometallurgical treatment of a chalcopyrite concentrate was investigated. The overall process is visualized to consist of low temperature chlorination-selective oxidation, followed by aqueous chloride leaching and SX-EW for producing electrolytic copper elemental sulfur and ferric oxide. In this article, the chlorination phase of the processes is described. Initially, the chlorination behavior of chalcopyrite-concentrate micro-pellets was investigated using a small batch-type fluidized bed reactor. The optimum conditions thereby established was used in continuous chlorination tests. The chlorinated products thus prepared were used in the selective oxidation phase of the investigation.

Jan 1, 1999

By G Varley

This paper describes the mining methods and strategy used to extract the 5 Orebody crown pillar at the Isa Lead Mine over the past five years. The bulk of the crown pillar was extracted by the use of sublevel open stope method. An uphole bench stope was mined to scavenge the remaining ore. Geomechanical issues associated with the crown pillar extraction are described. Stope sizes were gradually increased on a stope by stope basis. This has allowed the maximising of ore recovery while relevant risks were managed. The principles in designing ore rib pillars against various types of fill materials are also described.

Jan 1, 2002

By Robert S. Gärtner

The selective aluminum extraction by 3 different calixarenes (p-tert-butyl-calix[4]arene-tetra¬2-acetic-acid-ethyl-ester, p-tert-butyl-calix[4]arene-tetra-2-acetic-acid and p-tert-butyl-calix-[4]arene-di-2-acetic-acid-ethyl-ester) from an industrial pickling bath solution was studied. The pickling bath solution contained hydrofluoric and phosphoric acid as its main components. The aluminum removal was not successful and also no significant extraction of trace metals present was observed.

Jan 1, 1999

By J. E. Sepulveda

Tar sand deposits in the. Stare of Utah contain more than 25 billion barrels of in-place bitumen, Although thirty times smaller than the well-known Athabasca tar sands, Utah tar sands do represent a significant domestic energy resource comparable to the national crude oil reserves (31.3 billion barrels), The term "tar sand" refers to a consolidated mixture of bitumen and sand, Based upon a detailed analysis of the physical and chemical properties of both the bitumen and the sand, a hot-water extraction process for Utah tar sands is currently being developed in our laboratories at the University of Utah. This process involves intense agitation of the tar sand in a hot caustic solution and subsequent separation of the bitumen by a modified froth flotation technique., Experimental results indicated that, for a given tar sand sample, percent solids and caustic concentration were the two most important variables controlling the performance of the digestion stage, These variables were identified by means of an experimental, factorial design, in which coefficients of separation greater than 0.90 were realized. Although preliminary in nature, the experimental evidence gathered in this investigation seems to indicate that a hot-water extraction process for Utah tar sands would allow for the efficient utilization of this important energy resource.

Jan 1, 1978

By M. H. Dehghanpoor, M. Zivdar, M. Torabi

"A hydrometallurgical route was developed to extract metals such as gold, silver, copper, and selenium from anode slime from Sarcheshmeh Copper Complex in Iran. For the extraction of copper by leaching, the anode slime was heated and stirred with 4 M sulphuric acid in the presence of oxygen. Optimal conditions for recovery of copper were temperature 80°C, mixing time 5 hours, and oxygen flow rate 2 L/min, resulting in a copper recovery of 94.47%. Silver and selenium were dissolved by leaching anode slime from which the copper had been removed with nitric acid. For gold extraction, anode slime was heated with aqua regia at 90°, and the gold then extracted with 2-ethyl-hexanol at a concentration of 0.5 M and phase ratio of 4. The extract was then stripped with soda solution at pH=10.5 and a phase ratio of 5. Finally, gold was recovered by precipitation with oxalic acid at a ratio of mass to volume 10 g/L. Total gold recovery was 80%. IntroductionDuring the electrorefining of copper, some metals are accumulated in the byproduct anode slime, which is an important source for recycling and recovery of these metals (Petkova, 1994). In this paper, a hydrometallurgical route is described for the recovery of precious metals from copper anode slime of Sarcheshmeh Copper Complex, which is located in southeastern Iran .Copper anode slime is black or gray powder with a particle size less than 200 mesh. Approximately 2 to 20 kg of anode slime is produced per ton of copper cathode. The slime is characterized by higher amount of Ag, Se, Pb, and Cu compared to other metals and a very low Au content (Khaleghi and Ghader, 2013).The copper anode slimes are composed of 11.69% selenium, 3.93% copper, 5.26% silver, 0.13% gold, and 45% barite, plus lead, tellurium, antimony, sulphur, and silica with small amounts of nickel, iron, zinc, and bismuth. Gold is one of the most important noble metals due to its wide applications in industry and economic importance, so recovery of gold from slime is more appealing than that of other metals. According to the World Gold Council (2013), the demand for gold has increased during the last decade. This increase is due not only to the increasing demands of the jewellery market, but also to the increasing demand for gold in industrial as well as medical applications (Ranjbar et al., 2014)."

Jan 1, 2016

By E. A. Brocchi, P. K. Jena

Complete extraction of copper from Salobo chalcopyrite concentrate can be achieved in less than 10 minutes by chlorination of the dry concentrate with Cl2 at 450 degrees C and in 5 minutes by chlorination of an aqueous slurry containing 5 wt% concentrate at 30 degrees C. In general, slurry chlorination appears to be faster than dry chlorination. The kinetics of dry chlorination of copper sulphide are controlled by an adsorption mechanism with an activation energy of 6.1 kcal/mole. The rate is independent of chlorine partial pressure when pCl2 exceeds 0.4 atm. In slurry chlorination the dissolution of copper sulphide follows a topochemical reaction model and the rate of chlorination decreases with increase in pulp density and also temperature. Dissolved chlorine appears to take part in the reaction in atomic or ionic form.

Jan 4, 1992

By Vinay Kumar

The present investigation describes R & D studies carried out for recovery of copper from the sulfate solution expected from the leaching of e-wastes in presence of minor constituents such as cadmium, zinc and nickel using solvent extraction process. In order to extract copper in continuous mode in mixer settler unit (MSU), basic studies have been made to optimize the experimental condition using 5%LIX84 in kerosene. Subsequently, the solvent extraction of copper was made in MSU maintaining leach solution flow rate 4.0 L/h and A/O ratio 1. The results showed complete extraction (~97%) of copper in three stages at A/O ratio 1 from the aqueous solution containing 1.98g/L Cu at pH 1.91 in presence of impurities. Loaded metal was completely stripped after scrubbing with 10% sulfuric acid in two stages. The stripped solution could be used for metal/ salt recovery by electrolysis/ crystallization.

Jan 1, 2010

By Michael Moats, Weston Hartzell

The stable domestic supply of gallium, indium, and germanium has been identified as a critical need for the USA. Electric arc furnace dusts processed to recover zinc produce a process residue that could be a potential source of these critical materials. An industrial zinc leach residue was characterized to determine the predominant mineral phases and leached with common mineral acids. Atmospheric agitated leaching using sulfuric acid and hydrochloric acid were examined to determine the extractions of gallium, indium, and germanium as a function of concentration, temperature, and time. Extractions of gallium were found to be similar to iron in all experiments. The maximum percentage of Ga, Ge, and In leached into solution were 82%, ~100%, and 89%, respectively.

Aug 8, 2023

By M. S. Moats, W. C. Hartzell

The stable domestic supply of gallium, indium, and germanium has been identified as a critical need for the United States. Electric arc furnace dusts, processed to recover zinc, produce a residue that could be a potential source of these critical materials. An industrial zinc leach residue was characterized to determine its particle size, chemical composition, and predominant mineral phases. Heated, atmospheric, agitated leaching using sulfuric acid and hydrochloric acid was examined to determine the extractions of gallium, indium, and germanium as a function of concentration and temperature. Extractions of gallium were found to be similar to iron in all experiments. The maximum percentage of Ga, Ge, and In leached into solution were 71%, 63%, and 48%, respectively.

Feb 1, 2023

By E. Lovera

ABSTRACT: The current study analyzes the feasibility of an odd operation: to obtain, using a properly tailored drilling and blasting scheme, blocks suitable for the production of dimension stone from tunnel driving. Clearly, a compromise must be found between the rate of progression and the achievement of workable blocks. As a case study, a civil work under consideration in northern Italy was examined. The work was planned to cross a conglomerate that has traditionally been locally exploited for the production of highly prized paving and lining stones with excellent strength and aesthetic features. Natural exposures and mined-out quarries were available for tests. The relevant rock data are given, blast designs are shown (within the limitations of contour accuracy), and the test program is described.

Jan 1, 2011

By C. R. Zegarra

Extraction of manganese, gold, and silver from a low-grade manganiferous-silver ore was investigated by thiourea leaching followed by standard cyanidation. The levels of reagent concentrations in this investigation were 0.0 -1.0 M thiourea and 0.0 -1.0 M sulfuric acid. Temperature and agitation speed were maintained at Z5 °c and 300 rpm, respectively. The dissolution of gold, and silver was shown to be dependent mainly on sulfuric acid and thiourea concentrations. In general, 50.0 % Ag, 98.0 % Au, and 75 % Mn were recovered from a Mn-Ag ore by thiourea leaching. Overall silver extraction of 98.0 % was obtained by cyanidation after thiourea leaching. Thiourea leaching of sodium bisulfite leach residues was also studied, and the total extraction of gold and silver were 97 % and 40 %, respectively. Finally, a two-stage thiourea leach was also investigated.

Jan 1, 1988

By R. A. Pyper

Laboratory leaching experiments were conducted to ascertain the effectiveness of acidic solutions of thiourea, CS(NH2)2, for dissolving gold from finely disseminated gold ores. The ore tested was from the Chipmunk orebody of the Northumberland mining district in Nye County, Nevada, USA. Extractions of up to 90 percent were attained from the ore. Extraction was shown to be dependent on thiourea concentration, ferric sulfate oxidant concentration, acid concentration, and leaching time. Optimum conditions were an ambient temperature leach near pH 1.0 utilizing 100-200 kg/t thiourea and 50 kg/t ferric sulfate for 8 to 24 hours.

Jan 1, 1981

By Peng Lv, Shiqian Liu, Bin Xu, Qian Li, Yongbin Yang, Tao Jiang

The treatment process of a low-grade refractory gold ore containing sulfide minerals and carbonaceous matters was studied in this work. The gold extraction of this ore by all-sliming cyanidation was only 11.75%. Hence, a pretreatment was necessary. In this paper, a flotation-preoxidation-cyanide leaching process was developed. The concentrate from the flotation procedure was processed using different preoxidation methods. A concentrate containing 34.08g/t of gold with the gold recovery ratio of 81.20% was obtained by flotation. After roasting, microwave heating or alkaline pressure oxidation, the gold cyanidation ratio reached 82.37%, 81.26% and 71.09% respectively. Roasting was an effective, reliable and mature technique to oxidize sulfide minerals and carbonaceous matters. Roasting and microwave heating both produced dangerous environmental pollutants while alkaline pressure oxidation was eco-friendly.

Jan 1, 2015

By Chr. Kersch

This project further develops supercritlcal fluid extraction as an industrial soil remediation process. Heavy metals are removed from sand using CO2, The effect of the type of complexing ligands, pressure and water content on the extraction efficiency is investigated.

Jan 1, 1999

By N. Melnyk, H W. Habgood

The conventional low temperature process for extracting' helium from natural gas involves liquefying the whole gas stream in order to remove the relatively small fraction of helium. A process based on the selective diffusion of helium through a semi-permeable barrier is, in principle, more economical and flexible, particularly for the treatment of small re-serves and low concentrations. The well-known permeability of glass to helium offers the possibility of such a diffusion process and McAfee of the Bell telephone Laboratories showed in 1958 that practical separations could be achieved by passing natural gas over bundles of fine capillary glass tubing. Developmental studies have been carried out involving larger units and more extended field tests than those of McAfee. Fine capillary tubing of Pyrex glass 0.0035 in. diameter was prepared by drawing ordinary 6 mm. laboratory tubing in a furnace. Extraction units were pre-pared containing about 10,000 such tubes, 4 ft. long and cemented inside

Jan 1, 1961