Search Documents

By Joseph D. Davis, G. S. Scott, Palmer B. Place

In the course of investigations made by the Bureau of Mines in cooperation with the Trent Process Corporation, into the properties of mixtures of oil and coal, a comparative study was ma.de of the 'behavior of these mixtures and their cons ti tuents on destructive distillation. Mixtures of a petroleum oil and bitminous coal were first distilled under carefully controlled conditions, and then charges of the eame oil and coal were distilled separately under similar conditions. The quantity and quality of the distillation products were determined, and. resul. ts were compared. This comparison furnished a basis tor judging whether grea, ... er values in products can be obtained by distillation of oil and coal in mixtures than· b:, their separate distillation. In making the mixtures, the method used in t~e Trent process for cleaning coal was followed. The paste or plastic emulsion of oil and coal obtained is called "amalgam".••• When finely pulverized wet coal is mixed with approximately one-third its weight of. oil and agitated with a large excass of waj;er, the coal and oil agglomer-. ate to form a paste or amalgam. A large portion of the extraneous ash original.17 in the coal remains suspended in the water, with which it can be decanted from the amalgam. Ir the latter is now thoroughly drained and kneaded after the manner ot working butter, most of the excess water enclosed can be removed. This, .in brief, constitutes the Trent process for cleaning coal, The effectiveness of the process for cleaning coal has been studied••••. by the Bureau, and the results of the study show, in general, a high ash reduction an:l good recovery of combus ti bl e f'rom coals of medi ,mi and hi~ rg,nk. With coals of tht lowest rank, such as li@!Rlites, the process is only moderately auccessf'ul, owing to the difficulty attending the preparation of coherent amalgams, Oil losses to wate~ and refuse are small, and apparently it would be practical to rotate the same oil in the cleaning process if some efficient method were devised for recovering it from the amalgam, so a distillation process naturally suggested itself.

Dec 1, 1921

By Y. FUJII, E. CHANDA, J. KODAMA, D. FUKUDA, M. NISHIHARA, Y. NAKAYAMA, P. SINKALA

For over 40 years, Mufulira underground copper mine has been recording incidents of rockburst. Laboratory tests and numerical analyses were carried out to understand the rockburst mechanism at the Mufulira mine. Rockburst did not occur in the chain pillars or at the mining face, but mainly in the mining drives along diminishing pillars or ahead of the mining face. RQD suggested that the rock mass in the rockburst areas was relatively intact. Laboratory tests confirmed that the rock at Mufulira mine is very strong and brittle. Elastic stress analyses for the rockburst sites by 3D displacement discontinuity method (DDM) indicated very high stress in the chain pillars and low-stress concentration at the sites of rockburst during the initial mining stages. However, there was no apparent positive correlation between the elastically calculated normal stress values and the occurrences of rockbursts. The 2D elastic FEM analysis was conducted under the concentrated stress by DDM and indicated that some stress increase with face advance for the rockburst in the vicinity of the mining face. However, stress severity indicated almost no increase, and the rockbursts cannot be explained as an instantaneous rock mass failure due to stress increase by mining. Therefore, a creep damage model was proposed to clarify the mechanism of the rockbursts. Cumulative rock damage was evaluated for the edge elements of each sidewall of the mining drives, based on the normal stresses by 3D DDM. The rockburst occurrences were well hindcasted. A method to estimate the volume of the rockburst source was proposed, and a likely result was obtained.

Aug 12, 2022

By Yuchen Wu, Jing Mei, GUOZHONG LIU, KE GAO, Songjie Tian, Jianwei Cheng, Yu Wang, Yuhang Wu, Hui Wang

The stability and integrity of protective coal pillars between the longwall working face and development roadways are greatly affected by the mining activities such as the development face advancing or retreat mining. Due to underground strata pressure, the coal pillar cracks could be further developed and then the air leakage passages (mainly cracks) could be produced greatly. The air circulation caused by the atmospheric pressure difference between the two sides of the coal pillar may also provide suitable conditions for the possible spontaneous combustion of the residual coal in the mine gob. In this paper, a typical the protective coal pillar in a Chinese coal mine is studied. The deformation and stress of coal pillars during the mining process of longwall working face are simulated by using FLAC3D. The displacement and strain of coal pillars are analyzed. Two indexes, the linear fracture rate (LFR) and area fracture rate (AFR), are introduced to characterize the development of internal cracks’ development within coal pillars. By using field measurement, the air leakage intensity distribution due to coal pillar cracks is obtained; the equation of air leakage resistance of coal pillar under the influence of mining is derived. Then, the possible location of large air leakage of coal pillar is determined, which can be used as guidelines to study the possibilities of coal spontaneous combustions happening in pillar or mine gob. The research results help to control such potential hazards in advance.

Jun 16, 2022

By Cheng Li, Yanlei Wang, Lingrui Kong, Jianxin Tang, Fang Yuan

Coal mined-out areas have a significant impact on mining safety and affect the pressure distributions of neighboring coal faces. The PFC3D software is used to study the goaf mechanical characteristics, and the core loading test verifies the rationality of the numerical simulation method. The results from the numerical modeling showed that the void ratio, particle size ratio, and particle size distribution of the rock particle sample (RPS) had a significantly remarkable influence on the compression deformation characteristics of the rock block. The parallel-bond tensile strength and parallel-bond cohesion had a notable impact on the compression deformation traits of the rock block only when the axial stress level was lower than 12 MPa. By contrast, when the axial stress exceeded 5 MPa, the effective modulus significantly influenced the compression deformation features. However, the stiffness ratio, loading rate, and parallel-bond friction angle had almost no effect on the compression deformation characteristics. Furthermore, when the stress level was less than 10 MPa, the stress–strain curves from the rock core samples’ numerical simulation and loading tests were approximately linear. In addition, the Pearson correlation coefficients of the stress–strain curves suggest that the goaf zone’s core numerical simulation results had a robust correlation with the loading test results. The findings of this study can serve as a reference for the field application of PFC3D software and safety assessments in goaves.

Jan 18, 2022

By Gillies A. D S

Rail, port and shipping charges represent 30 to 50 per cent of landed costs for Australian coal mines selling to Asia. This proportion is higher for sales to Europe, yet it is in Europe where Australian producers are aiming for increased market share. The landed cost of coal to the international customer is the key parameter which determines market competitiveness. The objective of this study is to examine Australian export coal competitiveness in terms of transport distance. The approach used examines world coking coal and steaming coal production and the transport distances between major exporting regions and importing countries. Reference is made to the importance of land transport costs and a comparative approach for emphasising the relative magnitude of this factor is developed. Models developed are examined in terms of Australia's exports and a conclusion is reached that a reduction in rail freight costs would be an effective measure for improving the competitiveness of Australia's coal industry.

Jan 1, 1994

By Yuting Xue, Gamal Rashed, Zoheir Khademian, Morgan Sears

Mining has been recognized among the most hazardous industries in the United States, despite the significant reduction in injury and fatality rates over the past century. This study focuses on the ground-fall incidents classified in the Mine Safety and Health Administration (MSHA) database as “fall of roof, back, or brow from in-place” and “fall of face, rib, pillar, side, or highwall.” The main objective of this study is to conduct a comprehensive statistical analysis of the reported ground-fall incidents from 2010 through 2019 including both coal and metal/non-metal mines. Since most of the ground-fall injuries and fatalities occurred in underground coal mines and were attributed to falls of roof and rib, an additional analysis was directed to evaluate roof- and rib-fall incident trends in underground coal mines associated with the mining method, coal-seam thickness, mine size, and the seasonal effects.

By P. -A. Bosse, J. Robitaille, P. Blatter

The LaRonde ore is a Cu-Zn-Pb ore with gold (3-4 g/t) and silver (60-100 g/t). The precious metals are recovered with copper concentrate, zinc concentrate and cyanidation of zinc tails via Merrill Crowe precipitation. Subsequent to a recent mill expansion, excessive gold was reporting to zinc concentrate with a concurrent decrease in gold to copper concentrate. Owing to the higher return obtained from the metal, the mill endeavors to recover additional gold and silver to the copper concentrate and minimize the placement of precious metals to the zinc concentrate. A gold deportment study showed that the gold occurs mainly as küstelite, with a moderate amount of electrum and a minor amount of native gold. It also showed that various sulfur-based Au-and/or Ag-bearing coatings on liberated küstelite and electrum were the major mineralogical factors that caused gold and silver to report to zinc concentrate. By frequency, such coatings were observed on 70-80% of total liberated gold particles reporting to the zinc concentrate. Based on the gold deportment and the chemistry of the coatings, the collector chemistry was reviewed and a new collector was added into the circuit which resulted in a significant increase in gold and silver recovery to the copper concentrate. The information obtained from the mineralogy confirmed and guided other process optimization. In this paper, the authors will describe the process mineralogy of the LaRonde ores, and in particular, the mineralogical evidence diagnosing the problem. Reference will also be made to the rationale behind how the problem was solved, the results achieved, and future steps in optimization.

Jan 1, 2005

By J. C. Gathje

Newmont acquired the Phoenix Project through the acquisition of Battle Mountain Gold in 2000. Shortly after the acquisition, Newmont Metallurgical Services (NMS) and Nevada Operations began development work on a process to Pressure Oxidize (PDX) precious metal rich copper concentrates from Phoenix using the Lone Tree PDX facilities at Valmy, Nevada. The high precious metals content of the Phoenix concentrate - Au up to -300 g/t and especially Ag, up to -1700 g/t - led Newmont to the development of a High Temperature PDX process that achieves high cyanide leach recovery of Au and Ag, from the PDX solids, without the requirement for a messy and expensive "lime boil" or sulphate destruction process. Base metals content in Phoenix concentrates range from: 15-25 % for Cu, 1-10 % for Zn and 0-2 % for Pb. Excellent solution extraction of Cu and Zn is achieved while Pb is precipitated in the PDX residue. In addition to achieving high Au and Ag recovery this process produces very clean PDX discharge liquors that require minimum effort to remove contaminant metals and PDX solids that have superior settling and filtration characteristics. All of these factors contribute to lower capital and operating costs for the overall process. This paper describes the laboratory and PDX pilot plant developments for this process.

Jan 1, 2004

By Yongheng Jiang, Wentong Wang, Haoming Luo, Chuanju Liu, Qianjun Zhang, Sha Guo

Rock burst has always been a major problem in deep underground engineering with high stress, and rock burst strength evaluation has become an important research topic. To effectively predict the rock burst hazard in underground rock mass engineering, a cloud model (CM) rock burst intensity evaluation method based on the CRITIC method and order relation analysis method (G1) was proposed in this paper. First, a rock’s uniaxial compressive strength σc, tangential stress σθ, uniaxial tensile strength σt, ratio of uniaxial compressive strength to tensile strength σc/σt (brittleness coefficient), ratio of tangential stress to uniaxial compressive strength σθ/σc (stress coefficient), elastic deformation energy index Wet, and depth of cover H were selected as evaluation indices of rock burst intensity. Ninety-five groups of rock burst measured data at home and abroad were selected, and the objective weight and subjective weight of each index were calculated by using the CRITIC method and G1 method, respectively. The comprehensive weight was determined according to the combined weighting method of game theory, and the sensitivity of each evaluation index was analyzed. By utilizing a forward cloud generator, the membership degrees of different rock burst grades were calculated, and then the rock burst intensity grades of the samples were evaluated and compared with the evaluation results of the CRITIC-CM method and G1-CM method and the actual grades. Finally, the rock burst classification ability of the model was analyzed. To better verify the accuracy and reliability of this model, the rock burst case of the W39 line in the Chengchao Iron Mine was analyzed by using this model. The research results show that the rock burst evaluation results based on CRITIC-G1-CM are basically consistent with the actual rock burst grade, and the rock burst intensity grade evaluation model has good practicability and reliability.

Sep 1, 2023

By Haitao Wang, Shen Wang, Dongyin Li, Yongjia Xu, Jinzhao Liu, Xiangjun Chen

The safe and efficient driving of the roadway along the gob is becoming an increasing challenge due to the influence of the integrity and bearing capacity of the side coal and rock mass in the gob under the roof cutting mining mode. The mechanism of protection of the gob-side roadway is shown by modeling the influence of roof cutting and the application of a destress technique on the lateral coal and rock mass zones. The distribution characteristics of stress, displacement, and fracture in the overburden are analyzed by numerical simulation method under the three working conditions. The results indicate (1) construction of row holes and blasting can form artificial structure’s fracture plane above the roadway, which can effectively cut the connection of overburden. The artificial structure’s fracture plane decreases the peak value of the lateral coal body’s support pressure. The peak point and the critical location of the stress reduction area are both transferred to the deep part at the same time, providing adequate space for the gob-side roadway. (2) The stress arch foot in the lateral rock mass rises to the rock layer at the bottom of the roof cutting plane after top cutting, as does the high-pressure area of deviator stress. The fracture plane prevents lateral coal and rock mass instability and limits the negative effects of roof deformation above the gob-side roadway. (3) The triangle slip fracture zone moves to over the roof cutting drilling zone due to the fracture plane, showing a high position compared to its original zone.

Jul 11, 2023

By Gang Yang, Manchao He, Chengzhang Gao, Jun Zhang, Yayun Li, Jun Yang, Shilin Hou, Ben Liu, Yajun Wang, Jianning Liu

To explore the mechanism of roof directional breaking in gob-side entry formed automatically without coal pillars, the numerical simulation was used to study the deformation movement of roof, the deformation evolution of roadway, and the stress distribution of roadway under roof directional breaking and non-roof directional breaking. Based on the results, the deformation movement of roof is divided into three stages: the goaf roof collapse stage, the basic roof deformation stage, and the basic roof stability stage. The goaf is filled with gangue due to the broken expansion characteristics of the collapsed rock under the roof directional breaking. Due to the supporting force of gangue, the deformation of the basic roof under the roof directional breaking is smaller than that under the non-roof directional breaking, which reduces the influence of the deformation of the basic roof on the deformation of the roadway roof and improves the integrity of the roadway. At the same time, roof directional breaking cuts off the stress transfer path of partial roof, which weakens the peak stress convergence on the arc side, transfers the peak stress convergence to deeper, and improves the stability of roadway. Finally, a field test was carried out to further verify the accuracy of the numerical simulation. The field test results are in good agreement with the numerical simulation results. The roadway deformation is small and meets the requirements of safety production. It is proved that roof directional breaking plays a positive role in improving the stability of the roadway.

Dec 22, 2022

By Éder Domingos Oliveira, Leandro Viana Teixeira, Carlos Antonio Morais, Ruberlan Gomes Silva

The purity of rare earth products depends on the ability of the reagents used to selectively promote the precipitation of the rare earth elements (REE) from impurities present in sulfuric liquors. The present study aims at investigating the conditions required to precipitate REE, either as rare earth oxalates or carbonates, from purified rare earth sulfuric liquor with a low Al3+ and UO2 2+ and a very high Ca2+, Mg2+, Mn2+, and SO4 2− impurity content. The rare earth sulfuric liquor was obtained in a previous study by the reaction of a rare earth ore with sulfuric acid, pyrolysis at 700 °C/2 h, cooling at 20 °C, and water leaching. The impurities such as Fe3+, Th4+, and PO4 3− were completely removed from the liquor in two consecutive neutralization steps. In order to recover the REE, the purified rare earth liquor was then treated with oxalic acid and sodium carbonate. Rare earth oxides (REO) precipitated with oxalic acid displayed a very high purity (99.2% w/w) and low impurity content. In contrast, the rare earth carbonates precipitated with sodium carbonate presented a comparatively lower REO content (68.5% w/w) and 94.2% of purity, but with a higher content of impurities. Better precipitating conditions were achieved at 60 °C, compared with 20 °C, and under stoichiometric reagent consumption, with REE precipitation efficiencies higher than 96%. The dosage above the stoichiometric condition caused the precipitation of calcium oxalates and co-precipitation of rare earth sulfates when oxalic acid is used, and precipitation of calcium, manganese, and uranium carbonates and also a co-precipitation of rare earth sulfate when sodium carbonate were used. An integrated flowsheet to produce a high-quality rare earth product from rare earth sulfuric liquor containing some impurities is proposed.

By Mingyang Li, Yan Lv, Xiaolong Ma, Xudong Gao, Jie Zhao, Yingyi Zhang

The reduction process of pre-oxidized ilmenite concentrate powder in 30%CO–70%N2 atmosphere was characterized by thermogravimetric and differential thermogravimetric (TG-DTG) analysis system at the temperature from 1073 to1223 K. The isothermal reduction results show that the reduction process is divided into three stages and the corresponding apparent activation energies are obtained by iso-conversional method and model-fitting method, respectively. For the first stage, the conversion degree increases sharply with increasing time, and the reduction process is controlled by the random nucleation and subsequent growth model (A2 model). For the second stage, the conversion degree increases slowly with increasing time, and the reduction process is controlled by the diffusion of carbon monoxide in the reduced layer (D1 model). For the third stage, the reduction processes at different temperatures are controlled by the diffusion of carbon monoxide in the reduced layer (1073 K and D1 model), phase boundary chemical reaction (1123 K and R2 model), random nucleation and subsequent growth (1173 to 1223 K, A2, and A3 models), respectively. For the whole reduction process, the apparent activation energies obtained by iso-conversional method and model-fitting method are 71.72 and 31.92 kJ mol−1 , respectively

By H. L. Gilbert

Zircon sand may be reacted with sodium hydroxide at 600° C. to form sodium zirconate and sodium silicate. Sodium zirconate is water insoluble and so may be washed free of sodium silicate. The sodium zirconate may then be converted to zirconyl chloride by the action of hydrochloric acid and the zirconyl chloride crystals separated by cooling the solution. This approach produces zirconyl chloride of satisfactory purity with less cost than is involved in buying anhydrous zirconium chloride and converting it. A proposed design for a plant is given, INTRODUCTION This work was conducted by the Rare Metals Branch as a part of research on zirconium at the Bureau of Mines Northwest Electrodevelopment Laboratories, Albany, Oreg., under the guidance of S. M. Shelton, Regional Director. The work was supervised by W. W. Stephens, head of the Rare Metals Branch (now with Carborundum Metals Corp.).

Jan 1, 1954

By Jos. R. Guiteras

This paper describes the operations of the St. Joe Mining & Milling Co. in Boulder County, Colo., as of June 1936. Later a brief visit was made to the mine in September 1936; information obtained at that time has also been recorded. The company operates a gold mine, the Grand Republic, in the Sugar Loaf mining district; a 100-ton flotation mill in Lefthand Canyon near Gold Hill; and a custom sampling punt, the Boulder Ore Sampling Works, at Boulder, Colo.

Jan 1, 1937

By C. W. Van Noy

The procedure suggested in this report is intended for the use of engineers, esters, accountants, etc., in estimating the cost of chemical-type operations. It is intended to over operating costs, not investment costs, as the latter have been covered numerous other publications. However, as capital investment costs are reflected to a high degree in operating costs, it is important to point out that accuracy of investment costs is highly essential. Therefore, all factors that might be included under plant -capital costs should be considered, such as requirements of shops, employees' housing, etc. The procedure is designed primarily for use in types of chemical oper¬ations, such as the production of synthetic liquid fuels, anhydrous ammonia, and others of like or similar nature. Yet, no attempt has been made to cover the entire chemical industry.

Jan 1, 1949

By Walter Kawa

Bureau of Mines research on the hydrogenation of coal has been concerned with developing processes that could be used to supplement the Nation's petroleum and natural gas resources. Motor fuel was produced in a subsidized coal hydrogenation industry in Europe prior to 1945, but the process used is still not economical and other methods of producing liquid and gaseous fuels from coal are being investigated. As an aid to the planning of coal hydrogenation research, a literature survey was made of processes or methods of hydrogenating coal that differ from the subsidized or conventional process. This report contains a bibliography of unconventional methods of hydrogenating coal and a brief discussion of the economics of the conventional method. A general discussion of unconventional methods is included, and the advantages and disadvantages are pointed out where possible. The survey supplements a previous Bureau of Mines survey3 and a comprehensive review published in 1930.4

Jan 1, 1964

By G. H. Damon

Since 1963, Bureau of Mines Information Circular 8179 has served the mining industry as a fundamental safety guide in the field of blasting agents. In the intervening 14 years, many changes have occurred, and this report presents revised and new recommendations which recognize these changes. For example, AN-FO is now supplied mostly premixed, whereas in 1963 much of it was mixed by the blaster; aluminum metal (A1) and other fuels are now often added to AN-FO to increase strength, and flake aluminum powder is used as a sensitizer in water gels; and water gels or slurries that are now extensively used were just coming into practical use in 1963. To provide the widest possible margin of safety, some of the Bureau's recommendations are more stringent than existing regulations,

Jan 1, 1977

By J. Pasini

The Bureau of Mines has investigated novel methods of stimulating petroleum production from reservoirs in the Appalachian Region. An important consideration in applying stimulative production methods is the control and removal of solid precipitates from the boreholes of production wells. Where paraffin-base crude oils are produced, as in the Appalachian Region, the accumulation of paraffin may be particularly troublesome. Paraffin deposition is a major production problem that has confronted the petroleum industry for many years. Although considerable effort has been expended by industry and government, a suitable solution has not been found because of the individuality and complex nature of the deposits. Remedial methods used to prevent or remove paraffin fall generally into four classes: (1) Chemical, (2) physical, (3) operative, and (4) combination. Each class has many subclasses that apply to particular problems in different oil- producing areas. Recently, chemical inhibitors and the sonic pump have assisted operators in preventing and removing paraffin deposits. Because these methods are relatively new, their degree of application has not been completely evaluated.

Jan 1, 1963

By J Benn, V Kuznetsov, G Timms, A Spain

Earthen covers are now widely used in the mining industry to control the generation rate and/or release rate of low quality drainage from piles of sulfidic minewastes. Covers are usually designed to reduce the water infiltration rate and in some cases may also reduce the oxygen flux to the underlying sulfides. Engineered covers have only been used since the 1980s, however, and there is very little field data on their performance in the longer term. This lack of information has implications for the degree of confidence that can be placed on the predictions of the environmental impacts of sulfidic minewastes, for the acceptance of close-out criteria by regulatory authorities and for the financial liability of the mining industry. Covers were placed on sulfidic waste rock dumps at the abandoned Rum Jungle uranium mine during 1984 - 1985. These covers were designed to reduce the water infiltration to less than five per cent of incident rainfall by both water shedding and storage-release mechanisms. Regular monitoring by the Australian Nuclear Science and Technology Organisation (ANSTO) demonstrated that the covers performed better than the design criterion for around ten years, but infiltration rates have subsequently increased. There is a 66 per cent probability that the infiltration rate now exceeds five per cent of incident rainfall. The cover on the largest pile, WhiteÆs heap, was sampled in pits dug at eight locations. Sampling was carried out at the end of the monsoonal wet season and again at the end of the ædryÆ season. This, together with laboratory testing, enabled cover performance to be assessed against five criteria: design, construction, cover material characteristics, physico-chemical characteristics and biological characteristics. We are of the opinion that the design of the cover was suitable to achieve the objectives of stability, water shedding, storage-release, and provision of a substrate for vegetation growth. Over most of the surface of the heap, the construction of the covers, drains and erosion prevention structures was in accordance with design specifications. However, several small and localised bare patches on the upper surface of WhiteÆs heap coincide with a reduced cover thickness, which is likely to have been due to poor construction in those patches. The construction of covers on minewastes is dependent on an adequate source of material meeting design specifications. From our limited examination, it appears that there was shortage of material for each of the three zones û a lower impervious clay layer, the moisture storage-release layer and the upper erosion-resistant layer for vegetative growth. An indication of this was that the upper layers in some areas were observed to be thinner than specified. We are of the opinion that this shortage of suitable material has been responsible for some of the changes observed ten years after emplacement. Physical and geotechnical testing indicated that the cover materials no longer meet the original specifications. In particular, the permeability at the 8 locations was found to be greater than specified, by up to several orders of magnitude. The higher permeability may explain the higher observed rainfall infiltration and moisture content of the waste rock. This increased permeability appears to be due to a combination of biological and physical processes û galleries formed by termites and ants and an extensive system of shrinkage/desiccation cracks formed by the development of a polygonal blocky structure involving the entire lower clay layer. The desiccation cracks may fill with coarser illuviated materials and form a conduit through which roots access the underlying waste rock. Measurements were made of oxygen flux into the heap as cover layers were excavated in the pits. They indicated that the full cover currently reduces the oxygen flux to 20 - 23 per cent of that into bare waste and that this reduction seems to be proportional to the cover thickness. It was also found that the oxygen flux into the cover is about four times higher at the end of the dry season than at the end of the wet season and that the difference is due primarily to the difference in moisture content of the cover. Recommendations are made for the design and construction of covers.

Jan 1, 2003