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By Fernando Henrique Gomes de Souza

Techniques which use a spring to supply the bias force to actuator are well adopted since they are inexpensive and simple to construct. In this work it was design an actuator concept using bias-type device technique, which comprises two coils that mutually push against each other to supply the stroke. For the coils springs, it was used a wire of NiTi shape memory alloys (SMA) and a wire of 400 grade maraging steel as construction materials.

Aug 8, 2018

By S. Gupta

Froth flotation is a process commonly employed for the selective separation of phosphate from unwanted mineral. Column flotation has become widely accepted in the mineral processing industry, including phosphate industries, due to its ability to improve selectivity, lower operating cost, lower capital cost, and superior control. In this work, a hybrid model is developed that combines a physicochemical model with artificial neural networks. The physicochemical model is based on axial dispersion with first order collection rates. A new approach, in which both frankolite (the desired mineral containing phosphate) and gangue (undesired product) are modeled, enables prediction of grade of the recovered product. Thus, two basic parameters are required in this model: flotation rate constants for frankolite and gangue. Artificial neural networks are used to predict flotation rate constants. The model also takes into account the particle size distribution and predicts grade and recovery for each particle size range. The model then combines grade and recovery for each particle size range to determine the overall grade and recovery of the column. The model is validated against laboratory column data.

Jan 1, 1998

By Xingming Zhang, Huawei Zhang, Yanxiang Li

"A hybrid porous metal with nano-micro double scale pore size and regular-random bimodal porous structure has been fabricated by unidirectional solidification of a lotus-type alloy followed by dealloying treatment to the base alloy. The base alloy selected is a Cu-Mn binary alloy. The lotus-type porous Cu-Mn alloy with straight pores of several hundred micrometers in diameter was manufactured by unidirectional solidification with a mould casting process. Dealloying treatment was then done to the lotus-type porous structure of Cu-Mn alloy. The solid Cu-Mn alloy wall of the lotus-type porous structure was transformed to random porous structure of dozens to hundreds nanometers. The influence of corrosion parameters, such as the current and time in electrochemical corrosion, temperature and corrosion agent in chemical corrosion, on the nano-porous structure formed has been studied systematically.1. IntroductionA hybrid porous metal is a kind of cellular structure with different porous or cellular forms inside, which possesses special properties and can be applied in many fields as fuel cells, catalysis, sensors, etc. Several means have been developed to fabricate this kind of porous material [1-2]. In this paper, a novel process of Gasar plus dealloying is introduced to fabricate a new form of hybrid porous metal with nano-micro double size and regular-random bimodal structure.The Gasar process, also called the metal-gas eutectic directional solidification, that invented by Shapovalov [3] in Ukraine and now in USA some twenty years ago, is used to fabricate porous metals with regularly aligned pores basing on the solubility difference of a gaseous element in solid and liquid metal. Nakajima and his colleagues [4] in Japan studied this process further and called this kind of structure a lotus-type porous metal. They put more attention to various fabrication techniques and properties of lotus-type porous metals. Li heading a group [5-6] in P.R. China studied the mechanism of Gasar process and process controlling techniques. The Gasar pore structure and porosity can be controlled by processing parameters, and a regular Gasar structure with oriented pores distributing uniformly in the solid matrix can be obtained under optimized processing parameters."

Jan 1, 2014

By Michel Carreau

Renewable assets have large upfront capital costs but minimal operating expenses over their lifetimes. In some instances, deals can be structured so that direct capital investment is feasible, with paybacks typically within 5-7 years. In others, the burden of renewable CAPEX must be removed in order to create an attractive alternative to fossil-fuel-fired generation. Hatch has designed and oversees the construction of a renewable installation, which is financed, owned and operated by a special-purpose entity. Renewable energy is then delivered to the mining company via a customized power purchase agreement at a price that is lower than the levelized cost of fossil fuels. In this way, the mining company removes the burden of the renewable energy CAPEX from its balance sheet, thus freeing up capital, decreasing risk, and making the predictable, lower cost of renewable power more attractive than the variable cost of fossil fuels. This paper presents the above business model and success stories of hybrid power at remote sites (wind and solar coupled with diesel engine).

Aug 1, 2013

By G Metzner, R Rodriguez, C Savage

OK Tedi Mining Ltd. (OTML) is in the process of optimising the concentrator performance. One aspect that has been recently implemented is an upgrade of the existing expert control philosophy on the grinding circuit and this will be the topic of this paper. Ore grinding in SAG mills is a multi-input multi-output (MIMO) process subject to several disturbances, most typical being quick acting disturbances such as changes in ore characteristics like hardness and particle size and slow acting disturbances such as ball charge variations and liner wear. The OTML SAG mills treat ore from diverse ore bodies and receive fresh feed subject to large changes in particle size. These circumstances make these mills particularly challenging to control. In this paper, a comparative analysis is presented between the performance of the OTML SAG mill #2 before and after the commissioning of a hybrid control strategy. The strategy uses Expert Knowledge combined with advanced disturbance rejection to reduce the variability of the main process variables, especially pressure and power. It further optimises the overall operation by driving the SAG mill #2 against process constraints (e.g. high power, high motor temperature and high scats recycle rate) and maintaining the operation at or near this point. This strategy is implemented by a combination of the manipulated variables (i.e. fresh feed tonnage and % solids) at any given time.The paper will present trends and a statistical analysis of the comparative results of the mill operation over a period of months, showing a 30% reduction in mill power / pressure variability and a 12% improvement in average power drawn. An increase in throughput was also observed, but cannot be conclusively attributed to the change in mill control due to other changes that were made to the SAG mill #2 during the period of comparison. An additional benefit includes better acceptance from the operators with improved consistency of the SAG mill #2 operation across shifts.The paper will also discuss further improvements envisaged in the continued optimisation of the grinding control circuit.CITATION:Savage, C, Rodriguez, R and Metzner, G, 2013. Hybrid process control strategy for the Ok Tedi Mining Ltd semi-autogenous grinding mill #2 - A comparative analysis, in Proceedings MetPlant 2013 , pp 202-214 (The Australasian Institute of Mining and Metallurgy: Melbourne).

Jul 15, 2013

By Jéssica Vicente Luiz, Rayander Martins Pimenta, Everton Pedroza dos Santos

The Hybrid Pelletized Sinter (HPS) is a agglomeration process that involves the combination of conventional sintering and pelletizing techniques and can be used with the purpose of obtaining improvements in the agglomeration stage of iron ore, and one of the great advantages of the process is the use of a wide particle size range of the ore. In this way, the superfines of low-cost ores, which are improper in sintering, can be used in the HPS process for the formation of the quasi-particle. The use of HPS with the sintering plants of the industries presented throughout the study, enabled an increase in productivity, decreased fuel utilization and reduced slag formation in blast furnaces. Thus, the present study aims to present a review of the literature on the Hybrid Pelletized Sinter (HPS) process and its main characteristics, as well as the results obtained by the companies that adopted the process.

Oct 1, 2019

By Graeme Smart, Thomas Fiala

"Yorkville Plaza II, a 40-storey signature condominium residence, is scheduled to open on Avenue Road in Toronto’s prestigious Bloor-Yorkville neighbourhood in spring 2017. In close proximity to Toronto’s subway system, the new tower requires six levels of underground parking, founded in wet, silty sand.Isherwood Geostructural Engineers (Isherwood) was retained in April 2012 by developer Camrost-Felcorp to provide a shoring and excavation solution to address the challenging site conditions. A 31-storey upscale residential building under renovation with three levels of parking, owned by Camrost-Felcorp, flanks the site on the north. Situated on the eastern border is a 7-storey building with three levels of parking. Avenue Road, a four-lane arterial road that brings heavy commuter traffic into downtown Toronto, runs along the western border, and on the southern border of the site is a busy City road that brings traffic into the popular Yorkville area. The tunnel for the Toronto Transit Commission’s (TTC) overburdened east-west subway is located 14.5 m to the south, running below an existing 26-storey neighbouring building. Electrical and communication utilities (Bell) are closely located along the southern side. Non-documented existing excavation shoring, installed in the early 1970s, on the southern and western sides compounded the difficulties presented by the TTC tunnel.This paper presents the unique, non-conventional hybrid shoring solutions Isherwood developed to address the challenges presented by the site, as well as other complications that surfaced during the project: non-encroachment requirements (no tiebacks) beneath uncooperative neighbours, tight geometry to install shoring, and Toronto’s two coldest winters in decades.THE PROJECTBecause of circumstances associated with this site, for this project Isherwood designed two unique shoring walls which drew on their experience and expertise they had gained over the last 40 years. The following is the story of this site:Yorkville is an affluent neighbourhood in the heart of Toronto with a vibrant mix of high-rise towers, residential homes, tony restaurants and flagship shops. The development requires six levels of underground parking (a 20m deep excavation), with three levels undermining the high-rise buildings to the north and east and extending into wet, silty sand.Isherwood was retained in the spring of 2012 to design the excavation shoring. Isherwood’s scope also included field support, design, verification and monitoring. Finite Element Analysis was employed to confirm Isherwood’s design and anticipated movement of the south shoring wall and the TTC subway tunnel.The existing site was severed in two, with the proposed condominium tower slated for the southern portion. On the north half of the site stands a 31-storey building (Yorkville Plaza I at 21 Avenue Road), with three levels of underground parking, sitting on belled caissons which were one foot from the back of the proposed shoring wall so this would have to be considered in relation to the design and drilling methods. Constructed in the early 1970s, Yorkville Plaza I is currently being converted from the Four Seasons hotel to luxury condominiums by Camrost-Felcorp. To the east, directly adjacent to the proposed shoring, stands a 7-storey building (164 Cumberland Road) with three levels of parking, supported on spread footings founded on stiff clayey silt. The tunnel for the TTC’s busy east-west subway, a double box structure built by cut-and-cover in the 1960s, is located 14.5 m to the south, 9 m below grade, and running below an existing 26-storey building. Bell fibre optic communication cables and electrical lines, along with storm and sanitary sewers, are situated on the south and west sides of the site, leaving limited room to install shoring. Due to the heavy volume of commuter traffic on the four-lane arterial road (Avenue Road) to the west, site access and lane closure were not permitted here."

Jan 1, 2015

By Nadir Ansari, Brian W. Wilson, Marina S. W. Li

"A hybrid Deep Mixing (DM) shoring system was recently constructed for a high-rise development in downtown Vancouver, British Columbia, Canada for the temporary support of a five-level basement excavation. The site is bounded by an existing bridge off-ramp structure along its longest side and by city streets on the other two sides, which formed a truncated triangle in plan. A conventional secant pile wall was installed along the longest side, about 380 ft (116 m) in length, of the site. Hybrid shoring walls (HSW) 1 and 2 were installed along two shorter sides with each being 235 to 246 ft (72 to 75 m) long. HSW 3 completed the excavation support system along the shortest side with a length of about 55 ft (17 m). Cutter soil mixing (CSM) was proposed by the excavation and shoring design-build team in lieu of conventional secant piling. CSM was the preferred method to construct the infill panels between soldier piles because of the speed at which the shoring system could be constructed in the variable fill, peat, wood waste and overburden. Design ConsiderationsTo minimize the impact on buried utilities along the outside perimeter of the excavation, the temporary shoring was designed to limit the lateral displacements to less than 0.8 in (20 mm). Factors taken into consideration for shoring design included the lateral earth pressures from the fill and native soils, groundwater pressures, temporary construction loads (e.g., crane or heavy plant/equipment), and permanent structural requirements. The subsurface conditions at this site typically consisted of fill (cohesive and granular), overlying peat and/or wood waste, overlying clayey silt to sandy silt, overlying weathered to dense to very dense clayey silt till to sandy silt till with silt layers. Localized, perched groundwater was observed within the fill, peat, wood waste and sandy silt layers above the dense till."

Jan 1, 2017

By Zhi Zhang

The ever increasing demand of high performance rolls in the late finishing stands (F5 – F7) for hot strip mills (HSM) requires better product solutions from roll suppliers. Roll development activities never stop at Union Electric Åkers (UEÅ) in order to meet the requirement. The HYBRID STEEL, a new concept of roll materials especially for the late finishing stands in the HSM, is successfully developed in UEÅ. This paper reviewed the development of previous ICDP as well as enhanced ICDP (eICDP) roll materials, and, the novel HYBRID STEEL roll grade. Rolls manufactured by this new grade have been used in several European mills. A significant improvement over the enhanced ICDP rolls has been observed.

Oct 30, 2017

By Roy H. Werner

The environmental demands on the mining industry coupled with rising production costs have created a need for a low cost sludge removal system. The HYDRA* system meets these demands by offering a unique means of removing settled solids from the bottom of a clarifier or a thickener. This underflow system combines experience and proven concepts to form a low cost sludge removal system. The HYDRA system incorporates a flexible design that can be adapted to any settling area. The components are readily available and cost less than a conventional clarifier or thickener. Existing technology developed by preparation engineers provides for retrieval and recovery of mine preparation plant refuse. However, past retrieval methods have been extremely costly. The HYDRA system, because of its low cost, makes the complete process of retrieval and recovery economically feasible. This allows wasted resources to be converted to a saleable product.

Jan 1, 1975

By D. L. Millar

The hydraulic air compressor (HAC) is driven only by water, held up by a dam, to create relatively low head (typically 10-20 metres), such that the developed hydropower is used to cause flow in openings deeper underground. Air is entrained in the water at the inlet to the sub-surface openings (an air to water volume ratio of 1:1 is reported to be optimal) and is compressed as it is carried along by the deepening water flow. At depth, and with lower water velocities arising from larger cross sectional area tunnels, air bubbles separate out of the water flow and are collected in a receiver space above the flowing water. Water, free of air, then passes back up a return shaft (up-pipe) and rejoins the river or stream flow. In principle, an HAC can produce any pressure and flow rate required, given large enough shafts and enough water supply with head sufficient to overcome frictional resistance in the sub-surface tunnels. Practically, as air solubility in water increases with pressure, HAC installations with depths greater than 100 metres may lead to higher rates of compressed air loss, without special separation measures. A modern HAC application for mine refrigeration and cooling is presented.

Aug 1, 2013

By Frank A. Jerabek

Problems of mine backfilling and fill material deposited underground, the characteristics and relationship between the deposited fill material and overlying ground, and the practical applications and limitations of hydraulic backfilling as ground support are discussed. A great variety of materials ranging from coal washery refuse to concentrator tailings is used as hydraulic fill. Some materials will solidify and cement; others will resemble quicksand, Hydraulic fill as ground support is more efficient in inclined mine openings than in horizontal mine openings, where it cannot be placed tightly to the back. This and other deficiencies of hydraulic backfilling led to the development of pneumatic stowing. Research work in hydraulic backfilling at the Pennsylvania State University is also discussed. This research work includes the investigation of segregation in the discharged fill slurry, the quantity of solids escaping in the drain liquid, the relationship of escaping solids to slurry concentration and discharge rate, and the compressibility of fine fill material.

Jan 1, 1965

By W. J. C. Pothas

This paper describes the state of the art in backfilling techniques used on East Driefontein Gold Mine. Areas covered are the preparation plant, the distribution plant, the pipeline network and finally placement techniques. The in-situ performance of placed backfill has been assessed by the Chamber of Mines Research Organization, and results to date will be shared. Details of the backfill expansion programme that will enable this facility to be made available to all working places are included. Benefits obtained by the introduction of backfilling are described, together with certain management aspects to be considered in the control of quality and quantity of support supplied via a pipeline.

Jan 1, 1988

The hydraulic backfilling of mine tailings has proven very successful at the Homestake Mine in Lead, South Dakota. It allows greater versatility, selectivity and safety in mining. It has also minimized surface subsidence and underground rock movement. The tight filling also eliminates underground fires. This paper explains the hydraulic backfill method used and the problems encountered by so doing.

Jan 1, 1973

By III Scotland

Genstar's underground mine at Texas, MD experienced a failure of the mine roof and subsequent damage to an underground backfill caused by surface floodwaters. A hydraulic backfilling program was developed in house to stabilize temporary repairs to the mine roof, replace 2300 yards of pneumatically stowed backfill, and complete a permanent repair to the mine roof. A flowable backfill material was developed, tested, and later marketed as the result of experience gained during this project. In addition, Genstar personnel developed backfilling techniques to meet the requirements of the repairs and completed work without the additional expense of non company services or contractors.

Jan 1, 1992

By Richard Maclin Stewart

A priest at Shenandoah, Pa., one day persuaded the president of the Philadelphia & Reading Coal & Iron Co. to slush breaker waste and culm into old mine workings in order to save his church from being destroyed by surface subsidence. The year was 1864, the project was successful, and history recorded the first use of hydraulic backfilling. Shortly afterward, the method was applied to several eastern coal mines for area fill to control subsidence. In 1884, hydraulic backfilling was used to control a mine fire in the Schuylkill region of Pennsylvania. The idea was taken to Europe by German engineers and developed successfully at the Myslovitz colliery in Upper Silesia in 1901. From there it was applied to several mines throughout Europe.

Jan 4, 1958

By Bryan J. Lane, Paul N. Worsey

The recommended maximum explosive weight for boulder blasting using internal charges is 0.1 O-kg/m” (3.5 oz./yd) (Olofsson, 1988). Normally this charge results in excessive scattering and flyrock, creating increased liability for the operator, especially in congested areas. An alternative technique using smaller explosive charges is being developed at the University of Missouri - Rolla. It is designed to reduce boulder scatter, flyrock and fumes and allows shooting in close proximity, using common blasting products.

Jan 1, 1999

By C. S. Allen

WITH increased coal production and mechanization of coal mines many transportation problems arise. The main objective is to bring the coal to the tipple or dump it as quickly as possible. Larger and faster haulage locomotives or two locomotives connected in tandem have been adopted to solve the problem. Motor equipment, gears and control systems of locomotives to be placed on these hauls are carefully studied to meet these requirements, by an analysis of motor characteristic curves with the corresponding tractive effort curves, in order to determine the correct load for maximum efficiency and to determine the approximate schedule. Control equipment is usually considered to be the controller and resistance. Sometimes accelerating curves are calculated in order to obtain smooth starting in the least possible time without slipping the wheels. Train control is very important, but why limit this to acceleration? Deceleration or retardation of the locomotive is a part of the train control and should be given as much consideration as the control for acceleration. TYPES OF BRAKING Common braking systems for mine locomotives utilize screw-type mechanical brakes, dynamic braking and the air brake. For gathering and haulage locomotives, the screw-type mechanical brake is regarded as standard. A brake of this kind cannot be applied without much effort and lapse of time. Motormen, like other people, follow the path of least resistance, and therefore have their brakes ready for instant application-which means that the shoes are virtually dragging. Even then, a motorman bucks and plugs the motors to gain time and avoid as much physical effort as possible. "Bucking of motors" consists in turning the reverse cylinder of the controller to parallel position corresponding to the opposite direction of travel while the locomotive is in motion, without applying power from an external source. When this occurs, both motors tend to act as series generators, because the armatures are revolving and there is residual magnetism in the field circuit. Owing to slight differences in motor manufacture, one of these will generate a slightly higher potential and will overcome the generated voltage of the second and tend to drive it as a motor in the reverse direction. This action retards the locomotive but is very severe on the segments of the reverse cylinder and on the motor commutators. "Plugging motors" is the application of power to the motors corresponding to the opposite direction of travel. In order to "plug" the motors it is necessary first to "buck" them (which reverses the connections to the motors) and then to apply

Jan 1, 1941

By Q. Zhang

The necessary capability of the gravity transportation pipeline system for cemented coal gangue backfilling at the Suncun Coal Mine, China, is about 74.4 m3?h-1 according to mining production and working times in the mine. It is estimated that the working velocity and maximum pipe length-backfill depth ratio of the backfill system are 3.82m?s-1 and 5.4, respectively and that the probable backfill capability of the system is 110.18m3?h-1. Results of hydraulic calculations for the backfill transportation system show that the designed backfill system is reliable in flowability and sufficient for backfill capability needs.

May 1, 2007

Hydraulic transport of coal has been used for many years on the West Coast of New Zealand to extract small blocks of steeply dipping coal. Recent development at Strongman 2 Mine has seen the use of high pressure monitors to cut coal and a corresponding increase in the scale of production.This paper provides a brief introduction to hydraulic mining, describes the present system used at Strongman 2 and discusses future potential development.

Jan 1, 1998