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By Cathy Aimone-Martin, Robert Brentar, Brent Meins, James Lauer

Vibration measurements of multi-story structures in an urban environment began 3 years ago in New York City during close-in blasting to adopt correct measurement procedures and recommend revised ground vibration limits that best characterize cracking potential in mid- to high-rise structures. Two broad categories of structures included non-engineered 4- to 6-story multi-family unreinforced brick masonry buildings, built from the late 1800s to around 1930, and post-WWII, high-rise structures of reinforced concrete and steel rising 12 to 40 stories. In-ground vibration limits similar to those recommended by the U.S. Bureau of Mines safe criteria, developed for 1- and 2-story residential structures, are imposed by the New York City Fire Code. However, these limits are often lowered by project engineers or New York Department of Buildings when blasting is planned near buildings designated Landmark or historic and classified as fragile or vibration-sensitive. Seismograph measurements to determine compliance with in-ground velocity limits currently employ geophones mounted to basement walls and on concrete slabs overlying rock. These measurements cannot be correlated with upper structure cracking potential and are often exceeded, resulting in excessive and costly downtime to allow post-blast damage investigations.

Jan 1, 2014

By Andrew J. Brennan, Jonathan A. Knappett, Lewis Hamilton, Michael J. Brown

"Abstract This paper investigates the compressive behaviour of screw piles in sands and the key design parameters which control this. These types of foundation elements have typically been used as screw anchors onshore (i.e. for their tensile capacity), but there is increasing interest in their potential use as compression piles for supporting offshore marine renewable energy (MRE) devices (e.g. wind and tidal turbines) in deeper water. For such foundation applications, the compressive capacity is as important as the tensile capacity and is not well understood, particularly in cohesionless soils which are a likely seabed condition in MRE applications. A 1-g laboratory study was initially conducted on small scale model screw piles in sand beds of various relative density between 25 – 88%. These experiments were used to validate a Finite Element (FE) model having a stress-dependent constitutive model, making it useful for future up-scaling of the pile size for field applications. Following validation, the FE model was used to conduct a parametric study on the effects of flange spacing ratio (s/Dflange) and flange to shaft diameter ratio (Dflange/Dshaft). By using a validated FE model for this study, it was possible to observe the failure mechanisms (through the shear strain distribution) within the soil and correlate these with the pile capacity. This information was then used to comment on the most optimal (cost-effective) pile design for supporting compressive loads. This study represents a key step towards producing design tools appropriate for the design of screw piles in MREapplications.IntroductionAs defined in this paper, screw piles consist of a central small diameter hollow steel shaft, around which thin circular steel flanges run. Their principle of operation is that the flanges are spaced so as to trap the soil between them, thereby acting as an equivalent solid pile of the outer flange diameter, with a fully-rough ‘shaft’ interface (as shearing is soil-soil). One of the most important design decisions relates to the spacing of the flanges – if the flanges are spaced too far apart, then the soil will not be effectively trapped and the pile have a lower axial capacity and stiffness (controlled by the shaft friction along the central shaft and the bearing resistance arising from the individual flanges; If the flanges are spaced too close together, then there are potentially flanges which are not contributing to the pile capacity, therefore making the pile more expensive than it needs to be."

Jan 1, 2014

By A. Arik

An accurate estimation of mining block grades continues to be a challenging task for ore reserve practitioners. Two of the factors that affect the accuracy of the estimates are the estimation method used and the variability of the mineralization in the deposit. The objectives of the study are twofold: Firstly, to see how different estimation methods perform on a given deposit. Secondly, to determine the impact of particular nature of the mineralization on the results. The comparison of several estimation methods for the prediction accuracy is performed using the conditional simulation results as the basis.

Jan 1, 2000

An examination of the Census of Fatal Occupational Injuries (CFOI) data for the period 1992-1995 shows that 659 fatalities occurred in the mining industry as defined by the SIC. Oil and gas accounted for slightly more than one-half of all fatalities (figure 1-1). The coal industry had the highest fatality rate for the 4-year period, with 35.6 deaths per 100,000 full-time workers, followed by metal (23.1 per 100,000), oil and gas (23.1 per 100,000), and nonmetal (20.1 per 100,000). The fatality rate for all U. S. industries during this same period was 5.1 per 100,000 full-time workers. Figure 1-2 compares the fatal injury rates by year for the four major industry sectors of mining to the fatality rate for all industries combined. Figure 1-3 compares age-specific fatality rates in the mining industry to those seen for U. S. industry as a whole. Fatality rates for all industries combined were lowest for young workers and steadily increased in relation to workers' ages. In the mining industry, fatality rates by age group show a U-shaped curve. Young workers under 20 years of age had the highest injury rate (54.6 per 100,000), followed by workers aged 20-24 (50.8 per 100,000) and workers over age 65 (37.7 per 100,000). Table 1-1 shows the distribution of injuries by type of injury event. The mining industry, in comparison with all industries, had a considerably larger proportion of fatalities classified as caught in or crushed by collapsing materials (9.1% and 1.9%, respectively) and fires and explosions (10.0% and 3.1%, respectively). Transportation events comprised the largest proportion of fatal injuries in both the mining industry and all industries. Within the mining industry only, transportation accounted for the largest proportion of fatalities in all mining sectors except coal. A more detailed examination of the transportation events within the mining industry showed that highway incidents (50.5%) were the most common, followed by nonhighway incidents (22.2%), pedestrian incidents (10.6%), and those incurred during rail, water, and air transport (15.7%). Incidents involving caught in or crushed by collapsing materials comprised a higher percentage of injuries in the coal and metal sectors, while fall-from-height incidents were more frequent in the oil and gas sector. The classification system used in CFOI for type of injury event is not compatible with any variables contained in the MSHA data; therefore, direct comparisons are not attempted. [ ]

Jan 5, 2000

By J. Sandford, S. Hennings

EXECUTIVE SUMMARY An approach borrowed from the petroleum industry was applied to the gas development evaluation for the Bulga underground coal mine in New South Wales, Australia. The results enabled the coal mine operator, Xstrata Coal, to systematically plan the extraction of gas in harmony with mine production planning of multiple coal seams. This has allowed for a more proactive approach in preparing the resources and infrastructure needed to capture the gas and accelerate coal mining while maintaining their high level of commitment to safety. Norwest has for decades used gas recovery simulation models to assist the petroleum industry and the coal bed methane (CBM) industry in understanding and forecasting fluid saturations and flow behavior. Norwest developed a similar process with Xstrata to migrate existing mine data at Bulga into reservoir simulation models to study various drainage alternatives. An interesting feature to the evaluation was also developing an understanding of test procedures and nomenclature from the mining industry to properly translate the data for input in simulators developed for the petroleum and CBM industries. The model was then calibrated to actual field data collected from drainage pilot tests that Norwest helped design and monitor at Bulga. The resulting calibrated predictions were then used to develop budgets, schedules, resource requirements, and alternatives for capturing the gas and delivering it to market ahead of mining. Increasing revenue, reducing emissions, improving schedules and cutting costs for the mining operations have all contributed to justifying this advanced approach at Bulga. It has also allowed Xstrata to expand their focus to the sizable gas reserves in seams not currently planned for mining. Several of these seams would be economic gas development targets once the gas recovery infrastructure is installed for the mine. The evaluation process was refined throughout this project and the resulting approach will benefit Xstrata with their broader strategic development of resources in the Hunter Valley and beyond to their worldwide operations.

Jan 1, 2007

By S. M. Rupprecht

"SynopsisOver the last decade in South Africa, there has been a significant increase in the number of mining operations, both open pit and underground, which use independent contractors to carry out mining activities. Often mine owners will choose the contractor option without fully understanding the consequences of undertaking this option. Traditionally, contract mining has come at a cost premium of about 15% to 20% compared to an owner mining scenario. However, due to the large number of junior mining companies entering the mining arena in South Africa contract mining rates have increased, with cost premiums as high as 50% being reported. This paper looks at the merits of owner mining versus contract mining and describes under what conditions it may be favourable to select the one option over the other. In addition, the methodology of entering into contract negotiations with the objective of establishing a fair and sustainable relationship is discussed.IntroductionOver the last decade in South Africa, there has been a significant increase in the number of mining operations, both open pit and underground, which use independent contractors to carry out mining activities. Surface mining, for example, may use contractors to conduct drilling and blasting operations or load and haul operations. Underground mining may contract out work such as shaft sinking, mining, support, construction work, cover drilling, sweeping and vampings. Common surface operations such as mineral beneficiation, waste disposal, security, and product transport may also be outsourced to contractors.Many companies have a business model that utilizes contractors for the entire mining cycle, maintaining a small head office to provide direction and control. The difficulty with this option is that often mining companies will choose the contractor option without fully understanding the implications."

Jan 1, 2015

By G. E. McElroy

[The ventilation of development faces in mines for diluting gas or dust concentrations aid in hot mines for providing air-motion cooling affect, by fan-pipe units discharging high-velocity streams of air close to the face, is an important phase of mitre ventilation. The effectiveness of such units depends largely on the air-flow distribution between-the pipe discharge said the face, a subject on which little definite information is available. A study of the air, flow from grills into rooms3/ has provided sore basic data, but under conditions so different from mine fan-pipe installations in development ends that tae data to are of doubtful application to mine installa¬tions, owing to differences in air-flow conditions. The purposes of this report is to present and discuss the results of an initial series of tests of a general investigation designed to yield definite laws and design data for the discharge of fan-pine lines in nines. The s series was planned to yield preliminary data on the effects of velocity of discharge, size and shape of tripe, and adjacent calls on the air-flow distribution. Tents were made on 10-inch pine with seven different end conditions and one change of wall condition. Changes in size and shape of discharge wore made b y short transformation pieces directly at the discharge end, with the result that effects due to contraction and expansion of the flow, which proved to be of much greater importance than was expected, totally obscured any normal effects cue to size anti shape. The results of this series of tests, therefore, relate to 10-inch pipe with various discharge designs is and ago se reported.]

Jan 1, 1940

By Peter Fischer

Reducing mining costs has become such an important factor in the German coal industry that operators are forced to work only those areas where production costs can be kept low. These areas will normally be located close to the mine shafts because they are easily accessible. Even the shaft pillar is now being considered as part of the winning zone. Before working coal in shaft pillar zones it is essential to assess the impact this will have on the shaft lining. There is a huge difference between sliding and strata-anchored shaft systems. However, if the overburden comprises lightweight soil both types of shaft will have a tendency to protrude from the surrounding ground. This paper presents the geomechanical reasons underlying this reaction and the methods used for predicting and measuring it.

Jan 1, 2007

By Kazem Oraee

In underground coal mining, particularly room-and-pillar methods, the coal pillars play a significant role in roof stability. If the pillar dimensions are increased, the pillar bearing capacity also increases, but more coal remains in the pillar and therefore the recovery of mining operation decreases. Therefore, determining the optimum pillar dimension based on technical, economical and performance parameters is important. In this paper, the coal pillar is designed by using the concept of ground reaction curve (GRC). For this purpose, the GRC for coal pillars is drawn and then the elastic and plastic zone of coal pillar behavior is determined. Based on elastic and plastic zone, different equations are presented to draw a pillar reaction curve and the process of coal pillar design based on GRC is explained. As a case study, this new technique is applied to study the coal pillar state in Tabas coal mine of Iran. The results show that the presented new approach is successfully used in the design of the optimum coal pillar dimensions, and also determines the elastic and plastic behavior limit, which is important especially for the logical design of yield pillars.

Jan 1, 2009

By E. Fahrenkrog, D. Sbartaro, E. N. Cifuentes

An intelligent supervisor using expert system tools and applied to a crushing plant has been developed with a structure based on a model of a human operator. It consists of a knowledge base containing a qualitative model of the process and a rules base with the heuristic logic used by an operator when supervising a plant. The simulation results obtained show the potential of this type of system to supervise the automatic operation of a plant. There has been very significant development in artificial intelligence over the last two decades. Within this development, two approaches can be distinguished, (Winston, 1984). The "model approach," in which the main objective is to understand and model the be¬havior of living systems. The second approach is the "engineering approach." Here, systems capable of performing tasks usually requiring human intelligence are created. As part of this latter approach, knowledge engineering and its main achievement, expert systems, have been developed. Expert systems arose from the need to incorporate the abilities of a human expert in solving realistic problems in which the conventional approach has great difficulties. The first successful applications of expert systems were in medical diagnosis, geophysics, and fault detection. However, since 1971, when Fu (1971; defined intelligent control as the inter action of artificial intelligence and automatic control, some significant developments in the use of artificial intelligence tools for process control have been achieved (Astrom, 1986; Pinto 1988; Fahrenkrog, 1988; and Porter 1987). The modern control theory has made important advances. And, although successful in some applications, it has failed to cope with the practicalities of many industrial processes. As a result, the automatic operation of a plant has been confined to a small region around a normal operating point and to periods without any great disturbance. One of the main reasons for this is the lack of accurate and structured knowledge of the processes involved. Despite this, operators applying their knowledge, experience, and a little intuition, often obtain good results controlling the plant in such situations. Considering the above, the next obvious step is to include similar reasoning capacities in a computational system. The development of such an expert supervisory system prototype applied to a mineral crushing plant is presented. Problem description The problem is to conceive a control system with the ability to handle quali-

Jan 1, 1989

By P. D. R. Maltby

"1. INTRODUCTIONMy talk today will discuss a new development in the thickening of slurries and clarification of waste water - the Enviro-Clear thickener. Several industrial installations of the thickener have been made in North America in the following applications:1.,water clarification in sugar beet processing plants.2.,separation of pregnant liquors from solid wastes following acid leaching in uranium mills3.,clarification of waste water from coal treatment plants as described in a paper in the June 1975 transactions of the SME entitled ""Application and Utilization of the Enviro Clear Thickener in a U.S. Steel Coal Preparation Plant"" by A.A. Terchnik, D.T. King and J.S. Anderson.2. HISTORYThe application of the Enviro-Clear thickener can be traced back to the filing of U.S. Patent 3523889 in 1970 by the inventor F. Eis. The claims of this patent are shown in Slide 1.The new concept was developed for sugar beet processing by the Spreckels Division of Amstar Corporation, and several such thickeners have subsequently been installed in various sugar beet plants. The Enviro-Clear Co. or New York took over the world-wide manufacturing and marketing of the thickener. Experience in the sugar beet industry indicated that the Enviro-Clear thickener volume requirements could be reduced to as low as one tenth that of a conventional type thickener. Various coal samples were supplied by U.S. Steel Research Laboratories for testing. The tests indicated that feed rate loadings of 3 gpm/ft.2 could be obtained by the Enviro-Clear thickener. Such results led to several industrial applications in the coal industry. Subsequently other branches of the mineral processing industry have come to learn of the possibilities of using this thickener. Slide 2 shows a list of commercial Enviro-Clear installations at the end of 1975."

Jan 1, 1976

By D R. Carr

The installation of the Flotation Capacity Project flow sheet in the copper concentrator at Mount Isa Mines Limited has recently been completed. The project involved increasing the flotation capacity with Wemco tank cells and Jameson cells as well as changing the copper cleaner circuit layout. The engineering design and construction for the brownfield expansion had significant involvement from operational, maintenance and technical personnel adopting the same approach as the highly successful George Fisher project in the Lead/Zinc Concentrator at MIM. The involvement of people familiar with the concentrator allowed for smooth integration of the changes into an operating concentrator with minimal downtime. Detailed circuit analysis over many years identified opportunities for improvements in the flotation circuit for both grade and recovery. This paper describes the program of work that led to the Copper Concentrator Flotation Capacity Project, and the implementation of the circuit expansion and flow sheet changes that resulted in an overall improvement in the circuit recovery.

Jan 1, 2003

By Jogeshwar P. Singh, Ahmed AlaaEldin, Mohamed Ashour

The presented methodology allows the determination of the response of laterally loaded battered long piles in sandy soils based on the soil-pile interaction. The Strain Wedge (SW) model which was originally developed for laterally loaded vertical piles is modified to assess the behavior of laterally loaded battered piles with the consideration of soil and pile properties. The method predicts the pile-head response and associated p-y curves. The presented soil-pile model accounts for the variation of the direction and magnitude of the batter angles from the vertical position. Unlike current practice, the proposed technique also provides the p-y curves for battered piles in sandy soils based on soil and pile properties (i.e., sand relative density, friction angle, pile geometry, etc.). The proposed methodology has been validated through a number of comparisons with full/model-scale pile load tests. INTRODUCTION The influence of pile battering on the lateral response of piles is rarely studied in the literature. Over the last decades and as suggested by Kubo (1962) and Zhang et al. (1999), a p-y multiplier is applied to predict the response of laterally loaded battered piles from an equivalent vertical one. Several researchers conducted model-scale piles load tests to understand the behavior of battered piles subjected to lateral load (Juvekar and Pise 2008; Meyerhof and Ranjan 1973; Meyerhof and Yalcin 1994). However, such tests were conducted on model piles with diameters less than 30 mm which may not have reflected actual soil-pile interaction. Battered piles are generally categorized as positive or negative battered piles according to the angle of pile installation as shown in Fig. 1. From the small-scaled and numerical models of battered piles, it was found that the lateral capacity of negative battered piles is larger than that of vertical ones. On the other hand, the positive battered piles have lower lateral capacity when compared to vertical piles (Fan-ren and Ji-Ming 2011; Juvekar and Pise 2008; Manoppo 2010; Reese et al. 2004; and Reese and Van Impe 2011).

Jan 1, 2018

By Mohsen Mohammadi, Edward Cyr

"To date, several studies have been performed on the static mechanical properties of SLM-AlSi10Mg alloy. There have also been more recent studies on the relation between scan strategy, texture, and mechanical properties of SLM metals and composites. However, there is a huge knowledge gap in the available literature regarding texture and mechanical behavior of SLM-AlSi10Mg alloy under high strain rates. Therefore, in this study, dynamic mechanical behavior of AlSi10Mg_200C alloy manufactured by DMLS technique was investigated at high strain rates ranging from 900/s to 1700/s using Split Hopkinson Pressure Bar. Texture using X-ray diffraction technique of the initial samples were measured. The yield strength, peak flow stress, and ductility increased in all samples with increase of strain rate. TEM studies have also revealed evidence of continuous dynamic recrystallization in grains after 900/s–1700/s strain-rate tests. A Taylor polycrystal crystal plasticity constitutive model was then developed to capture and predict the texture evolution and mechanical response under dynamic loading, using plastic work as a critical parameter for the onset of recrystallization.INTRODUCTION Additive manufacturing (AM) powder techniques are among the fastest advancing breakthroughs in manufacturing in recent years, defined by a bottom-up layer by layer process of joining with energy input from lasers or electron beam (Herzog et al., 2016; Gibson et al., 2015). Among alloys fabricated by SLM, AlSi10Mg is of high interest to industry and academia due to its low density, high specific strength and excellent corrosion resistance, making this alloy a viable contender for aerospace, automotive, and marine applications. Circumstances such as car crash or bird aircraft strike hazards subject potential additively manufactured AlSi10Mg parts to impact loadings. This drives an interest in understanding and predicting dynamic behaviour of these alloys. AlSi10Mg is the AM counterpart of A360 die-cast aluminum, which possess hypoeutectic microstructure (Li et al., 2015). Up to the present time, many studies have presented the mechanical properties of SLM-AlSi10Mg alloy. The mechanical properties and microstructure of AlSi10Mg produced by selective laser melting (SLM) or DMLS techniques can be controlled using different parameters, such as feedstock powder (Asgari et al., 2017), and process parameters (Olakanmi et al., 2015). The microstructure and mechanical properties of AlSi10Mg can also be controlled using post heat treatment after SLM process Li et al., 2016). The mechanical properties of SLM-AlSi10Mg are sensitive to strain rate and can both change under quasi-static (Rosenthal et al., 2017) and high strain rates (Asgari et al., 2018). However, a significant knowledge gap in available literature regarding modeling these behaviours, and especially micromechanical modeling of dynamic behaviour."

Jan 1, 2018

By Raymond B. Ladoo

"The name bentonite has been applied to a group or series of clay-like materials characterized by an alkaline oxide and alkaline earth content of 5 to 10 per cent, fine grain Giza, high absorptive powers, and usually very strong colloidal properties.Bentonite probably represents no mineral of fixed composition, and its physical properties vary considerably. The type material from Wyoming is light yellow or greenish yellow in color, but from other localities it may be cream colored, white, gray, pink, dark brown or even black. It is exceedingly fine grained, very plastic and highly absorbent. The appearance may be dull or powdeay, but a freshly cut surface usually has a waxy luster. Some varieties have the appearance of wax and may be cut into very thin, translucent shavings. The fracture of the type material is roughly conchoidal, that of other varieties is platey and shale-like, while still others have no typical fracture. Bentonite is highly absorbent; .hen wetted it will absorb more than three times its weight or seven times its volume of water. Some varieties when wetted with water expand to more than six times (some experimenters report eight times) their original volume. The wetted material is exceedingly smooth and soft and feels like soft soap. Unlike most clays, bentonite is easily fusible at a comparatively low temperature.Under a high-power microscope bentonite seems to consist of extremely small, more or less rounded, grains of uniform size, but the texture of most varieties is so fine that individual grains can not be distinguished.Some varieties when finely ground and thoroughly agitated with water will stay in suspension indefinitely, forming a translucent gelatinous mass. The addition of small amounts of acids or sodium chloride seems to have little or no tendency to raid coagulation or settling. Other varieties of similar analysis and appearance go into suspension more easily, but settle out again in a comparatively short time. It has been suggested that the material which stays in suspension indefinitely is a true colloid of the emulsion or lyophilic type."

Oct 1, 1921

By T Albinson

Mexican epithermal deposits can be broadly grouped into two types based on their contained metals, distribution, associated igneous rocks and fluid inclusion compositions. Silver-gold deposits (eg Tayoltita) mostly occur in the western part of northernMexico where host rocks consist of Eocene, intermediate composition volcanic and intrusive rocks; fluid inclusion studies indicate that mineralising fluids were <300¦C and dilute (=3 eq. wt. % NaCl). In contrast, silver-lead-zinc deposits (eg Fresnillo) mostly occur in the central part of northern Mexico where they are temporally associated with Oligocene-Miocene volcanic rocks and intrusions of felsic composition, but commonly hosted within underlying Paleozoic-Mesozoic sedimentary rocks; fluid inclusion studies indicate that mineralizing fluids ranged from 200 to 400 ¦C and were saline (=10 eq. wt. % NaCl). The distribution of these two deposit types, crosscutting major crustal sutures, and the close spatial-temporal relationships between mineralisation and magmatism, together suggest that magmatic processes were more important in the formation of mineralising solutions, as a source of both ligands and metals, than the segments of crust hosting deposits.

Jan 1, 1995

The development of the potential supply analytic system has advanced to the point that quantitative estimates of economically recoverable resources can be made as the final step of the traditional regional mineral resource assessment process. In 1983, the BOM and the ADGGS jointly developed a methodology to quantitatively assess the potential for undiscovered yet economically recoverable minerals within a designated geographic area. This methodology was first applied in the assessment of the undiscovered mineral potential of the Kantishna Hills, Alaska (White et al., 1987). At that time the assessment procedure combined a series of technical judgements regarding the major geologic, engineering and economic factors that influenced the occurrence and exploitation of mineral resources in the Kantishna Hills area. Since then the methodology has been further developed and enhanced, particularly with respect to the engineering and economic analysis components. The resulting Potential Supply Analysis System (PSAS) was recently used to evaluate the economic potential of selected types of undiscovered precious-metal deposits in the Tonopah quadrangle of Nevada (Gunther, et al., 1988) and, with some enhancements, has been used to estimate the' economic value of the undiscovered mineral potential of the WMNRA/SNCA study area. The PSAS has been designed to address five basic questions about the mineral potential of an area: 1) What alternative states of geologic nature are possible in the area of interest (e.g. How many and what types of undiscovered deposits could be present and what might be their grade, tonnage and depth attributes?) ?;

Jan 1, 2011

By H. Akbari

The ordinary Portland cement (OPC) is the key pozzalonic component of the concrete mix, widely used as the construction material world-wide. Billions of tons of OPC are used in the construction industry each year. However, calcinations of limestone and silica that produce OPC also produce almost an equal amount of CO2 during the cement manufacturing process. Thus, OPC production accounts for nearly 7% of all anthropogenic CO2 emission each year. The main objective of this study was to develop a geopolymer-based composite to be used as a substitute for OPC in concrete application to significantly lower the carbon foot print of the construction industry. A waste material produced during the coal combustion process was used as the main raw material for the geopolymer-based composite. It was mostly the non-metallic content of the F-type fly ash produced from the combustion of bituminous coal. The authors envisioned to extract some of the valuable metal oxides from fly ash prior to using the major non-metallic portion of the fly ash for geopolymer concrete application. The results obtained from this study exhibited that the compressive strength of the geopolymer concrete compares favorably with that of the conventional concrete prepared using the OPC.

Feb 27, 2013

Grinding and Flowing Investigation on Dry Stirred Ball Milling in Order to Determine the Influence of Grinding Aids Huge difficulties of the great ultra fine ground material production in dry stirred ball mill are the cohesion and agglomeration of the particles. During grinding the material stick on the grinding wall and the grinding media furthermore the grinds start cohere, making aggregation and agglomeration to appear. Due to these effects the particle size will not decrease after a certain value during grinding and the energy demand increases significantly. According to experience on fine grinding in ball mill, it is well known that these effects can be reduced with the use of grinding aids. The influence of grinding aids has three different effects: due to the adsorption strength reduction (Rebinder effect) the grinding resistance of the material decreases; the surface energy diminishes and the agglomeration liability decreases; and the flow properties of material improve. The aim of this study is to investigate the flow properties of fine grinds and the effect of grinding aids on flow properties in case of dry stirred ball milling. In addition, the influence of grinding aids was investigated based on the particle size distribution and specific surface area of grinds and the specific energy demand of grinding. The examinations were carried out with three different model materials (limestone, clinker, quartz) using the usually applied grinding aid. The flow properties were measured by the Jenike shear cell; the particle size distribution and specific surface area were measured by laser particle size analyser (Fritsch Analysette 22), grinding energy demand was measured with microcomputer controlled digital energy meter. It can be said that under certain measuring circumstances the influence of grinding aid on flow properties can be demonstrated by Jenike shear cell, so the grinding result is in correlation with the flow properties of grind.

Sep 13, 2010

By H. C. Fuller

This paper discusses 105 production runs at Boulder City, Nev., in which titanium metal was made in 200-pound batches. It describes the equipment and techniques used in preparing raw material, the reduction process, and the removal of the reaction mass from the reaction vessel. Also, some data on man-hour requirements are presented. The main emphasis was on producing ductile-grade titanium and developing a standard procedure for obtaining a consistently pure product. Some departures from techniques used before were found to be desirable. The most important of these was the use of a sealed room with a controlled dry atmosphere in which the reaction vessel was opened and the reaction mass removed. This minimized the moisture taken up by the magnesium chloride in the reaction mass, and it could be purified successfully by vacuum distillation. Using the dry room also made it possible to leave al-inch shell of the reaction material on the walls of the vessel, which lowered the iron contamination and eliminated the labor and time-consuming job of cleaning the vessel after each reduction. Another change was lowering of the temperature during reduction to 750° C. instead of 850° C. This was found to give good results more consistently. The first poke to break the crust during reduction was eliminated, as it was found to be unnecessary and only added more work and was another possible way of introducing air. A rotating feed arm was installed in the reaction vessel to distribute the titanium tetrachloride over a larger area and, thus, prevent local overheating. The process, conducted in a batchwise manner as described and followed by good purification and fusion, produces a metal adequate in quality for nearly all purposes.

Jan 1, 1952