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By K. H. Lee

The rate of beryllium dissolution from a low-grade ore was studied in sulfuric acid solutions. The effect of stirring speed, sulfuric acid concentration, particle size and temperature on the rate of dissolution of beryllium was established. The results of the study showed that the dissolution rate is independent of stirring speed within the range of 250-1000 rpm but depends on 1/2 power of the sulfuric acid concentration. The dissolution rate increases exponentially with decrease in particle size and the maximum attainable rate of extraction with respect to particle size is 6.6 x 10 mol dm min. The apparent activation energy (^E) for the dissolution reaction is 54.4 kJ/mol (13.0 kcal/mol). Based on this magnitude of the activation energy, it is concluded that a surface chemical reaction is the rate limiting step for the temperature range (70° -100°C) investigated.

Jan 1, 1988

By Hans-Werner Tonscheidt

Introduction The endeavours to mechanise the shaft sinking operations have led to the development of shaft boring using a V-Mole. The method implies competent ground and a pilot hole of sufficient verticality. This connects the top and the bottom of the shaft and serves for air ventilation and the transport of mullock. The shaft boring machine - nick name V-Mole - with a general pattern similar to a tunnel-borer reames the pilot hole to the designed diameter of the shaft. (Figure 1) The excavating of the rock, the removal of the mullock from the face and the lining of the shaft wall are done simultaneously. If they can be done also continuously this than creates a high potential of productivity. The verticality of the shaft can be garanteed due to the laser beam guided steering system. The diameter of the shaft is variable in steps of 0.5 m between 6.0 and 10 m in accordance with the need. It decides the capacity of the V-Mole to be applied. The depth of the shaft does not depend on the machine. It is practically unlimited as long as a suitable pilot hole is available. Up to 1988 almost 12.656 m of shaft have been drilled on 40 individual projects in Germany and the U.S.A. using a V-Mole. The rocks penetrated were Carboniferous sediments consisting of Sandstones, Shales, Conglomerates and Coal seams. The average uniaxial compressive strength was in the range of 300 - 700 Mpa with a maximum of 1700 Mpa in some singular sandstones.

Jan 1, 1991

By Lyman H. Hart

Michiquillay is a major copper deposit situated about 70 km (44 miles) northeast of Cajamarca in northern Peru (Fig. 1). It occurs largely in quartz monzonite in a shatter zone produced by the intersection of northwest- and northeast-trending fault systems. The geology is described by Hollister and Sirvas (1974). The ore deposit was drilled in 1963-1964 by Asarco, with results indicating a resource of 575 Mt (634 million st) averaging 0.72% Cu-0.03% Mo. A decision to bring the project to production has been deferred because world capacity to produce copper has been more than adequate to serve world requirements since 1964. The chain of events leading to the discovery of Michiquillay was set in motion by a decision by the management responsible for the Chilete mine to undertake an investigation of the surrounding area for a possible supplementary source of mill feed to bolster its decreasing lead-zinc reserves. Chilete, located 100 km (62 miles) inland from Pacasmayo, is the most northerly, important mining project in Peru, and little was known of the mineral potential north and east of that point. Relatively unimpressive reports of Colonial silver mining had attracted little investigation, and little was known of the regional geology. One study by Benavides (1956) had been made of the Cretaceous in the region of Cajamarca.

Jan 1, 1991

By P. C. Kapur

For mineral processing spirals, mathematical force equilibrium models are sought to extend the spiral performance envelop. In Part 1 of this report, a complete geometric description of the helical spiral and its trough or channel contour is provided. The secondary circulatory fluid motion in the transverse direction that develops when water flows down a tightly turning curvilinear path and its implications for gravity separation are discussed. Different forces that act on the particle during its passage through the spiral are enumerated and quantified for a better appreciation of their relative contributions and roles in the separation process. Three force equilibrium models from the hydrology literature on sed iment transport are employed to simulate a typical spiral. While the results are promising in that the models mimic the broad performance characteristics of the spiral, what is needed is a more general spiral model taking explicit cognizance of the missing components essential to the spiral description. These are such components as centrifugal force and the steep tangential slope of the channel deck. Results of this latter exercise are deferred to Part 2.

Jan 1, 1996

By R. C. Milici

Historical production data and reserve decline rates can be used both to predict future coal production rates and to estimate when the reserve will be depleted. Reserve estimates inferred herein from historical production data and decline rates are commonly lower than estimates made from geologic data. The latter include significant amounts of lower quality (deeper, thinner, higher sulfur) coal which may be mined when the better deposits are depleted.

Jan 1, 1997

By M. D. Flavel, J. C. Motz, G. V. Jergensen

Introduction Compared to the gyratory crusher, the cone crusher is character¬ized by its higher speed and a flat crushing chamber design which is intended to give a high capacity and reduction ratio for materials suitable to this type of processing. The aim is to retain material longer in the crushing chamber to do more work on material as it is being processed. A concept of how a piece of stone might flow through a secondary crushing chamber is shown in Fig. 45. The number of times material will be nipped during crushing will depend on material size, friability, and the geometry of the crushing chamber as well as its speed and eccentric throw. Cone crushers are usually specified in terms of closed-side setting (CSS) and a given quantity of material passing a particular square-mesh screen size. A criterion of product passing closed-side setting is often available. This value will vary according to the particular crusher design and the details of its applica¬tion. Essentially, cone crushers can be classified into distinct types, depending on their duty. Crusher sizes for all duties are described by terms arising out of common industry usage, such as 3-ft, 7-ft, etc., which refer to the crushing-head (mantle) diameter. At present the range of sizes available varies from approximately 2 to 10 ft diam. Weights vary in the range of 5 to 200 tons, and connected horsepowers range from 10 through 700. There are so many variations that specifics should be obtained from machine manufacturers. The crushing chambers that are fitted to various machines are also often referred to by terms arising out of common usage, such as standard for secondary crushers, and short head for tertiary crush¬ers, which refer specifically to the Symons design. Also used are more specific but equally vague descriptions, such as coarse, intermedi¬ate, and fine chambers. Some manufacturers such as Allis-Chalmers with their Hydrocone crushers refer to the model number of the machine by the feed opening and the diameter of the mantle. For example, a Model 10-84 Hydrocone crusher has an 84-in. diam man¬tle, and is capable of accepting a 10-in. diam sphere at the feed point to the crushing chamber. Rexnord and Telsmith define crushing cavi¬ties in their capacity tables as feed openings at minimum recommended discharge settings (closed-side settings). Each practice offers guidelines which should be carefully defined for the specific crushing problem. The utilization of a cone crusher depends on how well it is controlled and the features of the circuit in which it operates. Normally, it will operate in the range of 75 to 85% of the peak capacity. It is likely that industry pressures will call for a standarized de¬ applied crushing power. Experience has shown that the crushing process is more controllable if certain reduction ratios are adhered to for each stage. Technically, this is defined as that size of feed (in. or mm) of which 80% will pass, divided by the size of the product (in. or mm) which 80% will pass. Secondary Crushers These are the cone crushers which accept suitable feed size material either prepared by a primary crusher or occurring naturally, and reduce it to a size suitable for marketing in one stage, or make feed for subsequent crushing or grinding stages. Secondary crushers have feed openings of 4 to 25 in. in the larger (7-ft) models down to a 2'/a to 4 in. in the smallest 24-in. models. Reduction ratios normally range between 3:1 and seldom more than 5:1. In the 7-ft models, the cone crusher typically makes a product all passing 2 in., but this is dependent on the machine design and properties of the material being treated. Secondary crushers most commonly operate in open circuit. They also are operated in closed circuit with a vibrating screen, depending upon product requirements and conditions where the reduction ratio does not cause excessive power draw and build-up of circulating load. Screening ahead of secondary crushers is generally recommended, especially where the feed contains more than 25% material smaller than the desired closed-side setting. Tertiary Crushers These are cone crushers that normally take secondary crusher product and reduce it to a marketable product or make it suitable for subsequent comminution steps. The reduction achieved is a func¬tion of the crusher design and the properties of the material to be treated. The reduction ratio is normally in the range between 1.5 and 2 to 1, and seldom more than 3 to 1. The tertiary crusher normally operates in closed circuit with a vibrating screen and makes a product smaller than all passing 'h or 5/8 in. Fine Crushers Sometimes these machines are called sand crushers and are called by various manufacturer brand names, such as Gyradisc, Hydrofine, V.F.C., and others. A cross section of a Symons Gyradisc crusher is shown in Fig. 46. Essentially, these crushers would be used in a fourth-stage crushing operation, but could be called on to reduce a screened feed size fraction from a secondary or primary crushing operation. This type of crusher normally receives feed no coarser than 1'h in. that is scalped of all over-sized material and operates in closed circuit with a vibrating screen. For average materials, typical product is '/e in. top size, although a -10 mesh product can be produced on those materials having suitable characteristics. The crusher is nor¬mally operated in a separate circuit from the main crushing plant because of the variations in output rates that are caused by varying physical properties in the feed. The reduction ratio is generally less than 2:1, and circulating loads are generally high. More interparticle crushing takes place in these machines than with conventional cone crushers and capacities can be more sensitive to changes in moisture content, feed size graduation, and other physical properties. Design Features For the various applications, crusher manufacturers normally have a range of crushers of different sizes and power ratings to select from.

Jan 1, 1985

By Carl G. Bock

INTRODUCTION The Washington Metropolitan Area Transit Authority (WMATA) has let a contract for the excavation of three rock stations, spaced about 3550' (1082m) apart, beneath Connecticut Avenue in Washington, D.C. Two previous rock stations have been completed, one of which had a crown pilot tunnel excavated to explore geologic conditions that would be encountered during the station excavation. This pilot tunnel was primarily for inspection by bidders and design was based on core hole information. The other rock station had no pilot tunnel and was also designed on the basis of core hole information. The three rock station areas, which are the subject of this paper, have been explored by crown pilot tunnels and an as-built report, with geologic maps and sections, has been prepared, for use by the design engineer as the basis of design for support of the structures. The geotechnical report describes the geologic structure in detail and relates it to excavation and support of the three crown pilot tunnels and the running tunnels which will be enlarged to create the 58'W x 44'H x 700'(+)L (17.6m x 13.3m x 212m +) stations. The information was complete enough to permit the design engineer to visualize the geologic structure and compute loads for the various types of rock conditions. It was therefore possible to determine the size and spacing of the steel sets for the several different conditions of rock structure encountered in the pilot tunnels.

Jan 1, 1976

By R. F. Davis

The evaluation and selection of coals for producing metallurgical coke is indeed a com- plex process simply because coal is a complex and variable substance which is sensitive to how it is treated from the time it is mined until it is transformed into coke. A review of the the more common evaluation tests made on coal and how the test results are applied in commercial practice. Parameters used to select coal blends for wet and preheated charges should also be of interest.

Jan 1, 1980

By A. Frank Alsobrook

DOUG HALBE: Thanks, Terry. And in spite of your introductory comments, I'm going to attempt to continue our hallowed tradition of saying nice things about the speakers. This is really a serious comment now. We, as mineral processing and mill people, don't often talk to people outside our general operating area. One thing that we've tried to do in this operators' symposium is get speakers from various types of plant operations to help illustrate all the things we have in common. Our next speaker is from the industrial minerals area. I think there's a lot to be learned from industrial minerals operations. Some of the people in the last session learned some things about fine grinding in industrial mineral operations. I was a little surprised to see people there grind to 2 microns. Our next speaker is Frank Alsobrook. Frank is another nonmetallurgical engineer. He has a degree in geology, a master's of science from the University of Wisconsin. He's had his own very successful consulting company for a number of years. This is your 11th anniversary, Frank? Very good. He's also the immediate past chair of the industrial minerals division. I think the folks at the speakers' table should be ashamed. You have been so rowdy that Frank chose to sit in the audience. [laughter] We'd like you to come up now, Frank, and tell us some things that you've seen that might be useful to us. INTRODUCTION FRANK ALSOBROOK: The three topics addressed briefly are (1) teamwork and operations modeling, (2) the pitfalls of capital conservatism, and (3) the potential for by-product recovery. Ideas for improvements in these areas are not unique to industrial minerals but apply to metal mining and processing operations, as well. Several additional topics are suggested at the end of the paper.

Jan 1, 1998

By Y. Luo

Highwall mining, which is a relatively new mining method, is a preferred and often the only feasible method for extracting coal reserve left by surface mining operations in areas with steep terrain and in closely spaced thin coal seams. Though its safety record is comparable to that of surface mining, failures of mine structures in highwall mines, especially the highwall, have occurred. Methods for the systematic designing of highwall mines to meet the safety and operational challenges are still evolving. This paper presents the results of research into improving the existing design methods and developing new ones for highwall mining operations. The design methodology is aimed at ensuring structural stability of the highwall, roof, web and barrier pillars and preventing subsidence. It takes into consideration the major ground control challenges of soft and layered mine roofs, and interactions from mining closely spaced coal seams. An optimization design process applying a pressure arch concept can be incorporated to improve the recovery rate of coal reserve. A computer program based on the design methodology was developed.

Jan 1, 2015

By M. A. Vergara, J. A. Botín

"The decline of the “super cycle” has placed an end to a decade of production-focused strategies, with operating cost growing at rates higher than production. Today, the sector is placed on a tough ride and forced to shift focus to cash preservation and efficient cost management. However, most cost management systems in the minerals industry are not conceived as value driving tools but to meet financial accounting and reporting needs. This research draws from a the development of an innovative cost management methodology that applies Activity-Based Bottom-Up cost budgeting and continuous improvement tools to develop a value-driven cost management system for sustainable improvement of operational efficiency and cost reduction. The methodology was successfully tested in the Andina underground mine III Panel sector of Corporation del Cobre (CODELCO), in Chile. INTRODUCTION Cost management is fundamental to profitability of any industrial project. Even more essential in mining, an industry that deals with commodities, which prices are dictated by the market and are beyond the management capacity of the company. The end of the mining “super cycle” and the advent in 2008 of the Global Financial Crisis (GFC), placed an end to a decade of production focused strategies, with operating cost growing at rates higher than production. The sector was placed on a tough ride and forced to shift focus to cash preservation and efficient cost management. Many mining companies have seen themselves into the urgent need of cost management systems capable of achieving sustainable productivity gains and consistent profitability. Cost management is composed of three main processes: estimation, budgeting and control [1]. A number of conventional techniques have been used for cost estimation and budgeting for many years. However, most cost control systems in the minerals industry cannot be referred to as “cost management” since they are conceived to fulfil accounting and reporting needs, rather than to improve operational efficiency [2]. In general, conventional cost budgeting and control systems in mining use a “top-down” methodology, which lacks of necessary details, and fail as a management tool leading to undesirable results [3]."

Jan 1, 2016

By J. H. Dietz

The electric assist option for diesel-electric trucks can improve truck productivity while maintaining the inherent flexibility of a truck and shovel operation. In addition, the resulting cost reductions offer a rapid investment payback for many mine situations. A review of the present technology and performance experiences verify the projected benefits in productivity and operating cost. New technologies can further improve the productivity/cost scenario.

Jan 1, 1984

By Richard C. Corson

The objective of blending materials in a bedding pile is to reduce the variation in successive samples taken from the materials to be blended. In designing a bedding and reclaiming operation, several mechanisms are available to effect the reduction of variability, or increase in homogeneity, of the materials. These mechanisms can act before stacking, in the stacking process, in reclaiming and after reclaiming. In evaluating alternative methods of stacking and reclaiming, the potential user must judge each method on the basis of certain criteria; the capital cost of the equipment, the allowable absolute variability of the reclaimed product and the effectiveness of blending. Several stacking and reclaiming methods have been tested using a computer simulation. Based on the results of this program, factors were developed to describe the effectiveness of blending for chevron stacking of discrete materials and preblended materials, bucket wheel reclaiming and drum reclaiming. From these factors, the total effectiveness of a combined stacking and reclaiming system can be determined.

Jan 1, 1985

By J. Kallioinen

The development of mechanical flotation cells has resulted in larger and better cells. This has led to flotation banks with only a few units, even in large-scale operations. This equipment development makes the old operational considerations ineffective. The flotation cell must be considered as a single reactor unit capable of handling specific tasks and getting excellent metallurgical performance. The result of the unit reactor concept development was the new large TankCell that comes in sizes up to 113 m3 (4,000 cu ft). The TankCell construction includes new modified rotor-stator designs, new tank geometries and a froth-handling capability independent from subprocesses taking place in the pulp (i.e., air addition). The conventional idea of a single flotation cell type for fine, intermediate and coarse materials does not give optimal results. Optimal flotation of coarse and fine particles needs different mechanism designs, impeller tip speeds and different froth control objectives.

Jan 1, 1995

By Edward J. Karkoska

The film you see is a slow motion view of a typical half million ton taconite blast at one of Erie's mines. This blast is made up of 220 drill holes and a total of 325 thousand pounds of blasting agent. The second view of the same shot is taken by a remote control hi speed camera located 1500' directly in front of the blast. Shortly you will see some violent camera movement as the air blast shock wave strikes the camera location. As the blasting sequence progresses the rock fly becomes evident, and if you will look closely amidst the clouds of smoke, rock fragments weighing up to 1/2 ton begin to cascade into view. These missles are the chief concern of blast security. The next camera shot at 4000 frames/second vividly describes the primacord firing lines detonating the blast. Travelling at 22,000 ft./sec., this white snake of fire travels to each hole, detonating the blasting agent. Before we get into the matter of blast security, let me locate our operation for those of you not acquainted with Minnesota's iron ranges and tell you something about our company.

Jan 1, 1969

By Frank J. Skudrzyk, Vladimir F. Petrov

In compliance with the current Russian environmental legis­lation, possible impact of industrial activities on the environment is restricted by acceptable limiting values (maximal allowable concentrations - MAC) of individual chemical substances in the natural environment - water, atmospheric air and soils. These norms have federal status and are valid for the whole territory of Russia. Disposal of the substances, for which no MAC is estab­lished, is forbidden by the law. Many gold mining companies use cyanide in precious metal recovery. This paper overviews the Russian experience in pro­tection of natural water reservoirs from technogenic impact of cyanic technologies. Major toxic compounds, contained in liquid and solid rejects from hydrometallurgical treatment of gold ore using cyanidation, are cyanides (CN), thiocyanates (SCN) and cyanide metal com­plexes. Unlike western classification of various cyanide types, in Russia any inorganic cyanide compounds (simple and in com­plexes with metals), with the exception of iron cyanide com­plexes, are considered toxic and the acceptable limiting value is established for them. MAC is 0.05 mg/I for fish reservoirs and 0.1 mg/I for drinking water. For iron cyanide complexes MAC is 0.15 mg/I for fish reservoirs and 0.25 mg/I for drinking water. Russian norms for thiocyanates are practically as rigid - the acceptable limiting value for them in fish reservoirs is at the level of 0.07mg/l (0.15 mg/I for potassium thiocyanate) and for drinking water - O. lmg/1. Norms for metals are established on the basis of total content regardless of the form in which they are present in water - as cations or complex ions. It should be noted, that in case several toxic compounds of the same limiting value (for cyanides, thiocyanates and base metals the limiting value is toxicological) are present in water. Their allowable concentra­tion is calculated as the sum of actual concentration of each com­pound, divided by the corresponding acceptable limiting value, with the result not to exceed one (compounding effect). Differences in cyanide classification and the necessity to include thiocyanates dictate different analytical methods. This, in a number of cases, results in certain discrepancies in analytical results. Until recently chlorination was used as a basic process of detox­ification of wastewaters. Calcium hypochlorite powder or hypochlorite pulp, prepared of lime milk and chlorine shipped to the plant, were used as a reagent. Chlorination is an efficient method: it allows to completely destroy plain and complex cyanide, in addition to iron complexes, and thiocyanates. A good example of high efficiency chlorination can be found at the Mnogovershinniy mill near the Okhotsk Sea located in the salmon spawning area, for which we designed an automated chlorination plant for tailings dam. Since plant start-up ten years ago, the required concentrations of cyanides and thiocyanates have been kept at the MAC level required by environmental regulatory agen­cies and no harmful affects on ichthyofauna has been reported. One major drawback of chlorination is high cost of the major reagent, as well as secondary contamination of detoxified waters by chlorides. Secondary contamination by chlorides becomes obvious in the course of detoxification of wastewaters of com­plex composition, which require increased reagent consumption. Recent changes in economic conditions in Russia caused the necessity to direct efforts to reduce the costs of precious metals recovery, and in particular, wastewater treatment. We have con­ducted certain work in this direction and obtained positive results. We hope that our experience described below will be of interest to other specialists particularly taking into account the current low gold prices.

Jan 1, 1998

By Sandeep Kumar Jeripotula, Govinda Raj Mandela, Aruna Manglapady

Dumper operators are frequently exposed to whole body vibration (WBV) in surface mines. Surface mining activities involve the amalgamation of comparatively high intensity of vibration and extended exposure durations. Efficient risk reduction mandates knowing of important phases of a task that poses a threat to health of dumper operators. So far in India very limited studies have been reported on WBV exposure with regard to surface mines. This paper evaluates WBV of dumper operators based on ISO 2631-1:1997 Standards and European Union (EU) Directive 2002 for different phases of job cycle. Six dumpers were considered for this study and the vibration measurements were made for all the four phases of the job cycle by placing the triaxial accelerometer on the operator’s seat-surface and at the seat-back, independently. The findings of the study revealed that the haulage task (loaded travel and empty travel) remains the chief contributor to vibration exposure according to seat-surface and seat-back measurements. Maximum frequency weighted root mean square (RMS) of 1.12 m/s2 and 1.09 m/s2 were reported for empty travel task for seat-surface and seat-back measurements, respectively. For seat-surface measurements based on RMS, Z axis remains as the dominant axis of vibration for all the dumpers during haulage task, whereas for seat-back measurements, the dominant axis varies between X and Y. Exposure action value (EAV) based on RMS has exceeded the threshold value of 0.5 m/s2 for all the dumpers during loaded travel and empty travel for seat-surface as well as for seat-back measurements.

By J. Kretschmann, K. van de Loo, J. Brune

In 2018, the German Federal government decided to phase-out the energy production using coal-fired power plants and to terminate lignite mining completely by 2038 at the latest. This decision will impact approximately 60,000 jobs. It will have an enormous impact on the socioeconomic development especially in all German lignite mining regions. To avoid economic and political friction, it is of utmost importance to achieve a sustainable transition towards a post-mining era and to offer residents in the mining districts perspectives for a good future that include adequate job opportunities. In this context, the German government is providing massive structural aids early on. As previous closure experiences from the German hard coal mining industry have shown, it takes at least a generation to overcome the effects of a strategic closing decision of this magnitude. Therefore, the planned closure process appears to be a long time at first glance. In fact, however, it is not.

Mar 2, 2022

By Gary Brieley

Until well into the 20th century, most construction work was performed under the auspices of a master builder or in a manner that would be described today as design-build. In addition, many civil engineers served as ?interns? under the tutelage of a master builder in order to learn how to design and construct a certain type of structure. This was certainly the case for tunneling projects with various individuals having been identified as tunneling experts as a result of successfully completed projects The master builder approach began to change in the early 1900s to a model that would be referred to today as design-bid-build. A design-bid-build approach to project procurement gives the owner more control over the final product and al-lows the contractor to know exactly what is expected of them before the work is constructed. As a result of this transition in project procurement, civil engineering schools placed a greater emphasis on the training of ?design? professionals. This article will document how the training of tunnel design professionals progressed within the United States. Although it is difficult to generalize about the hundreds of tunnels that were constructed in the first four decades of the 20th century, there is one project that stands out as having resulted in a university program related directly to tunneling and that is the Chicago Subway. During a visit to the United States in 1938, Dr. Karl Terzaghi met a student named Ralph Peck who was then studying at Harvard University in a pro-gram established by Arthur Casagrande. Shortly thereafter, Terzaghi traveled to Chicago for a lecture and was asked to consult on the Chicago subway project that was then under construction. The Chicago subway was being constructed in clay, and the owners were worried about possible settlements to nearby buildings. Terzaghi asked Peck to serve as his field engineer for that project. Thus was established one of the most productive relationships in the history of civil engineering in the United States. Peck, who would become Dr. Peck, moved to Chicago in 1939 to participate in an extensive research project that con-tinued until subway construction was halted in 1941 because of World War II. During that time, the cost of subway construction in Chicago was reduced substantially as a result of Peck?s observations and Terzaghi?s recommendations. In fact, it was reported that subway construction in Chicago cost less than one-half of similar projects in London even though the clay in London is considerably stiffer compared to Chicago. Upon the completion of his work on the Chicago Subway, Peck accepted a professorship with the University of Illinois in Champaign/Urbana.

Jun 1, 2010

By A. Peppas

Perlite is a naturally occurring siliceous rock, which can be expanded from four to twenty times its original volume when heated at a temperature close to its softening point. The expanded perlite is characterized by increased sound and thermal insulating properties. However, the conventionally expanded perlite products have high porosity and low mechanical properties that limit the range of their applications in the construction and chemical industry. The present work aims at the development of new closed porous microcellular material from perlite with enhanced mechanical and physical properties to be applied in new applications, like joint compounds, functional fillers for special paint types, special blasters and mortars, artificial marble. For the production of these new materials a vertical electrically heated furnace with six different heating zones and controlled gradient temperature profile was used. The effect of major process parameters, like temperature and air flow, on the quality of the produced materials was studied using Greek perlite from Milos Island. The quality of the new products was evaluated in terms of their bulk density, compression strength, water and oil absorption, surface area and pore volume. The experimental results show that the produced materials are characterised by improved mechanical and physical properties compared to the conventionally expanded perlite products.

Jan 1, 2006