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By Michelle Stokes, Alexandra Miller, Campbell McKenzie

"The ancestral Ringarooma River in northeast Tasmania has transported alluvial tin and other heavy minerals from their onshore source of stanniferous Devonian granites downstream into what is now Ringarooma Bay. Previous exploration work has demonstrated the presence of potentially economic tin mineralisation within the palaeochannels and terraces associated with the submerged river.The offshore tin resource lies directly on the seabed or with less than 2 m of overburden, and within 5 - 50 m water depths in the wider bay area. The main river channel continues offshore for at least 13 km, with high tin grades found within the palaeochannel but also dispersed across the sea floor as a sheet wash, a result of Quaternary sea level change reworking the placer deposits. This drowned portion of the coastal plain contains a continuation of rich tin leads as low gradient anastomosing channels, and has been delineated by marine seismic and drilling activity since the 1960s. Tin grades in the Tertiary and Quaternary alluvial profiles vary from 50 - 300 g/m3, with the highest concentrations in the coarser basal horizons. A previous offshore explorer estimated a resource of 194 Mm3 at 150 - 250 g/m3.Kenex Ltd created 3D models of the paleochannels and the mineralisation with the aim of better constraining the resource estimate and identifying additional depositional areas. The modelling was undertaken with the input of geophysical data, bathymetry and geochemical sampling of the seabed surface and from historic offshore drill holes. A prospectivity model covering Ringarooma Bay was produced to target tin-bearing gravels. Predictive maps were created to represent various features of the offshore mineral system, including assessing gradient changes in palaeochannels and their sinuosity. The model identifies areas with higher potential for alluvial tin mineralisation and will be used to focus the exploration programme over tenements currently held by Kenex Ltd."

Sep 1, 2014

By Joyce Lappin-Randolph

In 1977, Vertical Crater Retreat (VCR) Mining was developed at the Homestake Mine and by 1983 had become a fully integrated mining method contributing 60% to total underground production. VCR has proven successful for continuous ore blocks exceeding 55,100 tons (50,000 st) with dips greater than 60" and provides a productivity average of 39 tons (35 st) per man shift (tpms) which is 92% greater than Open Cut-and-Fill. Discontinuous ore bodies, small pods, or flat structures not amenable to bulk systems are mined with Mechanized Cut-and-Fill (MCF) and have been able to achieve a 32 tpms (29 st) average productivity. Small, low grade, remnant ore bodies were not economically viable with large scale bulk techniques and couldn't support the development required for a MCF system. As a result, Homestake began researching modified bulk mining methods to increase production rates and maintain safety, while lowering costs. A modified version of VCR with significantly diminished development was prototyped in an effort to reduce initial capital investment and expedite the production phase. This modified method is called Small Block Vertical Crater Retreat (S. B. VCR). Geology The Homestake Gold Mine is located in the northern Black Hills of South Dakota at Lead. Having been active since 1876, it now extends from the surface to the 2,440 m (8000 ft) level underground.

Jan 1, 1987

By C. Flores, R. Y. Wan, M. C. Fuerstenau, T. S. Jordan

Most oxidized manganiferous silver ores contain manganese associated with silver and are not amenable to conventional silver extraction methods, including direct standard cyanidation techniques. However, it is known that dissolution of the manganese might yield a suitable material from which silver can be recovered by conventional methods. In the segregation process, which involves heating the ore with a small quantity of salt and with a source of reducing agent to 680°C - 800°C, the silver is volatilized, migrates and is reduced to metallic silver particles. Conventional cyanide leaching is applied to the resulting calcine. Laboratory investigations have been conducted on a manganiferous silver ore analyzing 0.02 % Cu, 0.09 % Pb, 0.33 % Zn, 12.55 % Mn and 187 g/ton Ag to study the influence of roasting temperature and time, quantity of salt and quantity of coke on silver extraction by the application of segregation roasting followed by cyanidation. Cyanide leaching tests were carried out at room temperature on the segregated calcines produced by using an alkaline cyanide solution containing 2.0 lb/ton of NaCN at pH 11 for 72 hours. The results indicated that 97.8 % of silver extraction can be attained at 850°C, with 2.0 % salt, 1.0 % Coke and 30 minutes of roasting time.

Jan 1, 1993

By James C. Cobb

Middle Pennsylvanian (Desmoinesian) coals of certain areas of the Illinois and Forest City Basins contain epigenetic sphalerite and associated minerals in veins, clastic dikes, cleat, and other small-scale structural features. The presence of sphalerite in these coals records information about the geology of coals and coal basins, and represents a potential source for zinc as a byproduct of coal production. Origin of Sphalerite in Coal The origin of sphalerite in coal suggested by Cobb (1) involves sphalerite precipitation from zinc-bearing ?Na-Ca-Cl brines upon contact with sources of sulfur in the coal bed, e.g., pyrite, H2S, and organic sulfur. These brines were essentially at the temperature of the host coals as determined by fluid-inclusion thermometry and vitrinite-reflectance studies. The migration of these brines into coal beds may have been caused by compaction of sediments due to continued sediment loading of the coal basins. Zones of high permeability such as sandstones and the coals themselves presumably acted as conduits for the movement of the brines. The open spaces where sphalerite was deposited resulted from minor deformation associated with differential compaction and cleat formation enhanced by volume shrinkage during coalification.

Jan 1, 1982

By Juan C. Diaz, Juan P. Carmona, Manuel Z. Salgado, Oscar J. Restrepo

The “Teaching Kids” project is an educational initiative for young people and children from elementary schools. It is carried out by Mining, Geological, and Environmental Engineering students from the SME Student Chapter of the Universidad Nacional de Colombia, Medellin. The primary purpose of the Teaching Kids project is to share knowledge about geosciences and mineral resources in a didactic and attractive way, emphasizing the importance of identifying the use of minerals in daily life and responsible and sustainable mining in our society. Furthermore, this project aims to promote the importance of pursuing geoscience majors in the new generations and improve the mining industry’s public perception. Different methodologies related to early childhood education are implemented, such as gamification, in which the dynamics of games are adapted during the development of workshops to teach and learn in an active and motivated environment. Furthermore, the Montessori Method is used. It implements textbooks, sensory mineral boxes, and presentations to allow learning through experimentation itself (Montessori 2003). The implementation of this methodology has been successful; it has shown high engagement, participation, and retention of the basic concept of geoscience and mining.

Feb 1, 2025

Twenty field-scale tests were conducted in a 28 MW pulverized coal power plant in Healy, Alaska, to examine mill power consumption in relation to coal grind size. The intent in this field-scale study was to verify if grind size truly impacted power consumption by a detectable amount. The regression model developed from the data indicates that grind size does impact mill power consumption, with finer grinds consuming significantly more power than coarser grinds. However, other factors such as coal hardness (i.e., the lower the Hardgrove Grindability Index, or the harder the coal, the higher the power consumption) and mill throughput (i.e., the higher the throughput, the higher the power consumption) had to be included before the impact of grind size could be isolated. It was also observed that combining amperage and flow rate into a single parameter, i.e., specific amperage, hurt modeling. Cost analysis based on the regression model indicate a power savings of $19,972 per year if the coal were ground to 50% passing 76 mm rather than the industry standard of 70% passing 76 mm. The study also demonstrated that size reduction constituted a significant portion of the power consumption.

Jan 1, 2008

Researchers at National Institute for Occupational Safety and Health (NIOSH) are investigating how fiber-reinforced shotcrete mix designs can be extrapolated from proven designs employing wire mesh. This paper explains the results of round determinate panel tests and relates the flexural strength and toughness of fiber-reinforced shotcrete to known energy absorbing properties of wire mesh. The energy absorbed with central deflection is strongly influenced by the amount of fibres. The higher the energy absorption the more load cracked shotcrete can support. Two types of fiber-reinforced shotcrete were investigated, one with steel fiber and another with polyfiber. The residual load supported in Round Determinate Panel Tests can be matched with the strength of wire mesh, thus providing equivalent bag strength values for fiber reinforced shotcrete panels. There is also evidence of a panel crack width comparison to the load holding capabilities of the fiber in the shotcrete mixes. In practice, this provides designers with a method for comparing the ground support provided by fiber-reinforced shotcrete with that supplied by wire mesh.

Jan 1, 2010

By Peter Cammack

Where raw coal from a mine is treated in dense medium separators ash in the washed product is generally very consistent, provided control of the medium suspension is maintained at a given specific gravity. When, however, the washing process is a Baum jig or other similar apparatus, making a separation at rather arbitrary gravities, the control of the product ash is less accurate, particularly in those cases where the design capacity of the washbox is exceeded by the load of high ash fines. In either of these cases an instantaneous measurement of ash while not essential would be desirable, to check the quality of the washed product and provide operator or management with instantaneous warning of changes in ash. Nearly 60% of all British coal mined goes for electricity generation, to burn at 17% ash, and since the overall average ash content of raw coal as mined is about 30% and varies within a range of 18 ? 40%, incombustible material has to be removed. The ash specification could be met either by total washing, or by washing part and blending the clean coal produced with the remaining untreated coal. Some plants use a straight tonnage split, but generally speaking in Britain it has been found more economical to screen and wash the oversize only. In either case for effective quality control in blending an instantaneous determination of the ash content of the product as it is made has been found essential, since standard ash determination by pyrolysis methods is lengthy and provides information too late to be used in the control of plants blending at the rate of 1000 ton/h.

Jan 1, 1976

By David J. Collins

The emergence of activated charcoal adsorption as the most popular recovery method for precious metals, has led to numerous innovations aimed at increasing the efficiency of the process. This article describes a change in traditional charcoal transfer methods which will aid in reducing charcoal attrition losses. Studies have shown that significant charcoal attrition takes place during transfer, be it when using airlifts or centrifugal pumps. Tests conducted at Pinson Mines indicated a 4 to 8% loss to the minus 20 mesh fraction of charcoal after three (3) hours of pumping charcoal. Tests conducted while the author was at Jerritt Canyon indicated that charcoal transfer was a major contributor to charcoal losses; a decrease in the amount of coarse charcoal (plus 12 mesh) and an increase in the amount of finer charcoal (minus 16 plus 20 mesh) was noted as charcoal was moved to the head of the adsorption circuit.

Jan 1, 1998

By Byron M. Jones

The use of computers in system analysis is well established. Analog computers have been used for this purpose since about 1940. As the power of digital computers increased and their cost decreased, much of the analysis formerly done by analog computers has been diverted to digital computers. The mathematical foundation for system analysis was laid between the years 1700 and 1900. In the 1930?s, telephone repeater amplifiers were designed using systems analysis techniques. From 1940 to 1960 systems were analyzed using either direct simulation or LaPlace transforms. Since 1960 analytical methods have been expanded to include linear vector space theory. All of these methods are being used to analyze the dynamic behavior of mining machinery.

Jan 1, 1974

By D. Kruse, M. Sanaei

"3D finite element models of the Segmentally Lined Shaft (SLS) structure are simulated as means of numerical analyses of the system’s structural behavior. Top-down constructed rings, comprised of precast concrete segments, create a large diameter, relatively shallow underground space that can be utilized for various applications. To further investigate the effects of soil conditions and different loadings on the shaft structure, the FE model was run under various boundary conditions. Simulations include a) effects of various soil layers on the SLS, including a circumferential boundary of modified ground, b) effects of various soil layers on the SLS without any ground modification, c) Seismic analysis of the SLS with ground modification and d) Seismic analysis of the SLS without any ground modification. Comparing the analyses outcomes emphasizes the significance of the inclusion of the ground modification boundary in the structural performance of the SLS. INTRODUCTION TO SLS Underground structures are classically built rectangular in shape, which normally requires a two-step construction process beginning with installation of temporary shoring to support earth loads during the excavation, followed by the construction of the permanent structure. Attractive and practical alternatives are circular shafts referred to as segmentally lined shafts (SLS). The structure consists of a stacked series of rings formed from an assemblage of precast concrete segments. Top-down constructed systems of large diameter, relatively shallow SLS structures provide both temporary earth support during excavation and permanent structural support for many civil and building applications. The circular shafts sustain the lateral earth pressure mainly through hoop-stress mechanism, resulting in improved stability and structural efficiency. Cylindrical shell structures with large diameter to wall thickness ratios are prone to buckling under external pressure. In typical designs of small diameter shafts and tunnel linings with small diameter to wall thickness ratios, nonlinear buckling analysis (i.e., nonlinear geometric analysis) is usually not considered, since the buckling capacities for those structures are much higher than typical pressures encountered at their design depths. With an economically viable wall thickness, buckling becomes a critical issue, which should be addressed, for circular shafts with very large diameters. In the design and construction of the SLS, the stability of the structure can be improved by modifying the soil surrounding the circumference of the shaft to a limited thickness and to about 10 ft below the finished shaft structure. This thick wall of soil mixed with cement creates a composite integrated structure while serving additional purposes such as ground control and ground water seepage cutoff."

Jan 1, 2016

By J. E. deMasi

Over the past 12 years, Exxon Coal U.S.A., Inc. has shipped over 150 million tons of coal from two mines, Rawhide and Caballo, located in the Gillette, Wyoming, area. These mines are operated by The Carter Mining Company, a division of Exxon Coal. Shipments have moved to more than 25 electric utility plants in the west, midwest, southwest, and south. The customer plants have represented a wide variety of configurations, sizes. design criteria, emission standards, and operations in different parts of the country. We have learned a great deal about the performance of Gillette area coals in utility power plants during this period. This paper covers some of the highlights of Exxon's experience with these coals in customer plants. I will focus specifically on things mining engineers may be able to do to make the product better for the customer's use.

Jan 1, 1989

By VIVEK KUMAR HIMANSHU, PK SINGH, AK MISHRA, MP ROY, RAVI SHANKAR

Underground blasting has many challenges. The primary aim of blast designers is to optimize drilling and blasting parameters to deal with the associated challenges. Optimizing these parameters is currently based on various rules of thumb, which have many site-specific limitations. Accordingly, computation of these parameters using empirical rock fragmentation predictors can be useful for blast designers. This paper presents the results of work on burden-spacing determination by back-calculation from the empirical Kuz-Ram model for underground stope ring blasting.

Raises are widely constructed underground in hard rock mining for ventilation, material transport or emergency escape. The four major raise excavation methods, Drop Raise, Conventional, Alimak and Raise Bore can be divided into two categories from ground control point of view, one ground support can be installed during excavation, the other not. Excavation method must be chosen carefully to keep the raise wall in stable state during excavation and make sure enough rock stand-up time to install ground support if needed. If rock quality is permitted and there is no strict space limitation, raise bore method which is the only method that ground support can not be installed after the whole excavation is finished should be considered first because it is faster, cheaper, safer and less disturbance to the hosting rock. Support may or may not be needed depends on the purpose of the raise and rock quality. In high quality hosting rocks, if the raise is only for ventilation or material transfer, support may be not needed. If it is for emergency escape or escape and ventilation, which provide or require personnel access, the whole raise must be supported either in high or low quality rock. Based on on site data collection, construction and raise utilization, this paper gave out the rule of thumb how to decide an excavation method. After purpose of the raise, required raise diameter (size) and raise site options being known, geotechnical data collection is the next important step in a raise project.

Jan 1, 2011

By Paul D. Tomlingson

Part one of this two-part series covers conceptualizing and developing a maintenance information system. It explains what information is necessary to manage such a system. Next month, part two will discuss using this type of system with administrative information, including error and absentee reports as well as open work files. Introduction There is no doubt that quality, timely, and accurate information can make a solid contribution to maintenance cost reduction objectives. Yet, despite obvious benefits, methods being used to acquire information systems are proving costly, frustrating, and often unsuccessful. Those needing the information are disappointed. Mine managers, hoping to reduce costs with quality information, are instead seeing no system, no savings, and massive spending on information endeavors of questionable benefit. Options Any software vendor will happily sell you his program. Numerous mining organizations, having "gone to the cleaners" themselves, will gladly make their programs available to help cover huge trial and error development costs. Any package can only be a generalization. Any program bought from some other organization must undergo numerous modifications to make it work properly. In the process the initial cost is doubled. Many mining maintenance organizations do not know how to go about the task of conceptualizing, developing, installing, and effectively using a maintenance management information system. Consequently, many have hedged their primary responsibility of specifying what information they want, how they will get it, and how they will use it effectively. Into this void have jumped many who claim they can help. But some may not understand the special information needs of maintenance in the mining industry. By default, the whole scene of maintenance information systems has become confused and in need of clarification. A Starting Point Four broad phases are used to organize the steps by which maintenance acquires an effective maintenance management information system and initiates its use. Conceptualization is an identification of needs, factors that influence development, and an assessment of support for the system. Development is a plan of action for bringing the conceptualized information system to life. Consideration is given to the practical aspects of collecting field data, processing it, and converting it into useful information. Implementation consists of those actions by which the newly developed system is integrated into the organization and put in the hands of its personnel so that its value can be derived. Use addresses the means by which personnel use the information to accomplish maintenance improvement objectives. These phases are preceded by establishing the need for the information system. They are followed by a requirement to measure its success (Fig. 1). Conceptualizing the Information System Responsibilities - The information system user must acquire the system best suited for its use. A step-by-step process is essential to avoid many serious problems than can easily occur. The most important step is to clearly identify its objectives and lay out a course of action to achieve those objectives. The major reason for the failure to achieve information objectives is not carrying out this responsibility. Maintenance cannot delegate the task to data processing. It can obtain technical assistance but it must retain responsibility. Nor can maintenance purchase

Jan 7, 1985

By T. M. Barczak

Pumpable roof supports provide an alternative approach to secondary support in underground mining. Unlike all other supports that are either partially or fully prefabricated prior to being transported into the mine, the pumpable support is fabricated in place in the mine entry. This reduces the underground material handling efforts and thus the injuries historically associated with in-mine support construction. On-site fabrication also facilitates application of the support in areas that are inaccessible to transportation equipment such as scoops or rail cars, making it ideal for many bleeder applications. One of the main advantages of the pumpable support is that it fully bridges from the mine floor to the roof, thereby eliminating the requirement of ?topping off? the support with wooden wedges or crib blocks that soften most other support responses. This report examines the development of modern pumpable roof support technology and provides a full description of the performance capabilities of each of the support products now on the market.

Jan 1, 2008

By David A. Lindsey

In this paper, we present a physiographic classification of gravel deposits, identify some field measures of aggregate quality, and describe sampling strategies for mapping aggregate quality in the Front Range Urban Corridor of Colorado. Gravel occurs in four types of deposits along the Front Range of Colorado: (1) piedmont alluvial fans, (2) high dissected terraces, (3) high (continuous) terraces, and (4) floodplains and low terraces. The four deposit types are the basis for definition of gravel-deposit models, which differ in geologic environment, deposit characteristics, deposit size, environmental impacts of mining, and post-mining use. Of the four types, floodplains and low-terrace deposits have been exploited most for gravel. High terraces also have been mined. Deposits of high dissected terraces and dissected alluvial fans have produced minor amounts of gravel, mostly for use as local fill. Studies to identify useful field measures of aggregate quality and to determine the appropriate scale for sampling were conducted on gravel deposits beneath the flood-plain and low terraces of the South Platte River north of Denver and the Cache la Poudre River between Ft. Collins and Greeley. Gravel deposits of the South Platte were selected for study because they represent the last major resource of gravel for aggregate in the Denver metropolitan area. The Cache la Poudre valley is the primary source of gravel aggregate for rapidly urbanizing areas around Ft. Collins and Greeley. Of all the field measures of gravel quality, the most important is particle size. Various parameters that measure particle size were investigated, but the easiest to determine, and the most useful to the aggregate industry, are measures of the proportion of coarse sizes. Particle size varies widely in gravels of the urban corridor. Gravel lithology, particularly the presence of deleterious particles such as reactive volcanic rocks and decomposed rocks, must be determined to assess aggregate quality. Studies of South Platte and Cache la Poudre gravels have not revealed large proportions of deleterious lithologies. Studies of particle shape revealed only small numbers of physically weak shapes in both the South Platte and Cache la Poudre gravels. Particle shape does not appear to vary from place to place in the gravels. Rounding, or the ab¬sence of angular corners, may play a role in the tendency of loose gravel to yield under load. South Platte and Cache la Poudre gravels are rounded, and rounding tends to increase upstream. Before the quality of gravel in a valley can be assessed, the stratigraphy of the gravel must be known because it affects sample design. If only a single gravel layer is to be studied, only the thickness of the gravel must be known before sampling. If, however, more than one layer of gravel-distinguished by particle size, sorting, or lithology-is present, sampling must take into account the thickness and distribution of each layer. For example, three gravel layers of different particle size underlie the floodplain and low terraces of the South Platte. The tributary Cache la Poudre, on the other hand, contains gravel layers that can be distinguished only locally and vary slightly in particle size. Sampling experiments were conducted on gravel bars in the South Platte River and in gravel pits on the floodplain and low terraces of the South Platte and Cache la Poudre Rivers. Experimental results indicate that, even where sample error is large, regional and stratigraphic variation may be measured if it is large relative to sample error. Using vertical trench samples weighing an average of 40-90 pounds, down-stream decrease in coarse particle size was mapped for Cache la Poudre gravel, and differences among superposed gravel beds were measured for South Platte gravel.

Jan 1, 1999

By Dale R. Ralston, Roy E. Williams, Gerry V. Winter, George L. Bloomsburg

The literature on four different topics is re¬viewed herein for purposes of mathematical mod¬eling of mine water inflow. The first of the topics reviewed is modeling of fissured or fractured ma¬terials; the second is general Darcy based flow models; the third is field methods for determining fracture flow properties; and the fourth is methods used presently for determining mine water inflows. The four topics are considered in the foregoing order. FRACTURE FLOW MODEL Two basic types of fracture flow models have been developed. The first type uses various tech¬niques for space averaging to obtain the equations. Systems are considered in which the porous media properties vary smoothly enough and the fracturing is sufficiently profuse and well distributed that the locally averaged properties are meaningful when viewed on the macroscopic scale. The final result is that a coefficient is used which is similar to saturated hydraulic conductivity and in many cases, simply is hydraulic conductivity. In other cases, the coefficient is apparent hydraulic conductivity be¬cause the response from flow in the fractures is more rapid than flow in the pore spaces. Faust and Mercer (1980) refers to this method as the contin¬uum approach. Some of the papers on this type of problem are by Duguid (1973), Verner et al. (1974), Owili-Eger (1975), Duguid and Abel (1974), duPrey and Weill (1974), and O'Neill (1978). Duguid and Lee (1977) also considered heat flow in the fluid and the porous medium. These papers all result in various types of computer programs. Some papers on this topic that do not result in computer programs are by Snow (1968, 1969) and Streltsova (1976). Some of the foregoing articles consider con¬solidation of the porous media and the resulting effect on hydraulic conductivity. Barenblatt et al. (1960) developed an analytical solution for fracture flow and discussed the time that is involved in the drainage process and the effect that fracture flow has on the drainage time. The second type of fracture flow model con¬siders the width of the fractures as a function of the pressure in the field. Faust and Mercer (1980) refers to this method as the discontinuum approach. This approach often requires two finite element programs that consider the stress in the material and the flow in the fractures separately. The pro¬grams are then linked to arrive at the final solution. Some of the articles that consider the interrela¬tionship between pressure and the size of the frac¬ture but do not use computer solutions are Gringarten et al. (1975), Narasimhan and Palen (1979), and Witherspoon et al. (1979). Papers that use a linked computer program between stress and flow are by Ayatollahi (1978), Gale et al. (1974), and Noorishad et al. (1971). Ayatollahi's program is primarily for the petroleum industry because it does not consider the effect of gravity. Ayatollahi assumes that pressure effects are very large in com¬parison to gravity effects. This assumption would apply only to very deep aquifers. Articles that consider fracture flow on a more applied basis are by Wittke et al. (1972), who con¬siders that the flow is entirely through fissures and negligible through the pores of the rock. Gringarten and Witherspoon (1972) developed type curves that may be used for analysis of fracture flow systems; the curves are based on the assumption that it is possible to distinguish between aquifers with hor¬izontal and vertical fractures and that it is possible to analyze the system as an equivalent anisotropic homogeneous porous medium with a single fracture with much higher permeability. DARCY FLOW MODELS The Darcy flow models of greatest interest to mine water inflow prediction are those which allow

Jan 1, 1986

By R. Mensah-Biney

The NC State University Minerals Research Laboratory (MRL) and Waste Reduction Partners (WRP) of the Land of Sky Regional Council joined efforts in 2000 to initiate a technically sound and practical program for the management of high-volume coal combustion by-products (CCBs) in North Carolina. The accumulation of CCBs from coal burning boilers throughout the state of North Carolina posed a substantial storage problem, and the area was overripe for an effective management program, which would be environmentally sustainable. In particular, the public utility generators had filled storage ponds on their properties, and the storage overload had grown to critical proportions. Much the same situation existed for paper mill biosolids, which were stored on site in landfill cells along with daily output of CCBs from the mill boilers. A conversion process via the patented pyro-process12 (US Patent No. 5,342,442) to produce synthetic light weight aggregates (LWA) from CCBs and paper mill sludge was conceived to process large quantities of both these waste materials. MRL and WRP initiated and formed a consortium that brought together academia, private industry and state agencies to evaluate the production of LWA by the pyro-process. The industry partners included representatives from the power companies, industrial ash generators, expediters for coal ash products, as well as concrete block manufacturers. It was important to welcome interested parties from not only the western North Carolina area and other parts of the state but also from neighboring states including Tennessee, South Carolina and Georgia. Membership of this consortium evolved during the intervening years to include the following participants and supporters: Progress Energy Carolinas; Duke Energy; Santee Cooper; Full Circle Solutions; Land-of-Sky Regional Council; NC Department of Pollution Prevention and Environmental Assistance; Ecusta Business Development Center; Blue Ridge Paper Products; Jackson Paper and Manufacturing Company; Miller Perlite; Appalachian Products; General Shale Brick; Metromont Materials; Small Business Technology Development Center of the University of North Carolina system and North Carolina State University The initial development program conducted at the Minerals Research Laboratory (MRL) was to formulate an acceptable LWA product, which fulfilled user specifications for light weight concrete block and structural concrete application. Support work and program coordination efforts were furnished by retired technical volunteers in WRP. The work advanced steadily, using proven technologies well established in the mineral industry, to generate a very satisfactory LWA. The consortium then concluded that a more comprehensive CCB conversion program would have more appeal for full scale manufacture and commercialization, if a variety of products from CCB separation were generated. This product assortment would include bottom ash, low carbon fly ash, recovered carbon of high purity, as well as the synthetic LWA. The bottom ash would serve the concrete block market, the fly ash was in demand for ready-mix concrete, and the high carbon product could be pelletized and used as a fuel for reburn or by the steel industry, and the LWA was a sought-after component for light weight concrete applications. After scouting all these potential markets and finding them to be viable, the consortium then inaugurated an integrated pilot plant program for the CCB separation and conversion. The plan was organized in three (3) parts: (1) Phase I ? bench scale evaluation studies (2) Phase II continuous pilot plant evaluation and (3) Phase III ? conceptual commercial plant design including marketing efforts and attraction of business entrepreneurs to build a full scale manufacturing plant. Phase II would serve to validate the process in a continuous mode and produce substantial quantities of products for preliminary marketing efforts and for demonstration-of-use purposes. The consortium agreed to the name, CAROLINA ASH PRODUCTS, (CAP), for the integrated pilot plant program. The products generated might be designated with the CAP label as: bottom ash would be named CAP Granules, low carbon fly ash would become CAP Ash, recovered high carbon product would be CAP Carbon, and LWA would have the name CAP Stone. Phase II of the program processed 20 tons (18 t) of ponded ash from Progress Energy storage at a rate of 600 lb (271 kg) of raw ash per hour with favorable results. PRELIMINARY STUDIES Prior to committing laboratory research and development effort as well as support and coordination activities to this program, it was necessary to determine (1) the level of need for a freshly launched CCB reutilization program in this state and (2) what degree of versatility was necessary for such a process. State agency records and a survey of recent boiler operations indicated that in the state of North Carolina at least 77 facilities manage CCBs from their boiler operations. Despite continuing development efforts in more eastern parts of the state, the use of CCBs for commercial applications has not increased to a level which alleviates the need to store vast quantities in private monofills on the generator?s property. More than 1.25 million tons (1.13 million t) of CCBs are landfilled in NC annually, with 300,000 tons (271,985 t) per year generated in western NC alone. Many different boiler types, which span both very old units and those that are modern and efficient, were to be found. These included stoker-fired units, pulverized coal boilers, slag-tap furnaces, and fluidized bed combustion boilers covering a range of sizes. Any systems designed to separate CCB components from all these sources and convert them to useful secondary products would need broad processing latitude and flexibility. Up to the present there has been a paucity of research done in the western part of the state to find productive alternatives to storage in landfills. With tipping fees in our largest landfill now approaching $40 per ton ($44 per t) and escalating transportation fees (about $200 per truckload up to 40 tons, traveling a distance of 25 miles), the problem has become urgent both economically and ecologically. A well-designed, integrated wet process for CCB separation into value-added products had much potential to be less expensive than landfilling as well as to provide saleable materials with acceptable profit margins. These preliminary investigations also revealed that other major waste streams, in particular paper mill sludge and municipal and animal waste biosolids were important candidates for priority attention. Since these biosolids could furnish the organic component of a synthetic LWA product, they could be consumed as part of the same program. This added interest value to a growing list of partners to support and participate in the program.

Jan 1, 2009

By Staff

Minerals contribute to U.S. gross domestic product (GDP) at several levels - from mining and processing to the manufacturing of finished products. In 2010, the estimated real GDP of the United States increased by 2.8 percent compared with 2009 and the estimated nominal GDP was about $14.6 trillion (Table 1).Trends in various sectors of the domestic economy are often rejected in mineral production and consumption rates. For instance, continued declines in the construction industry during 2010 were rejected in further reductions in the production and consumption of cement, construction sand and gravel, crushed stone and gypsum, which are used almost exclusively in construction. Performances in other sectors were mixed and less easily characterized. Recovery from the economic decline of 2008-2009 became apparent in 2010, as prices for many mineral commodities continued to rise with increasing demand for those materials or the products in which they are found.

Jan 1, 2011