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By Jiayao Wang, Jian Chen, Leiting Shen, Hongyang Wang, Zeping Cao, Ziru Wang

Large amounts of by-products, including coal gangue, circulating fluidized bed (CFB) slag, and coal fly ash (CFA), are generated during mining, washing and burning of high alumina coal (HAC). The stockpile of these by-products of HAC will cause the pollution of air, water and soil. Meanwhile, the unbalanced regional distribution of bauxite and alumina production has been a critical challenge for the sustainability of world alumina refineries, especially for China. Therefore, economical extraction of alumina from by-products of HAC not only resolves the environmental pollution problems caused by stockpile but also decreases the dependence degree of import bauxite in China. Considering the fact that powder alumina can only be produced by alkali methods, the alkali extraction of alumina from by-products of HAC is summarized in this paper. Based on the formation process of by-products of HAC, the principle, research status, and problem of existing methods were analyzed and discussed, as well as the forecast of research trend. The analyses indicate that simplex recovery of alumina from byproducts of HAC generates large amounts of leaching residue (red mud) with difficulty for disposing, while comprehensive extraction of alumina and silica meets the research trend for clean and high-value utilization.

Aug 25, 2023

By M. L. Leming

Introduction In the decades since silica gel was first identified in material exuding from cracked concrete, a great deal of research has been conducted regarding the chemical reactions between the alkalies found in portland cement and silica found in aggregates. The reaction is complex and one that is not yet completely predictable, especially from the point of view of developing specifications that are appropriate to all situations. This paper is not intended to be a rigorous review of the research findings but is an attempt to provide a simplified review of the mechanisms of the alkali-silica reaction (ASR), so that one can better understand the implications of the specifications, test results and effects on structures. In addition, the contractual relationships between the aggregate supplier and one of their major clients, the concrete supplier, will be examined with regard to the ASR. ASR basics Silica. Silica (silicon oxide) may exist in naturally occurring aggregates in various forms and in combination with a number of other elements. When the silica is completely crystalline, such as in quartz, it is chemically and mechanically stable. Quartz silica is impermeable and reacts only on the surface of the crystal, where the silicon and oxygen bonds are broken. Because the surface area per unit volume of most quartz is low, the reactivity is also low. Completely amorphous (noncrystalline) silica is, on the other hand, more porous and very reactive. The less "crystalline" the silica is in the aggregate, the more reactive. Silica that has melted and cooled quickly without recrystallizing, creating a glassy material (such as in certain volcanic aggregates), has a very low state of crystallization and will be much more reactive in an alkaline solution. Crystalline silica that has been transformed by heat and pressure may have a large quantity of strain energy stored in the crystal lattice. The presence of this higher energy will make the silica more likely to react. The "strained quartz" found in many metamorphic aggregates means that these aggregates are potentially susceptible to deleterious alkali silica reactivity, although the rate of reaction is typically much slower than with aggregates composed of or containing glassy or amorphous silicas. Another problem may exist with aggregates in which the silica is primarily crystalline. In aggregates such as chert, in which the silica exists as very fine crystals (i.e., crypto- or microcrystalline), the very high surface energies between the crystals contribute to alkali sensitivity. Therefore, the potential reactivity of an aggregate is seen to be a function of both the degree of crystallization of the silica in the aggregate and the amount of energy stored in the crystal structure, whether due to a large quantity of microcrystalline silica, a high strain energy stored in the crystals or some combination of these factors. The surface area per unit volume of the reactive silica will also affect the rate of reaction, because a larger surface area of reactive silica will have more opportunity to react. Obviously, the reactivity of the aggregate is also affected by the silica content. However, in this case, the results are not quite so obvious. A discussion of the effect of silica content will be postponed until after a discussion of the contribution of the cement paste. Paste characteristics. Hydrated portland cement is a very alkaline material with a pore solution pH typically in excess of 12. The alkaline environment of moist concrete provides an ideal place for noncrystalline or cryptocrystalline silica to react. However, not all alkalies are equal in their effects. Calcium compounds react with glassy silica to form calcium silicate hydrate, commonly abbreviated C-S-H a poorly crystalline material that can occur in several forms and chemical compositions. C-S-H was at one time called tobermorite gel, because it was chemically similar to the naturally occurring crystalline mineral tobermorite and because it had a gel-like (noncrystalline) structure when viewed under an optical microscope. The formation of C-S-H is the basis for both portland cement hydration and reaction with, for example, fly ash. C-S-H is relatively stable. Although drying will cause some shrinkage and rewetting will cause some expansion, the volume stability of the C-S-H is very good compared to the volume stability of most alkali silica gels. Alkali silica gels with high sodium contents, for example, are nonstable compared to C-S-H.

Jan 1, 1997

By M. L. Leming

The mechanisms of Alkali-Silica Reactivity (ASR) are briefly reviewed, test methods are examined, and typical specifications are discussed. In addition, views on responsibility of the aggregate supplier regarding specifications are presented.

Jan 1, 1995

By Xiaolong Bi, Shaohua Luo, Longjiao Chang, Shiyuan Cao, Jianan Liu

iliary agent was proposed. The mineralogical transformation and silicon extraction kinetics of laterite nickel ore in alkaline hydrothermal treatment were studied. The effects of reaction temperature (175 ~ 250℃), molar ratios of sodium hydroxide to ore (1.05 ~ 1.2:1), and laterite nickel ore particle size (44 ~ 178 μm) on the extraction ratio of silica were investigated by using the shrinking core model. The results show that the extraction ratio of silica increases with the increase of reaction temperature, sodium hydroxide to ore molar ratio, reaction time, and the decrease of raw ore particle size. The kinetic analysis shows that the separation of silica in laterite ore can be described by internal diffusion model. The apparent activation energy (Ea) of the reaction was 8.87 kJ mol− 1, and the kinetic modeling was established.

Dec 2, 2021

By P. N. H. Bhakta, X. P. V. Lei

The U.S. Bureau of Mines developed an alkaline oxidative pretreatment to increase the recovery of gold from refractory sulfide ores containing arsenopyrite (FeAsS) and/or pyrite (FeS2). Pretreatment of a low grade ore containing 0.4% FeAsS, 3.5% FeS2, and 2.74g/mt Au with 1.2m NaOH, 40 psig o2, 100° C, and 4 hr in a 2-L autoclave resulted in 94 to 96% sulfide oxidation. cyanidation of the pretreated residue resulted in 88% Au extraction compared to <20% Au extraction for untreated ore. Cyanide consumption was 0.25 kg NaCN per metric ton of ore. A flowsheet for treating sulfidic low-grade gold ore is proposed.

Jan 1, 1990

By Stanley Lefond

The health of the industrial minerals industry appears to be improving year by year. In fact, preliminary information suggests that only three commodities (asbestos, bromine, and sulfur-other) failed to show a production gain in 1984 over 1983. In 1983, 10 commodities failed to post gains and six remained constant. The total value of industrial mineral production in 1984 was $16.7 billion, up $1.4 billion from 1983. Cement, clays, gypsum, and crushed stone production increased. Since these are used in housing and construction, this suggests these industries are moving out of their recent doldrums. Barite and clay production also improved in 1984. Local US barite production, however, still has a long way to go to attain the 1981 high of 2.6 Mt (2.9 million st). Barite imports remain high. But they are not as high as the 1982 importation of 2 Mt (2.3 million st). Bentonite production in 1984 increased 20% in volume and 25% in value over the previous year. This suggests improvement in the drilling industry and an increase in demand for iron ore pelletizing grades. All in all, the industrial mineral industry is alive and well. And it shows signs of great improvement in the next few years. Many thanks to those industrial mineral technical committee members for their assistance in assembling this industrial minerals review: M. F. Dibble, H. W. Allen, G. H. Gallup, S. G. Ampian, D. W. L. Spry, H. G. Fleshman, and L. J. Czel.

Jan 5, 1985

By J. Humphrey

Introduction The weight of a Mining Truck can be affected by field modifications, the selection of items like tires, rims or even the conditions in which it operates. Truck performance and the compliance with a number of ISO standards, e.g. braking, steering and ROPS are dependent on truck weight. It is critical that truck owners understand the impact of changes in weight1. What makes this even more difficult for owners to evaluate is that there is no standard terminology or definitions for Mining Truck weights. This paper discusses and defines weight terminology, how it applies to performance and standards and the impact on the application of Mining Trucks.

Jan 1, 2007

By A. G. Yapo, T. W. Camm

"All-in sustaining cost is a metric used by mining companies to reflect the cost of gold mining in a consistent format useful to both investors and mining professionals. Cost reporting focused on the direct cost of mining and processing ore was summarized in the non-GAAP cash cost developed by the Gold Institute in 1996. In 2013, a group of mining companies, working with the World Gold Council, developed a more inclusive approach to reporting costs designed to solve the dilemma of showing a more comprehensive reflection of recurring costs involved in producing gold, without discouraging investors. INTRODUCTION Mining today plays a key role in the development of our civilization as a source of essential raw material and provider of essential fuels, producer of jobs, and a factor in support of the international balance of monetary payment (Camm, 2014). Professionals in mining locate, develop, design and manage ore deposits in an environmentally safe and profitable manner. As mineral deposits become increasingly scarce, new challenges face the industry. A current trend is to an increased emphasis on underground mining techniques for deeper deposits. Operations are safer today than before as companies understand better their work environment and the importance of mining responsibly. A continual challenge for the industry is accurately reflecting the costs and selling price of ore. An enduring characteristic of mining is the situation where the market typically determines the price of a commodity; the main control a company has on the bottom line is to control the cost of production. An attempt to bring light and clarity on the cost of their business will give a better idea to investors on the true profitability of the mining business. Gold producers face this struggle to accurately reflect the cost of production while also seeking to attract the interest of the investment community (Hill, 2013). In order to have a consistent format to report on their production costs, leading gold producers through their alliance inside the World Gold Council (WGC), worked on the adoption of a new cost framework: the All-in Sustaining Cost (AISC) and All-in Cost (AIC). Since 1996, the traditional cash cost reporting has focused only on the mining and processing costs incurred in mining an ounce of gold, which included the costs of goods sold (labor, energy, and consumables costs) and royalties (Table 1). But cash cost reporting ignores many important aspects, like sustaining capital, general and administrative expenses, and site rehabilitation at the end of the mine life (Whelan, 2013). The cash cost was used to attract many investors into the business. In fact the high gross margin (sales minus cash costs) has been promoted the past decades by the industry instead of the net or operating margin. As a result, even when the gold price was high, nearly $1900 per ounce in August 2011, gold producers were not reporting excessive profits in their cash flow / income statements, to the disappointment and incomprehension of investors (Milstead, 2014). The truth was simply that the other costs omitted in the traditional cash cost were reducing the apparent profits."

Jan 1, 2017

By A. G. Yapo, T. W. Camm

"Mining plays a key role in the development of modern civilization as a source of essential raw materials and provider of essential fuels, producer of jobs and a factor in support of the international balance of monetary payment (Camm, 2014). Professionals in mining locate, develop, design and manage ore deposits in an environmentally safe and profitable manner. As mineral deposits become increasingly scarce, new challenges face the industry. A current trend is to an increased emphasis on underground mining techniques for deeper deposits. Operations are safer now than before as companies understand better their work environment and the importance of mining responsibly.A continual challenge for the industry is accurately reflecting the costs and selling price of ore. An enduring characteristic of mining is the situation where the market typically determines the price of a commodity; the main control a company has on the bottom line is to control the cost of production.An attempt to bring light and clarity to the cost of their business will give a better idea to investors on the true profitability of the mining business. Gold producers face this struggle to accurately reflect the cost of production while also seeking to attract the interest of the investment community (Hill, 2013). In order to have a consistent format to report on their production costs, leading gold producers, through their alliance inside the World Gold Council (WGC), worked on the adoption of a new cost framework: the all-in sustaining cost (AISC) and all-in cost (AIC).Since 1996, the traditional cash cost reporting has focused only on the mining and processing costs incurred in mining an ounce of gold, which included the costs of goods sold (labor, energy, and consumables costs) and royalties (Table 1). But cash cost reporting ignores many important aspects, like sustaining capital, general and administrative expenses and site rehabilitation at the end of the mine life (Whelan, 2013). The cash cost was used to attract many investors into the business. In fact, the high gross margin (sales minus cash costs) has been promoted in past decades by the industry instead of the net or operating margin. As a result, even when the gold price was high, nearly $61/g ($1,900/oz) in August 2011, gold producers were not reporting excessive profits in their cash flow/income statements, to the disappointment and incomprehension of investors (Milstead, 2014). The truth was simply that the other costs omitted in the traditional cash cost were reducing the apparent profits.The disconnect led to a need for more accurate cost reporting in order to win back investor confidence and provide better understanding of gold mining economics. In 2012, the senior gold mining companies, including Gold Fields, Barrick Gold Corp. and Newmont Mining Corp., worked with the WGC to develop a new measure. This resulted in the June 2013 publication of the new framework AISC and AIC, which has been widely embraced by the sector since Jan. 1, 2014 (WGC, 2013).The adoption of the new cost template would have the dilemma of showing the real profitability of gold mine properties, which might alleviate taxes from governments and legislators, but it might also scare off investors toward more lucrative industries if not winning back their confidence."

Jan 9, 2017

By Shawn McWilliams, Aini Sun, Mike Lichte, Greg Colzani

The Allegheny County Sanitary Authority (ALCOSAN) adopted its Clean Water Plan (CWP) in May 2020, as part of a federal consent decree to comply with the USEPA’s Combined Sewer Overflow (CSO) Control Policy. Planned improvements include constructing a new regional storage/conveyance tunnel system, promoting green infrastructure/ source control, and expanding the treatment plant. Preliminary planning for the tunnel system was completed in October 2020. The Ohio River Tunnel (ORT) project is the first of three tunnel projects that make up the regional tunnel system. The ORT project began final design in 2021. This paper discusses the advancements made to the ORT preliminary planning concepts considering property availability, alignment optimization, tunnel boring machine evaluation, contract packaging and delivery schedules.

Jun 13, 2023

By Paul A. Roy

The North Shore Connector Project for the Port Authority of Allegheny County constructs twin Tunnel Boring Machine (TBM) tunnels through cohesive soils and rock beneath the Allegheny River and a narrow city street in Pittsburgh, PA. The tunnel alignment includes an historic building on shallow foundations, modern buildings on deep foundations, and an office building constructed directly over the alignment during the design of the tunnel sections. This paper provides an overview and update of the general site conditions, TBM tunnel design, and support of excavation for the TBM launching pit. Deformation limits, ground improvement, monitoring and mitigation plans are also discussed.

Jan 1, 2008

By S. P. Singh

To understand the intricate nature of blast damage and counter the associated problems, small-scale blasting experiments were performed on hydrostone blocks. Tests were then conducted during a drifting operation in a quartzite quarry. Blast damage was assessed by different techniques. On the basis of the experimental results, the effects of the energy partitioning characteristics of explosives on the damage were identified.

Jan 1, 1993

By S. P. Singh

In order to understand the intricate nature of blast damage mechanism and to counter the associated problems, small scale blasting experiments were performed on hydrostone, concrete and granite. This was followed by a 2.4 m x 2.7 m (8&apos;x 9&apos;) drifting operation in a quartzite quarry. Interior as well as exterior damage was assessed by different techniques. On the basis of the experimental results, the effect of explosive characteristics on the damage was examined.

Jan 1, 1992

By R. J. Snoby, P. Grotjohann

In processing heavy-mineral sands, the low feed concen¬tration and respective high value of the desired minerals require high-capacity production and sharp classification/ separation techniques to reduce the specific production costs. This paper describes the new allfux® separator, which can economically accomplish these criteria. The separator is a two-stage process that combines rising current and fluidized-bed technology. This allows for the treatment of ex¬tremely high mass flows in a single unit. This paper reports on test work performed on coal, iron ore and heavy minerals.

Jan 1, 2000

By P. Grotjohann

In processing heavy mineral sands, the low feed concentration and respective high value of the desired minerals require high capacity production and sharp classification/separation techniques to reduce the specific production costs. The allflux® separator, a new process system introduced to the heavy mineral industry, meets these criteria in an economical way. Its two-stage process, a combination of rising current and fluidized bed technology, allows the treatment of extremely high massflows in a single unit. Using concepts that have proven successful in processing concrete sands for many years, testwork in coal, iron ore, and heavy minerals looks very promising.

Jan 1, 1998

By Warren D. Stanford

The Alligator Ridge mine is a near-surface gold mine located in a remote area 113 km (70 miles) northwest of Ely, NV. The deposit was discovered in 1976 by a lone prospector working under a grubstake contract for Amselco Minerals Inc. Evaluation of mine potential proceeded quickly. Favorable drilling results led to feasibility and mine design studies by the end of 1978. Mine construction began in early 1980. By September of that year, the process plant was fully operational. The first gold was poured a few months later. Alligator Ridge is designed to produce 1.9 t (60,000 oz) of gold each year. The projected mine life, based on proven reserves, is to mid-1988. However, Amselco is actively conducting exploration nearby for additional reserves to extend the mine&apos;s life. Amselco, a subsidiary of the British Petroleum Co., is based in Denver, CO. The company is mine operator and jointly owns the project with Nerco Minerals Inc., a wholly-owned subsidiary of Pacific Power and Light. Alligator Ridge is Amselco&apos;s first US mining operation. Geology Alligator Ridge, so named because it appears in outline to be an alligator at rest, contains disseminated micron gold embedded in iron-streaked siltstones. Although definitive conclusions have not been drawn on age and origin, the gold ore bodies are probably young by geological standards. They were formed in a recent volcanic period still evidenced in parts of Nevada by geysers and hot springs. As these superheated solutions rose through the permeable siltstones, they deposited minerals in the rock and formed the present gold ore bodies. During 1977, an extensive soil geochemical sampling program with additional geologic mapping and outcrop sampling were conducted. The results generated several drill targets. Initial drilling was performed in November and December 1977, and ore grade mineralization was encountered in the first drill hole. The Alligator Ridge mine is unusual in relation to other and more recent western US mineral discoveries in that it occupies an area that had no previous mining history. The ore deposits are hosted in upper Paleozoic sedimentary rocks that consist predominantly of a thick carbonate sequence. The main ore host is the Devonian-Mississippian Pilot shale, which occurs locally as a sequence of thin bedded calcareous, carbonaceous siltstones and claystones. The maximum observed thickness of the Pilot section in the mine area is about 140 m (460 ft). Rocks in the Alligator Ridge area have been folded into a series of low amplitude anticlines and synclines that strike north-south and plunge to the south at about 20°, with limbs that dip nearly 20°. The folds have been truncated and deformed by later high-angle faults that generally strike northwest. Although multiple stages of movement are evident on the fault systems, the youngest period of activity is along the major northeast trend. The predominant structural pattern in the area is of the basin- and range-type high angle normal faults. Alligator Ridge is actually a horst block between two basin and range faults. Vantage Ore Deposits There are three principal ore deposits within the Vantage Basin and several smaller satellite mineralized areas. The three Vantage deposits are encompassed in a mineralized zone that covers an area 915 m (3,000 ft) long and 305 m (1,000 ft) wide. All mineralized zones have been outlined by more than 600 rotary drill holes, with an average depth of 150 m (500 ft). Mineralization occurs in both carbonaceous and oxidized rocks. The carbonaceous gold-bearing material is not amenable to current heap leaching practice. Therefore, only oxidized ores are now treated. The carbonaceous gold-bearing material is segregated and stockpiled as it is encountered during mining. The three ore bodies occur along a north-northeast strike, with mineralization becoming progressively deeper from north to south. The ore block dimen-

Jan 6, 1984

By M. J. Shulman

The exploration geologist is frequently confronted with the problem of allocating his resources, i.e., exploration effort, among various areas. Although geologic, financial, and logistic considerations influence the allocations, no objective criterion is usually given that determines the optimal allocation. Maximizing the expected gain in information, subject to the constraint of a limited exploration budget, is used as the objective criterion to allocate airborne reconnaissance effort. The information function, I(x), quantifies the expected gain in information, where x is the scale of exploration. To calculate the information function, the following probabilities are required: the probability that an area contains a deposit; the probability that an anomaly is produced by the target; and the probability that an anomaly is produced by a barren area (false signal). Alternatively, the barren areas can be replaced by other targets. To illustrate the allocation method, the optimal number of line kilometers, i.e., the optimal line spacing per area, is determined for an aeromagnetic survey for iron in Egypt.

Jan 1, 1987

By M. J. Shulman

The exploration geologist is frequently confronted with the problem of allocating his resources, i.e., exploration effort, among various areas. Although geologic, financial and logistic considerations influence the allocations, no objective criterion is usually given which determines the optimal allocation. Maximizing the gain in information, subject to the constraint of a limited exploration budget, is used as the objective criterion to allocate reconnaissance effort. The information function, I(x), quantifies the expected gain in information, where x is the scale of exploration. To calculate the information function the following data are necessary: 1. The probability that an area contains a target must be estimated. 2. For each scale of exploration, four probabilities must be estimated: the probability that an anomaly is produced by the target; the probability that an anomaly is not produced by the target; the probability that an anomaly is produced by a barren area (false signal); and the probability that an anomaly is not produced by a barren area. Alternatively, the barren area can be replaced by other targets. To illustrate the allocation model, the optimal number of line kilometers/line spacing per area is determined for an aeromagnetic survey for iron in Egypt.

Jan 1, 1985

By Thomas R. Kuesel

In traditional construction contracting practice, the owner allocated almost all risks to the contractor, saying in effect, "you deal with all construction problems and all third parties, and don&apos;t bother me." In this same tradition, the architect or engineer designed a structure in its finished condition, and if he thought about the construction problems that might be involved in building it, he was careful not to express any opinions on these matters in the contract documents. This feudal attitude fostered two results: 1. Contractors added high contingencies to their bids to cover the costs of risks. 2. Litigation of construction contract claims blossomed. Broadly, the owners lost--the courts reallocated many risks the owners thought they had laid on the contractor. Thoughtful owners and engineers recognized that owners were paying for risks twice --once in bid contingencies and a second time in court. Meanwhile, contractors were not getting rich; they were losing money on delays and disputes, and just about getting even (if they were lucky) in court. And construction law was becoming an increasingly lucrative field--for lawyers. Furthermore, with the growing influx of lawyers onto the construction scene, the owner-contractor-engineer relationship became increasingly an adversary one. The emphasis came to be on culpability rather than capability--who could be held responsible for breaching some contract clause, not who might find a solution to some common problem. This game was played with equal vigor by owners and contractors.

Jan 1, 1979

By John C. Braithwaite

Gold production commenced in New Zealand during the gold rush of 1861, and recovery to date is over 900 tonnes, almost 60% of which was alluvial. New Zealand pioneered development of bucket line dredges during the 1880&apos;s. The advent of the modern hydraulic excavator and increased gold price led to a resurgence in alluvial production with about one hundred plants in operation in 1988. The processing plants are mainly floating, with throughputs of 50-100m3/hr fed by backhoes of 20-40 tonne operating weight. Some larger plants with more sophisticated recovery systems have commenced over the last few years, with the largest using a 180 tonne backhoe.

Jan 1, 1989