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By I Zulkarnain, H Permana, R A. Binns

Through an ambitious but relatively low-cost program of marine fieldwork, laboratory investigations and technology-transfer and training activities, three Indonesia-Australia-led marine expeditions were undertaken aboard KR Baruna Jaya VIII between 2001 and 2003. These IASSHA (Indonesia-Australia Survey for Submarine Hydrothermal Activity) cruises have sought to discover and investigate a variety of potential ore forming hydrothermal systems in a range of tectonic settings. All cruises have been successful, both scientifically and from the point of view of training, creation of capabilities and capacity building for such research in Indonesia. Over 60 scientists and technicians from Indonesian and Australian institutions and agencies have been involved. Three new sites and a possible fourth site of hydrothermal activity were discovered in the Sangihe arc in northern Sulawesi. Surveys in the Tomini basin tested a hypothesis based on previous data which suggested this might be an isolated anoxic, brine-filled basin over 2000 m deep where igneous heat sources existed to generate hydrothermal mineralisation. The bay, however, was found to be open to adjacent deep ocean circulation, and there was no evidence of massive base metal sulfides. Subdued evidence of hydrothermal activity was found in the Sunda Strait associated with the famous Krakatau volcano and the extension of the seismically active Semangko Fault. The BANDAMIN program (Indonesia-Germany) covered a portion of the Banda arc in eastern Indonesia, and also found evidence of recent hydrothermal activity and epithermal sulfide mineralisation.

Jan 1, 2004

A series of petrological studies were carried out on the characteristics of alteration and mineralisation in mainly structural-controlled (Deep Star, Meikle, Deep Post) and predominantly lithological-controlled (Post-Betze-Screamer and West Leeville) gold deposits in the northern district of the Carlin trend, Nevada. Alteration and mineralisation in these deposits are hosted in a sequence of calcareous clastic units of the Devonian Popovich Formation, into which have been emplaced a number of Jurassic intrusions, and syn- to post-mineral Eocene dikes. Four hydrothermal events have been recognised in these deposits: an initial Devonian base metal system and early diagenesis; a Mississippian stage of alteration in conjunction with burial metamorphism; contact and hydrothermal alteration and base metal-gold mineralisation associated with the emplacement of the Jurassic intrusions; and a Carlin-style gold system related to Eocene magmatism.

Jan 1, 2004

By C. S. Giggins, F. S. Pettit

The oxidation properties of Ni-Cr alloys with fine grains, coarse grains, and deformed surface layers have been studied at temperatures of 900" and 1100°C in 0.1 atm of oxygen. The oxidation rates of alloys containing between 10 and 30 wt pct Cr have been found to be dependent upon the grain size of the alloy. Finegrained alloys had smaller oxidation rates than coarsegvained alloys because of the selective oxidation of chromium at alloy grain boundaries. In this compositional range alloys with deformed surface layers behaved similar to fine-grained alloys due to recrys-tallization of the deformed surface layer. In the preceding paper1 it was found that during the oxidation of Ni-Cr alloys, the volume fraction of precipitated Cr2O3 could be greater at alloy grain boundaries than at other areas of the alloy surface. In the case of alloys with chromium concentrations equal to or greater than 30 pct,* the volume fraction of Cr2O3 *AIL compositions are given as weight percent unless specified otherwise. precipitated at grain boundaries and within grains on the alloy surface both exceeded the critical amount required for lateral growth of the Cr2O3 particles and the surfaces of these alloys were completely covered with a continuous, external layer of Cr203 during oxidation. However, in the case of alloys with chromium concentrations between approximately 5 to 30 pct, the volume fraction of precipitated Cr2O3 exceeded the critical value required for external scale formation only at grain boundaries.but not within the interior of the grains. Consequently, the surfaces of these alloys had external scales of Cr3O3 over the grain boundaries but internal Cr2O3 subscales with external scales of NiO away from the grain boundaries. Under these latter conditions, it was found that chromium could diffuse laterally in the alloy from those areas covered with an external layer of Cr2O3, i.e., grain boundaries, to areas where the Cr2O3 was present as a subscale. This diffusion of chromium resulted in an increase in the volume fraction of Cr2O3 precipitated in the sub-scale zone and continuous layers of Cr2O3 could be formed at the subscale front in these regions. For the alloys used in the previous studies,' continuous layers of Cr2O3 were formed on Ni-20Cr alloys in the subscale regions after approximately 30 hr of oxidation at 900°C. For shorter periods of oxidation, the Cr2O3 layer was semicontinuous with the continuous portion at the subscale front emanating from points where the Cr2O3 had been formed as an external scale over alloy grain boundaries. Some lateral growth of a Cr2O3 layer in the subscale region was observed on Ni-15Cr and even Ni-10Cr alloys but this layer was never continuous after 30 hr of oxidation. These results indicate that the selective oxidation of chromium in Ni-Cr alloys with chromium contents between 5 to 30 pct may be dependent upon the grain size of the alloy. Fine-grained specimens in this compositional range should have a larger fraction of the surface covered with external Cr2O3 than coarsegrained specimens and the subscale areas required to be sealed via lateral diffusion of chromium should be smaller. It is therefore to be expected that a continuous layer of Cr2O3 can be formed on alloys in this compositional range after short periods of oxidation providing the alloy grain-size is sufficiently small. bo studieS2,3 have established that the oxidation behavior of alloys can be significantly influenced by pretreatments which produce mechanically deformed surfaces. It has been found that deformed surfaces usually promote the selective oxidation of elements in alloys and it is believed that these effects are due to rapid diffusion of elements in the deformed layer. In view of the previous results,' which showed that alloy grain boundaries may play an important role in the selective oxidation of chromium in Ni-Cr alloys, deformed surfaces may promote the selective oxidation of elements in alloys as a result of the numerous grain boundaries formed on the alloy surfaces via recrys-tallization during heating to the oxidation temperature. The purpose of the present studies was to determine the effect of alloy grain size and surface deformation on the selective oxidation of chromium in Ni-Cr alloys at temperatures of 900" and 1100°C in 0.1 atm of oxygen. EXPERIMENTAL The average grain diameter of the alloys used in the previous studies1 was not less than 0.04 mm and alloys with compositions between 5 and 30 pct chromium had average grain diameters between 0.04 and 0.14 mm. Since the oxidation kinetics were already available for these relatively coarse-grained alloys, it was desirable to use these same alloys in the present studies. The surfaces of the alloys listed in Table I of the previous paper were deformed by using a Model F S.S. White Industrial Airbrasive Unit, which delivered a controlled mixture of 25 µ Al2O3 particles in a stream of dry air at high velocity against the surface of a specimen. The amount of surface deformation produced by this treatment was not determined but a re-crystallized layer about 15 µ thick was formed upon annealing deformed specimens. The grain size at the surface of the specimens was reduced to an average grain diameter of 0.01 mm by annealing the deformed specimens, i.e., grit-blasted,

Jan 1, 1970

By M Fishwick Tapia

This paper was prepared and translated from the final report of the investigation into the Codelco Chile Salvador DivisionÆs air blast which occurred in the Inca-West area. In this section of the block cave mine, a stable arch formed covering an area of approximately 15 000 m2 . This zone subsequently collapsed producing a massive air blast. The collapse followed a series of planned extraction activities and occurred on 5 December 1999. This paper discusses the cave back arching event and the measures that were taken in order to induce the controlled collapse. This was to minimise risk to personnel, equipment and installations. The results obtained to date are presented.

Jan 1, 2000

By Bob Rautenberg, Luminita Calin

The Tunnel and Reservoir Plan (TARP), commonly known as the Deep Tunnel Project, was developed by the Metropolitan Water Reclamation District of Greater Chicago as a two-phase solution to the problem of waterway pollution and basement flooding due to sewer system backups created by the combined sewer overflows. With only one contract left before completion of the Phase I tunnels—the 12.4 km(7.7 mi.) long Little Calumet leg—the pollution control phase of the 175.7 km(109.2 mi.) long system will be 93% complete, once the Torrence Avenue tunnel project comes to an end. This paper describes the Torrence Avenue tunnel project, currently under construction by the joint venture of Kenny (Sponsor) / Kiewit / Shea. Mining of the10.4 km (34,151 feet) long and 8.3 m (27'-4") diameter mainline tunnel was completed in a record thirty-one-weeks period and the concrete lining is nearing completion. Details on the complete muck handling system, numerous mining and concrete lining records will be given.

Jan 1, 2001

By J. A. Woolf, E. S. Leaver, A. P. Towne

"INTRODUCTION A report giving experiments dealing with factors affecting the floatation of the most commonly occurring silver minerals was published years ago. At that time we could not obtain suitable samples of many of the so-called sulfo-salts of the base metals, which are generally silver--bearing and which comprise an appreciable percentage of the natural silver ores. Since Leaver and Woolf's work was published, samples of impure tennantite and enargite have been obtained, and considerable experimental flotation work has been done with synthetic mixtures prepared from these samples. During the present national emergency, research dealing solely with the recovery of gold and silver must necessarily be curtailed. However, many deposits of strategic minerals and critical base metals contain an appreciable amount of gold and silver, the recovery of which would aid greatly in recovering the strategies by taking care of a considerable part of the cost of treatment. Because of this, the recovery of precious metals should not be overlooked entirely. As the Bureau of Mines is now utilizing all of its facilities for the development of increased domestic productions of strategic and critical minerals, this is the last report not concerned primarily with such minerals that will be published until the war ends."

Sep 1, 1942

By C R. Fountain, R J. Sinclair

The zinc industry is dominated by the electrolytic zinc (EZ) process. The EZ process has a low tolerance for impurities, resulting in tight concentrate specifications. Many mining companies sacrifice zinc recovery in order to meet smelter specifications. Some have ore-bodies that cannot be economically developed because too much metal has to be sacrificed, or it is just not possible to meet the specification. The BUKA Zinc Process (BZP) has been developed as a method of producing high-quality zinc from a wide range of concentrates. It can have lower capital and operating costs than the conventional zinc and lead production routes. Advantages accrue from increases in metal recovery during concentrating, smelting and refining; the elimination of most of the capital and operating costs associated with lead smelting; reduced transport costs; lower zinc refining costs; reduced refinery residue disposal costs; and reduced future environmental liabilities. This paper describes results of testwork that has been undertaken to demonstrate the viability of the BZP on both test rig and laboratory-bench scale.

Jan 1, 1998

By Zenjiro Asaki, Teruo Tanabe

"To clarify the formation of light rare earth (R =Ce, Pr, Nd or Sm) -Fe compounds in the reduction-diffusion (RD) process, two kinds of experiments were carried out: (a) RD experiment in which briquettes composed of R oxide powder, Fe (particles or wire) and CaH2 were reacted, and (b) immersion experiment, where an Fe plate was immersed into R-Fe melt having the composition of Fe-side liquidus line in Fe crucible. The compound formation was examined by using XRD, SEM and EPMA. The formation rates of RzFe17 measured by the RD experiment were compared with those obtained by the immersion experiment. The growth rates of compounds obtained in the RD experiment for Pr-Fe and Nd-Fe systems were much lower than those obtained in the immersion experiment. This result was explained by the difference of the reduction rates of R oxides by Ca. The parabolic rate constants for the formation of RzFe17 were separated in two groups of (a) Pr-Fe and Nd-Fe systems and (b) Ce-Fe and Sm-Fe systems. This was discussed in connection with the difference of their crystal structures and the driving force of diffusion. The parabolic rate constants for the formation of compounds in Ce-Fe and Sm-Fe systems decreased in the order of RFez, RFe3 and RzFe17.IntroductionTo understand reaction behaviors in the production of rare earth (R) -iron intermetallic compounds, which have excellent magnetic properties, is very important from engineering point of view. And the reduction-diffusion (RD) process<O has recently attracted attention as one of the promising processes to economically produce R-related materials. A few fundamental studies on the compounds formation in the RD process have previously been reported. Qi, Hino and Yazawa(2) observed the formation of R(Nd, Sm)-Fe and R-Co compounds in the process from various view points. Song and Ogawa(3) measured the growth rates of Nd-Fe and Sm-Fe compounds by using Nd or Sm vapor supplied from Nd-Ca or Sm-Ca melts. The authors have also carried out fundamental studies (4)-(8) to clarify the rate and mechanism in the production of R-Fe intermetallic compounds."

Jan 1, 1998

By Alastair Torrance, George Boucher

The authors were involved in the Trial Blast work at Chek Lap Kok, the site of the new Hong Kong Airport. As part of that work a series of computer programs including 3x30, QFRAG, DESIGNER and 3DMUCK was employed to predict various aspects of the trial blast programme. These aspects included fragmentation and muckpiie shape. This provided an excellent opportunity for these programs to be calibrated, verified and compared under controlled conditions. The results indicated that computer simulation has reached a high level of sophistication and good correlation between prediction and measured results was found.

Jan 1, 1994

By A. E. Nagel, J. E. Carpetta, M. G. Zabetakis, T. D. Moore

The method of moving averages was found useful in assessing the nature of methane emission in coal mines. Emission rates were influenced markedly by the presence of abandoned oil and gas wells in the vicinity of the mine. Such wells appeared to increase the flow rate of methane into the mine by a factor of 2 to 30 in an active mine in the Pittsburgh coal seam.

Jan 1, 1972

By T. A. Utigard

To improve recoveries of Ni, Cu and Co in the Inco flash furnace, a new operating concept was investigated. By adding sufficient coke to form a supernatant coke layer, a reducing barrier would form allowing for improved reduction of descending oxidized sulfide mineral particles formed in the flame. The objective of this investigation was to study the kinetic mechanism and efficiency of the coke layer to produce a sulfur deficient matte. The mechanism and rate of carbon reduction of each of the phases formed in the flash flame, i.e. sulfides and oxysulfides were investigated by means of X-ray visualization tests. Graphite-slag reduction was also conducted for comparison purposes. In the case of slag, poor wettability and the formation of a gas film on the surface of the carbon reductant are often blamed for limiting the reaction surface area that ultimately results in poor reaction kinetics. The X-ray visualization tests confirmed that matte and oxysulfide wet coke better than slag and that the rates of reduction of matte and oxysulfide are faster than that of slag.

Jan 1, 2005

By J. H. Bilbrey

A recording thermobalance ,vas used to determine the rates of oxidation of mol-ten tin over the temperature range 550°-900° C. Oxidation rates were found to vary widely for a given temperature, as previously reported by other investigators. 1 X-ray diffraction data indicated that the probable cause of these variations was the development of preferred orientations in the crystals forming the oxide film. No reasons for the differences in degree of preferred orientation were discovered. For relating the weight of the oxide formed (w) to the time of oxidation (t) an equation of the form wn = kt was found to best represent the experimental data. INTRODUCTION In the course of conducting investigations on the feasibility of using selective oxidation techniques for the purification of various metals in the molten state it was soon discovered that data on the oxidation of molten metals and alloys were very scarce. In contrast to the many hundreds of publications on the oxidation of metals in the solid state there are relatively few articles on the rates of molten-metal oxidation. In view of this scarcity of data, it was decided to institute a series of investigations into the oxidation processes of molten nonferrous metals and alloys with the expectation that the information derived could be put to practical use in developing and improving refining processes based on selective oxidation. This report is the first of a series in which oxidation data for molten nonferrous metals and alloys are presented.

Jan 1, 1955

By A. D. Randolph

Comminution represents one of the major costs of mineral recovery from low-grade ores. Efficient mineral recovery in a typical low-grade ore grinding-flo¬tation process depends on grinding the ore small enough to liberate mineralization without producing excessive slimes, which would result in higher power and flotation reagent costs. Size criteria for efficient grinding should be stated in terms of the distribution of mineralization sizes, but as the mineralization-size distribution is difficult to determine, less desirable criteria of absolute particle-size distribution (PSD) are used in practice. Thus, there is considerable incentive to be able to analyze and predict the PSD performance of grinding circuits for control and optimization of the process. Any realistic model of a grinding circuit must account for recycle of oversize material; such oversize recycle adds to the total mill load and limits total production rate. Simulation of such closed-circuit operation to study grind factors affecting total throughput can be done in a straightforward fashion provided recycle calculations can be added to an accurate input-output model of PSD in the grinding mill itself. Such a total simulation of mill performance is of obvious practical value in assessing the practicality and benefits of various over-all mill control schemes and/or modes of operation. For example, considerable interest has been shown in the development of continuous on-line particle-size sensors and such instruments should be an operating reality in a few years. A total closed-circuit PSD model of this type would be invaluable in the utilization of, and in predicting the pay-out from, such an on-line particle-size sensor. The purpose of this paper is to present a new approach to the development of an input-output PSD model of a grinding mill. The model is continuous in the par¬ticle size coordinate, L, and is based on the principle of a particle population balance along the particle size coordinate. Most previous studies of the grinding unit operation attempt to relate power

Jan 1, 1971

A joint statistical report released by the U.S. Department of Commerce and U.S. Securities and Exchange Commission indicates that business investment in new plants and equipment is expected to total $81.8 billion during 1971. This figure is based on the findings of a survey conducted in late April and May and reflects about a 1 ½ % decrease in investments from the $83.1 billion projected in February. Mining, on the other hand, is still in a bullish mood and is expected to spend $1.99 billion in 1971 compared to $1.89 billion in 1970 and $1.86 billion in 1969. Based on figures quoted above, mining investment in 1971 should show a 5.2% increase over 1970. Carl E. Bagge, president of the National Coal Association, was the dedicatory speaker at the new Milton R. Young Station of the Minnkota Power Cooperative in North Dakota. This new power plant incorporates many innovations which have overcome the problems of using the low-cost lignite abundant in the area. According to Bagge, this development and President Nixon&apos;s recent request for an extra $10 million for coal gasification plants is helping the region lead the way in providing for the power needs of the future. He also maintains that gasification of coal can reconcile coal consumption with the demand for cleaner air, and also assure the nation of adequate pipeline gas.

Jan 1, 1971

One of the major changes in the resource industry in the nineties has been the re- internationalisation of the industry. The history of the resource business has been one of companies from the developed world utilising the cash flows from their operations to explore and develop mines in less developed regions of the world. This resource development has progressively generated wealth and economic development, which in tum, has led to a new generation of exploration and mining projects. &nbsp; InSouth America, Chile had led the way in a mining resurgence, now closely followed by Argentina, Brazil, Venezuela and Peru. Although Chile has long had a significant copper mining industry, the pre-nationalisation phase was driven by American capital; the current phase has been spearheaded by RTZ - BHP at Escondida with Canadian junior companies, in particular, providing major speculative impetus. The Australian junior companies have not been significant in South America. &nbsp; Although Canadian and USA exploration appears to be in decline, the mining industry, particularly in gold, is buoyant in North America. Interestingly, a number of listed and unlisted Australian companies are active, particularly in United States exploration. &nbsp; Australian-based companies have dominated the South-East Asian exploration scene, especially in the Vietnam region. To date, the combination of political and legislative uncertainties have failed to lead to significant resource developments in this region. The area remains one of great potential, as exemplified by the exciting developments in Indonesia. &nbsp; The Philippines has a history of mining, and this has been dominated by both local and North American operators. Both large and small Australian resource companies have a presence in the Philippines, and the development of the copper-gold potential could be impressive over the next decade. &nbsp; The tales of the undeveloped mineral potential of China are probably rivalled only by the supposed strings of virgin Russian orebodies! Many Australian companies appear to have looked but few have chosen to proceed with Chinese developments. There seems little likelihood that China will, in the foreseeable future, rival South America as a target for Australian and North American resource capital. &nbsp; Papua New Guinea has had an active, albeit chequered history in mining, with Australia long being the predominant source of exploration and development funds. The developing nation status of PNG has generated extreme uncertainty, with the current exploration scene all but dead. Most recently, the international flotation of Lihir Gold has tested the international and Australian investment community&apos;s commitment to PNG resource development. &nbsp; The Australian exploration scene continues buoyant, although dominated by gold. The base metals scene is generating, on average, one significant base metal mine developed every couple of years. This is probably the fastest rate of significant base metal development in Australia&apos;s history. &nbsp; The gold scene has been one of incredible dynamics, and there is no evidence that this momentum is waning. The development of new exploration techniques, together with a number of the companies reaching a critical size, has added to the momentum in the industry.

Jan 1, 1995

By RUSSELL S. DAVIES, Andrew Allan, John W. Buch

This is a progress report for the period February 1, 1949, to August 15, 1949, covering experiments with lightweight shearing machines for developing thin, steeply pitching anthracite beds. The over-all objective at the time an underground test section was established on July 30, 1946, was to improve mining above the gangway by developing methods for mechanization of pitch mining. Following the preliminary cutting tests in the gangway with the German machines, it became evident that the use of machines of this type indicated advantages for development work that could not be overlooked and warranted investigation. An agreement was reached with the cooperating company that this be done. Thus, the objectivo in the period covered by this report has been to obtain operating data to uso in comparing hand and machine methods of driving development openings. In obtaining the machine-mining data, 78 feet of gangway, 108 feet of heading, and 80 foot of chute work were driven. Hand-mining data are authentic for the mining condition. It has been shown that full mechanization is two and one-half times as fast as conventional hand methods on a lineal-feet- advance-per-shift basis and costs but little more than one-third as much. Tho machines are air-powered; there is less shattering of the coal bed by blasting; water sprays are used to allay' dust; coal is loaded by machine; no rock is taken; timber is not dislodgod by heavy blasting charges; and it may be said, except for the development of a means for transporting timber to the face, that the tasks for the miner are less arduous, and the working face equally as safe, or safer, than in driving by hand. Face timbering remains the greatest time- consuming cycle item, and steps are being taken to correct this. More than 50 percent of the cycle time is now usod for face-timbering work.

Jul 1, 1951

By Douglas A. Anderson

It is quite common for people exposed to blast vibrations to ask questions such as "How big was that blast on the Richter Scale?" Although it is tempting to dismiss such questions out of hand, for the lay person it is understandable that something which shakes their house should have some sort of measure attached to it. Since a layman doesn't usually know about particle velocity, frequency or the other terms used in describing and regulating blast vibration, the Richter Scale is usually the only measure they can relate to.

Jan 1, 1994

By J. D. Budai, D. H. Lowndes, D. P. Norton, D. K. Christen, B. C. Chakoumakos, J. R. Thompson, B. C. Sales

"Artificially-layered structures, consisting of (Sr,Ba,Ca)CuO2 layers in the tetragonal, ""infinite layer"" crystal structure, have been grown by pulsed-laser deposition. Superlattice chemical modulation is observed for structures with SrCuO2 and (Sr,Ca)CuO2 layers as thin as a single unit cell (~3.4 Å). In addition, novel thin film superconductors were formed by using the constraint of epitaxy to stabilize SrCuO2/BaCuO2 superlattices in the infinite layer structure. Using this approach, two new structural families, Ba2Srn-1CUn+l O2n+2+ d) and Ba4Srn-1CUn+3O2n+6+ d, have been synthesized which superconduct at temperatures as high as 70 K. These results represent not only the synthesis of new structural families of superconductors, but also demonstrate that pulsed-laser deposition and epitaxial stabilization can be effectively used to engineer artificially-layered thin-film materials.Advances in the understanding of epitaxial thin-film growth of the cuprates have heightened interest in creating artificially layered superconductors.(1-3) The layered structure of the copper oxide superconductors opens the possibility of forming novel materials by carefully controlling the epitaxial growth of sub-units of the crystal structures. Thin-film growth methods offer unique opportunities for the atomic engineering of new high-temperature superconducting (HTSc) materials through the ability to form artificially layered crystal structures.(4,S) Moreover, the surfaces of single-crystal substrates provide an ""atomic template"" that can be used to stabilize epitaxial films in metastable crystal structures.An important development in forming new HTSc compounds by artificially-layered epitaxy has been the epitaxial growth of (Sr,Ca)CuO2 films in the so-called infinite layer structure.(6-17) This material, which can be considered the parent compound of all of the copper oxide superconductors, has a relatively simple, layered structure consisting of CUO2 planes separated by planes of alkaline earth elements.(18) Bulk synthesis of (Sr,Ca)CuO2 with the tetragonal, infinite layer structure generally requires the use of high pressure and high temperature bulk processing techniques.(19-24) However, recent experiments show that this metastable compound can be epitaxially stabilized at less than atmospheric pressure, resulting in the growth of tetragonal (Sr,Ca)CuO2 single crystal thin films of the infinite layer defect perovskite structure by pulsed-laser deposition (PLD) over a wide range of growth conditions.(6-17)"

Jan 1, 1994

By Robert K. Koch

The reactions of alumina and alumina monohydrate with wet hydrogen fluoride gas were studied by the Federal Bureau of Mines to determine the feasibility of producing commercial-grade aluminum fluoride from offgases generated by pyrohydrolysis of siliceous fluorspars. The test results showed than an aluminum fluoride reactor operating at maximum efficiency could retain 96 percent of the fluorine contained in off-gases generated by pyrohydrolysis of siliceous fluorspar. The requirements are a reactor temperature of 200° C. and a reactor entrance gas containing 5 mole-percent hydrogen fluoride. Partial pressure equilibrium constants were determined for the reaction of alumina monohydrate and wet hydrogen fluoride gas from 200° to 350° C. and for the reaction of alumina and wet hydrogen fluoride gas from 350° to 700° C. Both reactions are reversible, and they proceed in directions that are dependent upon the temperature and the relative HF:H2O concentration. Logarithms of the equilibrium constants were used to plot the reaction isobars; these can be used to calculate the theoretical maximum efficiency of a reactor processing wet hydrogen fluoride gas between 200° and 700° C. The theoretical maximum efficiency decreases with increasing temperature.

Jan 1, 1961

By R. Owen

The vision-based approach to process control involving fine particles in harsh on-line environments is discussed in this paper. The sensor equipment at the process location, consisting of a light source and a CCD camera provides RS-170 B&W video output. The video can be seen on a process monitor in the control room and is sent to a computer based Vision Processor. The Vision Processor contains a video digitizer and Canty developed software that extracts process information. The iron mine application controls thickener agent feed rate and thus settling pond overflow clarity. The sensor is mounted in the overflow flume of the outdoor settling pond and is used year around in the Minnesota weather. Alternate control system needs a low flow water sample which is subject to freezing in winter. The computer based vision processor provides 4-20 mA analog outputs for real time control as well as file archive for a history record.

Jan 1, 2001