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By Thomas A. Phillips

The Bureau of Mines presents an economic evaluation of its leach- electrolysis process for recovering lead from galena concentrate. In this process, galena concentrate is leached at 200° F with a ferric chloride-brine solution to extract lead while leaving sulfur in the residue, which is discarded. The solution after leaching is concentrated and cooled to 100° F by vacuum evaporation to crystallize lead chloride from which metallic lead and chlorine are produced by fused-salt electrolysis. Chlorine is used to regenerate the spent leach solution before it is recycled. A cost estimate was prepared for a plant capable of producing 300 tons per day of lead, 330 days per year. The fixed capital cost on a third-quarter 1977 basis Fs $27,500,000, and the estimated operating cost without a charge for the concentrate is 4.9 cents per pound of lead product. Assuming a selling price for corroding-grade lead of 31 cents per pound and a charge for the concentrate of $332 per ton, the interest rate of return on investment after taxes is 16 percent. The leach-electrolysis process, therefore, appears to be economically attractive under the assumed market conditions.

Jan 1, 1978

By Z. H. Zhou

It is difficult to remove cadmium from raw indium using only electrolytic refining because their standard potentials are similar. In this paper, physical and chemical methods were used to remove Cd from raw indium. Indium metal is vacuum refined for two hours at 400°C with a vacuum pressure of 20 Pa. In this process, 99.70% of the Cd can be removed. The removal rate of Cd reaches 90% to 95% when indium is further smelted for 10 minutes in a 20% glycerin solution of KI and I2 at 180°C. When pre-indium is electrolytic refined in an In2(SO4)3-H2SO4 system, in which the indium content is 80 to 100 g/L, the pH is 2.0-3.0 and the current density is 80 to 100 A/m2, the contents of the impurities decrease and the purity of the indium product reaches 99.99%.

Jan 1, 2007

By B. K. Belle

The use of diesel engine locomotives in South African mines can be traced to Van Dyk Consolidated Mines Ltd on the Witwatersrand gold mines in 1928 as a replacement for battery locomotives. The advantages and disadvantages were recognized in those days, and surprisingly, there are no significant additions to this list, but only refinements. In the absence of any Occupational Exposure Limit (OEL) for Diesel Particulate Matter (DPM) in SA, the Mine Safety and Health Administration (USA) rule is currently being used as a benchmark for the ventilation engineering designs. This paper discusses the ongoing SA journey of measurement and limitations of exposure data for ventilation planning and regulatory purposes. The currently accepted DPM limits are based upon the belief that they are economically and technically feasible for the mines to reach and are not necessarily health based. For SA underground platinum mines, a median TC/EC ratio of 1.8 with a range of 1.2 to 5.8 was observed. For SA coal mines, a median TC/EC ratio of 1.44 with a range of 1.25 to 2.13 was observed. While it is common practice in the USA to use the ratio of TC/EC for metal mines to be 1.3, the ratio found in local platinum mines is 2.2 and for coal mines, the ratio was 1.53 which is lower than Australian studies, i.e., 1.96. It has been shown that a need for critical analysis of TC/EC ratios exists, and possible reasons for variance must be understood before stringent adoption of overseas recommended limits for DPM. It is hoped that the findings from this paper would provide input to scientific approaches in developing appropriate conversion factors, limits for DPM and also in ensuring appropriate error factors (currently 1.14 for TC and 1.2 for EC) for compliance determination.

Jan 1, 2009

By Fadeela Saloojee, Frank K. Crundwell

"Pressure leaching is an option for copper recovery from chalcopyrite. Leaching takes place at high temperatures and pressures in the presence of an oxidising agent. This work shows how the performance of pressure leaching circuits may be improved by optimising the configuration of autoclaves and the heat-removal method. The objective was achieved by creating an autoclave model by combining mass balances, energy balances and population balances. A base-case circuit consisting of a single autoclave was chosen, and this base case was compared with options for increasing capacity by adding more autoclaves to the circuit. These capacity–increase options include circuits in which the additional autoclave is added in parallel, in series and in series with thickening between the two autoclaves. The copper extraction, productivity and cooling requirements for these options are compared. The series circuit with inter-stage thickening has the highest extraction and productivity, however, the cooling duty in the first autoclave is high. In addition to comparing circuit options, three options for heat removal were investigated: cooling coils, quench water and flash recycling. The flash-recycle option results in the highest copper extraction, and the quench-water option gives the lowest copper extraction. INTRODUCTION Background Copper sulfide ores and concentrates containing chalcopyrite are typically hard to leach under atmospheric conditions. Smelting of these ores may also be a challenge, due to the inability of smelting processes to handle low-grade ores, as well as impurities such as arsenic and antimony. Alternative hydrometallurgical routes to treating chalcopyrite are therefore required. One option is pressure leaching, which is the focus of this work. In the pressure leaching process, sulfide ores and concentrates are leached in autoclaves at temperatures of 200 to 220°C and a pressure of about 3000 kPa (Schlesinger et al., 2011). An oxidising agent, usually oxygen, is required to oxidise sulfide ions to sulfate ions. The oxidation of sulfur to sulfate is exothermic; consequently, a method of heat removal is necessary in order to maintain the temperature in the autoclave."

Jan 1, 2015

By A. J. Rigby

Refractory linings in converters or anode furnaces used to over-oxidize the blister copper will suffer rapid deterioration, due to prolonged contact with copper oxide-rich slag. Nitrogen stirring with COP KIN porous plugs and use of SEMTECH OPC in converters and anode refining vessels can considerably reduce both refractory wear and processing times. In addition, careful control of the vessel atmosphere and the use of real-time optical process control minimize both slag volume and contact time with the vessel refractory.

Jan 1, 2005

By Thomas Fraser

"INTRODUCTION The Santa River Valley of northern Peru contains extensive deposits of a good-grade anthracite that offer one of the most accessible sources of solid-fuel supply for South America. This region is served by the narrow-gage railroad of the Corporation Peruana del Santa, which taps the coal fields along the Chuquicara River and terminates at the port of Chimbote, where facilities have been provided for loading coal into ocean-going vessels.This Government-sponsored corporation is prosecuting a vigorous program of development in this region, envisaging an intensively industrialized area around Chimbot Bay, fueled and powered by the anthracite of the upper valley and a hydroelectric generating plant now being constructed in the Cahn del Fate, where the Santa River has cut through the coastal range of the Andes.This development also includes the construction of extensive irrigation works to greatly expand agricultural production in the valley and thus estab¬lish the basis for a prosperous, well-balanced, industrial and agricultural community. It is hardly necessary to point out the importance of the local anthracite-mining industry to this general plan.At the invitation of the Peruvian Government, through the agency of David Dasso, chairman of Corpoacion Peruana del Santa, a technical mission was sent to Peru in March, April, and May 1945 to examine these coals and assist the corporation in promoting preparation of the coal for most effective use in the contemplated expansion of industry and trade."

Feb 1, 1948

By McHenry Mosier

The Bureau of Mines, United States Department of the Interior, has established a testing adit on the Government reservation at Mount Weather, Virginia, to facilitate research on the fundamentals of mining under actual metal-mining conditions. A number of sites in several Eastern States were investigated, but Mount Weather was selected because the rock seemed best suited for rock drilling and other mining tests and because the ground was already owned by the Federal Government, the site having been acquired in 1902 for use of the Weather Bureau. The testing adit has an advantage over an active metal mine for certain investigations because variable conditions affecting any particular research problem can be controlled and maintained in a fixed status, whereas in an operating mine this seldom is feasible. Operations were begin in September 1936, with a crew of four laborers under a resident engineer. The laborers were recruited from nearby farms, and although they had no previous mining experience, they have developed into satisfactory miners.

Jan 1, 1939

By Alain Blouin, Mohamad Sabsabi, Aissa Harhira, Paul Bouchard, Greg Lithgow

"The objective of this study was to demonstrate the application of Laser-Induced Breakdown Spectroscopy (LIBS) to the continuous analysis of online monitoring of Al, Mg, Ni, Mn, Si and Fe in nickel ore limonite and saprolite slurry samples. Analysis was performed on slurry samples in air at atmospheric pressure. Two pure samples of limonite and saprolite were used. Mixtures of the two samples in varying proportions were used to build calibration curves, study the influence of solid/liquid ratio, and evaluate short and long term reproducibility. The LIBS measurement of these elements is independent of the water content (from 70-85%, the range allowed by our setup). Repeatability of the measurement and long term reproducibility (from day-to-day) were below 1.2 % and 2% respectively for all the elements studied in our conditions. The results obtained showed that an industrial LIBS analyzer could provide the chemical composition of the six elements Al, Mg, Ni, Mn, Si and Fe within 1-2 minutes.IntroductionThe metal-producing industry faces the major challenge of increasing productivity, reducing costs, and maximizing benefits from existing equipment. By pyrometallurgy, metal making involves the basic steps of charging the furnace, melting the charge and refining. By hydrometallurgy, the metal refining is carried out through the dissolution of the metal by chemical reaction and electrolysis. During refining either by pyrometallurgy or hydrometallurgy, it is critical that operating parameters be adjusted and controlled so that the chemistry of the melt or the solution is within predetermined limits. Presently, the complete turnaround time for sampling, sample transfer, analysis and communication of the results to the operators is often 30 minutes or more."

Jan 1, 2016

By L Bartsch, M Kelahan, E Wingate, J-S David

The use of column flotation cells for recovery of phosphate is becoming more common practice in certain parts of the world (Brazil, Russia) where igneous phosphate ores are processed. Igneous phosphates are generally finer grained (< 200µm) than some of the traditional sedimentary phosphates (<400µm). Australian phosphate from the Georgina basin is sedimentary, but has a much finer grain size (typically < 106µm) than similar deposits in North Africa and the USA.In 2013, Arianne Phosphate completed a bankable feasibility study for the development of their igneous phosphate deposit at the Lac a Paul site in Quebec. Initially, lab test work and bench scale piloting indicated that using traditional mechanical flotation would be able to produce adequate concentrate grade and an economic level of recovery, but would necessitate the installation of a complex and operationally challenging flotation circuit. Later pilot plant testing using column cells resulted in a significant reduction in process complexity and facilitated the processing of the -20µm ore fraction which resulted in a 10% increase in P2O5 recovery and a 5% increase in concentrate grade %P2O5.Flotation column testing achieved a concentrate grade of 38.6% P2O5 at a P2O5 recovery of 90%. Using a mechanical flotation cell circuit, the concentrate grade was 36.4% P2O5 with a P2O5 recovery of only 78.8%. A noticeable feature of the testing was the simplicity of the column flotation circuit configuration (Rougher + 2 stages of cleaning + Cleaner Scavenger) compared to the mechanical flotation cell circuit (Rougher + Scavenger + 3 stages of cleaning).The financial benefit for this case study was estimated using a sales price of US$ 195/t FOB for a 38.6% P2O5 product, and an assumed cost of production of US$ 95/t, the netback price is calculated at US$100/t. For a daily milling rate of 55,000t/d, the improved flotation performance provides additional concentrate production of 1,203t/d. Using the netback price calculated above, this calculates to additional gross profit of US$ 120,260/d.Annualised, this equals US$ 40.7 million in additional revenue for a similar or reduced CAPEX.The use of column flotation on fine grained phosphate ore types often requires fine grinding and desliming to liberate the phosphate value, such as the Australian sedimentary phosphate ores. This may enable the development of deposits previously regarded as uneconomic.This paper discusses the potential benefits available to operators, and developers of new projects, for the use of column flotation cells in their metallurgical circuits as assessed by an engineering company.CITATION:Wingate, E, Kelahan, M, David, J-S and Bartsch, L, 2015. Does it make cent$ to use flotation columns for phosphate beneficiation?, in Proceedings MetPlant 2015, pp 353–365 (The Australasian Institute of Mining and Metallurgy: Melbourne).

Sep 7, 2015

By Alvin Kaufman

To aid industry and Government in planning water developments the Bureau of Mines in 1963 canvassed mineral producers to determine water use in 1962. Water use by the mineral industry comprises only 2 percent of the water withdrawn by industry as a whole. The major water-using mineral industries are natural gas processing, phosphate rock, sand and gravel, and iron ore. Analysis indicated the following conclusions: 1. Total water use and new water intake is dependent on the quantity of material processed and the process water requirements of the particular industry or commodity. 2. Recirculation is dependent on the processing requirements of a particular commodity, the manner in which the water is used, cooling and condensing requirements in certain large industries, the quality of new water intake, and the need to treat new and discharged water. 3. Consumed water is dependent on the quantity of water recirculated, the temperature and humidity in the area, and the proportion of water used for cooling and condensing. 4. A threefold increase in water use by the mineral industry by 1985 is forecast

Jan 1, 1966

By T. Lux, M. Hanel, Degel, A. Filzwieser, R., H. Joubert

It is the increasing demand for an economic and cost saving operation mode that requires effective cooling in order to achieve low refractory wear and good furnace lifetime, which is making cooling technology an important aspect of furnace operation. In addition, the requirements for safety are getting more and more into focus. However, the use of water—today’s standard cooling medium—has major drawbacks as it can cause problems both during furnace start up and operation, namely hydration problems, corrosion, and explosion. Not to forget the severe risks for the operators as well as economical damage in case of a malfunctioning water cooling system. With this new and patented cooling technology ILTEC and the ionic liquid IL-B2001 as the cooling medium, it is possible to realise a water-free cooling solution and therefore the door is wide open to rethink existing and conventional cooling solutions. Furthermore, there is also the chance to recover heat from the process in a more efficient way. However, since the technology is novel and unique there are a lot of concerns and doubts regarding safety for plant operators and employees. The paper is intended to cover both: highlighting the enormous potential of the technology but also to eliminate concerns mainly caused by rumour and unawareness. INTRODUCTION All of us are aware of the risks when water is used as a coolant and placed in the vicinity of the liquid metal phase. Unsuitable design solutions or wrong operation modes of the furnaces or failures of refractories can cause a direct contact of water with liquid metal. The consequences can lead to equipment failures, vessel destruction but even worse to injuries and even fatalities. Over the past decades, countless incidences were reported. Fatal accidents caused by water coming into contact with liquid metal happen every year (Oterdoom, 2014; Filzwieser, Konetschnik, Filzwieser, Wallnerm & Preiss, 2014). With the novel ionic liquid cooling technology virtually all negative effects of a water cooled system regarding safety are eliminated and even additional benefits can be provided (Voermann, Ham, Merry, Veenstra, & Hutchinson, 1999;Verscheure, Kyllo, Filzwieser, Blanpain & Wollants 2006; Wallner, Filzwieser & Kleicker 2006). The fact that no explosion occurs when IL-B2001 gets in contact with molten metal results in a revolutionary solution for the metallurgical industry in terms of safety—new safety standards can be achieved.

Jan 1, 2019

By Tom Olsen, Tom Ohrling, Peter Taggart, Chris Martin

"North American Palladium commissioned the new concentrator at the Lac des Iles mine in the summer of 2001. The 15,000 tonnes per day mill replaced the existing 2,400 tonnes per day facility, as part of a major mine expansion.At Lac des Iles, the grain size distribution of the platinum group minerals (PGM) is bi-modal. Roughly two-thirds of the PGM are relatively coarse-grained, and often associated with fast floating copper and nickel sulphides. The remainder is ultra-fine, and locked in silicates, which poses a special challenge to the metallurgist. The previous mill typically recovered just the fast-floating mineralisation, but to achieve target recoveries, the new mill has to recover a substantial amount of the ultra-fine PGM. The metallurgical challenges associated with the recovery of fine-grained PGM in the talcous Lac des Iles ores, are described.The paper describes the approach used in circuit optimisation, and how metallurgical and operational optimisation raised palladium recoveries by more than 6% in six months, by tuning the circuit to recover some of the ultra-fine PGM mineralisation.BACKGROUNDThe Lac des Iles mine, owned and operated by North American Palladium Limited, is located about 115 kilometres north of Thunder Bay, Ontario. The mine originally opened in December 1993, and prior to 2001 included a mill capable of handling 2,400 tonnes per day of ore delivered from the nearby Roby pit.Following an intensive exploration programme conducted in 1999, and a detailed feasibility study, conducted in 2000, North American Palladium initiated a mine expansion project, the objective being to expand milling throughput from 2,400 tonnes per day to 15,000 tonnes per day. This required construction of an entirely new mill, which was commissioned in May 2001."

Jan 1, 2003

By Ryan Higbie, King Chin, Matthew Anderson, Mike Huggins, Rian Johnson, Dave Sinsheimer

"The Permanent Canal Closures and Pumps (PCCP) project is the capstone piece of New Orleans’ extensive hurricane risk-reduction system constructed following Hurricane Katrina. The project consists of three discrete pump stations and flood gates on the shore of Lake Pontchartrain which provide a storm surge barrier and pump rainwater from the City of New Orleans’ primary drainage canals. The depth of the pump station structures ranged between 39 and 45 feet below sea-level. USACE developed the PCCP project for design-build delivery; granting the project team latitude to develop innovative, cost effective solutions for the project. The use of OPEN CELLTM cofferdams to construct the pump station structures was one such innovation. OPEN CELL structures utilize the strength of the retained soil to anchor cellular sheet pile face arcs; allowing a free-field of construction within the cofferdam. This cofferdam design did not require ground improvement or dewatering around the perimeter of the cofferdam. The free-field cofferdams streamlined construction and large equipment installation within the structures with no encumbrance from internal bracing. Meticulous force-based design, soil-structure numerical modeling, and physical testing were all techniques used to present and gain USACE acceptance of the design on this vital element of the work.PROJECT DESCRIPTIONThe Permanent Canal Closures and Pumps (PCCP) project is the capstone piece of the City of New Orleans’ extensive hurricane risk-reductions system constructed following Hurricane Katrina in 2005. The project encompasses three separate pump stations and floodgate structures located at the mouths of three outfall canals (17th Street, Orleans, and London) on the south shore of Lake Pontchartrain. These three canals, running from the south to north, act as the primary conduits for discharging water from the New Orleans area. Prior to Hurricane Katrina, these canals were operated with pump stations two to three miles upstream of the mouths at Lake Pontchartrain. This left long stretches of levee on each side of the canals exposed to storm surges entering from the lake. Three levee failures occurred along these canals during Katrina; two at London Canal and one at 17th Street Canal. The failures resulted in major flooding of the surrounding neighborhoods, significant damages, and loss of life.Following initial canal levee repairs after Hurricane Katrina, USACE, in partnership with the Louisiana Coastal Protection and Restoration Authority (CPRA), took action to move the line of flood protection to the mouths of these three canals at the edge of the lake. By cutting off the storm surges from Lake Pontchartrain at the entrance to the canal, over ten miles of canal levee would no longer be exposed to storm surge water elevations, significantly decreasing the risk of failure."

Jan 1, 2017

By F. Fraas, J. E. Conley

"The problem of recovering potash from the mineral polyhalite (K2SO4.MgSO4.2CaSO4.2H2O), occurring in large quantities in the salt beds of Texas and New Mexico, has been under investigation at the Nonmetallic Minerals Experiment Station of the U. S. Bureau of Mines continuously since 1928. Most of the results previously obtained have been published in technical journals and in a series of Bureau of Mines Reports of Investigations.The experiments described in the present report were performed to ascertain whether a continuous countercurrent extraction of calcined polyhalite by hot water would yield satisfactory recoveries and concentrations of sium sulphate in the top liquor. Previous investigation by Storch 4 had shown that the rate of solution of uncalcined polyhalite was too slow to be of value in an industrial process, and Storch and Clarke 5 had demonstrated that calcination of the polyhalite greatly, accelerated the rate of solution in hot water, allowing most of the potassium sulphate to be readily extracted."

Sep 1, 1933

By Christophe Thiébaut

Keywords: Pyrochemistry, Salts Treatment, Distillation The pyrochemical purification of metal generates spent salts. When this metal is an actinide such as plutonium, the slags cannot be discarded and are thus disposed in nuclear facility. In order to handle with these slags, the decision has been taken to reduce stored quantities. The development of a pyrochemical treatment is in progress in the CEA Valduc centre. The feed salt, typically composed of various Pu and Am species contained into monovalent or divalent chloride matrix, is first oxidized to convert the actinides into oxides. Then the chlorides are separated from the actinide oxides by vacuum distillation. Temperatures higher than 750°C for monochloride salts mixture NaCl/KCl and higher than 1100°C for divalent CaCl2 base salts, are required to produce an industrial flow of vaporization. Inactive qualification of the process for NaCl/KCl base salt has been carried out with lanthanide surrogates. Then, a pilot equipment, called distillator has been designed and built for production-scale distillation of NaCl/KCl and CaCl2 oxidized plutonium salts. Industrial flows of vaporization have been obtained with this pilot equipment : about 4 g/cm²/h for NaCl/KCl at 800?900°C and 1 Pa, and more than 1,5 g/cm²/h for CaCl2 base salts between 1000?1200°C at 0.1 Pa. The last step, now in progress, is the integration of the distillator into a glove box.

Jan 1, 2005

By R. E. Whitehead

"Alkali/alumina and MgO/alumina molar ratio plots graphically portray both chemical and mineralogical changes accompanying potassic, phyllic, argillic, chloritic, and alunitic alteration of quartz monzonites and granodiorites hosting porphyry (as well as lode and greisen) ore deposits. The molar ratio plots can be used to identify different types of alteration. In most cases, the identification based on molar ratios coincides with petrographic data. In those instances where the molar ratio and petrographic identifications do not agree, the mineralogy might need to be re-examined. Hydrothermal alteration studies using trace elements could benefit from the application of complementary alkali/alumina molar ratio plots.Le diagramme des rapports molaires alkali/alumine et MgO/alumine illustre clairement les changements chimiques et minéralogiques qui accompagnent les altérations potassique, phyllique, argillique, chloritique, and alunitique des monzonites à quartz et des granodiorites encaissant les gîtes de type porphyrique, ainsi que des veines et des greisens qui leur sont associés. Les diagrammes de rapports molaires peuvent être utilisés pour identifier divers types d’altération. Dans la plupart des cas, l’identification basée sur les rapports molaires est en accord avec celle basée sur les données pétrographiques. Là ou il y a désaccord entre les rapports molaires et les données pétro-graphiques, il peut être nécessaire de réexaminer la minéralogie. Les études de l’altération hydro-thermale accompagnées d’une étude des éléments traces auraient avantage à utiliser un diagramme des rapports molaires alkali/alumine."

Jan 1, 2009

The amount of liquid retained in a porous bed is determined by weighing a column containing the bed.The column is attached to the free end of a cantilevered beam, and changes in weight are determined by calibrated strain gauges (which form a resistance bridge) attached near the fixed cnd of the beam. By coupling the output from the strain gauges to an amplifier and a recorder, a continuous record of changes in the drainage characteristics of the bed may be obtained.

Jan 1, 1968

By Darelle T. Janse van Rensburg

Some of the more recent developments in Paint Technology are solvent free materials. These coatings have mainly been formulated to overcome the negative attributes of solvent-based coatings, i.e. environmental, safety and health risks, potential for solvent entrapment and osmotic blistering, as well as the formation of micro-pores during the curing process. Two solvent free liquid epoxy coatings have been used extensively on power generation plant. However, very little is known regarding their long-term performance under different exposure conditions, as well as whether these coatings actually perform better than their solvent-borne counterparts. In addition, solvent free materials are generally used where outage periods are restricted and coatings need to be applied within a very short period. Though these materials have reportedly much shorter curing times than other conventional solvent-borne coatings, little is known regarding their limits with respect to maximum film thicknesses and being put into service while still being wet/partially uncured. The latter has become common practice at many power stations in the past two years or so. In addition, the application and curing methods of solvent free materials are different to that of solvent-borne materials, and may require equipment and application process changes. This paper covers the application and performance properties of solvent free coatings in comparison to solvent-borne materials primarily intended for immersion service. Numerous coatings were evaluated under immersed static and cyclic hydrostatic pressures. Other tests included short curing / early immersion tests, dry-to-touch and dry-through curing times, adhesion tests, surface tolerance tests, etc. The results show that the solvent free materials have clear benefits with respect to safety, health, environmental and long-term performance, but will be more difficult to apply compared to solvent-borne materials.

Jan 1, 2006

Study on Mechanism of Sphalerite Flotation in the Presence of Main Metal Ions by Molecular Mechanics

Sep 13, 2010

By Virgil A. Marple

The objective of this contract was to investigate time-integrated and real-time methods for determining the diesel exhaust particulate concentration in underground mines, in particular, coal mines. The microorifice uniform deposit impactor (MOUDI) is recommended for obtaining the time-integrated measurement of the size distribution. The mass concentration of diesel exhaust particles can be obtained from the particle size distribution of mine aerosols. On a mass basis, diesel exhaust particles are primarily in the submicrometer size range while coal dust particles are larger. Size distribution measurements made in the laboratory and in three underground coal mines exhibited two distinct modes with the diesel exhaust particles in the smaller particle mode and the coal particles in the larger particle mode. The point of separation between the two modes occurred in the 0.7 to 1.0 pm size range. The separation was found to be independent of mass fraction of the diesel exhaust particles, particle concentration and sampling site. Methods recommended for further consideration as real-time monitors of diesel exhaust aerosols in mines are photometers and filter pressure drop techniques. A preclassifier would be required in both cases to separate the larger dust particles from the sample. The Metrex Mineral/Diesel Photometer should also be investigated further once the electronics problems are eliminated.

Jan 1, 1986