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By J. A. Finch

"A method of sampling and presenting bubbles for imaging for use in full-size flotation cells is described. The device (bubble viewer) comprises a tube attached to a sealed glass viewing chamber. The assembly is first filled with frother-containing water (to prevent coalescence) and the tube immersed at the desired location below the froth. For a few minutes bubbles are collected in the viewer free from slurry and are readily imaged. To reduce bubble overlap and the problem of defining the plane of view, the viewing chamber has a sloped side. Bubbles rise, encounter this slope, spread into a single plane and slide up. This simple expedient virtually eliminates overlap and provides an unambiguous focus plane - the underside of the sloped glass. The bubble image is captured and processed to give size data. The bubble viewer has been employed at several concentrators on different types of flotation cells. Examples of the images are given. The impact of position in the cell and the effect of changing gas rate on bubble size are illustrated. This technique provides a sensitive measure of the effects of process variables on bubble size.INTRODUCTIONDespite the extensive use of flotation in the mineral processing industry, the methodology employed for cell design is largely based on empirical rules rather than on first principles. One of the main reasons for this state of affairs is that the local flow structures encountered in industrial-scale machines are very complex. These flow structures are difficult to simulate under the controlled conditions of the laboratory and the difficulty to solve the mathematical models that treat the randomness of such flows also mean theoretical treatment is limited. Understanding flotation cell hydrodynamics requires reliable data, which involves the implementation of measurement techniques capable of performing both at the laboratory- and the industrial-scale, In addition, it is desirable that such techniques are amenable to automation to reduce extensive manual intervention in the data collection process."

Jan 1, 2002

By John J. Dran

Large mining companies use a number of sophisticated analytical techniques for introducing the element of risk into the valuation of mineral reserve sites. These methods include, but are not limited to, sensitivity analysis, computer simulation, conditional probability, and portfolio theory. Such techniques enable the managements of these large companies to have an awareness of the many possible ramifications of their investment decisions. On the other hand, small mining companies and individuals in the mining business, due to limited financial and technical resources, still rely primarily on single point estimates of the value of mineral reserves. These small miners introduce the aspect of risk only through the application of an appropriate "speculative" discount rate. This paper illustrates the application of a technique for the introduction of risk into investment analysis. The method appears to be most suitable for use by small mining companies and individuals contemplating a large investment in a new mineral reserve site.

Jan 1, 1974

By A. Romero, M. Carvalho, D. L. Millar

"The number of underground mines replacing diesel by battery powered mobile equipment is growing worldwide. The latter produces locally zero emissions and less heat, improving air quality in the working areas, and can potentially reduce energy costs due to lower ventilation requirements and in the face of higher fuel prices. However, there is a lack of systematic approaches to evaluate the potential economic benefit of switching from diesel mobile technologies to electric ones. This paper presents a method to answer the question of whether a mine with known operating conditions should invest in battery-powered electric equipment to reduce its total costs. Furthermore, this method provides the optimal number of electric and diesel equipment in relationship with their impact on the ventilation system and the total costs of running the mine from the energy perspective. A case study of an underground mine in Northern Ontario (Canada) is presented to validate the method proposed. The scenarios studied include the specific climatic conditions of the region, and the possibility to use heat recovery for the ventilation system. Overall, results show that the use of electric mobile plants is cost competitive, especially so when electricity cost can be lowered through load-shedding strategies.INTRODUCTIONOf the multiple advantages of using electrical vehicles (EV) underground in mining, the potential increase in air quality and comfort is the most significant (Paraszczak, Svedlund, Fytas, and Laflamme, 2014). Until recently, fully battery-powered electrical underground heavy duty machinery (i.e., loaders or trucks) were not available, so that tethered and trolley assisted vehicles were the only electric alternatives to diesel powered vehicles (Bétournay et al., 2011). Today, several commercial battery-based alternatives are available (General Electric Fairchild, 2015; RDH Mining Equipment, 2015; Paraszczak et al., 2014). Operational details can be found in Ewing (2015). The main battery technology used (Lithium Iron Phosphate, LiFePO4, or LFP) was already anticipated in Bétournay et al. (2011) as a good candidate for these types of vehicles. More details on these batteries, along with state of the art and future perspectives can be found in Zubi, Dufo-López, Carvalho, and Pasaoglu, (2018)."

Jan 1, 2019

As the high-grade copper deposits in the world become depleted, there is an increasing focus on developing lower-grade ores which contain problematic impurities such as arsenic. Indeed, many high-arsenic ore bodies remain undeveloped because of their high arsenic levels. Separation of arsenic from copper at the beneficiation stage is difficult using the current processing techniques and invariably copper concentrates produced from these ores contain high arsenic levels, sometimes so high as to make them unacceptable to copper smelters. New, sustainable approaches are needed to allow development of high-arsenic copper ores while at the same time minimizing arsenic dispersion into the biosphere. The most promising route for separating arsenic from copper at the flotation stage centers on the use of pulp potential control. In recent years CSIRO has demonstrated at laboratory scale, for a number of high-arsenic copper ores, that crude flotation separation between arsenic-bearing minerals and copper-bearing minerals can be made. The differences in specific minerals responses to changes in pulp potential and pulp pH are exploited for this separation. Such separations nominally produce a low-arsenic high-copper concentrate and a low-copper high-arsenic concentrate. The former can be smelted without penalty, while the latter requires further treatment to capture and stabilize the arsenic and to recover the residual copper. Consideration has now been given to treatment options for the high-arsenic low-copper product. A pyrometallurgical option, involving a low temperature roast to selectively fume off the arsenic and leave a high-copper calcine, coupled with an arsenic stabilization step, has been demonstrated in the laboratory, and a preliminary techno-economic evaluation shows the process to be economically favorable. These results were recently published. CSIRO has now investigated an alternate hydrometallurgical option, involving atmospheric alkaline sulphide leaching of the high-arsenic product, where the arsenic is selectively dissolved leaving a copper-rich leach residue. The leaching testwork was carried at on the same high-arsenic low-copper material used in the roasting studies, enabling a techno-economic comparison of the alternate roasting and leaching treatment options to be made. The alkaline leaching work is briefly described and the results of the process option comparison presented and discussed. Keywords: arsenic, copper, economics, enargite, ore flotation, tennantite INTRODUCTION

Sep 1, 2012

By Nawshad Haque, Leanne Smith, Hal Aral, Joseph Cho, Warren Bruckard

"Water availability is one of the principal parameters in determining the feasibility of mining projects in arid and semi-arid regions. The volumetric water footprint (VWF) of a conceptual model of a copper flotation plant was found to be 2.45 kL/t Cu ore, compared with an actual measurement reported in the literature of 2.72 kL/t Cu ore. The flowsheet considered included mineral processing stages such as crushing, screening, grinding, classification, separation, flotation, thickening and filtration. The effect of a number of variables on the VWF was evaluated, including solid/liquid ratio, feed mass flowrate, ore loss, water loss, moisture content of ore, ore grade and water recycling. The use of seawater with recycling provided the most environmental and economic advantage among several scenarios evaluated. The study assumed a price of $1/kL freshwater, $4/kL for transport over a 200 km distance at 2,000 m altitude and $4/kL for water treatment. The water related cost of the desalinated seawater use scenario was A$493/t Cu concentrate, while the water related costs of fresh water and blended water scenarios were A$308/t and A$268/t Cu concentrate, respectively. The water related cost (fresh water scenario) accounted for 44% to 49% of the entire mining and processing costs that included drilling, blasting, loading, hauling, crushing, grinding and concentrating. The total overall cost was A$435/t Cu concentrate for the seawater with recycling, compared to A$451/t Cu concentrate for the fresh water with recycling case.INTRODUCTIONReducing the water footprint (WFP) by utilising alternative water sources has been a focus of mining projects due to increasing concerns about water scarcity and growing energy costs. The global mining industry can expect to experience fresh water shortages in the future, and saline or hyper-saline water may be the only available water source to process minerals in arid regions. Extensive studies on alternative water sources (e.g. seawater, desalinated seawater, blended water) and the reuse of process water have recently been conducted (Moreno, Aral, Cuevas, Monardes, Adaro, Norgate & Bruckard, 2011; Aral, Mead, Cuevas, Davey & Bruckard, 2010). Such studies provide sustainable and economic strategies for mines and concentrators in the arid or semi-arid regions of the world such as in Chile, Peru, Indonesia, and Portugal. More work, however, is needed to confirm water consumption data for different base metal flowsheets and use this data to develop water models that can lead to reduced WFPs and more sustainable water usage in the mining industry."

Jan 1, 2016

By V. Panayotov

Slag and by-products of metallurgy bear valuable components and their processing raises an in-creasing interest. Coke and iron have to be separated and other components have to be depressed, in order to obtain sellable high quality copper concentrates. Use of classical mineral processing technologies, such as magnetic separation, sulphidization, hydrometallurgy, etc. yields copper concentrates with grade of 4%~6% Cu. Copper is lost in tailings and the whole technological cycle is low profitable. Technology proposed applies an electrochemical treatment of the industrial water entering the flotation cycle. Iron and iron compounds that do not bear Cu, coke and gangue materials are depressed during the copper flotation. Copper concentrate of grade of 9.8%~10% Cu is obtained at simultaneous increase of Ag recovery by 8%~10%. As a result company profitableness is increased. Technology proposed is easy to implement, it does not require changes in the existing technology flow-sheet, and additional investment is low. The flotation process can be aided by a specially developed system for real-time analysis of the obtained copper concentrate which allows in-time corrections in the flotation parameters and entire process control. Applied flotation schemes, technological parameters and results obtained are described.

Jan 1, 2014

By N. D. Dementieva

Based on lab and pilot-plant tests to recover gold, silver and lead of a Russian deposit, a collective and flotation concentration flow sheet with lead and sulfide concentrates was proposed. The type of the deposit is gold-sulfide-quartz-bearing. The recovery of gold, silver, and lead to a lead concentrate was 47.4%, 68.1% and 70.7%, respectively. The grade of gold and silver grade was 170 g/t and 372 g/t, respectively. The mass percent of lead, zinc and arsenic mass percent was 41.7%, 0.34% and 0.63%, respectively. The recovery of gold and silver recovery to a sulfide concentrate was 50.1% and 28.8% at the grade of gold 20.5 g/t and silver 66.2 g/t. Sulfide concentrate with arsenic mass percent ~3% was biooxidised followed by CIL and obtaining metal at the site as well as zinc concentrate from bioleaching solutions with zinc mass percent 45% at its 64% recovery. The total gold and silver recovery using a developed technology with the account of their treatment at a polymetallic plant was 92.2% and 93.7%, respectively.

Sep 1, 2012

By Gary T. Brill

In the presentation, the development and new applications of the jet grouting technique in the North America are briefly introduced at first and followed by the outline and advantages of Jet Grouting. Several recent projects for jet grouting are presented in which the applications to underpinning and excavation support, foundation, groundwater barrier and seismic stabilization are briefly discussed.

Feb 10, 2003

By K. E. Waters, J. E. Nesset, F. Rosenblum, J. A. Finch

An advanced laboratory-scale weathering apparatus has been developed at McGill University to study the effects of weathering (ambient temperature oxidation) on the self-heating of sulphides. Previous work by the authors has shown that the problematic self-heating of sulphides is inherently linked to the degree of oxidation (weathering) of the minerals: un-oxidized active sulphides exhibit little or no self-heating while the same material when weathered can generate extensive self-heating bringing temperatures well above 100 0C. In this study the effects of environmental conditions (weathering time, ambient temperature, sample moisture, relative humidity, and oxygen content) were evaluated with respect to the self-heating response of a pentlandite-pyrrhotite nickel sulphide concentrate.

Jan 1, 2015

By E. Maritz

"The localized uniform conditioning (LUC) technique was proposed by Marat Abzalov in 2006. The technique converts conventional uniform conditioning (UC) grade-tonnage curves into single grade values attached to each smallest mining unit (SMU). This is achieved by ranking the SMUs within a panel in increasing order of their grade (based on the direct kriging of SMUs). This ranking is then used to localize the conventional UC grade-tonnage curves for each panel by dividing them into classes and computing their mean grades, which are assigned to the SMUs. The quality of this localization process will depend heavily on the validity of the grade patterns predicted by the direct kriging of the SMUs. Abzalov noted that where the distribution of data available for the direct kriging of the SMU is characterized by strong short-range variability, the advantages of using the LUC approach may be more limited. Consequently, a study was undertaken to determine how valid the predicted grade patterns of a typical Birimian-style gold deposit (with high nugget effect and strong short-range variability) might be expected to be. This was determined by comparing the direct SMU kriging ranking (based on sparse data) with the grade control model ranking (based on close-spaced data and the best available estimate of the deposit). The results showed a satisfactory correlation between these rankings and it was concluded that, although the grade patterns predicted by the direct kriging of the SMUs may be less meaningful for deposits exhibiting strong short-range continuity, there is nevertheless a convincing relationship with the actual (or best available) rankings. Therefore, the LUC technique is still considered to be useful for this style of deposit. IntroductionFor adequate technical and financial evaluation of a project, attempts should be made to estimate the recoverable resources – the portion of the in situ resource that can be economically extracted by mining. To achieve this, the estimates of the tonnage and grade of the mineralization should be produced above a given economic cut-off and should take into consideration the proposed mining selectivity."

Jan 1, 2016

By L. Tafaghodi, S. Sarbishei

"Following the depletion of nickel sulfide ores, laterites are considered as one of the main sources for producing nickel and cobalt. One of the primary steps in pyrometallurgical extraction of nickel from laterites involves partial reduction of the ore at temperatures below 1000°C. Studying the kinetics of laterite reduction provides valuable information on reducibility of nickel laterites using coal as a reductant. The present study investigates the reduction behavior of a nickel laterite by thermal gravimetric analysis and differential scanning calorimetry. Non-isothermal reduction tests and X-ray diffraction analysis were performed to find the main reactions that occur during the process. The kinetic parameters were calculated by Coats-Redfern method. The general model of simple reaction f(a)=(1-a)n was used for calculating kinetic parameters.INTRODUCTION Nickel (Ni) naturally occurs in the form of sulfide and laterite ores. Laterite ores are mainly available in tropical regions. Weathering phenomena during millions of years has led to the formation of several layers with specific mineralogy (Butt & Cluzel, 2013). The three main layers downward are limonite, smectite, and saprolite (Crundwell et al., 2011). Although laterites are the most available nickel ore resource (70%), their share in the overall Ni production is limited to 40% (Crundwell et al., 2011). The main reasons for not materializing the full potential of laterites are as follows (Ray et al., 1985): •,Laterite ores contain high water content (free and combined) which in turn results in high energy consumption of the extraction process. •,As Ni is present in the form of solid solution in laterites, physical upgrading methods such as flotation are not effective in increasing the Ni content before the extraction process. •,Extracting Ni from sulfide ores involve exothermic reactions which are beneficial due to decreasing the overall energy requirement of the process, however there is not efficient release of energy in the process of extracting Ni from laterite ores."

Jan 1, 2017

By M. E. Karabin, R. J. O'Malley

"A mathematical model of the roll casting process has been developed which predicts macro-variables, such as roll separating force, roll torque, and strip exit speed for a range of roll speeds. Continuum variables, such as interface pressure, interface shear stress, freeze-front shape, and internal temperature distribution are also predicted.The model consists of two independent segments: solidification and rolling. The solidification model is two-dimensional (thickness and rolling direction) and is capable of handling alloy solidification. The solidification model is employed until solidification through the thickness is complete, then the rolling solution is activated.The rolling model is a one-dimensional (rolling direction) mechanical solution based on the von Karman approach, coupled with a two-dimensional thermal solution. The flow stress is expressed as a function of the average through-thickness temperature of the strip.Experiments were performed using a laboratory roll caster to test and refine the model. Experimental strip exit temperatures were used as input to the model. Experimental and predicted roll torque and strip exit speea were forced into agreement at a single reference roll speed to obtain values for the coefficient of friction and the interfacial heat transfer coefficient. Using these values, good agreement was obtained between predicted and experimental torque and strip exit speed over the entire range of roll speeds examined."

Jan 1, 1986

By Dai Wang

Stoppings are necessary ventilation control devices for effective air distribution underground. However, one of the major problems underground mining has is that every stopping is a potential leaking source. Since air always flows from a point of high pressure to one of lower pressure, and the total pressure at every point in intake airways is higher than that in the return airways, air will always tend to leak from intake to return (Tien, 1996). In many mines, less than half of the air entering the mine actually gets to the working areas; the rest of it simply short-circuits directly to return airways through leaky stoppings instead (Timko and Thimons, 1983). Leakage through a stopping occurs because of pressure drops across the stopping and available leaky path in stoppings. Empirical equation has been widely used to characterize the relation the amount of leakage and variables that affect leakage. However the use of this equation requires accurate information for constants which are not always readily available. It is the attempt of this paper to derive an equation similar to the Atkinson Equation that can readily be applied to characterize pressure-leakage relationship for any given stopping.

Jan 1, 1998

By Y Wang

Inadequate goaf gas control may lead to gas exceedances in the ventilation return air, which will trip power in longwalls and cause production stoppage. To effectively control gas emissions, Australian mines heavily rely on drilling vertical goaf holes to capture coalmine methane before it migrates to mine openings. The wide application of goaf gas drainage may change the goaf pressure distribution, lead to more ventilation air leakage, and consequently increase gas explosion and spontaneous combustion risks. This paper focuses on analysing goaf gas drainage production data from a case study longwall mine in Australia. The correlation between suction pressure, total flow rate, gas flow rate and air leakage rate were analysed in detail as the face-to-hole distance changes. Suction pressure is found to be positively correlated with total flow rate, and their correlation also varies at different goaf locations due to various goaf compaction and flow resistance. This paper also proposed a theoretical method to calculate the goaf resistance of ventilation air leakage pathways. Based on several basic assumptions and different goaf drainage scenarios, the leakage airflow pathway resistance in the goaf at different face-to-hole distances can be calculated. The model results suggested that the resistance of air leakage pathways from the working face to individual goaf holes increased with the face-to-hole distance. The resistance results can also be used to calculate the corresponding permeability at the same position, which can be used as input data for CFD or Ventsim models.

Oct 12, 2022

By A. E. Wells

IN 1866, Thomas Graham1 called attention to the volume of gases, three times the volume of the sample, evolved from a meteoric iron heated in an evacuated porcelain tube. From that time to this the occurrence and significance of gases in metals have been the subject of investigation by many workers, among whom Sieverts,2 Iwasé3 and 0. W. Ellis4 stand preeminent. Sieverts and Iwasé concerned themselves with the solubility of a number of gases in metals in the liquid and solid states. They determined the absorption coefficients of these gases, and in all cases found a sharp change in solubility at the melting point of the metals. Ellis analyzed the gases evolved by solidifying copper and those occluded by the solidified metal. Lobley and Jepson5 endeavored to determine the effects of hydrogen, carbon monoxide and nitrogen on the porosity of copper that was allowed to solidify in the presence of each gas after 30 min. exposure to it in the

Jan 1, 1930

By A. Baydusa, K. Barron

A theory for cutter roof failure in coal mines has been developed. It is shown that the key parameters influencing the likelihood of cutter roof failure are the rock strength, the vertical stress (depth) and the horizontal to vertical stress ratio. The support force necessary to prevent the development of this mode of failure is, in most cases, so high as to make it impractical to apply a force of such magnitude. It is, therefore, better to allow the failure to occur and to design a bolting system to support the dead weight load of the failed block. This is probably best achieved by using a yielding bolt system (such as split set bolts) which is anchored well beyond the top of the potential failure block. The maximum potential caving height determined from this theoretical approach compares favourably with field observations reported in the literature.

Jan 1, 1999

By John Dorn

THE phenomenon of diffusion, according to the most prevalent conceptions at the present time, undoubtedly played an important part in the formation and distribution of metals and minerals in the earth's crust. Apparently there is good evidence that in the geological rate of cooling diffusion caused numerous materials to separate into individual masses or into duplex structures. As is well known, the early steels were made by cementation; that is, by heating wrought ferrous metal in contact with carburizing materials so as to produce a relatively high carbon content on the surface. If the process was continued long enough, the carbon diffused throughout the piece. A more homogeneous product depended upon further heating and forging, so that the carbon diffused to a fairly uniform concentration throughout the metal. In the modern metallurgical industry, diffusion is the basis for many operations; for example, the production of hard surfaces oil steels by carburizing, nitriding, cementing with chromium, silicon, boron and beryllium. Castings or ingots as they solidify do not have homogeneous structures, but these structures are made largely homogeneous by suitable process of heat-treating and the resulting diffusion. It is in modern physical metallurgy, however, that we become greatly concerned about the mechanism of the phenomenon of diffusion. The rates of diffusion, effect of temperature and time on diffusion, and the relation of diffusion to the many properties of the parent metal and the diffusing metal have become important; also, we are concerned with the diffusion of a single metal into a complex alloy. For example, what is the mechanism whereby carbon and nitrogen travel into steel? What is the effect of alloying elements in the ferrous material on the rates of diffu-sions? What is the effect of simultaneous diffusion of carbon and nitro-gen? How does chromium, beryllium, boron, or the like, diffuse into the steel, and what are the effects of alloying elements in the steel previous to the cementation process? These inquiries are by no means limited

Jan 1, 1937

By L. B. Lindemuth

To those who are in a position to carry the thought to a conclusion; I would like to present a theory for the cause of blisters in galvanized sheets. Blisters that are caused from piping and shrinkage cavities will not be considered because the reason for their formation is entirely obvious. Blisters that occur periodically with no apparent system of ocation, number, size or grouping, and then disappear with no. apparent change in manufacturing method, are the ones to which this theory would apply. Examination of blisters of the latter type has shown that they contain hydrogen gas at atmospheric pressure, and that occasionally traces of oxide or sulfide are found on the inner surface of the blisters. These two characteristics have led to the rather general idea that hydrogen gas generated in pickling, and that iron oxide supposed to be inherent in the ingot and causing weak spots were, in some manner, responsible for the development of blisters in galvanizing. The theory which I wish to advance is that these blisters are caused by moisture that has penetrated the steel after the annealing operation. This moisture comes from the atmosphere, or from pickling or washing and when it is suddenly expanded into superheated steam in galvanizing, the increase in volume is so great that it cannot escape with sufficient rapidity through the small opening where it entered as moisture.The pressure so generated forces the sheet apart along those lines of lamination ;hat may be found in practically all flat sections of steel rolled comparatively cold. The increase in volume. from moisture to steam at 800° F. is 2244 times the original volume of the moisture. The pressure generated by ;he moisture heated to 800° F. and entirely confined would be enough to expand or explode any container. This would explain the source of sufficient pressure to cause a sheet to blister.

Jan 3, 1927

By C. P. Crawford

Bureau of Mines Technical Paper 172, by S. H. Katz and H. C. Porter, entitled "Effects of Moisture on the Spontaneous Heating of Stored Coal", says at the outset, "Spontaneous fires in storage piles of bituminous coal' have been the source of trouble and loss since the industrial utilization of coal began. In Europe the idea arose that spontaneous combustion is more liable to happen during wet weather than during dry. Statements favoring or opposing this idea have crept into the literature. Conflicting conclusions, based on experiment as well as opinions based on observations of various degrees of reliability, are given in most of the recorded discussions of the subject. "Because of the uncertainty of the effect of moisture and its seeming importance among the conditions that affect spontaneous combustion in stored coal, the work described in this paper was undertaken by the Bureau of Mines. The experiments showed that a coal from Illinois oxidized faster when dry, whereas a sample of Pittsburgh coal oxidized faster when moist. These discordant results and similarly inconsistent results from the observations of different investigators may be coupled with the fact that under actual conditions of, storing, both coal and air always contain a considerable amount of moisture." The foregoing report of the investigations of the Bureau demonstrates that the mystery of spontaneous combustion has not yet been solved. This fact adds to the fascination of the subject. I became interested in the matter about ten years ago in observing what was probably one of the best exhibitions of this phenomenon. The old dump at Castle Gate No. 1 Mine contained boney coal and track cleanings generally. In winter when snow fell upon this old dump, the snow was soon melted by the heat of the dump which was comparatively warm at all times. Within 48 hours afterward little blue flames were in evidence on the surface of the pile. Few of the gas feeders were sufficiently constant to maintain a steady flame at any given point, but shifting emissions of gas were ignited one by another, resulting in a continuous popping and apparent running about of the flames. Another interesting exhibition of spontaneous heating was to be seen a few years ago in the storage coal piles of the local sugar factories. This coal was piled in concrete lined pits and the latter were filled with water. However, or this occasion the coal extended above the surface of the water. At every plant where this condition existed the coal was affected heating, and in each case the affected area was in a plane horizontal to and from 8 to 1.4 inches above the water level. The height of the hot area above the surface of the water appeared to be affected by the fineness of the coal. It is well known that oily rags have a tendency to heat when allowed to accumulate in some location protected from free air circulation. For some reason, as yet unknown, this does not apply to petroleum or its derivatives. Now, the most common explanation of spontaneous combustion is that the combustible material oxidizes by being brought into contact with air in the presence of moisture, the theory being that the moisture acts as a catalytic agent. My theory is that spontaneous combustion is due to oxidation of combustible matter by free oxygen carried in solution by a liquid, the oxidation taking place only as, when, and at the place where this oxygen is released from solution by the evaporation of the liquid. Also, this oxidation takes place to some degree regardless of the condition of the combustible-whether it be lump coal, coal dust, straw, wheat flour, coke, or any other combustible but, as the speed of oxidation is directly influenced by temperature, it follows that spontaneous combustion only becomes noticeable or serious in cases where the resulting heat' cannot escape as fast as it is generated.

Jan 1, 1925

By M. Aushouri, S. H. Mansouri, N. Aminizadeh

A thermo-chemical model of the Peirce-Smith copper converter has been developed to predict the molten temperature. The primary assumption of the model was that all matte, slag and gaseous phases in the converter were in thermal and chemical equilibrium. In this model, the matte components were considered only as copper, iron and sulfur elements. In the slag making stage, all the reacted iron was converted to fayalite. The reaction rate of iron and oxygen in this stage was considered to be constant. The converter temperature was calculated by heat balance over time. The model was validated by a detailed comparison with measured industrial data. A good agreement was obtained. The converter temperature depends on process parameters such as oxygen efficiency and molten emissivity.

Jan 1, 2007