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By Yoshio Hiramatsu

In Toyoha mine near Sapporo, the ground temperature is very high, perhaps due to inflow of hot mineral water, the origin of which may be rock masses intruded by the igneous activity in the Tertiary period. The rock masses are found about 2 km east of the mine, their temperature being estimated at from 770 to 870 K at a depth of 3 km. In this mine several veins bearing zinc and lead ores have been mined down to the depth of 300 m from the level of the main entry, of which altitude is 551 m above the sea level. Formerly no attempt was made at development of the deeper part of the mine than the 350 m level from the main entry. Let us indicate hereafter the levels in this mine in such a way that the level 300 m deep from the main entry is denoted as 300 mL. Since 1974, however, the 450 mL of Tajima vein has been developed by deepening No. 5 Shaft to, and by driving drifts in the level. Much hot mineral water has been flowing into the drifts from rock. After twenty-eight months from the beginning of development, the total length of excavation amounted to about 1300 m. The success in development so far may be attributed to cooling rock and air with chilled water and to adopting heat-resisting explosives and detonators. This cooling costed very much and for further development in this level a more effective and economical cooling is desired if possible. To obtain fundamental data for designing an economical cooling, the authors investigated, as a preliminary study, the heat balance in the main drift of 450 mL, by measuring the temperatures of air, rock, hot mineral water, the rates of flow of air and water and so on, in August 1976. They are now carrying out continual measurements of the variations in rock temperature, air temperature and humidity with time. The present paper describes the details of the preliminary study.

Jan 1, 1980

By E. Mokgwamme, T. Goff, M. Mvalelwa, P. Spratt, P. Bezuidenhout, P. Nkosi, H. Joubert, G. de Villiers

Sibanye-Stillwater recently completed a partial sidewall rebuild on Furnace 1 at its Marikana smelter complex. The project involved matte taphole maintenance, which required the removal and subsequent replacement of 18 composite copper-graphite coolers and a section of the lower refractory sidewall. These composite copper-graphite coolers are a newly developed cooling design by Tenova Pyromet, and this rebuild project provided valuable insight into the performance of the composite coolers. The novel composite cooler design was implemented to serve as a safeguard against localised wear and corrosion in the furnace sidewall, particularly at the slag-concentrate interface, where chloride-accelerated sulphidation has been identified as a dominant degradation mechanism affecting the copper cooling elements. The composite cooler design is unique in that all the exposed sides of the water-cooled copper elements are fully encapsulated in graphite, which protects the copper from corrosive sulphur- and chlorinebearing gases and condensates. This sidewall cooling system was designed to improve corrosion resistance, stabilise freeze lining formation, and extend the campaign life of the furnace sidewall. The partial sidewall rebuild was executed during a planned maintenance shutdown with the main objective of replacing the matte taphole lintel bricks. This paper serves as a case study that compares and evaluates the operational performance of the composite coolers before and after the rebuild. The installation method is discussed to highlight the approach taken to ensure a sound installation while minimising downtime, as well as to present some lessons learned in the process.

Mar 6, 2026

By F C. D Michelin

As mines get deeper, the critical underground temperature limits will be exceeded, and an increasing number of mines will need to implement, expand or modify cooling systems. Surface cooling plants have many advantages over underground cooling such as efficient heat rejection, and lower relative capital cost; however the delivery of cooling through long underground distances can result in lost refrigeration capacity before the chilled air reaches the areas it is needed most. Refrigeration plants are therefore often overdesigned in size and capacity to compensate for underground losses.More mines are now utilising real-time monitoring and automated control of ventilation airflow and fan systems to ensure the conditions underground are safe and productive, and power consumption is efficiently managed. There may be significant opportunities to extend ventilation monitoring and control into the refrigeration delivery and control system.Energy reduction is an effective way to reduce costs and CO2 emissions, which is an increasingly important part of corporate governance. More efficient refrigeration control is a further step toward reducing energy consumption. This paper looks at an added step in how real-time monitoring can assist in controlling the output and chilled air delivery of a cooling plant. The requirements, implementation, benefits and challenges will be discussed.

Oct 12, 2022

By B Belle, M Biffi

Cooling of coal mines in the Bowen Basin, characterised by steep geothermal gradient, is presently achieved mostly through rental surface bulk air cooling in summer months. This paper argues that future mines will be required to focus their cooling resources more intensively to manage a challenging thermal environment where virgin coal temperatures of over 50¦C at a depth of 500 m are expected. Currently, mine cooling systems are employed to maintain the wet bulb temperatures (WBT) to below 27¦C at which point the risks of heat stroke or other heat-related issues are manageable. The capacities of these systems are in the range of 6 MWR to 10 MWR. The relationship between high working temperature environments and injury frequency rates is well established. Therefore, provision of appropriate cooling strategies and understanding their optimum performance and suitability are important to Australian coal mines of the future. This paper evaluates the underground temperature profiles of deep, gassy coal mines with propensity for spontaneous combustion and proposes the long-term cooling pathways to effectively manage thermal hazards. Thermodynamic modelling is performed on a longwall face and includes air leakage effects from goaf streams at various locations along the longwall face. The strategy summarises the application of underground bulk air cooling, chilled water sprays on the shearer and the resulting temperature profiles. Considering the new mining projects planned for the Bowen Basin region, a review of implementable cooling strategies such as mid-gate mobile bulk air coolers (BACs), spot coolers, underground bulk air cooling and the use of chilled water to enhance the positional efficiency of cooling plants, are discussed in this paper. Finally, the comparison of ærentalÆ versus æownershipÆ of cooling plants is analysed as part of long-term cooling strategies.CITATION:Belle, B and Biffi, M, 2013. Cooling pathways for deep Australian longwall coal mines of the future, in Proceedings The Australian Mine Ventilation Conference , pp 223-236 (The Australasian Institute of Mining and Metallurgy: Melbourne).

Jul 1, 2013

By Austin Whillier, Duncan Mitchell

The problem of heat stress underground in the gold mines is approached on the basis of the heat transfer between the human body and the underground environment. Experimental measurements of radiant and convective heat transfer and a theoretical calculation of maximum evaporative heat transfer enable the maximum cooling power of an environment to be calculated in terms of the dry-bulb and wet-bulb temperature, the mean radiant temperature, the wind speed and the barometric pressure. For most underground applications the cooling power can be expressed as a function of wet-bulb temperature and wind speed only. The relative importance of wind speed and wet-bulb temperature can be assessed: in working places where wind speed is low additional cooling of workmen can be achieved better by increased wind speed than by decreased wet-bulb temperature. The wet kata reading proves to be of limited value as an index of heat stress because environments with equal wet kata do not necessarily have the same cooling power. Finally, thermal equilibrium with the environment is possible when cooling power equals or exceeds the rate of metabolic heat generation. The rates of metabolic heat generation for various underground tasks are indicated.

By N. B. Pilling

THE development of a proper treatment for shells in connection with war contracts has brought to our attention the fact that the temperature of the liquid bath in which steel is quenched has a decided influence on the speed of cooling in the case of some liquids and very little in the case of others. Widely different physical results have been obtained by the use of water spray, water immersion, and oil immersion and further experiment has shown that the quenching effect of water used as a spray or an immersion varies greatly with the temperature of the water. The present experiments were undertaken with the idea of obtaining information of a quantitative nature regarding the quenching properties of a number of liquids used commercially in hardening steel. The general features of such cooling media are common knowledge and in the literature may be found records of numerous attempts to evaluate the cooling power of a liquid when used as a quenching bath. Much, if not most, of the data given on this subject is in the form of a simple statement of the time required for a certain heated mass to cool between two arbitrary temperatures when immersed in the liquid, quite regardless of the path of the temperature change. Our own purpose has been somewhat different. We have attempted to isolate that property of these. liquids having to do with their ability to absorb heat rapidly, as distinct from the behavior of a considerable mass when exposed to different thermal environments. More specifically, from the data obtained through autographically recorded cooling curves of a small standard mass quenched under various conditions, we have tried to analyze the mechanism of heat absorption by the several liquids, measure the changes in its rate as a function of the temperature of the surface of transference, and ascertain the influence of the temperature of -the liquid itself upon both.

Jan 9, 1919

H. M. HOWE, Bedford Hills, N. Y.-One wonders, whether it might not be well to check, by a rather simple and direct way, the inferences that would be drawn from this investigation. Suppose we quench, in these various liquids cylinders of steel, selecting material that is not likely to split in hardening, and then examine their cross-sections micro-scopically. If the cylinder is of any size, you will find a series of concentric bands, a very hard band, a softer band, and a hard band-but it seems that here would be a way of checking the inferences from the cooling curves by comparing these waves of hardness obtained in similar speci-mens quenched in different liquids. One would think that there would be great promise in that way. One's first thought is to quench similar pieces of steel, similarly heated, in different liquids and determine their hardness. I suppose many of us have tried that. We then meet the-difficulty that it is not the most rapid cooling that gives the greatest hardness. There is an intermediate rate of cooling that gives maximum hardness so that you can not by any simple method as that check this cooling method. But it seems possible

Jan 12, 1919

The subject of heat sources in deep hard rock mines, the limitation of forced ventilation to cope with these heat loads and the sizing of refrigeration plants to boost the cooling effect of the ventilation air are discussed. The development of plant selection criteria and operating experience at North Broken Hill Limited is outlined. Future options for North Broken Hill Limited and like deep mines are summarised.

Jan 1, 1982

By R. C. Head

The investigation describe the history of copper in the seventties, as well as indicates the forecast the probable trend of the Copper Industry over the coming decade, and second, to stimulate some discussion on what is a somewhat controversial subject. At the same point, the period of surplus production from about 1972 to 1976-1977, during part of which some voluntary restriction on output maybe necessary. In consecuence, its a necessity for forward planning so that, by 1973-1974, new mines maybe developing to preserve the continuity of supply .

Nov 20, 1969

By John Petty, John Loviza

Single sentence describing content-- "The best ally an Explosives Engineer can have in a court of law is a regulations enforcer stating all codes and standards were met on a jobsite".

Jan 1, 1996

By W. A. Vine

Next year, in 1964, Butte will celebrate its Centennial. It was in May, 1864, that the first recorded mining activity took place. During that summer, several rich placers were found on Silver Bow Creek and its tributaries, and a gold rush followed. As placer mining proceeded in the creek beds, the quartz lodes on the hillsides were located and the veins were prospected. Mining in Butte entered its second phase when the rich silver mines, the Alice, Moulton, and Lexington, were opened. The silver boom lasted until the decline in the price of silver in the early 1890's forced the closure of many of the mines. An indication of the beginning of the copper mining era in Butte was in 1866 when it was noticed that green copper carbonate discolored some of the, lode material. It was not until ten years later, however, that the Anaconda and St. Lawrence claims were located by Michael and Ed Hickey. The claims were sold in 1880 to Marcus Daly and in 1881, Daly obtained financing and organized the Anaconda Silver Mining Company to exploit the vein The silver venture was a failure because of the predominance of copper which diluted the bullion to only 400 fine.

Jan 1, 1963

By Herbert F. ?Buck? Darling

A bridge replacement project in Rochester, NY, encountered difficulties when it was determined that rock below one pier was sloping downward toward the river at an angle of 42 degrees versus anticipated 12 degrees. Cofferdam design and construction became very difficult. The unanticipated subsurface conditions delayed the project by eighteen months and increased the cofferdam cost by almost $3.0 million ($US) when direct costs and associated delays were taken into account. The initial approach after discovery of the problem was to use the same type pier design and modify the cofferdam accordingly. This resulted in a cofferdam 12 meters (39.4 feet) deep on the shore side and 18 meters (59.0 feet) deep on the water side. The design used a master pile system to attain required wall strength and used rock anchors to prevent the cofferdam from moving toward the river. The pier foundation was then redesigned by the owner using revised seismic parameters. The original stepped footing carved into rock was replaced by caissons socketed into the rock beneath a large tremie concrete placement. The revised pier and cofferdam designs caused a shift from a mostly land based cofferdam, excavation, and rock removal project into an almost entirely water based cofferdam, caisson drilling, and tremie construction project. These design changes resulted in a reliable, safe, and unusual cofferdam and construction method. All of this was accomplished within a very narrow worksite with a railroad on one side, and the river with its public and commercial freighter traffic on the other. In addition, the existing two-leaf drawbridge was to be maintained in place which put further limitations on the water borne equipment. The engineering and construction considerations, problems, and solutions related to these cofferdams and pier foundations are presented.

Jan 1, 2013

By Donald M. Keagy

How many times have you said or heard someone say, 'What are you doing right now?" And how many times have you heard the reply, "Breathing air!" Probably never, or at most only a few times in a facetious vein. Breathing air is absolutely necessary to sustain human life, and yet most of us take it completely for granted. Beginning ten to fifteen years ago there was growing concern on the part of the general public that pollution of the air is a threat to man's health and welfare. Concurrently much thought and effort was devoted to the task of defining and resolving the problem of air pollution. In the course of this effort it has become quite clear that our National policy in this regard should be founded upon three basic axioms: (1) Action should not be postponed until emergency conditions make it compulsory; (2) The air cannot be purified after it is polluted, and (3) Air pollution control cannot be accomplished without close cooperation among all levels of government, industry, and the public.

Jan 1, 1967

Design and test a high-production coal mining machine that generates less respirable dust. Background Current coal cutting systems generate excessive amounts of airborne respirable dust and fines during the mining process. Dust control technologies, including dust dilution by ventilation and suppression by water sprays, are not always able to reduce dust levels sufficiently. The U.S. Bureau of Mines (USBM) has designed a cutting system that reduces respirable dust generated by the cutting action of the drum. This cutting system, based on geometric principles developed in the 1500's, makes use of a constant depth, linear cut to remove coal at deeper cut depths and at lower rotary speeds than a conventional rotary drum. A comparison of the linear and rotary cut paths is shown in figure 1. Approach A full-scale prototype of the linear cutting concept was valuated under laboratory conditions to determine its performance relative to standard rotary drums. Results of these evaluations show production of fewer fines, or more uniform product size, a significant reduction in the amount of airborne dust, and reduced torque and power requirements (figure 2). On the basis of these results, a contract effort was undertaken by McCracken and Associates of Bristol, TN, to design a linear cutting head for underground testing.

Jan 1, 1995

A number of cooperative studies have been carried out as preliminary work for drafting a standard for application of granulated slag sand for concrete, and the following conclusions were reached 1 The ten kinds of granulated slag sands pro- duced in Japan satisfy the national standard for fine aggregate in terms of physical and chemical properties. 2 Mortar and concrete tests conducted with granulated slag sand revealed that, although with slight differences in the extent, gran- ulated slag sands used in these tests were applicable'as fine aggregate for concrete, 3 The pumpability test by a concrete pump carried out on concrete with two kinds of now commercially available granulated slag sand demonstrated that the pump pressure feeding is applicable in the same manner as in the case of ordinary concrete. These tests permitted' preparation of a draft standard for application of granulated slag sand, and the results formed the first step toward utilizing this material as a sub- stitute for natural sand.

Jan 1, 1979

By J. G. Thompson

THE methods employed for the determination of oxides and oxygen in ferrous materials may be roughly classed in two groups, "wet" methods and "hot" methods, the first group including the iodine, electrolytic, mercuric chloride, hydrochloric acid, nitric acid, and chlorine methods; the second group including the vacuum-fusion and hydrogen-reduction methods. The wet methods depend upon preferential solubility in a selected medium to separate the metallic portion of the sample from the oxygen-containing constituents. Subsequent analysis of the insoluble residue permits the isolation and separate determination of individual oxides and compounds. The hot methods depend upon the reduction of the oxide constituents of the sample by means of carbon or hydrogen at elevated temperatures. With the exception of the recently developed fractional vacuum-fusion method, the hot methods do not identify individual oxides and compounds but yield only a single value represent-ing the sum of the oxygen contents of several or all of the oxide con-stituents present. With such diversity in the principles and. aims of the different groups, it is not surprising that concordance of results by differ-ent methods has usually been difficult to obtain. The present cooperative attempt to define more rigorously than has been possible heretofore the accuracy and limits of usefulness of the vari-ous methods, originated in correspondence between Dr. John Johnston, Director of Research of the United States Steel Corporation, and other interested metallurgists. The plan was, briefly, to submit identical samples to a number of laboratories for analysis by different methods and to collate the results of these analyses. The project was endorsed by the Iron and Steel Division of the American Institute of Mining and Metal-lurgical Engineers at the annual meeting in February, 1933, and has been conducted under the joint sponsorship of the Iron and Steel Division and the National Bureau of Standards. The latter organization undertook

Jan 1, 1936

By Anoop Sattineni

Over the past decade the use of BIM in the AEC industry has grown several fold and with it the number of standards available for implementing BIM. The ?National BIM Standard? by buildSmart Alliance, the ?Contractor Guide to BIM? by the Associated General Contractors of America, the ?BIM Project Execution Planning Guide and Templates? from Penn State University, the ?BIM Roadmap? by the US Army Corps of Engineers are some of the several BIM guidelines that are currently available to the AEC industry practitioners. Some of these guidelines are as comprehensive as defining BIM and the associated taxonomy while others are meant to be used on an individual project basis. From a contractor?s perspective one of the key benefits of using BIM is for the purpose of collision detection and coordination. This research has found that currently available guidelines do not address these issues adequately. For instance, the currently available guidelines do not allow the subcontractor to quickly communicate issues such as naming conventions and color schemes within the model, to the general contractor. Consequently general contractors and sub-contractors find themselves making changes to their BIM deliverables based on each other?s abilities and levels of adoption, apart from reason?s stemming from use of different software platforms. This paper describes how a group of contractors and subcontractors from Atlanta and Birmingham in the United States came together to create and adopt a ?Coordination Guidelines for Virtual Design and Construction?. These guidelines were specifically created with the purpose of streamlining the construction coordination process using BIM. This paper describes how the guidelines created differ from other guidelines currently available in the industry.

Aug 1, 2013

By C. Tom Blevins

The purpose of this paper is to discuss production and roof control problems associated with directional lateral stresses in an in situ stress field and the approach that Inland Steel Coal Company made in trying to cope with them. Before proceeding, a description of the mine location, product, geology, restraints, and mine history is in order. The mine is located in Hamilton County in Southeastern Illinois. It produces a high volatile metalurgical coal and is slated to produce 2.1 MTY. Product ion is in the Illinois No. 5 seam at a depth of 930 feet, approximately 490 feet below sea level. The scam height averages from 5.5 to 6.0 feet throughout the reserves with height increasing in the eastern reserve area to approximately feet and a 5 Foot average in the West. The scam tends to dip to the North, North East, but is locally very undulating. The Galatia channel washout outlines the eastern boundary of the reserves and there is a split coal area toward the central part of the property than runs south-southeast. The top above the #5 seam is laminated medium gray shale called Dykersburg. Individual shale bedding planes vary locally From ½ to 1" in thickness to a more normal thickness of 1 to 1 ½ with some areas being interlayed by thin carboncous material. The top normally must be considered as materially competent. Even though the mine is still relatively small in area with only 1.3 million tons of total production to (late, we have encountered dense zones of slicker sides and premining, stress cracks (joints). There are also areas of siltstone, that vary from a few inches to several feet thick, and areas of rider coal, clay instrusions, and rolls. We have crossed lineament concentrations that show strong evidence of corelation to localise top problems. These are being monitored closely to see their predictability on our present and future mining conditions. The face cleat runs N 55° E and butt cleat runs S. 25° E. On a regional basis, there are several anticlinal belts that trend in a northerly direction. The one major restraint is that Inland does not own surface subsidence rights. Therefore, a partial extraction mining plan is being followed. The Holland-Gaddy formula for pillar strength design is used to calculate theortical pillar sides. When production began in March of 1979, it was noted that ground control problems occurred as we drove north entries. East-west cross cuts tended to have better working conditions. This phenomia occurred from a couple hundred feet, but seemed to dispate as we got away from the men and material shafts. Once the production shaft was connected and enough entries extended for installation of belts, ground control problems were again experienced in north-south headings. It was also observed that when mining north-south headings with east-west crosscuts, if the crosscut was driven through ahead and supported, the intersection was stable upon entry connection. This held true even where fairly extreme ground control, problems were encountered. The reverse held true. when driving east-west headings with north-south crosscuts. At this time, we started searching in earnest for a working theory to explain this roof phenomia. It also became the first step of what eventually was a four step sequence to derive a workable solu¬tion to the problem. The combination of the many geological changes and the fact that north-south condition was at times intermitent, helped to disguise the stress field. The mine also being in a fairly virgin area with no mines in approximately 25 milt, radius, meant we didn't have a reliable case history to examine. Various theories were researched before it was concluded that our primary ground control problem was a directional lateral stress Field, with the major stress axis in an east-west direction. The second stop of the procedure was then to test. mining methods and determine if these stresses could be modified to a

Jan 1, 1982

By R. A. Wagstaff

Since the time of the early Egyptians, the use of copper: has been a boon to the life of most of the civilized world. Its use has been varied; in many connections, the art by which it attained its greatest usefulness has been lost. In this paper an endeavor will be made to take into consideration some of the many changes that have occurred during the last 40 years of copper-smelting operations. During that period the copper blast furnace has been almost forced out of existence by new methods of ore concen-tration—first, gravity concentration, and then flotation. These new methods of concentration introduced many new factors into the metallurgy of copper. The product was wet, it was fine and it was high grade. To overcome all these factors many changes have been necessary throughout the smelting agenda. New equipment has been necessary for transportation, unloading, sampling, bedding and moisturing in all smelting plants, especially the custom smelter' During the early days of "flotation," little was known about filtering or the use of an alkaline circuit; often the concentrate going to the smelter contained 2' to '5 Per cent moisture. It is easy to imagine the difficulty arising with a product of this nature when it had to be shoveled by hand labor. To meet these conditions, mechanical unload- ing and sampling devices were soon developed. In many instances such good progress was made that actual costs for handling this unfavorable product were lower than those formerly incurred on the old product. Today most sampling of copper ores and concentrates is being done by mechanical sampling, pipe or augur sampling, or shovel sampling. Where concentrates are uniform in metal content, a great many of the plants now use pipe or augur sampling. For spotty ores, the old shovel sample with cone and quartering during the final stages is still in' use. Where big tonnages are handled, mechanical sampling of concentrates is being done, with satisfactory results. To curtail slow and tedious cutting and mixing procedure, mechanical mixing boxes, splitters and cutters are used to cut down labor costs. Milling As crude ores become scarcer, the use of milling operations increases. The few crude ores that are still smelted are used as fluxing types. To use these ores finer grinding has been found advantageous. This has made for better bedding and fluxillg conditions, which in turn makes for faster smelting, lower fuel consumption and better metal recovery. The degree of fineness is more or less determined by the nature of the product. Most plants have set a standard of through 3/8-in. mesh screen for roaster -reverberatory smelting and through 3/4-in. mesh screen for converter fluxes. For some refractory Ores, even finer grinding has been found to be advantageous for good reverberatory smelting-

Jan 1, 1944

By Leonard Larson

Before direct or wet smelting of copper concentrate was adopted at the McGill smelter, in November 1932, actual furnace smelting tests had indicated the possibility of smelting between 400 and 500 dry tons of wet concentrate per furnace day. Under calcine smelting practice, solid charge up to 116; tons per furnace day had been smelted. It was realized that in order to smelt wet tonnage in equivalent amount per furnace day, a higher combustion rate and higher temperatures would be necessary within the furnace. The reverberatory furnace considered in the following history of wet-smelting developments is a unit rz7 ft. long and 28 ft. 8 in. wide, inside dimensions (Fig. I). This furnace was in operation through all the years from 1934 to date. During 1933, the first complete year of direct or wet smelting, the plant was on a curtailed copper-production basis and the available concentrate tonnage to be smelted was limited. The average coal-firing rate in the reverberatory for that year was 124 tons per furnace day. This rate was lower than the average for years immediately preceding under calcine smelting practice. With this coal-firing rate, an average of 391 tons of new metal-bearing material (N.M.B.M.) was smelted per furnace day. The following year, 1934, the coal-firing rate was increased to 139 tons and the smelting rate increased to 448 tons N.M.B.M. per fur- nace day. In succeeding years production required that either more tonnage be smelted in the one furnace or an additional furnace be placed in operation. With this situation confronting the smelting department, it was determined to continue the program of increasing the coal-firing rate and also to intensify the temperature in the smelting zone of the furnace. In order to accoinplish this, various improvements were made to aid combustion within the furnace. The burners were enlarged, increased primary air was supplied to the burners, and changes were made in the furnace to enlarge and streamline the outlet, thus increasing the furnace draft. The coal-firing rate was increased yearly until 1937 when the firing rate averaged 210 tons per furnace day. Thereafter the firing rate fluctuated according to character of charge and production requirements. In general, however, with the same character of charge the smelting rate increased in almost direct proportion to the increases in firing rate. Table I shows the average coal-firing rate, smelting rate, and other pertinent data for the direct-smelting years of 1933 to 1939 inclusive, the first fivc months of 1940 and May 1940. These figures show that the water evaporated in the waste-heat boilers was in almost direct proportion to the coal-firing rate. In making comparisons in the table, it should be borne in mind that the figures, except for May 1940, are yearly averages. Because of changes in character of charge or operating conditions, records for individual days or even months

Jan 1, 1944