Search Documents

Discussion of the paper of L. A. DELANO, presented at the St. Louis meeting, October, 1917, and printed in Bulletin No. 129, September, 1917, pp. 1267 to 1286. L. A. DELANO.-Since this paper was written, our daily mill tonnage has increased, from 2100 tons to 2700 tons a clay. We now use 11,000 lb. of chrome-steel balls of 2 ½ -in. maximum diameter, for an average crushing capacity of 275 tons per 24 hr., this giving a much higher crushing efficiency. I wish to call attention to two typographical errors in my paper as published. On page 1271, Table 1, the screen analysis of ore at the Bonne Terre mill should be stated in inches instead of mesh. - On page 1272, "the rolls average 185 tons per 24 hr., and have shown by test that 250 tons per hour can be maintained" should, of course, read "250 tons per 24 hours." THE CHAIRMAN (0. M. BILHARZ, Miami, Okla.).-Is the increased mill capacity due to improvement in the re-crushing of middlings or to keeping middlings out of circulation and treating them separately? L. A. DELANO.-AS was shown in Mr. Rabling's paper (Bulletin No. 128, p. 1161) the tonnage was raised by about 400 tons by simply changing the arrangement of screen openings in the jig bed and using punched plate instead of woven-wire screen. Then, by adding a ball-mill, we are taking from the jigs a much larger tonnage of middlings than before or as much as the ball-mill will crush. By sending the ball-mill product to tables and flotation, the jig capacity for original ore is increased. CHAIRMAN BILHARZ.-In your opinion, the satisfactory operation of a Hancock jig on a given ore requires adjustment of the length of the different screens and careful selection of screen openings? L. A. DELANO.-I think it does. In order to decide what screen openings to use on the jigs, we did a great deal of experimental work, making screen analyses of the various hutch products, and then hand-sorting the galena, middlings and chat from each size screen to determine the percentage of galena in each. Then adjusting our jig screens, we gradually worked the process up to a very efficient basis. ERNEST GAYFORD, Salt Lake City, Utah.-I would like too ask Mr. Delano whether the work of the Allen cone has been quite as satisfactory as the manufacturers claim for it.

Jan 1, 1918

By W. H. A. Timm

Lake Dufault Mines, Limited, is located ten miles north of Noranda, Quebec, Canada. Following discovery of a copper-zinc orebody late in 1961, metallurgical investigations of diamond drill core were conducted by Lakefield Research Limited during 1962 and 1963. These were followed by pilot-plant tests in May and June of 1964, utilizing underground development ore. Milling operations commenced on August 16, 1964, and reached rated capacity of 1300 tpd by October 1, 1964. Since that time, tonnage was gradually increased to a maximum of 1400 tpd and since January 1, 1968, gradually decreased to the present rate of 1100 tpd due to an increase in the hardness of the ore. The ore milled from start-up until January 1968, was mainly massive sulfides, consisting of a complex mixture of iron, Copper, zinc, and minor amounts of lead sulfides with important associated values in gold, silver and cadmium (average specific gravity of 3-8). From January 1968 until the present, the ore being processed is described geologically as a boxwork of sulfide stringers of chalcopyrite, pyrite, and pyrrhotite with some local dissemination in siliceous rhyolite (average specific gravity 2.9) supplemented by the massive copper-zinc ore. The limited size of the orebody and the mining method employed (open stoping by blasthole and slash benching methods) would have

Jan 1, 1970

By B. H. Cody

THE Morenci concentrator of the Phelps Dodge Corporation is a part of the project that was completed after five years had been spent in development of the open-pit mine, equipment and process testing in the former No. 6 concentrator, and construction of the reduction works. The reduction works, of which the concentrator is a part, is about a mile and a quarter southeast of Morenci, on the highway that leads up Morenci Canyon. The concentrator has a nominal capacity for the treatment of 45,000 tons of ore daily. The original plant, which has a rated capacity of 25,000 tons of ore daily and is now in its fifth year of operation, began production on Jan. 30, 1942. The addition, to increase the capacity 8o pct, began operation on Dec. 1, 1943. The equipment of the original plant has been described in MINING AND METALLURGY (May 1942). No changes in equipment were recommended for installation in the concentrator extension and only one major change, forced by a shortage of maintenance labor, has since been made. Metallurgical treatment has been altered in some ways as experiments progressed and as labor and economic conditions dictated. No complete description of the operation of the concentrator has been published, so this paper will record such operating and equipment changes as have been necessary, the operating methods that have been developed and the metallurgical results that have been obtained. Descriptions are given in the order of the processes with a flowsheet and an equipment list of each process for convenient reference. The questions asked by engineer visitors have guided the detail in which operation and maintenance are described. During the period Jan. 30, 1942 to Sept. 1, 1946, ore milled has totaled 43,595,253 dry tons, from which 1,643,885 tons of concentrate have been made, containing an indicated production of 783,164,809 lb of copper. The principal results obtained in operation of the concentrator during the years 1942 to 1945, inclusive, and to Sept. 1, 1946 are shown in Table 1. A graphic general flowsheet of the plant is given in Fig I. ORE The Morenci ore that is now being treated is a medium-hard monzonite porphyry in which the principal sulphide minerals are chalcocite and pyrite. A minor amount of covellite is present. Chalcopyrite and bornite have been observed under the microscope. The chalcocite occurs mainly as a coating on pyrite. Some of the coatings are so thick that the pyrite presents the appearance of being an inclusion in chalcocite. Some are less than one micron thick and are barely visible at 500 diameters magnification of a polished cross section. Some chalcocite is present as a dissemination in the gangue. Various oxidized copper minerals are present as a result of oxidation in place but they represent a minor proportion of the copper minerals of the ore body. Oxidation

Jan 1, 1947

By D. L., Hayes

THE concentration of zinc ore in Wisconsin is a comparatively simple process, although it presents problems that must be overcome in an efficient manner in such a way that installation and operating costs are low. As the ore deposits are small, the first cost of the concentrating plant must be low; while the low margin of profit makes it necessary to have the minimum operating costs. The original mills were copied from those of the Joplin district, as most of them were built and operated by Joplin millmen. These served the purpose well; they made a clean concentrate, which was the chief requirement at that time, as most 'of the mines were' considerably 'richer than the average at the present time, and wages and supplies were also considerably lower. ' The apparatus used at present has changed very little in principle. . The grizzly opening has gradually been increased to 12 in. and sometimes no grizzly 'is used. The crusher, gradually grew in size, the largest crusher has -an opening of about 24 by 13 in. and a 7/8-in. throw on the. eccentric shaft.

Jan 1, 1921

By Norman Weiss

There was a time in the early history of man's use of metals when ore could be directly reduced to usable form by the use of fire. In those days the term "milling," or its many synonyms signifying the concentration of an ore's metallic con- tents before smelting, was little known. Centuries later, even before Agricola, or even before the Greek and Roman civilizations, simple means were found to concentrate metallic minerals that possessed special characteristics such as high specific gravity, hardness, magnetic response, or simple appearance. In this way, the art of milling became valuable to civilization because it eliminated most of the cost and labor of transporting and melting the worthless nonmetallic part of an ore. As civilization became more dependent upon metals and solid fuels, the art of ore dressing (one of our synonyms) increased in importance and complexity, until today it has become a gigantic industry firmly based upon a mature but rapidly advancing technology. Technically trained people are needed in growing numbers to serve this industry.

Jan 1, 1970

By Vas P. Kenyen

Introduction Autogenous, semi-autogenous, and conventional grinding circuits are used to process ores. Current emphasis, though, is towards the use of the first two systems. The reason is the generally lower initial investment required for an autogenous or semi-autogenous circuit as compared to a conventional comminution circuit. However, the effect of operating costs that will significantly affect overall comminution economics is not considered in this evaluation. About 70% of the energy in a mineral processing plant is used in the comminution circuit. Until the 1974 oil embargo, energy was relatively inexpensive. Since that time, the cost of energy has escalated 40-fold. As a result, energy cost now forms a significant portion of operating costs in comminution. According to a survey conducted by General Electric Co. (Powers, 1982), the price of electricity will continue to rise 15% to 20% per year, in spite of the current oil glut. Both autogenous and semi-autogenous grinding circuits consume more energy than the conventional comminution circuit. Higher consumption ranging from 16% to 35% has been reported in the literature (Bassarear, 1982; Gjerdrum. 1979; Betts, 1982; and Christie, 1979). Consequently, even a small increase in energy costs is likely to have a significant impact on operating costs. Therefore, the economic decision of selecting an optimal comminution circuit is important. More than ever before, it is now critical to include in the evaluation of communition circuits not only the capital costs, but also the operating costs; in particular, the expected energy cost over the life of the operation. Failure to do this may lead to a less than optimal comminution circuit. Design A comminution system should be designed only after bench-scale or pilot plant testing of a representative sample. Conventional crushing and grinding circuits can be designed on the basis of the Bond Work Index (Rowland and Kjos, 1980). Over the years, sizing of full-scale rod and ball mills from Bond Work Index data has become well established. Autogenous and semi-autogenous mills cannot be sized based on bench-scale tests. Pilot plant tests are necessary to determine the amenability of the ore, critical size buildup, and power requirements. For this study, conventional and semi-autogenous grinding circuits were designed for ore throughput of 12, 24, 36, 48, 72, and 90 kt/d (13,200, 26,400, 39,600, 52,000, 79,200, and 99,000 stpd). Rod and ball mills were scaled up on the basis of the Bond Work Index. A two-stage semi-autogenous grinding circuit was designed on the basis of pilot plant test results. In designing a grinding system, emphasis was placed on operating flexibility. The largest commercially available equipment was

Jan 10, 1984

By J R. Brinkmann, S G. Giltner

Nearly all of the South African gold mining industry still uses fuse and igniter-cord initiation systems. Over the past 30 years numerous attempts at developing new initiation systems have not yielded a viable alternative. New initiation systems for narrow stopes are currently being developed by various concerns and the likelihood of these efforts producing feasible alternatives is greatly improved due to the recent advances in electronics technology. The greatest potential benefit of alternative initiation systems is increased production rates through improvements in accuracy and reliability of firing over that of fuse/igniter-cord. Another important feature is the capability of millisecond delay firing as this can lead to reduced stope cleaning times by way of enhanced rock throw and improved fragmentation characteristics.

Jan 1, 1989

By Jochen Franke, Derek D. Lichti

"This paper gives a brief introduction and presents recent enhancements in the MillMapper technology developed for thickness gauging and condition monitoring of liners in grinding mills used for mineral comminution. It also introduces the recent expansion of MillMapper functionality aimed at mill operational optimization. MillMapper uses calibrated laser scanner data captured inside a mill to determine thickness at several million points on all liner surfaces at feed, shell, and discharge ends with millimeter accuracy. Data capture takes nominally 5 minutes, hence interruption to mill operation is negligible.The paper is structured as follows. First, a review of the technology and discussion of recentlyimplemented innovations such as liner change out forecasting, automatic ball charge volume and weight measurement, and automatic mill liner volume/weight measurement for mill operational control or load cell calibration are presented. Combined weight information provides control over load related issues such as load fill levels for relining, or start-up load after reline. Feature descriptions are followed by a listing of the numerous advantages over existing techniques and the benefits to operations. Results from the application of MillMapper are presented throughout.INTRODUCTIONThe need for thickness gauging of liners of grinding mills used for mineral comminution is well known but the task is rarely completed to a satisfactory standard. Liner failure resulting from excessive wear can have expensive consequences. Furthermore, mill performance as well as liner wear are known to be correlated to lifter bar geometry (Napier-Munn et al., 1999; Rajamanni et al., 2005). At present, the following techniques are routinely used to gauge the thickness of mill liners:1. Visual inspection;2. Ultrasonic thickness gauging (for steel liners); and3. Physical inspection (e.g. nail inserted in rubber liners)"

Jan 1, 2008

This paper describes the MillMapper technology developed for condition monitoring of liners and other operational parameters in grinding mills used for mineral comminution, by presenting a case study of its application. MillMapper provides maintenance engineers, operations managers and process and plant metallurgists with quantitative, accurate and reliable condition monitoring data for informed decision making regarding the maintenance and metallurgical aspects of such mills. MillMapper uses calibrated laser scanners for the capture of three-dimensional surface representations inside a mill during a shutdown so as to determine shell, feed and discharge liner thickness at a resolution of several million data points, a procedure that nominally takes five minutes to complete. Once several data sets over time have been collected inside a mill, MillMapper can be used for liner wear, liner wear zone, liner weight, ball charge volume, ball charge weight and intelligent profile tracking over time. Liner tracking in combination with site defined reline and failure criteria and with throughput tonnage data is utilised for change out prediction of each separate liner segment type.

Jan 1, 2008

By Pierre Lacoste-Bouchet, Ian Orford, Mike Cooper

"The Brunswick Mine ore requires fine grinding to achieve liberation of minerals. With 25mm slugs as the grinding media in the ball mill, there was a limitation of a P80 of 25 microns on the CuPb regrind circuit. Results from pilot plant testing showed that the separation efficiency could be increased through fine grinding with a P80 of 15 microns.Options considered were the capital expenditure for new fine grinding equipment such as a vertimill or the use of the present ball mill equipment with smaller media. The Wheelabrator Allevard Enterprise (WAE) millpebs product was chosen because it was a smaller media with a distribution of steel pellets between 5 to 12 mm.With millpebs the grinding product was reduced in size from a P80 of 25 microns to a P80 of less than 19 microns. The power draw to achieve the finer grind was 13% lower while the media consumption was 57% higher.The millpebs grinding media was also tested on the zinc regrind mill. The purpose of the trial was to understand what the media consumption and power draw would be with the charge lowered to achieve an equivalent grind as obtained with the slugs. The media consumption was approximately the same and the power draw was reduced by 30%.INTRODUCTIONThe Brunswick Mine ore is a complex Pb-Zn-Cu-Ag sulphide ore with the grain size of the minerals varying from submicron blebs to particles up to several mm in size. The ore is ground progressively finer in stages. The first step of grinding occurs in the SAG mill circuit. The product sizing 80% passing 95 microns is fed to the CuPb prefloat stage (Cormier et al 2002). The tails from the prefloat is then further ground to a P80 of 35 microns for the CuPb rougher flotation. The final liberation for the CuPb circuit takes place in the CuPb regrind circuit. The regrinding mill further liberates the cleaner scavenger concentrate, second cleaner tails and third cleaner tails. The reasoning for the progressive grinding is to achieve fine grinding without having galena over ground due to its high specific gravity that preferentially sends it to the cyclone underflow."

Jan 1, 2006

By Christopher J. Farrow

This paper describes the grinding circuits installed at two remote sites in northern Canada. One is Cominco's Polaris Project at Little Cornwallis Island; a barge-mounted lead/zinc concentrator. The other is Echo Bay Mines' Lupin Project at Contwoyto Lake, 400 km northeast of Yellowknife, a gold mine, all components of which had to be flown to the site. Logistics and considerations of operating and maintenance presented challenges which were met by innovative design. The evolution of the grinding circuits is discussed. Both plants are operating at design throughput.

Jan 1, 1983

By B. K. Mishra, R. K. Rajamani, R. Venugopal, P. Songfack

Millsoft is a computer-simulation software that predicts the performance of large industrial grinding mills. This software surpasses all other tumbling-mill analysis techniques available today because it is based on fundamental laws of physics instead of empirical correlations. Graphical user interface (GUI) forms simplify the specification of the following design and operating parameters: mill diameter, length, speed, charge density and size distribution, lifter material and geometry. All of these parameters are taken into account in the discrete element numerical technique that constitutes the essence of the simulation software. In turn, the software produces a visual animation of grinding-charge motion, predicts mill power and gives the distribution of impact energy. In this paper, a case study of an 8.5-m-(28 ft-) diam SAG mill is used to illustrate the application of Millsoft for mill design and trouble shooting.

Jan 1, 2000

By Sydney Mantsho, Toni Streczynski, Manuel Gonzalez

"In 2013, the commissioning of the MillStar Stabilisation and FloatStar Stabilisation and Optimisation controllers were completed at the Cerro Bayo Silver (Ag) mine in Patagonia, Chile. The MillStar control system has stabilised the feed to the SAG mill as well as the density at the discharge end of the SAG mill and ball mill. The FloatStar Stabilisation and Optimisation controllers have successfully stabilised and optimised the flotation circuit to ensure consistent product quality within desired specifications.The mill feed is controlled utilising the MillStar Solids Feed controller. Additionally, the solids to liquid ratio into the SAG mill was controlled utilising the Mill Inlet Ratio controller in conjunction with the Solids Feed controller. The discharge end of the milling process is a highly interactive and complex system. The use of a Robust Nonlinear Model Predicative Controller (RNMPC) was ideally suited to control this section of the process. On the Cerro Bayo milling circuit, the RNMPC was used to control the mill discharge sump level and the primary cyclone feed density to produce a more consistent feed to the flotation circuit.Three levels of the FloatStar control system were installed, for flotation stability, concentrate flow stability as well as grade optimisation. The Level Stabiliser was used to stabilise the level control on 6 flotation banks. The Flow Optimiser was commissioned on the Rougher, Scavenger and Cleaner concentrate sumps to stabilise concentrate flow from the flotation cells. The Grade Recovery Optimiser was commissioned on the Roughers section. A number of instrumentation challenges were identified which limited the overall benefit derived from the system. Once these were addressed, the performance was optimised. The overall benefit provided by the system was observed in terms of the improvements in Ag recovery."

Jan 1, 2014

By Steven Hoerger

Mixed integer linear programming (MILP) production scheduling models can be used to evaluate if tonnage improvement projects will deliver value over all time periods and whether new bottlenecks will be created. These MILP models can evaluate the interconnected effects of mine and process capacities, mining locations, cutoff grades, stockpiles, and orebody grade/tonnage distributions. A case study compares potential value creation from a mine capacity increase, a mill capacity increase, or a simultaneous increase in all capacities. For perspective, project valuations for capacity increases are compared against valuations for cost reduction projects, mine planning improvements such as phase design, dynamic cutoff grades and stockpiling, and the impact of geostatistics improvements in the areas of block model accuracy and ore control selectivity.

Feb 1, 2024

By AIME

TO say that Milton Fies has been active in promoting the Southern Research Institute is a masterpiece of understatement. He is a director and trustee who was in on the ground floor when plans were first made for the Institute and since it became an actuality early in 1945 his interest and efforts continue. He talked about it at the last regional meeting of the Birmingham Section of the A.F.A. and has talked all over the South-and when he makes a speech he has really prepared it. He does not try to rival a political spellbinder, but his careful, concise English is always well thought out and to the point. Southern Research might be called his present hobby as it has been for the past two or three years. Another major interest has been his encouragement and training of engineering students. Active in the formation of the Student Chapter of the A.I.M.E. at the University of Alabama, for several years he saw to it that the students had a prominent engineer at each monthly meeting, usually taking them down to Tuscaloosa from Birmingham in his own automobile. He has also been keenly interested in the mining engineering activities at Tuscaloosa, both in the Bureau of Mines and the University.

Jan 1, 1946

The One Hundred Eighteenth Meeting of the. Institute was held at the Milwaukee Auditorium, on Tuesday,. Oct. 8, to Thursday, Oct. 10, inclusive, 1918, under the joint auspices of the Committee on Iron and Steel (Chairman, Prof. J. W. Richards), and the Institute of Metals Division (Chairman, William M. Corse), and simultaneously with sessions of the American Foundrymen's Association and of the. American Malleable Castings Association. It was preeminently a war meeting. It was attended by 104 members of the Institute. The social features, so far as the members of this Institute were concerned, were slight, but generous and appropriate entertainment was offered to the ladies, consisting of automobile sight-seeing trips, reception, concert and dance on Tuesday evening, a theatre party Wednesday evening, and -a banquet in-the Auditorium Thursday evening, at which the speakers were Charles M. Schwab, Director General of the United States Shipping Board Emergency Fleet Corporation, Major A. Radclyffe Dugmore, and W. H. Blood, Jr., Assistant to the President of the American International Shipbuilding Corporation. A joint session was held on Tuesday morning, at which an address of welcome was delivered by Hon. Emanuel L. Phillipp, Governor of Wisconsin, with a response by Benjamin D. Fuller, President of the American Foundrymen's Association, and the following addresses: Activities of the Army Ordnance Department, Especially as Applied to Foundry Matters. By C. S. Koch, Cannon Section, Production Division, Ordnance Department. Washington. D. C.

Jan 11, 1918

Jan 1, 1919

Jan 1, 1925

The 118th, meeting of the Institute, which has been arranged primarily for the benefit of the Institute of Metals Division and of those members who are particularly interested in iron and steel, will be held in the Milwaukee Auditorium, Milwaukee, Wis., on Oct. 8 to 11, 1918. This date has been selected because at that time, and at the same place, the American Foundrymen's Association and the American Malleable Castings Association will hold meetings. A notable exhibit of metallurgical and mechanical processes and products, at which over 165 firms will be represented, has been arranged in Machinery Hall, of the Auditorium Building. Wherever practicable, the machinery will be in operation. The program of the Institute's sessions was published in Bulletin 141. A special announcement of the meeting, together with a program of the sessions of the American Foundrymen's Association, has been mailed to every member who was thought to be directly interested in the meeting. A report of the meeting-and of the discussion of papers will be printed in the December Bulletin.

Jan 10, 1918

A special meeting of the Institute, at which the Institute of Metals Division will join with those members who are most interested in iron and steel, and in coal and coke, will be held in Milwaukee, Wis., October 8 to 11, 1918. The technical program is as follows: INSTITUTE OF METALS DIVISION Tuesday morning, October 8: The Metallography of Tungsten, by My Jeffries. (Bulletin No. 138, p. 1037.) The Constitution of the Tin Bronzes, by S. L. Hoyt. Paper, title not given, by C. H. Mathewson. Notes on Babbitt and Babbitted Bearings, by Jesse L. Jones. (Bulletin. No. 140, p. 1397.) Oxygen and Sulphur in the Melting of Copper Cathodes, by S. Skowronski. (Bulletin No. 135, p. 645.) The Relation of Sulphur to the Overpoling of Copper, by S. Skowronski. (Bulletin No. 135, p. 651); with discussion by Philip L. Gill. (Bulletin. No. 140, p. 1156.)

Jan 9, 1918