Mineral Processing Engineering

Grinding Circuit Control

Cyprus Pima has two concentrators, one with a conventional crushing-grinding circuit and the other using semiautogenous grinding followed by ball mills.

Old Mill Flowsheet

The original mill was constructed in 1956 but has been expanded three times so that by 1967 there were ten sections having a total capacity of 36,000 tpd. Subsequent revisions have increased this capacity to about 40,000 tpd. Mine ore is fed to a conventional three-stage crushing plant with final product, averaging about 25% – ½ inch, being conveyed to fine ore bins

New Mill Flowsheet

A completely new and separate primary crusher was constructed for the new mill which was put on stream late in 1971. Present capacity of the new mill is about 19,000 tpd. The new primary is identical with the existing one except that the crusher discharge is fed to a Barber-Greene radial stacker conveyor that can serve both the old mill stockpile and the new mill stockpile.

One unique feature of the grinding circuit is a provision to use the cyclone feed sump as a sump common to both ball mills or as individual sumps to allow the ball mill circuits to be operated separately. Another advantage is that when one semiautogenous mill

By |2019-01-12T18:48:47+00:00January 9th, 2019|Categories: Grinding|Tags: |Comments Off on Grinding Circuit Control

Grate-Kiln Operations for Better Pellet Quality

This paper describes some of the latest improvements that have been incorporated or planned by the Cleveland-Cliffs Iron Company to reduce operating costs and improve pellet quality. The Cleveland-Cliffs Iron Company operates and manages mining, beneficiation, and pelletizing operations in Michigan, Canada, and Western Australia.

Operating/Maintenance Cost Savings

Cleveland-Cliffs Iron Company, in December, 1976, embarked on an extensive test program utilizing various intensive mixing devices in an attempt to reduce present bentonite consumption in the pelletizing operations while maintaining pellet quality. Bentonite mixing devices tested at the LKAB straight-grate plant at Malmberget, Sweden reportedly have resulted in decreases in bentonite consumption.

The dual horizontal compartment-type mixer contains two muller wheels and two plows which rotate from a center shaft. Muller wheels at a controlled pressure agitate the mix through a special kneading, smearing, spatulate action. Two plows sweep the mix to an air operated bottom discharge door. Capacities range from 7.1 metric tonne/ hour (7 long ton/hour) to 508 metric tonne/hour (500 long ton/hour).

In testing the pellet plant feed materials from each of the operations, the first test series included firing of fresh plant green balls in the pot-grate and batch rotary kiln in order to avoid green ball degradation. The

By |2019-01-12T18:48:14+00:00January 9th, 2019|Categories: Steel|Tags: |Comments Off on Grate-Kiln Operations for Better Pellet Quality

Gearless Ball Mill Operation

The reliability of large diameter, high horsepower ball mill is paramount when large production and minimum downtime is required. The 17 ft. x 56 ft. double compartment ball mill at St. Lawrence Cement Company has the first gearless drive built in North America and has the world’s largest hydrodynamic bearings currently built and running. The machine has seen three years operation and has met its specifications.

Structural Design of Mill and Bearings

The performance of the gearless drive is affected by the structural design of the mill particularly its stiffness characteristics. A knowledge of the mill internal dynamics is required both for the design of the mill and behaviour of the gearless drive.

From geometry and known weight of charge and a knowledge of the bearing friction. The load torque curve for various angles can be established. The gearless motor can then be sized to the torque requirements.

The full line representing theoretical values, the dotted line representing measured data. The difference between the curves represents the acceleration of the machine. There is a primary acceleration curve, followed by a secondary deceleration and then by a tertiary acceleration.

Structural Design of the Bearing

The Aerofall Hydrodynamic bearing design has run many years of successful

By |2019-01-12T18:43:19+00:00January 9th, 2019|Categories: Grinding|Tags: |Comments Off on Gearless Ball Mill Operation

Topaz Flotation

Samples of a topaz-bearing gneiss from Jefferson County, Colorado, and a topaz-bearing schist from Chesterfield County, South Carolina, were obtained for the investigation. These are the areas outlined by USGS as containing probable commercial quantities of topaz. Partial chemical analyses of the samples are shown in table 1.

Mineralogical examination of the Colorado gneiss showed it consisted primarily of topaz and quartz with some muscovite and small amounts of rutile and zircon. The topaz was essentially liberated in fractions finer than 100 mesh.

The South Carolina schist contained primarily a topaz-andalusite mixture with quartz, and minor amounts of pyrite, muscovite, magnetite, and feldspar. The topaz occurred as both cleavage fragments and as fine-grained aggregates. The fine-grained aggregates outnumbered the clear cleavage fragments by a factor of approximately five to one. In the fine-grained aggregates it was virtually impossible to distinguish between topaz and andalusite. Both these minerals were intermixed in the fine-grained matrix material and apparently did not possess a completely ordered lattice. Many of the aggregates were heavily iron-stained. Most of the topaz was liberated at 65 mesh.

Beneficiation Studies

Initial considerations of concentration techniques to be studied indicated that flotation procedures should be emphasized. Although gravity techniques had been proposed

By |2019-01-12T18:36:20+00:00January 6th, 2019|Categories: Non-Metallic & Industrial|Tags: |Comments Off on Topaz Flotation

Flotation of Insoluble Slimes from Potash Ore

Filtration of the insoluble slimes flotation concentrates recovered 87 to 90 percent of the brine. Flotation concentrate filtration rates were 7 times faster than the filtration rates of mechanically deslimed products.

Potash losses in the deslime product and process brine requirements increase as the insol content increases. Therefore, improved methods to remove inso lslimes are needed that will (1) reduce potash losses in the insol slimes product, (2) lower the process brine requirements, and (3) increase subsequent potash recovery after insol slimes removal. In this regard, several insol-slimes-flotation methods have been offered as alternatives to mechanical desliming.

Experimental Materials

A run-of-mill potash ore sample with a high water-insol content from the Carlsbad, N. Mex. Petrographic and X-ray diffraction analysis of the ore indicated that sylvite (KCl) and halite (NaCl) were the major minerals present. The sylvite contained minor amounts of included hematite, which gave this mineral a distinct red color. Minor amounts of polyhalite (MgSO4·K2SO4·2CaSO4·2H2O), leonite (MgSO4·K2SO4·4H2O), and kainite (KCl·MgSO4·2.75H2O) were also present. The water-insoluble fraction of the ore contained abundant magnesite, chlorite, and illite.

Experimental Procedures

Settling tests were performed in 200-milliliter graduated cylinders on the insol-slimes fraction of each ore. The feed for these settling tests was prepared by diluting

By |2019-01-12T18:24:19+00:00January 4th, 2019|Categories: Flotation|Tags: |Comments Off on Flotation of Insoluble Slimes from Potash Ore

Fireclays in Refractories – Evaluation & Utilization

The high quality fireclays of missouri are generally differentiated by the user as the softer, somewhat plastic, “bond” clays and the so-called flint clays suitable for a fired or unfired aggregate portion of a brick composition. The semi-plastic “bond” clays are mined in a producing area of northeast missouri including montgomery, audrain, callaway, monroe, and lincoln counties. In this geographic area the clays are the members of the cheltenham formation and occur in rather large lenses in which the usable members may approach 15 meters in thickness and an area of 60 to 80 acres. Overburden is dependent on the surface topography and, in our operations, varies from 8 meters to 25 meters. It can be up to 36 meters in the prairie uplands, but this is rarely strip mined.

The flint clays of missouri are characterized by their lack of plasticity even when finely divided, a variable degree of hardness much greater than the bond clays, and a strong resistance to slaking. Pyrometric cone equivalent extends over a range of cone 33 (1745 c) to cone 35 (1785 c), with alumina content in the range of plus or minus 39% in the raw state, and a silica content typically of

By |2019-01-12T18:14:08+00:00January 3rd, 2019|Categories: Non-Metallic & Industrial|Tags: |Comments Off on Fireclays in Refractories – Evaluation & Utilization

Copper & Silver Recovery from a Complex Sulfide Concentrate by Ferrous Chloride Oxygen Leaching

Marketing complex sulfide concentrates that contain a variety of metals along with arsenic and antimony has always presented a problem. This situation has been compounded recently by increased smelting costs and the closure of several smelters. These factors have stimulated interest in the development of hydrometallurgical procedures for recovering metal values from sulfide concentrates.

Chlorination and acid-oxygen leaching procedures have been investigated for recovering metal values from sulfide concentrates. Favorable metal recovery values are obtained with the chlorination technique. However, the system results in the dissolution of metals such as iron and arsenic, and complex separation schemes are required to separate and remove these metals. The acid-oxygen leaching technique is more selective, but high metal extraction is not common. Also, some of the iron is extracted into solution, and additional processing steps are required to remove it.

More recently, Haver and Wong developed a ferric chloride leaching technique for treating chalcopyrite and galena concentrates . In this system the metal sulfide is oxidized by ferric chloride to produce metal chloride and elemental sulfur,

CuFeS2 + 4FeCl3 → CuCl2 + 5FeCl2 + 2S……………………………………………………(1)

PbS + 2FeCl3 → PbCl2 + S + 2FeCl2…………………………………………………………..(2)

The system successfully treats classical concentrates such as chalcopyrite and galena, but

By |2019-01-12T18:13:06+00:00January 3rd, 2019|Categories: Hydrometallurgy|Tags: |Comments Off on Copper & Silver Recovery from a Complex Sulfide Concentrate by Ferrous Chloride Oxygen Leaching

Feldspar Flotation using Non-Hydrofluoric Acid System

The response of feldspar flotation to tallow diamine dioleate collector in the presence of sulfuric acid is studied using, batch flotation experiments. Application of this non- hydrofluoric acid (non-HF) reagent system in the flotation of mineralogically and chemically different feldspar ores is compared with that of the conventional hydrofluoric acid system. The dependence of flotation recovery and concentrate grade on feed particle size distribution, conditioning time, pulp density, and pH, combined variation of collector and acid addition rates, sodium hydroxide concentration in the collector solution, and initial pulp pH prior to conditioning is studied. The results have been discussed in relation to applicability of the non-HF system to plant trials, and the nature of the collector adsorption in the selective flotation of feldspar.

Reagents and Test Samples

In the experimental investigations the following reagents were used: industrial grade collectors- Duomeen TDO and Armac T, and acids hydrofluoric and sulfuric. Both Duomeen TDO and Armac T are manufactured by Armak, Industrial Chemicals Division. Armac T is a typicallly used collector in the presence of hydrofluoric acid in the conventional flotation of feldspar.

Since Duomeen TDO is not soluble in water, it is dissolved by heating water to approximately 50° C, adding

By |2019-01-12T18:11:24+00:00January 3rd, 2019|Categories: Flotation|Tags: |Comments Off on Feldspar Flotation using Non-Hydrofluoric Acid System

Feed to Zero in Heavy Medium Cyclones

Dutch State Mines [D.S.M.] introduced the Heavy Medium Cyclone into the United States for cleaning fine coal about three decades ago. Since that time the general industry practice has been to deslime the raw coal at 28 Mesh (0. 59mm) size. The plus 28M material is fed to the Heavy Medium Cyclone for cleaning, and the 28M x 0 fraction is processed by other means (e. g. flotation or hydrocyclones).

Undeslimed Feed

Recognizing the capability of the Heavy Medium Cyclone to clean raw coal sizes below the conventional 28 mesh using a properly designed purging circuit, the single circuit Heavy Medium Cyclone Plants, using undeslimed feed, naturally evolved. During the last few years the energy environment in the United States has mandated an increasing trend towards lower ash and sulfur products. Coupled with a deterioration in the quality of many raw coals due to the enforcement of new safety provisions.

One disadvantage of the single circuit, over using a separate circuit for cleaning the 28M x 200M fraction, is that there is no separate control over the separating gravity of the two fractions, and the nature of the Heavy Medium Cyclone is to progressively clean smaller particles at higher specific gravities

By |2019-01-12T17:36:16+00:00January 2nd, 2019|Categories: Classification|Tags: |Comments Off on Feed to Zero in Heavy Medium Cyclones

Extraction of Nickel and Cobalt from Acidic Solutions

LIX63 in combination with DNNS selectively extracts nickel and/or cobalt from acidic leach liquors with pH values as low as 1.0. Nickel/cobalt and cobalt/nickel selectivities are achieved by varying the relative concentrations of LIX63 and DNNS. Increasing LIX63 concentration retards both extraction and stripping rates while DNNS has the opposite effect. Slope analyses of equilibrium data indicate that both LIX63 and DNNS are present in the extracted complexes.

Experimental

LIX63 was used as received from General Mills. DNNS was prepared by repeatedly contacting the commercial product NaSUL-AS (trade name for the ammonium salt of dinonylnaphthalene sulfonic acid, marketed by R. T. Vanderbilt) with 600 gpl H2SO4 until titration showed that conversion to the acid form was complete. To mixtures of the two extractants, Solvesso 150, a product of Exxon, was added as diluent.

The nickel loading tests were performed with an aqueous solution (4.2 gpl Ni, pH 1.1) obtained by sulfuric acid leaching of laterite ore. Using conventional shakeouts, each organic mixture was loaded at O/A = 1/5 for 60 minutes. The long contact time and high A/O ratio were used to ensure that each mixture was loaded to capacity. Cobalt loading tests were performed with a synthetic cobalt sulfate solution

By |2019-01-12T17:34:35+00:00January 2nd, 2019|Categories: Hydrometallurgy|Tags: |Comments Off on Extraction of Nickel and Cobalt from Acidic Solutions

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