size of gold ore fed into the gyratory crusher at grisben mine

crushing products size and shape -what to expect

crushing products size and shape -what to expect

I have madea number of general remarks regarding the character of product delivered by crushers of various types, and under different conditions of operation. Generalities are of value only if we have some standard to which comparisons may be referred; therefore, we should like to present more specific information on the kind of product to be expected from crushing equipment under average operating conditions. Much of the data on which sizing/designcurves and tables are based comes from operations involving those two very important types: gyratory and jaw crushers; therefore these curves and tables are more nearly representative of the work of these types than of rolls or hammermills. They may be used for these latter types however if due allowance is made for peculiarities of each type, as pointed out in the descriptions of the different machines.

The preparation of a set of product gradation curves involves a considerable amount of work in the collection of the necessary test data, and a certain degree of discrimination in sorting such data and weeding out erroneous results. There are several reasons why no set of product gradation curves can be regarded as more than reasonably close approximations. First among these is the variation in physical structure of the many materials for which crushers are used; rocks exhibit a high degree of rugged individualism in their reaction to crushing. This variation is frequently quite pronounced between different ledges in the same quarry.

Gradation of the crusher feed also has its effect upon the product analysis. This is true even of screened feed, although deviations from the average are not likely to be so wide as they are for unscreened material, such as quarry-run or mine-run rock. We have commented on other variable factors, such as choke versus regulated feed, straight versus curved concaves, and so forth.

Fortunately, most materials do follow a certain definite gradation pattern and, by averaging a large number of test results, it is possible to plot a group of curves which can be classed as fairly close approximations. Even though approximate, these curves are of great value in crushing-plant design, or in the solution of problems concerning additions or alterations in the plant flowsheet. They simplify the problem of selecting secondary and tertiary crushers, as well as elevating and conveying equipment, and they are invaluable in the calculation of screen sizes. In short, they eliminate much of the old-time guess work in the preparation of the plant flowsheet.

Gyratory and jaw crushers are always rated at certain open-side or close-side discharge settings. In order that we may select the particular curve, of a group of curves, which will most nearly represent the product of a crusher having any given discharge setting, it is important to know approximately what percentage of the total output will pass a screen opening of equal dimension. It was universal practice in past years to designate such screen openings as ring-size for the very logical reason that the leading screen of that day, the revolving type, was, almost without exception, fitted with sections having round holes. Now that the vibrating screen, with its wire cloth or square-punched steel plate sections, has pre-empted the field there is no longer any excuse for adhering to the ring-size product designation.Above is alist of the approximate percentages of product passing a square opening test sieve whose holes are equal to the discharge setting of the crusher. Several different conditions are tabulated, and each condition is accompanied by estimates for four different classes of material.

In gravel pit operations it will usually be found that some one of these listed base rocks will predominate, and no great error will be introduced if this predominant rock is used as the basis for product calculations. Most base rocks will be close enough in physical structure to one of the listed varieties so that the percentages can be used for them without serious error. The same statement applies to the product gradation curves to be discussed. It must be remembered that the entire process of securing and compiling data of this nature is, at best, one which is susceptible of only approximate results.

It was formerly the custom to consider one set of product gradation, or screen analysis, curves as being suitable to represent the products of both primary (unscreened) and secondary (screened) feeds, making no allowance for the undersize material which is always present, to some extent, in quarry-run and mine-run materials. The average quarry does not produce as much of this undersize rock as the average mine, but the usual practice in mining operations is to scalp off most of the undersize ahead of the primary crusher, whereas this practice is the exception rather than the rule in quarry operations. As a matter of fact, where the secondary crushers are fitted with straight concaves, or jaw plates, as used to be standard practice, the dif-ference between product curves on screened and unscreened feed was not significant, and no great discrepancy was introduced by considering them under the one heading.

With the introduction of non-choking concaves in the standard gyratory crushers and reduction crushers, and the development of high speed fine-reduction crushers with high choke points, it soon became apparent that there was a substantial difference in the screen analyses of the two kinds of product, that is, crusher products on unscreened and screened feeds. The difference is especially significant in the lower part of the curve, where undersize in the feed would naturally show up, and where the cleaner breaking of the non-choke crushing chamber would likewise be reflected.

Here above isshown a family of curves for primary crushing of unscreened feed, such as the average quarry-run material in which the undersize (minus crusher setting) rock is present in proportions normally resulting from blasting operations. The same curves may be used for mining operations with stationary bar grizzlies ahead of the primary crusher.

In such operations the amount of undersize going into the crusher will usually be about the same as for the quarry operation without pre-scalping. It should be noted that the test data on which these curves are based were taken from gyratory and jaw crusher operations, but, as we have stated before, they may be used for other types of crushers if allowance is made for the characteristics peculiar to each type. As a matter of fact, so far as crushers of the Fairmount single-roll type are concerned, there is a natural compensation which brings the curves fairly well into line. The Fairmount crusher is inherently a somewhat cleaner breaking machine than either the standard gyratory or standard jaw types, but the class of rock for which the former crusher is largely used is usually subject to greater than average degradation during the blasting and loading operations in the quarry, which tends to level out the difference in crushing performance.Using Crusher and Screen Charts

The method of using the curves is so simple as to require little comment. The vertical axes represent material sizes, which may be taken as either square or round openings; provided of course that the same shape of opening is used throughout any particular analysis. The horizontal axes represent cmmdative percentages passing corresponding screen openings. If we wish to check the product to be expected from a crusher set at some predetermined discharge opening, we first refer to the table showing the approximate percentage of product which will pass an opening equivalent to the crusher setting. This gives us a point in the group of curves which may, or may not, be exactly on one of them. In the latter case we interpolate by following an imaginary curve between the two curves on either side of our point. We can thus tabulate cumulative percentages passing all of the product sizes in which we may be interested. Non-cumulative percentages; which are important because they are used to determine expected amounts of specific products are simply the difference between the upper and lower cumulative percentages for the particular product limits under consideration.

For those not familiar with the use of product gradation curves an example may be helpful. Suppose that a tentative selection of a 3.5 open- side discharge setting has been made for a standard gyratory primary crusher to be used for crushing quarry-run limestone. Referring to the table which lists percentages of product passing an equivalent square opening, we find that 85 to 90% of the crusher product should pass a 3.5 square opening. Choosing the lower percentage, to be on the conservative side,, we follow the horizontal line, denoting the 3.5 product size in the curve chart, over to the vertical line marking the 85% value. We find that the point we have established does not fall directly upon any of the group of curves, but lies so close to one of them that it may be used without appreciable error into our calculations.

Let us suppose that we wish to know how much of the product of our primary crusher will be retained on a 1.5 square opening screen, so that we may estimate the size and number of secondary crushers required to recrush the plus 1.5 contingent. Following the curve down to the 1.5 line, we find that 43% of the primary crusher output may be expected to pass this screen opening; 57% will be retained, which means that we must provide secondary crushing capacity to take care of 57 tons for each 100 tons fed to the primary crusher.

Occasionally it happens that we wish to scalp off a salable product from the output of the primary crusher; for example, a plus 1.5 minus 3.5 material for highway base- rock. The difference between the cumulative percentages at the 3.5 and 1.5 points on the curve gives us the amount, of such product to be expected from the output of the primary crusher This is 85 minus 43, or 42% of the primary crusher product.

If our problem had covered a crushing condition calling for 80 instead of 85%passing the opening equivalent to the crusher setting, we would have found that our point fell exactly on a curve, regardless of what crusher setting we had selected. This is because all of the family of curves are based on the 80% line. Obviously a group of curves might be based on any percentage line, but it is usual practice to choose the 80 or 85% values.

It will be noted that the curves bend upward in very marked fashion above the 75-85% region. This simply reflects the tendency of practically all materials to slab, or spall, to some extent in the crusher. As a matter of fact, product gradation in this upper range (above the open- side setting of the crusher) is of a distinctly uncertain and variable nature, and about all that a group of curves can do is to reflect the general tendency. Fortunately the exact screen analysis in this fraction of the primary crusher output is recrushed in succeeding stages, and all that is required is to know approximately how much of it there will be to recrush.

Although the group of curves we have been considering are intended for calulations involving primary crushing operations, they may also be used for secondary crusher products in those cases where no screening is performed between primary and secondary stages. Such an arrangement is seldom encountered in modern plant design, except where large jaw crushers, set very wide, are followed by a secondary, usually of the standard gyratory type, to reduce further the very coarse output of the jaw crusher to a size which can be handled by the recrushing, screening, and elevating equipment in the balance of the plant. In such cases it is simplest to consider the two-stage set-up as a single machine with discharge opening equal to that of the secondary crusher.

The group of curves on the rightischarted from screen analyses of the products of crushers receiving screened feed. They are useful in predicting the character of output from secondary and tertiary crushers, and are of great value in the preparation of plant flowsheets, and in calculating vibrating screen capacities. Their use in the latter connection will be discussed in the screening section of this series.

There is no need for extended comment on this group of curves; the method of taking off cumulative percentages, and non-cumulative fractions, is exactly the same as for the chart we previously discussed. The difference in the shape of these curves is attributable to the absence of fines in the crusher feed, and to the cleaner breaking action of the modem reduction crusher.

The product gradation curves for screened feed, described under the preceding sub-heading, can be used as a basis for calculating approximate screen analysis of products from closed-circuit crushing stages, but the values cannot be taken directly from the curves.

For example, consider a crusher set to turn out a product 70% of which will pass a 5/8 square opening, and in closed circuit with a screen which is equipped to remove the minus 3/4 product. Thecurve shows that approximately 85% of the crusher product will pass the 3/4 square openings.

Suppose that we wish to know how much minus 0.25 fines we may expect from the circuit.We do not go to the curve which touches the 100 percent ordinate at the 3/4 value; we calculate the percentage from the same curve which was used to predict the proportion of minus 0.75 in the crusher discharge. This curve shows approximately 29 percent of minus 3/4 in the material as it comes from the crusher, or 29 tons of fines in each 100 tons of crusher output. But, for the circulating load, we are only interested in that fraction of the crusher output which will pass the 3/4 screen, which is 85 tons.That part of the product gradation curve which lies below the 85 percent valuerepresents the gradation of the finished product, and 29 tons out of each 85 would be minus 0.25.

Let x equal percentage of minus 0.25 in the finished product, then x:100=29:85 or x = 34.1 percent of minus 0.25 rock from the closed circuit operation. Any other size of product may be estimated in a similar manner. Note that if we had used a curve touching the 100 percent ordinate at the 0.75 value, we would have arrived at a value approximately 50 percent for the minus 0.25 fraction; a value which is obviously erroneous for rock of average characteristics. We will comment on closed circuit crushing, and upon certain assumptions which have to be made in closed circuit calculations, in a later discussion of reduction-crushing.

Although the long established practice of designating crusher products by ring-size is not compatible with present-day screening practice, there are occasions when it is desirable to convert our calculations from one shape of opening to the other. So far as the curves themselves are concerned, once we have established the shape of screen openinground or squarewe can use them for either so long as we stick to one shape throughout the process of taking off percentages-passing. If, as occasionally happens, we have to deal with both shapes of screen opening in the same set of calculations, one or the other of them must be converted to equivalent sizes of the opposing shape. For example, if most of the screen openings are to be square, but one or two of them must be round, the round-hole sizes should be expressed in terms of equivalent square openings.

Inasmuch as the table of crusher settings versus equivalent product percentages is based on square openings, it is necessary to convert to equivalent round openings before this table can be used for such openings.

Below is the information needed to make conversions from round to square holes, or vice versa. The two columns at the left showing equivalent sizes for flat testing screens, are the columns to use in connection with crusher product calculations.Admittedly, listings of equivalent round and square holes, such as we show in this table, can be only approximately correct for the many different materials with which we must deal in crushing and screening computations. The infinite variety of shapes encountered renders absolute accuracy an impossible attainment. Practical experience, however, indicates that the comparisons shown in our table are in most cases close enough for all practical purposes.

Product SizeCorresponding Size Holes Through a flat testing screen Allis-Chalmers vibrating screenRevolving Screen Round holes Square holesRound holes Square holesRound holes 1/83/325/321/85/32 3/83/327/323/161/4 1/43/149/321/41/16 1/21/411/321/123/8 3/83/107/163/81/2 1/43/81/23/163/18 1/21/101/41/25/8 3/21/25/81/1811/10 3/82/1011/106/83/4 11/105/83/411/107/8 3/411/107/83/41 7/83/415/187/81 1/8 17/81 1/1612/101 1/4 1 3/811 2/181 1/181 3/8 1 1/41 1/161 3/81 1/71 2/14 1 3/81 1/81 1/161 1/41 3/4 1 1/21 1/41 3/181 3/81 7/8 1 5/81 3/81 3/41 3/102 1 3/41 1/21 7/81 3/162 1/4 1 7/81 5/821 3/42 3/8 21 3/42 1/81 7/82 1/2 2 1/81 7/82 1/422 5/8 2 1/41 15/182 3/82 1/162 3/4 2 3/822 1/22 1/82 11/16 2 1/22 1/82 6/82 1/43 1/8 2 5/82 1/42 3/42 3/83 5/12 2 3/42 3/82 7/82 1/23 1/2 2 7/82 1/232 5/83 5/8 32 5/83 1/42 3/43 3/4 3 1/42 3/43 1/234 3 1/233 3/43 1/44 3/8 3 3/43 1/443 1/24 3/4 43 1/24 1/43 3/45 4 1/23 7/84 3/44 1/85 1/2 54 1/45 1/44 1/26 1/4 5 1/24 3/45 3/456 7/8 65 1/46 1/25 1/27 1/2 6 1/25 1/275 3/48 767 1/26 1/28 3/4 7 1/26 1/2879 3/8 878 3/47 1/210 8 1/27 1/49 1/47 3/410 1/2 97 3/49 1/28 1/411 1/4 9 1/28108 1/211 3/4 108 1/210 1/2912 1/2

victoria gold declares commerical production at eagle oxide heap leach mine in the yukon - international mining

victoria gold declares commerical production at eagle oxide heap leach mine in the yukon - international mining

Victoria Gold Corp has declared commercial production at the Eagle Gold Mine in Canadas Yukon on July 1, 2020. All facilities required at this stage of the mine life are complete. Mining, crushing, processing and maintenance operations are performing at a high level. The companys first reporting period under commercial production will be the 3rd quarter ended September 30, 2020. It is the largest gold mine in Yukons history.

The mine is a heap leach operation (three-stage crushing plant, in-valley heap leach and carbon-in-leach adsorption-desorption gold recovery plant) and will have an average annual production of 210,000 oz/y at an AISC cost of <$800/oz. The open pit has a 1:1 strip ratio and the heap peach is operating at 76% recovery. In Q1 2020, 946,479 t of ore were mined and 1,565,964 t of waste with 887,700 of ore stacked with a 0.83 g/t grade. Open pit mining will focus on the various Eagle pit phases with the smaller Olive pit coming into production in 2028. Open pit mining and loading of the heap leach facilities will be completed in Q2 of 2031. The constructed primary heap leach pad (HLP) will accommodate up to 90 M t of ore and is located approximately 1.2 km north of the Eagle Zone orebody, in the Ann Gulch valley.

Ore above 0.30 g/t from the Eagle pit is sent to a three-stage crushing plant. The crushing circuit consists of one 375 kW primary gyratory crusher, one 932 kW secondary cone crusher and three, parallel 932 kW tertiary cone crushers. Crushing plant feed material, with a maximum top size of 1,000 mm, is trucked from the open pits and dumped directly into the primary gyratory crusher at a throughput of approximately 29,500 t/d. The primary crusher will operate 365 days a year, while the secondary and tertiary crushers will only operate 275 days when ore is stacked on the HLPs. From Q2 through Q4 of each year, stockpiled crushed ore is reclaimed via a loader/hopper/conveyor system to the secondary crusher. Crushed ore reclaiming is done at 470 t/h, and combined with the primary crusher discharge, at a total rate of 39,200 t/d, to the secondary and tertiary crushing circuits. The tertiary product, screen undersize at P80 of 6.5 mm, feeds a series of conveyors and grasshopper conveyors to a radial stacker on the HLP. Lime is added to the tertiary screen discharge conveyor for pH control.

ROM ore (less than 0.30 g/t but above the cut-off grade of 0.15 g/t) is sent directly from the Eagle pit to the primary HLP during the stacking months, and to the ore stockpile during the stockpiling months (January to March). The ROM ore is reclaimed from the stockpile using a loader and trucks and taken to the primary HLP. The ROM ore will be segregated from the crushed ore but will be placed within the overall primary HLP.

The mine operates a Caterpillar fleet of 22 m3 6040 hydraulic shovels and 140 t 785 trucks with 12 m3 front-end loaders. This fleet is supported by drills, graders, and track and dozers. Benches are mined at a height of 10 m in both ore and waste with an overall 20 m effective bench height based on a double-bench final wall configuration.

Site activities continue to progress well and all facilities and operations are now at or approaching design capacity. This consistent production combined with materially positive operating cash flow has allowed Victoria management to declare commercial production as of July 1, 2020., said John McConnell, President & CEO. Achievement of commercial production is a meaningful and memorable accomplishment that the entire team is proud to be part of. Special thanks goes to so many contributors, including the local communities and the First Nation of Na-Cho Nyak Dun who have helped us make Eagle a reality.

The company says it continues to follow strict COVID-19 protocols at the Eagle Mine site as well as across the companys work locations. Yukon is currently in Phase 2 of lifting COVID-19 restrictions. Personnel from Yukon and British Columbia are no longer required to self-isolate prior to coming to site, however, all workers from outside the Canadian territories and BC will self-isolate in Whitehorse for 14 days prior to traveling to site. The Eagle Mine site continues to operate on a 4 week in/4 week out schedule rather than the normal pre-COVID-19 2 week in/2 week out schedule.

Victoria Golds 100%-owned Dublin Gulch gold property is situated in central Yukon Territory, Canada, approximately 375 km north of the capital city of Whitehorse, and approximately 85 km from the town of Mayo. The property is accessible by road year round, and is located within Yukon Energys electrical grid. It covers an area of approximately 555 square kilometres, and is the site of the companys Eagle and Olive Gold Deposits. The Eagle Gold Mine is Yukons newest operating gold mine. The mine is six hours by road to Whitehorse and eight hours by road to Port of Skagway, Alaska in the US.

major mines & projects | geita mine

major mines & projects | geita mine

The Geita Greenstone Belt (GGB) hosts several world-class shear-hosted Archaean lode gold deposits and forms the northern portion of the regional Sukumaland Greenstone Belt, itself one of several belts that comprise the Lake Victoria Goldfields. Other gold mines hosted in the Lake Victoria Goldfields include Golden Pride, Bulyanhulu, Tulawaka, Buzwagi and North Mara.The east-west oriented GGB is 60km in length, up to 15km wide. The Geita terrain is comprised of upper- to mid-Nyanzian greenschist facies units, made up of clastic sediments, black shales, banded iron formation (BIF) and volcaniclastics. These have been intruded by a variety of felsic to mafic intrusive bodies, dykes and sills. Regional north-northeasterly structures hosting Proterozoic gabbro dykes are also prominent geological features in the area.North-west trending deformation corridors divide the GGB into three distinct sub-terrains, namely the Nyamulilima Terrain in the west (hosting the Star and Comet, Ridge 8 and Roberts deposits), the Central Terrain in the central part (hosting the Nyankanga, Geita Hill, Lone Cone and Chipaka deposits) and the Kukuluma Terrain to the north-east (hosting the Matandani, Kukuluma and Area 3 West deposits).Geitas gold mineralisation is preferentially hosted in BIF, cherts and ironstones that have been affected by both ductile and brittle deformation associated with shear zones. The shears exploit fold axial planes as well as the contacts between the supracrustal and intrusive rocks.The GGB has been through a protracted history of deformation, which resulted in a large-scale synformal configuration in the Central Terrain, with west-northwest trending limbs connected by a north-east trending hinge zone. The deposits of the Central Terrain are mainly located within the relatively low-strain hinge zone. The Nyankanga deposit is hosted in a BIF-dominated supracrustal package that is extensively intruded by, and locally form a roof-pendant within the dioritic Nyankanga Intrusive Complex. At Geita Hill, dioritic rocks are present as sills and dykes intruded into a supracrustal sequence that has been subject to extensive polyphase folding. To the west, the Nyamulilima Terrain comprises a semi-circular structure surrounding intrusive centers, which internally encompasses structural systems of variable scale that locally control gold mineralisation. At Star and Comet, a folded sedimentary package of BIF intercalated with clastic and tuffaceous meta-sediments is intruded by a tonalitic complex.The Kukuluma Terrain trends west-northwesterly, with sub-vertical limbs being dominant over compressed, multiphase folded zones. The three major deposits in the area (Kukuluma, Matandani and Area 3) are located along a 5km long east southeast mineralisation trend. The geology of the deposits is dominated by volcano-sedimentary rocks that are polydeformed and intruded by syn- to latefolding diorite bodies. Host rocks for mineralisation are fine-grained iron-rich clastic sediments, cherts, BIF and tuffaceous rocks, with local intercalated carbonaceous shales.Gold mineralisation at Nyankanga occurs within a northeast-trending and northwest-dipping anastomosing shear system, typically along the lowermost shears, with higher grade mineralisation mainly proximal to the basal contact of BIF packages. Mineralisation is associated with chlorite-carbonate-silica alteration and pyrite-dominant sulphide in the damage zones surrounding the shear surfaces as veins, veinlets, local breccias and sulphide replacement of magnetite layers. At Geita Hill, mineralisation at the deposit scale is controlled by a narrow NE-trending and NW-dipping shear zone that exploits the axial surfaces of F3 folds. The bulk of the ore is also carried by damage zones adjacent to the main shear. At Star and Comet, a major mineralised shear zone runs NNW-SSE through the deposit where it is localised along the contact of BIF and tonalite. An envelope of mostly brittle deformation up to 10m thick affecting both lithologies occurs either side of the shear zone and controls distribution of mineralisation. Most of the gold mineralisation is hosted in pyrrhotite patches associated with strong silicification together with carbonate alteration.Within the Kukuluma Terrain, steeply dipping ductile/brittle gold-fertile shear zones are developed along, or close to, the edges of an elongate diorite body, hosted in iron-rich host rocks and locally exploiting axial surfaces of tight folds. Gold mineralisation in the Kukuluma terrain is strongly associated with pyrrhotite, pyrite and arsenopyrite concentrations, accompanied by strong carbonate and silica alteration of host rocks. Gold is present in gold minerals and sulphides, dominantly in arsenopyrite.

Mining at Geita uses both open pit and underground mining methods. Open pit mining at Nyankanga Cut 8 was completed in 2020. Work has commenced to establish the next open pit operation at Nyamulilima Cuts 1 and 2. This mining is done utilising truck and shovel, operated by GGM, with a contractor providing drill and blast support. Star and Comet underground has successfully transitioned to owner mining, and the mining contractor African Underground Mining Services is used at Nyankanga and Geita Hill for underground development as well as stoping. The mining method is a combination of LOS and TOS. Cemented aggregate fill backfill is used at Nyankanga to fill the primary stopes. Ore is hauled from the Star and Comet and Nyankanga underground operations to the central run-of-mine (ROM) pad by the Geita surface mining fleet.

The majority of the ore from the pit is dumped onto the run-of-mine (ROM) stockpile, and then fed into the gyratory crusher by a front end loader. The plant design is such that all ore passes through this crusher. The crusher feed rate is higher than the plant design rate which is currently targeted at around 640 tonnes per hour, and there is a buffer stockpile with a total capacity of around 100,000 tonnes. Reasonable stock of critical crusher spares is always maintained to ensure minimum delays in the crushing operation.The ore is crushed in a three stage crushing circuit and the crushed product is deposited on the fine ore stockpile. A conveyor belt transfers the ore form the fine ore stockpile directly into the SAG Mill feed.The SAG mill is 9.14m in diameter, and 5.5m long. The underflow from the primary cyclones passes into the, 6.71m in diameter and 9.6m in length, Ball Mill. This mill operates in closed circuit with the cyclones. Two 48 inch Knelson Concentrators are used for gravity gold recovery.

Gravity separationSmeltingACACIA reactorHydrochloric acid (reagent)Filter press plantCalciningCarbon re-activation kilnDewateringConcentrate leachAgitated tank (VAT) leachingCarbon in leach (CIL)ElutionSolvent Extraction & ElectrowinningCyanide (reagent)

The process plant includes:- Primary, secondary and tertiary crushing plants - Semi-autogenous grinding (SAG) mill and ball mill- SAG mill scats recycle line - (Scats/pebble crusher was decommissioned) - G-max Cyclones- High rate thickener- Pre-oxidation in the first 2 tanks followed by a ten stage carbon-in-leach (CIL) process- Gold recovery circuit (Elution, Electrowinning and Smelting)- Gravity concentration section within the milling and classification circuit, where the gravity gold is recovered using Knelson concentrators and an intensive cyanidation process.Two 48 inch Knelson Concentrators are used for gravity gold recovery. The concentrate from the gravity circuit (Knelson concentrators) enters a closed circuit Acacia Reactor from where the solution is pumped to the gold room where it is passed through a dedicated electro winning cell.The overflow material from the cyclones passes through linear screens, before ........

primary crusher selection & design

primary crusher selection & design

The crusher capacities given by manufacturers are typically in tons of 2,000 lbs. and are based on crushing limestone weighing loose about 2,700 lbs. per yard3 and having a specific gravity of 2.6. Wet, sticky and extremely hard or tough feeds will tend to reduce crusher capacities.

Selectiingwhat size a crusher needs to be is based on factors such as the F80 size of the rocks to be crushed, the production rate, and the P80 desired product output size. Primary crushers with crush run-of-mine rock from blast product size to what can be carried by the discharge conveyor or fit/math the downstream process.A typical example of primary crushing is reducing top-size from 900 to 200 mm.

Ultimately, the mining sequence will certainly impact the primary crusher selection. Where you will mine ore and where from, is a deciding factor not so much for picking between a jaw or gyratory crusher but its mobility level.

The mom and dad of primary crushers are jaw and gyratory crushers. In open-pit mines where high tonnage is required, thegyratory crushers are typically the choice as jaw crushers will not crush over 500 TPH with great ease. There are exceptions like MPI Mineral Park in AZ where 50,000 TPD was processed via 2 early century vintage jaw crushers of a:

The rated capacity at 5 closed-side setting was 490 stph based on standard 100lbs/ft3 feed material. These crushers were fed a very fine ore over a 4 grizzly which allowed the 1000 TPH the SAG mills needed.

In under-ground crushing plants where the diameter of the mine-shaft a skip forces limits on rock size, a jaw crusher will be the machine of choice. Again, if crushing on surface, both styles of stone crushing machines should be evaluated.

compare gyratory crusher vs jaw crusher

compare gyratory crusher vs jaw crusher

To accomplish this reduction in size takes several steps or stages of crushing and grinding. Primary crushing is the first of these stages. Generally speaking there are two types of primary crushers, lets compare them: GYRATORY CRUSHER or a JAW CRUSHER. Although they dont look anything like they do have similarities that put them into the same class of crusher.

Their CRUSHING SPEEDS are the same, 100 to 200 revolutions per minute. They both break the ore by COMPRESSION. That is they both break the rock by squeezing it until it breaks. On the average their final product will measure about seven inches at its widest point. And finally they both can be built to accept a rock up to sixty inches across.

Even if they are much alike, each of the two types of crushers has its own uniqueness. Because of this difference each type of crusher has its own environment that it operates best or at least better in, than the other.As an example, a gyratory crusher can be fed from two sides and handle ore that tends to slab. Also its design allows a higher speed motor with a high reduction ratio between the motor and the crushing surface. This is an important consideration as it means money saved in energy costs. A jaw crusher on the other hand requires a flywheel to store energy but can be used on the tougher ores due to its box frame construction. To be effective it must be fed from one side only but it handles square block-like ore well.

There is another comparison that should be taken into consideration, that is the amount of space that each takes. The Jaw crusher is the smaller of the two and its single feed point will make it a logical choice for underground workings. In the actual operation of the crushers, they both have similarities as well as differences so lets take each one separately and discuss its design and its problems. Considering the title of this chapter is Primary Crushing (Gyratory) we should discuss that one first.

In the introduction I mentioned that the purpose of a concentrator was to produce a concentrate of which ever mineral was being mined. To be able to recover this mineral it is necessary to reduce the ore in size until the mineral is LIBERATED. This means that the ore must be reduced in size until it is fine enough to be able to separate the mineral from the unwanted rock. In the Vocabulary of the metallurgist, at this point of the operation the unwanted rock will be termed the GANGUE material. You will notice that the terminology used for the ore will change depending upon the stage of concentration. The reason for this is to keep technical communication accurate.

gyratory and cone crusher - sciencedirect

gyratory and cone crusher - sciencedirect

Detail descriptions of designs are given of large gyratory crushers that are used as primary crushers to reduce the size of large run-of-mine ore pieces to acceptable sizes. Descriptions of secondary and tertiary cone crushers that usually follow gyratory crushers are also given in detail. The practical method of operation of each type of gyratory crusher is indicated and the various methods of computing operating variables such as speed of gyration, capacities and power consumption given are prescribed by different authors. The methods of calculations are illustrated to obtain optimum operating conditions of different variables of each type using practical examples.

major mines & projects | eagle gold mine

major mines & projects | eagle gold mine

The Dublin Gulch property (Eagle Gold Mine) is underlain by upper Proterozoic to lower Paleozoic clastic sedimentary rocks that have undergone regional deformation including Cretaceous age thrust faulting and subsequent granitoid intrusions. Mineralization is associated with granitic intrusive bodies, here described as the Eagle Zone and Olive Zone gold deposits, which are hosted primarily in granodioritic rocks. The gold deposits occur within the Tombstone Gold Belt, located in the eastern portion of the Tintina Gold Province, which also hosts the Brewery Creek deposit and other gold occurrences in the Yukon.The property is located on the northern limb of the McQuesten Antiform and is underlain by Proterozoic to Lower Cambrian-age Hyland Group metasediments and the Dublin Gulch intrusion, a granodioritic stock. The Dublin Gulch Stock is comprised of four intrusive rock phases, the most significant of which is Granodiorite. The stock has been dated at approximately 93 Mega annum (Ma).The metasediments are the product of greenschist-grade regional metamorphism. Proximal to the Dublin Gulch Stock, these metasediments have undergone metasomatism and contact metamorphism. A hornfelsic thermal halo surrounds the stock and within the halo, the metasediments have been altered to schist, marble and skarn.The Eagle and Olive zones belong to the RIRGS class (Reduced Intrusion-Related Gold Systems) of mineral deposits.The Eagle Zone gold occurrence is localized at the narrowest exposed portion of the stock. The Eagle Zone mineralization is comprised of sub-parallel extensional quartz veins that are best developed within the granodiorite.Sulphides account for less than 5% of vein material and occur in the centre, on the margin, and disseminated throughout the veins. The most common sulphide minerals are pyrrhotite, pyrite, arsenopyrite, chalcopyrite, sphalerite, bismuthinite, molybdenite and galena. Secondary potassium feldspar is the dominant mineral in alteration envelopes. Sericite-carbonate is generally restricted to narrow vein selvedges, although alteration zones of this type also occur with no obvious relation to veins. Gold mineralization also occurs within the metasedimentary rock package immediately adjacent to the granodiorite.The Eagle Zone is the principal concentration of mineralization within the property. The Eagle Zone is irregular in plan and is approximately 1,600 m long (east-west) and 600 m wide north-south. The Eagle Zone is near-vertical and has been traced for about 500 m below surface. Current drilling indicates that the mineralization is relatively continuous along this length and is open in several directions, including at depth. Mineralization occurs as elemental gold, both as isolated grains and most commonly in association with arsenopyrite, and less commonly with pyrite and chalcopyrite. The sulphide content in the veins is typically less than 5%, and is less than 0.5% within the deposit overall, with 1 to 4% carbonate (calcite) present.The Olive Zone gold occurrence is localized at the contact zone on the northwest flank of the granodiorite intrusive and located 2.5 km northeast of the Eagle Zone. Olive measures approximately 20 to 80 m in width, 900 m in length, and has been drilled to approximately 175 to 250 m in depth. Over 97% of the gold mineralization in the Olive Zone is hosted in granodiorite.Compared to Eagle, the Olive mineralization is more associated with sulphides and quartz-sulphide veining in an interpreted shear-zone setting. An oxidation zone and a transition zone, from near total oxidation to only sulphides, have been defined. Veins can be only sulphides or sulphides with white quartz. Pyrite plus arsenopyrite (or arsenical pyrite) and quartz-pyrite veins are common, within the overall NE trending zone of mineralization.

The Eagle Gold Mine comprises the Eagle and Olive deposits which are mined using open pit methods. Open pit mining will focus on the various Eagle pit phases with the smaller Olive pit coming into production in 2028. - Year 2019: Completed pre-stripping the Eagle pit and transitioned into production phase. - Year 2020: First year of full production with heap leach stacking and processing after preproduction and ramp up period have completed. - Year 2021: Mining in Eagle Phase 1 and 2 will continue with waste stripping of Phase 3 commencing. - Years 2022-2024: Mining at the Eagle Phase 1 be completed in late 2022, with Phase 2 ending in 2024, while Phase 3 continues over the entire period. ROM material is expected to start hauling to the secondary HLP at the start of 2024.- Years 2025 to 2027: The primary HLP is expected to reach the crush ore capacity in 2027 and remainder of crush ore is conveyed to the secondary HLP near the Olive deposit.- Years 2028 to 2031: Mining at Eagle Phase 3 is completed in 2030. The Olive open pit commences in 2028 and is completed at the middle of 2031.The open pits are designed with 10 m benches in both waste and ore headings with adequate phase geometry to achieve a maximum production rate of 31M t/year. Mining is scheduled to advance sequentially through the pits and various internal phases with several phases active at any one time. Given the required production rate and pit geometries, vertical advance rates average eight benches per year, with frequent requirement for ramp development and opening of new benches.Based on the selected bench height (drilling occurs on 10 m high benches) and the production schedule requirements, a production drill with a 190 mm hole diameter was selected for both waste and ore. The blast design assumes the use of a 65% ANFO / 35% Emulsion blend for dry holes, and a 30% ANFO / 70% Emulsion blend for wet holes. Given the climatic conditions of the project area, 20% wet blast holes were assumed. Diesel hydraulic excavators were selected as the primary loading equipment, supported by front-end loaders (FEL) and a smaller hydraulic backhoe. The main criterion for loading equipment selection is the ability to effectively load trucks with payloads of 136 t, while allowing for somewhat selective mining. As such, front shovels with a 22 m3 bucket primarily undertake the mining of ore and waste material, while the 12 m3 FELs and smaller excavator complement the main shovel fleet (e.g. lower, confined benches of the open pits). The truck fleet for the project was selected to match the selected loading fleet, and resulted in the final selection of CAT 785 trucks with a payload of 136 t.Waste rock material produced from the Eagle and Olive pits was divided into three categories: - Metasedimentary - Rock which is highly weathered and foliated and generally shows poor mechanical properties. - Intrusive - Rock exhibiting a similar weathering pattern as the metasedimentary but has a noticeably higher inherent strength and a higher structural integrity. - Miscellaneous -Includes topsoil (thickness from 0.2 to 0.5 m) and colluvium (thickness from 2 to 7 m).Eagle waste rock will be hauled to one of two waste rock storage areas immediately to the south (Platinum Gulch WRSA) and north (Eagle Pup WRSA) of the open pit which results in short haul distances. Olive waste rock will be hauled to a waste rock storage area immediately south-west of the open pit (Olive WRSA).

Crushing and Ore Handling Primary crusher: a gyratory crusher with a stationary rock breaker in open circuit, producing a finalproduct P80 of approximately 115 mm; Secondary crusher: a vibrating screen and cone crusher operating in open circuit, producing a finalproduct P80 of approximately 21 mm; Tertiary crushers: three vibrating screens and three cone crushers operating in reverse closedcircuit, producing a final product P80 of 6.5 mm, and; Heap placement: crushed material is conveyed to the HLP by overland conveyor.ROM ore is trucked from the open pits and dumped directly into a primary feed hopper. The primary crusher, a 375-kW gyratory crusher, crushes ROM material from a maximum feed size of 1,000 mm down to a P80 of approximately 115 mm.The primary crushing plant is designed to operate 365 days per year at a rate of 29,500 t/d. During the winter months, January to March, the crushed material will be conveyed and stacked on the winter stockpile. Between April, up to the end of December, the primary crusher product is fed directly onto the secondary crushing feed conveyor. The material from the winter stockpile is reclaimed at a rate of 470 t/h by front-end loader (FEL), and conveyed to the secondary crushing feed conveyor for a combined feed of 39,200 t/d.If the crushing plant is down, the mine haul trucks dump onto the ROM stockpile. A FEL will be used to reclaim the ROM material and deliver the material to the dump pocket. The ROM stockpile can also be used to feed the crusher, if the mining operations are suspended. Ore from the secondary crushing feed conveyor is transported to the secondary vibrating double deck screen. Screened undersize material is conveyed to the tertiary crushing feed conveyor. The screened oversize feeds the 932-kW secondary cone crusher. The secondary cone crusher product discharges onto the tertiary crushing feed conveyor. Ore from the tertiary crushing feed conveyor is transported to the tertiary ore stockpile. The material from the stockpile is reclaimed by belt feeders to three tertiary vibrating double deck screens. The oversize material from the screens feeds the tertiary crushers, each installed with 932 kW motors. The crusher product returns to the tertiary crusher feed conveyor. The undersize material, with a target P80 of 6.5 mm, is transferred by overland conveyors to the HLP for stacking, by a series of grasshoppers that feed a radial stacker.Lime is added to the stockpile feed conveyor from the 200-t lime silo by screw conveyor for pH control, at a rate of 1 kg/t to 1.5 kg/t.

The gold recovery process was designed on the basis of leaching approximately 13M t of ore per year with an average gold head grade of 0.64 g/t (ROM and crushed ore combined) at an overall gold recovery of 77%. The three-stage crushing plant operates at a nominal primary crushing rate of 29,500 t/d, 365 days per year and a secondary and tertiary crushing rate of 39,200 t/d, 275 days per year. During the coldest part of the year (January through March), fine crushing and HLP loading activities are suspended. Barren solution, made up of a cyanide-caustic mixture, is pumped at a nominal rate of 2,070 m3 /h to a network of supply piping and drip emitters on the HLPs. Pregnant solution is collected in a sump near the bottom of the HLPs and pumped to the 8 t/d carbon ADR plant for gold extraction and the production of gold dor.The gold ore processing facilities include the following unit operations:Crushing and Ore Handling Primary crusher: a gyra ........

Related Equipments