Crushing Plant Design and Layout ConsiderationsCrushing Circuit A shows a small simple layout for use in mills up to 100 tons. In order to keep the flowsheet simple, and because of the use of the forced feed type of crusher, we can crush small tonnages up to 100 tons per day with a very simple arrangement; using a stationary or vibrating grizzly ahead of the crusher and then crushing the oversize before conveying into the fine ore bin. Elevators are often used for this purpose but are not recommended on very sticky ore.
In Crushing Circuit A the chute leading from the stationary or vibrating grizzly should be steep, for wet, sticky ore will build up if there is not a nearly vertical drop on to the conveyor. If the bottom of the conveyor is in a pit, plenty of room should be allowed in back of the tail pulley for the mill operator to shovel if necessary. A drain should be provided in case of floods or spills in the mill. The conveyor should not be placed at an elevation of more than 20 degrees. The fine ore bin should preferably be a deep bin in which storage capacity for at least a 36 hour supply of ore should be provided. In other words, for a 100 ton mill, this fine ore bin should have a capacity of at least 150 tons.
Crushing CircuitB shows the use of a secondary crusher for handling larger tonnages. The type of secondary crusher will vary according to the characteristics of the ore. Usually a cone type crusher is recommended for this secondary crushing, although in many cases a jaw crusher can be used as the secondary crusher, setting up the jaws closer than in the primary crushing operation. The interchangeability of parts is important if the two crushers are of the same size. The jaw crusher is the simplest and most fool-proof of secondary crushers. Rolls are often used where the shearing action of a roll crusher and a minimum amount of slimes are desired. However, rolls ordinarily should not be used to produce a feed finer than 1/8 and a reduction of 4 to 1 should be the maximum between the feed and discharge. Rolls have often been condemned because of the use of too small diameter rolls, cheap and poorly designed units.
For larger intermediate crushing the well-known cone gyratory crushers are recommended. Crushing Circuit B shows the use of a secondary cone crusher in the circuit between the primary crusher and the fine ore bin. A vibrating screen removes the undersize before the feed enters the secondary crusher. On small- tonnage plants, particularly on a steep millsite, this FLOWSHEET B is highly recommended, for both the primary crusher and the secondary crusher can be kept in a building in close proximity to each other.
Crushing Circuit C shows the modification of Crushing Circuit B where a light-weight, secondarycrusher can be placed over the fine ore bin. Oftenthe fine ore bin is strong enough, together with additional steel supports, to make this simple arrangement practical.
Crushing Circuit D shows a very practical arrangement even for large-tonnage plants, enabling both theprimary crusher and the secondary crusher to be inthe same crushing building and to utilize the minimum amount of conveying. There is a great deal ofmerit to this crushing layout D, for the same conveyor belt can handle the products from two crushersand thus the minimum amount of conveyor equipment and building space is required. In most instances this crushing arrangement D will prove tobe most practical from the first cost as well as from anoperating point of view.
Crushing Circuit E was at one time the most common arrangement for a crushing plant in which largetonnages were handled. This arrangement was recommended where compactness and space were not asimportant factors as under the arrangement D.Crushing CircuitE covers the fundamental factors ofa good crushing plant if floor space and expense arenot critical.
In all of the above Crushing Circuit flowsheets we recommend amagnetic head pulley or a permanent magnet aheadof the secondary crusher to remove injurious magneticmaterial, particularly the detachable drill bits whichare now becoming so common in many of our miningoperations.One can readily see the importance of this magnetic protection, particularly since in many mines the throwing down of worn out drill bits is an every-day occurrence. The removal of the fines from the crushed material before each crushing stage is also a very important step in good crushing practice.
This flow diagram shows a three-stage gravel plant schematically. It shows the interrelationships and functions of the various components of the plant. This sort of diagram can be used to advantage in working out the solution of an aggregate plant problem.
We should consider how the work is done by crushing machines, hammermills and pure impact crushers lift the kinetic energy of the material to a level where on sudden impingement against a stationary plate breakage occurs.
These two cone crushing configurations are commercially available and have entirely different concepts of the amount of ore being crushed as a proportion of the total feed, for the example shown (fig, 2), we are comparing two machines engaged in fine crushing with feed top size of 30 mm. This shows the smaller eccentric throw, longer chamber crusher can be expected to make a finer product at the same close side setting compared to the larger throw, short chamber machine, this is because it is working on a greater proportion of the feed, for further discussion, i will define this ability to inject energy per unit of feed as the power rate of the crusher.
you will notice from these results that in each case crushers 2 and 3, with the smaller eccentric throws, made a higher percentage of finer products even though in the case of crusher 3 the close side setting was 40 percent more open.
Dividing the power consumed by the tons of size produced gave remarkably similar power per ton figures, results from other tests on other sized crushers processing many different materials seem to confirm that cone type crushers use the same energy to reduce similar quantities of material to the same size. The efficiency in the application of energy converted to useful work by the crusher, therefore, appears independent of eccentric throw.
The only variables in the process which we can control routinely are feed rate and setting change to the crusher. These affect the power consumed at the drive motor and rate of energy input as follows.
At fixed settings (fig 5) near the point of economic operating capacity, feed rate versus power drawn has a linear relationship. Power rate tends to remain a constant.With variable setting, power changes in an exponential relationship (fig 6).
This example shows that for a very small change in setting there is a big change in power drawn, because for a small change in setting there is little volumetric change there will also be an exponential relationship in crusher setting versus energy per ton of feed (power rate) which is a direct measure of reduction, as is shown in fig, 7.
It should be obvious that if we can change the setting of the crusher whilst it is operating, we can affect both the productivity (consumed power) and, through the power rate the amount of reduction within the constraints set by the eccentric throw, speed and chamber configuration,
An important point which is often overlooked by plant design and application people is that the crusher must have an adequate amount of evenly distributed feed, fig, 8 shows the effect of poor and good feed distribution. If the feed is right the crusher will have maximum productivity (highest average crushing force) for minimum mechanical stress, a crusher cannot normally be fed properly from a vibrating screen discharge, this is why we have shown surge bins with pan or belt feeders in the diagrams that follow on plant discussions.
Construction aggregate, or simply "aggregate", is a broad category of coarse particulate material used in construction, including sand, gravel, crushed stone, slag, recycled concrete and geosynthetic aggregates. Aggregates are the most mined material in the world. Aggregates are a component of composite materials such as concrete and asphalt concrete; the aggregate serves as reinforcement to add strength to the overall composite material.
Aggregate production line manufactured by DSMAC aims for producing crushed stone aggregate. Crushed stone aggregate is produced from many natural deposits including: limestone, granite, trap rock and other durable mineral resources.
Large stone quarry and sand and gravel operations exist near virtually all population centers. These are capital -intensive operations, utilizing large earth-moving equipment, belt conveyors, and machines specifically designed for crushing and separating various sizes of aggregate, to create distinct product stockpiles.
DSMAC is a premier supplier of crushing and screening equipment, and related auxiliary equipment in China. We provide complete crushers and screen machines for producing all types of aggregate. One unit of DSMAC aggregate production line can produce up to 800-1000 TPH, the grain size will be 0-5mm, 5-10 mm, 10-20mm, 20-40mm, 40-60mm and even larger.
The vibrating feeder is mainly used for continuously and evenly feeding coarse crusher, screening fine aggregate, and thus enhances crusher capacity. It has been widely used for crushing and screening in the industries of mine, coal mine, etc.
DSMAC has endeavored to design and manufacture jaw crusher which is a type of highly-efficient and energy-saving crushing equipment. It is usually applied for coarse, intermediate and fine crushing of most type of stone.
The vibrating screen moves in a circular motion with multiple layers and high efficiency. The vibrating screen is designed with the barrel type of eccentric shaft vibration exciter and eccentric block to adjust the swing.
The linear vibrating screen is a new kind of high efficiency screening equipment which vibrates with a vibration motor. The linear screen features reliable performance, low consumption, little noise, long service life, high screening efficiency, etc.
Two of the most common crushing applications are two- and three-stage crushing processes. When deciding on whether to have two or three crushing stages, certain factors need to be considered in order to optimize the crushing process and achieve the best capacity and cost-efficiency. These are the
One of the key things is to fully understand and know your operations characteristics, as every quarry is unique. There are multiple different crushing processes and the way that they should be operated to achieve the optimal crushing process depends on many factors. This is one example of many applications and illustrates one potential case where this kind of crushing process could be optimal to produce the desired end product.
Feed material characteristics impact on what kind of crusher should be used and what kind of settings are suitable for processing the feed material. For example, the size and type of feed material determines the achievable reduction ratio of the crusher.
For example, when producing 0/32 mm end product, two crushers may be enough to produce the desired end product cost-efficiently and in accordance with the quality requirements. However, when the desired size of the end product gets smaller, for example, 0/16 mm, two crushers may not be enough, and it might be worth considering adding a third crusher to the crushing process for optimal aggregates production.
But how to determine the number of crushers in practice? Here's a practical tip: Check the maximum feed size of the primary crusher and compare that to the desired final product size. As a guiding principle, a reduction ratio of 4 is generally considered as the maximum of any jaw or cone crusher. If the ratio of feed material and end product size is 16:1, you need 2 crushers, and this is calculated by multiplying 4 with 4. If the ratio would be, lets say 20:1, you would need 3 crushers.
Some easily crushable rock types can be crushed in two stages and some harder rock types in turn require to be processed in three stages or more. If you attempt to process these types of rocks with crushers that are not optimal for processing them, the crushers will not be operated in their best operating range. This leads to increases in operative costs due to such things as higher wear of wear parts.
One common counterargument for not investing in additional crushers is naturally to save money. However, that is a devious misconception as producing fine aggregate with only two crushers oftentimes has a negative effect on both final product quality and quantity/capacity. It is possible to meet the size range even without an optimized process, but in order to meet the customers quality requirements, the process needs to be designed and built to meet those as well.
The argument on costs can also be examined from the equipment use point of view. All crushers are built to perform optimally in certain conditions, and if they are run constantly in non-optimal conditions, there will be an inevitable increase in cost per ton of production. This includes excess wear, but it can also be seen as not getting the most out of the investment. Luckily, there is always the option of optimizing the process.
So, if your target is to produce fine end products (for example, 0/16 mm) and aim for optimal crusher use and avoid breakages and rapid wear of wear parts, adding a third crusher as part of the crushing process would make production more optimal. Crushing in three stages enables the primary jaw crusher to be operated with a larger setting by accepting more and larger size feed material which in turn increases the life of wear parts and lowers operating costs as wear cost per crushed ton is higher. With three crushers, the settings can be also adjusted and fine-tuned more easily compared to two-stage crushing, which makes it easier to make finer end products.
Lets start with the primary jaw crusher, the Nordberg C120. For a two-stage crushing plant with the feed material properties in this example, it is not possible to squeeze the CSS any tighter than 100 mm as the power limit is the limiting factor. In the three-stage plant, we can open the C120s CSS to 150 mm, as the GP300S secondary cone crusher with its large feed opening can handle the coarser product of the jaw with ease, without any downtime caused by bridging or blockages.
A more open CSS of the jaw increases the capacity of the plant, and the feed flows visibly easier through the jaw. In this example, increasing the CSS of the C120 from 100 mm to 150 mm increases the crushed ton per one set of fixed jaw die by over 60%. This significant increase is enabled by the large feed opening of the GP Secondary cone crusher. Speaking of the GP300S, in this example, the fines are scalped away, but due to the GP Secondaries steep cavity profile, the crusher would be tolerant to fines being fed straight into the crusher as well.
One wisdom relating to all cone crushers is that, generally speaking, the end products quality is the best around the product size which is closest to the CSS used in the crusher. Knowing this, with three crushers, it is possible to tune the GP300Ss CSS close to 16/32 mm, and the tertiary GP330 cone crusher to 8/16 mm, maximizing the possibility of excellent product size for all of the end product gradations. With just two crushers, this wouldnt be possible, and some compromises have to be made.
In addition to improved quality, a third crusher will also increase the capacity of the process. As can be seen from the example, the overall end product tonnage in a two-stage plant is around 300 mtph, and in a three-stage one it is almost 500 mtph. Even though the quality and capacity of the process increases, the energy consumption will still stay the same as both plants would still have the same 1.06 kWh/t consumption.
Understanding the crushing stages and the type of crusher best suited for each stage can simplify equipment selection. Each type of crusher is different and is used to achieve a specific end result. Similarly, it is expected that at the end of each crushing stage a certain throughput will be available for the next stage of the process. Aggregate producers who pair the right crusher with the right stage will be the most efficient and, in turn, the most profitable.Next, the crusher supplier will share the following content with you.
Most aggregate producers are well versed in crushing plant selection and know that equipment can be selected based on specification sheets and gradation calculations alone. Nevertheless, the theoretical conclusions must always be weighed against the material at hand and the practical experience with the operation, maintenance, and economics of the different solutions.
The primary task of the coarse crusher is to make it possible to transport the material on a conveyor belt. In most aggregate crushing plants, primary crushing is performed in a jaw crusher, although a rotary primary crusher can also be used. Impact crushers may also be the best choice if the material is easily crushed and not excessively worn.
The most important characteristics of a coarse crusher are capacity and the ability to accept raw material without clogging. Large primary crushers are more expensive to purchase than smaller machines. For this reason, the investment cost calculation for a primary crusher is weighed against the cost of blasting the raw material to a smaller size.
In most cases, trucks deliver the raw material to a fixed primary plant. The cost of fuel, tires, maintenance, and return on investment should also be considered. In cases where producers crush at the quarry, a pit-mounted portable coarse crusher may be an economically sound solution. In modern plants, it is often advantageous to use a portable primary crusher so that it can follow the movement of the work face from which the raw material is extracted.
The purpose of intermediate crushing is to produce a variety of coarser fractions or to prepare material for final crushing. If a medium crusher is used for railroad ballast, the quality of the product is important.
In other cases, there is usually no quality requirement, but the product must be suitable for fine crushing. In most cases, the goal is to obtain the greatest possible reduction at the lowest possible cost.
In most cases, the fine crushing and cubing functions are combined in one crushing stage. Selecting a crusher for tertiary crushing requires both practical experience and theoretical knowledge. This is where manufacturers should ensure that experienced application specialists are brought in to ensure that the system is designed correctly.
Rotor centrifugal crusher, abbreviated as impact crusher, commonly known as sand making machine, is a kind of high-energy and low-consumption impact crusher with an international advanced level. Its performance plays an irreplaceable role in various ore fine crushing equipment and is currently the best effective, practical, and reliable stone crushing machine. It is widely used in metal and non-metal ores, cement, refractory materials, abrasives, glass raw materials, construction materials, artificial sand making, river pebbles, mountain rocks, etc.If you want to get more information about the wholesale best crusher price welcome to contact us.
There are no set rules for determining whether the secondary stage should consist of one single crusher, or of two or more machines operating in parallel. The decision must be made upon the merits of each problem. If the required receiving opening necessitates the selection of a crusher whose capacity equals or exceeds that of the primary crusher there is no object in going to a two-stage arrangement. Frequently this will be the case where a primary jaw crusher is to be followed by a gyratory machine. On the other hand, if the primary is a large gyratory, and the full output of this crusher is to gauge the. output of the plant, it will be necessary to install a, battery of two or more gyratories for the secondary reduction. The number and size of these will depend upon the size of the primary, its setting, the type of secondary to be used, and its setting. It is desirable that the multiple set-up be selected in even numbers, rather than odd; that is, either two or four units, rather than three. The difficulties in achieving an equitable distribution of feed into three units has been amply demonstrated in a number of plants.
From the standpoint of flexibility there is something to be said in favor of the multiple secondary stage, although the advantages are not so pronounced here as they are in the reduction crushing stages, unless of course the secondary stage is likewise a finishing stage. When the secondary stage is simply an open-circuit step in the over-all reduction flowline, the advantage of the multiple unit rests in the fact that single machines may be taken out of service for repairs without total interruption of the plant operation, although the feed rate must be reduced unless enough excess capacity is installed in this stage to permit cutting one machine out of service without affecting the average flow-rate through the plant. It is questionable if this much excess capacity is ever justified in a two-unit secondary stage; on the other hand, if the stage is to comprise four or more units, it is sound engineering to provide such extra capacity. The answer must in any case he predicated upon the relative importance of uninterrupted full-capacity operation.
Much of the foregoing discussion of secondary crushing stages will apply equally well to any succeeding stage, especially so if the stage is to run in open circuit. The cardinal factors of capacity, feed size and product size must he checked in very much the same fashion, keeping in mind the probable difference in types of crushers to be used. Usually, when we arrive at the third stage in a crushing plant, we are dealing with reduction or fine-reduction crushers where the feed size, as established by the open-side setting of the preceding stage, must be checked against the maximum one-way dimension of rock that the reduction crusher will nip. This comparison is usually all that is required to assure an adequate receiving opening, but it should be kept in mind that this maximum nip-dimension is not the full radial receiving- opening of the reduction-type crusher. In our own lines of reduction and fine-reduction crushers this differential in full, and effective, receiving opening applies to the Superior reduction crusher, the Newhouse crusher (with full-curve, non-choking concaves), and the Hydrocone crusher, To assist in the selection of machines of these types the following table has been prepared to show the maximum one-way dimension of rock that each machine will nip. These dimensions are for minimum crusher settings. In the case of the first generationcrushers they will increase by whatever amount the proposed setting exceeds the minimum. For both of these machines the figures apply to full-curve, non-choking concaves.
Two sets of maximum-nip dimensions are listed for the Hydrocone crushers; one for abrasive and one for non-abrasive material. An examination of the cross section through the crushing chamber of any flared-top shell crusher will make it clear that the effective receiving opening decreases as the head is raised. When crushing abrasive material, mantle and concave wear is relatively rapid as compared to the wear when crushing non-abrasive rock; furthermore, the wear is, comparatively, more rapid in the lower part of the crushing chamber, in contrast to the more even wear on non-abrasives. Hence, as the head is brought to its top position in adjusting for this wear, the effective receiving opening will be somewhat less for the crusher operating on abrasive rock. The effective openings listed are for the top position of the head; at lower positions the opening will be slightly more.
In making our check of receiving opening VSdischarge opening of the preceding stage, we should observe the same precaution suggested for the primary-secondary combination: the discharge setting against which we check the nip-dimension of our crusher should be the maximum opening at which we have reason to believe the preceding crusher will ever be operated. Usually secondary crushers can be, and are, maintained more closely to the established setting than are the larger primary machines, some of which are without means of adjustment other than resetting of concaves or replacement of mantles; nevertheless it is extremely difficult in actual practice to maintain crusher settings within narrow limits with a few exceptions, and some margin should be allowed for this.
If the secondary stage is to consist of one or more standard type gyratory crushers, with or without non-choking concaves, the radial receiving opening should be not less than 2.5 to 3 times the open-side discharge setting of the primary crusher. The larger ratio should be observed for primary jaw crushers, because of the slabbing propensities of this type. Thus, if the primary is one of the 84 class of jaw crushers set at 10 in., the secondary machine should be not less than a 30 gyratory with straight concaves, or a 36 size if fitted with non-choking concaves (32 receiving opening). A primary gyratory, set at 6 may be followed by one or more 16 crushers with straight concaves, or by the 20 size if fitted with non-choking concaves (16.5 receiving opening).
When the secondary stage is to consist of gyratory crushers of the reduction type,the ratio may be somewhat lower than those for the standard machines because, for a comparable radial receiving opening, these reduction types have larger diameter crushing chambers and, hence, longer openings (as measured parallel to the spider arms. Usually from 2 to 2.5 times the primary crusher setting will be satisfactory. These cylindrical-top-shell crushers, when fitted with reversible, full-curve non-choking concaves, have effective receiving openings which are considerably less than the radial distance from top-of-head to top-of-concaves. This effective receiving opening must be at least as large as the maximum open-side setting at which the primary crusher will ever be operated (that is, when mantle and concaves or jaw plates are worn thin).
Fine-reduction crushers, such as the Hydrocone, also have effective receiving openings which are smaller than their full rated openings; therefore one must observe the same precaution in selecting sizes of these machines as with the reduction types mentioned in the preceding paragraph. In selecting crushers of the roll type to follow a preceding stage the maximum permissible nip-dimension must be not less than the maximum discharge setting of such preceding stage; and the length of roll face should be at least 4 to 5 times this setting.
Hammermills should have a minimum throat opening not less than double the setting of a preceding stage of either gyratory or jaw crusher; and the lateral throat opening should be from 4 to 5 times such setting. Although their characteristics are not particularly favorable for secondary or reduction crushing service, jaw crushers are sometimes so used, for example, in portable and semi-portable plants and in small mining installations. Usually the machines are the single-toggle or cam-actuated types, with receiving openings whose lateral dimension is at least double the dimension from top-to-top of the jaw plates. The lateral opening should be at least twice the discharge setting of the preceding stage, and when non-choking jaw plates are used the effective nip opening must be checked against this discharge setting, just as is done for the gyratory types.
Regardless of the number of stages of reduction in the plant, the primary crusher, at least in those plants designed to handle shovel-loaded rock, is usually set at or near the minimum safe discharge setting for which it is designed, although as we have stated, this setting may not be strictly maintained over a long period of time. This practice of utilizing the full permissible reduction-ratio of the primary crusher is quite sound from several standpoints. The primary crusher represents a substantial investment, and the user is justified in his desire to obtain from it all the reductiop* of which it is capable. Furthermore, the machine is likely to have some excess capacity as compared to the succeeding units in the plant, even at its minimum setting. When such is the case there is nothing to be gained by operating it at a coarser setting. Thirdly, if the primary is a medium or large size machine, its minimum setting will be wide enough to obviate any excessive creation of fines by attrition; in any event the difference in percentage of fines produced at the minimum setting, as compared to any coarser setting, will not seriously affect the percentage of fines in the finished plant product. Unless the material is very hard and tough, or contains a viscid admixture which makes it difficult to get through the crusher, everything is in favor of working the primary at its maximum safe ratio-of-reduction.
The arguments in the preceding paragraph do not always hold good for the secondary stage. Here the discharge settings are much finer, and the ratio-of-reduction begins to have a significant influence upon the percentage of fines that will show up in the plant product. Therefore, where minimum fines are desired, the amount of work done in the secondary stage should be held within conservative limits. The characteristics of non-choking are to be minimized, unless the setting of the secondary stage is to be quite coarse.
For the combination of large jaw crusher followed by a gyratory of the 30 or 36 size, there is no particular reason why the maximum reduction-ratio cannot be utilized through both stages, especially if interstage scalping is employed. These secondaries are quite large; in fact such crushers serve as primaries in medium size crushing plants; and their minimum settings are wide enough to permit operating them in the manner suggested without excessive fines production.
This open-circuit, stage-crushing system is an excellent arrangement for the commercial crushing plant, because it tends to minimize production of fines, especially so if the ratio of reduction, per stage, is held within moderate limits. The system can be carried out to a point where relatively little tonnage need be handled in closed-circuit, as has been exemplified in a number of plants during recent years. As an example: a plant is running, let us say, with a final, close-circuited stage that is taking anoriginal feed of about 100 tons per hour, with a circulating load of about 25 tons/hour through this stage. If a small clean-up crusher is installed to handle the 25 tons oversize; this machine being set somewhat finer, of course, than the larger machine; the circulating load through this smaller crusher can generally be held within 5 tons per hour, and the feed rate to the former final-stage can be increased by the amount of the circulating load which has been removed from it. This practice of adding clean-up crushers to an existing flow-line is becoming increasingly popular, particularly where the demand for smaller sizes of product has been throwing a heavy strain on existing equipment.
Open-circuit, stage-crushing is equally well adapted to the preparation of feed for grinding mills. For such service the reduction per stage need not be limited with a view to minimizing fines; otherwise, the design factors are much the same as for the aggregates plant. Nothing that we have said here should be construed as antagonistic to the closed-circuit, crushing-stage. which is a very necessary adjunct to most minerals-reduction plants. What we are trying to convey is the fact that material which has been through a pressure-type crusher once can be processed more efficiently, for further reduction, in another crusher, or crushers, with smaller discharge setting; and, that circulating loads should be held to a minimum by carrying the stage-crushing system through to its logical limit.