rock crushing rule of thumb

Gyratory crusher: feed diameter 0.75 to 1.5m; reduction ratio 5:1 to 10:1, usually 8:1; capacity 140 to 1000 kg/s; Mohs hardness <9. More suitable for slabby feeds than jaw crusher. [reduction by compression].

crusher efficiency calculations

The following example demonstrates a method of selecting the components of an aggregate plant. Good component efficiency and part performance pre-evaluation is essential to a solid design. The aggregate production requires the consideration of several crushers, feeders and screens. This is not intended to be a typical situation, though it does involve common crusher and screen units often used in aggregate plants.

Quarry rock of 12 in. maximum size is to be handled in a two-stage crusher plant at the rate of 70 tons per hour. The maximum size of output is to be 1 in., and separation of materials over 1 in. size and the minus 1 in. in the output is required. Select a jaw crusher like those included in this table.

The screens to be considered are a 1-in. screen with an estimated capacity of 2.7 tph/sq ft and a 1-in. screen with a capacity of 2.1 tph/sq ft. The solution will include the selection of adequate and economical crushers for the two stages and the sizes of screens between them and below the secondary stage.

For the primary crusher a jaw crusher will probably be most economical. A jaw crusher, like 2036 in the Jaw Crusher Table here above, would be able to take the maximum 12 in. size quarry stone but it would not have the required 70 tph capacity needed. To have the needed capacity a jaw crusher like the 2042 or 2436 sizeswill have to be selected overloading the secondary crusher.

A grid chart or curve for the selected crusher shows that, for a 2-in. setting, 54% of the material will pass a 1-in. screen, or 46% will be retained (this is like Jaw Crusher capacity table abovewhere 48% passes a 1 in. screen). The 46% of 70 tph gives the 32 tph fed to the secondary crusher shown in Figure below as a roll crusher.

A twin-roll crusher is selected, like those given inthe Roll Crusher capacityTable above, to serve as the reduction crusher. The smallest, 24 x 16 roll crusher shown in theRoll Crusher capacity Table above has enough capacity with a setting of 1 in. but the maximum size feed will be too large, that is, the stage of reduction is not large enough. The maximum size of feed coming from the discharge of the primary crusher with a setting of 2 is about 3 in. as may be found in this Table.

Considering a 30-in. diameter roll crusher the maximum size particle that can be nipped with the roll crusher set at 1 in. according to this Equation is F = 0.085(15) + 1.0 = 2.28 in. <3 in. feed. It will take larger than a 40-in. diameter roll crusher. A better solution would be to use a larger jaw crusher set at 1 in., then a roll crusher from the Roll Crusher capacityTable above could be used. If the output of this crushing process should have less material of the +1-in. size, the larger crusher could be operated with a closed circuit. That is, the oversize in the output could be recirculated through the roll crusher without exceeding the rated capacity of the crusher. Then all material leaving that crusher with a 1-in. setting would be of a minus 1-in. size.

Another possible solution to this problem would be to use a gyratory crusher for the primary crushing stage. A gyratory like Telsmith model1110 could be set at 1 in. in an open circuit with a capacity for 260 tph. The maximum size of stone in the output is estimated to be approximately 2 1/8 in. Then all the output from the primary crusher could be nipped by a 40 in. diameter twin-roll crusher with a 1-in. setting according to the Roll Crusher capacityTable above. The specifications and manufactured limitations, rather than economy, generally govern the selection of crushers.

To find the required areas of screen, the rate of feed of material as well as gradation of the feed must be known. The 1-in. screen under the jaw crusher is the top deckno deck correction factor will be necessary. Therefore, the 1-in. screen will need to be at least 70/2.7 = 29.9 sq ft in area. It must be at least 36 in. wide for an 18 x 36 jaw crusher. So a 4-ft by 8-ft screen would be acceptable. The 1-in. screen is a second deck for the 38 tph from the jaw crusher, so the deck correction factor is 0.90 and that screen capacity is 2.1 x 0.9 = 1.89 tph/sq ft.

The screen area needed under the jaw crusher is 38/1.89 = 20.1 sq ft. For the 1-in. screen below the roll crusher the capacity has no correction factor and the area needed is 32/2.1 = 15.2 sq ft. To handle the output from a 40 x 24 roll crusher the screen will have to be at least 24 in. wide. Perhaps it will be more effective to use one continuous screen of at least 20.1 + 15.2 = 35.3 sq ft. A 4-ft by 10-ft 1 in. screen should be satisfactory.

prodeva recycling equipment

If you need processing equipment for your MRF or Recycling Center, Prodeva can help. We have been manufacturing and supplying processing equipment since 1958, this gives us nearly 40 years experience in the size reduction field.

Prodeva offers a complete line of conveyors, crusher and shredder models for processing bottles, cans (aluminum or steel), plastic and glass. Our equipment is used world-wide for recovery, recycling, scrap, and disposal facilities, both public and private. Every piece is engineered and field-tested for profitable operations.

Equipment Manufactured by Prodeva Conveyors Glass Crushers Steel Can Flatteners Flattener Blowers Plastic Perforators Plastic Shredders Magnetic Separators Glass Grinders Equipment Supplied by Prodeva Overhead Magnetic Separators Eddy Current Separators Trommell Screens Disc Screens Air Classifiers

Equipment Supplied by Prodeva Overhead Magnetic Separators Eddy Current Separators Trommell Screens Disc Screens Air Classifiers

development of a model estimating energy consumption values of primary and secondary crushers | springerlink

Most of the costs in open pit quarry operations occur in crushing and grinding processes. Therefore, the management of crushinggrinding processes is very important. Many researchers investigated the effects of pile size distribution and specific charge values occurring as a result of blasting on crusher energy consumptions and provided some cost reductions in the crushers by using suitable explosive. However, these researchers did not sufficiently use discontinuity characteristics of the blasting surface and resistance values of the rock while making these studies. In this study, 15 blasting tests were also realized at two different limestone quarries. Correlations estimating the energy values consumed by primary and secondary crushers were developed by using discontinuity characteristics of blasting surfaces in blast tests, specific charge, and uniaxial compressive strength values of the rock, and compared with energy consumption values measured real timely in the crushers. Very limited error margins were observed in these comparisons. Material exit size at primary crusher must be 15cm and material exit size at secondary crusher must be 7.5cm. In addition, primary crusher was of jaw type and secondary crusher was of hammer type.

The authors wish to thank The Scientific and Technological Research Council of Turkey for providing funding for this research project and Western Anatolia Cement Factory for their help during field studies.

Tosun, A., Konak, G. Development of a model estimating energy consumption values of primary and secondary crushers. Arab J Geosci 8, 11331144 (2015). https://doi.org/10.1007/s12517-013-1260-3

jaw crusher | primary crusher in mining & aggregate - jxsc mine

Product Introduction JXSC jaw type rock crusher is usually used as a primary crusher and secondary crusher to reduce the size of medium-hard materials to smaller physical size. Jaw rock crushers are capable of working with the mobile crushing station, underground crushing because of its related small volume. Capacity: 1-1120TPH Max Feeding Size: 120-1200mm Application Mining, metallurgy, building materials, quarrying, gravel & sand making, aggregate processing, recycling, road and railway construction and chemical industry, etc. Suitable Material Granite, marble,basalt, limestone, coal, quartz, pebble, iron ore, copper ore, etc.

40 years of manufacturing and engineering experience keep us innovative and knowledge in the rock break machines and its applications, which thus provide reliable industry rocks crushers and solutions for every customer using jaw crusher manufacturers JXSC machines to meet their production goals. The jaw crusher machine family consists of different sized models that are designed to bring maximum output with minimum cost. Some workplaces have limited conditions and are unable to provide electricity or are underpowered. According to these conditions, JXSC specially designed diesel jaw crusher. The diesel-jaw crusher is actually with electric, but the original jaw crusher was added with a diesel engine equipment that a dual-purpose crusher.

JXSC the crushers machine with a non-welded frame has been proved that it has outstanding solid and durable strength. All the alloy casting frame components turn out that with premium quality, wear-resistant property.

The design of pitman and long stoke improves productivity and reduction. A wider feeding material opening increases the volume of insulating material and makes the ore material entering the crushers crushing chamber smoothly. A sharp angle makes the materials flow down speed faster and reduces the wear cost. Besides, the strike force could be stronger thus increase the production efficiency as well as the reduction ratio.

Types of jaw crushers: on the basis of the stone break equipment size and capacity can divide into a heavy and small(mini) portable jaw rock crushers. According to the working principle can be split into single toggle and double toggle jaw rock crushers machine.

A series of jaw stone crushers use compressive and squeezing force for reducing materials. This physical force is created by the two jaw plates, one of which is a movable plate and another is fixed, both of them are made of manganese. A V-shaped cavity, crushing chamber, is formed and the hydraulic discharge gap width of the crushing chamber, we can determine the suited feeding material size and discharging size, the width of top feeding is larger than that of bottom discharging.

Jaw crusher is a heavy-duty machine that crushes hard materials. So its hence muse be robustly constructed. Crusher frame is made from steel or cast iron. The jaws are made of cast steel. The liners are made fromNi-hard, Ni-Cr alloyed cast iron or manganese steel which can replaceable and use to reduce frame wear. The cheek plates are also made from hard alloy steel and installed to the sides of the crushing chamber to protect the frame from wear.

The jaws can be made in smooth or corrugated, but often corrugated. Because the latter crushing the hard and abrasive ores is better. The angle between the jaws is usually less than 26. This is because a large angle will cause the particle to slip which non-crush.

It uses curved plates to avoid the near the discharge of jaw crusher blocking. The bottom of the swinging jaw is concave, and the relative lower part of the fixed jaw is convex. The materials reduction in size when nears the exit. So the material is distributed over a larger area, and the jaws plates wear less.

The type of crushed materials determines how to design the max amplitude of swing of the jaw and the amplitude adjusted by changing the eccentric. The length from 1 to 7 cm depends on the crusher machine size. Jaw crushers are supplied in sizes up to 1,600 mm (gape)1,900 mm (width). For coarse crushing application (closed set~300 mm), capacities range up to 1200 tph.

Jaw crusher parts must have some wear after a period of use, but the easily damaged parts will wear out more. The price of crushing equipment with the same specifications and handling capacity is different in the material of parts.

Guard Plate The guard plate is made of high-quality high manganese steel, which is located between the fixed plate and the movable plate. The whole body is mainly to protect the jaw crusher frame wall.

Toothed Plate Tooth plate is divided into movable and fixed tooth plate, but both is made from high manganese steel casting. In order to prolong its service life, its shape is designed to be symmetrical. That is when one end of the wear can be used to turn the head. The movable and the fixed teeth plate are the main parts for stone crushing. So the movable teeth plate is installed on the movable jaw to protect the movable jaw.

Toggle Plate The toggle plate is a cast iron piece that has been precisely calculated. It is not only a force transmission component but also the safety parts of the crusher. When the crusher falls into the non-crushing material and makes the machine beyond the normal load, the toggle plate will immediately break. Then the crusher machine stops operation, thus avoiding the damage of the whole machine. The toggle plate and the toggle plate spacer adopt the rolling contact model which less attrition under normal use. It just needs smear a layer of grease on the contact surface is ok.

Triangular Belt When the motor transmits power, the triangle belt is connected with the pulley and the grooved pulley of the motor to drive the eccentric shaft and make the moving jaw move back and forth according to the predetermined track.

The tooth plate of the most jaw crushers are made of manganese steel, bearing linings are made of babbitt alloy, sliding blocks are made of carbon steel, toggle plates are made of cast iron, springs are made of 60SiMn. Regular Inspection and maintenance of the machine can extend its service life. In order to reduce customer costs, we will generally be in the purchase of customers are advised to buy some spare parts. Because once the parts need to be replaced, the temporary purchase will take some time. The wait time may cause the entire breakage line to suspend operations, thereby increasing operating costs.

In short, the jaw stone crushers are mainly used for primary crusher, the crushing stone is relatively large. The types of crusher machine's chamber are deep and no dead zone. It improves that the feeding capacity and output. The crushing ratio is large and the product particle size is even. Shim type outlet adjustment device, reliable and convenient, large hydraulic adjustment range that increased the flexibility of the equipment. Simple structure, reliable work and low operation cost. The adjustment range of hydraulic discharge opening is large, which can meet the requirements of different users, low noise and less dust.

Impact crusher for crushing medium-hard stones, and mostly used for secondary crusher. The impact crushers have a big feeding port, high crushing cavity, high material hardness, big block size and little stone powder. Convenient maintenance, economic and reliable, high comprehensive benefit.

Jiangxi Shicheng stone crusher manufacturer is a new and high-tech factory specialized in R&D and manufacturing crushing lines, beneficial equipment,sand-making machinery and grinding plants. Read More

cone crushers | mclanahan

A Cone Crusher is a compression type of machine that reduces material by squeezing or compressing the feed material between a moving piece of steel and a stationary piece of steel. Final sizing and reduction is determined by the closed side setting or the gap between the two crushing members at the lowest point. As the wedge or eccentric rotates to cause the compression within the chamber, the material gets smaller as it moves down through the wear liner as the opening in the cavity gets tighter. The crushed material is discharged at the bottom of the machine after they pass through the cavity.

A Cone Crusher will deliver a 4:1 to 6:1 reduction ratio. As we set the closed side setting tighter to create a finer output, we also reduce the volume or throughput capacity of the machine. Generally speaking, multiplying the closed side setting by two is a good guide to the top size of the gradation exiting the machine.

The technology that makes a MSP Cone Crusher outperform competitive cones on the market is the combination of all of the factors of performance i.e. balanced eccentric, higher speeds, fulcrum point position, and stroke. By using sound engineering with years of field testing a truly tried and tested new Cone Crusher has emerged.

A balanced eccentric coupled with a fulcrum point ideally placed over the crushing chamber yields highly effective compression crushing. This allows higher eccentric speeds to maximize performance without disruptive forces. The eccentric stroke is designed to work with the eccentric speed and fulcrum position to produce higher yields and minimize recirculating loads. The torque and resultant crushing forces are as effective as virtually any Cone Crusher on the market.

Spiral bevel gears provide the turning force to the eccentric. The spiral gear is mounted on a sturdy countershaft of the Cone Crusher, which rides in bronze bushings. The gears are precision cut for quiet operation. Misalignment problems are eliminated.

The MSP Cone Crusher features one of the largest volume displacements by a crusher head. When there is a large volume of material displaced this way, it means that more material is crushed in each cycle, more material can be fed to fill the larger void left when the crushing head recedes, and more material flows through the crusher due to the larger throughput and gyrating cycles allowing material to drop further. The benefits of high efficiency, greater crushing force and high capacity coupled with the durability the market expects are the reasons why this design is the best way to increase your productivity and profitability.

Sleeve bearings make removal and installation of the MSP Cone Crusher head and main shaft simple. The tapered main shaft fits into a large opening at the upper end of the tapered eccentric bushing. The shaft does not require precise alignment. It can be inserted from a vertical position and will self-align.

With the MSP Cone Crushers automatic hydraulic overload relief system, the crusher immediately opens in the event of an overload. This action reduces the crushing pressure, allowing the obstruction to pass through the chamber. After the chamber has been cleared, the hydraulic control system automatically returns the crusher to its original setting. Shock loads on the crusher are reduced for longer component life.

MSP Cone Crushers are built to make your operations run more smoothly and easily. Its simple and easy to read control panel provides you with the necessary information to properly run your crusher. For example, the MSP Cone Crusher shows you the exact cone setting to allow the operator to stay on top of a critical set point.

To enhance your Cone Crusher's life and maintain optimal crushing capacities, an automatic liner change reminder is included for your convenience. When the new mantle and liners are installed, the automated reminder is reset. As the crusher operates, the system will track production capacities and calculate the liner wear rate. When the cone liners reach the maximum wear point, it sends a flashing reminder to 'change cone' on the cone setting meter. After the wear parts are changed, simply reset the automated reminder system and continue efficient, reliable crushing.

The MSP Cone Crushers are built heavier than most competitive Cone Crushers. The extra weight means lower stress on the machine, which results in longer operational life. There is no question that the proper use of mass makes for more durable crushers. Additionally, a broad array of manganese liners is offered for each size MSP Cone. A unique and patented feature allows the Liners to fit without the use of any backing material. Improved Chamber matching with crusher feeds virtually eliminates any trial and error.

All these factors combine to give producers more effective compression crushing. This reduces liner wear, which reduces wear cost and allows higher yields, resulting in decreased overall cost per ton of finished product.

In the Symons principle, which is utilized by the MSP Cone Crusher, each cycle is timed so that the feed material and the upward thrust of the crushing head meet at the moment of maximum impact. The optimum speed of gyration and the large eccentric throw produce two important results: 1) the rapidly closing head catches the falling feed material and delivers the extremely high crushing force and 2) on the other side of the chamber the rapidly receding head allows material to fall freely to the next point of impact or exit the chamber. The combination of superior crushing force and free flow of material in the MSP Cone Crusher results in production levels that are unsurpassed and means lower power consumption per ton.

Ten years of testing went into the final combination of speed, stroke, and head angle to deliver the most efficient use of power. Greater efficiency delivers lower power consumption, reduced cost per ton, less maintenance and higher profits.

The power input imparted by the driven eccentric results in a bearing force in opposition to the crushing force at a point on the lower portion of the main shaft. The bearing force as it is transmitted to the main shaft provides the required moment to crush the rock. The distance between the bearing force and the fulcrum point is called the force arm. The longer the force arm, the greater the momentum, which produces a greater crushing force.

Crushing loads are distributed over a large spherical bearing. The socket liner keeps full contact with the crushing head ball and carries all of the vertical component and part of the horizontal. The long force arm, represented by the main shaft, reduces the load transmitted through the eccentric bushing.

Capacities and product gradations produced by Cone Crushers are affected by the method of feeding, characteristics of the material fed, speed of the machine, power applied, and other factors. Hardness, compressive strength, mineral content, grain structure, plasticity, size and shape of feed particles, moisture content, and other characteristics of the material also affect production capacities and gradations. Gradations and capacities are most often based on a typical, well-graded choke feed to the crusher. Well-graded feed is considered to be 90% to 100% passing the closed side feed opening, 40% to 60% passing the midpoint of the crushing chamber on the closed side (average of the closed side feed opening and closed side setting), and 0 to 10% passing the closed side setting. Choke feed is considered to be material located 360 degrees around the crushing head and approximately 6 above the mantle nut. Maximum feed size is the average of the open side feed opening and closed side feed opening.

Minimum closed side setting may vary depending on crushing conditions, the compressive strength of the material being crushed, and stage of reduction. The actual minimum closed side setting is that setting just before the bowl assembly lifts minutely against the factory recommended pressurized hydraulicrelief system.

Overall, industry acceptance of the Symons principle and performance, the McLanahan Cone Crusher works to deliver lower recirculating loads at higher tonnage rates with lower maintenance costs by combining:

A general rule of thumb for applying Cone Crushers is the reduction ratio. A crusher with coarse style liners would typically have a 6:1 reduction ratio. Thus, with a 34 closed side setting, the maximum feed would be 6 x 34 or 4.5 inches. Reduction ratios of 8:1 may be possible in certain coarse crushing applications. Fine liner configurations typically have reduction ratios of 4:1 to 6:1.

The difference between the volume displaced by the crushing head when it is fully closed and fully open is called the displacement volume. A large displacement volume results in greater capacity because:

In order to maintain the maximum levels of capacity, gradation, and cubical product, a Cone Crusher must be choke-fed at all times. The best way to keep a choke-feed to the ConeCrusher is with a surge bin (or hopper) and feeder that are located prior to the crusher. Choke-feeding is almost impossible to achieve without a hopper and feeder.

There are a number of different criteria to consider when selecting the right chambers for your crushing needs. However, the one that must always be considered isthat you have a well-graded feed to the chamber. A well-graded feed is generally thought to be 90 to 100% passing the closed-side feed opening, 40 to 60% passing the midpoint, and 0 to 10% passing the closed-side setting.

One thing you should never do is place a new concave liner in a crusher with a worn mantleor place a new mantle in a crusher with a concave liner. Why? If you have properly selected the replacement component, you will change the complete profile of the Cone Crusher by mating new and worn components. The receiving opening will tend to close down, restricting the feed from entering the chamber and causing a reduction in tons per hour.

If the liner is wearing evenly throughout the chamber, you should consider changing out the manganese when it has worn down to about 1" (2.5 cm) thick at the bottom. At about 3/4" to 5/8" (1.9 to 1.6 cm) thick, the manganese will crack, causing the backing material to begin to disintegrate. This, in turn, will cause the liners to break loose. If this should happen, continued operation could destroy the seat on the support bowl or the head of the Cone Crusher.

McLanahan Symons Principle (MSP) Cone Crushers utilize a combination of improved factors of performance, which are enhanced by the Symons Principle of crushing, as well as the latest hydraulic features and electrical features that create a modern, efficient, reliable and durable Cone Crusher that ultimately leads to a faster ROI. MSP Cone Crushers are designed to make your operation run more smoothly and easily, as well as ensuring lower operating costs and minimal downtime so that MSP Cone Crushers are more frequently fully operational and processing optimal amounts of material.

Efficiency can be defined by the ratio of the work done by a machine to the energy supplied to it. To apply what this means to your crusher, in your reduction process you are producing exactly the sizes your market is demanding. In the past, quarries produced a range of single-size aggregate products up to 40 mm in size. However, the trend for highly specified aggregate has meant that products have become increasingly finer. Currently, many quarries do not produce significant quantities of aggregate coarser than 20 mm; it is not unusual for material coarser than 10 mm to be stockpiled for further crushing.

jaw crusher - an overview | sciencedirect topics

The mechanism of movement of rocks down the crusher chamber determines the capacity of jaw crushers. The movement can be visualised as a succession of wedges (jaw angles) that reduce the size of particles progressively by compression until the smaller particles pass through the crusher in a continuous procession. The capacity of a jaw crusher per unit time will therefore depend on the time taken for a particle to be crushed and dropped through each successive wedge until they are discharged through the bottom. The frequency of opening and closing of the jaws, therefore, exerts a significant action on capacity.

Following the above concepts, several workers, such as Hersam [6]. Gaudin [7], Taggart [8], Rose and English [9], Lynch [3], Broman [10], have attempted to establish mathematical models determining the capacity.

Although it is not truly applicable to hard rocks, for soft rocks it is reasonably acceptable [1]. This expression, therefore, is of limited use. The expressions derived by others are more appropriate and therefore are discussed and summarised here.

Rose and English [9] determined the capacity of a jaw crusher by considering the time taken and the distance travelled by the particles between the two plates after being subjected to repeat crushing forces between the jaws. Therefore, dry particles wedged between level A and level B (Figure4.4) would leave the crusher at the next reverse movement of the jaw. The maximum size of particle dropping out of the crusher (dMAX) will be determined by the maximum distance set at the bottom between the two plates (LMAX). The rate at which the crushed particles pass between the jaws would depend on the frequency of reversal of the moving jaw.

The distance, h, between A and B is equal to the distance the particle would fall during half a cycle of the crusher eccentric, provided the cycle frequency allows sufficient time for the particle to do so. If is the number of cycles per minute, then the time for one complete cycle is [60/] seconds and the time for half a cycle is [60/2]. Thus, h, the greatest distance through which the fragments would fall freely during this period, will be

Then for a fragmented particle to fall a distance h in the crusher, the frequency must be less than that given by Equation (4.10). The distance h can be expressed in terms of LMIN and LMAX, provided the angle between the jaws, , is known. From Figure4.4, it can be seen that

Rose and English [9] observed that with increasing frequency of the toggle movement the production increased up to a certain value but decreased with a further increase in frequency. During comparatively slower jaw movements and frequency, Rose and English derived the capacity, QS, as

Equation (4.12) indicates that the capacity, QS, is directly proportional to frequency. At faster movement of the jaws where the particle cannot fall the complete distance, h, during the half cycle, QF was found to be inversely proportional to frequency and could be expressed by the relation

The relationship between the frequency of operation and capacity of the jaw crusher can be seen in Figure4.5. This figure is plotted for values of LT=0.228m, W=1.2m, LMIN=0.10m, R=10, G=1 and the value of varied between 50 and 300rpm.

It should be noted that while considering the volume rates, no consideration was made to the change of bulk density of the material or the fractional voidage. However, during the crushing operation the bulk density of the ore changes as it passes down the crusher. The extent of the change depends on

PK is considered a size distribution function and is related to capacity by some function (PK). As the particles decrease in size, while being repeatedly crushed between the jaws, the amount of material discharged for a given set increases. Rose and English related this to the set opening and the mean size of the particles that were discharged. Defining this relation as it can be written as

The capacity is then dependant on some function which may be written as (). Equations (4.16) and (4.17) must, therefore, be incorporated into the capacity equation. Expressing capacity as mass of crusher product produced per unit time, capacity can be written as

The bulk density of the packing will depend on the particle size distribution. The relation between PK and (PK) and and () is shown in Figure4.6. It is based on a maximum possible bulk density of 40%.

As the closed set size must be less than the feed size, () may be taken as equal to 1 for all practical purposes. The maximum capacity of production can be theoretically achieved at the critical speed of oscillation of the moving jaw. The method of determining the critical speed and maximum capacity is described in Section4.2.3

The capacity of a jaw crusher is given by the amount of crushed material passing the discharge opening per unit time. This is dependent on the area of the discharge opening, the properties of the rock, moisture, crusher throw, speed, nip angle, method of feeding and the amount of size reduction.

In order to calculate the capacity of crushers, Taggart [8] considered the size reduction, R80, as the reduction ratio of the 80% passing size of the feed, F80, and product, P80. This may be written as

Hersam [6] showed that at a fixed set and throw, a decrease in feed size reduced the reduction ratio and increased the tonnage capacity. A fraction of the crusher feed is usually smaller than the minimum crusher opening at the discharge end (undersize) and, therefore, passes through the crusher without any size reduction. Thus, as the feed size decreases, the amount actually crushed becomes significantly less than the total feed. The crusher feed rate can increase to maintain the same crushing rate. Taggart expressed the relationship between crusher capacity and reduction ratio in terms of a reduction ton or tonne, QR defined as

The reduction tonnage term is dependent on the properties of the material crushed so that for a given reduction ratio, the crusher capacity will vary for different materials. Taggart attempted to compensate for this by introducing the comparative reduction tonne, QRC, which is related to the reduction tonne by the expression

The comparative reduction tonne is a standard for comparison and applies for the crushing conditions of uniform full capacity feeding of dry thick bedded medium-hard limestone where K=1. The factor K is determined for different conditions and is a function of the material crushability (kC), moisture content (kM) and crusher feeding conditions (kF). K is expressed as

To evaluate K, the relative crushability factor, kC, of common rocks was considered and is given in Table4.2. In the table, the crushability of limestone is considered standard and taken as equal to 1.

The moisture factor, kM, has little effect on primary crushing capacities in jaw crushers and could be neglected. However when clay is present or the moisture content is high (up to 6%) sticking of fine ores on the operating faces of the jaws is promoted and will reduce the production rate. The moisture effect is more marked during secondary crushing, where a higher proportion of fines are present in the feed.

The feed factor kF, applies to the manner in which the crusher is fed, for example, manually fed intermittently or continuously by a conveyor belt system. In the latter case, the rate of feeding is more uniform. The following values for factor kF are generally accepted:

The reduction ratio of the operation is estimated from screen analysis of the feed and product. Where a screen analysis is not available, a rough estimate can be obtained if the relation between the cumulative mass percent passing (or retained) for different size fractions is assumed to be linear (Figure4.7).

Figure4.7 is a linear plot of the scalped and unscalped ores. The superimposed data points of a crusher product indicate the fair assumption of a linear representation. In the figure, a is the cumulative size distribution of the unscalped feed ore (assumed linear) and b is the cumulative size distribution of the scalped ore. xS is the aperture of the scalping screen and d1 and d2 are the corresponding sizes of the scalped and unscalped feed at x cumulative mass percentage. Taking x equal to 20% (as we are required to estimate 80% that is passing through), it can be seen by simple geometry that the ratio of the 80% passing size of the scalped feed to the 80% passing size of the unscalped feed is given by

Run of mine granite is passed through a grizzly (45.7cm) prior to crushing. The ore is to be broken down in a jaw crusher to pass through a 11.5cm screen. The undersize is scalped before feeding to the jaw crusher. Assuming the maximum feed rate is maintained at 30t/h and the shapes of feed and product are the same and the crusher set is 10cm, estimate the size of jaw crusher required and the production rate.

Substituting values, assuming cubic-shaped particles where the shape factor=1.7, we haveF80=0.81.745.7+0.210=64.15cmandP80=0.81.711.5=15.64cmR80=64.1515.64=4.10HenceQRC=22.744.100.64=145.4t/h

For a jaw crusher the thickness of the largest particle should not normally exceed 8085% of the gape. Assuming in this case the largest particle to be crushed is 85% of the gape, then the gape of the crusher should be=45.7/0.85=53.6cm and for a shape factor of 1.7, the width should be=45.7 1.7=78cm.

From the data given by Taggart (Figure4.8), a crusher of gape 53.6cm would have a comparative reduction tonnage of 436 t/h. The corresponding crushing capacity would beQT=4360.644.10=68.1t/hand is thus capable of handling the desired capacity of 22.74 t/h.

To determine the capacity of jaw and gyratory crushers, Broman [10] divided the crusher chamber into different sections and determined the volume of each section in terms of the angle that the moving jaw subtended with the vertical. Broman suggested that the capacity per stroke crushed in each section would be a function of the top surface and the height of the section. Referring to Figure4.9, if is the angle of nip between the crusher jaws and LT and LMAX are the throw and open side setting, respectively, then

Michaelson [8] expressed the jaw crusher capacity in terms of the gravity flow of a theoretical ribbon of rock through the open set of the crusher times a constant, k. For a rock of SG 2.65, Michaelsons equation is given as

For a set of crusher sizes and set openings, the calculations obtained from the work of Rose and English and others can be compared with data from equipment manufacturers. Figure4.10 shows a plot of the results. Assuming a value of SC of 1.0, the calculations show an overestimation of the capacity recommended by the manufacturers. As Rose and English pointed out, the calculation of throughput is very dependent on the value of SC for the ore being crushed. The diagram also indicates that the calculations drop to within the installed plant data for values of SC below 1.0. Most other calculation methods tend to estimate higher throughputs than the manufacturers recommend; hence, the crusher manufacturers should always be consulted.

The Values Used in the Calculation were 2.6 SG, (PK)=0.65, ()=1.0 and SC=0.51.0 (R&E); k=0.4 (Hersam); k=0.3 (Michaelson); k=1.5 (Broman) and =275rpm. The Max and Min Lines Represent the Crushers Nominal Operating Capacity Range.

Jaw crushers are heavy-duty machines and hence must be robustly constructed. The main frame is often made from cast iron or steel, connected with tie-bolts. It is commonly made in sections so that it can be transported underground for installation. Modern jaw crushers may have a main frame of welded mild steel plate.

The jaws are usually constructed from cast steel and fitted with replaceable liners, made from manganese steel, or Ni-hard, a Ni-Cr alloyed cast iron. Apart from reducing wear, hard liners are essential to minimize crushing energy consumption by reducing the deformation of the surface at each contact point. The jaw plates are bolted in sections for simple removal or periodic reversal to equalize wear. Cheek plates are fitted to the sides of the crushing chamber to protect the main frame from wear. These are also made from hard alloy steel and have similar lives to the jaw plates. The jaw plates may be smooth, but are often corrugated, the latter being preferred for hard, abrasive ores. Patterns on the working surface of the crushing members also influence capacity, especially at small settings. The corrugated profile is claimed to perform compound crushing by compression, tension, and shearing. Conventional smooth crushing plates tend to perform crushing by compression only, though irregular particles under compression loading might still break in tension. Since rocks are around 10 times weaker in tension than compression, power consumption and wear costs should be lower with corrugated profiles. Regardless, some type of pattern is desirable for the jaw plate surface in a jaw crusher, partly to reduce the risk of undesired large flakes easily slipping through the straight opening, and partly to reduce the contact surface when crushing flaky blocks. In several installations, a slight wave shape has proved successful. The angle between the jaws is usually less than 26, as the use of a larger angle causes particle to slip (i.e., not be nipped), which reduces capacity and increases wear.

In order to overcome problems of choking near the discharge of the crusher, which is possible if fines are present in the feed, curved plates are sometimes used. The lower end of the swing jaw is concave, whereas the opposite lower half of the fixed jaw is convex. This allows a more gradual reduction in size as the material nears the exit, minimizing the chance of packing. Less wear is also reported on the jaw plates, since the material is distributed over a larger area.

The speed of jaw crushers varies inversely with the size, and usually lies in the range of 100350rpm. The main criterion in determining the optimum speed is that particles must be given sufficient time to move down the crusher throat into a new position before being nipped again.

The throw (maximum amplitude of swing of the jaw) is determined by the type of material being crushed and is usually adjusted by changing the eccentric. It varies from 1 to 7cm depending on the machine size, and is highest for tough, plastic material and lowest for hard, brittle ore. The greater the throw the less danger of choking, as material is removed more quickly. This is offset by the fact that a large throw tends to produce more fines, which inhibits arrested crushing. Large throws also impart higher working stresses to the machine.

In all crushers, provision must be made for avoiding damage that could result from uncrushable material entering the chamber. Many jaw crushers are protected from such tramp material (often metal objects) by a weak line of rivets on one of the toggle plates, although automatic trip-out devices are now common. Certain designs incorporate automatic overload protection based on hydraulic cylinders between the fixed jaw and the frame. In the event of excessive pressure caused by an overload, the jaw is allowed to open, normal gap conditions being reasserted after clearance of the blockage. This allows a full crusher to be started under load (Anon., 1981). The use of guard magnets to remove tramp metal ahead of the crusher is also common (Chapters 2 and 13Chapter 2Chapter 13).

Jaw crushers are supplied in sizes up to 1,600mm (gape)1,900mm (width). For coarse crushing application (closed set~300mm), capacities range up to ca. 1,200th1. However, Lewis et al. (1976) estimated that the economic advantage of using a jaw crusher over a gyratory diminishes at crushing rates above 545th1, and above 725th1 jaw crushers cannot compete.

In hardening and martempering conditions austenitic manganese steel was free from carbides both at the grain boundaries and in the grains. Hence, the crusher jaws produced with austenitic manganese in these conditions eradicated brittle failure experienced in locally produced crusher jaws.

Hardening followed by tempering precipitated carbide at the grain boundaries and in the grains instead of reducing the residual stress associated with hardening. The volume fraction of these carbides, however, increased with tempering temperature.

In martempering conditions austenitic manganese steel had better plastic flows due to a decrease in overall thermal gradient and reduction in residual stresses associated with heat-treatment operations. This gave a better combination of hardness and toughness than austenitic manganese steel in hardening conditions used for the production of imported crusher jaws.

Srikanth [7] used a jaw crusher to create37m coal dust particles. Coal samples were obtained from coal mines in addition to some samples from the same source as Thakur's samples. They used a Microtrac Standard Range Analyzer (SRA) and Small Particle Analyser (SPA), which measured projected area (and hence diameter) using laser scattering and diffraction, respectively. The data were combined and plotted on a RosinRammler graph (discussed in Chapter 8). Their main findings were as follows:

Higher rank coals produced more total dust (<15m) and respirable dust (<7m). Semianthracite coal produced 3.7 times more total dust and 4.2 times more respirable dust compared with high-volatile bituminous coal.

The RosinRammler graph distribution parameter, n, was also rank dependent. The value for n was 0.68, 0.84, 0.90, and 0.95 for semianthracite, low-volatile coal, high-volatile bituminous coal, and subbituminous coals, respectively. This is similar to findings by Thakur (refer to Chapter 8 in the book).

A material is crushed in a Blake jaw crusher such that the average size of particle is reduced from 50 mm to 10 mm with the consumption of energy of 13.0 kW/(kg/s). What would be the consumption of energy needed to crush the same material of average size 75 mm to an average size of 25 mm:

The size range involved by be considered as that for coarse crushing and, because Kick's law more closely relates the energy required to effect elastic deformation before fracture occurs, this would be taken as given the more reliable result.

In an investigation by the U.S. Bureau of Mines(14), in which a drop weight type of crusher was used, it was found that the increase in surface was directly proportional to the input of energy and that the rate of application of the load was an important factor.

This conclusion was substantiated in a more recent investigation of the power consumption in a size reduction process which is reported in three papers by Kwong et al.(15), Adams et al.(16) and Johnson etal.(17). A sample of material was crushed by placing it in a cavity in a steel mortar, placing a steel plunger over the sample and dropping a steel ball of known weight on the plunger over the sample from a measured height. Any bouncing of the ball was prevented by three soft aluminium cushion wires under the mortar, and these wires were calibrated so that the energy absorbed by the system could be determined from their deformation. Losses in the plunger and ball were assumed to be proportional to the energy absorbed by the wires, and the energy actually used for size reduction was then obtained as the difference between the energy of the ball on striking the plunger and the energy absorbed. Surfaces were measured by a water or air permeability method or by gas adsorption. The latter method gave a value approximately double that obtained from the former indicating that, in these experiments, the internal surface was approximately the same as the external surface. The experimental results showed that, provided the new surface did not exceed about 40 m2/kg, the new surface produced was directly proportional to the energy input. For a given energy input the new surface produced was independent of:

Between 30 and 50 per cent of the energy of the ball on impact was absorbed by the material, although no indication was obtained of how this was utilised. An extension of the range of the experiments, in which up to 120 m2 of new surface was produced per kilogram of material, showed that the linear relationship between energy and new surface no longer held rigidly. In further tests in which the crushing was effected slowly, using a hydraulic press, it was found, however, that the linear relationship still held for the larger increases in surface.

In order to determine the efficiency of the surface production process, tests were carried out with sodium chloride and it was found that 90 J was required to produce 1 m2 of new surface. As the theoretical value of the surface energy of sodium chloride is only 0.08 J/m2, the efficiency of the process is about 0.1 per cent. Zeleny and Piret(18) have reported calorimetric studies on the crushing of glass and quartz. It was found that a fairly constant energy was required of 77 J/m2 of new surface created, compared with a surface-energy value of less than 5 J/m2. In some cases over 50 per cent of the energy supplied was used to produce plastic deformation of the steel crusher surfaces.

The apparent efficiency of the size reduction operation depends on the type of equipment used. Thus, for instance, a ball mill is rather less efficient than a drop weight type of crusher because of the ineffective collisions that take place in the ball mill.

Further work(5) on the crushing of quartz showed that more surface was created per unit of energy with single particles than with a collection of particles. This appears to be attributable to the fact that the crushing strength of apparently identical particles may vary by a factor as large as 20, and it is necessary to provide a sufficient energy concentration to crush the strongest particle. Some recent developments, including research and mathematical modelling, are described by Prasher(6).

The main sources of RA are either from construction and ready mixed concrete sites, demolition sites or from roads. The demolition sites produce a heterogeneous material, whereas ready mixed concrete or prefabricated concrete plants produce a more homogeneous material. RAs are mainly produced in fixed crushing plant around big cities where CDWs are available. However, for roads and to reduce transportation cost, mobile crushing installations are used.

The materiel for RA manufacturing does not differ from that of producing NA in quarries. However, it should be more robust to resist wear, and it handles large blocks of up to 1m. The main difference is that RAs need the elimination of contaminants such as wood, joint sealants, plastics, and steel which should be removed with blast of air for light materials and electro-magnets for steel. The materials are first separated from other undesired materials then treated by washing and air to take out contamination. The quality and grading of aggregates depend on the choice of the crusher type.

Jaw crusher: The material is crushed between a fixed jaw and a mobile jaw. The feed is subjected to repeated pressure as it passes downwards and is progressively reduced in size until it is small enough to pass out of the crushing chamber. This crusher produces less fines but the aggregates have a more elongated form.

Hammer (impact) crusher: The feed is fragmented by kinetic energy introduced by a rotating mass (the rotor) which projects the material against a fixed surface causing it to shatter causing further particle size reduction. This crusher produces more rounded shape.

However, the gyratory crusher is sensitive to jamming if it is fed with a sticky or moist product loaded with fines. This inconvenience is less sensitive with a single-effect jaw crusher because mutual sliding of grinding surfaces promotes the release of a product that adheres to surfaces.

The profile of active surfaces could be curved and studied as a function of the product in a way to allow for work performed at a constant volume and, as a result, a higher reduction ratio that could reach 20. Inversely, at a given reduction ratio, effective streamlining could increase the capacity by 30%.

The theoretical work of Rose and English [11] to determine the capacity of jaw crushers is also applicable to gyratory crushers. According to Rose and English, Equation (5.4) can be used to determine the capacity, Q, of gyratory crushers:

Capacities of gyratory crushers of different sizes and operation variables are published by various manufacturers. The suppliers have their own specifications which should be consulted. As a typical example, gyratory crusher capacities of some crushers are shown in Tables5.5 and 5.6.

About 100g heavy metal contaminated construction and demolition (C&D) waste is weighed and preliminarily crushed by a jaw crusher. Then the crushed C&D waste is mixed well and reduced by quartering twice. After that, the sample is dried at 100C for 1h. An electromagnetic crusher is used as a fine crushing for about 46min. Crushed sample is placed in a polypropylene screw-cap plastic bottles for storage.

Teflon crucibles used for digestion should be soaked in 1:1 nitric acid for 12h, wash with distilled water, and dry for later use. Volumetric flasks should be soaked in 1:1 nitric acid for 12h and washed with distilled water.

Before digestion, 0.10000.3000g of C&D waste powder is accurately weighed and evenly spread on the bottom of Teflon crucibles. Then they are placed in oven and dried for 2h at 120C together till constant weight. Aqua regia (18mL) (hydrochloric acid:nitric acid=3:1) is added, and 2mL 40% hydrofluoric acid is added 10min later. The crucibles with lids on are placed on an electric heating plate at 180C and heated till the solid waste is dissolved. Then, 30mL deionized water is added and the heating should be continuously maintained till the solution is vaporized to 23mL. Transfer the liquid to a 25mL plastic volumetric flask after it is cooled down, in which the volumetric flask should be washed with 1% nitric acid solution three times. Add deionized water to a certain volume and filter through 0.22m membrane. Place the solution at 4C for analysis.