hammer crusher capacity

hammer mill crusher & grinder

hammer mill crusher & grinder

The hammer mill is the best known and by far the most widely used crushing device employing the impact principle of breaking and grinding stone. Thus far we have described machines which do a portion of their work by impact, but the only machine described in which this action plays an important role was the sledging roll type and particularly the Edison roll crusher and in these machines impact is supplemented to a substantial degree by a positive and powerful sledging action by teeth which are rigidly attached to massive rolls.

The hammermill, fundamentally, is a simple mechanism. The orthodox machine comprises a box-like frame, or housing, a centrally disposed, horizontal-shaft rotating element (rotor) on which the hammers are mounted, and usually a set of circumferentially arranged grates in the lower part of the housing. The rotor consists of a shaft carried in bearings at either side of the housing, and the hammer centre of multi-flange drum or spool shape. The flanges of this drum-like assembly are drilled near their outer edges for hinge pins to which the inner ends of the hammers or hammer arms are attached. The hammers themselves are made in a variety of styles and shapes. Sometimes the hammer arm and head are cast, or forged, integrally; in other designs as in the impactorthe arms and hammer head are separate pieces.

The grates usually consist of a transversely arranged series of tapered, wear-resisting steel bars, which form a cage of circular cross section across the lower part of the housing just below the hammer path. The spacing of these steel bars varies quite widely, depending upon the size of product and upon the characteristics of the material to be crushed. The spacing may be anything from % in. or slightly less, up to several inches, and in some machines may be dispensed with entirely for coarse products and closed-circuit operation.

Hammermills may be connected directly to the driving motor, or driven by a flat belt or V-belts. The two latter methods have one material advantage over the direct drive; they permit speed adjustments to achieve optimum performance for each particular set of conditions.

In the impact-hammer-mill, a cross-sectional view of which is shown here on the left,the process is, in one important respect, a reversal of that just described. The material enters the machine on the up-running side of the rotor, where it is struck by the hammers as they start their sweep across the upper part of the housing. The top of the crushing chamber is lined with a series of breaker plates whose impact faces are involute with respect to the hammer circle, so that material hurled by the hammers impinges squarely against these surfaces regardless of the striking point. The action in this impact zone is a succession of violent blows, first from hammer-to-material and then from material-to-breaker plate, and so on through the several stages of the involute series. As contrasted to the type previously described, most of the work in this crusher is done in the breaker-plate zone; the grates function chiefly as a scalping grizzly, and the clearance between hammers and grates is relatively large. A certain amount of impact breaking does take place between hammers and grates, but this is secondary to the work done against the involute plates. On friable material this machine will deliver a medium fine (0.25 to 3/8) product with some, or even all, of the grates removed.

The capacity of any given size and type of hammermill depends upon several factors. The character of the material influences the performance of this machine to a greater degree than it does that of any of the crushers previously discussed. It is only natural that this should be the case; all of the energy consumed in the crushing chamber is delivered by free-swinging hammers, and it is to be expected that there would be a considerable difference in the effect of these impact blows upon materials of varying physical structure. Higher speeds will of course produce better shattering effect to take care of hard rock, but there are definite limits, both from mechanical and operational standpoints, to the speed of any particular mill.

Speed, or velocity, while it is the very life of the hammermill, may also function to limit the amount of feed that the mill will take. Thus, in any given machine, the number of rows of hammers used will affect capacity. Or, to state it a little more clearly, for any combination of speed, feed size, and number of rows of hammers there is a definite limit to the amount of material that the mill will receive.

This is understandable when it is considered, for example, that in a machine running 1500 RPM, with four rows of hammers, the receiving opening is swept by a row of hammers 100 times each second, and there is obviously a limit to the amount of material that can enter the space between two successive hammer rows in this short period of time.

We find that for some combinations of feed size and product size, more production can be obtained with only two rows of hammers, rather than three, or more. Radial velocity of the material entering the mill will naturally have a direct bearing upon the amount that will drop in between the rows of hammers. Thus, in a well designed mill the feed spout is always so arranged that the material falls, rather than flows, into the crushing zone.

It is hardly necessary to state that the size of product directly affects the capacity of a hammermill, just as it does any type of crusher. The finer the product the more work the machine must do; furthermore, the grate bars, when any are used, must be spaced closer, which means that the open area of the grate section is reduced.

When the grate bars are spaced widely, or dispensed with, and the sizing is done over a closed-circuited screen, product size has the same direct influence upon capacity because, the finer the screen openings, the more return load and, hence, the less original feed that can be handled by the mill.

Size of feed affects capacity, but not always in the inverse proportion which might, at first thought appear to be logical. For example, suppose we were operating a medium-size hammermill on limestone, turning out a 10-mesh product. We know that this machine will handle more tonnage if we feed it with, say, 3 maximum size rock, as compared with a feed of 10 or 12 maximum size; which accords with the logical expectation. However, if we further reduce the feed size to, say 12 maximum, we find that our will increase very little if at all; in fact it may actually decrease. This apparent anomaly is explained by the fact that the effect of impact upon a free body of material varies directly with the mass of the body; consequently the energy absorption, and hence the shattering effect, is much greater on the 3 piece than it is on the 1/2 particle.

Because all these variables that we have noted have an influence upon the capacity of the hammermill, it is impossible to present a comprehensive tabulation of capacity ratings which can be relied upon for any and all materials. We can however do so for any one material, as we did for the Fairmount crusher. It is convenient and logical that this should be a medium limestone in this case also, because hammermills are applied extensively to crushing, and pulverizing, that kind of rock.

Above is theapproximate capacity ratings of the various sizes of hammermill (impact crushers), on medium limestone, and for various grate bar spacings. Unless the prospective hammermill user has operational data on which to predicate his selection of a new machine for some specific service, the safest procedure is to have his material tested, either in the field or in the laboratory, in a mill of the type he proposes to install.

The shattering effect of the blows delivered by hammers travelling at velocities as high as 200 Feet/Second is conducive to both of these results. It is natural to expect that gradation of the hammermill product would vary somewhat for materials of differing friability, and results verify this expectation. Furthermore, speed has a definite influence upon product gradation; high speeds increase fines, and vice versa. The effect of impact at extremely high speed is, on friable material, almost explosive, the action being more aptly designated as pulverizing, rather than crushing. Lower impact velocities have a more moderate breaking effect, and if the material is able to clear the crushing chamber before it is struck too many times, the low speed hammermill will turn out a fairly uniformly graded product on material of average friability.

The design of the crushing chamber will also affect product gradation. In general, those machines which perform most of their work by straight impact action will turn out a more uniformly graded product than mills which depend upon interaction between hammers and grates for most of their reduction. This is only natural in view of the fact that attritional grinding is minimized in the former type of mill.

What is intended to take place inside a hammermill is the uniform, efficient reduction of the material introduced into the grinding chamber. This particle reduction occurs as a result of the impact between a rapidly moving hammer and a relatively slow moving particle. If sufficient energy is transferred during the collision, the particle breaks and is accelerated towards the screen. Depending on the particle size and the angle of approach, it either passes through the screen or rebounds from the screen into the rapidly moving hammers again. As materials move through the grinding chamber they tend to approach hammer tip speed. Since reduction only occurs when a significant energy is transferred from the hammer to the particle (large difference in velocities), less grinding takes place when the particles approach hammer tip speed. Many manufacturers incorporate devices within their mills to interrupt this product flow, allowing impact and reduction to continue. Tear circle hammermills have a more positive, natural redirection of product at the inlet than full circle design machines. While the basic operational concepts are the same for all hammermills, the actual unit operating conditions change rather dramatically depending on the materials being processed. Grains such as corn, wheat, sorghum and various soft stocks, like soybean meal, tend to be friable and easy to grind. Fibrous, oily, or high moisture products, like screenings, animal proteins, and grains like oats and barley, on the other hand, are very tough and require much more energy to reduce.Consequently, the hammermill setup that works well for one will not necessarily work for the other. The following discussion covers such factors as tip speeds, hammer patters and position, horsepower ratios (to hammer and screen area), and air assist systems. Little space is devoted to screen sizes (perforation or hole size) since processing variables would make any hard and fast statements nearly impossible.

The Jeffrey Swing is a relatively small Hammermill Pulverizer and is made in several types and a large number of sizes for handling large or small capacities and light, medium, or heavy work. Some of the materials being successfully reduced by this pulverizer are coal, coke, copper ore, barytes, gypsum, kaolin, magnesite, chalk, clay, cement rock, dolomite rock, phosphate rock, and limestone.

This machine operates on the principle of reducing the material by striking it while in suspension, as opposed to attrition. The material is fed into the top of the machine and falls into the path of the rapidly revolving hammers. Different degrees of reduction may be had by simply varying the speed of the machine.

This unit is of extra heavy construction and consequently is well adapted for severe duty. The hinged breaker plate is adjustable while operating and is fitted with a heavy renewable liner. Shafting is high carbon forged steel and is fitted with discs which are of heavy plate and cast steel, carefully balanced. Screen bars may be high carbon steel, tool steel, or manganese steel as desired. Jeffrey Swing Hammer Pulverizers have heavy cast iron frames and are lined with renewable chilled iron liners. Hammers are made of materials best suited for the particular job. Highest grade radial ball bearings are used and they are readily accessible for inspection and oiling. This keeps power consumption to a minimum and maintenance and repair part costs are extremely low, even for most types of heavy duty.

A metal catcher attachment is available for use on all sizes of pulverizers where tramp iron may be encountered. It may be specified when unit is ordered or obtained later and installed when need arises.Let us make recommendations for your pulverizer installation. Information required is type of material to be handled, tonnagesize of feed, and desired size of product. Belt or motor drive maybe used as required.

hammer crusher | industry hammer mills - jxsc machine

hammer crusher | industry hammer mills - jxsc machine

Capacity 1-100 TPH Feeding Size350 mm ApplicationHammer crusher can crush medium hardness and brittle materials, such as limestone, slag, coke, coal, etc. Our hammer crushers are widely used in mining, cement, coal, metallurgy, building materials, highway, combustion, and other industries. Our Services

What is a hammer millA hammer mill is a rock crusher used in various industries to reduce the material size, such as limestone, coal, slags, gypsum, glass. It uses of high-speed rotary hammer to impact the ore, the finished product size is adjustable by controlling the grate openings, rotor speed, hammer capacity, etc. Hammer mill, same as hammer crusher, hammer breaker, can crush the 600-1800mm materials to below 25 or 25 mm. Sometimes, the hammer mill crusher is named by the application fields, such as coal crusher, coke crusher, limestone hammer crusher, brick crusher, cement hammer crusher, etc. Our hammer crusher typessingle rotor and double rotor hammer crusher; directional and reversible hammer crusher; vertical shaft, ring hammer crusher, swing hammer crusher; fixed and mobile hammer crusher. hammers materialchromium alloy (containing 20% 27% chromium) OurpriceHammer crusher price is varied by the capacity and base material. JXSC tailor-made the best configuration for different working requirements, longer service time, less maintenance. Contact us to get the best stone hammer crusher machine price. Advantages of hammer crusher machineEasy adjustment of product size; high grinding capability; easy maintenance, a quick exchange of wear parts; stable operation.

Hammer Crusher Partscrushing chamber, rotor shaft, frame, impact hammer, grate bars, motor, flywheel, grate, pallets and lining, dust seal, overload protection device. Hammer Crusher Working principleMaterial are fed into the hammer crusher, that is subject to rotation, high-speed impact and collision are broken. Qualified crushed ore is discharged through the grate, the larger size materials continue to be crushed and shattered until they reached the required size. Hammer Crusher ManufacturerJXSC manufactures various industrial hammer mills, hammer crushers and laboratory use small hammer mills to accomplish your size reduction needs. Our rugged hammer mills employ a rain of continual, high-speed hammer blows to impact crush, grind or shred of a diverse range of materials. Other rock crusher machines like roll crusher, impact crusher, jaw crusher, cone crusher, etc.Common Faults Solutions Hammer crusher in cement plantImpact hammer crusher (cement crusher) combines the advantages of ring hammer crusher, impact crusher, optimizes the grinding chamber, obtains a better fine crushing effect. Coal crusher hammervaried in different capacity requirements, the coal crusher hammer type generally have small capacity hammer crusher (5-55m/h) and the heavy hammer crusher (100-3200t/h).

pcsw series two-stage superfine crushing non-clogging hammer crusher large capacity double roller crusher for sale,mining crushing equipment mine crushing & screening

pcsw series two-stage superfine crushing non-clogging hammer crusher large capacity double roller crusher for sale,mining crushing equipment mine crushing & screening

Two rotors in the upper and lower stages, the ratio of reduction is larger, and the output particle size is finer. The crushing efficiency below 3mm can reach 95%. No sieve bottom, and high-humidity materials will never be blocked. Unique bidirectional gap adjustment technology can greatly increase the service life of the hammer head. The hydraulic opening and closing device, not only light, fast, safe and reliable, but also easy to maintain. Ultra-high wear-resistant hammer head, long service life.

Adopts full-pass design, no sieve bottom, effectively preventing the problem of sticky and wet materials blocking. Equipped with a hydraulic opening device, the crushing chamber is easy to open and easy to replace wearing parts. Hammer head and liner adopt new material, new structure and new technology, with high strength and high wear resistance. Specialized design according to users actual situation, timely supply of spare parts. High wear-resistant dual alloy composite casting hammer head, using the latest centrifugal pressure casting, has the advantages of high hardness, high wear resistance, high toughness, long service life, strong impact resistance etc. The special thickened hammer head design effectively improves the impact resistance and stability of the hammer head. Split hammer design structure, simple and convenient replacement of hammer head, low maintenance cost of accessories.

PCSW Series Two-stage superfine crushing non-clogging hammer crusher is composed of two sets of rotors connected in series. The solid material crushed by the hammer of the upper rotor is immediately crushed again by the hammer of the rapidly rotating lower pole rotor. The materials in the inner cavity collide with each other, crush, and then discharge.

highly capacity hammer mill crushing machine - mining & construction solutions from henan dewo machinery

highly capacity hammer mill crushing machine - mining & construction solutions from henan dewo machinery

Dewo machinery can provides complete set of crushing and screening line, including Hydraulic Cone Crusher, Jaw Crusher, Impact Crusher, Vertical Shaft Impact Crusher (Sand Making Machine), fixed and movable rock crushing line, but also provides turnkey project for cement production line, ore beneficiation production line and drying production line. Dewo Machinery can provide high quality products, as well as customized optimized technical proposal and one station after- sales service.

Capacity:1-2t/h; Hammer Quality:48pcs; Weight:1.5t; Product descriptionHammer mill is one wood crusher machine that can produce sawdust. the raw material of hammer mill for sale are wood chips, wood shavings, agricultural straw, stalk, rice husk, peanut shell, corn cob,

High capacity wood crushing hammer mill. Feature: JLSD1500 is new version wood sawdust machine, improved from traditional sawdust making machine, solved the problem of dusty working in enclosed workshop by equipping with special dust collector.

High crushing ratio (generally 10-25, high up to 50), 5. high production capacity, uniform products, low energy consumption simple structure, easy operation and maintenance, etc. Rock Hammer Mill Applications. Hammer crusher is used for crushing all kinds of medium hard and weak abrasive materials.

Hammer Mill Crusher engaging in crushing various rocks and stones with comprehensive strength not higher than 320 MPa into fine and micro fine powders, is widely used in metallurgy, mining, chemical, cement, coal, sand-making, coal gangue, construction, refractory materials and ceramic industries.

The hammer mill machine mainly smashes grain such as peanut, soybeans, corn, wheat and cut grass or straw. The raw material is pulverized by a high-speed rotating of blade and hammers. Corn grinding machine is equipped with different screens according to the different size of raw material, and customers can choose the right screen according to ...

The KE Series is a high capacity lump breaker featuring a dual rotor design and is ideal for high tonnage and tough to process materials. Ranging in sizes from laboratory scale to heavy industrial, the KE Series is available in carbon or stainless steel construction with dual counter- revolving, high torque rotors tailored to individual ...

high capacity 100 800 hammer crusher. The europeantype hammer crusher is of high capacity, high crushing ratio, simple structure, uniform output granularity as well as low electricity consumption, and is easy to maintain and lt lt type dia

animal feed crusher and mixer hammer mill alibaba hammer mill. 9FC-360 works with 7.5kw motor. It is composed of base, motor, grinding plate, hopper, cyclone, etc. Grinding plate is corrugated with fast rotating rotators which effectively crush corn into power.

Dewo machinery can provides complete set of crushing and screening line, including Hydraulic Cone Crusher, Jaw Crusher, Impact Crusher, Vertical Shaft Impact Crusher (Sand Making Machine), fixed and movable rock crushing line, but also provides turnkey project for cement production line, ore beneficiation production line and drying production line.

hammer crusher | hxjq

hammer crusher | hxjq

Processing Materials: silica, iron ore, granite, gangue, river pebbles, calcite, limestone, bluestone, coal, gypsum, glass, cement, bricks, tiles, and some mental ores.

Hammer crusher is also called hammer mill crusher or industrial hammer mill, which can be used in the dry or wet crushing processes. It can crush materials into the required size in one time to save lots of energy and investment costs.

According to different features of different materials, HXJQ has improved the hammer crusher in its structure, application and function, and developed coal hammer crusher, glass hammer crusher, ceramic hammer crusher, cement hammer crusher, gypsum hammer crusher, limestone hammer crusher, quartz hammer crusher, etc.

1. Reversible type hammer crusher is often used for fine crushing process, and the finished products are uniform and fine. Reversible type hammer crusher has a large crushing ratio and can work stably.

2. Irreversible type hammer crusher is usually used for medium crushing process. Because its rotors can't rotate back and forth, it is also called as the impact hammer crusher. Irreversible type hammer crusher combines the advantages of hammer crusher and impact crusher and performs well in the crushing process. It is a technical and compact crushing machine with the features of low energy consumption, high capacity and low price.

Hammer crusher is used to crush materials with medium hardness and low corrosivity. The compressive strength of materials processed should be no more than 200Mpa, and water content should be lower than 15%.

Hammer crushing equipment is suitable for processing coal, gypsum, brick, tile, limestone, quartz, iron ore, granite, basalt, gangue, river pebble, calcite, wollastonite, bluestone, glass, cement, and other metal ores. Also, it is used to crush wood, paper, construction waste and recycled asbestos fiber, etc.

Besides, the hammer crushing machine can be not only applied in the crushing process and sand making process, but also can be adopted as the secondary crushing equipment to replace cone crusher and impact crusher, and used in the beneficiation processing line.

Hammer is made of high-quality manganese steels and treated by strict heat processing and then it becomes single austenite. After the process, the service life has been prolonged 4 times than traditional hammer crushing machines and working efficiency has been improved more than 30%.

The crushing process of hammer crushing machine is that the power drives the hammer to crush materials, and the crushed materials are impacted on the counterattack plate, and then the materials rebounded by the counterattack plate hit the materials impacted by the hammerhead.

Hammer crusher mainly relies on the impact force to complete the crushing. When the hammer crusher works, the motor drives the rotor in high-speed rotation. The materials are sent into the crusher chamber evenly and after a high-speed impact of hammer, the material is crushed into a smaller size.

The material larger than the sieve mesh is remained in the screening plate for further impacting and grinding. The material smaller than the sieve mesh is discharged from the hammer crushing machine to the material piles.

HXJQ as one of the professional hammer crusher manufacturers in China, mainly produces jaw crusher, cone crusher, hammer crusher, impact crusher, sand making machine, vibrating screen, feeding machine, sand washing machine and supporting equipment such as dust collector and conveyors, etc.

HXJQ undertakes various construction projects of large-capacity sand and aggregate production lines and serves from the equipment design, manufacturing, project survey, production line design, construction, equipment installation and debugging to after-sales service.

estimate jaw crusher capacity

estimate jaw crusher capacity

My friend Alex the SAG Mill Expert, says this equation you picked up doesnt look right.The numerator is calculating the volume of one swing of a jaw, times thedensity of material in the chamber, times the number of cycles perminute. This should give you the mass of material crushed per minute.

The example youve given is missing information needed to calculate theA term it doesnt tell you the height of the crushing chamber. The two measurements youve got are the top opening width and top openinglength; A should be the jaw throw (not given) times the crushing chamber height (also not given).

Tables hereincontain information that is typical of output from crushers discussed above. The capacities are based on the crusher receiving full, continuous feed of clean, dry, friable stone weighing 100 lb/cu ft.

These capacity tables show several significant differences between the two common types of primary crushers. A jaw crusher has a wider range of settingsgenerally, a maximum of two to three times the smallest setting. The tables also show that for a comparable maximum size of feed and setting, a gyratory crusher has a much greater capacity than a jaw crusher. Thegyratory crusher obtains this advantage only at the cost of greater power to drive the crusher.

The selection of an appropriate primary crusher for a given use has to be based on a consideration of several factors. These are not limited to the design features of the crusher. If the feed is blasted rock from a quarry, the size and method of handling the feed influence crusher selection. For instance, a power shovel is limited by the dimensions of the dipper in the maximum size of rock it can handle well. It may be that the bucket of a 1- yd shovel would be too small to load the maximum size rock allowed in a jaw crusher with a 42-in. opening.

If a 60-in. gyratory crusher is to process material from a quarry where a shovel loads the raw material, the shovel would probably have to have a dipper capacity of at least 5 cu yd to be compatible. It may be more economical to change the blasting pattern to produce larger rock that can be handled by a larger loader-hauler combination and still fit in the primary crusher. Generally, a large reduction ratio will be required of the primary crusher.

If gravel has relatively small maximum particle sizes, a large feed opening is not needed. It may be more economical to feed all of the pit-run material into the primary crusher rather than to remove the part that is already smaller than the crusher setting. That calls for a crusher with a higher capacity. There are many feasible solutions to the crusher selection problem, so the aggregate producer must select crushers with total operations and economics in mind.The selection of reduction crushers is also a complex problem.

The economic selection of any particular crusher depends on the ability of the crusher to handle the maximum size of feed, reducing this at the highest possible reduction ratio and least cost for the original installation, maintenance, and power. For any particular aggregate production plant, it is advisable to make preliminary determinations of the types of crushers needed. If most of the feed is coarse and stage crushing is required, primary crushers that meet the requirements of reduction and economy and have straight crushing surfaces may be most economical.

Where only a very small percentage of the feed approaches the size of the feed opening of the crusher,nonchoking crushing surfaces in a high capacity crusher may be advisable for the sake of economy. If the plant requires several stages, and several different types of crushers could be used for each stage, the costs of each feasible combination must be analyzed to find the crusher plant with the least total cost.

hammer crusher at best price in india

hammer crusher at best price in india

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impact crusher - an overview | sciencedirect topics

impact crusher - an overview | sciencedirect topics

The impact crusher (typically PE series) is widely used and of high production efficiency and good safety performance. The finished product is of cube shape and the tension force and crack is avoided. Compared with hammer crusher, the impact crusher is able to fully utilize the high-speed impact energy of entire rotor. However, due to the crushing board that is easy to wear, it is also limited in the hard material crushing. The impact crusher is commonly used for the crushing of limestone, coal, calcium carbide, quartz, dolomite, iron pyrites, gypsum, and chemical raw materials of medium hardness. Effect of process conditions on the production capacity of crushed materials is listed in Table8.10.

Depending on the size of the debris, it may either be ready to enter the recycling process or need to be broken down to obtain a product with workable particle sizes, in which case hydraulic breakers mounted on tracked or wheeled excavators are used. In either case, manual sorting of large pieces of steel, wood, plastics and paper may be required, to minimise the degree of contamination of the final product.

The three types of crushers most commonly used for crushing CDW materials are the jaw crusher, the impact crusher and the gyratory crusher (Figure 4.4). A jaw crusher consists of two plates, with one oscillating back and forth against the other at a fixed angle (Figure 4.4(a)) and it is the most widely used in primary crushing stages (Behera etal., 2014). The jaw crusher can withstand large and hard-to-break pieces of reinforced concrete, which would probably cause the other crushing machines to break down. Therefore, the material is initially reduced in jaw crushers before going through any other crushing operation. The particle size reduction depends on the maximum and minimum size of the gap at the plates (Hansen, 2004).

An impact crusher breaks the CDW materials by striking them with a high-speed rotating impact, which imparts a shearing force on the debris (Figure 4.4(b)). Upon reaching the rotor, the debris is caught by steel teeth or hard blades attached to the rotor. These hurl the materials against the breaker plate, smashing them into smaller particle sizes. Impact crushers provide better grain-size distribution of RA for road construction purposes, and they are less sensitive to material that cannot be crushed, such as steel reinforcement.

Generally, jaw and impact crushers exhibit a large reduction factor, defined as the ratio of the particle size of the input to that of the output material. A jaw crusher crushes only a small proportion of the original aggregate particles but an impact crusher crushes mortar and aggregate particles alike and thus generates a higher amount of fine material (OMahony, 1990).

Gyratory crushers work on the same principle as cone crushers (Figure 4.4(c)). These have a gyratory motion driven by an eccentric wheel. These machines will not accept materials with a large particle size and therefore only jaw or impact crushers should be considered as primary crushers. Gyratory and cone crushers are likely to become jammed by fragments that are too large or too heavy. It is recommended that wood and steel be removed as much as possible before dumping CDW into these crushers. Gyratory and cone crushers have advantages such as relatively low energy consumption, a reasonable amount of control over the particle size of the material and production of low amounts of fine particles (Hansen, 2004).

For better control of the aggregate particle size distribution, it is recommended that the CDW should be processed in at least two crushing stages. First, the demolition methodologies used on-site should be able to reduce individual pieces of debris to a size that the primary crusher in the recycling plant can take. This size depends on the opening feed of the primary crusher, which is normally bigger for large stationary plants than for mobile plants. Therefore, the recycling of CDW materials requires careful planning and communication between all parties involved.

A large proportion of the product from the primary crusher can result in small granules with a particle size distribution that may not satisfy the requirements laid down by the customer after having gone through the other crushing stages. Therefore, it should be possible to adjust the opening feed size of the primary crusher, implying that the secondary crusher should have a relatively large capacity. This will allow maximisation of coarse RA production (e.g., the feed size of the primary crusher should be set to reduce material to the largest size that will fit the secondary crusher).

The choice of using multiple crushing stages mainly depends on the desired quality of the final product and the ratio of the amounts of coarse and fine fractions (Yanagi etal., 1998; Nagataki and Iida, 2001; Nagataki etal., 2004; Dosho etal., 1998; Gokce etal., 2011). When recycling concrete, a greater number of crushing processes produces a more spherical material with lower adhered mortar content (Pedro etal., 2015), thus providing a superior quality of material to work with (Lotfi etal., 2017). However, the use of several crushing stages has some negative consequences as well; in addition to costing more, the final product may contain a greater proportion of finer fractions, which may not always be a suitable material.

Reduction of the broken rock material, or oversized gravel material, to an aggregate-sized product is achieved by various types of mechanical crusher. These operations may involve primary, secondary and even sometimes tertiary phases of crushing. There are many different types of crusher, such as jaw, gyratory, cone (or disc) and impact crushers (Fig. 15.9), each of which has various advantages and disadvantages according to the properties of the material being crushed and the required shape of the aggregate particles produced.

Fig. 15.9. Diagrams to illustrate the basic actions of some types of crusher: solid shading highlights the hardened wear-resistant elements. (A) Single-toggle jaw crusher, (B) disc or gyrosphere crusher, (C) gyratory crusher and (D) impact crusher.

It is common, but not invariable, for jaw or gyratory crushers to be utilised for primary crushing of large raw feed, and for cone crushers or impact breakers to be used for secondary reduction to the final aggregate sizes. The impact crushing machines can be particularly useful for producing acceptable particle shapes (Section 15.5.3) from difficult materials, which might otherwise produce unduly flaky or elongated particles, but they may be vulnerable to abrasive wear and have traditionally been used mostly for crushing limestone.

Reduction of the broken rock material, or oversized gravel material, to an aggregate-sized product is achieved by various types of mechanical crusher. These operations may involve primary, secondary and even sometimes tertiary phases of crushing. There are many different types of crusher, such as jaw, gyratory, cone (or disc) and impact crushers (Figure 16.8), each of which has various advantages and disadvantages according to the properties of the material being crushed and the required shape of the aggregate particles produced.

Fig. 16.8. Diagrams to illustrate the basic actions of some types of crusher: solid shading highlights the hardened wear-resistant elements (redrawn, adapted and modified from Ref. 39). (a) Single-toggle jaw crusher, (b) disc or gyrosphere crusher, (c) gyratory crusher, and (d) impact crusher.

It is common, but not invariable, for jaw or gyratory crushers to be utilised for primary crushing of large raw feed, and for cone crushers or impact breakers to be used for secondary reduction to the final aggregate sizes. The impact crushing machines can be particularly useful for producing acceptable particle shapes (section 16.5.3) from difficult materials, which might otherwise produce unduly flaky or elongated particles, but they may be vulnerable to abrasive wear and have traditionally been used mostly for crushing limestone.

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.

The type of crusher and number of processing stages have considerable influence on the shape and size of RA. In general, for the same size, RAs tend to be coarser, more porous and rougher than NAs, due to the adhered mortar content (Dhir etal., 1999). After the primary crushing, which is normally performed using jaw crushers (Fong etal., 2004), it is preferable to adopt a secondary crushing stage (with cone crushers or impact crushers) (CCANZ, 2011) to further reduce the size of the CDW, producing more regularly shaped particles (Barbudo etal., 2012; Ferreira etal., 2011; Fonseca etal., 2011; Pedro etal., 2014, 2015; Gonzlez-Fonteboa and Martnez-Abella, 2008; Maultzsch and Mellmann, 1998; Dhir and Paine, 2007; Chidiroglou etal., 2008).

CDW that is subjected to a jaw crushing stage tends to result only in flatter RA (Ferreira etal., 2011; Fonseca etal., 2011; Hendriks, 1998; Tsoumani etal., 2015). It is possible to produce good-quality coarse RA within the specified size range by adjusting the crusher aperture (Hansen, 1992). In addition, the number of processing stages needs to be well thought out to ensure that the yield of coarse RA is not affected and that the quantity of fine RA is kept to the minimum (Angulo etal., 2004). This is because the finer fraction typically exhibits lower quality, as it accumulates a higher amount of pulverised old mortar (Etxeberria etal., 2007b; Meller and Winkler, 1998). Fine RA resulting from impact crushers tends to exhibit greater angularity and higher fineness modulus compared with standard natural sands (Lamond etal., 2002; Hansen, 1992; Buyle-Bodin and Hadjieva-Zaharieva, 2002).

One of the commonly known issues related to the use of RCA is its ability to generate a considerable amount of fines when the material is used (Thomas etal., 2016). As the RCA particles are moved around, they impact against one another, leading to the breakage of the friable adhered mortar, which may give rise to some technical problems such as an increase in the water demand of concrete mixes when used as an NA replacement (Thomas etal., 2013a,b; Poon etal., 2007).

The coarse fraction of RMA tends to show a higher shape index owing to the shape of the original construction material (e.g., perforated ceramic bricks) (De Brito etal., 2005). This can pose a problem in future applications as RMA may not compact as efficiently as RCA or NA (Khalaf and DeVenny, 2005). Its shape index may be reduced if the material is successively broken down to a lower particle size (De Brito etal., 2005).

Impact crushers (e.g., hammer mills and impact mills) employ sharp blows applied at high speed to free-falling rocks where comminution is by impact rather than compression. The moving parts are beaters, which transfer some of their kinetic energy to the ore particles upon contact. Internal stresses created in the particles are often large enough to cause them to shatter. These forces are increased by causing the particles to impact upon an anvil or breaker plate.

There is an important difference between the states of materials crushed by pressure and by impact. There are internal stresses in material broken by pressure that can later cause cracking. Impact causes immediate fracture with no residual stresses. This stress-free condition is particularly valuable in stone used for brick-making, building, and roadmaking, in which binding agents (e.g., tar) are subsequently added. Impact crushers, therefore, have a wider use in the quarrying industry than in the metal-mining industry. They may give trouble-free crushing on ores that tend to be plastic and pack when the crushing forces are applied slowly, as is the case in jaw and gyratory crushers. These types of ore tend to be brittle when the crushing force is applied instantaneously by impact crushers (Lewis et al., 1976).

Impact crushers are also favored in the quarry industry because of the improved product shape. Cone crushers tend to produce more elongated particles because of their ability to pass through the chamber unbroken. In an impact crusher, all particles are subjected to impact and the elongated particles, having a lower strength due to their thinner cross section, would be broken (Ramos et al., 1994; Kojovic and Bearman, 1997).

Figure 6.23(a) shows the cross section of a typical hammer mill. The hammers (Figure 6.23(b)) are made from manganese steel or nodular cast iron containing chromium carbide, which is extremely abrasion resistant. The breaker plates are made of the same material.

The hammers are pivoted so as to move out of the path of oversize material (or tramp metal) entering the crushing chamber. Pivoted (swing) hammers exert less force than they would if rigidly attached, so they tend to be used on smaller impact crushers or for crushing soft material. The exit from the mill is perforated, so that material that is not broken to the required size is retained and swept up again by the rotor for further impacting. There may also be an exit chute for oversize material which is swept past the screen bars. Certain design configurations include a central discharge chute (an opening in the screen) and others exclude the screen, depending on the application.

The hammer mill is designed to give the particles velocities of the order of that of the hammers. Fracture is either due to impact with the hammers or to the subsequent impact with the casing or grid. Since the particles are given high velocities, much of the size reduction is by attrition (i.e., particle on particle breakage), and this leads to little control on product size and a much higher proportion of fines than with compressive crushers.

The hammers can weigh over 100kg and can work on feed up to 20cm. The speed of the rotor varies between 500 and 3,000rpm. Due to the high rate of wear on these machines (wear can be taken up by moving the hammers on the pins) they are limited in use to relatively non-abrasive materials. They have extensive use in limestone quarrying and in the crushing of coal. A great advantage in quarrying is the fact that they produce a relatively cubic product.

A model of the swing hammer mill has been developed for coal applications (Shi et al., 2003). The model is able to predict the product size distribution and power draw for given hammer mill configurations (breaker gap, under-screen orientation, screen aperture) and operating conditions (feed rate, feed size distribution, and breakage characteristics).

For coarser crushing, the fixed hammer impact mill is often used (Figure 6.24). In these machines the material falls tangentially onto a rotor, running at 250500rpm, receiving a glancing impulse, which sends it spinning toward the impact plates. The velocity imparted is deliberately restricted to a fraction of the velocity of the rotor to avoid high stress and probable failure of the rotor bearings.

The fractured pieces that can pass between the clearances of the rotor and breaker plate enter a second chamber created by another breaker plate, where the clearance is smaller, and then into a third smaller chamber. The grinding path is designed to reduce flakiness and to produce cubic particles. The impact plates are reversible to even out wear, and can easily be removed and replaced.

The impact mill gives better control of product size than does the hammer mill, since there is less attrition. The product shape is more easily controlled and energy is saved by the removal of particles once they have reached the size required.

Large impact crushers will reduce 1.5m top size ROM ore to 20cm, at capacities of around 1500th1, although units with capacities of 3000th1 have been manufactured. Since they depend on high velocities for crushing, wear is greater than for jaw or gyratory crushers. Hence impact crushers are not recommended for use on ores containing over 15% silica (Lewis et al., 1976). However, they are a good choice for primary crushing when high reduction ratios are required (the ratio can be as high as 40:1) and the ore is relatively non-abrasive.

Developed in New Zealand in the late 1960s, over the years it has been marketed by several companies (Tidco, Svedala, Allis Engineering, and now Metso) under various names (e.g., duopactor). The crusher is finding application in the concrete industry (Rodriguez, 1990). The mill combines impact crushing, high-intensity grinding, and multi-particle pulverizing, and as such, is best suited in the tertiary crushing or primary grinding stage, producing products in the 0.0612mm size range. It can handle feeds of up to 650th1 at a top size of over 50mm. Figure 6.22 shows a Barmac in a circuit; Figure 6.25 is a cross-section and illustration of the crushing action.

The basic comminution principle employed involves acceleration of particles within a special ore-lined rotor revolving at high speed. A portion of the feed enters the rotor, while the remainder cascades to the crushing chamber. Breakage commences when rock enters the rotor, and is thrown centrifugally, achieving exit velocities up to 90ms1. The rotor continuously discharges into a highly turbulent particle cloud contained within the crushing chamber, where reduction occurs primarily by rock-on-rock impact, attrition, and abrasion.

This crusher developed by Jaques (now Terex Mineral Processing Solutions) has several internal chamber configurations available depending on the abrasiveness of the ore. Examples include the Rock on Rock, Rock on Anvil and Shoe and Anvil configurations (Figure 6.26). These units typically operate with 5 to 6 steel impellers or hammers, with a ring of thin anvils. Rock is hit or accelerated to impact on the anvils, after which the broken fragments freefall into the discharge chute and onto a product conveyor belt. This impact size reduction process was modeled by Kojovic (1996) and Djordjevic et al. (2003) using rotor dimensions and speed, and rock breakage characteristics measured in the laboratory. The model was also extended to the Barmac crushers (Napier-Munn et al., 1996).

Figure 9.1 shows common aluminum oxide-based grains. Also called corundum, alumina ore was mined as early as 2000 BC in the Greek island of Naxos. Its structure is based on -Al2O3 and various admixtures. Traces of chromium give alumina a red hue, iron makes it black, and titanium makes it blue. Its triagonal system reduces susceptibility to cleavage. Precious grades of Al2O3 are used as gemstones, and include sapphire, ruby, topaz, amethyst, and emerald.

Charles Jacobs (1900), a principal developer, fused bauxite at 2200C (4000F) before the turn of the 20th century. The resulting dense mass was crushed into abrasive particles. Presently, alumina is obtained by smelting aluminum alloys containing Al2O3 in electric furnaces at around 1260C (2300F), a temperature at which impurities separate from the solution and aluminum oxide crystallizes out. Depending upon the particular process and chemical composition there are a variety of forms of aluminum oxide. The poor thermal conductivity of alumina (33.5W/mK) is a significant factor that affects grinding performance. Alumina is available in a large range of grades because it allows substitution of other oxides in solid solution, and defect content can be readily controlled.

For grinding, lapping, and polishing bearing balls, roller races, and optical glasses, the main abrasive employed is alumina. Its abrasive characteristics are established during the furnacing and crushing operations, so very little of what is accomplished later significantly affects the features of the grains.

Aluminum oxide is tougher than SiC. There are four types of gradations for toughness. The toughest grain is not always the longest wearing. A grain that is simply too tough for an application will become dull and will rub the workpiece, increasing the friction, creating heat and vibrations. On the other hand, a grain that is too friable will wear away rapidly, shortening the life of the abrasive tool. Friability is a term used to describe the tendency for grain fractures to occur under load. There is a range of grain toughness suitable for each application. The white friable aluminum oxide is almost always bonded by vitrification. It is the main abrasive used in tool rooms because of its versatility for a wide range of materials. In general, the larger the crystals, the more friable the grain. The slower the cooling process, the larger are the crystals. To obtain very fine crystals, the charge is cooled as quickly as possible, and the abrasive grain is fused in small pigs of up to 2ton. Coarse crystalline abrasive grains are obtained from 5 to 6ton pigs allowed to cool in the furnace shell.

The raw material, bauxite, containing 8590% alumina, 25% TiO2, up to 10% iron oxide (Fe2O3), silica, and basic oxides, is fused in an electric-arc furnace at 2600C (4700F). The bed of crushed and calcined bauxite, mixed with coke and iron to remove impurities, is poured into the bottom of the furnace where a carbon starter rod is laid down. A couple of large vertical carbon rods are then brought down to touch and a heavy current applied. The starter rod is rapidly consumed, by which time the heat melts the bauxite, which then becomes an electrolyte. Bauxite is added over several hours to build up the volume of melt. Current is controlled by adjusting the height of the electrodes, which are eventually consumed in the process.

After cooling, the alumina is broken up and passed through a series of hammer, beater, crush, roller, and/or ball mills to reduce it to the required grain size and shape, producing either blocky or thin splintered grains. After milling, the product is sieved to the appropriate sizes down to about 40 m (#400). The result is brown alumina containing typically 3% TiO2. Increased TiO2 content increases toughness while reducing hardness. Brown alumina has a Knoop hardness of 2090 and a medium friability.

Electrofused alumina is also made using low-soda Bayer process alumina that is more than 99% pure. The resulting alumina grain is one of the hardest, but also the most friable, of the alumina family providing a cool cutting action. This abrasive in a vitrified bond is, therefore, suitable for precision grinding.

White aluminum oxide is one of the most popular grades for micron-size abrasive. To produce micron sizes, alumina is ball-milled or vibro-milled after crushing and then traditionally separated into different sizes using an elutriation process. This consists of passing abrasive slurry and water through a series of vertical columns. The width of the columns is adjusted to produce a progressively slower vertical flow velocity from column to column. Heavier abrasive settles out in the faster flowing columns while lighter particles are carried over to the next. The process is effective down to about 5 m and is also used for micron sizing of SiC. Air classification has also been employed.

White 99% pure aluminum oxide, called mono-corundum, is obtained by sulfidation of bauxite, which outputs different sizes of isometric corundum grains without the need for crushing. The crystals are hard, sharp, and have better cleavage than other forms of aluminum oxides, which qualifies it for grinding hardened steels and other tough and ductile materials. Fine-grained aluminum oxide with a good self-sharpening effect is used for finishing hardened and high-speed steels, and for internal grinding.

Not surprisingly, since electrofusion technology has been available for the last one hundred years, many variations in the process exist both in terms of starting compositions and processing routes. For example:

Red-brown or gray regular alumina. Contains 9193% Al2O3 and has poor cleavage. This abrasive is used in resinoid and vitrified bonds and coated abrasives for rough grinding when the risk of rapid wheel wear is low.

Chrome addition. Semi-fine aloxite, pink with 0.5% chromium oxide (Cr2O3), and red with 15% Cr2O3, lies between common aloxite, having less than 95% Al2O3 and more than 2% TiO2, and fine aloxite, which has more than 95% Al2O3 and less than 2% TiO2. The pink grain is slightly harder than white alumina, while the addition of a small amount of TiO2 increases its toughness. The resultant product is a medium-sized grain available in elongated, or blocky but sharp, shapes. Ruby alumina has a higher chrome oxide content of 3% and is more friable than pink alumina. The grains are blocky, sharp edged, and cool cutting, making them popular for tool room and dry grinding of steels, e.g., ice skate sharpening. Vanadium oxide has also been used as an additive giving a distinctive green hue.

Zirconia addition. Aluminazirconia is obtained during the production process by adding 1040% ZrO2 to the alumina. There are at least three different aluminazirconia compositions used in grinding wheels: 75% Al2O3 and 25% ZrO2, 60% Al2O3 and 40% ZrO2, and finally, 65% Al2O3, 30% ZrO2, and 5% TiO2. The manufacture usually includes rapid solidification to produce a fine grain and tough structure. The resulting abrasives are fine grain, tough, highly ductile, and give excellent life in medium to heavy stock removal applications and grinding with high pressures, such as billet grinding in foundries.

Titania addition. Titaniaaloxite, containing 95% Al2O3 and approximately 3% Ti2O3, has better cutting ability and improved ductility than high-grade bauxite common alumina. It is recommended when large and variable mechanical loads are involved.

Single crystal white alumina. The grain growth is carefully controlled in a sulfide matrix and is separated by acid leaching without crushing. The grain shape is nodular which aids bond retention, avoiding the need for crushing and reducing mechanical defects from processing.

Post-fusion processing methods. This type of particle reduction method can greatly affect grain shape. Impact crushers such as hammer mills create a blocky shape while roll crushers cause splintering. It is possible, using electrostatic forces to separate sharp shapes from blocky grains, to provide grades of the same composition but with very different cutting actions.

The performance of the abrasive can also be altered by heat treatment, particularly for brown alumina. The grit is heated to 11001300 C (20152375 F), depending on the grit size, in order to anneal cracks and flaws created by the crushing process. This can enhance toughness by 2540%.

Finally, several coating processes exist to improve bonding of the grains in the grinding wheel. Red Fe2O3 is applied at high temperatures to increase the surface area for better bonding in resin cut-off wheels. Silane is applied for some resin bond wheel applications to repel coolant infiltration between the bond and abrasive grit, and thus protect the resin bond.

A limitation of electrofusion is that the resulting abrasive crystal structure is very large; an abrasive grain may consist of only one to three crystals. Consequently, when grain fracture occurs, the resulting particle loss may be a large proportion of the whole grain. This results in inefficient grit use. One way to avoid this is to dramatically reduce the crystal size.

The earliest grades of microcrystalline grits were produced as early as 1963 (Ueltz, 1963) by compacting a fine-grain bauxite slurry, granulating to the desired grit size, and sintering at 1500C (2735F). The grain shape and aspect ratio could be controlled by extruding the slurry.

One of the most significant developments since the invention of the Higgins furnace was the release in 1986, by the Norton Company, of seeded gel (SG) abrasive (Leitheiser and Sowman, 1982; Cottringer et al., 1986). This abrasive was a natural outcome of the wave of technology sweeping the ceramics industry at that time to develop high strength engineering ceramics using chemical precipitation methods. This class of abrasives is often termed ceramic. SG is produced by a chemical process. In a precursor of boehmite, MgO is first precipitated to create 50-m-sized aluminamagnesia spinel seed crystals. The resulting gel is dried, granulated to size, and sintered at 1200C (2200F). The resulting grains are composed of a single-phase -alumina structure with a crystalline size of about 0.2m. Defects from crushing are avoided; the resulting abrasive is unusually tough but self-sharpening because fracture now occurs at the micron level.

With all the latest technologies, it took significant time and application knowledge to understand how to apply SG. The abrasive was so tough that it had to be blended with regular fused abrasives at levels as low as 5% to avoid excessive grinding forces. Typical blends are now five SGs (50%), three SGs (30%), and one SG (10%). These blended abrasive grades can increase wheel life by up to a factor of 10 over regular fused abrasives, although manufacturing costs are higher.

In 1981, prior to the introduction of SG, the 3M Co. introduced a solgel abrasive material called Cubitron for use in coated abrasive fiber discs (Bange and Orf, 1998). This was a submicron chemically precipitated and sintered material but, unlike SG, had a multiphase composite structure that did not use seed grains to control crystalline size. The value of the material for grinding wheel applications was not recognized until after the introduction of SG. In the manufacture of Cubitron, alumina is co-precipitated with various modifiers such as magnesia, yttria, lanthana, and neodymia to control microstructural strength and surface morphology upon subsequent sintering. For example, one of the most popular materials, Cubitron 321, has a microstructure containing submicron platelet inclusions which act as reinforcements somewhat similar to a whisker-reinforced ceramic (Bange and Orf, 1998).

Direct comparison of the performance of SG and Cubitron is difficult because the grain is merely one component of the grinding wheel. SG is harder (21GPa) than Cubitron (19GPa). Experimental evidence suggests that wheels made from SG have longer life, but Cubitron is freer cutting. Cubitron is the preferred grain in some applications from a cost/performance viewpoint. Advanced grain types are prone to challenge from a well-engineered, i.e., shape selected, fused grain that is the product of a lower cost, mature technology. However, it is important to realize that the wheel cost is often insignificant compared to other grinding process costs in the total cost per part.

The SG grain shape can be controlled by extrusion. Norton has taken this concept to an extreme and in 1999 introduced TG2 (extruded SG) grain in a product called ALTOS. The TG2 grains have the appearance of rods with very long aspect ratios. The resulting packing characteristics of these shapes in a grinding wheel create a high strength, lightweight structure with porosity levels as high as 70% or even greater. The grains touch each other at only a few points, where a bond also concentrates in the same way as a spot weld. The product offers potential for higher stock removal rates and higher wheelspeeds due to the strength and density of the resulting wheel body (Klocke and Muckli, 2000).

Recycling of concrete involves several steps to generate usable RCA. Screening and sorting of demolished concrete from C&D debris is the first step of recycling process. Demolished concrete goes through different crushing processes to acquire desirable grading of recycled aggregate. Impact crusher, jaw crusher, cone crusher or sometimes manual crushing by hammer are preferred during primary and secondary crushing stage of parent concrete to produce RA. Based on the available literature step by step flowchart for recycling of aggregate is represented in Fig. 1. Some researchers have also developed methods like autogenous cleaning process [46], pre-soaking treatment in water [47], chemical treatment, thermal treatment [48], microwave heating method [49] and mechanical grinding method for removing adhered mortar to obtain high quality of RA. Depending upon the amount of attached mortar, recycled aggregate has been classified into different categories as shown in Fig. 2.

Upon arrival at the recycling plant, CDW may either enter directly into the processing operation or need to be broken down to obtain materials with workable particle sizes, in which case hydraulic breakers mounted on tracked or wheeled excavators are used. In either case, manual sorting of large pieces of steel, wood, plastics and paper may be required, to minimize the degree of contamination.

The three types of crushers most used for crushing CDW are jaw, impact, and gyratory crushers (Fig.8). A jaw crusher consists of two plates fixed at an angle (Fig.8a); one plate remains stationary while the other oscillates back and forth relative to it, crushing the material passing between them. This crusher can withstand large pieces of reinforced concrete, which would probably cause other types of crushers to break down. Therefore, the material is initially reduced in jaw crushers before going through other types. The particle size reduction depends on the maximum and minimum size of the gap at the plates. Jaw crushers were found to produce RA with the most suitable grain-size distribution for concrete production (Molin etal., 2004).

An impact crusher breaks CDW by striking them with a high speed rotating impact, which imparts a shearing force on the debris (Fig.8b). Materials fall onto the rotor and are caught by teeth or hard steel blades fastened to the rotor, which hurl them against the breaker plate, smashing them to smaller-sized particles. Impact crushers provide better grain-size distribution of RA for road construction purposes and are less sensitive to material that cannot be crushed (i.e. steel reinforcement).

Gyratory crushers, which work on the same principle as cone crushers (Fig.8c), exhibit a gyratory motion driven by an eccentric wheel and will not accept materials with large particle sizes as they are likely to become jammed. However, gyratory and cone crushers have advantages such as relatively low energy consumption, reasonable amount of control over particle size and production of low amount of fine particles.

Generally, jaw and impact crushers have a large reduction factor, defined as the relationship between the input's particle size and that of the output. A jaw crusher crushes only a small proportion of the original aggregate particles but an impact crusher crushes mortar and aggregate particles alike, and thus may generate twice the amount of fines for the same maximum size of particle (O'Mahony, 1990).

In order to produce RA with predictable grading curve, it is better to process debris in two crushing stages, at least. It may be possible to consider a tertiary crushing stage and further, which would undoubtedly produce better quality coarse RA (i.e. less adhered mortar and with a rounder shape). However, concrete produced with RA subjected to a tertiary crushing stage may show only slightly better performance than that made with RA from a secondary crushing stage (Gokce etal., 2011; Nagataki etal., 2004). Furthermore, more crushing stages would yield products with decreasing particle sizes, which contradicts the mainstream use of RA (i.e. coarser RA fractions are preferred, regardless of the application). These factors should be taken into account when producing RA as, from an economical and environmental point of view, it means that relatively good quality materials can be produced with lower energy consumption and with a higher proportion of coarse aggregates, if the number of crushing stages is prudently reduced.

hammer crusher, hammer crusher machine, hammering machine, hammer mill crusher - xinhai

hammer crusher, hammer crusher machine, hammering machine, hammer mill crusher - xinhai

Hammer Crusher is composed of rack, rotor, sieve bar, hammer, etc. Motor drives rotor through transmission belt, and materials are crushed due to the collision between hammer and materials produced by the rotation of rotor.

gyratory crusher vs. hammer crusher | quarrying & aggregates

gyratory crusher vs. hammer crusher | quarrying & aggregates

Hammer crusher has become a commonly used crushing equipment in quarries and cement plants due to its large capacity and short process. Gyratory crusher is a new type of coarse crushing equipment used in large-scale crushing production lines in mines and quarries. Both are in appearance and principle. It is quite different from the structure.

The gyratory crusher can handle 3000t/h mine and aggregate crushing easily, and the gyratory crusher can even reach 5000t/h or higher (some manufacturers have introduced that its largest model has a capacity of 9000t when it is broken), and its production capacity is usually 2-3 times of jaw crush, especially suitable for large-scale production lines.

The production capacity of hammer crusher is generally not more than 2000t/h. This is mainly due to product design. The hammer crusher has no counterweight wheel design. The hammer crusher with a very large volume is not very safe, which also restricts its large One reason for this, so in terms of production capacity, it cant be compared with the cyclical breakdown.

The gyratory crusher is generally used as a coarse crushing equipment, and the fine crushing equipment and sand making equipment will be configured according to the production requirements. Multi-stage crushing is considered to be more in line with the high-quality finished material process, and the compressive strength and crushing value are better. Well, there are few cracks, and it meets the relevant industry standards and can also meet the requirements of higher-performance concrete.

For small and medium-sized production lines, the hammer crusher has a short process, simple process (compared to multi-stage crushing), and one machine for two purposes. Advantages such as cement or sandstone) are welcomed by some users.

hammer crusher - eastman rock crusher

hammer crusher - eastman rock crusher

Hammer crusher is a kind of rock crusher equipment which can crush materials with compressive strength no more than 150MPa.ApplicationsMining, refractory material, cement, sand & gravel, concrete sand, dry mortar, mechanical sand, and so on operations.MaterialsCement, coal, white subdivision, gypsum, alum, brick, tile, limestone and other soft-medium hardness materials.

We not only can provide you with various types of rock crusher, but also can design reasonable crushing process for you free. Contact us to get the high configuration of equipment with competitive price now!

hammer crusher | hammer mill crushers for sale jxsc mine

hammer crusher | hammer mill crushers for sale jxsc mine

Hammer Crusher Application Field Mining, metallurgy, building material, cement, quarrying, gravel & sand making, aggregate processing, recycling, and chemical industry, etc. Suitable Material Limestone, slag, pebble, rock gold ore, salt, concrete, coal, coke and other materials in the primary/secondary crushing and fine crushing operations.

Hammer stone crusher is a kind of equipment that crushes materials in the form of impact. Crushing the size of 600-1800 mm material to 25m or less. Hammermill machine can not only be used in stone crusher plant, sand plant, but also can replace the cone crusher in the mineral processing.

JXSC hammer mill machine that hammerhead adopts a new technology cast which wear-resistant and impact-resistant. The airframe structure of the hammer mill is seal which solves the problems of dust pollution and dust leakage in the crushing workshop. And it is easy to maintain.

1. Hammerhead uses new cast technology which with wear-resistant and impact-resistant characteristic. 2. Can adjust the granularity size. 3. The seal structure that solves the problems of dust pollution and dust leakage in the crushing workshop. 4. The overall design of hammer crushing equipment has the advantages of beautiful appearance, compact structure, few wearing parts, convenient maintenance, etc.

Hammermill crusher mainly rely on impact energy to complete the crushing of materials. When the hammer mill rock crusher works, the motor drives the rotor to rotate at high speed, and the material enters the crusher cavity evenly. The hammerhead with high speed turns impacts and tears the material lead to the materials are crushed.

At the same time, the material from the high-speed rotating hammerhead to the baffle and screen strip in the frame under the gravity effect. The material larger than the size of the screen hole remains on the screen plate and continues to be hit and ground by the Hammer. Then finally through the sieve plate discharge machine until the crusher material size discharge.

The advantages of the hammer: The ratio of crushing is large, generally is 10-25, high up to 50. High production capacity. uniform products. Less over-powder phenomenon. Simple structure, light equipment quality. Simple operation and maintenance, etc. The series hammer crusher products are suitable for crushing all kinds of medium hardness and brittle materials, such as limestone, coal, salt, gypsum, alum, brick, tile, coal gangue and so on. The compressive strength of the crushed material shall not exceed 150 MPA.

The series of crushers are mainly used in cement, coal preparation, power generation, building materials, and compound fertilizer industries. It can crush the raw materials of different sizes into uniform particles for the next working procedure. Reliable mechanical structure, high production efficiency, good applicability.

But the hammer crusher also has some disadvantages, such as the hammer and grate screen wear quickly. When crushing hard materials, they wear out faster. When crushing sticky wet materials, it is easy to plug the screen seam of the grate. Therefore, it is easy to cause shut down, so the moisture content of the material should not exceed 10 %. When milling hard objects, the hammer and lining plate have big wear. And the consumptive metal material is much, often needs to replace the wear-and-tear piece.

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

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