The size requirement of the primary rock crusher is a function of grizzly openings, ore chute configuration, required throughput, ore moisture, and other factors. Usually, primary crushers are sized by the ability to accept the largest expected ore fragment. Jaw crushers are usually preferred as primary crushers in small installations due to the inherent mechanical simplicity and ease of operation of these machines. Additionally, jaw crushers wearing parts are relatively uncomplicated castings and tend to cost less per unit weight of metal than more complicated gyratory crusher castings. The primary crusher must be designed so that adequate surge capacity is present beneath the crusher. An ore stockpile after primary crushing is desirable but is not always possible to include in a compact design.
Many times the single heaviest equipment item in the entire plant is the primary crusher mainframe. The ability to transport the crusher main frame sometimes limits crusher size, particularly in remote locations having limited accessibility.
In a smaller installation, the crushing plant should be designed with the minimum number of required equipment items. Usually, a crushing plant that can process 1000s of metric tons per operating day will consist of a single primary crusher, a single screen, a single secondary cone crusher, and associated conveyor belts. The discharge from both primary and secondary crushers is directed to the screen. Screen oversize serves as feed to the secondary crusher while screen undersize is the finished product. For throughputs of 500 to 1,000 metric tons per operating day (usually 2 shifts), a closed circuit tertiary cone crusher is usually added to the crushing circuit outlined above. This approach, with the addition of a duplicate screen associated with the tertiary cone crusher, has proven to be effective even on ores having relatively high moisture contents. Provided screen decks are correctly selected, the moist fine material in the incoming ore tends to be removed in the screening stages and therefore does not enter into subsequent crushing units.
All crusher cavities and major ore transfer points should be equipped with a jib-type crane or hydraulic rock tongs to facilitate the removal of chokes. In addition, secondary crushers must be protected from tramp iron by suspended magnets or magnetic head pulleys. The location of these magnets should be such that recycling of magnetic material back into the system is not possible.
Crushing plants for the tonnages indicated may be considered to be standardized. It is not prudent to spend money researching crusher abrasion indices or determining operating kilowatt consumptions for the required particle size reduction in a proposed small crushing plant. Crushing installations usually are operated to produce the required mill tonnage at a specified size distribution under conditions of varying ore hardness by the variation of the number of operating hours per day. It is normal practice to generously size a small crushing plant so that the daily design crushing tonnage can be produced in one, or at most two, operating shifts per working day.
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 , pre-soaking treatment in water , chemical treatment, thermal treatment , microwave heating method  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.
A full line of crushing and screening plants and systems designed for the most challenging applications like processing concrete with the toughest, high-volume steel rebar, with ease. Processing the most abrasive hard rock without equipment fatigue. Tough enough to work for these applications, powerful enough to work for you, no matter what youre crushing.
Eagle Crusher knows the demands you face every day on the job site. Thats why we consistently lead the industry in new product innovations. Explore whats new in our lineup of heavy-duty crushing and screening plants and systems.
Eagle Crusher started as a family business with a rich heritage going back more than 100 years. Eagle is still a family-owned business today, operating from that same rich heritage. A heritage that puts customers first, and treats you like youre one of the family, with unsurpassed service and support, long after the sale, to make your job easier and your business more profitable.
You wont find more expert purchasing advice or better financing programs than with our Eagle Crusher financing team. Same-day quotes. 100% financing with qualified credit. Flexible payment options. Competitive terms and conditions.
Particle-size reduction, or comminution, is often required to prepare bulk material samples for testing. Crushing is often the initial step with materials such as mineral ores or aggregates using varying combinations of force, impact, and compression to initiate fracturing in the materials.
Call(866) 511-7720 for Pricing Bronneberg Engine Crusher Engine crushers provide an easy way to increase profit from car recycling activities since an engine crusher enables you to recover the aluminum from an engine or gearbox. The Bronneberg engine crusher is engineered to process car engines, gearboxes, and aluminum wheels. It is easy to operate and built to last. It has a pusher cylinder with 125 tons of crushing force. The entire box of the machine is equipped with HARDOX wears plates. This engine crusher has a sophisticated system that enables you to adjust the opening of the exit, which controls the size of the output material. Crushing engines and gearboxes enables you to easily separate the valuable aluminum from the steel. The Bronneberg engine crusher is designed to work in a fully automatic cycle after the loading hopper is filled. It is available with a diesel or electric drive. The machine also has the option to be equipped with a vibrating table with a drum magnet or with a horizontal belt with overbelt magnet. This powerful machine will likely pay for itself with the profit it generates within a relatively short time frame (one year or longer). Contact us using our online form or by calling (866) 511-7720 to purchase a Bronneberg engine crusher or ask any questions you may have. Bronneberg Engine Crusher Product Specs Dimensions: 107 x 57 x 130 Hopper dimensions: 59 x 39 Compression force: 125 T Weight: 14,700lbs Charging box dimensions: 43 x 39 Why Do You Need Engine Crushers? Car engines, gearboxes, and aluminum wheels all have valuable aluminum parts. An engine crusher reduces these things into small particles, enabling the aluminum to be separated from the ferrous and other metallic components. This makes sorting much easier and significantly increases the profitability of your car recycling activities. Trust Us for Your Industrial Recycling Machines Solid Equipment Company specializes in top of the line recycling equipment. For reclaiming value from old car engines, gearboxes, and aluminum wheels, weve teamed with Bronneberg to supply the latest technology in engine crushing. If you are interested in purchasing Bronneberg engine crushers, contact Solid Equipment Company today! Bronneberg is well-known around the world for producing reliable, quality, and innovative machines that are designed to last. Solid Equipment Company is proud to be one of the few exclusive North American distributors of Bronneberg equipment. We provide a wide range of industrial recycling equipment, in addition to engine crushers. Wherever you are located in the United States we can take care of your industrial recycling equipment needs; we process orders anywhere in the United States. We are committed to working with our customers to provide the best equipment for their needs. We are invested in the profitability of your endeavors! Contact Solid Equipment Company for Your New or Used Engine Crushers Our experts can help you to solve any of your industrial recycling challenges. The Bronneberg engine crusher is powerful, easy to operate, and built to last. They provide a great way to increase the profitability of car recycling activities. Contact Solid Equipment Company now for your Bronneberg engine crushers anywhere nationwide by calling (866) 511-7720!
The Bronneberg engine crusher is engineered to process car engines, gearboxes, and aluminum wheels. It is easy to operate and built to last. It has a pusher cylinder with 125 tons of crushing force. The entire box of the machine is equipped with HARDOX wears plates.
This engine crusher has a sophisticated system that enables you to adjust the opening of the exit, which controls the size of the output material. Crushing engines and gearboxes enables you to easily separate the valuable aluminum from the steel. The Bronneberg engine crusher is designed to work in a fully automatic cycle after the loading hopper is filled.
It is available with a diesel or electric drive. The machine also has the option to be equipped with a vibrating table with a drum magnet or with a horizontal belt with overbelt magnet. This powerful machine will likely pay for itself with the profit it generates within a relatively short time frame (one year or longer).
Car engines, gearboxes, and aluminum wheels all have valuable aluminum parts. An engine crusher reduces these things into small particles, enabling the aluminum to be separated from the ferrous and other metallic components. This makes sorting much easier and significantly increases the profitability of your car recycling activities.
Solid Equipment Company specializes in top of the line recycling equipment. For reclaiming value from old car engines, gearboxes, and aluminum wheels, weve teamed with Bronneberg to supply the latest technology in engine crushing.
If you are interested in purchasing Bronneberg engine crushers, contact Solid Equipment Company today! Bronneberg is well-known around the world for producing reliable, quality, and innovative machines that are designed to last. Solid Equipment Company is proud to be one of the few exclusive North American distributors of Bronneberg equipment.
We provide a wide range of industrial recycling equipment, in addition to engine crushers. Wherever you are located in the United States we can take care of your industrial recycling equipment needs; we process orders anywhere in the United States. We are committed to working with our customers to provide the best equipment for their needs. We are invested in the profitability of your endeavors!
Our experts can help you to solve any of your industrial recycling challenges. The Bronneberg engine crusher is powerful, easy to operate, and built to last. They provide a great way to increase the profitability of car recycling activities.
DELUMPER Lump Breakers and Crushers break solids, lumps and agglomerates down to desired size with a once-through, non-churning, crushing action that produces minimal fines. They reduce plant downtime, increase processing speed and improve product consistency. These units are precision manufactured and aligned for smooth operation with low vibration or noise.
Franklin Miller offers a wide variety of crushers and lump breakers with processors to meet almost any application. Our powerful units are designed to handle capacities from 50 lbs an hour to 1000 tons per hour. DELUMPER Crushers can also be customized to meet the exacting requirements of a customer's applications including easy maintenance, custom sizes, and special materials.
DELUMPER Lump Breakers can handle wet, sticky, dry, hard or soft substances. They tear through chemicals, lumps, agglomerates, ore, filter cake, ash, sugar, food, plastics and more. The units are available in various sizes with single, dual or triple-shaft configurations for capacities up to 1000 tons per hour.
DELUMPER Lump Breakers are used in a wide variety of orientations. Our units can handle dry or wet applications in either in-line or gravity configurations. These powerful lump breakers can be customized to meet the requirements of your operation and configuration.
The PIPELINE DELUMPER In-line Processor converts a solids-laden stream into a fully suspended homogeneous flow instantly. It stops settling out, clustering and over pressure. The reduced particles are entrained in the stream, away from the pipe walls. Scale is dislodged from reactors, silos and tanks and is crushed before it can impede the flow.
The PIPELINE DELUMPER improves product quality, blend and consistency. It instantly reduces tough solids to a uniform output size. This unit improves mixing, drying and dissolving operations. Nozzles are kept clear and sensitive media is protected. The result is reduced downtime, a process that is in better control, and with substantial savings to the operation.
DELUMPER Crushers reduce lumps, crush minerals, improve product consistency, facilitate mixing, drying and conveying, and keep process lines running smoothly. These units have extraordinary processing capabilities on a wide range of materials including chemicals, sugar, food, minerals, urea, ammonium nitrate, salts, colors, plastics, pharmaceuticals and more.
DELUMPER L series lump breakers typically employ no screens. Instead, specially designed teeth mounted on a smooth, rotating drum, intermesh with sizing combs, reducing solids to their basic grain size without overgrind, heat rise or fines. Lumps up to the full inlet opening size can be processed. The unit runs at low speed and creates little vibration or noise.
DELUMPER S4 Crushers feature precision operation, easy interior access, clean-in-place capability, and a meticulously polished finish. A convenient side door provides fast and easy access to the interior of the cutting chamber for maintenance. The S4 employs a direct gear drive for smooth and quiet operation as well as low maintenance. The unit features a teflon shaft seal to protect bearings and keep the product in the chamber. The drum can be quickly removed for cleaning or change-out. The drum with teeth and shaft are one piece with all fasteners located outside the cutting chamber.
DELUMPER LP Processors are ruggedly constructed of heavy plate and channel for long, dependable service. These units are precision manufactured and aligned for smooth operation with low vibration or noise. The bodies are constructed with ample mounting flanges for connection to ducts, hoppers, feeds or valves. The DELUMPER LP models are supplied in one-piece bodies, lip-type seals and heavy tapered roller bearings.
DELUMPER Multi-Shaft Crushers models are provided in a number of configurations to fit many application requirements, in standard (LP) and Ultra-Heavy-Duty (LP-HD) versions. These units feature: direct gear drives, shaft seals and heavy-duty bearings. The DELUMPER TWIN-LP lump breaker features multiple high profile LP cutters stacked on heavy parallel shafts. Each tooth is constructed for precise balance, interchangeability and smooth operation.
The teeth are mounted in a staggered pattern around the shaft diameter to assure smooth continuous operation, reduced power consumption and optimal feeding. The rugged extended LP teeth rotate through a heavy bar grating with a low friction design. The teeth are typically supplied with leading edges to crack the feed with a pick-like action and handle solids with reduced shock and power consumption.
Franklin Miller has extensive engineering know-how and manufacturing capabilities to meet your processing needs. We can provide a variety of options and accessories for our wide range of standard DELUMPER lump breakers or we can provide a fully custom engineered solution.
Our equipment can be provided stand-alone, with stand and hopper, with a control system or as part of a complete engineered system, which can include conveyors, feeders, bag dump and unload stations and more. Our test facility can be your resource for determining the best size reduction solution to meet your needs.
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Williams is an industry-leading roll crusher manufacturer and designer for high-quality roll crushers with desirable benefits such as high throughput capacity, minimal maintenance requirements, low cost per ton operation, and more. Learn more about our heavy-duty roll crushers below or contact our sales engineers to talk about your application needs.
A combination of impact, shear, and compression are the forces necessary to perform the crushing and size reduction in a Williams roll crusher. The material enters the roll crusher machine and is impacted by the roll as it rotates. Then, as the material is pulled between a crushing plate or rolls, shear and compression forces act upon the material. The rolls act as flywheels, contributing to smooth operation and efficient use of power. Roll crushing surfaces operate at a fixed distance apart, as opposed to the continually changing distances in a jaw or cone crusher. This creates a more consistent product size.Roll crushers are low in profile and relatively easy to install. They can be fed with a minimum of headroom, or even choke fed. Adjustments are simple andinternal parts are readily accessible.
Typical feed materials for Williams Roll Crushers include: bauxite, cement clinker, chalk, cinders, clay, coal, glass, gypsum, limestone, burnt lime, rock salt, sandstone, shale, sulfur ore, sea shells, and sewer sludge clinker. Single Roll Crushers, sometimes called lump breakers, can also be used for breaking frozen or agglomerated materials.
Williams Roll Crushers are used in a variety of industries such as, mining recycling, and power industries. Interested in learning more about the Williams Roll Crushers for your specific industry and application? Contact our sales engineers!
Choosing between a single roll crusher and double roll crusher depends upon the type of feed material, feed size, product size desired, and consistency of both feed and product. Both single and double roll crushers operate most efficiently with dry, friable materials. However, single roll machines have been widely and successfully used for the reduction of moist clays. They also have been long used as primary and secondary coal crushers, both at mine sites and power plants, where a minimum of fines is desired.
Williams single roll crushers reduce via a combination of impact, shear, and compression. The rolls are always toothed in patterns suited to the feed material. Single Roll Crushers generally handle larger feed sizes at higher reduction ratios in higher capacities and are particularly well suited to be used as lump breakers.
Double roll crushers reduce primarily through compression, although some shear is obtained with toothed rolls. Rolls for these crushers come in combinations of smooth, corrugated, and toothed designs. Double Roll Crushers produce a finer product at lower reduction ratios and capacities.
Oversized, heat-treated, alloy steel shafts plus self-aligning, roller-type bearings assure long life and maximum use of power. Jackshafts for control of roller speed are standard on double roll crushers, optional on larger Single Roll Crushers.
Heavy-duty compression springs permit movement of floating roll to pass tramp metal and other uncrushables, avoiding overload and damage. Smaller Single Roll Crushers are equipped with a shear pin release.
Faces Tooth patterns and corrugations to fit feed material; abrasion-resistant alloy; easily replaceable. Ash Crushers have additional features including dust-tight design and sealed cover plates for breaker plate access.
Williams Single Roll Crushers are also available in a 15 inch (381mm) diameter dust-tight version for applications such where it would be expensive to have dust collection air. Already well known for rugged construction, low profile, high reduction ratio, and economical cost, Williams Dust-Tight Ash Single Roll Crushers also have easy access to the rotor for maintenance. These dust-tight roll crushers are perfect for applications such as crushing ash, limestone, coal, or glass.
Portable crusher plant is a new product. It is designed for construction waste crushing. According to the need of configuration, different crushing industry, first crushing and then screening or first screening and then crushing, screening can also be carried out separately. Portable crusher plant can also be combined into two-stage crushing and screening system or three-stage crushing and screening system based on actual needs. It has features as independent operation, flexible combination and strong adaptability.
Our portable crushing configurations are equipped with the advanced technology to enhance productivity, serviceability, portability and safety. We have customized service for particular needs. These plants are designed and produced to be personalized for your specific application.
Our company is professional at designing and producing construction machinery, such as asphalt mixing plant, dry mortar plant, crushing plant, concrete batching plant. Our equipment meet the requirements of national industrial standards. If you want to buy a reliable crushing plant, contact with us now!
Pay attention to the maintenance of bearings. The injected oil must be a well-sealed and clean lubricating oil. In addition, the main crushing equipment of mobile crushing plants generally adopts jaw crusher, impact crusher and cone crusher, it is suggested that user and manufacturers should adopt forced lubrication system to prevent the rust of rotating bearings, roll bearings and all gears. Note: mobile crushing plant requires oil injection maintenance of bearings, including rotating bearings, roll bearings and all gears.
It is necessary to pay attention to the replacement of the worn parts of the mobile crushing plant and to prevent greater damage to the machine and, in normal times, to check the degree of wear of the parts.
Impact crusher is used in coarse crushing, intermediate crushing and fine crushing of materials like limestone, coal, calcium carbide, quartz, dolomite, sulfide iron ore, gypsum, chemical raw materials, etc.
Cone crusher can perform unparalleled crushing function in operations of coarse crushing, fine crushing and superfine crushing. Cone crusher can finely crush various ores and rocks with different high hardness, like iron ore, nonferrous metal, emery, bauxite, quartz sand, brown aluminum oxide, basalt, etc.
Mobile stone crusher planthasshortlength.The independent movable chassis can be used for different crushing equipment, so that the wheelbase is shorter and the turning radius is smaller, so that the machine can travel flexibly in the operation area or on the highway.
The mobile plant has compact structure. It adopts the integrated installation form of feeding, transportation, crushing and so on, which can not only eliminate the complicated operation of component installation, but also reduce the consumption of materials and man-hours. The reasonable and compact space layout of the machine does not occupy the space, but also improves the flexibility of the site stationed.
According to the different crushing process requirements, the mobile crushing plantcan form the process of crushingfirst and then screening according to the customers demand. And the crushing plantcan be combined into two segments, or a three-stage broken screening system, according to the actual demand. In addition, the equipment can run independently, and has high flexibility in operation and transportation.
Reducing the cost of material transportation is mainly manifested in that the mobile crushing station can process the material on the spot. The biggest advantage of this is that the transportation cost of the material is greatly reduced.
Maintenance is convenient for machinery to obtain a good after-sales reputation. After optimizing and strengthening the design of the mobile crushing station, it further accepts the advantages of higher strength, better performance and more compact structure.
The mobile crushing station can not only be used independently, but also can provide a more flexible machine process configuration for different requirements of the customers so as to meet the requirements of the user to move and break the machine, move and sieve, and make the logistics transfer more direct and effective, and the cost can be maximized.