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how does a roller crusher work

how a roller crusher crush coal gangue | fote machinery

how a roller crusher crush coal gangue | fote machinery

Coal gangue is an abandoned rock discharged during coal mining and processing. When mining coal, the rock layers or bottom plates from the roof of the coal seam, as well as the various types of rock excavated and blasted from around the coal seam during the excavation are all called coal gangue.

Coal gangue utilization is an important part of comprehensive utilization of resources. The utilization of coal gangue can increase the economic benefits of coal enterprises, improve coal mine production structure and environmental quality.

In China, the total installed capacity of generators of low calorific value fuel such as coal gangue reached 28 million kW, and the single unit capacity was from 6 to 300 MW. The annual utilization of coal gangue was 140 million tons, and the annual power generation was 160 billion kWh.

Since the 1970s, the US Bureau of Mines has sampled and analyzed all coal gangue hills and made comprehensive plans for coal gangue utilization. For example, the heat energy is directly recovered from the burning coal gangue mountain for both recovering the heat and controlling pollution.

Because coal gangue brick products have characteristics of lightweight, high strength, good load-bearing seismic performance, excellent thermal insulation, heat insulation and sound insulation, so it is a broad market.

Road construction and backfilling are also important ways for comprehensive utilization of coal gangue. The use of coal gangue as engineering packing materials do not require an increase in cost and need a large amount of use, which brings good economic efficiency to the coal mine.

There are three main types of coal gangue for chemical use: the first is to extract a rare element in coal gangue by various methods, such as Ga, Se, Ti, Co, etc. The second is to recover beneficial mineral products such as kaolin; the third is the production of silicon, aluminum, sulfur and other inorganic chemical products.

The use of coal gangue fertilizer is mainly based on the fact that coal gangue contains rich organic carbon, and the organic matter content in the soil can be greatly increased after being applied to the soil.

The roll crusher is mainly suitable for fine crushing operations with a feed size of less than 150 mm and a finished product size of 100 mesh to 2 mm. What are the advantages of the roll crusher in use?

Compared with the striking type crushing equipment, the biggest disadvantage of the roll crusher is that the "crushing ratio" is relatively small, the particle size of the product changes with the wear of the gap of the roller, and the crushing effect on the sheet-like material is poor.

Therefore, the most important thing about using the roll crusher is the method of stepwise crushing. When crushing coal gangue, it should go through three processes of "coarse-middle-fine crushing".

The surface of the roll crusher is easily worn to grooves and makes the gap between the rolls larger, thereby reducing the crushing effect. When the roller is new, the gap between the two rollers is the smallest, and the fineness of the crushing is the best.

Therefore, to obtain a good coal gangue crushing product, the work we have to do is to minimize the variation value from fine to coarse, and to control the crushing particle size within the allowable range to ensure the quality of the product.

When crushing coal gangue, to achieve the target particle size, three processes of "coarse-middle-fine crushing" are usually carried out. According to the previous configuration experience, we configure a detailed crushing production line for the 10t/h coal gangue:

Raw material warehouseGZD6502300 vibrating feederPE400600 jaw crusher2PG0640 roll crusher3YK1237 vibrating screenDMC64 dust collectorfinished silo (also several B500 conveyors of different lengths).

It can be seen from the above that when there are three specifications of the finished coal gangue, the jaw crusher can be used as the first crush, and the roll crusher is used for the medium and fine crushing.

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roll crusher manufacturer & design | williams crusher

roll crusher manufacturer & design | williams crusher

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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.

laboratory roll crusher

laboratory roll crusher

The 911MPELRC Laboratory Roll Crushers are typically applied in laboratory or pilot plant applications after primary reduction of the infeed material. Roll crushers operate with a minimum of dust generation and produce a material with a tight size envelope containing a minimum of fines.

Designed for rapid, controlled size reduction of ore, mineral or rock prior to metallurgical testing or further milling or grinding the 911MPELRC Laboratory Roll Crusher has is built with two off same diameter individually powered contra-rotating rolls, so the nipping process produces an ideal crushing environment for a wide variety of materials.

Primary Crushing and for Mid Range Primary Crushing. The crushing capacity and the end-fineness of the sample material depends on the type of crusher and on the breaking characteristics of the sample material.

how does different stone crusher work?

how does different stone crusher work?

In the process of mineral processing, the operation of reducing the particle size to 20-5mm is called crushing, and the corresponding equipment is stone crusher. Commonly used stone crushing equipment are: jaw crusher, cone crusher, impact crusher, roller crusher, hammer crusher, etc.

The cone crusher can be divided into three types: coarse crushing, medium crushing and fine crushing according to its particle size range. It has the characteristics of large crushing ratio, uniform product size, high production efficiency, low energy consumption and easy adjustment of the discharge port.

The impact crusher has the characteristics of large crushing ratio, high crushing efficiency, low power consumption, less over crushing phenomenon, strong adaptability, small equipment volume, light weight, simple structure, easy manufacturing, convenient maintenance and so on. It is mainly used as medium and fine crushing equipment for various materials, and also as coarse crushing equipment.

The new type of sand making machine adopts modular structure design, which can be exchanged instantly. When processing materials, different crushing principles can be selected according to the properties of materials and the requirements of materials. There are two crushing forms of stone or stone iron, which can crush materials on demand.

Roller crusher can be divided into single roller, double roller, three roller and four roller according to the number of rollers. It has the characteristics of simple and compact structure, reliable operation, low cost, convenient adjustment of crushing particle size ratio and less over crushing particle size. Mainly used for medium and fine crushing of brittle and tough materials.

The composite crusher rotor adopts a new design structure, adopts the impact crusher steel disc structure and the hammer crusher's hammer disc staggered arrangement structure, and its structural design effectively enhances the crushing performance and improves the production efficiency of the equipment.

The material falls vertically from the upper part of the machine into the high-speed rotating impeller. Under the action of high-speed centrifugal force, it will shunt with another part in an umbrella form around the impeller to produce high-speed impact and crushing. After the materials collide with each other, they will be The material between the casings is crushed by multiple collisions and frictions formed by the eddy current between the materials, and is discharged directly from the lower part to form a closed circuit for multiple cycles. The screening equipment controls to reach the required finished product particle size.

Hammer crusher is similar to impact crusher in structure. It is mainly used for crushing medium hard and weak abrasive materials, such as limestone, coal, asbestos, cement clinker, metal slag, feed, etc.

roll crusher - an overview | sciencedirect topics

roll crusher - an overview | sciencedirect topics

Roll crushers are generally not used as primary crushers for hard ores. Even for softer ores, such as chalcocite and chalcopyrite, they have been used as secondary crushers. Choke feeding is not advisable as it tends to produce particles of irregular size. Both open and closed circuit crushing is employed. For close circuit the product is screened with a mesh size much less than the set.

Figure6.4 is a typical set-up where ores crushed in primary and secondary crushers are further reduced in size by a rough roll crusher in an open circuit followed by finer size reduction in a closed circuit by a roll crusher. Such circuits are chosen as the feed size to standard roll crushers normally does not exceed 50mm.

A distinct class of roll crushers is referred to as sizers. These are more heavily constructed units with slower rotation, and direct drive of the rolls rather than belt drives. They have a lower profile, allowing material to be easily fed by loaders, and are a good choice for portable crushers at the mine that reduce the coal in size for conveying to the preparation plant. An example of these units is shown in Fig.9.4.

9.4. (a) Primary sizer with attached feeder. The large motors and gearboxes drive the relatively low-speed toothed rolls that break the coal. (b) Haulage truck dumping coal directly into the feed hopper for a primary sizer, which discharges onto a product belt. (c) Tertiary sizer for crushing coal to the desired size for a preparation plant.

Their lower speeds are claimed to reduce fines generation, while lending themselves to high throughput applications. Sizers can either have the rolls rotate towards each other to carry feed between the rolls to be broken, or can be constructed as tertiary sizers with the rolls rotating away from each other. With tertiary sizers, feed coal is added between the rolls, and much of the fine material falls through. The coarser material is then carried to the outside to be broken against fixed sizing combs. This design increases the capacity by producing two main product streams instead of one, and also minimizes overcrushing by removing a large fraction of the fines. Tertiary sizer capacities range from 440 tons/h (400 metric tons/h) for 2448 inch (61122cm) rolls producing a 2-inch (5cm) product, up to 3968 tons/h (3600 metric tons/h) for 2096 inch (51244cm) rolls producing a 10-inch (25cm) product (Alderman and Edmiston, 2010).

A typical coal handling package using sizers would comprise a dump pocket discharging to a primary sizer discharging to a product belt, as shown in Fig.9.4b. This product belt would then feed a secondary or tertiary sizer, such as is shown in Fig.9.4c, which may include intermediate screening to remove product prior to subsequent stages of breakage. Typical size ranges would start with run-of-mine coal feeding to the primary sizer at 2000mm, and reducing to 350mm. The secondary sizer would receive this coal and discharge at a nominal 125mm, followed by a tertiary sizer/screen combination to generate a 50mm topsize preparation plant feed (FLSmidth, 2011).

The intermediate crushing in the cut roll crusher is mainly used for the crushing of brittle materials like concrete and clay sintered bricks, along with the compression of rough materials like wood and fabric (to avoid being too small in size) after the coarse (primary) crushing. The selective crushing in this process is good for the separation of impurities. Impact crushers are commonly applied in intermediate crushing. However, when used in crushing of mixed C&D waste, the wood and fabric materials will be broken and mixed in recycled aggregate materials by the high-speed operating rotors and are difficult to be separated.

Although not widely used in the minerals industry, roll crushers can be effective in handling friable, sticky, frozen, and less abrasive feeds, such as limestone, coal, chalk, gypsum, phosphate, and soft iron ores.

Roll crusher operation is fairly straightforward: the standard spring rolls consist of two horizontal cylinders that revolve toward each other (Figure 6.14(a)). The gap (closest distance between the rolls) is determined by shims which cause the spring-loaded roll to be held back from the fixed roll. Unlike jaw and gyratory crushers, where reduction is progressive by repeated nipping action as the material passes down to the discharge, the crushing process in rolls is one of single pressure.

Roll crushers are also manufactured with only one rotating cylinder (Figure 6.14(b)), which revolves toward a fixed plate. Other roll crushers use three, four, or six cylinders, although machines with more than two rolls are rare today. In some crushers the diameters and speeds of the rolls may differ. The rolls may be gear driven, but this limits the distance adjustment between the rolls. Modern rolls are driven by V-belts from separate motors.

The disadvantage of roll crushers is that, in order for reasonable reduction ratios to be achieved, very large rolls are required in relation to the size of the feed particles. They therefore have the highest capital cost of all crushers for a given throughput and reduction ratio.

The action of a roll crusher, compared to the other crushers, is amenable to a level of analysis. Consider a spherical particle of radius r, being crushed by a pair of rolls of radius R, the gap between the rolls being 2a (Figure 6.15). If is the coefficient of friction between the rolls and the particle, is the angle formed by the tangents to the roll surfaces at their points of contact with the particle (the angle of nip), and C is the compressive force exerted by the rolls acting from the roll centers through the particle center, then for a particle to be just gripped by the rolls, equating vertically, we derive:

The coefficient of friction between steel and most ore particles is in the range 0.20.3, so that the value of the angle of nip should never exceed about 30, or the particle will slip. It should also be noted that the value of the coefficient of friction decreases with speed, so that the speed of the rolls depends on the angle of nip, and the type of material being crushed. The larger the angle of nip (i.e., the coarser the feed), the slower the peripheral speed needs to be to allow the particle to be nipped. For smaller angles of nip (finer feeds), the roll speed can be increased, thereby increasing the capacity. Peripheral speeds vary between about 1ms1 for small rolls, up to about 15ms1 for the largest sizes of 1,800mm diameter upwards.

Equation 6.6 can be used to determine the maximum size of rock gripped in relation to roll diameter and the reduction ratio (r/a) required. Table 6.1 gives example values for 1,000mm roll diameter where the angle of nip should be less than 20 in order for the particles to be gripped (in most practical cases the angle of nip should not exceed about 25).

Unless very large diameter rolls are used, the angle of nip limits the reduction ratio of the crusher, and since reduction ratios greater than 4:1 are rare, a flowsheet may require coarse crushing rolls to be followed by fine rolls.

Smooth-surfaced rolls are usually used for fine crushing, whereas coarse crushing is often performed in rolls having corrugated surfaces, or with stub teeth arranged to present a chequered surface pattern. Sledging or slugger rolls have a series of intermeshing teeth, or slugs, protruding from the roll surfaces. These dig into the rock so that the action is a combination of compression and ripping, and large pieces in relation to the roll diameter can be handled. Toothed crushing rolls (Figure 6.16) are typically used for coarse crushing of soft or sticky iron ores, friable limestone or coal, where rolls of ca. 1m diameter are used to crush material of top size of ca. 400mm.

Wear on the roll surfaces is high and they often have a manganese steel tire, which can be replaced when worn. The feed must be spread uniformly over the whole width of the rolls in order to give even wear. One simple method is to use a flat feed belt of the same width as the rolls.

Since there is no provision for the swelling of broken ore in the crushing chamber, roll crushers must be starvation fed if they are to be prevented from choking. Although the floating roll should only yield to an uncrushable body, choked crushing causes so much pressure that the springs are continually activated during crushing, and some oversize escapes. Rolls should therefore be used in closed circuit with screens. Choked crushing also causes inter-particle comminution, which leads to the production of material finer than the gap of the crusher.

The objective of sample preparation is to prepare test samples from a parent sample or individual primary increments, Fig.5.19 for analysis. Sample preparation includes all procedures that a sample is subjected to in order to produce a reduced mass of sample (analysis sample) that is representative of the parent sample and from which subsamples of relatively small mass can be used directly for analysis. Samples for general analysis (proximate, ultimate, calorific value, total sulphur, etc.) are typically milled samples with 95% passing 0.212mm. Standard AS4264.1 stipulates that the minimum mass required for general analysis is 30g.

However, some laboratory analyses will require larger sample masses. Some examples from AS 4264.1 include Hardgrove grindability index (AS 1038.20) which requires 1kg at 4.75mm top size, and total moisture (AS 1038.1 Method A and B) 300g at 4mm. However, the principles of preparing a representative analysis sample from the original coal sample are the same.

Taking the ash determination as an example: 1g of coal is used in a single ash determination, and that 1g has to be representative of the coal sample. At a top size of 0.212mm the sampling constant, Ks, for most coals will be very small and this constant combined with a 1g mass of coal enables the variance contribution from the IH of the analysis sample to be almost insignificant and therefore a high level of precision can be expected.

Apart from exploration samples, most samples received by laboratories are from mechanical sampling systems at coal handling facilities at mine sites, ports or power stations. In some areas where coal is being sold across land boarders such as the MongolianChinese border, most samples will be extracted directly from haulage trucks. Many samples, such as ship loading samples and some coal preparation plant samples, are produced by multistage mechanical sampling systems. Other samples may be produced from single-stage samplers. As a result, laboratories can receive samples in a wide range of conditions, most importantly sample mass, moisture content and particle size distributions. Sample preparation procedures have to be tailored to suit the samples and the proposed testing and analyses procedures that the sample has been collected for.

In some instances the particle size reduction may be omitted before sample subdivision, for example at the first stage after collection of the primary increment. However, generally before subdivision (subsampling) the particle size should be reduced.

In each case at every stage, the process recognises the relationships between the number of increments, sample mass and particle size to sampling variance, as each stage is a standalone sampling exercise.

Hammers mills comprise a set of swinging hammers attached to a rotating shaft (Fig.5.22). Typically, they are fed a 4mm top size coal to produce analysis samples with >95% passing 0.212mm. They have a device for feeding the coal into the mill. This is often a screw-type feeder. They also usually have a screen on the outlet to ensure that the entire sample achieves a specific top size. Hammer mills tend to generate excessive fines and should not be used in some instances, such as preparation of samples for petrographic analysis and Hardgrove grindability index determination.

Ring mills comprise a cylindrical canister and lid, a steel ring, and a smaller steel cylinder that fits inside the canister (Fig.5.23). The coal is placed in the canister with the ring and the cylinder, and the lid is attached. This is then placed in a jig that moves the canister in a circular motion. The movement of the various metal components within the canister crushes the coal. There is some concern that these mills can become heated and that this may affect the coal quality, particularly CSN values. This type of mill is particularly useful for crushing low mass samples as sample loss is kept to a minimum. Automated ring mills have been in use in laboratories handling large sample volumes to ensure consistent milling and improved productivity.

Roll crushers are comprised of two steel cylinders (Fig.5.24). The coal is crushed as it passes between the cylinders. This type of crusher is useful when preparing samples with a minimum of fines generation.

Incremental division is a manual method of subdivision that can provide precise subsamples. This method requires that the coal is well mixed prior to division. The coal is spread onto a flat surface in the form of a rectangle in a thickness approximately three times the nominal top size of the sample. A grid pattern is marked out on the sample (usually composed of at least 20 rectangles in a 54 grid) and a single increment is obtained from each square. The increment is removed from the sample using a suitable scoop and bump plate to prevent the increment from falling out of the scoop. Incremental division is used almost exclusively in obtaining the final (0.212mm) laboratory sample after the hammer mill operation, because of excessive dust losses by other methods.

Rotary sample division (rsd) is the most common method for subdivision of large samples in coal laboratories. The rotary sample divider (Fig.5.25) comprises a feed hopper, a device for feeding the coal at a constant rate (usually a vibratory feeder) and a number of sector-shaped canisters formed into a cylinder on a rotating platform. The uniform coal stream produces a falling stream of coal that is collected in the rotating canisters, dividing the sample into representative parts.

As the coal particles move through the feed hopper there is a high potential that some segregation and grouping will occur. To counter the effect that this may having on sample preparation variance it is advisable to ensure that each canister cuts the falling stream at least 20 times, i.e. there are at least twenty rotations of the turntable as the coal flows into the canisters. Additionally, it is a good practice to combine material collected in two or more canisters to form the divided increment or subsample. When doing so, canisters that are opposite each other in the rotary sample divider should be selected for recombination. The machine pictured in Fig.5.25 is set to divide a sample into eight divisions. If the requirement was to extract a quarter of the sample for analysis, two of the 1/8th divisions would be recombined.

Riffles (Fig.5.26) are less regularly used in laboratories. Riffles divide the coal into halves by allowing the coal to fall through a set of parallel slots of uniform width. Adjacent slots feed opposite containers. The width of the slots should be at least three times the nominal top size of the coal. There should be at least eight slots for each half of the riffle.

Fractional shovelling may be used for subsampling when a large rotary sample divider is not available. In this process, the coal is formed into a conical heap. Successive shovels of coal are removed from the base of the heap and are placed into daughter heaps. The shovels of coal should be allocated consecutively and systematically to each daughter heap.

Shredding rubber waste reduces the volume of used tires. Generally, the cost of shredding increases with the need to obtain pieces as small as possible. For grinding, rubber wastes are initially processed through mechanical cutters, roll crushers and screw shredders. To obtain finer particles, shear crushers and granulators are used. The final processing of rubber wastes is with high-temperature shredding equipment, such as rotary shredders, where degradation occurs during compression simultaneously with shear and wear (Mikulionok, 2015). In the initial phase, shredding rubber wastes results in dimensions of approximately 7.6210.16cm. These pieces are then placed in cutters that reduce the size to 0.630.63cm (Rafique, 2012).

Granulators are used in the second step of the recycling process, where pieces of waste tyres are grinded in the large-sized granulators to produce a large quantity of granules. The use of pulverises can reduce the rubber granulated material into fine powder. The rubber particles size can range from a few micrometres up to centimetres.

Rotary Breakers (Fig. 1). The rotary breaker serves two functionsnamely, reduction in top size of ROM and rejection of oversize rock. It is an autogenous size-reduction device in which the feed material acts as crushing media.

Roll Crusher. For a given reduction ratio, single-roll crushers are capable of reducing ROM material to a product with a top size in the range of 20018mm in a single pass, depending upon the top size of the feed coal. Double-roll crushers consist of two rolls that rotate in opposite directions. Normally, one roll is fixed while the other roll is movable against spring pressure. This permits the passage of tramp material without damage to the unit. The drive units are normally equipped with shear pins for overload protection.

Process is designed to reduce the size of large pieces with minimum production of dust. Two main types of breakers are used in Great Britain, viz. (a) Pick Breaker and (b) Bradford Breaker. Other crushers commonly used are jaw crushers, roll crushers, disc crushers, cone crushers and hammer crushers.

Pick breakerdesigned to imitate the action of miners' picks. Strong pick blades are mounted rigidly on a solid steel frame moving slowly up and down. Coal passes under the picks on a slowly moving horizontal plate conveyor belt. The amount of breakage is roughly controlled by the height to which picks are raisedupper limit is 0.5 m Typical performances: 450 ton/hr with a 2-m-wide machine. Size reduction from 500 mm to 300 mm. Several machines may be placed in series, with screens in between to remove fines. Main advantageminimum production of fines can be achieved. Fines production is controlled by the diameter and spacing of picks. Reduction in diameter and increase in spacing, decrease the proportion of fines.

Bradford breakerScreens break and removes large pieces of accidental material, e.g. pit props, chains or tramp iron, in one operation. Consists essentially of a massive cylindrical screen or Trommel, with fins fitted longitudinally inside the screen. These raise the lumps of coal as the cylinder rotates, until they fall, break, and are screened. Unbroken material passes out of the end of the cylinder. Production of fines is also small. Capacity of machine: up to 600 ton/hr.

Blake jaw crusher. Consists of a heavy corrugated crushing plate, mounted vertically in a hollow rectangular frame. A similar moving plate (moving jaw) is attached at a suitable angle to a swinging lever, arranged so that the reciprocating movement opens and closes the gap between the plates, the greater movement being at the top. The machine is available with top opening up to 2 2.7 m. Usual capacity up to 300 ton/hr. Horsepower required: up to 150.

Corrugated and toothed roll crushers. Two heavily toothed, or corrugated, cylindrical rollers (Fig. 10.1) are mounted horizontally and revolve in opposite directions. (Towards each other at the top side or nip, one being spring loaded.) Alternatively, a single roll may revolve against a breaker plate. Capacity of a 1.5 m-long machine with a 300 mm opening and roll speed 40 r.p.m. is about 350 ton/hr, with a power consumption of about 200 h.p. Best results are obtained by the use of several rolls in series, with screens between.

Run-of-mine coal produced by mechanized mining operations contains particles as small as fine powder and as large as several hundred millimeters. Particles too large to pass into the plant are crushed to an appropriate upper size or rejected where insufficient recoverable coal is present in the coarse size fractions. Rotary breakers, jaw crushers, roll crushers, or sizers are used to achieve particle size reduction. Crushing may also improve the cleanability of the coal by liberating impurities locked within composite particles (called middlings) containing both organic and inorganic matter. The crushed material is then segregated into groups having well-defined maximum and minimum sizes. The sizing is achieved using various types of equipment including screens, sieves, and classifying cyclones. Screens are typically employed for sizing coarser particles, while various combinations of fine coal sieves and classifying cyclones are used for sizing finer particles. Figure 2 shows the typical sizes of particles that can be produced by common types of industrial sizing equipment.

The sponge masses as produced by vacuum distillation have to be prepared before melting. The nine ton mass of sponge has to be crushed to about 12mm size pieces. The sponge in contact with retort wall and the push plates have a high likelihood of contamination with iron and nickel since these metals are soluble in titanium. The top of the mass may also have some contamination of iron and nickel from reaction with the radiation shield and substoichiometeric chlorides. To remove this contamination the outer skin of the sponge mass is removed by use of powered chisels. This material is downgraded from aerospace use and used in less critical applications. The sponge mass then is sliced radially to one to 5cm sections with a large guillotine or similar blade. The bottom section of the mass is removed first as this likely has the most amount of iron incorporated into the sponge. The sponge mass is removed from the working table, so this material can be segregated from the balance of the mass. At this point the mass is placed back on the table, sliced and then sent to a crushing circuit. Titanium sponge is malleable material, thus traditional mineral processing equipment such as roll or jaw crushers are not as effective as high shear shredding machines such as rotary shears or single rotor/anvil shears in preparing sponge with limited very fine particle generation.

Dust generation in the crushing process is a very important aspect of operation. Control of the dust by collection and washing of equipment on a periodic basis is very important to reduce the risks of fire in the processing of sponge. Care has to be taken to avoid working on equipment when dust present as titanium metal fires are difficult to extinguish; a class D extinguisher or rock salt are used to suppress the first. The high temperature of the fire and the low melting point of iron-titanium eutectic can result in melting of equipment, supports or piping in these plants if a fire does occur.

The core of the sponge mass has the lowest level of metal contamination. To harvest the material for applications that need low iron and low nickel levels, it is necessary to core the mass. This is done in several ways; the mass can be upended and the guillotine blade can be used to remove thick layers of outer skin, or chisels can be used to remove the outer layers. Control of the lot by separation during the crushing campaign is used to separate the high-purity products from the normal grades of sponge. Control of the nickel level in the magnesium used in the reduction is also important. Removal of as much stainless steel in piping, retorts and metal reservoirs is also important, as nickel in the magnesium will be incorporated into the sponge. Small concentrations of nickel in magnesium can take a long time to be purged from the process. Control of the quality of magnesium used for make up in the VDP process is as important, as some magnesium can be contaminated with nickel during production. Iron is not as significant an issue as its solubility in magnesium is low.

dual roll crushers, how they function

dual roll crushers, how they function

Roll crushers have a theoretical MAXIMUM reduction ratio of 4:1. If a 2 inch particle is fed to the roll crusher the absolute smallest size one could expect from the crusher is 1/2 inch. Roll crushers will only crush material down to a minimum particle size of about 10 Mesh (2 mm). A roll crusher crushes using compression, with two rolls rotating about a shaft, towards the gap between the rolls. The gap between the rolls is set to the size of product desired, with the realization that the largest feed particle can only be 4 times the gap dimension. The particles are drawn into the gap between the rolls by their rotating motion and a friction angle formed between the rolls and the particle, called the nip angle. The two rolls force the particle between their rotating surface into the ever smaller gap area, and it fractures from the compressive forces presented by the rotating rolls. Some major advantages of roll crushers are they give a very fine product size distribution and they produce very little dust or fines. Rolls crushers are effectively used in minerals crushing where the ores are not too abrasive and they are also used in smaller scale production mining of more abrasive metal ores, such as gold. Coal is probably the largest user of roll crushers, currently, though. Coal plants will use roll crushers, either single roll or double roll, as primary crushers, reducing the ROM coal. Usually, these crushers will have teeth or raised forms on the face of the roll. (Roll crushers used for minerals and metal ores have smooth faced rolls.)

The particles are drawn into the gap between the rolls by their rotating motion and a friction angle formed between the rolls and the particle, called the nip angle. The two rolls force the particle between their rotating surface into the ever smaller gap area, and it fractures from the compressive forces presented by the rotating rolls. Some major advantages of roll crushers are they give a very fine product size distribution and they produce very little dust or fines. Rolls crushers are effectively used in minerals crushing where the ores are not too abrasive and they are also used in smaller scale production mining of more abrasive metal ores, such as gold. Coal is probably the largest user of roll crushers, currently, though. Coal plants will use roll crushers, either single roll or double roll, as primary crushers, reducing the ROM coal. Usually, these crushers will have teeth or raised forms on the face of the roll. (Roll crushers used for minerals and metal ores have smooth faced rolls.)

roller crushers in iron mining, how does the degradation of hadfield steel components occur? - sciencedirect

roller crushers in iron mining, how does the degradation of hadfield steel components occur? - sciencedirect

The performance of the crusher steel component is a function of abrasion-impact process.Two wear/damage scales: micro- and macro scales were observed.Dynamic recrystallization on the working surface of the Hadfield steel was detected.Mechanical twinning was the main deformation mechanism.Crack propagation was observed trough with carbides at the grain boundaries.Cracks propagated along the grain boundaries related to the (111) orientation.

This work shows, for the first time, a systematic wear and damage analysis on a novelty roller crusher component used in the iron ore mining industry. Crusher suffers from complex abrasive-impact load during the comminuting the mineral ore in processing plants, which induce severe damage and defects that can result in a decreased performance or in a crusher breakage. The wear mechanisms and the extent of deformation have been studied by microhardness measurements, optical microscopy (OM), scanning electron microscopy (SEM) including electron backscattering diffraction (EBSD) and transmission electron microscopy (TEM). It was found that the abrasive-impact contact causes a significant hardness increment of over 700HV, around three times than initial state of the base material, and the strain hardening extends up to a depth in the extremely deformed region above 18mm from the worn surface. SEM results of worn surfaces showed the impact and abrasion damages. Microstructure cross-section analyses exhibited the deformed microstructure is composed of bands and deformation twins. Also, it was observed the presence of crack propagated along with the large carbides at the grain boundaries. EBSD analysis of cracked and non-crack areas revealed that the high-distorted Taylor factor grains accompanied by grains oriented {111} parallel to the abrasive-impact dynamic load direction were susceptible to fatigue crack formation and propagation. Near to the cracks, a significant increase in dislocation density was found compared to other deformed regions, suggesting that these regions had a high level of stored energy resulting in an exhaust of the ability of plastic deformation. TEM results confirm the formation of nanoscale grains on the deformed surface layer.

how crusher works | howstuffworks

how crusher works | howstuffworks

Crusher made its debut in true monster-truck style: The two prototypes entered a Carnegie Mellon University building to blaring music and flashing lights. One Crusher stood by while its counterpart proceeded to roll over and crush piles of cars that would have most monster trucks backing up with their tails between their legs. Crusher is no typical truck. It can drive right over a 4-foot vertical wall while carrying 8,000 pounds of cargo.

Crusher is an unmanned ground vehicle (UGV) funded by DARPA and designed by Carnegie Mellon's National Robotics Engineering Center (NREC). The thrust of the Crusher project which builds on another NREC-designed UGV called Spinner (Crusher is sometimes called Spinner version 2.0) is pretty much the thrust of all of the military-funded research and development in the UGV world right now: increased perception capabilities, autonomy and ruggedness. The U.S. Army would like few things more than an unmanned, silent tank that can carry limitless payload, defend itself against the enemy and speed unfettered across terrain that would have the Hummer curled up in fetal position.

The Crusher probably will never see mass production. The cost would be too high (the designers don't even quote a number). It's designed as a functioning prototype to test various technologies the NREC is developing as part of a program called UPI.

UPI stands for Unmanned Ground Combat Vehicle PerceptOR (off-road) Integration, a DARPA-funded mouthful that encompasses experiments to "assess the capabilities of large scale, unmanned ground vehicles (UGV) operating autonomously in a wide range of complex, off-road terrains" [ref]. The 6.5-ton Crusher weighs nearly 30 percent less than Spinner and can carry more cargo. The only thing the NREC left out of Spinner's upgrade is the ability to keep on truckin' if it's flipped upside down. No word on why that cool function disappeared, although logic would suggest it was either to make some of Crusher's other upgraded functions possible or to cut a high-cost capability that may not be crucial to UPI's main mission.

According to the NREC, Crusher's technology is six to 10 years from real-world implementation. While smaller, human-controlled robots have made it onto the battlefield already (see How Military Robots Work), massive, unmanned robots like Crusher are still in laboratories. The complexity of the perception and control systems necessary for a large-scale robot to handle unknown terrain and conditions are still in the research-and-development stage. Crusher's perception and navigation systems are prototypes intended as test platforms for increasingly innovative approaches to ground combat vehicles that require no human input to carry out their mission.

In the next section, we'll take a look at some of those systems. Since Crusher is first and foremost a military project, complete details aren't available for the general public, but HowStuffWorks has managed nonetheless to find out some interesting information.

Crusher's skeleton is made of aluminum and titanium. Its hull is an aluminum space frame (an open structure of connecting rods) with ultra-sturdy titanium nodes joining the rods for added strength in the likely event of collisions with large, hard objects. Immediately below the hull is a skid plate - basically a suspended, shock-mounted steel "bumper" that stands as a first-defense, protecting the hull from initial contact with the likes of boulders, tree stumps and steps.

To keep it moving over obstacles and generally unfriendly terrain, Crusher sports a six-wheel, all-wheel-drive system powered by a hybrid diesel-electric setup that allows for nearly silent operation - a handy characteristic in recon work. A 78-horsepower, turbo-diesel engine acts as a generator in the system, outputting a continuous 58 kilowatts (kW) of power to charge Crusher's 300-volt, 18.7-kW, lithium-ion battery pack. The batteries in turn run six 210-kW electric motors, one situated in each of the six wheel hubs. Each motor produces 282 horsepower. Like most hybrid-electric power systems, Crusher makes use of regenerative braking to return some power to the batteries each time it slows down (see How Hybrid Cars Work to learn about regenerative braking). The vehicle can run on silent battery power alone for 2 to 10 miles (3 to 16 km) depending on speed and cargo load.

Since each wheel is independently powered, if one or two die, Crusher can keep going. It needs only four of the six wheels to maintain its capabilities. And if it finds itself in sudden need of a turnaround -- say, surrounded on three sides by unpassable barriers - it can use its skid-steer ability, a turning radius of zero, to quickly about-face with no wiggle room at all.

To fit under low-hanging obstacles, face rocky terrain or better hide from the enemy, Crusher has a zero-to-30-inch (76-cm) adjustable ride height. In addition to height adjustment, Crusher's suspension can travel a full 30 inches to absorb shock, and it features adjustable stiffness for varying ground conditions. We were able to locate an under-the-hood view of Spinner, Crusher's predecessor - remember that Crusher is an upgraded version of Spinner 1.0:

Crusher's powerful frame, six-wheel-drive setup and extreme suspension capabilities enable the UGV to travel at high speeds, currently up to 26 mph (42 kph), over difficult terrain, facing obstacles like ditches, boulders, steep inclines and vertical barriers up to 4 feet, all without missing a beat.

Sturdiness, power and silence make Crusher an ideal scouting tool, but it's primarily the UGV's autonomy system that DARPA has so far shelled out $35 million to develop. The NREC hasn't released much detailed information about the UPI system, but says that "this technology spreads sensing abilities across the entire vehicle to help balance its perception and also support vehicle areas that may be less adept at sensing the environment. The [sensing] software will also let Crusher 'learn' and apply previously gathered information to new obstacles."

We do know that the perception hardware consists mainly of LADAR (laser detection and ranging) units and camera arrays. A LADAR unit sends out a laser beam to scan an area and measures how long it takes for the beam to be reflected back to the unit's laser sensor. Crusher has eight of these units - four scanning the environment horizontally and four scanning vertically. It uses six pairs of stereo-vision cameras for depth perception and four color cameras to apply a color pixel to each point of distance determined by the LADAR sensor.

The most recent incarnation of Crusher features an 18-foot telescoping mast for collecting data from a higher vantage point. The mast may incorporate parts of the LADAR and camera assembly seen above, or it may simply add an additional set of sensors to the perception system.

With all of the LADAR and camera data combined, Crusher's onboard CPU creates a 3-D picture of the landscape in which Crusher is traveling. The CPU is a 700-MHz Pentium 3 that controls Crusher's mechanical activities and runs the navigation software that handles sensor-data processing. An inertial measurement unit (IMU) detects Crusher's altitude, position and direction of movement using a combination of accelerometers (tilt sensors) and gyroscopes, so Crusher is always aware of its own motion and position relative to the landscape. The UGV also has a built-in GPS receiver and computer-based GPS database that includes pre-programmed terrain data.

So far, field experiments have shown that Crusher is well on its way to true autonomy. In testing, Crusher moved from GPS waypoint to GPS waypoint spaced more than 0.6 miles (1 km) apart without any outside control. Using its perception and navigation systems, Crusher can react to obstacles on the fly - it doesn't need an operator to tell it what to do when it hits something. It can climb an incline greater than 40 degrees, drive right over a 4-foot step and cross an 80-inch trench using its own decision-making capabilities. The trench-crossing ability is especially cool - Crusher's tires are mounted in such a way that they can drop down to support the vehicle while it's crossing a gap.

The size and weight specifications mean that a single C-130H cargo plane can carry two Crushers into battle anywhere in the world. As of August 2006, Crusher has been fitted with a Rafael Mini Typhoon mount that holds a .50 caliber rifle, pointing to the possibility that combat roles may become an increasingly prominent focus in the development of autonomy technology for military vehicles. In the next section, we'll take a look at the future of the Crusher prototype and find out how it fits in with the overall trend in military research and development.

As of 2006, the U.S. military has deployed approximately 4,000 battle robots for active duty. The military uses these robots primarily to "sniff out" bombs and clear buildings and other enclosed structures. The Army's Future Combat Systems (FCS) program is looking to spend about $300 million to fund updates to expand the roles of battlefield robots. The FCS seeks robotic mules that can carry cargo alongside troops over uneven terrain and much larger unmanned vehicles that can operate with no human input to scout areas and patrol borders, sending crucial data back to troops. If these large, autonomous vehicles can also carry huge payloads over difficult terrain without losing speed, that'd be an added bonus. Crusher or something like it would be ideal in the latter roles.

Crusher itself will probably not see deployment. It's mostly a research project and will be in testing and experimentation until 2008. At that time, the NREC will turn the Crusher technology over to DARPA so it can be applied to related projects, most of which fall under the domain of the Future Combat System. The FCS is running development programs like the Armed Reconnaissance Vehicle (ARV), which aims to realize a fully autonomous, battle-ready vehicle for reconnaissance missions; and the Autonomous Navigation System (ANS), an overarching program to develop common-platform autonomy capabilities for a wide range of military robots. The overall goal of FCS is seamless integration of both manned and unmanned vehicles, ground and air, into a structure that can be managed via a single, web-like control system.

By way of FCS, we may see Crusher-like vehicles supporting troops in battle operations in five to 10 years. They'll most likely start out in reconnaissance roles and then transition into combat, supporting troops as opposed to replacing them. But Crusher's cutting-edge autonomy technology is not military specific. The NREC envisions and has in the works research projects that utilize the systems developed for Crusher in civilian applications. In a decade, we could see autonomous vehicles performing risky tasks in areas like farming, mining and construction, ultimately transferring some of the danger faced by humans in these fields onto replaceable robotic counterparts that feel no pain.

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