Machine study of laboratory Rolls-crushers.

Theory:-

Rock crusher, also known as ore crusher, plays a vital part in crushing various types of rocks and ores. There are two types of rock crushers in actual production, that is, primary crusher and secondary crusher. Secondary crushers mainly handle rocks of smaller particle size that have already been impacted and crushed from their original size. In recent years, with the rapid development of infrastructure projects, rock crushers have found more applications in various fields and industries, such as mining, chemical industry, road construction, metallurgy, construction and so on. In this passage, several types of commonly used secondary crushers will be listed as follows.

1. Impact crusher:-

According to the nature of the materials to be crushed in actual production, impact crushers can be used for secondary crushing as well primary crushing. During operation, materials will be first fed into the crushing chamber for continuous and repeated impacting and crushing by large hammers. When the materials have been crushed to the proper particle size, they will finally be discharged from the lower part of the discharge opening. In general, impact crushers can be divided into two types, including horizontal shaft impact crusher (HSI for short), which uses hammers that swing on a rotating shaft, and vertical shaft impact crusher (VSI for short), which “throws” the material against a surface by means of the rock’s velocity to break it apart.

2. Cone Crushers :-

As a type of frequently used secondary crusher, cone crusher’s working principle is quite similar to that of the gyratory crusher. Nevertheless, the difference is that the crushing chamber in a cone crusher isn’t as steep as it is in a gyratory crusher and the positions of the different crushing zones are more parallel.

3. Roll Crusher:-

Name of roll crusher properly indicates its operating mode. The rocks and ores to be crushed will be processed between two large steel wheels, which press down on the materials and then crush the materials into smaller particle sizes to meet customers’ specific requirements.

 

Roller mills are suitable machines for fine crushing, which leads to extreme exposure of the feed in case of somewhat coarse intergrown ore avoiding further fine milling.The roll crusher equipment is a very potential force in market development of the crushing plant, roll crusher plays an important role in the process of crushing materials, the material is repeatedly crushed by the broken parts. Compared with hammer crusher and impact crusher, in the crushing of materials, the roll crusher equipment is more suitable for crushing brittle materials. Roll crusher equipment has large crushing ratio and can up to 50. This roll crusher can be used to crushing limestone in cement industry. Any company and business that use of the roll crusher equipment or are using the production of roll crusher has a deeper understanding of the improvement the utilization of crushing materials. Spare parts of roll crusher equipment is easy to replace, and has a corresponding reduction in maintenance expense. This machine is suitable for a very large hardness of materials or used for soft materials. Roll crusher equipment in daily use, the maintenance of the machine must be aware of. In particular, the operators need to pay attention to maintenance of the roller of roll crusher equipment, because the easiest to wear and consumption is the roller.

OPERATING PRINCIPLE:-

The feed material is crushed between two counter-clockwise rotating rollers to a degree of fineness allowing it to fall through a slit at the bottom. In the event that the pressure becomes too great, the rollers deflect outwardly, increasing the gap between them and consequently also the final grain size.

AREAS OF APPLICATION:-

Crushing of brittle ore in preparation of hydromechanic gravimetric sorting of medium-sized grain fractions.

REMARKS:

• Roll crushers are known for producing a ground product with a very low proportion of fines.
• 30 - 200 g of hard-steel wear per ton throughput depending on hardness and tenacity of the feed material.
• The roll crushing of hard minerals (igneous rocks, hard ores, gravel sediments) uses smooth Jaws, whereas the rollers for crushing medium hard or soft material (e.g. Iimestone, anhydrite, sedimentary Iron ores, etc. or salts, clays, soft brown coal, etc.) are fluted or serrated.
• The roller diameters should equal approx. 20 times that of that largest grain-size contained in the fee.

SUITABILITY FOR SMALL-SCALE MINING:-

Roller mills are suitable machines for fine crushing, which leads to extreme exposure of the feed in case of somewhat coarse intergrown ore avoiding further fine milling.

 

Manufacturer:- Millan, Volcan, Denver

TECHNICAL DATA:

Dimensions:

approx. 0.7 × 0.7 × 1.5 m, roller die 25 cm or more

Weight:

approx. 350 kg

Extent of Mechanization:

 fully mechanized

Power Required:

starting at approx: 5 kW

Form of           Driving Energy:

electric motor, internal combustion engine

Alternative Forms:

possibly hydromechanic

Mode of Operation:

continuous

Throughput/Capacity:   

approx. 700 kg/in

Technical Efficiency:

degree of comminution between 3:1 and 4:1

ECONOMIC DATA:

Investment Costs:

Denver mill, 2 t/h: 18.900 US $, Volcan mill, 500 kg/h: 5000 US $, Millan mill approx. 6500 DM including motor fob La Paz

Operating Costs:

labor costs, energy costs, minimal wear  

Side View of Machine:-

            

Crushers and their types

Crusher:-

A crusher is a machine designed to reduce large rocks into smaller rocks, gravel, or rock dust. Crushers may be used to reduce the size, or change the form, of waste materials so they can be more easily disposed of or recycled, or to reduce the size of a solid mix of raw materials (as in rock ore), so that pieces of different composition can be differentiated.

Types of crushers:-

Crushers are divided into two main categories on the basis of crushing property.

• Primary crusher
• Secondary crushers

Primary Crushers:-

The primary crusher mainly refers to the jaw crusher and impact crusher. They reduce 1.5 meter feed to approximately 10-20 cm particles.In the designing of a crushing plant of any nature and size, to select the right type and size of primary gyratory crusher is of great significance. Generally speaking, this machine is the largest and most expensive single item in the plant; a mistake in the choice may lead to a full replacement. Therefore, you have to pay close attention when choosing primary crushers. The following tips may be helpful for the selection of primary crushers.

• The name, hardness, humidity of material
• Pay attention to the hourly, daily or yearly capacity
• The discharging granularity or the final particle size of the finished products
• Crushing machine type and size
• Feeding method

Secondary Crushers:-

Secondary crushers mainly handle rocks of smaller particle size that have already been impacted and crushed from their original size. They reduce feed in .5-2 cm particles.In recent years, with the rapid development of infrastructure projects, rock crushers have found more applications in various fields and industries, such as mining, chemical industry, road construction, metallurgy, construction etc.

 

Table Of Different Types Of Crushers:-

 

 

Jaw Crusher:-

A jaw or toggle crusher consists of a set of vertical jaws, one jaw being fixed and the other being moved back and forth relative to it by a cam or pitman mechanism. The jaws are farther apart at the top -than at the bottom, forming a tapered chute so that the material is crushed progressively smaller and smaller as it travels downward until it is small enough to escape from the bottom opening. The movement of the jaw can be quite small, since complete crushing is not performed in one stroke.

Gyratory Crusher:-

A gyratory crusher is similar in basic concept to a jaw crusher, consisting of a concave surface and a conical head;both surfaces are typically lined with manganese steel surfaces. The inner cone has a slight circular movement, but does not rotate; the movement is generated by an eccentric arrangement. As with the jaw crusher, material travels downward between the two surfaces being progressively crushed until it is small enough to fall out through the gap between the two surfaces.

 

 

Cone Crusher:-

 

A cone crusher is similar in operation to a gyratory crusher, with less steepness in the crushing chamber and more of a parallel zone between crushing zones. A cone crusher breaks rock by squeezing the rock between an eccentrically gyrating spindle, which is covered by a wear resistant mantle, and the enclosing concave hopper, covered by a manganese concave or a bowl liner. As rock enters the top of the cone crusher, it becomes wedged and squeezed between the mantle and the bowl liner or concave. Large pieces of ore are broken once, and then fall to a lower position (because they are now smaller) where they are broken again. This process continues until the pieces are small enough to fall through the narrow opening at the bottom of the crusher.

Impact Crusher:-

 

mpact crushers involve the use of impact rather than pressure to crush material. The material is contained within a cage, with openings on the bottom, end, or side of the desired size to allow pulverized material to escape. This type of crusher is usually used with so ft and non-abrasive material such as coal, seeds, limestone, gypsum or soft metallic ores. There are two types of impact crushers: horizontal shaft impactor and vertical shaft impactor.

Horizontal shaft impactor (HSI) / Hammer mill:-

The HSI crushers break rock by impacting the rock with hammers that fixed upon the outer edge of a spinning rotor. The practical use of HSI crushers is limited to soft mat erials and non abrasive materials, such as limestone, phosphate, gypsum, weathered shales.

Vertical shaft impactor (VSI):-

VSI crushers use a different approach involving a high speed rotor with wear resistant tips and a crushing chamber designed to 'throw' the rock against. The VSI crushers utilize velocity rather than surface force as the predominant force to break rock. In its natural state, rock has a jagged and uneven surface. Applying surface force (pressure) results in unpredictable and typically non-cubicle resulting particles. Utilizing velocity rather than surface force allows the breaking force to be applied evenly both across the surface of the rock as well as through the mass of the rock. Rock, regardless of size, has natural fissures (faults) throughout its structure. As rock is 'thrown' by a VSI Rotor against a solid anvil, it fractures and breaks along these fissures. Final particle size can be controlled by 1) the velocity at which the rock is thrown against the anvil and 2) the distance between the end of the rotor and the impact point on the anvil.

Mineral Sizers:-

The basic concept of the mineral Sizer, is the use of two rotors with large teeth, on small diameter shafts, driven at a low speed by a direct high torque drive system. This design produces three major principles which all interact when breaking materials using Sizer Technology. The unique principles are; The Three-Stage Breaking Action, The Rotating Screen Effect, and The Deep Scroll Tooth Pattern.

  

The Three-Stage Breaking Action: Initially, the material is gripped by the leading faces of opposed rotor teeth. These subject the rock to multiple point loading, inducing stress into the material to exploit any natural weaknesses. At the second stage, material is broken in tension by being subjected to a three point loading, applied between the front tooth faces on one rotor, and rear tooth faces on the other rotor. Any lumps of material that still remain oversize, are broken as the rotors chop through the fixed teeth of the breaker bar, thereby achieving a three dimensional controlled product size.

 

Reductoin ratio:-

It is ratio of maximum size of feed to the maximun size of product. The average number of pieces the raw feed rock is reduced into.

Reduction ratio= Maximum size of feed/Maximum size of product

Different reduction ratios are given;