ROLL

CRUSHERS

SIZE REDUCTION SIZE REDUCTION INVOLVES REDUCING THE SIZE OF PARTICLES SO AS TO GET

MORE PRODUCTS.

LAWS INVOLVED IN SIZE REDUCTION ARE : RITTENEGER’S LAW ,KICK’S LAW

AND BOND’S LAW .

FORCES INVOLVED IN SIZE REDUCTION ARE IMPACT, COMPRESSION,

ATTRITION AND SHEARING.

TYPES OF CRUSHERS Crushers are classified according to the stage of crushing which they

accomplish, such as: Primary,Secondary,Tertiary

A primary crusher receives the stone directly from a quarry after blasting,

and produces the first reduction in size.

The output of the primary crusher is fed to a secondary crusher, which

further reduces the stone size. Some of the stone may pass through four or

more crushers before it is reduced to the desired size.

The degree of breakage is spread over several stages as a means of

closely controlling product size and limiting waste material.

As stone passes through a crusher, the reduction in size may be expressed

as reduction ratio.

The reduction ratio is the ratio of crusher feed size to product size.

ROLL CRUSHER Roll crushers are used for producing additional reductions in the sizes of stone after the

output of a quarry has been subjected to one or more stages of prior crushing.

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 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.

ROLL CRUSHER CIRCUIT DIAGRAM

SINGLE ROLL CRUSHERS

DOUBLE ROLL CRUSHER Working Principle and Structure of Double Roller Crusher

1.this series of roll crusher is mainly formed by the roller, roller support bearing, compression

and adjusting device, drive components etc.

2.the adjustment of the particle size: between the two rollers equipped with adjustment

device like pads or wedge.The wedge-shaped device has a adjusting bolt on top, when the

adjustment bolt pull up the wedge, the wedge will push the

movable roller away from the fixed roller,then the gap

between two rollers is larger and produce larger particle

size. When the wedge falls down, with the effect of the

compression springs, the movable roller makes the gap

become smaller between two rollers and thus produce

the smaller particle size. Pad device can adjust the output

size by changing the quantity of the pads or its thickness,

Adding more pads,larger gap between two rollers, andwhen reducing the pads,it comes the smaller gap and

smaller output size.

3.drive device is composed of two electric motors.V-belt drags the rollers

through drive of the grooved pulley, move and rotate in the relative direction.

In the crushing, the materials enter the feed opening and through the rollers,

rolled and grinded, the finished products will discharge from under the

chassis.

4.for safety, drive part should install the security cover according to the actual

situation respectively.

Application of Double Roller Crusher

The double roll crusher is applied in the industry of cement, chemical,

electric power, metallurgy, building materials, refractories and other sectors

for crushing medium hard materials such as medium and fine crushing of

limestone, slag, coke, coal and other materials.It is more superior than

ordinary crushers especially in the construction Materials Industry like pisolite

and greenbean shake production

SMOOTH ROLL CRUSHERS

TOOTHED ROLL CRUSHER CONTAIN 1 OR 2 CURVED ROLL WORKING AGAINST A STATIONARY CURVED

BEAKER PLATE

THEY ARE MORE VERSATILE THAN SMOOTH ROLL CRUSHER BUT CANNOT

HANDLE VERY HARD SOLIDS

THEY OPERATE BY COMPRESSION,IMPACT AND SHEAR AND SO IT CAN

REDUCE MUCH LARGER PARTICLES

SUITABLE FOR FRIABLE AND BRITTLE MATERIALS LIKE COAL, SOFT LIMESTONE,

SLAG,CLAY ETC

CAPACITY OF ROLL CRUSHERThe capacity of a roll crusher will vary with:

The kind of stone

The size of feed

The size of the finished product

The width of rolls

The speed at which the rolls rotate

The extent to which the stone is fed uniformly into the crusher.

POWER CONSUMPTION OF ROLL CRUSHERS

WITHIN THE SAME REDUCTION RATIO POWER CONSUMPTION OF ROLL CRUSHER VARY WIDELY

THE POWER REQUIRED COULD BE GIVEN BY GENERAL EQUATION :

ANGLE OF NIP

PROBLEMQUESTION

IF CRUSHING ROLLS, 1M IN DIAMETER ,ARE SET SO THAT THE

CRUSHING SURFACES ARE 12.5mm APART AND THE ANGLE OF NIP IS

31.WHAT IS THE MAXIMUM SIZE OF PARTICLES THAT SHOULD BE FED TO

THE ROLLS ?

ANSWER

THE PARTICLE SIZE MAY BE OBTAINED FROM :

cos ∞ =(r1+b)/(r2+b)In this case, 2 ∞ = 31

cos ∞ = 0.964b = 12.5/2 =6.25 mm = 0.00625 mr1 = ½ = 0.5 m

0.964 = (0.5 + 0.00625)/(0.5+r2)r2 = 0.025 m = 25mm

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