Comminution-Grinding (PPT) Flashcards by RevicVince Rosales

THE OPERATION OF APPLYING
A FORCE ON THE PARTICLE TO
BREAK IT IS CALLED ____

SIZE REDUCTION

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____ IS A GENERAL TERM FOR SIZE REDUCTION THAT MAY BE APPLIED WITHOUT REGARD TO THE ACTUAL BREAKAGE
MECHANISM INVOLVED.

COMMINUTION

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FRACTURE IN THE PARTICLE
OCCURS AS A RESULT OF
____.

APPLICATION OF A FORCE

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WHEN A FORCE IS APPLIED
ON A PARTICLE, ____
WILL DEVELOP WITHIN THE
PARTICLE. WHEN THIS
STRESS EXCEEDS ULTIMATE
STRESS, THE PARTICLE WILL ____
___

STRESS

BREAK

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occurs when a force (shear force) acts parallel to
the surface of the particle.

ATTRITION OR ABRASION

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causes immediate fracture with no residual stresses.

IMPACT

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can be applied at either a fast or a slow rate. Under the conditions of slow compression, energy applied is just sufficient to load comparatively few regions of the particle to the fracture point and only a few particles result. Their size is
comparatively close to the original particle size. Under the conditions of rapid loading such as in high velocity impact, applied energy is well in excess of that required for fracture.

COMPRESSIVE FORCE

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the edges or corners of a particle will break due to the application of oblique forces, generally impact forces, on the particle.

CHIPPING

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“𝑒𝑛𝑒𝑟𝑔𝑦 𝑜𝑓 𝑏𝑟𝑒𝑎𝑘𝑎𝑔𝑒 𝑖𝑠 𝑑𝑖𝑟𝑒𝑐𝑡𝑙𝑦 𝑝𝑟𝑜𝑝𝑜𝑟𝑡𝑖𝑜𝑛𝑎𝑙
𝑡𝑜 𝑡ℎ𝑒 𝑎𝑚𝑜𝑢𝑛𝑡 𝑜𝑓 𝑛𝑒𝑤 𝑠𝑢𝑟𝑓𝑎𝑐𝑒𝑠𝑝𝑟𝑜𝑑𝑢𝑐𝑒𝑑”

RITINGGER’S LAW

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“the work input is proportional to the new
crack tip length produced in particle breakage”

BOND’S LAW

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IS THE REPRESENTATION OF THE
HARDNESS OF THE MATERIAL OR THE
RESISTANCE OF THE MATERIAL TO
BREAKING OR CRUSHING. IT ALSO
REPRESENTS THE AMOUNT OF ENERGY
THAT IS NECESSARY TO REDUCE THE
MATERIAL INTO A SPECIFIED SIZE FROM A
SPECIFIED INITIAL SIZE ALSO.

WORK INDEX

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EASE WITH WHICH
MATERIALS CAN BE COMMINUTED

ORE GRINDABILITY

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TYPES OF COMMINUTION OPERATION

CRUSHING
GRINDING

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is that operation or group of
operations in a Mineral Beneficiation
plant whose object is to reduce large
lumps to fragments, the coarsest
particles in the crushed product being
1/20 inch or more in size. The size of
coarsest particles is 1/2 inch in many
cases.

CRUSHING

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The ratio of the maximum size of the particle in the feed to the maximum size of the particle in the product.

REDUCTION RATIO

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CLASSIFICATIONS OF CRUSHER

Primary crushers

JAW CRUSHER
GYRATORY CRUSHER

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CLASSIFICATIONS OF CRUSHER

SECONDARY CRUSHER

Reduction gyratory, Cone crusher, Rolls crusher

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CLASSIFICATIONS OF CRUSHER

TERTIARY CRUSHER

SHORT-HEAD CONE CRUSHER

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CLASSIFICATIONS OF CRUSHER

FINE CRUSHER

IMPACT CRUSHER

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CLASSIFICATIONS OF CRUSHER

SPECIAL CRUSHER

Bradford Breaker, Toothed Roll crusher

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Consist of two jaw plates set at an acute angle, to
each other which forms crushing chamber.
One jaw is fixed and kept vertical, the other jaw is
a movable or swing jaw and is moved to approach
and recede alternately from the fixed jaw.

JAW CRUSHER

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has 1 toggle plate.
It has less weight and thus cheap

SINGLE-TOGGLE TYPE

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has 2 toggle
plates and can crush materials that are
brittle, tough, and abrasive

DOUBLE TOGGLE TYPE

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If the swing jaw is pivoted at
the top, it has a fixed
receiving area and variable
discharge area.

BLAKE CRUSHER

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If the swing jaw is pivoted at the bottom, it has a fixed discharge area and variable receiving area

DODGE CRUSHER

If the swing jaw is pivoted at an intermediate position, it has both variable receiving and discharge areas

UNIVERSAL CRUSHER

distance between the 2 jaw plates at the feed opening

GAPE

distance between the 2 jaw plates at the discharge opening

SET

MINIMUM DISTANCE | SA BLAKE CRUSHER NI

CLOSED SET

MAXIMUM DISTANCE | SA BLAKE JAPON NI

OPEN SET

MAXIMUM AMPLITUDE | SA BLAKE

THROW

They consist of two vertical truncated conical shells of which the outer hallow conical shell is stationary and the inner solid conical shell is made to gyrate. In a ____ the inner conical shell is pointing up and outer conical shell is pointing down

GYRATORY CRUSHER

FIXED CRUSHING SURFACE IN GYRATORY CRUSHER

CONCAVE

MOVEABLE CRUSHING SURFACE IN GYRATORY CRUSHER

MANTLE

____ is the modification of gyratory which has straight or curved heads and concaves and used for secondary crushing.

REDUCTION GYRATORY CRUSHER

The ____ is a modified gyratory. Both the outer and inner conical shells are pointing up

CONE CRUSHER

The most widely used type of cone crusher.

SIMONS CONE CRUSHER

The ____ is another type having a spherical steel head and used for tertiary crushing.

TELSMITH GYRASPHERE

❖Used for tertiary crushing. ❖Short, Flat-angle liners.

GYRADISC

Can handle clay/plastic feed material Can easily be installed in underground mines Requires less floor area Maintenance required

JAW CRUSHER

greater capacity than jaw crusher cannot handle clayey materials its large sections makes it difficult to install underground requires large floor area lesser maintenance required

GYRATORY CRUSHER

short spindle spindle is not suspended downward flare bowl spring-protected bowl

CONE CRUSHER

longer spindle suspended spindle upward flare concave no spring for concave

GYRATORY CRUSHER

____ consists of two smooth heavy horizontal cylinders revolving towards each other and the feed material is nipped between the rolls and pulled downward through the rolls by friction.

ROLL CRUSHER

____ reduce the particles by impact forces applied through sharp blows of fixed or free-swinging hammers revolving about central rotor at high speed to the free-falling particles against stationary surfaces.

IMPACT CRUSHER

# HAMMER MILL (PIVOTED) ❖Hammers can weigh up to ____ kg ❖Feed size up to ____ cm ❖Rotor speeds between ____ RPM

100KG 20CM 500-3000 RPM

# HAMMER MILL (FIXED) ❖Used for coarser crushing ~____𝑚𝑒𝑡𝑒𝑟𝑠 ❖ Rotor speed is ____ RPM ❖Feed rate ____ MT/h

1.5 METERS 250-500 RPM 1500-3000 MT/h

It consists of a slightly inclined cylindrical chamber with a perforated wall and rotates about its axis at a low rpm

BRADFORD CRUSHER

In a roll crusher, the force of compression and friction makes the particles to crush. Rolls are subjected to high pressure so that comminution takes place by compressive forces as well as by inter-particle breakage. The force applied to the crushing zone is controlled by a hydro-pneumatic springs

HIGH PRESSURE GRINDING ROLLS

Impact crushing + High-intensity grinding + multi-particle pulverizing

TIDCO BARMAC CRUSHERS

WHEN THE MATERIAL FED TO THE CRUSHER IS AT A SLOW RATE, THE INDIVIDUAL PARTICLES ARE CRUSHED FREELY

FREE CRUSHING

WHEN THE MATERIAL FED TO THE CRUSHER IS AT A HIGH RATE, THE CRUSHER IS CHOKED, AND IT PREVENTS THE COMPLETE DISCHARGE OF CRUSHED PRODUCT

CHOKED FEEDING

THE FEED MATERIAL IS REDUCED BY ONE CRUSHER. THE PRODUCT OF THIS CRUSHER IS SCREENED, AND ONLY OVERSIZE MATERIAL IS CRUSHED BY ANOTHER CRUSHER OF SMALL SIZE AS THE THROUGHPUT IS LESS

OPEN CIRCUIT CRUSHING OPERATION

THE OVERSIZE MATERIAL FROM THE SCREEN IS FED BACK TO THE SAME CRUSHER AS THE CIRCULATING LOAD

CLOSED CIRCUIT CRUSHING OPERATION

AN OPERATION USED FOR THE SEPARATION OF PARTICLES ACCORDING TO THEIR SIZES.

SCREENING

WHY USE INDUSTRIAL SCREENING?

❖Sizing and classifying materials. ❖To grade materials. ❖To prepare a closely sized feed. ❖Trash removal and media recovery. ❖Dewatering. ❖Desliming.

MATERIAL FACTORS SA SCREENING

❖BULK DENSITY OF THE MATERIAL. ❖SIZE AND SIZE DISTRIBUTION OF THE PARTICLES. ❖SIZE OF THE PARTICLE RELATIVE TO THE APERTURE. ❖SHAPE OF THE PARTICLE. ❖MOISTURE CONTENT OF THE MATERIAL.

MACHINE FACTORS SA SCREENING

❖ SIZE OF THE APERTURE. ❖ SHAPE OF THE APERTURE. ❖ SIZE OF THE SCREEN SURFACE. ❖ PERCENT OPENING AREA. ❖ ANGLE OF INCIDENCE OF THE PARTICLE ON THE SCREEN SURFACE. ❖ SPEED AT WHICH THE PARTICLE STRIKES THE SCREEN SURFACE. ❖ THICKNESS OF THE MATERIAL ON THE SCREEN SURFACE. ❖ BLINDING OF THE SCREEN SURFACE. ❖ TYPE OF SCREENING. ❖ TYPE OF MOTION GIVEN TO THE SCREEN SURFACE. ❖ SLOPE OF THE SCREEN DECK. ❖ MECHANICAL DESIGN FOR SUPPORTING AND TIGHTENING THE SCREEN DECK.

Detachment or freeing of dissimilar particles from each other (valuable mineral particles and gangue mineral particles)

LIBERATION

Contains both valuable and gangue minerals

MIDDLING PARTICLES

# TYPES OF MIDDLING FURTHER SIZE REDUCTION INCREASE LIBERATION

RECTILINEAR

# TYPES OF MIDDLING DIFFICULT TO LIBERATE

VEIN

# TYPES OF MIDDLING FURTHER REDUCTION WILL INCREASE LIBERATION BUT A SIGNIFICANT PART ARE STILL VERY HARD TO LIBERATE

SHELL

# TYPES OF MIDDLING VERY FINE REDUCTION TREATMENT

OCCLUSIONS

When the run-of-mine ore is reduced in size to grain size of valuable mineral, all the valuable mineral particles exist as free particles, no matter whether remaining particles are free or locked particles of gangue minerals.

INTERGRANULAR LIBERATION

If the physical properties of the adjacent minerals are not so dissimilar, comminution to grain size does not result in rupturing the bond between adjacent dissimilar minerals. Fracture occurs across the grains producing locked particles. Hence to detach valuable mineral, the ore is further reduced in size.

TRANSGRANULAR LIBERATION

The percent of that mineral liberated and occurring as free particles in relation to the total amount of the same mineral present intheore.

DEGREE OF LIBERATION

Localized stresses at the surface, occurs when insufficient energy is applied to cause significant fracture of the particles

ABRASION

Occurs when energy applied is just sufficient to load comparatively few regions of the particles to the fracture 25 point

CLEAVAGE

The applied energy is well in excess of which is required for fracture

SHATTER

CONSISTS OF A HORIZONTAL ROTATING STEEL SHELL SUPPORTED BY END BEARINGS ON WHICH HALLOW TRUNNIONS REVOLVE

GRINDING MILL

is the last stage of the comminution process. The particles are reduced from a maximum upper feed size of 3/8 inch, to some upper limiting product size ranging between 35 mesh and 200 mesh (420 microns and 74 microns).

GRINDING

used in Dry Grinding.

VIBRATORY FEEDER

the material is fed by gravity

SPOUT FEEDER

the entire mill feed enters the drum, and an internal spiral carries it and fed to the mill.

DRUM FEEDER

the material is fed to the drum and the scoop picks it up and fed to the mill. ____ are sometimes used in place

SCOOP FEEDER

❖ lined by replaceable liners usually made of alloy steel but sometimes of rubber. ❖ Some types of liners are smooth, shiplap, wave, wedge bar, rib, stepped, osborn, lorain, etc.

INTERIOR OF GRINDING MILL

❑Loose crushing bodies ❑Either steel balls, rods, pebbles ❑Attrition or shearing forces

GRINDING MEDIA

THE INTERNAL WORKING FACES OF MILLS CONSIST OF RENEWABLE LINERS, WHICH MUST WITHSTAND IMPACT, BE WEAR RESISTANT, AND PROMOTE THE MOST FAVORABLE MOTION OF THE CHARGE

MILL SHELL LINERS

the mill shell is rotated, and motion is imparted to the charge via the mill shell. The grinding medium may be steel rods, balls, or rock itself.

TUMBLING MILLS

the mill shell with either a horizontal or a vertical orientation is stationery and motion is imparted to the charge by the movement of an internal stirrer.

STIRRED MILLS

TYPES OF DISCHARGE

OVERFLOW GRATE DISCHARGE

CRUSHED ORE + WATER + GRINDING MEDIUM

Mill Charge

uses steel or iron balls as grinding medium. ____ usually have a length to diameter ratio of 1.5 to 1.0

BALL MILL

According to the shape of the mill, the ball mills are classified as ____ and cylindrical mills

CYLINDROCONICAL

An ____ where no balls occupy this zone during operation.

EMPTY ZONE

A ____ where no grinding takes place.

DEAD ZONE

A ____ where balls roll on each other and grinding takes place by slippage between ball layers before they are lifted.

ZONE OF CIRCULAR PATH

A ____ where the balls spread out and falldown.

ZONE OF PARABOLIC PATH

simple rolling of one ball over the other

CASCADING

FREE FALL OF BALLS

Cataracting

As the speed of the mill increases, the balls are lifted higher and a stage is reached where the balls are carried around the shell and never allowed to fall.

CENTRIFUGING

- the material is fed at both ends of the mill. - The product is discharged through a 70 circumferential port at the centre of the shell.

CENTER PERIPHERAL DISCHARGE MILL

- the material is fed at one end of the mill. - the ground product is discharged from the other end.

END PERIPHERAL DISCHARGE MILL

discharge grates are fitted through which pulp flows freely and lifted-up to the level of the discharge trunnion

GRATE DISCHARGE MILL

The material is fed at one end and the product is discharged through the other end by overflow

OVERFLOW DISCHARGE MILL

❖A ____ is a grinding mill where length to diameter ratio is 3 to 5. ❖It is also known as a pebble mill as it uses ceramic pebbles made of flint or porcelain as the grinding media.

TUBE MILL

are used when iron contamination in the product is highly objectionable such as in the manufacture of paints, pigments, cosmetics, etc.

PEBBLE MILL

❖____use coarse ore particles as grinding medium. ❖Grinding is achieved by the action of ore particles on each other when particles of ore of different sizes are rotated together in a tumbling mill.

AUTOGENOUS MILL

❖Autogenous grinding differs from grinding with metal balls or rods in that the breakage is much more confined to zones of weakness in the rock, such as ____ and ____.

CRYSTAL SURFACES AND FINE CRACKS

uses a combination of the ore and a reduced charge of balls or rods as a grinding medium to overcome the difficulties encountered in autogenous grinding.

SEMI AUTOGENOUS MILL

IS USUALLY CARRIED OUT WITH 20–35% WATER BY WEIGHT. THE CHIEF ADVANTAGES OF ____ ARE INCREASED CAPACITY (AS MUCH AS 15%) FOR A GIVEN SIZE OF EQUIPMENT AND LESS POWER CONSUMPTION PER TON OF THE PRODUCT.

WET GRINDING

____ IS USED WHENEVER PHYSICAL OR CHEMICAL CHANGES IN THE MATERIAL OCCUR IF WATER IS ADDED. IT CAUSES LESS WEAR ON THE LINERS AND GRINDING MEDIA

DRY GRINDING

IS THE TERM USED TO DESIGNATE THE SIZE OF THE GROUNDED PRODUCT IN TERMS OF THE PERCENTAGE OF THE MATERIAL PASSING THROUGH A GIVEN MESH

MESH OF GRIND

WHEN A GRINDING MILL IS FED WITH A MATERIAL, IT SHOULD BE AT A RATE CALCULATED TO PRODUCE THE CORRECT PRODUCT IN ONE PASS

OPEN CIRCUIT GRINDING

WHEN THE MATERIAL OF THE REQUIRED SIZE IS REMOVED BY A CLASSIFIER FROM THE GROUND PRODUCT TO SEND TO THE SUBSEQUENT OPERATION AND OVERSIZE IS RETURNED TO THE SAME GRINDING MILL

CLOSED CIRCUIT GRINDING

THE AMOUNT OF SOLIDS BY WEIGHT FED BACK TO THE GRINDING MILL

CIRCULATING LOAD