Sieve analysis

Aim of the Experiment: To study the sieve analysis of weighted powder sample.

Apparatus Required:

1. Laboratory model sieve shaker various mesh number.
2. Weighting Machine
3. Pan etc.

Mineral Used: 100 gm of coal powder



Theory:

Sieve analysis is more commonly known as screening. After crushing the raw material, the product obtained is very fine powder of desired size. The principle behind the screening process is differential separation of particles of sample based on size and shape.

Sieves are arranged in descending or ascending order of the mesh size. The various screen technique are Hand Screening Automatic Screening

Wet and dry Screening 

In the experiment we use automatic screening number of different automatic screen machine which are available. The machine causes a circular motion of material on screen and a below is delivered to the sieves. Once for each revolution, the frame doesn’t over load screen. It gives good result for dried materials only.
Screening process is divided in to two stages. The test sieves are designated by normal aperture which is ideal diameter of round roles of sieves.

Different types of test screening are: 

 German standard

 American standard

 Taylor standard used in USA

 British standard sieves

All these sieves are designed by mesh numberMesh Number:

 Mesh number is defined as the number of sieves/ openings per liner inch.

Importance of Sieves Analysis: 

1. It determines quality of grinding process.

2. It gives data regarding degree of liberation of valuable minerals. Efficiency of machine is known by knowing the output and can be controlled.

Procedure:

The powder sample is first weighed accurately to 100 gm and then sieves are arranged properly with the pan at the bottom end sieve no BS40 at the top. The sieve with powder is properly packed and proper stirring required and after 15 minutes the sieves are taken out. All the powder gets distributed according to the size distributionResult: Sieves analysis of a given sample of material (coal powder) is obtained and graph plotted shows that particles get distributed according to the size range of sieves used.

Discussion:

Particle gets distribution according to their size which in turn indicates how efficient the process is i. e. grinding process. It also tells us the degree of liberation. One of the hindrances to perfect the sieves analysis is adherence of extremely fine particles to coarser particles or to each other through
electrostatic action or because of moisture or dried salts.

Froth floatation technique.

Aim of the Experiment: - To study the froth floatation of given sample of Ore.

Apparatus required:- Coal(fine size), pine oil (frother), Kerosene(activator).

Theory:

It is process of rendering a mixture of finely ground minerals susceptible to gravitational separation.
This is done by selective adhesives of air bubbles to the mineral species.
The surface characteristic of a important and used as criteria for separation. The surface properties;

1) Surface tension

2) Surface energy

3) Contact angle

Some particles adhere to air bubble (air water interface) in the pulp, some to water i.e. wetted.
In this process adhesion is effective between air and small mineral particles so that the specific gravity of the minerals air associated conglomerate is less than that of pulp. This makes the conglomerate to rise in the pulp. The floating mineralized forth is then mechanically separated from the pulp.
The cause of the process of floatation is the extensive tendency of the mineral particles to adhere to air & other to water. This is due to the difference in physico chemical surface properties of particles of different minerals.In flotation the concentrate is usually transferred to the froth, leaving the gangue in the pulp (tailing). This is called direct floatation. In indirect floatation, gangue is separated in froth & concentrate sinks at the bottom.

PRINCIPLE: It is a physio- chemical separation process that whiteless the reference in surface properties of the valuable minerals and the unwanted gangue materials. The process of minerals being recovered by flotation from pulp comprises 3 mechanism-

1) Selective attachment of the air bubbles

2) Entraiment in the water which passes through the forth.

3) Physial entrapment between particles in the foloth attached to the air bubbles.

Flotation Chemical: 

Many chemicals are used in floatation process in order to

1) Modify the surface the surface of the mineral to make the hydrophobic or aero phobic. (Adhesive
to air)

2) Make forth more stable.

3) Increase the effect of chemicals (catalyst) used to make minerals hydrophobic.

4) To attain desired condition of PH in the feed pulp. Process:

1. ½ tank water

2. So gm powder fine + pine oil+ Kerosen+ Soapsolh(tank)

3. Stirring for 5 min.

4. Start compressor

5. Collect forth in a sieve (250 mesh)

6. Dry at drier

Collector:

Collectors are organic compound which when added in small quantity to the pulp absorb selectively on the mineral surface (mineral-water interface) and increase its hydrophobicity so that they can attach to the air bubble. Collectors may be ionizing or non ionizing compounds. Ionizing collector may ionize or dissociate into ions in water. Non-ionizing compounds which are partially insoluble render mineral water repellant by forming a thin film.

Comparison with Gravity Separation: 

1. Gravity separation is simple compared to forth flotation which is complex various chemicals are used to change the surface property in flotation.

2. Gravity separation in environmental friendly while forth flotation deals with dust.

3. Gravity separation can be used if the liberation takes place at a coarser size range, while forth flotation is used for fine size range.

4. Gravity separation is economical while forth flotation used expensive chemicals.

Forther:

Its main function is to produce stable forth in the process and also to maintain the PH of the pulp

Akins classifier

Aim Of The Experiment: - Classification of ore by using Akin’s classifier.

Apparatus Required: - Laboratory model Akin’s classifier.

Material: Mineral Lumps, Ore Lumps.

Theory: Akin’s classifier is used in dry grinding media. In is used in a continuous operating classifier. Akin’s classifier consists of two cylinders

Objective: - Akins classifier is widely used to control material size from Ball Mill in the beneficiation process, separate mineral sand and fine mud in the gravity concentration, and clean mud and water in washing mineral process.

Theory

Akins classifier is used in a dry grinding media. It is used in a continuous operating classifier. Akins classifier consists of two cylinders and feed is introduced from its apex. When operation is started the discharge from apex of the cylinder gives coarser particles. The coarser particle subsequently go to the extruder channels. Classifiers of this type consist of a tank having an inclined bottom, a lower overflow for fines and an elevated discharge for coarse sands, with a screw or spiral conveying element disposed in the tank for moving settled sands from the pool below the overflow level to the sands discharge.

Principle:

Classification is a method of separation process which is separates the mixing of minerals into two or more products on the basis of the velocity (depends of on the)
 (1) Specification Gravity,
 (2) Size,
 (3)Shape
with which the grain falls through a fluid medium. For fine particles wet medium is generally applied When a solid particle fall freely in vacuum micron resistance present which can’t be ignore falling in water or air. This envois resistance in releases with increase of the velocity of the particle. When equilibrium is allotted between the grain rational and fluid resistance forces, the body reaches its terminal velocity and body reaches at equilibrium rate.

Classifier consist of essentially of a sorting column in which a fluid is rising at a uniform rate which be

Overflow (Particles with terminal velocity < V)

Fluid velocity (V)
Spigot product (Particles with terminal velocity > V)

Particles introduced in the sorting column either sink or rise according to whether there terminal velocities are greater or lesser than the upward velocity of the fluid. The sorting column therefore separates the feed into two products—an overflow consisting of particles with terminal velocity lesser than the velocity of the fluid and the over flow of Spigot product of particles with terminal velocity greater than the rising velocity.

Procedure:

1kg. of mineral is taken. The minerals are fed to the classifier at a particular feed rate and start the machine and collect the data of the feed retain and overflow and under flow retain. 

Calculation:

Efficiency (E) = [(x+y)/z] X 100

Where, x = wt. of coarser particle
y = wt. of fine particle
z = wt. of the feedAnd Efficiency is always given by

Efficiency (E) = [c X (f -t)/f X (c-t)] X 100

Where, c = wt. of the overflow particle
t = wt. of the underflow particle
f = wt. of the feed.

Result:

Conclusion: In Akin’s classifier the product size rang can be changed by adjusting the velocity of feed rate. The efficiency of the classifier is usually in the range of 50 to 80%.

Wilfley Table

Aim of the Experiment: Concentration of ore with the help of Wilfley Table.

Apparatus required: Laboratory model Wilfley Table.

Theory: The shaking or Wilfiey table consist of a substantially plane surface (the deck), inclined slightly from the horizontal and shaken with an asymmetrical motion in the direction of the long axis. Asymmetrical motion means, the stroke of the table is faster in one direction and slower in opposite direction. Usually the back- stroke is faster compared to forward stoke. The wash water flows over the table at right-angle to the direction of jog. Longitudinal cleats or riffles are fixed on the table surface in the direction of the table movement.

The feed is introduced through the feed box at the upper corner of the table. As the feed hits the deck, it is fanned out by combination of differential motion transversely flowing water. The jolts cause the heavier particles to work down of form the bottom layer and travel in the through formed by the riffles.

The lighter gangue materials are thrown into suspension and discharge over the edge of the table opposite the feed box by the flowing wash water. The heavier minerals finally arrange themselves on
the smooth unrifled proportion of the table when they encounter the full force of the wash water. The middlings are selected in that corner of the table which is intermediate between concentrate and tailing.

The reciprocating (to and fro) speed of the riffle table is usually 200-300 strokes/ minutes with amplitude of 12-15mm. the coarser feed requires larger stroke length.

Constructional Features of Wilfley Table:

The Wilfley laboratory table was equipped with a conventional twelve-inch by thirty-inch riffled deck and a standard Wilfley head motion. The total concentration area of the deck was 360 square inches.
Special treatment of cleats or riffles is required as they constitute part off the consumables items in the working of wilfley table which required frequent replacement. The cleats are usually made up wood with a maximum height of 1 cm and maximum width of 1 cm. the riffles are tapered from one end toanother. They are so placed that they form channels of around 1 cm width and 1 cm deep which
trappers to zero depth at the opposite end. All the cleats end along a diagonal line imagined on the Wilflely table which approximately divides the total surface area of the table in the ratio of 2:1. This
means 2/3 of the total surface area of the table is cleated and rest 1/3 portion is unriffled.

The surface of the wilfley is lined with rubber or linoleum to restrict the wear of the wooden table surface and also increase roughness or friction. Riffles along with linoleum lining the capacity of the table.

Working Principle Wilfley Table:

The points of the compass are used for clarity in describing the operation of the Wilfley shaking table. The feed is screened to <3mm and fed into a small hopper above the north-east corner of the shaking table, where it is mixed with clean water. The resulting slurry is introduced to the north-east corner of the shaking table and begins to spread southwards as a thin film. The feed fan outs towards the edge of the table, allowing the operator to see exactly what is happening, and to decide where to subdivide the fan into distinct streams each dominated by a particular mineral. The shaking motion has a slow westward stroke and rapid return eastward stroke – often with a bump. This induces settled particles to crawl in a juddering manner westward along the table with the thin film of slurry. The shaking is usually very rapid with a frequency of 4 to 5.5 strokes per second. The shaking displacement is usually half to one inch to-and-fro. A set of low riffles aligned east-west guide the heavies ever westward to fall off the south-west corner of the table into a hopper as a continuous discharge. Meanwhile, a spray bar introduces clean ‘wash water’ along the north edge of the table, sending a thin film of clean water southward to encounter the riffles and the westward flowing slurry. The wash water mixes with the slurry and overrides the riffles taking the lighter particles with it to spill over the southern edge as a continuous discharge of tailings.

Characteristics of Shaking table operation

1. Under idealized conditions particles segregate into four groups:-

a. Light- large

b. Large- heavy

c. Small- light

d. Small- heavy

2. The angle of inclination of shaking table depends on the minerals handled. Tonnage handled

depends on:-

a. Size of the feed.

b. Whether the operation is roughing or cleaning. c. The difference in Sp. Gs., between the mineral that are to be separated.

d. Average specific gravity of the mineral to be treated.

3. Capacity of the wilfley table

It varies with table size and many other associated factors. But in general a table size of 4ftx 2ft has a capacity as high as 200 tons/ 24hrs.
4. Cost of operation
a. Power 0.5-0.8kw/hrs.
b. Repairing cost of the cleats & deck as and when required.[1]

reference

[1] Mukuldev Khunte, Process Waste Generation and Utilization in Steel Industry, International Journal of Industrial and Manufacturing Systems Engineering. Vol. 3, No. 1, 2018, pp. 1-5. doi: 10.11648/j.ijimse.20180301.11

Ball mill

Aim of the Experiment: Grinding of ore using Ball Mill.

Apparatus required: - Laboratory model Ball Mill.

Objective: To carry out the fine grinding of ore by using ball mill, that means the product size less than 6mm and up to 200 mesh (74µm).

Theory: Ball mills may be continuous or batch type. In this mill the grinding media and the ore to be ground are rotated around the axis of the mill. Due to the friction between lining- balls, lining-ore lumps, both are carried up angle, the inner wall of the shell nearly to the top, from where the grinding media is thus utilized in reducing the size of the particles as the reduction of the mill is continued. In fact the grinding process in the ball mill is attributed to following force working simultaneously on the particles.

 The working forces are: 

a. Cascading (attraction between the particles)
b. Cataracting (Impact of the ball on the particle)
c. Inter particle collision and rubbing.
d. Wear forces at the lining of the mill

Effective grinding depends on the rotational speed of the mill. If the mill operate at a low speed ball will be carried up along the inner wall to certain height, but not large enough to give an impact force. Rather, they roll over each other or slip over. This type of operational condition is known as “cascading”.

If the speed is raised, the balls start moving up further along the inner wall and suddenly fall from a greater height imparting an impact force at the bottom of the mill. The impact is largely responsible for most of the grinding. This condition is known as “Cataracting”.

If the speed of the rotation becomes too high, the balls are carried over and over again all along the inner lining as if they are sticking to the inner wall and there is hardly any grinding. This condition is known as centrifuging of the mil 

Constructional Features of Ball Mill:

Ball mill can be classified according to the
1. Shape of the mill
2. Method of discharge of the ground ore
3. Weather the grinding is conducted dry or wet.

1. Shape of the mills:

a. Cylinder- conical mills- Harding mill (Where feed & discharge ends is fixed.)
b. Cylindrical mill – The usual ball mills.
Mechanical Construction: A ball mill has three important sections as
a. Cylindrical Shell
b. Inner surface or liners
c. Balls or grinding media.

Cylindrical Shell: 

It is the rotating hollow cylinder partially filled with the balls. The ore to be crushed is feed through the turnnion at one end and the product is discharge through a similar turnnion at the other end. The material for the hollow shell is usually high strength steel. The steel axis is either horizontal or at smaller angle to the base. Large ball mills have a length of 4-4.25m, diameter of 3mts using balls of 25-125mm size.
Inner surface or liners: As the grinding process involve impact and attraction the interior of the ball mails is lined with replaceable wear resisting liners. The liners are usually manganese alloy steels, stones or rubber. Least wear takes place on rubber lined interior. As the coefficient of friction between balls and steel liner is large, the balls are taken to a higher height along the inner wall of the steel and dropped down on the ore to be crushed with a larger impact force resulting in better grinding.
Balls or grinding media: The balls are usually cast steel unless otherwise stated in some cases flint balls may be used. The diameter of the grinding media varies from 1”-5”. The optimum size of the ball is proportional to the square root of the feed size. The ball wear is usually in the range of 450gms to 1250gms per tons of ore crushed and the liner wear range form 0.50-205 gms per ton of ground ore.

Working Principle Ball Mill:

i. Ball mill is a horizontal cylinder, in and out of the hollow shaft and grind the first parts. According to the particle size of grinding material selection, material by hollow shaft ball mill feed end into the cylinder body. When the ball mill cylinder rotation, grinding medium because of inertia and centrifugal force effect, the effect of friction, making it nearby cylinder on the cylinderliner.When was brought to a certain height, thrown by its own gravity, the whereabouts of the grinding medium like projectile of cylinder body of the material to break.

ii. Material composed of feeding device through the hollow shaft spiral evenly into the mill first. The warehouse with ladder plate or corrugated plate, built in all kinds of steel ball, cylinder rotate falling after the ball to a certain height, the centrifugal force is generated on the material and grinding effect. Material after the first storehouse to coarse grinding, the single plate into the second warehouse every storehouse. Within the warehouse with a flat plate with steel ball, will further grinding material. Powder through the unloading Bi board, finish grinding homework.

iii. Cylinder in the process of turning, grinding medium has slipped phenomenon. In the process of slide to the material to grinding effect, in order to effectively use the grinding effect, the teaching material particle size and a large, generally 20 grinding fine time, the mill cylinder body with every storehouse board separated into two parts, namely become two bin. The material is steel ball break into the first storehouse. Material into the second warehouse, steel section for material grinding, fine grinding qualified material from the discharge end of the hollow shaft discharge, material of feed particles small mill, such as sand ii slag, coarse fly ash. Mill barrel cannot set partition, into a single warehouse tube mill. Grinding medium can also use the steel section.

Observation Table: 

S.N
Particle size before crushing
Initial weight
weight after 5min
weight after 10 min
Weight after 15min
Reduction ratio after 15 min




Calculation:

Reduction Ratio: The reduction ratio that can be obtained by use of ball mill is large compared to reduction ratios obtainable with primary or secondary crusher. Instead of 5-8 it may range from 50-100 for a ball mill classifier circuit. If reduction ratio is high along with large capacity it is more economical to arrange ball mills in series. The first is a coarse grinder having reduction ratio of 20 and the last one is fine grinder having reduction ratio of 5.

Capacity: The capacity of the ball mill depends upon its size, hardness of the ore, reduction ratio attempted. Ball mills yield 1-50 ton/hr of powder with 90% passing through 200# (mesh) screen.

Roll crusher

Aim of the Experiment: Crushing of ore using Roll crusher.

Apparatus Required: Laboratory model Roll Crusher, Feed material.

Theory: A roll crusher a piece of heavy-duty equipment used in mining and industrial processes. For reduction in size of ore/mineral. It consist of a pair of large wheels or cylinders mounted on horizontal axis. When rocks, ore, and other materials pass between the two cylinders, they are crushed or ground into smaller pieces. A roll crusher can be used in a wide variety of applications, including concrete recycling, mining, and mineral or metal production.

 In a standard double roll crusher, the two cylinders each feature a steel or ceramic finish. A hopper or bin above the rollers drops rocks and other materials down into the gap between cylinders. The two cylinders rotate in opposite directions to force all materials into the space between the two units as it falls. The friction between the two wheels crushes the material, which then falls into a collection bin below the unit. To get a desired size of product the set gap can be adjusted. The surface of the roll crusher may be smooth or textured, depending on the applications. Roll crushers used to crush rocks and other heavy-duty materials generally feature teeth or spikes along the surface of each cylinder. Smooth-faced cylinders are used to crush more delicate materials, including minerals and some metals.

Constructional Features of Roll Crusher: The two rolls are heavy and rigid ones. The material is cast steel and wear resisting. Both the rolls are positively driven towards each outer by motor. The heavy rolls turn on parallel horizontal plane having the roll centers at the same height separated by a distance ‘d’. The feed caught between the rolls are broken by compressive force and drop down bellow. The rolls turn towards each other at the same speed. They have narrow faces but having large diameter so they can nip moderately large lumps. Typically rolls are 600mm long with 300 mm diameter. Roll speed ranges from 50-300 rpm. The feed size varies from 12mm to 20mm. the product size mainly depends on the roll separation distance ‘d’

.

Working Principle:

i. The crushing rolls are individually driven in counter- rotation by electro-motors with coupling and gears via V-belts.

ii. The crushing material is feeded into the machine by means of conveyors or similar aggregates while it is spread over the whole width of the roll.

iii. An optimum use of the crushing tools and a uniform belt charging are thus achieved.

iv. Roller diameter, tooth form and circumferential speed are adjusted to the type and the size of the feeding material in relation to the required final grain size.

v. Rolls can be operated both wet and dry. Dry crushing causes less wear and gives lower output.

vi. Best operation in choke feeding.

Observation:

S.n	Sample Weight	Max. Size of the Feed	Max. Size of the product	Length of Gape	Length of Set	Time taken to crush material	Weight after crushing (only desired size)	Reduction Ratio

Calculation:

Reduction Ratio: The reduction ratio of average feed size to the average product size is known as reduction ratio.

Capacity:

Theoretical Capacity tons/ hr, C= 0.0034NDWS

 The capacity of the roll crusher mainly depends on their speed (N, rpm), Width of the face (W) Diameter of the roll (D) {all in inches} Set (s) the inter roll distance Specific gravity of rock ( ) lb/in3 Note: The actual capacity is considerably less and only around 10-30% of the theoretical capacity. If the set is nil, the capacity is nil.

References:
1.911metalurgist.com
2.Google Images

Jaw Crusher

Aim of the experiment: Crushing of ore using Jaw crusher.

Apparatus Required: Laboratory model Jaw Crusher, materials (for crushing), Vernier calipers.

Objective: To study the jaw crusher and measure the reduction ratio and capacity of the crusher.

Theory :“Crushing Process” is defined as the group of operation in a mineral dressing process whose object is to reduce large lumps to fragment.

“Crusher” is slow speed machines for coarse size reduction of large quantities of solids by using compressive force. The main significance of an ideal or grinder should: -

i.                     Have a large capacity.

ii.                   Require a small input per unit wet of production.

iii.                 Yield a product of single size or required size distribution.

Constructional Features of Jaw
 Crusher: The crusher mainly consists of:

1)      Frame 2) Fixed jaw plate 3) Left and right protecting boards 4) Movable jaw plate 5) Movable jaw 6) Eccentric shaft 7) Toggle plate 8) Toggle seat 9) Components and parts such as oil pressure lifter

The motor drives eccentric shaft via a belt fixed in a grooved pulley, which can make movable jaw move repeatedly so it can crush more material. Fixed jaw plate of frame front wall is fastened depending on left and right protecting boards and holding down bolts, while movable jaw plate is pressed tightly on movable jaw depending on battens. When the jaw plates are abraded (usually under side of the jaw Toggle plate) can not only bear the weight of movable jaw, but also protect other parts of the machine from hurting. When un-broken foreign materials come into crushing cavity which results in heavy load increase of toggle plate, the toggle plate breaks down itself to cut off the heavy load so as to protect other parts of the jaw crushers. Toggle seat is fastened on ear seat of the jaw crusher’s two sides by draw bolts; depend on hydraulic pressure lifter (lifting bolts) to lift out toggle seat, change pad thickness, and i.e. be able to adjust the width of discharge outlet. As the name suggest a jaw crusher has two jaws set to from a V shape at the top through which feed is admitted in to the jaws. One of the jaw is fixed to the main frame of the crusher almost vertically while the outer than the movable. The swinging jaw reciprocate in a horizontal plane and make an angle an 20-30 degree with the stationary jaw and is driven by an eccentric so as to that it applying a great compressive force on the ore lumps caught between the jaws. On the jaws, replaceable crushing faces are fixed by nut & bolt arrangement. The crushing faces are made from “Hardfiled Manganese” steels. When extensive wear is observed on any of the faces it is replaced by new one. The crushing jaw faces are flat. Initially the large lump is caught at the top and is broken materials drop to the bottom space (set). The jaw running speed vary from 100-400 rpm (100-400 times).

Jaw Crushers are basically in two types

(1) Blake jaw Crusher, (2) Dodge jaw Crusher

Blake jaw Crusher

The movable jaw is hinged at the top so that greatest amplitude of motion is at bottom of the crushing face.

Dodge jaw Crusher

The movable jaw is hinged at the bottom so that greatest amplitude of motion is at top of the crushing face.

Working Principle:

i.                    Before starting the experiment inspect the machine. Check the motor and gear drives.

ii.                  Set the jaw plate distance through using jaw plate moving handles. After setting of the jaw plates close the handles carefully.

iii.                Fill the raw material hopper before starting of crushing.

iv.                 After completion of primary preparation the start the motor.

v.                   Collect crushed material for the observation.

Observation Table:

Sample weight	Max size of feed (mm)	Max size of product (mm)	Length of gap(mm)	Length of set(mm)	Time taken to crush (sec)	Weight of feed after crushing

Calculation

1.      Reduction Ratio: The reduction ratio of average feed size to the average product size is known as reduction ratio.

2.      Capacity: The capacity of the jaw crusher mainly depends on the length and width and width of receiving operation and the width of the discharge. As per target, the empirical formula for capacity of jaw crusher is,

T=0.6LS

Where T=T is the capacity tons per hour

 L= Length of receiving opening in inches.

S= Set or Width of discharge opening in inches