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Gravity Concentaration By Jigs Experiment Engineering Essay

Jiging is one of the specific gravitation separation methods.The method separate minerals of different specific gravitation by their comparative motion in response to gravitation. Particle size is besides of import in jigging.If the provender is closely sized, it is easy to acquire good separation with narrow specific gravitation range.Jigging is suited for the sizes between 25 millimeters and 75 micrometers for minerals and suited for 20 centimeter and 0.5 centimeter for coal.

2 ) Theory:

Jig is an unfastened armored combat vehicle filled with H2O that has screen at the top and spigot or hutch compartment at the bottom.Jig bed may hold heavy harsh stuff ( tormenting stuff ) .

Jigs have screen, stroke length hutch compartment under the screen and ragging, a bed of heavy stuff.

There are two actions at work.First one is most of import 1 that is the consequence of hindered settling.When the slurry is subjected to several pulsations before it exists the shadowings weir of the gigue, better separation will acquire.

After repeated pulsations, particles become stratified.Heavy stuffs are settle at the underside and light atoms settle at the top.The other action is the consequence of the water.Upward flow of H2O offprints atoms by their specific gravitation.

Some conditions present in jigging action are ;

1 ) Therminal Velocity: Initially atoms have an acceleration and increasing velocity.When equilibrium is achieved, atoms reach their terminal speed and they settle down at changeless rate.

2 ) Free Settling: The sinking of atoms in fluid.

3 ) Hindered Settling: The hindered subsiding conditions prevail when the proportion of solids in the mush increases.The consequence of atom herding becomes more evident and falling rate of atoms Begins to decrease.The system begins to act as a heavy liquid whose denseness is that of the mush instead than that of the bearer liquid.

Mechanisms ;

1 ) Differential Initial Acceleration: The initial acceleration is dependent merely on the densenesss of the solid and the fluid.It is necessaryu that short jigging rhythm to divide little heavy atoms to light atoms.

2 ) Consolidation Trickling: In consolidation phase, where the big atoms in the bed come near to each other go forthing comparatively big interstices filled with exhausting H2O running down as a consequence of the suction portion of the work stoppage.

Separation may be achieved over the screen or trough the screen in jigging.

The operation parametric quantities of gigues are ;

1 ) Dilution: It is the sum of water.High dilution is necessary to take big measure of stuffs.

2 ) Screen Aperture: It must be every bit big as possible, consistent with provender size to minimise opposition to flux.

3 ) Stroke and Frequency: Stroke is traveling distance of the Piston and it depends on atom size.Frequency is the figure of stroke per clip.

4 ) Feed Rate and Particle Size Range: Jigs have high unit capacity and can accomplish good recovery in atom size under 150 autopsy.

3 ) Aim:

-To observe the stratification procedure

-As a map of the value of concentration standards, detecting the rate of stratification

-To observe the consequence of the tormenting stuff

-To observe the effects of the operating variables

4 ) MATERIALS AND EQUIPMENT:

-multi compartment Piston type research lab gigue steel balls as tormenting stuff

-crushed heavy mineral with the size of -3mm +0,5mm

-crushed light stuff humor the size of -3mm +0,5mm

-chromite

5 ) Procedure:

-prepare a mixture of heavy and light minerals

-fill the gigue humor hutch H2O

-add the provender

-add steel balls as tormenting stuff

-start the gigue and detect the stratification

-empty the graded stuff

-collect the light merchandise

6 ) Discussion:

a ) Jig: The methods operate by differences in specific gravitation. Jigs rely on stratification in a bed of coal when the carrying H2O is pulsed. The shale tends to transgress, and the cleaner coal rises. The basic gigue, Baum Jig, is suited for larger provender sizes. Although the Baum Jig can clean a broad scope of coal sizes, it is most effectual at 10-35 millimeter. A alteration of the Baum Jig is the Batac Jig which is used for cleaning all right coals. The coal is stratified by bubbling air straight through the coal-water-refuse mixture in this cleansing unit.

For intermediate sizes the same rules are applied, although the pulsation may be from the side or from under the bed. In add-on, a bed or difficult heavy mineral is used to heighten the stratification and prevent remixing. The mineral is normally feldspar, dwelling of balls of silicates of about 60 millimeters size.

Jigs offer cost effectual engineering with a clean coal output of 75-85 % at approximately 34 % ash content. The gigues are used more often than dense-medium vass because of their larger capacities and cheaper costs.

B ) Baum gigue and Batac gigues:

I ) Baum gigue: A Baum gigue with a screen deck comprising, in combination, a figure of H2O cisterns each holding a feed terminal and a discharge terminal and arranged in a series-paralleled system withsymmetrical air Chamberss opened at the underside and located beneath the screen deck transversally to the axis of the gigue, said symmetrical air Chamberss consisting home bases as subdivisions of a cylindrical surface, the symmetricalness axes of said air Chamberss beingdeflected from the perpendicular by an angle of 5 & A ; Acirc ; & A ; deg ; to 15 & A ; Acirc ; & A ; deg ; toward said feed terminal, said Chamberss holding asymmetric usher vanes displaceable in a horizontal way.

two ) Batac gigue: There is one decisive difference between an BATAC gigue and a Baum gigue: The H2O current is non generated in an air Chamberss are intermittently supplied with tight air by an electronically controlled valve or flap system ( pulse generator ) . That air is intermittently discharged from the system ( at atmospheric force per unit area ) after completion of the upward shot. Gesture is imparted to the H2O inside the gigue as a map of the force per unit area generated inside the air Chamberss. Furthermore make-up H2O is added at the lowest location of every jigging chamber to escalate the upward current and to stifle the downward current. The provender is stratified harmonizing to its denseness by the throbing gesture of the H2O: when fixing coal, e.g. , in garbage, middlings and clean coal.

The heavy fraction of the graded natural stuff is sensed by floats in conformity with the merchandise qualities required. The system provides for controlled backdown of the heavy fraction over a discharge device. Jigging of great breadths are equipped with independently runing discharge devices fitted with separate detector and hydraulic units. This constellation ensures optimum merchandise qualities over the full gigue breadth even in instance of non-uniform stuff distribution.

The parts of the batac gigue:

recess

garbage mercantile establishment

garbage roll uping hopper

middlings mercantile establishment

middlings roll uping hopper

discharge devices

clean coal flood

air Chamberss

make-up H2O

air-distributing tabes

air-distributing armored combat vehicle

waste-air collection armored combat vehicle

waste-air tubings with silencers

valve control system

Operating parametric quantities of gigues: The monitoring and control of gigue centrifuges is effected by supervising the clip fluctuation within a jig rhythm of at least one runing parametric quantity of the gigue, and pull stringsing the operating parametric quantity ( s ) to bring forth the sought after signifier of the clip fluctuation within the gigue rhythm. Operating parametric quantities include bed voidage, H2O degree, atom speed in the bed and H2O or air force per unit area.

degree Celsius ) An illustration of flow sheet:

In the flow sheet below, you can see the inside informations of this jigging procedure as it exists on a Superior factory floor. Copper stone from the cast enters the classifier and is directed to one of four gigue screens. These gigues work in tandem and both Cu and shadowings are removed during the procedure ( the T and C in the diagram ) . The middlings are so sent on to a distributer box, which sends the shadowings off to one of four series of polishing gigues. More Cu and shadowings are removed as the middlings are sent on to the wash floor.

7 ) Consequence:

In this experiment, we have learned the working rule of the gigue, the consequence of the tormenting bed, the stratification procedure, the consequence of runing parametric quantities of gigues. Jig separate the minerals by the consequence of specific gravitation, and some other forces such as hindered dregss of minerals etc. and the minerals has a bed ( stratification ) by agencies of an upward H2O and the aid of the tormenting bed. In add-on, there are some parametric quantities which consequence the separation. They are design parametric quantities such as shot and frequence and runing parametric quantities such as provender rate and atom size scope. Furthermore, if we supply a narrow size scope of the minerals to be separated, we can increase the consequence of specific gravitation and hold a good separation.

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