Type of classifier

Sizing and Classification in Mineral Processing : types of different kind of classifier on basis their settling velocities in water or air.

1. Types of Classifiers Submitted to : Mr. Rohit Rawal Present by : Nanak Ram Patel Roll no : 18umie1217

2. CONTENTS CLASSIFICATION WET CLASSSIFICATION Spiral classifier Hydraulic classifier Hydro cyclone classifier DRY CLASSIFICATION Gravitational classfiers Gravitational inertial classifiers Centrifugal classifiers REFERENCE

3. CLASSIFICATION Classification is define as a method of separating mixtures of mineral particles into two or more products according to their settling velocities in water or air . The velocity of particles in a fluid medium is depend on : The size of the particles S pecific gravity Shape of the particles .

4. TYPES OF CLASSIFIERS Based on their separation principles classifiers are classified into two types:- Wet classification Spiral classifiers Hydraulic classifier Hydro cyclone classifiers 2. Dry classification Gravitational classifiers Gravitational inertial classifiers Centrifugal classifiers

5. WET CLASSIFICATION Wet classifiers are based on the principle that separation of coarse particles from fine particles by water or any other liquid . In wet classifiers coarse particles move faster than fine particles at equal density. High density particles move faster than low density particles at equal size. Basically they all work according to the principle that the particles are suspended in water which has a slight upward movement relative to the particles. Particles below a certain size and density are carried away with the water- flow, whereas the coarser and heavier particles settle.

6. SPIRAL CLASSIFIER The spiral classifier is also called as helical classifier . Spiral can be of single pitch or double pitch. It is made by combining a gravity settler of rectangular section with a sloped transport spiral for the sediment. It consists of a semi cylindrical trough (a trough which is semi-circular in cross- section) inclined to the horizontal. Wet classification with spiral classifiers using separation by gravity typically covers the size range of 100-1000 micrometers .

7. SPIRAL CLASSIFIER The spiral rotates about the axis with in the tank. The sediments, at the lower end are collected by the spiral, and lifted upwards. If the spiral rotates in the clockwise direction from the top end, then the sediments will move upwards. There are three designs of semi cylindrical troughs are available. 1. Straight side design : coarse separations 2. Modified flare design : intermediate to fine 3. Full flare design : fine to very fine

8. HYDRO CYCLONE CLASSIFIER Hydro-cyclones are used by in mining industry to separate minerals based on size and density . Slurry is given a vigorous rotation in the cyclone which generates a radial force field . Large/dense particles are driven to the outer regions and underflow, while small and light particles are attracted to the core and overflow. Covering the size range of 10 micrometers to 100 micrometers . Although the hydro cyclone by nature is a size controlling machine the number of applications in mineral are many such as ( i ) classification in grinding circuits, (ii) dewatering and thickening, (iii) desliming and washing, (iv) enrichment of heavy minerals (dense media separation)

9. HYDRAULIC CLASSIFIER Hydraulic classifier is a device used to concentrate an ore based on difference between the densities of ore and gangue particles . This process is called levigation . The powered ore is feed into a conical reservoir. A strong current of water agitates the powered ore, lighter gangue particles rise up while heavier ore particle sink down.

10. DRY CLASSIFICATION Dry classifiers are based on the air fluidization . Air classification is a process of separating categories of materials by way differences in their respective aerodynamic characteristics . Dry classification using separation by centrifugal force typically covers the range of 5 micrometers to 150 micrometers . The process consists of interaction of a moving stream air , material particles, and the gravitational force within a confined volume . The confined volume in which the separation takes place is called an Air classifier . Air classifiers may be one of a number of designs. The three principle group of designs are horizontal , inclined ,vertical .

11. GRAVITATIONAL CLASSIFIER Gravitational classifier are design for coarser separation in the range of 12 mesh size 100 mesh size . Gravitational classifiers are suitable for closing grinding circuits, de-dusting of coarser feeds, reducing a high feed loading rate to a finer classifier and it can also be used as a density separator. Process :

12. GRAVITATIONAL INERTIAL CLASSIFIERS

13. CENTRIFUGAL CLASSIFIERS

14. REFERENCES Mineral Processing by Pryore.J Course of mi n ing Geo l o g y by R.N.P.Arogyaswamy Basics in Mineral Processing Ore dressing by Robert H. Richards, S.B

15. Thank you !!