Dry Centrifugal Col Lector.ppt By Hitarth Mihs-istar

Dry Centrifugal Collector

By: – Hitarth Mehta MIHS - 08IH06 ISTAR

Outline ü Types of ind. Collectors ü Dry centrifugal collectors ü Types of diff. DCC 1) single collectors 2) Multiclones ü Designing of collectors ü Advantages & limitations

Types of Dust Collectors

Dry Centrifugal Collection › relies on inertia › move gas in a curved path

(vanes) › large particulates collected on a separator wall

Centrifugal collectors [contd.] Ø Cyclonic action for dust separation Ø Dust stream enters & spun rapidly

Ø Cf

created by circular-flow throws particle towards the wall of cyclone

Ø Finally collected underneath Ø “Cyclonic separation”

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Dry centrifugal collector [According to design]

Single cyclone collector v “Dual Vortex” v Main vortex spirals downwards v Carries most of coarser dust v Inner vortex –near the bottom of the cyclone v Carries finer dust & air spirals upword

Multiple-cyclone separators “Multiclones”  Consists no. of small dia. Cyclones operating parallely  Common gas inlet & outlet  Operates on same principle as on single 

Multiple-cyclone separators[contd.] Multiclones are more efficient Longer & smaller in dia. Longer length provides longer residence time while smaller dia creates greater centrifugal force Which results in better separation of particulates Pressure drop is higher then that of single cyclone separators

B . Dry centrifugal collector [According to mechanism]

Gravity separators gravitational and centrifugal forces  Cyclonic separation  When fluid or gas enters the cyclone with high enough pressure, a spiral flow is created  Rough particles, being heavier, are thrown into the wall of the separator where they sink down into the bottom of the separator where they are removed 

Inertial separator   

inertia and gravity to separate dust particles by slowing the flow of dusty air stream When speed of the dusty air stream is slowed down, heavier dirt particles settle out from the air stream by gravity and fall into a hopper where they are collected.

separate dust from the stream by using a settling chamber (a large box) in ductwork carrying dusty air

A baffle plat in the path of the dusty air stream to slow it down. The air stream strikes the baffle plate and undergoes a sudden change in direction

Dynamic precipitators Also operates on principle of centrifugal force  Combination of specially designed centrifugal fan & dust collector  Cf generated by rotating blades pushes the particles in the air stream to the tips of the blades  From where they drawn off  Unsuitable for sticky & fibrous material  Fairly efficient:- 5-20 microns in dia. 

High efficiency centrifugal collectors High-efficiency separators use a high velocity vortex centrifugal action for higher separation efficiency or for pneumatic conveying.  This type requires continuous discharge from the separator by the addition of a surge hopper for material storage. 

Designing Commercially available in wide verity of designs All depends on centrifugal force to separate dust from air stream “The magnitude of Cf which can be exerted on a particle is a funcnof particle mass and angular acceleration” Letter is dependent on air velocities in collectors

Factors influencing Design 1) 2) 3) 4) 5)

Concn & particle size of contaminant Degree of collection required Characteristics of gas / air stream Characteristics of contaminant Methods of disposal

Applications Many industrial processes like ii. Milling iii. Grinding iv. Abrasive blasting v. Welding , etc. uses dust collectors to improve quality of air inside the pant

Applications [contd.] v In industrial facilities, centrifugal collectors are used with LEV v Mainly it is used in chemical ind. v Moderate-sized dust such as wood dust,shavings,chip s v 10-40 microns

Advantages Least costly & most frequently used Used as Primary or precollectors Low maintenance cost Low operating cost Relatively small in size Little pressure drop May use in series to increase efficiency

Limitation “Because of today’s more stringentemission standard , the use of dry centrifugal collator is limited almost exclusively to produce recovery applications” Not effective for finer/Respirable i.e dust particles < 5 micron Cyclones used in series may have a large pressure drops Mostly used only as secondary standard

Summery  DCCs

are mainly used for pre-cleaning  Most commonly used for all type of medium from coarse to fine  Except < 5micron dia. Particles  Low cost & maintenance  All kind of sizes  Collection efficiency of 10 to 100microns with Multiclones.

References Handbook of heating , ventilating & airconditioning  Time-saver standards for Architectural design  Basics of industrial hygiene by Debra Nims 

Internet:- Wikipedia , thermax.com  Directindustry.com  www.dustcollectorexperts.com/ cyclone/ 

Thank you

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