Dry Centrifugal Collector

By: – Hitarth MehtaMIHS - 08IH06

ISTAR

Outline

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

Types of Dust Collectors

Dry mechanical collectors

Wet collectors & scrubbers

Fabric collectors

ESP

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.]

Cyclonic action for dust separation

Dust stream enters & spun rapidly

Cf created by circular-flow

throws particle towards the wall of cyclone

Finally collected underneath

“Cyclonic separation”

A. Dry centrifugal collector[According to design]

1) Single cyclone collector

2) Multiple cyclone collector

Single cyclone collector

“Dual Vortex” Main vortex spirals

downwards Carries most of

coarser dust Inner vortex –near

the bottom of the cyclone

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 forceWhich results in better separation of particulatesPressure drop is higher then that of single cyclone separators

B . Dry centrifugal collector[According to mechanism]

Gravity separators

Inertial separators

Dynamic precipitators

Cyclone collectors

High efficiency centrifugal collectors

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.

Inertial separator

i) settling collectors

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 designsAll depends on centrifugal force to separate dust from air stream “The magnitude of Cf which can be exerted on a particle is a funcn of particle mass and angular acceleration”Letter is dependent on air velocities in collectors

Factors influencing Design

1) Concn & particle size of contaminant2) Degree of collection required3) Characteristics of gas / air stream4) Characteristics of contaminant5) Methods of disposal

Applications

Many industrial processes likei. Millingii. Grindingiii. Abrasive blastingiv. Welding , etc. uses dust collectors to improve quality of

air inside the pant

Applications [contd.]

In industrial facilities, centrifugal collectors are used with LEV

Mainly it is used in chemical ind.

Moderate-sized dust such as wood dust,shavings,chips

10-40 microns

Advantages

Least costly & most frequently usedUsed as Primary or precollectorsLow maintenance cost Low operating costRelatively small in sizeLittle pressure dropMay use in series to increase efficiency

Limitation

“Because of today’s more stringent emission 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 micronCyclones used in series may have a large pressure dropsMostly 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 & air-conditioning

Time-saver standards for Architectural design

Basics of industrial hygiene by Debra Nims

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

24

Question ?????