separators

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Separators in the cement industry

Second generation separators:

6.1

Introduction:

Also called: Cyclones separators.

As the 1st generation, the material to be classified is dispersed in the area where the separation is created by a

distribution plate.

The air flow required for the separation is produced by an external fan.

The separator material feed is carried out mechanically by means of suitable continuous conveyors.

Fines are conveyed in external cyclones.

Fresh air entry and air exit to filter.

The fan that moves the air is a more efficient design and has a considerably reduced dust loading.

These separators have a better separation efficiency due to the external fan and the cyclones.

Comparison between cyclones and conventional separators:

The diagram here below shows the specific surface (Blaine) produced

in order to achieve a certain percentage of residue on 30µm (From Duda Cement Data Book).

For example, to get 20% residue on 30µm, a turbo separator needs to produce a cement at 3200-3900 Blaine and a

separator with cyclones 3000-3600 Blaine.

Click on the picture to enlarge

Here a non-exhaustive list of cyclones separators:

Wedag ZUB (KHD)

Cyclopol (Polysius)

SKET (ZAB Co.)

FCB cyclones

Other copies from former Eastern Europe

6.2

Advantages of 2nd generation dynamic separators:

Possibility of mechanical adjustments

Possibility of very large flow rates

Flexibility to produce products of different qualities

Better efficiency than the conventional separators

Less power consumption

Reduced wear on the separator internals (especially the fan)

6.3

Disadvantages of 2nd generation dynamic separators:

More space needed

Less efficient than cage separators

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6.4

Principle of operation:

The material is fed at the top of the separator.

Material falls and is dispersed in the circulating air by the distribution plate.

The air stream is generated by an external fan and recirculated. Possibly, there is a regulated fresh air inlet

in the part of the duct going to the separator.

There is an exit where air is removed to a dedusting filter in order to maintain a constant underpressure

inside the system.

The coarse material is separated by aspiration inside the main casing and goes out via the bottom conical device.

As a certain number of fines particles are entrained downwards with coarse particles, the air flow returning to the

separating area has a second chance to pick up any fines in the rejects.

The air with some amount of fine material is going back to the separating zone through the air vanes.

The fine material exits by the top of the separator and the air flow enters into the cyclones through the gas pipe.

The material is separated in the cyclones and exits through the bottom of these.

The cleaned air (the dust content is generally less than 15 g/m³) is recirculated via the fan.

It has been observed that the air flow speed in 2nd generation separators is in the order of 30% of the

air speed for conventional separators.

See the figure below:

Click on the picture to enlarge

6.5

Possibilities of adjustments:

Main adjustments:

Speed of counterblades

Fan speed

Fan damper

Other possible adjustments:

To remove or increase the counterblades number

To increase the distribution plate diameter

To decrease the distance between the distribution plate and the counterblades

Summary of the adjustments and consequences:

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6.6

Parameter of dimensioning:

The Specific Separator load

The values depend from a supplier to an other one:

6.7

Different designs:

Wedag ZUB (KHD):

Cyclopol (Polysius):

SKET (ZAB):

6.8

Second generation separators data sheet:

The data sheet allows to have a good idea of the second generation separators efficiency.

The different data are explained herebelow:

Click on the picture to enlarge

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SpreadsheetConverter

The fields with the red border are required.