63 Reverse

Grinding with ball mill systems Separating

Separating

2

HGRS

Tikaria_Mill Workshop

SEPT-07

Separating process

Air

FR

3

HGRS

Tikaria_Mill Workshop

SEPT-07

Separation in 3rd Generation Separator Basic function:  Material enters the separator at

Feed

Centrifugal Forces

the top.  Air stream is generated by

external fan.  Material falls down between rotor

Air Guide vanes

Air

Turning cage rotor

and guide vanes. Fines are sucked in. Coarse particles are accelerated by rotor and stopped by guide vanes, where they slip down and leave the casing at the bottom.  Fine material exits with airflow at

the lower/upper part of the casing Returns

Air with fines

the rotational speed of rotor. 7

Source: Chr. Pfeiffer QDK Separator

HGRS

 Product fineness is adjustable by

Tikaria_Mill Workshop

SEPT-07

What is the separating efficiency dependent on?  Material: 

fineness - Feed (A) - Fines (F)

A

Tromp curve

- Return (R)

Amount of feed  Feed distribution  Air: 

V F

Volume (V [m3/h])  Distribution  The fineness relationship mill filter / separator fines 

R 8

HGRS

Tikaria_Mill Workshop

SEPT-07

Possible causes that limit the separating efficiency The typical situations for 3rd generation separators are:  Uneven airflow and/or feed distribution to the rotor

 Reduced separating airflow due to:   

Separator fan damper (or speed) not at maximum Fan nominal too low Limited rotor speed due to mechanical problems or insufficient nominal capacity of the motor and/or gear box

 Contamination of the fines by coarse product  Separator fines much finer than final product

9

HGRS

Tikaria_Mill Workshop

SEPT-07

Tromp curve key parameter Tromp value [%] 100

Separator fines

Separator return

Bypass

[mm] 10

HGRS

Tikaria_Mill Workshop

SEPT-07

Tromp curve key parameter Tromp value [%]

Coarse in fines

100

Separator fines

Separator return

Bypass

[mm] 11

HGRS

Tikaria_Mill Workshop

SEPT-07

Amount of material  Circulating load:

A, F & R en [t/h] A=F+R  Circulating load factor: u=

A

A

[-]

F

V

F

R 12

HGRS

Tikaria_Mill Workshop

SEPT-07

Separator performance (1/2) 6.0 5.5

High

Circulating load factor u [-]

5.0 4.5 4.0

Normal 3.5 3.0 2.5 2.0

Low

1.5 1.0 2'500

3'000

3'500

4'000

4'500

5'000

5'500

6'000

Cement fineness [cm2/g] 13

HGRS

Tikaria_Mill Workshop

SEPT-07

Separator performance (2/2) 50 45 40

High potential By pass [%]

35 30

Medium potential 25 20 15 10

Low potential

5 0 1.0

1.5

2.0

2.5

3.0

3.5

4.0

4.5

5.0

5.5

6.0

Circulating load factor u [-] 14

HGRS

Tikaria_Mill Workshop

SEPT-07

Air volume  Separator specific feed load Asl =

A

X 1’000 [kg/m3]

A

V Asl < 2.5 [kg/m3]  Separator specific fines load Fsl =

F

X 1’000 [kg/m3]

V

V

Fsl < 0.7 [kg/m3] F

R 15

HGRS

Tikaria_Mill Workshop

SEPT-07

Air distribution

Air

FR

 Lower air speed

Finer product

 Higher airspeed

Coarser product 16

HGRS

Tikaria_Mill Workshop

SEPT-07

Uneven airflow distribution  Uneven airflow distribution can

be identified from (1/2):  Observation of the ducting configuration: - General arrangement - Relative position inlet / outlet air ducts 





Uneven wear of paintings or steel along the guide vanes height Uneven wear of paintings or steel along the rotor blades height Low separator efficiency despite low material specific loads 17

HGRS

Tikaria_Mill Workshop

SEPT-07

How to determine the airflow profile  Uneven airflow distribution can

be identified and evaluated from (2/2): 





Airspeed mapping at the inlet of the separator volute Static pressure profile in each duct ( ) Fineness comparison of the fines at each cyclone (mass balance for each cyclone)

18

HGRS

Tikaria_Mill Workshop

SEPT-07

Solutions for even airflow profile  Even airflow distribution with

air guide plates  The positioning and length of

the air guide plates should be done considering the air flow distribution in the ducting (start from where the air is already evenly distributed)

Too short Good Laminar and even flow across whole duct section 19

HGRS

Tikaria_Mill Workshop

SEPT-07

Feed distribution

< 50 [mm]

20

HGRS

Tikaria_Mill Workshop

SEPT-07

Symptoms of uneven material distribution  Uneven wear of paintings or

steel of the impact ring  Uneven pressure loss and

fineness of the fines in a cyclone air separator  Separator efficiency is low in

spite of low material specific loads  Configuration of airslides from

separator discharge to the separator feed point(s)

21

HGRS

Tikaria_Mill Workshop

SEPT-07

Solutions evaluation  Even as much as possible

material load to all separator feeding points: 

 

Adjust / install splitters Install mixing boxes Change airslides configuration

22

HGRS

Tikaria_Mill Workshop

SEPT-07

The fineness relationship mill filter / separator fines

MF F

If F finer than C check:

C

 Send MF to the separator feed  Cut finer at the static separator (if any)  Reduce mill ventilation  Consider a static separator (or cyclone) 23

HGRS

Tikaria_Mill Workshop

SEPT-07

Separator operating point (1/2) 100 95

Iso - fineness line

Rotor speed [%] of nominal

90 85

3’500 [cm2/g]

80 75 70 65 60 55 50 45 40

10 15 20 25 30 35 40 45 50 55 60 65 70 75 80 85 90 95 100

Air [%] of nominal 24

HGRS

Tikaria_Mill Workshop

SEPT-07

Separator operating point (2/2) 100

Bypass 3

95

Rotor speed [%] of nominal

90

Bypass 2

85 80

By pass 1

75 70 65

Bypass 1 > Bypass 2 > Bypass 3

60 55 50

CONCLUSION is to operate the fan at 100%

45 40 10 15 20 25 30 35 40 45 50 55 60 65 70 75 80 85 90 95 100

Air [%] of nominal 25

HGRS

Tikaria_Mill Workshop

SEPT-07

Grinding with Ball Mill Systems

Separators

What is separating? Splitting a given material by particle diameter Balls with 2, 4 and 10 mm diameter

> 3 mm

Separation by cutpoint of 3mm (e.g. by sieving) Problem: Efficiency of separation is never perfect

< 3 mm 27

HGRS

Tikaria_Mill Workshop

SEPT-07

Separation efficiency  The efficiency of a separation device (e.g. mill

separator) is a measure of the proportion of unseparated material following the separation process. It indicates how much fines is in the coarse fraction remaining and how much coarse is in the fines.

 The efficiency is very much dependent on the separator.

Modern cage rotor separators show a far better efficiency than older static and dynamic separators.

28

HGRS

Tikaria_Mill Workshop

SEPT-07

Basic working principles Separators  Particles are accelerated by a vortex or a

rotating device into the direction of the separator wall (Fz).  The big particles hit the wall (in older

separators) or the guide vanes (in 3rd gen. Separators) and slip down because they are too heavy for transport by the air stream.  The small and light particles are carried

out by the separator air (FL) stream supplied by an internal (older separators) or an external fan. The centrifugal force is smaller than the impulse of the air flow.  Changes of airflow or distributor (rotor)

speed (consequence higher centrifugal forces) lead to different product fineness. 29

HGRS

Tikaria_Mill Workshop

SEPT-07

Main Separators used in Cement works Type

Main features

Static separators and cyclones

No moving parts / fineness adjustment via mechanical modification

Dynamic separators 1st Generation

Counter blades, distributor plate and internal fan/Fineness control by mechanical adjustment or counter blade speed change

Dynamic separators 2nd Generation

Features as 1st Gen. / but external fans and cyclones

Dynamic separators 3rd Generation

Cage rotor instead of counter blades and distributor plate (variable speed drive) / external fan / fineness control by rotor speed change 30

HGRS

Tikaria_Mill Workshop

SEPT-07

Static separators and cyclones Cyclone

Basic function:

fines

 Material enters the cyclone

in the air stream at the top. immersion tube

 A vortex is generated.

feed

 A fine vortex with opposite cylindrical part

conical part

view from top

turning direction is generated at the bottom and carries the fine material back to the top.  Coarse material goes to the

walls because of centrifugal forces, slips down and leaves at the bottom.  Fine material exits at top via

the immersion tube. 31

tailings

HGRS

Tikaria_Mill Workshop

SEPT-07

Static separators and cyclones

Cyclones of a cement mill separator

32

HGRS

Tikaria_Mill Workshop

SEPT-07

Static separator and cyclones fines

Grit separator immersion tube

adjustable blades

adjusting device

Basic function:  Material enters the

separator in air stream at the bottom.  A vortex is generated in the

top of the grit cone by the blades.  Coarse material goes to the housing cone tailings cone

walls because of centrifugal forces, slips down and leaves at the bottom.  Fine material exits at the

rad.pos.

top via the immersion tube.  Product fineness is

tailings

adjustable by changing the blade position. feed

HGRS

33

Tikaria_Mill Workshop

SEPT-07

Static separator and cyclones Grit separator

Adjusting device blades

34

HGRS

Tikaria_Mill Workshop

SEPT-07

Static separator and cyclones Basic function:

KHD V-separator

 Material enters the

separator from the top

Air + Fines

 Coarse material slips down Air

from plate to plate and leaves at the bottom.  Fine material leaves the

separator at top together with the air.

Plates

Returns HGRS

35

Tikaria_Mill Workshop

SEPT-07

Dynamic separators 1st Generation 6

12

Basic function: 5

11 9 16

7

separator at the top.  Coarse material goes to the

10 8

 Material enters the

4

1

3 15 2

Sturtevant 13

walls because of centrifugal forces generated by the distributor plate and counter blades, slips down at the grit cone wall and leaves at the bottom (13).  Fine material exits at the

bottom of the casing (14). 14

1 fines chamber 2 3 4 5 6 7 8

HGRS

tailings cone air vane inside drum fineness control valve rod gear reducer main shaft and distributing hub distributing plate

9 10 11 12 13 14

fan cone counterblades main fan blades feed spout and intake cone tailings outlet fines outlet

15 air inlet 16 air outlet

Tikaria_Mill Workshop

 Product fineness is

adjusted by counter blade position and rods (5) (No counter blade speed adjustment is possible!)

36 SEPT-07

Dynamic separators 1st Generation (Sturtevant) Internal Fan

Counter blades

External adjustment of fineness control valve rods 37

HGRS

Tikaria_Mill Workshop

SEPT-07

Dynamic separators 1st Generation Polysius Turbopol

Air vanes Grit cone

Distributor plate

Counter blades

Internal Fan

38

HGRS

Tikaria_Mill Workshop

SEPT-07

Dynamic separators 1st Generation (Example: Pfeiffer Heyd) Basic function: 8

 Material enters the separator at

the top.

9 10

 Air stream is generated by internal

7

fan (9).

4

5

1

 Coarse material goes to the walls

because of centrifugal forces, generated by the distributor plate and counter blades, slips down at the grit cone wall and leaves at the bottom (11).

6 3

Airflow 2

 Fine material is sucked into the 11 1 fines chamber 2 3 4 5 6

tailings cone air vane separation chamber distributor + counterblades distributor plate

HGRS

outside chamber (1) and exits at the bottom of the casing (12).

12 7 8 9 10 11 12

fines chamber counter blades fan shaft fan blades feed spout tailings outlet fines outlet

Tikaria_Mill Workshop

 Product fineness is adjustable

usually by rotational speed of the plate and counter blades (6+7). 39 SEPT-07

Dynamic separators 1st Generation Separator Type Heyd

Variable speed drive for counter blades and distributor plate

Fan Motor

Fan

Counter blades Feed spout

Distributor plate

40

HGRS

Tikaria_Mill Workshop

SEPT-07

Dynamic Separators of 2nd Generation 8

7

1 separation chamber 6

5 11

11 1

14 4 15 3

13

tailings cone

7 8 9 10 11 12

gearbox

air vanes distributor plate counterblades feed spout

motor fines outlet tailings outlet cyclones air duct to fan

13 fan 14 dust collecting

9

9

2 3 4 5 6

pipe to filter

15 return air duct

2

Polysius Cyclopol 10 HGRS

41

Tikaria_Mill Workshop

SEPT-07

Dynamic Separators of 2nd Generation (Wedag)

to filter Air flow direction

fresh air

42

HGRS

Tikaria_Mill Workshop

SEPT-07

Dynamic Separators of 2nd Generation Basic function:  Material enters the separator at the top.

 Air stream is generated by the external fan and

is recirculated.  Coarse material is separated by fan suction into

the main casing and leaves at the bottom via a pendulum flap.  Fine material exits at the top of the casing by

airflow and enters the cyclone via gas duct. The material separated by the cyclones leaves at the bottom and goes into air slides. A part of the recirculated air together with the fine dust from the cyclones goes to a filter.  Product fineness is adjustable usually by

rotational speed of the plate and counter blades. 43

HGRS

Tikaria_Mill Workshop

SEPT-07

Dynamic Separators of 2nd Generation

Counter blades

Distributor plate 44

HGRS

Tikaria_Mill Workshop

SEPT-07

Separators of 3rd Generation Basic function: Feed

Centrifugal Forces

 Material enters the separator at

the top.  Air stream is generated by

external fan.  Material falls down between rotor Air Guide vanes

Air

Turning cage rotor

and guide vanes. Fines are sucked in. Coarse particles are accelerated by rotor and stopped by guide vanes, where they slip down and leave the casing at the bottom.  Fine material exits with airflow at

the lower/upper part of the casing Returns

Air with fines

 Product fineness is adjustable by

the rotational speed of rotor. 45

HGRS

Tikaria_Mill Workshop

SEPT-07

Main parts cage rotor separator Cage rotor

Bars

Guide vanes (in bad shape)

46

HGRS

Tikaria_Mill Workshop

SEPT-07

Separators of 3rd Generation 11

Example: Polysius Sepol 5

10

3

5

2

1

4

9

6 7

8

1 guide vanes 2 rotor blades 3 distributor plate 4 rotor shaft 5 feed spouts 6 sealing

HGRS

Tikaria_Mill Workshop

7 air + fines outlet 8 tailings outlet 9 air inlet 10 gear box 11 motor

47 SEPT-07

Separators of 3rd Generation Basic function:

Drive

Example: FLS O-Sepa Air outlet + fines

Prim. air

Sec. air

Sealing

the top.  Airstream is generated by

external fan.

Feed

 Material falls down between the

Distributor

Tert. air

 Material enters the separator at

Guide vanes Rotor

Fines

Coarses Coarses

rotor and guide vanes. Fines are sucked in. Coarse particles are accelerated by the rotor and stopped by guide vanes, where they slip down and leave the casing with the tailings outlet.  Fine material exits with the

Centrifugal force

Air force

airflow at the upper part of the casing .  Product fineness is adjustable by

the rotational speed of the rotor. Prim.air

HGRS

Gravity force

Tikaria_Mill Workshop

48 SEPT-07

Separators of 3rd Generation Example: O&K cross-flow separator feed spout

gearbox

Basic function:  Material enters the separator at

motor

the top. distributor plate

 Airstream is generated by an air inlet

external fan. air guide vanes

rotor blades separating zone

fines coarses

air + fines outlet

tailings outlet

shaft

HGRS

Tikaria_Mill Workshop

 Material falls down between the

rotor and guide vanes. Fines are sucked in. Coarse particles are accelerated by the rotor and stopped by the guide vanes, where they slip down and leave the casing via the tailings outlet.  Fine material exits with the

airflow at the lower part of the casing .  Product fineness is adjustable

by the rotational speed of the rotor. 49 SEPT-07

Separators of 3rd Generation (FLS SEPAX)

50

HGRS

Tikaria_Mill Workshop

SEPT-07

Separators of 3rd Generation (FLS SEPAX) Basic function of the compact version:  Material enters the separator at the bottom with the air stream. The air

stream is generated by an external fan.  Material enters the rotor in the air stream via guide vanes. Fines are

sucked in. Coarse particles are accelerated by the rotor and stopped by guide vanes, where they slip down and leave the casing on the side.  Fine material exits with the airflow at the top of the casing .

 Product fineness is adjustable by the rotational speed of the rotor.

Additional functions roller press version:  Roller Press slabs enter desagglomerator under the compact separator

where they are crushed  Fines go up in the air stream to the separator  Coarses fall down and pass through the grit separator, where additional

fines are separated und go up in the air stream. Rejects go back to the press HGRS

Tikaria_Mill Workshop

51 SEPT-07

Separators of 3rd Generation (Polysius Sepol SM) Basic function: Rotor drive

 Material enters the separator at

the bottom with the air stream (e.g. air swept mill)

Fines with air

 Air stream is generated by an

external fan. Rotor

 Material enters the rotor in the air

stream via guide vanes. Fines are sucked in. Coarse particles are accelerated by the rotor and stopped by guide vanes, where they slip down and leave the casing at the bottom.

Guide vanes

Inspection doors

 Fine material exits with the airflow Returns

at the top of the casing .  Product fineness is adjustable by

Airflow with material from mill

HGRS

Tikaria_Mill Workshop

the rotational speed of the rotor.

52 SEPT-07

Separators of 3rd Generation (KHD Sepmaster) Sepmaster SKS-D (for RP* circuits) feed material

Sepmaster SKS-LS (for ASM**)

feed material

desagglomerator rotor

air+fines

air+fines impact ring

air and fine product

coarse fraction 2

coarse fraction 1 feed material+air

* Roller Press

HGRS

coarse product

Tikaria_Mill Workshop

** Air Swept Mill 53 SEPT-07

Separators of 3rd Generation (KHD Sepmaster) Sepmaster SKS 5

4 7

3

6

2

9

1

1

guide vanes

2

rotor blades

3

distributor plate

4

rotor shaft

5

feed spout

6

sealing

7

air + fines outlet

8

tailings outlet

9

air inlet

10 gear box 11 motor

11

10 8

HGRS

Tikaria_Mill Workshop

54 SEPT-07

Separators of 3rd Generation (KHD Sepmaster) Basic function:  Material enters the separator at the top.

 Air stream is generated by external fan.  Material falls down between the rotor and guide vanes. Fines are

sucked into the rotor. Coarse particles are accelerated by the rotor and stopped by guide vanes, where they slip down and leave the casing at the bottom.  Fine material exits the separator with the airflow at the top of the casing

.  Product fineness is adjustable by the rotational speed of the rotor.  Special features SKS-D: Additionally equipped with slab

desagglomerator at the top (use in roller press circuits)  Special features SKS-LS: Used for air swept mills. Function is very

similar to Polysius Sepol SM. 55

HGRS

Tikaria_Mill Workshop

SEPT-07

Separators of 3rd Generation (Pfeiffer QDK) Basic function:

Rotor drive

 Material enters the separator at

the top.  Air stream is generated by

external fan.  Material falls down between the

rotor and guide vanes. Fines are sucked in. Coarse particles are accelerated by the rotor and stopped by guide vanes, where they slip down and leave the casing at the bottom.

Air inlet

Air +Fines  Fine material exits with the airflow at the lower part of the casing .

 Product fineness is adjustable by

Rotor Returns HGRS

the rotational speed of the rotor. 56

Tikaria_Mill Workshop

SEPT-07

Separators of 3rd Generation (vertical roller mill ; Loesche) Basic function:

Feed

 Material enters the separator at Separator drive

the bottom with the air stream.

 Air stream is generated by

Air Air

external fan. Cage rotor

 Material enters the rotor in the air Guide vanes

Returns flow

Conical casing

stream via guide vanes. Fines are sucked in. Coarse particles are accelerated by the rotor and stopped by guide vanes, where they slip down, leave the grit cone at the bottom and fall back on to the grinding table.

 Fine material exits with the airflow Grit cone

Airflow with material from grinding table

HGRS

Tikaria_Mill Workshop

at the top of the casing .  The product fineness is adjustable

by rotational speed of the rotor.57 SEPT-07

Separators of 3rd Generation (Vertical roller mill) Reject cone

Cage rotor

Guide vane system 58

HGRS

Tikaria_Mill Workshop

SEPT-07

Separators of 3rd Generation (coal grinding) in VRM Basic function:  Coal from the grinding table enters the

separator at the bottom with the air stream. (Used in vertical roller mills)  Air stream is generated by external fan.  Material enters the rotor in the air

stream via guide vanes. Fines are sucked in. Coarse particles are accelerated by the rotor and stopped by guide vanes, where they slip down and leave the casing at the bottom.  Fine material exits with the airflow at the

top of the casing .  Product fineness is adjustable by the

rotational speed of the rotor. Pfeiffer RTKM Separator for coal mills HGRS

Tikaria_Mill Workshop

59 SEPT-07

Separator arrangements in grinding circuits Single Pass design Fresh-Air

1

Mainly used where high cooling is required

3 Product

4 2

1

Feed bins

2

Mill with water injection

3

Separator with filter

4

Mill dedusting filter

HGRS

Tikaria_Mill Workshop

60 SEPT-07

Separator arrangements in grinding circuits Standard Arrangement 1st Generation Separator

4a 1

4

3 5

Product 2

1

Feed bins

2

Mill with water injection

3

Separator with filter

4

Mill dedusting filter

4a

Grit separator

5

Optional cement cooler

HGRS

Tikaria_Mill Workshop

61 SEPT-07

Separator arrangements in grinding circuits Cyclone Air Separator 1 3

Product

4 2

1

Feed bins

2

Mill with water injection

3

Separator with cyclone and dedusting filter

4

Mill dedusting filter

HGRS

Tikaria_Mill Workshop

62 SEPT-07

Potential Problems  Wear /  Clogging

 Wear  Sealing not tight

 Wear  Wear  Blades too short 63

HGRS

Tikaria_Mill Workshop

SEPT-07

Potential Problems  Wear,clogging  uneven feed distribution

 Wear

 Wear

64

HGRS

Tikaria_Mill Workshop

SEPT-07

Potential Problems

 Wear  Sealing not tight

 Wear

 Guide vanes not

correctly adjusted  Wear  Breakouts HGRS

Tikaria_Mill Workshop

65 SEPT-07

Potential Problems / clogging Cage rotor separator casing partly clogged guide vane system

Material deposits due to insufficient airflow or airflow distribution

66

HGRS

Tikaria_Mill Workshop

SEPT-07

Reduced separation efficiency 1st and 2nd generation dynamic separators

Gap between internal fan and separating chamber bigger than 5 [mm]

Reduced number of counter blades

Gap between counter blades and wall of separating chamber bigger than 10 [mm]

Possible consequence: Desired fineness can not be achieved anymore 67

HGRS

Tikaria_Mill Workshop

SEPT-07