05 Separating
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Transcript of 05 Separating
Separating
Grinding with ball mill systems
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SEPT-07HGRS Tikaria_Mill Workshop
Separating
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Separating process
FRAir
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Separation in 3rd Generation SeparatorBasic function:
Material enters the separator at the top.
Air stream is generated by external fan.
Material falls down between 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
Product fineness is adjustable by the rotational speed of rotor.
Source: Chr. Pfeiffer QDK Separator
Feed
Air
Turning cage rotor
Centrifugal Forces
Returns Air with fines
AirGuide vanes
Feed
Air
Turning cage rotor
Centrifugal Forces
Returns Air with fines
AirGuide vanes
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What is the separating efficiency dependent on?
F
A
R
V
Tromp curve
Material: fineness
- Feed (A)
- Fines (F)
- Return (R) Amount of feed Feed distribution
Air: Volume (V [m3/h]) Distribution
The fineness relationship mill filter / separator fines
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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
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[m]
Tromp curve key parameterTromp value [%]
100
Separator fines
Separator return
Bypass
Pro
bab
ili t
y fo
r a
pa r
t ic l
e to
be
in t
he
r et u
r n
The BYPASS is one of the best indicator of the
separator efficiency
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[m]
Tromp curve key parameterTromp value [%]
100
Separator fines
Separator return
Bypass
Ag
glo
me r
a tio
n
Coarse in fines
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Circulating load:
A, F & R en [t/h]A = F + R
Circulating load factor:
Amount of material
A
R
V
F
u =A
F[ - ]
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Separator performance (1/2)
1.0
1.5
2.0
2.5
3.0
3.5
4.0
4.5
5.0
5.5
6.0
2'500 3'000 3'500 4'000 4'500 5'000 5'500 6'000
Cement fineness [cm2/g]
Circ
ulat
ing
load
fact
or u
[-]
Normal
Low
High
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Separator performance (2/2)
0
5
10
15
20
25
30
35
40
45
50
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 [-]
By
pass
[%]
Low potential
Medium potential
High potential
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Air volume
Separator specific feed load
A
R
V
F
Asl =V
AX 1’000 [kg/m3]
Asl < 2.5 [kg/m3]
Separator specific fines load
Fsl =V
FX 1’000 [kg/m3]
Fsl < 0.7 [kg/m3]
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Lower air speed Finer product
Higher airspeed Coarser product
Air distribution
FRAir
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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
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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)
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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)
Laminar and even flow across whole
duct section
Good
Too short
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Feed distribution
< 50 [mm]
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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)
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Solutions evaluation
Even as much as possible material load to all separator feeding points: Adjust / install splitters Install mixing boxes Change airslides
configuration
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The fineness relationship mill filter / separator fines
If F finer than C check:
Send MF to the separator feed
Cut finer at the static separator (if any)
Reduce mill ventilation
Consider a static separator (or cyclone)
F
C
MF
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Separator operating point (1/2)
40
45
50
55
60
65
70
75
80
85
90
95
100
10 15 20 25 30 35 40 45 50 55 60 65 70 75 80 85 90 95 100
Air [%] of nominal
Ro
tor
spee
d [
%]
of
no
min
al
3’500 [cm2/g]
Iso - fineness line
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Separator operating point (2/2)
40
45
50
55
60
65
70
75
80
85
90
95
100
10 15 20 25 30 35 40 45 50 55 60 65 70 75 80 85 90 95 100
Air [%] of nominal
Ro
tor
spee
d [
%]
of
no
min
al
By pass 1
Bypass 2
Bypass 3
Bypass 1 > Bypass 2 > Bypass 3
CONCLUSION is to operate the fan at 100%
Grinding with Ball Mill Systems
Separators
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What is separating?Splitting a given material by particle diameter
Balls with 2, 4 and 10 mm diameter
Separation by cutpoint of 3mm (e.g. by sieving)
> 3 mm
< 3 mm
Problem: Efficiency of separation is never perfect
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Separation efficiency
The efficiency of a separation device (e.g. mill separator) is a measure of the proportion of un-separated 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.
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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.
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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
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Static separators and cyclones
Cyclone Basic function:
Material enters the cyclone in the air stream at the top.
A vortex is generated.
A fine vortex with opposite 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.
view from top
tailings
feed
fines
immersion tube
cylindrical part
conical part
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Static separators and cyclones
Cyclones of a cement mill separator
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Static separator and cyclones
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 walls because of centrifugal forces, slips down and leaves at the bottom.
Fine material exits at the top via the immersion tube.
Product fineness is adjustable by changing the blade position.
housing cone
tailings cone
adjusting device
rad.pos.
immersion tube
tailings
feed
fines
adjustable blades
Grit separator
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Static separator and cyclones
Adjusting device blades
Grit separator
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Static separator and cyclonesBasic function:
Material enters the separator from the top
Coarse material slips down from plate to plate and leaves at the bottom.
Fine material leaves the separator at top together with the air.
Air
Returns
Air + Fines
Plates
KHD V-separator
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Dynamic separators 1st Generation
Basic function:
Material enters the separator at the top.
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 (13).
Fine material exits at the bottom of the casing (14).
Product fineness is adjusted by counter blade position and rods (5) (No counter blade speed adjustment is possible!)
8
9
2
4
10
16
14
13
15
fines chamber1
2
3
4
5
6
9
10
11
12
tailings cone
air vane
inside drum
fineness control valve rod
gear reducer
fan cone
counterblades
main fan blades
feed spout and intake cone
tailings outlet
fines outlet
7
8
13
14
15
16main shaft and distributing hub
distributing plate
air inlet
air outlet
1
3
5
6
7
11
12
Sturtevant
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Dynamic separators 1st Generation (Sturtevant)
Internal Fan
Counter blades
External adjustment of fineness control valve rods
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Dynamic separators 1st Generation
Internal Fan
Distributor plateAir vanes Grit cone
Counter blades
Polysius Turbopol
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Dynamic separators 1st Generation (Example: Pfeiffer Heyd)
Basic function:
Material enters the separator at the top.
Air stream is generated by internal fan (9).
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).
Fine material is sucked into the outside chamber (1) and exits at the bottom of the casing (12).
Product fineness is adjustable usually by rotational speed of the plate and counter blades (6+7).
fines chamber1
2
3
4
5
6
7
89
10
11
12
1
2
3
45
6
7
8
9
10
1112
tailings cone
air vane
separation chamber
distributor + counterblades
distributor plate
fines chamber
fan shaft
fan blades
feed spout
tailings outlet
fines outlet
counter blades
Airflow
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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
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Dynamic Separators of 2nd Generation
separation chamber
tailings cone
air vanes
distributor plate
counterblades
feed spout
gearbox
motor
return air duct
dust collecting
fan
air duct to fan
cyclones
tailings outlet
fines outlet
pipe to filter
8 7
14
11
6
11
5
1
9
2
9
10
3
4
1315
1
15
23
45
6
7
89
1011
12
13
14
Polysius Cyclopol
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Dynamic Separators of 2nd Generation (Wedag)
to filter
fresh air
Air flow direction
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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.
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Dynamic Separators of 2nd Generation
Counter blades
Distributor plate
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Separators of 3rd Generation
Feed
Air
Turning cage rotor
Centrifugal Forces
Returns Air with fines
AirGuide vanes
Basic function:
Material enters the separator at the top.
Air stream is generated by external fan.
Material falls down between 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
Product fineness is adjustable by the rotational speed of rotor.
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Main parts cage rotor separator
Cage rotor
Bars
Guide vanes (in bad shape)
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Separators of 3rd Generation
Example: Polysius Sepol
1
23
45
6
9
10
11
7
8
1 2
3
4
5
6
5
11
7
8
9
10
guide vanes
rotor blades
distributor plate
rotor shaft
feed spouts
air + fines outlet
tailings outlet
air inlet
gear box
sealing
motor
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Separators of 3rd Generation
Example: FLS O-Sepa
Air outlet+ fines
Drive
Prim.
air
Tert.
air
Sec.
air
Feed
Sealing
Fines
Distributor
Guidevanes
Rotor
Coarses
Centrifugal force
Air force
Gravity forcePrim.air
Coarses
Basic function:
Material enters the separator at the top.
Airstream 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 with the tailings outlet.
Fine material exits with the airflow at the upper part of the casing .
Product fineness is adjustable by the rotational speed of the rotor.
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Separators of 3rd Generation
Basic function:
Material enters the separator at the top.
Airstream is generated by an 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 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.
air inlet
rotorblades
air guidevanes
motor
shaft
tailings outletair + finesoutlet
distributor plate
separatingzone
coarsesfines
feed spout gearbox
Example: O&K cross-flow separator
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Separators of 3rd Generation (FLS SEPAX)
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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
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Separators of 3rd Generation (Polysius Sepol SM)Basic function:
Material enters the separator at the bottom with the air stream (e.g. air swept mill)
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 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.Airflow with material from mill
Returns
Fines with air
Rotor
Inspection doors
Rotor drive
Guide vanes
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Separators of 3rd Generation (KHD Sepmaster)
Sepmaster SKS-D (for RP* circuits) Sepmaster SKS-LS (for ASM**)
air and fineproduct
feed material feed material
impact ring
rotordesagglomerator
coarse product
air+fines
feed material+air
coarse fraction 2
coarse fraction 1
air+fines
* Roller Press ** Air Swept Mill
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Separators of 3rd Generation (KHD Sepmaster)
Sepmaster SKS
1
2
3
4
5
6
7
8
9
10
11
guide vanes
rotor blades
distributor plate
rotor shaft
feed spout
air + fines outlet
tailings outlet
air inlet
gear box
sealing
motor
1
2
3
4
5
67
8
9
1011
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SEPT-07HGRS Tikaria_Mill Workshop
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.
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Separators of 3rd Generation (Pfeiffer QDK)
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 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 lower part of the casing .
Product fineness is adjustable by the rotational speed of the rotor.
Rotor drive
Rotor
Air inlet
Air +Fines
Returns
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Separators of 3rd Generation (vertical roller mill ; Loesche)
Feed
AirAir
Returns flow
Separator drive
Guide vanes
Cage rotor
Grit cone
Conical casing
Airflow with material from grinding table
Basic function:
Material enters the separator at the bottom with the air stream.
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, leave the grit cone at the bottom and fall back on to the grinding table.
Fine material exits with the airflow at the top of the casing .
The product fineness is adjustable by rotational speed of the rotor.
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Separators of 3rd Generation (Vertical roller mill)
Guide vane system
Reject cone
Cage rotor
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Separators of 3rd Generation (coal grinding) in VRMBasic 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
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Separator arrangements in grinding circuits
3
4
1
2
Product
Single Pass design
Mainly used where high cooling is required
Fresh-Air
1 Feed bins
2 Mill with water injection
3 Separator with filter
4 Mill dedusting filter
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Separator arrangements in grinding circuits
5
41 3
4a
2
Product
1 Feed bins
2 Mill with water injection
3 Separator with filter
4 Mill dedusting filter
4a Grit separator
5 Optional cement cooler
Standard Arrangement 1st Generation Separator
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Separator arrangements in grinding circuits
4
1
2
3
Product
1 Feed bins
2 Mill with water injection
3 Separator with cyclone and dedusting filter
4 Mill dedusting filter
Cyclone Air Separator
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Potential Problems
Wear
Blades too short
Wear /
Clogging
Wear
Wear
Sealing not tight
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Potential Problems
Wear,clogging
uneven feed distribution
Wear
Wear
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Potential Problems
Wear
Breakouts
Wear
Sealing not tight
Wear
Guide vanes not correctly adjusted
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Potential Problems / clogging
Cage rotor separator casing
partly clogged guide vane system
Material deposits due to insufficient airflow or airflow distribution
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Reduced separation efficiency 1st and 2nd generation dynamic separators
Gap between internal fan and separating chamber bigger than 5 [mm]
Gap between counter blades and wall of separating chamber bigger than 10 [mm]
Reduced number of counter blades
Possible consequence: Desired fineness can not be achieved anymore