Download - tromp curve dynamic seperator.pdf
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Modernisation of Mill Separators Presented by Dr Joe Khor
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Cemtech Asia 2014 - Kuala Lumpur JK/17.06.2014
1. Introduction
2. Characterisation of separator performance
3. Replacement of 1st generation separators in a German
cement plant (Case Study 1)
4. Modification of a 3rd generation separator in a Malaysian
cement plant (Case Study 2)
5. Investment consideration
6. Conclusion / Discussion
Contents
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Cemtech Asia 2014 - Kuala Lumpur JK/17.06.2014
1. Introduction
Separators in grinding
o Cement manufacture is energy intensive: consuming
typically > 3,000 MJ of fuel/t-clinker and > 90 kWh of
electricity/t-cement;
o Approximately two-third of the electricity consumed is used
for the grinding of raw materials, fuels and cement;
o Grinding is inherently an inefficient process -especially
when mills are operating in open circuit- but closed circuit
mills may also not be as efficient as they should be when
equipped with separators of the older design.
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Cemtech Asia 2014 - Kuala Lumpur JK/17.06.2014
1. Introduction
Grinding without separator: open circuit mill
o In open circuit, material
leaving the mill must comply to
the finished product fineness,
entailing over-grinding &
wasted energy, at times also
overheating & coating of the
mill, which can adversely
affect the mill performance;
o The PSD of the product is
wider & for cement, the higher
coarse fraction can results in
lower strength. Coarse Fine
% r
eta
ined
PSD - Open circuit
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Cemtech Asia 2014 - Kuala Lumpur JK/17.06.2014
1. Introduction
Grinding with separator closed circuit mill
o In closed circuit, the finished
product is separated externally
& the material leaving the mill
can be ground coarser: the mill
residence time is lower, over-
grinding reduced, throughput
higher & specific energy
consumption lower;
o The PSD of the product is
narrower & for cement, the
strength generally higher.
Conventional
Separator
High
Efficiency
Separator %
reta
ined
PSD - Closed circuit
Coarse Fine
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Cemtech Asia 2014 - Kuala Lumpur JK/17.06.2014
Principle of dynamic air separation
o Air separator relies on the balance of
opposing drag (FD) & centrifugal (FC)
forces imparted by the air stream on
the particles as they spiral down the
casing by gravity (FG), to cause the
particles to be either moved into the
rotating cage & discharged as fines,
or continued to spiral down &
discharged as rejects for return to
the mill
FC
FRf
FD
(FG)
1. Introduction
Separator Feed
Separator
Rejects
FRc
Separator
Fines
Separation is imperfect due to uneven air/material distribution, turbulence, particle shape, obstruction of the descending particles, agglomeration, etc
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Cemtech Asia 2014 - Kuala Lumpur JK/17.06.2014
Characterisation of separator performance
o Efficiency -or selectivity- of a separator is a function of the
particle size & is generally characterised by the percentage
of a given particle size in the feed discharged in the rejects;
o Plotting the size selectivity [T(x)] against the particle size [x]
produces a Tromp Curve, which is used to define the separator performance in terms of :
Bypass, Cut size, Sharpness of cut or separation, Imperfection, Agglomeration / mechanical state, of the separator.
2. Separator performance
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Cemtech Asia 2014 - Kuala Lumpur JK/17.06.2014
Tromp Curve
o Tromp curve of perfect
separation -such as by sieving-
is characterized by a step
function from 0 to 100 %, or
perfect sharpness of separation
o Tromp curve of air separator is
imperfect and shows the particle
size selectivity [T(x)] with a
rightward slope indicating the
sharpness of separation & a
minimum value called BYPASS
2. Separator performance
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Cemtech Asia 2014 - Kuala Lumpur JK/17.06.2014
Construction of a Tromp curve
The 1st step is to calculate the average recovery of the
separator fines & reject, vf & vg :
Where:
Vf = fraction of fines as a function of particle size [wt-%]
Vg = fraction of reject as a function of particle size [wt-%]
Qa(x) = fractional amount of feed passing size x [wt-%]
Qf(x) = fractional amount of fines passing size x [wt-%]
Qg(x) = fractional amount of reject passing size x [wt-%]
%100)()(
)()(
xQxQ
xQxQv
gf
ga
f %100)()(
)()(
xQxQ
xQxQv
gf
af
g
2. Separator performance
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Cemtech Asia 2014 - Kuala Lumpur JK/17.06.2014
Particle size selectivity [T(x)] is calculated for each
particle size analysis from the laboratory as follows:
Where::
Qa(x) = amount of feed passing size x [wt-%];
Qg(x) = amount of rejects passing size x [wt-%];
Vg = separator rejects as a function of particle size;
)(
)()(
xQ
xQvxT
a
g
g
Calculating the size selectivity of separator
2. Separator performance
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Cemtech Asia 2014 - Kuala Lumpur JK/17.06.2014
The circulating load [u] of a separator is calculated from
the particles size analysis as follows:
Where:
Vf = separator fines as a function of particle size;
Qa(x) = fractional amount of separator feed of size x [wt-%];
Qf(x) = fractional amount of separator fines of size x [wt-%];
Qg(x) = fractional amount of separator reject of size x [wt-%];
)()(
)()(1
xQxQ
xQxQ
vu
ga
gf
f
Calculating the circulating load
2. Separator performance
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Cemtech Asia 2014 - Kuala Lumpur JK/17.06.2014
Bypass
o Bypass is the most important
value: the lower the bypass,
the higher the efficiency
o A high bypass is an indication
of over-grinding & energy
wasting
o Bypass of the latest generation
high efficiency separator
should be < 10%
2. Separator performance
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Cemtech Asia 2014 - Kuala Lumpur JK/17.06.2014
Cut size
o Cut size is defined as that
particle size (x50) of which
half the particles are collected
as fines & half in the rejects
o If the sharpness of separation
is poor, >50% of the finest
particle sizes may end up in
the rejects so that no definite
cut size exists.
o Cut size of the latest
generation high efficiency
separator should be < 15 m
2. Separator performance
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Cemtech Asia 2014 - Kuala Lumpur JK/17.06.2014
Imperfection
o The imperfection is given by:
o Imperfection of the latest
generation high efficiency
separators should be < 0.35
50
2575
2
)(
x
xxI
2. Separator performance
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Cemtech Asia 2014 - Kuala Lumpur JK/17.06.2014
Sharpness of separation
o Sharpness of separation is
defined by Eder as follows:
o Sharpness of the latest
generation high efficiency
separator should be > 0.50
75
25
x
xx
2. Separator performance
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Cemtech Asia 2014 - Kuala Lumpur JK/17.06.2014
Comparison of separator performance
Generation 1st 2nd 3rd Latest
CPB
Bypass [%] 30 - 60 10 - 35 8 - 20 2 - 10
Min. Cut size [m] > 20 15 - 20 < 15 < 15
Imperfection [-] > 0.50 0.35 - 0.50 < 0.4 < 0.35
Sharpness of cut - < 0.5 > 0.45 > 0.5
Max Blaine [cm/g] 3,800 4,500 5,500 6,000
The latest CPB G4 separator is develped based on extensive CFD modelling & pilot plant trial;
It has an extremely low by-pass of 2 - 10% depending on the product fineness, and can improve mill output / energy consumption by as
much as 20 25%.
2. Separator performance
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Cemtech Asia 2014 - Kuala Lumpur JK/17.06.2014
Replacement of G1 separators in Phoenix Cement*,
Beckum, Germany (2010)
3. Case Study 1
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Cemtech Asia 2014 - Kuala Lumpur JK/17.06.2014
Project outline
Existing plant data (CM 1)
Ball mill 3.8 m x 12 m L equipped with Horizontal Impact Crusher & 2 x 1st generation Heyd separators (installed 1969)
Cement type : CEM I 32.5 R & 42.5 R, CEM II/A-LL 32.5 R
Fineness : 3,800 - 4,200 cm2/g (according to Blaine)
Objectives / Constraints Improve cement early strength Produce high strength cement (> 5,000 cm2/g) Reduce production cost Adaption of restricted plant space Minimal production interruption from changing-over
3. Case Study 1
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Cemtech Asia 2014 - Kuala Lumpur JK/17.06.2014
CPB study & findings
Plant inspection, including axial & circuit sampling to determine the existing mill & separator performance;
Zeisel test to verify the clinker grindability;
Confirmed low performance of Heyd separator due to: - low bypass / separation efficiency,
- low sharpness of separation,
- insufficient range of fineness setting.
3. Case Study 1
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Cemtech Asia 2014 - Kuala Lumpur JK/17.06.2014
Replace the two1st generation Heyd separators with a single QDK 29-NZ high efficiency separator with the
following specifications:
Rated air flow : 143,350 Am3/h Operating temperature : 120 C Installed motor rating : 200 kW Max. feed rate : 258 tph Max. fine product : 115 tph
CPB recommendations
Adapt the ball charge to the new operating conditions & higher product fineness required for the new type
of cement to be produced.
3. Case Study 1
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Cemtech Asia 2014 - Kuala Lumpur JK/17.06.2014
Project implementation - adaptation to restricted
plant layout / space & minimise stoppage time
2 existing Heyd
separators 1 new QDK
separator
Existing
Ball Mill
Erection & commissioning (6 weeks)
Swith-over
(3d)
2 new
Cyclones
3. Case Study 1
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Cemtech Asia 2014 - Kuala Lumpur JK/17.06.2014
Production rate & fineness of CEM II/A-LL 32.5R
after the modernisation
3. Case Study 1
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Cemtech Asia 2014 - Kuala Lumpur JK/17.06.2014
Production rate of CEM II/A-LL 32.5 R of equivalent
strengths from the Heyd and QDK29-N separator
Sample
Separator
Blaine
fineness
[cm/g]
+63 m
residue
[%]
2-day
early strength
[N/mm]
28-day
final strength
[N/mm]
Production
Rate
[%]
CEM II/A-LL 32,5R Heyd 4,100 6.5 8 24 48 100
CEM II/A-LL 32,5R QDK29-NZ 4,144 < 1 31 59 110
CEM II/A-LL 32,5R QDK29-NZ 3,844 1 27 54 112
CEM II/A-LL 32,5R QDK29-NZ 3,450 2 4.5 25 49 120
3. Case Study 1
Cement produced with the new QDK separator at lower fineness has lower residue and the equivalent early and late strength
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Cemtech Asia 2014 - Kuala Lumpur JK/17.06.2014
Comparison of the 63-m residue of CEM II/A-LL 32.5R
from the old Heyd & new QDK29-N separator
3. Case Study 1
Old
New
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Cemtech Asia 2014 - Kuala Lumpur JK/17.06.2014
Tromp curves of the new QDK29-N separator for
various cement types
o For CEM I 32.5 R (3,044
cm2/g) -corresponded to
the new production
capacity (light blue)- the
bypass is < 5%
o For CEM I 52.5 R (5,005
cm2/g) -unable to produce
previously (olive green)-
the bypass is < 10%
3. Case Study 1
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Cemtech Asia 2014 - Kuala Lumpur JK/17.06.2014
Results Before After Difference
Cement type CEM II A-CC 32.5R
Fineness acc Blaine cm2/g 4,100 3,450
Residue 63 m % 6.5 8.0 2 4.5
Output t/h 68 84 + 23.5%
Power consumption kWh/t 37 30.4 - 17.8%
Cement quality 2 D N/mm2 24 25 + 1
Cement quality 28 D N/mm2 48 49 + 1
3. Case Study 1
Overall benefits of the separator replacement
Specific energy savings of approx 10% for CEM I 42.5 R
Production of CEM I 52.2 R for new market
* Refer ZKG 12, 2011 for more details
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Modification of a competitor-modified CPB G3
separator in Holcim Malaysia, Pasir Gudang (2014)
4. Case Study 2
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Cemtech Asia 2014 - Kuala Lumpur JK/17.06.2014
Project outline
Reasons / objectives of the modification The original CPB separator installed in 1997 was modified
by a competitor in 2008 to attempt to improve performance
Instead, performance worsened due to excessive vibration & cement residue also increased
CPB was requested to propose a solution at minimal investment & production interruption
4. Case Study 2
Existing plant data Ball mill 4.4 m x 12.75 m L, equipped with roller press Competitor-modified CPB separator QDK 36-N Cement types: HTS, HDC, HEW, HRF, HQC. Fineness: 3,800 - 4,200 cm2/g (according to Blaine) R 45 m: < 3.5%
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Cemtech Asia 2014 - Kuala Lumpur JK/17.06.2014
CPB study & findings
Plant inspection -including axial & circuit sampling- to determine the existing mill & separator performance;
Confirmed high vibration due to insufficient stiffness of the modified rotating cage;
Competitor-modified air Inlet guide vanes unsatisfactory;
Gap of the modified labyrinth seal is excessive, allowing coarse particles entrainment in the fines;
Ball charge should be optimised, mill ventilation improved, separator motor & sealing air fan upgraded to further
improve the performance out of the project scope
4. Case Study 2
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Cemtech Asia 2014 - Kuala Lumpur JK/17.06.2014
Differences in CPB & competitor design of rotating cage
The blades spacing were wider -170 mm cf 40 mm in CPB
design- bolted -not welded- & resulted in decreased cage
stiffness, even with the stiffener ring
4. Case Study 2
Stiffener ring
170 mm
Bolted
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Cemtech Asia 2014 - Kuala Lumpur JK/17.06.2014
Overview of the CPB & competitor rotating cage design
4. Case Study 2
CPB-design Competitor-design
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Cemtech Asia 2014 - Kuala Lumpur JK/17.06.2014
4. Case Study 2
Differences in CPB & competitor design of air guide vanes
CPB-design Competitor-design
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Cemtech Asia 2014 - Kuala Lumpur JK/17.06.2014
4. Case Study 2
135 mm
25 mm
The gap between the inlet spiral
housing & modified rotating cage
was 135 mm, compared with 90
mm in CPB design
The labyrinth seal gap between the
fines exhaust duct & modified
rotating cage was 25 mm,
compared with 3 mm in the CPB
confined air seal
Differences in CPB & competitor design of inlet & air seal
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Cemtech Asia 2014 - Kuala Lumpur JK/17.06.2014
There was no deflection plate at
start of the inlet spiral housing
4. Case Study 2
Position of deflection plate
in CPB QDK separator
Differences in CPB & competitor design of spiral air inlet
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Cemtech Asia 2014 - Kuala Lumpur JK/17.06.2014
CPB recommended re-modifications
4. Case Study 2
Feed inlet chutes
Distributor plate
Air guide vanes
Rotating cage
Confined air seal
* Opportunity taken to also renew the cartridge bearings in the shut-down
1
2
3
4
5
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Cemtech Asia 2014 - Kuala Lumpur JK/17.06.2014
Confined air seal & cartridge bearing of CPB separator
Arrangement of the
confined air seal in
CPB separator
Cartridge bearing
4. Case Study 2
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Cemtech Asia 2014 - Kuala Lumpur JK/17.06.2014
Installation of the CPB air guide vanes, confined air
seal & rotating gage
4. Case Study 2
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Cemtech Asia 2014 - Kuala Lumpur JK/17.06.2014
Installation of the CPB feed distributor plate
4. Case Study 2
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Cemtech Asia 2014 - Kuala Lumpur JK/17.06.2014
Dismantling & assembly of the CPB cartridge bearing
after refurbishing
4. Case Study 2
Renewal of cartridge
bearings during the
shut-down
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Cemtech Asia 2014 - Kuala Lumpur JK/17.06.2014
Final assembly of the CPB re-modified QDK separator
4. Case Study 2
Modification took less than 10 days from start to finish
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Cemtech Asia 2014 - Kuala Lumpur JK/17.06.2014
Original
CPB
Latest CPB
Competitor
Tromp curve before & after the modification
o CPB original (1997):
Bypass > 15%
o Competitor-modified (2013):
Bypass > 34%
o CPB latest (2014):
Bypass < 3%
4. Case Study 2
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Cemtech Asia 2014 - Kuala Lumpur JK/17.06.2014
Results Units Before After Difference
Cement type HRF
Blaine fineness cm2/g 3,892 3,674 -218
+45 m residue % 2.81 2.40 -0.41
Output t/h 113 122 9
Power consumption kWh/t 47.7 45.6 -2.1
Cement quality 7 D N/mm2 40.0 40.0 0.0
Cement quality 28 D N/mm2 51.1 51.9 0.8
4. Case Study 2
Summary of the improvement results*
For HQC, output increased by 10 t/h & power reduced by 4 kWh/t ROI estimated to be < 4 months, without considering higher sales
* Mill has not been fully optimised by CPB; data provided by Holcim Malaysia
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Cemtech Asia 2014 - Kuala Lumpur JK/17.06.2014
ROI of a separator modification project in Germany*
CEM II/A-LL 32.5 R Basis: 7,200 h/yr running
Total investment 210,000
Electricity saving (38.8 34.1) kWh/t x 127 t/h x 7,200 h/yr = 4,297,680 kWh/yr
Electricity cost saving at
av. cost of 0.08/kWh 0.08 /kWh x 4,297,680 kWh/yr = 343,814 /yr
Return on investment 7.3 month (on electricity saving)
Production increase (127 111) t/h x 7,200 h = 115,200 t/yr
Extra sales at 10 /t profit 115,200 t/yr x 10 /t = 1,152,000 /yr
Total benefits 1,495,814 /yr (on electricity & sales)
Return on investment 1.7 months (electricity + extra sales)
5. Investment consideration
* Based on data of Heidelberger Cement Schelklingen Works
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Cemtech Asia 2014 - Kuala Lumpur JK/17.06.2014
1.Separators play an important role in mill performance:
affecting the output, power consumption & cement quality;
2.Poor performance of separators are often overlooked, due
to either their locations out of sight, out of mind- or failure to audit & benchmark the performance;
3.The latest CPB separators are highly efficient -capable of
achieving bypass of < 5% for most cement types &
improve mill performance by as much as 25%, as well as
ability to produce higher Blaine / quality cement;
4.Higher grinding efficiency & cement quality means higher
margin & market shares -ROI is typically < 6 months- as
well as a lower carbon foot-print for the environment.
6. Conclusion
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Cemtech Asia 2014 - Kuala Lumpur JK/17.06.2014
Thank you
for your
attention, any
questions or
comments?
6. Discussion
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