STANDARDIZED FILTER TESTS OF METAL WORKING FLUID MIST ... · Development of a standardized test...
Transcript of STANDARDIZED FILTER TESTS OF METAL WORKING FLUID MIST ... · Development of a standardized test...
STANDARDIZED FILTER TESTS OF METAL WORKING FLUID MIST SEPARATORS
Dipl.-Ing. Thomas Laminger
Vienna University of Technology
Institute of Chemical Engineering
Mechanical Process Engineering and Clean Air Technology
Institute of Chemical EngineeringInstitut für Verfahrenstechnik, Umwelttechnik und Technische Biowissenschaften
Vienna University of TechnologyTechnische Universität Wien
CONTENT
2
Introduction
• Background information about Metal Working Fluid
• Usage of mist separators in enclosed machine centers
Standardized test procedure for metal working fluid mist separators
• Analogies of standardized test procedures for dust filter media
• Filter test rig for mist separators
• Set-up and main components
• Measurement device for metal working fluid mist emissions
• Liquid storage inside a mist filter
• Time evolution of the liquid storage and its effect on the pressure drop behavior
• Accelerated filter ageing procedure
Determination of filtration specific properties and classification of filter media
• Classification procedure
• Demonstrative measurement example
• Comparison of achieved results of different filter media
Summary
Outlook
Institute of Chemical EngineeringInstitut für Verfahrenstechnik, Umwelttechnik und Technische Biowissenschaften
Vienna University of TechnologyTechnische Universität Wien
INTRODUCTION
Background
Metal working fluid (MWF) is used in the metal working industry:
– Cooling and lubrication
– Removal of metal chips
Emission of droplet and vapor
About 50% of the oil is used as oil/water-emulsion [1].
- Mineral, synthetic or ester oil base
- Additives (emulsifier, stabilizer, biocides, fungicides, …)
MWF-mist emissions can cause
• skin disease (dermatitis, allergies, oil acne)
• disease of the respiratory path
• cancer, …
Measurement and monitoring of the working environment is necessary and regulated by law.
Preventive measures
• Proper working process and adequate metal working fluid
• Scheduled metal working fluid care and maintenance
• Use of exhausts
• Total enclosed machines with filter system to reduce theemission (droplets and vapor)
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[1] Betrieblicher Umweltschutz in Baden-Württenberg. www.umweltschut-bw.de (2010)
www.zerspanungtechnik.at (2010): full enclosed machining center
(www.fuchs-oil.de, www.tradenote.net (2010): cutting process
Institute of Chemical EngineeringInstitut für Verfahrenstechnik, Umwelttechnik und Technische Biowissenschaften
Vienna University of TechnologyTechnische Universität Wien
FULL ENCLOSED MACHINING CENTER
material machining
Mist
separator
www.handte.de (2010): air ventilation system
Oil
Emulsion
Oil +
Emulsion
Dust
Oil +
Dust
Oil +
Emulsion
+Swarf
Dust
Dust +
Swarft
Institute of Chemical EngineeringInstitut für Verfahrenstechnik, Umwelttechnik und Technische Biowissenschaften
Vienna University of TechnologyTechnische Universität Wien
INTRODUCTION
Types of mist separators
Different separators can be distinguished by theirfiltration mechanism [2]:• Filtering separators• Electrostatic precipitators• Centrifugal collectors • Combinations
5
42%
52%
5%
1%
Types of mist separators[2]
Filtering separators
Electrostatic precipitators
Centrifugal collectors
Combinations
[2] Riss, B.: Erfassung und Abscheidung von Kühlschmierstoff-Emissionen: Erhebung zumStand der Technik in Österreich. In: Zusammenfassung der Vorträger derFachveranstaltung „Kühlschmierstoffe“ der AUVA Österreich; Wien, 20. November 2007.
Clean
gas
Raw
gas
Drainage
1
2
34
www.handte.de (2010): “OEL SMOKE STOP”
1) Pre-separator (Inlet)2) 1-stage filter3) 2-stage filter4) HEPA filter
2
3
4
Institute of Chemical EngineeringInstitut für Verfahrenstechnik, Umwelttechnik und Technische Biowissenschaften
Vienna University of TechnologyTechnische Universität Wien
INTRODUCTION
Filtering separators
To compare filtration specific parameters (e.g. e.g. pressuredrop, separation efficiency) of MWF-mist separators nostandards or norms, as they are available for cleanable dustfilters or particulate air filters, exist.
Purpose of the work
Development of a standardized test procedure for metalworking fluid mist separators (filtering separators) withemulsion as test substance.
1. Filter test rig2. Measurement device for MWF emission3. Test procedure4. System for classification
Institute of Chemical EngineeringInstitut für Verfahrenstechnik, Umwelttechnik und Technische Biowissenschaften
Vienna University of TechnologyTechnische Universität Wien
ANALOGIES TO NORMS AND STANDARDS FOR DUST FILTER
Content/object transferable for mist separators
Filter test rig Filter test rig for mist separators + measurement devices
Test substance (s) MWF-emulsion (mineral oil, synthetic oil)
Test condition of the filter Stationary liquid equilibrium – steady state condition
Filtration specific parametersPressure drop, total holdup, oil holdup, fractional separation efficiency
respective MWF
Classification and characterization10-stage classification system respective the fractional separation efficiency
of several particle sizes (ÖNORM Z1263)
7
• DIN EN 1822: High Efficiency Particulate Air Filters (HEPA and ULPA)
• US-Standard ANSI/ASHRAE Standard 52.2-50007: Method of Testing General Ventilation Air-Cleaning Devices for Removal Efficiency by Particle Size
• EN 779: Particulate air filters for general ventilation
• VDI 3926: Testing of cleanable filter media
Institute of Chemical EngineeringInstitut für Verfahrenstechnik, Umwelttechnik und Technische Biowissenschaften
Vienna University of TechnologyTechnische Universität Wien
FILTER TEST RIG
• Aerosol generator (Austrian Patent A 1658/2003) generation of a test aerosol conditioning of the sucked-off air
• Ageing nozzle• Filter holder• CYCL-FID-Measurement device Online detection of vapor and droplet
concentration
Components Measured and calculated values
• Pressure drop• Drainage flow• Oil concentration of the drainage flow and the
emulsion tank• Raw gas and clean gas concentration
Total holdup (stored emulsion inside the filter) Oil holdup (stored oil inside the filter) Separation efficiency
8
Institute of Chemical EngineeringInstitut für Verfahrenstechnik, Umwelttechnik und Technische Biowissenschaften
Vienna University of TechnologyTechnische Universität Wien
CYCL-FID-MEASUREMENT DEVICE
Components and measurement principle
The variation of the Cut-Off-Diameter (0.3-1.0-3.0-10µm)according to definitions of maximum workplace concentration values(e.g. PM10, PM4, PM2.5) creates several emission fractions.
The fraction with the smallest cut-off diameter includes per definition the vapor fraction of the mist emission.
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Online-Measurement device for the detection of metal working fluid mist emission (concentration of droplet and vapor)Austrian Patent A 1390/2005; European Patent EP 1757927 A2, US-Patent US 7523642 B2
Emission(Droplet+Vapor)
Cyclone
Sampling
Classifier
Oil concentration
FIDEvaporator
measurement
Cut-Off-diameter
Vapor
Droplets( Ø<Cut-Off)+Vapor
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CYCL-FID-MEASUREMENT DEVICE: MEASUREMENT PRINCIPLE
0.3 1.0 3.0
Vapor andDroplets <0.3 µm
10.0
Cut-Off-diameter [µm]
FID
-co
nce
ntr
atio
n
[pp
mp
rop
ane
equ
ival
ent]
Cut-Off-diameter [µm]
FID
-co
nce
ntr
atio
n
[pp
mp
rop
ane
equ
ival
ent]
<1.0
<3.0
<10.0
<0.3
0.3 1.0 3.0 10.0
Vapor
Droplets
Raw gas
Cut-Off-diameter [µm]
FID
-Co
nce
ntr
atio
n
[pp
mp
rop
ane
equ
ival
ent]
<1.0<3.0
<10.0
<0.3
0.3 1.0 3.0 10.0 0.3 1.0 3.0 10.0
Cut-Off-diameter [µm]
FID
-co
nce
ntr
atio
n
[pp
mp
rop
ane
equ
ival
ent]
Clean gas
10
Institute of Chemical EngineeringInstitut für Verfahrenstechnik, Umwelttechnik und Technische Biowissenschaften
Vienna University of TechnologyTechnische Universität Wien
CYCL-FID-MEASUREMENT DEVICE: MEASUREMENT PRINCIPLE
0.3 1.0 3.0 10.0
Cut-Off-diameter [µm]
FID
-Co
nce
ntr
atio
n
[pp
mp
rop
ane
equ
ival
ent]
0.3 1.0 3.0 10.0
Cut-Off-diameter [µm]
FID
-Co
nce
ntr
atio
n
[pp
mp
rop
ane
equ
ival
ent]
Clean gas
Raw gas
Cut-Off-diameter [µm]
Frac
tio
nal
sep
arat
ion
ef
fici
ency
[%
]
Vapor andDroplets <0.3 µm
Calculation of the fractional separation efficiency:
Ei……………Fractional separation efficiency of the emission fraction i [%]
CClean(i)…..Clean gas concentration of the emission fraction i [mg/m³ or ppm]
CRaw(i)…….Raw gas concentration of the emission fraction i [mg/m³ or ppm]
100*(i)C
(i)C1E
Raw
Cleani
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Institute of Chemical EngineeringInstitut für Verfahrenstechnik, Umwelttechnik und Technische Biowissenschaften
Vienna University of TechnologyTechnische Universität Wien
LIQUID STORAGE INSIDE A FILTER MEDIUM
Filtering separators
a. The behavior of pressure drop and holdup of a filter medium for MWF emulsion?
b. Where the stored liquid (holdup) is distributed inside a filter medium?
c. How can a steady state can be achieved in a relatively short time (accelerated aging filter media)? Test procedure
Within a filtering mist filter a complex dynamic system isforming consisting of separated and coalesced droplets,drained-off liquid, re-entrained droplets and the air whichpasses through the filter.
Due to the rearrangement of liquid within the filter (=holdup),the air flow conditions within the filter, respectively furtherfiltration specific parameters (e.g. pressure drop, separationefficiency), continuously change until the steady stateequilibrium is achieved.
Raw gas Clean gas
Drainage
Droplets Droplets(Re-Entrainment)
Mist filter
Institute of Chemical EngineeringInstitut für Verfahrenstechnik, Umwelttechnik und Technische Biowissenschaften
Vienna University of TechnologyTechnische Universität Wien
LIQUID STORAGE INSIDE A FILTER MEDIUM
Balancing the emulsion mass flows of a filter medium allows the calculationof the total stored emulsion (total holdup). Balancing the oil mass (by the oil concentration) of the emulsion flows it is possible to calculate the stored oil mass (oil holdup).
Raw gasClean gas
Drainage
Filter mediumTotal emulsion balance
Water balance
Oil balance
Holdup
t
0
totaldrainageclenraw dt)mmm(holdup(t) Total
t
0
waterdrainagecleanraw dt)mmm(holdup(t) Water
t
0
oildrainagecleanraw dt)mmm(holdup(t) Oil
oildrainage,total drainage,oildrainage, c(t)*(t)m(t)m
raw,totalraw,totaloilraw, c(t)*(t)m(t)m
13
lclean,totalclean,totaoilclean, c(t)*(t)m(t)m
With t=infinite:
Stationary total holdup
Stationary water holdup
Stationary oil holdup
Institute of Chemical EngineeringInstitut für Verfahrenstechnik, Umwelttechnik und Technische Biowissenschaften
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0
100
200
300
400
0 500 1000 1500 2000
Ho
ldu
p[g
]
Time [min]
Oil holdup
Water holdup
Total holdup
LIQUID STORAGE INSIDE A FILTER MEDIUM
14
Time evolution of the pressure drop and holdup
A high increase of the pressure drop within100 minutes.Another 1000 minutes necessary to reach a steady state pressure drop.
0
200
400
600
800
1000
1200
0 500 1000 1500 2000
Pre
ssu
red
rop
[Pa]
Time [min]
Kühlschmier-Emulsion (10 Vol-%)
Separation of MWF-emulsion within the filter medium:• Slow growth of the oil holdup.• The stationary pressure drop is linked to
the attainment of a stationary oil holdup.
Emulsion (10 Vol%)
Institute of Chemical EngineeringInstitut für Verfahrenstechnik, Umwelttechnik und Technische Biowissenschaften
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400
600
800
1000
0 100 200 300 400
Pre
ssu
red
rop
[Pa]
Total holdup [g]
LIQUID STORAGE INSIDE A FILTER MEDIUM
15
Pressure drop vs. Holdup Pictures ofthe clean gas side
60 min
120 min
240 min
1800 min
30 min
Four stages of the filter medium aging:1. Wetting the fibers with drops2. Coalescence of the droplets along the fibers3. Rearrangement of the holdup inside the filter4. Steady-state equilibrium
1
2 3
4
Institute of Chemical EngineeringInstitut für Verfahrenstechnik, Umwelttechnik und Technische Biowissenschaften
Vienna University of TechnologyTechnische Universität Wien
Air flow
Filter depth
Filt
er h
eigh
t
FILTER MODEL TO SIMULATE THE LIQUID DISTRIBUTION WITHIN A FILTER
Air
Liquid
Air
Liquid
Liquid holdup
Assumptions:
1. Filter is mounted vertical. Air
flow is horizontal.
2. Each cell has the same
properties.
3. No flow across the upper and
lower filter’s borders.
4. Air and liquid flows uniformly
to the filter.
5. Liquid becomes fully
separated within the first filter
layer.
16
10x10 cell representing the cross area
Filt
er h
eigh
t
To estimate the liquid distribution within a filter a simulation model was derived.
Institute of Chemical EngineeringInstitut für Verfahrenstechnik, Umwelttechnik und Technische Biowissenschaften
Vienna University of TechnologyTechnische Universität Wien
STEPWISE ITERATION
LH
Aout
AH
Lout
Ain
Lin
Operation parametersLin,raw gas (“Liquid flow to the filter“)Ain,raw gas (“Air flow to the filter“)
Process parametersβ…Deviation angular of fiber orientation to verticalK…Air flow constantζ….Minimum liquid retention number
Iteration procedure1) Start condition (t0) (“dry filter”)Air holdup (AHt0)= Cell volumeLiquid holdup (LHt0)=0
2) Calculation for each cell Porosity εi,j, Volume specific surface AV, Air flow resistance αi,j =f(LH) Air flow Aout Filter pressure drop (∆pFilter)Liquid saturation S Lout Filter liquid holdup (LHFilter)
3) Calculation of the following air and liquid holdup (t1)AHt1=AHt0 + ∑Lin,t0 –∑Lout,t0
FHt1=FHt0 + ∑ Fin,t0 –∑Fout,t0
……
17
t0 t1=t0+Δt
(1)Start
(2)Air and liquid flows
(3)New air and liquid holdup
Iteration steps
t2=t1+Δt
etc.
Institute of Chemical EngineeringInstitut für Verfahrenstechnik, Umwelttechnik und Technische Biowissenschaften
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18
Stepwise development of the liquid holdup-profil of the model filter
Fluid accumulation at the filter clean gas side results in a pressure drop increase, despite an approximately equal holdup.
Mean
STEPWISE ITERATION
Institute of Chemical EngineeringInstitut für Verfahrenstechnik, Umwelttechnik und Technische Biowissenschaften
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ACCELERATED FILTER AGEING: AGEING NOZZLE
The development of the stationary pressure drop relies on the relative slowly forming oil holdup. To shorten the time to form the stationary oil holdup more oil is needed to be brought to the filter in a shorter time.
Hence the time to reach a steady state pressure drop (=Ageing time) should be reduced by increasing the emulsion mass flow to the filter.
Ageing nozzleup to 1g/( cm²/min) filter area specific mass flow (=filter loading)
Top view
Side view
Ring with fine holes
Emulsion pump
Filter medium200
350
350
200x200
19
Institute of Chemical EngineeringInstitut für Verfahrenstechnik, Umwelttechnik und Technische Biowissenschaften
Vienna University of TechnologyTechnische Universität Wien
0
200
400
600
800
1000
1200
0 100 200 300 400 500 600
Pre
ssu
re d
rop
[P
a]
Time [min]
Filter medium: Wire/glass-fiber filterTest substance 10% Emulsion, mineral oilFilter face velocity: 5000m³/(m²/h)
B
A
0
200
400
600
800
1000
1200
0 100 200 300 400 500 600
Pre
ssu
re d
rop
[P
a]
Time [min]
Filter medium: Wire/glass-fiber filterTest substance 10% Emulsion, mineral oilFilter face velocity: 5000m³/(m²/h)Filter loading: 0,05 and 0.45g/(cm²/min)
ACCELERATED FILTER AGEING: TEST PROCEDURE
20
The same stationary pressure drop
is achieved with (A) accelerated
and (B) non accelerated filter
ageing procedure.
1) „Accelerated Ageing“transfer the filter in a stationary condition using the ageing nozzle and the aerosol generator
2) „Stabilizing“shut down of the ageing nozzle – using only the aerosol generator
3) „Measuring“measuring the stationary raw and clean gas concentration with the CYCL-FID-measurement device
AB
Ageing timefilter loading 0.45g/(cm²/min)
Ageing timefilter loading 0.05g/(cm²/min)
With high filter loading values the
ageing time respectively the filter test
time can be reduced to a few hours.
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CORRELATION BETWEEN THE AGEING TIME AND THE FILTER LOADING
21
• With increasing filter loading the ageing time decreases.
• The ageing time of the HEPA-filter depends mostly on the filter loading.
• For an optimal filter loading the finest filter can be used:
Potential irreversible damage of the filter structure >1g/(cm²/min).
For about 2 hours maximum test time 0.5g/(cm²/min) is sufficient.
Ageing time = time to reach a stationary pressure dropFilter loading = filter area specific mass flow
10
100
1000
0,01 0,10 1,00
Age
ing
tim
e [
min
]
Filter loading [g/(cm²min)]
120 min
0.5 g/(cm²min)
Institute of Chemical EngineeringInstitut für Verfahrenstechnik, Umwelttechnik und Technische Biowissenschaften
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Filter-class
Minimal requested separation efficiency (%)
<0.3µm
(including
vapor)
0.3-1µm 1-3µm 3-10µm
1 - - 0≤E3<35 0≤E4<50
2 - - 35≤E3<45 50≤E4<60
3 - 0≤E2<35 45≤E3<55 60≤E4<70
4 - 35≤E2<45 55≤E3<65 70≤E4<80
5 - 45≤E2<55 65≤E3<75 80≤E4<85
6 - 55≤E2<65 75≤E3<85 85≤E4<90
7 0≤E1<5 65≤E2<75 85≤E3<90 90≤E4<95
8 5≤E1<10 75≤E2<85 90≤E3<95 95≤E4
9 10≤E1<20 85≤E2<95 95≤E3 95≤E4
10 20≤E1 95≤E2 95≤E3 95≤E4
Filter-classes:1-3: Pre-Separators, Coarse wire mesh …4-6: Coarse glass-fiber filter, wire/glass-fibre filters …7-10: Fine glass-fiber filters, HEPA filters …
Further report values:Airflow rate, Test substance, stationary pressure drop, total holdup, oil holdup …
CLASSIFICATION SYSTEM FOR METAL WORKING FLUID MIST SEPARATORS
ÖNORM Z1263: 10-stage classification systemStationary fractional separation efficiency of several particle sizes after an accelerated filter ageing
Institute of Chemical EngineeringInstitut für Verfahrenstechnik, Umwelttechnik und Technische Biowissenschaften
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DEMONSTRATIVE MEASUREMENT EXAMPLE
Test filter
Fine wire/glass-fiber filter, 200x200x40mm
Test parameters
Filter face velocity: 5000m³/(m²h)
Test substance: 10% emulsion, mineral oil
Filter loading (ageing nozzle): 0.5g/(cm²/min)
Test aerosol concentration: 56mg/m³
23
0
10
20
30
40
50
60
0
1
2
3
4
5
6
0,1 1 10
Sum
(d
Cm
) [m
g/m
³]
dC
m [
mg/
m³]
Particle size[µm]
Test aerosol: Particle size distribution (PCS 2010, Palas ®)
Aerosol generator: 7500rpm; 1.2l/min emulsion flow
Institute of Chemical EngineeringInstitut für Verfahrenstechnik, Umwelttechnik und Technische Biowissenschaften
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0
100
200
300
400
500
0 50 100 150 200
Ho
ldu
p [
g]
Time [min]
Oil holdup
Total holdup
6
8
10
12
14
16
0 50 100 150 200Oil
con
cen
trat
ion
[%
]
Raw gas emulsion
Drainage emulsion
0
200
400
600
800
1000
1200
1400
0 50 100 150 200Dra
inag
e [
g/m
in].
Pre
ssu
re d
rop
[P
a]
Pressure drop
Drainage
Filter medium: Fine wire/glass-fiber filterTest substance: 10% Emulsion, mineral oilFilter face velocity: 5000m³/(m²h)Filter loading: 0,5 g/(cm²/min)
TIME DEVELOPMENT AND STATIONARY VALUES OF THE PRESSURE DROP,TOTAL HOLDUP AND OIL HOLDUP
StabilizingAccelerated Ageing Measuring
24
Stationary pressure drop: 686Pa
Stationary total holdup: 213g
Stationary oil holdup: 125g
Institute of Chemical EngineeringInstitut für Verfahrenstechnik, Umwelttechnik und Technische Biowissenschaften
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STATIONARY RAW GAS AND CLEN GAS CONCENTRATION AND THE FRACTIONAL SEPARATION EFFICIENCY IN FOUR FRACTIONS
25
0%
20%
40%
60%
80%
100%
0,0
0,4
0,8
1,2
1,6
2,0
<0.3µm 0.3-1µm 1-3µm 3-10µm
Fraction
al sep
aration
efficie
ncy [%
]
FID
co
nce
ntr
atio
n [
pp
m]
Particle size range
Raw gas
Clean gas
Fractional separation efficiency
Filter medium: Fine wire/glass-fiber filterFilter face velocity: 5000m³/(m²h)Test substance: 10% Emulsion, mineral oilTest aerosol concentration: 56mg/m³
Fractionalseparationefficiency:<0.3µm: 0.240.3-1µm: 0.65
Filter medium: Fine wire/glass-fiber filterFilter face velocity: 5000m³/(m²h)Test substance: 10% Emulsion, mineral oilTest aerosol concentration: 56mg/m³
Stationary fractional separationefficiency:<0.3µm: 0.240.3-1µm: 0.651-3µm: 0.983-10µm: 0.98
Filter-
class
Minimal requested separation efficiency (%)
<0.3µm 0.3-1µm 1-3µm 3-10µm
1 - - 0≤E3<35 0≤E4<50
2 - - 35≤E3<45 50≤E4<60
3 - 0≤E2<35 45≤E3<55 60≤E4<70
4 - 35≤E2<45 55≤E3<65 70≤E4<80
5 - 45≤E2<55 65≤E3<75 80≤E4<85
6 - 55≤E2<65 75≤E3<85 85≤E4<90
7 0≤E1<5 65≤E2<75 85≤E3<90 90≤E4<95
8 5≤E1<10 75≤E2<85 90≤E3<95 95≤E4
9 10≤E1<20 85≤E2<95 95≤E3 95≤E4
10 20≤E1 95≤E2 95≤E3 95≤E4
Filter reach Filter-class 7
Institute of Chemical EngineeringInstitut für Verfahrenstechnik, Umwelttechnik und Technische Biowissenschaften
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COMPARISION: STATIONARY PRESSURE DROP, TOTAL HOLDP AND OIL HOLDUP OF DIFFERENT FILTER MEDIA
Six filter media with different filter fineness were tested with the accelerated filter ageing procedure.Within 2-3 hours a steady state condition was reached and the stationary pressure drop, total holdup and oil holdup were determined.
0,01
0,1
1
10
100
(sta
tio
nar
y p
ress
ure
dro
p –
try
pre
ssu
re d
rop
)/s
tat.
to
tal h
old
up
[P
a/g]
26
1st stage
For economical reasons the 2nd and 3rd filter stage must be protected from large quantity of liquid mass.
2nd stage
3rd
stage
0
100
200
300
400
500
600
0
200
400
600
800
1000
1200
Stat
. to
tal h
old
up
[g]
Stat
. oil
ho
ldu
p [
g]
Stat
ion
ary
pre
ssu
re d
rop
[P
a]
Stat. Pressure drop [Pa]
Stat. Total holdup [g]
Stat. Oil holdup [g]
Filter face velocity: 2000 and 5000m³/(m²h)Test substance: 10% Emulsion, mineral oilTest aerosol concentration: 56mg/m³
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0,0
0,2
0,4
0,6
0,8
1,0
<0,3µm 0,3-1µm 1-3µm 3-10µm
Frac
tio
nal
se
par
atio
n e
ffic
ien
cy [
-]
Particle size range
Baffle plate
Coarse wire mesh
Coarse glass-fibre filter
Fine wire/glass-fibre filter
Fine glass-fibre filter
HEPA filter
Filter face velocity: 2000 and 5000m³/(m²h)Test substance: 10% Emulsion, mineral oilTest aerosol concentration: 56mg/m³
27
COMPARISION: STATIONARY FRACTIONAL SEPARATION EFFICIENCY OF DIFFERENT FILTER MEDIA
• With increasing “filter fineness” the fractional separation efficiency increases.
• The largest differences of the fraction separation efficiencies are in the particle size range between 0,3-1µm.
Specified separation efficiency (solid particles) according to EN779: >99%
CYCL-FID-Measurements includes also the vapour phase:
Low vapour reduction!
Institute of Chemical EngineeringInstitut für Verfahrenstechnik, Umwelttechnik und Technische Biowissenschaften
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0123456789
10
Filt
er-
clas
s
Filter face velocity: 2000 or 5000 m³/(m²h)Filter loading: 0.5g/cm²/min (ageing nozzle)Test substance: 10% Emulsion, mineral oilTest aerosol concentration: 56mg/m³
RESULTED FILTER-CLASSES OF THE SIX TESTED MWF MIST FILTERS
Increasing filter-class
Filters with finer structure reach higher filter-class values
Institute of Chemical EngineeringInstitut für Verfahrenstechnik, Umwelttechnik und Technische Biowissenschaften
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SUMMARY
• In analogy to existing norms and standards for dust filters a standardized test procedure for metal working fluid mist filters was developed:
A filter test rig with its main components was presented. The CYCL-FID-measurementdevice and the principle to measure the droplet and vapor concentration of a mist emission in several particle size fractions was shown.
A three-step filter test procedure (accelerated filter ageing) was described using an ageing nozzle which allows the determination of the stationary filtration specific parameters which are pressure drop, total holdup, oil holdup and the fractional separation efficiency in a relative short test time.
A classification system with 10 filter-classes for MWF mist filters was proposed. The system includes four particle size ranges (<0,3µm/0.3-1µm/1-3µm/3-10µm) with minimal requested separation efficiencies. The particle size range “<0.3µm” includes also the vapor fraction of the mist emission.
• With the filter test rig, the developed accelerated filter ageing procedure and the classification system it is now possible to evaluate and compare different mist separators in a very short time.
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