STANDARDIZED FILTER TESTS OF METAL WORKING FLUID MIST ... · Filter test rig Filter test rig for mist separators Test substance (s) MWF‐emulsion (mineral oil, synthetic oil) Test

STANDARDIZED FILTER TESTS OF METAL WORKING FLUID MIST SEPARATORS

TEMPUS MEETING VIENNA15 – 19th November 2010

Dipl.-Ing. Thomas LamingerUniv. Prof. Dr. Wilhelm Höflinger

Vienna University of TechnologyInstitute 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

Proposal of a standardized test procedure for metal working fluid mist separators

Summary

Outlook

• 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 of mist separators in a stationary condition− Demonstrative measurement example− Comparison of achieved results of different filter media

• Background information about Metal Working Fluid• Usage of mist separators in enclosed machine centers



INTRODUCTION

BackgroundIn Germany about 80.000t per year of lubrication oil is used in the metal working industry. About 50% of the oil is used as oil/water‐emulsionwhich leads to 600.000t/a used metal working fluid (MWF) [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)[1] Betrieblicher Umweltschutz in Baden‐Württenberg. www.umweltschut‐bw.de (2010)

3

www.zerspanungtechnik.at (2010): full enclosed machining center

www.tradenote.net (2010): cutting process



FULL ENCLOSED MACHINING CENTER: AIR VENTILATION

Fire protection

Swarf capture air stream

Clean air exhaust

Mist ventilation

material machining

Mist separator

www.handte.de (2010): air ventilation system



MULTISTAGE MIST SEPARATOR

Clean gas

Raw gas

Drainage

1

2

34

State of the art filter systems use multistage mist separators:

1)Pre-separator (Inlet)2)1-stage filter3)2-stage filter4)HEPA filter

www.handte.de (2010): OEL SOKE STOP



INTRODUCTION

Types of mist separators

Different separators can be distinguished by theirfiltration mechanism [2]:•Filtering separators•Electrostatic precipitators•Centrifugal collectors •Combinations

Filtering separators

6

42%

52%

5%

1%

Types of mist separators[2]

Filtering separators

Electrostatic precipitatorsCentrifugal collectors

Combinations

For MWF‐mist separators no standards or norms as they are available for cleanable dust filters or particulate air filters exist.

Purpose of the work

Development of a standardized test procedure for metal working fluid mist separators (filtering separators) with emulsion as test substance.

[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.



PROPOSAL OF A STANDARDIZED TEST PROCEDURE

Content/object transferable for mist separators

Filter test rig Filter test rig for mist separators

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 characterizatione.g. 10‐stage classification system respective the fractional separation efficiency of several particle sizes

7

Analogies to norms and standards for dust filter

• 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



FILTER TEST RIG

• Aerosol generator− 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



CYCL‐FID‐MEASUREMENT DEVICE

Components and measurement principle

The variation of the Cut‐Off‐Diameter (0,3‐1‐3‐10µm)according to definitions of maximum workplace concentration values(zB. PM10, PM4, PM2,5, etc.) creates several emission fractions.

The fraction with the smallest cut‐off diameter includes per definition the vapor fraction of the mist emission.

• Measuring the clean gas concentration of 4 fractions +

• Measuring the raw gas concentration of 4 fractions

Fractional separation efficiency of 4 fractions

Classifier(Cyclone)

EmissionDroplets+ Vapor

Droplets(Ø<Cut‐Off)+ Vapor

Measurement

(FID)Evaporator

Droplets(Ø>Cut‐Off)

Vapor

9

Online‐Measurement device for the detection of metal working fluid mistemission (concentration of droplet and vapor)

Flame‐Ionization‐Detector (FID)



CYCL‐FID‐MEASUREMENT DEVICE: MEASUREMENT PRINCIPLE

0,3 1,0 3,0

<0,3

1,0 –

0,3

3,0 –

1,0

10,0

–3,0

Vapor andDroplets <0,3 µm


10,0Cut‐Off‐diameter [µm]

FID‐con

centratio

n [ppm

prop

ane

equivalent]

Cut‐Off‐diameter [µm]

FID‐con

centratio

n [ppm

prop

ane

equivalent]

<1,0

<3,0

<10,0

<0,3

0,3 1,0 3,0 10,0

VaporVapor

DropletsDroplets

Raw gasRaw gas


FID‐Con

centratio

n [ppm

prop

ane

equivalent]

<1,0<3,0

<10,0

<0,3

0,3 1,0 3,0 10,0 0,3 1,0 3,0

<0,3

1,0 –

0,3

3,0 –

1,0

10,0

–3,0


FID‐con

centratio

n [ppm

prop

ane

equivalent]

Clean gas

Clean gas

10



CYCL‐FID‐MEASUREMENT DEVICE: MEASUREMENT PRINCIPLE

0,3 1,0 3,0

<0,3

1,0 –

0,3

3,0 –

1,0

10,0

–3,0


FID‐Con

centratio

n [ppm

prop

ane

equivalent]

0,3 1,0 3,0

<0,3

1,0 –

0,3

3,0 –

1,0

10,0

–3,0


FID‐Con

centratio

n [ppm

prop

ane

equivalent]

Clean gas

Clean gas

Raw gasRaw gas

<0,30,3 ‐ 1,0

1,0 ‐ 3,0

3,0 ‐ 10,0


Fractio

nal sep

aration

efficiency [%

]



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)C

1ERaw

Cleani −=

11



LIQUID STORAGE INSIDE A FILTER MEDIUM

Balancing the emulsion mass flows of a filter medium allows the calculationof the total stored emulsion (total holdup). And from there including the oil concentration of the emulsion flows it is possible to calculate the stored oil mass (oil holdup).

Raw gasClean gas

Drainage

Filter medium Total emulsion balance

Water balance

Oil balance

Holdup

∫ −−=

t0

t o t a ld r a i n a g ec l e nr a w d t)mmm(h o l d u p ( t ) T o t a l &&&

∫ −−=

t0

w a t e rd r a i n a g ec l e a nr a w d t)mmm(h o l d u p ( t ) W a t e r &&&

∫ −−=

t0

o i ld r a i n a g ec l e a nr a w d t)mmm(h o l d u p ( t ) O i l &&&

oildrainage,total drainage,oildrainage, c(t)*(t)m(t)m && =

raw,totalraw,totaloilraw, c(t)*(t)m(t)m && =

12

lclean,totalclean,totaoilclean, c(t)*(t)m(t)m && =

With t=infinite:

Stationary total holdup

Stationary water holdup

Stationary oil holdup



LIQUID STORAGE INSIDE A FILTER MEDIUM

13

Results(Long time test run using only the aerosol generator)

•The pressure drop still increases although the drainage reaches quickly a stationary value.

•The oil concentration of the drainage emulsion is slightly lower as the oil concentration of the raw gas emulsion

the oil holdup within the filter rises.

•Due to the separation of the oil/water‐emulsion the oil holdup increases relative slowly compared to the total holdup. The growing oil holdup enhances the filtration resistance and therefore the pressure drop increases until the oil holdup reaches a steady state.



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

200x

200

14



B

A

ACCELERATED FILTER AGEING: TEST PROCEDURE

15

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.



CORRELATION BETWEEN THE AGEING TIME AND THE FILTER LOADING

16

• 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



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

17

Test aerosol: Particle size distribution (PCS 2010, Palas ®)

Aerosol generator: 7500rpm; 1,2l/min emulsion flow



TIME DEVELOPMENT AND STATIONARY VALUES OF THE PRESSURE DROP,TOTAL HOLDUP AND OIL HOLDUP

StabilizingAccelerated Ageing Measuring

Pressure

dropPress

ure

drop

18

Total

holdup

Total

holdup

Oil holdup

Oil holdup

Stationary pressure drop: 686Pa

Stationary total holdup: 213g

Stationary oil holdup: 125g



STATIONARY RAW GAS AND CLEN GAS CONCENTRATION AND THE FRACTIONALSEPARATION EFFICIENCY IN FOUR FRACTIONS

19



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.

20

1st stageFor economical reasons the 2nd and 3rd filter stage must be protected from large quantity of liquid mass.

2nd stage

3rd

stage



21

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.

According to EN 779

Specified separation efficiency (solid particles) according to EN779: >99%

CYCL‐FID‐Measurements includes also the vapour phase:

Low vapour reduction!



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‐measurement device and the principle to measure the droplet and vapor concentration of a mist emission in several particle size fractions was shown.It was further presented that balancing the liquid mass flows of a filter medium allows the calculation of the total holdup, water holdup and oil holdup.

• Using an emulsion as test substance it was found out that the relative slow forming oil holdup limits the achievement of a stationary pressure drop of filter media (ageing time). Therefore an ageing nozzle was used to enhance the liquid mass flows to the filter respectively to shorten the ageing time.

22



SUMMARY

• A three‐step filter test procedure for an accelerated filter ageing was described 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.

• The accelerated filter ageing procedure was tested using six different filters.

− With this accelerated ageing procedure the stationary filtration specific values could be determined within 2‐3 hours test time.

− The pressure drop of 2nd and 3rd filter stage increase dramatically even with small liquid amounts and therefore pre‐stage filters should protect them.

− The stationary fractional separation efficiency in the particle size range <0,3µm of the tested filter media achieved with the CYCL‐FID‐measurement method were generally low. A comparison with specified fraction separation values according to EN 779 indicated a poor vapor reduction property of the filters.

23



OUTLOOK

• Development of a classification procedure using e.g. the stationary fractional separation efficiency in several particle size ranges.

• Implementation of a filter test norm or standard (e.g. ÖNORM).



THANK YOU FOR YOUR ATTENTION!

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Documents

STANDARDIZED FILTER TESTS OF METAL WORKING FLUID MIST ... · Filter test rig Filter test rig for mist separators Test substance (s) MWF‐emulsion (mineral oil, synthetic oil) Test