nanofibers - home - national air filtration...

9. Symposium Textile Filter in Chemnitz, 2008

NAFA Technical Seminar

Phoenix AZ, 2012

Nanofibers

New Developments in Filtration

Dr. Andreas Seeberger

Mike Harriman

Abb.: 26, FotoNr.: 0606A00035, 630 : 1 50 µm

Abb.: 4, FotoNr.: 0606A00011, 1140 : 1 50 µm


• Located in Greensboro, NC • Manufacturer of synthetic filters

IREMA-FILTER and Aeolus Filter Corp.

• Established 1997

2

• German Company • Manufacturer of synthetic filter media

• Manufacturer of pleated products

Industry HVAC Automotive

Synthetic Filter Media for

9. Symposium Textile Filter in Chemnitz, 2008 3

Let´s talk about fibers

What do you think when you hear „nanofibers“ ?

Small ?

New technologies ?

High performance filters ?

Applications ?

Use it ?

Today´s objective

Background information on fine and nanofiber filtration

Capabilities for current air filtration requirements


History of Nanofibers in Filtration Technical Characteristics of Nanofibers Production Technologies Performance in Filtration Applications

High Efficiency Filtration Progressive Media Design

Examples

Summary

Outline

4




Examples

Summary

Outline

5


A brief overview

The development of fine and nanofibers for filtration

• Conventional and natural man made fibers were > 10 µm

• Development of microfibers brought fibers < 10µm

• Microglass nanofibers (0.4 µm) widely available for decades

• Electrospun nanofibers used for 25 years, increasingly for 10-12 years

• Since 2000 nanofibers in focus of intensive research

• Meltspun polymer nanofibers since 2007

• Today: established products, ongoing R&D, new technologies




Examples

Summary

Outline

7


Definition of Nanotechnology

Ant (~ 5 mm)

Dust Mite

(~ 200 μm)

Human hair

(~ 60-120 μm wide)

DNA

(~ 1-1/2 nm)

5 Atoms of silicon

(~ 1nm)

Head of a pin

(~ 1-2 mm)

Micro Electro

Mechanical Devices (~ 10-100 μm wide)

Red blood

cells Pollen

grain

Carbon Nanotube

(~ 2 nm diameter)

Abb.: 26, FotoNr.: 0606A00035, 630 : 1 50 µm

Nanofibers

(~ 20-500 nm)

10-2

10-3

10-4

10-5

10-6

10-7

10-8

10-9

10-10

1 cm

10 mm

1

mm

1 nm

0,1 mm

100 μm

0,01

mm 10 μm

10 μm

100 nm

0,01

μm 10 nm

0,1 nm

Visible

Spectrum

Millisc

ale

M

icro

sca

le

Na

no

sca

le

Red blood cell with

white cell

(~ 2-5 μm)

Stacks of clay mineral

pletelets, each platelet with ~ 1 nm thickness

http://de.wikipedia.org/wiki/Bild:Red_White_Blood_cells.jpg


Definition of Nanofibers for Filtration

The definition of nanofibers for filtration

Today: Nanotechnology = smaller than 0.1 µm (100 nm)

Common in filtration: Fiber diameter < 0.5 µm (500 nm)

Former barrier to achieve fiber diameters < 1 µm

Start of „nano“-effects from 500 nm and below




Examples

Summary

Outline

10


Production Technologies

Electrospinning

Island-In-The-Sea

Centrifuge Spinning

Manufacturing

Techniques Meltblown

Wet Laid Microglass Others

Glass Fiber

Synthetic


Glass fibers

Source: Owens Corning Fiberglas Corporation, Journal of the Air Pollution Control Association 1962


Wet-laid microglass production

Source: I. Lappas, Filtrex ASIA, New-Delhi 2010 / / Dynatec

Distributor Web Formation Binder Application Drying


Microglass Composition

Composition „E“-Glass „C-Glas“

Silicon dioxide 52-56 % 60-65 %

Calcium oxide 16-25 % -

Aluminium oxide 12-16 % 2- 6 %

Boron oxide 8-13 % 2- 7 %

Sodium and

potassium oxide

0- 1 % 8-12 %

Mognesium

oxide

0- 6 %

-

Magnesium

oxide and

calcium oxide

- 15-20 %

Binder Systems

Latex

Melamine

Phenolic

Epoxy


Microglass characteristics

Microglass filter media

• Can have very low fiber diameters (0.3 µm)

• Is available with large variety of filtration characteristics

• Is filter media of choice for high efficiency (HEPA) applications

• Has advantages and disadvantages

(efficiency vs. handling/moisture resistance/shedding

• Is tried to be replaced in increasing number of applications

• Is NOT focus of today´s presentation


Polymer Nanofibers

Polymer Nanofibers

Tissue engineering scaffold

Adjustable biodegradation rate

Better cell attachment

Contraollable cell directional growth

Wound dressing

Prevents scar

Bacterial shielding

Medical prosthesis

Lower stress concentration

Higher fracture strength

Heamostatic devices

Higher efficiency in fluid

adsorption

Sensor devices

Higher sensitivity

For celd, arteries and veins

Electrical conductors

Ultra small devices

Optical applications

Liquid crystal optical

shutters

Material reinforcement

Higher fracture toughness

Higher delamination resistance

Protective clothing

Breathable fabric that

blocks chemicals

Filter media

Improved

performance

Cosmetics

High utilization

Higher transfer rate

Drug delivery

Increased dissolution rate

Drug-nanofiber interlace


Island-In-The-Sea

Spinning of bicomponent fibers

Island-in-the-sea structure

Different geometries

Dissolving sea-polymer

Advantages Disadvantages

Standard spinning processes for bico-fibers

Narrow diameter range

Nano-range not easy achievable

Solvent use

Two-step-process

Source: Kuraray


Electrospinning


Fiber diameters as low as 50 nm

Various polymers applicable

Homogeneous fiberdiameters

Low production rate

Use of environmentally critical solvents

Two-step-process

Fibers only in layers


Meltblown


normal operation: fiber diameters of

only 1-2 microns

Recently increasing R&D

activities

New improvements for finer fiber diameters

polymer

hot air hot air

polymer

fibers

air air

spinneret

High productivity

Solvent free

Single step process


History of Nanofibers in Filtration Technical Characteristics of Nanofibers Production Technologies

Performance in Filtration Applications


Examples

Summary

Outline

20


The impact of nanofibers on filtration

Decreasing pressure drop

Increasing collection efficiency

Improved media design possibilities

2

f

0

d

ftUp

η = viscosity

df = diameter of the fiber

t = thickness of filter

U0 = face velocity of filter

α = Volume fraction of fibers in a filter

porosity1volumetotal

volumefiber

Slip Flow Effect

High inner surface area

More distinct progressivity

fr

Kn


Filtration Markets for polymeric nanofiber products

Dust Collection

HEPA Filtration

HVAC

Vacuum Cleaners Automotive

Fuel Filtration EDM

Battery Separator Protective Clothing


High Efficiency Synthetic Filter Media

Electrete Product Nanofiber Product

High efficiency products

Well balanced pressure drop

No or little discharge

Very reliable filtration

Mostly medium efficiencies

Very low initial resistance

Strong discharge possible

„Insecure“ performance

All hydrophobic synthetic media show electrete effects of different strength

Combination of nanofiber and electrete technology

Influence of electrete effect only detectable by discharge treatment


Approach of IREMA and AEOLUS: Integrated Nanofiber Technology

Integration of polymer nanofibers into nonwoven material

Inline Process

Solvent free fabrication of fibers with different diameters

Task specific fiber diameters for filtration

Gradient control of nanofiber distribution

Enhanced filtration performance

One-layer pleatable filter material

Unmixed Material

Patented Technology


Integrated Nanofiber Technology for improved filter media

Developing of new

synthetic filter media

•Higher mechanical efficiencies

•Higher capacities

•Low pressure drops

Nanofiber products not only

for high efficiency filtration,

but also for basic fine dust

filtration and even

prefiltration applications !


Investigations on filter

discharge treatments

• Nordtest / SINTEF

• ASHRAE research projects RP 1189/1190

• EUROVENT 2004 round robin test

• R&D of filter companies

Still lack of information/transparency

Treatment methods

• Superfine KCl

• Isopropyl alcohol (IPA)

• Soot

• Detergents

Objects

• Investigate influence of electrostatic charges

• Inactivation by impinging particles

• Long term stability / natural decay rate

• Efficiency prediction in real applications

Fine dust filtration for Merv 13-A applications – Discharge Treatments


Fine dust filtration for Merv 13-A applications – Filter Media

Stabilisation zone

Transition region

Nanofiber zone

Mechanical protection

Fine dust filter media IFN 80 – showing full potential of nanotechnology !


Comparison of treatments for synthetic filter media

ASHRAE 52.2

Appendix J

• Conditioning step:

superfine KCl

(sub 0.1 µ)

• Loading until

minimum efficiency

(0.4 µ KCl) is

reached

prEN779:2010

• Isopropyl alcohol

(IPA)treatment to

simulate discharge

effects

• Minimum DEHS

efficiencies must be

reached (0.4 µ):

F7: 35 %

F8: 55 %

F9: 70 %

Diesel soot

• Diesel soot

nanoparticles

treatment to

investigate effects

on efficiency

• sub 0.1 µm particles

Independent Testing


EN779: F7 panel filter with integrated nanofibers

EN779:2010 test of panel filter with IREMA IFN80 nanofiber

media

Cond.: 593x593x95 mm, EN779 standard test, 3400 m3 h-1

0

10

20

30

40

50

60

70

80

90

100

0,1 1 10

DEH

S Ef

fici

en

cy [%

]

Particle Size [µm]

Efficiency DEHS [%] untreated

prEN779:2010

• Isopropyl alcohol

(IPA) treatment to

simulate discharge

effects

• Minimum DEHS

efficiencies must

be reached (0.4 µ):

F7: 35 %

0

10

20

30

40

50

60

70

80

90

100

0,1 1 10

DEH

S Ef

fici

en

cy [%

]

Particle Size [µm]


Efficiency DEHS [%] completely immersed in IPA and dried for 24 h

F7 filter class


Ashrae 52.2: Merv 13 panel filter with integrated nanofibers

Ashrae 52.2 test of panel filter with IFN80 nanofiber media

Cond.: 593x593x95 mm, Ashrae Dust, 3350 m3 h-1

ASHRAE 52.2

Standard

• KCl efficiency

0

10

20

30

40

50

60

70

80

90

100

0,1 1 10

Effi

cie

ncy

[%]

Particle Size [µm]


Efficiency DEHS [%] discharged by IPA

Efficiency KCl [%] untreated


Ashrae conditioning characteristics

Average number distribution of ambient

air particles from the Pittsburgh Air Quality Study (PAQS)

Atmospheric Environment 38 (2004) 3275–3284

0

5000

10000

15000

20000

25000

30000

0,001 0,01 0,1 1

Co

un

ts

Particle Size [µm]

KCl conditioning aerosol

Particle size distribution at Ashrae 52.2

conditioning step

Peak at 40 nm


0

10

20

30

40

50

60

70

80

90

100

0,1 1 10

Effi

cie

ncy

[%]

Particle Size [µm]


Efficiency DEHS [%] discharged by IPA

Efficiency KCl [%] untreated

Efficiency KCl [%] discharged by superfine KCl

32

Ashrae 52.2: Merv 13-A panel filter w. integrated nanofibers

Ashrae 52.2 test of panel filter with IFN80 nanofiber media

including Appendix J conditioning step

Cond.: 593x593x95 mm, Ashrae Dust, 3350 m3 h-1

ASHRAE 52.2

Appendix J

• Conditioning step:

superfine KCl

(sub 0.1 µ)

• Loading until

minimum

efficiency (0.4 µ

KCl) is reached

• No p increase

during loading

MERV 13-A


Variability of Ashrae 52.2 KCl Conditioning

Ashrae 52.2 test of non-electret filters including Appendix J conditioning step

in different US laboratories

Air Media (Fall 2008) 12-13


Soot loadig: F7 integrated nanofiber media

0

50

100

150

200

250

300

350

0,01 0,1 1

Par

ticl

e n

um

be

r [1

0k]

Particle size [µm]

Particle size distribution of soot

Peak at 70 nm

Efficiencies of various aerosols on IREMA IFN80 nanofiber media

Cond.: velocity approx. 0.15 m/s, efficiency measurements with NaCl and soot

0

10

20

30

40

50

60

70

80

90

100

0,1 1 10

Effi

cie

ncy

[%

]

Particle size [µm]

Initial Efficiency NaCl

Initial efficiency KCl

Initial efficiency DEHS

Measurement of

NaCl efficiency



Soot loading on IREMA IFN80 nanofiber media

Cond.: velocity 0.15 m/s, efficiency measurements with NaCl

0

10

20

30

40

50

60

70

80

90

100

0,01 0,1 1 10

Effi

cie

ncy

NaC

l [%

]

Particle size [µm]

Initial Efficiency (APS)

+50 Pa soot (APS)

No efficiency

drop during soot

loading seen


0

10

20

30

40

50

60

70

80

90

100

0,01 0,1 1 10

Effi

cie

ncy

NaC

l [%

]

Particle size [µm]

Initial Efficiency (SMPS)

Initial Efficiency (APS)

+50 Pa soot (SMPS)

+50 Pa soot (APS)

36


Soot loading on IREMA IFN80 nanofiber media

Cond.: measurements at velocity 0.15 m/s, efficiency measurements with NaCl, no merging procedure of SMPS and APS results


Evaluation of IFN80 nanofiber media

Nanofibers strongly reduce influence of electrostatics

High mechanical efficiencies

Different discharge treatments successfully passed

No loss of filter class with IPA treatment

Sub 0.1 µm KCl particles seem to have strongest influence

Soot particles virtually have no severe effect

Very reliable filtration results under any conditions!


Fine dust filtration for Merv 13-A applications – Filter Media

Saving energy by progressive media design ?


Dust holding capacity of different panel filters

Cond.: 593x593x95 mm, measurement according to EN779 (Standard), 3400 m3 h-1

Dust holding capacity of micro and nanofiber products

0

100

200

300

400

500

0 50 100 150 200

p

[Pa]

Dust holding capacity [g]

Media A (Fiberglass)

Media B (Synthetic Microfiber)

Media C (Synthetic Microfiber)


Dust holding capacity of micro and nanofiber products

Dust holding capacity of different panel filters

Cond.: 593x593x95 mm, measurement according to EN 779 (Standard), 3400 m3 h-1

0

100

200

300

400

500

0 50 100 150 200

p

[Pa]

Dust holding capacity [g]

Media A (Fiberglass)Media B (Synthetic Microfiber)Media C (Synthetic Microfiber)Media D (Synthetic Nanofiber)


400

450

500

550

600

650

700

0 50 100 150 200

Tota

l co

sts

[€]

Operation time [d]

Annual costs (operation and service)

Total costs F7

Total costs IFN 80

41

Energy demand and lifetime costs

E = Q p t

1000

E Energy demand [kWh]

Q Flow rate [m3 s-1]

p Pressure drop [Pa]

t Time [h]

Fan efficiency [-]

Assumptions:

Dust concentration: 1 g Ashrae/day

Flow rate: 3400 m3 h-1

Energy costs: 0,15 €/kWh

Cost per filter: 60 €/filter

Labour costs: 15 €/change

Annual Energy costs: Total costs:

Media C: 390,59 € 705,25 €

Media D: 335,93 € (- 14,0 %) 562,17 € (-20,3%)


Nanofiber filtration for Merv 13-A applications – Filter Media

Nanofiber filter media – Washable mini pleats?


0.0

25.0

50.0

75.0

100.0

New Filter Loaded Filter 1st Washing 2nd Washing 3rd Washing

Effi

cie

ncy

NaC

l @

50

0 fp

m

0.3 - 0.5 µm

0.5-1.0 µm

43

Nanofiber filtration for Merv 13-A applications – Washable Filter Media

Efficiency measurements after several dust loading and washing procedures

Cond.: 24 x 24 x 4, 2000 cfm, ISO fine dust, washing with clear water

Important !

• Mechanical

protection of

nanofibers

• Sufficient nanofiber

concentraiton


Nanofiber filtration for Merv 13-A applications – Washable Filter Media

Resistance measurements after several dust loading and washing procedures

Cond.: 24 x 24 x 4, 2000 cfm, ISO fine dust, washing with clear water

0.0

0.2

0.4

0.6

0.8

1.0

1.2

1.4

1.6

1.8

2.0

100 300 500 700

Pre

ssu

re D

rop

[in

ch w

.g.]

Air Flow [fpm]

New Filter

Loaded Filter

1st Washing

2nd Washing

3rd Washing


Other examples I: nanofiber filter media for high efficiency filters

High efficiency filters

up to 95 DOP

•Increased

nanofiber density

•Coarse fibers only for stabilization

•Very good mechanical stability


Other examples II: nanofiber filter media for prefilters ?!

0

50

100

150

200

250

300

350

0.00

0.05

0.10

0.15

0.20

0.25

0.30

0.35

0.40

Standard Nanofiber Standard Nanofiber

DH

C A

shra

e D

ust

@ 1

.8''

Init

ial R

esi

stan

ce i

nch

w.g

. @ 5

00

fpm Pressure Drop

- 35%DHC

+ 69%

Improvement of prefilter (MERV10) by innovative media design using nanofibers

Cond.: 24 x 24 x 4, 2000 cfm, ASHRAE 52.2 and EN779 tests




Examples

Summary

Outline

47


HVAC:

Nanofibers / Electrostatics / Energy Efficiency

• Push back of electrostatics by nanofibers

• Washability of filters possible if nanofibers

protected and mechanically stable

• Improved progressivity by nanofibers

for higher DHC

• Enhanced energy efficieny

• High and low efficiency filters with nanofibers

possible

Summary and Outlook


Nanofiber filter media - beyond filtration…

Department of Applied Art

University of Applied Science Zwickau


Thank you !

nanofibers - home - national air filtration...

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