DESIGN OF VACUUM CLEANED DUST FILTER · Filter test rig with vacuum cleaning 12 SMPS w l Flow...

Technische Universität WienVienna University of Technology

Institute of Chemical EngineeringInstitut für Verfahrenstechnik, Umwelttechnik und Techn. Biowissenschaften

DESIGN OF VACUUM CLEANED DUST FILTER

Thomas Laminger

Johannes Wolfslehner

Wilhelm Höflinger

Vienna University of Technology

Institute of Chemical Engineering

Mechanical Process Engineering and Clean Air Technology



Introduction

• Fibrous dust industry

Textile, paper, tabaco, wood…

Glass wool, high temperature mineral wool, asbestos…

• Fibrous dust in air ventilation systems

Low mass but high volume concentration of fibres

Mixtures with fine particular dust

High air volume flows

• Fibre length and diameter

Second Cut Cotton Linters (< 3-6mm, Ø 20µm)

Acetate fibres (< 500µm, Ø 0,3-10µm)

Cellulose fibres (<1mm, Ø 20µm)

2



Introduction

• Filter systems with vacuum cleaning

using suck-off nozzle

Small suck-off nozzle regenerates large

filter area

Main air flow with high air flow ratio,

low dust concentration

Secondary air flow with low air flow ratio,

high dust concentration

(secondary filter system e.g. cyclone, cleanable

filter media…)

3

Filter medium

Clean gas

Raw gas

Pressure drop

Suck-off nozzle

Secondaryfilter system

Traverse movement



Introduction

• Filter systems with vacuum cleaning

using suck-off nozzle

Stationary filter media

Panel filter with traverse moving suck-off nozzle

Drum filter with rotating suck-off nozzle

Disk filter with rotating suck-off nozzle

Stationary suck-off nozzle

Rotating drum filter

Rotating disk filter

Moving belt filter Suck-off nozzles

Rotating drum filterwww.draftair.com

Panel filterwww.sasasis.net



Aim

• Design of vacuum cleaned apparatusbased on filtration specific parameters(filter media, dust concentration,air volume flow, pressure drop…) Filter area

Module number

Suck-off nozzle traverse velocity(or e.g. drum rotation speed)

5

Moving belt filterwww.micropul.com

Compact drum filterwww.ltg-ag.de



Cleaning pattern andsuck-off nozzle traverse length• Suck-off nozzle moves along

the traverse length (l) with a traverse velocity (vn).

• Ideally each pattern becomes regenerated once within the regeneration time (T):

• Various cleaning pattern possible (serpentine, spiral…)

Traverse length l

Suck-off nozzle(traverse velocity vn)

𝑇 =𝑙

𝑣𝑛

Rotating filter drumLarge nozzle

Panel filterwith spiral cleaning pattern

Small nozzle,screwing pattern



Dust distributionon filter media

• Filter area has an uneven dust and air flow distribution: pattern with low dust mass and

high air velocity behind the suck-off nozzle

pattern with high dust mass und low air flow velocity in front of the suck-off nozzle

• Air flow ( 𝑉) through the filter media area (A) defines a mean air flow velocity ( 𝑣):

Spiral shaped cleaning pattern

High dust mass,low air velocity

Low dust mass,high air velocity

Medium dust mass,medium air velocity

Rotating disk filterwww.pneumafil.com

𝑣 = 𝑉

𝐴



Pressure drop across the filter area

8

∆p𝑚= 𝐾1. 𝜇. 𝑣 +1

2. 𝐾2 . 𝜇. 𝑣². 𝑐. 𝑇

Analogies to equations of the mean pressure drop of a bag-house filter

∆p𝑚 Mean pressure drop [Pa] 𝑣 Mean air velocity [m/s]

T Filtration period [s]K1 Specific filter medium resistance value [1/m]K2 Specific cake resistance value [m/kg]µ Air viscosity [Pa.s]c Dust concentration [kg/m³]

n-1

∆pm

Filtration period Tfor a vacuum cleaned filter

(traverse movement of the suck-off nozzle)

1 2 3 …… n

Time

Pre

ssu

red

rop

1

2

3Suck-off nozzle

n

∆pm

Filtration period Tfor a baghouse with 3 bags

(3 sequential jet-pulse-cleanings)

Bag 1

Time

Pre

ssu

red

rop

1 2 3

Jet-pulse

Bag 2 Bag 3

𝑉 constant 𝑉 constant



Pressure drop across the filter area

9

Analogies to equations of the mean pressure drop of a bag-house filter

∆p𝑚 Mean pressure drop [Pa] 𝑣 Mean air velocity [m/s]

T Filtration period [s]K1 Specific filter medium resistance value [1/m]K2 Specific cake resistance value [m/kg]µ Air viscosity [Pa.s]c Dust concentration [kg/m³]

𝑇 =nozzle traverse length

mean nozzle traverse velocity=

𝑙

𝑣𝑛

∆p𝑚= 𝐾1. 𝜇. 𝑣 +1

2. 𝐾2 . 𝜇. 𝑣2. 𝑐.

𝑙

𝑣𝑛

Including the nozzle traverse length (l) and the nozzle traverse velocity (vn)

∆p𝑚= 𝐾1. 𝜇. 𝑣 +1

2. 𝐾2 . 𝜇. 𝑣². 𝑐. 𝑇

∆𝐩𝒎,𝒎𝒊𝒏= 𝑲𝟏. 𝝁. 𝒗 +𝟏

𝟐.𝑲𝟐 . 𝝁. 𝒗

𝟐. 𝒄.𝒍

𝒗𝒏,𝒎𝒂𝒙

𝑇𝑚𝑖𝑛 =𝑙

𝑣𝑛 ,𝑚𝑎𝑥

Limited by a maximum nozzle traverse velocity (vn,max)



Determination of the number of parallel working filter elements (m) and suck-off nozzles at given air volume flow and pressure drop

Modular design with m parallel filter elements with mparallel working suck-off nozzles is needed if the required mean pressure drop is lower than the minimum mean pressure drop of a filter module (∆𝑝𝑚,𝑟𝑒𝑞𝑢𝑖𝑟𝑒𝑑 < ∆𝑝𝑚,𝑚𝑖𝑛).

10

𝑣 = V

A𝑓𝑖𝑙𝑡𝑒𝑟=

V

m. A𝑒𝑙𝑒𝑚𝑒𝑛𝑡

∆𝑝𝑚 = 𝐾1 ∙ 𝜇 ∙ V

m ∙ A𝑒𝑙𝑒𝑚𝑒𝑛𝑡+1

2∙ 𝐾2 ∙ 𝜇 ∙

V

m ∙ A𝑒𝑙𝑒𝑚𝑒𝑛𝑡

2

∙ 𝑐 ∙𝑙

v𝑛,𝑚𝑎𝑥

m =A𝑓𝑖𝑙𝑡𝑒𝑟

A𝑒𝑙𝑒𝑚𝑒𝑛𝑡=

𝐾1. 𝜇 + 𝐾1. 𝜇2 + 2. 𝐾2. 𝜇. 𝑐.

𝑙v𝑛,𝑚𝑎𝑥

. ∆𝑝𝑚

0,5

2.∆𝑝𝑚 𝑉A𝑒𝑙𝑒𝑚𝑒𝑛𝑡

Similar equations for drum filter can be derived (e.g. rotation speed).

K1 and K2 are needed!



Determination of specific filter medium resistance value (K1) and specific cake resistance value (K2)

11

∆p𝑚=1

2. 𝐾2 . 𝜇. 𝑣2. 𝑐. 𝑙 .

1

𝑣𝑛+ 𝐾1. 𝜇. 𝑣

dy k x

Mea

n p

ress

ure

dro

p (

Δp

m)

[Pa]

Inverse nozzle traverse speed 1/vn [s/m]

𝑲𝟏. 𝝁. 𝒗

𝒕𝒂𝒏𝜶 =𝟏

𝟐.𝑲𝟐 . 𝝁. 𝒗². 𝒄. 𝒍α

Operation point 2Nozzle traverse velocity vn2 < vn1

Operation point 1Nozzle traverse

velocity vn1

1/vn1 1/vn2

Δpm2

Δpm1

Linear regression

Δpm2

Δpm1

Pre

ssu

re d

rop

(Δ

p)

[Pa]

Time (t) [s]

Operation point 1Nozzle traverse velocity vn1

Operation point 2Nozzle traverse velocity vn2 < vn1

Experimental measurements using a filter apparatus (e.g. drum filter or filter test rig)



Filter test rig with vacuum cleaning

12

SMPS

Flo

w

con

tro

l

Flow control

Dust and Fiberdisperser

Soot generator

HEPA filter

Suck-off nozzle

Suck-offair flow

Test filter

Mainair flow

Lineardrive

PCS

Pressure drop

Suck-off nozzle

Linear drive carrier

Soot generator

Fiber and dust disperser

Horizontal vacuum cleaning housing

Vertical air channel



Filter holder,Suck-off cleaning pattern• Rectangular filter sample

(30x10cm) becomes vacuum cleaned by a meander shaped cleaning pattern.Suck-off nozzle is shifted at right and left end positions.

• Suck-off nozzle traverse velocity (vn) is adjustable(30 to 400mm/min).

13

Filter sample(300x100mm)

Suck-off-nozzle(nozzle traverse velocity vn)

50

100

50

300

5

Traverse length (l)2x300mm

Filter holder



14

Material Air permeability

@ 200Pa [l/(m²s)]

Mass per unit area

[g/m²]

Filter medium A PPS/PTFE 560 660

Filter medium B PPS/PTFE 740 480

Filter medium C PPS/PPS 1500 320

Filter media properties [1]

Materials and test parameters

• Three high voluminous filter media.

• Pural SB test dust; Dust concentration 200mg/m³.

• Filter face velocity 0,69m/s

• Suck-off air velocity at nozzle 12m/s

• Five different nozzle traverse velocities(3; 5; 10; 11; 27cm/min) for about 20min each.

• Pressure drop over time was measured.

Polfaser-Vlieswirkstoff, Faserfeinheit: 7,0 dtex

Wirbelvliesstoff

High voluminous stitch-bonded nonwoven layer

Hydro entangled layer

Filter mediumSächsisches Textilforschungsinstitut (STFI)

[1] W. Höflinger, T. Laminger, J. Wolfslehner: “Operation parameters of vacuum cleaned filters”; Journal of Chemical, Nuclear, Metallurgical and Materials Engineering; 8 (2014).



15

Exemplary measurement result

~3h test time per filter medium

0

200

400

600

800

1000

0 5000 10000

Pre

ssu

re d

rop

(Δ

p)

[Pa]

Time [s]

3

4

5

2

1

(1) vn: 2.6mm/s(2) vn: 0.8mm/s(3) vn: 0.5mm/s(4) vn: 1.6mm/s(5) vn: 0.6mm/s

Filter medium ATest dust: Pural SBRaw gas concentration: 200mg/m³Filter face velocity: 0,69m/sSuck-off air velocity at nozzle: 12m/s

Start

y = 0,2703x + 177

0

200

400

600

800

0 500 1000 1500 2000

Me

an p

ress

ure

dro

p (Δ

pm

) [P

a]

Inverse nozzle traverse speed (1/vn) [s/m]

Filter medium ATest dust: Pural SBRaw gas concentration: 200mg/m³Filter face velocity: 0,69m/sSuck-off air velocity at nozzle: 12m/s

K1: 1.50e7 [1/m]K2: 7.33e8 [m/kg]

3

4

5

2

1

Start

Linear regressionExperimental measurement



16

Comparison of regressed parameters K1 and K2

Specific filter medium resistance values (K1) decrease with filter media air permeability.

0,0E+00

5,0E+06

1,0E+07

1,5E+07

2,0E+07

Spec

ific

filt

er m

edia

res

ista

nce

(K

1)

[1/m

]

0,0E+00

2,0E+08

4,0E+08

6,0E+08

8,0E+08

1,0E+09

Spec

ific

cak

e re

sist

ance

(K

2)

[m/k

g]

Test dust: Pural SBRaw gas concentration: 200mg/m³Filter face velocity: 0,69m/sSuck-off air velocity at nozzle: 12m/s

Specific cake resistance values (K2) resulted in the same magnitude, which indicates that the cake formation of the used test dust does not dependent on the filter medium material.

Air permeability

@ 200Pa [l/(m²s)]

Filter medium A 560

Filter medium B 740

Filter medium C 1500



Calculation example for module number (m) at given air volume flow with variable pressure drop• Filter module (design,

geometry, cleaning pattern…) based on filter test rig’s parameters.

• Filter and dust resistance values based on presented experimental determined K1 and K2.

• Variable parameters: nozzle traverse velocity and mean pressure drop

Lower module numbers with higher nozzle traverse velocity and with higher mean pressure drop level.

17

0

2

4

6

8

10

12

14

16

18

0 200 400 600 800

Cal

cula

ted

nu

mb

er o

r m

od

ule

s m

[-]

Mean pressure drop Δpm [Pa]

2cm/min

5cm/min

10cm/min

Test dust: Pural SBRaw gas concentration: 200mg/m³Filter face velocity: 0,69m/sSuck-off air velocity at nozzle: 12m/sVolume flow: 450m³/hK1: 1,5.107 1/mK2: 7,4.108 m/kgµ: 17µPa.s

Module filter area: 0,03m²Traverse length: 0,6m

Nozzle traverse velocity vn



Summary

• Design equations for vacuum dust filter based on analogies to multi-bag house filters were derived which relates the traverse velocity of the suck-off nozzle and the specific filter cake resistance and a filter medium resistance parameter to estimate the mean pressure drop of a vacuum cleaned filter apparatus.

• A calculation model for the number of parallel working modules of large filter apparatus was elaborated.

• A new filter test rig with vacuum cleaning was built and used to determine specific filter media and dust resistance values.

• It was shown by experiment using three high voluminous filter media samples that the presented calculation model to derive the specific filter medium resistance value and the specific cake resistance value are possible and can easily be done within a few hours.

• Based on the experimental data of the specific filter resistance value and the specific cake resistance value, an estimation of the needed number of parallel working small filter modules (m) as a function of the pressure drop level and nozzle traverse velocity was presented.

18

Date post:	22-Jun-2020
Category:	Documents
Upload:	others
View:	1 times
Download:	0 times

DESIGN OF VACUUM CLEANED DUST FILTER · Filter test rig with vacuum cleaning 12 SMPS w l Flow...

Documents