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
Technische Universität WienVienna University of Technology
Institute of Chemical EngineeringInstitut für Verfahrenstechnik, Umwelttechnik und Techn. Biowissenschaften
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
Technische Universität WienVienna University of Technology
Institute of Chemical EngineeringInstitut für Verfahrenstechnik, Umwelttechnik und Techn. Biowissenschaften
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
Technische Universität WienVienna University of Technology
Institute of Chemical EngineeringInstitut für Verfahrenstechnik, Umwelttechnik und Techn. Biowissenschaften
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
Technische Universität WienVienna University of Technology
Institute of Chemical EngineeringInstitut für Verfahrenstechnik, Umwelttechnik und Techn. Biowissenschaften
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
Technische Universität WienVienna University of Technology
Institute of Chemical EngineeringInstitut für Verfahrenstechnik, Umwelttechnik und Techn. Biowissenschaften
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
Technische Universität WienVienna University of Technology
Institute of Chemical EngineeringInstitut für Verfahrenstechnik, Umwelttechnik und Techn. Biowissenschaften
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
Technische Universität WienVienna University of Technology
Institute of Chemical EngineeringInstitut für Verfahrenstechnik, Umwelttechnik und Techn. Biowissenschaften
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
Technische Universität WienVienna University of Technology
Institute of Chemical EngineeringInstitut für Verfahrenstechnik, Umwelttechnik und Techn. Biowissenschaften
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)
Technische Universität WienVienna University of Technology
Institute of Chemical EngineeringInstitut für Verfahrenstechnik, Umwelttechnik und Techn. Biowissenschaften
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).
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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!
Technische Universität WienVienna University of Technology
Institute of Chemical EngineeringInstitut für Verfahrenstechnik, Umwelttechnik und Techn. Biowissenschaften
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)
Technische Universität WienVienna University of Technology
Institute of Chemical EngineeringInstitut für Verfahrenstechnik, Umwelttechnik und Techn. Biowissenschaften
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
Technische Universität WienVienna University of Technology
Institute of Chemical EngineeringInstitut für Verfahrenstechnik, Umwelttechnik und Techn. Biowissenschaften
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
Technische Universität WienVienna University of Technology
Institute of Chemical EngineeringInstitut für Verfahrenstechnik, Umwelttechnik und Techn. Biowissenschaften
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).
Technische Universität WienVienna University of Technology
Institute of Chemical EngineeringInstitut für Verfahrenstechnik, Umwelttechnik und Techn. Biowissenschaften
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
Technische Universität WienVienna University of Technology
Institute of Chemical EngineeringInstitut für Verfahrenstechnik, Umwelttechnik und Techn. Biowissenschaften
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
Technische Universität WienVienna University of Technology
Institute of Chemical EngineeringInstitut für Verfahrenstechnik, Umwelttechnik und Techn. Biowissenschaften
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.
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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
Technische Universität WienVienna University of Technology
Institute of Chemical EngineeringInstitut für Verfahrenstechnik, Umwelttechnik und Techn. Biowissenschaften
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
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