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1
Cite paper as: I.S. Al-Attar, R.J. Wakeman, E.S. Tarleton and A. Husain, 2010, Physical and chemical characterization of Kuwaiti
atmospheric dust and synthetic dusts: Effects on the pressure drop and fractional efficiency of HEPA filters, 10th International
Conference for Enhanced Building Operations, Kuwait, October 26-28.
PHYSICAL AND CHEMICAL CHARACTERIZATION OF KUWAITI ATMOSPHERIC DUST AND
SYNTHETIC DUSTS: EFFECTS ON THE PRESSURE DROP AND FRACTIONAL EFFICIENCY
OF HEPA FILTERS
I.S. Al-Attar1, R.J. Wakeman1,2, E.S.Tarleton1 (e.s.tarleton@lboro.ac.uk) and A. Husain3
1Department of Chemical Engineering, Loughborough University, LE11 3TU, UK.
2Consultant Chemical Engineer, Exeter, UK.
3Kuwait Institute for Scientific Research, Department of Building and Energy Technologies P.O.
Box 24885, Safat, 305-343, Kuwait.
ABSTRACT
The importance of clean air to the indoor air quality affecting the well-being of human occupants
and rising energy consumption has highlighted the critical role of air filter performance. Actual
performance of air filters installed in air handling units in Kuwait tends to deviate from the
performance predicted by laboratory results. Therefore, accurate filter performance prediction is
important to estimate filter lifetime, and to reduce energy and maintenance operating costs. To
ensure appropriate filter selection for a specific application, particulate contaminants existing in
Kuwaiti atmospheric dust were identified and characterized. This paper compares the physical and
chemical characterization of Kuwaiti atmospheric dust with the available commercial synthetic
dusts. It also tests full scale HEPA pleated V-shaped filters used in Heating Ventilation and Air
Conditioning (HVAC) and gas turbine applications. The effects of different synthetic dust types and
their particle size distributions on the pressure drop and fractional efficiency using DEHS testing
according to DIN 1822 is studied.
KEYWORDS
Air filters; Fractional efficiency; Gas cleaning; Glass fibre; HEPA filter; Permeability; Pressure drop.
FILTRATION OF AIR
Air filtration is a complex process which is influenced by several factors pertaining to the dust
physical and chemical characteristics. To better understand and evaluate the filtration process and
influential parameters affecting the filtration performance of air filters, an in-depth analysis of the
dust must be conducted.
Although several authors have studied the performance of clean filters1-3 and other authors have
considered dust loaded filters4-5, the literature is generally limited to the study of flat filters. Studies
have considered loading samples of filters with monodispersed6 and polydispersed7 aerosols.
Literature on the testing of HEPA pleated filters is limited8-10. Other authors have studied the
effects of particle size on the pressure rise11-15 of filters but did not consider a full scale HEPA filter
constructed in a V-shape cartridge with variable pleating density. This paper investigates the effect
of synthetic polydispersed dust type and pleat density on filter design and performance in terms of
fractional efficiency and pressure drop.
FILTER PROPERTIES
The experimental work involved the testing of glass fibre pleated cartridges of HEPA Class H10
according to DIN 182216. Eight filters were manufactured by EMW Filtertechnik with pleating
densities varying from 28 to 34 pleats per 100 mm. Table 1 lists all the filters used for testing with
their corresponding surface areas. The manufactured filters were divided into two groups, A and
2
Cite paper as: I.S. Al-Attar, R.J. Wakeman, E.S. Tarleton and A. Husain, 2010, Physical and chemical characterization of Kuwaiti
atmospheric dust and synthetic dusts: Effects on the pressure drop and fractional efficiency of HEPA filters, 10th International
Conference for Enhanced Building Operations, Kuwait, October 26-28.
B. Both groups underwent similar testing procedures and were challenged with DEHS to give data
for the initial fractional efficiency. Figure 1 shows the face dimensions of 592 x 592 mm with a
depth of 400 mm. The filter cassette has a V-shape bank which contains eight pleated media
panels.
The glass fibre media used in these filters is shown in Figure 2. Glass fibre filtration media was
selected for all experiments as it exhibits better resistance to high temperatures and has smaller
fibre size compared to synthetic media. Glass fibre media are highly porous with a low resistance
to air flow. Filter performance is affected by several variables such as filter medium thickness,
permeability, packing density, fibre diameter as well as the design of the filter module itself.
Operating conditions such as filtration velocity and temperature also affect the filter performance, in
addition to the characteristics of the aerosol such as particle size distribution, particle shape and
density. The properties of the media are listed in Table 2.
Dust Characterization
Kuwaiti and synthetic dusts were characterized physically and chemically to better understand their
behaviour in the filtration process. The physical and chemical characteristics of synthetic dust
were examined to choose one that represents Kuwaiti atmospheric dust.
Chemical Characterization – EDAX
The three synthetic dusts, ASHRAE, SAE Fine and SAE Coarse, were analyzed using Energy
Dispersive Analysis X-ray (EDAX) to determine their chemical composition. Analysis showed that
Kuwaiti atmospheric dust is mainly silica and also contains aluminium, calcium, iron and some
traces of potassium and magnesium. On the other hand, ASHRAE and SAE Coarse dust contain
carbon and also consist of mainly silica. SAE Fine dust contains aluminium, calcium and traces of
potassium. From such chemical analysis the ASHRAE dust seems to be closest to the Kuwaiti
dust from a silica content standpoint. However, analysis of ASHRAE dust does not show any
presence of aluminium, calcium and traces of potassium which are found in Kuwaiti dust. SAE
Fine and Coarse on the other hand, contain aluminium, calcium and traces of potassium, but have
higher silica content than Kuwaiti dust. In all Kuwaiti dust samples, the silica contents were higher
than that of the ASHRAE content. Furthermore, ASHRAE dust contains cotton lint as shown in
Figure 3 which is absent in Kuwait dust.
While it is difficult to decide on the most representative dust using EDAX analysis, the SAE Fine
dust seems to be the closest to Kuwaiti atmospheric dust from a chemical composition standpoint.
Table 3 lists the chemical composition of samples of Kuwait atmospheric, ASHRAE, SAE Fine and
SAE Coarse dusts.
Particle Size Distribution
While it is hard to obtain a commercially produced dust that fits the physical and chemical
characterization of Kuwaiti atmospheric dust, particle size analyses can give the particle size
distribution of Kuwaiti samples. Ten samples of Kuwaiti atmospheric dust were obtained from the
Kuwait Scientific Research Centre (KISR). The dust samples were sized using a Malvern
MasterSizer in order to determine the particle size distribution. Each sample was inserted into an
ultrasonic bath for one minute to ensure that the dust was dispersed. A 300RF lens was used to
provide measurements in the size range between 0.05 and 880 µm. Since the Kuwaiti
atmospheric dust was found from EDAX analysis to be mainly silica, a refractive index of 1.5 was
used. The same refractive index was used for the synthetic dusts. Figure 4 shows the particle
size distribution comparison between Kuwaiti atmospheric dust and the commercial synthetic dusts
selected for analysis.
3
Cite paper as: I.S. Al-Attar, R.J. Wakeman, E.S. Tarleton and A. Husain, 2010, Physical and chemical characterization of Kuwaiti
atmospheric dust and synthetic dusts: Effects on the pressure drop and fractional efficiency of HEPA filters, 10th International
Conference for Enhanced Building Operations, Kuwait, October 26-28.
Sizing measurements revealed that the dust size distribution of ASHRAE dust was dissimilar to the
all of ten Kuwait dust samples as shown in Table 4. The size distribution of SAE Coarse dust was
also different from the Kuwaiti particle size distribution. This signified that each dust has different
settling velocities, which increase rapidly with particle size and density. The particle size
distribution of the SAE Fine seems to be the closest to Kuwaiti atmospheric dust. It can also be
noticed that SAE Coarse and Fine dust can be considered as upper and lower limits in terms of
size distribution in comparison to Kuwaiti atmospheric dust. Therefore, those two types were used
for this study to conduct the comparisons of filter performance.
Table 4 lists the measured values of the mean diameters, volume mean diameters and surface
area mean diameters of synthetic dusts in addition to the Kuwaiti dust. The measured specific
surface area mean diameter of ASHRAE and SAE coarse dust particles by Malvern MasterSizer
are 1.84 µm and 1.75 µm, respectively. Both measurements are lower than the surface area mean
diameter of the Kuwait dust which has a range of 3.22 to 5.74 µm. The drag force is affected by
the surface area of the particle which in turn means the drag force created by ASHRAE dust
particle is lower than the Kuwait one. The mean surface area of SAE fine dust particles is 3.73
m2/g which falls within the Kuwait atmospheric dust range of specific surface area mean diameter.
Kuwaiti and Test Dusts
Most of the filters used in Kuwait are evaluated using ASHRAE dust and hence this dust was
considered in the study in order to assess its appropriateness for filter performance via its
similarities in physical and chemical characteristics to Kuwaiti atmospheric dust. The synthetic
dusts selected were ASHRAE, SAE 726 Coarse, and SAE 726 Fine to include two different size
distribution dusts. ASHRAE synthetic dust is composed by weight of 72% standardized SAE 726
Fine dust (Arizona road dust), 23% powdered carbon and 5% cotton linters. Standardized air
cleaner test dust is classified from dust gathered in a desert area in Arizona. It is predominantly
silica and has a mass mean diameter of approximately 7.7 µm, a geometric standard deviation of
approximately 3.6, and density of approximately 2.7 g/cm³.
The powdered carbon is carbon black in powder form, with ASTM D3765 CTAB surface of 27±3
m2/g, ASTM D2414 DBP adsorption of 0.68±0.7 cm2/g, and ASTM D3265 tint strength of 43±4.
The SAE 726 Fine test dust is composed of mineral dust, predominantly silica with other oxides
present. It has a specific gravity17 2.6-2.7 g/cm3. On other hand, SAE 726 Coarse dust is a
naturally occurring mineral, which is predominantly SiO2 with other oxides present. It has a mass
mean diameter of approximately 7.7 µm, a geometric standard deviation of approximately 3.6, and
density between 2.6 and 2.7 g/cm³.
Reasons for Dust Selection
The particle shapes of the Kuwaiti atmospheric dust along with ASHRAE synthetic, SAE 726
Coarse, and SAE 726 Fine dusts were examined using a scanning electron microscope. Figures
5-7 show that SAE Coarse and Fine dusts as well the Kuwait atmospheric dust are mainly non-
spherical particles. The drag force varies with the particle shape which in turn affects the
aerodynamic behaviour. A spherical particle has higher velocity than an irregular particle with the
same weight18. The aerodynamic behaviour of particles affects the filtration performance of air
filters. Therefore, the angular velocity of irregular dust particles should be considered, and a
modified equation of motion for spherical particles may be used to describe the non-spherical
particle dynamics with more accuracy.
Clearly, the ASHRAE dust is not representative of Kuwaiti atmospheric dust as far as the particle
shape is concerned. The SAE 726 Coarse and SAE 726 Fine dusts seem to be closer in this
regard. However, particle shape similarity is not sufficient to select a representative dust since
particle size distribution and density measurements will also play a role in the verification process.
4
Cite paper as: I.S. Al-Attar, R.J. Wakeman, E.S. Tarleton and A. Husain, 2010, Physical and chemical characterization of Kuwaiti
atmospheric dust and synthetic dusts: Effects on the pressure drop and fractional efficiency of HEPA filters, 10th International
Conference for Enhanced Building Operations, Kuwait, October 26-28.
The true densities of all dusts were measured using a pycnometer. From a true density standpoint,
all synthetic dusts have different densities when compared to the Kuwait atmospheric dust.
However, SAE 726 Fine dust may be closer in terms of density than ASHRAE dust. The true
densities of the dusts are listed in Table 5.
For the scope of this experimental work, a series of filters (series A) were challenged by SAE Fine
dust while the series B filters were challenged by SAE Coarse dust. Scanning electron microscope
images at the same scale are shown of both dusts in Figures 6 and 7 for comparison purposes. It
is evident that the SAE Fine contains finer particles when compared to the SAE Coarse dust. Dust
particles of both dusts seem to have similar shape.
Particulate Matter in Kuwait Atmosphere
Several filter samples from different locations in Kuwait were examined using a scanning electron
microscope to identify common air contaminants existing in the Kuwaiti atmosphere. Figure 8
shows SEM examination which revealed pollen grains deposition on the surface of the filter media.
Pollen grains discharged by weeds, grasses and trees are capable of causing hay fever19, and
most are hygroscopic and therefore vary in mass with humidity20. A pollen count of 10 to 25 may
make hay fever sufferers experience the first symptoms. The pollen grain found in the SEM
examination of the filter media used in Kuwait ranged in size between 10 and 60 μm.
Filter Efficiency Using Test Dusts
Description of initial filter behaviour constitutes a small part of filter lifetime. While the study of
clean filter performance is important, it does not predict the behaviour of the same filter during dust
loading. When particle deposition begins to take place within the filtration medium, the filter’s inner
mechanical structure changes causing the overall efficiency and pressure drop to (generally)
increase. Eventually, particles collect other particles leading to dendrite formation which would
finally lead to dust cake formation. To better understand dust loaded filter performance, filter
series A and B were loaded with SAE Coarse and SAE Fine dust, respectively. Fractional
efficiencies were measured after each dust feed, i.e. every 500 m3/h increment, stating at 500
m3/h. On the other hand, the pressure drop responses were measured every five minutes at a
single flow rate of 3500 m3/h.
EFFECT OF PLEATING DENSITY ON PRESSURE RISE
A filter with 28 pleats per 100 mm was loaded with AC coarse dust. 1000 g of dust was loaded in
four increments of 250 g. The pressure rise was always linear with time. The 1000 g was mainly
deposited within the depth of the filter without a significant dust cake formation. Figure 9 shows
the pressure drop response for different pleating densities for filter group A after each dust loading
stage.
As dust starts to be fed into the filter by means of a dust feeder, dust settlement into the depth of
the filtration medium around the fibre and the rise in pressure drop is negligible. This is the so
called the stationary filtration stage and it is represented by a linear response as shown in Figure
10. Filter 34A has the lowest pressure drop and a linear response which could mean that the 1000
g of dust was not enough to make the filter depart from stationary depth filtration to non-stationary
filtration and finally to dust cake formation. Furthermore, filter 34A has the highest losses in
surface area whilst filter 38A has the least losses in surface area. However, filter 28A satisfies the
efficiency requirement and its pressure drop response is acceptable and a linear response is still
exhibited. In other words, the 1000 g also did not form dust cake on the filter surface. This
indicates that filter 28A is more economical from a cost point of view as well as from efficiency and
pressure drop standpoints.
5
Cite paper as: I.S. Al-Attar, R.J. Wakeman, E.S. Tarleton and A. Husain, 2010, Physical and chemical characterization of Kuwaiti
atmospheric dust and synthetic dusts: Effects on the pressure drop and fractional efficiency of HEPA filters, 10th International
Conference for Enhanced Building Operations, Kuwait, October 26-28.
Figure 10a illustrates the pressure drop response after the fourth dust feed for filter 28 A and B for
SAE Coarse and Fine dust, respectively. It is evident that the pressure drop response is higher for
SAE Fine dust which indicates that fine particles tend to penetrate further through the filter medium
compared to the coarse particles of the SAE Coarse dust. SAE Fine dust particles settling into the
depth of filtration medium effectively cause the fibre diameter to increase and consequently
changes to the depth of the filter as well as the porosity. This leads to increases in the drag force
for the filter matrix. Since the drag force is directly proportional to the pressure drop, an increase in
the latter is expected and was in fact observed experimentally as shown in Figure 10b. Similar
observation and comment can be made for filter 30A and B as shown in Figure 10, however, the
difference in the pressure drop response are smaller. This is attributed to the fact that the pleats
are closer to each other in the 34 pleats/100 mm density compared to the 28 pleats/100 mm
density.
Figure 11 shows pressure drop response versus mass deposited per surface area for filters from
series A which indicates that a higher pleating density yields a lower pressure drop (this does not
consider the losses of surface area during operation). Filter 28A exhibits the highest pressure drop
response when compared with the other pleat densities. On the other hand, the response of filter
34A show the least response in pressure drop due to the high surface area provided. Figure 11
shows pressure drop response versus mass deposited per surface area for filter series B using the
Fine test dust; the differences in pressure drop with varying pleating density are smaller when
compared with the Coarse dust used with series A filters. This is due to the fact that finer particles
are more penetrating and are capable of occupying interstitial spaces inside the filter medium
which is responsible for the rise in pressure drop of the filter.
The pressure drop response for the 34A and B filters are shown in Figure 12, which illustrates that
the pressure drop response is smaller compared to the 28 pleat filters shown in Figure 11. It can
be concluded that solid particles depositing within the fibrous structure change the geometry of the
porous matrix which leads to substantial variations in the pressure drop and filtration efficiency.
EFFECT OF MASS OF COARSE DUST LOADED ON FILTER EFFICIENCY FOR DIFFERENT
PLEATING DENSITIES
The fractional efficiencies were plotted versus particle size for filter 28A after each dust feed of 250
g. All dust loading and efficiency measurements were measured at 3500 m3/h. Figure 13
illustrates the increase of efficiency for each dust feed of SAE Coarse dust as particle size and
dust mass loading increases. Clearly, as more dust is loaded into the depth of the filter medium so
additional changes in the inner structure occur. Consequently, permeability decreases and as a
results the pressure drop response increases. Furthermore, such effect is associated with an
increase in efficiency and the fourth dust feed records the highest efficiency.
Figure 14 illustrates the effect of mass loading on efficiency for different pleating densities after the
first dust feed. In addition, filter 32A recorded the lowest dust loaded efficiency after the fourth
feed. This excludes filter 32A from the competition for an optimal pleat count selection. Filter 34A
recorded the highest dust loaded efficiency among other filters in its series, however, as the
particle size increases so its efficiency recorded the lowest dust loaded efficiency. Furthermore,
Filter 34A recorded the highest losses in surface area prior to dust loading.
CONCLUSIONS
ASHRAE dust is not representative of Kuwaiti atmospheric dust, due to differences in its
physical and chemical characteristics. SAE 726 Fine dust is more representative of Kuwaiti
dust.
6
Cite paper as: I.S. Al-Attar, R.J. Wakeman, E.S. Tarleton and A. Husain, 2010, Physical and chemical characterization of Kuwaiti
atmospheric dust and synthetic dusts: Effects on the pressure drop and fractional efficiency of HEPA filters, 10th International
Conference for Enhanced Building Operations, Kuwait, October 26-28.
Kuwaiti atmospheric dust is mainly non-spherical particles and silica based. It also contains
other contaminants such as pollen.
The particle size distribution of Kuwaiti dust falls between the SAE Fine and SAE Coarse size
distributions. Therefore, these synthetic dusts effectively act as lower and upper size
distribution limits for the Kuwaiti atmospheric dust, respectively.
The pressure drop response of SAE Fine dust was higher than that of the SAE Coarse
particles. This suggests that the smaller particles are more penetrating than coarse particle for
a given filtration medium which is in this case the H1012 with fibre size range between 0.8-6
µm. This is in agreement with previous studies11-14.
The MPPS (Most Penetrating Particle Size) decreases with increasing filter face velocity for all
pleating densities of a given surface area and filter medium. The MPPS increases slightly or
remains the same as the pleating density increases.
Filter class H10 efficiency requirement according to Standard DIN 1822 was achieved at flow
rates of 2000-2500 m3/h for most filters. On the other hand, a higher filter class (H11) was
achieved for a flow rate of 500 m3/h for filters with 28 pleat/100 mm density.
REFERENCES
1. Davies C.N., 1973, Air Filtration, New York, Academic Press.
2. Brown R.C., 1993, Air filtration: An integrated approach to the theory and application of fibrous
filters, Oxford, Pergamon Press.
3. Letourneau P., Mulcey Ph. and Vendel J., 1990, Aerosol penetration inside HEPA filtration
media, Proc. 21st DOE/NRC Nuclear Air Cleaner Conference, CONF-900813.
4. Lee K.W. and Liu B.Y.H., 1982, Theoretical study of aerosol filtration by fibrous filters, Aerosol
Science and Technology, 1(2), 147-161.
5. Liu B.Y.H. and Rubow K.L., 1986, Air filtration by fibrous media, in ‘Fluid Filtration: Gas’, 1,
ASTM STP 975, (Ed.) R.R. Raber, American Society for Testing and Materials, Philadelphia,
PA. 1-12.
6. Japuntich D.A., Stenhouse J.I.T., and Liu B.Y.H., 1994, Experimental results of solid
monodisperse particle clogging of fibrous filters, J. Aerosol Sci., 25(2), 385-393.
7. Thomas D., Penicot P., Contal P., Leclerc D. and Vendel J., 2001, Clogging of fibrous filters by
solid aerosol particles: Experimental and modelling study, Chemical Engineering Science,
56(11), 3549-3561.
8. Wakeman R.J., Hanspal N.S., Waghode A.N. and Nassehi V., 2005, Analysis of pleat crowding
and medium compression in pleated cartridge filters, Trans IChemE, 83(A10), 1246-1255.
9. Chen D.R., Pui D.H. and Liu B.Y.H., 1995, Optimization of pleated filter designs using a finite-
element numerical model, Aerosol Science and Technology, 23, 579-590.
10. Fabbro L D., Laborde J.C., Merlin P. and Ricciardi L., 2002, Air flows and pressure drop
modelling for different pleated industrial filters, Filtration & Separation, 39(1), 34-40.
7
Cite paper as: I.S. Al-Attar, R.J. Wakeman, E.S. Tarleton and A. Husain, 2010, Physical and chemical characterization of Kuwaiti
atmospheric dust and synthetic dusts: Effects on the pressure drop and fractional efficiency of HEPA filters, 10th International
Conference for Enhanced Building Operations, Kuwait, October 26-28.
11. Payet S., Boulaud D., Madelaine G. and Renoux A., 1992, Penetration and pressure drop of
HEPA filter after loading with submicron liquid particles, J. Aerosol Sci., 23, 723-735.
12. Novick V.J. and Klaseen J.F., 1998, Predicting pressure response characteristics across
particle loaded filters, in Advances in Aerosol Filtration, (Ed.) K.R. Spurny, pp.337-348, Lewis
Publishers, Boca Raton.
13. Snyder C.A. and Pring R.T., 1955, Design considerations in filtration of hot gases, Ind.
Engineering Chemistry, 47, 960-966.
14. Pich J., 1966, Theory of Aerosol filtration by fibrous filters and membrane, in Aerosol Science,
(Ed.) C.N. Davies, pp.223-285, Academic Press, London.
15. Stenhouse J.I.T., Japuntich D.A. and Liu B.Y.H., 1992, The behaviour of fibrous filters in the
initial stages of filter loading, J. Aerosol Sci., 23(S1), 761-764.
16. EN 1822-5:2000 High Efficiency Air Filters (HEPA and ULPA) – Part 5 Determining the
efficiency of a filter element.
17. ANSI/ASHRAE 1999, ASHRAE Standard 52.2: Method of testing general ventilation air-
cleaning devices for removal efficiency by particle size, American Society of Heating,
Refrigerating and Air-Conditioning Engineers, Atlanta, GA.
18. Dorman R.G., 1974, Dust Control and Air Cleaning, Pergamon Press, Oxford.
19. Soloman W.R. and Mathews K.P., 1978, Aerobiology and inhalant allergens, in Allergy:
Principles and Practices, (Eds.) Middleton E., Reed C.E. and Ellis E.F., CV Mosby, St Louis.
20. ASHRAE 2001, ASHRAE Handbook: Fundamentals, American Society of Heating,
Refrigerating and Air-Conditioning Engineers, Atlanta, GA.
8
Cite paper as: I.S. Al-Attar, R.J. Wakeman, E.S. Tarleton and A. Husain, 2010, Physical and chemical characterization of Kuwaiti
atmospheric dust and synthetic dusts: Effects on the pressure drop and fractional efficiency of HEPA filters, 10th International
Conference for Enhanced Building Operations, Kuwait, October 26-28.
FIGURES AND TABLES
Figure 1: Pleated filter with V shape design (EMW Filtertechnik).
Figure 2: Image of the glass fibre HEPA filter medium (Class H10 according to DIN 1822).
9
Cite paper as: I.S. Al-Attar, R.J. Wakeman, E.S. Tarleton and A. Husain, 2010, Physical and chemical characterization of Kuwaiti
atmospheric dust and synthetic dusts: Effects on the pressure drop and fractional efficiency of HEPA filters, 10th International
Conference for Enhanced Building Operations, Kuwait, October 26-28.
Figure 3: The existence of cotton lint in ASHRAE dust.
Figure 4: Particle size distribution comparison between Kuwaiti atmospheric dust (Sample 1) and
commercially available dusts.
10
Cite paper as: I.S. Al-Attar, R.J. Wakeman, E.S. Tarleton and A. Husain, 2010, Physical and chemical characterization of Kuwaiti
atmospheric dust and synthetic dusts: Effects on the pressure drop and fractional efficiency of HEPA filters, 10th International
Conference for Enhanced Building Operations, Kuwait, October 26-28.
Figure 5: Scanning electron micrograph (SEM) of Kuwait atmospheric dust.
Figure 6: SEM of SAE Fine dust.
60 µm
60 µm
11
Cite paper as: I.S. Al-Attar, R.J. Wakeman, E.S. Tarleton and A. Husain, 2010, Physical and chemical characterization of Kuwaiti
atmospheric dust and synthetic dusts: Effects on the pressure drop and fractional efficiency of HEPA filters, 10th International
Conference for Enhanced Building Operations, Kuwait, October 26-28.
Figure 7: SEM of SAE Coarse dust.
Figure 8: SEM of air filters used in air conditioning units in Kuwait.
60 µm
12
Cite paper as: I.S. Al-Attar, R.J. Wakeman, E.S. Tarleton and A. Husain, 2010, Physical and chemical characterization of Kuwaiti
atmospheric dust and synthetic dusts: Effects on the pressure drop and fractional efficiency of HEPA filters, 10th International
Conference for Enhanced Building Operations, Kuwait, October 26-28.
Figure 9: Behaviour of the time dependent particle deposition in different pleating density filters
(series A) at a flow rate of 3500m3/h.
(a) (b)
Figure 10: Pressure drop responses for filter 28 A (Coarse dust) and B (Fine dust) after the fourth
dust feed.
13
Cite paper as: I.S. Al-Attar, R.J. Wakeman, E.S. Tarleton and A. Husain, 2010, Physical and chemical characterization of Kuwaiti
atmospheric dust and synthetic dusts: Effects on the pressure drop and fractional efficiency of HEPA filters, 10th International
Conference for Enhanced Building Operations, Kuwait, October 26-28.
Fourth Dust B series
Mass Deposited (g/m2)
0 2 4 6 8 10
Pressure drop (Pa)
180
190
200
210
220
230
240
250
260
270
280
290
Filter 28B, 28 pleats/100mm, As=24.6 m2
Filter 30B, 30 pleats/100mm, As= 26.6 m2
Filter 32B, 32 pleats/100mm, As= 27.3 m2
Filter 34B, 34 pleats/100mm, As=28.9 m2
Figure 11: Pressure drop response versus mass deposited per surface area for filter series B using
SAE Fine dust.
Time (min)
0 5 10 15 20 25 30 35 40 45 50 55 60 65
Pressure drop (Pa)
140
150
160
170
180
190
200
210
220
230
34A loaded with SAE coarse dust
34B loaded with SAE fine dust
Figure 12: Pressure drop response for filter 34A and B after the fourth dust feed.
14
Cite paper as: I.S. Al-Attar, R.J. Wakeman, E.S. Tarleton and A. Husain, 2010, Physical and chemical characterization of Kuwaiti
atmospheric dust and synthetic dusts: Effects on the pressure drop and fractional efficiency of HEPA filters, 10th International
Conference for Enhanced Building Operations, Kuwait, October 26-28.
Particle Size [m]
0.1 1
Efficiency [%]
92
93
94
95
96
97
98
99
100
1st dust (250 grams)
2nd dust (500 grams)
3rd dust (750 grams)
4th dust (1000 grams)
Figure 13: Efficiency after each SAE Coarse dust feeding stage.
Particle Size [m]
0.1 1
Efficiency [%]
92
93
94
95
96
97
98
99
100
Filter 28A
Filter 30A
Filter 32A
Filter 34A
Figure 14: Efficiency after the fourth SAE Coarse dust feeding stage for different pleating density.
15
Cite paper as: I.S. Al-Attar, R.J. Wakeman, E.S. Tarleton and A. Husain, 2010, Physical and chemical characterization of Kuwaiti
atmospheric dust and synthetic dusts: Effects on the pressure drop and fractional efficiency of HEPA filters, 10th International
Conference for Enhanced Building Operations, Kuwait, October 26-28.
Filter
Pleat density
(pleats/100 mm)
Surface area
(m2)
28A
28
23.9
28B
28
24.6
30A
30
26.6
30B
30
26.6
32A
32
27.3
32B
32
27.3
34A
34
28.8
34B
34
28.9
Table 1: The filters tested and their surface areas.
HEPA (H10) filter medium
Fibre diameter range
0.5-8.5 µm
Average fibre diameter
2.1 µm
Media thickness
500 µm
Packing density
0.06 µm
Porosity
94%
Fibre shape
circular
Table 2: Properties of the filter medium.
Element
Kuwait atmospheric
ASHRAE
SAE Fine
SAE Coarse
O
42.25
23.30
49.80
45.37
C
-
55.88
-
19.70
Mg
3.62
-
-
-
Al
7.75
-
4.31
-
Si
29.18
20.82
38.80
34.93
Ca
9.39
-
3.02
-
Fe
7.80
-
-
-
K
-
-
4.07
-
Total
100.00
Table 3: The chemical composition of Kuwait atmospheric dust.
16
Cite paper as: I.S. Al-Attar, R.J. Wakeman, E.S. Tarleton and A. Husain, 2010, Physical and chemical characterization of Kuwaiti
atmospheric dust and synthetic dusts: Effects on the pressure drop and fractional efficiency of HEPA filters, 10th International
Conference for Enhanced Building Operations, Kuwait, October 26-28.
Mean particle
size (µm)
Volume mean
diameter (µm)
Surface area mean
diameter (µm)
Specific surface
area (m2/g)
KWT 1
5.03
14.14
1.34
4.47
KWT 2
5.11
25.85
1.21
4.94
KWT 3
4.94
27.63
1.04
5.74
KWT 4
8,54
35.52
1.31
4.58
KWT 5
6.94
21.44
1.54
3.54
KWT 6
13.24
31.09
1.69
3.22
KWT 7
6.43
34.20
1.16
4.71
KWT 8
6.26
18.15
1.35
4.43
KWT 9
6.36
26.86
1.45
4.13
KWT 10
7.32
26.86
1.53
3.93
ASHRAE
5.63-8.00
51.15
3.27
1.84
SAE Fine
10.24
36.23
1.61
3.73
SAE Coarse
33.18
57.18
3.41
1.75
Table 4: Various experimental relevant diameters and properties of the Kuwaiti and synthetic dusts
studied.
Dust
Mean measured
density (g/cm³)
Standard deviation of
the three samples
ASHRAE 52/76
2.233
0.0416
SAE 726 Coarse
2.593
0.0611
SAE 726 Fine
2.613
0.0681
Kuwait atmospheric
2.436
0.0737
Table 5: True density measurements for the Kuwaiti and synthetic dusts.
