Iran. J. Environ. Health. Sci. Eng., 2006, Vol. 3, No. 1, pp. 5-8
AIR POLLUTION CONTROL THROUGH KILN RECYCLING BY-PASS DUST
IN A CEMENT FACTORY
1
F. Mohsenzadeh *2J. Nouri, 3A. Ranjbar, 2M. Mohammadian Fazli, 2A. A. Babaie
1
2
Department of Biology, Faculty of Science ,University of Bouali Sina, Hamadan, Iran
Department of Environmental Health Engineering, School of Public Health and Center for Environmental Research,
Tehran University of Medical Sciences, Tehran, Iran
3
School of Paramedical Sciences, Arak University of Medical Sciences, Arak, Iran
Received 13 February 2005; revised 20 May 2005; accepted 25 November 2005
ABSTRACT
Air pollution is a major problem in the industrial areas. Cement dust is one of the important environmental
pollutants. In this study the possibility of dust recycling especially kiln dust which has significant
importance regarding air pollution in the cement plant, was examined. Tehran cement factory is one of the
most important Iranian factories which is located in Tehran. This factory produces high volume of
pollutants that are released to in environment. The possibility of reusing of kiln by pass returned dust has
been examined in this factory. Different percentages of kiln by-pass dust of this factory were added to
products and outcomes of its presence in parameters such as chemical compound, granulation, primary and
final catch time, volume expansion, consumed water and resistance of mortar were surveyed. The result
indicated that by adding the amounts of 3-8 dust the mortar resistance increase, but adding more than 15%,
the mortar resistance has been decreased. Survey in consumed water proved that adding dust to cement, the
trend for consuming water is decreased. After dust addition dust, primary and final catch time were
compared in different samples and data which showed decrease in dust added samples. Cements with dust
added showed increase in auto clave expansion. Overally, results proved that, the best percentage rate of
dust addition to the cement was 15%.
Key words: Cement, by pass dust, kiln, resistance, volume expansion
INTRODUCTION
Over the centuries, air pollution has increased from
a local nuisance to a global problem (Emberlin
1998). Cement industry is one of the most
important and strategic industries in Iran. However,
its air pollution has been a serious problem. The
primary related pollution is dust, which industrial
countries have allocated tremendous efforts in
reducing its volume. Dust in different stages of a
production line of cement is dispersed and by
suitable dust catcher will be collected. The
collected dust, often from combination point of
view is similar to circulation materials at the same
area of process and for this reason is returned to
the production line (Mohsenzadeh, et al., 2006).
In the past, cement kiln dust was kept as industrial
wastage, but recently it is emphasized for its
*Corresponding author E-mail: jnouri@tums.ac.ir
Tel: +98 21 8895 4914, Fax: +98 21 8895 0188.
application, because a considerable amount of
energy has been to be paid for its preparation,
calcinations and so discarding it, bring out wastage
of energy and cost. On the other hand, due to
consideration of high volume of the collected dust,
a lot of costs were allocated by collection and
destroying it, due to have some special chemical
compound which, has adverse environmental
effects (Chehregani, 2005). Different scientific
and technical sources and the following applications
have been introduced. As reinforcement in asphalt
concretes, it helps its high strength and life (Debell,
M., 1997), as it contains materials such as K2O,
CaO,Na2O helps to stabilization of sewage sludge
(Holdereank Seminar, 2000). By pass dust of
rotating kiln due to fine granulation can absorb SO2
from power supplies (Tettmar, B. et al., 2003).
On the other hand, after washing the dusts with
5
Iran. F.
J. Mohsenzadeh,
Environ. Health.et Sci.
2006, Vol.
3, EFFICIENCY
No. 1, pp. 5-8OF...
al., Eng.,
COMPARING
THE
water, (which resulted in dissolution of unfavorable
alkaline and chloride ingredients) with drying , the
dust is returned to raw materials of production line,
of course, it requires consumption of water and
results in its dirtiness (Yazeed, S.A. et al., 1994).
One of the other applications is chemical fertilizer
or artificial soil. The other application is production
of clinker from dust through a reactor or fluid bed,
preparation of brick and other construction
materials (Makrom, 1999). Among the mentioned
processes, attention can be paid to direct
application of by-pass dust from cement kiln as
additive. Because firstly, it causes increase in
cement production and secondly, its easiness and
cost without consuming energy and without any
process for conducting any operation (Chehregani,
2005). By-pass dusts are from outlet gases in
suspension kiln and in inverse conditions are in
circulation with materials. These dusts due to
alkaline materials and volatility of raw material and
perhaps fuel, have high volatility and probably with
cooling in some sections of baking process, they
are deposited and causes catching and interior
cycles. Its production quality is in term of type of
materials, production technology. Operational
conditions a re 3 up to 20 percentages of
production, for example in a kiln with capacity of
2000 tons per day, and in the cement production
about 10 up to 12 tons per hour are produced.
Distribution of by pass dust granulation of cement
kiln includes 80-90 percentage of particles less than
45 microns. Particles less than 4 micron constitutes
about 30% of total dust (Debell, 1998 and
Wirthwein, 2002).
MATERIALS AND METHODS
Sample preparation
The sample were prepared to assess percentage
of optimize added by-pass dust (returned dust) to
the product. The cement preparation samples
were type 2 from Tehran cement factory:
a.These samples are contained no by-pass dust
for assessment.
b.Samples contained by-pass dust, have been
coded respectively according to Table 1.
6
Table 1: Coding of samples with different percents
of by pass dust
Amount of by pass dust
(percent)
3
4
5
6
7
8
9
15
20
Sample code
S1
S2
S3
S4
S5
S6
S7
S8
S9
The samples were mixed and homogenized. And
also tests were conducted for assessment as
follows:
pressure resistance test
For evaluation, influences of by-pass kiln on
cement properties were prepared, in section 4-1
according to DIN 1164 under bending and pressure
test. The tested samples from cement according
to DIN196-1 EN and distilled water in proportion
to 1: 3: 0.5 was prepared and after mixing and
molding, it was kept in a wet room for 24 hours.
Then samples were brought out of mould and
were put in water with 20+1 °C. Then tested
samples were put in pressure resistance test for
3, 7 and 28 days, respectively.
catch time test
For assessment of primary and final catch time,
the Vikat units were used. Standard cement paste,
which is required for this purpose and also the
measuring of cement expansion, was necessary,
and prepared from lab samples. Extent of
consumed water is determined for the paste and
then, each sample is under test for final and
primary catch time.
expansion test and auto-clave
In this process for determination of probable
influence of by-pass dust in hydrate cement
properties and especially auto-clave expansion,
tested samples with percentage of determined
were water provided and after 24 hours from
preparation of mortar and molding in the wet room,
we put them in the auto-clave under 2 MPa
pressure and three hours in 215 °C (ASTM C151-64)
after elapse of the time, and cooling of samples,
Iran. J. Environ. Health. Sci. Eng., 2006, Vol. 3, No. 1, pp. 5-8
longitudinal variations were measured precisely
and their expansion was specified in mm
percentage.
cement to the amount of 3-8 percentage, the
resistance of cement will be increased and adding
dust more than 15% gives rise to reduction in
resistance of cement.
RESULTS
500
3 days
450
7 days
400
28 days
2
Compressive strength (kg/cm )
Results of resistance measurement
The outcomes of bending and pressure resistance
of samples on days 3,7 and 28 are presented in Fig.
1. The outcomes show that by adding dust to
350
300
250
200
150
100
50
0
0
5
10
Kiln dust percentage
15
20
25
Fig.1: Results of resistance measurements of samples
Results of catch time test
For determination of final and primary catch time,
the vilcat unit was applied. Then each sample, were
put under test for primary and final catch time.
Outcomes of these surveys are reflected in Table
3 results proved that adding dust, the final and
primary catch time of cement in the most samples
is decreased but in some samples, including
samples with 20% dust, the primary catch time
Table 2: Results of catch time test for samples with
different percents of by pass dust
Sample
code
Control
S1
S2
S3
S4
S5
S6
S7
S8
S9
Percent of
additive
dust
0
3
4
5
6
7
8
9
15
20
Ratio of
water
to cement
0.262
0.260
0.255
0.250
0.251
0.256
0.245
0.248
0.244
0.226
Initial
catch
(mm)
182
180
180
176
165
172
160
178
185
156
has been increased. In samples with 3% dust, the
final catch time increased.
Results of autoclave expansion test
Results of autoclave expansion test are presented
in Table 3, which shows that by adding dust to
cement, it causes expansion of autoclave. Also
Table 4 shows results of test for determination of
special range of tested samples.
Table 3: Results of autoclave expansion test and specific
surface for samples with different percents of by pass dust
Final catch
(mm)
Sample
code
255
258
232
215
207
196
225
236
232
226
Control
S1
S2
S3
S4
S5
S6
S7
S8
S9
Percent of
additive
dust
0
3
4
5
6
7
8
9
15
20
specific
surface
(cm2/g)
2800
2900
2960
3010
3100
3160
3200
3220
3420
3550
autoclave
expansion (%)
0.080
0.090
0.097
0.099
0.100
0.102
0.104
0.105
0.110
0.120
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Iran.
J. Environ. Health.
Eng., 2006,
Vol.EFFICIENCY
3, No. 1, pp.OF...
5-8
F. Mohsenzadeh,
et al.,Sci.
COMPARING
THE
DISCUSSION
Fig. 1 shows that the increase in by pass dust
percentage to cement, first causes relative increase
in pressure resistance. Of course, this trend has
been changed with increase in by pass dust
(returned dust) and gradually loss in sample
resistance. This trend has been seen in all samples
and is the reason for considerably cement phases
decrease (C3S,C2S) with increase in dust
percentage to cement. According to Table 2,
increase in percentage of by-pass dust (returned
dust), creates regular trend at considerable
decrease or increase ratio of water to cement of
tested samples. Anyhow, in this respect, in some
sources, the increase of water to cement has been
mentioned (Paus, 2001 and Abo-El-Enein, 2001)
but against this viewpoint has been seen in some
tests. Changes in relation with primary catch time
with increase in by-pass dust percentage are not
considerable but final catch with increase in by
pass dust, sometimes increased and in some cases,
showed decrease. Although increase trend in final
catch time is predicted because the increase in by
pass dust brings about reduction in cement phases
and overshadows their hydration process for
creation of catch (Cehregani, 2005 and Abo-ElEnein, 2001). Results of autoclave expansion tests
(Table 3) show that amount of autoclave expansion
which were increased by adding dust to cement.
In this process, it is predicted that increase in by
pass dust brings about increase in samples of
alkaline materials and increase alkaline expansion.
Anyhow, by-pass dust, due to having semi
calcinations materials, includes free lime (and
probably MgO) and this incr ease, ca uses
expansion of samples. Increase in percentage of
by pass dust in samples, brings about increase in
their special range. Due to fine granulation,
by-pass dust was foreseeable and is from
advantages of by pass dust application to cement.
The surveys prove that adding kiln by pass dust to
cement may be considered as a cheap and easy
process. This process preserves raw materials
sources, saving energy consumption and prevent
is pollution in the environment. With due
consideration to outcomes from resistance stand
point, the best quantity for adding by-pass dust to
the cement, is the MAX curve in Fig 1. In this
8
position, the percentage of added dust to optimum
added by pass dust is shown. Anyhow tiny increase
of by pass dust, in spite of loss of pressure
resistance in samples, is still acceptable conditions.
The change in other important parameters of test
concerning cement quality has been acceptable
and this application process of by-pass dust has
been confirmed. Thus, due to positive quality tests
of cement resulted from mixture with percentage
of by-pass dust and also easy conditions for
application of this type of dust in cement mills of
plants due to suitable mixture, preventing from
environmental pollution and preserving natural
sources, it is a suitable proposal. The ENV 197
standard under caption of tiny additives(zero up
to 5 percentage) is admissible in case of passing
relevant tests.
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