Thermal analysis for identification of E-beam nanosize ammonium sulfate

Article abstract of DOI:10.1007/s10973-005-0968-z

Thermal decomposition of nanosize ammonium sulfate obtained as a by-product in a new electron-beam technology cleaning up waste gases from thermal power stations was studied. DTA-TG-DTG curves were used to characterize thermal properties of the new products obtained under different technological conditions. High quality of ammonium sulfate from Merck was used as a reference material. Ammonium sulfate was the main component in all the products and their thermal behavior was similar to that of the reference. Only the solid product obtained with the highest norm of ammonia contained about 3.2% ammonium nitrate. Thermoanalytical methods can successfully be applied for control the quality of the by-products from E-beam desulfurization technology. It was found that the thermal stability of the nanosize ammonium sulfate was the same as that of the reference ammonium sulfate.

Full text of DOI:10.1007/s10973-005-0968-z

Journal of Thermal Analysis and Calorimetry, Vol. 82 (2005) 813–817
THERMAL ANALYSIS FOR IDENTIFICATION OF E-BEAM NANOSIZE
AMMONIUM SULFATE
1
V. Petkova , Y. Pelovski and V. Hristova
*
2
2
1
Central Laboratory of Mineralogy and Crystallography, Bulgarian Academy of Sciences, 1113 Sofia, Acad.
G. Bonchev Str. Bl. 107, Bulgaria
University of Chemical Technology and Metallurgy; 1756 Sofia 8 Kliment Ohridski Blvd., Bulgaria
2
Thermal decomposition of nanosize ammonium sulfate obtained as a by-product in a new electron-beam technology cleaning up
waste gases from thermal power stations was studied. DTA-TG-DTG curves were used to characterize thermal properties of the new
products obtained under different technological conditions. High quality of ammonium sulfate from Merck was used as a reference
material. Ammonium sulfate was the main component in all the products and their thermal behavior was similar to that of the refer-
ence. Only the solid product obtained with the highest norm of ammonia contained about 3.2% ammonium nitrate. Thermoanalyti-
cal methods can successfully be applied for control the quality of the by-products from E-beam desulfurization technology. It was
found that the thermal stability of the nanosize ammonium sulfate was the same as that of the reference ammonium sulfate.
Keywords: ammonium sulfate, electron-beam technology, SEM, thermal properties, XRD
Introduction
nium sulfate, collected as a by-product, is a very fine
powder. The specific impurity in it is ammonium ni-
trate and some other micro-components as, for exam-
ple, heavy metals. Because of the short time of solid
phase formation, radiation effect and specific impuri-
ties (especially the explosive ammonium nitrate) a
reasonable question came out about the stability and
properties of this by-product and its possibilities to be
used as a nitrogen fertilizer or a component of other
mixed fertilizers.
Thermo-chemical decomposition of the by-prod-
uct, obtained from demonstration electron-beam in-
stallation in Maritsa-East 2 thermal power station, us-
ing different technological conditions, is the main ob-
jective of the present paper. At the same time the
study should give evidence that the thermal analysis
could be successfully applied for control the quality
of the new industrial product, as it was shown for
other environmental applications [9, 10].
Ammonium sulfate, released as a by-product from
different technologies, contains specific impurities,
crystal size and structures, affecting its thermal stabil-
ity and other properties [1–6]. Up to now the main
productions, releasing ammonium sulfate as a
by-product, are methylmetacrylate and caprolactame
productions as well as cleaning systems of waste
gases from coke production. Application of the new
electron-beam technology (EBT) for the purification
of waste gases from industrial installations, mainly
thermal power stations, will generate large quantities
of ammonium sulfate, containing ammonium nitrate
as the main impurity, the latter being less stable than
the former. The by-product is usually used as a fertil-
izer and its thermal stability and properties are impor-
tant for the application of the by-product as a fertilizer
or as a component of the mixed fertilizers [3–7]. Up to
now there are no published studies about the thermal
behavior of ammonium sulfate obtained from the ap-
plication of EBT and it is quite understandable, be-
cause EBT is a new technology and only little indus-
trial scale installations are in operation. The main
efforts were taken to find out the optimal technologi-
cal parameters to control the processes and to achieve
better purification effects [8]. Ammonium sulfate in
this process is formed in the gas phase where there is a
field of accelerated electrons. The process is very fast
and the reaction time is from 5 to 15 s. The ammo-
Materials and methods
Ammonium sulfate, p.a. grade from Merck Ltd. contain-
ing 99.5%mass (NH ) SO , with impurities of 0.001%
4 2 4
-
–
NO , 0.0003% Cl , 0.0005% PO , 0.0002% Fe,
3-
3
4
0.00002% As and 0.0002% specified by the supplier as
other heavy metals, was used as a reference (Sample 1).
The nanosize by-products ammonium sulfate were pro-
cessed with different norms of ammonia in the electron
*
Author for correspondence: vilma_bg@yahoo.com
1
388–6150/$20.00
Akadémiai Kiadó, Budapest, Hungary
Springer, Dordrecht, The Netherlands
©
2005 Akadémiai Kiadó, Budapest

PETKOVA et al.
Table 1 Content of components in the studied by-products
+
4
-
3
2-
4
Sample
No.
Norm of
NH
NH /
NO /
mass%
SO /
Others/ppm
3
mass%
26.51
26.91
20.86
mass%
70.89
71.67
70.38
2
3
4
0.4
0.7
0.9
0.08
963 Zn, 22 Cu, 4 Mo, 3 Cd, 18 Ni, 14 Pb, 5 As
647 Zn, 16 Cu, 2 Mo, 2 Cd, 18 Ni, 8 Pb, 3 As
441 Zn, 3 Cu, 2 Mo, 1 Cd, 14 Ni, 3 Pb, 2 As
0.14
2.11
beam field. Ammonia was supplied at the level of 0.4,
.7 and 0.9 from the stoichiometric norm. These sam-
could be formed. In the higher temperature range
(»629–750 K) NH HSO might decompose to ammo-
0
4
4
ples are labeled 2, 3 and 4, respectively. Analysis of the
studied by-products has shown that they contain mainly
nia, water vapour and sulphur oxides. (NH ) H(SO )
4 3 4 2
could in part be transformed to (NH ) S O . The resi-
4
2
2
8
+
-
2-
NH , NO and SO ions in the form of ammonium
sulfate and ammonium nitrate (Table 1).
due fully decomposed at a temperature range
913–1033 K, where a new portion of gases evolved.
Analysis of the results from TG-DTA curves, X-ray
diffraction data and the literature data [11, 12] sug-
gests that the decomposition process of ammonium
sulfate could be described by the following reactions.
In the first stage (»511–629 K) with a mass loss
of 17.8%:
4
3
4
Thermal analysis in the temperature range
88–1373 K was carried out with a Stanton Redcroft
2
–
1
thermal analyzer. Heating rate was 10 K min and
mass of samples was 10.00±0.3 mg. Flow rate of air
–
6
3
–1
was 0.83·10 m s . DRON X-ray analyzer with
CuK radiation and scanning electron microscopy
a
(
SEM) technique were also applied. PHILIPS PH
(
NH
2(NH ) SO = (NH ) H(SO ) +NH
3
4
)
2
SO
4
= NH
4
HSO
4
+NH
3
(1)
(2)
type SEM 515 electron microscope in a secondary
emission mode was used.
4
2
4
4 3
4 2
In the second stage (»625–750 K), with a mass
loss of 77.6%:
Results and discussion
(
NH ) H(SO ) = 2NH HSO +NH
3
(3)
4
3
4 2
4
4
DTA, TG and DTG curves of the reference ammo-
nium sulfate and of ammonium sulfate-by-products
with different ammonia norms are shown in Figs 1–4.
The different stages of mass loss during the thermal
treatment of the reference and nanosize by-products
ammonium sulfate are summarized in Table 2. X-ray
diffractograms data confirm just the presence of am-
monium sulfate in samples 2 and 3 and ammonium
sulfate plus ammonium nitrate in sample 4.
(
NH ) H(SO ) +½O = (NH ) S O +NH +H O(4)
2
4
3
4 2
2
4 2
2
8
3
NH
HSO
= NH
+SO
+H
O
(5)
4
4
3
3
2
The experimental mass loss in the first stage was
higher than the calculated one and it confirms that re-
action (1) was the principal reaction. During this tem-
perature range the impurity of ammonium nitrate also
decomposed and possibly reactions (3) and (5) from
the second stage also had already begun.
The thermal decomposition of the reference am-
monium sulfate showed a few stages process (Table 2
and Fig. 1), where the first stage was in the tempera-
ture range »511–629 K. Ammonium sulfate released
The recorded mass loss of 1% at temperatures
above 750 K suggests that reaction (4) was not the
dominant one during the second stage of transforma-
tions. We assume that limited quantities of
NH and as a result NH HSO and (NH ) H(SO )
3 4 4 4 3 4 2
(
NH ) H(SO ) were transformed to (NH ) S O . At
4 3 4 2 4 2 2 8
Fig. 2 DTA, TG and DTG curves of ammonium sulfate
by-product at 0.4 ammonia norm
Fig. 1 DTA, TG and DTG curves of Merck p.a. quality am-
monium sulfate
814
J. Therm. Anal. Cal., 82, 2005

THERMAL ANALYSIS FOR IDENTIFICATION OF E-BEAM NANOSIZE AMMONIUM SULFATE
Table 2 Mass loss of pure and nanosize by-products ammonium sulfate at different stages of the thermal analysis
Sample No.
Temperature/K
Mass losses/%
Start
Stage’s mass
losses/%
Inflection point
Start
511
629
750
End
629
End
17.8
95.4
96.4
1
1
1
582
709
–
0.0
17.8
95.4
17.8
77.6
1.0
750
1273
2
2
2
591
699
–
496
616
741
616
741
0.0
16.1
92.8
16.1
92.8
94.4
16.1
76.7
1.6
1273
3
3
3
590
704
–
509
617
753
617
752
0.5
17.2
95.5
17.2
95.5
96.8
16.7
78.3
1.3
1273
4
4
4
4
371
595
705
–
339
512
624
744
394
624
0.5
4.3
3.2
21.5
99.1
99.2
2.7
17.2
77.6
0.1
744
21.5
99.1
1273
higher temperatures (NH ) S O also decomposed, re-
8
stage. At the second stage of the intermediate decom-
position the temperature range and the mass losses
were almost the same.
4
2
2
leasing gases, according to reaction 6:
NH ) S O = 2NH +2SO +H O+½O
2
(
(6)
4
2
2
8
3
3
2
Figure 5 shows SEM micrographs of the reference
ammonium sulfate and of ammonium sulfate by-prod-
ucts with different ammonia norms. From the Figure it is
obvious that the crystal size in all samples was quite uni-
form and the shape was not affected by the ammonia
norm. On the base of the uniform crystal size we may
state that the by-products, obtained from the E-beam in-
stallation, were nanoproducts. Thermal stability of the
by-products was very similar to the standard ammonium
sulfate and from this point of view the by-products cov-
ered the requirements for such type of fertilizers. The
ammonium nitrate as an impurity, in the studied ranges,
did not have significant effect on the thermal stability of
the ammonium sulfate.
The TG-curves of ammonium sulfate by-product
samples (Table 2 and Figs 2–4) confirmed that the
mass losses fitted quite well with the above shown
mechanism of thermal decomposition of ammonium
sulfate and they are in good agreement with the two
thermal
DTA-curves. The differences for sample 4 (about
.7% mass loss and an additional endo-effect re-
endo-effects,
registered
from
the
2
corded at a lower temperature range 339–394 K) are
not surprising, because the content of ammonium ni-
trate in the by-product is higher and the ammonium
nitrate is less stable. The decomposition and transfor-
mation of ammonium sulfate, according to reactions
(
1) and (2) for the by-products, started at a little bit
The chemical analysis confirms that the ammo-
nium sulfate by-products content of nutrients like nitro-
gen, sulfur, Zn, Cu and Mo were in the range of standard
higher temperature, but the mass losses were very
close to that of the reference ammonium sulfate at this
Fig. 3 DTA, TG and DTG curves of ammonium sulfate
by-product at 0.7 ammonia norm
Fig. 4 DTA, TG and DTG curves of ammonium sulfate
by-product at 0.9 ammonia norm
J. Therm. Anal. Cal., 82, 2005
815

PETKOVA et al.
4 2 4
Fig. 5 SEM micrographs of the reference and by-products ammonium sulfate with different norms of ammonia; (NH ) SO
a – Merck, magnification 100, marker 100 mm; b – Merck, magnification 400, marker 100 mm; c – N=0.4, magnification
400, marker 10 mm; d – N=0.4, magnification 1000, marker 10 mm; e – N=0.7, magnification 2600, marker 10 mm;
1
f – N=0.7, magnification 1400, marker 10 mm; g – N=0.9, magnification 1300, marker 10 mm; h – N=0.9, magnifica-
tion 600, marker 100 mm
816
J. Therm. Anal. Cal., 82, 2005

THERMAL ANALYSIS FOR IDENTIFICATION OF E-BEAM NANOSIZE AMMONIUM SULFATE
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DOI: 10.1007/s10973-005-6859-5
J. Therm. Anal. Cal., 82, 2005
817