International Journal
on Marine Navigation
and Safety of Sea Transportation
Volume 4
Number 4
December 2010
441
1 INTRODUCTION
The range of materials, which must be transported
by sea and stored, is gradually increasing. Today we
need observe more consideration of aspects of trans-
portation of large quantity of dangerous goods. The
term dangerous is limited to substances which have
the potential to cause major accident risk from fire,
explosion or toxic release. Including also oxidizing
and explosives materials, which during transport
might be initiated by fire, impact, resulting from
badly packed or was out of specification explosives.
In the International Maritime Dangerous Goods
Code the information concerning various aspects of
sea handling of hazardous materials is contained.
Official regulations and supplementary documenta-
tion of the hazardous properties of materials can be
found in this code. It is an important source of basic
information and a guide to shipping of hazardous
goods for a ship staff.
Oxidizers are dangerous goods in accordance
with International Maritime Dangerous Goods Code
(IMDG Code), belong to 5.1 class, they are not nec-
essarily flammable, but able to intensify the fire by
emission oxygen. Oxidizers may be elements, acids,
or solid substances (e.g. nitrates salts). Some oxidiz-
ing substances have toxic or corrosive properties, or
have been identified as harmful to the marine envi-
ronment. They will react in contact with reducing
reagents. Hence oxidizing agent will invariably ac-
celerate the rate of burning of combustible material.
The National Fire Protection Association in United
Stated classified oxidizing substances according the
stability [Burke, 2004]:
Class1 – Solid or liquid that readily yields oxygen
or oxidizing gas or that readily reacts to oxidizer
combustible materials.
Class 2 – Oxidizing material can cause spontane-
ous ignition when contact with combustible materi-
als.
Class 3 – Oxidizing substances that can undergo
vigorous self sustained decomposition when cata-
lyzed or exposed to heat.
Class 4 – Oxidizing articles that can undergo an
explosive reaction when catalyzed or exposed to
heat, shock or friction.
Among the fertilizers mentioned in the IMDG
Code the most dangerous are nitrates(V), belong to
Application of Thermal Analysis and Trough
Test for Determination of the Fire Safety of
Some Fertilizers Containing Nitrates
K. Kwiatkowska-Sienkiewicz & P. Kalucka
Gdynia Maritime University,
Department of Chemistry and Industrial Commodity Science, Poland
ABSTRACT: The studies on how a fire on board accidents may be prevented have been actively carried out
at both the national and international levels. This paper provides an outlook on fire safety assessment con-
cerning nitrates fertilizers in sea transport. The investigation was aimed at comparison two methods of classi-
fication and assignment to a packing group of solid fertilizers of class 5.1 of International Maritime Danger
Goods Code. First research was conducted in accordance with the test method described in the United Nations
Recommendations on the Transport of Dangerous Goods, Manual of Test and Criteria, Part III, 34.4.1 “Test
for oxidizing solids”. The second method was the differential thermal analysis (DTA) where the basis was the
determination the temperature change rate during thermal reaction. According to two used tests, the investi-
gated fertilizers belong to 5.1 class and require to packaging group III of the International Maritime Danger
Goods Code. The DTA method gives more quantitative information about fire risk on the ship than method
recommended in International Maritime Danger Goods Code.
442
oxidizers of class 5.1 of danger goods and ammoni-
um salts [IMDG Code]. Pure ammonium nitrate, the
base of fertilizers, belong to compounds transported
in limited quantities (UN 0222 –ammonium nitrate,
with more than 0,2% combustible substance) Am-
monium nitrate UN 1942 with not more than 0,2%
total combustible substances including any organic
substance calculated as carbon during transport the
temperature of material should not be above 40
0
C.
Do not ventilate this cargo.
Ammonium nitrate based fertilizers UN 2067,
UN 2071,UN 2067 may transported in bulk. Fertiliz-
ers: potassium nitrate – UN 1486, sodium nitrate UN
1498 and sodium and potassium nitrate mixtures UN
1499, calcium nitrate UN 1454 may be also trans-
ported in bulk [BC Code]. Nitrates fertilizers are
highly hygroscopic and will cake if wet. They be-
long to cargo group A and B (Group A consists of
cargoes which may liquefy if shipped at a moisture
content in excess of their transportable limit. Group
B consists of cargoes which possess chemical hazard
which could give rise to dangerous situation on the
ship) [Appendix A and B BC Code, 2001].
A major fire aboard a ship carrying these materi-
als may involve a risk of explosion in the event of
contamination by combustible materials or strong
confinement. An adjacent detonation may also in-
volve a risk of explosion. During thermal decom-
pose nitrate fertilizers giving toxic gases and gases
which support to combustion. Dust of fertilizers
might be irritating to skin and mucous membranes.
Classification of oxidizing substances to class 5.1
is based on test described in the IMDG Code and
Manual of Tests and Criteria [UN Recommendations
Part III]. In this test, the investigated substances
were mixed with cellulose, which is a combustible
material, in ratios of 1:1 and 4:1, by mass, of sub-
stance to cellulose. The mixtures were ignited and
the burning time was noted and compared to a refer-
ence mixture, in ratio 3:7, by mass, of potassium
bromate(V) to cellulose.
The assignation criteria to the packaging groups
are based on a physical or chemical property of
goods. There are at present no established good cri-
teria for determining packaging groups. (To packag-
ing group I belongs substances great danger, II -
medium danger, or III, minor danger).
If a mixture of test substance and cellulose burns
equal to or less than the reference mixture, this indi-
cates that the combustion of the combustible materi-
al (cellulose) is enhanced by the test substance and
the test substance has oxidizing (fire enhancing)
properties and is classified in class 5.1. This also
means that oxidizing substance is assigned to a
packing group III (if the criteria of packing group I
and II are not met). Next the burning time is com-
pared with those from the packing group I or II ref-
erence standards, 3:2 and 2:3 ratios, by mass, of po-
tassium bromate(V) and cellulose. Any substance
which, in both the 4:1 and 1:1 sample-to-cellulose
ratio (by mass) tested, does not ignite and burn, or
exhibits mean burning times greater than that of a
3:7 mixture (by mass) of potassium bromate(V) and
cellulose, is not classified as class 5.1.
Using these criteria we test a big mass sample of
component which involve larger volumes of toxic
gases, as opposed to a differential thermal analysis,
where the basis is the determination the temperature
change rate during thermal decomposition.
Using differential thermal analysis (DTA) we can
registration quality and quantity changes during dy-
namic heating of investigated materials in time.
The self-heating or thermally explosive behavior
of individual chemicals is closely related to the ap-
pearance of thermogravimetry-differential thermal
analysis (TG-DTA) curve with its course.
In previous examinations of mixtures of oxidizers
with cellulose and flour wood [Michałowski, Bar-
cewicz 1997, Michałowski Barcewaicz 1998,
Michałowski, Rutkowska, Barcewicz 2000, Kwiat-
kowska-Sienkiewicz et al 2006, Kwiatkowska-
Sienkiewicz 2008] the temperature change rates
[
0
C/s] were calculated into 1 milimole of an oxidizer
and tested oxidizing substances were blended with
combustible substance in mass ratio 5:1.
According to later experiments not classified to
class 5.1 any substances which temperature change
rate are lower than 0,2 [
0
C/s].
To packaging group III should be assigned sub-
stances, which during thermal analysis mixtures oxi-
dants with cellulose, the temperature change rate
values are between 0,2 to 1,4 [
0
C/s].
To packaging group II should be assigned sub-
stances blended with cellulose of with the tempera-
ture change rate values are between 1,4 to 5,0 [
0
C/s].
To packaging group I belong of mixtures oxidizes
with cellulose which temperature change rate values
exceed 5,0 [
0
C/s].
Later and now in experiments used cellulose as
combustible material. Cellulose belongs to polysac-
charides, develop free radicals on heating. The free
radicals in cellulose thermolysates is cellulose varie-
ty dependent. The generation of free radicals on
heating is time and temperature dependent whereas
in termoanalitical studies exposure to heat is for
relatively short time. All polysaccharides (e.g.
starch) during heating generated free radicals
[Ciesielski, Tomasik 1998, Ciesielski, Tomasik,
Baczkowicz 1998].
In practice, during long transport combustible ma-
terials and commodities containing polysaccharides
we can observe self-heating effect, specially, if poly-
saccharides are blended with oxidizers. Free radical
exposed during thermal reaction polysaccharides
443
mixed with nitrates (V) (nitrates(V) belongs to 5.1
class dangers goods), gives possibility self-heating
and self-ignition chemical reaction.
In these paper fertilizers, containing sodium, po-
tassium, calcium and ammonium nitrates, blended
with cellulose was investigated.
This examinations whereas basing on potassium
bromated (V) blends with cellulose (in mass ratio
2:3 and 7:7) as a standard shows that class 5.1 in-
cludes substances which temperature change rate
was greater than temperature change rate of mixture
of potassium bromated (V) with cellulose, in mass
ratio 3:7 – 0,96 [ºC/s].
To the III packaging group should be assigned
substances, which during thermal analysis mixtures
oxidants with cellulose, the temperature change rate
values are between 0,96– 1,82 [ºC/s].
II packaging group involves crossing value of the
temperature change rate under 1,82 [ºC/s].
In this paper we concerned on comparison two
methods of assignation to class 5.1 and classification
to packing groups. The first one is recommended by
United Nations [UN Recommendations] and second
one, differential thermal analyze is using in chemis-
try.
2 EXPERIMENTAL
Determination according to IMDG Code and UN
Recommendations test and DTA method were car-
ried out using the same blends oxidants/fertilizer and
cellulose.
The following substances were blended with cel-
lulose in mass ratio 1:1 or 1:4
− sodium nitrate (V ) pure for analysis,
− ammonium nitrate based fertilizer with 30% ni-
trogen,
− nitro-chalk with 27,5% nitrogen,
− calcium nitrate based fertilizer with 15% nitro-
gen,
− potassium nitrate based fertilizer with 14% nitro-
gen,
− as reference material - potassium bromate(V)
pure for analysis blended with cellulose in mass
ratio 3:7 and 2:3.
In experiments used microcrystalline cellulose,
grade Vivapur type 101, particle size >250 µm (60
mesh), bulk density 0.26 – 0.31 g/ml.
Mean burn time of trials mixtures fertilizes and
cellulose are presented in Table 1.
Chemical reaction course during the heating can
be investigated by means of differential thermal
analysis (DTA) method. Using thermal analysis
(DTA), the changes of mass, temperature and heat-
ing effects curves are recorded.
Thermal decomposition with self-ignition effect
is demonstrated in Fig.1:
Figure 1. Self –ignition effect monitored by DTA method
[Kwiatkowska-Sienkiewicz, Barcewicz 2001]
The following outputs were recorded during
measurements using DTA method.
− T – the temperature change curve which is a
straight line till the mixture flash point is reached,
with a district peak in the self-ignition region, es-
pecially during reaction of very active oxidizers,
− DTA curve – gives information about heat ef-
fects,
− TG curve - of mass change during the reaction,
beginning of self-ignition process - T
1
,
maximum of self-ignition reaction – T
2
,
maximum temperature increase: T
2
-T
1
= ∆T,
temperature change time (from T
1
to T
2
) ∆t,
The temperature increase value was determined
from the temperature change curve T on the basis of
its deflection out of the straight line, in the peak re-
gion. On the ground of the above mentioned data
following parameters could be calculated. The tem-
perature change rates [
o
C/s] were calculated by di-
viding the temperature increase (∆T) by the time of
self-ignition effect (∆t), counted into 1 g of a ferti-
lizers/oxidizers. At first pure oxidants and fertilizers
were tested. Then mixtures of fertilizers with cellu-
lose and oxidizers substance with cellulose were
tested. Thermal treatment of pure oxidizers or the
blends were heated from room temperature to
500
o
C. The procedure was run in the air under dy-
namic condition. The rate temperature increase was
10
o
C/min. Ceramic crucibles were taken. Paulik-
Paulik-Erdley 1500 Q Derivatograph (Hungary) was
used. The measurements were carried out three
times. Decomposition initiating temperatures of the
compounds, and his blends with cellulose were read
from the recorded curves.
The temperature change rates [
o
C/s] were calcu-
lated from the curves DTA and T by dividing the
444
temperature increase by the time of self-ignition ef-
fect, calculated into 1 g of an oxidizer or multicom-
pound fertilizer.
3 RESULTS
The results of performed thermal reactions of oxi-
dizers/fertilizers and cellulose are presented in Ta-
bles 1 and 2.
On the basis of results of the test described in
Manual of Test and Criteria all examinated fertiliz-
ers, according to IMDG Code, belong to class 5.1 of
Dangerous Goods and require packaging group III.
The results of second method of performed ther-
mal reactions between cellulose and selected ferti-
lizers are presented in Tables 2 and 3. Blends of po-
tassium bromate(V) and cellulose in mass ratio 3:7
and 2:3 are the standards in classification using dif-
ferential thermal analyses tests (we used the same
standards like in Manual Test recommended by
IMDG Code).
Table 1. Determination risk of fire oxidizers/fertilizers accord-
ing to Manual Test and Criteria IMDG Code
Sample
to
cellu-
lose.
Burn rate
[cm/min.]
Proposed
Samppl
e
Stand
ard
Class
IMDG
Paca-
ging-
group
nitrate ferti-
lizer
(30% N)
1:1
1,38
0,83
5.1
III
4:1
1,08
fertilizer
(27,5% N)
1:1
0,93
0,83
5.1
III
4:1
0,20
nitrate
based
fertilizer
(15% N)
1:1
0,92
0,83
5.1
III
4:1
0
nitrate
based
fertilizer
1:1
2,18
0,83
5.1
III
4:1
0
nitrate (V)
(p.a.)
1:1
2,71
0,83
5.1
III
4:1
0
bromate
(V) (p.a. )
(standard)
2:3
10
10
5.1
II
3:7
0,83
0,83
5.1
III
Table 2. Thermal decomposition oxidizers/fertilizers and his
blends with cellulose using DTA method
Oxidizers
Sam-
ple
to
cellu-
lose
Ignition tem-
perature [ºC]
Tempera-
ture
change rate
[ºC/s]
Egzo+
Endo-
reacti-
on
Oxi-
dizer
Ox. –
cell.
Ox.
Ox.-
cell.
nitrate
based ferti-
lizer (30%
N)
1:1
335
205,4
1,6
7
1.68
+
4:1
211,7
1,68
+
fertilizer
(27,5% N)
1:1
338
197,3
0,5
1,7
+
4:1
218,3
1,74
+
nitrate
based
fertilizer
(14% N)
1:1
_
*
*
_
4:1
315,3
0,95
_
trate (V)
(p.a.)
1:1
_
*
320
_
1,16
+
4:1
326
1,44
+
bromate
(V) (p.a.)
3:7
455
329,3
2,6
0,96
+
2:3
190
1.82
*- (not observed ignitron until 500°C)
Ox. – oxidizer/fertilizer
cell. - cellulose
Table 3. Assignment of the fertilizers to the packaging group
based on temperature change rate
Name of the
fertilizer
Temperature
change rate
[°C/s]
Assigned
packaging
group
Proposed
class of
IMDG Code
Ammonium
nitrate based
fertilizer
(30% N)
1,68
III
5.1
Nitro-chalk
fertilizer
(27,5% N)
1,74
III
5.1
Potassium
nitrate based
fertilizer
(14% N)
0,96
III
5.1
Sodium nitra-
te (V)
1,44
III
5.1
Potassium
bromate (V)
(Standard)
0,96÷1,81
III
5.1
The ignition temperature and temperature change
rate make it possible to assess packaging group of
investigated fertilizers, belong to class 5.1 of danger
goods.
The blends of fertilizers and cellulose had lower
ignition temperature then pure oxidizers. Hence
those fertilizers will invariably accelerate the rate of
burning with combustible materials. Pure potassium
445
and sodium nitrates, high ionic compounds, had
thermal decompose in higher temperatures than
500
0
C, but the mixtures with combustible material –
cellulose were decomposed in temperature about
320
0
C. All blends fertilizers and cellulose decom-
posed in lower temperatures than pure oxidizes.
During reactions observed generally exothermic
processes and weight losses. It’s very dangerous in
shipping, especially of bulk cargo. Fertilizers con-
taining nitrates and ammonium salts, during fire on
the boat, lost stowage mass about 1/3 to ½ .
The results differential thermal analyze suggest
similar effects like in the tests recommended by
IMDG Code; all investigated fertilizers belong to
5.1. class of dangerous goods and require to packag-
ing group III.
After comparison these two methods of assigna-
tion to class 5.1 and packaging group’s data thermal
analyze gives quantitative information about thermal
effects (melting, self-heating, self-ignition) and loss
mass during heating. During Manual Test (according
IMDG Code) we have only qualitative data burning
time of blends oxidizers with cellulose. In Manual
Test was use big probe - 30g blends of oxidizer and
cellulose, in DTA method only - 300 ÷500 mg.
Differential thermal analyze is objective chemical
method which could make it possible to determine
the criteria of assignment of oxidizers to packaging
groups, required for sea transport. Data DTA method
gives more information about fire risk assessment
that Manual Test recommended by IMDG Code.
4 CONCLUSION
Manual Test recommended in IMDG Code informs
only qualitative about burning time special trial form
of oxidizer – cellulose blends.
The comparison two methods of classification and
assignment to a packing group of solid substances of
class 5.1 of IMDG Code indicate, that differential
thermal analyze (DTA method) gives objective,
quantitative information about fire risk on the boat.
Using this method, during heating we can regis-
tration changes of temperature, loss mass, melting
point temperatures mixtures before self-heating,
self-ignition and explosive effects.
Data based on the differential thermal analysis
gives more information about fire risk assessment
that Manual Test recommended by IMDG Code.
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