guidance for the compatibility of fertilizer blending...
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e u r o p e a n f e r t i l i z e r m a n u f a c t u r e r s a s s o c i a t i o n
JUNE 2006
GUIDANCE FOR THE COMPATIBILITY OFFERTILIZER BLENDING MATERIALS
Copyright 2006-EFMA
EUROPEAN FERTILIZER MANUFACTURERS’ ASSOCIATION
AVE. E. VAN NIEUWENHUYSE 4B-1160 BRUSSELS
BELGIUM
C O N T E N T S
1
G U I D A N C E F O R T H E C O M P A T I B I L I T Y O F F E R T I L I Z E R B L E N D I N G M A T E R I A L S
1. Introduction 2
2. Scope 3
3. Blending materials and general considerations 4
3.1 General 4
3.2 Nitrate-Containing Substances 4
3.3 Other Materials and General Notes 5
4. Relative humidity 7
5. Compatibility data 9
6. References 12
Prepared by EFMA – June 2006
DISCLAIMER:The information and guidance provided in this document is given in good faith. EFMA, its members and staff accept
no liability for any loss or damage arising from the use of this guidance.
1 . I N T R O D U C T I O N
2
G U I D A N C E F O R T H E C O M P A T I B I L I T Y O F F E R T I L I Z E R B L E N D I N G M A T E R I A L S
A large number of blended fertilizers are produced from basic primary fertilizer products (e.g.ammonium nitrate, urea, and mono-ammonium phosphate) and natural materials (e.g. rock phosphate,potassium chloride). All such materials are not necessarily compatible with each other and some mayproduce undesirable effects when mixed with others. These undesirable effects can include, for example,chemical reaction(s) and physical effects (e.g. stickiness which can cause handling difficulties, moisturemigration giving rise to caking tendency).
The Handbook of Solid Fertiliser Blending: Code of Good Practice for Quality produced by TheEuropean Fertiliser Blenders Association (Ref. 1), gives some information about these potentialcompatibility problems. EFMA has reviewed this information and has produced this guidance with awider scope by including most commonly used blending materials.
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G U I D A N C E F O R T H E C O M P A T I B I L I T Y O F F E R T I L I Z E R B L E N D I N G M A T E R I A L S
2 . S C O P E
Only solid blending components which are sources of primary (N, P and K) and/or secondary (e.g. Ca,Mg) nutrients are considered here. These blending components also include complex granularNPK/NP/NK fertilizers but fluid materials and micronutrients such as zinc and copper are notconsidered.
The assessment concerning compatibility is based on considerations of safety (e.g. chemical reactioncausing release of toxic gases), production problems (e.g. liquid formation, state of stickiness, corrosivemix due to free acidity) and/or quality aspects (e.g. high tendency for caking). It is important to notethat legislative controls e.g. limits imposed by classification schemes, impurity levels etc. are nottaken into account in this assessment. For example, regulations concerning safety and classification willhave a bearing on the limits of total combustible/organic matter and total ammonium nitrate levels.
It is important to bear in mind that most regulations define Ammonium Nitrate as mixtures containingNH4
+ and NO3- ions irrespective of their source materials which, for example, could be ammonium
phosphate and sodium nitrate. Manufacturers are advised to consider the legislative controls and identify‘no-go’ areas up-front prior to going into the compatibility aspects.
4
G U I D A N C E F O R T H E C O M P A T I B I L I T Y O F F E R T I L I Z E R B L E N D I N G M A T E R I A L S
3.1 General
A range of blending components is available and the common ones are listed in the Compatibility Table(see page 10). Some blending materials such as calcium cyanamide and basic slag are not included in thetable as they are not widely used. Some relevant information about them is given in another guidancedocument from EFMA, dealing with the storage and handling and transportation of solid ammoniumnitrate based and other fertilizers. If in doubt seek expert advice when using an unlisted/uncommoncomponent.
3.2 Nitrate-Containing Substances
Nitrates are important sources of nitrogen, particularly in European climatic conditions and the mainones are ammonium nitrate, potassium nitrate, sodium nitrate and calcium nitrate. Most of them possessoxidising properties and thus can support combustion but differ in their thermal behaviour andreactivity. Their main properties, related to the potential hazards, are summarised below (Ref: 2).
3.2.1 Ammonium Nitrate
Solid ammonium nitrate (AN) can exist in a number of different crystalline forms.Transitions from one form to another are accompanied by changes in the bulk density.This can lead to product break-down due to thermal cycling, unless it is stabilised againstthis effect by suitable conditioners. AN melts at 169°C and, when heated further,decomposes releasing gases containing mainly water vapour, NOx and ammonia. Theexothermic decomposition, which is a complex set of exothermic reactions, isaccompanied by reversible endothermic dissociation and is catalysed by a number ofsubstances. AN has oxidising properties and will, if involved in a fire, intensify the fireeven in the absence of air. AN, particularly the fertilizer grade, is difficult to detonate.The sensitivity to detonation depends on a number of factors such as bulk density,porosity and temperature.
3 . B L E N D I N G M AT E R I A L S A N D G E N E R A L C O N S I D E R AT I O N S
5
G U I D A N C E F O R T H E C O M P A T I B I L I T Y O F F E R T I L I Z E R B L E N D I N G M A T E R I A L S
For fertilizer application, EU regulations require the use of the dense grade, which haslow porosity and a high resistance to detonation. It must be able to pass the EUResistance to Detonation Test.
It is important to note that the AN content can be derived from different sources ofnitrate ions and ammonium ions, as described in section 2 above. Also, the classificationof the blend may be affected if there is an excess of nitrate ions above those derived fromactual or calculated AN.
3.2.2 Potassium Nitrate
Potassium nitrate has a melting point around 334°C. Commercially it is available in bothgranular and crystalline forms. It is not combustible, however it has oxidising propertiesand will, if involved in a fire, intensify the fire even in the absence of air. Above 400°C itdecomposes and liberates oxides of nitrogen. Potassium nitrate is not sensitive todetonation.
3.2.3 Sodium Nitrate
Sodium nitrate has a melting point close to 308°C. It is not combustible, however it hasoxidising properties and will, if involved in a fire, intensify the fire even in the absenceof air. When heated to decomposition, it gives off toxic gases, which include oxides ofnitrogen. Sodium nitrate is not sensitive to detonation.
3.2.4 Calcium Nitrate
Pure calcium nitrate (chemical formula Ca(NO3)2) is not normally traded as a fertilizer.Fertilizer grade calcium nitrate (chemical formula 5Ca(NO3)2.NH4NO3.10H2O) isessentially the hydrated ammonium calcium nitrate double salt. It is not classified as anoxidising material but. as with other nitrates, it should not be mixed with combustiblematerials, alkalis and acids. Its ammonium nitrate component decomposes above 190°C,whereas the calcium nitrate component decomposes above 500°C and the thermaldecomposition products are mainly nitrogen oxides.
3.3 Other Materials and General Notes
The following points should be noted:
• The compatibility data are based on the assumption that the components have typicaland acceptable moisture content and thermal stability.
• In general the presence of anti-caking agents and additives in fertilizers may affect theircompatibility.
• The type of manufacturing process used can also affect the product properties, e.g.materials made by the nitrophosphate process may behave differently from those madeby the mixed acid phosphate route.
• Calcium sulphate as listed does not cover impure by-product gypsum.
• Limestone and dolomite generally refer to mined material.
• Calcium nitrate refers to the fertilizer grade material which contains 12% water, is adouble salt and is not classified as Class 5.1 oxidiser.
• Rock phosphate is listed in two forms: normal mineral and acidulated rock which,although this is not normally the case, can contain some free acid.
• Elemental sulphur can give rise to the formation of dust, particularly in the mixingprocess and this dust can present a potential “dust explosion” hazard.
6
G U I D A N C E F O R T H E C O M P A T I B I L I T Y O F F E R T I L I Z E R B L E N D I N G M A T E R I A L S
• Where AN forms a part of the blend, care should be taken to ensure that the specifiedlimits of total combustible/organic substances, including any coating oil, are notexceeded in the blend.
• In some countries there may be restrictions regarding the use of coating oil or the typeof oil. This point should be taken into consideration.
• The addition of certain micronutrients such as copper or manganese to chloridecontaining AN-based blends can enhance the thermal decomposition potential. This mayconvert a non-classified type to a self-sustaining decomposition type. An appropriateassessment should be made.
The overall approach to the evaluation and selection of blend composition is outlined in Figure 1.
FIGURE 1
7
G U I D A N C E F O R T H E C O M P A T I B I L I T Y O F F E R T I L I Z E R B L E N D I N G M A T E R I A L S
Some fertilizer materials are hygroscopic which means they can pick up moisture from humid air. TheCritical Relative Humidity (CRH) is the property which is used as an indicator of the degree of likelyinteraction with atmospheric moisture. It is the value of the relative humidity of the surrounding air,above which the material absorbs moisture and below which it does not. Thus, the lower the CRH thegreater the tendency to pick up moisture from the atmosphere. It is, therefore, desirable to have highvalues of the CRH for the raw materials and the finished fertilizers. CRH values are measured orcalculated at 30°C and the values tend to decrease slightly with increase in temperature.
In most cases the CRH for blended or compound fertilizers is below the average derived from theircomponents. This drop in the CRH can be significantly high in some cases. A blend consisting ofammonium nitrate and urea is an extreme example of this effect. Such a blend picks up moisture veryquickly and is difficult to handle in a dry state. This can be a significant factor to consider in the selectionof the blend components. CRH values of pure components and blends based on them are summarised inTable 1 (Ref: 3 ). It should be borne in mind that these values are for pure salts and the correspondingcommercial materials may have slightly different values depending on any impurities present.
4 . R E L AT I V E H U M I D I T Y
8
G U I D A N C E F O R T H E C O M P A T I B I L I T Y O F F E R T I L I Z E R B L E N D I N G M A T E R I A L S
Tabl
e 1
Cri
tical
Rel
ativ
e H
umid
ities
of
Pur
e S
alts
and
Mix
ture
s at
30°
C (
86°F
)
E
TA
RTI
N M
UIC
LA
C
7.6 4
ET
AR
TIN
MU I
NO
MM
A
E
TA
RTI
N M
UID
OS
4.95
5.32
A
ER
U
4 .27 3.64
7.73
E
DIR
OLH
C M
UIN
OM
MA
5.27
6.54 1.81
-
4.15 -
9.15‡
E
TA
HPL
US
MUI
NO
MM
A
2.77 9.75
3 .26 -
- ‡
E
TA
HP
SO
HP
MU I
NO
MM
AID
2.97
3.17 4. 65
E
DIR
OLH
C M
UIS
SA
TO
P
5 .2 8 *27
- *26
- *95
-
0.22<
9 .76‡
9.66
‡ 5 .37
3.063 .17‡
E
TA
RTI
N M
UIS
SA
TO
P
0.48 * 07
E
TA
HP
SO
HP
MU I
NO
MM
AO
NO
M
5 .09 6.87
- 2. 96
9.7 6 2. 56
5. 46 9.9 5
4 .1 3
8.25‡
*8 7 8. 57
- 2. 56
8 .36 0 .85
8.27‡
E
TA
HP
SO
HP
MUI
CLA
CO
NO
M
6.19 8.9 5
*87 7. 78
9 .3 7 1 .5 6
1 .8 6 8.25
2.6 4-‡
E
TA
HPL
US
MUI
SS
AT
OP
6.3 9
8.88 8.7 8
1.6 7‡
2.96
‡3 .37
‡
0 .97 8.7 8
18 * 77
4 .18 3.17
5.17-‡
3.6 9
* A
ppro
xim
ate
valu
es o
btai
ned
by T
VA
(T
enne
ssee
Val
ley
Aut
horit
y) (
Ref
. 3).
Oth
er d
ata
are
from
lite
ratu
re.
‡ U
nsta
ble
salt
pair;
the
valu
e gi
ven
is fo
r th
e st
able
pai
r.
9
G U I D A N C E F O R T H E C O M P A T I B I L I T Y O F F E R T I L I Z E R B L E N D I N G M A T E R I A L S
5 . C O M P AT I B I L I T Y D ATA
The compatibility data are presented in three categories as follows:
1. Compatible (indicated in green): No undesirable effect is predicted.
2. Limited compatibility (indicated in yellow): Blends are permitted but there may be a risk of the blendbeing incompatible in some cases or situations e.g. if one or more of the components is out ofspecification or contains abnormal levels of an objectionable substance such as free acid. Anappropriate risk assessment should be carried out, as necessary.
3. Incompatible (indicated in red): Considered as not being compatible and, therefore, not to be mixed.
For categories 2 and 3 the explanation/reason for the categorisation is given by way of a serial numberin the box and a footnote for each allocated number. No explanation is deemed necessary for compatiblemixes.
10
G U I D A N C E F O R T H E C O M P A T I B I L I T Y O F F E R T I L I Z E R B L E N D I N G M A T E R I A L S
Tabl
e 2
Com
patib
ility
of
vari
ous
fert
ilize
r m
ater
ials
ET
AR
TIN
MUI
NO
MM
A
)E
NO
TS
EMIL/
ET I
MOL
OD
+ N
A( E
TA
RTI
N M
UIN
OM
MA
MUI
CLA
C
)E
DA
RG
RE
ZI LIT
RE
F( E
TA
RTI
N M
UICL
AC
18
ET
AR
TIN
ET
AH
P LU
S M
U IN
OM
MA
2 0
1
ET
AR
TIN
MUI
DO
S/E
TA
RTI
N M
UIS
SA
TO
P
01
2E
TA
HPL
US
MUI
NO
MM
A
32
01
23 1
AE
RU
44
01
4E
TA
HP
SO
HP
KC
OR
21
E
TA
HP
SO
HP
KC
OR
DE
TA
LU
DIC
A
55
6 1
ET
AH
PS
OH
P R
EP
US
ELPI
RT/
ELG
NIS
59
01
971
ET
AH
PS
OH
P M
UIN
OM
MA
ON
OM
01
ET
AH
PS
OH
P M
U IN
OM
MAI
D
01
91
91E
TA
HP
SO
HP
MUI
SS
AT
OP
ON
OM
01
EDI
ROL
HC
MUI
SS
AT
OP
66
01
68 1
)E
TIR
ES
E IK(
ET
AH
PLU
S M
UIS
EN
GA
M /E
TA
HPL
US
MUI
SS
AT
OP
11
)D
ES
AB
NA(
KN ,
PN ,
KP
N
66
01
641
64
55
6 )
DE
SA
B A
ER
U( K
N ,P
N ,K
PN
44
01
45 1
61
614
ET
AH
PLU
S M
UICL
AC/
ETI
MOL
OD/
EN
OT
SE
MIL
91
91 )
LA
TN
EM
ELE(
RU
HPL
US
77
01
77
7
e lbita pmo
C
d/
or s
afet
y ba
sed)
na y lla cisyhp ,yllacimehc( yti li bi tap
moc d e timi L
d/or
saf
ety
base
d)n a yll
a cisyhp ,y llaci
me hc( el bitapm oc nI
11
G U I D A N C E F O R T H E C O M P A T I B I L I T Y O F F E R T I L I Z E R B L E N D I N G M A T E R I A L S
FO
OT
NO
TE
S F
OR
TH
E N
UM
BE
RS
IN
TH
E B
OX
ES
IN
TA
BL
E 2
1.D
ue t
o th
e hy
gros
copi
c be
havi
our
of b
oth
prod
ucts
, the
typ
e of
sta
bilis
atio
n of
the
am
mon
ium
nitr
ate
grad
e co
uld
influ
ence
the
sto
rage
pro
pert
ies.
2.
Con
side
r th
e sa
fety
impl
icat
ions
reg
ardi
ng t
he d
eton
abili
ty o
f the
ble
nd (
AN
/AS
mix
ture
s) a
nd le
gisla
tive
impl
icat
ions
.
3.C
onsi
der
the
safe
ty i
mpl
icat
ions
reg
ardi
ng t
he d
eton
abili
ty o
f th
e bl
end
(AN
/AS
mix
ture
s),
the
impa
ct o
f fr
ee a
cid
and
orga
nic
impu
ritie
s, i
f pr
esen
t, an
d le
gisla
tive
impl
icat
ions
.
4.M
ixtu
re w
ill q
uick
ly b
ecom
e w
et a
nd a
bsor
b m
oist
ure
resu
lting
in t
he fo
rmat
ion
of li
quid
or
slurr
y. T
here
cou
ld a
lso b
e sa
fety
impl
icat
ions
.
5.If
free
aci
d is
pre
sent
it c
ould
cau
se a
ver
y slo
w d
ecom
posi
tion
of A
N, a
ffec
ting,
for
exam
ple,
the
pac
kagi
ng.
6.C
onsi
der
the
poss
ibili
ty o
f sel
f-su
stai
ning
dec
ompo
sitio
n an
d th
e ov
eral
l lev
el o
f oil
coat
ing.
7.Su
lphu
r is
com
bust
ible
and
can
rea
ct w
ith n
itrat
es e
.g. A
N, K
NO
3an
d N
aNO
3.
8.D
ue t
o th
e hy
gros
copi
c be
havi
our
of b
oth
prod
ucts
the
typ
e of
sta
bilis
atio
n of
the
am
mon
ium
nitr
ate
base
d fe
rtili
ser
coul
d in
fluen
ce t
he s
tora
ge p
rope
rtie
s.
9.C
onsi
der
the
moi
stur
e co
nten
t of
the
SS
P/T
SP.
10.
Con
side
r th
e re
lativ
e hu
mid
ity d
urin
g bl
endi
ng.
11.
Ris
k of
for
mat
ion
of g
ypsu
m.
12.
No
expe
rien
ce b
ut t
his
can
be e
xpec
ted
to b
e co
mpa
tible
. Con
firm
by
test
and
/or
anal
ysis
.
13.
Con
side
r im
puri
ties
in A
S a
nd t
he d
rop
in t
he c
ritic
al r
elat
ive
hum
idity
of
the
blen
d.
14.
Con
side
r th
e lik
ely
impa
ct o
f ad
ditio
nal n
itrat
e.
15.
Con
side
r th
e po
ssib
ility
of
amm
oniu
m p
hosp
hate
/pot
assi
um n
itrat
e re
actio
n w
ith u
rea
and
the
rela
tive
hum
idity
dur
ing
blen
ding
, to
avoi
d ca
king
.
16.
If f
ree
acid
is p
rese
nt, t
here
is a
pos
sibi
lity
of h
ydro
lysi
s of
ure
a gi
ving
am
mon
ia a
nd c
arbo
n di
oxid
e.
17.
For
mat
ion
of v
ery
stic
ky u
rea
phos
phat
e.
18.
Pot
entia
l cak
ing
prob
lem
due
to
moi
stur
e.
19.
If f
ree
acid
is p
rese
nt, c
onsi
der
the
risk
of
a re
actio
n e.
g. n
eutr
alis
atio
n w
ith a
mm
onia
and
aci
d at
tack
with
car
bona
tes.
12
G U I D A N C E F O R T H E C O M P A T I B I L I T Y O F F E R T I L I Z E R B L E N D I N G M A T E R I A L S
6 . R E F E R E N C E S
1. European Fertiliser Blenders Association, 2005, Handbook of Solid Fertiliser Blending Code ofGood Practice for Quality, second edition, European Fertiliser Blenders Association, AvenueGaston Phoebus, 64231 Lescar Cedex, France.
2. EFMA (1992), Handbook for the Safe Storage of Ammonium Nitrate Based Fertilizers. Revisionin progress and publication due in 2006 as Guidance for the Storage, Handling and Transportationof Solid Mineral Fertilizers.
3. Clayton W E, 1984, Humidity Factors Affecting Storage and Handling of Fertilizers, InternationalFertilizer Development Center, Muscle Shoals, AL 35662, USA.
Avenue E. van Nieuwenhuyse, 4B-1160 BrusselsBelgiumTel: +32 2 675 35 50Fax: +32 2 675 39 61E-mail: main@efma.be
For more information about EFMAvisit the web-site www.efma.org
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