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.

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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

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

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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

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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