GUIDANCE FOR COMPATIBILITY OF FERTILIZER BLENDING MATERIALSIssue
20142GUIDANCE FOR COMPATIBILITY OF FERTILIZER BLENDING
MATERIALSContents1.INTRODUCTION32. SCOPE33. BLENDING MATERIALS
& GENERAL CONSIDERATIONS43.1General43.2Nitrate-Containing
Substances43.2.1Ammonium Nitrate43.2.2Potassium Nitrate53.2.3Sodium
Nitrate53.2.4Calcium Nitrate53.3Other Materials and General
Notes54.RELATIVE HUMIDITY85.COMPATIBILITY
DATA106.REFERENCES13DISCLAIMER:This document has been produced for
the beneft of the members of Fertlizers Europe. The informaton and
guidance provided in this document is given in good faith.
Fertlizers Europe, its members, consultants and staf accept no
liability for any loss or damage arising from the use of this
guidance. As regulatons are up-dated from tme to tme, readers are
advised to consult the up-to-date informaton. Editon 2006
Fertlizers Europe 201431.
INTRODUCTIONAlargenumberofblendedfertlizersareproducedfrombasicprimaryfertlizer
products(e.g.ammoniumnitrate,urea,andmono-ammoniumphosphate)and
natural materials (e.g. rock phosphate, potassium chloride). All
such materials are not
necessarilycompatblewitheachotherandsomemayproduceundesirableefects
when mixed with others. These undesirable efects can include, for
example, chemical
reacton(s)andphysicalefects(e.g.stckinesswhichcancausehandlingdifcultes,
moisture migraton giving rise to caking tendency). The Handbook of
Solid Fertliser Blending: Code of Good Practce for Quality produced
byTheEuropeanBlendersAssociaton(Ref.1),givessomeinformatonaboutthese
potentalcompatbilityproblems.FertlizersEuropehasreviewedthisinformaton
and has produced this guidance with wider scope by including most
commonly used blending materials.2. SCOPE
Onlysolidblendingcomponentswhicharesourcesofprimary(N,PandK)and/or
secondary (e.g. Ca, Mg) nutrients are considered here. These
blending components also include complex granular NPK/NP/NK
fertlizers but fuid materials and micronutrients such as zinc and
copper are not
considered.Theassessmentconcerningcompatbilityisbasedonconsideratonsofsafety(e.g.
chemicalreactoncausingreleaseoftoxicgases),productonproblems(e.g.liquid
formaton, state of stckiness, corrosive mix due to free acidity)
and/or quality aspects (e.g. high tendency for caking). It is
important to note that legislatve controls e.g. limits imposed by
classifcaton schemes, impurity levels etc. are not taken into
account in
theassessment.Forexample,regulatonsconcerningsafetyandclassifcatonwould
have a bearing on the limits of total combustble/organic mater and
total ammonium nitrate
level.ItisimportanttobearinmindthatmostregulatonsdefneAmmoniumNitrateas
mixturescontainingNH4+andNO3-ionsirrespectveoftheirsourcematerials,which
for example, could be ammonium phosphate and sodium nitrate.
Manufacturers are advised to consider the legislatve controls and
identfy no-go areas up-front prior to going into the compatbility
aspects.43. BLENDING MATERIALS & GENERAL
CONSIDERATIONS3.1GeneralArangeofblendingcomponentsisavailableandthecommononesarelistedinthe
CompatbilityTable(page12).Someblendingmaterialssuchascalciumcyanamide
and basic slag are not included in the table as they are not widely
used. Some relevant informaton about them is given in another
guidance document from Fertlizers Europe, dealing with storage and
handling and transportaton of solid ammonium nitrate based and
other fertlizers. If in doubt, seek expert advice when using an
unlisted/uncommon component.3.2Nitrate-Containing
SubstancesNitratesareimportantsourcesofnitrogen,partcularlyintheEuropeanclimatc
conditons and the main ones are ammonium nitrate, potassium
nitrate, sodium nitrate and calcium nitrate. Most of them possess
oxidising propertes and thus can support combuston but difer in
their thermal behaviour and reactvity. Their main propertes related
to the potental hazards are summarised below (Ref. 2).
3.2.1Ammonium
NitrateSolidammoniumnitrate(AN)canexistinanumberofdiferentcrystallineforms.
Transitons from one form to another are accompanied by changes in
the bulk density.
Thiscanleadtoproductbreak-downduetothermalcycling,unlessitisstabilised
against this efect by suitable conditoners. AN melts at 169C and,
when heated further,
decomposesreleasinggasescontainingmainlywatervapour,NOxandammonia.
Theexothermicdecompositon,whichisacomplexsetofexothermicreactons,is
accompanied by reversible endothermic dissociaton and is catalysed
by a number of substances. AN has oxidising propertes and will, if
involved in a fre, intensify the fre even in the absence of air.
AN, partcularly the fertlizer grade, is difcult to detonate.
Thesensitvitytodetonatondependsonanumberoffactorssuchasbulkdensity,
porosity and
temperature.Forfertlizerapplicaton,EUregulatonsrequiretheuseofthedensegrade,which
has low porosity and a high resistance to detonaton. It must be
able to pass the EU Resistance to Detonaton Test.It is important to
note that AN content can be derived from diferent sources of
nitrate
ionsandammoniumions,asdescribedinsecton2above.Also,theclassifcatonof
the blend may be afected if there is an excess of nitrate ions
above those derived from actual or calculated AN. 563.2.2Potassium
NitratePotassiumnitratehasameltngpointaround334C.Commerciallyitisavailablein
bothgranularandcrystallineforms.Itisnotcombustble,howeverithasoxidising
propertesandwill,ifinvolvedinafre,intensifythefreevenintheabsenceofair.
Above 400C it decomposes and liberates oxides of nitrogen.
Potassium nitrate is not sensitve to detonaton.3.2.3Sodium
NitrateSodium nitrate has a meltng point close to 308C. It is not
combustble, however, it has oxidising propertes and will, if
involved in a fre, intensify the fre even in the absence of air.
When heated to decompositon, it gives of toxic gases, which include
oxides of nitrogen. Sodium nitrate is not sensitve to
detonaton.3.2.4Calcium NitratePure calcium nitrate (chemical
formula Ca(NO3)2) is not normally traded as a fertlizer.
Fertlizergradecalciumnitrate(chemicalformula5Ca(NO3)2.NH4NO3.10H2O)is
essentally the hydrated ammonium calcium nitrate double salt. It is
not classifed as an oxidising material, but as with other nitrates,
it should not be mixed with combustble
materials,alkalisandacids.Itsammoniumnitratecomponentdecomposesabove
190C,whereasthecalciumnitratecomponentdecomposesabove500Candthe
thermal decompositon products are mainly nitrogen oxides. 3.3Other
Materials and General NotesThe following points should be
noted:Thecompatbilitydataarebasedontheassumptonthatthecomponentshave
typical and acceptable moisture content and thermal stability.In
general the presence of ant-caking agents and additves in
fertlizers may afect their compatbility.
Thetypeofmanufacturingprocessusedcanalsoafecttheproductpropertes,
e.g. materials made by the nitrophosphate process may behave
diferently from those made by 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 fertlizer grade material which
contains 12% water, is a double salt and is not classifed 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.Elementalsulphurcangiverisetoformatonofdust,partcularlyinthemixing
7process and this dust can present a potental dust explosion
hazard.
WhereANformsapartoftheblend,careshouldbetakentoensurethatthe
specifed limits of total combustble/organic substances, including
any coatng oil, are not exceeded in the blend.In some countries
there may be restrictons regarding the use of coatng oil or the
type of oil. This point should be taken into consideraton. The
additon of certain micronutrients such as copper or manganese to
chloride
containingAN-basedblendscanenhancethethermaldecompositonpotental.
This may convert a non-classifed type to a self-sustaining
decompositon type.An appropriate assessment should be made.The
overall approach to the evaluaton and selecton of blend compositon
is outlined in Figure 1.Select blend analysis(N:P:K)Select raw
materialsCalculate composition of proposed blendDoes formulation
meet regulations?Check compatibility for each pair of blend
componentReview formulation.Change raw materials and/or blend N:P:K
analysis or abandonYellowRedOK to produceCheck footnote &
assess if acceptableGreenNoYesNo YesFIGURE1: BLENDING LOGIC
DIAGRAM9FIGURE1: BLENDING LOGIC DIAGRAM4.RELATIVE
HUMIDITYSomefertlizermaterialsarehygroscopicwhichmeanstheycanpickupmoisture
from humid air. The Critcal Relatve Humidity (CRH) is the property
which is used as
anindicatorofthedegreeoflikelyinteractonwiththeatmosphericmoisture.Itis
thevalueoftherelatvehumidityofthesurroundingair,abovewhichthematerial
absorbs moisture and below which it does not. Thus, the lower the
CRH the greater the tendency to pick up moisture from the
atmosphere. It is, therefore, desirable to have high values of the
CRH for the raw materials and the fnished fertlizers. CRH values
are measured or calculated at 30C and the values tend to decrease
slightly with increase in temperature.In most cases, the CRH for
blended or compound fertlizers is below the average derived from
their components. This drop in the CRH can be signifcantly high in
some cases. A blend consistng of ammonium nitrate and urea is an
extreme example of this efect. Such a blend picks up moisture very
quickly and it is difcult to handle in a dry state. This can be a
signifcant factor to consider in the selecton of the blend
components.
CRHvaluesofpurecomponentsandblendsbasedonthemaresummarisedin Table
1 (Ref. 3). It should be borne in mind that these values are for
pure salts and the corresponding commercial materials may have
slightly diferent values depending on any impurites
present.10CALCIUM NITRATEAMMONIUM NITRATEPOTASSIUM
SULPHATEMONOCALCIUM PHOSPHATEMONOAMMONIUM PHOSPHATEPOTASSIUM
NITRATEPOTASSIUM CHLORIDEDIAMMONIUM PHOSPHATEAMMONIUM
SULPHATEAMMONIUM CHLORIDEUREASODIUM NITRATETABLE I: CRITICAL
RELATIVE HUMIDITIES OF PURE SALTS AND MIXTURES AT 30C (86F)*
Approximate values obtained by TVA (Tennessee Valley Authority)
(Ref.3). Other data are from literature** Unstable salt pair; the
value given is for the stable pair115.COMPATIBILITY DATAThe
compatbility data are presented in three categories as
follows:1.Compatble (indicated in green): No undesirable efect is
predicted.2.Limitedcompatbility(indicatedinyellow):Blendsarepermitedbuttheremay
be a risk of the blend being incompatble in some cases or situatons
e.g. if one or more of the components is out of specifcaton or
contains abnormal levels ofan objectonable substance such as free
acid. An appropriate risk assessment should be carried out, as
necessary.3.Incompatble (indicated in red): Considered as not being
compatble and, therefore, should not be mixed. For categories 2 and
3 the explanaton/reason for the categorisaton is given by way of a
serial number in the box and footnote for each allocated number. No
explanaton is deemed necessary for compatble mixes.AMMONIUM
NITRATECALCIUM NITRATE (FERTILIZER GRADE)CALCIUM AMMONIUM NITRATE
(AN + DOLOMITE/LIMESTONE)AMMONIUM SULPHATE NITRATEPOTASSIUM
CHLORIDEMONO POTASSIUM PHOSPHATEDIAMMONIUM PHOSPHATEMONOAMMONIUM
PHOSPHATESINGLE/TRIPLE SUPER PHOSPHATEACIDULATED ROCK PHOSPHATEROCK
PHOSPHATEUREAAMMONIUM SULPHATEPOTASSIUM NITRATE / SODIUM
NITRATELIMESTONE/DOLOMITE/CALCIUM SULPHATENPK, NP, NK (UREA
BASED)NPK, NP, NK (AN BASED)POTASSIUM SULPHATE/MAGNESIUM SULPHATE
(KIESERITE)SULPHUR (ELEMENTAL)TABLE 2: COMPATIBILITY OF VARIOUS
FERTILIZER MATERIALSCompatbleLimited compatbility (chemically,
physically and/or safety based)Incompatble (chemically, physically
and/or safety based)13FOOTNOTES FOR THE NUMBERS IN THE BOXES IN
TABLE 21.Due to the hygroscopic behaviour of both products, the
type of stabilisaton of the ammonium nitrate grade could infuence
storage
propertes.2.Considerthesafetyimplicatonsregardingdetonabilityoftheblend(AN/AS
mixtures) and legislatve
implicatons.3.Considerthesafetyimplicatonsregardingdetonabilityoftheblend(AN/AS
mixtures),impactoffreeacidandorganicimpurites,ifpresent,andlegislatve
implicatons.
4.Mixturewillquicklybecomewetandabsorbmoistureresultnginformatonof
liquid or slurry. There could also be safety implicatons.5.If free
acid is present it could cause very slow decompositon of AN,
afectng, for example,
packaging.6.Considerthepossibilityofself-sustainingdecompositonandtheoveralllevelof
oil coatng.7.Sulphur is combustble and can react with nitrates e.g.
AN, KNO3 and NaNO3.8.Due to the hygroscopic behaviour of both
products, the type of stabilisaton of the ammonium nitrate based
fertlizer could infuence the storage propertes.9.Consider the
moisture content of the SSP/TSP.10.Consider the relatve humidity
during blending.11.Risk of formaton of gypsum.12.No experience but
this can be expected to be compatble. Confrm by test and/or
analysis.13.Consider impurites in AS and the drop in the critcal
relatve humidity of the blend.14.Consider the likely impact of
additonal nitrate.15.Consider the possibility of ammonium
phosphate/potassium nitrate reacton with urea and relatve humidity
during blending to avoid caking.16.If free acid present, there is a
possibility of hydrolysis of urea giving ammonia and carbon
dioxide.17.Formaton of very stcky urea phosphate.18.Potental caking
problem due to
moisture.19.Iffreeacidispresent,considertheriskofareactone.g.neutralisatonwith
ammonia and acid atack with
carbonates.146.REFERENCES1.EuropeanFertliserBlendersAssociaton,2005,HandbookofSolid
FertliserBlendingCodeofGoodPractceforQuality,secondediton. European
Fertliser Blenders Associaton, Avenue Gaston Phoebus, 64231 Lescar
Cedex, France.2.Fertlizers Europe, Guidance for the Storage,
Handling and Transportaton of Solid Mineral Fertlizers
(2007).3.Clayton W E, 1984, Humidity Factors Afectng Storage and
Handling of Fertlizers. Internatonal Fertlizer Development Center,
Muscle Shoals, AL 35662, USA.15ProductStewardshipisdefnedasthe
managementofthesafety,healthand
environmentalaspectsofaproductthroughout
itslifecycleinanethicallyresponsibleway.Itis
ResponsibleCareasappliedtoproducts.Inour
applicatonofProductStewardshipwecoverthe total value chain, but
also address additonal issues such as Best Practces that are not
necessarily just dealing with the product characteristcs.The
Product Stewardship Program covers mineral
fertlizers,theirrawmaterialsandintermediate
products.www.productstewardship.eu Avenue E. van Nieuwenhuyse 4/6
B-1160, Brussels, BelgiumTel: +32 2 675 3550Fax: +32 2 675
3961main@fertilizerseurope.comwww.fertilizerseurope.comtwitter.com/FertilizersEuro
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