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HANDBOOKOFSOLIDFERTILISERBLENDING-CodeofGoodPracticeforQuality 1
EUROPEANFERTILIZERBLENDERSASSOCIATION
HANDBOOKOFSOLID
FERTILISERBLENDING
CodeofGoodPracticeforQualityThirdEdition
EditedbyJoGilbertsonandEstelleVallin
2016
www.european-blenders.org
89rueMagenta53000LAVAL,France
ThishandbookisalsoavailableinFrenchorGerman
HANDBOOKOFSOLIDFERTILISERBLENDING-CodeofGoodPracticeforQuality 2
CONTENTS
1. INTRODUCTION…………………………………………………………………………………….....……………………….4 1.1 BlendedFertilisers.............................................................................................................4
1.2 FertiliserBlenders..............................................................................................................4
1.3 ServicesandSoilAnalysis..................................................................................................5
2. DEFINITIONS.................................................................................................................................63. RAWMATERIALS..........................................................................................................................8
3.1 ChemicalProperties...........................................................................................................9
3.1.1 Compatibility.......................................................................................................93.2 PhysicalProperties...........................................................................................................11
3.2.1 ParticleSize.......................................................................................................113.2.2 Density..............................................................................................................123.2.3 Shape.................................................................................................................133.2.4 ParticleHardness..............................................................................................133.2.5 DustContent.....................................................................................................133.2.6 FlowRate..........................................................................................................13
3.3 Storage.............................................................................................................................13
3.3.1 MoisturePick-up...............................................................................................153.3.2 Contamination..................................................................................................16
3.4 Screening..........................................................................................................................17
3.5 SamplingandTesting.......................................................................................................17
3.6 MicronutrientsandConditioningAgents.......................................................................17
3.6.1 Micronutrients..................................................................................................173.6.2 ConditioningAgents.........................................................................................17
4. BLENDINGEQUIPMENT.............................................................................................................184.1 Selection...........................................................................................................................18
4.1.1 Weighing...........................................................................................................184.1.2 VolumetricFeeding..........................................................................................194.1.3 Mixers................................................................................................................204.1.4 LoadingEquipment...........................................................................................20
4.2 Testing/Calibration..........................................................................................................20
4.3 Operations.......................................................................................................................20
HANDBOOKOFSOLIDFERTILISERBLENDING-CodeofGoodPracticeforQuality 3
5. SEGREGATION............................................................................................................................215.1 FlowSegregation.............................................................................................................21
5.2 TransportSegregation.....................................................................................................25
5.3 SpreadingSegregation.....................................................................................................25
5.4 EFBAQualityRecommendations....................................................................................30
6. SAFETYCLASSIFICATION–LABELLING-DISTRIBUTION...........................................................316.1 LabellingandMarkingofFertilisers................................................................................31
6.2 LabellingandClassificationofHazardousSubstancesandMixtures…………………………32
6.3 SafetyDataSheets…………………………………………………………………………………………………..34
7. QUALITYCONTROL.....................................................................................................................36 7.1 RawMaterials..................................................................................................................36
7.2 FinishedProducts.............................................................................................................36
8. SAMPLINGANDANALYSIS.........................................................................................................378.1 Sampling...........................................................................................................................37
8.1.1 SamplingQuantity............................................................................................388.1.2 SamplingEquipment........................................................................................398.1.3 SampleDivider..................................................................................................40
8.2 ChemicalAnalysis............................................................................................................40
8.3 PhysicalTests...................................................................................................................40
8.3.1 TestMethodforSieveAnalysis........................................................................418.3.2 TestMethodforLooseBulkDensity................................................................428.3.3 TestMethodforAngleofRepose………………………………………………………………43
8.4 Examples..........................................................................................................................44
9. FORMULATION...........................................................................................................................4710. REFERENCES................................................................................................................................48
HANDBOOKOFSOLIDFERTILISERBLENDING-CodeofGoodPracticeforQuality 4
1. INTRODUCTION
ThisHandbookof SolidFertiliserBlendinghasbeenpreparedby theEuropeanFertilizerBlendersAssociation(EFBA)tohelpmembersachievetheirtargets:
1 Theidentificationofcropneeds,inconsultationwithfarmercustomers.
2 Theproductionofhighqualityblendedfertilisersfortheagriculturalmarkettosatisfytheseneeds.
3 Theaccuratedeliveryandspreadingofthesefertilisers.
Thishandbooksetsoutadvicewhich,iffollowed,shouldleadtoimprovedqualityoffinishedproducts,andawideracceptabilityofblendedfertilisersintheEuropeanmarketplace.
1.1 BLENDEDFERTILISERS
Theblendingofsolidgranularmaterialstoproduceawiderangeofcompoundfertilisershasbeensuccessfullypractisedforover40years.Insomecountriesblendsformbyfarthemajorproportionofcompoundfertiliserssold.
Blendedfertilisershavethreemainadvantagesovercomplexfertilisers. Thefirstisthatofversatility,thesecondisasimplematterofeconomicsandthethirdisabetterprotectionoftheenvironment.Usingalimitednumberofbasematerials,analmostinfiniterangeofcompoundscanbeproduced.These can be specificallymatched to local soil conditions and plant needs, thus avoiding excessnutrientswhichmayentertheenvironment.Multiplehandlingof thebasicrawmaterialssuchasphosphaterock, isavoidedbymaintaining theprimaryproductionprocessesat thesourceof thenutrients. Thematerialswhichthenneedtobetransportedtotheagriculturalareascontainthehighestpossibleamountsofnutrients,thusreducingoverallcosts.
Themaindisadvantageofblended fertilisers, incomparisonwithcomplex fertilisers, is theriskofsegregationofthecomponentsduringhandlingorspreading. However,thisbookshowshowtoavoidsegregation.
1.2 FERTILISERBLENDERS
Blenders,incommonwithotherfertiliserproducers,haveaclearresponsibilitytoensurethattheirproductsareofhighquality. Rawmaterialproducershaveaclearresponsibilitytoensurethatthematerialstheysupplytotheblendersarealsoofaconsistentlyhighqualityandconformtotheagreedspecifications. Thatistosay,theysupplymaterialsofguaranteedanalysisintermsoftheirnutrientcontentsandphysicalproperties.
Theblenderisresponsibleforhischoiceofequipmentandforspecifyingthequalityofrawmaterialshe ispurchasing. Inadditionhehasaresponsibilitytocheckthequalityoftherawmaterialshereceivesandtomonitorhisproductionatallstagestoensurefinishedproductsareofthehighestquality.
HANDBOOKOFSOLIDFERTILISERBLENDING-CodeofGoodPracticeforQuality 5
Fertiliserblendersarehandlingmaterialswhich,ifmismatchedormishandled,canresultinverypoorqualityfinishedfertiliserwhichwillnottransport,storeorspreadsatisfactorily.
There isacleareconomicbenefit tosuppliersandusersalike in improvingthequalityofblendedfertilisers. Poorqualityproductscanhaveseriousconsequences,bothlegalandfinancial.
TheSolidFertiliserBlendingHandbookcontainspracticaladvicetohelpmanufacturersachievehighqualityblends.
1.3 SERVICESANDSOILANALYSIS
Whilsttheblender’sresponsibilityfortheproducteffectivelyfinisheswithitsdeliverytofarm,theresponsibilitytoprovideascompleteaserviceaspossibledoesnot. Indeed,withmodernsystemsofcustomblending,theresponsibilitystartsandfinishesonthefarm.
Blending can be considered to be a complete system provided for the farmer, startingwith soilsampling,analysingitsnutrientrequirements,andfinishingwiththeaccuratespreadingofthecorrectblendofnutrients.
HANDBOOKOFSOLIDFERTILISERBLENDING-CodeofGoodPracticeforQuality 6
2. DEFINITIONS
Throughoutthishandbookthegeneraltermsblendandblendingareusedtodenotetheproductandtheprocessofmixinggranularmaterials. Blendedfertilisersmaybesuppliedtofarmersinbagsorin bulk. The term bulk-blend is reserved for situations where the blend is handled (stored,transported)inbulkratherthaninbags.
Blendsdonotnecessarilyconsistofmixturesofstraightfertilisersorsinglecompounds. Ablendoftwoorthreegranularcomplexfertiliserswillstillbeablendedfertiliser.
Anumberofotherspecifictermsareusedandthesearedefinedasfollows:
Blendedfertiliser:Fertiliserobtainedbydryphysicalblendingofvariousrawfertilisers,withoutanychemicalreaction.
Complexfertiliser:Compoundfertiliserobtainedbychemicalreaction,byliquidsolutionor,inthesolidstate,bygranulationandhavingadeclarablecontentofatleasttwoofthemajornutrients.
Note 1: For the solid granules, each particle contains all the nutrients approximately in theirdeclarablecontent.
Note2:SomeCompaniesusetheterm“uniform”tomeanacomplexfertiliserandtoindicatetheproductisnotablend.
Compoundfertiliser:Fertiliserhavingadeclarablecontentofatleasttwoofthenutrientsnitrogen,phosphorusandpotassium,obtainedchemicallyorbyblending,orboth.
Note:With thesedefinitions,monoanddi-ammoniumphosphatesandpotassiumnitratearenot“straights”butareNPandNKcomplexfertilisersrespectively.
d50 (Meanparticlesize):Thatsizesuchthathalftheparticles,bymass,arelargerthanthatsizeandhalfaresmaller.
Granularfertiliser:Solidfertiliserformedintoparticlesofapredeterminedmeansizebygranulation.
Note: Insomecountries,thistermisoften(wrongly)usedtomeancomplexfertilisers.
Granulation:Techniqueusingprocessessuchasagglomeration,accretion,compaction,tomodifytheparticlesize.
Granulometricspreadindex(GSI):Measureofthespreadofparticlesizesandameansofexpressingthegranulometricspread.
Increment:Representativequantityofmaterialtakenfromasamplingunit.
Lot: Totalquantityofmaterial, assumed tohave the samecharacteristics, tobe sampledusingaparticularsamplingplan.
HANDBOOKOFSOLIDFERTILISERBLENDING-CodeofGoodPracticeforQuality 7
Meanparticlesize(d50):Thatsizesuchthathalftheparticles,bymass,arelargerthanthatsizeandhalfaresmaller.
Particlesize:Dimensionwhichcorrespondstothesmallestsieveaperturesizethroughwhichaparticlewillpassifpresentedinthemostfavourableattitude.
Particlesizeanalysisbysieving:Divisionofasamplebysievingintosizefractions.
Rawmaterial:Solid,granularmaterialusedasacomponentinablendedfertiliser.
Note: Some of these materials are not the basic source materials which provide the nitrogen,phosphateandpotash. Inthesecases,theyareoftenknownasintermediatesorpre-mix.
Segregation:Differentialmovementofparticleswithinamixtureduetodifferencesintheirsize,shapeordensity,resultingintheirseparation.
Sieving:Processofseparatingamixtureofparticlesaccordingtotheirsizesbyoneormoresieves.
Sizeguidenumber(SGN):100timesthed50measuredinmillimetres
Spreadingwidth:Distancebetweentheextremeleftandrightpointswherethefertiliserarrivesontheground.
Straight fertiliser: Qualification generally given to a nitrogenous, phosphatic or potassic fertiliserhavingadeclarablecontentofonlyoneoftheplantnutrientsnitrogen,phosphorusorpotassium.
Note: It is possible for a straight fertiliser to be a blend. For example a mixture of granularammoniumnitrateandgranularammoniumsulphatewouldbeastraightnitrogenfertiliser.
Testsieving:Sievingwithoneormoretestsieves.
Workingwidth:Distancebetweeneachpassage(generallybetween12and48m)whenspreadingfertilisers.
Definitions of other technical termsmay be found in EN 12944 Fertilisers and LimingMaterials,Vocabulary,Part1[8].
HANDBOOKOFSOLIDFERTILISERBLENDING-CodeofGoodPracticeforQuality 8
3. RAWMATERIALS
Thequalityofthefinishedproductdependsalmostentirelyontherawmaterials.Goodblendingstartswithgoodrawmaterials. Itisnotrealistictoexpecttomakegoodqualityblendedfertilisersfrompoorrawmaterials. Thespecification,purchaseandcheckingofrawmaterialsmustbethefirstpriorityoftheblender.
Every rawmaterial should be bought to as tight a specification as possible. Deliveriesmust becheckedregularly,preferablybyindependentinspectors,toensureconsistentquality.Allsamplingandtestingshouldbecarriedoutusingmethodsagreedbetweensupplierandpurchaser,basedeitheronNationalorEuropeanlegislationoronacceptedInternationalStandards(CEN,ISOetc.). Moreinformationaboutsamplingwillbefoundinsection8.
Whilstmany fertiliser rawmaterialsmaybeconsideredtobecommodities, rather thanspecialitychemicals, theopportunisticpurchaseof spotconsignmentsofdoubtfuloriginandquality isNOTRECOMMENDED.Norawmaterialshouldbepurchasedwithoutanagreedcontractualspecificationcovering,asaminimum,theregistrationtoREACH,thechemicalanalysisandtheparticlesizedetails.
3.1 CHEMICALPROPERTIES
Thenutrientcontentofeachrawmaterialusedmustbeknowninordertoprepareformulationsfor the different compounds required. Raw material suppliers should be asked to supplycertificatesofanalysisforeachlargeconsignment. Whereconsignmentsdiffermarkedlytheyshouldbestoredseparatelyandtheformulationsadjustedtotakeaccountofthetrueanalysisfigures(seeChapter9)
Thewatercontentofeachrawmaterialusedmustbeknowninordertoensurecompatibilitybetweenrawmaterials.
In all cases it is advisable tomakeoccasional randomchecksby arranging for representativesamplestobetakenbyindependentinspectors. Thesesamplesshouldbeanalysedassoonaspossibleandbeforetheconsignmentisused.
3.1.1 Compatibility
Somerawmaterialsarenotcompatiblewithothersandblendscontainingsuchmixtureswillbeofverypoorquality. Thecompatibilitydataarepresentedinthetablebelowinthreecategories(Figure1).
FurtherinformationregardingcompatibilitymaybefoundinReference13
HANDBOOKOFSOLIDFERTILISERBLENDING-CodeofGoodPracticeforQuality 9
Figure1.COMPATIBILITYOFVARIOUSSOLIDINORGANICFERTILIZERS
Ammon
iumNitrate
CalciumAmmon
iumNitrate
Calciumnitrate(fe
rtilizerg
rade
)
Ammon
iumsu
lphatenitrate
PotassiumNitrate/S
odiumnitrate
Ammon
iumsu
lphate
Urea
RockPho
sphate
Partiallyacidu
latedrockpho
sphate
Single/Trip
lesu
perp
hosphate
Mon
oammon
iumpho
sphate
Diam
mon
iumpho
sphate
Mon
opo
tassiumpho
sphate
Potassiumchloride
Potassiumsu
lphate/m
agne
sium
sulphate(kieserite)
NPK
,NP,NK(ANbased
)
NPK
,NP,NK(Ureabased)
Limestone
/dolom
ite/calcium
sulphate/Calcium
carbo
nate
Sulphu
r(elem
ental)
AmmoniumNitrate
1 2 3 NC1 4 4 5 5
NC1
NC2
CalciumAmmoniumNitrate 6 2 2 NC1 7 5 5 NC
1 NC2
Calciumnitrate(fertilizergrade) 1
6 8 8 8 8 8 8 8 8 8 9 8 8 8
Ammoniumsulphatenitrate 2 2 8 2 NC1 10 4 7 5 5 NC
1 NC2
Potassium Nitrate/ Sodiumnitrate
8 2 11 12 13 NC
2Ammoniumsulphate 3
2 8 11 5
Urea NC1
NC1 8 NC
1 14 15 16 NC1
RockPhosphate
10
Partially acidulated rockphosphate 4
4 14 17
Single/Triplesuperphosphate 4
7 8 7 15 17 4 14 17
Monoammoniumphosphate
8
Diammoniumphosphate
8 17 17
Monopotassiumphosphate
8
Potassiumchloride 5
5 8 5 16 5
Potassium sulphate/magnesiumsulphate(kieserite)
9
NPK,NP,NK(ANbased) 5 5 8 5 12 5 NC1 4 5 NC
1 NC2
NPK,NP,NK(Ureabased) NC1
NC1 8 NC
1 13 14 NC1
Limestone/dolomite/calciumsulphate/Calciumcarbonate
17
Sulphur(elemental) NC2
NC2 8 NC
2NC2 NC
2
Compatible
Limitedcompatibilitylinked
toqualityissues
Limitedcompatibilityrelated
tosafetyorregulatoryissues
NC NotCompatible
DISCLAIMER:ThisdocumenthasbeenproducedforthebenefitofthemembersofFertilizersEurope.Theinformationandguidanceprovidedinthisdocumentisgiveningoodfaith.FertilizersEurope,itsmembers,consultantsandstaffacceptnoliabilityforanylossordamagearisingfromtheuseofthisguidance.
HANDBOOKOFSOLIDFERTILISERBLENDING-CodeofGoodPracticeforQuality 10
Notesforthenumbersintheboxesinthecompatibilitytable
LimitedCompatibility 1. Duetothehygroscopicbehaviourofbothproducts,thetypeofstabilisationofthe
ammoniumnitrategradecouldinfluencestorageproperties. 2. Considerthesafetyimplicationsregardingdetonabilityoftheblend(AN/ASmixtures)and
legislativeimplications. 3. Considerthesafetyimplicationsregardingdetonabilityoftheblend(AN/ASmixtures),
impactoffreeacidandorganicimpurities,ifpresent,andlegislativeimplications. 4. IffreeacidispresentitcouldcauseveryslowdecompositionofAN,affecting,forexample,
packaging. 5. Considerthepossibilityofself-sustainingdecompositionandtheoveralllevelofoilcoating. 6. Duetothehygroscopicbehaviourofbothproducts,thetypeofstabilisationofthe
ammoniumnitratebasedfertilizercouldinfluencethestorageproperties. 7. ConsiderthemoisturecontentoftheSSP/TSP. 8. Considertherelativehumidityduringblending. 9. Riskofformationofgypsum. 10. Noexperiencebutthiscanbeexpectedtobecompatible.Confirmbytestand/oranalysis. 11. ConsiderimpuritiesinASandthedropinthecriticalrelativehumidityoftheblend. 12. Considerthelikelyimpactofadditionalnitrate. 13. Considerthepossibilityofammoniumphosphate/potassiumnitratereactionwithureaand
relativehumidityduringblendingtoavoidcaking. 14. Iffreeacidpresent,thereisapossibilityofhydrolysisofureagivingammoniaandcarbon
dioxide. 15. Formationofverystickyureaphosphate. 16. Potentialcakingproblemduetomoisture. 17. Iffreeacidispresent,considertheriskofareactione.g.neutralisationwithammoniaand
acidattackwithcarbonates.
NotCompatible
NC1. Mixturewillquicklybecomewetandabsorbmoistureresultinginformationofliquidor slurry.Therecouldalsobesafetyimplications. NC2. Sulphuriscombustibleandcanreactwithnitratese.g.AN,KNO3andNaNO3.
Fromthechart,itisclearthatureaandammoniumnitrateshouldneverbeusedtogetherasthemixturewillquicklybecomewetandabsorbmoisture. Blendscontainingureaandsingleortriplesuperphosphatemayalsobecomestickyandcake. Suchblendsshouldneverbebagged. Mixtures of di-ammonium phosphate and superphosphates should be avoided as chemicalreactionsmaytakeplacewhichcanleadtocakingorchangesinthesolubilityofthephosphate.
Forreasonsofsafety,itisveryimportanttoavoidblendingammoniumnitrateorrawmaterialscontainingammoniumnitratewithanyorganicmaterials.
HANDBOOKOFSOLIDFERTILISERBLENDING-CodeofGoodPracticeforQuality 11
3.2 PHYSICALPROPERTIES
Themost important physical property - as far as blending is concerned - is the particle sizedistribution.
Theparticlesizedistributionmustbeknowninsomedetailandthespecificationmustincludeafulldescriptionofthisproperty. Attheveryleast,themeanparticlesize(asmeasuredbythed50)mustbespecified. Ideally,thespecificationshouldincludeameasureofthegranulometricspread index (GSI) and shouldalso includemaximumvalues for theamountsofoversize (forexample>5mm)andfines(forexample<1mm).
Theshapeandthedensityofparticlescouldhaveaninfluenceonthebehaviourofthefertiliserduringspreading.
Otherphysicalcharacteristics tobespecifiedmust include“freeflowing”and“dust free”andpossiblyhardnessandimpactresistance. However,thesepropertiesaremuchmoredifficulttoassessusingstandardtestmethods. Morerealistically,itisbettertospecifythatsuitableanti-cakingand/oranti-dust treatment isappliedtotherawmaterialandthat itshouldnotbreakdownduringhandling.
In all cases it is advisable tomakeoccasional randomchecksby arranging for representativesamples tobe taken and assessedby independent inspectors. It is also recommended thatsamplesbetakenduringthedeliveryandtestedforsizedistributionattheblendingplant.SeeSection5.4)
3.2.1 ParticleSize
Thekeyfactorinproducingqualityblendsisthesizecompatibilityoftherawmaterials. Unlessalltheingredientsarewellmatched,segregationwilltakeplaceeverytimetheblendishandledinbulk. Thiswill leadtounevennessofchemicalanalysisandpossibly,unevenspreadingofnutrientsonthecrops.
Theparticlesizedistributioncanbeexpressedinanumberofwaysbutallrelyonasieveanalysisofthematerial. Itisessentialthereforethatblendersshouldhavethefacilitytocarryoutafullsieveanalysisoftheirrawmaterials(seechapter8).
Anumberofsimplefieldtestdevicesareavailablebutthesearelimitedintheirabilitytomeasureparticlesizedistributionadequately. Theyarehowever,veryusefultocarryoutspotchecksonrawmaterialsbeingfedtotheblender.
The official method of test sieving is fully described in European Standard EN 1235 andAmendment A1 [3]. A number of numerical parametersmay be calculated from the sieveanalysis. Theseincludethemeanparticlesize(d50)andgranulometricspreadindex(GSI). Inviewoftheimportanceofsizedistribution,fulldescriptionsoftheseparametersandtheuseofthevarioussystemsaredescribedbelow.
HANDBOOKOFSOLIDFERTILISERBLENDING-CodeofGoodPracticeforQuality 12
However,forthebestresults,itisrecommendedthatafullsizedistributioncurveisplottedforallrawmaterialsamplestested. Adescriptionofthetestsievingtechniqueisgiveninparagraph8.3.1. Sizedistributioncurvescanreadilybesuperimposedtogiveaquickcomparisonandanindicationofcompatibility.
Themeanparticlesize(d50)isdeterminedusingthefollowingequation:(1)
( )( ) ( )nn
nn
nn zz
ccczd 50 1
150 -
--
+= ++
Where:
1 znisthenominalsievemeshinmmforwhichthecumulativeundersizeisnearesttobutbelow50%bymass
2 zn+1isthenominalsievemeshinmmforwhichthecumulativeundersizeisnearesttobutabove50%bymass
3 cnisthecumulativepercentageundersizeforsieven
4 cn+1isthecumulativepercentageundersizeforsieven+1
NOTE:d84andd16arecalculatedinthesamewaybysubstituting84and16respectivelyfor50inequation(1)above.
Anexcellentmeasureof thespreadofparticlessizescanbeobtainedusing thewholeof thelinearpart(betweend84andd16)ofthedistributioncurveobtainedfromthesieveanalysis. Thevaluesofd84andd16maybefounddirectlyfromthegraphorbycalculation. Thespreadisthedifferencebetweenthetwo:
1684 dd -=D
An important value, known as the Granulometric Spread Index (GSI), is derived from thefollowingformula:
100 d 2 50
D=GSI
or100
d 2
50
1684 ddGSI -=
3.2.2 BulkDensity
ThebulkdensityofthefertilisermaybemeasuredinaccordancewithEN1236(Loosedensity)[4]orEN1237(tappeddensity)[5]. Thegeneralprincipleistoweighthecontentsofacylinderofaknownvolume. Forthetappeddensity,thecylinderissubjecttovibrationsandcompactionoccurs. Thisvalueisalwayshigherthantheloosedensity.
HANDBOOKOFSOLIDFERTILISERBLENDING-CodeofGoodPracticeforQuality 13
The density of the fertiliser can have an influence on the behaviour of the particles duringspreadingonthefield. Severesegregationmayoccur if thedensitiesareverydifferent (seesection5.3).
Generally,theloosebulkdensityoffertilisersisbetween900and1100kg/m³butextremevaluescan be between 750 and 1350 kg/m³. In practice these extreme values rarely occursimultaneously.
3.2.3 Shape
Themeasurementoftheshapeofthefertiliserparticlesisnoteasy. Generally,itisnecessarytouseimageanalysistechniques. However,themeasurementoftheangleofreposeofaheapformedbyafertiliserflowingfromafunnelcanbeausefulguidetothisparameter. ThemethodisstandardisedinEN12047[6]anddescribedinparagraph8.3.3. Anglesofreposevaryfromabout30°forthemostsphericalproductsto40°forthemostangular.
3.2.4 ParticleHardness
Duringhandlingandspreading,thefertiliserwillbesubmittedtostresseswhichcanbreaktheparticles,forexampletheimpactwiththevanesduringspreading. Thisprocessleadstotheproductionofsmallgrainswhichcausesomeproblems(segregation,caking). Forthisreasonthe particles should be of a sufficient hardness. Unfortunately, the test methods are notstandardised because of the variability of the measurement and the evolution of theseparameterswithtime. Iftheparticlehardnessislow,thefertilisermaycontaintoomanysmallparticlesandthusmaynolongermeetthequalitycriteria(seesection5.4).
3.2.5 DustContent
Somefertilisershavethetendencytoproducelargeamountsofdust. Thiscancauseproblemsintheneighbourhoodoftheplantandaccentuatestheriskofcaking. Thereisnostandardtestmethodbutwithsomeexperiencetherawmaterialspresentingthisproblemareeasilydetected.
3.2.6 FlowRate
Normally,thefertilisermustflowfreely. Ifthereisanycakingorsomereactionbetweenthecomponentsorwithmoisture,theflowabilityofthefertilisercanbereduced. Thiscanleadtoproblemsforallthehandlingoperations.
AstandardmethodforthemeasureoftheflowratehasbeendevelopedasEN13299[7]. About2kgoffertiliserisplacedinastandardfunnelwhichhasaclosedapertureof25mmdiameter. Thentheapertureisopenedandthetimefor2kgtoflowoutofthefunnelismeasured. Theapparatusiscalibratedwithdefinedglassspheres.
HANDBOOKOFSOLIDFERTILISERBLENDING-CodeofGoodPracticeforQuality 14
Table1:Commonblendingrawmaterials
Name Abbr Formula N P2O5 K2O SO3 MgO CaO
AmmoniumNitrate
AN NH4NO3 33-34,5
CalciumAmmoniumNitrate
CAN CaCO3/NH4NO3 26-28 11
AmmoniumSulphateNitrate
ASN (NH4)2SO4/NH4NO3 26 35
AmmoniumSulphate
AS (NH4)2SO4 21 60
Urea CO(NH2)2 46 Superphosphates:SingleSuperphosphateTripleSuperphosphate
SSPTSP
Ca(H2PO4)2*Ca(H2PO4)2*
18-2045-48
303
PotassiumChloride
MOP KCl 60-62
PotassiumSulphate
SOP K2SO4 50 45
Korn-Kali® KCl/MgSO4 40 12 6 PotassiumMagnesiumSulphate
K2SO4+MgSO4 30 42 10
AmmoniumPhosphates:Di-ammoniumPhosphateMono-ammoniumPhosphate
DAPMAP
(NH4)2HPO4
NH4H2PO4
1812
46-4852-53
CalciumCarbonate
CaCO3 52
CompactedDolomite
CaCO3-MgCO3 20 30
MagnesiumCarbonate
MgCO3 10 40
Kieserite MgSO4 50 25-28
HANDBOOKOFSOLIDFERTILISERBLENDING-CodeofGoodPracticeforQuality 15
3.3 STORAGE
Rawmaterialstoragemustbearrangedtoavoid:
1 segregationwithinthematerials
2 crosscontamination
3 deteriorationofthephysicalquality.
Storagemustbearrangedtoensureadequateidentificationoftherawmaterials.
Therecommendedtypeofstorageisthehorizontaloropenbinlayout. Ideallythebinshouldbefedfroma conveyorbelt systemwith thedischarge fittedwithananti-segregation systemsuchas aspinnerorflowsplitter(Figure5).
TheEuropeanFertiliserManufacturers'Association(EFMA)haspublisheddetailedguidanceonthesafestorageoffertilisers.[12]
3.3.1 MoisturePick-up
Somefertiliserrawmaterialsarehygroscopicwhichmeanstheycanpickupmoisturefromhumidair. Storesholdingthesematerialsshouldbeair-conditionedorthematerialshouldbecoveredwhennotbeingused. Figure2showsthecriticalrelativehumidityforanumberofcommonblendcomponentsandmixtures.Thelowerthecriticalrelativehumidity,themoremoisturewillbetakenfromtheair. Generallythephosphatesincludingtheammoniumphosphateshaveahighcriticalrelativehumidityand thus almost never present hygroscopic problems. The opposite applies to nitrates such ascalciumammoniumnitrate,ammoniumnitrate,andespeciallycalciumnitrate.
Forblendedandcomplexfertilisersthecriticalrelativehumidityinmostcasesisbelowtheaveragederivedfromitscomponents. ThiscanbeseenwhenlookingatthedataforPKandNPKfertilisers. Anextremeexampleforthisisdemonstratedbythecriticalrelativehumidityofablendconsistingofurea and ammoniumnitrate. Such ablendwouldpickupmoisture soquickly that itwouldbeimpossibletohandleitinadrystate,evenifspreadingoccursimmediatelyafterblending.
HANDBOOKOFSOLIDFERTILISERBLENDING-CodeofGoodPracticeforQuality 16
Figure 2:Critical relative humidity of fertiliser salts andmixtures [15]. Values are % relativehumidityat30°C.
3.3.2 Contamination
Crosscontaminationofrawmaterialsshouldbeavoidedasthiswillobviouslyaffecttheirchemicalanalysisandhencethefinalanalysisoftheblends.
Ammoniumnitrateandothermaterials containingammoniumnitratemustbekeptwell clearoforganicmaterials.
COMPONENT CRIT. REL. HUMIDITY
Triple Superphosphate
Mono-ammonium Phosphate
Di-ammonium Phosphate
Ammonium Sulphate
Potassium Chloride
Urea
Sodium Nitrate
Calcium Ammonium Nitrate
Ammonium Nitrate
Calcium Nitrate
BLENDS OR COMPOUNDS
PK Fertilizers
NPK Fertilizers
Urea - Ammonium Nitrate
Average data for 30 °C from Adams, Merz et al.,Runge et al., Silverberg, Löhner.
93,6 %
91,6 %
82,5 %
79,9 %
77,0 %
74,6 %
72,4 %
61,3 %
59,4 %
46,7 %
69,4 %
64,7 %
18,1 %
HANDBOOKOFSOLIDFERTILISERBLENDING-CodeofGoodPracticeforQuality 17
Goodhousekeepingisvitaltoanyblendingoperation.Allspillagesshouldbesweptupassoonaspossible andall equipment kept clean. Overhead conveyorsmustbe kept in good condition tominimise spillage into other storage areas. Theuse of special chutes to avoid excessive dust isstronglyrecommended.
FurtherinformationonthepreventionofcontaminationisgiveninReference12
3.4 SCREENING
Rawmaterialsshouldbescreenedbeforebeingfedtotheblendingunittoremoveanylumpsorfineswhichmayhaveformedduringstorage.Ifscreeningisperformedafterweighingandblending,someoftherawmaterialwillbelostandthiswillalterthecompositionofthefinalmix. Insuchcasestherecanbenocontrolonthefinalanalysisoftheblend. Inaddition,thescreeningprocessmayseriouslyun-mixthecomponents. Theuseofascalpingscreen(forexample10mmmesh)toremoveanylumpswhichmayhaveformedinthesystem,isacceptable.
3.5 SAMPLINGANDTESTING
Randomspotchecksoftherawmaterialsbeingfedtotheblenderarerecommended. Thesemaybesimplechecksoftheparticlesizedistributionbut ifthere isanydoubt,representativesamplesshouldbetakenandexaminedfully.
Forfurtherinformationaboutsamplingandphysicaltestmethods,refertoChapter8.
3.6 MICRONUTRIENTSANDCONDITIONINGAGENTS
3.6.1 Micronutrients
It is relatively simple to add micronutrients to blended fertilisers either as granular or powdermaterials, but the homogeneity of distribution is particularly important. As a guide, granularmaterialsshouldnotbeusedifthemicronutrientcarrierrepresentslessthan5%ofthetotalweight. Inthesecasesitispreferabletoaddthemicronutrientinpowderformwithabindingagenttoensuregoodadherencetothegranules.Suitablebindingagentsincludeheavyviscosityoils,UANsolutionsandwater. Alternatively,themicronutrientsmaybeaddedasasolutionwhichissprayeddirectlyontotheblendinthemixer. Notehowever,thatoilshouldnotbeusedwhenammoniumnitrateformspartoftheformulation.
Somenationalregulationsdonotallowtheuseofoil:pleasecheckthispointcarefully.
3.6.2 ConditioningAgents
Anti-cakingagentsarenotnormallyrequired if theproduct is tobeused immediately. Productswhicharetobestoredorbaggedmayrequiretheadditionofasmallamountofanti-cakingagent. Itisrecommendedthatadust-suppressantisaddedtotheblend.
Conditioningagentsmaybeappliedinthesameoperationasthemicronutrients.
HANDBOOKOFSOLIDFERTILISERBLENDING-CodeofGoodPracticeforQuality 18
4. BLENDINGEQUIPMENT
Allblendingplantsshouldincludethefollowingequipment:
1 Weighingorotherproportioningdevice(s)
2 Drymixer
3 Loadingorbaggingequipment
Inaddition,somecontrolequipmentisdesirablebutnotessentialiftheotherequipmentisreliable.4.1 SELECTION
Thishandbookdoesnotsetouttorecommendequipmentoveranyotherbuttherearevarioustypesandtheircharacteristicsandadvantagesaredifferent. Thecapacityoftheequipmentshouldbechosentomatchoutputrequirementsintermsoftonnesperhourandtonnageperweek.
4.1.1 Weighing
Inbatchoperations,thewholeequipmentmaybemountedonaloadcellorbeltweighersmaybeused. Forcontinuousblending,individualbeltweighersmaybefittedtothebeltsfeedingtherawmaterialstothemixer. Thesizeandtypeofsuchequipmentshouldbechosentomatchtheplantsizeandoutputsrequired.
4.1.1.1UnitBatchWeighing
Thesearethemostpopularsystems.Theoutputsrangefrom20to100tonnesperhour. Smallersystemshaveafloormountedhopperwithload-celldigitalreadout,fedfromafrontendloader. Therawmaterialsareweighedintheproportionsdeterminedbytheformulation. Batchesarethenconveyedtothemixingunit.
Largerunitsarenormallyfedfromoverheadholdinghoppers.
4.1.1.2ContinuousWeighing
Thesesystemsprovideacontinuousfeedtothemixerbybeltconveyorsandmaybecontinuousbeltweighersorconstantratefeeders.Intheformertherawmaterialsarefedontofixedspeedextractorweighbeltsfittedwithload-cells.Variationsinweightaretransmittedtothecontrolunitwhichadjuststhehoppergateopening.Constantratefeedershaveafixedhoppergateopeningandthebeltspeediscontinuouslyadjustedtothepredeterminedrateofoutput. Aloadcellcontinuouslymonitorstheamountofmaterialontheextractorconveyorandsendssignalstothemotorspeedcontrolunit.
Inbothsystems,informationfromtheindividualweightorspeedcontrollersisfedtoacentralcontrolunitwhichcanbepre-setfortherequiredoutput.
HANDBOOKOFSOLIDFERTILISERBLENDING-CodeofGoodPracticeforQuality 19
4.1.2 VolumetricFeeding
Forsomeblendingoperationsitissufficienttousevolumetricmeasuringoftherawmaterialstoobtainthecorrectproportionsintheblend. Aseparatehopper,usuallyfedbyfrontendloader,mustbeprovidedforeachrawmaterial. Allthecomponentsarehandledsimultaneouslyandtheunitsarecontrolledtogivetherequiredblendratio.
Thissystemhowever,reliesonconsistentrawmaterialdensitiesandmanyuncontrollablevariablesmaycausechangesinthebulkdensity. Oneofthesefactorswillbetheparticlesizesofthegranulesandthesemayvarythroughoutastorageheap.
4.1.3 Mixers
Theblendingequipmentisamajordeterminingfactorintheproductionofgoodqualityblends.
Differentdesignsofmixersareavailablesuchasrotatingdrums,coneendedtiltingmixers,stationarymixerswithinternalpaddles,verticalmixersandvolumetricmixerswithvariablespeedscrews. Inaddition,blendingmaybecarriedoutwithouttheuseofaspecificmixer. Inthissystemallrawmaterialsarefedontoacollectorbeltconveyorand,aseachmaterialisconstantlyfedatthecorrectweight,allmaterialsareconstantlylayeredontothebeltinthecorrectformulationratio. Thusacrosssectionofthatbeltwillatanytimehavethecorrectnutrientcontent. Subsequentmixingatbeltchangeoversastheblendmovesthroughtheremainderoftheplantensuresacorrectmixatalltimes.
The choice of design will depend on individual circumstances and is outside the scope of thishandbook. However,oneaspectofmixingwhichisofimportanceisthemixingtime.Mixingtimesarenormallyaroundtwominutesandtimesabove5minutesarenotrecommendedbecauseoftheriskofparticlebreakdownanddeteriorationofthemixingquality.
Afterinstallation,themixermustbetestedtodeterminethatsatisfactorymixingisachieved. Itisrecommendedthatacoefficientofvariationoflessthan10%isachieved. Descriptionsofmixingtestscanbefoundinreferences[1]and[11].
4.1.4 LoadingEquipment
Atallstagesafterthemixing,greatcaremustbetakentoavoidsegregationoftheblendcomponents. Thismeansthatconingmustbeavoidedatallstages.
Thefinalsectionoftheblendingplantmayincludereceivinghoppersforbulkloadingorbaggingbutinthesimplestcasetheblendedmaterialmaybeloadeddirectlyontotrucksfromaconveyorsystem.
Further information on equipmentmay be obtained frommanufacturers or by reference to theliterature[16],[18],[19],[27]and[29].
HANDBOOKOFSOLIDFERTILISERBLENDING-CodeofGoodPracticeforQuality 20
4.2 TESTING/CALIBRATION
Asaminimumcontrol,recordsmustbekeptofall formulations,batchrecords,weightorvolumesettingsandrawmaterialanalysesandsources. Inadditionthefollowingaretoberecommended:
1 Regularchecksofweighingorvolumetricmeasuringequipment(minimumfrequency,oncepermonth)
2 Frequentcheckweighingforbaggedmaterial
3 Randomchecksofthechemicalanalysisoffinishedproducts(minimumfrequency,onceaweek)
FurtherinformationisgiveninChapters7and8
4.3 OPERATIONS
Fullwrittenoperatinginstructionsmustbeavailableforallpersonnel. Operatingproceduresshouldbewelldocumentedandreviewedatregularintervals. AccreditationtoISO9000isnotessentialbutisrecommendedasitoffersanindependentassessmentofallprocedures.
HANDBOOKOFSOLIDFERTILISERBLENDING-CodeofGoodPracticeforQuality 21
5. SEGREGATION
Segregation is the separation of particles due to differences in physical characteristics. Forsegregationtotakeplacetheremustbemovementbetweentheparticles.
Variouscharacteristicsmaycausesegregationbutthemostcommonareparticlesize,particledensityandparticleshape. Thesize iscertainlyby far themost important factortoexplainsegregationduringflow. Duringspreading,thethreepropertiesplayarole,theshapebeingtheleastimportantandthesizeagainhavingadominatingeffect.
From the above it is seen that segregation may occur during manufacture, bulk transport (andhandling)orduringapplicationtothesoilorcrops. Theeffectsasseenbythecropsmaybethesameinallcasesunlessremixingtakesplaceduringlaterhandlingstages.
ThefollowingextractfromStairmand[26]dealswiththeproblemsofstorageinhoppersandthisisrelevanttobulkhandling,baggingoperationsandspreading.
“Thetwomainfactorsareavoidanceofsegregationinfillingandemptyingandensuringthehopperwillbe“self-clearing.” Inexaminingthequestionofsegregationinfilling…ifthematerialischargedintothehopperfromasinglepoint,thecoarserparticleswillmigratetotheouteredgesandacentralcoreofmaterialcontaininganexcessoffineswillform. Ifnowfillingisdiscontinuedandthehopperisallowedtodischargeitwilldosoinzones…Ifthezonescontainparticlesofdifferentsizesduetosegregation in filling,nodevice fittedat theconedischargetoremixcanpossiblybeeffective. Ifhowever,thehopperisfilledwithoutsegregation,littlesegregationwilloccurwhenemptying.”
By applying the above to blending, it can be seen that the avoidance of segregation and thesubsequenthandlingoftheproduct,isthemostimportantpartofanyblendingprocess. Thismaybeachievedinthreeways:
1 Thecarefulmatchingoftheblendcomponents
2 Thedesignofhoppers(seeLeonard[19])
3 Theloadingmethodsofthehoppersandvehicles,etc.
The origin of the segregation is always a difference of physical properties leading to a physicalseparationoftheparticleswhichmayormaynotresultinachemicalsegregation. Sizesegregationmayalsooccurwithinrawmaterialsorcomplexfertilisersbutthiswillhaveno(orverylittle)effectonthe chemical content. However, in bulk blends, physical segregation often leads to chemicaldifferences.
5.1 FLOWSEGREGATION
Care must be taken when storing any material to avoid size segregation in the storage heaps. Whenevergranularmaterialfallsfreelytoformaconeorpartcone,thelargerparticleswilltendtorundowntheoutsidewiththesmallerparticlesremainingnearthecentreofthecone. Shouldthishappen,theremaybequitelargevariationsinsizecharacteristicsbetweenvariouspartsofaheapandthiscouldhaveseriouseffectsonallfertilisers(Figure3). Batchestakenfromasegregatedheapcan
HANDBOOKOFSOLIDFERTILISERBLENDING-CodeofGoodPracticeforQuality 22
thusdiffer inparticlesizes,and thiswillaffect thespreadingwidthofacentrifugal spreaderwithstraight,blendedandcomplexfertilisers.
Figure3. Illustrationofflowsegregationwhenconingoccursduringloading[15]
Theremaybesomeremixingatlaterhandlingstages. Suchremixingmaybecausedsimplybytippingabagoffertiliseroutintoahopperorevenmoresimplybyturningalooselyfilledbagover. Remixingmay also occur during loading and unloading of bulk fertiliser (Figure 4). However, systematicremixingcanrarelybecountedon.
Figure4. Remixingofsegregatedfertiliserwhenunloadingbins[15]
vertical storage, full cone(vert. cross - section)
horizontal storage, half cone(vertical cross - section)
coarse granulesdominating
loading
loading
fine granulesdominating
Unloading bins in vertical direction
Unloading large horizontal bins by payloader
Mass - flow
Remixingoccurs aftersegregation
Mass - flow forced by stirringin bins of a spreader.Remixing occurs.
Core - flow
Unloadingstarts inthe center.Thus finesare unloadedfirst. stirring
device
Some remixing occurs, but when unloading starts,coarse particles dominate. And when the left part of the bin in taken, fines prevail.
spreader - bins
HANDBOOKOFSOLIDFERTILISERBLENDING-CodeofGoodPracticeforQuality 23
Itisessentialthatallhandlingequipmentisconstructedtominimisesegregation.Theuseofspeciallydesignedchutesisrecommendedtoavoidsegregationandexcessiveamountsoffreedust.
Examplesoftechniqueswhichmaybeusedtoavoidsegregationinclude(Figure5):
“Eggcrate”bafflesinsquareorrectangularhoppers,
Concentricconedistributorsforcylindricalhoppers,
Flexiblespoutsfordirectloadingequipment.
Figure5–Preventionofsegregationinhoppers[18]
Inthecaseofrawmaterials,thesegregationismainlyasizesegregationwhichhaslittleeffectonthechemicalcontent. Forblends,theriskistohavebothsizeandchemicalsegregation.
Testsoffillingandemptyingcontainershaveshownthatgranulometricsegregationiswelllinkedwiththegranulometricspreadindex(Figure6). Itisrecommendedthatthegranulometricspreadindex
S ubd iv id ing the hopperload ing
vertica l c ross-section horiz . cross-section
in te rna l egg - c ra te ba fflesprevent the fo rm ationo f a la rge cone
S ubd iv id ing the feed ing - linevertica l c ross-section horiz . cross-section
d is tribu to r cons is tingo f severa l concen tric conespreven ts fo rm ationo f a la rge fe rtilize r - cone
V ary ing the load ing - po in t
m oving conveyor spou t
load ing
HANDBOOKOFSOLIDFERTILISERBLENDING-CodeofGoodPracticeforQuality 24
oftheblendislimitedtobelow20. ThismeansthattherawmaterialsmusthaveanevenlowerGSI(seeTable2page30)
Thefiguresbelowdistinguishthreerangesofsegregation:Lowsegregationmeansthatforthegivendifferenceofpropertythefinalsegregationhaslittleimpact–Mediumisthesituationwherethefinalsegregationbeginstobesignificantbutifthereisanotherunfavourablecondition,forexamplelowoverlappingduringspreading,thefinalresultmaybebad–Highistheworstsituationwheretherearenegativeeconomicand/orenvironmentalconsequences.
Figure6:Relationbetween size segregationandGSIofbulkblendswhenemptyinga container(segregationisthedifferenceofd50betweenthefirstandthelastthirdofemptyingacontainer)[20]
Chemicalsegregationisrelatedtotheabsolutesumofthedifferenceofd16andd84ofeachcomponent(Figure7). Thismeansthatifthefineparticlescomefromonerawmaterialandthecoarseparticlesfromanother,thesizesegregationinducesachemicalsegregation.
0
5
10
15
20
25
30
35
40
45
10 20 30 40 50
Granulometric Spread Index of the blend (GSI)
Diff
eren
ce o
f the
d50
of t
he b
lend
(%)
Med
.Size
segr
egat
ion
Low
Hig
h
HANDBOOKOFSOLIDFERTILISERBLENDING-CodeofGoodPracticeforQuality 25
Figure7:Chemicalsegregationinrelationwiththeabsolutesumofthedifferencesofd16andd84ofthecomponents.[20]
5.2 TRANSPORTSEGREGATION
Itisoftensaidthatblendsaresubjectedtoserioussegregationduringvehicletransportbutthisisnottrue. Thelevelofvibrationintransportvehiclesisnothighenoughtoinduceamovementofthefertiliser. In fact, the segregationoccurswhen filling (andemptying) the container asdescribedabove.
Duringtransport,onlypercolationofverysmallgrainsbetweenthe largeronescanoccur. Withcommonfertilisers,thisphenomenonappearsifthereareparticlessmallerthan0,5mm. Abovethissize,theprocessistooslowtohavearealimpactonthefinalproduct.
5.3 SPREADINGSEGREGATION
Blenders should have some knowledge of the kinds of spreading equipment available and theadvantagesanddisadvantagesofthesewhenusingblendedfertilisers. Blendersshouldbepreparedand able to advise farmers on the type of equipment to use and the setting up, calibration andmaintenancenecessary. Thismeansthattheyshouldbepreparedtogiveasmuchinformationaspossibleaboutthephysicalqualityoftheirproducts.Suchinformationmayincludethecomposition,bulkdensityandflowcharacteristicsaswellastheparticlesizedistribution. Thisisanotherreasonforkeepingadequaterecordsofrawmaterialsandproductbatches.
Centrifugal, pneumatic, and auger spreaders are available. The segregation inducedbyphysicaldifferencesofthefertiliserparticlesmaybeduetotrickling,asisthecasewithaugerspreaders,ormaybecausedbytheaerodynamicresistanceoftheparticleswhenthrownthroughtheair,aswithcentrifugalandpneumaticspreaders.
0 10 20 30 40 50 60 70 80
Difference between raw materials (absolute sum of difference d16 and d84/d50mel)
Segr
egat
ion
Low
Med
.H
igh
HANDBOOKOFSOLIDFERTILISERBLENDING-CodeofGoodPracticeforQuality 26
However,anysegregationduringspreadingmaybecompletelycompensatedforbytheoverlappingofadjacentspreadingswaths. Thisleadstothequestion,howmuchoverlapping?
Asageneralguide,pneumaticspreaderswillnotinducesegregationbecauseofthelargeamountofoverlapping(fromthespouts). Theeffectsofsegregationfromcentrifugalspreaderswillbereducedbyoverlapping.
Auger spreaders will segregate heavily. Since these spreaders, when correctly adjusted have arectangularlateralmassdistribution,nooverlappingoccursandthusalsonoreductionofsegregationtakesplace. Forthisreason,augerspreadersarenotrecommendedforblendedfertilisers. Furtherinformationmaybefoundinreference[2].
InWestern Europe, themost common devices are centrifugal spreaders with two discs. Theirworkingwidths(widthbetweentractortracks)varybetween12andmorethan36m. Thespreadingwidthcanreachmorethan50m.
HANDBOOKOFSOLIDFERTILISERBLENDING-CodeofGoodPracticeforQuality 27
Segregationoccursduring spreadingdue tophysical differencesbetween the componentsof theblended fertiliser. The larger,heavierandmore spherical theparticlesare, the further theyarespread. Thesizeanddensityarethemajorfactors(Figure8,Figure9andFigure10).
Thechartsshowthesegregationasafunctionofthedifferenceofagivenphysicalproperty(size,densityorshape). Theconsideredblendshavetwocomponentsinaproportionof50%andthesearephysicallysimilarexceptfortheanalysedproperty.
Figure8:Evolutionofthesegregationwiththedifferenceofd50betweenthetwocomponents[20]
Figure9:Evolutionofthesegregationwiththedifferenceofdensitybetweenthetwocomponents.[20]
0% 10% 20% 30% 40%
d50 difference between raw materials (%)
Segr
egat
ion
Low
Med
ium
Hig
h
0% 10% 20% 30% 40% 50% 60% 70%
Loose density difference between raw materials (%)
Segr
egat
ion
Low
Med
ium
Hig
h
HANDBOOKOFSOLIDFERTILISERBLENDING-CodeofGoodPracticeforQuality 28
Figure10:Evolutionofthesegregationwiththedifferenceofshapebetweenthetwocomponents.[20]
In practice, the components present differences for more than one physical property and eachdifferencecanaccentuateorreducethefinalsegregation. Forexample,sizedifferencebetweencomponentscancompensateforadensitydifferenceandviceversa. Thelarger,heavierandmoresphericaltheparticlesare,thefurthertheyarespread. Forexample,ureawhichhasalowdensityincomparisonwithother fertilisersshould ideallyhave largesizedparticleswithad50near themaximumtoleranceinordertolimitspreadingsegregation.
The final impact of segregation during spreading can be significantly reduced by appropriateoverlappingbetweenthepasses. Indeed,thesegregationisgenerallymarkedinsuchawaythatonecomponenttendstoaccumulatebehindthespreaderandanothertendstobespreadfurther. Iftheoverlappingbetweenthepassesissufficient,ateachplaceinthefieldthefinalquantityoffertilisercomesfromtwopasses(Figure11,topandcentre). Withagoodspreadercorrectlyadjusted,itisevenpossible forworkingwidthsup to24or28m. However, forbadlyadjusted spreaders thesegregation remains. Practically,acorrectoverlappingmeans that thespreadingwidthmustbeaboutdoubletheworkingwidth. Sowithaworkingwidthof24m,itmeansthatthespreadingwidthmustapproach48m. Figure11,below,showsanexampleofinsufficientoverlapping,resultingfromaworkingwidthwhichismuchgreaterthanhalfthespreadingwidth.
0% 20% 40% 60% 80% 100%
Elongation (shape) difference between raw materials (%)
Segr
egat
ion
Low
Med
ium
Hig
h
HANDBOOKOFSOLIDFERTILISERBLENDING-CodeofGoodPracticeforQuality 29
Figure11:Illustrationoftheoverlappingforthesamebulkblendbutforworkingwidthsof20,28and36m.[21]
0%
20%
40%
60%
80%
100%
120%
140%
-28 -26 -24 -22 -20 -18 -16 -14 -12 -10 -8 -6 -4 -2 0 2 4 6 8 10 12 14 16 18 20 22 24 26 28
Distance from the axis passage (m)
Spre
ad q
uant
ity (%
)
Dose (% ) Central passage Left passage Right passage
Left Right
Overlapping
Working width = 20 m
0%
20%
40%
60%
80%
100%
120%
140%
-28 -26 -24 -22 -20 -18 -16 -14 -12 -10 -8 -6 -4 -2 0 2 4 6 8 10 12 14 16 18 20 22 24 26 28
Distance from the axis passage (m)
Spre
ad q
uant
ity (%
)
Dose (% ) Central passage Left passage Right passage
Working width = 28 m
Overlapping Overlapping
Left Right
0%
20%
40%
60%
80%
100%
120%
140%
-28 -26 -24 -22 -20 -18 -16 -14 -12 -10 -8 -6 -4 -2 0 2 4 6 8 10 12 14 16 18 20 22 24 26 28
Distance from the axis passage (m)
Spre
ad q
uant
ity (%
)
Dose (% ) Central passage Left passage Right passage
O verlapping
Left Right
O verlapping
Working width = 36 m
HANDBOOKOFSOLIDFERTILISERBLENDING-CodeofGoodPracticeforQuality 30
Anotherimportantpointtomentionisthatwithhigherworkingwidths,itbecomesdifficulttofindthecorrectadjustment. Thisisnotonlythecasewithblendsbutalsowithstraightorcomplexfertilisers. Theuseofacontrolkitiscertainlyrecommendedforthefarmer(Figure12below).
Figure12:Illustrationofakittomeasurespreadingquality
Goodadviceforfarmersistolimittheworkingwidthinordertoobtainanimportantoverlapping. Inpracticethismeanschoosingaworkingwidth lowerthan24or28mwithahighperformancespreader.
5.4 EFBAQUALITYRECOMMENDATIONS
Toreducesegregationproblems,itisrecommendedtoblendrawmaterialshavingsimilarphysicalproperties, themost importantbeing thesizeof theparticles. TheEuropeanFertilizerBlendersAssociation (EFBA) has defined quality recommendations for the particle sizes (Table 2). Therecommendationsconcentrateonad50around3,25mmwithalimitedgranulometricspreadindex(GSI). Iftherawmaterialscomplywiththeserecommendations,flowsegregationisnotsignificantandspreading segregationonlyoccurs if thereare importantdensityand/or shapedifferences. Thishappensonlywhencertainspecificfertilisersareused.
Table2-Targetsandtolerancesforthegranulationofblendcomponents.
EFBATargetsandTolerancesforthegranulationofrawmaterialsforfertiliserblending
Verbalnotation Physicaldimension MeanParticleSize d50inmm 3,25
mm ±0,25mm
FineParticles <1mm,%ofmass 0% 0,25%CoarseParticles >5mm,%ofmass 0% 1%MainRange 2,5–4,0mm,%ofmass 90% ±5%GranulometricSpreadIndex(GSI)
100 d 2
50
1684 ddGSI -=
<18
ItisassumedthatthesieveanalysisiscarriedoutaccordingtoEuropeanStandardEN1235/A1.EFBArecommendstheuseofthesesevensieves:1,00mm–2,50mm–2,80mm–3,15mm–3,55mm–4,00mm–5,00mm(thejustificationforthesesievesislinkedtotherecommendations)
HANDBOOKOFSOLIDFERTILISERBLENDING-CodeofGoodPracticeforQuality 31
6. SAFETYCLASSIFICATION–LABELLING-DISTRIBUTION
Blendersmustbeawareofthehazardsassociatedwithrawmaterialsandfertilisers,especiallythosecontaining ammonium nitrate. Recognition of the hazards is made simpler by classificationsystemssuchas thosepreparedby theUnitedNations (UN), InternationalMaritimeOrganisation(IMO)andtheEuropeanCommission(EC). AllproductsmustbelabelledaccordingtoNationalandEuropeanRegulationsandinsomecircumstancesonlypackagedfertilisersmaybesuppliedtotheenduser.
FullaccountshouldbetakenofallindustryguidanceandCodesofPracticesuchasthosepreparedbyFertilizersEurope[12,13]
6.1–Labellingandmarketingoffertilisers AnyfertilisersplacedontheEuropeanornationalmarketmustbecorrectlylabelledinaccordancewitheithernationalorECregulations,dependantonthemarketinwhichitistobesold.Theseregulationsnormallycovermatterssuchasnutrientcontent,safetyandprotectionoftheenvironment.Mineralfertilisers,offeredforsaleontheEuropeanmarket,needtocomplywithEuropeanCouncilRegulation2003/2003/EC[25]. Forpackedblendedfertilisers,thelabellinginformationmustbeplacedonthepackaginginaconspicuousposition.Labelsmustbeattachedtothepackageortowhateversystemisusedforclosingit.Markingsmustbe,andmustremain,indelibleandclearlylegible(2003/2003/EC,Art.10).Forbulkblendedfertilisers,thesemarkingsmayappearontheaccompanyingdocuments(2003/2003/EC,Art.7).MarkingsmustappearinatleastthenationallanguageorlanguagesoftheMemberStateinwhichtheECfertiliserismarketed.
HANDBOOKOFSOLIDFERTILISERBLENDING-CodeofGoodPracticeforQuality 32
Figure13:ExampleofEClabelforasolidmineralfertiliseraccordingtoEC2003/2003. 6.2–Labellingandclassificationofhazardoussubstancesandmixtures(CLPregulation):hazardlabellingEuropeanRegulation1272/2008/ECconcernstheclassification,labellingandpackagingofsubstancesandmixtures[23].Itisknownbyitsabbreviatedform,‘theCLPRegulation’orjustplain‘CLP’.
TheCLPRegulationadoptstheUnitedNations’GloballyHarmonisedSystemontheclassificationandlabellingofchemicals(GHS)acrossallEuropeanUnioncountries.
Beforemanufacturing,eachblendedfertilisercontaininghazardoussubstancefromrawmaterialmustbeclassifiedaccordingtotheCLPregulations.
Theclassificationoftheblendedfertilisersdependsontheconcentrationofhazardoussubstancesinthefinalproduct.Allclassifiedfertilisersrequirehazardlabelling.
Name or trade name and address of the manufacturer
TRADE NAME OF THE FERTILIZER
EC FERTILISER
NPK fertiliser blend (Ca0) (S03) 7 - 14 - 25 (2) (14)
7 % of total nitrogen (N) 7% of ammoniacal nitrogen (N)
14 % of Phosphorous pentoxide (P2O
5) soluble in neutral
ammonium citrate and in water 13,1 % of water-soluble phosphorous pentoxide (P
2O
5)
25 % of water-soluble potassium oxide (K2O)
2% of water-soluble calcium oxide (CaO) 14 % of total sulphur trioxide (SO
3)
11,5% water-soluble sulphur trioxide (SO3)
xx kg net
Company name and address
Type denomination followed by « blend »
Indication of main nutrients (N, P and K) complying to 2003/2003/EC regulation
Optional identification of secondary nutrients
Net or gross mass + tare mass
HANDBOOKOFSOLIDFERTILISERBLENDING-CodeofGoodPracticeforQuality 33
Figure14:ExampleofhazardlabellingaccordingtoCLPregulationforafertilisercontainingover3%oftriplesuperphosphate.
Thesizeofthelabelisalsodefinedaccordingtopackagingvolume:Packagingvolume Labelsize(mmm) Pictogramsize(mm)>500liters(BigBag) Mini148x210 Mini46x46>50litersand≤500liters Mini105x148 Mini32x32>3litersand≤50liters Mini74x105 Mini23x23≤3liters Mini52x74ifpossible Mini10x10(16x16ifpossible)
Thelabelofafertiliserwhichdoesnotmeetthecriteriaforclassificationashazardousbutcontainsahazardoussubstanceinaconcentrationlevelwithsafetydatasheetavailableondemandshallbearthestatement:EUH210—‘Safetydatasheetavailableonrequest’.
Forammoniumnitrate,theOxidizingpictogramfromCLPcanbereplacedbytheADRpictogram(5.1class)onthelabelbutH272hazardstatementshallremain.
TRADE NAME OF THE FERTILIZER
NPK fertiliser blend (Ca0) (S03) 7 - 14 - 25 (2) (14)
Contains triple superphosphate triple (n°EINECS : 266-030-3, n° CAS : 65966-95-4)
DANGER H318 : Causes serious eye damage
P280 : Wear protective gloves/protective clothing/eye protection/face protection.
P305+P351+P338 : IF IN EYES: Rinse cautiously with water for several minutes. Remove contact lenses if present, and easy to do. Continue rinsing.
P310: Immediately call a POISON CENTRE or doctor/physician.
xx kg net Company name, address, phone number
Name, address, phone number of supplier(s)
signal word, hazard and precautionary statements
Nominal quantity of fertiliser in packaging
(except if mentioned elsewhere on the packaging)
Product identifiers
Hazard pictogram (in colour, covering at least 1/15th of the label, minimum size 1 cm²)
Type denomination name Name and identification number of hazardous substances contributing to classification (4 max except if > 4 hazard classes, then à 1 for each hazard)
Trade name
HANDBOOKOFSOLIDFERTILISERBLENDING-CodeofGoodPracticeforQuality 34
6.3 –Regulationrelatedtohazardoussubstancesandmixtures(REACHregulation):Safetydatasheet(SDS)
REACHRegulation1907/2006/EConRegistration,Evaluation,Authorisation&RestrictionsofChemicals)definesSafetyDataSheetasthemaininformationvectoronproducthazardsandgoodpractices(Art.31)[24].
ASafetyDataSheet(SDS)ismandatoryandistobepro-activelyprovidedtotheclientifthefinalproductisclassifiedashazardousinaccordancewithCLPRegulation.
ASDSistobeprovidedtotherecipientathisrequestwhenthefertiliserdoesnotmeetthecriteriaforclassificationashazardousinaccordancewithCLP,butcontains:
• 1%ormoreofasubstanceclassifiedashazardous • 0.1%ormoreofasubstanceclassifiedaspersistent,bioaccumulativeandtoxicorvery
persistentandverybioaccumulativewhichisonthelistofsubstancessubmittedtoauthorisation(REACH)
• asubstanceforwhichthereareCommunityworkplaceexposurelimits.
AnySDSshallbeprovidedfreeofcharge.
Forfertilisersclassifiedashazardous,theSDSshalltobeprovidedonpaperorelectronicallynolaterthanthedateonwhichthefertiliserisfirstsupplied(REACHArt.31-8).Thereisnoneedtoprovideitateachdelivery.
UpdatesofSDSshallbeprovidedtoallformerrecipientstowhomfertiliserhasbeensuppliedwithinthepreceding12months(REACHArt.31-9)
SDSshallbeprovidedinthelanguageofthecountrywheretheproductissold.
SDSshallfollowtheproductfromitsmanufacturetoit’senduse:
Distributionàforwardingofsupplier’sSDStotheclient.
PackagingàTransmissionofaSDSinthenamethecompanyresponsibleforplacingthefertiliseronthemarket.
BlendingàTransmssionofaSDSspecifictotheblendedfertiliserinthenamethecompanyresponsibleforplacingthefertiliseronthemarket.
Thesafetydatasheetshallbedatedandshallcontainthefollowingheadings:
1.identificationofthesubstance/mixtureandofthecompany/undertaking; 2.hazardsidentification; 3.composition/informationoningredients; 4.first-aidmeasures; 5.fire-fightingmeasures;
HANDBOOKOFSOLIDFERTILISERBLENDING-CodeofGoodPracticeforQuality 35
6.accidentalreleasemeasures; 7.handlingandstorage; 8.exposurecontrols/personalprotection; 9.physicalandchemicalproperties; 10.stabilityandreactivity; 11.toxicologicalinformation; 12.ecologicalinformation; 13.disposalconsiderations; 14.transportinformation; 15.regulatoryinformation; 16.otherinformation.AsetofStandardisedSafetyDatasheetsforthemostcommonfertilisersareavailableonrequest.
Keystepsaccordingtohazardoussubstancesregulation:
ðCheckifpresenceofhazardoussubstancesinrawmaterials:superphosphates,ammoniumnitrate…ðClassifythenewfertiliserinaccordancetohazardoussubstancesregulation(CLP)ðLabelthenewfertiliserinaccordancewithhazardoussubstancesregulation(CLP)whenneededðCreatetheSafetyDataSheetinaccordancewithREACHifneeded
HANDBOOKOFSOLIDFERTILISERBLENDING-CodeofGoodPracticeforQuality 36
7. QUALITYCONTROL
Blendersshoulddrawuparoutinequalitycontrolscheduletoincludethesamplingandanalysisofrawmaterialsandproductsaswellaschecksonrawmaterialweighersand/orfeedersandcheckweighingoffinishedbaggedproducts.
7.1 RAWMATERIALS
Theamountofqualitycontrolofrawmaterialsdependsonthereliabilityofthesuppliers. Ifsuppliesarereceivedfromsinglesources,experiencewillsoonestablishthedegreeofcontrolneeded. Ifrawmaterialsarepurchasedfromavarietyofsources,extracontrolisessential.
RandomsamplesfromeachconsignmentshouldbetakenasdescribedinChapter8,forreferencepurposes. Thesesamplescanbesentforanalysiswheneverthereisreasonfordoubtbuttheyshouldbecarefullylabelledwithdateandoriginandkeptforatleastthreemonths.
Asmentioned in section 3.2, theparticle size distribution of the rawmaterials is themostimportantpropertytobecontrolled. RepresentativesamplesofrawmaterialfeedsshouldbetakenandtestedasdetailedinChapter8atregularintervalswithaminimumfrequencyofoncepershift.Afullsieveanalysisshouldbecarriedoutoneachrawmaterial.
7.2 FINISHEDPRODUCTS
AllblendershaveanobligationtomeettherequirementsoftheirNationalFertiliserRegulationsandforthosefertiliserswhicharemarketedasECfertilisers,commonRegulationEC2003/2003[25]applies throughout theCommunity. NationalRegulationswill coverproductswhicharenot declared as EC fertilisers. It should be noted that in caseswhere the farmer does notpurchasea fertiliserwitha specifiednutrient ratio, forexample, ifhepurchaseshisownrawmaterialsandcontracts theblender tomix them forhim,allofficial controls for theblendedfertilisermaynotapply.
The regulations set out the tolerances on the declared chemical analysis for all fertilisers. Fertilisersnotmeetingthesetolerancesmayresultinprosecutionandpenalty. Itisthereforerecommendedthatsomedegreeofqualitycontrolisexercisedbyblenders(auto-control).
The amount of quality control requiredwill depend verymuch on the scale of the blendingoperation. Forsimplesmallscalebatchblendingoperationsitmaybesufficienttorelyontheprinciplethat“whatgoesinmustcomeout”. However,eventheseoperationswillneedsomeregularcontroloftheweighingequipment.
Forlargescalecontinuousoperations,considerationshouldbegiventofullautomatedon-linesamplingandanalysis.
Inbetweenthesetwoextremes,itisrecommendedthatonerepresentativerandomsampleistakenfromoneofthegradesmadeeachday. Iflaboratoryfacilitiesareavailableonsite,thesesamples should be analysed daily. If outside contract laboratory services are used, thefrequencyofanalysis shouldbeat leastone sampleperweek, selectedat random from theweek’scollection.
Recordsshouldbekeptofallsamplestakenandanalysescarriedout.
HANDBOOKOFSOLIDFERTILISERBLENDING-CodeofGoodPracticeforQuality 37
8. SAMPLINGANDANALYSIS
8.1 SAMPLING
Representative sampling of any material requires special techniques and equipment. Fulldetails are outside the scope of this handbook but it is recommended that blenders followrecognisedsamplingmethodssuchasthosesetoutinEuropeanStandardEN1482Part1[9].
Itisessentialthatallsamplesarecorrectlytakentoensuretheirrepresentativity. Thereisnopoint in taking and analysing unrepresentative samples. The quality of the measurementsmade on the samples depends on their representativity. This is particularly important forblendedfertiliserswheretheriskofheterogeneityishigher.
AsstipulatedbyCEN,blendedsamplesmustalwaysbetakenfrommaterialinmotion,eitherinfreefalloronconveyorsystems.Itisessentialtosamplethroughthewholestreamratherthanfrom the same part of the stream. Suitable automated equipment is available for mostcircumstancesandistoberecommendedwheneverpossible.
Fortheblendproduceritisimportanttoknowthesamplingandmeasurementmethodsandthenecessary equipment. Generally, all of this is described in standards which are regularlyupdated.Blendersarerecommendedtostudythelatestversionsofsamplingandmeasurementstandards.
Whenasampleofanygranularmattermustbetaken,somequestionsshouldbeasked:
1 WhatquantitymustItake?
2 Howmanyincrementstoobtainthisquantity?
3 Howtotakethesamples?
Finallythesamplemustbereducedinordertoobtainafinalsampleforanalysis(usuallyabout250gforsievingtestand500gforachemicalanalysis). Thusafterthesamplingthereisalsoareductionstep. FulldetailsofreductionmethodsaregiveninEN1482Part2.
HANDBOOKOFSOLIDFERTILISERBLENDING-CodeofGoodPracticeforQuality 38
8.1.1 SamplingQuantity
The minimum quantity of sample recommended is given in EN 1482 Part 1. Therecommendationsaresummarisedasfollows:
Table4:Recommendedquantitytosampleforbaggedproducts
NumberofbagsMinimalnumberofincrements<5bagsAsamplefromeachbag4<numberofbags<114bags10<numberofbags<401Wholenumberabove thesquare rootof the
numberofbags>400bags20bags
If theweightofabag is less than5kg,a completebag is consideredasa sub-sample. Thenumberofselectedbagscanbehigherifthefinalquantityofthesampleisnotsufficient. Forbagsof50kg,thecontentmustideallybedividedinordertoobtainarepresentativesample(seeparagraph8.1.3). SamplingthecontentsofanIBC(bigbag)isnoteasy. Thebestsolutionistosampleduringemptying,butthisisnotalwayspossible. FurtherinformationisgiveninEN1482Part1.
Table5:Numberofsamplingunitsfromwhichincrementalsamplesaretobetakenfromabulklot
LotSizeMinimumnumberofsamplingunits25torless10Morethan25tandlessthan401tThenearestwholenumberabovethesquarerootof4timesthe
numberoftonnespresentMorethan400t40
Thedatafromthistablecanbeexpressedinamorepracticalway(Table6).
HANDBOOKOFSOLIDFERTILISERBLENDING-CodeofGoodPracticeforQuality 39
Table6:Numberofincrementsbyvehicletosampleforbulkproducts.
Numberofincrementstobetakenduringemptyingofeachdeliverytruckorwagon
LotSize
Truck Wagon25t
Wagon60t
25t 10 10 50t 7 1575t 6 100t 5 150t 4 200t 4 300t 3 500t 2 600t 2 2 41000t 1 1 31250t 1 1 12500t ½ ½ 1
Theamountoffertiliserforanincrementisabout250gforrawmaterialsand500gforblends.
8.1.2 SamplingEquipment
Appropriate samplingequipment is essential. Thereare various automated systems forusewithconveyorbelts. Thesearecertainlyrecommendediftherearelargeamountsoffertiliserhandled. Forsmallerdeliveries,manualsamplingismoresuitable. Asuitabletypeofsamplingcup is described in EN 1482 Part 1 [9] and is essential for sampling from falling streams ofmaterials(Figure15). Informationaboutthenumberofincrementstobetakenmustbegiventotheoperator(Table6).
Figure15:Exampleofasamplingcupanditsuse.
HANDBOOKOFSOLIDFERTILISERBLENDING-CodeofGoodPracticeforQuality 40
8.1.3 SampleDivider
Rotarysampledividersarerecommended,particularlywhensieveanalysisistobecarriedoutorwhenblendsarebeingtested. Riffledividersmaybeusedforrawmaterialsbutarelesssuitableforblendedproducts. Descriptionsofthesedividers(Figure16)canbefoundinEN1482[9]. Itisimportanttorememberthatforthemeasurementofthephysicalproperties,theparticlesmustnotbecrushed,butforchemicalanalysis,itisrecommendedtocrushtheparticlesbeforethefinalreductionofthesample.
Figure16:Illustrationofrotaryorriffledividers.
8.2 CHEMICALANALYSIS
Standardreferencetestmethodsformostofthecommonchemicalanalysesusedforfertilisermaterials may be found in EC Directives, National Standards, European and InternationalStandardsandtheAOACMethodsofAnalysisHandbook. Itisnotessentialthatthesemethodsare used for routine process control and simpler, often automated, methods are available. However,allsuchmethodsmustbeevaluatedagainstoneoftherecognisedstandards.
8.3 PHYSICALTESTS
Recognisedstandardtestmethodsexistforseveralphysicalproperties.Theinterestofblendersshould focus on test sieving and bulk density (see section 3.2). Some laboratories have anaccreditation for these special measurements. No Standard methods are available for such
HANDBOOKOFSOLIDFERTILISERBLENDING-CodeofGoodPracticeforQuality 41
propertiesascakingandfreedust.
Samplingisalsoafundamentalstepforphysicaltestingbecauseofthesegregationthatoccursnaturally. Thisisparticularlythecaseforsieveanalysisbecauseofthesizesegregationwhenthereisaflowoffertiliser(whichisalwaysthecaseforbulkproducts).
Anotherpointisthatforphysicaltesting,thequantityneededforthefinalsamplemaybemorethan5kg.Thismeansthatthenumberorthemassofsub-samplesmustbesufficienttoachievethis.
8.3.1 TestMethodforSieveAnalysis(ThefollowingmethodisasummaryofEN1235/A1)
8.3.1.1Principle:
Dry sieving of a sample of fertiliser material with one or more test sieves, using a mechanicalsievingmachine.
8.3.1.2Apparatus:
• Balance,capableofweighingtothenearest0,1g.• Stainlesssteelwovenwiretestsieves,200mmdiameter,withalidandreceiverforthesieves.
• Mechanicalshaker(sievingmachine),capableofimpartingbothhorizontalandverticalmotiontothematerialonthesetofsieves.
• Stopwatch• Softbrush
8.3.1.3Procedure:
Reducethesampletoapproximately250g,preferablyusingarotarysampledivider,orifoneisnotavailable,ariffledivider. Selectsevensievestocovertherangeofparticlesizeexpectedandassembleinascendingorderofaperturesizeontopofthereceiver.(SeenoteatthebottomofTable2)
Weighthetestportiontothenearest0,1gandplaceitonthetopsieveandfitthelid. Placethesetofsieveswiththesampleontheshakerandshakefor10minutes.
Removethesievesfromthenest,startingfromthetopandweighthequantityretained oneachsieveandinthereceiver,tothenearest0,1g.Removeanyparticlestrappedin themeshbybrushingfromunderneath.
Sumthemassesofthefractionsretainedonthesievesandinthereceiverandcheckthat the total mass is within 2,5g of the original mass. Calculate each fraction mass as a percentage of the sum of the masses and draw up a table showing the cumulative percentagepassingeachsieve.
Thepercentageofmaterialretainedinthereceiver(x0)andoneachsieve(xn)isobtained fromtheformula:
HANDBOOKOFSOLIDFERTILISERBLENDING-CodeofGoodPracticeforQuality 42
100 mm
t
n ´=nX
Wheremnisthemassonsieven mtisthetotalmass(m0+m1+…) Xnisthemass%retainedonsievenThecumulativeundersizeisdefinedbytheformula:
Cn=X0+X1+X2+…+Xn-1WhereCnisthecumulative%undersizeforsieven
8.3.2 TestMethodforLooseBulkDensity (ThefollowingmethodisasummaryofEN1236)
8.3.2.1Principle:
Weighingaknownvolumeofthefertiliser.
8.3.2.2Apparatus:
• Balance,capableofweighingtothenearest1g.• Cylinderofaknownvolume,V(approx.1litreanddiameteraround60mm).• Standardfunnelwithanapertureof25mmdiameter.
Figure17:Illustrationoftheequipmentfortheloosedensitymeasurement.
HANDBOOKOFSOLIDFERTILISERBLENDING-CodeofGoodPracticeforQuality 43
8.3.2.3Procedure:
Placethesampleoffertiliserinthefunnelwiththeapertureclosed. Weightheemptycylinderandplaceitunderthefunnel. Opentheapertureofthefunnelandallowthefertilisertoflowintothecylinder. Whenthecylinderisfull,closethefunnelandremovethe excess fertiliser above the cylinder with a spatula. Weigh the cylinder and itscontentsandcalculatetheweightoffertiliser(minkg).
Theloosebulkdensityisgivenbythefollowingformula:
Vm =r
8.3.3 TestMethodforAngleofRepose (ThefollowingmethodisasummaryofEN12047)
8.3.3.1Principle:
Measurementofthediameterofaheapofagivenheightandcalculationoftheangleof theheap.
8.3.3.2Apparatus:
• Funnel(apertureof25mmdiameter)placedat120mmaboveasurface.• Horizontalsurfaceof750x750mm,withfourlinespresentinganangleof45°betweenthemandtracedatthecentreofthesurface.
Figure18:Illustrationoftheequipmentfortheangleofreposemeasurement.
HANDBOOKOFSOLIDFERTILISERBLENDING-CodeofGoodPracticeforQuality 44
8.3.3.3Procedure:
Placeabout5kgfertiliserinthefunnelwiththeapertureclosed. Opentheapertureandallowthefertilisertoflowfreelyontothesurfaceandformaheap. Theflowstopswhentheheapreachesthebottomofthefunnel. Measurethefourdiametersontheplate.
Calculatetheaveragediameter(d inmm). Thevalueoftheangleofreposeisobtainedbythefollowingformula:
÷øö
çèæ=
25 - d240arctan a
8.4 EXAMPLES
Thissectiongivessomeexamplesoftheresultsofphysicaltestsonfertilisers. Thedatausedare realistic but the actual physical properties will vary considerably for the same productdependingonitsorigin[14].
Usingthemeasurementmethodsdescribedintheprevioussection,thefollowingresultswereobtainedforthreedifferentfertilisers,A,BandC. (Table7).
Table7:Exampleofdatafromthelaboratoryforphysicaltestingofthreefertilisers.
Fertiliser
A B C
Sievingtest
<1,00mm 0,1g 0,5g 8,2g
1,00to2,50mm 1,2g 9,3g 35,6g
2,50to2,80mm 5,3g 19,9g 45,2g
2,80to3,15mm 36,7g 68,1g 51,9g
3,15to3,55mm 115,2g 79,6g 46,8g
3,55to4,00mm 67,7g 51,2g 35,3g
4,00to5,00mm 15,9g 13,2g 21,7g
>5,00mm 2,1g 2,1g 5,2g
Total 244,2g 243,9g 249,9g
HANDBOOKOFSOLIDFERTILISERBLENDING-CodeofGoodPracticeforQuality 45
Loosebulkdensity
Weightof1litre(V=0,001m³) 1,000kg 0,750kg 0,950kg
Angleofrepose
Averagediameterbaseofthe
heap( d )400mm 400mm 325mm
Byapplyingtheformulaeitispossibletodeterminethephysicalpropertiesofthesefertilisers.
Table8:ExampleofcalculationforthephysicalpropertiesoffertiliserA.
SievingTest Weight Percentage CumulativePercentage
<1,00mm 0,1g 0,1/244,2=0,04% 0,04%1,00to2,50mm 1,2g 1,2/244,2=0,49% 0,04+0,49=0,53%2,50to2,80mm 5,3g 5,3/244,2=2,17% 2,17+0,53=2,70%2,80to3,15mm 36,7g 36,7/244,2=15,03% 5,03+2,70%=17,73%3,15to3,55mm 115,2g 115,2/244,2=47,17% 47,17+17,73=64,91%3,55to4,00mm 67,7g 27,72/244,2=27,72% 27,72/244,2=27,72%4,00to5,00mm 15,9g 15,9/244,2=6,51% 6,51+92,63=99,14%>5,00mm 2,1g 2,1/244,2=0,86% 0,86+99,14=100,00%TOTAL 244,2g
With the sieving test data, it is possible to determine the mean particle size (d50) and theGranulometricSpreadIndex(GSI). Thed16isjustunder3,15mm,thed50isbetween3,15mmand3,55mmand thed84 isbetween3,55mmand4,00mm. Theuseof theequation (seeparagraph3.2.1)leadstothefollowingresults:
( ) mm 3,11 2,80 - 3,15 2,70 - 17,73
2,70 - 16 2,80 16 =+=d
( ) mm 3,42 3,15 - 3,55 17,73 - 64,91
17,73 - 50 3,15 50 =+=d
( ) mm 3,86 3,55 - 4,00 64,91 - 92,63
64,91 - 84 3,55 84 =+=d
10,96 100 3,42 2
3,11 - 3,86 =´´
=GSI
Thegraphicrepresentationofthecumulativepercentageconfirmsthecalculatedvalues(Figure19).
HANDBOOKOFSOLIDFERTILISERBLENDING-CodeofGoodPracticeforQuality 46
Figure19:Exampleofgranulometriccurveandgraphicdeterminationofd16,d50andd84.
Thesamemethodofcalculationisusedfortheotherfertilisers(Table9).
Table9:PhysicalpropertiesoffertilisersA,BandC.
Comparingthefertilisers,thefollowingcommentsmaybemade. Thethreeproductshavead50inaccordancewiththerecommendations(Table2). FertiliserAhasaverylowGSImeaningthatallparticlesareofsimilarsize. AttheotherextremefertiliserChasahighGSIbecauseofitshighcontentofsmallparticles. FertiliserBhasa lowbulkdensityandfertiliserChasahighangleofreposebecauseofitsmoreangularparticles.
Fertiliser
A B C
d16 3,11mm 2,85mm 2,34mm
d50 3,42mm 3,27mm 3,04mm
d84 3,86mm 3,79mm 3,83mm
GSI 10,96 14,42 24,55
Loosebulkdensity(ρ) 1000kg/m³ 750kg/m³ 950kg/m³
Angleofrepose(α) 32,6° 32,6° 38,7
0102030405060708090
100
1 1,5 2 2,5 3 3,5 4 4,5 5Sieve dimensions (mm)
Cum
ulat
ive
perc
enta
ge (%
)
3,11 3,42 3,86
d16
d84
d50
HANDBOOKOFSOLIDFERTILISERBLENDING-CodeofGoodPracticeforQuality 47
9. FORMULATION
Thecalculationofblendformulationsisnotadifficultprocessbutitisanessentialrequirementforproducinggoodqualityblends. Theprocessveryoften isperformedbya computerandcombinedwithweigherormeteringcontrols.
Recordsshouldbekeptofeachformulationandthiscanbesimplifiedbytheuseofastandardformatinthecomputer.
Foraccurateformulationtheactualrawmaterialanalysesshouldbeusedbutstandardanalysesarehelpfulasafirstapproximation.
Example:
Productrequired: 20 10 11
Rawmaterialsavailable: N P2O5 K2O
CalciumAmmoniumNitrate(27%Nitrogen) 27 0 0DiammoniumPhosphate(18%Nitrogen46%P2O5) 18 46 0PotassiumChloride(60%K2O) 0 0 60Filler 0 0 0
1 Toobtain11%K2Ointhefinalproductrequires18,5%PotassiumChloride.
2 To obtain 10% P2O5 in the final product requires 22% Di-ammoniumPhosphateandthiswillprovide3,9%Nitrogen.
3 Theremaining16,1%Nitrogeninthefinalproductwillrequire59,5%CalciumAmmoniumNitrate.
4 Totalrawmaterialsrequiredaddsupto100%ofthetotalspaceandthusnofillerisrequired.
Formulationpertonneofproductisthus:
• 595kgofCalciumAmmoniumNitrate
• 220kgofDi-ammoniumPhosphate
• 185kgofPotassiumChloride
NOTE:
Formulationscontaininglessthan5%ofanyingredientshouldbeavoidedastherewillbedifficultiesinmixingthissmallamountevenlythroughoutthemixture.
HANDBOOKOFSOLIDFERTILISERBLENDING-CodeofGoodPracticeforQuality 48
10. REFERENCES
CopiesofthelistedStandardsmaybeobtainedfromtheNationalStandardsOrganisation(e.g.AFNORinFrance,DINinGermanyandBSIintheUK).
1 BalayHL,ColeCAandRutlandDW,BulkBlendingMixingEfficiencyTests.Proceedings32ndFertiliserIndustryRoundTable,Atlanta,October1982
2 Proposal:COMIFER,Guided’optimisationdel’épandagedesengraisminérauxsolides,Edition2009/2010
3 CEN,EuropeanStandard /A1.TestSieving(2003)
4 CEN,EuropeanStandardEN1236.Determinationofbulkdensity(loose)
5 CEN,EuropeanStandardEN1237.Determinationofbulkdensity(tapped)
6 CEN,EuropeanStandardEN12047.Measurementofstaticangleofrepose
7 CEN,EuropeanStandardEN13299.Determinationoftheflowrate
8 CEN,EuropeanStandardEN12944VocabularyPart1,Part2andPart3
9 CEN,EuropeanStandardEN1482.Sampling Parts1&2
10 ChevalJ-L,UpdateontheCanadianQualityAssuranceProgramandSGN.PublicationN°44,AAPFCO1991
11 ColeCA,BalayHLandRutlandDW,BulkBlendingMixingEfficiencyTest.Proceedings35thFertiliserIndustryRoundTable,Atlanta,October1985
12 Guidance for the Storage, Handling and Transportation of Solid Mineral Fertilisers. PublishedbyEFMA(2007)
13 GuidancefortheCompatibilityofFertilizerBlendingMaterials. PublishedbyFertilizersEurope(2016)
14 Guillon D. Enquête granulométrique sur lesmatières premières pour les engrais de mélange.RencontresInternationalesdel’AFCOME,Strasbourg,novembre2003.
15 Heege H. Quality of raw materials for fertilizer-blends: defining a standard. RencontresInternationalesdel’AFCOME,Strasbourg,novembre2003.
16 HignettTP,BulkBlendingofFertilisers:PracticesandProblems.Proc.Fert.Soc.N°87,March1965
17 IFA/EFMA,SelectedTestsConcerningtheSafetyAspectsofFertilisers.1992
18 LanceGEN,TheoryofFertiliserBlending.Proc.Fert.Soc.N°387,December1996
HANDBOOKOFSOLIDFERTILISERBLENDING-CodeofGoodPracticeforQuality 49
19 LeonardJE,TechnologyofFertiliserBlending.Proc.Fert.Soc.N°388,December1996
20 Miserque O. Analyse de l’influence des caractéristiques physiques des particulesd’engraissurlecomportementdesmélanges. PhDthesis–UniversityofLiège,FacultyofAppliedSciences-Belgium–2005.
21 MiserqueO.,OestgesO.,BruartJ. Thespreadingofbulkblendswitha largeworkingwidthspreader. RencontresInternationalesdel’AFCOME,Strasbourg,novembre2003.
22 PerbalG,TheThermalStabilityofFertiliserscontainingAmmoniumNitrate.Proc.Fert.Soc.N°124,November1971
23 Regulation1272/2008/ECoftheEuropeanParliamentandoftheCouncilonclassification,labellingandpackagingofsubstancesandmixtures,amendingandrepealingDirectives67/548/EEC and 1999/45/EC, and amending Regulation (EC) No 1907/2006 OJ353/131.12.2008andimplementinglegislation
24 Regulation1907/2006/EC of the European Parliament and of the Council on theRegistration, Evaluation, Authorisation and Restriction of Chemicals (REACH)OJ396/130.12.1996andimplementinglegislation
25 Regulation2003/2003/ECoftheEuropeanParliamentandoftheCouncilof13October2003relatingtofertilisers. OJ304/121.11.2003andimplementinglegislation
26 StairmandCJ,ThescreeningandSegregationofFertiliserMaterials.Proc.Fert.Soc.N°74,November1962
27 TaylorL,LatestTechnologyandMethodsUsedforBulkBlendingandFertiliserStorageintheUnitedStates.Proc.Fert.Soc.N°256,April1987
28 TheFertiliserInstitute,BulkBlendQualityControlManual.Washington,Spring1996
29 YoungTM,BlendinginIreland.Proc.Fert.Soc.N°255,April1987