Refractory brick

Introduction

Refractorybricksarereferredtoasfirebricks.Refractorymadeoffire-resistantclayorotherrefractorymaterials.Paleyelloworbrown.Mainlyusedforbuildingsmeltingfurnaces,itcanwithstandhightemperaturesof1,580℃-1,770℃.Alsocalledfirebrick.Refractorymaterialwithacertainshapeandsize.Accordingtothepreparationprocess,itcanbedividedintofiredbricks,non-firedbricks,fusedbricks(fusedcastbricks),refractoryandheatinsulationbricks;accordingtotheshapeandsize,itcanbedividedintostandardbricks,ordinarybricks,special-shapedbricks,etc.Itcanbeusedashigh-temperaturebuildingmaterialsandstructuralmaterialsforbuildingkilnsandvariousthermalequipment,andcanwithstandvariousphysicalandchemicalchangesandmechanicaleffectsathightemperatures.Forexample,refractoryclaybricks,highaluminabricks,silicabricks,magnesiabricks,etc.

Features

Ownproperties

1.Chemicalcomposition:themaincomponentsdeterminethequalityandcharacteristicsoftherefractorymaterial

2.Bulkdensity:Theweightperunitvolumeandthehighdensityindicatethatthecompactnessisgood,andthestrengthmaybehigh,butthethermalconductivitymaybelarge.3.Apparentporosity:Nospecificrequirementsaremade,butasamanufacturer,theobviousporesmustbestrictlycontrolled.

4.Loadsofteningtemperature:alsocalledhightemperatureloadstartingdeformationtemperature,thisparameterisveryimportant,markingtheresistanceofthematerialtohightemperature

5.Thermalshockresistance:resistancetosharptemperatureAbilitytochangewithoutbeingdestroyed

6.Compressivestrength:theabilitytowithstandthemaximumpressure(normaltemperature)

7.Flexuralstrength:theabilitytowithstandshearpressure

8.Linearchangerate:Itisalsocalledreburninglinechangeorresiduallinechange,whichreferstothechangeinvolumeexpansionandcontractioneverytimethesametemperaturechanges.Ifeachexpansionandcontractionisthesame,wedefinesuchalinearchangeRateis0

Physicalandchemicalproperties

1.Wearresistance:

2.Thermalconductivity:heatflowperunitareathroughthematerialundertheconditionofunittemperaturegradientThespeedisrelatedtotheporosity.

3.Impactresistance:Noneedtoexplainit,theimpactresistanceisgood,andtheservicelifeislong

4.Slagresistance:resistanceathightemperaturesTheabilityofslagtocorrodewithoutbeingdestroyed

Classification

Accordingtothedifferentcomponentsofrefractorybricks,itcanbedividedintofivecategories,namely:silica-aluminarefractorybricks,alkalineseriesRefractorybricks,carbon-containingrefractorybricks,zirconium-containingrefractorybricks,heat-insulatingrefractorybricks.Anystoveisnotonlybuiltwithonetypeofrefractorybrick,butrequirestheuseofdifferentrefractorybricks.Thecomponentsofthesefivetypesofrefractorybricksareintroducedindetailbelow.

1.Silica-aluminarefractorybricksarereportedtobebasedonthephasediagramoftheAL2O3-SiO2binarysystemasthebasictheory,mainlyincludingthefollowing.

(1)Silicabricksrefertorefractorybrickscontainingmorethan293%SiOandarethemainvarietiesofacidrefractorybricks.Itismainlyusedforbuildingcokeovens,andalsousedforthevaultsandotherload-bearingpartsofthermalkilnsforvariousglass,ceramics,carboncalciners,andrefractorybricks.Itisalsousedinthehigh-temperatureload-bearingpartsofhotblaststoves,butnotUsedinthermalequipmentbelow600°Candwithlargetemperaturefluctuations.

(2)Claybricks.Claybricksaremainlycomposedofmullite(25%-50%),glassphase(25%-60%),cristobaliteandquartz(upto30%).composition.Usuallyhardclayisusedastherawmaterial,pre-calcinedmaturematerial,thenmixedwithsoftclay,andmoldedbysemi-drymethodorplasticmethod,andthetemperatureis1300～1400Ctoburnclaybrickproducts.Youcanalsoaddasmallamountofwaterglass,cementandotherbinderstomakeunburnedproductsandamorphousmaterials.Itisarefractorybrickcommonlyusedinblastfurnaces,hotblaststoves,heatingfurnaces,powerboilers,limekilns,rotarykilns,ceramicsandrefractorybrickfiringkilns.

(3)Highaluminarefractorybricks.Themineralcompositionofhighaluminarefractorybricksiscorundum,mulliteandglassphase.ItscontentdependsontheratioofAL2O3/SiO2andthetypeandquantityofimpurities,whichcanbebasedonthecontentofAL2O3.Carryouttheclassificationofrefractorybricks.Therawmaterialsarehighaluminabauxiteandsillimanitenaturalores,aswellasthosemixedwithfusedcorundum,sinteredalumina,syntheticmullite,andclinkercalcinedwithaluminaandclayindifferentproportions.Itismostlyproducedbysinteringmethod.Buttheproductsalsoincludefusedcastbricks,fusedgrainbricks,unburnedbricksandunshapedrefractorybricks.Highaluminarefractorybricksarewidelyusedinthesteelindustry,non-ferrousmetalindustryandotherindustries.

(4)Corundumrefractorybrick.CorundumbrickreferstoakindofrefractorybrickwiththecontentofAL2O3notlessthan90%andthemainphaseofcorundum.Itcanbedividedintosinteredcorundumbrickandfusedcorundumbrick.

2.Alkalineseriesofrefractorybricks.AlkalinerefractorybricksrefertorefractoryproductswithalkalineoxidessuchasMg0andCaOasthemaincomponents.Themainvarietiesareasfollows.

(1)Magnesiarefractorybricksrefertorefractorybrickswithmagnesiteasrawmaterial,periclaseasthemaincrystalphase,andMgOcontentabove80%-85%.Itsproductsaredividedintotwocategories:metallurgicalmagnesiaandmagnesiaproducts.Dependingonthechemicalcompositionanduse,thereareMartinsand,ordinarymetallurgicalmagnesia,ordinarymagnesiabrick,magnesiasilicabrick,magnesiaaluminabrick,magnesiacalciumbrick,magnesiacarbonbrickandothervarieties.Magnesiarefractorybrickisthemostimportantproductamongalkalinerefractorybricks.Ithashighrefractorinessandgoodresistancetoalkalineslagandironslag.Itisanimportanthigh-graderefractorybrick.Mainlyusedforopenhearthfurnace,oxygenconverter,electricfurnaceandnon-ferrousmetalsmelting.

(2)Dolomitebrickisanalkalinerefractorybrickproducedwithdolomiteasthemainrawmaterial.Itiswidelyusedinalkalineconverters,andcanalsobeusedastheinnerliningofsomerefiningladleoutsidethefurnace.

(3)Forsteriterefractorybrickisarefractorybrickwithforsterite2MgO·SiO2asthemaincomposition.Itismainlyusedforcheckerbricksinopenhearthregenerators,bricksforingots,furnacebottomsofheatingfurnaces,andalsohasgooduseeffectsincoppersmeltingfurnaces.

3.Carbon-containingrefractorybricks.Carbon-containingrefractorybricksaremadeofcarbonorcarboncompounds.Refractorybrickproductscontainingdifferentformsofcarbonasthemaincomponentaremainlydividedintothefollowingcategories.

(1)Carbonbrickisahigh-temperatureneutralrefractorybrickproductmadeofcarbonaceousmaterialsasthemainrawmaterialandaddinganappropriateamountofbinder.Carbonbricksarewidelyusedinmasonryblastfurnacebottom,hearth,hearthandlowerpartofthefurnacebody.Itcanincreasethecontinuousoperationtimeoftheblastfurnaceandprolongtheservicelife.Inaddition,carbonbricksarealsowidelyusedintheelectrochemicalindustry,chemicalindustry,petrochemicalindustry,electroplatingindustry,ferroalloyindustrialfurnaces(orequipmentlinings),acid,lyetankliningsandpipelines,andsmeltingofnon-ferrousmetals(suchasLead,aluminum,tin,etc.)furnacelining.

(2)Graphiterefractoryproductsarerefractorymaterialsmadeofnaturalgraphiteasrawmaterialandclayasabinder.Suchproductsincludegraphiteclaycrucibles,distillationtanks,caststeelplugbricks,nozzlebricksandsteelbucketliningbricks.Amongthem,graphiteclaycruciblesforsteelmakingandsmeltingofnon-ferrousmetalsarethemostproducedandwidelyused.

(3)Siliconcarbiderefractoryproductsareadvancedrefractorymaterialsproducedfromsiliconcarbide(SiC).Ithasgoodwearresistanceandcorrosionresistance,hightemperaturestrength,highthermalconductivity,lowlinearexpansioncoefficient,andgoodthermalshockresistance.Insteelsmelting,itcanbeusedforladlelining,nozzles,plugs,blastfurnacebottomandhearth,tappingtroughs,converterandelectricfurnacetaps,heatingfurnaceswithoutwater-cooledsliderails,etc.Inthesmeltingofnon-ferrousmetals(zinc,copper,aluminum,etc.),itiswidelyusedinstills,rectificationtowertrays,electrolytictanksidewalls,moltenmetalpipelines,suctionpumps,andsmeltingmetalcrucibles.Inthesilicateindustry,itiswidelyusedasashedandmufflematerialforvariouskilns,suchasmufflefurnaceliningandsaggers.Inthechemicalindustry,itismostlyusedinoilandgasgenerators,organicwastecalciners,petroleumgasifiersanddesulfurizationfurnaces.Inaddition,itcanbeusedasrocketnozzlesandhigh-temperaturegasturbinebladesinspacetechnology.

4.Zirconium-containingrefractorybricks.Itbelongstoanacidicmaterial.Itisaproductmadefromnaturalzirconsand(ZrSiO2).Zirconiumrefractorybricksaredifferentfromsilicon-aluminumrefractorybricksandcarbon-containingrefractorybricks.Ithasgoodslagresistance,lowthermalexpansionrate,thermalconductivitydecreaseswithincreasingtemperature,highloadsofteningtemperature,andhighwearresistance.Ithasgoodthermalshockresistanceandhasbecomeanimportantmaterialinvariousindustrialfields.Withthedevelopmentofcontinuouscastingandvacuumdegassingtechnologyinthemetallurgicalindustry,zirconrefractorybricksareusedmoreandmorewidely,mainlyinthefollowingcategories.

(1)Zirconbricks,inthesteelmakingprocess,usethetappingdegassingmethod,andzirconrefractorieshavegoodcorrosionresistanceandthermalshockresistancetomoltenslagandmoltensteel,Andsuitableforworkingunderreducedpressure,itiswidelyusedinthemetallurgicalindustrytobuilddegassingsteelladlelining,alsousedasstainlesssteelladlelining,continuouscastingsteelladlelining,castingbrick,Plugbricks,sleevebricksandhightemperatureinductionfurnacelining,etc.Zirconrefractorybrickshavehighresistancetoacidicslagandglass,sotheyarealsowidelyusedinseverelydamagedpartsofglassfurnacesformeltingthemostactiveglass.Zirconrefractoriesalsohavethepropertyofnotbeingpenetratedbymetalaluminum,aluminumoxideanditsmoltenslag,soithasalsoobtainedgoodeffectsonthefurnacebottomofaluminumsmelting.

(2)AZSfusedbrick,alsoknownasfusedzirconiacorundumbrick,withthedevelopmentoftheglassindustry,AZSfusedbrickhasbecomeanecessaryrefractorymaterialforthekeypartsoftheglassfurnace.Itresiststhecorrosivenessofmoltenglass.

(3)AZSre-sinteredfusedbricksaremainlyusedtobuildthebottomandwallsofglasskilnsandthermalequipmentsuchasheatstoragecheckerbricks.

(4)Zirconiummullitefusedbricks,whicharecharacterizedbydensecrystalstructure,highloadsofteningtemperature,goodthermalshockresistance,highmechanicalstrengthatroomtemperatureandhightemperature,andwearresistanceGood,goodthermalconductivity,andexcellentresistancetoslagerosion.Thiskindofproducthasawiderangeofuses,suchasthedischargeportofmetallurgicalheatingfurnaces,soakingfurnaces,calciumcarbidefurnaces,andthewallsofglassmeltingfurnaces.Theuseeffectisverygood.

5.Insulationrefractorybricks.Referstorefractorieswithhighporosity,lowbulkdensityandlowthermalconductivity.Thermalinsulationrefractoriesarealsocalledlightweightrefractories.Itincludesthefollowingcategories.

(1)High-aluminumheat-insulatinglightweightrefractorybricks.Itisaheat-insulatinglightweightrefractorybrickwithbauxiteasthemainAL2O3contentofnotlessthan48%.Theproductionprocessadoptsthefoammethodortheburn-outadditionmethod.High-aluminumheat-insulatinglightweightrefractorybrickscanbeusedtobuildheat-insulatinglayersandpartsthatarenotcorrodedandscouredbystronghigh-temperaturemoltenmaterials.Whenindirectcontactwiththeflame,thesurfacecontacttemperatureofgeneralhigh-aluminumheat-insulatingrefractorybricksshallnotbehigherthan1350℃.Mulliteheat-insulatingrefractorybrickscandirectlycontacttheflame,andhavethecharacteristicsofhightemperatureresistance,highstrength,andsignificantenergy-savingeffect.Itissuitablefortheliningofpyrolysisfurnace,hotairfurnace,ceramicrollerkiln,electricporcelaindrawerkilnandvariousresistancefurnaces.

(2)Clay-basedheat-insulatinglightweightrefractorybricksareheat-insulatingrefractorybrickswith30%to48%AL2O3contentmadeofrefractoryclayasthemainrawmaterial.Theproductionprocessadoptstheburn-outaddingcharactermethodandthefoammethod.Usingrefractoryclay,floatingbeads,andrefractoryclayclinkerasrawmaterials,addingbindersandsawdust,batching,mixing,molding,drying,andfiringtoobtainaproductwithabulkdensityof0.3to1.5g/cm3.Theoutputofclayinsulatingbricksaccountsformorethanhalfofthetotaloutputofinsulatingrefractorybricks.

TheChinesestandard(GB3994-1983)dividesclaythermalinsulationbricksintoNG-1.5,NG-1.3a,NG-1.3b,NG-1.0,NG-0.9,NG-0.8,NG—0.7,NG—0.6,NG—0.5,NG—0.410grades.

(3)Diatomiteheat-insulatinglightweightrefractorybricksareheat-insulatingrefractoryproductsmadeofdiatomiteasthemainrawmaterial.Itismainlyusedinheatinsulationlayerbelow900℃.

TheChinesestandard(GB3996-1983)dividesdiatomiteinsulationproductsintoGG—0.7a,GG—0.7b,GG—0.6,GG—0.5a,GG—accordingtotheirbulkdensity.Therearesixgradesof0.5bandGG—0.4.

(4)Floatingbeadbricksareheat-insulatingrefractoryproductsmadeoffloatingbeadsasthemainrawmaterial.Floatingbeadsarehollowaluminumsilicateglassbeadsfloatedfromflyashfromthermalpowerplants.Ithaslightbody,thinwall,hollow,smoothsurface,hightemperatureresistanceandgoodheatinsulationperformance.Usingtheseexcellentcharacteristicsoffloatingbeads,alightweightheat-insulatingrefractorymaterialwithexcellentheatpreservationperformancecanbemanufactured.Theproductionoffloatingbeadbrickscanbeformedbyasemi-drymethod.

Case

Refractorymaterials

1.Highaluminabricks:Al2O3contentisgreaterthan75,refractorinessishigherthanclaybricks,andacidandalkalicorrosionresistanceisgood.Suitableforcementkilnfiringzone,etc.,withlongservicelifebuthighprice

2.Dolomitebricks:goodkiln-hangingperformanceandgoodcorrosionresistance,butsomebrickscontainf-CaO,whichiseasytoHydration,difficulttotransportandstore,lessusedinproduction

3.Magnesiachromebricks:goodforhangingkilnskins,mostlyusedforfiringzones,thedisadvantageispoorthermalshockresistance,pluspositivehexavalentCrishighlytoxic,andthenumberofcountriesthatproduceandusemagnesia-chromebricksintheworldisgraduallydecreasing.Theproductionunitsthatcurrentlyusethisbrickcanfindsubstitutesassoonaspossible.

4.Spinelbricks:mostlyusedforexcessivebelts,seismicperformanceGood,goodresistancetoreduction,butpoorrefractoriness

5.Anti-strippingbrick:ThisbrickcontainsasmallamountofZrO,whichwillcauseMarkovphasetransformationtoformfinecracksduringtheheatingprocess,whichhasstrongresistanceAlkaline,goodpeelingresistanceandslagresistance

6.Phosphatebricks:lowrefractoriness,buthighstrength,goodthermalshockresistance,mostlyusedincastorcoolers,kilnhoods,etc.

7.Siliconcarbidebricks:hightemperatureresistance(about1800degrees,loadsofteningtemperatureis1620-1640),lowthermalexpansioncoefficient,goodresistancetorapidcoldandheatwearresistance,suitableforcoolingzoneandkilnopening

8.Silicabrick:goodthermalshock,highstrength,goodabrasionresistance,suitableforexcessivebelting.

Refractorysoil

Folkstoves.Akindofsoilisusedforthesetofhearth.

Clay-basedrefractorysoil

1.Featuresanduses:Clay-basedrefractorybricksareweaklyacidicrefractorymaterialswithgoodthermalstability,suitableforhotblaststovesandvariousboilerlinings,Andflue,smokechamber,etc.

2.Productspecifications:standard,general,special,andspecial-shapedbricks.Physicalandchemicalpropertiesofclayrefractorybricks.

Refractoryclay

Refractoryclayproductscomeinmanyforms,andtheirbasicqualityrequirementsarealuminahigherthan38%(usually42-47%)andlowironandlowalkalimetalcontent.Theseproductscanbeuncalcinedorcalcined,andincludehigh-performancecalcinedproductssuchasmullite.

Refractoryclaysareusedintheproductionofshapedandamorphous(monolithic)refractories.Brickproductsincludefireclaybricks,suchasblastfurnacecheckerbricksandhighaluminabricks,suchassupportbricksusedintheliningofhorizontalinductionfurnacesandverticalinductionfurnaces.Intheamorphousmaterialsector,thereareavarietyofproductsconsumed,suchasrefractoryclay,plasticmaterialsforoverloading,highaluminaplastics,refractoryclayandhighaluminacastables.

Therefractoryclayismainlycomposedofhydratedaluminumsilicate,anditsmolecularformulaisAl2O3·2SiO2·2H2O(ie39.5%alumina,46.5%silicaand14%water).Inthisgroupofminerals,kaolinisthemostabundant.

Refractoryclay,flintclay(flintclay,orhardclay),ballclay(plasticclay,orplasticclay),andkaolins.However,itscommonfeatureisthatthesemineralscontainkaolinite,anditscompositionis20-45%Al2O3,<3%Fe2O3and<3%Na2+K2O.

Whenkaoliniteiscalcinedundertheconditionofgraduallyincreasingtemperature,itsmineralphasechangescontinuously,andmetakaolin(Al2Si2O7)isformedatabout550℃,andspinelisformedatabout1000℃Stone(spinel,(Al2O3)2(SiO2)3+SiO2),atabout1100℃,theformationofpseudo-mullite(pseudo-mullite,[Al2O3·SiO2]2).Another"refractoryclay"productismullite(3Al2O3·2SiO2),whichcanbemadebycalcininghighaluminakaolinandbauxitickaolinat1200-1500°C.Atthesetemperatures,themainmineralphasesoftheclaytransformintomullite,cristobaliteandaglassyphase.

⒈Refractoryclay

Thisisakindofsiliceousclayrichinhydratedaluminumsilicate,whichisnotdeformed,cracked,softenedandpastelessathightemperatureTheabilitytochange.Lowiron,calciumandalkalimetals,thecompositionisclosetokaolin,andthebettergradeaftercalcinationcontainsatleast35%Al2O3("MiningTerminologyDictionary",editedbytheAmericanGeologicalSociety).

⒉Flintclay

Asmooth,flint-likerefractoryclayrock,mainlycomposedofkaolin,withcleavageinashell-likesection,whichresistsmaturationinwater.Millinginwaterforalongtimewillproduceplasticity("MiningTerminologyDictionary",AmericanGeologicalAssociation).

⒊Cookedrefractoryclay

Itisapartofthemixtureusedintheproductionofrefractorybricks.Itiscomposedofcalcinedclayorregroundbricks.,Alsoknownas(clay)clinker,theEnglishnameischamotte("MiningTerminologyDictionary",AmericanGeologicalAssociation).

⒋Diasporeclay

Thisisamaterialmainlycomposedof(diaspore)diaspore(or-diaspore)andbondedbyrefractoryclay.Thepurestdiasporeclayoftencontains70-80%Al2O3aftercalcination.

⒌Chineseclay

●Softclay(includingballclay),refractoryclayandkaolin:<45%Al2O3

●Flintclay(commonlyknowninChina"Cokegem"),kaolinandhighaluminaore:>45%Al2O3

●Highaluminaclayclinker(alsocalled"cookedbauxite"):75-90%Al2O3

⒍Refractoryclay/refractoryclaymortar

Withcalcinedrefractoryclayorbrokenrefractoryclaybrick,orbothrawfireclay(rawfireclay),allcomponentsofwhicharegroundGrindtotheappropriatefineness("MiningTerminologyDictionary",AmericanGeologicalSociety).

Manufacturingprocess

Thepublicwelfarepropertiesofrefractoryrawmaterialsmainlydependonthemineralcompositionandparticlecompositionoftherawmaterials,andarecloselyrelatedtothemanufacturingprocessofrefractorymaterials.Suchpropertiesmainlyincludeparticlesizeandparticlesizedistribution,finenessandspecificsurfacearea,plasticityandbonding,dryingshrinkageandfiringshrinkage,sinteringtemperatureandsinteringrange,etc.

1.Particlesizeandparticlesizedistribution

Theparticlesizereferstotheparticlesizeoftherefractoryrawmaterial.ParticleSizeDistribution(PSD)referstothepercentagebyweightofparticlesofeachparticlesizelevelinacontinuousrangeofdifferentparticlesizelevels(expressedinmm,μmormeshmesh).Theparticlesizedistributionofclayrawmaterialshasagreatinfluenceonitsplasticity,dryingperformanceandsinteringperformance.Theparticlesizedistributionofrawmaterialsalsohasasignificanteffectonthebulkdensity,porosity,mechanicalstrengthandthermalshockstabilityofrefractoryproducts.Inordertoobtainrefractorymaterialswithstablequality,inadditiontotherequirementsforthechemicalmineralcompositionoftherawmaterials,thereshouldalsobeclearrequirementsfortheparticlesizedistribution.

Thedeterminationofparticlesizedistributionusuallyusessieveanalysisandparticleanalyzer.Sieveanalysisincludesdrysievingandwatersieving.Duetothelimitationofthesieveaperture,sievinganalysisissuitableforthedeterminationoftheparticledistributionofcoarserparticles(>10μm).Particleanalyzersareusuallyusedtodeterminethesizedistributionofclayandfineparticlesofdifferentialgrade.

Second,finenessandspecificsurfacearea

Finenessindicatesthedegreeofthicknessofthepowderedrawmaterial,oftenexpressedbythepercentageofsieveresidueorspecificsurfaceareaof​​astandardsieve,Itcanalsobeexpressedasthepercentagecompositionoftheparticlesizeortheaveragediameterperunitweightofthematerial.Thereisnostrictdifferencebetweenfinenessandparticlesize,buttheformerisusedtoexpressthethicknessoffinepowderedrawmaterials.

Specificsurfaceareareferstothesurfaceareaperunitmassofrawmaterials,andtheunitism/g.Thespecificsurfaceintegratestheexternalsurfaceareaandtheinternalsurfacearea.Theidealnon-porousrawmaterialhasonlytheexternalsurfacearea;buttherawmaterialwithporeshasaninternalsurfaceareainadditiontothesurfacearea.Therearemanymethodsformeasuringthespecificsurfacearea,suchasgasadsorptionmethod,organicmoleculeadsorptionmethodandgaspermeationmethod.

3.Plasticityandassociativity

Thematerialdeformswithoutcrackingafterbeingsubjectedtoexternalforce.Aftertheexternalforceisreleased,thedeformedformremainsandtheThepropertythatdoesnotreturntoitsoriginalstateiscalledplasticity.Plasticityisanimportantmoldingprocessindexforbondingclay.Plasticityisrelatedtotheabilityofsolidparticlestoabsorbwater,specificsurfaceareaandwatervolume.Forexample,afteraddingwatertoclay,awaterfilmisadsorbedonthesurfaceofalargenumberofclayparticles,sothattheparticlesarenotonlyeasytoslideunderexternalforce,butalsohaveacertainbindingforce.,Whichhashighplasticity.

Themeasurementofplasticityhasplasticityindexmethodandplasticityindexmethod,anditcanalsobemeasuredbyplasticitymoisture.Theplasticityindexreferstothevariationrangeofthewatercontentwhentheclayisinaplasticstate,anditsvalueisequaltothedifferencebetweentheliquidlimit(liquidlimit)andtheplasticlimit(plasticlimit).Theliquidlimitistheupperlimitofwatercontentwhenthemudisinaplasticstate.Whenthewatercontentexceedstheliquidlimit,themudisinasemi-solidstate.Thedifferencebetweentheliquidlimitandtheplasticlimit,expressedasapercentage,istheplasticityindex.

Theplasticityindexrepresentsthemoldingperformanceofthemud.Themethodistoprocessthemudmassintoaspherewithadiameterof45mm,placeitinaplasticizer,andcompressitwithgravityuntilcracksbegintoappear.Theplasticityindexisthedegreeofdeformationofthemudballundertheactionofexternalforce,thatis,theproductofstressandstrain.Thecalculationformulaisasfollows:

TheplasticityindexS=(d－b)G

where：D——theoriginaldiameterofthemudball,cm;

b——theheightofthemudballafterbeingcompressedbygravity,cm;

G——themudballappearsfirstwhencompressedTheloadwhencracked,kg

Theplasticityofclaycanbedividedintofourlevelsaccordingtotheplasticityindexorplasticityindex.ThecorrespondingrelationsarelistedinTable1.

Table1Plasticitygradeofclay

Therearemanyfactorsthataffecttheplasticityofclay.Oneisthegenerationage,mineraltype,crystalformandcrystallinityofclayminerals.Kaolincomposedofkaolinitewithhighdegreeoforderhaslowplasticity;kaolincomposedofkaolinitewithlowdegreeoforderistheopposite.Inaddition,theparticlesize,cationexchangeability,andexchangeablecationtypesofclayallaffectitsplasticity.TheplasticitycomparisonsofseveralcommonlyusedbindingclaysarelistedinTable2.

Inactualproduction,themainmethodstoincreasetheplasticityofrawmaterialsare:

①Selectmaterialsandremovenon-plasticimpurities,suchasquartz,etc.;

②Finelygrindtheselectedmaterialtoincreaseitsdispersion;

③Addanappropriateamountofplasticmaterialbindingagent,suchaspulpwasteliquid,dextrin,etc.;

④VacuumthemudExtrusiontreatment;

⑤Extendthetrappingtime.

Thecombinationofrawmaterialsreferstothecombinationofclay-basedrawmaterialsandnon-plasticrawmaterialstoformplasticmudmassesandhavecertaindryingstrengthcapabilities.Thebindingpropertiesofthebindingclayareusuallyreflectedbytheamountofstandardquartzsand(particlecomposition0.25～0.15mmaccountingfor70%,0.15～0.09mmaccountingfor30%)andtheflexuralstrengthafterdrying.Generally,clayswithstrongplasticityhavestrongbindingcapacity(thereareexceptions,suchasNanningballclayisverypure,fine-grained,andhasgoodplasticity.However,duetoitslargesurfaceenergy,itabsorbsmorewaterandsyneresisduringdrying,resultinginmorefissures.Thedrystrengthispoor.Itsplasticityindexcanreach36-47,whiletheflexuralstrengthisonly0.48Mpa.

Developmentprospects

WiththecontinuousdevelopmentofChina'scementindustry,theHigherrequirementsarealsoputforward.Therefractoryindustry,whichhasreliedonextensiveeconomicgrowthforalongtime,shouldincreaseitsadjustmenteffortstoadapttotheneedsofthenewsituation.

ThereisanindustryconcentrationintherefractoryindustryinChina’scementindustry.Low,viciouscompetition,shortageofrawmaterialsandotherproblems,onlybyacceleratingthereorganizationandintegrationofrefractorymaterialsproductionenterprisesforcementkilnscantheyadapttotherapiddevelopmentofthecementindustry.Atthesametime,enterprisesshouldalsostrengthencooperationwithscientificresearchinstitutesanduserunits.Large-scaleindustry-university-researchcooperationhasachievednewbreakthroughsinthetechnologyofgreenrefractorymaterials,andstrivetoachievesubstantialbreakthroughsinsomekeygreenrefractorymaterialstechnologyandpopularizationandapplicationinashortperiodoftime.

DevelopgreenRefractorymaterialstrategyisanimportantdevelopmentstrategyrelatedtothesustainabledevelopmentofChina’scurrentandfuturerefractorymaterialsindustry.

Theupcoming"RefractoryMaterialIndustryAccessStandards"willsurelypromotetheeliminationofbackwardproductioninthenextfewyearsProcessequipment,cultivatingleadingenterprises,andpromotingthedevelopmentoftheindustryinthedirectionoflarge-scaleintensification.

Ofcourse,whiledevelopinggreenrefractories,productqualitymustalsobeguaranteed.Themainreasonforthelowlifeofrefractorymaterialsismanufacturer’sproduction.Theequipmentisbackwardandthefrictionbrickpressisusedformolding.Thelevelofautomationinthebatching,molding,firingandinspectionprocessesislow,theproductqualityfluctuatesgreatly,andthesizedeviationislarge;themasonrymethodisimproper.Inuse,inordertopreventtheoccurrenceofrefractorymaterialsThephenomenonofbricks,excessiveuseofsteelplatesforlocking,causestherefractorymaterialstoexpandgreatlyduringheating,andexcessivepressuredamagestherefractorybricks;thedegreeoffinemanagementislow.

TosolvetheproblemofshortlifeofrefractorymaterialsSomecompanieshavebeguntodevelopenergy-savingproducts,suchasreplacingmagnesia-aluminumspinelbrickswithhigherthermalconductivitywithsilicobricks(high-aluminumsiliconcarbidematerials)toreduceheatloss,reduceheatconsumptionpertonofclinker,andsaveenergy.Magnesia-ironspinelbricksreplacedirectmagnesia-chromebricksandtheuseofmagnesia-chromebricksinrotarykilns,effectivelyavoidingchromiumpollution.

Infact,cementcompaniesshouldfocusontheprocessconditionsandrawclinkerofcementkilns.,Fuelrequirements,reasonableselectionofrefractorymaterials,suchastheuseofhighstrength,lowthermalexpansion,andgoodthermalshockresistance,toreducethedamagetotherefractorymaterialsduringheating.Atthesametime,thedesignplanshouldbeoptimizedandimprovedRefinedmanagementlevel,improvetheoperationrateofcementkilns,andreducetheconsumptionofrefractorymaterialspertonofclinker.

Expertsparticipatinginthereviewmeetingofthe"RegulationsfortheUseofRefractoriesforCementRotaryKilns"organizedbytheChinaBuildingMaterialsFederationAfterdeliberationandunanimouslypassedthestandarddraftforreview,markingthesuccessfulcompletionofthefirstdomesticandforeigncementkilnrefractorymaterialsstandardfortheuseoftechnicalregulations,Willbeofgreatsignificancetopromotethestandardizationofrefractorymaterialsusedincementkilns,promotethedevelopmentoftheindustry,andtransformandupgrade.