制盐工艺流程

盐田饱和卤水直接进蒸发罐真空制盐工艺介绍靳志玲（中盐制盐工程技术研究院，天津300450）内容摘要：利用滩田饱和卤水直接进蒸发罐蒸发结晶制取氯化钠，在制盐过程中采取三次洗涤方法，除去钙镁离子，以获得纯度超过99.1%的氯化钠和浓度较高的制盐母液。关键词：滩田饱和卤水真空精制盐1简介目前，国内大部分井矿盐企业采用以井矿盐卤为原料，北方部分生产企业采用原盐化成饱和盐水再精制真空盐的生产方法。随着国内“两碱”的迅速发展和人民生活水平的提高，原盐供需矛盾已越来越突出。特别是在海盐区，以原盐溶解成饱和卤水再生产精制盐，不仅增加了原盐的消耗，而且降低了盐田面积的使用效率，增加投资，生产成本高，不同程度上影响了食用盐生产企业的经济效益，造成许多食用盐定点生产企业减产、亏损，直接影响了百姓的生活。而采用滩田饱和卤水直接进蒸发罐制盐，即可以节约结晶面积，其母液还可以为生产氯化钾、氯化镁等盐化工产品提供高质量原料苦卤，达到充分利用卤水中的各种有效成分，实现零排放、无污染、循环经济的目的。工艺流程简述卤水经滩田日晒蒸发，至饱和后引入一个卤水库中储存。卤水库的作用，一是储存一定量的饱和卤水，以备真空制盐生产的需要；二是卤水在此有一定的停留时间，可以使其中的一些杂质颗粒沉淀下来，达到净化卤水的目的。净化后的饱和卤水从卤水库引出后，进入蒸发制盐车间的精卤桶。采用预热后的卤水进罐，顺流转料、末效排盐浆，集中排母液的方式进行生产。I效蒸发罐盐箱中的盐排到II效下循环管中，II效盐箱中的盐排到III效下循环管中，III效盐箱中的盐排到IV效下循环管中，最后集中在IV效盐箱；IV效排出盐浆，同时由IV效分离罐排出母液。工艺流程简图见图1。

生蒸汽原料卤水闪发汽I效二次蒸汽I效蒸发罐闪发汽II效二次蒸汽 III效二次蒸汽II效蒸发罐4.III效蒸发罐IAw效二次蒸汽^母液不凝汽去真空泵混合冷凝器r冷却水冷却水回锅炉

冷凝水I效闪发桶I效平衡桶冷凝水II冷凝水□效闪发桶皿效平衡桶皿效闪发桶

W平横桶冷凝水一预热器原料卤水生蒸汽原料卤水闪发汽I效二次蒸汽I效蒸发罐闪发汽II效二次蒸汽 III效二次蒸汽II效蒸发罐4.III效蒸发罐IAw效二次蒸汽^母液不凝汽去真空泵混合冷凝器r冷却水冷却水回锅炉

冷凝水I效闪发桶I效平衡桶冷凝水II冷凝水□效闪发桶皿效平衡桶皿效闪发桶

W平横桶冷凝水一预热器原料卤水生活用水 ►预热器冷凝水冷凝水原料卤水冷凝水冷凝水盐浆工艺的优缺点运用该工艺已在中国北方建设了一个年产15万吨的真空制盐生产线，相比再制盐生产工艺，其实施效果如下：本工艺采用饱和卤水制盐，不需要淡水化原盐，淡水消耗低，可节约淡水资源，根据生产情况，1t盐消耗淡水1.4-0.2m3，而再制盐生产工艺需要淡水3.5-4.53.73m3，吨盐节约了2.1-4.3m3淡水。2） 节约日晒盐场土地，减少原盐消耗，提高了盐田利用率对再制盐生产线来说，一般生产It精制盐需要消耗1.2t日晒原盐，年产15万t的精制盐需要18万t原盐，需要结晶面积136.36公顷（按目前中国北方盐场有效结晶单产16501/公顷，有效面积占80%）,采用饱和卤水直接进蒸发罐工艺，不需要饱和卤水进结晶池继续蒸发制盐，只需要建设一个约2公顷的饱和卤库，因此，节约了土地面积134.36公顷，节省的结晶面积可用于增加日晒盐产量85471，按日晒盐销售价160元/t计算，日晒盐增加产值136.8万元。如果土地按3万元/亩计算，节约土地价值为6000多万元。3） 采用三次洗涤方法洗涤盐浆以去除钙镁离子，使氯化钠含量超过99.4%，精制盐达到优级盐质量。蒸发结晶过程中盐浆会夹带大量的母液，母液中含有大量的钙、镁杂质，因此，采用三次不同的洗涤方式洗涤盐浆，提高精制盐质量。4）用饱和卤水直接生产精制盐母液损失小，提高了母液的利用率，实现盐化联产采用盐田饱和卤水直接生产优级真空精制盐工艺，每产1t精制盐副产母液约1.7m3，以年产15万t精制盐计算，全年可产生25.5万m3蒸发母液，且排出的苦卤氯化钾含量达到了24〜30g/l,浓度为29〜34°Be',钠镁比值为1.4〜0.6,排出的苦卤中氯化钾总含量为6589t，氯化镁总量为36540t，硫酸镁总量为18900t，氯化钠总量为37600t,溴总量510t。而年产18万t原盐，排出的苦卤量一般只有18万m3,经过复晒、渗透损失、沟道输送进入化工厂后只有原来的45%左右，也就是说还有8.1万m3，这时氯化钾总含量为2036t，氯化镁总量为15280t,硫酸镁总量为7727.4t,氯化钠总量为11128t,溴总量162t。因此，该工艺可为盐化工生产提供更多的原料，提高了生产效率，降低了各种消耗，节约能源。该工艺排出的制盐蒸发母液温度在55.04°C以上，可通过管道直接进入下步生产氯化钾的工序，生产氯化钾产品，节约氯化钾生产过程中所需热量，折标煤1157吨/年5） 由于滩田饱和卤水较化盐卤水氯化钠含量低，因此单位产品的蒸发水量较高，吨盐产品电、蒸汽消耗量较大，能耗较高。6） 蒸发设备换热面积较化盐溶解工艺稍高，因此设备投资相对较高，但由于节省大量盐田结晶面积，总体投资低。与原盐溶解再制盐工艺技术经济指标比较国内海盐区生产真空盐的工艺主要有滩田饱和卤水进罐蒸发制盐和原盐溶解制成饱和卤水蒸发制盐两种方法。原盐溶解制成饱和卤水蒸发制盐工艺优缺点有：（1）需建结晶池，工程总体投资较高；（2）单位产品蒸发水量小，设备投资稍低，（3）吨盐消耗电、蒸汽量较小；（4）水消耗较大，吨盐产品耗水2.4m3，（5）蒸发母液损失大。比较两种制盐方法技术经济指标如表。表主要经济技术指标比较项目再制盐生产饱和卤水直接进罐生产投资：结晶池投资550万元0蒸发设备投资9701080单位产品投资335元/吨306元/吨消耗指标：原煤0.23吨0.21吨原盐1.25吨一1.15吨0.00吨卤水0.007.5m3白水3.545m31.4-0.2m3电50-70度50-70度两种工艺在投资和单位产品生产成本中有较大的差别，饱和卤水法单位产品总投资低于原盐溶解法，单位产品成本低于原盐溶解法30％。5.结论对于北方海盐区生产精制盐企业来说，利用滩田饱和卤水直接进蒸发罐制取精制盐是一个较好的生产工艺，节约投资，节约土地，特别是将宝贵的原盐溶解成饱和卤水再进行制盐是对土地资源的浪费，再有其生产成本低，企业有较高的利润空间；排出的制盐母液综合利用生产钾、溴、镁等产品，使卤水全部吃干榨净，没有废物排放，减少了环境污染，有利于可持续发展。Newtechnologyofproducingrefinedsaltbyaddingsaltfield

saturatedbrineintoevaporatordirectlyJinzhilingGeJinyang(SaltResearchInstituteChinaNaturalSaltIndustryCorporation,TianJin300450)Abstract:AfterMakingsalinesaturatedbrineflowinevaporatingpot,thesodiumchlorideisobtainedbyevaporativecrystallization.Calciumandmagnesiumionscanberemovedbywashingsaltthreetimesinordertogetthesodiumchloridethatthepurityisover99.1percentandthemotherliquorthathavehighconcentration.Keywords:salinesaturatedbrine,vacuum,refinesaltmagnesiumchlorideetc.inorderto1BRIEFINTRODUCTION makeuseofallkindsofeffectiveAtpresent,thematerialsofmakingvacuumsaltareusingthewellandrocksaltinmostofthewellandrocksaltcorporationsandthesaturatedbrinegotbydissolvingcrudesalt.Alongwiththerapiddevelopmentofcausticalkaliandsodiumcarbonateandthegrowthinthepeople'slivingstandard,thecontradictionofcrudesaltinsupplyandrequireismoreandmorestoodout.Particularlyintheseasaltareas,productingrefinesaltwithsaturatedbrinethatisgotbydissolvingcrudesaltcanincreasetheconsumptionofrawsalt,reducetheavailabilityfactorofsaltfield,addinvestmentandproductioncost.Thiswillinfluencetheeconomicefficiencyofediblesaltmanufacturingenterprises,makethemreduceoutputandaffectpeople'slive.However,usingthemethodofmakingsalinesaturatedbrineflowinevaporatingpotandthenobtainingsodiumchloridebyevaporativecrystallizationcansavingcrystalarea.Furthermore,themotherliquorcanbeusedasmaterialtoproducechemicallyproductssuchaspotassiumchloride,constituentsinthebrineandachievetheobjectsofnodischarge,nopollutionandcirculatingeconomy.2.INDICATIONOFTHEPROCESSFLOWAfterbeingsolarizedtosaturationinbeachfieldbrinewasinductedtobrinetankandstored.Ontheonehandbrinetankcanstoresomesaturatedbrinethatisusedtoproducevacuumsalt.Ontheotherhand,brinehavesomeresidencetimeheresosomeimpuritiescanbedepositedinordertomakethebrinebepurified.Afterbeingdrawoutedfrombrinetankthecleanedsaturatedbrinewaspumpedtofinebrinetankinthemanufacturesaltplant.Andproductioncanbegoneonbyusingthemethodsofpreheatingbrine,transferringstuffinparallelflow,dischargingsaltslurryinthelasteffectandexportingmotherliquorconcentratedly.Thesaltinthefirsteffecttankisdischargedtothecirculationpipeofthesecondeffect,Thesaltinthesecondeffecttankisdischargedtothecirculationpipeofthethirdeffect,Thesaltinthethirdeffecttankisdischarged fourtheffecttankwherethesaltslurrytothecirculationpipeofthefourthandthemotherliquoraredischarged.effect.Atlastthesaltiscollectedinthe Fig.1isthediagramoftheprocessflow.生蒸汽原料卤水闪发汽I效二次蒸汽I效蒸发罐盐II效一次烝汽III效二次蒸汽 W效二次蒸汽II不凝汽去真空泵回锅炉

冷凝水I效闪发桶I效平衡桶冷凝水预热器冷凝水闪发汽II冷凝水冷凝水原料卤水III效蒸发罐W臓闪发汽W效蒸发罐混合冷凝器生蒸汽原料卤水闪发汽I效二次蒸汽I效蒸发罐盐II效一次烝汽III效二次蒸汽 W效二次蒸汽II不凝汽去真空泵回锅炉

冷凝水I效闪发桶I效平衡桶冷凝水预热器冷凝水闪发汽II冷凝水冷凝水原料卤水III效蒸发罐W臓闪发汽W效蒸发罐混合冷凝器冷却水冷却水 4原料卤水□效闪发桶皿效平衡桶皿效闪发桶

W平横桶冷凝水一冷凝水冷凝水+盐浆预热器生活用水 >Figure.1Diagramoftheprocessflow3.RELATIVEMERITSOFTHEPROCESSInthenorthofChinaaproductionlinehasbeenbuiltwiththisprocess,whichcanproduce1.5milliontonssaltperyear.Comparingwithreworksaltproductionprocess,theeffectofthisprocessisasfollows:Thesaturatedbrineisusedinthisprocesstaketheplaceofdissolvingcrudesaltwithfreshwater.Suchcanreducetheconsumptionoffreshwaterandsavetheresource.Accordingtotheproduceconditions,producing1tonsaltwillconsume1.4-0.2m3freshwater.Andthatifusethereworkingsaltprocess3.5-4.53m3freshwaterwillbeused.Thatistosay2.1-4.3m3freshwatercanbesavedcorrespondingto1tonsalt.Savingthesolarsaltfield,reducetheconsumptionofcrudesalt,increasetheavailabilityofthesaltfield.Forthereworkingsaltproductionline,asageneralruleproducing1tonrefinesaltwillconsume1.2tonssolarsalt.Producing1.5milliontonrefinesaltneeds1.8milliontonscrudesaltand136.36hectarecrystalarea(Accordingtotheexperiencethatonehectarecanproduce1650toncrystalandtheeffectiveareais80percent).Usingtheprocessthatthesaturatedbrineispumpedtoevaporatingtankdirectlythebrineneednotevaporateincrystalpondbutforasaturatedbrinestoreroomofabout2hectare.Suchcansavesurfaceareaof134.36hectareandthisareacanbeusedtoincrease8547tonoutputofsolarsalt.Hencetheproductivevalueofsolarsaltwillincrease136.8tenthousandyuanaccordingtothemarketpriceofsolarsaltwhichis160yuan/t.Andlandvalueof60millionyuancanbesavedifthelandis30,000yuanpermou.Adoptingthemethodofwashingsaltthreetimesinordertogetridofcalciumandmagnesiumions,makethepurityofsodiumchlorideexceed99.4%andmaketherefinesaltreachfirstquality.Intheprocessofevaporativecrystallizationmuchmotherliquorwillexistinsaltslurry.Themotherliquorcontainsalotofimpurityofcalciumandmagnesium.Sosaltslurryiswashedinthreedifferentwaysinordertoimprovethequalityofrefinesalt.Usingthesaturatedbrinetoproducerefinesaltcanreducetheconsumeofmotherliquors,enhanceit'savailabilityandrealizetheproductionofsaltandchemicalstogether.Theprocessthatproducingexcellentvacuumsaltwithsalinasaturatedbrinedirectlycanget1.7m3motherliquorinrelationto1trefinesalt.Onthebaseof150,000tonrefinesalt,wecanget255,000m3evaporationmotherliquor.Inbitterbrinewhoseconcentrationis29〜340Be'thecontentofpotassiumchlorideis24〜30g/landtheratioofsodiumandmagnesiumis1.4〜0.6.And6589tpotassiumchloride,36540tmagnesiumchloride,18900tmagnesiumsulfate,37600tsodiumchlorideand510tbrominearecontainedinthebitterbrine.Thebitterbrineisabout180,000m3inrelationto180,000tcrudesalt.Afterbeingsolarizedrepeatedlyandconsumingforfilterthebrineisleft45%whenitispumpedtochemicalplant.Thatistosaythereare81,000m3brine.Bynowthereare2036tpotassiumchloride,15280tmagnesiumchloride,7727.4tmagnesiumsulfate,11128tsodiumchlorideand162tbromine.Sotheprocesscanprovidemorematerialforsaltandchemicalsplants,heightenproductionefficiency,reduceallkindsofconsumptionandsaveenergy.Thetemperatureofthemotherliquorgotfromthisprocessisover55.04°C.Soitcanbepumpedtothepotassiumchlorideprocesswithpipetoproducepotassiumchloride.Suchwillsavetheheatquantityintheprocessofproducingpotassiumchloride.Andtheheatquantityisequalto11578t/ystandardcoal.Becausethecontentofsodiumchlorideinthebeachsaturatedbrineislowerthanthecontentinthebrinethatisgotbydissolvingsalt,theevaporatedwaterofunitproduceishigher,theelectricityandsteamconsumptionaremore.Thatistosaytheenergyconsumptionishigher.Theheatexchangeareaisalittlerbiggerthantheprocessofdissolvingsalt,sotheequipmentinvestmentishigher.Butbecauseofsavingalotofsalinacrystalareathetotalinvestmentislower.4.COMPARETHEECONOMICINDICATORSWITHTHEPROCESSOFDISSOLVINGCRUDESALTANDTHENREMAKINGSALTInChinaTherearetwomainmethodstoproducingvacuumsaltinseasaltarea.Oneispumpingthebeachsaturatedbrineintoevaporatingpot.Theotherisusingthesaturatedbrinegotbydissolvingcrudesalt.Comparingthesecondmethodwiththefirstmethodthe

relativemeritsofthesecondmethodisasfollows(:1)needtobuildcrystalpondandthetotalinvestmentishigher.(2)Theevaporatedwaterofunitproductissmallerandtheequipmentinvestmentislower.(3)Theconsumingofelectricityandsteamislower.(4)Theconsumingofwaterismoreand2.4m3waterwillbeconsumedinrelationto1tonsalt.(5)Thelossofmotherliquorisbigger.Theeconomicindicatorsofthetwomethodsareasfollows:ComparisonofthemaineconomicandtechnicalnormsItemTheprocessbydissol